JP4083253B2 - Seamless belt - Google Patents

Description

上記式に示すような関係を用いることにより、フッ化ビニリデン樹脂の数平均分子量Ｍｎ、および重量平均分子量Ｍｗの値を、上記メルトフローレートの値（Ａ）に容易に換算することが可能となる。
【００２６】
ここに、フッ化ビニリデン樹脂のＭｎおよびＭｗは、例えば、下記条件のＧＰＣ分析により容易に測定することが可能である。したがって、例えば、導電性シームレスベルトの製品からカーボンブラックを分離した後のフッ化ビニリデン樹脂のＭｎおよびＭｗの値を、本発明における「カーボンブラックと混合する前のフッ化ビニリデン樹脂」のメルトフローレートに容易に換算することができる。
【００２７】
＜ＧＰＣ分析条件＞
ＧＰＣ装置：Waters社製、商品名：１５０ｃ
カラムの種類および大きさ：Shodex ＡＤ８０Ｍ／Ｓ、３０ｃｍ
カラム温度：７０℃
移動相の組成：ジメチルアセトアミド
流速：０．５ｍｌ／ｍｉｎ
検出器：ＲＩ（屈折率）
（厚み測定）
成形物の厚みは、下記条件下「ダイヤルゲージ厚み計」で測定可能である。
【００２８】
ダイヤルゲージ厚み計：小野測器社製、商品名：ＤＧ−９１１
（四探針法による表面抵抗率）
本発明においては、１０⁰〜４×１０⁵Ω／□の範囲の表面抵抗率は、下記条件の下で四探針法により測定する。より具体的には、図１の模式斜視図を参照して、四探針プローブを構成する４本の探針（三菱化学社製、間隔Ｓ＝１．５ｍｍ）を、ベルト試料１の表面に対して、７０ｇ重／本の圧力で押しつけた後、上記四探針プローブの両端の針２ａおよび２ｂに電流（Ｉ＝０.１μＡ）を印加する。この際、四探針プローブの内側の針２ｃおよび２ｄ間に生ずる抵抗Ｒ（単位：Ω）を測定する。該測定結果に基づき、表面抵抗率ρ_s（単位：Ω／□）＝Ｒ×Ｆとして求める。ただし、Ｆは四探針プローブの抵抗率補正係数（Ｆ＝４．５３２）である。このような四探針法の詳細については、公知文献（例えば、ＳＲＩＳ−２３０１、ＡＳＴＭ−Ｄ９９１）を参照することができる。
【００２９】
測定装置：ロレスタＦＰ（商品名、三菱化学社製）
四探針プローブ（商品名：ＰＳプローブ、三菱化学社製）
（リング電極法による表面抵抗率）
本発明においては、４×１０⁵〜１０¹²Ω／□の範囲の表面抵抗率（ただし、ρ_s＝４×１０⁵Ω／□の表面抵抗率は、上述した四探針法による）は、図２の模式斜視図に示すようなリング状プローブ３（内側の電極３ａの外径＝５．９ｍｍ、外側の電極３ｂの内径＝１１．０ｍｍ、外径＝１７．８ｍｍ）を用いて、下記条件の下でリング電極法により測定する。
【００３０】
より具体的には、図３の模式斜視図を参照して、測定ステージ４（商品名：レジテーブルＦＬ、三菱化学社製、大きさ３００×２００×１０ｍｍ）のテトラフルオロエチレン樹脂（テフロン）面上に、表面抵抗率を測定すべきサンプル５を載せ、該サンプル５の表面上に、前記したリング状プローブ３を約１ｋｇ重の圧力で押しつけた後、該プローブ３の電極３ａと電極３ｂとの間に１０Ｖの電圧を印加して、その際にプローブ３の電極３ａと電極３ｂとの間に流れる電流を、コネクター切り替えボックス６（表面抵抗率測定モードとしておく）を介して上記プローブ３に接続された測定装置７で表面抵抗率ρ_s（単位：Ω／□）を求める（ハイレスタＩＰのディスプレイにΩ／□単位でρ_sが直接に表示される）。このようなリング電極法による表面抵抗率（および後述する体積抵抗率）測定法の詳細については、ＪＩＳ Ｋ−６９１１を参照することができる。
【００３１】
測定装置：ハイレスタＩＰ（三菱化学社製）
プローブ：ＨＲＳプローブ（三菱化学社製）
（体積抵抗率）
図５の模式図を参照して、本発明においては、１０¹⁰〜１０¹²Ωｍの範囲の体積抵抗率は、リング状電極を有するレジシティビティセル８（ヒューレツトパッカード社製、内側の電極８ａの外径２６．０ｍｍ、外側の電極８ｂの内径３８．０ｍｍ、外側の電極８ｂの外径４０．０ｍｍ；図６に模式斜視図を示す）に荷重７ｋｇでサンプル（図示せず）をはさみ、内側の電極８ａと対向電極８ｃとの間に１０Ｖの電圧を（厚み方向に）印加したときの体積抵抗率ρ_vを、測定装置９（ヒューレットパッカード社製）で求める。
【００３２】
測定装置：ＨＰ４３３９Ａハイレジスタンスメータ（ヒユーレットバッカード社製）
測定セル：ＨＰ１６００８Ｂ（ヒユーレットパツカード社製）
本発明においては、１０⁵〜１０¹⁰Ωｍの範囲の体積抵抗率は、図２の模式斜視図に示すようなリング状プロープ３を用いて、下記条件の下でリング電極法により測定する。より具体的には、図３の模式斜視図参照して、測定ステージ４の金届面上に体積抵抗率を測定すべきサンプル５を載せ、該サンプル５の表面上に前記したリング状プロープ３を約１ｋｇ重の圧カで押しつけた後、該プロープ３の電極３ａと４との間に１０Ｖの電圧を（厚み方向に）印加して、コネクター切り替えボックス６（体積抵抗率測定モードとしておく）を介して上記プロープ３に接続された測定装置で体積抵抗率ρ_vを求める。
【００３３】
測定装置：ハイレスタＩＰ（三菱化学社製）
プローブ：ＨＲＳプローブ（三菱化学社製）
本発明においては、１０⁰〜１０⁵Ωｍの範囲の体積抵抗率は、図２の模式斜視図に示すようなリング状プロープ３を用いて、下記条件の下でリング電極法により測定する。具体的な測定方法は１０⁵〜１０¹⁰Ωｍの範囲の体積抵抗率の測定方法と同様であるが、測定装置には図５の測定装置７に代えてデジタルハイテスタ（日置電機社製）を用い、電極３ａと４との間に０．４５Ｖの電圧を印加したときの抵抗値Ｒ（単位：Ω）から、体積抵抗率ρ_vを下の式で求める。
【００３４】
ρv＝Ｒ×Ｓ／ｔ
（但し、Ｓは電極３ａの面積、ｔはサンプルの厚みである。）
測定装置：デジタルハイテスタ（日置電機社製）
プローブ：ＨＲＳプローブ（三菱化学社製）
（平均値の算出）
上述した厚み、表面抵抗率、および体積抵抗率の測定は、これらの値を測定すべき導電性シームレスベルト試料の表面積１ｍ²当たり任意に選んだ２０点の測定点について測定し、その最大値、最小値、平均値（算術平均）を求める。
【００３５】
（平均厚み）
本発明の導電性シームレスベルトを「輪切り」する前のチューブの厚みは、ダイスから押し出された樹脂の厚みと、該樹脂の引き取りスピードとによって決定される。溶融状態の樹脂の厚みは、通常は１ｍｍ程度であるため、これを１／５０程度に薄くすることによって、２０μｍ程度の厚みの導電性シームレスベルトを得ることが可能となる。導電性シームレスベルトの「平均厚み」が２０μｍ未満では、導電性が不充分となったり、ばらついたりし易くなる傾向があり、更には成形時・使用時等に破断し易くなる傾向がある。他方、この「平均厚み」が１００μｍを超えると、導電性シームレスベルトの柔軟性が低下するために、該ベルトをゴムロールに被覆した場合に、基材たるゴムの弾力性低下が著しくなる傾向がある。また、「平均厚み」が１００μｍを超える場合には、導電性シームレスベルトの成形時に該ベルトに付いたピンチ癖、引き取り癖、等のカールや折り目がロール被覆後も目立つようになり、ロールの表面性を損ねる傾向がある。
【００３６】
本発明においては、上記の平均厚みは、２０〜１００μｍ（更には２０〜５０μｍ）であることが好ましい。
【００３７】
（フッ化ビニリデン樹脂）
本発明においては、温度２３０℃、荷重２．１６Ｋｇ（ＪＩＳ−７２１０準拠）において測定されたメルトフローレートが４．５ｇ／１０ｍｉｎ．以上（好ましくは５．０ｇ／１０ｍｉｎ．以上、更に好ましくは５．５ｇ／１０ｍｉｎ．以上）のフッ化ビニリデン樹脂を用いる。
【００３８】
このようなフッ化ビニリデン樹脂としては、ポリフッ化ビニリデンが単独で好適に使用可能であるが、必要に応じて、フッ化ビニリデンと他のフッ化オレフィンモノマー（好ましくは、六フッ化プロピレンおよび／又は四フッ化エチレン）との共重合体を、上記ポリフッ化ビニリデンにマイナー成分として添加することが好ましい。
【００３９】
このようにフッ化ビニリデン共重合体をポリフッ化ビニリデンに添加する場合、該共重合体の添加は、成形されたベルトに柔軟性を与える傾向がある一方で、該共重合体が添加されたブレンド樹脂の結晶化を妨げることによって導電性の低下を引き起こしたり、あるいはチューブへの成形時に成形ダイスの内径、外形規制リングに粘着作用をもたらす傾向がある。したがって、該共重合体をブレンドした結果得られるブレンド樹脂（すなわち、ポリフッ化ビニリデン＋フッ化ビニリデン共重合体）全体の体積を１００部とした場合、フッ化ビニリデン共重合体の添加量は５〜５０体積部（更には１０〜４０体積部）であることが好ましい。該フッ化ビニリデン共重合体を構成するフッ化ビニリデンモノマーの重量を１００部とした場合、該共重合体を構成する「他のフッ化オレフィンモノマー」（好ましくは六フッ化プロピレンおよび／又は四フッ化エチレン）の添加量は、１〜３０重量部（更には５〜１５重量部）であることが好ましい。
