JP4734598B2 - Production method of soft ferrite - Google Patents
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【０００１】
【産業上の利用分野】
本発明は電子写真現像用キャリヤに適するソフトフェライトの製造法に係り, より詳しくは，適正な飽和磁化値 (σS) を有するＭｎＯ−ＭｇＯ−Ｆｅ2Ｏ3 系ソフトフェライトを製造する方法に関する。
【０００２】
【従来の技術】
２成分系の電子複写機用現像剤に用いられるキャリヤ（電子写真現像用キャリヤ）には，様々な特性（磁気特性，摩擦帯電性，耐久性，流動性など）が要求されるが，基本的な要件として，静電抵抗値と飽和磁化値（σS）がその機種に応じた適正値に調整されていなければならない。とくに化学量論近傍の組成を有するソフトフェライトは抵抗値が高くなり，画像濃度の低下と階調性の変化率が小さくなるので静電抵抗値を適正に調整することが必要である。この抵抗値の調整法としては，特公昭６２−３７７８２号公報のように焼成時の雰囲気を調整する方法や，特開平７−２０６５８号公報のように，ソフトフェライト中のＰ含有量を調節する方法などが知られている。
【０００３】
一方，このようなキャリヤ用ソフトフェライトとして，マンガン−マグネシウム系フェライト（ＭｎＯ−ＭｇＯ−Ｆｅ2Ｏ3 系フェライト）が知られている。しかし，静電抵抗値を通常のキャリヤに要求される１０8Ω・ｃｍレベルに保持しながら，一般的な飽和磁化値５０〜６５emu/g を安定して維持するＭｎＯ−ＭｇＯ−Ｆｅ2Ｏ3 系フェライトを製造することは困難であった。
【０００５】
【発明が解決しようとする課題】
ＭｎＯ−ＭｇＯ−Ｆｅ2Ｏ3系フェライトでは、意図する飽和磁化値を有するように製造する条件が未知であり、このために、飽和磁化値を制御する製造法は確立されていなかった。
【０００６】
【課題を解決する手段】
本発明によれば，酸化物原料を焼成してＭｎＯ−ＭｇＯ−Ｆｅ2Ｏ3 系ソフトフェライトを製造するさいに，酸素ガスが０.５〜５vol.％で残部が不活性ガスからなる混合ガス雰囲気中で焼成することを特徴とするソフトフェライトの製造法，さらには，酸化物原料を焼成してＭｎＯ−ＭｇＯ−Ｆｅ2Ｏ3 系のソフトフェライトを製造するさいに，該酸化物原料にリンを０.０１〜５重量％配合し，酸素ガスが０.５〜５vol.％で残部が不活性ガスからなる混合ガス雰囲気中で焼成することを特徴とするソフトフェライトの製造法を提供する。この製法により，混合ガス雰囲気中の酸素濃度を（場合によってはさらに原料中のリン濃度を）前記範囲内の特定の値に選択すれば，意図する飽和磁化値に精度よく的中させることができる。該焼成品は解砕分級することにより，電子写真現像用キャリヤに適した粉体となる。
【０００７】
【発明の実施の形態】
本発明は，電子写真現像用キャリヤに適したＭｎＯ−ＭｇＯ−Ｆｅ2Ｏ3 系ソフトフェライトの製造法に関するが，ＭｎＯ−ＭｇＯ−Ｆｅ2Ｏ3 系フェライトのうちでも（Ｍｎ＋Ｍｇ）：Ｆｅとの原子比が，ほぼ１：１の組成を有するフェライト，すなわち一般式で（Ｍｎ＋Ｍｇ）Ｏ・Ｆｅ2Ｏ3の組成を有するものが望ましく，この場合のＭｎ／Ｍｇの原子比も１／10〜10／１，好ましくは１／５〜５／１であるのがよい。Ｍｎ／Ｍｇの原子比が１／10未満では飽和磁化が著しく低下して電子写真用キャリヤに適さなくなり，またＭｎ／Ｍｇの原子比が10／１を超えるとＭｎの価数が不安定化し，ソフトフエライトを形成し難くなる。
【０００８】
このような組成のフェライトは，目標組成となるように原料を調合し，仮焼，粉砕，乾燥，造粒，焼成，解砕，分級の諸工程を経て製造することができる。
【０００９】
〔原料調合〕
ＭｎＯ−ＭｇＯ−Ｆｅ2Ｏ3系フェライトを構成する各成分の原料調合にあたっては，マンガン源としてはＭｎ3Ｏ4やＭｎＣＯ3など,マグネシウム源としてはＭｇ（ＯＨ)2，ＭｇＯ, ＭｇＣＯ3など，鉄源としてはＦｅ2Ｏ3 を使用し，これら原料中のＭｎ, ＭｇおよびＦｅの組成比が意図するフェライトの組成比に相当するように，各原料を秤量調合する。そのさい，リンを含有させる場合には，Ｍｎ, ＭｇおよびＦｅの酸化物換算量に対してリン量（リン元素量）が０.０１〜５重量％，好ましくは０.１〜１重量％の範囲となるように，リンを単体または酸化物等の形態で配合する。
