JP4801617B2 - Conductive zinc oxide particles and method for producing the same - Google Patents
Conductive zinc oxide particles and method for producing the same Download PDFInfo
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- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 title claims description 172
- 239000002245 particle Substances 0.000 title claims description 89
- 239000011787 zinc oxide Substances 0.000 title claims description 80
- 238000004519 manufacturing process Methods 0.000 title claims description 18
- 239000007864 aqueous solution Substances 0.000 claims description 51
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 30
- 229910052799 carbon Inorganic materials 0.000 claims description 30
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 18
- 238000006243 chemical reaction Methods 0.000 claims description 17
- 239000000243 solution Substances 0.000 claims description 17
- 238000000034 method Methods 0.000 claims description 12
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 11
- 229910000288 alkali metal carbonate Inorganic materials 0.000 claims description 10
- 150000008041 alkali metal carbonates Chemical class 0.000 claims description 10
- 229910052751 metal Inorganic materials 0.000 claims description 9
- 150000003751 zinc Chemical class 0.000 claims description 9
- 150000003752 zinc compounds Chemical class 0.000 claims description 9
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical compound [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 claims description 8
- 238000010304 firing Methods 0.000 claims description 7
- 239000002184 metal Substances 0.000 claims description 7
- 239000011701 zinc Substances 0.000 claims description 6
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 5
- 229910052725 zinc Inorganic materials 0.000 claims description 5
- 239000011592 zinc chloride Substances 0.000 claims description 4
- 235000005074 zinc chloride Nutrition 0.000 claims description 4
- ONDPHDOFVYQSGI-UHFFFAOYSA-N zinc nitrate Chemical compound [Zn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ONDPHDOFVYQSGI-UHFFFAOYSA-N 0.000 claims description 4
- 150000002484 inorganic compounds Chemical class 0.000 claims description 3
- 229910010272 inorganic material Inorganic materials 0.000 claims description 3
- 230000001590 oxidative effect Effects 0.000 claims description 2
- NWONKYPBYAMBJT-UHFFFAOYSA-L zinc sulfate Chemical compound [Zn+2].[O-]S([O-])(=O)=O NWONKYPBYAMBJT-UHFFFAOYSA-L 0.000 claims description 2
- 229960001763 zinc sulfate Drugs 0.000 claims description 2
- 229910000368 zinc sulfate Inorganic materials 0.000 claims description 2
- 239000002244 precipitate Substances 0.000 description 22
- 239000010408 film Substances 0.000 description 21
- 239000007788 liquid Substances 0.000 description 14
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 12
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 10
- 239000011248 coating agent Substances 0.000 description 10
- 238000000576 coating method Methods 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 9
- 239000011164 primary particle Substances 0.000 description 9
- 238000005406 washing Methods 0.000 description 8
- 238000009826 distribution Methods 0.000 description 7
- 238000002156 mixing Methods 0.000 description 7
- 239000000047 product Substances 0.000 description 7
- 239000000428 dust Substances 0.000 description 6
- 239000000843 powder Substances 0.000 description 6
- 229910000029 sodium carbonate Inorganic materials 0.000 description 5
- 235000017550 sodium carbonate Nutrition 0.000 description 5
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 238000004220 aggregation Methods 0.000 description 3
- 230000002776 aggregation Effects 0.000 description 3
- 239000011324 bead Substances 0.000 description 3
- 125000004432 carbon atom Chemical group C* 0.000 description 3
- 230000004927 fusion Effects 0.000 description 3
- -1 hydroxide ions Chemical class 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 238000005245 sintering Methods 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000010409 thin film Substances 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000007561 laser diffraction method Methods 0.000 description 2
- 239000003973 paint Substances 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- UOURRHZRLGCVDA-UHFFFAOYSA-D pentazinc;dicarbonate;hexahydroxide Chemical compound [OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[Zn+2].[Zn+2].[Zn+2].[Zn+2].[Zn+2].[O-]C([O-])=O.[O-]C([O-])=O UOURRHZRLGCVDA-UHFFFAOYSA-D 0.000 description 2
- 229910000027 potassium carbonate Inorganic materials 0.000 description 2
- 235000011181 potassium carbonates Nutrition 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 230000005070 ripening Effects 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 239000004925 Acrylic resin Substances 0.000 description 1
- 229920000178 Acrylic resin Polymers 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 229920000297 Rayon Polymers 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- PTFCDOFLOPIGGS-UHFFFAOYSA-N Zinc dication Chemical compound [Zn+2] PTFCDOFLOPIGGS-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000012295 chemical reaction liquid Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000002537 cosmetic Substances 0.000 description 1
- 239000002019 doping agent Substances 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000003112 inhibitor Substances 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- YWXYYJSYQOXTPL-SLPGGIOYSA-N isosorbide mononitrate Chemical compound [O-][N+](=O)O[C@@H]1CO[C@@H]2[C@@H](O)CO[C@@H]21 YWXYYJSYQOXTPL-SLPGGIOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 239000011736 potassium bicarbonate Substances 0.000 description 1
- 235000015497 potassium bicarbonate Nutrition 0.000 description 1
- 229910000028 potassium bicarbonate Inorganic materials 0.000 description 1
- TYJJADVDDVDEDZ-UHFFFAOYSA-M potassium hydrogencarbonate Chemical compound [K+].OC([O-])=O TYJJADVDDVDEDZ-UHFFFAOYSA-M 0.000 description 1
- 229940086066 potassium hydrogencarbonate Drugs 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
- 239000002964 rayon Substances 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 1
- 235000017557 sodium bicarbonate Nutrition 0.000 description 1
- GCLGEJMYGQKIIW-UHFFFAOYSA-H sodium hexametaphosphate Chemical compound [Na]OP1(=O)OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])O1 GCLGEJMYGQKIIW-UHFFFAOYSA-H 0.000 description 1
- 235000019982 sodium hexametaphosphate Nutrition 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 238000001132 ultrasonic dispersion Methods 0.000 description 1
- 229910000010 zinc carbonate Inorganic materials 0.000 description 1
- UGZADUVQMDAIAO-UHFFFAOYSA-L zinc hydroxide Chemical compound [OH-].[OH-].[Zn+2] UGZADUVQMDAIAO-UHFFFAOYSA-L 0.000 description 1
- 229910021511 zinc hydroxide Inorganic materials 0.000 description 1
- 229940007718 zinc hydroxide Drugs 0.000 description 1
Landscapes
- Inorganic Compounds Of Heavy Metals (AREA)
- Conductive Materials (AREA)
Description
本発明は、透明性に優れ且つ低抵抗の導電膜を得ることができる導電性酸化亜鉛粒子及びそれを製造するための方法に関する。 The present invention relates to conductive zinc oxide particles that can provide a conductive film having excellent transparency and low resistance, and a method for producing the same.
