JPH054669B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and more particularly, to an electrophotographic photoreceptor having a photosensitive layer with excellent durability that does not cause image quality deterioration due to repeated use. [Prior Art] 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 also easy to form into films and have high productivity. It is characterized by this. An electrophotographic photoreceptor is repeatedly subjected to various image forming processes in an electrophotographic apparatus, and during this process, the photoreceptor is required to exhibit stable characteristics. However, electrophotographic photoreceptors using organic photoconductors as described above have the disadvantage that, after repeated use, image quality deterioration such as a decrease in image density due to a decrease in charging ability and image blurring due to a decrease in surface resistance is likely to occur. be. The cause of these deteriorations is thought to be largely influenced by corona discharge. That is, when a photoreceptor is used in a copying machine, it is constantly exposed to an atmosphere of corona discharge, and as copies are repeatedly made, ozone, NO _x , and
It is believed that organic photoconductors are degraded by active substances such as nitric acid. In particular, electrophotographic photoreceptors using organic photoconductors are often used with negative charging, but in the case of negative corona charging, the amount of ozone generated is greater than that of positive charging. This is one of the factors that makes it more susceptible to deterioration than other photoreceptors. In addition, after copying is completed, the part of the photoreceptor directly below the corona charger that has stopped rotating deteriorates, and the charging ability of that part deteriorates significantly, a phenomenon called dormant memory. considered to be an influence. Conventionally, methods for preventing such deterioration of electrophotographic photoreceptors have been disclosed in JP-A-57-122444, JP-A-58-120260, JP-A-61-156131, and JP-A-62- As described in Publication No. 105151, it has been proposed to add various additives such as antioxidants, ultraviolet absorbers, and photodegradation inhibitors. However, none of these methods can be said to be practically sufficient against deterioration of the electrophotographic photoreceptor, and are insufficient to suppress the decrease in dark area potential (V _D ), that is, the charging potential. Furthermore, when additives are added, the additive itself acts as a trapping agent for charge movement, causing an increase in the bright area potential (V _L ), which actually worsens the electrophotographic characteristics. There are also some disadvantages. [Problems to be Solved by the Invention] An object of the present invention is to provide an electrophotographic photoreceptor that prevents deterioration due to active substances such as ozone, NO _x , and nitric acid, and does not cause any adverse effects on electrophotographic characteristics. be. A further object of the present invention is to provide an electrophotographic photoreceptor that has high potential stability even after repeated use and can always maintain high quality images. [Means for Solving the Problems] The present inventors have investigated the causes of such photoreceptor deterioration and have repeatedly studied improvement methods. As a result, the inventors have found that at least certain The inventors have discovered that by adding these two types of compounds, a photoreceptor can be obtained which has a sufficient deterioration prevention effect and does not have any adverse effects on other electrophotographic properties, and has completed the present invention. 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 has at least the general formula ()

【formula】

[However, X ₁ is

[expression] or

[Formula] In which 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 () [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. ] An electrophotographic photoreceptor characterized by containing a compound represented by the following. The present invention also provides an electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductor on a conductive support, wherein the photosensitive layer has the general formula ()

【formula】

[However, X ₁ is

[expression] or

〔Example〕

Next, the present invention will be specifically explained using examples. Example 1 An aluminum cylinder with a diameter of 80 mm and a length of 360 mm was used as a conductive support.
% methanol solution was applied by dipping method to form a 0.5 μm thick undercoat layer. Next, the structural formula below 10 parts (parts by weight, same below) of trisazo pigment,
Polyvinyl butyral resin (Eslec BL-S,
(manufactured by Sekisui Chemical) and 50 parts of cyclohexanone were dispersed using a sand mill device using glass beads. 100 parts of methyl ethyl ketone was added to this dispersion and applied onto the undercoat layer to form a charge generation layer with a thickness of 0.2 μm. Next, the following structural formula A charge transport layer coating solution was prepared by dissolving 10 parts of a stilbene compound and 10 parts of polycarbonate resin (Panlite L-1250 manufactured by Teijin Chemicals) in 50 parts of dichloromethane and 10 parts of monochlorobenzene. 1 for this,
3,5-trimethyl-2,4,6-tris-(3,
5-di-t-butyl-4-hydroxybenzyl)
Benzene (THBZ-1):

