JP4249314B2 - Image forming method and image forming apparatus - Google Patents

Description

【００１０】
本発明者らの検討によると、本発明で対象としているような現像方式を用いてドット再現性の良い画像を得るには、５μｍ以下の小粒径トナーの寄与率が非常に高いことが判明した。ここで、トナー粒子が４０個数％未満の場合は、ドット再現性および画像濃度が劣り鮮明な画像が得られず、８０個数％を越えると、トナー粒子相互の凝集状態が生じ易く、本来の粒径以上のトナー塊となるため、流動性が悪化し、荒れた画質となり、解像性を低下させるのみではなく、濃度ムラが極端に悪化する等の欠点を有していた。好ましくは５０〜７０個数％の範囲が最もよい。ここで、トナー体積平均粒径、体積分布の標準偏差、変動係数、５μｍ以下の個数％の測定は、種々の方法によって測定可能であるが、本発明では米国コールター・エレクトロニクス社製のコールターカウンターＴＡIIを用いた。
【００１１】
前記体積平均粒径（Ｍ）のトナーのうち粒径が２μｍより大きく、かつ、前記トナーの体積平均粒径（Ｍ）＋２μｍの粒径未満の範囲にある粒径のトナー粒子が、上記の式を満たす場合に、本発明のプロセスにおける小粒径トナーの使用においても濃度ムラが少なく、本発明の方法を問題なく成立させることが可能であることを見い出した。ここで、平均円形度（ＳＦ１）はトナー表面の滑らかさを表わす形状指数で、トナー表面が滑らかで円（球）形に近いほど、１．００に近い値になるものである。この形状指数が０．９４０以上、より好ましくは０．９４４以上のときは、トナー表面が充分に滑らかな為、トナー粒子自体が持っている流動性が向上し、トナー小粒径化による流動性悪化に起因した濃度ムラが改善されることが判明し、該新規プロセスにおいて小粒径トナーの使用が充分可能であることが見い出された。このことは、本プロセスにおいてトナー円形度の値が小粒径トナー使用の分極点になっていると考えられる。なお、前記形状指数の測定は、東亜医用電子株式会社製ＦＰＩＡ−１０００フロー式粒子像分析装置を用いた画像解析によりもとめられる。
【００１２】
次に本発明のトナーに用いられる材料について詳細に説明する。
本発明に使用される結着樹脂としては、ポリスチレン、ポリｐ−クロロスチレン、ポリビニルトルエンなどのスチレンおよびその置換体の単重合体；スチレン−ｐ−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−ビニルトルエン共重合体、スチレン−ビニルナフタリン共重合体、スチレン−アクリル酸メチル共重合体、スチレン−アクリル酸エチル共重合体、スチレン−アクリル酸ブチル共重合体、スチレン−アクリル酸オクチル共重合体、スチレン−メタクリル酸メチル共重合体、スチレン−メタクリル酸エチル共重合体、スチレン−メタクリル酸ブチル共重合体、スチレン−α−クロルメタクリル酸メチル共重合体、スチレン−アクリロニトリル共重合体、スチレン−ビニルメチルエーテル共重合体、スチレン−ビニルエチルエーテル共重合体、スチレン−ビニルメチルケトン共重合体、スチレン−ブタジエン共重合体、スチレン−イソプレン共重合体、スチレン−アクリロニトリル−インデン共重合体、スチレン−マレイン酸共重合体、スチレン−マレイン酸エステル共重合体などのスチレン系共重合体が挙げられる。
【００１３】
また、下記の樹脂を混合して使用することもできる。ポリメチルメタクリレート、ポリブチルメタクリレート、ポリ塩化ビニル、ポリ酢酸ビニル、ポリエチレン、ポリプロピレン、ポリエステル、ポリウレタン、ポリアミド、エポキシ樹脂、ポリビニルブチラール、ポリアクリル酸樹脂、ロジン、変性ロジン、テルペン樹脂、フェノール樹脂、脂肪族または脂環族炭化水素樹脂、芳香族系石油樹脂、塩素化パラフィン、パラフィンワックスなどが挙げられる。
【００１４】
また、特に圧力定着用に好適な結着樹脂としては、下記のものを挙げることができ、混合して使用できる。
ポリオレフィン（低分子量ポリエチレン、低分子量ポリプロピレン、酸化ポリエチレンポリ４弗化エチレンなど）、エポキシ樹脂、ポリエステル樹脂、スチレン−ブタジエン共重合体（モノマー比５〜３０：９５〜７０）、オレフィン共重合体（エチレン−アクリル酸共重合体、エチレン−アクリル酸エステル共重合体、エチレン−メタクリル酸共重合体、エチレン−メタクリル酸エステル共重合体、エチレン−塩化ビニル共重合体、エチレン−酢酸ビニル共重合体、アイオノマー樹脂）、ポリビニルピロリドン、メチルビニルエーテル−無水マレイン酸共重合体、マレイン酸変性フェノール樹脂、フェノール変性テルペン樹脂等。
【００１５】
更に、本発明の磁性トナー中に含まれる磁性材料としては、マグネタイト、ヘマタイト、フェライト等の酸化鉄、鉄、コバルト、ニッケルのような金属あるいはこれら金属のアルミニウム、コバルト、銅、鉛、マグネシウム、スズ、亜鉛、アンチモン、ベリリウム、ビスマス、カドミウム、カルシウム、マンガン、セレン、チタン、タングステン、バナジウムのような金属の合金およびその混合物などが挙げられる。
【００１６】
これらの強磁性体は、平均粒径が０．１〜２μｍ程度のものが望ましく、トナー中に含有させる量としては樹脂成分１００重量部に対し約１０〜２００重量部、特に好ましくは樹脂成分１００重量部に対し２０〜１００重量部である。
また、本発明のトナーに含有される帯電制御剤としては、従来公知のものが全て使用できる。正帯電制御剤としては、ニグロシン、塩基性染料、塩基性染料のレーキ顔料、四級アンモニウム塩化合物他等が挙げられ、負帯電制御剤としては、モノアゾ染料の金属塩、サリチル酸、ナフトエ酸、ダイカルボン酸の金属錯体等が挙げられる。
【００１７】
また、本発明に用いられる疎水性無機微粉末としては、公知のものを用いることができるが、疎水性シリカ微粉末、疎水性チタン微粉末等が好ましい。また、本発明で用いられる疎水性シリカ粒子は、公知のものが使用できる。
シランカップリング剤、シリコーンワニス、シリコーンオイル、有機ケイ素化合物また官能基を有するこれらの物質などの疎水化処理剤としては、例えば、ヘキサメチルジシラザン、ヘキサメチレンジシラザン、トリメチルシラン、トリメチルクロルシラン、トリメチルエトキシシラン、ジメチルジクロルシラン、メチルトリクロルシラン、ベンジルジメチルクロルシラン、クロルメチルジメチルクロルシラン、ジクロロジメチルシラン、トリオルガノシリルメルカプタン、トリメチルシリルメルカプタン、ビニルジメチルアセトキシシラン、ジメチルエトキシシラン、ジメチルジメトキシシラン、ジフェニルジエトキシシラン、アミノプロピルトリメトキシシラン、ジプロピルアミノプロピルトリメトキシシラン、ジブチルアミノプロピルトリメトキシシラン、ジブチルアミノプロピルメチルジメトキシシラン、トリメトキシシリル−γ−プロピルフェニルアミン等がある。シリコーンオイルとしては、メチルシリコーンオイル、ジメチルシリコーンオイル、フェニルメチルシリコーンオイル、クロルフェニルメチルシリコーンオイル、アルキル変性シリコーンオイル、脂肪酸変性シリコーンオイル、アミノ変性シリコーンオイル、ポリオキシアルキル変性シリコーンオイル等がある。これらは１種類あるいは２種類以上の混合物で用いられる。
以上のような処理においては単一の処理あるいは種々の処理を併用してもよい。
【００１８】
また、本発明で用いられる疎水性チタン粒子は、公知のものが使用できる。表面処理剤としては、メチルハイドロジェンポリシロキサン、ジメチルポリシロキサン、メチルフェニルポリシロキサン等の各種のシリコーンオイル、メチルトリメトキシシラン、エチルトリメトキシシラン、ヘキシルトリメトキシシラン、オクチルトリメトキシシラン、デシルトリメトキシシラン、オクタデシルトリメトキシシラン、ジメチルジメトキシシラン、オクチルトリエトキシシラン、ｎ−オクタデシルジメチル（３−（トリメトキシシリル）プロピル）アンモニウムクロライド等の各種のアルキルシラントリオロメチルエチルトリメトキシシラン、ヘプタデカフルオロデシルトリメトキシシラン等の各種のフルオロアルキルシラン、特にビニルトリメトキシシラン、γ−アミノプロピルトリメトキシシラン等のシランカップリング剤に代表されるシラン系・チタン系・アルミ系・アルミナ−ジルコニア系等の各金属系カップリング剤のいずれの処理剤も使用可能であり、これらを二種以上を混合している。