導電性酸化亜鉛は、樹脂、塗料、フィルム、繊維等に配合されて帯電防止のために用いられている。また導電性酸化亜鉛から形成される薄膜はその透明性の故に、透明電極として用いられる。導電性酸化亜鉛から形成される薄膜の導電性を高めることを目的として、酸化亜鉛に各種ドーパントを添加することが提案されている。例えば特許文献１には正三価以上の原子価を有する元素を含有する酸化亜鉛系透明導電性膜において、該元素としてアルミニウム、チタン又はクロムを用いることが提案されている。また特許文献２には、IIIB族元素、IVB族元素及びＦｅよりなる群から選択される少なくとも一種の元素が固溶した導電性酸化亜鉛粉末が提案されている。 Conductive zinc oxide is blended in resins, paints, films, fibers and the like and used for antistatic purposes. A thin film formed from conductive zinc oxide is used as a transparent electrode because of its transparency. For the purpose of increasing the conductivity of a thin film formed from conductive zinc oxide, it has been proposed to add various dopants to zinc oxide. For example, Patent Document 1 proposes to use aluminum, titanium, or chromium as the element in a zinc oxide-based transparent conductive film containing an element having a positive trivalent or higher valence. Patent Document 2 proposes a conductive zinc oxide powder in which at least one element selected from the group consisting of IIIB group elements, IVB group elements and Fe is dissolved.
前記の特許文献２においては、導電性酸化亜鉛粉末の製造方法として、（１）酸化亜鉛の水性スラリーに炭酸アルカリ塩を反応させて塩基性炭酸亜鉛を得る工程、（２）該塩基性炭酸亜鉛を加熱熟成する工程、（３）得られる熟成液に、IIIB族元素、IVB族元素及びＦｅよりなる群から選択される少なくとも一種の元素の水溶性塩を混合して再熟成する工程、（４）該熟成物を脱水し乾燥させる工程、（５）得られた乾燥物を焼成する工程、（６）該焼成物を解砕する工程からなる方法が提案されている。しかし、この方法で得られた酸化亜鉛粉末を始めとして、従来提案されている導電性酸化亜鉛粉末から形成される薄膜は、高い透明性と低い電気抵抗を十分に両立するものではなかった。 In the above-mentioned Patent Document 2, as a method for producing a conductive zinc oxide powder, (1) a step of reacting an alkali carbonate with an aqueous zinc oxide slurry to obtain basic zinc carbonate, (2) the basic zinc carbonate (3) a step of mixing the obtained ripening solution with a water-soluble salt of at least one element selected from the group consisting of Group IIIB elements, Group IVB elements and Fe, and ripening the mixture (4) A method comprising a step of dehydrating and drying the aged product, (5) a step of firing the obtained dried product, and (6) a step of crushing the fired product is proposed. However, the thin films formed from the conventionally proposed conductive zinc oxide powders including the zinc oxide powder obtained by this method have not sufficiently achieved both high transparency and low electrical resistance.
これらの先行技術とは別に、一次粒子が面状に集合した酸化亜鉛を含有するメーキャップ化粧料用の紫外線遮蔽用組成物が知られている（特許文献３参照）。この酸化亜鉛は、炭酸ナトリウム及び水酸化ナトリウムを含むアルカリ調整液と塩化亜鉛水溶液とを混合し、得られた沈殿物を水洗濾過した後に４００℃で焼成することで製造される。この製造においては、沈殿物の水洗濾過が３回行われるので、水洗後の沈殿物には炭酸イオンやナトリウムイオン等はほとんど残留していないと考えられる。このようして得られた酸化亜鉛は面状のものなので、透明性を高めることが容易でない。したがってこの酸化亜鉛は、透明導電性膜の原料としてふさわしいものとは言えない。 Apart from these prior arts, an ultraviolet shielding composition for makeup cosmetics containing zinc oxide in which primary particles are assembled in a planar shape is known (see Patent Document 3). This zinc oxide is produced by mixing an alkali adjusting solution containing sodium carbonate and sodium hydroxide and an aqueous zinc chloride solution, washing the resulting precipitate with water, filtering and firing it at 400 ° C. In this production, since the precipitate is washed and filtered three times, it is considered that almost no carbonate ions, sodium ions, etc. remain in the precipitate after washing with water. Since the zinc oxide thus obtained is planar, it is not easy to increase transparency. Therefore, it cannot be said that this zinc oxide is suitable as a raw material for the transparent conductive film.
したがって本発明の目的は、前述した従来技術が有する欠点を解消し得る導電性酸化亜鉛粒子及びその製造方法を提供することにある。 Accordingly, an object of the present invention is to provide conductive zinc oxide particles and a method for producing the same, which can eliminate the disadvantages of the above-described prior art.
本発明は、無機化合物の状態の炭素を含み、炭素の含有量が０．０５〜０．５重量％であることを特徴とする導電性酸化亜鉛粒子を提供するものである。 The present invention provides conductive zinc oxide particles comprising carbon in the form of an inorganic compound and having a carbon content of 0.05 to 0.5% by weight.
また本発明は、水溶性亜鉛塩を含む第１の水溶液と、水溶性炭酸塩を含む第２の水溶液とを混合して難溶性の亜鉛化合物を生成させ、次いで反応液の導電率が３００〜７００μＳに低下するまで該反応液を水洗した後に、該亜鉛化合物を乾燥させ焼成を行うことを特徴とする導電性酸化亜鉛粒子の製造方法を提供するものである。 In the present invention, a first aqueous solution containing a water-soluble zinc salt and a second aqueous solution containing a water-soluble carbonate are mixed to form a poorly soluble zinc compound, and then the conductivity of the reaction solution is 300 to 300. The present invention provides a method for producing conductive zinc oxide particles, characterized in that the reaction mixture is washed with water until reduced to 700 μS, and then the zinc compound is dried and fired.
本発明の導電性酸化亜鉛粒子によれば、高い透明性と低い電気抵抗を有する導電性透明膜を形成することができる。また本発明の製造方法によれば、該導電性酸化亜鉛粒子を容易に得ることができる。 According to the conductive zinc oxide particles of the present invention, a conductive transparent film having high transparency and low electrical resistance can be formed. Moreover, according to the manufacturing method of this invention, this electroconductive zinc oxide particle can be obtained easily.
