JP3972185B2 - Negatively chargeable toner - Google Patents

Description

【００４５】
表１に示すとおり、バインダー樹脂１００重量部に対して、着色剤は０.５重量部〜１５重量部、好ましくは１重量部〜１０重量部であり、また、離型剤は１重量部〜１０重量部、好ましくは２.５重量部〜８重量部であり、更に、荷電制御剤は０.１重量部〜７重量部、好ましくは０.５重量部〜５重量部である。
【００４６】
この例の粉砕法トナー８にあっては、転写効率の向上を目的として、球形化処理により円形度がアップされている。粉砕法トナー８の円形度をアップさせるためには、
(A) 粉砕工程で、比較的丸い球状で粉砕可能な装置、例えば機械式粉砕機として知られるターボミル（川崎重工（株）製）を使用すれば円形度は０.９３まで可能である。
または、
(B) 粉砕したトナーを市販の熱風球形化装置サーフュージングシステムＳＦＳ−３型（日本ニューマチック工業（株）製）を使用すれば円形度は１.００まで可能である。
【００４７】
この例の粉砕法トナー８の望ましい円形度（球状化係数）は０.９１以上であり、これにより良好な転写効率が得られる。そして、円形度は０.９７まではクリーニングブレードにより、それ以上ではブラシクリーニングを併用することでクリーニングすることができる。
【００４８】
また、このようにして得られる粉砕法トナー８としては、個数基準の５０％径である平均粒径（Ｄ₅₀）が９μｍ以下、好ましくは４.５μｍ〜８μｍに設定される。これにより、粉砕法トナー８の粒子径が比較的小粒子径となり、この小粒子径トナーに外添剤として疎水性の負帯電性シリカ１５ａ,１５ｂと疎水性のアルミナーシリカ複合酸化物微粒子１３および導電性微粒子１４とを併用することで、疎水性の負帯電性シリカの量を、従来のシリカ微粒子を単独用いた場合の疎水性の負帯電性シリカの量よりも少なくすることができるので、定着性が向上する。
なお、本発明におけるトナー粒子等における平均粒径と円形度は、シスメックス株式会社製のＦＰＩＡ２１００で測定する値である。
【００４９】
更に、この粉砕法トナー８にあっては、外添剤１２の総量（重量）がトナー母粒子８ａの重量に対して０.５重量％（ｗｔ％）以上４.０重量％以下に設定されるが、好ましくは、１.０重量％から３.５重量％の範囲に設定するのがよい。これにより、粉砕法トナー８をフルカラートナーとして使用したときに逆転写トナーの発生を抑える効果を発現することができる。なお、外添剤１２を総量で４.０重量％以上添加すると、トナー表面より遊離したり、定着性を悪化させる要因となる。
【００５０】
次に、重合法によるトナー母粒子８ａを用いた負帯電性トナー（以下、重合法トナーという）８の作製について説明する。
重合法トナー８としては、懸濁重合法、乳化重合法、分散重合法等がある。懸濁重合法においては、重合性単量体（モノマー）、着色顔料、離型剤とを、必要により更に、染料、重合開始剤、架橋剤、荷電制御剤、その他の添加剤を添加した混合物を溶解又は分散させた単量体組成物を、懸濁安定剤（水溶性高分子、難水溶性無機物質）を含む水相中に攪拌しながら添加して造粒し、重合させて所望の粒子サイズを有する着色重合トナー粒子を形成することができる。
【００５１】
また、乳化重合法においては、単量体と離型剤を必要により更に重合開始剤、乳化剤（界面活性剤）などを水中に分散させて重合を行い、次いで凝集過程で着色剤、荷電制御剤と凝集剤（電解質）等を添加することによって所望の粒子サイズを有する着色トナー粒子を形成することができる。
重合法トナー作製に用いられる材料において、着色剤、離型剤、荷電制御剤、流動性改良剤に関しては、上記の粉砕トナーと同様の材料が使用できる。
【００５２】
重合性単量体（モノマー）としては、公知のビニル系モノマーが使用可能であり、例えば、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、α−メチルスチレン、ｐ−メトキシスチレン、ｐ−エチルスチレン、ビニルトルエン、２，４−ジメチルスチレン、ｐ−ｎ−ブチルスチレン、ｐ−フェニルスチレン、ｐ−クロルスチレン、ジビニルベンゼン、アクリル酸メチル、アクリル酸エチル、アクリル酸プロピル、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−オクチル、アクリル酸ドデシル、アクリル酸ヒドロキシエチル、アクリル酸２−エチルヘキシル、アクリル酸フェニル、アクリル酸ステアリル、アクリル酸２−クロルエチル、メタクリル酸メチル、メタクリル酸エチル、メタクリル酸プロピル、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、メタクリル酸ヒドロキシエチル、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、アクリル酸、メタクリル酸、マレイン酸、フマル酸、ケイ皮酸、エチレングリコール、プロピレングリコール、無水マレイン酸、無水フタル酸、エチレン、プロピレン、ブチレン、イソブチレン、塩化ビニル、塩化ビニリデン、臭化ビニル、フッ化ビニル、酢酸ビニル、プロピレン酸ビニル、アクリロニトリル、メタクリルニトリル、ビニルメチルエーテル、ビニルエチルエーテル、ビニルケトン、ビニルヘキシルケトン、ビニルナフタレン等が挙げられる。なお、フッ素含有モノマーとしては例えば２，２，２−トリフルオロエチルアクリレート、２，２，３，３−テトラフルオロプロピルアクリレート、フッ化ビニリデン、三フッ化エチレン、四フッ化エチレン、トリフルオロプロピレンなどはフッ素原子が負荷電制御に有効であるので使用が可能である。
【００５３】
乳化剤（界面活性剤）としては公知のものが使用可能である。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、ラウリン酸ナトリウム、ステアリン酸カリウム、オレイン酸カルシウム、ドデシルアンモニウムクロライド、ドデシルアンモニウムブロマイド、ドデシルトリメチルアンモニウムブロマイド、ドデシルピリジニウムクロライド、ヘキサデシルトリメチルアンモニウムブロマイド、ドデシルポリオキシエチレンエーテル、ヘキサデシルポリオキシエチレンエーテル、ラウリルポリオキシエチレンエーテル、ソルビタンモノオレアートポリオキシエチレンエーテル等がある。
【００５４】
重合開始剤としては、公知のものが使用可能である。例えば、過硫酸カリウム、過硫酸ナトリウム、過硫酸アンモニウム、過酸化水素、４，４’−アゾビスシアノ吉草酸、ｔ−ブチルハイドロパーオキサイド、過酸化ベンゾイル、２，２’−アゾビス−イソブチロニトリル等がある。
【００５５】
凝集剤（電解質）としては、公知のものが使用可能である。例えば、塩化ナトリウム、塩化カリウム、塩化リチウム、塩化マグネシウム、塩化カルシウム、硫酸ナトリウム、硫酸カリウム、硫酸リチウム、硫酸マグネシウム、硫酸カルシウム、硫酸亜鉛、硫酸アルミニウム、硫酸鉄等が挙げられる。
【００５６】
乳化重合法トナー８における成分比（重量）を表２に示す。
【００５７】
【表２】

