JP2004240026A - Image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide image forming methods which impart high charging potential to an organic photoreceptor, suppress occurrence of image defects, such as black spots and voids, which tend to occur when gradation and sharpness are improved, and ensure broad gradation and good sharpness required by a color image, etc., and to provide an image forming apparatus using these image forming method. <P>SOLUTION: The organic photoreceptor has an intermediate layer of a resin layer formed using at least one selected from organometallic compounds and silane coupling agents between a conductive support and a photosensitive layer. The potential of an unexposed part (VH) of an electrostatic latent image in a development position satisfies an expression of 900 V≤¾VH¾≤1,500 V, and a relation between the potential of the unexposed part (VH) and DC bias potential (VDC) applied to a developing sleeve is within a specified range. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００７１】
（式中、Ｘはハロゲン原子を表し、ｎは０〜１の数を示す）。前記Ｘが塩素原子の場合ｎは０〜０．５が好ましく、０〜０．１がより好ましい。
【００７２】
本発明ではこのチタニルフタロシアニン顔料の中で、Ｃｕ−ＫαＸ線に対するＸ線回折のブラッグ角（２θ±０．２°）において、２７．２°に最大ピークを有するチタニルフタロシアニン（オキシチタニルフタロシアニン）、同２θ±０．２において、７．５°、２８．５°に顕著なピークを有するチタニルフタロシアニン顔料を用いることが好ましい。これらのチタニルフタロシアニン顔料は温湿度の環境変動が生じた場合に、環境メモリを発生し、黒帯状の画像欠陥を発生したり、高温高湿環境中で黒ポチが発生したり、或いは長時間の連続プリントにより、画像濃度の低下を発生しやすい特性を有しているが、本発明の中間層と組み合わせた場合、このような欠点が解消され、良好な電子写真画像を得ることができる。
【００７３】
電荷発生層にＣＧＭの分散媒としてバインダーを用いる場合、バインダーとしては公知の樹脂を用いることができるが、最も好ましい樹脂としてはホルマール樹脂、ブチラール樹脂、シリコーン樹脂、シリコーン変性ブチラール樹脂、フェノキシ樹脂等が挙げられる。バインダー樹脂と電荷発生物質との割合は、バインダー樹脂１００質量部に対し２０〜６００質量部が好ましい。これらの樹脂を用いることにより、繰り返し使用に伴う残留電位増加を最も小さくできる。電荷発生層の膜厚は０．１μｍ〜２μｍが好ましい。
【００７４】
電荷輸送層
電荷輸送層には電荷輸送物質（ＣＴＭ）及びＣＴＭを分散し製膜するバインダー樹脂を含有する。その他の物質としては必要により酸化防止剤等の添加剤を含有しても良い。
【００７５】
電荷輸送物質（ＣＴＭ）としては公知の電荷輸送物質（ＣＴＭ）を用いることができる。例えばトリフェニルアミン誘導体、ヒドラゾン化合物、スチリル化合物、ベンジジン化合物、ブタジエン化合物などを用いることができる。これら電荷輸送物質は通常、適当なバインダー樹脂中に溶解して層形成が行われる。これらの中で繰り返し使用に伴う残留電位増加を最も小さくできるＣＴＭは高移動度で、且つ組み合わされるＣＧＭとのイオン化ポテンシャル差が０．５（ｅＶ）以下の特性を有するものであり、好ましくは０．３０（ｅＶ）以下である。
【００７６】
ＣＧＭ、ＣＴＭのイオン化ポテンシャルは表面分析装置ＡＣ−１（理研計器社製）で測定される。
【００７７】
電荷輸送層（ＣＴＬ）に用いられる樹脂としては、例えばポリスチレン、アクリル樹脂、メタクリル樹脂、塩化ビニル樹脂、酢酸ビニル樹脂、ポリビニルブチラール樹脂、エポキシ樹脂、ポリウレタン樹脂、フェノール樹脂、ポリエステル樹脂、アルキッド樹脂、ポリカーボネート樹脂、シリコーン樹脂、メラミン樹脂並びに、これらの樹脂の繰り返し単位構造のうちの２つ以上を含む共重合体樹脂。又これらの絶縁性樹脂の他、ポリ−Ｎ−ビニルカルバゾール等の高分子有機半導体が挙げられる。
【００７８】
これらＣＴＬのバインダーとして最も好ましいものはポリカーボネート樹脂である。ポリカーボネート樹脂はＣＴＭの分散性、電子写真特性を良好にすることにおいて、最も好ましい。バインダー樹脂と電荷輸送物質との割合は、バインダー樹脂１００質量部に対し１０〜２００質量部が好ましい。又、電荷輸送層の膜厚は１０〜４０μｍが好ましい。
【００７９】
表面層
感光体の表面層（保護層）として、シロキサンポリカーボネートや架橋タイプのシロキサン系樹脂をバインダーとした層を設けてもよい。
【００８０】
上記では本発明の最も好ましい感光体の層構成を例示したが、本発明では上記以外の感光体層構成でも良い。
【００８１】
感光層、中間層、表面層等の層形成に用いられる溶媒又は分散媒としては、ｎ−ブチルアミン、ジエチルアミン、エチレンジアミン、イソプロパノールアミン、トリエタノールアミン、トリエチレンジアミン、Ｎ，Ｎ−ジメチルホルムアミド、アセトン、メチルエチルケトン、メチルイソプロピルケトン、シクロヘキサノン、ベンゼン、トルエン、キシレン、クロロホルム、ジクロロメタン、１，２−ジクロロエタン、１，２−ジクロロプロパン、１，１，２−トリクロロエタン、１，１，１−トリクロロエタン、トリクロロエチレン、テトラクロロエタン、テトラヒドロフラン、ジオキソラン、ジオキサン、メタノール、エタノール、ブタノール、イソプロパノール、酢酸エチル、酢酸ブチル、ジメチルスルホキシド、メチルセロソルブ等が挙げられる。本発明はこれらに限定されるものではないが、ジクロロメタン、１，２−ジクロロエタン、メチルエチルケトン等が好ましく用いられる。また、これらの溶媒は単独或いは２種以上の混合溶媒として用いることもできる。
【００８２】
又、これらの各層の塗布溶液は塗布工程に入る前に、塗布溶液中の異物や凝集物を除去するために、金属フィルター、メンブランフィルター等で濾過することが好ましい。例えば、日本ポール社製のプリーツタイプ（ＨＤＣ）、デプスタイプ（プロファイル）、セミデプスタイプ（プロファイルスター）等を塗布液の特性に応じて選択し、濾過をすることが好ましい。
【００８３】
次に有機電子写真感光体を製造するための塗布加工方法としては、浸漬塗布、スプレー塗布、円形量規制型塗布等の塗布加工法が用いられるが、感光層の上層側の塗布加工は下層の膜を極力溶解させないため、又、均一塗布加工を達成するためスプレー塗布又は円形量規制型（円形スライドホッパ型がその代表例）塗布等の塗布加工方法を用いるのが好ましい。なお保護層は前記円形量規制型塗布加工方法を用いるのが最も好ましい。前記円形量規制型塗布については例えば特開昭５８−１８９０６１号公報に詳細に記載されている。
【００８４】
本発明の画像形成方法に係るトナーについて説明する。
本発明の画像形成方法に用いる現像剤中のトナーは、体積平均粒径が３．０〜７．０μｍであり、トナーの５０％個数粒径をＤｐ５０とすると、０．７×Ｄｐ５０以下のトナーの個数が１０個数％以下であることを特徴とする。
【００８５】
又、現像剤中のトナーは、体積平均粒径が３．０〜７．０μｍであり、トナーの５０％体積粒径（Ｄｖ５０）と５０％個数粒径（Ｄｐ５０）の比（Ｄｖ５０／Ｄｐ５０）が１．０〜１．１５、体積粒径の大きい方からの累積７５％体積粒径（Ｄｖ７５）と、個数粒径の大きい方からの累積７５％個数粒径（Ｄｐ７５）の比（Ｄｖ７５／Ｄｐ７５）が１．０〜１．２０、且つ粒径が０．７×（Ｄｐ５０）以下のトナーの個数が１０個数％以下であることを特徴とする。
【００８６】
上記のようなトナーを含有する現像剤を、前記した特定の有機感光体、前記１式及び２式を満足するような従来の現像条件よりは強い電界強度の条件下で反転現像を行うことにより、高電界下で発生しやすいエッジ現象を防止し、その結果文字チリが少なく、階調性、鮮鋭性が良好な電子写真画像を得ることができる。
【００８７】
本発明者等は、トナー中の小粒径成分の比率が高いと、現像後のトナー画像で、エッジ現象が高くなりやすく、その結果、文字チリが発生し、階調性が不十分な電子写真画像になりやすい。本発明では、現像時のエッジ現象の増大を防止するには、トナー中の小粒径成分の比率を、トナーの５０％個数粒径をＤｐ５０とすると、０．７×Ｄｐ５０以下のトナーの個数が１０個数％以下にすることにより達成でき、その結果、転写時に発生しやすい文字チリを防止でき、階調性、鮮鋭性が良好な電子写真画像を得ることが出来る。
【００８８】
又、本発明に用いるトナーは、小粒径成分の比率を小さくすると同時に、より単分散に近い分布を持たせることにより、より一層の効果を得ることができる。即ち、本発明に用いるトナーは、トナーの５０％体積粒径（Ｄｖ５０）と５０％個数粒径（Ｄｐ５０）の比（Ｄｖ５０／Ｄｐ５０）が１．０〜１．１５、該トナーの体積粒径の大きい方からの累積７５％体積粒径（Ｄｖ７５）と、前記トナーの前記個数粒径の大きい方からの累積７５％個数粒径（Ｄｐ７５）の比（Ｄｖ７５／Ｄｐ７５）が１．０〜１．２０であり、全トナー中において、粒径が０．７×（Ｄｐ５０）以下のトナーの個数が１０個数％以下の粒度分布で構成されることにより、階調性、鮮鋭性が、非常に良好で、エッジ効果や文字チリの発生しない優れた電子写真画像を得ることができる。
【００８９】
本発明に係るトナー（以下、単にトナーともいう）について説明する。
まず、本発明に係るトナーの体積粒径、個数粒径及び、前記体積粒径と前記個数粒径との比について説明する。
【００９０】
本発明に記載の効果を得る観点から、本発明に係るトナーは、粒径分布として単分散であることが好ましく、５０％体積粒径（Ｄｖ５０）と５０％個数粒径（Ｄｐ５０）の比（Ｄｖ５０／Ｄｐ５０）が１．０〜１．１５であることが必要であるが、好ましくは１．０〜１．１３である。
【００９１】
また、転写性や現像性の変動幅を抑制するためには、トナーの大きい方からの累積７５％体積粒径（Ｄｖ７５）と７５％個数粒径（Ｄｐ７５）の比（Ｄｖ７５／Ｄｐ７５）が１．０〜１．２０であることが必要であるが、好ましくは、１．１〜１．１９である。さらに、全トナー中において、粒径が０．７×（Ｄｐ５０）以下のトナーの個数が１０個数％以下であることが必要であるが、好ましくは、５個数％〜９個数％である。
【００９２】
本発明に係るトナーの５０％体積粒径（Ｄｖ５０）は３μｍ〜７μｍが好ましく、更に、好ましくは３．５μｍ〜６．５μｍである。また、本発明に係るトナーの５０％個数粒径（Ｄｐ５０）は、２μｍ〜６．５μｍが好ましく、更に好ましくは、２．５μｍ〜６μｍである。この範囲とすることにより、本発明の効果をより顕著に発揮することができる。
【００９３】
ここで、大きい方からの累積７５％体積粒径（Ｄｖ７５）或いは累積７５％個数粒径（Ｄｐ７５）とは、粒径の大きな方からの頻度を累積し、全体積の和或いは個数の和に対して、それぞれが７５％を示す粒径分布部位の体積粒径或いは個数粒径で表す。
【００９４】
本発明において、５０％体積粒径（Ｄｖ５０）、５０％個数粒径（Ｄｐ５０）、累積７５％体積粒径（Ｄｖ７５）、累積７５％個数粒径（Ｄｐ７５）等は、コールターカウンターＴＡ−ＩＩ型或いはコールターマルチサイザー（コールター社製）で測定することが出来る。
【００９５】
本発明に係るトナーの構成成分、トナーの構成成分である結着樹脂の成分、その製造などについて説明する。
【００９６】
本発明に係るトナーは着色剤、結着樹脂などを少なくとも含有するが、前記トナーは、粉砕・分級工程を経て製造してもよく、下記に示すような重合性単量体を重合して得た樹脂粒子を用いてトナーを作製する、いわゆる重合法で製造してもよい。重合法を用いてトナーを製造する場合には樹脂粒子を塩析／融着する工程を有する製造方法が特に好ましい。
【００９７】
重合法に用いられる重合性単量体としては、ラジカル重合性単量体を構成成分として用い、必要に応じて架橋剤を使用することができる。また、以下の酸性基を有するラジカル重合性単量体または塩基性基を有するラジカル重合性単量体を少なくとも１種類含有させることが好ましい。
【００９８】
（１）ラジカル重合性単量体
ラジカル重合性単量体成分としては、特に限定されるものではなく従来公知のラジカル重合性単量体を用いることができる。また、要求される特性を満たすように、１種または２種以上のものを組み合わせて用いることができる。
【００９９】
具体的には、芳香族系ビニル単量体、（メタ）アクリル酸エステル系単量体、ビニルエステル系単量体、ビニルエーテル系単量体、モノオレフィン系単量体、ジオレフィン系単量体、ハロゲン化オレフィン系単量体等が挙げられる。
【０１００】
芳香族系ビニル単量体としては、例えば、スチレン、ｏ−メチルスチレン、ｍ−メチルスチレン、ｐ−メチルスチレン、ｐ−メトキシスチレン、ｐ−フェニルスチレン、ｐ−クロロスチレン、ｐ−エチルスチレン、ｐ−ｎ−ブチルスチレン、ｐ−ｔｅｒｔ−ブチルスチレン、ｐ−ｎ−ヘキシルスチレン、ｐ−ｎ−オクチルスチレン、ｐ−ｎ−ノニルスチレン、ｐ−ｎ−デシルスチレン、ｐ−ｎ−ドデシルスチレン、２，４−ジメチルスチレン、３，４−ジクロロスチレン等のスチレン系単量体およびその誘導体が挙げられる。
【０１０１】
（メタ）アクリル酸エステル系単量体としては、アクリル酸メチル、アクリル酸エチル、アクリル酸ブチル、アクリル酸−２−エチルヘキシル、アクリル酸シクロヘキシル、アクリル酸フェニル、メタクリル酸メチル、メタクリル酸エチル、メタクリル酸ブチル、メタクリル酸ヘキシル、メタクリル酸−２−エチルヘキシル、β−ヒドロキシアクリル酸エチル、γ−アミノアクリル酸プロピル、メタクリル酸ステアリル、メタクリル酸ジメチルアミノエチル、メタクリル酸ジエチルアミノエチル等が挙げられる。
【０１０２】
ビニルエステル系単量体としては、酢酸ビニル、プロピオン酸ビニル、ベンゾエ酸ビニル等が挙げられる。
【０１０３】
ビニルエーテル系単量体としては、ビニルメチルエーテル、ビニルエチルエーテル、ビニルイソブチルエーテル、ビニルフェニルエーテル等が挙げられる。
【０１０４】
モノオレフィン系単量体としては、エチレン、プロピレン、イソブチレン、１−ブテン、１−ペンテン、４−メチル−１−ペンテン等が挙げられる。
【０１０５】
ジオレフィン系単量体としては、ブタジエン、イソプレン、クロロプレン等が挙げられる。
【０１０６】
ハロゲン化オレフィン系単量体としては、塩化ビニル、塩化ビニリデン、臭化ビニル等が挙げられる。
【０１０７】
（２）架橋剤
架橋剤としては、トナーの特性を改良するためにラジカル重合性架橋剤を添加しても良い。ラジカル重合性架橋剤としては、ジビニルベンゼン、ジビニルナフタレン、ジビニルエーテル、ジエチレングリコールメタクリレート、エチレングリコールジメタクリレート、ポリエチレングリコールジメタクリレート、フタル酸ジアリル等の不飽和結合を２個以上有するものが挙げられる。
【０１０８】
（３）酸性基を有するラジカル重合性単量体または塩基性基を有するラジカル重合性単量体
酸性基を有するラジカル重合性単量体または塩基性基を有するラジカル重合性単量体としては、例えば、カルボキシル基を有する重合性単量体、スルホン酸基を有する重合性単量体、第１級アミン、第２級アミン、第３級アミン、第４級アンモニウム塩等のアミン系の重合性単量体が挙げられる。
【０１０９】
カルボキシル基を有する重合性単量体としては、アクリル酸、メタクリル酸、フマール酸、マレイン酸、イタコン酸、ケイ皮酸、マレイン酸モノブチルエステル、マレイン酸モノオクチルエステル等が挙げられる。
【０１１０】
スルホン酸基を有する重合性単量体としては、スチレンスルホン酸、アリルスルホコハク酸、アリルスルホコハク酸オクチル等が挙げられる。
【０１１１】
これらは、ナトリウムやカリウム等のアルカリ金属塩あるいはカルシウムなどのアルカリ土類金属塩の構造であってもよい。
【０１１２】
塩基性基を有するラジカル重合性単量体としては、アミン系の化合物があげられ、ジメチルアミノエチルアクリレート、ジメチルアミノエチルメタクリレート、ジエチルアミノエチルアクリレート、ジエチルアミノエチルメタクリレート、および上記４化合物の４級アンモニウム塩、３−ジメチルアミノフェニルアクリレート、２−ヒドロキシ−３−メタクリルオキシプロピルトリメチルアンモニウム塩、アクリルアミド、Ｎ−ブチルアクリルアミド、Ｎ，Ｎ−ジブチルアクリルアミド、ピペリジルアクリルアミド、メタクリルアミド、Ｎ−ブチルメタクリルアミド、Ｎ−オクタデシルアクリルアミド；ビニルピリジン、ビニルピロリドン；ビニルＮ−メチルピリジニウムクロリド、ビニルＮ−エチルピリジニウムクロリド、Ｎ，Ｎ−ジアリルメチルアンモニウムクロリド、Ｎ，Ｎ−ジアリルエチルアンモニウムクロリド等を挙げることができる。
【０１１３】
本発明に用いられるラジカル重合性単量体としては、酸性基を有するラジカル重合性単量体または塩基性基を有するラジカル重合性単量体が単量体全体の０．１〜１５質量％使用することが好ましく、ラジカル重合性架橋剤はその特性にもよるが、全ラジカル重合性単量体に対して０．１〜１０質量％の範囲で使用することが好ましい。
【０１１４】
〔連鎖移動剤〕
分子量を調整することを目的として、一般的に用いられる連鎖移動剤を用いることが出来る。連鎖移動剤としては、特に限定されるものではなく例えばオクチルメルカプタン、ドデシルメルカプタン、ｔｅｒｔ−ドデシルメルカプタン、ｎ−オクチル−３−メルカプトプロピオン酸エステル、四臭化炭素およびスチレンダイマー等が使用される。
【０１１５】
〔重合開始剤〕
本発明に用いられるラジカル重合開始剤は水溶性であれば適宜使用が可能である。例えば過硫酸塩（過硫酸カリウム、過硫酸アンモニウム等）、アゾ系化合物（４，４′−アゾビス４−シアノ吉草酸及びその塩、２，２′−アゾビス（２−アミジノプロパン）塩等）、パーオキシド化合物等が挙げられる。
【０１１６】
更に上記ラジカル性重合開始剤は、必要に応じて還元剤と組み合わせレドックス系開始剤とする事が可能である。レドックス系開始剤を用いる事で、重合活性が上昇し重合温度の低下が図れ、更に重合時間の短縮が期待できる。
【０１１７】
重合温度は、重合開始剤の最低ラジカル生成温度以上であればどの温度を選択しても良いが例えば５０℃から９０℃の範囲が用いられる。但し、常温開始の重合開始剤、例えば過酸化水素−還元剤（アスコルビン酸等）の組み合わせを用いる事で、室温またはそれ以上の温度で重合する事も可能である。
【０１１８】
〔界面活性剤〕
前述のラジカル重合性単量体を使用して重合を行うためには、界面活性剤を使用して水系媒体中に油滴分散を行う必要がある。この際に使用することのできる界面活性剤としては特に限定されるものでは無いが、下記のイオン性界面活性剤を好適なものの例として挙げることができる。
【０１１９】
イオン性界面活性剤としては、スルホン酸塩（ドデシルベンゼンスルホン酸ナトリウム、アリールアルキルポリエーテルスルホン酸ナトリウム、３，３−ジスルホンジフェニル尿素−４，４−ジアゾ−ビス−アミノ−８−ナフトール−６−スルホン酸ナトリウム、オルト−カルボキシベンゼン−アゾ−ジメチルアニリン、２，２，５，５−テトラメチル−トリフェニルメタン−４，４−ジアゾ−ビス−β−ナフトール−６−スルホン酸ナトリウム等）、硫酸エステル塩（ドデシル硫酸ナトリウム、テトラデシル硫酸ナトリウム、ペンタデシル硫酸ナトリウム、オクチル硫酸ナトリウム等）、脂肪酸塩（オレイン酸ナトリウム、ラウリン酸ナトリウム、カプリン酸ナトリウム、カプリル酸ナトリウム、カプロン酸ナトリウム、ステアリン酸カリウム、オレイン酸カルシウム等）が挙げられる。
【０１２０】
また、ノニオン性界面活性剤も使用することができる。具体的には、ポリエチレンオキサイド、ポリプロピレンオキサイド、ポリプロピレンオキサイドとポリエチレンオキサイドの組み合わせ、ポリエチレングリコールと高級脂肪酸とのエステル、アルキルフェノールポリエチレンオキサイド、高級脂肪酸とポリエチレングリコールのエステル、高級脂肪酸とポリプロピレンオキサイドのエステル、ソルビタンエステル等をあげることができる。
【０１２１】
本発明において、これらは、主に乳化重合時の乳化剤として使用されるが、他の工程または使用目的で使用してもよい。
【０１２２】
〔着色剤〕
着色剤としては無機顔料、有機顔料、染料を挙げることができる。
【０１２３】
無機顔料としては、従来公知のものを用いることができる。具体的な無機顔料を以下に例示する。
【０１２４】
黒色の顔料としては、例えば、ファーネスブラック、チャンネルブラック、アセチレンブラック、サーマルブラック、ランプブラック等のカーボンブラック、更にマグネタイト、フェライト等の磁性粉も用いられる。
【０１２５】
これらの無機顔料は所望に応じて単独または複数を選択併用する事が可能である。また顔料の添加量は重合体に対して２〜２０質量％であり、好ましくは３〜１５質量％が選択される。
【０１２６】
磁性トナーとして使用する際には、前述のマグネタイトを添加することができる。この場合には所定の磁気特性を付与する観点から、トナー中に２０〜６０質量％添加することが好ましい。
【０１２７】
有機顔料及び染料としても従来公知のものを用いることができる。具体的な有機顔料及び染料を以下に例示する。
【０１２８】
マゼンタまたはレッド用の顔料としては、Ｃ．Ｉ．ピグメントレッド２、Ｃ．Ｉ．ピグメントレッド３、Ｃ．Ｉ．ピグメントレッド５、Ｃ．Ｉ．ピグメントレッド６、Ｃ．Ｉ．ピグメントレッド７、Ｃ．Ｉ．ピグメントレッド１５、Ｃ．Ｉ．ピグメントレッド１６、Ｃ．Ｉ．ピグメントレッド４８：１、Ｃ．Ｉ．ピグメントレッド５３：１、Ｃ．Ｉ．ピグメントレッド５７：１、Ｃ．Ｉ．ピグメントレッド１２２、Ｃ．Ｉ．ピグメントレッド１２３、Ｃ．Ｉ．ピグメントレッド１３９、Ｃ．Ｉ．ピグメントレッド１４４、Ｃ．Ｉ．ピグメントレッド１４９、Ｃ．Ｉ．ピグメントレッド１６６、Ｃ．Ｉ．ピグメントレッド１７７、Ｃ．Ｉ．ピグメントレッド１７８、Ｃ．Ｉ．ピグメントレッド２２２等が挙げられる。
【０１２９】
オレンジまたはイエロー用の顔料としては、Ｃ．Ｉ．ピグメントオレンジ３１、Ｃ．Ｉ．ピグメントオレンジ４３、Ｃ．Ｉ．ピグメントイエロー１２、Ｃ．Ｉ．ピグメントイエロー１３、Ｃ．Ｉ．ピグメントイエロー１４、Ｃ．Ｉ．ピグメントイエロー１５、Ｃ．Ｉ．ピグメントイエロー１７、Ｃ．Ｉ．ピグメントイエロー９３、Ｃ．Ｉ．ピグメントイエロー９４、Ｃ．Ｉ．ピグメントイエロー１３８、Ｃ．Ｉ．ピグメントイエロー１８０、Ｃ．Ｉ．ピグメントイエロー１８５、Ｃ．Ｉ．ピグメントイエロー１５５、Ｃ．Ｉ．ピグメントイエロー１５６、等が挙げられる。
【０１３０】
グリーンまたはシアン用の顔料としては、Ｃ．Ｉ．ピグメントブルー１５、Ｃ．Ｉ．ピグメントブルー１５：２、Ｃ．Ｉ．ピグメントブルー１５：３、Ｃ．Ｉ．ピグメントブルー１６、Ｃ．Ｉ．ピグメントブルー６０、Ｃ．Ｉ．ピグメントグリーン７等が挙げられる。
【０１３１】
また、染料としてはＣ．Ｉ．ソルベントレッド１、同４９、同５２、同５８、同６３、同１１１、同１２２、Ｃ．Ｉ．ソルベントイエロー１９、同４４、同７７、同７９、同８１、同８２、同９３、同９８、同１０３、同１０４、同１１２、同１６２、Ｃ．Ｉ．ソルベントブルー２５、同３６、同６０、同７０、同９３、同９５等を用いる事ができ、またこれらの混合物も用いる事ができる。
【０１３２】
これらの有機顔料及び染料は所望に応じて単独または複数を選択併用する事が可能である。また顔料の添加量は重合体に対して２〜２０質量％であり、好ましくは３〜１５質量％が選択される。
【０１３３】
着色剤は表面改質して使用することもできる。その表面改質剤としては、従来公知のものを使用することができ、具体的にはシランカップリング剤、チタンカップリング剤、アルミニウムカップリング剤等が好ましく用いることができる。
【０１３４】
本発明に係るトナーは離型剤を併用してもよく、例えば、ポリプロピレン、ポリエチレンなどの低分子量ポリオレフィンワックス、パラフィンワックス、フィッシャートロプシュワックス、エステルワックス等を離型剤として使用することが出来る。また、本発明においては、下記一般式（３）で示されるエステルワックスを好ましく用いることが出来る。
【０１３５】
一般式（３）
Ｒ_１−（ＯＣＯ−Ｒ_２）_ｎ
式中、ｎは１〜４の整数を表すが、好ましくは２〜４であり、さらに好ましくは３〜４、特に好ましくは４である。
【０１３６】
Ｒ_１、Ｒ_２は置換基を有しても良い炭化水素基を示す。
Ｒ_１：炭素数＝１〜４０、好ましくは１〜２０、更に好ましくは２〜５
Ｒ_２：炭素数＝１〜４０、好ましくは１３〜２９、更に好ましくは１２〜２５
以下に、本発明に係るエステル基を有する結晶性化合物の具体例を示すが、本発明はこれらに限定されない。
【０１３７】
【化２】