以下本発明を、その好ましい実施形態に基づき説明する。本発明の導電性酸化亜鉛粒子（以下、単に酸化亜鉛粒子ともいう）は、炭素を含んでいることによって特徴付けられる。「炭素を含む」とは酸化亜鉛粒子中に、炭素が何らかの形態（例えば炭素を含む化合物や原子団の形態）で含有されていることを言う。後述する製造方法に鑑みると、炭素は無機化合物の状態で酸化亜鉛粒子中に存在していると考えられる。換言すれば、炭素原子は、少なくとも炭素原子どうし及び／又は炭素原子と水素原子が結合してなる有機化合物の状態では存在していないと考えられる。本発明の導電性酸化亜鉛粒子が炭素を含み、その量が酸化亜鉛粒子全体に対して０．０５〜０．５重量％、好ましくは０．０８〜０．３重量％、更に好ましくは０．０８〜０．２重量％であることによって、本発明の酸化亜鉛粒子を用いて形成された導電性透明膜は、高い透明性と低い電気抵抗を有するものとなる。 Hereinafter, the present invention will be described based on preferred embodiments thereof. The conductive zinc oxide particles of the present invention (hereinafter also simply referred to as zinc oxide particles) are characterized by containing carbon. “Containing carbon” means that the zinc oxide particles contain carbon in some form (for example, a compound containing carbon or an atomic group). In view of the production method described later, it is considered that carbon is present in the zinc oxide particles in an inorganic compound state. In other words, it is considered that carbon atoms do not exist at least in the state of an organic compound formed by bonding carbon atoms and / or carbon atoms and hydrogen atoms. The conductive zinc oxide particles of the present invention contain carbon, and the amount thereof is 0.05 to 0.5% by weight, preferably 0.08 to 0.3% by weight, more preferably 0.8%, based on the entire zinc oxide particles. By being 08 to 0.2% by weight, the conductive transparent film formed using the zinc oxide particles of the present invention has high transparency and low electrical resistance.
前記のとおり、本発明の酸化亜鉛粒子に含まれる炭素は極めて微量であるため、炭素がどのような形態で酸化亜鉛粒子中に含有されているのか同定することは困難である。したがって、炭素のどのような作用によって前記の効果が奏されるのかは明確ではない。しかし酸化亜鉛粒子中に含有される炭素の量が０．０５重量％未満の場合には、透明性向上に寄与する炭素の量が不足してしまい、低電気抵抗を維持しつつ高い透明性を達成することができない。同様に、炭素の量が０．５重量％を超えると過剰の炭素が透明性を妨害し、やはり低電気抵抗を維持しつつ高い透明性を達成することができない。 As described above, since the amount of carbon contained in the zinc oxide particles of the present invention is extremely small, it is difficult to identify in what form carbon is contained in the zinc oxide particles. Therefore, it is not clear what kind of action of carbon exerts the above effect. However, when the amount of carbon contained in the zinc oxide particles is less than 0.05% by weight, the amount of carbon that contributes to transparency improvement is insufficient, and high transparency is maintained while maintaining low electrical resistance. Cannot be achieved. Similarly, if the amount of carbon exceeds 0.5% by weight, excess carbon interferes with transparency, and high transparency cannot be achieved while still maintaining low electrical resistance.
本発明において、酸化亜鉛粒子に含まれる炭素の量は、堀場製作所製の炭素・硫黄分析装置ＥＭＩＡ−３２０Ｖ（商品名）によって測定される。 In the present invention, the amount of carbon contained in the zinc oxide particles is measured by a carbon / sulfur analyzer EMIA-320V (trade name) manufactured by Horiba.
上述のとおり本発明の酸化亜鉛粒子は、所定量の炭素を含むことで上述の効果を奏するものである。これに対して従来の酸化亜鉛粒子は、種々の金属元素をドープさせることで、高い透明性と低い電気抵抗を有する導電性透明膜の形成を図っている。しかし、従来用いられている金属元素のなかには環境負荷の高い重金属元素も含まれることから、その使用は避けられがちである。これに対して本発明の酸化亜鉛粒子は金属元素がドープされていなくても、金属元素がドープされた酸化亜鉛粒子よりも優れたものとなる。このことは、環境負荷の軽減の点から極めて有利である。また、金属元素がドープされていないことで、酸化亜鉛粒子の色相のバランスが良好になるという利点もある。 As described above, the zinc oxide particles of the present invention exhibit the above-described effects by containing a predetermined amount of carbon. In contrast, conventional zinc oxide particles are doped with various metal elements to form a conductive transparent film having high transparency and low electrical resistance. However, heavy metal elements having a high environmental load are included in the conventionally used metal elements, and their use tends to be avoided. On the other hand, the zinc oxide particles of the present invention are superior to the zinc oxide particles doped with a metal element even if the metal element is not doped. This is extremely advantageous from the viewpoint of reducing the environmental load. Further, since the metal element is not doped, there is also an advantage that the hue balance of the zinc oxide particles becomes good.
炭素を含む本発明の酸化亜鉛粒子は、従来の酸化亜鉛粒子と比較して、その外観が大きく異なる点にも特徴の一つ有している。具体的には、従来の酸化亜鉛粒子は白色のものであるのに対し、本発明の酸化亜鉛粒子は黄色味を帯びたものである。このような外観の違いは、本発明の酸化亜鉛粒子が炭素を含んでいることに起因していると考えられる。本発明の酸化亜鉛粒子が呈する色を、Ｌ＊ａ＊ｂ＊系表色系色座標（光源：Ｄ６５、視野角：１０°）で表すと、Ｌ値が９５〜９９、特に９６〜９８であり、ａ値が−６．０〜０、特に−５〜−４であり、ｂ値が１０〜１５、特に１２〜１５であることが好ましい。 One feature of the zinc oxide particles of the present invention containing carbon is that the appearance of the zinc oxide particles is significantly different from that of conventional zinc oxide particles. Specifically, the conventional zinc oxide particles are white, whereas the zinc oxide particles of the present invention are yellowish. Such a difference in appearance is considered to be caused by the fact that the zinc oxide particles of the present invention contain carbon. When the color exhibited by the zinc oxide particles of the present invention is represented by L * a * b * color system color coordinates (light source: D65, viewing angle: 10 °), the L value is 95 to 99, particularly 96 to 98. Yes, it is preferable that a value is -6.0-0, especially -5-5, and b value is 10-15, especially 12-15.