【００１０】
ここで，リン量の配合について，Ｍｎ, ＭｇおよびＦｅの酸化物に対する換算量で表しているが，これは，後の焼成工程でＭｎＯ−ＭｇＯ−Ｆｅ2Ｏ3 系フェライトとなるＭｎ，ＭｇおよびＦｅの各酸化物の合計量に対して，Ｐ元素が０.０１〜５重量％，好ましくは０.１〜１重量％の範囲となるように調合すると言うことである。配合されたＰは焼成工程では酸化物の形態で含有されることになる。Ｐ含有量が０.０１重量％未満では飽和磁化および抵抗値の制御に対して効果がなく，他方，Ｐ含有量が５重量％を超えるとソフトフエライトの形成が困難になる。
【００１１】
〔仮焼工程〕
調合された原料はよく混合したうえ，加熱炉中で６００〜１０００℃の温度に大気雰囲気中で加熱し，１〜５時間保持して仮焼する。これにより，炭酸塩や水酸化物等の形態で調合した原料は実質的に酸化物の形態の塊状物となり，揮発性成分や非金属介在物などは分解・蒸発除去される。
【００１２】
〔粉砕・乾燥・造粒工程〕
得られた仮焼品は，冷却後，粉砕機例えば振動ミルで１μｍ程度まで粉砕し，次いで水を加えて７０％程度の粗スラリーとし，これをボールミル等で湿式粉砕する。これにより，微細に粉砕された仮焼粉のスラリーが得られる。この仮焼粉スラリーに，必要に応じてポリカルボン酸等の分散剤を加えたうえ，例えば噴霧乾燥機で噴霧乾燥するか，或いはペレタイザーで造粒し，１０〜５００μｍの球状ペレットにして乾燥する。
【００１３】
〔焼成工程〕
前記の造粒品を焼成してフェライトとするが，この焼成工程の雰囲気を制御することにより，意図する飽和磁化（σs）をもつソフトフェライトを得ることができることがわかった。すなわち，実質上フェライト組成と同等の酸化物組成を有した仮焼粉を，実際にフェライトに焼成するに十分な温度，例えば１１００〜１２００℃に少なくとも６０分間保持する焼成処理を行う場合，雰囲気中の酸素分圧が低くなると飽和磁化が増加することがわかった。より具体的には，他の条件は一定にして，空気から窒素ガスにまで雰囲気中の酸素分圧を連続的に変化させると，それに追従して飽和磁化も連続的に上昇するので，意図する飽和磁化を得るには，それが得られる酸素分圧を採用すればよい。
【００１４】
この雰囲気中の酸素分圧の制御は，不活性ガス中の酸素濃度を調整することによって行い，実際には窒素ガス中の酸素濃度を調整するのがよく，窒素ガス中の酸素濃度が０.５〜５vol.％の範囲において，所定の値となるように調整するのがよい。酸素濃度が５vol.％を超えるとキャリヤに要求される飽和磁化に達せず，逆に０.５vol.％未満ではキャリヤに要求されるよりも大きな飽和磁化を有する可能性がある。
【００１５】
なお，リンを含有させた場合には，酸素濃度と飽和磁化の関係が適正なＰ含有量ではそのＰ含有量に応じて飽和磁化が増大する方向に変位する。したがって，酸素濃度とＰ含有量の両方から飽和磁化を適正な値に制御することができる。
【００１６】
〔解砕・分級工程〕
フェライトに焼成された焼成品は解砕機で解砕し，解砕粉を分級または篩分けしてキャリヤとして適正な粒度のものを採取する。例えば平均粒子径が７０μｍ程度のＭｎＯ−ＭｇＯ−Ｆｅ2Ｏ3 系ソフトフェライト粒子を得る。
【００１８】
【実施例】
【００１９】
〔実施例１〕
ＭｎＯ・ＭｇＯ・Ｆｅ2Ｏ3 のフェライト組成となるように，Ｍｎ源としてのＭｎＣＯ3, Ｍｇ源としてのＭｇ（ＯＨ)2，鉄源としてのＦｅ2Ｏ3 を，それぞれＭｎＣＯ3：２５モル％，Ｍｇ（ＯＨ)2：２５モル％, Ｆｅ2Ｏ3 ：５０モル％の割合で混合して，原料調合を行なった。
【００２０】
前記の混合粉を，加熱炉で９００℃で３時間大気雰囲気で加熱して仮焼した。得られた仮焼品を冷却後，振動ミルでほぼ１μｍ大に粉砕し，乾燥粉に対して１重量％の割合で分散剤（商品名：サンノプコＳＮデイスパーサント５４６８）を水と共に加えてスラリー濃度が７０％のスラリーとした。このスラリーを湿式ボールミルに装填して湿式粉砕し，得られた懸濁液をスプレードライヤに供給し，平均粒径が８０μｍ程度の乾燥粒子からなる造粒品を得た。
【００２１】