【０１３８】
【化３】

【０１３９】
これらエステルワックスは、樹脂粒子中に含有され、樹脂粒子を融着させて得られるトナーに良好な定着性（画像支持体に対する接着性）を付与する機能を有する。
【０１４０】
本発明に用いられる離型剤の添加量は、トナー全体に１質量％〜３０質量％が好ましく、更に好ましくは２質量％〜２０質量％であり、更に好ましくは３〜１５質量％である。また、本発明のトナーは、上記の重合性単量体中に前記離型剤を溶解させたものを水中に分散し、重合させ、樹脂粒子中に離型剤として上記のようなエステル系化合物を内包させた粒子を形成させ、着色剤粒子ととも塩析／融着する工程を経て作製されたトナーが好ましい。
【０１４１】
本発明に係るトナーは、着色剤、離型剤以外にトナー用材料として種々の機能を付与することのできる材料を加えてもよい。具体的には荷電制御剤等が挙げられる。これらの成分は前述の塩析／融着段階で樹脂粒子と着色剤粒子と同時に添加し、トナー中に包含する方法、樹脂粒子自体に添加する方法等種々の方法で添加することができる。
【０１４２】
荷電制御剤も同様に種々の公知のもので、且つ水中に分散することができるものを使用することができる。具体的には、ニグロシン系染料、ナフテン酸または高級脂肪酸の金属塩、アルコキシル化アミン、第４級アンモニウム塩化合物、アゾ系金属錯体、サリチル酸金属塩あるいはその金属錯体等が挙げられる。
【０１４３】
本発明に係るトナーに用いられる外添剤について説明する。
本発明に係るトナーには、流動性、帯電性の改良およびクリーニング性の向上などの目的で、いわゆる外添剤を添加して使用することができる。これら外添剤としては特に限定されないが、種々の無機微粒子、有機微粒子及び滑剤を使用することができる。
【０１４４】
無機微粒子としては、従来公知のものを使用することができる。具体的には、シリカ、チタン、アルミナ微粒子等が好ましく用いることができる。これら無機微粒子としては疎水性のものが好ましい。具体的には、シリカ微粒子として、例えば日本アエロジル社製の市販品Ｒ−８０５、Ｒ−９７６、Ｒ−９７４、Ｒ−９７２、Ｒ−８１２、Ｒ−８０９、ヘキスト社製のＨＶＫ−２１５０、Ｈ−２００、キャボット社製の市販品ＴＳ−７２０、ＴＳ−５３０、ＴＳ−６１０、Ｈ−５、ＭＳ−５等が挙げられる。
【０１４５】
チタン微粒子としては、例えば、日本アエロジル社製の市販品Ｔ−８０５、Ｔ−６０４、テイカ社製の市販品ＭＴ−１００Ｓ、ＭＴ−１００Ｂ、ＭＴ−５００ＢＳ、ＭＴ−６００、ＭＴ−６００ＳＳ、ＪＡ−１、富士チタン社製の市販品ＴＡ−３００ＳＩ、ＴＡ−５００、ＴＡＦ−１３０、ＴＡＦ−５１０、ＴＡＦ−５１０Ｔ、出光興産社製の市販品ＩＴ−Ｓ、ＩＴ−ＯＡ、ＩＴ−ＯＢ、ＩＴ−ＯＣ等が挙げられる。
【０１４６】
アルミナ微粒子としては、例えば、日本アエロジル社製の市販品ＲＦＹ−Ｃ、Ｃ−６０４、石原産業社製の市販品ＴＴＯ−５５等が挙げられる。
【０１４７】
また、有機微粒子としては数平均一次粒子径が１０〜２０００ｎｍ程度の球形の有機微粒子を使用することができる。このものとしては、スチレンやメチルメタクリレートなどの単独重合体やこれらの共重合体を使用することができる。
【０１４８】
滑剤には、例えばステアリン酸の亜鉛、アルミニウム、銅、マグネシウム、カルシウム等の塩、オレイン酸の亜鉛、マンガン、鉄、銅、マグネシウム等の塩、パルミチン酸の亜鉛、銅、マグネシウム、カルシウム等の塩、リノール酸の亜鉛、カルシウム等の塩、リシノール酸の亜鉛、カルシウムなどの塩等の高級脂肪酸の金属塩が挙げられる。
【０１４９】
これら外添剤の添加量は、トナーに対して０．１〜５質量％が好ましい。
外添剤の添加方法としては、タービュラーミキサー、ヘンシエルミキサー、ナウターミキサー、Ｖ型混合機などの種々の公知の混合装置が挙げられる。
【０１５０】
本発明に係る静電荷像現像用トナーの製造方法について説明する。
《製造工程》
本発明のトナーは、離型剤を溶解した上記記載のような重合性単量体または重合性単量体溶液を水系媒体中に分散し、ついで重合法により離型剤を内包した樹脂粒子を調整する工程、前記樹脂粒子分散液を用いて水系媒体中で樹脂粒子を融着させる工程、得られた粒子を水系媒体中より濾過し界面活性剤などを除去する洗浄工程、得られた粒子を乾燥させる工程、さらに乾燥させて得られた粒子に外添剤などを添加する外添剤添加工程などから構成される重合法で製造することが好ましい。ここで樹脂粒子としては着色された粒子であってもよい。また、非着色粒子を樹脂粒子として使用することもできる、この場合には、樹脂粒子の分散液に着色剤粒子分散液などを添加した後に水系媒体中で融着させることで着色粒子とすることができる。
【０１５１】
特に、融着の方法としては、重合工程によって生成された樹脂粒子を用いて塩析／融着する方法が好ましい。また、非着色の樹脂粒子を使用した場合には、樹脂粒子と着色剤粒子を水系媒体中で塩析／融着させることができる。
【０１５２】
また、着色剤や離型剤に限らず、トナーの構成要素である荷電制御剤等も本工程で粒子として添加することができる。
【０１５３】
なお、ここで水系媒体とは主成分として水からなるもので、水の含有量が５０質量％以上であるものを示す。水以外のものとしては、水に溶解する有機溶媒を挙げることができ、例えば、メタノール、エタノール、イソプロパノール、ブタノール、アセトン、メチルエチルケトン、テトラヒドロフランなどをあげることができる。好ましくは樹脂を溶解しない有機溶媒である、メタノール、エタノール、イソプロパノール、ブタノールのようなアルコール系有機溶媒が特に好ましい。
【０１５４】
本発明での好ましい重合法としては、モノマー中に離型剤を溶解したモノマー溶液を臨界ミセル濃度以下の界面活性剤を溶解させた水系媒体中に機械的エネルギーによって油滴分散させた分散液に、水溶性重合開始剤を加え、ラジカル重合させる方法をあげることができる。この場合、モノマー中に油溶性の重合開始剤を加えて使用してもよい。
【０１５５】
この油滴分散を行うための分散機としては特に限定されるものでは無いが、例えばクレアミックス、超音波分散機、機械式ホモジナイザー、マントンゴーリンや圧力式ホモジナイザー等をあげることができる。
【０１５６】
着色剤自体は表面改質して使用してもよい。着色剤の表面改質法は、溶媒中に着色剤を分散し、その中に表面改質剤を添加した後昇温し反応を行う。反応終了後、ろ過し同一の溶媒で洗浄ろ過を繰り返し乾燥させ表面改質剤で処理された顔料を得る。
【０１５７】
着色剤粒子は着色剤を水系媒体中に分散して調製される方法がある。この分散は、水中で界面活性剤濃度を臨界ミセル濃度（ＣＭＣ）以上にした状態で行われることが好ましい。
【０１５８】
顔料分散時の分散機は特に限定されないが、好ましくはクレアミックス、超音波分散機、機械的ホモジナイザー、マントンゴーリンや圧力式ホモジナイザー等の加圧分散機、サンドグラインダー、ゲッツマンミルやダイヤモンドファインミル等の媒体型分散機が挙げられる。
【０１５９】
ここで使用される界面活性剤は、前述の界面活性剤を使用することができる。塩析／融着を行う工程は、樹脂粒子及び着色剤粒子とが存在している水中にアルカリ金属塩やアルカリ土類金属塩等からなる塩析剤を臨界凝集濃度以上の凝集剤として添加し、ついで樹脂粒子のガラス転移点以上に加熱することで塩析を進行させると同時に融着を行う工程である。
【０１６０】
ここで、塩析剤であるアルカリ金属塩及びアルカリ土類金属塩は、アルカリ金属として、リチウム、カリウム、ナトリウム等が挙げられ、アルカリ土類金属として、マグネシウム、カルシウム、ストロンチウム、バリウムなどが挙げられ、好ましくはカリウム、ナトリウム、マグネシウム、カルシウム、バリウムが挙げられる。また塩を構成するものとしては、塩素塩、臭素塩、沃素塩、炭酸塩、硫酸塩等が挙げられる。
【０１６１】
トナーの粒径分布を達成するための方法としては特に限定されないが、例えば分級などの手法による制御や会合時における温度や時間、さらには会合を終了させるための停止方法の制御などの手法を使用することができる。
【０１６２】
特に好ましい製造方法として、水中での会合時間、会合温度、停止速度などを制御する方法をあげることができる。すなわち、塩析／融着で行う場合、塩析剤を添加した後に放置する時間をできるだけ短くすることが好ましい。この理由として明確では無いが、塩析した後の放置時間によって、粒子の凝集状態が変動し、粒径分布が不安定になったり、融着させたトナーの表面性が変動したりする問題が発生する。この塩析剤を添加する温度は特に限定されない。
【０１６３】
本発明では、樹脂粒子の分散液をできるだけ速やかに昇温し、樹脂粒子のガラス転移温度以上に加熱する方法を使用することが好ましい。この昇温までの時間としては３０分未満、好ましくは１０分未満である。さらに、昇温を速やかに行う必要があるが、昇温速度としては、１℃／分以上が好ましい。上限としては特に明確では無いが、急速な塩析／融着の進行により粗大粒子の発生を抑制する観点で、１５℃／分以下が好ましい。特に好ましい形態としては、塩析／融着をガラス転移温度以上になった時点でも継続して進行させる方法をあげることができる。この方法とすることで、粒子の成長とともに融着が効果的に進行させることができ、最終的なトナーとしての耐久性を向上することができる。
【０１６４】
さらに、会合時に２価の金属塩を使用して塩析／融着することで特に粒径を制御することが可能となる。この理由としては明確ではないが、２価の金属塩を使用することで塩析時の斥力が大きくなり、界面活性剤の分散能を効果的に抑制することが可能となり、結果として流刑分布を制御することが可能となったものと推定される。
【０１６５】
また、塩析／融着を停止するために１価の金属塩及び水を添加することが好ましい。このものを添加することにより、塩析を停止させることができ、結果として大粒径成分や小粒径成分の存在を抑制することが可能となる。
【０１６６】
樹脂粒子を水系媒体中で会合あるいは融着させる重合法トナーでは、融着段階での反応容器内の媒体の流れおよび温度分布を制御することで、さらには融着後の形状制御工程において加熱温度、攪拌回転数、時間を制御することで、トナー全体の形状分布および形状を任意に変化させることができる。
【０１６７】
すなわち、樹脂粒子を会合あるいは融着させる重合法トナーでは、反応装置内の流れを層流とし、内部の温度分布を均一化することができる攪拌翼および攪拌槽を使用して、融着工程および形状制御工程での温度、回転数、時間を制御することにより、本発明の形状係数および均一な形状分布を有するトナーを形成することができる。この理由は、層流を形成させた場で融着させると、凝集および融着が進行している粒子（会合あるいは凝集粒子）に強いストレスが加わらず、かつ流れが加速された層流においては攪拌槽内の温度分布が均一である結果、融着粒子の形状分布が均一になると推定される。さらに、その後の形状制御工程での加熱、攪拌により融着粒子は徐々に球形化し、トナー粒子の形状を任意に制御できる。
【０１６８】
本発明のトナーを所定の形状に制御するためには、塩析と融着を同時進行させることが好ましい。凝集粒子を形成した後に加熱する方法ではその形状に分布を生じやすく、さらに微粒子の発生を抑制することができない。すなわち、凝集粒子を水系媒体中で攪拌しながら加熱するために凝集粒子の再分断が発生し、小粒径の成分が発生しやすいものと推定される。
【０１６９】
本発明に用いられる現像剤について説明する。
キャリアと混合して二成分現像剤として用いること場合にはキャリアの磁性粒子として、鉄、フェライト、マグネタイト等の金属、それらの金属とアルミニウム、鉛等の金属との合金等の従来から公知の材料を用いることが出来る。特にフェライト粒子が好ましい。上記磁性粒子は、その体積平均粒径としては１５〜１００μｍ、より好ましくは２５〜８０μｍのものがよい。
【０１７０】
キャリアの体積平均粒径の測定は、代表的には湿式分散機を備えたレーザ回折式粒度分布測定装置「ヘロス（ＨＥＬＯＳ）」（シンパティック（ＳＹＭＰＡＴＥＣ）社製）により測定することができる。
【０１７１】
キャリアは、磁性粒子が更に樹脂により被覆されているもの、あるいは樹脂中に磁性粒子を分散させたいわゆる樹脂分散型キャリアが好ましい。コーティング用の樹脂組成としては、特に限定は無いが、例えば、オレフィン系樹脂、スチレン系樹脂、スチレン−アクリル系樹脂、シリコーン系樹脂、エステル系樹脂或いはフッ素含有重合体系樹脂等が用いられる。また、樹脂分散型キャリアを構成するための樹脂としては、特に限定されず公知のものを使用することができ、例えば、スチレン−アクリル系樹脂、ポリエステル樹脂、フッ素系樹脂、フェノール樹脂等を使用することができる。
【０１７２】
本発明の画像形成方法はカラー画像を形成する画像形成方法としても用いることができる。
【０１７３】
図４は本発明の一実施の形態を示すカラー画像形成装置の断面構成図である。このカラー画像形成装置は、タンデム型カラー画像形成装置と称せられるもので、複数組の画像形成部１０Ｙ，１０Ｍ，１０Ｃ，１０Ｋと、無端ベルト状中間転写体ユニット７と、給紙搬送手段２１及び定着手段（定着工程でもある）２４とから成る。画像形成装置の本体Ａの上部には、原稿画像読み取り装置ＳＣが配置されている。
【０１７４】
イエロー色の画像を形成する画像形成部１０Ｙは、第１の像担持体としてのドラム状の感光体１Ｙの周囲に配置された帯電手段（帯電工程でもある）２Ｙ、露光手段（露光工程でもある）３Ｙ、現像手段（現像工程でもある）４Ｙ、一次転写手段（一次転写工程でもある）としての一次転写ローラ５Ｙ、クリーニング手段（クリーニング工程でもある）６Ｙを有する。マゼンタ色の画像を形成する画像形成部１０Ｍは、第１の像担持体としてのドラム状の感光体１Ｍ、帯電手段２Ｍ、露光手段３Ｍ、現像手段４Ｍ、一次転写手段としての一次転写ローラ５Ｍ、クリーニング手段６Ｍを有する。シアン色の画像を形成する画像形成部１０Ｃは、第１の像担持体としてのドラム状の感光体１Ｃ、帯電手段２Ｃ、露光手段３Ｃ、現像手段４Ｃ、一次転写手段としての一次転写ローラ５Ｃ、クリーニング手段６Ｃを有する。黒色画像を形成する画像形成部１０Ｋは、第１の像担持体としてのドラム状の感光体１Ｋ、帯電手段２Ｋ、露光手段３Ｋ、現像手段４Ｋ、一次転写手段としての一次転写ローラ５Ｋ、クリーニング手段６Ｋを有する。
【０１７５】
無端ベルト状中間転写体ユニット７は、複数のローラにより巻回され、回動可能に支持された半導電性エンドレスベルト状の第２の像担持体としての無端ベルト状中間転写体７０を有する。
【０１７６】
画像形成部１０Ｙ，１０Ｍ，１０Ｃ，１０Ｋより形成された各色の画像は、一次転写手段としての一次転写ローラ５Ｙ，５Ｍ，５Ｃ，５Ｋにより、回動する無端ベルト状中間転写体７０上に逐次転写されて、合成されたカラー画像が形成される。給紙カセット２０内に収容された記録媒体（記録紙ともいう）としての用紙Ｐは、給紙手段２１により給紙され、複数の中間ローラ２２Ａ，２２Ｂ，２２Ｃ，２２Ｄ、レジストローラ２３を経て、二次転写手段（二次転写工程でもある）としての二次転写ローラ５Ａに搬送され、用紙Ｐ上に二次転写してカラー画像が一括転写される。カラー画像が転写された用紙Ｐは、定着手段２４により定着処理され、排紙ローラ２５に挟持されて機外の排紙トレイ２６上に載置される。
【０１７７】
一方、二次転写手段としての二次転写ローラ５Ａにより用紙Ｐにカラー画像を転写した後、用紙Ｐを曲率分離した無端ベルト状中間転写体７０は、クリーニング手段６Ａにより残留トナーが除去される。
【０１７８】
画像形成処理中、一次転写ローラ５Ｋは常時、感光体１Ｋに圧接している。他の一次転写ローラ５Ｙ，５Ｍ，５Ｃはカラー画像形成時にのみ、それぞれ対応する感光体１Ｙ，１Ｍ，１Ｃに圧接する。
【０１７９】
二次転写ローラ５Ａは、ここを用紙Ｐが通過して二次転写が行われる時にのみ、無端ベルト状中間転写体７０に圧接する。
【０１８０】
また、装置本体Ａから筐体８を支持レール８２Ｌ，８２Ｒを介して引き出し可能にしてある。
【０１８１】
筐体８は、画像形成部１０Ｙ，１０Ｍ，１０Ｃ，１０Ｋと、無端ベルト状中間転写体ユニット７とから成る。
【０１８２】
画像形成部１０Ｙ，１０Ｍ，１０Ｃ，１０Ｋは、垂直方向に縦列配置されている。感光体１Ｙ，１Ｍ，１Ｃ，１Ｋの図示左側方には無端ベルト状中間転写体ユニット７が配置されている。無端ベルト状中間転写体ユニット７は、ローラ７１，７２，７３，７４を巻回して回動可能な無端ベルト状中間転写体７０、一次転写ローラ５Ｙ，５Ｍ，５Ｃ，５Ｋ、及びクリーニング手段６Ａとから成る。
【０１８３】
【実施例】
以下、実施例をあげて本発明を詳細に説明するが、本発明の様態はこれに限定されない。尚、下記文中「部」とは「質量部」を表す。
【０１８４】
実施例１
以下のようにして、実施例、比較例に用いる感光体１〜５を作製した。
【０１８５】

