JP3814497B2 - Image forming apparatus - Google Patents

Description

【０１０４】
そして、この塗布液をアルミニウム素管上にディップコート法にて塗布し、１００℃で１時間乾燥させて、膜厚２５μmの感光層３を形成させ、単層型とした。
【０１０５】
この感光層３の動的押し込み硬さは２０ｋｇｆ／ｍｍ²であった。ただし、表面保護層をつけないで測定をおこなった。
【０１０６】
次に表面保護層４を表１に示す成膜条件により５０００Åの厚みでカーボン（Ｃ）からなるアモルファス層を成膜形成する。
【０１０７】
ＮＯガスは、最初に０．８ｓｃｃｍにて導入し、２００分間で漸次増大し、最後に１１ｓｃｃｍにまで多くしている。このようにＮＯガスを導入することで、図5に示すように直線的な酸素濃度勾配を設ける。
【０１０８】
【表１】

【０１０９】
この表面保護層４は動的押し込み硬さが３００ｋｇｆ／ｍｍ²であり、弗素原子含有量が５原子％、酸素原子含有量が０．０１原子％である。これらの含有量の測定については、２次イオン質量分析法（Secondary Ion Mass Spectrometry：ＳＩＭＳ）にておこなった。
【０１１０】
かくして得られた本発明の感光体を前記の画像形成装置５（京セラ株式会社製エコシスＬＳ−１７００改造機、湿式現像：トナー平均粒径２．５μｍ）に搭載し、この装置５に設けられた感光体加熱用ヒーターのスイッチングを常時ＯＦＦにして、感光体加熱をおこなわなかった。そして、カールソン法で画像形成して、３０万枚のランニングテストをおこない、画像流れと画質を測定したところ、画像流れが発生せず、画質についても、かぶりやスジ等がなく、まったく問題のない結果が得られた。
【０１１１】
（例２）
次に（例１）に示す感光体を作製するに当り、感光層３をまったく同一の構成にして、さらに表面保護層４については、ＮＯガスの導入量を変え、その他の成膜条件を（例１）の感光体と同じにて設定し、各種感光体を作製した。
すなわち、表面保護層４を成膜形成するに際し、ＮＯガスの導入量を成膜とともに、漸次増大させたが、具体的には、酸素原子含有量は有機感光層との界面近傍の濃度を０．００００８原子％（ＮＯガス量：０．５ｓｃｃｍ）に設定し、そして、図5に示すように直線的に酸素濃度を自由表面に向けて高くしている。いずれの感光体も硬度は２５０〜３５０ｋｇｆ／ｍｍ²の範囲内にある。
これら各感光体において、表面保護層に弗素原子を含有させない場合、さらにそれぞれに弗素原子を０．０５〜５０原子％の濃度でもって含有させることで、これら各感光体の画質および画像流れを測定したところ、表２に示すような結果が得られた。なお、同表中、酸素原子含有量は、表面保護層全体の平均値である。その酸素原子の平均含有量が０．００００８原子％の場合には、層厚方向にわたって一定の濃度であることを示し、それ以下の平均含有量の場合には、漸次濃度を減少させ、それ以上の平均値の場合には、漸次濃度を増大させた場合を示す。
【０１１２】
【表２】

【０１１３】
画像流れは３３℃、８５％湿度の環境下で８時間放置し、その画質を４段階に評価し、◎印は画像変化がまったくなく、きわめて良好な画像が得られた場合であり、○印は画像変化が若干認められるがこともあるが、実用上支障がない場合であり、△印は一部画像が流れた場合であり、×印は全面にわたって画像が流れた場合である。
【０１１４】
画質も４段階にて評価し、黒ベタ、白ベタおよびハーフトーン画像にて評価し、◎印は黒ベタ濃度低下・白ベタにおいてかぶりがまったく確認されず、またハーフトーン画像にスジがまったく発生せず、きわめて良好な画質が得られた場合であり、○印は黒ベタ濃度低下が若干現れたり、またはハ−フト−ン画像にスジが若干認められることもあるが、実用上支障がない場合であり、△印はハーフトーン画像の一部にスジが発生したり、または黒ベタ濃度の低下、もしくは白ベタでのかぶりが若干発生している場合であり、×印はハーフトーン画像にスジが発生したり、または黒ベタ濃度が低下したり、もしくは白ベタにかぶりが発生し、実用にまったく適していない場合である。
【０１１５】
表２から明らかなとおり、酸素原子含有量が０．０００１〜１．０原子％、かつ弗素原子含有量が０．１〜２５原子％にすることで、画像流れおよび画質の双方が優れていることがわかる。特に、画質については、黒ベタ濃度低下・白ベタにおいてかぶりがまったく確認されず、またハーフトーン画像にスジがまったく発生せず、きわめて良好な画質が得られた。
【０１１６】
しかし、酸素原子含有量が０．０００１原子％未満では光メモリーが悪く、かぶりが発生したり、一部で密着性が悪くなり、剥離が発生し、ハーフトーン画像にキズの発生も見られた。
【０１１７】
また、酸素原子含有量が１．０原子％を超えるとトラップ準位の増加による残留電位の上昇により、黒ベタ濃度の低下が見られ、さらに、表面硬度の低下よりキズの発生も見られた。
【０１１８】
弗素原子含有量が０．１原子％未満では、弗素による撥水性の効果が不充分となり、画像流れを発生した。また、２５原子％を超える含有量にするのは製造上難しく、無理に作製しようとするとクラックが発生したり（50原子％）、硬度が極端に低くなり（30原子％）、キズが発生した。
（例３）
（例１）に示す成膜条件に対して、ＮＯガスの導入に当り、濃度勾配を設けるよう流量比を変えて、本発明の感光体Ｃを作製した。その他の成膜条件や層構成は、（例１）の感光体と同一にしている。
【０１１９】
ＮＯガスは、最初に０．５ｓｃｃｍにて導入し、漸次増大し、最後に１１ｓｃｃｍにまで多くしているが、本例においては、前述した図５に示すような濃度勾配でもって作製した。
【０１２０】
これに対し、比較例の感光体Ａ、Ｂ、Ｄを作製した。感光体Ａについては、表面保護層を設けない場合、感光体Ｂでは、ＮＯガスの導入量を成膜中一定（５ｓｃｃｍ）にしている。また、感光体Ｄでは、ＮＯガスは、最初に１１ｓｃｃｍにて導入し、５０分間で漸次減少し、最後に０．５ｓｃｃｍにまで下げている。
そして、各感光体について（例１）に示すように感光体特性の評価手段でもって評価したところ、表３に示すような結果が得られた。ただし、いずれの感光体Ａ〜Ｄも酸素の平均含有量が０．０１〜０．１原子％、弗素含有量が３〜６原子％の範囲内にある。
【０１２１】
【表３】

【０１２２】
表３に示す結果から明らかなとおり、表面保護層の酸素原子の濃度勾配が感光体特性に大きな影響を与えており、本発明の感光体Ｃにおいては、帯電能および光感度特性に優れ、しかも、残留電位が小さくなっていることがわかる。これら帯電能、光感度特性および残留電位について、３段階に評価し、○印は良好であり、△印はやや良好であり、×印は実用に適していないことを示す。
本発明者は、酸素原子の濃度がフラットになっている感光体Ｂに比べて、表面側に高濃度である感光体Ｃの方が、光感度および残留電位の点で優れた結果が得られているが、その理由について、感光層３との界面での電気整合性がよく、これによってキャリアの移動がしやすくなっており、また、表面保護層内においても同様にキャリアが移動しやすくなったためであると考える。さらに、濃度勾配を逆にした感光体Ｄについては、光感度および残留電位が極端に悪くなり、実用上支障があるが、その点については、キャリアの移動が極端に劣化したためであると考える。
（例４）
（例３）においては、本発明の感光体Ｃを作製するに当り、ＮＯガスは、最初に０．５ｓｃｃｍにて導入し、漸次増加させ、最後に１１ｓｃｃｍにまで多くして、前述した図５に示すような濃度勾配でもって作製したが、これに代えて、図３、図４および図６に示すような濃度勾配でもって酸素を含有してもほぼ同じ良好な結果が得られたことを実験にて確かめた。
【０１２３】
詳細には、ＮＯガスは、最初に０．５ｓｃｃｍにて導入し、図３に示すように指数関数的に増加させ、最後に１１ｓｃｃｍにまで多くした感光体を作製し、その感光体特性を測定したところ、表４に示すような結果が得られた。同図中、その感光体を図３でもって表示している。
【０１２４】
さらにＮＯガスは、最初に０．５ｓｃｃｍにて導入し、０．５ｓｃｃｍで６０分間成膜し、その後、図４に示すように１１ｓｃｃｍにまで多くした感光体や、図６に示すように０．５ｓｃｃｍで１８０分間成膜させた後、最後の２０分間の成膜においては徐々に１１ｓｃｃｍまで増加させた感光体も作製し、その感光体特性を測定した。
【０１２５】
【表４】

