JP2005017470A - Electrophotographic photoreceptor, process cartridge, image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor which has stable chargeability and sensitivity, ensures less fluctuation in charge potential or residual potential, prevents the occurrence of image defects such as black spots and moire, and can produce an electrophotographic image of high image density, in a high temperature and high humidity environment and in a low temperature and low humidity environment, and to provide a process cartridge using the electrophotographic photoreceptor, an image forming apparatus and an image forming method. <P>SOLUTION: In the electrophotographic photoreceptor having an interlayer and a photosensitive layer on an electroconductive substrate, the interlayer comprises an anatase type titanium dioxide pigment containing 100 ppm to 2.0 mass% of a transition metal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

上記成分を混合し、サンドミル分散機を用い、１０時間、バッチ式にて分散して、中間層分散液を作製した。
【０１１７】
電荷発生層
下記成分を混合し、サンドミル分散機を用いて分散し、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。
【０１１８】

電荷輸送層
下記成分を混合し、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、乾燥膜厚２４μｍの電荷輸送層を形成し、感光体１を作製した。
【０１１９】

感光体２〜２１の作製
アルミニウム基体の表面粗さＲｚ、中間層の粒子、バインダー樹脂、中間層の乾燥膜厚等の組成を表１、２のように変更した以外は感光体１と同様にして感光体２〜２１を作製した。
【０１２０】
【化１】

【０１２１】
【表１】

【０１２２】
【表２】

【０１２３】
上表中、
Ａ１はニオブ元素を０．５質量％含有したアナターゼ形酸化チタン（アナターゼ化度：１００％）
Ａ２はニオブ元素を１．０質量％含有したアナターゼ形酸化チタン（アナターゼ化度：９５％）
Ａ３はニオブ元素を３００ｐｐｍ含有したアナターゼ形酸化チタン（アナターゼ化度：１００％）
Ａ４はニオブ元素を１．８質量％含有したアナターゼ形酸化チタン（アナターゼ化度：９２％）
Ａ５はニオブ元素を７０ｐｐｍ含有したアナターゼ形酸化チタン（アナターゼ化度：１００％）
Ａ６はニオブ元素を２．２質量％含有したアナターゼ形酸化チタン（アナターゼ化度：９２％）
ＥＬＶＡＸ４２６０はエチレン系共重合樹脂（デュポン社製）
Ｘ１０１０はポリアミド樹脂（ダイセル・デグサ（株）製）
ＮＬ２５３２、ＮＬ２２４９Ｅはポリウレタン樹脂（三井化学社製）
スーパクロンは変性ポリオレフィン樹脂（日本製紙社製）
ＳＧ２０００は変性ポリオレフィン樹脂（（株）鉛市）
上記表中、中間層の膜厚は中間層塗布乾燥後、均一膜厚部分をランダムに１０ケ所測定し、その平均値を中間層の膜厚とする。膜厚測定器は渦電流方式の膜厚測定器ＥＤＤＹ５６０Ｃ（ＨＥＬＭＵＴ ＦＩＳＣＨＥＲ ＧＭＢＴＥ ＣＯ社製）を用いて行った。
【０１２４】
尚、表１、表２中、表面処理とはアナターゼ形酸化チタン顔料の表面に施した表面処理に用いた物質を示す（但し、シリカ・アルミナはアナターゼ形酸化チタン顔料の表面に析出した物質を示す）。
【０１２５】
又、表１、表２中のバインダーの体積抵抗の測定は以下のようにして行った。
体積抵抗の測定条件
測定条件；ＪＩＳ：Ｋ６９１１−１９７５に準ずる。
【０１２６】

評価
得られたサンプルをコニカ（株）製の反転現像方式デジタル複写機「Ｋｏｎｉｃａ７０８５」改造機（スコロトロン帯電器、半導体レーザ像露光器（波長６８０ｎｍ）、反転現像手段を有するＡ４紙８５枚／分機）に搭載し、帯電器のグリッド電圧を−７５０Ｖに調整し、低温低湿（ＬＬ：１０℃２０％ＲＨ）、常温常湿（ＮＮ：２０℃６０％ＲＨ）、高温高湿（ＨＨ：３０℃８０％ＲＨ）にて、各環境毎に、Ａ４紙、各１万枚の連続コピー画像を作製し、画像評価を行った。又、高温高湿（３０℃８０％ＲＨ）の未露光部電位ＶＨＨ、露光部電位ＶＨＬおよび低温低湿（１０℃２０％ＲＨ）の未露光部電位ＶＬＨ、露光部電位ＶＬＬを測定し、｜ΔＶＨ｜（ＶＨＨ−ＶＨＬの絶対値）及び｜ΔＶＬ｜（ＶＬＨ−ＶＬＬの絶対値）を算出した。尚、上記電位評価は各環境条件での１万枚の連続コピー終了後、直ちに電位計で測定した。又、画像濃度、カブリ、黒ポチ、モアレ、鮮鋭性の評価は下記のようにして行った。
【０１２７】
「Ｋｏｎｉｃａ７０８５」改造機の作動条件
感光体のラインスピード；４２０ｍｍ／秒
像露光工程から現像工程までの移動時間；０．１０８秒
帯電条件
帯電器；スコロトロン帯電器（負帯電）
帯電電位の目標；−７５０Ｖ
露光条件
べた黒画像電位の目標；−５０Ｖ
露光ビーム；レーザは６８０ｎｍの半導体レーザを使用
現像条件
現像剤は、Ｋｏｎｉｃａ７０８５用現像剤を使用した。
【０１２８】
転写条件
転写極；コロナ帯電方式（正帯電）
分離条件
分離爪ユニットの分離手段を用いた。
【０１２９】
クリーニング条件
クリーニングブレードをカウンター方向に当接したクリーニング手段を用いた。
【０１３０】
評価項目及び評価基準
画像濃度；低温低湿（ＬＬ：１０℃２０％ＲＨ）、高温高湿（ＨＨ：３０℃８０％ＲＨ）で評価
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。多数枚のコピーで残留電位が増加すると、画像濃度が低下する。各１万枚コピー後のべた黒画像部で測定した。
【０１３１】
◎：低温低湿、高温高湿とも黒ベタ画像が１．２より高い（良好）
○：低温低湿、高温高湿とも黒ベタ画像が１．０以上、１．２以下（実用上問題なし）
×：低温低湿、高温高湿の何れかで黒ベタ画像が１．０未満（実用上問題あり）
カブリ；低温低湿（ＬＬ：１０℃２０％ＲＨ）、高温高湿（ＨＨ：３０℃８０％ＲＨ）で評価
カブリ濃度はべた白画像をマクベス社製ＲＤ−９１８を使用し反射濃度で測定した。該反射濃度は相対濃度（複写していないＡ４紙の濃度を０．０００とする）で評価した。
【０１３２】
◎；低温低湿、高温高湿とも濃度が０．０１０未満（良好）
○；低温低湿、高温高湿とも濃度が０．０１０以上、０．０２０以下（実用上問題ないレベル）
×；低温低湿、高温高湿の何れかで濃度が０．０２０より高い（実用上問題となるレベル）
黒ポチ（低温低湿又は高温高湿の黒ポチが多い方で判定した）
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。
【０１３３】
◎：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）
モアレの評価（常温常湿のハーフトーン画像や白地画像で評価した。）
◎：ハーフトーン画像や白地画像共、モアレ発生なし（良好）
○：ハーフトーン画像で軽微なモアレ発生（実用性に問題なし）
×：ハーフトーン画像又は白地画像で顕著なモアレ発生（実用性に問題有り）
鮮鋭性
画像の鮮鋭性は、低温低湿（１０℃２０％ＲＨ）、高温高湿（３０℃８０％ＲＨ）の両環境において画像を出し評価した。３ポイント、５ポイントの文字画像を形成し、下記の判断基準で評価した。
【０１３４】
◎；低温低湿、高温高湿とも３ポイント、５ポイントとも明瞭であり、容易に判読可能（良好）
○；低温低湿、高温高湿の何れかで３ポイントは一部判読不能、５ポイントは明瞭であり、容易に判読可能（実用性に問題なし）
×；低温低湿、高温高湿の何れかで３ポイントは殆ど判読不能、５ポイントも一部あるいは全部が判読不能（実用性に問題有り）
評価結果を表３に示す。
【０１３５】
【表３】