上記中間層塗布液を調製し、洗浄済みの円筒状アルミニウム基体上に浸漬塗布法で塗布し、１２０℃２０分で乾燥し、乾燥膜厚０．５μｍの中間層を形成した。
【０１８６】

上記組成物を混合し、サンドミルを用いて分散し、電荷発生層塗布液を調製した。この塗布液を浸漬塗布法で塗布し、前記中間層の上に乾燥膜厚０．３μｍの電荷発生層を形成した。
【０１８７】

上記組成物を混合し、溶解して電荷輸送層塗布液を調製した。この塗布液を前記電荷発生層の上に浸漬塗布法で塗布し、１００℃３０分で乾燥し、乾燥膜厚２３μｍの電荷輸送層を形成し感光体１を作製した。
【０１８８】
感光体２の作製
感光体１の作製において、中間層塗布液の組成を下記のように変更し、乾燥膜厚を１．５μｍに変更した以外は同様にして感光体２を作製した。
【０１８９】

感光体３の作製感光体１の作製において、中間層塗布液の組成を下記のように変更した以外は同様にして感光体３を作製した。
【０１９０】
中間層（ＵＣＬ）塗布液
シランカップリング剤「ＫＢＭ−９０３」（信越化学社製） ３００ｇ
水 ３０ｍｌ
エタノール １０００ｍｌ
感光体４の作製
感光体１の作製において、中間層塗布液の組成を下記のように変更した以外は同様にして感光体４を作製した。
【０１９１】

感光体５の作製（比較例感光体）
感光体１の中間層を下記の中間層塗布液に代え、乾燥膜厚を０．７μｍに変更した他は１と同様にして、感光体５の感光体を作製した。
【０１９２】
中間層（ＵＣＬ）塗布液
ポリアミド樹脂「ＣＭ−８０００」（東レ社製） １５０ｇ
２−プロパノール １５００ｍｌ
メタノール ８５００ｍｌ
尚、各層の膜厚は、中間層の固形分の付量で計算したが、塗布乾燥後、均一膜厚部分をランダムに１０ケ所測定し、その平均値の膜厚もほぼ同様の膜厚を示している。膜厚測定は光検出方式の膜厚測定器ＭＣＰＤ−１０００（瞬間マルチ測光検出器：大塚電子（株））を用いて行った。
【０１９３】
《現像剤》
《ラテックス１の製造》
撹拌装置、温度センサー、冷却管、窒素導入装置を付けた５０００ｍｌのセパラブルフラスコに予めアニオン系活性剤（ドデシルベンゼンスルフォン酸ナトリウム：ＳＤＳ）７．０８ｇをイオン交換水（２７６０ｇ）に溶解させた溶液を添加する。窒素気流下２３０ｒｐｍの撹拌速度で撹拌しつつ、内温を８０℃に昇温させた。一方で例示化合物１９）７２．０ｇをスチレン１１５．１ｇ、ｎ−ブチルアクリレート４２．０ｇ、メタクリル酸１０．９ｇからなるモノマーに加え、８０℃に加温し溶解させ、モノマー溶液を作製した。ここで循環経路を有する機械式分散機により上記の加熱溶液を混合分散させ、均一な分散粒子径を有する乳化粒子を作製した。ついで、重合開始剤（過硫酸カリウム：ＫＰＳ）０．８４ｇをイオン交換水２００ｇに溶解させた溶液を添加し８０℃にて３時間加熱、撹拌することでラテックス粒子を作製した。引き続いて更に重合開始剤（ＫＰＳ）７．７３ｇをイオン交換水２４０ｍｌに溶解させた溶液を添加し、１５分後、８０℃でスチレン３８３．６ｇ、ｎ−ブチルアクリレート１４０．０ｇ、メタクリル酸３６．４ｇ、ｎ−オクチル−３−メルカプトプロピオン酸エステル１４．０ｇの混合液を１２０分かけて滴下した。滴下終了後６０分加熱撹拌させた後４０℃まで冷却しラテックス粒子を得た。
【０１９４】
このラテックス粒子をラテックス１とする。
《着色粒子の製造》
（着色粒子１Ｂｋの製造）
ｎ−ドデシル硫酸ナトリウム＝９．２ｇをイオン交換水１６０ｍｌに撹拌溶解する。この液に、撹拌下、リーガル３３０Ｒ（キャボット社製カーボンブラック）２０ｇを徐々に加え、ついで、クレアミックスを用いて分散した。大塚電子社製の電気泳動光散乱光度計ＥＬＳ−８００を用いて、上記分散液の粒径を測定した結果、重量平均径で１１２ｎｍであった。この分散液を「着色剤分散液１」とする。
【０１９５】
前述の「ラテックス１」１２５０ｇとイオン交換水２０００ｍｌ及び「着色剤分散液１」を、温度センサー、冷却管、窒素導入装置、攪拌装置を付けた５リットルの四つ口フラスコに入れ撹拌する。３０℃に調整した後、この溶液に５モル／リットルの水酸化ナトリウム水溶液を加え、ｐＨを１０．０に調整した。ついで、塩化マグネシウム６水和物５２．６ｇをイオン交換水７２ｍｌに溶解した水溶液を攪拌下、３０℃にて５分間で添加した。その後、２分間放置した後に、昇温を開始し、液温度９０℃まで５分で昇温する（昇温速度＝１２℃／分）。その状態で粒径をコールターカウンターＴＡＩＩにて測定し、体積平均粒径が４．３μｍになった時点で塩化ナトリウム１１５ｇをイオン交換水７００ｍｌに溶解した水溶液を添加し粒子成長を停止させ、さらに継続して液温度８５℃±２℃にて、８時間加熱撹拌し、塩析／融着させる。その後、６℃／ｍｉｎの条件で３０℃まで冷却し、塩酸を添加し、ｐＨを２．０に調整し、撹拌を停止した。生成した着色粒子を下記条件で濾過／洗浄し、その後、４０℃の温風で乾燥し、着色粒子を得た。このものを「着色粒子１Ｂｋ」とする。
【０１９６】
（着色粒子２Ｂｋ、３Ｂｋ、４Ｂｋ及び５Ｂｋの製造）
着色粒子１Ｂｋの製造において、表１に記載の製造条件に変更した以外は同様にして、着色粒子２Ｂｋ〜５Ｂｋを各々、製造した。
【０１９７】
（着色粒子６Ｂｋ〜８Ｂｋの製造）
着色粒子１Ｂｋの製造において、表１に記載の製造条件に設定し、且つ、体積平均粒径が３．０μｍになった時点で粒子成長を停止させて、各々、着色粒子６Ｂｋ〜８Ｂｋを製造した。
【０１９８】
（着色粒子９Ｂｋ、１０Ｂｋの製造）
着色粒子１Ｂｋの製造において、表１に記載の製造条件に設定し、且つ、体積平均粒径が６．５μｍになった時点で粒子成長を停止させ、各々、着色粒子９Ｂｋ、１０Ｂｋを製造した。
【０１９９】
（着色粒子１１Ｂｋの製造）
着色粒子１Ｂｋの製造において、表１に記載の製造条件に設定し、且つ、体積平均粒径が２．６μｍになった時点で粒子成長を停止させ、各々、着色粒子１１Ｂｋを製造した。
【０２００】
（着色粒子１２Ｂｋの製造）
着色粒子１Ｂｋの製造において、表１に記載の製造条件に設定し、且つ、体積平均粒径が７．０μｍになった時点で粒子成長を停止させ、各々、着色粒子１２Ｂｋを製造した。
【０２０１】
着色粒子の製造条件を表１、最終的に得られた着色粒子の各々の物性を表２に示す。
【０２０２】
【表１】

【０２０３】
【表２】

【０２０４】
（トナー粒子の製造）
得られた着色粒子１Ｂｋ〜１２Ｂｋに、各々、疎水性シリカ（数平均一次粒子径＝１２ｎｍ、疎水化度＝６８）を１質量％及び疎水性酸化チタン（数平均一次粒子径＝２０ｎｍ、疎水化度＝６３）を０．５質量％添加し、ヘンシェルミキサーにより混合してトナー１Ｂｋ〜１２Ｂｋを得た。
【０２０５】
なお、トナーの形状及び粒径等の物性は表２に示した着色粒子の物性データとと同一であった。
【０２０６】
（現像剤の製造）
上記トナー粒子の各々に対してシリコーン樹脂を被覆した体積平均粒径６０μｍのフェライトキャリアを混合し、トナー濃度が６％の現像剤１Ｂｋ〜１２Ｂｋを各々、製造した。
【０２０７】
《評価》
上記感光体を図１及び図２の構造を基本的に有するデジタル複写機（スコロトロン帯電器、半導体レーザ像露光器、反転現像手段を有する）に設定し、複写実験を行った。この実験においては図２のプロセス制御部のメモリー中に未露光部目標電位のプログラムを組み込み、自動的に現像位置の未露光部目標電位が設定されるようにデジタル複写機を改造した。又、現像バイアス電位（Ｖｂｉａｓ）も目標値に自動的に設定されるように改造した。この複写実験の画像形成に際し、前記電位センサーにより未露光部電位を測定し、目標値の未露光部電位が得られていない場合は、制御部を通して、未露光部目標電位を達成するために、帯電手段の出力値を制御した。
【０２０８】
《画像評価》
上記デジタル複写機に各感光体、現像剤、現像位置の未露光部電位（ＶＨ）及び現像スリーブに印加する直流バイアス電位（ＶＤＣ）を表３、表４のように組み合わせて（組み合わせＮｏ．１〜４５）、高温高湿：ＨＨ（３０℃、８０％ＲＨ）、低温低湿：ＬＬ（１０℃、１０％ＲＨ）環境で、Ａ４紙、各５万枚の画素率７％の文字画像の複写を行い、スタート時及び１万枚コピー毎に白べた画像、ハーフトーン画像等の複写を行い、黒ポチ等の画像欠陥の有無を確認した。表３、表４に結果を示す。
【０２０９】
尚、上記デジタル複写機のその他の評価条件は下記の条件に設定した。
露光条件
露光部電位目標：−５０Ｖ〜−１５０Ｖにする露光量に設定。
【０２１０】
露光ビーム：ドット密度８００ｄｐｉ（ｄｐｉとは２．５４ｃｍ当たりのドット数）の像露光を行った。レーザビームスポット面積：０．８×１０^−９ｍ^２、レーザは６８０ｎｍの半導体レーザを使用
転写条件
転写極；コロナ帯電方式
分離条件：分離爪ユニットの分離手段を用いた
クリーニング条件
クリーニング部に硬度７０°、反発弾性６５％、厚さ２（ｍｍ）、自由長９ｍｍのクリーニングブレードをカウンター方向に線圧１８（ｇ／ｃｍ）となるように重り荷重方式で当接した。
【０２１１】
評価基準
黒ポチ（スタート時及び１万枚コピー毎に白べた画像で評価）
黒ポチについては、周期性が感光体の周期と一致し、目視できる黒ポチが、Ａ４サイズ当たり何個あるかで判定した。
【０２１２】
◎：０．４ｍｍ以上の黒ポチ頻度：全ての複写画像が３個／Ａ４以下（良好）
○：０．４ｍｍ以上の黒ポチ頻度：４個／Ａ４以上、１０個／Ａ４以下が１枚以上発生（実用上問題なし）
×：０．４ｍｍ以上の黒ポチ頻度：１１個／Ａ４以上が１枚以上発生（実用上問題有り）
白ヌケ（スタート時及び１万枚コピー毎にハーフトーン画像で評価）
白ヌケについては、周期性が感光体の周期と一致し、目視できる白ヌケが、Ａ４サイズ当たり何個あるかで判定した。
【０２１３】
◎：０．４ｍｍ以上の白ヌケ頻度：全ての複写画像が５個／Ａ４以下（良好）
○：０．４ｍｍ以上の白ヌケ頻度：６個／Ａ４以上、２０個／Ａ４以下が１枚以上発生（実用上問題なし）
×：０．４ｍｍ以上の白ヌケ頻度：２１個／Ａ４以上が１枚以上発生（実用上問題有り）
エッジ現象（ＨＨ、ＬＬ各５万枚コピー毎に評価）
ＨＨ及びＬＬ条件で各５万枚の連続コピー終了毎に、２ｃｍ幅の相対反射濃度０．５のベタ画像部を０．１ｍｍ幅で濃度測定し、中心部濃度と端部近傍の最大濃度の差でエッジ現象を評価した。
【０２１４】
◎：中心部濃度と端部近傍の最大濃度の差が０．０２より小さい（良好）
○：中心部濃度と端部近傍の最大濃度の差が０．０２〜０．０６（実用上問題なし）
×：中心部濃度と端部近傍の最大濃度の差が０．０６より大きい（実用上問題有り）
文字チリ（ＨＨ、ＬＬ各５万枚コピー毎に評価）
０．１ｍｍの線で作製された５ｃｍの幅の格子画像を先端部に有するオリジナル画像をコピーして評価した。評価はコピー画像を２０倍に拡大し、線の連続性及びチリの発生状況を観察した。
【０２１５】
◎：チリが無く、細線が連続している（良好）
○：チリが目視では判定できないレベルで軽微に発生し、細線が連続している（実用上問題なし）
△：チリが目視でも観察できるレベルで発生しているが細線は連続している（実用性再検討要）
×：チリが目視でも観察できるレベルで発生し、細線も断続する箇所が発生している（実用上問題有り）
画像濃度、階調性及び鮮鋭性の評価
上記評価条件を常温常湿（２０℃、６０％ＲＨ）環境に変更し、白画像から黒ベタ画像まで６０段階の階調段差を持つオリジナル画像を複写し、画像濃度と階調性を評価した。評価は複写画像の階調濃度をマクベス社製ＲＤ−９１８を使用して測定。紙の反射濃度を「０」とした相対反射濃度で測定した
（画像濃度）
◎：黒ベタ部濃度が１．３以上（良好）
○：黒ベタ部濃度が１．０〜１．３未満（実用上問題なし）
△：黒ベタ部濃度が０．７〜１．０未満（再評価が必要）
×：黒ベタ部濃度が０．７未満（実用上問題あり）
（階調性）
◎：階調性が４１段差以上（良好）
○：階調性が２１〜４０段差（実用上問題なし）
△：階調性が１１〜２０段差（実用性の再検討要：階調性が重視されない画質では実用性あり）
×：階調性が１０段差以下（実用上問題あり）
（鮮鋭性）
画像の鮮鋭性は、環境条件の厳しいＨＨ及びＬＬ環境において画像を出し、文字潰れで評価した。文字サイズ（ポイント）が異なる文字画像を形成し、下記の判断基準で評価した。
【０２１６】
◎：４ポイント以下の文字が明瞭であり、容易に判読可能（良好）
○：６ポイント以下の文字が明瞭であり、容易に判読可能（実用上問題なし）
△：８ポイント以下の文字が明瞭であり、容易に判読可能（再評価が必要）
×：８ポイントの文字の一部又は全部が判読不能（実用上問題あり）
【０２１７】
【表３】

