JP3909801B2 - Method for producing toner for developing electrostatic image - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、静電荷像現像用トナーの製造方法に関し、さらに詳しくは、適切な粒度と粒子形状を有し、過小微粉の発生が抑制されたトナーを低減されたエネルギーで得ることのできる静電荷像現像用トナーの製造方法に関するものである。
【０００２】
【従来の技術】
潜像担持体に静電潜像を形成し、これを現像剤によって可視化して記録画像を得る電子複写機、プリンター又はファクシミリー等の画像形成装置においては、粉体状のトナーを用いる乾式の現像装置が広く使用されている。
近年、この静電荷像現像装置においては、デジタル式複写機、レーザープリンター等の発展により、高画質化への要求が高いものとなってきている。
特に、プリンターにあっては、現状では、３００ｄｐｉという高画質化が主流であるが、今後は、４８０ｄｐｉ、６００ｄｐｉへと高画質化は一層、進展することが予想されている。
このような状況下、用いるトナーの小粒径化はさらに厳しく要求されることは必至である。
しかしながら、小粒径のトナーは、トナー粒子の凝集、付着を生じやすく、現像の際、トナーがトナー補給部から現像部へ供給されにくくなり、現像部から感光体へトナーが適切に乗りにくくなって、画像濃度が低下し転写不良を起こしやすいという現象を生じる。
このような現象は、トナーの小粒径化が進むほど顕著となるものである。
したがって、静電荷像現像用トナーにあっては、一方で、トナーの小粒径化が望まれ、他方では、過小微粉を含まないトナーが望まれているのである。
【０００３】
一般にトナーは、トナー原料を混合し、押出機等を用いて溶融混練してトナー用組成物を調製し、次いで、この組成物を冷却した後、粉砕することによって製造される。
トナー用組成物の粉砕は、通常、粗粉砕、中位粉砕を経て、最後に微粉砕される。
トナーの製造においては、この粉砕はきわめて重要な因子であって、優れた画質を形成する上から、適切な粒度と粒子形状を有するよう粉砕することが必要である。
また、過粉砕されたトナーは画像に地汚れ現象を生じ、粉砕不十分なトナーは転写不良の原因となり画質の低下を招くこととなるので、粉砕の態様はより一層重要となる。
これまでに、トナーの製造方法として、まず、混合されたトナー原料を押出機から板状等に溶融押し出して、冷却固化したトナー用組成物を、ハンマー式粉砕機により粗粉砕し、次いで、衝撃式粉砕機によって中位粉砕し、最後にジェット式粉砕機によって微粉砕する方法（特開昭５８−４２０５７号公報、特公平８−２０７６２号公報）が知られている。
しかしながら、この従来の製造方法においては、ジェット式粉砕機を用いる微粉砕のため、過小微粉の発生が１５〜５０％ときわめて多く、平均粒径が小さいものとなる他、粒子の円形度も不十分であった。
したがって、過小微粉を除去するために別途の装置を必要とし、生産効率に劣るという問題があった。
また、粉砕、特に微粉砕に要するエネルギーが大きく、経済的に有利な製造方法とは言い難いものであった。
【０００４】
【発明が解決しようとする課題】
本発明は、このような従来技術の欠点を解消し、適切な粒度と粒子形状を有し、過小微粉の発生が抑制されたトナーを低減されたエネルギーで得ることのできる静電荷像現像用トナーの製造方法を提供することをその課題とするものである。
【０００５】
【課題を解決するための手段】
本発明者らは、上記課題を解決すべく鋭意検討を重ねた結果、本発明を完成するに到ったものである。
すなわち、本発明によれば、少なくとも樹脂及び着色剤を含有してなるトナー用組成物を予備粉砕し、次いで微粉砕して静電荷像現像用トナーを製造する方法であって、該トナー用組成物を、重量平均粒径が２０〜１００μｍで、円形度０．９０以下の粒子の含有量が５０％以下の粒子となるよう予備粉砕した後、得られた予備粉砕物を微粉砕して、重量平均粒径が５〜１３μｍで、円形度０．９０以下の粒子の含有量が３０％以下であり、粒径が５μｍ以下の過小微粉の含有量が個数含有率で１５％以下である微粉砕物を得ることを特徴とする静電荷像現像用トナーの製造方法が提供される。
【０００６】
【発明の実施の形態】
本発明においては、まず、少なくとも樹脂及び着色剤を含有してなるトナー用組成物を調製する。
ここにおいて用いる樹脂としては、ポリスチレン樹脂、スチレン−アクリル酸共重合体、スチレン−メタクリル酸共重合体、スチレン−アクリル酸エステル共重合体、スチレン−メタクリル酸エステル共重合体、ポリエステル樹脂、エポキシ樹脂、ポリアミド樹脂、ポリビニルアセタール樹脂等、結着樹脂として公知の樹脂を挙げることができる。
また、着色剤としては、カーボンブラック、ベンジジン系黄色顔料、フォロインイエロー、アセト酢酸アニリド系不溶性アゾ顔料、ネノアゾ染料、アゾメチレン系色素等、公知の着色剤が挙げられる。
この樹脂と着色剤との配合割合に特に制限はないが、通常は、重量基準で樹脂／着色剤が、１００／５〜１００／３０、好ましくは、１００／１０〜１００／２０である。
また、樹脂と着色剤は、その合計量として、トナー全成分に対し、通常は、重量基準で８５〜９９．５％、好ましくは、９５〜９８．５％配合される。