【０１３６】
表３より、１００ｐｐｍ〜２質量％の範囲のニオブ元素を含有したアナターゼ形酸化チタンを含有する中間層を有する本発明の感光体１〜１９はニオブ元素が７０ｐｐｍのアナターゼ形酸化チタン顔料を用いた感光体２０或いはニオブ元素が２．２質量％のアナターゼ形酸化チタン顔料を用いた感光体２１に比し、高温高湿、低温低湿での未露光部電位及び露光部電位の安定性に優れ、十分な電位差｜ΔＶＨ｜及び｜ΔＶＬ｜を有することから、画像濃度が十分で且つカブリ濃度が小さくしかも黒ポチ等の改良効果が顕著であり、その結果鮮鋭性が良好な電子写真画像を得ている。特に、導電性支持体の表面粗さＲｚが０．５〜２．５μｍで且つ中間層の樹脂の体積抵抗が３０℃８０％ＲＨ条件下で１０^１２Ωｃｍ以上且つ３０℃８０％ＲＨの体積抵抗（Ａ）と１０℃２０％ＲＨの体積抵抗（Ｂ）の比（Ａ／Ｂ）が１〜１／１００の範囲にあり、中間層の膜厚が膜厚がＲｚ〜１０μｍの感光体１〜６、１０〜１３、１５〜１７は改善効果が大きい。一方、感光体２０は未露光部電位ＶＨＨの低下、ＶＬＬの電位上昇が大きく、画像濃度の低下、カブリの発生を起し、その結果鮮鋭性も低下している。又、ニオブ元素を２．２質量％含有する感光体２１は黒ポチの発生が著しく、その結果鮮鋭性も低下している。
【０１３７】
【発明の効果】
実施例からも明らかなように、本発明の構成を有する電子写真感光体を用いることにより、環境変化に対する電位変動が小さく、且つ黒ポチやモアレ等も発生しない良好な電子写真感光体を得ることができる。又該電子写真感光体を用いた良好な電子写真画像を達成できるプロセスカートリッジ、画像形成装置及び画像形成方法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構成図である。
【符号の説明】
５０ 感光体ドラム（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
５４３、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
７０ プロセスカートリッジ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic photosensitive member used in the fields of copying machines and printers, a process cartridge using the electrophotographic photosensitive member, an image forming apparatus, and an image forming method.
[0002]
[Prior art]
The electrophotographic photosensitive member (hereinafter also simply referred to as a photosensitive member) has a wider range of material selection and superior environmental suitability than inorganic photosensitive members such as a selenium-based photosensitive member and an amorphous silicon photosensitive member, There are significant advantages such as low production costs, and in recent years, organic photoreceptors have become the mainstream in place of inorganic photoreceptors.
[0003]
On the other hand, in recent electrophotographic image forming methods, as a hard copy printer of a personal computer, and in an ordinary copying machine, image processing of LEDs and lasers is easy due to the ease of image processing and deployment to a multifunction machine. A digital image forming method as a light source has rapidly spread, and a technique for producing a digital high-quality electrophotographic image has been developed. For example, image exposure is performed with a laser beam with a small spot area, the density of the dot latent image is increased to form a high-definition latent image, the latent image is developed with a small particle size toner, and a high-quality electrophotographic image The technology for producing is disclosed. (Patent Document 1)
In addition, recent electrophotographic apparatuses such as digital copying machines and printers have been reduced in size and speed, and both high sensitivity corresponding to high speed and long life due to improved wear resistance are required as photoreceptor characteristics. Yes.
[0004]
In order to satisfy the above-mentioned demands for higher image quality, smaller size, and higher speed, the organic photoreceptor has good charging characteristics and sensitivity, and further has low dark decay. Appropriateness for reversal development which is most suitable for image development is required.
[0005]
In order to satisfy the above-described demands for higher image quality, smaller size, and higher speed, it is necessary to increase the time response of the sensitivity of the photoreceptor. In order to satisfy these requirements, organic photoreceptors have been developed in which a photosensitive layer is functionally separated into a charge generation layer and a charge transport layer, and high sensitivity and high speed of the charge generation layer and the charge transport layer have been pursued.
[0006]
However, when these high-sensitivity and high-speed charge generation materials and charge transport materials are used, there is a problem that the stability of chargeability and sensitivity is likely to deteriorate. That is, there is a problem that the charging potential is likely to decrease or the residual potential is likely to increase under a high temperature and high humidity environment or a low temperature and low humidity environment.
[0007]
That is, the deterioration in the stability of the charging potential and sensitivity reduces the difference between the unexposed portion potential (VH) and the exposed portion potential (VL) on the photoreceptor in reversal development, and at the same time lowers the image density. The potential difference between the unexposed potential (VH) and the DC bias potential (VDC) between the photosensitive member and the developing sleeve is also reduced, and image defects such as black spots are likely to occur.
[0008]
In order to solve the problem of image defects such as stabilization of the charging potential and black spots, a technique using an intermediate layer for an organic photoreceptor has been developed. For example, an organic photoreceptor having a structure in which an intermediate layer is provided between a conductive substrate and a photosensitive layer, and titanium oxide particles are dispersed in a resin in the intermediate layer is known. In addition, a technique for an intermediate layer containing titanium oxide subjected to surface treatment is also known. For example, titanium oxide surface-treated with iron oxide or tungsten oxide (Patent Document 2), titanium oxide surface-treated with an amino group-containing coupling agent (Patent Document 3), titanium oxide surface-treated with an organosilicon compound (Patent Document 3) Patent Document 4), an intermediate layer using titanium oxide surface-treated with methylhydrogenpolysiloxane (Patent Document 5), dendritic titanium oxide surface-treated with a metal oxide or an organic compound (Patent Document 6) An organophotoreceptor has been proposed.
[0009]
However, even under these harsh environments such as high temperature and high humidity using these technologies, the prevention of black spots is not sufficient, or the residual potential rises due to repeated use, and the exposure portion potential rises. There is a problem that the image density cannot be obtained sufficiently.
[0010]
Further, proposals have been made to more precisely control the crystal structure of titanium oxide to improve the increase in residual potential and exposure portion potential due to the occurrence of black spots and repeated use. For example, an intermediate layer containing anatase-type titanium oxide pigment (hereinafter also referred to as anatase-type titanium oxide or anatase-type titanium oxide particles) has been proposed (Patent Document 7). Anatase-type titanium oxide has a lower volume resistance than rutile-type titanium oxide. Therefore, the intermediate layer can be made thicker, and the thickness of the anatase-type titanium oxide hides the irregularities on the conductive support. While it tends to prevent charge injection from the support, it tends to increase the dark decay of the charged potential and increase fog in reversal development. The patent document has a solution to such conflicting problems. It is insufficient.
[0011]
A method of forming the intermediate layer by dispersing the titanium oxide particles or the like in a polyamide resin is widely known. However, mainly used as a polyamide resin in this case, a copolymerized polyamide resin or a methoxymethylated polyamide resin mainly composed of a chemical structure with few carbon chains between amide bonds such as 6-nylon has a high water absorption rate. Such an intermediate layer using polyamide tends to be highly environmentally dependent. As a result, the residual potential increases due to repeated use, the charging characteristics under high temperature and high humidity are likely to change, and image defects such as black spots Is likely to occur.
[0012]
Copolymer polyamide resin composed of structural units with many carbon chains between amide bonds, such as 12-nylon resin, has a low water absorption rate and is therefore an effective material for producing a photoreceptor with low environmental dependency. is expected. However, such polyamides are insoluble in ordinary organic solvents and are not suitable for the production of photoreceptors. There is an example in which polyamide is used with improved solubility by methoxymethylation (Patent Documents 8 and 9). However, since methoxymethylation significantly increases water absorption, it is difficult to sufficiently reduce image defects such as black spots. .
[0013]
[Patent Document 1]
[Patent Document 1] Japanese Patent Laid-Open No. 2001-255685
[Patent Document 2]
Japanese Patent Laid-Open No. 4-303846
[Patent Document 3]
JP-A-9-96916 [0016]
[Patent Document 4]
JP-A-9-258469 [0017]
[Patent Document 5]
JP-A-8-328283 Publication
[Patent Document 6]
Japanese Patent Laid-Open No. 11-344826
[Patent Document 7]
JP-A-11-327188 [0020]
[Patent Document 8]
Japanese Patent Laid-Open No. 5-72787
[Patent Document 9]
Japanese Patent Laid-Open No. 6-186767 [0022]
[Problems to be solved by the invention]
The object of the present invention is to stabilize the chargeability and sensitivity in a high-temperature and high-humidity environment or a low-temperature and low-humidity environment, to reduce fluctuations in the charging potential and residual potential, prevent the occurrence of image defects such as black spots and moire, It is to provide an electrophotographic photosensitive member capable of producing an electrophotographic image having a high density, and to reduce the chargeability and sensitivity that are likely to occur when a high-sensitivity, high-speed charge generation material or charge transport material is used. And providing an electrophotographic photoreceptor capable of producing an electrophotographic image having a high image density by preventing the occurrence of image defects such as black spots and moire, with small fluctuations in charging potential and residual potential. To provide a process cartridge, an image forming apparatus, and an image forming method using a photographic photosensitive member.
[0023]
[Means for Solving the Problems]
In order to prevent the occurrence of image defects such as black spots, the chargeability and sensitivity are stable in the high-temperature and high-humidity environment and the low-temperature and low-humidity environment, and the fluctuations of the charged potential and residual potential are small. A substance having a rectifying property with respect to charge carriers is contained between the conductive support and the photosensitive layer, exhibits stable rectification characteristics against temperature and humidity fluctuations, and is high with respect to charge injection from the conductive support. The present invention has been achieved by finding that it is effective to install an intermediate layer capable of exhibiting a blocking effect. That is, the object of the present invention is achieved by taking the following configuration.
