JPH0830894B2 - Electrophotographic photoreceptor - Google Patents

Description

The present invention relates to an electrophotographic photosensitive member, and more particularly to an electrophotographic photosensitive member having a photosensitive layer excellent in durability without image deterioration due to repetition.

[Prior Art] In recent years, many electrophotographic photoreceptors using an organic compound as a photoconductor have been developed. Most of those put into practical use have a form in which a photoconductor is functionally separated into a charge generating material and a charge transporting material.

An electrophotographic photosensitive member using such an organic photoconductor,
Due to the flexibility of material design, further improvement of electrophotographic characteristics such as sensitivity and photoresponsiveness is expected, and it is characterized by easy film formation and high productivity.

By the way, the electrophotographic photosensitive member is repeatedly subjected to various image forming processes in the electrophotographic apparatus, and during that time, the photosensitive member is required to exhibit stable characteristics. However, in the electrophotographic photoreceptor using the organic photoconductor as described above, deterioration in image quality such as image density loss due to decrease in charging ability and image bleeding due to decrease in surface resistance occurs in repeated use. It has the drawback of being easy.

One of the causes of such deterioration is considered to be the influence of corona discharge. That is, when a photoconductor is used in a copying machine, it is constantly exposed to the atmosphere of corona discharge, and the organic photoconductor is deteriorated by active species such as ozone generated by the corona discharge during repeated copying. It is thought to receive. In particular, electrophotographic photoreceptors using organic photoconductors are often used with negative charging, but negative corona charging produces more ozone than positive charging. It is said to be one of the factors that are more susceptible to deterioration than the photoconductors.

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

[Problems to be Solved by the Invention] In order to solve the above-mentioned drawbacks, the present invention prevents deterioration by adding a specific antioxidant to a photosensitive layer in an electrophotographic photoreceptor, and has electrophotographic characteristics. At the same time, it is an object of the present invention to provide an electrophotographic photosensitive member which does not cause any adverse effect.

[Means and Actions for Solving Problems] The inventors of the present invention have investigated the factors of the deterioration of the photoconductor as described above, and have studied the improvement method. By adding an antioxidant, a photoreceptor having a sufficient deterioration preventing effect and having no adverse effect on other electrophotographic characteristics was obtained, and thus the present invention was completed.

That is, the present invention is an electrophotographic photoreceptor comprising a photosensitive layer containing an organic photoconductor on a conductive substrate, wherein the photosensitive layer contains a compound represented by the following general formula (1). It is composed of an electrophotographic photosensitive member.

General formula In the formula, R is X ₂ represents a hydrogen atom, an alkenyl group having 2 to 10 carbon atoms or an alkyl group having 1 to 10 carbon atoms.

 The present invention will be described in detail below.

The photosensitive layer containing an organic photoconductor in the present invention is a single-layer type photoreceptor in which a charge-generating material and a charge-transporting material whose functions are separated are mixed, or a charge-generating layer containing a charge-generating material and a charge containing a charge-transporting material. It takes a form such as a laminated photoreceptor in which a transport layer is laminated.

As the charge generating material, organic dyes such as pyrylium, thiopyrylium dyes, phthalocyanine pigments, anthanthrone pigments, perylene pigments, dibenzpyrenequinone pigments, pyranthrone pigments, azo pigments, indigo pigments and quinacridone pigments are used.

Examples of the charge transport material include pyrazoline-based, hydraone-based, stilbene-based, triphenylamine-based, benzidine-based, oxazole-based, indole-based, and carbazole-based compounds.

In the single-layer type photoreceptor, the above-mentioned charge generating material and charge transporting material are dispersed and dissolved in an appropriate binder resin, and a layer is formed on a conductive substrate by coating.

On the other hand, the laminated-type photoreceptor has a charge generation layer on a conductive substrate,
There are those in which the charge transport layer is laminated in this order, or those in which the charge transport layer and the charge generation layer are laminated in this order. In this case, as a method for forming the charge generation layer, there are a method of dispersing and dissolving the charge generation material in a binder resin and a solvent, and a method of vapor deposition, spattering, and the like.

