JP4532721B2 - Method for producing magnetic toner - Google Patents

Description

【００３８】
【数１】

【００３９】
【数２】

【００４０】
また、モード円形度は、円形度を０．４０から１．００までを０．０１毎に６１分割し、測定した粒子の円形度をそれぞれの円形度に応じて各分割範囲に割り振り、円形度頻度分布において頻度値が最大となるピークの円形度である。
【００４１】
なお、本発明で用いている測定装置である「ＦＰＩＡ−１０００」は、各粒子の円形度を算出後、平均円形度及びモード円形度の算出に当たって、粒子を得られた円形度によって、円形度０．４０〜１．００を６１分割したクラスに分け、分割点の中心値と頻度を用いて平均円形度及びモード円形度の算出を行う算出法を用いている。しかしながら、この算出法で算出される平均円形度及びモード円形度の各値と、上述した各粒子の円形度を直接用いる算出式によって算出される平均円形度及びモード円形度の各値との誤差は、非常に少なく、実質的には無視できる程度のものであり、本発明においては、算出時間の短絡化や算出演算式の簡略化の如きデータの取り扱い上の理由で、上述した各粒子の円形度を直接用いる算出式の概念を利用し、一部変更したこのような算出法を用いても良い。
【００４２】
具体的な測定方法としては、界面活性剤を約０．１ｍｇ溶解している水１０ｍｌに磁性トナー約５ｍｇを分散させて分散液を調製し、超音波（２０ｋＨｚ，５０Ｗ）を分散液に５分間照射し、分散液濃度を５０００〜２万個／μｌとして、前記装置により測定を行い、３μｍ以上の円相当径の粒子群の平均円形度及びモード円形度を求める。
【００４３】
本発明における「平均円形度」とは、磁性トナーの凹凸の度合いの指標であり、磁性トナーが完全な球形の場合１．０００を示し、磁性トナーの表面形状が複雑になるほど平均円形度は小さな値となる。
【００４４】
なお、本測定において３μｍ以上の円相当径の粒子群についてのみ円形度を測定する理由は、３μｍ未満の円相当径の粒子群にはトナー粒子とは独立して存在する外部添加剤の粒子群も多数含まれるため、その影響によりトナー粒子群についての円形度が正確に見積もれないからである。
【００４５】
本発明の磁性トナーは、含有する磁性体の体積平均粒径をＡ、スチレン中における前記磁性体のストークス径をＢとすると、１．０≦Ｂ／Ａ≦３．５であり、好ましくは１．０≦Ｂ／Ａ≦２．８であり、より好ましくは１．０≦Ｂ／Ａ≦２．２である。
【００４６】
「スチレン中でのストークス径」とは、スチレン１０ｇに対し、磁性体８ｇをいれ、ホモジナイザー（２０ｋＨｚ，５０Ｗ）にて３分間分散させた後、タービスキャン（Ｆｏｒｍａｌ ａｃｔｉｏｎ社製）にて沈降速度Ｖを求め、以下の式から求めた値である。
【００４７】
タービスキャンは、一定時間毎に上記溶液の粒子界面の位置を測定する装置であり、透過光により測定を行った。これにより得られた粒子界面の移動距離と移動に要した時間から、沈降速度を求めるものである。具体的には、上記混合溶液をサンプル管に約５ｃｍの高さになるように入れ、ａｕｔｏｍａｔｉｃ ｓｃａｎにてスキャン間隔を３分、スキャン回数を１６１回とし、２３℃，６０％ＲＨにて測定を行う。
【００４８】
【数３】

ここで、Ｖは粒子の移動速度（ｍ／ｓ）、ρｃはスチレンの密度（９００ｋｇ／ｍ³）、ρｐは磁性体の密度（ｋｇ／ｍ³）、ｇは重力定数（９．８１ｍ／ｓ²）、νはスチレンの動的粘度（８．１×１０^-7ｍ／ｓ）、φは溶液中における磁性体の体積分率である。
【００４９】
なお、磁性体の密度は真密度計により測定した値を用いた。具体的にはマイクロメリティックス アキュピック１３３０（島津製作所）を用いた。
【００５０】
また、磁性体の体積平均粒径は、透過型電子顕微鏡を用いて測定する。具体的には、エポキシ樹脂中へ観察すべきトナー粒子、あるいは、磁性体を十分に分散させた後、温度４０℃の雰囲気中で２日間硬化させ得られた硬化物を、ミクロトームにより薄片状のサンプルとして、透過型電子顕微鏡（ＴＥＭ）において１万倍ないしは４万倍の拡大倍率の写真で、視野中の一次粒径と確認できる磁性体粒子１００個を測定して求めた。また、画像解析装置により粒子径を測定することも可能である。
【００５１】
ここで、ストークス径が大きいということは、スチレン中での磁性体の分散粒径が大きいことを意味し、磁性体の体積平均粒径との比、即ち、Ｂ／Ａが大きなものはスチレン中で磁性体が数個から複数個凝集した状態で存在することを示唆する。このような状態においては、本発明において好適なトナーの製造方法である、懸濁重合法（後述）でトナーを製造した場合、造粒後の油滴中での磁性体の分散が不十分であり、トナー粒子中で磁性体が合一・凝集した形で存在することになる。そのため、一次粒径が小さな磁性体を用いても、Ｂ／Ａが大きなものはトナー中での磁性体の分散粒径が大きなものとなってしまい、トナーの隠ぺい力が低下するために、着色力は劣るものとなってしまう。
【００５２】
さらに、ストークス径が大きいもの、即ち、重合性単量体中での磁性体の沈降速度が速いものは、造粒時においてはトナー組成物（重合性単量体、磁性体等）が不均一になり易く、粒度分布が広いものとなってしまい、さらに、液滴形成後の重合時においては、液滴中での磁性体の偏在、それに伴う離型剤の偏在を引き起こしてしまう（偏在がひどい場合、トナー粒子の半分に磁性体、残りの半分に離型剤が存在する場合もある）。ここで、特に、離型剤の偏在が生じると、トナー表面に離型剤の一部が露出してしまうため、あるいは、離型剤成分がしみ出し易くなるため、高温高湿環境下での耐久性が劣るものとなってしまう。
【００５３】
また、磁性体の分散性が悪いトナーから得られる画像、特に、ハーフトーン画像において、赤味の強い画像が得られ、画像品位が劣るものとなる。この理由については定かではないが、トナー中での磁性体の偏在により、磁性体が粗に、あるいは、密に存在する部分で長波長側の光が吸収されにくく（あるいは、反射されやすく）なっているためであると考えている。
【００５４】
このため、小粒径の磁性体を用いても、Ｂ／Ａが大きいものは、着色力が上がらず、且つ、赤味の強い画像が得られてしまう。このため、Ｂ／Ａは３．５以下であることが必要である。
【００５５】
一方、ストークス径が小さいということは、スチレン中での磁性体の分散粒径はほぼ一次粒径に近い状態であることを意味し、Ｂ／Ａが１．０未満となるとは考えにくい。
【００５６】
このため、１．０≦Ｂ／Ａ≦３．５とすることで、着色力、及び、高温高湿下での耐久性に優れ高品位な画像を得ることができる。
【００５７】
ストークス径は磁性体の処理剤、処理方法、及び磁性体の分散方法により調整することが可能である。これは次の理由によるものであると考えている。
【００５８】
第一に、磁性体表面は親水性であり、重合性単量体は疎水性である。このため、磁性体表面の疎水化処理が不均一であると、磁性体の良好な分散性は得られない。また、物理的に（機械的あるいは超音波分散等）磁性体を分散させても、表面処理が不均一な磁性体は再び凝集してしまい、ストークス径は大きなものとなってしまう。
【００５９】
第二に、均一な処理であっても、分散媒である重合性単量体と磁性体のなじみが良くないものは、磁性体の分散が劣るものとなる。
【００６０】
従来、重合トナーに使用される磁性体の表面改質に関しては、数多く提案されている。例えば、特開昭５９−２００２５４号公報、特開昭５９−２００２５６号公報、特開昭５９−２００２５７号公報、特開昭５９−２２４１０２号公報等に磁性体の各種シランカップリング剤処理技術が提案されており、特開昭６３−２５０６６０号公報では、ケイ素元素含有磁性粒子をシランカップリング剤で処理する技術が開示されている。
【００６１】
しかしながら、これらの処理により磁性体表面の疎水化を均一に行うことが困難であるという問題があり、したがって、磁性体同士の合一や疎水化されていない磁性体粒子の発生を避けることができず、ストークス径は大きくなり、粒度分布も広いものとなってしまう。また、疎水化磁性酸化鉄を用いる例として特開昭５４−８４７３１号公報にアルキルトリアルコキシシランで処理した磁性酸化鉄を含有するトナーが提案されている。この磁性酸化鉄の添加により、確かにトナーの電子写真諸特性は向上しているものの、磁性酸化鉄の表面活性は元来小さく、処理の段階で合一粒子が生じたり、疎水化が不均一であったりで、必ずしも満足のいくものではない。また、小粒径の磁性体を用いた場合、均一な処理がより困難なものとなり、本発明に適用するにはさらなる改良が必要である。さらに、磁性体の内包性向上のため、処理剤等を多量に使用したり、高粘性の処理剤等を使用した場合、疎水化度は確かに上がるものの、粒子同士の合一等が生じてストークス径は逆に大きなものとなってしまう。
【００６２】
このように、従来の表面処理磁性体を用いた重合トナーでは、表面処理の均一性は必ずしも達成されておらず、着色力の向上、高温高湿下での高耐久性を得ることは難しい。
【００６３】
そこで、本発明の磁性トナーに使用される磁性体においては、その粒子表面を疎水化する際、水系媒体中で、磁性体粒子を一次粒径となるよう分散しつつカップリング剤を加水分解しながら表面処理する方法を用いることが非常に好ましい。この疎水化処理方法は気相中で処理するより、磁性体粒子同士の合一が生じにくく、また疎水化処理による磁性体粒子間の帯電反発作用が働き、磁性体はほぼ一次粒子の状態で表面処理される。
【００６４】
カップリング剤を水系媒体中で加水分解しながら磁性体表面を処理する方法は、クロロシラン類やシラザン類のようにガスを発生するようなカップリング剤を使用する必要もなく、さらに、これまで気相中では磁性体粒子同士が合一しやすくて、良好な処理が困難であった高粘性のカップリング剤も使用できるようになり、疎水化の効果は絶大である。
【００６５】
本発明に係わる磁性体の表面処理において使用できるカップリング剤としては、例えば、シランカップリング剤、チタンカップリング剤等が挙げられる。より好ましく用いられるのはシランカップリング剤であり、一般式
Ｒｍ ＳｉＹｎ
［式中、Ｒはアルコオキシ基を示し、ｍは１〜３の整数を示し、Ｙはアルキル基、ビニル基、グリシドキシ基、メタクリル基の如き炭化水素基を示し、ｎは１〜３の整数を示す。］
で示されるものである。
【００６６】
例えばビニルトリメトキシシラン、ビニルトリエトキシシラン、ビニルトリス（βメトキシエトキシ）シラン、β−（３，４エポキシシクロヘキシル）エチルトリメトキシシラン、γ−グリシドキシプロピルトリメトキシシラン、γ−グリシドキシプロピルメチルジエトキシシラン、γ−アミノプロピルトリエトキシシラン、Ｎ−フェニル−γ−アミノプロピルトリメトキシシラン、γ−メタクリロキシプロピルトリメトキシシラン、ビニルトリアセトキシシラン、メチルトリメトキシシラン、ジメチルジメトキシシラン、フェニルトリメトキシシラン、ジフェニルジメトキシシラン、メチルトリエトキシシラン、ジメチルジエトキシシラン、フェニルトリエトキシシラン、ジフェニルジエトキシシラン、ｎ−ブチルトリメトキシシラン、イソブチルトリメトキシシラン、トリメチルメトキシシラン、ヒドロキシプロピリトリメトキシシラン、ｎ−ヘキサデシルトリメトキシシラン、ｎ−オクタデシルトリメトキシシラン等を挙げることができる。
【００６７】
この中で、磁性体の分散性の向上には、２重結合を有するシランカップリング剤を用いることが好ましく、フェニルトリメトキシシラン、γ−メタクリロキシプロピルトリメトキシシランがより好ましい。これは、特に懸濁重合を行う場合、２重結合を有するカップリング剤で処理すると、磁性体と重合性単量体とのなじみが良好になるためであると考えられ、トナー粒子中での磁性体の分散性が良好なものとなる。
【００６８】
しかし、これら２重結合を有するカップリング剤のみの使用では、磁性体に十分な疎水性を持たせることは困難であり、疎水性が十分で無い磁性体がトナー表面に露出する等の影響により、トナーの粒度分布も広いものとなってしまう。この理由は定かではないが、カップリング剤自身の疎水性や、磁性体表面の活性基との反応性、及び、磁性体表面の被覆性が劣ることによるものであると考えている。このため、十分な疎水性を得るために以下の式で示されるアルキルトリアルコキシシランカップリング剤を併用することがより好ましい。
【００６９】
Ｃ_p Ｈ_2p+1−Ｓｉ−（ＯＣ_q Ｈ_2q+1）₃
［式中、ｐは２〜２０の整数を示し、ｑは１〜３の整数を示す。］
【００７０】
上記式におけるｐが２より小さいと、疎水化処理は容易となるが、疎水性を十分に付与することが困難であり、トナー粒子からの磁性粒子の露出を抑制するのが難しくなる。またｐが２０より大きいと、疎水性は十分になるが、磁性体粒子同士の合一が多くなり、磁性体粒子を十分に分散性させることが困難になり、着色力が劣り、高温高湿下での耐久性も劣る。
【００７１】
また、ｑが３より大きいと、シランカップリング剤の反応性が低下して疎水化が十分に行われにくくなる。
【００７２】
特に、式中のｐが２〜２０の整数（より好ましくは、３〜１５の整数）を示し、ｑが１〜３の整数（より好ましくは、１又は２の整数）を示すアルキルトリアルコキシシランカップリング剤を使用するのが良い。
【００７３】
その処理量は磁性体１００質量部に対して、シランカップリング剤の総量が０．０５〜２０質量部、好ましくは０．１〜１０質量部であり、磁性体の表面積やカップリング剤の反応性に応じて処理剤の量を調整することが好ましい。
【００７４】
ここで、「水系媒体」とは、水を主要成分としている媒体である。具体的には、水系媒体として水そのもの、水に少量の界面活性剤を添加したもの、水にｐＨ調整剤を添加したもの、水に有機溶剤を添加したものが挙げられる。界面活性剤としては、ポリビニルアルコールの如きノンイオン系界面活性剤が好ましい。界面活性剤は、水に対して０．１〜５質量％添加するのが良い。ｐＨ調整剤としては、塩酸の如き無機酸が挙げられ、有機溶剤としてはアルコール類等が挙げられる。
【００７５】
撹拌は、例えば撹拌羽根を有する混合機（具体的には、アトライター、ＴＫホモミキサーの如き高剪断力混合装置）で、磁性体粒子が水系媒体中で、一次粒子になるように充分におこなうのが良い。
【００７６】
なお、複数種のシランカップリング剤を用いる場合、同時、あるいは時間差をもって複数種のカップリング剤を投入し、磁性体の処理を行う。
【００７７】
こうして得られる磁性体は粒子の凝集が見られず、個々の粒子表面が均一に疎水化処理されているため、ストークス径は小さなものとなり、磁性体の分散性は良好なものとなる。
【００７８】
本発明のトナーにおいて用いられる磁性体は、リン、コバルト、ニッケル、銅、マグネシウム、マンガン、アルミニウム、珪素などの元素を含んでもよい。また、磁性体は四三酸化鉄、γ−酸化鉄等、酸化鉄を主成分とするものであり、これらを１種または２種以上併用して用いられる。これら磁性体は、窒素吸着法によるＢＥＴ比表面積が好ましくは２〜３０ｍ²／ｇ、特に３〜２８ｍ²／ｇ、更にモース硬度が５〜７のものが好ましい。
【００７９】
磁性体の形状としては、多面体、８面体、６面体、球形、針状、鱗片状などがあるが、多面体、８面体、６面体、球形等の異方性の少ないものが画像濃度を高める上で好ましい。こういった磁性体の形状はＳＥＭなどによって確認することができる。
【００８０】
磁性体の体積平均粒径としては０．０５〜０．４μｍが好ましく、より好ましくは０．１〜０．３μｍである。体積平均径が０．０５μｍ未満の場合、黒色度の低下が顕著となり、白黒用トナーの着色剤としては着色力が不十分となるうえに、磁性体どうしの凝集が強くなるため、分散性が悪化する。また、磁性体表面の均一性処理が非常に困難なものとなる。一方、体積平均粒径が０．４μｍを超えてしまうと、一般の着色剤と同様に着色力が不足するようになる。加えて、体積平均粒径が０．４μｍより大きな磁性体を用いると、本発明の如き、小粒径トナー用の着色剤として使用する場合、個々のトナー粒子に均一に磁性粒子を分散させることが確率的に困難となり、トナーの均一帯電性が損なわれる。
【００８１】
本発明に用いられる磁性体は、体積平均変動係数が３５以下であることが好ましい。体積平均変動係数が３５より大きいということは、磁性体の粒度分布が広いことを意味する。このような磁性体を使用すると、磁性体表面の処理の均一性が劣るとともに、トナー中での分散性が悪化する。
【００８２】
なお、体積平均変動係数は次式により求めるものと定義する。
【００８３】
【数４】

【００８４】
本発明に用いる磁性体の疎水化度は２５〜９５％であることが好ましく、より好ましくは３５〜９５％である。疎水化度は磁性体表面の処理剤の種類、及び、量により任意に変えることが可能である。「疎水化度」とは磁性体の疎水性を示しており、疎水化度が低いものは親水性が高いことを意味する。そのため、疎水化度が低い磁性体を用いた場合、本発明に好適に用いられる懸濁重合法では、造粒中に磁性体が水系に移行してしまい、粒度分布がブロードになると共に、磁性体がトナー表面に露出、あるいはトナーから遊離して存在することになり好ましくない。また、重合性単量体中での分散性も劣るものとなる。一方、疎水化度を９５％超とするためには、磁性体表面の処理剤を多量に使用せねばならず、この様な状態では磁性体の合一が生じ易く、処理の均一性が損なわれてしまう。
【００８５】
なお、本発明における疎水化度とは以下の方法により測定されたものである。
【００８６】
磁性体の疎水化度の測定は、メタノール滴定試験により行う。メタノール滴定試験は、疎水化された表面を有する磁性体の疎水化度を確認する実験的試験である。
【００８７】
メタノールを用いた疎水化度測定は次のように行う。磁性体０．１ｇを容量２５０ｍｌのビーカーの水５０ｍｌに添加する。その後メタノールを液中に徐々に添加し滴定を行う。この際メタノールは液底部より供給し、緩やかに撹拌しながら行う。磁性粒子の沈降終了は、液面に磁性体の浮遊物が確認されなくなった時点とし、疎水化度は、沈降終了時点に達した際のメタノール及び水混合液中のメタノールの体積百分率としてあらわされる。
【００８８】
本発明のトナーに用られる磁性体は、結着樹脂１００質量部に対して、１０質量部乃至２００質量部を用いることが好ましい。さらに好ましくは２０〜１８０質量部を用いることが良い。１０質量部未満ではトナーの着色力が乏しく、カブリの抑制も困難である。一方、２００質量部を超えると、トナー担持体への磁力による保持力が強まり現像性が低下したり、個々のトナー粒子への磁性体の均一な分散が難しくなるだけでなく、定着性が低下してしまう。
【００８９】
なお、トナー中の磁性体の含有量の測定は、パーキンエルマー社製熱分析装置「ＴＧＡ７」で測定した。測定方法は、窒素雰囲気下において昇温速度２５℃／分で常温から９００℃までトナーを加熱し、１００℃から７５０℃まで間の減量質量％を結着樹脂量とし、残存質量を近似的に磁性体量とした。
【００９０】
本発明に係わる磁性トナーに用いられる磁性体は、例えばマグネタイトの場合、下記方法で製造される。
【００９１】
第一鉄塩水溶液に、鉄成分に対して当量または当量以上の水酸化ナトリウムの如きアルカリを加え、水酸化第一鉄を含む水溶液を調製する。調製した水溶液のｐＨをｐＨ７以上（好ましくはｐＨ８〜１４）に維持しながら空気を吹き込み、水溶液を７０℃以上に加温しながら水酸化第一鉄の酸化反応をおこない、磁性酸化鉄粒子の芯となる種晶をまず生成する。
【００９２】
次に、種晶を含むスラリー状の液に、前に加えたアルカリの添加量を基準として約１当量の硫酸第一鉄を含む水溶液を加える。液のｐＨを６〜１４に維持しながら空気を吹込みながら水酸化第一鉄の反応をすすめ、種晶を芯にして磁性酸化鉄粒子を成長させる。酸化反応がすすむにつれて液のｐＨは酸性側に移行していくが、液のｐＨは６未満にしない方が好ましい。酸化反応の終期に液のｐＨを調整し、磁性酸化鉄が一次粒子になるよう十分に撹拌し、カップリング剤を添加して十分に混合撹拌し、撹拌後に濾過し、乾燥し、軽く解砕することで疎水性処理磁性酸化鉄粒子が得られる。あるいは、酸化反応終了後、洗浄、濾過して得られた酸化鉄粒子を、乾燥せずに別の水系媒体中に再分散させた後、再分散液のｐＨを調整し、十分撹拌しながらシランカップリング剤を添加し、カップリング処理を行っても良い。
【００９３】
いずれにせよ、酸化反応終了後に乾燥工程を経ずに表面処理を行うことが肝要であり、本発明のトナーにおける重要なポイントである。
【００９４】
第一鉄塩としては、一般的に硫酸法チタン製造に副生する硫酸鉄、鋼板の表面洗浄に伴って副生する硫酸鉄の利用が可能であり、更に塩化鉄等が可能である。
【００９５】
水溶液法による磁性酸化鉄の製造方法は一般に反応時の粘度の上昇を防ぐこと、及び、硫酸鉄の溶解度から鉄濃度０．５〜２ｍｏｌ／ｌが用いられる。硫酸鉄の濃度は一般に薄いほど製品の粒度が細かくなる傾向を有する。また、反応に際しては、空気量が多いほど、そして反応温度が低いほど微粒化しやすい。
【００９６】
このようにして製造された疎水性磁性体粒子を材料とした磁性トナーを使用することにより、安定したトナーの帯電性が得られ、転写効率が高く、高画質及び高安定性が可能となる。
【００９７】
本発明のトナーは、磁場７９．６ｋＡ／ｍ（１０００エルステッド）における磁化の強さが１０〜５０Ａｍ²／ｋｇ（ｅｍｕ／ｇ）である磁性トナーであることが重要である。これは、現像装置内に磁気力発生手段を設けることで、磁性トナーではトナーの漏れを防止でき、トナーの搬送性或いは撹拌性を高められるばかりでなく、トナー担持体上に磁力が作用するように磁気力発生手段を設けることで、磁性トナーが穂立ちを形成するため、トナーの飛散を防止することが容易となる。
【００９８】
トナーの磁場７９．６ｋＡ／ｍにおける磁化の強さが１０Ａｍ²／ｋｇ未満であると、上記の効果が得られず、トナー担持体上に磁力を作用させるとトナーの穂立ちが不安定となり、トナーへの帯電付与が均一に行えないことによるカブリ、画像濃度ムラ、転写残トナーの回収不良等の画像不良を生じる易くなる。一方、トナーの磁場７９．６ｋＡ／ｍにおける磁化の強さが５０Ａｍ²／ｋｇよりも大きいと、トナーに磁力を作用させると磁気凝集によりトナーの流動性が著しく低下し、現像性が低下しトナーがダメージを受けやすくなり、トナー劣化が著しくなる。さらに、転写性も低下することで転写残トナーが増加し好ましくない。
【００９９】
なお、本発明において磁性トナーの飽和磁化の強さは、振動型磁力計ＶＳＭ Ｐ−１−１０（東英工業社製）を用いて、２５℃の室温にて外部磁場７９．６ｋＡ／ｍで測定した。また、磁性体の磁気特性は、２５℃の室温にて外部磁場７９６ｋＡ／ｍで測定した。
【０１００】
本発明のトナーは、高画質化のため、より微小な潜像ドットを忠実に現像するため、トナーの重量平均粒径が３〜１０μｍ、更には４〜９μｍであることが好ましい。
【０１０１】
重量平均粒径が３μｍ未満のトナーにおいては、転写効率の低下から感光体上の転写残トナーが多くなり、接触帯電工程での感光体の削れやトナー融着の抑制が難しくなる。さらに、トナー全体の表面積が増えることに加え、粉体としての流動性及び撹拌性が低下し、個々のトナー粒子を均一に帯電させることが困難となることからカブリや転写性が悪化傾向となり、削れや融着以外にも画像の不均一ムラの原因となりやすいため、本発明で使用するトナーには好ましくない。また、トナーの重量平均粒径が１０μｍを超える場合には、文字やライン画像に飛び散りが生じやすく、高解像度が得られにくい。さらに装置が高解像度になっていくと１０μｍ超のトナーは１ドットの再現が悪化する傾向にある。
【０１０２】
また、本発明においては、重量平均粒径／数平均粒径の比が１．４０以下であることが好ましく、より好ましくは１．３５以下である。重量平均粒径／数平均粒径の比が１．４０より大きいということはトナーの粒度分布が広いことを意味し、選択現像が生じ易くなると共に、帯電量分布も広くなり、カブリの増加や転写性の低下を招き好ましくない。
【０１０３】
ここで、トナーの平均粒径及び粒度分布はコールターカウンターＴＡ−ＩＩ型あるいはコールターマルチサイザー（コールター社製）等、種々の方法で測定可能であるが、本発明においてはコールターマルチサイザー（コールター社製）を用い、個数分布、体積分布を出力するインターフェイス（日科機製）及びＰＣ９８０１パーソナルコンピューター（ＮＥＣ製）を接続し、電解液は１級塩化ナトリウムを用いて１％ＮａＣｌ水溶液を調製する。たとえば、ＩＳＯＴＯＮ Ｒ−ＩＩ（コールターサイエンティフィックジャパン社製）が使用できる。測定法としては、前記電解水溶液１００〜１５０ｍｌ中に分散剤として界面活性剤、好ましくはアルキルベンゼンスルフォン酸塩を０．１〜５ｍｌ加え、更に測定試料を２〜２０ｍｇ加える。試料を懸濁した電解液は超音波分散器で約１〜３分間分散処理を行ない前記コールターマルチサイザーによりアパーチャーとして１００μｍアパーチャーを用いて、２μｍ以上のトナー粒子の体積、個数を測定して体積分布と個数分布とを算出した。
【０１０４】
それから、本発明に係わる体積分布から求めた体積基準の重量平均粒径（Ｄ４）、個数分布から求めた個数基準の長さ平均粒径、数平均粒径（Ｄ１）を求めた。
【０１０５】
本発明の磁性トナーは鉄及び鉄化合物の遊離率が０．０５〜３．００％であることが好ましく、より好ましくは０．０５〜１．５０％、最も好ましくは０．０５〜１．００％である。鉄及び鉄化合物の遊離率とは、パーティクルアナライザー（ＰＴ１０００：横河電機（株）製）により測定されたものである。
【０１０６】
パーティクルアナライザーはＪａｐａｎ Ｈａｒｄｃｏｐｙ９７論文集の６５〜６８頁に記載の原理で測定を行う。具体的には、前記装置はトナー等の微粒子を一個づつプラズマへ導入し、微粒子の発光スペクトルから発光物の元素、粒子数、粒子の粒径を知ることができる。
【０１０７】
この中で、「遊離率」とは、結着樹脂の構成元素である炭素原子の発光と、鉄原子の発光の同時性から次式により求めたものと定義する。
【０１０８】
【数５】

