JP3670134B2 - Powder-to-powder adhesion measuring apparatus, powder-to-powder adhesion measuring method, and image forming apparatus and image forming method - Google Patents

Description

【００２１】
トナーの凝集度Ｃは、ホソカワミクロン製のパウダーテスタＰＴ−Ｎ型を使用し、次の方法により測定した。パウダーテスタに３種類のメッシュを装着し（フルイ目開き、上段７５μｍ、中段４５μｍ、下段２２μｍ）、トナーサンプルを２ｇ上段のメッシュに載せ、振幅目盛が１ｍｍ振幅する状態で、３０秒間振動させる。各メッシュ上に残ったトナーの重量からトナーの凝集度を次式により算出する。
【００２２】
◎
【数１】

【００２３】
ここで示したトナーの凝集度は、トナーの流動性を示す特性値であり、値の小さいほど流動性が向上する傾向がみられる。各種トナーとＰＲＥＴＥＲ６５０用２成分現像剤のキャリアを混合し、現像剤とした。各種現像剤に対して荷電電位や露光量などの作像条件を設定し、中間転写ベルト上に直径３ｍｍの円形のトナー像を形成した。さらに、中間転写ベルトを切りだし、図５のように、円形のアルミ基板上に貼り合わせ、試料基板２を作成した。試料基板（アルミ基板）２の試料面（中間転写ベルトの一部）２ａ上に形成したトナー層は帯電しているため、トナー粒子間のクーロン反発力や基板との鏡像力が働いていると考えられる。これらの力の影響を考察するために、各トナー種に対して、中間転写ベルト上のトナー帯電量Ｑ（μＣ／ｇ）とトナー付着量Ｍ（ｍｇ／ｃｍ²）を変化させた複数の試料面２ａを作成した。トナー帯電量Ｑ及びトナー付着量Ｍは既知の面積のトナー画像に対して吸引式ファラデーケージ法で測定した。こうして作成した試料基板２を保持部材７に装着し、保持部材７をロータ６に、ロータ６を遠心分離装置５にセットする。
【００２４】
さらに、遠心分離装置５を作動させると、トナー粒子は遠心力によりトナー層表面から分離し、受け基板３（直径 本体：８ｍｍ、トナー受け範囲：５．２ｍｍ）に付着する。トナーの受ける遠心力Ｆは、前述の式（６）から求められる。なお、ｄ：トナー粒径、ρ：トナー比重１．２ｇ／ｃｍ³、ｒ：遠心半径６４．４７ｍｍ、ｆ：分離回転数ｒｐｍとする。
【００２５】
Ｆ＝（π³／５４００）×ρ×ｄ³×ｒ×ｆ² （６）
本実施例では、試料基板２から分離するトナー数が比較的多いため、効率的な評価法として、受け基板３上の一個一個のトナー粒径は測定せず、平均粒径ｄ＝７．５μｍであるとしてトナー粒子数のみを計数する方法を採用した。すなわち、受け基板３の付着面３ａの中央部をＣＣＤ顕微鏡カメラ（キーエンス社製ハイパーマイクロスコープ）で拡大観察し、ビデオプリンタで出力した。２００倍レンズを用いた場合、ビデオプリント上では７７倍の倍率になり、一画面では横１．４ｍｍ×縦１．１ｍｍ＝１．５４ｍｍ²の面積を観察できる。拡大写真をスキャナ４９を用いて４００ｄｐｉ×４００ｄｐｉ白黒写真モードでパーソナルコンピュータ（粉体間付着力測定装置本体側）に取り込み、画像処理手段４８（画像処理ソフト（イメージプロプラス））を用いて、２値化処理、計数処理を行い、トナー粒子数とトナー粒子部分が占める画素数すなわちトナーの受け基板３上への投影面積を計数した。
【００２６】
また、後述の方法で、トナー層中央部の最表層のトナー粒子が分離し始める回転数ｆを決定し、式（６）からトナーを分離するために必要な遠心力Ｆを求めた。トナー層の遠心分離を行う際、問題となるのが取り扱うトナー数の多さである。画像処理ソフトで付着面３ａ上のトナー粒子数を計数する場合、トナー数が多くなると、複数のトナー粒子が重なって大きな一つの粒子として計数されるようになる。そこで、本実施例では、トナー粒子数ではなく、トナー粒子部分が占有する総面積（投影面積）を用いて分離回転数を決定する方法を採用した。
【００２７】
ここで、本実施例で測定した全サンプルに対して、付着面３ａ上のトナー粒子数とトナー部投影面積（画像処理の画素数）の関係を図６に示す。１枚のビデオプリント内のトナー部の画素数が１×１０⁵個程度までは画素数とトナー粒子数との間に直線的な関係が成り立っている。これは、トナー数が１０００個程度までは一粒一粒が独立して付着していることを意味している。これに対して、トナー部の画素数が２×１０⁵個以上になると、トナー粒子数は約１８００個程度で飽和してしまう。これは、トナー数が１８００個程度以上になると、付着面３ａ上でトナー粒子同士が重なってしまうことを意味している。すなわち、本実施例では、独立状態決定工程１０８において、受け基板３上のトナー数１８００個またはトナー部画素数２×１０⁵個が、トナー粒子が独立状態を取り得る最大数であると求められる。また、この状態では、トナー粒子の固まりが分離しているのではなく、トナー粒子が一粒一粒独立して分離していると考えられる。本実施例における独立状態の評価基準としては、遠心力の増加と共にトナー層の表層から分離し始めたトナーが累積し、１８００個（画素数２×１０⁵個）程度飛んだ時点の回転数を分離回転数ｆと決めた。ビデオプリント画面の全面積での画素数は約２．４×１０⁶個であるから、単純に考えると、表層トナーの約８％が分離した状態である。この状態でトナー粒子は一粒一粒独立して分離していると考えられる。
【００２８】
ここで、本実施例における３種類のトナーａ，ｂ，ｃについて、遠心回転数に対する分離トナー数の変化を図７〜図９に示す。なお、横軸には遠心回転数（ｒｐｍ）を、縦軸には累積のトナー部画素数を対数で表した。前述の独立状態決定工程１０８で決定した画素数２×１０⁵個の位置は矢印で示した。また、表２に各条件での試料面２ａ上のトナー帯電量Ｑ（μＣ／ｇ）とトナー付着量Ｍ（ｍｇ／ｃｍ²）の測定結果を示した。
【００２９】
◎
【表２】

【００３０】
前記の各条件に対して、累積の画素数が２×１０⁵個になるロータ回転数を、分離回転数ｆとして決定し、式（６）でトナー粒径を７．５μｍとして遠心力Ｆを計算した。この遠心力Ｆは表層のトナー粒子を分離するために必要な力であり、トナー粒子間に働く静電的な力と非静電的付着力の両者の影響を反映している。遠心力Ｆの計算結果を表３に示す。何れのトナーに対しても、トナー帯電量Ｑが大きいほどトナーを分離するための遠心力Ｆが大きく、トナー付着量Ｍが大きいほど遠心力Ｆが小さい傾向がある。
【００３１】
◎
【表３】

【００３２】
本実施例では、図１０に示すような、鏡像力による付着状態のモデルを考え、解析することにより、トナー粒子間の非静電的付着力を決定する。表層のトナー粒子の中心に点電荷が存在すると仮定し、この点電荷に働く基板との鏡像力のみを考慮する。点電荷ｑは、トナー帯電量Ｑ（μＣ／ｇ）に比例し、基板と点電荷の距離ｈは、トナー付着量Ｍ（ｍｇ／ｃｍ²）にほぼ比例する。従って、点電荷に働く鏡像力ＦはＦ∝（ｑ／ｈ）²∝［Ｑ／Ｍ］²に比例する。この計算結果も表３に示した。
【００３３】
ここで、本実施例による鏡像力モデルでの解析方法に基づいて遠心力を整理した結果を図１１に示す。なお、縦軸は表層のトナーが分離し始める遠心力Ｆｓ、横軸は［Ｑ／Ｍ］²の計算値を示す。［Ｑ／Ｍ］²の値は鏡像力に比例すると考えられるが、その絶対値自体に意味はない。各トナーとも、バラツキはあるものの、直線的な増加傾向が認められる。これにより、横軸をゼロに外挿したときの遠心力が非静電的なトナー粒子間の付着力Ｆｔを表すと考えられる。すなわち、以下の関係式（７）が成り立つ。但し、Ａは定数である。
【００３４】
Ｆｓ＝Ｆｔ＋Ａ×（Ｑ／Ｍ）² （７）
さらに、非静電的なトナー粒子間の付着力Ｆｔとトナー凝集度の相関を図１２に示す。トナーへの外添剤添加量の減少と共に、トナー凝集度が増加し、非静電的トナー間付着力が増加することが定量的に確認できた。
なお、前記トナー付着量Ｍの代わりにトナー層の厚さＨを測定した。トナー層厚さＨはキーエンス社の表面形状測定顕微鏡ＶＦ７５００を用いて測定した。図１３にトナー付着量Ｍとトナー層厚さＨの相関を示す。両者にはほぼ比例関係が成り立つ。従って、式（７）と同様に式（８）が成り立ち、Ｆｔを測定することができた。但し、Ｂは定数である。
【００３５】
Ｆｓ＝Ｆｔ＋Ｂ×（Ｑ／Ｈ）² （８）
本実施例の更なる検討の結果、前述した転写工程でのトナーの飛び散り、いわゆる転写チリ現象は、トナー帯電量とトナー付着量、さらに本実施例の方法により測定したトナー間付着力の三つの特性値で記述できることを見いだした。転写チリが多いほど、ライン間のような非画像部に見えるトナー粒子数が多くなる。この非画像部に散ったトナー数から転写チリレベルを評価した。本実施例では、中間転写ベルト上の２００μｍ幅のライン状トナー画像をＣＣＤ顕微鏡カメラで撮影し、その拡大写真をスキャナ４９からパーソナルコンピュータに白黒連続調画像として取り込んだ。市販の画像処理ソフトを用いて、連続調の写真画像を２値化してトナー粒子部分とベルト部分の輪郭を強調、分離した。前記画像処理ソフトの計数機能を用いてトナー粒子部分の個数（オブジェクト数）を計数し、長さ１ｍｍ当たりのラインエッジ部から飛び散ったトナー粒子の個数を算出した。この数値を「ライン散りトナー数Ｎ（個／ｍｍ）」と定義した。また、中間転写ベルト上のトナー帯電量Ｑ及びトナー付着量Ｍは吸引式ファラデーケージ法で測定し、２００μｍ幅のライン画像を既知の長さ分だけ吸引、採集した。採集したトナーによる誘起電荷量ｑと重量ｍから単位重量当たりのトナーの電荷量を算出し、平均トナー帯電量Ｑ（μＣ／ｇ）として表す。また、ライン画像の拡大写真からライン幅の平均値を求めてライン画像の面積ａを算出し、単位面積当たりのトナーの重量をトナー付着量Ｍ（ｍｇ／ｃｍ²）として表す。
【００３６】
ここで、図１４に、中間転写ベルト上でのライン散りトナー数Ｎと、中間転写ベルト上のトナー付着量Ｍの相関を示す。Ｍ＝０．８〜１．０ｍｇ／ｃｍ²程度までのトナー付着量が比較的少ない場合はマゼンタトナーの単色画像で、それ以上トナー付着量が多い場合はシアントナーの上にマゼンタトナーを重ねた２色重ね画像で実験した。また、トナーとして前述のトナーａを用いた。また、帯電能力のみが異なる３種類のキャリアによる現像剤を作成し、中間転写ベルト上のトナー帯電量Ｑをパラメータとして変化させた。キャリアの帯電能力は製造過程の焼成温度を変化させてコントロールした。帯電能力の高い順にキャリアＡ、キャリアＢ、キャリアＣとした。図１４では、ライン散りトナー数Ｎはトナー付着量Ｍの増加と共に急激に増加する。また、トナー帯電量Ｑが大きいほどライン散りトナー数Ｎも大きい。本発明者の検討では、転写チリが実用上許容できるレベルは、中間転写ベルト上でのライン散りトナー数が１３０個／ｍｍとした。トナー荷電量が大きい場合は中間転写ベルト上でのトナー付着量を低減しなければならない。すなわち、中間転写ベルト上の画像領域内でトナー付着量が最も多くなる部分でのトナー付着量が少なくなるような作像条件を設定しなければならない。逆に、トナー帯電量を小さくすれば、中間転写ベルト上での最大トナー付着量が多くても許容される。図１４中の三つの曲線は、「Ｎ＝ αＭ⁴Ｑ²＋β」の特性を表し、α＝０．２８、β＝１８で同一である。この特性とトナー付着量Ｍとトナー帯電量Ｑに対する転写チリの実験結果はよく一致している。同様に、外添剤の添加量が異なる前記３種類のトナーａ，ｂ，ｃを使用し、トナー凝集度またはトナー間付着力をパラメータとして変化させた結果を図１５に示す。
【００３７】
この図１５においても、トナー付着量Ｍの増加に伴う散りトナー数Ｎの増加は同様である。また、外添剤量の減少によってトナー凝集度またはトナー間付着力が大きくなるほど、散りトナー数が減少する傾向がある。図１５中の三つの曲線も、「Ｎ＝ αＭ⁴Ｑ²＋β」の特性を表し、トナーａではα＝０．２８、β＝１８、トナーｂではα＝０．１２、β＝１４、トナーｃではα＝０．０８、β＝１０となった。この特性と転写チリの実験結果はよく一致している。
【００３８】
