JP2005043456A - Fixing member evaluation method, fixing belt, and thermal fixing roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaluation method by which whether a fixing belt is excellent or not in toner releasability, flexibility and elasticity can be evaluated easily. <P>SOLUTION: The fixing belt 20 with an elastic layer 22 and a releasing layer 23 laminated on a base material 21 is subjected to a universal hardness test in a depth of 1-4 μm from the surface of the releasing layer 23. If the universal harness HU in a depth of 1 μm is ≤30 [N/mm<SP>2</SP>] and the universal hardness HU in a depth of 4 μm is ≤2 [N/mm<SP>2</SP>], the fixing belt 20 is evaluated as an acceptable product. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

ここで、Ｆ：試験荷重［Ｎ］
Ｓ：試験荷重下での圧子の表面積［ｍｍ^２］
ｈ：試験荷重下での押し込み深さ［ｍｍ］
である。また、圧子は四角錐の対面角度１３６°のダイヤモンド圧子（ビッカース圧子）である。
【００６８】
本実施の形態では、定着ベルト２０に対して、試験環境温度２５℃の下で、離型層２３表面側から深さ１μｍ乃至４μｍにおけるユニバーサル硬さ試験を行って、深さ１μｍにおけるユニバーサル硬さＨＵが、ＨＵ≦３０［Ｎ／ｍｍ^２］であり、深さ４μｍにおけるユニバーサル硬さＨＵが、ＨＵ≦１２［Ｎ／ｍｍ^２］であれば、当該定着ベルト２０は合格品であると評価する。
【００６９】
また、本実施の形態では、定着ベルト２０に対して、試験環境温度２００℃の下で、離型層２３表面側から深さ１μｍ乃至４μｍにおけるユニバーサル硬さ試験を行って、深さ１μｍにおけるユニバーサル硬さＨＵが、ＨＵ≦１０［Ｎ／ｍｍ^２］であり、深さ４μｍにおけるユニバーサル硬さＨＵが、ＨＵ≦４［Ｎ／ｍｍ^２］であれば、当該定着ベルトは合格品であると評価する。
【００７０】
ここで、試験環境温度２５℃は室温に相当し、また験環境温度２００℃はトナー定着時に定着ベルトが晒されるランニング温度に相当している。そして、離型層２３表面側から深さ１μｍにおけるユニバーサル硬さＨＵの上限は、試験環境温度２５℃のときは３０［Ｎ／ｍｍ^２］に、試験環境温度２００℃のときは１０［Ｎ／ｍｍ^２］にそれぞれ設定され、室温の下でのユニバーサル硬さＨＵはランニング温度の下でのユニバーサル硬さＨＵの３倍となっている。また、離型層２３表面から深さ４μｍにおけるユニバーサル硬さＨＵの上限は、試験環境温度２５℃のときは１２［Ｎ／ｍｍ^２］に、試験環境温度２００℃のときは４［Ｎ／ｍｍ^２］にそれぞれ設定され、同様に、室温の下でのユニバーサル硬さＨＵはランニング温度の下でのユニバーサル硬さＨＵの３倍となっている。
【００７１】
これにより、離型層２３の表面から深さ１μｍ乃至４μｍにおけるユニバーサル硬さ試験を、室温の下と定着ベルト２０のランニング温度の下で行って、離型層２３の表面から同じ深さにおけるユニバーサル硬さＨＵを比較したとき、室温の下でのユニバーサル硬さＨＵがランニング温度の下でのユニバーサル硬さＨＵの３倍であれば、当該定着ベルト２０は合格品であると評価することもできる。
【００７２】
なお、本実施の形態では定着ベルトについて説明してきたが、本発明は、芯金つまり基材の上に、弾性層、離型層が積層された構造の加熱定着ローラについての評価にも適用できる。
【００７３】
【実施例】
次に、ユニバーサル硬さが画像特性に与える影響についての試験を行った。
記録紙上に未定着画像を形成させ、下記の条件で熱定着装置により記録紙上に定着させた。この際、表面のユニバーサル硬さが異なる定着ベルトを用い、定着後の梨地画像（光沢ムラ）との対応をとった。
評価画像（未定着画像）
トナー：マゼンタ色
付着量：０．８〜０．９ｍｇ／ｃｍ^２
紙種：Ｔ６２００（６２ｋｇ紙）
【００７４】
ここで、本実施例の定着ベルトを用いたフルカラー熱定着装置について説明する。本熱定着装置には、図３に示すように定着ベルト２０が用いられている。定着ベルト２０は、加熱ローラ３１と定着ローラ３２間に巻き回しされて、適当なテンション（テンションを掛けるための機構は図示省略）が掛けられている。また、定着ローラ３２に平行に加圧ローラ３３が配置され、定着ローラ３２に巻き回しされた定着ベルトは、加圧ローラ３３によって定着ローラ３２側に圧接されている（圧接機構は図示省略）。
【００７５】
加圧ローラ３３によって定着ベルト２０を圧接する方式は、図３（Ａ）と図３（Ｂ）のように大きく分けて２つある。図３（Ａ）の方式（リコー社製：Ｉｍａｇｉｏ ｃｏｌｏｒ ３１００等）は、ニップ部が加圧ローラ３３と定着ローラ３２により（定着ベルトを介して）形成されるのみである。これに対して、図３（Ｂ）の方式（リコー社製：Ｉｐｓｉｏ ｃｏｌｏｒ ８０００等）は、加圧ローラ３３と定着ローラ３２から成るニップ部の他に、その前部側にベルトが這い回ることで形成されるニップ部を有する。この違いにより、立ち上がり時間、搬送性、紙分離性などに違いが発生するが、本実施例では定着ベルトの検討を目的としたことから、定着方式を図３（Ａ）の方式に固定し、ベルトによる画像品質への影響を調査した。
【００７６】
また、図３において、加熱ローラ３１の内部には、加熱のためのハロゲンランプ３４が設置されている。このハロゲンランプ３４は、定着温度、線速、立ち上がり時間、およびベルト表面温度バラツキの仕様（規格）により、本数、消費電力が調整される。一般的には、図３（Ａ）の方式では、加熱ローラ３１、定着ローラ３２、および加圧ローラ３３の全てにハロゲンランプ３４が設置され、図３（Ｂ）の方式では、加熱ローラ３１および加圧ローラ３３にハロゲンランプ３４が設置される。
【００７７】
試験条件は以下のとおりである。

【００７８】
梨地画像評価については、下記に示すランク評価を行った（各ランクの中間は０．５とする）。
ランク５：顕著な梨地状ムラ無し 合格レベル
ランク４：ランク３とランク５の中間 合格レベル
ランク３：部分的に梨地状のムラが発生 合格レベル
ランク２：ランク１とランク３の中間 不合格レベル
ランク１：画像全体にわたって梨地状ムラが発生 不合格レベル
図４は本発明に係る画像形成装置の概略構成を示している。図４の画像形成装置は４連タンデム方式のフルカラープリンタで、図３（Ａ）に示した熱定着装置が内蔵されている。
【００７９】
このフルカラープリンタは、イエロー、マゼンタ、シアン、ブラックの４色のトナー像をそれぞれ形成する４組の画像形成部４１Ｙ，４１Ｍ，４１Ｃ，４１Ｂｋを備えている。画像形成部４１Ｙ，４１Ｍ，４１Ｃ，４１Ｂｋの下方には、プーリ４２，４３間に巻き回しされた搬送ベルト４４が設けられている。この搬送ベルト４４は駆動装置（図示省略）によって矢印ｂ方向に駆動され、画像形成部４１Ｙ，４１Ｍ，４１Ｃ，４１Ｂｋを通して記録紙Ｐを搬送する。
【００８０】
ここでは、画像形成部４１Ｙ，４１Ｍ，４１Ｃ，４１Ｂｋの各々は同じ構成をなしているので、イエロー用の画像形成部４１Ｙにづいてだけ説明し、他の色用の画像形成部４１０Ｍ，４１Ｃ，４１Ｂｋについては、画像形成部４１Ｙと同一部分には同一数字を付して詳細な説明を省略する。
【００８１】
画像形成部４１Ｙは、その略中央位置に搬送ベルト４４に転接された感光体ドラム４５Ｙを有する。感光体ドラム４５Ｙの周囲には、感光体ドラム４５Ｙの表面を所定の電位に帯電させる帯電装置４６Ｙ、帯電されたドラム表面を色分解された画像信号に基づいて露光し、ドラム表面上に静電潜像を形成する露光装置４７Ｙ、ドラム表面上に形成された静電潜像にイエロートナーを供給して現像する現像装置４８Ｙ、現像したトナー像を搬送ベルト４４で搬送される記録紙Ｐ上に転写する転写ローラ４９Ｙ、転写されずにドラム表面に残留した残留トナーを除去するクリーナ５０Ｙ、および図示しないドラム表面に残留した電荷を除去する除電ランプが、感光体ドラム４５Ｙの回転方向に沿って順に配設されている。
【００８２】
搬送ベルト４４の一側（図中右側）には、記録紙Ｐを搬送ベルト４４上に給紙するための給紙機構５１が配設されている。また、搬送ベルト４４の他側（図中左側）には熱定着装置５２が配設され、搬送ベルト４４によって搬送された記録紙Ｐは、連続的に熱定着装置５２に供給される。
【００８３】
熱定着装置５２は、図３（Ａ）でも示したように、加熱ローラ３１と、加熱ローラ３１の下方に配設された定着ローラ３２とを有し、これら加熱ローラ３１と定着ローラ３２間に無端状の定着ベルト２０が巻き回しされている。また、定着ローラ３２の下方には加圧ローラ３３が配設され、定着ベルト２０は加圧ローラ３３によって定着ローラ３２に圧接されている。なお、図４には示してないが、加熱ローラ３１、定着ローラ３２、加圧ローラ３３の各内部にはハロゲンランプ３４（図３（Ａ）参照）が設けられている。
【００８４】
そして、搬送ベルト４４から供給された記録紙Ｐは、定着ベルト２０と加圧ローラ３３との間を通過するときに加熱・加圧され、記録紙Ｐ上のトナー像が定着される。トナー像定着後の記録紙Ｐは排紙ローラ５３，５４を介して搬送路下流側に排紙される。
【００８５】
次に、図３（Ｂ）に示した熱定着装置を内蔵した画像形成装置（フルカラープリンタ）について説明する。この画像形成装置も、図４に示した画像形成部４１Ｙ，４１Ｍ，４１Ｃ，４１Ｂｋ、搬送ベルト４４、および給紙機構５１を有している。この画像形成装置は、図５に示すように、加熱ローラ３１と、加熱ローラ３１の斜め下方に配設された定着ローラ３２とを有し、これら加熱ローラ３１と定着ローラ３２間に無端状の定着ベルト２０が巻き回しされている。定着ローラ３２の下方には加圧ローラ３３が配設され、定着ベルト２０は加圧ローラ３３によって定着ローラ３２に圧接されている。加熱ローラ３１および加圧ローラ３３の内部にはハロゲンランプ３４が設けられている。
【００８６】
加熱ローラ３１は、バネなどの図示していない付勢手段によって、定着ローラ３２から離間する方向に付勢され、これにより、定着ベルト２０に適当な所定の張力を与えるようになっている。
【００８７】
定着ローラ３２は、芯金３２Ａと、この芯金３２Ａを被覆する耐熱多孔質層の弾性体層３２Ｂとを有する。この定着ローラ３２は、バネなどの図示していない付勢手段によって、加圧ローラ３３を圧接する方向に付勢されている。
【００８８】
また、定着ローラ３２は、定着ローラ３２の軸心を頂点として、定着ローラ３２の軸心と加熱ローラ３１の軸心とを結ぶ直線と、加熱ローラ３１の軸心と加圧ローラ３３の軸心とを結ぶ直線とによって挟まれる角が鋭角をなすように、加圧ローラ３３に当接されている。これにより、加圧ローラ３３が定着ローラ３２に対向しない部位で定着ベルト２０に当接する第１の定着部Ａと、加圧ローラ３３が定着ベルト２０を介して定着ローラ３２に当接する第２の定着部Ｂとが形成され、これら定着部Ａ，Ｂで記録紙を挟持し加熱するようになっている。
【００８９】
また、加熱ローラ３１、加圧ローラ３３に対向してサーミスタ５５が配置され、加熱ローラ３１および加圧ローラ３３はサーミスタ５５によって温度が検知されている。
【００９０】
なお、図中、符号５６は定着される記録紙を第１の定着部Ａに向けて案内するガイドを示している。また、符号５７はオフセット防止用オイルの塗布ローラを、符号５８はクリーニングローラをそれぞれ示している。
【００９１】
（実施例１）
一般的に梨地画像は、高光沢画像でより顕著となることが知られている。前述した定着条件で、定着温度１６０〜１７０℃の際に、光沢５〜８％（マゼンタ色：０．８〜０．９ｍｇ／ｃｍ^２）となるトナー（トナー１）、および、光沢度１０〜１５％（マゼンタ色：０．８〜０．９ｍｇ／ｃｍ^２）となるトナー（トナー２）を使用し、画像の光沢を変化させ、ユニバーサル硬さとの関係を調査した。
【００９２】
図６〜図９にユニバーサル硬さと梨地ランクの関係を示す。その結果をまとめると、ユニバーサル硬さＨＵが、以下の（１）式および（２）式に示す範囲に、または（３）式および式（４）式に示す範囲にあれば、良好な光沢均一性（ランク３以上）の画質を得ることができた。
【００９３】
試験環境温度が２５℃のとき、離型層表面からの深さ１μｍにおけるユニバーサル硬さＨＵ１、および離型層表面からの深さ４μｍにおけるユニバーサル硬さＨＵ２は、
ＨＵ１≦３０ ［Ｎ／ｍｍ^２］ ・・・・・・・（１）
ＨＵ２≦１２ ［Ｎ／ｍｍ^２］ ・・・・・・・（２）
試験環境温度が２００℃のとき、離型層表面からの深さ１μｍにおけるユニバーサル硬さＨＵ３、および離型層表面からの深さ４μｍにおけるユニバーサル硬さＨＵ４は、
ＨＵ３≦１０ ［Ｎ／ｍｍ^２］ ・・・・・・・（３）
ＨＵ４≦ ４ ［Ｎ／ｍｍ^２］ ・・・・・・・（４）
（１）〜（４）式の結果より、試験環境温度が２５℃または２００℃の場合は、押し込み深さ１μｍ〜４μｍの範囲内の任意の押し込み深さにおけるユニバーサル硬さが予測できる。また、押し込み深さが１μｍまたは４μｍの場合は、任意の試験環境温度（樹脂が分解するような温度は除く）におけるユニバーサル硬さが予測できる。
【００９４】
次に、押し込み深さとして１μｍまたは４μｍを選択した理由について説明する。従来技術でも述べたように、ベルト（部材）の硬さと光沢の均一性については、明確な特性値化が行われていない。特に、光沢の均一性に影響を及ぼすものが、基材の撓みまでを含めたベルト全体の柔軟性なのか、もしくはベルトの最も外側の、極表面の柔軟性なのか、という点である。極表面の硬さを測定する場合には、離型層の最低膜厚は１０μｍ程度であることから、前述した測定上の膜厚制限から、押し込み深さは１μｍ以下であることが必要である。ベルトを積層体（基材＋弾性層＋離型層）と考える場合には、より深い押し込み深さでの測定が可能であり、例えば、基材５０μｍ、弾性層２００μｍ、離型層３０μｍであれば、全体で２８０μｍであることから、２８μｍまでの押し込み深さが可能となる。本発明者等は、１〜２０μｍまでの押し込み深さでのユニバーサル硬さと光沢均一性に相関があることを確認した。
【００９５】
押し込み深さは、この１μｍ、４μｍが特別の意味を持つわけではない、例えば、この中間の２μｍまたは３μｍでも同じように、光沢均一性との相関が得られる。ただし、この際使用したベルト（部材）を押し込み深さ１μｍ、４μｍで測定した場合には、本実施例で提示した範囲での硬さ−光沢均一性の関係が得られたということである。
【００９６】
また、試験環境温度として２５℃または２００℃を選択した理由について説明する。ドイツ規格ＤＩＮ５０３５９−１では測定温度を１０〜３５℃と規定している。このことから本実施例では、２５℃を測定温度とした。また、今回使用した、フィッシャースコープ Ｈ−１００では測定温度を変化させることができることから、定着温度に近い２００℃の環境下でも測定を行い、光沢均一性との対応を見た。
【００９７】
図６〜図９より、トナー１の方がトナー２よりも梨地画像に対する余裕度が高いことが分かる。つまり、画像の光沢度が増加すると光沢ムラ（梨地）が多く出る傾向にある。これは、基本的に高光沢画像を得るためには、トナーを充分に溶融させ、粘度を低くさせた上で、記録紙に定着させるが、この低粘度状態のトナーは、より柔軟性の高い部材表面で押圧させることが必要となることを示している。
【００９８】
次に、定着ベルトの構成がユニバーサル硬さに及ぼす影響について検討した。ここでは、表１に示すように、弾性層と離型層の材質や膜厚が異なる定着ベルト（実験例１〜５、比較例１〜７）について、それらのユニバーサル硬さ、耐久性および離型性を検討した。
【００９９】
【表１】