[0024]
1. An electrophotographic photosensitive member having an intermediate layer and a photosensitive layer on a conductive substrate, wherein the intermediate layer contains an anatase-type titanium oxide pigment containing a transition metal in an amount of 100 ppm to 2.0% by mass. body.
[0025]
2. In an electrophotographic photosensitive member having an intermediate layer and a photosensitive layer on a conductive substrate, the surface roughness Rz of the conductive substrate is 0.5 to 2.5 μm, and the intermediate layer contains 100 ppm to 2.0 mass of transition metal. An electrophotographic photoreceptor comprising an anatase-type titanium oxide pigment.
[0026]
3. 3. The electrophotographic photosensitive member according to 1 or 2, wherein the transition metal is a transition element having an atomic number of 21 to 30 or 39 to 48.
[0027]
4). 4. The electrophotographic photosensitive member according to any one of items 1 to 3, wherein the transition metal is a niobium element having an atomic number of 41.
[0028]
5. 5. The electrophotographic photosensitive member according to any one of items 1 to 4, wherein the anatase-type titanium oxide pigment has an anatase degree of 90 to 100%.
[0029]
6). 6. The electrophotographic photoreceptor according to any one of 1 to 5, wherein the anatase titanium oxide pigment is subjected to a surface treatment with a reactive organosilicon compound.
[0030]
7. 7. The electrophotographic photosensitive member according to any one of items 1 to 6, wherein the anatase-type titanium oxide pigment has a number average primary particle size of 10 nm to 200 nm.
[0031]
8). 8. The electrophotographic photosensitive member according to any one of 1 to 7, wherein the film thickness T of the intermediate layer has a relationship of the surface roughness Rz and the following formula (1).
[0032]
Formula (1) 0.7Rz <= T <= 20 (micrometer)
9. 9. The electrophotographic photosensitive member according to any one of 1 to 8, wherein the photosensitive layer has a layer structure of a charge generation layer and a charge transport layer.
[0033]
10. An electrophotographic photosensitive member having an anatase-type titanium oxide pigment having an intermediate layer and a photosensitive layer on a conductive substrate, the intermediate layer containing 100 ppm to 2.0% by mass of a transition metal, and the electrophotographic photosensitive member Uniformly charging means, latent image forming means for forming an electrostatic latent image on the charged electrophotographic photosensitive member, developing means for developing the electrostatic latent image on the electrophotographic photosensitive member, and the electrophotographic Transfer means for transferring the toner image visualized on the photosensitive member onto the transfer material, neutralizing means for removing the charge on the electrophotographic photosensitive member after the transfer, and remaining on the electrophotographic photosensitive member after the transfer A process cartridge which is integrally supported with at least one of cleaning means for removing toner and is detachably attachable to an image forming apparatus main body.
[0034]
11. An electrophotographic photosensitive member, a charging unit for uniformly charging the electrophotographic photosensitive member, a latent image forming unit for forming an electrostatic latent image on the charged electrophotographic photosensitive member, and an electrostatic latent image on the electrophotographic photosensitive member In an image forming apparatus having developing means for developing an image and transfer means for transferring a toner image visualized on the electrophotographic photosensitive member onto a transfer material, the electrophotographic photosensitive member is placed on a conductive substrate. An image forming apparatus comprising an intermediate layer and a photosensitive layer, wherein the intermediate layer contains an anatase-type titanium oxide pigment containing 100 ppm to 2.0% by mass of a transition metal.
[0035]
12 12. An image forming method comprising forming an electrophotographic image using the image forming apparatus described in 11 above.
[0036]
Hereinafter, the present invention will be described in detail.
The electrophotographic photosensitive member of the present invention is an electrophotographic photosensitive member having an intermediate layer and a photosensitive layer on a conductive substrate, the intermediate layer containing an anatase-type titanium oxide pigment containing 100 ppm to 2.0% by mass of a transition metal. It is characterized by that.
[0037]
The electrophotographic photosensitive member of the present invention is an electrophotographic photosensitive member having an intermediate layer and a photosensitive layer on a conductive substrate, and the surface roughness Rz of the conductive substrate is 0.5 to 2.5 μm. Contains an anatase-type titanium oxide pigment containing 100 ppm to 2.0% by mass of a transition metal.
[0038]
Since the electrophotographic photosensitive member of the present invention has the above-described configuration, the sensitivity and the residual potential are less dependent on the environment, and even if the use condition is suddenly changed from a high temperature and high humidity environment to a low temperature and low humidity environment, the electrophotographic photosensitive member is stable. An image is obtained, and when a digital image is formed by reversal development, the occurrence of image defects such as black spots and moire is prevented in any environment, and the image density is high and the sharpness is good. Can be formed.
[0039]
Titanium oxide pigments include three pigments having different crystal structures of anatase, rutile, and bromite, and the anatase-type titanium oxide pigment of the present invention (hereinafter also simply referred to as anatase-type titanium oxide) has a refractive index of 2.55 and a crystal The form is a tetragonal white titanium oxide pigment having a lattice constant with a of 0.378 nm and c of 0.947 nm.
[0040]
In the present invention, an anatase-type titanium oxide pigment containing transition metal in an intermediate layer in an amount of 100 ppm (1 ppm means 1 / 1,000,000 in mass ratio) to 2.0 mass% is dispersed in a binder resin to form a conductive substrate. By forming an intermediate layer between the photosensitive layer and the photosensitive layer, even if the environmental conditions of temperature and humidity change, the change in charging characteristics and sensitivity characteristics is small, and as a result, image defects such as black spots that are likely to occur in reversal development are eliminated. Generation | occurrence | production can be prevented and an electrophotographic image with favorable sharpness can be obtained. If the transition metal is less than 100 ppm, the dark decay of the charged potential tends to increase, and the image density tends to decrease and fogging tends to occur. On the other hand, when the transition metal is more than 2.0% by mass, the black polyester resin is easily generated. The transition metal content of the anatase-type titanium oxide pigment is more preferably 300 ppm to 1.8% by mass.
[0041]
The concentration of niobium element in the whole anatase-type titanium oxide particles of the present invention can be analyzed by quantitative analysis by ICP (inductively coupled plasma emission spectrometry).
[0042]
In addition to the above-described effects, the intermediate layer having the above structure is placed on a conductive substrate (Rz: 0.5 to 2.5 μm) whose surface is roughened. In addition to improving the film formation, there is a remarkable effect in preventing the occurrence of moiré that tends to occur during image formation using image exposure light such as laser light. Further, in order to prevent black spots that are likely to be generated by roughening the surface of the conductive substrate, the thickness of the intermediate layer of the present invention is preferably 0.7 Rz or more and 20 μm or less. Furthermore, the film thickness T of the intermediate layer is more preferably Rz or more and 10 μm or less. If the thickness T of the intermediate layer is less than 0.7 Rz, black spots are likely to occur, and if it is thicker than 20 μm, the residual potential tends to increase and the image density tends to decrease.
[0043]
The transition metal contained in the anatase titanium oxide pigment of the present invention means a transition element having an atomic number of 21 to 30, or 39 to 48, 57 to 80. Among these transition elements, a transition element having an atomic number of 21 to 30 or 39 to 48 having a size almost equal to or smaller than that of titanium ions in the titanium oxide pigment is preferable.
[0044]
Among the transition metals, niobium element having an atomic number of 41 having an ion radius close to that of titanium ion is most preferable. An electrophotographic photosensitive member containing an anatase-type titanium oxide pigment containing 100 ppm to 2.0% by mass of niobium element in an intermediate layer has a rectifying property of the intermediate layer (passes negative charge carriers in the charge generation layer, and is a conductive support. The property of blocking the positive charge from the light source), the dark decay is small, the charging stability is sufficiently secured, and image defects such as black spots can be sufficiently prevented. In addition, by forming the film thickness of the intermediate layer containing the anatase-type titanium oxide pigment containing 100 ppm to 2.0 mass% of niobium element into a sufficient film thickness according to the relationship of the above formula (1) The above-described effects can be achieved more reliably.
[0045]
The anatase-type titanium oxide pigment of the present invention can be produced by a known sulfuric acid method. That is, it is obtained by heating and hydrolyzing a solution containing titanium sulfate and titanyl sulfate to produce a hydrous titanium dioxide slurry, and dehydrating and firing the titanium dioxide slurry. Hereinafter, the manufacturing method of the anatase type titanium oxide pigment containing a niobium element is described.
[0046]
