JP3698203B2 - Negatively charged toner and method for producing the same - Google Patents

Description

【００４０】
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０.５〜１５重量部、好ましくは１〜１０重量部であり、また、離型剤は１〜１０重量部、好ましくは２.５〜８重量部であり、更に、荷電制御剤は０.１〜７重量部、好ましくは０.５〜５重量部であり、更に、流動性改良剤は０.１〜５重量部、好ましくは０.５〜４重量部である。
【００４１】
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をアップさせることがよい。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。
【００４２】
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。
【００４３】
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％径である平均粒子径（Ｄ₅₀）が９μｍ以下、好ましくは４.５〜８μｍ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と疎水性ルチルアナターゼ型酸化チタン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子径と円形度は、シスメックス株式会社製のＦＰＩＡ２１００で測定する値である。
【００４４】
更に、この粉砕法トナー８にあっては、外添剤の総量（重量）がトナー母粒子の重量に対して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、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。
【００４５】
次に、重合法によるトナー母粒子を用いたトナー（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。
【００４６】
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。
【００４７】
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。
【００４８】
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。
【００４９】
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。
【００５０】
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。
【００５１】
乳化重合法トナー８における成分比（重量）を表２に示す。
【００５２】
【表２】

【００５３】
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０.０３〜２、好ましくは０.１〜１重量部であり、また、界面活性剤０.０１〜０.１重量部であり、更に、離型剤は１〜４０重量部、好ましくは２〜３５重量部であり、更に、荷電制御剤は０.１〜７重量部、好ましくは０.５〜５重量部であり、着色剤は１〜２０重量部、好ましくは３〜１０重量部であり、更に、凝集剤（電解質）は０.０５〜５重量部、好ましくは０.１〜２重量部である。
【００５４】
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をアップさせることがよい。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。
【００５５】
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。
【００５６】
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。
【００５７】
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％径である平均粒子径（Ｄ₅₀）が９μｍ以下、好ましくは４.５〜８μｍ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として疎水性の負帯電性シリカと疎水性ルチルアナターゼ型酸化チタン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、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子径と円形度は、シスメックス株式会社製のＦＰＩＡ２１００で測定する値である。
【００５８】
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、外添剤の総量（重量）がトナー母粒子の重量に対して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。
【００５９】
このように構成されたこの例の負帯電トナー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、図２に示すように小粒子径の疎水性の負帯電性シリカ１３がトナー母粒子８ａに埋没し易くなる。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ルチルアナターゼ型酸化チタン１５が仕事関数差による接触電位差で埋没疎水性の負帯電性シリカ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り、かつ大粒子径の疎水性の負帯電性シリカ１４および大粒子径の疎水性の正帯電性シリカ１６がトナー母粒子８ａの表面に固着していることから、トナー母粒子８ａの表面が疎水性の負帯電性シリカ１３,１４、疎水性ルチルアナターゼ型酸化チタン１５、および疎水性の正帯電性シリカ１６によりまんべんなく覆われるようになる。
【００６０】
したがって、疎水性ルチルアナターゼ型酸化チタン１５の有するトナー母粒子８ａに埋没し難い特質と電荷調整機能とがより効果的に活かすことができるようになり、疎水性の負帯電性シリカ１３,１４の有する負帯電性能および流動性という固有の特性と、疎水性ルチルアナターゼ型酸化チタン１５の有する比較的低抵抗でかつ負の過帯電防止特性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。これにより、負帯電トナー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。したがって、負帯電トナー８はその負帯電がより一層長期にわたり安定し、連続印字における安定した画像品質を与えるようになる。
【００６１】
更に、これに加えて、大粒子径の正帯電性シリカ１６がマイクロキャリヤの機能を発揮するため、トナー母粒子８ａの帯電の立ち上がりを早くできる。これにより、逆転写トナーおよびカブリが更に一層効果的に抑制されるようになる。
特に、大粒子径の正帯電性シリカ１６の添加量（重量）は、疎水性の負帯電性シリカ１３,１４の総添加重量の３０％以下に設定することが、疎水性の負帯電性シリカ１３,１４の前述の機能を損なわなく、大粒子径の正帯電性シリカ１６の機能を効果的に発揮できるので、好ましい。
【００６２】
また、疎水性の負帯電性シリカ１３,１４の合計量（重量）を疎水性ルチルアナターゼ型酸化チタン１５および疎水性の正帯電性シリカ１６の合計量（重量）より多く添加することで、負帯電トナー８の負帯電がより一層長期にわたり安定する。したがって、非画像部のカブリがより一層抑制されるとともに転写効率が更に向上し、更に逆転写トナーの発生がより効果的に抑制されるようになる。
【００６３】
更に、同じ量の流動化剤を添加しても、大粒子径の正帯電性シリカ１６を使用した方が小粒子径の正帯電性シリカを使用した場合に比べて定着性を低下させることがなく、カブリや逆転写トナーも少なくなる。
【００６４】
図３は、この例の負帯電トナー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４は、この例の負帯電トナー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３および図４中、１は有機感光体、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は負帯電トナー、９は転写材、１０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。
【００６５】
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５（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。
【００６６】
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。
【００６７】
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、酸化亜鉛等の金属酸化物を含有させてもよい。
【００６８】
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。
【００６９】
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、１０〜１０００重量部の範囲で用いられる。
【００７０】
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。
【００７１】
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。
【００７２】
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２５〜３００重量部の範囲で用いられる。
【００７３】
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。
【００７４】
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、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、０.０５〜１０μｍの範囲、好ましくは０.１〜３μｍである。また、電荷輸送層１ｄでは５〜５０μｍの範囲、好ましくは１０〜４０μｍである。
【００７５】
また、有機単層型感光体１は、図５（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。
【００７６】
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。
【００７７】
各成分の組成比は、バインダー４０〜７５重量％、電荷発生剤０.５〜２０重量％、電荷輸送剤１０〜５０重量％、増感剤０.５〜３０重量％であり、好ましくはバインダー４５〜６５重量％、電荷発生剤１〜２０重量％、電荷輸送剤２０〜４０重量％、増感剤２〜２５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。
【００７８】
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１５〜４０μｍ、好ましくは２０〜３５μｍで塗布・乾燥されて単層有機感光体層１ｅとされる。
【００７９】
そして、このように構成された有機感光体１は直径２４〜８６ｍｍで表面速度６０〜３００ｍｍ／ｓで回転する感光体ドラムであり、コロナ帯電器２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。
【００８０】
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、負帯電トナー８が収納されており、図３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。
【００８１】
現像ローラ１１は、例えば直径１６〜２４ｍｍ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 〜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。
【００８２】
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２０〜６０ｇｆ／ｃｍで押圧され、現像ローラ１１上のトナー層厚を５〜２０μｍ、好ましくは６〜１５μｍ、トナー粒子の積層形態としては略１〜２層、好ましくは１〜１.８層とされるとよい。
【００８３】
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１００〜３５０μｍ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−２００〜−５００Ｖであり、これに重畳する交流電圧（ＡＣ）としては１.５〜３.５ｋＨｚ、Ｐ−Ｐ電圧１０００〜１８００Ｖ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。
【００８４】
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。
【００８５】
また、紙等の転写材９や中間転写媒体（図３には不図示；後述する図５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２０〜７０ｇｆ／ｃｍ、好ましくは２５〜５０ｇｆ／ｃｍとするとよい。
【００８６】
図３に示す非接触現像プロセスおよび図４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６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。
【００８７】
次に、本発明の画像形成装置に用いられる負帯電トナーの作製例、およびこの負帯電トナーを用いた、図３に示す基本構成を有する図６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６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。
【００８８】
（負帯電トナーの作製例）
負帯電トナー８は、いずれも、前述の重合法トナーと粉砕法トナーの両トナーについて作製した。その場合、各例のトナーの作製に用いた流動性改良剤（外添剤）は、長軸長が２０ｎｍで、シランカップリング処理された疎水性のルチルアナターゼ型酸化チタン（２０ｎｍ）、平均一次粒子径が７ｎｍである小粒子径の、ヘキサメチルジシラン（ＨＭＤＳ）により表面処理された疎水性の負帯電性気相法シリカ（７ｎｍ）、平均一次粒子径が１２ｎｍである小粒子径の、同様にして疎水化された負帯電性気相法シリカ（１２ｎｍ）、平均一次粒子径が１６ｎｍである小粒子径の、同様にして疎水化された負帯電性気相法シリカ（１６ｎｍ）、平均一次粒子径が４０ｎｍである大粒子径の、同様にして疎水化された負帯電性気相法シリカ（４０ｎｍ）、平均一次粒子径が３０ｎｍである大粒子径のアミノシラン（ＡＳ）により正帯電性に表面処理された疎水性の正帯電性気相法シリカ（３０ｎｍ）▲１▼（後述の表４に示すシリカ▲１▼）のいずれかの組合せである。また、本発明の比較例のために、平均一次粒子径が１２ｎｍである小粒子径の、同様にして疎水化された２種類の正帯電性気相法シリカ（１２ｎｍ）▲２▼,▲３▼（後述の表４に示すシリカ▲２▼,▲３▼）を作製した。これらの仕事関数Φを測定した結果を表３に示す。なお、各仕事関数Φは、前述の理研計器（株）製の光電子分光装置ＡＣ−２により、照射光量５００ｎＷで測定した。
【００８９】
【表３】

【００９０】
表３からわかるように、各疎水化処理されたルチルアナターゼ型酸化チタン（２０ｎｍ）の仕事関数Φは５.６４ｅＶであり、このときの規格化光電子収率は８.４であった。また、負帯電性気相法シリカ（７ｎｍ）の仕事関数Φは５.１８ｅＶであり、規格化光電子収率は６.１であった。更に、負帯電性気相法シリカ（１２ｎｍ）の仕事関数Φは５.２２ｅＶであり、規格化光電子収率は５.１であった。更に、負帯電性気相法シリカ（１６ｎｍ）の仕事関数Φは５.１９ｅＶであり、規格化光電子収率は６.８であった。更に、負帯電性気相法シリカ（４０ｎｍ）の仕事関数Φは５.２４ｅＶであり、規格化光電子収率は５.２であった。更に、正帯電性気相法シリカ（３０ｎｍ）▲１▼の仕事関数Φは５.３７ｅＶであり、規格化光電子収率は１１.５であった。更に、正帯電性気相法シリカ（１２ｎｍ▲２▼の仕事関数Φは５.１３ｅＶであり、規格化光電子収率は１０.７であった。更に、正帯電性気相法シリカ（１２ｎｍ）▲３▼の仕事関数Φは５.１４ｅＶであり、規格化光電子収率は７.８であった。
【００９１】
(1) 乳化重合法トナーの実施例と比較例の作製
(a) 実施例１、比較例１、比較例２および比較例３の乳化重合法トナーの作製
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。
【００９２】
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。
【００９３】
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。
【００９４】
得られたシアントナーの母粒子は、測定の結果、平均粒子径が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、重量比で、流動性改良剤であるヘキサメチルジシラザン（ＨＭＤＳ）で表面処理した負帯電性疎水性シリカの平均一次粒子径が約７ｎｍの小粒子径負帯電シリカ１３を１重量％、同様に表面処理した負帯電性疎水性シリカの平均一次粒子径が約４０ｎｍの大粒子径負帯電シリカ１４を１重量％添加混合して添加混合トナーを作製した。
【００９５】
そして、疎水性のシリカをアミノシラン（ＡＳ）で表面処理した表４に示す３種類の正帯電性疎水性シリカを用意し、前述の添加混合トナーに、これらの正帯電性疎水性シリカをそれぞれ重量比で０.５重量％添加して、それぞれ、本発明の実施例１のトナー、比較例１および２の各トナーを作製した。また、作製した添加混合トナーにこれらの正帯電性疎水性シリカのいずれをも添加しないトナー（つまり、添加混合トナー）を比較例３のトナーとした。
【００９６】
【表４】

