JP2004109687A - Method and apparatus for forming image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method and image forming apparatus capable of obtaining a high quality image with excellent fixability for a long period of time by preventing a belt-shaped fixing member from being smeared with a wax and suppressing decrease in image gross to prevent a deterioration in image quality even when an oilless toner containing wax is used to perform fixing by a heating-cooling-and-peeling type fixing method. <P>SOLUTION: In this image forming method and image forming apparatus, a toner image is fixed on a recording medium by heating, pressing and then cooling the recording medium supporting the transferred toner image and belt-shaped fixing member which are overlapped, and thereafter peeling the recording medium from the belt-shaped fixing member. The toner contains at least a binding resin, a coloring matter and wax. The belt-shaped fixing member has a surface layer wherein a wax single body contained in the toner is melted at 140°C and an advancing contact angle after hardening at room temperature is 50 degrees or more. <P>COPYRIGHT: (C)2004,JPO

Description

【００２４】
（式中、Ｒ^１０は、非置換又は置換の一価炭化水素基、ｘは１以上の整数、ａ，ｅはそれぞれ０又は１、ｂ，ｄはそれぞれ１〜４の整数、ｃは０〜８の整数である。）
（Ｂ）１分子中に２個以上の≡ＳｉＨ基を含有し、上記フルオロカーボンシロキサンゴム組成物中の脂肪族不飽和基量に対して上記≡ＳｉＨ基の含有量が１〜４倍モル量であるオルガノポリシロキサン及び／又はフルオロカーボンシロキサン、
（Ｃ）充填剤、
（Ｄ）有効量の触媒。
【００２５】
（１１）トナー像が転写された記録媒体とベルト状定着部材を重ねた状態で加熱及び加圧し、冷却した後に前記記録媒体をベルト状定着部材から剥離することにより、前記トナー像を前記記録媒体に定着させる定着手段を有する画像形成装置において、
前記トナーは、結着樹脂、着色剤、及びワックスを少なくとも含有しており、前記ベルト状定着部材は、前記トナーの含有するワックス単体を１４０℃で溶融、室温固化後の前進接触角が５０度以上を示す表面層を有することを特徴とする画像形成装置。
【００２６】
【発明の実施の形態】
以下、本発明を詳細に説明する。
本発明の画像形成方法は、結着樹脂、着色剤、及びワックスを少なくとも含有したトナーを用い、トナー像が転写された記録媒体とベルト状定着部材を重ねた状態で加熱及び加圧し、冷却した後に記録媒体をベルト状定着部材から剥離することにより、トナー像を記録媒体に定着させる定着工程を有し、この加熱後冷却剥離方式の定着工程で用いるベルト状定着部材として、前記トナーの含有するワックス単体を１４０℃で溶融、室温固化後の前進接触角が５０度以上を示す表面層（以下、「前進接触角が５０度以上の表面層」ということがある）を有するものを用いることを特徴とする。
【００２７】
このような加熱後冷却剥離方式の定着工程においては、トナーに含まれるワックスは、加熱されることでトナーの結着樹脂より先に溶融し、ベルト状定着部材表面に付着する。そして、冷却されると、溶融して付着した当該ワックスは固化される。この際、ワックスが溶融して、濡れ性よくベルト状定着部材表面に付着してしまうと、ワックスは固化した後、ベルト状定着部材表面から剥離され難くなり残留することとなり、一方、ワックスが溶融して、濡れ性が悪くベルト状定着部材表面に付着すると、ワックスは固化した後、ベルト状定着部材表面から容易に剥離され残留しなくなると考えられる。そこで、本発明では、ワックスを含むトナーを用い、且つ上述の加熱後冷却剥離方式の定着工程のようなベルト状定着部材の表面でワックスが溶融・固化されるシステムにおいても、前進接触角が５０度以上の表面層を有するベルト状定着部材を用いることで、ベルト状定着部材表面に溶融したワックスを濡れ性が良く付着させることなく、ワックスが固化した後、ベルト状定着部材表面に残留させることなく綺麗に剥離させて、長期に渡り、紙粉、トナーの外添剤などのが付着せず、ベルト状定着部材の表面性の変化を防止する。
【００２８】
ベルト状定着部材は、その表面（表面層）がとして、前記トナーの含有するワックス単体を１４０℃で溶融、室温固化後の前進接触角が５０度以上を示すが、好ましくは、５５度以上であり、より好ましくは６０度以上である。この前進接触角が、５０度を下回ると、ワックスが溶融したときに、濡れ性よくベルト状定着部材表面に付着してしまい、ワックスが固化した後、ベルト状部材表面から剥離され難く残留することとなり、紙粉、トナーの外添剤などが、付着、混入し、ベルト状定着部材の表面性が経時的に変化してしまう。
【００２９】
ここで、前進接触角の測定方法を次に記載する。評価用のワックスの塊は、ワックスの粉体をＰＴＦＥ（ポリテトラフルオロエチレン）板上に散布し、１４０℃で３０分、加熱、冷却後に半球状となった１個の重量が５±２ｍｇのものを選別。アルミニウムの平板に表面層材料を３０〜２００μｍ形成した評価サンプルを準備。前記評価サンプルの表面に前記ワックスの塊の半球状の面が評価サンプルの表面に向くように置く。恒温槽に入れ、室温から１４０℃まで１時間程度で昇温。当該温度で１時間保持。加熱源を切り、当該温度より室温まで２時間程度で降温。評価サンプルに対する前進接触角を残した半球状のワックスの塊を得る。これを接触角計（ＦＡＣＥ　ＣＡ−Ｘ型：協和界面科学株式会社製）により、５つの評価サンプルで接触角を測定し、得られる５点の平均値を、評価サンプルとワックスの示す前進接触角の値として用いている。なお、室温固化後と１４０℃での前進接触角は、大差無く、傾向も変わらないことを確認している。下記表１に、代表的な表面層構成材料種とワックス種との前進接触角の値を示す。
【００３０】
【表１】

【００３１】
―ベルト状定着部材―
ベルト状定着部材は、例えば、ベース層と、ベース層上に形成される一定の層厚を有する表面層と、からなる。また、ベース層と表面層の間に接着層を設けてもよい。ベルト状定着部材の形態は、画像形成装置に適したベルト形状であればよく、特に無端ベルトが好適である。
【００３２】
ベース層は、耐熱性及び機械的強度が要求され、ニッケル、アルミニウム、ステンレス等の金属シートや、ＰＥＴ、ＰＢＴ、ポリイミド、ポリイミドアミド等の樹脂フィルムを用いることができる。前記樹脂は導電性粉体などを添加分散して、体積抵抗率を制御されていてもよく、カーボンブラックを添加分散して、体積抵抗率を制御した無端ベルト状のポリイミドベルトを使用することもできる。さらに、長尺のポリイミドシートの両端部をパズル上に組合せ、熱圧着部材を用いて熱圧着し、無端ベルト状に仕立てたものを使用することもできる。
【００３３】
ベース層の厚みは、２０〜２００μｍの範囲が好ましく、より好ましくは３０〜１５０μｍの範囲、さらに好ましくは４０〜１３０μｍの範囲が適している。ベース層の厚みが２０μｍより薄いと、加熱冷却時の寸法安定性や、強度が不足する。２００μｍを越えると、ベルト状定着部材の比熱が増大して熱移動量が低下し、転写速度やサイクルタイムの低下につながる。
【００３４】
接着層としては、シリコーンゴムの接着に通常使用されるプライマー類などを適用できる。プライマー類としては、例えば、アミノシラン系カップリング剤、クロロシラン系カップリング剤、クロロメチルシラン系カップリング剤、シアノシラン系カップリング剤、チタン酸エステル系カップリング剤などが挙げられるが、これらに限定されるものではない。これらの中で、アミノシラン系カップリング剤及びチタン酸エステル系カップリング剤が好ましく用いられる。さらには、フルオロカーボンシロキサンゴムのように設計されたプライマーも好ましく用いられる。
【００３５】
表面層としては、表面が上記前進接触角が５０度以上となる材料を含んで構成されていれば、特に制限はいが、例えば、フルオロカーボンシロキサンゴムを含んで構成されるゴム層（以下、フルオロカーボンシロキサンゴム層ということがある）が好適に挙げられる。また、表面層は複数層から構成されていてもよく、例えば、２層構成の場合、シリコーンゴムを含んで構成されるゴム層（以下、シリコーンゴム層ということがある）と、当該ゴム層上に設けられるフルオロカーボンシロキサンゴムを含んで構成されるゴム層と、の構成が好適に挙げられる。
【００３６】
フルオロカーボンシロキサンゴム層を構成するフルオロカーボンシロキサンゴムは、主鎖にパーフルオロアルキルエーテル基及び／又はパーフルオロアルキル基を有するものが好ましい。
【００３７】
特に、フルオロカーボンシロキサンゴム層としては、（Ａ）下記一般式（１）のフルオロカーボンシロキサンを主成分とし、脂肪族不飽和基を有するフルオロカーボンポリマー、（Ｂ）１分子中に２個以上の≡ＳｉＨ基を含有し、上記フルオロカーボンシロキサンゴム組成物中の脂肪族不飽和基量に対して上記≡ＳｉＨ基の含有量が１〜４倍モル量であるオルガノポリシロキサン及び／又はフルオロカーボンシロキサン、（Ｃ）充填剤、（Ｄ）有効量の触媒を含有するフルオロカーボンシロキサンゴム前駆体組成物の硬化物で構成されてなることが好ましい。
【００３８】
この場合、（Ａ）成分のフルオロカーボンポリマーは、下記一般式（１）で示される繰り返し単位を有するフルオロカーボンシロキサンを主成分とし、脂肪族不飽和基を有するものである。この脂肪族不飽和基は、一価の脂肪族不飽和炭化水素基であり、好ましくは炭素数２〜３であり、具体的にはビニル基、アリル基、エチニル基等の炭素数２〜３のアルケニル基が例示され、特にビニル基が好適である。この場合、脂肪族不飽和基は分子鎖末端にあることが好ましく、例えばビニルジアルキルシリル基、ジビニルアルキルシリル基、トリビニルシリル基を主鎖に有することが好ましい。なお、この場合のアルキル基は炭素数１〜８、特にメチル基が好ましい。
【００３９】
【化３】

【００４０】
ここで、上記式（１）において、Ｒ^１０は非置換又は置換の好ましくは炭素数１〜８の一価炭化水素基であり、好ましくは炭素数１〜８のアルキル基又は炭素数２〜３のアルケニル基であり、特にメチル基であることが好ましい。ａ，ｅはそれぞれ０又は１、ｂ，ｄはそれぞれ１〜４の整数、ｃは０〜８の整数である。また、ｘは１以上の整数、好ましくは１０〜３０である。このような（Ａ）成分としては、下記式（２）で示すものを挙げることができる。
【００４１】
【化４】

【００４２】
（Ｂ）成分は、１分子中に２個以上の≡ＳｉＨ基を含有し、この≡ＳｉＨ基がフルオロカーボンシロキサン組成物中の脂肪族不飽和基量の１〜４倍モル量であるオルガノポリシロキサン及び／又はフルオロカーボンである。
【００４３】
ここで、≡ＳｉＨ基を有するオルガノポリシロキサンとしては、ケイ素原子に結合した水素原子を分子中に少なくとも２個有するオルガノハイドロジェンポリシロキサンを挙げることができる。
【００４４】
また、本発明で用いるフルオロカーボンシロキサンゴム組成物においては、（Ａ）成分のフルオロカーボンポリマーが脂肪族不飽和基を有するものであるときには、硬化剤として上述したオルガノハイドロジェンポリシロキサンを使用することができる。即ち、この場合には、フルオロカーボンシロキサン中の脂肪族不飽和基と、オルガノハイドロジェンポリシロキサン中のケイ素原子に結合した水素原子との間で生ずる付加反応によって硬化物が形成されるものである。このようなオルガノハイドロジェンポリシロキサンとしては、付加硬化型のシリコーンゴム組成物に使用される種々のオルガノハイドロジェンポリシロキサンを使用することができるが、本発明においては特に下記（α）、（β）のものが好適に使用される。
（α）下記式（３）〜（５）で表されるオルガノハイドロジェンポリシロキサン、
【００４５】
【化５】

