JP3725712B2 - Method for producing film-coated powder - Google Patents
Method for producing film-coated powder Download PDFInfo
- Publication number
- JP3725712B2 JP3725712B2 JP30728398A JP30728398A JP3725712B2 JP 3725712 B2 JP3725712 B2 JP 3725712B2 JP 30728398 A JP30728398 A JP 30728398A JP 30728398 A JP30728398 A JP 30728398A JP 3725712 B2 JP3725712 B2 JP 3725712B2
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- JP
- Japan
- Prior art keywords
- film
- powder
- reaction
- metal
- coated powder
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 239000000843 powder Substances 0.000 title claims description 162
- 238000004519 manufacturing process Methods 0.000 title claims description 29
- 238000006243 chemical reaction Methods 0.000 claims description 105
- 239000002245 particle Substances 0.000 claims description 82
- 229910052751 metal Inorganic materials 0.000 claims description 62
- 239000002184 metal Substances 0.000 claims description 62
- 238000003756 stirring Methods 0.000 claims description 47
- 239000007853 buffer solution Substances 0.000 claims description 44
- 239000000758 substrate Substances 0.000 claims description 39
- 238000000034 method Methods 0.000 claims description 32
- 150000003839 salts Chemical class 0.000 claims description 30
- 230000015572 biosynthetic process Effects 0.000 claims description 26
- 238000010438 heat treatment Methods 0.000 claims description 18
- 230000005291 magnetic effect Effects 0.000 claims description 16
- 239000003125 aqueous solvent Substances 0.000 claims description 14
- 239000000696 magnetic material Substances 0.000 claims description 11
- 230000008569 process Effects 0.000 claims description 6
- 239000012528 membrane Substances 0.000 claims description 5
- 230000010355 oscillation Effects 0.000 claims description 5
- 239000012266 salt solution Substances 0.000 claims description 4
- 239000010408 film Substances 0.000 description 186
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 81
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 72
- 239000007864 aqueous solution Substances 0.000 description 52
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 51
- 239000010410 layer Substances 0.000 description 49
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 44
- 239000007787 solid Substances 0.000 description 41
- 239000000377 silicon dioxide Substances 0.000 description 40
- 238000005406 washing Methods 0.000 description 40
- 239000006228 supernatant Substances 0.000 description 37
- 239000000725 suspension Substances 0.000 description 37
- 239000007788 liquid Substances 0.000 description 29
- 229910044991 metal oxide Inorganic materials 0.000 description 28
- 150000004706 metal oxides Chemical class 0.000 description 28
- WFDIJRYMOXRFFG-UHFFFAOYSA-N Acetic anhydride Chemical compound CC(=O)OC(C)=O WFDIJRYMOXRFFG-UHFFFAOYSA-N 0.000 description 27
- 239000000047 product Substances 0.000 description 27
- 238000000576 coating method Methods 0.000 description 25
- 238000005755 formation reaction Methods 0.000 description 25
- 239000011248 coating agent Substances 0.000 description 23
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 23
- 239000000243 solution Substances 0.000 description 23
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 22
- 239000002585 base Substances 0.000 description 22
- 238000001035 drying Methods 0.000 description 21
- 238000002156 mixing Methods 0.000 description 20
- 238000004140 cleaning Methods 0.000 description 19
- 239000012153 distilled water Substances 0.000 description 19
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 18
- 239000000203 mixture Substances 0.000 description 18
- 239000006185 dispersion Substances 0.000 description 16
- 239000007888 film coating Substances 0.000 description 16
- 238000009501 film coating Methods 0.000 description 16
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 14
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- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 11
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- 239000012299 nitrogen atmosphere Substances 0.000 description 11
- 239000001103 potassium chloride Substances 0.000 description 11
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- 235000019353 potassium silicate Nutrition 0.000 description 11
- 239000002994 raw material Substances 0.000 description 11
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 description 10
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- 239000007790 solid phase Substances 0.000 description 9
- DCKVFVYPWDKYDN-UHFFFAOYSA-L oxygen(2-);titanium(4+);sulfate Chemical compound [O-2].[Ti+4].[O-]S([O-])(=O)=O DCKVFVYPWDKYDN-UHFFFAOYSA-L 0.000 description 8
- -1 titanium halides Chemical class 0.000 description 8
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- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 6
- 239000002253 acid Substances 0.000 description 6
- 239000003513 alkali Substances 0.000 description 6
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 6
- 239000006247 magnetic powder Substances 0.000 description 6
- 239000000463 material Substances 0.000 description 6
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- 238000001556 precipitation Methods 0.000 description 6
- 239000002904 solvent Substances 0.000 description 6
- 229910052719 titanium Inorganic materials 0.000 description 6
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- 238000001132 ultrasonic dispersion Methods 0.000 description 6
- 229910000859 α-Fe Inorganic materials 0.000 description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 5
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- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 5
- 238000010792 warming Methods 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 4
- 238000004220 aggregation Methods 0.000 description 4
- 239000007810 chemical reaction solvent Substances 0.000 description 4
- 239000011651 chromium Substances 0.000 description 4
- 229910052804 chromium Inorganic materials 0.000 description 4
- 229910017052 cobalt Inorganic materials 0.000 description 4
- 239000010941 cobalt Substances 0.000 description 4
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 4
- 229910000000 metal hydroxide Inorganic materials 0.000 description 4
- 150000004692 metal hydroxides Chemical class 0.000 description 4
- 239000002244 precipitate Substances 0.000 description 4
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 4
- 229910001887 tin oxide Inorganic materials 0.000 description 4
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 4
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 3
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 3
- 230000009471 action Effects 0.000 description 3
- 239000013522 chelant Substances 0.000 description 3
- 230000008021 deposition Effects 0.000 description 3
- 229910001337 iron nitride Inorganic materials 0.000 description 3
- 230000005415 magnetization Effects 0.000 description 3
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 3
- 238000002310 reflectometry Methods 0.000 description 3
- 229910052709 silver Inorganic materials 0.000 description 3
- 239000004332 silver Substances 0.000 description 3
- HPGGPRDJHPYFRM-UHFFFAOYSA-J tin(iv) chloride Chemical compound Cl[Sn](Cl)(Cl)Cl HPGGPRDJHPYFRM-UHFFFAOYSA-J 0.000 description 3
- 229910052726 zirconium Inorganic materials 0.000 description 3
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 2
- 229910000531 Co alloy Inorganic materials 0.000 description 2
- DHMQDGOQFOQNFH-UHFFFAOYSA-N Glycine Chemical compound NCC(O)=O DHMQDGOQFOQNFH-UHFFFAOYSA-N 0.000 description 2
- 229920002153 Hydroxypropyl cellulose Polymers 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- 229910000990 Ni alloy Inorganic materials 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 2
- 238000013019 agitation Methods 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- 229910052788 barium Inorganic materials 0.000 description 2
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 2
- 229910052797 bismuth Inorganic materials 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- 150000001735 carboxylic acids Chemical class 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
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- 238000010924 continuous production Methods 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000004070 electrodeposition Methods 0.000 description 2
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- 230000005294 ferromagnetic effect Effects 0.000 description 2
- 239000003302 ferromagnetic material Substances 0.000 description 2
