JPH05303216A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To provide an electrophotographic sensitive body giving high image density. CONSTITUTION:This electrophotographic sensitive body has an electric conductive substrate, an electric charge generating layer and an electric charge transferring layer formed on the substrate as essential constituent elements and contains an aniline compd. represented by the formula in the electric charge transferring layer as the uppermost layer. In the formula, each of R1 and R2 is alkyl, R1 and R2 may form a ring in combination with N and A is cyano or nitro.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member, and more particularly to an electrophotographic photosensitive member containing a specific compound which provides a high image density.

[0002]

2. Description of the Related Art In recent years, electrophotographic copying machines and printers have been remarkably developed, and various types of models having various forms, types, and functions have been developed according to their uses, and correspondingly, photoconductors used for them have also been developed. A wide variety of things are being developed. Conventionally, inorganic compounds have been mainly used as electrophotographic photoreceptors from the viewpoint of sensitivity and durability. Examples of such an inorganic compound include zinc oxide, cadmium sulfide, and selenium. However, these often use harmful substances, and their disposal poses a problem and causes pollution. Further, when selenium having a good sensitivity is used, it is necessary to form a thin film on a conductive substrate by a vapor deposition method or the like, resulting in poor productivity and high cost.

In recent years, amorphous silicon has attracted attention as a non-polluting inorganic photoconductor, and research and development thereof have been advanced. However, although these are also excellent in sensitivity, the productivity is extremely poor because the plasma CVD method is mainly used when forming a thin film, and the photoreceptor cost and the running cost are large.

On the other hand, the organic photoreceptor can be incinerated,
It has the advantage of being pollution-free, and many of them can be formed into thin films by coating and are easy to mass-produce. Therefore, it has an advantage that the cost can be significantly reduced and that various shapes can be processed according to the application. However, with respect to the organic photoconductor, problems remain in its sensitivity and durability, and it is strongly desired to develop an organic photoconductor with high sensitivity and high durability.

Various methods have been proposed as means for improving the sensitivity of the organic photoconductor, but at present, a function-separated photoconductor having a two-layer structure in which the functions are separated into a charge generation layer and a charge transport layer is mainly used. Has become. For example, the charge generated in the charge generation layer by exposure is injected into the charge transport layer, transported through the charge transport layer to the surface, and the surface charge is neutralized to form an electrostatic latent image on the surface of the photoreceptor. To be done. Compared to the single-layer type, the function-separated type is less likely to trap the generated charges, and each layer does not hinder its function,
Charge can be efficiently transported to the surface of the photoreceptor (US Pat. No. 2,803,541).

As the organic charge generating material used in the charge generating layer, a compound which absorbs the energy of irradiated light and efficiently generates charges is selected and used.
Azo pigments (JP-A-54-14967), metal-free phthalocyanine pigments (JP-A-60-19146), metal phthalocyanine pigments (JP-A-57-146255), squarylium salts (JP-A-63). -113462 gazette) etc. can be mentioned.

As the charge transport material used in the charge transport layer, it is necessary to select a compound having a high charge injection efficiency from the charge generation layer and a high charge mobility in the charge transport layer. For that purpose, a compound having a small ionization potential or a compound which easily generates a cation radical is selected. For example, a triarylamine derivative (JP-A-58-58) is used.
123542), hydrazone derivatives (JP-A-57-101844).
Gazette), oxadiazole derivative (JP-B-34-5466), pyrazoline derivative (JP-B-52-4188),
Stilbene derivative (JP-A-58-198043), triphenylmethane derivative (JP-B-45-555), 1,3-
Butadiene derivatives (JP-A-62-287257) and the like have been proposed. As described above, various proposals have been made for increasing the sensitivity.

[0008]

However, with the popularization of printers, so-called "black" like black is required in solid images, and the current printers have not reached that range yet. Even if the sensitivity is excellent, the image density is often low. The method of adjusting the image density is currently performed by changing the contrast potential, but in this method, for example, when the image density is increased, the toner adheres to the background, resulting in poor image quality. Will end up. Therefore, it is strongly desired in the art to change the essence of the photoconductor and the toner to increase the image density.

[0009]

Generally, the image density is determined in the developing section and the transfer section in the electrophotographic process. That is, it depends on how much toner adheres to the photoconductor in the developing unit and how much toner is transferred from the photoconductor to the paper in the transfer unit. They are,
It is controlled by adjusting the force acting between the toner and the photoconductor. The force that acts between the photoconductor and the toner is mainly the electrostatic attraction that acts between the photoconductor surface charge and the surface charge of the toner, and the Van der Waals force that acts between the photoconductor and the dipole of the toner. I can give you two. If these can be arbitrarily changed, an arbitrary image density should be obtained.