【００５８】
表２に示すとおり、重合性モノマー１００重量部に対して、重合開始剤は０.０３重量部〜２重量部、好ましくは０.１重量部〜１重量部であり、また、界面活性剤０.０１重量部〜０.１重量部であり、更に、離型剤は１重量部〜４０重量部、好ましくは２重量部〜３５重量部であり、更に、荷電制御剤は０.１重量部〜７重量部、好ましくは０.５重量部〜５重量部であり、着色剤は１重量部〜２０重量部、好ましくは３重量部〜１０重量部であり、更に、凝集剤（電解質）は０.０５重量部〜５重量部、好ましくは０.１重量部〜２重量部である。
【００５９】
この例の重合法トナー８にあっても、転写効率の向上を目的として、球形化処理により円形度がアップされている。重合法トナー８の円形度の調節法としては、
(A) 乳化重合法は２次粒子の凝集過程で温度と時間を制御することで、円形度を自由に変えることができ、その範囲は０.９４〜１.００である。
また、
(B) 懸濁重合法では、真球のトナーが可能であるため、円形度は０.９８〜１.００の範囲となる。また、円形度を調節するためにトナーのＴｇ温度以上で加熱変形させることで、円形度を０.９４〜０.９８まで自由に調節することが可能となる。
【００６０】
重合法トナー８は上記の方法以外の分散重合法でも作ることができ、例えば特開平６３−３０４００２号公報に開示されている方法でも作製できる。この場合には、形状が真球に近い形となるため、形状を制御するには、例えばトナーのＴｇ温度以上で加圧し、所望のトナー形状にすることができる。
【００６１】
前述の粉砕法トナー８の場合と同様に、この例の重合法トナー８の望ましい円形度（球状化係数）は０.９５以上であり、円形度が０.９７まではクリーニングブレードにより、それ以上ではブラシクリーニングを併用することでクリーニングすることができる。
【００６２】
このようにして得られる重合法トナー８においても、個数基準の５０％径である平均粒径（Ｄ₅₀）が９μｍ以下、好ましくは４.５μｍ〜８μｍに設定される。これにより、重合法トナー８の粒子径が比較的小粒子径となり、この小粒子径トナーに外添剤１２として疎水性の負帯電性シリカ１５ａ,１５ｂと疎水性の導電性微粒子１４とアルミナーシリカ複合酸化物微粒子１３とを併用することで、疎水性の負帯電性シリカ１５ａ,１５ｂの量を、従来のシリカ微粒子を単独用いた場合の疎水性の負帯電性シリカの量よりも少なくすることができるので、定着性が向上する。
なお、この重合法トナー８の場合にも、トナー粒子等における平均粒径と円形度は、シスメックス株式会社製のＦＰＩＡ２１００で測定する値である。
【００６３】
更に、この重合法トナー８にあっても、前述の粉砕法トナーと同様に、外添剤１２の総量（重量）がトナー母粒子８ａの重量に対して０.５重量％以上４.０重量％以下に設定されるが、好ましくは、１.０重量％から３.５重量％の範囲に設定するのがよい。これにより、重合法トナー８をフルカラートナーとして使用したときに逆転写トナーの発生を抑える効果を発現することができる。なお、外添剤１２を総量で４.０重量％以上添加すると、トナー表面より飛散したり、定着性を悪化させる要因となる。
【００６４】
外添剤１２であるアルミナーシリカ複合酸化物微粒子１３は、乾式トナーにおける帯電特性の安定化、流動性改良を目的として用いられるものである。このアルミナーシリカ複合酸化物微粒子１３は、例えば特許第２５３３０６７号公報に開示されているケイ素ーアルミニウム複合酸化物微粉末の製法等により作成することができる。以下に、この特許公報に開示の製法における作製工程について示す。
(1) ケイ素ハロゲン化物およびアルミニウムハロゲン化物を蒸発させ、それぞれの蒸気をキャリアガスとともに複合ユニット中で空気、酸素および水素と均一複合する。
(2) 次いで、得られた複合蒸気をバーナーに供給し、燃焼室内で焔内反応させ、得られたガスおよび固体を熱交換ユニット中で冷却する。
(3) ガスを固体から分離し、生成物に付着しているハロゲン化物残分を湿った空気を用いた熱処理により除去し、アルミナーシリカ複合酸化物微粒子１３が得られる。
【００６５】
図２は前述の特許第２５３３０６７号公報に開示されているアルミナーシリカ複合酸化物微粒子を製造するためのバーナー装置である。図中、１０１は燃焼室、１０２は二重ジャケット管、１０３は環状ダイヤフラム、１０４は内側管、１０５は外側管、１０６は水冷焔管である。
【００６６】
燃焼室１０１には二重ジャケット管１０２が突出させられ、二重ジャケット管１０２の内側管１０４からは水素１.４Ｎｍ³／ｈ、空気５.５Ｎｍ³／ｈおよび予め蒸発させたガス状ＳｉＣｌ₄１.３０ｋｇ／ｈの割合で混合した２００℃の熱混合蒸気が導入され、次いで、この熱混合蒸気に予め３００℃で蒸発させたガス状ＡｌＣｌ₃２.３４ｋｇ／ｈの割合で付加供給されて焔管中に導入されるとともに付加的に空気１２Ｎｍ³／ｈが供給されて燃焼させられる。この際、燃焼室１０１には空気が導入され、また、環状ダイヤフラム１０３から付加的に空気が導入される。焔中では、生成する水と塩化物との急激な反応が生じ、アルミナーシリカ複合酸化物微粒子が形成される。焔管通過後に、生じた粉末はフィルターまたはサイクロンを使用して分離され、また、粉末に付着した塩酸分が除去される。得られるアルミナーシリカ複合酸化物微粒子の組成はＡｌ₂Ｏ₃６５重量％、ＳｉＯ₂３５重量％であり、一次平均粒子径は１４ｎｍ、ＢＥＴ比表面積７４ｍ²／ｇ、体積抵抗率１０¹²Ω・ｃｍである。得られたアルミナーシリカ複合酸化物微粒子はジメチルシラン（ＤＭＳ）により疎水化処理される。
【００６７】
このアルミナーシリカ複合酸化物微粒子１３中のアルミナ（Ａｌ₂Ｏ₃）とシリカ（ＳｉＯ₂）との割合は、ケイ素ハロゲン化物およびアルミニウムハロゲン化物の供給量、水素供給量、ケイ素ハロゲン化物およびアルミニウムハロゲン化物の供給量、水素供給量、空気供給量等の反応条件により適宜調整される。
【００６８】
アルミナーシリカ複合酸化物微粒子１３におけるＡｌ₂Ｏ₃とＳｉＯ₂との重量比は、Ａｌ₂Ｏ₃の含有量が５５重量％〜８５重量％、ＳｉＯ₂の含有量が４５重量％〜１５重量％の範囲にできる。また、アルミナーシリカ複合酸化物微粒子１３は焔内中で粒子化されることにより非晶質構造で、十分な微粒子状性を有し、ＢＥＴ法による比表面積が２０ｍ²／ｇ〜２００ｍ²／ｇのものとなる。更に、アルミナーシリカ複合酸化物微粒子３の一次粒子径は７ｎｍ〜８０ｎｍ、好ましくは１０ｎｍ〜４０ｎｍであり、個数基準で２０ｎｍ以上が３０％以上である。更に、アルミナーシリカ複合酸化物微粒子１３は重量比でトナー母粒子８ａの量に対して、０.１重量％〜３重量％、好ましくは０.２重量％〜２重量％の割合で添加するとよい。アルミナーシリカ複合酸化物微粒子１３はブロードな粒径分布を有するので、少量の添加でも連続印字における外添剤１２粒子のトナー母粒子８ａ中への埋没を生じ難いものとすることができる。また、アルミナーシリカ複合酸化物微粒子１３の大粒子径部分により転写効率を向上させることができ、また、その大粒子径部分は大きすぎることがないので、像担持体表面の異常な偏摩耗を防止できる。
【００６９】
また、この例の負帯電性トナー８のアルミナーシリカ複合酸化物微粒子１３は、５.０ｅＶ〜５.４ｅＶの範囲の第１の仕事関数と５.４ｅＶ〜５.７ｅＶの範囲の第２の仕事関数の２種類の仕事関数を示すとともに、トナー母粒子８ａの仕事関数が５.３ｅＶ〜５.６５ｅＶであって、アルミナーシリカ複合酸化物微粒子１３の第１の仕事関数より大きく、また第２の仕事関数より小さく設定されている。
【００７０】
このアルミナーシリカ複合酸化物微粒子１３の仕事関数の一例について、前述の表面分析装置を用いて測定して得られたデータにより説明する。表面分析装置による測定で得られたアルミナーシリカ複合酸化物微粒子１３に関するデータを図３および図４に示す。
【００７１】
前述の表面分析装置においては、単色光の励起エネルギーについて低い方から高い方にスキャンし、光電子の放出が始まるエネルギー（仕事関数）を測定するものであり、仕事関数のデータは、横軸にとった励起エネルギー（Photon Energy）と縦軸にとった規格化光電子収率（Emmission Yield）との関係から得られる。
【００７２】
すなわち、アルミナーシリカ複合酸化物微粒子１３は、その仕事関数が、励起エネルギーと規格化光電子収率との関係において、図３に示すように屈曲点（Ａ）における励起エネルギー５.１８ｅＶと図４に示すように屈曲点（Ｂ）における励起エネルギー５.６２ｅＶであり、２種類の仕事関数を有することがわかる。そして、アルミナーシリカ複合酸化物微粒子１３はアルミナとシリカとの単なる混合酸化物粒子に比して仕事関数の差が大きく、トナー母粒子８ａに外添されると正と負の２つの摩擦帯電サイトを与えやすいものであることが判明した。その詳細な理由は不明であるが、アルミナーシリカ複合酸化物微粒子１３がＳｉＯ₂粒子とＡｌ₂Ｏ₃粒子との単なる混合物ではないことに起因するものと考えられる。
【００７３】
このようなアルミナーシリカ複合酸化物微粒子１３における正の摩擦帯電サイトにトナー母粒子８ａが接触すると、単なる混合物粒子に比してトナー粒子を確実に負に帯電して正帯電トナーを減少させることができる。また、負の摩擦帯電サイトにトナー母粒子８ａが接触すると、トナー粒子の過剰な負帯電性を抑制できるので、安定した負帯電性トナーとすることができる。
【００７４】
アルミナーシリカ複合酸化物微粒子１３は、ケイ素ハロゲン化物およびアルミニウムハロゲン化物のそれぞれの蒸発量を目的に応じて変化させて、前述のようにキャリアガスと一緒に混合ユニット中で空気、酸素および水素と均一に混合し、焔内加水分解することにより得られるが、その製造条件を制御することにより第１と第２の仕事関数を制御でき、前述のような５.０ｅＶ〜５.４ｅＶの範囲の第１の仕事関数と５.４ｅＶ〜５.７ｅＶの範囲の第２の仕事関数の種類の仕事関数を示すものにすることができる。
【００７５】
また、この例の負帯電性トナー１３は、前述のように外添剤１２としてアルミナーシリカ複合酸化物微粒子１３とともにこのアルミナーシリカ複合酸化物微粒子１３の仕事関数より大きくかつトナー母粒子８ａの仕事関数と同一かあるいは略同一の仕事関数を有する金属酸化物微粒子１６が用いられる。この金属酸化物微粒子１６としては、ルチルアナターゼ型酸化チタン（仕事関数５.６４ｅＶ）、ルチル型酸化チタン（仕事関数５.６１ｅＶ）、アナターゼ型酸化チタン（仕事関数５.６４ｅＶ）、チタン酸ストロンチウム（ＴｉＯ₃Ｓｒ；仕事関数５.６２ｅＶ）等を用いることができる。
【００７６】
更に、このアルミナーシリカ複合酸化物微粒子１３の仕事関数より小さくかつトナー母粒子８ａの仕事関数より小さい仕事関数を有する導電性微粒子１４が用いられる。この導電性微粒子１４としては、導電性二酸化ケイ素、導電性酸化チタン、導電性酸化アルミニウム、導電性酸化亜鉛、導電性酸化錫等を用いることができる。）
【００７７】
その場合、トナーの流動性を向上してチリをなくすとともに現像装置のトナー規制部材による均一な薄層を形成するため、特に、疎水性のルチルアナターゼ型酸化チタンや導電性酸化チタンおよび導電性酸化アルミニウムが好ましい。
【００７８】
このルチルアナターゼ型酸化チタンはルチル型酸化チタンとアナターゼ型酸化チタンとが所定の混晶比で用いられており、例えば前述の特開２０００−１２８５３４号公報に開示されている製造方法により製造することができる。この疎水性ルチルアナターゼ型酸化チタン（図１に符号１４で示す）は紡錘形状を呈しており、その長軸径が０.０２μｍ〜０.１０μｍであるとともに、長軸と短軸との軸径比が２〜８に設定されている。このルチルアナターゼ型酸化チタンの場合は、負帯電性シリカ１５ａ,１５ｂの平均一次粒子径の間に、ルチルアナターゼ型酸化チタンの短軸径がくるように設定される。
【００７９】
このように、アルミナーシリカ複合酸化物微粒子１３より小さな仕事関数を有する導電性微粒子１４をこのアルミナーシリカ複合酸化物微粒子１３とともに用いることにより、トナー母粒子８ａに帯電した電荷を逃して帯電調整し、過帯電を防止することができる。すなわち、アルミナーシリカ複合酸化物微粒子１３を入れすぎると、アルミナーシリカ複合酸化物微粒子のシリカ成分が負帯電サイトとして機能することからトナーが負に過帯電して画像濃度が低下するようになるが、導電性微粒子１４をアルミナーシリカ複合酸化物微粒子１３とともに添加することにより、トナー母粒子８ａの過帯電を防止できる。
【００８０】
更に、外添剤１２として用いられる２種類の疎水性の負帯電性シリカ１５ａ,１５ｂのうち、一方の負帯電性シリカ１５ａの平均一次粒子径は２０ｎｍ以下、好ましくは７ｎｍ〜１６ｎｍであり、また、他方の負帯電性シリカ１５ｂの平均一次粒子径は３０ｎｍ以上、好ましくは４０ｎｍ〜５０ｎｍに設定されている。
【００８１】
更に、本発明の負帯電性トナー８は、外添剤１２として、前述のアルミナーシリカ複合酸化物微粒子１３および前述の導電性微粒子１４の他に、必要に応じて他の外添剤を添加することもできる。例えば、他の外添剤として、フッ化マグネシウム、炭化ケイ素、炭化ホウ素、炭化チタン、炭化ジルコニウム、窒化ホウ素、窒化チタン、窒化ジルコニウム、マグネタイト、二硫化モリブデン、ステアリン酸アルミニウム、ステアリン酸マグネシウム、ステアリン酸亜鉛、ステアリン酸カルシウム、チタン酸バリウム、ケイ素金属塩の各微粒子を使用することができる。その他の樹脂微粒子の例としては、アクリル樹脂、スチレン樹脂、フッ素樹脂等がある。
【００８２】
外添剤１２の粒子は、シランカップリング剤、チタンカップリング剤、高級脂肪酸、シリコーンオイル等で疎水化処理して使用することが好ましい。疎水化処理剤としては、例えば、ジメチルジクロルシラン、オクチルトリメトキシシラン、ヘキサメチルジシラザン、シリコーンオイル、オクチルートリクロシラン、デシルートリクロルシラン、ノニルートリクロシラン、（４−ｉｓｏ−プロピルフェニル）−トリクロルシラン、ジヘキシルジクロシラン、（４−ｔ−ブチルフェニル）−トリクロシラン、ジペンチルージクロルシラン、ジヘキシル−ジクロルシラン、ジオクチル−ジクロルシラン、ジノニル−ジクロルシラン、ジデシル−ジクロルシラン、ジ−２−エチルヘキシル−ジクロルシラン、ジ−３,３−ジメチルペンチル−ジクロルシラン、トリヘキシル−クロルシラン、トリオクチル−クロルシラン、トリデシル−クロルシラン、ジオクチル−メチル−クロルシラン、オクチル−ジメチル−クロルシラン、（４−iso−プロピルフェニル）−ジエチル−クロルシラン等が例示される。
【００８３】
本発明の負帯電性トナー８にあっては、前述のようにトナー母粒子８ａに対するアルミナーシリカ複合酸化物微粒子１３の添加量は、０.１重量％〜３重量％、好ましくは０.２重量％〜２重量％である。また、トナー母粒子８ａに対する導電性微粒子１４の添加量は０.０５重量％〜１.５重量％、好ましくは０.１重量％〜１.０重量％である。また、トナー母粒子８ａに対する全外添剤１２粒子の添加量は、０.５重量％〜５重量％、好ましくは１重量％〜４重量％の割合とするとよい。
【００８４】
更に、本発明の負帯電性トナー８は、アルミナーシリカ複合酸化物微粒子１３を外添したトナー粒子において、トナー母粒子８ａをその仕事関数が５.３ｅＶ〜５.７ｅＶ、好ましくは５.４ｅＶ〜５.６５ｅＶのものとし、かつ、トナー母粒子８ａの仕事関数がアルミナーシリカ複合酸化物微粒子１３の第１の仕事関数より大きく、また、アルミナーシリカ複合酸化物微粒子１３の第２の仕事関数より小さいものと設定することを特徴としている。これにより、カブリをより低減でき、転写効率をより向上させることができることが判明した。トナー母粒子８ａの仕事関数がこのアルミナーシリカ複合酸化物微粒子１３の２種類の仕事関数の間にないと、本発明のような２種類の仕事関数の間にある場合と比較して、クリーニングトナーが増大する。
【００８５】
トナー母粒子８ａと外添剤１２とは、前述のヘンシェルミキサー、Ｖ型ブレンダー、反転ミキサー、ハイスピードミキサ、サイクロミックス、アキシャルミキサー等の公知の複合機に投入されて、トナー母粒子８ａに対して外添剤１２粒子が付着処理され、本発明の負帯電性トナー８が得られる。
【００８６】
このようにして得られる負帯電性トナー８の仕事関数は５.３５ｅＶ〜５.８ｅＶであり、好ましくは５.４ｅＶ〜５.７５ｅＶである。なお、像担持体表面の仕事関数より負帯電性トナー８の仕事関数を大きくすることにより、カブリをより低減でき、転写効率をより向上させることができる。また、像担持体面の仕事関数より負帯電性トナー８の仕事関数を小さくすると、トナー規制部材による現像ローラへのトナー薄層規制に際して、帯電量が下がり「帯電不足」の現象を生じることがあるが、本発明のように各仕事関数が設定されることで、この「過帯電」の現象を抑制することができる。
【００８７】
また、本発明の負帯電性トナー８は、粉砕法トナーにあっては、個数基準の平均粒径が５μｍ〜１０μｍ、好ましくは６μｍ〜９μｍであり、また、重合法トナーにあっては、個数５０％粒子径（Ｄ₅₀）が、８μｍ以下、好ましくは４.５μｍ〜８μｍであり、３μｍ以下が１０％以下であり、好ましくは５％以下の粒径分布を有するものである。
【００８８】
一般に、粉砕法トナーと重合法トナーとを問わず、トナー粒子径を小さくすると、シリカ粒子の添加量を増す必要があり、そのためトナーの帯電量が初期では大きくなり過ぎるという問題がある。また、印字が進むにつれ、埋没または飛散によりシリカ粒子の有効表面量が減少してトナー帯電量が低下し、画像濃度変動やカブリ量が増大してトナー消費量が増加する傾向にあり、トナーとしては使用し難いという問題がある。これに対して、アルミナーシリカ複合酸化物微粒子１３を外添剤１２として用いると、その粒度分布がブロードであり、外添剤１２粒子の埋没等の問題を抑制できるものであり、また、第１と第２の仕事関数の差を大きくできるので、印字期間を通じ安定した負帯電性トナーとすることができる。
【００８９】
更に、本発明の負帯電性トナー８としては、粉砕法、重合法のいずれの場合においても、円形度（球状化係数）を０.９４以上とするとよく、望ましくは、０.９５以上である。円形度（球状化係数）０.９７まではクリーニングブレードにより、それ以上ではブラシクリーニングを併用するとよい。円形度（球状化係数）を０.９４以上とすることにより、転写効率を向上させることができる。
【００９０】
このように構成されたこの例の負帯電性トナー８においては、重合法トナーおよび粉砕法トナーのいずれでも、小粒子径の疎水性の負帯電性シリカおよび導電性微粒子１４がトナー母粒子８ａに付着する。この疎水性の負帯電性シリカ１３の仕事関数より大きい仕事関数の疎水性アルミナーシリカ複合酸化物微粒子１３および疎水性の金属酸化物微粒子１６がそれぞれ仕事関数差による接触電位差でトナー母粒子８ａに付着した負帯電性シリカ１３に固着してトナー母粒子８ａから遊離することが少なくなる。したがって、トナー母粒子８ａの表面が疎水性アルミナーシリカ複合酸化物微粒子１３、疎水性の金属酸化物微粒子１６、疎水性の負帯電性シリカ１５ａ,１５ｂおよび導電性微粒子１４によりまんべんなく覆われるようになる。
【００９１】
したがって、導電性微粒子１４の有する比較的低い電気抵抗（例、導電性酸化チタン４１.８Ω・ｃｍ）の電荷調整機能をより効果的に活かすことができるとともに、アルミナーシリカ複合酸化物微粒子１３の有するトナーの凝集機能をより効果的に活かすことができるようになる。
すなわち、疎水性の負帯電性シリカ１５ａ,１５ｂの有するトナーの負帯電機能およびトナーの流動性向上機能という固有の特性と、導電性微粒子１４の有する負の過帯電防止機能およびトナーの流動性向上機能という固有の特性と、アルミナーシリカ複合酸化物微粒子１３の有するトナーの凝集性向上機能という固有の特性とが相乗された機能をトナー母粒子８ａに付与することができる。
【００９２】
これにより、負帯電性トナー８の流動性低下を防止できるとともに負の過帯電を防止できることから、より良好な負帯電特性を得ることができるようになり、その結果、逆転写トナーの発生およびカブリを効果的に抑制することができる。また、トナーの流動性を向上させて線画像の境目に発生する前述のチリを防止でき、画像のシャープ性を向上できるとともに、トナーの凝集性を向上させて線画像の中心部に発生する前述の中抜けを防止することができる。
したがって、負帯電性トナー８はその負帯電がより一層長期にわたり安定し、中抜けを生じなくシャープ性を有する、連続印字における安定した画像品質を与えることができるようになる。
【００９３】
図５は、この例の負帯電性トナー８を用いた非接触一成分現像方式の一例を模式的に示す図であり、図６は、この例の負帯電性トナー８を用いた接触一成分現像方式の一例を模式的に示す図である。図５および図６中、１は像担持体である有機感光体、２はコロナ帯電器、３は露光、４はクリーニングブレード、５は転写ローラ、６は供給ローラ、７は規制ブレード、８は負帯電性トナー、９は転写材、１０は現像器、１１は現像ローラであり、Ｌは非接触一成分現像プロセスにおける現像ギャップである。
【００９４】
有機感光体１としては、有機感光層が単層の有機単層型でもよいし、有機感光層が多層の有機積層型でもよい。
有機積層型感光体１は、図７（ａ）に示すように導電性支持体１ａ上に、下引き層１ｂを介して、電荷発生層１ｃおよび電荷輸送層１ｄからなる感光層を順次積層したものである。
【００９５】
導電性支持体１ａとしては、公知の導電性支持体が使用可能であり、例えば体積抵抗１０¹⁰Ω・ｃｍ以下の導電性を示すもの、例えばアルミニウム合金に切削等の加工を施した管状物やポリエチレンテレフタレートフィルム上にアルミニウムを蒸着あるいは導電性塗料により導電性を付与した管状物、導電性ポリイミド樹脂を形成してなる管状物とから形成することができる。なお、他の形状例としては、ベルト状、板状、シート状支持体等が例示でき、また、他の材料、形状例として、ニッケル電鋳管やステンレス管などをシームレスにした金属ベルト等も好適に使用することができる。
【００９６】
導電性支持体１ａ上に設けられる下引き層１ｂとしては公知の下引き層が使用可能である。例えば、下引き層１ｂは接着性を向上させ、モワレを防止し、上層の電荷発生層１ｃの塗工性を改良、露光時の残留電位を低減させるなどの目的で設けられる。下引き層１ｂに使用する樹脂はその上に電荷発生層１ｃを有する感光層を塗工する関係上、感光層に使用する溶剤に対して耐溶解性の高い樹脂であることが望ましい。使用可能な樹脂としては、ポリビニルアルコール、カゼイン、ポリアクリル酸ナトリウム等の水溶性樹脂、酢酸ビニル、共重合ナイロン、メトキシメチル化ナイロン等のアルコール可溶性樹脂、ポリウレタン、メラミン樹脂、エポキシ樹脂等であり、単独または２種以上の組み合わせで使用することができる。また、これらの樹脂に二酸化チタン、酸化亜鉛等の導電性微粒子を含有させてもよい。
【００９７】
電荷発生層１ｃにおける電荷発生顔料としては、公知の材料が使用可能である。例えば、金属フタロシアニン、無金属フタロシアニンなどのフタロシアニン系顔料、アズレニウム塩顔料、スクエアリック酸メチン顔料、カルバゾール骨格を有するアゾ顔料、トリフェニルアミン骨格を有するアゾ顔料、ジフェニルアミン骨格を有するアゾ顔料、ジベンゾチオフェン骨格を有するアゾ顔料、フルオレン骨格を有するアゾ顔料、オキサジアゾール骨格を有するアゾ顔料、ビススチルベン骨格を有するアゾ顔料、ジスチリルオキサジアゾール骨格を有するアゾ顔料、ジスチリルカルバゾール骨格を有するアゾ顔料、ペリレン系顔料、アントラキノン系または多環キノン系顔料、キノンイミン系顔料、ジフェニルメタンおよびトリフェニルメタン系顔料、ベンゾキノンおよびナフトキノン系顔料、シアニンおよびアゾメチン系顔料、インジゴイド系顔料、ビスベンズイミダゾール系顔料などが挙げられる。これらの電荷発生顔料は、単独または２種以上の組み合わせで使用することができる。
【００９８】
電荷発生層１ｃにおけるバインダー樹脂としては、ポリビニルブチラール樹脂、部分アセタール化ポリビニルブチラール樹脂、ポリアリレート樹脂、塩化ビニル−酢酸ビニル共重合体等を挙げることができる。バインダー樹脂と前記電荷発生物質の構成比は、重量比でバインダー樹脂１００重量部に対して、１０重量部〜１０００重量部の範囲で用いられる。
【００９９】
電荷輸送層１ｄを構成する電荷輸送物質としては公知の材料が使用可能であり、電子輸送物質と正孔輸送物質とがある。電子輸送物質としては、例えばクロルアニル、テトラシアノエチレン、テトラシアノキノジメタン、２，４，７−トリニトロ−９−フルオレノン、パラジフェノキノン誘導体、ベンゾキノン誘導体、ナフトキノン誘導体などの電子受容性物質が挙げられる。これらの電子輸送物質は、単独または２種以上の組み合わせで使用することができる。
【０１００】
正孔輸送物質としては、オキサゾール化合物、オキサジアゾール化合物、イミダゾール化合物、トリフェニルアミン化合物、ピラゾリン化合物、ヒドラゾン化合物、スチルベン化合物、フェナジン化合物、ベンゾフラン化合物、ブタジエン化合物、ベンジジン化合物、スチリル化合物およびこれらの化合物の誘導体が挙げられる。これらの電子供与性物質は単独または２種以上の組み合わせで使用することができる。
【０１０１】
電荷輸送層１ｄ中には、これらの物質の劣化防止のために酸化防止剤、老化防止剤、紫外線吸収剤などを含有することもできる。
電荷輸送層１ｄにおけるバインダー樹脂としては、ポリエステル、ポリカーボネート、ポリスルホン、ポリアリレート、ポリビニルブチラール、ポリメチルメタクリレート、ポリ塩化ビニル樹脂、塩化ビニル−酢酸ビニル共重合体、シリコーン樹脂などを用いることができるが、電荷輸送物質との相溶性、膜強度、溶解性、塗料としての安定性の点でポリカーボネートが好ましい。バインダー樹脂と電荷輸送物質の構成比は、重量比でバインダー樹脂１００重量部に対して２５重量部〜３００重量部の範囲で用いられる。
【０１０２】
電荷発生層１ｃ、電荷輸送層１ｄを形成するためには、塗布液を使用するとよく、溶剤はバインダー樹脂の種類によって異なるが、例えばメタノール、エタノール、イソプロピルアルコール等のアルコール類、アセトン、メチルエチルケトン、シクロヘキサノン等のケトン類、Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジメチルアセトアミド等のアミド類、テトラヒドロフラン、ジオキサン、エチレングリコールモノメチルエーテル類等のエーテル類、酢酸メチル、酢酸エチル等のエステル類、クロロホルム、塩化メチレン、ジクロルエチレン、四塩化炭素、トリクロルエチレン等の脂肪族ハロゲン化炭化水素、あるいはベンゼン、トルエン、キシレン、モノクロルベンゼン等の芳香族類等を用いることができる。
また、電荷発生顔料の分散には、サンドミル、ボールミル、アトライター、遊星式ミル等の機械式の方法を用いて分散と混合を行うとよい。
【０１０３】
下引き層１ｂ、電荷発生層１ｃおよび電荷輸送層１ｄの塗工法としては、浸漬コーティング法、リングコーティング法、スプレーコーティング法、ワイヤーバーコーティング法、スピンコーティング法、ブレードコーティング法、ローラーコーティング法、エアナイフコーティング法等の方法を用いる。また、塗工後の乾燥は常温乾燥後、３０℃〜２００℃の温度で３０から１２０分間加熱乾燥することが好ましい。これらの乾燥後の膜厚は電荷発生層１ｃでは、０.０５μｍ〜１０μｍの範囲、好ましくは０.１μｍ〜３μｍである。また、電荷輸送層１ｄでは５μｍ〜５０μｍの範囲、好ましくは１０μｍ〜４０μｍである。
【０１０４】
また、有機単層型感光体１は、図７（ｂ）に示すように上述した有機積層型感光体１において説明した導電性支持体１ａ上に、同様の下引き層１ｂを介して、電荷発生剤、電荷輸送剤、増感剤等とバインダー、溶媒等からなる単層有機感光層１ｅを塗布形成することにより作製される。有機負帯電単層型感光体については、例えば特開２０００−１９７４６号公報に開示されている方法に準じて作製するとよい。
【０１０５】
単層有機感光層１ｅにおける電荷発生剤としてはフタロシアニン系顔料、アゾ系顔料、キノン系顔料、ペリレン系顔料、キノシアトン系顔料、インジゴ系顔料、ビスベンゾイミダゾール系顔料、キナクリドン系顔料が挙げられ、好ましくはフタロシアニン系顔料、アゾ系顔料である。電荷輸送剤としてはヒドラゾン系、スチルベン系、フェニルアミン系、アリールアミン系、ジフェニルブタジエン系、オキサゾール系等の有機正孔輸送化合物が例示され、また、増感剤としては各種の電子吸引性有機化合物であって電子輸送剤としても知られているパラジフェノキノン誘導体、ナフトキノン誘導体、クロラニル等が例示される。バインダーとしてはポリカーボネート樹脂、ポリアリレート樹脂、ポリエステル樹脂等の熱可塑性樹脂が例示される。
【０１０６】
各成分の組成比は、バインダー４０重量％〜７５重量％、電荷発生剤０.５重量％〜２０重量％、電荷輸送剤１０重量％〜５０重量％、増感剤０.５重量％〜３０重量％であり、好ましくはバインダー４５重量％〜６５重量％、電荷発生剤１重量％〜２０重量％、電荷輸送剤２０重量％〜４０重量％、増感剤２重量％〜２５重量％である。溶剤としては、下引き層に対して、溶解性を有しない溶媒が好ましく、トルエン、メチルエチルケトン、テトラヒドロフラン等が例示される。
【０１０７】
各成分は、ホモミキサー、ボールミル、サンドミル、アトライター、ペイントコンディショナー等の攪拌装置で粉砕・分散混合され、塗布液とされる。塗布液は、下引き層上にディップコート、リングコート、スプレーコート等により乾燥後の膜厚１５μｍ〜４０μｍ、好ましくは２０μｍ〜３５μｍで塗布・乾燥されて単層有機感光体層１ｅとされる。
【０１０８】
そして、このように構成された有機感光体１は直径２４ｍｍ〜８６ｍｍで表面速度６０ｍｍ／ｓ〜３００ｍｍ／ｓで回転する感光体ドラムであり、コロナ帯電器２等の帯電部材によりその表面が均一に負帯電された後、記録すべき情報に応じた露光３が行なわれることにより、感光体ドラムの表面に静電潜像が形成される。
【０１０９】
現像ローラ１１を有する現像器１０は、一成分現像器１０であり、有機感光体１上に負帯電性トナー８を供給することで有機感光体１における静電潜像を反転現像し、可視像化するものである。現像器１０には、負帯電性トナー８が収納されており、図５に示すように反時計方向で回転する供給ローラ６によりトナーを現像ローラ１１に供給する。現像ローラ１１は図示のごとく反時計方向に回転し、供給ローラ６により搬送されたトナー８をその表面に吸着した状態で、時計方向に回転する有機感光体１との接触部に搬送し、有機感光体１上の静電潜像を可視像化する。
【０１１０】
現像ローラ１１は、例えば直径１６ｍｍ〜２４ｍｍで、金属製のパイプにメッキやブラスト処理したローラ、あるいは中心軸周面にＮＢＲ、ＳＢＲ、ＥＰＤＭ、ウレタンゴム、シリコンゴム等からなる体積抵抗値１０⁴ Ω・ｃｍ〜１０⁸ Ω・ｃｍ、硬度が４０°〜７０°（アスカーＡ硬度）の導電性弾性体層が形成されたもので、このパイプのシャフトや中心軸を介して、図示していない電源より現像バイアス電圧が印加される。
【０１１１】
規制ブレード７としてはＳＵＳ、リン青銅、ゴム板、金属薄板にゴムチップの貼り合わせたもの等が使用されるが、現像ローラ１１に対して図示しないスプリング等の付勢手段により、あるいは弾性体としての反発力を利用して線圧２０ｇｆ／ｃｍ〜６０ｇｆ／ｃｍで押圧され、現像ローラ１１上のトナー層厚を５μｍ〜２０μｍ、好ましくは６μｍ〜１５μｍ、トナー粒子の積層形態としては略１層〜２層、好ましくは１層〜１.８層とされるとよい。
【０１１２】
図５に示す非接触現像方式の画像形成装置では、現像ローラ１１と有機感光体１とを現像ギャップＬを介して対向させるものであるが、現像ギャップＬとしては１００μｍ〜３５０μｍとするとよく、また、図示しないが直流電圧（ＤＣ）の現像バイアスとしては−２００Ｖ〜−５００Ｖであり、これに重畳する交流電圧（ＡＣ）としては１.５ｋＨｚ〜３.５ｋＨｚ、Ｐ−Ｐ電圧１０００Ｖ〜１８００Ｖの条件とするとよい。また、非接触現像方式にあって、反時計方向に回転する現像ローラ１１の周速としては、時計方向に回転する有機感光体１に対して１.０〜２.５、好ましくは１.２〜２.２の周速比とするとよい。
【０１１３】
現像ローラ１１は図示のごとく反時計方向に回転し、供給ローラ６により搬送された負帯電性トナー８をその表面に吸着した状態で有機感光体１との対向部に負帯電性トナー８を搬送するが、有機感光体１と現像ローラ１１との対向部において、交流電圧を重畳して印加することにより、負帯電性トナー８は現像ローラ１１表面と有機感光体１表面との間で振動することにより現像される。本発明にあっては、交流電圧の印加により現像ローラ１１表面と有機感光体１表面との間でトナー８が振動する間にトナー粒子と現像ローラ１１表面とが接触させることができるので、これによっても、小粒子径の正帯電トナーを負帯電させることができ、カブリトナーを減少させることができるものと考えられる。
【０１１４】
また、紙等の転写材９や中間転写媒体（図５には不図示；後述する図８に図示）は可視像化された有機感光体１と転写ローラ５との間に送られるが、転写ローラ５による有機感光体１への押し圧荷重を、接触現像方式と同程度の２０ｇｆ／ｃｍ〜７０ｇｆ／ｃｍ、好ましくは２５ｇｆ／ｃｍ〜５０ｇｆ／ｃｍとするとよい。
【０１１５】
図５に示す非接触現像プロセスおよび図６に示す非接触現像プロセスを、それぞれイエローＹ、シアンＣ、マゼンタＭ、ブラックＫからなる４色のトナー（現像剤）による現像器と感光体１を組み合わせれば、フルカラー画像を形成することのできるフルカラー画像形成装置となる。このフルカラー画像形成装置としては、図８に示す４色の各現像器と回転可能な１つの潜像担持体からなる４サイクル方式（詳細は後述）、４色の各現像器と各潜像担持体とを１列に並べたタンデム方式、および、１つの潜像担持体と４色の回転可能な現像器を組み合わせたロータリー方式がある。
【０１１６】
次に、本発明の負帯電性トナーの作製例、およびこの負帯電性トナーを用いた、図５および図６に示す基本構成を有する図８に示す非接触または接触一成分現像プロセスによる画像形成装置の有機感光体、転写媒体の製造例について説明する。なお、図８に示す画像形成装置は接触一成分現像プロセスを行うこともでき、後述する作像化試験では、この画像形成装置を用いて接触一成分現像プロセスによる試験も行った。ただし、以下の説明においては、基本的にこの画像形成装置は非接触一成分現像プロセスを行うものとしている。
【０１１７】
次に、本発明の負帯電性トナーの製造例を示す。その場合、負帯電性トナー（１）ないし（４）は重合法により製造されたトナーであり、また、負帯電性トナー（５）ないし（８）は粉砕法で製造されたトナーの例である。
【０１１８】
［負帯電性トナー（１）の製造例］
スチレンモノマー８０重量部、アクリル酸ブチル２０重量部、およびアクリル酸５重量部からなるモノマー混合物を、
・水 １０５重量部
・ノニオン乳化剤 １重量部
・アニオン乳化剤 １.５重量部
・過硫酸カリウム ０.５５重量部
からなる水溶性混合物に添加し、窒素気流中下で攪拌して７０℃で８時間重合を行った。重合反応後冷却し、乳白色の粒子径０.２５μｍの樹脂エマルジョンを得た。
【０１１９】
次に、
・この樹脂エマルジョン ２００重量部
・ポリエチレンワックスエマルジョン｛三洋化成工業（株）製｝ ２０重量部
・フタロシアニンブルー ７重量部
を、界面活性剤のドデシルベンゼンスルホン酸ナトリウム０.２重量部を含んだ水中へ分散し、ジエチルアミンを添加してｐＨを５.５に調整後攪拌しながら電解質の硫酸アルミニウムを０.３重量部を加え、次いでＴＫホモミキサーで高速攪拌し、分散を行った。
【０１２０】
更に、スチレンモノマー４０重量部、アクリル酸ブチル１０重量部、サリチル酸亜鉛５重量部を水４０重量部と共に追加し、窒素気流下で攪拌しながら同様にして９０℃に加熱し、過酸化水素を加えて５時間重合し、粒子を成長させた。重合停止後、この二次粒子の会合と造膜結合強度を上げるため、ｐＨを５以上に調整しながら９５℃に昇温し、５時間保持した。その後、得られた粒子を水洗いし、４５℃で真空乾燥を１０時間行ってシアントナーの母粒子を得た。
【０１２１】
得られたシアントナーの母粒子は、前述のＦＰＩＡ２１００装置で平均粒径および円形度を測定するとともに、前述のＡＣ−２型表面分析装置で仕事関数を測定した結果、平均粒径が６.８μｍ、円形度が０.９８のトナーであり、その仕事関数は前述の表面分析装置により測定した結果、５.５７ｅＶであった。このシアントナーの母粒子に対し、流動性改良剤である平均一次粒子径が約１２ｎｍでかつ仕事関数が５.２２ｅＶの疎水性シリカを重量比で１％、平均一次粒子径が約４０ｎｍでかつ仕事関数が５.２４ｅＶの疎水性シリカを０.５重量％添加混合して添加混合し、シアントナー（１）を作製した。得られたシアントナー（１）は前述の各装置を用いて測定した結果、平均粒径が６.８６μｍ、円形度が０.９８３、仕事関数が５.５４ｅＶであった。
【０１２２】
［負帯電性トナー（２）の製造例］
前述のシアントナー（１）において、同様にしてフタロシアニンブルーの顔料の代わりに顔料をキナクリドンに変更し、また二次粒子の会合と造膜結合強度を上げる温度を９０℃のままで行い、マゼンタトナー（２）を同様に作製した。前述のシアントナー（１）と同様にして、マゼンタトナー（２）の母粒子およびマゼンタトナー（２）の平均粒径、円形度、および仕事関数を測定した結果、トナー母粒子の平均粒子径が６.９μｍ、円形度が０.９７、仕事関数が５.６５ｅＶ、マゼンタトナー（２）の平均粒径が６.９６μｍ、円形度が０.９７５で、仕事関数が５.６１ｅＶであった。
【０１２３】
［負帯電性トナー（３）および（４）の製造例］
前述のマゼンタトナー（２）において、顔料をピグメントイエロー１８０とカーボンブラックとに変えた以外はマゼンタトナー（２）と同様にして重合を行い、流動性改良剤を添加し、イエロートナー（３）とブラックトナー（４）とを作製した。このとき、イエロートナー（３）は、トナー母粒子の平均粒子径が６.９３μｍ、円形度が０.９６８、仕事関数が５.５５ｅＶ、イエロートナー（３）の平均粒径が７.０１μｍ、円形度が０.９７１、仕事関数が５.５２ｅＶであった。また、ブラックトナー（４）は、トナー母粒子の平均粒径が６.８９μｍ、円形度が０.９６５、仕事関数が５.４９ｅＶ、ブラックトナー（４）の平均粒径が７.０８μｍ、円形度が０.９７５、仕事関数が５.４５ｅＶであった。
【０１２４】
［負帯電性トナー（５）の製造例］
芳香族ジカルボン酸とアルキレンエーテル化ビスフェノールＡとの重縮合ポリエステルと該重縮合ポリエステルの多価金属化合物による一部架橋物の５０：５０（重量比）混合物｛三洋化成工業（株）製｝１００重量部、マゼンタ顔料のカーミン６Ｂ重量部、離型剤として融点が１５２℃、重量分子量Ｍｗが４０００のポリプロピレン１重量部、および荷電制御剤としてのサリチル酸金属錯体Ｅ−８１｛オリエント化学工業（株）製｝４重量部をヘンシェルミキサーを用い、均一混合した後、内温１３０℃の二軸押し出し機で混練し、冷却した。冷却物を２ｍｍ角以下に粗粉砕し、次いでジェットミルで微粉砕し、ローター回転による分級装置により分級し、平均粒径６.２μｍで、円形度０.９０５の分級トナー母粒子を得た。分級したトナー母粒子に対して、重量比で０.２％の疎水性シリカ（平均一次粒子径７ｎｍ、比表面積２５０ｍ²／ｇ）を加え、表面処理を行った後、熱風球形化装置サーフュージングシステムを用い、熱処理温度２５０℃に設定し、部分的に球形化処理を行い、その後、同様にして再度分級し、平均粒径７.３５μｍ、円形度０.９４０のマゼンタトナーの母粒子を得た。また、このトナー母粒子の仕事関数は、測定の結果、５.５０ｅＶであった。
【０１２５】
得られたトナー母粒子に対して、前述のトナー（１）で使用した２種類の疎水性シリカのうち、小粒子径のシリカを平均一次粒子径が約７ｎｍ、仕事関数が５.１８ｅＶの疎水性シリカを０.５重量％、更に、平均一次粒子径が約１２ｎｍの前述の疎水性シリカを０.５重量％、そして大粒子径のシリカの平均一次粒子径が約４０ｎｍ、仕事関数が５.２４ｅＶの疎水性シリカを０.５重量％添加し、更に、平均一次粒子径が約１７ｎｍ、第１の仕事関数が５.１８ｅＶで第２の仕事関数が５.６２ｅＶの疎水性アルミナーシリカ複合酸化物微粒子を０.５重量％、金属酸化物微粒子として平均一次粒子径が約２０ｎｍ、仕事関数が５.６４ｅＶのルチルアナターゼ型酸化チタンを０.３重量％および平均一次粒子径が０.２３μｍ、仕事関数が５.００ｅＶの導電性酸化アルミニウムを０.４重量％添加混合し、マゼンタトナー（５）を作製した。このとき、マゼンタトナー（５）は、平均粒子径が約７.３８μｍ、円形度が０.９４、仕事関数が５.５６ｅＶであった。
【０１２６】
［負帯電性トナー（６）、（７）、（８）の製造例］
前述のマゼンタトナー（５）の製造例に従い、同様にしてシアントナー（６）（シアントナー顔料としてフタロシアニンブルーを使用）、イエロートナー（７）（イエロートナー顔料としてピグメントイエロー９３を使用）およびブラックトナー（８）（ブラックトナー顔料としてカーボンブラックを使用）を作製した。
【０１２７】
このとき、シアントナー（６）は、そのトナー母粒子の平均粒子径が約７.２１μｍ、円形度が０.９４１、仕事関数が５.４０ｅＶであり、シアントナー（６）の平均粒子径と円形度がいずれもほぼマゼンタトナー（５）とほぼ同じであり、仕事関数が５.４４ｅＶであった。また、イエロートナー（７）は、そのトナー母粒子の平均粒子径が約７.０３μｍ、円形度が０.９４１、仕事関数が５.５３ｅＶであり、イエロートナー（７）の平均粒子径と円形度がいずれもほぼマゼンタトナー（５）とほぼ同じであり、仕事関数が５.６１ｅＶであった。更に、ブラックトナー（８）は、そのトナー母粒子の平均粒子径が約７.２６μｍ、円形度が０.９４０、仕事関数が５.６１ｅＶであり、ブラックトナー（８）の平均粒子径と円形度がいずれもほぼマゼンタトナー（５）とほぼ同じであり、仕事関数が５.６５ｅＶであった。
【０１２８】
（非接触または接触一成分現像プロセスによる画像形成装置の例）
図５に示す非接触一成分現像プロセスによる画像形成装置あるいは図６に示す接触一成分現像プロセスによる画像形成装置として、図８に示す非接触現像プロセスおよび接触現像プロセスが可能なフルカラープリンタがある。このフルカラープリンタを示す図８において、１００は像担持体ユニットが組み込まれた像担持体カートリッジである。この例では、感光体カートリッジとして構成されていて、感光体と現像部ユニットが個別に装着できるようになっており、本発明の相対関係にある仕事関数を有する負帯電用電子写真感光体（以下、単に感光体ともいう）１４０が図示しない適宜の駆動手段によって図示矢印方向に回転駆動される。感光体１４０の周りにはその回転方向に沿って、帯電手段として帯電ローラ１６０、現像手段としての現像器１０（Ｙ、Ｍ、Ｃ、Ｋ）、中間転写装置３０、およびクリーニング手段１７０が配置される。
【０１２９】
帯電ローラ１６０は、感光体１４０の外周面に当接してその外周面を一様に帯電させる。一様に帯電した感光体１４０の外周面には露光ユニット４０によって所望の画像情報に応じた選択的な露光Ｌ１がなされ、この露光Ｌ１によって感光体１４０上に静電潜像が形成される。この静電潜像は現像器１０によって現像剤が付与されて現像される。
【０１３０】
現像器１０としてイエロー用の現像器１０Ｙ、マゼンタ用の現像器１０Ｍ、シアン用の現像器１０Ｃ、およびブラック用の現像器１０Ｋが設けられている。これら現像器１０Ｙ、１０Ｃ、１０Ｍ、１０Ｋはそれぞれ揺動可能に構成されている。そして、選択的に一つの現像器の現像ローラ（現像剤担持体）１１のみが、非接触現像プロセスの場合は感光体１４０に対して所定の現像ギャップＬを置いてセットされ、また、接触現像プロセスの場合は感光体１４０に圧接し得るようになっている。これらの現像器１０は、感光体における仕事関数と相対関係にある仕事関数を有する負帯電性トナーを現像ローラ上に保持しているものであり、これらの現像器１０はイエローＹ、マゼンタＭ、シアンＣ、ブラックＫのうちのいずれかのトナーを感光体１４０の表面に付与して感光体１４０上の静電潜像を現像する。現像ローラ１１は硬質のローラ、例えば表面を粗面化した金属ローラで構成されている。現像されたトナー像は、中間転写装置３０の中間転写ベルト３６上に転写される。クリーニング手段１７０は、上記転写後に感光体１４０の外周面に付着しているトナーＴを掻き落とすクリーナブレードと、このクリーナブレードによって掻き落とされたトナーを受けるクリーニングトナー回収部とを備えている。
【０１３１】
中間転写装置３０は、駆動ローラ３１と、４本の従動ローラ３２、３３、３４、３５と、これら各ローラの周りに張架された無端状の中間転写ベルト３６とを有している。駆動ローラ３１は、その端部に固定された図示しない歯車が感光体１４０の駆動用歯車とかみ合っていることによって感光体１４０と略同一の周速で回転駆動され、したがって中間転写ベルト３６が感光体１４０と略同一の周速で図示矢印方向に循環駆動されるようになっている。
【０１３２】
従動ローラ３５は駆動ローラ３１との間で中間転写ベルト３６がそれ自身の張力によって感光体１４０に圧接される位置に配置されており、感光体１４０と中間転写ベルト３６との圧接部において、一次転写部Ｔ１が形成されている。従動ローラ３５は、中間転写ベルトの循環方向上流側において一次転写部Ｔ１の近くに配置されている。
【０１３３】
駆動ローラ３１には中間転写ベルト３６を介して図示しない電極ローラが配置されており、この電極ローラを介して中間転写ベルト３６の導電性層に一次転写電圧が印加される。従動ローラ３２は、テンションローラであり、図示しない付勢手段によって中間転写ベルト３６をその張り方向に付勢している。従動ローラ３３は二次転写部Ｔ２を形成するバックアップローラである。このバックアップローラ３３には中間転写ベルト３６を介して二次転写ローラ３８が対向配置されている。二次転写ローラには二次転写電圧が印加され、図示しない接離機構により中間転写ベルト３６に対して接離可能になっている。従動ローラ３４はベルトクリーナ３９のためのバックアップローラである。ベルトクリーナ３９は図示しない接離機構により中間転写ベルト３６に対して接離可能になっている。
【０１３４】
中間転写ベルト３６は、導電層と、この導電層上に形成され、感光体１４０に圧接される抵抗層とを有する複層ベルトで構成されている。導電層は合成樹脂からなる絶縁性基体の上に形成されており、この導電層に前述した電極ローラを介して一次転写電圧が印加される。なお、ベルト側縁部において、抵抗層が帯状に除去されることによって導電層が帯状に露出し、この露出部に電極ローラが接触するようになっている。
【０１３５】
中間転写ベルト３６が循環駆動される過程で、一次転写部Ｔ１において、感光体１４０上のトナー像が中間転写ベルト３６上に転写され、中間転写ベルト３６上に転写されたトナー像は、二次転写部Ｔ２において、二次転写ローラ３８との間に供給される用紙等のシート（記録材）Ｓに転写される。シートＳは、給紙装置５０から給送され、ゲートローラ対Ｇによって所定のタイミングで二次転写部Ｔ２に供給される。５１は給紙カセット、５２はピックアップローラである。
【０１３６】
二次転写部Ｔ２で二次転写されたトナー像が定着器６０で定着され、排紙経路７０を通って装置本体のケース８０上に形成されたシート受け部８１上に排出される。なお、この画像形成装置は、排紙経路７０として互いに独立した２つの排紙経路７１、７２を有しており、定着装置６０を通ったシートはいずれかの排紙経路７１又は７２を通って排出される。また、この排紙経路７１、７２はスイッチバック経路をも構成しており、シートの両面に画像を形成する場合には排紙経路７１又は７２に一旦進入したシートが、返送ローラ７３を通って再び二次転写部Ｔ２に向けて給紙されるようになっている。
【０１３７】
次に、画像形成装置の各構成部材の製造例を説明する。
｛有機感光体（ＯＰＣ１）の製造例｝
この製造例の有機感光体（ＯＰＣ１）１の作製では、まず、アルミ素管の径８５.５ｍｍの導電性支持体１ａの周面に、下引き層１ｂとして、アルコール可溶性ナイロン｛東レ（株）製「ＣＭ８０００」｝の６重量部とアミノシラン処理された酸化チタン微粒子４重量部とをメタノール１００重量部に溶解、分散させてなる塗工液をリングコーティング法で塗工し、温度１００℃で４０分乾燥させ、膜厚１.５μｍ〜２μｍの下引き層１ｂを形成した。
【０１３８】
次いで、の下引き層１ｂ上に、電荷発生顔料としてのオキシチタニウムフタロシアニン１重量部と、ブチラール樹脂｛ＢＸ−１、積水化学（株）製｝１重量部と、ジクロルエタン１００重量部とを、φ１ｍｍのガラスビーズを用いたサンドミルで８時間分散させて顔料分散液を得た。得られた顔料の分散液をこの下引き層１ｂ上に、リングコーティング法で塗工し、８０℃で２０分間乾燥させ、膜厚０.３μｍの電荷発生層１ｃを形成した。
【０１３９】
この電荷発生層１ｃ上に、下記構造式（１）のスチリル化合物の電荷輸送物質４０重量部とポリカーボネート樹脂（パンライトＴＳ、帝人化成（株）製）６０重量部をトルエン４００重量部に溶解させ、乾燥膜厚が２２μｍになるように浸漬コーティング法で塗工、乾燥させて電荷輸送層１ｄを形成し、２層からなる感光層を有する有機積層型感光体１（ＯＰＣ１）を作製した。
得られた有機積層型感光体１の一部を切り欠いて試料片とし、この試料片の仕事関数は前述のＡＣ−２型表面分析装置を用い、照射光量５００ｎＷで測定したところ、５.４８ｅＶを示した。
【０１４０】
【化１】