【０１２６】
この表に示す結果から明らかなとおり、本発明の各感光体（図３、図４、図６）においては、帯電能および光感度特性に優れ、しかも、残留電位が小さくなっていることがわかる。
（例５）
（例１）の成膜条件に対して、Ｈ₂ガスの導入量を変えることで、表面保護層４の動的押し込み硬さを変えた感光体を作製し、それぞれの感光体について（例１）と同様に画像流れと画質を評価測定したところ、表５〜表７に示すような結果が得られた。ただし、いずれの感光体も酸素含有量が０．０１〜０．１原子％、弗素含有量が３〜６原子％の範囲内にある。
【０１２７】
【表５】

【０１２８】
【表６】

【０１２９】
【表７】

【０１３０】
これらの各表に示す結果から明らかなとおり、表面保護層の動的押し込み硬度が有機感光層に比べて１０倍〜６０倍の範囲であれば、画質および画像流れの双方が優れていることがわかる。
【０１３１】
しかし、１０倍未満になると耐刷による削れが大きくなり、ハーフトーン画像にキズが発生する。また、６０倍を超えると硬度差から密着性等が低減し、クラックおよび剥離が発生した。
【０１３２】
本発明者は表面保護層の硬度が同等でも削れ方が違ってくるのは、下地の有機感光層の硬度が影響しており、有機感光層の硬度が低いとクッションの役目を果たし、表面保護層の硬度が低くても耐久性に問題がなくなり、よって、有機感光層と表面保護層の硬度差が耐久性向上にとって重要であると考える。
（例６）
（例５）で作製された感光体に対し、画像形成装置のトナ−粒径を変えた時の画質評価（解像度：1200dpi）をしたところ、表８〜表１０に示すような結果が得られた。これは、最初に適正画像（トナ−粒径が小さいと感光体へのトナ−付着を防止するため、ブレ−ド圧が強くなっている）への調整を行なった後の評価結果である。
表８は有機感光層の硬度が１５kgf/mm²の場合であり、表９は有機感光層の硬度が２０kgf/mm²の場合であり、表１０は有機感光層の硬度が３０kgf/mm²の場合である。
【０１３３】
【表８】