The present invention is in that point. By adding a specific aniline compound to the outermost surface layer of the photoreceptor, the electrostatic attraction and the Van der Waals force are increased and the toner in the developing section is improved. It aims to increase the amount of adhesion and, on the other hand, to obtain a high image density without deteriorating the transfer efficiency.

That is, according to the present invention, in an electrophotographic photosensitive member having an electrically conductive support and a charge generation layer and a charge transport layer provided thereon as indispensable constituents, the charge transport layer which is the outermost surface layer is And an aniline compound represented by the general formula (1).

[0012]

[Chemical 2]

[0013] (wherein, R _1, R ₂ represents an alkyl group, and R ₁
R ₂ may form a ring together with the nitrogen atom. A represents a cyano group or a nitro group. ) In order to increase the image density, it is necessary to increase the electrostatic attractive force and the Van der Waals force acting between the toner and the photoconductor, and for that purpose, the compound represented by the general formula (1) is used. It has been found that inclusion on the photoreceptor surface is effective.

Although the above is effective for improving the image density at the developing portion, it is preferable that the force acting between the photosensitive member and the toner at the transfer portion is small. However, the transfer efficiency does not extremely deteriorate unless an ionic compound is used, and the aniline compound represented by the general formula (1) in the present invention is a neutral compound, and it hardly affects the transfer efficiency. It is a thing.

As described above, in order to increase the image density, it is effective to increase the electrostatic attractive force and the Van der Waals force, and to include a compound on the surface of the photoreceptor, which does not reduce the transfer efficiency. Is. Therefore, in the present invention, the image density can be increased by including the aniline compound represented by the general formula (1) in the outermost surface layer. The aniline compound represented by the general formula (1) is synthesized by a known method and is not particularly limited.

In the general formula (1), R ₁ and R ₂ each represent an alkyl group, and R ₁ and R ₂ may form a ring together with a nitrogen atom, but the alkyl group is preferably one having 6 or less carbon atoms. Chosen,
Examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group and an n-hexyl group. When R ₁ and R ₂ form a ring with a nitrogen atom, a 4-membered ring, a 5-membered ring, a 6-membered ring, a 7-membered ring,
An 8-member ring or the like is selected. A represents a cyano group or a nitro group.

The aniline compound represented by the general formula (1) has a large dipole moment, which is 3D or more, and an electrostatic attractive force acting between the electrophotographic photoreceptor and the toner containing them in the outermost surface layer. The Van der Waals force becomes great. The ionization potential of the aniline compound represented by the general formula (1) is larger than that of the charge transport material,
It does not become a trap for charge transfer. Below, the general formula
Specific examples of the aniline compound represented by (1),
The present invention is not limited to these.

[0018]

[Chemical 3]

[0019]

[Chemical 4]

[0020]

[Chemical 5]

The electrophotographic photosensitive member of the present invention is characterized by containing the aniline compound represented by the general formula (1) in the outermost surface layer. The structure of the organic photoconductor is mainly of a function separation type as shown in FIG. 1, that is, the conductive support 1, the charge generation layer 2, and the charge transport layer 3 are essential components and are laminated in this order. .. In this case, the outermost layer is the charge transport layer,
The aniline compound represented by the general formula (1) is included in the charge transport layer.

The electrophotographic photoreceptor of the present invention containing the aniline compound represented by the general formula (1) in the charge transport layer will be described in detail below. As the base material of the conductive support used in the present invention, a metal such as aluminum or nickel, a metal vapor-deposited polymer film, a metal laminated polymer film, or the like can be used, and a drum shape, a sheet shape, a belt shape, or the like. Either form can be used.

A charge generation layer is provided on this conductive support. The charge generation layer is a charge generation material, a binder as necessary,
And if necessary, an additive, a vapor deposition method, a CVD method,
It can be prepared by a method such as a coating method. The charge generating material is not particularly limited, and any organic material or inorganic material can be suitably used as long as it absorbs specific light to be irradiated and efficiently generates charges. As the organic charge generating material, for example, perylene pigment, polycyclic quinone pigment, metal-free phthalocyanine, metal phthalocyanine,
Examples thereof include bisazo pigments, trisazo pigments, thiapyrylium salts, squarium salts, and azurenium pigments.

