JP2004151349A - Electrophotographic photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor having stable potential and image properties under entire atmosphere from low temperature and low humidity to high temperature and high humidity. <P>SOLUTION: In the photoreceptor in which an intermediate layer and photosensitive layer are laminated in turn on a conductive supporting body, the intermediate layer contains two or more kinds of conductive particles different in the primary particle diameter, the ratio A:B between the largest and the smallest average particle diameters A and B is 12:1-30:1, and the B is ≤0.05 μm. A content of the conductive particle in the intermediate layer is ≥25 vol% and ≤50 vol%, and the ratio of the A is ≤15%. The volume resistance value of the intermediate layer at 23°C/55 RH% is 1×10E5 to 1×10E7 Ωcm. <P>COPYRIGHT: (C)2004,JPO

Description

ポリカーボネート樹脂（ユーピロン Ｚ−２００、三菱瓦斯化学製）５０質量部をモノクロルベンゼン４００質量部に溶解した溶液を、前記電荷発生層の上に浸漬塗布し、１２０℃で１時間加熱乾燥して厚み２４μｍの電荷輸送層を形成した。
【００７３】
このようにして作製した本発明の電子写真感光体を、図１に示されるような構成を有するヒューレットパッカード製ＬＢＰ「レーザージェット４０００」（プロセススピード９４．２ｍｍ／ｓｅｃ）を、以下のプロセス条件に設定を変更して評価を行った。
【００７４】
電子写真感光体暗部電位 −５５０Ｖ
電子写真感光体明部電位 −１５０Ｖ
現像バイアス −３５０Ｖ（直流電圧のみ）
評価は、低温低湿（１５℃、１０％ＲＨ）および高温高湿（３０℃、８０％ＲＨ）の環境下で初期画像評価を行った。画像の評価は以下の様に行った。プリント画像書き出しから電子写真感光体１の回転部分に２５ｍｍ角の正方形のベタ黒部を並べ、電子写真感光体の２回転目以降に１ドットを桂馬パターンで印字したハーフトーンのテストチャートでゴーストを評価した。また、プリント全面に１ドットを桂馬パターンで印字したハーフトーンのテストチャート及びベタ黒、ベタ白画像によりポチ、カブリ画像の評価を行った。評価結果を表１に示す。
【００７５】
次いで、低温低湿（１５℃、１０％ＲＨ）および高温高湿（３０℃、８０％ＲＨ）の環境下で、Ａ４サイズ紙に面積比率４％印字の文字パターンで１０，０００枚の連続画出し試験を行い、画像評価を行った。評価結果を表１に示す。
【００７６】
評価の結果、この感光体は、表１に示すように低温低湿および高温高湿においても、初期、連続１０，０００枚耐久後も、いずれの環境でも安定した電位を示し、不要な黒点画像やカブリ、ゴースト、干渉縞のない非常に優れた画質の画像が安定して得られた。
【００７７】
実施例２〜５
実施例１の中間層を、下記の塗工液を用いて形成した中間層にかえ、その他は実施例１と同様にして、実施例２〜５のそれぞれの電子写真感光体を作製した。こうして作製した各電子写真感光体について、実施例１と同様にして評価した。その結果を表１に示す。
【００７８】
実施例２の塗工液
・実施例１と同様の硫酸バリウム微粒子からなる粉体 ２０質量部
・アンチモン含有の酸化スズの被覆層を有する酸化チタン微粒子からなる粉体（ＥＣ−２１０、チタン工業製、一次粒子の平均粒径０．５μｍ、比重４．６） ２０質量部
・酸化スズ含有酸化インジウム微粒子（ＩＴＯ，三菱マテリアル製、一次粒子の平均粒径０．０３μｍ、比重７．１） ８０質量部
・実施例１と同様のレゾール型フェノール樹脂 ７０質量部
・２−メトキシ−１−プロパノール １００質量部
実施例３の塗工液
実施例１におけるアンチモン含有酸化スズ微粒子に替え、タンタルドープした酸化スズ微粒子からなる粉体（一次粒子の平均粒径０．０２μｍ、比重６．１）を用いたほかは実施例１と同様にして塗工液を作製した。
【００７９】
実施例４の塗工液
・実施例１で用いたレゾール型フェノール樹脂に代えて、ポリエステルポリウレタン（ニッポラン２３０４、日本ポリウレタン製）を用いたほかは実施例１と同様にして塗工液を作製した。
【００８０】
実施例５の塗工液
・実施例１で用いたレゾール型フェノール樹脂７０質量部に代え、下記構造式のポリアミド酸樹脂（重量平均分子量８５００）５０質量部を用い、２−メトキシ−１−プロパノール１００質量部に替えＮ，Ｎ−ジメチルアセトアミド１７０質量部用いて、実施例１と同様にして塗工液を作製した。
【００８１】
【化２】

実施例６及び７
実施例２において中間層の膜厚をそれぞれ１０μｍ、２５μｍとしたほかは実施例２と同様にして、電子写真感光体を作製し、評価を行った。
【００８２】
比較例１〜３
実施例１の中間層を、下記の塗工液を用いて形成した中間層に代え、その他は実施例１と同様にして、比較例１および２のそれぞれの電子写真感光体を作製した。
【００８３】
こうして作製した各電子写真感光体について、実施例１と同様にして評価した。その結果、表１に示す。
【００８４】
比較例１の塗工液
・酸素欠損型の酸化スズの被覆層を有する硫酸バリウム微粒子からなる粉体（被覆率５０質量％、一次粒子の平均粒径０．６μｍ、比重５．１） １５０質量部
・実施例１と同様のレゾール型フェノール樹脂 ７５質量部
・メチルセロソルブ ６０質量部
・メタノール １５質量部
【００８５】
比較例２の塗工液
・アンチモン含有の酸化スズ微粒子からなる粉体（Ｔ−１、三菱マテリアル製）１２０質量部
・実施例１と同様のレゾール型フェノール樹脂 ７０質量部
・２−メトキシ−１−プロパノール ８０質量部
【００８６】
比較例３の塗工液
・酸素欠損型の酸化スズの被覆層を有する硫酸バリウム微粒子からなる粉体（被覆率５０質量％、一次粒子の平均粒径０．６μｍ、比重５．１） ７０質量部
・アンチモン含有の酸化スズの被覆層を有する酸化チタン微粒子からなる粉体（ＥＣ−２１０、チタン工業製、一次粒子の平均粒径０．５μｍ、比重４．６） ７０質量部
・実施例１と同様のレゾール型フェノール樹脂 ７０質量部
・メチルセロソルブ ６０質量部
・メタノール １５質量部
【００８７】
比較例４
実施例１において用いた酸化スズを被覆した硫酸バリウム粒子に代えて、酸化スズを被覆していない硫酸バリウム粒子を用いたほかは実施例１と同様にして電子写真感光体を作製し、評価した。結果を表１に示す。
【００８８】
比較例５及び６
実施例２において、中間層の膜厚をそれぞれ５μｍ、３０μｍとしたほかは実施例２と同様にして電子写真感光体を作製し、評価した。結果を表１に示す。なお、比較例６の感光体は中間層にクラックが発生したため評価は行わなかった。
【００８９】
【表１】

【００９０】
【発明の効果】
本発明による電子写真感光体によれば、低温低湿から高温高湿下に至る全環境下に対して、安定した良好な画像形成を実現することができる。
【図面の簡単な説明】