【０１４１】
｛有機感光体（ＯＰＣ２）の製造例｝
有機感光体（ＯＰＣ１）１において、導電性支持体１ａにシームレスの厚さ４０μｍで直径８５.５ｍｍのニッケル電鋳管を用い、また、電荷発生顔料としてチタニルフタロシアニンを用い、更に、電荷輸送物質に下記構造式（２）のジスチリル化合物を用い、それ以外は製造例１と同様にして有機積層型感光体（ＯＰＣ２）１を作製した。この有機積層型感光体の仕事関数を同様に測定すると、５.５０ｅＶであった。
【０１４２】
【化２】

【０１４３】
（現像ローラ１１の作製例）
現像ローラ１１は、直径１８ｍｍのアルミパイプ表面にニッケルメッキ（厚さ２３μｍ）を施し、表面粗さ（Ｒａ）４μｍの表面を得た。この現像ローラ１１表面の一部を切り欠き、同様にして仕事関数を測定したところ、４.５８ｅＶであった。
【０１４４】
（トナー規制ブレードの作製例）
トナー規制ブレード７は、厚さ８０μｍのＳＵＳ板に厚さ１.５ｍｍの導電性ウレタンフゴムチップを導電性接着剤で貼り付けて作製し、このときにウレタン部の仕事関数は約５ｅＶとした。
【０１４５】
（中間転写装置の転写媒体の作製例）
中間転写装置３０の転写媒体である中間転写ベルト３６における導電層である中間導電性層を、
アルミニウムを蒸着した厚さ１３０μｍのポリエチレンテレフタレート樹脂フィルム上に、
・塩化ビニル−酢酸ビニル共重合体 ３０重量部
・導電性カーボンブラック １０重量部
・メチルアルコール ７０重量部
からなる均一分散液を、厚さが２０μｍになるようにロールコーティング法にて塗工乾燥することにより、形成した。
【０１４６】
次いで、この中間導電性層上に、抵抗層である転写層を、

の組成を混合分散してなる塗工液を厚さ１０μｍとなるようにロールコーティング法にて同様に塗工乾燥して、形成した。
【０１４７】
そして、この塗工シートを長さ５４０ｍｍに裁断し、塗工面を上にして端部を合わせ、超音波溶着を行うことにより中間転写ベルト３６を作製した。この中間転写ベルト３６の体積抵抗は２.５×１０¹⁰Ω・ｃｍであった。また、仕事関数は５.３７ｅＶ、規格化光電子収率６.９０を示した。
【０１４８】
（定着器の作製例）
定着器６０はヒータローラおよびプレスローラの二本の加圧ローラ（約３８ｋｇｆの荷重）を備えている。ヒータローラはハロゲンランプ６００ｗを内蔵し、シリコンゴム２.５ｍｍ（６０°ＪＩＳＡ）上にＰＦＡを厚み５０μｍに成膜してφ４０に形成した。また、プレスローラはハロゲンランプ３００ｗを内蔵し、シリコンゴム２.５ｍｍ（６０°ＪＩＳＡ）上にＰＦＡを厚み５０μｍに成膜してφ４０に形成した。定着温度は１９０℃に設定している。
【０１４９】
このように構成されたフルカラープリンタの作動の概要は次の通りである。
(i) 図示しないホストコンピュータ等（パーソナルコンピュータ等）からの印字指令信号（画像形成信号）が画像形成装置の制御部９０に入力されると、感光体１４０、現像器１０の各ローラ１１、および中間転写ベルト３６が回転駆動される。
【０１５０】
(ii) 感光体１４０の外周面が帯電ローラ１６０によって一様に帯電される。
(iii) 一様に帯電した感光体１４０の外周面に、露光ユニット４０によって第１色目（例えばイエロー）の画像情報に応じた選択的な露光Ｌ１がなされ、イエロー用の静電潜像が形成される。
【０１５１】
(iv) 感光体１４０には、第１色目の例えばイエロー用の現像器１０Ｙの現像ローラのみが感光体１４０に対して所定の現像ギャップＬをおいてセットされるかまたは感光体１４０に接触し、これによって上記静電潜像が非接触現像または接触現像され、第１色目のイエローのトナー像が感光体１４０上に形成される。
(v) 中間転写ベルト３６には、上記トナーの帯電極性と逆極性の一次転写電圧が印加され、感光体１４０上に形成されたトナー像が一次転写部Ｔ１において中間転写ベルト３６上に転写される。このとき、二次転写ローラ３８およびベルトクリーナ３９は中間転写ベルト３６から離間している。
【０１５２】
(vi) 感光体１４０上に残留しているトナーがクリーニング手段１７０によって除去された後、除去手段４１から除電光Ｌ２によって感光体１４０が除電される。
(vii) 上記(ii)〜(vi)の動作に必要に応じて繰り返される。すなわち、上記印字指令信号に応じて第２色目、第３色目、第４色目と繰り返され、上記印字指令信号の内容に応じたトナー像が中間転写ベルト３６上において重ね合わされて形成される。
【０１５３】
(viii) 所定のタイミングで給紙装置５０からシートＳが給送され、シートＳの先端が二次転写部Ｔ２に達する直前あるいは達した後に（要するにシートＳ上の所望の位置に、中間転写ベルト３６上のトナー像が転写されるタイミングで）二次転写ローラ３８が中間転写ベルト３６上のトナー像（基本的には４色のトナー像が重ね合わせられたフルカラー画像）がシートＳ上に転写される。また、ベルトクリーナ３９が中間転写ベルト３６に当接し、二次転写後に中間転写ベルト３６上に残留しているトナーが除去される。
【０１５４】
(ix) シートＳが定着装置６０を通過することによってシートＳ上のトナー像が定着し、その後、シートＳが所定の位置に向け（両面印刷でない場合にはシート受け部８１に向け、両面印刷の場合にはスイッチバック経路７１または７２を経て返送ローラ７３に向け）搬送される。
【０１５５】
次に、本発明の負帯電トナーの実施例について説明する。
（実施例１）
この実施例１で使用した外添剤１２の仕事関数の一覧表を表３に示す。その場合、導電性微粒子１４としてこの実施例では導電性のアナターゼ型酸化チタンを用いている。
【０１５６】
【表３】

【０１５７】
前述のように、アルミナーシリカ複合酸化物微粒子１３は屈曲点があって第１と第２の２つの仕事関数を有しており、表３には、外添剤▲４▼のアルミナーシリカ複合酸化物微粒子１３の２つの仕事関数が示されている。これらの仕事関数がそれぞれ前述の正と負の摩擦帯電サイトを与えると考えられる。
【０１５８】
そこで、この実施例１では、前述のシアントナー（１）に対して、ジメチルシラン（ＤＭＳ）により表面処理された疎水性アルミナ−シリカ複合酸化物微粒子｛かさ密度７５ｇ／Ｌ、平均一次粒子径１７ｎｍ、比表面積１１０ｍ²／ｇ、シリカ３５／アルミナ６５の重量構成比（混晶比）｝を０.５重量％、更に、導電性のアナターゼ型酸化チタン（平均一次粒子径０.０６３μｍ、比表面積４５.２ｍ²／ｇ）を、表４に示す重量比で添加混合したトナー１ー▲１▼ないし１ー▲５▼をそれぞれ作製した。
【０１５９】
【表４】

