JP3608616B2

JP3608616B2 - Method for manufacturing conductive member

Info

Publication number: JP3608616B2
Application number: JP2001245287A
Authority: JP
Inventors: 正中島; 裕子前田; 薬師寺　　学; 隆博川越; 完治井上
Original assignee: Bridgestone Corp
Current assignee: Bridgestone Corp
Priority date: 1996-06-17
Filing date: 2001-08-13
Publication date: 2005-01-12
Anticipated expiration: 2017-06-16
Also published as: JP2002146065A

Description

【０００１】
【発明の属する技術分野】
本発明は、帯電防止機能を有する包装部材、帯電防止機能を有する衝撃吸収部材、特に電子写真プロセスなどで使用される現像部材や転写部材として好適に使用される導電性部材の製造方法に関する。
【０００２】
【従来の技術及び発明が解決しようとする課題】
近年、電子写真技術の進歩にともなってレーザプリンターや乾式複写機などの画像形成装置に用いられる導電性部材の性能に対する要求も厳しくなっており、とりわけ現像，転写等のプロセスに用いにれる弾性ローラの性能が注目されている。
【０００３】
従来、このような用途に用いられる導電性部材は、金属又は金属酸化物の粉末や、ウィスカー，カーボンブラックなどの導電性フィラーを混入して所定の抵抗値に調整したゴムやウレタンなどからなる高分子エラストマー材料や高分子フォーム材料により形成されていた。これらの導電性部材を電子写真プロセスにおける現像部材や転写部材として用いる場合に要求される性能は、１×１０^４〜１×１０^１２Ωｃｍ程度の中抵抗領域で所定の電気抵抗を有しているだけにとどまらず、低温低湿時と高温高湿時とで電気抵抗の変動幅が小さく、かつ連続して通電した際の電気抵抗の変動幅が少ないことである。
【０００４】
ところが、金属や金属酸化物の粉末、又はウィスカーやアセチレンブラック，ケッチェンブラック等の導電性カーボンブラックなどの導電性フィラーを混入することにより所定の抵抗値に調整した高分子エラストマーや高分子フォーム等からなる導電性部材は、製造時の電気抵抗に位置ばらつきが大きく、特にカーボンブラックを用いた導電性部材には、通常、連続通電により電気抵抗が徐々に増大するという欠点がある。
【０００５】
また、導電性部材を得る別の手段として、過塩素酸リチウム，過塩素酸ナトリウム，過塩素酸カルシウムなどの無機イオン物質、陽イオン性界面活性剤、両性イオン界面活性剤、過塩素酸テトラエチルアンモニウム，過塩素酸テトラブチルアンモニウム，ホウフッ化テトラブチルアンモニウム等の４級アンモニウム塩などの有機イオン物質よりなる導電剤及び／又は親水性のポリエーテルやポリエステル等の帯電防止剤を混入して所定の抵抗値に調整したゴムやウレタンなどからなる高分子エラストマーや高分子フォーム材料を用いる方法もある。
【０００６】
しかしながら、このような物質を混入することにより所定の抵抗値に調整した高分子エラストマーや高分子フォーム材料などで形成した導電性部材は、低温低湿時と高温高湿時とで電気抵抗の変動幅が大きいという欠点がある。
【０００７】
本発明は、上記事情に鑑みなされたもので、連続通電による電気抵抗の増大が小さく、かつ低温低湿時と高温高湿時とでの電気抵抗の変動幅も小さく、更に電気抵抗の位置ばらつきが小さく、電子写真プロセスにおける現像部材や転写部材として好適に使用される導電性部材を得ることを目的とする。
【０００８】
【課題を解決するための手段及び発明の実施の形態】
本発明者は、上記目的を達成するため鋭意検討を行った結果、ゴムやウレタン樹脂に導電剤を添加してなる導電性の高分子エラストマー又は高分子フォーム材料を注入成形、射出成形又は押出成形により所望の形状に成形した後、成形物に研磨・研削処理や切削加工などの所定の後加工を施して、導電性部材を得る場合に、上記後加工後に熱処理を施すことにより、温度１５℃，相対湿度１０％の条件下における測定電圧１０００Ｖでの電気抵抗が、温度３２．５℃，相対湿度８５％の条件下における測定電圧１０００Ｖでの電気抵抗の１０倍以下であり、かつ電力１０ｍＷで連続通電した後の温度１５℃，相対湿度１０％の条件下における測定電圧１０００Ｖでの電気抵抗が、連続通電前の同条件下における測定電圧１０００Ｖでの電気抵抗の３倍以下である優れた電気的物性を有する導電性部材を得ることが可能であり、このような導電性部材であれば、電子写真プロセスにおける現像部材や転写部材として用いた場合でも、十分満足し得る性能を使用環境の変動や連続通電にかかわらず確実に発揮し得ることを見い出し、本発明を完成したものである。
【０００９】
従って、本発明は、ゴム又はウレタン樹脂に導電剤を添加してなる導電性の高分子エラストマー又は高分子フォーム材料を注入成形、射出成形又は押出成形により所望の形状に成形した後、成形物に研磨・研削処理又は切削加工あるいはこれらの両方を行う後加工を施して、導電性部材を得る導電性部材の製造方法において、上記後加工後に熱処理を施すことを特徴とする導電性部材の製造方法を提供する。