このトナー用組成物は、ロールミル、ニーダ等の混練機によって溶融、混合、分散を行って、調製される。
このときの混練温度は、用いる樹脂が溶融する温度であればよい。
このトナー用組成物には、上記樹脂及び着色剤の外に、電荷制御剤、離型剤、外添剤等が配合されていてもよい。
【０００７】
本発明においては、次いで、このようにして調製されたトナー用組成物を、冷却固化、及び必要に応じ慣用の方法で０．３〜２０ｍｍ程度の粒径に粗粉砕した後、予備粉砕する。
この予備粉砕に当たっては、機械式粉砕が好ましく、この粉砕に用いる粉砕機としては、たとえば、ホソカワミクロン社製ＡＣＭパルベライザー、日本ニューマチック社製ファインミル、奈良機械社製ハイブリタイザー等が挙げられる。
【０００８】
これら機械式粉砕機は、その回転軸に支持され外周面に、母線と平行な多数の凹凸部を周方向に連続して形成した回転子と、この回転子の外側に１．５ｍｍ以上の微小間隙を設けて嵌装され内周面に、母線と平行な多数の凹凸部を周方向に連続して形成された筒体とを備え、粉砕物を上記微小間隙からなる粉砕室で粉砕する粉砕機であり、回転子の周速度が１００ｍ／ｓ未満で運転される。
このような衝突型機械式粉砕機にあっては、分級機構を備えたものが望ましい。
この予備粉砕においては、その粉砕に要する粉砕全実負荷動力は、５０〜３００ｋｇ／ｈの原料フィードに対し０．２５〜２１０ｋｗ・ｈ、好ましくは、０．５〜１４０ｋｗ・ｈである。
ここに、粉砕全実負荷動力とは、粉砕時の全負荷動力からトナー組成物を供給しない場合の全負荷動力を差し引いたものを言う。
【０００９】
本発明は、上記トナー用組成物を上記のとおり予備粉砕することによって得られる予備粉砕物の重量平均粒径を２０〜１００μｍ、好ましくは、２０〜７０μｍとし、円形度０．９０以下の粒子の含有量が５０％以下、好ましくは、３０％以下とするものである。
また、この予備粉砕物の平均円形度は、０．８５〜０．９５である。
重量平均粒径が、２０μｍ未満のときは、処理能力低下による原単位負荷動力の減少や発熱によるトナー融着によって継続不能となり、１００μｍを超えると、平均円形度が低下し、次工程で表面粉砕による過粉砕が生じることがあるので好ましくない。
円形度が０．９０以下である粒子の量が、５０％を超えると、重量平均径が高く次工程による表面粉砕が増加し過粉砕となることがあるので好ましくない。
また、予備粉砕物の平均円形度が、０．８５未満のときは、さらに重量平均径が高く次工程による表面粉砕が増加し過粉砕となることがあるので好ましくない。
【００１０】
重量平均粒径の測定は、コールター測定方法によって行う。この方法は次のとおりである。
コールターカウンターを用いて、電解液は一級塩化ナトリウムを使用し、１％ＮａＣｌ水溶液を調整する。この電界水溶液１０〜１５ｍｌ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ルスフォン酸塩を０．５〜５ｍｌ加え、さらに測定試料を２〜２０ｍｇ加えて、超音波分散器で約１〜３分分散処理を行う。別のビーカーに電界水溶液１００〜２００ｍｌを入れ、その中に上記サンプル分散液を所定の濃度になるように加える。上記コールターカウンターは、１００μｍのアパーチャーを用いて個数基準として２〜４０μｍの粒子の粒度分布を測定し、２〜４０μｍの重量分布と個数分布を算出して、重量分布から重量平均径を求める。各チャンネルの代表値としては、中心値を用いる。
【００１１】
また、円形度とは、下記式（１）で表されるものを言う。
【数１】
Ｂ：粒子の投影像の周囲の長さ
円形度は、粉砕物粒子の周囲の形状の単純さないし複雑さを表す形状指数であり、粉砕物粒子の周囲の形状が滑らかで円に近いほど、１．０００に近づく。そして、その円形度が１に近づくにつれて、その粒子の球形度が高くなることを示す。
また、平均円形度は、粒子７０００〜１３０００個の円形度の平均値である。
各粒子の円形度は、東亜医用電子（株）製のフロー式粒子像の分析装置「ＦＰＩＡ−１０００」を用いて測定する。
【００１２】
本発明は、続いて、上記のようにして得られた予備粉砕物を、衝撃・剪断力による機械式粉砕機を用いて微粉砕することによる静電荷像現像用トナーの製造方法である。
この機械式粉砕機は、回転軸に支持された外周面に、母線と平行な多数の凹凸面を周方向に連続して形成した回転子と、この回転子の外側に１．５ｍｍ未満の微小間隙をあけて嵌装された内周面に、母線と平行な多数の凹凸部を周方向に連続して形成した筒体とを備え、予備粉砕物を上記微小間隙からなる粉砕室で微粉砕する粉砕機であり、回転子の周速度が１００ｍ／ｓ以上で運転される。
この衝撃・剪断力による微粉砕に用いる粉砕機としては、ターボ工業（株）製ターボミル、日清エンジニアリング（株）製スーパーローター、川崎重工（株）製クリプトロン、ホソカワミクロン（株）製イノマイザー等を挙げることができる。
この微粉砕においては、予備粉砕物１ｋｇを粉砕するために要する動力、粉砕実負荷動力を、０．０５〜０．９０ｋｗ・ｈ／ｋｇ、好ましくは、０．１〜０．８ｋｗ・ｈ／ｋｇと低減されたものとすることができる。
予備粉砕時のトナー形状が丸みを帯びていること又は微粉砕時に必要以上に動力をかけなくてもよい適切な粒子となっているためである。