本発明の酸化亜鉛粒子は、従来の酸化亜鉛粒子と比較して比表面積が大きい点にも特徴の一つを有している。具体的には、比表面積が好ましくは２０〜４０ｍ2／ｇ、更に好ましくは２５〜３５ｍ2／ｇという大きな値になっている。本発明の酸化亜鉛粒子がこのような大きな比表面積を有する理由については明確ではないが、本発明者らはその理由を次のように推測している。後述する製造方法によって生ずる中間生成物である亜鉛化合物の沈殿物中には炭素が含まれている。該沈殿物はこれを焼成することで酸化亜鉛粒子が得られる。この焼成中に、該沈殿物中に含まれる炭素が焼結防止剤として作用することで、粒子同士の融着の進行が妨げられ、酸化亜鉛粒子の粒径が過度に大きくなることが防止され、それによって比表面積も大きくなると推測される。 The zinc oxide particles of the present invention are also characterized by a large specific surface area compared to conventional zinc oxide particles. Specifically, the specific surface area of preferably 20 to 40 m 2 / g, more preferably has a large value of 25~35m 2 / g. Although the reason why the zinc oxide particles of the present invention have such a large specific surface area is not clear, the present inventors presume the reason as follows. Carbon is contained in the precipitate of the zinc compound, which is an intermediate product produced by the production method described later. The precipitate is fired to obtain zinc oxide particles. During this firing, the carbon contained in the precipitate acts as an anti-sintering agent, preventing the fusion of particles from progressing and preventing the zinc oxide particles from becoming excessively large in particle size. Therefore, it is presumed that the specific surface area is also increased.
前記の焼結中に粒子どうしの融着の進行が妨げられることに起因して、本発明の酸化亜鉛粒子は、その一次粒子の粒径が小さなものとなる。具体的には、顕微鏡観察によって測定される一次粒子の平均粒径が好ましくは５〜１００ｎｍ、更に好ましくは１０〜５０ｎｍという小粒径のものとなる。酸化亜鉛粒子の粒径が小さいことに起因して、該粒子を原料としてインクを調製すると、該粒子の分散性が良好になる。その結果、このインクを用いて導電膜を形成すると該導電膜の透明性が極めて高くなるという有利な効果が奏される。一次粒子の平均粒径は、透過型電子顕微鏡によって倍率３万倍で撮影された粒子の写真を用い、個々の粒子のうち最も長い部分の長さを測定し、その平均値を算出することで求められる。測定に用いられるサンプル数はＮ＝５０以上とする。 The zinc oxide particles of the present invention have a small primary particle size due to the fact that the progress of fusion between the particles is prevented during the sintering. Specifically, the average particle diameter of primary particles measured by microscopic observation is preferably 5 to 100 nm, more preferably 10 to 50 nm. Due to the small particle size of the zinc oxide particles, when an ink is prepared using the particles as a raw material, the dispersibility of the particles is improved. As a result, when a conductive film is formed using this ink, there is an advantageous effect that the transparency of the conductive film becomes extremely high. The average particle size of primary particles is obtained by measuring the length of the longest part of individual particles using a photograph of particles taken at a magnification of 30,000 with a transmission electron microscope and calculating the average value. Desired. The number of samples used for measurement is N = 50 or more.
本発明の酸化亜鉛粒子は、その一次粒子の形状に特に制限はなく、球状や針状、板状等、或いは不定形であり得る。一次粒子の形状は、後述する製造条件によって適宜調整可能である。 The shape of the primary particles of the zinc oxide particles of the present invention is not particularly limited, and may be spherical, needle-like, plate-like, or irregular. The shape of the primary particles can be appropriately adjusted according to the production conditions described later.
上述の一次粒子の粒径と関係するが、本発明の酸化亜鉛粒子はレーザー回折法により測定された粒度分布がシャープなものである。具体的には、レーザー回折法により測定された粒度分布におけるＤ50値が好ましくは０．５〜３．０μｍ、更に好ましくは１．０〜２．０μｍであり、Ｄ90値が好ましくは２．０〜４．０μｍ、更に好ましくは２．０〜３．０μｍである。 Although related to the particle size of the primary particles described above, the zinc oxide particles of the present invention have a sharp particle size distribution measured by a laser diffraction method. Specifically, the D 50 value in the particle size distribution measured by the laser diffraction method is preferably 0.5 to 3.0 μm, more preferably 1.0 to 2.0 μm, and the D 90 value is preferably 2. It is 0-4.0 micrometers, More preferably, it is 2.0-3.0 micrometers.
本発明の酸化亜鉛粒子は導電性を有するものである。導電性の程度は、圧粉抵抗値で表して好ましくは１．０×１０5〜１．０×１０9Ω・ｃｍ、更に好ましくは１．０×１０5〜１．０×１０7Ω・ｃｍである。この範囲の圧粉抵抗値は、酸化亜鉛粒子から導電膜を形成するのに十分に低い値である。圧粉抵抗値の測定方法は、後述する実施例において説明する。 The zinc oxide particles of the present invention are conductive. The degree of conductivity is preferably 1.0 × 10 5 to 1.0 × 10 9 Ω · cm, and more preferably 1.0 × 10 5 to 1.0 × 10 7 Ω · cm, expressed as a dust resistance value. cm. The dust resistance value in this range is sufficiently low to form a conductive film from zinc oxide particles. The measuring method of the dust resistance value will be described in the examples described later.
次に、本発明の酸化亜鉛粒子の好ましい製造方法について説明する。本製造方法は、以下の（イ）ないし（ハ）の工程に大別される。
（イ）水溶性亜鉛塩を含む第１の水溶液と、水溶性炭酸塩を含む第２の水溶液とを混合して難溶性の亜鉛化合物を生成させる。
（ロ）反応液の導電率が３００〜７００μＳ（マイクロジーメンス）になるまで該反応液を水洗する。
（ハ）反応液中の亜鉛化合物を乾燥させ焼成を行い酸化亜鉛粒子を得る。
以下、これらの工程についてそれぞれ詳述する。
Next, the preferable manufacturing method of the zinc oxide particle of this invention is demonstrated. This production method is roughly divided into the following steps (a) to (c).
(A) A first aqueous solution containing a water-soluble zinc salt and a second aqueous solution containing a water-soluble carbonate are mixed to form a hardly soluble zinc compound.
(B) The reaction solution is washed with water until the conductivity of the reaction solution reaches 300 to 700 μS (micro Siemens).
(C) The zinc compound in the reaction solution is dried and baked to obtain zinc oxide particles.
Hereinafter, each of these steps will be described in detail.