【００４６】
上記式中、ｓ及びｔは０以上の整数、ｕは２以上の整数である。また、Ｒ^２は、脂肪族不飽和結合を有しない非置換又は置換の一価炭化水素基であり、炭素数が１〜１２、より望ましくは１〜８のものが好ましく、具体的にはメチル基，エチル基，イソプロピル基，ブチル基等のアルキル基、シクロヘキシル基，シクロペンチル基等のシクロアルキル基、フェニル基，トリル基，キシリル基等のアリール基、ベンジル基，フェニルエチル基等のアラルキル基、クロロメチル基，クロロプロピル基，クロロシクロヘキシル基，３，３，３−トリフルオロプロピル基等のハロゲン化炭化水素基、２−シアノエチル基等のシアノ炭化水素基等が例示される。このうち特に好ましいのは、メチル基、エチル基、フェニル基、３，３，３−トリフルオロプロピル基である。Ｒ^４はケイ素原子と含フッ素有機基Ｒｆとの間に介在する二価の基であり、脂肪族不飽和結合を有しない二価の炭化水素基又は一般式−Ｒ^５−Ｏ−Ｒ^６−（但し、Ｒ^５及びＲ^６は脂肪族不飽和結合を有しない二価の炭化水素基である）で表されるエーテル基を有する二価の炭化水素基であり、これらは炭素数１〜８のものが好ましい。具体的には下記に示すものが挙げられる。
【００４７】
【化６】

【００４８】
なお、Ｒ^４のうちで特に好適な基は、−ＣＨ_２ＣＨ_２−，−ＣＨ_２ＣＨ_２ＣＨ_２−，−ＣＨ_２ＣＨ_２ＣＨ_２−Ｏ−ＣＨ_２−である。Ｒ_ｆはパーフルオロアルキル基又はパーフルオロアルキルエーテル基である。パーフルオロアルキル基としては式Ｃ_ｐＦ_２ｐ＋１（但し、ｐは４〜１０の整数である）で表されるものが例示され、特に好適な基はＣ_６Ｆ_１３−，Ｃ_８Ｆ_１７−，Ｃ_１０Ｆ_２１−である。パーフルオロアルキルエーテル基としては特に炭素数が５〜１５のものが好ましく、具体的には下記のものが例示される。
【００４９】
【化７】

【００５０】
（β）下記式（６）で示される（ＣＨ_３）_２ＨＳｉＯ_０．５単位とＳｉＯ_２単位とからなる共重合体。
【００５１】
【化８】

【００５２】
なお、これらのオルガノハイドロジェンポリシロキサンの２５℃における粘度は、通常、１，０００ｃＳｔ以下であることが好ましい。上述したオルガノハイドロジェンポリシロキサンは、一般にその≡ＳｉＨ基の数が、（Ａ）成分のフルオロカーボンシロキサン中の脂肪族不飽和炭化水素基１個に対して、少なくとも１個、特に１〜５個となるような割合で配合することが好適である。
【００５３】
また、≡ＳｉＨ基を有するフルオロカーボンとしては、上記式（１）の単位又は式（１）においてＲ^１０がジアルキルハイドロジェンシロキシ基であり、かつ末端がジアルキルハイドロジェンシロキシ基又はシリル基等のＳｉＨ基であるものが好ましく、下記式（７）で示すものを挙げることができる。
【００５４】
【化９】