【００９７】
表４に示すように、実施例１のトナーに使用した正帯電性疎水性シリカ（シリカ▲１▼）は、フェライトキャリアに対する正帯電性が＋１５０μｃ／ｇであり、また平均一次粒子径は約３０ｎｍである。また、比較例１のトナーに使用した正帯電性疎水性シリカ（シリカ▲２▼）は、フェライトキャリアに対する正帯電性が＋２８０μｃ／ｇであり、また平均一次粒子径は約１２ｎｍである。更に、比較例２のトナーに使用した正帯電性疎水性シリカ（シリカ▲３▼）は、フェライトキャリアに対する正帯電性が＋３８０μｃ／ｇであり、また平均一次粒子径は約１２ｎｍである。これらのシリカ▲１▼、▲２▼および▲３▼の各仕事関数は、前述に測定結果から明らかなようにシアントナーの母粒子の仕事関数より小さい。また、実施例１および比較例１ないし３の各トナーの仕事関数は、測定の結果、それぞれ５.５１ｅＶ、５.５０ｅＶ、５.５０ｅＶ、５.４５ｅＶであった。
【００９８】
(b) 実施例２、比較例４、比較例５および比較例６の乳化重合法トナーの作製
前述の実施例１のシアンの乳化重合法トナーの作製において、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、円形度が０.９７で、トナー母粒子の仕事関数が５.６５ｅＶのマゼンタトナーのトナー母粒子を作製した。そして、外添剤処理を本発明の実施例１のトナーおよび比較例１ないし３の各トナーの場合と同様にして行い、それぞれ、本発明の実施例２、比較例４ないし６の各トナーを作製した。このとき、シリカ▲１▼、▲２▼および▲３▼の各仕事関数はいずれもマゼンタトナーの母粒子の仕事関数より小さく、また、実施例２および比較例４ないし６の各トナーの仕事関数は、測定の結果、それぞれ５.５９ｅＶ、５.５８ｅＶ、５.５８ｅＶ、５.５３ｅＶであった。
【００９９】
(c) 実施例３の乳化重合法トナーの作製
前述の実施例１のシアントナーに、ルチルアナターゼ型で混晶比がルチル１０％、アナターゼ型９０％のシランカップリング剤で疎水化処理したルチルアナターゼ型酸化チタン（疎水化度５８％、比表面積１５０ｍ²／ｇ）を０.５％を添加混合し、更に表４に示すシリカ▲１▼を０.５％添加混合して、本発明の実施例３のトナーを作製した。このとき、ルチルアナターゼ型酸化チタンの仕事関数は、負帯電性シリカ１３,１４および正帯電性シリカ１６の各仕事関数よりも大きく、シアントナーのトナー母粒子８ａの仕事関数とほぼ同じかあるいはそれより大きく設定されている。具体的な測定の結果、ルチルアナターゼ型酸化チタンの仕事関数は５.６４ｅＶであり、また、実施例３のトナーの仕事関数は、５.５８ｅＶであった。
【０１００】
(2) 粉砕法トナーの実施例の作製
(a) 実施例４、実施例５、比較例７、および比較例８の粉砕法トナーの作製
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重量部に、シアン顔料のフタロシアニンブルー５重量部、離型剤として融点が１５２℃、Ｍｗが４０００のポリプロピレン３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て均一混合した後、内温１５０℃の二軸押し出し機で混練し、冷却した。この冷却物を２ｍｍ角以下に粗粉砕し、更にこの粗粉砕品をジェットミルで微粉砕し、分級装置により分級し、平均粒子径７.６μｍで、円形度０.９１のトナーを得た。また、このトナー母粒子の仕事関数は、測定の結果、５.４６ｅＶであった。
【０１０１】
得られたトナー母粒子に対して、重量比で、流動性改良剤であるヘキサメチルジシラザン（ＨＭＤＳ）で表面処理した負帯電性疎水性シリカの平均一次粒子径が約１２ｎｍのものを０.８重量％、同様に表面処理した負帯電性疎水性シリカの平均一次粒子径が約４０ｎｍのものを０.５重量％添加混合し、この添加混合トナーに、ルチルアナターゼ型で混晶比がルチル型１０重量％、アナターザ型が９０％のシランカップリング剤で疎水化処理したルチルアナターゼ型酸化チタン（疎水化度５８％、比表面積１５０ｍ²／ｇ）を０.４重量％添加混合して添加混合トナーを作製した。
【０１０２】
そして、疎水性のシリカをアミノシラン（ＡＳ）で表面処理した表４に示す大粒子径（平均一次粒子径：約３０ｎｍ）の正帯電性疎水性シリカ（シリカ▲１▼）を０.２％添加混合し、本発明の実施例４のトナーを作製した。また、同様に処理した表４に示す小粒子径（平均一次粒子径：約１２ｎｍ）の正帯電性疎水性シリカ（シリカ▲２▼）を０.２％添加混合し、比較例７のトナーを作製した。また、これらの正帯電性疎水性シリカを添加しない比較例８のトナーを作製した。
【０１０３】
更に、フタロシアニンブルーの代わりに顔料をキナクリドンに変更しかつ前述と同様にしてトナー母粒子を作製した。作製したトナー母粒子の仕事関数は、測定の結果、５.５７ｅＶであった。このトナー母粒子を前述の実施例４と同じようにして外添剤処理を行うことで、本発明の実施例５のトナーを作製した。測定の結果、実施例４および５、比較例７および８の各トナーの仕事関数は、それぞれ、５.４５ｅＶ、５.５６ｅＶ、５.４４ｅＶ、５.４６ｅＶであった。
【０１０４】
(b) 実施例６および実施例７の粉砕法トナーの作製
前述の本発明の実施例４のトナーの作製例にしたがって、顔料をピグメントイエロー１８０を使用したイエロートナー母粒子およびカーボンブラックを使用したブラックトナー母粒子を作製した。これらのトナー母粒子の仕事関数は、測定の結果、イエロートナー母粒子の仕事関数が５.６２ｅＶ、また、ブラックトナー母粒子の仕事関数が５.７２ｅＶであった。そして、これらのイエロートナー母粒子およびブラックトナー母粒子に対して、前述の実施例４のトナーの場合と同じようにして外添剤処理を行い、それぞれ本発明の実施例６および７の各トナーを作製した。測定の結果、実施例６および７の各トナーの仕事関数は、それぞれ、５.６１ｅＶおよび５.７１ｅＶであった。
【０１０５】
（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３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４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６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６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。
【０１０６】
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。
【０１０７】
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。
【０１０８】
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。
【０１０９】
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。
【０１１０】
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。
【０１１１】
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。
【０１１２】
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。
【０１１３】
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。
【０１１４】
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［図３および図４では１、図６では１４０］の製造例１）
製造例１の有機積層型感光体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１.５〜２μｍの下引き層１ｂを形成した。
【０１１５】
次いで、電荷発生顔料としてのオキシチタニルフタロシアニン顔料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、得られた顔料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。
【０１１６】
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、市販の表面分析装置｛ＡＣ−２型、理研計器（株）製｝を用い、照射光量５００ｎＷで測定したところ、５.４８ｅＶを示した。
【０１１７】
【化１】

【０１１８】
（有機感光体［図３および図４では１、図６では１４０］の製造例２）
製造例２の有機積層型感光体１の作製では、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、電荷輸送剤に下記構造式（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１（ＯＰＣ２）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。
【０１１９】
【化２】

【０１２０】
（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。
【０１２１】
（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。
【０１２２】
（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。
【０１２３】
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。
【０１２４】
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。
【０１２５】
（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。
【０１２６】
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。
【０１２７】
(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。
【０１２８】
(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。
【０１２９】
(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。
【０１３０】
(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。
【０１３１】
(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。
【０１３２】
(作像化の試験およびその試験結果）
（作像試験１）
図６に示す非接触現像プロセスが可能で有機感光体１を使用した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の明電位−６００Ｖ、有機感光体１の暗電位−８０Ｖ、ＤＣ現像バイアス−３００Ｖ、ＡＣ現像バイアス１.３５ｋＶ、ＡＣ周波数２.５ｋＨｚ）で、シアン現像器１０（Ｃ）に表４に示す本発明の実施例１のトナー、比較例１および２の各トナーをそれぞれセットし、ベタ画像濃度を約１.１〜１.２前後になるように作像した。その時の現像ローラ１１上のシアントナーの帯電特性量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。また、その時の有機感光体１上のカブリトナーをテープ転写法で測定するとともに、２色目印字時における転写ベルト３６から有機感光体１上に移る逆転写トナーも同様にしてテープ転写法で測定した。なお、テープ転写法とはトナー上に住友３Ｍ製のメンディングテープを貼り付け、カブリトナーや逆転写トナーをテープ上に転写し、次いで白紙上に貼り付けてテープ上から反射濃度計で濃度測定を行うもので、測定値よりテープ濃度を差し引いてカブリ濃度や逆転写濃度とを規定する。測定結果を表５に示す。
【０１３３】
【表５】