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- 230000003760 hair shine Effects 0.000 description 2
- 239000001863 hydroxypropyl cellulose Substances 0.000 description 2
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- 229910052738 indium Inorganic materials 0.000 description 2
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
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- 238000005259 measurement Methods 0.000 description 2
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- 238000006386 neutralization reaction Methods 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
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- 239000003960 organic solvent Substances 0.000 description 2
- 150000003891 oxalate salts Chemical class 0.000 description 2
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 238000004544 sputter deposition Methods 0.000 description 2
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- 244000248349 Citrus limon Species 0.000 description 1
- 235000005979 Citrus limon Nutrition 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- FEWJPZIEWOKRBE-JCYAYHJZSA-N Dextrotartaric acid Chemical compound OC(=O)[C@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-JCYAYHJZSA-N 0.000 description 1
- 239000004471 Glycine Substances 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical class [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- KDYFGRWQOYBRFD-UHFFFAOYSA-N Succinic acid Natural products OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 description 1
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- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 239000007983 Tris buffer Substances 0.000 description 1
- QVYYOKWPCQYKEY-UHFFFAOYSA-N [Fe].[Co] Chemical compound [Fe].[Co] QVYYOKWPCQYKEY-UHFFFAOYSA-N 0.000 description 1
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- 229910000287 alkaline earth metal oxide Inorganic materials 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000007743 anodising Methods 0.000 description 1
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- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
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- 239000006172 buffering agent Substances 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- KDYFGRWQOYBRFD-NUQCWPJISA-N butanedioic acid Chemical compound O[14C](=O)CC[14C](O)=O KDYFGRWQOYBRFD-NUQCWPJISA-N 0.000 description 1
- 229910052793 cadmium Inorganic materials 0.000 description 1
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-N carbonic acid Chemical compound OC(O)=O BVKZGUZCCUSVTD-UHFFFAOYSA-N 0.000 description 1
- 150000007942 carboxylates Chemical class 0.000 description 1
- 150000001734 carboxylic acid salts Chemical class 0.000 description 1
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 1
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- 239000000084 colloidal system Substances 0.000 description 1
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- 238000002425 crystallisation Methods 0.000 description 1
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- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000005034 decoration Methods 0.000 description 1
- TYIXMATWDRGMPF-UHFFFAOYSA-N dibismuth;oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Bi+3].[Bi+3] TYIXMATWDRGMPF-UHFFFAOYSA-N 0.000 description 1
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- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 1
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- LENZDBCJOHFCAS-UHFFFAOYSA-N tris Chemical compound OCC(N)(CO)CO LENZDBCJOHFCAS-UHFFFAOYSA-N 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- ZXAUZSQITFJWPS-UHFFFAOYSA-J zirconium(4+);disulfate Chemical compound [Zr+4].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O ZXAUZSQITFJWPS-UHFFFAOYSA-J 0.000 description 1
Description
【０００１】
【発明の属する技術分野】
本発明は粉体粒子の表面を別の物質で多層に被覆し、複合機能を発揮する粉体の製造技術に関するものであり、詳しくは基体粒子の表面に水系溶媒中で反応させて形成した膜を有する膜被覆粉体の製造方法に関するものである。
【０００２】
【従来の技術】
粉体の表面を他の物質の膜で被覆することにより、その粉体の性質を改善したり、その性質に多様性を与えることが知られ、従来そのための方法として種々の手段が提案されている。
例えば、物体の表面に保護や装飾のために膜を形成する被覆技術には、塗着法、沈着法、スパッタリング、真空蒸着法、電着法や陽極酸化法等多くの手段が知られている。しかし、塗着法や沈着法では膜の厚みを均一にすることが困難であり、スパッタリングや真空蒸着法では膜厚の厚い被膜を得ることが困難である。また、電着法や陽極酸化法は被処理物を電極とする関係上粉体の処理には向かないという問題点を有している。
種々の技術分野における進歩に伴い、特異な性質を備えた粉体、特に金属粉体或は金属化合物粉体を求める要望が増しており、粉体、特に金属粉体または金属化合物粉体だけが備える性質の他に別の性質を合わせ持ち、複合した機能を有する粉体が求められている。これらの粉体を製造するには、基体粒子の上に均一な厚さの金属酸化物膜等を複数層設けることが考えられた。
【０００３】
上記のような新しい要求に応えられる複合した性質を有し、複合した機能を果たし得る粉体、特に金属または金属化合物粉体を提供するための金属酸化物の形成方法の有用なものとして、先に、本発明者らは、金属粉体又は金属酸化物粉体を金属アルコキシド溶液中に分散し、該金属アルコキシドを加水分解するとにより、金属酸化物の皮膜を形成し、金属または金属化合物の基体の表面に、均一な０．０１〜２０μｍの厚みの、前記基体を構成する金属とは異種の金属を成分とする金属酸化物膜を有する粉体を発明した（特開平６ー２２８６０４号公報）。
【０００４】
この粉体において、前記の金属酸化物膜を複数層設ける場合には、前記膜の各層の厚さを調整することにより特別の機能を与えることができるものであって、例えば、基体の表面に、屈折率の異なる被覆膜を、光の４分の１波長に相当する厚さで設けるようにすると、光はすべて反射される。この手段を鉄、コバルト、ニッケルなどの金属粉末或は金属の合金粉末、或いは窒化鉄の粉末などの磁性体を基体とするものに適用すると、光を全反射して白色に輝く磁性トナー用磁性粉体を得ることができる。さらに、その粉体の上に着色層を設け、その上に樹脂層を設ければ、カラー磁性トナーが得られることを開示している。
また、本発明者らは前記の粉体を更に改良し、金属酸化物膜単独ではなく、金属酸化物膜と金属膜とを交互に複数層有するようにした粉体も開示した（特開平７ー９０３１０号公報）。これはカラー磁性トナー等として優れた性質を有するものである。
【０００５】
更に、本発明者らは多層膜の物質の組み合わせおよび膜厚を制御することにより、多層膜の反射光干渉波形を調製できることを見出した。すなわち染料や顔料を用いずとも、基体の表面に複数の屈折率の異なる薄い被覆膜（二酸化ケイ素膜、チタニア膜、ポリスチレン膜、金属銀膜等）を有し、この多層膜の光干渉作用により着色され、長期保存においても安定な色調のカラー粉体を提供することを開示した（ＷＯ９６／２８２６９）。
【０００６】
しかしながら、前記金属粉体又は金属化合物粉体の表面に金属酸化物の被膜を形成するために、金属アルコキシドの加水分解による方法は、溶媒として、引火性の高い有機系のものを使用し、原料として、高価な化合物である金属アルコキシドを使用しなければならない。引火性の高い有機溶媒を用いるためには、製造施設を防爆設備としたり、温度、湿度の管理が厳しく、それを用いて製造した製品の価格も総合的に当然高価なものとなる。
これに対して金属塩の反応により、金属塩水溶液からの沈殿で被膜を形成する方法がある。しかしこの方法で使用する溶媒は、酸やアルカリが強いものである。このため、基体粒子として金属等を直接該反応に用いた場合には、基体が酸やアルカリに溶け侵されるため、好ましい膜被覆粉体が得られない。
また、これに対して、基体粒子の表面に、先に金属アルコキシドの加水分解等による方法で酸やアルカリに不活性な被膜を作ってから、前記金属塩水溶液からの沈澱による被膜の形成を行うことが開示された（特開平１０ー１７０２号公報）。
しかしながら、どうしても、コスト高で危険性の高い金属アルコキシドの加水分解による方法を用いなけれならないという問題がある。
【０００７】
また、前記金属塩の反応による被膜形成は、酸、アルカリの中和や加熱条件によっては、固相成分の析出が過度になり、基体表面で均一な厚さの膜にならず、液相中に固相のみが析出したり、膜被覆粉体同志が固着することがあり、好ましい膜厚制御をできる状態にならない。
更にこれに対して、本発明者らは、ｐＨ一定の水系溶媒中で基体粒子の表面に金属塩からの反応により被膜を形成する方法を見い出した（特願平９−２９８７１７）。これは、ｐＨ一定の水系溶媒、すなわち緩衝溶液を用いることにより酸、アルカリの影響が和らげられ、基体表面の侵食が防止される。また、この緩衝溶液を用いることにより、基体粒子の表面の電荷が一定に維持され、電気２重層が形成され、膜被覆粉体の凝集がなく分散粒子が得られるという効果があった。
【０００８】
【発明が解決しようとする課題】
しかしながら、上記のｐＨ一定の水系溶媒を用いる技術は基体が非磁性のものを用いる場合のみに、分散性が良好になるものである。
基体として、磁性体のものを用いた場合には、その磁性により上記電気２重層が破壊され、凝集が著しくなる。
これらの凝集に対して機械的撹拌を行うことが第一に考えられるが、被覆された直後の膜はゲル状であるため、撹拌力を強くする機械的分散方法では、被膜同志が機械的衝突により付着し、単体の膜被覆磁性体粒子を分散させることが困難となる。更に分散剤として、保護コロイドとなる、例えばヒドロキシプロピルセルロース（ＨＰＣ）等を添加する方法では、微量の添加でも反応液中に泡が発生し、基体粒子と反応液との接触が均等でなく均一な被膜形成を阻害するといった問題がある。
【０００９】
従って、本発明の目的は、上記従来技術の欠点を克服し、金属アルコキシドの加水分解による方法を用いない水系反応成膜による膜被覆粉体の製造において、基体表面で均一な厚さの被覆膜を形成し、液相中に固相のみが析出することがなく、基体として磁性体を用いた場合でも膜被覆粉体同志が凝集したり固着することがなく、好ましい膜厚制御ができる膜被覆粉体の製造方法を提供することにある。
【００１０】
【課題を解決するための手段】
本発明者らは、かかる現状に鑑み、鋭意研究の結果、製膜反応溶媒として、ｐＨ一定条件の水系溶媒を用いると同時に、膜被覆反応を超音波分散条件下で行うことにより、上記目的を達成できることを見出し、本発明に到達した。
すなわち、本発明の膜被覆粉体の製造方法は、
【００１２】
（１）基体粒子の表面に膜を形成する膜被覆粉体の製造方法において、該膜の少なくとも１層を、緩衝溶液が含まれることによりｐＨ一定条件である水系溶媒中、超音波発振下にて、金属塩からの反応により形成することを特徴とする膜被覆粉体の製造方法。
（２）前記基体粒子が磁性体であることを特徴とする前記（１）の膜被覆粉体の製造方法。
（３）前記磁性体からなる基体粒子の粒径が０．０５〜１０μｍであることを特徴とする前記（２）の膜被覆粉体の製造方法。
（４）前記反応中に粉体が沈降しない程度に攪拌を行うことを特徴とする前記（１）の膜被覆粉体の製造方法。
【００１３】
（５）金属塩からの反応による前記膜の形成が、基体粒子を分散した水系溶媒中に、膜成分原料である金属塩の溶液を添加することにより行うことを特徴とする前記（１）の膜被覆粉体の製造方法。
（６）金属塩からの反応による前記膜の形成中に、水系溶媒中で熱処理することを特徴とする前記（１）の膜被覆粉体の製造方法。
（７）金属塩からの反応による前記膜の形成後に、熱処理することを特徴とする前記（１）の膜被覆粉体の製造方法。
（８）金属塩からの反応により形成する前記膜の厚さを１０ｎｍ〜１０μｍとすることを特徴とする前記（１）の膜被覆粉体の製造方法。
（９）金属塩からの反応により前記膜を複数形成することを特徴とする前記（１）の膜被覆粉体の製造方法である。
【００１４】
本発明は製膜反応の際に、以下の操作および作用により、被膜にならない固相の析出が抑えられ、基体粒子の表面に均一な厚さの被膜を、所望の厚さで形成することができると推測する。▲１▼反応溶媒として、緩衡溶液を用い、ある一定のｐＨとすることにより、酸またはアルカリの影響が和らげられ、基体表面の侵食が防止される；▲２▼超音波分散により、基体粒子、特にマグネタイト粉等の磁性体の分散性を良くするばかりでなく、被膜成分の拡散性を良くし、更に、被膜同志の付着を防止し、被覆製膜された磁性体粒子の分散性をも良好にする；▲３▼適当な反応の速さで被膜成分を析出させ、被膜にならない固相の析出を抑制する。
上記の総合的作用により、膜被覆粉体の表面の電荷を一定に維持することができ、電気２重層の働きにより、膜被覆粉体の凝集がなく、分散粒子が得られる。
電気２重層の働きを生かすためにｐＨは、基体の物質と製膜反応により液中で形成される金属化合物の種類の組み合わせにより異なり、また、両者の等電点を避けることが好ましい。
【００１５】
本発明は上記の作用機構により、水溶性原料を用いるにも係わらず、基体として磁性体を用いた場合でも膜被覆粉体同志が凝集したり固着することがなく、好ましい膜厚制御ができる膜被覆粉体を容易に製造することを可能とすることが
できた。
また、水を溶媒として用いることにより、アルコキシド法に比べ安価な製造コストで製膜できるという効果が得られる。
【００１６】
【発明の実施の形態】
本発明の膜被覆粉体は上記のように、製膜反応溶媒としてｐＨ一定条件の水系溶媒を用い、同時に膜被覆反応を超音波分散条件下で、基体の表面への被膜形成反応により形成される。
本願発明では製膜反応を一定にするために、水系溶媒に緩衝剤を添加し緩衝溶液とするかあるいはあらかじめ用意された緩衝溶液が用いられる。また製膜反応の際には緩衝溶液以外の膜原料を添加し製膜する。製膜原料添加により製膜を行う際に、ｐＨが大きく変動する場合には、これを防ぐため、緩衝溶液を追加することが望ましい。
本発明で言うところのｐＨ一定とは、ｐＨが所定のｐＨの±２以内、好ましくは±１以内、より好ましくは±０．５以内を言う。
【００１７】
緩衡溶液は種々の系が用いられ、特に限定されないが、まず基体粒子が十分に分散できることが重要であり、同時に基体の表面に析出した金属水酸化物あるいは金属酸化物の膜被覆粉体も分散でき、かつ上記の緩やかな滴下反応により緻密な被膜が製膜ができる条件を満足するように選択する必要がある。
従って、本発明の膜被覆粉体の製造法は従来の金属塩溶液の反応による中和や等電点による析出、または加熱により分解して析出させる方法とは異なるものである。