さらに、図１６に、図１２で求めたトナー粒子間の非静電的付着力Ｆｔと図１４から求めた前記パラメータαの関係を示す。図中の曲線はα＝１．８／Ｆｔ（図１６でのＦｔの単位はｎＮ＝１０^-9Ｎ）の関係を示しており、実験結果とほぼ一致している。なお、転写チリ発生のメカニズムの詳細は明らかでないが、トナー粒子間の非静電的付着力Ｆｔ（Ｎ）、トナー付着量Ｍ、トナー帯電量Ｑの三つのパラメータの変化に対して、ライン散りトナー数Ｎは実験的には以下の経験式と良く一致することが明らかとなった。
【００３９】
Ｎ＝１．８Ｍ⁴Ｑ²／（Ｆｔ×１０⁹）＋β （βは１０〜２０程度） （９）
前述のように実用上許容できるライン散りトナー数Ｎは１３０個／ｍｍ程度以下であるから、βを１０〜２０として、
Ｎ−β＝１．８Ｍ⁴Ｑ²／（Ｆｔ×１０⁹）≦１１０〜１２０ （１０）
となる。従って、中間転写ベルト上の画像領域内で最もトナー量が多くなる部分に対して、以下の関係式（３）を満たすような作像条件を設定すれば、転写チリの少ない画像が得られる。
【００４０】
Ｍ⁴Ｑ²／（Ｆｔ×１０⁹）≦６０ （３）
前記関係式（３）において、トナー粒子間の非静電的付着力Ｆｔは、５×１０^-9Ｎ〜３×１０^-8Ｎの範囲であることが好ましい。Ｆｔが５×１０^-9Ｎよりも小さい場合、前記関係式（３）を満たすためには、トナー付着量Ｍまたはトナー帯電量Ｑを非常に小さくする必要がある。中間転写ベルト上で最もトナーが多い部分でのトナー付着量Ｍの低下は画像濃度の不足となり、トナー帯電量Ｑの低下はトナー凝集度の低下と重なってトナー飛散等の不具合を生じる。一方、Ｆｔが３×１０^-8Ｎよりも大きい場合は、転写チリに対してはライン散りトナー数Ｎが減少する減少する方向だが、現像時のトナー画像の粒状性の悪化やトナー補給時の搬送性の悪化等の不具合を生じる。
【００４１】
また、前記関係式（３）において、中間転写ベルト上でのトナー帯電量の絶対値が１０〜３０μＣ／ｇの範囲であることが好ましい。トナー帯電量の絶対値が１０μＣ／ｇより小さい場合、転写チリに対してはライン散りトナー数が減少する方向だが、トナー飛散や転写不良等の不具合を生じる。逆に、トナー帯電量の絶対値が３０μＣ／ｇよりも大きい場合も、転写性が不十分になる。
【００４２】
さらに、本実施例においては、中間転写ベルトの表面抵抗値が１０^８〜１０^１０ Ω／□であることが好ましい。表面抵抗値が１０^８ Ω／□よりも小さい場合、転写電圧がリークしてしまい、転写不良が発生する。逆に、表面抵抗値が１０^１０ Ω／□よりも大きい場合、ベルト転写工程後の中間転写ベルトの非画像部にマイナス電位を保持するようになる。従って、この残留電位を除去するための除電装値が必要になるという欠点がある。しかし、この非画像部の電荷保持は中間転写ベルト上での転写チリ低減には効果がある。すなわち、中間転写ベルト上で画像を形成するトナー粒子間にはトナーが持つマイナス電荷間にクーロン反発力が作用してトナー散りが発生するが、非画像部にマイナス電荷を保持している場合、非画像部のマイナス電荷とトナー電荷の間にクーロン反発力が作用し転写チリを抑制すると考えられる。このような場合、転写チリ低減には必ずしも関係式（３）の条件を満たす必要はなくなる。逆に言えば、関係式（３）は中間転写ベルトの表面抵抗値が１０ ^１０ Ω／□以下の場合に特に有効である。
【００４３】
《前記画像形成装置及び画像形成方法の第１の実施例》 次に、図１７を用い、前記の粉体間付着力測定方法の測定結果を適用したカラー画像形成装置について述べる。本実施例では、１本の感光体に対向して４色の現像器を並べて配置してあり、感光体上に異なる色成分毎に形成されるトナー像を中間転写ベルト上に順次重ねて転写し、その重ねて転写されたトナー像を転写紙等に一括転写することによって、カラー画像を得る１ドラム中間転写体方式を採用する。
【００４４】
図１７において、感光体ドラム３５（＝静電潜像担持体）はアルミ素管上に、下引き層、電荷発生層、電荷輸送層の順に重ねて製膜した機能分離型の感光層を有する。感光層の厚さは約２８μｍ、静電容量は約９０ｐＦ／ｃｍ²である。本実施例においては、感光体ドラム３５をスコロトロン帯電器２１で均一にマイナス帯電（約−６５０〜−７００Ｖ）した後、画像情報に応じたレーザ光を露光部２２に照射し、−１００Ｖ〜−５００Ｖの静電潜像を形成する。感光体の帯電電位や露光部電位を電位センサＡ２３で検出し、帯電条件や露光条件等を制御することもできる。すなわち、静電潜像を形成する形成手段は、スコロトロン帯電器２１、露光部２２、電位センサＡ２３等からなる。
【００４５】
また、現像部２４（＝現像手段）には４色の現像器が並べて配置されており、各色毎に静電潜像を現像する。乾式２成分現像剤を用い、感光体上の低電位部にマイナス帯電トナーを付着させる反転現像方式である。前記乾式２成分現像剤は平均粒径が７．５μｍの粉砕トナーと平均粒径が５０μｍの樹脂コートキャリアからなり、現像剤中のトナーの帯電量は、−１０〜−３０μＣ／ｇとした。トナーには外添剤として０．２〜０．８重量部のシリカ微粒子が添加されている。本実施例においては、現像バイアス値は約−５００〜−５５０Ｖとした。現像バイアスには交流成分を重畳させてもよい。現像後の位置にはＰセンサ２５が設置され、光学的反射率からトナー付着量を検出してプロセス条件を制御することもできる。
【００４６】
また、各色のトナー像は中間転写ベルト２６（＝トナー画像担持体）上に転写される。転写電圧の間接印加方式を採用しており、入口ローラ３２と出口ローラ３３の間に架け渡されたベルト部分が感光体に接離可能に構成されている。前記中間転写ベルト２６はポリカーボネート樹脂あるいはフッ素系樹脂等の中にカーボンブラックを分散させた単層の中抵抗体であり、厚さ約１５０μｍ、表面抵抗値は１０^８〜１０^１０ Ω／□、体積抵抗値は１０^９〜１０^１１Ωｃｍの範囲のものを用いた。また、入口ローラ３２は接地され、出口ローラ３３に＋１０００〜＋１５００Ｖ程度の転写電圧（Ｖｔ）が印加される。転写電圧（Ｖｔ）は図示していない電源より供給され、その出力値は図示していない制御部にて制御されている。以後、感光体から中間転写ベルト２６上への転写を「ベルト転写」と称す。なお、ベルト転写後の感光体上の残留トナーは、ＰＣＣ（クリーニング前チャージャ）２７によって帯電量が制御され、ドラムクリーニング装置２９でブラシ及びブレードで除去される。
【００４７】
本実施例においては、中間転写ベルト２６上に１色目のトナー画像が形成された後、２色目の作像動作を開始し、中間転写ベルト２６上に２色目のトナー像を重ねて転写する。この時、転写される順番毎に転写電圧を増加させていってもよい。フルカラー画像の場合、中間転写ベルト２６上に黒、シアン、マゼンタ、イエローの４色のトナー画像を順次形成した後、一括して記録紙３４上に転写する。中間転写ベルト２６上から記録紙３４上へのトナー像の転写は、紙転写ローラ３１で紙の裏側からプラス極性の電圧を印加する。以後、中間転写ベルト２６から記録紙３４上への転写を「ペーパー転写」と称す。ペーパー転写後の中間転写ベルト２６上に残留したトナーはクリーニング装置２８によって除去される。
【００４８】
《前記画像形成装置及び画像形成方法の第２の実施例》 本実施例の画像形成装置の構成は、第１の実施例（図１７）と概ね同様であるが、後述のように中間転写ベルト２６として、表面抵抗値が１０^９ Ω／□、体積抵抗値が１０^１０Ωｃｍの単層の中抵抗体を用いた。また、本実施例においては、前記粉体間付着力測定方法によって測定したトナー粒子間の非静電的付着力Ｆｔが８×１０^−９Ｎとなるトナーａを用い、シアンとマゼンタを２色重ねたブルーのライン部について最終画像での転写チリ品位を目視判定した。このように２色重ねた色の部分は、ペーパー転写工程前、すなわち、中間転写ベルト２６上でのトナー付着量が多くなり、転写チリが増加する。このような中間転写ベルト２６上でトナー付着量が最大となる部分において転写チリが低減できれば、これよりもトナー付着量が少ない部分でも確実に転写チリは低減する。また、前記中間転写ベルト２６は、エチレン−テトラ−フルオロエチレン（ＥＴＦＥ）樹脂の中にカーボンブラックを分散させた表面抵抗値が１０^９ Ω／□、体積抵抗値が１０^１０Ωｃｍの単層の中抵抗体であって、ベルト転写バイアス値は、１色目、２色目共に＋１２００Ｖとした。現像剤中のトナー帯電量はシアンとマゼンタ共に−３０μＣ／ｇ程度であった。ベルト転写工程後の中間転写ベルト２６上でのトナー帯電量の平均値Ｑは−１７．７μＣ／ｇであった。この時のライン散りトナー数は図１４中の●プロットの結果となり、中間転写ベルト上でのトナー付着量Ｍが１．１ｍｇ／ｃｍ^２以下では、「Ｍ^４Ｑ^２／（Ｆｔ×１０^９）≦６０」が成立し、転写チリは許容できるレベルであった。その他の不具合も発生しなかった。
【００４９】
なお、本実施例と比較するために、図１４中の●プロットの結果において、中間転写ベルト２６上でのトナー付着量Ｍを１．２ｍｇ／ｃｍ²以上にした場合、前記関係式「Ｍ⁴Ｑ²／（Ｆｔ×１０⁹）≦６０」が成立せず、転写チリが目立ち許容できなくなった。
《前記画像形成装置及び画像形成方法の第３の実施例》 本実施例の画像形成装置の構成は、第１の実施例（図１７）と概ね同様である。本実施例では、前記粉体間付着力測定方法で測定したトナー粒子間の非静電的付着力Ｆｔが２×１０^-8Ｎとなるトナーｃを用いた。現像剤中のトナー帯電量はシアンとマゼンタ共に−２８μＣ／ｇ程度であった。ベルト転写工程後の中間転写ベルト２６上でのトナー帯電量の平均値Ｑは−１７．４μＣ／ｇであった。この時のライン散りトナー数Ｎは図１５中の△プロットの結果となり、中間転写ベルト２６上でのトナー付着量Ｍが１．３６ｍｇ／ｃｍ²以下では、前記関係式「Ｍ⁴Ｑ²／（Ｆｔ×１０⁹）≦６０」が成立し、転写チリは許容できるレベルであった。その他の不具合も発生しなかった。
【００５０】
《前記画像形成装置及び画像形成方法の第４の実施例》 本実施例の画像形成装置の構成は、第１の実施例（図１７）と概ね同様である。本実施例では、第３の実施例と同様に、トナー粒子間の非静電的付着力Ｆｔが２×１０^-8Ｎとなるトナーｃを用いた。さらに、現像剤中のトナー濃度を低下させてトナー帯電量を増加させた。現像剤中のトナー帯電量はシアンとマゼンタ共に−４０μＣ／ｇ程度になった。ベルト転写工程後の中間転写ベルト２６上でのトナー帯電量Ｑは本実施例の範囲外の−３１μＣ／ｇになった。この時の中間転写ベルト２６上でのトナー付着量Ｍは１．００ｍｇ／ｃｍ²で、前記関係式「Ｍ⁴Ｑ²／（Ｆｔ×１０⁹）≦６０」が成立し、転写チリは許容できるレベルであった。しかし、中間転写ベルト２６上でのトナー帯電量が大き過ぎるため、ペーパー転写工程で転写不良が発生した。
【００５１】
《前記画像形成装置及び画像形成方法の第５の実施例》 本実施例の画像形成装置の構成は、第１の実施例（図１７）と概ね同様である。本実施例では、外添剤添加量が１．０重量部のトナーｄを用い、第４の実施例と同様に画像形成を行った。前記粉体間付着力測定方法で測定したトナー粒子間の非静電的付着力Ｆｔは４×１０^-9Ｎ程度となり本実施例の範囲外となった。現像剤中のトナー帯電量はシアンとマゼンタ共に−１５μＣ／ｇ程度であった。ベルト転写工程後の中間転写ベルト２６上でのトナー帯電量の平均値Ｑは−１１．５μＣ／ｇであった。この時の中間転写ベルト２６上でのトナー付着量Ｍが１．１ｍｇ／ｃｍ²では、前記関係式「Ｍ⁴Ｑ²／（Ｆｔ×１０⁹）≦６０」が成立し、転写チリは許容できるレベルであった。しかし、現像装置からのトナー飛散が発生した。
【００５２】
《前記画像形成装置及び画像形成方法の第６の実施例》 本実施例の画像形成装置の構成は、第１の実施例（図１７）と概ね同様である。本実施例では、キャリアＡと外添剤未添加のトナーｅを用い、第４の実施例と同様に画像形成を行った。前記粉体間付着力測定方法で測定したトナー粒子間の非静電的付着力Ｆｔは４×１０^-8Ｎ程度となり本実施例の範囲外となる。現像剤中のトナー帯電量はシアンとマゼンタ共に−２５μＣ／ｇ程度であった。ベルト転写工程後の中間転写ベルト２６上でのトナー帯電量の平均値Ｑは−１６μＣ／ｇであった。中間転写ベルト２６上でのトナー付着量Ｍが１．５ｍｇ／ｃｍ²では、前記関係式「Ｍ⁴Ｑ²／（Ｆｔ×１０⁹）≦６０」が成立し、転写チリは許容できるレベルであった。しかし、現像後のドット画像の粒状性が悪化した。
