JP2568269B2 - Electrophotographic photoreceptor - Google Patents

Description

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

[Conventional technology]

In recent years, many electrophotographic photoreceptors using organic compounds as photoconductors have been developed. Most of them that have been 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,
The flexibility of the material design is expected to further improve electrophotographic characteristics such as sensitivity and photoresponsiveness, and it is characterized by easy film formation and high productivity.

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, the electrophotographic photoreceptor using the organic photoconductor as described above has a drawback that image quality deterioration such as image bleeding due to a decrease in image density due to a decrease in charging ability and a decrease in surface resistance is likely to occur in repeated use. is there.

It is considered that the cause of these deteriorations is greatly influenced by corona discharge. That is, when a photoconductor is used in a copying machine, it is constantly exposed to the atmosphere of corona discharge, and organic light is generated by the active substances such as ozone, NO _x , and nitric acid generated by corona discharge during repeated copying. It is believed that the conductor is subject to degradation. 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 one of the factors that are more susceptible to deterioration than the photoconductors.

In addition, after copying is complete, the part directly below the corona charger that has stopped rotating deteriorates, and the charging ability of that part is significantly reduced. Is believed to be an impact.

Conventionally, as a method for preventing such deterioration of the electrophotographic photosensitive member, JP-A-57-122444 and JP-A-58-1202 are known.
60, JP 61-156131, JP 62-105151
It has been proposed to add various additives such as an antioxidant, an ultraviolet absorber, and a photodeterioration inhibitor as described in Japanese Patent Publication No. 1994-242242.

However, none of them is practically sufficient for deterioration of the electrophotographic photosensitive member, and the dark portion potential (V _D ),
That is, it is insufficient to suppress the decrease of the charging potential. In addition, by adding the additive, the additive itself acts as a trapping agent against the movement of electric charge, which causes an increase in the light portion potential ( _VL ), which is a detrimental effect on the electrophotographic characteristics. There is also.

[Problems to be solved by the invention]

An object of the present invention, ozone, NO _x, thereby preventing the deterioration caused by active substances such as nitric acid, it is to provide an electrophotographic photoreceptor which does not cause adverse effect to the electrophotographic characteristics.

A further object of the present invention is to provide an electrophotographic photosensitive member which has high potential stability against repeated use and which can always maintain a high quality image.

[Means for solving problems]

The inventors of the present invention have sought to find the cause of such deterioration of the photoconductor and have studied the improvement method, and as a result, by adding at least four specific compounds to the photoconductive layer containing the organic photoconductor. The present invention has been completed by finding that a photoconductor having a sufficient deterioration preventing effect and having no adverse effect on other electrophotographic characteristics can be obtained.

That is, the present invention provides an electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductor on a conductive support, wherein the photosensitive layer is at least the compound represented by the general formula (I). [However, X ₁ X ₂ represents H, an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms. ] And general formula (II) [However, X ₃ and X ₄ represent an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms. ] And general formula (III) [However, n and m represent an integer of 10 to 20, R ₁ and
R ₂ represents H or an alkyl group having 1 to 10 carbon atoms. ] And general formula (IV) [However, X is -S -, - S-S-, CH 2 l or CH = CH _p (l is an integer from 0 to, p is an integer of 1 to 5) indicates, X ₇ and X ₈ are H Represents an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms. ] It is an electrophotographic photoreceptor containing the compound shown by these.

 The present invention will be described in detail below.

The additives in the present invention are radical scavengers such as plastics and rubbers, phenol derivatives having three hindered phenol groups known as antioxidants, phosphite compounds known as hydroperoxide decomposing agents, and sulfoxide-based compounds. The compound and four basic pyridine compounds are used at the same time.

Although the mechanism of preventing deterioration by simultaneously using such four kinds of compounds is not clear at present, among the deteriorated substances generated by corona discharge, such as ozone and ozone, among the deteriorated substances generated by the interaction of the hindered phenol group, the phosphite group and the sulfide compound. It exerts an effect against radical deterioration factors such as NO _x , and the basic compound, pyridine compound, captures acidic substances such as HNO ₃ and HNO ₂ among the deterioration substances, and It is considered that the synergistic effect of the additive exerts an effect on prevention of deterioration of the photosensitive layer due to ozone and an active substance generated therewith.