本発明に使用される緩衡溶液としては、析出させる固相成分に依存し、特に限定されないが、Ｔｒｉｓ系、ホウ酸系、グリシン系、コハク酸系、乳酸系、酢酸系、酒石酸系、塩酸系等が挙げられる。
【００１８】
次に、超音波分散条件としては、種々の超音波発振装置が使用でき、例えば、超音波洗浄機の水槽を利用することができ、特に限定されない。しかし本発明の超音波分散の条件としては、発振装置の大きさ、反応容器の形状および大きさ、反応溶液の量、体積、基体粒子の量等によって変化してくるので、それぞれの場合において、適切な条件を選択すればよい。
【００１９】
本発明において、前記本発明の膜被覆粉体の基体としては、無機性物質からなる粉体が使用できる。前記本発明の無機性物質からなる粉体を構成する無機性物質としては、鉄、ニッケル、クロム、チタン、アルミニウム等の金属、また鉄−ニッケルや鉄−コバルト合金等の金属合金、さらには鉄・ニッケル合金窒化物や鉄・ニッケル・コバルト合金窒化物、また金属酸化物としては例えば鉄、ニッケル、クロム、チタン、アルミニウム、ケイ素（この場合ケイ素は金属に分類するものとする）等の酸化物の他、カルシウム、マグネシウム、バリウム等のアルカリ土類金属酸化物あるいはこれらの複合酸化物、粘土類、ガラス類等が挙げられる。
本発明においては、その目的の一つがカラー磁性トナーやカラー磁性インクのような磁性を有する粉体を製造することにあるので、その場合本発明の多層膜被覆粉体の基体としては強磁性体を使用することが好ましい。強磁性体としては鉄、ニッケル、クロム、チタン、アルミニウム等の透磁率の大きい金属でもよいが、フェライト、γ−酸化鉄のような強磁性酸化物や強磁性合金も使用される。
【００２０】
なお、前記特願平９−２９８７１７号に添付の明細書に記載の技術では、基体として磁性体を用いた場合には、その残留磁化による磁力によって、粉体同志が凝集しやすく十分な効果が得られなかった。
磁性粉体の残留磁化は、その粒径が０．０５〜１０μｍ、その中でも０．０５〜３μｍの範囲のものが大きく、さらにその中でも０．２〜０．３μｍのものが特に大きかった。
しかしながら、本発明の方法を用いることにより、基体として磁性体、特に残留磁化の大きいマグネタイト、Ｂａフェライト、Ｓｒフェライト、γ−ヘマタイト、コバルトフェライト等のフェライトあるいはこれらの混合フェライトなど、さらに上記粒径範囲の磁性粉体を用いても粉体同志の凝集が効果的に防止できる。
また、基体粒子の比重としては、０．１〜１０．５の範囲のものが用いられるが、流動性、浮遊性の面から０．１〜５．５が好ましく、より好ましくは０．１〜２．８、更に、好ましくは０．５〜１．８の範囲である。基体の比重が０．１未満では液体中での浮力が大きすぎ、膜を多層あるいは非常に厚くする必要があり、不経済である。一方、１０．５を超えると、浮遊させるための膜が厚くなり、同様に不経済である。
【００２１】
本発明においては、上記粉体基体粒子を屈折率が互いに異なる複数の被膜層を用い、各被膜層の屈折率および層厚を適宜選択して被覆することにより、その干渉色により着色しかつ可視光域以外にも特異的な干渉反射ピークを発現する粉体とすることができる。
前記したように、基体粒子の表面上に金属塩の反応により金属水酸化物膜あるいは金属酸化物膜を析出させるが、固相析出反応の溶媒として、緩衡溶液を用い、ある一定のｐＨで適当な速さで析出させる。
【００２２】
本発明において、金属塩として使用される金属は、鉄、ニッケル、クロム、チタン、亜鉛、アルミニウム、カドミウム、ジルコニウム、ケイ素、錫、鉛、リチウム、インジウム、ネオジウム、ビスマス、セリウム、アンチモン等の他、カルシウム、マグネシウム、バリウム等が挙げられる。また、これら金属の塩としては、硫酸、硝酸、塩酸、シュウ酸、炭酸やカルボン酸の塩が挙げられる。さらにまた、前記金属のキレート錯体も含まれる。本発明において使用される金属塩の種類は、その基体の表面に付与しようとする性質や製造に際して適用する手段に応じてそれに適するものが選択される。
【００２３】
これらの金属塩による金属酸化物等の膜は、複数層形成してもよく、またそれらの金属酸化物等の膜の上に、必要により金属アルコキシドの加水分解による金属酸化物等、また他の製膜方法による膜を形成することもできる。
このようにして、基体粒子の上に多層の膜を形成することができ、しかもその際、各層の厚さが所定の厚さをもつように形成条件を設定することにより、目的とする特性を得ることができるようにすることができ、また簡単な操作でかつ安価な原料である金属塩を用いて金属酸化物等の膜を多層に形成することができる。特に、高価な金属アルコキシドを原料とすることなく、多重層膜被覆粉体とすることができる点は重要な利点である。
【００２４】
本発明の膜被覆粉体を製造する方法では、多層被覆膜を連続した工程として製作しても良く、また、各被覆膜を１層ずつ製作、あるいは単層製作と複層連続製作を組み合わせるなど種々の方法で製作することができる。
本発明に係わる膜被覆粉体の粒径は、特に限定されず、目的に応じて適宜調整することができるが、通常は０．０１μｍ〜数ｍｍの範囲である。
【００２５】
本発明において、その１回に形成させる金属酸化物膜の膜の厚さとしては、５ｎｍ〜１０μｍの範囲とすることが可能であり、従来の形成法より厚くすることができる。
複数回に分けて形成する金属酸化物膜の合計の厚さとしては、前記したカラー磁性粉体の場合、その干渉による反射率が良い金属酸化物膜を形成するためには、１０ｎｍ〜２０μｍの範囲が好ましい、さらに好ましくは２０ｎｍ〜５μｍの範囲とすることである。粒径が制限されるなど特に薄い膜厚で可視光を干渉反射させるためには０．０２〜２．０μｍの範囲とすることが好ましい。
【００２６】
前記したようにして製造した基体粒子表面に金属酸化物膜等を有する粉体は、選択した基体粒子の材質、及びその表面に被覆した膜の金属酸化物の材質により、種々の性質を賦与することができるので、それぞれの目的の用途に適用することができる。例えば、基体粒子として磁性体の金属鉄、窒化鉄、マグネタイトなどを用い、その上の膜として前記磁性体に比べて屈折率のより低い二酸化ケイ素（シリカともいう）を被覆し、その外膜としてより屈折率の高いや酸化チタン（チタニアともいう）の層を被覆すれば、白色度の高い磁性粉が得られる。また、基体粒子として銀、銅あるいはアルミニウム（アルミナともいう）等の導体を用い、該金属層の上に金属酸化物として例えば酸化アルミニウムのような電気絶縁性の被覆膜を被覆すれば、電気絶縁性の表面層を有する熱伝導性粉体が得られる。
【００２７】
また、例えば、基体の表面に、屈折率の異なる被覆の厚さを、光の波長の４分の１に相当する厚さだけ設けると、干渉により光は大部分反射（フレネル反射）され、この作用を利用し、例えば鉄、コバルト、ニッケルなどの金属粉末あるいは合金粉末、あるいは窒化鉄の粉末などの磁性体を基体とし、この表面に銀あるいはコバルト等の高い反射率の金属層を設け、さらにその外側に前記金属より屈折率の低い二酸化ケイ素のような酸化物層を酸化物の屈折率と膜の厚さとの積が可視光の４分の１波長の厚さとして設け、さらにその上に厚さが物質の屈折率と膜の厚さとの積が可視光の４分の１波長の厚さの酸化チタンのような屈折率の高い酸化物層を被覆することにより光を反射して、白色に輝いた磁性トナー用磁性粉体を製造することができる。
また、製造された粉体を不活性ガス雰囲気の中で温度２００℃〜８００℃で熱処理することにより、さらに強固で白色度の高い粉体とすることができる。上記、粉体を熱処理する場合、熱処理された粉体の各層において物質の屈折率と膜の厚さとの積が可視光の４分の１波長の厚さになる条件が満たされなければならない。
【００２８】
さらにその粉体の上に着色層を設け、さらにその上に樹脂層を設ければ、カラー磁性トナーを製造することができる。なお、可視光の波長は幅があるので、磁性トナーを構成する粒子の酸化物と金属の各層の厚さは、物質の屈折率と膜の厚さとの積が可視光の４分の１波長の厚さに近い範囲で多少異なるようにしたものを交互に複数設けてもよい。
多層膜被覆粉体を干渉反射で着色するカラー粉体とする場合には、ＷＯ９６／２８２６９の方法を用いて設計し、製膜条件を調整し、目的の分光波長の光が反射されるように、高屈折率膜と低屈折率膜を交互にフレネル干渉に必要な膜の厚みに製膜する。
【００２９】
次に一例として、高屈折率の金属酸化物と低屈折率の金属酸化物の交互多層膜を形成する方法について具体的に説明する。まず、酸化チタンあるいは酸化ジルコニウムなどの被膜を形成する場合、酢酸／酢酸ナトリウム系等の緩衡溶液中に基体粒子を浸漬し超音波発振により分散し、チタンあるいはジルコニウムなどの金属塩である硫酸チタン、硫酸ジルコニウム等を原料とし、これら金属塩の水溶液を反応系に緩やかに滴下し、生成する金属水酸化物あるいは金属酸化物を基体粒子のまわりに析出させることにより行うことができる。この滴下反応の間、ｐＨは上記緩衡溶液のｐＨ（５．４）に保持される。
反応終了後、この粉体を固液分離し、洗浄・乾燥後、熱処理を施す。乾燥手段としては真空乾燥、自然乾燥のいずれでもよい。また、不活性雰囲気中で噴霧乾燥機などの装置を用いることも可能である。
なお、この場合の被覆膜である酸化チタンの形成は下記の反応式で示される。
Ｔｉ（ＳＯ4 ) 2 ＋２Ｈ2Ｏ→ＴｉＯ2 ＋４Ｈ2 （ＳＯ4 ) 2
【００３０】
続いて、二酸化ケイ素あるいは酸化アルミニウムなどの被膜を形成する場合、ＫＣｌ／Ｈ3ＢＯ3系等にＮａＯＨを加えた緩衡溶液中に上記のチタニアコート粒子を浸漬し超音波発振により分散し、ケイ素あるいはアルミニウムなどの金属塩であるケイ酸ナトリウム、塩化アルミニウム等を原料とし、これら金属塩の水溶液を反応系に緩やかに滴下し、生成する金属水酸化物あるいは金属酸化物を基体粒子のまわりに析出させることにより行うことができる。この滴下反応の間、ｐＨは上記緩衡溶液のｐＨ（９．０）に保持される。
反応終了後、この粉体を固液分離し、洗浄・乾燥後、熱処理を施す。この操作により、基体粒子の表面に屈折率の異なる２層の、金属酸化物膜を形成する操作を繰り返すことにより、多層の金属酸化物膜をその表面上に有する粉体が得られる。
なお、この場合の被覆膜である二酸化ケイ素の形成は下記の反応式で示される。
Ｎａ2ＳｉX Ｏ2X+1＋Ｈ2Ｏ→ＸＳｉＯ2＋２Ｎａ+＋２ＯＨ-
【００３１】
次に、本発明において製膜に使用する原料、特に金属塩について説明する。
高屈折率の膜を製膜するのに使用する原料としては、酸化チタン膜用には、チタンのハロゲン化物、硫酸塩等、酸化ジルコニウム膜用には、ジルコニウムのハロゲン化物、硫酸塩、カルボン酸塩、シュウ酸塩、キレート錯体等、酸化セリウム膜用には、セリウムのハロゲン化物、硫酸塩、カルボン酸塩、シュウ酸塩等、酸化ビスマス膜用には、ビスマスのハロゲン化物、硝酸塩、カルボン酸塩等、酸化インジウム膜用には、インジウムのハロゲン化物、硫酸塩等が好ましい。
また、低屈折率の膜を製膜するのに使用する原料としては、酸化ケイ素膜用には、ケイ酸ソーダ、水ガラス、ケイ素のハロゲン化物、アルキルシリケート等の有機ケイ素化合物とその重合体等、酸化アルミニウム膜用には、アルミニウムのハロゲン化物、硫酸塩、キレート錯体等、酸化マグネシウム膜用には、マグネシウムの硫酸塩、ハロゲン化物等が好ましい。
また、例えば酸化チタン膜の場合には、塩化チタンに硫酸チタンを混合すると、より低温で屈折率の高いルチル型の酸化チタン膜になる等の効果がある。
【００３２】
また、被覆の際の反応温度は各金属塩の種類に適した温度に管理して被覆することにより、より完全な酸化物膜を製作することができる。
水系溶媒中での基体の表面への被膜形成反応（固層析出反応）が遅すぎる場合には、反応系を加熱して固層析出反応を促進することもできる。但し、加熱の熱処理が過剰であると、該反応速度が速すぎて、過飽和な固層が膜にならず、水溶液中に析出し、ゲルあるいは微粒子を形成し、膜厚制御が困難になる。
【００３３】
被覆膜は製作後、蒸留水を加えながら傾斜洗浄を繰り返して、電解質を除去した後、乾燥・焼成等の熱処理を施し、固相中に含まれた水を除去して、完全に酸化物膜とすることが好ましい。また、製膜後の粉体を回転式チューブ炉などで熱処理することにより、固着を防ぐことができ、分散された粒子を得ることができる。
水酸化物膜あるいは酸化物膜を形成し、それを熱処理するには、各層を被覆する毎に熱処理しても良く、また、目的の多層膜を完成後最後に熱処理しても良い。
熱処理条件は反応系により異なるが、上記の熱処理温度としては２００〜１３００℃であり、好ましくは４００〜１１００℃である。２００℃以下では塩類や水分が残ってしまう事あり、１３００℃を超えて高くなると、膜と基体が反応し別の物質となることがあり、共に不適である。熱処理時間としては０．１〜１００時間であり、好ましくは０．５〜５０時間である。
【００３４】
【実施例】
以下に本発明を実施例によって更に具体的に説明するが、勿論本発明の範囲は、これらによって限定されるものではない。
【００３５】
〔実施例１〕
（シリカ膜の製膜）
室温で容器に０．３Ｍ塩化カリウムと０．３Ｍほう酸の混合水溶液２５０ｍｌと、０．４Ｍ水酸化ナトリウム水溶液１１５ｍｌを混合し緩衡液を調製する。
この緩衡液中（ｐＨ：約９．０）に、基体としてマグネタイト粉末（平均粒径０．７μｍ）５．０ｇを投入し、この混合溶液を入れた容器を、水を張った超音波洗浄機（（株）井内盛栄堂製、ＵＳ−６型）の水槽に入れ、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に４５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。
【００３６】
次に、あらかじめ用意した１０重量％の水ガラス（けい酸ナトリウム）水溶液をマイクロチューブポンプで、１．３４ｍｌ／分の滴下速度で、１８分間、攪拌している懸濁液中に滴下する。滴下終了後、更に１時間超音波発振および攪拌を続け、シリカ膜被覆反応を行う。
所定時間経過後、上澄液を取り除きイオン交換水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、１１０℃で乾燥させ、乾燥粉体の粒度測定を測定装置（日機装社製マイクロトラックＸ−１００）を用いて行った。粒度測定結果を表１に示す。
【００３７】
〔比較例１〕
（シリカ膜の製膜）
実施例１と同じ操作を行った。但し、製膜反応中に超音波を発振させず、攪拌のみを行った。粒度測定結果を表１に示す。
【００３８】
【表１】
表１から明らかなように、本発明に係わる実施例１のシリカ膜被覆マグネタイト粒子の５０％通過径は基体の原料マグネタイト粒子の５０％通過径とほぼ同じであり、満足すべき結果を得たが、比較例１のシリカ膜被覆マグネタイト粒子の５０％通過径は不満足なものであった。
【００４０】
〔実施例２〕
（シリカ・チタニア膜被覆粉体）
（１層目：シリカ膜の製膜）
室温で容器に０．３Ｍ塩化カリウムと０．３Ｍほう酸の混合水溶液２５０ｍｌと、０．４Ｍ水酸化ナトリウム水溶液１１５ｍｌを混合し緩衡液を調製する。
この緩衡液中（ｐＨ：約９．０）に、基体としてマグネタイト粉末（平均粒径０．７μｍ）５．０ｇを投入し、この混合溶液を入れた容器を、水を張った超音波洗浄機（（株）井内盛栄堂製、ＵＳ−６型）の水槽に入れ、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に４５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。
【００４１】
次に、あらかじめ用意した１０重量％の水ガラス（けい酸ナトリウム）水溶液をマイクロチューブポンプで、１．３４ｍｌ／分の滴下速度で、１８分間、攪拌している懸濁液中に滴下する。滴下終了後、更に１時間超音波発振および攪拌を続け、シリカ膜被覆反応を行う。
所定時間経過後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後得られた粉体は５００ｎｍ付近にボトムを有する黒色粉体１Ａを得た。
【００４２】
（２層目：チタニア膜の製膜）
あらかじめ、０．３Ｍ無水酢酸水溶液５０ｍｌと０．９Ｍ酢酸ナトリウム水溶液１００ｍｌおよび純水２５０ｍｌを混合した緩衡液（ｐＨ：５．４）を用意し、粉体１Ａを４ｇ投入後、シリカ膜の製膜の場合と同様に、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に５５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。
分散後、硫酸チタン水溶液（１２０ｇ／リットル）をマイクロチューブポンプで、０．５ｍｌ／分の滴下速度で滴下する。同時に超音波槽内の水を１００℃／時間で昇温し、この懸濁液を５５℃に保持する。滴下開始から８時間かけて硫酸チタン水溶液を滴下後、２時間反応させ、終了後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。
【００４３】
反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後得られた粉体は５００ｎｍ付近にピークを有し、反射率３０％であり、青緑色の粉体１Ｂを得た。
【００４４】
（３層目：シリカ膜の製膜）
室温で容器に０．３Ｍ塩化カリウムと０．３Ｍほう酸の混合水溶液２５０ｍｌと、０．４Ｍ水酸化ナトリウム水溶液１１５ｍｌを混合し緩衡液を調製する。
この緩衡液中（ｐＨ：約９．０）に、粉体１Ｂ（平均粒径０．７μｍ）５．０ｇを投入し、この混合溶液を入れた容器を、水を張った超音波洗浄機（（株）井内盛栄堂製、ＵＳ−６型）の水槽に入れ、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に４５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。
次に、あらかじめ用意した１０重量％の水ガラス（けい酸ナトリウム）水溶液をマイクロチューブポンプで、１．３４ｍｌ／分の滴下速度で、１８分間、攪拌している懸濁液中に滴下する。滴下終了後、更に１時間超音波発振および攪拌を続け、シリカ膜被覆反応を行う。
【００４５】
所定時間経過後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後得られた粉体は５３０ｎｍ付近にボトムを有する粉体１Ｃを得た。
【００４６】
（４層目：チタニア膜の製膜）
あらかじめ、０．３Ｍ無水酢酸水溶液５０ｍｌと０．９Ｍ酢酸ナトリウム水溶液１００ｍｌおよび純水２５０ｍｌを混合した緩衡液（ｐＨ：５．４）を用意し、粉体１Ｃを４ｇ投入後、シリカ膜の製膜の場合と同様に、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に５５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。
分散後、硫酸チタン水溶液（１２０ｇ／リットル）をマイクロチューブポンプで、０．５５ｍｌ／分の滴下速度で滴下する。同時に超音波槽内の水を１００℃／時間で昇温し、この懸濁液を５５℃に保持する。滴下開始から８時間かけて硫酸チタン水溶液を滴下後、２時間反応させ、終了後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。
【００４７】
反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後得られた粉体は４５０ｎｍ付近にピークを有し、反射率４３％であり、鮮やかシアン色の粉体１Ｄを得た。
【００４８】
〔実施例３〕
（４層シリカ・チタニア膜被覆粉体の熱処理）
実施例２と同じ条件で製造した４層膜被覆粉体を、窒素雰囲気の回転式チューブ炉で５００℃、０．５時間熱処理したところ、得られた粉体は４０３ｎｍにピークを有し、反射率４７％であり、鮮やか青色の粉体２Ｄを得た。
