JPH0264549A - electrophotographic photoreceptor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor, and more particularly, to an electrophotographic photoreceptor having a photosensitive layer with excellent durability and no deterioration in image quality due to repeated use.

[Conventional technology]

In recent years, many electrophotographic photoreceptors using organic compounds as photoconductors have been developed. Most of those that have been put to practical use have a form in which the photoconductor is functionally separated into a charge-generating material and a charge-transporting material.

Electrophotographic photoreceptors using such organic photoconductors are expected to further improve electrophotographic properties such as sensitivity and photoresponsiveness due to the flexibility of material design, and are easy to form into films and have high productivity. It is characterized by this.

However, it has been said that a major drawback of these photoreceptors is that they generally have low durability.

Durability can be roughly divided into durability of electrophotographic physical properties such as sensitivity, residual potential, charging ability, and image blur, and mechanical durability such as abrasion and scratches on the photoreceptor surface due to rubbing. It is known that the durability of the physical properties is caused by the deterioration of the charge transport material contained in the surface layer of the photoreceptor due to ozone, NOx, etc. generated from the corona charger.

Especially when the oxidation potential of the charge transport substance is less than 0.6V,
This deterioration was significant, and over time the image became distorted and characters became indistinguishable, a phenomenon known as image blurring. Therefore, in order to obtain high-quality images, it is essential to polish the surface of the photoreceptor to always present a fresh surface. However, as efforts have been made to improve mechanical durability by dispersing various lubricants on the surface of the photoreceptor, the amount of abrasion has decreased significantly, and deteriorated charge transport materials cannot be removed quickly, resulting in blurred images. The current situation is that the outbreak is becoming more obvious.

As a solution to these problems, we have proposed
As shown in Publication No. 50, it was discovered that it is effective to use a compound with an oxidation potential of 0.6 V or more as a charge transport substance contained in the surface layer, and a highly durable photoreceptor has been put into practical use. New problems have been pointed out depending on how photoreceptors are used. In other words, if a photoreceptor is left in a copying machine for a long period of time after being used continuously, a phenomenon occurs in which the charging ability of the portion of the photoreceptor close to the charger that performs corona discharge is apparently reduced, and the image is This is the appearance of white streaks, so-called white spots. This white-out phenomenon is a peculiar phenomenon when a charge transport material having an oxidation potential of 0.6V or more is used, and is not observed at all in a charge transport material having a low oxidation potential of less than 0.6V. The above-mentioned image blur and white spots are caused by ozone and NOx generated during corona discharge.
This is due to the fact that the oxidation potential of the charge transport substance is 0.
When the oxidation potential is less than 6V, the charge transport material itself is oxidized by the action of ozone and NOx on the surface of the photoreceptor, resulting in lower resistance and image blurring. Since ozone and NOx themselves are not susceptible to oxidation, ozone and NOx penetrate deep into the photoreceptor, oxidize the charge-generating material, and lower the resistance, promoting hole injection from the substrate, and the apparent upper potential increases. It is presumed that the white spot phenomenon occurs without any problems. This apparent drop in potential occurs even during the durability test, but because the drop in surface potential occurs uniformly on the surface of the photoreceptor, it is not observed as a white spot phenomenon, which is a partial drop in potential. When the battery is left after continuous use, a local potential drop near the charger where the ozone or NOx concentration is extremely high becomes noticeable as white spots.

[Problems to be solved by the present invention]

The present invention provides an electrophotographic photoreceptor that solves the above-mentioned problems. That is, an object of the present invention is to provide an electrophotographic photoreceptor capable of producing high-quality images without image blur or white spots.

Another object of the present invention is to provide an electrophotographic photoreceptor that has high durability and is capable of producing high-quality images with little surface wear and scratches caused by rubbing (and without image blurring or white spots). Another object of the present invention is to provide an electrophotographic photoreceptor that does not accumulate residual potential in repeated electrophotographic processes and can always produce high-quality images.

[Means for solving problems]

As a result of extensive studies in accordance with the above objective, the present inventors have found that even in a photoreceptor using a charge transport material with an oxidation potential of less than 0.6V, it is possible to reduce the amount of organic compounds with a specific structure (both by adding two kinds of them). The present invention was completed by discovering that it is possible to obtain a photoreceptor that prevents deterioration and does not cause image blurring.That is, the present invention provides an electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, in which the surface layer is A charge transport substance with an oxidation potential of less than 0.6V and the following general formula (1
) and (2).

The effect of adding the compounds of general formulas (1) and (2) is to protect the charge transport material from the oxidizing effects of ozone and NOx. That is, the compounds of general formulas (1) and (2) are preferentially oxidized by ozone and NOx over charge transport substances, and it is confirmed that the oxidized deterioration products do not have any adverse effects on other electrophotographic properties. Heading This is what led to the completion of the present invention. In particular, the present invention is characterized by the discovery that the best results can only be obtained by using both compounds, which have little effect when added alone.