As the binder used as necessary,
There is no particular limitation, for example, polycarbonate,
Condensation polymers such as polyarylate, polyester, polyamide; polyethylene, polystyrene, styrene-acrylic copolymer, polyacrylate, polymethacrylate, polyvinyl butyral, polyvinyl acetal, polyvinyl formal, polyvinyl alcohol, polyacrylonitrile, polyacrylamide, acrylonitrile- Addition polymers such as butadiene copolymers; polysulfones,
Polyether sulfone, silicone resin, phenoxy resin and the like are preferably used, and one kind or a mixture of two or more kinds can be used. The amount of the binder used is 0.1% by weight to 80% by weight based on the total weight of the charge generating layer.

Additives used as necessary include
For example, antioxidant, ultraviolet absorber, dispersant, adhesive,
Examples include sensitizers. The thickness of the charge generation layer is 0.1 μm to 5.0 μm, preferably 0.1 μm to 2.0 μm.

A charge transport layer is provided in the form of a thin film on the charge generation layer. In the present invention, the charge transport layer comprises a charge transport material, an aniline compound represented by the general formula (1), a binder, and an additive which is optionally used. The charge transport material used is not particularly limited as long as it is known as a charge transport material, and examples thereof include hydrazone compounds, stilbene compounds, butadiene compounds, triarylamine compounds, bistriarylamine compounds, carbazole compounds, polyvinylcarbazole. Examples thereof include compounds, oxadiazole compounds, oxazole compounds, pyrazoline compounds, triphenylmethane compounds and the like, and one kind or a mixture of two or more kinds can be used. The amount of charge transport material used is 20% of the total charge transport layer.
% To 90% by weight, preferably 30 to 80% by weight
% By weight.

The aniline compound represented by the general formula (1) is
One kind or a mixture of two or more kinds can be used. The amount of the aniline compound represented by the general formula (1) is 0.1% by weight to 50% by weight based on the entire charge transport layer,
It is preferably 0.1% by weight to 40% by weight. If the amount is larger than the above range, the amount of the charge transport material decreases and the sensitivity of the photoconductor decreases.

The binder used is not particularly limited as long as it is an insulating resin. For example, a condensation polymer such as polycarbonate, polyarylate, polyester, polyamide; polyethylene, polystyrene, styrene-acrylic copolymer. Addition polymers such as polyacrylate, polymethacrylate, polyvinyl butyral, polyvinyl acetal, polyvinyl formal, polyvinyl alcohol, polyacrylonitrile, polyacrylamide, acrylonitrile-butadiene copolymer; polysulfone, polyether sulfone, silicone resin, phenoxy resin, etc. It is preferably used, and one kind or a mixture of two or more kinds can be used. The amount of the binder used is 0.1% by weight to 80% by weight based on the total weight of the charge transport layer.

Additives used as necessary include
For example, antioxidant, ultraviolet absorber, dispersant, adhesive,
Examples include sensitizers, lubricants and plasticizers. The thickness of the charge transport layer is 10 μm to 50 μm, preferably 10 μm to
30 μm.

As described above, the general formula (1) in the present invention is
It is possible to obtain an electrophotographic photoreceptor containing the aniline compound represented by Since the charge transport layer, which is the outermost surface layer of the photoconductor, contains the aniline compound represented by the general formula (1) having a large dipole moment, the electrostatic attraction with the toner and the Van der Waals force are large. , Which gives a high image density.

On the other hand, it is said that when the dielectric constant of the photoconductor is large, that is, when the dipole moment is large, the charge mobility becomes small and the sensitivity becomes poor (JP-A-59).
-191044, JP-A-60-177345). It has also been pointed out that this is the cause of the reduction in resolution (Japanese Patent Laid-Open No. 59-229563). When such a phenomenon is observed, it can be solved by using a charge transport layer double layer type as shown in FIG. That is, the first charge transport layer 4 having a small dielectric constant is provided on the conductive support 1 and the charge generation layer 2 with a thickness of 10 μm to 25 μm, and the charge transport material, the aniline represented by the general formula (1), is provided thereon. 0.5 μm of the second charge transport layer 5 consisting of compound and binder
It may be provided with a thickness of 5 to 5 μm. Also in this case, as the charge transport material, the aniline compound represented by the general formula (1), and the binder, the same ones as described above can be used, and the amount used is also the same as the above.