【００４０】
本発明の導電性シームレスベルトにおいては、上記したポリフッ化ビニリデンあるいはフッ化ビニリデン共重合体ブレンド樹脂として、４．５ｇ／１０ｍｉｎ．以上のメルトフローレートを有するものが好適に使用可能である。
【００４１】
（導電性カーボンブラック）
導電性カーボンブラックの種類は、上記したフッ化ビニリデン樹脂との組合せにおいて１×１０⁰〜１×１０⁸Ω／□の表面電気抵抗率を有する導電性シームレスベルトを与える限り特に制限されないが、導電性を付与する観点からは、ＪＩＳ Ｋ−６２２１に規定するジブチルフタレート（ＤＢＰ）給油量が１００ｍｌ／１００ｇ以上（更には１５０ｍｌ／１００ｇ以上）の導電性カーボンブラックが好適に使用可能である。このようなカーボンブラックとしては、例えば、アセチレンブラック、ファーネスブラック等が好ましい。これらの導電性カーボンブラックは、必要に応じて、２種類以上組み合わせて使用しても良い。
【００４２】
導電性カーボンブラックの配合量は、用いるカーボンブラックの導電性によって異なるが、本発明においてはフッ化ビニリデン樹脂９４〜８４体積％に対して、導電性カーボンブラック６〜１６体積％である。更には、フッ化ビニリデン樹脂成物９２〜８７体積％に対して、導電性カーボンブラック８〜１３体積％であることが好ましい。カーボンブラックが６体積％未満では、ベルトとしての導電性が不均一になり易く、他方カーボンブラックが１６体積％を超えると、フッ化ビニリデン樹脂とカーボンブラックとからなる樹脂組成物の粘度が増大し、製膜時に破断し易くなる。
【００４３】
（他の添加物）
本発明の導電性シームレスベルトは、少なくとも、上述したフッ化ビニリデン樹脂とカーボンブラックとを含むが、必要に応じて、本発明の効果を妨げない範囲内で（すなわち、上記したメルトフローレートおよび表面電気抵抗率が達成できる範囲内で）他の添加物を含有していてもよい。このような添加剤としては、例えば、タルク、マイカ、シリカ、アルミナ、酸化チタン、酸化亜鉛、酸化鉄、水酸化アルミニウム、水酸化マグネシウム、水酸化アルミニウム、黒鉛、無機物、有機金属塩、酸化金属の粉末、繊維フィラーが挙げられる。これらの添加剤の添加量は、（フッ化ビニリデン樹脂＋カーボンブラック）の合計重量１００部に対して、１０重量部以下（更には５重量部以下）程度であることが好ましい。
【００４４】
上記した添加剤以外にも、本発明の導電性シームレスベルトは、必要に応じて、シームレスベルトないしプラスチック成形の分野で公知の添加剤、例えば、酸化防止剤、滑剤、可塑剤、有機顔料、無機顔料、紫外線防止剤、界面活性剤、架橋剤、カップリング剤等を本発明の効果を妨げない範囲内で含有していてもよい。
【００４５】
（表面／体積抵抗率）
本発明のシームレスベルトの表面電気抵抗率は１×１０⁰〜１×１０⁸Ω／□の範囲であるが、該導電性シームレスベルトを現像剤担持体の被覆チューブとして使用する場合には、１×１０⁴〜１×１０⁸Ω／□が好ましい。他方、該導電性シームレスベルトを、除電ベルトまたはロールに使用する場合には１×１０⁰〜１×１０⁶Ω／□が好ましい。
【００４６】
好適な電気的物性発現の点からは、本発明の導電性シームレスベルトの体積電気抵抗率は、１０¹〜１０⁸Ωｍ（更には、１０²〜１０⁴Ωｍ）の範囲にあることが好ましい。
【００４７】
本発明の導電性シームレスベルトが、均一な除電、帯電体として機能するために、該ベルトの表面及び裏面の表面電気抵抗率に関しては、その最大値が最小値の１〜３０倍以内にある。この最大値／最小値の比は、１〜１０倍以内（特に１〜５倍以内）であることが更に好ましい。
【００４８】
均一な除電・帯電体の点からは、本発明の導電性シームレスベルトの体積抵抗率に関しては、その最大値／最小値の比は、１〜３０倍以内（特に１〜１０倍以内）であることが好ましい。
【００４９】
（成形法）
本発明の導電性シームレスベルトの成形法は特に制限されないが、生産効率と成形の容易性とのバランスの点からは、上述したフッ化ビニリデン樹脂とカーボンブラックとを含む樹脂組成物をチューブ状に押出製膜し、該押出方向と垂直方向に切断（輪切り）して得ることが好ましい。
【００５０】
本発明において上記の樹脂組成物を押出し製膜する際には、予めフッ化ビニリデン樹脂成分とカーボンブラック（必要に応じてその他の添加剤）とを一軸押出機、二軸押出機、バンバリーミキサー、ロールミル、ニーダー等の混練機を用いてペレット状のコンパウンドにした後、ベルト形状に加工することが好ましいが、これらの混練機から直接シームレスベルトに加工することも可能である。混練機に投入する樹脂とカーボンブラックとは、ブラベンダ（Brabender）等の混合機で良く混合しておくことが望ましい。
【００５１】
上記の押出し成形法としては、生産効率の点からは、連続溶融押出成形法を用いることが好ましい。
【００５２】
シームレスベルトの望ましい連続溶融押出成形法としては、１軸スクリュー押出機とスパイラル環状ダイスを用いて、ダイスのリップから直下に押出し、内部冷却マンドレル方式によって内径を制御しながら引き取る方法等が挙げられる。この際、引き取りスピードを速めることによって、成形されたシームレスベルトを、ダイス直下の樹脂厚みの１／１０〜１／５０程度まで薄くすることが容易になる。
【００５３】
従来の導電性シームレスベルト製造技術においては、このような連続溶融押出成形法で薄膜化を行った際には、得られるベルトの導電性が失われたり、導電性が大きくばらついたり、あるいは成形品の破断を生じる傾向があった。これに対して、本発明においては、上述した特定のメルトフローレートを有するフッ化ビニリデン樹脂と、特定量の導電性カーボンブラックとの組合せに基づき、必要な電気抵抗値とその均一性を保ちつつ、良好な薄膜化を行うことが容易となる。
【００５４】
（使用法）
本発明の導電性シームレスベルトは、導電性および電気抵抗値の均一性が重要な用途に特に制限なく使用することが可能である。本発明の導電性シームレスベルトは、該ベルト単体で使用してもよく、また、必要に応じてローラ等の他の部材に被覆した状態（被覆チューブ）で使用されてもよい。
【００５５】
本発明の導電性シームレスベルトは、薄膜で、且つ、電気抵抗が均一な導電性を有するため、コピー機、カラーコピー機、レーザービームプリンター等の電子写真システムないし装置内の、多色画像形成用の中間転写装置、感光ドラムから紙等の被転写材へのトナー転写のための転写分離装置、トナーないし被転写材の搬送のための搬送装置、トナーないし被転写材の帯電のための帯電装置、帯電したトナーを感光ドラム上に（該ドラム上の静電潜像に対応させて）供給するための現像装置等において、好適に使用可能である。中でも、導電性の均一性がトナー画像の画質に直接に影響する現像剤担持体ないし転写ベルト（特に現像剤担持体）に特に好適である。
【００５６】
（電子写真システムに利用した例）
本発明の導電性シームレスベルトを電子写真システムに利用した例を、図４の模式断面図に示す。この図４の態様においては、導電性シームレスベルトは「現像剤担持体」としてゴムローラに被覆された状態で利用されている。
【００５７】
図４に記載の現像装置は、本発明の導電性シームレスベルトを装着してなる現像剤担持体１１と、該担持体１１に対して所定の間隔をおいて配置され、前記担持体１１により担持される現像剤１３の層を所定の厚さに規制する規制ロール部材１５とを有する。この現像装置により、前記担持体１１と規制ロール部材１５との間に、電圧印加手段１７により電圧を印加して、該規制ロール部材１５と担持体１１との間を通過する現像剤１３への帯電を行う。
【００５８】
図４の態様においては、上記により帯電させた現像剤１３を、潜像担持体たる感光ドラム１８上に形成した静電潜像１９に対して選択的に付着させて、該潜像１９の現像を行う。このような現像装置の詳細については、例えば、特開昭６１−１７３２７３号公報（第３〜５頁）を参照することができる。
【００５９】
図４の態様において、規制ロール１５（ロール１５に代えて、ゴムブレードが使用される場合もある）と、担持体１１との間は、実際には現像剤１３のごく薄い層を挟んで殆ど接触状態にあることが多いとされている。したがって、担持体１１に被覆される本発明の導電性シームレスベルトの厚さが薄い程、該担持体の基材（導電性シームレスベルトの下層）に使用されるゴムの弾力性を保持することが容易となり、担持体１１と規制ロール１５とのフィティングが良好となるため、担持体１１上に均一な現像剤の層を形成することが更に容易となる。
【００６０】
（評価方法）
本発明の導電性シームレスベルトを電子写真システムに用いた場合には、該ベルトの電気抵抗の均一性は、該ベルトを現像剤担持体、転写ベルト等として用いた場合の「ベタ黒」画像の均一性（電気抵抗が不均一だと、該ベタ画像にもムラが出る）によって評価することが可能である。
【００６１】