【図１】接触帯電方式の電子写真装置の一例を示す図である。
【符号の説明】
１ 電子写真感光体
２ 帯電ローラ
２Ａ バイアス電源
３ 露光
４ 現像器
５ 荷電粒子（トナー）
５ａ 可転写粒子像（トナー像）
５ｂ 被転写粒子
６ 用紙
７ 転写ローラ
７Ａ バイアス電源
８ クリーナー（クリーニング装置）
９ 給紙カセット
１０ 給紙ローラ
１１ レジストローラ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic photosensitive member, and more particularly, to an electrophotographic photosensitive member having high image uniformity and excellent durability.
[0002]
[Prior art]
Conventionally, as a photoreceptor used in an electrophotographic apparatus, a photoconductive layer provided mainly on selenium or a selenium alloy on a conductive support, and an inorganic photoconductive material such as zinc oxide and cadmium sulfide are used in a binder. Are generally known, and those using amorphous silicon-based materials are generally known. In recent years, however, due to low cost, high degree of freedom in photoreceptor design, no pollution, etc. Organic photoconductors have been widely used.
[0003]
The organic photoconductive compound can freely select the photosensitive wavelength range of the electrophotographic photoreceptor depending on the compound. For example, azo pigments exhibiting high sensitivity in the visible region are disclosed (for example, Patent References 1 and 2) and those having sensitivity up to the infrared region are disclosed (for example, see Patent References 3 and 4). Of these materials, those that exhibit sensitivity in the infrared region are used in laser beam printers (hereinafter abbreviated as LBPs) and LED printers that digitally form electrostatic latent images, and the demand for these materials is increasing. Is coming. As for printer devices, LED printers and LBP printers have become the mainstream in the recent market, and the resolution has been increased from 240, 300 dpi to 400, 600, 1200 dpi as the direction of technology. In addition, the functions of the copiers have also been enhanced, and the digitalization has been rapidly proceeding. The mainstream of digital machines is a method of forming an electrostatic latent image with a laser, and the direction of high resolution has been advanced like a printer.
[0004]
As a photoreceptor used for digitally forming an electrostatic latent image,
(1) Capable of charging to an appropriate potential in a dark place
(2) Less charge dissipation in dark places
(3) Charge can be quickly dissipated by light irradiation
And the like. In particular, regarding (3), it is necessary to have sensitivity to infrared light.
[0005]
Many phthalocyanine compounds have high sensitivity in the infrared region and are widely used in electrophotographic photoreceptors.
[0006]
Particularly in recent years, oxytitanium phthalocyanine (hereinafter abbreviated as TiOPc) has been widely used as a material having high sensitivity in the infrared region. Further, a photoreceptor using chlorogallium phthalocyanine (for example, see Patent Document 5) and a photoreceptor using hydroxygallium phthalocyanine (for example, see Patent Document 6) are disclosed. An electrophotographic photoreceptor using a high-sensitivity material represented by these phthalocyanine compounds for the charge generation layer has a very high sensitivity and has a sensitivity up to the infrared region. There is a drawback that the number of electrons is large, and electrons after holes are injected easily remain in the charge generation layer, so that potential fluctuation easily occurs as a kind of memory.
