JP2702176B2 - Electrophotographic photoreceptor - Google Patents

Description

The present invention relates to an electrophotographic photoreceptor, and more particularly, to an electrophotographic photoreceptor.
The present invention relates to an electrophotographic photoreceptor having a photosensitive layer having excellent durability and having little deterioration in image quality due to repeated use.

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

Such an electrophotographic photoreceptor using an organic photoconductor has an advantage that the productivity is high because the film forming property of the photosensitive layer is good, and since the material design is flexible, the sensitivity, It is expected that electrophotographic characteristics such as photoresponsiveness will be more excellent.

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 deterioration 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.

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

[Problems to be Solved by the Invention] Accordingly, an object of the present invention is to further improve prevention of image quality deterioration,
It is another object of the present invention to provide an antioxidant which does not adversely affect other electrophotographic characteristics.

[Means for Solving the Problems] According to the present invention, in an electrophotographic photosensitive member having a photosensitive layer containing an organic photoconductor, the photosensitive layer has a compound represented by the following structural formula (1) and a structural formula An electrophotographic photoreceptor comprising the compound represented by (2) is provided.

[Where X ₁ is X ₂ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms] [Where X ₁ is X ₂ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms, and R ₁ , R ₂ and R ₃ are a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. The invention will be described in detail.

The photosensitive layer containing an organic photoconductor in the present invention, a charge generation layer containing a single-layer type charge generation material that is contained in a state where a charge-separated charge generation material and a charge transport material are mixed, It takes a form such as a lamination type in which a charge transport layer containing a charge transport material is laminated.

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

As the charge transport material, pyrazoline-based, stilbene-based, triphenylamine-based, benzidine-based, oxazole-based, indole-based, carbazole-based compounds, and the like are used.

In the case of a single-layer type photoreceptor, the above-mentioned charge generating material and charge transporting material are appropriately dispersed and dissolved in a binder resin, and this is applied on a conductive substrate to form a photosensitive layer.

Further, as the laminated photoreceptor, there is a laminated photoconductor in which a charge generation layer and a charge transport layer are laminated on a conductive substrate in this order, or a laminate in which a charge transport layer and a 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 and the binder resin in a solvent, and a method of vapor deposition, sputtering, and the like. 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, the structural formula (1),
It is preferred that the compound represented by (2) be contained in the charge transport layer.

In the case of, the charge transport material and the binder resin are dispersed in a solvent, dissolved and applied to form a charge transport layer, and the charge generation material and the binder resin are dispersed in the solvent, dissolved and applied on the layer. To form a charge generation layer. 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 compounds of the structural formulas (1) and (2) are contained in the charge generation layer or both the charge generation layer and the charge transport layer.

In the present invention, an antioxidant having two hindered phenol groups (compound represented by the structural formula (1)) and an antioxidant having a hindered amino group (compound represented by the structural formula (2)) ). These two kinds of antioxidants have little effect when used alone, but when both are used in combination, they exhibit sufficient effects. The total content of the compounds of the formulas (1) and (2) is preferably from 0.2 to 20% by weight based on the weight of the photosensitive layer (the charge generation layer and / or the charge transport layer in the case of a laminated type). , 0.6 to 15% by weight. The ratio (A) / (B) of the content (A) of the compound of the formula (1) to the content (B) of the compound of the formula (2) is 0.1 / 1 to 1 / 0.1.
(Weight ratio), more preferably 0.3 / 1 to 1 / 0.3 (weight ratio).

If the total content is less than 0.2% by weight, the effect of preventing deterioration tends to be small.
It tends to give rise to adverse effects such as a rise in residual potential.

The mechanism for preventing the photosensitive layer from deteriorating due to ozone and the accompanying active substances mainly consists of hindered phenol groups,
Although the effect is exhibited by the hindered amino group, the effect is largely due to the synergistic action of both antioxidants.

The photosensitive layer of the present invention may further 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 ones, for example, a cylindrical or belt-like aluminum, iron, copper, or metal-deposited plastic film. If necessary, an intermediate layer such as an adhesive layer, a barrier layer, or a parallel layer may be provided between the base and the photosensitive layer.

[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 5% methanol solution of a polyamide resin (trade name: Amilan CM-8000, manufactured by Toray) was applied by dipping to a thickness of 0.5 μm. The undercoat layer was made.

Next, 10 parts (parts by weight, the same applies hereinafter) of a trisazo pigment having the following structural formula, Polyvinyl butyral resin (trade name: Eslec BL-
S, Sekisui Chemical) 6 parts and cyclohexanone 50 parts 1
It was dispersed by a sand mill using φ glass beads. To this dispersion, 100 parts of methyl ethyl ketone was added and coated on the undercoat layer to form a 0.2 μm thick charge generation layer.