The charge transport layer is formed by dissolving the charge transport material in a binder resin and laminating it on the charge generation layer.

In this case, the specific additive (the compound represented by the general formula (1)) in the invention is preferably contained in the charge transport layer.

On the other hand, when the charge generation layer is laminated on the charge transport layer,
Both layers are formed by applying the above-mentioned organic material together with a binder resin. At this time, it is preferable that the charge generation layer also contains a charge transport material.

In this case, the additive is preferably contained in the charge generation layer or both the charge generation layer and the charge transport layer.

The specific additive (the compound represented by the general formula (1)) in the present invention is an antioxidant having a hindered phenol group.

The addition amount is 0.1 to 1 with respect to the total weight of the photosensitive layer to be added.
A range of 0%, preferably 0.3-5% is suitable. If the added amount is less than 0.1%, there is no deterioration preventing effect, and if the added amount exceeds 10%, there are problems such as decreased sensitivity and increased residual potential.

The function of preventing the deterioration of the photosensitive layer due to ozone and the active gas accompanying it is mainly expressed by the hindered phenol group, but it is considered that the effect is greatly influenced by the structure of the compound itself.

Further, since the above-mentioned additive in the present invention has an isocyanurate structure in the molecule, it has good compatibility with a charge generating material or charge transporting material having polarity, and deterioration of electrophotographic characteristics due to addition can be minimized. It has features.

The photosensitive layer according to the invention may further contain known additives such as a lubricant for reducing abrasion resistance, a surface modifier, and a plasticizer for improving flexibility.

Examples of the conductive substrate include known ones, for example, cylindrical or belt-shaped aluminum, iron, copper or a metal-deposited plastic film.

If necessary, an intermediate layer such as an adhesive layer, a barrier layer or a smooth layer may be provided between the conductive substrate and the photosensitive layer.

Hereinafter, typical examples of the compound represented by the general formula (1) will be listed. The description format shows different Rs in the basic type.

Basic type Compound example (1) Compound example (2) Compound example (3) Compound example (4) Compound example (5) Compound example (6) Compound example (7) The electrophotographic photoconductor of the present invention can be used as a photoconductor 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 an ordinary copying machine.

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 5% methanol solution of a polyamide resin (trade name: Amilan CM-8000, manufactured by Toray Industries, Inc.) was dipped in the aluminum cylinder. It was applied to form an undercoat layer having a thickness of 0.5 μm.

Next, 10 parts by weight of trisazo pigment having the following structural formula (weight part, the same applies hereinafter), 6 parts of polyvinyl butyral (trade name S-REC BL-S, manufactured by Sekisui Chemical Co., Ltd.) and 50 parts of cyclohexane were dispersed by a sand mill device using glass beads. To this dispersion, 100 parts of methyl ethyl ketone was added and coated on the undercoat layer to form a charge generation layer having a thickness of 0.2 μm.

Next, 10 parts of a stilbene compound having the following structural formula, A charge transport layer coating solution was prepared by dissolving 10 parts of polycarbonate (trade name Penlight L-1250, manufactured by Teijin Chemicals Ltd.) in 50 parts of dichloromethane and 10 parts of monochlorobenzene.

Tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate (Compound Example (1)) was added to this.
0.04 parts, 0.3 parts, 0.6 parts, and 1.8 parts were added, respectively, and coated on the charge generation layer to form a charge transport layer having a thickness of 18 μm.

The electrophotographic photoconductors thus prepared were designated as photoconductor 1, photoconductor 2, photoconductor 3, and photoconductor 4, respectively, and as comparative samples, compound example (1) was not added, and the addition amount was 3 parts. A body 5 and a photoconductor 6 were created.

These photoconductors were set in an electrophotographic copying machine, and the characteristics were evaluated as follows.

The latent image conditions were set such that the dark portion potential (V _D ) and the light portion potential (V _L ) of the photoconductor were −650 V and −150 V, respectively.

 The image exposure amount at this time was determined and used as the initial sensitivity.