【０１３４】
【表９】

【０１３５】
【表１０】

【０１３６】
ここで、画質（解像度、キズ）を４段階に評価し、◎印は１ドットの再現性が良好で、しかも、感光体にキズの全くないきわめて良好な画像が得られた場合であり、○印は１ドットの再現性が若干悪くなっているが、実用上支障がない場合であり、△印は１ドットの再現性で一部が薄くなったり抜けたりしている場合であり、×印はドットの再現性が悪い（ドットが抜けて白くなっている）、もしくは、感光体にキズがつき画像に筋として現れた場合である。
【０１３７】
これらの表から明らかなとおり、表面保護層４の硬度が有機感光層の硬度に比べて１０倍〜６０倍にまで高硬度化されたことで、３ミクロン未満という平均粒径の小さい液体トナ−を使用しても、クリーニングが最適化におこなうことができ、トナー付着が発生せず、充分な耐久性および画像品質が得られた。
しかし、表面保護層４の硬度が有機感光層の硬度に比べて１０倍未満の場合に、トナー粒径が小さくなると、表面保護層４にキズが発生した。また、トナー粒径が大きくなると、解像度が不良となる。
【０１３８】
【発明の効果】
以上のとおり、本発明の画像形成装置によれば、導電性支持体上に有機感光層と表面保護層とを順次積層した感光体であって、上記表面保護層は酸素原子を０．０００１原子％〜１．０原子％の範囲で含有し、弗素原子を０．１原子％〜２５原子％の範囲で含有するアモルファスカーボンにて構成し、酸素原子を有機感光層と表面保護層との界面とは反対側の表面近傍にて高濃度になるよう濃度勾配を設けて、その硬度を前記有機感光層の硬度に比べて１０倍〜６０倍にした感光体と、この感光体の表面に電荷を付与する帯電手段と、感光体の帯電領域に対して光照射する露光手段と、これら帯電手段と露光手段とにより感光体表面に形成された静電潜像に対して液体トナー像を感光体の表面に形成する現像手段と、上記液体トナー像を被転写材に転写する転写手段と、転写後に感光体表面の残留液体トナーを除去するクリーニング手段とを配設したことで、表面保護層の密着性を高めて優れた耐刷性が得られ、さらにクリーニング性を高めて、高耐久性、高画質、高性能および高信頼性が達成できた。
【０１３９】
また、本発明によれば、表面の疎水性を高めたことで、画像流れが発生しなくなり、さらに電位特性のバラツキをなくすことで、感光体用のヒーターを設けなくてもよく、これにより、構造上簡単となり、製造歩留まりが向上し、さらに部品点数が少なくなることで低コスト化を達成した画像形成装置が提供できた。
【０１４０】
さらに本発明においては、３μｍ以下の液体トナーを使用してもクリーニング性を高め、これによって高解像度を達成した画像形成装置が提供できた。
【図面の簡単な説明】
【図１】 本発明の感光体の層構成を示す断面図である。
【図２】 本発明の画像形成装置の概略図である。
【図３】 本発明の感光体に係る表面保護層における層厚方向にわたる酸素の濃度勾配を示す線図である。
【図４】 本発明の基礎となった感光体に係る表面保護層における層厚方向にわたる酸素の濃度勾配を示す線図である。
【図５】 本発明の感光体に係る表面保護層における層厚方向にわたる酸素の濃度勾配を示す線図である。
【図６】 本発明の感光体に係る表面保護層における層厚方向にわたる酸素の濃度勾配を示す線図である。
【符号の説明】
１…感光体２…導電性基板３…感光層４…表面保護層５…画像形成装置６…コロナ帯電器７…露光器（ＬＥＤヘッド）８…液体トナー９…現像機１０…被転写材１１…転写器１２…クリーニング手段１３…除電手段１４…定着器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus equipped with a photoconductor in which an amorphous carbon surface protective layer is mainly formed on an organic photosensitive layer.
[0002]
[Prior art]
So-called OPC photoconductors (organic photoconductors) composed of photosensitive layers made of organic semiconductor materials are widely used because they offer high chargeability, low dark decay, and excellent photosensitivity for long wavelengths. Has been. In addition, when using the OPC photosensitive member, there is an advantage that a heater for heating the OPC photosensitive member is not used.
[0003]
However, the OPC photoreceptor has a problem that the surface hardness is small and the durability is inferior.
[0004]
In order to solve this problem, a technique has been proposed in which a high-hardness wear-resistant film composed mainly of carbon or carbon is laminated on a photosensitive layer (organic photosensitive layer) made of an organic semiconductor material ( JP-B-7-27268, JP-B-7-122757, JP-A-1-86158, JP-A-1-227161, Japanese Patent No. 2818881, Japanese Patent No. 2818882 and Japanese Patent No. 2997070).
[0005]
Thus, the following characteristics are required for coating the surface protective layer from an inorganic material on the organic photosensitive layer.
[0006]
(1) Visible light transmittance is high (a sufficient amount of light incident on the organic photosensitive layer can be secured). (2) It has a high hardness so that the surface is not damaged. (3) Excellent adhesion to the organic photosensitive layer and does not peel off due to mechanical contact or changes in temperature and humidity during actual use in a copying machine. (4) Harmless. (5) Excellent electrical matching with the organic photosensitive layer, and no residual potential, memory phenomenon, or lateral flow of charge (image flow) at the mismatched interface. (6) Under high temperature and high humidity conditions, image quality does not deteriorate and so-called image flow does not occur. (7) The organic photosensitive layer is made of a compound having poor heat resistance, so that the coating thereon is performed at room temperature to 100 ° C., and the organic photosensitive layer is not thermally deteriorated.
[0007]
Various technical developments have been made in response to the recent demand for such characteristics. For example, since a plasma organic polymer film can be obtained by using a hydrocarbon compound containing oxygen atoms, it is still laminated as a surface protective layer on the organic photosensitive layer, whereby adhesion, electrical compatibility and A technique for improving the environmental resistance has been proposed (see Japanese Patent Publication No. 7-27268).
[0008]
Further, it has been proposed that the same effect can be obtained even if a halogen atom is contained instead of the oxygen atom as described above (see Japanese Patent Publication No. 7-122757).
[0009]
Furthermore, a technique has been proposed in which the surface protective layer on the organic photosensitive layer is composed of an amorphous hydrocarbon film containing halogen atoms and oxygen atoms, thereby improving moisture resistance (Japanese Patent Laid-Open 1-86158).
[0010]
According to the publication, the amount of halogen atoms contained in the amorphous hydrocarbon film is 0.01 atomic percent to 50 atomic percent with respect to all constituent atoms, and the amount of oxygen atoms is 0.01 to 20 atomic percent. . Regarding the hardness, the organic photosensitive layer is about 5B to B, and the amorphous hydrocarbon film is about 4H.
[0011]
Further, a technique for increasing the water repellency by laminating a surface protective layer made of diamond-like carbon having an amorphous structure containing 1 atomic% or less of nitrogen and 2 atomic% or more of fluorine on the organic photosensitive layer (Japanese Patent No. 2997070). See), a surface protective layer mainly composed of carbon or carbon containing 30 atomic% or less of hydrogen on an organic photosensitive layer having a surface oxygen concentration of 1 atomic% or less. A technique for improving the adhesion to the photosensitive layer has been proposed (see Japanese Patent No. 2818882).
[0012]
Regarding the hardness, the Vickers hardness of the surface protective layer is 100-2500 kg / mm²And the difference in Vickers hardness from the organic photosensitive layer is 2500 kg / mm²The following techniques have been proposed (see Japanese Patent No. 3057165).
[0013]
Furthermore, a technique using an amorphous silicon photoconductor provided with an amorphous silicon carbide surface layer in order to use a liquid toner has been proposed (see Japanese Patent Application Laid-Open No. 10-239937).
[0014]
[Problems to be solved by the invention]
However, when actually using a photoreceptor in which a surface protective layer made of amorphous carbon is laminated on the organic photosensitive layer as described above, the originally planned durability cannot be obtained, and scratches and peeling occur. When the memory deteriorates and printing is performed under high temperature and high humidity, an image defect called image flow occurs.
[0015]
In order to prevent such durability and the occurrence of image blurring, a technique for incorporating a halogen atom, an oxygen atom, or a nitrogen atom in the surface protective layer has been proposed, but various characteristics including electrophotographic characteristics are sufficient. No photoconductor satisfying the above has been obtained.
[0016]
That is, according to the techniques described in Japanese Patent Publication Nos. 7-27268 and 7-122757, an image flow is generated, and the amount of shaving due to durability is large and scratches are generated.
[0017]
The technique proposed in Japanese Patent Application Laid-Open No. 1-86158 has improved the image flow, but on the other hand, the photoreceptor characteristics are reduced (such as a decrease in charging ability and an increase in residual potential), and surface hardness. Was low and inferior in durability. In addition, the surface protective layer contains both halogen atoms and oxygen atoms, thereby improving the adhesion of the surface protective layer and further improving the electrophotographic characteristics (reducing optical memory). On the other hand, the characteristics of the photoconductor have been deteriorated due to an increase in the content of oxygen atoms.
[0018]
Further, according to Japanese Patent No. 2997070, a technique for defining the oxygen concentration on the surface of the organic photosensitive layer is proposed in order to improve the adhesion of the surface protective layer. In addition to being extremely difficult to manage, the required performance could not be obtained depending on the deposition conditions.
[0019]
In addition, according to Japanese Patent No. 3057165, a technique for defining the hardness of the surface protective layer and the hardness difference from the organic photoreceptor is proposed in order to increase the durability of the photoreceptor. Is unclear, and there is no lower limit of the hardness difference, making it difficult to set the actual hardness. Furthermore, the hardness difference is 2500 kg / mm on a particularly soft organic photosensitive layer.²If a surface protective layer was provided, the adhesion decreased due to the difference in hardness, cracks and peeling occurred, and the required performance could not be obtained.
[0020]
In Japanese Patent Application Laid-Open No. 10-239937, the use of an inorganic amorphous silicon photoreceptor is excellent in suitability for a liquid toner, but on the other hand, the charging ability is insufficient and image performance such as contrast cannot be obtained. In addition, the liquid toner has a smaller average particle diameter than the dry toner, and the toner adheres to the photosensitive member, and cleaning is extremely difficult.
[0021]
On the other hand, recently, there is an increasing demand for higher image quality (particularly higher resolution). To that end, it is necessary to reduce the toner particle size. There is a limit to reducing the toner particle size in the dry toner, and there are almost no toners of less than 5 μm (usually 8-30 μm), and it is difficult for the dry toner to obtain a resolution exceeding 1200 dpi. It has become.
[0022]
On the other hand, when a liquid toner is used, it becomes easy to reduce the toner particle size, and in particular, by setting it to 3 μm or less, an image quality of 1200 dpi or more can be obtained.
[0023]
The present inventor made extensive studies in view of the above circumstances. As a result, a surface protective layer made of amorphous carbon was laminated on the organic photosensitive layer, and oxygen atoms were added to the amorphous carbon surface protective layer in an amount of 0.0001 atomic% to 1. In the range of 0 atom%, fluorine atoms are contained in the range of 0.1 atom% to 25 atom%, and oxygen atoms are high in the vicinity of the surface opposite to the interface between the organic photosensitive layer and the surface protective layer. By providing a concentration gradient so as to achieve a concentration, the hardness of the surface protective layer is increased to 10 to 60 times the hardness of the organic photosensitive layer, and the adhesion is further improved to prevent cracks and peeling. This will not cause image deterioration due to image flow and long-term use. In particular, even if a liquid toner having a small average particle diameter of less than 3 microns is used, the cleaning property is improved and sufficient durability and image quality are obtained. It was found that to be.
[0024]
The present invention has been completed based on the above knowledge, and its purpose is to improve the adhesion of the surface protective layer to obtain excellent printing durability, and further to improve the cleaning property, thereby providing high durability, high image quality and high performance. Another object of the present invention is to provide an image forming apparatus equipped with a photoconductor that achieves high reliability.
[0025]
Another object of the present invention is to increase the hydrophobicity of the surface, so that no image bleed occurs, and further, there is no need to provide a heater for the photoconductor by eliminating variations in potential characteristics. It is an object of the present invention to provide an image forming apparatus which is simple in structure, improves the manufacturing yield, and further reduces the cost by reducing the number of parts.
[0026]
Another object of the present invention is to provide an image forming apparatus that achieves high resolution by improving cleaning properties even when liquid toner of 3 μm or less is used.
[0027]
[Means for Solving the Problems]
  In the image forming apparatus of the present invention, an organic photosensitive layer and a surface protective layer are sequentially laminated on a conductive support, and the surface protective layer contains oxygen atoms in a range of 0.0001 atomic% to 1.0 atomic%. And made of amorphous carbon containing fluorine atoms in the range of 0.1 atomic% to 25 atomic%,A concentration gradient is continuously formed so that the concentration of the oxygen atoms gradually increases as it approaches the vicinity of the surface opposite to the interface between the organic photosensitive layer and the surface protective layer.The photosensitive member whose hardness is 10 to 60 times the hardness of the organic photosensitive layer, the charging means for applying a charge to the surface of the photosensitive member, and the charged region of the photosensitive member are irradiated with light. An exposure unit, and a developing unit that forms a liquid toner image on the surface of the photoreceptor with toner having an average particle diameter of 3 μm or less with respect to the electrostatic latent image formed on the surface of the photoreceptor by the charging unit and the exposure unit; A transfer means for transferring the liquid toner image to a transfer material and a cleaning means for removing residual liquid toner on the surface of the photosensitive member after transfer are provided.
In the image forming apparatus of the present invention, the oxygen concentration in the vicinity of the surface of the surface protective layer is set to 1.5 to 100 times the oxygen concentration on the interface side between the organic photosensitive layer and the surface protective layer. And
Furthermore, in the image forming apparatus of the present invention, the oxygen concentration in the vicinity of the surface of the surface protective layer is set to 4 to 20 times the oxygen concentration at the interface side between the organic photosensitive layer and the surface protective layer. .
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings.
FIG. 1 is an enlarged cross-sectional view of a main part of a photoreceptor mounted on the image forming apparatus of the present invention, and FIG. 2 is a diagram showing an outline of the image forming apparatus of the present invention.
[0029]
According to the photoreceptor 1 shown in FIG. 1, a photosensitive layer 3 which is the organic semiconductor layer is applied and formed on a conductive substrate 2, and a surface protective layer 4 is formed on the photosensitive layer 3 by a glow discharge decomposition method or the like. Laminated.
[0030]
The surface protective layer 4 is made of amorphous carbon containing oxygen atoms in the range of 0.0001 atomic% to 1.0 atomic% and fluorine atoms in the range of 0.1 atomic% to 25 atomic%.
[0031]
In addition, when the surface protective layer 4 contains oxygen atoms, a concentration gradient is provided so that the oxygen atoms have a high concentration in the vicinity of the surface opposite to the interface between the photosensitive layer 3 and the surface protective layer 4. .
[0032]
The photoreceptor 1 is mounted on the image forming apparatus shown in FIG.
The image forming apparatus 5 has a printer configuration, and includes a corona charger 6 on the peripheral surface of the photosensitive member 1, an exposure device 7 (LED head) that irradiates light after the charging, and a liquid toner image (particle size of 3 μm or less, for example, 1.5 μm) on the surface of the photosensitive member 1, a developing device 9 having a liquid toner 8, a transfer device 11 for transferring the liquid toner image to the transfer material 10, and a surface of the photosensitive member after transfer. A cleaning unit 12 for removing the residual liquid toner and a neutralizing unit 13 for removing the residual electrostatic latent image after the transfer are provided. Reference numeral 14 denotes a fixing device for fixing the liquid toner image transferred to the transfer material 10 by heat or pressure.
