JPS60254049A - Microcapsules - Google Patents

Abstract

PURPOSE:To improve fluidity, to stabilize surface property, and to prevent oozing of a core material, etc., by combining a silicone compd. incorporated in a resin for forming outer walls, with the resin through chemical combination. CONSTITUTION:As the silicone compd., a silicone resin oligomer or polymer contg. functional groups, such as hydroxyl groups capable of polymerizing with the cross-linking isocyanate of the monomer of polyurea or polyurethane resin for constituting the outer walls is used. A preferable silicone compd. contg. hydroxyl groups is silicone polycarbinol, and it is incorporated in the outer wall resin in an amt. of 1-70wt%, preferably, 3-50wt%. The silicone compd. can be chemically combined with the isocyanate, e.g., by reacting the silicone polycarbinol contg. OH groups with the cross-linking isocyanate to produce urethane bonds, and to form a modified polyisocyanate having a silicon skeleton, and it is used for forming the outer walls.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to microcapsules, and more particularly to microcapsules that can be suitably used as pressure fixing type microcapsule toner.

[Prior art]

In recent years, electrophotographic methods, electrostatic printing methods, electrostatic recording methods, etc. are used to form an electrostatic charge image based on image information, and this is developed with a developer toner to form a toner image. It is widely practiced to form a visible image by transferring an image to a transfer paper or the like and then fixing it.

Conventionally, toner for developing electrostatic images has been widely used in powder form, which is obtained by finely pulverizing thermoplastic resin as a binder and colorant such as carbon black dispersed therein. Yes, if it is a two-component toner,
Mix and stir with carriers such as iron powder and glass beads.
Also, if it is a one-component toner containing fine magnetic powder, it can be triboelectrified by stirring itself, and the electrostatic force can be used to develop an electrostatic image. For example, after the toner image is transferred, it is heated by a heating roller or the like and fixed.

However, in such toners, the toner particles are crushed during agitation for frictional charging and fine powder toner is generated, resulting in poor visible image quality, or the toner must be replaced with a new one early. In addition, since fusing is achieved by a heat fusing method, a long waiting time is required until the temperature of the fusing device rises to the required set temperature), and It requires a large amount of energy and can also cause a fire if paper jams occur, and in order to achieve reliable fixing, it is necessary to meet strict requirements in terms of temperature conditions, etc. is necessary.

Under such circumstances, research has recently begun on the use of so-called microcapsules as toners for developing electrostatic images.

This microcapsule type toner is in the form of a powder consisting of colored particles in which a core material composed of a liquid substance or a soft solid substance is enclosed in a fine resin capsule (outer wall). When this toner is used, it can be fixed by applying pressure using a pressure roller or the like to burst the capsule and release the core material inside.

Therefore, since no heating is required, there is an advantage that the above-mentioned problems in heat fixing can be significantly alleviated.

Regarding such microcapsule type toner that can be fixed under pressure, 1% patent publication No. 51-91724 and No. 52-1199
No. 37, 54-118249. No. 55-642
Techniques described in various publications such as No. 51 are known. but,
2 of the above techniques.

There are still problems such as offset phenomenon to the pressure roller, durability, stability, and storage stability.In particular, there are problems with pressure fixing properties on plain paper, etc., and fixing properties in microcapsule type toners. The components were either rigid or excessively plastically deformed, resulting in insufficient fixing properties.

Therefore, the inventor of the present invention has conducted intensive studies to improve the pressure fixing properties, and has found that it is insufficient to improve the fixing properties by simply improving the adhesion to paper, etc. It has been found that in order to prevent the material from peeling off from the surface, it is important to reduce the applied external force, that is, to make it slip.

Conventionally, a technique is known in which silicone oil, silicone resin, etc. are contained in the core material or outer wall in order to provide a lubricant effect (see Japanese Patent Application Laid-Open No. 11558-150968, etc.).
.

However, in the prior art, silicone resins and the like simply coexist or are mixed together, so they tend to leak out from the toner.

There is a drawback that the surface condition of the toner is easily changed, and in particular, the surface condition changes due to heat or the like.

Also, blending silicone oil or silicone resin is good for obtaining a low coefficient of friction (Japanese Patent Application Laid-Open No. 59-1998).
No. 4649, etc.), when producing powder such as toner, there is a drawback that fluidity is reduced.

