JP2004317705A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tandem system image forming apparatus in which toner images formed on latent image carriers are sequentially transported onto a recording material transported by a transport belt and in which transfer of a toner image transferred later is not adversely affected by a precedently transferred toner image. <P>SOLUTION: In the image forming apparatus in which latent image carriers for a plurality of colors are arranged, latent images formed on the latent image carriers are developed with toners and transferred to a transfer material on a transport belt for transporting a recording material and then fixation is carried out to form a color image, the latent image carriers are arranged in such a way that the work functions of the toners used for development decrease from the uppermost stream side of the transport belt toward the downstream side and development, transfer and fixation are carried out in the order of the decreasing work functions of the toners. Since toner scattering is prevented by improved adhesiveness of the toners, contamination in the image forming apparatus is prevented and a surface of the transport belt is not contaminated, therefore backside stain of paper can also be prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００２６】
図２は、本発明の画像形成装置を説明する図である。
図２は、本発明の画像形成装置における接触現像方式の一例を示すものであるが、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、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、静電潜像が形成される。
現像器１０は、一成分現像装置であり、有機感光体上に一成分非磁性トナーＴを供給することで有機感光体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。現像手段には、一成分非磁性トナーＴが収納されており、図示のごとく反時計方向で回転するトナー供給ローラ７によりトナーを現像ローラ９に供給する。現像ローラ９は反時計方向に回転し、トナー供給ローラ７により搬送されたトナーＴをその表面に保持した状態で有機感光体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。
【００２７】
現像ローラ９は、例えば直径１６〜２４ｍｍで、金属製管にめっきやブラスト処理したローラ、あるいは中心軸周面にブタジエンゴム、スチレンブタジエンゴム、エチレンプロピレンゴム、ウレタンゴム、シリコーンゴム等からなる体積抵抗値１０^４〜１０^８Ω─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、この管の軸等を介して図示しない電源より現像バイアス電圧が印加される。また、現像ローラ９、トナー供給ローラ７、トナー規制ブレード８からなる現像器１０は、図示しないばね等の付勢手段により有機感光体に押圧力１９．６〜９８．１Ｎ／ｍ、好ましくは２４．５〜６８．６Ｎ／ｍで、ニップが幅１〜３ｍｍとなるように圧接されるとよい。
【００２８】
規制ブレード８としてはステンレス、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、現像ローラに対して図示しないばね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２４５〜４９０ｍＮ／ｃｍで押圧され、現像ローラ上のトナー層厚を略１層から２層とすると良い。
【００２９】
また、感光体の暗電位としては−５００〜−７００Ｖ、明電位としては−５０〜−１５０Ｖ、図示していないが現像バイアス電圧としては−１００〜−４００Ｖとすると良く、現像ローラとトナー供給ローラとは同電位とすると良い。
接触現像方式にあっては、反時計方向に回転する現像ローラの周速を、時計方向に回転する有機感光体に対して１．１〜２．５、好ましくは１．２〜２．２の周速比とするとよく、これにより、小粒径のトナー粒子であっても、有機感光体との接触領域に充分なトナーを供給することができる。
【００３０】
また、規制ブレード、現像ローラにおけるそれぞれの仕事関数と、トナーの仕事関数との関係に格別の制限はないが、好ましくは規制ブレード、現像ローラにおけるそれぞれの仕事関数をトナーの仕事関数より小さくして、規制ブレードと接触するトナーを負に接触帯電させておくことにより、より均一な負帯電トナーとできる。また、規制ブレード８に電圧を印加してブレードに接触するトナーへ電荷注入してトナー帯電量を制御してもよい。
また、記録材１１は搬送用ベルト１２に載置されて可視像化された感光体１とバックアップローラ６との間に送られて転写される。
【００３１】
次に、図３は、本発明の画像形成装置における非接触現像方式の一例を示すものである。この方式にあっては、現像ローラ９と感光体１とを現像ギャップｄを介して対向させるものである。現像ギャップとしては１００〜３５０μｍとすると良く、また、図示しないが直流電圧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としては１．５〜３．５ｋＨｚ、Ｐ−Ｐ電圧１０００〜１８００Ｖの条件とすると良い。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の周速としては、時計方向に回転する有機感光体に対して１．１〜２．５、好ましくは１．２〜２．２の周速比とするとよい。
【００３２】
現像ローラ９は図示のごとく反時計方向に回転し、トナー供給ローラ７により搬送されたトナーＴをその表面に吸着した状態で有機感光体との対向部にトナーＴを搬送するが、有機感光体と現像ローラ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、トナーＴは現像ローラ表面と有機感光体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表面と有機感光体表面との間でトナーＴが振動する間にトナー粒子相互間で接触帯電が行われ、小粒径の正帯電トナーを負に帯電させることができ、カブリを減少させることができるものと考えられる。
【００３３】
また、記録材１０は搬送用ベルト１１に載置されて可視像化された感光体１とバックアップローラ６との間に送られるが、バックアップローラを用いる場合にはバックアップローラ６による感光体１への押圧力を、１８〜４５Ｎ／ｍ、好ましくは２６〜３８Ｎ／ｍとすると良い。
【００３４】
これにより、トナー粒子と記録材との接触を確実なものとすることができ、トナー粒子間の電荷（電子）の移動が起こり転写効率を向上できる。これに関しては、接触式現像方式も同様である。なお、非接触現像方式におけるその他の事項は、上述した接触現像方式と同様である。
【００３５】
図２、図３で示す現像プロセスをイエロー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装置となる。
【００３６】
紙搬送ベルトは、所定の体積抵抗を有する組成物を用いて製造することができる。例えば、組成物を形成するバインダーとしては、ゴム材料、例えばポリウレタン、ニトリルゴム（ＮＢＲ）、エチレンプロピレンゴム（ＥＰＤＭ）、シリコーンゴム等や、合成樹脂材料、例えば、ポリエステル、ポリエチレンテトラフタレート、ポリカーボネート、ポリフッ化ビニリデン等を、単独または複数種を組み合わせて使用することができる。また、導電性材料としては、例えばアセチレンブラック、ケッチェンブラック、ファーネスブラック等の導電性カーボンブラック類等を使用することができる。これらの材料に、分散剤、硬化剤等の材料を配合して、混練、押出、冷却、研磨等の工程を経てベルト基体が製造される。
また、ベルト基体は、特性の異なる材料、あるいは配合量を変えて製造した複数層を積層して製造したものであっても良い。積層することによって強度と電気的特性の調整が可能となり、特性の優れたものを製造することが可能となる。また、表面に各種の処理を加えて所望の特性の表層を形成しても良い。
紙搬送ベルトの厚みは、０．１ｍｍないし１．５ｍｍの範囲とすることが好ましく、体積抵抗は、１０^８ ないし１０^１１Ωｃｍとすることが好ましく、１０^８ Ωｃｍよりも小さい場合には紙の吸着性能が低下する。また、１０^１１Ωｃｍよりも大きい場合には、転写電圧や転写電流を大きくする必要があり、容積が大きなもの、となったり、あるいは定格が大きな高圧電源を必要とするので好ましくない。。
【００３７】
また、本発明に使用するタンデム方式のフルカラープリンターの概略正面図を図４に示す。
図４において、本実施形態の画像形成装置１０１は、ハウジング１０２と、ハウジング１０２の上部に形成された排紙トレイ１０３と、ハウジング１０２の前面に開閉自在に装着された扉体１０４を有し、ハウジング１０２内には、制御ユニット１０５、電源ユニット１０６、露光ユニット１０７、画像形成ユニット１０８、排気ファン１０９、転写ユニット１１０、給紙ユニット１１１が配設され、扉体１０４内には紙搬送ユニット１１２が配設されている。各ユニットは、本体に対して着脱可能な構成であり、メンテナンス時等には一体的に取り外して修理または交換を行うことが可能な構成になっている。
【００３８】
転写ユニット１１０は、ハウジング１０２の上方に配設され図示しない駆動源により回転駆動される駆動ローラ１１３と、駆動ローラ１１３の斜め下方に配設される従動ローラ１１４と、この２本のローラのみで間に張架されて図示矢印方向（反時計方向）へ循環駆動される紙搬送ベルト１１５と、紙搬送ベルト１１５の表面に当接するクリーニング手段１１６とを備え、従動ローラ１１４および紙搬送ベルト１１５が駆動ローラ１１３に対して図で左側に傾斜する方向に配設されている。これにより紙搬送ベルト１１５駆動時のベルト張り側（駆動ローラ１１３により引っ張られる側）１１７が下方に位置し、ベルト弛み側１１８が上方に位置するようにされている。
【００３９】
クリーニング手段１１６は、ベルト張り側１１７に設けられている。
また、紙搬送ベルト１１５の裏面には、後述する画像形成ユニット１０８を構成する各色毎の単色画像形成ユニットＹ，Ｍ，Ｃ，Ｋの画像担持体１２０に対向して板バネ電極からなる転写部材１２１がその弾性力で当接され、転写部材１２１には転写バイアスが印加されている。
【００４０】
画像形成ユニット１０８は、複数（本実施形態では４つ）の異なる色の画像を形成する単色画像形成ユニットＹ（イエロー用），Ｍ（マゼンタ用），Ｃ（シアン用），Ｋ（ブラック用）を備え、各単色画像形成ユニットＹ，Ｍ，Ｃ，Ｋにはそれぞれ、有機感光層、無機感光層を形成した感光体からなる画像担持体１２０と、画像担持体１２０の周囲に配設された、コロナ帯電器または帯電ローラからなる帯電手段１２２および現像手段１２３を有している。
【００４１】
各単色画像形成ユニットＹ，Ｍ，Ｃ，Ｋの画像担持体１２０が紙搬送ベルト１１５のベルト張り側１１７に当接されるようにされ、その結果、各単色画像形成ユニットＹ，Ｍ，Ｃ，Ｋも駆動ローラ１１３に対して図で左側に傾斜する方向に配設される。画像担持体１２０は、図示矢印に示すように、中間転写ベルト１１５と逆方向に回転駆動される。
【００４２】
露光ユニット１０７は、画像形成ユニット１０８の斜め下方に配設され、内部にポリゴンミラーモータ１２４、ポリゴンミラー１２５、ｆ−θレンズ１２６、反射ミラー１２７、折り返しミラー１２８を有し、ポリゴンミラー１２５から各色に対応した画像信号が共通のデータクロック周波数に基づいて変調形成されて射出され、ｆ−θレンズ１２６、反射ミラー１２７、折り返しミラー１２８を経て、各単色画像形成ユニットＹ，Ｍ，Ｃ，Ｋの画像担持体１２０に照射され、潜像を形成する。なお、各単色画像形成ユニットＹ，Ｍ，Ｃ，Ｋの画像担持体１２０への光路長は折り返しミラー１２８の作用によって実質的に同一の長さにされている。
【００４３】
次に、現像手段１２３について、単色画像形成ユニットＹを代表して説明する。本実施態様においては、各単色画像形成ユニットＹ，Ｍ，Ｃ，Ｋが図で左側に傾斜する方向に配設されているので、トナー収納容器１２９が斜め下方に傾斜して配置されている。
【００４４】
すなわち、現像手段１２３は、トナーを収納するトナー収納容器１２９と、このトナー収納容器１２９内に形成されたトナー貯蔵部１３０（図のハッチング部）と、トナー貯蔵部１３０内に配設されたトナー攪拌部材１３１と、トナー貯蔵部１３０の上部に区画形成された仕切部材１３２と、仕切部材１３２の上方に配設されたトナー供給ローラ１３３と、仕切部材１３２に設けられトナー供給ローラ１３３に当接される飛散防止ブレード１３４と、トナー供給ローラ１３３および画像担持体１２０に近接するように配設される現像ローラ１３５と、現像ローラ１３５に当接される規制ブレード１３６とから構成されている。
【００４５】
現像ローラ１３５およびトナー供給ローラ１３３は、図示矢印に示すように、画像担持体１２０の回転方向とは逆方向に回転駆動され、一方、攪拌部材１３１は供給ローラ１３３の回転方向とは逆方向に回転駆動される。トナー貯蔵部１３０において攪拌部材１３１により攪拌、運び上げられたトナーは、仕切部材１３２の上面に沿ってトナー供給ローラ１３３に供給され、供給されたトナーは可撓性材料によって作製された帯電ブレード（図示せず）と摺擦して供給ローラ１３３の表面の凹凸部への機械的付着力と摩擦帯電力による付着力によって、現像ローラ１３５の表面に供給される。
現像ローラ１３５に供給されたトナーは規制ブレード１３６により所定厚さに薄層化規制される。薄層化したトナー層は、画像担持体１２０へと搬送されて現像ローラ１３５と画像担持体１２０が近接する現像領域で画像担持体１２０の静電潜像を現像する。
【００４６】
また、画像形成時には、給紙ユニット１１１は、記録媒体Ｐの複数枚が積層保持されている給紙カセット１３８と、給紙カセット１３８から記録媒体Ｐを一枚ずつ給送するピックアップローラ１３９を備えている。
【００４７】
紙搬送ユニット１１２は、転写部への記録媒体Ｐの給紙タイミングを規定するゲートローラ対１４０（一方のローラはハウジング１０２側に設けられている）と、駆動ローラ１１３および紙搬送ベルト１１５、主記録材搬送路１４１と、定着手段１４２と、排紙ローラ対１４３と、両面プリント用搬送路１４４を備えている。定着手段１４２は、少なくも一方にハロゲンヒータ等の発熱体を内蔵した回転自在な定着ローラ対１４５と、この定着ローラ対１４５の少なくも一方側のローラを他方側に押圧付勢して転写された画像を記録材Ｐに押圧する押圧手段を有し、記録媒体に転写された画像は、定着ローラ対１４５の形成するニップ部で所定の温度で記録媒体に定着される。
【００４８】
本発明においては、紙搬送ベルト１１５が駆動ローラ１１３に対して図で左側に傾斜する方向に配設され、上部に定着手段１４２を配設したので画像形成装置の小型化を実現することができると共に、定着手段１４２で発生する熱が、左側に位置する露光ユニット１０７、搬送ベルト１１５および各単色画像形成ユニットＹ，Ｍ，Ｃ，Ｋへ悪影響をおよぼすことを防止することができる。
【００４９】
次に、トナーの仕事関数の測定に使用する測定セルについて説明する。
図５は、仕事関数測定用の試料測定セルを説明する図である。
図５（Ａ）に平面図を示し、図５（Ｂ）に側面図を示すように、試料測定セルＣ１は、直径１３ｍｍ、高さ５ｍｍのステンレス製円盤の中央に直径１０ｍｍで深さ１ｍｍのトナー収容用凹部Ｃ２を有する形状を有する。セルの凹部内にトナーを秤量スプーンを使用して突き固めないで入れた後、ナイフエッジを使用して表面を平らにした状態で測定に供する。
トナーを充填した測定セルを試料台の規定位置上に固定した後に、照射面積４ｍｍ角とし、エネルギー走査範囲４．２〜６．２ｅＶの条件で測定される。
また、照射光量は、トナーのような絶縁性が大きな材料や半導電性の材料は、照射光量５００ｎＷで測定したが、金属材料のような導電性の材料の場合には、照射光量１０ｎＷで測定した。
トナーの仕事関数測定時の規格化電子収率は、測定光量５００ｎＷで８以上とすることが好ましい。
【００５０】
図６は、他の形状の試料の仕事関数の測定方法を説明する図である。
中間転写媒体、潜像担持体のように、円筒形状の部材を試料とする場合には、円筒形状の部材を１〜１．５ｃｍの幅で切断し、ついで稜線に沿って横方向に切断して図７（Ａ）に形状を示すように、測定用試料片Ｃ３を得た後、図７（Ｂ）に示すように、試料台Ｃ４の規定位置上に、測定光Ｃ５が照射される方向に対して照射面が平行になるように固定する。これにより、放出される光電子Ｃ６が検知器Ｃ７、すなわち光電子倍像管により効率よく検知される。
【００５１】
本発明のトナーとしては、粉砕法および重合法により得られるトナーのいずれでも良いが、円形度が良好な重合法トナーが好ましい。
粉砕法トナーとしては、樹脂バインダーに少なくとも顔料を含有し、離型剤、荷電制御剤等を添加し、ヘンシェルミキサー等で均一混合した後、２軸押し出し機で溶融混練され、冷却後、粗粉砕−微粉砕工程を経て、分級処理され、さらに、外添粒子が付着されてトナー粒子とされる。
【００５２】