[0033]
In the Carlson method, the following processes (1) to (6) are repeated.
(1) The peripheral surface of the photoreceptor 1 is charged by the corona charger 6.
(2) An electrostatic latent image as a potential contrast is formed on the surface of the photoreceptor 1 by exposing the image with the exposure device 7.
(3) The electrostatic latent image is developed by the developing device 9. By this development, the black liquid toner adheres to the surface of the photoreceptor due to electrostatic attraction with the electrostatic latent image, and is visualized.
(4) A liquid toner image on the surface of the photoreceptor is electrostatically transferred by applying an electric field having a polarity opposite to that of the liquid toner from the back surface of the transfer material 10 such as paper, thereby obtaining an image on the transfer material 10. .
(5) The residual liquid toner on the surface of the photosensitive member is mechanically removed by the cleaning unit 12.
(6) The entire surface of the photosensitive member is exposed with strong light, and the remaining electrostatic latent image is removed by the charge eliminating unit 13.
[0034]
Although the image forming apparatus 5 has a printer configuration, if an optical system such as a lens or a mirror that transmits reflected light from a document is used instead of the exposure device 7, an image forming apparatus having a copier configuration is obtained.
[0035]
Further, according to the present invention, the cleaning means 12 for removing the residual liquid toner on the photoreceptor 1 includes a blade method, a fur brush method, a magnet brush method, etc., and any method is adopted. Even so, the residual liquid toner may be removed immediately. However, as the toner particle size becomes smaller, the adhesive force tends to increase. For this reason, the pressure applied to the photosensitive member such as a blade must be increased and removed. In order to meet this requirement, the photosensitive member 1 for a liquid toner is required to have a very high hardness that can withstand a strong pressure such as a blade.
[0036]
Therefore, in the present invention, the surface protective layer 4 contains oxygen atoms in the range of 0.0001 atomic% to 1.0 atomic% and fluorine atoms in the range of 0.1 atomic% to 25 atomic%. By being composed of amorphous carbon, the hardness of the surface protective layer 4 is remarkably increased, and the hardness is increased to 10 to 60 times the hardness of the organic photosensitive layer. Extremely high hardness that can withstand strong pressure is achieved.
[0037]
Moreover, by setting the hardness within such a range, even when a liquid toner having a small average particle diameter of 3 μm or less is used, cleaning can be performed optimally, toner adhesion does not occur, and sufficient durability is achieved. And image quality is obtained. In the present invention, the average particle diameter of the toner is represented by a number average.
[0038]
The liquid toner in the present invention may be of a conventionally known configuration, and is obtained by dispersing charged toner particles in a liquid having a high insulating property and a low dielectric constant. The pigment particles of about 3 μm are wrapped with resin.
[0039]
Typical examples of this resin include lauryl methacrylate, stearyl methacrylate, ethyl methacrylate, acrylic acid, methacrylic acid, dimethylaminomethyl methacrylate, and diethylaminoethyl methacrylate when expressed in terms of monomers.
[0040]
In addition, charge control materials are adsorbed to the resin, and polarities are determined by a selective adsorption model, such as naphthenic acid, octylic acid, calcium alkylbenzene sulfonate, and other acids between the toner particle surface and the bulk.・ A base model whose polarity is determined may be used.
[0041]
For such a liquid toner, a toner having a small diameter of 2 μm or less can be obtained by using a phase separation technique in which toner particles are precipitated from an organic solvent using a temperature difference.
[0042]
In the present invention, the particle size of the liquid toner is measured with a Coulter counter.
[0043]
As described above, according to the present invention, the pressure of the cleaning means 12 applied to the photosensitive member 1 is increased by using the liquid toner. However, when a blade or an elastic roller is used, the linear pressure is 30. A load of ˜350 g / cm is preferable. When an elastic roller is used, the rotation speed is preferably set to 1.0 to 1.60 times the rotation speed of the photoconductor, and the hardness is preferably set to 25 to 60 ° HS.
[0044]
In addition, with any cleaning method, the linear pressure (vertical force) is 1.2 to 2.5 times better than the condition that a good image can be obtained when dry toner is used. Images can be obtained. If it is less than 1.2 times, toner adhesion occurs, and if it exceeds 2.5 times, the surface of the photoconductor is excessively shaved and streaks are likely to occur in the image. If so, scratches will not occur. However, when the linear pressure becomes excessive, driving of the photosensitive member is added, thereby generating a chatter mark in an image called jitter.
[0045]
Next, the conductive substrate 2 and each layer of the photoreceptor 1 will be described in detail.
[0046]
About conductive substrate 2
Examples of the conductive substrate 2 include a metal conductor such as copper, brass, SUS, Al, and Ni, or a surface of an insulator such as glass and ceramic covered with a conductive thin film. The conductive substrate 2 may be a sheet-like, belt-like or web-like flexible conductive sheet, such as a metal sheet such as SUS, Al, Ni, or a polymer resin film such as polyester, nylon, polyimide, etc. A metal such as Al or Ni or a transparent conductive material such as tin oxide or indium tin oxide (ITO) or an organic conductive material coated thereon by vapor deposition is used.
[0047]
Specific configuration example of photosensitive layer 3
The photosensitive layer 3 includes a single-layer type photosensitive layer in which a charge transport agent is dispersed in the same photosensitive layer together with a charge generator, a charge generation layer containing a charge generator, and a charge transport layer containing a charge transport agent. However, the present invention can be applied to any of these.
[0048]
For a single-layer type photosensitive layer, a coating solution in which a charge generating agent, a charge transporting agent and a binder resin are dissolved or dispersed in a suitable organic solvent is applied onto a conductive substrate by a means such as coating and dried. Formed with. Such a single-layer type photosensitive layer has a simple layer structure and excellent productivity.
[0049]
As the charge transporting agent, either one or both of an electron transporting agent and a hole transporting agent can be used. In particular, a single-layer type photosensitive layer using both the above transporting agents has a positive charge and a negative charge in a single configuration. There is an advantage that it can respond.
[0050]
As the electron transport agent and the hole transport agent, it is desirable that the electron transport agent and the hole transport agent each have a good matching with the charge generation agent and can efficiently transport by extracting the electrons or holes generated in the charge generation agent.
[0051]
In addition, in a system in which an electron transport agent and a hole transport agent coexist, both form a charge transfer complex, which causes a decrease in charge transport ability in the entire photosensitive layer and prevents a decrease in sensitivity of the photoreceptor. Therefore, it is necessary to consider the combination of both transport agents. In other words, even when both transport agents are contained in the same layer at a high concentration where hole transport and electron transport occur efficiently, a charge transfer complex is not formed in the layer, and the hole transport agent converts holes into electrons. As the transport agent, it is desirable to select a combination of an electron transport material and a hole transport agent that can efficiently transport electrons.
[0052]
On the other hand, in the multilayer type photosensitive layer, first, a charge generation layer containing a charge generation agent is formed on a conductive substrate by means of vapor deposition or coating, and then a charge transport agent is bonded onto the charge generation layer. A coating liquid containing a coating resin is applied by means such as coating and dried to form a charge transport layer. In contrast to the above, a charge generation layer may be formed on a conductive substrate and a charge generation layer may be formed thereon.
[0053]
However, since the charge generation layer is much thinner than the charge transport layer, it is necessary to form a charge generation layer on a conductive substrate and then form a charge transport layer on the conductive substrate for protection. preferable.
[0054]
The layered photosensitive layer is selected to be either a positive or negative charge type depending on the order of formation of the charge generation layer and charge transport layer and the type of charge transport agent used in the charge transport layer.
[0055]
For example, as described above, in a layer structure in which a charge generation layer is formed on a chargeable substrate and a charge transport layer is formed thereon, when a hole transport agent is used as the charge transport agent of the charge transport layer, The photosensitive layer is negatively charged. In this case, the charge generation layer may contain an electron transport agent. As the electron transport agent to be contained in the charge generation layer, it is desirable that the electron transport agent has good matching with the charge generation agent and can efficiently transport by extracting the electrons generated by the charge generation agent.
[0056]
On the other hand, in the above layer configuration, when an electron transport agent is used as the charge transport agent of the charge generation layer, the photosensitive layer is a positively charged type. In this case, the charge generation layer may contain a hole transport agent.
[0057]
[Single-layer type photosensitive layer 3]
Since the electron transfer agent does not form a charge transfer complex with the hole transfer agent, it is particularly suitable for a single layer type photosensitive layer (photosensitive layer 3) in which the electron transfer agent and the hole transfer agent are used in combination.
[0058]
A single-layer type photosensitive layer is a single layer containing an electron transport agent, a charge generator, and a binder resin, and can handle both positive and negative charges, but does not require the use of negative corona discharge. Preferably used in molds. This single-layer type has advantages such as a simple layer structure and excellent productivity, suppression of the occurrence of film defects in the photosensitive layer, and improvement in optical characteristics since there are few interfaces between layers.
[0059]
The single-layer type that uses an electron transport agent in combination with a hole transport agent having excellent hole transportability does not cause an interaction between the electron transport agent and the hole transport agent. Even if it is contained in the layer, electron transport and hole transport can be efficiently performed, and a more sensitive photoreceptor can be obtained.
[0060]
In addition, in the single-layer type photosensitive layer 3 containing an electron acceptor together with an electron transport agent, the electron transport performance can be further improved, and a more sensitive photoreceptor can be obtained.
[0061]
In the single-layer type photosensitive layer 3, the electron transport agent may be contained in the range of 5 to 100 parts by weight, preferably 10 to 80 parts by weight with respect to 100 parts by weight of the binder resin. If the amount of the electron transfer agent is less than 10 parts by weight, the residual potential becomes high and the sensitivity may be insufficient. If the amount exceeds 500 parts by weight, crystallization may occur and the performance as a photoreceptor is sufficiently exhibited. Not.
[0062]
[Laminated photosensitive layer 3]
On the other hand, the laminated type is a layer in which a charge generation layer containing a charge generation agent and a charge transport layer containing a charge transfer agent are laminated in this order or in the reverse order.
[0063]
Since the charge generation layer is much thinner than the charge transport layer, it is preferable to form the charge generation layer on the conductive substrate and to form the charge transport layer thereon for protection.
[0064]
The laminated type photosensitive layer 3 is selected as a positive or negative charge type depending on the order of formation of the charge generation layer and the charge transport layer and the kind of the charge transport agent used in the charge transport layer. For example, when an electron transport agent such as a quinone derivative is used as the electron transport agent in the charge transport layer in the layer structure in which the charge generation layer is formed on the conductive substrate 2 and the charge transport layer is formed thereon. Becomes a positively charged photoreceptor. In this case, the charge generation layer may contain a hole transport agent or an electron transport agent. Here, when an electron acceptor is contained in the charge transporting layer, the electron transporting property is improved, so that a more sensitive layered type photoreceptor can be obtained.
[0065]
In the above layer structure, when a hole transporting agent is used as the charge transporting agent in the charge transporting layer, a negatively charged photoreceptor is obtained. In this case, the charge generation layer may contain an electron transport agent or an electron acceptor.
[0066]
The laminated photosensitive layer 3 includes a charge generation layer containing a charge generation agent and a binder resin, and a charge transport layer containing an electron transfer agent. The mixing ratio of the electron transport agent in the laminated type is 10 to 500 parts by weight, preferably 25 to 100 parts by weight, based on 100 parts by weight of the binder resin, for the same reason as in the case of the single layer type.
[0067]
As described above, the photosensitive member 1 can be applied to both a single layer type and a laminated type, but can be used for any positive or negative charging type, has a simple structure and is easy to manufacture, and forms a layer. The single layer type is preferable from the viewpoints of suppressing the film defects at the time, reducing the interface between the layers, and improving the optical characteristics.
[0068]
Next, various materials used for the photosensitive layer 3 will be described.
[0069]
<Charge generator>
Various phthalocyanine pigments, polycyclic quinone pigments, azo pigments, perylene pigments, indigo pigments, quinacridone pigments, azulenium salt pigments, squarylium pigments, cyanine pigments, pyrylium dyes, thiopyrylium dyes, xanthene dyes, quinoneimmune dyes, triphenylmethane dyes, styryl Organic photoconductive materials such as dyes, ansanthrone pigments, pyrylium salts, triphenylmethane pigments, selenium pigments, toluidine pigments, pyrazoline pigments, inorganic photoconductive materials such as selenium, tellurium, amorphous silicon, cadmium sulfide These can be used alone or in combination of two or more.