【０１６０】
これらのトナーについて、図５に模式的に示す非接触現像方式で、前述の有機感光体（ＯＰＣ１）１、前述の現像ローラ１１、中間転写装置３０の中間転写ベルト３６、およびトナー規制部材７を使用した図８に示すフルカラープリンタを用いて、現像ギャップＬを２２０μｍに設定した非接触現像方式（作像条件：有機感光体１の暗電位−６００Ｖ、有機感光体１の明電位−８０Ｖ、ＤＣ現像バイアス−３００Ｖ、ＡＣ現像バイアス（Ｐ−Ｐ電圧）１３２０Ｖ、ＡＣ周波数２.５ｋＨｚ）でベタ画像を出力してトナーの帯電特性試験を行った。そして、その時の現像ローラ１１上のトナーの平均帯電量ｑ／ｍ（μｃ／ｇ）と正帯電トナー量（個数％）を市販のホソカワミクロン（株）製の帯電量分布測定器（Ｅ−ＳＰＡＲＴアナライザＥＳＴ−３型）で測定した。これらのトナーの帯電特性測定結果を表４に示す。
【０１６１】
表４に示す測定結果から明らかなように、導電性のアナターゼ型酸化チタンの外添剤を添加するに従い、添加しない場合に比し、平均帯電量は少しずつ小さくなるが、正帯電トナー量は、その添加量が０.５重量％までは添加してもあまり増えないことがわかった。しかし、０.５重量％以上になると、平均帯電量が急に落ち込み、しかも、正帯電トナー量も急激に増大することがわかった。
【０１６２】
（実施例２）
前述の実施例１で使用したトナー１ー▲１▼ないし１ー▲５▼を用い、図５に模式的に示す非接触現像方式により、前述の有機感光体（ＯＰＣ１）１、前述の現像ローラ１１、中間転写装置３０の中間転写ベルト３６、およびトナー規制部材７を使用した図８に示すフルカラープリンタを用いて、作像試験を行った。このときの作像条件は、有機感光体１の暗電位−６００Ｖ、有機感光体１の明電位−８０Ｖ、ＤＣ現像バイアス−３００Ｖ、ＡＣ現像バイアス（Ｐ−Ｐ電圧）１３２０Ｖ、ＡＣ周波数２.５ｋＨｚ）であり、供給ローラと現像ローラが同電位である。
この作像試験の結果を表５および表６にそれぞれ示す。
【０１６３】
【表５】

【０１６４】
【表６】

【０１６５】
表６において、△は中抜けあるいはチリがある程度発生し、良好なベタ画像が得られなく、また、○は中抜けあるいはチリがほとんど発生しなく、良好なベタ画像が得られた結果を示す。
表５および表６に示す作像試験結果から明らかなように、シリカとアルミナーシリカ複合酸化物微粒子を外添剤として添加したトナー１ー▲１▼よりも、導電性微粒子である導電性のアナターザ型酸化チタンを添加したトナー１ー▲２▼やトナー１ー▲３▼の方がベタ画像濃度が向上するだけでなく、カブリ、逆転写トナーがさほど増えずに、中抜け、チリが少なくなることがわかった。
【０１６６】
なお、各トナーの転写効率は、トナー１ー▲１▼が６５.２％であったのに対し、導電性微粒子である導電性のアナターゼ型酸化チタンを添加するに従い向上し、その添加量が０.５重量％のときに最大なることがわかった。
【０１６７】
また、カブリおよび逆転写トナーのＯＤ値はテープ転写法で求めた。テープ転写法とは住友３Ｍ製のメンディングテープを感光体上に存在するトナー上に貼り付けてカブリトナーや逆転写トナーをテープ上に転写し、次いでこのメンディングテープおよび貼り付け前のメンディングテープをそれぞれ白紙上に貼り、これらの反射濃度をマクベスの反射濃度計で測定し、その測定値よりテープの反射濃度を差し引いた値をカブリおよび逆転写トナーの各反射濃度としている。また、転写効率は転写前後の感光体上に存在するトナーに前述のテープを貼り付け、剥がしたテープの重量を測定することで、その重量差により計算し求めた。逆転写トナーは１色目のベタ画像を作像し、次いで、２色目の白ベタ画像を作像させたときに、白ベタ画像に相当する非画像部となる感光体上に逆転写された１色目のシアントナーを逆転写トナーとして、テープ転写法で求めた値である。
【０１６８】
（実施例３）
この実施例３で使用した外添剤１２の導電性微粒子の仕事関数を表７に示す。そして、実施例１のトナー１−▲３▼と同様にして各導電性微粒子を表８に示す重量％を添加し、トナー１−▲６▼、トナー１−▲７▼およびトナー１−▲８▼を作製した。これらのトナーについて、実施例１と同様にして測定したトナーの帯電特性結果を表８に示す。
【０１６９】
【表７】

【０１７０】
【表８】

【０１７１】
表８に示す測定結果から明らかなように、導電性微粒子を添加することで、平均帯電量が過帯電にならないように抑えることができ、しかも、正帯電トナー量もさほど増えないことがわかった。
【０１７２】
（実施例４）
前述の実施例３で使用したトナー１−▲６▼ないし１−▲８▼を用い、実施例２と同様にして作像試験を行い、その結果を表９および表１０にそれぞれ示す。
【０１７３】
【表９】

【０１７４】
【表１０】

【０１７５】
表９および表１０に示す作像試験結果から明らかなように、シリカとアルミナーシリカ複合酸化物微粒子と導電性微粒子とを外添剤として添加したトナー１−▲６▼ないしトナー１ー▲８▼は、導電性微粒子を添加しないトナー１−▲１▼よりベタ画像濃度と転写効率が向上するだけでなく、カブリ、逆転写トナーがさほど増えずに、中抜け、チリが少なくなることがわかった。
【０１７６】
（実施例５）
この実施例５で使用したトナーはマゼンタトナー２およびマゼンタトナー５である。このときに使用した外添剤１２の仕事関数を表１１に示す。そして、実施例１のトナー１−▲３▼と同様にして各外添剤を表１２に示す重量％を追加添加し、トナー２−▲１▼およびトナー５−▲１▼を作製した。これらのトナーについて、実施例１と同様にして測定したトナーの帯電特性結果を表１２に示す。
【０１７７】
【表１１】

【０１７８】
【表１２】

【０１７９】
表１２に示す測定結果から明らかなように、導電性微粒子と金属酸化物を添加することで、平均帯電量が過帯電にならないように抑えることができ、しかも、正帯電トナー量を低減させることがわかった。
【０１８０】
（実施例６）
前述の実施例５で使用したトナー２−▲１▼および５−▲１▼を用い、実施例２と同様にして作像試験を行い、その結果を表１３および表１４にそれぞれ示す。
【０１８１】
【表１３】

【０１８２】
【表１４】

【０１８３】
表１３および表１４に示す作像試験結果から明らかなように、シリカとアルミナーシリカ複合酸化物微粒子と導電性微粒子だけでなく、金属酸化物である仕事関数の大きいルチルアナターゼ型酸化チタンを外添剤として添加したトナー２−▲１▼ないしトナー５ー▲１▼は、ベタ画像濃度と転写効率が向上させ、かつカブリ、逆転写トナーを更に低減させ、中抜け、チリがない高画質を与えることがわかった。
【０１８４】
（実施例７）
前述の実施例１で使用したトナー１−▲３▼の導電性酸化チタンの代わりに、表１１に示す導電性酸化アルミニウムを導電性微粒子として０.２重量％添加したトナー１−▲９▼を作製した。実施例１と同じようにしてトナーの帯電特性を測定し、その結果を表１５に再度トナー１ー▲１▼のデータとともに示す。また、これらのトナーを用いて、図６に模式的に示す接触現像方式を採用した図８に示すフルカラープリンタにて作像試験を行った。このときの作像条件は、有機感光体１にＯＰＣ２を用い、暗電位−６００Ｖ、明電位−８０Ｖ、ＤＣ現像バイアス−２００Ｖ、供給ローラと現像ローラを同電位に設定している。この作像試験結果を表１６に示す。
【０１８５】
【表１５】

【０１８６】
【表１６】

【０１８７】
表１５および表１６に示す結果より、導電性微粒子である導電性酸化アルミニウムを添加することにより、接触現像においても画像濃度と転写効率を向上させ、かつカブリ、逆転写トナーを低減させることがわかった。なお、中抜け、チリはともになく同程度の画質を与えた。
【０１８８】
前述のマゼンタトナー２ー▲１▼と同様にして、シアントナー（１）、イエロートナー（３）およびブラックトナー（４）の外添剤処理を行った。また、前述のマゼンタトナー５−▲１▼と同様にして、シアントナー（６）、イエロートナー（７）およびブラックトナー（８）の外添剤処理を行い、２組のトナーの製造方法が異なる４色のフルカラートナーを作製した。これらのトナーを図８に示すフルカラープリンタを用いて、低温・低湿（１０℃・２０％）、中温・中湿（２５℃・６０％）および高温・高湿（３５℃・８５％）の環境下で、各５０００枚の印字試験を行ったが、いずれにおいてもトナーの飛散もなく、安定したフルカラー画像が得られ、画質を比較しても、耐久後に画質の変化はほとんど見られなく、実質的に初期の画質が保持されることが確認できた。
【０１８９】
【発明の効果】
以上の説明から明らかなように、本発明の負帯電トナーによれば、アルミナーシリカ複合酸化物微粒子の有するトナーの凝集性向上機能という固有の特性と導電性微粒子の有するトナーの負の過帯電防止機能およびトナーの流動性の向上機能という固有の特性とを相乗した機能をトナー母粒子に付与しているので、負帯電性トナーの流動性低下を防止できるとともに、トナーの負の過帯電を防止できる。これにより、より良好な負帯電特性を得ることができるので、逆転写トナーの発生およびカブリを効果的に抑制できるようになる。また、トナーの流動性を向上できるので、線画像の境目に発生するチリを防止でき、画像のシャープ性を向上することができるとともに、トナーの凝集性を向上できるので、線画像の中心部に発生する中抜けを防止できる。
【０１９０】
したがって、負帯電性トナーの負帯電をより一層長期にわたり安定させることができるので、シャープ性を有する画像を作製できるとともに、連続印字における安定した画像品質を得ることができる。
しかも、トナーの流動性を向上できることで、トナー規制部材によりトナーの均一な薄層を形成することができるようになる。
【０１９１】
また、酸化アルミニウム−二酸化ケイ素複合酸化物微粒子が広い粒度分布を有していることから、この酸化アルミニウム−二酸化ケイ素複合酸化物微粒子をトナー母粒子内に確実に付着することができるので、転写効率を向上することができる。
【０１９２】
更に、酸化アルミニウム−二酸化ケイ素複合酸化物微粒子および導電性微粒子粒子の各平均一次粒子径より、平均一次粒子径がともに小さく、かつ酸化アルミニウム−二酸化ケイ素複合酸化物微粒子の大きい方の第２仕事関数および導電性微粒子粒子の仕事関数より、仕事関数がともに小さい２種類の疎水性の二酸化ケイ素を併用しているので、酸化アルミニウム−二酸化ケイ素複合酸化物微粒子の前述の固有の特性と導電性微粒子粒子の前述の固有の特性とに、疎水性の負帯電性二酸化ケイ素の有する負帯電機能および流動性という固有の特性が相乗された機能をトナー母粒子に付与できる。これにより、負帯電性トナーの流動性低下を防止できるとともに、負の過帯電を防止できることから、負帯電性トナーにより良好な負帯電特性を持たせることができ、逆転写トナーの発生およびカブリを更に効果的に抑制できる。
【０１９３】
更に、酸化アルミニウム−二酸化ケイ素複合酸化物粒子の第２仕事関数と略同一の金属酸化物微粒子を添加することで、より安定した帯電特性が得られ、その結果、ベタ画像濃度と転写効率の向上のみならず、カブリと逆転写トナーが低減されるようになる。
【０１９４】
また、酸化アルミニウム−二酸化ケイ素複合酸化物微粒子の仕事関数に屈曲点が存在することで、酸化アルミニウム−二酸化ケイ素複合酸化物微粒子は、正と負の摩擦サイトを有している。トナー母粒子が正の摩擦サイトに接触するとトナー母粒子が負に確実に帯電し、また負の摩擦サイトに接触するとトナー母粒子が正に帯電するので過剰に負に帯電したトナー母粒子の電荷を適切な値に調整されるようになる。
【０１９５】
このようにして、本発明の負帯電性トナーによれば、酸化アルミニウム−二酸化ケイ素複合酸化物微粒子の正の摩擦サイトと負帯電性二酸化ケイ素とにより負に帯電し、更に、トナー規制部材とトナー担持体表面とにより、より一層確実に負に摩擦帯電することができる。
【０１９６】
その場合、負帯電し易い低温低湿下はもちろん、負帯電し難い高温高湿下においても、酸化アルミニウム−二酸化ケイ素複合酸化物微粒子によりトナー母粒子を負に帯電することができるので、トナーはに安定した負帯電特性を維持することができ、また、連続印字においても同様に安定した帯電特性を維持できるので、印字品質を環境にほとんど影響されずに長期間にわたって高品質を維持することができる。
【０１９７】
更に、２種類の二酸化ケイ素の添加量（重量）を酸化アルミニウム−二酸化ケイ素複合酸化物微粒子と導電性微粒子との、あるいは金属酸化物微粒子との合計添加量（重量）より多くしているので、酸化アルミニウム−二酸化ケイ素複合酸化物微粒子と導電性微粒子と、あるいは金属酸化物微粒子とをこれらの２種類の二酸化ケイ素を介してトナー母粒子に確実に固着でき、トナー母粒子からの遊離を少なくできる。したがって、本発明の負帯電トナーは長期にわたって帯電を安定させることができるようになる。
【０１９８】
更に、２種類の二酸化ケイ素の平均一次粒子径より大きな粒子径の正と負の摩擦サイトを有する酸化アルミニウム−二酸化ケイ素複合酸化物微粒子を共存させているので、規制トナー層を均一に帯電でき、逆極性である正帯電のトナー量を減少することができる。
【０１９９】
これにより、感光体上のカブリトナーや逆転写トナー量を減らすことができ、転写効率をより一層向上できる。そして、転写効率を向上できることで、感光体や中間転写媒体上のクリーニングされるトナー量を少なくできるので、クリーニングが簡単になり、かつクリーニングトナーの回収容器を小さい容器にできる。
【図面の簡単な説明】
【図１】 本発明にかかる負帯電性トナーの実施の形態の一例を模式的に示す図である。
【図２】 特許第２５３３０６７号公報に開示されているアルミナーシリカ複合酸化物微粒子を製造するためのバーナー装置である。
【図３】 表面分析装置による測定で得られたアルミナーシリカ複合酸化物微粒子に関するデータの１つを示す図である。
【図４】 表面分析装置による測定で得られたアルミナーシリカ複合酸化物微粒子に関するデータの他の１つを示す図である。
【図５】 本発明にかかる負帯電性トナーが使用される画像形成装置の非接触現像プロセスの一例を模式的に示す図である。
【図６】 本発明にかかる負帯電性トナーが使用される画像形成装置の接触現像プロセスの一例を模式的に示す図である。
【図７】 図５および図６に示す画像形成装置の有機積層型感光体を示す図である。
【図８】 本発明の負帯電性トナーによる作像試験に用いた非接触現像プロセスおよび接触現像プロセスによる４サイクル方式のフルカラープリンターの一例を示す図である。
【図９】 従来の負帯電性トナーにおける中抜け現象およびチリの発生を示す図である。
【符号の説明】
１,１４０…有機感光体、２…コロナ帯電器、３…露光、４…クリーニングブレード、５…転写ローラ、６…供給ローラ、７…規制ブレード、８…負帯電性トナー（一成分非磁性トナー）、８ａ…トナー母粒子、９…転写材または転写媒体、１０…現像器、１１…現像ローラ、１２…外添剤、１３…アルミナーシリカ複合酸化物微粒子、１４…導電性微粒子、１５ａ,１５ｂ…疎水性の負帯電性シリカ（ＳｉＯ₂）、Ｌ…現像ギャップ[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to the technical field of a one-component non-magnetic toner that is used in an image forming apparatus that forms an image by electrophotography or the like and develops an electrostatic latent image on a latent image carrier of the image forming apparatus. In particular, the present invention belongs to the technical field of negatively chargeable toner which is a one-component nonmagnetic toner obtained by adding at least a hydrophobic external additive to toner base particles.
[0002]
[Prior art]
Conventionally, as a toner used in an image forming apparatus, a two-component toner is generally known and enables relatively stable development. However, a change in the mixing ratio between the developer and the magnetic carrier is likely to occur. It is necessary to maintain it. Therefore, one-component nonmagnetic toner has been developed. As this one-component non-magnetic toner, although one-component magnetic toner has been developed, there is a problem that a clear color image cannot be obtained due to the opacity of the magnetic material. Therefore, a negatively chargeable toner, which is a one-component nonmagnetic toner, has been developed as a color toner.
[0003]
By the way, in the toner used in the image forming apparatus, a surface treatment for externally adding external additive fine particles to the toner base particles has been conventionally performed for the purpose of improving charging stability, fluidity, durability stability, and the like. It has been broken.
[0004]
Conventionally, as external additives for toner, silicon dioxide (silica), aluminum oxide (alumina), and titanium oxide (titania) having negative charging property that imparts negative polarity to toner base particles are used singly or in combination. It is known. In this case, each of the external additives is generally used in combination of a plurality of types rather than a single type in order to make use of their characteristics.
[0005]
However, even a toner using a combination of a plurality of types of external additives as described above has the following problems. That is,
(1) Since the toner has a particle size distribution, there is a toner charge amount distribution, and it is inevitable that a positively charged toner is contained even if it is a negatively chargeable toner. As a result, particularly in an image forming apparatus that forms an image by negative charge reversal development, the toner adheres to the non-image portion of the latent image carrier (photoconductor), so that the amount of toner used increases substantially and at the same time There is a problem that the cleaning load increases.
(2) Along with this, it is necessary to separately provide a large container for storing the cleaning toner recovered by cleaning the residual toner after the transfer of the photoreceptor and the intermediate transfer medium. Moreover, as a result of an increase in the amount of toner used, the running cost of consumables increases.
{Circle around (3)} In order to prevent toner deterioration, if a large amount of silica is added to maintain the fluidity of the toner, the fluidity is improved, but the fixability is lowered.
(4) When silica is increased, the negative charging ability of the toner becomes too high and the printed image density decreases. Therefore, titania and alumina with relatively low electric resistance are added. Generally, titania and alumina have a primary particle size. Therefore, when the number of printed sheets increases, the toner is buried in the toner base particles, and these effects cannot be exhibited.
(5) In order to obtain a good full color toner, it is required to suppress the occurrence of reverse transfer toner as much as possible.
[0006]
Accordingly, titanium oxide adhered to the toner base particles with spindle-shaped rutile type titanium oxide, using rutile type titanium oxide containing anatase type titanium oxide and having a treatment layer treated with a silane coupling agent as an external additive. In the toner base particles, the anatase-type titanium oxide, which has good affinity with the silane coupling agent, is used to obtain a uniform coating of the silane coupling agent on the toner base particles. JP-A-2000-128534 proposes that stable charging characteristics can be obtained without reducing tribocharging and preventing overcharging to improve environment dependency, fluidity and caking resistance. Yes. According to the toner disclosed in this publication, the above problems (1) to (5) can be solved to some extent.
[0007]
In addition, by adding rutile / anatase mixed crystal type titanium oxide to hydrophobic silica as an external additive for toner, the flowability of toner can be improved in full color images without impairing color reproducibility and transparency. Japanese Patent Laid-Open No. 2001-83732 proposes to obtain a stable triboelectric chargeability regardless of the humidity environment, and to prevent toner scattering and prevent toner from being fogged to non-image areas. The toners disclosed in this publication can also solve the problems (1) to (4) to some extent.
[0008]
On the other hand, Japanese Patent No. 2533067 discloses that alumina-silica composite oxide fine particles are used for toner, and the alumina-silica composite oxide fine particles have a function of increasing the cohesiveness of the toner.
[0009]
[Problems to be solved by the invention]
By the way, when the aforementioned rutile / anatase type titanium oxide is used as an external additive, it is possible to improve toner charging characteristics and toner fluidity. However, if rutile / anatase type titanium oxide is simply used, there are the following problems. That is,
(6) When a line image is printed and transferred, the toner in the central portion of the line image is not transferred as shown in FIG. There's a problem. In this hollow-out phenomenon, the balance between the toner fluidity and the cohesive force is lost, so that the central portion of the toner forming the developed line image on the photosensitive member remains on the photosensitive member, and both edges are transferred. It is a phenomenon that results. This void phenomenon is particularly likely to occur in jumping development with AC bias in a non-contact development method.
[0010]
On the other hand, when the above-mentioned alumina-silica composite oxide fine particles are simply used, there are the following problems due to the toner cohesiveness. That is,
{Circle around (7)} When there is a large amount of reverse transfer toner and the average charge amount of the toner is small, it is conceivable that dust appears in the peripheral portion of the transferred image as shown in FIG.
[0011]
The present invention has been made in view of such circumstances. The object of the present invention is to reduce fog toner and reverse transfer toner as much as possible and to further improve transfer efficiency. An object of the present invention is to provide a negatively chargeable toner capable of preventing dust and maintaining stable chargeability.
[0012]
[Means for Solving the Problems]
  In order to solve the above-mentioned problems, the negatively chargeable toner of the invention of claim 1 is a negatively chargeable toner obtained by at least externally adding a hydrophobic external additive to the toner base particles. As the agent, at least hydrophobic aluminum oxide-silicon dioxide composite oxide particles and conductive fine particles having a work function smaller than that of the aluminum oxide-silicon dioxide composite oxide particles are used.The conductive fine particles are any one of conductive silicon dioxide, conductive titanium oxide, and conductive aluminum oxide, and the amount of the aluminum oxide-silicon dioxide composite oxide particles is based on the toner base particles. 0 by weight . It is set to 1 wt% to 3 wt% or less, and two types of hydrophobic and negatively charged silicon dioxides having different particle diameters are used as the external additive. The average primary particle diameter of the aluminum oxide-silicon dioxide composite oxide particles is set to be between the average primary particle diameters of silicon, and the average primary particle diameters of these two types of silicon dioxide are the conductivity The average primary particle diameter of the fine particles is set smaller than the two, and the work functions of the two types of silicon dioxide are both smaller than the larger second work function of the aluminum oxide-silicon dioxide composite oxide particles, and It is set larger than the work function of the conductive fine particlesIt is characterized by that.
[0013]
  The invention of claim 2As the external additive, hydrophobic metal oxide fine particles having a work function substantially the same as the second work function of the hydrophobic aluminum oxide-silicon dioxide composite oxide particles are further used. The metal oxide fine particles Is rutile-anatase type titanium oxideIt is characterized by that.
[0014]
  Furthermore, the invention of claim 3The addition amount (weight) of the two types of silicon dioxide is set larger than the total addition amount (weight) of the aluminum oxide-silicon dioxide composite oxide particles and the conductive fine particles.It is characterized by that.
[0015]
  Furthermore, the invention of claim 4The addition amount (weight) of the two types of silicon dioxide is set larger than the total addition amount (weight) of the aluminum oxide-silicon dioxide composite oxide particles, the conductive fine particles, and the metal oxide fine particles.It is characterized by that.
[0019]
[Action]
In the negatively chargeable toner of the present invention configured as described above, the intrinsic characteristics of the toner having the hydrophobic conductive fine particles such as the negative overcharge preventing function and the toner fluidity improving function, and the alumina-silica composite The toner mother particles are given a function that is synergistic with the inherent property of the oxide fine particles, which is a function of improving the cohesiveness of the toner.
[0020]
As a result, the fluidity of the negatively chargeable toner is prevented from being lowered and the toner is prevented from being negatively overcharged. As a result, better negative charge characteristics can be obtained. The solid density at the time of image printing can be particularly effectively increased at the time of non-contact development without increasing the image quality so much.
[0021]
In addition, the flowability of the toner is improved and dust is prevented from being generated at the boundary between the line images, the sharpness of the image is improved, and the cohesion of the toner is improved, so that the void is at the center of the line image. Occurrence is suppressed. In particular, this void is particularly effectively prevented in jumping development by AC bias in a non-contact development method.
[0022]
Therefore, the negatively chargeable toner is more stable in negative charge for a longer period of time, and an image having sharpness is produced, and stable image quality in continuous printing can be obtained.
In addition, since the fluidity of the toner is improved, a uniform thin layer of toner is formed by the toner regulating member.
[0023]
Further, since the aluminum oxide-silicon dioxide composite oxide particles have a wide particle size distribution (for example, the primary particle size distribution is 7 nm to 80 nm and the average primary particle size is about 17 nm), this aluminum oxide-silicon dioxide. The composite oxide particles are less likely to be embedded in the toner base particles, and reliably adhere to the toner base particles. Thereby, the transfer efficiency is improved.
[0024]
  Further, the average primary particle diameter of the aluminum oxide-silicon dioxide composite oxide particles is set to be between the average primary particle diameters of the two types of hydrophobic silicon dioxide. The average primary particle size is set smaller than the average primary particle size of the conductive fine particles, and their work function is the same as that of the aluminum oxide-silicon dioxide composite oxide fine particles.The larger secondSince it is set smaller than the work function and larger than the work function of the conductive fine particles, these two types of silicon dioxide and the conductive fine particles are fixed to the surface of the toner base particles, and then the aluminum oxide-silicon dioxide composite The oxide particles adhere to the surface of the toner base particles in the form of adhering to hydrophobic silicon dioxide and conductive fine particles attached to the toner base particles.
[0025]
Further, by using hydrophobic metal oxide fine particles having a work function substantially the same as the second work function of the hydrophobic aluminum oxide-silicon dioxide composite oxide particles, not only the fluidity of the toner but also the implementation described later. As shown in the example, the charging characteristics can be stabilized.
[0026]
Accordingly, the inherent characteristics of the above-described aluminum oxide-silicon dioxide composite oxide particles and the inherent characteristics of the conductive fine particle particles are inherent to the negative charging function and fluidity improving function of the hydrophobic negatively charged silicon dioxide. A function having a synergistic characteristic is imparted to the toner base particles. Further, by adding the function of the hydrophobic metal oxide fine particles, the negatively chargeable toner is prevented from lowering its fluidity, and negative overcharge is prevented. As a result, the generation and fogging of the reverse transfer toner are further effectively suppressed.
[0027]
Further, the presence of a bending point in the work function of the aluminum oxide-silicon dioxide composite oxide particles causes the aluminum oxide-silicon dioxide composite oxide particles to have positive and negative friction sites. When the toner base particles come into contact with the positive friction site, the toner base particles are positively charged negatively. When the toner base particles come into contact with the negative friction site, the toner base particles are positively charged. Will be adjusted to an appropriate value.
[0028]
In this way, the negatively chargeable toner of the present invention is negatively charged by the positive friction sites of the aluminum oxide-silicon dioxide composite oxide particles and the negatively chargeable silicon dioxide, and further, the toner regulating member and the toner carrier The surface is more reliably negatively triboelectrically charged.
[0029]
In this case, the toner base particles are made of aluminum oxide-silicon dioxide composite oxide particles not only under low temperature and low humidity where charge release is small and easy to be negatively charged, but also under high temperature and high humidity where charge tends to be released and difficult to be negatively charged. Since the toner is negatively charged, the toner maintains a stable negative charging characteristic and also maintains a stable charging characteristic in continuous printing, so the print quality is not affected by the environment so much and does not change over a long period of time. It will be a thing.
[0030]
  Furthermore, since the addition amount (weight) of the two types of silicon dioxide is larger than the total addition amount (weight) of the aluminum oxide-silicon dioxide composite oxide particles, the conductive fine particles, and the metal oxide fine particles, it is assumed that one silicon dioxide is added. Aluminum oxide-silicon dioxide composite oxide particles even if the part is embedded in the toner base particles2nd work function with larger oneAnd metal oxide fine particlesofWork functionWhenIs larger than the work function of the two types of silicon dioxide, it is firmly fixed to the toner base particles via these two types of silicon dioxide, and is less likely to be released from the toner base particles. Therefore, the negatively charged toner of the present invention becomes stable in charging over a long period of time.
[0031]
Further, regardless of whether the toner is a pulverized toner or a polymerized toner, it is difficult to uniformly charge the toner layer when the toner particle size is reduced. Aluminum oxide-silicon dioxide composite oxidation having an average primary particle size set to be between the average primary particle sizes of two types of silicon dioxide and having positive and negative friction sites The coexistence of the physical particles makes it possible to uniformly charge the regulated toner layer and to reduce the amount of positively charged toner having a reverse polarity.
[0032]
As a result, the amount of fog toner and reverse transfer toner on the photoreceptor is reduced, and the transfer efficiency is further improved. Further, since the transfer efficiency is improved, the amount of toner to be cleaned on the photosensitive member and the intermediate transfer medium is reduced, so that cleaning becomes simple and a cleaning toner collecting container can be a small container.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram schematically illustrating an example of an embodiment of a negatively chargeable toner according to the present invention.
As shown in FIG. 1, the negatively chargeable toner 8 in this example is a one-component nonmagnetic toner, and is configured by externally adding an additive 12 to toner base particles 8a. The external additive 12 includes hydrophobic aluminum oxide (alumina; Al₂O_Three) -Silicon dioxide (silica; SiO₂) Composite oxide particles (hereinafter referred to as alumina-silica composite oxide fine particles) 13, conductive fine particles 14 having a work function smaller than that of the toner base particles 8 a and the alumina-silica composite oxide fine particles 13; The average primary particle diameter of the alumina-silica composite oxide particles is set between the average primary particle diameters of the two types of silicon dioxide, and the work function is determined from the toner base particles 8a and the alumina-silica composite oxide fine particles 13. Two types of hydrophobic negatively charged silicon dioxide (negatively charged silica; SiO₂) 15a and 15b are used.
[0034]
Since the work functions of the hydrophobic negatively chargeable silicas 15a and 15b are smaller than those of the toner base particles 8a, the alumina-silica composite oxide fine particles 13 and the metal oxide fine particles 16, the negatively chargeable silica as shown in FIG. 15a and 15b and the conductive fine particles 14 adhere to the toner base particles 8a, and then the negatively charged silica 15a and 15b are bonded to the alumina-silica composite oxide fine particles 13 having a work function larger than these negatively charged silicas 15a and 15b. The metal oxide fine particles 16 adhere to the toner base particles 8a in contact with each other.
[0035]
In the negatively charged toner 8 of this example, the toner base particles 8a are given negative chargeability by hydrophobic negatively chargeable silicas 15a and 15b having a work function smaller than that of the toner base particles 8a. Further, the metal oxide fine particles having a work function which is larger than the work function of the toner base particles 8a or substantially the same as the work function of the toner base particles 8a (the work function difference is within 0.25 eV) and the conductivity is small. By mixing and using the fine particles 14, the toner base particles 8 a are prevented from being overcharged, and the toner fluidity is improved and relatively negative negatively charged toner adheres to the boundary of the line image. Chile to prevent is prevented. Further, by mixing and using the alumina-silica composite oxide fine particles 13, the cohesiveness of the toner is improved, and voids that occur when the toner is not transferred at the center of the line image are prevented.
[0036]
The work function (Φ) is measured by a surface analyzer {AC-2 type, manufactured by Riken Keiki Co., Ltd.) at an irradiation light amount of 500 nW, and is an energy necessary for taking out electrons from the substance. The smaller the work function, the easier it is to emit electrons, and the larger the work function, the harder it is to emit electrons. Therefore, when a substance with a small work function is brought into contact with a substance with a large work function, a substance with a small work function is positively charged, while a substance with a large work function is negatively charged, but the work function itself takes out electrons from the substance. Therefore, the energy (eV) is quantified.
[0037]
The toner base particles 8a used in the negatively chargeable toner 8 of this example configured as described above can be produced by either a pulverization method or a polymerization method, but the toner base particles used for full color are preferably used. It is good to make by a polymerization method. Hereinafter, the production of the toner base particles 8a will be described.
[0038]
First, production of a negatively chargeable toner (hereinafter referred to as a pulverized toner) 8 using toner base particles 8a by a pulverization method will be described.
The pulverized toner 8 is obtained by uniformly mixing a resin binder with a pigment (colorant), a release agent, and a charge control agent with a Henschel mixer, melting and kneading with a biaxial extruder, and after cooling, coarse pulverization-fine pulverization step Then, an external additive 12 is further externally added to the toner base particles 8 a obtained by the classification process to obtain a negatively charged toner 8.
[0039]
As the binder resin, a known toner resin can be used, for example, polystyrene, poly-α-methylstyrene, chloropolystyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer. Polymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-acrylic acid ester- Styrene or a styrene-substituted product is obtained with a styrene resin such as a methacrylic acid ester copolymer, a styrene-α-chloroacrylic acid methyl copolymer, a styrene-acrylonitrile-acrylic acid ester copolymer, or a styrene-vinyl methyl ether copolymer. Containing homopolymer or copolymer, poly Ester resin, epoxy resin, urethane modified epoxy resin, silicone modified epoxy resin, vinyl chloride resin, rosin modified maleic acid resin, phenyl resin, polyethylene, polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl acrylate Polymers, xylene resins, polyvinyl butyral resins, terpene resins, phenol resins, aliphatic or alicyclic hydrocarbon resins, and the like can be used alone or in combination. In particular, in the present invention, styrene-acrylic acid ester resins, styrene-methacrylic acid ester resins, polyester resins, and epoxy resins are preferable. In the present invention, the binder resin preferably has a glass transition temperature of 50 ° C to 75 ° C and a flow softening temperature of 70 ° C to 150 ° C.
[0040]
As the colorant, a known toner colorant can be used. For example, carbon black, lamp black, magnetite, titanium black, chrome yellow, ultramarine blue, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa Yellow G, rhodamine 6G, calco oil blue, quinacridone, benzidine yellow, rose bengal, malachite green lake, Quinoline Yellow, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 184, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 180, C.I. I. Solvent Yellow 162, C.I. I. Pigment blue 5: 1, C.I. I. Dye and pigment such as CI Pigment Blue 15: 3 can be used alone or in combination.
[0041]
As the release agent, a known toner release agent can be used. Examples thereof include paraffin wax, micro wax, micro crystallin wax, cadilla wax, carnauba wax, rice wax, montan wax, polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax and the like. Among these, it is preferable to use polyethylene wax, polypropylene wax, carnauba wax, ester wax and the like.
[0042]
As the charge adjusting agent, a known toner charge adjusting agent can be used. For example, oil black, oil black BY, Bontron S-22 (manufactured by Orient Chemical Industries, Ltd.), Bontron S-34 (manufactured by Orient Chemical Industries, Ltd.), salicylic acid metal complex E-81 (Orient Chemical Industries, Ltd.) Manufactured), thioindigo pigment, sulfonylamine derivative of copper phthalocyanine, Spiron Black TRH (manufactured by Hodogaya Chemical Co., Ltd.), calixarene compound, organic boron compound, fluorine-containing quaternary ammonium salt compound, monoazo metal complex, Aromatic hydroxyl carboxylic acid metal complexes, aromatic dicarboxylic acid metal complexes, polysaccharides and the like can be mentioned. Of these, colorless or white toners are preferred for color toners.
[0043]
The component ratio (weight ratio) in the pulverized toner 8 is shown in Table 1.
[0044]
[Table 1]