【００５５】
（Ｃ）成分の充填剤としては、一般的なシリコーンゴム組成物に使用されている種々の充填剤を用いることができる。例えば、煙霧質シリカ、沈降性シリカ、カーボン粉末、二酸化チタン、酸化アルミニウム、石英粉末、タルク、セリサイト及びベントナイト等の補強性充填剤、アスベスト、ガラス繊維、有機繊維等の繊維質充填剤などを例示することができる。
【００５６】
これらの充填剤は、（Ａ）成分１００部（重量部、以下同じ）に対して０．１〜３００部、特に１〜２００部の割合で配合されることが好適である。この充填剤の配合量が０．１部未満の場合には、十分な補強効果を得ることができず、また３００部を超える割合で配合された場合には、硬化物の機械的強度が低下するという不都合を生じるおそれがある。
【００５７】
（Ｄ）成分の触媒としては、付加反応用触媒として公知とされている塩化白金酸、アルコール変性塩化白金酸、塩化白金酸とオレフィンとの錯体、白金黒又はパラジウムをアルミナ、シリカ、カーボンなどの担体に担持したもの、ロジウムとオレフィンとの錯体、クロロトリス（トリフェニルフォスフィン）ロジウム（ウィルキンソン触媒）、ロジウム（ＩＩＩ）アセチルアセトネートなどのような周期律表第ＶＩＩＩ族元素又はその化合物が例示されるが、これらの錯体はアルコール系、エーテル系、炭化水素などの溶剤に溶解して用いることが好ましい。これらの白金族金属系触媒の配合量は、触媒の有効量であればよいが、通常、（Ａ）成分１００部に対して、白金族金属換算で１〜５００ｐｐｍ、特に５〜２０ｐｐｍの割合で使用することが好ましい。
【００５８】
フルオロカーボンシロキサンゴム前駆体組成物においては、耐溶剤性を向上させるという本発明の目的を損なわない範囲において、種々の配合剤を添加することができる。例えば、ジフェニルシランジオール、低重合度の分子鎖末端水酸基封鎖ジメチルポリシロキサン、ヘキサメチルジシラザン等の分散剤、酸化第一鉄、酸化第二鉄、酸化セリウム、オクチル酸鉄等の耐熱性向上剤、顔料等の着色剤等を必要に応じて配合することができる。
【００５９】
シリコーンゴム層を構成するシリコーンゴムとしては、特に制限はないが、例えば、例えば、ジメチルシリコーンゴム、メチルビニルシリコーンゴム、メチルフェニルシリコーンゴム、フルオロシリコーンゴム、等が挙げられる。これらのシリコーンゴムは、加熱加硫（ＨＴＶ）ものであってもよいし、室温硬化（ＲＴＶ）であってもよい。また、重合形態は付加型、縮合型のどちらであってもよい。
【００６０】
ベルト状定着部材は、耐熱性樹脂製及び金属製のチューブ状ベルト本体（ベース層）の外表面に、構成に応じて、シリコンゴム前駆体組成物で塗布、硬化後、上記フルオロカーボンシロキサンゴム前駆体組成物で塗布、硬化することによって得られるが、塗布方法としては、ブレードコーティング法、ワイヤ一バーコーティング法、リングコーティング法、スプレーコーティング法、浸漬コーティング法、フローコーティング法、ビードコ一ティング法、エアーナイフコーティング法、カーテンコーティング法等の通常の方法を用いることができる。これらの中でも、浸漬コーティング法が、表面層のシームレス塗布、量産性、コスト、膜厚の均一性等の点で有利であり、特に好ましい。フルオロカーボンシロキサンゴム前駆体組成物に対しては、必要に応じてｍ−キシレンヘキサフロライド、パーフロロアルカン、パーフロロ（２−ブチルテトラヒドロフラン）、ベンゾトリフロライド等の溶剤で希釈して適当な粘度の塗工液とし、塗布することができる。シリコンゴム前駆体組成物に対しては、必要に応じてヘキサン、ヘプタン、シクロヘキサン、トルエン、キシレン等の溶剤で希釈して適当な粘度の塗工液とし、塗布することができる。
【００６１】
これらゴム層を構成する材料の前駆体組成物は、供給形態が一液型、二液型、重合形態が付加型、縮合型などを任意に選択しうる。
【００６２】
表面層の厚さ（複数層で構成される場合総厚）は、３００μｍ以下が好ましく、１〜３００μｍの範囲がより好ましく、さらに好ましくは５〜２００μｍの範囲、特に好ましくは１０〜１００μｍの範囲が適している。１μｍより薄いと、弾性が不足してゴム層を加える効果がなくなり、定着性に問題が生じたり、耐久性が不足したりする。３００μｍを越えると、ベルト状定着部材の比熱が増大して熱移動量が低下し、転写速度やサイクルタイムの低下につながる。
但し、表面層が複数層で構成される場合、下層（最表面層に対しベース層側の層）の膜厚が、上層（最表面層側の層）の膜厚よりも厚いことが、強度や耐熱性などの観点から好ましい。具体的には、上記２層構成でいえば、シリコーンゴムゴム層の膜厚は、フルオロカーボンシロキサンゴム層の膜厚よりも厚いことが好適である。
【００６３】
表面層（ゴム層）を構成する材料の硬度（ＪＩＳＫ６３０１「加流ゴム物性試験方法」で測定）は、５〜８０の範囲が好ましく、より好ましくは１０〜７０の範囲、さらに好ましくは２０〜６０の範囲が適している。ＪＩＳ　Ａ　５　未満のものでは、強度が低下し耐久性に問題がある。また、ＪＩＳＡ８０を超えると、表面層の膜厚に係らず剛性が大きくなり、ベルト状定着部材と記録媒体との密着性が低下して、冷却が不完全な時に剥離が起こるようになり、画質上の欠陥となって顕れる問題が生ずる。
【００６４】
ここで、図１〜図４に、ベルト状定着部材の一例を示す断面概略図を示す。図１のベルト状定着部材１は、ベース層２上にフルオロカーボンシロキサンゴム層３を積層したものである。図２ではベース層２上にシリコーンゴム層４を設け、フルオロカーボンシロキサンゴム層３を積層したものである。ここでは、ベース層２と自己接着性に優れた材料を用いている。図３のベルト状定着部材１は、図１のベース層２上に接着層５を介してフルオロカーボンシロキサンゴム層３を積層したものである。ここでは、ゴム層３が自己接着性の劣る材料を用いている。図４のベルト状定着部材１は、図２のベース層２上に接着層５を介してシリコーンゴム層４を設け、フルオロカーボンシロキサンゴム層３を積層したものである。ここでは、ゴム層４が自己接着性の劣る材料を用いている。
【００６５】
―画像形成方法―
本発明の画像形成方法では、結着樹脂、着色剤、及びワックスを少なくとも含有したトナーを用い、静電潜像担持体上に形成したトナー像を記録媒体上に転写（或いは中間転写体などを介して記録媒体上に転写）する工程と、記録媒体とベルト状定着部材を重ねた状態で加熱及び加圧し、冷却した後に記録媒体をベルト状定着部材から剥離することにより、トナー像を記録媒体に定着させる定着工程とを経て、記録媒体上に画像が形成される。なお、定着工程は、複数回行なっても良く、この複数回の定着工程のうち、上記ベルト状定着ベルトを用いた加熱後冷却剥離方式の定着工程を少なくとも一回含む。
【００６６】
本発明の画像形成方法において、トナーを構成する材料は特に制限はないが、ワックスは、示唆走査熱量計により測定されるＤＳＣ曲線で吸熱開始温度が４０℃以上、より好ましくは５０℃以上のものを使用する。ＤＳＣ曲線での吸熱開始温度が４０℃より低いと、複写機内やトナーボトル内でトナーの凝集が発生してしまう。吸熱開始温度は、ワックスを構成する分子量分布のうち低分子量成分の含有量、ワックスがその構造中にもつ極性基の種類、量に左右される。一般に、高分子量化すれば融点とともに吸熱開始温度も上昇するが、ワックス本来の低溶融温度と低粘度を損なってしまう。このため、ワックスの分子量分布のうち、これら低分子量のものだけを、分子蒸留、溶剤分別、ガスクロマトグラフ分別等の方法で、選別して除くことが有効である。
【００６７】
ワックスは、融点が８０〜１２０℃の範囲にあり、かつ、１２０℃において１〜２００センチポアズ、より好ましくは１〜１００センチポアズの溶融粘度を示すことが望ましい。融点が８０℃未満では、ワックスの相変化温度が低すぎ、耐ブロッキング性が劣ったり、複写機内温度が高くなった時に現像性が悪化したりする。融点が１２０℃を超える場合には、ワックスの相変化温度が高すぎ、省エネルギーの観点で望ましくない。また、２００センチポアズより高い溶融粘度ではトナーからの溶出が弱く、定着剥離性が不十分となってしまう。
【００６８】
本ワックスは、次のようなワックスから得られるものである。パラフィンワックス及びその誘導体、モンタンワックス及びその誘導体、マイクロクリスタリンワックス及びその誘導体、フィッシャートロプシュワックス及びその誘導体、ポリオレフィンワックス及びその誘導体等である。誘導体には、酸化物、ビニルモノマーとの重合体、グラフト変性物が含まれる。この他に、アルコール、脂肪酸、植物系ワックス、動物系ワックス、鉱物系ワックス、エステルワックス、酸アミド等も利用できる。
【００６９】
ワックスのトナーに対する添加量は、１〜１５重量％、より好ましくは３〜１３重量％である。ワックスが１重量％より少ないと、十分な定着ラチチュード（トナーのオフセットなしに定着できる定着ロールの温度範囲）が得られない。一方、１０重量％より多いと、トナーから脱離して遊離しているワックス量が増えて、現像剤担持体への汚染が生じ易くなる。また、トナーの粉体流動性が悪化し、静電潜像を形成する感光体表面に遊離ワックスが付着して、静電潜像が正確に形成できなくなる。さらに、ワックスは結着樹脂と比較して透明性が劣るため、ＯＨＰ等の画像の透明性が低下して、黒ずんだ投影像となってしまう。
【００７０】
以下、本発明の画像形成方法に好適に適用される画像形成装置（本発明の画像形成装置）をついて説明する。
【００７１】
図５に示す画像形成装置は、ベルト式定着装置２５を内蔵した画像形成装置本体２０からなる。なお、図中、その他、主要部は省略する。
【００７２】
図５に示す画像形成装置における画像形成装置本体２０では、潜像担持体に潜像を形成する潜像形成され、該潜像を少なくともトナーを含む現像剤を用いて現像し、潜像担持体担持体上にトナー画像を得て、トナー画像が中間転写体を介して記録媒体上に転写される。その後、ベルト式定着装置２５において、定着が行なわれ、トナー画像が記録媒体上に形成される。
【００７３】
図６に示す画像形成装置は、ロール式定着装置２５ａを内蔵した画像形成装置本体２０と、ベルト式定着装置５８を内蔵した二次定着ユニット５０とからなる。なお、図中、その他、主要部は省略する。
【００７４】
図６に示す画像形成装置では、画像形成装置本体２０に内蔵されたロール式定着装置２５ａにより一次定着と、二次定着ユニット５０に内蔵されたベルト式定着装置５８による二次定着を行なう構成となっている。
【００７５】
図６に示す画像形成装置における画像形成装置本体２０では、潜像担持体に潜像を形成する潜像形成され、該潜像を少なくともトナーを含む現像剤を用いて現像し、潜像担持体担持体上にトナー画像を得て、トナー画像が中間転写体を介して記録媒体上に転写される。その後、ロール式定着装置２５ａにおいて、一次定着が行なわれ、記録媒体は二次定着ユニット５０に搬送される。
【００７６】
二次定着ユニット５０は、画像形成装置本体２０から排出される記録媒体が導入される導入口５１を備えており、この導入口５１の内部には、記録媒体の搬送路を切り替える切り替えゲート５２が設けられている。画像形成装置本体２０から排出される記録媒体に対して、二次定着を施さず、そのまま外部の第１排出トレイ５５上に排出する場合には、切り替えゲート５２によって搬送路が上方の第１の搬送路５３に切り替えられ、排出ロール５４によって第１排出トレイ５５上に排出される。
【００７７】
一方、画像形成装置本体２０から排出される記録媒体に対して、二次定着処理を施す場合には、切り替えゲート５２によって搬送路が下方の第２の搬送路５６に切り替えられ、搬送ベルト５７によって、ベルト式定着装置５８に搬送され、当該ベルト式定着装置５８により定着処理を受けて、排出ロール５９によって第２の排出トレイ６０に排出される。
【００７８】
以下、ベルト式定着装置２５（５８）について説明する。
ベルト式定着装置２５（５８）は、図７に示すように、加熱ロール６１と、剥離ロール６２とウォーク制御ロール６３とからなる３つのロールにより回動可能に張架された定着ベルト６４（ベルト状定着部材）、及び定着ベルト６４を介して加熱ロール６１に圧接する加圧ロール６５とを備えている。
【００７９】
ベルト式定着装置５８による定着処理は、定着ベルト６４と加圧ロール６５との圧接部７２を、定着ベルト６４側にトナー像が位置するように記録媒体を通過させて、トナー像を加熱加圧することにより定着し、前記定着ベルト６４がある程度冷却された状態で、当該定着ベルト６４から記録媒体１０を剥離されるように構成されているものである。
【００８０】
加熱ロール６１は、例えば、アルミニウムやステンレス等からなる金属製コアの表面に、ＪＩＳ　Ｋ６２５３に基づき測定されるゴム硬度が、好ましくは２０〜６０°の範囲であるシリコーンゴム等からなる弾性体層を、好ましくは１ｍｍ〜３ｍｍの範囲の厚さで被覆し、さらに、弾性体層の表面にＰＦＡチューブ等からなる離型層を被覆して、所定の外径に形成したものが用いられる。
【００８１】
加熱ロール６１の内部には、加熱源として、発熱量が、好ましくは３００〜３５０Ｗの範囲であるハロゲンランプが配設されている。ハロゲンランプ６９により、加熱ロール６１の表面温度が所定の温度（好ましくは１３０〜１９５℃の範囲）となるように加熱する。
【００８２】
また、加圧ロール６５としては、例えば、加熱ロール６１と同様に構成したものが用いられ、アルミニウムやステンレス等からなる金属製コアの表面に、ＪＩＳ　Ｋ６２５３に基づき測定されるゴム硬度が、好ましくは２０°〜６０°の範囲であるシリコーンゴム等からなる弾性体層６７を、厚さが好ましくは１ｍｍ〜３ｍｍの範囲で被覆し、更に、弾性体層の表面にＰＦＡチューブ等からなる離型層を被覆して、所定の外径に形成したものが用いられる。
【００８３】
加圧ロール６５の内部には、加熱源として、発熱量が、好ましくは、３００Ｗ〜３５０Ｗの範囲であるハロゲンランプが配設されている。ハロゲンランプ６９により、加圧ロール６５の表面温度が所定の温度（好ましくは８５℃〜１５５℃の範囲）となるように内部から加熱される。尚、加圧ロール６５においては、加熱源を省略してもよい。
【００８４】
加熱ロール６１と加圧ロール６５とは、定着ベルト６４を介して、図示しない加圧手段により、好ましくはニップ圧が１００ｋＰａ〜２００ｋＰａの範囲で互いに圧接するように構成されている。
【００８５】
定着ベルト６４は、既述の如く、加熱ロール６１と、剥離ロール６２と、ウォーク制御ロール６３と、からなる３つのロールにより周動可能に張架されており、図示しない駆動源により回転駆動される加熱ロール６１により、所定の移動速度で周動される。定着ベルト６４としては、上述のベルト状定着ベルトが用いられる。
【００８６】
また、定着ベルト６４の内面側には、加熱ロール６１と剥離ロール６２との間に、定着ベルト６４を強制的に冷却する冷却用ヒートシンク７０が配設されている。冷却用ヒートシンク７０により、定着ベルト６４に密着している定着後の記録媒体が冷却される。この際、定着ベルト６４は、剥離ロール６２付近において、５０℃〜８０℃の範囲に冷却される。
なお、定着ベルト６４には、冷却用ヒートシンク７０と加熱ロール６１との間に、定着ベルト６４に一定のテンションを付与する小径のテンションロール７１が配設されている。
【００８７】
ベルト式定着装置２５（５８）では、トナー画像Ｔが転写された記録媒体１０（或いは一次定着された記録媒体１０）が、圧接部７２を図７の左から右方向へ通過する。この時、記録媒体１０はトナー画像Ｔが加熱ロール６１側に位置するようにして圧接部７２に導入される。記録媒体１０は、圧接部７２を通過する間に、トナー画像Ｔが記録媒体１０表面で加熱溶融されて定着される。
【００８８】
その後、定着ベルト６４の表面に密着した記録媒体１０は、密着した状態で、定着ベルト６４と共に搬送される。その間、定着ベルト６４は冷却用のヒートシンク７０によって強制的に冷却されるため、トナー画像Ｔが定着されたトナー画像Ｔも冷却されて固化する。この際、冷却により記録媒体１０のコシが回復する。定着ベルト６４に密着している記録媒体１０は、そのコシが回復したため、剥離ロール６２により、定着ベルト６４から剥離される。記録媒体１０が剥離された定着ベルト６４の表面は、クリーナ７３によって残留トナー等が除去され、次の定着処理に備える。
【００８９】
【実施例】
以下、本発明を、実施例を挙げてさらに具体的に説明する。ただし、これら各実施例は、本発明を制限するものではない。
【００９０】
（実施例１）
ベルト状基材として周長５２７．８ｍｍ×幅４２０ｍｍ×厚さ７５μｍの大きさであり、カーボンブラックを添加して体積抵抗率をＲｖ＝１０^１２Ω・ｃｍに調整したポリイミド製のベース層上に、フルオロカーボンシロキサンゴム前駆体組成物であるＳＩＦＥＬ６１０（信越化学工業社製）：１００重量部とフッ素系溶媒（ｍ−キシレンヘキサフロライド、パーフロロアルカン、パーフロロ（２−ブチルテトラヒドロフラン）の混合溶剤）：１０重量部により調整した塗布液を浸漬塗布により塗膜を形成後、１２０℃：１０分の一次加硫、１８０℃：４時間の二次加硫を行い、表面層としてフルオロカーボンシロキサンゴム層（４０μｍの膜厚）を有するベルト状定着部材を得た。
【００９１】
このベルト状定着部材を、図５に示す画像形成装置とほぼ同様な構成の富士ゼロックス社製　ＤｏｃｕＣｅｎｔｅｒＣｏｌｏｒ５００（ＤＣＣ５００）［但し、定着装置を図７に示したベルト式定着装置に改造したもの］に装着し、ＤＣＣ５００用の４色の現像剤（トナーに含まれるワックス種はＰＷ７２５）を使用してフルカラー画像の形成し、ベルト状定着部材の表面がＡ４換算で１００ｋｐｖの繰り返しの評価を行ったところ、初期と変わらない画像を得ることができた。なお、トナーに含まれるワックスとしてＰＷ７２５を用いた場合、ベルト状定着部材表面の前進接触角は６５±２度である。
【００９２】
（実施例２）
実施例１で得たベルト状定着部材を、図６に示す画像形成装置とほぼ同様な構成の富士ゼロックス社製　ＤＣＣ５００［但し、図７に示したベルト式定着装置を内蔵した二次定着ユニットを装着させたもの］に装着し、ＤＣＣ５００用の４色の現像剤（トナーに含まれるワックス種はＰＷ７２５）を使用してフルカラー画像の形成し、ベルト状定着部材の表面がＡ４換算で１００ｋｐｖの繰り返しの評価を行ったところ、初期と変わらない画像を得ることができた。
なお、トナーに含まれるワックスとしてＰＷ７２５を用いた場合、ベルト状定着部材表面の前進接触角は６５±２度である。
【００９３】
（実施例３）
実施例１で得たベルト状定着部材を、図５に示す画像形成装置とほぼ同様な富士ゼロックス社製　ＤＣＣ５００［但し、定着装置を図７に示したベルト式定着装置に改造したもの］に装着し、富士ゼロックス社製　ＤｏｃｕＰｒｉｎｔＣ６２０用の４色の現像剤（トナーに含まれるワックス種はカルバナワックス）を使用してフルカラー画像の形成し、ベルト状定着部材の表面がＡ４換算で１００ｋｐｖの繰り返しの評価を行ったところ、初期と変わらない画像を得ることができた。
なお、トナーに含まれるワックスとしてカルバナワックスを用いた場合、ベルト状定着部材表面の前進接触角は６０±２度である。
【００９４】
（実施例４）
実施例１で得たベルト状定着部材を、図５に示す画像形成装置とほぼ同様な富士ゼロックス社製　ＤＣＣ５００［但し、定着装置を図７に示したベルト式定着装置に改造したもの］に装着し、富士ゼロックス社製　ＤｏｃｕＰｒｉｎｔ　Ｃ１６１６用の４色の現像剤（トナーに含まれるワックス種はカルバナワックス）を使用してフルカラー画像の形成し、ベルト状定着部材の表面がＡ４換算で１００ｋｐｖの繰り返しの評価を行ったところ、初期と変わらない画像を得ることができた。
なお、トナーに含まれるワックスとしてカルバナワックスを用いた場合、ベルト状定着部材表面の前進接触角は６０±２度である。
【００９５】
（実施例５）
実施例１のベルト状定着部材における表面層形成材料として、フルオロカーボンシロキサンゴム前駆体組成物であるＳＩＦＥＬ６１１（信越化学工業社製）を使用した以外は、実施例１と同様にしてベルト状定着部材を製造し、繰り返し評価を行ったところ、初期と変わらない画像を得ることができた。
なお、トナーに含まれるワックスとしてＰＷ７２５を用いた場合、ベルト状定着部材表面の前進接触角は６３±２度である。
【００９６】
（実施例６）
実施例１のベルト状定着部材における表面層形成材料として、フルオロカーボンシロキサンゴム前駆体組成物であるＳＩＦＥＬ６５０（信越化学工業社製）を使用した以外は、実施例１と同様にしてベルト状定着部材を製造し、繰り返し評価を行ったところ、初期と変わらない画像を得ることができた。
なお、トナーに含まれるワックスとしてＰＷ７２５を用いた場合、ベルト状定着部材表面の前進接触角は６５±２度である。
【００９７】
（実施例７）
ベルト状基材として周長５２７．８ｍｍ×幅４２０ｍｍ×厚さ７５μｍの大きさであり、カーボンブラックを添加して体積抵抗率をＲｖ＝１０^１２Ω・ｃｍに調整したポリイミド製のベース層上に、シリコーンゴム用プライマーであるＤＹ３９−１１５（東レ・ダウコーニング・シリコーン社製）をウェスに含浸し塗布後、風乾３０分の後、シリコーンゴム前駆体組成物であるＤＹ３５−７９６ＡＢ（東レ・ダウコーニング・シリコーン社製）：１００重量部とｎ−ヘキサン：３０重量部により調整した塗布液を浸漬塗布により塗膜を形成、１２０℃：１０分の一次加硫を行い、シリコーンゴム層（膜厚４０μｍ）を得た。このシリコーンゴム層上に、フルオロカーボンシロキサンゴム前駆体組成物であるＳＩＦＥＬ６１０（信越化学工業社製）：１００重量部とフッ素系溶媒（ｍ−キシレンヘキサフロライド、パーフロロアルカン、パーフロロ（２−ブチルテトラヒドロフラン）の混合溶剤）：２０重量部により調整した塗布液を浸漬塗布により塗膜を形成後、１２０℃：１０分の一次加硫、１８０℃：４時間の二次加硫を行い、フルオロカーボンシロキサンゴム層（膜厚２０μｍ）を有するベルト状定着部材を得た。
【００９８】
このベルト状定着部材を、図５に示す画像形成装置とほぼ同様な構成の富士ゼロックス社製　ＤｏｃｕＣｅｎｔｅｒＣｏｌｏｒ５００（ＤＣＣ５００）［但し、定着装置を図７に示したベルト式定着装置に改造したもの］に装着し、ＤＣＣ５００用の４色の現像剤（トナーに含まれるワックス種はＰＷ７２５）を使用してフルカラー画像の形成し、ベルト状定着部材の表面がＡ４換算で１００ｋｐｖの繰り返しの評価を行ったところ、初期と変わらない画像を得ることができた。なお、トナーに含まれるワックスとしてＰＷ７２５を用いた場合、ベルト状定着部材表面の前進接触角は６５±２度である。
【００９９】
（比較例１）
実施例１のベルト状定着部材における表面層形成材料として、フルオロカーボンシロキサンゴム前駆体組成物の代わりに、シリコーンゴム前駆体組成物であるＤＹ３５−７９６ＡＢ（東レ・ダウコーニング・シリコーン社製）を使用した以外は実施例１と同様にしてベルト状定着部材を得た。実施例１と同様の繰り返し評価を行ったところ、１００ｋｐｖ後では、シリコーンゴム表面にワックスや現像剤と紙粉を含んだ物質が固着するところが現われ、均一画像を取ると、部分的に光沢が異なるところが目視で確認できるようになり、使用に耐えない画像となった。
なお、トナーに含まれるワックスとしてＰＷ７２５を用いた場合、ベルト状定着部材表面の前進接触角は４５±２度である。
【０１００】
（比較例２）
実施例１のベルト状定着部材における表面層形成材料として、フルオロカーボンシロキサンゴム前駆体組成物の代わりに、シリコーンゴム前駆体組成物であるＤＹ３５−７００２ＡＢ（東レ・ダウコーニング・シリコーン社製）を使用した以外は実施例１と同様にしてベルト状定着部材を得た。実施例１と同様の繰り返し評価を行ったところ、１００ｋｐｖ後では、シリコーンゴム層表面にワックスや現像剤と紙粉を含んだ物質が固着するところが現われ、均一画像を取ると、部分的に光沢が異なるところが目視で確認できるようになり、使用に耐えない画像となった。
なお、トナーに含まれるワックスとしてＰＷ７２５を用いた場合、ベルト状定着部材表面の前進接触角は４７±２度である。
【０１０１】
（比較例３）
実施例１で得たベルト状定着部材を、図５に示す画像形成装置とほぼ同様な富士ゼロックス社製　ＤＣＣ５００［但し、定着装置を図７に示したベルト式定着装置に改造したもの］に装着し、ワックスを含有しないトナーである、富士ゼロックス社製　ＤｏｃｕＣｏｌｏｒ　１２５５ＣＰ用の４色の現像剤を使用してフルカラー画像の形成し、ベルト状定着部材の表面がＡ４換算で１０ｋｐｖの繰り返しの評価を行ったところ、フロロカーボンシロキサンゴム表面に現像剤と紙粉を含んだ物質が固着するところが現われ、均一画像を取ると、部分的に光沢が異なるところが目視で確認できるようになり、使用に耐えない画像となった。
【０１０２】
（結果）
これら実施例の結果から、実施例１〜７はベルト状定着部材の表面がＡ４換算で１００ｋｐｖ（プリントボリューム）の繰り返しの評価を行ったところ、画質評価もいずれも良好であった。
これに対し、比較例１、２は、１００ｋｐｖ後では、シリコーンゴム表面にワックスや現像剤と紙粉を含んだ物質が固着するところが現われ、均一画像を取ると、部分的に光沢が異なるところが目視で確認できるようになり、使用に耐えない画像となった。比較例３は、ワックスを含有しないトナーを使用すると１０ｋｐｖ後では、フロロカーボンシロキサンゴム表面に現像剤と紙粉を含んだ物質が固着するところが現われ、均一画像を取ると、部分的に光沢が異なるところが目視で確認できるようになり、使用に耐えない画像となった。
このように、ワックスを含むトナー（現像剤）を用い、加熱後冷却剥離定着方式を行なうシステムにおいて、トナーの含有するワックス単体を１４０℃で溶融、室温固化後の前進接触角が、５０度以上を示す表面層を有するベルト状定着部材を用いることで、ベルト状定着部材の表面がＡ４換算で１００ｋｐｖの繰り返しの評価を行った後でも、画質の劣化を防止することが可能であることがわかる
。
【０１０３】
【発明の効果】
以上、本発明によれば、ワックスを含有するオイルレストナーを使用して加熱後冷却剥離型定着方式で定着を行なった場合にも、ベルト状定着部材のワックスによる汚染を防止して、画像グロスの低下を抑制して画質の劣化を抑制し、長期間にわたって、高画質で、定着性に優れた画像が得られる画像形成方法及び画像形成装置を提供することができる。
【図面の簡単な説明】
【図１】本発明に用いられるベルト状定着部材の一例を示す概略構成断面図である。
【図２】本発明に用いられるベルト状定着部材の他の一例を示す概略構成断面図である。
【図３】本発明に用いられるベルト状定着部材の他の一例を示す概略構成断面図である。
【図４】本発明に用いられるベルト状定着部材の他の一例を示す概略構成断面図である。
【図５】本発明の画像形成装置の一例を示す概略構成図である。
【図６】本発明の画像形成装置の他の一例を示す概略構成図である。
【図７】本発明の画像形成装置に内蔵されるベルト式定着装置の一例を示す概略構成図である。
【符号の説明】
１　ベルト状定着部材
２　ベース層
３　フルオロカーボンシロキサンゴム層（ゴム層（１））
４　シリコーンゴム層（ゴム層（２））
５　接着層
２０　画像形成装置本体
２５、５８　ベルト式定着装置
２５ａ　ロール式定着装置
５０　二次定着ユニット
６４　定着ベルト（ベルト状定着部材）[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, after transferring a toner image containing a wax to a recording medium, the recording medium and the belt-shaped fixing member are heated and pressed in a stacked state, and the recording medium is separated from the belt-shaped fixing member after cooling. The present invention relates to an image forming method and an image forming apparatus to which a fixing method for transferring and fixing the toner image on a recording medium is applied.
[0002]
[Prior art]
In general, toner used in an electrophotographic process is melt-kneaded by adding a colorant, a charge control agent, and a release agent to various resins, for example, a polyester resin, a styrene-acrylic resin, an epoxy resin, and the like, and uniformly dispersed. It is manufactured by a pulverization / classification method in which the mixture is pulverized to a predetermined particle size and then excessive coarse powder and fine powder are removed using a classifier. However, with the recent demand for higher image quality, toner It has become necessary to further reduce the particle size. In order to cope with these problems, a method of dispersing an oil phase composed of a monomer as a raw material of a resin and a colorant in an aqueous phase and directly polymerizing the oil phase to produce toner particles has been adopted. Also, due to the demand for energy saving, resins having a lower glass transition point and a lower softening point have been used so that fixing can be performed at a lower temperature.
[0003]
In a color toner mounted on a full-color copying machine or a printer, it is necessary that a multicolor toner is sufficiently mixed in a fixing process, and color reproducibility and transparency of an OHP image are important. In order to enhance the color mixing property, the color toner is generally formed of a low-molecular-weight resin having a sharper melting property than that of the black toner. For this reason, there is a problem that an offset easily occurs. Conventionally, a black toner having a high crystallinity and a relatively high melting point, such as polyethylene or polypropylene, is used in order to obtain the offset resistance of fixing. However, in a full-color color toner, an OHP image is used. The surface of the heat-fixing roller is made of silicone rubber or fluororesin, which has excellent releasability from toner, and does not contain wax because the transparency of the toner is impaired. The method of supplying the release liquid of (1) is adopted.
[0004]
Although this method is extremely effective in preventing the offset phenomenon of the toner, it requires an apparatus for supplying the anti-offset liquid, has poor rewriting properties of the output image, and has a sticky note or an adhesive tape. Problems, such as the absence of a device, occur. Further, there are also problems that the offset prevention liquid is heated and evaporated to give an unpleasant odor, and that contamination inside the machine is caused. For this reason, low melting point wax is used for toners, especially full color color toners, in order to achieve oillessness without impairing the properties required for color toners such as low-temperature fixability, sharp meltability, and small particle size. The contained toner is used.
[0005]
In the image forming method using the belt-shaped fixing member, the toner image formed on the electrostatic latent image carrier is transferred onto a recording medium, and then the recording medium is overlaid on the belt-shaped fixing member, heated and pressed, and cooled. And then fixing the toner image on the recording medium by peeling the recording medium from the belt-shaped fixing member. As a surface material, generally, silicone having excellent elasticity, heat resistance, releasability from toner and the like is used. Those using rubber are known.
[0006]
In the above-described image forming method, the toner image once melted is cooled to a temperature below the melting point and then separated, so that the toner image on the recording medium follows the surface shape of the belt-shaped fixing member. That is, the surface of the toner image roughly captures the surface shape of the belt-shaped fixing member as if taking a mold. If the surface of the belt-shaped fixing member is smooth, the toner image has a very high gloss, that is, a high gloss. On the other hand, if the surface of the belt-shaped fixing member is rough or cloudy, the gloss of the toner image is reduced.
[0007]
However, in the image forming method in which the toner containing the wax and the above-mentioned belt-shaped fixing member are combined, the fixing and the peeling are repeated, the wax remains on the belt-shaped fixing member, and the remaining wax contains paper powder and toner. The external additives and the like adhere and mix, and the surface property of the belt-shaped fixing member changes, and the gloss of the output image changes, which causes a problem of being recognized as a defect.
[0008]
When a belt-like fixing member having a silicone rubber layer formed on the surface is used, even if it is possible to obtain a problem-free releasability in the initial stage, heat history, discharge resistance, wax residue, paper, etc. Although the reason, such as the adhesion of powder, is not clear, there is a change with time in the releasability, and it is difficult to obtain the desired life while maintaining the initial image quality only by the characteristics of the silicone rubber. It has been found.
[0009]
Japanese Patent Publication No. 2906972 proposes the use of a fluorocarbon siloxane rubber for a fixing belt (belt-shaped fixing member). However, there is no description about a combination with a specific developer (toner). In addition, the recording medium is heated and pressurized in a state where the belt-shaped fixing member is superimposed on the recording medium, and after cooling, the recording medium is separated from the fixing member. There is no description about an image forming method to which the mold fixing method is applied.
[0010]
[Patent Document 1]
Patent Publication No. 2906972
[0011]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-described conventional problems and achieve the following objects. That is, an object of the present invention is to prevent the belt-shaped fixing member from being contaminated by wax even when fixing is performed by a cooling and peeling-type fixing method after heating using an oilless toner containing wax, thereby achieving image gloss. It is an object of the present invention to provide an image forming method and an image forming apparatus capable of suppressing deterioration in image quality by suppressing deterioration of the image quality and obtaining an image with high image quality and excellent fixability over a long period of time.
[0012]
[Means for Solving the Problems]
The inventors of the present invention have conducted extensive studies on a system in which a belt-type heating and cooling / peeling-type fixing system is used for fixing using a wax-containing oilless toner. Was found, which led to the present invention. That is, the present invention
[0013]
(1) The recording medium on which the toner image has been transferred and the belt-shaped fixing member are heated and pressed in a superposed state, and after cooling, the recording medium is peeled off from the belt-shaped fixing member. In the image forming method for fixing to
The toner contains at least a binder resin, a colorant, and a wax, and the belt-shaped fixing member melts the wax alone contained in the toner at 140 ° C. and has an advancing contact angle of 50 ° after solidification at room temperature. An image forming method comprising the surface layer described above.
[0014]
(2) The recording medium to which the toner image has been transferred is heated and pressed by a first fixing member, and heated and pressed with the recording medium on which the toner image is fixed and a second belt-shaped fixing member superposed, An image forming method for fixing the toner image on the recording medium by peeling the recording medium from the second belt-shaped fixing member after cooling,
The toner contains at least a binder resin, a colorant, and a wax, and the second belt-shaped fixing member melts the wax alone contained in the toner at 140 ° C., and advancing contact angle after solidification at room temperature. Has a surface layer showing a temperature of 50 degrees or more.
[0015]
(3) The belt-shaped fixing member has a surface layer on a base layer,
The image forming method according to (1) or (2), wherein the surface layer is a rubber layer including a fluorocarbon siloxane rubber.
[0016]
(4) The image forming method according to (3), wherein the thickness of the rubber layer including the fluorocarbon siloxane rubber is 300 μm or less.
[0017]
(5) The rubber layer comprising the fluorocarbon siloxane rubber is formed by applying a precursor composition of the fluorocarbon siloxane rubber on the surface of the base layer and curing the composition. ) Or (4).
[0018]
(6) the belt-shaped fixing member has a surface layer on the base layer;
(1) wherein the surface layer includes a rubber layer including a silicone rubber and a rubber layer including a fluorocarbon siloxane rubber provided on the rubber layer. ) Or (2).
[0019]
(7) The thickness of the rubber layer containing the silicone rubber is larger than the thickness of the rubber layer containing the fluorocarbon siloxane rubber, and the thickness of the entire rubber layer is 300 μm or less. The image forming method according to the above (6), wherein
[0020]
(8) The rubber layer containing the silicone rubber is formed by applying and curing a silicone rubber precursor composition on the surface of the base layer, and is formed containing the fluorocarbon siloxane rubber. (6) or (6) wherein the rubber layer is formed by applying a fluorocarbon siloxane rubber precursor composition to the surface of the rubber layer containing the silicone rubber and curing the composition. The image forming method according to 7).
[0021]
(9) The image forming method according to any one of (3) to (6), wherein the fluorocarbon siloxane rubber has a perfluoroalkyl ether group and / or a perfluoroalkyl group in a main chain.
[0022]
(10) In any one of the above (3) to (7), wherein the rubber layer containing the fluorocarbon siloxane rubber is a cured product of a precursor composition having the following components (A) to (D). The image forming method as described in the above.
(A) a fluorocarbon polymer containing a fluorocarbon siloxane having a repeating unit represented by the following general formula (1) as a main component and having an aliphatic unsaturated group;
[0023]
Embedded image