この造粒品を焼成炉に装填し，窒素ガス中の酸素濃度を調節した混合ガス中で１１００℃で３時間焼成した。本例では，酸素濃度を０vol.％，1.0 vol.％，2.0 vol.％および5.0 vol.％に調節した５例について焼成品を得た。各焼成品を解砕機で解砕したあと篩分けして平均粒径が７０μｍのソフトフェライト粉を得た。各フェライトの飽和磁化（σS) を測定し，その結果を表１に示した。また図１に酸素濃度と飽和磁化（σS) の関係をプロットした。これらの結果から，焼成時の酸素濃度と飽和磁化（σS) との間には所定の関係があり，酸素濃度が高くなると飽和磁化が低下するようになることがわかる。
【００２２】
〔実施例２〕
原料調合時に，ＭｎＯ・ＭｇＯ・Ｆｅ2Ｏ3 のフェライト組成に対して０.１重量％となるように単体のＰを配合した以外は，実施例１を繰り返した。得られた各フェライトの飽和磁化（σS) を表１に併記した。また本例の酸素濃度と飽和磁化の関係を図１に併記した。
【００２３】
〔実施例３〕
原料調合時に，ＭｎＯ・ＭｇＯ・Ｆｅ2Ｏ3 のフェライト組成に対して０.３重量％となるように単体のＰを配合した以外は，実施例１を繰り返した。得られた各フェライトの飽和磁化（σS) を表１に併記し，本例の酸素濃度と飽和磁化の関係を図１に併記した。
【００２４】
【表１】
表１および図１の結果から，焼成時の酸素濃度の増加に従って飽和磁化が所定の関係をもって減少することが明らかであり，また実施例１のようにＰ無添加の場合に比べてＰを添加すると，酸素濃度が低い領域ではＰの添加量の増加に従って一様に飽和磁化が増加する傾向にあることがわかる。
【００２６】
図２は，Ｐ添加量を横軸にして表１の飽和磁化とＰ量との関係を見たものであるが，図２から酸素濃度が低い領域ではＰ添加量とともに飽和磁化が増加する傾向にあることがわかる。
【００２７】
この結果から，ＭｎＯ・ＭｇＯ・Ｆｅ2Ｏ3 組成のフェライトの製造にさいして，意図する飽和磁化を得るには，焼成時の酸素濃度と，更にはＰ含有量をどのように設定すればよいか明らかである。
【００２８】
〔実施例４〕
Ｍｎ／Ｍｇの原子比が３／２で（Ｍｎ＋Ｍｇ）Ｏ・Ｆｅ2Ｏ3の組成となるように，ＭｎＣＯ3：３０モル％，Ｍｇ（ＯＨ)2：２０モル％, Ｆｅ2Ｏ3 ：５０モル％の割合で混合して，原料調合を行なった以外は，実施例１を繰り返した。得られた各フェライトの飽和磁化（σS) を表２に示した。また図３に酸素濃度と飽和磁化（σS) の関係をプロットした。これらの結果から，焼成時の酸素濃度と飽和磁化（σS) との間には所定の関係があり，酸素濃度が高くなると飽和磁化が低下するようになることがわかる。
【００２９】
〔実施例５〕
原料調合時に，目標フェライト組成に対して０.１重量％となるように単体のＰを配合した以外は，実施例４を繰り返した。得られた各フェライトの飽和磁化（σS) を表２に併記すると共に，その関係を図３に示した。
【００３０】
〔実施例６〕
原料調合時に，目標フェライト組成に対して０.３重量％となるように単体のＰを配合した以外は，実施例４を繰り返した。得られた各フェライトの飽和磁化（σS) を表２に併記すると共に，その関係を図３に示した。
【００３１】
【表２】
表２および図３の結果から，本例のフェライト組成の場合においても，焼成時の酸素濃度の増加に従って飽和磁化が所定の関係をもって減少することが明らかであり，また実施例５のようにＰ無添加の場合に比べてＰ添加の例では，酸素濃度が低い領域ではＰの添加量の増加に従って一様に飽和磁化が増加する傾向にあることがわかる。
【００３３】
図４は，Ｐ添加量を横軸にして表２の飽和磁化とＰ量との関係を見たものであるが，図４から酸素濃度が低い領域ではＰ添加量とともに飽和磁化が増加する傾向にあることがわかる。
【００３４】
したがって図３と図４から，Ｍｎ／Ｍｇ原子比３／２でＭｎとＭｇを含有する（Ｍｎ＋Ｍｇ）Ｏ・Ｆｅ2Ｏ3 系フェライトの製造にさいして，意図する飽和磁化を得るには，焼成時の酸素濃度と，更にはＰ含有量をどのように設定すればよいか明らかである。
【００３５】
〔比較例〕