First, niobium sulfate (water-soluble niobium compound) is added to a hydrous titanium dioxide slurry obtained by hydrolyzing a titanyl sulfate aqueous solution. The addition amount is suitably 0.15 to 5 mass% niobium sulfate as niobium ions with respect to the amount of titanium in the slurry (in terms of titanium dioxide). Specifically, (i) hydrous titanium dioxide slurry obtained by hydrolyzing 0.15 to 5% by mass of niobium sulfate as niobium ion to titanyl sulfate aqueous solution, or (ii) hydrolyzing titanyl sulfate aqueous solution A slurry obtained by adding 0.15 to 5% by mass of niobium sulfate as niobium ions to the hydrous titanium dioxide slurry obtained as described above can be used.
[0047]
The hydrous titanium dioxide slurry containing the niobium ions and the like is dehydrated and fired. In general, the firing temperature is suitably 850 to 1100 ° C. When the firing temperature is less than 850 ° C., firing is not sufficiently performed. On the other hand, if the temperature exceeds 1100 ° C., the particles are sintered and the dispersibility of the pigment is significantly impaired. Niobium ions added to the slurry are segregated on the particle surface during firing, and are contained in the surface layer in a large amount as niobium oxide. By this production method, an anatase-type titanium oxide pigment having an average primary particle diameter of 0.01 to 10 μm and containing 100 ppm to 2 mass% of niobium element can be obtained.
[0048]
The anatase-type titanium oxide of the present invention preferably has an anatase degree of 90 to 100%. By the above method, anatase-type titanium oxide having an anatase degree of almost 100% can be produced. Further, the intermediate layer of the present invention containing the anatase-type titanium oxide containing niobium element in this range has a good rectifying property and is stably achieved, and the above-described effects of the present invention are well achieved.
[0049]
Here, the degree of anatase is measured by measuring the intensity IA of the strongest interference line of anatase (surface index 101) and the intensity IR of the strongest interference line of rutile (surface index 110) in powder X-ray diffraction of titanium oxide, It is a value obtained by the following formula.
Degree of anataseization (%) = 100 / (1 + 1.265 × IR / IA)
In order to produce the anatase degree in the range of 90 to 100%, in the production of titanium oxide, an anatase degree of almost 100% is obtained by heating and hydrolyzing a solution containing titanium sulfate and titanyl sulfate as a titanium compound. A shaped titanium oxide is obtained. Further, when an aqueous solution of titanium tetrachloride is neutralized with an alkali, anatase-type titanium oxide having a high degree of anatase formation can be obtained.
[0050]
In the intermediate layer of the present invention, it is preferable to use a binder resin having a low temperature and humidity environment dependency. As such a binder resin, a binder resin having a ratio (A / B) of a volume resistance (A) of 30 ° C. and 80% RH to a volume resistance (B) of 10 ° C. and 20% RH of 1/100 is preferable. As specific examples, the following resins are preferred.
[0051]
That is, ELVAX4260 (manufactured by DuPont) as an ethylene copolymer resin, NL2532 (manufactured by Mitsui Chemicals) as a polyurethane resin, NL2249E (manufactured by Mitsui Chemicals), X1010 (manufactured by Daicel Degussa) as a polyamide resin, modified polyolefin Examples of the resin include Supercron (manufactured by Nippon Paper Industries Co., Ltd.), GS2000 (Lead City Co., Ltd.) and the like.
[0052]
In addition, the volume resistance of the resin is preferably 10 ¹² Ωcm or more, and more preferably 10 ¹² to 10 ¹⁶ Ωcm in both (A) and (B). If it is less than 10 ¹² Ωcm, image defects such as black spots are likely to occur, and if it is greater than 10 ¹⁶ Ωcm, the residual potential tends to increase, and the image density is likely to decrease during reversal development.
[0053]
The method for measuring the volume resistance will be described.
Measuring method of volume resistivity The volume resistivity was measured according to JIS K6911-1975. First, a binder resin sample formed in a disk shape having a diameter of about 100 mm and a thickness of 20 μm was measured using a resistance meter Hiresta IP (manufactured by Mitsubishi Yuka Co., Ltd.), and a value calculated from a resistance value after 1 minute was measured. Value. The measurement value under high temperature and high humidity conditions was measured after conditioning the sample for 24 hours in an environment of 30 ° C. and 80% RH. The measured value under low temperature and low humidity conditions was measured after conditioning the sample for 24 hours in an environment of 10 ° C. and 20% RH.
[0054]
The average particle diameter of the anatase titanium oxide is preferably in the range of 10 nm to 400 nm in the number average primary particle diameter, more preferably 20 nm to 200 nm, and particularly preferably 20 nm to 100 nm.
[0055]
An intermediate layer using anatase-type titanium oxide having a value of the number average primary particle size within the above range can be finely dispersed in the layer, and has sufficient potential stability, black spot generation and moire. Prevent image defects such as.
[0056]
For example, in the case of titanium oxide, the number average primary particle size of the anatase-type titanium oxide is magnified 10,000 times by observation with a transmission electron microscope, 100 particles are randomly observed as primary particles, and the ferret diameter is determined by image analysis. Measured as number average diameter.
[0057]
The anatase titanium oxide pigment is preferably subjected to a surface treatment with a reactive organosilicon compound. The surface treatment of the anatase titanium oxide pigment with the reactive organosilicon compound can be performed by the following wet method. The surface treatment of the reactive organosilicon compound means that a reactive organosilicon compound is used for the treatment liquid.
[0058]
That is, the anatase-type titanium oxide pigment is added to a solution obtained by dissolving or suspending the reactive organosilicon compound in an organic solvent or water, and this mixed solution is dispersed in a medium for several minutes to one day. And depending on the case, after heat-processing a liquid mixture, it passes through processes, such as filtration, It dries, and the anatase type titanium oxide pigment which coat | covered the surface with the organosilicon compound is obtained. Note that the reactive organosilicon compound may be added to a suspension in which titanium oxide is dispersed in an organic solvent or water.
[0059]
The amount of the reactive organosilicon compound used for the surface treatment is 0.1 to 10 parts by mass of the reactive organosilicon compound with respect to 100 parts by mass of the anatase-type titanium oxide pigment in the amount charged in the surface treatment. More preferably, 0.1 to 5 parts by mass is used. When the surface treatment amount is less than the above range, the surface treatment effect is not sufficiently imparted, and the rectifying action and dispersibility of the titanium oxide particles in the intermediate layer are deteriorated. Further, when the surface treatment amount exceeds the above range, the electrophotographic characteristics are deteriorated, and as a result, the residual potential is increased and the charged potential is decreased.
[0060]
Examples of the reactive organosilicon compound used in the present invention include compounds represented by the following general formula (1), and any compound that undergoes a condensation reaction with a reactive group such as a hydroxyl group on the surface of titanium oxide can be used. It is not limited to.
[0061]
General formula (1)
(R) _n -Si- (X) _4-n
(In the formula, Si represents a silicon atom, R represents an organic group in which carbon is directly bonded to the silicon atom, X represents a hydrolyzable group, and n represents an integer of 0 to 3.)
In the organosilicon compound represented by the general formula (1), the organic group in which carbon is directly bonded to the silicon represented by R includes alkyl such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl and dodecyl. Group, aryl group such as phenyl, tolyl, naphthyl, biphenyl, epoxy-containing group such as γ-glycidoxypropyl, β- (3,4-epoxycyclohexyl) ethyl, γ-acryloxypropyl, γ-methacryloxypropyl (Meth) acryloyl group, hydroxyl group such as γ-hydroxypropyl and 2,3-dihydroxypropyloxypropyl, vinyl group such as vinyl and propenyl, mercapto group such as γ-mercaptopropyl, γ-aminopropyl, Amino-containing groups such as N-β (aminoethyl) -γ-aminopropyl, γ-chloropropyl, , 1,1-tri fluoroalkyl propyl, nonafluorohexyl, halogen-containing groups such as perfluorooctylethyl, other nitro, and cyano-substituted alkyl group. Examples of the hydrolyzable group for X include alkoxy groups such as methoxy and ethoxy, halogen groups, and acyloxy groups.
[0062]
Moreover, the organosilicon compound represented by the general formula (1) may be used alone or in combination of two or more.
[0063]
Moreover, in the specific compound of the organosilicon compound represented by the general formula (1), when n is 2 or more, a plurality of R may be the same or different. Similarly, when n is 2 or less, the plurality of Xs may be the same or different. Moreover, when using 2 or more types of organosilicon compounds represented by General formula (1), R and X may be the same between each compound, and may differ.
[0064]
Moreover, a polysiloxane compound is mentioned as a preferable reactive organosilicon compound. In particular, methyl hydrogen polysiloxane is preferred. The polysiloxane compound having a molecular weight of 1000 to 20000 is generally easily available, and has a good function to prevent occurrence of black spots.
[0065]
Another surface treatment of the titanium oxide of the present invention is titanium oxide particles that have been surface treated with an organosilicon compound having a fluorine atom. It is preferable to perform the surface treatment with the organosilicon compound having a fluorine atom and the wet method described above.
[0066]
In the present invention, the surface of the titanium oxide particles is coated with a reactive organosilicon compound because photoelectron spectroscopy (ESCA), Auger electron spectroscopy (Auger), secondary ion mass spectrometry (SIMS), and diffuse reflection. This is confirmed by combining surface analysis techniques such as FI-IR.
[0067]
Another one of the surface treatments of the anatase-type titanium oxide pigment includes at least one kind of surface treatment selected from alumina, silica, and zirconia.
[0068]
