JP3887839B2 - One-component developer and electrophotographic image forming method using the same - Google Patents

Description

【００２８】
なお、上式中、球形と仮定したときの比表面積は、上記粒度分布測定機で測定した粒度分布からトナー粒子を真球状として仮定して得られる数値である。また、ＢＥＴ比表面積は、具体的にはフローソーブ２３００型（島津製作所製）を用いて窒素吸着法により測定される。
このようにして計算して得られるワーデル球形化度は、トナーの製造方法に依存して各様の数値を示す。ハイブリッド法で得られるワーデル球形化度の数値は通常０．６を超え、熱的球状化法の場合は通常０．８を超え、湿式造粒重合法で得られる粒子は通常０．９を超えるものである。このようにトナー粒子のワーデル球形化度が０．６を超える場合には、現像スリーブ上に形成されるトナー層当たりのトナー重量（トナー付着量）が大きくなるのでトナー消費量が悪化するなどの問題があり好ましくない。０．９を超える場合には、感光体上でのクリーニング不良が発生する場合もある。従って、本発明に用いるトナー粒子は上記した粉砕法によって得られたものであることが好ましい。しかし、通常の粉砕法により得られるトナー粒子のワーデル球形化度は０．３未満の場合が多く、この場合には現像スリーブ上での帯電が低く逆極性部分も多いので、得られる画像の中抜けがひどく、画像濃度やカブリの面でも難がある等の画質上の問題がある。
【００２９】
本発明において、粉砕法により得られるトナー粒子のワーデル球形化度を０．３〜０．６に制御するには、粉砕工程での望ましい粉砕装置の選定及びその粉砕条件の設定により行うのがよい。具体的な例示としては、まず、ターボミル（ターボ工業社製）やクリプトロン（川崎重工社製）等の高速回転式微粉砕機等の機械式粉砕機を用いて行う方法が好ましい。これらの機械式粉砕機は、高速回転するロータとケーシングとの微小間隙でのせん断及び摩砕作用により粉砕を行うものであって、トナー粒子の形状は粒子の角張りが取れた形状を得られやすい。従って、例えば、特開平６−２６２０９５号公報や特開昭６−２６２０９６号公報等に記載のようにロータ及びケーシングの形状や間隙距離等の各種条件を適宜選べば、前記の好ましいワーデル球形化度の範囲の粒子形状が得られる。別の方法としては、微粉砕機として流動層式ジェットミル等の流動層式粉砕機を採用する方法が好ましい。この方式のジェットミルは、従来多用される衝撃式ジェットミル（Ｉ式ジェットミル）が、衝突板と粒子との衝突による単純な衝撃作用で大部分の粉砕が行われるのでワーデル球形化度としては０．３未満の粒子しか得られないのに対し、流動層状態での被粉砕物粒子同士の衝撃と摩擦作用により粉砕が行われるので、適当な粉砕条件を選べば前記したワーデル球形化度の範囲の粒子形状が得られやすい。なお、以上の望ましい実施態様の粉砕機においては、必要に応じて温度調節された空気を粉砕室に供給するなどの各種の補助手段をとってもよい。
【００３０】
本発明の一成分現像剤は、これらのトナー粒子と脂肪酸金属塩粒子と流動性向上剤とから成る。
本発明において、脂肪酸金属塩粒子の粒子径は以下の式（１）及び（２）を満足しなければならない。
【００３１】
【数６】
Ｄｓ５０／Ｄｔ５０≦０．６ （１）
Ｄｓ８４／Ｄｓ１６≦６ （２）
【００３２】
ただし、式中、Ｄｔ５０はトナー粒子の体積５０％径を表し、Ｄｓ１６、Ｄｓ５０及びＤｓ８４はそれぞれ脂肪酸金属塩粒子の体積１６％径、５０％径及び８４％径を表す。なお、各体積粒子径は小粒子側からの累積分布から計算する。
【００３３】
従来から、脂肪酸金属塩は電子写真プロセスにおける接触摺擦工程（感光体とクリーニングブレード等）において、その減摩作用により摺擦をスムーズにして粒子の摩擦熱等による付着の防止に効果のあることが知られていた。本発明者らは、上記式（１）及び（２）を共に満たす特別な粒度分布を有する脂肪酸金属塩粒子を採用すれば、特に一成分現像剤において、上記の作用の他にトナー粒子の帯電性を高め、帯電量分布の逆極性部分を減らし、しかも帯電性の長期安定性も改善する作用があることを知得した。上記式（１）または（２）のうちのいずれかしか満足しない場合や両式とも満足しない場合は、良好な結果が得られないので好ましくない。
上記の粒子径及び粒度分布の測定は、前記した装置及び条件で行うのが望ましい。
【００３４】
本発明に係わる脂肪酸金属塩粒子は、上記式（１）及び（２）で示されるように、粒子径が小粒径でしかもその粒度分布の範囲が狭いことを特徴とする。式（１）において、Ｄｓ５０／Ｄｔ５０の値が０．６を超えて大きい場合には、脂肪酸金属塩粒子の粒径がトナー粒子の粒径に近づくか、それ以上に大きくなることを意味するので、こうした大粒子は現像剤中から脱落して系外に飛散しやすくなり装置を汚染するばかりか、画像上に大粒状のカブリとして検出されるようになるので好ましくない。Ｄｓ５０／Ｄｔ５０の値は０．５以下であることが好ましい。また、式（２）において、粒子の粒度分布の幅を表すＤｓ８４／Ｄｓ１６が６を超えて大きい場合には、粒子の粒度が不揃いなので現像剤の帯電性を長期にわたって安定に保つことが困難となり、画質の変動を抑制できない。Ｄｓ８４／Ｄｓ１６の値は５以下、中でも特に４以下であることが好ましい。なお、脂肪酸金属塩粒子の粒度分布は一山分布であるのが望ましい。
【００３５】
本発明に用いられる脂肪酸金属塩粒子の脂肪酸としては、酪酸、吉草酸、ラウリン酸、ミリスチン酸、パルミチン酸、ステアリン酸及びモンタン酸等の一価の飽和脂肪酸、アジピン酸、ピメリン酸、スベリン酸、アゼライン酸及びセバシン酸等の多価の飽和脂肪酸、クロトン酸及びオレイン酸等の一価の不飽和脂肪酸、並びにマレイン酸及びシトラコン酸等の多価の不飽和脂肪酸等を挙げることができ、本発明には８〜３５個の炭素元素を有する飽和または不飽和の脂肪酸が好ましく使用できるが、特にステアリン酸が望ましい。金属塩としては、リチウム、ナトリウム、カリウム、銅、ルビニウム、銀、亜鉛、マグネシウム、カルシウム、ストロンチウム、アルミニウム、鉄、コバルト、ニッケルの塩及びその混合物を含むがこれらには制限されない。上記した中でも、ステアリン酸と亜鉛、マグネシウム、カルシウム及びアルミニウムの中から選ばれる一種以上の金属とのステアリン酸金属塩がより望ましい。その中でも、特にステアリン酸亜鉛を用いるのが最適である。
【００３６】
流動性向上剤としては、公知の各種のものが使用可能である。例えば、乾式製法または湿式製法によるシリカ、アルミナ、チタニア等の金属酸化物が挙げられる。中でもその平均一次粒子径が約５〜５０ｎｍであるものが好ましい。また、その表面が疎水化処理されているものが望ましい。本発明に係わる疎水化処理剤の具体例としてはヘキサメチルジシラザン及びシリコンオイル等が挙げられる。そして、流動性向上剤としては、ヘキサメチルジシラザン及びシリコンオイルの中から選ばれる少なくとも一種の物質で疎水化処理されたシリカ微粒子であるのが最適である。このような微粒子は、凝集物による感光体傷の発生が極めて少なく、従ってそれに付随して起こる各種の画像欠陥が発生しにくい利点を有する。疎水化処理剤として、例えばジメチルジクロルシランを用いた場合、得られる流動性向上剤には粗大な凝集物が残存しやすい傾向にあり、感光体傷が発生する要因となる場合があるので好ましくない。
【００３７】
トナー粒子への脂肪酸金属塩粒子及び流動性向上剤の添加の方法は、高速流動式混合機等を用いて外添するのが好ましい。また、必要に応じてこれらの添加剤を事前に個別にあるいは混合して解砕して、粗大凝集物を除去してトナー粒子に外添してもよい。
これらの粒子の添加量は、トナー粒子１００重量部に対して、脂肪酸金属塩粒子を０．０１〜３重量部、より好ましくは０．０３〜１重量部添加させ、流動性向上剤を０．０５〜３重量部、より好ましくは０．１〜２重量部添加させるのがよい。
【００３８】
本発明に用いる一成分現像剤はトナー粒子が磁性を有する磁性一成分方式またはトナー粒子が実質的に非磁性である非磁性一成分方式のいずれにも適用される。また、カラー一成分現像剤として用いるのにも好適である。
以下、図１を例に本発明の画像形成方法を説明する。本図は非磁性一成分現像剤を用いる場合の例である。
本発明に用いられる現像スリーブ１は、通常、円柱状あるいは円筒状の形態の表面を現像剤６を担持する表面として用いる。材質は弾性体、剛体どちらでもよいが、感光体３と現像スリーブ１とが非磁性現像剤を介在して接触する、いわゆる接触現像方法においては弾性体を用いる方法が一般的である。また磁性現像剤を用いる場合は、マグネットを内包する金属製の剛体スリーブを用いるのが通例である。現像スリーブ１の表面は現像剤６の搬送性を上げる目的で適度な表面粗さを与えてもよい。またトナー粒子との適度な摩擦帯電が得られるような材質を考慮しなければならない。非磁性一成分接触型現像の場合、弾性体の現像スリーブ１の一般的な形態としては、導電性ゴムローラ（ＮＢＲゴム、シリコーンゴムなどに導電性粒子を分散含有させたものなど）を用いる。導電性ゴムの表面に誘電体層を設ける場合もある。
【００３９】
