JP2746300B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor, and more particularly, to an electrophotographic photoreceptor having a photosensitive layer having excellent durability and having less image quality deterioration due to repeated use. .

[Prior Art] In recent years, many electrophotographic photosensitive members using an organic compound as a photoconductor have been developed. Of those, most of those practically used have a form in which a photoconductor is functionally separated into a charge generation material and a charge transport material.

An electrophotographic photoreceptor using such an organic photoconductor,
It is an advantage that the productivity is high because the film forming property of the photosensitive layer is good, and the electrophotographic properties such as sensitivity and photo-response are expected to be more excellent because of the flexibility in material design. I have.

By the way, since an electrophotographic photoreceptor repeatedly undergoes various image forming processes by being repeatedly used in an electrophotographic apparatus, the photoreceptor is required to maintain stable characteristics. However, the electrophotographic photoreceptor using the organic photoconductor has a drawback that when repeatedly used, image quality is easily deteriorated such as a decrease in image density due to a decrease in charging ability and a blur of an image due to a decrease in surface resistance. ing.

One of the causes of image degradation is the influence of corona discharge. That is, when the photoreceptor is used in a copying machine, the photoreceptor is constantly exposed to the atmosphere of corona discharge, and the organic photoconductor is degraded by active species such as ozone generated by corona discharge as the copying is repeated. Conceivable. In addition, an electrophotographic photoreceptor using an organic photoconductor is often used with negative charge, in which case,
Since negative corona charging generates more ozone than positive corona charging, it is considered that the photoconductor is more likely to be degraded than other photoconductors used in positive charging.

Hitherto, as a method for preventing the deterioration of the electrophotographic photosensitive member as described above, it has been proposed to add various antioxidants (JP-A-57-122444, JP-A-58-120260, JP-A-61-260260). −
156131, JP-A-62-105151).

[Problems to be Solved by the Invention] The above-mentioned antioxidant can prevent image quality deterioration to some extent, but is practically further improved in the anti-oxidation effect, and also has an antioxidant effect which does not adversely affect other electrophotographic characteristics. Agents are desired.

[Means for Solving the Problems] According to the present invention, in an electrophotographic photosensitive member having a photosensitive layer containing an organic photoconductor on a conductive substrate, the photosensitive layer has a stilbene-based charge transport material and the following structural formula ( 1)
An electrophotographic photoreceptor comprising a compound represented by the formula (I) and further comprising a sulfur-based or phosphorus-based secondary antioxidant.

Hereinafter, the present invention will be described in detail.

In the present invention, the photosensitive layer containing an organic photoconductor is a single-layer type containing a charge-separating material and a charge-transporting material in a mixed state, and a charge-generating layer containing a charge-generating material. It takes a form such as a laminate type in which a charge transport layer containing a transport material is laminated.

As the charge generation material, organic dyes such as pyrylium, thiopyrylium dyes, phthalocyanine pigments, anthantrone pigments, perylene pigments, dibenzopyrene quinone pigments, pyranthrone pigments, azo pigments, indigo pigments, and quinacridone pigments are used.

As the charge transport material, a stilbene compound is used.

In the case of a single-layer type photoreceptor, the above-described charge generating material and charge transporting material are dispersed and dissolved in an appropriate binder resin, and the resultant is coated on a conductive substrate to form a photosensitive layer.

Further, as a laminated type photoreceptor, (1)
The charge generation layer and the charge transport layer may be laminated in this order, or (2) the charge transport layer and the charge generation layer may be laminated in this order.

In the case of (1), as a method for forming the charge generation layer, there are a method of dispersing and dissolving the charge generation material and the binder resin in a solvent, and a method of vapor deposition and sputtering. The charge transport layer disperses and dissolves the charge transport material and the binder resin in a solvent, and laminates the charge transport material and the binder resin on the charge generation layer. In this case, it is preferable that the compound represented by the structural formula (1) is contained in the charge transport layer.

In the case of (2), the charge transport material and the binder resin are dispersed and dissolved in a solvent to form a charge transport layer, and the charge generation material and the binder resin are dispersed and dissolved in the solvent on the layer. Then, a charge generation layer is formed by coating. At this time, it is preferable to include a charge transport material also in the charge generation layer. In this case, it is preferable that the compound of the structural formula (1) is contained in the charge generation layer or both the charge generation layer and the charge transport layer.

The content of the compound of the structural formula (1) is preferably in the range of 0.1 to 10% by weight, based on the total weight of the photosensitive layer (the charge generation layer and / or the charge transport layer in the case of the laminated type). Preferably, it is in the range of 0.3 to 5% by weight. If the content is less than 0.1% by weight, the effect of preventing deterioration tends to be small, and if it exceeds 10% by weight, adverse effects such as a decrease in sensitivity and an increase in residual potential tend to be caused.

The compound of the structural formula (1) alone has a very high antioxidant function, and O ₃ and NOx generated by corona discharge
In the present invention, a sulfur-based or phosphorus-based secondary antioxidant is further used in combination. Further, the photosensitive layer of the present invention may contain known additives such as a lubricant for reducing abrasion, a surface modifier, and a plasticizer for improving flexibility.