原料調合時に，焼成時の酸素濃度を７vol.％とするか，および／または目標フェライト組成に対して７重量％となるように単体のＰを配合した以外は，実施例４を繰り返した。各例で得られた各フェライトの飽和磁化（σS) を表２に比較例として併記した。酸素濃度が７vol.％でＰ無添加の場合には，そこそこの飽和磁化値をもつフェライトが得られているが，キャリヤとしての適正値よりも飽和磁化が低い。Ｐ含有量が７重量％では飽和磁化が極端に低くなり，キャリヤとしては不適である。
【００３６】
【発明の効果】
以上説明したように，本発明によると，フェライト焼成時の酸素濃度の制御によって，場合によってはさらにＰ含有量の制御によって，電子写真現像用キャリヤに要求される飽和磁化値を精度よく的中させることができるので，機種に応じた好ましい電子写真現像用キャリヤが高い歩留りで製造できる。
【図面の簡単な説明】
【図１】フェライト焼成雰囲気中の酸素濃度（vol.％）とフェライトの飽和磁化（emu/g ）との関係図である。
【図２】調合原料中のＰ濃度（wt％）とフェライトの飽和磁化（emu/g ）との関係図である。
【図３】他のフェライト組成におけるフェライト焼成雰囲気中の酸素濃度（vol.％）とフェライトの飽和磁化（emu/g ）との関係図である。
【図４】他のフェライト組成における調合原料中のＰ濃度（wt％）とフェライトの飽和磁化（emu/g ）との関係図である。[0001]
[Industrial application fields]
The present invention relates to a method for producing a soft ferrite suitable for a carrier for electrophotographic development, and more particularly to a method for producing a MnO—MgO—Fe 2 O 3 type soft ferrite having an appropriate saturation magnetization value (σ S ).
[0002]
[Prior art]
Various properties (magnetic properties, triboelectric charging, durability, fluidity, etc.) are required for carriers used in two-component electrophotographic copying machine developers (electrophotographic developing carriers). As a necessary requirement, the electrostatic resistance value and saturation magnetization value (σ S ) must be adjusted to appropriate values according to the model. In particular, a soft ferrite having a composition close to the stoichiometry has a high resistance value, and a decrease in image density and a change rate of gradation are small. Therefore, it is necessary to appropriately adjust the electrostatic resistance value. As a method for adjusting the resistance value, a method of adjusting the atmosphere during firing as disclosed in Japanese Patent Publication No. Sho 62-37782 or a P content in soft ferrite as disclosed in Japanese Patent Application Laid-Open No. 7-20658 is disclosed. Methods are known.