より具体的には例えば、導電性シームレスベルトを用いている市販の電子写真複写機に、本発明の導電性シームレスベルトを取り付けた後、該複写機の原稿台上に何らの物体を置かずに露光を行って、記録媒体たる紙上に「ベタ黒」画像を形成し、該ベタ画像の均一性を肉眼ないし拡大鏡（顕微鏡等、倍率２０倍程度）によって評価すればよい。
【００６２】
以下、実施例により本発明を更に具体的に説明する。
【００６３】
【実施例】
後述する実施例において用いた物性の測定方法は、以下の通りである
（１）メルトフローレート：ＪＩＳ−Ｋ７２１０に準拠し、温度２３０℃、荷重２．１６ｋｇで測定した。
【００６４】
成形物の厚み：ダイヤルゲージ厚み計で測定した。
【００６５】
（２）表面抵抗率：１０⁰〜１０⁵（未満）Ω／□の範囲は、ロレスタＦＰ（三菱化学社製）と四探針プローブ（同社製）を用い、印加電流０.１μＡで測定した。１０⁵〜１０¹²Ω／□の範囲は、ハイレスタＩＰ（三菱化学社製）と、ＨＲＳプローブ（同社製）と、測定ステージＦＬ（同社製）とを用いて、印加電圧１０Ｖで測定した。
【００６６】
（３）体積抵抗率：前述した方法により、抵抗率の値に対応した測定を行った。
【００６７】
上記した「厚み」、「表面抵抗率」および「体積抵抗率」は、ベルトの表面積１ｍ²に付き任意に２０点の位置を選んで測定し、それらの最大値、最小値、および平均値（算術平均）を求めた。
【００６８】
実施例１〜５および比較例１〜４
下記表１に示す組成の樹脂粉末と、カーボンブラックとを、ミキサー（東芝社製、商品名：ＭＸ−Ｃ２０Ｇ）を用いて約２分間充分に攪拌混合した後、単軸押出機（ユニオンプラスチック社製、商品名：ＵＥＶ−３０）を用いて、直径約５ｍｍ程度にペレット化した。このようにペレット化した原料を、１軸スクリュー押出機（プラ技研社製）を用いて、リップ外形（直径）５０ｍｍΦ、リップクリアランス１ｍｍのスパイラル環状ダイス（下記の表１に示す成形温度に保持）に供給し、該ダイスのリップから直下に、環状の溶融フィルム状で押出した。この際、該環状の溶融フィルムの内径を内径サイジングリングによって制御しつつ、該溶融フィルムをニップロールで直下に引き取り、流れ軸方向と直角に所定の寸法（約４００ｍｍ幅）に切断（輪切り）した。上記の内径サイジングリングは４０℃で水冷し、引き取りスピードを約８〜２０ｍ／ｍｉｎ．の範囲で調節することによって、下記表１に示すような所望の膜厚を有するシームレスベルトを得た。なお、比較例３の樹脂組成物を用いた場合には、シームレスベルトの引き取り時に該フィルムの破断が生じる傾向があった。
【００６９】
【表１】

上記表において、各略号の意味は、以下の通りである。
【００７０】
ＫＦ＃８５０：ポリフッ化ビニリデン、呉羽化学工業社製（メルトフローレート（ＭＦＲ）＝７．４ｇ／１０ｍｉｎ．，２３０℃）
ＫＦ＃１０００：ポリフッ化ビニリデン、呉羽化学工業社製（ＭＦＲ＝２．４ｇ／１０ｍｉｎ．，２３０℃）
ＫＦ＃１３００：ポリフッ化ビニリデン、呉羽化学工業社製（ＭＦＲ＝０．３ｇ／１０ｍｉｎ．，２３０℃）
ＫＦ＃２３００：フッ化ビニリデン−六フッ化プロピレン共重合体、呉羽化学工業社製（ＭＦＲ＝２．９ｇ／１０ｍｉｎ．，２３０℃）
ＫＦ＃８５０／ＫＦ＃２３００ブレンド樹脂（ＭＦＲ＝５．６ｇ／１０ｍｉｎ．，２３０℃）
ＡＢ：アセチレンブラック（電気化学工業社製、ＤＢＰ吸油量：１９０ｍｌ／１００ｍｇ）
上記した実施例・比較例により得られた導電性シームレスベルトの物性を、上記の表１、および下記の表２に示す。
【００７１】
【表２】

【００７２】
比較例５
成形用樹脂組成物の組成および成形温度を上記表１に示すように変更した以外は、実施例１と同様に実施したが、押出した樹脂が分解・発砲してしまい、溶融フィルム状に製膜することは不可能であった。
【００７３】
市販の電子写真複写機に、上述した実施例１および実施例５の導電性シームレスベルトをそれぞれ現像剤担持体として装着して、前述した画像形成テスト（ベタ黒画像の形成）を行ったところ、実施例５のベルトの方が、実施例１のベルトに比べて、肉眼観察によるムラが少なかった。
【００７４】
上述した表１および表２に示す結果を見れば、本発明に従う樹脂組成物が薄いシームレスベルトを安定して与えるのみならず、表面抵抗率および体積抵抗率のいずれについても優れた均一性を示す導電性シームレスベルトを与えることが理解できよう。
【００７５】
【発明の効果】
上述したように本発明によれば、メルトフローレートが４．５ｇ／１０ｍｉｎ．以上のフッ化ビニリデン樹脂９４〜８４体積％と、該フッ化ビニリデン樹脂中に分散された導電性カーボンブラック６〜１６体積％とを含む樹脂組成物からなるベルトであって；ベルト各部の表面電気抵抗率が１×１０⁰〜１×１０⁸Ω／□の範囲にあり、且つ、ベルトの表面及び裏面の表面電気抵抗率の最大値が最小値の１〜３０倍の範囲内にあるシームレスベルトが提供される。
【００７６】
本発明においては、上記した特定範囲のメルトフローレートを有するフッ化ビニリデン樹脂が、導電性カーボンブラックの特定量との組合せにおいて、該カーボンブラック粒子／構造の破壊を実質的に抑制しつつ、該カーボンブラックの良好且つ均一な分散を与えるため、薄膜で、且つ均一な電気抵抗を有する導電性シームレスベルトが提供される。
【図面の簡単な説明】
【図１】四探針法による表面電気抵抗率の測定法の一例を説明するための模式斜視図である。
【図２】リング状電極法による表面電気抵抗率測定において使用可能なリング状プローブの一例を示す模式斜視図である。
【図３】図２のリング状プローブを用いる表面／体積抵抗率測定法を説明するための模式斜視図である。
【図４】本発明の導電性シームレスベルトが使用可能な電子写真システム（現像装置）の一例を示す模式断面図である。
【図５】レジシティビティセルを用いる体積抵抗率測定法を説明するための模式図である。
【図６】図５の抵抗率測定において使用可能なレジシティビティセルの一例を示す模式斜視図である。
【符号の説明】
１…抵抗率測定用の導電性シームレスベルト試料、２ａ，２ｂ，２ｃ，２ｄ…抵抗率測定用の探針、３…リング状プローブ、４…抵抗率測定用のテーブル、５…試料、６…コネクタ切り替えボックス、７…抵抗率測定装置。[0001]
[Industrial application fields]
The present invention relates to a conductive seamless belt. More specifically, the present invention relates to a conductive seamless belt having a uniform electric resistance value that can be suitably used as a roller-coated tube such as a developer carrying member in an electrophotographic system, a static elimination belt, and the like.
[0002]
[Prior art]
Conventionally, for supporting, carrying or transporting a material to be transferred (for example, toner, developer, paper) such as a sheet or powder using an electric or electrostatic phenomenon such as charging, discharging or static elimination. Conductive seamless (or endless) belts are used in various fields and applications.
[0003]