Examples of the conductive substrate include known materials, for example, a cylindrical or belt-shaped aluminum, iron, copper, or metal-deposited plastic film. Further, an intermediate layer such as an adhesive layer, a barrier layer, and a smooth layer may be provided between the substrate and the photosensitive layer, if necessary.

[Examples] Next, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.

Example 1 An aluminum cylinder having a diameter of 80 mm and a length of 360 mm was used as a conductive substrate, and a polyamide resin (trade name:
A 5% methanol solution of Amilan CM-8000 (manufactured by Toray Co., Ltd.) was applied by an immersion method to form an undercoat layer having a thickness of 0.5 μm.

Next, 15 parts of a stilbene compound of the following structural formula A solution prepared by dissolving 10 parts of bisphenol Z-type polycarbonate resin in 50 parts of dichloromethane and 10 parts of monochlorobenzene was applied on the undercoat layer to form a charge transport layer having a thickness of 15 μm.

Next, 4 parts of a trisazo pigment having the following structural formula, 10 parts of bisphenol Z-type polycarbonate resin and 50 parts of cyclohexane were dispersed in a sand mill using 1φ glass beads for 20 hours (CG dispersion).

Next, polytetrafluoroethylene resin powder, a fluorinated acrylic oligomer as a dispersant, the stilbene compound, and a bisphenol Z-type polycarbonate resin were prepared. First, 10 parts of a bisphenol Z-type polycarbonate resin, 4 parts of a stilbene compound, and 0.15 part of a fluorinated acrylic oligomer are dissolved in 10 parts of dichloromethane and 40 parts of monochlorobenzene. To the solution thus obtained were added 1.5 parts of polytetrafluoroethylene resin powder, 0.5 parts of the compound of the structural formula (1), and 0.5 parts of a sulfur-based secondary antioxidant of the following structural formula (2), and the mixture was made of stainless steel. With a ball mill Dispersed for 40 hours (CT dispersion).

A mixture of a CG dispersion and a CT dispersion in a ratio of 1: 1 was applied on the charge transport layer, and a 5 μm-thick charge generation layer was formed to produce a photoreceptor.

This photoreceptor was mounted on an electrophotographic copying machine, and each characteristic was evaluated as follows. First, the dark area potential (V _D ) of the photoconductor,
The conditions of the latent image were set so that the bright portion potential ( _VL ) would be -650v and + 150v, respectively. Then, the potential after the 100,000-sheet continuous copying was measured to determine the increase in the reduction rate and V _L V _D. After that, the photoreceptor on which the portion located immediately below the corona charger was marked was left in a copying machine for 10 hours, and then the surface potentials of the marked portion and the other portions were measured.

As a result, even after the 100,000-sheet endurance test, the bright portion potential, the dark portion potential variation, and the rest memory were small, and high-quality copies were obtained.

Example 2 An undercoat layer was formed on an aluminum cylinder in the same manner as in Example 1. Next, disazo pigment 1 having the following structural formula
Parts, 10 parts of the stilbene compound used in Example 1, 10 parts of bisphenol Z type polycarbonate resin, 0.3 part of the compound of the structural formula (1), and 0.5 part of the compound of the structural formula (2)
Part was dispersed and dissolved in 60 parts of dichloromethane and 20 parts of monochlorobenzene, and a coating solution dissolved and coated on the undercoat layer was applied to a layer having a thickness of 16 μm.
A photoreceptor was prepared by forming a thick photosensitive layer.

The photosensitive member was evaluated in the same manner as in Example 1. As a result, even after the durability test of 100,000 sheets, the bright portion potential, the dark portion potential variation, and the rest memory were small, and a high-quality copy was obtained.

[Effects of the Invention] The electrophotographic photoreceptor of the present invention has extremely high potential stability of a bright portion potential, a dark portion potential, and a rest memory in a corona discharge environment, and always forms a stable and high quality image. I can do it. Further, the electrophotographic photoreceptor of the present invention can be used as a photoreceptor of a printer to which electrophotography is applied, such as a laser beam printer, an LED printer, an LCD printer, and a CRT printer, in addition to a normal copying machine.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Susumu Nagahara 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-1-257964 (JP, A) JP-A-1 -255861 (JP, A) JP-A 1-284859 (JP, A)

Claims (4)

(57) [Claims] An electrophotographic photosensitive member having a photosensitive layer containing an organic photoconductor on a conductive substrate, wherein the photosensitive layer contains a stilbene-based charge transport material and a compound represented by the following structural formula (1). And an electrophotographic photoreceptor further comprising a sulfur-based or phosphorus-based secondary antioxidant. 2. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer is formed by laminating a charge generation layer and a charge transport layer. 3. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer comprises a single layer containing a charge generation material and a charge transport material. 4. The electrophotographic photoconductor according to claim 1, wherein the content of the compound represented by the structural formula (1) is 0.1 to 10% by weight based on the weight of the contained photosensitive layer.