先ず（イ）の工程について説明する。第１の水溶液に用いられる水溶性亜鉛塩としては、例えば塩化亜鉛、硫酸亜鉛、硝酸亜鉛などが用いられる。尤も、水溶性である限りこれらに制限されるものではない。水溶性亜鉛塩は、単独で又は二種以上を組み合わせて用いることができる。第１の水溶液における水溶性亜鉛塩の濃度は、亜鉛イオンに基づき、０．０５〜１ｍｏｌ／ｌ、特に０．１〜０．６ｍｏｌ／ｌであることが、凝集が起こりにくい反応となる点から好ましい。 First, step (a) will be described. Examples of the water-soluble zinc salt used in the first aqueous solution include zinc chloride, zinc sulfate, and zinc nitrate. However, as long as it is water-soluble, it is not limited thereto. The water-soluble zinc salts can be used alone or in combination of two or more. The concentration of the water-soluble zinc salt in the first aqueous solution is 0.05 to 1 mol / l, particularly 0.1 to 0.6 mol / l, based on zinc ions, from the point that aggregation hardly occurs. preferable.
一方、第２の水溶液に用いられる水溶性炭酸塩としては、例えば炭酸ナトリウム、炭酸カリウム、炭酸水素ナトリウム、炭酸水素カリウムなどのアルカリ金属の炭酸塩を用いることが好ましい。尤も、水溶性である限りこれらに制限されるものではない。特に好ましい塩は、炭酸ナトリウムや炭酸カリウムである。水溶性炭酸塩は、単独で又は二種以上を組み合わせて用いることができる。 On the other hand, as the water-soluble carbonate used in the second aqueous solution, for example, an alkali metal carbonate such as sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate or the like is preferably used. However, as long as it is water-soluble, it is not limited thereto. Particularly preferred salts are sodium carbonate and potassium carbonate. A water-soluble carbonate can be used individually or in combination of 2 or more types.
第２の水溶液には、アルカリ金属の炭酸塩を始めとする水溶性炭酸塩に加えてアルカリ金属の水酸化物を含有させることが好ましい。これによって、凝集が防止され、透明性が確保されるという有利な効果が奏される。アルカリ金属の水酸化物としては、例えば水酸化ナトリウムや水酸化カリウムが用いられる。アルカリ金属の水酸化物は、単独で又は二種以上を組み合わせて用いることができる。 The second aqueous solution preferably contains an alkali metal hydroxide in addition to a water-soluble carbonate such as an alkali metal carbonate. As a result, advantageous effects of preventing aggregation and ensuring transparency can be obtained. As the alkali metal hydroxide, for example, sodium hydroxide or potassium hydroxide is used. Alkali metal hydroxides can be used alone or in combination of two or more.
第１の水溶液と第２の水溶液を混合する場合には、第１の水溶液に含まれる亜鉛１モルに対して、第２の水溶液に含まれるアルカリ金属の炭酸塩の量が、炭酸イオンを基準として好ましくは０．２〜２．０モル、更に好ましくは０．３〜０．７モルになるように、第２の水溶液に含まれるアルカリ金属の炭酸塩の濃度を調整するか、又は第１の水溶液と第２の水溶液との混合比率を調整することが好ましい。また、炭酸イオンと水酸化物イオンとのモル比（前者：後者）が、１：０．５〜１：９となるように、することも好ましい。 When mixing the first aqueous solution and the second aqueous solution, the amount of alkali metal carbonate contained in the second aqueous solution is based on carbonate ions with respect to 1 mol of zinc contained in the first aqueous solution. The concentration of the alkali metal carbonate contained in the second aqueous solution is adjusted so that it is preferably 0.2 to 2.0 mol, more preferably 0.3 to 0.7 mol, or the first It is preferable to adjust the mixing ratio of the aqueous solution of the second solution and the second aqueous solution. It is also preferable that the molar ratio of carbonate ions to hydroxide ions (the former: the latter) is 1: 0.5 to 1: 9.
また、第２の水溶液にアルカリ金属の水酸化物も含有されているときには、第１の水溶液に含まれる亜鉛１モルに対して、第２の水溶液に含まれるアルカリ金属の水酸化物の量が、水酸化物イオンを基準として好ましくは０．１〜１．７モル、更に好ましくは０．７〜１．２モルになるように、第２の水溶液に含まれるアルカリ金属の水酸化物の濃度を調整するか、又は第１の水溶液と第２の水溶液との混合比率を調整することが好ましい。 Further, when the second aqueous solution also contains an alkali metal hydroxide, the amount of the alkali metal hydroxide contained in the second aqueous solution is 1 mol of zinc contained in the first aqueous solution. The concentration of the alkali metal hydroxide contained in the second aqueous solution is preferably 0.1 to 1.7 mol, more preferably 0.7 to 1.2 mol based on the hydroxide ion. It is preferable to adjust the mixing ratio of the first aqueous solution and the second aqueous solution.
更に、第２の水溶液にアルカリ金属の水酸化物も含有されているときには、第１の水溶液に含まれる亜鉛１モルに対して、第２の水溶液に含まれるアルカリ金属の炭酸塩及びアルカリ金属の水酸化物の合計量が、炭酸イオン及び水酸化物イオンを基準として好ましくは１．３〜２モル、更に好ましくは１．３〜１．７モルになるように、第２の水溶液に含まれるアルカリ金属の炭酸塩及びアルカリ金属の水酸化物の濃度を調整するか、又は第１の水溶液と第２の水溶液との混合比率を調整することが好ましい。このように調整することで、後述する所望の酸化亜鉛を容易に得ることができる。 Further, when an alkali metal hydroxide is also contained in the second aqueous solution, the alkali metal carbonate and alkali metal contained in the second aqueous solution with respect to 1 mol of zinc contained in the first aqueous solution. It is contained in the second aqueous solution so that the total amount of hydroxide is preferably 1.3 to 2 mol, more preferably 1.3 to 1.7 mol, based on carbonate ions and hydroxide ions. It is preferable to adjust the concentration of the alkali metal carbonate and the alkali metal hydroxide, or to adjust the mixing ratio of the first aqueous solution and the second aqueous solution. By adjusting in this way, the desired zinc oxide mentioned later can be obtained easily.