【０１３４】
表５から明らかなように、大粒子径（粒子径：約３０ｎｍ）の疎水性の正帯電性シリカ１６を添加すると、大粒子径の正帯電性シリカ１６が添加されない比較例３のトナーより帯電量が上がり、また、カブリトナーや逆転写トナーが減少することが示された。また、小粒子径（粒子径：約１２ｎｍ）の疎水性の正帯電性シリカを添加した比較例１および２の各トナーでは、逆に帯電量の低下やカブリトナー濃度と逆転写トナー濃度の上昇をもたらすことが示された。したがって、正帯電性シリカでも、大粒子径の正帯電性シリカ１６の方が小粒子径の正帯電性シリカより帯電量を上げ、かつカブリ防止と逆転写防止に対して効果があることが分かった。
【０１３５】
（作像試験２）
本発明の実施例４のトナーと、比較例７および８の各トナーとについて、電子顕微鏡写真を撮影し、それぞれ、図７、図８および図９に示す。図７ないし９に示す電子顕微鏡写真から明らかなように、大粒子径の疎水性の正帯電性シリカ１６を０.２重量％添加した実施例４のトナーは、外添剤がトナー母粒子８ａの表面に強固に固着している状態を呈しているが、これに反して、小粒子径の疎水性の正帯電性シリカを添加した比較例７のトナーおよび正帯電性シリカを添加していない比較例３のトナーは、いずれも、外添剤がトナー母粒子８ａの表面から少し浮いた固着性の弱い状態で存在している状態を呈している。
【０１３６】
したがって、本発明の実施例４の負帯電トナー８は、トナー母粒子８ａの表面に強固に固着している外添剤の前述の機能が充分にかつ効果的に発揮できるが、比較例７および８の各負帯電トナーは、トナー母粒子８ａの表面が遊離し易く、外添剤の前述の機能が充分に発揮することができないことが分かった。すなわち、外添剤のトナー母粒子８ａへの固着性が弱いと、トナーの帯電性が低下し、連続印字により現像ローラ１１の表面からトナーが飛散するようになる。実際に図６に示すカラープリンタのシアン現像器１０（Ｃ）に各トナーをセットして１０００枚の連続印字を行い、現像ローラ１１周辺のトナー飛散を目視により比較したが、本発明の実施例４のトナーの飛散はほとんど見られなかったが、比較例７および８の各トナーの飛散は確認された。なお、実施例４のトナーと同様の外添処理を行った本発明の実施例５のトナーであるマゼンタトナーを用いて、同様に１０００枚の印字試験を行ったが現像ローラ１１周辺へのトナー飛散を目視では確認できなかった。
【０１３７】
（作像試験３）
実施例１のトナーの大粒子径の正帯電性シリカ１６の添加量を、０〜０.６重量％までふって、作像試験１と同様にして作像を行った。その結果を表６に示す。
【０１３８】
【表６】

【０１３９】
表６から明らかなように、正帯電性シリカ１６の添加量を０.６％以上にすると、帯電量が低下するとともにベタ画像濃度も低くなり、更に逆転写トナー量が多くなる傾向にあることが分かった。したがって、正帯電性シリカ１６の添加量としては、負帯電性シリカ１３,１４の総量に対して、３０％以下にすることが良好な結果を得ることができるので、好ましい。
【０１４０】
（作像試験４）
本発明の実施例３のトナーを用いて、前述の作像試験１と同様に作像を行った。作像の結果、この実施例３のトナーは実施例１のトナーに比し、帯電量が−２０μｃ／ｇ、ベタ平均画像濃度が１.３５０、カブリトナーＯＤ値がほぼ０、逆転写トナーＯＤ値もほぼ０をそれぞれ示し、実質上カブリトナーと逆転写トナーの発生がない非常に高画質な印字品質が得られることが分かった。これは、正帯電性シリカ１６に加えて、それよりも仕事関数の大きいルチルアナターゼ型酸化チタンを更に加えることで、より負の過帯電性が抑制されると同時に、正極性のトナーの発生が抑制されることによると考えられる。
【０１４１】
（作像試験５）
実施例４のトナーであるシアントナー、実施例５のトナーであるマゼンタトナー、実施例６のトナーであるイエロートナー、および実施例７のトナーであるブラックトナーの４色トナーと前述の構造式（２）で与えられる有機感光体１（ＯＰＣ２）とを組み合わせて、図６に示す接触現像方式が可能なフルカラープリンタを使用して接触現像方式によるフルカラーの作像を行った。この作像は、環境試験室内で１０℃の低温でＲＨ１５％の低湿、２３℃の常温でＲＨ６０％の常湿、および３５℃の高温でＲＨ６５％の高湿の各条件下で、５０００枚の各色合計で２０％デューティのフルカラー印字を行った。作像された画像品質をチェックしたが、現像部周辺のトナー飛散もなく、安定した画像品質を得ることができた。
【０１４２】
（作像試験６）
実施例２のトナーと比較例４ないし６とを用いて、作像試験５の接触現像方式で作像後、下記の定着器６０を使用して定着性の比較を行った。
定着器６０は、φ４０のヒータローラ｛ハロゲンランプ６００ｗ内蔵、シリコンゴム２.５ｍｍ（６０°ＪＩＳＡ）上にＰＦＡを厚み５０μｍに成膜｝とφ４０のプレスローラ｛ハロゲンランプ３００ｗ内蔵、シリコンゴム２.５ｍｍ（６０°ＪＩＳＡ）上にＰＦＡを厚み５０μｍに成膜｝の二本加圧ローラ（約３８ｋｇｆの加重）を用い、設定温度１９０℃にて定着を行い、各トナー間の定着性を比較した。綿布に２００ｇの重りをのせて、ベタ画像上に５０回擦り、擦る前後のベタ画像濃度を測定し、トナーの定着性を保持率（定着率）（％）に換算して、定着性の評価の指標とした。その結果を表７に示す。
【０１４３】
【表７】

