JP2004069992A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method capable of using a known toner, which prevents image deterioration caused by transfer, employs a method for simultaneously transferring and fixing (temporarily fixing), decreases pressure required for transfer and fixing, and obtains high image quality free from image deterioration. <P>SOLUTION: In the image forming method in which a belt is stretched between the pressure roller of a fixing device and a roller which is in contact with a photoreceptor and a toner image on the photoreceptor is transferred with the belt, single-component development is carried out using low-resistance toner which has a softening point Tm of 100 to 180°C and a volume resistivity of 1×10<SP>7</SP>to 1×10<SP>9</SP>Ωcm. The photoreceptor is an amorphous silicon photoreceptor drum and sandwiches transfer paper between the belt and itself to transfer the toner image under pressure. At the same time, the transfer paper is conveyed with the belt and then subjected to fixing under heat. <P>COPYRIGHT: (C)2004,JPO

Description

【００５８】
本発明のトナーは平均円形度が０．９２以上であることが好ましい。平均円形度が０．９２以上の場合、感光体上でのトナー像の集合状態が均一となり、圧力転写での転写率、転写品質が向上するためである。
【００５９】
平均円形度の測定は（株）ＳＹＳＭＥＸ製フロー式粒子像分析装置ＦＰＩＡ−２１００を用いて測定することができる。測定は、１級塩化ナトリウムを用いて１％ＮａＣｌ水溶液に調整した後０．４５μｍのフィルターを通した液５０〜１００ｍｌに分散剤として界面活性剤、好ましくはアルキルベンゼンスルフォン酸塩を０．１〜５ｍｌ加え、試料を１〜１０ｍｇ加える。これを、超音波分散機で１分間の分散処理を行い、粒子濃度を５０００〜１５０００個／μｌに調整した分散液を用いて測定を行なった。ＣＣＤカメラで撮像した２次元の画像面積と、同一の面積を有する円の直径を円相当径として、円相当径で０．６μｍ以上をＣＣＤの画素の精度から有効とし平均円形度の算出に用いた。平均円形度は、各粒子の円形度の算出を行い、この各粒子の円形度を足し合わせ、全粒子数で割り算することによって得ることができる。各粒子の平均円形度は、粒子像と同じ投影面積をもつ円の周囲長を粒子投影像の周囲長で割ることにより算出することができる。平均円形度が０．９２以上のトナーは、機械的な衝撃による粉砕や、熱処理による方法などで作ることができる。
【００６０】
本発明はトナーのガラス転移温度Ｔｇが５０〜８０℃であることが好ましい。５０〜８０℃とすることで、トナーの保存性や、定着における定着性を良好に保つことができるため好ましい。
【００６１】
Ｔｇの測定はＡＳＴＭ　Ｄ３４１８−８２に準じて行う。ＤＳＣ曲線は一度昇温、降温させた後、昇温速度１０℃／ｍｉｎで測定されたＤＳＣ曲線を用いる。
【００６２】
本発明はトナーの溶融粘度が１０００Ｐａ・ｓとなる温度が１２０〜１９０℃であることが好ましい。１２０〜１９０℃とすることで、定着におけるホットオフセット現象と、且つ熱定着性のバランスが取れることから好ましい。溶融粘度の測定はフローテスターＣＦＴ−５００Ｃ（島津製作所）で測定した値であり、測定条件は、押出圧力：１．９６１２ＭＰａ、昇温速度：６℃／ｍｉｎ、ダイ径：１．０ｍｍ、ダイ長さ：１．０ｍｍの条件下にて測定する。
なお、溶融粘度ηは下記の式により求める。
溶融粘度η＝τ／γ＝πＤ^４Ｐ／１２８ＬＱ
ただし、Ｐ：押出圧力（Ｐａ）
Ｑ＝Ｘ／１０×Ａ／ｔ
Ｄ：ダイ径（ｍｍ）
Ｌ：ダイ長さ（ｍｍ）
ｔ：計測時間（ｓ）
Ｘ：計測時間ｔに対するピストンの移動量（ｍｍ）
Ａ：ピストンの断面積（ｍｍ^２）
溶融粘度ηが１０００Ｐａ・ｓとなる温度を求める。
【００６３】
本発明はトナーのゆるみ見掛け密度が０．５０ｇ／ｃｃ以上であることが好ましい。０．５０ｇ／ｃｃ以上とすることで、トナーの凝集性がさらに強くなり、感光体上でのトナー像厚みが均一となり圧力転写での転写率、転写品質が良くなる。ゆるみ見掛け密度はパウダーテスター（ＰＴＮ型：ホソカワミクロン社製）を用い測定する。
【００６４】
次に、本発明のトナーに用いられる材料について詳細に説明する。結着樹脂としては従来公知の樹脂が全て使用可能である。例えば、スチレン、ポリ−α−スチルスチレン、スチレン−クロロスチレン共重合体、スチレン−プロピレン共重合体、スチレン−ブタジエン共重合体、スチレン−塩化ビニル共重合体、スチレン−酢酸ビニル共重合体、スチレン−マレイン酸共重合体、スチレン−アクリル酸エステル共重合体、スチレン−メタクリル酸エステル共重合体、スチレン−α−クロルアクリル酸メチル共重合体、スチレン−アクリロニトリル−アクリル酸エステル共重合体等のスチレン系樹脂（スチレン又はスチレン置換体を含む単重合体又は共重合体）、ポリエステル樹脂、エポキシ樹脂、塩化ビニル樹脂、ロジン変性マレイン酸樹脂、フェノール樹脂、ポリエチレン樹脂、ポリプロピレン樹脂、石油樹脂、ポリウレタン樹脂、ケトン樹脂、エチレン−エチルアクリレート共重合体、キシレン樹脂、ポリビニルブチラート樹脂などが挙げられる。
本発明では特にポリエステル樹脂が好ましい。ポリエステル樹脂は、アルコールとカルボン酸との縮重合によって得られる。使用されるアルコールとしては、例えばエチレングリコール、ジエングリコール、トリエチレングリコール、プロピレングリコール等のグリコール類、１、４−ビス（ヒドロキシメタ）シクロヘキサン、及びビスフェノールＡ等のエーテル化ビスフェノール類、その他二価のアルコール単量体、三価以上の多価アルコール単量体を挙げることができる。また、カルボン酸としては、例えばマレイン酸、フマール酸、フタル酸、イソフタル酸、テレフタル酸、コハク酸、マロン酸等の二価の有機酸単量体、１，２，４−ベンゼントリカルボン酸、１，２，５−ベンゼントリカルボン酸、１，２，４−シクロヘキサントリカルボン酸、１，２，４−ナフタレントリカルボン酸、１，２，５−ヘキサントリカルボン酸、１，３−ジカルボキシル−２−メチレンカルボキシプロパン、１，２，７，８−オクタンテトラカルボン酸等の三価以上の多価カルボン酸単量体を挙げることができる。また上記の樹脂は単独使用も可能であるが、二種類以上併用しても良い。また、これら樹脂の製造方法も特に限定されるものではなく、塊状重合、溶液重合、乳化重合、懸濁重合いずれも使用できる。
【００６５】
本発明では磁性体を含有する磁性トナーを使用する。これは、磁気バイアスの効果により、現像担持体からトナー飛散等を抑えることができるからである。磁性体の材料としては、従来公知の磁性体が全て使用可能である。例えば、マグネタイト、γ−酸化鉄、フェライト鉄、過剰型フェライトの如き酸化鉄；鉄、コバルト、ニッケルの如き磁性金属；酸化鉄又は磁性金属と、コバルト、スズ、チタン、銅、鉛、亜鉛、マグネシウム、マンガン、アルミニウム、珪素の如き金属との複合金属酸化物合金又は、混合物が挙げられる。これら磁性体の粒子は、平均粒径が０．０５〜１．０μｍの範囲内であることが好ましく、より好ましくは０．１〜０．６μｍの範囲内、さらに好ましくは、０．１〜０．４μｍの範囲内であることが良い。これらの磁性体の粒子は、窒素吸着法によるＢＥＴ比表面積が好ましくは１〜２０ｍ^２／ｇの範囲内、特に２．５〜１２ｍ^２／ｇの範囲内であることが良く、更にモース硬度が５〜７の範囲内であることが良い。磁性体の粒子の形状としては、８面体、６面体、球形、針状、鱗片状があるが、８面体、６面体、球形の異方性の少ないものが好ましい。上記磁性体を含有する磁性トナー粒子は、結着樹脂１００重量部に対し１０〜１５０重量部、好ましくは２０〜１２０重量部の磁性体を含有させたものが好ましい。１０重量部以下の場合は、トナーとしての磁化が弱いために現像スリーブにとどまる力が弱く、非画像部への飛散が起こり地肌汚れの発生がある。一方１５０重量部以上の場合は現像スリーブとの磁気的付着力が強くなり、トナーが感光体へ現像されにくくなり所望の画像濃度が得られなくなる。
【００６６】
本発明において使用される離型剤としては、カルナウバワックス、モンタンワックス、酸化ライスワックス、合成エステルワックス、固形シリコーンワニス、高級脂肪酸高級アルコール、モンタン系エステルワックス、低分子量ポリプロピレンワックス等、従来公知のいかなる離型剤を単独で又は組み合わせて使用することができるが、特にカルナウバワックス、モンタンワックス、酸化ライスワックス及び合成エステルワックスが、離型性がすぐれている点から好ましい。カルナウバワックスとしては、カルナウバヤシの葉から得られる天然のワックスであるが、微結晶のものが良く、酸価が５以下のものが結着樹脂中に均一分散が可能であることから好ましい。また、遊離脂肪酸脱離した低酸価タイプのものがさらに好ましい。
【００６７】
モンタンワックスについては、一般に鉱物より精製されたモンタン系ワックスを指し、カルナウバワックス同様、微結晶であり、酸価が５〜１４であることが好ましい。酸化ライスワックスは、米糠から抽出される米糠油を精製する際に、脱ろう又はウィンタリング工程で製出される粗ろうを精製して得られる天然ワックスであり、その酸価は、１０〜３０が好ましい。合成エステルワックスは単官能直鎖脂肪酸と単官能直鎖アルコールからエステル反応で合成される。また、これらの離型剤の使用量は、トナー結着樹脂成分１００重量部に対して１〜１５重量部の範囲が一般的であるが、本発明においては好ましくは２重量部以上、１０重量部以下が良い。
【００６８】
本発明の現像剤は、必要に応じて帯電制御剤を含有してもよい。帯電制御剤としては公知のものが全て使用でき、例えばニグロシン系染料、トリフェニルメタン系染料、クロム含有金属錯体染料、モリブデン酸キレート顔料、ローダミン系染料、アルコキシ系アミン、４級アンモニウム塩（フッ素変性４級アンモニウム塩を含む）、アルキルアミド、燐の単体又は化合物、タングステンの単体又は化合物、フッ素系活性剤、サリチル酸金属塩及び、サリチル酸誘導体の金属塩等である。具体的にはニグロシン系染料のボントロン０３、第四級アンモニウム塩のボントロンＰ−５１、含金属アゾ染料のボントロンＳ−３４、オキシナフトエ酸系金属錯体のＥ−８２、サリチル酸系金属錯体のＥ−８４、フェノール系縮合物のＥ−８９（以上、オリエント化学工業社製）、第四級アンモニウム塩モリブデン錯体のＴＰ−３０２、ＴＰ−４１５（以上、保土谷化学工業社製）、第四級アンモニウム塩のコピーチャージＰＳＹ　ＶＰ２０３８、トリフェニルメタン誘導体のコピーブルーＰＲ、第四級アンモニウム塩のコピーチャージ　ＮＥＧ　ＶＰ２０３６、コピーチャージ　ＮＸ　ＶＰ４３４（以上、ヘキスト社製）、ＬＲＡ−９０１、ホウ素錯体であるＬＲ−１４７（日本カ一リット社製）、銅フタロシアニン、ペリレン、キナクリドン、アゾ系顔料、その他スルホン酸基、カルボキシル基、四級アンモニウム塩等の官能基を有する高分子系の化合物が挙げられる。