[0003]
On the other hand, manganese-magnesium ferrite (MnO—MgO—Fe 2 O 3 ferrite) is known as such a soft ferrite for carriers. However, MnO—MgO—Fe 2 O 3 that stably maintains a typical saturation magnetization value of 50 to 65 emu / g while maintaining the electrostatic resistance value at the 10 8 Ω · cm level required for ordinary carriers. It has been difficult to produce ferrite.
[0005]
[Problems to be solved by the invention]
In the MnO—MgO—Fe 2 O 3 ferrite, the conditions for producing the intended saturation magnetization value are unknown, and for this reason, a production method for controlling the saturation magnetization value has not been established.
[0006]
[Means for solving the problems]
According to the present invention, when the oxide raw material is fired to produce the MnO—MgO—Fe 2 O 3 soft ferrite, the mixed gas is composed of 0.5 to 5 vol. A method for producing soft ferrite characterized by firing in an atmosphere, and further, when an oxide raw material is fired to produce an MnO-MgO-Fe 2 O 3 based soft ferrite, phosphorous is added to the oxide raw material. Is produced in a mixed gas atmosphere in which oxygen gas is contained in an amount of 0.5 to 5 vol.% And the balance is composed of an inert gas. With this manufacturing method, if the oxygen concentration in the mixed gas atmosphere (and possibly the phosphorus concentration in the raw material) is selected to a specific value within the above range, the intended saturation magnetization value can be accurately targeted. . The fired product is pulverized and classified to become a powder suitable for an electrophotographic developing carrier.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a method for producing a MnO—MgO—Fe 2 O 3 type soft ferrite suitable for an electrophotographic development carrier. Among MnO—MgO—Fe 2 O 3 type ferrites, (Mn + Mg): atoms with Fe A ferrite having a composition of approximately 1: 1, that is, a ferrite having a general formula of (Mn + Mg) O.Fe 2 O 3 is desirable, and in this case, the atomic ratio of Mn / Mg is also 1/10 to 10 / 1, preferably 1/5 to 5/1. When the atomic ratio of Mn / Mg is less than 1/10, the saturation magnetization is remarkably lowered to make it unsuitable for an electrophotographic carrier, and when the atomic ratio of Mn / Mg exceeds 10/1, the valence of Mn becomes unstable. It becomes difficult to form soft ferrite.
[0008]
Ferrite having such a composition can be manufactured through various processes of calcining, pulverization, drying, granulation, firing, pulverization, and classification by preparing raw materials so as to have a target composition.
[0009]
[Raw material preparation]
In preparing the raw materials for each component constituting the MnO-MgO-Fe 2 O 3 ferrite, manganese sources such as Mn 3 O 4 and MnCO 3 , magnesium sources such as Mg (OH) 2 , MgO, MgCO 3 , Fe 2 O 3 is used as the iron source, and each raw material is weighed and mixed so that the composition ratio of Mn, Mg and Fe in these raw materials corresponds to the intended composition ratio of ferrite. At that time, when phosphorus is contained, the phosphorus amount (phosphorus element amount) is 0.01 to 5% by weight, preferably 0.1 to 1% by weight with respect to the oxide equivalent amount of Mn, Mg and Fe. Phosphorus is blended in the form of a simple substance or an oxide so as to be in the range.
[0010]
Here, the amount of phosphorus is expressed in terms of the converted amount with respect to oxides of Mn, Mg, and Fe. This indicates that Mn, Mg, and MnO—MgO—Fe 2 O 3 -based ferrite in the subsequent firing step. It is said that the element P is blended so as to be in the range of 0.01 to 5% by weight, preferably 0.1 to 1% by weight, based on the total amount of each oxide of Fe. The compounded P is contained in the form of an oxide in the firing step. When the P content is less than 0.01% by weight, there is no effect on the saturation magnetization and the control of the resistance value. On the other hand, when the P content exceeds 5% by weight, it becomes difficult to form soft ferrite.
[0011]
[Calcination process]
The prepared raw materials are mixed well, heated in a heating furnace to a temperature of 600 to 1000 ° C. in an air atmosphere, and held for 1 to 5 hours and calcined. As a result, the raw material prepared in the form of carbonate, hydroxide, or the like becomes a massive substance in the form of oxide, and volatile components and non-metallic inclusions are decomposed and removed by evaporation.