For example, conventionally, an intermediate transfer device for forming a multicolor image in an electrophotographic system (or device) such as a copier, a color copier, or a laser beam printer, toner transfer from a photosensitive drum to a transfer material such as paper Transfer separation device for toner, transport device for transporting toner or transfer material, charging device for charging toner or transfer material, electrostatic latent image on the photosensitive drum Conductive seamless belts are frequently used in developing devices and the like for supply. By using such a conductive seamless belt, it is difficult to achieve with a single material roller (for example, a rubber roller) alone, but it is possible to impart desired electrical physical properties to the surface of the rotating body and make it compact or Achieving compatibility with high speed.
[0004]
In an electrophotographic copying machine or the like, in order to obtain a good image when the conductive seamless belt as described above is used for carrying or conveying toner (for example, as a developer carrying member, an intermediate transfer member, or a transfer separator). Therefore, it is extremely important to suppress the fusion of the toner to the conductive seamless belt (and the filming of the toner on the belt based on the fusion). Conventionally, from the viewpoint of emphasizing the suppression of toner fusion or filming, various conductive endless belts in which conductive carbon black is filled in a fluororesin that can be easily suppressed have been used. It was.
[0005]
[Problems to be solved by the invention]
However, many of these conventional conductive seamless belts vary in the electric resistance value that is important for the expression of the electrical properties of the belt, or the thickness (100 μm or more) of the belt does not affect the roll Since the adhesion was insufficient and folds and kink scratches were easily noticeable, they were unsatisfactory as roll coating materials or single belts.
[0006]
Furthermore, in the field of conductive seamless belts, in recent years, there has been an increasing demand for cost reductions. Therefore, seamless belts that are thin and have uniform electrical properties from the viewpoint of reducing raw material costs for expensive fluororesins. Was demanded.
[0007]
Usually, the conductive seamless belt as described above forms a tubular film by extrusion using an annular die or the like, and the tubular film has a predetermined length in a direction perpendicular to the axial direction (extrusion direction). It has been manufactured by sequentially “rounding”.
[0008]
However, in the method of manufacturing the conductive seamless belt as described above, in order to stably extrude the tube-shaped film before “round cutting”, the lip clearance of the annular die (the thickness of the film is adjusted). Having a function) is required to be at least several hundred μm to 1 mm. For this reason, in order to reduce the thickness of the seamless belt, it is necessary to increase the take-up speed at the time of forming the tubular film, or to introduce a drawing process of the tubular film obtained after the film formation. . For this reason, when the filling amount of carbon black in the fluororesin is small, the electric resistance of the conductive seamless belt obtained varies, or a phenomenon has occurred in which the resistance becomes higher than the design value. .
[0009]
On the other hand, if the filling amount of carbon black in the resin is simply increased, the viscosity of the resin composition will increase too much, and the tube-shaped film will be easily broken or the productivity will deteriorate. Has occurred.
[0010]
An object of the present invention is to provide a conductive seamless belt that solves the above-described problems of the prior art.
[0011]
Another object of the present invention is to provide a conductive seamless belt having a uniform electric resistance value that can be suitably used as a roller-coated tube such as a developer carrier in an electrophotographic system, a static elimination belt, and the like. is there.
[0012]
Another object of the present invention is to provide a conductive seamless belt which is a thin film and has uniform electric resistance.