【００５３】
《前記画像形成装置及び画像形成方法の第７の実施例》 本実施例の画像形成装置の構成は、第１の実施例（図１７）と概ね同様であるが、中間転写ベルト２６として、ポリカーボネート樹脂の中にカーボンブラックを分散させた表面抵抗値が１０^８ Ω／□、体積抵抗値が１０^１１Ωｃｍの単層の中抵抗体を用いた。その結果、現像剤中のトナー帯電量はシアンとマゼンタ共に−３０μＣ／ｇ程度であった。ベルト転写工程後の中間転写ベルト２６上でのトナー帯電量の平均値Ｑは−１７．７μＣ／ｇであった。中間転写ベルト２６上でのトナー付着量Ｍが１．０ｍｇ／ｃｍ^２では、前記関係式「Ｍ^４Ｑ^２／（Ｆｔ×１０^９）≦６０」が成立し、転写チリは許容できるレベルであった。中間転写ベルト２６上での残留電荷もなく、中間転写ベルト２６の除電装置を省略することができた。その他の不具合も発生しなかった。
【００５４】
《前記画像形成装置及び画像形成方法の第８の実施例》 本実施例の画像形成装置の構成は、第１の実施例（図１７）と概ね同様であるが、中間転写ベルト２６の表面に約２０μｍの高抵抗層を設けた。その表面層はＰＶｄＦ樹脂中に酸化チタンを分散させたもので、表面抵抗値は１０¹³Ωｃｍである。ベルト転写バイアス値は１色目のシアン転写時は＋１６００Ｖ、２色目のマゼンタ転写時には＋２０００Ｖとした。また、現像剤としてはトナーａを用いた。現像剤中のトナー帯電量はシアンとマゼンタ共に−２４μＣ／ｇ程度であった。ベルト転写工程後の中間転写ベルト２６上でのトナー帯電量Ｑが−１４．０μＣ／ｇ、トナー付着量Ｍが１．３７ｍｇ／ｃｍ²で、前記関係式「Ｍ⁴Ｑ²／（Ｆｔ×１０⁹）≦６０」を満たしていないが、中間転写ベルト２６上でのライン散りトナー数Ｎは５０個程度しかなく、転写チリは許容できるレベルであった。これは、中間転写ベルト２６上の非画像部のマイナス電荷がトナー散りを抑制したものと考えられる。しかし、そのマイナス電荷の影響で次の作像工程で転写ムラによる残像が発生した。
【００５５】
本実施例によれば、遠心分離法により粉体層最表面から粉体を分離するために必要な遠心力Ｆｓ（Ｎ）を測定し、試料面上の粉体層の単位面積当たりの付着量Ｍ（ｍｇ／ｃｍ²）及び粉体の平均帯電量Ｑ（μＣ／ｇ）の依存性から静電的な力の影響を分離できるので、粉体間の非静電的付着力Ｆｔ（Ｎ）を求めることができる。また、遠心分離法により粉体層最表面から粉体を分離するために必要な遠心力Ｆｓ（Ｎ）を測定し、試料面上の粉体層の厚さＨ（μｍ）及び粉体の平均帯電量Ｑ（μＣ／ｇ）の依存性から静電的な力の影響を分離できるので、粉体間の非静電的付着力Ｆｔ（Ｎ）を求めることができる。
【００５６】
また、本実施例によれば、試料基板２上に粉体を複数層以上の厚さに重ねて粉体層を形成する工程は、電子写真方式の現像工程により、静電潜像を形成したシート状の試料基板２上に粉体層を形成するようにしたので、均一な粉体層を形成できる。さらに、試料基板２上に粉体を複数層以上の厚さに重ねて粉体層を形成する工程は、電子写真方式の現像工程により、静電潜像を形成した粉体像担持体上に粉体層を形成した後、電子写真方式の転写工程により、粉体像をシート状の試料基板上に転写して形成するようにしたので、簡単な構成で粉体層を形成し、精度良く非静電的付着力を測定することができる。すなわち、トナーのような粉体間の非静電的付着力を定量的かつ効率的に測定できる。
【００５７】
さらに、本実施例によれば、トナー粒子間の非静電的付着力及びトナー画像担持体上でのトナー帯電量とトナー付着量の三つの特性値の関係を最適化できるので、転写チリの少ない高品質の画像を得ることができる。また、トナー画像担持体上でのトナー粒子間の非静電的付着力を最適化し、例えばトナー画像担持体上に形成したトナー画像のトナー粒子間の非静電的付着力Ｆｔ（Ｎ）が、５×１０^-9Ｎ〜３×１０^-8Ｎの範囲にあるようにしたので、転写チリを低減し、トナー飛散や現像ムラ等の異常画像の発生を抑制して、高品質の画像を得ることができる。あるいはトナー帯電量を最適化し、例えばトナー画像担持体上でのトナーの平均帯電量の絶対値が１０〜３０μＣ／ｇであるようにしたので、転写チリが少なく、トナー飛散や現像ムラのない高品質の画像を得ることができる。
【００５８】
また、本実施例によれば、トナー画像担持体がトナー画像を一時的に担持する中間転写ベルトであり、その中間転写ベルトの抵抗値を最適化し、例えば中間転写ベルトの表面抵抗値が１０^８〜１０^１０ Ω／□であるようにしたので、小型の装置で、転写チリが少なく、残像などのない高品質のカラー画像を得ることができる。
【００５９】
【発明の効果】
以上説明したように、本発明のによれば、遠心分離法により粉体層最表面から粉体を分離するために必要な遠心力Ｆｓ（Ｎ）を測定し、試料面上の粉体層の単位面積当たりの付着量Ｍ（ｍｇ／ｃｍ²）及び粉体の平均帯電量Ｑ（μＣ／ｇ）の依存性から静電的な力の影響を分離できるので、粉体間の非静電的付着力Ｆｔ（Ｎ）を求めることができる。また、遠心分離法により粉体層最表面から粉体を分離するために必要な遠心力Ｆｓ（Ｎ）を測定し、試料面上の粉体層の厚さＨ（μｍ）及び粉体の平均帯電量Ｑ（μＣ／ｇ）の依存性から静電的な力の影響を分離できるので、粉体間の非静電的付着力Ｆｔ（Ｎ）を求めることができる。よって、トナーのような粉体間の非静電的付着力を定量的に測定できる粉体間付着力測定装置及び粉体間付着力測定方法を提供することができる。
【００６０】
また、本発明によれば、前記粉体間付着力測定装置及び粉体間付着力測定方法を用いて、トナー粒子間の非静電的付着力及びトナー画像担持体上でのトナー帯電量とトナー付着量の三つの特性値の関係を最適化できるので、転写チリの少ない高品質の画像を得ることができる。よって、トナー画像形成後のトナーの飛び散りを低減できる画像形成装置及び画像形成方法を提供することができる。
【図面の簡単な説明】
【図１】本発明の一実施例における粉体間付着力測定装置の構成図である。
【図２】本発明の一実施例における粉体間付着力測定装置における遠心分離装置の測定セルを示す斜視図である。
【図３】本発明の一実施例における粉体間付着力測定装置における遠心分離装置の一部断面図である。
【図４】本発明の一実施例における粉体間付着力測定方法の概略を示すフローチャートである。
【図５】本発明の一実施例における粉体間付着力測定装置及び粉体間付着力測定方法における遠心分離サンプル図である。
【図６】本発明の一実施例における粉体間付着力測定装置及び粉体間付着力測定方法におけるトナー部面積とトナー粒子数の相関を示す図である。
【図７】本発明の一実施例における粉体間付着力測定装置及び粉体間付着力測定方法におけるトナーａの遠心分離結果を示す図である。
【図８】本発明の一実施例における粉体間付着力測定装置及び粉体間付着力測定方法におけるトナーｂの遠心分離結果を示す図である。
【図９】本発明の一実施例における粉体間付着力測定装置及び粉体間付着力測定方法におけるトナーｃの遠心分離結果を示す図である。
【図１０】本発明の一実施例における粉体間付着力測定装置及び粉体間付着力測定方法における鏡像力モデルを示す図である。
【図１１】本発明の一実施例における粉体間付着力測定装置及び粉体間付着力測定方法における鏡像力モデルによる遠心力の解析結果を示す図である。
【図１２】本発明の一実施例における粉体間付着力測定装置及び粉体間付着力測定方法におけるトナー凝集度とトナー間付着力の相関を示す図である。
【図１３】本発明の一実施例における粉体間付着力測定装置及び粉体間付着力測定方法におけるトナー付着量と厚さの相関を示す図である。
【図１４】本発明の一実施例における粉体間付着力測定装置及び粉体間付着力測定方法における転写チリとトナー付着の相関（トナー帯電量の変化）を示す図である。
【図１５】本発明の一実施例における粉体間付着力測定装置及び粉体間付着力測定方法における転写チリとトナー付着の相関（トナー凝集度の変化）を示す図である。
【図１６】本発明の一実施例における粉体間付着力測定装置及び粉体間付着力測定方法におけるトナー凝集度とパラメータαの相関を示す図である。
【図１７】本発明の一実施例における画像形成装置の構成図である。
【符号の説明】
１ 測定セル
２ 試料基板
２ａ 試料面
３ 受け基板
３ａ 付着面
５ 遠心分離装置
６ ロータ
４１ ＣＰＵ
４８ 画像処理手段
４９ スキャナ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a powder-to-powder adhesion measuring device and a powder-to-powder adhesion measuring method for measuring the adhesion between toner particles, and an image forming apparatus and an image capable of preventing scattering of toner particles using them. It relates to a forming method.
[0002]
[Prior art]
In the field of handling powder, it is important to grasp various characteristic values of the powder. As a method for measuring the adhesion force of a powder, a method for estimating a force necessary for separating the powder from an object to which the powder is adhered is generally used. As a method for separating powder from an object, a method using centrifugal force, vibration, impact, air pressure, electric field, magnetic field or the like is known. Among them, the method using centrifugal force is easy to quantitatively measure, and discussed the contribution of electrostatic attraction and van der Waals force in the adhesion of toner to the photoreceptor and the carrier `` CJMastrangelo, Photogr.Sci.Eng. , 26: 194-197 (1982), discussing charge distribution in toner particles, which is important in toner adhesion to a photoreceptor, "MHLee and J. Ayala, J. Image. Tech., 11: 279-". 284 (1985) ”and“ Kazuo Terao, Kiyoshi Shigehiro: Journal of Electrophotographic Society, 34 (1995) 83 ”, which discussed non-electrostatic toner adhesion that is difficult to quantify, were announced. ing.