本発明に用いられる層形成部材２は、角棒状の剛体、突起状の弾性体、板バネ状等のものの面や先端を利用するもの、ローラ、その他、あるいはそれらの複合型など各種が挙げられる。層形成部材２はそれ自身の弾性力あるいは現像スリーブ１の弾性力あるいは外部からの力あるいはそれらの複合力によって、現像スリーブ１に直線上に押圧されている。現像スリーブ１と層形成部材２との間には、特に電圧をかけない場合、短絡して同電位とする場合、５００Ｖ以下程度の電圧をかける場合などがある。層形成部材２の電気特性については、絶縁性のもの、導電体のものに電圧を印加する場合、あるいは導電体ではあるが電気的にはどこにも接続されずにフロートになっているものなど各種あるが、絶縁体の場合や導電体でも電気的にフロートである場合、つまり層形成部材２と現像スリーブ１との間に電圧を印加しない場合には逆帯電トナーによるカブリが発生しやすく、そうした場合、本発明は顕著に効果を発揮する。現像スリーブ１をこの直線上押圧に対して直角方向に摺るように相対移動させることにより現像剤粒子は押圧部を押し広げながら通過し、現像スリーブ１上に均一に塗布されて現像剤層を形成する。この押圧部の形態、圧力、組成、印加電圧によって、現像剤層厚、トナーの帯電量はコントロールされる。大局的には圧力が大きいほど塗布される現像剤層厚は薄く帯電量は高くなるが、形態、圧力、組成、印加電圧については複雑な物理、化学の現象となるので一概には議論できない。
【００４０】
静電潜像を保持する感光体３は、その表面に静電荷分布による静電潜像パターンを形成する。本発明の画像形成方法では、感光体３としてＯＰＣが用いられる。その一般的な形態はアルミなどの金属製の円筒または薄膜からなる導電性基材表面にポリカーボネート樹脂やアクリル樹脂等を含む有機感光材料を塗布して用いる。感光層の比誘電率は１〜５程度であり、層厚１０〜５０μｍ程度で使用されるのが一般的である。
【００４１】
画像形成の工程は、一般に用いられているゼログラフィーの原理に従い、コロナチャージャーや接触型のローラ方式やブラシ方式等による感光体帯電部材７によって均一帯電され、ランプやレーザー光等による露光の手順などを経て感光体３上に静電荷分布の潜像を形成する。このときの感光体３上の最大電位が、導電性基材を基準に絶対値で１００〜１２００Ｖ程度、より好ましくは３００〜９００Ｖ程度になるようにコントロールされる。
【００４２】
また、現像スリーブ１の相対的移動方向の層形成部材２より上流側に接触部材４を設けてもよい。接触部材４としては、現像剤６が自重と流動性によって現像スリーブ１に付着する力に加え積極的に現像剤６が現像スリーブ１に向かうものを用いる。例えば、スポンジ状やブラシ状の接触部材４に現像剤６を含ませて現像スリーブ１に摺り付ける方法が用いられる。このときの摩擦を利用して現像剤６の摩擦帯電を促進してもよい。この接触部材４に導電性の材料を用いて、現像剤６が現像スリーブ１へ向かう静電気力を与えるように現像スリーブ１との間に電圧をかけてもよい。また一般的にはローラ状のエンドレスな現像スリーブ１が用いられるため、感光体３への現像を終えたあとの残りの現像剤が付着した現像スリーブ１がこの接触部材４の部分に戻ってくるので、清掃手段を兼ねさせることもできる。その効果を積極的に利用したい場合には、逆に現像剤６が現像スリーブ１から離れる方向に力が加わるように電圧をかけてもよい。また、清掃と供給を兼ねる場合は現像剤６の帯電を上げる目的で交番電界を印加してもよい。
【００４３】
しかしながら、装置の低価格化を図る上では、現像スリーブ１と接触部材４との間に電圧を印加しない方法が好ましく、さらには接触部材４自体を使用しない方が好ましい。この場合には、トナー粒子の摩擦や電荷注入による帯電の機会が減少するため、画像中抜けやカブリなどの悪しき現象が発生しやすい。こうした場合に本発明は顕著な効果を発揮する。
また、図１〜２のような形態の現像器を用いる場合、現像スリーブ１の下方間隙より現像剤６が漏れる恐れがあるため、現像剤漏れ防止シール部材５を付けることが一般的である。
【００４４】
以上の工程により、現像剤層を形成した現像スリーブ１と潜像を形成した感光体３とを対向させ、現像剤６中の少なくともトナー粒子を転移させ潜像を顕像化する。
この際、飛翔現像等の非接触現像においては、５０〜５００μｍの間隙を形成させ静電気力で転移させる。接触現像の場合は、現像剤層を介して押圧され、潜像パターンに見合ったトナー粒子が静電気力で転移させる。トナー粒子を転移させたい潜像電位と白地としたい潜像電位との間に現像スリーブ１の電位を保つ方法が一般的である。
【００４５】
潜像パターンに転移したトナー粒子は、通常の複写機やレーザープリンタの場合、転写部材８によって紙やフィルムなどの被転写材へさらに転写される。この転写工程においては、被転写材を感光体に接触させて、背面よりコロナ放電により電荷を与える方法や導電性の転写ローラを押圧し電圧を印加する方法などが一般的である。ローラ転写等の圧力を加える転写工程の場合、画像中抜けが発生しやすい。その場合、本発明は顕著に効果を発揮する。
【００４６】
転写工程の後に、感光体上に残存するトナー粒子等の除去が感光体に当接するポリウレタン等のクリーニングブレード９での摺擦によって行われる。この際、ＯＰＣ感光体を用いると、クリーニング不良や感光体表面の研磨傷、さらには感光体へのトナー粒子等の付着または固着が起きやすく、そういった現象は画像上に致命的な欠陥として現れる。ＯＰＣ感光体とブレードクリーニングを組み合わせて行った場合のこうした問題の発生機構としては以下のように推定される。すなわち、ＯＰＣ感光体はその表面が高分子材料等を主体とするものである。このような高分子材料等は、第一にトナー粒子を介在するクリーニングブレードの押圧で弾性変形しやすい傾向にある。その場合はトナー粒子等のすり抜け現象を引き起こすのでクリーニング不良となって現れる。第二にその硬度が低いのでトナー粒子等を介在するクリーニングブレードとの継続的な摺擦によって、その表面に擦り傷、研磨傷がでやすく、また、それらの傷状欠陥にトナー粒子等が摩擦熱で擦り込まれて点状やフィルム状の融着現象が発生するために画像上の汚れとして検出されるものと考えられる。本発明はこのような現象に対して顕著な改良効果を発揮する。
【００４７】
【実施例】
以下、実施例により本発明を詳細に説明するが、本発明はその要旨を超えない限り、以下の実施例により限定されるものではない。なお、実施例及び比較例中、単に「部」とあるのはいずれも「重量部」を表す。
実施例１
以下に示す配合比により非磁性一成分現像剤を得た。
【００４８】
【表１】
ポリエステル樹脂 １００部
（テレフタル酸とビスフェノールＡのプロピレンオキシド付加物との縮合重合物）
帯電制御剤 クロム含金アゾ染料 ２部
（ボントロンＳ−３４、オリエント化学社製）
カーボンブラック ６部
（三菱カーボンブラックＭＡ１００、三菱化学社製）
低分子量ポリプロピレン ３部
（ビスコール５５０Ｐ、三洋化成社製）
【００４９】
製造は、上記の原材料を高速流動式混合機で混合し、２軸押し出し機で溶融混練した後、ハンマーミルで粗粉砕し、機械式粉砕機クリプトロン（川崎重工社製）で微粉砕した後、ジグザグ分級機（アルピネ社製）で分級した。トナー粒子の平均粒径Ｄｔ５０は１０．３μｍであった。また、ワーデル球形化度は０．３４であった。このトナー粒子１００部に対して、平均粒径Ｄｓ５０が２．９μｍ、Ｄｓ８４／Ｄｓ１６が２．８６であるステアリン酸亜鉛粒子を０．３部とヘキサメチルジシラザンで疎水化処理された平均一次粒子径約１０ｎｍのシリカ微粒子０．６部とを高速流動式混合機で外添して、一成分現像剤を作製した。以上の各粒度分布はＨｅｒｏｓ ＆ Ｒｏｄｏｓシステムで測定した。表１に現像剤中のトナー粒子、ステアリン酸亜鉛粒子、シリカ微粒子のまとめを記した。
【００５０】
実写評価装置として、市販の非磁性一成分現像方式を採用したプリンターを用いた。このプリンターの感光体は、表面層にポリカーボネート樹脂が含有される直径２４ｍｍφのドラム状の積層型ＯＰＣであり、クリーニング部材としてウレタンゴムのクリーニングブレードが感光体に接触押圧されている。また、現像装置は導電剤が含有されたゴム性の現像スリーブに対して、金属製のブレード（層形成部材）が押し当てられている。約１００００枚の印字が可能となるよう前記一成分現像剤をこの現像装置に一定量供給した。
【００５１】
評価方法は、上記プリンターを温度２５℃、相対湿度５５％の常温常湿雰囲気に設置して連続実写により行ったところ、その評価結果は優秀であり、１００００枚の実写を通じて、画像中抜け、画像濃度、カブリ等の画質は優秀であり、トナー飛散も問題なく良好であった。また、ＯＰＣ上でのクリーニング不良や現像剤粒子等の融着現象が見られず、耐久性も十分であった。
一方、本現像剤及びプリンターを温度３５℃、相対湿度８５％の高温高湿条件に持ち込み、同様の連続実写を行ったが、常温常湿環境での結果とほぼ同等の結果を得た。
さらに、本現像剤及びプリンターを温度１０℃、相対湿度２０％の低温低湿条件に持ち込み、同様の連続実写を行ったが、常温常湿環境での結果とほぼ同等の結果を得た。
【００５２】
実施例２
トナー粒子の平均粒径Ｄｔ５０が６．９μｍであり、そのワーデル球形化度が０．３７である以外は、実施例１と全く同様の処方及び製造方法でトナー粒子を得た。
以下、実施例１で用いたのと同じステアリン酸亜鉛とシリカ微粒子とを同様に添加して一成分現像剤を作製した。実写装置及び方法は実施例１と同様にして行った。
その結果、常温常湿環境、高温高湿環境及び低温低湿環境のいずれも、実施例１と同様に良好な結果を得た。
【００５３】
実施例３