[0013]
[Means for Solving the Problems]
As a result of diligent research, the present inventors have found that the surface resistivity by the four-probe method is closely related to the expression of the electrical properties of the conductive seamless belt, and further, the four-probe method. It has been found that a specific range of the surface resistivity by means of a conductive seamless belt with a thin film and uniform electric resistance.
[0014]
As a result of further research based on the above findings, the present inventor found that a combination of a vinylidene fluoride resin having a specific melt flow rate and a specific amount of conductive carbon black is a surface resistivity obtained by a four-probe method. It has been found that a specific range of the above can be realized, and further, a conductive seamless belt having a thin film and uniform electric resistance can be provided.
[0015]
  The conductive seamless belt of the present invention is based on the above knowledge, and more specifically, the melt flow rate is5.6-7.4 g / 10 min. A belt comprising a resin composition comprising 94 to 84% by volume of a vinylidene fluoride resin and 6 to 16% by volume of conductive carbon black dispersed in the vinylidene fluoride resin; surface electric resistance of each part of the belt Rate is 1x10⁰~ 1x10⁸It is in the range of Ω / □, the maximum value of the surface electrical resistivity on the front and back surfaces of the belt is in the range of 1 to 30 times the minimum value, and the average thickness is 20 to 100 μm. A conductive seamless belt for a coating tube of a developer carrier or a static elimination belt in an electrophotographic system.
[0016]
According to the knowledge of the present inventor, the conductive seamless belt of the present invention having the above-described configuration is a thin film and provides uniform electric resistance because the vinylidene fluoride resin having the above-described specific range of melt flow rate is used. However, in combination with a specific amount of conductive carbon black, the carbon black particles and structure are substantially destroyed, and the contact between the carbon black particles (important for the development of conductivity) is substantially suppressed, and the carbon It is presumed to give a good and uniform dispersion of black.
[0017]
On the other hand, in the conventional conductive seamless belt, the thin film and uniform electric resistance were not obtained, according to the knowledge of the present inventors, instability of contact between carbon black particles in the conventional resin composition It is also presumed that the phenomenon that the electrical resistance of the conductive seamless belt obtained varies or the resistance becomes higher than the design value due to the destruction of the particle structure.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described more specifically with reference to the drawings as necessary.
[0019]
(Conductive seamless belt)
  The conductive seamless belt of the present invention has a melt flow rate.5.6-7.4 g / 10 min. The vinylidene fluoride resin and conductive carbon black dispersed in the vinylidene fluoride resin. The surface electrical resistivity of each part of the belt is 1 × 10⁰~ 1x10⁸The maximum value of the surface electrical resistivity of the front and back surfaces of the belt is in the range of 1 to 30 times the minimum value.
[0020]
(Melt flow rate)
In the present invention, the melt flow rate (MFR) is measured according to JIS-K 7210 (A method; manual cutting method).
[0021]
More specifically, after the following MFR measuring device is cleaned, the device is kept at 230 ° C. for at least 15 minutes with a piston and a steel die conforming to the above JIS attached. 7 g of a pelletized vinylidene fluoride resin sample is put in a cylinder of the following measuring apparatus, a piston is placed on the resin, and the sample is filled by pressing it with a hand force. Finish within 1 minute). The time when the above filling is completed is set as a preheating start point, and time measurement is started from this point.
[0022]
The resin extruded 6 minutes after the start of preheating is discarded, and then the resin extruded for 30 seconds is used as a sample for mass measurement. After the sample for mass measurement thus obtained is naturally cooled to room temperature, the mass of the sample is accurately measured to the nearest 1 mg using a precision balance (trade name: AE200, manufactured by Mettler). The above measurement is performed three times in total, and the average value is obtained.
[0023]
MFR measuring device: manufactured by Toyo Seiki Co., Ltd., trade name: melt indexer
Test conditions: “Condition 14” in “Table 1” described in JIS-K 7210
Test temperature: 230 ° C
Test load: 2.16kg
Based on the result obtained by the above measurement, MFR is calculated by the following equation as the mass (g) of the sample extruded for 10 minutes.
[0024]
MFR (g / 10 min.) = (600 × m) / t
m: Average value of the mass of the cut sample obtained by the above measurement
t: Sampling time (30 seconds)
In the present invention, the above-described melt flow rate is, as a rule, measured for a vinylidene fluoride resin before being mixed with carbon black. According to the inventor's experiment, the melt flow rate (unit: g / 10 min., JIS-K7210 compliant, 230 ° C., value measured at 2.16 kg = A) is determined by gel permeation chromatography (GPC). And the number-average molecular weight Mn and the weight-average molecular weight Mw of the vinylidene fluoride resin measured by (1) have been found to have the following relationships.
[0025]

By using the relationship shown in the above formula, the values of the number average molecular weight Mn and the weight average molecular weight Mw of the vinylidene fluoride resin can be easily converted into the value (A) of the melt flow rate. .
[0026]
Here, Mn and Mw of the vinylidene fluoride resin can be easily measured by GPC analysis under the following conditions, for example. Therefore, for example, the values of Mn and Mw of the vinylidene fluoride resin after separating the carbon black from the conductive seamless belt product are the melt flow rates of the “vinylidene fluoride resin before being mixed with the carbon black” in the present invention. Can be easily converted to
[0027]
<GPC analysis conditions>
GPC device: manufactured by Waters, product name: 150c
Column type and size: Shodex AD80M / S, 30cm
Column temperature: 70 ° C
Mobile phase composition: Dimethylacetamide
Flow rate: 0.5 ml / min
Detector: RI (refractive index)
(Thickness measurement)
The thickness of the molded product can be measured with a “dial gauge thickness meter” under the following conditions.
[0028]
Dial gauge thickness gauge: Ono Sokki Co., Ltd., trade name: DG-911
(Surface resistivity by four probe method)
In the present invention, 10⁰~ 4x10^FiveThe surface resistivity in the range of Ω / □ is measured by the four-probe method under the following conditions. More specifically, referring to the schematic perspective view of FIG. 1, four probes (Mitsubishi Chemical Corporation, spacing S = 1.5 mm) constituting the four-probe probe are placed on the surface of the belt sample 1. On the other hand, after pressing with a pressure of 70 g weight / piece, a current (I = 0.1 μA) is applied to the needles 2a and 2b at both ends of the four-probe probe. At this time, the resistance R (unit: Ω) generated between the needles 2c and 2d inside the four-point probe is measured. Based on the measurement results, the surface resistivity ρ_s(Unit: Ω / □) = R × F. Here, F is a resistivity correction coefficient (F = 4.532) of the four-point probe. For details of such a four-point probe method, publicly known documents (for example, SRIS-2301, ASTM-D991) can be referred to.
[0029]
Measuring device: Loresta FP (trade name, manufactured by Mitsubishi Chemical Corporation)
Four-point probe (trade name: PS probe, manufactured by Mitsubishi Chemical Corporation)
(Surface resistivity by ring electrode method)
In the present invention, 4 × 10^Five-10¹²Surface resistivity in the range of Ω / □ (however, ρ_s= 4 × 10^FiveThe surface resistivity of Ω / □ is based on the above-described four-probe method. The ring probe 3 (outer diameter of inner electrode 3a = 5.9 mm, outer electrode 3b) as shown in the schematic perspective view of FIG. The inner diameter is 11.0 mm, the outer diameter is 17.8 mm, and the ring electrode method is used under the following conditions.