In addition, since the electrophotographic photoreceptor of the present invention has no deterioration of the charge transporting substance, it is fully applicable to increasing durability (reducing the amount of abrasion of the surface layer due to durability) by adding various lubricant powders. be.

The present invention will be explained in detail below.

The photosensitive layer in the present invention is a single-layer type photoreceptor in which a functionally separated charge generating substance and a charge transporting substance are mixed, or a stacked layer of a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance. It takes the form of a laminated photoreceptor.

Examples of charge generating substances include biryllium, thiopyrylium dyes, phthalocyanine pigments, anthoanthrone pigments,
Organic photoconductors such as perylene pigments, dibenzpyrenequinone pigments, vilanthrone pigments, azo pigments, indigo pigments, and quinacridone pigments are used.

The charge transport substance with an oxidation potential of less than 0.6 V is selected from organic photoconductors such as pyrazoline, hydrazone, stilbene, triarylmethane, oxazole, thiazole, carbazole compounds, and polyarylalkane compounds. Ru.

In the case of a single-layer type photoreceptor, the charge-generating substance and charge-transporting substance described above are dissolved or dispersed in a suitable binder resin, and a layer is formed on the conductive substrate by coating. On the other hand, the laminated type includes one in which 1) a charge generation layer and a charge transport layer are laminated on a conductive substrate, or 2) a layer in which a charge transport layer and a charge generation layer are laminated in this order. In the case of (1), methods for forming the charge generation layer include methods such as dispersing or dissolving a charge generation substance in a binder resin and a solvent and coating the mixture, vapor deposition, and sputtering. The film thickness is 5 μm or less, especially 0.01 to 3 μm
is preferred. In this case, an inorganic photoconductor such as selenium or amorphous silicon can also be used.

The charge transport layer is formed by dissolving the charge transport material described above in a binder resin having film-forming properties and laminating it on the charge generation layer. Film thickness is 5-4
0 Itm, especially 8 to 35 μm is preferred. The compound of the invention is in this case contained in the charge transport layer.

On the other hand, when a charge generation layer is laminated on the charge transport layer, both layers can be formed by applying the above-mentioned organic photoconductor together with a binder resin. At this time, a charge transport material is contained in the charge generation layer. In this case, the compound is contained in the charge generation layer or both the charge generation layer and the charge transport layer.

Specific examples of the compounds of general formulas (1) and (2) used in the present invention are shown below.

Furthermore, the lubricant powder that can be used in the present invention is selected from fluororesin powder, polyolefin powder, fluorocarbon powder, and the like. Fluororesin powder is preferred from the viewpoint of lubricant and mold release properties. As fluororesin powder,
Polyolefin powders include tetrafluoroethylene resin, trifluorochloride ethylene resin, tetrafluoroethylene hexafluoropropylene resin, vinyl fluoride resin, vinylidene fluoride resin, ethylene chloride difluoride, and their copolymers. As the binder, polyethylene, polypropylene, copolymers thereof, etc. can be used, and the appropriate amount of these lubricant powders to be added is 1-100% by weight based on the binder, particularly 1.5-30% by weight. % is preferred.

The added amount of the compounds (1) and (2) used in the present invention is preferably in the range of 0.2 to 20 wt%, preferably 0.6 to 15 wt% in terms of the weight fraction of the surface layer.

If the amount added is less than 0.2vvt%, the deterioration prevention effect is small (
If it exceeds 20 wt%, adverse effects such as a decrease in sensitivity and an increase in residual potential will occur.

When manufacturing the electrophotographic photoreceptor of the present invention, the substrate itself is conductive, such as aluminum,
Metals and alloys such as aluminum alloys and stainless steel can be used, and in addition, plastics and conductive materials have layers formed by vacuum deposition of aluminum, aluminum alloys, indium oxide, tin oxide, indium oxide-tin oxide alloys, etc. A substrate in which particles are coated on plastic, metal, or an alloy together with a suitable binder, a substrate in which plastic or paper is impregnated with conductive particles, a plastic containing a conductive polymer, etc. can be used.

A subbing layer having barrier and adhesive functions can also be provided between the conductive substrate and the photosensitive layer. The lower arch layer can be formed from casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenolic resin, polyamide, polyurethane, gelatin, aluminum oxide, and the like.

The thickness of the subbing layer is 01 μm to 40 μm, preferably 0.01 μm to 40 μm.
．． 3 μm to 3 μm is suitable.