実施例１で作製したトナー粒子を用い、このトナー粒子１００部に対して、平均粒径Ｄｓ５０が４．７μｍ、Ｄｓ８４／Ｄｓ１６が３．７１であるステアリン酸亜鉛粒子を０．３部とヘキサメチルジシラザンで疎水化処理された平均一次粒子径約３０ｎｍのシリカ微粒子１．０部とを添加する以外は、実施例１と同様にして一成分現像剤を作製した。
以下、実写評価は実写装置及び方法とも実施例１と同様にして行った。
その結果、常温常湿環境、高温高湿環境及び低温低湿環境のいずれも、実施例１と同様に良好な結果を得た。
【００５４】
実施例４
実施例１で用いたトナー粒子１００部に対して、実施例１で用いたステアリン酸亜鉛粒子０．３部とシリコーンオイルで疎水化処理された平均一次粒子径約１０ｎｍのシリカ微粒子０．６部とを添加する以外は実施例１と全く同様にして一成分現像剤を作製した。
以下、実写評価は実写装置及び方法とも実施例１と同様にして行った。
その結果、常温常湿環境、高温高湿環境及び低温低湿環境のいずれも、実施例１と同様に良好な結果を得た。
【００５５】
実施例５
実施例１に用いたトナー処方の原材料を高速流動式混合機で混合し、２軸押し出し機で溶融混練した後、ハンマーミルで粗粉砕し、機械式粉砕機クリプトロン（川崎重工社製）を用いて実施例１とは異なる粉砕条件で微粉砕した後、ジグザグ分級機（アルピネ社製）で分級した。トナー粒子の平均粒径Ｄｔ５０は９．８μｍであった。また、ワーデル球形化度は０．５１であった。このトナー粒子１００部に対して、実施例１で用いたのと同じステアリン酸亜鉛粒子０．３部とシリカ微粒子０．６部とを添加し、一成分現像剤を作製した。
以下、実写評価は実写装置及び方法とも実施例１と同様にして行った。
その結果、常温常湿環境、高温高湿環境及び低温低湿環境のいずれも、実施例１と同様に良好な結果を得た。
【００５６】
実施例６
実施例１に用いたトナー処方の原材料を高速流動式混合機で混合し、２軸押し出し機で溶融混練した後、ハンマーミルで粗粉砕し、流動層式ジェットミルＡＦＧ（ホソカワ社製）を用いて微粉砕した後、ジグザグ分級機（アルピネ社製）で分級した。トナー粒子の平均粒径Ｄｔ５０は８．７μｍであった。また、ワーデル球形化度は０．３５であった。このトナー粒子１００部に対して、実施例１で用いたのと同じステアリン酸亜鉛粒子０．３部とシリカ微粒子０．６部とを添加し、一成分現像剤を作製した。
以下、実写評価は実写装置及び方法とも実施例１と同様にして行った。
その結果、常温常湿環境、高温高湿環境及び低温低湿環境のいずれも、実施例１と同様に良好な結果を得た。
【００５７】
比較例１
実施例１に用いたトナー処方の原材料を高速流動式混合機で混合し、２軸押し出し機で溶融混練した後、ハンマーミルで粗粉砕し、Ｉ式ジェットミルＩＤＳ−２０（日本ニューマチック社製）を用いて微粉砕した後、ジグザグ分級機（アルピネ社製）で分級した。トナー粒子の平均粒径Ｄｔ５０は１０．２μｍであった。また、ワーデル球形化度は０．２４であった。このトナー粒子１００部に対して、実施例１で用いたのと同じステアリン酸亜鉛粒子０．３部とシリカ微粒子０．６部とを添加し、一成分現像剤を作製した。
以下、実写評価は実写装置及び方法とも実施例１と同様にして行った。
その結果、常温常湿環境下での実写で、初期的には良好な画質が得られたが、約２０００枚以降で画像中抜けが顕著になった他、実写期間を通じてカブリがやや高いなどの問題が見られるなど画質の低下が見られた。また、高温高湿環境下の実写で画像中抜けが一層悪化するという問題も観察された。
【００５８】
比較例２
実施例１で作製したトナー粒子を用い、このトナー粒子１００部に対して、平均粒径Ｄｓ５０が７．０μｍ、Ｄｓ８４／Ｄｓ１６が３．７７であるステアリン酸亜鉛粒子を０．３部とヘキサメチルジシラザンで疎水化処理された平均一次粒子径約１０ｎｍのシリカ微粒子０．６部とを添加する以外は、実施例１と同様にして一成分現像剤を作製した。
以下、実写評価は実写装置及び方法とも実施例１と同様にして行った。
その結果、実写初期から大粒状のカブリが発生して画質上好ましくなかった。
【００５９】
比較例３
実施例１で作製したトナー粒子を用い、このトナー粒子１００部に対して、平均粒径Ｄｓ５０が３．３μｍ、Ｄｓ８４／Ｄｓ１６が６．４３であるステアリン酸亜鉛粒子を０．３部とヘキサメチルジシラザンで疎水化処理された平均一次粒子径約１０ｎｍのシリカ微粒子０．６部とを添加する以外は、実施例１と同様にして一成分現像剤を作製した。
以下、実写評価は実写装置及び方法とも実施例１と同様にして行った。
その結果、実写初期においては良好な画質が得られたが、約３０００枚以降画像濃度の低下が見られるようになり、画質上問題があった。
【００６０】
比較例４
実施例１で作製したトナー粒子を用い、さらにハイブリッド法球形化装置ハイブリダイザー（奈良機械社製）で球形化処理を行った。得られたトナー粒子の平均粒径Ｄｔ５０は１０．５μｍであった。また、ワーデル球形化度は０．６８であった。このトナー粒子１００部に対して、実施例１で用いたのと同じステアリン酸亜鉛粒子０．３部とシリカ微粒子０．６部とを添加し、一成分現像剤を作製した。
以下、実写評価は実写装置及び方法とも実施例１と同様にして行った。
その結果、実写での文字の太りが見られ、ややシャープネスに欠ける画像であった。また、約７０００枚で現像剤が全て消費されて無くなり、それ以上の実写の継続は不可能であった。
【００６１】
実施例７
以下に示す配合比により磁性一成分現像剤を得た。
【００６２】
【表２】
スチレン系樹脂 １００部
（モノマー重量比：スチレン／ｎ−ブチルメタクリレート＝８０／２０）
帯電制御剤 クロム含金アゾ染料 ２部
（ボントロンＳ−３４、オリエント化学社製）
マグネタイト磁性粉 ６０部
（ＥＰＴ−５００、戸田工業社製）
低分子量ポリプロピレン ３部
（ビスコール５５０Ｐ、三洋化成社製）
【００６３】
製造は、上記の原材料を高速流動式混合機で混合し、２軸押し出し機で溶融混練した後、ハンマーミルで粗粉砕し、機械式粉砕機クリプトロン（川崎重工社製）で微粉砕した後、ジグザグ分級機（アルピネ社製）で分級した。トナー粒子の平均粒径Ｄｔ５０は７．５μｍであった。また、ワーデル球形化度は０．３６であった。このトナー粒子１００部に対して、平均粒径Ｄｓ５０が２．９μｍ、Ｄｓ８４／Ｄｓ１６が２．８６であるステアリン酸亜鉛粒子を０．３部とヘキサメチルジシラザンで疎水化処理された平均一次粒子径約１０ｎｍのシリカ微粒子０．６部とを高速流動式混合機で外添して、一成分現像剤を作製した。
【００６４】
実写評価装置として、市販の磁性一成分現像方式を採用したプリンターを改造して用いた。このプリンターの感光体は、表面層にポリカーボネート樹脂が含有される直径３０ｍｍφのドラム状の積層型ＯＰＣであり、クリーニング部材としてウレタンゴムのクリーニングブレードが感光体に接触押圧されている。また、現像装置はマグネットが内包されたステンレス性の現像スリーブに対して、ウレタンゴム製のブレード（層形成部材）が押し当てられている。約７０００枚の印字が可能となるよう前記一成分現像剤をこの現像装置に一定量供給した。
以下の評価方法は、実施例１とほぼ同様にして行った。
【００６５】
その結果、常温常湿雰囲気下での評価結果は優秀であり、７０００枚の実写を通じて、画像中抜け、画像濃度、カブリ等の画質は優秀であり、トナー飛散も問題なく良好であった。また、ＯＰＣ上でのクリーニング不良や現像剤粒子等の融着現象が見られず、耐久性も十分であった。
また、高温高湿条件での実写においては、実用上さほど問題のない程度の若干の画像濃度の低下が見られた他は、常温常湿環境での結果とほぼ同等の結果を得た。
さらに、低温低湿条件での実写においても、常温常湿環境での結果とほぼ同等の結果を得た。
【００６６】
【表３】

【００６７】
【発明の効果】
本発明の一成分現像剤及びそれを用いる画像形成方法により、以下の効果が得られるので、その工業的利用価値は高い。
（１）画像の中抜けがない良好な画質が得られる。
（２）画像濃度が高くてカブリが少なく、シャープネスに優れた良好な画質が得られる。
（３）トナー飛散がない。
（４）ＯＰＣ感光体へのクリーニング不良が発生しない。
（５）ＯＰＣ感光体への現像剤の固着や融着現象による汚染がない。
（６）各種の温度及び湿度の組合せ環境条件下でも画質変化が少ない。
（７）長期あるいは連続使用時においても画像濃度や画質劣化が少なく耐久性、信頼性が高い。
（８）少ないトナー消費量で充分な画質が得られる。
（９）新たに特別な装置を必要とせず、生産性にも優れコストパフォーマンスが高い。
【図面の簡単な説明】
【図１】本発明に使用できる画像形成方法の一例を示す図。
【図２】本発明に使用できる画像形成方法の他の一例を示す図。
【符号の説明】
１ 現像スリーブ
２ 層形成部材
３ 感光体
４ 接触部材
５ 現像剤漏れ防止シール部材
６ 一成分現像剤
７ 感光体帯電部材
８ 転写部材
９ クリーニングブレード[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a one-component developer used in an electrophotographic copying machine, a laser beam printer, and the like, and an electrophotographic image forming method using the same.