Examples of the compound represented by the general formula (I) in the present invention include 1,3,5-trimethyl-2,4,6-tris- (3,5-di-
t-butyl-4-hydroxybenzyl) benzene, 1,3,
5-Trimethyl-2,4,6-tris- (3,5-di-t-amyl-4-hydroxybenzyl) benzene, 1,3,5-trimethyl-2,4,6-tris- (3-t -Butyl-5-methyl-4-hydroxybenzyl) benzene, 1,3,5-trimethyl-2,4,6-tris- (3-t-amyl-5-isopropyl-4-hydroxybenzyl) benzene, 1, 3,5
-Trimethyl-2,4,6-tris- (3-t-amyl-5
-(1-butenyl) -4-hydroxybenzyl) benzene and the like can be mentioned. Particularly, X ₂ in the general formula (I) is an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 5 carbon atoms. preferable.

The compound represented by the general formula (II) in the present invention includes tris (2,4-di-t-butylphenyl) -phosphite and tris (2,4-di-t-acylphenyl).
-Phosphite, tris (2-t-butyl-4-methylphenyl) phosphite, tris (2-ethyl-4-methylphenyl) phosphite, tris (2-t-amyl-4- (1-butenyl) phenyl) phosphite and the like. Particularly, X ₃ and X ₄ in the general formula (II) are preferably an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 5 carbon atoms.

Further, specific examples of the compound represented by the general formula (III) in the present invention include dilauryl-3,3'-thiodipropionate, ditridecyl-3,3'-thiodipropionate and dimyristyl-3,3 '. -Thiodipropionate,
Lauryl-stearyl-3,3'-thiodipropionate, distearyl-3,3'-methyl-3,3'-thiodipropionate, distearyl-3-ethyl-3'-methyl-3,3 ' -Thiodipropionate and the like can be mentioned, and particularly, n and m in the general formula (III) are integers of 12 to 18, and R ₁ and R ₂ are preferably alkyl groups having 1 to 4 carbon atoms.

Further, specific examples of the compound represented by the general formula (IV) include 2,2'-bipyrazyl, 4,4'-bipyrazyl, 1,2-di (2-pyridyl) ethane, 1,3-di-4. -Pyridyl propane, di-2-pyridyl sulfide, di-2-pyridyl disulfide, 1,2-di-4-pyridyl ethylene, 5-
t-butyl-2 (3′-ethyl-2′-pyridyl) pyridine and the like, 1 is an integer of 0 to 4, p is an integer of 1 to 3, X ₇ and X ₈ are H, or have 1 carbon atom. Alkyl groups having 4 to 4 or alkenyl groups having 2 to 4 carbons are preferred.

The total addition amount of these compounds is in the range of 0.5 to 20%, preferably 2 to 15% with respect to the total weight of the photosensitive layer to be added, and the mixing ratio is 1: 0.2 to 5: 0.2 by weight. 5: 0.05-2
Especially, the range of 1: 0.5 to 2: 0.5 to 2: 0.1 to 1 is preferable. If the total amount added is less than 0.5%, the effect of preventing deterioration is not sufficient.
If it exceeds 0%, adverse effects such as sensitivity decrease and residual potential increase are likely to occur.

The photosensitive layer containing the four kinds of compounds of the present invention may be prepared by adding the four kinds of compounds of the present invention to a solution prepared by dissolving or dispersing an organic photoconductor and a binder resin described below in a suitable solvent and mixing them. Alternatively, it can be formed by coating and drying a coating liquid obtained by simultaneously mixing and dissolving or dispersing these.

The photosensitive layer containing the organic photoconductor in the present invention is a single-layer type photosensitive body in which a charge-generating material and a charge-transporting material whose functions are separated are mixed, or a charge-generating layer containing the charge-generating material, and a charge-transporting material. And a charge-transporting layer containing the same.