(Objective of the Invention J) Therefore, the object of the present invention is to provide microcapsules with good powder properties, and particularly with improved fluidity.

Another object of the present invention is to have stable surface properties.

To provide microcapsules free from leaching of core material.

[Structure of the Invention] As a result of extensive research, the present inventor discovered that a microcapsule consisting of a core material having mutually different physical properties or functions and an outer wall covering the core material, and a resin constituting the outer wall. It has been found that the above object can be achieved by microcapsules characterized in that a silicone compound contained in the resin is bonded to the resin by a chemical bond.

The present invention will be explained in detail below.

When the outer wall resin is mainly composed of a polyurea resin or a polyurethane resin, the silicone compound of the present invention includes a functional group ( Oligomers or polymers of silicone resins containing hydroxyl groups are used.

Examples of the hydroxyl group-containing silicone oligomer include polysiloxanes represented by the following general formula 0.

General formula [IJ In the above formula, Bl, B2 hydrogen, an alkyl group having 1 to 6 carbon atoms which may have a substituent (for example, a methyl group, an ethyl group, or an isopropyl group), an aryl group, and an aryl group. represents a phenyl group (e.g. tolyl group, xylyl group, benzyl group, phethyl group), and n is 5 to 250
is an integer of 0, and examples of the substituent include hydroxy, amine, argyl, aryl, alkyloxy, and aryloxy groups.

The hydroxyl group-containing silicone compound preferably used in the present invention is silicone polycarbinol.

The silicone polycarbinol can be a hydroxyl group-containing polysiloxane represented by the following general formula CnJ.

In the general formula, Bl and H2 are synonymous with the above general formula [0, and 几3 is a divalent bonding group, preferably having 1 to 6 carbon atoms.
hydrocarbon groups (e.g. methylene, ethylene and butylene groups), and L is from 2 to 30, preferably from lO to
It is an integer of 20.

The silicone polycarbinol can also be a grafted hydroxyl functional polysiloxane having the following general formula:
is the same as the above general formula (R' + R2 of IJ!'
I R6 is a divalent bonding group, preferably a hydrocarbon group having 1 to 6 carbon atoms (eg, methylene, ethylene, and butylene), and X and y are each independently selected from an integer of 2 to 15.

The molecular weight of the silicone carbinol is preferably 5,000 or less. If it exceeds 5,000, the thermal properties deteriorate, the strength and rigidity also decrease, and the material becomes soft.

The content of silicone carbinol in the outer wall resin is 1 to 7 Qwt%, preferably 3 to 50 wt%.

In the present invention, the above-mentioned silicone carbinol may be used alone, but a compound having another reactive functional group may be used in combination. Compounds having three or more reactive functional groups 1 For example, polyfunctional alcohols such as trimethylolpropane and polyvinyl alcohol; diethyltriamine, triethyl Polyfunctional amines such as tetramine can be used.

Especially if you want to increase the content of silicone compounds,
As silicone polycarbinol.

Preference is given to using compounds having alcohol functions grafted onto polydialkylsiloxanes, such as polydimethylsiloxanes.

In the present invention, a carbinol-modified polysiloxane resin can also be used as the hydroxyl group-containing silicone compound. The resin is an organofunctional polysiloxane containing a structural unit corresponding to the formula -0-8t(R)2-, in which R is an alkyl group having 1 to 4 carbon atoms or a #'i phenyl group. It is.

In the present invention, suitable starting materials are not only pure polysiloxanes containing organofunctional end groups known per se, but also siloxane polyoxyalkylene copolymers containing organofunctional end groups known per se. There may be.

Specific examples of polysiloxanes preferably used in the present invention include compounds represented by the following formula.

General formula■ (n: 5-29) The method for producing the above compound is as follows.

That is, 1, 1, 3, 3-tetramethyl-1, 3-hydroxymethyl disiloxane represented by the general formula below is equilibrated with octamethylcyclotetrasiloxane in the presence of sulfuric acid, or the West German patent application publication specification No. 1.236.50.5, obtained in a known manner.

General formula concave H3CH3 1 HOOH2Si OSt OH20H 1 H3CH3 The outer wall resin of the present invention preferably has a polyurethane resin or a polyurea resin as a main component, the polyurethane resin is obtained by the reaction of a crosslinkable incyanate and a polyol 7, and the polyurea resin is a crosslinkable It is obtained by the reaction of polyincyanate and polyamine.