【０１４４】
表７から明らかなように、実施例２のトナーは９５％の保持率（定着率）を示して負帯電性シリカの使用量の少ない比較例６のトナーと遜色なかったが、相対的に小粒子径シリカ１３のシリカ量が多い比較例４および５は保持率（定着率）９０％を示した。これにより、同じ量の流動化剤を添加しても、大粒子径の正帯電性シリカ１６を使用した方が定着性を低下させることはほぼないことがわかった。なお、小粒子径の負帯電性シリカ１３の平均一次粒子径を約１２ｎｍと約１６ｎｍに変更して同様の定着試験を行って調べたが、この傾向は逆転することはなく、正帯電性シリカの平均一次粒子径の大きい方が定着性を低下させることがなかった。
【０１４５】
【発明の効果】
以上の説明から明らかなように、本発明の画像形成装置によれば、疎水性の負帯電性外添剤が少なくとも添加されたトナー母粒子に、正帯電性を有する材料で表面処理され、かつ全体の仕事関数がトナー母粒子の仕事関数より小さく設定した疎水性の正帯電性外添剤を添加して、正帯電性外添剤がマイクロキャリヤの機能を発揮できるようにしているため、トナー母粒子の帯電の立ち上がりを早くでき、逆転写トナーおよびカブリを効果的に抑制できるようになる。
【０１４６】
また、疎水性の負帯電性シリカが疎水性ルチルアナターゼ型酸化チタンと併用されることにより、疎水性ルチルアナターゼ型酸化チタンの有するトナー母粒子に埋没し難い特質と電荷調整機能とをより効果的に活すことができる。したがって、疎水性の負帯電性シリカの有する負帯電性能および流動性という固有の特性と、疎水性ルチルアナターゼ型酸化チタンの有する比較的低抵抗でかつ負の過帯電防止特性という固有の特性とが相乗された機能をトナー母粒子に付与することができる。これにより、負帯電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ので、より良好な負帯電特性を得ることができ、その結果、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。
【０１４７】
しかも、平均一次粒子径の異なる２種類の疎水性の負帯電性シリカを用いることで、トナー母粒子の表面を疎水性の負帯電性シリカ、疎水性の正帯電性シリカ、および疎水性のルチルアナターゼ型酸化チタンによりまんべんなく覆うようにしているので、負帯電トナーの負帯電をより一層長期にわたり安定でき、連続印字におけるより安定した画像品質を与えることができる。特に、少なくとも平均一次粒子が小粒子径である疎水性の負帯電シリカを、疎水性の正帯電シリカと疎水性ルチルアナターゼ型酸化チタンの合計量より多く添加することで、負帯電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。
したがって、非画像部のカブリをより一層抑制できるとともに転写効率をより一層向上でき、更に逆転写トナーの発生をより効果的に抑制できるようになる。
【０１４８】
更に、流動化剤である正帯電性シリカを添加するにあたっては、大粒子径の正帯電性シリカを使用することで、小粒子径の正帯電性シリカを使用した場合に比べて定着性の低下を防止できる。
【０１４９】
更に、粉砕法トナーおよび重合法トナーを問わず、大小２種の粒子径の疎水性の負帯電性シリカ、疎水性の正帯電性シリカおよび疎水性ルチルアナターゼ型酸化チタンを併用することで疎水性の負帯電性シリカの量を少なくできるので、逆転写トナー、画像濃度の変動、および非画像部のカブリが更に効果的に抑制できるようになる。
【０１５０】
そして、逆転写トナーの発生をより効果的に抑制できることから、本発明の負帯電トナーをフルカラートナーとして使用したときに、画像濃度を長期にわたってより均一に維持できる。これにより、高品質のフルカラーの画像を長期にわたって得ることができる。
【０１５１】
更に、本発明の負帯電トナーの製造方法によれば、逆転写トナー、カブリトナー、および画像濃度の変動を効果的に抑制できる本発明の負帯電トナーを確実に製造することができる。
【図面の簡単な説明】
【図１】 本発明にかかる負帯電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】 図１に示す例の負帯電トナーの挙動を説明する説明図である。
【図３】 本発明にかかる負帯電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４】 本発明にかかる負帯電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５】 図３および図４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６】 本発明の負帯電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７】 本発明の実施例４の負帯電トナーを撮影した電子顕微鏡写真を示す図である。
【図８】 比較例７の負帯電トナーを撮影した電子顕微鏡写真を示す図である。
【図９】 比較例８の負帯電トナーを撮影した電子顕微鏡写真を示す図である。
【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…小粒子径の疎水性の負帯電性シリカ（ＳｉＯ₂）、１４…大粒子径の疎水性の負帯電性シリカ（ＳｉＯ₂）、１５…疎水性ルチルアナターゼ型酸化チタン（ＴｉＯ₂）、１６…大粒子径の疎水性の正帯電性シリカ（ＳｉＯ₂）、Ｌ…現像ギャップ[0001]
BACKGROUND OF THE INVENTION
The present invention is used in an image forming apparatus that forms an image by electrophotography or the like, and a one-component non-magnetic toner for developing an electrostatic latent image on a latent image carrier of the image forming apparatus and a method for manufacturing the same. In particular, the present invention belongs to a technical field of a negatively charged toner which is a one-component nonmagnetic toner obtained by adding at least an external additive having a negative charging property to toner base particles and a method for producing the same.
[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 charged 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,
{Circle around (1)} Even when an external additive is added to the toner, a charge amount distribution exists, and therefore, even if the toner is negatively charged, generation of a positively charged toner cannot be avoided. As a result, in an image forming apparatus that forms an image by negative charge reversal development, toner adheres to a non-image portion of a latent image carrier (photosensitive member), so that the amount of cleaning toner increases. Also, as the number of printed sheets increases, the external additive on the toner surface is buried, so the amount of the external additive that functions effectively effectively decreases, the fog toner amount further increases, and at the same time the toner charge amount increases. As a result, toner scattering occurs.
{Circle around (2)} 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.
(3) 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 electrical 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.
(4) 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. Japanese Patent Laid-Open No. 2000-128534 proposes obtaining stable charging characteristics without reducing frictional charging properties and improving environment dependency, fluidity and caking resistance. According to the toner disclosed in this publication, the above problems (1) to (4) 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 (3) described above to some extent.
[0008]
[Problems to be solved by the invention]
However, in the toner of each of the above-mentioned publications, the rutile type titanium oxide can suppress the titanium oxide from being embedded in the toner base particles, and can obtain a stable charging characteristic to some extent, and the anatase type titanium oxide has a fluidity. Although both the environmental dependency and the environmental dependency can be improved, the rutile / anatase type titanium oxide is merely used as an external additive, so that it is embedded in the toner base particles. It cannot be said that the difficult characteristics and the charge adjustment function are effectively utilized, and there is a limit to the obtained stable charging characteristics, improvement of fluidity, and improvement of environment dependency. That is, in order to more effectively solve the above problems (1) to (4), further improvement of the toner is required.
[0009]
The present invention has been made in view of such circumstances, and the object thereof is to further reduce the fogging of the toner in the non-image area, to further improve the transfer efficiency, and to further stabilize the charging characteristics. To provide a negatively charged toner and a method for producing the same.
Another object of the present invention is to provide a negatively charged toner that can more effectively suppress the occurrence of reverse transfer toner when used as a full color toner, and that can maintain the image density more uniformly and for a longer period of time, and a method for producing the same. It is to be.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the negatively charged toner according to the first aspect of the present invention has negative chargeability with respect to the toner base particles, and the overall work function is set smaller than the work function of the toner base particles. In the negatively charged toner to which at least the hydrophobic negatively chargeable external additive is added, the toner base particles are surface-treated with aminosilane having positive chargeability with respect to the toner base particles, and the whole work function is A hydrophobic positively chargeable external additive set smaller than the work function of the negatively chargeable externally added silica, and the negatively chargeable external additive is a hydrophobic negatively chargeable silica surface-treated with hexamethyldisilane, The positively chargeable external additive is a hydrophobic positively chargeable silica having a work function substantially equal to or larger than the work function of the toner base particles, and having a silane coupling function. The treated hydrophobic rutile-anatase type titanium oxide is added, and the hydrophobic negatively charged silica is added more than the total amount of the hydrophobic positively charged silica and the hydrophobic rutile-anatase type titanium oxide. It is characterized by having.
[0011]
In the invention of claim 2, the hydrophobic negatively chargeable silica is composed of negatively chargeable silica having an average primary particle diameter of a small particle diameter and negative chargeability of an average primary particle diameter larger than the small particle diameter. The hydrophobic positively chargeable silica composed of silica is characterized in that the average primary particle diameter is the same as or substantially the same as the negatively chargeable silica having the large particle diameter.
[0012]
Furthermore, in the method for producing a negatively charged toner according to the third aspect of the invention, the toner base particles and the negatively charged silica having a large and small particle diameter are first mixed, and then the hydrophobic rutile-anatase type titanium oxide is added to the mixture. The negatively charged toner is manufactured by adding and mixing, and further mixing the positively chargeable silica.
[0013]
Furthermore, the invention of claim 5 is characterized in that the hydrophobic negatively chargeable silica is composed of a negatively chargeable silica having an average primary particle size of a small particle size and a negative chargeability of which the average primary particle size is larger than the small particle size. The hydrophobic positively-charged silica is characterized in that the average primary particle diameter is the same as or substantially the same as the negatively-charged silica having the large particle diameter.
[0014]
Further, the invention of claim 6 is characterized in that the amount of the hydrophobic positively chargeable silica is set to 30% by weight or less of the total weight of the hydrophobic negatively chargeable silica.
Further, the invention of claim 7 is a pulverized toner using the toner base particles prepared by a pulverizing method or a polymerization toner using the toner base particles prepared by a polymerization method.
[0015]
Further, the invention of claim 8 is characterized in that the circularity is 0.91 or more.
Further, the invention of claim 9 is a 50% diameter (D ₅₀ ) Is 9 μm or less.
[0016]
Furthermore, in the method for producing a negatively charged toner according to the invention of claim 10, the toner base particles and the negatively chargeable silica having a large and small particle diameter are first mixed, and then the hydrophobic rutile-anatase type titanium oxide is added to the mixture. The negatively charged toner is manufactured by adding and mixing, and further mixing the positively chargeable silica.
[0017]
[Action]
In the negatively charged toner of the present invention configured as described above, the toner base particles to which at least a hydrophobic negatively charged external additive is added are made of a material having a positive chargeability with respect to the toner base particles. By adding a hydrophobic positively chargeable external additive that is surface-treated and has an overall work function smaller than the work function of the toner base particles, a hydrophobic negatively chargeable external additive and a hydrophobic Since each work function of the positively chargeable external additive is smaller than that of the toner base particles, both the negatively chargeable external additive and the positively chargeable external additive are directly attached to the surface of the toner base particles.
[0018]
Accordingly, since the positively chargeable external additive exhibits the function of the microcarrier, the toner base particles are quickly charged, and the reverse transfer toner and the fog are effectively suppressed.
[0019]
Further, by using hydrophobic negatively-charged silica in combination with hydrophobic positively-charged silica and hydrophobic rutile-anatase-type titanium oxide, each work function of negatively-charged silica and positively-charged silica can Since the work function is smaller, the hydrophobic negatively-charged silica and the hydrophobic positively-charged silica are directly attached to the toner base particles, and the work function of the hydrophobic rutile-anatase type titanium oxide is the same as that of the toner base particles. Since the work function is substantially the same as that of the hydrophobic negatively-charged silica, the hydrophobic rutile-anatase type titanium oxide adheres to the hydrophobic negatively-charged silica adhering to the toner base particles. It becomes attached to the surface of the particles.
[0020]
Therefore, the characteristics that are difficult to embed in the toner base particles of the hydrophobic rutile-anatase type titanium oxide and the charge adjustment function are more effectively utilized, and the negative charging performance and fluidity of the hydrophobic negatively charged silica. Thus, the toner base particles are given a function in which the inherent characteristics of the hydrophobic rutile-anatase type titanium oxide and the inherent characteristics of the relatively low resistance and negative overcharge prevention characteristics are combined. As a result, the negatively charged toner is prevented from lowering its fluidity and is prevented from being negatively overcharged, so that it has better negative charging characteristics. Furthermore, it is effectively suppressed.
[0021]
In addition, by using two types of hydrophobic negatively chargeable silica having different average primary particle diameters, the negatively chargeable silica having a small particle diameter is embedded in the toner base particles, and the work function is larger than the work function of the negatively chargeable silica. Hydrophobic rutile-anatase type titanium oxide of the function is less likely to be fixed to the negatively charged silica embedded by the contact potential difference due to the work function difference and released from the toner base particles, and the hydrophobic negatively charged silica having a large particle size In addition, since the hydrophobic positively-charged silica having a large particle size is fixed to the surface of the toner base particle, the surface of the toner base particle is a hydrophobic negatively-charged silica having a large and small particle size, and the hydrophobic positively chargeable property. Evenly covered with silica and hydrophobic rutile-anatase type titanium oxide, negatively charged toners have a more stable long-term negative charge and more stable in continuous printing So give the image quality. In particular, a negatively charged toner can be obtained by adding more hydrophobic negatively chargeable silica having an average primary particle having a smaller particle diameter than the total amount of hydrophobic positively charged silica and hydrophobic rutile-anatase type titanium oxide. Is more stable over a longer period of time.
Accordingly, the fogging of the non-image portion is further suppressed, the transfer efficiency is further improved, and the generation of the reverse transfer toner is further effectively suppressed.
[0022]
In addition, when adding positively-charged silica, which is a fluidizing agent, the use of large-particle-size positively-charged silica is less fixable than when small-particle-size positively-charged silica is used. And fog and reverse transfer toner are also reduced.
[0023]
Furthermore, it is necessary to increase the amount of hydrophobic negatively charged silica when the toner particle size is reduced, regardless of whether the toner is pulverized or polymerized, but when the amount of hydrophobic negatively charged silica is increased. Not only does the toner charge amount become too large in the initial stage, but the effective surface amount of the hydrophobic negatively-charged silica is reduced by embedding or scattering of the hydrophobic negatively-charged silica having a small particle diameter as printing progresses. The toner charge amount decreases. For this reason, not only the reverse transfer toner, the image density fluctuation, or the fog amount increases, but also the toner consumption tends to increase. However, the negatively charged toner of the present invention has hydrophobic properties of two kinds of large and small particle sizes. By using negatively-charged silica, hydrophobic positively-charged silica, and hydrophobic rutile-anatase-type titanium oxide in combination, the amount of hydrophobic negatively-charged silica can be reduced. In addition, fogging of the non-image portion is more effectively suppressed.
[0024]
Therefore, since the occurrence of reverse transfer toner is more effectively suppressed, when the negatively charged toner of the present invention is used as a full color toner, the image density is maintained more uniformly and for a longer period of time. As a result, a high-quality full-color image can be obtained over a long period of time.
[0025]
Furthermore, in the method for producing a negatively charged toner according to the present invention, the toner base particles and the negatively charged silica having a large and small particle diameter are first mixed, and then the hydrophobic rutile-anatase type titanium oxide is added to the mixture and mixed. Further, by mixing the positively chargeable silica, the hydrophobic rutile-anatase type titanium oxide is securely attached to the surface of the toner base particles in the form of being attached to the hydrophobic negatively charged silica attached to the toner base particles. Then, the positively chargeable silica is directly attached to the surface of the toner base particles. As a result, the reverse transfer toner, fog toner, and negatively charged toner of the present invention capable of effectively suppressing fluctuations in image density are reliably produced.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram schematically showing an example of an embodiment of a negatively charged toner according to the present invention.
As shown in FIG. 1, the negatively charged toner 8 in this example is a one-component non-magnetic toner, and is configured by externally adding an additive 12 to toner base particles 8a. The external additive 12 includes a hydrophobic negatively-charged silica (SiO 2) having a small average primary particle size and two large particle sizes. ₂ ) 13,14, hydrophobic rutile-anatase type titanium oxide (TiO) ₂ ) 15 and a hydrophobic positively-charged silica (SiO 2) having the same or almost the same diameter as the hydrophobic negatively-charged silica 14 having a large particle size ₂ ) 16 are used.
[0027]
The average primary particle diameter of the hydrophobic negatively chargeable silica 13 having a small particle diameter is 20 nm or less, preferably 7 to 16 nm (this notation means 7 nm to 16 nm. The same applies to other units). In addition, the average primary particle diameter of the hydrophobic negatively chargeable silica 14 having a large particle diameter is set to 30 nm or more, preferably 40 to 50 nm. Further, the hydrophobic rutile-anatase-type titanium oxide 15 uses rutile-type titanium oxide and anatase-type titanium oxide at a predetermined mixed crystal ratio. For example, the manufacturing method disclosed in the above-mentioned JP-A-2000-128534 Can be manufactured. This hydrophobic rutile-anatase type titanium oxide 15 has a spindle shape, and its major axis diameter is 0.02 to 0.10 μm, and the ratio of major axis to minor axis is set to 2 to 8. ing. Furthermore, the average primary particle diameter of the hydrophobic chargeable silica 16 is the same as or substantially the same as the particle diameter of the hydrophobic negatively chargeable silica 14 having a large particle diameter, and is 30 nm or more, preferably 40 to 50 nm. Is set.
[0028]
In the negatively charged toner 8 of this example, the toner base particle 8a is negative due to the hydrophobic negatively-charged silica 13, 14 having a work function (illustrated later) smaller than the work function of the toner base particle 8a (illustrated later). A work function (illustrated later) that is charged and has a work function that is greater than or equal to the work function of the toner base particles 8a (the work function difference is within 0.25 eV). By using the mixed hydrophobic rutile-anatase type titanium oxide 15, the toner base particles 8 a are prevented from being overcharged.
[0029]
Further, the hydrophobic positively chargeable silica 16 is surface-treated with a material such as aminosilane so as to be positively charged, and the work function of the whole is set smaller than the work function of the toner base particles 8a. The hydrophobic positively chargeable silica 16 imparts a positive charge to the toner base particles 8a.
[0030]
The work function (Φ) is measured by a surface analyzer (AC-2 manufactured by Riken Keiki Co., Ltd.) with an irradiation light quantity of 500 nW, and is the energy required to extract electrons from the substance. The smaller is, the easier it is to emit electrons, and the larger is, 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.
[0031]
The toner base particles used in the negatively charged toner 8 of this example configured as described above can be produced by either a pulverization method or a polymerization method, and the production will be described below.
[0032]
First, preparation of a negatively charged toner (hereinafter referred to as a pulverized toner) 8 using toner mother particles by a pulverization method will be described.
The pulverized toner 8 is obtained by uniformly mixing a resin binder with a pigment, a release agent, and a charge control agent using a Henschel mixer, melting and kneading with a biaxial extruder, cooling, and then subjecting to a coarse pulverization-fine pulverization process. The toner base particles 8a obtained by the treatment are further externally added with a fluidity improver which is an external additive to obtain a toner.
[0033]
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 to 75 ° C and a flow softening temperature of 100 to 150 ° C.
[0034]
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.
[0035]
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.
[0036]
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.
[0037]
Examples of the fluidity improver that is an external additive include at least the above-described hydrophobic negatively-charged silica 13 having a small particle size, the above-mentioned hydrophobic negatively-charged silica 14 having a large particle size, and the above-described hydrophobic rutile-anatase. The positively chargeable silica 16 having the same large particle diameter as or substantially the same as the negatively charged silica 14 having the large particle diameter and the type titanium oxide 15 is used. In addition, one or more other known fluidity improvers for inorganic and organic toners may be mixed and used. Other known fluidity improvers for inorganic and organic toners include, for example, alumina, magnesium fluoride, silicon carbide, boron carbide, titanium carbide, zirconium carbide, boron nitride, titanium nitride, zirconium nitride, magnetite, disulfide. Fine particles of molybdenum, aluminum stearate, magnesium stearate, zinc stearate, calcium stearate, titanate metal salts such as barium titanate and strontium titanate, and silicon metal salts can be used. These fine particles 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 other resin fine particles include acrylic resin, styrene resin, and fluororesin.
[0038]
The component ratio (weight ratio) in the pulverized toner 8 is shown in Table 1.
[0039]
[Table 1]