【００１９】
また、本発明のトナーは、必要に応じて添加物を混合してもよい。添加物としては、例えばテフロン、ステアリン酸亜鉛のごとき滑剤あるいは酸化セリウム、炭化ケイ素等の研磨剤、あるいは例えばコロイダルシリカ、酸化アルミニウムなどの流動性付与剤、ケーキング防止剤、あるいは例えばカーボンブラック、酸化スズ等の導電性付与剤、あるいは低分子量ポリオレフィンなどの定着助剤等がある。
【００２０】
着色剤としては、トナー用として公知のものが使用できる。黒色の着色剤としては、例えば、カーボンブラック、アニリンブラック、ファーネスブラック、ランプブラック等が使用できる。シアンの着色剤としては、例えば、フタロシアニンブルー、メチレンブルー、ビクトリアブルー、メチルバイオレット、アニリンブルー、ウルトラマリンブルー等が使用できる。マゼンタの着色剤としては、例えば、ローダミン６Ｇレーキ、ジメチルキナクリドン、ウォッチングレッド、ローズベンガル、ローダミンＢ、アリザリンレーキ等が使用できる。イエローの着色剤としては、例えば、クロムイエロー、ベンジジンイエロー、ハンザイエロー、ナフトールイエロー、モリブデンオレンジ、キノリンイエロー、タートラジン等が使用できる。
【００２１】
本発明に使用し得るキャリアとしては、公知のものが使用可能であり、例えば鉄粉、フェライト粉、ニッケル粉のごとき磁性を有する粉体、ガラスビーズ等およびこれらの表面を樹脂などで処理したものなどが挙げられる。
【００２２】
本発明におけるキャリアにコーティングし得る樹脂粉末としては、スチレン−アクリル共重合体、シリコーン樹脂、マレイン酸樹脂、フッ素系樹脂、ポリエステル樹脂、エポキシ樹脂等がある。スチレン−アクリル共重合体の場合は、３０〜９０重量％のスチレン分を有するものが好ましい。この場合スチレン分が３０重量％未満だと現像特性が低く、９０重量％を越えるとコーティング膜が硬くなって剥離しやすくなり、キャリアの寿命が短くなるからである。
また、本発明におけるキャリアの樹脂コーティングは、上記樹脂の他に接着付与剤、硬化剤、潤滑剤、導電材、荷電制御剤等を含有してもよい。
【００２３】
【発明の実施の形態】
図１は、本発明の現像装置の１例を採用した画像形成装置の現像装置要部の
概略構成図である。実際の実施例では本現像装置をリコー製複写機ＭＦ−２００を改造した改造機に組み込み評価した。以下その詳細について示す。
潜像担持体である感光体ドラム（１）の側方に配設された現像装置（１３）は、支持ケース（１４）、現像剤担持体としての現像スリーブ（１５）、現像剤収容部材（１６）、現像剤規制部材としての第１ドクターブレード（１７）等から主に構成されている。
【００２４】
感光体ドラム（１）側に開口を有する支持ケース（１４）は、内部にトナー（１８）を収容するトナー収容部としてのトナーホッパー（１９）を形成している。トナーホッパー（１９）の感光体ドラム（１）側寄りには、トナー（１８）と磁性粒子であるキャリアとからなる現像剤（２２）を収容する現像剤収容部（１６ａ）を形成する現像剤収容部材（１６）が、支持ケース（１４）と一体的に設けられている。また、現像剤収容部材（１６）の下方に位置する支持ケース（１４）には、対向面（１４ｂ）を有する突出部（１４ａ）が形成されており、現像剤収容部材（１６）の下部と対向面（１４ｂ）との間の空間によって、トナー（１８）を供給するためのトナー供給開口部（２０）が形成されている。
【００２５】
トナーホッパー（１９）の内部には、図示しない駆動手段によって回動されるトナー供給手段としてのトナーアジテータ（２１）が配設されている。トナーアジテータ（２１）は、トナーホッパー（１９）内のトナー（１８）をトナー供給開口部（２０）に向けて撹拌しながら送り出す。また、トナーホッパー（１９）の感光体ドラム（１）と対向する側には、トナーホッパー（１９）内のトナー（１８）の量が少なくなったときにこれを検知するトナーエンド検知手段（１４ｃ）が配設されている。
【００２６】
感光体ドラム（１）とトナーホッパー（１９）との間の空間には、現像スリーブ（１５）が配設されている。図示しない駆動手段で図の矢印方向に回転駆動される現像スリーブ（１５）は、その内部に現像装置（１３）に対して相対位置不変に配設された、磁界発生手段としての図示しない磁石を有している。
現像剤収容部材（１６）の、支持ケース（１４）に取り付けられた側と対向する側には、第１ドクターブレード（１７）が一体的に取り付けられている。第１ドクターブレード（１７）は、その先端と現像スリーブ（１５）の外周面との間に一定の隙間を保った状態で配設されている。
【００２７】
現像剤収容部材（１６）のトナー供給開口部（２０）の近傍に位置する部位には、規制部材としての第２ドクターブレード（２３）が配設されている。第２ドクターブレード（２３）はその自由端が現像スリーブ（１５）の外周面に対して一定の隙間を保つべく、現像スリーブ（１５）の表面に形成される現像剤（２２）の層の流れを妨げる方向、すなわち、自由端を現像スリーブ（１５）の中心に向けて、基端を現像剤収容部材（１６）に一体的に取り付けられている。
現像剤収容部（１６ａ）は、現像スリーブ（１５）の磁力が及ぶ範囲で、現像剤（２２）を循環移動させるに十分な空間を有するように構成されている。
【００２８】
なお、対向面（１４ｂ）は、トナーホッパー（１９）側から現像スリーブ（１５）側に向けて下向きに傾斜するよう、所定の長さにわたって形成されている。これにより、振動、現像スリーブ（１５）の内部に設けられた図示しない磁石の磁力分布のむら、現像剤（２２）中の部分的なトナー濃度の上昇等が発生した際に、第２ドクターブレード（２３）と現像スリーブ（１５）の周面との間から現像剤収容部（１６ａ）内のキャリアが落下しても、落下したキャリアは対向面（１４ｂ）で受けられて現像スリーブ（１５）側に移動し、磁力で現像スリーブ（１５）に磁着されて再び現像剤収容部（１６ａ）内に供給される。これにより現像剤収容部（１６ａ）内のキャリア量の減少を防止することができ、画像形成時における、現像スリーブ（１５）の軸方向での画像濃度ムラの発生を防止することができる。対向面（１４ｂ）の傾斜角度（α）としては５°程度がよく、また、所定の長さ（ｌ）としては好ましくは２〜２０ｍｍ、更に好ましくは３〜１０ｍｍ程度が望ましい。
【００２９】
上記構成により、トナーホッパー（１９）の内部からトナーアジテータ（２１）によって送り出されたトナー（１８）は、トナー供給開口部（２０）を通って現像スリーブ（１５）に担持された現像剤（２２）に供給され、現像剤収容部（１６ａ）へ運ばれる。そして、現像剤収容部（１６ａ）内の現像剤（２２）は、現像スリーブ（１５）に担持されて感光体ドラム（１）の外周面と対向する位置まで搬送され、トナー（１８）のみが感光体ドラム（１）上に形成された静電潜像と静電的に結合することにより、感光体ドラム（１）上にトナー像が形成される。
【００３０】
ここで、上記トナー像形成時における現像剤（２２）の挙動を説明する。現像装置（１３）に磁性キャリア（２２ａ）のみからなるスタート剤をセットすると、図２に示すように磁性キャリア（２２ａ）は現像スリーブ（１５）の表面に磁着されるものと現像剤収容部（１６ａ）内に収容されるものとに分かれる。現像剤収容部（１６ａ）内に収容された磁性キャリア（２２ａ）は、現像スリーブ（１５）の矢印ａ方向への回転に伴い、現像スリーブ（１５）内からの磁力によって矢印ｂ方向へ循環移動する。そして、現像スリーブ（１５）の表面に磁着された磁性キャリア（２２ａ）の表面と現像剤収容部（１６ａ）内で移動する磁性キャリア（２２ａ）の表面との境界部において界面（Ｘ）が形成（図２）される。