また、予備粉砕及び微粉砕における粉砕実負荷動力の比（予備粉砕動力：微粉砕動力）は、１：１０〜５：１０、好ましくは、２：１０〜４：１０である。
予備粉砕動力／微粉砕動力を、上記のようにすることによって、過粉砕の防止と消費エネルギーの低減化が図れるという利点が得られる。尚、粉砕実負荷動力は粉砕時の負荷動力から、予備粉砕物を供給しない場合の負荷動力を差引いたものを言う。
【００１３】
このように微粉砕して得られる微粉砕物は、重量平粒径が５〜１３μｍ、好ましくは、６〜１０μｍで、円形度０．９０以下の粒子の含有量が３０％以下、好ましくは、２０％以下であり、粒径が５μｍ以下の過小微粉の含有量が個数含有率で１５％以下、好ましくは、１０％以下のものである。
また、この微粉砕物の平均円形度は、０．９０〜０．９８である。
重量平粒径が５μｍ未満のときは、平均円形度が０．９８１〜０．９９５となり、１３μｍを超えると平均円形度が０．７〜０．８９９となることがあるので望ましくない。
円形度０．９０以下の粒子の含有量が３０％を超えると、微粉砕時の消費エネルギーが増加するので好ましくない。
また、粒径が５μｍ以下の過小微粉の含有量が１５％を超えるとトナー粒子の凝集、付着が顕著となるので好ましくない。
平均円形度が、０．９０未満のときは、予備粉砕の効果が得られないことがあるので好ましくない。
【００１４】
本発明は、少なくとも樹脂及び着色剤を含有してなるトナー用組成物を予備粉砕し、次いで微粉砕して静電荷像現像用トナーを製造する方法であるが、該予備粉砕物は、ホッパーから管路を通じて管路内を流通する気流によって微粉砕機に搬送させるのが好ましい。
この場合には、予備粉砕物の供給量（ｋｇ／ｈ）と微粉砕機に供給する気流の供給量（ｍ3／ｍｉｎ）との比〔予備粉砕物供給量／気流供給量〕を、１〜２００、好ましくは、３〜１５０となるよう制御することが望ましい。
予備粉砕物の供給量と気流の供給量との比を、上記のように制御することによって、粉砕時の発熱防止及び平均円形度０．９０以下の粒子含有量を低下できる等の利点を得ることができるからである。
【００１５】
本発明によって得られるトナーは、帯電量が安定し、良質な画像を与えるトナーとして適切な粒度と粒子形状を有し、画像の地汚れ現象の原因となる過小微粉の含有量が低減されたものである。
【００１６】
【実施例】
以下に、実施例を挙げて、本発明をさらに詳細に説明するが、本発明はこれら実施例になんら限定されるものではない。
なお、以下の「％」は、重量基準である。
【００１７】
実施例１
ポリエステル樹脂７５％、スチレン−アクリル共重合体１０％及びカーボンブラック１５％からなる配合物を、ロールミルを用い、１２０℃にて連続的に溶融混練機で混練した後、冷却固化して、トナー用組成物を調製した。
次いで、このトナー用組成物を、ホソカワミクロン社製ＡＣＭパルメライザーを用い、ローター周速を７０ｍ／ｓ、出口温度を３０℃として中位粉砕し、重量平均粒径が５０μｍ、円形度が０．９０以下である粒子の含有量が３０％、平均円形度が０．９３の粒子である予備粉砕物を得た。
続いて、この予備粉砕物を、ターボ工業社製（以下、同様である）ターボミルを用い、ローターと周方向の隙間を１．０ｍｍに設定し、ローター周速を１１０ｍ／ｓ、出口温度を３５℃として微粉砕し、重量平均粒径が９．５μｍ、円形度が０．９０以下である粒子の含有量が１５％、平均円形度が０．９６の粒子であって、粒径が５μｍ以下の過小微粉の含有量が、個数含有率で１０％の微粉砕物（トナー）を９０％の収率で得た。
このとき、予備粉砕に費やした粉砕実負荷動力は０．２１ｋｗ・ｈ／ｋｇで、微粉砕に費やした粉砕実負荷動力は０．７ｋｗ・ｈ／ｋｇであり、動力の比、予備粉粉砕動力：微粉砕動力は３：１０であった。
なお、粒度を整えるための分級機として、日鉄工業社製エルボージェットを用い、粒径測定は、コールターカウンター社のマルチサイザーを用いた。以下、同様である。
【００１８】
比較例
実施例１と同様にしてトナー用組成物を調製し、実施例１と同様の粉砕機を用いて、ローター周速をを７０ｍ／ｓ、出口温度を３０℃として中位粉砕し、重量平均粒径５０μｍ、円形度０．９０以下である粒子の含有量が５５％、平均円形度が０．８０の粒子である予備粉砕物を得た。
次いで、この予備粉砕物を、日本ニューマチック工業社製１式ミルと、粒度を整えるための日本ニューマチック工業社製ＤＳ分級機とを閉回路として微粉砕して、重量平均粒子径９．５μｍ、円形度が０．９０以下である粒子の含有量が１０％、平均円形度が０．９５の粒子であって、粒径が５μｍ以下の過小微粉の含有量が、個数含有率で１０％の微粉砕物（トナー）を８０％の収率で得た。
過小微粉の含有量は、トナー総量に対し、高いものであった。
このとき、予備粉砕に費やした粉砕実負荷動力は０．０４ｋｗ・ｈ／ｋｇで、微粉砕に費やした粉砕実負荷動力は０．８０ｋｗ・ｈ／ｋｇであり、動力の比、予備粉粉砕動力：微粉砕動力は０．５：１０であった。
【００１９】
実施例２
実施例１と同様にしてトナー用組成物を調製し、実施例１と同様の粉砕機を用いて、ローター周速をを７０ｍ／ｓ、出口温度を３０℃として中位粉砕し、重量平均粒径が５０μｍ、円形度が０．９０以下である粒子の含有量が３０％、平均円形度０．９３の粒子である予備粉砕物を得た。