[0030]
More specifically, referring to the schematic perspective view of FIG. 3, the tetrafluoroethylene resin (Teflon) surface of measurement stage 4 (trade name: register table FL, manufactured by Mitsubishi Chemical Corporation, size 300 × 200 × 10 mm) A sample 5 whose surface resistivity is to be measured is placed on the surface. After pressing the ring-shaped probe 3 on the surface of the sample 5 with a pressure of about 1 kg, the electrodes 3a and 3b of the probe 3 are A voltage of 10V is applied between the electrodes 3a and 3b, and the current flowing between the electrodes 3a and 3b of the probe 3 is applied to the probe 3 via the connector switching box 6 (in the surface resistivity measurement mode). Surface resistivity ρ with connected measuring device 7_s(Unit: Ω / □) (for HIRESTA IP display ρ in Ω / □ unit)_sIs displayed directly). JIS K-6911 can be referred to for details of the surface resistivity (and volume resistivity described later) measurement method by such a ring electrode method.
[0031]
Measuring device: Hiresta IP (Mitsubishi Chemical Corporation)
Probe: HRS probe (Mitsubishi Chemical Corporation)
(Volume resistivity)
With reference to the schematic diagram of FIG.^Ten-10¹²The volume resistivity in the range of Ωm is a resiliency cell 8 having a ring-like electrode (manufactured by Hewlett-Packard Company, outer diameter of inner electrode 8a is 26.0 mm, inner diameter of outer electrode 8b is 38.0 mm, outer electrode A sample (not shown) is sandwiched between an outer diameter 40.0 mm of 8b; a schematic perspective view shown in FIG. 6 with a load of 7 kg, and a voltage of 10 V is applied between the inner electrode 8a and the counter electrode 8c (in the thickness direction). ) Volume resistivity ρ when applied_vIs obtained with a measuring device 9 (manufactured by Hewlett-Packard Company).
[0032]
Measuring device: HP4339A high resistance meter (manufactured by Hülette Buckard)
Measurement cell: HP16008B (manufactured by Hülette Patcard)
In the present invention, 10^Five-10^TenThe volume resistivity in the range of Ωm is measured by the ring electrode method under the following conditions using a ring-shaped probe 3 as shown in the schematic perspective view of FIG. More specifically, referring to the schematic perspective view of FIG. 3, the sample 5 whose volume resistivity is to be measured is placed on the gold receiving surface of the measurement stage 4, and the ring-shaped probe 3 described above is placed on the surface of the sample 5. Is pressed with a pressure of about 1 kg, and a voltage of 10 V is applied between the electrodes 3a and 4 of the probe 3 (in the thickness direction), and the connector switching box 6 is set in the volume resistivity measurement mode. The volume resistivity ρ with a measuring device connected to the probe 3 via_vAsk for.
[0033]
Measuring device: Hiresta IP (Mitsubishi Chemical Corporation)
Probe: HRS probe (Mitsubishi Chemical Corporation)
In the present invention, 10⁰-10^FiveThe volume resistivity in the range of Ωm is measured by the ring electrode method under the following conditions using a ring-shaped probe 3 as shown in the schematic perspective view of FIG. The specific measurement method is 10^Five-10^TenThe measurement method is the same as that for measuring the volume resistivity in the range of Ωm, except that a digital high tester (manufactured by Hioki Electric Co., Ltd.) is used instead of the measuring device 7 in FIG. From the resistance value R (unit: Ω) when a voltage of .45 V is applied, the volume resistivity ρ_vIs obtained by the following formula.
[0034]
ρv = R × S / t
(However, S is the area of the electrode 3a, and t is the thickness of the sample.)
Measuring device: Digital HiTester (manufactured by Hioki Electric Co., Ltd.)
Probe: HRS probe (Mitsubishi Chemical Corporation)
(Calculation of average value)
The thickness, surface resistivity, and volume resistivity described above are measured using a surface area of 1 m of the conductive seamless belt sample whose values are to be measured.²Measurement is performed on 20 measurement points arbitrarily selected per hit, and the maximum value, minimum value, and average value (arithmetic average) are obtained.
[0035]
(Average thickness)
The thickness of the tube before “rounding” the conductive seamless belt of the present invention is determined by the thickness of the resin extruded from the die and the take-up speed of the resin. Since the thickness of the molten resin is usually about 1 mm, it is possible to obtain a conductive seamless belt having a thickness of about 20 μm by reducing the thickness to about 1/50. If the “average thickness” of the conductive seamless belt is less than 20 μm, the conductivity tends to be insufficient or tends to vary, and further tends to break during molding and use. On the other hand, when the “average thickness” exceeds 100 μm, the flexibility of the conductive seamless belt is lowered, and therefore, when the belt is coated on a rubber roll, the elasticity of the base rubber tends to be significantly reduced. . In addition, when the “average thickness” exceeds 100 μm, curls and creases such as pinch wrinkles, take-off wrinkles, etc. attached to the belt during molding of the conductive seamless belt become conspicuous even after the roll coating, There is a tendency to spoil the sex.
[0036]
In the present invention, the average thickness is preferably 20 to 100 μm (more preferably 20 to 50 μm).
[0037]
(Vinylidene fluoride resin)
In the present invention, the melt flow rate measured at a temperature of 230 ° C. and a load of 2.16 kg (conforming to JIS-7210) is 4.5 g / 10 min. The above vinylidene fluoride resin is used (preferably 5.0 g / 10 min. Or more, more preferably 5.5 g / 10 min. Or more).
[0038]
As such a vinylidene fluoride resin, polyvinylidene fluoride can be suitably used alone, but if necessary, vinylidene fluoride and other fluorinated olefin monomers (preferably propylene hexafluoride and / or It is preferable to add a copolymer with (tetrafluoroethylene) to the polyvinylidene fluoride as a minor component.
[0039]
Thus, when the vinylidene fluoride copolymer is added to polyvinylidene fluoride, the addition of the copolymer tends to give flexibility to the molded belt, while the blend to which the copolymer is added is added. There is a tendency that the conductivity is lowered by preventing the crystallization of the resin, or that the inner diameter of the forming die and the outer shape regulating ring are brought into a sticking action at the time of forming into a tube. Therefore, when the total volume of the blend resin (that is, polyvinylidene fluoride + vinylidene fluoride copolymer) obtained as a result of blending the copolymer is 100 parts, the amount of vinylidene fluoride copolymer added is 5 to 5. It is preferably 50 parts by volume (more preferably 10 to 40 parts by volume). When the weight of the vinylidene fluoride monomer constituting the vinylidene fluoride copolymer is 100 parts, “another fluorinated olefin monomer” (preferably propylene hexafluoride and / or tetrafluoride monomer) constituting the copolymer. It is preferable that the addition amount of (ethylene chloride) is 1 to 30 parts by weight (more preferably 5 to 15 parts by weight).
[0040]
In the conductive seamless belt of the present invention, 4.5 g / 10 min. As the above-mentioned polyvinylidene fluoride or vinylidene fluoride copolymer blend resin. What has the above melt flow rate can be used conveniently.
[0041]
(Conductive carbon black)
The type of conductive carbon black is 1 × 10 in combination with the above-mentioned vinylidene fluoride resin.⁰~ 1x10⁸As long as a conductive seamless belt having a surface electrical resistivity of Ω / □ is provided, there is no particular limitation. (Furthermore, 150 ml / 100 g or more) conductive carbon black can be suitably used. As such carbon black, for example, acetylene black, furnace black and the like are preferable. These conductive carbon blacks may be used in combination of two or more as required.
[0042]
Although the compounding quantity of electroconductive carbon black changes with electroconductivity of carbon black to be used, in this invention, it is 6-16 volume% of conductive carbon black with respect to 94-84 volume% of vinylidene fluoride resin. Furthermore, it is preferable that it is 8-13 volume% of conductive carbon black with respect to 92-87 volume% of vinylidene fluoride resin compositions. If the carbon black is less than 6% by volume, the conductivity of the belt tends to be non-uniform. On the other hand, if the carbon black exceeds 16% by volume, the viscosity of the resin composition composed of vinylidene fluoride resin and carbon black increases. It becomes easy to break during film formation.