[0007]
In principle, it is considered that the electrons left in the charge generation layer proceed to the interface between the charge generation layer and the charge transport layer for some reason, and lower the barrier property of hole injection near the interface.
[0008]
The phenomenon expressed when the photoconductor is actually used as an electrophotographic photosensitive member appears as a decrease in a bright portion potential and a residual potential during continuous printing. For example, when used in a development process (a so-called reversal development system) in which a dark potential portion is used as a non-development portion and a light potential portion is used as a development portion, which is often used in printers at present, the sensitivity at the place where light was applied during the previous printing is used. If the entire image is taken during the next print, the so-called ghost phenomenon, in which the previous print part appears black, will be noticeable.
[0009]
In particular, this phenomenon is remarkable in a photoreceptor using an intermediate layer or the like as an adhesive layer of the charge generation layer, and in an environment such as low temperature and low humidity, the volume resistance of the charge generation layer and the intermediate layer to electrons increases, so that electrons are generated in the charge generation layer. And the ghost phenomenon easily occurs.
[0010]
This phenomenon is particularly remarkable in a charging method in which the dark portion potential seen in contact charging or the like is forcibly made uniform.
[0011]
Such a ghost phenomenon tends to appear particularly in a halftone image, and becomes a particularly important problem in a color printer or the like in which a halftone image is emphasized.
[0012]
Organic photoreceptors currently in practical use are basically composed of a conductive support and a photoconductive layer formed on the support, in particular, a photoconductive layer in which a charge generation layer and a charge transport layer are laminated in this order. Made up of However, covering the defects of the conductive support, improving the coatability of the photoconductive layer, improving the adhesion between the photoconductive layer and the support, protecting the photoconductive layer from electrical destruction, improving the chargeability, It is effective to provide an intermediate layer between the photoconductive layer and the support for the purpose of improving the charge injection into the photoconductive layer. Therefore, the intermediate layer in the electrophotographic photosensitive member is required to have many functions such as covering property, adhesive property, mechanical strength, appropriate conductivity and electric barrier property.
[0013]
Conventionally, the following types have been proposed as intermediate layers.
(I) Resin thin film containing no conductive filler
(Ii) Resin thin film containing conductive filler
(Iii) The thin film of (i) is laminated on the thin film of (ii).
As the resin used for the intermediate layer of the type (i), solvent-soluble polyamide, polyvinyl alcohol, polyvinyl butyral, casein and the like are known. In particular, as a material for the intermediate layer, for example, a solvent-soluble polyamide resin capable of satisfying an appropriate conductivity and an electrical barrier property required for the intermediate layer is known to have a specified chemical structure. (See, for example, Patent Documents 7 to 9), and a method of adding an additive to a polyamide resin to suppress a change in electric resistance with respect to the environment is known (for example, see Patent Documents 10 to 12). ). Further, there has been known one in which a polyamide resin and another resin are mixed to adjust electric resistance to suppress the influence of the environment (for example, see Patent Documents 13 to 15).
[0014]
The intermediate layer using these resins can sufficiently perform its function even with an extremely thin film, for example, a thin film having a thickness of 0.1 μm or less. In order to eliminate the unevenness in film formation, a film thickness of 0.5 μm or more is required, and depending on the surface roughness of the substrate and the state of contamination, a film thickness of 1 μm or more is required. For example, when an aluminum cylinder is used as the conductive support, it is usually necessary to provide an intermediate layer of 10 μm or more in order to eliminate the influence of surface defects of the aluminum cylinder.
[0015]
However, when such a thick intermediate layer is formed, the injection property of the carrier generated in the charge generation layer is deteriorated, and the residual potential increases when used repeatedly, and image defects such as a decrease in print density occur. At the same time, the above-mentioned ghost phenomenon appears remarkably.
[0016]
Therefore, usually, the thickness of the intermediate layer is suppressed to about 1 μm by removing the surface defects of the aluminum cylinder by cutting with a diamond tool or the like, but the cost of the support increases due to the cutting and the like. There is.
[0017]
Also, when such a conductive support and an intermediate layer are used in a laser beam printer, it is necessary to prevent the image defect of the interference pattern caused by the refractive index and the film thickness of the photosensitive layer and the wavelength of the light source. It is the present situation that cutting work is performed to prevent this.
[0018]
On the other hand, since the thin films of (ii) and (iii) can be imparted with appropriate conductivity by dispersing the conductive filler, the thickness of the intermediate layer is set so as not to be affected by defects on the support. In addition to being able to use a low-cost conductive support that is not subjected to special surface processing, it is easy to quickly escape to the support without accumulating the electrons causing the ghost phenomenon by imparting appropriate conductivity. There are advantages. Further, it is also possible to prevent the image defect of the interference pattern by the dispersed filler. For example, an intermediate layer in which the intermediate layer contains two or more types of inorganic pigments having different average particle diameters has been reported (for example, see Patent Document 16).
[0019]
However, if the dispersibility of the conductive filler is poor, the electrical characteristics such as the resistance and the dielectric constant of the intermediate layer change, causing non-uniform charge injection, which greatly affects the potential characteristics and image quality. In addition, if the dispersibility of the filler is poor, the surface smoothness of the film becomes poor, which causes coating defects. Further, if the dispersion of the filler is poor, the adhesion to the support and the mechanical strength are also reduced.