[0024]
(Where R ¹⁰ Is an unsubstituted or substituted monovalent hydrocarbon group, x is an integer of 1 or more, a and e are each 0 or 1, b and d are each an integer of 1 to 4, and c is an integer of 0 to 8. )
(B) Two or more ≡SiH groups are contained in one molecule, and the content of the ≡SiH group is 1 to 4 times by mole based on the amount of the aliphatic unsaturated group in the fluorocarbon siloxane rubber composition. Certain organopolysiloxanes and / or fluorocarbon siloxanes,
(C) a filler,
(D) an effective amount of catalyst.
[0025]
(11) The recording medium on which the toner image has been transferred and the belt-shaped fixing member are heated and pressed in a superposed state, and after cooling, the recording medium is peeled off from the belt-shaped fixing member. An image forming apparatus having a fixing unit for fixing the
The toner contains at least a binder resin, a colorant, and a wax, and the belt-shaped fixing member melts the wax alone contained in the toner at 140 ° C. and has an advancing contact angle of 50 ° after solidification at room temperature. An image forming apparatus having the surface layer described above.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The image forming method of the present invention uses a toner containing at least a binder resin, a colorant, and a wax, and heats and presses and cools the recording medium on which the toner image has been transferred and the belt-shaped fixing member in an overlapping state. A fixing step of fixing the toner image to the recording medium by peeling the recording medium from the belt-shaped fixing member later, and including the toner as a belt-shaped fixing member used in the fixing step of the heating and cooling separation method. A wax having a surface layer having an advancing contact angle of 50 ° or more after solidifying the wax alone at 140 ° C. and solidifying at room temperature (hereinafter, sometimes referred to as a “surface layer having an advancing contact angle of 50 ° or more”) is used. Features.
[0027]
In such a fixing step of the cooling-separation method after heating, the wax contained in the toner is melted before being heated and adheres to the surface of the belt-shaped fixing member by heating. Then, when cooled, the wax that has melted and adhered is solidified. At this time, if the wax melts and adheres to the surface of the belt-shaped fixing member with good wettability, the wax hardens and is hardly peeled off from the surface of the belt-shaped fixing member and remains. Then, if the wax adheres to the surface of the belt-shaped fixing member due to poor wettability, it is considered that the wax solidifies and then easily peels off from the surface of the belt-shaped fixing member and does not remain. Therefore, in the present invention, even in a system in which the wax containing toner is used and the wax is melted and solidified on the surface of the belt-shaped fixing member as in the fixing step of the cooling-after-heating separation method described above, the advancing contact angle is 50 °. By using a belt-shaped fixing member having a surface layer of a degree or more, the wax that has melted onto the surface of the belt-shaped fixing member does not adhere well and the wax solidifies and then remains on the surface of the belt-shaped fixing member. The belt-like fixing member does not adhere to paper powder or toner external additives for a long period of time, preventing a change in the surface properties of the belt-shaped fixing member.
[0028]
The belt-shaped fixing member has a surface (surface layer) in which the wax alone contained in the toner is melted at 140 ° C. and the advancing contact angle after solidification at room temperature shows 50 ° or more, preferably 55 ° or more. Yes, more preferably at least 60 degrees. If the advancing contact angle is less than 50 degrees, when the wax is melted, it adheres to the surface of the belt-shaped fixing member with good wettability, and after the wax is solidified, the wax is hardly separated from the surface of the belt-shaped member and remains. Thus, paper powder, external additives of the toner, and the like are attached and mixed, and the surface property of the belt-shaped fixing member changes with time.
[0029]
Here, a method for measuring the advancing contact angle will be described below. The mass of the wax for evaluation was obtained by spraying a powder of wax on a PTFE (polytetrafluoroethylene) plate, heating at 140 ° C. for 30 minutes, and cooling and cooling. Sort out things. An evaluation sample prepared by forming a surface layer material of 30 to 200 μm on a flat aluminum plate was prepared. The wax mass is placed on the surface of the evaluation sample so that the hemispherical surface of the wax mass faces the surface of the evaluation sample. Put in a thermostat and raise the temperature from room temperature to 140 ° C in about 1 hour. Hold at this temperature for 1 hour. Turn off the heating source and let the temperature drop from the temperature to room temperature in about 2 hours. A hemispherical lump of wax is obtained, leaving an advancing contact angle with the evaluation sample. Using a contact angle meter (FACE CA-X: manufactured by Kyowa Interface Science Co., Ltd.), the contact angle was measured with five evaluation samples, and the average value of the five obtained points was determined as the advancing contact angle between the evaluation sample and the wax. Is used as the value of It has been confirmed that the advancing contact angle after solidification at room temperature and at 140 ° C. is not much different and the tendency does not change. Table 1 below shows values of advancing contact angles between typical surface layer constituent materials and waxes.
[0030]
[Table 1]