[0070]
《Hole transport agent》
Main compounds having high hole transport ability, for example, oxadiazole-based compounds such as 2,5-di (4-methylaminophenyl) -1,3,4-oxadiazole, 9- (4- Styryl compounds such as diethylaminostyryl) anthracene, carbazole compounds such as polyvinylcarbazole, organic polysilane compounds, pyrazoline compounds such as 1-phenyl-3 (p-dimethylaminophenyl) pyrazoline, hydrazone compounds, triphenylamine compounds , Indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, triazole compounds, nitrogen-containing cyclic compounds such as stilbene compounds, condensed polycyclic compounds Etc.
[0071]
A hole transport agent may be used alone or in combination of two or more. Further, when a hole transporting agent having film forming properties such as polyvinyl carbazole is used, the binder resin is not necessarily required.
[0072]
《Electron transport agent》
Examples of the electron transport agent include various compounds having a high electron transport ability, such as naphthoquinone compounds, pyrazoline compounds, benzoquinone compounds, diphenoquinone compounds, malononitrile, thiopyran compounds, tetracyanoethylene cyanoethylene, 2, 4, Examples thereof include 8-trinitrothioxanthone, dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, dinitroanthraquinone, succinic anhydride, maleic anhydride, dibromomaleic anhydride and the like.
[0073]
<Binder resin>
Conventionally known resins used for the photosensitive layer can be used. For example, styrene-butadiene copolymer, styrene-acrylonitrile resin, styrene-maleic acid copolymer, acrylic copolymer, styrene-acrylic copolymer, polyethylene, ethylene-vinyl acetate copolymer, chlorination Polyethylene, polyvinyl chloride, polypropylene, ionomer, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, polycarbonate, polyarylate, polysulfone, diallyl phthalate, ketone resin, polyvinyl butyral resin, polyether resin, polyester Thermoplastic resins such as resins; silicone resins, epoxy resins, phenol resins, urea resins, melamine resins, and other cross-linkable thermosetting resins; photo-curing types such as epoxy acrylates and urethane-acrylates Resin butter, and the like can be used.
[0074]
Furthermore, in addition to the above-described components, the photosensitive layer 3 has various conventionally known additives such as an antioxidant, a radical scavenger, a singlet quencher, and an ultraviolet absorber as long as the electrophotographic characteristics are not adversely affected. Deterioration preventing agents such as, softeners, plasticizers, surface modifiers, extenders, thickeners, dispersion stabilizers, waxes, acceptors, donors, and the like can be blended. In order to improve the sensitivity of the photosensitive layer, known sensitizers such as terphenyl, halonaphthoquinones, and acenaphthylene may be used in combination with the charge generator.
[0075]
In the single-layer type photosensitive layer 3, the charge generating agent may be blended in an amount of 0.1 to 50 parts by weight, preferably 0.5 to 30 parts by weight with respect to 100 parts by weight of the binder resin. When an electron transporting agent is included as the charge transporting agent, it may be blended at a ratio of 5 to 100 parts by weight, preferably 10 to 80 parts by weight, with respect to 100 parts by weight of the binder resin. In addition, when the hole transport agent is contained, the ratio of the hole transport agent may be 5 to 500 parts by weight, preferably 25 to 200 parts by weight with respect to 100 parts by weight of the binder resin. Furthermore, the thickness of the single-layer type photosensitive layer 3 is 5 to 100 μm, preferably 10 to 50 μm.
[0076]
On the other hand, in the laminated photosensitive layer 3, the charge generating agent and the binder resin constituting the charge generating layer can be used in various ratios, but the charge generating agent is used with respect to 100 parts by weight of the binder resin. 5 to 1000 parts by weight, preferably 30 to 500 parts by weight. When the hole transport agent or the electron transport agent is contained in the charge generation layer, the ratio thereof is 0.1 to 100 parts by weight, preferably 0.5 to 80 parts by weight with respect to 100 parts by weight of the binder resin. Good.
[0077]
The charge transporting agent and the binder resin constituting the charge transporting layer can be used in various proportions within a range that does not inhibit charge transport and a range that does not crystallize, but the charges generated in the charge generation layer by light irradiation. The charge transfer agent may be blended in an amount of 10 to 500 parts by weight, preferably 25 to 100 parts by weight with respect to 100 parts by weight of the binder resin. When the hole transport agent is contained in the charge transport layer, the ratio of the hole transport agent may be 5 to 200 parts by weight, preferably 10 to 80 parts by weight with respect to 100 parts by weight of the binder resin.
[0078]
In the single layer type, between the conductive substrate 2 and the photosensitive layer 3, and in the laminated type, between the conductive substrate 2 and the charge generation layer, between the conductive substrate 2 and the charge transport layer, or charge. A barrier layer may be formed between the generation layer and the charge transport layer as long as the characteristics of the photoreceptor are not impaired.
[0079]
[Method for Forming Photosensitive Layer 3]
A method for forming the photosensitive layer 3 having such a structure will be described. The charge generator, charge transport agent, and binder resin exemplified above are combined with an appropriate solvent, and known methods such as a roll mill, a ball mill, an attritor, a paint shaker, A dispersion liquid may be prepared by dispersing and mixing using a sonic disperser or the like, and this may be applied and dried by a known means.
[0080]
As the solvent for preparing the dispersion, various organic solvents can be used, for example, alcohols such as methanol, ethanol, isopropanol and butanol; aliphatic hydrocarbons such as n-hexane, octane and cyclohexane; benzene, Aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride and chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; acetone, methyl ethyl ketone Ketones such as cyclohexanone; esters such as ethyl acetate and methyl acetate; dimethylformaldehyde, dimethylformamide, dimethylsulfoxide, etc. It is. These solvents are used alone or in admixture of two or more.
[0081]
Further, a surfactant, a leveling agent or the like may be used in order to improve the dispersibility of the charge transport agent or charge generator and the smoothness of the photosensitive layer surface.
[0082]
Structure of the surface protective layer 4
The surface protective layer 4 contains carbon or carbon containing oxygen atoms in a content ratio of 0.0001 atomic% to 1.0 atomic% and further containing fluorine atoms in a content ratio of 0.1 atomic% to 25 atomic%. The hardness of this film is set to 10 times or more and 60 times or less than the hardness of the photosensitive layer 3 which is an organic photosensitive layer.
[0083]
Explaining this point in detail, the fluorine content may be 0.1 to 25 atomic%, preferably 2 to 20 atomic%, preferably less than 0.1 atomic%, based on the total amount of various atoms constituting the surface protective layer 4. In this case, image flow occurs, and when it exceeds 25 atomic%, the terminal portion increases in the bonded state, the network between atoms decreases, and the interatomic bond such as C-C decreases, thereby increasing the film strength. As a result, the film is scraped and scratched.
[0084]
Further, when the fluorine content exceeds 25 atomic%, it is inevitably difficult from the viewpoint of structure and glow discharge, and if the content is forced to increase, the photoreceptor characteristics and hardness are inferior.
[0085]
The oxygen content may be 0.0001 to 1.0 atomic%, preferably 0.01 to 0.5 atomic%, preferably 0.0001 atomic%, based on the total amount of various atoms constituting the surface protective layer 4. If it is less than the range, the adhesion and electrical consistency are poor, and peeling from the interface or the optical memory characteristics deteriorate.
[0086]
When the oxygen content exceeds 1.0 atomic%, various photoconductor characteristics such as increased trap levels due to deterioration of the surface protective layer film quality, increased residual potential, and decreased charging ability are deteriorated. Further, as the film density is further lowered, the surface hardness is lowered.
[0087]
In the present invention, as shown in FIGS. 3 to 6, a concentration gradient is provided so that oxygen atoms have a high concentration in the vicinity of the surface opposite to the interface between the photosensitive layer 3 and the surface protective layer 4.
[0088]
In each figure, on the horizontal axis, a is the interface between the photosensitive layer 3 and the surface protective layer 4, and b is the outermost surface (free surface) of the surface protective layer 4. The vertical axis represents the oxygen content. Note that these concentration gradients are merely examples, and the present invention is not limited thereto, and various other concentration gradients may be performed.
[0089]
Thus, when providing a concentration gradient so that oxygen atoms have a high concentration in the vicinity of the surface opposite to the interface between the photosensitive layer 3 and the surface protective layer 4, the average oxygen content ratio in the entire surface protective layer 4 is provided. May be 0.0001 to 1.0 atomic%, preferably 0.01 to 0.5 atomic%.
[0090]
The hardness of the surface protective layer 4 should be 10 to 60 times, preferably 20 to 50 times that of the organic photosensitive layer (photosensitive layer 3). If this ratio is less than 10 times, the hardness is not good. It becomes sufficient, and the durability (the cleaning ability is raised to prevent toner adhesion) cannot be satisfied. On the other hand, if it exceeds 60 times, the hardness difference is too large and the surface protective layer 4 is cracked.
[0091]
The hardness specified in the present invention is evaluated by dynamic indentation hardness. This dynamic indentation hardness is expressed in terms of dynamic hardness using an ultra-micro hardness meter (DUH-201 / 202) manufactured by Shimadzu Corporation.
[0092]
According to this measuring method, an indenter (triangular pancreas indenter) is pressed against a sample by an electromagnet, the pressing force is increased at a constant rate from a load of 0.1 gf to 2 gf, and the indenter enters the sample, The depth of penetration of the indenter into the sample is automatically measured. The size of the indentation generated at that time is measured with a microscope, and the hardness value is obtained from the plastic deformation.
[0093]
Thus, as described above, the surface protective layer 4 contains oxygen atoms in a content ratio of 0.0001 atomic% to 1.0 atomic% and further contains fluorine atoms in a content ratio of 0.1 atomic% to 25 atomic%. It is formed with carbon containing carbon or an amorphous carbon film mainly composed of carbon, and a concentration gradient is formed so that oxygen atoms have a high concentration in the vicinity of the surface opposite to the interface between the photosensitive layer 3 and the surface protective layer 4. In addition, by setting the hardness of the film to 10 times or more and 60 times or less compared to the hardness of the photosensitive layer 3 that is an organic photosensitive layer, excellent printing durability that can withstand the blade is obtained. The degree of scraping with toner or the like was remarkably reduced, so that an image was not generated and a high-performance photoconductor capable of obtaining a resolution of 1200 dpi or higher was obtained.
[0094]
In particular, a concentration gradient is provided so that oxygen atoms have a high concentration in the vicinity of the surface on the side opposite to the interface between the photosensitive layer 3 and the surface protective layer 4, thereby improving electrical compatibility at the interface with the photosensitive layer 3. This facilitates the movement of carriers, and also facilitates the movement of carriers in the surface protective layer. As a result, excellent results are obtained in terms of photosensitivity, residual potential, and resolution.
Further, the present inventor, as a suitable constituent element for exhibiting such an effect, has a surface opposite to the interface with respect to the concentration of oxygen atoms in the vicinity of the interface between the photosensitive layer 3 and the surface protective layer 4. It was confirmed by repeated experiments that the concentration of oxygen atoms in the vicinity should be 1.5 to 100 times, preferably 4 to 20 times.
Method for forming surface protective layer 4
The film is formed by the glow discharge method. The film forming condition is, for example, a degree of vacuum of 0.35 torr (4.6 × 10 6^-FivePa), a substrate temperature of 50 ° C., and a high-frequency power of 200 W are converted into plasma and laminated on the organic photosensitive layer.
[0095]
For this purpose, hydrocarbon gas, oxygen compound gas, and fluorine compound gas are used as the raw material gas for glow discharge, and commonly used hydrogen gas or argon gas is used as the carrier gas.
[0096]
The above hydrocarbon gas includes saturated hydrocarbons such as methane, ethane, propane, butane, pentane, hexane, heptane, octane, isobutane, isopentane, neopentane, isohexane, neohexane, dimethylbutane, methylhexane, ethylpentane, dimethylpentane. , Triptan, methylheptane, dimethylhexane, trimethylpentane, isononone and the like.
[0097]
The hardness of the amorphous carbon film constituting the surface protective layer 4 varies depending on the form of the film forming apparatus and the conditions during film formation (including the impurity doping amount). For example, the substrate temperature is increased, the dilution rate is increased, Hardness is increased by increasing the applied power.
[0098]
An oxygen compound gas is used to add oxygen atoms to the amorphous carbon film. Examples of the oxygen compound include inorganic compounds such as oxygen, ozone, water vapor, carbon monoxide, carbon dioxide, nitrogen monoxide and carbon suboxide, and organic compounds having functional groups or bonds such as hydroxyl groups and oxygen-containing heterocyclic rings. Etc.
[0099]
In order to add fluorine atoms to the amorphous carbon film, a fluorine compound gas is used. As this fluorine compound, inorganic compounds such as fluorine, hydrogen fluoride, chlorine fluoride, iodine fluoride and the like are used.
[0100]
The thickness of the surface protective layer 4 is preferably 0.1 to 2.5 μm. When the film thickness is thinner than 0.1 μm, durability due to film shaving cannot be secured, and it is affected by the base. On the other hand, when the film thickness exceeds 2.5 μm, the light transmittance is deteriorated and a residual potential is generated.
[0101]
【Example】
(Example 1)
The photosensitive layer 3 is applied and formed on a cylindrical substrate (outer diameter 30 mm, length 254 mm) made of Al having a purity of 99.9% to be used for a positively charged laser printer. This photosensitive layer 3 was formed as follows.
[0102]
50 parts by weight of X-type metal-free phthalocyanine as a charge generator, 100 parts by weight of polycarbonate as a binder resin, 800 parts by weight of tetrahydrofuran as a solvent, and 100 parts by weight of diethylaminobenzaldehyde diphenylhydrazone of Chemical Formula 1 as a hole transporting agent in a ball mill for 50 hours A coating solution for a single layer photoreceptor was prepared by mixing and dispersing.
[0103]
[Chemical 1]