【０１０９】
ここで、「炭素原子と鉄原子の同時発光」とは、炭素原子の発光から２．６ｍｓｅｃ以内に発光した鉄原子の発光を同時発光とし、それ以降の鉄原子の発光は鉄原子のみの発光とする。本発明ではトナー粒子は磁性体を多く含有しているため、炭素原子と鉄原子が同時発光するということは、トナー中に磁性体が分散していることを意味し、鉄原子のみの発光は、磁性体がトナーから遊離していることを意味すると言い換えることも可能である。
【０１１０】
具体的な測定方法としては、０．１％酸素含有のヘリウムガスを用い、２３℃で湿度６０％の環境にて測定を行い、トナーサンプルは同環境下にて１晩放置し、調湿したものを測定に用いる。また、チャンネル１で炭素原子（測定波長２４７．８６０ｎｍ、Ｋファクターは推奨値を使用）、チャンネル２で鉄原子（測定波長２３９．５６ｎｍ、Ｋファクターは３．３７６４を使用）を測定し、一回のスキャンで炭素原子の発光数が１０００から１４００個となるようにサンプリングを行い、炭素原子の発光数が総数で１００００個以上となるまでスキャンを繰り返し、発光数を積算する。この時、炭素元素の発光個数を縦軸に、元素の三乗根電圧を横軸にとった分布において、前記分布が極大を一つ有し、更に、谷が存在しない分布となるようにサンプリングし、測定を行う。そして、このデータを元に、全元素のノイズカットレベルを１．５０Ｖとし、上記計算式を用い、鉄及び鉄化合物の遊離率を算出する。
【０１１１】
また、荷電制御剤であるアゾ系の鉄化合物等といった、鉄原子を含有する無機化合物以外の材料もトナー中に含まれている場合があるが、こういった化合物は鉄原子と同時に有機化合物中の炭素も同時に発光するため、遊離の鉄原子としてはカウントされない。
【０１１２】
本発明者らが検討を行ったところ、鉄及び鉄化合物の遊離率とトナー表面への露出量には深い関連があり、遊離の磁性体量が３．００％以下であれば、おおむね磁性体のトナー表面への露出が抑制されるとともに、カブリが少なく、転写性も良好であることが判明した。これは、低抵抗の磁性体がトナー表面にほとんど存在しないためであり、安定した高い帯電量を得られるためであると考えている。
【０１１３】
鉄及び鉄化合物の遊離率は磁性体の疎水化度、粒度分布、処理の均一性等に依存するものであるが、一例として、磁性体の表面処理が不均一である場合、表面処理が充分に施されていない（親水性が強い）磁性体は、トナー中で合一、あるいは、凝集して存在すると共に、親水性が強いものは内包化されず、その一部あるいは全てがトナーから遊離してしまうことに起因する。また、疎水化度が低い磁性体を用いた場合も同様であると考えている。このため、特に磁性を用いる現像方式の場合、鉄及び鉄化合物の遊離率が高いものは、磁性体がトナー担持体上に蓄積してしまい、トナーの帯電性の低下、選択現像等を生じてしまう。さらに、このような磁性体を用いた場合、重合性単量体中での分散性も不十分なことから、着色力の低下、高温高湿下での耐久性の低下を招き易く、好ましくない。
【０１１４】
一方、鉄及び鉄化合物の遊離率が０．０５％より少ないと、実質的に磁性体はトナーから遊離していないことを意味する。このように鉄及び鉄化合物の遊離率が低いトナーは高い帯電量を有するものの、多数枚画出し時にトナーのチャージアップに起因する画像濃度の低下、及び、画像のがさつきが生じてしまう。
【０１１５】
これは、次の様な理由であると考えている。一般的に、トナー担持体上のトナーは感光体上へ全て現像されることは無く、現像直後においてもトナー担持体上にはトナーは存在する。特に磁性トナーを用いたジャンピング現像においてはその傾向が強く、現像効率はさほど高くない。さらに円形度の高いトナーは前述の通り、現像部において、均一な細い穂を形成しており、穂の先端部に存在するトナーから現像されてしまい、トナー担持体付近のトナーはなかなか現像されないものと考えられる。
【０１１６】
そのため、トナー担持体付近のトナーは繰り返し帯電部材による摩擦帯電を受け、チャージアップしてしまい、さらに現像されにくくなるという悪循環に陥ってしまう。また、この様な状態では、トナーの帯電均一性は損なわれ、画像のがさつきを生じてしまう。
【０１１７】
ここで、鉄及び鉄化合物の遊離率が０．０５％以上のトナーを用いた場合、遊離の磁性体あるいはトナー表面にわずかに存在している磁性体によりトナーのチャージアップが抑制されると共に、トナーの帯電量の均一性が促され、がさつきは抑制される。
【０１１８】
これらの理由により、鉄及び鉄化合物の遊離率は０．０５〜３．００％であることが好ましい。
【０１１９】
本発明に係わるトナーは離型剤を含有しているが、結着樹脂１００質量部に対し１．０〜３０質量部を含有することが好ましい。
【０１２０】
転写材上に転写されたトナー像はその後、熱・圧力等のエネルギーにより転写材上に定着され、半永久的画像が得られる。この際、熱ロール式定着が一般に良く用いられる。先述したように、重量平均粒径が１０μｍ以下のトナーを用いれば非常に高精細な画像を得ることができるが、粒径の細かいトナー粒子は紙等の転写材を使用した場合に紙の繊維の隙間に入り込み、熱定着用ローラーからの熱の受け取りが不十分となり、低温オフセットが発生しやすい。しかしながら、本発明に係わるトナーにおいて、適正量の離型剤を含有せしめることにより、高画質と定着性を両立させることが可能となる。
【０１２１】
本発明に係わる磁性トナーに使用可能な離型剤としては、パラフィンワックス、マイクロクリスタリンワックス、ペトロラクタム等の石油系ワックス及びその誘導体、モンタンワックスびその誘導体、フィッシャートロプシュ法による炭化水素ワックス及びその誘導体、ポリエチレンに代表されるポリオレフィンワックス及びその誘導体、カルナバワックス、キャンデリラワックス等天然ワックス及びその誘導体などで、誘導体には酸化物や、ビニル系モノマーとのブロック共重合物、グラフト変性物を含む。さらには、高級脂肪族アルコール、ステアリン酸、パルミチン酸等の脂肪酸、あるいはその化合物、酸アミドワックス、エステルワックス、ケトン、硬化ヒマシ油及びその誘導体、植物系ワックス、動物性ワックスなども使用できる。
【０１２２】
これらの離型剤成分のなかでも、示差走査熱量計により測定されるＤＳＣ曲線において、昇温時に４０〜１１０℃の領域に最大吸熱ピークを有するものが好ましく、４５〜９０℃の領域に有するものがより好ましい。上記温度領域に最大吸熱ピークを有することにより、低温定着に大きく貢献しつつ、離型性をも効果的に発現する。
【０１２３】
前記最大吸熱ピークが４０℃未満であると離型剤成分の自己凝集力が弱くなり、結果として耐高温オフセット性が悪化する。また、離型剤の浸み出しが生じ易くなり、トナーの帯電量が低下する。一方、前記最大吸熱ピークが１１０℃を超えると定着温度が高くなり低温オフセットが発生しやすくなり好ましくない。さらに、水系媒体中で造粒／重合を行い重合方法により直接トナーを得る場合、前記最大吸熱ピーク温度が高いと主に造粒中に離型剤成分が析出する等の問題を生じ、離型剤の分散性が悪化し、好ましくない。
【０１２４】
また、離型剤の含有量が１．０質量％未満では低温オフセット抑制効果に乏しく、３０質量％を超えてしまうと長期間の保存性が悪化すると共に、他のトナー材料の分散性が悪くなり、磁性トナーの流動性の悪化や画像特性の低下につながる。さらに多量のワックスを内包するために、トナー形状がいびつになりやすくなる。
【０１２５】
本発明のトナーには、荷電特性を安定化するために荷電制御剤を配合しても良い。荷電制御剤としては、公知のものが利用でき、特に帯電スピードが速く、かつ、一定の帯電量を安定して維持できる荷電制御剤が好ましい。さらに、トナーを直接重合法を用いて製造する場合には、重合阻害性が低く、水系分散媒体への可溶化物が実質的にない荷電制御剤が特に好ましい。
【０１２６】
具体的な化合物としては、ネガ系荷電制御剤としてサリチル酸、アルキルサリチル酸、ジアルキルサリチル酸、ナフトエ酸、ダイカルボン酸の如き芳香族カルボン酸の金属化合物、アゾ染料あるいはアゾ顔料の金属塩または金属錯体、スルホン酸又はカルボン酸基を側鎖に持つ高分子型化合物、ホウ素化合物、尿素化合物、ケイ素化合物、カリックスアレーン等が挙げられる。ポジ系荷電制御剤として四級アンモニウム塩、前記四級アンモニウム塩を側鎖に有する高分子型化合物、グアニジン化合物、ニグロシン系化合物、イミダゾール化合物等が挙げられる。
【０１２７】
荷電制御剤をトナーに含有させる方法としては、トナー母粒子内部に添加する方法と外部添加する方法がある。これらの荷電制御剤の使用量としては、結着樹脂の種類、他の添加剤の有無、分散方法を含めたトナー製造方法によって決定されるもので、一義的に限定されるものではないが、内部添加する場合は、好ましくは結着樹脂１００質量部に対して０．１〜１０質量部、より好ましくは０．１〜５質量部の範囲で用いられる。また、外部添加する場合、トナー１００質量部に対し、好ましくは０．００５から１．０質量部、より好ましくは０．０１から０．３質量部である。しかしながら、本発明の磁性トナーは、荷電制御剤の添加は必須ではなく、トナーの層厚規制部材やトナー担持体との摩擦帯電を積極的に利用することでトナー中に必ずしも荷電制御剤を含む必要はない。
【０１２８】
次に本発明のトナーの製造方法として好適に用いることのできる懸濁重合法による製造方法を説明する。
【０１２９】
本発明のトナーに使用される重合性単量体系を構成する重合性単量体としては以下のものが挙げられる。
【０１３０】
重合性単量体としては、スチレン・ｏ−メチルスチレン・ｍ−メチルスチレン・ｐ−メチルスチレン・ｐ−メトキシスチレン・ｐ−エチルスチレン等のスチレン系単量体、アクリル酸メチル・アクリル酸エチル・アクリル酸ｎ−ブチル・アクリル酸イソブチル・アクリル酸ｎ−プロピル・アクリル酸ｎ−オクチル・アクリル酸ドデシル・アクリル酸２−エチルヘキシル・アクリル酸ステアリル・アクリル酸２−クロルエチル・アクリル酸フェニル等のアクリル酸エステル類、メタクリル酸メチル・メタクリル酸エチル・メタクリル酸ｎ−プロピル・メタクリル酸ｎ−ブチル・メタクリル酸イソブチル・メタクリル酸ｎ−オクチル・メタクリル酸ドデシル・メタクリル酸２−エチルヘキシル・メタクリル酸ステアリル・メタクリル酸フェニル・メタクリル酸ジメチルアミノエチル・メタクリル酸ジエチルアミノエチル等のメタクリル酸エステル類、その他のアクリロニトリル・メタクリロニトリル・アクリルアミド等の単量体が挙げられる。
【０１３１】
これらの単量体は単独、または混合して使用し得る。上述の単量体の中でも、スチレンまたはスチレン誘導体を単独で、あるいはほかの単量体と混合して使用することがトナーの現像特性及び耐久性の点から好ましい。
【０１３２】
本発明に係わるトナーの製造においては、単量体系に樹脂を添加して重合しても良い。例えば、単量体では水溶性のため水性懸濁液中では溶解して乳化重合を起こすため使用できないアミノ基、カルボン酸基、水酸基、スルフォン酸基、グリシジル基、ニトリル基等、親水性官能基含有の単量体成分をトナー中に導入したいときには、これらとスチレンあるいはエチレン等、ビニル化合物とのランダム共重合体、ブロック共重合体、あるいはグラフト共重合体等、共重合体の形にして、あるいはポリエステル、ポリアミド等の重縮合体、ポリエーテル、ポリイミン等重付加重合体の形で使用が可能となる。こうした極性官能基を含む高分子重合体をトナー中に共存させると、このような高分子重合体がトナー表面に局在化しやすくなるため、離型剤、磁性体等の内包化が強力となり、耐ブロッキング性や現像性の良好なトナーを得ることができる。
【０１３３】
これらの樹脂の中でも特にポリエステル樹脂を含有することにより、その効果は大きなものとなる。これは次のような理由であると考えている。ポリエステル樹脂は、比較的極性の高い官能基であるエステル結合を数多く含むため、樹脂自身の極性が高くなる。その極性のため、水系分散媒中では液滴表面にポリエステルが偏在する傾向が強くなり、その状態を保ちながら重合が進行し、トナーとなる。このため、トナー表面にポリエステル樹脂が偏在することで表面状態や、表面組成が均一なものとなり、その結果、帯電性が均一になると共に、離型剤、磁性体の内包性が良好なこととの相乗効果により非常に良好な現像性を得ることができる。
【０１３４】
本発明に使用されるポリエステル樹脂は、例えばトナーの帯電性，耐久性および定着性などの物性をコントロールする上で、飽和ポリエステル樹脂、不飽和ポリエステル樹脂、あるいはその両者を適宜選択して使用することが可能である。
【０１３５】
本発明に使用されるポリエステル樹脂を構成するアルコール成分と酸成分を以下に例示する。
【０１３６】
アルコール成分としては、エチレングリコール、プロピレングリコール、１，３−ブタンジオール、１，４−ブタンジオール、２，３−ブタンジオール、ジエチレングリコール、トリエチレングリコール、１，５−ペンタンジオール、１，６−ヘキサンジオール、ネオペンチルグリコール、２−エチル−１，３−ヘキサンジオール、シクロヘキサンジメタノール、ブテンジオール、オクテンジオール、シクロヘキセンジメタノール、水素化ビスフェノールＡ、また式（Ｉ）で表されるビスフェノール誘導体；
【０１３７】
【化１】

［式中、Ｒはエチレンまたはプロピレン基であり、ｘ，ｙはそれぞれ１以上の整数であり、かつｘ＋ｙの平均値は２〜１０である。］
【０１３８】
あるいは式（Ｉ）の化合物の水添物、また、式（ＩＩ）で示されるジオール；
【０１３９】
【化２】

