JPH0736081B2 - Electrophotographic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an electrophotographic apparatus, and more particularly to a surface protective layer made of an amorphous material containing silicon atoms and carbon atoms and, if necessary, hydrogen atoms or halogen atoms. The present invention relates to an electrophotographic apparatus provided with the electrophotographic photosensitive member.

[Prior Art] Conventionally, an amorphous material containing silicon atoms and carbon atoms mainly for the purpose of surface protection and prevention of surface charge injection, and optionally a hydrogen atom or a halogen atom (X) (hereinafter referred to as "a- An electrophotographic apparatus including an electrophotographic photosensitive member having a surface protective layer made of SiC (H, X) ”is known.

Such a surface protective layer holds the electric potential of the surface of the photoconductor at a portion which becomes a dark portion when an electrostatic latent image is formed by exposure, and therefore has a role of preventing injection of charges from the surface of the layer into the photoconductive layer. is doing. Therefore, the surface protection layer should be at least 500
It is required to have a layer thickness of Å or more.

On the other hand, in the exposed portion, the photocarriers generated in the photoconductive layer to form a latent image cause the disappearance of the potential on the surface of the photosensitive member. It is necessary that the generated photocarriers can pass through the surface protective layer and reach the surface of the photoreceptor. For this reason,
The maximum thickness of the surface protective layer is usually 10,000 Å. It is said that if the layer thickness exceeds this value, the surface potential cannot be reduced to 0 even after strong exposure, resulting in a residual potential on the surface of the photoconductor, resulting in deterioration of image quality such as background fog. Caused problems.

For this reason, the upper and lower limits of the thickness of the surface protective layer are determined, but generally 2000 Å considering the manufacturing cost and durability.
Generally, the layer thickness is about the same.

By the way, in such an electrophotographic apparatus, in order to repeat copying, the surface of the photosensitive member is cleaned (cleaning) to remove the developer remaining on the surface of the photosensitive member in preparation for the next copying operation. As a cleaning method, conventionally, surface polishing cleaning by blade cleaning using a rubber blade or the like has been generally used.

In addition, foreign substances such as ozone products and transfer paper powder caused by exposure during copying are also adsorbed on the surface of the photoconductor. Especially, when the atmosphere of the apparatus is high in humidity, such foreign substances are detected. However, since such a foreign matter causes blurring of a copied image, it is necessary to remove it from the surface of the photoconductor in the same manner as the developer.

However, a-SiC (H, X) forming the surface protective layer is very hard (Vickers hardness is about 1000), which gives the photoreceptor excellent durability, but its surface abrasion amount is small, It was difficult to remove such foreign matter. For example, in the case of a conventional electrophotographic photosensitive member using a material having a small hardness such as a-Se (thus, the durability is inferior), even a blade cleaning with a rubber blade can reduce the hardness to 0.1.
The surface is scraped at about 2 (μm / 10,000 sheets), and the foreign substances such as the ozone product and the transfer paper powder that cause the image blur as described above are removed. However, since a-SiC (H, X) has a large hardness, the surface abrasion amount is about 5 to 10 (Å / 10,000 sheets). Therefore, in an electrophotographic photosensitive member having a surface protective layer made of a-SiC (H, X), an elastic cleaning roller having a larger amount of surface abrasion than such a blade is rubbed against the surface protective layer to give about 20 to The layer is polished at about 50 (Å / 10,000 sheets). Further, an abrasive may be added to the developer in order to improve the abrasiveness.

As described above, in the electrophotographic apparatus, the surface of the photoconductor is cleaned, but the cleaning roller is generally known as an excellent cleaning means capable of uniformly scraping the surface of the photoconductor. However, even when such a cleaning roller is used, partial abrasion unevenness may occur due to uneven distribution of the abrasive contained in the developer on the roller and adhesion. The unevenness appears as unevenness in the density of the copied image, which not only deteriorates the copy quality, but also only 50
A problem such as streaking in a copied image due to uneven shavings (difference in layer thickness of the surface protective layer) of about 0Å occurred, and the life of the electrophotographic photosensitive member was significantly shortened.

[Problems to be Solved by the Invention] The present invention has been made in view of the problems of the above-described conventional examples, and a main object of the present invention is to provide a novel image protection device that prevents image blurring and deterioration of durability as described above. An object is to provide an electrophotographic apparatus.