[0003]
Here, "M. Takeuchi, A. Onose, M. Anzai, R. Kojima and K. Kawai:" Proc. IS & T 7^th Int.Congress Adv.Non-Impact Printing Technology, 21991, vol.1, pp.200-208 "Measurement method of adhesion force of powder using centrifugal force (hereinafter referred to as centrifugal adhesion measurement) The method is referred to below. This centrifugal adhesion measuring method comprises a sample substrate to which powder is adhered, a receiving substrate to which powder separated from the sample substrate is adhered, and a spacer provided between the sample substrate and the receiving substrate. The measurement cell is placed in the rotor of the centrifuge, and the powder is separated from the sample substrate using the centrifugal force generated by the rotation of the rotor and attached to the receiving substrate. The image is taken into a computer, image processing is performed, the particle size of the powder is measured, the weight of the powder is obtained from the particle size and specific gravity of the powder, the weight of the powder and the rotation of the rotor In this method, the centrifugal force required for separation is calculated from the number to determine the adhesion force of each powder. As described above, there are many reports on the measurement of the adhesion between the powder and the flat surface, but there are few reports on the measurement of the adhesion between the powder.
[0004]
On the other hand, in the toner image transfer process used in the electrophotographic system, the toner particle group restrained by the electric field on the photosensitive member is moved to a uniform surface having no restraining force by a Coulomb force. There is a problem that it is easy. In addition, it is considered that the toner transferred onto the transfer body or the intermediate transfer body has a Coulomb repulsive force between the toner particles, which is one of the causes of the toner scattering after the transfer. Therefore, the adhesion force between the toner particles is an important characteristic value for the scattering of the toner. In particular, it is important to control non-electrostatic adhesion forces such as van der Waals force and liquid crosslinking force, and establishment of a method for quantitatively measuring the non-electrostatic adhesion forces is desired.
[0005]
Examples of this type of method include, for example, JP-A-2-282760, JP-A-5-333757, JP-A-6-167825, and JP-A-6-167826.
[0006]
[Problems to be solved by the invention]
In the above prior art, it is important to control the non-electrostatic adhesion between toner particles in the transfer process of a toner image used in an electrophotographic system, but non-electrostatic between powders such as toner is important. There has been a problem that a method for quantitatively and efficiently measuring the adhesive force has not been established.
[0007]
An object of the present invention is to improve such a problem and to measure a non-electrostatic adhesion force between powders such as toners quantitatively, and a method for measuring adhesion force between powders and a method for measuring adhesion force between powders Is to provide. Furthermore, another object of the present invention is to provide an image forming apparatus and an image forming method capable of reducing the scattering of toner after the toner image is formed by using the powder-to-powder adhesive force measuring apparatus and the inter-powder adhesive force measuring method. It is to provide.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an apparatus for measuring adhesion between powders according to the present invention is provided by separating a sample substrate having a sample surface on which a powder layer is formed by stacking powders in a thickness of a plurality of layers, from the powder layer. Centrifugal separation having a receiving substrate having an attachment surface to which the powder is adhered, a measurement cell comprising a spacer provided between the sample surface and the attachment surface, and a rotor for rotating the measurement cell An apparatus, an image acquisition means for acquiring an image of the powder adhered to the adhesion surface, an image of the powder obtained by the image acquisition means, and an analysis of the powder adhered on the receiving substrate From the relationship between the number and the projected area of the powder onto the receiving substrate, and the relationship between the number of the powder adhering to the adhesion surface obtained by the image processing means and the projected area, Adhered to the receiving substrate independently without adhering to each other Independent state determination means for determining the number of powders that can take the state and the projected area, and the relationship between the rotational speed of the rotor of the centrifugal separator and the projected area of the powder adhering to the receiving substrate, the individual powders are independent. From the rotor rotational speed determining means for determining the rotor rotational speed to be in the state, the average weight of the powder calculated from the average particle diameter and specific gravity of the powder adhered to the adhesion surface, and the rotational speed of the rotor An adhesion force deriving means for obtaining a centrifugal force necessary for separating the powder from the outermost surface of the powder layer formed on the surface; an adhesion amount per unit area of the powder layer on the sample surface; Non-electrostatic adhesion calculation means for calculating non-electrostatic adhesion force between powders using the average charge amount and the value of centrifugal force necessary to separate the powder from the outermost surface of the powder layer It is characterized by having.
[0009]
In order to achieve the above object, the inter-powder adhesion measuring method of the present invention creates a sample substrate having a sample surface on which a powder layer is formed by laminating powders in a thickness of a plurality of layers. A substrate creation step of creating a receiving substrate having an attachment surface to which the powder separated from the powder layer is attached; the sample substrate; the receiving substrate; a spacer provided between the sample surface and the attachment surface; A measurement cell creation step for creating a measurement cell comprising: a measurement cell installation step for installing the measurement cell in the rotor of a centrifuge having a rotor for rotating the measurement cell; and by rotation of the rotor A centrifugal separation step of separating the powder on the surface of the powder layer formed on the sample surface by centrifugal force and attaching the powder to the attachment surface; and taking out the measurement cell from the rotor to obtain the receiving substrate Receiving board acquisition worker And a powder number deriving step of obtaining an image of the powder adhering to the adhering surface and determining the number of powder adhering on the receiving substrate by analyzing the acquired image of the powder And by analyzing the image of the powder, a projection area deriving step for obtaining a projected area of the powder on the receiving substrate, and the relationship between the number of the powder adhering to the adhesion surface and the projection area, Independent state determination step for obtaining the number and projected area of powders that can take a state of being adhered to the receiving substrate independently without adhering to each other; the number of rotations of the rotor and the powder adhering to the receiving substrate From the relationship of the projected area of the body, the rotor rotational speed determination step for determining the rotor rotational speed at which each powder becomes an independent state, the average weight of the powder calculated from the average particle diameter and specific gravity of the powder, and the Based on the number of rotations of the rotor, the final powder layer formed on the sample surface An adhesion force deriving step for obtaining a centrifugal force required to separate the powder from the surface, an adhesion amount per unit area of the powder layer on the sample surface, an average charge amount of the powder, and a maximum powder layer And a non-electrostatic adhesive force calculating step for calculating a non-electrostatic adhesive force between the powders using a centrifugal force value necessary for separating the powder from the surface.
[0010]
  In order to achieve the above object, an image forming apparatus according to the present invention includes at least an electrostatic latent image carrier that carries an electrostatic latent image and an electrostatic latent image on the electrostatic latent image carrier according to image information. Forming means for forming an image; developing means for supplying a toner to the electrostatic latent image to make it visible; and a toner image carrier that carries the visualized toner image;SaidFt (N) is a non-electrostatic adhesion force between toner particles forming a toner image on the toner image carrier.Of the toner image carrierThe average value of the toner charge amount is Q (μC / g),Of the toner image carrierMaximum toner adhesion amount is M (mg / cm²), The following relational expression M⁴× Q²/ (Ft × 10⁹) ≦ 60, Q (μC / g), M (mg / cm ² And Ft (N) measured by the method for measuring adhesion between powders according to claim 6 and the surface resistance of the toner image carrier is set to a predetermined value.It is characterized by that.
[0011]
  In order to achieve the above object, the image forming method of the present invention irradiates at least a uniformly charged electrostatic latent image carrier with light in accordance with image information, and the image is formed on the electrostatic latent image carrier. An electrostatic latent image forming step for forming and supporting an electrostatic latent image, and a developing step for supplying toner to the electrostatic latent image to make it visible and supporting the visualized toner image on a toner image carrier AndToner image carrierNon-electrostatic adhesion force between toner particles forming a toner image of Ft (N),Of the toner image carrierThe average value of the toner charge amount is Q (μC / g),Of the toner image carrierMaximum toner adhesion amount is M (mg / cm²), The following relational expression M⁴× Q²/ (Ft × 10⁹) ≦ 60Q (μC / g), M (mg / cm) ² And Ft (N) measured by the method for measuring adhesion between powders according to claim 6 and the surface resistance of the toner image carrier is set to a predetermined value, and the developing step is executed. DoIt is characterized by that.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
<< Embodiment of the above-mentioned powder adhesion measuring apparatus and powder adhesion measuring method >> The powder adhesion measuring apparatus of this embodiment controls the entire apparatus as shown in FIG. CPU 41 for controlling the process of the inter-adhesion force measurement method, the centrifugal separator 5 used for measuring the inter-powder adhesion force such as toner, the interface 43, the CRT, and the like. In order to store the display means 44 for displaying the analysis results, the input means 45 such as a keyboard and a mouse, the memory 46 storing the control program of the CPU 41 and necessary data, the measurement data by the centrifugal separation device 42 and the analysis results thereof. An external storage device 47, a scanner 49 and an interface 50 for taking in an image of the powder observed and photographed by an optical microscope, a CCD camera, etc. An image for analyzing the image of the powder taken in via the channel 49 and determining the number of powders adhering to the receiving substrate 3 described later and the projected area of the powder on the receiving substrate 3 It has processing means 48 and the like. Further, as shown in FIG. 2, the centrifugal separator 5 includes a rotor 6 and a holding member 7 that rotate the measurement cell 1 shown in FIG. 3. The rotor 6 has a hole shape in a cross section perpendicular to the rotation center axis of the rotor 6 and has a sample installation portion 8 that supports the holding member 7 so as to be fitted. The holding member 7 includes a rod-like portion 7a and a cell holding portion 7b that holds the measurement cell 1 provided on the rod-like portion 7a.
[0013]
  With such a configuration, in the method for measuring adhesion between powders of this example,CPU41By controlling this, the non-electrostatic adhesion force between the powders such as toner is measured by the procedure shown in FIG. That is, a sample substrate 2 having a sample surface 2a formed by stacking powders in a thickness of a plurality of layers or more is prepared, and a receiving substrate 3 having an attachment surface to which the powder separated from the sample substrate 2 is attached is prepared. A measuring cell 1 comprising a receiving substrate creating step 101, a sample substrate 2, a receiving substrate 3, and a spacer 4 provided between a sample surface 2a of the sample substrate 2 and an attachment surface 3a of the receiving substrate 3 is provided. Measurement cell creation step 102 to be created, measurement cell placement step 103 for placing the measurement cell 1 in the rotor 6 of the centrifugal separator 5 having the rotor 6 for rotating the measurement cell 1, and rotation of the rotor 6 of the centrifugal separator 5 A centrifugal separation step 104 in which the powder on the surface of the powder layer formed on the sample surface 2 a is separated by the centrifugal force generated by the sample and attached to the attachment surface 3 a of the receiving substrate 3, and the measurement cell 1 is connected to the rotor 6 of the centrifugal separator 5. Take out from The receiving substrate obtaining step 105 for obtaining the receiving substrate 3 and the image of the powder adhering to the adhering surface 3a of the receiving substrate 3 are observed and photographed with an optical microscope or CCD camera (not shown), and the image is scanned by the scanner. 49, a powder number deriving step 106 for obtaining the number of powders adhered to the receiving substrate 3 by analyzing the acquired image using the image processing means 48, and a powder receiving substrate. 3, the projected area deriving step 107 for obtaining the projected area on the adhesion surface 3 a, and the relationship between the number of powders adhered to the adhesion surface 3 a of the receiving substrate 3 and the projection area, the individual powders are not adhered to each other independently. Independent state determination step 108 for obtaining the number of powders that can be attached to the receiving substrate 3 and the projected area, the number of rotations of the rotor 6 of the centrifugal separator 5 and the amount of powder that has adhered to the receiving substrate 3. Due to the projected area, it becomes independent The powder formed on the sample surface from the rotor rotational speed determination step 109 for determining the rotational speed of the rotor 6, the average weight of the powder calculated from the average particle diameter and specific gravity of the powder, and the rotational speed of the rotor 6 Adhesion force deriving step 110 for obtaining a centrifugal force necessary for separating the powder from the outermost surface of the body layer, and the adhesion amount per unit area of the powder layer on the sample surface (or the powder on the sample surface Thickness), the average charge of the powder, and the non-electrostatic adhesion force that calculates the non-electrostatic adhesion force between the powders from the centrifugal force required to separate the powder from the outermost surface of the powder layer And a calculation step 111.