バインダー樹脂としてはトナー用樹脂として使用されている合成樹脂が使用可能であり、例えばポリスチレン、ポリ−α−メチルスチレン、クロロポリスチレン、スチレン−クロロスチレン共重合体、スチレン−プロピレン共重合体、スチレン−ブタジエン共重合体、スチレン−塩化ビニル共重合体、スチレン−酢酸ビニル共重合体、スチレン−マレイン酸共重合体、スチレン−アクリル酸エステル共重合体、スチレン−メタクリル酸エステル共重合体、スチレン−アクリル酸エステル−メタクリル酸エステル共重合体、スチレン−α−クロルアクリル酸メチル共重合体、スチレン−アクリロニトリル−アクリル酸エステル共重合体、スチレン−ビニルメチルエーテル共重合体等のスチレン系樹脂でスチレン又はスチレン置換体を含む単重合体又は共重合体、ポリエステル樹脂、エポキシ樹脂、ウレタン変成エポキシ樹脂、シリコーン変成エポキシ樹脂、塩化ビニル樹脂、ロジン変性マレイン酸樹脂、フェニール樹脂、ポリエチレン、ポリプロピレン、アイオノマー樹脂、ポリウレタン樹脂、シリコーン樹脂、ケトン樹脂、エチレン−エチルアクリレート共重合体、キシレン樹脂、ポリビニルブチラール樹脂、テルペン樹脂、フェノール樹脂、脂肪族又は脂環族炭化水素樹脂等が単独又は複合して使用できる。
【００５３】
特に本発明においては、スチレン−アクリル酸エステル系樹脂、スチレン−メタクリル酸エステル系樹脂、ポリエステル樹脂が好ましい。バインダー樹脂としてはガラス転移温度が５０〜７５℃、フロー軟化温度が１００〜１５０℃の範囲が好ましい。
【００５４】
着色剤としては、トナー用着色剤が使用可能である。例えばカーボンブラック、ランプブラック、マグネタイト、チタンブラック、クロムイエロー、群青、アニリンブルー、フタロシアニンブルー、フタロシアニングリーン、ハンザイエローＧ、ローダミン６Ｇ、カルコオイルブルー、キナクリドン、ベンジジンイエロー、ローズベンガル、マラカイトグリーンレーキ、キノリンイエロー、Ｃ．Ｉ．ピグメント─レッド４８：１、Ｃ．Ｉ．ピグメント─レッド１２２、Ｃ．Ｉ．ピグメント─レッド５７：１、Ｃ．Ｉ．ピグメント─レッド１２２、Ｃ．Ｉ．ピグメント─レッド１８４、Ｃ．Ｉ．ピグメント─イエロー１２、Ｃ．Ｉ．ピグメント─イエロー１７、Ｃ．Ｉ．ピグメント─イエロー９７、Ｃ．Ｉ．ピグメント─イエロー１８０、Ｃ．Ｉ．ソルベント─イエロー１６２、Ｃ．Ｉ．ピグメント─ブルー５：１、Ｃ．Ｉ．ピグメント─ブルー１５：３等の染料および顔料を単独あるいは複合して使用できる。
【００５５】
離型剤としては、トナー用離型剤が使用可能である。例えばパラフィンワックス、マイクロワックス、マイクロクリスタリンワックス、キャデリラワックス、カルナウバワックス、ライスワックス、モンタンワックス、ポリエチレンワックス、ポリプロピレンワックス、酸化型ポリエチレンワックス、酸化型ポリプロピレンワックス等が挙げられる。中でもポリエチレンワックス、ポリプロピレンワックス、カルナバワックス、エステルワックス等を使用することが好ましい。
【００５６】
荷電調整剤としては、トナー用荷電調整剤が使用可能である。例えば、オイルブラック、オイルブラックＢＹ、ボントロンＳ−２２およびＳ−３４（オリエント化学工業製）、サリチル酸金属錯体Ｅ−８１、Ｅ−８４（オリエント化学工業製）、チオインジゴ系顔料、銅フタロシアニンのスルホニルアミン誘導体、スピロンブラックＴＲＨ（保土ヶ谷化学工業製）、カリックスアレン系化合物、有機ホウ素化合物、含フッ素４級アンモニウム塩系化合物、モノアゾ金属錯体、芳香族ヒドロキシルカルボン酸系金属錯体、芳香族ジカルボン酸系金属錯体、多糖類等が挙げられる。なかでもカラートナー用には無色ないしは白色のものが好ましい。
【００５７】
粉砕法トナーにおける成分比としては、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、また、荷電制御剤は０．１〜７重量部、好ましくは０．５〜５重量部である。
【００５８】
本発明の粉砕法トナーにあっては、転写効率の向上を目的とした場合、球形化処理されるとよく、そのためには、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（川崎重工業製）を使用すれば円形度は０．９３まで高めることができる。または、粉砕したトナーを熱風球形化装置（日本ニューマチック工業製）を使用することによって円形度を１．００まで高めることができる。
なお、本発明において、トナー粒子の平均粒径と円形度は、粒子像分析装置（シスメックス製 ＦＰＩＡ２１００）で測定した値である。
【００５９】
また、重合法トナーとしては、懸濁重合法、乳化重合法、分散重合法等により得られるトナーが挙げられる。懸濁重合法においては、重合性単量体、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複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）を含む水相中に撹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。
【００６０】
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、に関しては、上述した粉砕トナーと同様の材料が使用できる。
【００６１】
重合性単量体成分としては、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、テトラフルオロエチレン、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。
【００６２】
乳化剤（界面活性剤）としては、例えばドデシルベンゼン硫酸ナトリウム、テトラデシル硫酸ナトリウム、ペンタデシル硫酸ナトリウム、オクチル硫酸ナトリウム、オレイン酸ナトリウム、ラウリン酸ナトリウム、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。
【００６３】
重合開始剤としては、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。
【００６４】
凝集剤（電解質）としては、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。
【００６５】
重合法トナーの円形度の調節法としては、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、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。
また、トナーの個数平均粒径は、９μｍ以下であることが好ましく、８μｍ〜４．５μｍであることがより好ましい。９μｍよりも大きなトナーでは、１２００ｄｐｉ以上の高解像度で潜像を形成しても、その解像度の再現性が小粒子径のトナーに比べて低下し、また４．５μｍ以下になると、トナーによる隠蔽性が低下するとともに、流動性を高めるために外添剤の使用量が増大し、その結果、定着性能が低下する傾向があるので好ましくない。
【００６６】
次に、外添剤について説明する。本発明のトナー粒子には、外添剤として、シリカ粒子と、シリカの表面をチタン、スズ、ジルコニウムおよびアルミニウムから選ばれる少なくとも１種の金属の酸化物、水酸化物によって修飾した表面修飾シリカ粒子を含み、シリカ粒子に対して表面修飾シリカ粒子が重量比で１．５倍以下の比で含有されている。
【００６７】
また、その他の外添剤としては、各種の無機および有機のトナー用流動性改良剤が使用可能である。例えば、正帯電性シリカ、二酸化チタン、アルミナ、酸化ジルコニウム、マグネタイト、酸化亜鉛、炭酸カルシム、硫酸カルシウム、硫酸マグネシウム、フッ化マグネシウム、炭化ケイ素、炭化ホウ案、炭化チタン、炭化ジルコニウム、窒化ホウ素、窒化チタン、窒化ジルコニウム、二硫化モリブデン、ステアリン酸アルミニウム、ステアリン酸マグネシウム、ステアリン酸亜鉛、ステアリン酸カルシウム、チタン酸ストロンチウム等のチタン酸金属塩、ケイ素金属塩の各微粒子を使用するこるとができる。これらの微粒子は、シランカップリング剤、チタンカップリング剤、高級脂肪酸、シリコーンオイル等で疎水化処理して使用することが好ましい。その他の樹脂微粒子の例としては、アクリル樹脂、スチレン樹脂、フッ素樹脂等が挙げられる。流動性改良剤は単独あるいは混合して使用でき、その使用量はトナー１００重量部に対して０．１ないし５重量部、より好ましくは０．５ないし４．０重量部であることが好ましい。
【００６８】
シリカ粒子としては、ケイ素のハロゲン化物等から乾式で作製した粒子、およびケイ素化合物から液中で析出した湿式法によるもののいずれをも用いることができる。
そして、シリカ粒子の一次粒子の平均粒子径は、５ｎｍ〜５０ｎｍとすることが好ましく、１０ｎｍ〜４０ｎｍとすることがより好ましい。また、シリカ粒子の一次粒子の平均粒子径が５ｎｍより小さいと、トナーの母粒子に埋没しやすくなり、また、負に過帯電しやすくなる。そして、５０ｎｍを超えるとトナー母粒子の流動性付与効果が悪化し、トナーを均一に負に帯電させることが困難になる結果、逆帯電である正に帯電したトナー量が増加する傾向となる。
【００６９】
本発明においては、シリカ粒子として、個数平均粒径分布が異なるシリカを混合して用いることが好ましく、粒径が大きな外添剤を含有することによって、トナー粒子中に外添剤が埋まってしまうことを防止し、小径のシリカ粒子によって好ましい流動性を得ることができる。
具体的には、一方のシリカの個数平均一次粒子径が５ｎｍ〜２０ｎｍであることが好ましく、７〜１６ｎｍであることがより好ましい。また、他方のシリカの個数平均一次粒子径が３０ｎｍ〜５０ｎｍであることが好ましく、３０〜４０ｎｍである粒子を併用することがより好ましい。
【００７０】
なお、本発明における外添剤の粒径は、電子顕微鏡像によって観察して測定したものであり、個数平均粒子径を平均粒子径としている。
【００７１】
本発明において外添剤として使用するシリカ粒子は、シランカップリング剤、チタンカップリング剤、高級脂肪酸、シリコーンオイル等で疎水化処理して使用することが好ましく、例えばジメチルジクロルシラン、オクチルトリメトキシシラン、ヘキサメチルジシラザン、シリコーンオイル、オクチル−トリクロルシラン、デシル−トリクロルシラン、ノニル−トリクロルシラン、（４−ｉｓｏ −プロピルフェニル）−トリクロルシラン、（４−ｔ −ブチルフェニル）−トリクロルシラン、ジペンチル−ジクロルシラン、ジヘキシル−ジクロルシラン、ジオクチル−ジクロルシラン、ジノニル−ジクロルシラン、ジデシル−ジクロルシラン、ジドデシル−ジクロルシラン、（４−ｔ −ブチルフェニル）−オクチル−ジクロルシラン、ジデセニル−ジクロルシラン、ジノネニル−ジクロルシラン、ジ−２−エチルヘキシル−ジクロルシラン、ジ−３，３−ジメチルペンチル−ジクロルシラン、トリヘキシル−クロルシラン、トリオクチル−クロルシラン、トリデシル−クロルシラン、ジオクチル−メチル−クロルシラン、オクチル−ジメチル−クロルシラン、（４−ｉｓｏ −プロピルフェニル）−ジエチル−クロルシラン等が例示される。
【００７２】
また、シリカ粒子と、金属化合物によって表面を修飾したシリカをシリカ粒子に対して所定の量を併用することが好ましい。表面修飾シリカとしては、５０〜４００ｍ^２／ｇの比表面積を有するシリカ粒子を、チタン、スズ、ジルコニウムおよびアルミニウムから選ばれる少なくとも一種の水酸化物あるいは酸化物で被覆したものである。
【００７３】
これらの配合量は、シリカ粒子１００重量部に対し、１〜３０重量部のこれらの水酸化物、酸化物で被覆したスラリーとし、引き続いてスラリー中の固形分に対し、アルコキシシランを３〜５０重量部を被覆した後、アルカリで中和し、ろ過、洗浄、乾燥及び粉砕を行うことによって得ることができる。表面修飾シリカに使用するシリカ微粒子は、湿式法あるいは気相法で製造されたいずれの粒子を使用することができる。
【００７４】
また、シリカ粒子の表面修飾は、チタン、スズ、ジルコニウム、アルミニウムを少なくとも一種を含有する水系の溶液を使用することができ、例えば、硫酸チタン、四塩化チタン、塩化スズ、硫酸第一スズ、オキシ塩化ジルコニウム、硫酸ジルコニウム、硝酸ジルコニウム、硫酸アルミニウム、アルミン酸ナトリウム等を挙げることができる。
シリカ粒子をこれらの金属酸化物、水酸化物での表面修飾は、これらの金属化合物の水系溶液によってシリカ粒子のスラリーを処理することによっておこなうことができる。処理温度は、２０〜９０℃とすることが好ましい。
【００７５】
次いで、アルコキシシランによって被覆することによって、疎水化処理を行う。疎水化処理は、スラリーのｐＨを２〜６、好ましくはｐＨ３〜６に調整した後、少なくとも一種のアルコキシシランをシリカ微粒子１００重量部に対して３０ないし５０重量部を添加し、スラリーの温度を２０〜１００℃、好ましくは３０〜７０℃に調整し、加水分解及び縮合反応を行うことによって実現することができる。
【００７６】
また、アルコキシシランを添加した後には、スラリーを撹拌した後、ｐＨ４〜９、好ましくは５〜７とｐＨの調整を行って縮合反応を促進することが好ましい。ｐＨの調整は、水酸化ナトリウム、水酸化カリウム、炭酸ナトリウム、アンモニア水、アンモニアガス等を使用することができる。この様な処理を行うことで、均一に疎水化処理された安定な微粒子が得られる。
次いで、スラリーをろ過、水洗後に乾燥を行うことによって表面修飾されたシリカ微粒子を得ることができる。
乾燥は、１００〜１９０℃、好ましくは１１０〜１７０℃である。１００℃未満だと乾燥効率が悪く疎水化度が低くなるので好ましくない。また、１９０℃を超えると、炭化水素基の熱分解により変色と疎水化度の低下が起こるので好ましくない。
疎水化処理は、表面修飾シリカ粒子にアルコキシシランを添加した後にヘンシェルミキサー等を用いて被覆することもできる。
【００７７】
本発明において、これらの外添剤は、トナー母粒子１００重量部に対して０．０５〜２重量部とすることが好ましい。
０．０５重量部よりも少ない場合には、流動性付与、および過帯電防止に効果がなく、逆に２重量部を超えると、負帯電の電荷量が低下すると同時に、逆極性である正帯電のトナー量が増加し、カブリや逆転写トナー量を増加する結果となる。
【００７８】
【実施例】
以下に、実施例、比較例を示し本発明を説明する。
（トナー１の製造例）
スチレンモノマー８０重量部、アクリル酸ブチル２０重量部、およびアクリル酸５重量部からなるモノマー混合物を、水１０５重量部、ノニオン乳化剤（第一工業製薬製エマルゲン９５０）１重量部、アニオン乳化剤（第一工業製薬製ネオゲンＲ）１．５重量部、および過硫酸カリウム０．５５重量部の水溶液混合物に添加し、窒素気流中下で撹拌を行いながら７０℃で８時間重合を行った。重合反応後冷却し、乳白色の粒径０．２５μｍの樹脂エマルジョンを得た。
【００７９】
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（三洋化成工業製）２０重量部および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に調整後撹拌しながら硫酸アルミニウム０．３重量部を電解質として加え、次いで撹拌装置（ＴＫホモミキサー）で高速撹拌して分散を行った。
【００８０】
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、窒素気流下で撹拌しなが同様にして、９０℃に加熱し、過酸化水素水を加えて５時間重合し、粒子を成長させた。重合停止後会合粒子の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し、４５℃で真空乾燥を１０時間行った。平均粒径６．８μｍの円形度０．９８のシアントナーを得た。
なお、本実施例において円形度の測定は、フロー式粒子像解析装置（シスメックス株式会社製ＦＰＩＡ２１００）を用いて行い、下記式（１）で表現した。
Ｒ＝Ｌ_０／Ｌ_１…（１）
ただし、Ｌ_１は、測定対象のトナー粒子の投影像の周囲長（μｍ）である。
Ｌ_０は、測定対象のトナー粒子の投影像の面積に等しい真円の周囲長（μｍ）である。
【００８１】
得られたトナー１００重量部に対して、流動性改良剤である平均一次粒子径が１２ｎｍの疎水性シリカを１重量部、平均一次粒子径が４０ｎｍの疎水性シリカを０．７重量部添加混合し、次いで平均一次粒子径が約２０ｎｍの疎水性酸化チタンを０．５重量部と平均一次粒子径が約３０ｎｍの疎水性のシリカをアミノシランで表面処理した正帯電性疎水性シリカを０．４重量部添加混合しトナー１を得た。
【００８２】
なお、平均粒径は、電気抵抗法粒度分布測定装置（ベックマン─コールター社製マルチサイザーＩＩＩで測定した体積分布Ｄ５０で示した。
また、得られたトナーの仕事関数をは、５．５４ｅＶであったが、本実施例において仕事関数は、表面分析装置（理研計器製 ＡＣ−２型）によって、照射光量５００ｎＷで測定した値である。
【００８３】
（トナー２の製造例）
トナー１の製造例において、顔料のフタロシアニンブルーに代えてキナクリドンを用いた点を除き、トナーの製造例１と同様にして、二次粒子の会合と造膜結合強度を上げる温度を９０℃において行い、トナー２を作製した。得られたマゼンタトナーの円形度は０．９７２で仕事関数は５．６３ｅＶであった。このトナーの個数基準の平均粒径は６．９μｍであった。
【００８４】
（トナー３、４の製造例）
トナー２の製造例において、顔料をピグメントイエロー１８０とカーボンブラックに変えた以外はトナー２の製造例と同様にして重合を行い、流動性改良剤を添加し、円形度０．９７２、仕事関数５．５８ｅＶ、平均粒径７．０μｍのイエロートナー３と、円形度０．９７３、仕事関数５．４８ｅＶ、平均粒径６．９μｍのブラックトナー４を作製した。
【００８５】
（トナー５の製造例）
芳香族ジカルボン酸とアルキレンエーテル化ビスフェノールＡとの重縮合ポリエステルと該重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（三洋化成工業製 ハイマーＥＳ）１００重量部、シアン顔料のピグメントブルー１５：１を５重量部、離型剤として融点が１５２℃、重量平均分子量Ｍｗが４０００のポリプロピレン１重量部、および荷電制御剤としてのサリチル酸金属錯体Ｅ−８１（オリエント化学工業製）４重量部をヘンシェルミキサーを用い、均一混合した後、内温１３０℃の二軸押し出し機で混練し、冷却した。
【００８６】
冷却物を２ｍｍ角以下に粗粉砕し、次いでジェットミルで微粉砕し、ローター回転による分級装置により分級し、平均粒径６．２μｍで、円形度０．９０５の分級トナーを得た。分級したトナー１００重量部に対し、０．２重量部の疎水性シリカ（平均一次粒子径７ｎｍ、ＢＥＴ法比表面積２５０ｍ^２／ｇ ）を加え表面処理を行った後、熱風球形化装置（日本ニューマチック工業製）を用い、熱処理温度２００℃に設定し、部分的に球形化処理を行った後、同様にして再度分級し平均粒径６．３μｍ、円形度０．９４０のシアントナー５の母粒子を得た。このトナー母粒子に対し、トナー１と同様にして流動性改良剤を添加混合し、トナー５を作製した。得られたトナーの仕事関数を同様な方法で測定すると５．４８ｅＶであった。
【００８７】
（トナー６、７、８の製造例）
トナー５において、顔料をナフトールＡＳ系の６Ｂに変えた以外はトナー５と同様にして粉砕、分級、熱処理、再分級および表面処理を行い、平均粒径６．５μｍで円形度０．９４２のマゼンタトナー６を得た。このトナー６の仕事関数を測定したところ、５．５３ｅＶであった。
同様にして、トナー７（イエロートナーとしてピグメントイエロー９３を使用）およびトナー８（ブラックトナーとしてカーボンブラックを使用）を作製した。得られたトナーの平均粒径と円形度はほぼトナー６と同じ値を示し、またそれぞれのトナーの仕事関数は、５．５７ｅＶ（イエロー）および５．６３ｅＶ（ブラック）であった。