[0002]
[Prior art]
The use of a one-component developer can reduce the size of the developing device and the main body of the image forming apparatus, and these devices have the advantage of excellent reliability, such as maintainability. Hiring is increasing.
In the above-described apparatus, for the purpose of quickly charging the one-component developer and efficiently forming a thin layer of the developer on the developing sleeve, the layer forming member is preferably provided in contact with the developing sleeve. Has been done. In addition, as a photoconductor for holding an electrostatic latent image, various electrical characteristics can be obtained by selecting materials and the like, safety as a material is high, and processing into a drum, a sheet, a belt, and the like is easy. For this reason, organic photoconductors (OPC) are often used, and a rubber blade such as polyurethane is generally used as a cleaning method for residual particles after transfer of a developed image.
[0003]
As a one-component developer, a magnetic one-component developer in which a magnetic material is contained in the developer and a non-magnetic one-component developer not containing a magnetic material are known. As a method for producing these developers, a so-called pulverization method in which respective constituent materials are mixed, melt-kneaded, pulverized, and classified to obtain toner particles has become the mainstream. In order to improve the fluidity of the toner particles and to facilitate the formation of a developer layer on the developing sleeve, additives such as silica fine particles are added by external addition to be prepared as a one-component developer. .
[0004]
[Problems to be solved by the invention]
When developing with a one-component developer, the major issue is how to sufficiently charge the developer particles.
Further, since the surface of the OPC photoconductor is made of an organic polymer material and its hardness is smaller than that of the inorganic photoconductor, the surface of the OPC photoconductor is continuously rubbed with a cleaning blade interposing a developer. Wear and polishing streaks are likely to occur. In some cases, the developer is rubbed into the abrasive stripes, and a dot-like or film-like defect occurs on the photoreceptor. Such deterioration of the surface causes a significant decrease in the electrical characteristics of the photoconductor, and it is a problem to be improved that fatal contamination occurs in the obtained image.
[0005]
First, charging problems related to the development of developer particles will be described.
Originally, in a one-component developer, the charging mechanism of the developer particles is based on contact with the developing sleeve, so that the contact opportunity and contact time for charging are less than that of the two-component developer having carrier particles. As a result, the charge amount per particle becomes low, and the charge amount distribution as a developer must include a lot of reverse polarity parts. Furthermore, there is also a problem that the initial charge amount is lowered without being maintained when used for a long time. In the above, when the charge amount of the developer is low or there are many reverse polarity parts of the charge amount distribution, problems such as low image density of the obtained image or noticeable fogging occur, but the biggest problem This is because the transferability of developer particles in the transfer process is deteriorated, specifically, the transferred image is easily lost. An image dropout is a fatal problem in an image forming apparatus because characters and lines in an image portion are unclear. Further, there is a problem that the above problem is further promoted when there is a decrease in charge amount after long-term use and the stability is poor. The above problems tend to become more apparent when the developer particle size is reduced in accordance with the recent market demand for higher image quality.
[0006]
In order to improve these problems, by providing a layer forming member that is pressed against the developing sleeve on the apparatus side, the ability to impart charge to the developer particles is enhanced compared to the case of only the developing sleeve. The charge amount of the developer particles is relatively increased, and the reverse polarity portion of the charge amount distribution is reduced. Therefore, the image density and the void in the image tend to be improved, but the stability of the developer charge amount in the long-term use is not essentially improved, so that the image quality deteriorates when used for a long time. Still remains.
[0007]
Furthermore, since the hollowed out image is a transfer problem, there is an attempt to improve the hollowed out image by increasing the output of a transfer device (such as a corona charger or a roller charger) in the transfer process. However, with this method, even if the void is improved, ozone or NO_xThere arises a new problem that generation of (nitrogen oxides) becomes remarkable. Such a substance, particularly when OPC is used as a photoconductor, promotes oxidation of the OPC surface and adsorption of foreign matter and deteriorates its performance. Furthermore, since it is discharged out of the system, there is also a problem that adversely affects the human body and the environment.
[0008]
The charge amount of the developer is greatly influenced by the form factor of the developer particles. That is, as the developer particle shape becomes closer to a spherical shape, the charging point increases, so that there is an advantage that a developer having a high charge and a small amount of reverse polarity can be obtained, and that the charging stability is relatively excellent. Among them, the shape of particles obtained by a conventionally known wet granulation polymerization method, a thermal spheronization method using a spray dryer, a mechanical impact method known as a hybrid method, and the like is characteristic. However, toner particles that are too close to a spherical shape tend to increase the apparent density and excessively increase the amount of adhesion per toner layer, resulting in a problem that the toner consumption is large. Such a toner is a serious problem because a so-called single-use cartridge that develops an image with only a certain amount of toner filled in a toner supply container can only print a predetermined number of sheets or less. In addition, the obtained image quality may cause defects such as thick characters. Furthermore, image forming apparatuses using OPC as a photoconductor and using a blade as a cleaning member for the photoconductor are widely used. In such an image forming apparatus, a cleaning defect is originally generated on the OPC when cleaning particles. Although it has been pointed out that there is a problem that the photosensitive member and the image are contaminated, the use of toner particles close to the spherical shape further promotes the problem and tends to cause an extreme cleaning failure. Furthermore, many of these spheronization methods have a problem in terms of production efficiency, such as production yields are not necessarily good, special manufacturing equipment is required, and so on. On the other hand, the usual pulverization method is advantageous in terms of productivity, but the shape of the resulting particles is indeterminate, and there are few charging points on the particle surface, so various problems related to charging such as low charging as described above. There is. As described above, regarding the particle shape of the one-component developer related to the chargeability, it is considered that there is a range of the optimum shape (sphericity), but no proposal with excellent cost performance has been made.
[0009]
Next, the problem of contamination on the OPC by developer particles will be described.
This has the following problems in addition to the above-mentioned problem of poor cleaning.
In general, the fluidity of a one-component developer is important for forming a uniform layer on the developing sleeve. Therefore, in many cases, a large amount of a fluidity improver such as inorganic fine particles such as silica fine particles is externally added to the toner particles as a fluidity improver. Coarse aggregates are mixed in these inorganic fine particles, which damage the photoconductor, causing the developer to be fixed or fused from the starting point and cause image contamination. Therefore, removing the coarse agglomerates and adding them externally, or selecting and adding a fluidity improver that does not contain them originally, the phenomenon of photoconductor contamination certainly shows a tendency to decrease. Cannot be avoided. In addition, since such fine particles fall off from the toner particles or are embedded in the toner particle surface depending on use, the amount of the particles on the toner particle surface changes every moment. There is a problem in that the image quality is unstable due to fluctuations.
[0010]
As described above, there are still problems to be improved in the one-component developer, and each problem has been individually proposed, but a proposal for comprehensively solving the above problems has been made. There is no current situation. Moreover, the countermeasures on the apparatus side are limited, and countermeasures as a developer have been desired.
The present invention has been made in order to solve the above problems in view of the above-described situation, and an object of the present invention is to provide a one-component developer and an image forming method capable of obtaining a good image quality without image dropout. It is in.
Another object of the present invention is to provide a one-component developer and an image forming method capable of obtaining a good image quality with a high image density, a low fog, and excellent sharpness.
[0011]
Another object of the present invention is to provide a one-component developer and an image forming method free from toner scattering.
Another object of the present invention is to provide a one-component developer and an image forming method that do not cause poor cleaning of the OPC photoreceptor.
Another object of the present invention is to provide a one-component developer and an image forming method which are free from contamination due to fixing and fusing of the developer to the OPC photoreceptor.
Another object of the present invention is to provide a one-component developer and an image forming method with little change in image quality even under various environmental conditions of temperature and humidity.
[0012]
Another object of the present invention is to provide a one-component developer and an image forming method that are durable and reliable with little image density and image quality deterioration even during long-term or continuous use.
Another object of the present invention is to provide a one-component developer and an image forming method capable of obtaining a sufficient image quality with a small amount of toner consumption.
Another object of the present invention is to provide a one-component developer and an image forming method that do not require a new special apparatus and are excellent in productivity and high in cost performance.
[0013]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventors have determined that toner particles having specific characteristics, that is, toner particles having a specific particle diameter and having a specific sphericity and a specific particle size distribution. The inventors have found that the above object is satisfied by a one-component developer using fatty acid metal salt particles and a fluidity improver and an image forming method using the same, and have reached the present invention.
