【発明の詳細な説明】[Detailed description of the invention]
本発明は長波長域の光に対しても高感度である
電子写真用感光体に関する。
静電式複写機あるいは電算機プリンタなどに用
いられる電子写真用感光体は、例えばアルミニウ
ムから成る導電性の基体上に電荷の注入を制限す
る界面層を介してセレンから成る感光層を蒸着し
て造られる。このような感光体の感度を示す量子
効率、すなわち帯電した感光体に照射した光の光
子数に対するその光によつて減衰した電荷の電子
数の比は、第１図の曲線Ａに示すように光の波長
が長くなるに従い低下するとことが知られてい
る。しかし複写機に用いられる光源、例えばハロ
ゲンランプあるいはプリンタ等で用いられるレー
ザ光源は長波長を主波長とすることから、長波長
側での感度の向上が要求される。この要求を満た
すため、蒸着材料としてテルルを含有するセレン
を用いることは知られている。第１図の曲線Ｂ
は、一例として６重量％のテルルを含む感光体の
特性を示す。長波長側の量子効率が増大し、汎色
性への改良がはかられていることが解る。第２図
はセレンへのテルル含有量の半減衰露光量に対す
る影響を示す。即ち、色温度2000〓のタングステ
ンランプを用い5lxの照度で白色光を照射して帯
電電位が初期電位800Vの1/2になるまでの露光量
が、テルル含有量に応じてどのように変化するか
を測定した結果を示すものである。感度はこの半
減衰露光量に反比例するから、テルル含有量の増
加につれて長波長側の感度が高くなつたことが認
められる。
しかしテルル含有量の高いセレン・テルル合金
を使用して高波長域での感度を増大させた場合、
電荷保持率の低下すなわち暗減衰の増大あるいは
露光時の残留電位の増大などで認められるいわゆ
る疲労の増加を伴ない、感光体としての使用に耐
えなくなるという欠点がある。この欠点はセレン
中のテルルの高濃度に起因するものであり、本質
的に不可避であると考えられてきた。
本発明の目的はこの予盾を解決し、高波長域の
光に対しても高い感度を持つにもかゝわらず疲労
の少ない電子写真用感光体を提供することにあ
る。
この目的は導電性基体上に界面層を介して下記
の二つの層の順に積層して感光層とすることによ
つて達成される。
(1) 30μm以上の厚みを持ち、テルル５〜15重量
％を含むセレン・テルル合金からなる電荷保持
層。
(2) ３〜10μmの厚みを持ち、テルルを電荷保持
層におけるテル含有量以上に含むセレン・テル
ル合金からなる表面層。
以下具体例を参照しながら本発明をより詳しく
説明する。
先ず従来の感光体の製造工程を説明する。円筒
状のアルミニウム基体の表面に機械仕上げ加工を
ほどこし、硝酸処理によりその表面にアルミ酸化
物の界面層を形成した。この基体を回転軸の表面
上に支持し、蒸発源にテルル含有量13.5重量％の
セレン・テルル合金を入れ、基体を支持する軸の
温度を制御することにより基体の表面温度を76℃
に保持しながら蒸発源を300℃に加熱して真空蒸
着を行ない、65μmの膜厚の感光層を有する感光
体（試料１）を得た。この場合セレンの蒸気圧が
テルルの蒸気圧より高いための蒸発材料のテルル
含有量は蒸発の進行につれて高くなり、従つて感
光層は基体に近い側から遠い側に進むにつれて高
いテルル含有量を示し、その範囲はほゞ７〜14％
にわたつている。
次に本発明による感光体の製造工程を説明する
に、円筒状アルミニウム基体に、試料１の製造に
おいて行つたのと同一の処理を施して界面層を形
成した。別途、13.5重量％のテルルを含有するセ
レン・テルル合金を入れた第１蒸発源および22.5
重量％のテルルを含有するそれを入れた第２蒸発
源を用意し、これらを真空蒸着槽内に収容した。
基体表面を76℃に保持した状態で、先ず第１蒸発
源を300℃に加熱して55μmの膜厚を有する第１層
を形成した。この間第２蒸発源は175℃に保持し
ておいた。次に蒸着槽の真空を破ることなく、第
１蒸発源の加熱を停止し、第２蒸発源を320℃に
加熱して、第１層上に10μmの厚みを第２層を形
成した。
第３図は完成した感光体（試料２）を示し、ア
ルミニウム基体１上に界面層２を介して第１層３
および第２層４が順に積層されている。感光層中
のテルル含有量は蒸着の初期、すなわち基体１側
の方が低く蒸着の進むにつれて高くなり、第１層
３ではほゞ７〜13％の範囲に、第２層４ではほゞ
17〜20％の範囲にわたつている。
これら二つの感光体を常温常湿の暗中に72時間
放置した後、コロナ電圧5.5kVで帯電させ、色温
度2000〓のタングステンランプを用い5lxの照度
で白色光を照射して白色光半減衰露光量を、米国
コダツク社ラツテンフイルタNo.29を介して同じラ
ンプで赤色光を照射して赤色光半減衰露光量を、
同じランプで白色光を20lx・ｓ露光した後残留電
位を、また150lxの照度で温白色螢光灯により除
電を行つて帯除電を500回繰返した後の残留電位
で疲労をそれぞれ測定した結果を第１表に示す。
The present invention relates to an electrophotographic photoreceptor that is highly sensitive even to light in a long wavelength range. Electrophotographic photoreceptors used in electrostatic copying machines, computer printers, etc. are made by depositing a photosensitive layer made of selenium on a conductive substrate made of aluminum, for example, with an interfacial layer that limits charge injection. built. The quantum efficiency, which indicates the sensitivity of such a photoreceptor, that is, the ratio of the number of electrons in the charge attenuated by the light to the number of photons of light irradiated on the charged photoreceptor, is as shown in curve A in Figure 1. It is known that as the wavelength of light becomes longer, it decreases. However, since light sources used in copying machines, such as halogen lamps or laser light sources used in printers, have long wavelengths as their main wavelength, improvement in sensitivity on the long wavelength side is required. In order to meet this requirement, it is known to use selenium containing tellurium as a vapor deposition material. Curve B in Figure 1