あるいは式（ＩＩ）の化合物の水添物のジオールが挙げられる。
【０１４０】
２価のカルボン酸としてはフタル酸、テレフタル酸、イソフタル酸、無水フタル酸の如きベンゼンジカルボン酸またはその無水物；コハク酸、アジピン酸、セバシン酸、アゼライン酸の如きアルキルジカルボン酸またはその無水物、またさらに炭素数６〜１８のアルキルまたはアルケニル基で置換されたコハク酸もしくはその無水物；フマル酸、マレイン酸、シトラコン酸、イタコン酸の如き不飽和ジカルボン酸またはその無水物などが挙げられる。
【０１４１】
さらに、アルコール成分としてグリセリン、ペンタエリスリトール、ソルビット、ソルビタン、ノボラック型フェノール樹脂のオキシアルキレンエーテルの如き多価アルコールが挙げられ、酸成分としてトリメリット酸、ピロメリット酸、１，２，３，４−ブタンテトラカルボン酸、ベンゾフェノンテトラカルボン酸やその無水物の如き多価カルボン酸が挙げられる。
【０１４２】
前記ポリエステル樹脂の中では、帯電特性や環境安定性が優れており、その他の電子写真特性においてバランスのとれた前記のビスフェノールＡのアルキレンオキサイド付加物の場合が好ましく使用される。この化合物の場合には、定着性やトナーの耐久性の点においてアルキレンオキサイドの平均付加モル数は２〜１０が好ましい。
【０１４３】
前記ポリエステル樹脂は全成分中４５〜５５モル％がアルコール成分であり、５５〜４５モル％が酸成分であることが好ましい。
【０１４４】
前記ポリエステル樹脂は、本発明の製造方法においてトナー粒子表面に存在し、得られるトナー粒子が安定した帯電性を発現するためには、０．１〜５０ｍｇＫＯＨ／樹脂１ｇの酸価を有していることが好ましい。０．１ｍｇＫＯＨ／樹脂１ｇ未満だとトナー表面への存在量が絶対的に不足し、５０ｍｇＫＯＨ／樹脂１ｇを超えるとトナーの帯電性に悪影響を及ぼす。さらに本発明では、５〜３５ｍｇＫＯＨ／樹脂１ｇの酸価の範囲がより好ましい。
【０１４５】
本発明においては、得られるトナー粒子の物性に悪影響を及ぼさない限り２種以上のポリエステル樹脂を併用したり、例えば、シリコーンやフルオロアルキル基含有化合物により変性したりして物性を調整することも好適に行われる。
【０１４６】
また、このような極性官能基を含む高分子重合体を使用する場合、その平均分子量は５，０００以上が好ましく用いられる。５，０００未満、特に４，０００以下では、本重合体が表面付近に集中し易いことから、現像性や耐ブロッキング性等に悪い影響が起こり易くなり好ましくない。
【０１４７】
また、材料の分散性や定着性、あるいは画像特性の改良等を目的として上記以外の樹脂を単量体系中に添加しても良く、用いられる樹脂としては、例えば、ポリスチレン、ポリビニルトルエンなどのスチレン及びその置換体の単重合体；スチレン−プロピレン共重合体、スチレン−ビニルトルエン共重合体、スチレン−ビニルナフタリン共重合体、スチレン−アクリル酸メチル共重合体、スチレン−アクリル酸エチル共重合体、スチレン−アクリル酸ブチル共重合体、スチレン−アクリル酸オクチル共重合体、スチレン−アクリル酸ジメチルアミノエチル共重合体、スチレン−メタクリル酸メチル共重合体、スチレン−メタクリル酸エチル共重合体、スチレン−メタクリル酸ブチル共重合体、スチレン−メタクリル酸ジメチルアミノエチル共重合体、スチレン−ビニルメチルエーテル共重合体、スチレン−ビニルエチルエーテル共重合体、スチレン−ビニルメチルケトン共重合体、スチレン−ブタジエン共重合体、スチレン−イソプレン共重合体、スチレン−マレイン酸共重合体、スチレン−マレイン酸エステル共重合体などのスチレン系共重合体；ポリメチルメタクリレート、ポリブチルメタクリレート、ポリ酢酸ビニル、ポリエチレン、ポリプロピレン、ポリビニルブチラール、シリコーン樹脂、ポリエステル樹脂、ポリアミド樹脂、エポキシ樹脂、ポリアクリル酸樹脂、ロジン、変性ロジン、テルペン樹脂、フェノール樹脂、脂肪族または脂環族炭化水素樹脂、芳香族系石油樹脂などが単独或いは混合して使用できる。
【０１４８】
これら樹脂の添加量としては、単量体１００質量部に対し１〜２０質量部が好ましい。１質量部未満では添加効果が小さく、２０質量部よりも多く添加すると重合トナーの種々の物性設計が難しくなる。
【０１４９】
さらに、単量体を重合して得られるトナーの分子量範囲とは異なる分子量の重合体を単量体中に溶解して重合すれば、分子量分布の広い、耐オフセット性の高いトナーを得ることができる。
【０１５０】
本発明のトナーの製造において使用される重合開始剤としては、重合反応時に半減期０．５〜３０時間であるものを、重合性単量体１００質量部に対し０．５〜２０質量部の添加量で重合反応を行なうと、分子量１万〜１０万の間に極大を有する重合体を得、トナーに望ましい強度と適当な溶融特性を与えることができる。重合開始剤例としては、２，２’−アゾビス−（２，４−ジメチルバレロニトリル）、２，２’−アゾビスイソブチロニトリル、１，１’−アゾビス（シクロヘキサン−１−カルボニトリル）、２，２’−アゾビス−４−メトキシ−２，４−ジメチルバレロニトリル、アゾビスイソブチロニトリル等のアゾ系またはジアゾ系重合開始剤；ベンゾイルパーオキサイド、メチルエチルケトンパーオキサイド、ジイソプロピルパーオキシカーボネート、クメンヒドロパーオキサイド、２，４−ジクロロベンゾイルパーオキサイド、ラウロイルパーオキサイド、ｔ−ブチルパーオキシ２−エチルヘキサノエート等の過酸化物系重合開始剤が挙げられる。
【０１５１】
本発明のトナーを製造する際は、架橋剤を添加しても良く、好ましい添加量としては、重合性単量体１００質量部に対し０．００１〜１５質量部である。
【０１５２】
ここで架橋剤としては、主として２個以上の重合可能な二重結合を有する化合物が用いられ、例えば、ジビニルベンゼン、ジビニルナフタレン等のような芳香族ジビニル化合物；例えばエチレングリコールジアクリレート、エチレングリコールジメタクリレート、１，３−ブタンジオールジメタクリレート等のような二重結合を２個有するカルボン酸エステル；ジビニルアニリン、ジビニルエーテル、ジビニルスルフィド、ジビニルスルホン等のジビニル化合物；及び３個以上のビニル基を有する化合物；が単独もしくは混合物として用いられる。
【０１５３】
本発明のトナーの好適な製造方法である懸濁重合おいては、一般に上述のトナー組成物、すなわち重合性単量体中に磁性体、離型剤、可塑剤、荷電制御剤、架橋剤、場合によって着色剤等トナーとして必要な成分及びその他の添加剤、例えば重合反応で生成する重合体の粘度を低下させるために入れる有機溶媒、高分子重合体、分散剤等を適宜加えて、ホモジナイザー、ボールミル、コロイドミル、超音波分散機等の分散機によって均一に溶解または分散せしめた単量体系を、分散安定剤を含有する水系媒体中に懸濁する。このとき、高速撹拌機もしくは超音波分散機のような高速分散機を使用して一気に所望のトナー粒子のサイズとするほうが、得られるトナー粒子の粒径がシャープになる。重合開始剤添加の時期としては、重合性単量体中に他の添加剤を添加するとき同時に加えても良いし、水系媒体中に懸濁する直前に混合しても良い。また、造粒中、造粒直後、重合反応を開始する前に重合性単量体あるいは溶媒に溶解した重合開始剤を加えることもできる。
【０１５４】
造粒後は、通常の撹拌機を用いて、粒子状態が維持され且つ粒子の浮遊・沈降が防止される程度の撹拌を行なえば良い。
【０１５５】
本発明のトナーを製造する場合には、分散安定剤として公知の界面活性剤や有機・無機分散剤が使用でき、中でも無機分散剤が有害な超微粉を生じ難く、その立体障害性により分散安定性を得ているので反応温度を変化させても安定性が崩れ難く、洗浄も容易でトナーに悪影響を与え難いので、好ましく使用できる。こうした無機分散剤の例としては、燐酸カルシウム、燐酸マグネシウム、燐酸アルミニウム、燐酸亜鉛等の燐酸多価金属塩；炭酸カルシウム、炭酸マグネシウム等の炭酸塩；メタ硅酸カルシウム、硫酸カルシウム、硫酸バリウム等の無機塩；水酸化カルシウム、水酸化マグネシウム、水酸化アルミニウム等の水酸化物；シリカ、ベントナイト、アルミナ等の無機酸化物が挙げられる。
【０１５６】
これらの無機分散剤は、重合性単量体１００質量部に対して、０．２〜２０質量部を単独で使用することが望ましいが、超微粒子を発生し難いもののトナーの微粒化はやや苦手であるので、０．００１〜０．１質量部の界面活性剤を併用しても良い。
【０１５７】
界面活性剤としては、例えばドデシルベンゼン硫酸ナトリウム、テトラデシル硫酸ナトリウム、ペンタデシル硫酸ナトリウム、オクチル硫酸ナトリウム、オレイン酸ナトリウム、ラウリル酸ナトリウム、ステアリン酸ナトリウム、ステアリン酸カリウム等が挙げられる。
【０１５８】
これら無機分散剤を用いる場合には、そのまま使用しても良いが、より細かい粒子を得るため、水系媒体中にて前記無機分散剤粒子を生成させて用いることができる。例えば、燐酸カルシウムの場合、高速撹拌下、燐酸ナトリウム水溶液と塩化カルシウム水溶液とを混合して、水不溶性の燐酸カルシウムを生成させることができ、より均一で細かな分散が可能となる。このとき、同時に水溶性の塩化ナトリウム塩が副生するが、水系媒体中に水溶性塩が存在すると、重合性単量体の水への溶解が抑制されて、乳化重合による超微粒トナーが発生し難くなるので、より好都合である。重合反応終期に残存重合性単量体を除去するときには障害となることから、水系媒体を交換するか、イオン交換樹脂で脱塩したほうが良い。無機分散剤は、重合終了後酸あるいはアルカリで溶解して、ほぼ完全に取り除くことができる。
【０１５９】
前記重合工程においては、重合温度は４０℃以上、一般には５０〜９０℃の温度に設定して重合を行なう。この温度範囲で重合を行なうと、内部に封じられるべき離型剤やワックスの類が、相分離により析出して内包化がより完全となる。残存する重合性単量体を消費するために、重合反応終期ならば、反応温度を９０〜１５０℃にまで上げることは可能である。
【０１６０】
重合トナー粒子は重合終了後、公知の方法によって濾過、洗浄、乾燥を行い、無機微粉体を混合し表面に付着させることで、トナーを得ることができる。また、製造工程に分級工程を入れ、粗粉や微粉をカットすることも、本発明の望ましい形態の一つである。
【０１６１】
本発明に係わるトナーを粉砕法により製造する場合は、公知の方法が用いられるが、例えば、結着樹脂、磁性体、離型剤、荷電制御剤、場合によって着色剤等、トナーとして必要な成分及びその他の添加剤等をヘンシェルミキサー、ボールミル等の混合器により十分混合してから加熱ロール、ニーダー、エクストルーダーの如き熱混練機を用いて溶融混練して樹脂類をお互いに相溶せしめた中に磁性体等の他のトナー材料を分散又は溶解せしめ、冷却固化、粉砕後、分級、必要に応じて表面処理を行なってトナー粒子を得ることができる。分級及び表面処理の順序はどちらが先でもよい。分級工程においては生産効率上、多分割分級機を用いることが好ましい。
【０１６２】
粉砕工程は、機械衝撃式、ジェット式等の公知の粉砕装置を用いた方法により行うことができる。本発明に係わる特定の円形度を有するトナーを得るためには、さらに熱をかけて粉砕したり、あるいは補助的に機械的衝撃を加える処理をすることが好ましい。また、微粉砕（必要に応じて分級）されたトナー粒子を熱水中に分散させる湯浴法、熱気流中を通過させる方法などを用いても良い。
【０１６３】
機械的衝撃力を加える手段としては、例えば川崎重工社製のクリプトロンシステムやターボ工業社製のターボミル等の機械衝撃式粉砕機を用いる方法、また、ホソカワミクロン社製のメカノフージョンシステムや奈良機械製作所製のハイブリダイゼーションシステム等の装置のように、高速回転する羽根によりトナーをケーシングの内側に遠心力により押しつけ、圧縮力や摩擦力等の力によりトナーに機械的衝撃力を加える方法が挙げられる。
【０１６４】
機械的衝撃法を用いる場合においては、処理温度をトナーのガラス転移点Ｔｇ付近の温度（Ｔｇ±１０℃）を加える熱機械的衝撃が、凝集防止や生産性の観点から好ましい。さらに好ましくは、トナーのガラス転移点Ｔｇ±５℃の範囲の温度で行うことが、転写効率を向上させるのに特に有効である。
【０１６５】
さらにまた、本発明に係わるトナーは、特公昭５６−１３９４５号公報等に記載のディスク又は多流体ノズルを用い溶融混合物を空気中に霧化し球状トナーを得る方法や、単量体には可溶で得られる重合体が不溶な水系有機溶剤を用い直接トナーを生成する分散重合方法又は水溶性極性重合開始剤存在下で直接重合しトナーを生成するソープフリー重合方法に代表される乳化重合方法等を用いトナーを製造する方法でも製造が可能である。
【０１６６】
本発明に係わるトナーを粉砕法により製造する場合の結着樹脂としては、ポリスチレン、ポリビニルトルエンなどのスチレン及びその置換体の単重合体；スチレン−プロピレン共重合体、スチレン−ビニルトルエン共重合体、スチレン−ビニルナフタリン共重合体、スチレン−アクリル酸メチル共重合体、スチレン−アクリル酸エチル共重合体、スチレン−アクリル酸ブチル共重合体、スチレン−アクリル酸オクチル共重合体、スチレン−アクリル酸ジメチルアミノエチル共重合体、スチレン−メタクリル酸メチル共重合体、スチレン−メタクリル酸エチル共重合体、スチレン−メタクリル酸ブチル共重合体、スチレン−メタクリル酸ジメチルアミノエチル共重合体、スチレン−ビニルメチルエーテル共重合体、スチレン−ビニルエチルエーテル共重合体、スチレン−ビニルメチルケトン共重合体、スチレン−ブタジエン共重合体、スチレン−イソプレン共重合体、スチレン−マレイン酸共重合体、スチレン−マレイン酸エステル共重合体などのスチレン系共重合体；ポリメチルメタクリレート、ポリブチルメタクリレート、ポリ酢酸ビニル、ポリエチレン、ポリプロピレン、ポリビニルブチラール、シリコーン樹脂、ポリエステル樹脂、ポリアミド樹脂、エポキシ樹脂、ポリアクリル酸樹脂、ロジン、変性ロジン、テルペン樹脂、フェノール樹脂、脂肪族または脂環族炭化水素樹脂、芳香族系石油樹脂、パラフィンワックス、カルナバワックスなどが単独或いは混合して使用できる。特に、スチレン系共重合体及びポリエステル樹脂が現像特性や定着性等の点で好ましい。
【０１６７】
結着樹脂のガラス転移点温度（Ｔｇ）は、５０〜７０℃であることが好ましく、５０℃よりも低いとトナーの保存性が低下し、７０℃よりも高いと定着性に劣る。
【０１６８】
本発明においてトナーは、流動化剤として個数平均一次粒子径４〜８０ｎｍの無機微粉末が添加されることも好ましい形態である。無機微粉末は、トナーの流動性改良及びトナー母粒子の帯電均一化のために添加されるが、無機微粉末を疎水化処理するなどの処理によってトナーの帯電量の調整、環境安定性の向上等の機能を付与することも好ましい形態である。
【０１６９】
無機微粉末の個数平均一次粒子径が８０ｎｍよりも大きい場合、或いは８０ｎｍ以下の無機微粒子が添加されていない場合には、転写残トナーが帯電部材へ付着した際に帯電部材に固着し易くなり、安定して良好な帯電特性を得ることが困難である。また、良好なトナーの流動性が得られず、トナー粒子への帯電付与が不均一になり易く、カブリの増大、画像濃度の低下、トナー飛散等の問題を避けられない。無機微粒子の個数平均一次粒径が４ｎｍよりも小さい場合には、無機微粒子の凝集性が強まり、一次粒子ではなく解砕処理によっても解れ難い強固な凝集性を持つ粒度分布の広い凝集体として挙動し易く、凝集体の現像、像担持体或いは現像担持体等を傷つけるなどによる画像欠陥を生じ易くなる。トナー粒子の帯電分布をより均一とするためには無機微粒子の個数平均一次粒径は６〜３５ｎｍであることがより良い。
【０１７０】
本発明において、無機微粉末の個数平均一次粒子径の測定法は、走査型電子顕微鏡により拡大撮影したトナーの写真で、更に走査型電子顕微鏡に付属させたＸＭＡ等の元素分析手段によって無機微粉末の含有する元素でマッピングされたトナーの写真を対照しつつ、トナー表面に付着或いは遊離して存在している無機微粉末の一次粒子を１００個以上測定し、個数基準の平均一次粒径を求めることで測定できる。
【０１７１】
本発明で用いられる無機微粒子としては、シリカ，アルミナ，酸化チタンなどが使用できる。
【０１７２】
例えば、ケイ酸微粉体としては、ケイ素ハロゲン化物の蒸気相酸化により生成されたいわゆる乾式法又はヒュームドシリカと称される乾式シリカ、及び水ガラス等から製造されるいわゆる湿式シリカの両者が使用可能であるが、表面及びシリカ微粉体の内部にあるシラノール基が少なく、またＮａ₂Ｏ，ＳＯ₃ ^2-等の製造残滓の少ない乾式シリカの方が好ましい。また乾式シリカにおいては、製造工程において例えば、塩化アルミニウム，塩化チタン等、他の金属ハロゲン化合物をケイ素ハロゲン化合物と共に用いることによって、シリカと他の金属酸化物の複合微粉体を得ることも可能でありそれらも包含する。
【０１７３】
平均一次粒径が４〜８０ｎｍの無機微粒子の添加量は、トナー母粒子に対して０．１〜３．０質量％であることが好ましく、添加量が０．１質量％未満ではその効果が十分ではなく、３．０質量％超では定着性が悪くなる。
【０１７４】
なお、無機微粉末の含有量は、蛍光Ｘ線分析を用い、標準試料から作成した検量線を用いて定量できる。
【０１７５】
無機微粒子は、疎水化処理されたものであることが高温高湿環境下での特性から好ましい。トナーに添加された無機微粒子が吸湿すると、トナー母粒子の帯電量が著しく低下し、トナー飛散が起こり易くなる。
【０１７６】
疎水化処理の処理剤としては、シリコーンワニス、各種変性シリコーンワニス、シリコーンオイル、各種変性シリコーンオイル、シラン化合物、シランカップリング剤、その他有機硅素化合物、有機チタン化合物の如き処理剤を単独で或いは併用して処理しても良い。
【０１７７】
その中でも、シリコーンオイルにより処理したものが好ましく、より好ましくは、無機微粒子を疎水化処理すると同時或いは処理した後に、シリコーンオイルにより処理したものが高湿環境下でもトナー粒子の帯電量を高く維持し、トナー飛散を防止する上でよい。
【０１７８】
無機微粒子の処理方法としては、例えば第一段反応としてシリル化反応を行ないシラノール基を化学結合により消失させた後、第二段反応としてシリコーンオイルにより表面に疎水性の薄膜を形成することができる。
【０１７９】
上記シリコーンオイルは、２５℃における粘度が１０〜２００，０００ｍｍ²／ｓのものが、さらには３，０００〜８０，０００ｍｍ²／ｓのものが好ましい。１０ｍｍ²／ｓ未満では、無機微粒子に安定性が無く、熱および機械的な応力により、画質が劣化する傾向がある。２００，０００ｍｍ²／ｓを超える場合は、均一な処理が困難になる傾向がある。
【０１８０】
使用されるシリコーンオイルとしては、例えばジメチルシリコーンオイル、メチルフェニルシリコーンオイル、α−メチルスチレン変性シリコーンオイル、クロルフェニルシリコーンオイル、フッ素変性シリコーンオイル等が特に好ましい。
【０１８１】
シリコーンオイルの処理の方法としては、例えばシラン化合物で処理されたシリカとシリコーンオイルとをヘンシェルミキサー等の混合機を用いて直接混合してもよいし、シリカにシリコーンオイルを噴霧する方法を用いてもよい。あるいは適当な溶剤にシリコーンオイルを溶解あるいは分散せしめた後、シリカ微粉体を加え混合し溶剤を除去する方法でもよい。無機微粒子の凝集体の生成が比較的少ない点で噴霧機を用いる方法がより好ましい。
【０１８２】
シリコーンオイルの処理量はシリカ１００質量部に対し１〜４０質量部、好ましくは３〜３５質量部が良い。
【０１８３】
シリコーンオイルの量が少なすぎると良好な疎水性が得られず、多すぎるとカブリ発生等の不具合が生ずる。
【０１８４】
本発明で用いられるシリカは、トナーに良好な流動性を付与させるために、窒素吸着によるＢＥＴ法で測定した比表面積が２０〜３５０ｍ²／ｇ範囲内のものが好ましく、より好ましくは２５〜３００ｍ²／ｇのものが更に良い。
【０１８５】
比表面積はＢＥＴ法に従って、比表面積測定装置オートソーブ１（湯浅アイオニクス社製）を用いて試料表面に窒素ガスを吸着させ、ＢＥＴ多点法を用いて比表面積を算出する。
【０１８６】
また、本発明の磁性トナーは、クリーニング性向上等の目的で、さらに一次粒径３０ｎｍを超える（好ましくは比表面積が５０ｍ²／ｇ未満）、より好ましくは一次粒径５０ｎｍ以上（好ましくは比表面積が３０ｍ²／ｇ未満）の無機又は有機の球状に近い微粒子をさらに添加することも好ましい形態のひとつである。例えば球状シリカ粒子、球状ポリメチルシルセスキオキサン粒子、球状樹脂粒子等が好ましく用いられる。
【０１８７】
本発明に用いられる磁性トナーには、実質的な悪影響を与えない範囲内で更に他の添加剤、例えばテフロン粉末、ステアリン酸亜鉛粉末、ポリフッ化ビニリデン粉末の如き滑剤粉末；あるいは酸化セリウム粉末、炭化硅素粉末、チタン酸ストロンチウム粉末などの研磨剤；あるいは例えば酸化チタン粉末、酸化アルミニウム粉末などの流動性付与剤；ケーキング防止剤；また、逆極性の有機微粒子、及び無機微粒子を現像性向上剤として少量用いることもできる。これらの添加剤も表面を疎水化処理して用いることも可能である。
【０１８８】
次に、本発明のトナーを好適に用いることのできる画像形成装置の一例を図１に沿って具体的に説明する。
【０１８９】
図１において、１００は感光ドラムで、その周囲に一次帯電ローラー１１７、現像器１４０、転写帯電ローラー１１４、クリーナ１１６、レジスタローラー１２４等が設けられている。そして感光体１００は一次帯電ローラー１１７によって−７００Ｖに帯電される（印加電圧は交流電圧−２．０ｋＶｐｐ、直流電圧−７００Ｖｄｃ）。そして、レーザー発生装置１２１によりレーザー光１２３を感光体１００に照射することによって露光される。感光体１００上の静電潜像は現像器１４０によって一成分磁性トナーで現像され、転写材を介して感光体に当接された転写ローラー１１４により転写材上へ転写される。トナー画像をのせた転写材Ｐは搬送ベルト１２５等により定着器１２６へ運ばれ転写材上に定着される。また、一部感光体上に残されたトナーはクリーニング手段１１６によりクリーニングされる。
【０１９０】
現像器１４０は、図２に示すように感光体１００に近接してアルミニウム、ステンレス等非磁性金属で作られた円筒状のトナー担持体１０２（以下現像スリーブと称す）が配設され、感光体１００と現像スリーブ１０２との間隙は、図示されないスリーブ／感光体間隙保持部材等により約２２０μｍに維持されている。現像スリーブ内にはマグネットローラー１０４が現像スリーブ１０２と同心的に固定、配設されている。但し現像スリーブ１０２は回転可能である。マグネットローラー１０４には図示の如く複数の磁極が具備されており、Ｓ１は現像、Ｎ１はトナーコート量規制、Ｓ２はトナーの取り込み／搬送、Ｎ２はトナーの吹き出し防止に影響している。現像スリーブ１０２に付着して搬送される磁性トナー量を規制する部材として、弾性ブレード１０３が配設され弾性ブレード１０３の現像スリーブ１０２に対する当接圧により現像領域に搬送されるトナー量が制御される。現像領域では、感光体１００と現像スリーブ１０２との間に直流及び交流の現像バイアスが印加され、現像スリーブ上トナーは静電潜像に応じて感光体１００上に飛翔し可視像となる。
【０１９１】
【実施例】
以下、本発明を製造例及び実施例により具体的に説明するが、これは本発明をなんら限定するものではない。なお、以下の配合における部数は全て質量部である。
【０１９２】
（表面処理磁性体の製造例１）
硫酸第一鉄水溶液中に、鉄元素に対してｌ．０〜１．１当量の苛性ソーダ溶液、鉄元素に対しリン元素換算で１．０質量％のヘキサメタ燐酸ソーダ、鉄元素に対し珪素元素換算で１．０質量％の珪酸ソーダを混合し、水酸化第一鉄を含む水溶液を調製した。
【０１９３】
水溶液のｐＨを１３前後に維持しながら、空気を吹き込み、８０〜９０℃で酸化反応を行い、磁性粒子のスラリー液を得た。洗浄、濾過した後この含水スラリー液を一旦取り出した。このとき、含水サンプルを少量採取し、含水量を計っておいた。次に、この含水サンプルを乾燥せずに別の水系媒体中に再分散させた後、再分散液のｐＨを約６に調整し、十分撹拌しながらｎ−ヘキシルトリメトキシシランカップリング剤を磁性酸化鉄１００部に対し２．０部、γ−メタクリロキシプロピルトリメトキシシランカップリング剤を１．０部（磁性粒子の量は含水サンプルから含水量を引いた値として計算した）添加し、カップリング処理を行った。生成した疎水性磁性粒子を常法により洗浄、濾過、乾燥し、得られた粒子を十分解砕処理し、個数平均粒径が０．１２μｍであり、個数平均変動係数が８の表面処理磁性体１を得た。得られた磁性体のＢ／Ａを求めたところ、１．４であった。得られた磁性体の物性を表１に示す。
【０１９４】
（表面処理磁性体の製造例２）
表面処理磁性体の製造例１において、ｎ−ヘキシルトリメトキシシランカップリング剤２．０部をｎ−デシルトリメトキシシランカップリング剤１．５部とし、γ−メタクリロキシプロピルトリメトキシシランを１．５部としたこと以外は表面処理磁性体の製造例１と同様にして、表面処理磁性体２を得た。得られた磁性体の物性を表１に示す。
【０１９５】
（表面処理磁性体の製造例３）
表面処理磁性体の製造例２において、ｎ−デシルトリメトキシシランカップリング剤を１．２部とし、γ−メタクリロキシプロピルトリメトキシシランカップリング剤１．５部をフェニルトリメトキシシランカップリング剤１．８部としたこと以外は表面処理磁性体の製造例２と同様にして、表面処理磁性体３を得た。
得られた磁性体の物性を表１に示す。
【０１９６】
（表面処理磁性体の製造例４）
表面処理磁性体の製造例１において、ｎ−ヘキシルトリメトキシシランカップリング剤２．０部を１．４部としたこと以外は表面処理磁性体の製造例１と同様にして、表面処理磁性体４を得た。得られた磁性体の物性を表１に示す。
【０１９７】
（表面処理磁性体の製造例５）
表面処理磁性体の製造例１において、ｎ−ヘキシルトリメトキシシランカップリング剤２．０部を０．８部としたこと以外は表面処理磁性体の製造例１と同様にして、表面処理磁性体５を得た。得られた磁性体の物性を表１に示す。
【０１９８】
（表面処理磁性体の製造例６）
表面処理磁性体の製造例２において、ｎ−デシルトリメトキシシランカップリング剤１．５部を１．１部としたこと以外は表面処理磁性体の製造例２と同様にして、表面処理磁性体６を得た。得られた磁性体の物性を表１に示す。
【０１９９】
（表面処理磁性体の製造例７）
表面処理磁性体の製造例２において、ｎ−デシルトリメトキシシランカップリング剤１．５部を０．６部としたこと以外は表面処理磁性体の製造例２と同様にして、表面処理磁性体７を得た。得られた磁性体の物性を表１に示す。
【０２００】
（表面処理磁性体の製造例８）
表面処理磁性体の製造例２において、ｎ−デシルトリメトキシシランカップリング剤１．５０部を０．３部としたこと以外は表面処理磁性体の製造例２と同様にして、表面処理磁性体８を得た。得られた磁性体の物性を表１に示す。
【０２０１】
（表面処理磁性体の製造例９）
表面処理磁性体の製造例２において、処理剤をγ−メタクリロキシプロピルトリメトキシシランのみとし、添加量を１．５部としたこと以外は表面処理磁性体の製造例２と同様にして、表面処理磁性体９を得た。得られた磁性体の物性を表１に示す。
【０２０２】
（表面処理磁性体の製造例１０）
表面処理磁性体の製造例２において、処理剤をγ−メタクリロキシプロピルトリメトキシシランのみとし、添加量を５．０部としたこと以外は表面処理磁性体の製造例２と同様にして、表面処理磁性体１０を得た。得られた磁性体の物性を表１に示す。
【０２０３】
（表面処理磁性体の製造例１１）
表面処理磁性体の製造例１と同様に酸化反応を進め、酸化反応後に生成した磁性酸化鉄粒子を洗浄、濾過後、乾燥を行った。その後、得られた磁性酸化鉄１００部に対し、ｎ−ヘキシルトリメトキシシランカップリング剤２．０部、フェニルトリメトキシシランカップリング剤１．００部を用い気相中にて表面処理を行った。その後、次いで凝集している粒子を粉砕処理し、表面処理磁性体１１を得た。得られた磁性体の物性を表１に示す。
【０２０４】
（表面処理磁性体の製造例１２）
磁性酸化鉄粒子の製造例１において、添加する苛性ソーダ溶液の量及び反応条件を調整し、ｎ−デシルトリメトキシシランカップリング剤１．２部、γ−メタクリロキシプロピルトリメトキシシランを１．２部としたこと以外は表面処理磁性体の製造例２と同様にし、個数平均粒径が０．２８μｍの表面処理磁性体１２を得た。得られた磁性体の物性を表１に示す。
【０２０５】
（表面処理磁性体の製造例１３）
磁性酸化鉄粒子の合成時の硫酸第一鉄水溶液量を増やし、空気の吹き込み量を減少させ、ｎ−デシルトリメトキシシランカップリング剤１．４部、γ−メタクリロキシプロピルトリメトキシシランを１．４部としたこと以外は表面処理磁性体の製造例１１と同様にし、表面処理磁性体１３を得た。得られた磁性体の物性を表１に示す。
【０２０６】
（表面処理磁性体の製造例１４）
磁性酸化鉄粒子の製造例１において、添加する苛性ソーダ溶液の量及び反応条件を調整し、ｎ−デシルトリメトキシシランカップリング剤１．０部、γ−メタクリロキシプロピルトリメトキシシランを１．０部としたこと以外は表面処理磁性体の製造例２と同様にし、個数平均粒径が０．３７μｍの表面処理磁性体１４を得た。得られた磁性体の物性を表１に示す。
【０２０８】
（表面処理磁性体の製造例１５）
表面処理磁性体の製造例１同様に酸化反応を進め、酸化反応終了後に生成した磁性酸化粒子を洗浄、濾過、乾燥し、凝集している粒子を十分に解砕処理し磁性体を得た。この磁性体１００部を、γ−メタクリロキシプロピルトリメトキシシラン５．０部を含むトルエン溶液に分散させ、１００℃で３時間熱処理を行うと共に乾燥した。その後、凝集している粒子を十分に解砕処理し、表面磁性体１５を得た。得られた磁性体の物性を表１に示す。
【０２０９】
（表面処理磁性体の製造例１６）
表面処理磁性体の製造例１と同様に酸化反応を進め、酸化反応後に生成した磁性酸化鉄粒子を洗浄、濾過後、乾燥を行った。その後、得られた磁性酸化鉄１００部に対し、γ−メタクリロキシプロピルトリメトキシシランカップリング剤０．２部を用い気相中にて表面処理を行った。その後、次いで凝集している粒子を粉砕処理し、表面処理磁性体１６を得た。得られた磁性体の物性を表１に示す。
【０２１０】
【表１】