【００６９】
本発明に用いるトナーの着色剤としては、従来からトナー用着色剤として使用されてきた顔料及び染料の全てが適用される。具体的には、カーボンブラック、ランプブラック、鉄黒、群青、ニグロシン染料、アニリンブルー、カルコオイルブルー、オイルブラック、アゾオイルブラックなど特に限定されないが、特にアセチレンブラックやケッチェンブラック等の導電性カーボンブラックを用いることによって、本発明に使用するトナーの体積固有抵抗値を制御することができる。
着色剤の使用量は一般にトナー樹脂成分１００重量部に対し１〜１０重量部、好ましくは３〜７重量部である。
【００７０】
本発明の現像剤は、必要に応じて外添剤を含有してもよい。また外添剤としては、無機微粒子を好ましく用いることができる。この無機微粒子の一次粒子径は、５ｎｍ〜２μｍであることが好ましく、特に５ｎｍ〜５００ｎｍであることが好ましい。また、ＢＥＴ法による比表面積は、２０〜５００ｍ^２／ｇであることが好ましい。この無機微粒子の使用割合は、トナーの０．０１〜５重量％であることが好ましく、特に０．０１〜２．０重量％であることが好ましい。無機微粒子の具体例としては、例えばシリカ、アルミナ、酸化チタン、チタン酸バリウム、チタン酸マグネシウム、チタン酸カルシウム、チタン酸ストロンチウム、酸化亜鉛、酸化スズ、ケイ砂、クレー、雲母、ケイ灰石、ケイソウ土、酸化クロム、酸化セリウム、ベンガラ、三酸化アンチモン、酸化マグネシウム、酸化ジルコニウム、硫酸バリウム、炭酸バリウム、炭酸カルシウム、炭化ケイ素、窒化ケイ素などを挙げることができる。この他、高分子系微粒子たとえばソープフリー乳化重合や懸濁重合、分散重合によって得られるポリスチレン、メタクリル酸エステルやアクリル酸エステル共重合体やシリコーン、ベンゾグアナミン、ナイロンなどの重縮合系、熱硬化性樹脂による重合体粒子が挙げられる。
【００７１】
このような流動化剤は表面処理を行って、疎水性を上げ、高湿度下においても流動特性や帯電特性の悪化を防止することができる。例えばシランカップリング剤、シリル化剤、フッ化アルキル基を有するシランカップリング剤、有機チタネート系カップリング剤、アルミニウム系のカップリング剤などが好ましい表面処理剤として挙げられる。
【００７２】
本発明のトナーの製造方法は、従来公知の方法でよく、結着樹脂、離型剤、着色剤、その他場合によっては帯電制御剤等をミキサー等を用いて混合し、熱ロール、エクストルーダー等の混練機を用い混練する。ここで、練り温度、練り速度等の混練条件を変更し、カーボンブラックの分散性を変えることにより、本発明に使用するトナーの体積固有抵抗値を制御することができる。混練後は冷却固化し、これをジェットミル、ターボジェット、クリプトロン等の粉砕で粉砕し、その後分級し得られる。上記トナーに無機無粉末を添加するにはスーパーミキサー、ヘンシェルミキサーなどの混合機を用いる。
【００７３】
【実施例】
以下、本発明を下記の実施例によってさらに具体的に説明するが、本発明はこれに限定されるものではない。
各実施例で異なる現像剤を用意し、本発明の画像形成装置にて作像を行った時の転写率、定着性、粒状度と黒ベタ濃度の評価を図２の現像装置を図１の構成を有する画像形成装置に入れて行った。なお、実施例１〜９、比較例１〜３では、転写ベルトと感光体の間の圧力を２８０Ｎ／ｃｍ^２に設定し、ステアリン酸亜鉛ブロックバーを外し、表面摩擦係数が０．２８である感光体を用いた。
転写率、定着性、粒状度、黒ベタ濃度の評価は次の方法で行った。
（転写率の評価方法）
黒べたの２．５ｃｍ×２．５ｃｍパターンを作像したときの感光体上トナー重量、転写紙上トナー重量を測定し、下記式で評価を行った。
転写率＝（転写後の転写紙上トナー重量／現像後の感光体上トナー重量）×
１００　（％）
（定着性の評価方法）
２値のハーフトーン画像をプリントしたサンプルを得た。得られたサンプルにメンデイングテープ（３Ｍ社製）を貼り、一定の圧力を掛けた後、ゆっくり引き剥がした。その前後の画像濃度をマクベス濃度計により測定し、下記式にて定着性を算出した。
定着率＝〔メンデイングテープ引き剥がし後画像濃度／メンデイングテープ
引き剥がし前画像濃度〕×１００　（％）
（粒状度の評価方法）
２値のハーフトーン画像をプリントしたサンプルを得た。次に、大日本スクリーン社のＧｅｎａＳｃａｎ５０００スキャナで１０００ｄｐｉにて読み込み、画像データを得た。画像データから、濃度分布に変換し、前述した式にて粒状度を評価した。
（黒ベタ濃度の評価方法）
黒ベタの画像を出力し、手前側、中央部、奥側の画像濃度をマクベス濃度計で測定し３点平均した。
【００７４】
実施例１
（トナー処方）
ポリエステル樹脂　　　　　　　　　　　　　　　　　　　　　　　８８部
（重量平均分子量：２１０００００、Ｔｇ：８９℃）
ライスワックス　　　　　　　　　　　　　　　　　　　　　　　　　５部
カーボンブラック（ケッチェンブラックＥＣ：ケッチェンブラックインターナ
ショナル）　　　　　　　　　　　　　　　　　　　　　　　　　　　　３部
マグネタイト微粒子　　　　　　　　　　　　　　　　　　　　　　５０部
荷電制御剤（スピロンブラックＴＲ−Ｈ：保土谷化学）　　　　　　　１部
以上の処方で２軸エクストルーダーを用いて１２０℃で混練後、気流式粉砕機により粉砕、分級し重量平均粒径１１．０μｍ（重量平均粒径／個数平均粒径１．４０）とした後ヘンシェルミキサーを用い、シリカ（Ｒ−９７２　日本アエロジル）０．３重量％を混合し、表２に示す物性を持ったトナーＡを得た。
【００７５】
実施例２
（トナー処方）
ポリエステル樹脂　　　　　　　　　　　　　　　　　　　　　　　８８部
（重量平均分子量：１２８００００、Ｔｇ：８５℃）
ライスワックス　　　　　　　　　　　　　　　　　　　　　　　　　５部
カーボンブラック（ケッチェンブラックＥＣ：ケッチェンブラックインターナ
ショナル）　　　　　　　　　　　　　　　　　　　　　　　　　　　　３部
マグネタイト微粒子　　　　　　　　　　　　　　　　　　　　　　５０部
荷電制御剤（スピロンブラックＴＲ−Ｈ：保土谷化学）　　　　　　　１部
以上の処方で２軸エクストルーダーを用いて１２０℃で混練後、気流式粉砕機により粉砕、分級し重量平均粒径１１．０μｍ（重量平均粒径／個数平均粒径１．３２）とした後ヘンシェルミキサーを用い、シリカ（Ｒ−９７２　日本アエロジル）０．３重量％を混合し、表２に示す物性を持ったトナーＢを得た。
【００７６】
実施例３
（トナー処方）
スチレン−ｎ−ブチルアクリレート共重合体　　　　　　　　　　　８８部
（重量平均分子量：５７０００、Ｔｇ：５２℃）
ライスワックス　　　　　　　　　　　　　　　　　　　　　　　　　５部
カーボンブラック（ケッチェンブラックＥＣ：ケッチェンブラックインターナ
ショナル）　　　　　　　　　　　　　　　　　　　　　　　　　　　　３部
マグネタイト微粒子　　　　　　　　　　　　　　　　　　　　　　５０部
荷電制御剤（スピロンブラックＴＲ−Ｈ：保土谷化学）　　　　　　　１部
以上の処方で２軸エクストルーダーを用いて１２０℃で混練後、気流式粉砕機により粉砕、分級し重量平均粒径１１．０μｍ（重量平均粒径／個数平均粒径１．３１）とした後ヘンシェルミキサーを用い、シリカ（Ｒ−９７２　日本アエロジル）０．３重量％を混合し、表２に示す物性を持ったトナーＣを得た。
【００７７】
実施例４
（トナー処方）
スチレン−ｎ−ブチルアクリレート共重合体　　　　　　　　　　　８８部
（重量平均分子量：５７０００、Ｔｇ：５２℃）
ライスワックス　　　　　　　　　　　　　　　　　　　　　　　　　５部
カーボンブラック（ケッチェンブラックＥＣ：ケッチェンブラックインターナ
ショナル）　　　　　　　　　　　　　　　　　　　　　　　　　　　　３部
マグネタイト微粒子　　　　　　　　　　　　　　　　　　　　　　５０部
荷電制御剤（スピロンブラックＴＲ−Ｈ：保土谷化学）　　　　　　　１部
以上の処方で２軸エクストルーダーを用いて１２０℃で混練後、気流式粉砕機により粉砕、分級し重量平均粒径８．０μｍ（重量平均粒径／個数平均粒径１．３５）とした後ヘンシェルミキサーを用い、シリカ（Ｒ−９７２　日本アエロジル）０．３重量％を混合し、表２に示す物性を持ったトナーＤを得た。
【００７８】
実施例５
（トナー処方）
スチレン−ｎ−ブチルアクリレート共重合体　　　　　　　　　　　８８部
（重量平均分子量：５７０００、Ｔｇ：５２℃）
ライスワックス　　　　　　　　　　　　　　　　　　　　　　　　　５部
カーボンブラック（ケッチェンブラックＥＣ：ケッチェンブラックインターナ
ショナル）　　　　　　　　　　　　　　　　　　　　　　　　　　　　３部
マグネタイト微粒子　　　　　　　　　　　　　　　　　　　　　　５０部
荷電制御剤（スピロンブラックＴＲ−Ｈ：保土谷化学）　　　　　　　１部
以上の処方で２軸エクストルーダーを用いて１２０℃で混練後、機械式粉砕機により粉砕、分級し重量平均粒径８．０μｍ（重量平均粒径／個数平均粒径１．２５）とした後ヘンシェルミキサーを用い、シリカ（Ｒ−９７２　日本アエロジル）０．３重量％を混合し、表２に示す物性を持ったトナーＥを得た。
【００７９】
実施例６
（トナー処方）
スチレン−ｎ−ブチルアクリレート共重合体　　　　　　　　　　　８８部
（重量平均分子量：５７０００、Ｔｇ：５２℃）
ライスワックス　　　　　　　　　　　　　　　　　　　　　　　　　５部
カーボンブラック（ケッチェンブラックＥＣ：ケッチェンブラックインターナ
ショナル）　　　　　　　　　　　　　　　　　　　　　　　　　　　　３部
マグネタイト微粒子　　　　　　　　　　　　　　　　　　　　　　５０部
荷電制御剤（スピロンブラックＴＲ−Ｈ：保土谷化学）　　　　　　　１部
以上の処方で２軸エクストルーダーを用いて１２０℃で混練後、機械式粉砕機により粉砕、分級し重量平均粒径８．５μｍ（重量平均粒径／個数平均粒径１．２７）とした後ヘンシェルミキサーを用い、シリカ（Ｒ−９７２　日本アエロジル）０．３重量％を混合し、表２に示す物性を持ったトナーＦを得た。
【００８０】
実施例７
（トナー処方）
ポリエステル樹脂　　　　　　　　　　　　　　　　　　　　　　　５０部
（重量平均分子量：３１００００、Ｔｇ：６８℃）
スチレン−ｎ−ブチルアクリレート共重合体　　　　　　　　　　　４８部
（重量平均分子量：８５０００、Ｔｇ：６０℃）
カルナウバワックス　　　　　　　　　　　　　　　　　　　　　　　５部
カーボンブラック（ケッチェンブラックＥＣ：ケッチェンブラックインターナ
ショナル）　　　　　　　　　　　　　　　　　　　　　　　　　　　　３部
マグネタイト微粒子　　　　　　　　　　　　　　　　　　　　　　５０部
荷電制御剤（スピロンブラックＴＲ−Ｈ：保土谷化学）　　　　　　　１部
以上の処方で２軸エクストルーダーを用いて１２０℃で混練後、機械式粉砕機により粉砕、分級し重量平均粒径８．８μｍ（重量平均粒径／個数平均粒径１．２６）とした後ヘンシェルミキサーを用い、シリカ（Ｒ−９７２　日本アエロジル）０．３重量％を混合し、表２に示す物性を持ったトナーＧを得た。
【００８１】
実施例８
（トナー処方）
ポリエステル樹脂　　　　　　　　　　　　　　　　　　　　　　　５０部
（重量平均分子量：３１００００、Ｔｇ：６８℃）