[0043]
(Other additives)
The conductive seamless belt of the present invention contains at least the above-mentioned vinylidene fluoride resin and carbon black, and, if necessary, within a range not impeding the effects of the present invention (that is, the above-described melt flow rate and surface) Other additives may be included (within a range where electrical resistivity can be achieved). Examples of such additives include talc, mica, silica, alumina, titanium oxide, zinc oxide, iron oxide, aluminum hydroxide, magnesium hydroxide, aluminum hydroxide, graphite, inorganic substances, organometallic salts, and metal oxides. Examples thereof include powder and fiber filler. The amount of these additives added is preferably about 10 parts by weight or less (more preferably 5 parts by weight or less) with respect to 100 parts by weight as the total weight of (vinylidene fluoride resin + carbon black).
[0044]
In addition to the additives described above, the conductive seamless belt of the present invention may be added to additives known in the field of seamless belts or plastic molding, for example, antioxidants, lubricants, plasticizers, organic pigments, inorganics, if necessary. You may contain the pigment, the ultraviolet-ray inhibitor, surfactant, a crosslinking agent, a coupling agent, etc. in the range which does not prevent the effect of this invention.
[0045]
(Surface / Volume resistivity)
The surface electrical resistivity of the seamless belt of the present invention is 1 × 10⁰~ 1x10⁸In the range of Ω / □, when the conductive seamless belt is used as a coating tube for a developer carrier, 1 × 10^Four~ 1x10⁸Ω / □ is preferred. On the other hand, when the conductive seamless belt is used for a static elimination belt or a roll, 1 × 10⁰~ 1x10⁶Ω / □ is preferred.
[0046]
From the viewpoint of suitable electrical properties, the volumetric electrical resistivity of the conductive seamless belt of the present invention is 10¹-10⁸Ωm (Furthermore, 10²-10^FourΩm) is preferable.
[0047]
In order for the conductive seamless belt of the present invention to function as a uniform charge eliminating and charging body, the maximum value of the surface electrical resistivity on the front and back surfaces of the belt is within 1 to 30 times the minimum value. The ratio of the maximum value / minimum value is more preferably within 1 to 10 times (particularly within 1 to 5 times).
[0048]
From the standpoint of uniform charge removal / charged body, the ratio of the maximum value / minimum value is within 1 to 30 times (particularly within 1 to 10 times) with respect to the volume resistivity of the conductive seamless belt of the present invention. It is preferable.
[0049]
(Molding method)
The method for molding the conductive seamless belt of the present invention is not particularly limited. However, from the viewpoint of the balance between production efficiency and ease of molding, the resin composition containing the above-described vinylidene fluoride resin and carbon black is formed into a tube shape. It is preferable to obtain by extrusion film formation and cutting (round cutting) in a direction perpendicular to the extrusion direction.
[0050]
In the present invention, when the above resin composition is extruded and formed into a film, a vinylidene fluoride resin component and carbon black (other additives as required) are preliminarily mixed with a single screw extruder, a twin screw extruder, a Banbury mixer, It is preferable to form a pellet compound using a kneader such as a roll mill or a kneader, and then process into a belt shape. However, it is also possible to directly process into a seamless belt from these kneaders. It is desirable that the resin and carbon black charged into the kneading machine are well mixed with a mixer such as a Brabender.
[0051]
As the above extrusion molding method, it is preferable to use a continuous melt extrusion molding method from the viewpoint of production efficiency.
[0052]
Examples of a desirable continuous melt extrusion method for a seamless belt include a method of extruding directly from a lip of a die using a single screw extruder and a spiral annular die, and taking out while controlling an inner diameter by an internal cooling mandrel system. At this time, by increasing the take-up speed, the molded seamless belt can be easily thinned to about 1/10 to 1/50 of the resin thickness directly under the die.
[0053]
In the conventional conductive seamless belt manufacturing technology, when thinning is performed by such a continuous melt extrusion method, the conductivity of the resulting belt is lost, the conductivity varies greatly, or the molded product There was a tendency to cause breakage. On the other hand, in the present invention, based on the combination of the above-mentioned vinylidene fluoride resin having a specific melt flow rate and a specific amount of conductive carbon black, while maintaining a required electric resistance value and its uniformity. It is easy to make a good thin film.
[0054]
(how to use)
The conductive seamless belt of the present invention can be used without particular limitation in applications where conductivity and uniformity of electrical resistance are important. The conductive seamless belt of the present invention may be used alone, or may be used in a state where it is covered with another member such as a roller (coated tube) as necessary.
[0055]
Since the conductive seamless belt of the present invention is a thin film and has a uniform electrical resistance, it is for forming a multicolor image in an electrophotographic system or apparatus such as a copying machine, a color copying machine, or a laser beam printer. Intermediate transfer device, transfer separating device for transferring toner from a photosensitive drum to a transfer material such as paper, a transfer device for transferring toner or transfer material, and a charging device for charging toner or transfer material The toner can be suitably used in a developing device or the like for supplying charged toner onto the photosensitive drum (corresponding to the electrostatic latent image on the drum). Among them, the toner is particularly suitable for a developer carrier or a transfer belt (particularly a developer carrier) in which the uniformity of conductivity directly affects the image quality of a toner image.
[0056]
(Example of use in an electrophotographic system)
An example in which the conductive seamless belt of the present invention is used in an electrophotographic system is shown in the schematic cross-sectional view of FIG. In the embodiment of FIG. 4, the conductive seamless belt is used as a “developer carrying member” covered with a rubber roller.
[0057]
The developing device shown in FIG. 4 is provided with a developer carrier 11 on which the conductive seamless belt of the present invention is mounted, and a predetermined interval with respect to the carrier 11, and is carried by the carrier 11. And a regulating roll member 15 that regulates the layer of the developer 13 to be a predetermined thickness. By this developing device, a voltage is applied between the carrier 11 and the regulating roll member 15 by the voltage applying means 17, and the developer 13 passing between the regulating roll member 15 and the carrier 11 is applied to the developer 13. Perform charging.
[0058]
In the embodiment of FIG. 4, the developer 13 charged as described above is selectively attached to the electrostatic latent image 19 formed on the photosensitive drum 18 as a latent image carrier to develop the latent image 19. I do. For details of such a developing device, reference can be made to, for example, JP-A No. 61-173273 (pages 3 to 5).
[0059]
In the embodiment of FIG. 4, the regulation roll 15 (a rubber blade may be used instead of the roll 15) and the carrier 11 are actually almost sandwiched by a very thin layer of the developer 13. It is often said that they are in contact. Therefore, the thinner the conductive seamless belt of the present invention coated on the carrier 11, the more elastic the rubber used for the substrate of the carrier (lower layer of the conductive seamless belt) can be maintained. This facilitates the fitting between the carrier 11 and the regulating roll 15, so that it becomes easier to form a uniform developer layer on the carrier 11.
[0060]
(Evaluation methods)
When the conductive seamless belt of the present invention is used in an electrophotographic system, the uniformity of the electric resistance of the belt is that of a “solid black” image when the belt is used as a developer carrier, a transfer belt, or the like. It can be evaluated by uniformity (if the electric resistance is not uniform, the solid image is uneven).
[0061]
More specifically, for example, after attaching the conductive seamless belt of the present invention to a commercially available electrophotographic copying machine using a conductive seamless belt, no object is placed on the original platen of the copying machine. Exposure may be performed to form a “solid black” image on paper as a recording medium, and the uniformity of the solid image may be evaluated with the naked eye or a magnifying glass (such as a microscope, approximately 20 times magnification).