【０２１１】
磁性トナーの製造例１
イオン交換水７２０部に０．１Ｍ−Ｎａ₃ＰＯ₄水溶液４５０部、１Ｎ塩酸を１６部を投入し６０℃に加温した後、１．０Ｍ−ＣａＣｌ₂水溶液６７．７部を添加してＣａ₃（ＰＯ₄）₂を含む水系媒体を得た。
・スチレン ８０部
・ｎ−ブチルアクリレート ２０部
・飽和ポリエステル樹脂 ５部
・不飽和ポリエステル樹脂 １部
・負荷電性制御剤（モノアゾ染料系のＦｅ化合物） １部
・表面処理磁性体１ ８０部
【０２１２】
上記処方をホモジナイザーを用いて均一に分散混合した。
【０２１３】
この単量体組成物を６０℃に加温し、そこにエステルワックス（ＤＳＣにおける吸熱ピークの極大値７２℃）７部を添加混合溶解し、これに重合開始剤２，２’−アゾビス（２，４−ジメチルバレロニトリル）５部を溶解した。
【０２１４】
前記水系媒体中に上記重合性単量体系を投入し、６０℃，Ｎ₂雰囲気下においてＴＫ式ホモミキサー（特殊機化工業（株））にて１０，０００ｒｐｍで１５分間撹拌し、造粒した。その後パドル撹拌翼で撹拌しつつ、６０℃で４時間反応させた後、８０℃に昇温し、さらに５時間反応を行った。反応終了後、懸濁液を冷却し、塩酸を加えてｐＨ２以下で分散剤を溶解し、濾過，水洗，乾燥して重量平均粒径７．５μｍの黒色粒子１を得た。
【０２１５】
この黒色粒子１ １００部と、一次粒径１２ｎｍのシリカにヘキサメチルジシラザンで処理をした後シリコーンオイルで処理し、処理後のＢＥＴ値が１２０ｍ²／ｇの疎水性シリカ微粉体１．０部とをヘンシェルミキサー（三井三池化工機（株））で混合し、磁性トナー１を調製した。磁性トナー１の物性を表２に示す。
【０２１６】
磁性トナーの製造例２
イオン交換水７２０部に０．１Ｍ−Ｎａ₃ＰＯ₄水溶液４５０部、１Ｎ塩酸を１６部を投入し６０℃に加温した後、１．０Ｍ−ＣａＣｌ₂水溶液６７．７部を添加してＣａ₃（ＰＯ₄）₂を含む水系媒体を得た。
・スチレン ８０部
・ｎ−ブチルアクリレート ２０部
・飽和ポリエステル樹脂 ５部
・不飽和ポリエステル樹脂 １部
・負荷電性制御剤（モノアゾ染料系のＦｅ化合物） １部
・表面処理磁性体２ ８０部
【０２１７】
上記処方をホモジナイザーを用いて均一に分散混合した。
【０２１８】
この単量体組成物を６０℃に加温し、そこにエステルワックス（ＤＳＣにおける吸熱ピークの極大値７２℃）７部を添加混合溶解し、これに重合開始剤ｔ−ブチルパーオキシ２−エチルヘキサノエート４部を溶解した。
【０２１９】
前記水系媒体中に上記重合性単量体系を投入し、６０℃，Ｎ₂雰囲気下においてＴＫ式ホモミキサー（特殊機化工業（株））にて１０，０００ｒｐｍで１５分間撹拌し、造粒した。その後パドル撹拌翼で撹拌しつつ、８０℃で８時間反応させた。反応終了後、懸濁液を冷却し、塩酸を加えてｐＨ２以下で分散剤を溶解し、濾過，水洗，乾燥して重量平均粒径７．２μｍの黒色粒子２を得た。
【０２２０】
この黒色粒子２ １００部と、一次粒径１２ｎｍのシリカにヘキサメチルジシラザンで処理をした後シリコーンオイルで処理し、処理後のＢＥＴ値が１２０ｍ²／ｇの疎水性シリカ微粉体１．０部とをヘンシェルミキサー（三井三池化工機（株））で混合し、磁性トナー２を調製した。磁性トナー２の物性を表２に示す。
【０２２１】
磁性トナーの製造例３
表面処理磁性体１を表面処理磁性体３に変えたこと以外は磁性トナー２の製造例と同一とし、磁性トナー３を得た。磁性トナー３の物性を表２に示す。
【０２２２】
磁性トナーの製造例４
磁性トナーの製造例１で得た黒色粒子１ １００部と、一次粒径７ｎｍのシリカにヘキサメチルジシラザンで処理し、処理後のＢＥＴ値が２８０ｍ²／ｇの疎水性シリカ微粉体０．７部とをヘンシェルミキサー（三井三池化工機（株））を用い混合して、磁性トナー４を調製した。磁性トナー４の物性を表２に示す。
【０２２３】
磁性トナーの製造例５
磁性トナーの製造例１で得た黒色粒子１ １００部と、一次粒径９０ｎｍのシリカにヘキサメチルジシラザンで処理し、処理後のＢＥＴ値が２５ｍ²／ｇの疎水性シリカ微粉体３．５部とをヘンシェルミキサー（三井三池化工機（株））を用い混合して、磁性トナー５を調製した。磁性トナー５の物性を表２に示す。
【０２２４】
磁性トナーの製造例６
表面処理磁性体１の量を４０部としたこと以外は磁性トナーの製造例１と同様とし、磁性トナー６を得た。磁性トナー６の物性を表２に示す。
【０２２５】
磁性トナーの製造例７
表面処理磁性体１の量を１５０部としたこと以外は磁性トナーの製造例１と同様とし、磁性トナー７を得た。磁性トナー７の物性を表２に示す。
【０２２６】
磁性トナーの製造例８
エステルワックスの量を０．８部としたこと以外は磁性トナーの製造例２と同様とし、磁性トナー８を得た。磁性トナー８の物性を表２に示す。
【０２２７】
磁性トナーの製造例９
エステルワックスの量を３５部としたこと以外は磁性トナーの製造例２と同様とし、磁性トナー９を得た。磁性トナー９の物性を表２に示す。
【０２２８】
磁性トナーの製造例１０
エステルワックス７部をポリエチレンワックス（ＤＳＣにおける吸熱ピークの極大値１１５℃）３部に変えたこと以外は磁性トナーの製造例２と同様とし、磁性トナー１０を得た。磁性トナー１０の物性を表２に示す。
【０２２９】
磁性トナーの製造例１１
エステルワックス７部をポリエチレンワックス（ＤＳＣにおける吸熱ピークの極大値１１５℃）７部に変えたこと以外は磁性トナーの製造例２と同様とし、磁性トナー１１を得た。磁性トナー１１の物性を表２に示す。
【０２３０】
磁性トナーの製造例１２
表面処理磁性体２を表面処理磁性体４に変えたこと以外は磁性トナー２の製造例と同様とし、磁性トナー１２を得た。磁性トナー１２の物性を表２に示す。
【０２３１】
磁性トナーの製造例１３
表面処理磁性体２を表面処理磁性体５に変えたこと以外は磁性トナー２の製造例と同様とし、磁性トナー１３を得た。磁性トナー１３の物性を表２に示す。
【０２３２】
磁性トナーの製造例１４
表面処理磁性体２を表面処理磁性体６に変えたこと以外は磁性トナー２の製造例と同様とし、磁性トナー１４を得た。磁性トナー１４の物性を表２に示す。
【０２３３】
磁性トナーの製造例１５
表面処理磁性体２を表面処理磁性体７に変えたこと以外は磁性トナー２の製造例と同様とし、磁性トナー１５を得た。磁性トナー１５の物性を表２に示す。
【０２３４】
磁性トナーの製造例１６
表面処理磁性体２を表面処理磁性体８に変えたこと以外は磁性トナー２の製造例と同様とし、磁性トナー１６を得た。磁性トナー１６の物性を表２に示す。
【０２３５】
磁性トナーの製造例１７
表面処理磁性体２を表面処理磁性体９に変えたこと以外は磁性トナー２の製造例と同様とし、磁性トナー１７を得た。磁性トナー１７の物性を表２に示す。
【０２３６】
磁性トナーの製造例１８
表面処理磁性体２を表面処理磁性体１０に変えたこと以外は磁性トナー２の製造例と同様とし、磁性トナー１８を得た。磁性トナー１８の物性を表２に示す。
【０２３７】
磁性トナーの製造例１９
表面処理磁性体２を表面処理磁性体１１に変えたこと以外は磁性トナー２の製造例と同様とし、磁性トナー１９を得た。磁性トナー１９の物性を表２に示す。
【０２３８】
磁性トナーの製造例２０
表面処理磁性体２を表面処理磁性体１２に変えたこと以外は磁性トナー２の製造例と同様とし、磁性トナー２０を得た。磁性トナー２０の物性を表２に示す。
【０２３９】
磁性トナーの製造例２１
表面処理磁性体２を表面処理磁性体１３に変えたこと以外は磁性トナー２の製造例と同様とし、磁性トナー２１を得た。磁性トナー２１の物性を表２に示す。
【０２４０】
磁性トナーの製造例２２
表面処理磁性体２を表面処理磁性体１４に変えたこと以外は磁性トナー２の製造例と同様とし、磁性トナー２２を得た。磁性トナー２２の物性を表２に示す。
【０２４１】
磁性トナーの比較製造例１
表面処理磁性体２を表面処理磁性体１５に変えたこと以外は磁性トナー２の製造例と同様とし、磁性トナー２３を得た。磁性トナー２３の物性を表２に示す。
【０２４２】
磁性トナーの比較製造例２
表面処理磁性体２を表面処理磁性体１６に変えたこと以外は磁性トナー２の製造例と同様とし、磁性トナー２４を得た。磁性トナー２４の物性を表２に示す。
【０２４３】
磁性トナーの比較製造例３
表面処理磁性体２を表面処理磁性体１６に変え、黒色粒子を得た後、得られた黒色粒子を風力分級を行ったこと以外は磁性トナー２の製造例と同様とし、磁性トナー２５を得た。磁性トナー２５の物性を表２に示す。
【０２４４】
なお、上記各磁性トナーの製造例ならびに、比較製造例において、得られた磁性トナーの磁場７９．６ｋＡ／ｍにおける磁化の強さは、磁性トナー７が１８．１Ａｍ²／ｋｇであり、磁性トナー８が３８．４Ａｍ²／ｋｇ、他の磁性トナーはいずれも２４〜２８Ａｍ²／ｋｇであった。
【０２４５】
【表２】

【０２４６】
［実施例１］
画像形成装置として、ＬＢＰ−１７６０を改造し、概ね図１に示されるものを用いた。
【０２４７】
静電荷像坦持体の電位は、暗部電位Ｖｄ＝−６８０Ｖ、明部電位ＶＬ＝−１５０Ｖとした。また、静電荷像坦持体と現像スリーブとの間隙は２２０μｍとし、トナー担持体として下記の構成の層厚約７μｍ、ＪＩＳ中心線平均粗さ（Ｒａ）１．０μｍの樹脂層を、表面をブラストした直径１６φのアルミニウム円筒上に形成した現像スリーブを使用し、現像磁極８５ｍＴ（８５０ガウス）、トナー規制部材として厚み１．０ｍｍ、自由長０．５ｍｍのウレタン製ブレードを３９．２Ｎ／ｍ（４０ｇ／ｃｍ）の線圧で当接させた。
・フェノール樹脂 １００部
・グラファイト（粒径約７μｍ） ９０部
・カーボンブラック １０部
【０２４８】
次いで、現像バイアスとして直流バイアス成分Ｖｄｃ＝−４５０Ｖ、重畳する交流バイアス成分Ｖｐｐ＝１６００Ｖ、ｆ＝２４００Ｈｚを用いた。また、現像スリーブの周速は感光体周速（９４ｍｍ／ｓｅｃ）に対して順方向に１１０％のスピード（１０３ｍｍ／ｓｅｃ）とした。また、転写バイアスは直流１．５ｋＶとした。
【０２４９】
定着方法としてはＬＢＰ−１７６０のオイル塗布機能のない、フィルムを介してヒーターにより加熱加圧定着する方式の定着装置を用いた。この時加圧ローラはフッ素系樹脂の表面層を有するものを使用し、ローラの直径は３０ｍｍであった。また、定着温度は１６０℃、ニップ幅を７ｍｍに設定した。
【０２５０】
最初に、磁性トナー１をカートリッジに１００ｇ充填し、高温高湿下（３０℃，８０％ＲＨ）において、紙上のトナー量が０．８ｍｇ／ｃｍ²となるように調整し、画像濃度が１．４３のベタ黒画像を得た。次いで、１ｄｏｔ−２ｓｐａｃｅのハーフトーン画像を出したところ、赤味の無い鮮明な画像が得られた。
【０２５１】
その後、トナー劣化の促進試験として２時間空回転を行った後、印字率２％の横線のみからなる画像パターンで１０００枚の画出し試験を行った。なお、転写材としては７５ｇ／ｍ²の紙を使用した。
【０２５２】
その結果、磁性トナー１は、空回転直後、及び、１０００枚の画出し後において高い転写性を示し、非画像部へのカブリのない良好な画像が得られた。評価結果を表３に示す。
【０２５３】
本発明の実施例、ならびに、比較例中に記載の評価項目とその判断基準について述べる。
【０２５４】
＜画像濃度＞
画像濃度はベタ画像部を形成し、このベタ画像をマクベス反射濃度計（マクベス社製）にて測定を行った。
【０２５５】
＜画像の赤味＞
画像の赤味は１ｄｏｔ−２ｓｐａｃｅのハーフトーン画像を得、目視により赤味の判断を以下の基準で行った。
Ａ：全く赤味は感じられない。
Ｂ：やや赤味が感じられるものの、実用上問題の無いレベル。
Ｃ：赤味が強く、貧相な画像。実用上好ましくないレベル。
【０２５６】
＜転写効率＞
転写効率は、ベタ黒画像転写後の感光体上の転写残トナーをマイラーテープによりテーピングしてはぎ取り、紙上に貼ったもののマクベス濃度の値をＣ、転写後定着前のトナーの載った紙上にマイラーテープを貼ったもののマクベス濃度をＤ、未使用の紙上に貼ったマイラーテープのマクベス濃度をＥとした時、近似的に以下の式で計算した。
【０２５７】
【数６】

【０２５８】
上記の計算結果から得られた転写効率を以下の基準で判断した。
Ａ：転写効率が９６％以上。
Ｂ：転写効率が９２％以上、９６％未満。
Ｃ：転写効率が８９％以上、９２％未満。
Ｄ：転写効率が８９％未満。
【０２５９】
＜画質＞
画質の判断基準は、画像の均一性、細線再現性を総合的に評価したものである。なお、画像の均一性はベタ黒画像、ならびに、ハーフトーン画像で判断を行う。
Ａ：細線再現性、画像の均一性に優れ、鮮明な画像。
Ｂ：細線再現性、画像の均一性が若干劣るものの、良好な画像。
Ｃ：実用的には問題の無い画質。
Ｄ：細線再現性、画像の均一性が悪く、実用上好ましくない画像。
【０２６０】
＜カブリ＞
カブリの測定は、東京電色社製のＲＥＦＬＥＣＴＭＥＴＥＲ ＭＯＤＥＬ ＴＣ−６ＤＳを使用して測定した。フィルターは、グリーンフィルターを用い、カブリは下記の式より算出した。
【０２６１】
カブリ（反射率）（％）＝
標準紙上の反射率（％）−サンプル非画像部の反射率（％）
【０２６２】
なお、カブリの判断基準は以下の通り。
Ａ：非常に良好（１．５％未満）
Ｂ：良好（１．５％以上乃至２．５％未満）
Ｃ：普通（２．５％以上乃至４．０％未満）
Ｄ：悪い（４％以上）
【０２６３】
＜定着性＞
定着性は、初期から耐久終了までの画像サンプルの裏側に発生する汚れを観察し、発生の有無で判断を行う。
【０２６４】
［実施例２〜１５、参考例１〜４、実施例１６〜１８］
トナーとして、磁性トナー２〜２２を使用し、実施例１と同様の条件で画出し試験及び耐久性評価を行った。その結果、常温常湿下での画像濃度は高く、赤味も問題の無い画像が得られた。また、高温高湿下での画出し試験においてもいずれも大きな問題の無い結果が得られた。結果を表３に示す。
【０２６５】
［比較例１〜３］
トナーとして、磁性トナー２３〜２５を使用し、実施例１と同様の画像形成方法で画出し試験及び耐久性評価を行った。その結果、画像濃度が低く、耐久試験と共に画像濃度、転写効率の低下、カブリ、画質の悪化が生じた。これはトナー粒子内部での磁性体、離型剤の不均一な分散状態を反映しているものと考えられる。結果を表３に示す。
【０２６６】
【表３】