スチレン−ｎ−ブチルアクリレート共重合体　　　　　　　　　　　４８部
（重量平均分子量：１２００００、Ｔｇ：６５℃）
カルナウバワックス　　　　　　　　　　　　　　　　　　　　　　　５部
カーボンブラック（ケッチェンブラックＥＣ：ケッチェンブラックインターナ
ショナル）　　　　　　　　　　　　　　　　　　　　　　　　　　　　３部
マグネタイト微粒子　　　　　　　　　　　　　　　　　　　　　　５０部
荷電制御剤（スピロンブラックＴＲ−Ｈ：保土谷化学）　　　　　　　１部
以上の処方で２軸エクストルーダーを用いて１２０℃で混練後、機械式粉砕機により粉砕、分級し重量平均粒径７．５μｍ（重量平均粒径／個数平均粒径１．２５）とした後ヘンシェルミキサーを用い、シリカ（Ｒ−９７２　日本アエロジル）０．３重量％を混合し、表２に示す物性を持ったトナーＨを得た。
【００８２】
実施例９
（トナー処方）
ポリエステル樹脂　　　　　　　　　　　　　　　　　　　　　　　５０部
（重量平均分子量：３１００００、Ｔｇ：６８℃）
スチレン−ｎ−ブチルアクリレート共重合体　　　　　　　　　　　４８部
（重量平均分子量：１２００００、Ｔｇ：６５℃）
カルナウバワックス　　　　　　　　　　　　　　　　　　　　　　　５部
カーボンブラック（ケッチェンブラックＥＣ：ケッチェンブラックインターナ
ショナル）　　　　　　　　　　　　　　　　　　　　　　　　　　　　３部
マグネタイト微粒子　　　　　　　　　　　　　　　　　　　　　　７０部
荷電制御剤（スピロンブラックＴＲ−Ｈ：保土谷化学）　　　　　　　１部
以上の処方で２軸エクストルーダーを用いて１２０℃で混練後、機械式粉砕機により粉砕、分級し重量平均粒径７．５μｍ（重量平均粒径／個数平均粒径１．２５）とした後ヘンシェルミキサーを用い、シリカ（Ｒ−９７２　日本アエロジル）０．３重量％を混合し、表２に示す物性を持ったトナーＩを得た。
【００８３】
実施例１０
実施例９のトナーを使い、本発明の画像形成装置の転写ベルトと感光体の間の圧力を４５０Ｎ／ｃｍ^２に設定した以外は実施例９と同様にしたものを実施例１０とする。
【００８４】
実施例１１
実施例９のトナーを使い、本発明の画像形成装置のクリーニングブラシに当接するようにステアリン酸亜鉛ブロックバーを配置し、ブラシの回転により、ステアリン酸亜鉛を感光体に塗布するようにした以外は実施例１０同様にしたものを実施例１１とする。
【００８５】
実施例１２
実施例９のトナーを使い、本発明の画像形成方法を適用した画像形成装置の感光体の表面摩擦係数が０．２であるものを使用した以外は実施例１１と同様にしたものを実施例１２とする。
【００８６】
比較例１
（トナー処方）
ポリエステル樹脂　　　　　　　　　　　　　　　　　　　　　　　８８部
（重量平均分子量：１１２０００、Ｔｇ：５０℃）
ライスワックス　　　　　　　　　　　　　　　　　　　　　　　　　５部
カーボンブラック（ケッチェンブラックＥＣ：ケッチェンブラックインターナ
ショナル）　　　　　　　　　　　　　　　　　　　　　　　　　　　　３部
マグネタイト微粒子　　　　　　　　　　　　　　　　　　　　　　５０部
荷電制御剤（スピロンブラックＴＲ−Ｈ：保土谷化学）　　　　　　　１部
以上の処方で２軸エクストルーダーを用いて１２０℃で混練後、気流式粉砕機により粉砕、分級し重量平均粒径１１．０μｍ（重量平均粒径／個数平均粒径１．３５）とした後ヘンシェルミキサーを用い、シリカ（Ｒ−９７２　日本アエロジル）０．３重量％を混合し、表２に示す物性を持ったトナーＪを得た。
【００８７】
比較例２
（トナー処方）
ポリエステル樹脂　　　　　　　　　　　　　　　　　　　　　　　８８部
（重量平均分子量：２７１００００、Ｔｇ：９１℃）
ライスワックス　　　　　　　　　　　　　　　　　　　　　　　　　５部
カーボンブラック（ケッチェンブラックＥＣ：ケッチェンブラックインターナ
ショナル）　　　　　　　　　　　　　　　　　　　　　　　　　　　　３部
マグネタイト微粒子　　　　　　　　　　　　　　　　　　　　　　５０部
荷電制御剤（スピロンブラックＴＲ−Ｈ：保土谷化学）　　　　　　　１部
以上の処方で２軸エクストルーダーを用いて１２０℃で混練後、気流式粉砕機により粉砕、分級し重量平均粒径１１．０μｍ（重量平均粒径／個数平均粒径１．３２）とした後ヘンシェルミキサーを用い、シリカ（Ｒ−９７２　日本アエロジル）０．３重量％を混合し、表２に示す物性を持ったトナーＫを得た。
【００８８】
比較例３
（トナー処方）
ポリエステル樹脂　　　　　　　　　　　　　　　　　　　　　　　８８部
（重量平均分子量：１２８００００、Ｔｇ：８５℃）
ライスワックス　　　　　　　　　　　　　　　　　　　　　　　　　５部
カーボンブラック（＃４４　三菱化成工業社製）　　　　　　　　　１５部
マグネタイト微粒子　　　　　　　　　　　　　　　　　　　　　　５０部
荷電制御剤（スピロンブラックＴＲ−Ｈ：保土谷化学）　　　　　　　１部
以上の処方で２軸エクストルーダーを用いて１２０℃で混練後、気流式粉砕機により粉砕、分級し重量平均粒径１１．０μｍ（重量平均粒径／個数平均粒径１．４０）とした後ヘンシェルミキサーを用い、シリカ（Ｒ−９７２　日本アエロジル）０．３重量％を混合し、表２に示す物性を持ったトナーＬを得た。
【００８９】
【表２】

【００９０】
以上の結果を表３に示す。高品質の画像を形成するために転写率は８０％以上、定着率は７０％以上、粒状度は０．６０以下、黒ベタ濃度は１．４０以上が望ましい。望ましい値に満たない部分は灰色で網掛けしてある。本発明の請求項を満たすトナー物性で転写率、定着率、粒状度、黒ベタ濃度の品質を満足することが可能である。
【００９１】
【表３】

【００９２】
【発明の効果】
以上説明したように、請求項１によれば、感光体と、現像装置と、熱ローラ定着装置と、該定着装置の加圧ローラと感光体に接したローラとの間に張装したベルトにより感光体上のトナー画像を転写する転写装置を用いる画像形成方法において、軟化温度Ｔｍが１００〜１８０℃、体積固有抵抗が１×１０^７〜１×１０^９Ω・ｃｍの低抵抗トナーを用いた一成分現像で現像を行い、前記感光体としてアモルファスシリコン感光体よりなるドラムを用い、感光体とローラに張られたベルトの間に転写紙を挟みトナー像を圧力転写し、同時に転写紙をベルトで搬送し、加熱手段を通過させることによりトナー像を熱定着させることを特徴とする画像形成方法により、劣化のもっとも大きい転写手段で転写と同時にトナーを転写紙に固着させ、画像の劣化を防止し、静電転写時の放電の影響によるチリ、にじみなどの劣化を防ぐように圧力のみで転写し、転写紙上のトナーの塑性変形力を利用して転写紙に軽く付着させるので、転写時に画像劣化のない高品位の画質を得ることができる
【００９３】
請求項２によれば、前記トナーの重量平均粒径が３．０〜１０．０μｍであることを特徴とする請求項１記載の画像形成方法により、低抵抗トナーを用いて誘導電荷で現像する本発明の方式においては、トナーに電荷が蓄積されにくいため、電荷による転写が難しいが、圧力のみにより転写紙に転写と同時に一次定着するので、感光体上に形成されたトナー像は画像品質を悪化させることなく転写、定着され、良好な画像品質が得ることが可能となる。
【００９４】
請求項３によれば、前記転写ベルトと感光体の間の圧力が３００〜５００Ｎ／ｃｍ^２であることを特徴とする請求項１又は２に記載の画像形成方法により、表面硬度の高い感光体（ａ−Ｓｉ感光体等）を用いて、従来の静電的な転写でなく、しかも従来の圧力転写で用いる様な高い圧力を必要とせずに（およそ１／５程度の圧力）転写が可能で、新規なトナー（組成変形トナー）と組み合わせて転写と同時に仮定着を行うので、従来の大きな圧力を利用して転写・定着を行う場合に比べて、転写ローラ等に対する制約も少なく、強い押圧力による画像の劣化も、転写紙がちぎれる等の欠点がなく、良好な画像を得ることが可能となる。
【００９５】
請求項４によれば、前記感光体のクリーニング装置として、ブレードとブラシの併用方式を持ち、ブラシに当接するようにステアリン酸亜鉛のブロックバーを配置し、ブラシの回転により、ステアリン酸亜鉛を感光体に塗布することを特徴とする請求項１又は３に記載の画像形成方法により、ステアリン酸亜鉛の潤滑効果で、クリーニング性向上の他、圧接されたトナーが感光体と粘着する力を弱めた結果トナー間の粘着力が勝り、転写率をＵＰすることが可能となる。
【００９６】
請求項５によれば、前記トナーの粒径の分散度（重量平均粒径／個数平均粒径）が１．３以下であることを特徴とする請求項１又は２に記載の画像形成方法によれば、分散度が１．３以下の場合、圧力転写で圧が均一に加わり易くなるために転写にむらの発生が少なくなることから良好な画像を得ることが可能となる。
【００９７】
請求項６によれば、前記トナーの平均円形度が０．９２以上であることを特徴とする請求項１、２又は５のいずれか１項に記載の画像形成方法により、感光体上でのトナー像の集合状態が均一となり、圧力転写での転写率、転写品質を向上させることが可能となる。
【００９８】
請求項７によれば、前記トナーのガラス転移温度Ｔｇが５０〜８０℃であることを特徴とする請求項１、２又は５、６のいずれか１項に記載の画像形成方法により、トナーの保存性や、定着における定着性を良好に保つことが可能となる。
【００９９】
請求項８によれば、前記トナーの溶融粘度が１０００Ｐａ・ｓとなる温度が１２０〜１９０℃であることを特徴とする請求項１、２又は５から７のいずれか１項に記載の画像形成方法により、定着におけるホットオフセット現象と、且つ熱定着性のバランスを取ることが可能となる。
【０１００】
請求項９によれば、前記トナーのゆるみ見掛け密度が０．５０ｇ／ｃｍ^３以上であることを特徴とする請求項１、２又は５から８のいずれか１項に記載の画像形成方法により、トナーの凝集性をさらに強くし、感光体上でのトナー像厚みが均一となり圧力転写での転写率、転写品質を良くすることが可能となる。
【０１０１】
請求項１０によれば、前記感光体の表面摩擦係数が０．１０以上０．２２以下であることを特徴とする請求項１、３、４のいずれか１項に記載の画像形成方法により、摩擦係数が小さいほど圧力転写時のトナーとの離形性が良くなるために転写率は向上するが、摩擦係数が０．１０を下回ると、現像時にトナーと感光体との付着力が低下し、トナーを感光体に転写できなくなるという現象が発生し、現像剤の穂が、感光体の表面に転移されたトナー像を再度摺って、ずらしたり掻き落としたりしてしまい、文字エッジがかすれた状態となることを防ぐことが可能となる。
【図面の簡単な説明】
【図１】本発明の画像形成方法を適用した画像形成装置の概略側面図である。
【図２】図１の画像形成装置の現像ユニットの概略側面図である。
【符号の説明】
１　感光体
２　帯電器
３　露光手段
４　現像手段（現像装置）
５　転写手段
６　クリーニング手段
７　定着手段
３０　スキャナー
３１　半導体レーザ及びポリゴン
３２　レーザー光
３３　ミラー
４１　現像スリーブ
５２　転写ローラ
５３　転写ベルト
５４　転写ローラ
６１　クリーニングブレード
６２　ファーブラシ
６３　ステアリン酸亜鉛ブロックバー
７１　定着ローラ
７２　加圧ローラ
７３、７４　加熱手段（ヒータ）
１０１、１０６　転写材バンク
１０２、１０７　給紙ローラ
１０３、１０８　給紙コロ
１０４　レジストコロ
１０５　排紙コロ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming method, and more particularly, to an image forming method using a belt pressure transfer method.