【０１００】
ベルト構成は以下のとおりである。

【０１０１】
次に定着ベルト作製方法について説明する。弾性層成膜工法としてブレード塗装（溶剤等による希釈を行うことで、スプレー塗装、ディッピング塗装などでも作製可能）を用いた。また、本実施例では弾性層材料としてシリコーンゴムを用いたが、このシリコーンゴムは連続使用した際の上限温度が２００℃と耐熱性に優れることが知られている。前述したように、弾性層に用いられるゴム（エラストマー）材料としては、この他に、フロロシリコーンゴム、フッ素ゴム等も挙げられるが、スプレー塗装、ディッピング塗装、ブレード塗装、および注型などの多様な加工が可能なのは現在のところシリコーンゴムだけであり、また、コストの面でもシリコーンゴムが最も安価である。その結果、弾性層材料としては、２００μｍ程度の膜厚のものを、低バラツキで且つ表面平滑性を高くするためには、シリコーンゴムが現段階では最も適していることが分かった。
【０１０２】
離型層成膜工法としてスプレー塗装を用いた。なお、ポリイミド樹脂基体−弾性層間および弾性層−離型層間には、必要に応じてプライマーを使用してもベルト特性に大きな影響は与えない。
【０１０３】
表１より、基材−離型層間に弾性層を設けていない比較例１〜４では、前述した均一光沢画像のためのユニバーサル硬さ値を満たしていないことが分かる。
【０１０４】
また、弾性層を設けた構成では離型層膜厚の増加で、ユニバーサル硬さ値は大きくなっている（硬くなっている）ことが分かる。ユニバーサル硬さの測定法を、本発明のような樹脂およびゴム材料からなる対象物に対して適用した場合、「測定圧子の押し込み深さ」＝「表面に刺さった深さ」＋「表面が撓んだ深さ」となる。
【０１０５】
よって、弾性層上に離型層を形成させた場合には、弾性層硬さ＜離型層硬さであれば（一般的に成り立つと考えられる）、離型層膜厚が薄くなることで、弾性層の柔軟性がベルト表面（離型層表面）に現われやすくなる、つまり、「表面が撓んだ深さが」大きくなり、ユニバーサル硬さ値が小さくなったと考えられる。
【０１０６】
ＰＦＡ１はＰＦＡ２と比べて、柔軟性に劣る材質である。このフッ素樹脂の柔軟性（可撓性）の違いについて説明する。離型層に使用される材料は一般的にはフッ素樹脂が用いられるが、その種類の違い；ＦＥＰ、ＰＦＡ、ＰＴＦＥ…、分子量の違い、フィラー添加有無、および工法等により硬さが変化する。種類の違いについては、グレードによりその順序は前後するが、分子量については一般的に高分子量になるほど硬くなる。また、これらポリマーの違い以外にもフィラー添加による影響がある。
【０１０７】
フィラー添加は、耐摩耗性を向上させるために、カーボンブラック、ウィスカ、シリカ、シリコーンカーバイト、マイカ等が用いられ、導電性付与のためにカーボンブラック、金属酸化物等が用いられる。これらフィラー添加も一般的に材料を硬くする。
【０１０８】
表１に示すとおり、同じ構成（同じ膜厚）とした場合に、これら離型層の材料によってユニバーサル硬さに違いが出てくる。ＰＦＡ１はＰＦＡ２に比べて、膜厚の増加による梨地画像に対する余裕度が低い。本試験結果からも、離型層は弾性層の柔軟性を伝えるために、各離型層材料ごとに、その可撓性を考慮した膜厚設定が必要となることが分かる。
【０１０９】
比較例７は離型層を形成させずに弾性層（シリコーンゴム）が表面に露出した定着ベルトであるが、表面ユニバーサル硬さは非常に小さな値を持つ。しかしながら、耐久性、離型性の点で不充分である。具体的に耐久性の面では、連続通紙により、サーミスタ当接部および記録紙エッジ部により、シリコーンゴム表面の損傷が評価初期から発生する。離型性に関しても、フッ素樹脂離型層を設けた場合と比較し、コールドオフセット−ホットオフセットの定着可能温度幅が狭く、特に薄紙（４５ｋｇ紙）を記録紙とした場合に顕著である。以上のことから、弾性層の表面に離型層を形成させることが必要であることが分かる。
【０１１０】
梨地画像（特に高光沢画像の場合）の不具合を回避するためには、定着ベルト表面に柔軟性が必要であり、その特性値としてユニバーサル硬さを用いることが有効である。定着ベルト表面のユニバーサル硬さは、弾性層材質および膜厚、離型層の材質および膜厚により変化する。よって、これらの組み合わせを適当にし、ユニバーサル硬さが（１）式および（２）式に示した範囲に、または（３）式および（４）式に示した範囲に入れることで、光沢（画像）の均一性が得られる。
【０１１１】
しかしながら、表１の比較例７からも分かるとおり、ゴム材料が表面に露出した場合は耐久性および離型性の点で実使用上の不具合が発生することから、ＰＴＦＥ、ＰＦＡ、ＦＥＰ、およびこれらの混合物から成る離型層が必要である。
【０１１２】
また、弾性層を設けなくても、柔軟性が非常に高いフッ素樹脂が開発されれば、基材＋離型層でも前述した範囲にユニバーサル硬さを収めることは可能となるが、現段階では、基材＋弾性層＋離型層から成る３層構成が、光沢（画像）均一性、離型性および耐久性を全て満たすことが分かる。
【０１１３】
（実施例２）
次に、弾性層と離型層の材質や膜厚が異なる定着ベルト（実験例６〜１０）について、試験環境温度２５℃，６０℃，１００℃，１５０℃，２００℃の下で、押し込み深さ１μｍ，４μｍ，２０μｍとしてユニバーサル硬さ試験を行った。その試験結果を表２に示す。
【０１１４】
【表２】