【００１０】
ここで、熱処理によって、上述のような連続通電による電気抵抗の増大が小さく、かつ低温低湿時と高温高湿時とでの電気抵抗の変動幅も小さく、更に電気抵抗の位置ばらつきも小さい導電性部材が得られる理由は、必ずしも明かではないが、以下のように考えることができる。即ち、本発明の効果は、特に制限されるものではないが、ガスブラック、オイルファーネスブラック、サーマルブラック、インクブラック、導電性ブラック等のカーボンブラックなどからなる導電性フィラーを混入して導電性を調整した場合に特に顕著であり、このことから見るに、カーボンブラック等の導電性フィラーによって成形時に形成された導電パスを導電性高分子材料に応力が加わっていない状態で加熱することにより、導電性フィラーを高分子の熱運動で安定化，再配置することができ、これにより導電性部材の特性が向上するものと考えられる。
【００１１】
以下、本発明につき更に詳しく説明する。
本発明の導電性部材の製造方法は、ゴムやウレタン樹脂に導電剤を添加して導電性を調整した高分子エラストマーや高分子フォーム材料を用途に応じて所望の形状に成形した後、研磨・研削処理や切削加工などの後処理を施し、更にこれを熱処理するものである。
【００１２】
まず、材料としてゴムを用いる場合には、例えば天然ゴム（ＮＲ）、ブタジエンゴム（ＢＲ）、スチレンブタジエンゴム（ＳＢＲ）、イソプレンゴム（ＩＲ）、エチレンプロピレンゴム（ＥＰＭ，ＥＰＤＭ）、ニトリルゴム（ＮＢＲ）等のゴムに導電剤、硫黄や過酸化物等の架橋剤、老化防止剤、架橋反応促進剤等を混合した後、この混合物を所望の形状が型取りされた金型内に注入・射出成形する方法、又はこの混合物を押し出し成形する方法等の公知の成形方法を使用して加熱硬化させることにより、所望形状の導電性部材を得る方法が好ましく用いられるが、必要に応じて得られた導電性部材の表面を研磨・切削加工することもできる。
【００１３】
また、材料としてウレタンを用いる場合には、例えばポリエーテルポリオール、ポリエステルポリオール、ポリブタジエンポリオール、ポリイソプレンポリオール、グリセリンにポリエチレンオキサイドやポリプロピレンオキサイドを付加重合したポリオール、ポリエチレングリコール、プロパンジオール、ブタンジオール等のポリオール成分と、トリレンジイソシアネート（ＴＤＩ）、ジフェニルメタンジイソシアネート（ＭＤＩ）粗製ジフェニルメタンジイソシアネート（クルードＭＤＩ）、イソホロンジイソシアネート等のポリイソシアネート成分とからなるウレタンに導電剤、架橋反応触媒、整泡剤等を混合した後、この混合物を所望の形状が型取りされた金型内に注入・射出する方法、又はこの混合物を押し出し成形する方法等の公知の成形方法を使用して加熱硬化させることにより、所望形状の導電性部材を得る方法が好ましく用いられるが、必要に応じて得られた導電性部材の表面を研磨・研削加工することもできる。なお、ポリオール成分を予めイソシアネートによりプレポリマー化しておくこともできる。
【００１４】
なお、用途等によっては導電性部材を低硬度化する等の目的で、これらの材料を発泡体とすることも好ましい。材料の発泡方法は、特に限定されず、材料がゴムの場合には発泡剤による方法が好ましく、一方、材料がウレタンの場合には発泡剤による方法又は機械的な撹拌により気泡を混入する方法が好ましく採用される。
【００１５】
ここで、本発明の導電性部材に用いられる導電剤としては、例えば、ケッチェンブラック，電化ブラック等のガスブラック、ＳＦＲ級，ＧＰＦ級，ＦＥＦ級，ＨＡＦ級，ＩＳＡＦ級，ＳＡＦ級等のオイルファーネスブラック、ＦＴ級，ＭＴ級，旭サーマル等のサーマルブラック、三菱化学＃２５，＃３３，＃４４，＃４５，＃５２，＃９５，ＣＦ９等のインクブラック、三菱化学＃３０５０，＃３２５０等の導電性ブラック、デグザックＰｒｉｎｔｅｘ１５０Ｔ等のチャンネルブラック、コロンビアンＲａｖｅｎ７８０等の疑似ランプブラックやランプブラック、酸化スズ，酸化亜鉛，酸化チタン等の金属酸化物や酸化スズ，酸化亜鉛，酸化チタン等に導電性処理を施した表面処理金属酸化物、同フレークや同ウィスカー等の金属からなる導電性フィラーなどが挙げられる。これら導電剤の添加量はゴム又はウレタン等の主材料１００重量に対して０．０１〜５０重量部であることが好ましく、特に中抵抗領域で安定に抵抗を制御する観点からＤＢＰ吸油量が３０〜１２５ｍｌ／１００ｇ（ミディアムストラクチャー）のカーボンブラックを０．５〜１０重量部程度添加することが好ましい。
【００１６】
