JPH0394265A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain excellent basic characteristics, high quality stability and high durability and to allow the inexpensive formation by providing an A1 layer of the film thickness at which the average spectral transmittance in a visible region corresponds to a specific value and further an intermediate layer having a specific substantial volume resistance thereon, and then laminating photosensitive layers consisting of >=1 layers thereon. CONSTITUTION:The A1 layer of the film thickness at which the average spectral transmittance in the visible region corresponds to <=3%, the intermediate layer having >=10<6>OMEGA.cm substantial volume resistance and the photoconductive insulating layers consisting of >=1 layers are successively provided on a supporting base body. This A1 layer has the effect of enhancing the effective sensitivity by efficiently reflecting the incident light to the photosensitive body to the photosensitive body layer side. The intermediate layer thereon enhances the adhesiveness to the photosensitive layer and improves the potential holdability. The photosensitive member which has the excellent basic characteristics and the high durability and is relatively inexpensive is obtd. in this way.

Description

[Detailed description of the invention] [Industrial application field] [Industrial application field] The present invention relates to improvements in electrophotographic photoreceptors.

[Prior Art] Generally, in an electrophotographic method called xerography, a photoconductive insulating layer (hereinafter referred to as a photosensitive layer) is formed on the surface of a supporting substrate such as glass, plastic, paper, etc., on which a conductive layer is provided with a metal, a metal film, or a conductive paint. A photosensitive member is used.

The material and form of the supporting substrate are appropriately selected depending on the characteristics of the photosensitive material and the manufacturing method. When the photosensitive member is drum-shaped, Al or A1 alloy is often used as the substrate. When forming into a sheet, a plastic film whose surface is coated with metal is often used. In particular, a polyethylene terephthalate (hereinafter PET) film coated with A1 (metallized) is widely used as a support substrate for an organic photoreceptor (hereinafter referred to as OPC).

The reason why Al is widely used as a conductive material for electrodes is that it is relatively easy to form a film on a film, and Al easily creates a certain rectification property at the interface with the photosensitive layer.
This is because a high acceptance potential can be obtained without impairing electrical characteristics.

A typical form of OPC is a so-called multilayer/functionally separated type in which a charge generation layer is laminated on the electrode side and a charge transport layer is laminated thereon. That is, basically, a structure in which an insulating substrate, an A1 layer, a charge generation layer, and a charge transport layer are laminated in this order is one of the most widely used forms for electrophotographic photoreceptors at present. be.

In addition to the above-mentioned basic structure, in the case of a type in which one function of the photosensitive layer is separated, an intermediate layer is often provided between the charge generating layer and the electrode. Such an intermediate layer enhances the adhesion of the photosensitive layer, improves the potential retention, and furthermore contributes to improving the image quality by hiding various defects that may occur on the electrode surface. improve performance and reliability.

In devices that use a laser beam as incident light, the interface between the photosensitive layer and the intermediate layer may function as a diffusion layer to suppress interference. In any case, intermediate layers in electrophotographic photoreceptors are now part of a conventional layer configuration.

By the way, the charge transport layer of the multilayer/functionally separated OPC is generally made of a polymer in which a stilbene-based or hydrazone-based hole transport substance is dissolved. Since no organic compound has been found that exhibits practically effective electron mobility, functionally separated OPCs are usually used with negative charges.

The present inventors have found that some metals including Al have serious drawbacks, particularly as electrodes for photoreceptors used for negative charging, and have proposed some solutions to these problems prior to the present invention.

That is, the Al electrode is gradually anodized by repeated charging and exposure, and ultimately becomes an insulating thin film of oxide and loses its function. When the electrode is thin enough to transmit light, the speed of oxidation will be negligible depending on the durability of the photoreceptor. Incidentally, the advantages of the technique of making the photosensitive member transparent and utilizing efficient photostatic charge removal from the back side are already widely known. One of the previous inventions proposes that Ni-based, Fe-based, and Co-based oxidation-resistant alloys are particularly good as transparent electrode materials for OPC.

However, it is also true that these oxidation-resistant alloys still have some drawbacks. One of these is the low surface reflectance of these alloys. In contrast to Al, which is highly reflective enough to be used for the surface shape of a reflector, the surface of the above alloy is blackish.

Therefore, the light utilization efficiency (and eventually the sensitivity) of a photoreceptor using this as an electrode is relatively low. One of the other drawbacks lies in the high manufacturing costs.

Thin film formation of the alloy must be done by sputtering, and A1
Productivity is lower than vapor deposition. In addition, Ni, which is the material of the alloy,
．． ．． CoSCr, Mo, etc. are rare resources and expensive.

Therefore, it is important to develop a photosensitive member using Al as an electrode material, which has high sensitivity, high durability, and is inexpensive even if it sacrifices optical transparency. It remains extremely significant in the development of machines and printers.

As a result of intensive studies by the present inventors, in the photosensitive member provided with the above-mentioned intermediate layer, when Al is used as the electrode material, the relationship between the electrical conditions of the intermediate layer and the film thickness of the Al electrode is in principle. We have come to the conclusion that this determines the lifespan of photosensitive members.