【００８８】
（有機感光体（ＯＰＣ１）の製造例）
直径３０ｍｍのアルミニウム製の導電性支持体に、下引き層として、アルコール可溶性ナイロン（東レ製 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の下引き層を形成した。
【００８９】
この下引き層上に、電荷発生物質であるチタニルフタロシアニン１重量部とブチラール樹脂（積水化学製 ＢＸ−１）１重量部とジクロルエタン１００重量部とを、直径１ｍｍのガラスビーズを用いたサンドミルで８時間分散させた。
得られた顔料の分散液を、上記で作製した支持体を用いて、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の電荷発生層を形成した。
この電荷発生層上に、下記構造式（１）のジスチリル化合物の電荷輸送物質４０重量部とポリカカーボネート樹脂（帝人化成製 パンライトＴＳ）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を形成し、２層からなる感光層を有する有機感光体（ＯＰＣ１）を作製した。
得られた有機感光体の一部を切り欠いて試料片とし、その仕事関数を表面分析装置（理研計器製 ＡＣ−２型）を用い、照射光量５００ｎＷで測定したところ、５．５０ｅＶを示した。
【００９０】
◎
【化１】

【００９１】
（有機感光体（ＯＰＣ２）の製造例）
有機感光体（ＯＰＣ１）において、導電性支持体として直径４０ｍｍのアルミニウム製管を用いた点を除き同様にして有機感光体（ＯＰＣ２）を作製した。
この有機感光体の仕事関数を同様に測定したところ、５．４８ｅＶであった。
【００９２】
（規制ブレードの作製）
厚さ８０μｍのステンレス板に厚さ１．５ｍｍの導電性ウレタンチップを導電性接着剤で貼り付けて、ウレタン部の仕事関数を５ｅＶとした。
【００９３】
（紙搬送ベルト（１）の製造例）
ポリブチレンテレフタレート８５重量部、ポリカーボネート１５重量部およびアセチレンブラック（電気化学工業製）１５重量部を、窒素ガス雰囲気下でミキサーにより予備混合し、得られた混合物を引き続き窒素ガス雰囲気下で二軸押出し機により混練し、ペレットを得た。このペレットを、環状ダイスを有する１軸押出し機により２６０℃にて外径１７０ｍｍ、厚さ１６０μｍのチューブ状フィルムに押出した。次に押出した溶融チューブを、環状ダイスと同じ軸線上に支持している冷却インサイドマンドレルにより内径を規制し、冷却固化させてシームレスチューブを作製した。規定寸法に切断し、外径１７２ｍｍ、幅３４２ｍｍ、厚さ１５０μｍのシームレスベルトを得た。この紙搬送ベルトの体積抵抗は３．２×１０^８Ω─ｃｍであった。また、仕事関数は５．１９、規格化光電子収率１０．８８を示した。
【００９４】
更に、ウレタン変性エポキシ樹脂（旭電化工業製 アデカレジンＥＰＵ−８）１００重量部、導電性カーボンブラック（キャボット製、ＶＵＬＣＡＮＸＣ７２Ｒ）３．５重量部、高分子系分散剤（味の素ファインテクノ製 アジスパーＰＢ７１１）２．１重量部、トルエン ７５重量部をペイントコンディショナーにて２時間分散後、硬化剤（旭電化工業製 ＥＨ−２００）を８重量部加え、十分に撹拌し導電性下引き層の塗布液とした。この液を上記の表面にスプレーコートにより塗布乾燥（７０℃で６時間）し、厚さ１３μｍの表面層を設けた。この半導電性被覆層の仕事関数は、５．３６ｅＶであった。
【００９５】
実施例１
先に作製した有機感光体（ＯＰＣ１）、現像ローラ、規制ブレード、紙搬送ベルト（１）を装着した図４に示すタンデム方式のカラープリンターを用いて、前述したトナー１〜トナー４を装填した各トナー像形成手段を装着して、非接触１成分現像方式による画像形成試験を行った。
なお、画像形成に際しては、有機感光体の周速を１８０ｍｍ／ｓ、現像ローラの周速は有機感光体に対して周速比１．６とし、また、標準の作像条件を、感光体の暗電位は−６００Ｖ、明電位は−８０Ｖ、現像ローラと感光体のギャップを２１０μｍとし（ギャップコロで隙間を調整）、直流現像バイアス−２００Ｖに重畳する交流は周波数２．５ｋＨｚ、Ｐ−Ｐ電圧１４００Ｖの設定で、現像ローラと供給ローラは同電位とした。
【００９６】
そして、各色トナーのベタ印字時の感光体上の現像されたトナー付着量を最大０．５３ｍｇ／ｃｍ^２ 以下となるように制御しながら印字（温度２３℃、湿度５５ＲＨ％条件下）した。
また、前述のトナー規制ブレードの規制条件を変えて現像ローラ上のトナー搬送量を０．４ｍｇ／ｃｍ^２〜０．４３ｍｇ／ｃｍ^２となるように設定した。
画像形成条件は、感光体の暗電位を−６００Ｖ、明電位を−８０Ｖ、現像バイアスを−２００Ｖとし、現像ローラと供給ローラとは同電位とした。なお、一次転写部の電源には、直流の定電流電源を使用し、転写電流は１色目と４色目で電流値を制御し、１色目は８μＡ、２色目以降は２μＡずつ電流値を増加させて転写を行った。
【００９７】
図４に示すタンデム式カラープリンターは、感光体の近傍にクリーニング部材を有しないいわゆるクリーナレスプリンターとしている。印字試験は各色５％カラー原稿に相当する文字原稿を１００００枚、ＪＩＳ Ｘ ９２０１−１９９５準拠の標準画像データのＮ−２Ａ（カフェテリア）の画像を５０００枚連続印字した。
また、画像形成手段は、紙搬送ベルトの移動方向の上流側からトナーの仕事関数が大きいものから小さいものへと順に、逐次トナーの仕事関数の小さいトナー像形成手段を配置した。
【００９８】
本実施例では、第一番目のトナー像形成手段には黒トナーが装填されている。また、配置する順序を変更した時には、その都度画像データ処理の順番を変えて印字した。
この場合、出力印字画像の初期品質を、５％カラー原稿は１００００枚後の色ずれを、また、自然画像であるＮ−２Ａの出力印字画像では、全体の色ずれの変化を目視で確認した。
【００９９】
使用するトナーは、シアントナー１（記号Ｃ１、仕事関数：５．５４ｅＶ）、マゼンタトナー２（記号Ｍ２、仕事関数：５．６３ｅＶ）、イエロートナー３（記号Ｙ３、仕事関数：５．５８ｅＶ）およびブラックトナー４（記号ＢＫ４、仕事関数：５．４８ｅＶ）であり、記録材には電子写真用紙（富士ゼロックスサプライ製 ＰＰＣ用紙Ｌ）仕事関数：５．６１ｅＶを用いた。
その結果を表２に示す。
【０１００】
【表２】

【０１０１】
表２の結果から、本発明のようにトナーの仕事関数を大きいトナーより現像、転写を行うことにより、実質上クリーニング手段を装着しなくとも、クリーナレスの作像が可能であることが分かった。また、得られた印字物の色ずれもなく、良好な画質を与えるものであった。
【０１０２】
しかし、前述のトナー規制ブレードの規制条件を変えて現像ローラ上のトナー搬送量を０．５ｍｇ／ｃｍ^２ より多めに設定した規制条件、具体的には０．５２ｍｇ／ｃｍ^２ 前後の条件の場合、並びにベタ印字の有機感光体上の現像トナー付着量が０．５５ｍｇ／ｃｍ^２ 以上に設定した作像条件の場合には、クリーニング手段を設けないと実験例１の印字枚数を維持できないことが分かった。
この特性は、トナーを均一に負に帯電可能とし、かつ、有機感光体上の現像されたベタ印字時のトナー付着量を出来るだけ各トナー層間で均一に接触できる量以下にすることが必要である事を示すものである。
【０１０３】
実施例２
有機感光体としてＯＰＣ２を用い、クリーニング手段が取付けれるようにした点を除き実施例１と同様にして画像形成試験を行った。トナーには、シアントナー５（記号Ｃ５、仕事関数：５．４８ｅＶ）、マゼンタトナー５（記号Ｍ２、仕事関数：５．５３ｅＶ）、イエロートナー７（記号Ｙ７、仕事関数：５．５７ｅＶ）およびブラックトナー８（記号ＢＫ８、仕事関数：５．６３ｅＶ）を用い、記録材には電子写真用紙（富士ゼロックスサプライ製 ＰＰＣ用紙Ｌ）を用いて同様な印字試験評価を行った。
【０１０４】
また、紙搬送ベルトの移動方向の上流側から仕事関数が大きいトナーから仕事関数が小さなトナーへと、逐次トナー像形成手段を配置した。本実施例では、１番目のトナー像形成手段にはシアントナーが装填されており、黒トナーが装填されたトナー像形成手段は４番目に配置されている。また、配置する順序を変更した時には、その都度画像データ処理の順番を変えて印字した。
また、現像ローラと規制ブレードの構成は前述の通りとし、各色トナーの搬送量が０．４ｍｇ／ｃｍ^２〜４３ｍｇ／ｃｍ^２の範囲となるように規制ブレードの条件を設定した。なお、転写部の電源は定電流電源とし、１４μＡの定電流で一定とし連続印字を行った。。
【０１０５】
作像はＤＣの現像バイアス−２００Ｖに重畳するＡＣ周波数２．５ｋＨｚ、Ｐ−Ｐ電圧１４００Ｖの条件で印加し、各色５％カラー原稿に相当する文字原稿を１００００枚連続してプリントを行い、印字画像の品質の評価を行った。評価は、連続印字する前に前述の自然画のＪＩＳ Ｘ ９２０１−１９９５準拠の標準画像データのＮ−２Ａ「カフェテリア」の画像を出力した印字品質、とくに中間調の色ずれを重視し、各色５％原稿を２０００枚連続印字した後に１枚の自然画Ｎ−２Ａを印字し、この時の中間調の目視による変化を見た。明らかに色ずれが観察された場合には印字を中止し、その時の印字枚数で印字終了とした。
その結果を表３に示す。優は画像に問題がないもの、良は実用上許容できる範囲のもの、不良は色ずれが認められ画像品質が劣るものを示している。
【０１０６】
【表３】

【０１０７】
以上のように、本発明のように円形度が高く、仕事関数の大きいトナーより順に現像と転写を行うことにより、印字品質の劣化が無いことが示された。これは、トナー層間で電荷の移動が生じ、トナー層同士の密着性が高まり、飛び散りや色ずれの防止と転写効率が高まることで、安定した画像品質が維持できたと考えられる。しかし、現像と転写の順において、トナーの仕事関数をランダムにして現像、転写を行うと印字画像品質、特に色ずれに影響を及ぼすことが分かった。また、トナーの仕事関数の小さいトナー像形成手段を１段目にもってくることも良くないことが示された。
また、表３の結果から、本発明のようにトナーを、仕事関数が５．６ｅＶ前後と比較的大きい転写材に転写を直接行う場合には、トナー像形成手段の内、トナーの仕事関数の大きいトナー像形成手段を１段目に配置し、逐次トナーの仕事関数が小さくなるトナー像形成手段を配置することが好ましいことが分かる。
しかし、この時に有機感光体上の現像された１色のベタ画像の現像付着トナー量を０．６ｍｇ／ｃｍ^２ 以上に設定すると、転写効率が悪くなり、クリーニングトナー量の増大につながり、トナー量当たりの印字枚数が少なくなる結果、効率が悪いカラー画像形成装置となる。
また、実験例２では、クリーニングトナー量は各色５％原稿でＡ４版１００００枚印字で３０ｇであったが、他の比較実験例では、クリーニング量は５０ｇ〜８０ｇの範囲であった。
【０１０８】
【発明の効果】
本発明において、搬送ベルトによって搬送された記録材上に、潜像担持体上に形成されたトナー像を転写するタンデム方式のカラー画像形成装置において、搬送ベルト移動方向の上流側から、トナーの仕事関数の大きいものから小さいものへトナー像形成手段を配置し、紙上に現像、転写、定着工程を経てカラー画像を形成することにより、先に紙上に転写されたトナーが次のトナー像形成手段の感光体に逆転写することを防止し、かつ、トナー層同士の密着性が向上することにより色ずれ防止と色再現性に優れたカラー画像を形成することが可能となる。
また、トナー同士の密着性が向上することによって、トナー飛散が無くなるので画像形成装置内の汚染防止となるだけでなく、搬送ベルト表面を汚すこともないので、紙の裏面汚れの防止も可能となる。
【図面の簡単な説明】
【図１】図１は、記録材上のトナーの帯電の様子を説明する図である。
【図２】図２は、本発明の画像形成装置を説明する図である。
【図３】図３は、本発明の画像形成装置を説明する図である。
【図４】図４は、本発明のタンデム方式のフルカラープリンターの一例を説明する図である。
【図５】図５は、仕事関数の測定に使用する試料測定セルを説明する図である。
【図６】図６は、仕事関数の測定方法を説明する図である。
【符号の説明】
１…感光体、２…コロナ帯電器、３…露光、５…クリーニングブレード、６…バックアップローラ、７…トナー供給ローラ、８…規制ブレード、９…現像ローラ、１０…現像器、１０（Ｙ），１０（Ｍ），１０（Ｃ）、１０（Ｋ）…現像器、Ｔ…トナー、１１…記録材、１２…搬送ベルト、１０１…画像形成装置、１０２…ハウジング、１０３…排紙トレイ、１０４…扉体、１０５…制御ユニット、１０６…電源ユニット、１０７…露光ユニット、１０８…画像形成ユニット、１０９…排気ファン、１１０…転写ユニット、１１１…給紙ユニット、１１２…紙搬送ユニット、１１３…駆動ローラ、１１４…従動ローラ、１１５…紙搬送ベルト、１１６…クリーニング手段、１１７…ベルト張り側、１１８…ベルト弛み側、１２０…画像担持体、１２１…転写部材、１２２…帯電手段、１２３…現像手段、１２４…ポリゴンミラーモータ、１２５…ポリゴンミラー、１２６…ｆ−θレンズ、１２７…反射ミラー、１２８…折り返しミラー、Ｙ，Ｍ，Ｃ，Ｋ…単色画像形成ユニット、１２９…トナー収納容器、１３０…トナー貯蔵部、１３１…トナー攪拌部材、１３２…仕切部材、１３３…トナー供給ローラ、１３４…飛散防止ブレード、１３５…現像ローラ、１３６…規制ブレード、１３８…給紙カセット、１３９…ピックアップローラ、１４０…ゲートローラ対、１４１…主記録材搬送路、１４２…定着手段、１４３…排紙ローラ対、１４４…両面プリント用搬送路、１４５…定着ローラ対、Ｃ１…試料測定セル、Ｃ２…トナー収容用凹部、Ｃ３…測定用試料片、Ｃ４…試料台、Ｃ５…測定光、Ｃ６…光電子、Ｃ７…検知器[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that sequentially forms toner images on an image carrier using toners of a plurality of colors and transfers the images onto a recording medium such as paper. .
[0002]
[Prior art]
As an image forming apparatus, a photosensitive drum or a photosensitive belt (hereinafter, referred to as a photosensitive body) is rotatably supported, an electrostatic latent image is formed on a photosensitive layer of the photosensitive body, and the latent image is developed by a developer of a developing device. A four-cycle full-color image forming apparatus, which performs visualization and then transfers onto a recording material using a corona transfer, a transfer roller, a transfer drum or a transfer belt (hereinafter referred to as a transfer medium), and a plurality of photoconductors and a developing mechanism. 2. Description of the Related Art A tandem type full-color image forming apparatus is known in which a plurality of color images are sequentially superimposed and transferred onto a transfer medium on a transfer belt or a transfer drum or a recording material such as paper.
[0003]
Compared to a method in which an image obtained by developing an electrostatic latent image is transferred onto a transfer medium and then transferred onto a recording material, a method in which the developed electrostatic latent image is directly transferred onto a recording material such as paper uses a transfer medium. Since there is no need to provide an intermediate transfer mechanism such as that described above, the configuration is simple and the size can be reduced.
In particular, the tandem system in which image data is directly transferred onto a recording material is characterized in that the image recording apparatus can be reduced in size and a color image can be formed at a high speed.
[0004]
2. Description of the Related Art In a tandem type image forming apparatus, a color image having excellent image quality is formed in consideration of a transfer order and the like. For example, in a process of transferring to a transfer paper, a color image having a balanced hue can be obtained by increasing the amount of toner adhered on a photoconductor transferred earlier to the amount of toner adhered on a photoconductor transferred later. It has been proposed to obtain it (for example, Patent Document 1).
[0005]