[0002]
[Prior art]
The electrophotographic image forming method requires many steps. In the case of copying, the original is converted into an electric signal by a scanner or an optical system. In the case of a printer, the signal is directly input to the plotter. An electrical signal is applied to the photosensitive member as an optical image by writing a laser or the like, and an electrostatic latent image is formed on the charged photosensitive member. In the developing step, colored fine powder typified by toner is electrostatically attached to the latent image, and further electrostatically transferred to transfer paper in the transferring step.
[0003]
Recently, in the field of color, a method of transferring a toner image of three to four colors on an intermediate transfer member and transferring the toner image to transfer paper has been often used. Then, the toner is melted and fixed on the transfer paper by heat or the like to form an image.
[0004]
When image quality is considered, image degradation occurs in all of the above steps. In particular, it is well known that the image is greatly deteriorated in each of the development, transfer and fixing steps. For example, in the developing step, the toner is electrostatically attached to the latent image on the photoreceptor by an electric field around the toner on the photoreceptor. Image deterioration occurs with respect to the latent image. Such a problem has recently been improved by reducing the diameter of the toner, making it spherical, and reducing the diameter of the carrier.
[0005]
At present, in the transfer step, the transfer paper conveyed in synchronization with the photoreceptor to which the developed toner adheres is brought into contact with the photoreceptor, and is electrostatically transferred from the photoreceptor to the transfer paper by an electric field. However, there is a problem that image deterioration due to dust, bleeding, and the like becomes large electrostatically in a process in which the transfer paper and the photosensitive member are close to each other before and after the transfer process.
[0006]
The fixing step is also a step of fusing the toner to the transfer paper. If the fixing property is improved, the toner image spreads due to the melting of the toner. If there is a variation in the amount of toner adhered to the transfer paper, the variation in the dot diameter and the line width after fixing becomes large and deteriorates. Among the above-mentioned deterioration phenomena, the deterioration is particularly large in the transfer step, and as a result, image deterioration such as image blur and resolution is remarkable.
[0007]
Therefore, as a conventional technique of the present invention, it has been proposed to simultaneously perform the transfer step and the fixing step. For example, Japanese Patent Application Laid-Open No. 55-87156 discloses a method in which transfer to a sheet and fixing are performed simultaneously using an amorphous silicon photoreceptor and a heating and fixing roll.
[0008]
Japanese Patent Application Laid-Open No. 6-175512 also proposes a method for simultaneously performing transfer and fixing using thermal energy using a polymerized toner. However, in this publication, since the fixing device and the photoconductor are in close contact with each other, heat of fixing is directly transmitted to the photoconductor. Although a photoconductor having good heat resistance may be used as the photoconductor, a cooling device may be provided in order to transmit the temperature to a temperature at which the developing unit, toner, and cleaning unit around the photoconductor can be fixed. It is practically difficult when considering the rotational speed of the vehicle.
[0009]
In order to eliminate such an adverse effect on the system due to such heat, there has been proposed a method of performing simultaneous transfer and fixing only by pressure without heating. For example, in JP-A-3-186879, 1470 to 2450 N / cm²There has been proposed a method of fixing at a pressure of 0.1 mm.
[0010]
In Japanese Patent Application Laid-Open Nos. Hei 5-216354 and Hei 6-35341, toner formed on a photoconductor by a transfer fixing device facing the photoconductor is subjected to pressure transfer simultaneously using an amorphous silicon photoconductor and a capsule toner. A fixing method has been proposed. In any case, the pressure is large, the mechanism becomes large, the transfer paper is conveyed, and the system becomes large. This is a practical problem and has not been put to practical use.
[0011]
[Problems to be solved by the invention]
As described above, the method of fixing simultaneously with transfer by heat and pressure has been proposed as a technique for complete fixing. However, in the method of performing transfer and fixing simultaneously with the heat of the above-described conventional technology, the temperature around the photoconductor becomes high, and a large stress is applied to the toner in a developing and cleaning device, which poses a serious problem in practical use.
[0012]
Further, in the method in which the simultaneous transfer fixing is performed only by pressure, 980 N / cm is considered from the viewpoint of the transfer fixing property.²There are disadvantages, such as the necessity of the above, such as an increase in the size of the apparatus and generation of wrinkles on the fixing of transfer paper.
[0013]
Further, in the conventional invention using the above-described capsule toner, the capsule toner has many problems in practical use, and in particular, there is a problem that compatibility between development and fixing cannot be achieved, and there is a problem that the cost is too high. It is currently not used.
[0014]
Therefore, the present invention has been made to solve the above problems, without using a capsule toner, in a conventionally known image forming method that can use a toner, transfer without image deterioration due to transfer, namely, An object of the present invention is to provide a method for obtaining high-quality image without image deterioration by adopting a method of fixing toner on transfer paper at the time of transfer, and further reducing the conventionally reported pressure at the time of transfer and fixing. And
[0015]
[Means for Solving the Problems]
An image forming apparatus to which the image forming method of the present invention is applied includes an amorphous silicon photosensitive drum, a transfer unit including a transfer conveyance belt, and the like. The toner image formed on the photoreceptor drum is applied with pressure to the transfer paper sandwiched between the photoreceptor and the transfer means, so that the toner is fixed to the transfer paper simultaneously with the transfer. The transfer paper holding the toner image is conveyed by a transfer belt, and becomes a fixed image by heat fixing means provided in a downstream process. In this way, high quality image quality without image degradation during transfer can be obtained.
[0016]
Here, transfer paper toner sticking refers to a state in which the toner is bitten into the transfer paper due to plastic deformation of the toner and is not electrostatically transferred. As described above, image deterioration occurs in each of the steps of latent image formation, development, transfer, separation, and fixing. According to the present invention, the toner is fixed to the transfer paper at the same time as the transfer by the transfer means having the largest deterioration, thereby preventing the deterioration of the image. Further, transfer is performed only by pressure so as to prevent deterioration such as dust and bleeding due to the influence of electric discharge at the time of electrostatic transfer, and lightly adheres to the transfer paper using the plastic deformation force of the toner on the transfer paper. Then, a method of conveying the transfer paper to a fixing device and obtaining a final image is proposed.
[0017]
In order to solve the above-mentioned problems, in the invention according to claim 1, a photoconductor, a developing device, a heat roller fixing device, and a tension roller between the pressure roller of the fixing device and a roller in contact with the photoconductor are provided. An image forming method using a transfer device for transferring a toner image on a photoreceptor with a mounted belt, the softening temperature Tm is 100 to 180 ° C., and the volume resistivity is 1 × 10⁷~ 1 × 10⁹Developed by one-component development using a low-resistance toner of Ω · cm, using a drum made of amorphous silicon photoreceptor as the photoreceptor, sandwiching a transfer paper between the photoreceptor and a belt stretched over a roller, and forming a toner image. The main feature of this method is that the toner image is thermally fixed by transferring the transfer paper with a belt and passing the paper through a heating means.
[0018]
According to a second aspect of the invention, there is mainly provided the image forming method according to the first aspect, wherein the toner has a weight average particle diameter of 3.0 to 10.0 μm.
[0019]
According to the third aspect of the present invention, the pressure between the transfer belt and the photoconductor is 300 to 500 N / cm.²The main feature of the image forming method according to claim 1 or 2.
[0020]
According to a fourth aspect of the present invention, as the cleaning method of the photoconductor, a blade and a brush are used in combination, a block bar of zinc stearate is arranged so as to abut on the brush, and the zinc stearate is exposed by rotating the brush. The main feature is the image forming method according to claim 1 or 3 applied to a body.
[0021]
According to a fifth aspect of the present invention, there is provided the image forming method according to the first or second aspect, wherein a dispersion degree of a particle diameter of the toner (weight average particle diameter / number average particle diameter) is 1.3 or less. I do.
[0022]
According to a sixth aspect of the present invention, there is provided an image forming method according to any one of the first to fifth aspects, wherein the average circularity of the toner is 0.92 or more.
[0023]
According to a seventh aspect of the present invention, there is provided an image forming method according to any one of the first, second, fifth, and sixth aspects, wherein the glass transition temperature Tg of the toner is 50 to 80 ° C.
[0024]
In the invention according to claim 8, the image forming method according to any one of claims 1, 2, or 5 to 7, wherein the temperature at which the melt viscosity of the toner becomes 1000 Pa · s is 120 to 190 ° C. Features.
[0025]
According to the ninth aspect of the present invention, the loose apparent density of the toner is 0.50 g / cm.³The main feature is the image forming method according to any one of claims 1, 2 and 5 to 8 described above.
[0026]
According to a tenth aspect of the present invention, the image forming method according to any one of the first, third, and fourth aspects is characterized in that a surface friction coefficient of the photoconductor is 0.10 or more and 0.22 or less. .
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view of the entire image forming apparatus to which the image forming method according to the present invention is applied, and shows a photoconductor unit, a transfer device, and a fixing device of an imageio MF7070 (copier made by Ricoh) that are realized by modification.
[0028]
The image forming apparatus includes a drum-shaped photoconductor 1 as a recording medium therein. Around the photoreceptor 1, various means for performing an electrophotographic copying process, that is, a charger 2, an exposing means 3, a developing means 4, a transferring means 5, a cleaning means 6, and a fixing means 7, along the rotation direction indicated by the arrow Is arranged.