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

As the charge transport material, organic photoconductors such as pyrazoline-based, hydrazone-based, stilbene-based, triphenylamine-based, benzidine-based, oxazole-based, indole-based, and carbazole-based compounds are used.

In the case of a single-layer type photoreceptor, the above-described charge generation material and charge transport material are dissolved or dispersed in an appropriate binder resin, and a layer is formed on a conductive support by coating. On the other hand, as the laminated type, there is a laminated type in which 1) a charge generation layer and a charge transport layer are laminated in this order on a conductive support, or a 2) a charge transport layer and a charge generation layer are laminated in this order. In the case of 1), as a method of forming the charge generating layer, there are a method of dispersing or dissolving the charge generating material in a binder resin and a solvent and applying, a method such as vapor deposition and sputtering. Film thickness is 5μm or less, especially 0.01-3μ
m is preferred. In this case, it is also possible to use an inorganic photoconductor such as selenium or amorphous silicon. The charge transport layer is formed by dissolving the above-described charge transport material in a binder resin having a film forming property and laminating it on the charge generation layer. Film thickness is 5
.About.40 .mu.m, particularly preferably 8 to 35 .mu.m. In this case, the additive of the present 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 can be formed by applying the above-mentioned organic photoconductor together with a binder resin. At this time, it is preferable to include a charge transport material also in the charge generation layer. In this case, the additive is preferably contained in the charge generation layer or both the charge generation layer and the charge transport layer.

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

The electrophotographic photosensitive member of the present invention includes a laser beam printer, an LED printer, an LCD printer, a C, in addition to an ordinary copying machine.
It can be applied to photoconductors of various devices that apply electrophotographic methods such as RT printers.

〔Example〕

 Next, the present invention will be specifically described with reference to examples.

Example 1 An aluminum cylinder having a diameter of 80 mm and a length of 360 mm was used as a conductive support, and a 5% methanol solution of a polyamide resin (trade name: Amilan CM-8000, manufactured by Toray) was applied to the aluminum cylinder by a dipping method to form 0.5 μm. I got a thick undercoat layer.

Next, as the charge generation material, the following structural formula 10 parts of trisazo pigment (part by weight, the same applies hereinafter), polyvinyl butyral resin (Eslek BL-S, Sekisui Chemical Co., Ltd.)
6 parts and 50 parts of cyclohexanone were dispersed in a sand mill 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, as a charge transport material, Distillate 10 parts of stilbene compound and 10 parts of polycarbonate resin (Panlite L-1250, Teijin Chemicals) into dichloromethane 50
And 10 parts of monochlorobenzene to prepare a charge transport layer coating solution. To this, 1,3,5-trimethyl-2,4,6-tris- (3,5-di-t-butyl-4-hydroxybenzyl) benzene (THBZ-1): (Product name IRGANOX 1330: manufactured by Ciba-Gaiki Japan) and tris (2,4-di-t-butylphenyl) -phosphite (TBP-1): (IRGAFOS168: manufactured by Nippon Ciba Geigy) and distearyl-3,3′-thiodipropionate (TP-1): (Sumilizer TPS: Sumitomo Chemical Co., Ltd.) Furthermore, 1,3-di-4pyridylpropane (DPy-1): 0.4 parts, 2 parts were added at a mixing ratio of 1: 1: 1: 0.1,
Further, using the mixture added in the same manner as above at a mixing ratio of 1: 1: 1: 0.05, and the mixture added in the same manner as above at a mixing ratio of 1: 1: 1: 0.2, coating on the charge generation layer, An 18 μm thick charge transport layer was formed. The photoconductors manufactured in this manner are referred to as photoconductors 1, 2, 3, 4, 5 and 6, respectively.

For comparison, the photoconductor 7, TH without additive
BZ-1, TBP-1 and TP-1 at a mixing ratio of 1: 1: 0.4 part, 2 parts of photoconductor 8,9 and DPy-1 0.4 part, 2 parts of photoconductor 10, 11 were produced respectively.