その他の導電剤としては、例えばテトラシアノエチレン及び／又はその誘導体，テトラシアノキノジメタン及び／又はその誘導体，ベンゾキノン及び／又はその誘導体，クロルアニル及び／又はその誘導体，アントラキノン及び／又はその誘導体アントラセン及び／又はその誘導体，ジクロロジシアノベンゾキノン及び／又はその誘導体，フェロセン及び／又はその誘導体，フタロシアニン及び／又はその誘導体，テトラチアフルバレン及び／又はその誘導体等の電荷移動物質、過塩素酸リチウム，過塩素酸ナトリウム，過塩素酸カルシウム等の無機イオン物質、ラウリルトリメチルアンモニウムクロライド，ステアリルトリメチルアンモニウムクロライド，オクタデシル・トリメチルアンモニウムクロライド，変性脂肪酸，ジメトル・エチルアンモニウムエトサルフェート等の陽イオン性界面活性剤、ラウリルベタイン，ステアリルベタイン，ジメチル・アルキルラウリルベタイン等の両性イオン界面活性剤、過塩素酸テトラエチルアンモニウム，過塩素酸テトラブチルアンモニウム，ほうふっ化テトラブチルアンモニウム等の４級アンモニウム塩などの有機イオン物質からなる導電剤、親水性のポリエーテルやポリエステルなどの帯電防止剤などが挙げられ、これら導電剤の添加量はゴム又はウレタン等の主材料１００重量部に対して０．００１〜５重量部であることが好ましい。
【００１７】
これら導電剤の添加による抵抗値の調整は、特に制限されるものではないが、電子写真プロセスに用いられる現像部材や転写部材を得る場合には、通常、部材の電気抵抗が１×１０^４〜１×１０^１２Ωｃｍ程度の中抵抗領域となるように調整することができる。なお、上記導電剤は、１種類を単独で用いても２種以上を混合して用いてもよい。
【００１８】
本発明の製造方法は、このようにして所望の形状に形成した導電性部材に熱処理を施すことにより、導電性部材の電気的物性を最適化するものである。この場合、この熱処理の条件は、所望の電気的特性が得られるように導電性部材の材料や形態（形状や大きさ等）などに応じて適宜設定され、特に制限されるものではないが、通常は８０〜２００℃、特に９０〜１４０℃の温度で１分〜７２時間、特に１５分〜８時間処理する条件が好ましい。この場合、熱処理温度が８０℃未満であると熱処理による効果が得られない場合があり、一方２００℃を超えると、ローラ表面がべとついて感光体等を汚染するものとなってしまう場合がある。なお、加熱手段としては、乾熱オーブン、スチーム、温水浴等の公知の手段を用いることができる。また、この熱処理は、導電性部材を金型より取り出した状態で、研磨・切削加工後に行われる。
【００１９】
この熱処理によって、導電性部材の電気特性を最適化することが可能であり、具体的には、温度１５℃，相対湿度１０％の条件下における測定電圧１０００Ｖでの電気抵抗が、温度３２．５℃，相対湿度８５％の条件下における測定電圧１０００Ｖでの電気抵抗の１０倍以下で、かつ電力１０ｍＷで連続通電した後の温度１５℃，相対湿度１０％の条件下における測定電圧１０００Ｖでの電気抵抗が、連続通電前の同条件下における測定電圧１０００Ｖでの電気抵抗の３倍以下である導電性部材を得ることが可能である。なお、温度１５℃，相対湿度１０％の条件下における測定電圧１０００Ｖでの電気抵抗は、特に制限されるものではないが、上記温度３２．５℃，相対湿度８５％の条件下における測定電圧１０００Ｖでの電気抵抗の１／１００以上，１０倍以下であることが好ましく、また上記連続通電による通電時間は、特に制限されないが通常１５０時間程度とすることができる。
【００２０】
また、この熱処理工程では、成形工程において成形材料の金型へ注入・射出或いは押し出しを行った時の温度又は研磨・切削加工時の応力の非一様性によって発生する電気抵抗の位置ばらつきと応力を低減することができ、具体的には、ローラ状の導電性部材の場合、電圧１０００Ｖ，温度１５℃，相対湿度１０％の条件で、１ｃｍ幅の銅板を用いて長手方向で等間隔に６点、周方向で９０度毎に４方向の合計２４点における電気抵抗を評価したとき、電気抵抗の最低値と最高値との差を１０以内とすることができる。
【００２１】
更に、後述する実施例でも明らかなように、電気抵抗の電圧依存性も改善することができ、具体的には、温度２５℃，相対湿度５５％の環境で、電圧５００Ｖで測定した電気抵抗が１０００Ｖで測定した電気抵抗の２．５倍以下となるようにすることができる。
【００２２】
なお、この熱処理は、加熱により分子運動を活性化し、カーボンブラック等の導電性フィラーを再配置・安定化する観点から上述したカーボン等の導電性フィラーを含むゴム又はウレタン等の高分子材料からなる導電性部材に対して行うことが好ましい。更に、独立気泡を含むゴム又はウレタンの発泡体では、気泡の膨張・収縮による応力緩和が好影響を与えることとなる。
【００２３】
本発明の製造方法により得られる導電性部材の形態は、用途，目的等に応じて適宜選定されるものであり、特に制限されるものではないが、電子写真プロセス等による画像形成装置の現像機構で使用される現像部材や転写機構で使用される転写部材とする場合には、通常、芯金を中心に配置したローラ形状とすることが好ましい。また、この導電性部材は、このような画像形成装置の現像機構で使用される現像部材や転写機構で使用される転写部材として好適に使用されるものである。この場合、画像形成装置としては、例えば、図１に示したように、帯電ローラで一様に帯電させた感光体（画像形成体）表面に光学系からレーザービームを露光して静電潜像を形成し、この感光体表面に現像部材（図では、ローラ状）を備えた現像機構部から現像剤を供給して、上記静電潜像を可視画像化し、更にこの可視画像を転写ローラ（図では、ローラ状）を備えた転写機構部で普通紙等の記録媒体に転写する画像形成装置を例示することができる。そして、本発明製造方法により得られた導電性部材は、このような画像形成装置において、現像部材の表面に現像剤を担持して該現像剤の薄層を形成し、この状態で現像部材を画像形成体に接触又は近接させて画像形成体表面に上記現像剤を供給することにより、該画像形成体表面に可視画像を形成する現像機構部の現像部材や、転写部材に近接又は接触させて記録媒体を帯電させ、画像形成体表面に形成された可視画像を前記記録媒体に転写する転写機構部の転写部材として好適に使用されるものである。なお、図１では、画像形成体として表面に静電潜像を保持する感光体を用いた例を示したが、画像形成体は感光体等の潜像保持体に限定されるものではなく、表面に現像剤を供給して直接現像剤による画像を形成するものであってもよい。