[0014]
That is, the gist of the present invention is that toner particles, fatty acid metal salt particles and a fluidity improver are contained, the toner particles have a volume 50% diameter Dt50 of 5 to 12 μm, and the toner particles have a Wadel sphericity. 0.3 to 0.6, and the fatty acid metal salt particles have a volume 16% diameter Ds16, a 50% diameter Ds50, and an 84% diameter Ds84 satisfying the expressions (1) and (2).The fluidity improver is silica fine particles hydrophobized with at least one substance selected from hexamethyldisilazane and silicon oil.One-component developer characterized in that
[0015]
[Equation 3]
Ds50 / Dt50 ≦ 0.6 (1)
Ds84 / Ds16 ≦ 6 (2)
[0016]
  And a developer layer is formed on the developing sleeve by the layer forming member pressed against the developing sleeve, and the latent image formed on the photoreceptor having the organic photoconductor is developed with the layered developer, An electrophotographic image forming method in which a developed image is transferred from a photoreceptor to a transfer material, and then the photoreceptor is cleaned with a cleaning blade, the developer comprising toner particles, fatty acid metal salt particles, and fluidity The toner particles have a volume 50% diameter Dt50 of 5 to 12 μm, and the toner particles have a Wadel sphericity of 0.3 to 0.6, and the volume of the fatty acid metal salt particles 16% diameter Ds16, 50% diameter Ds50, and 84% diameter Ds84 satisfy Expressions (1) and (2).The flow improver is silica fine particles hydrophobized with at least one substance selected from hexamethyldisilazane and silicon oil.An electrophotographic image forming method comprising a one-component developer
[0017]
[Expression 4]
Ds50 / Dt50 ≦ 0.6 (1)
Ds84 / Ds16 ≦ 6 (2)
[0018]
Exist.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
The toner used in the present invention is a fine powder containing a thermoplastic binder resin, a colorant, and, if necessary, a charge control agent, a release agent, and other substances.
Among the toner constituent components, as the binder resin, various known materials suitable for the toner can be used. For example, polystyrene, polychlorostyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer Polymer, styrene-acrylate copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer and styrene- Phenyl acrylate copolymer, etc.), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-octyl methacrylate) Copolymer and styrene-methacrylic Styrene resins (homopolymers or copolymers containing styrene or styrene-substituted products) such as phenyl copolymers, styrene-α-chloroacrylate methyl copolymers, and styrene-acrylonitrile-acrylate copolymers , Vinyl chloride resin, rosin-modified maleic resin, phenol resin, epoxy resin, saturated polyester resin, unsaturated polyester resin, low molecular weight polyethylene resin, low molecular weight polypropylene resin, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene There are an ethyl acrylate copolymer resin, a xylene resin, a polyvinyl butyral resin, etc., which can be used alone or in any combination. Preferred resins for use in the present invention include styrene resins, saturated or unsaturated polyesters. Mention may be made of resin, and epoxy resin.
[0020]
Furthermore, the crosslinking binder resins described in JP-B-51-23354 and JP-A-50-44836, etc., or described in JP-B-55-6895 and JP-B-63-32180, etc. Non-crosslinked binder resins can also be used.
The softening point of the toner binder resin is preferably 100 to 180 ° C. as measured by a flow tester method. When the softening point is less than 100 ° C., fouling (so-called “hot offset” phenomenon) easily occurs during fixing, and when it exceeds 180 ° C., the fixing strength tends to deteriorate. The glass transition temperature of the binder resin preferably has a transition start (inflection point) of 50 ° C. or higher when measured with a differential thermal analyzer. When the glass transition temperature is less than 50 ° C., the thermal stability during long-term storage is poor, causing toner aggregation and solidification, which causes problems in use.
[0021]
As the colorant, any appropriate pigment or dye can be used as long as it is conventionally used. For example, inorganic pigments such as carbon black, titanium oxide, zinc white, alumina white, calcium carbonate and bitumen, organic pigments such as monoazo pigments, disazo pigments, copper phthalocyanine pigments and quinacridone pigments, dyes such as anthraquinone dyes and rhodamine dyes, etc. These are used alone or appropriately mixed according to the color of the corresponding toner. In the case of a non-magnetic-component developer, the content of the colorant may be an amount sufficient to color the toner so that a visible image can be formed by development, for example, 100 parts by weight of the binder resin. On the other hand, the colorant is preferably 3 to 20 parts by weight. In the case of a magnetic-component developer, a magnetic colorant such as magnetic iron oxides typified by magnetite and γ-iron oxide is included. In this case, the amount added is 100 weight of binder resin. The amount is preferably 20 to 200 parts by weight, particularly 30 to 120 parts by weight.
[0022]
As the charge control agent used in this toner, measures such as composition control of the binder resin to be used and composition control of the developing sleeve carrying the developer can be considered, but in order to obtain positive chargeability, normally In order to obtain the negative chargeability of the charge control agent, it is preferable that the toner contains a negative charge control agent. These may be appropriately selected from various known ones. Examples of the positive charge control agent include nigrosine dyes and modified products thereof, quaternary ammonium compounds described in JP-B-1-54694, JP-B-1-54695, JP-B-1-54696, and the like. Triphenylmethane compounds described in JP-A-51-455, JP-B-63-57787, JP-B-2-501506, etc., JP-A-3-119364, JP-A-3-202856, and JP Examples thereof include imidazole derivatives and metal complexes of imidazoles described in Kaihei 3-217851. Examples of negative charge control agents include metal-containing azo dyes described in JP-B-3-37183 and JP-B-2-16916, salicylic acid metal complexes described in JP-B-55-42752, and the like. Examples thereof include salicylic acid metal salts described in JP-A-63-163374 and calixarene compounds not containing metal elements described in JP-A No. 5-119535. As a method of incorporating the above charge control agent into the toner, there are a method of adding it inside the toner and a method of adding it externally. In the case of internal addition, the amount of these compounds used is usually 0.05 to 20 parts by weight, more preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the binder resin. Moreover, when adding externally, 0.01-10 weight part is preferable with respect to 100 weight part of resin.
[0023]
In addition, as an auxiliary agent that can be internally added to the toner for the purpose of improving thermal characteristics and physical characteristics, known ones can be used. For example, polyalkylene wax, paraffin wax, higher fatty acid as a release agent. And fatty acid amides. The addition amount is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin. As a method for producing toner particles, the following pulverization method can be used.
First, a binder resin, a colorant, a charge control agent, and the like, which are toner constituent materials, are blended at a predetermined ratio and mixed. As the apparatus at this time, a gravity drop type mixer such as a V blender or a ball mill, a high speed fluid mixer such as a Henschel mixer (made by Mitsui Miike Chemical Co., Ltd.), a super mixer (made by Kawata Co., etc.), or the like is used.
[0024]
After mixing, the mixture is melt kneaded. Examples of the apparatus used in the melt-kneading process include two or three rolls, a Banbury mixer, a uniaxial or biaxial extruder. In this step, a component having compatibility with the binder resin is melted with the resin, and a component such as a charge control agent that is not compatible with the binder resin is dispersed in the molten resin.
Next, after the melt-kneaded product is cooled and solidified, toner particles are produced through the steps of coarse pulverization, fine pulverization, and classification. A hammer mill, a cutter mill, etc. are used for coarse pulverization, and a mechanical pulverizer such as a high-speed rotary fine pulverizer, a jet pulverizer such as an impact jet mill or a fluidized bed jet mill, etc. are used for fine pulverization. A forced vortex centrifugal classifier or inertia classifier is used.
[0025]
When toner particles relating to the one-component developer of the present invention are obtained by a pulverization method, it is preferable that the volume 50% diameter Dt50 is 5 to 12 μm after pulverization and classification, because a high-quality image can be obtained. When the thickness is less than 5 μm, toner scattering is severe and fogging of the resulting image is deteriorated, and when it exceeds 12 μm, the sharpness of the obtained image tends to decrease, which is not preferable.
The particle size may be measured using a laser diffraction particle size distribution measuring system Heros & Rodos (manufactured by SYMPATEC, Germany) under the following conditions, but may also be performed using a coulter counter (manufactured by Coulter, USA). Good.
[0026]
Dispersion method: Fluid dispersion unit
Distributed air pressure: 2 bar
Lens focal length: 100mm
Measurement time: 3 seconds
Furthermore, the toner particles of the present invention need to be within a specific numerical range when the spheroidized state of the particle shape is expressed by the degree of wafer sphericity. Specifically, it is an essential requirement that the degree of spheroidization is 0.3 to 0.6. The Wardel spheroidity referred to in the present invention is expressed by the following equation.
[0027]
[Equation 5]

[0028]
In the above formula, the specific surface area assuming a spherical shape is a numerical value obtained by assuming that the toner particles are true spherical from the particle size distribution measured by the particle size distribution measuring device. The BET specific surface area is specifically measured by a nitrogen adsorption method using a flowsorb 2300 type (manufactured by Shimadzu Corporation).
The Wardel sphericity obtained by the calculation in this way shows various values depending on the toner production method. The numerical value of the Wardel spheroidization obtained by the hybrid method is usually over 0.6, the thermal spheronization method is usually over 0.8, and the particles obtained by the wet granulation polymerization method are usually over 0.9. Is. Thus, when the Wadel sphericity of the toner particles exceeds 0.6, the toner weight (toner adhesion amount) per toner layer formed on the developing sleeve is increased, so that the toner consumption is deteriorated. There is a problem and is not preferable. If it exceeds 0.9, a cleaning failure on the photosensitive member may occur. Accordingly, the toner particles used in the present invention are preferably obtained by the above-described pulverization method. However, the toner particles obtained by the usual pulverization method often have a Wadel sphericity of less than 0.3. In this case, the charge on the developing sleeve is low and there are many reverse polarity parts. There are problems in image quality such as severe omission and difficulty in image density and fog.