[0020]
So far, metals (for example, see Patent Document 17), metal oxides (for example, see Patent Document 18), metal nitrides (for example, see Patent Document 19), etc., have been reported as conductive fillers for the intermediate layer. Have been.
[0021]
However, the electrophotographic photoreceptor using the conventional conductive filler as the filler for the intermediate layer has a large environmental dependence such as temperature and humidity, and has a stable electric potential from low to low humidity to high and high humidity in all environments. It was difficult to produce a photoreceptor having characteristics and image characteristics. For example, in a low-temperature and low-humidity environment where the resistance of the intermediate layer is increased, when the photoreceptor is used repeatedly, electric charges are accumulated in the intermediate layer, the residual potential and the light portion potential increase, and a ghost phenomenon appears remarkably. On the other hand, under high temperature and high humidity, which causes a decrease in the resistance of the intermediate layer, the electric barrier capability of the intermediate layer was reduced, carrier injection from the support was accelerated, and a decrease in the dark area potential upon repeated use was observed. As a result, in addition to the decrease in image density under high temperature and high humidity, in the case of an electrophotographic printer performing reversal development, unnecessary black spots (black spots) and fog are likely to occur in the image. became.
[0022]
As described above, the characteristics of the photoconductor change with changes in the environment because the dispersibility of the conductive filler is poor or the amount of dispersion of the conductive filler itself is small. This is considered to be due to the change in the charge injecting property to. That is, it is considered that a local resistance change occurs in the intermediate layer, and the potential characteristics and the image characteristics are susceptible to environmental changes.
[0023]
[Patent Document 1]
JP-A-61-272754
[Patent Document 2]
JP-A-56-167759
[Patent Document 3]
JP-A-57-19576
[Patent Document 4]
JP-A-61-228453
[Patent Document 5]
JP-A-5-188615
[Patent Document 6]
JP-A-5-249716
[Patent Document 7]
JP-A-2-193152
[Patent Document 8]
JP-A-3-288157
[Patent Document 9]
JP-A-4-31870
[Patent Document 10]
JP-A-2-59458
[Patent Document 11]
JP-A-3-81778
[Patent Document 12]
JP-A-2-281262
[Patent Document 13]
JP-A-3-145652
[Patent Document 14]
JP-A-3-81778
[Patent Document 15]
JP-A-2-281262
[Patent Document 16]
JP-A-10-177267
[Patent Document 17]
JP-A-58-18105
[Patent Document 18]
JP-A-54-151843
[Patent Document 19]
JP-A-1-118848
[0024]
[Problems to be solved by the invention]
An object of the present invention is to provide an electrophotographic photoreceptor having stable potential characteristics and image characteristics in all environments from low temperature and low humidity to high temperature and high humidity.
[0025]
[Means for Solving the Problems]
The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor obtained by sequentially laminating an intermediate layer and a photosensitive layer on a conductive support, wherein the intermediate layer disperses two or more kinds of conductive particles having different primary particle diameters. And the ratio A: B of the average particle diameter of the primary particles A having the largest primary particle to the average particle diameter of the smallest primary particles B of the conductive particles is 12: 1 to 30: 1. The average particle size is 0.05 μm or less.
[0026]
More preferably, the content of the conductive particles in the intermediate layer is 25 vol% or more and 50 vol% or less, and the ratio of the largest average primary particle size of the conductive particles is 15 vol% or less.
[0027]
More preferably, the volume resistivity of the intermediate layer at 23 ° C./55 RH% is 10E5 to 10E7.
[0028]
Hereinafter, the present invention will be described in detail.
[0029]
The fact that the charge generating material has high sensitivity means that the charge generating material itself has good quantum efficiency and generates many carriers. Although the reason for the large number of generated carriers has not been clarified at the stage of research, the effects of oxygen and impurities are considered to be large. When a large amount of carriers are generated, if the same number of electrons as holes injected into the charge transport layer do not escape to the support side promptly, the ghost phenomenon described above occurs due to electrons remaining in the charge generation layer and the like.
[0030]
In order to prevent such image defects and prevent a ghost phenomenon from appearing on the image, it is necessary to uniformly and promptly inject and transfer charges between the charge generation layer and the intermediate layer, and between the intermediate layer and the support. In the intermediate layer in which the conductive particles are dispersed as in the present invention, the conductive particles are the point of charge injection. Therefore, it is important how the conductive particles are uniformly and abundantly dispersed in the intermediate layer.
[0031]
From the viewpoint of the uniformity of charge injection, the smaller the particle size of the conductive particles dispersed in the intermediate layer, the better, but the smaller the particle size of the conductive particles, the higher the resistance of the intermediate layer. Therefore, it is necessary to increase the amount of conductive particles added. Therefore, the amount of the conductive particles to be added must be determined in consideration of a resistance value capable of maintaining sufficient charge injection and movement in a low-temperature and low-humidity environment where the resistance of the intermediate layer tends to increase. However, when the added amount of the conductive particles is too large, cracks are generated in the intermediate layer, and problems arise in film formability, mechanical strength, and the like. As a result of the study by the present inventors, the content of the conductive particles in the intermediate layer is preferably 50 vol% or less, more preferably 25 to 50 vol%, based on the intermediate layer.