【００４９】
〔実施例４〕
（シリカ・チタニア膜被覆粉体、塩化チタン水溶液使用）
（１層目：シリカ膜の製膜）
室温で容器に０．３Ｍ塩化カリウムと０．３Ｍほう酸の混合水溶液２５０ｍｌと、０．４Ｍ水酸化ナトリウム水溶液１１５ｍｌを混合し緩衡液を調製する。
この緩衡液中（ｐＨ：約９．０）に、基体としてマグネタイト粉末（平均粒径０．７μｍ）５．０ｇを投入し、この混合溶液を入れた容器を、水を張った超音波洗浄機（（株）井内盛栄堂製、ＵＳ−６型）の水槽に入れ、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に４５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。
【００５０】
次に、あらかじめ用意した１０重量％の水ガラス（けい酸ナトリウム）水溶液をマイクロチューブポンプで、１．３４ｍｌ／分の滴下速度で、１８分間、攪拌している懸濁液中に滴下する。滴下終了後、更に１時間超音波発振および攪拌を続け、シリカ膜被覆反応を行う。
所定時間経過後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後得られた粉体は５００ｎｍ付近にボトムを有する黒色粉体３Ａを得た。
【００５１】
（２層目：チタニア膜の製膜）
あらかじめ、０．３Ｍ無水酢酸水溶液５０ｍｌと０．９Ｍ酢酸ナトリウム水溶液１００ｍｌおよび２．５Ｍ水酸化ナトリウム水溶液１６０ｍｌと純水５００ｍｌを混合した緩衡液（ｐＨ：５．４）を用意し、粉体３Ａを４ｇ投入後、シリカ膜の製膜の場合と同様に、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に５５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。
分散後、この懸濁液を５５℃に保持する。加温分散後、塩化チタン水溶液（２００ｇ／リットル）４０ｇをマイクロチューブポンプで、０．８ｍｌ／分の滴下速度で滴下する。滴下後、２時間反応させ、終了後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。
【００５２】
反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後、得られた粉体を、窒素雰囲気の投入型回転式チューブ炉で５００℃、０．５時間熱処理し、冷却後、粉体は４５０ｎｍにピークを有し、反射率３５％であり、鮮やかシアン色の粉体３Ｂを得た。
【００５３】
（３層目：シリカ膜の製膜）
室温で容器に０．３Ｍ塩化カリウムと０．３Ｍほう酸の混合水溶液２５０ｍｌと、０．４Ｍ水酸化ナトリウム水溶液１１５ｍｌを混合し緩衡液を調製する。
この緩衡液中（ｐＨ：約９．０）に、粉体３Ｂ（平均粒径０．７μｍ） ｇを投入し、この混合溶液を入れた容器を、水を張った超音波洗浄機（（株）井内盛栄堂製、ＵＳ−６型）の水槽に入れ、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に４５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。
次に、あらかじめ用意した１０重量％の水ガラス（けい酸ナトリウム）水溶液をマイクロチューブポンプで、１．３４ｍｌ／分の滴下速度で、１８分間、攪拌している懸濁液中に滴下する。滴下終了後、更に１時間超音波発振および攪拌を続け、シリカ膜被覆反応を行う。
【００５４】
所定時間経過後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後得られた粉体は３８５ｎｍ付近にボトムを有する粉体３Ｃを得た。
【００５５】
（４層目：チタニア膜の製膜）
あらかじめ、０．３Ｍ無水酢酸水溶液５０ｍｌと０．９Ｍ酢酸ナトリウム水溶液１００ｍｌおよび純水２５０ｍｌを混合した緩衡液（ｐＨ：５．４）を用意し、粉体３Ｃを１６ｇ投入後、シリカ膜の製膜の場合と同様に、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に５５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。分散後、この懸濁液を５５℃に保持する。
加温分散後、塩化チタン水溶液（２００ｇ／リットル）４０ｇをマイクロチューブポンプで、０．８ｍｌ／分の滴下速度で滴下する。
滴下終了後、更に２時間超音波発振および攪拌を続け、チタニア膜被覆反応を行う。終了後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。
【００５６】
反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後、得られた粉体を、窒素雰囲気の投入型回転式チューブ炉で５００℃、０．５時間熱処理した。冷却後、粉体は４１０ｎｍにピークを有し、反射率４７％であり、鮮やか青色の粉体３Ｄを得た。
【００５７】
〔実施例５〕
（シリカ・酸化すず膜被覆粉体）
（１層目：シリカ膜の製膜）
室温で容器に０．３Ｍ塩化カリウムと０．３Ｍほう酸の混合水溶液２５０ｍｌと、０．４Ｍ水酸化ナトリウム水溶液１１５ｍｌを混合し緩衡液を調製する。
この緩衡液中（ｐＨ：約９．０）に、基体としてマグネタイト粉末（平均粒径０．７μｍ）５．０ｇを投入し、この混合溶液を入れた容器を、水を張った超音波洗浄機（（株）井内盛栄堂製、ＵＳ−６型）の水槽に入れ、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に４５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。
【００５８】
次に、あらかじめ用意した１０重量％の水ガラス（けい酸ナトリウム）水溶液をマイクロチューブポンプで、１．３４ｍｌ／分の滴下速度で、２２分間、攪拌している懸濁液中に滴下する。滴下終了後、更に１時間超音波発振および攪拌を続け、シリカ膜被覆反応を行う。
所定時間経過後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後、得られた粉体を、窒素雰囲気の投入型回転式チューブ炉で３００℃、３０分間熱処理し、冷却した。粉体は４８０ｎｍにボトムを有する黒色の粉体５Ａを得た。
【００５９】
（２層目：酸化錫膜の製膜）
あらかじめ、０．３Ｍ無水酢酸水溶液５０ｍｌと０．９Ｍ酢酸ナトリウム水溶液１００ｍｌおよび２．５Ｍ水酸化ナトリウム水溶液１６０ｍｌと純水５００ｍｌを混合した緩衡液（ｐＨ：５．４）を用意し、粉体５Ａを１６ｇ投入後、シリカ膜の製膜の場合と同様に、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に５５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。
分散後、この懸濁液を５５℃に保持する。加温分散後、塩化すず水溶液（１９０ｇ／リットル）４８ｇをマイクロチューブポンプで、０．８ｍｌ／分の滴下速度で滴下する。滴下後、２時間反応させ、終了後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。
【００６０】
反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後、得られた粉体を、窒素雰囲気の投入型回転式チューブ炉で３００℃、３０分間熱処理し、冷却した。粉体は４４８ｎｍにピークを有し、反射率３２％であり、シアン色の粉体５Ｂを得た。
【００６１】
（３層目：シリカ膜の製膜）
室温で容器に０．３Ｍ塩化カリウムと０．３Ｍほう酸の混合水溶液２５０ｍｌと、０．４Ｍ水酸化ナトリウム水溶液１１５ｍｌを混合し緩衡液を調製する。
この緩衡液中（ｐＨ：約９．０）に、粉体５Ｂ（平均粒径０．７μｍ） ｇを投入し、この混合溶液を入れた容器を、水を張った超音波洗浄機（（株）井内盛栄堂製、ＵＳ−６型）の水槽に入れ、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に４５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。
次に、あらかじめ用意した１０重量％の水ガラス（けい酸ナトリウム）水溶液をマイクロチューブポンプで、１．３４ｍｌ／分の滴下速度で、２６分間、攪拌している懸濁液中に滴下する。滴下終了後、更に１時間超音波発振および攪拌を続け、シリカ膜被覆反応を行う。
【００６２】
所定時間経過後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後、得られた粉体を、窒素雰囲気の投入型回転式チューブ炉で３００℃、３０分間熱処理し、冷却した。粉体は５５０ｎｍ付近にボトムを有する粉体５Ｃを得た。
【００６３】
（４層目：酸化錫膜の製膜）
あらかじめ、０．３Ｍ無水酢酸水溶液５０ｍｌと０．９Ｍ酢酸ナトリウム水溶液１００ｍｌおよび２．５Ｍ水酸化ナトリウム水溶液１６０ｍｌと純水２５０ｍｌを混合した緩衡液（ｐＨ：５．４）を用意し、粉体５Ｃを１６ｇ投入後、シリカ膜の製膜の場合と同様に、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に５５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。分散後、この懸濁液を５５℃に保持する。
加温分散後、塩化すず水溶液（１９０ｇ／リットル）５２ｇをマイクロチューブポンプで、０．８ｍｌ／分の滴下速度で滴下する。
滴下終了後、更に２時間超音波発振および攪拌を続け、チタニア膜被覆反応を行う。終了後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。
【００６４】
反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後、得られた粉体を、窒素雰囲気の投入型回転式チューブ炉で６５０℃、３０分間熱処理し、冷却した。粉体は５８０ｎｍにピークを有し、反射率４４％であり、黄色の粉体５Ｄを得た。
【００６５】
（５層目：シリカ膜の製膜）
室温で容器に０．３Ｍ塩化カリウムと０．３Ｍほう酸の混合水溶液２５０ｍｌと、０．４Ｍ水酸化ナトリウム水溶液１１５ｍｌを混合し緩衡液を調製する。
この緩衡液中（ｐＨ：約９．０）に、粉体５Ｄ（平均粒径０．７μｍ） ｇを投入し、この混合溶液を入れた容器を、水を張った超音波洗浄機（（株）井内盛栄堂製、ＵＳ−６型）の水槽に入れ、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に４５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。
次に、あらかじめ用意した１０重量％の水ガラス（けい酸ナトリウム）水溶液をマイクロチューブポンプで、１．３４ｍｌ／分の滴下速度で、２８分間、攪拌している懸濁液中に滴下する。滴下終了後、更に１時間超音波発振および攪拌を続け、シリカ膜被覆反応を行う。
【００６６】
所定時間経過後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後、得られた粉体を、窒素雰囲気の投入型回転式チューブ炉で３００℃、３０分間熱処理し、冷却した。粉体は５５０ｎｍ付近にボトムを有する粉体５Ｅを得た。
【００６７】
（６層目：酸化錫膜の製膜）
あらかじめ、０．３Ｍ無水酢酸水溶液５０ｍｌと０．９Ｍ酢酸ナトリウム水溶液１００ｍｌおよび２．５Ｍ水酸化ナトリウム水溶液１６０ｍｌと純水２５０ｍｌを混合した緩衡液（ｐＨ：５．４）を用意し、粉体５Ｅを１６ｇ投入後、シリカ膜の製膜の場合と同様に、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に５５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。分散後、この懸濁液を５５℃に保持する。
加温分散後、塩化すず水溶液（１９０ｇ／リットル）５５ｇをマイクロチューブポンプで、０．８ｍｌ／分の滴下速度で滴下する。
滴下終了後、更に２時間超音波発振および攪拌を続け、チタニア膜被覆反応を行う。終了後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。
【００６８】
反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後、得られた粉体を、窒素雰囲気の投入型回転式チューブ炉で６５０℃、３０分間熱処理し、冷却した。粉体は４８０ｎｍにピークを有し、反射率５３％であり、青色の粉体５Ｆを得た。
【００６９】
〔実施例６〕
（シリカ・酸化チタン膜被覆粉体、膜内結晶化による反射率向上）
（１層目：シリカ膜の製膜）
室温で容器に０．３Ｍ塩化カリウムと０．３Ｍほう酸の混合水溶液２５０ｍｌと、０．４Ｍ水酸化ナトリウム水溶液１１５ｍｌを混合し緩衡液を調製する。
この緩衡液中（ｐＨ：約９．０）に、基体としてマグネタイト粉末（平均粒径０．７μｍ）５．０ｇを投入し、この混合溶液を入れた容器を、水を張った超音波洗浄機（（株）井内盛栄堂製、ＵＳ−６型）の水槽に入れ、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に４５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。
次に、あらかじめ用意した１０重量％の水ガラス（けい酸ナトリウム）水溶液をマイクロチューブポンプで、１．３４ｍｌ／分の滴下速度で、２２分間、攪拌している懸濁液中に滴下する。滴下終了後、更に１時間超音波発振および攪拌を続け、シリカ膜被覆反応を行う。
【００７０】
所定時間経過後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後、得られた粉体を、窒素雰囲気の投入型回転式チューブ炉で３００℃、３０分間熱処理し、冷却した。粉体は４８０ｎｍにボトムを有する黒色の粉体６Ａを得た。
【００７１】
（２層目：酸化チタン膜の製膜）
あらかじめ、０．３Ｍ無水酢酸水溶液５０ｍｌと０．９Ｍ酢酸ナトリウム水溶液１００ｍｌおよび２．５Ｍ水酸化ナトリウム水溶液１６０ｍｌと純水５００ｍｌを混合した緩衡液（ｐＨ：５．４）を用意し、粉体６Ａを１６ｇ投入後、シリカ膜の製膜の場合と同様に、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に５５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。
分散後、この懸濁液を５５℃に保持する。加温分散後、硫酸チタン水溶液（２００ｇ／リットル）４３ｇをマイクロチューブポンプで、０．８ｍｌ／分の滴下速度で滴下する。滴下後、２時間反応させ、終了後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。
【００７２】
反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後、得られた粉体を、窒素雰囲気の投入型回転式チューブ炉で６５０℃、２時間熱処理し、冷却した。粉体は５４８ｎｍにピークを有し、反射率４３％であり、緑色の粉体６Ｂを得た。
【００７３】
（３層目：シリカ膜の製膜）
室温で容器に０．３Ｍ塩化カリウムと０．３Ｍほう酸の混合水溶液２５０ｍｌと、０．４Ｍ水酸化ナトリウム水溶液１１５ｍｌを混合し緩衡液を調製する。
この緩衡液中（ｐＨ：約９．０）に、粉体６Ｂ（平均粒径０．７μｍ） ｇを投入し、この混合溶液を入れた容器を、水を張った超音波洗浄機（（株）井内盛栄堂製、ＵＳ−６型）の水槽に入れ、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に４５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。
次に、あらかじめ用意した１０重量％の水ガラス（けい酸ナトリウム）水溶液をマイクロチューブポンプで、１．３４ｍｌ／分の滴下速度で、２６分間、攪拌している懸濁液中に滴下する。滴下終了後、更に１時間超音波発振および攪拌を続け、シリカ膜被覆反応を行う。
【００７４】
所定時間経過後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後、得られた粉体を、窒素雰囲気の投入型回転式チューブ炉で３００℃、３０分間熱処理し、冷却した。粉体は４８０ｎｍ付近にボトムを有する粉体６Ｃを得た。
【００７５】
（４層目：酸化チタン膜の製膜）
あらかじめ、０．３Ｍ無水酢酸水溶液５０ｍｌと０．９Ｍ酢酸ナトリウム水溶液１００ｍｌおよび２．５Ｍ水酸化ナトリウム水溶液１６０ｍｌと純水２５０ｍｌを混合した緩衡液（ｐＨ：５．４）を用意し、粉体６Ｃを１６ｇ投入後、シリカ膜の製膜の場合と同様に、３６ｋＨZ 、６００Ｗの超音波を発振させ、同時に５５０ｒｐｍで攪拌しながら１０分間粒子を分散させる。分散後、この懸濁液を５５℃に保持する。
加温分散後、硫酸チタン水溶液（２００ｇ／リットル）４３ｇをマイクロチューブポンプで、０．８ｍｌ／分の滴下速度で滴下する。
滴下終了後、更に２時間超音波発振および攪拌を続け、チタニア膜被覆反応を行う。終了後、この懸濁液に蒸留水３００ｍｌを添加し、反応を停止する。
【００７６】
反応を停止した液の上澄液を取り除き純水３６０ｍｌを加え４００ｒｐｍにて５分洗浄攪拌を行う。なおこの操作を繰り返し洗浄操作を行うことにより、ｐＨ７程度まで洗浄する。
洗浄操作終了後、バットに移し、固形分を沈降させ、上澄液を除き、固液分離し、１１０℃で乾燥させる。
乾燥後、得られた粉体を、窒素雰囲気の投入型回転式チューブ炉で６５０℃、２時間熱処理し、冷却した。粉体は５８８ｎｍにピークを有し、反射率６２％であり、レモンイエロー色の粉体６Ｄを得た。
これは熱処理時間を長くすることにより酸化チタンがルチル（屈折率の高い酸化チタン）に結晶する割合が増えたためと考えられる。
【００７７】
【発明の効果】
以上説明したように、本発明は、製膜反応溶媒として、ｐＨ一定条件の水系溶媒を用いると同時に、膜被覆反応を超音波分散条件下で行うことにより、基体として磁性体を用いた場合でも、膜被覆粉体同志が凝集したり固着することがなく、液相中に固相のみを析出させることもなく、好ましい膜厚制御ができる膜被覆粉体を容易に製造することを可能とすることができた。
また、高価な化合物である金属アルコキシドや引火性の高い有機溶媒を用いることなく、水を溶媒として用い、製造施設も防爆設備を必要とせず、温度、湿度の管理も容易であり、総合的に製品の価格も安価に得られる機能性の高い、膜被覆粉体およびその製造方法を提供するという効果を奏する。[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a powder manufacturing technique in which the surface of a powder particle is coated with another substance in multiple layers and exhibits a composite function, and more specifically, a film formed by reacting the surface of a base particle in an aqueous solvent. Film-coated powder havingthe body'sIt relates to a manufacturing method.