[0029]
In the present invention, in order to control the Wadel sphericity of the toner particles obtained by the pulverization method to 0.3 to 0.6, it is preferable to select a desirable pulverizer in the pulverization step and set the pulverization conditions. . As a specific example, a method of using a mechanical pulverizer such as a high-speed rotary fine pulverizer such as a turbo mill (manufactured by Turbo Industry) or a kryptron (manufactured by Kawasaki Heavy Industries) is preferable. These mechanical pulverizers perform pulverization by a shearing and grinding action in a minute gap between a rotor that rotates at high speed and a casing, and the shape of toner particles can be obtained with a squared shape. Cheap. Therefore, for example, as described in JP-A-6-262095, JP-A-6-262096, and the like, if the various conditions such as the shape of the rotor and the casing and the gap distance are appropriately selected, the above-mentioned preferred Wadel sphericity degree is obtained. A particle shape in the range is obtained. As another method, a method in which a fluidized bed pulverizer such as a fluidized bed jet mill is employed as the fine pulverizer is preferable. In this type of jet mill, the impact-type jet mill (I-type jet mill), which has been widely used in the past, is mostly pulverized by a simple impact action caused by the collision between a collision plate and particles. While particles less than 0.3 can be obtained, pulverization is performed by impact and friction between particles to be pulverized in a fluidized bed state, so if the appropriate pulverization conditions are selected, the above-mentioned Wadel sphericity can be obtained. A range of particle shapes is easily obtained. In the pulverizer according to the above preferred embodiment, various auxiliary means such as supplying air adjusted in temperature to the pulverization chamber as required may be used.
[0030]
The one-component developer of the present invention comprises these toner particles, fatty acid metal salt particles, and a fluidity improver.
In the present invention, the particle diameter of the fatty acid metal salt particles must satisfy the following formulas (1) and (2).
[0031]
[Formula 6]
Ds50 / Dt50 ≦ 0.6 (1)
Ds84 / Ds16 ≦ 6 (2)
[0032]
In the formula, Dt50 represents the 50% diameter of the toner particles, and Ds16, Ds50, and Ds84 represent the 16%, 50%, and 84% diameters of the fatty acid metal salt particles, respectively. Each volume particle diameter is calculated from the cumulative distribution from the small particle side.
[0033]
Conventionally, fatty acid metal salts are effective in preventing contact due to frictional heat of particles by smoothing rubbing due to its anti-friction action in the contact rubbing step (photosensitive member and cleaning blade, etc.) in the electrophotographic process. Was known. If the fatty acid metal salt particles having a special particle size distribution satisfying both the above formulas (1) and (2) are employed, the present inventors can charge the toner particles in addition to the above-described effects, particularly in a one-component developer. It has been found that there is an effect of improving the chargeability, reducing the reverse polarity portion of the charge amount distribution, and improving the long-term stability of the chargeability. If only one of the above formulas (1) or (2) is satisfied, or if neither formula is satisfied, it is not preferable because good results cannot be obtained.
The measurement of the above particle diameter and particle size distribution is desirably performed with the above-described apparatus and conditions.
[0034]
The fatty acid metal salt particles according to the present invention are characterized in that the particle diameter is small and the range of the particle size distribution is narrow as indicated by the above formulas (1) and (2). In the formula (1), when the value of Ds50 / Dt50 is larger than 0.6, it means that the particle diameter of the fatty acid metal salt particles approaches or becomes larger than the particle diameter of the toner particles. Such large particles are not preferable because they fall out of the developer and are easily scattered outside the system, contaminating the apparatus, and are detected as large granular fog on the image. The value of Ds50 / Dt50 is preferably 0.5 or less. In Formula (2), when Ds84 / Ds16 representing the particle size distribution width is larger than 6 and the particle size is uneven, it becomes difficult to keep the developer chargeability stable over a long period of time. , Fluctuations in image quality cannot be suppressed. The value of Ds84 / Ds16 is preferably 5 or less, and particularly preferably 4 or less. The particle size distribution of the fatty acid metal salt particles is preferably a single distribution.
[0035]
As fatty acids of the fatty acid metal salt particles used in the present invention, monovalent saturated fatty acids such as butyric acid, valeric acid, lauric acid, myristic acid, palmitic acid, stearic acid and montanic acid, adipic acid, pimelic acid, suberic acid, And polyvalent unsaturated fatty acids such as azelaic acid and sebacic acid, monovalent unsaturated fatty acids such as crotonic acid and oleic acid, and polyunsaturated fatty acids such as maleic acid and citraconic acid. In this case, a saturated or unsaturated fatty acid having 8 to 35 carbon elements can be preferably used, but stearic acid is particularly desirable. Metal salts include, but are not limited to, lithium, sodium, potassium, copper, rubinium, silver, zinc, magnesium, calcium, strontium, aluminum, iron, cobalt, nickel salts and mixtures thereof. Among the above, a stearic acid metal salt of stearic acid and one or more metals selected from zinc, magnesium, calcium and aluminum is more desirable. Among these, it is most preferable to use zinc stearate.
[0036]
Various known agents can be used as the fluidity improver. For example, metal oxides such as silica, alumina, titania and the like by a dry manufacturing method or a wet manufacturing method can be given. Among them, those having an average primary particle size of about 5 to 50 nm are preferable. Further, it is desirable that the surface is hydrophobized. Specific examples of the hydrophobizing agent according to the present invention include hexamethyldisilazane and silicon oil. The fluidity improver is most preferably silica fine particles hydrophobized with at least one substance selected from hexamethyldisilazane and silicon oil. Such fine particles have the advantage that the occurrence of scratches on the photoreceptor due to aggregates is extremely small, and therefore various image defects that accompany it are unlikely to occur. When, for example, dimethyldichlorosilane is used as the hydrophobizing agent, coarse aggregates tend to remain in the resulting fluidity improver, which may be a cause of photoconductor scratches. Absent.
[0037]
The method for adding the fatty acid metal salt particles and the fluidity improver to the toner particles is preferably externally added using a high-speed fluid mixer or the like. If necessary, these additives may be pulverized individually or mixed in advance to remove coarse aggregates and externally added to the toner particles.
The amount of these particles added is 0.01 to 3 parts by weight, more preferably 0.03 to 1 part by weight of fatty acid metal salt particles, and 0.1 to 3 parts by weight of a fluidity improver with respect to 100 parts by weight of toner particles. It is good to add 05-3 weight part, More preferably, 0.1-2 weight part.
[0038]
The one-component developer used in the present invention is applied to either a magnetic one-component system in which toner particles are magnetic or a non-magnetic one-component system in which toner particles are substantially non-magnetic. It is also suitable for use as a color one-component developer.
Hereinafter, the image forming method of the present invention will be described with reference to FIG. This figure is an example in the case of using a non-magnetic one-component developer.
The developing sleeve 1 used in the present invention usually uses a columnar or cylindrical surface as a surface for supporting the developer 6. The material may be either an elastic body or a rigid body, but in a so-called contact development method in which the photoconductor 3 and the developing sleeve 1 are in contact with each other with a nonmagnetic developer interposed, a method using an elastic body is generally used. When a magnetic developer is used, it is usual to use a metal rigid sleeve that encloses a magnet. The surface of the developing sleeve 1 may have an appropriate surface roughness for the purpose of improving the transportability of the developer 6. Further, a material that can obtain an appropriate triboelectric charge with the toner particles must be considered. In the case of non-magnetic one-component contact development, as a general form of the developing sleeve 1 of an elastic body, a conductive rubber roller (NBR rubber, silicone rubber or the like in which conductive particles are dispersed and contained) is used. A dielectric layer may be provided on the surface of the conductive rubber.
[0039]
Examples of the layer forming member 2 used in the present invention include various types such as a rectangular bar-like rigid body, a protrusion-like elastic body, a plate spring-like surface and the like, a roller, and others, or a composite type thereof. . The layer forming member 2 is linearly pressed against the developing sleeve 1 by its own elastic force, the elastic force of the developing sleeve 1, the external force, or a combined force thereof. There is a case where no voltage is particularly applied between the developing sleeve 1 and the layer forming member 2, a case where a short circuit is applied to the same potential, and a case where a voltage of about 500 V or less is applied. Regarding the electrical characteristics of the layer forming member 2, there are various types such as an insulating material, a case where a voltage is applied to a conductor, or a conductor which is floated without being electrically connected anywhere. However, in the case of an insulator or a conductor that is electrically floating, that is, when no voltage is applied between the layer forming member 2 and the developing sleeve 1, fogging due to reversely charged toner is likely to occur. In this case, the present invention is remarkably effective. By relatively moving the developing sleeve 1 so as to slide in a direction perpendicular to the linear pressing, the developer particles pass through the pressing portion while spreading and are uniformly applied onto the developing sleeve 1 to form a developer layer. To do. The developer layer thickness and the toner charge amount are controlled by the form, pressure, composition, and applied voltage of the pressing portion. In general, the greater the pressure, the thinner the developer layer to be applied and the higher the charge amount. However, the form, pressure, composition, and applied voltage are complex physical and chemical phenomena that cannot be generally discussed.
[0040]
The photosensitive member 3 holding the electrostatic latent image forms an electrostatic latent image pattern based on electrostatic charge distribution on the surface thereof. In the image forming method of the present invention, OPC is used as the photoreceptor 3. In a general form, an organic photosensitive material containing polycarbonate resin, acrylic resin, or the like is applied to the surface of a conductive substrate made of a metal cylinder such as aluminum or a thin film. The relative dielectric constant of the photosensitive layer is about 1 to 5, and is generally used with a layer thickness of about 10 to 50 μm.
[0041]
The image forming process is uniformly charged by the photosensitive member charging member 7 using a corona charger, a contact roller method, a brush method, or the like according to a commonly used xerographic principle, and an exposure procedure using a lamp, laser light, or the like. Then, a latent image of electrostatic charge distribution is formed on the photoreceptor 3. The maximum potential on the photoconductor 3 at this time is controlled so as to be about 100 to 1200 V, more preferably about 300 to 900 V in absolute value with respect to the conductive base material.