[0012]
[Crushing, drying, granulation process]
The obtained calcined product is cooled, pulverized to about 1 μm with a pulverizer, for example, a vibration mill, and then added with water to form a coarse slurry of about 70%, which is wet pulverized with a ball mill or the like. Thereby, a finely pulverized calcined powder slurry is obtained. If necessary, a dispersant such as polycarboxylic acid is added to the calcined powder slurry and, for example, spray-dried with a spray dryer, or granulated with a pelletizer, and dried into 10-500 μm spherical pellets. .
[0013]
[Baking process]
The granulated product is fired into ferrite, and it was found that soft ferrite having the intended saturation magnetization (σ s ) can be obtained by controlling the atmosphere of the firing process. That is, when a calcining powder having an oxide composition substantially equivalent to the ferrite composition is subjected to a firing treatment in which the calcined powder is actually calcined into ferrite, for example, maintained at 1100 to 1200 ° C. for at least 60 minutes, It has been found that the saturation magnetization increases as the oxygen partial pressure decreases. More specifically, if other conditions are kept constant, and the oxygen partial pressure in the atmosphere is continuously changed from air to nitrogen gas, the saturation magnetization increases continuously following that change. In order to obtain saturation magnetization, the oxygen partial pressure at which it can be obtained may be employed.
[0014]
The oxygen partial pressure in the atmosphere is controlled by adjusting the oxygen concentration in the inert gas. In practice, the oxygen concentration in the nitrogen gas should be adjusted, and the oxygen concentration in the nitrogen gas should be zero. It is good to adjust so that it may become a predetermined value in the range of 5-5 vol.%. When the oxygen concentration exceeds 5 vol.%, The saturation magnetization required for the carrier is not reached. Conversely, when the oxygen concentration is less than 0.5 vol.%, There is a possibility that the saturation magnetization is larger than that required for the carrier.
[0015]
In addition, when phosphorus is contained, if the P content has an appropriate relationship between the oxygen concentration and the saturation magnetization, the saturation magnetization is displaced in the direction of increasing according to the P content. Therefore, the saturation magnetization can be controlled to an appropriate value from both the oxygen concentration and the P content.
[0016]
[Crushing and classification process]
The fired product fired into ferrite is crushed with a crusher, and the crushed powder is classified or sieved to obtain a carrier having an appropriate particle size. For example, MnO—MgO—Fe 2 O 3 soft ferrite particles having an average particle diameter of about 70 μm are obtained.
[0018]
【Example】
[0019]
[Example 1]
MnCO 3 as the Mn source, Mg (OH) 2 as the Mg source, Fe 2 O 3 as the iron source, MnCO 3 : 25 mol% so that the ferrite composition of MnO · MgO · Fe 2 O 3 is obtained. , Mg (OH) 2 : 25 mol%, Fe 2 O 3 : 50 mol% were mixed to prepare the raw materials.
[0020]
The mixed powder was calcined by heating at 900 ° C. for 3 hours in an air atmosphere in a heating furnace. The obtained calcined product is cooled, pulverized to approximately 1 μm by a vibration mill, and a dispersant (trade name: San Nopco SN Dispersant 5468) is added together with water at a ratio of 1% by weight to the dry powder. A slurry having a concentration of 70% was obtained. This slurry was loaded into a wet ball mill and wet pulverized, and the resulting suspension was supplied to a spray dryer to obtain a granulated product composed of dry particles having an average particle size of about 80 μm.
[0021]
This granulated product was loaded into a firing furnace and fired at 1100 ° C. for 3 hours in a mixed gas in which the oxygen concentration in nitrogen gas was adjusted. In this example, fired products were obtained for 5 cases in which the oxygen concentration was adjusted to 0 vol.%, 1.0 vol.%, 2.0 vol.%, And 5.0 vol.%. Each fired product was pulverized with a pulverizer and sieved to obtain a soft ferrite powder having an average particle size of 70 μm. The saturation magnetization (σ S ) of each ferrite was measured and the results are shown in Table 1. FIG. 1 plots the relationship between the oxygen concentration and the saturation magnetization (σ S ). From these results, it can be seen that there is a predetermined relationship between the oxygen concentration during sintering and the saturation magnetization (σ S ), and the saturation magnetization decreases as the oxygen concentration increases.