shows the properties of a photoreceptor containing 6% by weight tellurium as an example. It can be seen that the quantum efficiency on the long wavelength side increases and that panchromaticity is improved. FIG. 2 shows the effect of tellurium content on selenium on half-attenuation exposure. In other words, how does the amount of exposure to irradiate white light at an illuminance of 5lx using a tungsten lamp with a color temperature of 2000〓 until the charging potential becomes 1/2 of the initial potential of 800V change depending on the tellurium content? This shows the results of measurements. Since the sensitivity is inversely proportional to this half-attenuation exposure, it is recognized that the sensitivity on the long wavelength side increases as the tellurium content increases. However, if a selenium-tellurium alloy with a high tellurium content is used to increase the sensitivity in the high wavelength range,
This is accompanied by an increase in so-called fatigue, which is observed as a decrease in charge retention, that is, an increase in dark decay, or an increase in residual potential during exposure, and it has the disadvantage that it cannot withstand use as a photoreceptor. This drawback is due to the high concentration of tellurium in selenium and has been considered essentially unavoidable. An object of the present invention is to solve this problem and provide an electrophotographic photoreceptor that is highly sensitive to light in a high wavelength range and is less tiring. This object is achieved by laminating the following two layers in this order on a conductive substrate via an interface layer to form a photosensitive layer. (1) A charge retention layer having a thickness of 30 μm or more and made of a selenium-tellurium alloy containing 5 to 15% by weight of tellurium. (2) A surface layer made of a selenium-tellurium alloy having a thickness of 3 to 10 μm and containing tellurium in an amount greater than the tellurium content in the charge retention layer. The present invention will be explained in more detail below with reference to specific examples. First, the manufacturing process of a conventional photoreceptor will be explained. The surface of a cylindrical aluminum substrate was machined and treated with nitric acid to form an interfacial layer of aluminum oxide on the surface. This substrate is supported on the surface of a rotating shaft, a selenium-tellurium alloy with a tellurium content of 13.5% by weight is placed in the evaporation source, and the surface temperature of the substrate is raised to 76°C by controlling the temperature of the shaft that supports the substrate.