[0040]
As shown in Table 1, the colorant is 0.5 to 15 parts by weight, preferably 1 to 10 parts by weight, and the release agent is 1 to 10 parts by weight, preferably 100 parts by weight of the binder resin. The charge control agent is 0.1 to 7 parts by weight, preferably 0.5 to 5 parts by weight, and the fluidity improver is 0.1 to 5 parts by weight. The amount is preferably 0.5 to 4 parts by weight.
[0041]
In the pulverized toner 8 of this example, the circularity is preferably increased by a 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.
[0042]
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.
[0043]
Further, as the pulverized toner 8 obtained in this manner, the average particle diameter (D ₅₀ ) Is set to 9 μm or less, preferably 4.5 to 8 μm. Thereby, the particle diameter of the pulverized toner 8 becomes a relatively small particle diameter, and by using hydrophobic negatively-charged silica and hydrophobic rutile-anatase type titanium oxide as external additives in combination with the small particle diameter toner, Since 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, the fixability is improved.
In the present invention, the average particle diameter and circularity of the toner particles and the like are values measured with an FPIA 2100 manufactured by Sysmex Corporation.
[0044]
Further, in the pulverized toner 8, the total amount (weight) of the external additive is set to 0.5% by weight or more and 4.0% by weight or less with respect to the weight of the toner base particles. 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. If the total amount of the external additive is 4.0% by weight or more, it may be scattered from the toner surface or the fixing property may be deteriorated.
[0045]
Next, the production of a toner (hereinafter referred to as a polymerization toner) 8 using toner mother particles by a polymerization method will be described.
Examples of the polymerization toner 8 include a suspension polymerization method and an emulsion polymerization method. 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.
[0046]
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.
[0047]
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 Pills, 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.
[0048]
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.
[0049]
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.
[0050]
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.
[0051]
Table 2 shows the component ratio (weight) of the emulsion polymerization toner 8.
[0052]
[Table 2]