[0062]
Hereinafter, the present invention will be described more specifically with reference to examples.
[0063]
【Example】
The measurement methods of physical properties used in the examples described later are as follows.
(1) Melt flow rate: Measured at a temperature of 230 ° C. and a load of 2.16 kg in accordance with JIS-K7210.
[0064]
Molded product thickness: measured with a dial gauge thickness meter.
[0065]
(2) Surface resistivity: 10⁰-10^FiveThe range of (less than) Ω / □ was measured at an applied current of 0.1 μA using a Loresta FP (manufactured by Mitsubishi Chemical Corporation) and a four-point probe (manufactured by the same company). 10^Five-10¹²The range of Ω / □ was measured at an applied voltage of 10 V using a Hiresta IP (manufactured by Mitsubishi Chemical Corporation), an HRS probe (manufactured by the same company), and a measurement stage FL (manufactured by the same company).
[0066]
(3) Volume resistivity: Measurement corresponding to the value of resistivity was performed by the method described above.
[0067]
The above-mentioned “thickness”, “surface resistivity” and “volume resistivity” are 1 m of the surface area of the belt.²The position of 20 points was arbitrarily selected and measured, and the maximum value, the minimum value, and the average value (arithmetic average) were obtained.
[0068]
Examples 1-5 and Comparative Examples 1-4
The resin powder having the composition shown in Table 1 below and carbon black were sufficiently stirred and mixed for about 2 minutes using a mixer (trade name: MX-C20G, manufactured by Toshiba Corporation), and then a single screw extruder (Union Plastic Co., Ltd.). The product was pelletized to a diameter of about 5 mm using a product name: UEV-30). The raw material thus pelletized is a spiral annular die having a lip outer shape (diameter) of 50 mmΦ and a lip clearance of 1 mm using a single screw extruder (manufactured by Plastic Giken Co., Ltd.) (maintained at the molding temperature shown in Table 1 below). And extruded in the form of an annular molten film immediately below the lip of the die. At this time, while controlling the inner diameter of the annular molten film by an inner diameter sizing ring, the molten film was taken directly under a nip roll and cut into a predetermined dimension (about 400 mm width) perpendicularly to the flow axis direction. The inner diameter sizing ring is water-cooled at 40 ° C. and the take-up speed is about 8 to 20 m / min. By adjusting within the range, a seamless belt having a desired film thickness as shown in Table 1 below was obtained. When the resin composition of Comparative Example 3 was used, the film tended to break when the seamless belt was taken up.
[0069]
[Table 1]

In the above table, the meaning of each abbreviation is as follows.
[0070]
KF # 850: Polyvinylidene fluoride, manufactured by Kureha Chemical Industry Co., Ltd. (melt flow rate (MFR) = 7.4 g / 10 min., 230 ° C.)
KF # 1000: Polyvinylidene fluoride, manufactured by Kureha Chemical Industry Co., Ltd. (MFR = 2.4 g / 10 min., 230 ° C.)
KF # 1300: Polyvinylidene fluoride, manufactured by Kureha Chemical Industry Co., Ltd. (MFR = 0.3 g / 10 min., 230 ° C.)
KF # 2300: Vinylidene fluoride-hexafluoropropylene copolymer, manufactured by Kureha Chemical Industry Co., Ltd. (MFR = 2.9 g / 10 min., 230 ° C.)
KF # 850 / KF # 2300 blend resin (MFR = 5.6 g / 10 min., 230 ° C.)
AB: Acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., DBP oil absorption: 190 ml / 100 mg)
The physical properties of the conductive seamless belt obtained by the above-described Examples and Comparative Examples are shown in Table 1 above and Table 2 below.
[0071]
[Table 2]

[0072]
Comparative Example 5
Except for changing the composition of the molding resin composition and the molding temperature as shown in Table 1 above, it was carried out in the same manner as in Example 1, but the extruded resin was decomposed and fired to form a molten film. It was impossible to do.
[0073]
When the conductive seamless belts of Example 1 and Example 5 described above were mounted on a commercially available electrophotographic copying machine as a developer carrier, and the above-described image formation test (solid black image formation) was performed, Compared to the belt of Example 1, the belt of Example 5 had less unevenness due to visual observation.
[0074]
From the results shown in Tables 1 and 2, the resin composition according to the present invention not only stably gives a thin seamless belt, but also exhibits excellent uniformity in both surface resistivity and volume resistivity. It will be appreciated that a conductive seamless belt is provided.
[0075]
【The invention's effect】
As described above, according to the present invention, the melt flow rate is 4.5 g / 10 min. A belt comprising a resin composition comprising 94 to 84% by volume of the above-mentioned vinylidene fluoride resin and 6 to 16% by volume of conductive carbon black dispersed in the vinylidene fluoride resin; Resistivity is 1 × 10⁰~ 1x10⁸There is provided a seamless belt which is in the range of Ω / □ and whose maximum value of surface electrical resistivity on the front and back surfaces of the belt is in the range of 1 to 30 times the minimum value.
[0076]
In the present invention, the vinylidene fluoride resin having a melt flow rate in a specific range described above is combined with a specific amount of conductive carbon black while substantially suppressing the destruction of the carbon black particles / structure, In order to give good and uniform dispersion of carbon black, a conductive seamless belt having a thin film and uniform electric resistance is provided.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view for explaining an example of a method for measuring surface electrical resistivity by a four-probe method.
FIG. 2 is a schematic perspective view showing an example of a ring-shaped probe that can be used in surface electrical resistivity measurement by a ring-shaped electrode method.
3 is a schematic perspective view for explaining a surface / volume resistivity measuring method using the ring-shaped probe of FIG. 2; FIG.
FIG. 4 is a schematic cross-sectional view showing an example of an electrophotographic system (developing apparatus) in which the conductive seamless belt of the present invention can be used.
FIG. 5 is a schematic diagram for explaining a volume resistivity measuring method using a resiliency cell.
6 is a schematic perspective view showing an example of a resiliency cell that can be used in the resistivity measurement of FIG. 5. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Conductive seamless belt sample for resistivity measurement, 2a, 2b, 2c, 2d ... Probe for resistivity measurement, 3 ... Ring-shaped probe, 4 ... Table for resistivity measurement, 5 ... Sample, 6 ... Connector switching box, 7 ... resistivity measuring device.

Claims (5)

Melt flow rate is 5.6 to 7.4 g / 10 min. A belt comprising a resin composition comprising 94 to 84% by volume of a vinylidene fluoride resin and 6 to 16% by volume of conductive carbon black dispersed in the vinylidene fluoride resin;
The surface electrical resistivity of each part of the belt is in the range of 1 × 10 ⁰ to 1 × 10 ⁸ Ω / □, and the maximum value of the surface electrical resistivity on the front and back surfaces of the belt is in the range of 1 to 30 times the minimum value. In
An electrically conductive seamless belt for a developer carrying member covering tube or a static elimination belt in an electrophotographic system, wherein the average thickness is 20 to 100 μm.   The seamless belt according to claim 1, wherein the belt is a belt obtained by extruding the resin composition into a tube shape and then cutting the resin composition in a direction perpendicular to the extrusion direction.   The seamless belt according to claim 1, wherein the conductive carbon black is acetylene black.   The seamless belt according to claim 1, wherein the vinylidene fluoride resin is made of polyvinylidene fluoride.   The vinylidene fluoride resin is composed of polyvinylidene fluoride and a vinylidene fluoride-hexafluoropropylene copolymer and / or vinylidene fluoride-tetrafluoroethylene copolymer having a volume fraction smaller than that of the polyvinylidene fluoride. The seamless belt according to claim 4.

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