【０２６７】
【発明の効果】
本発明のトナーは、少なくとも結着樹脂、離型剤及び磁性体を有する平均円形度が０．９７０以上であり、重量平均粒径が３乃至１０μｍ、且つ、スチレン中でのストークス径が小さな、分散性の良い特殊な磁性体を含有し、シャープな粒度分布を有することにより、着色力が高く、高温高湿下においても良好な耐久性を有すると共に、赤味、カブリの無い高精細な画像を得ることができる。
【図面の簡単な説明】
【図１】本発明の実施例に用いた画像形成装置の一例を示す図である。
【図２】一成分現像用現像器の一例を示す図である。
【符号の説明】
１００ 感光体（像担持体、被帯電体）
１０２ 現像スリーブ（磁性トナー担持体）
１０３ 弾性ブレード（層規制部材）
１０４ マグネットローラー
１１４ 転写ローラー（転写部材）
１１６ クリーナー
１１７ 帯電ローラー（接触帯電部材）
１２１ レーザービームスキャナー（潜像形成手段、露光装置）
１２４ 給紙ローラー
１２５ 搬送部材
１２６ 定着装置
１４０ 現像装置
１４１ 撹拌部材
Ｐ 転写材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic toner used in an image forming method such as an electrophotographic method, an electrostatic recording method, a magnetic recording method, and a toner jet method.
[0002]
[Prior art]
Conventionally, many methods are known as electrophotographic methods. Generally, a photoconductive substance is used, and an electric latent image is formed on an electrostatic charge image carrier (photoconductor) by various means. Next, the latent image is developed with toner to form a visible image. If necessary, the toner image is transferred to a transfer material such as paper, and then the toner image is fixed on the transfer material by heat or pressure, etc. Is what you get.
[0003]
As a method of visualizing an electric latent image with toner, a cascade development method, a magnetic brush development method, a pressure development method, a magnetic brush development method using a two-component developer composed of a carrier and a toner, a toner carrier is a photoreceptor. Non-contact one-component development method that causes toner to fly from the toner carrier to the photoconductor in a non-contact manner, a contact one-component development method in which the toner carrier is pressed against the photoconductor and the toner is transferred by an electric field, and magnetic toner is used. A so-called jumping method is also used in which a rotating sleeve having a magnetic pole at the center is used to fly between the photosensitive member and the sleeve by an electric field.
[0004]
As a jumping method, for example, in Japanese Patent Application Laid-Open No. 54-43027, a thin insulating magnetic toner is applied onto a toner carrier, and this is triboelectrically charged. Then, this is converted into an electrostatic latent image under the action of a magnetic field. A method of developing in close proximity and facing each other without contact is disclosed. According to this method, the insulating magnetic toner is thinly coated on the toner carrier to allow sufficient frictional charging of the magnetic toner, and development without contacting the electrostatic latent image while supporting the magnetic toner by magnetic force. Therefore, transfer of the magnetic toner to the non-image portion, so-called fogging, is suppressed, and a high-definition image can be obtained.
[0005]
Such a one-component development method does not require carrier particles such as glass beads and iron powder as in the two-component method, and therefore the development apparatus itself can be reduced in size and weight. Furthermore, since the two-component development method needs to keep the toner concentration in the magnetic toner constant, a device for detecting the toner concentration and supplying a necessary amount of toner is required. Therefore, the developing device is also large and heavy here. Since such a device is not necessary in the one-component development method, it is preferable because it can be made small and light.
[0006]
Also, LED and LBP printers are the mainstream in the recent market as printer devices, and the direction of technology is higher resolution, that is, what was conventionally 240, 300 dpi is 400, 600, 800 dpi. The same applies to the copying machine. As a means for satisfying this requirement, toner particle size reduction is progressing, and JP-A-1-112253, JP-A-1-191156, JP-A-2-214156, and JP-A-2-284158. Japanese Patent Laid-Open Nos. 3-181952 and 4-162048 propose toners having a specific particle size distribution and a small particle size.
[0007]
On the other hand, the toner image formed on the photoconductor in the development process is transferred to the transfer material in the transfer process, but the transfer residual toner in the image area and the fog toner in the non-image area remaining on the photoconductor are cleaned in the cleaning process. Then, the toner is stored in the waste toner container. For this cleaning process, blade cleaning, fur brush cleaning, roller cleaning, and the like have been conventionally used. However, since such a cleaning device is provided, the size of the device is inevitably increased, which has been a bottleneck when attempting to make the device compact. For this reason, a system with little waste toner has been desired, and a toner having high transfer efficiency and low fog has been demanded.
[0008]
Further, from the viewpoint of ecology, reduction of toner consumption per unit number is also required. In order to reduce toner consumption, it is necessary to improve the coloring power of the toner. For this purpose, it is important to reduce the particle size of the colorant and to make the dispersion uniform.
[0009]
Conventionally, pigments, dyes, carbon black, and the like are generally used as toner colorants. In particular, in magnetic toners, magnetic materials are often used as colorants as they are. For this reason, in the magnetic toner, in order to improve the tinting strength of the toner, it is important to reduce the particle size and uniformly disperse the magnetic material. However, when the particle size of the magnetic material is reduced, in addition to the problem that the magnetic material itself becomes reddish, it is difficult to uniformly disperse it in the toner. Therefore, due to poor dispersion of the magnetic material, the resulting image becomes reddish. As a result, there arises a problem of degrading image quality.
[0010]
The magnetic toner used in such an image forming process has a binder resin and a colorant as main components, and in addition, additives such as a charge control agent and a release agent to bring out the necessary properties as a toner. It is common to contain.
[0011]
In recent years, copiers and printers have been increased in speed, but with this, there has been a demand for further fixing of toner at a lower temperature, which is accompanied by great improvements in adhesion of toner to the surface of a fixing member, so-called offset. Efforts have been made. In order to obtain good fixability on the transfer medium, a release agent is contained in the toner.
[0012]
For example, Japanese Patent Publication No. Sho 52-3304, Japanese Patent Publication No. 52-3305, Japanese Patent Laid-Open Publication No. 57-52574, and the like have disclosed techniques for incorporating a release agent in the toner.
[0013]
Also, JP-A-3-50559, JP-A-2-79860, JP-A-1-109359, JP-A-62-1166, JP-A-61-227354, JP-A-61-94062. JP-A-61-138259, JP-A-60-252361, JP-A-60-252360, JP-A-60-217366, etc. disclose techniques for containing waxes. Yes.
[0014]
However, since the release agent is generally not compatible with the binder resin or the magnetic material, it is relatively difficult to uniformly disperse the toner in the toner. The amount is not uniform, and it is not easy to achieve high image quality without fogging of non-image areas such as fog. Further, in such a toner, since the dispersibility of the release agent is non-uniform, a part of the release agent is exposed on the toner surface, or the release agent component is easily oozed out. Therefore, the toner deterioration is likely to be promoted during long-term use under high temperature and high humidity, and fog and deterioration of transferability are likely to be caused. In addition, dot reproducibility and fine line reproducibility become extremely poor due to toner deterioration.
[0015]
On the other hand, the developing method using magnetic toner has unstable factors related to the magnetic toner to be used. One of them is that a considerable amount of fine powdered magnetic material is mixed and dispersed in the magnetic toner, and a part of the magnetic material is exposed on the surface of the toner particles. As a result, fluctuation or deterioration of various characteristics required for the magnetic toner such as development characteristics, transferability, and durability of the magnetic toner is caused.
[0016]
When the magnetic toner containing the conventional magnetic body is used, the above-mentioned problem occurs because the magnetic body is exposed on the surface of the magnetic toner. That is, by exposing magnetic fine particles having relatively low resistance compared to the resin constituting the toner to the surface of the magnetic toner, the toner charging performance is lowered, the toner fluidity is lowered, and the fog is increased accordingly. In addition, transferability is deteriorated, and further, in long-term use, toner deterioration such as a decrease in image density caused by peeling of the magnetic material due to friction between the toners or the regulating member is caused.
[0017]
Conventional toners are manufactured as a toner having a desired particle size (pulverization method) after melt-mixing a binder resin, a colorant, etc., uniformly dispersing, pulverizing with a fine pulverizer, and classifying with a classifier. However, there is a limit to the material selection range for the toner particle size reduction. For example, the resin colorant dispersion must be sufficiently brittle and capable of being finely pulverized by an economically usable production apparatus. From this requirement, in order to make the resin colorant dispersion brittle, when the resin colorant dispersion is actually finely pulverized at a high speed, particles having a wide particle size range are easily formed, and in particular, a relatively large proportion of fine particles ( There arises a problem that excessively pulverized particles) are included therein. Further, such highly brittle materials are often further pulverized or powdered when used as developing toners in copying machines and the like.
[0018]
Further, in the pulverization method, magnetic iron oxide particles are essentially exposed on the surface of the toner, so that problems still remain in the fluidity of the toner and the charging stability in a harsh environment.
[0019]
In order to overcome such problems of the toner by the pulverization method, and further to satisfy the above-described requirements, a toner production method by the suspension polymerization method has been proposed.
[0020]
In general, toner by suspension polymerization (hereinafter referred to as polymerized toner) can be easily made into fine particles of toner, and further, since the shape of the obtained toner is spherical, it has excellent fluidity and is advantageous for high image quality. It becomes.
[0021]
However, by including a magnetic substance in the polymerized toner, its fluidity and charging characteristics are remarkably lowered and the coloring power is also inferior. This is because the magnetic particles are generally hydrophilic and therefore tend to be unevenly distributed on the toner surface, and the dispersion of the magnetic substance in the toner particles is insufficient. In order to solve this problem, it is important to modify the surface characteristics of the magnetic material.
[0022]
Many proposals have been made regarding surface modification for improving the dispersibility of a magnetic substance in a polymerized toner. For example, various silane coupling agent treatment techniques for magnetic materials are disclosed in Japanese Patent Application Laid-Open Nos. 59-200254, 59-2000025, 59-200277, and 59-224102. Japanese Laid-Open Patent Publication Nos. 63-250660 and 10-239897 disclose techniques for treating silicon element-containing magnetic particles with a silane coupling agent.
[0023]
However, although these treatments improve the dispersibility of the magnetic material in the toner to some extent, there is a problem that it is difficult to make the surface of the magnetic material hydrophobic uniformly. The generation of unmodified magnetic particles cannot be avoided, the inclusion of the magnetic material is not sufficient, and it is insufficient to improve the dispersibility in the toner to a good level.
[0024]
Japanese Patent Application Laid-Open No. 54-84731 discloses a technique for improving the inclusion of a magnetic material using a magnetic material obtained by oleophilic treatment of a magnetic material of 0.5 to 0.6 μm. However, when a magnetic material having a small particle size is used to increase the coloring power of the toner, the uniformity of the treatment is inferior, and there is room for improvement in improving the coloring power.
[0025]
Furthermore, in the polymerized toner as described above, if the dispersibility of the magnetic substance in the toner is poor, the release agent is unevenly distributed, and there is room for improvement in durability under high temperature and high humidity.
[0026]
Further, when the toner particle size is reduced, it becomes difficult to control the particle size distribution of the toner and the dispersion of the magnetic substance, the release agent and the like tends to be further deteriorated, and the various problems described above are sufficiently solved. Not.
[0027]
A method of adding inorganic fine powder as an external additive to toner base particles has been proposed and widely used for the purpose of improving toner flow characteristics and charging characteristics.
[0028]
For example, in JP-A-5-66608 and JP-A-4-9860, a method of adding an inorganic fine powder that has been subjected to a hydrophobic treatment or an inorganic fine powder that has been subjected to a hydrophobic treatment and then treated with silicone oil or the like. JP-A-61-249059, JP-A-4-264453, and JP-A-5-346682 propose a method of adding a hydrophobized inorganic fine powder and a silicone oil-treated inorganic fine powder in combination. Yes.
[0029]
However, in these proposals, the toner surface having a spherical shape such as a polymerized toner or a shape close to a spherical shape has a smooth toner surface, so that the deterioration of the external additive as described above tends to proceed and the resolution is improved. When toner particles having a smaller particle diameter are used, there is room for further improvement to improve the above-mentioned problems.
[0030]
[Problems to be solved by the invention]
An object of the present invention is to provide a magnetic toner that has a stable charging performance, has a high image density even when used for a long time under high temperature and high humidity, and can obtain a high-quality image.
[0031]
An object of the present invention is to provide a magnetic toner having excellent transferability and no fog.
[0032]
[Means for Solving the Problems]
  The present invention relates to a magnetic toner having magnetic toner particles containing at least a binder resin, a release agent and a magnetic material.Manufacturing methodIn
  The magnetic toner particles are obtained by suspending a polymerizable monomer composition containing at least a polymerizable monomer containing styrene as a main component, a release agent and a magnetic substance in an aqueous medium, and performing polymerization. And
  The magnetic body is magnetic iron oxide,
  The magnetic toner has an average circularity of 0.970 or more, a weight average particle diameter of 3 to 10 μm,
  The magnetic toner has a magnetization intensity of 10 to 50 Am at a magnetic field of 79.6 kA / m (1000 oersted).²/ Kg (emu / g),
  When the volume average particle size of the magnetic material is A and the Stokes diameter of the magnetic material in styrene is B, the magnetic material satisfies the following formula (1).And
    (1) 1.0 ≦ B / A ≦ 2.8
  The magnetic substance in the magnetic toner is hydrophobized with at least one silane coupling agent having no double bond and a silane coupling agent having a double bond,
  The silane coupling agent having no double bond is represented by the following formula:
    C _p H _{2p + 1} -Si- (OC _q H _{2q + 1} ) _Three
[In formula, p shows the integer of 6-20, q shows the integer of 1-3. ]
An alkyltrialkoxysilane coupling agent represented by:
  The silane coupling agent having a double bond is phenyltrimethoxysilane or γ-methacryloxypropyltrimethoxysilane.Magnetic toner characterized byManufacturing methodAbout.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
As a result of intensive studies by the present inventors, it has been found that when the average circularity of the toner is 0.970 or more, the transferability of the toner becomes very good. This is presumably because the contact area between the toner particles and the photoconductor is small, and the adhesion force of the toner particles to the photoconductor due to the mirror power, van der Waals force, or the like is reduced. Furthermore, since the circularity of the toner is very high, the magnetic toner can form uniform and narrow spikes at the developing portion, and can be developed faithfully to the latent image, and an improvement in image quality can be expected.
[0034]
Further, in the circularity distribution of the toner, when the mode circularity is 0.99 or more, it means that most of the toner particles have a shape close to a true sphere, and the above action becomes more remarkable, which is preferable. .
[0035]
Therefore, it is considered that when such toner is used, transfer efficiency is high, transfer residual toner is greatly reduced, toner fusion is prevented, and image defects are remarkably suppressed.
[0036]
In addition, since the toner has a circularity of 0.970 or more like the toner of the present invention, the rising of the toner on the toner carrier becomes fine and dense, and the charge is made uniform and fog is greatly reduced. To do.
[0037]

[0038]
[Expression 1]

[0039]
[Expression 2]

[0040]
In addition, the mode circularity is obtained by dividing the circularity from 0.40 to 1.00 into 61 units every 0.01, and assigning the measured particle circularity to each divided range according to each circularity. This is the circularity of the peak having the maximum frequency value in the frequency distribution.
[0041]
In addition, “FPIA-1000”, which is a measuring apparatus used in the present invention, calculates the circularity of each particle and then calculates the average circularity and the mode circularity. A calculation method is used in which 0.40 to 1.00 is divided into 61 classes, and the average circularity and mode circularity are calculated using the center value and frequency of the dividing points. However, an error between each value of the average circularity and the mode circularity calculated by this calculation method and each value of the average circularity and the mode circularity calculated by the calculation formula that directly uses the circularity of each particle described above. Is very small and substantially negligible.In the present invention, for the reasons of data handling such as short calculation time and simplification of calculation formula, Such a calculation method that is partially changed by using the concept of a calculation formula that directly uses the circularity may be used.
[0042]
As a specific measuring method, about 5 mg of magnetic toner is dispersed in 10 ml of water in which about 0.1 mg of a surfactant is dissolved to prepare a dispersion, and ultrasonic waves (20 kHz, 50 W) are applied to the dispersion for 5 minutes. Irradiation is performed and the dispersion concentration is set to 5000 to 20,000 / μl, and measurement is performed by the above-described apparatus to determine the average circularity and mode circularity of a particle group having a circle-equivalent diameter of 3 μm or more.
[0043]
The “average circularity” in the present invention is an index of the degree of unevenness of the magnetic toner, and is 1.000 when the magnetic toner is a perfect sphere, and the average circularity becomes smaller as the surface shape of the magnetic toner becomes more complicated. Value.
[0044]
In this measurement, the reason why the circularity is measured only for the particle group having an equivalent circle diameter of 3 μm or more is that the particle group of the external additive existing independently of the toner particles in the particle group having an equivalent circle diameter of less than 3 μm. This is because the circularity of the toner particle group cannot be accurately estimated due to the influence of such a large amount.
[0045]
The magnetic toner of the present invention is 1.0 ≦ B / A ≦ 3.5, preferably 1 where A is the volume average particle size of the magnetic material and B is the Stokes diameter of the magnetic material in styrene. 0.0 ≦ B / A ≦ 2.8, and more preferably 1.0 ≦ B / A ≦ 2.2.
[0046]
“Stokes diameter in styrene” means that 8 g of a magnetic material is added to 10 g of styrene, dispersed with a homogenizer (20 kHz, 50 W) for 3 minutes, and then settled at a sedimentation speed V by Turbiscan (manufactured by Formal Action). Is a value obtained from the following equation.
[0047]
Turbi scan is a device that measures the position of the particle interface of the solution at regular intervals, and was measured by transmitted light. The sedimentation velocity is determined from the distance traveled by the particle interface and the time required for the movement. Specifically, the above mixed solution is put in a sample tube so that the height is about 5 cm, the scan interval is 3 minutes with an automatic scan, the number of scans is 161, and the measurement is performed at 23 ° C. and 60% RH. Do.
[0048]
[Equation 3]

Here, V is the moving speed of particles (m / s), ρc is the density of styrene (900 kg / m^Three), Ρp is the density of the magnetic material (kg / m^Three), G is the gravitational constant (9.81 m / s)²), Ν is the dynamic viscosity of styrene (8.1 × 10^-7m / s), φ is the volume fraction of the magnetic substance in the solution.
[0049]
In addition, the value measured with the true density meter was used for the density of the magnetic material. Specifically, Micromeritics Accupic 1330 (Shimadzu Corporation) was used.
[0050]
The volume average particle diameter of the magnetic material is measured using a transmission electron microscope. Specifically, the toner particles to be observed in the epoxy resin or the cured product obtained by sufficiently dispersing the magnetic material for 2 days in an atmosphere at a temperature of 40 ° C. is formed into a flaky shape by a microtome. As a sample, it was determined by measuring 100 magnetic particles that can be confirmed as the primary particle size in the field of view with a transmission electron microscope (TEM) at a magnification of 10,000 to 40,000 times. It is also possible to measure the particle size with an image analyzer.
[0051]
Here, the large Stokes diameter means that the dispersed particle diameter of the magnetic substance in styrene is large, and the ratio of the volume average particle diameter of the magnetic substance, that is, the B / A is large. This suggests that several to several magnetic materials are present in an aggregated state. In such a state, when the toner is produced by a suspension polymerization method (described later), which is a preferred toner production method in the present invention, the dispersion of the magnetic substance in the oil droplets after granulation is insufficient. In other words, the magnetic substance is present in the toner particles in the form of coalesced and aggregated. For this reason, even if a magnetic material having a small primary particle size is used, those having a large B / A result in a large dispersion particle size of the magnetic material in the toner, and the hiding power of the toner is reduced. The power will be inferior.
[0052]
Furthermore, the toner composition (polymerizable monomer, magnetic substance, etc.) is not uniform during granulation when the Stokes diameter is large, that is, when the sedimentation rate of the magnetic substance in the polymerizable monomer is fast. And the particle size distribution becomes wide, and further, during the polymerization after the droplet formation, the magnetic substance is unevenly distributed in the droplet, and the release agent is unevenly distributed (the uneven distribution is caused). In severe cases, there may be a magnetic substance in half of the toner particles and a release agent in the other half). Here, in particular, when the release agent is unevenly distributed, a part of the release agent is exposed on the toner surface or the release agent component easily oozes out. It will be inferior in durability.
[0053]
In addition, in an image obtained from a toner having poor magnetic dispersibility, particularly a halftone image, a strong reddish image is obtained, resulting in poor image quality. Although the reason for this is not clear, the uneven distribution of the magnetic substance in the toner makes it difficult for light on the long wavelength side to be absorbed (or easily reflected) in the part where the magnetic substance is present roughly or densely. I think that is because.
[0054]
For this reason, even if a magnetic substance having a small particle diameter is used, an image with a large B / A does not increase the coloring power and an image with strong redness is obtained. For this reason, B / A needs to be 3.5 or less.
[0055]
On the other hand, the fact that the Stokes diameter is small means that the dispersed particle diameter of the magnetic substance in styrene is almost close to the primary particle diameter, and it is unlikely that B / A is less than 1.0.
[0056]
For this reason, by setting 1.0 ≦ B / A ≦ 3.5, it is possible to obtain a high-quality image having excellent coloring power and durability under high temperature and high humidity.
[0057]
The Stokes diameter can be adjusted by a magnetic material treatment agent, a treatment method, and a magnetic material dispersion method. We believe this is due to the following reasons.
[0058]
First, the magnetic surface is hydrophilic and the polymerizable monomer is hydrophobic. For this reason, if the hydrophobic treatment on the surface of the magnetic material is not uniform, good dispersibility of the magnetic material cannot be obtained. Further, even if the magnetic material is physically dispersed (such as mechanically or ultrasonically dispersed), the magnetic material with non-uniform surface treatment is aggregated again, and the Stokes diameter becomes large.
[0059]
Secondly, even if the treatment is uniform, the dispersion of the magnetic material is inferior if the polymerizable monomer that is the dispersion medium is not compatible with the magnetic material.
[0060]
Conventionally, many proposals have been made regarding surface modification of magnetic materials used in polymerized toners. For example, various silane coupling agent treatment techniques for magnetic materials are disclosed in Japanese Patent Application Laid-Open Nos. 59-200254, 59-2000025, 59-200277, 59-224102, and the like. Japanese Laid-Open Patent Publication No. 63-250660 discloses a technique for treating silicon element-containing magnetic particles with a silane coupling agent.
[0061]
However, there is a problem that it is difficult to uniformly hydrophobize the surface of the magnetic material by these treatments. Therefore, it is possible to avoid the unification of the magnetic materials and the generation of non-hydrophobized magnetic particles. Therefore, the Stokes diameter becomes large and the particle size distribution becomes wide. As an example of using hydrophobic magnetic iron oxide, Japanese Patent Application Laid-Open No. 54-84731 proposes a toner containing magnetic iron oxide treated with alkyltrialkoxysilane. Although the addition of this magnetic iron oxide has certainly improved the electrophotographic properties of the toner, the surface activity of the magnetic iron oxide is inherently small, and coalesced particles are formed at the processing stage, and the hydrophobicity is not uniform. It is not always satisfactory. In addition, when a magnetic material having a small particle diameter is used, uniform treatment becomes more difficult, and further improvement is required to apply to the present invention. Furthermore, in order to improve the inclusion of the magnetic material, when a large amount of treatment agent or the like is used, or when a highly viscous treatment agent is used, the degree of hydrophobicity will surely increase, but the particles will be united. Conversely, the Stokes diameter becomes large.
[0062]
Thus, in the conventional polymerized toner using the surface-treated magnetic material, the uniformity of the surface treatment is not necessarily achieved, and it is difficult to improve the coloring power and to obtain the high durability under high temperature and high humidity.
[0063]
Therefore, in the magnetic material used in the magnetic toner of the present invention, when the particle surface is hydrophobized, the coupling agent is hydrolyzed while dispersing the magnetic material particles in the aqueous medium so as to have a primary particle size. However, it is very preferable to use a surface treatment method. This hydrophobic treatment method is less likely to cause the magnetic particles to coalesce than the treatment in the gas phase, and the repulsive action between the magnetic particles due to the hydrophobic treatment works, so that the magnetic material is in a primary particle state. Surface treated.
[0064]
The method of treating the surface of the magnetic material while hydrolyzing the coupling agent in an aqueous medium does not require the use of a coupling agent that generates a gas, such as chlorosilanes and silazanes, and further, In the phase, magnetic particles can be easily combined with each other, and a highly viscous coupling agent that has been difficult to be processed can be used, so that the hydrophobizing effect is great.
[0065]
Examples of the coupling agent that can be used in the surface treatment of the magnetic material according to the present invention include a silane coupling agent and a titanium coupling agent. More preferably used is a silane coupling agent having a general formula
Rm SiYn
[Wherein, R represents an alkoxy group, m represents an integer of 1 to 3, Y represents a hydrocarbon group such as an alkyl group, a vinyl group, a glycidoxy group, or a methacryl group, and n represents an integer of 1 to 3. Show. ]
It is shown by.
[0066]
For example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (βmethoxyethoxy) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyl Diethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxy Silane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, n-butyltrimethoxysilane, isobutyl Le trimethoxysilane, trimethyl methoxysilane, hydroxypropyl Ritori silane, n- hexadecyl trimethoxy silane, can be mentioned n- octadecyl trimethoxysilane.
[0067]
Among these, in order to improve the dispersibility of the magnetic substance, it is preferable to use a silane coupling agent having a double bond, and phenyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane are more preferable. This is considered to be because, particularly when suspension polymerization is carried out, if the treatment is performed with a coupling agent having a double bond, the familiarity between the magnetic substance and the polymerizable monomer is improved. The dispersibility of the magnetic material is good.
[0068]
However, using only these coupling agents having a double bond makes it difficult to impart sufficient hydrophobicity to the magnetic material, due to the influence of exposure of the magnetic material with insufficient hydrophobicity to the toner surface. Further, the particle size distribution of the toner becomes wide. The reason for this is not clear, but it is thought to be due to the inferior hydrophobicity of the coupling agent itself, the reactivity with the active groups on the surface of the magnetic material, and the coverage on the surface of the magnetic material. For this reason, in order to obtain sufficient hydrophobicity, it is more preferable to use together an alkyltrialkoxysilane coupling agent represented by the following formula.
[0069]
C_p  H_{2p + 1}-Si- (OC_q  H_{2q + 1})_Three
[In formula, p shows the integer of 2-20, q shows the integer of 1-3. ]
[0070]
When p in the above formula is smaller than 2, the hydrophobizing treatment is easy, but it is difficult to sufficiently impart hydrophobicity, and it becomes difficult to suppress the exposure of the magnetic particles from the toner particles. On the other hand, when p is larger than 20, the hydrophobicity is sufficient, but the coalescence between the magnetic particles increases, making it difficult to sufficiently disperse the magnetic particles, the coloring power is inferior, the high temperature and the high humidity The durability under is also inferior.
[0071]
On the other hand, when q is larger than 3, the reactivity of the silane coupling agent is lowered and the hydrophobicity is not sufficiently performed.
[0072]
In particular, p in the formula represents an integer of 2 to 20 (more preferably an integer of 3 to 15), and q represents an integer of 1 to 3 (more preferably an integer of 1 or 2). A coupling agent should be used.
[0073]
The amount of treatment is 0.05 to 20 parts by mass, preferably 0.1 to 10 parts by mass of the silane coupling agent with respect to 100 parts by mass of the magnetic substance, and the surface area of the magnetic substance and the reaction of the coupling agent. It is preferable to adjust the amount of the treatment agent according to the property.
[0074]
Here, the “aqueous medium” is a medium containing water as a main component. Specific examples of the aqueous medium include water itself, water added with a small amount of a surfactant, water added with a pH adjusting agent, and water added with an organic solvent. As the surfactant, a nonionic surfactant such as polyvinyl alcohol is preferable. The surfactant is preferably added in an amount of 0.1 to 5% by mass with respect to water. Examples of the pH adjuster include inorganic acids such as hydrochloric acid, and examples of the organic solvent include alcohols.
[0075]
Stirring is sufficiently performed, for example, with a mixer having a stirring blade (specifically, a high shear force mixing device such as an attritor or a TK homomixer) so that the magnetic particles become primary particles in the aqueous medium. Is good.
[0076]
In the case where a plurality of types of silane coupling agents are used, a plurality of types of coupling agents are added at the same time or with a time difference to process the magnetic material.
[0077]
In the magnetic material thus obtained, no particle aggregation is observed, and the surface of each particle is uniformly hydrophobized, so that the Stokes diameter is small and the dispersibility of the magnetic material is good.
[0078]
The magnetic material used in the toner of the present invention may contain elements such as phosphorus, cobalt, nickel, copper, magnesium, manganese, aluminum, and silicon. Further, the magnetic substance is composed mainly of iron oxide such as triiron tetroxide and γ-iron oxide, and these are used alone or in combination of two or more. These magnetic materials preferably have a BET specific surface area by nitrogen adsorption method of 2 to 30 m.²/ G, especially 3 to 28m²/ G and a Mohs hardness of 5-7 are preferred.
[0079]
The shape of the magnetic body includes a polyhedron, an octahedron, a hexahedron, a sphere, a needle, a scale, and the like, but a polyhedron, an octahedron, a hexahedron, a sphere, and the like having low anisotropy increase the image density. Is preferable. The shape of such a magnetic material can be confirmed by SEM or the like.
[0080]
The volume average particle size of the magnetic material is preferably 0.05 to 0.4 μm, more preferably 0.1 to 0.3 μm. When the volume average diameter is less than 0.05 μm, the decrease in blackness becomes remarkable, the coloring power becomes insufficient as a colorant for black and white toner, and the cohesion between magnetic materials becomes strong, so that the dispersibility is high. Getting worse. In addition, the uniformity treatment of the magnetic surface becomes very difficult. On the other hand, when the volume average particle diameter exceeds 0.4 μm, the coloring power becomes insufficient as in the case of a general colorant. In addition, when a magnetic material having a volume average particle size larger than 0.4 μm is used, when used as a colorant for a small particle size toner as in the present invention, the magnetic particles are uniformly dispersed in individual toner particles. Becomes difficult to achieve, and the uniform chargeability of the toner is impaired.
[0081]
The magnetic material used in the present invention preferably has a volume average variation coefficient of 35 or less. That the volume average variation coefficient is greater than 35 means that the particle size distribution of the magnetic material is wide. When such a magnetic material is used, the uniformity of the treatment on the surface of the magnetic material is deteriorated and the dispersibility in the toner is deteriorated.
[0082]
The volume average variation coefficient is defined to be obtained by the following equation.
[0083]
[Expression 4]