【００３１】
次に、トナーホッパー（１９）にトナー（１８）がセットされると、トナー供給開口部（２０）より現像スリーブ（１５）に担持された磁性キャリア（２２ａ）にトナー（１８）が供給される。したがって、現像スリーブ（１５）は、トナー（１８）と磁性キャリア（２２ａ）との混合物である現像剤（２２）を担持することとなる。
【００３２】
現像剤収容部（１６ａ）内では、収容されている現像剤（２２）の存在により、現像スリーブ（１５）によって搬送される現像剤（２２）に対して、その搬送を停止させようとする力が働いている。そして、現像スリーブ（１５）に担持された現像剤（２２）の表面に存在するトナー（１８）が界面（Ｘ）へ搬送されると、界面（Ｘ）近傍における現像剤（２２）間の摩擦力が低下して界面（Ｘ）近傍の現像剤（２２）の搬送力が低下し、これにより界面（Ｘ）近傍での現像剤（２２）の搬送量が減少する。
【００３３】
一方、合流点（Ｙ）より現像スリーブ（１５）の回転方向上流側の現像剤（２２）には、上述の現像剤収容部（１６ａ）内のような、現像スリーブ（１５）によって搬送される現像剤（２２）に対して、その搬送を停止させるような力は作用しないので、合流点（Ｙ）へ搬送されてきた現像剤（２２）と界面（Ｘ）を搬送される現像剤（２２）との搬送量のバランスが崩れて現像剤（２２）の玉突状態が発生し、合流点（Ｙ）の位置が上昇して界面（Ｘ）を含む現像剤（２２）の層厚が増加する。また、第１ドクターブレード（１７）を通過した現像剤（２２）の層厚も徐々に増加し、この増加した現像剤（２２）が第２ドクターブレード（２３）によって掻き落とされる。
【００３４】
そして、第１ドクターブレード（１７）を通過した現像剤（２２）が所定のトナー濃度に達すると、第２ドクターブレード（２３）に掻き落とされて層状となった増加分の現像剤（２２）がトナー供給開口部（２０）を塞ぎ、この状態でトナー（１８）の取り込みが終了する。このとき、現像剤収容部（１６ａ）内ではトナー濃度が高くなることにより現像剤（２２）の嵩が大きくなり、これにより現像剤収容部（１６ａ）内の空間が狭くなることによって、現像剤（２２）が図の矢印ｂ方向に循環移動する移動速度も低下する。
【００３５】
このトナー供給開口部（２０）を塞ぐように形成された現像剤（２２）の層において、第２ドクターブレード（２３）に掻き落とされた現像剤（２２）は、移動して対向面（１４ｂ）で受けられるが、対向面（１４ｂ）が現像スリーブ（１５）側に向けて角度（α）で下方に傾斜し、かつ所定長さ（ｌ）を有しているため、現像剤（２２）の層の移動によるトナーホッパー（１９）への現像剤（２２）の落下を防止することができ、現像剤（２２）の量を常に一定に保つことができるので、トナー供給を常時一定に自己制御することが可能となる。
【００３６】
【実施例】
以下、本発明を下記の実施例によってさらに具体的に説明するが、本発明はこれに限定されるものではない。
なお、現像装置は前記構成中に示した図１、２の装置を用いた。また、部数はすべて重量部である。
【００３７】
本実施例等に用いるシリコーン樹脂を被覆層に有するキャリアの製造例を示す。これは公知の手段により行なうことができる。
［キャリア製造例１］
被覆層形成液の組成
シリコーン樹脂溶液（ＳＲ２１００ 東レシリコーン社製） １００部
カーボンブラック（＃４４ 三菱化成工業社製） ４部
トルエン １００部
上記処方をホモミキサーで３０分間分散して被覆層形成液を調製した。この被覆層形成液を平均粒径１００μｍの球状フェライト１０００重量部の表面に流動床型塗布装置を用いて被覆層を形成したキャリアＡを得た。
【００３８】
［実施例１〜３、比較例１〜４］
下記の現像剤を用いた。
ポリエステル樹脂 ９０部
スチレンメチルアクリレート １０部
マグネタイト微粒子 ３０部
低分子量ポリプロピレン ５部
含金属アゾ化合物 １部
上記組成の混合物をヘンシェルミキサー中で充分撹拌混合した後、ロールミルで１３０〜１４０℃の温度で約３０分間加熱溶融し、室温まで冷却後、得られた混練物をジェットミルまたは機械式粉砕機、風力分級機で粉砕分級し、所定の粒径および円形度のトナー母体を得た。このときの粒径・粒径分布、円形度の値は、ジェットミル中の滞留時間または機械式粉砕機の使用および風力分級機の条件の変更により変化させた。得られたトナー母体に所定の疎水性無機添加剤を所定量添加混合し、最終的なトナーとした。このトナー１３．０部に対し、上記キャリアＡ８７．０部とをボールミルで混合し現像剤を得た。この現像剤に前記ＭＦ−２００改造機を用いて複写実験を行なった。
【００３９】
各実施例のスタート時と１４万枚後の評価結果の平均を以下に示す評価に基づいて行なった結果を表１に示す。
＜画像濃度ムラ＞
全面ハーフトーンのチャートを用いてＡ４サイズで１５枚連続で出力した後の画像濃度ムラ（直前の画像の履歴）の発生の程度を、以下の判断基準により５段階で行なった。
◎：大変良い
○：良い
□：普通
△：悪い
×：大変悪い
＜ベタ均一性（画像濃度）＞
一部のベタ部を前後左右に各６点持ったＡ３サイズのチャートを用いて画像をＡ３サイズで出力し、その画像のベタ部６個所の位置の画像濃度を、マクベス反射濃度計で測定し、そのＩＤ（画像濃度）偏差について以下の判断基準により５段階で行なった。
◎：大変良い
○：良い
□：普通
△：悪い
×：大変悪い
＜ドット再現性＞
ドット再現性の評価を行なった。評価は以下の判断基準により５段階で行なった。
◎：大変良い
○：良い
□：普通
△：悪い
×：大変悪い
【００４０】
【表１】

【００４１】
【発明の効果】
以上、詳細かつ具体的な説明から明らかなように、トナー供給を常時一定に自己制御することができる簡単な構成でトナー濃度の調製を容易に行なうことができる特定の現像方式に用いるトナーにおいて、特定の粒径と円形度の範囲を満足することにより、コピー経時で高画質を有し、濃度ムラのない画像形成方法および画像形成装置を提供することができる。
【図面の簡単な説明】
【図１】本発明の画像形成装置の１例を示す図である。
【図２】本発明のトナー像形成時における現像剤の挙動を示す例である。
【符号の説明】
１ 潜像担持体（感光体ドラム）
１３ 現像装置
１４ 支持ケース
１４ａ 支持ケース突出部
１４ｂ 支持ケース対向面
１４ｃ トナーエンドセンサ
１５ 現像剤担持体（現像スリーブ）
１６ 現像剤収容部材
１６ａ 現像剤収容部
１７ 第１の規制部材（第１ドクターブレード）
１８ トナー
１９ トナー収容部（トナーホッパー）
２０ トナー供給開口部
２１ トナー供給手段（トナーアジテータ）
２２ 現像剤
２２ａ 磁性キャリア
２３ 第２の規制部材（第２ドクターブレード）
Ｘ 界面部（界面）
Ｙ 現像剤合流点
ａ 現像スリーブ回転方向
ｂ キャリア循環方向
α 対向面傾斜角度
ｌ 対向面長さ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming method and an image forming apparatus used for electrophotography, electrostatic printing, and the like.
[0002]
[Prior art]