By increasing the amount of toner to be developed and transferred first, the toner is reversely transferred onto the photoconductor for the next color during the development of the toner in the later development order, so that the amount of previously transferred toner is reduced. Then, the color balance is lost, so that the amount of adhesion is increased. It does not suppress the generation of the reverse transfer toner itself, and does not prevent the generation of the reversely charged toner.
[0006]
Further, in order to prevent the toner on the transfer body from being reversely transferred, the toner on the transfer body after the transfer is reversely transferred from both surfaces of the transfer body by increasing the adhesive force between the toner and the transfer body by pressure means. It has been proposed to prevent generation of toner (for example, Patent Document 2).
However, it is necessary to separately provide at least three pressure units, and there is a problem that the size of the image forming apparatus is increased and it is difficult to reduce the size of the apparatus.
[0007]
Further, in order to remove the reverse transfer toner, a reverse charge toner removing means having a charge polarity different from that of the toner is provided at least downstream of the transfer portion of the second and subsequent photoconductors as viewed from the upstream side in the moving direction of the recording material conveying body. Has been proposed (for example, Patent Document 3).
In this method, the generation of the reversely charged toner itself cannot be prevented, and the amount of waste toner increases. For this reason, it is necessary to provide a storage means for waste toner having a large capacity. could not.
[0008]
In addition, a color toner having a relatively small particle size is used to improve the quality of a formed color image, and a spherical toner is used to improve transfer efficiency. When the particle diameter of the toner is reduced, the fluidity of the toner is reduced, so that it becomes difficult to triboelectrically charge the toner with the surface of the developing roller and the regulating blade. As a result, sufficient charge cannot be applied. For this reason, the toner has an uneven distribution of charge amount, and it is unavoidable that the toner for negative charging contains a positively charged toner. Fog occurred.
[0009]
Also, in non-magnetic one-component development, it is known that the regulation pressure is increased in order to suppress fog. However, the toner is overcharged and the toner concentration during development is reduced, or the transfer efficiency is reduced. It tended to be lower. Therefore, it has been proposed that the amount of adhered toner on the developing roller after regulation is set in a desired range (for example, Patent Documents 4 to 7), but it is difficult to prevent generation of fog and reverse transfer toner. Was.
[0010]
Further, a full-color image forming method has been proposed in which the maximum adhesion amount of each color toner to a recording material is controlled to be equal to or less than a predetermined amount in order to improve the charging property and the granularity of the image quality by using a small particle size toner (Japanese Patent Application Laid-Open No. H10-157163). 8). However, although it is effective for improving the low-temperature fixability for uniformly heat-fixing the toner, it is insufficient for preventing the generation of the reverse transfer toner.
[0011]
Further, in an image forming apparatus in which images are transferred onto a recording material from a plurality of image bearing drums arranged sequentially, an image bearing drum for forming a black toner image is arranged at the most upstream position of a transport belt for transporting the recording material. An image forming apparatus has been proposed (for example, Patent Document 9).
Further, there has been proposed a color image forming apparatus which develops first with a yellow toner on the most upstream side and finally develops with a black toner on the most downstream side (for example, Patent Document 9).
These are all intended to prevent problems such as curling up of the cleaning blade when developing with black toner only, and are insufficient for preventing fog and reverse transfer toner and preventing color misregistration. there were.
[0012]
Further, it has been proposed to use a toner having a high average circularity and a plurality of kinds of silicon compounds, silicas, and the like having different particle diameters in combination, so as to obtain a toner having excellent transferability and cleaning properties and having no toner scattering or the like. (For example, Patent Documents 10 and 11).
However, no measures were taken to prevent the generation of reverse transfer toner.
[0013]
[Patent Document 1]
JP-A-9-319179
[Patent Document 2]
JP-A-7-64366
[Patent Document 3]
JP 2000-242152 A
[Patent Document 4]
JP-A-6-194943
[Patent Document 5]
JP-A-8-297413
[Patent Document 6]
JP-A-9-62030
[Patent Document 7]
JP-A-11-218957
[Patent Document 8]
JP-A-2002-131973
[Patent Document 9]
JP-A-7-306564
[Patent Document 10]
JP-A-2002-258567
[Patent Document 10]
JP-A-8-227171
[Patent Document 11]
JP-A-2000-3068
[0014]
[Problems to be solved by the invention]
The present invention relates to a tandem-type image forming apparatus that forms an image by sequentially transferring a toner image formed on a latent image carrier onto a recording material conveyed by a conveyance belt. Provided is an image forming apparatus in which transfer of a toner image to be transferred later is not adversely affected, and there is no color shift of the toner image of each color, excellent color reproducibility, and no toner scattering and generation of reverse transfer toner. The task is to do so.
[Means for Solving the Problems]
It is an object of the present invention to dispose a latent image formed on a plurality of latent image carriers and transfer the latent image formed on each latent image carrier to a recording material on a conveying belt for conveying the recording material after developing with toner. In the image forming apparatus that forms a color image by performing the above, a latent image carrier is disposed from the most upstream side to the downstream side of the transport belt so that the work function of the toner used for development is changed from large to small. Thus, the problem can be solved by an image forming apparatus in which development, transfer, and fixing are performed sequentially from toner having a large work function.
In this way, the work functions of the toner used for development are arranged in order from the largest to the smallest, so that the toner previously transferred onto the paper used as the recording material is used by the next toner image forming means. It is possible to prevent reverse transfer that moves to the photoconductor from occurring. In addition, since the adhesion between the toner layers of each color is improved, it is possible to form a color image having excellent color shift prevention and color reproducibility.
[0015]
Further, by arranging the latent image carriers of a plurality of colors and transferring the latent images formed on each latent image carrier to the recording material on the transport belt for transporting the recording material after development with toner, fixing is performed. In an image forming apparatus that forms a color image, a latent image carrier that forms a black toner image is disposed at the most upstream side or the most downstream side of the transport belt, and the work function of the toner used for developing other colors is reduced. This is an image forming apparatus in which latent image carriers are arranged in order from the upstream side to the downstream side, and development, transfer, and fixing are sequentially performed.
As described above, when an image is formed only with black toner by disposing the latent image carrier that forms an image using black toner on the most upstream side or the most downstream side, the image formation ratio using the black toner is usually high. Therefore, not only is it easy to replace the black toner unit, but also because it is located at the end, the black toner unit is made larger than the other color toner units, so that a monochrome image using black Can be increased. As a result, it is possible to provide an image forming apparatus with a reduced replacement frequency.