【０２１８】
【表４】

【０２１９】
表３、表４から明らかなように、本発明の画像形成方法、即ち、有機金属化合物及びシランカップリング剤から選択された少なくとも一種を用いて形成された樹脂層の中間層を有する感光体１〜４、現像剤中のトナーの体積平均粒径が３．０〜７．０μｍであり、トナーの５０％個数粒径をＤｐ５０とすると、０．７×Ｄｐ５０以下のトナーの個数が１０個数％以下、及び未露光部電位ＶＨと現像スリーブに印加する直流バイアス電位ＶＤＣが前記１式及び２式を同時に満たす場合（組み合わせＮｏ．１〜３、８〜１０、１５〜１７、２２〜３３）は黒ポチ、白ヌケ、エッジ現象、文字チリ、画像濃度、階調性、鮮鋭性共良好であるが、｜ＶＨ｜−｜ＶＤＣ｜が３０Ｖ（組み合わせＮｏ．６、１３、２０）だと、黒ポチが発生し、階調性、鮮鋭性が低下している。｜ＶＨ｜−｜ＶＤＣ｜が３５０Ｖ（組み合わせＮｏ．７、１４、２１）だと、弱帯電性トナーの付着に起因した白ヌケ、文字チリが発生し、階調性、鮮鋭性が低下している。又、｜ＶＨ｜が１５５０（組み合わせＮｏ．５、１２、１９）だと、静電破壊による黒ポチの欠陥が発生しており、エッジ現象、文字チリの評価も低下し、鮮鋭性が劣化している。｜ＶＨ｜が８５０Ｖ（組み合わせＮｏ．４、１１、１８）では、階調性が低下している。一方、本発明外の感光体５（組み合わせＮｏ．３４、３５）を用いた場合は黒ポチが発生しやすく、エッジ現象や文字チリの評価も低下しており、鮮鋭性が劣化している。又、本発明外のトナー（０．７×Ｄｐ５０以下のトナーの個数が１０個数％より大きいトナー）を用いた組み合わせ（組み合わせＮｏ．３６、３７）では、白ヌケが発生し、エッジ現象、文字チリも劣化し、鮮鋭性が低下しており、（組み合わせＮｏ．３８〜４１）では、白ヌケが発生し、文字チリも発生しており、鮮鋭性が低下している。本発明外のトナー（体積平均粒径が２．５μｍのトナー）を用いた組み合わせ（組み合わせＮｏ．４２、４３）では、白ヌケが発生し、エッジ現象、文字チリも発生しており、階調性、鮮鋭性が低下し、本発明外のトナー（体積平均粒径が７．５μｍのトナー）を用いた組み合わせ（組み合わせＮｏ．４４、４５）では、階調性、鮮鋭性が不十分である。
【０２２０】
実施例２
実施例１で用いたトナーの作製において、着色分散液中のリーガル３３０Ｒ（キャボット社製カーボンブラック）の代わりにＣ．Ｉ．ピグメントイエロー１８５（Ｙトナー）、Ｃ．Ｉ．ピグメントレッド１２２（Ｍトナー）、Ｃ．Ｉ．ピグメントブルー１５：３（Ｃトナー）を用いた他は同様にして、トナー１Ｂｋ、トナー４Ｂｋと同じような形状係数等を有する表５のトナー１Ｙ、１Ｍ、１Ｃ、４Ｙ、４Ｍ、４Ｃ６種を作製した。これらのトナーの形状及び粒径等の物性は表５に示す。
【０２２１】
【表５】

【０２２２】
〔現像剤の製造〕
上記トナー１Ｙ、１Ｍ、１Ｃ、４Ｙ、４Ｍ、４Ｃの各々１０質量部と、平均粒径４５μｍのフェライト粒子のコアに絶縁性樹脂を被覆したキャリア１００質量部とを混合することにより、評価用の現像剤１Ｙ、１Ｍ、１Ｃ、４Ｙ、４Ｍ、４Ｃを製造した。
【０２２３】
これらの現像剤１Ｂｋ、１Ｙ、１Ｍ、１Ｃの現像剤１群、及び現像剤４Ｂｋ、４Ｙ、４Ｍ、４Ｃの現像剤４群を用い、図４記載の中間転写体を有するカラー画像形成装置に、感光体１と同じ処方で作製した４本、感光体５と同じ処方で作製した４本の各感光体を組み合わせ、カラー画像を作製した。このとき、未露光部電位ＶＨと現像スリーブに印加する直流バイアス電位ＶＤＣの条件を表６のように組み合わせた。
【０２２４】
評価は、実施例１と同じ評価を行った。評価結果も併せて表６に示す。
【０２２５】
【表６】