In the dry two-component developer used in the two-component development method, fine toner particles are held on the surface of relatively large particles by the electric force generated by friction between both particles, and when close to the electrostatic latent image, The attracting force in the direction of the latent image with respect to the toner particles due to the electric field force formed by the electrostatic latent image overcomes the binding force between the toner particles and the carrier particles, and the toner particles are attracted and adhered onto the electrostatic latent image. The latent image is visualized. The developer is repeatedly used while replenishing the toner consumed by the development.
[0003]
Therefore, in this two-component development method, in order to obtain a stable image density, it is necessary to make the mixing ratio (toner density) of the carrier and the toner constant, and it is necessary to mount a toner replenishment mechanism and a sensor for that purpose. However, there is a drawback that the developing device becomes large and its operation mechanism becomes complicated.
On the other hand, in the one-component development method, unlike the two-component development method, a developer in which carrier particles and toner particles are mixed is not used, and an electric force generated by friction between the toner and the developing sleeve, or a toner and a magnet containing a magnetic substance, When the toner is held on the developing sleeve by the magnetic force between the built-in developing sleeves and the electrostatic latent image is brought close to the electrostatic latent image, the toner particles and the developing sleeve are attracted to the latent image by the electric field formed by the electrostatic latent image. The toner particles are attracted onto the electrostatic latent image, and the electrostatic latent image is visualized by overcoming the bonding force between them.
[0004]
Therefore, in the one-component developing method, it is not necessary to control the toner density, and there is an advantage that the developing device can be downsized. However, since the number of toner particles in the developing region is smaller than that in the two-component developing method, The development amount of the toner is not sufficient, and it is difficult to cope with a high-speed copying machine.
[0005]
On the other hand, a developing device that uses a two-component developer and does not require a toner density detecting means and takes in toner by the movement of the developer is known. However, in this developing device, the amount of toner taken in is different between a portion where the developer moves actively and a portion where the developer is not active, or a portion where the developer is high and a portion where the developer is low, and the toner density partially becomes unstable, resulting in an image density. Unevenness and fog are likely to occur. Therefore, a technique for solving density unevenness and fogging in the longitudinal direction of the apparatus by disposing two toner supply members in the toner hopper and allowing the developer to pass through a path formed by each toner supply member. This is disclosed in Japanese Patent No. 63-4282. However, in the technique disclosed in the above publication, since two toner supply members are used, there is a problem that the developing unit becomes large and the cost increases. Further, although a method for solving the above-described drawbacks has been proposed by the technique disclosed in Japanese Patent Application Laid-Open No. 9-197833, it has not been sufficient for eliminating the density unevenness described above.