That is, the present invention has a close relationship between the thickness of the surface protective layer and the sensitivity of the electrophotographic photosensitive member described above, and in order to improve the quality of the copied image including the deterioration of the image quality due to uneven shaving of the surface protective layer, It is extremely effective to increase the thickness of the surface protective layer, and the sensitivity of the photoreceptor to the thickness of the surface protective layer is extremely sensitive to the conventional thickness of around 2000 Å. It is based on the finding that it has become a cause of the necessity of sufficiently controlling the layer thickness at the time of forming the layer.

[Means for Solving the Problems] An electrophotographic apparatus of the present invention that achieves the above object has a photoconductive layer and a surface protective layer formed of an amorphous material containing silicon atoms and carbon atoms on a substrate. In an electrophotographic apparatus including an electrophotographic photosensitive member that is sequentially laminated, the protective layer has a layer thickness in the range of 400Å to 10000Å, and has a wavelength of 400 nm.
To the refractive index of the protective layer for light of 700 nm is 1.5 or more,
The photoconductive layer has a refractive index of 4.0 or less, and further comprises an elastic cleaning roller for rubbing the surface protective layer.

Hereinafter, the present invention will be described in detail with reference to the drawings as necessary.

FIG. 3 shows the spectral transmittance of a conventional electrophotographic photosensitive member in which the surface protective layer made of a-SiC (H, X) has a layer thickness of about 2000Å.

This curve has a shorter cycle on the shorter wavelength side, and a-SiC
When the surface protection layer made of (H, X) becomes thicker, it has the feature of shifting to the long wavelength side. Therefore, as the surface protective layer becomes thicker, a curve with a shorter period (not shown) appears in the wavelength range of FIG.

That is, FIG. 3 shows the change in the transmittance with respect to each wavelength when the surface protective layer has a layer thickness of about 2000 Å. In this case, the transmittance is constantly changing, and the wave length changes toward the shorter wavelength side. The mountain valley cycle becomes shorter. Then, as the surface protective layer becomes thicker, a portion having a shorter cycle of peaks and valleys appears in the graph of this wavelength range, and the portion having a shorter cycle moves to the longer wavelength side as the surface layer becomes thicker.

Therefore, the curve with a short cycle is a curve with a short cycle of peaks and valleys of a wavy curve, that is, a curve in which peaks and valleys are mixed.

Now, the exposure amount distribution of the irradiation light currently used in the electrophotographic photosensitive member has a shape almost close to the visibility curve as shown in FIG. 4, and the light amount distribution that actually reaches the photoconductive layer is shown. Is the product of FIG. 3 and FIG.

That is, the irradiation light having the exposure amount distribution as shown in FIG.
When an electrophotographic photoreceptor 4 having a surface protective layer 1 and a photoconductive layer 2 as shown in FIG. 2 to be described later is irradiated, the light first enters the surface protective layer 1 and the photoconductive layer 2 is formed on the surface of the layer 1. Will cause interference with the reflected light at the interface. Therefore, the amount of light that actually passes through the surface protective layer 1 and reaches the photoconductive layer 2 is, for example, the product of the spectral transmittance as shown in FIG. 3 and the exposure amount distribution as shown in FIG. The light reaches the photoconductive layer 2 having the spectral sensitivity as illustrated in FIG. 5 to generate photocarriers.

The vertical axis in FIG. 4 represents the exposure amount (exposure intensity), and its unit is an arbitrary unit (au). This is the maximum of the exposure intensity at each wavelength of the irradiation light, and the relative value is taken on the vertical axis from 1.0. From Fig. 4, the exposure intensity for each wavelength of the irradiation light is shown. You can know.

Further, FIG. 5 shows the spectral intensity of the photoconductive layer, and the vertical axis shows the photosensitivity at each wavelength relatively with the value of the wavelength showing the highest sensitivity being 1.0. Therefore, the vertical axis represents the sensitivity, but is in arbitrary units (au) as in FIG.

By the way, such interference varies depending on the layer thickness of the surface protective layer 1, but when the layer thickness of the surface protective layer 1 becomes thick,
As described above, a curve with a short cycle appears in the wavelength region as shown in the figure, and if the spectral transmittance changes,
The sensitivity of the electrophotographic photosensitive member 4 will change continuously. However, conventionally, little is known about the influence of the layer thickness of the surface protective layer 1 on the sensitivity of the electrophotographic photosensitive member 4, and the inventors of the present invention have diligently studied these influences. Layer thickness and electrophotographic photoreceptor 4
The present invention has been achieved by finding that the sensitivity of 1 has a relationship as illustrated in FIG.