[0045]
As shown in Table 1, with respect to 100 parts by weight of the binder resin, the colorant is 0.5 to 15 parts by weight, preferably 1 to 10 parts by weight, and the release agent is 1 to part by weight. 10 parts by weight, preferably 2.5 parts by weight to 8 parts by weight, and the charge control agent is 0.1 parts by weight to 7 parts by weight, preferably 0.5 parts by weight to 5 parts by weight.
[0046]
In the pulverized toner 8 of this example, the circularity is increased by the spheroidizing process for the purpose of improving the transfer efficiency. In order to increase the circularity of the pulverized toner 8,
(A) In a pulverization step, if a relatively round spherical device capable of being pulverized, for example, a turbo mill known as a mechanical pulverizer (manufactured by Kawasaki Heavy Industries, Ltd.), the circularity can reach 0.93.
Or
(B) If the pulverized toner is used with a commercially available hot-air spheronizer surfing system SFS-3 type (manufactured by Nippon Pneumatic Industry Co., Ltd.), the circularity can be up to 1.00.
[0047]
The desirable circularity (spheroidizing coefficient) of the pulverized toner 8 in this example is 0.91 or more, and thereby good transfer efficiency can be obtained. Then, the circularity can be cleaned by using a cleaning blade up to 0.97 and by using brush cleaning at higher than that.
[0048]
Further, the pulverized toner 8 thus obtained has an average particle diameter (D) which is 50% diameter based on the number.₅₀) Is set to 9 μm or less, preferably 4.5 μm to 8 μm. As a result, the particle diameter of the pulverized toner 8 becomes a relatively small particle diameter. Hydrophobic negatively chargeable silicas 15a and 15b and hydrophobic alumina-silica composite oxide fine particles 13 as external additives are added to the small particle diameter toner. In addition, by using together with the conductive fine particles 14, the amount of hydrophobic negatively chargeable silica can be made smaller than the amount of hydrophobic negatively chargeable silica when conventional silica fine particles are used alone. , Fixability is improved.
In the present invention, the average particle diameter and the circularity of the toner particles and the like are values measured with an FPIA 2100 manufactured by Sysmex Corporation.
[0049]
Further, in this pulverized toner 8, the total amount (weight) of the external additive 12 is set to 0.5 wt% (wt%) or more and 4.0 wt% or less with respect to the weight of the toner base particles 8a. However, it is preferable to set it in the range of 1.0% by weight to 3.5% by weight. Thereby, when the pulverized toner 8 is used as a full color toner, an effect of suppressing the generation of the reverse transfer toner can be exhibited. When the total amount of the external additive 12 is 4.0% by weight or more, it becomes free from the toner surface or deteriorates the fixing property.
[0050]
Next, production of a negatively chargeable toner (hereinafter referred to as polymerization method toner) 8 using toner mother particles 8a by polymerization method will be described.
Examples of the polymerization toner 8 include suspension polymerization, emulsion polymerization, and dispersion polymerization. In the suspension polymerization method, a mixture in which a polymerizable monomer (monomer), a color pigment, and a release agent are further added, if necessary, a dye, a polymerization initiator, a crosslinking agent, a charge control agent, and other additives. Is added to the aqueous phase containing the suspension stabilizer (water-soluble polymer, poorly water-soluble inorganic substance) with stirring, granulated and polymerized to obtain a desired composition. Colored polymerized toner particles having a particle size can be formed.
[0051]
In the emulsion polymerization method, if necessary, a polymerization initiator, an emulsifier (surfactant) and the like are further dispersed in water to carry out the polymerization, if necessary, and then a colorant and a charge control agent in the aggregation process. Colored toner particles having a desired particle size can be formed by adding a flocculant (electrolyte) and the like.
In the materials used for the production of the polymerization toner, the same materials as those of the above pulverized toner can be used for the colorant, release agent, charge control agent, and fluidity improver.
[0052]
As the polymerizable monomer (monomer), known vinyl monomers can be used. For example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene. , P-ethylstyrene, vinyltoluene, 2,4-dimethylstyrene, pn-butylstyrene, p-phenylstyrene, p-chlorostyrene, divinylbenzene, methyl acrylate, ethyl acrylate, propyl acrylate, acrylic acid n-butyl, isobutyl acrylate, n-octyl acrylate, dodecyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, methyl methacrylate, ethyl methacrylate , Methacrylate Pill, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, hydroxyethyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, acrylic acid, methacrylic acid, maleic acid, Fumaric acid, cinnamic acid, ethylene glycol, propylene glycol, maleic anhydride, phthalic anhydride, ethylene, propylene, butylene, isobutylene, vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propyleneate, Examples include acrylonitrile, methacrylonitrile, vinyl methyl ether, vinyl ethyl ether, vinyl ketone, vinyl hexyl ketone, and vinyl naphthalene. Examples of fluorine-containing monomers include 2,2,2-trifluoroethyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, vinylidene fluoride, ethylene trifluoride, tetrafluoroethylene, and trifluoropropylene. Can be used because fluorine atoms are effective for negative charge control.
[0053]
Known emulsifiers (surfactants) can be used. For example, sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, potassium stearate, calcium oleate, dodecyl ammonium chloride, dodecyl ammonium bromide, dodecyl trimethyl ammonium bromide, dodecyl pyridinium chloride Hexadecyl trimethyl ammonium bromide, dodecyl polyoxyethylene ether, hexadecyl polyoxyethylene ether, lauryl polyoxyethylene ether, sorbitan monooleate polyoxyethylene ether, and the like.
[0054]
A well-known thing can be used as a polymerization initiator. For example, potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, 4,4′-azobiscyanovaleric acid, t-butyl hydroperoxide, benzoyl peroxide, 2,2′-azobis-isobutyronitrile, etc. is there.
[0055]
As the flocculant (electrolyte), known ones can be used. Examples thereof include sodium chloride, potassium chloride, lithium chloride, magnesium chloride, calcium chloride, sodium sulfate, potassium sulfate, lithium sulfate, magnesium sulfate, calcium sulfate, zinc sulfate, aluminum sulfate, and iron sulfate.
[0056]
Table 2 shows the component ratio (weight) of the emulsion polymerization toner 8.
[0057]
[Table 2]