[0031]
-Belt-shaped fixing member-
The belt-shaped fixing member includes, for example, a base layer and a surface layer having a constant thickness formed on the base layer. Further, an adhesive layer may be provided between the base layer and the surface layer. The form of the belt-shaped fixing member may be a belt shape suitable for the image forming apparatus, and an endless belt is particularly preferable.
[0032]
For the base layer, heat resistance and mechanical strength are required, and a metal sheet of nickel, aluminum, stainless steel, or the like, or a resin film of PET, PBT, polyimide, polyimide amide, or the like can be used. The resin may be added and dispersed with a conductive powder or the like, and the volume resistivity may be controlled, and carbon black may be added and dispersed, and an endless belt-shaped polyimide belt having a controlled volume resistivity may be used. it can. Further, it is also possible to combine both ends of a long polyimide sheet on a puzzle, apply thermocompression using a thermocompression member, and prepare an endless belt.
[0033]
The thickness of the base layer is preferably in the range of 20 to 200 μm, more preferably in the range of 30 to 150 μm, and still more preferably in the range of 40 to 130 μm. If the thickness of the base layer is less than 20 μm, dimensional stability during heating and cooling and strength will be insufficient. If it exceeds 200 μm, the specific heat of the belt-shaped fixing member increases, and the amount of heat transfer decreases, leading to a decrease in transfer speed and cycle time.
[0034]
As the adhesive layer, primers or the like which are usually used for bonding silicone rubber can be applied. Examples of the primers include, but are not limited to, aminosilane-based coupling agents, chlorosilane-based coupling agents, chloromethylsilane-based coupling agents, cyanosilane-based coupling agents, titanate-based coupling agents, and the like. Not something. Of these, aminosilane-based coupling agents and titanate-based coupling agents are preferably used. Further, a primer designed like a fluorocarbon siloxane rubber is also preferably used.
[0035]
The surface layer is not particularly limited as long as the surface is composed of a material having the above-mentioned advancing contact angle of 50 degrees or more. For example, a rubber layer composed of a fluorocarbon siloxane rubber (hereinafter referred to as fluorocarbon siloxane) Rubber layer). The surface layer may be composed of a plurality of layers. For example, in the case of a two-layer constitution, a rubber layer containing silicone rubber (hereinafter, sometimes referred to as a silicone rubber layer) and a rubber layer And a rubber layer containing a fluorocarbon siloxane rubber provided in the above.
[0036]
The fluorocarbon siloxane rubber constituting the fluorocarbon siloxane rubber layer preferably has a perfluoroalkyl ether group and / or a perfluoroalkyl group in the main chain.
[0037]
In particular, as the fluorocarbon siloxane rubber layer, (A) a fluorocarbon polymer containing a fluorocarbon siloxane represented by the following general formula (1) as a main component and having an aliphatic unsaturated group, and (B) two or more ≡SiH groups per molecule. An organopolysiloxane and / or a fluorocarbon siloxane, wherein the content of the ≡SiH group is 1 to 4 times by mole based on the amount of the aliphatic unsaturated group in the fluorocarbon siloxane rubber composition; It is preferable to comprise a cured product of the agent and (D) a fluorocarbon siloxane rubber precursor composition containing an effective amount of a catalyst.
[0038]
In this case, the fluorocarbon polymer of the component (A) has a fluorocarbon siloxane having a repeating unit represented by the following general formula (1) as a main component and has an aliphatic unsaturated group. The aliphatic unsaturated group is a monovalent aliphatic unsaturated hydrocarbon group and preferably has 2 to 3 carbon atoms, and specifically has 2 to 3 carbon atoms such as a vinyl group, an allyl group, and an ethynyl group. The alkenyl group is exemplified, and a vinyl group is particularly preferred. In this case, the aliphatic unsaturated group is preferably at the terminal of the molecular chain, and for example, preferably has a vinyldialkylsilyl group, divinylalkylsilyl group, or trivinylsilyl group in the main chain. In this case, the alkyl group preferably has 1 to 8 carbon atoms, particularly a methyl group.
[0039]
Embedded image