These photoconductors were set in an electrophotographic copying machine (CLC1: made by Canon), and the characteristics were evaluated as follows. First, the dark area potential (V _D ) and light area potential (V _L ) of the photoconductor are set to -65
The latent image conditions were set to be 0V and −150V. The image exposure amount at that time was determined and used as the initial sensitivity. Next, after the continuous copying of 5,000 sheets, the potential was measured and the decrease rate of V _D and V _L
I asked for the rise. Then leave the photoconductor in the copier,
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.

Further, continuous copying of 5,000 sheets was performed (total of 10,000 sheets), after which the photoconductor was left in the copying machine and the surface potential after one week was measured by the same method as above. The part of the photoconductor located directly under the corona charger should be the same as the case of 5,000 sheets. The results are shown in Table 1.

As is clear from Table 1, the photoreceptors containing the four kinds of additives according to the present invention in the photosensitive layer exhibited a small decrease in the dark area potential and a good effect of preventing the deterioration in the repeated electrophotographic process. In particular, the deterioration of the portion directly below the corona charger due to being left for a long time is extremely small. In addition, there is no adverse effect on electrophotographic characteristics such as increase in bright area potential due to addition of additives.

On the other hand, in the case of the photoreceptor containing no additive, the dark portion potential is remarkably lowered due to the deterioration, and the portion directly below the corona charger is significantly deteriorated.

Example 2 As a charge generation material, the following structural formula was used. 10 parts of disazo pigment, 6 parts of polyvinyl butyral resin (ESREC BX-1, manufactured by Sekisui Chemical Co., Ltd.) and cyclohexanone
50 parts were dispersed by a sand mill apparatus using glass beads. To this dispersion, 100 parts of tetrahydrofuran was added and coated on the same conductive support and subbing layer as in Example 1.
A charge generation layer having a thickness of 2 μm was formed.

Next, as a charge transport material, the following structural formula Benzcarbazole compound of 8 parts, styrene-acrylic copolymer resin (Estyrene MS-200, manufactured by Nippon Steel Corp.) 1
0 part, 1,3,5-trimethyl-2,4,6-tris- (3,5-di-
t-amyl-5-hydroxybenzyl) benzene (THBZ
-2): And tris (2,4-di-t-amylphenyl) -phosphite (TBP-2): And dimyristyl-3,3'-thiodipropionate (T
P-2): (Sumilizer TPM: manufactured by Sumitomo Chemical Co., Ltd.) and 4,4′-bipyridyl (DPy-2): In a mixture ratio of 1: 1: 1: 0.3, 0.72 parts to 15 parts dichloromethane,
A solution dissolved in 45 parts of monochlorobenzene was applied onto the charge generation layer to form a charge transport layer having a thickness of 18 μm. This is the photoconductor 12.

The mixing ratio of these four additives is 1: 0.5: 0.5: 0.1.
A photoconductor was manufactured in the same manner except that it was added at a mixing ratio of 1: 2: 2: 1. These are referred to as photoconductors 13 and 14.

On the other hand, for comparison, a photoconductor 15 was produced without adding these four additives.

Table 2 shows the results of evaluating these photoconductors in the same manner as in Example 1.

As shown in Table 2, the photoreceptor containing the additive of the present invention has small potential fluctuation and is excellent in preventing deterioration.

Example 3 An undercoat layer was coated on a conductive support in the same manner as in Example 1. Next, the following structural formula 15 parts of stilbene compound, 10 parts of polycarbonate resin (Panlite L-1250 manufactured by Teijin Kasei) and 50 parts of dichloromethane
Part, a solution dissolved in 10 parts of monochlorobenzene was applied on the undercoat layer to form a charge transport layer having a thickness of 15 μm.