【０２２６】
表６からも明らかなように、中間転写体を用いた画像形成装置で作製したカラー画像も、上記実施例１のモノクロ画像の評価とほぼ同様の結果を示している。
【０２２７】
即ち、本発明の感光体、現像剤、未露光部電位ＶＨと現像スリーブに印加する直流バイアス電位ＶＤＣが前記１式及び２式を同時に満たす場合（組み合わせＮｏ．５１〜５３）は黒ポチ、白ヌケ、エッジ現象、文字チリ、画像濃度、階調性、鮮鋭性共良好であるが、感光体或いは現像剤が本発明外の組み合わせ（組み合わせＮｏ．５４〜５７）では、黒ポチ、白ヌケ、エッジ現象等が低下し、鮮鋭性が劣化したり（組み合わせＮｏ．５６、５７）、白ヌケ、文字チリが発生し、その結果、階調性や鮮鋭性が低下している（組み合わせＮｏ．５４、５５）。
【０２２８】
【発明の効果】
本発明の画像形成方法を用いることにより、黒ポチ、白ヌケ、エッジ現象、文字チリ等の画像欠陥の発生を防止し、且つ、高い画像濃度及び高階調性の電子写真画像が得られる。又、該画像形成方法を用いた画像性能の良好な画像形成装置を提供することが出来る。
【図面の簡単な説明】
【図１】本発明の画像形成方法の１例としての画像形成装置の断面図。
【図２】図１の感光体ドラムの帯電電位制御の構成を拡大した図。
【図３】未露光部目標電位の設定方法を説明する図。
【図４】本発明の一実施の形態を示すカラー画像形成装置の断面構成図である。
【符号の説明】
５０ 感光体ドラム（又は感光体）
５１ 帯電前露光部
５２ 帯電器
５３ 像露光器
５４ 現像器
５４１ 現像スリーブ
５４２ 搬送量規制部材
５４３ 現像剤攪拌搬送部材
５４４ 現像剤攪拌搬送部材
５４７ 電位センサー
５７ 給紙ローラー
５８ 転写電極
５９ 分離電極（分離器）
６０ 定着装置
６１ 排紙ローラー
６２ クリーニング器[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming method using an organic photoreceptor, and more particularly to an image forming method and an image forming apparatus for forming an electrostatic latent image on a photoreceptor by digital writing and performing reversal development.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a copying machine based on the Carlson method, which is the most typical electrophotographic method, a photoreceptor is uniformly charged, and then charges are erased imagewise by exposure to form an electrostatic latent image. Image formation has been performed by developing the electrostatic latent image with toner to visualize the image, and then transferring and fixing the toner to paper or the like.
[0003]
Until now, as an electrophotographic photoreceptor, an inorganic photoreceptor containing an inorganic photoconductive substance such as selenium, zinc oxide, cadmium or the like as a main component of a photosensitive layer has been widely used. However, many of these inorganic photoreceptors are harmful and have problems in environmental measures.
[0004]
Therefore, in recent years, organic photoreceptors using non-polluting organic substances have been actively developed and widely used. Above all, a function-separated type photoreceptor in which a charge generation function and a charge transport function are shared by different substances and a compound having desired characteristics can be selected from a wide range has been actively developed.
[0005]
In recent years, as a color image forming method by an electrophotographic method, a color image forming method of forming a color image on an electrophotographic photosensitive member by writing by digital signal processing has been actively performed.
[0006]
Therefore, the electrophotographic photoreceptor has good charging characteristics and sensitivity and low dark decay, as well as electrophotographic characteristics, wide gradation required for color images, and development of digital latent images. Appropriateness for the most suitable reversal development is required.
[0007]
That is, in order to broaden the gradation of an electrophotographic image, when the unexposed portion potential (VH) is increased in reversal development, minute defects of the potential are enlarged and black spots (color spots in the case of color) and color mixing become apparent. If it is lowered, sufficient gradation and image density cannot be obtained. Further, when the potential difference between the unexposed portion potential (VH) and the DC bias potential (VDC) between the photosensitive member and the developing sleeve is increased, minute defects in the potential are less likely to become apparent. And the problem that carrier adhesion easily occurs.
[0008]
When the electric potential (VH) of the unexposed portion is increased and the electric field intensity applied to the photosensitive member is increased, a phenomenon in which the edge portion potential of the electrostatic latent image rises becomes apparent, and the edge portion density of the toner image is also reduced. (Hereinafter, also referred to as an edge phenomenon), character dust tends to occur, and an image with poor gradation is likely to occur. In particular, when the edge phenomenon appears, in a color image that requires a large number of transfer steps of a toner image from a photoconductor to a recording sheet, character dust at the time of transfer and poor gradation are likely to appear.
[0009]
[Problems to be solved by the invention]
An object of the present invention is to provide an image forming method capable of obtaining a wide gradation property required for a color image or the like and good sharpness, imparting a high charging potential to an organic photoreceptor, It is an object of the present invention to provide an image forming method which reduces the occurrence of image defects such as black spots and white spots which are likely to occur when improving sharpness, and prevents toner and carrier from adhering. It is an object of the present invention to provide an image forming method capable of preventing an excessive edge phenomenon and a character dust which are likely to be generated when an electric potential is applied, and obtaining an electrophotographic image having a wide gradation and good sharpness. An object of the present invention is to provide an image forming apparatus using an image forming method.
[0010]
[Means for Solving the Problems]
As a result of repeated studies to solve the above-described problems, the present inventors have found that in order to obtain an electrophotographic image with good gradation and sharpness, a substantial development potential width (normal dynamic range (Referred to as the difference between the exposure potential and the bias potential), and at the same time, prevent excessive edge phenomena, which are likely to occur under high charging conditions caused by increasing the dynamic range, and The present inventors have found that it is necessary to improve the organic photoreceptor, developer and developing conditions that do not cause image defects such as black spots, white spots, and dust, and completed the present invention. That is, when forming an electrostatic latent image, the advantages of an organic photoreceptor having a small edge phenomenon and less occurrence of black spots and a developer capable of preventing the edge phenomenon and enabling a wide gradation and good sharpness can be obtained. The present invention was completed by examining development conditions that make use of the above, and finding out a combination in which a combination of these organic photoreceptor, developer, and development conditions produces a synergistic effect.
[0011]
That is, the object of the present invention is achieved by using the following configuration.
1. In an image forming method for forming an electrostatic latent image on an organic photoreceptor having a photosensitive layer on a conductive substrate and visualizing the electrostatic latent image into a toner image by reversal development, a toner used in the reversal development Assuming that the volume average particle diameter is 3.0 to 7.0 μm and the 50% number particle diameter of the toner is Dp50, the number of toners of 0.7 × Dp50 or less is 10 number% or less, The photoreceptor has an intermediate layer of a resin layer formed using at least one selected from an organic metal compound and a silane coupling agent between the conductive support and the photosensitive layer. The unexposed potential (VH) of the electrostatic latent image satisfies the following equation (1), and the relationship between the unexposed potential (VH) and the DC bias potential (VDC) applied to the developing sleeve satisfies the following equation (2). A characteristic image forming method.
[0012]
1 expression 900V ≦ | VH | ≦ 1500V
2 types 50V ≦ | VH | − | VDC | ≦ 300V
2. In an image forming method for forming an electrostatic latent image on an organic photoreceptor having a photosensitive layer on a conductive substrate and visualizing the electrostatic latent image into a toner image by reversal development, a toner used in the reversal development Has a volume average particle diameter of 3.0 to 7.0 μm and a ratio (Dv50 / Dp50) of 50% volume particle diameter (Dv50) to 50% number particle diameter (Dp50) of 1.0 to 1 .15, the ratio (Dv75 / Dp75) of the cumulative 75% volume particle size (Dv75) from the larger volume particle size to the cumulative 75% number particle size (Dp75) from the larger number particle size is 1.0 to 1.0; 1.20 and the number of toner particles having a particle size of 0.7 × (Dp50) or less is 10% by number or less, and the organic photoreceptor is an organic metal compound and a silane coupling between a conductive support and a photosensitive layer. In the resin layer formed using at least one selected from the agents The non-exposed potential (VH) of the electrostatic latent image at the developing position satisfies the following expression, and the unexposed potential (VH) and the DC bias potential ( (VDC) satisfying the following two expressions.
[0013]
1 expression 900V ≦ | VH | ≦ 1500V
2 types 50V ≦ | VH | − | VDC | ≦ 300V
3. Forming an electrostatic latent image corresponding to a yellow image on an organic photoreceptor having a photosensitive layer on a conductive substrate, developing the electrostatic latent image with a developer containing a yellow toner, Transferring the toner image formed on the carrier to the intermediate transfer member, forming an electrostatic latent image corresponding to the magenta image on the organic photoconductor, and developing the electrostatic latent image with a developer containing magenta toner. Developing, transferring the toner image formed on the organic photoreceptor to an intermediate transfer member, forming an electrostatic latent image corresponding to the cyan image on the organic photoreceptor, using a developer containing cyan toner Developing the electrostatic latent image, transferring the toner image formed on the organic photoreceptor to an intermediate transfer member, forming an electrostatic latent image corresponding to a black image on the organic photoreceptor, black The developer containing toner contains the electrostatic latent Developing an image, transferring a toner image formed on the organic photoreceptor to an intermediate transfer member, and transferring the toner image of each color transferred and formed on the intermediate transfer member to recording paper. At
When the volume average particle diameter of the toner in the developer is 3.0 to 7.0 μm and the 50% number particle diameter of the toner is Dp50, the number of toners of 0.7 × Dp50 or less is 10% by number. Wherein the organic photoreceptor has an intermediate layer of a resin layer formed using at least one selected from an organometallic compound and a silane coupling agent between the conductive support and the photosensitive layer. The unexposed potential (VH) of the electrostatic latent image at the developing position satisfies the following expression, and the relationship between the unexposed potential (VH) and the DC bias potential (VDC) applied to the developing sleeve is as follows. An image forming method characterized by satisfying the following two expressions.
[0014]
1 expression 900V ≦ | VH | ≦ 1500V
2 types 50V ≦ | VH | − | VDC | ≦ 300V
4. Forming an electrostatic latent image corresponding to a yellow image on an organic photoreceptor having a photosensitive layer on a conductive substrate, developing the electrostatic latent image with a developer containing a yellow toner, Transferring the toner image formed on the carrier to the intermediate transfer member, forming an electrostatic latent image corresponding to the magenta image on the organic photoconductor, and developing the electrostatic latent image with a developer containing magenta toner. Developing, transferring the toner image formed on the organic photoreceptor to an intermediate transfer member, forming an electrostatic latent image corresponding to the cyan image on the organic photoreceptor, using a developer containing cyan toner Developing the electrostatic latent image, transferring the toner image formed on the organic photoreceptor to an intermediate transfer member, forming an electrostatic latent image corresponding to a black image on the organic photoreceptor, black The developer containing toner contains the electrostatic latent Developing an image, transferring a toner image formed on the organic photoreceptor to an intermediate transfer member, and transferring the toner image of each color transferred and formed on the intermediate transfer member to recording paper. At
The toner in the developer has a volume average particle diameter of 3.0 to 7.0 μm, and a ratio (Dv50 / Dp50) of 50% volume particle diameter (Dv50) to 50% number particle diameter (Dp50) of the toner. Is 1.0 to 1.15, and the ratio (Dv75 / Dp75) of the cumulative 75% volume particle size (Dv75) from the larger volume particle size to the cumulative 75% number particle size (Dp75) from the larger number particle size. ) Is 1.0 to 1.20 and the number of toner particles having a particle size of 0.7 × (Dp50) or less is 10% by number or less, and the organic photoconductor is an organic photoconductor between the conductive support and the photosensitive layer. It has an intermediate layer of a resin layer formed using at least one selected from a metal compound and a silane coupling agent, and the unexposed potential (VH) of the electrostatic latent image at the developing position is represented by the following formula: Is satisfied, and the unexposed potential (VH) is directly applied to the developing sleeve. An image forming method, wherein a relationship with a current bias potential (VDC) satisfies the following two equations.
[0015]
1 expression 900V ≦ | VH | ≦ 1500V
2 types 50V ≦ | VH | − | VDC | ≦ 300V
5. 5. The image forming method according to any one of items 1 to 4, wherein the organometallic compound is a metal alkoxide or an organometallic chelate.
[0016]
6. The image forming method according to any one of claims 1 to 4, wherein the intermediate layer is a layer formed using an organic metal chelate and a silane coupling agent.
[0017]
7. 7. The image forming method according to the above item 5 or 6, wherein the organic metal chelate is a compound represented by the following general formula (1).
[0018]
General formula (1) (R₁O)_g-M- (K)_m
(Where R₁Is an alkyl group, and M represents zirconium, titanium or aluminum. K represents an acetoacetic ester residue or a β-diketone residue. g and m represent an integer of 1 or more. However, when M is zirconium or titanium, g + m is 4, and when M is aluminum, g + m is 3. )
8. The image forming method according to any one of Items 1 to 7, wherein the silane coupling agent is a compound represented by the following general formula (2).
[0019]
General formula (2) (Q)_p-Si (Y)_q-(A)_r
(Wherein, Q represents a halogen atom, an alkoxy group or an amino group, A represents an alkyl group or an aryl group, and Y represents -BOOC (R ') C = CH₂, -BNHR "or -BNH₂Represents R 'represents an alkyl group, R "represents an alkyl group or an aryl group, B represents an alkylene group or an alkylene group containing -O-, -NH-, -CO-, and p and q are integers of 1 or more. And r represents an integer of 0 or more, and p + q + r is 4.)
9. An image forming apparatus that forms an electrophotographic image by using the image forming method according to any one of the above items 1 to 8.
[0020]
Hereinafter, the present invention will be described in detail.
First, an image forming method and an image forming apparatus for reversal development according to the present invention will be described. An embodiment of an image forming apparatus according to the present invention will be specifically described with reference to the accompanying drawings, and a specific example of forming an image using the image forming apparatus and the developing device of the embodiment will be described. It will be clarified that the image forming method of the present invention can provide an image with satisfactory gradation and image density without black spots and fog.
[0021]
FIG. 1 is a sectional view of an image forming apparatus as an example of the image forming method of the present invention.
In FIG. 1, reference numeral 50 denotes a photoreceptor drum (photoreceptor) serving as an image carrier, which is a photoreceptor of the present invention in which an organic photosensitive layer is applied on the drum, and is driven to rotate clockwise while being grounded. Reference numeral 52 denotes a scorotron charger for uniformly charging the peripheral surface of the photosensitive drum 50 by corona discharge. Prior to the charging by the charger 52, in order to eliminate the history of the photoreceptor in the previous image formation, exposure by the pre-charging exposure unit 51 using a light emitting diode or the like may be performed to remove the charge on the peripheral surface of the photoreceptor.
[0022]
After the photosensitive member is uniformly charged, the image exposure device 53 performs image exposure based on the image signal. The image exposure device 53 in this figure uses a laser diode (not shown) as an exposure light source. The light on the photosensitive drum is scanned by the light whose optical path is bent by the reflection mirror 532 via the rotating polygon mirror 531 and the fθ lens and the like, and an electrostatic latent image is formed.
[0023]
Here, the unexposed portion potential of the photoreceptor of the present invention means the photoreceptor surface potential in a region where the charger 52 uniformly charges the photoreceptor surface and where image exposure is not performed. The exposed portion potential means the surface potential of the photoreceptor in the area where the image exposure has been performed. The potential measurement is performed by providing the potential sensor 547 at the developing position as shown in FIG.
[0024]
In the image forming method of the present invention, when forming an electrostatic latent image on a photoreceptor, an image exposure is performed with a spot area of 2000 μm.²It is preferable to use the following exposure beam. Even if such small-diameter beam exposure is performed, the organic photoreceptor of the present invention can faithfully form an image corresponding to the spot area. More preferable spot area is 100 to 800 μm²It is. As a result, an electrophotographic image with rich gradation can be achieved at 800 dpi (dpi is the number of dots per 2.54 cm) or more.
[0025]
The spot area of the exposure beam is defined as a light intensity distribution surface appearing on the cut surface when the exposure beam is cut along a plane perpendicular to the beam, and the light intensity is 1 / e of the maximum peak intensity.²It means an area corresponding to the above region.
[0026]
The light beam used includes a scanning optical system using a semiconductor laser, a solid-state scanner such as an LED or a liquid crystal shutter, and the like.²The area up to is the spot area.
[0027]
The electrostatic latent image is then developed using a developing device 54 in a developing step. A developing device 54 containing a developer including a toner and a carrier is provided on the peripheral edge of the photosensitive drum 50, and development is performed by a developing sleeve 541 that contains a magnet and rotates while holding the developer. The inside of the developing device 54 is composed of developer stirring / conveying members 544 and 543, a conveyance amount regulating member 542, and the like. The developer is agitated and conveyed and supplied to the developing sleeve. Controlled by member 542. The transport amount of the developer varies depending on the linear velocity of the applied organic electrophotographic photosensitive member and the specific gravity of the developer, but is generally 20 to 200 mg / cm.²Range.
[0028]
The developer is, for example, a carrier in which an insulating resin is coated around the above-described ferrite as a core, a colorant such as carbon black, a charge control agent, and a low molecular weight polyolefin of the present invention using the above-described styrene acrylic resin as a main material. The toner is a toner in which silica, titanium oxide, or the like is externally added to colored particles made of, and the developer is transported to a developing area with the layer thickness regulated by a transport amount regulating member, where development is performed. At this time, normally, a DC bias voltage and, if necessary, an AC bias voltage are applied to the developing sleeve 541 to perform development. Further, the developer is developed in a state of contact or non-contact with the photoconductor.
[0029]
After the image is formed, the recording paper P is fed to the transfer area by the rotation of the paper feed roller 57 at the time when the transfer timing is adjusted.
[0030]
In the transfer area, a transfer electrode (transfer device) 58 is pressed against the peripheral surface of the photosensitive drum 50 in synchronization with the transfer timing, and the fed recording paper P is sandwiched and transferred.
[0031]
Next, the recording paper P is neutralized by a separation electrode (separator) 59 which is brought into pressure contact with the transfer roller almost at the same time, separated by the peripheral surface of the photosensitive drum 50, conveyed to the fixing device 60, and pressed against the heat roller 601. After the toner is fused by heating and pressing the roller 602, the toner is discharged to the outside of the apparatus via the discharge roller 61. The transfer electrode 58 and the separation electrode 59 are retracted and separated from the peripheral surface of the photosensitive drum 50 after the recording paper P has passed, in preparation for the formation of the next toner image.
[0032]
On the other hand, after the recording paper P is separated, the photosensitive drum 50 removes and cleans the residual toner by pressing the blade 621 of the cleaning device 62 and receives the charge removal by the pre-charge exposure unit 51 and the charge by the charger 52 again. Enter the image forming process.
[0033]
Reference numeral 70 denotes a detachable process cartridge in which a photosensitive member, a charger, a transfer device, a separator, and a cleaning device are integrated.
[0034]
FIG. 2 is an enlarged view of the configuration of controlling the charging potential of the photosensitive drum 50 of FIG.
[0035]
Hereinafter, a method of measuring the potential of the unexposed portion and a process of adjusting the charged potential for correcting the potential of the unexposed portion will be described with reference to FIG.
[0036]
First, the photoconductor 50 is uniformly charged by the charger 52. An unexposed area that is not digitally exposed by the laser diode image exposure device 53 is formed on the charged photoconductor. The surface potential (unexposed portion potential) of the unexposed area is detected by the potential sensor 547, and the detected potential signal is transmitted to the process control unit 63 in FIG. The process controller 63 is a process controller that controls the band electrodes based on the potential signal from the potential sensor 547. The controller compares the potential signal from the potential sensor with the target potential signal, corrects the difference, and determines a correction signal that achieves the target potential. The high-voltage control unit 64 is a high-voltage control unit that receives a control signal from the process control unit 63 and supplies current and voltage to the charger 52. Based on the determined correction signal, a correction signal of a charging current and a charging grid voltage is output from the process controller to the high voltage control unit. The charged charging current and charging grid voltage are output. By repeating this process several times, the photoconductor potential (unexposed portion potential) at the potential sensor position can be corrected to the target potential.
[0037]
In order to accurately measure the unexposed portion potential at the developing position of the photoreceptor, it is preferable to attach the potential sensor to the developing position and remove the developing device if necessary. If the mounting position is far from the developing position, the potential dark decay amount from the potential sensor to the developing position may be calculated and corrected accordingly.
[0038]
Here, the development position indicates a position where the latent image on the photoconductor is developed by the developer. Specifically, the position where the photoconductor and the developing sleeve are closest to each other is regarded as the center of the development position. That is, in the present invention, the unexposed portion potential at the developing position indicates the surface potential of the unexposed portion when the photosensitive member is closest to the developing sleeve.
[0039]
There are various methods for setting the unexposed portion target potential. In the reversal developing method used in the present invention, the following method for setting the unexposed portion target potential (described with reference to FIG. 3) is preferable. Used.
[0040]
That is, as shown in FIG. 3, at the start of daily use of a printer or a copier or every predetermined number of prints, the photosensitive member is charged and image exposed, and the exposed portion potential (VL) after the image exposure is detected by a potential sensor. Detected by Based on the VL, a developing bias potential that controls the image density is set, and then, based on the developing bias potential, an unexposed portion target potential (VH) for preventing fogging is set.
[0041]
The condition of the reversal development of the present invention is that the unexposed portion potential (VH) at the developing position of the photoreceptor is 900 to 1500 V, more preferably 1000 to 1450 V in absolute value. The difference (developing bias) between VH and the DC bias potential (VDC) applied to the developing sleeve is 50 to 300 V, more preferably 70 to 250 V. Even under such high voltage conditions, when reversal development is performed using the photoreceptor and the developer of the present invention, the occurrence of black spots specific to reversal development is reduced, and the edge phenomenon and character dust are improved. An electrophotographic image with good gradation and sharpness can be obtained. If | VH | is lower than 900 V, the gradation tends to be low, and if it exceeds 1500 V, excessive edge phenomena occur, and image defects such as character dust and black dots tend to occur. If the difference | VH |-| VDC | is less than 50 V, image defects such as black spots are likely to occur, and if it exceeds 300 V, the occurrence of adhesion of weakly chargeable toner and the adhesion of carriers will increase.
[0042]
In the present invention, the distance (Dsd) between the organic photosensitive member and the developing sleeve carrying the developer is preferably 350 to 800 μm, and the linear velocity ratio between the photosensitive member and the developing sleeve is preferably in the range of 1: 1 to 1: 3.5. . When the Dsd exceeds 800 μm, the developing electric field is weakened, and the developability is reduced.
[0043]
The organic photoreceptor of the present invention has a photosensitive layer on a conductive substrate, and is formed between the conductive support and the photosensitive layer using at least one selected from an organometallic compound and a silane coupling agent. It is characterized by having an intermediate layer of a resin layer.
[0044]
Here, the resin layer formed using at least one selected from an organometallic compound or a silane coupling agent is a conductive support using a coating solution containing at least one organometallic compound or a silane coupling agent. Forming a coating film on the body and curing the coating film to form a resin layer having a ceramic structure having a metal oxide structure, a siloxane structure, or both structures. For the curing of the coating film, it is preferable to perform a heat treatment after the formation of the coating film. Hereinafter, the organometallic compound and the silane coupling agent will be described.
[0045]
《Organic metal compound, silane coupling》
Examples of the organometallic compound contained in the intermediate layer of the photoreceptor of the present invention include, for example, alkoxide compounds such as zirconium tetra-n-propylate, aluminum isopropylate, mono-sec-butoxyaluminum-i-propylate, and aluminum-sec-butylate. And groups 1a, 1b, 2a, 3a, 3b, 4a, 4b, 5a, 5b and 8b of the periodic table Organic molecules coordinated in the range of 3, 4, 6, and 8 molecules with a metal atom selected from the group consisting of acetoacetate, β-diketone, acetylacetone, catechol, ethylenediamine, o-phenylenebisdimethylaniline and the like as a chelating agent It may be a metal chelate compound.
[0046]
However, in the intermediate layer of the photoreceptor of the present invention, the organometallic compound represented by the general formula (1) is used as the organometallic compound, and the silane coupling agent represented by the general formula (2) is used in combination. It is preferable to include them.
[0047]
In the general formula (1), R₁Is a lower alkyl group, M represents a metal atom such as zirconium, titanium or aluminum, a chelating group K represents an acetoacetate residue or a β-diketone residue, and g and m represent integers of 1 or more. . However, when M is zirconium or titanium, g + m is 4, and when M is aluminum, g + m is 3.
[0048]
Specific examples of the organometallic chelate compound represented by the general formula (1) include, for example,
Diisopropoxy titanium (methyl acetoacetate)
Isobutoxy titanium tri (methyl acetoacetate)
Tributoxy titanium acetylacetonate
Aluminum diisopropoxy (methyl acetoacetonate)
Dibutoxy titanium bis (ethyl acetoacetonate)
Aluminum isobutoxy (acetylacetonate)
And the like.
[0049]
Next, in the silane coupling agent represented by the general formula (2), Q represents a halogen atom, a lower alkoxy group or an amino group which may have a substituent, and A represents a lower alkyl group, a phenyl group or a naphthyl group. And the organic functional group Y is -BOOC (R ') C = CH₂, -BNHR "or -BNH₂Represents R ′ represents a lower alkyl group; R ″ represents a lower alkyl group or an aryl group such as a phenyl group or a naphthyl group; and B represents a lower alkylene group or a lower alkylene group containing —O—, —NH—, and —CO—. P and q represent an integer of 1 or more, r represents an integer of 0 or more, and p + q + r is 4.
[0050]
Specific examples of the silane coupling agent represented by the general formula (2) include, for example,
γ-methacryloxypropyltrimethoxysilane
γ-methacryloxypropyltriethoxysilane
γ-methacryloxypropylmethyldimethoxysilane
Etc. can be given.
[0051]
In the present invention, the thickness of the intermediate layer is preferably from 0.1 to 10 μm, and particularly preferably from 0.1 to 5 μm.
[0052]
Solvents or dispersion media used for forming the intermediate layer, photosensitive layer and other resin layers of the present invention include n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, acetone , Methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, dichloromethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, trichloroethylene, Tetrachloroethane, tetrahydrofuran, dioxolan, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl chloride Cellosolve, and the like.
[0053]
The solvent for the intermediate layer coating solution is not limited to these, but methanol, ethanol, butanol, 1-propanol, isopropanol, and the like are preferably used. In addition, these solvents can be used alone or as a mixed solvent of two or more kinds.
[0054]
Further, as the intermediate layer coating solvent, it is preferable to use a mixed solvent of methanol and straight-chain alcohol having high resin solubility in order to prevent the occurrence of drying unevenness at the time of coating the intermediate layer. What mixed the linear alcohol with the ratio of 0.05-0.6 with respect to methanol 1 by volume ratio is good. By using a mixed solvent as the coating solvent in this manner, the evaporation rate of the solvent is appropriately maintained, and the occurrence of image defects due to drying unevenness during coating can be suppressed.
[0055]
As the coating method for producing the electrophotographic photoreceptor of the present invention, including the intermediate layer, a coating method such as dip coating, spray coating, and circular amount control type coating is used. It is preferable to use a coating method such as spray coating or circular amount control type (a typical example is a circular slide hopper type) in order to avoid dissolving the lower layer film as much as possible and to achieve uniform coating. . The spray coating is described in detail in, for example, JP-A-3-90250 and JP-A-3-269238, and the circular amount control type coating is described in detail in, for example, JP-A-58-189061. I have.
[0056]
By providing an intermediate layer of a resin layer formed using at least one selected from such an organometallic compound and a silane coupling agent on a conductive support and a photosensitive layer, a free carrier of the intermediate layer (conductive support) is provided. It is possible to enhance the blocking property of electrons and holes entering from the body, etc., and at the same time, it is possible to prevent edge phenomena that are likely to occur when forming a latent image under a high electric field, and as a result, image defects such as character dust , And an electrophotographic image having good gradation and sharpness can be obtained.
[0057]
Next, the structure of the photoconductor other than the intermediate layer, which is preferably used in the present invention, will be described.
[0058]
As the photoconductor of the present invention, for the purpose of the present invention, it is preferable to apply the intermediate layer of the present invention to an organic electrophotographic photoconductor (also referred to as an organic photoconductor).
[0059]
In the present invention, the organic photoreceptor refers to an electrophotographic photoreceptor constituted by providing an organic compound with at least one of a charge generation function and a charge transport function, which are indispensable for the configuration of the electrophotographic photoreceptor. And all known organic electrophotographic photoreceptors, such as a photoreceptor composed of an organic charge generating substance or an organic charge transporting substance, and a photoreceptor having a charge generating function and a charge transporting function formed of a polymer complex.
[0060]
The layer structure of the organic photoreceptor is not particularly limited, but basically includes a charge generation layer, a charge transport layer, or a charge generation / charge transport layer (a layer having both functions of charge generation and charge transport). Although it is composed of a photosensitive layer, a constitution in which a surface layer is coated thereon may be used. Further, the surface layer has a function of a protective layer and a function of transporting charges, and thus may be used instead of the charge transporting layer.
[0061]
Hereinafter, a specific configuration of the photoconductor used in the present invention will be described.
Conductive support
As the conductive support used in the photoreceptor of the present invention, a sheet-shaped or cylindrical conductive support is used.
[0062]
The cylindrical conductive support of the present invention means a cylindrical support required to be able to form an image endlessly by rotation, and has a straightness of 0.1 mm or less and a runout of 0.1 mm or less. Certain conductive supports are preferred. Exceeding the ranges of straightness and runout makes it difficult to form a good image.
[0063]
As a material for the conductive support, a metal drum such as aluminum or nickel, a plastic drum on which aluminum, tin oxide, indium oxide, or the like is deposited, or a paper / plastic drum coated with a conductive substance can be used. The conductive support has a specific resistance of 10 at room temperature.³Ωcm or less is preferable.
[0064]
The conductive support used in the present invention may have a surface on which a sealed alumite film is formed. The alumite treatment is usually performed in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, and sulfamic acid. Anodizing treatment in sulfuric acid gives the most preferable result. In the case of anodic oxidation treatment in sulfuric acid, it is preferable that the sulfuric acid concentration is 100 to 200 g / L, the aluminum ion concentration is 1 to 10 g / L, the liquid temperature is about 20 ° C., and the applied voltage is about 20 V. It is not limited. The average thickness of the anodic oxide coating is usually 20 μm or less, particularly preferably 10 μm or less.
[0065]
Middle class
In the present invention, the above-mentioned intermediate layer having a barrier function is provided between the conductive support and the photosensitive layer.
[0066]
Photosensitive layer
The photosensitive layer structure of the photoreceptor of the present invention may have a single-layer structure in which a charge generation function and a charge transport function are provided in one layer on the intermediate layer. It is preferable to adopt a configuration separated into a generation layer (CGL) and a charge transport layer (CTL). By adopting a configuration in which functions are separated, an increase in residual potential due to repeated use can be controlled to be small, and other electrophotographic characteristics can be easily controlled according to the purpose. In the negatively charged photoreceptor, it is preferable that a charge generation layer (CGL) is formed on the intermediate layer, and a charge transport layer (CTL) is formed thereon. In the case of a positively charged photoreceptor, the order of the layer configuration is opposite to that of the negatively charged photoreceptor. The most preferable constitution of the photosensitive layer of the present invention is a constitution of a negatively charged photoreceptor having the function separation structure.
[0067]
The configuration of the photosensitive layer of the function-separated negatively charged photoconductor will be described below.
Charge generation layer
The charge generation layer contains a charge generation material (CGM). As other substances, a binder resin and other additives may be contained as necessary.
[0068]
As the charge generation material (CGM), a known charge generation material (CGM) can be used. For example, phthalocyanine pigments, azo pigments, perylene pigments, azurenium pigments and the like can be used. Among these, CGM which can minimize the increase in residual potential due to repeated use has a steric and potential structure capable of forming a stable aggregated structure between a plurality of molecules, and specifically, a phthalocyanine having a specific crystal structure And CGM of a perylene pigment.
[0069]
As the phthalocyanine pigment, a titanyl phthalocyanine pigment having the following chemical structural formula is well known as a charge generating substance.
[0070]
Embedded image