【００２４】
本発明製造方法により得られた導電部材を用いた画像形成装置の現像機構及び転写機構は、通電時の抵抗上昇がほとんどなく長寿命であり、また従来から用いられているイオン導電剤によって導電性を付与した部材を用いた現像機構及び転写機構と比較して高温高湿時と低温低湿時とで電気抵抗の変動が少なく、電源の容量を小さくすることができるものである。
【００２５】
【実施例】
以下、実施例，比較例を示し、本発明をより具体的に説明するが、本発明は下記実施例に限定されるものではない。
［実施例１］
グリセリンにプロピレンオキサイドとエチレンオキサイドをランダムに付加し、そのエチレンオキサイド・ユニットの含有率が１２％、分子量３５００であるポリエーテルポリオール１００重量部、１，４−ブタンジオール６．０５重量部、トリレンジイソシアネート２２重量部、反応性シリコーン系界面活性剤４重量部、ジブチルチンジラウレート０．０１重量部、窒素吸着量により測定した比表面積６０ｍ^２／ｇでＤＢＰ吸油量６３ｍｌ／１００ｇのカーボンブラック６重量部をミキサーで混合し、その混合物を直径６ｍｍの金属製シャフトを中心に配設したモールドに注型し、１００℃で５時間キュアーしてから研磨し、直径１６．７ｍｍで長さ２１５ｍｍのウレタンフォーム転写ローラを作成した。次いで、この転写ローラを１００℃で２時間乾熱オーブンで熱処理した。
【００２６】
得られたローラを厚さ２ｍｍの銅板上に載せ、ローラ両端部に各々５００ｇの荷重をかけて上記銅板上に圧接しながら、１０００Ｖの電圧を印加して芯金と銅板との間の電気抵抗を測定した。その結果、２５℃／５５％（温度／湿度、以下同様）環境下での電気抵抗が６．６×１０^７Ω、３２．５℃／８５％環境下での電気抵抗が１．５×１０^８Ω、１５℃／１０％環境下での電気抵抗が２．０×１０^７Ωであった。
【００２７】
このローラを転写ローラとして図１に示した画像形成装置に組み込み、１５℃／１０％でグレースケール、黒ベタ、白ベタ画像を印刷したところ、いずれも良好な画像が得られた。
【００２８】
［実施例２］
研磨後の加熱処理温度を１２０℃としたこと以外は、実施例１と同様にして転写ローラを作成した。得られたローラにつき実施例１と同様に電気抵抗を測定したところ、２５℃／５５％環境下での電気抵抗が１．３×１０^８Ω、３２．５℃／８５％環境下での電気抵抗が２．３×１０^８Ω、１５℃／１０％環境下での電気抵抗が４．２×１０^７Ωであった。
【００２９】
このローラを転写ローラとして図１に示した画像形成装置に組み込み、１５℃／１０％でグレースケール、黒ベタ、白ベタ画像を印刷したところ、いずれも良好な画像が得られた。
【００３０】
［比較例１］
カーボンブラックの配合量を２．５重量部とし、研磨後の加熱処理を行わなかったこと以外は実施例１と同様に転写ローラを作成した。得られたローラにつき実施例１と同様に電気抵抗を測定したところ、２５℃／５５％環境下での電気抵抗が８．５×１０^７Ω、３２．５℃／８５％環境下での電気抵抗が８．０×１０^７Ω、１５℃／１０％環境下での電気抵抗が５．７×１０^７Ωであった。
【００３１】
このローラを転写ローラとして図１に示した画像形成装置に組み込み、１５℃／１０％でグレースケール、黒ベタ、白ベタ画像を印刷したところ、黒ベタ画像の両端部で転写不良が発生した。
【００３２】
転写ローラの評価
上記実施例１，２及び比較例１の転写ローラにつき、以下の項目による評価を行った。結果を表１に示す。
（１）連続通電
図１の画像形成装置の感光体をアルミ素管に変更し、温度／湿度が２５℃／５５％の環境下で、通電電力１０ｍＷで１５０時間連続して回転させた後、温度／湿度が１５℃／１０％の環境下に４８時間放置し、同環境下で厚さ２ｍｍの銅板上に載せ、ローラ両端部を各々５００ｇの力で圧接しながら１０００Ｖの電圧を印加して芯金と銅板との間の電気抵抗を測定し、この電気抵抗値を連続通電前の同環境下での電気抵抗値で割り算した値で評価した。
（２）電気抵抗の環境依存性
上述した各例の３２．５℃／８５％での電気抵抗値を１５℃／１０％での電気抵抗値で割り算した値で評価した。
（３）電気抵抗の位置ばらつき
電圧１０００Ｖ、温度１５℃、相対湿度１０％の条件で、１ｃｍ幅の銅板で長手方向に等間隔に６点、周方向で９０度毎に４方向の２４点で電気抵抗を測定し、最大抵抗値と最小抵抗値との差で評価した。
（４）電気抵抗の電圧依存性
温度２５℃、相対湿度５５％の環境下で、電圧５００Ｖで測定した電気抵抗を同環境下、電圧１０００Ｖで測定した電気抵抗で割り算した値で評価した。
【００３３】
【表１】