【０１１５】
ここで、実験例６〜１０における定着ベルトの弾性層および離型層の材質と膜厚は以下のとおりである。
実験例６
弾性層：シリコーンゴム、硬さ２５°（ＪＩＳ Ｋ ６３０１）、膜厚２００μｍ
離型層：材質Ａ、膜厚１５μｍ
実験例７
弾性層：シリコーンゴム、硬さ２５°（ＪＩＳ Ｋ ６３０１）、膜厚２００μｍ
離型層：材質Ｂ、膜厚３０μｍ
実験例８
弾性層：シリコーンゴム、硬さ２５°（ＪＩＳ Ｋ ６３０１）、膜厚２００μｍ
離型層：材質Ｃ、膜厚３０μｍ
実験例９
弾性層：シリコーンゴム、硬さ２５°（ＪＩＳ Ｋ ６３０１）、膜厚３００μｍ
離型層：材質Ｃ、膜厚１０μｍ
実験例１０
弾性層：シリコーンゴム、硬さ２５°（ＪＩＳ Ｋ ６３０１）、膜厚２００μｍ
離型層：材質Ｄ、膜厚２０μｍ
【０１１６】
表２において、（Ａ）は押し込み深さ１μｍの場合のデータを、（Ａ）は押し込み深さ４μｍの場合のデータを、（Ｃ）は押し込み深さ２０μｍの場合のデータをそれぞれ示している。また、（Ｄ）は各押し込み深さ１μｍ，４μｍ，２０μｍの平均値をまとめて示したものである。
【０１１７】
また、表２に示したデータについて、横軸に試験環境温度を、縦軸にユニバーサル硬さを取ってプロットすると、図１０のようになる。図１０において、（Ａ）は押し込み深さ１μｍの場合のグラフ、（Ｂ）は押し込み深さ４μｍの場合のグラフ、（Ｃ）は押し込み深さ２０μｍの場合のグラフである。また図１１は各押し込み深さ１μｍ，４μｍ，２０μｍの平均値をプロットしたグラフである。
【０１１８】
図１０および図１１より、試験環境温度が高くなればユニバーサル硬さは低下する傾向を示し、特に、押し込み深さが１μｍの場合はその傾向が顕著であることが分かる。
【０１１９】
さらに、上記実験例６〜１０の定着ベルト以外に１２個の定着ベルトを用意し、各定着ベルトについて、試験環境温度２５℃，２００℃の下で、押し込み深さ１μｍ，４μｍ，２０μｍとしてユニバーサル硬さ試験を行った。その試験結果を実施例６〜１０と共に図１２および図１３に示す。図１２および図１３において、横軸は押し込み深さを、縦軸はユニバーサル硬さをそれぞれ示しており、図１２は試験環境温度２５℃のときのグラフ、図１３は試験環境温度２００℃のときのグラフである。
【０１２０】
図１２および図１３より、押し込み深さ１μｍ〜４μｍまでは離型層や弾性層の柔軟性および弾力性が影響しているので、押し込み深さが大きくなるに伴ってユニバーサル硬さが急激に低下しているが、押し込み深さが４μｍを超えると、基材の影響が強くなってユニバーサル硬さがあまり低下しないことが分かる。
【０１２１】
以上のことから判断して、定着ベルト（又は加熱定着ローラ）の表面硬さを正確に測定するには、押し込み深さ１μｍ〜４μｍの範囲でユニバーサル硬さ試験を行うのが適していると言える。
【０１２２】
次に、上記各実験例のデータについて、図６〜図９と同様、横軸にユニバーサル硬さを、縦軸に梨地ランクを取って、プロットすると図１４〜図１９のようになる。図１４〜図１９において、ユニバーサル硬さと梨地ランクとの関係を、最小二乗法による直線の方程式、さらには相関係数として求めた。なお、図１４〜図１９はトナー２を用いた場合の結果である。
【０１２３】
ここで、図１４は試験環境温度が室温で押し込み深さが１μｍのとき、図１５は試験環境温度が室温で押し込み深さが４μｍのとき、図１６は試験環境温度が室温で押し込み深さが２０μｍのときである。また、図１７は試験環境温度が２００℃で押し込み深さが１μｍのとき、図１８は試験環境温度が２００℃で押し込み深さが４μｍのとき、図１９は試験環境温度が２００℃で押し込み深さが２０μｍのときである。図１４〜図１９から求めた相関係数を一覧表として表３に示す。
【０１２４】
【表３】

【０１２５】
表３（Ａ）は試験環境温度が２００℃のときのデータ、表３（Ｂ）は試験環境温度が室温のときのデータである。
【０１２６】
（実施例３）
既存のコピー機（例えば、リコー社製のＩｍａｇｉｏ ｃｏｌｏｒ ３１００）の定着条件における画質、耐久性、離型性等の実機特性について調査した。これらの実機特性はトナー、定着条件による影響が強い。例えば、耐久性に関しては、コピー（プリント）速度、分離爪の有無、ニップ部圧力などが影響する。また、離型性に関しては、トナーが強く影響する。つまり、上述した評価結果の中で、耐久性、離型性に関しては、想定しているコピー機やプリンタのスペックにより、必要値が変わってくる。
【０１２７】
具体的に述べると、低速で且つ機械寿命の短い機械では耐久性の低い材料や部材構成が許され、また温度制御の精度が高い機械（このような機械は定着可能温度領域が狭くても良い）や、高離型性のトナーを用いた場合には、定着用部材表面の離型性は若干の低下が許される。これら低スペックの機械を対象とした場合の部材構成、および材料について、以下のような検討を行った。
【０１２８】
《離型性評価》
上述のコピー機およびトナー２を用いて、離型性について評価した。シリコーンゴムは材料メーカから多様なグレードが供給されている。また、シリコーンゴム中には潤滑剤、離型剤を添加することができる。本実施例では、離型性について、定着用部材表面に水滴が接触したときの接触角と実機でのトナー離型性で評価した。
【０１２９】
定着用部材表面に水滴が接触したときの接触角、すなわち部材表面材料の接触角と離型性との関係を表４に示す。ここで、○は離型性がＰＦＡ材料と同等である場合を、×は定着可能温度領域が得られない場合を、△は○と×の中間の場合をそれぞれ表わしている。
【０１３０】
【表４】