Vacuum deposition was carried out by heating the evaporation source to 300° C. while maintaining the temperature to obtain a photoreceptor (sample 1) having a photosensitive layer with a thickness of 65 μm. In this case, since the vapor pressure of selenium is higher than that of tellurium, the tellurium content of the evaporated material increases as the evaporation progresses, and therefore the photosensitive layer exhibits a higher tellurium content as it progresses from the side closer to the substrate to the side farther away from the substrate. , the range is approximately 7-14%
spread across the country. Next, to explain the manufacturing process of the photoreceptor according to the present invention, a cylindrical aluminum substrate was subjected to the same treatment as in the manufacturing of Sample 1 to form an interface layer. Separately, a first evaporation source containing a selenium-tellurium alloy containing 13.5% by weight of tellurium and 22.5
A second evaporation source containing % tellurium by weight was prepared and housed in a vacuum deposition chamber.
While the substrate surface was maintained at 76° C., the first evaporation source was first heated to 300° C. to form a first layer having a thickness of 55 μm. During this time, the second evaporation source was maintained at 175°C. Next, without breaking the vacuum in the deposition tank, heating of the first evaporation source was stopped, and the second evaporation source was heated to 320° C. to form a second layer with a thickness of 10 μm on the first layer. FIG. 3 shows a completed photoreceptor (sample 2), in which a first layer 3 is deposited on an aluminum substrate 1 through an interfacial layer 2.
and second layer 4 are laminated in this order. The tellurium content in the photosensitive layer is lower at the initial stage of vapor deposition, that is, on the substrate 1 side, and increases as the vapor deposition progresses; in the first layer 3 it is in the range of about 7 to 13%, and in the second layer 4 it is in the range of about 7 to 13%.
It ranges from 17 to 20%. After leaving these two photoconductors in the dark at room temperature and humidity for 72 hours, they were charged with a corona voltage of 5.5kV, and exposed to white light at half-attenuation by irradiating them with white light at an illuminance of 5lx using a tungsten lamp with a color temperature of 2000㎓. The amount of red light is irradiated with the same lamp through Kodatsu's Ratten Filter No. 29, and the red light half-attenuation exposure amount is
The results of measuring fatigue were measured by the residual potential after exposure to white light for 20lx・s using the same lamp, and by the residual potential after static charge removal was repeated 500 times using a warm white fluorescent lamp at an illuminance of 150lx. Shown in Table 1.