[0002]
[Prior art]
It is known that coating the surface of a powder with a film of another substance improves the properties of the powder or gives diversity to the properties. Conventionally, various means have been proposed for this purpose. Yes.
For example, as a coating technique for forming a film on the surface of an object for protection or decoration, many means such as a coating method, a deposition method, a sputtering method, a vacuum deposition method, an electrodeposition method and an anodizing method are known. . However, it is difficult to make the film thickness uniform by a coating method or a deposition method, and it is difficult to obtain a thick film by sputtering or vacuum deposition. In addition, the electrodeposition method and the anodic oxidation method have a problem that they are not suitable for the processing of powder because of using the workpiece as an electrode.
With the progress in various technical fields, there is an increasing demand for powders having unique properties, particularly metal powders or metal compound powders, and only powders, particularly metal powders or metal compound powders, are required. There is a need for a powder that has other properties in addition to the properties it has and has a combined function. In order to produce these powders, it was considered to provide a plurality of layers of metal oxide films or the like having a uniform thickness on the base particles.
[0003]
As a useful method of forming metal oxides for providing powders having complex properties that can meet the new requirements as described above and capable of fulfilling complex functions, particularly metal or metal compound powders, Furthermore, the present inventors disperse metal powder or metal oxide powder in a metal alkoxide solution, and hydrolyze the metal alkoxide to form a metal oxide film, thereby forming a metal or metal compound substrate. Has invented a powder having a metal oxide film having a uniform thickness of 0.01 to 20 μm and a metal different from the metal constituting the substrate (Japanese Patent Laid-Open No. 6-228604) .
[0004]
In this powder, when a plurality of the metal oxide films are provided, a special function can be given by adjusting the thickness of each layer of the film, for example, on the surface of the substrate. When the coating films having different refractive indexes are provided with a thickness corresponding to a quarter wavelength of light, all the light is reflected. When this means is applied to a material based on a magnetic material such as iron, cobalt, nickel, or other metal powder, metal alloy powder, or iron nitride powder, the magnetic toner for magnetic toners shines white by totally reflecting light. A powder can be obtained. Furthermore, it is disclosed that a color magnetic toner can be obtained if a colored layer is provided on the powder and a resin layer is provided thereon.
In addition, the present inventors further improved the above powder and disclosed a powder in which a plurality of metal oxide films and metal films are alternately provided instead of a metal oxide film alone (Japanese Patent Laid-Open No. Hei 7). No. 90310). This has excellent properties as a color magnetic toner or the like.
[0005]
Furthermore, the present inventors have found that the reflected light interference waveform of the multilayer film can be prepared by controlling the combination of the materials of the multilayer film and the film thickness. In other words, without using dyes or pigments, the surface of the substrate has a plurality of thin coating films (silicon dioxide film, titania film, polystyrene film, metallic silver film, etc.) with different refractive indexes. It has been disclosed that a color powder having a color tone that is colored even by long-term storage is provided (WO96 / 28269).
[0006]
However, in order to form a metal oxide film on the surface of the metal powder or metal compound powder, the method by hydrolysis of the metal alkoxide uses a highly flammable organic material as the solvent, As metal alkoxides, which are expensive compounds, must be used. In order to use a highly flammable organic solvent, the production facility is made an explosion-proof facility, and the temperature and humidity are strictly controlled, and the price of the product manufactured using it is naturally expensive.
On the other hand, there is a method of forming a film by precipitation from an aqueous metal salt solution by reaction of the metal salt. However, the solvent used in this method is a strong acid or alkali. For this reason, when a metal or the like is directly used for the reaction as the base particles, the base is dissolved and invaded by acid or alkali, so that a preferable film-coated powder cannot be obtained.
On the other hand, after forming a film inactive to acid or alkali on the surface of the base particles by a method such as hydrolysis of metal alkoxide, the film is formed by precipitation from the aqueous metal salt solution. (Japanese Patent Laid-Open No. 10-1702).
However, there is a problem that a method using hydrolysis of metal alkoxide, which is costly and dangerous, must be used.
[0007]
In addition, the formation of a film by the reaction of the metal salt may result in excessive precipitation of solid phase components depending on acid or alkali neutralization or heating conditions, and a film having a uniform thickness on the substrate surface may not be formed. In this case, only the solid phase may precipitate or the film-coated powders may adhere to each other, and a preferable film thickness control cannot be achieved.
Furthermore, the present inventors have found a method of forming a film on the surface of the substrate particles by a reaction from a metal salt in an aqueous solvent having a constant pH (Japanese Patent Application No. 9-298717). This is because an aqueous solvent having a constant pH, that is, a buffer solution is used, so that the influence of acid and alkali is alleviated, and erosion of the substrate surface is prevented. Further, the use of this buffer solution has the effect that the surface charge of the substrate particles is kept constant, an electric double layer is formed, and dispersed particles can be obtained without aggregation of the film-coated powder.
[0008]
[Problems to be solved by the invention]
However, the above-described technique using an aqueous solvent having a constant pH improves the dispersibility only when a non-magnetic substrate is used.
When a magnetic substance is used as the substrate, the electric double layer is broken by the magnetism and the aggregation becomes remarkable.
Although mechanical agitation for these agglomerations is considered first, the film immediately after coating is in the form of a gel. Therefore, in the mechanical dispersion method in which the agitation force is increased, the films collide with each other. This makes it difficult to disperse the single film-coated magnetic particles. Furthermore, in the method of adding a protective colloid such as hydroxypropylcellulose (HPC) as a dispersant, bubbles are generated in the reaction solution even with a small amount of addition, and the contact between the base particles and the reaction solution is not uniform and uniform. There is a problem of inhibiting proper film formation.
[0009]
Accordingly, an object of the present invention is to overcome the above-mentioned drawbacks of the prior art and to coat the substrate surface with a uniform thickness in the production of film-coated powder by aqueous reaction film formation without using a method based on hydrolysis of metal alkoxide. Forms a film, and only the solid phase does not precipitate in the liquid phase, and even when a magnetic material is used as the substrate, the film-coated powders do not aggregate or adhere, and the film thickness can be controlled favorably. Coating powderthe body'sIt is to provide a manufacturing method.
[0010]
[Means for Solving the Problems]
As a result of earnest research, the present inventors have used the above-mentioned object by performing an aqueous film dispersion reaction under an ultrasonic dispersion condition at the same time as using a water-based solvent having a constant pH as a film formation reaction solvent. We have found that this can be achieved and have reached the present invention.
That is, the film-coated powder of the present inventionthe body'sThe manufacturing method is,
[0012]
(1) In the method for producing a film-coated powder in which a film is formed on the surface of the base particle, at least one layer of the film is subjected to ultrasonic oscillation in an aqueous solvent having a constant pH condition by containing a buffer solution. A process for producing a film-coated powder, which is formed by a reaction from a metal salt.
(2The above-mentioned base particle is a magnetic substance,1) Film-coated powder production method.
(3The particle size of the base particles made of the magnetic material is 0.05 to 10 μm.2) Film-coated powder production method.
(4The stirring is performed to such an extent that the powder does not settle during the reaction.1) Film-coated powder production method.
[0013]
(5The formation of the film by reaction from a metal salt is carried out by adding a solution of a metal salt as a film component raw material to an aqueous solvent in which base particles are dispersed.1) Film-coated powder production method.
(6And (b) heat-treating in an aqueous solvent during the formation of the film by reaction from a metal salt.1) Film-coated powder production method.
(7) Heat treatment after the formation of the film by reaction from a metal salt,1) Film-coated powder production method.
(8The thickness of the film formed by reaction from a metal salt is 10 nm to 10 μm.1) Film-coated powder production method.
(9A plurality of the films are formed by a reaction from a metal salt;1) Of film-coated powder.
[0014]
In the present invention, during the film-forming reaction, precipitation of a solid phase that does not become a film is suppressed by the following operations and actions, and a film having a uniform thickness can be formed on the surface of the base particle with a desired thickness. I guess you can. (1) By using a buffer solution as a reaction solvent and adjusting to a certain pH, the influence of acid or alkali is mitigated, and erosion of the substrate surface is prevented; and (2) substrate particles are obtained by ultrasonic dispersion. In particular, it not only improves the dispersibility of magnetic materials such as magnetite powder, but also improves the diffusibility of the coating components, and further prevents the coating from adhering to each other and improves the dispersibility of the coated magnetic particles. (3) The coating component is deposited at an appropriate reaction speed, and the solid phase that does not become a coating is prevented from being deposited.
Due to the above comprehensive action, the charge on the surface of the film-coated powder can be kept constant, and the action of the electric double layer prevents the film-coated powder from agglomerating and obtains dispersed particles.
In order to make use of the function of the electric double layer, the pH differs depending on the combination of the substance of the substrate and the kind of metal compound formed in the liquid by the film-forming reaction, and it is preferable to avoid the isoelectric point of both.
[0015]
According to the present invention, the film having a film thickness that allows preferable film thickness control without aggregation or adhesion of film-coated powders even when a magnetic material is used as a substrate, even though a water-soluble raw material is used. Making it possible to easily produce coated powders
did it.
Further, by using water as a solvent, it is possible to obtain an effect that a film can be formed at a lower production cost than the alkoxide method.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
As described above, the film-coated powder of the present invention is formed by a film-forming reaction on the surface of a substrate using an aqueous solvent having a constant pH condition as a film-forming reaction solvent and simultaneously carrying out the film-coating reaction under ultrasonic dispersion conditions. The
In the present invention, in order to make the film forming reaction constant, a buffering agent is added to an aqueous solvent to form a buffer solution, or a buffer solution prepared in advance is used. In the film forming reaction, film materials other than the buffer solution are added to form a film. When film formation is performed by adding a film forming raw material, if the pH fluctuates greatly, it is desirable to add a buffer solution to prevent this.