次いで、この予備粉砕物を、ターボミルを用い、粉砕ローターと周方向の隙間を１．０ｍｍに設定し、ローター周速を１１０ｍ／ｓ、微粉砕に供する予備粉砕物の供給量（ｋｇ／ｈ）と予備粉砕物を気流によって搬送して微粉砕に供する際にターボミルに供給する気流の供給量（ｍ3／ｍｉｎ）との比〔予備粉砕物供給量／気流供給量（ｇ／ｍ3）〕を１２０に設定して微粉砕し、重量平均粒子径が９．５μｍ、円形度が０．９０以下である粒子の含有量が１０％、平均円形度が０．９６３の粒子であって、粒径が５μｍ以下の過小微粉の含有量が、個数含有率で１０％の微粉砕物（トナー）を９３％の収率で得た。
このとき、予備粉砕に費やした粉砕実負荷動力は０．２３ｋｗ・ｈ／ｋｇで、微粉砕に費やした粉砕実負荷動力は０．７ｋｗ・ｈ／ｋｇであり、動力の比、予備粉粉砕動力：微粉砕動力は３．３：１０であった。
【００２０】
実施例３
実施例１と同様にしてトナー用組成物を調製し、実施例１と同様の粉砕機を用いて、ローター周速をを７５ｍ／ｓ、出口温度を３５℃として中位粉砕し、重量平均粒径が４０μｍ、円形度が０．９０以下である粒子の含有量が３５％、平均円形度０．９４の粒子である予備粉砕物を得た。
次いで、この予備粉砕物を、ターボミルを用い、ローターと周方向の隙間を１．２ｍｍに設定し、ローター周速を１２０ｍ／ｓ、入口温度と出口温度の差を３０℃になるように設定して微粉砕し、重量平均粒径が９．５μｍ、円形度が０．９０以下である粒子の含有量が２０％、平均円形度が０．９８の粒子であって、粒径が５μｍ以下の過小微粉の含有量が、個数含有率で１０％の微粉砕物（トナー）を９３％の収率で得た。
このとき、予備粉砕に費やした粉砕実負荷動力は０．２５ｋｗ・ｈ／ｋｇで、微粉砕に費やした粉砕実負荷動力は０．７ｋｗ・ｈ／ｋｇであり、動力の比、予備粉粉砕動力：微粉砕動力は３．６：１０であった。
【００２１】
実施例４
実施例１と同様にしてトナー用組成物を調製し、実施例１と同様の粉砕機を用いて、ローター周速をを７５ｍ／ｓ、出口温度を２５℃として中位粉砕し、重量平均粒径が３８μｍ、円形度が０．９０以下である粒子の含有量が３０％、平均円形度０．９４の粒子である予備粉砕物を得た。
次いで、この予備粉砕物を、ターボミルを用い、ローターと周方向の隙間を１．１ｍｍに設定し、ローター周速を１１５ｍ／ｓ、入口温度と出口温度の差を３５℃になるように設定して微粉砕し、重量平均粒径が９．５μｍ、円形度が０．９０以下である粒子の含有量が２０％、平均円形度が０．９８の粒子であって、粒径が５μｍ以下の過小微粉の含有量が、個数含有率で１０％の微粉砕物（トナー）を９４％の収率で得た。
このとき、予備粉砕に費やした粉砕実負荷動力は０．１５ｋｗ・ｈ／ｋｇで、微粉砕に費やした粉砕実負荷動力は０．４０ｋｗ・ｈ／ｋｇであり、動力の比、予備粉粉砕動力：微粉砕動力は３．８：１０であった。
【００２２】
実施例５
実施例１と同様にしてトナー用組成物を調製し、実施例１と同様の粉砕機を用いて、ローター周速をを７５ｍ／ｓ、出口温度を２５℃として中位粉砕し、重量平均粒径が３８μｍ、円形度が０．９０以下である粒子の含有量が３０％、平均円形度０．９４の粒子である予備粉砕物を得た。
次いで、この予備粉砕物を、ターボミルを用い、ローターと周方向の隙間を１．１ｍｍに設定し、ローター周速を１１５ｍ／ｓ、入口温度と出口温度の差を３５℃になるように設定して微粉砕し、重量平均粒径が９．５μｍ、円形度が０．９０以下である粒子の含有量が２５％、平均円形度が０．９８の粒子であって、粒径が５μｍ以下の過小微粉の含有量が、個数含有率で１０％の微粉砕物（トナー）を９４％の収率で得た。
このとき、予備粉砕に費やした粉砕実負荷動力は０．２１ｋｗ・ｈ／ｋｇで、微粉砕に費やした粉砕実負荷動力は０．７ｋｗ・ｈ／ｋｇであり、動力の比、予備粉粉砕動力：微粉砕動力は３：１０であった。
【００２３】
【発明の効果】
本発明によれば、帯電量が安定し、良質な画像を与えるトナーとして適切な粒度と粒子形状を有し、画像の地汚れ現象の原因となる過小微粉の発生が抑制されたトナーを低減されたエネルギーで得ることのできる静電荷像現像用トナーの製造方法が提供され、潜像担持体に静電潜像を形成し、これを現像剤によって可視化して記録画像を得る電子複写機、プリンター又はファクシミリー等の画像形成装置の設計、作製分野に寄与するところは多大である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a toner for developing an electrostatic charge image, and more specifically, an electrostatic charge capable of obtaining a toner having an appropriate particle size and particle shape and suppressing generation of excessively fine powder with reduced energy. The present invention relates to a method for producing a toner for image development.