[0006]
In recent years, toners used in electrophotographic development methods have been increasingly demanded for image quality, and are moving toward smaller particle sizes. An image forming apparatus using a digital image signal forms an image by forming a latent image of minute dots on a photosensitive member and developing the latent image. At this time, if the toner particle diameter is large, the toner protrudes from the latent image dots, and dots are not formed faithfully with respect to the latent image, and a high-quality image cannot be obtained. In order to solve this problem, toner having a particle size of 5 μm or less is an essential component for forming a high-quality image, and a technique for making full use of it is publicly available. As a typical example, a toner having a small particle diameter is used by defining the range of toner particles described in JP-B-7-60273, and the magnetic toner particles having a particle size of 5 μm or less fall within a range of 17 to 60% by number. Some have aimed to improve image quality by prescribing. However, within the scope of the patent, in the use of a specific process, the sharpness of the image, particularly in terms of the image density, is not sufficient, and there is a problem in terms of compatibility with density unevenness. . In addition, the one disclosed in Japanese Patent No. 2769849 aims to improve the image by increasing the number of particles of 5 μm or less to 60% by number or more. However, the toner particle size distribution is defined by defining the volume variation coefficient of the toner particles. This is a method for obtaining a high-quality image by using a relatively sharp distribution, which is problematic in terms of productivity in making a toner with a sharp distribution and is compatible with density unevenness. There was a problem. In addition, when dry toner is manufactured by a pulverization method, the shape is square and irregular, so that the fluidity is inferior compared to a spherical toner such as a polymerized toner. Due to the remarkable deterioration in fluidity caused by the reduction in the particle size as described above, the occurrence of defects such as deterioration of the density unevenness described above was observed.
[0007]
[Problems to be solved by the invention]
The present invention solves the above-described problems, reduces the number of parts, and integrates functions, whereby an image forming method and an image forming capable of obtaining a high-quality image while reducing size and cost. The purpose is to provide a device.
[0008]
[Means for Solving the Problems]
As a result of intensive studies, the inventors of the present invention have a magnetic field generating means inside, a developer carrier that carries and conveys a two-component developer containing toner and a magnetic carrier, and a developer carrier that is carried on the developer carrier. A first regulating member that regulates the amount of the developer conveyed; a developer containing unit that contains the developer scraped off by the first regulating member; and adjacent to the developer containing unit, A toner container for supplying toner to the developer carrying member, and changing the contact state between the developer and the toner by changing the toner concentration of the developer on the developer carrying member; An image forming method using a developing device that changes a toner intake state of a developer on a carrier, wherein the developer container transports the developer on the developer carrier rather than a first regulating member. A second restricting member disposed on the upstream side in the direction. The second restricting member is configured to restrict the passage of the developer when the toner density of the developer on the developer carrier increases and the layer thickness of the developer increases. A gap with the developer carrier is set, and the developer in the developer container moves in the developer container regardless of changes in the toner density of the developer on the developer carrier, and the developer When the toner density of the developer on the developer carrier reaches a predetermined toner density, the developer whose passage is restricted by the second restriction member is brought into contact with the developer on the developer carrier and the toner. The toner is collected in the portion, and the developer closes the contact portion to stop the toner intake state of the developer on the developer carrier, and the toner used is a binder resin, magnetic powder, and hydrophobic inorganic fine powder. The volume average particle diameter M (μm) of the toner is 4 to 7 μm. Satisfied, the toner particles having a particle size 5μm containing 40-80% by number, of particle size of the toner of the volume average particle diameter (M) is greater than 2 [mu] m, and the volume average particle diameter of the toner (M) It is possible to eliminate the above drawbacks by using an image forming method or an image forming apparatus using a developing device in which toner particles having a particle size in the range of less than +2 μm satisfy the value represented by the following general formula. I found it.
[0009]
[Expression 2]

[0010]
According to the study by the present inventors, it has been found that the contribution ratio of a small particle size toner of 5 μm or less is very high in order to obtain an image with good dot reproducibility using the developing method as the object of the present invention. did. Here, when the toner particles are less than 40% by number, the dot reproducibility and the image density are inferior, and a clear image cannot be obtained. Since the toner lump is larger than the diameter, the fluidity is deteriorated, the image quality becomes rough, and not only the resolution is lowered, but also the density unevenness is extremely deteriorated. A range of 50 to 70% by number is preferable. Here, the toner volume average particle diameter, the standard deviation of the volume distribution, the coefficient of variation, the number% of 5 μm or less can be measured by various methods. In the present invention, the Coulter Counter TAII manufactured by Coulter Electronics, Inc. of the United States is used. Was used.
[0011]
Among the toners having the volume average particle size (M), toner particles having a particle size larger than 2 μm and in the range of less than the volume average particle size (M) of the toner + 2 μm are expressed by the above formula. In the case of satisfying the above, it has been found that the density unevenness is small even in the use of the toner having a small particle diameter in the process of the present invention, and the method of the present invention can be established without any problem. Here, the average circularity (SF1) is a shape index representing the smoothness of the toner surface. The smoother the toner surface is, the closer to a circle (sphere), the closer to 1.00. When the shape index is 0.940 or more, more preferably 0.944 or more, the toner surface itself is sufficiently smooth, so that the fluidity of the toner particles themselves is improved, and the fluidity by reducing the toner particle size is reduced. It has been found that density unevenness due to deterioration is improved, and it has been found that the use of a small particle size toner is sufficiently possible in the new process. This is considered that the value of the toner circularity is the polarization point for using a small particle size toner in this process. The shape index is measured by image analysis using an FPIA-1000 flow type particle image analyzer manufactured by Toa Medical Electronics Co., Ltd.
[0012]
Next, materials used for the toner of the present invention will be described in detail.
Examples of the binder resin used in the present invention include styrene such as polystyrene, poly p-chlorostyrene, and polyvinyltoluene, and homopolymers of substituted styrene; styrene-p-chlorostyrene copolymer, styrene-propylene copolymer. Styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer Polymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene -Vinyl methyl ether copolymer, styrene- Nyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic Examples thereof include styrenic copolymers such as acid ester copolymers.
[0013]
Moreover, the following resin can also be mixed and used. Polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic Or an alicyclic hydrocarbon resin, an aromatic petroleum resin, chlorinated paraffin, paraffin wax, etc. are mentioned.
[0014]
In addition, examples of the binder resin particularly suitable for pressure fixing include the following, which can be used in combination.