[0014]
The measurement cell installation step 103 is executed by removing the rotor 6 of the centrifugal separator 5 and installing the measurement cell 1 in the removed rotor 6. Further, the centrifugal separation step 104 changes the rotational speed of the rotor 6 of the centrifugal separator 5 with respect to the same sample substrate 2, so that the powder adhering to the sample substrate 2 is exchanged at each rotational speed. It is executed by attaching to the attachment surface 3a. 1 to 3 as described above, the measurement cell installation step 103 includes a holding step for holding the measurement cell 1 by the cell holding portion 7b of the holding member 7, and a holding step. The member 7 is fitted to the sample setting portion 8, and the perpendicular of the sample surface 2 a of the sample substrate 2 and the perpendicular of the attachment surface 3 a of the receiving substrate 3 are both perpendicular to the rotation center axis of the rotor 6 of the centrifuge 5. The holding member 7 is installed in the rotor 6 of the centrifuge device 5 so that the sample surface 2a of the sample substrate 2 is located between the adhesion surface 3a of the receiving substrate 3 and the rotation center axis of the rotor 6 of the centrifuge device 5. Therefore, a large centrifugal force can be applied to the measurement cell 1 using the rotor 6.
[0015]
In this embodiment, the centrifugal force F received by the powder is determined by using the weight m of the powder, the rotation speed f (rpm) of the rotor, and the distance r from the central axis of the rotor to the powder adhesion surface of the sample substrate. It calculates | requires by following Formula (4).
F = m × r × (2πf / 60)²            (4)
Further, the weight m of the powder is obtained from the following equation (5) using the true specific gravity ρ and the equivalent circle diameter d of the powder.
[0016]
m = (π / 6) × ρ × d^Three            (5)
Further, the centrifugal force F received by the powder is obtained from the following equation (6) from the equations (1) and (2) described later.
F = (π^Three/ 5400) × ρ × d^Three× r × f²          (6)
When the toner layer on the sample surface is to be separated by centrifugal separation, the toner on the outermost surface of the toner layer includes centrifugal force due to rotation, non-electrostatic adhesion to other toners, and coulomb with other toners. The repulsive force and the image power with the sample surface are working. Here, when it is desired to measure the non-electrostatic adhesion force between toners, it is necessary to remove the influence of electrostatic force such as Coulomb repulsion force and mirror image force. In this example, the adhesion amount M per unit area of the powder layer on the sample surface (mg / cm²), When the average charge amount of the powder is Q (μC / g), and the centrifugal force required to separate the powder from the outermost surface of the powder layer is Fs (N), the adhesion amount M and / or the charge amount Centrifugal force Fs is obtained for a plurality of samples having different Qs, and non-electrostatic adhesion force Ft (N) between powders is calculated from the following relational expression (1). However, A is a constant.
[0017]
Ft = Fs−A × (Q / M)²          (1)
In addition, the thickness of the powder layer on the sample surface is H (μm), the average charge amount of the powder is Q (μC / g), and the centrifugal force necessary to separate the powder from the outermost surface of the powder layer is When Fs (N) is used, the centrifugal force Fs is obtained for a plurality of samples having different thicknesses H and / or charge amounts Q, and the non-electrostatic adhesion force between the powders is obtained from the following relational expression (2). Ft (N) is calculated. However, B is a constant.
[0018]
Ft = Fs−B × (Q / H)²          (2)
As the centrifugal separator 5, CP100α (maximum rotational speed: 100,000 rpm, maximum centrifugal acceleration: 800,000 × g) manufactured by Hitachi Koki Co., Ltd. was used. Moreover, the rotor 6 used Hitachi Koki angle rotor P100AT. The sample substrate 2, the receiving substrate 3, the spacer 4 and the holding member 7 are strong enough to withstand the large centrifugal force of the centrifugal separator 5, and can be rotated up to the maximum rotational speed of the centrifugal separator 5 when installed in the rotor 6. Since it is necessary to use a lightweight material that is less than or equal to a certain weight, an aluminum member was used. Further, it is desirable that the attachment surface 3a of the receiving substrate 3 be a smooth surface without any scratches, on which aluminum is deposited. By eliminating the scratches on the adhesion surface 3a, it is possible to prevent the scratches on the receiving substrate 3 from being measured during the toner particle measurement screen processing. Further, any sample surface 2a of the sample substrate 2 can be used as long as it can form a powder layer to be measured. The powder to be measured may be dropped from above on any sample surface, but in order to form a powder layer with a uniform thickness, the powder layer is applied by applying electrophotography. It is desirable to form. In particular, when the measurement target is toner, it is necessary to prepare a sample in a state where it is desired to actually measure the adhesion force between the toners. For example, when it is desired to measure the adhesion between toners of the toner image on the photoreceptor after the development process, it is desirable to use a sheet-like photoreceptor as the sample surface 2a. Further, when it is desired to measure the state after receiving the nip pressure or the like in the transfer process, it is desirable to attach actual paper, an OHP sheet, or the like to the sample substrate 2 as the sample surface 2a.
[0019]
Hereinafter, a more specific method for measuring the adhesion between powders will be described. In this embodiment, a Ricoh digital full-color copying machine PRETER650 is used for forming the toner layer. Also, three types of toners with different additives (H2000 silica) added based on the PRETER650 toner were prepared. Table 1 shows the measurement results of the degree of aggregation of various toners.
[0020]
◎
[Table 1]

[0021]
The toner aggregation degree C was measured by the following method using a powder tester PT-N type manufactured by Hosokawa Micron. Three types of meshes are attached to the powder tester (fluid opening, upper 75 μm, middle 45 μm, lower 22 μm), and a toner sample is placed on the 2 g upper mesh and vibrated for 30 seconds with an amplitude scale of 1 mm. The degree of toner aggregation is calculated from the weight of the toner remaining on each mesh by the following equation.
[0022]
◎
[Expression 1]

[0023]
The degree of toner aggregation shown here is a characteristic value indicating the fluidity of the toner. The smaller the value, the more the fluidity tends to improve. Various toners and a carrier of a two-component developer for PRETER 650 were mixed to obtain a developer. Image forming conditions such as charge potential and exposure amount were set for various developers, and a circular toner image having a diameter of 3 mm was formed on the intermediate transfer belt. Further, the intermediate transfer belt was cut out and bonded onto a circular aluminum substrate as shown in FIG. Since the toner layer formed on the sample surface (a part of the intermediate transfer belt) 2a of the sample substrate (aluminum substrate) 2 is charged, the Coulomb repulsive force between the toner particles and the mirror image force with the substrate are working. Conceivable. In order to consider the influence of these forces, the toner charge amount Q (μC / g) and the toner adhesion amount M (mg / cm) on the intermediate transfer belt for each toner type.²A plurality of sample surfaces 2a with varying) were prepared. The toner charge amount Q and the toner adhesion amount M were measured by a suction type Faraday cage method on a toner image having a known area. The sample substrate 2 thus prepared is mounted on the holding member 7, and the holding member 7 is set on the rotor 6 and the rotor 6 is set on the centrifuge 5.
[0024]
Further, when the centrifugal separator 5 is operated, the toner particles are separated from the surface of the toner layer by centrifugal force, and adhere to the receiving substrate 3 (diameter main body: 8 mm, toner receiving range: 5.2 mm). The centrifugal force F received by the toner can be obtained from the above equation (6). D: toner particle diameter, ρ: toner specific gravity 1.2 g / cm^Three, R: centrifugal radius 64.47 mm, f: separation rotation speed rpm.
[0025]
F = (π^Three/ 5400) × ρ × d^Three× r × f²          (6)
In this embodiment, since the number of toners separated from the sample substrate 2 is relatively large, as an efficient evaluation method, the particle size of each toner on the receiving substrate 3 is not measured, and the average particle size d = 7.5 μm. Therefore, a method of counting only the number of toner particles was adopted. That is, the central portion of the adhesion surface 3a of the receiving substrate 3 was enlarged and observed with a CCD microscope camera (Hypermicroscope manufactured by Keyence Corporation), and output with a video printer. When a 200x lens is used, the magnification is 77 times on the video print, and 1.4mm wide x 1.1mm long = 1.54mm on one screen.²Can be observed. The enlarged photograph is taken into a personal computer (on the powder adhesion measuring apparatus main body side) in a 400 dpi × 400 dpi black-and-white photography mode using a scanner 49, and 2 using an image processing means 48 (image processing software (Image Pro Plus)). A valuation process and a counting process were performed, and the number of toner particles and the number of pixels occupied by the toner particle portion, that is, the projected area of the toner on the receiving substrate 3 were counted.
[0026]
Further, the rotational speed f at which the outermost toner particles in the central portion of the toner layer began to be separated was determined by the method described later, and the centrifugal force F required to separate the toner was determined from Equation (6). The problem with the centrifugal separation of the toner layer is the large number of toners handled. When the number of toner particles on the adhesion surface 3a is counted by the image processing software, when the number of toners increases, a plurality of toner particles overlap to be counted as one large particle. Therefore, in this embodiment, a method of determining the separation rotation speed using not the number of toner particles but the total area (projected area) occupied by the toner particle portion is employed.
[0027]
Here, FIG. 6 shows the relationship between the number of toner particles on the adhesion surface 3a and the projected area of the toner portion (number of pixels for image processing) for all samples measured in this example. The number of pixels of the toner part in one video print is 1 × 10^FiveUp to about the number of pixels, a linear relationship is established between the number of pixels and the number of toner particles. This means that each toner particle is adhered independently up to about 1000 toners. In contrast, the number of pixels in the toner portion is 2 × 10.^FiveIf the number of toner particles exceeds 1, the number of toner particles is saturated at about 1800. This means that when the number of toners is about 1800 or more, the toner particles overlap on the adhesion surface 3a. That is, in this embodiment, in the independent state determination step 108, the number of toners on the receiving substrate 3 is 1800 or the number of pixels in the toner portion is 2 × 10.^FiveThe number is determined to be the maximum number that the toner particles can be in an independent state. In this state, it is considered that the toner particles are not separated but the toner particles are separated independently. As an evaluation standard for the independent state in this embodiment, the toner that started to separate from the surface layer of the toner layer with the increase of the centrifugal force accumulated, and 1800 (number of pixels: 2 × 10)^FiveThe number of revolutions at the time of flying was determined as the separation revolution number f. The number of pixels in the entire area of the video print screen is about 2.4 × 10.⁶Therefore, about 8% of the surface layer toner is in a separated state. In this state, the toner particles are considered to be separated independently.
[0028]
Here, with respect to the three types of toners a, b, and c in this embodiment, changes in the number of separated toners with respect to the number of centrifugal revolutions are shown in FIGS. The horizontal axis represents the centrifugal rotation speed (rpm), and the vertical axis represents the cumulative number of toner portion pixels in logarithm. The number of pixels determined in the independent state determination step 108 is 2 × 10^FiveEach position is indicated by an arrow. Table 2 shows the toner charge amount Q (μC / g) and the toner adhesion amount M (mg / cm) on the sample surface 2a under each condition.²) Measurement results are shown.
[0029]
◎
[Table 2]

[0030]
For each of the above conditions, the cumulative number of pixels is 2 × 10^FiveThe number of rotor rotations to be separated was determined as the separation rotation number f, and the centrifugal force F was calculated using the formula (6) with the toner particle size of 7.5 μm. The centrifugal force F is a force necessary for separating the toner particles on the surface layer, and reflects the influence of both electrostatic force and non-electrostatic adhesion force acting between the toner particles. The calculation result of the centrifugal force F is shown in Table 3. For any toner, the centrifugal force F for separating the toner increases as the toner charge amount Q increases, and the centrifugal force F tends to decrease as the toner adhesion amount M increases.
[0031]
◎
[Table 3]

[0032]
In the present embodiment, a non-electrostatic adhesion force between toner particles is determined by considering and analyzing a model of an adhesion state by a mirror image force as shown in FIG. Assuming that a point charge exists at the center of the toner particles on the surface layer, only the image force with the substrate acting on this point charge is considered. The point charge q is proportional to the toner charge amount Q (μC / g), and the distance h between the substrate and the point charge is the toner adhesion amount M (mg / cm²). Therefore, the mirror image force F acting on the point charge is F∝ (q / h)²∝ [Q / M]²Is proportional to The calculation results are also shown in Table 3.
[0033]
Here, the result of arranging the centrifugal force based on the analysis method using the image force model according to the present embodiment is shown in FIG. The vertical axis is the centrifugal force Fs at which the surface toner starts to separate, and the horizontal axis is [Q / M].²The calculated value of is shown. [Q / M]²The value of is considered to be proportional to the image force, but its absolute value itself has no meaning. Although there is variation in each toner, a linear increasing tendency is recognized. Thereby, it is considered that the centrifugal force when the horizontal axis is extrapolated to zero represents the adhesion force Ft between non-electrostatic toner particles. That is, the following relational expression (7) is established. However, A is a constant.
[0034]
Fs = Ft + A × (Q / M)²          (7)
Further, FIG. 12 shows a correlation between the adhesion force Ft between the non-electrostatic toner particles and the toner aggregation degree. It was quantitatively confirmed that the toner aggregation degree was increased and the non-electrostatic toner adhesion force was increased as the amount of the external additive added to the toner decreased.