Next, the potential after continuous copying of 5,000 sheets was measured to determine the rate of decrease in V _D and the amount of increase in V _L. afterwards,
The photoconductor was left in the copying machine and the surface potential after 10 hours was measured. At this time, the portion of the photosensitive member located immediately below the corona charger was marked during the standing, and the difference (ΔV _D ) from other portions was obtained. The results are shown.

The above-mentioned addition amount is a ratio to the weight of the photosensitive layer to which the compound example (1) is added, that is, the charge transport layer here. Increase in photoconductor V _L (V) ΔV _D (V) after standing 1 10 30 2 15 15 3 20 10 4 35 10 5 10 80 6 95 5 As is clear from the above results, regarding the photoconductor containing no additive Was repeatedly subjected to an electrophotographic process, and a significant decrease in dark area potential was observed. Also,
If the added amount is too large, there is an adverse effect that the bright part potential is significantly increased.

On the other hand, in the case of a photoreceptor having an appropriate content of the additive, the charging ability is not deteriorated so much and no practical problems are observed.

Example 2 As a charge generation material, a disazo pigment having the following structural formula was used.
Department, 6 parts of polyvinyl butyral (trade name S-REC BX-1, manufactured by Sekisui Chemical Co., Ltd.) and 50 parts of cyclohexanone were dispersed in a sand mill using glass beads. To this dispersion, 100 parts of tetrahydrofuran was added and coated on the same conductive substrate and undercoat layer as in Example 1 to form a charge generation layer having a thickness of 0.2 μm.

Next, as a charge transport material, 8 parts of a benzcarbazole compound having the following structural formula, Styrene-acrylic copolymer (trade name Styrene MS-20
0, 10 parts by Nippon Steel Chemical Co., Ltd. and Tris (3,5-
tert-amyl-4-hydroxybenzyl) isocyanurate (Compound example (2)) 0.36 parts with dichloromethane 15 parts,
A solution dissolved in 45 parts of monochlorobenzene was applied on the charge generation layer to form a charge transport layer having a thickness of 18 μm. This is the photoconductor 7.

On the other hand, for comparison, a sample without the additive of the compound example (2) was prepared and used as a photoreceptor 8.

Further, as a comparative sample, a photoconductor to which the following additives were added was prepared.

Additive 2,2'-butylidene bis- (2-tert-butyl-4-
Methylphenol) The photoconductor 9 is used.

N, N'-hexamethylenebis (3,5-di-tert-butyl-4-hydroxyhydrocinnamamide) The photoconductor 10 is used.

2,2'-thiobis- (4-methyl-6-tert-butylphenol) The photoconductor 11 is used.

Bis- (1,2,2,6,6-pentamethyl-4-piperidyl) -2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-n-butylmalonate The photoconductor 12 is used.

2-hydroxy-4-n-octoxybenzophenone The photoconductor 13 is used.

2- (2'-hydroxy-3'-tert-butyl-5 '
-Methylphenyl) -5-chlorobenzotriazole The photoconductor 14 is used.

The characteristics of these photoconductors were evaluated in the same manner as in Example 1. The initial V _D and V _L are set to −650 V and −15, respectively.
The amount of exposure at 0V was also measured. The results are shown.

ΔV _D (V) after leaving the photoreceptor 7 10 8 90 9 70 10 90 11 90 12 20 13 90 14 90 From the above results, it is clear that the additive of the compound example (2) prevents deterioration, and It can be seen that the above-mentioned antioxidant cannot obtain a sufficient effect or has a great adverse effect.

Example 3 An undercoat layer was coated on a conductive substrate in the same manner as in Example 1.

Next, 15 parts of a stilbene compound having the following structural formula, A solution prepared by dissolving 10 parts of polycarbonate (trade name: Panlite L-1250, manufactured by Teijin Chemicals Ltd.) 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 disazo pigment having the following structural formula, 7 parts of the styrylbenzene compound, the polycarbonate
10 parts, the additive of the compound example (1) was dispersed and dissolved in 0.63 parts, 150 parts of dichloromethane, and 50 parts of monochlorobenzene, and the coating composition was spray-coated on the charge transport layer to form a charge generation layer having a thickness of 5 μm. . This is referred to as a photoconductor 15.