Polyolefin (low molecular weight polyethylene, low molecular weight polypropylene, polyethylene oxide polytetrafluoroethylene, etc.), epoxy resin, polyester resin, styrene-butadiene copolymer (monomer ratio 5-30: 95-70), olefin copolymer (ethylene -Acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, ionomer Resin), polyvinylpyrrolidone, methyl vinyl ether-maleic anhydride copolymer, maleic acid-modified phenol resin, phenol-modified terpene resin, and the like.
[0015]
Furthermore, the magnetic material contained in the magnetic toner of the present invention includes iron oxides such as magnetite, hematite and ferrite, metals such as iron, cobalt and nickel, or aluminum, cobalt, copper, lead, magnesium and tin of these metals. And alloys of metals such as zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium, and mixtures thereof.
[0016]
These ferromagnetic materials desirably have an average particle diameter of about 0.1 to 2 μm. The amount of the ferromagnetic material to be contained in the toner is about 10 to 200 parts by weight, particularly preferably 100 parts by weight of the resin component. 20 to 100 parts by weight with respect to parts by weight.
In addition, as the charge control agent contained in the toner of the present invention, all conventionally known charge control agents can be used. Examples of positive charge control agents include nigrosine, basic dyes, lake dyes of basic dyes, quaternary ammonium salt compounds, etc., and examples of negative charge control agents include metal salts of monoazo dyes, salicylic acid, naphthoic acid, dyes, and the like. Examples include carboxylic acid metal complexes.
[0017]
As the hydrophobic inorganic fine powder used in the present invention, known ones can be used, but hydrophobic silica fine powder, hydrophobic titanium fine powder and the like are preferable. Moreover, a well-known thing can be used for the hydrophobic silica particle used by this invention.
Examples of hydrophobizing agents such as silane coupling agents, silicone varnishes, silicone oils, organosilicon compounds, and functional materials having these functional groups include hexamethyldisilazane, hexamethylenedisilazane, trimethylsilane, trimethylchlorosilane, Trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, benzyldimethylchlorosilane, chloromethyldimethylchlorosilane, dichlorodimethylsilane, triorganosilylmercaptan, trimethylsilylmercaptan, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyl Diethoxysilane, aminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyl Trimethoxysilane, dibutyl aminopropyl dimethoxysilane, there is trimethoxysilyl -γ- propylphenyl amine. Examples of the silicone oil include methyl silicone oil, dimethyl silicone oil, phenylmethyl silicone oil, chlorophenyl methyl silicone oil, alkyl-modified silicone oil, fatty acid-modified silicone oil, amino-modified silicone oil, and polyoxyalkyl-modified silicone oil. These are used in one kind or a mixture of two or more kinds.
In the above processes, a single process or various processes may be used in combination.
[0018]
Moreover, the well-known thing can be used for the hydrophobic titanium particle used by this invention. Surface treatment agents include various silicone oils such as methyl hydrogen polysiloxane, dimethyl polysiloxane, and methylphenyl polysiloxane, methyltrimethoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, and decyltrimethoxy. Various alkyl silanes such as silane, octadecyltrimethoxysilane, dimethyldimethoxysilane, octyltriethoxysilane, n-octadecyldimethyl (3- (trimethoxysilyl) propyl) ammonium chloride, heptadecafluorodecyl Various fluoroalkylsilanes such as trimethoxysilane, especially vinyltrimethoxysilane, γ-aminopropyltrimethoxysilane, etc. Typified by silane-titanium-based, aluminum-based, alumina agent - any treatment agent of each metal based coupling agents such as zirconia may be used, and these combination of two or more.
[0019]
Further, the toner of the present invention may be mixed with additives as necessary. Examples of additives include lubricants such as Teflon and zinc stearate, abrasives such as cerium oxide and silicon carbide, fluidity imparting agents such as colloidal silica and aluminum oxide, anti-caking agents, or carbon black and tin oxide. And a fixing aid such as a low molecular weight polyolefin.
[0020]
As the colorant, those known for toners can be used. As the black colorant, for example, carbon black, aniline black, furnace black, lamp black and the like can be used. Examples of cyan colorants include phthalocyanine blue, methylene blue, Victoria blue, methyl violet, aniline blue, and ultramarine blue. As the magenta colorant, for example, rhodamine 6G lake, dimethylquinacridone, watching red, rose bengal, rhodamine B, alizarin lake and the like can be used. Examples of yellow colorants include chrome yellow, benzidine yellow, hansa yellow, naphthol yellow, molybdenum orange, quinoline yellow, and tartrazine.
[0021]
As the carrier that can be used in the present invention, known ones can be used. For example, magnetic powder such as iron powder, ferrite powder, nickel powder, glass beads, etc., and their surfaces treated with a resin or the like Etc.
[0022]
Examples of the resin powder that can be coated on the carrier in the present invention include a styrene-acrylic copolymer, a silicone resin, a maleic acid resin, a fluorine resin, a polyester resin, and an epoxy resin. In the case of a styrene-acrylic copolymer, those having a styrene content of 30 to 90% by weight are preferred. In this case, when the styrene content is less than 30% by weight, the development characteristics are low, and when it exceeds 90% by weight, the coating film becomes hard and easily peeled, and the life of the carrier is shortened.
Moreover, the resin coating of the carrier in the present invention may contain an adhesion-imparting agent, a curing agent, a lubricant, a conductive material, a charge control agent and the like in addition to the resin.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic configuration diagram of a main part of a developing device of an image forming apparatus adopting an example of a developing device of the present invention. In an actual embodiment, this developing apparatus was incorporated into a modified machine obtained by modifying the Ricoh copier MF-200 for evaluation. The details are shown below.
The developing device (13) disposed on the side of the photosensitive drum (1) as a latent image carrier includes a support case (14), a developer sleeve (15) as a developer carrier, and a developer containing member ( 16) mainly composed of a first doctor blade (17) as a developer regulating member.
[0024]
The support case (14) having an opening on the side of the photosensitive drum (1) forms a toner hopper (19) as a toner storage portion for storing the toner (18) therein. A developer that forms a developer accommodating portion (16a) that accommodates a developer (22) composed of toner (18) and a carrier that is magnetic particles, near the photosensitive drum (1) side of the toner hopper (19). The housing member (16) is provided integrally with the support case (14). The support case (14) positioned below the developer accommodating member (16) is formed with a protrusion (14a) having a facing surface (14b), and a lower portion of the developer accommodating member (16). A toner supply opening (20) for supplying toner (18) is formed by the space between the opposing surface (14b).
[0025]
Inside the toner hopper (19), a toner agitator (21) is disposed as a toner supply means rotated by a drive means (not shown). The toner agitator (21) sends the toner (18) in the toner hopper (19) toward the toner supply opening (20) while stirring. Further, on the side of the toner hopper (19) facing the photosensitive drum (1), a toner end detecting means (14c) for detecting when the amount of toner (18) in the toner hopper (19) decreases. ) Is arranged.