Instead of the toner adhesion amount M, the thickness H of the toner layer was measured. The toner layer thickness H was measured using a surface shape measuring microscope VF7500 manufactured by Keyence Corporation. FIG. 13 shows the correlation between the toner adhesion amount M and the toner layer thickness H. A proportional relationship is established between the two. Therefore, equation (8) was established in the same manner as equation (7), and Ft could be measured. However, B is a constant.
[0035]
Fs = Ft + B × (Q / H)²          (8)
As a result of further examination of the present embodiment, toner scattering in the transfer process described above, so-called transfer dust phenomenon, is caused by three factors, namely, toner charge amount and toner adhesion amount, and adhesion force between toners measured by the method of this embodiment. We found that it can be described with characteristic values. The more transfer dust, the greater the number of toner particles that can be seen in the non-image area between the lines. The transfer dust level was evaluated from the number of toners scattered in the non-image area. In this example, a 200 μm wide line-shaped toner image on the intermediate transfer belt was taken with a CCD microscope camera, and the enlarged photograph was taken as a monochrome continuous tone image from the scanner 49 to a personal computer. Using commercially available image processing software, the continuous tone photographic image was binarized to emphasize and separate the contours of the toner particle portion and the belt portion. The number of toner particle portions (number of objects) was counted using the counting function of the image processing software, and the number of toner particles scattered from the line edge per 1 mm length was calculated. This value was defined as “number of line scattered toner N (pieces / mm)”. Further, the toner charge amount Q and the toner adhesion amount M on the intermediate transfer belt were measured by a suction type Faraday cage method, and a 200 μm width line image was sucked and collected by a known length. The charge amount of the toner per unit weight is calculated from the induced charge amount q and weight m of the collected toner, and is expressed as an average toner charge amount Q (μC / g). Further, the average value of the line width is obtained from the enlarged photograph of the line image, the area a of the line image is calculated, and the toner weight per unit area is expressed as the toner adhesion amount M (mg / cm²).
[0036]
Here, FIG. 14 shows a correlation between the number N of scattered toner on the intermediate transfer belt and the toner adhesion amount M on the intermediate transfer belt. M = 0.8 to 1.0 mg / cm²When the amount of toner adhesion was relatively small, a magenta toner single-color image was used. When the amount of toner adhesion was larger than that, a two-color superimposed image in which magenta toner was superimposed on cyan toner was used. Further, the toner a described above was used as the toner. Further, developers with three types of carriers that differ only in charging ability were prepared, and the toner charge amount Q on the intermediate transfer belt was changed as a parameter. The charging ability of the carrier was controlled by changing the firing temperature during the production process. Carrier A, carrier B, and carrier C were used in descending order of charging ability. In FIG. 14, the number N of scattered toner is abruptly increased as the toner adhesion amount M is increased. Further, the larger the toner charge amount Q, the larger the number N of scattered toner. According to the study of the present inventors, the level that transfer dust is practically acceptable is 130 toner / mm of line scattering toner on the intermediate transfer belt. When the toner charge amount is large, the toner adhesion amount on the intermediate transfer belt must be reduced. That is, the image forming conditions must be set so that the toner adhesion amount is reduced at the portion where the toner adhesion amount is the largest in the image area on the intermediate transfer belt. On the contrary, if the toner charge amount is reduced, even if the maximum toner adhesion amount on the intermediate transfer belt is large, it is acceptable. The three curves in FIG. 14 are “N = αM^FourQ²+ Β ”, which is the same when α = 0.28 and β = 18. The experimental result of transfer dust with respect to this characteristic and the toner adhesion amount M and the toner charge amount Q are in good agreement. Similarly, FIG. 15 shows the results of using the three types of toners a, b, and c with different amounts of external additives and changing the toner aggregation degree or the adhesion force between the toners as parameters.
[0037]
Also in FIG. 15, the increase in the number N of scattered toner with the increase in the toner adhesion amount M is the same. Further, the number of scattered toners tends to decrease as the degree of toner aggregation or the adhesion between toners increases as the amount of external additive decreases. The three curves in FIG. 15 also show “N = αM^FourQ²In the toner a, α = 0.28, β = 18, the toner b is α = 0.12, β = 14, the toner c is α = 0.08, and β = 10. This characteristic agrees well with the experimental results of transcription dust.
[0038]
Further, FIG. 16 shows the relationship between the non-electrostatic adhesion force Ft between the toner particles obtained in FIG. 12 and the parameter α obtained from FIG. The curve in the figure is α = 1.8 / Ft (the unit of Ft in FIG. 16 is nN = 10^-9N), which is almost in agreement with the experimental results. The details of the transfer dust generation mechanism are not clear, but the line scattering is caused by changes in three parameters of non-electrostatic adhesion force Ft (N) between toner particles, toner adhesion amount M, and toner charge amount Q. The number of toners N was experimentally found to be in good agreement with the following empirical formula.
[0039]
N = 1.8M^FourQ²/ (Ft × 10⁹) + Β (β is about 10-20) (9)
As described above, since the number N of line scattering toners that can be practically accepted is about 130 / mm or less, β is set to 10 to 20,
N-β = 1.8M^FourQ²/ (Ft × 10⁹) <= 110-120 (10)
It becomes. Therefore, if an image forming condition that satisfies the following relational expression (3) is set for the portion of the image area on the intermediate transfer belt where the toner amount is the largest, an image with less transfer dust can be obtained.
[0040]
M^FourQ²/ (Ft × 10⁹) ≦ 60 (3)
In the relational expression (3), the non-electrostatic adhesion force Ft between toner particles is 5 × 10.^-9N-3x10^-8A range of N is preferable. Ft is 5 × 10^-9If it is smaller than N, in order to satisfy the relational expression (3), it is necessary to make the toner adhesion amount M or the toner charge amount Q very small. A decrease in the toner adhesion amount M at the portion where the toner is the most on the intermediate transfer belt results in an insufficient image density, and a decrease in the toner charge amount Q overlaps with a decrease in the toner aggregation degree to cause problems such as toner scattering. On the other hand, Ft is 3 × 10^-8If it is larger than N, the number of scattered toner on the transfer dust decreases and the number N of toner decreases. However, problems such as deterioration of toner image granularity during development and transportability deterioration during toner replenishment occur. .
[0041]
In the relational expression (3), the absolute value of the toner charge amount on the intermediate transfer belt is preferably in the range of 10 to 30 μC / g. When the absolute value of the toner charge amount is smaller than 10 μC / g, the number of scattered toner is reduced with respect to transfer dust, but problems such as toner scattering and transfer failure occur. On the contrary, when the absolute value of the toner charge amount is larger than 30 μC / g, the transferability becomes insufficient.
[0042]
  Furthermore, in this embodiment, the surface resistance value of the intermediate transfer belt is 10⁸-10¹⁰ Ω / □It is preferable that The surface resistance value is 10⁸ Ω / □If it is smaller than the range, the transfer voltage leaks, and transfer failure occurs. Conversely, the surface resistance value is 10¹⁰ Ω / □Is greater than the negative potential, the negative potential is held in the non-image portion of the intermediate transfer belt after the belt transfer process. Therefore, there is a drawback that a static elimination value is required to remove this residual potential. However, this charge retention in the non-image area is effective in reducing transfer dust on the intermediate transfer belt. That is, between the toner particles forming the image on the intermediate transfer belt, the Coulomb repulsive force acts between the negative charges of the toner to cause toner scattering, but when the negative charge is held in the non-image portion, It is considered that the Coulomb repulsive force acts between the negative charge of the non-image area and the toner charge to suppress transfer dust. In such a case, it is not always necessary to satisfy the relation (3) for reducing transfer dust. In other words, the relational expression (3) is for the intermediate transfer belt.The surface resistance value is 10 ¹⁰ Ω / □This is particularly effective in the following cases.
[0043]
<< First Example of Image Forming Apparatus and Image Forming Method >> Next, a color image forming apparatus to which the measurement result of the above-described adhesion between powders measurement method is applied will be described with reference to FIG. In this embodiment, four color developing devices are arranged side by side so as to face one photoconductor, and toner images formed for different color components on the photoconductor are sequentially superimposed and transferred onto the intermediate transfer belt. In addition, a one-drum intermediate transfer body system is used in which a color image is obtained by transferring the superimposed toner images onto transfer paper or the like.
[0044]
In FIG. 17, a photosensitive drum 35 (= electrostatic latent image carrier) has a function-separated type photosensitive layer formed on an aluminum base tube in the order of an undercoat layer, a charge generation layer, and a charge transport layer. . The photosensitive layer has a thickness of about 28 μm and a capacitance of about 90 pF / cm.²It is. In this embodiment, the photosensitive drum 35 is uniformly negatively charged (about −650 to −700 V) by the scorotron charger 21, and then the exposure unit 22 is irradiated with laser light corresponding to the image information to obtain −100 V to −100 V. A 500V electrostatic latent image is formed. It is also possible to detect the charging potential of the photosensitive member or the exposure portion potential by the potential sensor A23 and control the charging conditions, the exposure conditions, and the like. That is, the forming means for forming the electrostatic latent image includes the scorotron charger 21, the exposure unit 22, the potential sensor A23, and the like.
[0045]
The developing unit 24 (= developing means) is provided with four color developing devices arranged to develop an electrostatic latent image for each color. This is a reversal development method in which a negatively charged toner is attached to a low potential portion on a photoreceptor using a dry two-component developer. The dry two-component developer comprises a pulverized toner having an average particle diameter of 7.5 μm and a resin-coated carrier having an average particle diameter of 50 μm, and the charge amount of the toner in the developer was −10 to −30 μC / g. To the toner, 0.2 to 0.8 parts by weight of silica fine particles are added as an external additive. In this embodiment, the developing bias value is about −500 to −550V. An AC component may be superimposed on the developing bias. A P sensor 25 is installed at a position after development, and the process condition can be controlled by detecting the toner adhesion amount from the optical reflectance.
[0046]
  The toner images of the respective colors are transferred onto the intermediate transfer belt 26 (= toner image carrier). A transfer voltage indirect application method is employed, and a belt portion stretched between the entrance roller 32 and the exit roller 33 is configured to be able to contact and separate from the photoreceptor. The intermediate transfer belt 26 is a single-layer medium resistor in which carbon black is dispersed in polycarbonate resin or fluorine resin, and has a thickness of about 150 μm and a surface resistance value of 10⁸-10¹⁰ Ω / □The volume resistance value is 10⁹-10¹¹The thing of the range of ohm-cm was used. Further, the entrance roller 32 is grounded, and a transfer voltage (Vt) of about +1000 to +1500 V is applied to the exit roller 33. The transfer voltage (Vt) is supplied from a power source (not shown), and the output value is controlled by a control unit (not shown). Hereinafter, the transfer from the photosensitive member onto the intermediate transfer belt 26 is referred to as “belt transfer”. The residual toner on the photoconductor after the belt transfer is controlled by a PCC (pre-cleaning charger) 27 and removed by a drum cleaning device 29 with a brush and a blade.
[0047]
In this embodiment, after the first color toner image is formed on the intermediate transfer belt 26, the second color image forming operation is started, and the second color toner image is transferred onto the intermediate transfer belt 26 in an overlapping manner. At this time, the transfer voltage may be increased for each transfer order. In the case of a full-color image, four color toner images of black, cyan, magenta, and yellow are sequentially formed on the intermediate transfer belt 26 and then transferred onto the recording paper 34 at a time. To transfer the toner image from the intermediate transfer belt 26 to the recording paper 34, a positive polarity voltage is applied from the back side of the paper by the paper transfer roller 31. Hereinafter, the transfer from the intermediate transfer belt 26 onto the recording paper 34 is referred to as “paper transfer”. The toner remaining on the intermediate transfer belt 26 after the paper transfer is removed by a cleaning device 28.