【formula】

(Product name IRGANOX1330: manufactured by Ciba Geigy Japan) and tris(2,4-di-t-butylphenyl)-phosphite (TBP-1): (IRGAFOS168: manufactured by Ciba Geigy Japan) at a mixing ratio of 1:1 with 0.4 parts and 2 parts added respectively, and with a mixing ratio of 0.5:1 as described above.
Further, the mixture added as described above at a mixing ratio of 1:0.5 was used and coated on the charge generation layer to form a charge transport layer having a thickness of 18 μm. The photoreceptors manufactured in this way are referred to as photoreceptors 1, 2, 3, 4, 5, and 6, respectively. Furthermore, as comparison samples, photoconductor 7 with no additive added, photoconductors 8 and 9 with 0.4 parts and 2 parts of THBZ-1 added alone, and 0.4 parts of TBP-1 alone.
Photoreceptors 10 and 11 were manufactured by adding 1 part and 2 parts, respectively. These photoreceptors are installed in an electrophotographic copying machine,
The characteristics were evaluated as follows. First, set the dark area potential (V _D ) and light area potential (V _L ) of the photoreceptor to -
The latent image conditions were set to 650V and -150V. The image exposure amount at that time was determined and used as the initial sensitivity. Next, the potential was measured after 5000 sheets were continuously copied, and the rate of decrease in V _D and the increase in V _L were determined. Thereafter, the photoreceptor was left in a copying machine, and the surface potential was measured after 10 hours. At this time, the part of the photoreceptor that was located directly under the corona charger during the standing period was marked, and the difference (ΔV _D ) from the other part was determined. Furthermore, 5,000 copies were made continuously (total of 10,000 copies)
(sheet copy) The same measurements as above were carried out. The part of the photoconductor located directly under the corona charger should be the same as in the case of 5000 sheets. These results are shown in Table 1. Further, photoreceptors were manufactured with various additive mixing ratios and amounts added, and similar evaluations were conducted. The results are shown in Table 2. The amounts added in the table are weight ratios to the weight of the added photosensitive layer, that is, the charge transport layer here.

【table】

【table】

[Table] As is clear from Tables 1 and 2, the photoreceptor containing the two types of additives of the present invention in the photosensitive layer shows a small decrease in dark area potential during repeated electrophotographic processes. It has an excellent effect of preventing deterioration, and especially the deterioration of the portion directly below the corona charger is extremely small. Furthermore, there is no adverse effect on electrophotographic properties such as an increase in bright area potential due to the addition of additives. On the other hand, in the photoreceptor that does not contain additives, a significant decrease in dark area potential due to deterioration is observed.
The area directly below the corona charger is also severely degraded. Furthermore, although the addition of either one of them provides some improvement in terms of deterioration compared to a photoreceptor in which no addition is made, it cannot be said to be sufficient compared to the present invention. Example 2 As a charge generating material, the following structural formula 10 parts of the disazo pigment, 6 parts of polyvinyl butyral resin (Eslec BX-1, manufactured by Sekisui Chemical Co., Ltd.), and 50 parts of cyclohexanone were dispersed using a sand mill device using glass beads. 100 parts of tetrahydrofuran was added to this dispersion, and the mixture was coated on the same conductive support and undercoat layer as in Example 1 to form a charge generation layer with a thickness of 0.2 μm. Next, as a charge transport material, the following structural formula 8 parts of benzcarbazole compound, 10 parts of styrene-acrylic copolymer resin (Estyrene MS-200, manufactured by Nippon Steel Chemical Co., Ltd.), 1,3,5-trimethyl-
2,4,6-tris-(3,5-di-t-amyl-5-hydroxybenzyl)benzene (THBZ
-2):

【formula】

and tris(2,4-di-t-amylphenyl)-phosphite (TBP-2): in a mixing ratio of 1:1, 0.72 parts of dichloromethane, 15
A solution prepared by dissolving 45 parts of monochlorobenzene was applied onto the charge generation layer to form a charge transport layer with a thickness of 18 μm. This will be referred to as photoreceptor 19. On the other hand, for comparison, photoreceptor 20 was manufactured without adding THBZ-2 and TBP-2. Further, as comparative samples, photoreceptors using the additives shown in Table 3 either singly or in a mixture (mixing ratio 1/1) were manufactured in the same manner.

【table】

【table】

[Table] Properties of these photoreceptors were evaluated in the same manner as in Example 1. We also measured the amount of light when the initial V _D and V _L were set to −650 V and −150 V, respectively.
These results are shown in Table 4.