Next, 10 parts of a stilbene compound of the following structural formula, polycarbonate 10 parts of a resin (trade name: Panlite L-1250, manufactured by Teijin Chemicals Ltd.) was dissolved in 50 parts of dichloromethane and 10 parts of monochlorobenzene to prepare a coating solution for the charge transport layer. This coating solution was further added with N, N'-bis [3- (3 ', 5'-di-tert-butyl-
4'-Hydroxyphenyl) pyropionyl] hydrazine (HPH-1) and bis- (1,2,2,6,6-pentamethyl-
4-piberidyl) -2- (3,5-di-t-butyl-4-
Hydroxybenzyl) 2-n-butyl malonate (PHM
-1) was added at a mixing ratio of 1/1, a total of 0.4 parts and 2.0 parts, respectively, added at a mixing ratio of 0.5 / 1 as described above, and added at a mixing ratio of 1 / 0.5 as described above. The resultant was applied on the charge generation layer to form a charge transport layer having a thickness of 18 μm. The photoconductors thus formed were respectively named photoconductor 1,
2,3,4,5,6. Further, the photoreceptors 7, 8 with a mixing ratio of 1/1 and the added amount of 6 parts, with no additive added, and with HPH-1 and PHM-1 alone in comparison, 2.0 parts were added. ,
Made 9,10.

These photoconductors were installed in an electrophotographic copying machine, and each characteristic was evaluated as follows. First, the conditions of the latent image were set such that the dark portion potential (V _D ) and the bright portion potential (V _L ) of the photoreceptor were -650 V and -150 V, respectively. The amount of image exposure at that time was determined and used as the initial sensitivity. Then, the potential after the continuous copying of 5000 sheets was measured to determine the increase in the reduction rate and V _L V _D. After that, the photoreceptor that marked the part located immediately below the corona charger was left in the copier for 10 hours, and then the surface potential of the marked part and other parts was measured, and the difference (ΔV _D ) was measured. I asked. Table 1 shows the results.

Next, a photosensitive member was prepared by varying the mixing ratio and the amount of the additive, and the same evaluation was performed. Table 2 shows the results.

The amount of addition shown in the table is a ratio to the weight of the added photosensitive layer, that is, the charge transport layer here.

As is evident from Tables 1 and 2, the photoreceptors not containing the compounds of formulas (1) and (2) showed a remarkable decrease in the dark area potential after repeated electrophotographic processes.
The effect was small when only one of the compounds of the formulas (1) and (2) was used.

On the other hand, the photoreceptor in which the content of the compound of the formula (1) and the compound of the formula (2) are appropriate and the mixing ratio is excellent, the chargeability is remarkably reduced and excellent, and there is no practical adverse effect. Was. In addition, when the addition amount was 25% by weight, the light portion potential increased.

Example 2 10 parts of a disazo pigment having the following structural formula as a charge generation material, Polyvinyl butyral resin (trade name: S-REC BX-
1. Sekisui Chemical Co., Ltd.) and 6 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 substrate and undercoating layer as in Example 1 to form a 0.2 μm thick charge generating layer.

Next, a benzcarbazole compound of the following structural formula is used as a charge transporting material. 8 parts, 10 parts of a styrene-acrylic copolymer resin (trade name: Estyrene MS-200, manufactured by Nippon Steel Chemical Co., Ltd.), and N, N'-bis [3- (3,5-di-t-acyl-4-hydroxy) Phenyl) propionyl] hydrazine (HPH-2), bis-
(N-ethyl-2,2,6,6-tetramethyl-4-piperidyl) -2 (3,5-di-t-acyl-4-hydroxybenzyl) 2-n-butylmalonate (PHM-2) The mixing ratio 1
/ 1 0.72 parts dichloromethane 15 parts, monochlorobenzene
The solution dissolved in 45 parts was applied on the above-mentioned charge generation layer and 18 μm
A thick charge transport layer was formed. This is designated as Photoconductor-21.

On the other hand, for comparison, a sample to which neither HPH-2 nor PHM-2 was added was prepared and used as a photoreceptor 22. Further, a photoreceptor to which additives shown in Table 2 were added was prepared as a comparative sample.

The characteristics of these photosensitive members were evaluated in the same manner as in Example 1. The initial V _D and V _L are -650 V and -150 V, respectively.
Was also measured. Table 4 shows the results.

As shown in Table 4, when the effect of preventing deterioration due to the combined use of the compounds of the formulas (1) and (2) is clear, at the same time, only the other antioxidant or the combined use with the other antioxidant is used. It turns out that a sufficient effect cannot be obtained or other adverse effects are large.