As a method for dispersing lubricant powder, general dispersion means are used, namely,
A homogenizer, an ultrasonic wave, a ball mill, a vibrating ball mill, a sand mill, an attriter, a roll mill, etc. can be used. The lubricant powder is added to the binder dissolved in a suitable solvent, and then dispersed by the above-mentioned dispersion method. This is prepared by mixing an appropriate amount with a solution in which the binder, the electrotransport material, and the compounds of general formulas (1) and (2) are dissolved. Furthermore, various dispersion aids can be added to improve the dispersibility when dispersing the lubricant powder.

Coating can be performed using a coating method such as a dip coating method, a spray coating method, a Meyer bar coating method, or a blade coating method. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying can be carried out at 30° C. to 200° C. for a period of 5 minutes to 2 hours, either stationary or with ventilation.

The oxidation potential in the present invention is determined by using a saturated calomel electrode as a reference electrode and a 0.0. Using IN (n-Bu)4N''1FCI O4-acetonitrile solution as the electrolyte, the potential of the working electrode was swept with a potential sweeper, and the peak position of the obtained current-potential curve was directly determined as the value of the oxidation potential. That is, first, the sample is 0.I N (
nBu)4N"Cj? Oa-Dissolve in an electrolytic solution of acetonitrile solution to a concentration of 5 to 10 mmol1%. Then, apply a voltage to this sample solution and change the voltage linearly from a low potential to increase the current. A current-potential curve is determined by measuring the change in .The potential value corresponding to the first inflection point of the current value in this current-potential curve is defined as the oxidation potential of the present invention.

The electrophotographic photoreceptor of the present invention can be applied to photoreceptors of various devices to which electrophotography is applied, such as ordinary copying machines, laser beam printers, LED printers, LCD printers, and CRT printers.

The present invention will be explained below with reference to Examples.

Example 1 An aluminum cylinder of 80φ x 360mm was prepared as a base.

On the other hand, 100 parts (parts by weight, the same shall apply hereinafter) of conductive powder coated with tin oxide containing 10% antimony oxide so as to be 75% by weight relative to titanium oxide, 100 parts of resol-based phenolic resin and 30 parts of methanol. In addition to a solution consisting of 100 parts of methyl cellosolve, the paint was dispersed using a ball mill. This paint was applied by dip coating onto the substrate.
It was heated and cured at 40°C for 30 minutes to form a 20 μm conductive layer.

On top of this, 1 part of polyamide resin (6-66-610-124 nylon copolymer) and 3 parts of 8-nylon resin (methoxymethylated 6 nylon, methoxylation rate 30%) were added from 50 parts of methanol and 40 parts of butanol. A coating liquid dissolved in a solvent was applied by dipping, and after drying at 70°C for 110 minutes, a 0.5 μm thick undercoat layer was formed.

Next, the following structural formula (3) Next, as a charge transport material, a hydrazone compound of the following structural formula (4) (oxidation potential 0.57 V (abbreviation CT=-1)),
10 parts of bisazo pigment of the following structural formula (5) (HPH-1), 5 parts of polyvinyl butyral resin
1 part and 100 parts of cyclohexanone were dispersed for 20 hours in a sand mill apparatus using lφ glass beads. 50 to 100 (appropriate) parts of tetrahydrofuran were added to this dispersion and applied onto the undercoat layer, followed by drying for 5 minutes to form a charge generation layer with a thickness of 0.12 μm.

A compound of the following structural formula (6:) (PHM-1) and a bisphenol A type polycarbonate resin as a binding agent binder were prepared.

First, 20 parts of polycarbonate resin and charge transport material (4)
20 parts and 0.4 parts each of compounds (5) and (6) as additives were dissolved in 100 parts of monochlorobenzene,
Furthermore, 20 parts of dichloroethane was added to prepare a charge transport layer coating solution. This solution was applied onto the generation layer and dried with hot air at 100° C. for 90 minutes to form a charge transport layer with a thickness of 20 μm. This photoreceptor was mounted on a copying machine (modified Canon NP-3525 copying machine) from which the developer and cleaner unit had been removed, and the charging and exposure process was repeated 10,000 times. Immediately thereafter, a copy was made using a copying machine (Canon NP-3525), and the copied image was visually observed. No image blurring occurred and a high-quality image could be obtained.

Furthermore, regarding this photoreceptor, copying machines (Canon type NP-3
525) for printing 5,000 sheets, and after leaving it in a copying machine for 3 days, copies were made. The image was clear and of high quality, and no white spots were observed even in positions corresponding to areas close to the parasitic device during storage.

Comparative Example 1 A photoreceptor was prepared in the same manner as in Example 1, except that the additives used in Example 1 were not added, and the same tests as in Example 1 were conducted. The image was blurred over the entire image, making it impossible to distinguish the characters. However, no white spots were observed at positions corresponding to areas close to the charger.