[0040]
Here, in the above formula (1), R ¹⁰ Is preferably an unsubstituted or substituted monovalent hydrocarbon group having 1 to 8 carbon atoms, preferably an alkyl group having 1 to 8 carbon atoms or an alkenyl group having 2 to 3 carbon atoms, particularly a methyl group. Is preferred. a and e are each 0 or 1, b and d are each an integer of 1 to 4, and c is an integer of 0 to 8. X is an integer of 1 or more, preferably 10 to 30. Examples of such a component (A) include those represented by the following formula (2).
[0041]
Embedded image

[0042]
Component (B) is an organopolysiloxane containing two or more ≡SiH groups in one molecule, wherein the １〜SiH groups are 1 to 4 times the molar amount of the aliphatic unsaturated groups in the fluorocarbon siloxane composition. And / or fluorocarbons.
[0043]
Here, examples of the organopolysiloxane having a ≡SiH group include an organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms in a molecule.
[0044]
In the fluorocarbon siloxane rubber composition used in the present invention, when the fluorocarbon polymer as the component (A) has an aliphatic unsaturated group, the above-mentioned organohydrogenpolysiloxane can be used as a curing agent. . That is, in this case, a cured product is formed by an addition reaction occurring between the aliphatic unsaturated group in the fluorocarbon siloxane and the hydrogen atom bonded to the silicon atom in the organohydrogenpolysiloxane. As such an organohydrogenpolysiloxane, various organohydrogenpolysiloxanes used in addition-curable silicone rubber compositions can be used. In the present invention, the following (α), (β) Is preferably used.
(Α) an organohydrogenpolysiloxane represented by the following formulas (3) to (5),
[0045]
Embedded image

[0046]
In the above formula, s and t are integers of 0 or more, and u is an integer of 2 or more. Also, R ² Is an unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, and preferably has 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and specifically, a methyl group or an ethyl group Alkyl groups such as isopropyl, butyl and the like, cycloalkyl groups such as cyclohexyl and cyclopentyl, aryl groups such as phenyl, tolyl and xylyl, aralkyl groups such as benzyl and phenylethyl, chloromethyl groups, Examples thereof include halogenated hydrocarbon groups such as chloropropyl group, chlorocyclohexyl group, and 3,3,3-trifluoropropyl group, and cyano hydrocarbon groups such as 2-cyanoethyl group. Among them, particularly preferred are a methyl group, an ethyl group, a phenyl group and a 3,3,3-trifluoropropyl group. R ⁴ Is a divalent group interposed between the silicon atom and the fluorine-containing organic group Rf, and is a divalent hydrocarbon group having no aliphatic unsaturated bond or a general formula -R ⁵ -OR ⁶ -(However, R ⁵ And R ⁶ Is a divalent hydrocarbon group having no aliphatic unsaturated bond), and preferably has 1 to 8 carbon atoms. Specific examples include the following.
[0047]
Embedded image

[0048]
Note that R ⁴ Among the particularly preferred groups are -CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ -O-CH ₂ -. R _f Is a perfluoroalkyl group or a perfluoroalkyl ether group. The perfluoroalkyl group is represented by the formula C _p F _{2p + 1} (Where p is an integer of 4 to 10), and a particularly preferable group is C. ₆ F _Thirteen −, C ₈ F ₁₇ −, C ₁₀ F ₂₁ -. As the perfluoroalkyl ether group, those having 5 to 15 carbon atoms are particularly preferable, and specific examples include the following.
[0049]
Embedded image

[0050]
(Β) (CH represented by the following formula (6) ₃ ) ₂ HSiO _0.5 Unit and SiO ₂ A copolymer comprising units.
[0051]
Embedded image

[0052]
In addition, it is preferable that the viscosity of these organohydrogenpolysiloxanes at 25 ° C. is usually 1,000 cSt or less. The above-mentioned organohydrogenpolysiloxane generally has a number of ≡SiH groups of at least 1, especially 1 to 5, relative to one aliphatic unsaturated hydrocarbon group in the fluorocarbon siloxane of the component (A). It is preferable to mix them in such a ratio.
[0053]
Further, as the fluorocarbon having a ≡SiH group, a unit represented by the above formula (1) or R ¹⁰ Is preferably a dialkylhydrogensiloxy group and the terminal is a dialkylhydrogensiloxy group or a SiH group such as a silyl group, and examples thereof include those represented by the following formula (7).
[0054]
Embedded image