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

Next, 15 parts of a stilbene compound of the following structural formula, polycarbonate resin A solution prepared by dissolving 10 parts (trade name: Panlite L-1250, manufactured by Teijin Chemicals) in 50 parts of dichloromethane and 10 parts of monochlorobenzene was applied on the undercoat layer to form a charge transporting layer having a thickness of 15 μm.

Next, 4 parts of a disazo pigment having the following structural formula, 7 parts of the stilbene compound, The polycarbonate resin 10 parts, HPH-1, PHM-1 mixing ratio 1/1 is 0.63 part, dichloromethane dichloromethane 150 parts, in monochlorobenzene 50 parts, decomposed, dissolved coating solution was spray-coated on the charge transport layer, A charge generation layer having a thickness of 5 μm was formed. This is designated as photoconductor 30.

On the other hand, a photoreceptor 31 to which HPH-1 and PHM-1 were not added was prepared. When these photosensitive members are positively charged, V _D = + 650 V, V _L = + 15
The voltage was set so as to be 0 V, and the following evaluation was performed in the same manner as in the related art. The results are shown in Table-5.

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

Next, 1 part of a disazo pigment having the following structural formula, 10 parts of a benzcarbazole compound used in Example 2, 10 parts of a polycarbonate resin (trade name: Panlite L-1250, manufactured by Teijin Chemicals), N, N'-bis [3- (3-t-acyl-5-t) -Butyl-4-hydroxyphenyl) propionyl] hydrazine (HPH-3) and bis- (N-propyl-2,2,6,6-tetramethyl-4-piperidyl) -2
-(3-t-acyl-5-butyl-4-hydroxybenzyl) 2-n-butylmalonate (PHM-3) at a mixing ratio of 1
0.3 parts for / 1, 60 parts of dichloromethane, 20 parts of monochlorobenzene
Apply the paint dispersed and dissolved in the undercoat layer on the undercoat layer.
A photosensitive layer having a thickness of μm was formed.

This is referred to as a photoconductor 32. On the other hand, HPH-3 / PHM-
3 A photosensitive layer not added was formed, and this was designated as photosensitive member 33.

Table 5 also shows the results of the same evaluation as in Example 3 for these photoconductors.

Example 5 The compounds shown in Table 6 were used as antioxidants, and the mixing ratio was 1 /
1. A photoconductor was prepared in the same manner as in Example 1, except that the addition amount was 10%.

Table 8 shows the results of similar evaluations of the photoconductors shown in Table 7.
Shown in

Example 6 Regarding the photoconductors 2, 8 and 21 prepared in Examples 1 and 2, after 5,000 copies in the above-described characteristic evaluation, 45,000 copies were further made. As a result, with respect to the photoreceptors 2 and 4 to which the antioxidant was added, even after the 50,000-sheet durability test, there was no decrease in image quality compared to the initial stage, and a stable high contrast and an image without unevenness were obtained. On the other hand, in the photosensitive member 8 of the comparative sample to which the antioxidant was not added, the image density was remarkably reduced after about 15,000 sheets of durability. In addition, an image having extremely unevenness was obtained due to a potential drop generated when the copying machine was left idle after copying was completed.

Additives used in Examples (HPH-1-6, PHM-1-6)
Are summarized in Table 9.

[Effects of the Invention] As described above, the electrophotographic photoreceptor of the present invention has extremely high potential stability in a corona discharge environment, and can always form a stable and high-quality image. Further, the electrophotographic photoreceptor 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.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Fumio Sumino 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-63-168654 (JP, A)

Claims (5)

(57) [Claims] 1. An electrophotographic photosensitive member having a photosensitive layer containing an organic photoconductor on a conductive substrate, wherein the photosensitive layer comprises a compound represented by the following structural formula (1) and a compound represented by the structural formula (2): An electrophotographic photoreceptor comprising a compound represented by the formula: [Where X ₁ is X ₂ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms] [Where X ₁ is X ₂ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms, and R ₁ , R ₂ and R ₃ are a hydrogen atom or an alkyl group having 1 to 10 carbon atoms] 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 composition according to claim 1, wherein the total content of the compound represented by the structural formula (1) and the compound represented by the structural formula (2) is 0.2 to 20% by weight based on the weight of the photosensitive layer contained. 2. The electrophotographic photosensitive member according to 1. 5. The ratio (A) / (B) of the content (A) of the compound represented by the structural formula (1) to the content (B) of the compound represented by the structural formula (2) is 0.1 / 1. Up to 1 / 0.1 (weight ratio)
5. The electrophotographic photoreceptor according to claim 1, wherein