[0002]
[Prior art]
In an image forming apparatus such as an electronic copying machine, a printer, or a facsimile machine that forms an electrostatic latent image on a latent image carrier and visualizes the latent image with a developer to obtain a recorded image, a dry type toner using powdery toner is used. Developing devices are widely used.
In recent years, the development of digital copying machines, laser printers, and the like has increased the demand for higher image quality in this electrostatic image developing apparatus.
Particularly for printers, at present, the mainstream is to achieve high image quality of 300 dpi, but it is expected that image quality will be further improved to 480 dpi and 600 dpi in the future.
Under such circumstances, it is inevitable that the use of a toner having a smaller particle size is required more severely.
However, toner with a small particle size tends to cause aggregation and adhesion of toner particles, and during development, it is difficult for the toner to be supplied from the toner replenishing unit to the developing unit, and it is difficult for the toner to properly get on the photoreceptor from the developing unit. As a result, a phenomenon occurs in which the image density is lowered and transfer defects are likely to occur.
Such a phenomenon becomes more prominent as the toner particle size decreases.
Therefore, in the toner for developing an electrostatic image, on the one hand, it is desired to reduce the particle size of the toner, and on the other hand, a toner containing no excessively fine powder is desired.
[0003]
In general, a toner is produced by mixing toner raw materials, melt-kneading using an extruder or the like to prepare a toner composition, then cooling the composition and then pulverizing it.
The toner composition is usually pulverized through coarse pulverization and intermediate pulverization, and finally finely pulverized.
In the production of toner, this pulverization is a very important factor, and in order to form an excellent image quality, it is necessary to pulverize the toner to have an appropriate particle size and particle shape.
Further, since the excessively pulverized toner causes a background smear phenomenon on the image, and the insufficiently pulverized toner causes a transfer failure and causes a reduction in image quality, the pulverization mode becomes even more important.
Up to now, as a toner production method, first, the mixed toner raw material is melt-extruded from an extruder into a plate shape, etc., and the cooled and solidified toner composition is roughly pulverized by a hammer-type pulverizer, and then impacted There is known a method (Japanese Patent Laid-Open No. 58-42057, Japanese Patent Publication No. 8-20762) in which medium pulverization is performed by a type pulverizer and finally fine pulverization is performed by a jet pulverizer.
However, in this conventional manufacturing method, since fine pulverization is performed using a jet type pulverizer, the generation of excessively fine powder is as high as 15 to 50%, the average particle diameter is small, and the circularity of the particles is not good. It was enough.
Accordingly, there is a problem that a separate device is required to remove the excessively fine powder, resulting in poor production efficiency.
Further, the energy required for pulverization, particularly fine pulverization is large, and it is difficult to say that it is an economically advantageous production method.
[0004]
[Problems to be solved by the invention]
The present invention eliminates the disadvantages of the prior art, and provides an electrostatic charge image developing toner having an appropriate particle size and particle shape and capable of obtaining toner with reduced generation of excessively fine powder with reduced energy. It is an object of the present invention to provide a manufacturing method.
[0005]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.
That is, according to the present invention, a toner composition comprising at least a resin and a colorant is preliminarily pulverized and then finely pulverized to produce an electrostatic charge image developing toner comprising the toner composition. After preliminarily pulverizing the product so that the content of particles having a weight average particle diameter of 20 to 100 μm and circularity of 0.90 or less is 50% or less, the obtained pre-pulverized product is finely pulverized, The weight average particle diameter is 5 to 13 μm, the content of particles having a circularity of 0.90 or less is 30% or less, and the content of ultrafine powder having a particle diameter of 5 μm or less is 15% or less in number content. There is provided a method for producing a toner for developing an electrostatic charge image, characterized by obtaining a pulverized product.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, first, a toner composition containing at least a resin and a colorant is prepared.
As the resin used here, polystyrene resin, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, polyester resin, epoxy resin, Known resins such as polyamide resin and polyvinyl acetal resin can be listed as binder resins.
Examples of the colorant include known colorants such as carbon black, benzidine yellow pigment, followin yellow, acetoacetanilide anilide insoluble azo pigment, nenoazo dye, azomethylene dye.
Although there is no restriction | limiting in particular in the mixture ratio of this resin and a coloring agent, Usually, resin / coloring agent is 100/5-100/30, Preferably, it is 100/10-100/20 on a weight basis.
The total amount of the resin and the colorant is usually 85 to 99.5%, preferably 95 to 98.5%, based on the weight, based on the total amount of toner components.
The toner composition is prepared by melting, mixing, and dispersing using a kneader such as a roll mill or a kneader.
The kneading temperature at this time may be a temperature at which the resin used melts.
In addition to the resin and the colorant, the toner composition may contain a charge control agent, a release agent, an external additive, and the like.