[0058]
As shown in Table 2, with respect to 100 parts by weight of the polymerizable monomer, the polymerization initiator is 0.03 part by weight to 2 parts by weight, preferably 0.1 part by weight to 1 part by weight. 0.01 part by weight to 0.1 part by weight, the mold release agent is 1 part by weight to 40 parts by weight, preferably 2 parts by weight to 35 parts by weight, and the charge control agent is 0.1 part by weight. -7 parts by weight, preferably 0.5-5 parts by weight, the colorant is 1-20 parts by weight, preferably 3-10 parts by weight, and the flocculant (electrolyte) is 0.05 to 5 parts by weight, preferably 0.1 to 2 parts by weight.
[0059]
Even in the polymerization method toner 8 in this example, the circularity is increased by the spheroidizing process for the purpose of improving the transfer efficiency. As a method of adjusting the circularity of the polymerization toner 8,
(A) In the emulsion polymerization method, the degree of circularity can be freely changed by controlling the temperature and time during the aggregation process of secondary particles, and the range thereof is 0.94 to 1.00.
Also,
(B) In the suspension polymerization method, since a true spherical toner is possible, the circularity is in the range of 0.98 to 1.00. In addition, the degree of circularity can be freely adjusted from 0.94 to 0.98 by heating and deforming at a temperature equal to or higher than the Tg temperature of the toner in order to adjust the degree of circularity.
[0060]
The polymerization toner 8 can be prepared by a dispersion polymerization method other than the above method, for example, by the method disclosed in JP-A-63-304002. In this case, since the shape is close to a true sphere, in order to control the shape, for example, pressurization can be performed at a temperature equal to or higher than the Tg temperature of the toner to obtain a desired toner shape.
[0061]
As in the case of the pulverized toner 8 described above, the desirable circularity (spheroidizing coefficient) of the polymerization toner 8 in this example is 0.95 or more, and until the circularity is 0.97, it is further increased by a cleaning blade. Then, it can clean by using brush cleaning together.
[0062]
Also in the polymerization toner 8 thus obtained, the average particle diameter (D₅₀) Is set to 9 μm or less, preferably 4.5 μm to 8 μm. As a result, the particle diameter of the polymerization toner 8 becomes a relatively small particle diameter. Hydrophobic negatively chargeable silicas 15a and 15b, hydrophobic conductive fine particles 14 and alumina as an external additive 12 are added to the small particle diameter toner. By using together with the silica composite oxide fine particles 13, the amount of the hydrophobic negatively chargeable silica 15a, 15b is made smaller than the amount of the hydrophobic negatively chargeable silica when the conventional silica fine particles are used alone. Therefore, the fixing property is improved.
Also in the case of the polymerization toner 8, the average particle diameter and the circularity of the toner particles and the like are values measured by an FPIA 2100 manufactured by Sysmex Corporation.
[0063]
Further, even in this polymerization toner 8, the total amount (weight) of the external additive 12 is 0.5% by weight or more and 4.0% by weight with respect to the weight of the toner base particles 8a, as in the above-mentioned pulverization toner. %, But preferably it is set in the range of 1.0% to 3.5% by weight. Thereby, when the polymerization toner 8 is used as a full color toner, an effect of suppressing the generation of the reverse transfer toner can be exhibited. If the external additive 12 is added in a total amount of 4.0% by weight or more, it may be scattered from the toner surface or the fixing property may be deteriorated.
[0064]
The alumina-silica composite oxide fine particles 13 as the external additive 12 are used for the purpose of stabilizing charging characteristics and improving fluidity in dry toners. The alumina-silica composite oxide fine particles 13 can be prepared, for example, by a method for producing a silicon-aluminum composite oxide fine powder disclosed in Japanese Patent No. 2533067. The production process in the manufacturing method disclosed in this patent publication will be described below.
(1) Evaporate silicon halide and aluminum halide, and uniformly mix each vapor with air, oxygen and hydrogen in a composite unit together with a carrier gas.
(2) Next, the obtained composite vapor is supplied to a burner to cause a reaction in the combustion chamber in the combustion chamber, and the obtained gas and solid are cooled in a heat exchange unit.
(3) The gas is separated from the solid, and the halide residue adhering to the product is removed by heat treatment using moist air, whereby alumina-silica composite oxide fine particles 13 are obtained.
[0065]
FIG. 2 shows a burner device for producing alumina-silica composite oxide fine particles disclosed in the aforementioned Japanese Patent No. 2533067. In the figure, 101 is a combustion chamber, 102 is a double jacket tube, 103 is an annular diaphragm, 104 is an inner tube, 105 is an outer tube, and 106 is a water cooling tube.
[0066]
A double jacket tube 102 projects from the combustion chamber 101, and hydrogen 1.4 Nm from the inner tube 104 of the double jacket tube 102.^Three/ H, air 5.5 Nm^Three/ H and pre-evaporated gaseous SiCl_FourA 200 ° C. hot mixed steam mixed at a rate of 1.30 kg / h was introduced and then gaseous AlCl previously evaporated at 300 ° C. into this hot mixed steam_ThreeIt is additionally supplied at a rate of 2.34 kg / h and is introduced into the pipe and additionally air is 12 Nm.^Three/ H is supplied and burned. At this time, air is introduced into the combustion chamber 101 and air is additionally introduced from the annular diaphragm 103. In the soot, an abrupt reaction between the generated water and chloride occurs, and alumina-silica composite oxide fine particles are formed. After passing through the tub, the resulting powder is separated using a filter or cyclone and the hydrochloric acid adhering to the powder is removed. The composition of the resulting alumina-silica composite oxide fine particles is Al₂O_Three65% by weight, SiO₂35% by weight, primary average particle size is 14 nm, BET specific surface area is 74 m²/ G, volume resistivity 10¹²Ω · cm. The obtained alumina-silica composite oxide fine particles are hydrophobized with dimethylsilane (DMS).
[0067]
Alumina in the alumina-silica composite oxide fine particles 13 (Al₂O_Three) And silica (SiO₂)) Is appropriately adjusted depending on the reaction conditions such as the supply amount of silicon halide and aluminum halide, the supply amount of hydrogen, the supply amount of silicon halide and aluminum halide, the supply amount of hydrogen, the supply amount of air, and the like.
[0068]
Al in alumina-silica composite oxide fine particles 13₂O_ThreeAnd SiO₂The weight ratio of₂O_ThreeContent of 55 wt% to 85 wt%, SiO₂The content of can be in the range of 45 wt% to 15 wt%. In addition, the alumina-silica composite oxide fine particles 13 are made into an amorphous structure by being granulated in a cage, have a sufficient fine particle property, and have a specific surface area of 20 m by the BET method.²/ G-200m²/ G. Furthermore, the primary particle diameter of the alumina-silica composite oxide fine particles 3 is 7 nm to 80 nm, preferably 10 nm to 40 nm, and 20 nm or more is 30% or more on a number basis. Further, the alumina-silica composite oxide fine particles 13 are added at a ratio of 0.1% to 3% by weight, preferably 0.2% to 2% by weight, based on the amount of the toner base particles 8a. Good. Since the alumina-silica composite oxide fine particles 13 have a broad particle size distribution, it is possible to prevent the external additive 12 particles from being embedded in the toner base particles 8a in continuous printing even when added in a small amount. In addition, the transfer efficiency can be improved by the large particle diameter portion of the alumina-silica composite oxide fine particles 13 and the large particle diameter portion is not too large. Can be prevented.
[0069]
Further, the alumina-silica composite oxide fine particles 13 of the negatively chargeable toner 8 of this example have a first work function in the range of 5.0 eV to 5.4 eV and a second work function in the range of 5.4 eV to 5.7 eV. The work function of the toner base particles 8a is 5.3 eV to 5.65 eV, which is larger than the first work function of the alumina-silica composite oxide fine particles 13, and shows two work functions. The work function is set smaller than 2.
[0070]
An example of the work function of the alumina-silica composite oxide fine particles 13 will be described with reference to data obtained by measurement using the aforementioned surface analyzer. The data regarding the alumina-silica composite oxide fine particles 13 obtained by the measurement by the surface analyzer are shown in FIGS.
[0071]
In the surface analyzer described above, the excitation energy of monochromatic light is scanned from low to high, and the energy (work function) at which photoelectron emission starts is measured. Work function data is plotted on the horizontal axis. It is obtained from the relationship between the excited energy (Photon Energy) and the normalized photoelectron yield (Emmission Yield) taken on the vertical axis.
[0072]
That is, the alumina-silica composite oxide fine particles 13 have an excitation energy of 5.18 eV at the inflection point (A) as shown in FIG. 3 in terms of the work function between the excitation energy and the normalized photoelectron yield. The excitation energy at the bending point (B) is 5.62 eV, as shown in FIG. The alumina-silica composite oxide fine particles 13 have a large work function difference as compared with the simple mixed oxide particles of alumina and silica, and two positive and negative triboelectric charges are added to the toner base particles 8a. It turns out that the site is easy to give. The detailed reason is unknown, but the alumina-silica composite oxide fine particles 13 are made of SiO.₂Particles and Al₂O_ThreeThis is thought to be due to the fact that it is not a simple mixture with particles.
[0073]
When the toner base particles 8a come into contact with the positive triboelectric charging sites in the alumina-silica composite oxide fine particles 13, the toner particles are surely negatively charged as compared with the mere mixture particles to reduce the positively charged toner. Can do. Further, when the toner base particles 8a come into contact with the negative frictional charging site, the excessive negative charging property of the toner particles can be suppressed, so that a stable negative charging toner can be obtained.
[0074]
The alumina-silica composite oxide fine particles 13 change the evaporation amounts of silicon halide and aluminum halide according to the purpose, and in the mixing unit together with air, oxygen and hydrogen together with the carrier gas as described above. It can be obtained by mixing uniformly and hydrolyzing in the straw, but by controlling the production conditions, the first and second work functions can be controlled, and the range of 5.0 eV to 5.4 eV as described above The first work function and the second work function type work function in the range of 5.4 eV to 5.7 eV can be shown.
[0075]
Further, the negatively chargeable toner 13 of this example is larger than the work function of the alumina-silica composite oxide fine particles 13 together with the alumina-silica composite oxide fine particles 13 as the external additive 12 as described above, and the toner base particles 8a. Metal oxide fine particles 16 having a work function that is the same as or substantially the same as the work function are used. The metal oxide fine particles 16 include rutile anatase type titanium oxide (work function 5.64 eV), rutile type titanium oxide (work function 5.61 eV), anatase type titanium oxide (work function 5.64 eV), strontium titanate ( TiO_ThreeSr; work function 5.62 eV) can be used.
[0076]
Further, conductive fine particles 14 having a work function smaller than the work function of the alumina-silica composite oxide fine particles 13 and smaller than the work function of the toner base particles 8a are used. As the conductive fine particles 14, conductive silicon dioxide, conductive titanium oxide, conductive aluminum oxide, conductive zinc oxide, conductive tin oxide, or the like can be used. )
[0077]
In that case, hydrophobic rutile-anatase-type titanium oxide, conductive titanium oxide and conductive oxidation are used to improve the fluidity of the toner to eliminate dust and to form a uniform thin layer by the toner regulating member of the developing device. Aluminum is preferred.
[0078]
This rutile-anatase type titanium oxide is made of rutile-type titanium oxide and anatase-type titanium oxide in a predetermined mixed crystal ratio. For example, the rutile-anatase type titanium oxide should be produced by the production method disclosed in the above-mentioned JP-A-2000-128534. Can do. This hydrophobic rutile-anatase-type titanium oxide (indicated by reference numeral 14 in FIG. 1) has a spindle shape, the major axis diameter is 0.02 μm to 0.10 μm, and the major axis and minor axis diameters. The ratio is set to 2-8. In the case of this rutile-anatase type titanium oxide, the minor axis diameter of the rutile-anatase type titanium oxide is set between the average primary particle diameters of the negatively chargeable silicas 15a and 15b.
[0079]
As described above, by using the conductive fine particles 14 having a work function smaller than that of the alumina-silica composite oxide fine particles 13 together with the alumina-silica composite oxide fine particles 13, the charge charged on the toner base particles 8a is released to adjust the charge. In addition, overcharging can be prevented. That is, if too much alumina-silica composite oxide fine particles 13 are added, the silica component of the alumina-silica composite oxide fine particles functions as a negatively charged site, so that the toner is negatively overcharged and the image density decreases. However, by adding the conductive fine particles 14 together with the alumina-silica composite oxide fine particles 13, overcharging of the toner base particles 8 a can be prevented.
[0080]
Further, of the two types of hydrophobic negatively chargeable silicas 15a and 15b used as the external additive 12, one negatively chargeable silica 15a has an average primary particle diameter of 20 nm or less, preferably 7 nm to 16 nm. The average primary particle diameter of the other negatively chargeable silica 15b is set to 30 nm or more, preferably 40 nm to 50 nm.
[0081]
Further, in the negatively chargeable toner 8 of the present invention, as the external additive 12, in addition to the above-mentioned alumina-silica composite oxide fine particles 13 and the above-mentioned conductive fine particles 14, other external additives are added as necessary. You can also For example, as other external additives, magnesium fluoride, silicon carbide, boron carbide, titanium carbide, zirconium carbide, boron nitride, titanium nitride, zirconium nitride, magnetite, molybdenum disulfide, aluminum stearate, magnesium stearate, stearic acid Fine particles of zinc, calcium stearate, barium titanate, and silicon metal salt can be used. Examples of other resin fine particles include acrylic resin, styrene resin, and fluororesin.
[0082]
The particles of the external additive 12 are preferably used after being hydrophobized with a silane coupling agent, a titanium coupling agent, a higher fatty acid, silicone oil or the like. Examples of the hydrophobizing agent include dimethyldichlorosilane, octyltrimethoxysilane, hexamethyldisilazane, silicone oil, octylutecrochlorosilane, decylutetrichlorosilane, nonirute trichlorosilane, and (4-iso-propylphenyl). -Trichlorosilane, dihexyl dichlorosilane, (4-t-butylphenyl) -trichlorosilane, dipentyl-dichlorosilane, dihexyl-dichlorosilane, dioctyl-dichlorosilane, dinonyl-dichlorosilane, didecyl-dichlorosilane, di-2-ethylhexyl-dichlorosilane, Di-3,3-dimethylpentyl-dichlorosilane, trihexyl-chlorosilane, trioctyl-chlorosilane, tridecyl-chlorosilane, dioctyl-methyl-chlorosilane, octyl- Examples thereof include dimethyl-chlorosilane and (4-iso-propylphenyl) -diethyl-chlorosilane.
[0083]
In the negatively chargeable toner 8 of the present invention, as described above, the addition amount of the alumina-silica composite oxide fine particles 13 with respect to the toner base particles 8a is 0.1 wt% to 3 wt%, preferably 0.2. % To 2% by weight. The amount of the conductive fine particles 14 added to the toner base particles 8a is 0.05% by weight to 1.5% by weight, preferably 0.1% by weight to 1.0% by weight. Further, the amount of all external additives 12 particles added to the toner base particles 8a is 0.5% to 5% by weight, preferably 1% to 4% by weight.
[0084]
Further, in the negatively chargeable toner 8 of the present invention, the toner base particles 8a in the toner particles to which the alumina-silica composite oxide fine particles 13 are externally added have a work function of 5.3 eV to 5.7 eV, preferably 5.4 eV. The work function of the toner base particles 8a is larger than the first work function of the alumina-silica composite oxide fine particles 13, and the second work of the alumina-silica composite oxide fine particles 13 is .about.5.65 eV. It is characterized by setting it to be smaller than the function. As a result, it has been found that fog can be further reduced and transfer efficiency can be further improved. If the work function of the toner base particles 8a is not between the two types of work functions of the alumina-silica composite oxide fine particles 13, the cleaning is performed as compared with the case of being between the two types of work functions as in the present invention. Toner increases.
[0085]
The toner base particles 8a and the external additive 12 are introduced into a known complex machine such as the above-mentioned Henschel mixer, V-type blender, reverse mixer, high speed mixer, cyclomix, axial mixer, etc. Thus, the 12 particles of the external additive are attached and the negatively chargeable toner 8 of the present invention is obtained.
[0086]
The work function of the negatively chargeable toner 8 obtained in this manner is 5.35 eV to 5.8 eV, preferably 5.4 eV to 5.75 eV. In addition, by making the work function of the negatively chargeable toner 8 larger than the work function of the surface of the image carrier, the fog can be further reduced and the transfer efficiency can be further improved. Further, if the work function of the negatively chargeable toner 8 is made smaller than the work function of the surface of the image carrier, the amount of charge decreases when the toner thin layer is regulated on the developing roller by the toner regulating member, and the phenomenon of “insufficient charging” may occur. However, by setting each work function as in the present invention, this “overcharge” phenomenon can be suppressed.
[0087]
The negatively chargeable toner 8 of the present invention has a number-based average particle size of 5 μm to 10 μm, preferably 6 μm to 9 μm in the pulverized toner, and the number of toner in the polymerized toner. 50% particle size (D₅₀) Is 8 μm or less, preferably 4.5 μm to 8 μm, 3 μm or less is 10% or less, and preferably has a particle size distribution of 5% or less.
[0088]
In general, if the toner particle diameter is reduced regardless of whether the toner is a pulverized toner or a polymerized toner, it is necessary to increase the amount of silica particles added, and there is a problem that the charge amount of the toner becomes too large at the initial stage. As printing progresses, the effective surface amount of silica particles decreases due to embedding or scattering, the toner charge amount decreases, the image density variation and fogging amount increase, and the toner consumption tends to increase. Has a problem that it is difficult to use. On the other hand, when the alumina-silica composite oxide fine particles 13 are used as the external additive 12, the particle size distribution is broad, and problems such as burying of the external additive 12 particles can be suppressed. Since the difference between the first work function and the second work function can be increased, a stable negatively chargeable toner can be obtained throughout the printing period.
[0089]
Further, the negatively chargeable toner 8 of the present invention may have a circularity (spheroidization coefficient) of 0.94 or more, preferably 0.95 or more, in both the pulverization method and the polymerization method. . Up to circularity (spheroidizing coefficient) of 0.97 is preferably used with a cleaning blade, and above that with brush cleaning. By setting the circularity (spheroidizing coefficient) to 0.94 or more, transfer efficiency can be improved.
[0090]
In the negatively chargeable toner 8 of this example configured as described above, in both the polymerization toner and the pulverization toner, the hydrophobic negatively chargeable silica having a small particle diameter and the conductive fine particles 14 become toner base particles 8a. Adhere to. The hydrophobic alumina-silica composite oxide fine particles 13 and the hydrophobic metal oxide fine particles 16 having a work function larger than the work function of the hydrophobic negatively-charged silica 13 are respectively transferred to the toner base particles 8a by a contact potential difference due to the work function difference. It is less likely to adhere to the adhered negatively chargeable silica 13 and be released from the toner base particles 8a. Therefore, the surface of the toner base particles 8 a is covered evenly with the hydrophobic alumina-silica composite oxide fine particles 13, the hydrophobic metal oxide fine particles 16, the hydrophobic negatively chargeable silicas 15 a and 15 b and the conductive fine particles 14. Become.
[0091]
Therefore, the charge adjusting function of the conductive particles 14 having a relatively low electric resistance (eg, conductive titanium oxide 41.8 Ω · cm) can be utilized more effectively, and the alumina-silica composite oxide particles 13 The toner aggregation function can be utilized more effectively.
In other words, the intrinsic characteristics of the toner negatively charging function and the toner fluidity improving function of the hydrophobic negatively charged silicas 15a and 15b, the negative overcharge preventing function of the conductive fine particles 14 and the improvement of the toner fluidity. The toner base particle 8a can be provided with a function in which the characteristic characteristic of the function and the characteristic characteristic of the alumina-silica composite oxide fine particle 13 have the characteristic of improving the cohesiveness of the toner.
[0092]
As a result, the fluidity of the negatively chargeable toner 8 can be prevented from being lowered and negative overcharge can be prevented, so that better negative charge characteristics can be obtained. As a result, the occurrence of reverse transfer toner and fogging can be achieved. Can be effectively suppressed. In addition, the above-described dust generated at the boundary of the line image can be prevented by improving the fluidity of the toner, the sharpness of the image can be improved, and the aggregation property of the toner can be improved to be generated at the center of the line image. Can be prevented.
Therefore, the negatively chargeable toner 8 can be stable for a long period of time, and can provide stable image quality in continuous printing having sharpness without causing voids.
[0093]
FIG. 5 is a diagram schematically showing an example of a non-contact one-component developing system using the negatively chargeable toner 8 of this example, and FIG. 6 is a single contact component using the negatively chargeable toner 8 of this example. It is a figure which shows an example of a developing system typically. 5 and 6, 1 is an organic photoconductor as an image carrier, 2 is a corona charger, 3 is exposure, 4 is a cleaning blade, 5 is a transfer roller, 6 is a supply roller, 7 is a regulating blade, and 8 is Negatively chargeable toner, 9 is a transfer material, 10 is a developing device, 11 is a developing roller, and L is a developing gap in a non-contact one-component developing process.
[0094]
The organic photoreceptor 1 may be an organic single layer type in which the organic photosensitive layer is a single layer or an organic laminated type in which the organic photosensitive layer is a multilayer.
As shown in FIG. 7A, the organic multi-layer photosensitive body 1 is formed by sequentially laminating a photosensitive layer composed of a charge generation layer 1c and a charge transport layer 1d on a conductive support 1a via an undercoat layer 1b. Is.
[0095]
As the conductive support 1a, a known conductive support can be used.^TenConductives having a conductivity of Ω · cm or less, for example, tubular materials obtained by cutting aluminum alloys, tubular materials obtained by depositing aluminum on a polyethylene terephthalate film or imparting conductivity by a conductive paint, conductive polyimide resins It can form from the tubular thing formed by forming. Examples of other shapes include belt-like, plate-like, and sheet-like supports, and examples of other materials and shapes include metal belts that are seamlessly made of nickel electroformed tubes and stainless steel tubes. It can be preferably used.
[0096]
As the undercoat layer 1b provided on the conductive support 1a, a known undercoat layer can be used. For example, the undercoat layer 1b is provided for the purpose of improving adhesion, preventing moire, improving the coatability of the upper charge generation layer 1c, and reducing the residual potential during exposure. The resin used for the undercoat layer 1b is preferably a resin having a high resistance to dissolution with respect to the solvent used for the photosensitive layer because a photosensitive layer having the charge generation layer 1c is applied thereon. Usable resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as vinyl acetate, copolymer nylon, and methoxymethylated nylon, polyurethane, melamine resin, and epoxy resin. It can be used alone or in combination of two or more. These resins may contain conductive fine particles such as titanium dioxide and zinc oxide.
[0097]
A known material can be used as the charge generation pigment in the charge generation layer 1c. For example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, azulenium salt pigments, squaric acid methine pigments, azo pigments having a carbazole skeleton, azo pigments having a triphenylamine skeleton, azo pigments having a diphenylamine skeleton, dibenzothiophene skeleton Azo pigments having a fluorene skeleton, azo pigments having an oxadiazole skeleton, azo pigments having a bis-stilbene skeleton, azo pigments having a distyryl oxadiazole skeleton, azo pigments having a distyrylcarbazole skeleton, perylene Pigments, anthraquinone or polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments Indigoid pigments, and bisbenzimidazole pigments. These charge generation pigments can be used alone or in combination of two or more.
[0098]
Examples of the binder resin in the charge generation layer 1c include polyvinyl butyral resin, partially acetalized polyvinyl butyral resin, polyarylate resin, and vinyl chloride-vinyl acetate copolymer. The constituent ratio of the binder resin and the charge generating material is used in the range of 10 to 1000 parts by weight with respect to 100 parts by weight of the binder resin.
[0099]
A known material can be used as the charge transport material constituting the charge transport layer 1d, and there are an electron transport material and a hole transport material. Examples of the electron transporting material include electron accepting materials such as chloranil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, paradiphenoquinone derivatives, benzoquinone derivatives, and naphthoquinone derivatives. . These electron transport materials can be used alone or in combination of two or more.
[0100]
As hole transport materials, oxazole compounds, oxadiazole compounds, imidazole compounds, triphenylamine compounds, pyrazoline compounds, hydrazone compounds, stilbene compounds, phenazine compounds, benzofuran compounds, butadiene compounds, benzidine compounds, styryl compounds, and these compounds And derivatives thereof. These electron donating substances can be used alone or in combination of two or more.
[0101]
The charge transport layer 1d may contain an antioxidant, an anti-aging agent, an ultraviolet absorber and the like for preventing the deterioration of these substances.
As the binder resin in the charge transport layer 1d, polyester, polycarbonate, polysulfone, polyarylate, polyvinyl butyral, polymethyl methacrylate, polyvinyl chloride resin, vinyl chloride-vinyl acetate copolymer, silicone resin, and the like can be used. Polycarbonate is preferred in view of compatibility with the charge transport material, film strength, solubility, and stability as a paint. The composition ratio of the binder resin and the charge transport material is used in a range of 25 to 300 parts by weight with respect to 100 parts by weight of the binder resin.
[0102]
In order to form the charge generation layer 1c and the charge transport layer 1d, a coating solution may be used, and the solvent varies depending on the type of the binder resin. For example, alcohols such as methanol, ethanol, isopropyl alcohol, acetone, methyl ethyl ketone, cyclohexanone Ketones such as N, N-dimethylformamide, amides such as N, N-dimethylacetamide, ethers such as tetrahydrofuran, dioxane and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, chloroform, chloride Aliphatic halogenated hydrocarbons such as methylene, dichloroethylene, carbon tetrachloride, and trichloroethylene, or aromatics such as benzene, toluene, xylene, and monochlorobenzene can be used.
The charge generating pigment may be dispersed and mixed using a mechanical method such as a sand mill, ball mill, attritor, or planetary mill.
[0103]
Coating methods for the undercoat layer 1b, the charge generation layer 1c and the charge transport layer 1d include dip coating, ring coating, spray coating, wire bar coating, spin coating, blade coating, roller coating, and air knife. A method such as a coating method is used. The drying after coating is preferably performed by drying at room temperature, followed by heat drying at a temperature of 30 ° C. to 200 ° C. for 30 to 120 minutes. The film thickness after drying in the charge generation layer 1c is in the range of 0.05 μm to 10 μm, preferably 0.1 μm to 3 μm. In the charge transport layer 1d, the thickness is in the range of 5 μm to 50 μm, preferably 10 μm to 40 μm.
[0104]
Further, the organic single-layer type photoreceptor 1 is charged on the conductive support 1a described in the organic laminated photoreceptor 1 described above via a similar undercoat layer 1b as shown in FIG. 7B. It is produced by coating and forming a single-layer organic photosensitive layer 1e composed of a generator, a charge transport agent, a sensitizer and the like, a binder, a solvent and the like. The organic negatively charged single layer type photoconductor may be produced according to the method disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-19746.
[0105]
Examples of the charge generator in the single-layer organic photosensitive layer 1e include phthalocyanine pigments, azo pigments, quinone pigments, perylene pigments, quinothiaton pigments, indigo pigments, bisbenzimidazole pigments, and quinacridone pigments. Are phthalocyanine pigments and azo pigments. Examples of the charge transport agent include hydrazone-based, stilbene-based, phenylamine-based, arylamine-based, diphenylbutadiene-based, oxazole-based organic hole-transporting compounds, and sensitizers include various electron-withdrawing organic compounds. Examples thereof include paradiphenoquinone derivatives, naphthoquinone derivatives and chloranil which are also known as electron transport agents. Examples of the binder include thermoplastic resins such as polycarbonate resin, polyarylate resin, and polyester resin.
[0106]
The composition ratio of each component is as follows: binder 40 wt% to 75 wt%, charge generating agent 0.5 wt% to 20 wt%, charge transport agent 10 wt% to 50 wt%, sensitizer 0.5 wt% to 30 wt%. % By weight, preferably 45% to 65% by weight of binder, 1% to 20% by weight of charge generator, 20% to 40% by weight of charge transport agent, and 2% to 25% by weight of sensitizer. . The solvent is preferably a solvent that is not soluble in the undercoat layer, and examples thereof include toluene, methyl ethyl ketone, and tetrahydrofuran.
[0107]
Each component is pulverized / dispersed and mixed with a stirrer such as a homomixer, a ball mill, a sand mill, an attritor, or a paint conditioner to obtain a coating solution. The coating solution is applied and dried on the undercoat layer by dip coating, ring coating, spray coating or the like so as to have a film thickness of 15 μm to 40 μm, preferably 20 μm to 35 μm after drying to form a single-layer organic photoreceptor layer 1e.
[0108]
The organic photoreceptor 1 configured as described above is a photosensitive drum rotating at a surface speed of 60 mm / s to 300 mm / s with a diameter of 24 mm to 86 mm, and the surface thereof is made uniform by a charging member such as the corona charger 2. After being negatively charged, exposure 3 is performed according to information to be recorded, whereby an electrostatic latent image is formed on the surface of the photosensitive drum.
[0109]
A developing device 10 having a developing roller 11 is a one-component developing device 10, which reversely develops an electrostatic latent image on the organic photoreceptor 1 by supplying a negatively chargeable toner 8 onto the organic photoreceptor 1, so that it is visible. It is to be imaged. A negatively chargeable toner 8 is stored in the developing device 10, and the toner is supplied to the developing roller 11 by a supply roller 6 that rotates counterclockwise as shown in FIG. 5. The developing roller 11 rotates counterclockwise as shown in the drawing, and with the toner 8 conveyed by the supply roller 6 adsorbed on the surface thereof, the developing roller 11 conveys the toner to the contact portion with the organic photoreceptor 1 rotating clockwise. The electrostatic latent image on the photoreceptor 1 is visualized.
[0110]
The developing roller 11 is, for example, a roller having a diameter of 16 mm to 24 mm and a metal pipe plated or blasted, or a volume resistance value 10 made of NBR, SBR, EPDM, urethane rubber, silicon rubber or the like on the peripheral surface of the central shaft.^Four Ω · cm to 10⁸ A conductive elastic layer having a resistance of Ω · cm and a hardness of 40 ° to 70 ° (Asker A hardness) is formed, and a developing bias voltage is supplied from a power source (not shown) through the shaft and central axis of the pipe. Applied.
[0111]
As the regulating blade 7, SUS, phosphor bronze, rubber plate, a thin metal plate and a rubber chip bonded to each other are used, but the developing roller 11 is biased by a spring or the like (not shown) or as an elastic body. The repulsive force is used to press the toner at a linear pressure of 20 gf / cm to 60 gf / cm, and the toner layer thickness on the developing roller 11 is 5 μm to 20 μm, preferably 6 μm to 15 μm. Layers, preferably 1 to 1.8 layers.
[0112]
In the non-contact developing type image forming apparatus shown in FIG. 5, the developing roller 11 and the organic photoreceptor 1 are opposed to each other through the developing gap L. The developing gap L may be 100 μm to 350 μm. Although not shown, the development bias of the direct current voltage (DC) is -200 V to -500 V, and the alternating voltage (AC) superimposed thereon is 1.5 kHz to 3.5 kHz, and the PP voltage is 1000 V to 1800 V. It is good to do. Further, in the non-contact developing method, the peripheral speed of the developing roller 11 rotating counterclockwise is 1.0 to 2.5, preferably 1.2 with respect to the organic photoreceptor 1 rotating clockwise. A peripheral speed ratio of ~ 2.2 is preferable.
[0113]
The developing roller 11 rotates counterclockwise as shown in the drawing, and the negatively chargeable toner 8 conveyed by the supply roller 6 is conveyed to the portion facing the organic photoreceptor 1 with the negatively charged toner 8 adsorbed on the surface thereof. However, the negatively chargeable toner 8 vibrates between the surface of the developing roller 11 and the surface of the organic photoreceptor 1 by applying an alternating voltage superimposed on the opposing portion of the organic photoreceptor 1 and the developing roller 11. To be developed. In the present invention, the toner particles can be brought into contact with the surface of the developing roller 11 while the toner 8 vibrates between the surface of the developing roller 11 and the surface of the organic photoreceptor 1 by application of an alternating voltage. Therefore, it is considered that a positively charged toner having a small particle diameter can be negatively charged and fog toner can be reduced.
[0114]
Further, a transfer material 9 such as paper or an intermediate transfer medium (not shown in FIG. 5; shown in FIG. 8 to be described later) is sent between the organic photoreceptor 1 visualized and the transfer roller 5. The pressing load applied to the organic photoreceptor 1 by the transfer roller 5 is 20 gf / cm to 70 gf / cm, preferably 25 gf / cm to 50 gf / cm, which is the same as that of the contact developing method.
[0115]
The non-contact development process shown in FIG. 5 and the non-contact development process shown in FIG. 6 are combined with a developing device and a photoreceptor 1 using four color toners (developers) composed of yellow Y, cyan C, magenta M, and black K, respectively. Then, a full color image forming apparatus capable of forming a full color image is obtained. As this full-color image forming apparatus, a four-cycle system (details will be described later) comprising the four color developing devices and one rotatable latent image carrier shown in FIG. There are a tandem system in which the bodies are arranged in a row, and a rotary system in which one latent image carrier and a four-color rotatable developing device are combined.
[0116]
Next, an example of production of the negatively chargeable toner of the present invention, and image formation using the negatively chargeable toner by the non-contact or contact one-component development process shown in FIG. 8 having the basic configuration shown in FIGS. An example of manufacturing the organic photoreceptor and transfer medium of the apparatus will be described. Note that the image forming apparatus shown in FIG. 8 can also perform a contact one-component development process. In the image formation test described later, a test using the contact one-component development process was also performed using this image forming apparatus. However, in the following description, this image forming apparatus basically performs a non-contact one-component development process.
[0117]
Next, production examples of the negatively chargeable toner of the present invention will be shown. In that case, the negatively chargeable toners (1) to (4) are toners produced by a polymerization method, and the negatively chargeable toners (5) to (8) are examples of toners produced by a pulverization method. .
[0118]
[Production Example of Negatively Charged Toner (1)]
A monomer mixture comprising 80 parts by weight of styrene monomer, 20 parts by weight of butyl acrylate, and 5 parts by weight of acrylic acid,
・ 105 parts by weight of water
-Nonionic emulsifier 1 part by weight
・ Anionic emulsifier 1.5 parts by weight
・ 0.55 parts by weight of potassium persulfate
The mixture was added to the water-soluble mixture consisting of the following, stirred in a nitrogen stream, and polymerized at 70 ° C. for 8 hours. After the polymerization reaction, the mixture was cooled to obtain a milky white resin emulsion having a particle size of 0.25 μm.
[0119]
next,
・ 200 parts by weight of this resin emulsion
・ Polyethylene wax emulsion {manufactured by Sanyo Chemical Industries Ltd.} 20 parts by weight
・ Phthalocyanine blue 7 parts by weight
Is dispersed in water containing 0.2 part by weight of sodium dodecylbenzenesulfonate as a surfactant, pH is adjusted to 5.5 by adding diethylamine, and 0.3 part by weight of aluminum sulfate as an electrolyte is stirred. Then, the mixture was stirred at high speed with a TK homomixer and dispersed.
[0120]
Further, 40 parts by weight of styrene monomer, 10 parts by weight of butyl acrylate and 5 parts by weight of zinc salicylate were added together with 40 parts by weight of water, and the mixture was heated to 90 ° C. while stirring under a nitrogen stream, and hydrogen peroxide was added. And polymerized for 5 hours to grow particles. After the polymerization was stopped, the temperature was raised to 95 ° C. and maintained for 5 hours while adjusting the pH to 5 or more in order to increase the association of the secondary particles and the film-forming bond strength. Thereafter, the obtained particles were washed with water and vacuum dried at 45 ° C. for 10 hours to obtain mother particles of cyan toner.
[0121]
The average particle diameter and circularity of the obtained cyan toner mother particles were measured with the FPIA 2100 apparatus, and the work function was measured with the AC-2 type surface analysis apparatus. As a result, the average particle diameter was 6.8 μm. The toner has a circularity of 0.98, and its work function was 5.57 eV as measured by the surface analyzer. 1% by weight of hydrophobic silica having a mean primary particle size of about 12 nm and a work function of 5.22 eV as a fluidity improver, and a mean primary particle size of about 40 nm with respect to the mother particles of the cyan toner. A cyan toner (1) was prepared by adding and mixing 0.5 wt% of hydrophobic silica having a work function of 5.24 eV. The obtained cyan toner (1) was measured using the above-mentioned devices, and as a result, the average particle size was 6.86 μm, the circularity was 0.983, and the work function was 5.54 eV.
[0122]
[Production Example of Negatively Charged Toner (2)]
Similarly, in the above-described cyan toner (1), the pigment is changed to quinacridone instead of the phthalocyanine blue pigment, and the temperature for increasing the association of the secondary particles and the film-forming bond strength is maintained at 90 ° C. (2) was prepared in the same manner. As in the case of the cyan toner (1), the average particle diameter, circularity, and work function of the mother particles of the magenta toner (2) and the magenta toner (2) were measured. The 6.9 μm, the circularity was 0.97, the work function was 5.65 eV, the average particle size of the magenta toner (2) was 6.96 μm, the circularity was 0.975, and the work function was 5.61 eV.
[0123]
[Production Examples of Negatively Charged Toners (3) and (4)]
In the magenta toner (2) described above, polymerization was performed in the same manner as the magenta toner (2) except that the pigment was changed to Pigment Yellow 180 and carbon black, and a fluidity improver was added to obtain the yellow toner (3). A black toner (4) was prepared. At this time, the yellow toner (3) has an average particle size of toner base particles of 6.93 μm, a circularity of 0.968, a work function of 5.55 eV, and an average particle size of yellow toner (3) of 7.01 μm, The circularity was 0.971 and the work function was 5.52 eV. The black toner (4) has an average particle diameter of toner base particles of 6.89 μm, a circularity of 0.965, a work function of 5.49 eV, and an average particle diameter of black toner (4) of 7.08 μm, circular. The degree was 0.975 and the work function was 5.45 eV.
[0124]
[Example of production of negatively chargeable toner (5)]
50:50 (weight ratio) mixture of polycondensed polyester of aromatic dicarboxylic acid and alkylene etherified bisphenol A and a partially cross-linked product of the polycondensed polyester with a polyvalent metal compound {manufactured by Sanyo Chemical Industries Ltd.} 100 weight Parts, carmine 6B parts by weight of magenta pigment, 1 part by weight of polypropylene having a melting point of 152 ° C. and a weight molecular weight Mw of 4000 as a release agent, and a salicylic acid metal complex E-81 as a charge control agent {manufactured by Orient Chemical Co., Ltd. } After 4 parts by weight were uniformly mixed using a Henschel mixer, they were kneaded with a twin screw extruder having an internal temperature of 130 ° C. and cooled. The cooled product was coarsely pulverized to 2 mm square or less, then finely pulverized by a jet mill, and classified by a classifier by rotating a rotor to obtain classified toner base particles having an average particle diameter of 6.2 μm and a circularity of 0.905. 0.2% by weight of hydrophobic silica (average primary particle diameter: 7 nm, specific surface area: 250 m) based on the classified toner base particles²/ G), and after surface treatment, using a hot air spheronizer surfing system, set the heat treatment temperature to 250 ° C., partially spheronize, then classify again in the same way, average Mother particles of magenta toner having a particle size of 7.35 μm and a circularity of 0.940 were obtained. Further, the work function of the toner base particles was 5.50 eV as a result of measurement.
[0125]
Of the two types of hydrophobic silica used in the toner (1), the obtained toner base particles have a small particle diameter of about 7 nm and an average primary particle diameter of about 7 nm and a work function of 5.18 eV. 0.5% by weight of the active silica, 0.5% by weight of the above-mentioned hydrophobic silica having an average primary particle diameter of about 12 nm, and an average primary particle diameter of large silica of about 40 nm and a work function of 5 Hydrophobic alumina-silica having 0.54% by weight of hydrophobic silica of .24 eV, an average primary particle diameter of about 17 nm, a first work function of 5.18 eV and a second work function of 5.62 eV The composite oxide fine particles are 0.5% by weight, the average primary particle size is about 20 nm as metal oxide fine particles, the rutile-anatase type titanium oxide having a work function of 5.64 eV is 0.3% by weight, and the average primary particle size is 0.5. 23 μm, work function is 5.00 eV Conductive aluminum oxide added and mixed 0.4 wt%, to prepare a magenta toner (5). At this time, the magenta toner (5) had an average particle diameter of about 7.38 μm, a circularity of 0.94, and a work function of 5.56 eV.
[0126]
[Production Example of Negatively Charged Toner (6), (7), (8)]
In accordance with the above-described production example of magenta toner (5), cyan toner (6) (using phthalocyanine blue as cyan toner pigment), yellow toner (7) (using pigment yellow 93 as yellow toner pigment) and black toner (8) (using carbon black as the black toner pigment) was prepared.
[0127]
At this time, the cyan toner (6) has an average particle size of the toner base particles of about 7.21 μm, a circularity of 0.941, a work function of 5.40 eV, and the cyan toner (6) has an average particle size of The circularity was almost the same as that of magenta toner (5), and the work function was 5.44 eV. The yellow toner (7) has an average particle diameter of the toner base particles of about 7.03 μm, a circularity of 0.941, a work function of 5.53 eV, and the average particle diameter of the yellow toner (7) is circular. The degrees were almost the same as those of the magenta toner (5), and the work function was 5.61 eV. Further, the black toner (8) has an average particle diameter of the toner base particles of about 7.26 μm, a circularity of 0.940, a work function of 5.61 eV, and the average particle diameter of the black toner (8) is circular. The degrees were almost the same as those of the magenta toner (5), and the work function was 5.65 eV.
[0128]
(Example of image forming apparatus by non-contact or contact one-component development process)
As an image forming apparatus using the non-contact one-component development process shown in FIG. 5 or an image forming apparatus using the contact one-component development process shown in FIG. 6, there is a full-color printer capable of the non-contact development process and the contact development process shown in FIG. In FIG. 8 showing this full-color printer, reference numeral 100 denotes an image carrier cartridge in which an image carrier unit is incorporated. In this example, a negative charge electrophotographic photosensitive member (hereinafter referred to as a negative photosensitive electrophotographic photosensitive member (hereinafter referred to as a photosensitive member cartridge) having a work function having a relative relationship of the present invention is configured as a photosensitive member cartridge, and the photosensitive member and the developing unit can be individually mounted. (Also simply referred to as a photoconductor) 140 is driven to rotate in the direction of the arrow shown by an appropriate driving means (not shown). A charging roller 160 as a charging unit, a developing device 10 (Y, M, C, K) as a developing unit, an intermediate transfer device 30 and a cleaning unit 170 are arranged around the photosensitive member 140 along the rotation direction. The
[0129]
The charging roller 160 contacts the outer peripheral surface of the photoconductor 140 and uniformly charges the outer peripheral surface. The exposure unit 40 selectively exposes L1 according to desired image information on the outer peripheral surface of the uniformly charged photoreceptor 140, and an electrostatic latent image is formed on the photoreceptor 140 by this exposure L1. The electrostatic latent image is developed with a developer applied by the developing device 10.
[0130]
As the developing unit 10, a yellow developing unit 10Y, a magenta developing unit 10M, a cyan developing unit 10C, and a black developing unit 10K are provided. These developing units 10Y, 10C, 10M, and 10K are configured to be swingable. Only the developing roller (developer carrier) 11 of one developing unit is selectively set with a predetermined developing gap L with respect to the photosensitive member 140 in the case of the non-contact developing process, and contact developing In the case of a process, the photosensitive member 140 can be pressed. These developing units 10 hold negatively chargeable toners having a work function relative to the work function of the photosensitive member on the developing roller. These developing units 10 include yellow Y, magenta M, The toner of either cyan C or black K is applied to the surface of the photoconductor 140 to develop the electrostatic latent image on the photoconductor 140. The developing roller 11 is a hard roller, for example, a metal roller having a roughened surface. The developed toner image is transferred onto the intermediate transfer belt 36 of the intermediate transfer device 30. The cleaning unit 170 includes a cleaner blade that scrapes off the toner T adhering to the outer peripheral surface of the photoconductor 140 after the transfer, and a cleaning toner recovery unit that receives the toner scraped off by the cleaner blade.
[0131]
The intermediate transfer device 30 includes a driving roller 31, four driven rollers 32, 33, 34, and 35, and an endless intermediate transfer belt 36 that is stretched around these rollers. The driving roller 31 is rotationally driven at substantially the same peripheral speed as that of the photosensitive member 140 by a gear (not shown) fixed to the end of the driving roller 31 engaging with the driving gear of the photosensitive member 140, so that the intermediate transfer belt 36 is photosensitive. The body 140 is driven to circulate in the direction indicated by the arrow at substantially the same peripheral speed as the body 140.
[0132]
The driven roller 35 is disposed at a position where the intermediate transfer belt 36 is pressed against the photoconductor 140 by its own tension between the driven roller 35 and the primary roller at the press-contact portion between the photoconductor 140 and the intermediate transfer belt 36. A transfer portion T1 is formed. The driven roller 35 is disposed near the primary transfer portion T1 on the upstream side in the circulation direction of the intermediate transfer belt.
[0133]
An electrode roller (not shown) is disposed on the driving roller 31 via an intermediate transfer belt 36, and a primary transfer voltage is applied to the conductive layer of the intermediate transfer belt 36 via this electrode roller. The driven roller 32 is a tension roller, and biases the intermediate transfer belt 36 in the tension direction by a biasing means (not shown). The driven roller 33 is a backup roller that forms the secondary transfer portion T2. A secondary transfer roller 38 is disposed opposite to the backup roller 33 via an intermediate transfer belt 36. A secondary transfer voltage is applied to the secondary transfer roller, and the secondary transfer roller can be brought into and out of contact with the intermediate transfer belt 36 by a contact / separation mechanism (not shown). The driven roller 34 is a backup roller for the belt cleaner 39. The belt cleaner 39 can be brought into and out of contact with the intermediate transfer belt 36 by a contact and separation mechanism (not shown).
[0134]
The intermediate transfer belt 36 includes a multilayer belt having a conductive layer and a resistance layer formed on the conductive layer and pressed against the photoreceptor 140. The conductive layer is formed on an insulating substrate made of a synthetic resin, and a primary transfer voltage is applied to the conductive layer via the electrode roller described above. Note that the conductive layer is exposed in a belt shape by removing the resistance layer in a belt shape at the belt side edge, and the electrode roller is brought into contact with the exposed portion.
[0135]
In the process in which the intermediate transfer belt 36 is circulated, the toner image on the photoconductor 140 is transferred onto the intermediate transfer belt 36 at the primary transfer portion T1, and the toner image transferred onto the intermediate transfer belt 36 is transferred to the secondary transfer belt 36. In the transfer portion T2, the image is transferred to a sheet (recording material) S such as paper supplied between the secondary transfer roller 38 and the transfer portion T2. The sheet S is fed from the sheet feeding device 50 and is supplied to the secondary transfer unit T2 by the gate roller pair G at a predetermined timing. Reference numeral 51 denotes a paper feed cassette, and 52 denotes a pickup roller.
[0136]
The toner image secondarily transferred by the secondary transfer portion T2 is fixed by the fixing device 60, and is discharged onto the sheet receiving portion 81 formed on the case 80 of the apparatus main body through the paper discharge path 70. This image forming apparatus has two paper discharge paths 71 and 72 that are independent from each other as the paper discharge path 70, and the sheet that has passed through the fixing device 60 passes through one of the paper discharge paths 71 or 72. Discharged. The sheet discharge paths 71 and 72 also constitute a switchback path. When an image is formed on both sides of a sheet, the sheet once entered the sheet discharge path 71 or 72 passes through the return roller 73. The paper is fed again toward the secondary transfer portion T2.
[0137]
Next, an example of manufacturing each component of the image forming apparatus will be described.
{Example of production of organic photoreceptor (OPC1)}
In the production of the organic photoconductor (OPC1) 1 of this production example, first, an alcohol-soluble nylon {Toray Industries, Inc.) is used as an undercoat layer 1b on the peripheral surface of a conductive support 1a having an aluminum tube diameter of 85.5 mm. "CM8000"} 6 parts by weight and 4 parts by weight of aminosilane-treated titanium oxide fine particles were dissolved and dispersed in 100 parts by weight of methanol, and a coating solution was applied by a ring coating method. Then, an undercoat layer 1b having a film thickness of 1.5 μm to 2 μm was formed.
[0138]
Next, on the undercoat layer 1b, 1 part by weight of oxytitanium phthalocyanine as a charge generating pigment, 1 part by weight of butyral resin {BX-1, manufactured by Sekisui Chemical Co., Ltd.), and 100 parts by weight of dichloroethane, A pigment dispersion was obtained by dispersing for 8 hours in a sand mill using glass beads. The obtained pigment dispersion was applied onto the undercoat layer 1b by a ring coating method and dried at 80 ° C. for 20 minutes to form a charge generation layer 1c having a thickness of 0.3 μm.
[0139]
On this charge generation layer 1c, 40 parts by weight of a charge transport material of a styryl compound of the following structural formula (1) and 60 parts by weight of a polycarbonate resin (Panlite TS, manufactured by Teijin Chemicals Ltd.) are dissolved in 400 parts by weight of toluene. Then, coating and drying were performed by a dip coating method so that the dry film thickness was 22 μm to form a charge transport layer 1d, and an organic laminated photoreceptor 1 (OPC1) having a photosensitive layer composed of two layers was produced.
A part of the obtained organic laminated photoreceptor 1 was cut out to obtain a sample piece, and the work function of this sample piece was measured with the above-mentioned AC-2 type surface analyzer at an irradiation light amount of 500 nW, and found to be 5.48 eV. showed that.
[0140]
[Chemical 1]