[0029]
The exposure unit 3 scans the laser beam 32 by operating the semiconductor laser and the polygon 31 based on a signal according to image information read by the scanner 30, and forms an electrostatic latent image on the photoconductor 1 through the mirror 33. The photoconductor 1 uses an amorphous silicon photoconductor. The electrostatic latent image formed on the photoreceptor 1 is developed by a developing sleeve 41 arranged in the developing means 4 to form a toner image. On the other hand, the transfer paper is fed from the transfer paper banks 101 and 106 where the transfer paper is stored by the paper feed rollers 102 and 107, and further fed by the paper feed rollers 103 and 108. Rollers 104 are resist rollers 104 for transporting the transfer paper in synchronization with the toner image on the photoreceptor. Conventionally, the rollers 104 are formed on the photoreceptor 1 by the transfer means 5 on the transfer paper thus fed. The transferred toner image is electrostatically transferred. The transfer paper carrying the toner image is conveyed to the fixing means 7 through the transfer belt 53 and is fixed, and then discharged out of the apparatus. Incidentally, 52 and 54 are transfer rollers for supporting the transfer belt 53.
[0030]
On the other hand, the untransferred portion and the contaminated photoconductor 1 are cleaned by the blade 61 mounted on the cleaning means 6 and the next image forming step is started. Here, a brush 62 is provided between the zinc stearate 63 and the photoreceptor 1 in consideration of the effect of improving the cleaning efficiency of the photoreceptor 1 and the releasability of the transfer paper during transfer, which will be described later. In order to make it easier to clean the residual toner and the like on the photosensitive drum 1 with the blade 61, zinc stearate 63 is applied to the photoreceptor.
[0031]
The fixing unit 7 is a necessary component in the present invention in order to completely fix the toner whose composition has been changed by the transfer unit 5 described later. The basic configuration includes a fixing roller 71 having a heating means 74 (hereinafter, referred to as a “heater”) such as a halogen lamp, and a pressing roller 72 pressed against the fixing roller 71. The fixing roller 71 is provided with an elastic layer of silicone rubber or the like having a rubber hardness of about 42 HS (Asuka C) with a thickness of 400 μm on the surface of a core metal (not shown) having an outer diameter of φ50, and for the purpose of preventing toner adhesion due to viscosity. Thus, a resin surface layer such as a fluororesin having good releasability is formed. The thickness of the elastic layer is usually preferably about 100 to 500 μm in consideration of image quality and heat transfer efficiency at the time of fixing. The resin surface layer is formed of a tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA) tube or the like, and its thickness is preferably about 10 to 50 μm in consideration of mechanical deterioration. By using the fixing roller having such a configuration, image quality in fixing is remarkably improved. A temperature detecting means is provided on the outer peripheral surface of the fixing roller 71, and the heater 74 is controlled so that the surface temperature of the fixing roller 71 is kept substantially constant at about 165 ° C.
[0032]
The pressure roller 72 has an outer diameter φ38 core metal surface coated with an anti-offset layer such as tetrafluoroethylene-perfluoroalkylvinyl ether (PFA) or polytetrafluoroethylene (PTFE). As in the case of the fixing roller 71, a heater 73 may be provided in the cored bar. In particular, when the elastic layer is not provided, the temperature of the roller 72 at the time of stop is well reduced.
[0033]
In the fixing device having such a configuration, the fixing roller 71 and the pressure roller 72 are configured to have a surface pressure of 9.3 N / cm.²To form a fixing nip width: about 10 mm. The fixing unit 7 is driven by a driving unit (not shown) separate from the photoconductor so as to pinch and convey the transfer paper. At this time, the fixing roller 71 is controlled to a predetermined temperature by the heater 74, and when the toner image on the transfer paper passes between the two rollers, the toner image melts while receiving pressure, exits the roller pair, and is cooled. As a result, the image is fixed on the transfer paper as a permanent image.
[0034]
By providing the elastic layer on the fixing roller, the surface of the toner image and the contact point with the transfer paper are more closely contacted, and the fixing property, the unevenness of the density and the unevenness of the gloss are reduced, and a high-quality fixed image can be obtained. it can.
[0035]
Next, a characteristic configuration of the present invention will be described. In the present invention, a one-component developing method using a magnetic conductive toner is used. In the one-component development using the conductive toner, a 0.5-3.0 mm magnetic brush is formed on a developing sleeve which has a built-in magnet and is grounded to the earth with respect to the latent image on the photoconductor. It is configured.
[0036]
As for the developing mechanism, the magnetic brush rubs the photosensitive member having the latent image with the magnetic brush of only toner. At that time, induced charge is generated in the toner by the charge on the photoconductor, and a high-quality toner corresponding to the charge on the photoconductor is developed. On the other hand, when a toner having a high resistance is used, development is performed by an electric field around the toner and a charge of the toner by the photoconductor, the developing sleeve, and the carrier. This development has an edge effect due to the effect of the electric field, and is developed thicker in character and wider in area than the latent image. Further, the developed image may be rubbed and blurred due to the rubbing of the carrier, which leads to deterioration of the image. In the case of a low-resistance toner, there is no edge effect, and further development can be performed faithfully to a latent image, resulting in high image quality.
[0037]
The feature of the present invention resides in the transfer unit 5. The conventional transfer process is an electrostatic transfer method using static electricity, but the present invention resides in that transfer is performed using pressure. Further, in combination with a toner described later, transfer and assumed attachment (light fixation of a toner image to transfer paper) are performed with a smaller pressing force than before. When performing transfer and fixing using a large pressure as in the past, not only is the transfer roller and the like limited, so that a sufficient transfer mechanism cannot be easily made, but also the disadvantage that the image is degraded by strong pressing force and the transfer paper is torn. Have.
[0038]
A feature of the present invention is that a photosensitive member having a high surface hardness (for example, Vickers hardness: 1500 to 2000 kg / mm)²(A-Si photoreceptor of the order of magnitude), not the conventional electrostatic transfer effect, but also the one used in conventional pressure transfer (for example, 1500 to 2500 N / cm).²The present invention provides a simultaneous transfer-fixing method in which transfer can be performed without the need for high pressure (approximately 1/5 pressure) and a temporary transfer is performed simultaneously with transfer in combination with a new toner (compositionally deformed toner). ing.
[0039]
The transfer roller 52 is formed of a silicone rubber material having a hardness of about 80 Hs (by an Aska C hardness meter) with a thickness of 0.5 mm on the surface of a metal cylinder to have an elastic structure. Although this is not an important structure of the present invention, it is advantageous because it absorbs variations in the surface pressure on the transfer belt 53 and can easily secure the surface pressure. Contact width is about 0.5mm, pressing force is 450N / cm in surface pressure²It has become. Surface pressure is 600N / cm²When the above is satisfied, the transfer rate is improved, but the toner image and the transfer paper are crushed, which leads to deterioration of the image. 250N / cm²If it is less than this, sufficient transfer characteristics cannot be obtained (transfer rate deteriorates, transfer unevenness occurs). Further, it is desirable that the transferred toner image is lightly fixed on the transfer paper so that the toner image is not disturbed when the sheet is conveyed after the transfer. In order to obtain a good transfer image of the image, a surface pressure that can secure a transfer rate of 80% or more is desirable.
[0040]
The surface pressure is determined by the hardness and contact width of the roller, and is about 300 to 500 N / cm.²Is a preferable range. In this embodiment, 450 N / cm in Examples 10 to 12 described later.²To ensure a transfer rate of 94% or more. The transfer roller 52 is an important roller for pressure transfer, and is driven in synchronization with the photoconductor so that the photoconductor and the transfer belt 53 have substantially the same speed in the pressure contact area.
[0041]
Although the transfer belt 53 is not the gist of the present invention, the effects of the present invention can be obtained as long as the transfer belt 53 is made of a material and a shape which does not damage the pressure and the surface of the photoreceptor such as a pressure contact flaw. Here, the base material is constituted by a nickel electroformed seamless belt having a thickness of about 100 μm, a silicone rubber material having a hardness of about 80 Hs (by an Aska C hardness meter) having a thickness of 300 μm is provided on the outside thereof, and a fluororesin layer is further formed thereon. It is provided. By mounting the transfer belt having such a configuration, the required pressure can be easily secured, the speed fluctuation with the photosensitive member can be suppressed, and toner contamination on the transfer belt 53 can be prevented. The transfer belt 53 is hung between a roller 54 and an appropriate tension.
[0042]
The photoreceptor used in the present invention has a surface hardness of 500 kg / mm.²(Vickers hardness) or more, the effects of the present invention can be obtained. As described above, the toner has a pressing force at the time of transfer: about 250 to 600 N / cm.²When the hardness of the photoconductor is reduced, the photoconductor is destroyed and does not exhibit good electrostatic characteristics.
[0043]
In this embodiment, the surface hardness is 1200 kg / mm.²(Vickers hardness) All layers having a-Si photoreceptor were used, but usually 1500 to 2000 kg / mm²It is. Organic photoreceptor is usually 20-40kg / mm²About 60 kg / mm for the Se-Te photoconductor.²Degree, As₂Se₃150 kg / mm even when using a coating layer of kneaded polyester silica²All are 500kg / mm²The required photoreceptor requirements are not met.
[0044]
The next required photoreceptor characteristic is the surface friction coefficient of the surface. The smaller the coefficient of friction, the better the releasability from the toner during pressure transfer, so that the transfer rate is improved. Therefore, the smaller the coefficient of friction is, the more desirable the photoreceptor characteristics at the time of pressure transfer are. On the other hand, as a problem when the friction coefficient is reduced more than necessary, a phenomenon occurs in which the adhesive force between the toner and the photoconductor during development is reduced, and the toner cannot be transferred to the photoconductor as intended. Particularly, in a system in which the developer is developed while being in contact with the photoreceptor, the problem occurs remarkably. This is because the ears of the developer slide the toner image transferred to the surface of the photoconductor again to shift or scrape the toner image. As an image characteristic when this phenomenon occurs, a character edge is particularly blurred. It is known that this phenomenon occurs remarkably when the coefficient of friction falls below 0.10 as measured by the Euler belt method.
[0045]
In Examples 11 and 12, as shown in FIG. 1, the cleaning means 6 is provided with a function of applying zinc stearate 63, and has a friction coefficient of 0.22 measured by the Euler belt method. The lubricating effect of the zinc stearate 63 improves the cleaning performance, and also reduces the adhesive force of the pressed toner to the photoconductor, so that the adhesive force between the toners is superior and the transfer rate is increased.
[0046]
The Euler belt method employed in the present invention as a method for quantifying the photoreceptor surface friction coefficient will be described. A belt-shaped measuring agent prepared by cutting medium-quality high-quality paper so that the paper-making direction is in the longitudinal direction is brought into contact with a quarter of the outer periphery of the cylindrical photoreceptor surface, a load of 100 g is applied to the lower end, and a lower end is applied to the upper end. Connect the force gauge. Next, the force gauge is moved at a constant speed, and the value of the force gauge when the belt starts moving is read and calculated by the following equation.
μ = 2 / π × ln (F / W)
μ: Coefficient of static friction
F: Force gauge reading
W: Load (100g)
The effects of the present invention are best exhibited by adopting all these photoreceptor characteristics.However, environmental stability and stability over time have an effect on image quality. .
[0047]
Since the toner on the transfer paper is already input in the fixing unit 7 in a compositionally deformed state, sufficient fixing properties can be obtained at a lower temperature of the fixing roller 71 than in the related art. In this embodiment, the fixing is performed by controlling the surface temperature of the central portion of the fixing roller to 160 ° C. In addition, the heater disposed on the pressure roller 72 can prevent the temperature of the pressure roller from lowering when the transfer paper passes, and can fix the image efficiently, so that a stable and uniform image can be obtained.
