JPH0259761A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve sensitivity and continuous stability by incorporating a specific triarylamine deriv. into a charge transfer layer. CONSTITUTION:The triarylamine deriv. expressed by the formula I is incorporated as the charge transfer material into the photosensitive body. In the formula I, X1 and X2 respectively denote hydrogen or lower alkyl groups which may be the same as or different form each other; Ar1 to Ar4 respectively denote substd. or unsubstd. aryl groups which may be the same as or different from each other. The charge transfer layer is formed by dissolving the triarylamine deriv. expressed by the formula I together with a binder in a solvent and applying the soln. onto a charge generating layer, then drying the coating. The photosensitive body which exhibits the high sensitivity and low residual potential and is not deteriorated in characteristics even in repetitive use is obtd. in this way.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a functionally separated laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are laminated, which exhibits high sensitivity and low residual potential, and which exhibits no deterioration of characteristics even after repeated use. A triarylamine derivative represented by the following general formula (I): (In the above formula, X and X2 may be the same or different from each other, each represents hydrogen or a lower alkyl group, and A r l + A r Z + A r 3 and Ar
may be the same or different and each represents a substituted or unsubstituted aryl group) as a charge transport substance.

[Industrial application field]

The present invention relates to an electrophotographic photoreceptor, and more specifically, to a functionally separated layered electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are laminated. The electrophotographic photoreceptor of the present invention includes:
It can be widely and advantageously used in fields such as copying machines and printers.

[Conventional technology]

As is well known, electrophotographic photoreceptors can be widely applied to copying machines, printers, etc. that utilize electrophotography.

Further, the electrophotographic process consists of the steps of charging, exposure, development, transfer, and fixing, and printed matter can be obtained by repeating these steps. Here, charging applies a uniform positive or negative electrostatic charge to the surface of the photoreceptor having photoconductivity.

In the subsequent exposure process, an electrostatic latent image corresponding to the image information is formed on the photoreceptor by irradiating it with laser light or the like to erase the surface charge on a specific portion.

Next, this latent image is electrostatically developed with powder ink generally called toner, thereby forming a visible toner image on the photoreceptor. Finally, this toner image is electrostatically transferred onto recording paper and fused using heat, light, pressure, or the like. Through such a series of processes, desired printed matter can be obtained.

Conventionally, inorganic photoreceptors typified by selenium-based photoreceptors have been widely used as photoreceptors having photoconductivity as described above.

However, while this inorganic photoreceptor has the characteristics of being highly sensitive, resistant to mechanical abrasion, and suitable for high-speed, large-scale machines, it must be manufactured using a vacuum deposition method and is harmful to the human body. Due to the high cost and maintenance-free, small-sized and maintenance-free
The problem was that it was difficult to apply to low-cost machines.

Organic photoreceptors have been developed as an alternative to inorganic photoreceptors. Organic photoreceptors can be manufactured by a coating method, making it easy to reduce costs through mass production.Compared to inorganic photoreceptors that use inorganic substances such as selenium, organic photoreceptors have a wider range of material selection, so non-toxic compounds can be selected. It is also possible to make it maintenance-free by disposing of it by the user.
It has the following characteristics.

In particular, a functionally separated laminated photoreceptor in which a charge generation layer and a charge transport layer are laminated is attracting attention. Here, the charge generation layer has a function of absorbing incident light and generating electron-hole pairs (carrier pairs), and the charge transport layer retains a charge on its surface, and the charge generation layer It has the function of transporting one of the carriers generated in the process to the surface of the photoreceptor to form an electrostatic latent image. The charge generation layer may be a vapor-deposited film of a charge generation substance that absorbs light and generates carrier pairs, or
Alternatively, it is formed by dispersing it in a binder resin. Azo pigments, phthalocyanine, and the like are known as charge-generating substances, and polyester, polyvinyl butyral, and the like are used as binder resins. The charge transport layer is formed by dissolving a charge transport material having carrier transport ability in a binder resin. Charge transport materials include electron transport charge transport materials such as trinitrofluorenone and chloranil, which have the property of transporting electrons, and hole transport charge transport materials such as hydrazone and pyrazoline, which have the property of transporting holes. Polycarbonate, styrene-acrylic, etc. are used as the binder resin.

By separating the functions of the photoreceptor into two layers, the charge generation layer and the charge transport layer, it is possible to select the optimal compound for each function almost independently, resulting in improved sensitivity, spectral characteristics, and charge retention. It is possible to improve mechanical properties such as high-speed response and mechanical wear resistance.