In the present invention, the constant pH means that the pH is within ± 2 of the predetermined pH, preferably within ± 1, and more preferably within ± 0.5.
[0017]
Various buffering solutions are used and are not particularly limited. First, it is important that the base particles are sufficiently dispersible. At the same time, metal hydroxide or metal oxide film-coated powder deposited on the surface of the base is also used. It is necessary to select so as to satisfy the conditions that can be dispersed and a dense film can be formed by the gentle dropping reaction.
Therefore, the production method of the film-coated powder of the present invention is different from the conventional method of neutralization by reaction of metal salt solution, precipitation by isoelectric point, or decomposition and precipitation by heating.
The buffer solution used in the present invention depends on the solid phase component to be precipitated, and is not particularly limited. However, Tris, boric acid, glycine, succinic acid, lactic acid, acetic acid, tartaric acid, hydrochloric acid And the like.
[0018]
Next, as an ultrasonic dispersion condition, various ultrasonic oscillators can be used. For example, a water tank of an ultrasonic cleaning machine can be used, and is not particularly limited. However, the ultrasonic dispersion conditions of the present invention vary depending on the size of the oscillation device, the shape and size of the reaction vessel, the amount of reaction solution, the volume, the amount of substrate particles, etc. Appropriate conditions may be selected.
[0019]
In the present invention, a powder made of an inorganic substance can be used as the substrate of the film-coated powder of the present invention. Examples of the inorganic substance constituting the powder composed of the inorganic substance of the present invention include metals such as iron, nickel, chromium, titanium, and aluminum, metal alloys such as iron-nickel and iron-cobalt alloys, and iron.・ Nickel alloy nitride, iron / nickel / cobalt alloy nitride, and metal oxides such as iron, nickel, chromium, titanium, aluminum, silicon (in this case, silicon shall be classified as metal) In addition, alkaline earth metal oxides such as calcium, magnesium and barium, or complex oxides thereof, clays, glasses and the like can be mentioned.
In the present invention, one of the purposes is to produce a magnetic powder such as a color magnetic toner or a color magnetic ink, and in this case, the substrate of the multilayer film-coated powder of the present invention is a ferromagnetic material. Is preferably used. The ferromagnetic material may be a metal having a high magnetic permeability such as iron, nickel, chromium, titanium, or aluminum, but a ferromagnetic oxide or a ferromagnetic alloy such as ferrite or γ-iron oxide is also used.
[0020]
In the technique described in the specification attached to the above Japanese Patent Application No. 9-298717, when a magnetic material is used as the substrate, the powders are likely to aggregate due to the magnetic force due to the residual magnetization. It was not obtained.
The remanent magnetization of the magnetic powder has a particle size of 0.05 to 10 μm, particularly in the range of 0.05 to 3 μm, and particularly in the range of 0.2 to 0.3 μm.
However, by using the method of the present invention, a magnetic material as a substrate, particularly ferrite such as magnetite, Ba ferrite, Sr ferrite, γ-hematite, cobalt ferrite, etc. having a large residual magnetization, or a mixed ferrite thereof can be used. Even if the magnetic powder is used, aggregation of the powders can be effectively prevented.
The specific gravity of the base particles is in the range of 0.1 to 10.5, but is preferably 0.1 to 5.5, more preferably 0.1 to 0.1 from the viewpoint of fluidity and buoyancy. 2.8, more preferably in the range of 0.5 to 1.8. If the specific gravity of the substrate is less than 0.1, the buoyancy in the liquid is too large, and the film needs to be multilayered or very thick, which is uneconomical. On the other hand, if it exceeds 10.5, the film for floating becomes thick, which is similarly uneconomical.
[0021]
In the present invention, the powder base particles are coated with a plurality of coating layers having different refractive indexes and appropriately selected the refractive index and layer thickness of each coating layer, so that they are colored by the interference color and visible. It can be set as the powder which expresses a specific interference reflection peak besides an optical region.
As described above, a metal hydroxide film or a metal oxide film is deposited on the surface of the base particle by the reaction of a metal salt, but a buffer solution is used as a solvent for the solid phase deposition reaction, and at a certain pH. Precipitate at an appropriate rate.
[0022]
In the present invention, the metal used as the metal salt is iron, nickel, chromium, titanium, zinc, aluminum, cadmium, zirconium, silicon, tin, lead, lithium, indium, neodymium, bismuth, cerium, antimony, etc. Calcium, magnesium, barium etc. are mentioned. Examples of these metal salts include sulfuric acid, nitric acid, hydrochloric acid, oxalic acid, carbonic acid and carboxylic acid salts. Furthermore, chelate complexes of the above metals are also included. The type of metal salt used in the present invention is selected according to the properties to be imparted to the surface of the substrate and the means applied during production.
[0023]
A plurality of layers of these metal salt films such as metal oxides may be formed. If necessary, a metal oxide obtained by hydrolysis of a metal alkoxide or the like may be formed on the metal oxide film. A film formed by a film forming method can also be formed.
In this way, a multilayer film can be formed on the substrate particles, and at that time, by setting the formation conditions so that the thickness of each layer has a predetermined thickness, the desired characteristics can be obtained. In addition, it is possible to form a multi-layered film of a metal oxide or the like using a metal salt which is a simple material and is an inexpensive raw material. In particular, it is an important advantage that a multilayer film-coated powder can be obtained without using an expensive metal alkoxide as a raw material.
[0024]
In the method for producing a film-coated powder according to the present invention, a multilayer coating film may be produced as a continuous process, and each coating film is produced one layer at a time, or a single layer production and a multi-layer continuous production. It can be manufactured by various methods such as combining.
The particle diameter of the film-coated powder according to the present invention is not particularly limited and can be appropriately adjusted according to the purpose, but is usually in the range of 0.01 μm to several mm.
[0025]
In the present invention, the thickness of the metal oxide film formed at one time can be in the range of 5 nm to 10 μm, and can be made thicker than the conventional forming method.
As the total thickness of the metal oxide film formed in a plurality of times, in the case of the above-described color magnetic powder, in order to form a metal oxide film having a good reflectivity due to the interference, it is 10 nm to 20 μm. The range is preferable, and more preferably 20 nm to 5 μm. In order to interference-reflect visible light with a particularly thin film thickness such as a limited particle size, it is preferably in the range of 0.02 to 2.0 μm.
[0026]
The powder having a metal oxide film or the like on the surface of the substrate particles produced as described above imparts various properties depending on the material of the selected substrate particles and the material of the metal oxide of the film coated on the surface. Therefore, it can be applied to each intended use. For example, magnetic metal iron, iron nitride, magnetite, etc. are used as base particles, and silicon dioxide (also referred to as silica) having a lower refractive index than that of the magnetic material is coated thereon, and the outer film thereof is used as the outer film. If a layer of titanium oxide (also called titania) having a higher refractive index is coated, a magnetic powder having a high whiteness can be obtained. In addition, if a conductor such as silver, copper or aluminum (also referred to as alumina) is used as the base particle, and an electrically insulating coating film such as aluminum oxide is coated on the metal layer as the metal oxide, A thermally conductive powder having an insulating surface layer is obtained.
[0027]
Further, for example, when the thickness of the coating having a different refractive index is provided on the surface of the substrate by a thickness corresponding to one-fourth of the wavelength of light, light is mostly reflected (Fresnel reflection) due to interference. For example, a metal material such as iron, cobalt, nickel, or an alloy powder, or a magnetic material such as iron nitride powder is used as a base, and a highly reflective metal layer such as silver or cobalt is provided on the surface. An oxide layer such as silicon dioxide having a refractive index lower than that of the metal is provided on the outside of the oxide layer so that the product of the refractive index of the oxide and the thickness of the film is a thickness of a quarter wavelength of visible light. Reflecting light by coating an oxide layer with a high refractive index, such as titanium oxide, whose thickness is the product of the refractive index of the substance and the thickness of the film, which is a quarter wavelength of visible light, It is possible to produce magnetic powder for magnetic toner that shines white. Kill.
In addition, the produced powder can be heat-treated at a temperature of 200 ° C. to 800 ° C. in an inert gas atmosphere to obtain a powder having a higher strength and a higher whiteness. When the powder is heat-treated, the condition that the product of the refractive index of the substance and the thickness of the film is a quarter wavelength of visible light in each layer of the heat-treated powder must be satisfied.
[0028]
Furthermore, a color magnetic toner can be produced by providing a colored layer on the powder and further providing a resin layer thereon. Since the wavelength of visible light varies, the thickness of the oxide and metal layers of the particles constituting the magnetic toner is the product of the refractive index of the substance and the thickness of the film, which is a quarter wavelength of visible light. It is also possible to alternately provide a plurality of different ones in a range close to the thickness.
When the multilayer coating powder is a color powder colored by interference reflection, it is designed using the method of WO96 / 28269, the film forming conditions are adjusted, and the light having the desired spectral wavelength is reflected. The high refractive index film and the low refractive index film are alternately formed to a film thickness necessary for Fresnel interference.
[0029]
Next, as an example, a method for forming an alternating multilayer film of a high refractive index metal oxide and a low refractive index metal oxide will be specifically described. First, when forming a film such as titanium oxide or zirconium oxide, the base particles are immersed in a buffer solution such as acetic acid / sodium acetate and dispersed by ultrasonic oscillation, and titanium sulfate which is a metal salt such as titanium or zirconium. Alternatively, zirconium sulfate or the like can be used as a raw material, and an aqueous solution of these metal salts can be slowly dropped into the reaction system, and the resulting metal hydroxide or metal oxide can be precipitated around the base particles. During this dropping reaction, the pH is maintained at the pH of the buffer solution (5.4).
After completion of the reaction, this powder is separated into solid and liquid, washed and dried, and then subjected to heat treatment. The drying means may be either vacuum drying or natural drying. It is also possible to use a device such as a spray dryer in an inert atmosphere.
In addition, formation of the titanium oxide which is a coating film in this case is shown by the following reaction formula.
Ti (SOFour )2 + 2H2O → TiO2 + 4H2 (SOFour )2
[0030]
Subsequently, when a film such as silicon dioxide or aluminum oxide is formed, KCl / HThreeBOThreeThe above titania-coated particles are immersed in a buffer solution in which NaOH is added to the system and dispersed by ultrasonic oscillation, and the metal salt such as silicon or aluminum such as sodium silicate, aluminum chloride or the like is used as a raw material. This can be carried out by slowly dropping an aqueous solution of the above into the reaction system and precipitating the metal hydroxide or metal oxide to be produced around the base particles. During this dropping reaction, the pH is maintained at the pH of the buffer solution (9.0).
After completion of the reaction, this powder is separated into solid and liquid, washed and dried, and then subjected to heat treatment. By this operation, by repeating the operation of forming two layers of metal oxide films having different refractive indexes on the surface of the base particles, a powder having a multilayer metal oxide film on the surface can be obtained.
In this case, the formation of silicon dioxide, which is a coating film, is represented by the following reaction formula.
Na2SiXO2X + 1+ H2O → XSiO2+ 2Na++ 2OH-
[0031]
Next, raw materials used for film formation in the present invention, particularly metal salts will be described.
The raw materials used to form a film having a high refractive index include titanium halides and sulfates for titanium oxide films, and zirconium halides, sulfates and carboxylic acids for zirconium oxide films. Salts, oxalates, chelate complexes, etc., for cerium oxide films, cerium halides, sulfates, carboxylates, oxalates, etc., for bismuth oxide films, bismuth halides, nitrates, carboxylic acids For indium oxide films such as salts, indium halides, sulfates and the like are preferable.
In addition, as a raw material used to form a film having a low refractive index, for silicon oxide films, organic silicon compounds such as sodium silicate, water glass, silicon halide, alkyl silicate, and polymers thereof are used. For aluminum oxide films, aluminum halides, sulfates, chelate complexes, etc. are preferred, and for magnesium oxide films, magnesium sulfates, halides, etc. are preferred.
Further, for example, in the case of a titanium oxide film, mixing titanium sulfate with titanium chloride has an effect of becoming a rutile type titanium oxide film having a higher refractive index at a lower temperature.
[0032]
Further, a more complete oxide film can be produced by controlling the reaction temperature at the time of coating to a temperature suitable for the type of each metal salt.
When the film formation reaction (solid layer deposition reaction) on the surface of the substrate in the aqueous solvent is too slow, the solid layer deposition reaction can be promoted by heating the reaction system. However, if the heat treatment for heating is excessive, the reaction rate is too high, and the supersaturated solid layer does not become a film, but precipitates in an aqueous solution, forms gels or fine particles, and film thickness control becomes difficult.
[0033]
After the production of the coating film, repeated washing with tilted water while adding distilled water to remove the electrolyte, followed by heat treatment such as drying and baking, removing the water contained in the solid phase to completely remove the oxide. A film is preferred. Further, by heat-treating the powder after film formation in a rotary tube furnace or the like, sticking can be prevented and dispersed particles can be obtained.
In order to form a hydroxide film or an oxide film and heat-treat it, it may be heat-treated every time each layer is coated, or may be finally heat-treated after the target multilayer film is completed.
The heat treatment conditions vary depending on the reaction system, but the heat treatment temperature is 200 to 1300 ° C, preferably 400 to 1100 ° C. Below 200 ° C., salts and moisture may remain. When the temperature exceeds 1300 ° C., the film and the substrate may react with each other to form different substances, both of which are unsuitable. The heat treatment time is 0.1 to 100 hours, preferably 0.5 to 50 hours.
[0034]
【Example】
The present invention will be described more specifically with reference to the following examples. However, the scope of the present invention is not limited to these examples.
[0035]
[Example 1]
(Silica film formation)
A buffer solution is prepared by mixing 250 ml of a mixed aqueous solution of 0.3 M potassium chloride and 0.3 M boric acid and 115 ml of a 0.4 M aqueous sodium hydroxide solution at room temperature.