FIG. 6 is a diagram for explaining the relationship between the thickness of the surface protective layer and the sensitivity of the electrophotographic photosensitive member. As shown in Examples described later, a having a refractive index of 3.4 for a light having a wavelength of 400 nm to 700 nm is 3.4. An electrophotographic image in which a surface protective layer made of a-SiC (H, X) having a refractive index in the wavelength range of 1.9 is evenly laminated to a thickness of about 5000Å on a photoconductive layer made of -Si (H, X). It is an example of a protective layer layer thickness-sensitivity curve obtained by measuring the sensitivity of the photoconductor at a desired layer thickness while gradually scraping the surface of the photoconductor.

FIG. 6 shows the measured value of the amount of light required to obtain a contrast of 350V. Specifically, it is the result of measuring the amount of light required to charge the photoreceptor and bring the surface potential to 50V. Therefore, the vertical axis here represents the sensitivity, and the unit is
It will be lux / sec / 350V.

As is clear from FIG. 6, when the thickness of the surface protective layer is thin, the sensitivity changes greatly due to the change in the layer thickness, whereas when the surface protective layer becomes thick, the sensitivity change decreases.
Moreover, it can be seen that the sensitivity gradually converges so as to reduce the change width. By the way, in FIG. 6, when the thickness is 4000 Å or more within the layer thickness range of the present invention, the sensitivity change is within a small range of about ± 2%.

As described above, when the surface protection layer is thin, the sensitivity change of the electrophotographic photosensitive member is large, while when the surface protection layer is thick, the sensitivity change is small. Therefore, with a conventional layer thickness of about 2000Å, the difference in the layer thickness of the surface protective layer due to uneven abrasion immediately affects the sensitivity of the electrophotographic photoreceptor, resulting in deterioration of image quality such as image blurring. Since the layer thickness of the layer is set to a thick range of 4000 to 10000Å, even if the protective layer is unevenly scraped, the sensitivity change of the electrophotographic photosensitive member due to the change in the thickness of the surface protective layer due to the uneven scraping is small. Does not cause a drop in In addition, since the sensitivity change with respect to the layer thickness change of the surface protective layer is small, the latitude of the layer thickness at the time of forming the layer is widened, high accuracy is not required for the layer thickness management at the time of forming the surface protective layer, and the product defect rate is reduced. As a result, the manufacturing cost can be reduced and the durability can be improved.

FIG. 2 shows an example of the electrophotographic photosensitive member according to the present invention.

The electrophotographic photosensitive member 4 of this example is one in which a photoconductive layer 2 and a surface protective layer 1 are sequentially laminated on a substrate 3 made of a conductive material such as Al or stainless steel. Although not particularly described above, various functional layers such as an antireflection layer may be provided as necessary in addition to these layers.

The shape of the substrate may be a desired one depending on the driving method of the electrophotographic photosensitive member 4 and the like. Conductive materials such as Al and stainless are generally used as the material of the base material. However, for example, various conductive materials such as various plastics and ceramics, such as those having no conductivity, are vapor-deposited with a conductive material. Those provided can also be used.

If the photoconductive layer 2 has photoconductivity,
Although it may be organic or inorganic, in order to make the present invention effective, an inorganic photoconductor having a refractive index of 4.0 or less for light having a wavelength of 400 nm to 700 nm is preferably used. When the refractive index exceeds 4.0, the thickness of the protective layer that causes sensitivity convergence as shown in the above-mentioned protective layer thickness-sensitivity curve becomes large, and the effect of the present invention may not always be sufficiently exerted. Therefore, the refractive index is preferably 4.0 or less.

As the inorganic photoconductor used for such a photoconductive layer 2,
For example, silicon atoms and hydrogen atoms are typically amorphous materials containing halogen atoms (abbreviated as “a-Si (H, X)”) or a-Se. The layer thickness of the photoconductive layer 2 is not particularly limited, but is preferably about 15 to 50 μm considering the manufacturing cost.