The alumina treatment, silica treatment, and zirconia treatment are treatments for precipitating alumina, silica, or zirconia on the surface of anatase-type titanium oxide. The alumina, silica, and zirconia deposited on these surfaces are water of alumina, silica, and zirconia. Japanese products are also included.
[0069]
The treatment of alumina and silica may be performed simultaneously, but it is particularly preferable to perform the alumina treatment first and then the silica treatment. Further, the amount of treatment of alumina and silica when treating alumina and silica is preferably higher than that of alumina.
[0070]
The surface treatment of anatase titanium oxide with a metal oxide such as alumina, silica, and zirconia can be performed by a wet method. For example, anatase-type titanium oxide subjected to surface treatment of silica or alumina can be produced as follows.
[0071]
When anatase type titanium oxide is used, titanium oxide particles (number average primary particle size: 50 nm) are dispersed in water at a concentration of 50 to 350 g / L to form an aqueous slurry. Add aluminum compound. Thereafter, alkali or acid is added for neutralization, and silica or alumina is precipitated on the surface of the titanium oxide particles. Subsequently, filtration, washing, and drying are performed to obtain the target surface-treated titanium oxide. When sodium silicate is used as the water-soluble silicate, it can be neutralized with an acid such as sulfuric acid, nitric acid or hydrochloric acid. On the other hand, when aluminum sulfate is used as the water-soluble aluminum compound, it can be neutralized with an alkali such as sodium hydroxide or potassium hydroxide.
[0072]
In addition, the amount of the metal oxide used for the surface treatment is 0.1 to 50 parts by mass, more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the titanium oxide particles in the amount charged in the surface treatment. These metal oxides are used. In the case of using alumina and silica as described above, for example, in the case of anatase-type titanium oxide particles, it is preferable to use 1 to 10 parts by mass with respect to 100 parts by mass of titanium oxide particles, and the amount of silica is larger than that of alumina. Is preferred.
[0073]
The intermediate layer of the present invention contains the surface-treated anatase-type titanium oxide pigment in a proportion of 10 to 10,000 parts by mass, preferably 50 to 1,000 parts by mass, with respect to 100 parts by mass of the binder resin. By using the surface-treated titanium oxide within this range, the dispersibility of the titanium oxide can be kept good, a black layer is not generated, and a good intermediate layer with little initial potential fluctuation can be formed.
[0074]
Next, the electrophotographic photosensitive member used in the present invention will be described.
[0075]
The electrophotographic photoreceptor of the present invention is preferably an organic photoreceptor. An organic photoconductor means an electrophotographic photoconductor formed by providing an organic compound with at least one of a charge generation function and a charge transport function essential for the construction of an electrophotographic photoconductor. It contains all known organic electrophotographic photoreceptors such as a photoreceptor composed of a substance or an organic charge transport material, a photoreceptor composed of a polymer complex with a charge generation function and a charge transport function.
[0076]
Conductive substrate (conductive support)
As the conductive substrate used in the photoreceptor of the present invention, either a sheet or a cylindrical substrate may be used, but a cylindrical conductive substrate is preferable in order to design the image forming apparatus compactly.
[0077]
The cylindrical conductive substrate of the present invention means a cylindrical substrate necessary to be able to form an endless image by rotating, and the conductivity within a range of 0.1 mm or less in straightness and 0.1 mm or less in deflection. These substrates are preferred. Exceeding the roundness and shake range makes it difficult to form a good image.
[0078]
As the conductive material, a metal drum such as aluminum or nickel, a plastic drum deposited with aluminum, tin oxide, indium oxide or the like, or a paper / plastic drum coated with a conductive substance can be used. The conductive substrate preferably has a specific resistance of 10 ³ Ωcm or less at room temperature.
[0079]
As the conductive substrate used in the present invention, a substrate having a sealed anodized film formed on the surface thereof may be used. The alumite treatment is usually performed in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, sulfamic acid, etc., but anodizing treatment in sulfuric acid gives the most preferable result. In the case of anodizing in sulfuric acid, the sulfuric acid concentration is preferably 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 preferably about 20 V. It is not limited. The average film thickness of the anodized film is usually 20 μm or less, particularly preferably 10 μm or less.
[0080]
In the electrophotographic photosensitive member of the present invention, it is preferable that the surface roughness of the conductive substrate is 10 to 10 and the average surface roughness Rz is 0.5 to 2.5 μm. By installing an intermediate layer having anatase-type titanium oxide containing the transition metal of the present invention on a conductive substrate processed to such a surface roughness, even if using interference light such as a laser, moire Generation | occurrence | production can be prevented efficiently.
[0081]
Definition and measurement method of surface roughness Rz Rz in the present invention means a value of a reference length of 0.25 mm described in JIS B0601-1982. That is, it is the difference between the average height of the top five peaks and the average height of the bottom five valleys over a distance of the reference length of 0.25 mm.
[0082]
In Examples described later, the roughness Rz was measured with a surface roughness meter (Surfcoder SE-30H manufactured by Kosaka Laboratory Ltd.). However, other measuring devices may be used as long as the measuring device produces the same result within the error range.
[0083]
The surface roughness Rz of the conductive substrate can be processed within the scope of the present invention by using a sandblasting method or the like by cutting the surface of the conductive substrate or causing fine particles to collide with the substrate surface. . Further, it can be processed within the scope of the present invention by chemical surface treatment such as anodizing.
[0084]
Intermediate Layer In the present invention, it is preferable to provide the above intermediate layer having a barrier function between the conductive substrate and the photosensitive layer.
[0085]
Photosensitive layer The photosensitive layer structure of the photoreceptor of the present invention may be a single-layered photosensitive layer structure in which a charge generation function and a charge transport function are provided on the intermediate layer, but more preferably the function of the photosensitive layer. The charge generation layer (CGL) and the charge transport layer (CTL) may be separated from each other. By adopting a configuration in which the functions are separated, an increase in the 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 photoconductor, 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 positively charged photoconductor, the order of the layer configuration is the reverse of that in the negatively charged photoconductor. The most preferred photosensitive layer structure of the present invention is a negatively charged photoreceptor structure having the function separation structure.
[0086]
The structure of the photosensitive layer of the function-separated negatively charged photoreceptor will be described below.
Charge generation layer The charge generation layer contains a charge generation material (CGM). Other substances may contain a binder resin and other additives as necessary.
[0087]
A known charge generation material (CGM) can be used as the charge generation material (CGM). For example, a phthalocyanine pigment, an azo pigment, a perylene pigment, an azulenium pigment, or the like can be used. Among these, the CGM that can minimize the increase in residual potential due to repeated use has a three-dimensional and potential structure that can form a stable aggregate structure among a plurality of molecules. Specifically, a phthalocyanine having a specific crystal structure. CGM of pigments and perylene pigments. For example, CGMs such as titanyl phthalocyanine having a maximum peak at a Bragg angle 2θ of 27.2 ° with respect to Cu—Kα rays and benzimidazole perylene having a maximum peak at 2θ of 12.4 have little deterioration due to repeated use. Potential increase can be reduced.
[0088]
When a binder is used as the CGM dispersion medium in the charge generation layer, a known resin can be used as the binder, but the most preferred resins include formal resin, butyral resin, silicone resin, silicone-modified butyral resin, phenoxy resin, and the like. Can be mentioned. The ratio of the binder resin to the charge generating material is preferably 20 to 600 parts by mass with respect to 100 parts by mass of the binder resin. By using these resins, the increase in residual potential associated with repeated use can be minimized. The thickness of the charge generation layer is preferably 0.01 μm to 2 μm.
[0089]
Charge Transport Layer The charge transport layer contains a charge transport material (CTM) and a binder resin that forms a film by dispersing CTM. Other substances may contain additives such as antioxidants as necessary.
[0090]
As the charge transport material (CTM), for example, a triphenylamine derivative, a hydrazone compound, a styryl compound, a benzidine compound, a butadiene compound, or the like can be used. These charge transport materials are usually dissolved in a suitable binder resin to form a layer. Among these, the combined use of CTM capable of minimizing the increase in residual potential due to repeated use has a characteristic that the difference in ionization potential between the CTMs is 0.5 (eV) or less, preferably 0.25 ( eV) or less.
[0091]
The ionization potential of CGM and CTM is measured with a surface analyzer AC-1 (manufactured by Riken Keiki Co., Ltd.).
[0092]
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. Resin, silicone resin, melamine resin, and copolymer resin containing two or more of repeating units of these resins. In addition to these insulating resins, high molecular organic semiconductors such as poly-N-vinylcarbazole can be used.