[0026]
A developing sleeve (15) is disposed in the space between the photosensitive drum (1) and the toner hopper (19). The developing sleeve (15) that is rotationally driven by the driving means (not shown) in the direction of the arrow in the drawing is provided with a magnet (not shown) serving as a magnetic field generating means disposed in the interior thereof so as not to change relative position to the developing device (13). Have.
A first doctor blade (17) is integrally attached to the developer accommodating member (16) on the side facing the side attached to the support case (14). The first doctor blade (17) is disposed in a state where a certain gap is maintained between its tip and the outer peripheral surface of the developing sleeve (15).
[0027]
A second doctor blade (23) serving as a restricting member is disposed at a portion of the developer accommodating member (16) located in the vicinity of the toner supply opening (20). The flow of the developer (22) layer formed on the surface of the developing sleeve (15) is such that the free end of the second doctor blade (23) maintains a certain gap with respect to the outer peripheral surface of the developing sleeve (15). The base end is integrally attached to the developer accommodating member (16) with the free end facing the center of the developing sleeve (15).
The developer accommodating portion (16a) is configured to have a sufficient space to circulate and move the developer (22) as long as the magnetic force of the developing sleeve (15) reaches.
[0028]
The opposing surface (14b) is formed over a predetermined length so as to incline downward from the toner hopper (19) side toward the developing sleeve (15) side. As a result, when vibration, uneven magnetic distribution of a magnet (not shown) provided in the developing sleeve (15), a partial increase in toner concentration in the developer (22), or the like occurs, the second doctor blade ( 23) and the peripheral surface of the developing sleeve (15), even if the carrier in the developer accommodating portion (16a) falls, the dropped carrier is received by the opposing surface (14b) and is on the developing sleeve (15) side. And is magnetically attached to the developing sleeve (15) by a magnetic force and is supplied again into the developer accommodating portion (16a). Thereby, it is possible to prevent a decrease in the amount of carrier in the developer accommodating portion (16a), and it is possible to prevent occurrence of uneven image density in the axial direction of the developing sleeve (15) during image formation. The inclination angle (α) of the facing surface (14b) is preferably about 5 °, and the predetermined length (l) is preferably 2 to 20 mm, more preferably about 3 to 10 mm.
[0029]
With the above configuration, the toner (18) sent out from the inside of the toner hopper (19) by the toner agitator (21) passes through the toner supply opening (20), and the developer (22) carried on the developing sleeve (15). ) And is carried to the developer accommodating portion (16a). The developer (22) in the developer accommodating portion (16a) is carried on the developing sleeve (15) and conveyed to a position facing the outer peripheral surface of the photosensitive drum (1), and only the toner (18) is transferred. A toner image is formed on the photosensitive drum (1) by electrostatically coupling with the electrostatic latent image formed on the photosensitive drum (1).
[0030]
Here, the behavior of the developer (22) during the toner image formation will be described. When a starting agent consisting only of a magnetic carrier (22a) is set in the developing device (13), the magnetic carrier (22a) is magnetically attached to the surface of the developing sleeve (15) as shown in FIG. (16a). The magnetic carrier (22a) accommodated in the developer accommodating portion (16a) circulates in the direction of arrow b by the magnetic force from the inside of the developing sleeve (15) as the developing sleeve (15) rotates in the direction of arrow a. To do. An interface (X) is present at the boundary between the surface of the magnetic carrier (22a) magnetically attached to the surface of the developing sleeve (15) and the surface of the magnetic carrier (22a) moving in the developer accommodating portion (16a). Formed (FIG. 2).
[0031]
Next, when the toner (18) is set in the toner hopper (19), the toner (18) is supplied from the toner supply opening (20) to the magnetic carrier (22a) carried on the developing sleeve (15). . Therefore, the developing sleeve (15) carries the developer (22) which is a mixture of the toner (18) and the magnetic carrier (22a).
[0032]
In the developer accommodating portion (16a), a force for stopping the conveyance of the developer (22) conveyed by the developing sleeve (15) due to the presence of the accommodated developer (22). Is working. When the toner (18) existing on the surface of the developer (22) carried on the developing sleeve (15) is conveyed to the interface (X), the friction between the developers (22) in the vicinity of the interface (X). The force decreases and the transport force of the developer (22) in the vicinity of the interface (X) decreases, thereby reducing the transport amount of the developer (22) in the vicinity of the interface (X).
[0033]
On the other hand, the developer (22) upstream of the developing sleeve (15) in the rotation direction from the junction (Y) is conveyed by the developing sleeve (15) as in the developer accommodating portion (16a). Since the developer (22) does not have a force to stop the conveyance, the developer (22) conveyed to the junction (Y) and the developer (22) conveyed through the interface (X). ) Is unbalanced and the developer (22) is struck, the junction (Y) is raised, and the layer thickness of the developer (22) including the interface (X) is increased. To do. Further, the layer thickness of the developer (22) that has passed through the first doctor blade (17) gradually increases, and the increased developer (22) is scraped off by the second doctor blade (23).
[0034]
Then, when the developer (22) that has passed through the first doctor blade (17) reaches a predetermined toner concentration, the developer (22) is increased by being scraped off by the second doctor blade (23). Closes the toner supply opening (20), and in this state, the toner (18) is taken up. At this time, in the developer accommodating portion (16a), the toner density is increased, so that the bulk of the developer (22) is increased, and thereby the space in the developer accommodating portion (16a) is narrowed, thereby developing the developer. The moving speed at which (22) circulates in the direction of arrow b in the figure also decreases.
[0035]
In the developer (22) layer formed so as to close the toner supply opening (20), the developer (22) scraped off by the second doctor blade (23) moves to the opposite surface (14b). However, since the opposing surface (14b) is inclined downward at an angle (α) toward the developing sleeve (15) and has a predetermined length (l), the developer (22) The developer (22) can be prevented from dropping onto the toner hopper (19) due to the movement of the toner layer, and the amount of the developer (22) can be kept constant. It becomes possible to control.
[0036]
【Example】
Hereinafter, the present invention will be described more specifically with reference to the following examples, but the present invention is not limited thereto.
The developing apparatus used was the apparatus shown in FIGS. All parts are parts by weight.
[0037]
An example of producing a carrier having a silicone resin used in the present embodiment or the like in the coating layer is shown. This can be done by known means.
[Carrier Production Example 1]
Composition of coating layer forming liquid Silicone resin solution (SR2100, manufactured by Toray Silicone Co., Ltd.) 100 parts Carbon black (# 44, manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) 4 parts Toluene 100 parts The above formulation is dispersed with a homomixer for 30 minutes to form a coating layer forming liquid. Prepared. A carrier A in which the coating layer was formed on the surface of 1000 parts by weight of spherical ferrite having an average particle diameter of 100 μm by using a fluidized bed coating apparatus was obtained from this coating layer forming liquid.