[0048]
  << Second Embodiment of Image Forming Apparatus and Image Forming Method >> The configuration of the image forming apparatus of the present embodiment is substantially the same as that of the first embodiment (FIG. 17), but an intermediate transfer belt as will be described later. 26, the surface resistance value is 10⁹ Ω / □,Volume resistance value is 10¹⁰A single-layer medium resistor of Ωcm was used. In this embodiment, the non-electrostatic adhesion force Ft between toner particles measured by the method for measuring adhesion between powders is 8 × 10.^-9Using the toner a which becomes N, the transfer dust quality in the final image was visually determined for the blue line portion in which two colors of cyan and magenta were overlaid. In this way, the two-color superimposed color portion increases the amount of toner adhesion before the paper transfer process, that is, on the intermediate transfer belt 26, and the transfer dust increases. If the transfer dust can be reduced in the portion where the toner adhesion amount is maximum on the intermediate transfer belt 26, the transfer dust is surely reduced even in the portion where the toner adhesion amount is smaller than this. The intermediate transfer belt 26 has a surface resistance value of 10 in which carbon black is dispersed in ethylene-tetra-fluoroethylene (ETFE) resin.⁹ Ω / □The volume resistance value is 10¹⁰It is a single-layer medium resistor of Ωcm, and the belt transfer bias value is +1200 V for both the first color and the second color. The toner charge amount in the developer was about −30 μC / g for both cyan and magenta. The average value Q of the toner charge amount on the intermediate transfer belt 26 after the belt transfer process was −17.7 μC / g. At this time, the number of scattered toner in the line is the result of the ● plot in FIG. 14, and the toner adhesion amount M on the intermediate transfer belt is 1.1 mg / cm.²In the following, “M⁴Q²/ (Ft × 10⁹) ≦ 60 ”was established, and transfer dust was at an acceptable level. Other problems did not occur.
[0049]
For comparison with the present embodiment, in the result of the ● plot in FIG. 14, the toner adhesion amount M on the intermediate transfer belt 26 is 1.2 mg / cm.²In this case, the relational expression “M^FourQ²/ (Ft × 10⁹) ≦ 60 ”was not established, and transfer dust was not noticeably acceptable.
<< Third Embodiment of Image Forming Apparatus and Image Forming Method >> The configuration of the image forming apparatus of the present embodiment is substantially the same as that of the first embodiment (FIG. 17). In this embodiment, the non-electrostatic adhesion force Ft between toner particles measured by the method for measuring adhesion between powders is 2 × 10.^-8Toner c to be N was used. The toner charge amount in the developer was about −28 μC / g for both cyan and magenta. The average value Q of the toner charge amount on the intermediate transfer belt 26 after the belt transfer process was −17.4 μC / g. At this time, the number N of scattered toner in the line is the result of the Δ plot in FIG.²In the following, the relational expression “M^FourQ²/ (Ft × 10⁹) ≦ 60 ”was established, and transfer dust was at an acceptable level. Other problems did not occur.
[0050]
<< Fourth Embodiment of Image Forming Apparatus and Image Forming Method >> The configuration of the image forming apparatus of the present embodiment is substantially the same as that of the first embodiment (FIG. 17). In this embodiment, as in the third embodiment, the non-electrostatic adhesion force Ft between the toner particles is 2 × 10.^-8Toner c to be N was used. Further, the toner charge amount was increased by lowering the toner concentration in the developer. The toner charge amount in the developer was about −40 μC / g for both cyan and magenta. The toner charge amount Q on the intermediate transfer belt 26 after the belt transfer process was −31 μC / g outside the range of the present embodiment. At this time, the toner adhesion amount M on the intermediate transfer belt 26 is 1.00 mg / cm.²Then, the relational expression “M^FourQ²/ (Ft × 10⁹) ≦ 60 ”was established, and transfer dust was at an acceptable level. However, since the toner charge amount on the intermediate transfer belt 26 is too large, transfer failure occurred in the paper transfer process.
[0051]
<< Fifth Embodiment of Image Forming Apparatus and Image Forming Method >> The configuration of the image forming apparatus of the present embodiment is substantially the same as that of the first embodiment (FIG. 17). In this example, image formation was performed in the same manner as in the fourth example, using toner d having an additive additive amount of 1.0 part by weight. The non-electrostatic adhesion Ft between toner particles measured by the method for measuring adhesion between powders is 4 × 10.^-9N, which is out of the range of this example. The toner charge amount in the developer was about −15 μC / g for both cyan and magenta. The average value Q of the toner charge amount on the intermediate transfer belt 26 after the belt transfer process was −11.5 μC / g. At this time, the toner adhesion amount M on the intermediate transfer belt 26 is 1.1 mg / cm.²Then, the relational expression “M^FourQ²/ (Ft × 10⁹) ≦ 60 ”was established, and transfer dust was at an acceptable level. However, toner scattering from the developing device occurred.
[0052]
<< Sixth Embodiment of Image Forming Apparatus and Image Forming Method >> The configuration of the image forming apparatus of the present embodiment is substantially the same as that of the first embodiment (FIG. 17). In this example, image formation was performed in the same manner as in the fourth example using the carrier A and the toner e with no external additive added. The non-electrostatic adhesion Ft between toner particles measured by the method for measuring adhesion between powders is 4 × 10.^-8N, which is outside the scope of this embodiment. The toner charge amount in the developer was about −25 μC / g for both cyan and magenta. The average value Q of the toner charge amount on the intermediate transfer belt 26 after the belt transfer process was −16 μC / g. The toner adhesion amount M on the intermediate transfer belt 26 is 1.5 mg / cm.²Then, the relational expression “M^FourQ²/ (Ft × 10⁹) ≦ 60 ”was established, and transfer dust was at an acceptable level. However, the graininess of the dot image after development deteriorated.
[0053]
  << Seventh Embodiment of Image Forming Apparatus and Image Forming Method >> The configuration of the image forming apparatus of the present embodiment is substantially the same as that of the first embodiment (FIG. 17). The surface resistance value obtained by dispersing carbon black in the resin is 10⁸ Ω / □,Volume resistance value is 10¹¹A single-layer medium resistor of Ωcm was used. As a result, the toner charge amount in the developer was about −30 μC / g for both cyan and magenta. The average value Q of the toner charge amount on the intermediate transfer belt 26 after the belt transfer process was −17.7 μC / g. The toner adhesion amount M on the intermediate transfer belt 26 is 1.0 mg / cm.²Then, the relational expression “M⁴Q²/ (Ft × 10⁹) ≦ 60 ”was established, and transfer dust was at an acceptable level. There was no residual charge on the intermediate transfer belt 26, and the neutralization device for the intermediate transfer belt 26 could be omitted. Other problems did not occur.
[0054]
<< Eighth Embodiment of the Image Forming Apparatus and Image Forming Method >> The configuration of the image forming apparatus of this embodiment is substantially the same as that of the first embodiment (FIG. 17), but the surface of the intermediate transfer belt 26 is arranged. A high resistance layer of about 20 μm was provided. The surface layer is obtained by dispersing titanium oxide in PVdF resin, and the surface resistance is 10¹³Ωcm. The belt transfer bias value was set to +1600 V during cyan transfer of the first color and +2000 V during magenta transfer of the second color. Further, toner a was used as a developer. The toner charge amount in the developer was about −24 μC / g for both cyan and magenta. The toner charge amount Q on the intermediate transfer belt 26 after the belt transfer step is −14.0 μC / g, and the toner adhesion amount M is 1.37 mg / cm.²Then, the relational expression “M^FourQ²/ (Ft × 10⁹) ≦ 60 ”is not satisfied, but the number N of scattered toner on the intermediate transfer belt 26 is only about 50, and the transfer dust is an acceptable level. This is considered that the negative charge on the non-image portion on the intermediate transfer belt 26 suppresses toner scattering. However, due to the negative charge, an afterimage due to transfer unevenness occurred in the next image forming process.
[0055]
According to this example, the centrifugal force Fs (N) required to separate the powder from the outermost surface of the powder layer is measured by the centrifugal separation method, and the amount of adhesion per unit area of the powder layer on the sample surface M (mg / cm²) And the dependence of the average charge amount Q (μC / g) of the powder, the influence of the electrostatic force can be separated, and the non-electrostatic adhesion force Ft (N) between the powders can be obtained. In addition, the centrifugal force Fs (N) required to separate the powder from the outermost surface of the powder layer is measured by a centrifugal separation method, and the thickness H (μm) of the powder layer on the sample surface and the average of the powder Since the influence of electrostatic force can be separated from the dependency of the charge amount Q (μC / g), the non-electrostatic adhesion force Ft (N) between the powders can be obtained.
[0056]
Further, according to the present example, the step of forming a powder layer by stacking a plurality of powders on the sample substrate 2 to form a powder layer formed an electrostatic latent image by an electrophotographic development process. Since the powder layer is formed on the sheet-like sample substrate 2, a uniform powder layer can be formed. Furthermore, the process of forming a powder layer by stacking a plurality of layers of powder on the sample substrate 2 is performed on the powder image carrier on which an electrostatic latent image is formed by an electrophotographic development process. After the powder layer is formed, the powder image is transferred onto the sheet-like sample substrate by an electrophotographic transfer process, so the powder layer can be formed with a simple structure and with high accuracy. Non-electrostatic adhesion can be measured. That is, the non-electrostatic adhesion force between powders such as toner can be measured quantitatively and efficiently.
[0057]
Further, according to the present embodiment, the relationship between the three electrostatic property values of the non-electrostatic adhesion force between the toner particles and the toner charge amount and the toner adhesion amount on the toner image carrier can be optimized. A few high quality images can be obtained. Further, the non-electrostatic adhesion force between the toner particles on the toner image carrier is optimized. For example, the non-electrostatic adhesion force Ft (N) between the toner particles of the toner image formed on the toner image carrier is obtained. 5 × 10^-9N-3x10^-8Since it is in the range of N, it is possible to reduce transfer dust and suppress the occurrence of abnormal images such as toner scattering and development unevenness, thereby obtaining a high-quality image. Alternatively, the toner charge amount is optimized so that, for example, the absolute value of the average charge amount of the toner on the toner image bearing member is 10 to 30 μC / g. A quality image can be obtained.
[0058]
  Further, according to this embodiment, the toner image carrier is an intermediate transfer belt that temporarily carries a toner image, and the resistance value of the intermediate transfer belt is optimized. For example, the surface resistance value of the intermediate transfer belt is 10⁸-10¹⁰ Ω / □Therefore, it is possible to obtain a high-quality color image with little transfer dust and no afterimage with a small apparatus.
[0059]
【The invention's effect】
As described above, according to the present invention, the centrifugal force Fs (N) required for separating the powder from the outermost surface of the powder layer is measured by the centrifugal separation method, and the powder layer on the sample surface is measured. Amount of adhesion per unit area M (mg / cm²) And the dependence of the average charge amount Q (μC / g) of the powder, the influence of the electrostatic force can be separated, and the non-electrostatic adhesion force Ft (N) between the powders can be obtained. In addition, the centrifugal force Fs (N) required to separate the powder from the outermost surface of the powder layer is measured by a centrifugal separation method, and the thickness H (μm) of the powder layer on the sample surface and the average of the powder Since the influence of electrostatic force can be separated from the dependency of the charge amount Q (μC / g), the non-electrostatic adhesion force Ft (N) between the powders can be obtained. Therefore, it is possible to provide a powder-to-powder adhesion measuring apparatus and a powder-to-powder adhesion measuring method that can quantitatively measure non-electrostatic adhesion between powders such as toner.
[0060]
In addition, according to the present invention, the non-electrostatic adhesion force between the toner particles and the toner charge amount on the toner image carrier can be obtained using the powder adhesion force measuring device and the powder adhesion measurement method. Since the relationship between the three characteristic values of the toner adhesion amount can be optimized, a high-quality image with little transfer dust can be obtained. Therefore, it is possible to provide an image forming apparatus and an image forming method that can reduce scattering of toner after toner image formation.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an apparatus for measuring adhesion between powders in one embodiment of the present invention.
FIG. 2 is a perspective view showing a measurement cell of a centrifugal separator in an apparatus for measuring adhesion between powders in one embodiment of the present invention.
FIG. 3 is a partial cross-sectional view of a centrifugal separator in the apparatus for measuring adhesion between powders in one embodiment of the present invention.
FIG. 4 is a flowchart showing an outline of a method for measuring adhesion between powders in one embodiment of the present invention.
FIG. 5 is a sample of a centrifugal separation in a powder adhesion measuring apparatus and a powder adhesion measurement method according to an embodiment of the present invention.
FIG. 6 is a diagram showing a correlation between the toner area and the number of toner particles in the inter-powder adhesion measuring device and the inter-powder adhesion measuring method according to an embodiment of the present invention.
FIG. 7 is a diagram illustrating a result of centrifugal separation of toner a in the powder-to-powder adhesion measuring apparatus and the powder-to-powder adhesion measuring method according to an embodiment of the present invention.
FIG. 8 is a diagram showing a result of centrifugal separation of toner b in an apparatus for measuring adhesion between powders and a method for measuring adhesion between powders in one example of the present invention.
FIG. 9 is a diagram showing a result of centrifugal separation of toner c in an apparatus for measuring adhesion between powders and a method for measuring adhesion between powders in one example of the present invention.
FIG. 10 is a diagram showing an image force model in the inter-powder adhesion measuring device and the inter-powder adhesion measuring method in one embodiment of the present invention.