[0093]
The most preferred binder for these CTLs is polycarbonate resin. The polycarbonate resin is most preferable in improving the dispersibility and electrophotographic characteristics of CTM. The ratio of the binder resin to the charge transport material is preferably 10 to 200 parts by mass with respect to 100 parts by mass of the binder resin. The thickness of the charge transport layer is preferably 10 to 50 μm. The charge transport layer of the present invention may have a multilayer structure of two or more layers, and the uppermost layer may have a function as a protective layer.
[0094]
The charge transport layer preferably contains an antioxidant. Typical examples of the antioxidants prevent the action of oxygen on auto-oxidizing substances existing in the electrophotographic photosensitive member or on the surface of the electrophotographic photosensitive member under conditions of light, heat, and discharge. It is also a substance having a suppressing property.
[0095]
That is, the solvent or dispersion medium used for forming the intermediate layer, photosensitive layer, and other resin layers of the present invention includes 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, dioxolane, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, Ruserosorubu, and the like.
[0096]
As a means for dispersing the surface-treated titanium oxide used for the preparation of the intermediate layer coating solution, any means such as a sand mill, a ball mill, or an ultrasonic dispersion may be used.
[0097]
As the coating processing method for producing the electrophotographic photosensitive member of the present invention including the intermediate layer, coating processing methods such as dip coating, spray coating, and circular amount regulation type coating are used. In order to achieve a uniform coating process, it is preferable to use a coating process method such as spray coating or circular amount regulation type (a typical example is a circular slide hopper type). . The spray coating is described in detail in, for example, JP-A-3-90250 and JP-A-3-269238, and the circular amount-regulating coating is described in detail in, for example, JP-A-58-189061. Yes.
[0098]
Next, the image forming method and the image forming apparatus of the present invention will be described.
FIG. 1 is a cross-sectional configuration diagram of an image forming apparatus as an example of the image forming method of the present invention.
[0099]
In FIG. 1, reference numeral 50 denotes a photosensitive drum (photosensitive member) which is an image bearing member, which is a photosensitive member coated with an organic photosensitive layer on the drum, and is grounded and rotated clockwise. Reference numeral 52 denotes a scorotron charger (charging means, charging step), which uniformly charges the circumferential surface of the photosensitive drum 50 by corona discharge. Prior to the charging by the charger 52, the peripheral surface of the photosensitive member may be discharged by performing exposure by the pre-charging exposure unit 51 using a light emitting diode or the like in order to eliminate the history of the photosensitive member in the previous image formation.
[0100]
After uniform charging of the photoreceptor, image exposure based on the image signal is performed by an image exposure unit 53 as an image exposure unit (image exposure process). The image exposure unit 53 in this figure uses a laser diode (not shown) as an exposure light source. Scanning on the photosensitive drum is performed by the light whose optical path is bent by the reflection mirror 532 through the rotating polygon mirror 531 and the fθ lens, and an electrostatic latent image is formed.
[0101]
The electrostatic latent image is then developed by a developing device 54 as developing means (developing step). A developing device 54 containing a developer composed of toner and carrier is provided on the periphery of the photosensitive drum 50, and development is performed by a developing sleeve 541 that contains a magnet and rotates while holding the developer.
[0102]
The arrival time (Td) from the image exposure process to the development process is shortened at a high process speed, and the electrophotographic photosensitive member having insufficient high-speed adaptability does not complete the potential reduction due to the image exposure even when reaching the development process. . Even if the electrophotographic photosensitive member is applied to a high-speed process in which the arrival time (Td) from the image exposure process to the development process is 110 msec or less, a sufficient potential reduction is completed in the development process. Degradation of high speed is small, and it has sufficient high speed adaptability even in a low temperature and low humidity environment.
[0103]
The arrival time (Td) from the image exposure process to the development process of the present invention is the position at the completion of the image exposure light irradiated on the photoconductor (position A on the photoconductor) and the position where toner begins to adhere by development. The distance (| A to B |) on the photoconductor between (position B on the photoconductor) is divided by the linear velocity of the photoconductor (surface linear velocity of the photoconductor) during the image forming operation.
[0104]
In general, reversal development is performed in a digital image forming method. Here, reversal development is performed by charging the surface of a photosensitive member uniformly by a charger 52, that is, a region where image exposure is performed, that is, an exposed portion of the photosensitive member. This is an image forming method in which a potential (exposed area) is visualized by a developing process (means). On the other hand, the unexposed portion potential is not developed by the developing bias potential applied to the developing sleeve 541.
[0105]
The inside of the developing device 54 is composed of developer agitating / conveying members 544 and 543, a conveying amount regulating member 542, and the like, and the developer is agitated and conveyed and supplied to the developing sleeve. Controlled by member 542. The developer transport amount varies depending on the linear velocity and developer specific gravity of the applied electrophotographic photosensitive member, but is generally in the range of ^{20 to} 200 mg / cm ² .
[0106]
The developer is, for example, a carrier composed of the above-mentioned ferrite as a core and coated with an insulating resin around it, and a coloring material such as carbon black, a charge control agent, and a low molecular weight polyolefin mainly composed of the above-mentioned styrene acrylic resin. The toner is composed of a toner in which silica, titanium oxide, or the like is externally added to the particles. The developer is transported to the development area with the layer thickness regulated by a transport amount regulating member, and development is performed. At this time, usually, development is performed by applying a DC bias between the photosensitive drum 50 and the developing sleeve 541 and, if necessary, an AC bias voltage. Further, the developer is developed in contact with or not in contact with the photoreceptor. The potential of the photosensitive member is measured by providing a potential sensor 547 above the development position as shown in FIG.
[0107]
The recording paper P is fed to the transfer area by the rotation operation of the paper feed roller 57 when the transfer timing is ready after the image formation.
[0108]
In the transfer area, a transfer electrode (transfer means: transfer device) 58 is operated on the peripheral surface of the photosensitive drum 50 in synchronization with the transfer timing, and the charged recording paper P is charged with a polarity opposite to that of the toner. Transfer the toner.
[0109]
Next, the recording paper P is neutralized by a separation electrode (separator) 59, separated by the peripheral surface of the photosensitive drum 50 and conveyed to the fixing device 60, and the toner is removed by heating and pressurization of the heat roller 601 and the pressure roller 602. After the welding, the sheet is discharged to the outside of the apparatus via the sheet discharge roller 61. The transfer electrode 58 and the separation electrode 59 stop the primary operation after passing through the recording paper P, and prepare for the next toner image formation. In FIG. 1, a transfer band electrode of corotron is used as the transfer electrode 58. The transfer electrode setting conditions vary depending on the process speed (peripheral speed) of the photosensitive member and cannot be specified. For example, the transfer current is set to +100 to +400 μA, and the transfer voltage is set to +500 to +2000 V. can do.
[0110]
On the other hand, after the recording paper P is separated, the photosensitive drum 50 removes and cleans residual toner by pressure contact of the blade 621 of the cleaning device (cleaning means) 62, and again performs charge removal by the pre-charge exposure unit 51 and charging by the charger 52. Then, the next image forming process is started.
[0111]
Reference numeral 70 denotes a detachable process cartridge in which a photoconductor, a charger, a transfer device, a separator, and a cleaning device are integrated.
[0112]
The image forming method and the image forming apparatus of the present invention are generally applicable to electrophotographic apparatuses such as electrophotographic copying machines, laser printers, LED printers, and liquid crystal shutter printers, but also display, recording, and light printing using electrophotographic technology. It can also be widely applied to apparatuses such as plate making and facsimile.
[0113]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this. In the following text, “part” means part by mass.
[0114]
A photoreceptor used for evaluation was produced as follows.
Preparation intermediate layer 1 of photoreceptor 1
The following intermediate layer coating solution is applied by a dip coating method onto a washed cylindrical aluminum substrate (processed to a surface roughness Rz: 1.0 μm by cutting) to form an intermediate layer 1 having a dry film thickness of 1.0 μm. did.
[0115]
The following intermediate layer dispersion is diluted twice with the same mixed solvent, and is allowed to stand overnight and then filtered (filter; rigesh mesh filter made by Nippon Pole Co., Ltd., nominal filtration accuracy: 5 microns, pressure: 50 kPa). Produced.
[0116]