[0042]
Further, the contact member 4 may be provided upstream of the layer forming member 2 in the relative movement direction of the developing sleeve 1. As the contact member 4, a member in which the developer 6 is directed toward the developing sleeve 1 in addition to the force that the developer 6 adheres to the developing sleeve 1 due to its own weight and fluidity is used. For example, a method of including a developer 6 in a sponge-like or brush-like contact member 4 and sliding the developer 6 on the developing sleeve 1 is used. Frictional charging of the developer 6 may be promoted using the friction at this time. A conductive material may be used for the contact member 4, and a voltage may be applied between the developing sleeve 1 and the developer 6 so as to apply an electrostatic force toward the developing sleeve 1. Further, since a roller-like endless developing sleeve 1 is generally used, the developing sleeve 1 to which the remaining developer after the development on the photosensitive member 3 is attached returns to the contact member 4 portion. Therefore, it can also serve as a cleaning means. When it is desired to positively use the effect, a voltage may be applied so that a force is applied in the direction in which the developer 6 moves away from the developing sleeve 1. Further, when both cleaning and supply are performed, an alternating electric field may be applied for the purpose of increasing the charging of the developer 6.
[0043]
However, in order to reduce the cost of the apparatus, a method in which no voltage is applied between the developing sleeve 1 and the contact member 4 is preferable, and it is more preferable not to use the contact member 4 itself. In this case, since the chances of charging due to toner particle friction and charge injection are reduced, bad phenomena such as image dropout and fogging are likely to occur. In such a case, the present invention exhibits a remarkable effect.
When a developing device having a configuration as shown in FIGS. 1 and 2 is used, the developer 6 may leak from the lower gap of the developing sleeve 1, so that it is common to attach the developer leakage prevention seal member 5.
[0044]
Through the above steps, the developing sleeve 1 on which the developer layer is formed and the photoreceptor 3 on which the latent image is formed face each other, and at least toner particles in the developer 6 are transferred to visualize the latent image.
At this time, in non-contact development such as flight development, a gap of 50 to 500 μm is formed and transferred by electrostatic force. In the case of contact development, the toner particles that are pressed through the developer layer and match the latent image pattern are transferred by electrostatic force. A general method is to maintain the potential of the developing sleeve 1 between the latent image potential to which toner particles are to be transferred and the latent image potential to be white.
[0045]
The toner particles transferred to the latent image pattern are further transferred to a transfer material such as paper or film by the transfer member 8 in the case of a normal copying machine or laser printer. In this transfer process, a method of bringing a transfer material into contact with a photosensitive member and applying a charge from the back by corona discharge or a method of applying a voltage by pressing a conductive transfer roller is generally used. In the transfer process in which pressure such as roller transfer is applied, image dropout is likely to occur. In that case, the present invention is remarkably effective.
[0046]
After the transfer process, toner particles remaining on the photosensitive member are removed by rubbing with a cleaning blade 9 made of polyurethane or the like that contacts the photosensitive member. At this time, if an OPC photoconductor is used, cleaning failure, polishing scratches on the surface of the photoconductor, and adhesion or fixation of toner particles to the photoconductor are likely to occur, and such a phenomenon appears as a fatal defect on the image. The occurrence mechanism of such a problem when combined with the OPC photoreceptor and blade cleaning is estimated as follows. That is, the surface of the OPC photoreceptor is mainly composed of a polymer material or the like. Such a polymer material or the like tends to be easily elastically deformed by pressing of a cleaning blade interposing toner particles. In that case, the toner particles pass through and cause a cleaning failure. Secondly, because of its low hardness, continuous rubbing with a cleaning blade that interposes toner particles, etc., tends to cause scratches and polishing scratches on the surface, and toner particles etc. are caused by frictional heat on these flawed defects. This is considered to be detected as a stain on the image because a spot-like or film-like fusion phenomenon occurs due to rubbing. The present invention exhibits a remarkable improvement effect against such a phenomenon.
[0047]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by a following example, unless the summary is exceeded. In Examples and Comparative Examples, “parts” simply means “parts by weight”.
Example 1
A non-magnetic one-component developer was obtained with the following blending ratio.
[0048]
[Table 1]
100 parts of polyester resin
(Condensation polymer of terephthalic acid and propylene oxide adduct of bisphenol A)
Charge control agent Chrome-containing azo dye 2 parts
(Bontron S-34, manufactured by Orient Chemical)
Carbon black 6 parts
(Mitsubishi Carbon Black MA100, manufactured by Mitsubishi Chemical Corporation)
3 parts low molecular weight polypropylene
(Biscol 550P, Sanyo Kasei Co., Ltd.)
[0049]
For production, the above raw materials are mixed with a high-speed fluid mixer, melt-kneaded with a twin-screw extruder, coarsely pulverized with a hammer mill, and finely pulverized with a mechanical pulverizer Kryptron (manufactured by Kawasaki Heavy Industries). Then, it was classified with a zigzag classifier (manufactured by Alpine). The average particle diameter Dt50 of the toner particles was 10.3 μm. The Wardel spheroidization degree was 0.34. With respect to 100 parts of the toner particles, 0.3 parts of zinc stearate particles having an average particle diameter Ds50 of 2.9 μm and Ds84 / Ds16 of 2.86 and average primary particles hydrophobized with hexamethyldisilazane A one-component developer was prepared by externally adding 0.6 parts of silica fine particles having a diameter of about 10 nm using a high-speed fluid mixer. Each of the above particle size distributions was measured with a Heros & Rodos system. Table 1 summarizes the toner particles, zinc stearate particles, and silica particles in the developer.
[0050]
A commercially available non-magnetic one-component developing system printer was used as a live-action evaluation apparatus. The photoconductor of this printer is a drum-shaped laminated OPC with a diameter of 24 mmφ whose surface layer contains a polycarbonate resin, and a urethane rubber cleaning blade is pressed against the photoconductor as a cleaning member. In the developing device, a metal blade (layer forming member) is pressed against a rubber-like developing sleeve containing a conductive agent. A fixed amount of the one-component developer was supplied to the developing device so that about 10,000 sheets could be printed.
[0051]
The evaluation method was that the printer was installed in a room temperature and normal humidity atmosphere at a temperature of 25 ° C. and a relative humidity of 55%. The result of the evaluation was excellent, and the evaluation result was excellent. The image quality such as density and fog was excellent, and the toner scattering was good without any problem. Further, no cleaning failure on the OPC and no fusing phenomenon such as developer particles were observed, and the durability was sufficient.
On the other hand, the developer and the printer were brought into a high temperature and high humidity condition at a temperature of 35 ° C. and a relative humidity of 85%, and the same continuous shooting was performed.
Further, the developer and the printer were brought into a low-temperature and low-humidity condition at a temperature of 10 ° C. and a relative humidity of 20%, and the same continuous shooting was performed, but the results were almost the same as those in a room temperature and humidity environment.
[0052]
Example 2
Toner particles were obtained by the same formulation and production method as in Example 1 except that the average particle diameter Dt50 of the toner particles was 6.9 μm and the Wardel spheroidization degree was 0.37.
Thereafter, the same zinc stearate and silica fine particles used in Example 1 were added in the same manner to prepare a one-component developer. The actual photographing apparatus and method were performed in the same manner as in Example 1.
As a result, good results were obtained in the same manner as in Example 1 in all of the normal temperature and normal humidity environment, the high temperature and high humidity environment, and the low temperature and low humidity environment.
[0053]
Example 3
Using toner particles prepared in Example 1, 0.3 parts of zinc stearate particles having an average particle diameter Ds50 of 4.7 μm and Ds84 / Ds16 of 3.71 are added to 100 parts of the toner particles, and hexamethyl. A one-component developer was prepared in the same manner as in Example 1 except that 1.0 part of silica fine particles having an average primary particle diameter of about 30 nm hydrophobized with disilazane was added.
Hereinafter, the evaluation of the actual image was performed in the same manner as in Example 1 for both the actual image capturing apparatus and the method.
As a result, good results were obtained in the same manner as in Example 1 in all of the normal temperature and normal humidity environment, the high temperature and high humidity environment, and the low temperature and low humidity environment.
[0054]
Example 4
With respect to 100 parts of the toner particles used in Example 1, 0.3 part of the zinc stearate particles used in Example 1 and 0.6 part of silica fine particles having an average primary particle diameter of about 10 nm hydrophobized with silicone oil A one-component developer was prepared in the same manner as in Example 1 except that and were added.
Hereinafter, the evaluation of the actual image was performed in the same manner as in Example 1 for both the actual image capturing apparatus and the method.
As a result, good results were obtained in the same manner as in Example 1 in all of the normal temperature and normal humidity environment, the high temperature and high humidity environment, and the low temperature and low humidity environment.
[0055]
Example 5
The raw materials of the toner formulation used in Example 1 were mixed with a high-speed fluid mixer, melt-kneaded with a twin screw extruder, coarsely pulverized with a hammer mill, and a mechanical pulverizer Kryptron (manufactured by Kawasaki Heavy Industries) was used. After pulverizing under pulverization conditions different from those in Example 1, the mixture was classified by a zigzag classifier (manufactured by Alpine). The average particle diameter Dt50 of the toner particles was 9.8 μm. Moreover, the Wardel spheroidization degree was 0.51. To 100 parts of the toner particles, 0.3 parts of the same zinc stearate particles and 0.6 parts of silica fine particles used in Example 1 were added to prepare a one-component developer.
Hereinafter, the evaluation of the actual image was performed in the same manner as in Example 1 for both the actual image capturing apparatus and the method.
As a result, good results were obtained in the same manner as in Example 1 in all of the normal temperature and normal humidity environment, the high temperature and high humidity environment, and the low temperature and low humidity environment.