Photoreceptors for electrophotography - In particular, in so-called OPC, the presence of an intermediate layer and A
The value of the l electrode is obvious, and identifying its desirable structural relationships is ultimately the most important step in developing high-performance, durable, and low-cost electronic copiers and printers. This is an important technical matter and an urgent social issue.

[Problems to be Solved by the Invention] In view of the above circumstances, the present invention provides an Al electrode and an intermediate layer that have excellent basic characteristics, high quality stability, and high durability, and are relatively inexpensive. An object of the present invention is to provide an electrophotographic photoreceptor having the following characteristics.

[Means for Solving the Problem] The above problem is solved by forming an Al layer on the surface of the supporting substrate with a thickness corresponding to an average spectral transmittance of 3% or less in the visible range, and further having an Al layer with a thickness equivalent to an average spectral transmittance of 3% or less in the visible range, and further having a substantial volume resistivity of 106 Ω·cam. The problem was solved by an electrophotographic photoreceptor formed by providing the above intermediate layer and then laminating one or more photosensitive layers.

In the structure of the photoreceptor, the Al layer has the effect of increasing the effective sensitivity by efficiently reflecting light incident on the photoreceptor toward the photoreceptor layer. The intermediate layer on top of the photosensitive layer enhances the adhesion of the photosensitive layer, improves the potential retention, and also hides various defects that may occur on the electrode surface, contributing to the improvement of image quality. Improve component performance and reliability.

As for the intermediate layer, a layer made of resin alone is preferable in consideration of adhesion, potential retention, and the effect of preventing the occurrence of image defects.

The lower volume resistivity of the intermediate layer limits the combinations of charge generating materials and charge transport materials. If the charge injection property from the charge generation layer to the charge transport layer is high, it is easy to obtain high sensitivity, but the potential retention property is relatively low, and to improve this, an intermediate layer with a certain degree of high resistance is required. There is no easy way to calculate the optimal resistance value, but from the inventor's experience, the effective volume resistance is approximately 106Ω・ell.
It is. Within this range, the intermediate layer may contain various resistance controlling materials, such as metals/carbon/oxides of indium, tin, antimony, etc./electrolytes. Furthermore, in order to have the function of preventing laser light interference, fine particles of metals/metal oxides, silicides, sulfides, fluorides, hydroxides, etc./minerals such as talc, clay, mica, and diatoms are added. May be dispersed.

Main materials for the intermediate layer include, for example, polyvinyl alcohol, polyvinyl butyral, polyvinyl acetal, polyamide, polymethyl methacrylate, polyester, casein, gelatin, cellulose derivatives, epoxy resin, phenol resin, phenoxy resin, acrylic-styrene copolymer, Examples include acrylic/styrene ψ butadiene copolymer, polyurethane, nitrile rubber, and chloroprene rubber.

The thicker the intermediate layer, the higher the electric field applied to the intermediate layer when charging the photoreceptor, resulting in a higher so-called residual potential. Therefore, the thickness is preferably 1 μm or less, more preferably It is 0.7 μm or less.

The thickness of the Al electrode layer can be arbitrarily selected considering only the electrical function. However, in reality, when the resistance of the intermediate layer is set within the above range, the film thickness must be equivalent to an average spectral transmittance of 3% or less in the visible range for the following reasons.

As mentioned above, the Al electrode is gradually anodized by repeated charging and exposure, and ultimately loses its function completely. Since this is an electrochemical reaction, the reaction rate naturally depends on the electric field strength in the reaction area. In photoreceptors with an intermediate layer, this electric field strength is determined by the electrical resistance of the intermediate layer.

When such resistance is low, charges can move in the lateral direction of the intermediate layer, thereby reducing the electric field strength applied to the electrode/intermediate layer interface and ultimately suppressing anodic oxidation. vice versa,
If the resistance of the intermediate layer is high, specifically 106Ω・elm
In the above cases, it is necessary to thicken the Al electrode layer at least to the extent that anodic oxidation can be avoided. The thickness of the A1 electrode layer corresponding to an average spectral transmittance of 3% in the visible region corresponds to its limit in fact.

The photosensitive material may be arbitrarily selected in consideration of desired characteristics, but in consideration of sensitivity, ease of controlling characteristics, mass production, stability, durability, safety, etc., a functionally separated type using an organic material is recommended. The OPC is good. It is also a photosensitive material that can take full advantage of the advantages of the present invention.

[Example] Hereinafter, the details of the present invention will be specifically explained with reference to Examples.

Example 1 On a 100 μa thick PET film, an A1 layer having a thickness corresponding to an average spectral transmittance (hereinafter simply referred to as transmittance) of 2% in the visible range was formed by vapor deposition.

Thereon, as an intermediate layer, an alcohol-soluble polyamide resin layer was applied to a thickness of 0.5 μm.

On the substrate prepared by the above method, a charge generation layer 'C' (pigment/resin, weight ratio 2.5/L) is formed by dispersing a bisazo pigment represented by the following formula (I) in a butyral resin at a wavelength of 5.
The coating was applied to a film thickness equivalent to a transmittance of 4% at 83 questions.