[0053]
As shown in Table 2, with respect to 100 parts by weight of the polymerizable monomer, the polymerization initiator is 0.03 to 2, preferably 0.1 to 1 part by weight, and the surfactant is 0.01 to 0.1 part. In addition, the release agent is 1 to 40 parts by weight, preferably 2 to 35 parts by weight, and the charge control agent is 0.1 to 7 parts by weight, preferably 0.5 to 5 parts by weight. The colorant is 1 to 20 parts by weight, preferably 3 to 10 parts by weight, and the flocculant (electrolyte) is 0.05 to 5 parts by weight, preferably 0.1 to 2 parts by weight.
[0054]
Even in the polymerization method toner 8 of this example, it is preferable to increase the circularity by a 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.
[0055]
The polymerization toner 8 can be produced by a dispersion polymerization method other than the above method, and can also be produced, for example, by a 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 is performed at a temperature equal to or higher than the Tg temperature of the toner to obtain a desired toner shape.
[0056]
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.
[0057]
Also in the polymerization toner 8 obtained in this way, the average particle diameter (D ₅₀ ) Is set to 9 μm or less, preferably 4.5 to 8 μm. Thereby, the particle diameter of the polymerization toner 8 becomes a relatively small particle diameter, and by using hydrophobic negatively-charged silica and hydrophobic rutile-anatase type titanium oxide as an external additive in combination with the small particle diameter toner, Since 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.
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.
[0058]
Further, in this polymerization toner 8 as well, the total amount (weight) of the external additive is 0.5% by weight or more and 4.0% by weight or less with respect to the weight of the toner base particles, as in the above-mentioned pulverized toner. However, it is preferably set in the range of 1.0 wt% to 3.5 wt%. 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. When the total amount of the external additives is 4.0% by weight or more, it becomes free from the toner surface or deteriorates the fixability.
[0059]
In the negatively charged toner 8 of this example configured as described above, in both the polymerization method toner and the pulverization method toner, as shown in FIG. 2, the hydrophobic negatively chargeable silica 13 having a small particle diameter is the toner base particle 8a. It becomes easy to be buried in. A hydrophobic rutile-anatase type titanium oxide 15 having a work function larger than the work function of the hydrophobic negatively chargeable silica 13 is fixed to the buried hydrophobic negatively chargeable silica 13 by the contact potential difference due to the work function difference, and the toner base particles 8a. And the large-diameter hydrophobic negatively-charged silica 14 and the large-particle-size hydrophobic positively-charged silica 16 are fixed to the surface of the toner base particles 8a. The surface of the mother particle 8 a is evenly covered with the hydrophobic negatively charged silica 13, 14, the hydrophobic rutile-anatase type titanium oxide 15, and the hydrophobic positively charged silica 16.
[0060]
Therefore, the characteristics that are difficult to be embedded in the toner base particles 8a of the hydrophobic rutile-anatase type titanium oxide 15 and the charge adjusting function can be utilized more effectively, and the hydrophobic negatively-charged silica 13 and 14 can be effectively utilized. The toner base particle 8a has a function in which the inherent characteristics of negative charging performance and fluidity possessed and the inherent characteristics of the hydrophobic rutile-anatase-type titanium oxide 15 which are relatively low resistance and negative overcharge prevention characteristics are combined. Can be granted. As a result, the fluidity of the negatively charged toner 8 can be prevented from being lowered and negative overcharge can be prevented. As a result, better negative charge characteristics can be obtained. As a result, generation and fogging of the reverse transfer toner can be prevented. It can be effectively suppressed. Therefore, the negatively charged toner 8 is more stable in negative charge for a longer period of time, and gives a stable image quality in continuous printing.
[0061]
In addition to this, the positively chargeable silica 16 having a large particle diameter exhibits the function of a microcarrier, so that the rising of the charge of the toner base particles 8a can be accelerated. As a result, the reverse transfer toner and fog are more effectively suppressed.
In particular, the addition amount (weight) of the positively charged silica 16 having a large particle size is set to 30% or less of the total added weight of the hydrophobic negatively charged silica 13, 14. 13 and 14 are preferable because the functions of the positively chargeable silica 16 having a large particle diameter can be effectively exhibited without impairing the aforementioned functions.
[0062]
Further, the total amount (weight) of the hydrophobic negatively-charged silica 13, 14 is added more than the total amount (weight) of the hydrophobic rutile-anatase-type titanium oxide 15 and the hydrophobic positively-charged silica 16. The negative charging of the charged toner 8 is stabilized for a longer period. Accordingly, the fogging of the non-image portion is further suppressed, the transfer efficiency is further improved, and the generation of the reverse transfer toner is further effectively suppressed.
[0063]
Further, even when the same amount of fluidizing agent is added, the use of the positively-charged silica 16 having a large particle diameter may lower the fixing property compared to the case where a positively-charged silica having a small particle diameter is used. Less fog and reverse transfer toner.
[0064]
FIG. 3 is a diagram schematically showing an example of a non-contact one-component development method using the negatively charged toner 8 of this example, and FIG. 4 is a contact one-component development method using the negatively charged toner 8 of this example. FIG. 3 and 4, 1 is an organic photoreceptor, 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, 8 is a negatively charged toner, 9 Is a transfer material, 10 is a developing roller, and L is a developing gap in a non-contact one-component developing process.
[0065]
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. 5A, 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 an electroconductive support 1a via an undercoat layer 1b. Is.
[0066]
As the conductive support 1a, a known conductive support can be used. ^Ten Those having conductivity of Ω · cm or less, for example, tubular materials obtained by cutting aluminum alloy, tubular materials obtained by depositing aluminum on polyethylene terephthalate film or imparting conductivity by 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.
[0067]
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. Moreover, you may make these resins contain metal oxides, such as titanium dioxide and a zinc oxide.
[0068]
As the charge generation pigment in the charge generation layer 1c, a known material can be used. 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.
[0069]
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 component 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.
[0070]
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.
[0071]
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.
[0072]
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.
[0073]
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.
[0074]
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 coating. Method such as law is used. In addition, the drying after coating is preferably performed by drying at room temperature and then heating and drying at a temperature of 30 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 to 10 μm, preferably 0.1 to 3 μm. In the charge transport layer 1d, the thickness is in the range of 5 to 50 μm, preferably 10 to 40 μm.
[0075]
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. 5B. 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.
[0076]
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.
[0077]
The composition ratio of each component is 40 to 75% by weight of binder, 0.5 to 20% by weight of charge generator, 10 to 50% by weight of charge transport agent, and 0.5 to 30% by weight of sensitizer, preferably binder. 45 to 65% by weight, charge generating agent 1 to 20% by weight, charge transporting agent 20 to 40% by weight, and sensitizer 2 to 25% by weight. The solvent is preferably a solvent that is not soluble in the undercoat layer, and examples thereof include toluene, methyl ethyl ketone, and tetrahydrofuran.
[0078]
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 to 40 μm, preferably 20 to 35 μm, to obtain a single-layer organic photoreceptor layer 1e.
[0079]
The organic photoreceptor 1 thus configured is a photoreceptor drum having a diameter of 24 to 86 mm and rotating at a surface speed of 60 to 300 mm / s. After the surface is uniformly negatively charged by the corona charger 2, By performing exposure 3 according to information to be recorded, an electrostatic latent image is formed on the surface of the photosensitive drum.
[0080]
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 charged toner 8 onto the organic photoreceptor 1, thereby forming a visible image. It is to become. A negatively charged 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. 3. 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.
[0081]
The developing roller 11 is, for example, a roller having a diameter of 16 to 24 mm, 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 -10 ⁸ 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 applied from a power source (not shown) through the shaft and central axis of the pipe. Is done.
[0082]
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. It is pressed at a linear pressure of 20 to 60 gf / cm using a repulsive force, and the toner layer thickness on the developing roller 11 is 5 to 20 μm, preferably 6 to 15 μm. Is preferably 1 to 1.8 layers.
[0083]
In the non-contact developing type image forming apparatus, 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 to 350 μm, and is not shown. The development bias of the direct current voltage (DC) is -200 to -500 V, and the alternating voltage (AC) superimposed on this is preferably 1.5 to 3.5 kHz and a PP voltage of 1000 to 1800 V. 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.
[0084]
The developing roller 11 rotates counterclockwise as shown in the drawing, and the negatively charged toner 8 conveyed by the supply roller 6 is conveyed to the portion facing the organic photoreceptor 1 while adsorbed on the surface thereof. The negatively charged toner 8 is developed by vibrating between the surface of the developing roller 11 and the surface of the organic photosensitive member 1 by applying an alternating voltage superimposed on the opposing portion of the organic photosensitive member 1 and the developing roller 11. Is done. 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.
[0085]
Further, a transfer material 9 such as paper or an intermediate transfer medium (not shown in FIG. 3; shown in FIG. 5 described later) is sent between the organic photoreceptor 1 and the transfer roller 5 visualized. The pressing load applied to the organic photoreceptor 1 by the transfer roller 5 is 20 to 70 gf / cm, preferably 25 to 50 gf / cm, which is the same as that of the contact developing method.
[0086]
The non-contact development process shown in FIG. 3 and the non-contact development process shown in FIG. 4 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 shown in FIG. 6 and a rotatable latent image carrier (described later), the four color developing devices and the latent image carriers. 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.
[0087]
Next, an example of producing a negatively charged toner used in the image forming apparatus of the present invention, and an image obtained by the non-contact or contact one-component development process shown in FIG. 6 having the basic configuration shown in FIG. 3 using the negatively charged toner. An example of producing an organic photoreceptor and a transfer medium of the forming apparatus will be described. Note that the image forming apparatus shown in FIG. 6 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.
[0088]
(Example of production of negatively charged toner)
The negatively charged toner 8 was prepared for both the above-described polymerization toner and pulverization toner. In that case, the fluidity improver (external additive) used in the preparation of the toner of each example is a hydrophobic rutile-anatase type titanium oxide (20 nm) having a major axis length of 20 nm and subjected to a silane coupling treatment. Hydrophobic negatively chargeable vapor phase silica (7 nm) surface-treated with hexamethyldisilane (HMDS) having a small particle diameter of 7 nm, the same as that of a small particle diameter having an average primary particle diameter of 12 nm Hydrophobized negatively chargeable vapor phase method silica (12 nm), small particle size with an average primary particle size of 16 nm, similarly hydrophobicized negatively chargeable vapor phase method silica (16 nm), average primary Positively charged by a large particle size of 40 nm, negatively charged negatively charged vapor-phase silica (40 nm), and aminosilane (AS) of large particle size having an average primary particle size of 30 nm. surface Physical hydrophobic positively chargeable fumed silica (30nm) ▲ 1 ▼ (silica shown in Table 4 below ▲ 1 ▼) is any combination of. Further, for the comparative example of the present invention, two types of positively charged gas phase method silica (12 nm) having a small particle diameter and an average primary particle diameter of 12 nm that have been similarly hydrophobized (12 nm) (2), (3) (Silica (2), (3) shown in Table 4 described later) was produced. The results of measuring these work functions Φ are shown in Table 3. In addition, each work function (PHI) was measured by the above-mentioned photoelectron spectrometer AC-2 by Riken Keiki Co., Ltd. with the irradiation light quantity 500nW.
[0089]
[Table 3]

[0090]
As can be seen from Table 3, the work function Φ of each hydrophobized rutile-anatase-type titanium oxide (20 nm) was 5.64 eV, and the normalized photoelectron yield at this time was 8.4. Further, the work function Φ of the negatively chargeable vapor phase silica (7 nm) was 5.18 eV, and the normalized photoelectron yield was 6.1. Further, the work function Φ of the negatively chargeable vapor phase silica (12 nm) was 5.22 eV, and the normalized photoelectron yield was 5.1. Furthermore, the work function Φ of negatively chargeable vapor phase silica (16 nm) was 5.19 eV, and the normalized photoelectron yield was 6.8. Further, the work function Φ of the negatively chargeable vapor phase silica (40 nm) was 5.24 eV, and the normalized photoelectron yield was 5.2. Further, the work function Φ of the positively chargeable vapor phase silica (30 nm) (1) was 5.37 eV, and the normalized photoelectron yield was 11.5. Furthermore, the positively chargeable vapor phase method silica (12 nm 2 has a work function Φ of 5.13 eV and a normalized photoelectron yield of 10.7. Further, the positively chargeable vapor phase method silica (12 nm) The work function Φ of (3) was 5.14 eV, and the normalized photoelectron yield was 7.8.
[0091]
(1) Preparation of examples of emulsion polymerization toner and comparative examples
(a) Production of emulsion polymerization toners of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3
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.
[0092]
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.
[0093]
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 termination of the polymerization, 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.
[0094]
As a result of the measurement, the mother particles of the obtained cyan toner are toners having an average particle diameter of 6.8 μm and a circularity of 0.98. The work function of the toner particles is 5.57 eV as measured by the surface analyzer. Met. A small particle size negative charge having an average primary particle size of about 7 nm of negatively chargeable hydrophobic silica surface-treated with hexamethyldisilazane (HMDS), which is a fluidity improver, by weight ratio with respect to the mother particles of the cyan toner. An additive mixed toner was prepared by adding 1% by weight of silica 13 and 1% by weight of negatively-charged hydrophobic silica 14% having a large average particle diameter of about 40 nm and having an average primary particle diameter of about 40 nm.
[0095]
Then, three kinds of positively charged hydrophobic silicas shown in Table 4 in which hydrophobic silica was surface-treated with aminosilane (AS) were prepared, and these positively charged hydrophobic silicas were respectively added to the above-mentioned additive mixed toner. The toner of Example 1 of the present invention and the toners of Comparative Examples 1 and 2 were prepared by adding 0.5% by weight, respectively. Further, a toner in which none of these positively chargeable hydrophobic silicas was added to the prepared additive mixed toner (that is, additive mixed toner) was used as the toner of Comparative Example 3.
[0096]
[Table 4]