[0032] In the charge transporting layer two-layer type, the first charge transport layer 4 having a thickness (d ₁₎ and the second charge-transporting layer 5 having a thickness (d ₂₎ is, d _1>
d ₂ and the dielectric constant of the photoreceptor is close to that of the first charge transport layer. Therefore, an increase in electrostatic attraction with the toner can hardly be expected, but the sensitivity, durability, and resolution are excellent. On the other hand, the Van der Waals force is related to the dipole moment of the surface of the photoconductor, and it becomes larger, and the image density becomes higher accordingly. In the present invention, both the function separation type and the charge transport layer double layer type described above can be used, and a high image density is provided.

[0033]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 4.1 g of X-type metal-free phthalocyanine, 4.1 g of polyvinyl butyral (S-REC BM-2, manufactured by Sekisui Chemical Co., Ltd.),
Cyclohexanone 200g, Glass beads (1φ) 650g
Was placed in a sand mill and kneaded for 2 hours to prepare a charge generation layer coating material. Using this paint, the surface of the aluminum cylinder (30φ) with a mirror finish has a film thickness of 0.15 after drying.
Dip coating was performed so that the thickness became μm, and the coating was dried. Next, 80 g of a butadiene compound represented by the following formula (CT-1)
10 g of the aniline compound represented by (2) and 80 g of a polycarbonate resin (Lexan 131-111, manufactured by Engineering Plastics Co., Ltd.) were dissolved in 450 g of dichloroethane to prepare a charge transport layer coating material. A dip coating was applied onto the charge generation layer previously coated with this coating so that the film thickness after drying was 25 μm, and the coating was dried.

[0035]

[Chemical 6]

The electrophotographic characteristics of the drum-shaped electrophotographic photosensitive member produced as described above were evaluated by a drum xerography tester. When charged at a corona voltage of −5.5 kV, the initial surface potential V ₀ was −750 V. The surface potential V ₂ after standing for 2 seconds in the dark was −740V. Then, the semiconductor laser (1 μW) having an oscillation wavelength of 780 nm was irradiated to determine the half-exposure amount E _1/2, which was 0.23 μJ / cm ² , and the residual potential V _R was −4.8 V. Next, after repeating the above operation 5,000 times, V ₀ , V ₂ , E _1/2 , and V _R were measured, and they were −740 V, −730 V, 0.24 μJ / cm ² , and −1, respectively.
It was 9.7 V and showed high sensitivity and high durability. On the other hand, a print test was carried out by mounting the electrophotographic photosensitive member manufactured by the same method as described above on a commercially available laser beam printer of the reversal phenomenon method by the blade cleaning method. As a result, the initial image density (ID) was 1.5 (measured with a Macbeth densitometer), BG (background) was 0.13 (color difference meter 1001DP,
It was measured by Nippon Denshoku Industries Co., Ltd., and after printing 5,000 sheets, ID = 1.5 and BG = 0.14, showing high image density.

Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1 except that the aniline compound represented by the formula (2) was omitted from the charge transport layer, and electrophotographic characteristics were evaluated by the same method. as a result,
Early _{V 0, V 2, E 1/2} , V R , respectively -740 V, -73
It was 0 V, 0.23 μJ / cm ² , and −2.5 V. Next, after repeating the above operation 5,000 times, V ₀ , V ₂ , E _1/2 , and V _R were measured, and were -730 V, -710 V, and 0.25 μJ / cm ² , respectively.
It was -17.7V, and showed high sensitivity and high durability. However, when the electrophotographic photosensitive member produced by the same method as the above was mounted on a commercially available laser beam printer of a reversal phenomenon method by a blade cleaning method and a print test was performed, initial ID was 1.2, BG was 0.29, and After printing 5,000 sheets, ID = 1.1 and BG = 0.29, and the image density was low.

Examples 2 to 8 Electrophotographic photoreceptors were prepared in the same manner as in Example 1 except that the aniline compound shown in Table 1 was used instead of the aniline compound represented by the formula (2). Characteristic,
And the ID was measured. The results are shown in Table 1. As can be seen from these, all showed high image density.

[0039]

[Table 1]

Example 9 In Example 1, as the charge transport material, the compound represented by the formula (CT-1) was used.
In place of the butadiene compound represented by
-2) A photoconductor was prepared in the same manner except that the hydrazone compound represented by -2) was used, and the electrophotographic characteristics were evaluated by the same method.