[0141]
{Example of production of organic photoreceptor (OPC2)}
In the organic photoreceptor (OPC1) 1, a nickel electroformed tube having a seamless thickness of 40 μm and a diameter of 85.5 mm is used for the conductive support 1 a, titanyl phthalocyanine is used as a charge generating pigment, and a charge transport material is used. An organic laminated photoreceptor (OPC2) 1 was produced in the same manner as in Production Example 1 except that a distyryl compound represented by the following structural formula (2) was used. The work function of this organic laminated photoreceptor was measured in the same manner and was 5.50 eV.
[0142]
[Chemical 2]

[0143]
(Example of production of developing roller 11)
The developing roller 11 was subjected to nickel plating (thickness: 23 μm) on the surface of an aluminum pipe having a diameter of 18 mm to obtain a surface having a surface roughness (Ra) of 4 μm. When a part of the surface of the developing roller 11 was cut out and the work function was measured in the same manner, it was 4.58 eV.
[0144]
(Example of production of toner regulating blade)
The toner regulating blade 7 was prepared by attaching a 1.5 mm thick conductive urethane rubber chip to a 80 μm thick SUS plate with a conductive adhesive. At this time, the work function of the urethane part was about 5 eV.
[0145]
(Example of production of transfer medium for intermediate transfer device)
An intermediate conductive layer which is a conductive layer in the intermediate transfer belt 36 which is a transfer medium of the intermediate transfer device 30 is
On a polyethylene terephthalate resin film having a thickness of 130 μm deposited with aluminum,
・ 30 parts by weight of vinyl chloride-vinyl acetate copolymer
・ Conductive carbon black 10 parts by weight
・ Methyl alcohol 70 parts by weight
A uniform dispersion liquid was formed by coating and drying by a roll coating method so that the thickness became 20 μm.
[0146]
Next, a transfer layer which is a resistance layer is formed on the intermediate conductive layer.