（イ）の工程においては、第１の水溶液に第２の水溶液を添加し、反応液を撹拌することで反応系のｐＨを上昇させ反応を起こさせる。第２の水溶液の添加は、一括でもよく徐々にでもよいが、第２の水溶液を徐々に添加して、反応系のｐＨを徐々に上昇させると、低電気抵抗で且つ透明性の高い酸化亜鉛粉末を首尾良く得ることができるので好ましい。これに対して、第２の水溶液に第１の水溶液を添加した場合には、所望の酸化亜鉛粉末を得ることができない。反応温度は４０〜７０℃、特に５５〜６０℃であることが好ましい。反応時間は１５〜９０分、特に３０〜６０分であることが好ましい。反応によって、反応液中には難溶性の亜鉛化合物の沈殿が生じる。この沈殿物の詳細は未だ明確ではないが、本発明者らは亜鉛の水酸化物と炭酸塩の複合体、例えばＺｎ（ＯＨ）ｘ（ＣＯ3）ｙ（式中、ｘ及びｙはｘ＋２ｙ＝２を満たす数を示す）ではないかと推測している。 In the step (a), the second aqueous solution is added to the first aqueous solution, and the reaction solution is stirred to raise the pH of the reaction system and cause the reaction. The second aqueous solution may be added all at once or gradually. However, when the pH of the reaction system is gradually increased by gradually adding the second aqueous solution, zinc oxide having low electrical resistance and high transparency is obtained. It is preferable because the powder can be obtained successfully. On the other hand, when the first aqueous solution is added to the second aqueous solution, a desired zinc oxide powder cannot be obtained. The reaction temperature is preferably 40 to 70 ° C, particularly 55 to 60 ° C. The reaction time is preferably 15 to 90 minutes, particularly 30 to 60 minutes. Due to the reaction, a hardly soluble zinc compound is precipitated in the reaction solution. The details of this precipitate are not yet clear, but we have a complex of zinc hydroxide and carbonate, such as Zn (OH) x (CO 3 ) y, where x and y are x + 2y = It is estimated that the number is 2).
次に（ロ）の工程について説明する。本工程においては、亜鉛化合物の沈殿が生じた反応液を水洗することで、該沈殿物を含む液の導電率を３００〜７００μＳとし、好ましくは５００〜７００μＳ、更に好ましくは５００〜６００μＳにする。この洗浄の度合いは、得られる酸化亜鉛粒子の透明性に影響を及ぼす。水洗は、例えば反応液をリパルプ洗浄し、次いで固液分離する操作を必要な回数繰り返すことで行われる。前記の沈殿物中には、上述した亜鉛塩、炭酸塩、水酸化物に由来するカチオンやアニオン等の不純物、特に炭酸イオンが含有されているところ、前記の水洗を導電率が前記の範囲になるまで行うことで、該沈殿物に含まれる炭酸イオンの含有量を適切な値にすることができる。導電率が前記の下限値未満の場合には、前記の沈殿物に含まれる炭酸イオンの量が少なくなりすぎ、得られる酸化亜鉛粒子から形成される導電膜の透明性を十分に高めることが容易でなくなる。一方、導電率が前記の上限値を超える場合には、不純物が多くなりすぎ、得られる酸化亜鉛粒子の抵抗を十分に低減させることが容易でなくなる。なお従来の製造方法においては、水洗を十分に行い導電率を３００μＳ未満にすることが通常である。 Next, step (b) will be described. In this step, the reaction liquid in which the precipitation of the zinc compound occurs is washed with water so that the conductivity of the liquid containing the precipitate is 300 to 700 μS, preferably 500 to 700 μS, and more preferably 500 to 600 μS. This degree of washing affects the transparency of the resulting zinc oxide particles. The washing with water is performed, for example, by repeating the operation of repulping the reaction solution and then separating the solid and liquid as many times as necessary. The precipitate contains impurities such as cations and anions derived from the zinc salts, carbonates, and hydroxides described above, particularly carbonate ions. The conductivity of the water washing is within the above range. By carrying out until it becomes, the content of the carbonate ion contained in this precipitate can be made into an appropriate value. When the conductivity is less than the lower limit, the amount of carbonate ions contained in the precipitate is too small, and it is easy to sufficiently enhance the transparency of the conductive film formed from the obtained zinc oxide particles. Not. On the other hand, when the electrical conductivity exceeds the above upper limit, the amount of impurities becomes excessive, and it is not easy to sufficiently reduce the resistance of the obtained zinc oxide particles. In the conventional manufacturing method, it is usual to sufficiently wash with water and make the conductivity less than 300 μS.
次に（ハ）の工程について説明する。上述の（ロ）の工程で得られた沈殿物を固液分離し、得られた固形分を乾燥する。固液分離には、例えば沈殿物を含む液を濾過したり、沈殿物を含む液から水を蒸発させたりする方法が用いられる。分離された沈殿物を乾燥して得られた乾燥体は、適当な大きさに粉砕されて粉体となされる。この粉体に含まれる炭素の量は、０．０５〜０．５重量％、特に０．０５〜０．１５重量％であることが好ましい。この粉体を酸化性雰囲気中、例えば大気雰囲気中で焼成する。焼成によって目的とする酸化亜鉛（ＺｎＯ）粒子が得られる。焼成温度は４００〜７００℃、特に５００〜６００℃であることが好ましい。また焼成時間は３０〜１２０分、特に６０〜９０分であることが好ましい。 Next, step (c) will be described. The precipitate obtained in the step (b) is subjected to solid-liquid separation, and the obtained solid content is dried. For solid-liquid separation, for example, a method of filtering a liquid containing a precipitate or evaporating water from the liquid containing a precipitate is used. A dried product obtained by drying the separated precipitate is pulverized to an appropriate size to obtain a powder. The amount of carbon contained in the powder is preferably 0.05 to 0.5% by weight, particularly 0.05 to 0.15% by weight. This powder is fired in an oxidizing atmosphere, for example, in an air atmosphere. The intended zinc oxide (ZnO) particles are obtained by firing. The firing temperature is preferably 400 to 700 ° C, particularly 500 to 600 ° C. The firing time is preferably 30 to 120 minutes, particularly preferably 60 to 90 minutes.
先に述べたとおり、（ロ）の工程で得られた沈殿物には炭酸イオンが含まれているので、該沈殿物を（ハ）の工程にしたがい焼成すると、焼成中に、該沈殿物中に含まれる炭酸イオンに由来する炭素が焼結防止剤として作用する。これによって粒子同士の融着の進行が妨げられ、酸化亜鉛粒子の粒径が過度に大きくなることが防止される。このようにして得られた酸化亜鉛粒子は、炭酸イオンに由来する炭素を含有したものとなる。また、以上の製造方法においては、製造工程中に金属元素を添加しないので、得られる酸化亜鉛粒子は、金属元素がドープされていないものとなる。 As described above, since the precipitate obtained in the step (b) contains carbonate ions, when the precipitate is baked according to the step (c), The carbon derived from the carbonate ions contained in the metal acts as a sintering inhibitor. As a result, the progress of fusion between the particles is hindered, and the particle size of the zinc oxide particles is prevented from becoming excessively large. The zinc oxide particles thus obtained contain carbon derived from carbonate ions. Moreover, in the above manufacturing method, since a metal element is not added during the manufacturing process, the obtained zinc oxide particles are not doped with a metal element.