【０１３１】
接触角が９５度以上得られる材料であれば、定着温度領域が得られることが分かった。この結果より、耐久性は低いが、定着用部材表面に適当なシリコーンゴムを用いることによって、離型層としてフッ素樹脂を特に用いなくても、当該定着用部材を定着装置として使用できる可能性がある。また、逆に十分に柔軟性があって（つまり、ユニバーサル硬さＨＵが、試験環境温度２５℃の下で測定したときは（１）式および（２）式を満足し、試験環境温度２００℃の下で測定したときは（３）式および（４）式を満足する状態）、かつ接触角が９５度以上のフッ素樹脂を用いれば、弾性層を形成することなく、当該定着用部材を定着装置として使用できる。
【０１３２】
《耐久性評価》
定着用部材表面にはサーミスタ、分離爪などが当接される。これらによる摩耗量を調査した結果を図２０に示す。
【０１３３】
ここで、評価機として爪摩耗量測定用単体試験機を用い、また定着用部材としては、肉厚２００μｍのシリコーンゴムの弾性層、および耐摩耗性に劣るＰＦＡ２の離型層を有する加熱定着ローラを使用した。そして、１００，０００枚相当のの通紙時における加熱定着ローラ表面の摩耗量を測定した。また、摩耗量は触針式粗さ計のプロファイルから測定した。
【０１３４】
爪の荷重は定着条件、線速などにより変化するが、安定した分離機能を得るためには１５ｇ程度は必要である。荷重の低い場合でも４μｍ程度は摩耗することから、離型層膜厚は５μｍ以上は必要である。
【０１３５】
上記検討結果をまとめると、画像特性（光沢の均一性）に関しては、部品表面のユニバーサル硬さＨＵを（１）式および（２）式を満足する範囲か、または（３）式および（４）式を満足する範囲とすることで、良好な品質が得られるが、離型性および耐久性に関しては、コピー機、プリンタのスペック、使用トナーにより要求特性が変化する。中速機もしくは高速機（高スペック機）などでは、比較的高い離型性、耐久性が要求されることから、弾性層上に離型層を設けた構成が望ましいが、低速機（低スペック機）では弾性層単体または離型層単体で用いることも可能である。
【０１３６】
【発明の効果】
以上説明したように、本発明によれば、トナー離型性、柔軟性および弾力性に優れているか否かを簡単に評価できるので、高品質の定着用部材を選択して熱定着装置もしくは画像形成装置に組み込むことによって、画像ムラのない高品質の画像を得ることができる。
【０１３７】
また、トナー離型性、柔軟性、弾力性に優れた定着ベルトおよび定着ローラを実現できる。
【０１３８】
また、弾性層としてシリコーンゴムを使用することで、安定した膜厚、平滑な表面が得られる。
【０１３９】
さらに、離型層がＰＴＦＥ、ＰＦＡ、ＦＥＰのうちの少なくとも一つを成分として含んでいるので、十分な離型性および耐久性も確保できる。
【図面の簡単な説明】
【図１】本発明に係る定着ベルトを示しており、（Ａ）はその断面図、（Ｂ）は（Ａ）のａ部の拡大断面図である。
【図２】定着ベルトによって記録紙上のトナーが定着する様子を示した説明図である。
【図３】（Ａ）は熱定着装置の一例による構成図、（Ｂ）は熱定着装置の他の例による構成図である。
【図４】図３（Ａ）の熱定着装置を内蔵した画像形成装置の概略構成図である。
【図５】図３（Ｂ）の熱定着装置を内蔵した画像形成装置の縦断面図である。
【図６】ユニバーサル硬さと梨地ランクとの関係を示した図である。
【図７】ユニバーサル硬さと梨地ランクとの関係を示した図である。
【図８】ユニバーサル硬さと梨地ランクとの関係を示した図である。
【図９】ユニバーサル硬さと梨地ランクとの関係を示した図である。
【図１０】試験環境温度とユニバーサル硬さとの関係を示しており、（Ａ）は押し込み深さ１μｍのときの図、（Ｂ）は押し込み深さ４μｍのときの図、（Ｃ）は押し込み深さ２０μｍのときの図である。
【図１１】試験環境温度とユニバーサル硬さとの関係を示しており、図８に示したデータの平均値をプロットしたときの図である。
【図１２】押し込み深さとユニバーサル硬さとの関係を示した図である。
【図１３】押し込み深さとユニバーサル硬さとの関係を示した図である。
【図１４】ユニバーサル硬さと梨地ランクとの関係を示した図である。
【図１５】ユニバーサル硬さと梨地ランクとの関係を示した図である。
【図１６】ユニバーサル硬さと梨地ランクとの関係を示した図である。
【図１７】ユニバーサル硬さと梨地ランクとの関係を示した図である。
【図１８】ユニバーサル硬さと梨地ランクとの関係を示した図である。
【図１９】ユニバーサル硬さと梨地ランクとの関係を示した図である。
【図２０】爪荷重と摩耗量との関係を示した図である。
【図２１】画像形成装置の概略構成図である。
【符号の説明】
２０ 定着ベルト
２１ 基材
２２ 弾性層
２３ 離型層
３１ 加熱ローラ
３２ 定着ローラ
３３ 加圧ローラ
３４ ハロゲンランプ
４１Ｙ，４１Ｍ，４１Ｃ，４１Ｂｋ 画像形成部
４４ 搬送ベルト
４５Ｙ，４５Ｍ，４５Ｃ，４５Ｂｋ 感光体ドラム
４６Ｙ，４６Ｍ，４６Ｃ，４６Ｂｋ 帯電装置
４７Ｙ，４７Ｍ，４７Ｃ，４７Ｂｋ 露光装置
４８Ｙ，４８Ｍ，４８Ｃ，４８Ｂｋ 現像装置
４９Ｙ，４９Ｍ，４９Ｃ，４９Ｂｋ 転写ローラ
５２ 熱定着装置
Ｐ 記録紙[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing member evaluation method for evaluating a fixing belt and a heat fixing roller used in an electrophotographic apparatus and the like, as well as a fixing belt and a heat fixing roller.
[0002]
[Prior art]
FIG. 21 is a schematic diagram of an image production process of the electrophotographic apparatus, and shows an image creation process of a black and white image. In the case of an image creation process of a full-color image, although not shown in the figure, each developing device that develops four colors of red (magenta), blue (cyan), yellow (yellow), and black (black); And a mechanism for superimposing the four colors.
[0003]
An electrophotographic apparatus (for example, a copying machine or a laser printer) has a rotating photosensitive drum 1, and the photosensitive layer of the photosensitive drum 1 is uniformly charged by using a charging device 2, and then is supplied from a laser scanning unit. Exposure is performed with a laser beam 3. Further, the electrophotographic apparatus develops the electrostatic latent image on the photosensitive drum 1 with toner in the developing device 4 to form a toner image, and transfers the toner image onto the recording paper 6 in cooperation with the transfer roller 5. 7 is a power pack for applying a voltage to the charging device 2, 8 is a surface potential meter for measuring the surface potential of the photosensitive drum 1, and 9 is a cleaning device for cleaning the surface of the photosensitive drum 1.
[0004]
Next, a thermal fixing device that thermally fixes the toner image transferred onto the recording paper 6 will be described. 2. Description of the Related Art Conventionally, a roller-type heat fixing device 10 as shown in the upper left part of FIG. 21 is known as a device for heat-fixing toner for black and white images (only black toner). The heat fixing device 10 includes a heat fixing roller 11 and a pressure roller 12 that is disposed in parallel to the heat fixing roller 11 and sandwiches the recording paper 6 between the heat fixing roller 11. The heat fixing roller 11 has a metal core made of a hollow cylindrical body such as aluminum, and an adhesion preventing layer made of a fluororesin layer for preventing adhesion of toner is provided on the outer peripheral surface of the metal core. In addition, a heater such as a halogen lamp (not shown) is installed in the hollow portion of the metal core along the center line in the heat fixing roller 11, and the roller body is heated from the inside by the radiant heat of the heater. Then, by passing the recording paper 6 between the heat fixing roller 11 and the pressure roller 12, the toner on the recording paper 6 is softened (melted) by the heat of the heat fixing roller 11. It is fixed on the recording paper 6 by the pressure.
[0005]
Heat-fixing rollers with fluororesin layers as described above are excellent in toner releasability, but inferior in flexibility and elasticity, and are therefore compatible with full-color copiers and full-color laser printers that require gloss. Can not do it. In these glossy image full-color copying machines and laser printers, four color toners are used, and when fixing a color image, these color toners must be mixed in a molten state. That is, the toners of four colors are made to have a low melting point so that they can be easily melted, and a plurality of types of color toners are wrapped around the surface of the heat fixing roller so as to be uniformly mixed in the molten state. For this reason, it is one of the important characteristics that the surface of the heat fixing roller has appropriate flexibility and elasticity (see, for example, Patent Document 1).
[0006]
On the other hand, a belt-type thermal fixing device 15 as shown in the lower left part of FIG. 21 is also known. In the heat fixing device 15, a film-like fixing belt 18 is wound between a fixing roller 16 and a heating roller 17, and a pressure roller 19 is disposed in parallel to the fixing roller 16. Then, after the fixing belt 18 is heated by the heating roller 17, the recording paper 6 is heated when passing between the fixing roller 16 and the pressure roller 19, thereby fixing the toner image on the recording paper 6. Is done.
[0007]
Since the surface of the fixing belt 18 is formed of a rubber elastic layer such as silicone rubber or fluorine rubber, the flexibility and elasticity are excellent. However, since the toner releasability is insufficient, a toner offset phenomenon is caused. Is likely to occur.
[0008]
Therefore, recently, a fixing belt or a heat fixing roller in which a rubber elastic layer is provided on a base material and a release material such as a fluororesin is coated thereon has been proposed.
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-198201
[0010]
[Problems to be solved by the invention]
However, when a release layer such as a fluororesin is coated on the rubber elastic layer as in the above-described conventional technique, one of the important characteristics as a fixing belt and a heat fixing roller is an appropriate surface flexibility and There is a problem that elasticity is lowered.
[0011]
When the toner is fixed using a fixing belt or a heat fixing roller that does not have appropriate flexibility and elasticity, a texture (image unevenness) is generated in the image. In addition, when an image is fixed on an OHP sheet, the light transmittance is deteriorated.
[0012]
If we can easily know whether the surface of the fixing belt or heat-fixing roller has appropriate flexibility and elasticity, the above-mentioned problems should not occur. There was no method for comprehensively evaluating the hardness of the release layer in consideration of the effect of the layer.
[0013]
An object of the present invention is to provide a fixing component evaluation method capable of easily evaluating whether toner releasability, flexibility and elasticity are excellent, as well as a fixing belt excellent in toner releasability, flexibility and elasticity, and It is to provide a heat fixing roller.
[0014]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 performs a universal hardness test at a depth of 1 μm to 4 μm from the surface side of the fixing member to the fixing member used for toner fixing. The universal hardness HU at a depth of 1 μm is HU ≦ 30 [N / mm²The universal hardness HU at a depth of 4 μm is HU ≦ 12 [N / mm²], The fixing member is evaluated as an acceptable product.
[0015]
As a result of various studies on fixing a toner image developed on paper, an OHP film, or the like so as not to cause image unevenness, the present inventors have determined that German standard DIN 50359-1 It has been found that the optimum method is to evaluate the surface hardness of the fixing member using the universal hardness HU defined in (1), which is characterized in that it can be described in more detail.
[0016]
Specifically, the universal hardness HU when the depth of indentation from the surface of the fixing member is 1 μm to 4 μm is measured. For example, when the depth is 1 μm, HU ≦ 30 [N / mm²] When the depth is 4 μm, HU ≦ 12 [N / mm²], It is determined that the fixing member is an acceptable product.
[0017]
The universal hardness test is performed at a test environment temperature of 25 ° C. as in claim 2.
[0018]
The universal hardness test can be performed at a test environment temperature of 200 ° C. as in claim 3. That is, the invention according to claim 3 is a universal hardness test at a depth of 1 μm to 4 μm from the surface side of the fixing member at a test environment temperature of 200 ° C. with respect to the fixing member used for toner fixing. The universal hardness HU at a depth of 1 μm is HU ≦ 10 [N / mm²The universal hardness HU at a depth of 4 μm is HU ≦ 4 [N / mm²], The fixing member is evaluated as an acceptable product.
[0019]
It is desirable that the fixing member shown in claim 1 or 3 has a contact angle of 95 degrees or more when a water droplet contacts the surface thereof, as in claim 4.
[0020]
Here, the test environment temperature of 25 ° C. corresponds to room temperature, and the test environment temperature of 200 ° C. corresponds to the running temperature at which the fixing member is exposed during toner fixing. The upper limit of the universal hardness HU at a depth of 1 μm from the surface of the fixing member is 30 [N / mm when the test environment temperature is 25 ° C.²] When the test environment temperature is 200 ° C., 10 [N / mm]²The universal hardness HU at room temperature is three times the universal hardness HU under the running temperature. Further, the upper limit of the universal hardness HU at a depth of 4 μm from the surface of the fixing member is 12 [N / mm when the test environment temperature is 25 ° C.²] When the test environment temperature is 200 ° C., 4 [N / mm]²Similarly, the universal hardness HU at room temperature is three times the universal hardness HU under the running temperature. Thereby, claim 5 can be derived.
[0021]
That is, according to the fifth aspect of the present invention, a universal hardness test at a depth of 1 μm to 4 μm from the surface of the fixing member is performed at room temperature and the fixing member running on the fixing member used for toner fixing. When the universal hardness at the same depth from the surface of the fixing member is compared under the temperature, if the universal hardness at room temperature is three times the universal hardness under the running temperature The fixing member is evaluated as an acceptable product.
[0022]
Claims 6 to 12 are inventions relating to an evaluation method for evaluating a fixing member when the fixing member has a three-layer structure including a base material, an elastic layer, and a release layer. That is, according to the present invention, the elastic member and the release layer are laminated on the base material and the fixing member used for toner fixing is 1 μm to 4 μm in depth from the release layer surface side. Universal hardness test is conducted and universal hardness HU at a depth of 1 μm is HU ≦ 30 [N / mm²The universal hardness HU at a depth of 4 μm is HU ≦ 12 [N / mm²], The fixing member is evaluated as an acceptable product.
[0023]
The universal hardness test is performed at a test environment temperature of 25 ° C. as in claim 7.
[0024]
The universal hardness test can be performed at a test environment temperature of 200 ° C. as in claim 8. That is, the invention according to claim 8 is directed to a fixing member in which an elastic layer and a release layer are laminated on a substrate and used for toner fixing, at a test environment temperature of 200 ° C., the release layer. A universal hardness test at a depth of 1 μm to 4 μm from the surface side and a universal hardness HU at a depth of 1 μm is HU ≦ 10 [N / mm²The universal hardness HU at a depth of 4 μm is HU ≦ 4 [N / mm²], The fixing member is evaluated as an acceptable product.
[0025]
As for the release layer shown in Claim 6 or 8, as in Claim 9, it is desirable that the contact angle when the water droplet contacts the surface is 95 degrees or more.
[0026]
A tenth aspect of the invention is characterized in that, in the sixth or eighth aspect, the elastic layer is formed of silicone rubber.
[0027]
The invention according to claim 11 is the invention according to claim 6, 8 or 9, wherein the release layer comprises a tetrafluoroethylene resin (PTFE), a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin (PFA), And at least one of tetrafluoroethylene / hexafluoropropylene copolymer resin (FEP) as a component.
[0028]
According to a twelfth aspect of the present invention, in the sixth or eighth aspect, the fixing member is a fixing belt or a heat fixing roller.
[0029]
Claims 13 to 21 are inventions relating to a fixing belt, and claims 17 to 21 are inventions relating to a fixing belt having a three-layer structure comprising a base material, an elastic layer and a release layer.
[0030]
According to a thirteenth aspect of the present invention, in a fixing belt used for toner fixing, when measured at a test environment temperature of 25 ° C., the universal hardness HU at a depth of 1 μm from the belt surface is HU ≦ 30 [N / mm.²The universal hardness HU at a depth of 4 μm is HU ≦ 12 [N / mm²].
[0031]
According to the fourteenth aspect of the present invention, in a fixing belt used for toner fixing, when measured at a test environment temperature of 200 ° C., the universal hardness HU at a depth of 1 μm from the belt surface is HU ≦ 10 [N / mm.²The universal hardness HU at a depth of 4 μm is HU ≦ 4 [N / mm²].
[0032]
It is desirable that the fixing belt shown in claim 13 or 14 has a contact angle of 95 degrees or more when a water droplet contacts the surface thereof, as in claim 15.
[0033]
According to a sixteenth aspect of the present invention, in the fixing belt used for toner fixing, a universal hardness test at a depth of 1 μm to 4 μm from the belt surface is performed at a room temperature and a running temperature of the belt. When the universal hardness at the same depth is compared, the universal hardness under the room temperature is three times the universal hardness under the running temperature.
[0034]
In the fixing belt in which an elastic layer and a release layer are laminated on a substrate, the depth from the release layer surface side is measured when measured at a test environment temperature of 25 ° C. Universal hardness HU at 1 μm is HU ≦ 30 [N / mm²The universal hardness HU at a depth of 4 μm is HU ≦ 12 [N / mm²].
[0035]
In the fixing belt in which an elastic layer and a release layer are laminated on a substrate, the depth of 1 μm from the surface of the release layer is measured when measured at a test environment temperature of 200 ° C. Universal hardness HU at HU ≦ 10 [N / mm²The universal hardness HU at a depth of 4 μm is HU ≦ 4 [N / mm²].
[0036]
It is desirable that the release layer shown in claim 17 or 18 has a contact angle of 95 degrees or more when water droplets are in contact with the surface thereof, as in claim 19.
[0037]
According to a twentieth aspect of the present invention, in the seventeenth or eighteenth aspect, the elastic layer is made of silicone rubber.
[0038]
The invention according to claim 21 is the invention according to claim 17, 18 or 19, wherein the release layer comprises a tetrafluoroethylene resin (PTFE), a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin (PFA), And at least one of tetrafluoroethylene / hexafluoropropylene copolymer resin (FEP) as a component.
[0039]
Hereinafter, claims 22 to 30 are inventions relating to heat-fixing rollers, of which claims 26 to 30 are inventions relating to heat-fixing rollers having a three-layer structure comprising a base material, an elastic layer and a release layer. is there.
[0040]
According to a twenty-second aspect of the present invention, in a heat-fixing roller used for toner fixing, when measured at a test environment temperature of 25 ° C., the universal hardness HU at a depth of 1 μm from the roller surface is HU ≦ 30 [N / mm²The universal hardness HU at a depth of 4 μm is HU ≦ 12 [N / mm²].
[0041]
According to a twenty-third aspect of the present invention, in a heat-fixing roller used for toner fixing, when measured at a test environment temperature of 200 ° C., the universal hardness HU at a depth of 1 μm from the roller surface is HU ≦ 10 [N / mm²The universal hardness HU at a depth of 4 μm is HU ≦ 4 [N / mm²].
[0042]
The heat fixing roller according to claim 22 or 23, as in claim 24, preferably has a contact angle of 95 degrees or more when a water droplet contacts the surface.
[0043]
According to a twenty-fifth aspect of the present invention, in the heat-fixing roller used for toner fixing, a universal hardness test at a depth of 1 μm to 4 μm from the roller surface is performed at room temperature and at the running temperature of the roller. When the universal hardness at the same depth is compared, the universal hardness under room temperature is three times the universal hardness under running temperature.
[0044]
According to a twenty-sixth aspect of the present invention, in the heat-fixing roller in which an elastic layer and a release layer are laminated on a base material, the depth from the release layer surface side when measured at a test environment temperature of 25 ° C. Universal hardness HU at 1 μm is HU ≦ 30 [N / mm²The universal hardness HU at a depth of 4 μm is HU ≦ 12 [N / mm²].
[0045]
According to a twenty-seventh aspect of the present invention, in a heat-fixing roller in which an elastic layer and a release layer are laminated on a base material, the depth from the release layer surface side when measured at a test environment temperature of 200 ° C. Universal hardness HU at 1 μm is HU ≦ 10 [N / mm²The universal hardness HU at a depth of 4 μm is HU ≦ 4 [N / mm²].
[0046]
As for the release layer shown in Claim 26 or 27, as for Claim 28, it is desirable for the contact angle when a water droplet contacts the surface to be 95 degree | times or more.
[0047]
According to a twenty-ninth aspect, in the twenty-sixth or twenty-seventh aspect, the elastic layer is formed of silicone rubber.
[0048]
The invention according to claim 30 is the invention according to claim 26, 27 or 28, wherein the release layer comprises a tetrafluoroethylene resin (PTFE), a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin (PFA), And at least one of tetrafluoroethylene / hexafluoropropylene copolymer resin (FEP) as a component.
[0049]
A thirty-first aspect is an invention relating to a thermal fixing device. That is, the invention described in claim 31 is a heating roller heated by a heating source, a fixing roller arranged in parallel with the heating roller, and stretched between the heating roller and the fixing roller. A fixing belt that is heated by the roller and rotated by the two rollers, and a pressure roller that is in pressure contact with the surface of the fixing belt and forms a nip portion between the fixing belt, The fixing belt according to any one of claims 13 to 21 is mounted as the fixing belt.
[0050]
A thirty-second aspect of the present invention relates to an image forming apparatus, and is characterized in that the thermal fixing apparatus according to the thirty-first aspect is incorporated.
[0051]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1A and 1B show a fixing belt 20 according to the present invention. FIG. 1A is a sectional view thereof, and FIG. As shown in FIG. 1, the fixing belt 20 includes a belt base material 21, an elastic layer 22, and a release layer 23. The belt base material 21, the elastic layer 22, and the release layer 23 are laminated in this order. .
[0052]
The base material 21 is formed of a heat resistant material. As the heat-resistant material, a metal material such as SUS or nickel, or a heat-resistant resin such as polyimide, polyamideimide, or fluorine resin is used. In the case of a metal material, it is desirable that the film thickness of the belt base material 21 is 100 μm or less in consideration of the belt deflection. In the case of a heat-resistant resin, the thickness of the base material 21 is desirably 30 to 200 μm from the viewpoint of heat capacity and strength. In this case, considering the shortening of the rise time, the heat capacity is small, that is, it is advantageous that the film thickness of the base material 21 is thin. In consideration of the belt strength, the film thickness of the base material 21 is advantageous. Then, it judges comprehensively and the film thickness of the base material 21 is determined as 30-200 micrometers.
[0053]
The elastic layer 22 is provided in order to obtain a uniform image without uneven glossiness. By providing the elastic layer 22, the belt surface becomes flexible. Also, silicone rubber is used as the material of the elastic layer 22 because of its heat resistance at the fixing temperature (200 ° C. or less). The thickness of the elastic layer is preferably about 200 μm.
[0054]
Materials used for the release layer 23 include tetrafluoroethylene resin (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin (PFA), and tetrafluoroethylene / hexafluoropropylene copolymer. Examples thereof include fluorine resins such as coalesced resin (FEP), mixtures of these resins, and those obtained by dispersing these fluorine resins in heat resistant resins. The film thickness of the release layer is preferably about 20 μm.
[0055]
When the release layer 23 covers the elastic layer 22, toner release properties and prevention of paper powder adhesion can be achieved without using silicone oil or the like (oilless). However, since these resins having releasability generally do not have elasticity like rubber materials, when the release layer 23 is formed thick on the elastic layer 22, uneven gloss may occur. . That is, in order to achieve both prevention of gloss unevenness and ensuring releasability of toner and paper powder, it is necessary to form a release layer 23 that does not impair the flexibility of the elastic layer 22. For this purpose, it is necessary that the material of the release layer 23 be as flexible as possible and the film thickness be thin.
[0056]
As described above, the problem of the fixing belt including the base material 21, the elastic layer 22, and the release layer 23 includes optimization of the surface state and characteristic value. The surface of the belt comes into contact with the unfixed toner image, and heat is applied to the toner to fix it on the recording paper. When the belt surface is uneven, the contact state between the crest and trough portions Will be different. This difference in contact state naturally appears as a difference in heat transfer and pressure on the toner, resulting in uneven gloss. The elastic layer 22 has an effect of reducing the difference in the contact state between the peaks and valleys by elasticity.
[0057]
Next, the influence of the belt surface state on image uniformity and fixing characteristics will be described with reference to FIG.
[0058]
First, regarding image uniformity, as described above, it is considered that unevenness of gloss (image) is caused by a difference in contact state of unevenness (mountain and valley) on the belt surface. When pressed by the fixing roller and the pressure roller, the peak portion is crushed and becomes flat due to the elasticity of the belt surface, but the state differs depending on the size and shape of the elasticity. When the material of the belt surface is the same, only the effect due to the shape is obtained. Therefore, the smaller and smaller the ridges, the less the contact state variation due to the unevenness. Note that when the gloss (image) is non-uniform (gloss unevenness), it looks like the surface of a pear and is also called pear.
[0059]
Next, fixing characteristics (release properties) will be described. The fixing characteristic here means releasability (fixing temperature width = hot offset temperature−cold offset temperature). That is, how the fixing temperature range changes depending on the surface condition of the belt. The cold offset is generally a state where the toner is not sufficiently fixed on the recording paper, and is caused by insufficient melting of the toner (fixing temperature is low) and insufficient pressure between the belt and the recording paper.
[0060]
As a method for evaluating the surface condition of the belt, there is a surface roughness. Commonly used characteristic values include center line average roughness Ra, ten-point average roughness Rz, and the like. When Ra and Rz are large, the heat transfer to the toner and the pressurizing force at the valleys are low, and there is a high possibility of causing a cold offset.
[0061]
Hot offset is a phenomenon in which melted toner adheres and remains on the belt surface, and occurs when the adhesion force between the belt and the toner becomes larger than the cohesive force of the toner. When the belt surface material is the same, the larger the contact area with the toner, the greater the adhesion between the belt and the toner.
[0062]
Next, the method of making the surface hardness characteristic value performed in the present invention will be described.
As described in the prior art, the surface hardness, which is another important characteristic of the surface, is correlated with the gloss (image) uniformity, which is the main image quality characteristic of the full-color fixing device, and the OHP sheet image translucency. As a result, it is difficult to reproduce stable image quality.
[0063]
Therefore, the present inventors examined the correlation between the surface hardness of the belt and the image quality by using the universal hardness HU defined by the German standard DIN 50359-1. As a result of the examination, it has been found that there is a high correlation between “HU when the indentation depth from the surface is constant” and “gloss (image) uniformity (pear texture)”.
[0064]
Here, the universal hardness HU will be described.
Conventionally, the measurement of minute surface hardness, like the micro Vickers method, is to obtain the surface hardness by applying a load, pushing the indenter into the material surface, and measuring the residual indentation after unloading with a microscope. there were. On the other hand, the universal hardness measuring method directly reads the indentation depth of the indentation in a state where a load is applied to the indenter to obtain the hardness. At this time, not only the indentation depth of one point but also the load is gradually increased to the set load, and the indentation depth for each increasing test load is measured. Therefore, it is possible to measure the micro surface hardness of an elastic body that hardly leaves a trace of indenter entry and the hardness of a non-uniform surface layer.
[0065]
However, there are the following two points to be noted during measurement.
-About the film thickness of a test piece, 10 times or more of indentation depth is required.
When the measurement uncertainty is 10% or less, the indentation depth needs to be 20 times or more the surface roughness Ra of the test piece surface.
[0066]
The surface roughness Ra of a general fixing member is about 0.1 to 0.2 μm. In this case, the indentation depth is required to be 2 to 4 μm or more. By smoothing such as polishing, The minimum indentation depth can be lowered.
[0067]
Universal hardness HU is calculated | required from the following formula | equation.