[0084]
The degree of hydrophobicity of the magnetic material used in the present invention is preferably 25 to 95%, more preferably 35 to 95%. The degree of hydrophobicity can be arbitrarily changed depending on the kind and amount of the treatment agent on the surface of the magnetic material. The “hydrophobic degree” indicates the hydrophobicity of the magnetic substance, and a substance having a low degree of hydrophobicity means that the hydrophilicity is high. Therefore, when a magnetic material having a low degree of hydrophobicity is used, the suspension polymerization method suitably used in the present invention causes the magnetic material to move to an aqueous system during granulation, resulting in a broad particle size distribution and magnetic properties. It is not preferable because the body is exposed on the toner surface or is separated from the toner. Moreover, the dispersibility in a polymerizable monomer will also be inferior. On the other hand, in order to make the degree of hydrophobicity over 95%, it is necessary to use a large amount of the treatment agent on the surface of the magnetic material. In such a state, the magnetic material is likely to be united, and the uniformity of the processing is impaired. It will be.
[0085]
The degree of hydrophobicity in the present invention is measured by the following method.
[0086]
The degree of hydrophobicity of the magnetic material is measured by a methanol titration test. The methanol titration test is an experimental test for confirming the degree of hydrophobicity of a magnetic material having a hydrophobic surface.
[0087]
Hydrophobization degree measurement using methanol is performed as follows. 0.1 g of magnetic material is added to 50 ml of water in a 250 ml beaker. Thereafter, methanol is gradually added to the liquid and titration is performed. At this time, methanol is supplied from the bottom of the liquid and is gently stirred. The end of sedimentation of magnetic particles is the time when the suspended matter of magnetic material is no longer confirmed on the liquid surface, and the degree of hydrophobicity is expressed as the volume percentage of methanol in the methanol and water mixture when the end of sedimentation is reached. .
[0088]
The magnetic material used in the toner of the present invention preferably uses 10 to 200 parts by mass with respect to 100 parts by mass of the binder resin. More preferably, 20 to 180 parts by mass are used. If it is less than 10 parts by mass, the coloring power of the toner is poor, and it is difficult to suppress fogging. On the other hand, when the amount exceeds 200 parts by mass, the holding force by the magnetic force on the toner carrying member is increased and the developing property is lowered, and it is difficult not only to uniformly disperse the magnetic material into individual toner particles, but also the fixing property is lowered. Resulting in.
[0089]
The content of the magnetic substance in the toner was measured with a thermal analyzer “TGA7” manufactured by PerkinElmer. In the measurement method, the toner is heated from normal temperature to 900 ° C. at a temperature increase rate of 25 ° C./min in a nitrogen atmosphere, and the weight loss from 100 ° C. to 750 ° C. is defined as the binder resin amount, and the residual mass is approximately calculated. The amount of magnetic material was used.
[0090]
For example, in the case of magnetite, the magnetic material used in the magnetic toner according to the present invention is manufactured by the following method.
[0091]
An aqueous solution containing ferrous hydroxide is prepared by adding an alkali such as sodium hydroxide in an amount equivalent to or higher than the iron component to the ferrous salt aqueous solution. Air was blown in while maintaining the pH of the prepared aqueous solution at pH 7 or higher (preferably pH 8 to 14), and iron oxide was oxidized while heating the aqueous solution to 70 ° C. or higher. First, a seed crystal is formed.
[0092]
Next, an aqueous solution containing about 1 equivalent of ferrous sulfate is added to the slurry-like liquid containing seed crystals based on the amount of alkali added previously. While maintaining the pH of the solution at 6 to 14, the reaction of ferrous hydroxide is promoted while blowing air, and magnetic iron oxide particles are grown with the seed crystal as the core. As the oxidation reaction proceeds, the pH of the liquid shifts to the acidic side, but the pH of the liquid is preferably not less than 6. Adjust the pH of the solution at the end of the oxidation reaction, stir well so that the magnetic iron oxide becomes primary particles, add the coupling agent, stir well, stir, filter, dry, and lightly crush after stirring By doing so, hydrophobic treated magnetic iron oxide particles can be obtained. Alternatively, after completion of the oxidation reaction, the iron oxide particles obtained by washing and filtering are redispersed in another aqueous medium without drying, and then the pH of the redispersion is adjusted and the silane is stirred well. A coupling agent may be added to perform the coupling treatment.
[0093]
In any case, it is important to perform the surface treatment after the oxidation reaction without passing through the drying step, which is an important point in the toner of the present invention.
[0094]
As the ferrous salt, iron sulfate generally produced as a by-product in the production of sulfuric acid titanium, iron sulfate produced as a by-product with the surface cleaning of the steel sheet can be used, and iron chloride or the like can be used.
[0095]
In the method for producing magnetic iron oxide by the aqueous solution method, an iron concentration of 0.5 to 2 mol / l is generally used from the viewpoint of preventing the viscosity from increasing during the reaction and the solubility of iron sulfate. Generally, the lower the iron sulfate concentration, the finer the particle size of the product. Further, in the reaction, the larger the amount of air and the lower the reaction temperature, the easier the atomization.
[0096]
By using the magnetic toner made of the hydrophobic magnetic particles produced as described above, stable toner charging property can be obtained, transfer efficiency is high, and high image quality and high stability are possible.
[0097]
The toner of the present invention has a magnetization strength of 10 to 50 Am at a magnetic field of 79.6 kA / m (1000 oersted).²It is important that the magnetic toner be / kg (emu / g). This is because the magnetic toner can prevent leakage of the toner by providing a magnetic force generating means in the developing device, so that not only the toner transportability or agitation can be improved, but also the magnetic force acts on the toner carrier. By providing the magnetic force generating means on the magnetic toner, the magnetic toner forms spikes, which makes it easy to prevent the toner from scattering.
[0098]
The toner has a magnetization intensity of 10 Am at a magnetic field of 79.6 kA / m.²If it is less than / kg, the above-mentioned effects cannot be obtained, and if magnetic force is applied to the toner carrier, the rising of the toner becomes unstable and fogging and image density due to inability to uniformly apply charging to the toner. Image defects such as unevenness and poor recovery of transfer residual toner are likely to occur. On the other hand, the strength of magnetization at a magnetic field of 79.6 kA / m is 50 Am.²When it is larger than / kg, when a magnetic force is applied to the toner, the fluidity of the toner is remarkably reduced due to magnetic aggregation, the developing property is lowered, the toner is easily damaged, and the toner is remarkably deteriorated. Further, transferability is lowered, and untransferred toner increases.
[0099]
In the present invention, the saturation magnetization strength of the magnetic toner is determined by using an oscillating magnetometer VSM P-1-10 (manufactured by Toei Kogyo Co., Ltd.) at an external magnetic field of 79.6 kA / m at a room temperature of 25 ° C. It was measured. The magnetic properties of the magnetic material were measured at a room temperature of 25 ° C. with an external magnetic field of 796 kA / m.
[0100]
The toner of the present invention preferably has a weight average particle diameter of 3 to 10 μm, more preferably 4 to 9 μm, in order to develop finer latent image dots faithfully in order to improve image quality.
[0101]
In a toner having a weight average particle size of less than 3 μm, the transfer residual toner on the photoconductor increases due to a decrease in transfer efficiency, and it becomes difficult to suppress the photoconductor scraping and toner fusion in the contact charging step. Furthermore, in addition to the increase in the surface area of the entire toner, the fluidity and agitation as a powder decrease, and it becomes difficult to uniformly charge individual toner particles, so fog and transferability tend to deteriorate, Other than scraping and fusing, it tends to cause non-uniform image unevenness, which is not preferable for the toner used in the present invention. When the weight average particle diameter of the toner exceeds 10 μm, the characters and the line image are likely to be scattered and high resolution is difficult to obtain. Further, as the apparatus becomes higher in resolution, toner of more than 10 μm tends to deteriorate the reproduction of one dot.
[0102]
In the present invention, the ratio of weight average particle diameter / number average particle diameter is preferably 1.40 or less, and more preferably 1.35 or less. When the ratio of the weight average particle diameter / number average particle diameter is greater than 1.40, it means that the toner particle size distribution is wide, and selective development is likely to occur, the charge amount distribution is also widened, fogging increases, The transferability is lowered, which is not preferable.
[0103]
Here, the average particle size and particle size distribution of the toner can be measured by various methods such as Coulter Counter TA-II type or Coulter Multisizer (manufactured by Coulter Co.). In the present invention, Coulter Multisizer (manufactured by Coulter Co., Ltd.). ) Is connected to an interface (manufactured by Nikka) and a PC9801 personal computer (manufactured by NEC), and a 1% NaCl aqueous solution is prepared using first-grade sodium chloride. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used. As a measuring method, 0.1 to 5 ml of a surfactant, preferably alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte solution in which the sample is suspended is dispersed for about 1 to 3 minutes using an ultrasonic disperser, and the volume distribution is determined by measuring the volume and number of toner particles of 2 μm or more using the 100 μm aperture as the aperture by the Coulter Multisizer. And the number distribution were calculated.
[0104]
Then, a volume-based weight average particle diameter (D4) obtained from the volume distribution according to the present invention, a number-based length average particle diameter and a number average particle diameter (D1) obtained from the number distribution were obtained.
[0105]
In the magnetic toner of the present invention, the liberation rate of iron and iron compounds is preferably 0.05 to 3.00%, more preferably 0.05 to 1.50%, and most preferably 0.05 to 1.00. %. The liberation rate of iron and iron compounds is measured by a particle analyzer (PT1000: manufactured by Yokogawa Electric Corporation).
[0106]
The particle analyzer performs the measurement according to the principle described on pages 65-68 of the Japan Hardcopy 97 papers. Specifically, the apparatus can introduce fine particles such as toner into the plasma one by one, and can know the element of the luminescent material, the number of particles, and the particle size of the particles from the emission spectrum of the fine particles.
[0107]
In this, “free rate” is defined as the value obtained by the following equation from the simultaneous emission of carbon atoms, which are constituent elements of the binder resin, and the emission of iron atoms.
[0108]
[Equation 5]

[0109]
Here, “simultaneous light emission of carbon atoms and iron atoms” means that light emission of iron atoms emitted within 2.6 msec from light emission of carbon atoms is simultaneous light emission, and light emission of iron atoms thereafter is light emission of only iron atoms. And In the present invention, since toner particles contain a large amount of magnetic substance, the simultaneous emission of carbon atoms and iron atoms means that the magnetic substance is dispersed in the toner. In other words, this means that the magnetic material is released from the toner.
[0110]
As a specific measurement method, helium gas containing 0.1% oxygen was used and the measurement was performed in an environment of 60% humidity at 23 ° C., and the toner sample was left to stand overnight in the same environment to adjust the humidity. Things are used for measurement. Also, channel 1 measures carbon atoms (measurement wavelength 247.860 nm, K factor uses recommended value), and channel 2 measures iron atoms (measurement wavelength 239.56 nm, K factor uses 3.3964). In this scan, sampling is performed so that the number of light emission of carbon atoms is 1000 to 1400, and the scan is repeated until the total number of light emission of carbon atoms reaches 10,000 or more, and the number of light emission is integrated. At this time, in the distribution in which the number of light emission of the carbon element is on the vertical axis and the cube root voltage of the element is on the horizontal axis, the distribution is sampled so that it has a maximum and further has no valley. And measure. Based on this data, the noise cut level of all elements is set to 1.50 V, and the liberation rate of iron and iron compounds is calculated using the above formula.
[0111]
In addition, toners may contain materials other than inorganic compounds containing iron atoms, such as azo-based iron compounds that are charge control agents. These compounds are also present in organic compounds at the same time as iron atoms. This carbon also emits light at the same time, so it is not counted as a free iron atom.
[0112]
As a result of investigations by the present inventors, there is a deep relationship between the liberation rate of iron and iron compounds and the exposure amount on the toner surface, and if the amount of free magnetic substance is 3.00% or less, the magnetic substance is almost the same. It was found that the toner surface was suppressed from being exposed to the toner surface, fog was small, and transferability was good. This is because a low-resistance magnetic material hardly exists on the toner surface, and it is considered that a stable high charge amount can be obtained.
[0113]
The liberation rate of iron and iron compounds depends on the degree of hydrophobicity of the magnetic material, the particle size distribution, the uniformity of the treatment, etc. As an example, when the surface treatment of the magnetic material is not uniform, the surface treatment is sufficient The magnetic material that is not applied (strongly hydrophilic) exists in the toner in a united or aggregated state, and those that are strongly hydrophilic are not encapsulated, and some or all of them are released from the toner. This is due to the fact that The same applies to the case where a magnetic material having a low degree of hydrophobicity is used. For this reason, especially in the case of a developing method using magnetism, those having a high liberation rate of iron and iron compounds cause the magnetic material to accumulate on the toner carrier, resulting in a decrease in toner chargeability and selective development. End up. Further, when such a magnetic material is used, the dispersibility in the polymerizable monomer is insufficient, which is not preferable because it tends to cause a decrease in coloring power and a decrease in durability under high temperature and high humidity. .
[0114]
On the other hand, if the liberation rate of iron and iron compound is less than 0.05%, it means that the magnetic substance is not substantially liberated from the toner. As described above, a toner with a low liberation rate of iron and iron compounds has a high charge amount, but when a large number of sheets are printed, a decrease in image density due to toner charge-up and a rough image are caused.
[0115]
This is considered to be the following reason. Generally, the toner on the toner carrier is not completely developed on the photosensitive member, and the toner exists on the toner carrier even immediately after development. This tendency is particularly strong in jumping development using magnetic toner, and the development efficiency is not so high. Further, as described above, toner with a high degree of circularity forms uniform thin spikes at the developing section, and is developed from the toner present at the tip of the spike, and the toner near the toner carrier is hardly developed. it is conceivable that.
[0116]
For this reason, the toner in the vicinity of the toner carrying member repeatedly receives frictional charging by the charging member, is charged up, and falls into a vicious circle in which development becomes difficult. Further, in such a state, the toner charging uniformity is impaired, and the image becomes rough.
[0117]
Here, when a toner having a liberation rate of iron and iron compound of 0.05% or more is used, toner charge-up is suppressed by a free magnetic material or a magnetic material slightly present on the toner surface, and Uniformity of the charge amount of the toner is promoted, and rattling is suppressed.
[0118]
For these reasons, the liberation rate of iron and iron compounds is preferably 0.05 to 3.00%.
[0119]
The toner according to the present invention contains a release agent, but preferably contains 1.0 to 30 parts by mass with respect to 100 parts by mass of the binder resin.
[0120]
The toner image transferred onto the transfer material is then fixed on the transfer material with energy such as heat and pressure to obtain a semi-permanent image. At this time, heat roll type fixing is generally used. As described above, if a toner having a weight average particle size of 10 μm or less is used, a very high-definition image can be obtained. However, a toner particle having a small particle size is a paper fiber when a transfer material such as paper is used. , The heat receiving from the heat fixing roller is insufficient, and low temperature offset is likely to occur. However, it is possible to achieve both high image quality and fixability by incorporating an appropriate amount of a release agent in the toner according to the present invention.
[0121]
Release agents that can be used for the magnetic toner according to the present invention include petroleum waxes such as paraffin wax, microcrystalline wax, petrolactam and derivatives thereof, montan wax and derivatives thereof, hydrocarbon waxes and derivatives thereof according to the Fischer-Tropsch method, Polyolefin waxes represented by polyethylene and derivatives thereof, natural waxes such as carnauba wax and candelilla wax and derivatives thereof, and the derivatives include oxides, block copolymers with vinyl monomers, and graft modified products. Furthermore, fatty acids such as higher aliphatic alcohols, stearic acid and palmitic acid, or compounds thereof, acid amide waxes, ester waxes, ketones, hydrogenated castor oil and derivatives thereof, plant waxes, animal waxes and the like can also be used.
[0122]
Among these release agent components, those having a maximum endothermic peak in the region of 40 to 110 ° C. when the temperature rises are preferable in the DSC curve measured by a differential scanning calorimeter, and those in the region of 45 to 90 ° C. Is more preferable. By having the maximum endothermic peak in the above temperature range, the mold releasability is effectively expressed while greatly contributing to low-temperature fixing.
[0123]
When the maximum endothermic peak is less than 40 ° C., the self-aggregation force of the release agent component becomes weak, and as a result, the high temperature offset resistance is deteriorated. In addition, the release agent tends to ooze out, and the charge amount of the toner decreases. On the other hand, if the maximum endothermic peak exceeds 110 ° C., the fixing temperature becomes high and low temperature offset tends to occur, which is not preferable. Further, when directly granulating / polymerizing in an aqueous medium and obtaining a toner directly by the polymerization method, if the maximum endothermic peak temperature is high, a problem such as precipitation of a release agent component mainly occurs during granulation, The dispersibility of the agent deteriorates, which is not preferable.
[0124]
Further, if the content of the release agent is less than 1.0% by mass, the effect of suppressing the low temperature offset is poor, and if it exceeds 30% by mass, the long-term storage stability is deteriorated and the dispersibility of other toner materials is also deteriorated. As a result, the fluidity of the magnetic toner deteriorates and the image characteristics deteriorate. Furthermore, since a large amount of wax is included, the toner shape tends to become distorted.
[0125]
The toner of the present invention may contain a charge control agent in order to stabilize the charge characteristics. As the charge control agent, a known one can be used, and a charge control agent that has a high charging speed and can stably maintain a constant charge amount is particularly preferable. Further, when the toner is produced using a direct polymerization method, a charge control agent having a low polymerization inhibitory property and substantially free from a solubilized product in an aqueous dispersion medium is particularly preferable.
[0126]
Specific compounds include, as negative charge control agents, metal compounds of aromatic carboxylic acids such as salicylic acid, alkylsalicylic acid, dialkylsalicylic acid, naphthoic acid and dicarboxylic acid, metal salts or metal complexes of azo dyes or azo pigments, sulfones Examples thereof include a polymer compound having an acid or carboxylic acid group in the side chain, a boron compound, a urea compound, a silicon compound, and a calixarene. Examples of positive charge control agents include quaternary ammonium salts, polymer compounds having the quaternary ammonium salt in the side chain, guanidine compounds, nigrosine compounds, imidazole compounds, and the like.
[0127]
As a method of incorporating a charge control agent into the toner, there are a method of adding the toner inside the toner base particles and a method of adding it externally. The amount of these charge control agents used is determined by the toner production method including the type of binder resin, the presence or absence of other additives, and the dispersion method, and is not uniquely limited. When added internally, it is preferably used in the range of 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the binder resin. In the case of external addition, the amount is preferably 0.005 to 1.0 part by mass, more preferably 0.01 to 0.3 part by mass with respect to 100 parts by mass of the toner. However, in the magnetic toner of the present invention, it is not essential to add a charge control agent, and the toner does not necessarily contain the charge control agent by actively utilizing frictional charging with the toner layer thickness regulating member or the toner carrier. There is no need.
[0128]
Next, a production method by a suspension polymerization method that can be suitably used as a production method of the toner of the present invention will be described.
[0129]
Examples of the polymerizable monomer constituting the polymerizable monomer system used in the toner of the present invention include the following.
[0130]
Examples of the polymerizable monomer include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-ethylstyrene, methyl acrylate, ethyl acrylate, Acrylic esters such as n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, etc. , Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, Methacrylic acid esters such as methacrylic acid, dimethylaminoethyl methacrylate diethylaminoethyl, other acrylonitrile-methacrylonitrile-monomer acrylamide.
[0131]
These monomers can be used alone or in combination. Among the above-mentioned monomers, styrene or a styrene derivative is preferably used alone or mixed with other monomers from the viewpoint of the developing characteristics and durability of the toner.
[0132]
In the production of the toner according to the present invention, a resin may be added to the monomer system for polymerization. For example, hydrophilic functional groups such as amino groups, carboxylic acid groups, hydroxyl groups, sulfonic acid groups, glycidyl groups, nitrile groups, etc. that cannot be used because monomers are water-soluble and dissolve in aqueous suspension to cause emulsion polymerization. When it is desired to introduce the monomer components contained in the toner into a copolymer, such as a random copolymer of these and a vinyl compound such as styrene or ethylene, a block copolymer, or a graft copolymer, Alternatively, it can be used in the form of a polycondensate such as polyester or polyamide, or a polyaddition polymer such as polyether or polyimine. When such a high molecular polymer containing a polar functional group is allowed to coexist in the toner, such a high molecular polymer is likely to be localized on the surface of the toner. A toner having good blocking resistance and developability can be obtained.
[0133]
Among these resins, the effect is greatly increased by containing a polyester resin. This is considered to be the following reason. Since the polyester resin contains many ester bonds which are functional groups having relatively high polarity, the polarity of the resin itself becomes high. Due to its polarity, polyester tends to be unevenly distributed on the surface of the droplets in the aqueous dispersion medium, and polymerization proceeds while maintaining this state, resulting in a toner. For this reason, the uneven distribution of the polyester resin on the toner surface makes the surface state and surface composition uniform, and as a result, the charging property becomes uniform and the encapsulating property of the release agent and magnetic substance is good. Due to this synergistic effect, very good developability can be obtained.
[0134]
For the polyester resin used in the present invention, for example, a saturated polyester resin, an unsaturated polyester resin, or both are appropriately selected and used for controlling physical properties such as chargeability, durability, and fixability of the toner. Is possible.
[0135]
The alcohol component and acid component which comprise the polyester resin used for this invention are illustrated below.
[0136]
As alcohol components, ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexane Diol, neopentyl glycol, 2-ethyl-1,3-hexanediol, cyclohexanedimethanol, butenediol, octenediol, cyclohexenedimethanol, hydrogenated bisphenol A, and bisphenol derivatives represented by formula (I);
[0137]
[Chemical 1]