[0056]
Example 6
The raw materials of the toner formulation used in Example 1 were mixed with a high-speed fluid mixer, melt-kneaded with a twin screw extruder, coarsely pulverized with a hammer mill, and fluidized bed jet mill AFG (manufactured by Hosokawa) was used. After fine pulverization, classification was performed with a zigzag classifier (manufactured by Alpine). The average particle diameter Dt50 of the toner particles was 8.7 μm. The Wardel spheroidization degree was 0.35. To 100 parts of the toner particles, 0.3 parts of the same zinc stearate particles and 0.6 parts of silica fine particles used in Example 1 were added to prepare a one-component developer.
Hereinafter, the evaluation of the actual image was performed in the same manner as in Example 1 for both the actual image capturing apparatus and the method.
As a result, good results were obtained in the same manner as in Example 1 in all of the normal temperature and normal humidity environment, the high temperature and high humidity environment, and the low temperature and low humidity environment.
[0057]
Comparative Example 1
The raw materials for the toner formulation used in Example 1 were mixed with a high-speed fluid mixer, melt-kneaded with a twin screw extruder, coarsely pulverized with a hammer mill, and I-type jet mill IDS-20 (manufactured by Nippon Pneumatic Co., Ltd.). ) And finely pulverized using a zigzag classifier (manufactured by Alpine). The average particle diameter Dt50 of the toner particles was 10.2 μm. Moreover, the Wardel spheroidization degree was 0.24. To 100 parts of the toner particles, 0.3 parts of the same zinc stearate particles and 0.6 parts of silica fine particles used in Example 1 were added to prepare a one-component developer.
Hereinafter, the evaluation of the actual image was performed in the same manner as in Example 1 for both the actual image capturing apparatus and the method.
As a result, good image quality was initially obtained in live-shooting under normal temperature and humidity conditions. However, image dropout became noticeable after about 2000 shots, and fog was slightly high throughout the live-shooting period. Deterioration in image quality was seen, including problems. In addition, a problem was observed in which the hollowed out image was further deteriorated in a live-action photograph in a high temperature and high humidity environment.
[0058]
Comparative Example 2
Using the toner particles produced in Example 1, 0.3 parts of zinc stearate particles having an average particle diameter Ds50 of 7.0 μm and Ds84 / Ds16 of 3.77 with respect to 100 parts of the toner particles are hexamethylated. A one-component developer was prepared in the same manner as in Example 1 except that 0.6 part of silica fine particles having an average primary particle diameter of about 10 nm that had been hydrophobized with disilazane was added.
Hereinafter, the evaluation of the actual image was performed in the same manner as in Example 1 for both the actual image capturing apparatus and the method.
As a result, large-grain fogging occurred from the beginning of actual shooting, which was not preferable in terms of image quality.
[0059]
Comparative Example 3
Using the toner particles produced in Example 1, 0.3 parts of zinc stearate particles having an average particle diameter Ds50 of 3.3 μm and Ds84 / Ds16 of 6.43 with respect to 100 parts of the toner particles and hexamethyl A one-component developer was prepared in the same manner as in Example 1 except that 0.6 part of silica fine particles having an average primary particle diameter of about 10 nm that had been hydrophobized with disilazane was added.
Hereinafter, the evaluation of the actual image was performed in the same manner as in Example 1 for both the actual image capturing apparatus and the method.
As a result, good image quality was obtained in the initial stage of actual shooting, but a decrease in image density was observed after about 3000 sheets, and there was a problem in image quality.
[0060]
Comparative Example 4
Using the toner particles produced in Example 1, spheronization treatment was further performed using a hybrid method spheronizer Hybridizer (manufactured by Nara Machinery Co., Ltd.). The obtained toner particles had an average particle diameter Dt50 of 10.5 μm. Moreover, the Wadel spheroidization degree was 0.68. To 100 parts of the toner particles, 0.3 parts of the same zinc stearate particles and 0.6 parts of silica fine particles used in Example 1 were added to prepare a one-component developer.
Hereinafter, the evaluation of the actual image was performed in the same manner as in Example 1 for both the actual image capturing apparatus and the method.
As a result, the image was thickened in live action, and the image was slightly lacking in sharpness. Further, about 7000 sheets, all the developer was consumed and it was impossible to continue the actual shooting.
[0061]
Example 7
A magnetic one-component developer was obtained with the following blending ratio.
[0062]
[Table 2]
100 parts of styrene resin
(Monomer weight ratio: styrene / n-butyl methacrylate = 80/20)
Charge control agent Chrome-containing azo dye 2 parts
(Bontron S-34, manufactured by Orient Chemical)
Magnetite magnetic powder 60 parts
(EPT-500, manufactured by Toda Kogyo Co., Ltd.)
3 parts low molecular weight polypropylene
(Biscol 550P, Sanyo Kasei Co., Ltd.)
[0063]
For production, the above raw materials are mixed with a high-speed fluid mixer, melt-kneaded with a twin-screw extruder, coarsely pulverized with a hammer mill, and finely pulverized with a mechanical pulverizer Kryptron (manufactured by Kawasaki Heavy Industries). Then, it was classified with a zigzag classifier (manufactured by Alpine). The average particle diameter Dt50 of the toner particles was 7.5 μm. The Wardel spheroidization degree was 0.36. With respect to 100 parts of the toner particles, 0.3 parts of zinc stearate particles having an average particle diameter Ds50 of 2.9 μm and Ds84 / Ds16 of 2.86 and average primary particles hydrophobized with hexamethyldisilazane A one-component developer was prepared by externally adding 0.6 parts of silica fine particles having a diameter of about 10 nm using a high-speed fluid mixer.
[0064]
As a live-action evaluation device, a commercially available printer using a magnetic one-component development system was modified and used. The photoconductor of this printer is a drum-shaped laminated OPC with a diameter of 30 mmφ containing a polycarbonate resin in the surface layer, and a urethane rubber cleaning blade is pressed against the photoconductor as a cleaning member. In the developing device, a blade (layer forming member) made of urethane rubber is pressed against a stainless steel developing sleeve containing a magnet. A fixed amount of the one-component developer was supplied to the developing device so that about 7000 sheets could be printed.
The following evaluation methods were performed in substantially the same manner as in Example 1.
[0065]
As a result, the evaluation result in a normal temperature and humidity atmosphere was excellent, and through 7000 actual images, the image quality such as image dropout, image density, and fog was excellent, and the toner scattering was also satisfactory without any problem. Further, no cleaning failure on the OPC and no fusing phenomenon such as developer particles were observed, and the durability was sufficient.
In actual shooting under high-temperature and high-humidity conditions, the result was almost the same as the result in a normal temperature and normal humidity environment except that a slight decrease in image density was observed with no practical problem.
Furthermore, even in live-shooting under low-temperature and low-humidity conditions, the results were almost the same as the results under normal temperature and humidity conditions.
[0066]
[Table 3]

[0067]
【The invention's effect】
The following effects can be obtained by the one-component developer of the present invention and the image forming method using the same, and the industrial utility value is high.
(1) It is possible to obtain a good image quality without any missing image.
(2) Good image quality with high image density and low fog and excellent sharpness can be obtained.
(3) No toner scattering.
(4) No cleaning failure occurs on the OPC photoreceptor.
(5) There is no contamination due to the fixing of the developer to the OPC photoreceptor or the fusing phenomenon.
(6) There is little change in image quality even under combined environmental conditions of various temperatures and humidity.
(7) There is little deterioration in image density and image quality even during long-term or continuous use, and durability and reliability are high.
(8) A sufficient image quality can be obtained with a small amount of toner consumption.
(9) No special equipment is required, and productivity is excellent and cost performance is high.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of an image forming method that can be used in the present invention.
FIG. 2 is a diagram showing another example of an image forming method that can be used in the present invention.
[Explanation of symbols]
1 Development sleeve
Two-layer forming member
3 Photoconductor
4 Contact members
5 Developer leakage prevention seal member
6 One-component developer
7 Photoconductor charging member
8 Transfer member
9 Cleaning blade

Claims (6)

Toner particles, fatty acid metal salt particles and a fluidity improver, the toner particles have a 50% volume Dt50 of 5 to 12 μm, and the toner particles have a Wadel sphericity of 0.3 to 0.6. there are state, and are not 16% by volume of said fatty acid metal salt particle diameter Ds16,50% diameter Ds50 and 84% diameter Ds84 satisfies the formula (1) and (2), is flowable improver hexamethylphosphoric one-component developer which is a hydrophobized silica fine particles with at least one substance selected from the disila disilazane and silicone oil.
(Equation 1) Ds50 / Dt50 ≦ 0.6 (1)
Ds84 / Ds16 ≦ 6 (2) The one-component developer according to claim 1, wherein the toner particles are non-magnetic toner particles. The one-component developer according to claim 1, wherein the toner particles are magnetic toner particles. A developer layer is formed on the developing sleeve by a layer forming member pressed against the developing sleeve, and the latent image formed on the photoreceptor having the organic photoconductor is developed with the layered developer, and developed. An electrophotographic image forming method in which a transferred image is transferred from the photoconductor to a transfer material, and then the photoconductor is cleaned with a cleaning blade, wherein the developer includes toner particles, fatty acid metal salt particles, and fluidity improvement. The toner particles have a 50% volume Dt50 of 5 to 12 μm, the toner particles have a Wadel sphericity of 0.3 to 0.6, and the fatty acid metal salt particles have a volume of 16 at least% diameter Ds16,50% diameter Ds50 and 84% diameter Ds84 are achieved, thereby satisfying the expression (1) and (2), the flowable enhancing agent is selected from hexamethyldisilazane and silicone oil Electrophotographic image forming method which is a one-component developing agent which is a fine silica particles having been hydrophobic-treated with seed material.
(Expression 2) Ds50 / Dt50 ≦ 0.6 (1)
Ds84 / Ds16 ≦ 6 (2)  5. The electrophotographic image forming method according to claim 4, wherein the toner particles are non-magnetic toner particles.  The electrophotographic image forming method according to claim 4, wherein the toner particles are magnetic toner particles.

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