On the other hand, a photoconductor is prepared by adding a photoconductor to which the above-mentioned additive is not added, and named photoconductor 16.

By positively charging these photoconductors, V _D : + 650V, V _L : + 150V
The following evaluation was performed in the same manner as described above. The results are shown.

Example 4 An undercoat layer was coated on a conductive substrate in the same manner as in Example 1.

Next, 1 part of a disazo pigment having the following structural formula, 0.3 parts of 10 parts of the benzcarbazole compound used in Example 2, 10 parts of polycarbonate (described above), and tris (3-tert-butyl-5-tert-amyl-4-hydroxybenzyl) isocyanurate (Compound Example (3)) were used. Part was dispersed and dissolved in 60 parts of dichloromethane and 20 parts of monochlorobenzene, and the thus-obtained coating material was applied on the undercoat layer to form a 16 μ-layer photosensitive layer.

 This is referred to as a photoconductor 17.

On the other hand, for comparison, a photoconductor having a photoconductive layer to which the above additive is not added is prepared, and is referred to as photoconductor 18.

These photoreceptors were evaluated in the same manner as in Example 3. The results are shown.

Example 5 A photoconductor was prepared in the same manner as in Example 1 except that the following additives were used.

Additive Tris (3-tert-butyl-4-methyl-4-hydroxybenzyl) isocyanurate (Compound Example (4)) A photoreceptor 19 is used.

Tris (3-tert-amyl-4-ethyl-4-hydroxybenzyl) isocyanurate (Compound Example (5)) A photoreceptor 20 is used.

Tris (3-tert-butyl-4-isopropyl-4-
Hydroxybenzyl) isocyanurate (Compound Example (6)) Photoreceptor 21 is used.

Tris (3-tert-butyl-4-butenyl-4-hydroxybenzyl) -isocyanurate (Compound Example (7)) A photoreceptor 22 is used.

The same evaluations were performed on these photoconductors, and the results are shown.

Initial Sensitivity (lux, sec) of Photoreceptor 19 3.3 20 3.2 21 3.4 22 3.35 Example 6 In the above-described characteristic evaluation, the photoconductor 2, the photoconductor 5 and the photoconductor 7 prepared in Example 1 and Example 2 were evaluated.
After 5,000 copies, another 45,000 copies were made. As a result, regarding the photoconductor 2 and the photoconductor 7 to which the antioxidant specified in the present invention is added, the image quality is not deteriorated after the endurance of 50,000 sheets as compared with the initial stage, and the contrast is high stably and the image is even. was gotten.

On the other hand, in Comparative Sample Photoreceptor 5 to which the above-mentioned antioxidant was not added, the image density was remarkably reduced from around 15,000 sheets. Also, due to the drop in potential that occurs when the device is left at rest after copying, the image becomes very uneven.

[Advantages of the Invention] The electrophotographic photoreceptor of the present invention has extremely high potential stability under a corona discharge environment, and can always obtain stable and high-quality images.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masaaki Hiroshi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Fumio Sumino 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Noboru Kashimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masafumi Hisamura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. ( 72) Inventor Tomohiro Kimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP 62-105151 (JP, A) JP 57-1222444 (JP, A) Special Kaisho 61-156131 (JP, A)

Claims (4)

[Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer containing an organic photoconductor on a conductive substrate, wherein the photosensitive layer contains a compound represented by the following general formula (1). Electrophotographic photoreceptor. General formula In the formula, R is X ₂ represents a hydrogen atom, an alkenyl group having 2 to 10 carbon atoms or an alkyl group having 1 to 10 carbon atoms. 2. The method according to claim 1, wherein the photosensitive layer comprises a charge generation layer and a charge transport layer, and at least one of them contains the compound represented by the general formula (1). Electrophotographic photoreceptor. 3. The electrophotographic photoconductor according to claim 1, wherein the amount of the compound represented by the general formula (1) added is 0.1 to 10% with respect to the total weight of the photosensitive layer. . 4. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer is a mixture of a charge generating material and a charge transporting material.