【００３４】
【発明の効果】
以上説明したように、本発明によれば、電気抵抗の位置ばらつきが小さく、かつ電気抵抗の印加電圧依存性が少なく、また低温低湿時と高温高湿時とで電気抵抗の変動幅が小さく、しかも連続通電した後であっても電気抵抗の変動幅が小さい導電性部材が得られる。また、この導電性部材を画像形成装置の現像，転写等のプロセスに利用することにより、良好な画像を長期に亘って確実に得ることができる。
【図面の簡単な説明】
【図１】本発明の導電性部材が装着される画像形成装置の一例を示す模式図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a packaging member having an antistatic function, an impact absorbing member having an antistatic function, particularly a conductive member suitably used as a developing member or a transfer member used in an electrophotographic process.
[0002]
[Prior art and problems to be solved by the invention]
In recent years, with the advancement of electrophotographic technology, the requirements for the performance of conductive members used in image forming apparatuses such as laser printers and dry copying machines have become stricter, especially elastic rollers used in processes such as development and transfer. The performance of is attracting attention.
[0003]
Conventionally, conductive members used for such applications are made of a metal or metal oxide powder, rubber or urethane adjusted to a predetermined resistance value by mixing conductive fillers such as whiskers and carbon black. It was formed of a molecular elastomer material or a polymer foam material. The performance required when these conductive members are used as a developing member or a transfer member in an electrophotographic process has a predetermined electric resistance in a medium resistance region of about 1 × 10 ⁴ to 1 × 10 ¹² Ωcm. In addition to this, the fluctuation range of electric resistance is small at low temperature and low humidity and high temperature and high humidity, and the fluctuation range of electric resistance when energized continuously is small.
[0004]
However, a polymer elastomer or polymer foam adjusted to a predetermined resistance value by mixing a conductive filler such as metal or metal oxide powder or conductive carbon black such as whisker, acetylene black, ketjen black, etc. The conductive member made of the above has a large positional variation in the electric resistance at the time of manufacture, and the conductive member using carbon black in particular has a drawback that the electric resistance gradually increases due to continuous energization.
[0005]
In addition, as another means for obtaining a conductive member, inorganic ionic substances such as lithium perchlorate, sodium perchlorate, and calcium perchlorate, cationic surfactants, zwitterionic surfactants, tetraethylammonium perchlorate , A conductive agent made of an organic ionic substance such as a quaternary ammonium salt such as tetrabutylammonium perchlorate or tetrabutylammonium borofluoride and / or an antistatic agent such as a hydrophilic polyether or polyester is mixed to give a predetermined resistance. There is also a method of using a polymer elastomer or a polymer foam material made of rubber or urethane adjusted to a value.
[0006]
However, a conductive member formed of a polymer elastomer or a polymer foam material adjusted to a predetermined resistance value by mixing such a substance has a fluctuation range of electric resistance between low temperature and low humidity and high temperature and high humidity. Has the disadvantage of being large.
[0007]
The present invention has been made in view of the above circumstances, and the increase in electric resistance due to continuous energization is small, the fluctuation range of the electric resistance between low temperature and low humidity and high temperature and high humidity is small, and there is further variation in the position of the electric resistance. An object of the present invention is to obtain a conductive member that is small and is suitably used as a developing member or a transfer member in an electrophotographic process.
[0008]
Means for Solving the Problem and Embodiment of the Invention
As a result of intensive studies to achieve the above object, the inventor has conducted injection molding, injection molding or extrusion molding of a conductive polymer elastomer or polymer foam material obtained by adding a conductive agent to rubber or urethane resin. When the conductive material is obtained by subjecting the molded product to a predetermined post-processing such as polishing / grinding or cutting after forming into a desired shape by the heat treatment after the post-processing, a temperature of 15 ° C. The electrical resistance at a measurement voltage of 1000 V under the condition of 10% relative humidity is 10 times or less than the electrical resistance at a measurement voltage of 1000 V at a temperature of 32.5 ° C. and a relative humidity of 85%, and the power is 10 mW. The electrical resistance at a measurement voltage of 1000 V under the conditions of a temperature of 15 ° C. and a relative humidity of 10% after continuous energization is the electrical resistance at the measurement voltage of 1000 V under the same conditions before continuous energization. It is possible to obtain a conductive member having excellent electrical properties that is three times less than the above, and such a conductive member is sufficient even when used as a developing member or a transfer member in an electrophotographic process. The present invention has been completed by finding that satisfactory performance can be surely exhibited regardless of changes in the use environment or continuous energization.
[0009]
Therefore, in the present invention, a conductive polymer elastomer or polymer foam material obtained by adding a conductive agent to rubber or urethane resin is molded into a desired shape by injection molding, injection molding or extrusion molding, and then formed into a molded product. A method for producing a conductive member, wherein a post-processing for performing polishing / grinding or cutting or both of them to obtain a conductive member is performed, wherein a heat treatment is performed after the post-processing. I will provide a.
[0010]
Here, by heat treatment, the increase in electrical resistance due to continuous energization as described above is small, the variation range of electrical resistance between low temperature and low humidity and high temperature and high humidity is small, and the electrical resistance has small positional variation. The reason why the member is obtained is not necessarily clear, but can be considered as follows. That is, the effect of the present invention is not particularly limited, but the conductivity can be improved by mixing conductive fillers such as carbon black such as gas black, oil furnace black, thermal black, ink black, and conductive black. This is particularly noticeable when adjusted. From this, it can be seen that the conductive path formed at the time of molding with a conductive filler such as carbon black is heated in a state where no stress is applied to the conductive polymer material. It is considered that the conductive filler can be stabilized and rearranged by the thermal motion of the polymer, thereby improving the characteristics of the conductive member.
[0011]
Hereinafter, the present invention will be described in more detail.
The method for producing a conductive member of the present invention comprises forming a polymer elastomer or a polymer foam material whose conductivity is adjusted by adding a conductive agent to rubber or urethane resin into a desired shape according to the use, and then polishing and polishing. Post-processing such as grinding or cutting is performed, and this is further heat-treated.
[0012]
First, when rubber is used as a material, for example, natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber (IR), ethylene propylene rubber (EPM, EPDM), nitrile rubber (NBR). ) Etc. are mixed with a conductive agent, a cross-linking agent such as sulfur or peroxide, an anti-aging agent, a cross-linking reaction accelerator, etc., and then this mixture is injected and injected into a mold having a desired shape. A method of obtaining a conductive member having a desired shape by heat-curing using a known molding method such as a molding method or a method of extruding this mixture is preferably used. The surface of the conductive member can also be polished and cut.
[0013]