Where F: test load [N]
S: Surface area of the indenter under the test load [mm²]
h: Indentation depth under test load [mm]
It is. The indenter is a diamond indenter (Vickers indenter) having a square pyramid facing angle of 136 °.
[0068]
In the present embodiment, a universal hardness test is performed on the fixing belt 20 at a depth of 1 μm to 4 μm from the surface side of the release layer 23 at a test environment temperature of 25 ° C., and a universal hardness at a depth of 1 μm. HU is HU ≦ 30 [N / mm²The universal hardness HU at a depth of 4 μm is HU ≦ 12 [N / mm²], The fixing belt 20 is evaluated as an acceptable product.
[0069]
In the present embodiment, a universal hardness test is performed on the fixing belt 20 at a depth of 1 μm to 4 μm from the surface side of the release layer 23 at a test environment temperature of 200 ° C. Hardness HU is HU ≦ 10 [N / mm²The universal hardness HU at a depth of 4 μm is HU ≦ 4 [N / mm²], The fixing belt is evaluated as an acceptable product.
[0070]
Here, the test environment temperature of 25 ° C. corresponds to room temperature, and the test environment temperature of 200 ° C. corresponds to the running temperature at which the fixing belt is exposed during toner fixing. The upper limit of the universal hardness HU at a depth of 1 μm from the surface of the release layer 23 is 30 [N / mm when the test environment temperature is 25 ° C.²] When the test environment temperature is 200 ° C., 10 [N / mm]²The universal hardness HU at room temperature is three times the universal hardness HU under the running temperature. The upper limit of the universal hardness HU at a depth of 4 μm from the surface of the release layer 23 is 12 [N / mm when the test environment temperature is 25 ° C.²] When the test environment temperature is 200 ° C., 4 [N / mm]²Similarly, the universal hardness HU at room temperature is three times the universal hardness HU under the running temperature.
[0071]
Thus, a universal hardness test at a depth of 1 μm to 4 μm from the surface of the release layer 23 is performed at room temperature and under the running temperature of the fixing belt 20, and the universal hardness test at the same depth from the surface of the release layer 23 is performed. When the hardness HU is compared, if the universal hardness HU at room temperature is three times the universal hardness HU under the running temperature, the fixing belt 20 can also be evaluated as an acceptable product. .
[0072]
Although the fixing belt has been described in the present embodiment, the present invention can also be applied to evaluation of a heat fixing roller having a structure in which an elastic layer and a release layer are laminated on a core metal, that is, a base material. .
[0073]
【Example】
Next, a test was conducted on the effect of universal hardness on image characteristics.
An unfixed image was formed on the recording paper, and was fixed on the recording paper by a thermal fixing device under the following conditions. At this time, a fixing belt having a different universal hardness on the surface was used to cope with a satin image (gloss unevenness) after fixing.
Evaluation image (unfixed image)
Toner: Magenta
Amount of adhesion: 0.8 to 0.9 mg / cm²
Paper type: T6200 (62kg paper)
[0074]
Here, a full-color thermal fixing device using the fixing belt of this embodiment will be described. As shown in FIG. 3, the fixing belt 20 is used in the heat fixing apparatus. The fixing belt 20 is wound between the heating roller 31 and the fixing roller 32, and an appropriate tension (a mechanism for applying the tension is not shown) is applied. A pressure roller 33 is disposed in parallel with the fixing roller 32, and the fixing belt wound around the fixing roller 32 is pressed against the fixing roller 32 by the pressure roller 33 (the pressure contact mechanism is not shown).
[0075]
There are roughly two methods of pressing the fixing belt 20 with the pressure roller 33 as shown in FIGS. 3A and 3B. In the method of FIG. 3A (Ricoh Co., Ltd .: Imagio color 3100), the nip portion is only formed by the pressure roller 33 and the fixing roller 32 (via the fixing belt). On the other hand, in the method of FIG. 3B (Ricoh Co., Ltd .: Ipsio color 8000, etc.), in addition to the nip portion composed of the pressure roller 33 and the fixing roller 32, the belt crawls on the front side. It has a nip part formed by. Due to this difference, a difference occurs in the rise time, transportability, paper separation property, etc. However, in this embodiment, since the purpose is to examine the fixing belt, the fixing method is fixed to the method of FIG. The effect of belt on image quality was investigated.
[0076]
In FIG. 3, a halogen lamp 34 for heating is installed inside the heating roller 31. The number and the power consumption of the halogen lamps 34 are adjusted according to the specifications (standards) of the fixing temperature, the linear velocity, the rise time, and the belt surface temperature variation. In general, in the method of FIG. 3A, halogen lamps 34 are installed in all of the heating roller 31, the fixing roller 32, and the pressure roller 33, and in the method of FIG. A halogen lamp 34 is installed on the pressure roller 33.
[0077]
The test conditions are as follows.