[0016]
Further, in the above image forming apparatus, the toner is a non-magnetic one-component toner.
The image forming apparatus uses a negatively charged toner and a reversal developing device.
In the above image forming apparatus, the latent image carrier is a negatively charged organic photoconductor.
In the above-described image forming apparatus, the recording material conveying belt stretched in the image forming apparatus may be disposed obliquely with respect to a horizontal direction.
Thus, by providing the conveying belt in the oblique direction and arranging the latent image carrier also in the oblique direction, it is possible to provide an image forming apparatus with good volume efficiency that effectively utilizes the space inside the image forming apparatus. Can be.
Further, the amount of toner developed on the latent image carrier is 0.5 mg / cm. ² The above-described image forming apparatus uses a non-magnetic one-component toner regulated as follows.
As described above, the amount of the toner adhered on the latent image carrier is set to 0.55 mg / cm. ² By doing so, it is possible to keep the primary transfer voltage on the recording material low, and as a result, it is possible to suppress discharge to the non-image portion during primary transfer between the intermediate transfer medium and the latent image carrier. This makes it possible to prevent the transferred toner image from scattering or scattering.
This effect is achieved by developing the toner in order from the one having the largest work function, so that the primary transfer voltage does not need to be sequentially increased, so that a high-quality color toner image can inevitably be obtained.
[0017]
In the above-described image forming apparatus, the recording material may be paper or a synthetic resin film.
The image forming apparatus described above, wherein the peripheral speed of the developing roll is higher than that of the latent image carrier, the peripheral speed ratio is 1.1 to 2.5, and the rotation direction of the image carrier and the developing roll is the same. It is.
As described above, in order to obtain a necessary amount of toner adhered to the development on the latent image carrier, by making the peripheral speed difference of the developing member a predetermined value, uniform charge of toner and electron (charge) due to work function difference are obtained. A high-quality color toner image with high transfer characteristics due to movement and no color shift or scattering can be obtained.
[0018]
A color image is formed by arranging the latent image carriers of a plurality of colors and transferring the latent images formed on each latent image carrier to a recording material on a transport belt for transporting the recording material after developing with toner. In the toner used in the image forming apparatus for forming a toner image, a latent image carrier is arranged from the most upstream side to the downstream side of the transport belt so that the work function of the toner used for development is in descending order, and the fluidity of the toner is A toner in which the modifier contains at least hydrophobic silica and hydrophobic titania.
The toner has a peripheral length (μm) L of the projected image of the toner particles obtained by measuring the projected image of the toner particles. ₁ And the perimeter (μm) L of a perfect circle equal to the area of the projected image of the toner particles ₀ , L ₀ / L ₁ Is a toner having a circularity of 0.94 or more.
The toner described above, which is a toner having a number-based average particle diameter of 4.5 to 9 μm.
Further, the toner is the above-mentioned toner formed by polymerizing at least one of a monomer and an oligomer of a polymerizable organic compound while containing a colorant.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention provides a so-called tandem type color image in which a plurality of latent image carriers for forming images of different colors are sequentially arranged on a recording material by forming a plurality of latent image carriers for forming images of different colors on the latent image carrier. In the forming apparatus, a toner image forming unit including a latent image carrier is arranged in order from a work function having a large toner to a work function having a small work function from the upstream side in the moving direction of the conveying belt, and developing, transferring, and fixing on a recording material. By forming a color image through the process, it is possible to prevent the toner previously transferred on the recording material from moving to the photosensitive member of the next toner image forming unit and performing reverse transfer, thereby improving the adhesion between the toner layers. It has been found that the improvement enables formation of a color image excellent in color shift prevention and color reproducibility.
[0020]
The work functions of the constituent members including the toner, the latent image carrier, and the transport belt in the present invention will be described.
The work function (Φ) of a substance is known as the energy required to extract electrons from the substance, and the smaller the work function, the easier it is to emit electrons, and the larger the work function, the harder it is to emit electrons. Therefore, when a substance having a small work function is brought into contact with a substance having a large work function, a substance having a small work function is positively charged, and a substance having a large work function is negatively charged.
The work function is measured by the following measurement method, is quantified as energy (eV) for extracting electrons from the substance, and is calculated by contact between a toner composed of various substances and various members in an image forming apparatus. The chargeability can be evaluated.
[0021]
The work function (Φ) is measured using a surface analyzer (AC-2, manufactured by Riken Keiki, low energy electron counting system). In the present invention, in the apparatus, a deuterium lamp is used, the irradiation light amount is set to 500 nW, monochromatic light is selected by a spectroscope, the irradiation area is set to 4 mm square, and the energy scanning range is 3.4 to 6. The sample is irradiated at 2 eV and a measurement time of 10 sec / 1. The work function is obtained by detecting photoelectrons emitted from the sample surface, and the work function is measured with a repetition accuracy (standard deviation) of 0.02 eV. In addition, as a measurement environment for ensuring data reproducibility, a sample left for 24 hours was used as a measurement sample under conditions of a use temperature and humidity of 25 ° C. and 55% RH.
[0022]
FIG. 1 is a diagram for explaining how toner is charged on a recording material.
FIG. 1A shows an example of development and transfer of a composite solid image, in which toners are arranged in a line.
The development and transfer to the recording material R are performed in the order of the work function of the toner from Φ (large) to Φ (small), and the toner adheres to the recording material R on the transport belt B electrostatically. Electrons (charges) move in the direction of the charge transfer direction EL indicated by the arrow, and the charge of the toner at the uppermost portion is reduced. Therefore, the toner does not separate due to repulsive force, the overlap is good, and the direction of the transfer electric field EF is different. It is considered that the transfer efficiency becomes higher because of being the same.
Further, as shown in Table 1, the work function of paper for a copying machine and a printer generally used shows a value of about 5.6 eV, and when a toner smaller than the work function of paper is transferred, the toner becomes positive. Tends to be charged.
[0023]
In order to electrostatically hold the toner on the recording material when the toner layer has one or more layers, considering that the back transfer electrode TE has a positive polarity, the charge amount of the toner is negative. Larger amounts are more advantageous. When a plurality of layers of toner are superimposed, the negative state is maintained when the work function of the toner of the first layer is at least 5.6 eV which is the work function of the recording material, which is more advantageous for holding on the recording material. .
In the case of one layer or less, if the charge distribution of the toner is sufficiently distributed on the negative side due to the regulation of the thin layer during development, that is, the substantially one layer regulation, the amount converted to the positive toner becomes negligible. The occurrence of reverse transfer toner rarely causes a problem.
Further, in the present invention, a belt having a work function smaller than the work function of the recording material is used as the transport belt. However, since the transfer electric field works more effectively, a favorable result in transfer can be obtained. .
[0024]
FIG. 1B shows an example of development and transfer of a halftone image, in which toners are adjacent to each other. The development and transfer are performed in the order of the toner work function being large, and the toner is electrostatically attached to the recording material R on the conveyance belt B. As in FIG. 1A, electrons (charges) move in the direction of the arrow, and the charge on the uppermost toner is reduced. Therefore, the toner does not separate due to repulsion, the overlap is improved, and the transfer electric field is reduced. Since the directions are the same, it is considered that the transfer efficiency is increased, and the transfer is maintained as in the case of the composite toner shown in FIG. 1A, and the influence of the reverse transfer toner can be suppressed to a minimum.
[0025]
[Table 1]

[0026]
FIG. 2 is a diagram illustrating the image forming apparatus of the present invention.
FIG. 2 shows an example of a contact developing system in the image forming apparatus of the present invention. The photosensitive member 1 is a photosensitive drum rotating at a surface speed of 60 to 300 mm / s with a diameter of 24 to 86 mm, and a corona charger. After the surface is uniformly negatively charged by 2, exposure 3 according to the information to be recorded is performed, thereby forming an electrostatic latent image.
The developing device 10 is a one-component developing device, which reversely develops an electrostatic latent image on the organic photoconductor by supplying a one-component non-magnetic toner T onto the organic photoconductor to visualize the image. The developing means contains a one-component non-magnetic toner T, and supplies the toner to the developing roller 9 by a toner supply roller 7 which rotates counterclockwise as shown. The developing roller 9 rotates in the counterclockwise direction, transports the toner T transported by the toner supply roller 7 to a contact portion with the organic photoconductor while holding the toner T on the surface thereof, and forms an electrostatic latent image on the organic photoconductor 1. Is visualized.
[0027]
The developing roller 9 is, for example, a roller having a diameter of 16 to 24 mm and having a metal pipe plated or blasted, or a volume resistance made of butadiene rubber, styrene butadiene rubber, ethylene propylene rubber, urethane rubber, silicone rubber, or the like on the peripheral surface of the central shaft. Value 10 ⁴ -10 ⁸ A conductive elastic layer having a 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 a shaft of the tube. Further, the developing device 10 including the developing roller 9, the toner supply roller 7, and the toner regulating blade 8 applies a pressing force of 19.6 to 98.1 N / m, preferably 24 to the organic photosensitive member by an urging means such as a spring (not shown). It is preferable that the nip is pressure-contacted so as to have a width of 1 to 3 mm at a pressure of 0.5 to 68.6 N / m.
[0028]
As the regulating blade 8, stainless steel, phosphor bronze, a rubber plate, a thin metal plate with a rubber chip bonded thereto, or the like is used, but the urging means such as a spring (not shown) against the developing roller or a repulsion as an elastic body is used. It is preferable that the toner is pressed at a linear pressure of 245 to 490 mN / cm using a force, and the thickness of the toner layer on the developing roller is reduced from approximately one layer to two layers.
[0029]
The dark potential of the photoreceptor is preferably −500 to −700 V, the bright potential is −50 to −150 V, and although not shown, the developing bias voltage is preferably −100 to −400 V. Should be the same potential.
In the case of the contact developing method, the peripheral speed of the developing roller rotating counterclockwise is set to 1.1 to 2.5, preferably 1.2 to 2.2 with respect to the organic photoconductor rotating clockwise. It is preferable that the peripheral speed ratio is set so that sufficient toner can be supplied to the contact area with the organic photoreceptor even if the toner particles have a small particle diameter.
[0030]
There is no particular limitation on the relationship between the work function of the regulating blade and the developing roller and the work function of the toner, but preferably the work function of the regulating blade and the developing roller is made smaller than the work function of the toner. By making the toner in contact with the regulating blade negatively charged, a more uniform negatively charged toner can be obtained. Alternatively, a voltage may be applied to the regulating blade 8 to inject electric charge into the toner that comes into contact with the blade to control the toner charge amount.
In addition, the recording material 11 is sent to and transferred between the photoconductor 1 and the backup roller 6 which are placed on the transport belt 12 and visualized.
[0031]
Next, FIG. 3 shows an example of a non-contact developing method in the image forming apparatus of the present invention. In this method, the developing roller 9 and the photosensitive member 1 are opposed to each other via a developing gap d. The developing gap is preferably set to 100 to 350 μm, and although not shown, the developing bias of the DC voltage is −200 to −500 V, and the AC voltage superimposed thereon is 1.5 to 3.5 kHz, PP It is preferable to set the voltage to 1000 to 1800 V. Further, in the non-contact developing system, the peripheral speed of the developing roller rotating counterclockwise is 1.1 to 2.5, preferably 1.2 to 2.5 with respect to the organic photoconductor rotating clockwise. It is preferable to set the peripheral speed ratio to 0.2.
[0032]
The developing roller 9 rotates in the counterclockwise direction as shown in the figure, and transports the toner T to a portion opposed to the organic photoconductor in a state where the toner T transported by the toner supply roller 7 is attracted to the surface thereof. The toner T is developed by vibrating between the surface of the developing roller and the surface of the organic photoreceptor by applying an AC voltage in a superimposed manner at a portion opposing the developing roller. In the present invention, contact charging is performed between toner particles while the toner T vibrates between the surface of the developing roller and the surface of the organic photoreceptor by application of an AC voltage, and a positively charged toner having a small particle diameter is formed. It is considered that the toner can be negatively charged and fog can be reduced.
[0033]
Further, the recording material 10 is sent between the backup roller 6 and the photosensitive member 1, which is placed on the transport belt 11 and visualized, and when the backup roller is used, the photosensitive member 1 by the backup roller 6 is used. The pressing force is preferably 18 to 45 N / m, and more preferably 26 to 38 N / m.
[0034]
As a result, contact between the toner particles and the recording material can be ensured, and charges (electrons) move between the toner particles, so that transfer efficiency can be improved. In this regard, the same applies to the contact type developing system. Other items in the non-contact developing method are the same as those in the contact developing method described above.
[0035]
An apparatus capable of forming a full-color image by combining the developing process shown in FIGS. 2 and 3 with a developing device using four color toners (developers) of yellow Y, cyan C, magenta M, and black K and a photosensitive member. It becomes.
[0036]
The paper transport belt can be manufactured using a composition having a predetermined volume resistance. For example, as a binder for forming the composition, rubber materials such as polyurethane, nitrile rubber (NBR), ethylene propylene rubber (EPDM), and silicone rubber, and synthetic resin materials such as polyester, polyethylene tetraphthalate, polycarbonate, and polyolefin are used. Vinylidene chloride and the like can be used alone or in combination of two or more. In addition, as the conductive material, for example, conductive carbon blacks such as acetylene black, Ketjen black, and furnace black can be used. A belt base is manufactured by mixing materials such as a dispersant and a curing agent with these materials, and performing processes such as kneading, extrusion, cooling, and polishing.
Further, the belt base may be formed by laminating a plurality of layers made of materials having different characteristics or different amounts. By laminating, it is possible to adjust the strength and the electric characteristics, and it is possible to manufacture a product having excellent characteristics. Further, a surface layer having desired characteristics may be formed by applying various treatments to the surface.
The thickness of the paper transport belt is preferably in the range of 0.1 mm to 1.5 mm, and the volume resistance is 10 mm. ⁸ Or 10 ¹¹ Ωcm, preferably 10 ⁸ If it is smaller than Ωcm, the adsorbing performance of paper decreases. Also, 10 ¹¹ If it is larger than Ωcm, it is necessary to increase the transfer voltage and the transfer current, which results in a large volume or a high-voltage power supply with a large rating, which is not preferable. .
[0037]
FIG. 4 is a schematic front view of a tandem type full-color printer used in the present invention.
4, the image forming apparatus 101 according to the present embodiment includes a housing 102, a paper discharge tray 103 formed on an upper portion of the housing 102, and a door 104 that is openably and closably mounted on a front surface of the housing 102. A control unit 105, a power supply unit 106, an exposure unit 107, an image forming unit 108, an exhaust fan 109, a transfer unit 110, and a paper feed unit 111 are provided in the housing 102. Are arranged. Each unit is configured to be detachable from the main body, and is configured to be integrally detachable for repair or replacement during maintenance or the like.