In order to chemically bond the silicone compound of the present invention in the above reaction, 1. For example, a silicone polycarbinol containing a hydroxyl group is reacted with a crosslinkable incyanate to form a urethane bond, and a modified polyvalent inocyanate having a silicon skeleton is formed. It is converted into cyanate and then utilized for the outer wall forming reaction.

Examples of the crosslinkable isocyanate used in the present invention include the following.

■) Hexamethylene diisocyanate 0ON (OH2) 6NOO Commercial product name: "Sumidur H" (manufactured by Sumitomo Bayer Urethane) 2) Hexamethylene diisocyanate adduct commercial product name =
"Sumigiel N" (manufactured by Sumitomo Bayer Urethane) 3) Metaphenylene diisocyanate 0O 4) Toluylene diisocyanate OO Commercial product name: "Suminate 80" (manufactured by Sumitomo Chemical Industries, Ltd.) "Hiren TM Co (manufactured by DuPont) 5) 2.4-) Rylene diisocyanate OO Commercial product name: "Sumijil T" (manufactured by Sumitomo Bayer Urethane Co., Ltd.) Reaction product of lylene diisocyanate and trimethylolpropane Commercial product name: "Sumijil L" (Sumitomo Bayer Urethane Co., Ltd.) (manufactured by Urethane Co., Ltd.) Commercial product name: [Corone・-)LJ (manufactured by Nippon Polyurethane Industries Co., Ltd.) ? ) 3.3'-dimethyl-diphenyl-4,4'-diisocyanate CH3CH3 Commercial product name: "Hyren H" (Depon M) [Suminate BTJ (manufactured by Sumitomo Chemical Co., Ltd.) 8) Diphenylmethane-4,4'-diisocyanate commercially available Product name: [Millionate MTJ (manufactured by Nippon Polyurethane Industries Co., Ltd.) r l5onate 125M J (manufactured by Kasei Upjohn Co., Ltd.) "Sumidur 44S" (manufactured by Sumitomo Bayer Urethane Co., Ltd.) 9) 3.3'-dimethyl-diphenylmethane-4,4
'-diisocyanate Commercial product name: "Hiren DMM J (manufactured by Devon Co., Ltd.) 10) Triphenylmethane-triincyanate OO Commercial product name = "Sumidur R" (manufactured by Sumitomo Bayer Urethane Co., Ltd.) 11) Polymethylene phenyl isocyanate Commercial product name:
l-Sumidur 44V' 10 J (manufactured by Sumitomo Bayer Urethane Co., Ltd.) "Millionate M" (Nippon Polyurethane Industry Co., Ltd. M) 12) 2-phthacine-1,5-diisocyanate Ne.

Commercial product name = "Sumidil 15" (manufactured by Sumitomo Bayer Urethane) 13) Dicyclohexylmethane diisocyanate Commercial product name = "Desmodur W" (manufactured by Sumitomo Bayer Urethane) 14) Diphenyl ether-4,4'-diincyanate Commercial product name: "Suminate E" (manufactured by Sumitomo Chemical Co., Ltd.) Specific examples of polyols or polyamines that react with the above polyisocyanates to yield polyurethane resins or polyurea resins include the following.

l) Polyol Diols such as ethylene glycol, propylene glycol, -butylene glycol, hexamethylene glycol, triols such as glycerin, trimethylolpropane, trimethylolkotane, 1,2,6-hexanetriol, pentaerythritol, and Water etc. 2) Polyamines ethylenediamine, hexamethylenediamine, diethylenetriamine, iminobispropylamine, phenylenediamine, xylenediamine.

Triethylenetetramine Although the case where polyurethane or polyurea resin is mainly used as the outer wall resin has been described above, the present invention is also applicable to cases where polyamide resin or polyester resin is used as the main material.

As the silicone compound of the present invention used in that case, any silicone compound can be used as long as it has a group that reacts with the functional group of the acid chloride.

Specifically, the silicone compound mentioned separately can be used.