[0055]
As the filler of the component (C), various fillers used in general silicone rubber compositions can be used. For example, fumed silica, precipitated silica, carbon powder, titanium dioxide, aluminum oxide, quartz powder, reinforcing fillers such as talc, sericite and bentonite, asbestos, glass fibers, and fibrous fillers such as organic fibers. Examples can be given.
[0056]
These fillers are preferably blended in a proportion of 0.1 to 300 parts, especially 1 to 200 parts, per 100 parts (part by weight, the same applies hereinafter) of the component (A). When the amount of the filler is less than 0.1 part, a sufficient reinforcing effect cannot be obtained, and when the amount is more than 300 parts, the mechanical strength of the cured product decreases. May be inconvenient.
[0057]
As the catalyst of the component (D), chloroplatinic acid, alcohol-modified chloroplatinic acid, a complex of chloroplatinic acid and an olefin, platinum black or palladium can be used as a catalyst for addition reaction, such as alumina, silica and carbon. Examples thereof include those supported on a carrier, a complex of rhodium and an olefin, an element of Group VIII of the Periodic Table such as chlorotris (triphenylphosphine) rhodium (Wilkinson's catalyst), rhodium (III) acetylacetonate or a compound thereof. However, it is preferable to use these complexes by dissolving them in solvents such as alcohols, ethers, and hydrocarbons. The amount of the platinum group metal-based catalyst may be any as long as it is an effective amount of the catalyst, and is usually 1 to 500 ppm, particularly 5 to 20 ppm in terms of platinum group metal with respect to 100 parts of the component (A). It is preferred to use.
[0058]
In the fluorocarbon siloxane rubber precursor composition, various compounding agents can be added as long as the object of the present invention of improving solvent resistance is not impaired. For example, dispersants such as diphenylsilanediol, dimethylpolysiloxane having a low degree of polymerization, and hydroxyl-blocked at the molecular chain end, hexamethyldisilazane, and heat-resistance improvers such as ferrous oxide, ferric oxide, cerium oxide, and iron octylate And a coloring agent such as a pigment can be added as necessary.
[0059]
The silicone rubber constituting the silicone rubber layer is not particularly limited, and includes, for example, dimethyl silicone rubber, methyl vinyl silicone rubber, methylphenyl silicone rubber, fluorosilicone rubber, and the like. These silicone rubbers may be heat vulcanized (HTV) or room temperature cured (RTV). The polymerization form may be either an addition type or a condensation type.
[0060]
The belt-shaped fixing member is coated with a silicon rubber precursor composition according to the configuration on the outer surface of a tubular belt body (base layer) made of a heat-resistant resin or a metal, and after curing, the fluorocarbon siloxane rubber precursor is used. It is obtained by coating and curing with the composition, and the coating method includes blade coating, wire bar coating, ring coating, spray coating, dip coating, flow coating, bead coating, air coating. Conventional methods such as a knife coating method and a curtain coating method can be used. Among these, the dip coating method is advantageous in terms of seamless application of the surface layer, mass productivity, cost, uniformity of film thickness, and the like, and is particularly preferable. The fluorocarbon siloxane rubber precursor composition is diluted with a solvent such as m-xylene hexafluoride, perfluoroalkane, perfluoro (2-butyltetrahydrofuran), benzotrifluoride or the like to have an appropriate viscosity, if necessary. It can be applied as a coating liquid. The silicone rubber precursor composition can be diluted with a solvent such as hexane, heptane, cyclohexane, toluene, or xylene to form a coating liquid having an appropriate viscosity, if necessary, and applied.
[0061]
The precursor composition of the material constituting these rubber layers can be arbitrarily selected from a one-part supply type, a two-part supply form, and an addition type or condensation type as a polymerization form.
[0062]
The thickness of the surface layer (total thickness when composed of a plurality of layers) is preferably 300 μm or less, more preferably 1 to 300 μm, still more preferably 5 to 200 μm, and particularly preferably 10 to 100 μm. Are suitable. When the thickness is less than 1 μm, the elasticity is insufficient and the effect of adding the rubber layer is lost, so that a problem is caused in the fixing property or the durability is insufficient. If it exceeds 300 μm, the specific heat of the belt-shaped fixing member increases, and the amount of heat transfer decreases, leading to a decrease in transfer speed and cycle time.
However, when the surface layer is composed of a plurality of layers, the strength of the lower layer (the layer on the base layer side with respect to the outermost layer) must be larger than the thickness of the upper layer (the layer on the uppermost layer). It is preferable from the viewpoint of heat resistance and the like. Specifically, in the above two-layer configuration, it is preferable that the thickness of the silicone rubber rubber layer be larger than the thickness of the fluorocarbon siloxane rubber layer.
[0063]
The hardness of the material constituting the surface layer (rubber layer) (measured by JIS K6301 “Test method for physical properties of flowing rubber”) is preferably in the range of 5 to 80, more preferably in the range of 10 to 70, and still more preferably 20 to 60. The range is suitable. If it is less than JIS A5, the strength is reduced and there is a problem in durability. On the other hand, if it exceeds JISA80, the rigidity increases irrespective of the thickness of the surface layer, the adhesion between the belt-shaped fixing member and the recording medium is reduced, and peeling occurs when cooling is incomplete, and A problem that appears as the above defect occurs.
[0064]
Here, FIGS. 1 to 4 are schematic cross-sectional views showing an example of the belt-shaped fixing member. The belt-shaped fixing member 1 shown in FIG. 1 is obtained by laminating a fluorocarbon siloxane rubber layer 3 on a base layer 2. In FIG. 2, a silicone rubber layer 4 is provided on a base layer 2 and a fluorocarbon siloxane rubber layer 3 is laminated. Here, a material having excellent self-adhesiveness with the base layer 2 is used. The belt-shaped fixing member 1 in FIG. 3 is obtained by laminating a fluorocarbon siloxane rubber layer 3 on the base layer 2 in FIG. Here, the rubber layer 3 is made of a material having poor self-adhesiveness. The belt-shaped fixing member 1 shown in FIG. 4 has a structure in which a silicone rubber layer 4 is provided on the base layer 2 shown in FIG. Here, a material in which the rubber layer 4 has poor self-adhesiveness is used.
[0065]
-Image formation method-
In the image forming method of the present invention, a toner image formed on an electrostatic latent image carrier is transferred onto a recording medium using a toner containing at least a binder resin, a colorant, and a wax (or an intermediate transfer body or the like). And transferring the toner image onto the recording medium by heating and pressurizing the recording medium and the belt-shaped fixing member in an overlapped state, and then cooling and releasing the recording medium from the belt-shaped fixing member. An image is formed on the recording medium through a fixing step of fixing the image on the recording medium. The fixing step may be performed a plurality of times, and among the plurality of fixing steps, at least one fixing step of a cooling-after-heating peeling method using the belt-shaped fixing belt is included.
[0066]
In the image forming method of the present invention, the material constituting the toner is not particularly limited, and the wax has a heat absorption onset temperature of 40 ° C. or higher, more preferably 50 ° C. or higher on a DSC curve measured by a differential scanning calorimeter. Use If the heat absorption start temperature in the DSC curve is lower than 40 ° C., aggregation of toner occurs in a copying machine or a toner bottle. The endothermic onset temperature depends on the content of low molecular weight components in the molecular weight distribution of the wax and the type and amount of polar groups in the structure of the wax. In general, when the molecular weight is increased, the endothermic onset temperature increases with the melting point, but the original low melting temperature and low viscosity of the wax are impaired. For this reason, it is effective to select and remove only those low molecular weight substances from the molecular weight distribution of the wax by a method such as molecular distillation, solvent fractionation, gas chromatography fractionation, and the like.
[0067]
It is desirable that the wax has a melting point in the range of 80 to 120 ° C. and shows a melt viscosity at 120 ° C. of 1 to 200 centipoise, more preferably 1 to 100 centipoise. If the melting point is less than 80 ° C., the phase change temperature of the wax is too low, the blocking resistance is poor, and the developing property is deteriorated when the temperature in the copying machine is high. When the melting point exceeds 120 ° C., the phase change temperature of the wax is too high, which is not desirable from the viewpoint of energy saving. On the other hand, if the melt viscosity is higher than 200 centipoise, the elution from the toner is weak, and the fixing and releasability becomes insufficient.
[0068]
The present wax is obtained from the following wax. Paraffin wax and its derivatives, montan wax and its derivatives, microcrystalline wax and its derivatives, Fischer-Tropsch wax and its derivatives, polyolefin wax and its derivatives, and the like. Derivatives include oxides, polymers with vinyl monomers, and graft-modified products. In addition, alcohols, fatty acids, vegetable waxes, animal waxes, mineral waxes, ester waxes, acid amides and the like can also be used.
[0069]
The amount of the wax added to the toner is 1 to 15% by weight, and more preferably 3 to 13% by weight. If the amount of the wax is less than 1% by weight, sufficient fixing latitude (temperature range of a fixing roll that can fix without toner offset) cannot be obtained. On the other hand, if the content is more than 10% by weight, the amount of wax detached and released from the toner increases, and the developer carrier is likely to be contaminated. Further, the powder fluidity of the toner deteriorates, and free wax adheres to the surface of the photoreceptor on which the electrostatic latent image is formed, so that the electrostatic latent image cannot be accurately formed. Further, the wax is inferior in transparency as compared to the binder resin, so that the transparency of an image such as an OHP is reduced, resulting in a dark projected image.
[0070]
Hereinafter, an image forming apparatus (image forming apparatus of the present invention) suitably applied to the image forming method of the present invention will be described.
[0071]
The image forming apparatus shown in FIG. 5 includes an image forming apparatus main body 20 in which a belt-type fixing device 25 is built. In the drawing, other main parts are omitted.
[0072]
In the image forming apparatus main body 20 of the image forming apparatus shown in FIG. 5, a latent image for forming a latent image is formed on the latent image carrier, and the latent image is developed using a developer containing at least toner. A toner image is obtained on a carrier, and the toner image is transferred onto a recording medium via an intermediate transfer member. Thereafter, fixing is performed in the belt-type fixing device 25, and a toner image is formed on the recording medium.
[0073]
The image forming apparatus shown in FIG. 6 includes an image forming apparatus main body 20 containing a roll type fixing device 25a and a secondary fixing unit 50 containing a belt type fixing device 58. In the drawing, other main parts are omitted.
[0074]
The image forming apparatus shown in FIG. 6 has a configuration in which the primary fixing is performed by the roll-type fixing device 25 a built in the image forming apparatus main body 20 and the secondary fixing is performed by the belt-type fixing device 58 built in the secondary fixing unit 50. Has become.
[0075]
In the image forming apparatus main body 20 of the image forming apparatus shown in FIG. 6, a latent image for forming a latent image is formed on the latent image carrier, and the latent image is developed using a developer containing at least toner. A toner image is obtained on a carrier, and the toner image is transferred onto a recording medium via an intermediate transfer member. After that, primary fixing is performed in the roll-type fixing device 25a, and the recording medium is conveyed to the secondary fixing unit 50.
[0076]
The secondary fixing unit 50 includes an inlet 51 through which a recording medium discharged from the image forming apparatus main body 20 is introduced. Inside the inlet 51, a switching gate 52 for switching a conveyance path of the recording medium is provided. Is provided. In the case where the recording medium discharged from the image forming apparatus main body 20 is discharged onto the external first discharge tray 55 without being subjected to the secondary fixing, the transfer gate is moved upward by the switching gate 52 to the first position. The sheet is switched to the transport path 53, and is discharged onto the first discharge tray 55 by the discharge roll 54.
[0077]
On the other hand, when the recording medium discharged from the image forming apparatus main body 20 is subjected to the secondary fixing process, the transport path is switched to the lower second transport path 56 by the switching gate 52, and the transport belt 57 The sheet is conveyed to a belt-type fixing device 58, undergoes a fixing process by the belt-type fixing device 58, and is discharged to a second discharge tray 60 by a discharge roller 59.
[0078]
Hereinafter, the belt-type fixing device 25 (58) will be described.
As shown in FIG. 7, the belt-type fixing device 25 (58) includes a fixing belt 64 (belt) rotatably stretched by three rolls including a heating roll 61, a peeling roll 62, and a walk control roll 63. Fixing member), and a pressure roll 65 that is in pressure contact with the heating roll 61 via a fixing belt 64.
[0079]
In the fixing process by the belt-type fixing device 58, the pressure contact portion 72 between the fixing belt 64 and the pressure roll 65 is passed through a recording medium such that the toner image is located on the fixing belt 64 side, and the toner image is heated and pressed. Thus, the recording medium 10 is separated from the fixing belt 64 in a state where the fixing belt 64 is cooled to some extent.
[0080]
The heating roll 61 has, for example, an elastic layer made of silicone rubber or the like having a rubber hardness measured in accordance with JIS K6253 preferably in the range of 20 to 60 ° on a surface of a metal core made of aluminum or stainless steel. Preferably, the elastic layer is coated with a thickness in the range of 1 mm to 3 mm, and the surface of the elastic layer is coated with a release layer made of a PFA tube or the like to form a predetermined outer diameter.
[0081]
Inside the heating roll 61, a halogen lamp having a heating value in a range of preferably 300 to 350 W is provided as a heating source. The heating roll 61 is heated by the halogen lamp 69 such that the surface temperature of the heating roll 61 becomes a predetermined temperature (preferably in the range of 130 to 195 ° C.).
[0082]
Further, as the pressure roll 65, for example, one configured in the same manner as the heating roll 61 is used, and the rubber hardness measured based on JIS K6253 is preferably applied to the surface of a metal core made of aluminum, stainless steel, or the like. An elastic layer 67 made of silicone rubber or the like having a range of 20 ° to 60 ° is preferably covered with a thickness of 1 mm to 3 mm, and a release layer made of a PFA tube or the like is further provided on the surface of the elastic layer. Which are formed to have a predetermined outer diameter.
[0083]
Inside the pressure roll 65, a halogen lamp having a calorific value of preferably 300 W to 350 W is provided as a heating source. The halogen lamp 69 heats the pressure roll 65 from the inside such that the surface temperature thereof becomes a predetermined temperature (preferably in the range of 85 ° C. to 155 ° C.). In the pressure roll 65, a heating source may be omitted.
[0084]
The heating roll 61 and the pressure roll 65 are configured to be in pressure contact with each other via a fixing belt 64 by a pressure unit (not shown), preferably at a nip pressure in the range of 100 kPa to 200 kPa.
[0085]
As described above, the fixing belt 64 is circumferentially stretched by three rolls including a heating roll 61, a peeling roll 62, and a walk control roll 63, and is rotationally driven by a driving source (not shown). The heating roller 61 is rotated at a predetermined moving speed. As the fixing belt 64, the above-described belt-shaped fixing belt is used.
[0086]
A cooling heat sink 70 for forcibly cooling the fixing belt 64 is provided between the heating roll 61 and the peeling roll 62 on the inner surface side of the fixing belt 64. The cooling heat sink 70 cools the fixed recording medium that is in close contact with the fixing belt 64. At this time, the fixing belt 64 is cooled to a range of 50 ° C. to 80 ° C. in the vicinity of the peeling roll 62.
The fixing belt 64 is provided with a small-diameter tension roll 71 that applies a certain tension to the fixing belt 64 between the cooling heat sink 70 and the heating roll 61.
[0087]
In the belt-type fixing device 25 (58), the recording medium 10 onto which the toner image T has been transferred (or the recording medium 10 on which the primary fixing has been performed) passes through the pressing portion 72 from left to right in FIG. At this time, the recording medium 10 is introduced into the press contact portion 72 such that the toner image T is located on the heating roll 61 side. While the recording medium 10 passes through the pressure contact portion 72, the toner image T is heated and melted on the surface of the recording medium 10 and fixed.
[0088]
After that, the recording medium 10 in close contact with the surface of the fixing belt 64 is conveyed together with the fixing belt 64 in a state of close contact. During that time, the fixing belt 64 is forcibly cooled by the cooling heat sink 70, so that the toner image T on which the toner image T is fixed is also cooled and solidified. At this time, the stiffness of the recording medium 10 is restored by cooling. The recording medium 10 which is in close contact with the fixing belt 64 is separated from the fixing belt 64 by the separation roll 62 because the stiffness of the recording medium 10 is restored. The residual toner and the like are removed from the surface of the fixing belt 64 from which the recording medium 10 has been separated by the cleaner 73, and the surface is prepared for the next fixing process.
[0089]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples. However, these embodiments do not limit the present invention.
[0090]
(Example 1)
The belt-shaped substrate has a size of 527.8 mm in circumference, 420 mm in width and 75 μm in thickness, and has a volume resistivity of Rv = 10 by adding carbon black. ¹² On a polyimide base layer adjusted to Ω · cm, 100 parts by weight of a fluorocarbon siloxane rubber precursor composition SIFEL610 (manufactured by Shin-Etsu Chemical Co., Ltd.): 100 parts by weight and a fluorinated solvent (m-xylene hexafluoride, perfluoroalkane) , A mixed solvent of perfluoro (2-butyltetrahydrofuran)): a coating solution adjusted to 10 parts by weight, a dip coating to form a coating film, primary vulcanization at 120 ° C. for 10 minutes, and secondary vulcanization at 180 ° C. for 4 hours. Sulfurization was performed to obtain a belt-shaped fixing member having a fluorocarbon siloxane rubber layer (film thickness of 40 μm) as a surface layer.
[0091]
This belt-shaped fixing member is attached to a DocuCenterColor500 (DCC500) manufactured by Fuji Xerox Co., Ltd. having substantially the same configuration as the image forming apparatus shown in FIG. 5 [however, the fixing device is modified into a belt-type fixing device shown in FIG. 7]. Then, a full-color image was formed using a four-color developer for DCC500 (the type of wax contained in the toner was PW725), and the surface of the belt-shaped fixing member was evaluated at 100 kpv repetition in A4 conversion. An image that was not different from the initial one could be obtained. When PW725 is used as the wax contained in the toner, the advancing contact angle on the surface of the belt-shaped fixing member is 65 ± 2 degrees.
[0092]
(Example 2)
The belt-shaped fixing member obtained in Example 1 was replaced with a DCC500 manufactured by Fuji Xerox Co., Ltd. having substantially the same configuration as the image forming apparatus shown in FIG. 6 [however, a secondary fixing unit incorporating a belt-type fixing device shown in FIG. A full-color image is formed using a four-color developer for DCC500 (the type of wax contained in the toner is PW725), and the surface of the belt-shaped fixing member is repeated at 100 kpv in A4 format. As a result, an image which was the same as the initial image could be obtained.
When PW725 is used as the wax contained in the toner, the advancing contact angle on the surface of the belt-shaped fixing member is 65 ± 2 degrees.
[0093]
(Example 3)
The belt-shaped fixing member obtained in Example 1 is mounted on a DCC500 manufactured by Fuji Xerox Co., which is almost the same as the image forming apparatus shown in FIG. 5 [however, the fixing apparatus is modified into a belt-type fixing apparatus shown in FIG. 7]. Then, a full-color image is formed using a four-color developer for DocuPrint C620 manufactured by Fuji Xerox Co., Ltd. (the wax type contained in the toner is carbana wax), and the surface of the belt-shaped fixing member is repeated at 100 kpv in A4 conversion. As a result of the evaluation, it was possible to obtain an image unchanged from the initial image.
When carbana wax is used as the wax contained in the toner, the advancing contact angle on the surface of the belt-shaped fixing member is 60 ± 2 degrees.
[0094]
(Example 4)
The belt-shaped fixing member obtained in Example 1 is mounted on a DCC500 manufactured by Fuji Xerox Co., which is almost the same as the image forming apparatus shown in FIG. 5 [however, the fixing apparatus is modified into a belt-type fixing apparatus shown in FIG. 7]. Then, a full-color image is formed using a four-color developer for DocuPrint C1616 manufactured by Fuji Xerox Co., Ltd. (the wax type contained in the toner is carbana wax), and the surface of the belt-shaped fixing member is repeated at 100 kpv in A4 conversion. As a result, an image which was the same as the initial image could be obtained.
When carbana wax is used as the wax contained in the toner, the advancing contact angle on the surface of the belt-shaped fixing member is 60 ± 2 degrees.
[0095]
(Example 5)
A belt-like fixing member was prepared in the same manner as in Example 1, except that SIFEL611 (manufactured by Shin-Etsu Chemical Co., Ltd.), which is a fluorocarbon siloxane rubber precursor composition, was used as the surface layer forming material in the belt-like fixing member of Example 1. When manufactured and repeatedly evaluated, an image unchanged from the initial one could be obtained.
When PW725 is used as the wax contained in the toner, the advancing contact angle on the surface of the belt-shaped fixing member is 63 ± 2 degrees.
[0096]
(Example 6)
A belt-like fixing member was prepared in the same manner as in Example 1, except that SIFEL650 (manufactured by Shin-Etsu Chemical Co., Ltd.), which is a fluorocarbon siloxane rubber precursor composition, was used as the surface layer forming material in the belt-like fixing member of Example 1. When manufactured and repeatedly evaluated, an image unchanged from the initial one could be obtained.
When PW725 is used as the wax contained in the toner, the advancing contact angle on the surface of the belt-shaped fixing member is 65 ± 2 degrees.
[0097]
(Example 7)
The belt-shaped substrate has a size of 527.8 mm in circumference, 420 mm in width and 75 μm in thickness, and has a volume resistivity of Rv = 10 by adding carbon black. ¹² DY39-115 (manufactured by Dow Corning Toray Silicone Co., Ltd.), a primer for silicone rubber, was impregnated and applied onto the polyimide base layer adjusted to Ω · cm, and then air-dried for 30 minutes. DY35-796AB, a body composition (manufactured by Dow Corning Toray Silicone Co., Ltd.): 100 parts by weight and a coating solution prepared with 30 parts by weight of n-hexane are dip-coated to form a coating film, and 120 ° C. for 10 minutes. Primary vulcanization was performed to obtain a silicone rubber layer (film thickness 40 μm). On this silicone rubber layer, 100 parts by weight of SIFEL610 (manufactured by Shin-Etsu Chemical Co., Ltd.), which is a fluorocarbon siloxane rubber precursor composition, and a fluorine-based solvent (m-xylene hexafluoride, perfluoroalkane, perfluoro (2-butyltetrahydrofuran) A) mixed solvent): a coating solution adjusted to 20 parts by weight is formed by dip coating to form a coating film, and then subjected to primary vulcanization at 120 ° C. for 10 minutes and secondary vulcanization at 180 ° C. for 4 hours to obtain a fluorocarbon siloxane rubber A belt-shaped fixing member having a layer (film thickness: 20 μm) was obtained.
[0098]
This belt-shaped fixing member is attached to a DocuCenterColor500 (DCC500) manufactured by Fuji Xerox Co., Ltd. having substantially the same configuration as the image forming apparatus shown in FIG. 5 [however, the fixing device is modified into a belt-type fixing device shown in FIG. 7]. Then, a full-color image was formed using a four-color developer for DCC500 (the type of wax contained in the toner was PW725), and the surface of the belt-shaped fixing member was evaluated at 100 kpv repetition in A4 conversion. An image that was not different from the initial one could be obtained. When PW725 is used as the wax contained in the toner, the advancing contact angle on the surface of the belt-shaped fixing member is 65 ± 2 degrees.
[0099]
(Comparative Example 1)
As the surface layer forming material in the belt-shaped fixing member of Example 1, DY35-796AB (manufactured by Dow Corning Toray Silicone Co., Ltd.), which is a silicone rubber precursor composition, was used instead of the fluorocarbon siloxane rubber precursor composition. A belt-shaped fixing member was obtained in the same manner as in Example 1 except for the above. When the same repetitive evaluation was performed as in Example 1, after 100 kpv, a substance including wax, a developer and paper powder was fixed on the surface of the silicone rubber, and when a uniform image was taken, the gloss was partially different. However, it became visually recognizable, and the image was unusable.
When PW725 is used as the wax contained in the toner, the advancing contact angle on the surface of the belt-shaped fixing member is 45 ± 2 degrees.
[0100]
(Comparative Example 2)
In place of the fluorocarbon siloxane rubber precursor composition, DY35-7002AB (manufactured by Dow Corning Toray Silicone Co., Ltd.), which is a silicone rubber precursor composition, was used as the surface layer forming material in the belt-shaped fixing member of Example 1. A belt-shaped fixing member was obtained in the same manner as in Example 1 except for the above. When the same repetitive evaluation as in Example 1 was performed, after 100 kpv, a substance including wax, a developer and paper powder was fixed on the surface of the silicone rubber layer, and when a uniform image was taken, the gloss was partially reduced. The difference can be visually confirmed, and the image is unusable.
When PW725 is used as the wax contained in the toner, the advancing contact angle on the surface of the belt-shaped fixing member is 47 ± 2 degrees.
[0101]
(Comparative Example 3)
The belt-shaped fixing member obtained in Example 1 is mounted on a DCC500 manufactured by Fuji Xerox Co., which is almost the same as the image forming apparatus shown in FIG. 5 [however, the fixing apparatus is modified into a belt-type fixing apparatus shown in FIG. 7]. Then, a full-color image is formed using a four-color developer for DocuColor 1255CP manufactured by Fuji Xerox Co., Ltd., which is a toner containing no wax, and the surface of the belt-shaped fixing member is repeatedly evaluated at 10 kpv in A4 conversion. However, a substance containing a developer and paper powder appeared to adhere to the surface of the fluorocarbon siloxane rubber, and when a uniform image was taken, it became possible to visually check the part with a different gloss visually, and an image that was unusable for use became.
[0102]
(result)
From the results of these examples, in Examples 1 to 7, when the surface of the belt-shaped fixing member was evaluated for repetition of 100 kpv (print volume) in A4 conversion, the image quality evaluation was all good.
On the other hand, in Comparative Examples 1 and 2, after 100 kpv, a substance containing wax, a developer and paper powder appeared to adhere to the surface of the silicone rubber, and when a uniform image was taken, the place where the gloss was partially different was visually observed. And the image became unusable. In Comparative Example 3, when a toner containing no wax was used, after 10 kpv, a substance containing a developer and paper powder adhered to the surface of the fluorocarbon siloxane rubber, and when a uniform image was obtained, the gloss was partially different. It became visually recognizable, and the image was unusable.
As described above, in a system in which the toner is cooled and peeled off and fixed using the toner (developer) containing the wax, the wax alone contained in the toner is melted at 140 ° C., and the advancing contact angle after solidification at room temperature is 50 ° or more. It can be seen that the use of the belt-shaped fixing member having the surface layer having the following conditions can prevent the deterioration of the image quality even after the surface of the belt-shaped fixing member has been repeatedly evaluated at 100 kpv in A4 conversion.
.
[0103]
【The invention's effect】
As described above, according to the present invention, even when fixing is performed by a cooling and peeling type fixing method after heating using an oilless toner containing a wax, contamination of the belt-shaped fixing member by the wax can be prevented, and image gloss can be reduced. Thus, it is possible to provide an image forming method and an image forming apparatus capable of suppressing deterioration of image quality and suppressing deterioration of image quality and obtaining an image with high image quality and excellent fixability over a long period of time.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an example of a belt-shaped fixing member used in the present invention.
FIG. 2 is a schematic sectional view showing another example of a belt-shaped fixing member used in the present invention.
FIG. 3 is a schematic sectional view showing another example of a belt-shaped fixing member used in the present invention.
FIG. 4 is a schematic sectional view showing another example of the belt-shaped fixing member used in the present invention.
FIG. 5 is a schematic configuration diagram illustrating an example of the image forming apparatus of the present invention.
FIG. 6 is a schematic configuration diagram illustrating another example of the image forming apparatus of the present invention.
FIG. 7 is a schematic configuration diagram illustrating an example of a belt-type fixing device built in the image forming apparatus of the present invention.
[Explanation of symbols]
1 belt-shaped fixing member
2 Base layer
3. Fluorocarbon siloxane rubber layer (rubber layer (1))
4 Silicone rubber layer (rubber layer (2))
5 Adhesive layer
20 Image Forming Apparatus Main Body
25, 58 Belt-type fixing device
25a Roll type fixing device
50 Secondary fixing unit
64 Fixing belt (belt-shaped fixing member)