[0038]
The transfer unit 110 includes only a drive roller 113 disposed above the housing 102 and rotationally driven by a drive source (not shown), a driven roller 114 disposed diagonally below the drive roller 113, and only these two rollers. A paper transport belt 115 stretched and circulated in the direction of the arrow (counterclockwise) in the drawing is provided, and a cleaning unit 116 is in contact with the surface of the paper transport belt 115. The driven roller 114 and the paper transport belt 115 It is arranged in a direction inclined leftward in the figure with respect to the driving roller 113. As a result, the belt tension side (the side pulled by the drive roller 113) 117 when the paper transport belt 115 is driven is located below, and the belt slack side 118 is located above.
[0039]
The cleaning means 116 is provided on the belt tension side 117.
A transfer member formed of a leaf spring electrode is provided on the back surface of the paper transport belt 115 so as to face the image carrier 120 of the single-color image forming units Y, M, C, and K for each color constituting the image forming unit 108 described later. The transfer member 121 is contacted by the elastic force, and a transfer bias is applied to the transfer member 121.
[0040]
The image forming units 108 form single-color image forming units Y (for yellow), M (for magenta), C (for cyan), and K (for black) that form a plurality of (four in this embodiment) images of different colors. Each of the single-color image forming units Y, M, C, and K is provided with an image carrier 120 made of a photoconductor on which an organic photosensitive layer and an inorganic photosensitive layer are formed, and disposed around the image carrier 120. And a developing means 123 including a corona charger or a charging roller.
[0041]
The image carriers 120 of each of the single-color image forming units Y, M, C, and K are brought into contact with the belt tension side 117 of the paper transport belt 115, and as a result, each of the single-color image forming units Y, M, C, and K is also arranged in a direction inclined leftward in FIG. The image carrier 120 is driven to rotate in the direction opposite to the intermediate transfer belt 115 as shown by the arrow in the figure.
[0042]
The exposure unit 107 is disposed diagonally below the image forming unit 108, has a polygon mirror motor 124, a polygon mirror 125, an f-θ lens 126, a reflection mirror 127, and a return mirror 128 therein. Is modulated and formed based on the common data clock frequency and emitted, passes through the f-θ lens 126, the reflection mirror 127, and the return mirror 128, and is output from each of the monochrome image forming units Y, M, C, and K. Irradiation is performed on the image carrier 120 to form a latent image. The optical path length of each of the monochrome image forming units Y, M, C, and K to the image carrier 120 is made substantially the same length by the action of the folding mirror 128.
[0043]
Next, the developing unit 123 will be described with reference to the monochrome image forming unit Y. In the present embodiment, since the single-color image forming units Y, M, C, and K are arranged in the direction inclined leftward in the figure, the toner storage container 129 is arranged obliquely downward.
[0044]
That is, the developing unit 123 includes a toner storage container 129 that stores the toner, a toner storage unit 130 (hatched portion in the drawing) formed in the toner storage container 129, and a toner storage unit 130 that is disposed in the toner storage unit 130. The agitating member 131, a partition member 132 defined above the toner storage unit 130, a toner supply roller 133 disposed above the partition member 132, and abut on the toner supply roller 133 provided on the partition member 132. The developing roller 135 includes a scattering prevention blade 134, a developing roller 135 disposed close to the toner supply roller 133 and the image carrier 120, and a regulating blade 136 abutting on the developing roller 135.
[0045]
The developing roller 135 and the toner supply roller 133 are driven to rotate in the direction opposite to the rotation direction of the image carrier 120 as shown by the arrow in the drawing, while the stirring member 131 is driven in the direction opposite to the rotation direction of the supply roller 133. It is driven to rotate. The toner stirred and carried by the stirring member 131 in the toner storage unit 130 is supplied to the toner supply roller 133 along the upper surface of the partition member 132, and the supplied toner is charged by a charging blade (made of a flexible material). (Not shown), and is supplied to the surface of the developing roller 135 by mechanical adhesion to the uneven portion on the surface of the supply roller 133 and adhesion by frictional band power.
The toner supplied to the developing roller 135 is regulated by the regulating blade 136 to a predetermined thickness. The thinned toner layer is conveyed to the image carrier 120 and develops an electrostatic latent image on the image carrier 120 in a development area where the developing roller 135 and the image carrier 120 are close to each other.
[0046]
During image formation, the paper supply unit 111 includes a paper supply cassette 138 on which a plurality of recording media P are stacked and held, and a pickup roller 139 for feeding the recording media P from the paper supply cassette 138 one by one. ing.
[0047]
The paper transport unit 112 includes a pair of gate rollers 140 (one roller is provided on the housing 102 side) that regulates the timing of feeding the recording medium P to the transfer unit, a driving roller 113, a paper transport belt 115, The image forming apparatus includes a recording material conveyance path 141, a fixing unit 142, a discharge roller pair 143, and a double-sided printing conveyance path 144. The fixing means 142 includes a rotatable fixing roller pair 145 having at least one built-in heating element such as a halogen heater, and at least one roller of the fixing roller pair 145 is pressed and urged to the other side to be transferred. The image transferred to the recording medium is fixed to the recording medium at a predetermined temperature at a nip formed by the fixing roller pair 145.
[0048]
In the present invention, the paper conveying belt 115 is disposed in the direction inclined leftward in the figure with respect to the driving roller 113, and the fixing means 142 is disposed on the upper part, so that the image forming apparatus can be downsized. At the same time, it is possible to prevent the heat generated by the fixing unit 142 from affecting the exposure unit 107, the transport belt 115, and the single-color image forming units Y, M, C, and K located on the left side.
[0049]
Next, the measurement cell used for measuring the work function of the toner will be described.
FIG. 5 is a diagram illustrating a sample measurement cell for work function measurement.
As shown in a plan view in FIG. 5A and a side view in FIG. 5B, the sample measuring cell C1 has a diameter of 10 mm and a depth of 1 mm at the center of a stainless steel disk having a diameter of 13 mm and a height of 5 mm. It has a shape having a toner storage recess C2. After the toner is put into the concave portion of the cell without tamping using a weighing spoon, the surface is flattened using a knife edge and then subjected to measurement.
After the measurement cell filled with the toner is fixed on a prescribed position of the sample table, the irradiation area is measured to be 4 mm square and the energy scanning range is 4.2 to 6.2 eV.
In addition, the irradiation light amount was measured at an irradiation light amount of 500 nW for a material having a large insulating property such as toner and a semiconductive material, but was measured at an irradiation light amount of 10 nW for a conductive material such as a metal material. did.
The normalized electron yield at the time of measuring the work function of the toner is preferably 8 or more at a measured light amount of 500 nW.
[0050]
FIG. 6 is a diagram illustrating a method for measuring the work function of a sample having another shape.
When a cylindrical member is used as a sample, such as an intermediate transfer medium and a latent image carrier, the cylindrical member is cut at a width of 1 to 1.5 cm, and then cut laterally along the ridge line. 7 (A), the measurement sample C3 is obtained, and as shown in FIG. 7 (B), the direction in which the measurement light C5 is irradiated onto the specified position of the sample table C4. Is fixed so that the irradiation surface is parallel to Thus, the emitted photoelectrons C6 are efficiently detected by the detector C7, that is, the photomultiplier.
[0051]
As the toner of the present invention, any of a toner obtained by a pulverization method and a polymerization method may be used, but a polymerization method toner having good circularity is preferable.
As a pulverized toner, a resin binder contains at least a pigment, a release agent, a charge control agent, and the like are added, uniformly mixed with a Henschel mixer or the like, melt-kneaded with a twin-screw extruder, cooled, and coarsely pulverized. -Through a pulverizing step, the particles are classified, and externally added particles are attached to form toner particles.
[0052]
As the binder resin, a synthetic resin used as a resin for a toner can be used. For example, polystyrene, poly-α-methylstyrene, chloropolystyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene- Butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylate copolymer, styrene-methacrylate copolymer, styrene-acryl Styrene resin such as acid ester-methacrylic acid ester copolymer, styrene-α-methyl methacrylate copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, styrene-vinyl methyl ether copolymer Homopolymer containing substituent Or copolymer, polyester resin, epoxy resin, urethane modified epoxy resin, silicone modified epoxy resin, vinyl chloride resin, rosin modified maleic resin, phenyl resin, polyethylene, polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, Ethylene-ethyl acrylate copolymer, xylene resin, polyvinyl butyral resin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin and the like can be used alone or in combination.
[0053]
Particularly, in the present invention, a styrene-acrylate resin, a styrene-methacrylate resin, and a polyester resin are preferable. The binder resin preferably has a glass transition temperature of 50 to 75 ° C and a flow softening temperature of 100 to 150 ° C.
[0054]
As the colorant, a colorant for toner can be used. For example, carbon black, lamp black, magnetite, titanium black, chrome yellow, ultramarine, 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. Dyes and pigments such as CI Pigment Blue 15: 3 can be used alone or in combination.
[0055]
As the release agent, a release agent for toner can be used. Examples include paraffin wax, microwax, microcrystalline wax, cadelilla wax, carnauba wax, rice wax, montan wax, polyethylene wax, polypropylene wax, oxidized polyethylene wax, and oxidized polypropylene wax. Among them, it is preferable to use polyethylene wax, polypropylene wax, carnauba wax, ester wax and the like.
[0056]
As the charge adjusting agent, a charge adjusting agent for toner can be used. For example, oil black, oil black BY, Bontron S-22 and S-34 (manufactured by Orient Chemical Industry), salicylic acid metal complexes E-81, E-84 (manufactured by Orient Chemical Industry), thioindigo pigments, sulfonylamine of copper phthalocyanine Derivatives, Spiron Black TRH (manufactured by Hodogaya Chemical Industry), calixarene-based compounds, organic boron compounds, fluorinated quaternary ammonium salt-based compounds, monoazo metal complexes, aromatic hydroxylcarboxylic acid-based metal complexes, aromatic dicarboxylic acid-based metals Complexes, polysaccharides and the like. Above all, a colorless or white color toner is preferred.
[0057]
As the component ratio in the pulverized toner, 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 with respect to 100 parts by weight of the binder resin. , Preferably 2.5 to 8 parts by weight, and the charge control agent is 0.1 to 7 parts by weight, preferably 0.5 to 5 parts by weight.
[0058]
In the pulverization method toner of the present invention, in order to improve the transfer efficiency, it is preferable that the toner is subjected to spheroidizing treatment. For that purpose, in the pulverization step, a device that can be pulverized into a relatively round spherical shape, for example, a mechanical type The roundness can be increased to 0.93 by using a turbo mill (manufactured by Kawasaki Heavy Industries) known as a pulverizer. Alternatively, the degree of circularity can be increased to 1.00 by using a hot-air sphering apparatus (manufactured by Nippon Pneumatic) of the pulverized toner.
In the present invention, the average particle size and circularity of the toner particles are values measured by a particle image analyzer (FPIA2100 manufactured by Sysmex Corporation).
[0059]
Examples of the polymerization method toner include a toner obtained by a suspension polymerization method, an emulsion polymerization method, a dispersion polymerization method, or the like. In the suspension polymerization method, a polymerizable monomer, a coloring pigment, a release agent and, if necessary, a dye, a polymerization initiator, a cross-linking agent, a charge control agent, and a compound added with other additives are dissolved or dissolved. The dispersed monomer composition is added to an aqueous phase containing a suspension stabilizer (a water-soluble polymer, a poorly water-soluble inorganic substance) with stirring, granulated, polymerized, and polymerized to a desired particle size. Color polymerized toner particles can be formed.
[0060]
In the emulsion polymerization method, polymerization is carried out by dispersing a polymerization initiator and an emulsifier (surfactant) in water, if necessary, further including a monomer and a release agent, and then coagulating with a colorant and a charge controlling agent in the coagulation process. By adding an agent (electrolyte) or the like, colored toner particles having a desired particle size can be formed.
In the materials used for preparing the polymerization toner, the same materials as the above-mentioned pulverized toner can be used for the colorant, the release agent, and the charge control agent.
[0061]
As the polymerizable monomer component, known vinyl monomers can be used, and examples thereof include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, and p-methylstyrene. -Ethylstyrene, vinyltoluene, 2,4-dimethylstyrene, pn-butylstyrene, p-phenylstyrene, p-chlorostyrene, divinylbenzene, methyl acrylate, ethyl acrylate, propyl acrylate, n-acrylate Butyl, isobutyl acrylate, n-octyl acrylate, dodecyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, methyl methacrylate, ethyl methacrylate, methacryl Propyl acid, 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 propylene acid, acrylonitrile, Examples include methacrylonitrile, vinyl methyl ether, vinyl ethyl ether, vinyl ketone, vinyl hexyl ketone, and vinyl naphthalene. In addition, as a fluorine-containing monomer, for example, 2,2,2-trifluoroethyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, vinylidene fluoride, ethylene trifluoride, tetrafluoroethylene, trifluoropropylene, etc. Since fluorine atoms are effective in controlling negative charge, they can be used.
[0062]
Examples of the emulsifier (surfactant) include 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.
[0063]
Examples of the polymerization initiator include potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, 4,4′-azobiscyanovaleric acid, t-butyl hydroperoxide, benzoyl peroxide, 2,2′-azobis- Isobutyronitrile and the like.
[0064]
Examples of the coagulant (electrolyte) 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. No.
[0065]
As a method of adjusting the circularity of the polymerization toner, the emulsion polymerization method can freely change the circularity by controlling the temperature and time during the aggregation process of the secondary particles, and the range is 0.94 to 1. .00. Further, in the suspension polymerization method, since a spherical toner is possible, the circularity is in a range of 0.98 to 1.00. Further, by performing the heating deformation at a temperature equal to or higher than the Tg temperature of the toner in order to adjust the circularity, the circularity can be freely adjusted from 0.94 to 0.98.
Further, the number average particle size of the toner is preferably 9 μm or less, more preferably 8 μm to 4.5 μm. With toner larger than 9 μm, even if a latent image is formed at a high resolution of 1200 dpi or more, the reproducibility of the resolution is lower than that of a toner having a small particle diameter. , The amount of the external additive used to increase the fluidity increases, and as a result, the fixing performance tends to decrease.
[0066]
Next, the external additive will be described. The toner particles of the present invention include, as an external additive, silica particles and surface-modified silica particles obtained by modifying the surface of silica with an oxide or hydroxide of at least one metal selected from titanium, tin, zirconium and aluminum. And the surface-modified silica particles are contained in a weight ratio of 1.5 times or less of the silica particles.