When the microcapsule of the present invention is used as a microcapsule type toner, the outer wall resin is used as the capsule, and the core material is a liquid substance or a soft solid substance containing a colorant. The liquid substance or soft solid substance may be one having fluidity or plasticity, and the viscosity is lθ~100 at a temperature of 60°C.
The one with 10,000 cps is preferable. Specific examples include liquid polybutene, liquid polychloroprene, liquid polybutadiene,
Epoxidized soybean oil, epoxidized triglyceride, epoxidized monoester, adipic acid polyester, liquid polyester, chlorinated paraffin, trimellitic acid ester, vegetable oils such as soybean oil, silicone oil, mineral oil, polymethyl acrylate, polyacrylic Butyl acid, polylauryl methacrylate, oligomer of acrylic ester,
Styrene thread monomer oligomer, styrene and alkyl acrylate copolymer oligomer, styrene and alkyl methacrylate copolymer oligomer, polyvinyl acetate,
Petroleum residues such as asphalt and kiltunide, as well as linoleic acid, lylinic acid, oleic acid, elaidic acid, and eleostearic acid.

Esters of unsaturated fatty acids such as lyrunelaidic acid, gadolenic acid, erucic acid, arachidonic acid, curbanodonic acid, α-lycanic acid, linseed oil, eno oil, tung oil, castor oil, hemp oil, kapok oil, poppy seed oil , sesame oil, rice bran oil, safflower oil, soybean oil, corn oil, rapeseed oil,
Vegetable oils that are drying or semi-drying oils such as sunflower oil and cottonseed oil, copolymers of acetylene and butadiene, dicyclopentadiene oligomers, synthetic drying oils such as "Finton" (manufactured by Nippon Zeon Co., Ltd.), and others. For example, in order to obtain a microcapsule type toner suitable as a magnetic toner used as a -component toner, the core material contains a colorant.

Fine magnetic powder may be contained as part or all of the colorant.

As the coloring agent, any one selected from pigments, dyes, etc. can be used, and specific examples include carbon black, nigrosine dye (0, 1, No., 50415B),
7 Nilin Blue (0,1,Na50405), Calcooilip/l/-(C,I, NαazoicBl
ue 3), chrome yellow o-(0,l-No,
l 4090), Ultramarine Blue (0,1,N
o, 77103), Devon Oil Red (0,1,N
α26105), Orient Oil Red + 330
(0,I.

Na60505 )s Quinoline x o -(0,1
, No. 47005), methylene blue chloride (0
,,1,.

Arashi 520.15), Phthalocyanine Blue (0, I.

N [L741'60), malachite green oxalay) (0,1, 42000), lamp black (o
.

L No, 77266), o-su-87 gal (0
, 1, Na45435), oil black, azo oil black, and others can be used alone or in combination. These colorants may be contained in a proportion such that the toner as a final product contains about 3 to 20% by weight.

The magnetic material may be a ferromagnetic metal or alloy such as ferrite, magnetite, iron, cobalt, or nickel, or a compound containing these elements, or a material that does not contain a ferromagnetic element but is subjected to appropriate heat treatment. Mention may therefore be made of alloys which exhibit ferromagnetic properties, such as alloys of the type called Heusler alloys containing manganese and copper, such as manganese-copper-aluminum, manganese-copper-tin, or chromium dioxide, among others.

Specifically, as magnetite, BPT-1000,
EFT-500, MRMB-450 (manufactured by Toda Kogyo Co., Ltd.), BL-100, BL-120, BL-200,
BL-220, BL-500, BL-520, BL-8
P, RB-BL, RB-20 (manufactured by Titan Kogyo Co., Ltd.)
etc. are preferably used.

These magnetic substances are uniformly dispersed in the pressure fixing material in the form of fine powder with an average particle size of 0.1 to 1 μm.

The content is 20 to 7 parts per 100 parts by weight of toner.
0 parts by weight, preferably 40 to 70 parts by weight.

Further, the content of the pressure fixing substance contained in the core material in the toner is 5 to 45 parts by weight, preferably 15 to 35 parts by weight.

The above-mentioned microcapsule type toner can be manufactured by using an in-5-itu polymerization method, a method using a combination of in-altu polymerization and interfacial polymerization.

For example, an example of a manufacturing method preferably used in the present invention is as follows.