【表】
第１表より明らかなように本発明の実施例であ
る試料２は１層の感光層を有する試料１にくらべ
て高波長域を含めて感度が向上すると共に疲労が
少なく、また電荷保持率の低下も僅かである。
次にこれら２本の感光体試料を温白色螢光灯１
本を光源に用いた静電式複写機に装着し画像出し
を行つたところ、試料２では非常に鮮明で良質の
画像が得られ、連続１万枚コピーに対しても画像
は高濃度を有しかつ地汚れ、ゴーストなどの欠陥
の出ることがなかつた。一方試料１では良質な画
像を得ることができなかつた。
本発明は長波長域での量子効率の向上をはかる
ためにテルル含有量の高い表面層を設け、その下
に暗中において高抵抗を有して感光層表面の電荷
を保持するとともに光減衰時に表面層に発生した
電荷担体を速かに導電性基板に移動させるよう低
いテルル含有量の電荷保持層を設ける。電荷保持
層のテルル含有量は５〜15重量％の範囲に調整さ
れるが、これは15％をこえると抵抗が低くなりす
ぎて電荷を保持しなくなり、また５％より低いと
疲労による残留電位の問題が生じてくるからであ
る。表面電荷層の厚みはセレン感光体の誘電率が
所望の値になるように調整されるがそのためには
最低30μmを必要とする。表面層のテルル含有量
は電荷保持層中の最大のテルル濃度より高くさ
れ、電子写真用特性に応じて例えば表面濃度を20
重量％に抑える。表面層の厚みは露光により電荷
担体の発生に最低必要な3μm以上で発生した電子
が深部にトラツプされることのないように10μm
以下にされる。
上述のように本発明に基づく電子写真感光体
は、二つの蒸発源を用いて形成される２層の感光
層により、特に長波長域の感度の高い高感度、低
疲労のものであり、複写機、プリンタあるいはフ
アクシミリ等にその達せられる工業上の効果は大
きい。[Table] As is clear from Table 1, Sample 2, which is an example of the present invention, has improved sensitivity including in the high wavelength range, less fatigue, and less charge compared to Sample 1, which has a single photosensitive layer. There is also a slight decrease in retention rate. Next, these two photoreceptor samples were heated under a warm white fluorescent lamp 1.
When images were produced by attaching a book to an electrostatic copying machine that used a light source, sample 2 produced very clear and high-quality images, and the images had high density even after 10,000 continuous copies. Furthermore, there were no defects such as background stains or ghosts. On the other hand, with Sample 1, it was not possible to obtain a good quality image. In order to improve the quantum efficiency in the long wavelength region, the present invention provides a surface layer with high tellurium content under the surface layer, which has high resistance in the dark and retains the charge on the surface of the photosensitive layer. A charge retention layer with a low tellurium content is provided so that charge carriers generated in the layer are rapidly transferred to the conductive substrate. The tellurium content of the charge retention layer is adjusted to a range of 5 to 15% by weight, but if it exceeds 15%, the resistance will become too low and will no longer retain charge, and if it is lower than 5%, residual potential due to fatigue will occur. This is because the problem arises. The thickness of the surface charge layer is adjusted so that the dielectric constant of the selenium photoreceptor becomes a desired value, and for this purpose a minimum thickness of 30 μm is required. The tellurium content of the surface layer is made higher than the maximum tellurium concentration in the charge retentive layer, e.g.
Reduce to % by weight. The thickness of the surface layer is 10 μm to prevent electrons generated at the minimum thickness of 3 μm, which is required for generation of charge carriers due to exposure, from being trapped deep inside.
be made below. As described above, the electrophotographic photoreceptor according to the present invention has two photosensitive layers formed using two evaporation sources, has high sensitivity, particularly in the long wavelength region, and is low in fatigue. The industrial effect it can bring to machines, printers, facsimile machines, etc. is great.
【図面の簡単な説明】[Brief explanation of the drawing]
第１図は露光する光の波長に関してセレンおよ
びセレン・テルル合金感光層の量子効率を示す線
図、第２図はテルル含有量に関して白色光に対す
る半減衰露光量を示す線図、第３図は本発明に基
づく感光層の構成を説明する断面図である。
１……導電性基体、２……界面層、３……電荷
保持層、４……表面層。
Fig. 1 is a diagram showing the quantum efficiency of selenium and selenium-tellurium alloy photosensitive layers with respect to the wavelength of the exposing light, Fig. 2 is a diagram showing the half-attenuation exposure amount for white light with respect to tellurium content, and Fig. 3 is a diagram showing the half-attenuation exposure amount for white light with respect to the tellurium content. FIG. 2 is a cross-sectional view illustrating the structure of a photosensitive layer according to the present invention. DESCRIPTION OF SYMBOLS 1... Conductive substrate, 2... Interface layer, 3... Charge retention layer, 4... Surface layer.