[0067]
As other external additives, various inorganic and organic fluidity improvers for toner can be used. For example, positively chargeable silica, titanium dioxide, alumina, zirconium oxide, magnetite, zinc oxide, calcium carbonate, calcium sulfate, magnesium sulfate, magnesium fluoride, silicon carbide, boron carbide plan, titanium carbide, zirconium carbide, boron nitride, nitrided Fine particles of titanium, zirconium nitride, molybdenum disulfide, aluminum stearate, magnesium stearate, zinc stearate, calcium stearate, strontium titanate, and other metal titanate and silicon metal salts can be used. These fine particles are preferably used after being subjected to a hydrophobic treatment 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. The fluidity improver can be used alone or as a mixture, and the amount is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 4.0 parts by weight, based on 100 parts by weight of the toner.
[0068]
As the silica particles, both particles prepared by a dry method from a halide of silicon or the like and particles obtained by a wet method precipitated in a liquid from a silicon compound can be used.
The average primary particle diameter of the silica particles is preferably 5 nm to 50 nm, more preferably 10 nm to 40 nm. When the average particle diameter of the primary particles of the silica particles is smaller than 5 nm, the silica particles are easily buried in the base particles of the toner and easily overcharged negatively. If it exceeds 50 nm, the effect of imparting fluidity of the toner base particles is deteriorated, and it becomes difficult to uniformly negatively charge the toner. As a result, the amount of positively charged toner, which is reversely charged, tends to increase.
[0069]
In the present invention, as the silica particles, it is preferable to use a mixture of silicas having different number average particle size distributions. By containing an external additive having a large particle size, the external additives are buried in the toner particles. This can prevent such a situation, and a preferable fluidity can be obtained by the small-diameter silica particles.
Specifically, one silica preferably has a number average primary particle diameter of 5 nm to 20 nm, more preferably 7 nm to 16 nm. Further, the other silica preferably has a number average primary particle diameter of 30 nm to 50 nm, more preferably 30 to 40 nm.
[0070]
In addition, the particle diameter of the external additive in the present invention is measured by observing with an electron microscope image, and the number average particle diameter is defined as the average particle diameter.
[0071]
The silica particles used as an external additive in the present invention are preferably used after being subjected to a hydrophobizing treatment with a silane coupling agent, a titanium coupling agent, a higher fatty acid, a silicone oil, etc., for example, dimethyldichlorosilane, octyltrimethoxy. Silane, hexamethyldisilazane, silicone oil, octyl-trichlorosilane, decyl-trichlorosilane, nonyl-trichlorosilane, (4-iso-propylphenyl) -trichlorosilane, (4-t-butylphenyl) -trichlorosilane, dipentyl -Dichlorosilane, dihexyl-dichlorosilane, dioctyl-dichlorosilane, dinonyl-dichlorosilane, didecyl-dichlorosilane, didodecyl-dichlorosilane, (4-t-butylphenyl) -octyl-dichlorosilane, didece Le-dichlorosilane, dinonenyl-dichlorosilane, di-2-ethylhexyl-dichlorosilane, di-3,3-dimethylpentyl-dichlorosilane, trihexyl-chlorosilane, trioctyl-chlorosilane, tridecyl-chlorosilane, dioctyl-methyl-chlorosilane, octyl-dimethyl-chlorosilane , (4-iso-propylphenyl) -diethyl-chlorosilane and the like.
[0072]
In addition, it is preferable to use a predetermined amount of silica particles and silica whose surface has been modified with a metal compound in combination with the silica particles. As surface-modified silica, 50 to 400 m ² / G of silica particles having a specific surface area of at least one selected from titanium, tin, zirconium and aluminum.
[0073]
The compounding amount is 1 to 30 parts by weight of a slurry coated with these hydroxides and oxides with respect to 100 parts by weight of silica particles, and then 3 to 50 parts by weight of alkoxysilane with respect to the solid content in the slurry. After coating the parts by weight, it can be obtained by neutralizing with an alkali, filtering, washing, drying and pulverizing. As the silica fine particles used for the surface-modified silica, any particles produced by a wet method or a gas phase method can be used.
[0074]
For the surface modification of the silica particles, an aqueous solution containing at least one of titanium, tin, zirconium, and aluminum can be used.For example, titanium sulfate, titanium tetrachloride, tin chloride, stannous sulfate, Zirconium chloride, zirconium sulfate, zirconium nitrate, aluminum sulfate, sodium aluminate and the like can be mentioned.
Surface modification of silica particles with these metal oxides and hydroxides can be performed by treating a slurry of silica particles with an aqueous solution of these metal compounds. The processing temperature is preferably 20 to 90 ° C.
[0075]
Next, a hydrophobic treatment is performed by coating with an alkoxysilane. In the hydrophobizing treatment, after adjusting the pH of the slurry to 2 to 6, preferably 3 to 6, 30 to 50 parts by weight of at least one alkoxysilane is added to 100 parts by weight of the silica fine particles, and the temperature of the slurry is reduced. It can be realized by adjusting the temperature to 20 to 100 ° C, preferably 30 to 70 ° C, and performing a hydrolysis and condensation reaction.
[0076]
After the addition of the alkoxysilane, the slurry is preferably stirred and then adjusted to pH 4 to 9, preferably 5 to 7, to accelerate the condensation reaction. The pH can be adjusted using sodium hydroxide, potassium hydroxide, sodium carbonate, aqueous ammonia, ammonia gas, or the like. By performing such a treatment, stable fine particles that have been uniformly hydrophobized can be obtained.
Next, the slurry is filtered, washed with water, and then dried to obtain surface-modified silica fine particles.
Drying is carried out at 100 to 190C, preferably 110 to 170C. If the temperature is lower than 100 ° C., the drying efficiency is poor and the degree of hydrophobicity is low, which is not preferable. On the other hand, when the temperature exceeds 190 ° C., discoloration and a decrease in the degree of hydrophobicity are caused by thermal decomposition of the hydrocarbon group, which is not preferable.
In the hydrophobizing treatment, alkoxysilane may be added to the surface-modified silica particles and then coated with a Henschel mixer or the like.
[0077]
In the present invention, these external additives are preferably used in an amount of 0.05 to 2 parts by weight based on 100 parts by weight of the toner base particles.
When the amount is less than 0.05 part by weight, there is no effect in imparting fluidity and preventing overcharging. On the other hand, when the amount is more than 2 parts by weight, the amount of negatively charged electric charge is reduced, and at the same time, the oppositely charged positively charged. Increases the fog amount and the amount of reverse transfer toner.
[0078]
【Example】
Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.
(Production Example of Toner 1)
A monomer mixture consisting of 80 parts by weight of a styrene monomer, 20 parts by weight of butyl acrylate, and 5 parts by weight of acrylic acid was mixed with 105 parts by weight of water, 1 part by weight of a nonionic emulsifier (Emulgen 950, manufactured by Daiichi Kogyo Seiyaku), The mixture was added to an aqueous solution mixture of 1.5 parts by weight of Neogen R) manufactured by Kogyo Seiyaku and 0.55 parts by weight of potassium persulfate, and polymerized at 70 ° C. for 8 hours while stirring under a nitrogen stream. After the polymerization reaction, the mixture was cooled to obtain a milky white resin emulsion having a particle size of 0.25 μm.
[0079]
Next, 200 parts by weight of this resin emulsion, 20 parts by weight of polyethylene wax emulsion (manufactured by Sanyo Chemical Industries) and 7 parts by weight of phthalocyanine blue were dispersed in water containing 0.2 part by weight of sodium dodecylbenzenesulfonate as a surfactant. After adjusting the pH to 5.5 by adding diethylamine, 0.3 parts by weight of aluminum sulfate was added as an electrolyte with stirring, followed by high-speed stirring with a stirrer (TK homomixer) to perform dispersion.
[0080]
Further, 40 parts by weight of a 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 in the same manner as described above. Water was added and polymerization was carried out for 5 hours to grow particles. After the termination of the polymerization, in order to increase the bonding strength of the associated particles, the temperature was raised to 95 ° C. while adjusting the pH to 5 or more, and the temperature was maintained for 5 hours.
Thereafter, the obtained particles were washed with water and vacuum dried at 45 ° C. for 10 hours. A cyan toner having an average particle size of 6.8 μm and a circularity of 0.98 was obtained.
In this example, the circularity was measured using a flow-type particle image analyzer (FPIA2100 manufactured by Sysmex Corporation) and expressed by the following equation (1).
R = L ₀ / L ₁ … (1)
Where L ₁ Is the peripheral length (μm) of the projected image of the toner particles to be measured.
L ₀ Is the perimeter (μm) of a perfect circle equal to the area of the projected image of the toner particles to be measured.
[0081]
To 100 parts by weight of the obtained toner, 1 part by weight of hydrophobic silica having an average primary particle diameter of 12 nm as a fluidity improver and 0.7 part by weight of hydrophobic silica having an average primary particle diameter of 40 nm were added and mixed. Then, 0.5 parts by weight of hydrophobic titanium oxide having an average primary particle diameter of about 20 nm and 0.4 parts by weight of positively chargeable hydrophobic silica obtained by surface-treating hydrophobic silica having an average primary particle diameter of about 30 nm with aminosilane. The toner 1 was obtained by adding and mixing parts by weight.
[0082]
The average particle size was represented by a volume distribution D50 measured with an electric resistance particle size distribution analyzer (Multisizer III manufactured by Beckman Coulter, Inc.).
The work function of the obtained toner was 5.54 eV. In the present embodiment, the work function is a value measured by a surface analyzer (AC-2, manufactured by Riken Keiki) at an irradiation light amount of 500 nW. is there.
[0083]
(Production Example of Toner 2)
The toner 1 was manufactured at a temperature of 90 ° C. to increase the association of the secondary particles and the film forming bond strength in the same manner as in the manufacturing example 1 of the toner except that quinacridone was used instead of the phthalocyanine blue pigment. Thus, a toner 2 was prepared. The circularity of the obtained magenta toner was 0.972, and the work function was 5.63 eV. The average particle size based on the number of the toner was 6.9 μm.
[0084]
(Production Examples of Toners 3 and 4)
Polymerization was carried out in the same manner as in the production example of Toner 2 except that the pigment was changed to Pigment Yellow 180 and carbon black in the production example of Toner 2, a fluidity improver was added, the circularity was 0.972, and the work function was 5 A yellow toner 3 having a diameter of 0.58 eV and an average particle diameter of 7.0 μm and a black toner 4 having a circularity of 0.973, a work function of 5.48 eV and an average particle diameter of 6.9 μm were produced.
[0085]
(Production Example of Toner 5)
100 parts by weight of a 50:50 (weight ratio) mixture of a polycondensed polyester of an aromatic dicarboxylic acid and an alkylene etherified bisphenol A and a partially crosslinked product of the polymerized polyester with a polyvalent metal compound (Hymer ES manufactured by Sanyo Chemical Industries); 5 parts by weight of pigment blue 15: 1 of cyan pigment, 1 part by weight of polypropylene having a melting point of 152 ° C. and a weight average molecular weight Mw of 4000 as a releasing agent, and a metal salicylate complex E-81 as a charge control agent (Orient Chemical Industries, Ltd.) 4 parts by weight) were uniformly mixed using a Henschel mixer, kneaded with a twin screw extruder at an internal temperature of 130 ° C., and cooled.
[0086]
The cooled product was roughly pulverized to 2 mm square or less, then finely pulverized by a jet mill, and classified by a classifier using a rotor to obtain a classified toner having an average particle diameter of 6.2 μm and a circularity of 0.905. For 100 parts by weight of the classified toner, 0.2 parts by weight of hydrophobic silica (average primary particle diameter 7 nm, BET specific surface area 250 m) ² / G) and subjected to a surface treatment. Then, using a hot-air sphering apparatus (manufactured by Nippon Pneumatic Industries, Ltd.), the heat treatment temperature was set to 200 ° C., the spheroidizing treatment was partially performed, and classification was performed again in the same manner. Then, mother particles of cyan toner 5 having an average particle diameter of 6.3 μm and a circularity of 0.940 were obtained. To the toner base particles, a fluidity improver was added and mixed in the same manner as in the case of the toner 1 to prepare a toner 5. The work function of the obtained toner was measured by the same method and found to be 5.48 eV.
[0087]
(Production Examples of Toners 6, 7, and 8)
In toner 5, pulverization, classification, heat treatment, re-classification and surface treatment were performed in the same manner as toner 5 except that the pigment was changed to naphthol AS-based 6B, and a magenta toner having an average particle diameter of 6.5 μm and a circularity of 0.942 was used. Toner 6 was obtained. The work function of this toner 6 was 5.53 eV when measured.
Similarly, toner 7 (using Pigment Yellow 93 as a yellow toner) and toner 8 (using carbon black as a black toner) were prepared. The average particle size and circularity of the obtained toner were almost the same as those of the toner 6, and the work functions of the respective toners were 5.57 eV (yellow) and 5.63 eV (black).
[0088]
(Production Example of Organic Photoconductor (OPC1))
As a subbing layer, 6 parts by weight of alcohol-soluble nylon (CM8000 manufactured by Toray) and 4 parts by weight of aminosilane-treated titanium oxide fine particles were dissolved and dispersed in 100 parts by weight of methanol on an aluminum conductive support having a diameter of 30 mm. The resulting coating solution was applied by a ring coating method and dried at a temperature of 100 ° C. for 40 minutes to form an undercoat layer having a thickness of 1.5 to 2 μm.
[0089]
On this undercoat layer, 1 part by weight of titanyl phthalocyanine as a charge generating substance, 1 part by weight of a butyral resin (BX-1 manufactured by Sekisui Chemical) and 100 parts by weight of dichloroethane were added by a sand mill using glass beads having a diameter of 1 mm. Time dispersed.
The obtained pigment dispersion was applied by a ring coating method using the support prepared above, and dried at 80 ° C. for 20 minutes to form a 0.3 μm-thick charge generation layer.
On this charge generation layer, 40 parts by weight of a charge transport material of a distyryl compound represented by the following structural formula (1) and 60 parts by weight of a polycarbonate resin (Panlite TS manufactured by Teijin Chemicals) are dissolved in 400 parts by weight of toluene. Was applied by a dip coating method and dried to form a charge transporting layer, so that an organic photoreceptor (OPC1) having a two-layered photosensitive layer was prepared.
A part of the obtained organic photoreceptor was cut out to form a sample piece, and its work function was measured with a surface analyzer (AC-2 type manufactured by Riken Keiki Co., Ltd.) at an irradiation light amount of 500 nW and showed 5.50 eV. .
[0090]
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Embedded image

[0091]
(Example of manufacturing organic photoconductor (OPC2))
An organic photoconductor (OPC2) was prepared in the same manner as the organic photoconductor (OPC1) except that an aluminum tube having a diameter of 40 mm was used as a conductive support.
The work function of this organic photoreceptor was measured in the same manner and found to be 5.48 eV.
[0092]
(Preparation of the regulation blade)
A conductive urethane chip having a thickness of 1.5 mm was attached to a stainless steel plate having a thickness of 80 μm with a conductive adhesive, and the work function of the urethane portion was set to 5 eV.