The above components were mixed and dispersed in a batch system for 10 hours using a sand mill disperser to prepare an intermediate layer dispersion.
[0117]
Charge generation layer The following components were mixed and dispersed using a sand mill disperser to prepare a charge generation layer coating solution. This coating solution was applied by a dip coating method to form a charge generation layer having a dry film thickness of 0.3 μm on the intermediate layer.
[0118]

Charge transport layer The following components were mixed and dissolved to prepare a charge transport layer coating solution. This coating solution was applied onto the charge generation layer by a dip coating method to form a charge transport layer having a dry film thickness of 24 μm.
[0119]

Preparation of photoconductors 2 to 21 The same as photoconductor 1 except that the composition of aluminum substrate surface roughness Rz, intermediate layer particles, binder resin, intermediate layer dry film thickness, etc. was changed as shown in Tables 1 and 2. Photoconductors 2 to 21 were prepared.
[0120]
[Chemical 1]

[0121]
[Table 1]

[0122]
[Table 2]

[0123]
In the table above,
A1 is anatase type titanium oxide containing 0.5% by mass of niobium element (degree of anatase conversion: 100%)
A2 is anatase-type titanium oxide containing 1.0% by mass of niobium element (anatase degree: 95%)
A3 is anatase-type titanium oxide containing 300 ppm of niobium element (degree of anatase conversion: 100%)
A4 is anatase-type titanium oxide containing 1.8% by mass of niobium element (degree of anatase conversion: 92%)
A5 is anatase titanium oxide containing 70 ppm of niobium element (degree of anatase conversion: 100%)
A6 is anatase-type titanium oxide containing 2.2% by mass of niobium element (degree of anatase conversion: 92%)
ELVAX 4260 is an ethylene copolymer resin (manufactured by DuPont).
X1010 is a polyamide resin (manufactured by Daicel Degussa)
NL2532, NL2249E are polyurethane resins (Mitsui Chemicals)
Supercron is a modified polyolefin resin (manufactured by Nippon Paper Industries Co., Ltd.)
SG2000 is a modified polyolefin resin (Lead City Co., Ltd.)
In the above table, the film thickness of the intermediate layer is measured by randomly measuring 10 portions of the uniform film thickness after coating and drying the intermediate layer, and the average value is taken as the film thickness of the intermediate layer. The film thickness measuring device was an eddy current type film thickness measuring device EDDY560C (manufactured by HELMUT FISCHER GMBTE CO).
[0124]
In Tables 1 and 2, surface treatment means the material used for the surface treatment applied to the surface of the anatase-type titanium oxide pigment (however, silica / alumina is the substance deposited on the surface of the anatase-type titanium oxide pigment). Show).
[0125]
The volume resistance of the binders in Tables 1 and 2 was measured as follows.
Measurement conditions for volume resistance Measurement conditions: According to JIS: K6911-1975.
[0126]