In this buffer solution (pH: about 9.0), 5.0 g of magnetite powder (average particle size 0.7 μm) is added as a substrate, and the container containing the mixed solution is subjected to ultrasonic cleaning with water. It is placed in a water tank of a machine (US-6 type, manufactured by Iuchi Seieido Co., Ltd.), and ultrasonic waves of 36 kHz and 600 W are oscillated, and particles are dispersed for 10 minutes while stirring at 450 rpm.
[0036]
Next, a 10% by weight water glass (sodium silicate) aqueous solution prepared in advance is dropped into the stirring suspension at a dropping rate of 1.34 ml / min for 18 minutes with a microtube pump. After completion of the dropping, the ultrasonic wave oscillation and stirring are continued for another hour to carry out a silica film coating reaction.
After a predetermined time, the supernatant is removed, 360 ml of ion exchange water is added, and washing and stirring are performed at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the powder was dried at 110 ° C., and the particle size of the dried powder was measured using a measuring device (Microtrack X-100 manufactured by Nikkiso Co., Ltd.). The particle size measurement results are shown in Table 1.
[0037]
[Comparative Example 1]
(Silica film formation)
The same operation as in Example 1 was performed. However, ultrasonic waves were not oscillated during the film forming reaction, and only stirring was performed. The particle size measurement results are shown in Table 1.
[0038]
[Table 1]
As is apparent from Table 1, the 50% passage diameter of the silica film-coated magnetite particles of Example 1 according to the present invention was almost the same as the 50% passage diameter of the raw material magnetite particles of the substrate, and satisfactory results were obtained. However, the 50% passage diameter of the silica film-coated magnetite particles of Comparative Example 1 was unsatisfactory.
[0040]
[Example 2]
(Silica / Titania coating powder)
(First layer: Silica film)
A buffer solution is prepared by mixing 250 ml of a mixed aqueous solution of 0.3 M potassium chloride and 0.3 M boric acid and 115 ml of a 0.4 M aqueous sodium hydroxide solution at room temperature.
In this buffer solution (pH: about 9.0), 5.0 g of magnetite powder (average particle size 0.7 μm) is added as a substrate, and the container containing the mixed solution is subjected to ultrasonic cleaning with water. It is placed in a water tank of a machine (US-6 type, manufactured by Iuchi Seieido Co., Ltd.), and ultrasonic waves of 36 kHz and 600 W are oscillated, and particles are dispersed for 10 minutes while stirring at 450 rpm.
[0041]
Next, a 10% by weight water glass (sodium silicate) aqueous solution prepared in advance is dropped into the stirring suspension at a dropping rate of 1.34 ml / min for 18 minutes with a microtube pump. After completion of the dropping, the ultrasonic wave oscillation and stirring are continued for another hour to carry out a silica film coating reaction.
After a predetermined time has elapsed, 300 ml of distilled water is added to this suspension to stop the reaction. The supernatant liquid after the reaction is removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated into liquid and dried at 110 ° C.
The powder obtained after drying gave a black powder 1A having a bottom near 500 nm.
[0042]
(Second layer: Titania film formation)
A buffer solution (pH: 5.4) prepared by mixing 50 ml of a 0.3 M acetic anhydride aqueous solution, 100 ml of a 0.9 M sodium acetate aqueous solution and 250 ml of pure water was prepared in advance. As in the case of the membrane, an ultrasonic wave of 36 kHz and 600 W is oscillated, and the particles are dispersed for 10 minutes while stirring at 550 rpm.
After the dispersion, a titanium sulfate aqueous solution (120 g / liter) is dropped with a microtube pump at a dropping rate of 0.5 ml / min. At the same time, water in the ultrasonic bath is heated at 100 ° C./hour, and this suspension is kept at 55 ° C. After dropping the titanium sulfate aqueous solution over 8 hours from the start of dropping, the reaction is allowed to proceed for 2 hours. After completion, 300 ml of distilled water is added to the suspension to stop the reaction.
[0043]
The supernatant liquid after the reaction is removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated into liquid and dried at 110 ° C.
The powder obtained after drying had a peak in the vicinity of 500 nm, a reflectance of 30%, and a blue-green powder 1B was obtained.
[0044]
(3rd layer: Silica film formation)
A buffer solution is prepared by mixing 250 ml of a mixed aqueous solution of 0.3 M potassium chloride and 0.3 M boric acid and 115 ml of a 0.4 M aqueous sodium hydroxide solution at room temperature.
In this buffer solution (pH: about 9.0), 5.0 g of powder 1B (average particle size 0.7 μm) is added, and the container containing the mixed solution is placed in an ultrasonic cleaner filled with water. It is put into a water tank (manufactured by Iuchi Seieido Co., Ltd., US-6 type), and ultrasonic waves of 36 kHz and 600 W are oscillated, and particles are dispersed for 10 minutes while stirring at 450 rpm.
Next, a 10% by weight water glass (sodium silicate) aqueous solution prepared in advance is dropped into the stirring suspension at a dropping rate of 1.34 ml / min for 18 minutes with a microtube pump. After completion of the dropping, the ultrasonic wave oscillation and stirring are continued for another hour to carry out a silica film coating reaction.
[0045]
After a predetermined time has elapsed, 300 ml of distilled water is added to this suspension to stop the reaction. The supernatant liquid after the reaction is removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated into liquid and dried at 110 ° C.
The powder obtained after drying gave powder 1C having a bottom near 530 nm.
[0046]
(Fourth layer: Titania film)
A buffer solution (pH: 5.4) prepared by mixing 50 ml of 0.3 M acetic anhydride aqueous solution, 100 ml of 0.9 M sodium acetate aqueous solution and 250 ml of pure water was prepared in advance. As in the case of the membrane, an ultrasonic wave of 36 kHz and 600 W is oscillated, and the particles are dispersed for 10 minutes while stirring at 550 rpm.
After the dispersion, a titanium sulfate aqueous solution (120 g / liter) is dropped with a microtube pump at a dropping rate of 0.55 ml / min. At the same time, water in the ultrasonic bath is heated at 100 ° C./hour, and this suspension is kept at 55 ° C. After dropping the titanium sulfate aqueous solution over 8 hours from the start of dropping, the reaction is allowed to proceed for 2 hours. After completion, 300 ml of distilled water is added to the suspension to stop the reaction.
[0047]
The supernatant liquid after the reaction is removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated into liquid and dried at 110 ° C.
The powder obtained after drying had a peak in the vicinity of 450 nm, had a reflectance of 43%, and obtained a bright cyan powder 1D.
[0048]
Example 3
(Heat treatment of 4-layer silica / titania coating powder)
When the four-layer film-coated powder produced under the same conditions as in Example 2 was heat-treated at 500 ° C. for 0.5 hour in a rotary tube furnace in a nitrogen atmosphere, the obtained powder had a peak at 403 nm and was reflected. The ratio was 47%, and a bright blue powder 2D was obtained.
[0049]
Example 4
(Silica / titania film coated powder, titanium chloride aqueous solution used)
(First layer: Silica film)
A buffer solution is prepared by mixing 250 ml of a mixed aqueous solution of 0.3 M potassium chloride and 0.3 M boric acid and 115 ml of a 0.4 M aqueous sodium hydroxide solution at room temperature.
In this buffer solution (pH: about 9.0), 5.0 g of magnetite powder (average particle size 0.7 μm) is added as a substrate, and the container containing the mixed solution is subjected to ultrasonic cleaning with water. It is placed in a water tank of a machine (US-6 type, manufactured by Iuchi Seieido Co., Ltd.), and ultrasonic waves of 36 kHz and 600 W are oscillated, and particles are dispersed for 10 minutes while stirring at 450 rpm.
[0050]
Next, a 10% by weight water glass (sodium silicate) aqueous solution prepared in advance is dropped into the stirring suspension at a dropping rate of 1.34 ml / min for 18 minutes with a microtube pump. After completion of the dropping, the ultrasonic wave oscillation and stirring are continued for another hour to carry out a silica film coating reaction.
After a predetermined time has elapsed, 300 ml of distilled water is added to this suspension to stop the reaction. The supernatant liquid after the reaction is removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated into liquid and dried at 110 ° C.
The powder obtained after drying gave a black powder 3A having a bottom near 500 nm.
[0051]
(Second layer: Titania film formation)
A buffer solution (pH: 5.4) prepared by mixing 50 ml of a 0.3 M acetic anhydride aqueous solution, 100 ml of a 0.9 M sodium acetate aqueous solution, and 160 ml of a 2.5 M sodium hydroxide aqueous solution and 500 ml of pure water is prepared in advance. After adding 4 g, as in the case of forming a silica film, an ultrasonic wave of 36 kHz and 600 W is oscillated, and the particles are dispersed for 10 minutes while stirring at 550 rpm.
After dispersion, the suspension is kept at 55 ° C. After warming dispersion, 40 g of titanium chloride aqueous solution (200 g / liter) is dropped with a microtube pump at a drop rate of 0.8 ml / min. After dropping, the reaction is allowed to proceed for 2 hours. After completion, 300 ml of distilled water is added to the suspension to stop the reaction.
[0052]
The supernatant liquid after the reaction is removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated into liquid and dried at 110 ° C.
After drying, the obtained powder was heat-treated at 500 ° C. for 0.5 hour in a charging rotary tube furnace in a nitrogen atmosphere, and after cooling, the powder had a peak at 450 nm and a reflectance of 35%. A bright cyan powder 3B was obtained.
[0053]
(3rd layer: Silica film formation)
A buffer solution is prepared by mixing 250 ml of a mixed aqueous solution of 0.3 M potassium chloride and 0.3 M boric acid and 115 ml of a 0.4 M aqueous sodium hydroxide solution at room temperature.
In this buffer solution (pH: about 9.0), powder 3B (average particle size 0.7 μm) g was added, and the container containing the mixed solution was placed in an ultrasonic cleaner (( The product is placed in a water tank manufactured by Iuchi Seieido Co., Ltd. (US-6 type), and ultrasonic waves of 36 kHz and 600 W are oscillated, and the particles are dispersed for 10 minutes while stirring at 450 rpm.
Next, a 10% by weight water glass (sodium silicate) aqueous solution prepared in advance is dropped into the stirring suspension at a dropping rate of 1.34 ml / min for 18 minutes with a microtube pump. After completion of the dropping, the ultrasonic wave oscillation and stirring are continued for another hour to carry out a silica film coating reaction.
[0054]
After a predetermined time has elapsed, 300 ml of distilled water is added to this suspension to stop the reaction. The supernatant liquid after the reaction is removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated into liquid and dried at 110 ° C.
The powder obtained after drying gave powder 3C having a bottom near 385 nm.
[0055]
(Fourth layer: Titania film)
A buffer solution (pH: 5.4) prepared by mixing 50 ml of a 0.3 M acetic anhydride aqueous solution, 100 ml of a 0.9 M sodium acetate aqueous solution and 250 ml of pure water was prepared in advance. As in the case of the membrane, an ultrasonic wave of 36 kHz and 600 W is oscillated, and the particles are dispersed for 10 minutes while stirring at 550 rpm. After dispersion, the suspension is kept at 55 ° C.
After warming dispersion, 40 g of titanium chloride aqueous solution (200 g / liter) is dropped with a microtube pump at a drop rate of 0.8 ml / min.
After completion of the dropwise addition, ultrasonic wave oscillation and stirring are continued for another 2 hours to perform a titania film coating reaction. After completion, 300 ml of distilled water is added to the suspension to stop the reaction.
[0056]
The supernatant liquid after the reaction has been removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated, and dried at 110 ° C.
After drying, the obtained powder was heat-treated at 500 ° C. for 0.5 hour in a charging type rotary tube furnace in a nitrogen atmosphere. After cooling, the powder had a peak at 410 nm, a reflectance of 47%, and a bright blue powder 3D was obtained.
[0057]
Example 5
(Silica / tin oxide coating powder)
(First layer: Silica film)
A buffer solution is prepared by mixing 250 ml of a mixed aqueous solution of 0.3 M potassium chloride and 0.3 M boric acid and 115 ml of a 0.4 M aqueous sodium hydroxide solution at room temperature.
In this buffer solution (pH: about 9.0), 5.0 g of magnetite powder (average particle size 0.7 μm) is charged as a substrate, and the container containing the mixed solution is subjected to ultrasonic cleaning with water. It is placed in a water tank of a machine (US-6 type, manufactured by Iuchi Seieido Co., Ltd.), and ultrasonic waves of 36 kHz and 600 W are oscillated, and particles are dispersed for 10 minutes while stirring at 450 rpm.
[0058]
Next, a 10% by weight water glass (sodium silicate) aqueous solution prepared in advance is dropped into the stirring suspension at a dropping rate of 1.34 ml / min with a microtube pump for 22 minutes. After completion of the dropwise addition, ultrasonic wave oscillation and stirring are continued for another hour to carry out a silica film coating reaction.
After a predetermined time has elapsed, 300 ml of distilled water is added to this suspension to stop the reaction. The supernatant liquid after the reaction has been removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated, and dried at 110 ° C.
After drying, the obtained powder was heat-treated at 300 ° C. for 30 minutes in a charging rotary tube furnace in a nitrogen atmosphere and cooled. As a powder, black powder 5A having a bottom at 480 nm was obtained.
[0059]
(Second layer: Film formation of tin oxide film)
A buffer solution (pH: 5.4) prepared by mixing 50 ml of a 0.3 M aqueous acetic anhydride solution, 100 ml of a 0.9 M aqueous sodium acetate solution and 160 ml of a 2.5 M aqueous sodium hydroxide solution and 500 ml of pure water is prepared in advance. After adding 16 g of particles, as in the case of forming a silica film, an ultrasonic wave of 36 kHz and 600 W is oscillated, and at the same time, the particles are dispersed for 10 minutes while stirring at 550 rpm.