以上の方法によって得られた酸化亜鉛粒子は、例えばこれを溶媒やバインダ等と混合することで、透明導電膜の形成用のインクとして用いられる。また、帯電防止用の導電性付与剤として各種樹脂や塗料、フィルム、繊維等に配合することもできる。 The zinc oxide particles obtained by the above method are used as ink for forming a transparent conductive film, for example, by mixing it with a solvent, a binder or the like. Moreover, it can also mix | blend with various resin, a coating material, a film, a fiber, etc. as an electroconductivity imparting agent for antistatic.
以下、実施例により本発明を更に詳細に説明する。しかしながら本発明の範囲はかかる実施例に制限されるものではない。 Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples.
〔実施例１〕
純水４００リットルに、塩化亜鉛２２．５ｋｇ、濃塩酸１．５リットルを投入し、完全溶解させた。更に純水を加え６００リットルにメスアップし、第１の水溶液を得た。この水溶液を加熱して６０℃で一定とした。これとは別に、炭酸ナトリウム７．５ｋｇを純水１００リットルに溶解させた。次いで２５重量％水酸化ナトリウム水溶液２７．５リットルを投入した。更に純水を加え１５０リットルにメスアップし、第２の水溶液を得た。
[Example 1]
In 400 liters of pure water, 22.5 kg of zinc chloride and 1.5 liters of concentrated hydrochloric acid were added and completely dissolved. Further, pure water was added to make up the volume to 600 liters to obtain a first aqueous solution. This aqueous solution was heated to a constant temperature of 60 ° C. Separately, 7.5 kg of sodium carbonate was dissolved in 100 liters of pure water. Next, 27.5 liters of 25% by weight aqueous sodium hydroxide solution was added. Further, pure water was added to make up the volume to 150 liters to obtain a second aqueous solution.
次に、撹拌した状態の第１の水溶液に、第２の水溶液を６０分間にわたって徐々に滴下した。反応液の温度は６０℃に保った。滴下完了後、更に６０分間撹拌を行い反応を進行させた。これにより、反応液中には沈殿が生じた。 Next, the second aqueous solution was gradually added dropwise to the stirred first aqueous solution over 60 minutes. The temperature of the reaction solution was kept at 60 ° C. After completion of the dropwise addition, the reaction was allowed to proceed by further stirring for 60 minutes. Thereby, precipitation occurred in the reaction solution.
生成した沈殿物をリパルプ洗浄し、次いでヌッチェにて固液分離を行う操作を繰り返し行い、該沈殿物を含む液の導電率を４００μＳにした。次いで、固液分離を行って得られた固形分を、１２０℃で１５時間乾燥させた。得られた乾燥体をフォースミルで粉砕した。粉砕物を、大気中で５５０℃、１時間焼成した。これにより目的とする酸化亜鉛粉末を得た。得られた酸化亜鉛粉末は、不定形の一次粒子の凝集体であった。この酸化亜鉛粉末をボールミルで粉砕した。 The generated precipitate was repulped and then subjected to solid-liquid separation in Nutsche, and the conductivity of the liquid containing the precipitate was set to 400 μS. Next, the solid content obtained by solid-liquid separation was dried at 120 ° C. for 15 hours. The obtained dried product was pulverized with a force mill. The pulverized product was fired in the air at 550 ° C. for 1 hour. As a result, the intended zinc oxide powder was obtained. The obtained zinc oxide powder was an aggregate of amorphous primary particles. This zinc oxide powder was pulverized with a ball mill.
〔実施例２〕
実施例１において、沈殿物を含む液の導電率が６００μＳになるまで洗浄を行う以外は実施例１と同様にして酸化亜鉛粉末を得た。
[Example 2]
In Example 1, a zinc oxide powder was obtained in the same manner as in Example 1 except that washing was performed until the conductivity of the liquid containing the precipitate reached 600 μS.
〔比較例１〕
第２の水溶液として、純水１００リットルに２５重量％水酸化ナトリウム水溶液２７．５リットルを投入し、更に純水を加え１５０リットルにメスアップしたものを用いた。また、沈殿物を含む液の導電率が５００μＳになるまで洗浄した。これら以外は実施例１と同様にして酸化亜鉛粒子を得た。
[Comparative Example 1]
As the second aqueous solution, 27.5 liters of a 25 wt% sodium hydroxide aqueous solution was added to 100 liters of pure water, and pure water was further added to make up to 150 liters. Moreover, it wash | cleaned until the electrical conductivity of the liquid containing a deposit became 500 microseconds. Except for these, zinc oxide particles were obtained in the same manner as in Example 1.
〔比較例２〕
第２の水溶液として、純水１００リットルに炭酸ナトリウム２１．８ｋｇを溶解させ、更に純水を加えて１５０リットルにメスアップしたものを用いた。また、沈殿物を含む液の導電率が５００μＳになるまで洗浄した。これら以外は実施例１と同様にして酸化亜鉛粒子を得た。
[Comparative Example 2]
As the second aqueous solution, a solution obtained by dissolving 21.8 kg of sodium carbonate in 100 liters of pure water and further adding pure water to make up to 150 liters was used. Moreover, it wash | cleaned until the electrical conductivity of the liquid containing a deposit became 500 microseconds. Except for these, zinc oxide particles were obtained in the same manner as in Example 1.
〔比較例３〕
実施例１において、沈殿物を含む液の導電率が１５００μＳになるまで洗浄を行う以外は実施例１と同様にして酸化亜鉛粉末を得た。
[Comparative Example 3]
In Example 1, a zinc oxide powder was obtained in the same manner as in Example 1 except that washing was performed until the conductivity of the liquid containing the precipitate reached 1500 μS.
〔比較例４〕
実施例１において、沈殿物を含む液の導電率が５０μＳになるまで洗浄を行う以外は実施例１と同様にして酸化亜鉛粉末を得た。
[Comparative Example 4]
In Example 1, a zinc oxide powder was obtained in the same manner as in Example 1 except that washing was performed until the conductivity of the liquid containing the precipitate reached 50 μS.