[0007]
In the present invention, the toner composition thus prepared is then cooled and solidified, and if necessary, roughly pulverized to a particle size of about 0.3 to 20 mm by a conventional method, and then preliminarily pulverized.
In this preliminary pulverization, mechanical pulverization is preferable. Examples of the pulverizer used for the pulverization include an ACM pulverizer manufactured by Hosokawa Micron Corporation, a fine mill manufactured by Nippon Pneumatic Co., Ltd., and a hybridizer manufactured by Nara Machinery Co., Ltd.
[0008]
These mechanical pulverizers have a rotor that is supported by the rotating shaft and has a large number of concave and convex portions parallel to the busbars formed on the outer peripheral surface thereof continuously in the circumferential direction, and a minute size of 1.5 mm or more outside the rotor. A pulverization comprising a cylindrical body in which a large number of concavo-convex portions parallel to the generatrix are continuously formed in the circumferential direction and is fitted with a gap, and pulverized material is pulverized in a pulverization chamber composed of the above-mentioned minute gaps. The rotor is operated at a circumferential speed of the rotor of less than 100 m / s.
In such a collision type mechanical pulverizer, it is desirable to have a classification mechanism.
In this preliminary pulverization, the pulverization actual load power required for the pulverization is 0.25 to 210 kw · h, preferably 0.5 to 140 kw · h with respect to the feed of 50 to 300 kg / h.
Here, the pulverization total actual load power means a value obtained by subtracting the full load power when the toner composition is not supplied from the full load power during pulverization.
[0009]
In the present invention, the pre-pulverized product obtained by pre-pulverizing the toner composition as described above has a weight average particle diameter of 20 to 100 μm, preferably 20 to 70 μm, and particles having a circularity of 0.90 or less. The content is 50% or less, preferably 30% or less.
Moreover, the average circularity of this preliminary ground material is 0.85-0.95.
When the weight average particle diameter is less than 20 μm, it becomes impossible to continue due to reduction of the basic unit load power due to a decrease in processing capacity or toner fusion due to heat generation, and when it exceeds 100 μm, the average circularity decreases and surface grinding is performed in the next step. This is not preferable because over-grinding may occur.
If the amount of particles having a circularity of 0.90 or less exceeds 50%, the weight average diameter is high, and surface pulverization in the next step may increase, resulting in excessive pulverization.
In addition, when the average circularity of the pre-ground product is less than 0.85, the weight average diameter is further high and surface pulverization in the next step may be increased, resulting in excessive pulverization.
[0010]
The weight average particle diameter is measured by a Coulter measurement method. This method is as follows.
Using a Coulter counter, 1% NaCl aqueous solution is prepared using primary sodium chloride as the electrolyte. In 10 to 15 ml of this electric field aqueous solution, 0.5 to 5 ml of a surfactant, preferably alkylbenzene sulfonate is added as a dispersant, and 2 to 20 mg of a measurement sample is further added, and about 1 to 3 minutes with an ultrasonic disperser. Perform distributed processing. In another beaker, 100 to 200 ml of the aqueous electric field solution is put, and the sample dispersion liquid is added therein to a predetermined concentration. The Coulter counter measures the particle size distribution of 2 to 40 μm particles on a number basis using a 100 μm aperture, calculates the weight distribution and number distribution of 2 to 40 μm, and obtains the weight average diameter from the weight distribution. A central value is used as a representative value of each channel.
[0011]
Moreover, circularity means what is represented by following formula (1).
[Expression 1]
The average circularity is an average value of circularity of 7000 to 13000 particles.
The circularity of each particle is measured using a flow type particle image analyzer “FPIA-1000” manufactured by Toa Medical Electronics Co., Ltd.
[0012]
The present invention is a method for producing a toner for developing an electrostatic charge image by subsequently finely pulverizing the preliminary pulverized material obtained as described above using a mechanical pulverizer using impact and shearing force.
This mechanical pulverizer has a rotor in which a large number of concave and convex surfaces parallel to the generatrix are continuously formed in the circumferential direction on the outer peripheral surface supported by the rotating shaft, and a micrometer of less than 1.5 mm outside the rotor. The inner peripheral surface fitted with a gap is provided with a cylindrical body in which a number of concave and convex portions parallel to the generatrix are continuously formed in the circumferential direction. The pulverizer is operated at a circumferential speed of the rotor of 100 m / s or more.
As the pulverizer used for fine pulverization by the impact / shearing force, a turbo mill manufactured by Turbo Industry Co., Ltd., a super rotor manufactured by Nisshin Engineering Co., Ltd., a kryptron manufactured by Kawasaki Heavy Industries, Ltd., an inomizer manufactured by Hosokawa Micron Co., Ltd., etc. Can be mentioned.
In this fine pulverization, the power required to pulverize 1 kg of the preliminary pulverized product and the pulverized actual load power are 0.05 to 0.90 kw · h / kg, preferably 0.1 to 0.8 kw · h / kg. And can be reduced.
This is because the toner shape at the time of preliminary pulverization is rounded or appropriate particles that do not require excessive power during pulverization.
In addition, the ratio of pulverization actual load power in preliminary pulverization and fine pulverization (preliminary pulverization power: fine pulverization power) is 1:10 to 5:10, preferably 2:10 to 4:10.
By setting the preliminary pulverization power / fine pulverization power as described above, there can be obtained an advantage that over-pulverization can be prevented and energy consumption can be reduced. The pulverized actual load power is obtained by subtracting the load power when the pre-ground product is not supplied from the load power at the time of pulverization.