[0078]
For the satin image evaluation, the following rank evaluation was performed (the middle of each rank is 0.5).
Rank 5: No noticeable pear-like unevenness Passing level
Rank 4: Intermediate level between Rank 3 and Rank 5
Rank 3: Some pear-like unevenness occurs.
Rank 2: Intermediate between Rank 1 and Rank 3 Failure level
Rank 1: Satin texture occurs throughout the image.
FIG. 4 shows a schematic configuration of the image forming apparatus according to the present invention. The image forming apparatus shown in FIG. 4 is a quadruple tandem type full-color printer and incorporates the thermal fixing device shown in FIG.
[0079]
This full-color printer includes four sets of image forming units 41Y, 41M, 41C, and 41Bk that respectively form yellow, magenta, cyan, and black toner images. A conveyor belt 44 wound between pulleys 42 and 43 is provided below the image forming units 41Y, 41M, 41C, and 41Bk. The transport belt 44 is driven in the direction of arrow b by a driving device (not shown), and transports the recording paper P through the image forming units 41Y, 41M, 41C, and 41Bk.
[0080]
Here, since each of the image forming units 41Y, 41M, 41C, and 41Bk has the same configuration, only the image forming unit 41Y for yellow will be described, and the image forming units 410M, 41C, and 41 for other colors will be described. With regard to 41Bk, the same parts as those of the image forming unit 41Y are denoted by the same numerals, and detailed description thereof is omitted.
[0081]
The image forming unit 41Y has a photosensitive drum 45Y that is in rolling contact with the transport belt 44 at a substantially central position thereof. Around the photosensitive drum 45Y, a charging device 46Y for charging the surface of the photosensitive drum 45Y to a predetermined potential, the charged drum surface is exposed based on the color-separated image signal, and the surface of the drum is electrostatically charged. An exposure device 47Y that forms a latent image, a developing device 48Y that supplies yellow toner to the electrostatic latent image formed on the drum surface and develops it, and a developed toner image on the recording paper P that is conveyed by the conveying belt 44 A transfer roller 49Y for transferring, a cleaner 50Y for removing residual toner remaining on the drum surface without being transferred, and a charge eliminating lamp for removing electric charge remaining on the drum surface (not shown) are sequentially provided along the rotation direction of the photosensitive drum 45Y. It is arranged.
[0082]
A paper feed mechanism 51 for feeding the recording paper P onto the transport belt 44 is disposed on one side (right side in the drawing) of the transport belt 44. A thermal fixing device 52 is disposed on the other side (left side in the drawing) of the conveying belt 44, and the recording paper P conveyed by the conveying belt 44 is continuously supplied to the thermal fixing device 52.
[0083]
As shown in FIG. 3A, the thermal fixing device 52 includes a heating roller 31 and a fixing roller 32 disposed below the heating roller 31, and between the heating roller 31 and the fixing roller 32. An endless fixing belt 20 is wound. A pressure roller 33 is disposed below the fixing roller 32, and the fixing belt 20 is pressed against the fixing roller 32 by the pressure roller 33. Although not shown in FIG. 4, a halogen lamp 34 (see FIG. 3A) is provided inside each of the heating roller 31, the fixing roller 32, and the pressure roller 33.
[0084]
The recording paper P supplied from the transport belt 44 is heated and pressurized when passing between the fixing belt 20 and the pressure roller 33, and the toner image on the recording paper P is fixed. The recording paper P after the toner image is fixed is discharged to the downstream side of the conveying path via the discharge rollers 53 and 54.
[0085]
Next, an image forming apparatus (full color printer) incorporating the heat fixing device shown in FIG. 3B will be described. This image forming apparatus also includes the image forming units 41Y, 41M, 41C, and 41Bk, the conveyance belt 44, and the paper feeding mechanism 51 shown in FIG. As shown in FIG. 5, the image forming apparatus includes a heating roller 31 and a fixing roller 32 disposed obliquely below the heating roller 31, and an endless shape is provided between the heating roller 31 and the fixing roller 32. The fixing belt 20 is wound. A pressure roller 33 is disposed below the fixing roller 32, and the fixing belt 20 is pressed against the fixing roller 32 by the pressure roller 33. A halogen lamp 34 is provided inside the heating roller 31 and the pressure roller 33.
[0086]
The heating roller 31 is urged in a direction away from the fixing roller 32 by an urging means (not shown) such as a spring, thereby applying an appropriate predetermined tension to the fixing belt 20.
[0087]
The fixing roller 32 includes a cored bar 32A and a heat-resistant porous layer elastic body layer 32B that covers the cored bar 32A. The fixing roller 32 is urged in a direction in which the pressure roller 33 is pressed by an urging means (not shown) such as a spring.
[0088]
The fixing roller 32 has a straight line connecting the axis of the fixing roller 32 and the axis of the heating roller 31 with the axis of the fixing roller 32 as a vertex, and the axis of the heating roller 31 and the axis of the pressure roller 33. Is in contact with the pressure roller 33 so that the angle between the straight line connecting the two and the straight line is an acute angle. As a result, the first fixing unit A that contacts the fixing belt 20 at a portion where the pressure roller 33 does not face the fixing roller 32, and the second that the pressure roller 33 contacts the fixing roller 32 via the fixing belt 20. The fixing unit B is formed, and the fixing unit A and B hold the recording paper and heat it.
[0089]
A thermistor 55 is disposed opposite the heating roller 31 and the pressure roller 33, and the temperature of the heating roller 31 and the pressure roller 33 is detected by the thermistor 55.
[0090]
In the figure, reference numeral 56 denotes a guide for guiding the recording paper to be fixed toward the first fixing unit A. Reference numeral 57 denotes an offset preventing oil application roller, and reference numeral 58 denotes a cleaning roller.
[0091]
Example 1
In general, it is known that a satin image becomes more prominent in a high-gloss image. Under the fixing conditions described above, when the fixing temperature is 160 to 170 ° C., the gloss is 5 to 8% (magenta color: 0.8 to 0.9 mg / cm²) And a glossiness of 10 to 15% (magenta color: 0.8 to 0.9 mg / cm)²The toner (toner 2) is used, the gloss of the image is changed, and the relationship with the universal hardness is investigated.
[0092]
6 to 9 show the relationship between the universal hardness and the satin rank. Summarizing the results, if the universal hardness HU is in the range shown in the following formulas (1) and (2), or in the range shown in the formulas (3) and (4), good gloss uniformity The image quality (rank 3 or higher) could be obtained.
[0093]
When the test environment temperature is 25 ° C., the universal hardness HU1 at a depth of 1 μm from the release layer surface and the universal hardness HU2 at a depth of 4 μm from the release layer surface are:
HU1 ≦ 30 [N / mm²] (1)
HU2 ≦ 12 [N / mm²] (2)
When the test environment temperature is 200 ° C., the universal hardness HU3 at a depth of 1 μm from the release layer surface and the universal hardness HU4 at a depth of 4 μm from the release layer surface are:
HU3 ≦ 10 [N / mm²] (3)
HU4 ≦ 4 [N / mm²] (4)
From the results of the formulas (1) to (4), when the test environment temperature is 25 ° C. or 200 ° C., the universal hardness at an arbitrary indentation depth within the indentation depth range of 1 μm to 4 μm can be predicted. In addition, when the indentation depth is 1 μm or 4 μm, universal hardness at any test environment temperature (excluding the temperature at which the resin decomposes) can be predicted.
[0094]
Next, the reason why 1 μm or 4 μm is selected as the indentation depth will be described. As described in the prior art, the characteristic values of the belt (member) hardness and gloss uniformity are not clearly defined. In particular, what affects the gloss uniformity is the flexibility of the entire belt including the bending of the substrate or the flexibility of the outermost surface of the belt. When measuring the hardness of the pole surface, since the minimum film thickness of the release layer is about 10 μm, the indentation depth needs to be 1 μm or less due to the above-mentioned measurement film thickness limitation. . When the belt is considered as a laminate (base material + elastic layer + release layer), it is possible to measure at a deeper indentation depth, for example, the base material is 50 μm, the elastic layer is 200 μm, and the release layer is 30 μm. For example, since it is 280 μm as a whole, it is possible to push in up to 28 μm. The present inventors have confirmed that there is a correlation between universal hardness and gloss uniformity at an indentation depth of 1 to 20 μm.
[0095]
As for the indentation depth, 1 μm and 4 μm do not have a special meaning. For example, even in the middle 2 μm or 3 μm, the correlation with the gloss uniformity is obtained. However, when the belt (member) used at this time was measured with an indentation depth of 1 μm and 4 μm, the relationship between hardness and gloss uniformity in the range presented in this example was obtained.
[0096]
The reason why 25 ° C. or 200 ° C. is selected as the test environment temperature will be described. German standard DIN 50359-1 defines the measurement temperature as 10 to 35 ° C. Therefore, in this example, 25 ° C. was set as the measurement temperature. Moreover, since the measurement temperature can be changed with the Fischerscope H-100 used this time, the measurement was performed even in an environment of 200 ° C. close to the fixing temperature, and the correspondence with the gloss uniformity was observed.
[0097]
6 to 9, it can be seen that the toner 1 has a higher margin for the satin image than the toner 2. That is, as the glossiness of the image increases, gloss unevenness (pear texture) tends to increase. Basically, in order to obtain a high gloss image, the toner is sufficiently melted and the viscosity is lowered and then fixed on the recording paper. This low viscosity toner is more flexible. It shows that it is necessary to press on the member surface.
[0098]
Next, the influence of the configuration of the fixing belt on the universal hardness was examined. Here, as shown in Table 1, with respect to fixing belts (Experimental Examples 1 to 5, Comparative Examples 1 to 7) having different materials and film thicknesses of the elastic layer and the release layer, their universal hardness, durability, and separation The type was examined.
[0099]
[Table 1]

[0100]
The belt configuration is as follows.