FIG. 11 is a diagram showing the analysis result of the centrifugal force by the mirror image force model in the inter-powder adhesion measuring apparatus and the inter-powder adhesion measuring method in one embodiment of the present invention.
FIG. 12 is a diagram showing a correlation between a toner aggregation degree and an adhesion force between toners in a powder adhesion force measuring device and a powder adhesion force measurement method according to an embodiment of the present invention.
FIG. 13 is a diagram showing the correlation between the toner adhesion amount and the thickness in the inter-powder adhesion measuring apparatus and the inter-powder adhesion measuring method in one embodiment of the present invention.
FIG. 14 is a diagram showing a correlation (change in toner charge amount) between transfer dust and toner adhesion in an inter-powder adhesion measuring apparatus and inter-powder adhesion measuring method according to an embodiment of the present invention.
FIG. 15 is a diagram showing a correlation (change in toner aggregation degree) between transfer dust and toner adhesion in an apparatus for measuring adhesion between powders and a method for measuring adhesion between powders in one example of the present invention.
FIG. 16 is a diagram showing a correlation between a toner aggregation degree and a parameter α in the inter-powder adhesion measuring apparatus and the inter-powder adhesion measuring method according to an embodiment of the present invention.
FIG. 17 is a configuration diagram of an image forming apparatus according to an embodiment of the present invention.
[Explanation of symbols]
1 Measurement cell
2 Sample substrate
2a Sample surface
3 receiving substrate
3a Adhering surface
5 Centrifugal separator
6 Rotor
41 CPU
48 Image processing means
49 Scanner

Claims (12)

A sample substrate having a sample surface on which a powder layer in which a plurality of layers of powder are stacked to form a thickness is formed, a receiving substrate having an attachment surface to which powder separated from the powder layer is attached, and the sample surface and A centrifuge having a measurement cell composed of a spacer provided between the adhesion surface and a rotor for rotating the measurement cell;
Image acquisition means for acquiring an image of the powder adhered to the adhesion surface;
Image processing means for analyzing the image of the powder acquired by the image acquisition means, and determining the number of powders adhering on the receiving substrate and the projected area of the powder on the receiving substrate; ,
From the relationship between the number of powders adhering to the adhesion surface determined by the image processing means and the projected area,
Independent state determination means for obtaining the number and projected area of powders that can take a state of being independently adhered on the receiving substrate without being adhered to each other;
From the relationship between the rotor rotational speed of the centrifugal separator and the projected area of the powder adhered on the receiving substrate, the rotor rotational speed determining means for determining the rotor rotational speed at which each powder is in an independent state;
The powder is separated from the outermost surface of the powder layer formed on the sample surface from the average weight of the powder calculated from the average particle diameter and specific gravity of the powder adhered to the adhesion surface and the rotational speed of the rotor. An adhesion force deriving means for obtaining a centrifugal force necessary to
Using the adhesion amount per unit area of the powder layer on the sample surface, the average charge amount of the powder, and the value of the centrifugal force necessary to separate the powder from the outermost surface of the powder layer, Non-electrostatic adhesive force calculating means for calculating the non-electrostatic adhesive force between,
A device for measuring the adhesion between powders. The non-electrostatic adhesion force calculating means includes an adhesion amount M (mg / cm ² ) per unit area of the powder layer on the sample surface, an average charge amount of the powder Q (μC / g), and a powder When the centrifugal force required to separate the powder from the outermost layer is Fs (N) and the constant is A, the centrifugal force Fs is obtained for a plurality of samples having different adhesion amounts M and charge amounts Q. , The following relational expression
Ft = Fs−A × (Q / M) ²
The non-electrostatic adhesion force Ft (N) between powders is calculated from the powder. A sample substrate having a sample surface on which a powder layer in which a plurality of layers of powder are stacked to form a thickness is formed, a receiving substrate having an attachment surface to which powder separated from the powder layer is attached, and the sample surface and A centrifuge having a measurement cell composed of a spacer provided between the adhesion surface and a rotor for rotating the measurement cell;
Image acquisition means for acquiring an image of the powder adhered to the adhesion surface;
Image processing means for analyzing the image of the powder acquired by the image acquisition means, and determining the number of powders adhering on the receiving substrate and the projected area of the powder on the receiving substrate; ,
From the relationship between the number of powders adhering to the adhesion surface determined by the image processing means and the projected area,
Independent state determination means for obtaining the number and projected area of powders that can take a state of being independently adhered on the receiving substrate without being adhered to each other;
From the relationship between the rotor rotational speed of the centrifugal separator and the projected area of the powder adhered on the receiving substrate, the rotor rotational speed determining means for determining the rotor rotational speed at which each powder is in an independent state;
The powder is separated from the outermost surface of the powder layer formed on the sample surface from the average weight of the powder calculated from the average particle diameter and specific gravity of the powder adhered to the adhesion surface and the rotational speed of the rotor. An adhesion force deriving means for obtaining a centrifugal force necessary to
Using the thickness of the powder layer on the sample surface, the average charge amount of the powder, and the value of the centrifugal force necessary to separate the powder from the outermost surface of the powder layer, A non-electrostatic adhesive force calculating means for calculating the electric adhesive force;
A device for measuring the adhesion between powders. The non-electrostatic adhesion force calculating means is configured such that the thickness of the powder layer on the sample surface is H (μm), the average charge amount Q (μC / g) of the powder, and the powder from the outermost surface of the powder layer. When the centrifugal force required for separation is Fs (N) and the constant is B, the centrifugal force Fs is obtained for a plurality of samples having different thicknesses H and charge amounts Q, and the following relational expression is obtained.
Ft = Fs−B × (Q / H) ²
The non-electrostatic adhesion force Ft (N) between the powders is calculated from the above. Create a sample substrate having a sample surface on which a powder layer is formed by laminating powder in multiple layers or more,
A substrate creating step of creating a receiving substrate having an attachment surface to which the powder separated from the powder layer is attached;
A measurement cell creating step of creating a measurement cell composed of the sample substrate, the receiving substrate, and a spacer provided between the sample surface and the adhesion surface;
A measurement cell installation step of installing the measurement cell in the rotor of a centrifuge having a rotor for rotating the measurement cell;
A centrifugal separation step of separating the powder on the surface of the powder layer formed on the sample surface by the centrifugal force caused by the rotation of the rotor and attaching the powder to the adhesion surface;
A receiving substrate acquisition step of taking out the measurement cell from the rotor and acquiring the receiving substrate;
Obtaining an image of the powder adhering to the adhering surface, and analyzing the obtained image of the powder to obtain the number of powders adhering on the receiving substrate,
By analyzing the powder image, a projected area deriving step for obtaining a projected area of the powder on the receiving substrate;
From the relationship between the number of powders adhering to the adhering surface and the projected area, the number of powders and the projected area that can take the state of individual powders adhering to the receiving substrate independently without adhering to each other are obtained. A state determination process;
From the relationship between the rotational speed of the rotor and the projected area of the powder adhering to the receiving substrate, a rotor rotational speed determination step for determining the rotor rotational speed at which each powder is in an independent state;
Necessary for separating the powder from the outermost surface of the powder layer formed on the sample surface from the average weight of the powder calculated from the average particle diameter and specific gravity of the powder and the rotational speed of the rotor. Adhesive force derivation process for obtaining centrifugal force;
Using the adhesion amount per unit area of the powder layer on the sample surface, the average charge amount of the powder, and the value of the centrifugal force necessary to separate the powder from the outermost surface of the powder layer, A non-electrostatic adhesive force calculating step for calculating a non-electrostatic adhesive force between,
A method for measuring the adhesion between powders, comprising: In the non-electrostatic adhesion calculation step, the amount of adhesion M (mg / cm ² ) per unit area of the powder layer on the sample surface, the average charge amount of the powder Q (μC / g), powder When the centrifugal force required to separate the powder from the outermost layer is Fs (N) and the constant is A, the centrifugal force Fs is obtained for a plurality of samples having different adhesion amounts M and charge amounts Q. , The following relational expression
Ft = Fs−A × (Q / M) ²
The non-electrostatic adhesion force Ft (N) between the powders is calculated from the powder. Create a sample substrate having a sample surface on which a powder layer is formed by laminating powder in multiple layers or more,
A substrate creating step of creating a receiving substrate having an attachment surface to which the powder separated from the powder layer is attached;
A measurement cell creating step of creating a measurement cell composed of the sample substrate, the receiving substrate, and a spacer provided between the sample surface and the adhesion surface;
A measurement cell installation step of installing the measurement cell in the rotor of a centrifuge having a rotor for rotating the measurement cell;
A centrifugal separation step of separating the powder on the surface of the powder layer formed on the sample surface by the centrifugal force caused by the rotation of the rotor and attaching the powder to the adhesion surface;
A receiving substrate acquisition step of taking out the measurement cell from the rotor and acquiring the receiving substrate;
Obtaining an image of the powder adhering to the adhering surface, and analyzing the obtained image of the powder to obtain the number of powders adhering on the receiving substrate,
By analyzing the powder image, a projected area deriving step for obtaining a projected area of the powder on the receiving substrate;
From the relationship between the number of powders adhering to the adhering surface and the projected area, the number of powders and the projected area that can take the state of individual powders adhering to the receiving substrate independently without adhering to each other are obtained. A state determination process;
From the relationship between the rotational speed of the rotor and the projected area of the powder adhering to the receiving substrate, a rotor rotational speed determination step for determining the rotor rotational speed at which each powder is in an independent state;
Necessary for separating the powder from the outermost surface of the powder layer formed on the sample surface from the average weight of the powder calculated from the average particle diameter and specific gravity of the powder and the rotational speed of the rotor. Adhesive force derivation process for obtaining centrifugal force;
Using the thickness of the powder layer on the sample surface, the average charge amount of the powder, and the value of the centrifugal force necessary to separate the powder from the outermost surface of the powder layer, A non-electrostatic adhesive force calculating step for calculating electric adhesive force;
A method for measuring the adhesion between powders, comprising: In the non-electrostatic adhesive force calculating step, the thickness of the powder layer on the sample surface is H (μm), the average charge amount Q (μC / g) of the powder, and the powder is removed from the outermost surface of the powder layer. When the centrifugal force required for separation is Fs (N) and the constant is B, the centrifugal force Fs is obtained for a plurality of samples having different thicknesses H and charge amounts Q, and the following relational expression is obtained.
Ft = Fs−B × (Q / H) ²
The non-electrostatic adhesion force Ft (N) between powders is calculated from the above, The method for measuring the adhesion force between powders according to claim 7. At least an electrostatic latent image carrier that carries an electrostatic latent image, a forming unit that forms an electrostatic latent image on the electrostatic latent image carrier in accordance with image information, and a toner supply to the electrostatic latent image Development means for visualizing the toner, and a toner image carrier that carries the visualized toner image,
The non-electrostatic adhesion force between the toner particles forming the toner image of the toner image carrier Ft (N), the average value of the toner charge amount of the toner image bearing member Q (μC / g), the toner image When the maximum toner adhesion amount on the carrier is M (mg / cm ² ), the following relational expression
M ⁴ × Q ² / (Ft × 10 ⁹ ) ≦ 60
The Q (μC / g), the M (mg / cm ² ), and the Ft (N) value measured by the method for measuring the adhesion between powders according to claim 6 are set so as to satisfy An image forming apparatus, wherein the surface resistance of the image carrier is set to a predetermined value . Use a toner whose non-electrostatic adhesion force Ft (N) between toner particles of a toner image formed on the toner image carrier is in the range of 5 × 10 ⁻⁹ N to 3 × 10 ⁻⁸ N. The image forming apparatus according to claim 9. An electrostatic latent image forming step of irradiating at least a uniformly charged electrostatic latent image carrier in accordance with image information to form and carry an electrostatic latent image on the electrostatic latent image carrier; A developing process for supplying toner to the electrostatic latent image to visualize it, and carrying the visualized toner image on a toner image carrier,
The non-electrostatic adhesion force between the toner particles forming the toner image of the toner image carrier Ft (N), the average value of the toner charge amount of the toner image bearing Q (μC / g), the toner image bearing When the maximum toner adhesion amount on the body is M (mg / cm ² ), the following relational expression
M ⁴ × Q ² / (Ft × 10 ⁹ ) ≦ 60
The Q (μC / g), the M (mg / cm ² ), and the Ft (N) value measured by the method for measuring the adhesion between powders according to claim 6 are set so as to satisfy An image forming method , wherein the developing step is executed by setting a surface resistance of an image carrier to a predetermined value . The non-electrostatic adhesion force Ft (N) between toner particles of a toner image formed on the toner image carrier is in the range of 5 × 10 ⁻⁹ N to 3 × 10 ⁻⁸ N. Item 12. The image forming method according to Item 11.

Images