[0041]

[Chemical 7]

As a result, initial V ₀ , V ₂ , E _1/2 and V _R were -760 V, -750 V, 0.39 μJ / cm ² and -6.8 V, respectively. Next, after repeating the above operation 5,000 times, V ₀ , V ₂ ,
When E _1/2 and V _R were measured, they were −750 V and −74, respectively.
It was 0 V, 0.40 μJ / cm ² , and -41.5 V. When an electrophotographic photosensitive member manufactured by the same method as above was mounted on a commercially available laser beam printer of the reversal phenomenon method by a blade cleaning method, a print test was conducted, and the initial ID was 1.5.
, BG is 0.16, and after printing 5,000 sheets, ID = 1.5
, BG = 0.16, and although the sensitivity was not so high, the image density was high.

Comparative Example 2 A photoconductor was prepared in the same manner as in Example 9 except that the aniline compound represented by the formula (2) was omitted from the charge transport layer, and electrophotographic characteristics were evaluated by the same method. as a result,
Initial V ₀ , V ₂ , E _1/2 and V _R are −780V and −760, respectively.
V, 0.40 μJ / cm ² , and -9.2 V. Then, after repeating 5,000 times the _{operation, V 0, V 2, E} 1/2, was measured V _R, respectively -770 V, -760 V, 0.43μJ / cm 2,
It was -54.3V. However, when an electrophotographic photosensitive member manufactured by the same method as above was attached to a commercially available laser beam printer of a reversal phenomenon method by a blade cleaning method, a print test was performed, the initial ID was 1.1, and BG was
0.29, and after printing 5,000 sheets, ID = 0.9, BG =
The image density was 0.29 and the image density was low.

Example 10 4.1 g of X-type metal-free phthalocyanine, 4.1 g of polyvinyl butyral (S-REC BM-2, manufactured by Sekisui Chemical Co., Ltd.),
Cyclohexanone 200g, Glass beads (1φ) 650g
Was placed in a sand mill and kneaded for 2 hours to prepare a charge generation layer coating material. Using this paint, the surface of the aluminum cylinder (30φ) with a mirror finish has a film thickness of 0.15 after drying.
Dip coating was performed so that the thickness became μm, and the coating was dried. Next, 80 g of the butadiene compound represented by the formula (CT-1), 80 g of a polycarbonate resin (Lexan 131-111, manufactured by Engineering Plastics Co., Ltd.) were added to dichloroethane 4
It was dissolved in 50 g to prepare a coating material for the first charge transport layer. The film thickness after drying on the charge generation layer previously coated with this paint is
The first charge transport layer was prepared by dip coating and drying to a thickness of 20 μm. Next, 80 g of the butadiene compound represented by the formula (CT-1), 10 g of the aniline compound represented by the formula (2), and 80 g of a polycarbonate resin (Z-200, manufactured by Mitsubishi Gas Chemical Co., Inc.) were dissolved in 450 g of toluene. A coating material for the second charge transport layer was prepared. A second charge-transporting layer was prepared by dip-coating the first charge-transporting layer previously coated with the coating composition so that the film thickness after drying was 5 μm and drying.

The charge transport layer two-layer type electrophotographic photosensitive member produced as described above was evaluated in the same manner as in Example 1.
As a result, the initial V ₀ , V ₂ , E _1/2 , and V _R are -760, respectively.
V, -740V, 0.24 μJ / cm ² , and -0.3V. Next, after repeating the above operation 5,000 times, V ₀ , V ₂ , E _1/2 , V
_{When R} was measured, it was -750 V, -730 V, and 0.
It was 24 μJ / cm ² and −4.4 V, and was higher in sensitivity and higher in durability than Example 1. On the other hand, when an electrophotographic photosensitive member manufactured by the same method as above was mounted on a commercially available laser beam printer of the reversal phenomenon method by a blade cleaning method, a print test was conducted, and the initial ID was 1.5 and BG was 0.15.
After printing 5,000 sheets, ID = 1.5, BG = 0.16
And showed a high image density.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a function-separated electrophotographic photosensitive member.

FIG. 2 is a schematic cross-sectional view of a two-layer charge transport layer electrophotographic photoreceptor.

[Explanation of symbols]

 1 Conductive Support 2 Charge Generation Layer 3 Charge Transport Layer 4 First Charge Transport Layer 5 Second Charge Transport Layer

Claims (1)

[Claims] 1. An electrophotographic photosensitive member comprising a conductive support, and a charge generation layer and a charge transport layer provided on the conductive support as essential components, and the following general formula in a charge transport layer which is an outermost surface layer: An electrophotographic photoreceptor comprising the aniline compound represented by (1). [Chemical 1] (In the formula, R ₁ and R ₂ represent an alkyl group, and R ₁ and R ₂ may form a ring together with a nitrogen atom. A represents a cyano group or a nitro group.)