A coating solution obtained by mixing and dispersing the composition was similarly applied and dried by a roll coating method so as to have a thickness of 10 μm.
[0147]
Then, this coated sheet was cut to a length of 540 mm, the coated surface was faced up, the ends were aligned, and ultrasonic welding was performed to produce an intermediate transfer belt 36. The volume resistance of the intermediate transfer belt 36 is 2.5 × 10.^TenIt was Ω · cm. The work function was 5.37 eV, and the normalized photoelectron yield was 6.90.
[0148]
(Fixer preparation example)
The fixing device 60 includes two pressure rollers (a load of about 38 kgf), a heater roller and a press roller. The heater roller contained a halogen lamp 600w, and PFA was formed to a thickness of 50 μm on silicon rubber 2.5 mm (60 ° JISA) to a thickness of φ40. The press roller contained a halogen lamp 300w, and PFA was formed to a thickness of 50 μm on silicon rubber 2.5 mm (60 ° JISA) to a thickness of φ40. The fixing temperature is set to 190 ° C.
[0149]
The outline of the operation of the full-color printer configured as described above is as follows.
(i) When a print command signal (image formation signal) from a host computer (not shown) or the like (personal computer or the like) is input to the control unit 90 of the image forming apparatus, the photosensitive member 140, each roller 11 of the developing device 10, and The intermediate transfer belt 36 is driven to rotate.
[0150]
(ii) The outer peripheral surface of the photoreceptor 140 is uniformly charged by the charging roller 160.
(iii) The exposure unit 40 selectively exposes L1 according to the image information of the first color (for example, yellow) on the outer peripheral surface of the uniformly charged photoreceptor 140, thereby forming an electrostatic latent image for yellow. Is done.
[0151]
(iv) On the photoconductor 140, only the developing roller of the developing device 10Y for the first color, eg, yellow, is set with a predetermined developing gap L with respect to the photoconductor 140 or comes into contact with the photoconductor 140. As a result, the electrostatic latent image is subjected to non-contact development or contact development, and a yellow toner image of the first color is formed on the photoreceptor 140.
(v) The intermediate transfer belt 36 is applied with a primary transfer voltage having a polarity opposite to the charging polarity of the toner, and the toner image formed on the photoreceptor 140 is transferred onto the intermediate transfer belt 36 at the primary transfer portion T1. The At this time, the secondary transfer roller 38 and the belt cleaner 39 are separated from the intermediate transfer belt 36.
[0152]
(vi) After the toner remaining on the photoconductor 140 is removed by the cleaning unit 170, the photoconductor 140 is neutralized by the neutralizing light L2 from the removing unit 41.
(vii) The above operations (ii) to (vi) are repeated as necessary. That is, the second color, the third color, and the fourth color are repeated according to the print command signal, and a toner image according to the content of the print command signal is superimposed on the intermediate transfer belt 36 to be formed.
[0153]
(viii) The sheet S is fed from the sheet feeding device 50 at a predetermined timing, and immediately before or after the leading edge of the sheet S reaches the secondary transfer portion T2 (in short, an intermediate transfer belt at a desired position on the sheet S). The secondary transfer roller 38 transfers the toner image on the intermediate transfer belt 36 (basically, a full-color image in which four color toner images are superimposed) onto the sheet S at the timing when the toner image on 36 is transferred. Is done. Further, the belt cleaner 39 contacts the intermediate transfer belt 36, and the toner remaining on the intermediate transfer belt 36 after the secondary transfer is removed.
[0154]
(ix) The toner image on the sheet S is fixed by passing the sheet S through the fixing device 60, and then the sheet S is directed to a predetermined position (in the case of non-double-sided printing, toward the sheet receiving unit 81, double-sided printing) In this case, the toner is conveyed to the return roller 73 via the switchback path 71 or 72.
[0155]
Next, examples of the negatively charged toner of the present invention will be described.
Example 1
Table 3 shows a list of work functions of the external additive 12 used in Example 1. In this case, conductive anatase type titanium oxide is used as the conductive fine particles 14 in this embodiment.
[0156]
[Table 3]

[0157]
As described above, the alumina-silica composite oxide fine particle 13 has a bending point and has the first and second work functions. Table 3 shows the alumina-silica of the external additive (4). Two work functions of the composite oxide fine particles 13 are shown. These work functions are considered to give the aforementioned positive and negative triboelectric charging sites, respectively.
[0158]
Thus, in Example 1, hydrophobic alumina-silica composite oxide fine particles surface-treated with dimethylsilane (DMS) for the cyan toner (1) described above {bulk density 75 g / L, average primary particle diameter 17 nm. , Specific surface area 110m²/ G, weight ratio of silica 35 / alumina 65 (mixed crystal ratio)} is 0.5% by weight, and conductive anatase-type titanium oxide (average primary particle size 0.063 μm, specific surface area 45.2 m).²/ G) was added and mixed in the weight ratios shown in Table 4 to prepare toners 1- (1) to 1- (5), respectively.
[0159]
[Table 4]

[0160]
For these toners, the above-mentioned organic photoreceptor (OPC1) 1, the above-described developing roller 11, the intermediate transfer belt 36 of the intermediate transfer device 30, and the toner regulating member 7 are formed by the non-contact development method schematically shown in FIG. 8 using the full-color printer shown in FIG. 8, a non-contact development method in which the development gap L is set to 220 μm (imaging conditions: dark potential of the organic photoreceptor 1 -600 V, bright potential of the organic photoreceptor 1 -80 V, DC A solid image was output at a developing bias of -300 V, an AC developing bias (PP voltage) of 1320 V, and an AC frequency of 2.5 kHz, and a toner charging characteristic test was performed. Then, the average charge amount q / m (μc / g) of the toner on the developing roller 11 and the positively charged toner amount (number%) at that time are measured by a charge amount distribution measuring device (E-SPART analyzer) manufactured by Hosokawa Micron Corporation. EST-3 type). Table 4 shows the charging characteristics measurement results of these toners.
[0161]
As is apparent from the measurement results shown in Table 4, as the external additive of conductive anatase-type titanium oxide was added, the average charge amount gradually decreased as compared with the case where it was not added, but the positively charged toner amount was It was found that even when the addition amount was 0.5% by weight, it did not increase much. However, it was found that when the amount was 0.5% by weight or more, the average charge amount suddenly dropped and the amount of positively charged toner also increased rapidly.
[0162]
(Example 2)
Using the toner 1- (1) to 1- (5) used in Example 1 described above and the non-contact developing method schematically shown in FIG. 5, the organic photoreceptor (OPC1) 1 and the developing roller described above are used. 11. An image forming test was performed using the intermediate transfer belt 36 of the intermediate transfer device 30 and the full color printer shown in FIG. 8 using the toner regulating member 7. The image forming conditions at this time are: dark potential of the organic photoreceptor 1 -600 V, bright potential of the organic photoreceptor 1 -80 V, DC developing bias -300 V, AC developing bias (PP voltage) 1320 V, AC frequency 2.5 kHz. The supply roller and the developing roller have the same potential.
The results of this imaging test are shown in Table 5 and Table 6, respectively.
[0163]
[Table 5]

[0164]
[Table 6]

[0165]
In Table 6, Δ indicates that some voids or dust is generated and a satisfactory solid image cannot be obtained, and ○ indicates that a void image or dust is hardly generated and a satisfactory solid image is obtained.
As is apparent from the imaging test results shown in Tables 5 and 6, the conductive fine particles are more conductive than the toner 1- (1) in which silica and alumina-silica composite oxide fine particles are added as external additives. Toner 1- (2) and Toner 1- (3) added with anataza-type titanium oxide not only improve the solid image density, but also the fog and reverse transfer toner do not increase so much. I found out that
[0166]
The transfer efficiency of each toner was 65.2% for toner 1-1, but improved as the conductive anatase-type titanium oxide, which is conductive fine particles, was added. It was found that the maximum was 0.5% by weight.
[0167]
Further, the OD value of fog and reverse transfer toner was determined by a tape transfer method. What is the tape transfer method? A Sumitomo 3M mending tape is affixed onto the toner present on the photoconductor to transfer fog toner and reverse transfer toner onto the tape, and then this mending tape and mending before application The tapes were each affixed on white paper, and the reflection densities thereof were measured with a Macbeth reflection densitometer, and the values obtained by subtracting the reflection density of the tape from the measured values were used as the reflection densities of fog and reverse transfer toner. Further, the transfer efficiency was calculated and obtained from the difference in weight by attaching the tape to the toner present on the photoreceptor before and after transfer and measuring the weight of the peeled tape. The reverse transfer toner forms a solid image of the first color, and then reverse-transferred onto the photoconductor that is a non-image portion corresponding to the white solid image when the white solid image of the second color is formed. This is a value obtained by a tape transfer method using cyan toner of a color as a reverse transfer toner.
[0168]
(Example 3)
Table 7 shows the work function of the conductive fine particles of the external additive 12 used in Example 3. Then, in the same manner as in the toner 1- (3) of Example 1, each conductive fine particle was added with the weight% shown in Table 8 to make toner 1- (6), toner 1- (7) and toner 1- (8). ▼ was prepared. Table 8 shows the results of charging characteristics of the toners measured in the same manner as in Example 1 for these toners.
[0169]
[Table 7]

[0170]
[Table 8]

[0171]
As is apparent from the measurement results shown in Table 8, it was found that by adding conductive fine particles, the average charge amount can be suppressed from becoming overcharged, and the positively charged toner amount does not increase so much. .
[0172]
Example 4
Using toners 1- (6) to 1- (8) used in Example 3 described above, an image formation test was performed in the same manner as in Example 2, and the results are shown in Table 9 and Table 10, respectively.
[0173]
[Table 9]

[0174]
[Table 10]

[0175]
As is apparent from the imaging test results shown in Tables 9 and 10, Toner 1- (6) to Toner 1- (8) in which silica, alumina-silica composite oxide fine particles and conductive fine particles are added as external additives. ▼ indicates that not only the toner 1- (1) to which conductive fine particles are not added, but also solid image density and transfer efficiency are improved, and fog and reverse transfer toner do not increase so much, and voids and dust are reduced. It was.
[0176]
(Example 5)
The toners used in Example 5 are magenta toner 2 and magenta toner 5. Table 11 shows work functions of the external additive 12 used at this time. Then, in the same manner as in Toner 1- (3) of Example 1, each external additive was additionally added in the weight% shown in Table 12 to prepare Toner 2- (1) and Toner 5- (1). Table 12 shows the charging characteristics of the toners measured in the same manner as in Example 1 for these toners.
[0177]
[Table 11]

[0178]
[Table 12]

[0179]
As is apparent from the measurement results shown in Table 12, by adding conductive fine particles and metal oxide, the average charge amount can be suppressed from being overcharged, and the amount of positively charged toner can be reduced. I understood.
[0180]
(Example 6)
Using toners 2- (1) and 5- (1) used in Example 5 above, an image formation test was performed in the same manner as in Example 2, and the results are shown in Table 13 and Table 14, respectively.
[0181]
[Table 13]

[0182]
[Table 14]

[0183]
As is apparent from the imaging test results shown in Tables 13 and 14, not only silica, alumina-silica composite oxide fine particles and conductive fine particles, but also a rutile-anatase type titanium oxide having a large work function as a metal oxide was removed. Toner 2- (1) to toner 5- (1) added as an additive improves solid image density and transfer efficiency, further reduces fog and reverse transfer toner, and achieves high image quality without voids and dust. I knew that to give.
[0184]
(Example 7)
In place of the conductive titanium oxide of toner 1- (3) used in Example 1 described above, toner 1- (9) containing 0.2% by weight of conductive aluminum oxide as conductive fine particles shown in Table 11 was added. Produced. The toner charging characteristics were measured in the same manner as in Example 1, and the results are shown in Table 15 together with the toner 1- (1) data. Further, using these toners, an image formation test was conducted with the full-color printer shown in FIG. 8 adopting the contact development method schematically shown in FIG. As the image forming conditions at this time, the OPC 2 is used for the organic photoreceptor 1, the dark potential is −600V, the light potential is −80V, the DC developing bias is −200V, and the supply roller and the developing roller are set to the same potential. The imaging test results are shown in Table 16.
[0185]
[Table 15]

[0186]
[Table 16]

[0187]
From the results shown in Table 15 and Table 16, it can be seen that addition of conductive aluminum oxide, which is conductive fine particles, improves image density and transfer efficiency in contact development, and reduces fogging and reverse transfer toner. It was. The image quality was almost the same with no void or dust.
[0188]
In the same manner as the above-described magenta toner 2- (1), the external additive treatment of cyan toner (1), yellow toner (3) and black toner (4) was performed. Similarly to the above-described magenta toner 5- (1), the cyan toner (6), yellow toner (7) and black toner (8) are treated as external additives, and the production methods of the two sets of toners are different. Four color full-color toners were prepared. Using these toners, the full-color printer shown in FIG. 8 is used for low-temperature / low-humidity (10 ° C / 20%), medium-temperature / medium-humidity (25 ° C / 60%), and high-temperature / high-humidity (35 ° C / 85%) environments. Below, a printing test was performed on each of 5000 sheets. In any case, there was no scattering of toner, and a stable full-color image was obtained. It was confirmed that the initial image quality was maintained.
[0189]
【The invention's effect】
As is apparent from the above description, according to the negatively charged toner of the present invention, the intrinsic property of the toner-agglomeration improving function of the alumina-silica composite oxide fine particles and the negative overcharge of the toner of the conductive fine particles Since the toner base particles have a function that synergizes with the inherent characteristics of the prevention function and the toner fluidity improvement function, it is possible to prevent the negatively charged toner from flowing down and to prevent negative overcharge of the toner. Can be prevented. As a result, better negative charging characteristics can be obtained, so that the generation and fogging of reverse transfer toner can be effectively suppressed. In addition, since the fluidity of the toner can be improved, dust generated at the boundary of the line image can be prevented, the sharpness of the image can be improved, and the cohesiveness of the toner can be improved. It is possible to prevent the occurrence of voids.
[0190]
Therefore, the negative charge of the negatively chargeable toner can be stabilized for a longer period of time, so that an image having sharpness can be produced and a stable image quality in continuous printing can be obtained.
In addition, since the fluidity of the toner can be improved, a uniform thin layer of toner can be formed by the toner regulating member.
[0191]
Further, since the aluminum oxide-silicon dioxide composite oxide fine particles have a wide particle size distribution, the aluminum oxide-silicon dioxide composite oxide fine particles can be reliably adhered to the toner base particles, so that the transfer efficiency can be improved. Can be improved.
[0192]
  Further, aluminum oxide-silicon dioxide composite oxide fine particles and conductive fine particleEach average primary particle size ofThan,Both the average primary particle diameter is small and the work function is smaller than the work function of the larger second work function and conductive fine particle of the aluminum oxide-silicon dioxide composite oxide fine particle.Since two types of hydrophobic silicon dioxide are used in combination, the above-mentioned specific characteristics of the aluminum oxide-silicon dioxide composite oxide fine particles and the above-mentioned specific characteristics of the conductive fine particles are hydrophobic negative charges. Thus, the toner base particles can be provided with a function in which the inherent characteristics of the negative silicon dioxide and the fluidity are combined. As a result, the fluidity of the negatively chargeable toner can be prevented from being lowered, and negative overcharge can be prevented. Therefore, the negatively chargeable toner can have better negative charge characteristics, and the generation and fogging of the reverse transfer toner can be prevented. Furthermore, it can suppress effectively.
[0193]
Furthermore, by adding metal oxide fine particles that are substantially the same as the second work function of the aluminum oxide-silicon dioxide composite oxide particles, more stable charging characteristics can be obtained, resulting in improved solid image density and transfer efficiency. In addition, fog and reverse transfer toner are reduced.
[0194]
In addition, since the bending point exists in the work function of the aluminum oxide-silicon dioxide composite oxide fine particles, the aluminum oxide-silicon dioxide composite oxide fine particles have positive and negative friction sites. When the toner base particles come into contact with the positive friction site, the toner base particles are positively charged negatively. When the toner base particles come into contact with the negative friction site, the toner base particles are positively charged. Will be adjusted to an appropriate value.
[0195]
Thus, according to the negatively chargeable toner of the present invention, the positive friction site of the aluminum oxide-silicon dioxide composite oxide fine particles and the negatively chargeable silicon dioxide are negatively charged. The surface of the carrier can be more reliably negatively triboelectrically charged.
[0196]
In this case, the toner base particles can be negatively charged by the aluminum oxide-silicon dioxide composite oxide fine particles not only at low temperature and low humidity, which is easily negatively charged, but also at high temperature and high humidity, which is difficult to be negatively charged. Stable negative charging characteristics can be maintained, and stable charging characteristics can be maintained in continuous printing as well, so that high quality can be maintained over a long period of time with almost no environmental impact. .
[0197]
Furthermore, since the addition amount (weight) of two types of silicon dioxide is larger than the total addition amount (weight) of aluminum oxide-silicon dioxide composite oxide fine particles and conductive fine particles, or metal oxide fine particles, Aluminum oxide-silicon dioxide composite oxide fine particles and conductive fine particles, or metal oxide fine particles can be securely fixed to the toner base particles via these two types of silicon dioxide, and release from the toner base particles can be reduced. . Therefore, the negatively charged toner of the present invention can stabilize the charging over a long period of time.
[0198]
Furthermore, since the aluminum oxide-silicon dioxide composite oxide fine particles having positive and negative friction sites having a particle size larger than the average primary particle size of the two types of silicon dioxide coexist, the regulated toner layer can be uniformly charged, The amount of positively charged toner having a reverse polarity can be reduced.
[0199]
Thereby, the amount of fog toner and reverse transfer toner on the photoreceptor can be reduced, and the transfer efficiency can be further improved. Further, since the transfer efficiency can be improved, the amount of toner to be cleaned on the photoconductor and the intermediate transfer medium can be reduced, so that cleaning is simplified and the cleaning toner collecting container can be made a small container.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating an example of an embodiment of a negatively chargeable toner according to the present invention.
FIG. 2 is a burner apparatus for producing alumina-silica composite oxide fine particles disclosed in Japanese Patent No. 2533067.
FIG. 3 is a diagram showing one of data relating to alumina-silica composite oxide fine particles obtained by measurement with a surface analyzer.
FIG. 4 is a diagram showing another one of data relating to alumina-silica composite oxide fine particles obtained by measurement with a surface analysis apparatus.
FIG. 5 is a diagram schematically illustrating an example of a non-contact development process of an image forming apparatus in which a negatively chargeable toner according to the present invention is used.
FIG. 6 is a diagram schematically illustrating an example of a contact development process of an image forming apparatus in which a negatively chargeable toner according to the present invention is used.
7 is a view showing an organic laminated photoreceptor of the image forming apparatus shown in FIGS. 5 and 6. FIG.
FIG. 8 is a diagram illustrating an example of a four-cycle full color printer using a non-contact development process and a contact development process used in an image formation test using a negatively chargeable toner according to the present invention.
FIG. 9 is a diagram illustrating a void phenomenon and generation of dust in a conventional negatively chargeable toner.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,140 ... Organic photoreceptor, 2 ... Corona charger, 3 ... Exposure, 4 ... Cleaning blade, 5 ... Transfer roller, 6 ... Supply roller, 7 ... Restriction blade, 8 ... Negative chargeable toner (one component nonmagnetic toner) 8a ... toner base particles, 9 ... transfer material or transfer medium, 10 ... developing device, 11 ... developing roller, 12 ... external additive, 13 ... alumina-silica composite oxide fine particles, 14 ... conductive fine particles, 15a, 15b ... Hydrophobic negatively charged silica (SiO₂), L ... Development gap

Claims (4)

In the negatively chargeable toner obtained by at least externally adding a hydrophobic external additive to the toner base particles,
As the external additive, at least hydrophobic aluminum oxide-silicon dioxide composite oxide particles and conductive fine particles having a work function smaller than the work function of the aluminum oxide-silicon dioxide composite oxide particles are used. And
The conductive fine particles are any one of conductive silicon dioxide, conductive titanium oxide, and conductive aluminum oxide,
The aluminum oxide - The amount of silicon dioxide composite oxide particles, the toner mother particles is set to a 0 from 1 wt% 3 wt% or less by weight,.
As the external additive, two types of hydrophobic and negatively charged silicon dioxide having different particle diameters are used,
The average primary particle diameter of the aluminum oxide-silicon dioxide composite oxide particles is set between the average primary particle diameters of these two types of silicon dioxide, and the average primary particles of these two types of silicon dioxide The diameter is set smaller than the average primary particle diameter of the conductive fine particles, and the work function of two types of silicon dioxide is the second work function of the larger one of the aluminum oxide-silicon dioxide composite oxide particles. And a negatively chargeable toner set to be larger than the work function of the conductive fine particles . As the external additive, hydrophobic metal oxide fine particles having a work function substantially the same as the second work function of the hydrophobic aluminum oxide-silicon dioxide composite oxide particles are further used. The metal oxide fine particles it is negatively chargeable toner according to claim 1, characterized in that the rutile-anatase type titanium oxide emissions. Claim 1, characterized in that it is set larger than the total amount of the conductive fine particles with silicon dioxide composite oxide particles (by weight) - the amount of two kinds of silicon dioxide (weight) of the aluminum oxide The negatively chargeable toner described. The addition amount (weight) of the two types of silicon dioxide is set to be larger than the total addition amount (weight) of the aluminum oxide-silicon dioxide composite oxide particles, the conductive fine particles, and the metal oxide fine particles. The negatively chargeable toner according to claim 2 .

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