After dispersion, the suspension is kept at 55 ° C. After heating and dispersing, 48 g of tin chloride aqueous solution (190 g / liter) is dropped with a microtube pump at a drop rate of 0.8 ml / min. After dropping, the reaction is allowed to proceed for 2 hours. After completion, 300 ml of distilled water is added to the suspension to stop the reaction.
[0060]
The supernatant liquid after the reaction has been removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated, and dried at 110 ° C.
After drying, the obtained powder was heat-treated at 300 ° C. for 30 minutes in a charging rotary tube furnace in a nitrogen atmosphere and cooled. The powder had a peak at 448 nm, had a reflectance of 32%, and obtained cyan powder 5B.
[0061]
(3rd layer: Silica film formation)
A buffer solution is prepared by mixing 250 ml of a mixed aqueous solution of 0.3 M potassium chloride and 0.3 M boric acid and 115 ml of a 0.4 M aqueous sodium hydroxide solution at room temperature.
In this buffer solution (pH: about 9.0), powder 5B (average particle size 0.7 μm) g was put, and the container containing the mixed solution was placed in an ultrasonic cleaner (( The product is placed in a water tank manufactured by Iuchi Seieido Co., Ltd. (US-6 type), and ultrasonic waves of 36 kHz and 600 W are oscillated, and the particles are dispersed for 10 minutes while stirring at 450 rpm.
Next, a 10% by weight aqueous solution of water glass (sodium silicate) prepared in advance is dropped into the stirring suspension at a dropping rate of 1.34 ml / min with a microtube pump for 26 minutes. After completion of the dropping, the ultrasonic wave oscillation and stirring are continued for another hour to carry out a silica film coating reaction.
[0062]
After a predetermined time has elapsed, 300 ml of distilled water is added to this suspension to stop the reaction. The supernatant liquid after the reaction has been removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated, and dried at 110 ° C.
After drying, the obtained powder was heat-treated at 300 ° C. for 30 minutes in a charging rotary tube furnace in a nitrogen atmosphere and cooled. As a powder, a powder 5C having a bottom near 550 nm was obtained.
[0063]
(Fourth layer: Tin oxide film formation)
A buffer solution (pH: 5.4) prepared by mixing 50 ml of 0.3 M acetic anhydride aqueous solution, 100 ml of 0.9 M sodium acetate aqueous solution and 160 ml of 2.5 M sodium hydroxide aqueous solution and 250 ml of pure water was prepared in advance. After adding 16 g of particles, as in the case of forming a silica film, an ultrasonic wave of 36 kHz and 600 W is oscillated, and at the same time, the particles are dispersed for 10 minutes while stirring at 550 rpm. After dispersion, the suspension is kept at 55 ° C.
After heating and dispersing, 52 g of an aqueous tin chloride solution (190 g / liter) is dropped with a microtube pump at a drop rate of 0.8 ml / min.
After completion of the dropwise addition, ultrasonic wave oscillation and stirring are continued for another 2 hours to perform a titania film coating reaction. After completion, 300 ml of distilled water is added to the suspension to stop the reaction.
[0064]
The supernatant liquid after the reaction has been removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated, and dried at 110 ° C.
After drying, the obtained powder was heat-treated at 650 ° C. for 30 minutes in a nitrogen type charging rotary tube furnace and cooled. The powder had a peak at 580 nm and a reflectivity of 44%, and a yellow powder 5D was obtained.
[0065]
(5th layer: Silica film)
A buffer solution is prepared by mixing 250 ml of a mixed aqueous solution of 0.3 M potassium chloride and 0.3 M boric acid and 115 ml of a 0.4 M aqueous sodium hydroxide solution at room temperature.
In this buffer solution (pH: about 9.0), powder 5D (average particle size 0.7 μm) g was added, and the container containing the mixed solution was placed in an ultrasonic cleaner (( The product is placed in a water tank manufactured by Iuchi Seieido Co., Ltd. (US-6 type), and ultrasonic waves of 36 kHz and 600 W are oscillated, and the particles are dispersed for 10 minutes while stirring at 450 rpm.
Next, a 10% by weight aqueous solution of water glass (sodium silicate) prepared in advance is dropped into the stirring suspension at a dropping rate of 1.34 ml / min with a microtube pump for 28 minutes. After completion of the dropping, the ultrasonic wave oscillation and stirring are continued for another hour to carry out a silica film coating reaction.
[0066]
After a predetermined time has elapsed, 300 ml of distilled water is added to this suspension to stop the reaction. The supernatant liquid after the reaction has been removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated, and dried at 110 ° C.
After drying, the obtained powder was heat-treated at 300 ° C. for 30 minutes in a charging rotary tube furnace in a nitrogen atmosphere and cooled. As a powder, a powder 5E having a bottom near 550 nm was obtained.
[0067]
(Sixth layer: Film formation of tin oxide film)
A buffer solution (pH: 5.4) prepared by mixing 50 ml of a 0.3 M aqueous acetic anhydride solution, 100 ml of a 0.9 M aqueous sodium acetate solution, 160 ml of a 2.5 M aqueous sodium hydroxide solution and 250 ml of pure water is prepared in advance. After adding 16 g of particles, as in the case of forming a silica film, an ultrasonic wave of 36 kHz and 600 W is oscillated, and at the same time, the particles are dispersed for 10 minutes while stirring at 550 rpm. After dispersion, the suspension is kept at 55 ° C.
After warming dispersion, 55 g of tin chloride aqueous solution (190 g / liter) is dropped with a microtube pump at a drop rate of 0.8 ml / min.
After completion of the dropwise addition, ultrasonic wave oscillation and stirring are continued for another 2 hours to perform a titania film coating reaction. After completion, 300 ml of distilled water is added to the suspension to stop the reaction.
[0068]
The supernatant liquid after the reaction has been removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated, and dried at 110 ° C.
After drying, the obtained powder was heat-treated at 650 ° C. for 30 minutes in a nitrogen type charging rotary tube furnace and cooled. The powder had a peak at 480 nm, had a reflectance of 53%, and obtained a blue powder 5F.
[0069]
Example 6
(Silica / titanium oxide film-coated powder, improved reflectivity by in-film crystallization)
(First layer: Silica film)
A buffer solution is prepared by mixing 250 ml of a mixed aqueous solution of 0.3 M potassium chloride and 0.3 M boric acid and 115 ml of a 0.4 M aqueous sodium hydroxide solution at room temperature.
In this buffer solution (pH: about 9.0), 5.0 g of magnetite powder (average particle size 0.7 μm) is added as a substrate, and the container containing the mixed solution is subjected to ultrasonic cleaning with water. It is placed in a water tank of a machine (US-6 type, manufactured by Iuchi Seieido Co., Ltd.), and ultrasonic waves of 36 kHz and 600 W are oscillated, and particles are dispersed for 10 minutes while stirring at 450 rpm.
Next, a 10% by weight water glass (sodium silicate) aqueous solution prepared in advance is dropped into the stirring suspension at a dropping rate of 1.34 ml / min with a microtube pump for 22 minutes. After completion of the dropping, the ultrasonic wave oscillation and stirring are continued for another hour to carry out a silica film coating reaction.
[0070]
After a predetermined time has elapsed, 300 ml of distilled water is added to this suspension to stop the reaction. The supernatant liquid after the reaction has been removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated, and dried at 110 ° C.
After drying, the obtained powder was heat-treated at 300 ° C. for 30 minutes in a charging rotary tube furnace in a nitrogen atmosphere and cooled. As a powder, black powder 6A having a bottom at 480 nm was obtained.
[0071]
(Second layer: Titanium oxide film)
A buffer solution (pH: 5.4) prepared by mixing 50 ml of 0.3 M acetic anhydride aqueous solution, 100 ml of 0.9 M sodium acetate aqueous solution and 160 ml of 2.5 M sodium hydroxide aqueous solution and 500 ml of pure water was prepared in advance. After adding 16 g of particles, as in the case of forming a silica film, an ultrasonic wave of 36 kHz and 600 W is oscillated, and at the same time, the particles are dispersed for 10 minutes while stirring at 550 rpm.
After dispersion, the suspension is kept at 55 ° C. After warming dispersion, 43 g of titanium sulfate aqueous solution (200 g / liter) is dropped with a microtube pump at a drop rate of 0.8 ml / min. After dropping, the reaction is allowed to proceed for 2 hours. After completion, 300 ml of distilled water is added to the suspension to stop the reaction.
[0072]
The supernatant liquid after the reaction has been removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated, and dried at 110 ° C.
After drying, the obtained powder was heat treated at 650 ° C. for 2 hours in a charging type rotary tube furnace in a nitrogen atmosphere and cooled. The powder had a peak at 548 nm, had a reflectance of 43%, and green powder 6B was obtained.
[0073]
(3rd layer: Silica film formation)
A buffer solution is prepared by mixing 250 ml of a mixed aqueous solution of 0.3 M potassium chloride and 0.3 M boric acid and 115 ml of a 0.4 M aqueous sodium hydroxide solution at room temperature.
In this buffer solution (pH: about 9.0), powder 6B (average particle size 0.7 μm) g was added, and the container containing the mixed solution was placed in an ultrasonic cleaner (( The product is placed in a water tank manufactured by Iuchi Seieido Co., Ltd. (US-6 type), and ultrasonic waves of 36 kHz and 600 W are oscillated, and the particles are dispersed for 10 minutes while stirring at 450 rpm.
Next, a 10% by weight aqueous solution of water glass (sodium silicate) prepared in advance is dropped into the stirring suspension at a dropping rate of 1.34 ml / min with a microtube pump for 26 minutes. After completion of the dropping, the ultrasonic wave oscillation and stirring are continued for another hour to carry out a silica film coating reaction.
[0074]
After a predetermined time has elapsed, 300 ml of distilled water is added to this suspension to stop the reaction. The supernatant liquid after the reaction has been removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated, and dried at 110 ° C.
After drying, the obtained powder was heat-treated at 300 ° C. for 30 minutes in a charging rotary tube furnace in a nitrogen atmosphere and cooled. As a powder, a powder 6C having a bottom near 480 nm was obtained.
[0075]
(Fourth layer: Titanium oxide film)
A buffer solution (pH: 5.4) prepared by mixing 50 ml of 0.3 M acetic anhydride aqueous solution, 100 ml of 0.9 M sodium acetate aqueous solution, 160 ml of 2.5 M sodium hydroxide aqueous solution and 250 ml of pure water was prepared in advance. After adding 16 g of particles, as in the case of forming a silica film, an ultrasonic wave of 36 kHz and 600 W is oscillated, and at the same time, the particles are dispersed for 10 minutes while stirring at 550 rpm. After dispersion, the suspension is kept at 55 ° C.
After warming dispersion, 43 g of titanium sulfate aqueous solution (200 g / liter) is dropped with a microtube pump at a drop rate of 0.8 ml / min.
After completion of the dropwise addition, ultrasonic wave oscillation and stirring are continued for another 2 hours to perform a titania film coating reaction. After completion, 300 ml of distilled water is added to the suspension to stop the reaction.
[0076]
The supernatant liquid after the reaction has been removed is removed, 360 ml of pure water is added, and the mixture is washed and stirred at 400 rpm for 5 minutes. In addition, it wash | cleans to about pH 7 by repeating this operation and performing washing | cleaning operation.
After completion of the washing operation, the product is transferred to a vat, the solid content is allowed to settle, the supernatant is removed, the solid is separated, and dried at 110 ° C.
After drying, the obtained powder was heat treated at 650 ° C. for 2 hours in a charging type rotary tube furnace in a nitrogen atmosphere and cooled. The powder had a peak at 588 nm, had a reflectance of 62%, and obtained a lemon yellow powder 6D.
This is presumably because the proportion of titanium oxide crystallized into rutile (titanium oxide with a high refractive index) increased by increasing the heat treatment time.
[0077]
【The invention's effect】
As described above, the present invention uses an aqueous solvent having a constant pH as a film-forming reaction solvent, and at the same time performs a film coating reaction under an ultrasonic dispersion condition, so that even when a magnetic material is used as a substrate. It is possible to easily manufacture a film-coated powder capable of controlling the preferred film thickness without causing the film-coated powders to agglomerate or adhere to each other and to precipitate only the solid phase in the liquid phase. I was able to.
In addition, without using expensive metal alkoxides or highly flammable organic solvents, water is used as a solvent, manufacturing facilities do not require explosion-proof equipment, and temperature and humidity are easily controlled. There is an effect of providing a highly functional film-coated powder and a method for producing the same that can be obtained at a low price.
Claims (9)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30728398A JP3725712B2 (en) | 1998-10-28 | 1998-10-28 | Method for producing film-coated powder |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30728398A JP3725712B2 (en) | 1998-10-28 | 1998-10-28 | Method for producing film-coated powder |
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| JP3725712B2 true JP3725712B2 (en) | 2005-12-14 |
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| JP3565421B2 (en) * | 1999-04-13 | 2004-09-15 | 日鉄鉱業株式会社 | White powder and method for producing the same |
| JP4684549B2 (en) * | 2003-12-10 | 2011-05-18 | Ｎｅｃトーキン株式会社 | Ferrite coated particulate manufacturing equipment |
| CN105121070B (en) * | 2013-04-17 | 2018-01-02 | 株式会社村田制作所 | Composite oxides coated metal powder, its manufacture method, conductive paste and monolithic ceramic electronic component using composite oxides coated metal powder |
| JP7109222B2 (en) * | 2018-03-27 | 2022-07-29 | Ｊｘ金属株式会社 | Coated metal powder, method for producing the same, and laminate-molded article using the metal powder |
| JP7454425B2 (en) * | 2019-05-24 | 2024-03-22 | 日鉄鉱業株式会社 | Method for producing cobalt ferrite particles and cobalt ferrite particles produced thereby |
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