[0104]
Then, this coating solution was applied on an aluminum base tube by a dip coating method and dried at 100 ° C. for 1 hour to form a photosensitive layer 3 having a film thickness of 25 μm, thereby forming a single layer type.
[0105]
The dynamic indentation hardness of the photosensitive layer 3 is 20 kgf / mm.²Met. However, the measurement was performed without a surface protective layer.
[0106]
Next, an amorphous layer made of carbon (C) having a thickness of 5000 mm is formed and formed on the surface protective layer 4 under the film forming conditions shown in Table 1.
[0107]
NO gas is initially introduced at 0.8 sccm, gradually increases in 200 minutes, and finally increases to 11 sccm. By introducing the NO gas in this way, a linear oxygen concentration gradient is provided as shown in FIG.
[0108]
[Table 1]

[0109]
This surface protective layer 4 has a dynamic indentation hardness of 300 kgf / mm.²The fluorine atom content is 5 atomic% and the oxygen atom content is 0.01 atomic%. These contents were measured by secondary ion mass spectrometry (SIMS).
[0110]
The photoreceptor of the present invention thus obtained was mounted on the image forming apparatus 5 (Ecosys LS-1700 modified machine manufactured by Kyocera Corporation, wet development: toner average particle diameter 2.5 μm) and provided in this apparatus 5. The switching of the heater for heating the photoconductor was always turned off, and the photoconductor was not heated. Then, the image was formed by the Carlson method, the running test of 300,000 sheets was performed, and the image flow and image quality were measured. As a result, there was no image flow, and there was no fog, streak, etc., and no problem at all. Results were obtained.
[0111]
(Example 2)
Next, in manufacturing the photoreceptor shown in (Example 1), the photosensitive layer 3 is made to have the same configuration, and the surface protective layer 4 is changed in the amount of NO gas introduced, and other film formation conditions are set ( Various photoconductors were prepared by setting the same as the photoconductor of Example 1).
That is, when the surface protective layer 4 was formed, the amount of NO gas introduced was gradually increased along with the film formation. Specifically, the oxygen atom content was reduced to 0% near the interface with the organic photosensitive layer. 0.00008 atomic% (NO gas amount: 0.5 sccm), and the oxygen concentration is increased linearly toward the free surface as shown in FIG. All photoreceptors have a hardness of 250 to 350 kgf / mm.²It is in the range.
In each of these photoreceptors, when no fluorine atom is contained in the surface protective layer, the image quality and image flow of each of these photoreceptors are measured by further containing fluorine atoms at a concentration of 0.05 to 50 atomic%. As a result, the results shown in Table 2 were obtained. In the table, the oxygen atom content is an average value of the entire surface protective layer. When the average content of oxygen atoms is 0.00008 atomic%, it indicates that the concentration is constant throughout the thickness direction, and when the average content is less than that, the concentration is gradually decreased and beyond In the case of the average value, the case where the concentration is gradually increased is shown.
[0112]
[Table 2]