[0032]
In addition, when the particle size of the conductive particles is small, the surface roughness of the intermediate layer becomes small, and interference fringes may occur. Therefore, the surface of the intermediate layer needs to have an appropriate surface roughness. As a result of investigations by the present inventors, the roughness is 1 to 2 μm in Rz, more preferably 1.2 to 1.8 μm.
[0033]
On the other hand, as a result of investigations by the present inventors, the resistance value of the intermediate layer capable of maintaining sufficient charge injection and movement in a low-temperature and low-humidity environment is such that the volume resistivity at 23 ° C./55 RH% is 1 × 10E5 to 1 × 10E7Ω ·. cm.
[0034]
The present inventors have studied and found that the intermediate layer dispersedly contains two or more types of conductive particles having different primary particle diameters, and the average particle diameter of the primary particles of the conductive particles is the largest A and the smallest one. When the ratio A: B of the average particle diameter of B is 12: 1 to 30: 1 and the average particle diameter of B is 0.05 μm or less, the above conditions are satisfied, and image defects such as ghost, fog, black spots, etc. The present invention was found to provide an electrophotographic photoreceptor excellent in durability and excellent in durability.
[0035]
The conductive particles that can be used in the present invention include ZnO and TiO. ₂ , SnO ₂ , In ₂ O ₃ , SiO ₂ , Sb ₂ O ₃ Such metal oxides are suitable, and these can be used alone or in combination.
[0036]
Further, in order to increase the particle size of the conductive particles, those obtained by coating these metal oxide fine particles on base particles having a large particle size may be used. It is not necessary that the base particles have conductivity. ₂ , BaSO ₄ It is possible to use inorganic fine particles having no conductivity, such as.
[0037]
The average particle size of the conductive particles of the present invention is a value measured by a centrifugal sedimentation method.
[0038]
As the binder resin used in the intermediate layer of the present invention, for example, phenol resin, polyurethane, polyamide, polyimide, polyamideimide, polyamic acid, polyvinyl acetal, epoxy resin, acrylic resin, melamine resin, polyester, and the like are preferable. These resins may be used alone or in combination of two or more. These resins have good adhesiveness to the support, improve the dispersibility of the conductive particles used in the present invention, and have good solvent resistance after film formation. Among the above resins, phenol resins, polyurethanes and polyamic acids are particularly preferred.
[0039]
The intermediate layer can be formed, for example, by dipping or applying a solvent using a Meyer bar or the like.
[0040]
In order to improve the dispersibility of the conductive particles, the surface of the conductive particles may be treated with a treatment agent such as a coupling agent (such as a silane coupling agent or a titanium coupling agent) or a silicone oil. Further, the treatment agent may be contained in a binder of the intermediate layer.
[0041]
The thickness of the intermediate layer is preferably 10 to 25 μm, more preferably 15 to 20 μm. The volume resistivity of the intermediate layer is preferably 1 × 10E5 to 1 × 10E7 Ω · cm. In the present invention, the volume resistivity is measured by applying an intermediate layer to be measured on an aluminum plate, forming a gold thin film on the intermediate layer, and measuring the current flowing between both electrodes of the aluminum plate and the gold thin film by pA. It was determined by measuring with a meter.
[0042]
A leveling agent may be added to the intermediate layer in order to enhance surface properties.
[0043]
The photosensitive layer of the present invention may be a single layer or a laminated structure composed of at least a charge generation layer and a charge transport layer.
[0044]
When the photosensitive layer is a single layer, a charge generation substance and a charge transport substance are contained in the same layer, and photo carriers are generated and moved in the same layer.
[0045]
When the photosensitive layer has a laminated structure, the order of laminating the charge generating layer containing the charge generating substance and the charge transporting layer containing the charge transporting substance may be the order of the charge generating layer and the charge transporting layer from the support side. The reverse is also acceptable.
[0046]
Examples of the charge generating material include azo pigments (eg, monoazo, bisazo, trisazo, etc.), metal and metal-free phthalocyanine pigments, indigo pigments (eg, indigo, thioindigo, etc.), and quinone pigments (eg, anthantrone , Pyrenequinone, etc.), perylene pigments (for example, perylene anhydride, perylene imide, etc.), squalium pigments, pyrylium, thiapyrylium salts, triphenylmethane pigments and the like. In addition, inorganic materials such as selenium, selenium-tellurium, and amorphous silicon can also be used as the material for generating cargo.
[0047]
As the charge transport material, there are an electron transport material and a hole transport material. Examples of the electron transport material include 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, chloranil, and tetracyanoquinodimethane. Examples of the hole transport material include polycyclic aromatic compounds (eg, pyrene, anthracene, etc.) and heterocyclic compounds (eg, carbazole, indole, imidazole, oxazole, thiazole, oxadiazole, pyrazole, pyrazoline, thiadiazole, triazole, etc.). Hydrazone compounds (eg, p-diethylaminobenzaldehyde-N, N-diphenylhydrazone, N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, etc.), styryl compounds (eg, α-phenyl-4 ′) —N, N-diaminostilbene, 5- [4- (di-p-tolylamino) benzylidene] -5H-dibenzo [a, d] dicycloheptene and the like, benzidine compounds, triarylamine compounds and the like.