The insinate compound to which the silicone compound is chemically bonded, the pressure fixing substance, the colorant, and the polymerization initiator are mixed uniformly, and then this mixture is dispersed in water containing an appropriate dispersion stabilizer. The mixture is poured into a medium and stirred, etc. The mixture is divided into fine particles to be dispersed and suspended, and to this state, a compound having a group that reacts with the above-mentioned incyanate group is added, and the mixture is reacted and encapsulated. 1. Next, the inside is polymerized and stirring is continued until the completion of 1 reaction. Thereafter, the solid matter is separated and dried to obtain a microcapsule type toner.

In the above method, in order to control the particle size of the obtained toner, it is sufficient to control the particle size of the fine particles of the mixture in the reaction system. This can be achieved by means of controlling the stirring force while monitoring it.

In order to mix and disperse the colorant into the mixture, a ball mill, an attritor, a sand grinder, etc. may be used, but the colorant may also be treated with a silane coupling agent, a titanium coupling agent, etc. Good and
Alternatively, a dispersion improver such as lecithin for dispersing inorganic substances into organic substances may be added.

As a means for dispersing the mixture of the liquid substances and the like in the dispersion line, mechanical stirring means such as a homomixer, homojetter, Waring blender, etc., or ultrasonic dispersion is used. It is actually necessary to add a dispersion stabilizer to the dispersion medium, thereby maintaining a stable suspension state during the polymerization reaction.

Examples of dispersion stabilizers include water-soluble polymer substances such as gelatin, gelatin f1, polyvinyl alcohol, polystyrene sulfonic acid, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxyglobil cellulose, sodium carboxymethyl cellulose, and sodium polyacrylate, and anionic substances. Hydrophilic surfactants such as surfactants, nonionic surfactants, cationic surfactants, colloidal silica, alumina, tricalcium phosphate, ferric hydroxide, titanium hydroxide, aluminum hydroxide, etc. Inorganic colloidal substances and others can be effectively used. Of course, two or more of these dispersion stabilizers may be used in combination, and appropriate auxiliary agents may also be used together.

Although the particle size of the microcapsule toner is not subject to any lateral restrictions, the average particle size is usually 5 to 50 μm, preferably 5 to 30 μm.

Further, the thickness of the outer wall and the particle size of the core material may be the same as in the case of conventional microcapsule type toner.

When the microcapsule type toner contains fine magnetic powder, it is used alone as a developer, and when it does not contain fine magnetic powder, it is mixed with a carrier to form a two-component developer. It can be adjusted and used.

As the carrier, iron powder, glass peas, etc., or resin-coated products thereof are used, although there are no particular limitations, and the mixing ratio with the toner is 0 toner to 100 parts by weight of carrier.
．． 5 to 10 parts by weight, preferably 1 to 5 parts by weight. Further, the particle size of the carrier used is 25-1000 .mu.m, preferably 30-500 .mu.m.

Although the case where a microcapsule-type toner is obtained using the microcapsules of the present invention has been described above, the toner is not limited thereto, and may be used, for example, for pressure-sensitive copying paper or medicine.

It may also be used as capsules for livestock, fragrances, cosmetics, and adhesives. [Effects of the Invention] According to the present invention, since the silicone compound is bonded to the outer wall resin by bonding, the following capsules can be used. As is clear from the Examples, it is possible to provide microcapsules with improved fluidity, stable surface properties, and no oozing of the core material.

〔Example〕

Examples of the present invention will be described below, but the embodiments of the present invention are not limited to these. In addition"
"Parts" means 9 parts by weight unless otherwise specified.

Example 1 (in LIjtu polymerization method) The above composition was dispersed in a sand mill for about 1 hour.

Get magnetic ink. Colloidal tricalcium phosphate 1 prepared separately from trisodium phosphate and calcium chloride
．． 4&, sodium dodecylbenzenesulfonate 0.06.
A dispersion liquid in which p is uniformly dispersed in 800% of water is prepared. Next, the magnetic ink was dispersed into this dispersion using a homojetter at a rotational speed of 8000 to 9000 rpm for about 10 minutes to form oil droplets of about 5 to 20 μm.

This dispersion was transferred to a fourth flask and reacted at 75° C. for 8 hours at a stirring speed of 200 rpm. The dispersion stabilizer was decomposed and removed by a post-reaction reaction, followed by washing with water and drying to obtain the toner of the present invention. This toner will be referred to as "Toner I".