[0071]
(Wherein, X represents a halogen atom, and n represents a number from 0 to 1). When X is a chlorine atom, n is preferably from 0 to 0.5, more preferably from 0 to 0.1.
[0072]
In the present invention, among these titanyl phthalocyanine pigments, titanyl phthalocyanine (oxytitanyl phthalocyanine) having a maximum peak at 27.2 ° at a Bragg angle (2θ ± 0.2 °) of X-ray diffraction with respect to Cu-Kα X-ray, It is preferable to use a titanyl phthalocyanine pigment having remarkable peaks at 7.5 ° and 28.5 ° at 2θ ± 0.2. These titanyl phthalocyanine pigments generate environmental memory when black and white image defects occur when environmental fluctuations in temperature and humidity occur, or black spots occur in a high-temperature and high-humidity environment, or for a long time. Although continuous printing has a characteristic that image density tends to decrease, when combined with the intermediate layer of the present invention, such a defect is eliminated and a good electrophotographic image can be obtained.
[0073]
In the case where a binder is used as a dispersion medium of CGM in the charge generation layer, a known resin can be used as the binder, but the most preferable resin is a formal resin, a butyral resin, a silicone resin, a silicone-modified butyral resin, a phenoxy resin, and the like. No. The ratio between the binder resin and the charge generating substance is preferably from 20 to 600 parts by mass per 100 parts by mass of the binder resin. By using these resins, an increase in residual potential due to repeated use can be minimized. The thickness of the charge generation layer is preferably from 0.1 μm to 2 μm.
[0074]
Charge transport layer
The charge transport layer contains a charge transport material (CTM) and a binder resin that disperses the CTM and forms a film. As other substances, additives such as antioxidants may be contained as necessary.
[0075]
As the charge transport material (CTM), a known charge transport material (CTM) can be used. For example, triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine compounds, butadiene compounds and the like can be used. These charge transporting substances are usually dissolved in a suitable binder resin to form a layer. Among these, the CTM that can minimize the increase in residual potential due to repeated use has a high mobility and a characteristic that the ionization potential difference with the CGM to be combined is 0.5 (eV) or less, and is preferably 0. .30 (eV) or less.
[0076]
The ionization potential of CGM and CTM is measured with a surface analyzer AC-1 (manufactured by Riken Keiki Co., Ltd.).
[0077]
Examples of the resin used for the charge transport layer (CTL) include polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, and polycarbonate. Resins, silicone resins, melamine resins, and copolymer resins containing two or more of the repeating unit structures of these resins. In addition to these insulating resins, polymer organic semiconductors such as poly-N-vinyl carbazole may be used.
[0078]
The most preferred binder for these CTLs is a polycarbonate resin. Polycarbonate resins are most preferred in improving the dispersibility and electrophotographic properties of CTM. The ratio between the binder resin and the charge transporting material is preferably from 10 to 200 parts by mass per 100 parts by mass of the binder resin. The thickness of the charge transport layer is preferably from 10 to 40 μm.
[0079]
Surface layer
As a surface layer (protective layer) of the photoreceptor, a layer using siloxane polycarbonate or a crosslinkable siloxane-based resin as a binder may be provided.
[0080]
Although the most preferred layer configuration of the photoreceptor of the present invention has been described above, other layer configurations of the photoreceptor may be used in the present invention.
[0081]
Solvents or dispersion media used for forming layers such as a photosensitive layer, an intermediate layer, and a surface layer include n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, acetone, and methyl ethyl ketone. , Methyl isopropyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, dichloromethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethane , Tetrahydrofuran, dioxolan, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cellosolve, etc. And the like. Although the present invention is not limited to these, dichloromethane, 1,2-dichloroethane, methyl ethyl ketone and the like are preferably used. In addition, these solvents can be used alone or as a mixed solvent of two or more kinds.
[0082]
Further, it is preferable that the coating solution for each of these layers is filtered through a metal filter, a membrane filter or the like in order to remove foreign substances and aggregates in the coating solution before entering the coating step. For example, it is preferable to select a pleated type (HDC), a depth type (profile), a semi-depth type (profile star), etc., manufactured by Nippon Pall Co., Ltd. in accordance with the characteristics of the coating solution, and then perform filtration.
[0083]
Next, as a coating processing method for manufacturing an organic electrophotographic photoreceptor, coating processing methods such as dip coating, spray coating, and circular amount control type coating are used. In order to prevent the film from being dissolved as much as possible and to achieve a uniform coating process, it is preferable to use a coating process method such as spray coating or coating with a circular amount control type (a typical example is a circular slide hopper type). It is most preferable that the protective layer be formed by the above-mentioned circular amount-regulating coating method. The circular amount control type coating is described in detail in, for example, JP-A-58-189061.
[0084]
The toner according to the image forming method of the present invention will be described.
The toner in the developer used in the image forming method of the present invention has a volume average particle diameter of 3.0 to 7.0 μm, and assuming that the 50% number particle diameter of the toner is Dp50, 0.7 × Dp50 or less. Is 10% by number or less.
[0085]
The toner in the developer has a volume average particle diameter of 3.0 to 7.0 μm, and a ratio (Dv50 / Dp50) of the 50% volume particle diameter (Dv50) to the 50% number particle diameter (Dp50) of the toner. 1.0 to 1.15, the ratio (Dv75 / Dv75 / Dv75) of the cumulative 75% volume particle size (Dv75) from the larger volume particle size to the cumulative 75% number particle size (Dp75) from the larger number particle size. Dp75) is 1.0 to 1.20, and the number of toner particles having a particle size of 0.7 × (Dp50) or less is 10% by number or less.
[0086]
By performing reversal development on the developer containing the toner as described above under the condition of the specific organic photoreceptor, the electric field strength stronger than the conventional development condition satisfying the above formulas (1) and (2), An edge phenomenon which is likely to occur under a high electric field is prevented, and as a result, an electrophotographic image with less character dust, good gradation and sharpness can be obtained.
[0087]
When the ratio of the small particle size component in the toner is high, the inventors of the present invention tend to increase the edge phenomenon in the toner image after development, and as a result, character dust occurs and the gradation is insufficient. Easy to become photographic images. In the present invention, in order to prevent the edge phenomenon from increasing during development, the ratio of the small particle size component in the toner is defined as 50% of the toner particle size, and the particle size is defined as Dp50. Can be achieved by setting the content to 10% by number or less. As a result, it is possible to prevent character dust that easily occurs at the time of transfer, and to obtain an electrophotographic image with good gradation and sharpness.
[0088]
Further, the toner used in the present invention can obtain a further effect by reducing the ratio of the small particle size components and having a distribution closer to monodispersion. That is, the toner used in the present invention has a ratio (Dv50 / Dp50) of 50% volume particle diameter (Dv50) to 50% number particle diameter (Dp50) of 1.0 to 1.15, and a volume particle diameter of the toner. The ratio (Dv75 / Dp75) of the cumulative 75% volume particle size (Dv75) from the larger toner particle size to the cumulative 75% number particle size (Dp75) from the larger number particle size of the toner is 1.0 to 1 .20, and the total number of toner particles having a particle size of 0.7 × (Dp50) or less has a particle size distribution of 10% by number or less. It is possible to obtain an excellent electrophotographic image which is good and free from edge effects and character dust.
[0089]
The toner according to the present invention (hereinafter, also simply referred to as toner) will be described.
First, the volume particle diameter and the number particle diameter of the toner according to the present invention and the ratio between the volume particle diameter and the number particle diameter will be described.
[0090]
From the viewpoint of obtaining the effects described in the present invention, the toner according to the present invention is preferably monodispersed in terms of particle size distribution, and the ratio (50% volume particle size (Dv50)) to 50% number particle size (Dp50) ( Dv50 / Dp50) needs to be 1.0 to 1.15, but is preferably 1.0 to 1.13.
[0091]
Further, in order to suppress the fluctuation range of the transferability and the developability, the ratio (Dv75 / Dp75) of the 75% volume particle diameter (Dv75) and the 75% number particle diameter (Dp75) from the larger toner is 1 0.01 to 1.20, but preferably 1.1 to 1.19. Further, the number of toner particles having a particle size of 0.7 × (Dp50) or less needs to be 10% by number or less in all the toners, but is preferably 5% to 9% by number.
[0092]
The 50% volume particle diameter (Dv50) of the toner according to the present invention is preferably 3 μm to 7 μm, and more preferably 3.5 μm to 6.5 μm. Further, the 50% number particle size (Dp50) of the toner according to the present invention is preferably 2 μm to 6.5 μm, and more preferably 2.5 μm to 6 μm. By setting the content within this range, the effects of the present invention can be more remarkably exhibited.
[0093]
Here, the cumulative 75% volume particle size (Dv75) or the cumulative 75% number particle size (Dp75) from the larger one is the frequency from the larger particle size is accumulated and the sum of the total volume or the sum of the number is calculated. On the other hand, it is expressed by the volume particle size or the number particle size of the particle size distribution portions each showing 75%.
[0094]
In the present invention, the 50% volume particle size (Dv50), the 50% number particle size (Dp50), the cumulative 75% volume particle size (Dv75), the cumulative 75% number particle size (Dp75), and the like are based on Coulter Counter TA-II. Alternatively, it can be measured with a Coulter Multisizer (manufactured by Coulter).
[0095]
The components of the toner according to the present invention, the components of the binder resin that is a component of the toner, and the production thereof will be described.
[0096]
Although the toner according to the present invention contains at least a colorant, a binder resin, and the like, the toner may be produced through a pulverizing / classifying step, and is obtained by polymerizing a polymerizable monomer as shown below. It may be manufactured by a so-called polymerization method in which a toner is manufactured using the resin particles obtained. When a toner is produced by a polymerization method, a production method having a step of salting out / fusing resin particles is particularly preferable.
[0097]
As the polymerizable monomer used in the polymerization method, a radical polymerizable monomer is used as a component, and a crosslinking agent can be used as necessary. It is preferable that at least one of the following radical polymerizable monomers having an acidic group or a radical polymerizable monomer having a basic group is contained.
[0098]
(1) Radical polymerizable monomer
The radical polymerizable monomer component is not particularly limited, and a conventionally known radical polymerizable monomer can be used. Further, one kind or a combination of two or more kinds can be used so as to satisfy required characteristics.
[0099]
Specifically, aromatic vinyl monomers, (meth) acrylate monomers, vinyl ester monomers, vinyl ether monomers, monoolefin monomers, diolefin monomers And halogenated olefin monomers.
[0100]
Examples of the aromatic vinyl monomer include, for example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, p-ethylstyrene, and p-methylstyrene. -N-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, 2, Styrene-based monomers such as 4-dimethylstyrene and 3,4-dichlorostyrene, and derivatives thereof.
[0101]
(Meth) acrylic ester monomers include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, methacrylic acid Examples thereof include butyl, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, stearyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate.
[0102]
Examples of the vinyl ester monomer include vinyl acetate, vinyl propionate, and vinyl benzoate.
[0103]
Examples of the vinyl ether monomer include vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, vinyl phenyl ether and the like.
[0104]
Examples of the monoolefin-based monomer include ethylene, propylene, isobutylene, 1-butene, 1-pentene, 4-methyl-1-pentene, and the like.
[0105]
Examples of the diolefin-based monomer include butadiene, isoprene, and chloroprene.
[0106]
Examples of the halogenated olefin-based monomer include vinyl chloride, vinylidene chloride, and vinyl bromide.
[0107]
(2) Crosslinking agent
As a crosslinking agent, a radical polymerizable crosslinking agent may be added in order to improve the properties of the toner. Examples of the radical polymerizable crosslinking agent include those having two or more unsaturated bonds such as divinylbenzene, divinylnaphthalene, divinylether, diethylene glycol methacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, and diallyl phthalate.
[0108]
(3) Radical polymerizable monomer having an acidic group or radical polymerizable monomer having a basic group
Examples of the radical polymerizable monomer having an acidic group or the radical polymerizable monomer having a basic group include, for example, a polymerizable monomer having a carboxyl group, a polymerizable monomer having a sulfonic acid group, And amine-based polymerizable monomers such as secondary amines, secondary amines, tertiary amines, and quaternary ammonium salts.
[0109]
Examples of the polymerizable monomer having a carboxyl group include acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, cinnamic acid, monobutyl maleate, and monooctyl maleate.
[0110]
Examples of the polymerizable monomer having a sulfonic acid group include styrene sulfonic acid, allyl sulfosuccinic acid, octyl allyl sulfosuccinate, and the like.
[0111]
These may have a structure of an alkali metal salt such as sodium or potassium or an alkaline earth metal salt such as calcium.
[0112]
Examples of the radical polymerizable monomer having a basic group include amine compounds, such as dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, and quaternary ammonium salts of the above four compounds. 3-dimethylaminophenyl acrylate, 2-hydroxy-3-methacryloxypropyltrimethylammonium salt, acrylamide, N-butylacrylamide, N, N-dibutylacrylamide, piperidylacrylamide, methacrylamide, N-butylmethacrylamide, N-octadecylacrylamide Vinyl pyridine, vinyl pyrrolidone; vinyl N-methylpyridinium chloride, vinyl N-ethylpyridinium chloride, N, N-diali Ammonium chloride, N, N-diallyl-ethyl ammonium chloride, and the like.
[0113]
As the radical polymerizable monomer used in the present invention, a radical polymerizable monomer having an acidic group or a radical polymerizable monomer having a basic group is used in an amount of 0.1 to 15% by mass of the entire monomer. The radical polymerizable crosslinking agent is preferably used in an amount of 0.1 to 10% by mass based on the total amount of the radical polymerizable monomer, though it depends on its properties.
[0114]
(Chain transfer agent)
For the purpose of adjusting the molecular weight, a commonly used chain transfer agent can be used. The chain transfer agent is not particularly limited, and for example, octyl mercaptan, dodecyl mercaptan, tert-dodecyl mercaptan, n-octyl-3-mercaptopropionate, carbon tetrabromide, styrene dimer, and the like are used.
[0115]
(Polymerization initiator)
The radical polymerization initiator used in the present invention can be appropriately used as long as it is water-soluble. For example, persulfates (potassium persulfate, ammonium persulfate, etc.), azo compounds (4,4'-azobis-4-cyanovaleric acid and its salts, 2,2'-azobis (2-amidinopropane) salts, etc.), peroxides And the like.
[0116]
Further, the radical polymerization initiator can be used as a redox initiator in combination with a reducing agent, if necessary. By using the redox initiator, the polymerization activity is increased, the polymerization temperature is lowered, and the polymerization time can be further reduced.
[0117]
As the polymerization temperature, any temperature may be selected as long as it is equal to or higher than the lowest radical generation temperature of the polymerization initiator, and for example, a range of 50 ° C. to 90 ° C. is used. However, it is also possible to polymerize at room temperature or higher by using a combination of a polymerization initiator started at room temperature, for example, a hydrogen peroxide-reducing agent (such as ascorbic acid).
[0118]
(Surfactant)
In order to perform polymerization using the above-mentioned radical polymerizable monomer, it is necessary to disperse oil droplets in an aqueous medium using a surfactant. The surfactant that can be used at this time is not particularly limited, but the following ionic surfactants can be mentioned as preferred examples.
[0119]
Examples of the ionic surfactant include sulfonates (sodium dodecylbenzenesulfonate, sodium arylalkylpolyethersulfonate, 3,3-disulfondiphenylurea-4,4-diazo-bis-amino-8-naphthol-6). Sodium sulfonate, ortho-carboxybenzene-azo-dimethylaniline, sodium 2,2,5,5-tetramethyl-triphenylmethane-4,4-diazo-bis-β-naphthol-6-sulfonate), sulfuric acid Ester salts (sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, etc.), fatty acid salts (sodium oleate, sodium laurate, sodium caprate, sodium caprylate, sodium caproate, sodium stearate) Beam, calcium oleate and the like).
[0120]
Further, a nonionic surfactant can also be used. Specifically, polyethylene oxide, polypropylene oxide, a combination of polypropylene oxide and polyethylene oxide, an ester of polyethylene glycol and higher fatty acid, an alkylphenol polyethylene oxide, an ester of higher fatty acid and polyethylene glycol, an ester of higher fatty acid and polypropylene oxide, a sorbitan ester Etc. can be given.
[0121]
In the present invention, these are mainly used as emulsifiers at the time of emulsion polymerization, but they may be used for other steps or purposes.
[0122]
(Colorant)
Examples of the coloring agent include inorganic pigments, organic pigments, and dyes.
[0123]
Conventionally known inorganic pigments can be used. Specific examples of the inorganic pigment are shown below.
[0124]
As the black pigment, for example, carbon black such as furnace black, channel black, acetylene black, thermal black and lamp black, and magnetic powder such as magnetite and ferrite are also used.
[0125]
These inorganic pigments can be used alone or in combination of two or more as desired. The amount of the pigment to be added is 2 to 20% by mass, preferably 3 to 15% by mass, based on the polymer.
[0126]
When used as a magnetic toner, the above-mentioned magnetite can be added. In this case, from the viewpoint of imparting predetermined magnetic properties, it is preferable to add 20 to 60% by mass to the toner.
[0127]
Conventionally known organic pigments and dyes can also be used. Specific organic pigments and dyes are exemplified below.
[0128]
Pigments for magenta or red include C.I. I. Pigment Red 2, C.I. I. Pigment Red 3, C.I. I. Pigment Red 5, C.I. I. Pigment Red 6, C.I. I. Pigment Red 7, C.I. I. Pigment Red 15, C.I. I. Pigment Red 16, C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 53: 1, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123, C.I. I. Pigment Red 139, C.I. I. Pigment Red 144, C.I. I. Pigment Red 149, C.I. I. Pigment Red 166, C.I. I. Pigment Red 177, C.I. I. Pigment Red 178, C.I. I. Pigment Red 222 and the like.
[0129]
Examples of orange or yellow pigments include C.I. I. Pigment Orange 31, C.I. I. Pigment Orange 43, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 15, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 94, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 180, C.I. I. Pigment Yellow 185, C.I. I. Pigment yellow 155, C.I. I. Pigment Yellow 156, and the like.
[0130]
Examples of green or cyan pigments include C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 2, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 60, C.I. I. Pigment Green 7 and the like.
[0131]
Examples of the dye include C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95, etc., and mixtures thereof can also be used.
[0132]
These organic pigments and dyes can be used alone or in combination as required. The amount of the pigment to be added is 2 to 20% by mass, preferably 3 to 15% by mass, based on the polymer.
[0133]
The colorant can be used after surface modification. As the surface modifier, a conventionally known one can be used, and specifically, a silane coupling agent, a titanium coupling agent, an aluminum coupling agent and the like can be preferably used.
[0134]
The toner according to the present invention may use a release agent in combination. For example, low molecular weight polyolefin wax such as polypropylene and polyethylene, paraffin wax, Fischer-Tropsch wax, ester wax and the like can be used as the release agent. Further, in the present invention, an ester wax represented by the following general formula (3) can be preferably used.
[0135]
General formula (3)
R₁-(OCO-R₂)_n
In the formula, n represents an integer of 1 to 4, preferably 2 to 4, more preferably 3 to 4, and particularly preferably 4.
[0136]
R₁, R₂Represents a hydrocarbon group which may have a substituent.
R₁: Carbon number = 1 to 40, preferably 1 to 20, more preferably 2 to 5
R₂: Carbon number = 1 to 40, preferably 13 to 29, more preferably 12 to 25
Hereinafter, specific examples of the crystalline compound having an ester group according to the present invention are shown, but the present invention is not limited thereto.
[0137]
Embedded image