The surface protective layer 1 has a thickness of 4000 Å to 10000 Å and a refractive index of 1.5 for light having a wavelength of 400 nm to 700 nm.
It is necessary to do the above. The layer thickness of the protective layer 1 is 4000
If it is less than Å, the sensitivity of the layer 1 to the thickness change is large, and the object of the present invention cannot be achieved. On the other hand, 1000
If it exceeds 0Å, a residual potential is generated during exposure and the image quality is deteriorated. On the other hand, if the refractive index is less than 1.5, the thickness of the surface protective layer 1 that causes the sensitivity convergence as described above becomes large, and the object of the present invention cannot be sufficiently achieved.

The surface protective layer 1 is formed of a-SiC (H, X), but it is preferable to increase the amount of C to some extent in order to further improve durability.

An example of the electrophotographic apparatus of the present invention using such an electrophotographic photosensitive member is shown in FIG. Incidentally, the apparatus of this example is suitable when a cylindrical electrophotographic photosensitive member is used, but the electrophotographic apparatus of the present invention is not limited to this example,
The shape of the photoreceptor may be a desired shape such as an endless belt shape.

In FIG. 1, 4 is an electrophotographic photosensitive member according to the present invention, and 5 is a primary charger that charges the photosensitive member 4 for forming an electrostatic latent image. Reference numeral 6 is a developing device for supplying a developing material (toner) to the photoconductor 4 on which the electrostatic latent image is formed, and 7 is a transfer charging device for transferring the toner on the surface of the photoconductor to the transfer material. Reference numeral 8 is a cleaner for purifying the surface of the photoconductor. In this example, in order to effectively uniformly delete the surface of the photoconductor, the surface of the photoconductor is cleaned using the elastic roller 8-1 and the cleaning blade 8-2 as described above, but either one may be used. Absent. However, in order to make the present invention effective, it is preferable to provide at least the elastic cleaning roller 8-1. Reference numerals 9 and 10 denote an AC static eliminator and a static eliminator for neutralizing the surface of the photoconductor in preparation for the next copying operation, 13 is a transfer material such as paper, and 14 is a transfer material feed roller.

The copy image is formed using such an apparatus, for example, as follows.

First, the electrophotographic photosensitive member 4 is rotated in the direction of the arrow at a predetermined speed, and the surface of the photosensitive member 4 is uniformly charged by using the primary charger 5. Next, the image exposure A is performed on the charged surface of the photoconductor 4 to form an electrostatic latent image of the image on the surface of the photoconductor 4. When the portion of the surface of the photoconductor 4 on which the electrostatic latent image is formed passes through the installation portion of the developing device 6, toner is supplied to the surface of the photoconductor 4 by the developing device 6, and the electrostatic latent image is transferred to the toner. The toner image is visualized (developed) by 6a, and further, the toner image reaches the installation portion of the transfer charger 7 as the photosensitive member 4 rotates, and is transferred to the transfer material 13 sent by the feed roller 14 there. It is.

After completion of the transfer, the residual toner is removed from the surface of the electrophotographic photosensitive member 4 by the cleaner 8 in preparation for the next copying process, and further the static eliminator 9 and the static eliminator 10 are set so that the potential of the surface becomes zero or almost zero. Neutralized by 1
Finish the copying process twice.

[Examples] Examples of the present invention will be shown below.

Example 1 A photoconductive layer 2 made of a-Si (H, X) having a refractive index of 3.4 was uniformly laminated on a cylindrical aluminum substrate 3 to a thickness of about 25 μm, and then a- was formed on the photoconductive layer 2. Refractive index of SiC (H, X) 1.
9 surface protection layer 1 is evenly laminated to a thickness of about 5000Å,
An electrophotographic photosensitive member 4 as illustrated in FIG. 2 was obtained.

While shaving the electrophotographic photosensitive member 4 gradually to a uniform thickness, the photosensitive member 4 is irradiated with light having the exposure amount distribution shown in FIG. 4, and the sensitivity of the photosensitive member 4 to the layer thickness of the surface protective layer 1 is increased. The result of the calculation is shown in FIG.

As is clear from FIG. 6, the change in sensitivity decreases as the layer thickness of the surface protective layer increases, and the change is ± 2 over 4000 Å.
It converged within%.