[0101]
Next, a fixing belt manufacturing method will be described. Blade coating (can be produced by spray coating or dipping coating by diluting with a solvent or the like) was used as the elastic layer deposition method. In this example, silicone rubber was used as the elastic layer material. However, it is known that this silicone rubber has an excellent upper limit temperature of 200 ° C. when continuously used. As described above, other rubber (elastomer) materials used for the elastic layer include fluorosilicone rubber, fluororubber, etc., but there are various types such as spray coating, dipping coating, blade coating, and casting. At present, only silicone rubber can be processed, and silicone rubber is the cheapest in terms of cost. As a result, it was found that silicone rubber having the thickness of about 200 μm is the most suitable at this stage in order to reduce the variation and increase the surface smoothness.
[0102]
Spray coating was used as a release layer film forming method. In addition, even if a primer is used between the polyimide resin substrate and the elastic layer and between the elastic layer and the release layer as needed, the belt characteristics are not greatly affected.
[0103]
From Table 1, it can be seen that Comparative Examples 1 to 4 in which no elastic layer is provided between the base material and the release layer do not satisfy the universal hardness value for the uniform gloss image described above.
[0104]
Further, it can be seen that the universal hardness value is increased (hardened) as the release layer thickness increases in the configuration in which the elastic layer is provided. When the universal hardness measurement method is applied to an object made of a resin and a rubber material as in the present invention, “indentation depth of measurement indenter” = “depth stuck in the surface” + “surface bending It ’s “depth of depth”.
[0105]
Therefore, when the release layer is formed on the elastic layer, if the elastic layer hardness <the release layer hardness (which is generally considered to be valid), the release layer film thickness is reduced. It is considered that the flexibility of the elastic layer tends to appear on the surface of the belt (the surface of the release layer), that is, the “depth at which the surface is bent” increases and the universal hardness value decreases.
[0106]
PFA1 is a material inferior to PFA2 in flexibility. The difference in flexibility (flexibility) of the fluororesin will be described. Generally, a fluororesin is used as the material used for the release layer, but the hardness varies depending on the kind of difference; FEP, PFA, PTFE..., Difference in molecular weight, presence or absence of filler addition, construction method, and the like. The order of the types differs depending on the grade, but the molecular weight generally becomes harder as the molecular weight increases. In addition to the difference in these polymers, there is an effect due to the addition of filler.
[0107]
For the filler addition, carbon black, whisker, silica, silicone carbide, mica, or the like is used to improve wear resistance, and carbon black, metal oxide, or the like is used to impart conductivity. These filler additions generally also harden the material.
[0108]
As shown in Table 1, when the same configuration (the same film thickness) is adopted, the universal hardness varies depending on the material of the release layer. PFA1 has a lower margin for a satin image due to an increase in film thickness than PFA2. Also from this test result, it is understood that the release layer needs to have a film thickness setting in consideration of the flexibility for each release layer material in order to convey the flexibility of the elastic layer.
[0109]
Comparative Example 7 is a fixing belt in which an elastic layer (silicone rubber) is exposed on the surface without forming a release layer, but the surface universal hardness has a very small value. However, the durability and releasability are insufficient. Specifically, in terms of durability, the surface of the silicone rubber is damaged from the initial stage of the evaluation by the thermistor contact portion and the recording paper edge portion by continuous paper feeding. The releasability is also narrower when the cold offset-hot offset fixing temperature range is narrower than when a fluororesin release layer is provided, and is particularly prominent when thin paper (45 kg paper) is used as recording paper. From the above, it can be seen that it is necessary to form a release layer on the surface of the elastic layer.
[0110]
In order to avoid problems with satin images (particularly in the case of high gloss images), the fixing belt surface needs to be flexible, and it is effective to use universal hardness as the characteristic value. The universal hardness of the fixing belt surface varies depending on the elastic layer material and film thickness, and the release layer material and film thickness. Therefore, by combining these combinations appropriately and putting the universal hardness in the range shown in the formulas (1) and (2), or in the range shown in the formulas (3) and (4), the gloss (image) ) Uniformity.
[0111]
However, as can be seen from Comparative Example 7 in Table 1, when the rubber material is exposed on the surface, there are problems in practical use in terms of durability and releasability. Therefore, PTFE, PFA, FEP, and these A release layer consisting of a mixture of
[0112]
Even if an elastic layer is not provided, if a highly flexible fluororesin is developed, it is possible to keep the universal hardness within the above-mentioned range even with the base material + release layer. It can be seen that the three-layer structure composed of the base material + elastic layer + release layer satisfies all of gloss (image) uniformity, release property and durability.
[0113]
(Example 2)
Next, with respect to fixing belts (Experimental Examples 6 to 10) having different materials and film thicknesses of the elastic layer and the release layer, the indentation depth is 25 ° C., 60 ° C., 100 ° C., 150 ° C., 200 ° C. A universal hardness test was conducted at 1 μm, 4 μm, and 20 μm. The test results are shown in Table 2.
[0114]
[Table 2]

[0115]
Here, the materials and film thicknesses of the elastic layer and the release layer of the fixing belt in Experimental Examples 6 to 10 are as follows.
Experimental Example 6
Elastic layer: Silicone rubber, hardness 25 ° (JIS K 6301), film thickness 200 μm
Release layer: Material A, film thickness 15 μm
Experimental Example 7
Elastic layer: Silicone rubber, hardness 25 ° (JIS K 6301), film thickness 200 μm
Release layer: Material B, film thickness 30 μm
Experimental Example 8
Elastic layer: Silicone rubber, hardness 25 ° (JIS K 6301), film thickness 200 μm
Release layer: Material C, film thickness 30 μm
Experimental Example 9
Elastic layer: Silicone rubber, hardness 25 ° (JIS K 6301), film thickness 300 μm
Release layer: Material C, film thickness 10 μm
Experimental Example 10
Elastic layer: Silicone rubber, hardness 25 ° (JIS K 6301), film thickness 200 μm
Release layer: Material D, film thickness 20 μm
[0116]
In Table 2, (A) shows data when the indentation depth is 1 μm, (A) shows data when the indentation depth is 4 μm, and (C) shows data when the indentation depth is 20 μm. (D) collectively shows the average values of the indentation depths of 1 μm, 4 μm, and 20 μm.
[0117]
Further, when plotting the data shown in Table 2 with the test environment temperature on the horizontal axis and the universal hardness on the vertical axis, it is as shown in FIG. 10, (A) is a graph when the indentation depth is 1 μm, (B) is a graph when the indentation depth is 4 μm, and (C) is a graph when the indentation depth is 20 μm. FIG. 11 is a graph plotting average values of the indentation depths of 1 μm, 4 μm, and 20 μm.
[0118]
10 and 11, it can be seen that the universal hardness tends to decrease as the test environment temperature increases, and that the tendency is particularly remarkable when the indentation depth is 1 μm.
[0119]
Furthermore, 12 fixing belts were prepared in addition to the fixing belts of the above experimental examples 6 to 10, and each fixing belt was tested with a universal hardness of 1 μm, 4 μm, and 20 μm with an indentation depth of 25 ° C. and 200 ° C. The test was conducted. The test results are shown in FIGS. 12 and 13 together with Examples 6-10. 12 and 13, the horizontal axis indicates the indentation depth, and the vertical axis indicates the universal hardness. FIG. 12 is a graph when the test environment temperature is 25 ° C., and FIG. 13 is the case when the test environment temperature is 200 ° C. It is a graph of.
[0120]
From FIG. 12 and FIG. 13, since the indentation depth of 1 μm to 4 μm is affected by the flexibility and elasticity of the release layer and elastic layer, the universal hardness sharply decreases as the indentation depth increases. However, it can be seen that when the indentation depth exceeds 4 μm, the influence of the substrate becomes strong and the universal hardness does not decrease so much.
[0121]
Judging from the above, in order to accurately measure the surface hardness of the fixing belt (or heat fixing roller), it can be said that it is suitable to perform a universal hardness test in the range of 1 μm to 4 μm indentation depth. .
[0122]
Next, the data of the above experimental examples are plotted as shown in FIGS. 14 to 19 with the universal hardness on the horizontal axis and the satin rank on the vertical axis, as in FIGS. 6 to 9. 14 to 19, the relationship between the universal hardness and the satin rank was obtained as a linear equation by the least square method, and further as a correlation coefficient. 14 to 19 show results when the toner 2 is used.
[0123]
Here, FIG. 14 shows the test environment temperature at room temperature and the indentation depth is 1 μm, FIG. 15 shows the test environment temperature at room temperature and the indentation depth is 4 μm, and FIG. This is when it is 20 μm. FIG. 17 shows a test environment temperature of 200 ° C. and an indentation depth of 1 μm, FIG. 18 shows a test environment temperature of 200 ° C. and an indentation depth of 4 μm, and FIG. Is 20 μm. Table 3 shows the correlation coefficients obtained from FIGS. 14 to 19 as a list.
[0124]
[Table 3]

[0125]
Table 3 (A) shows data when the test environment temperature is 200 ° C., and Table 3 (B) shows data when the test environment temperature is room temperature.
[0126]
(Example 3)
The actual machine characteristics such as image quality, durability, releasability and the like under fixing conditions of an existing copying machine (for example, Imagio color 3100 manufactured by Ricoh Company) were investigated. These actual machine characteristics are strongly influenced by toner and fixing conditions. For example, regarding the durability, the copying (printing) speed, the presence / absence of a separation claw, the nip portion pressure, and the like influence. Further, the toner strongly affects the releasability. In other words, among the evaluation results described above, the required values for durability and releasability vary depending on the specs of the assumed copying machine and printer.
[0127]
Specifically, a low-speed machine with a short mechanical life allows a material or member structure with low durability, and a machine with high temperature control accuracy (such a machine may have a narrow fixing temperature range). In the case of using a highly releasable toner, a slight decrease in the releasability of the fixing member surface is allowed. The following studies were made on the member configuration and materials when targeting these low-spec machines.
[0128]
<Evaluation of releasability>
Using the above-mentioned copying machine and toner 2, the releasability was evaluated. Various grades of silicone rubber are supplied by material manufacturers. A lubricant and a release agent can be added to the silicone rubber. In this example, the releasability was evaluated by the contact angle when water droplets contacted the surface of the fixing member and the toner releasability in the actual machine.
[0129]
Table 4 shows the contact angle when water droplets contact the surface of the fixing member, that is, the relationship between the contact angle of the member surface material and the releasability. Here, .largecircle. Represents the case where the releasability is equivalent to that of the PFA material, x represents the case where the fixable temperature region cannot be obtained, and .DELTA. Represents the case between the circle and x.
[0130]
[Table 4]