[0138]
Embedded image

[0139]
These ester waxes are contained in the resin particles and have a function of imparting good fixability (adhesion to the image support) to a toner obtained by fusing the resin particles.
[0140]
The amount of the release agent used in the present invention is preferably from 1% by mass to 30% by mass, more preferably from 2% by mass to 20% by mass, and still more preferably from 3% to 15% by mass, based on the whole toner. Further, the toner of the present invention is obtained by dissolving the release agent in the polymerizable monomer in water, dispersing the polymer in water, polymerizing the resin, and releasing the ester compound as a release agent in resin particles as described above. Is preferable, a toner produced through a process of forming particles containing therein, and salting out / fusing with the colorant particles.
[0141]
The toner according to the present invention may include a material capable of imparting various functions as a toner material in addition to the colorant and the release agent. Specific examples include a charge control agent. These components can be added simultaneously with the resin particles and the colorant particles in the above-mentioned salting-out / fusion step, and can be added by various methods such as a method of including in the toner and a method of adding to the resin particles themselves.
[0142]
Similarly, various known charge control agents, which can be dispersed in water, can be used. Specific examples include a nigrosine dye, a metal salt of naphthenic acid or a higher fatty acid, an alkoxylated amine, a quaternary ammonium salt compound, an azo metal complex, a metal salt of salicylic acid or a metal complex thereof.
[0143]
The external additive used in the toner according to the present invention will be described.
The toner according to the present invention can be used by adding a so-called external additive for the purpose of improving fluidity, chargeability and cleaning property. These external additives are not particularly limited, but various inorganic fine particles, organic fine particles, and lubricants can be used.
[0144]
Conventionally known inorganic fine particles can be used. Specifically, silica, titanium, alumina fine particles and the like can be preferably used. These inorganic fine particles are preferably hydrophobic. Specifically, as the silica fine particles, for example, commercially available products R-805, R-976, R-974, R-972, R-812, R-809 manufactured by Nippon Aerosil Co., Ltd., HVK-2150 manufactured by Hoechst, H -200, commercial products TS-720, TS-530, TS-610, H-5, MS-5, etc., manufactured by Cabot Corporation.
[0145]
As the titanium fine particles, for example, commercially available products T-805 and T-604 manufactured by Nippon Aerosil Co., Ltd., and commercially available products MT-100S, MT-100B, MT-500BS, MT-600, MT-600SS, JA- manufactured by Teika Co., Ltd. 1. Commercial products TA-300SI, TA-500, TAF-130, TAF-510, TAF-510T manufactured by Fuji Titanium, IT-S, IT-OA, IT-OB, IT- manufactured by Idemitsu Kosan Co., Ltd. OC and the like.
[0146]
Examples of the alumina fine particles include commercial products RFY-C and C-604 manufactured by Nippon Aerosil Co., Ltd., and commercial products TTO-55 manufactured by Ishihara Sangyo Co., Ltd.
[0147]
In addition, spherical organic fine particles having a number average primary particle diameter of about 10 to 2000 nm can be used as the organic fine particles. As this, a homopolymer such as styrene or methyl methacrylate or a copolymer thereof can be used.
[0148]
Examples of the lubricant include salts of zinc, aluminum, copper, magnesium, calcium, etc. of stearic acid, salts of zinc, manganese, iron, copper, magnesium, etc. of oleic acid, and salts of zinc, copper, magnesium, calcium, etc. of palmitic acid. Metal salts of higher fatty acids such as salts of linoleic acid such as zinc and calcium, and salts of ricinoleic acid such as zinc and calcium.
[0149]
The addition amount of these external additives is preferably 0.1 to 5% by mass based on the toner.
Examples of the method of adding the external additive include various known mixing devices such as a turbular mixer, a Hensiel mixer, a Nauter mixer, and a V-type mixer.
[0150]
The method for producing the electrostatic image developing toner according to the present invention will be described.
"Manufacturing process"
The toner of the present invention is obtained by dispersing a polymerizable monomer or a polymerizable monomer solution as described above in which a release agent is dissolved in an aqueous medium, and then resin particles containing the release agent by a polymerization method. Adjusting step, step of fusing resin particles in an aqueous medium using the resin particle dispersion, washing step of filtering the resulting particles from an aqueous medium to remove a surfactant, etc., It is preferable to manufacture by a polymerization method including a drying step, an external additive adding step of adding an external additive and the like to the particles obtained by further drying, and the like. Here, the resin particles may be colored particles. In addition, non-colored particles can be used as resin particles.In this case, colored particles are obtained by adding a colorant particle dispersion or the like to a dispersion of resin particles and then fusing the dispersion in an aqueous medium. Can be.
[0151]
In particular, as a fusion method, a method of salting out / fusion using resin particles produced in the polymerization step is preferable. When non-colored resin particles are used, the resin particles and the colorant particles can be salted out / fused in an aqueous medium.
[0152]
Further, not only the colorant and the release agent, but also a charge control agent or the like, which is a component of the toner, can be added as particles in this step.
[0153]
Here, the aqueous medium is composed of water as a main component and has a water content of 50% by mass or more. Examples of the solvent other than water include an organic solvent soluble in water, such as methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran. Alcohol organic solvents such as methanol, ethanol, isopropanol and butanol, which are preferably organic solvents which do not dissolve the resin, are particularly preferred.
[0154]
As a preferred polymerization method in the present invention, a monomer solution obtained by dissolving a release agent in a monomer is dispersed in an aqueous medium in which a surfactant having a critical micelle concentration or lower is dissolved by oil droplets by mechanical energy into a dispersion liquid. And a method of adding a water-soluble polymerization initiator to carry out radical polymerization. In this case, an oil-soluble polymerization initiator may be added to the monomer before use.
[0155]
The disperser for performing the oil droplet dispersion is not particularly limited, and examples thereof include Clearmix, an ultrasonic disperser, a mechanical homogenizer, a Menton-Gaulin, a pressure homogenizer, and the like.
[0156]
The colorant itself may be used after surface modification. In the method for modifying the surface of a colorant, the colorant is dispersed in a solvent, the surface modifier is added thereto, and then the temperature is raised to cause a reaction. After completion of the reaction, the mixture is filtered, washed and filtered repeatedly with the same solvent, and dried to obtain a pigment treated with a surface modifier.
[0157]
There is a method in which the colorant particles are prepared by dispersing the colorant in an aqueous medium. This dispersion is preferably performed in a state where the surfactant concentration in water is equal to or higher than the critical micelle concentration (CMC).
[0158]
The dispersing machine at the time of dispersing the pigment is not particularly limited, but is preferably a medium such as CLEARMIX, an ultrasonic dispersing machine, a mechanical homogenizer, a pressure dispersing machine such as Menton Gorin or a pressure homogenizer, a sand grinder, a Getzman mill or a diamond fine mill. Type dispersing machine.
[0159]
As the surfactant used here, the above-mentioned surfactant can be used. In the step of performing salting out / fusion, a salting out agent composed of an alkali metal salt, an alkaline earth metal salt, or the like is added as a coagulant having a critical coagulation concentration or more in water in which resin particles and colorant particles are present. Then, the step of heating the resin particles to a temperature equal to or higher than the glass transition point to promote salting out and simultaneously perform fusion.
[0160]
Here, the alkali metal salt and the alkaline earth metal salt which are salting-out agents include lithium, potassium, and sodium as the alkali metal, and magnesium, calcium, strontium, barium, and the like as the alkaline earth metal. And preferably potassium, sodium, magnesium, calcium and barium. Examples of the salt include chloride, bromide, iodine, carbonate, sulfate and the like.
[0161]
The method for achieving the particle size distribution of the toner is not particularly limited. For example, a method such as control by classification or the like, control of temperature and time at the time of association, and control of a stop method for terminating the association are used. can do.
[0162]
As a particularly preferred production method, a method of controlling the association time in water, the association temperature, the stop speed, and the like can be mentioned. That is, in the case of salting out / fusing, it is preferable that the time for which the salting out agent is allowed to stand after addition is as short as possible. Although the reason for this is not clear, there is a problem that the aggregation state of the particles fluctuates due to the standing time after salting out, the particle size distribution becomes unstable, and the surface properties of the fused toner fluctuate. appear. The temperature at which the salting-out agent is added is not particularly limited.
[0163]
In the present invention, it is preferable to use a method in which the temperature of the dispersion of the resin particles is raised as quickly as possible and the temperature is equal to or higher than the glass transition temperature of the resin particles. The time until the temperature rise is less than 30 minutes, preferably less than 10 minutes. Further, it is necessary to raise the temperature quickly, but the rate of temperature increase is preferably 1 ° C./min or more. Although the upper limit is not particularly clear, it is preferably 15 ° C./min or less from the viewpoint of suppressing generation of coarse particles due to rapid progress of salting out / fusion. As a particularly preferred embodiment, there can be mentioned a method in which salting out / fusion is continued even when the temperature exceeds the glass transition temperature. With this method, the fusion can be effectively advanced together with the growth of the particles, and the durability of the final toner can be improved.
[0164]
Furthermore, the salting out / fusion using a divalent metal salt at the time of association makes it possible to particularly control the particle size. Although the reason for this is not clear, the use of a divalent metal salt increases the repulsive force during salting out, making it possible to effectively suppress the dispersing ability of the surfactant, and as a result, the exile distribution is reduced. It is presumed that control has become possible.
[0165]
Further, it is preferable to add a monovalent metal salt and water to stop salting out / fusion. By adding this, salting out can be stopped, and as a result, the presence of a large particle size component or a small particle size component can be suppressed.
[0166]
In the case of a polymerization toner in which resin particles are associated or fused in an aqueous medium, by controlling the flow and temperature distribution of the medium in the reaction vessel at the fusion stage, the heating temperature is further increased in the shape control step after fusion. The shape distribution and shape of the entire toner can be arbitrarily changed by controlling the number of rotations and time of stirring.
[0167]
That is, in the polymerization method toner in which the resin particles are associated or fused, the flow in the reaction device is made laminar, and the fusing step and the agitation tank are performed by using a stirring blade and a stirring tank capable of making the internal temperature distribution uniform. By controlling the temperature, the number of revolutions, and the time in the shape control step, it is possible to form a toner having a shape factor and a uniform shape distribution according to the present invention. The reason for this is that when fusion is performed in a place where a laminar flow is formed, strong stress is not applied to the particles that are undergoing aggregation and fusion (association or aggregated particles), and the flow is accelerated in a laminar flow. It is presumed that as a result of the uniform temperature distribution in the stirring tank, the shape distribution of the fused particles becomes uniform. Further, the fused particles gradually become spherical by heating and stirring in the subsequent shape control step, and the shape of the toner particles can be arbitrarily controlled.
[0168]
In order to control the toner of the present invention into a predetermined shape, it is preferable to carry out salting out and fusion simultaneously. In the method of heating after forming the aggregated particles, the shape tends to be distributed, and the generation of fine particles cannot be suppressed. That is, it is presumed that since the aggregated particles are heated while being stirred in the aqueous medium, reaggregation of the aggregated particles occurs, and a component having a small particle diameter is likely to be generated.
[0169]
The developer used in the present invention will be described.
When used as a two-component developer by mixing with a carrier, conventionally known materials such as metals such as iron, ferrite and magnetite, and alloys of these metals with metals such as aluminum and lead as the magnetic particles of the carrier Can be used. Particularly, ferrite particles are preferable. The magnetic particles preferably have a volume average particle size of 15 to 100 μm, more preferably 25 to 80 μm.
[0170]
The volume average particle diameter of the carrier can be typically measured by a laser diffraction particle size distribution analyzer “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.
[0171]
The carrier is preferably a carrier in which magnetic particles are further coated with a resin, or a so-called resin-dispersed carrier in which magnetic particles are dispersed in a resin. Although there is no particular limitation on the resin composition for coating, for example, an olefin resin, a styrene resin, a styrene-acrylic resin, a silicone resin, an ester resin, a fluorine-containing polymer resin, or the like is used. The resin for constituting the resin dispersion type carrier is not particularly limited, and a known resin can be used. For example, a styrene-acrylic resin, a polyester resin, a fluororesin, a phenol resin, or the like is used. be able to.
[0172]
The image forming method of the present invention can also be used as an image forming method for forming a color image.
[0173]
FIG. 4 is a cross-sectional configuration diagram of a color image forming apparatus according to an embodiment of the present invention. This color image forming apparatus is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an endless belt-shaped intermediate transfer body unit 7, a sheet feeding and conveying unit 21, Fixing means (also a fixing step) 24. An original image reading device SC is arranged above the main body A of the image forming apparatus.
[0174]
The image forming unit 10Y that forms a yellow image includes a charging unit (also a charging step) 2Y and an exposing unit (also an exposure step) disposed around a drum-shaped photoconductor 1Y as a first image carrier. 3), a developing unit (also a developing step) 4Y, a primary transfer roller 5Y as a primary transfer unit (also a primary transfer step), and a cleaning unit (also a cleaning step) 6Y. The image forming unit 10M that forms a magenta image includes a drum-shaped photoconductor 1M as a first image carrier, a charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roller 5M as a primary transfer unit, It has a cleaning unit 6M. The image forming unit 10C for forming a cyan image includes a drum-shaped photoconductor 1C as a first image carrier, a charging unit 2C, an exposure unit 3C, a developing unit 4C, a primary transfer roller 5C as a primary transfer unit, It has cleaning means 6C. The image forming unit 10K for forming a black image includes a drum-shaped photosensitive member 1K as a first image carrier, a charging unit 2K, an exposing unit 3K, a developing unit 4K, a primary transfer roller 5K as a primary transfer unit, and a cleaning unit. Has 6K.
[0175]
The endless belt-shaped intermediate transfer body unit 7 has an endless belt-shaped intermediate transfer body 70 as a semiconductive endless belt-shaped second image carrier that is wound around a plurality of rollers and rotatably supported.
[0176]
Images of each color formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred onto the rotating endless belt-shaped intermediate transfer body 70 by primary transfer rollers 5Y, 5M, 5C, and 5K as primary transfer units. Then, a combined color image is formed. A sheet P as a recording medium (also referred to as a recording sheet) stored in a sheet cassette 20 is fed by a sheet feeding unit 21 and passes through a plurality of intermediate rollers 22A, 22B, 22C, 22D and registration rollers 23. The sheet is conveyed to a secondary transfer roller 5A as a secondary transfer unit (also a secondary transfer step), and is secondary-transferred onto the sheet P to collectively transfer color images. The paper P to which the color image has been transferred is subjected to a fixing process by the fixing unit 24, and is held by a paper discharge roller 25 and placed on a paper discharge tray 26 outside the apparatus.
[0177]
On the other hand, after the color image is transferred onto the sheet P by the secondary transfer roller 5A as the secondary transfer unit, the residual toner is removed by the cleaning unit 6A from the endless belt-shaped intermediate transfer body 70 from which the sheet P is separated by curvature.
[0178]
During the image forming process, the primary transfer roller 5K is always in pressure contact with the photoconductor 1K. The other primary transfer rollers 5Y, 5M, and 5C are in pressure contact with the corresponding photoconductors 1Y, 1M, and 1C only during color image formation.
[0179]
The secondary transfer roller 5A is in pressure contact with the endless belt-shaped intermediate transfer body 70 only when the sheet P passes through the secondary transfer roller 5A to perform secondary transfer.
[0180]
Further, the housing 8 can be pulled out from the apparatus main body A via the support rails 82L and 82R.
[0181]
The housing 8 includes image forming units 10Y, 10M, 10C, and 10K, and an endless belt-shaped intermediate transfer unit 7.
[0182]
The image forming units 10Y, 10M, 10C, and 10K are arranged in tandem in the vertical direction. An endless belt-shaped intermediate transfer unit 7 is disposed on the left side of the photoconductors 1Y, 1M, 1C, and 1K in the figure. The endless belt-shaped intermediate transfer body unit 7 includes an endless belt-shaped intermediate transfer body 70 that can rotate around rollers 71, 72, 73, and 74, primary transfer rollers 5Y, 5M, 5C, and 5K, and a cleaning unit 6A. Consists of
[0183]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples, but embodiments of the present invention are not limited thereto. In the following description, “parts” means “parts by mass”.
[0184]
Example 1
Photoconductors 1 to 5 used in Examples and Comparative Examples were produced as follows.
[0185]

The intermediate layer coating solution was prepared, applied by dip coating onto a washed cylindrical aluminum substrate, and dried at 120 ° C. for 20 minutes to form an intermediate layer having a dry film thickness of 0.5 μm.
[0186]

The above composition was mixed and dispersed using a sand mill to prepare a charge generating layer coating liquid. This coating solution was applied by dip coating to form a charge generation layer having a dry film thickness of 0.3 μm on the intermediate layer.
[0187]

The above composition was mixed and dissolved to prepare a charge transport layer coating solution. This coating solution was applied on the charge generation layer by a dip coating method, and dried at 100 ° C. for 30 minutes to form a charge transport layer having a dry film thickness of 23 μm.
[0188]
Production of photoconductor 2
Photoreceptor 1 was prepared in the same manner as in photoreceptor 1, except that the composition of the coating solution for the intermediate layer was changed as follows, and the dry film thickness was changed to 1.5 μm.
[0189]

Preparation of Photoconductor 3 Photoconductor 3 was prepared in the same manner as in preparation of photoconductor 1, except that the composition of the coating solution for the intermediate layer was changed as follows.
[0190]
Middle layer (UCL) coating solution
300 g of silane coupling agent “KBM-903” (manufactured by Shin-Etsu Chemical Co., Ltd.)
30 ml of water
Ethanol 1000ml
Production of photoconductor 4
Photoreceptor 4 was prepared in the same manner as in photoreceptor 1 except that the composition of the coating solution for the intermediate layer was changed as described below.
[0191]

Preparation of Photoconductor 5 (Comparative Photoconductor)
A photoreceptor 5 was prepared in the same manner as in 1, except that the intermediate layer of the photoreceptor 1 was replaced with the following intermediate layer coating solution, and the dry film thickness was changed to 0.7 μm.
[0192]
Middle layer (UCL) coating solution
150 g of polyamide resin "CM-8000" (manufactured by Toray Industries, Inc.)
1500 ml of 2-propanol
8500 ml of methanol
The thickness of each layer was calculated based on the solid content of the intermediate layer. After coating and drying, the uniform thickness portion was randomly measured at 10 locations, and the average thickness was almost the same. Is shown. The film thickness was measured using a photo-detection type film thickness measuring device MCPD-1000 (Instant multi-photometric detector: Otsuka Electronics Co., Ltd.).
[0193]
《Developer》
<< Manufacture of latex 1 >>
A solution in which 7.08 g of an anionic surfactant (sodium dodecylbenzenesulfonate: SDS) was previously dissolved in ion-exchanged water (2760 g) in a 5000 ml separable flask equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing device. Is added. The internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream. On the other hand, 72.0 g of Exemplified Compound 19) was added to a monomer composed of 115.1 g of styrene, 42.0 g of n-butyl acrylate, and 10.9 g of methacrylic acid, heated to 80 ° C. and dissolved to prepare a monomer solution. The heated solution was mixed and dispersed by a mechanical disperser having a circulation path to produce emulsified particles having a uniform dispersed particle diameter. Next, a solution in which 0.84 g of a polymerization initiator (potassium persulfate: KPS) was dissolved in 200 g of ion-exchanged water was added, and the mixture was heated and stirred at 80 ° C. for 3 hours to produce latex particles. Subsequently, a solution prepared by dissolving 7.73 g of a polymerization initiator (KPS) in 240 ml of ion-exchanged water was added. After 15 minutes, 383.6 g of styrene, 140.0 g of n-butyl acrylate, 36. A mixed solution of 4 g and 14.0 g of n-octyl-3-mercaptopropionate was added dropwise over 120 minutes. After completion of the dropwise addition, the mixture was heated and stirred for 60 minutes, and then cooled to 40 ° C. to obtain latex particles.
[0194]
This latex particle is referred to as Latex 1.
《Manufacture of colored particles》
(Production of colored particles 1Bk)
9.2 g of sodium n-dodecyl sulfate is dissolved in 160 ml of ion-exchanged water with stirring. 20 g of Regal 330R (carbon black manufactured by Cabot Corporation) was gradually added to this liquid with stirring, and then dispersed using CLEARMIX. The particle diameter of the dispersion was measured using an electrophoretic light scattering photometer ELS-800 manufactured by Otsuka Electronics Co., Ltd., and as a result, the weight average diameter was 112 nm. This dispersion is referred to as “colorant dispersion 1”.
[0195]
1250 g of the above-mentioned "latex 1", 2000 ml of ion-exchanged water and "colorant dispersion liquid 1" are stirred in a 5-liter four-necked flask equipped with a temperature sensor, a cooling tube, a nitrogen introducing device, and a stirring device. After adjusting the temperature to 30 ° C., a 5 mol / liter aqueous sodium hydroxide solution was added to the solution to adjust the pH to 10.0. Then, an aqueous solution in which 52.6 g of magnesium chloride hexahydrate was dissolved in 72 ml of ion-exchanged water was added at 30 ° C. for 5 minutes with stirring. Thereafter, after standing for 2 minutes, heating is started and the temperature is raised to 90 ° C. in 5 minutes (heating rate = 12 ° C./min). In this state, the particle size is measured with a Coulter Counter TAII, and when the volume average particle size becomes 4.3 μm, an aqueous solution in which 115 g of sodium chloride is dissolved in 700 ml of ion-exchanged water is added to stop the particle growth, and further continued. Then, the mixture is heated and stirred at a liquid temperature of 85 ° C. ± 2 ° C. for 8 hours to carry out salting out / fusion. Thereafter, the mixture was cooled to 30 ° C. at 6 ° C./min, hydrochloric acid was added to adjust the pH to 2.0, and stirring was stopped. The resulting colored particles were filtered / washed under the following conditions, and then dried with warm air at 40 ° C. to obtain colored particles. This is referred to as “colored particles 1Bk”.
[0196]
(Production of colored particles 2Bk, 3Bk, 4Bk and 5Bk)
In the production of the colored particles 1Bk, colored particles 2Bk to 5Bk were produced in the same manner except that the production conditions shown in Table 1 were changed.
[0197]
(Production of colored particles 6Bk to 8Bk)
In the production of the colored particles 1Bk, the production conditions shown in Table 1 were set, and when the volume average particle diameter reached 3.0 μm, the particle growth was stopped, and colored particles 6Bk to 8Bk were produced, respectively. .
[0198]
(Production of colored particles 9Bk and 10Bk)
In the production of the colored particles 1Bk, the production conditions shown in Table 1 were set, and when the volume average particle diameter reached 6.5 μm, the particle growth was stopped, and colored particles 9Bk and 10Bk were produced, respectively.
[0199]
(Production of colored particles 11Bk)
In the production of the colored particles 1Bk, the production conditions described in Table 1 were set, and when the volume average particle diameter reached 2.6 μm, the particle growth was stopped, and each of the colored particles 11Bk was produced.
[0200]
(Production of colored particles 12Bk)
In the production of the colored particles 1Bk, the production conditions shown in Table 1 were set, and when the volume average particle diameter became 7.0 μm, the particle growth was stopped, and each of the colored particles 12Bk was produced.
[0201]
Table 1 shows the production conditions of the colored particles, and Table 2 shows the physical properties of each of the finally obtained colored particles.
[0202]
[Table 1]