[0013]
The finely pulverized product obtained by fine pulverization in this way has a weight average particle size of 5 to 13 μm, preferably 6 to 10 μm, and a content of particles having a circularity of 0.90 or less, preferably 30% or less, The content of the ultrafine powder having a particle size of 20 μm or less and a particle size of 5 μm or less is 15% or less, preferably 10% or less in terms of the number content.
The average circularity of the finely pulverized product is 0.90 to 0.98.
When the weight average particle size is less than 5 μm, the average circularity is 0.981 to 0.995, and when it exceeds 13 μm, the average circularity may be 0.7 to 0.899, which is not desirable.
When the content of particles having a circularity of 0.90 or less exceeds 30%, energy consumption during pulverization increases, which is not preferable.
Further, if the content of the excessively fine powder having a particle diameter of 5 μm or less exceeds 15%, toner particles are agglomerated and adhered, which is not preferable.
When the average circularity is less than 0.90, the effect of preliminary pulverization may not be obtained, which is not preferable.
[0014]
The present invention is a method for producing a toner for developing an electrostatic image by pre-pulverizing a toner composition containing at least a resin and a colorant, and then finely pulverizing the toner composition. It is preferable that the fine pulverizer is transported by an air flow flowing through the pipe line.
In this case, the ratio [preliminary pulverized material supply amount / airflow supply amount] of the supply amount (kg / h) of the preliminary pulverized product to the supply amount of airflow (m 3 / min) supplied to the fine pulverizer is 1 It is desirable to control to 200 to 200, preferably 3 to 150.
By controlling the ratio of the supply amount of the preliminary pulverized product and the supply amount of the airflow as described above, there are advantages such as prevention of heat generation during pulverization and reduction of the content of particles having an average circularity of 0.90 or less. Because it can.
[0015]
The toner obtained by the present invention has a stable charge amount, an appropriate particle size and particle shape as a toner that gives a high-quality image, and a content of an excessively small powder that causes a background stain phenomenon of the image is reduced. It is.
[0016]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
The following “%” is based on weight.
[0017]
Example 1
A compound consisting of 75% polyester resin, 10% styrene-acrylic copolymer and 15% carbon black was kneaded continuously at 120 ° C. with a melt kneader using a roll mill, and then cooled and solidified for use in toners. A composition was prepared.
Next, this toner composition was moderately ground using an ACM Palmerizer manufactured by Hosokawa Micron Co., Ltd. at a rotor peripheral speed of 70 m / s, an outlet temperature of 30 ° C., a weight average particle diameter of 50 μm, and a circularity of 0.90. A pre-ground product having the following particle content of 30% and an average circularity of 0.93 was obtained.
Subsequently, the preliminary pulverized product was set to a rotor and circumferential clearance of 1.0 mm using a turbo mill (hereinafter the same) turbo mill manufactured by Turbo Industry Co., the rotor peripheral speed was 110 m / s, and the outlet temperature was 35. Finely pulverized at 0 ° C., particles having a weight average particle size of 9.5 μm, a circularity of 0.90 or less, a content of 15%, an average circularity of 0.96, and a particle size of 5 μm or less A finely pulverized product (toner) having a content of 10% in terms of the number content was obtained in a yield of 90%.
At this time, the pulverization actual load power spent for pre-grinding was 0.21 kw · h / kg, and the pulverization actual load power spent for fine pulverization was 0.7 kw · h / kg. : The pulverization power was 3:10.
In addition, as a classifier for adjusting the particle size, an Elbow Jet manufactured by Nippon Steel Industry Co., Ltd. was used, and a particle size measurement was performed using a multisizer manufactured by Coulter Counter. The same applies hereinafter.
[0018]
Comparative Example A toner composition was prepared in the same manner as in Example 1. Using the same pulverizer as in Example 1, medium pulverization was performed with a rotor peripheral speed of 70 m / s and an outlet temperature of 30 ° C. A pre-ground product having a particle size of 55% and a circularity of 0.90 or less and a mean circularity of 0.80 was obtained.
Next, the pre-pulverized product was finely pulverized as a closed circuit using a 1 type mill manufactured by Nippon Pneumatic Industry Co., Ltd. and a DS classifier manufactured by Nippon Pneumatic Industry Co., Ltd. for adjusting the particle size, and the weight average particle size was 9.5 μm. The content of particles having a circularity of 0.90 or less is 10%, the average circularity is 0.95, and the content of fine particles having a particle size of 5 μm or less is 10% in terms of number content. Was obtained in a yield of 80%.
The content of the excessively fine powder was higher than the total amount of toner.
At this time, the pulverization actual load power spent for preliminary pulverization was 0.04 kw · h / kg, and the pulverization actual load power spent for fine pulverization was 0.80 kw · h / kg. : The pulverization power was 0.5: 10.
[0019]
Example 2
A toner composition was prepared in the same manner as in Example 1, and using a pulverizer similar to that in Example 1, medium pulverization was performed with a rotor peripheral speed of 70 m / s and an outlet temperature of 30 ° C. A pre-ground product having a particle size of 50%, a circularity of 0.90 or less, a content of 30%, and an average circularity of 0.93 was obtained.
Next, the preliminary pulverized product was supplied to the pulverized rotor using a turbo mill, the clearance between the pulverization rotor and the circumferential direction was set to 1.0 mm, the rotor peripheral speed was 110 m / s, and the supply amount of the preliminary pulverized product to be pulverized (kg / h) Ratio of the airflow supplied to the turbo mill when the preliminarily pulverized material is conveyed and finely pulverized (m 3 / min) [preliminary pulverized material supply amount / airflow supply amount (g / m 3 )] Is set to 120 and is finely pulverized, particles having a weight average particle diameter of 9.5 μm, a circularity of 0.90 or less and a content of 10% and an average circularity of 0.963, A finely pulverized product (toner) having a content of excessively fine powder having a diameter of 5 μm or less and a number content of 10% was obtained in a yield of 93%.