[0097]
As shown in Table 4, the positively chargeable hydrophobic silica (silica (1)) used in the toner of Example 1 has a positive chargeability to the ferrite carrier of +150 μc / g and an average primary particle size of about 30 nm. It is. In addition, the positively chargeable hydrophobic silica (silica (2)) used in the toner of Comparative Example 1 has a positive chargeability to the ferrite carrier of +280 μc / g and an average primary particle size of about 12 nm. Further, the positively chargeable hydrophobic silica (silica (3)) used in the toner of Comparative Example 2 has a positive chargeability with respect to the ferrite carrier of +380 μc / g and an average primary particle size of about 12 nm. The work functions of these silicas (1), (2) and (3) are smaller than the work functions of the cyan toner base particles, as is apparent from the measurement results. The work functions of the toners of Example 1 and Comparative Examples 1 to 3 were 5.51 eV, 5.50 eV, 5.50 eV, and 5.45 eV, respectively, as a result of measurement.
[0098]
(b) Preparation of emulsion polymerization toners of Example 2, Comparative Example 4, Comparative Example 5 and Comparative Example 6
In the preparation of the cyan emulsion polymerization toner of Example 1 described above, the pigment was 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 was maintained at 90 ° C. Thus, toner mother particles of magenta toner having a circularity of 0.97 and a toner mother particle work function of 5.65 eV were prepared. The external additive treatment was performed in the same manner as in the toner of Example 1 of the present invention and the toners of Comparative Examples 1 to 3, and the toners of Example 2 and Comparative Examples 4 to 6 of the present invention were respectively used. Produced. At this time, the work functions of silica (1), (2) and (3) are all smaller than the work function of the mother particles of the magenta toner, and the work functions of the toners of Example 2 and Comparative Examples 4 to 6 are as follows. Were 5.59 eV, 5.58 eV, 5.58 eV, and 5.53 eV, respectively, as a result of measurement.
[0099]
(c) Production of emulsion polymerization toner of Example 3
The rutile-anatase type titanium oxide hydrophobized with the silane coupling agent of the rutile-anatase type mixed crystal ratio of 10% rutile and 90% anatase type to the cyan toner of Example 1 (hydrophobic degree 58%, specific surface area) 150m ² / G) was added and mixed in an amount of 0.5%, and 0.5% of silica (1) shown in Table 4 was added and mixed to prepare a toner of Example 3 of the present invention. At this time, the work function of the rutile-anatase type titanium oxide is larger than the work functions of the negatively chargeable silicas 13 and 14 and the positively chargeable silica 16, and is substantially the same as or equal to the work function of the toner base particles 8a of the cyan toner. It is set larger. As a result of specific measurement, the work function of rutile-anatase type titanium oxide was 5.64 eV, and the work function of the toner of Example 3 was 5.58 eV.
[0100]
(2) Production of examples of pulverized toner
(a) Preparation of pulverized toners of Example 4, Example 5, Comparative Example 7, and Comparative Example 8
50:50 (weight ratio) mixture of polycondensed polyester of aromatic dicarboxylic acid and alkylene etherified bisphenol A and a partially cross-linked product of polycondensed polyester with a polyvalent metal compound (manufactured by Sanyo Chemical Industries, Ltd.) 100 weight 5 parts by weight of cyan pigment phthalocyanine blue, 3 parts by weight of polypropylene having a melting point of 152 ° C. and a Mw of 4000 as a release agent, and a salicylic acid metal complex E-81 (manufactured by Orient Chemical Co., Ltd.) as a charge control agent ) After 4 parts by weight were uniformly mixed using a Henschel mixer, the mixture was kneaded with a twin screw extruder having an internal temperature of 150 ° C. and cooled. This cooled product was coarsely pulverized to 2 mm square or less, and this coarsely pulverized product was finely pulverized by a jet mill and classified by a classifier to obtain a toner having an average particle diameter of 7.6 μm and a circularity of 0.91. Further, the work function of the toner base particles was 5.46 eV as a result of measurement.
[0101]
The obtained toner base particles have a weight ratio of about 0.1 nm of negatively chargeable hydrophobic silica surface-treated with a fluidity improver hexamethyldisilazane (HMDS) having an average primary particle diameter of about 12 nm. 0.5% by weight of 8% by weight of the same surface-treated negatively charged hydrophobic silica having an average primary particle diameter of about 40 nm is added and mixed, and the mixed toner is a rutile-anatase type mixed crystal ratio of rutile. Rutile-anatase type titanium oxide hydrophobized with a silane coupling agent of 10% by weight type and 90% anataza type (hydrophobic degree 58%, specific surface area 150 m ² / G) was added and mixed at 0.4% by weight to prepare an additive mixed toner.
[0102]
Then, 0.2% of positively charged hydrophobic silica (silica (1)) having a large particle size (average primary particle size: about 30 nm) shown in Table 4 in which hydrophobic silica was surface-treated with aminosilane (AS) was added. The toner of Example 4 of the present invention was prepared by mixing. Further, 0.2% of positively charged hydrophobic silica (silica (2)) having a small particle diameter (average primary particle diameter: about 12 nm) shown in Table 4 was similarly added and mixed, and the toner of Comparative Example 7 was mixed. Produced. Further, a toner of Comparative Example 8 in which these positively charged hydrophobic silica was not added was prepared.
[0103]
Further, toner base particles were prepared in the same manner as described above by changing the pigment to quinacridone instead of phthalocyanine blue. The work function of the produced toner base particles was 5.57 eV as a result of measurement. The toner base particles were subjected to an external additive treatment in the same manner as in Example 4 to prepare a toner of Example 5 of the present invention. As a result of the measurement, the work functions of the toners of Examples 4 and 5 and Comparative Examples 7 and 8 were 5.45 eV, 5.56 eV, 5.44 eV, and 5.46 eV, respectively.
[0104]
(b) Preparation of pulverized toner of Example 6 and Example 7
According to the toner preparation example of Example 4 of the present invention, yellow toner base particles using Pigment Yellow 180 and black toner base particles using carbon black were prepared. As a result of measurement, the work functions of these toner base particles were 5.62 eV for the yellow toner base particles and 5.72 eV for the black toner base particles. Then, these yellow toner base particles and black toner base particles were subjected to external additive treatment in the same manner as in the case of the toner of Example 4, and the toners of Examples 6 and 7 of the present invention were respectively obtained. Was made. As a result of the measurement, the work functions of the toners of Examples 6 and 7 were 5.61 eV and 5.71 eV, respectively.
[0105]
(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. 3 or an image forming apparatus using the contact one-component development process shown in FIG. 4, there is a full-color printer capable of the non-contact development process and the contact development process shown in FIG. In FIG. 6 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
[0106]
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.
[0107]
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 charged toners having a work function relative to the work function of the photosensitive member on the developing roller, and these developing units 10 include yellow Y, magenta M, cyan. The toner of either C or black K is applied to the surface of the photoreceptor 140 to develop the electrostatic latent image on the photoreceptor 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.
[0108]
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.
[0109]
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.
[0110]
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 and 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).
[0111]
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.
[0112]
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 portion 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.
[0113]
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.
[0114]
Next, an example of manufacturing each component of the image forming apparatus will be described.
(Production Example 1 of organic photoreceptor [1 in FIGS. 3 and 4, 140 in FIG. 6))
In the production of the organic laminated photoreceptor 1 of Production Example 1, first, an alcohol-soluble nylon {manufactured by Toray Industries, Inc.) is used as an undercoat layer 1b on the peripheral surface of an aluminum base tube having a diameter of 85.5 mm. “CM8000”} and 6 parts by weight of aminosilane-treated titanium oxide fine particles in 100 parts by weight of methanol were dissolved and dispersed in a coating solution by the ring coating method, and the temperature was 100 ° C. for 40 minutes. By drying, an undercoat layer 1b having a film thickness of 1.5 to 2 μm was formed.
[0115]
Next, 1 part by weight of oxytitanyl phthalocyanine pigment as a charge generating pigment, 1 part by weight of butyral resin {BX-1, Sekisui Chemical Co., Ltd.}, 100 parts by weight of dichloroethane, and a sand mill using φ1 mm glass beads For 8 hours to obtain a pigment dispersion, and the obtained pigment dispersion is applied on the undercoat layer 1b by a ring coating method and dried at 80 ° C. for 20 minutes to obtain a charge having a thickness of 0.3 μm. The generation layer 1c was formed.
[0116]
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 is cut out to obtain a sample piece, and the work function of this sample piece is irradiated using a commercially available surface analyzer {AC-2 type, manufactured by Riken Keiki Co., Ltd.}. When measured with an amount of light of 500 nW, it showed 5.48 eV.
[0117]
[Chemical 1]

[0118]
(Production Example 2 of an organic photoreceptor [1 in FIGS. 3 and 4, 140 in FIG. 6))
In the production of the organic laminated photoreceptor 1 of Production Example 2, a nickel electroformed tube having a seamless thickness of 40 μm and a diameter of 85.5 mm was used for the conductive support 1a, and the distyryl of the following structural formula (2) was used as the charge transfer agent. An organic multilayer photoreceptor 1 (OPC2) was prepared in the same manner as in Production Example 1 except that the compound was used. The work function of this organic laminated photoreceptor was measured in the same manner and was 5.50 eV.
[0119]
[Chemical formula 2]

[0120]
(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 with 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.
[0121]
(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.
[0122]
(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.
[0123]
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.
[0124]
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. ^Ten It was Ω · cm. The work function was 5.37 eV, and the normalized photoelectron yield was 6.90.
[0125]
(Fixer preparation example)
The fixing device 60 includes two pressure rollers (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.
[0126]
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.
[0127]
(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.
[0128]
(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.
[0129]
(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.
[0130]
(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.
[0131]
(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.
[0132]
(Imaging test and test results)
(Image formation test 1)
A non-contact development method in which the development gap L is set to 220 μm using a full-color printer capable of the non-contact development process shown in FIG. 6 and using the organic photoreceptor 1 (imaging condition: bright potential of the organic photoreceptor 1 −600 V) Example 1 of the present invention shown in Table 4 in the cyan developing device 10 (C) with the dark potential of the organic photoreceptor 1 of −80 V, DC developing bias of −300 V, AC developing bias of 1.35 kV, and AC frequency of 2.5 kHz. And the toners of Comparative Examples 1 and 2 were set, and images were formed so that the solid image density was about 1.1 to 1.2. The charge characteristic amount of the cyan toner on the developing roller 11 at that time was measured with a commercially available charge amount distribution measuring device E-SPART analyzer EST-3 type manufactured by Hosokawa Micron Corporation. Further, the fog toner on the organic photoreceptor 1 at that time was measured by the tape transfer method, and the reverse transfer toner transferred from the transfer belt 36 to the organic photoreceptor 1 at the time of printing the second color was also measured by the tape transfer method. . The tape transfer method is a method in which Sumitomo 3M's mending tape is affixed onto the toner, fog toner or reverse transfer toner is transferred onto the tape, and then affixed onto white paper, and the density is measured with a reflection densitometer from the tape. The fog density and reverse transfer density are defined by subtracting the tape density from the measured value. Table 5 shows the measurement results.
[0133]
[Table 5]

[0134]
As is apparent from Table 5, when the hydrophobic positively-charged silica 16 having a large particle size (particle size: about 30 nm) is added, the toner is charged more than the toner of Comparative Example 3 to which the positively-charged silica 16 having a large particle size is not added. It was shown that the amount increased and fog toner and reverse transfer toner decreased. Further, in the toners of Comparative Examples 1 and 2 to which hydrophobic positively chargeable silica having a small particle size (particle size: about 12 nm) is added, the charge amount is decreased and the fog toner concentration and the reverse transfer toner concentration are increased. It was shown to bring Therefore, it can be seen that, even with positively chargeable silica, the positively chargeable silica 16 having a large particle diameter is more effective than the positively chargeable silica having a small particle diameter, and is more effective in preventing fogging and preventing reverse transfer. It was.
[0135]
(Image formation test 2)
Electron micrographs were taken of the toner of Example 4 of the present invention and the toners of Comparative Examples 7 and 8, and are shown in FIGS. 7, 8 and 9, respectively. As is apparent from the electron micrographs shown in FIGS. 7 to 9, the toner of Example 4 to which 0.2% by weight of hydrophobic positively-charged silica 16 having a large particle size was added had toner base particles 8a as external additives. On the other hand, the toner of Comparative Example 7 to which a hydrophobic positively chargeable silica having a small particle size was added and the positively chargeable silica were not added. All of the toners of Comparative Example 3 exhibit a state in which the external additive is slightly floated from the surface of the toner base particles 8a and is in a weakly fixed state.
[0136]
Therefore, the negatively charged toner 8 of Example 4 of the present invention can sufficiently and effectively exert the above-described functions of the external additive firmly fixed to the surface of the toner base particles 8a. It was found that each of the negatively charged toners No. 8 easily releases the surface of the toner base particles 8a, and the above-described functions of the external additive cannot be sufficiently exhibited. That is, if the adhesion of the external additive to the toner base particles 8a is weak, the chargeability of the toner is lowered and the toner is scattered from the surface of the developing roller 11 by continuous printing. Actually, each toner was set in the cyan developing device 10 (C) of the color printer shown in FIG. 6 and 1000 sheets were continuously printed, and the toner scattering around the developing roller 11 was visually compared. Although the scattering of the toner of No. 4 was hardly observed, the scattering of the toners of Comparative Examples 7 and 8 was confirmed. In addition, using the magenta toner that is the toner of Example 5 of the present invention that has been subjected to the same external addition process as that of the toner of Example 4, a 1000-sheet printing test was similarly performed. Scattering could not be confirmed visually.
[0137]
(Image formation test 3)
Image formation was performed in the same manner as in image formation test 1 with the addition amount of the positively chargeable silica 16 having a large particle size of the toner of Example 1 being 0 to 0.6% by weight. The results are shown in Table 6.
[0138]
[Table 6]