[0048]
When the photosensitive layer is a single layer, the thickness of the photosensitive layer is preferably 5 to 100 μm, more preferably 10 to 60 μm. The single photosensitive layer preferably contains a charge generating substance and a charge transporting substance in an amount of 10 to 70% by mass, more preferably 20 to 70% by mass.
[0049]
When the photosensitive layer has a laminated structure, the thickness of the charge generation layer is preferably 0.001 to 5 μm, more preferably 0.05 to 2 μm, and the thickness of the charge transport layer is preferably 5 to 40 μm, more preferably 10 to 30 μm. The charge generating layer preferably contains a charge generating substance in an amount of 10 to 100% by mass, more preferably 40 to 100% by mass. The charge transport layer preferably contains a charge transport material in an amount of 20 to 80% by mass, more preferably 30 to 70% by mass.
[0050]
The electrophotographic photoreceptor of the present invention can be obtained by forming a material for the photosensitive layer on a support by vacuum evaporation or by combining it with an appropriate binder resin.
[0051]
As the binder resin for the photosensitive layer, for example, polyvinyl acetal, polycarbonate, polyarylate, polystyrene, polyester, polyacetate, polymethacrylate, acrylic resin, cellulose resin and the like are preferably used.
[0052]
Depending on the kind of the material of the photosensitive layer, free carriers may be injected from the intermediate layer into the photosensitive layer, which lowers the charging ability of the photosensitive member and greatly affects image characteristics. In such a case, if necessary, a barrier layer (for example, an appropriate resin thin film) having an electrical barrier property is provided between the intermediate layer and the photosensitive layer to effectively suppress the injection of the free carrier. can do. As the barrier layer, for example, polyvinyl alcohol, polyvinyl methyl ether, polyacrylic acids, methyl cellulose, ethyl cellulose, polyglutamic acid, casein, water-soluble resin such as starch, polyamide, polyimide, polyamide imide, polyamic acid, melamine resin, epoxy resin, Resins such as polyurethane and polyglutamic acid ester can be used. In particular, polyamide is preferable as the barrier layer in terms of coating properties, adhesion, solvent resistance, electrical barrier properties, resistance, and the like. As the polyamide, low-crystalline or non-crystalline copolymerized nylon which can be applied in a solution state is suitable. The thickness of the barrier layer is preferably from 0.1 to 2 μm.
[0053]
In the electrophotographic photoreceptor of the present invention, a protective layer may be provided on the photosensitive layer. The protective layer is mainly composed of a resin. As a material constituting the protective layer, for example, polyester, polyurethane, polyarylate, polyethylene, polystyrene, polybutadiene, polycarbonate, polyamide, polypropylene, polyimide, polyamide imide, polysulfone, polyallyl ether, polyacetal, nylon, phenol resin, acrylic resin, Examples include silicone resin, epoxy resin, urea resin, allyl resin, alkyd resin, and butyral resin. The thickness of the protective layer is preferably 0.05 to 15 μm, more preferably 1 to 10 μm.
[0054]
The conductive support is made of a metal or alloy such as aluminum, aluminum alloy, copper, titanium, and stainless steel, or a polymer material such as polyethylene terephthalate, polybutylene terephthalate, phenolic resin, polypropylene, and polystyrene, and further, such as hard paper. It can be manufactured using materials. The shape of the support is preferably cylindrical, belt-like or sheet-like. When the material constituting the support has a high volume resistance, it is necessary to conduct a conductive treatment. The conductive treatment can be performed by forming a conductive thin film on the support or dispersing a conductive substance in the support.
[0055]
The electrophotographic photoreceptor of the present invention can be widely used in electrophotographic applications such as electrophotographic copying machines, laser beam printers, CRT printers, LED printers, liquid crystal printers, facsimile machines, and laser plate making.
[0056]
The electrophotographic photoreceptor according to the present invention can realize stable potential characteristics and good image formation in all environments from low temperature and low humidity to high temperature and high humidity.
[0057]
Next, an electrophotographic apparatus provided with the electrophotographic photosensitive member of the present invention will be described.
[0058]
FIG. 1 shows an example of a contact charging type electrophotographic apparatus. This example is a transfer type copier or printer.
[0059]
Reference numeral 1 denotes a drum type electrophotographic photosensitive member to which the present invention is applied. The electrophotographic photosensitive member 1 is driven to rotate at a predetermined peripheral speed (process speed) in the clockwise direction of arrow A.
[0060]
Reference numeral 2 denotes a charging roller that is a contact charging member as a charging unit. The charging roller 2 rotates following the rotation of the photoreceptor 1 pressed against the charging roller, and a DC voltage on which an AC voltage is superimposed is applied from a bias power supply 2A. The charging roller 2 uniformly charges the peripheral surface of the photoconductor 1 to a predetermined polarity and potential by a contact charging method.
[0061]
The charged surface of the photoreceptor 1 is irradiated with exposure 3 of target image information by exposure means (not shown) such as an image forming exposure means for a document image, a laser beam scanner, etc., and the surface of the photoreceptor 1 corresponds to the target image information. The formed electrostatic latent image is formed.
[0062]
The formed electrostatic latent image is visualized as a transferable particle image (toner image) 5 a by a charged particle (toner) 5 of a developing device 4 by normal development or reverse development.