[0038]
[Examples 1 to 3, Comparative Examples 1 to 4]
The following developers were used.
Polyester resin 90 parts Styrene methyl acrylate 10 parts Magnetite fine particles 30 parts Low molecular weight polypropylene 5 parts Metal-containing azo compound 1 part A mixture of the above composition is sufficiently stirred and mixed in a Henschel mixer, and then at a temperature of 130 to 140 ° C in a roll mill, about 30 After heating and melting for minutes and cooling to room temperature, the obtained kneaded product was pulverized and classified with a jet mill, a mechanical pulverizer, or an air classifier to obtain a toner base having a predetermined particle size and circularity. The particle size / particle size distribution and circularity at this time were changed by changing the residence time in the jet mill or the use of a mechanical pulverizer and the conditions of the air classifier. A predetermined amount of a predetermined hydrophobic inorganic additive was added to and mixed with the obtained toner base material to obtain a final toner. A developer was obtained by mixing 13.0 parts of this toner with 87.0 parts of carrier A by a ball mill. The developer was subjected to a copying experiment using the MF-200 modified machine.
[0039]
Table 1 shows the results obtained based on the evaluations shown below, which are averages of the evaluation results at the start of each example and after 140,000 sheets.
<Image density unevenness>
The degree of occurrence of image density unevenness (history of the immediately preceding image) after continuous output of 15 sheets of A4 size using a full-surface halftone chart was performed in five stages according to the following criteria.
◎: Very good ○: Good □: Normal △: Bad ×: Very bad <Solid uniformity (image density)>
Using an A3 size chart with 6 points of solid parts in the front, back, left, and right, an image is output in A3 size, and the image density at the position of the 6 solid parts of the image is measured with a Macbeth reflection densitometer. The ID (image density) deviation was determined in five stages according to the following criteria.
◎: Very good ○: Good □: Normal △: Bad ×: Very bad <Dot reproducibility>
The dot reproducibility was evaluated. Evaluation was performed in five stages according to the following criteria.
◎: Very good ○: Good □: Normal △: Bad ×: Very bad [0040]
[Table 1]

[0041]
【The invention's effect】
As described above, as is clear from the detailed and specific description, in the toner used for a specific developing method that can easily adjust the toner concentration with a simple configuration capable of always self-controlling the toner supply, By satisfying the specific particle size and circularity range, it is possible to provide an image forming method and an image forming apparatus that have high image quality over time and have no density unevenness.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of an image forming apparatus according to the present invention.
FIG. 2 is an example showing the behavior of a developer during toner image formation according to the present invention.
[Explanation of symbols]
1 Latent image carrier (photosensitive drum)
13 Developing Device 14 Support Case 14a Support Case Projection 14b Support Case Opposing Surface 14c Toner End Sensor 15 Developer Carrier (Developing Sleeve)
16 Developer accommodating member 16a Developer accommodating portion 17 First regulating member (first doctor blade)
18 Toner 19 Toner container (toner hopper)
20 Toner supply opening 21 Toner supply means (toner agitator)
22 Developer 22a Magnetic carrier 23 Second regulating member (second doctor blade)
X interface (interface)
Y developer junction point a developing sleeve rotation direction b carrier circulation direction α opposing surface inclination angle l opposing surface length

Claims (2)

A developer carrier having a magnetic field generating means therein and carrying and transporting a two-component developer containing toner and a magnetic carrier, and an amount of the developer carried and carried by the developer carrier. A first regulating member to be regulated, a developer containing portion that contains the developer scraped off by the first regulating member, and a toner adjoining the developer containing portion and supplying toner to the developer carrying member A toner container, and a change in toner density of the developer on the developer carrying member changes a contact state between the developer and the toner, thereby taking in the toner of the developer on the developer carrying member. An image forming method using a developing device that changes a state, wherein the developer accommodating portion is disposed on the upstream side in the transport direction of the developer on the developer carrier relative to the first regulating member. 2 restriction members, and the second restriction member When the developer toner density on the developer carrier increases and the developer layer thickness increases, a gap with the developer carrier is set to restrict the passage of the increased amount of the developer. Regardless of the change in the toner concentration of the developer on the developer carrier, the developer in the developer container moves in the developer container and the toner concentration of the developer on the developer carrier When the toner concentration reaches a predetermined toner concentration, the developer whose passage is restricted by the second restriction member accumulates in the contact portion between the developer and the toner on the developer carrier, and the developer is in contact with the toner. The toner used by the developer on the developer carrier is stopped by closing the portion, and the toner used has at least a binder resin, magnetic powder and hydrophobic inorganic fine powder, and the volume average particle size of the toner Diameter M (μm) satisfies 4-7 μm, particle size of 5 μm or less The toner particles contain 40 to 80% by number having, among particle diameter of the toner of the volume average particle diameter (M) is greater than 2 [mu] m, and a range of less than the particle size of the volume average particle diameter (M) + 2 [mu] m of the toner An image forming method, wherein the toner particles having a particle size satisfy a value represented by the following general formula:

A developer carrier having a magnetic field generating means therein and carrying and transporting a two-component developer containing toner and a magnetic carrier, and an amount of the developer carried and carried by the developer carrier. A first regulating member to be regulated, a developer containing portion that contains the developer scraped off by the first regulating member, and a toner adjoining the developer containing portion and supplying toner to the developer carrying member A toner container, and a change in toner density of the developer on the developer carrying member changes a contact state between the developer and the toner, thereby taking in the toner of the developer on the developer carrying member. An image forming method using a developing device that changes a state, wherein the developer accommodating portion is disposed on the upstream side in the transport direction of the developer on the developer carrier relative to the first regulating member. 2 restriction members, and the second restriction member When the developer toner density on the developer carrier increases and the developer layer thickness increases, a gap with the developer carrier is set to restrict the passage of the increased amount of the developer. Regardless of the change in the toner concentration of the developer on the developer carrier, the developer in the developer container moves in the developer container and the toner concentration of the developer on the developer carrier When the toner concentration reaches a predetermined toner concentration, the developer whose passage is restricted by the second restriction member accumulates in the contact portion between the developer and the toner on the developer carrier, and the developer is in contact with the toner. The toner used by the developer on the developer carrier is stopped by closing the portion, and the toner used has at least a binder resin, magnetic powder and hydrophobic inorganic fine powder, and the volume average particle size of the toner Diameter M (μm) satisfies 4-7 μm, particle size of 5 μm or less 40 to 80% by number of toner particles having a volume average particle size (M) of which the particle size is larger than 2 μm and the toner volume average particle size (M) +2 μm. An image forming apparatus, wherein the toner particles having a particle size satisfy a value represented by the following general formula:

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