[0022]
[Example 2]
Example 1 was repeated except that, when the raw materials were prepared, single P was added so as to be 0.1% by weight with respect to the ferrite composition of MnO.MgO.Fe 2 O 3 . The saturation magnetization (σ S ) of each obtained ferrite is shown in Table 1. The relationship between the oxygen concentration and the saturation magnetization in this example is also shown in FIG.
[0023]
Example 3
Example 1 was repeated except that, when the raw materials were prepared, single P was added so as to be 0.3% by weight with respect to the ferrite composition of MnO.MgO.Fe 2 O 3 . The saturation magnetization (σ S ) of each obtained ferrite is also shown in Table 1, and the relationship between the oxygen concentration and the saturation magnetization in this example is also shown in FIG.
[0024]
[Table 1]
From the results of Table 1 and FIG. 1, it is clear that the saturation magnetization decreases with a predetermined relationship as the oxygen concentration during firing is increased, and P is added as compared with the case where P is not added as in Example 1. Then, it can be seen that in the region where the oxygen concentration is low, the saturation magnetization tends to increase uniformly as the amount of addition of P increases.
[0026]
FIG. 2 shows the relationship between the saturation magnetization and the P amount in Table 1 with the P addition amount as the horizontal axis. From FIG. 2, the saturation magnetization tends to increase with the P addition amount in the region where the oxygen concentration is low. You can see that
[0027]
From this result, in order to obtain the intended saturation magnetization in the production of ferrite having the composition of MnO.MgO.Fe 2 O 3 , how should the oxygen concentration during firing and further the P content be set? It is clear.
[0028]
Example 4
MnCO 3 : 30 mol%, Mg (OH) 2 : 20 mol%, Fe 2 O 3 : 50 so that the atomic ratio of Mn / Mg is 3/2 and the composition is (Mn + Mg) O · Fe 2 O 3. Example 1 was repeated except that the raw materials were prepared by mixing at a mole percentage. Table 2 shows the saturation magnetization (σ S ) of the obtained ferrites. FIG. 3 plots the relationship between oxygen concentration and saturation magnetization (σ S ). From these results, it can be seen that there is a predetermined relationship between the oxygen concentration during sintering and the saturation magnetization (σ S ), and the saturation magnetization decreases as the oxygen concentration increases.
[0029]
Example 5
Example 4 was repeated except that single P was added so as to be 0.1% by weight with respect to the target ferrite composition at the time of raw material preparation. The saturation magnetization (σ S ) of each ferrite obtained is shown together in Table 2, and the relationship is shown in FIG.
[0030]
Example 6
Example 4 was repeated except that single P was blended so as to be 0.3% by weight with respect to the target ferrite composition at the time of raw material preparation. The saturation magnetization (σ S ) of each ferrite obtained is shown together in Table 2, and the relationship is shown in FIG.
[0031]
[Table 2]
From the results of Table 2 and FIG. 3, it is clear that even in the case of the ferrite composition of this example, the saturation magnetization decreases with a predetermined relationship as the oxygen concentration increases during firing. It can be seen that the saturation magnetization tends to increase uniformly in the region where the oxygen concentration is low in the region where the oxygen concentration is low as compared with the case where no oxygen is added.
[0033]
FIG. 4 shows the relationship between the saturation magnetization and the P content in Table 2 with the P addition amount as the horizontal axis. From FIG. 4, the saturation magnetization tends to increase with the P addition amount in the region where the oxygen concentration is low. You can see that
[0034]
Therefore, from FIG. 3 and FIG. 4, in order to obtain the intended saturation magnetization in the production of (Mn + Mg) O.Fe 2 O 3 system ferrite containing Mn and Mg at an Mn / Mg atomic ratio of 3/2, It is clear how the oxygen concentration and the P content should be set.
[0035]
[Comparative Example]
Example 4 was repeated except that the oxygen concentration during firing was set to 7 vol.% And / or single P was added so as to be 7% by weight with respect to the target ferrite composition at the time of raw material preparation. The saturation magnetization (σ S ) of each ferrite obtained in each example is shown in Table 2 as a comparative example. When the oxygen concentration is 7 vol.% And P is not added, a ferrite having a moderate saturation magnetization value is obtained, but the saturation magnetization is lower than the appropriate value as a carrier. When the P content is 7% by weight, the saturation magnetization becomes extremely low, which is not suitable as a carrier.