[0131]
It has been found that if the material can obtain a contact angle of 95 degrees or more, a fixing temperature region can be obtained. From this result, the durability is low, but by using an appropriate silicone rubber on the surface of the fixing member, there is a possibility that the fixing member can be used as a fixing device without using a fluororesin as the release layer. is there. On the other hand, there is sufficient flexibility (that is, when the universal hardness HU is measured at a test environment temperature of 25 ° C., the equations (1) and (2) are satisfied, and the test environment temperature is 200 ° C. If the fluororesin having a contact angle of 95 degrees or more is used, the fixing member can be fixed without forming an elastic layer. Can be used as a device.
[0132]
《Durability evaluation》
A thermistor, a separation claw, and the like are brought into contact with the surface of the fixing member. The result of investigating the amount of wear by these is shown in FIG.
[0133]
Here, a unit testing machine for measuring the amount of nail wear is used as an evaluation machine, and a fixing member is a heat fixing roller having a 200 μm thick silicone rubber elastic layer and a PFA 2 release layer inferior in wear resistance. It was used. Then, the amount of wear on the surface of the heat-fixing roller when 100,000 sheets were passed was measured. The amount of wear was measured from the profile of a stylus roughness meter.
[0134]
The load on the nail varies depending on fixing conditions, linear velocity, etc., but about 15 g is necessary to obtain a stable separation function. Even when the load is low, about 4 μm wears, so the release layer thickness needs to be 5 μm or more.
[0135]
Summarizing the above examination results, regarding the image characteristics (gloss uniformity), the universal hardness HU of the part surface is within the range satisfying the expressions (1) and (2), or the expressions (3) and (4). By satisfying the formula, good quality can be obtained, but with regard to releasability and durability, required characteristics vary depending on the copying machine, printer specifications, and toner used. Medium-speed machines or high-speed machines (high-spec machines) require relatively high release properties and durability, so a configuration with a release layer on the elastic layer is desirable, but low-speed machines (low-spec machines) Machine) can be used as a single elastic layer or a single release layer.
[0136]
【The invention's effect】
As described above, according to the present invention, it is possible to easily evaluate whether or not the toner releasability, flexibility and elasticity are excellent. Therefore, a high-quality fixing member is selected and the heat fixing device or image is selected. By incorporating it in the forming apparatus, a high-quality image without image unevenness can be obtained.
[0137]
In addition, a fixing belt and a fixing roller excellent in toner releasability, flexibility, and elasticity can be realized.
[0138]
Further, by using silicone rubber as the elastic layer, a stable film thickness and a smooth surface can be obtained.
[0139]
Furthermore, since the release layer contains at least one of PTFE, PFA, and FEP as a component, sufficient release properties and durability can be secured.
[Brief description of the drawings]
1A and 1B show a fixing belt according to the present invention, in which FIG. 1A is a cross-sectional view thereof, and FIG. 1B is an enlarged cross-sectional view of a portion a of FIG.
FIG. 2 is an explanatory diagram showing how toner on a recording sheet is fixed by a fixing belt.
3A is a configuration diagram of an example of a thermal fixing device, and FIG. 3B is a configuration diagram of another example of a thermal fixing device.
FIG. 4 is a schematic configuration diagram of an image forming apparatus incorporating the thermal fixing device of FIG.
FIG. 5 is a longitudinal sectional view of an image forming apparatus incorporating the thermal fixing device of FIG.
FIG. 6 is a diagram showing a relationship between universal hardness and satin rank.
FIG. 7 is a diagram showing a relationship between universal hardness and satin rank.
FIG. 8 is a diagram showing the relationship between universal hardness and satin rank.
FIG. 9 is a diagram showing the relationship between universal hardness and satin rank.
10A and 10B show the relationship between the test environment temperature and universal hardness. FIG. 10A is a diagram when the indentation depth is 1 μm, FIG. 10B is a diagram when the indentation depth is 4 μm, and FIG. It is a figure at the time of 20 micrometers.
11 shows the relationship between the test environment temperature and the universal hardness, and is a graph when the average value of the data shown in FIG. 8 is plotted.
FIG. 12 is a diagram showing a relationship between indentation depth and universal hardness.
FIG. 13 is a diagram showing a relationship between an indentation depth and universal hardness.
FIG. 14 is a diagram showing the relationship between universal hardness and satin rank.
FIG. 15 is a diagram showing the relationship between universal hardness and satin rank.
FIG. 16 is a diagram showing a relationship between universal hardness and satin rank.
FIG. 17 is a diagram showing a relationship between universal hardness and satin rank.
FIG. 18 is a diagram showing the relationship between universal hardness and satin rank.
FIG. 19 is a diagram showing the relationship between universal hardness and satin rank.
FIG. 20 is a diagram showing a relationship between a claw load and a wear amount.
FIG. 21 is a schematic configuration diagram of an image forming apparatus.
[Explanation of symbols]
20 Fixing belt
21 Base material
22 Elastic layer
23 Release layer
31 Heating roller
32 Fixing roller
33 Pressure roller
34 Halogen lamp
41Y, 41M, 41C, 41Bk Image forming unit
44 Conveyor belt
45Y, 45M, 45C, 45Bk photoconductor drum
46Y, 46M, 46C, 46Bk charging device
47Y, 47M, 47C, 47Bk exposure equipment
48Y, 48M, 48C, 48Bk Development device
49Y, 49M, 49C, 49Bk Transfer roller
52 Thermal fixing device
P Recording paper

Claims (32)

A universal hardness test is performed on a fixing member used for toner fixing at a depth of 1 μm to 4 μm from the surface side of the fixing member.
Universal hardness HU at a depth of 1 μm
HU ≦ 30 [N / mm ² ]
The universal hardness HU at a depth of 4 μm is
HU ≦ 12 [N / mm ² ]
If so, the fixing member evaluation method is characterized in that the fixing member is evaluated as an acceptable product. The fixing member evaluation method according to claim 1,
A fixing member evaluation method, wherein the universal hardness test is performed at a test environment temperature of 25 ° C. A universal hardness test is performed on a fixing member used for toner fixing at a depth of 1 μm to 4 μm from the surface side of the fixing member at a test environment temperature of 200 ° C.
Universal hardness HU at a depth of 1 μm
HU ≦ 10 [N / mm ² ]
The universal hardness HU at a depth of 4 μm is
HU ≦ 4 [N / mm ² ]
If so, the fixing member evaluation method is characterized in that the fixing member is evaluated as an acceptable product. In the fixing member evaluation method according to claim 1 or 3,
A fixing member evaluation method, wherein a contact angle when a water droplet contacts the surface of the fixing member is 95 degrees or more. For a fixing member used for toner fixing, a universal hardness test at a depth of 1 μm to 4 μm from the surface of the fixing member is performed at a room temperature and a running temperature of the fixing member.
When the universal hardness at the same depth from the surface of the fixing member is compared, if the universal hardness under room temperature is three times the universal hardness under the running temperature, the fixing member passes. A fixing member evaluation method, wherein the fixing member is evaluated as a product. A universal hardness test at a depth of 1 μm to 4 μm from the surface of the release layer is performed on a fixing member used for toner fixing by laminating an elastic layer and a release layer on a substrate.
Universal hardness HU at a depth of 1 μm
HU ≦ 30 [N / mm ² ]
The universal hardness HU at a depth of 4 μm is
HU ≦ 12 [N / mm ² ]
If so, the fixing member evaluation method is characterized in that the fixing member is evaluated as an acceptable product. The fixing member evaluation method according to claim 6,
A fixing member evaluation method, wherein the universal hardness test is performed at a test environment temperature of 25 ° C. For a fixing member in which an elastic layer and a release layer are laminated on a substrate and used for toner fixing, a universal hard member having a depth of 1 μm to 4 μm from the release layer surface side at a test environment temperature of 200 ° C. To test
Universal hardness HU at a depth of 1 μm
HU ≦ 10 [N / mm ² ]
The universal hardness HU at a depth of 4 μm is
HU ≦ 4 [N / mm ² ]
If so, the fixing member evaluation method is characterized in that the fixing member is evaluated as an acceptable product. In the fixing member evaluation method according to claim 6 or 8,
A fixing member evaluation method, wherein a contact angle when a water droplet contacts the surface of the release layer is 95 degrees or more. In the fixing member evaluation method according to claim 6 or 8,
The method for evaluating a fixing member, wherein the elastic layer is formed of silicone rubber. The fixing member evaluation method according to claim 6, 8 or 9,
The release layer is made of tetrafluoroethylene resin (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin (PFA), and tetrafluoroethylene / hexafluoropropylene copolymer resin (FEP). A fixing member evaluation method comprising at least one of them as a component. In the fixing member evaluation method according to claim 6 or 8,
The fixing member evaluation method, wherein the fixing member is a fixing belt or a heat fixing roller. In a fixing belt used for toner fixing,
When measured at a test ambient temperature of 25 ° C,
Universal hardness HU at a depth of 1 μm from the belt surface is
HU ≦ 30 [N / mm ² ]
The universal hardness HU at a depth of 4 μm is
HU ≦ 12 [N / mm ² ]
A fixing belt characterized by being. In a fixing belt used for toner fixing,
When measured at a test ambient temperature of 200 ° C,
Universal hardness HU at a depth of 1 μm from the belt surface is
HU ≦ 10 [N / mm ² ]
The universal hardness HU at a depth of 4 μm is
HU ≦ 4 [N / mm ² ]
A fixing belt characterized by being. The fixing belt according to claim 13 or 14,
A fixing belt having a contact angle of 95 degrees or more when water droplets contact the belt surface. For a fixing belt used for toner fixing, a universal hardness test at a depth of 1 μm to 4 μm from the belt surface is performed at room temperature and under the running temperature of the belt, and the universal hardness at the same depth from the belt surface is compared. A fixing belt characterized in that the universal hardness under room temperature is three times the universal hardness under running temperature. In a fixing belt in which an elastic layer and a release layer are laminated on a substrate,
When measured at a test ambient temperature of 25 ° C,
Universal hardness HU at a depth of 1 μm from the surface of the release layer is
HU ≦ 30 [N / mm ² ]
The universal hardness HU at a depth of 4 μm is
HU ≦ 12 [N / mm ² ]
A fixing belt characterized by being. In a fixing belt in which an elastic layer and a release layer are laminated on a substrate,
When measured at a test ambient temperature of 200 ° C,
Universal hardness HU at a depth of 1 μm from the surface of the release layer is
HU ≦ 10 [N / mm ² ]
The universal hardness HU at a depth of 4 μm is
HU ≦ 4 [N / mm ² ]
A fixing belt characterized by being. The fixing belt according to claim 17 or 18,
A fixing belt having a contact angle of 95 degrees or more when water droplets contact the surface of the release layer. The fixing belt according to claim 17 or 18,
The fixing belt, wherein the elastic layer is made of silicone rubber. The fixing belt according to claim 17, 18 or 19,
The release layer is made of tetrafluoroethylene resin (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin (PFA), and tetrafluoroethylene / hexafluoropropylene copolymer resin (FEP). A fixing belt comprising at least one of them as a component. In a heat fixing roller used for toner fixing,
When measured at a test ambient temperature of 25 ° C,
Universal hardness HU at a depth of 1 μm from the roller surface
HU ≦ 30 [N / mm ² ]
The universal hardness HU at a depth of 4 μm is
HU ≦ 12 [N / mm ² ]
A heat-fixing roller, characterized in that In a heat fixing roller used for toner fixing,
When measured at a test ambient temperature of 200 ° C,
Universal hardness HU at a depth of 1 μm from the roller surface
HU ≦ 10 [N / mm ² ]
The universal hardness HU at a depth of 4 μm is
HU ≦ 4 [N / mm ² ]
A heat-fixing roller, characterized in that The heat fixing roller according to claim 22 or 23,
The heat-fixing roller, wherein a contact angle when a water droplet contacts the roller surface is 95 degrees or more. In a heat fixing roller used for toner fixing, a universal hardness test at a depth of 1 μm to 4 μm from the roller surface is performed at a room temperature and a running temperature of the roller to obtain a universal hardness at the same depth from the roller surface. A heat-fixing roller characterized in that, when compared, the universal hardness at room temperature is three times the universal hardness under running temperature. In a heat fixing roller in which an elastic layer and a release layer are laminated on a substrate,
When measured at a test ambient temperature of 25 ° C,
Universal hardness HU at a depth of 1 μm from the surface of the release layer is
HU ≦ 30 [N / mm ² ]
The universal hardness HU at a depth of 4 μm is
HU ≦ 12 [N / mm ² ]
A heat-fixing roller, characterized in that In a heat fixing roller in which an elastic layer and a release layer are laminated on a substrate,
When measured at a test ambient temperature of 200 ° C,
Universal hardness HU at a depth of 1 μm from the surface of the release layer is
HU ≦ 10 [N / mm ² ]
The universal hardness HU at a depth of 4 μm is
HU ≦ 4 [N / mm ² ]
A heat-fixing roller, characterized in that The heat fixing roller according to claim 26 or 27,
A heat fixing roller, wherein a contact angle when water droplets contact the surface of the release layer is 95 degrees or more. The heat fixing roller according to claim 26 or 27,
The heat-fixing roller, wherein the elastic layer is made of silicone rubber. The heat fixing roller according to claim 26, 27 or 28,
The release layer is made of tetrafluoroethylene resin (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin (PFA), and tetrafluoroethylene / hexafluoropropylene copolymer resin (FEP). A heat fixing roller comprising at least one of them as a component. A heating roller heated by a heating source, a fixing roller arranged in parallel with the heating roller, and stretched between the heating roller and the fixing roller, heated by the heating roller and driven to rotate by the both rollers A heat fixing device comprising: a fixing belt; and a pressure roller that is pressed against the surface of the fixing belt and forms a nip portion between the fixing belt,
A thermal fixing apparatus comprising the fixing belt according to any one of claims 13 to 21 as the fixing belt. An image forming apparatus comprising the heat fixing device according to claim 31.

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