[Wherein, R is an ethylene or propylene group, x and y are each an integer of 1 or more, and the average value of x + y is 2 to 10. ]
[0138]
Or hydrogenated compound of formula (I), or diol of formula (II);
[0139]
[Chemical 2]

Or the diol of the hydrogenated compound of the compound of a formula (II) is mentioned.
[0140]
As the divalent carboxylic acid, benzene dicarboxylic acid such as phthalic acid, terephthalic acid, isophthalic acid, phthalic anhydride or the anhydride thereof; alkyl dicarboxylic acid such as succinic acid, adipic acid, sebacic acid, azelaic acid or the anhydride, Furthermore, succinic acid substituted with an alkyl or alkenyl group having 6 to 18 carbon atoms or an anhydride thereof; unsaturated dicarboxylic acid such as fumaric acid, maleic acid, citraconic acid, itaconic acid or the anhydride thereof may be used.
[0141]
Furthermore, polyhydric alcohols such as glycerin, pentaerythritol, sorbit, sorbitan, and oxyalkylene ethers of novolac type phenol resins can be cited as the alcohol component, and trimellitic acid, pyromellitic acid, 1,2,3,4- Examples thereof include polyvalent carboxylic acids such as butanetetracarboxylic acid, benzophenonetetracarboxylic acid and anhydrides thereof.
[0142]
Among the polyester resins, the alkylene oxide adduct of bisphenol A, which is excellent in charging characteristics and environmental stability and balanced in other electrophotographic characteristics, is preferably used. In the case of this compound, the average number of added moles of alkylene oxide is preferably 2 to 10 in terms of fixability and toner durability.
[0143]
It is preferable that 45-55 mol% of the said polyester resin is an alcohol component, and 55-45 mol% is an acid component in all the components.
[0144]
The polyester resin is present on the surface of the toner particles in the production method of the present invention, and the obtained toner particles have an acid value of 0.1 to 50 mg KOH / resin 1 g in order to develop stable chargeability. It is preferable. If it is less than 0.1 mg KOH / resin 1 g, the amount existing on the toner surface is absolutely insufficient, and if it exceeds 50 mg KOH / resin 1 g, the chargeability of the toner is adversely affected. Furthermore, in the present invention, the acid value range of 5 to 35 mg KOH / resin 1 g is more preferable.
[0145]
In the present invention, as long as the physical properties of the toner particles obtained are not adversely affected, it is also preferable to adjust the physical properties by using two or more kinds of polyester resins together, for example, by modifying with silicone or a fluoroalkyl group-containing compound. To be done.
[0146]
Moreover, when using the high molecular polymer containing such a polar functional group, the average molecular weight is preferably 5,000 or more. If it is less than 5,000, especially 4,000 or less, the present polymer tends to concentrate near the surface, and this is not preferred because it tends to adversely affect developability and blocking resistance.
[0147]
In addition, resins other than those described above may be added to the monomer system for the purpose of improving the dispersibility and fixing properties of the material or image characteristics. Examples of the resin used include styrene such as polystyrene and polyvinyltoluene. And styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-methacrylic acid Acid butyl copolymer, styrene-dimethylaminoethyl methacrylate copolymer Polymer, Styrene-vinyl methyl ether copolymer, Styrene-vinyl ethyl ether copolymer, Styrene-vinyl methyl ketone copolymer, Styrene-butadiene copolymer, Styrene-isoprene copolymer, Styrene-maleic acid copolymer Styrene copolymers such as styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacryl Acid resins, rosins, modified rosins, terpene resins, phenol resins, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins and the like can be used alone or in combination.
[0148]
As addition amount of these resin, 1-20 mass parts is preferable with respect to 100 mass parts of monomers. If it is less than 1 part by mass, the effect of addition is small, and if it is added more than 20 parts by mass, it becomes difficult to design various physical properties of the polymerized toner.
[0149]
Furthermore, if a polymer having a molecular weight different from the molecular weight range of the toner obtained by polymerizing the monomer is dissolved in the monomer and polymerized, a toner having a wide molecular weight distribution and high offset resistance can be obtained. it can.
[0150]
As the polymerization initiator used in the production of the toner of the present invention, a polymerization initiator having a half-life of 0.5 to 30 hours is 0.5 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer. When the polymerization reaction is carried out in an added amount, a polymer having a maximum between 10,000 and 100,000 in molecular weight can be obtained, and the toner can have desirable strength and appropriate melting characteristics. Examples of polymerization initiators include 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile) Azo or diazo polymerization initiators such as 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile; benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, Examples thereof include peroxide-based polymerization initiators such as cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, and t-butylperoxy 2-ethylhexanoate.
[0151]
In producing the toner of the present invention, a crosslinking agent may be added, and a preferable addition amount is 0.001 to 15 parts by mass with respect to 100 parts by mass of the polymerizable monomer.
[0152]
Here, as the crosslinking agent, a compound having two or more polymerizable double bonds is mainly used, for example, an aromatic divinyl compound such as divinylbenzene, divinylnaphthalene, etc .; for example, ethylene glycol diacrylate, ethylene glycol diester Carboxylic acid ester having two double bonds such as methacrylate, 1,3-butanediol dimethacrylate, etc .; Divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone, etc .; and having three or more vinyl groups Are used alone or as a mixture.
[0153]
In suspension polymerization, which is a preferred production method of the toner of the present invention, generally, the above-described toner composition, that is, a magnetic substance, a release agent, a plasticizer, a charge control agent, a crosslinking agent, in the polymerizable monomer, In some cases, components necessary as a toner such as a colorant and other additives, for example, an organic solvent, a high molecular weight polymer, a dispersing agent, etc., which are added to lower the viscosity of the polymer produced by the polymerization reaction, are appropriately added, and a homogenizer, A monomer system uniformly dissolved or dispersed by a dispersing machine such as a ball mill, a colloid mill, or an ultrasonic dispersing machine is suspended in an aqueous medium containing a dispersion stabilizer. At this time, the particle size of the obtained toner particles becomes sharper by using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser to obtain a desired toner particle size all at once. The polymerization initiator may be added at the same time as other additives are added to the polymerizable monomer, or may be mixed immediately before being suspended in the aqueous medium. Also, during the granulation, a polymerization initiator dissolved in a polymerizable monomer or a solvent can be added immediately after granulation and before starting the polymerization reaction.
[0154]
After granulation, stirring may be performed using a normal stirrer to such an extent that the particle state is maintained and particle floating and sedimentation are prevented.
[0155]
In the production of the toner of the present invention, known surfactants and organic / inorganic dispersants can be used as dispersion stabilizers. In particular, inorganic dispersants are less likely to produce harmful ultra fine powders, and their steric hindrance prevents dispersion stability. Therefore, even if the reaction temperature is changed, the stability is not easily lost, the washing is easy and the toner is not adversely affected. Examples of such inorganic dispersants include polyvalent metal phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate and zinc phosphate; carbonates such as calcium carbonate and magnesium carbonate; calcium metasuccinate, calcium sulfate and barium sulfate. Inorganic salts; hydroxides such as calcium hydroxide, magnesium hydroxide, and aluminum hydroxide; inorganic oxides such as silica, bentonite, and alumina.
[0156]
These inorganic dispersants are desirably used alone in an amount of 0.2 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer. However, although it is difficult to generate ultrafine particles, it is somewhat difficult to atomize the toner. Therefore, you may use 0.001-0.1 mass part surfactant together.
[0157]
Examples of the surfactant include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, sodium stearate, potassium stearate and the like.
[0158]
When these inorganic dispersants are used, they may be used as they are, but in order to obtain finer particles, the inorganic dispersant particles can be generated and used in an aqueous medium. For example, in the case of calcium phosphate, a sodium phosphate aqueous solution and a calcium chloride aqueous solution can be mixed with high-speed stirring to produce water-insoluble calcium phosphate, which enables more uniform and fine dispersion. At the same time, a water-soluble sodium chloride salt is produced as a by-product. However, if a water-soluble salt is present in the aqueous medium, dissolution of the polymerizable monomer in water is suppressed, and ultrafine toner is generated by emulsion polymerization. This is more convenient. When removing the residual polymerizable monomer at the end of the polymerization reaction, it becomes an obstacle, so it is better to replace the aqueous medium or desalinate with an ion exchange resin. The inorganic dispersant can be almost completely removed by dissolving with an acid or alkali after completion of the polymerization.
[0159]
In the polymerization step, the polymerization is performed at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. When the polymerization is carried out in this temperature range, the release agent and wax to be sealed inside are precipitated by phase separation, and the encapsulation is more complete. In order to consume the remaining polymerizable monomer, the reaction temperature can be increased to 90 to 150 ° C. at the end of the polymerization reaction.
[0160]
The polymerized toner particles are filtered, washed, and dried by a known method after the polymerization is completed, and the toner can be obtained by mixing and adhering the inorganic fine powder to the surface. Moreover, it is one of the desirable forms of this invention to put a classification process in a manufacturing process and to cut coarse powder and fine powder.
[0161]
When the toner according to the present invention is produced by a pulverization method, a known method is used. For example, a binder resin, a magnetic material, a release agent, a charge control agent, and a coloring agent depending on circumstances, a component necessary as a toner. And other additives are mixed thoroughly by a mixer such as a Henschel mixer and a ball mill, and then melted and kneaded using a heat kneader such as a heating roll, kneader, and extruder to make the resins compatible with each other. The toner particles can be obtained by dispersing or dissolving other toner materials such as a magnetic material, cooling and solidifying, pulverizing, classification, and surface treatment as necessary. Either the classification or the surface treatment may be performed first. In the classification step, it is preferable to use a multi-division classifier in terms of production efficiency.
[0162]
The pulverization step can be performed by a method using a known pulverizer such as a mechanical impact type or a jet type. In order to obtain a toner having a specific degree of circularity according to the present invention, it is preferable to further heat and pulverize or to add a mechanical impact as an auxiliary. Further, a hot water bath method in which finely pulverized (classified as necessary) toner particles are dispersed in hot water, a method of passing in a hot air stream, or the like may be used.
[0163]
As a means for applying a mechanical impact force, for example, a method using a mechanical impact type pulverizer such as a kryptron system manufactured by Kawasaki Heavy Industries, Ltd. or a turbo mill manufactured by Turbo Industry Co., a mechano-fusion system manufactured by Hosokawa Micron Co., Ltd. or Nara Machinery Co., Ltd. There is a method of applying a mechanical impact force to the toner by a force such as a compressive force or a frictional force by pressing the toner to the inside of the casing by a centrifugal force with a blade rotating at a high speed as in a device such as a hybridization system manufactured by the manufacturer.
[0164]
In the case of using the mechanical impact method, a thermomechanical impact in which the processing temperature is a temperature in the vicinity of the glass transition point Tg (Tg ± 10 ° C.) of the toner is preferable from the viewpoint of preventing aggregation and productivity. More preferably, it is particularly effective to improve the transfer efficiency to carry out at a temperature in the range of the glass transition point Tg ± 5 ° C. of the toner.
[0165]
Furthermore, the toner according to the present invention is a method for obtaining a spherical toner by atomizing a molten mixture into air using a disk or a multi-fluid nozzle described in JP-B-56-13945, etc. The emulsion polymerization method represented by the dispersion polymerization method for directly producing a toner using an aqueous organic solvent in which the polymer obtained in 1 is insoluble or the soap-free polymerization method for producing the toner by directly polymerizing in the presence of a water-soluble polar polymerization initiator, etc. The toner can also be manufactured by a method of manufacturing toner.
[0166]
As a binder resin when the toner according to the present invention is produced by a pulverization method, styrene such as polystyrene and polyvinyltoluene and a homopolymer of a substituted product thereof; a styrene-propylene copolymer, a styrene-vinyltoluene copolymer, Styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylamino acrylate Ethyl copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer Coalescence, styrene-vinyl ethyl acetate Styrene copolymers such as styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer Combined; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, fat Aromatic or alicyclic hydrocarbon resins, aromatic petroleum resins, paraffin wax, carnauba wax and the like can be used alone or in combination. In particular, a styrene copolymer and a polyester resin are preferable in terms of development characteristics, fixing properties, and the like.
[0167]
The glass transition temperature (Tg) of the binder resin is preferably 50 to 70 ° C. If the temperature is lower than 50 ° C., the storage stability of the toner is lowered, and if it is higher than 70 ° C., the fixability is inferior.
[0168]
In the present invention, the toner is preferably added with inorganic fine powder having a number average primary particle size of 4 to 80 nm as a fluidizing agent. Inorganic fine powder is added to improve the fluidity of the toner and to make the toner base particles evenly charged. However, the inorganic chargeable powder is treated to make it hydrophobic and adjust the toner charge amount and improve the environmental stability. It is also a preferable form to provide such functions.
[0169]
When the number average primary particle diameter of the inorganic fine powder is larger than 80 nm, or when inorganic fine particles of 80 nm or less are not added, it becomes easy to adhere to the charging member when the transfer residual toner adheres to the charging member, It is difficult to stably obtain good charging characteristics. In addition, good toner fluidity cannot be obtained, and charging to toner particles is likely to be uneven, and problems such as increased fog, decreased image density, and toner scattering cannot be avoided. When the number average primary particle size of the inorganic fine particles is smaller than 4 nm, the inorganic fine particles become more cohesive and behave as aggregates with a wide particle size distribution that are not primary particles but have strong cohesive properties that are difficult to break even by crushing treatment. It is easy to cause image defects due to development of aggregates, damage to the image carrier or development carrier, and the like. In order to make the charge distribution of the toner particles more uniform, the number average primary particle size of the inorganic fine particles is preferably 6 to 35 nm.
[0170]
In the present invention, the method of measuring the number average primary particle size of the inorganic fine powder is a photograph of the toner magnified by a scanning electron microscope, and the inorganic fine powder by an elemental analysis means such as XMA attached to the scanning electron microscope. Measure 100 or more primary particles of inorganic fine powder adhering to or liberating from the toner surface while comparing photographs of the toner mapped with the elements contained in the toner, and obtain the average primary particle size based on the number. Can be measured.
[0171]
Silica, alumina, titanium oxide, etc. can be used as the inorganic fine particles used in the present invention.
[0172]
For example, as the silicic acid fine powder, both a so-called dry method produced by vapor phase oxidation of silicon halide or dry silica called fumed silica, and so-called wet silica produced from water glass can be used. However, there are few silanol groups on the surface and inside the silica fine powder, and Na₂O, SO_Three ^2-For example, dry silica with less production residue is preferred. In dry silica, it is also possible to obtain composite fine powders of silica and other metal oxides by using other metal halogen compounds such as aluminum chloride and titanium chloride together with silicon halogen compounds in the production process. They are also included.
[0173]
The addition amount of inorganic fine particles having an average primary particle size of 4 to 80 nm is preferably 0.1 to 3.0% by mass with respect to the toner base particles, and the effect is obtained when the addition amount is less than 0.1% by mass. It is not sufficient, and if it exceeds 3.0% by mass, the fixability becomes poor.
[0174]
In addition, content of inorganic fine powder can be quantified using the analytical curve created from the standard sample using the fluorescent X ray analysis.
[0175]
The inorganic fine particles are preferably hydrophobized in view of characteristics in a high temperature and high humidity environment. When the inorganic fine particles added to the toner absorb moisture, the charge amount of the toner base particles is remarkably reduced, and the toner is likely to scatter.
[0176]
As treatment agents for hydrophobic treatment, treatment agents such as silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane compounds, silane coupling agents, other organic silicon compounds, and organic titanium compounds may be used alone or in combination. And may be processed.
[0177]
Among them, those treated with silicone oil are preferable, and more preferably, those treated with silicone oil at the same time or after the hydrophobic treatment of the inorganic fine particles maintain the charge amount of the toner particles high even in a high humidity environment. In order to prevent toner scattering.
[0178]
As a method for treating inorganic fine particles, for example, a silylation reaction can be performed as a first-stage reaction to eliminate silanol groups by chemical bonding, and then a hydrophobic thin film can be formed on the surface with silicone oil as a second-stage reaction. .
[0179]
The silicone oil has a viscosity at 25 ° C. of 10 to 200,000 mm.²/ S, even 3,000-80,000mm²/ S is preferred. 10mm²If it is less than / s, the inorganic fine particles are not stable, and the image quality tends to deteriorate due to heat and mechanical stress. 200,000mm²If it exceeds / s, uniform processing tends to be difficult.
[0180]
As the silicone oil used, for example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, fluorine modified silicone oil and the like are particularly preferable.
[0181]
As a method for treating silicone oil, for example, silica treated with a silane compound and silicone oil may be directly mixed using a mixer such as a Henschel mixer, or a method of spraying silicone oil on silica may be used. Also good. Alternatively, after dissolving or dispersing silicone oil in a suitable solvent, silica fine powder may be added and mixed to remove the solvent. A method using a sprayer is more preferable in that the formation of inorganic fine particle aggregates is relatively small.
[0182]
The treatment amount of the silicone oil is 1 to 40 parts by mass, preferably 3 to 35 parts by mass with respect to 100 parts by mass of silica.
[0183]
If the amount of silicone oil is too small, good hydrophobicity cannot be obtained, and if it is too large, problems such as fogging occur.
[0184]
The silica used in the present invention has a specific surface area of 20 to 350 m as measured by the BET method by nitrogen adsorption in order to impart good fluidity to the toner.²/ G is preferable, more preferably 25-300m²/ G is even better.
[0185]
In accordance with the BET method, the specific surface area is obtained by adsorbing nitrogen gas to the sample surface using a specific surface area measuring device Autosorb 1 (manufactured by Yuasa Ionics) and calculating the specific surface area using the BET multipoint method.
[0186]
The magnetic toner of the present invention further exceeds the primary particle size of 30 nm (preferably having a specific surface area of 50 m for the purpose of improving the cleaning property).²/ G), more preferably the primary particle size is 50 nm or more (preferably the specific surface area is 30 m).²It is also one of preferable modes to add inorganic or organic fine particles close to spherical shape (less than / g). For example, spherical silica particles, spherical polymethylsilsesquioxane particles, spherical resin particles and the like are preferably used.
[0187]
The magnetic toner used in the present invention may further contain other additives, for example, a lubricant powder such as a Teflon powder, a zinc stearate powder, a polyvinylidene fluoride powder, or a cerium oxide powder, Abrasives such as silicon powder and strontium titanate powder; or fluidity-imparting agents such as titanium oxide powder and aluminum oxide powder; anti-caking agents; and small amounts of organic fine particles of opposite polarity and inorganic fine particles as developability improvers It can also be used. These additives can also be used after hydrophobizing the surface.
[0188]
Next, an example of an image forming apparatus that can suitably use the toner of the present invention will be specifically described with reference to FIG.
[0189]
In FIG. 1, reference numeral 100 denotes a photosensitive drum, and a primary charging roller 117, a developing device 140, a transfer charging roller 114, a cleaner 116, a register roller 124, and the like are provided around the photosensitive drum. The photoreceptor 100 is charged to −700 V by the primary charging roller 117 (applied voltages are AC voltage −2.0 kVpp, DC voltage −700 Vdc). Then, exposure is performed by irradiating the photosensitive member 100 with a laser beam 123 by the laser generator 121. The electrostatic latent image on the photoconductor 100 is developed with a one-component magnetic toner by the developing device 140 and transferred onto the transfer material by the transfer roller 114 in contact with the photoconductor via the transfer material. The transfer material P on which the toner image is placed is conveyed to the fixing device 126 by the conveying belt 125 or the like and fixed on the transfer material. In addition, toner remaining on a part of the photoconductor is cleaned by the cleaning unit 116.
[0190]
As shown in FIG. 2, the developing device 140 is provided with a cylindrical toner carrier 102 (hereinafter referred to as a developing sleeve) made of a nonmagnetic metal such as aluminum or stainless steel in the vicinity of the photosensitive member 100. The gap between 100 and the developing sleeve 102 is maintained at about 220 μm by a sleeve / photoreceptor gap holding member (not shown). A magnet roller 104 is fixed and arranged concentrically with the developing sleeve 102 in the developing sleeve. However, the developing sleeve 102 is rotatable. The magnet roller 104 is provided with a plurality of magnetic poles as shown in the figure. S1 affects development, N1 regulates the toner coat amount, S2 takes in / conveys toner, and N2 affects toner blowout prevention. An elastic blade 103 is provided as a member for regulating the amount of magnetic toner that adheres to the developing sleeve 102 and is conveyed, and the amount of toner conveyed to the developing region is controlled by the contact pressure of the elastic blade 103 against the developing sleeve 102. . In the developing region, a DC and AC developing bias is applied between the photoconductor 100 and the developing sleeve 102, and the toner on the developing sleeve flies onto the photoconductor 100 in accordance with the electrostatic latent image and becomes a visible image.
[0191]
【Example】
Hereinafter, the present invention will be specifically described with reference to production examples and examples, but this does not limit the present invention in any way. In addition, all the parts in the following mixing | blending are a mass part.
[0192]
(Production Example 1 of Surface-treated Magnetic Material)
In ferrous sulfate aqueous solution, l. 0 to 1.1 equivalent of caustic soda solution, 1.0 mass% sodium hexametaphosphate in terms of phosphorus element with respect to iron element, 1.0 mass% sodium silicate in terms of silicon element with respect to iron element are mixed, and hydroxylated An aqueous solution containing ferrous iron was prepared.
[0193]
While maintaining the pH of the aqueous solution at around 13, air was blown and an oxidation reaction was performed at 80 to 90 ° C. to obtain a slurry solution of magnetic particles. After washing and filtering, this hydrous slurry liquid was once taken out. At this time, a small amount of water-containing sample was collected and the water content was measured. Next, this water-containing sample was re-dispersed in another aqueous medium without drying, and then the pH of the re-dispersed liquid was adjusted to about 6, and the n-hexyltrimethoxysilane coupling agent was magnetically stirred with sufficient stirring. To 100 parts of iron oxide, 2.0 parts and 1.0 part of γ-methacryloxypropyltrimethoxysilane coupling agent (the amount of magnetic particles was calculated as the water content minus the water content) were added, and the cup Ring treatment was performed. The produced hydrophobic magnetic particles are washed, filtered, and dried by a conventional method, and the obtained particles are sufficiently crushed, and the number average particle diameter is 0.12 μm and the number average variation coefficient is 8. 1 was obtained. It was 1.4 when B / A of the obtained magnetic body was calculated | required. Table 1 shows the physical properties of the obtained magnetic substance.
[0194]
(Production Example 2 of Surface-treated Magnetic Material)
In Production Example 1 of the surface-treated magnetic material, 2.0 parts of n-hexyltrimethoxysilane coupling agent is 1.5 parts of n-decyltrimethoxysilane coupling agent, and γ-methacryloxypropyltrimethoxysilane is 1. A surface-treated magnetic body 2 was obtained in the same manner as in Production Example 1 of the surface-treated magnetic body except that the amount was 5 parts. Table 1 shows the physical properties of the obtained magnetic substance.
[0195]
(Production Example 3 of Surface-treated Magnetic Material)
In Production Example 2 of the surface-treated magnetic material, 1.2 parts of n-decyltrimethoxysilane coupling agent and 1.5 parts of γ-methacryloxypropyltrimethoxysilane coupling agent are phenyltrimethoxysilane coupling agent 1 The surface-treated magnetic body 3 was obtained in the same manner as in Production Example 2 of the surface-treated magnetic body except that the amount was 8 parts.
Table 1 shows the physical properties of the obtained magnetic substance.
[0196]
(Production Example 4 of Surface-treated Magnetic Material)
The surface-treated magnetic body was manufactured in the same manner as in Surface-treated magnetic body Production Example 1 except that 2.0 parts of the n-hexyltrimethoxysilane coupling agent was changed to 1.4 parts. 4 was obtained. Table 1 shows the physical properties of the obtained magnetic substance.
[0197]
(Surface-treated magnetic material production example 5)
In the surface-treated magnetic body production example 1, the surface-treated magnetic body was prepared in the same manner as in the surface-treated magnetic body production example 1 except that 2.0 parts of the n-hexyltrimethoxysilane coupling agent was changed to 0.8 part. 5 was obtained. Table 1 shows the physical properties of the obtained magnetic substance.
[0198]
(Surface Treatment Magnetic Production Example 6)
The surface-treated magnetic body was manufactured in the same manner as in Surface-treated magnetic body Production Example 2 except that 1.5 parts of the n-decyltrimethoxysilane coupling agent was changed to 1.1 parts. 6 was obtained. Table 1 shows the physical properties of the obtained magnetic substance.
[0199]
(Surface treatment magnetic material production example 7)
In the surface-treated magnetic body production example 2, the surface-treated magnetic body was manufactured in the same manner as in the surface-treated magnetic body production example 2 except that 1.5 parts of the n-decyltrimethoxysilane coupling agent was 0.6 parts. 7 was obtained. Table 1 shows the physical properties of the obtained magnetic substance.
[0200]
(Production Example 8 of Surface-treated Magnetic Material)
The surface-treated magnetic body was manufactured in the same manner as in Surface-treated magnetic body Production Example 2 except that 1.50 parts of the n-decyltrimethoxysilane coupling agent was changed to 0.3 parts. 8 was obtained. Table 1 shows the physical properties of the obtained magnetic substance.
[0201]
(Production Example 9 of Surface-treated Magnetic Material)
In Production Example 2 of the surface-treated magnetic material, the surface treatment was carried out in the same manner as in Production Example 2 of the surface-treated magnetic material except that the treatment agent was only γ-methacryloxypropyltrimethoxysilane and the addition amount was 1.5 parts. A treated magnetic body 9 was obtained. Table 1 shows the physical properties of the obtained magnetic substance.
[0202]
(Surface-treated magnetic material production example 10)
In Production Example 2 of the surface-treated magnetic material, the surface treatment was carried out in the same manner as in Production Example 2 of the surface-treated magnetic material except that the treatment agent was only γ-methacryloxypropyltrimethoxysilane and the addition amount was 5.0 parts. A treated magnetic body 10 was obtained. Table 1 shows the physical properties of the obtained magnetic substance.
[0203]
(Production Example 11 of Surface-treated Magnetic Material)
The oxidation reaction was advanced in the same manner as in Production Example 1 of the surface-treated magnetic material, and the magnetic iron oxide particles produced after the oxidation reaction were washed, filtered and dried. Thereafter, 100 parts of the obtained magnetic iron oxide was subjected to surface treatment in the gas phase using 2.0 parts of n-hexyltrimethoxysilane coupling agent and 1.00 part of phenyltrimethoxysilane coupling agent. . Thereafter, the agglomerated particles were pulverized to obtain a surface-treated magnetic body 11. Table 1 shows the physical properties of the obtained magnetic substance.
[0204]
(Surface Treatment Magnetic Production Example 12)
In Production Example 1 of magnetic iron oxide particles, the amount of caustic soda solution to be added and the reaction conditions were adjusted, and 1.2 parts of n-decyltrimethoxysilane coupling agent and 1.2 parts of γ-methacryloxypropyltrimethoxysilane were added. The surface-treated magnetic body 12 having a number average particle diameter of 0.28 μm was obtained in the same manner as in Production Example 2 of the surface-treated magnetic body except for the above. Table 1 shows the physical properties of the obtained magnetic substance.
[0205]
(Production Example 13 of Surface-treated Magnetic Material)
The amount of ferrous sulfate aqueous solution during the synthesis of the magnetic iron oxide particles was increased, the amount of air blown was decreased, and 1.4 parts of n-decyltrimethoxysilane coupling agent and γ-methacryloxypropyltrimethoxysilane were added. A surface-treated magnetic body 13 was obtained in the same manner as in Production Example 11 of the surface-treated magnetic body except that the amount was 4 parts. Table 1 shows the physical properties of the obtained magnetic substance.
[0206]
(Surface treatment magnetic material production example 14)
In Production Example 1 of magnetic iron oxide particles, the amount of caustic soda solution to be added and the reaction conditions were adjusted, and 1.0 part of n-decyltrimethoxysilane coupling agent and 1.0 part of γ-methacryloxypropyltrimethoxysilane were added. The surface-treated magnetic body 14 having a number average particle size of 0.37 μm was obtained in the same manner as in Production Example 2 of the surface-treated magnetic body except that. Table 1 shows the physical properties of the obtained magnetic substance.
[0208]
  (Example of surface-treated magnetic material production15)
  The oxidation reaction was advanced in the same manner as in Production Example 1 of the surface-treated magnetic body, and the magnetic oxide particles produced after the completion of the oxidation reaction were washed, filtered and dried, and the aggregated particles were sufficiently crushed to obtain a magnetic body. 100 parts of this magnetic material was dispersed in a toluene solution containing 5.0 parts of γ-methacryloxypropyltrimethoxysilane, heat-treated at 100 ° C. for 3 hours and dried. After that, the agglomerated particles are sufficiently crushed and surface magnetic material15Got. Table 1 shows the physical properties of the obtained magnetic substance.
[0209]
  (Example of surface-treated magnetic material production16)
  The oxidation reaction was advanced in the same manner as in Production Example 1 of the surface-treated magnetic material, and the magnetic iron oxide particles produced after the oxidation reaction were washed, filtered and dried. Thereafter, 100 parts of the obtained magnetic iron oxide was subjected to a surface treatment in a gas phase using 0.2 part of a γ-methacryloxypropyltrimethoxysilane coupling agent. After that, the agglomerated particles are then pulverized and surface-treated magnetic material16Got. Table 1 shows the physical properties of the obtained magnetic substance.
[0210]
[Table 1]