When urethane is used as the material, for example, polyether polyol, polyester polyol, polybutadiene polyol, polyisoprene polyol, polyol obtained by addition polymerization of polyethylene oxide or polypropylene oxide to glycerin, polyol such as polyethylene glycol, propanediol, butanediol, etc. After mixing a conductive agent, a cross-linking reaction catalyst, a foam stabilizer, etc., with urethane composed of the components and polyisocyanate components such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI) crude diphenylmethane diisocyanate (crude MDI), isophorone diisocyanate , A method of injecting and injecting this mixture into a mold having a desired shape, or a method of extruding this mixture A method of obtaining a conductive member having a desired shape by heat-curing using a known molding method is preferably used, but the surface of the obtained conductive member can be polished and ground as necessary. . The polyol component can be prepolymerized with isocyanate in advance.
[0014]
In addition, it is also preferable to make these materials into a foam for the purpose of reducing the hardness of the conductive member depending on the application. The foaming method of the material is not particularly limited, and when the material is rubber, a method using a foaming agent is preferable. On the other hand, when the material is urethane, a method using a foaming agent or a method of mixing bubbles by mechanical stirring is used. Preferably employed.
[0015]
Here, as the conductive agent used in the conductive member of the present invention, for example, gas black such as ketjen black, electrified black, oil such as SFR class, GPF class, FEF class, HAF class, ISAF class, SAF class, etc. Thermal black such as furnace black, FT grade, MT grade, Asahi Thermal, ink black such as Mitsubishi Chemical # 25, # 33, # 44, # 45, # 52, # 95, CF9, Mitsubishi Chemical # 3050, # 3250, etc. Conductive black, channel black such as Dexac Printex 150 T, pseudo lamp black such as Colombian Raven 780 and lamp black, metal oxide such as tin oxide, zinc oxide, titanium oxide, tin oxide, zinc oxide, titanium oxide, etc. It is made of a surface-treated metal oxide that has been subjected to a conductive treatment, or a metal such as the same flake or whisker. A conductive filler and the like. The addition amount of these conductive agents is preferably 0.01 to 50 parts by weight with respect to 100 parts by weight of the main material such as rubber or urethane. In particular, the DBP oil absorption is 30 from the viewpoint of controlling the resistance stably in the middle resistance region. It is preferable to add about 0.5 to 10 parts by weight of carbon black of ˜125 ml / 100 g (medium structure).
[0016]
Examples of other conductive agents include tetracyanoethylene and / or its derivatives, tetracyanoquinodimethane and / or its derivatives, benzoquinone and / or its derivatives, chloranil and / or its derivatives, anthraquinone and / or its derivatives anthracene and / Or its derivatives, dichlorodicyanobenzoquinone and / or its derivatives, ferrocene and / or its derivatives, phthalocyanine and / or its derivatives, tetrathiafulvalene and / or its derivatives, charge transfer materials, lithium perchlorate, perchloric acid Inorganic ionic substances such as sodium and calcium perchlorate, lauryl trimethyl ammonium chloride, stearyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride, modified fatty acid, dimethol ethyl Cationic surfactants such as ammonium ethosulphate, amphoteric surfactants such as lauryl betaine, stearyl betaine, dimethyl alkyl lauryl betaine, tetraethylammonium perchlorate, tetrabutylammonium perchlorate, tetrabutylammonium fluoride Examples include conductive agents made of organic ionic substances such as quaternary ammonium salts such as antistatic agents such as hydrophilic polyethers and polyesters, and the addition amount of these conductive agents is 100 parts by weight of a main material such as rubber or urethane. It is preferable that it is 0.001-5 weight part with respect to this.
[0017]
The adjustment of the resistance value by the addition of these conductive agents is not particularly limited, but in the case of obtaining a developing member or a transfer member used in an electrophotographic process, the electrical resistance of the member is usually 1 × 10 ⁴ to It can be adjusted to be a medium resistance region of about 1 × 10 ¹² Ωcm. In addition, the said electrically conductive agent may be used individually by 1 type, or may mix and use 2 or more types.
[0018]
The manufacturing method of the present invention optimizes the electrical properties of the conductive member by subjecting the conductive member thus formed to a desired shape to a heat treatment. In this case, the conditions for this heat treatment are appropriately set according to the material and form (shape, size, etc.) of the conductive member so as to obtain desired electrical characteristics, and are not particularly limited. Usually, conditions for treatment at a temperature of 80 to 200 ° C., particularly 90 to 140 ° C. for 1 minute to 72 hours, particularly 15 minutes to 8 hours are preferable. In this case, if the heat treatment temperature is less than 80 ° C., the effect of the heat treatment may not be obtained. On the other hand, if the heat treatment temperature exceeds 200 ° C., the roller surface may become sticky and may contaminate the photoreceptor. . In addition, as a heating means, well-known means, such as a dry heat oven, a steam, a warm water bath, can be used. Further, this heat treatment is performed after polishing / cutting in a state where the conductive member is taken out of the mold.
[0019]
By this heat treatment, the electrical characteristics of the conductive member can be optimized. Specifically, the electrical resistance at a measurement voltage of 1000 V under the conditions of a temperature of 15 ° C. and a relative humidity of 10% is a temperature of 32.5. Electricity at a measurement voltage of 1000 V at a temperature of 15 ° C. and a relative humidity of 10% after continuous energization at a power of 10 mW and not more than 10 times the electrical resistance at a measurement voltage of 1000 V under the conditions of ℃ and relative humidity of 85% It is possible to obtain a conductive member whose resistance is not more than three times the electric resistance at a measurement voltage of 1000 V under the same conditions before continuous energization. The electrical resistance at a measurement voltage of 1000 V under the conditions of a temperature of 15 ° C. and a relative humidity of 10% is not particularly limited, but the measurement voltage of 1000 V under the conditions of the temperature of 32.5 ° C. and the relative humidity of 85% is not limited. It is preferable that the electric resistance is 1/100 or more and 10 times or less, and the energization time by the continuous energization is not particularly limited, but can usually be about 150 hours.
[0020]
Also, in this heat treatment process, the position variation and stress of electrical resistance generated due to the temperature at the time of injection, injection or extrusion of the molding material into the mold in the molding process or the non-uniformity of stress at the time of polishing / cutting. Specifically, in the case of a roller-shaped conductive member, a 6 cm-long copper plate having a width of 1 cm is used at regular intervals under the conditions of a voltage of 1000 V, a temperature of 15 ° C., and a relative humidity of 10%. When the electrical resistance at a total of 24 points in 4 directions is evaluated every 90 degrees in the point and circumferential directions, the difference between the minimum value and the maximum value of the electrical resistance can be within 10 or less.
[0021]
Further, as will be apparent from the examples described later, the voltage dependence of the electrical resistance can also be improved. Specifically, the electrical resistance measured at a voltage of 500 V in an environment of a temperature of 25 ° C. and a relative humidity of 55% is obtained. The electric resistance measured at 1000 V can be 2.5 times or less.
[0022]
This heat treatment is made of a polymer material such as rubber or urethane containing the above-described conductive filler such as carbon from the viewpoint of activating molecular motion by heating and rearranging and stabilizing the conductive filler such as carbon black. It is preferable to carry out with respect to the conductive member. Furthermore, in a rubber or urethane foam containing closed cells, stress relaxation due to expansion and contraction of the bubbles has a positive effect.