[Table] As shown in Table 4, the photoreceptor containing the additive of the present invention has small potential fluctuations and is excellent in preventing deterioration. On the other hand, other additives or different combinations may not be sufficient to prevent deterioration.
Or it turns out that the harm is great. Example 3 A subbing layer was coated on a conductive support in the same manner as in Example 1. Next, the structural formula below A solution prepared by dissolving 15 parts of the stilbene compound and 10 parts of polycarbonate resin (Panlite L-1250 manufactured by Teijin Kasei) in 50 parts of dichloromethane and 10 parts of monochlorobenzene was applied onto the undercoat layer to form a charge transport layer with a thickness of 15 μm. . Next, the structural formula below 4 parts of the disazo pigment, 7 parts of the stilbene compound
parts, 10 parts of the above polycarbonate resin, THBZ-
1. Disperse TBP-1 at a mixing ratio of 1/1 in 0.63 parts, 150 parts of dichloromethane, and 50 parts of monochlorobenzene,
The dissolved paint was spray coated onto the charge transport layer to form a charge generation layer with a thickness of 5 μm. This will be referred to as a photoreceptor 35. On the other hand, photoreceptor 36 was manufactured without adding THBZ-1/TBP-1. When these photoconductors are positively charged, V _D = +650V, V _L
= +150V, and the following evaluation was conducted in the same way as before. The results are shown in Table 5. Example 4 A subbing layer was coated on a conductive support in the same manner as in Example 1. Next, the structural formula below 1 part of the disazo pigment, 10 parts of the benzcarbazole compound used in Example 2, 10 parts of polycarbonate resin (Panlite L-1250 manufactured by Teijin Chemicals), 1,3,
5-trimethyl-2,4,6-tris-(3-t
-amyl-5-t-butyl-4-hydroxybenzyl)benzene (THBZ-3):

【formula】

and tris(2-t-amyl-4-t-butylphenyl)-phosphite (TBP-3): 0.3 parts at a mixing ratio of 1/1, 60 parts of dichloromethane,
A coating solution dispersed and dissolved in 20 parts of monochlorobenzene was applied onto the above-mentioned undercoat layer to produce a 16 μm thick photosensitive layer. This will be referred to as a photoreceptor 37. On the other hand, for comparison, a photosensitive layer to which THBZ-3/TBP-3 was not added was manufactured, and this was designated as photoreceptor 38. These photoreceptors were evaluated in the same manner as in Example 3, and the results are also listed in Table 5.

[Table] Example 5 A photoreceptor was produced in the same manner as in Example 1 except that the compounds shown in Table 6 were used as additives and the mixing ratio was 1/1 and the amount added was 10%. These results are shown in Table 7.

【table】

【table】

【table】

[Table] Example 6 As an additive, 1,3,5-trimethyl-2,
4,6-tris(3,5-di-t-butyl-4-
hydroxybenzyl)benzene (THBZ-1),
Tris(2,4-di-t-butylphenyl)phosphite (TBP-1), and distearyl-
3,3'-thiodipropionate (TP-1): (Sumilizer TPS: manufactured by Sumitomo Chemical Industries), the mixing ratio of these was 1:1:2, and the amount added was 10.
A photoreceptor 48 was manufactured in the same manner as in Example 1 except that the amount was changed to %. In addition, TP-1 was converted into dimyristyl-3,3'-thiodipropionate (TP-2): (Sumilizer TPM: manufactured by Sumitomo Chemical Industries) and lauryl-stearyl-3,3'-thiodipropionate (TP-3):

[Formula] Photoreceptors 49 and 50 were manufactured in the same manner except that ((Cyarox1212: manufactured by ACC) was replaced. These photoreceptors were evaluated in the same manner as in Example 1. The results are shown in Table 8. For comparison, photoreceptor 2 added two types of compounds, THBZ-1 and TBP-1, photoreceptor 7 without additives,
Table 8 also shows the evaluation results of Photoreceptor 51 to which only 10% of TP-1 was added.

〔Effect of the invention〕

As explained above, according to the present invention, which is a photoreceptor containing a combination of specific additives, deterioration of the photoreceptor due to active substances such as ozone can be prevented without adversely affecting electrophotographic characteristics. It has excellent potential stability in a corona discharge environment and can always form stable, high-quality images.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductor on a conductive support, the photosensitive layer having at least the general formula () [Formula] [However, X ₁ represents [Formula] or [Formula], and 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 () [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. ] An electrophotographic photoreceptor characterized by containing a compound represented by the following. 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer has a laminated structure of a charge generation layer and a charge transport layer. 3 In an electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductor on a conductive support, the photosensitive layer has the general formula () [Formula] [However, X ₁ represents [Formula] or [Formula], and 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 () [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 () [However, n and m represent integers of 10 to 20,
R ₁ and R ₂ represent H or an alkyl group having 1 to 10 carbon atoms. ] An electrophotographic photoreceptor characterized by containing a compound represented by the following. 4. The electrophotographic photoreceptor according to claim 3, wherein the photosensitive layer has a laminated structure of a charge generation layer and a charge transport layer.