[0048]
It is important to effect the composition of the toner at the time of transfer by utilizing the pressure as described above, but the physical properties of the toner are important for obtaining the effect of the invention. That is, the toner sinks into the transfer paper at a transfer pressure as low as possible, and adhesiveness is obtained between the toners. It is further desired that the effects of the present invention can be exerted by achieving the toner images which are more clearly arranged on the photosensitive member by the developing means.
[0049]
The present invention develops a toner image by developing an electrostatic latent image formed on a photoreceptor with toner, transfers the formed toner image to transfer paper by pressure, and transports the transfer paper and passes through a heating unit. The toner has a volume resistivity of 1 × 10⁹The image forming method is characterized in that the toner is a magnetic toner having a Ω · cm or less and a softening temperature Tm of 100 to 180 ° C.
[0050]
In a method of developing with an induced charge using a low-resistance toner, the charge is hardly accumulated in the toner, so that the transfer by the charge is difficult. Therefore, in the primary fixing in which the toner image is fixed on the transfer paper simultaneously with the transfer only by the pressure, the toner image formed on the photoconductor is transferred and fixed without deteriorating the image quality.
[0051]
The volume resistivity of the toner of the present invention is 1 × 10⁹Ω · cm or less is essential. 1 × 10⁹In the case of Ω · cm or less, charge injection is likely to occur during development, so that good image quality can be obtained. The volume resistivity of the toner was measured by measuring 3.0 g of the toner at 6 t / cm.²Is applied and measured by a TR-10C type dielectric loss measuring device (Ando Electric Co., Ltd.). The frequency is 1 KHz, RATIO is 11 × 10^-9It is.
[0052]
It is essential that the softening temperature Tm of the toner of the present invention is 100 to 180 ° C. When Tm is 100 ° C. or lower, storage stability and image granularity deteriorate. On the other hand, when the temperature is 180 ° C. or higher, the heat fixing property in fixing deteriorates. This is shown by the evaluation results of Examples 1 to 3 and Comparative Examples 1 and 2 described later. The softening temperature Tm is measured with a flow tester CFT-500C (Shimadzu Corporation). The measurement conditions were as follows: Extrusion pressure: 1.9612 MPa, heating rate: 6 ° C./min, die diameter: 1.0 mm, die length: 1.0 mm. I do.
[0053]
The weight average particle diameter of the toner is preferably from 3.0 to 10.0 μm. The smaller the toner particle size, the better the image quality. It is preferable that the toner particle diameter is 3.0 to 10.0 μm because deterioration of toner productivity and flowability can be prevented, and good image quality can be obtained.
[0054]
In the present invention, the degree of dispersion of the toner particle diameter (weight average particle diameter / number average particle diameter) is preferably 1.3 or less. When the degree of dispersion is 1.3 or less, it is preferable because the pressure is easily applied uniformly by pressure transfer, so that the occurrence of unevenness in transfer is reduced. For the measurement of the weight average particle size and the number average particle size, Coulter MULTISIZER IIe was used. The aperture diameter is 100 μm.
[0055]
As for the image quality, the volume and area after the transfer of the toner image and after the fixing change, and the image quality deteriorates. This phenomenon is particularly remarkable in the case of digital development, and the reproducibility of independent dots is greatly affected. Halftone densities should be uniform, but micro-density irregularities can give a rough impression to the naked eye. The physical evaluation value of the roughness is the granularity. The noise can be measured by a Wiener spectrum which is a frequency characteristic of the density fluctuation. If the density fluctuation component whose average value is 0 is f (x),
F (u) = ∫f (x) exp (−2πiux) dx
WS (u) = F (u)²
Where u is the spatial frequency.
The granularity (GS) is a value obtained by integrating the product of WS and visual frequency characteristics (Visual / Transfer / Function: VTF), and is expressed by the following equation.
GS = exp (−1.8 <D>) ∫WS (u)^1/2VTF (u) du
exp (−1.8 <D>) is a coefficient for correcting the difference between the density and the brightness perceived by a person. <D> represents the average value of the density.
The granularity has a high correlation with the subjective evaluation of the smoothness of the image.
The smaller the value of the granularity, the smoother the image quality becomes, and the larger the value of the granularity, the rougher the image quality becomes.
[0056]
Table 1 shows an example of the particle size distribution of the toner used in the present invention. In addition, Coulter MULTIZER IIe was used for the measurement. The aperture diameter is 100 μm.
[0057]
[Table 1]

[0058]
The toner of the present invention preferably has an average circularity of 0.92 or more. This is because, when the average circularity is 0.92 or more, the aggregated state of the toner images on the photoconductor becomes uniform, and the transfer rate and transfer quality in pressure transfer are improved.
[0059]
The average circularity can be measured using a flow particle image analyzer FPIA-2100 manufactured by SYSMEX CORPORATION. The measurement is performed by adjusting a 1% NaCl aqueous solution using primary sodium chloride, and then adding 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, as a dispersant to 50 to 100 ml of a 0.45 μm-filtered liquid. In addition, add 1-10 mg of sample. This was subjected to a dispersion treatment for 1 minute by an ultrasonic disperser, and the measurement was performed using a dispersion liquid in which the particle concentration was adjusted to 5000 to 15000 particles / μl. The diameter of a circle having the same area as a two-dimensional image area captured by a CCD camera is defined as a circle equivalent diameter, and a circle equivalent diameter of 0.6 μm or more is effective from the accuracy of CCD pixels and used for calculating the average circularity. Was. The average circularity can be obtained by calculating the circularity of each particle, adding the circularity of each particle, and dividing by the total number of particles. The average circularity of each particle can be calculated by dividing the perimeter of a circle having the same projected area as the particle image by the perimeter of the particle projected image. The toner having an average circularity of 0.92 or more can be produced by pulverization by mechanical impact, a method by heat treatment, or the like.
[0060]
In the present invention, the glass transition temperature Tg of the toner is preferably 50 to 80 ° C. The temperature of 50 to 80 ° C. is preferable because the storage stability of the toner and the fixability in fixing can be kept good.
[0061]
The Tg is measured according to ASTM D3418-82. As the DSC curve, a DSC curve measured once at a temperature rising rate of 10 ° C./min after the temperature is once increased and decreased.
[0062]
In the present invention, the temperature at which the melt viscosity of the toner becomes 1000 Pa · s is preferably 120 to 190 ° C. It is preferable to set the temperature to 120 to 190 ° C. because a balance between the hot offset phenomenon in fixing and the heat fixing property can be obtained. The measurement of the melt viscosity is a value measured by a flow tester CFT-500C (Shimadzu Corporation), and the measurement conditions are: extrusion pressure: 1.9612 MPa, heating rate: 6 ° C./min, die diameter: 1.0 mm, die length Length: Measured under the condition of 1.0 mm.
The melt viscosity η is determined by the following equation.
Melt viscosity η = τ / γ = πD⁴P / 128LQ
Here, P: extrusion pressure (Pa)
Q = X / 10 × A / t
D: Die diameter (mm)
L: Die length (mm)
t: Measurement time (s)
X: the amount of movement of the piston with respect to the measurement time t (mm)
A: Piston cross-sectional area (mm²)
The temperature at which the melt viscosity η becomes 1000 Pa · s is determined.
[0063]
In the present invention, the loose apparent density of the toner is preferably 0.50 g / cc or more. When the content is 0.50 g / cc or more, the cohesiveness of the toner is further increased, the thickness of the toner image on the photoconductor is made uniform, and the transfer rate and transfer quality in pressure transfer are improved. The loose apparent density is measured using a powder tester (PTN type: manufactured by Hosokawa Micron Corporation).
[0064]
Next, the materials used for the toner of the present invention will be described in detail. As the binder resin, all conventionally known resins can be used. For example, styrene, poly-α-stillstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene Styrene such as maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl acrylate copolymer, styrene-acrylonitrile-acrylic acid ester copolymer Resin (monopolymer or copolymer containing styrene or a substituted styrene), polyester resin, epoxy resin, vinyl chloride resin, rosin-modified maleic resin, phenol resin, polyethylene resin, polypropylene resin, petroleum resin, polyurethane resin, Ketone resin, ethylene-ethyl alcohol Examples include a acrylate copolymer, a xylene resin, and a polyvinyl butyrate resin.
In the present invention, a polyester resin is particularly preferred. The polyester resin is obtained by condensation polymerization of an alcohol and a carboxylic acid. Examples of the alcohol used include glycols such as ethylene glycol, diene glycol, triethylene glycol, and propylene glycol, 1,4-bis (hydroxymeth) cyclohexane, and etherified bisphenols such as bisphenol A, and other divalent alcohols. Alcohol monomers and trihydric or higher polyhydric alcohol monomers can be exemplified. Examples of the carboxylic acid include divalent organic acid monomers such as maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, and malonic acid; 1,2,4-benzenetricarboxylic acid; , 2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methylenecarboxy Examples include trivalent or higher polyvalent carboxylic acid monomers such as propane and 1,2,7,8-octanetetracarboxylic acid. The above resins can be used alone or in combination of two or more. Also, the method for producing these resins is not particularly limited, and any of bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization can be used.
[0065]
In the present invention, a magnetic toner containing a magnetic material is used. This is because the effect of the magnetic bias can suppress toner scattering from the developing carrier. As the material of the magnetic material, all conventionally known magnetic materials can be used. For example, iron oxides such as magnetite, γ-iron oxide, ferrite iron and excess ferrite; magnetic metals such as iron, cobalt and nickel; iron oxides or magnetic metals, and cobalt, tin, titanium, copper, lead, zinc and magnesium , Manganese, aluminum, and composite metal oxide alloys or mixtures with metals such as silicon. These magnetic particles preferably have an average particle diameter in the range of 0.05 to 1.0 μm, more preferably in the range of 0.1 to 0.6 μm, and still more preferably 0.1 to 0 μm. It may be within the range of 0.4 μm. These magnetic particles preferably have a BET specific surface area of 1 to 20 m by the nitrogen adsorption method.²/ G, especially 2.5 to 12 m²/ G, and Mohs hardness in the range of 5-7. The shape of the magnetic particles may be octahedral, hexahedral, spherical, acicular, or scaly, but octahedral, hexahedral, or spherical with low anisotropy is preferred. The magnetic toner particles containing the magnetic substance preferably contain the magnetic substance in an amount of 10 to 150 parts by weight, preferably 20 to 120 parts by weight based on 100 parts by weight of the binder resin. When the amount is less than 10 parts by weight, since the magnetization as the toner is weak, the force of staying on the developing sleeve is weak, and the toner is scattered to the non-image portion to cause background stain. On the other hand, when the amount is 150 parts by weight or more, the magnetic adhesion to the developing sleeve becomes strong, so that the toner is hardly developed on the photosensitive member, and a desired image density cannot be obtained.
[0066]
The release agent used in the present invention includes carnauba wax, montan wax, oxidized rice wax, synthetic ester wax, solid silicone varnish, higher fatty acid higher alcohol, montan ester wax, low molecular weight polypropylene wax and the like, which are conventionally known. Any release agent can be used alone or in combination. Carnauba wax, montan wax, oxidized rice wax and synthetic ester wax are particularly preferable because of their excellent release properties. The carnauba wax is a natural wax obtained from carnauba palm leaves, but a microcrystalline wax is preferred, and a wax having an acid value of 5 or less is preferable because it can be uniformly dispersed in a binder resin. Further, a low acid value type from which free fatty acids have been eliminated is more preferable.