[0023]
The form of the conductive member obtained by the production method of the present invention is appropriately selected according to the use, purpose and the like, and is not particularly limited. However, the developing mechanism of the image forming apparatus by an electrophotographic process or the like In the case of a developing member used in the above and a transfer member used in a transfer mechanism, it is usually preferable to have a roller shape centered on a cored bar. The conductive member is preferably used as a developing member used in the developing mechanism of such an image forming apparatus or a transfer member used in the transfer mechanism. In this case, as an image forming apparatus, for example, as shown in FIG. 1, an electrostatic latent image is obtained by exposing a surface of a photosensitive member (image forming member) uniformly charged by a charging roller to a laser beam from an optical system. The developer is supplied from a developing mechanism having a developing member (roller shape in the figure) on the surface of the photoconductor to make the electrostatic latent image visible, and this visible image is transferred to a transfer roller ( In the drawing, an image forming apparatus for transferring to a recording medium such as plain paper by a transfer mechanism portion having a roller shape) can be exemplified. In such an image forming apparatus, the conductive member obtained by the manufacturing method of the present invention carries a developer on the surface of the developing member to form a thin layer of the developer. By supplying the developer to the surface of the image forming body in contact with or close to the image forming body, the developing member of the developing mechanism that forms a visible image on the surface of the image forming body or the transfer member is brought close to or in contact with the image forming body. The recording medium is preferably used as a transfer member of a transfer mechanism unit that charges a recording medium and transfers a visible image formed on the surface of the image forming body to the recording medium. FIG. 1 shows an example in which a photoconductor that holds an electrostatic latent image on the surface is used as the image forming body, but the image forming body is not limited to a latent image holding body such as a photoconductor, A developer may be supplied to the surface to form an image directly with the developer.
[0024]
The developing mechanism and transfer mechanism of the image forming apparatus using the conductive member obtained by the manufacturing method of the present invention have a long life with little increase in resistance when energized, and are electrically conductive by the conventionally used ionic conductive agents. Compared with a developing mechanism and a transfer mechanism using a member provided with a high temperature and high humidity and a low temperature and low humidity, there is little variation in electrical resistance, and the capacity of the power source can be reduced.
[0025]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to the following Example.
[Example 1]
Propylene oxide and ethylene oxide are randomly added to glycerin. The content of ethylene oxide units is 12%, and the molecular weight is 3,500. Polyether polyol 100 parts by weight, 1,4-butanediol 6.05 parts by weight, tolylene 22 parts by weight of isocyanate, 4 parts by weight of reactive silicone surfactant, 0.01 part by weight of dibutyltin dilaurate, 6 parts by weight of carbon black with a specific surface area of 60 m ² / g measured by nitrogen adsorption and 63 ml / 100 g of DBP oil absorption Is mixed with a mixer, the mixture is poured into a mold centered on a metal shaft with a diameter of 6 mm, cured at 100 ° C. for 5 hours, polished, and urethane foam with a diameter of 16.7 mm and a length of 215 mm A transfer roller was created. Next, the transfer roller was heat-treated at 100 ° C. for 2 hours in a dry heat oven.
[0026]
The obtained roller was placed on a copper plate having a thickness of 2 mm, and a voltage of 1000 V was applied by applying a load of 500 g to both ends of the roller and pressing on the copper plate to apply electrical resistance between the core metal and the copper plate. Was measured. As a result, the electrical resistance in an environment of 25 ° C./55% (temperature / humidity, the same applies below) is 6.6 × 10 ⁷ Ω, and the electrical resistance in an environment of 32.5 ° C./85% is 1.5 × 10. The electric resistance in an environment of ⁸ Ω and 15 ° C./10% was 2.0 × 10 ⁷ Ω.
[0027]
When this roller was incorporated in the image forming apparatus shown in FIG. 1 as a transfer roller and a gray scale, black solid, or white solid image was printed at 15 ° C./10%, good images were obtained in all cases.
[0028]
[Example 2]
A transfer roller was prepared in the same manner as in Example 1 except that the heat treatment temperature after polishing was 120 ° C. When the electrical resistance of the obtained roller was measured in the same manner as in Example 1, the electrical resistance in a 25 ° C./55% environment was 1.3 × 10 ⁸ Ω, and the electrical resistance in a 32.5 ° C./85% environment. The resistance was 2.3 × 10 ⁸ Ω, and the electrical resistance in a 15 ° C./10% environment was 4.2 × 10 ⁷ Ω.
[0029]
When this roller was incorporated in the image forming apparatus shown in FIG. 1 as a transfer roller and a gray scale, black solid, or white solid image was printed at 15 ° C./10%, good images were obtained in all cases.
[0030]
[Comparative Example 1]
A transfer roller was prepared in the same manner as in Example 1 except that the amount of carbon black was 2.5 parts by weight and the heat treatment after polishing was not performed. When the electrical resistance of the obtained roller was measured in the same manner as in Example 1, the electrical resistance in a 25 ° C./55% environment was 8.5 × 10 ⁷ Ω, and the electrical resistance in a 32.5 ° C./85% environment. The resistance was 8.0 × 10 ⁷ Ω, and the electrical resistance in a 15 ° C./10% environment was 5.7 × 10 ⁷ Ω.
[0031]
When this roller was incorporated in the image forming apparatus shown in FIG. 1 as a transfer roller and a gray scale, black solid, or white solid image was printed at 15 ° C./10%, transfer failure occurred at both ends of the black solid image.
[0032]
Evaluation of transfer roller The transfer rollers of Examples 1 and 2 and Comparative Example 1 were evaluated according to the following items. The results are shown in Table 1.
(1) Continuous energization The photoconductor of the image forming apparatus in FIG. 1 is changed to an aluminum tube, and continuously rotated for 150 hours at an energizing power of 10 mW in an environment of temperature / humidity of 25 ° C./55% Leave for 48 hours in an environment with a temperature / humidity of 15 ° C./10%, place it on a 2 mm thick copper plate in the same environment, and apply a voltage of 1000 V while pressing both ends of the roller with a force of 500 g each. The electrical resistance between the cored bar and the copper plate was measured, and the electrical resistance value was evaluated by dividing the electrical resistance value by the electrical resistance value in the same environment before continuous energization.
(2) Environmental dependence of electrical resistance The electrical resistance value at 32.5 ° C./85% of each example described above was evaluated by dividing the electrical resistance value by 15 ° C./10%.
(3) Electrical resistance position variation voltage of 1000V, temperature of 15 ° C, relative humidity of 10%, 1 cm wide copper plate with 6 points at regular intervals in the longitudinal direction, 24 points in 4 directions every 90 degrees in the circumferential direction The electrical resistance was measured and evaluated by the difference between the maximum resistance value and the minimum resistance value.
(4) Voltage dependence of electrical resistance Under the environment of temperature 25 ° C. and relative humidity 55%, the electrical resistance measured at a voltage of 500V was evaluated by the value divided by the electrical resistance measured at a voltage of 1000V under the same environment.
[0033]
[Table 1]