[0063]
Next, the toner image is transferred from a paper feed cassette 9 to a nip portion (transfer portion) of the photoreceptor 1 and a transfer roller 7 as a transfer means pressed against the photoreceptor 1 by a paper feed roller 10 and a registration roller 11. The transferred particles 5b adhere to the sheet 6 fed one by one at the timing. To the transfer roller 7, a bias voltage having a polarity opposite to the charge retained in the toner 5 is applied from a bias power supply 7 </ b> A.
[0064]
The sheet 6 to which the toner image has been transferred is separated from the surface of the photoreceptor 1 and is conveyed to a fixing unit (not shown) to undergo a fixing process of the toner image.
[0065]
After the transfer of the toner image, the surface of the photoreceptor 1 is cleaned by a cleaner (cleaning device) 8 to remove adhered contaminants such as untransferred toner, and is repeatedly used for image formation.
[0066]
【Example】
Example 1
20 parts by mass of barium sulfate fine particles having an oxygen-deficient tin oxide coating layer (coverage: 50% by mass, average primary particle diameter: 0.6 μm, specific gravity: 5.1) and antimony-containing tin oxide fine particles 100 parts by mass of powder (T-1, manufactured by Mitsubishi Materials, average particle size of primary particles 0.02 μm, specific gravity 6.6) and resol-type phenol resin (Plyofen J-325, manufactured by Dainippon Ink and Chemicals, A solution consisting of 70 parts by mass (solid content 70%) and 100 parts by mass of 2-methoxy-1-propanol was dispersed in a ball mill for about 20 hours.
[0067]
The dispersion thus prepared was applied on an aluminum plate by a Meyer bar to form a film having a thickness of 15 μm, and the volume resistivity was measured by the method described above. ⁷ Ω · cm.
[0068]
Next, this dispersion is applied on an aluminum cylinder (outer diameter 30 mm, length 260.5 mm) (surface roughness Ry 5 μm) by an immersion method, and is heated and cured at 140 ° C. for 30 minutes to form a 15 μm thick intermediate layer. Was formed. When the surface roughness Rz of the intermediate layer at this time was measured, it was 1.6 μm. The roughnesses Ry and Rz are based on 1994 JIS.
[0069]
Next, a solution prepared by dissolving 10 parts by mass of a copolymerized nylon resin (Amilan CM8000, manufactured by Toray) in a mixed solution of 60 parts by mass of methanol and 40 parts by mass of butanol was applied onto the intermediate layer by dip coating. After heating and drying for 0.5 minutes, a barrier layer having a thickness of 0.5 μm was formed.
[0070]
Next, a solution composed of 4 parts by mass of an oxytitanium phthalocyanine pigment, 2 parts by mass of a polyvinyl butyral resin (BX-1, manufactured by Sekisui Chemical Co., Ltd.), and 34 parts by mass of cyclohexanone was dispersed by a sand mill for 8 hours, and then 60 parts by mass of tetrahydrofuran was added. Thus, a dispersion for the charge generation layer was prepared. This dispersion was applied onto the above barrier layer by dip coating, and dried by heating at 80 ° C. for 10 minutes to form a charge generation layer. The thickness of the charge generation layer was 0.2 μm.
[0071]
Next, 50 parts by mass of a triarylamine compound represented by the following structure:
[0072]
Embedded image

A solution prepared by dissolving 50 parts by mass of a polycarbonate resin (Iupilon Z-200, manufactured by Mitsubishi Gas Chemical Co., Ltd.) in 400 parts by mass of monochlorobenzene was applied onto the charge generating layer by dip coating, and heated and dried at 120 ° C. for 1 hour to obtain a thickness of 24 μm. Was formed.
[0073]
The electrophotographic photoreceptor of the present invention produced in this manner was converted from a Hewlett-Packard LBP “Laser Jet 4000” (process speed of 94.2 mm / sec) having a configuration as shown in FIG. 1 under the following process conditions. The evaluation was performed by changing the settings.
[0074]
Electrophotographic photosensitive member dark area potential -550V
Electrophotographic photosensitive member light section potential -150V
Development bias -350V (DC voltage only)
For the evaluation, initial image evaluation was performed in an environment of low temperature and low humidity (15 ° C., 10% RH) and high temperature and high humidity (30 ° C., 80% RH). The evaluation of the image was performed as follows. A ghost is evaluated on a halftone test chart in which a solid black portion of 25 mm square is arranged on the rotating portion of the electrophotographic photosensitive member 1 from the start of print image printing, and one dot is printed in a Keima pattern after the second rotation of the electrophotographic photosensitive member. did. In addition, evaluation of spot and fog images was performed using a halftone test chart in which one dot was printed in a Keima pattern over the entire print surface and a solid black and solid white image. Table 1 shows the evaluation results.
[0075]
Then, under an environment of low temperature and low humidity (15 ° C., 10% RH) and high temperature and high humidity (30 ° C., 80% RH), 10,000 sheets of continuous image were printed on A4 size paper in a character pattern of 4% area ratio printing. A test was performed to evaluate the image. Table 1 shows the evaluation results.
[0076]
As a result of the evaluation, as shown in Table 1, this photoreceptor shows a stable electric potential in any environment even at low temperature and low humidity and high temperature and high humidity even after the initial and continuous running of 10,000 sheets. An image with very good image quality without fog, ghosts and interference fringes was obtained stably.