[0139]
As is apparent from Table 6, when the addition amount of the positively chargeable silica 16 is 0.6% or more, the charge amount decreases, the solid image density also decreases, and the amount of reverse transfer toner tends to increase. I understood. Therefore, it is preferable that the addition amount of the positively chargeable silica 16 is 30% or less with respect to the total amount of the negatively chargeable silicas 13 and 14, since good results can be obtained.
[0140]
(Image formation test 4)
Using the toner of Example 3 of the present invention, image formation was performed in the same manner as in the image formation test 1 described above. As a result of image formation, the toner of this Example 3 has a charge amount of −20 μc / g, a solid average image density of 1.350, a fog toner OD value of almost 0, and a reverse transfer toner OD as compared with the toner of Example 1. The values were almost 0, respectively, and it was found that a very high quality print quality with substantially no fog toner and no reverse transfer toner was obtained. This is because, in addition to the positively chargeable silica 16, further adding a rutile-anatase type titanium oxide having a work function larger than that suppresses the negative overcharge property and simultaneously generates positive toner. It is thought to be due to being suppressed.
[0141]
(Image formation test 5)
The four-color toners of the cyan toner as the toner of Example 4, the magenta toner as the toner of Example 5, the yellow toner as the toner of Example 6, and the black toner as the toner of Example 7 and the above structural formula ( In combination with the organic photoreceptor 1 (OPC2) given in 2), full-color image formation by the contact development method was performed using a full-color printer capable of the contact development method shown in FIG. This image was created in an environmental test room under conditions of 5000 ° C. at a low temperature of 10 ° C., low humidity of RH 15%, normal temperature of 23 ° C., normal humidity of 60% RH, and high temperature of 35 ° C. and high humidity of RH 65%. 20% duty full color printing was performed for each color. The quality of the formed image was checked, but there was no toner scattering around the developing portion, and a stable image quality could be obtained.
[0142]
(Image formation test 6)
Using the toner of Example 2 and Comparative Examples 4 to 6, after image formation by the contact development method of the image formation test 5, the fixing property was compared using the fixing device 60 described below.
The fixing device 60 has a φ40 heater roller {with halogen lamp 600w built-in, PFA film deposited on silicon rubber 2.5 mm (60 ° JISA) to a thickness of 50 μm} and a φ40 press roller {with halogen lamp 300w built-in, silicon rubber 2.5 mm. Fixing was performed at a set temperature of 190 ° C. using two pressure rollers (weight of about 38 kgf) of PFA formed on (60 ° JISA) to a thickness of 50 μm}, and the fixing properties between the toners were compared. Place a 200 g weight on a cotton cloth, rub 50 times on a solid image, measure the solid image density before and after rubbing, and convert the toner fixability into a retention rate (fixing rate) (%) to evaluate the fixability. It was used as an index. The results are shown in Table 7.
[0143]
[Table 7]

[0144]
As is apparent from Table 7, the toner of Example 2 showed a retention rate (fixing rate) of 95% and was not inferior to the toner of Comparative Example 6 in which the amount of negatively charged silica used was small. Comparative Examples 4 and 5 having a large silica amount of the particle size silica 13 showed a retention rate (fixing rate) of 90%. Accordingly, it was found that even when the same amount of the fluidizing agent was added, the fixability was hardly lowered when the positively chargeable silica 16 having a large particle diameter was used. In addition, the average primary particle diameter of the negatively-charged silica 13 having a small particle diameter was changed to about 12 nm and about 16 nm, and the same fixing test was conducted, but this tendency was not reversed, and the positively-charged silica was not reversed. The larger average primary particle diameter of the toner did not lower the fixing property.
[0145]
【The invention's effect】
As is apparent from the above description, according to the image forming apparatus of the present invention, the toner base particles to which at least the hydrophobic negatively chargeable external additive is added are surface-treated with a material having a positive chargeability, and A hydrophobic positively chargeable external additive whose overall work function is set smaller than that of the toner base particles is added so that the positively chargeable external additive can function as a microcarrier. The rising of the charge of the mother particles can be accelerated, and the reverse transfer toner and fog can be effectively suppressed.
[0146]
In addition, hydrophobic negatively-charged silica is used in combination with hydrophobic rutile-anatase-type titanium oxide, making it more effective for the characteristics and charge-adjusting function of hydrophobic rutile-anatase-type titanium oxide that are difficult to embed in the toner base particles. You can make use of it. Therefore, there are inherent characteristics such as negative charging performance and fluidity possessed by hydrophobic negatively-charged silica, and inherent characteristics such as relatively low resistance and negative overcharge preventing characteristics possessed by hydrophobic rutile-anatase type titanium oxide. A synergistic function can be imparted to the toner base particles. As a result, the fluidity of the negatively charged toner can be prevented from being lowered and negative overcharge can be prevented, so that a better negative charge characteristic can be obtained. As a result, the generation and fogging of the reverse transfer toner can be more effectively performed. Can be suppressed.
[0147]
In addition, by using two types of hydrophobic negatively chargeable silica having different average primary particle diameters, the surface of the toner base particles is made hydrophobic negatively charged silica, hydrophobic positively charged silica, and hydrophobic rutile. Since the anatase-type titanium oxide is uniformly covered, the negative charge of the negatively charged toner can be stabilized for a longer period of time, and more stable image quality can be provided in continuous printing. In particular, the negatively charged toner of the negatively charged toner is added by adding more hydrophobic negatively charged silica whose average primary particle is a small particle size than the total amount of the hydrophobic positively charged silica and the hydrophobic rutile-anatase type titanium oxide. Can be stabilized for a longer period of time.
Therefore, the fogging of the non-image portion can be further suppressed, the transfer efficiency can be further improved, and the occurrence of the reverse transfer toner can be further effectively suppressed.
[0148]
In addition, when adding positively-charged silica, which is a fluidizing agent, the use of large-particle-size positively-charged silica reduces the fixability compared to the case of using small-particle-size positively-charged silica. Can be prevented.
[0149]
Furthermore, regardless of whether the toner is a pulverized toner or a polymerized toner, the hydrophobic negatively-charged silica of two kinds of large and small particle sizes, the hydrophobic positively-charged silica, and the hydrophobic rutile-anatase type titanium oxide are used in combination to make the toner hydrophobic Since the amount of negatively chargeable silica can be reduced, reverse transfer toner, image density fluctuations, and non-image area fog can be more effectively suppressed.
[0150]
Since the occurrence of reverse transfer toner can be more effectively suppressed, the image density can be more uniformly maintained over a long period of time when the negatively charged toner of the present invention is used as a full color toner. Thereby, a high-quality full-color image can be obtained over a long period of time.
[0151]
Furthermore, according to the method for producing a negatively charged toner of the present invention, the reversely transferred toner, the fog toner, and the negatively charged toner of the present invention capable of effectively suppressing fluctuations in image density can be reliably produced.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating an example of an embodiment of a negatively charged toner according to the present invention.
FIG. 2 is an explanatory diagram for explaining the behavior of the negatively charged toner in the example shown in FIG. 1;
FIG. 3 is a diagram schematically illustrating an example of a non-contact development process of an image forming apparatus in which a negatively charged toner according to the present invention is used.
FIG. 4 is a diagram schematically illustrating an example of a contact development process of an image forming apparatus in which a negatively charged toner according to the present invention is used.
FIG. 5 is a diagram showing an organic laminated photoreceptor of the image forming apparatus shown in FIGS. 3 and 4.
FIG. 6 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 charged toner according to the present invention.
7 is a view showing an electron micrograph of a negatively charged toner according to Example 4 of the present invention. FIG.
FIG. 8 is a view showing an electron micrograph of a negatively charged toner of Comparative Example 7 taken.
9 is a view showing an electron micrograph of the negatively charged toner of Comparative Example 8. FIG.
[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 ... Regulation blade, 8 ... Negatively charged 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 ... hydrophobic negatively-charged silica (SiO2) having a small particle diameter ₂ ), 14 ... Hydrophobic negatively charged silica (SiO2) with large particle size ₂ 15 ... hydrophobic rutile-anatase type titanium oxide (TiO) ₂ ), 16 ... Hydrophobic positively charged silica (SiO 2) having a large particle size ₂ ), L ... Development gap

Claims (3)

Negatively charged toner having at least a hydrophobic negatively chargeable external additive having negative chargeability with respect to toner mother particles and having an overall work function smaller than that of the toner mother particles In
A hydrophobic positively chargeable external additive that is surface-treated with aminosilane having a positive chargeability with respect to the toner base particles and has an overall work function set smaller than the work function of the toner base particles is added. And
The negatively chargeable external additive is a hydrophobic negatively chargeable silica surface-treated with hexamethyldisilane, and the positively chargeable external additive is a hydrophobic positively chargeable silica,
A hydrophobic rutile-anatase type titanium oxide having a work function that is substantially the same as or larger than the work function of the toner base particles and that has been subjected to silane coupling treatment is added,
The negatively charged toner according to claim 1, wherein the hydrophobic negatively charged silica is added in a larger amount than the total amount of the hydrophobic positively charged silica and the hydrophobic rutile-anatase type titanium oxide . The hydrophobic negatively chargeable silica is composed of negatively chargeable silica having an average primary particle diameter of a small particle diameter and negatively chargeable silica having an average primary particle diameter of a larger particle diameter than the small particle diameter. positively chargeable silica is negatively charged toner of claim 1, wherein the average primary particle diameter, wherein the same or substantially the same as the negatively chargeable silica having a large particle diameter. A method for producing the negatively charged toner according to claim 2 , comprising:
First, the toner base particles and the large and small particle size negatively chargeable silica are mixed, then the hydrophobic rutile-anatase type titanium oxide is added to and mixed with the mixture, and the positively chargeable silica is further mixed. Thus, the negatively charged toner is manufactured.

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