Claims (11)

The toner image is fixed to the recording medium by heating and pressing the recording medium onto which the toner image has been transferred and the belt-shaped fixing member in a superposed state, and then, after cooling, peels off the recording medium from the belt-shaped fixing member. In the image forming method,
The toner contains at least a binder resin, a colorant, and a wax, and the belt-shaped fixing member melts the wax alone contained in the toner at 140 ° C. and has an advancing contact angle of 50 ° after solidification at room temperature. An image forming method comprising the surface layer described above. The recording medium on which the toner image has been transferred is heated and pressed by the first fixing member, and heated and pressed in a state where the recording medium on which the toner image is fixed and the second belt-shaped fixing member are stacked, and then cooled. An image forming method for fixing the toner image to the recording medium by peeling the recording medium from a second belt-shaped fixing member,
The toner contains at least a binder resin, a colorant, and a wax, and the second belt-shaped fixing member melts the wax alone contained in the toner at 140 ° C., and advancing contact angle after solidification at room temperature. Has a surface layer showing a temperature of 50 degrees or more. The belt-shaped fixing member has a surface layer on a base layer,
The image forming method according to claim 1, wherein the surface layer is a rubber layer including a fluorocarbon siloxane rubber. 4. The image forming method according to claim 3, wherein a thickness of the rubber layer including the fluorocarbon siloxane rubber is 300 μm or less. 5. The rubber layer comprising the fluorocarbon siloxane rubber is formed by applying a fluorocarbon siloxane rubber precursor composition to the surface of the base layer and curing the composition. The image forming method described in the above. The belt-shaped fixing member has a surface layer on the base layer,
The said surface layer is comprised by the rubber layer comprised containing the silicone rubber, and the rubber layer comprised containing the fluorocarbon siloxane rubber provided on the said rubber layer, The characterized by the above-mentioned. Or the image forming method according to 2. The thickness of the rubber layer containing the silicone rubber is larger than the thickness of the rubber layer containing the fluorocarbon siloxane rubber, and the thickness of the entire rubber layer is 300 μm or less. The image forming method according to claim 6, wherein The rubber layer including the silicone rubber is formed by applying and curing a silicone rubber precursor composition on the surface of the base layer, and the rubber layer including the fluorocarbon siloxane rubber. The image according to claim 6 or 7, wherein the image is formed by applying a fluorocarbon siloxane rubber precursor composition to a surface of a rubber layer including the silicone rubber and curing the composition. Forming method. The image forming method according to any one of claims 3 to 6, wherein the fluorocarbon siloxane rubber has a perfluoroalkyl ether group and / or a perfluoroalkyl group in a main chain. The image forming method according to any one of claims 3 to 7, wherein the rubber layer containing the fluorocarbon siloxane rubber is a cured product of a precursor composition having the following components (A) to (D).
(A) a fluorocarbon polymer containing a fluorocarbon siloxane having a repeating unit represented by the following general formula (1) as a main component and having an aliphatic unsaturated group;

(Wherein, R ¹⁰ is an unsubstituted or substituted monovalent hydrocarbon group, x is an integer of 1 or more, a and e are each 0 or 1, b and d are each an integer of 1 to 4, c is 0 to 0) It is an integer of 8.)
(B) Two or more ≡SiH groups are contained in one molecule, and the content of the ≡SiH group is 1 to 4 times by mole based on the amount of the aliphatic unsaturated group in the fluorocarbon siloxane rubber composition. Certain organopolysiloxanes and / or fluorocarbon siloxanes,
(C) a filler,
(D) an effective amount of catalyst. The toner image is fixed to the recording medium by heating and pressing the recording medium onto which the toner image has been transferred and the belt-shaped fixing member in a superposed state, and then, after cooling, peels off the recording medium from the belt-shaped fixing member. In an image forming apparatus having a fixing unit,
The toner contains at least a binder resin, a colorant, and a wax, and the belt-shaped fixing member melts the wax alone contained in the toner at 140 ° C. and has an advancing contact angle of 50 ° after solidification at room temperature. An image forming apparatus having the surface layer described above.

Images