The sample obtained was converted into a reversal development type digital copying machine “Konica 7085” manufactured by Konica, Inc. (a scorotron charger, a semiconductor laser image exposure device (wavelength 680 nm), 85 sheets of A4 paper having reversal development means / min.) And the grid voltage of the charger is adjusted to -750 V, low temperature and low humidity (LL: 10 ° C, 20% RH), normal temperature and normal humidity (NN: 20 ° C, 60% RH), high temperature and high humidity (HH: 30 ° C, 80 ° C) % RH), continuous copy images of A4 paper and 10,000 sheets were prepared for each environment, and image evaluation was performed. Further, the unexposed portion potential VHH, the exposed portion potential VHL at high temperature and high humidity (30 ° C. and 80% RH), the unexposed portion potential VLH and the exposed portion potential VLL at low temperature and low humidity (10 ° C. and 20% RH) are measured, and | ΔVH | (Absolute value of VHH−VHL) and | ΔVL | (absolute value of VLH−VLL) were calculated. The potential evaluation was measured with an electrometer immediately after the continuous copying of 10,000 sheets under each environmental condition. The evaluation of image density, fog, black spots, moire and sharpness was performed as follows.
[0127]
Operating conditions of “Konica 7085” remodeling machine Photoreceptor line speed; 420 mm / sec Travel time from image exposure process to development process; 0.108 sec charging condition charger; Scorotron charger (negative charging)
Target of charging potential; -750V
Target of black image potential with exposure condition: -50V
Exposure beam; Laser used a semiconductor laser of 680 nm. Development conditions A developer for Konica 7085 was used as the developer.
[0128]
Transfer conditions Transfer pole: Corona charging method (positive charging)
Separation Conditions Separation means of a separation claw unit was used.
[0129]
Cleaning conditions A cleaning means having a cleaning blade in contact with the counter direction was used.
[0130]
Evaluation item and evaluation standard image density: Measured using low temperature and low humidity (LL: 10 ° C., 20% RH) and high temperature and high humidity (HH: 30 ° C., 80% RH) using RD-918 manufactured by Macbeth. The relative reflection density was measured with the paper reflection density set to “0”. As the residual potential increases on multiple copies, the image density decreases. Measurements were taken at the solid black image portion after 10,000 copies each.
[0131]
A: Black solid image is higher than 1.2 for both low temperature and low humidity and high temperature and high humidity (good)
○: Black solid image of 1.0 or more and 1.2 or less for both low temperature and low humidity and high temperature and high humidity (no problem in practical use)
×: Black solid image is less than 1.0 in either low temperature and low humidity or high temperature and high humidity (practical problem)
Fog: Evaluation at low temperature and low humidity (LL: 10 ° C., 20% RH), high temperature and high humidity (HH: 30 ° C., 80% RH) The fog density was measured by reflection density using a solid white image RD-918 manufactured by Macbeth. The reflection density was evaluated by a relative density (the density of A4 paper not copied is 0.000).
[0132]
A: Concentration is less than 0.010 (good) for both low temperature and low humidity and high temperature and high humidity
○: Concentration of 0.010 or more and 0.020 or less for both low temperature and low humidity and high temperature and high humidity (a level that causes no practical problems)
X: Concentration is higher than 0.020 at either low temperature and low humidity or high temperature and high humidity (a level that causes practical problems)
Black spots (judged by those with a lot of low temperature, low humidity or high temperature, high humidity)
For black spots, the periodicity coincided with the period of the photoreceptor, and it was determined how many black spots per A4 size were visible.
[0133]
：: Black spot frequency of 0.4 mm or more: All copied images are 3 / A4 or less (good) ○: Black spot frequency of 0.4 mm or more: 4 / A4 or more, 10 / A4 or less is 1 or more Occurrence (no problem in practical use)
×: Black spot frequency of 0.4 mm or more Frequency: 11 / A4 or more occurs (practical problem)
Moire evaluation (Evaluation was performed using a halftone image at normal temperature and humidity and a white background image.)
◎: No moiré in both halftone images and white background images (good)
○: Minor moire generated in halftone image (no problem in practical use)
×: Remarkable moire generated in halftone image or white background image (problem in practical use)
The sharpness of the sharp image was evaluated by producing an image in both low temperature and low humidity (10 ° C., 20% RH) and high temperature, high humidity (30 ° C., 80% RH) environments. 3-point and 5-point character images were formed and evaluated according to the following criteria.
[0134]
◎: 3 points and 5 points are clear for both low temperature and low humidity and high temperature and high humidity, easy to read (good)
○: 3 points are partially illegible in either low temperature, low humidity or high temperature and high humidity, 5 points are clear and easily readable (no problem in practical use)
×: 3 points are almost unreadable for low temperature and low humidity or high temperature and high humidity, 5 points are partially or completely unreadable (there is a problem in practical use)
The evaluation results are shown in Table 3.
[0135]
[Table 3]

[0136]
From Table 3, the photoconductors 1 to 19 of the present invention having an intermediate layer containing anatase-type titanium oxide containing niobium element in the range of 100 ppm to 2% by mass used anatase-type titanium oxide pigment having a niobium element of 70 ppm. Compared to the photoreceptor 20 or the photoreceptor 21 using anatase-type titanium oxide pigment containing 2.2% by mass of niobium element, the stability of the unexposed portion potential and the exposed portion potential at high temperature and high humidity and low temperature and low humidity is excellent. Since it has sufficient potential differences | ΔVH | and | ΔVL |, the image density is sufficient, the fog density is small, and the improvement effect such as black spots is remarkable. As a result, an electrophotographic image having good sharpness can be obtained. Yes. In particular, the conductive substrate has a surface roughness Rz of 0.5 to 2.5 μm, and the volume resistance of the intermediate layer resin is 10 ¹² Ωcm or more and 30 ° C. and 80% RH under the conditions of 30 ° C. and 80% RH. The ratio (A / B) of the volume resistance (B) of (A) to 10 ° C. and 20% RH is in the range of 1 to 1/100, and the intermediate layer has a thickness of Rz to 10 μm. 6, 10-13, 15-17 have a large improvement effect. On the other hand, the photoreceptor 20 has a large decrease in the unexposed portion potential VHH and a large increase in the VLL potential, which causes a decrease in image density and occurrence of fogging. As a result, the sharpness is also decreased. Further, the photoreceptor 21 containing 2.2% by mass of the niobium element is remarkably blackened, and as a result, sharpness is also lowered.
[0137]
【The invention's effect】
As is clear from the examples, by using the electrophotographic photosensitive member having the configuration of the present invention, a good electrophotographic photosensitive member that has a small potential fluctuation with respect to environmental changes and that does not generate black spots or moire is obtained. Can do. Further, it is possible to provide a process cartridge, an image forming apparatus and an image forming method capable of achieving a good electrophotographic image using the electrophotographic photosensitive member.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram of an image forming apparatus as an example of an image forming method of the present invention.
[Explanation of symbols]
50 Photosensitive drum (photosensitive member)
51 Pre-charging exposure unit 52 Charging device 53 Image exposure device 54 Developing device 541 Developing sleeves 543 and 544 Developer stirring and conveying member 547 Potential sensor 57 Feed roller 58 Transfer electrode 59 Separating electrode (separator)
60 Fixing Device 61 Paper Discharge Roller 62 Cleaning Device 70 Process Cartridge

Claims (12)

An electrophotographic photosensitive member having an intermediate layer and a photosensitive layer on a conductive substrate, wherein the intermediate layer contains an anatase-type titanium oxide pigment containing a transition metal in an amount of 100 ppm to 2.0% by mass. body. In an electrophotographic photosensitive member having an intermediate layer and a photosensitive layer on a conductive substrate, the surface roughness Rz of the conductive substrate is 0.5 to 2.5 μm, and the intermediate layer contains 100 ppm to 2.0 mass of transition metal. An electrophotographic photosensitive member comprising an anatase-type titanium oxide pigment. The electrophotographic photosensitive member according to claim 1 or 2, wherein the transition metal is a transition element having an atomic number of 21 to 30 or 39 to 48. The electrophotographic photosensitive member according to any one of claims 1 to 3, wherein the transition metal is a niobium element having an atomic number of 41. The electrophotographic photoreceptor according to any one of claims 1 to 4, wherein the anatase-type titanium oxide pigment has an anatase degree of 90 to 100%. The electrophotographic photosensitive member according to claim 1, wherein the anatase titanium oxide pigment is subjected to a surface treatment with a reactive organosilicon compound. The electrophotographic photosensitive member according to claim 1, wherein the anatase-type titanium oxide pigment has a number average primary particle size of 10 nm to 200 nm. The electrophotographic photosensitive member according to claim 1, wherein the film thickness T of the intermediate layer has a relationship of the surface roughness Rz and the following formula (1).
Formula (1) 0.7Rz ≦ T ≦ 20 (μm) The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer has a layer structure of a charge generation layer and a charge transport layer. An electrophotographic photosensitive member having an anatase-type titanium oxide pigment having an intermediate layer and a photosensitive layer on a conductive substrate, the intermediate layer containing 100 ppm to 2.0% by mass of a transition metal, and the electrophotographic photosensitive member Uniformly charging means, latent image forming means for forming an electrostatic latent image on the charged electrophotographic photosensitive member, developing means for developing the electrostatic latent image on the electrophotographic photosensitive member, and the electrophotographic Transfer means for transferring the toner image visualized on the photosensitive member onto the transfer material, neutralizing means for removing the charge on the electrophotographic photosensitive member after the transfer, and remaining on the electrophotographic photosensitive member after the transfer A process cartridge which is integrally supported with at least one of cleaning means for removing toner and can be detachably attached to an image forming apparatus main body. An electrophotographic photosensitive member, a charging unit for uniformly charging the electrophotographic photosensitive member, a latent image forming unit for forming an electrostatic latent image on the charged electrophotographic photosensitive member, and an electrostatic latent image on the electrophotographic photosensitive member In an image forming apparatus having developing means for developing an image and transfer means for transferring a toner image visualized on the electrophotographic photosensitive member onto a transfer material, the electrophotographic photosensitive member is placed on a conductive substrate. An image forming apparatus comprising an intermediate layer and a photosensitive layer, wherein the intermediate layer contains an anatase-type titanium oxide pigment containing 100 ppm to 2.0% by mass of a transition metal. An image forming method comprising forming an electrophotographic image using the image forming apparatus according to claim 11.

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