[0113]
The image flow is left in an environment of 33 ° C. and 85% humidity for 8 hours, and the image quality is evaluated in 4 stages. The mark ◎ indicates that there is no image change and a very good image is obtained. Although some image changes may be observed, there is no practical problem. The Δ mark indicates that a part of the image has flowed and the X mark indicates that the image has flowed over the entire surface.
[0114]
The image quality is also evaluated in four stages, with black solids, white solids and halftone images. The ◎ mark shows no reduction in black solid density and no fogging in the white solids, and no streaks appear in the halftone images. In this case, a very good image quality is obtained. A black circle indicates a slight decrease in the black solid density or a slight streak may be observed in the halftone image, but there is no practical problem. △ mark indicates a case where streaks occur in a part of a halftone image, or a black solid density is reduced or a slight solid fog occurs, and an X mark indicates a halftone image. This is the case where streaks occur, the black solid density decreases, or the white solid is fogged and is not suitable for practical use.
[0115]
As is apparent from Table 2, both the image flow and the image quality are excellent by setting the oxygen atom content to 0.0001 to 1.0 atomic% and the fluorine atom content to 0.1 to 25 atomic%. I understand that. In particular, with regard to the image quality, no fogging was confirmed at all in black solid density reduction and white solid, and no streak was generated in the halftone image, and an extremely good image quality was obtained.
[0116]
However, when the oxygen atom content is less than 0.0001 atomic%, the optical memory is poor, fogging occurs, adhesion is partially deteriorated, peeling occurs, and scratches are seen in the halftone image. .
[0117]
In addition, when the oxygen atom content exceeds 1.0 atomic%, the residual potential is increased due to the increase of the trap level, so that the black solid density is decreased, and further, the generation of scratches is observed due to the decrease of the surface hardness. .
[0118]
When the fluorine atom content was less than 0.1 atomic%, the effect of water repellency due to fluorine became insufficient, and image blur was generated. In addition, it is difficult to manufacture at a content exceeding 25 atomic%, and cracks may occur (50 atomic%), the hardness will be extremely low (30 atomic%), and scratches may occur when trying to forcibly produce it. .
(Example 3)
The photoconductor C of the present invention was produced by changing the flow rate ratio so as to provide a concentration gradient when introducing NO gas with respect to the film forming conditions shown in Example 1. Other film forming conditions and layer configurations are the same as those of the photoconductor of Example 1.
[0119]
The NO gas was first introduced at 0.5 sccm, gradually increased, and finally increased to 11 sccm. In this example, the NO gas was prepared with a concentration gradient as shown in FIG.
[0120]
On the other hand, photoconductors A, B, and D of comparative examples were produced. For the photoconductor A, when no surface protective layer is provided, in the photoconductor B, the amount of NO gas introduced is constant during film formation (5 sccm). In the photoreceptor D, NO gas is first introduced at 11 sccm, gradually decreases in 50 minutes, and finally decreases to 0.5 sccm.
As shown in (Example 1) for each photoconductor, the photoconductor characteristics were evaluated by means for evaluating the photoconductor characteristics. The results shown in Table 3 were obtained. However, all the photoreceptors A to D have an average oxygen content of 0.01 to 0.1 atomic% and a fluorine content of 3 to 6 atomic%.
[0121]
[Table 3]