[0203]
[Table 2]

[0204]
(Production of toner particles)
To the obtained colored particles 1Bk to 12Bk, 1% by mass of hydrophobic silica (number-average primary particle size = 12 nm, degree of hydrophobicity = 68) and hydrophobic titanium oxide (number-average primary particle size = 20 nm, hydrophobicization) were respectively added. 0.5% by mass) and mixed with a Henschel mixer to obtain toners 1Bk to 12Bk.
[0205]
The physical properties such as the shape and particle size of the toner were the same as the physical property data of the colored particles shown in Table 2.
[0206]
(Manufacture of developer)
A ferrite carrier coated with a silicone resin and having a volume average particle diameter of 60 μm was mixed with each of the toner particles to prepare developers 1Bk to 12Bk each having a toner concentration of 6%.
[0207]
《Evaluation》
The photoreceptor was set in a digital copying machine (having a scorotron charger, a semiconductor laser image exposure device, and a reversal developing means) basically having the structure shown in FIGS. 1 and 2, and a copying experiment was performed. In this experiment, the program of the unexposed portion target potential was incorporated into the memory of the process control section in FIG. 2, and the digital copying machine was modified so that the unexposed portion target potential at the developing position was automatically set. Further, the development bias potential (Vbias) was modified so that it was automatically set to the target value. During the image formation of this copying experiment, the unexposed portion potential is measured by the potential sensor, and if the unexposed portion potential of the target value is not obtained, in order to achieve the unexposed portion target potential through the control unit, The output value of the charging means was controlled.
[0208]
《Image evaluation》
The photoconductor, developer, unexposed portion potential (VH) of the developing position, and DC bias potential (VDC) applied to the developing sleeve in the digital copying machine are combined as shown in Tables 3 and 4 (combination No. 1). 45), high temperature and high humidity: HH (30 ° C., 80% RH), low temperature and low humidity: LL (10 ° C., 10% RH) environment, copy of A4 paper, 50,000 sheets of character image with pixel rate of 7% for each 50,000 sheets Then, at the start and every 10,000 copies, a white solid image, a halftone image, etc. were copied, and the presence or absence of image defects such as black dots was confirmed. Tables 3 and 4 show the results.
[0209]
The other evaluation conditions of the digital copying machine were set as follows.
Exposure conditions
Exposure part potential target: Set to the exposure amount to be -50V to -150V.
[0210]
Exposure beam: Image exposure was performed at a dot density of 800 dpi (dpi is the number of dots per 2.54 cm). Laser beam spot area: 0.8 × 10^-9m², Use 680nm semiconductor laser
Transfer conditions
Transfer pole; corona charging method
Separation conditions: using the separation means of the separation claw unit
Cleaning conditions
A cleaning blade having a hardness of 70 °, a rebound resilience of 65%, a thickness of 2 (mm) and a free length of 9 mm was brought into contact with the cleaning portion by a weight load method so as to have a linear pressure of 18 (g / cm) in the counter direction.
[0211]
Evaluation criteria
Black spot (Evaluated with a solid white image at the start and every 10,000 copies)
Regarding the black spots, the periodicity coincided with the cycle of the photoreceptor, and the number of visible black spots per A4 size was determined.
[0212]
：: Frequency of black spots of 0.4 mm or more: All copied images are 3 copies / A4 or less (good)
：: Black spots of 0.4 mm or more Frequency: 1 or more of 4 / A4 or more and 10 / A4 or less (no problem in practical use)
×: Black spots of 0.4 mm or more Frequency: 11 pieces / A4 or more occurred one or more sheets (a problem in practical use)
Missing white (Evaluated with a halftone image at the start and every 10,000 copies)
As for the white spots, the periodicity coincided with the period of the photoconductor, and the number of visible white spots per A4 size was determined.
[0213]
：: Frequency of white spots of 0.4 mm or more: All copied images 5 / A4 or less (good)
：: White spotting frequency of 0.4 mm or more: Frequency of 6 or more and 20 or less of A4 or less occurred (no problem in practical use)
×: White drop of 0.4 mm or more Frequency: 21 / A4 or more one or more (problem in practical use)
Edge phenomenon (evaluated every 50,000 copies of HH and LL)
After each continuous copy of 50,000 sheets under the HH and LL conditions, the density of a 2 cm wide solid image portion having a relative reflection density of 0.5 was measured with a width of 0.1 mm, and the central density and the maximum density near the edge were measured. The edge phenomenon was evaluated by the difference.
[0214]
：: The difference between the central density and the maximum density near the end is smaller than 0.02 (good)
：: The difference between the central density and the maximum density near the edge is 0.02 to 0.06 (no problem in practical use)
X: The difference between the central density and the maximum density near the end is larger than 0.06 (a problem in practical use)
Character Chile (HH, LL, evaluated every 50,000 copies)
An original image having a grid image of 5 cm width made of 0.1 mm lines at the tip was copied and evaluated. For evaluation, the copy image was magnified 20 times, and the line continuity and the occurrence of dust were observed.
[0215]
：: No dust, continuous fine lines (good)
：: Dust is slightly generated at a level that cannot be visually judged, and fine lines are continuous (no problem in practical use)
Δ: Dust is generated at a level that can be visually observed, but fine lines are continuous (reconsideration of practicality is required)
×: Dust is generated at a level that can be visually observed, and there are places where thin lines are interrupted (there is a problem in practice).
Evaluation of image density, gradation and sharpness
The above evaluation conditions were changed to a normal temperature and normal humidity (20 ° C., 60% RH) environment, an original image having 60 steps of gradation from a white image to a solid black image was copied, and the image density and gradation were evaluated. . In the evaluation, the gradation density of the copied image was measured using RD-918 manufactured by Macbeth. The relative reflection density was measured with the reflection density of the paper set to “0”.
(Image density)
A: Black solid portion density of 1.3 or more (good)
：: Black solid portion density of 1.0 to less than 1.3 (no problem in practical use)
Δ: Black solid portion density of 0.7 to less than 1.0 (re-evaluation required)
×: Density of black solid portion is less than 0.7 (practical problem)
(Gradation)
A: Gradation of 41 steps or more (good)
：: 21 to 40 steps of gradation (no problem in practical use)
Δ: Difference in gradation from 11 to 20 steps (reconsideration of practicality is necessary: practicality is required for image quality where gradation is not important)
×: gradation is 10 steps or less (there is a problem in practice)
(Sharpness)
The sharpness of the image was evaluated by displaying an image in an HH or LL environment where the environmental conditions were severe, and by character collapse. Character images having different character sizes (points) were formed and evaluated according to the following criteria.
[0216]
◎: Characters of 4 points or less are clear and easily legible (good)
：: Characters of 6 points or less are clear and easily legible (no problem in practical use)
△: Characters of 8 points or less are clear and easily legible (re-evaluation required)
×: Some or all of the 8-point characters are illegible (practical problem)
[0217]
[Table 3]

[0218]
[Table 4]

[0219]
As is clear from Tables 3 and 4, the image forming method of the present invention, that is, the photoconductor 1 having the intermediate layer of the resin layer formed using at least one selected from the organometallic compounds and the silane coupling agents 4, the volume average particle diameter of the toner in the developer is 3.0 to 7.0 μm, and when the 50% number particle diameter of the toner is Dp50, the number of toners of 0.7 × Dp50 or less is 10% by number. Hereinafter, and when the unexposed portion potential VH and the DC bias potential VDC applied to the developing sleeve simultaneously satisfy the above formulas 1 and 2 (combinations Nos. 1 to 3, 8 to 10, 15 to 17, 22 to 33). Black spots, white spots, edge phenomena, character dust, image density, gradation, and sharpness are all good, but if | VH |-| VDC | is 30 V (combination Nos. 6, 13, and 20), black Spots occur, gradation, sharp Sex has declined. When | VH |-| VDC | is 350 V (combination Nos. 7, 14, 21), white dropouts and character dust due to the adhesion of the weakly chargeable toner occur, and the gradation and sharpness deteriorate. I have. When | VH | is 1550 (combination Nos. 5, 12, and 19), defects of black spots due to electrostatic destruction occur, and the evaluation of edge phenomenon and character dust decreases, and the sharpness deteriorates. ing. When | VH | is 850 V (combinations Nos. 4, 11, and 18), the gradation is reduced. On the other hand, when the photoreceptor 5 (combinations Nos. 34 and 35) outside the present invention is used, black spots are likely to occur, and the evaluation of the edge phenomenon and character dust is reduced, and the sharpness is deteriorated. Further, in the combination (combination Nos. 36 and 37) using the toner outside the present invention (the toner in which the number of toners of 0.7 × Dp50 or less is more than 10% by number), white dropout occurs, and the edge phenomenon and the character The dust also deteriorates, and the sharpness is reduced. In (Combination Nos. 38 to 41), white dropouts and character dust are also generated, and the sharpness is reduced. In a combination (combinations Nos. 42 and 43) using a toner other than the present invention (a toner having a volume average particle diameter of 2.5 μm), white dropouts, edge phenomena and character dust occur, and gradation The combination (combinations Nos. 44 and 45) using toners (toners having a volume average particle diameter of 7.5 μm) outside the present invention is insufficient in gradation and sharpness. .
[0220]
Example 2
In the preparation of the toner used in Example 1, C.I. instead of Legal 330R (carbon black manufactured by Cabot Corporation) in the colored dispersion. I. Pigment Yellow 185 (Y toner), C.I. I. Pigment Red 122 (M toner), C.I. I. Pigment Blue 15: 3 (C toner) was used in the same manner, and the toners 1Y, 1M, 1C, 4Y, 4M, and 4C6 shown in Table 5 having the same shape factor and the like as the toner 1Bk and the toner 4Bk were produced. did. Table 5 shows the physical properties such as the shape and particle size of these toners.
[0221]
[Table 5]

[0222]
(Manufacture of developer)
10 parts by mass of each of the toners 1Y, 1M, 1C, 4Y, 4M, and 4C and 100 parts by mass of a carrier obtained by coating a core of ferrite particles having an average particle diameter of 45 μm with an insulating resin were mixed for evaluation. Developers 1Y, 1M, 1C, 4Y, 4M, and 4C were produced.
[0223]
Using one group of the developers 1Bk, 1Y, 1M, and 1C, and four groups of the developers 4Bk, 4Y, 4M, and 4C, the color image forming apparatus having the intermediate transfer member illustrated in FIG. A color image was prepared by combining four photoconductors manufactured with the same prescription as the photoconductor 1 and four photoconductors manufactured with the same prescription as the photoconductor 5. At this time, the conditions of the unexposed portion potential VH and the DC bias potential VDC applied to the developing sleeve were combined as shown in Table 6.
[0224]
The evaluation was the same as in Example 1. Table 6 also shows the evaluation results.
[0225]
[Table 6]

[0226]
As is clear from Table 6, the color image produced by the image forming apparatus using the intermediate transfer member also shows almost the same results as the evaluation of the monochrome image of Example 1 described above.
[0227]
That is, when the photoconductor, developer, unexposed portion potential VH and the DC bias potential VDC applied to the developing sleeve of the present invention simultaneously satisfy the above formulas 1 and 2 (combination Nos. 51 to 53), black spots and white Although the dropping, edge phenomenon, character dust, image density, gradation, and sharpness are all good, when the photoconductor or developer is a combination other than the present invention (combination Nos. 54 to 57), black spots, white dropouts, Edge phenomena and the like are reduced, sharpness is deteriorated (combination Nos. 56 and 57), white spots and character dust are generated, and as a result, gradation and sharpness are reduced (combination No. 54). , 55).
[0228]
【The invention's effect】
By using the image forming method of the present invention, it is possible to prevent the occurrence of image defects such as black spots, white spots, edge phenomena, and character dust, and to obtain an electrophotographic image having high image density and high gradation. Further, it is possible to provide an image forming apparatus having good image performance using the image forming method.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an image forming apparatus as one example of an image forming method of the present invention.
FIG. 2 is an enlarged view of a configuration of controlling a charging potential of a photosensitive drum in FIG. 1;
FIG. 3 is a view for explaining a method of setting an unexposed portion target potential.
FIG. 4 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of the present invention.
[Explanation of symbols]
50 Photoconductor drum (or photoconductor)
51 Exposure section before charging
52 Charger
53 Image exposure unit
54 Developer
541 development sleeve
542 conveyance amount regulating member
543 Developer stirring and conveying member
544 Developer stirring and conveying member
547 Potential sensor
57 Paper feed roller
58 Transfer electrode
59 Separation electrode (separator)
60 Fixing device
61 Paper ejection roller
62 Cleaning device

Claims (9)

In an image forming method for forming an electrostatic latent image on an organic photoreceptor having a photosensitive layer on a conductive substrate and visualizing the electrostatic latent image into a toner image by reversal development, a toner used in the reversal development Assuming that the volume average particle diameter is 3.0 to 7.0 μm and the 50% number particle diameter of the toner is Dp50, the number of toners of 0.7 × Dp50 or less is 10 number% or less, The photoreceptor has an intermediate layer of a resin layer formed using at least one selected from an organic metal compound and a silane coupling agent between the conductive support and the photosensitive layer. The unexposed potential (VH) of the electrostatic latent image satisfies the following equation (1), and the relationship between the unexposed potential (VH) and the DC bias potential (VDC) applied to the developing sleeve satisfies the following equation (2). A characteristic image forming method.
1 expression 900V ≦ | VH | ≦ 1500V
2 types 50V ≦ | VH | − | VDC | ≦ 300V In an image forming method for forming an electrostatic latent image on an organic photoreceptor having a photosensitive layer on a conductive substrate and visualizing the electrostatic latent image into a toner image by reversal development, a toner used in the reversal development Has a volume average particle diameter of 3.0 to 7.0 μm and a ratio (Dv50 / Dp50) of 50% volume particle diameter (Dv50) to 50% number particle diameter (Dp50) of 1.0 to 1 .15, the ratio (Dv75 / Dp75) of the cumulative 75% volume particle size (Dv75) from the larger volume particle size to the cumulative 75% number particle size (Dp75) from the larger number particle size is 1.0 to 1.0; 1.20 and the number of toner particles having a particle size of 0.7 × (Dp50) or less is 10% by number or less, and the organic photoreceptor is an organic metal compound and a silane coupling between a conductive support and a photosensitive layer. In the resin layer formed using at least one selected from the agents The non-exposed potential (VH) of the electrostatic latent image at the developing position satisfies the following expression, and the unexposed potential (VH) and the DC bias potential ( (VDC) satisfying the following two expressions.
1 expression 900V ≦ | VH | ≦ 1500V
2 types 50V ≦ | VH | − | VDC | ≦ 300V Forming an electrostatic latent image corresponding to a yellow image on an organic photoreceptor having a photosensitive layer on a conductive substrate, developing the electrostatic latent image with a developer containing a yellow toner, Transferring the toner image formed on the carrier to the intermediate transfer member, forming an electrostatic latent image corresponding to the magenta image on the organic photoconductor, and developing the electrostatic latent image with a developer containing magenta toner. Developing, transferring the toner image formed on the organic photoreceptor to an intermediate transfer member, forming an electrostatic latent image corresponding to the cyan image on the organic photoreceptor, using a developer containing cyan toner Developing the electrostatic latent image, transferring the toner image formed on the organic photoreceptor to an intermediate transfer member, forming an electrostatic latent image corresponding to a black image on the organic photoreceptor, black The developer containing toner contains the electrostatic latent Developing an image, transferring a toner image formed on the organic photoreceptor to an intermediate transfer member, and transferring the toner image of each color transferred and formed on the intermediate transfer member to recording paper. At
When the volume average particle diameter of the toner in the developer is 3.0 to 7.0 μm and the 50% number particle diameter of the toner is Dp50, the number of toners of 0.7 × Dp50 or less is 10% by number. Wherein the organic photoreceptor has an intermediate layer of a resin layer formed using at least one selected from an organometallic compound and a silane coupling agent between the conductive support and the photosensitive layer. The unexposed potential (VH) of the electrostatic latent image at the developing position satisfies the following expression, and the relationship between the unexposed potential (VH) and the DC bias potential (VDC) applied to the developing sleeve is as follows. An image forming method characterized by satisfying the following two expressions.
1 expression 900V ≦ | VH | ≦ 1500V
2 types 50V ≦ | VH | − | VDC | ≦ 300V Forming an electrostatic latent image corresponding to a yellow image on an organic photoreceptor having a photosensitive layer on a conductive substrate, developing the electrostatic latent image with a developer containing a yellow toner, Transferring the toner image formed on the carrier to the intermediate transfer member, forming an electrostatic latent image corresponding to the magenta image on the organic photoconductor, and developing the electrostatic latent image with a developer containing magenta toner. Developing, transferring the toner image formed on the organic photoreceptor to an intermediate transfer member, forming an electrostatic latent image corresponding to the cyan image on the organic photoreceptor, using a developer containing cyan toner Developing the electrostatic latent image, transferring the toner image formed on the organic photoreceptor to an intermediate transfer member, forming an electrostatic latent image corresponding to a black image on the organic photoreceptor, black The developer containing toner contains the electrostatic latent Developing an image, transferring a toner image formed on the organic photoreceptor to an intermediate transfer member, and transferring the toner image of each color transferred and formed on the intermediate transfer member to recording paper. At
The toner in the developer has a volume average particle diameter of 3.0 to 7.0 μm, and a ratio (Dv50 / Dp50) of 50% volume particle diameter (Dv50) to 50% number particle diameter (Dp50) of the toner. Is 1.0 to 1.15, and the ratio (Dv75 / Dp75) of the cumulative 75% volume particle size (Dv75) from the larger volume particle size to the cumulative 75% number particle size (Dp75) from the larger number particle size. ) Is 1.0 to 1.20 and the number of toner particles having a particle size of 0.7 × (Dp50) or less is 10% by number or less, and the organic photoconductor is an organic photoconductor between the conductive support and the photosensitive layer. It has an intermediate layer of a resin layer formed using at least one selected from a metal compound and a silane coupling agent, and the unexposed potential (VH) of the electrostatic latent image at the developing position is represented by the following formula: Is satisfied, and the unexposed potential (VH) is directly applied to the developing sleeve. An image forming method, wherein a relationship with a current bias potential (VDC) satisfies the following two equations.
1 expression 900V ≦ | VH | ≦ 1500V
2 types 50V ≦ | VH | − | VDC | ≦ 300V The image forming method according to claim 1, wherein the organometallic compound is a metal alkoxide or an organic metal chelate. The image forming method according to claim 1, wherein the intermediate layer is a layer formed using an organic metal chelate and a silane coupling agent. 7. The image forming method according to claim 5, wherein the organic metal chelate is a compound represented by the following general formula (1).
General formula (1) (R ₁ O) _g -M- (K) _m
(In the formula, R ₁ is an alkyl group, M represents zirconium, titanium, or aluminum. K represents an acetoacetate ester residue or a β-diketone residue. G and m each represent an integer of 1 or more. , M is zirconium or titanium, g + m is 4, and when M is aluminum, g + m is 3.) The image forming method according to any one of claims 1 to 7, wherein the silane coupling agent is a compound represented by the following general formula (2).
General formula (2) (Q) _p -Si (Y) _q- (A) _r
(Wherein, Q represents a halogen atom, an alkoxy group or an amino group, A is .Y represents an alkyl group or an aryl group represents _{-BOOC (R ') C = CH} 2, -BNHR " or -BNH _2. R 'represents an alkyl group, R "represents an alkyl group or an aryl group, B represents an alkylene group or an alkylene group containing -O-, -NH-, -CO-, and p and q are integers of 1 or more. And r represents an integer of 0 or more, and p + q + r is 4.) An image forming apparatus which forms an electrophotographic image by using the image forming method according to claim 1.

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