[0067]
The montan wax generally refers to a montan-based wax refined from a mineral, and is preferably a microcrystal and has an acid value of 5 to 14 like carnauba wax. Oxidized rice wax is a natural wax obtained by refining crude wax produced in a dewaxing or wintering step when refining rice bran oil extracted from rice bran, and has an acid value of 10 to 30. preferable. Synthetic ester wax is synthesized from a monofunctional linear fatty acid and a monofunctional linear alcohol by an ester reaction. The use amount of these release agents is generally in the range of 1 to 15 parts by weight with respect to 100 parts by weight of the toner binder resin component, but in the present invention, preferably 2 to 10 parts by weight. Less than a part is good.
[0068]
The developer of the present invention may optionally contain a charge control agent. As the charge control agent, any known charge control agents can be used. For example, nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (fluorine-modified) (Including quaternary ammonium salts), alkyl amides, simple substances or compounds of phosphorus, tungsten simple substances or compounds, fluorine-based activators, metal salts of salicylic acid, and metal salts of salicylic acid derivatives. Specifically, bontron 03 of a nigrosine dye, bontron P-51 of a quaternary ammonium salt, bontron S-34 of a metal-containing azo dye, E-82 of an oxynaphthoic acid metal complex, and E-82 of a salicylic acid metal complex 84, phenolic condensate E-89 (all manufactured by Orient Chemical Industries), quaternary ammonium salt molybdenum complex TP-302, TP-415 (all manufactured by Hodogaya Chemical Industry), quaternary ammonium Copy charge of salt PSY @ VP2038, copy blue PR of triphenylmethane derivative, copy charge of quaternary ammonium salt NEG @ VP2036, copy charge NX @ VP434 (all from Hoechst), LRA-901, LR-147 which is a boron complex (Manufactured by Nippon Carlit Co., Ltd.), copper phthalocyanine, perylene, quinac Don, azo pigments, sulfonate group, carboxyl group, and polymer compounds having a functional group such as a quaternary ammonium salt.
[0069]
As the colorant of the toner used in the present invention, all pigments and dyes conventionally used as colorants for toner are applied. Specifically, carbon black, lamp black, iron black, ultramarine blue, nigrosine dye, aniline blue, calco oil blue, oil black, azo oil black and the like are not particularly limited, but particularly conductive carbon such as acetylene black and Ketjen black. By using black, the volume resistivity of the toner used in the present invention can be controlled.
The amount of the colorant used is generally 1 to 10 parts by weight, preferably 3 to 7 parts by weight, per 100 parts by weight of the toner resin component.
[0070]
The developer of the present invention may contain an external additive as needed. As the external additive, inorganic fine particles can be preferably used. The primary particle diameter of the inorganic fine particles is preferably from 5 nm to 2 μm, and particularly preferably from 5 nm to 500 nm. The specific surface area by the BET method is 20 to 500 m.²/ G. The use ratio of the inorganic fine particles is preferably from 0.01 to 5% by weight of the toner, and particularly preferably from 0.01 to 2.0% by weight. Specific examples of the inorganic fine particles include, for example, silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, silica sand, clay, mica, wollastonite, and diatomaceous Examples include earth, chromium oxide, cerium oxide, red iron oxide, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride. In addition, polymer fine particles such as polystyrene obtained by soap-free emulsion polymerization, suspension polymerization, or dispersion polymerization, polycondensation systems such as methacrylate and acrylate copolymers, silicone, benzoguanamine, and nylon, and thermosetting resins Polymer particles.
[0071]
Such a fluidizing agent can be subjected to a surface treatment to increase hydrophobicity and prevent deterioration of fluidity and charging properties even under high humidity. For example, a silane coupling agent, a silylating agent, a silane coupling agent having a fluorinated alkyl group, an organic titanate-based coupling agent, an aluminum-based coupling agent, and the like are preferable surface treatment agents.
[0072]
The method for producing the toner of the present invention may be a conventionally known method, in which a binder resin, a release agent, a colorant, and in some cases, a charge control agent and the like are mixed using a mixer or the like, and then heated rolls, an extruder, or the like. And kneading using a kneading machine. Here, by changing the kneading conditions such as the kneading temperature and the kneading speed, and changing the dispersibility of the carbon black, the volume specific resistance value of the toner used in the present invention can be controlled. After kneading, the mixture is cooled and solidified, pulverized by pulverization using a jet mill, turbojet, kryptron or the like, and then classified. A mixer such as a super mixer or a Henschel mixer is used to add the inorganic powder to the toner.
[0073]
【Example】
Hereinafter, the present invention will be described more specifically with reference to the following examples, but the present invention is not limited thereto.
A different developer was prepared in each embodiment, and the transfer rate, fixability, granularity, and solid black density when an image was formed by the image forming apparatus of the present invention were evaluated. The test was carried out in an image forming apparatus having the above configuration. In Examples 1 to 9 and Comparative Examples 1 to 3, the pressure between the transfer belt and the photoconductor was 280 N / cm.², The zinc stearate block bar was removed, and a photoreceptor having a surface friction coefficient of 0.28 was used.
The following methods were used to evaluate the transfer rate, fixability, granularity, and solid black density.
(Evaluation method of transfer rate)
The weight of the toner on the photoreceptor and the weight of the toner on the transfer paper when a black solid 2.5 cm × 2.5 cm pattern was formed were measured and evaluated by the following formula.
Transfer rate = (weight of toner on transfer paper after transfer / weight of toner on photoconductor after development) ×
100 (%)
(Method of evaluating fixability)
A sample on which a binary halftone image was printed was obtained. Mending tape (manufactured by 3M) was applied to the obtained sample, and after applying a certain pressure, it was slowly peeled off. The image density before and after that was measured by a Macbeth densitometer, and the fixability was calculated by the following equation.
Fixing rate = [image density after peeling of the mending tape / mending tape
Image density before peeling] x 100% (%)
(Evaluation method of granularity)
A sample on which a binary halftone image was printed was obtained. Next, image data was obtained by reading at 1000 dpi with a GenaScan 5000 scanner manufactured by Dainippon Screen. The image data was converted into a density distribution, and the granularity was evaluated by the above-described equation.
(Evaluation method for solid black density)
A solid black image was output, and the image densities on the near side, the center, and the back side were measured with a Macbeth densitometer and averaged over three points.
[0074]
Example 1
(Toner prescription)
Polyester resin 88 parts
(Weight average molecular weight: 2100000, Tg: 89 ° C)
Rice wax 5 parts
Carbon black (Ketjen Black EC: Ketjen Black Internal
Optional) 3 copies
Magnetite fine particles 50 parts
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part
After kneading at 120 ° C. using a twin-screw extruder with the above formulation, pulverizing and classifying with a pneumatic pulverizer to obtain a weight average particle diameter of 11.0 μm (weight average particle diameter / number average particle diameter 1.40). Using a Henschel mixer, 0.3% by weight of silica (R-972 (Nippon Aerosil)) was mixed to obtain Toner A having the physical properties shown in Table 2.
[0075]
Example 2
(Toner prescription)
Polyester resin 88 parts
(Weight average molecular weight: 1280000, Tg: 85 ° C)
Rice wax 5 parts
Carbon black (Ketjen Black EC: Ketjen Black Internal
Optional) 3 copies
Magnetite fine particles 50 parts
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part
After kneading at 120 ° C. using a twin-screw extruder with the above formulation, pulverizing and classifying with an air-flow type pulverizer to obtain a weight average particle diameter of 11.0 μm (weight average particle diameter / number average particle diameter 1.32). Using a Henschel mixer, 0.3% by weight of silica (R-972 (Nippon Aerosil)) was mixed to obtain Toner B having the physical properties shown in Table 2.
[0076]
Example 3
(Toner prescription)
Styrene-n-butyl acrylate copolymer 88 parts
(Weight average molecular weight: 57000, Tg: 52 ° C)
Rice wax 5 parts
Carbon black (Ketjen Black EC: Ketjen Black Internal
Optional) 3 copies
Magnetite fine particles 50 parts
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part
After kneading at 120 ° C. using a twin-screw extruder with the above formulation, pulverizing and classifying with an air-flow type pulverizer to obtain a weight average particle diameter of 11.0 μm (weight average particle diameter / number average particle diameter 1.31). Using a Henschel mixer, 0.3% by weight of silica (R-972 (Nippon Aerosil)) was mixed to obtain Toner C having the physical properties shown in Table 2.
[0077]
Example 4
(Toner prescription)
Styrene-n-butyl acrylate copolymer 88 parts
(Weight average molecular weight: 57000, Tg: 52 ° C)
Rice wax 5 parts
Carbon black (Ketjen Black EC: Ketjen Black Internal
Optional) 3 copies
Magnetite fine particles 50 parts
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part
After kneading at 120 ° C. using a twin-screw extruder with the above formulation, pulverizing and classifying with an air-flow type pulverizer to obtain a weight average particle size of 8.0 μm (weight average particle size / number average particle size 1.35). Using a Henschel mixer, 0.3% by weight of silica (R-972 (Nippon Aerosil)) was mixed to obtain Toner D having the physical properties shown in Table 2.
[0078]
Example 5
(Toner prescription)
Styrene-n-butyl acrylate copolymer 88 parts
(Weight average molecular weight: 57000, Tg: 52 ° C)
Rice wax 5 parts
Carbon black (Ketjen Black EC: Ketjen Black Internal
Optional) 3 copies
Magnetite fine particles 50 parts
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part
After kneading at 120 ° C. using a twin-screw extruder with the above formulation, pulverizing and classifying with a mechanical pulverizer to obtain a weight average particle size of 8.0 μm (weight average particle size / number average particle size 1.25). Using a Henschel mixer, 0.3% by weight of silica (R-972 (Nippon Aerosil)) was mixed to obtain a toner E having the physical properties shown in Table 2.
[0079]
Example 6
(Toner prescription)
Styrene-n-butyl acrylate copolymer 88 parts
(Weight average molecular weight: 57000, Tg: 52 ° C)
Rice wax 5 parts
Carbon black (Ketjen Black EC: Ketjen Black Internal
Optional) 3 copies
Magnetite fine particles 50 parts
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part
After kneading at 120 ° C. using a twin-screw extruder with the above formulation, pulverizing and classifying with a mechanical pulverizer to obtain a weight average particle size of 8.5 μm (weight average particle size / number average particle size 1.27). Using a Henschel mixer, 0.3% by weight of silica (R-972 (Nippon Aerosil)) was mixed to obtain a toner F having the physical properties shown in Table 2.
[0080]
Example 7
(Toner prescription)
50% polyester resin
(Weight average molecular weight: 310,000, Tg: 68 ° C)
Styrene-n-butyl acrylate copolymer (48 parts)
(Weight average molecular weight: 85000, Tg: 60 ° C)
Carnauba wax 5 parts
Carbon black (Ketjen Black EC: Ketjen Black Internal
Optional) 3 copies
Magnetite fine particles 50 parts
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part
After kneading at 120 ° C. using a twin-screw extruder with the above formulation, pulverizing and classifying with a mechanical pulverizer to obtain a weight average particle size of 8.8 μm (weight average particle size / number average particle size 1.26). Using a Henschel mixer, 0.3% by weight of silica (R-972 (Nippon Aerosil)) was mixed to obtain a toner G having the physical properties shown in Table 2.
[0081]
Example 8
(Toner prescription)
50% polyester resin
(Weight average molecular weight: 310,000, Tg: 68 ° C)
Styrene-n-butyl acrylate copolymer (48 parts)
(Weight average molecular weight: 120,000, Tg: 65 ° C)
Carnauba wax 5 parts
Carbon black (Ketjen Black EC: Ketjen Black Internal
Optional) 3 copies
Magnetite fine particles 50 parts
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part
After kneading at 120 ° C. using a twin-screw extruder with the above formulation, pulverizing and classifying with a mechanical pulverizer to obtain a weight average particle size of 7.5 μm (weight average particle size / number average particle size 1.25). Using a Henschel mixer, 0.3% by weight of silica (R-972 (Nippon Aerosil)) was mixed to obtain Toner H having the physical properties shown in Table 2.