[0034]
【The invention's effect】
As described above, according to the present invention, the variation in the position of the electrical resistance is small, the applied voltage dependence of the electrical resistance is small, and the fluctuation range of the electrical resistance is small between low temperature and low humidity and high temperature and high humidity. Moreover, even after continuous energization, a conductive member having a small fluctuation range of electric resistance can be obtained. Further, by using this conductive member for processes such as development and transfer of the image forming apparatus, a good image can be reliably obtained over a long period of time.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus to which a conductive member of the present invention is attached.

Claims

A conductive polymer elastomer or polymer foam material made by adding a conductive agent to rubber or urethane resin is molded into a desired shape by injection molding, injection molding or extrusion molding, and then polished, ground or cut into the molded product In the manufacturing method of the electroconductive member which gives the electroconductive member by giving the post process which performs a process or both of these, The manufacturing method of the electroconductive member characterized by performing heat processing after the said post process.

The method for producing a conductive member according to claim 1, wherein the heat treatment conditions are a temperature of 80 to 200 ° C and a treatment time of 1 minute to 72 hours.

The method for producing a conductive member according to claim 1 or 2, wherein a urethane foam material to which a conductive agent is added is formed into a desired shape, subjected to the post-processing, and then heat-treated.

The method for producing a conductive member according to claim 1, wherein the conductive agent is a conductive filler.

The method for producing a conductive member according to claim 4, wherein the conductive filler is carbon black.

The electrical resistance at a measurement voltage of 1000 V under the conditions of a temperature of 15 ° C. and a relative humidity of 10% is not more than 10 times the electrical resistance at a measurement voltage of 1000 V under the conditions of a temperature of 32.5 ° C. and a relative humidity of 85%, and The electrical resistance at a measurement voltage of 1000 V under a condition of a temperature of 15 ° C. and a relative humidity of 10% after continuous energization with an electric power of 10 mW is not more than three times the electrical resistance at a measurement voltage of 1000 V under the same conditions before continuous energization. It is a manufacturing method for obtaining an electroconductive member, The manufacturing method of the electroconductive member of any one of Claims 1-5.

It is a manufacturing method for obtaining the elastic roller used for an electrophotographic process as an electroconductive member, The manufacturing method of the electroconductive member of any one of Claims 1-6.