Example 2 (In 5 itu polymerization and interfacial polymerization method) 3 parts of dimethylpolysiloxane dicarbinol and 20 parts of chloroform were mixed. After adding 20 parts of toluylene diisocyanate (TDI), the mixture was heated and stirred at 50°C for 2 hours, and after cooling, 30 parts of lauryl methacrylate and magnetic powder (
r-Fe304. BL-520゜Titan Kogyo Co., Ltd.) 50
Part 1 Dispersion aid (TOP-0) 006 Part 1 Polymerization initiator (D
-65) Add 1.2 parts.

These were mixed and stirred for about 1 hour using a sand grinder to uniformly mix and disperse the mixture to obtain a magnetic ink.

Separately, add 14g of colloidal tricalcium phosphate prepared from trisodium phosphate and calcium chloride, and 0.06g of sodium dotecylbenzenesulfonate to 800mf of water!
Prepare a uniformly dispersed dispersion.

Next, 200 g of the magnetic ink was added to this dispersion.
', using a homojetter (#4!! Sukika Kogyo Co., Ltd.) at a rotation speed of 8,000 to 9,000 rpm, under observation with an optical microscope, oil droplets of approximately 5 to 20 μm in size were obtained.
Then, the dispersion was transferred to a fourth 2Il flask, and while stirring at low speed, an aqueous solution 7 (Icc) in which xylylenediamine 3011 was dissolved was added over about 15 minutes at room temperature. Stir for 1 minute, then gradually increase the temperature to 80
The microcapsules were reacted for 7 hours at .degree. C. to obtain microcapsules having a core of a polymer of lauryl methacrylate and an outer wall of a urethane polymer to which the silicone compound of the present invention was chemically bonded.

Next, this was cooled, 40 cc of concentrated hydrochloric acid was added to decompose and remove the dispersion stabilizer tricalcium phosphate, and the mixture was filtered, washed with water, and dried to obtain the microcapsule type toner of the present invention. This toner will be referred to as "toner 2."

Comparative Example 1 A toner was obtained in the same manner as in Example 1 except that dimethylpolysiloxane dicarbinol was removed. This toner is referred to as "comparison toner I."

Experimental Example Fluidity Evaluation Fluidity was measured for each of the present invention toners 1 and 2 and comparative toner 1 obtained as described above. The evaluation method was based on the quietness density described below. This method is a method for evaluating fluidity, and is a simple method for evaluating fluidity in systems where there is no large difference in density, such as the 91-wire system, and the larger the value, the better the fluidity. be.

(Measurement method) To make it simple for laboratory purposes, place a cone-shaped funnel on top of a 20-mesh graduated cylinder, gently drop the microcapsule-type toner from above through a 100-mesh sieve, and measure the weight of the 20-mesh toner. Then, the quietness density was calculated.

(Measurement Results) The results are shown in Table 1. It can be seen that the toner of the present invention has good fluidity.

A certain amount of toner was placed in a replenishment box on a U-Bix-1200 developing machine, development was performed, and the state in which the toner was replenished as the toner was consumed was observed. Items that partially adhere to the supply box and are not evenly replenished are marked with a "-" mark, and items that are evenly replenished are marked with a "○" mark.

The results of evaluation using the above method are shown in Table 1.

The amount of charge was measured by the blow-off method. The measured values are as shown in Table-1.

Table-1 Procedural amendment (currently dated July 2, 1985 Manabu Shiga, Commissioner of the Japan Patent Office l Indication of the case Patent application No. 1989-89287 2 Name of the invention Microcapsule 3 Person making the amendment Relationship to the case Applicant name Title (127) Konishiroku Photo Industry Co., Ltd. 4 agents
160 Address 5th floor, 2nd Building, 1o-11 Nishi-Shinjuku 7-chome, Shinjuku-ku, Tokyo Date of notice of reasons for refusal Voluntary 6 Number of inventions increased by amendment 0 7 Specification subject to amendment (detailed description of the invention) Explanation column) Contents of amendment (Japanese Patent Application No. 1989-89287) The structural formula on the bottom line of page 13 of the specification is amended as follows.

Record that's all

Claims (1)

[Claims] In a microcapsule consisting of a core material having mutually different physical properties or functions and an outer wall covering the core material, a silicone compound contained in a resin constituting the outer wall is bonded to the resin through a chemical bond. Microcapsules characterized by