Example 2 The above CT-1 as a charge transport material, oxidation potential of 0.54V
A compound of the following structural formula (7) (abbreviated as CT-2), and the following structural formula (8) (abbreviated as CT-3) with an oxidation potential of 0.47V.
The above-mentioned HPH compounds can also be used as two additives with specific structures.
Using the compounds shown in Table 1 in addition to -1 and PHM-1,
Example 1 About the photoconductor produced in the same manner as Example 1
Table 2 shows the results of the same evaluation.

Comparative Examples 2 to 8 Photoreceptors were prepared and evaluated in the same manner as in Example 1, using CT-2 and CT-3 as charge transport materials and without adding the compound of the present invention.

In addition, using CT-1 as a charge transport material, compound HP
Photoreceptors containing 1 wt % of H-1 or PHM-1 were prepared and evaluated in the same manner as in Example 1.

Further, a photoreceptor (without additives) using a charge transport material having an oxidation potential of 0.6 parts or more shown in Table 3 was prepared and evaluated in the same manner as in Example 1.

Part 3 table The results are summarized in Table 4.

Example 22 In addition to the charge transport substance, additives, and polycarbonate resin used in Example 1, polytetrafluoroethylene resin powder and a fluorine-based acrylic oligomer were prepared as a dispersant.

First, 20 parts of polycarbonate resin, 20 parts of hydrazone compound, and 0.6 part of fluorine-based acrylic oligomer are dissolved in 100 parts of monochlorobenzene. Then in this 4
Add 6 parts of fluorinated ethylene resin powder and disperse in a stainless steel ball mill for 40 hours, then add additives THPM-1 and B.
A charge transport layer coating solution was prepared by adding 20 parts of a dichloromethane solution in which 1 part of each of ZT-1 was dissolved. This liquid was applied onto the charge generation layer and dried with hot air at 100° C. for 90 minutes to form a charge transport layer with a thickness of 20 μm.

This photoconductor was installed in the copying machine used in Example 1, and the copying machine was subjected to image duplication for 10,000 copies. Copied images were visually observed, but no image blurring occurred and high-quality images were obtained. I was able to get it. At this time, the thickness of the surface layer was removed by 1.5μ.
It was m.

Further, this photoreceptor was left in a copying machine for 3 days and then copies were made, but no white spots were observed on the copied images and the quality was high.

Examples 23 to 29 As lubricant powder, polytetrafluoroethylene resin powder, polyvinylidene fluoride resin powder, polynifluorodichloride ethylene resin powder, polyethylene powder, polypropylene powder,
CT-1 to 3 above using carbon fluoride as a charge transport material
A photoreceptor was prepared and evaluated in the same manner as in Example 22 using the compounds shown in Table 1 as additives. The results are shown in Table 5.

As described above, an electrophotographic photoreceptor made by adding two or more types of additives having a specific structure to a charge transport material with an oxidation potential of less than 0.6 V has no deterioration of the charge transport material, resulting in blurred images. This is to ensure that high-quality images can always be obtained without the occurrence of problems. Further, even if the copying machine is left in a copying machine for a long time, white spots corresponding to the portions close to the charger do not occur, and high-quality images are always obtained.

Furthermore, those to which various lubricant powders are added can always obtain high-quality images even after being used for 10,000 sheets of paper, realizing highly durable photoreceptors.

〔Effect of the invention〕

As described above, the electrophotographic photoreceptor of the present invention containing a charge transport material with an oxidation potential of less than 0.6 V and two or more types of additives having a specific structure has extremely high durability in a corona discharge environment and always Stable, high-quality images can be obtained. Furthermore, the combination with various lubricant powders improves mechanical durability, making it possible to obtain a highly durable electrophotographic photoreceptor.

Claims (2)

[Claims] (1) In an electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, the surface layer contains a charge transport material with an oxidation potential of less than 0.6 V and a compound represented by the following general formulas (1) and (2). An electrophotographic photoreceptor comprising: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (1) (In the formula, X_1 represents ▲There are mathematical formulas, chemical formulas, tables, etc.▼ or ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and X_2 is H, 2 to 10. Represents an alkenyl group having 1 to 10 carbon atoms or an alkyl group having 1 to 10 carbons.) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(2) (In the formula, X_1 is ▲There are mathematical formulas, chemical formulas, tables, etc.) or ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and X_2 represents H, an alkenyl group having 2 to 10 carbons, or an alkyl group having 1 to 10 carbons, and R_
1, R_2 and R_3 represent H or an alkyl group having 1 to 10 carbons. ) (2) The electrophotographic photosensitive material according to claim 1, wherein the surface layer contains a lubricant powder selected from the group consisting of fluororesin powder, polyolefin powder, and fluorocarbon powder. body.