[0077]
Examples 2 to 5
The electrophotographic photosensitive members of Examples 2 to 5 were produced in the same manner as in Example 1 except that the intermediate layer of Example 1 was replaced with an intermediate layer formed using the following coating liquid. Each electrophotographic photoreceptor thus produced was evaluated in the same manner as in Example 1. Table 1 shows the results.
[0078]
Coating liquid of Example 2
・ Powder made of the same barium sulfate fine particles as in Example 1 20 parts by mass
20 parts by mass of a powder composed of titanium oxide fine particles having a coating layer of antimony-containing tin oxide (EC-210, manufactured by Titanium Co., Ltd., average primary particle diameter 0.5 μm, specific gravity 4.6)
-80 parts by mass of tin oxide-containing indium oxide fine particles (ITO, manufactured by Mitsubishi Materials Corporation, average particle size of primary particles 0.03 μm, specific gravity 7.1)
-70 parts by mass of the same resol-type phenol resin as in Example 1
・ 2-methoxy-1-propanol 100 parts by mass
Coating liquid of Example 3
In the same manner as in Example 1 except that a powder of tantalum-doped tin oxide fine particles (average primary particle diameter: 0.02 μm, specific gravity: 6.1) was used instead of the antimony-containing tin oxide fine particles in Example 1, A coating solution was prepared.
[0079]
Coating liquid of Example 4
A coating liquid was prepared in the same manner as in Example 1 except that a polyester polyurethane (Nipporan 2304, manufactured by Nippon Polyurethane) was used instead of the resol-type phenol resin used in Example 1.
[0080]
Coating liquid of Example 5
-Instead of 70 parts by mass of the resole-type phenol resin used in Example 1, 50 parts by mass of a polyamic acid resin having the following structural formula (weight average molecular weight: 8500) was used, and 100 parts by mass of 2-methoxy-1-propanol was used. A coating solution was prepared in the same manner as in Example 1 using 170 parts by mass of N-dimethylacetamide.
[0081]
Embedded image

Examples 6 and 7
An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 2, except that the thickness of the intermediate layer was changed to 10 μm and 25 μm, respectively.
[0082]
Comparative Examples 1-3
Electrophotographic photoreceptors of Comparative Examples 1 and 2 were produced in the same manner as in Example 1 except that the intermediate layer of Example 1 was replaced with an intermediate layer formed using the following coating liquid.
[0083]
Each electrophotographic photoreceptor thus produced was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0084]
Coating liquid of Comparative Example 1
150 parts by mass of barium sulfate fine particles having an oxygen-deficient tin oxide coating layer (coverage: 50% by mass, average primary particle diameter: 0.6 μm, specific gravity: 5.1)
-75 parts by mass of the same resol type phenol resin as in Example 1
・ Methyl cellosolve 60 parts by mass
・ Methanol 15 parts by mass
[0085]
Coating liquid of Comparative Example 2
-120 parts by mass of a powder composed of antimony-containing tin oxide fine particles (T-1, manufactured by Mitsubishi Materials)
-70 parts by mass of the same resol-type phenol resin as in Example 1
・ 80 parts by mass of 2-methoxy-1-propanol
[0086]
Coating liquid of Comparative Example 3
70 parts by mass of barium sulfate fine particles having an oxygen-deficient tin oxide coating layer (coverage ratio: 50% by mass, average particle size of primary particles: 0.6 μm, specific gravity: 5.1)
70 parts by mass of a powder composed of titanium oxide fine particles having a coating layer of antimony-containing tin oxide (EC-210, manufactured by Titanium Co., Ltd., average primary particle size 0.5 μm, specific gravity 4.6)
-70 parts by mass of the same resol-type phenol resin as in Example 1
・ Methyl cellosolve 60 parts by mass
・ Methanol 15 parts by mass
[0087]
Comparative Example 4
An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that barium sulfate particles not coated with tin oxide were used instead of the barium sulfate particles coated with tin oxide used in Example 1. . Table 1 shows the results.
[0088]
Comparative Examples 5 and 6
An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 2 except that the thickness of the intermediate layer was changed to 5 μm and 30 μm, respectively. Table 1 shows the results. The photoconductor of Comparative Example 6 was not evaluated because cracks occurred in the intermediate layer.
[0089]
[Table 1]

[0090]
【The invention's effect】
According to the electrophotographic photoreceptor of the present invention, stable and good image formation can be realized in all environments from low temperature and low humidity to high temperature and high humidity.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of a contact charging type electrophotographic apparatus.
[Explanation of symbols]
1. Electrophotographic photoreceptor
2 Charging roller
2A bias power supply
3 Exposure
4 Developing device
5 charged particles (toner)
5a Transferable particle image (toner image)
5b Transferred particles
6 paper
7 Transfer roller
7A bias power supply
8 Cleaner (cleaning device)
9 Paper cassette
10 Paper feed roller
11 Registration roller

Claims (1)

In an electrophotographic photoreceptor comprising an intermediate layer and a photosensitive layer sequentially laminated on a conductive support, the intermediate layer contains two or more kinds of conductive particles having different primary particle diameters in a dispersed manner. When the ratio A: B of the primary particles having the largest average particle diameter A to the smallest primary particle B is 12: 1 to 30: 1, and the average particle diameter of the B is 0.05 μm or less. An electrophotographic photosensitive member, comprising:

Images