Example 2 After preparing an electrophotographic photosensitive member having the same surface protective layer thickness of 5000Å as in Example 1, the surface protective layer of the photosensitive member was partially shaved, and the protective layer had a layer thickness difference of about 500Å. The unevenness is provided. The electrophotographic photosensitive member having such irregularities was mounted on the electrophotographic apparatus illustrated in FIG. 1 and a paper passing durability test of 10,000 sheets was carried out.

The results are shown in Table 1. With each of the transfer papers, a good-quality transfer image free from image defects such as density unevenness and streaks was obtained.

Comparative Example 1 An electrophotographic photosensitive member having a layer thickness difference of about 500 Å is formed in the same manner as in Example 2 except that the surface protective layer has a thickness of 2000 Å. It was mounted on the electrophotographic apparatus of No. 1 and a paper passing durability test of 10,000 sheets was carried out.

The results are shown in Table 1. The obtained image was inferior in image quality with a large density difference from the initial stage of paper passing, and streaks were observed in the latter period.

Example 3 A paper passing durability test was conducted in the same manner as in Example 2 except that the surface protective layer had a thickness of 8000Å.

The results are shown in Table 1, and the same high quality image as in Example 2 was obtained.

Examples 4 and 5 Except that a surface protective layer made of a-SiC (H, X) having a refractive index of 3.0 was provided and the layer thicknesses of the layers were 5000Å (Example 4) and 8000Å (Example 5). A paper passing durability test was conducted in the same manner as in Example 2.

The results are shown in Table 1, and the same high quality image as in Example 2 was obtained.

Comparative Example 2 A paper passing durability test was conducted in the same manner as in Comparative Example 1 except that the surface protective layer having the same refractive index of 3.0 as in Example 4 had a thickness of 2000 Å.

The results are shown in Table 1, and as in Comparative Example 1, the image quality was large with a large density difference and was inferior.

Comparative Example 3 A paper passing durability test was conducted in the same manner as in Comparative Example 1 except that a surface protective layer made of a-SiC (H, X) having a refractive index of 1.0 was provided and the layer thickness of the layer was set to 5000Å.

The results are shown in Table 1, and as in Comparative Example 1, the image quality was large with a large density difference and was inferior.

[Effects of the Invention] As described above, according to the present invention, a new image that does not cause image quality deterioration such as density unevenness of a copied image due to layer thickness unevenness of the surface protective layer and is excellent in durability is also provided. A new electrophotographic device can be provided. In particular, regarding the durability, as shown in the examples, even if a layer thickness unevenness of about 500 Å does not cause deterioration of image quality, if the abrasion amount of the surface protection layer is set to about 20 to 50 Å, Protective layer Layer thickness 5000Å
With such a level, it is possible to add durability with a guarantee of 500,000 sheets. Further, since the latitude at the time of forming the surface protective layer is widened, high accuracy is not required for the layer thickness control at the time of forming the layer, and the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an example of an electrophotographic apparatus of the present invention, FIG. 2 is a schematic sectional view of an example of an electrophotographic photosensitive member used in the electrophotographic apparatus of the present invention, and FIG. 3 is a surface protective layer. The spectral transmittance of a conventional electrophotographic photosensitive member having a layer thickness of about 2000Å, Fig. 4 is an example of the exposure amount distribution used in the electrophotographic apparatus, Fig. 5 is an example of the spectral sensitivity curve of the electrophotographic photosensitive member, FIG. 6 is an example of the surface protective layer thickness-sensitivity curve of the electrophotographic photosensitive member obtained in Example 1. 1; surface protective layer, 2; photoconductive layer 3; substrate, 4; electrophotographic photoreceptor 5; primary charger, 6; developing unit 7; transfer charger, 8; cleaner 9; AC neutralizer, 10; neutralization lamp 13; Transfer material, 14; Feed roller

Claims (1)

[Claims] 1. An electrophotographic apparatus comprising an electrophotographic photosensitive member comprising a substrate and a photoconductive layer and a surface protective layer made of an amorphous material containing silicon atoms and carbon atoms, which are sequentially laminated on the substrate. The layer thickness of the protective layer is in the range of 4000 Å to 10000 Å, and the refractive index of the protective layer for light having a wavelength of 400 nm to 700 nm is 1.5 or more, the refractive index of the photoconductive layer is 4.0 or less, further An electrophotographic apparatus comprising an elastic cleaning roller that rubs a surface protective layer.