At this time, the pulverization actual load power spent for preliminary pulverization was 0.23 kw · h / kg, and the pulverization actual load power spent for fine pulverization was 0.7 kw · h / kg. : The pulverization power was 3.3: 10.
[0020]
Example 3
A toner composition was prepared in the same manner as in Example 1, and using a pulverizer similar to that in Example 1, medium pulverization was performed with a rotor peripheral speed of 75 m / s and an outlet temperature of 35 ° C. A pre-ground product having particles with a diameter of 40 μm, a circularity of 0.90 or less and a content of 35% and an average circularity of 0.94 was obtained.
Next, the preliminary pulverized product was set using a turbo mill, the clearance between the rotor and the circumferential direction was set to 1.2 mm, the rotor peripheral speed was set to 120 m / s, and the difference between the inlet temperature and the outlet temperature was set to 30 ° C. Finely pulverized, particles having a weight average particle size of 9.5 μm, a circularity of 0.90 or less, a content of 20%, an average circularity of 0.98, and a particle size of 5 μm or less. A finely pulverized product (toner) having an excessively fine powder content of 10% in number content was obtained in a yield of 93%.
At this time, the actual load power consumed for pre-grinding was 0.25 kW · h / kg, and the actual load power consumed for fine pulverization was 0.7 kw · h / kg. : The pulverization power was 3.6: 10.
[0021]
Example 4
A toner composition was prepared in the same manner as in Example 1, and using a pulverizer similar to that in Example 1, medium pulverization was performed with a rotor peripheral speed of 75 m / s and an outlet temperature of 25 ° C. A pre-ground product having a particle size of 38 μm, a circularity of 0.90 or less, a particle content of 30%, and an average circularity of 0.94 was obtained.
Next, the preliminary pulverized product was set using a turbo mill, the clearance between the rotor and the circumferential direction was set to 1.1 mm, the rotor peripheral speed was set to 115 m / s, and the difference between the inlet temperature and the outlet temperature was set to 35 ° C. Finely pulverized, particles having a weight average particle size of 9.5 μm, a circularity of 0.90 or less, a content of 20%, an average circularity of 0.98, and a particle size of 5 μm or less. A finely pulverized product (toner) having an excessively fine powder content of 10% in number content was obtained in a yield of 94%.
At this time, the pulverization actual load power spent for pre-grinding was 0.15 kw · h / kg, and the pulverization actual load power spent for fine pulverization was 0.40 kw · h / kg. : The pulverization power was 3.8: 10.
[0022]
Example 5
A toner composition was prepared in the same manner as in Example 1, and using a pulverizer similar to that in Example 1, medium pulverization was performed with a rotor peripheral speed of 75 m / s and an outlet temperature of 25 ° C. A pre-ground product having a particle size of 38 μm, a circularity of 0.90 or less, a particle content of 30%, and an average circularity of 0.94 was obtained.
Next, the preliminary pulverized product was set using a turbo mill, the clearance between the rotor and the circumferential direction was set to 1.1 mm, the rotor peripheral speed was set to 115 m / s, and the difference between the inlet temperature and the outlet temperature was set to 35 ° C. Finely pulverized, particles having a weight average particle size of 9.5 μm, a circularity of 0.90 or less and a content of 25% and an average circularity of 0.98, and a particle size of 5 μm or less. A finely pulverized product (toner) having an excessively fine powder content of 10% in number content was obtained in a yield of 94%.
At this time, the pulverization actual load power spent for pre-grinding was 0.21 kw · h / kg, and the pulverization actual load power spent for fine pulverization was 0.7 kw · h / kg. : The pulverization power was 3:10.
[0023]
【The invention's effect】
According to the present invention, it is possible to reduce a toner having a stable charge amount, an appropriate particle size and particle shape as a toner that gives a high-quality image, and suppressing generation of an excessively small powder that causes a background stain phenomenon of the image. The present invention provides a method for producing a toner for developing an electrostatic charge image that can be obtained with high energy, and forms an electrostatic latent image on a latent image carrier and visualizes it with a developer to obtain a recorded image. There is a great deal of contribution to the field of designing and producing image forming apparatuses such as facsimiles.
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000389264A JP3909801B2 (en) | 1999-12-21 | 2000-12-21 | Method for producing toner for developing electrostatic image |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP36262699 | 1999-12-21 | ||
| JP11-362626 | 1999-12-21 | ||
| JP2000389264A JP3909801B2 (en) | 1999-12-21 | 2000-12-21 | Method for producing toner for developing electrostatic image |
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| Publication Number | Publication Date |
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| JP2001242662A JP2001242662A (en) | 2001-09-07 |
| JP3909801B2 true JP3909801B2 (en) | 2007-04-25 |
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| JP2000389264A Expired - Lifetime JP3909801B2 (en) | 1999-12-21 | 2000-12-21 | Method for producing toner for developing electrostatic image |
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| JP (1) | JP3909801B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP5293024B2 (en) * | 2008-09-11 | 2013-09-18 | 富士ゼロックス株式会社 | Photofixing toner, photofixing developer, toner cartridge, and image forming apparatus |
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| JP2001242662A (en) | 2001-09-07 |
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