[0036]
【The invention's effect】
As described above, according to the present invention, the saturation magnetization value required for the electrophotographic developing carrier can be accurately targeted by controlling the oxygen concentration at the time of firing the ferrite and, in some cases, further by controlling the P content. Therefore, a preferable electrophotographic developing carrier according to the model can be manufactured with a high yield.
[Brief description of the drawings]
FIG. 1 is a relationship diagram between oxygen concentration (vol.%) In a ferrite firing atmosphere and saturation magnetization (emu / g) of ferrite.
FIG. 2 is a graph showing the relationship between the P concentration (wt%) in the blended raw material and the saturation magnetization (emu / g) of ferrite.
FIG. 3 is a relationship diagram between oxygen concentration (vol.%) In a ferrite firing atmosphere and saturation magnetization (emu / g) of ferrite in another ferrite composition.
FIG. 4 is a diagram showing the relationship between the P concentration (wt%) in the blended raw material and the saturation magnetization (emu / g) of ferrite in other ferrite compositions.
Claims (5)
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| JP26733399A JP4734598B2 (en) | 1999-09-21 | 1999-09-21 | Production method of soft ferrite |
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| JP2006323211A (en) * | 2005-05-19 | 2006-11-30 | Dowa Mining Co Ltd | Carrier for electrophotographic development, method for manufacturing same and electrophotographic developer |
| JP4781015B2 (en) * | 2005-06-03 | 2011-09-28 | パウダーテック株式会社 | Ferrite carrier core material for electrophotography, ferrite carrier for electrophotography, production method thereof, and developer for electrophotography using the ferrite carrier |
| US20080070150A1 (en) | 2006-09-14 | 2008-03-20 | Konica Minolta Business Technologies, Inc. | Carrier and two-component developer composed of the carrier |
| JP5038002B2 (en) * | 2007-04-10 | 2012-10-03 | Ｄｏｗａエレクトロニクス株式会社 | Carrier core material for electrophotographic developer and method for producing the same, carrier for electrophotographic developer, and electrophotographic developer |
| JP5366069B2 (en) * | 2008-03-26 | 2013-12-11 | パウダーテック株式会社 | Ferrite particles and manufacturing method thereof |
| JP5089657B2 (en) * | 2009-06-29 | 2012-12-05 | Ｄｏｗａエレクトロニクス株式会社 | Carrier core material for electrophotographic developer and method for producing the same, carrier for electrophotographic developer, and electrophotographic developer |
| JP5748258B2 (en) * | 2009-09-29 | 2015-07-15 | Ｄｏｗａエレクトロニクス株式会社 | Carrier core material for electrophotographic developer and method for producing the same |
| JP2011107286A (en) * | 2009-11-13 | 2011-06-02 | Dowa Electronics Materials Co Ltd | Carrier core material for electrophotographic development, method for producing the same, carrier for electrophotographic development and two-component electrophotographic developer |
| JP5478322B2 (en) * | 2010-03-30 | 2014-04-23 | Ｄｏｗａエレクトロニクス株式会社 | Ferrite particles, electrophotographic developer carrier, electrophotographic developer using the same, and method for producing ferrite particles |
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| JPS58145621A (en) * | 1982-02-12 | 1983-08-30 | Tdk Corp | Magnetic carrier particle |
| JPH067272B2 (en) * | 1985-08-30 | 1994-01-26 | 同和鉄粉工業株式会社 | Method for producing ferrite carrier for electrophotographic developer |
| JPS61291421A (en) * | 1986-04-25 | 1986-12-22 | Tdk Corp | Production of ferrite powder for magnetic toner for electrophotography |
| JP3157066B2 (en) * | 1993-06-29 | 2001-04-16 | 同和鉄粉工業株式会社 | Method for adjusting static resistance of carrier for electrophotographic development |
| JP3595702B2 (en) * | 1997-10-21 | 2004-12-02 | キヤノン株式会社 | Magnetic particles for charging, electrophotographic apparatus and process cartridge |
| JP3562787B2 (en) * | 1998-01-08 | 2004-09-08 | パウダーテック株式会社 | Ferrite carrier for electrophotographic developer and electrophotographic developer using the carrier |
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