Next, the following structural formula Disazo pigment 4 parts, the stilbene compound 7 parts, the polycarbonate resin 10 parts, THBZ-1, TBP as an additive
-1, TP-1 and DPy-1, 0.63 parts of mixing ratio 1/1/1 / 0.2,
A coating material dispersed and dissolved in 150 parts of dichloromethane and 50 parts of monochlorobenzene was spray-coated on the charge transport layer to form a charge generation layer having a thickness of 5 μm. This is photoconductor 16
And

On the other hand, a photoconductor 17 was produced without adding these four additives.

By positively charging these photoconductors, V _D = + 650V, V _L = + 150V
, And the following evaluation was performed in the same manner as in the prior art. The results are shown in Table 3.

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

The following structural formula 1 part of the disazo pigment, 10 parts of the benzcarbazole compound used in Example 2, a polycarbonate resin (Panlite L
-1250 Teijin Chemicals) 10 parts, 1,3,5-trimethyl-2,4,6
-Tris- (3-t-amyl-5-t-butyl-4-hydroxybenzyl) benzene (THBZ-3): And tris (2-t-amyl-4-t-butylphenyl) -phosphite (TBP-3): And lauryl-stearyl-3,3'-thiodipropionate (TP-3): (Manufactured by Cyarox 1212: ACC) and 1,2-di (2-pyridyl) ethane (DPy-3): 0.42 parts at a mixing ratio of 1/1/1 / 0.1, 60 parts of dichloromethane,
A coating liquid dispersed and dissolved in 20 parts of monochlorobenzene was coated on the undercoat layer described below to produce a photosensitive layer having a thickness of 16 μm. This is referred to as a photoconductor 18. On the other hand, for comparison, a photosensitive layer was prepared without adding these four additives, and this is designated as photoreceptor 19. Table 3 also shows the results of the same evaluations as in Example 3 performed on these photoreceptors.

Example 5 Using the compounds shown in Tables 1 and 4 as additives, a photoconductor was prepared and evaluated in the same manner as in Example 1 except that the mixing ratio was 1/1/1 / 0.1 and the addition amount was 10%. . The results are shown in Table 5.

Example 6 Photoreceptors 2,7,12 produced in Examples 1 and 2, Example 5
With respect to the photoconductor 24 manufactured in (1), 10,000 copies were made in the above-mentioned characteristic evaluation, and then 40,000 copies were made. As a result, with respect to the photoconductors 2, 12 and 24 to which the additives were added, the image quality was not deteriorated compared to the initial stage even after 50,000 sheets were durable, and the contrast was stably high, and an image without unevenness was obtained. On the other hand, the photoconductor 7 to which no additive is added is 1
The decrease in image density became noticeable around the endurance of 5,000 sheets.
In addition, the image became extremely uneven due to the potential drop that occurred when the device was left at rest after the copying was completed.

[Effects of the Invention] As described above, according to the present invention, which is a photoreceptor containing a combination of specific additives, according to the present invention, the activity of ozone or the like can be maintained without adversely affecting the electrophotographic characteristics for a long period of time. It is possible to prevent the photoreceptor from being deteriorated by a substance, have excellent potential stability under a corona discharge environment, and always form a stable and high-quality image.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shin Nagahara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-1-319043 (JP, A) JP-A-57 -171343 (JP, A) JP 64-44949 (JP, A)

Claims (2)

(57) [Claims] 1. An electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductor on a conductive support, wherein the photosensitive layer is at least of the general formula (I). [However, X ₁ X ₂ represents H, an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms. ] And general formula (II) [However, X ₃ and X ₄ represent an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms. ] And general formula (III) [However, n and m represent an integer of 10 to 20, X ₅ and
X ₆ represents H or an alkyl group having 1 to 10 carbon atoms. ] And general formula (IV) [However, X is -S-, -SS-, CH _{2 l} or
CH = CH _p (l is an integer from 0 to 10 and p is an integer from 1 to 5)
And X ₇ and X ₈ represent H, an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms. ] An electrophotographic photosensitive member comprising a compound represented by: 2. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer has a laminated structure of a charge generation layer and a charge transport layer.