[0082]
Example 9
(Toner prescription)
50% polyester resin
(Weight average molecular weight: 310,000, Tg: 68 ° C)
Styrene-n-butyl acrylate copolymer (48 parts)
(Weight average molecular weight: 120,000, Tg: 65 ° C)
Carnauba wax 5 parts
Carbon black (Ketjen Black EC: Ketjen Black Internal
Optional) 3 copies
Magnetite fine particles 70 parts
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part
After kneading at 120 ° C. using a twin-screw extruder with the above formulation, pulverizing and classifying with a mechanical pulverizer to obtain a weight average particle size of 7.5 μm (weight average particle size / number average particle size 1.25). Using a Henschel mixer, 0.3% by weight of silica (R-972 (Nippon Aerosil)) was mixed to obtain Toner I having the physical properties shown in Table 2.
[0083]
Example 10
Using the toner of Example 9, the pressure between the transfer belt and the photoreceptor of the image forming apparatus of the present invention was increased to 450 N / cm.²A tenth embodiment is similar to the ninth embodiment except that the setting is set to.
[0084]
Example 11
Except that the toner of Example 9 was used, a zinc stearate block bar was arranged so as to be in contact with the cleaning brush of the image forming apparatus of the present invention, and zinc stearate was applied to the photoreceptor by rotating the brush. What is similar to the tenth embodiment is the eleventh embodiment.
[0085]
Example 12
An image forming apparatus to which the image forming method of the present invention was applied using the toner of Example 9 except that the photosensitive member had a surface friction coefficient of 0.2 was used. It is assumed to be 12.
[0086]
Comparative Example 1
(Toner prescription)
Polyester resin 88 parts
(Weight average molecular weight: 112000, Tg: 50 ° C)
Rice wax 5 parts
Carbon black (Ketjen Black EC: Ketjen Black Internal
Optional) 3 copies
Magnetite fine particles 50 parts
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part
After kneading at 120 ° C. using a twin-screw extruder with the above formulation, pulverizing and classifying with an air-flow type pulverizer to obtain a weight average particle diameter of 11.0 μm (weight average particle diameter / number average particle diameter 1.35). Using a Henschel mixer, 0.3% by weight of silica (R-972 (Nippon Aerosil)) was mixed to obtain Toner J having the physical properties shown in Table 2.
[0087]
Comparative Example 2
(Toner prescription)
Polyester resin 88 parts
(Weight average molecular weight: 2710000, Tg: 91 ° C)
Rice wax 5 parts
Carbon black (Ketjen Black EC: Ketjen Black Internal
Optional) 3 copies
Magnetite fine particles 50 parts
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part
After kneading at 120 ° C. using a twin-screw extruder with the above formulation, pulverizing and classifying with an air-flow type pulverizer to obtain a weight average particle diameter of 11.0 μm (weight average particle diameter / number average particle diameter 1.32). Using a Henschel mixer, 0.3% by weight of silica (R-972 (Nippon Aerosil)) was mixed to obtain Toner K having the physical properties shown in Table 2.
[0088]
Comparative Example 3
(Toner prescription)
Polyester resin 88 parts
(Weight average molecular weight: 1280000, Tg: 85 ° C)
Rice wax 5 parts
Carbon black (# 44 manufactured by Mitsubishi Kasei Kogyo) 15 parts
Magnetite fine particles 50 parts
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part
After kneading at 120 ° C. using a twin-screw extruder with the above formulation, pulverizing and classifying with an air-flow type pulverizer to obtain a weight average particle diameter of 11.0 μm (weight average particle diameter / number average particle diameter 1.40). Using a Henschel mixer, 0.3% by weight of silica (R-972 (Nippon Aerosil)) was mixed to obtain a toner L having the physical properties shown in Table 2.
[0089]
[Table 2]

[0090]
Table 3 shows the above results. In order to form a high quality image, it is desirable that the transfer rate is 80% or more, the fixing rate is 70% or more, the granularity is 0.60 or less, and the solid black density is 1.40 or more. Areas below the desired value are shaded gray. The quality of the transfer rate, the fixing rate, the granularity, and the solid black density can be satisfied by the physical properties of the toner satisfying the claims of the present invention.
[0091]
[Table 3]

[0092]
【The invention's effect】
As described above, according to the first aspect, the photoconductor, the developing device, the heat roller fixing device, and the belt stretched between the pressure roller of the fixing device and the roller in contact with the photoconductor are used. In an image forming method using a transfer device for transferring a toner image on a photoconductor, a softening temperature Tm is 100 to 180 ° C., and a volume resistivity is 1 × 10 5⁷~ 1 × 10⁹Developed by one-component development using a low-resistance toner of Ω · cm, using a drum made of amorphous silicon photoreceptor as the photoreceptor, sandwiching transfer paper between the photoreceptor and a belt stretched over a roller, and forming a toner image. The toner image is transferred at the same time as the transfer unit with the largest deterioration by the image forming method characterized in that the transfer paper is conveyed by a belt and the toner image is heat-fixed by passing through a heating unit at the same time. It is fixed on paper to prevent image deterioration, and is transferred only with pressure to prevent deterioration such as dust and bleeding due to the influence of discharge during electrostatic transfer, and is transferred using the plastic deformation force of toner on transfer paper. Lightly adheres to paper, so high-quality image quality with no image degradation during transfer can be obtained
[0093]
According to the second aspect, the toner has a weight average particle diameter of 3.0 to 10.0 μm, and is developed with an induced charge using a low-resistance toner by the image forming method according to the first aspect. In the method of the present invention, it is difficult to accumulate electric charge in the toner, so it is difficult to transfer by electric charge. Transfer and fixing are performed without deterioration, and good image quality can be obtained.
[0094]
According to claim 3, the pressure between the transfer belt and the photoconductor is 300 to 500 N / cm.²The image forming method according to claim 1, wherein a photosensitive member having a high surface hardness (such as an a-Si photosensitive member) is used instead of the conventional electrostatic transfer. The transfer is possible without the need for a high pressure (approximately 1/5 pressure) as used in the pressure transfer of (1), and the temporary attachment is performed simultaneously with the transfer in combination with a new toner (composition deformed toner). Compared to the case where transfer and fixing are performed using a large pressure, there are fewer restrictions on the transfer roller and the like, and there is no problem such as deterioration of the image due to a strong pressing force, and no defects such as tearing of the transfer paper, and a good image can be obtained. It becomes possible.
[0095]
According to claim 4, the cleaning device for the photoreceptor has a combined use of a blade and a brush, and a block bar of zinc stearate is arranged so as to abut on the brush. 4. The image forming method according to claim 1 or 3, wherein the lubricating effect of zinc stearate improves the cleaning property and reduces the adhesive force of the pressed toner to the photoreceptor. As a result, the adhesive force between the toners is superior, and the transfer rate can be increased.
[0096]
According to claim 5, the degree of dispersion of the particle diameter of the toner (weight average particle diameter / number average particle diameter) is 1.3 or less, the image forming method according to claim 1 or 2, wherein According to this, when the degree of dispersion is 1.3 or less, a uniform image can be easily applied by pressure transfer, and the occurrence of unevenness in transfer is reduced, so that a good image can be obtained.
[0097]
According to a sixth aspect, the average circularity of the toner is 0.92 or more, and the image forming method according to any one of the first, second, and fifth aspects, further comprising: The aggregated state of the toner images becomes uniform, and the transfer rate and transfer quality in pressure transfer can be improved.
[0098]
According to claim 7, the glass transition temperature Tg of the toner is 50 to 80 ° C, and the toner according to any one of claims 1, 2 or 5, and 6 is used. It is possible to maintain good storability and fixability in fixing.
[0099]
8. The image forming apparatus according to claim 1, wherein the temperature at which the melt viscosity of the toner becomes 1000 Pa.s is 120 to 190 [deg.] C. The method makes it possible to balance the hot offset phenomenon in fixing and the heat fixing property.
[0100]
According to claim 9, the loose apparent density of the toner is 0.50 g / cm.³The image forming method according to any one of claims 1, 2 and 5 to 8, further strengthening the cohesiveness of the toner and making the toner image thickness on the photoreceptor uniform. It is possible to improve the transfer rate and transfer quality in pressure transfer.
[0101]
According to the tenth aspect, the image forming method according to any one of the first to third aspects, wherein the surface friction coefficient of the photoconductor is 0.10 or more and 0.22 or less. The smaller the friction coefficient is, the better the releasability from the toner during pressure transfer is. Therefore, the transfer rate is improved. However, if the friction coefficient is less than 0.10, the adhesive force between the toner and the photoreceptor during development decreases. The phenomenon that the toner cannot be transferred to the photoreceptor occurs, and the developer spikes the toner image transferred to the surface of the photoreceptor again, causing the toner image to be shifted or scraped off. It is possible to prevent the state of being left.
[Brief description of the drawings]
FIG. 1 is a schematic side view of an image forming apparatus to which an image forming method of the present invention is applied.
FIG. 2 is a schematic side view of a developing unit of the image forming apparatus of FIG.
[Explanation of symbols]
1 photoreceptor
2 charger
3) Exposure means
4 Developing means (developing device)
5 Transfer means
6 Cleaning means
7) Fixing means
30 scanner
31mm semiconductor laser and polygon
32 laser light
33 mirror
41mm developing sleeve
52 transfer roller
53 transfer belt
54 ° transfer roller
61 cleaning blade
62 fur brush
63 zinc stearate block bar
71 fixing roller
72 ° pressure roller
73, 74 Heating means (heater)
101,106 Transfer material bank
102, 107 paper feed roller
103, 108 paper feed roller
104 resist roller
105mm ejection roller

Claims (10)

A photoconductor, a developing device, a heat roller fixing device, and a transfer device that transfers a toner image on the photoconductor by a belt stretched between a pressure roller of the fixing device and a roller in contact with the photoconductor are used. In the image forming method, development is performed by one-component development using a low-resistance toner having a softening temperature Tm of 100 to 180 ° C. and a volume resistivity of 1 × 10 ⁷ to 1 × 10 ⁹ Ω · cm. Using a drum made of a silicon photoreceptor, a transfer paper is sandwiched between a photoreceptor and a belt stretched over a roller to transfer the toner image under pressure, and at the same time, the transfer paper is conveyed by a belt and passed through a heating means to form a toner image. An image forming method, wherein the image is thermally fixed. 2. The image forming method according to claim 1, wherein the toner has a weight average particle diameter of 3.0 to 10.0 [mu] m. The image forming method according to claim 1, wherein a pressure between the transfer belt and the photoconductor is 300 to 500 N / m ² . As a method for cleaning the photoreceptor, a blade and a brush are used in combination, a block bar of zinc stearate is arranged so as to be in contact with the brush, and by rotating the brush, zinc stearate is applied to the photoreceptor. The image forming method according to claim 1, wherein: 3. The image forming method according to claim 1, wherein the degree of dispersion of the particle diameter of the toner (weight average particle diameter / number average particle diameter) is 1.3 or less. 6. The image forming method according to claim 1, wherein the average circularity of the toner is 0.92 or more. The image forming method according to claim 1, wherein the glass transition temperature Tg of the toner is 50 to 80 ° C. 8. The image forming method according to claim 1, wherein the temperature at which the toner has a melt viscosity of 1000 Pa · s is 120 to 190 ° C. 9. 9. The image forming method according to claim 1, wherein the loose apparent density of the toner is 0.50 g / cm ³ or more. 10. The image forming method according to claim 1, wherein a surface friction coefficient of the photoconductor is 0.10 or more and 0.22 or less.

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