[0211]
Production example 1 of magnetic toner
0.1M Na in 720 parts of ion exchange water_ThreePO_FourAfter 450 parts of aqueous solution and 16 parts of 1N hydrochloric acid were added and heated to 60 ° C., 1.0 M-CaCl₂Add 67.7 parts of aqueous solution and add Ca._Three(PO_Four)₂An aqueous medium containing was obtained.
・ 80 parts of styrene
・ N-butyl acrylate 20 parts
・ Saturated polyester resin 5 parts
・ Unsaturated polyester resin 1 part
・ Negative charge control agent (monoazo dye-based Fe compound) 1 part
・ 80 parts of surface-treated magnetic material
[0212]
The above formulation was uniformly dispersed and mixed using a homogenizer.
[0213]
This monomer composition was heated to 60 ° C., and 7 parts of ester wax (maximum endothermic peak 72 ° C. in DSC) was added, mixed and dissolved therein, and the polymerization initiator 2,2′-azobis (2 , 4-dimethylvaleronitrile) was dissolved.
[0214]
The polymerizable monomer system is charged into the aqueous medium, and 60 ° C., N₂In an atmosphere, the mixture was stirred for 15 minutes at 10,000 rpm with a TK homomixer (Special Machine Industries Co., Ltd.) and granulated. Then, while stirring with a paddle stirring blade, the mixture was reacted at 60 ° C. for 4 hours, then heated to 80 ° C., and further reacted for 5 hours. After completion of the reaction, the suspension was cooled, hydrochloric acid was added to dissolve the dispersant at a pH of 2 or lower, filtered, washed with water, and dried to obtain black particles 1 having a weight average particle diameter of 7.5 μm.
[0215]
100 parts of the black particles 1 and silica having a primary particle diameter of 12 nm were treated with hexamethyldisilazane and then treated with silicone oil, and the BET value after treatment was 120 m.²Magnetic toner 1 was prepared by mixing 1.0 part of / g hydrophobic silica fine powder with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 2 shows the physical properties of the magnetic toner 1.
[0216]
Production example 2 of magnetic toner
0.1M Na in 720 parts of ion exchange water_ThreePO_FourAfter 450 parts of aqueous solution and 16 parts of 1N hydrochloric acid were added and heated to 60 ° C., 1.0 M-CaCl₂Add 67.7 parts of aqueous solution and add Ca._Three(PO_Four)₂An aqueous medium containing was obtained.
・ 80 parts of styrene
・ N-butyl acrylate 20 parts
・ Saturated polyester resin 5 parts
・ Unsaturated polyester resin 1 part
・ Negative charge control agent (monoazo dye-based Fe compound) 1 part
・ Surface treatment magnetic material 2 80 parts
[0217]
The above formulation was uniformly dispersed and mixed using a homogenizer.
[0218]
This monomer composition was heated to 60 ° C., and 7 parts of ester wax (maximum endothermic peak 72 ° C. in DSC) was added and dissolved therein. 4 parts of hexanoate were dissolved.
[0219]
The polymerizable monomer system is charged into the aqueous medium, and 60 ° C., N₂In an atmosphere, the mixture was stirred for 15 minutes at 10,000 rpm with a TK homomixer (Special Machine Industries Co., Ltd.) and granulated. Thereafter, the mixture was reacted at 80 ° C. for 8 hours while stirring with a paddle stirring blade. After completion of the reaction, the suspension was cooled, hydrochloric acid was added to dissolve the dispersant at a pH of 2 or lower, filtered, washed with water, and dried to obtain black particles 2 having a weight average particle diameter of 7.2 μm.
[0220]
100 parts of the black particles 2 and silica having a primary particle diameter of 12 nm were treated with hexamethyldisilazane and then treated with silicone oil, and the BET value after treatment was 120 m.²Magnetic toner 2 was prepared by mixing 1.0 part of / g hydrophobic silica fine powder with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 2 shows the physical properties of the magnetic toner 2.
[0221]
Production example 3 of magnetic toner
A magnetic toner 3 was obtained in the same manner as in the production example of the magnetic toner 2 except that the surface-treated magnetic body 1 was changed to the surface-treated magnetic body 3. Table 2 shows the physical properties of the magnetic toner 3.
[0222]
Production example 4 of magnetic toner
100 parts of the black particles 1 obtained in Production Example 1 of magnetic toner and silica having a primary particle diameter of 7 nm were treated with hexamethyldisilazane, and the BET value after the treatment was 280 m.²Magnetic toner 4 was prepared by mixing 0.7 parts of / g hydrophobic silica fine powder with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 2 shows the physical properties of the magnetic toner 4.
[0223]
Magnetic toner production example 5
100 parts of black particles 1 obtained in Production Example 1 of magnetic toner and silica having a primary particle diameter of 90 nm were treated with hexamethyldisilazane, and the BET value after treatment was 25 m.²Magnetic toner 5 was prepared by mixing 3.5 parts of / g hydrophobic silica fine powder with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 2 shows the physical properties of the magnetic toner 5.
[0224]
Production example 6 of magnetic toner
Magnetic toner 6 was obtained in the same manner as in magnetic toner production example 1 except that the amount of surface-treated magnetic material 1 was 40 parts. Table 2 shows the physical properties of the magnetic toner 6.
[0225]
Production example 7 of magnetic toner
Magnetic toner 7 was obtained in the same manner as in magnetic toner production example 1 except that the amount of surface-treated magnetic material 1 was 150 parts. Table 2 shows the physical properties of the magnetic toner 7.
[0226]
Production example 8 of magnetic toner
Magnetic toner 8 was obtained in the same manner as in magnetic toner production example 2 except that the amount of ester wax was 0.8 part. Table 2 shows the physical properties of the magnetic toner 8.
[0227]
Production example 9 of magnetic toner
A magnetic toner 9 was obtained in the same manner as in Production Example 2 of the magnetic toner except that the amount of the ester wax was 35 parts. Table 2 shows the physical properties of the magnetic toner 9.
[0228]
Production example 10 of magnetic toner
Magnetic toner 10 was obtained in the same manner as in magnetic toner production example 2 except that 7 parts of ester wax was changed to 3 parts of polyethylene wax (maximum value of endothermic peak in DSC 115 ° C.). Table 2 shows the physical properties of the magnetic toner 10.
[0229]
Magnetic toner production example 11
Magnetic toner 11 was obtained in the same manner as in magnetic toner production example 2, except that 7 parts of ester wax was changed to 7 parts of polyethylene wax (maximum value of endothermic peak in DSC 115 ° C.). Table 2 shows the physical properties of the magnetic toner 11.
[0230]
Magnetic toner production example 12
A magnetic toner 12 was obtained in the same manner as in the production example of the magnetic toner 2 except that the surface-treated magnetic body 2 was changed to the surface-treated magnetic body 4. Table 2 shows the physical properties of the magnetic toner 12.
[0231]
Magnetic toner production example 13
A magnetic toner 13 was obtained in the same manner as in the production example of the magnetic toner 2 except that the surface-treated magnetic body 2 was changed to the surface-treated magnetic body 5. Table 2 shows the physical properties of the magnetic toner 13.
[0232]
Magnetic toner production example 14
A magnetic toner 14 was obtained in the same manner as in the production example of the magnetic toner 2 except that the surface-treated magnetic body 2 was changed to the surface-treated magnetic body 6. Table 2 shows the physical properties of the magnetic toner 14.
[0233]
Magnetic toner production example 15
A magnetic toner 15 was obtained in the same manner as in the production example of the magnetic toner 2 except that the surface-treated magnetic body 2 was changed to the surface-treated magnetic body 7. Table 2 shows the physical properties of the magnetic toner 15.
[0234]
Production example 16 of magnetic toner
A magnetic toner 16 was obtained in the same manner as in the production example of the magnetic toner 2 except that the surface-treated magnetic body 2 was changed to the surface-treated magnetic body 8. Table 2 shows the physical properties of the magnetic toner 16.
[0235]
Production example 17 of magnetic toner
A magnetic toner 17 was obtained in the same manner as in the production example of the magnetic toner 2 except that the surface-treated magnetic body 2 was changed to the surface-treated magnetic body 9. Table 2 shows the physical properties of the magnetic toner 17.
[0236]
Production example 18 of magnetic toner
A magnetic toner 18 was obtained in the same manner as in the production example of the magnetic toner 2 except that the surface-treated magnetic body 2 was changed to the surface-treated magnetic body 10. Table 2 shows the physical properties of the magnetic toner 18.
[0237]
Magnetic toner production example 19
A magnetic toner 19 was obtained in the same manner as in the production example of the magnetic toner 2 except that the surface-treated magnetic body 2 was changed to the surface-treated magnetic body 11. Table 2 shows the physical properties of the magnetic toner 19.
[0238]
Magnetic toner production example 20
A magnetic toner 20 was obtained in the same manner as in the production example of the magnetic toner 2 except that the surface-treated magnetic body 2 was changed to the surface-treated magnetic body 12. Table 2 shows the physical properties of the magnetic toner 20.
[0239]
Magnetic toner production example 21
A magnetic toner 21 was obtained in the same manner as in the production example of the magnetic toner 2 except that the surface-treated magnetic body 2 was changed to the surface-treated magnetic body 13. Table 2 shows the physical properties of the magnetic toner 21.
[0240]
Magnetic toner production example 22
A magnetic toner 22 was obtained in the same manner as in the production example of the magnetic toner 2 except that the surface-treated magnetic body 2 was changed to the surface-treated magnetic body 14. Table 2 shows the physical properties of the magnetic toner 22.
[0241]
Comparative production example 1 of magnetic toner
A magnetic toner 23 was obtained in the same manner as in the production example of the magnetic toner 2 except that the surface-treated magnetic body 2 was changed to the surface-treated magnetic body 15. Table 2 shows the physical properties of the magnetic toner 23.
[0242]
Comparative production example 2 of magnetic toner
A magnetic toner 24 was obtained in the same manner as in the production example of the magnetic toner 2 except that the surface-treated magnetic body 2 was changed to the surface-treated magnetic body 16. Table 2 shows the physical properties of the magnetic toner 24.
[0243]
Comparative production example 3 of magnetic toner
The magnetic toner 25 was obtained in the same manner as in the production example of the magnetic toner 2 except that the surface-treated magnetic body 2 was changed to the surface-treated magnetic body 16 to obtain black particles, and the obtained black particles were subjected to air classification. It was. Table 2 shows the physical properties of the magnetic toner 25.
[0244]
In the magnetic toner production examples and the comparative production examples, the magnetic toner 7 has a magnetization intensity of 18.1 Am at a magnetic field of 79.6 kA / m.²/ Kg and magnetic toner 8 is 38.4 Am²/ Kg, 24 to 28 Am for all other magnetic toners²/ Kg.
[0245]
[Table 2]

[0246]
[Example 1]
As the image forming apparatus, LBP-1760 was remodeled, and the apparatus generally shown in FIG. 1 was used.
[0247]
The potential of the electrostatic image carrier was set to dark part potential Vd = −680V and light part potential VL = −150V. Further, the gap between the electrostatic charge image carrier and the developing sleeve is 220 μm, and the surface of the toner carrier is a resin layer having a layer thickness of about 7 μm and a JIS centerline average roughness (Ra) of 1.0 μm as described below. Using a developing sleeve formed on a blasted aluminum cylinder having a diameter of 16φ, a developing magnetic pole of 85 mT (850 gauss), a toner regulating member having a thickness of 1.0 mm and a free length of 0.5 mm urethane blade of 39.2 N / m ( 40 g / cm).
・ Phenolic resin 100 parts
・ 90 parts of graphite (particle size: about 7μm)
・ 10 parts of carbon black
[0248]
Next, a DC bias component Vdc = −450 V, an overlapping AC bias component Vpp = 1600 V, and f = 2400 Hz were used as the developing bias. The peripheral speed of the developing sleeve was 110% (103 mm / sec) in the forward direction with respect to the peripheral speed of the photosensitive member (94 mm / sec). The transfer bias was set to 1.5 kV DC.
[0249]
As a fixing method, there was used a fixing device of LBP-1760 which does not have an oil application function and which is fixed by heating and pressing with a heater through a film. At this time, a pressure roller having a fluororesin surface layer was used, and the diameter of the roller was 30 mm. The fixing temperature was set to 160 ° C., and the nip width was set to 7 mm.
[0250]
First, 100 g of magnetic toner 1 is filled in a cartridge, and the toner amount on paper is 0.8 mg / cm at high temperature and high humidity (30 ° C., 80% RH).²And a solid black image having an image density of 1.43 was obtained. Next, when a halftone image of 1 dot-2 space was produced, a clear image without redness was obtained.
[0251]
Then, after performing idle rotation for 2 hours as a toner deterioration promotion test, an image print test of 1000 sheets was performed with an image pattern consisting only of horizontal lines with a printing rate of 2%. As a transfer material, 75 g / m²Paper was used.
[0252]
As a result, the magnetic toner 1 exhibited high transferability immediately after idling and after 1,000 images were printed, and a good image without fogging on non-image areas was obtained. The evaluation results are shown in Table 3.
[0253]
The evaluation items described in the examples of the present invention and the comparative examples and the judgment criteria thereof will be described.
[0254]
<Image density>
The image density formed a solid image portion, and this solid image was measured with a Macbeth reflection densitometer (manufactured by Macbeth).
[0255]
<Reddish image>
As for the redness of the image, a halftone image of 1 dot-2 space was obtained, and the redness was visually judged based on the following criteria.
A: No redness is felt.
B: Although a slight reddish color is felt, there is no practical problem.
C: Strong reddish and poor image. Practically unfavorable level.
[0256]
<Transfer efficiency>
The transfer efficiency is determined by tapering the transfer residual toner on the photoconductor after the solid black image transfer with a Mylar tape and pasting it on the paper. The Macbeth density value is C, and the Mylar is applied on the paper with the toner after the fixing before the transfer. When the Macbeth concentration of the tape affixed was D, and the Macbeth concentration of Mylar tape affixed on unused paper was E, the following formula was used for approximation.
[0257]
[Formula 6]

[0258]
The transfer efficiency obtained from the above calculation results was judged according to the following criteria.
A: Transfer efficiency is 96% or more.
B: Transfer efficiency is 92% or more and less than 96%.
C: Transfer efficiency is 89% or more and less than 92%.
D: Transfer efficiency is less than 89%.
[0259]
<Image quality>
The image quality criterion is a comprehensive evaluation of image uniformity and fine line reproducibility. The uniformity of the image is determined using a solid black image and a halftone image.
A: A clear image excellent in fine line reproducibility and image uniformity.
B: A good image although the fine line reproducibility and image uniformity are slightly inferior.
C: Image quality with no practical problem.
D: An image unfavorable for practical use due to poor fine line reproducibility and image uniformity.
[0260]
<Fog>
The fog was measured using a REFECTMETER MODEL TC-6DS manufactured by Tokyo Denshoku. The filter used was a green filter, and fog was calculated from the following formula.
[0261]
Fog (reflectance) (%) =
Reflectivity on standard paper (%)-Reflectance of sample non-image area (%)
[0262]
The criteria for fogging are as follows.
A: Very good (less than 1.5%)
B: Good (1.5% or more to less than 2.5%)
C: Normal (2.5% or more to less than 4.0%)
D: Poor (4% or more)
[0263]
<Fixability>
The fixability is determined by observing the stain on the back side of the image sample from the initial stage until the end of the durability, and whether or not it occurs.
[0264]
  [Example 215, Reference Examples 1-4, Examples 16-18]
  As the toner, magnetic toners 2 to 22 were used, and an image printing test and durability evaluation were performed under the same conditions as in Example 1. As a result, an image having a high image density under normal temperature and humidity and no problem with redness was obtained. In addition, in the image drawing test under high temperature and high humidity, results without any major problems were obtained. The results are shown in Table 3.
[0265]
[Comparative Examples 1-3]
As the toner, magnetic toners 23 to 25 were used, and an image formation test and durability evaluation were performed by the same image forming method as in Example 1. As a result, the image density was low, and the image density, transfer efficiency decreased, fog, and image quality deteriorated along with the durability test. This is considered to reflect a non-uniform dispersion state of the magnetic substance and the release agent inside the toner particles. The results are shown in Table 3.
[0266]
[Table 3]

[0267]
【The invention's effect】
The toner of the present invention has an average circularity of at least 0.970 having at least a binder resin, a release agent and a magnetic material, a weight average particle diameter of 3 to 10 μm, and a small Stokes diameter in styrene. It contains a special magnetic material with good dispersibility and has a sharp particle size distribution, so it has high coloring power, good durability even under high temperature and high humidity, and high-definition images without redness and fog. Can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of an image forming apparatus used in an embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of a developing unit for one-component development.
[Explanation of symbols]
100 photoconductor (image carrier, charged body)
102 Developing sleeve (magnetic toner carrier)
103 Elastic blade (layer regulating member)
104 Magnet roller
114 Transfer roller (transfer member)
116 Cleaner
117 Charging roller (contact charging member)
121 Laser beam scanner (latent image forming means, exposure device)
124 Paper feed roller
125 Conveying member
126 Fixing device
140 Developer
141 Stirring member
P transfer material

Claims (1)

In a method for producing a magnetic toner having magnetic toner particles containing at least a binder resin, a release agent and a magnetic substance,
The magnetic toner particles are obtained by suspending a polymerizable monomer composition containing at least a polymerizable monomer containing styrene as a main component, a release agent and a magnetic substance in an aqueous medium, and performing polymerization. And
The magnetic body is magnetic iron oxide,
The magnetic toner has an average circularity of 0.970 or more, a weight average particle diameter of 3 to 10 μm,
The magnetic toner has a magnetization intensity of 10 to 50 Am ² / kg (emu / g) in a magnetic field of 79.6 kA / m (1000 oersted),
The volume average particle diameter of the magnetic material A, when a B Stokes diameter of the magnetic body in the styrene, wherein the magnetic material meets the following formula (1),
(1) 1.0 ≦ B / A ≦ 2.8
The magnetic substance in the magnetic toner is hydrophobized with at least one silane coupling agent having no double bond and a silane coupling agent having a double bond,
The silane coupling agent having no double bond is represented by the following formula:
_{C p H 2p + 1 -Si- (} OC q H 2q + 1) 3
[In formula, p shows the integer of 6-20, q shows the integer of 1-3. ]
An alkyltrialkoxysilane coupling agent represented by:
A method for producing a magnetic toner , wherein the silane coupling agent having a double bond is phenyltrimethoxysilane or γ-methacryloxypropyltrimethoxysilane .

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