〔評価〕
実施例及び比較例で得られた酸化亜鉛粒子について、炭素含有量、粒度分布、比表面積、圧粉抵抗値、色相を以下の方法で測定した。また、一次粒子の平均粒径を先に述べた方法で測定した。更に得られた酸化亜鉛粒子を原料とするインクを調製し、そのインクから形成された塗膜の抵抗値及びヘイズを測定した。これらの結果を表１に示す。
[Evaluation]
About the zinc oxide particle obtained by the Example and the comparative example, carbon content, a particle size distribution, a specific surface area, a dust resistance value, and the hue were measured with the following method. Moreover, the average particle diameter of the primary particles was measured by the method described above. Furthermore, an ink using the obtained zinc oxide particles as a raw material was prepared, and a resistance value and a haze of a coating film formed from the ink were measured. These results are shown in Table 1.
（１）炭素含有量
堀場製作所製の炭素・硫黄分析装置ＥＭＩＡ−３２０Ｖ（商品名）を用いて測定した。
（２）粒度分布
日機装製のレーザー回折粒度分布測定装置であるマイクロトラック（商品名）を用いて測定した。測定に際しては、前分散として１重量％ヘキサメタリン酸ナトリウム水溶液中で超音波分散を５分間行った。
（３）比表面積
ユアサアイオニクス（株）製のモノソーブ（商品名）を用いＢＥＴ法（Ｈｅ／Ｎ2混合ガス）にしたがい測定した。
（４）圧粉抵抗値
粒子を５０ｋｇｆの圧力で０．５分間プレスし、直径２５ｍｍ、厚み５ｍｍペレットを作製した。得られたペレットの抵抗値を、ダイヤインスツルメンツ製のＰＤ−４１（商品名）を用い、四探針法により測定した。
（５）色相
スガ試験機製のＳＭカラーコンピューター（商品名）を用いて測定した。
(1) Carbon content It measured using the carbon and sulfur analyzer EMIA-320V (brand name) by Horiba.
(2) Particle size distribution The particle size distribution was measured using Microtrac (trade name), which is a laser diffraction particle size distribution measuring device manufactured by Nikkiso. In the measurement, ultrasonic dispersion was performed for 5 minutes in a 1% by weight sodium hexametaphosphate aqueous solution as a pre-dispersion.
(3) was measured in accordance with the specific surface area Yuasa Ionics Co., Ltd. MONOSORB (trade name) BET method using (the He / N 2 mixed gas).
(4) Powder resistance value The particles were pressed at a pressure of 50 kgf for 0.5 minutes to produce pellets having a diameter of 25 mm and a thickness of 5 mm. The resistance value of the obtained pellet was measured by a four-probe method using PD-41 (trade name) manufactured by Dia Instruments.
(5) Hue Measured using an SM color computer (trade name) manufactured by Suga Test Instruments.
（６）インクの調製
酸化亜鉛９ｇとメチルエチルケトン１５．６ｇを、５０ｍＬのポリ瓶中で混合し、スラリーＡを得た。次に、スラリーＡに対してアクリル樹脂（三菱レーヨン製のダイヤナールＬＲ１６７）５．４ｇを添加した。これをスラリーＢとする。スラリーＢ中へジルコニアビーズを入れ、ビーズミル（ペイントシェーカー）で２時間分散を行った。この分散液からジルコニアビーズを取り除き、透明導電性酸化亜鉛インクを得た。
（７）塗膜の抵抗値
得られたインクを用い、バーコータで塗膜を形成した。塗膜を８０℃で乾燥させた後、その抵抗値をダイヤインスツルメンツ製のＭＣＰ−ＨＴ２５０ ハイレスタＩＰ（商品名）を用い、二探針法により測定した。
（８）ヘイズ
得られたインクを用い、バーコータで塗膜を形成した。塗膜を８０℃で乾燥させた後、日本電色工業（株）製のヘイズメータであるＭＯＤＥＬ １００１ＤＰ（商品名）によってヘイズを測定した。測定はＪＩＳ ７１０５に準拠し、積分球式測定法により行った。ヘイズは（散乱光／全光線透過光）×１００から算出される。
(6) Preparation of Ink 9 g of zinc oxide and 15.6 g of methyl ethyl ketone were mixed in a 50 mL plastic bottle to obtain slurry A. Next, 5.4 g of acrylic resin (Dianar LR167 manufactured by Mitsubishi Rayon) was added to the slurry A. This is designated as slurry B. The zirconia beads were put into the slurry B and dispersed for 2 hours with a bead mill (paint shaker). The zirconia beads were removed from this dispersion to obtain a transparent conductive zinc oxide ink.
(7) Resistance value of coating film Using the obtained ink, a coating film was formed with a bar coater. After the coating film was dried at 80 ° C., the resistance value was measured by a two-probe method using MCP-HT250 Hiresta IP (trade name) manufactured by Dia Instruments.
(8) Haze Using the obtained ink, a coating film was formed with a bar coater. After the coating film was dried at 80 ° C., haze was measured by MODEL 1001DP (trade name), which is a haze meter manufactured by Nippon Denshoku Industries Co., Ltd. The measurement was performed by an integrating sphere measurement method in accordance with JIS 7105. The haze is calculated from (scattered light / total light transmitted light) × 100.
表１に示す結果から明らかなように、実施例の酸化亜鉛粒子（本発明品）は、比較例の酸化亜鉛粒子に比べ、これを用いたインクの塗膜の抵抗値が低く且つ透明性が高いものであることが判る。
注目すべきは、比較例１及び２の酸化亜鉛粒子は、実施例１及び２の酸化亜鉛粒子に比較して圧粉抵抗値が低いにもかかわらず、塗膜に形成したときの抵抗値が極めて高くなってしまう点である。この理由は、比較例１及び２の酸化亜鉛粒子は凝集しているためである。凝集した酸化亜鉛粒子は圧粉抵抗値が低くなるが、逆に凝集していることに起因して分散性が悪くなり、塗膜に形成したときの抵抗値が高くなってしまう。なお比較例１及び２の酸化亜鉛粒子が凝集していることは、粒度分布におけるＤ90値が大きいことで裏付けられる。
As is apparent from the results shown in Table 1, the zinc oxide particles of the example (product of the present invention) have a lower resistance value and transparency of the ink coating using the zinc oxide particles of the comparative example. It turns out that it is expensive.
It should be noted that although the zinc oxide particles of Comparative Examples 1 and 2 have a lower dust resistance value than the zinc oxide particles of Examples 1 and 2, the resistance value when formed in a coating film is low. This is a very high point. This is because the zinc oxide particles of Comparative Examples 1 and 2 are agglomerated. Aggregated zinc oxide particles have a low dust resistance, but conversely, due to aggregation, the dispersibility deteriorates and the resistance when formed on a coating film increases. The fact that the zinc oxide particles of Comparative Examples 1 and 2 are agglomerated is supported by the large D 90 value in the particle size distribution.
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