[0122]
As is apparent from the results shown in Table 3, the concentration gradient of oxygen atoms in the surface protective layer has a great influence on the photoreceptor characteristics. In the photoreceptor C of the present invention, the charging ability and the photosensitivity characteristics are excellent. It can be seen that the residual potential is small. These charging ability, photosensitivity characteristics and residual potential are evaluated in three stages. Good marks are good, good marks are good, and bad marks are not suitable for practical use.
The present inventor obtained superior results in terms of photosensitivity and residual potential of the photoconductor C having a higher concentration on the surface side than the photoconductor B having a flat oxygen atom concentration. However, for this reason, the electrical compatibility at the interface with the photosensitive layer 3 is good, which facilitates the movement of carriers, and similarly, the carriers easily move within the surface protective layer. I think this is because Furthermore, for the photoconductor D having a reversed density gradient, the photosensitivity and the residual potential are extremely deteriorated, which impedes practical use. However, it is considered that the movement of the carrier is extremely deteriorated.
(Example 4)
In (Example 3), in producing the photoreceptor C of the present invention, the NO gas is first introduced at 0.5 sccm, gradually increased, and finally increased to 11 sccm. However, instead of this, even if oxygen was contained with the concentration gradient as shown in FIGS. 3, 4 and 6, almost the same good results were obtained. It was confirmed by experiment.
[0123]
Specifically, NO gas is first introduced at 0.5 sccm, is increased exponentially as shown in FIG. 3, and is finally increased to 11 sccm, and its characteristics are measured. As a result, the results shown in Table 4 were obtained. In FIG. 3, the photoconductor is shown in FIG.
[0124]
Further, NO gas is first introduced at 0.5 sccm, and a film is formed at 0.5 sccm for 60 minutes. Thereafter, the photoconductor is increased to 11 sccm as shown in FIG. After the film was formed at 5 sccm for 180 minutes, a photoconductor gradually increased to 11 sccm was formed in the final 20 minutes of film formation, and the characteristics of the photoconductor were measured.
[0125]
[Table 4]

[0126]
As is apparent from the results shown in this table, each of the photoconductors of the present invention (FIGS. 3, 4, and 6) is excellent in charging ability and photosensitivity, and has a small residual potential. .
(Example 5)
For the film forming conditions of Example 1, H₂By changing the amount of gas introduced, photoconductors having different indentation hardnesses of the surface protective layer 4 were produced, and image flow and image quality were evaluated and measured for each photoconductor in the same manner as in (Example 1). Results as shown in Tables 5 to 7 were obtained. However, all the photoconductors have an oxygen content of 0.01 to 0.1 atomic% and a fluorine content of 3 to 6 atomic%.
[0127]
[Table 5]

[0128]
[Table 6]

[0129]
[Table 7]

[0130]
As is clear from the results shown in these tables, both the image quality and the image flow are excellent when the dynamic indentation hardness of the surface protective layer is in the range of 10 to 60 times that of the organic photosensitive layer. Recognize.
[0131]
However, if the ratio is less than 10 times, the shaving due to the printing durability increases, and the halftone image is scratched. Moreover, when it exceeded 60 times, adhesiveness etc. reduced from the hardness difference, and the crack and peeling generate | occur | produced.
[0132]
The inventor of the present invention is different in how the surface protection layer has the same hardness because the hardness of the underlying organic photosensitive layer is affected. If the hardness of the organic photosensitive layer is low, it acts as a cushion and protects the surface. Even if the hardness of the layer is low, there is no problem in durability. Therefore, it is considered that the difference in hardness between the organic photosensitive layer and the surface protective layer is important for improving the durability.
(Example 6)
When the image quality evaluation (resolution: 1200 dpi) was performed on the photoconductor produced in (Example 5) when the toner particle size of the image forming apparatus was changed, the results shown in Tables 8 to 10 were obtained. It was. This is an evaluation result after first adjusting to an appropriate image (when the toner particle size is small, the blade pressure is increased in order to prevent toner adhesion to the photosensitive member).
Table 8 shows that the hardness of the organic photosensitive layer is 15 kgf / mm²Table 9 shows the hardness of the organic photosensitive layer is 20 kgf / mm.²Table 10 shows that the hardness of the organic photosensitive layer is 30 kgf / mm.²This is the case.
[0133]
[Table 8]

[0134]
[Table 9]

[0135]
[Table 10]

[0136]
Here, the image quality (resolution, scratch) was evaluated in four stages, and ◎ indicates that one dot has good reproducibility and a very good image without any scratch on the photoreceptor is obtained. The mark indicates that the reproducibility of 1 dot is slightly worse, but there is no practical problem. The mark △ indicates that the reproducibility of 1 dot is partially thinned or missing. Is when the dot reproducibility is poor (dots are missing and white), or the photoconductor is scratched and appears as streaks in the image.
[0137]
As is clear from these tables, the liquid protective toner having a small average particle diameter of less than 3 microns is obtained by increasing the hardness of the surface protective layer 4 to 10 to 60 times that of the organic photosensitive layer. Even when used, the cleaning could be optimized, no toner adhesion occurred, and sufficient durability and image quality were obtained.
However, when the surface protective layer 4 is less than 10 times the hardness of the organic photosensitive layer and the toner particle size becomes small, the surface protective layer 4 is scratched. Further, when the toner particle size increases, the resolution becomes poor.
[0138]
【The invention's effect】
As described above, according to the image forming apparatus of the present invention, there is provided a photoreceptor in which an organic photosensitive layer and a surface protective layer are sequentially laminated on a conductive support, and the surface protective layer contains 0.0001 atoms of oxygen atoms. It is comprised of amorphous carbon containing fluorine atoms in the range of 0.1 atomic percent to 25 atomic percent, and oxygen atoms in the interface between the organic photosensitive layer and the surface protective layer. A photoreceptor having a concentration gradient in the vicinity of the surface opposite to the surface and having a hardness 10 to 60 times that of the organic photosensitive layer, and a charge on the surface of the photoreceptor. A charging means for applying light, an exposure means for irradiating light to a charged region of the photosensitive member, and a liquid toner image on the electrostatic latent image formed on the surface of the photosensitive member by the charging means and the exposing means. Developing means formed on the surface of the toner and the liquid toner image By providing transfer means for transferring to the material and cleaning means for removing residual liquid toner on the surface of the photoreceptor after transfer, the adhesion of the surface protective layer is improved and excellent printing durability is obtained. High durability, high image quality, high performance, and high reliability were achieved.
[0139]
In addition, according to the present invention, since the surface hydrophobicity is increased, the image flow is not generated, and the variation in the potential characteristics is eliminated, so that it is not necessary to provide a heater for the photoconductor. It is possible to provide an image forming apparatus that is simple in structure, improves the manufacturing yield, and further reduces the cost by reducing the number of parts.
[0140]
Furthermore, in the present invention, even when a liquid toner having a particle size of 3 μm or less is used, the image forming apparatus can be provided in which the cleaning property is improved and thereby high resolution is achieved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a layer structure of a photoreceptor of the present invention.
FIG. 2 is a schematic view of an image forming apparatus of the present invention.
FIG. 3 is a diagram showing a concentration gradient of oxygen in the layer thickness direction in the surface protective layer according to the photoreceptor of the present invention.
FIG. 4 of the present inventionBecame the basisFIG. 3 is a diagram showing an oxygen concentration gradient across a layer thickness direction in a surface protective layer according to a photoreceptor.
FIG. 5 is a diagram showing a concentration gradient of oxygen in the layer thickness direction in the surface protective layer according to the photoreceptor of the present invention.
FIG. 6 is a diagram showing a concentration gradient of oxygen in the layer thickness direction in the surface protective layer according to the photoreceptor of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photoconductor 2 ... Conductive substrate 3 ... Photosensitive layer 4 ... Surface protection layer 5 ... Image forming apparatus 6 ... Corona charger 7 ... Exposure device (LED head) 8 ... Liquid toner 9 ... Developing machine 10 ... Transfer material 11 ... transfer device 12 ... cleaning means 13 ... static elimination means 14 ... fixing device

Claims (3)

An organic photosensitive layer and a surface protective layer are sequentially laminated on the conductive support, and the surface protective layer contains oxygen atoms in the range of 0.0001 atomic% to 1.0 atomic%, and fluorine atoms of 0.1%. It consists of amorphous carbon contained in the range of atomic% to 25 atomic%, and the concentration of the oxygen atoms gradually increases as it approaches the vicinity of the surface opposite to the interface between the organic photosensitive layer and the surface protective layer, A photoconductor having a continuous density gradient and having a hardness 10 to 60 times that of the organic photosensitive layer, a charging means for applying a charge to the surface of the photoconductor, and charging of the photoconductor An exposure means for irradiating the area with light, and an electrostatic latent image formed on the surface of the photoreceptor by the charging means and the exposure means, a liquid toner image is formed on the surface of the photoreceptor with a toner having an average particle size of 3 μm or less. Development means for forming Image forming apparatus is disposed a transfer unit that transfers the liquid toner image to a transfer material, and a cleaning means for removing residual liquid toner on the photoreceptor surface after transfer. The oxygen concentration in the vicinity of the surface of the surface protective layer is set to 1.5 to 100 times the oxygen concentration on the interface side between the organic photosensitive layer and the surface protective layer. 1 The image forming apparatus according to claim 2. The oxygen concentration in the vicinity of the surface of the surface protective layer is set to 4 to 20 times the oxygen concentration on the interface side between the organic photosensitive layer and the surface protective layer. 1 The image forming apparatus according to claim 2.

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