[0093]
(Example of manufacturing the paper transport belt (1))
85 parts by weight of polybutylene terephthalate, 15 parts by weight of polycarbonate and 15 parts by weight of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.) were premixed by a mixer under a nitrogen gas atmosphere, and the resulting mixture was twin-screw extruded under a nitrogen gas atmosphere. The mixture was kneaded by a machine to obtain pellets. The pellet was extruded at 260 ° C. into a tubular film having an outer diameter of 170 mm and a thickness of 160 μm by a single screw extruder having an annular die. Next, the inner diameter of the extruded molten tube was regulated by a cooling inside mandrel supported on the same axis as the annular die, and cooled and solidified to produce a seamless tube. It was cut to a specified size to obtain a seamless belt having an outer diameter of 172 mm, a width of 342 mm, and a thickness of 150 μm. The volume resistance of this paper transport belt is 3.2 × 10 ⁸ Ω─cm. The work function was 5.19 and the normalized photoelectron yield was 10.88.
[0094]
Further, 100 parts by weight of a urethane-modified epoxy resin (Adeka Resin EPU-8 manufactured by Asahi Denka Kogyo), 3.5 parts by weight of conductive carbon black (VULCANXC72R manufactured by Cabot), and a polymer dispersant (Ajispar PB711 manufactured by Ajinomoto Fine-Techno) 2 After dispersing 1 part by weight and 75 parts by weight of toluene in a paint conditioner for 2 hours, 8 parts by weight of a curing agent (EH-200 manufactured by Asahi Denka Kogyo) was added, and the mixture was sufficiently stirred to obtain a coating liquid for the conductive undercoat layer. . This solution was applied to the above surface by spray coating and dried (at 70 ° C. for 6 hours) to provide a surface layer having a thickness of 13 μm. The work function of this semiconductive coating layer was 5.36 eV.
[0095]
Example 1
Each of the toners 1 to 4 described above was loaded by using a tandem type color printer shown in FIG. 4 equipped with the organic photoreceptor (OPC1), the developing roller, the regulating blade, and the paper transport belt (1) previously manufactured. An image forming test was performed by a non-contact one-component developing system with the toner image forming means mounted.
In forming an image, the peripheral speed of the organic photoconductor is set to 180 mm / s, the peripheral speed of the developing roller is set to a peripheral speed ratio of 1.6 to the organic photoconductor, and standard image forming conditions are set to The dark potential is -600 V, the bright potential is -80 V, the gap between the developing roller and the photoreceptor is 210 m (the gap is adjusted with a gap roller), the alternating current superimposed on the DC developing bias of -200 V is 2.5 kHz in frequency, and the PP voltage is At a setting of 1400 V, the developing roller and the supply roller were set to the same potential.
[0096]
Then, the amount of the developed toner adhered on the photoconductor at the time of solid printing of each color toner is set to a maximum of 0.53 mg / cm. ² Printing was performed (under the conditions of a temperature of 23 ° C. and a humidity of 55 RH%) while controlling as follows.
Further, by changing the regulation condition of the toner regulation blade, the toner conveyance amount on the developing roller is set to 0.4 mg / cm. ² ~ 0.43mg / cm ² It was set to be.
The image forming conditions were as follows: the dark potential of the photoconductor was -600 V, the bright potential was -80 V, the developing bias was -200 V, and the developing roller and the supply roller had the same potential. A DC constant current power supply is used as a power supply for the primary transfer unit. The transfer current is controlled by the first and fourth colors, and the current value is increased by 8 μA for the first color and 2 μA for the second and subsequent colors. Transfer was performed.
[0097]
The tandem-type color printer shown in FIG. 4 is a so-called cleanerless printer having no cleaning member near the photoconductor. In the printing test, 10,000 sheets of a character original corresponding to a 5% color original of each color were continuously printed, and 5000 sheets of an N-2A (cafeteria) image of standard image data based on JIS X9201-1995 were continuously printed.
Further, the image forming means is a toner image forming means having a small work function of the toner sequentially from the one having a large work function of the toner to the one having a small work function from the upstream side in the moving direction of the paper conveying belt.
[0098]
In this embodiment, the first toner image forming means is loaded with black toner. When the order of arrangement was changed, the order of image data processing was changed each time printing was performed.
In this case, the initial quality of the output print image was visually checked for color misregistration after 10,000 sheets for a 5% color original, and the change in overall color misregistration for an N-2A output print image as a natural image. .
[0099]
The toners used are cyan toner 1 (symbol C1, work function: 5.54 eV), magenta toner 2 (symbol M2, work function: 5.63 eV), yellow toner 3 (symbol Y3, work function: 5.58 eV), and Black toner 4 (symbol BK4, work function: 5.48 eV), and a recording material used was electrophotographic paper (PPC paper L, manufactured by Fuji Xerox Supply Co.); work function: 5.61 eV.
Table 2 shows the results.
[0100]
[Table 2]

[0101]
From the results in Table 2, it was found that by performing development and transfer with toner having a larger work function of toner as in the present invention, it is possible to form a cleaner-less image substantially without installing a cleaning unit. . In addition, there was no color shift of the obtained printed matter, and good image quality was provided.
[0102]
However, the toner conveyance amount on the developing roller was changed to 0.5 mg / cm ² Regulation conditions set more frequently, specifically 0.52 mg / cm ² Under the conditions before and after, and when the amount of developing toner adhered on the solid-colored organic photoconductor is 0.55 mg / cm ² Under the image forming conditions set as described above, it was found that the number of printed sheets in Experimental Example 1 could not be maintained unless the cleaning means was provided.
This property requires that the toner can be uniformly negatively charged, and that the amount of toner adhered during solid printing developed on the organic photoreceptor be as small as possible so as to make uniform contact between the toner layers. It indicates something.
[0103]
Example 2
An image forming test was performed in the same manner as in Example 1 except that OPC2 was used as the organic photoreceptor and a cleaning unit was attached. The toner includes cyan toner 5 (symbol C5, work function: 5.48 eV), magenta toner 5 (symbol M2, work function: 5.53 eV), yellow toner 7 (symbol Y7, work function: 5.57 eV), and black toner. The same print test evaluation was performed using toner 8 (symbol BK8, work function: 5.63 eV) and electrophotographic paper (PPC paper L manufactured by Fuji Xerox Supply Co.) as a recording material.
[0104]
Further, the toner image forming means is sequentially arranged from the toner having a large work function to the toner having a small work function from the upstream side in the moving direction of the paper conveying belt. In this embodiment, the first toner image forming means is loaded with cyan toner, and the toner image forming means loaded with black toner is located fourth. Further, when the arrangement order was changed, the image data processing order was changed and printed each time.
The configuration of the developing roller and the regulating blade is as described above, and the transport amount of each color toner is 0.4 mg / cm. ² ~ 43mg / cm ² The conditions of the regulating blade were set so as to fall within the range of The power supply of the transfer section was a constant current power supply, and a constant current of 14 μA was used for constant printing to perform continuous printing. .
[0105]
The image is applied under the conditions of an AC frequency of 2.5 kHz superimposed on a DC developing bias of -200 V and a peak-to-peak voltage of 1400 V, and a character original corresponding to a 5% color original of each color is continuously printed on 10,000 sheets and printed. The quality of the image was evaluated. Evaluation was made on the print quality of the N-2A “cafeteria” image of the standard image data based on JIS X 9201-1995 of the natural image described above before continuous printing, and with particular emphasis on the color shift of halftone, %, One natural image N-2A was printed after continuous printing of 2000 originals, and the change in halftone was visually observed. When the color shift was clearly observed, the printing was stopped, and the printing was terminated with the number of prints at that time.
Table 3 shows the results. “Excellent” indicates that there is no problem in the image, “Good” indicates that the image is in a practically acceptable range, and “Defective” indicates that the image quality is inferior due to color shift.
[0106]
[Table 3]

[0107]
As described above, it was shown that by performing development and transfer in order from a toner having a high circularity and a large work function as in the present invention, there is no deterioration in print quality. This is presumably because charge transfer occurred between the toner layers, the adhesion between the toner layers was increased, and scattering and color misregistration were prevented and transfer efficiency was increased, thereby maintaining stable image quality. However, it has been found that performing development and transfer with a random work function of toner in the order of development and transfer affects print image quality, particularly color shift. It was also found that it is not good to bring the toner image forming means having a small work function of the toner to the first stage.
Further, from the results in Table 3, when the toner is directly transferred to a transfer material having a relatively large work function of about 5.6 eV as in the present invention, the toner work function of the toner image forming means is used. It can be seen that it is preferable to arrange the large toner image forming unit on the first stage and arrange the toner image forming unit that sequentially reduces the work function of the toner.
However, at this time, the amount of toner adhered to the developed one-color solid image on the organic photoreceptor was 0.6 mg / cm. ² With the above setting, the transfer efficiency is deteriorated, which leads to an increase in the amount of cleaning toner, and the number of printed sheets per toner amount is reduced. As a result, an inefficient color image forming apparatus is obtained.
In addition, in Experimental Example 2, the amount of cleaning toner was 30 g for 10,000 sheets of A4 size printing on a 5% original of each color, but in other comparative experimental examples, the cleaning amount was in the range of 50 g to 80 g.
[0108]
【The invention's effect】
In the present invention, in a tandem-type color image forming apparatus that transfers a toner image formed on a latent image carrier onto a recording material conveyed by a conveyance belt, the toner work is performed from the upstream side in the conveyance belt movement direction. By arranging the toner image forming means from a function having a large function to a function having a small function and forming a color image through a developing, transferring and fixing process on paper, the toner transferred on the paper first is used as a toner image forming means for the next toner image forming means. By preventing reverse transfer to the photoreceptor and improving the adhesion between the toner layers, it becomes possible to form a color image that is excellent in color shift prevention and color reproducibility.
In addition, since the adhesion between toners is improved, toner scattering is eliminated, so that not only contamination in the image forming apparatus is prevented, but also the surface of the conveying belt is not stained, so that it is possible to prevent the back surface of the paper from being stained. Become.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a state of charging of a toner on a recording material.
FIG. 2 is a diagram illustrating an image forming apparatus according to the present invention.
FIG. 3 is a diagram illustrating an image forming apparatus according to the present invention.
FIG. 4 is a diagram illustrating an example of a tandem-type full-color printer according to the present invention.
FIG. 5 is a diagram illustrating a sample measuring cell used for measuring a work function.
FIG. 6 is a diagram for explaining a method of measuring a work function.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photoreceptor, 2 ... Corona charger, 3 ... Exposure, 5 ... Cleaning blade, 6 ... Backup roller, 7 ... Toner supply roller, 8 ... Regulator blade, 9 ... Developing roller, 10 ... Developing device, 10 (Y) , 10 (M), 10 (C), 10 (K): developing device, T: toner, 11: recording material, 12: conveyor belt, 101: image forming apparatus, 102: housing, 103: paper discharge tray, 104 .., Door unit, 105 control unit, 106 power unit, 107 exposure unit, 108 image forming unit, 109 exhaust fan, 110 transfer unit, 111 paper feed unit, 112 paper transport unit, 113 drive Roller, 114: driven roller, 115: paper transport belt, 116: cleaning means, 117: belt tension side, 118: belt slack side, 120: image carrier 121: transfer member, 122: charging means, 123: developing means, 124: polygon mirror motor, 125: polygon mirror, 126: f-θ lens, 127: reflection mirror, 128: folding mirror, Y, M, C, K .., A single-color image forming unit, 129, a toner storage container, 130, a toner storage section, 131, a toner stirring member, 132, a partition member, 133, a toner supply roller, 134, a scattering prevention blade, 135, a developing roller, and 136, a regulating blade. Reference numerals 138, a paper feed cassette, 139, a pickup roller, 140, a gate roller pair, 141, a main recording material conveying path, 142, a fixing unit, 143, a discharge roller pair, 144, a double-sided print conveying path, 145, a fixing roller Pair, C1: sample measurement cell, C2: toner storage recess, C3: measurement sample piece, C4: sample table, C5 ... Measurement light, C6 ... Photoelectron, C7 ... Detector

Claims (13)

A color image is formed by arranging the latent image carriers of a plurality of colors and transferring the latent images formed on each latent image carrier to a recording material on a transport belt for transporting the recording material after developing with toner. In the image forming apparatus, the latent image carrier is arranged from the most upstream side to the downstream side of the conveyor belt so that the work function of the toner used for development is changed from a large work function to a small work function. An image forming apparatus wherein development, transfer, and fixing are performed sequentially from toner. A color image is formed by arranging the latent image carriers of a plurality of colors and transferring the latent images formed on each latent image carrier to a recording material on a transport belt for transporting the recording material after developing with toner. In the image forming apparatus, a latent image carrier that forms a black toner image is arranged at the most upstream side or the most downstream side of the conveyor belt, and the work function of the toner used for developing the other colors is on the upstream side. An image forming apparatus characterized in that a latent image carrier is arranged downstream from a large image to a small image and development, transfer, and fixing are sequentially performed. 3. The image forming apparatus according to claim 1, wherein the toner is a non-magnetic one-component toner. 4. The image forming apparatus according to claim 1, wherein a negatively charged toner and a reversal developing device are used. The image forming apparatus according to claim 1, wherein the latent image carrier is a negatively charged organic photoreceptor. 6. The image forming apparatus according to claim 1, wherein the recording material conveying belt stretched in the image forming apparatus is disposed obliquely to a horizontal direction. The image according to any one of claims 1 to 6, wherein a non-magnetic one-component toner in which an amount of toner developed on the latent image carrier is regulated to 0.5 mg / cm ² or less is used. Forming equipment. The image forming apparatus according to any one of claims 1 to 7, wherein the recording material is paper or a synthetic resin film. The peripheral speed of the developing roll is higher than that of the latent image carrier, the peripheral speed ratio is 1.1 to 2.5, and the rotation direction of the image carrier and the developing roll is the same. An image forming apparatus according to claim 1. A color image is formed by arranging a plurality of latent image carriers and forming the latent images formed on each latent image carrier by a toner image, transferring the latent image to a transfer material on a conveyance belt for recording material conveyance, and then fixing the latent image. In the toner used in the image forming apparatus for forming a toner image, a latent image carrier is arranged from the most upstream side to the downstream side of the transport belt so that the work function of the toner used for development is in descending order, and the fluidity of the toner is A toner characterized in that the improver contains at least hydrophobic silica and hydrophobic titania. The toner has a ratio of a peripheral length (μm) L ₁ of the projected image of the toner particles obtained by measuring the projected image of the toner particles to a peripheral length (μm) L ₀ of a perfect circle equal to the area of the projected image of the toner particles. the toner of claim 10, wherein the circularity represented by _L 0 / _{L 1} is characterized in that at least 0.94. The toner according to claim 10, wherein the toner has a number-based average particle diameter of 4.5 to 9 μm. The toner according to any one of claims 10 to 12, wherein the toner is formed by polymerizing at least one of a monomer and an oligomer of a polymerizable organic compound while containing a colorant. .

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