The evaluation results of the electrical properties and durability of this product are shown in Table 1 along with other examples and comparative examples described below.

Example 2 The compound of formula (1) in Example 1 was replaced with a hydrazone compound of formula (2) below, and the other conditions were the same.

Then, a charge transport layer (compound/resin weight ratio of 9/10) formed by dissolving a stilbene compound represented by the following formula (1) in polycarbonate was coated thereon to a thickness of 27 μm.

H3C C2H5 Comparative Example 1 The electrode layer of Example 1 was changed to an A1 vapor deposited layer with a transmittance equivalent to 5%, and the other conditions were the same.

Comparative Example 2 The electrode layer of Example 1 was changed to an Al vapor-deposited layer with a transmittance equivalent to 5%, and tin oxide doped with 3% antimony oxide and having an average particle size of 0.8 μm was added to polymethyl methacrylate. An intermediate layer having a thickness of t μm in which 80 wt% was dispersed was applied, and the other conditions were the same as in the example.

Comparative Example 3 Hast equivalent to 50% transmittance of the Al electrode layer of Example 1
Elloy C (NiMo alloy) layer was used, and the other aspects were the same as in Example 1. lastelloy
The C layer was formed by sputtering.

Example 3 Al was vapor-deposited to a thickness of about 3,500 mm on the surface of a phenol pipe with an outer diameter of 80 mm and a wall thickness of 7 III mm, and a polyamide intermediate layer (62 νt%) of titanium oxide with an average particle size of 0.6 μω was dispersed thereon ( A 1 μm layer (laser light interference prevention layer) was formed.

A charge generation layer (pigment/resin,
Then, a charge transport layer (compound/resin, weight ratio 7/10) containing a stilbene compound represented by the above formula (1) was coated to a thickness of 28 μm. . However, each resin used was the same as in Example 1.

Comparative Example 4 The A1 electrode layer of Example 2 was approximately 150λ, and the rest were as in Example 2.
The same as

Note that the thickness of the Al thin layer corresponding to an average spectral transmittance of 3% in the visible range does not exceed 3000λ. In addition, the film thickness is 200
The A1 layer below λ has a transmittance of 30% or more. Therefore, Example 3 is a structure that belongs to the present invention, and Comparative Example 4 is a structure that is outside the scope of the present invention.

(Measurement and Evaluation of Photoreceptor) Five types of samples except Example 3 were measured and evaluated using Paper Analyzer SP428 manufactured by Kawaguchi Electric Seisakusho.

The charging property was determined by setting the discharge current to -24 μA (when not rotating) and looking at the potential (V2) after 2 seconds of charging in dynamic mode.

The sensitivity is 4.51uX of light and an initial voltage of -800V.
Viewed at half-exposure ffi (E+., 2). Also,
The potential after 30 seconds of exposure was defined as the residual potential (Vr).

Using the same paper analyzer, set the light intensity to 45 lux,
Free? 1 [Continuous 1 under the condition that the current is 9.6 μA (during rotation)
Electrostatic fatigue was applied for 5 hours, and then the same conditions as before fatigue were applied.
The chargeability, sensitivity, and residual potential were measured using the method. (The * in Table 1 indicates the characteristic value after fatigue.) Only in Example 2, the drum-shaped photosensitive section {of Measured using a test device. Therefore, table −
All values of 1 are mutually comparable.

Note that the resistance value of the intermediate layer was roughly calculated from the time constant of charge potential decay of a single thin film produced separately from the photoreceptor.

Table 1 As is clear from the measurement results of the examples and comparative examples shown in Table 1, the average transmittance in the visible range is between the Al electrode layer equivalent to 3% or less and the effective volume resistivity 106 Ω・cm or more. By using these layers together, it is possible to obtain a photosensitive member with high sensitivity, good potential retention, and high durability.

Note that the material, structure, manufacturing method, etc. of the photosensitive member shown in the examples are not the essence of the present invention, and therefore do not limit the main technology of the present invention.

Furthermore, this patent does not specify any of the various additional techniques, such as material, manufacturing, mechanical, process, etc., that have heretofore been arbitrarily applied to photosensitive members and elements of image forming apparatuses.

Effects of the Invention] As described above, according to the present invention, it is possible to obtain an electrophotographic photosensitive member that has excellent basic characteristics and high durability, and is relatively inexpensive.

Claims (3)

[Claims] (1) On the support substrate, in order, an Al layer with a thickness equivalent to an average spectral transmittance of 3% or less in the visible region, and an Al layer with a substantial volume resistance of 10^
An electrophotographic photoreceptor characterized by having an intermediate layer of 6 Ω·cm or more and a photoconductive insulating layer consisting of one or more layers. (2) The electrophotographic photoreceptor according to claim 1, wherein the photoconductive insulating layer is comprised of a charge generation layer and a charge transport layer from the intermediate layer side. (3) The charge generation layer is a layer in which an azo pigment is dispersed in a resin, and the charge transport layer is a layer in which a hydrazone-based, triphenylamine-based, or phenylstilbene-based charge transfer agent is dispersed in a resin. The electrophotographic photoreceptor according to claim 2, wherein the electrophotographic photoreceptor is a compatible one.