[Problem to be solved by the invention]

However, conventional organic photoreceptors still have lower sensitivity than inorganic photoreceptors such as selenium, and therefore are difficult to apply to high-speed printers. Furthermore, as the charge-transporting material used in conventional photoreceptors is repeatedly subjected to the charging-exposure process for forming electrostatic latent images, it deteriorates due to ozone generated during charging and laser irradiation with brightness. This causes a decrease in printing quality due to a decrease in charging potential and an increase in residual potential.

Therefore, an object of the present invention is to provide an electrophotographic photoreceptor that exhibits high sensitivity and low residual potential, and whose characteristics do not deteriorate even after repeated use.

[Means to solve the problem]

The above object, according to the present invention, is a triarylamine derivative represented by the following general formula (I): (In the above formula, Xl and X2 may be the same or different from each other, and are hydrogen or lower alkyl and Ar+ + Arz + Arz and Ar4 may be the same or different from each other and each represents a substituted or unsubstituted group) as a charge transport substance. This can be achieved by a separate laminated electrophotographic photoreceptor.

The triarylamine derivative of general formula (I) used as a charge transport material in the present invention preferably has
Xl and X2 in the formula are hydrogen or a methyl group,
A lower alkyl group such as an ethyl group or a propyl group, and Ar, , Ar2, Ar3 and Ar are unsubstituted or a halogen such as chlorine or bromine, or a lower alkyl group such as a methyl group, an ethyl group or a propyl group, methoxy group,
It is a lower alkoxy group such as an ethoxy group or a butoxy group, or a phenyl group or a naphthyl group substituted with another group. Such trialamine derivatives can be prepared according to conventional methods from commercially available triarylamine as a starting material.

Previous generation (I) that can be advantageously used in the present invention
Typical examples of triarylamine derivatives are listed in Table 1 below.

As explained in the prior art section, the electrophotographic photoreceptor according to the present invention has a layer structure of a functionally separated layered photoreceptor in which a charge generation layer and a charge transport layer are laminated. An example of such a photoreceptor is a photoreceptor as shown in FIG. 1. An electrophotographic photoreceptor 5 includes a support 1, a charge generation layer 2 and a charge transport layer sequentially laminated thereon. It consists of 3.

The photosensitive layer 4 refers to a laminate of the charge generation layer 2 and the charge transport layer 3. Note that, if necessary, the positions of layer 2 and layer 3 can be reversed to reverse the direction of current flow.

In the electrophotographic photoreceptor of the present invention, the support may be anything as long as it is conductive and can ground the photoreceptor, such as various metal cylinders, cylinders made of conductive resin or paper, and insulating materials. It is possible to use a cylinder in which metal is vapor-deposited or laminated on the surface of the cylinder, a conductive organic thin film on an insulating cylinder, a film having the same structure as above, and the like.

Various dyes and pigments such as azo-based, phthalocyanine-based, indigo-based, perylene-based, squarylium-based, quinone-based, etc. are used as the charge-generating substance that should constitute or be contained in the charge-generating layer. However, particularly when phthalocyanine pigments are used, good sensitivity can be obtained. As the phthalocyanine, various metal phthalocyanines can be used, such as metal-free phthalocyanine, copper phthalocyanine, aluminum chloride phthalocyanine, titanyl phthalocyanine, vanadyl phthalocyanine, and indium phthalocyanine.

The charge generation layer is formed by vapor depositing the above charge generation substance on the support, or by coating and drying a mixture dispersed in a solvent together with a binder resin. Binder resins include polyester, polyvinyl alcohol,
Various resins such as polyvinyl acetal, polyamide, epoxy, and silicone, or various organic compounds with film-forming properties such as casein can be used, and the material is selected in consideration of adhesion to the substrate and dispersibility of the charge-generating substance. .

The solvent is selected depending on the charge generating substance and binder resin used, but examples include tetrahydrofuran, dioxane, methanol, ethanol, hexane, ether, dichloromethane, dichloroethane, benzene, toluene, chlorobenzene, xylene, methyl cellosolve, ethyl cellosolve, and ethyl acetate. Various organic solvents such as these can be used alone or in combination. Methods for coating the support include dip coating, spray coating, wire barcode coating, and doctor blade coating. Film thickness is approximately 0.01~
It is desirable to set the amount to 3 points, especially about 1 p or less.

The charge transport layer is prepared by dissolving a triarylamine derivative represented by the general formula (r) in a solvent together with a binder resin,
It is formed by coating on the charge generation layer and drying it.

As the binder resin for the charge transport layer, known binder resins such as polyester, polycarbonate, polystyrene, polyacrylonitrile, acrylic-styrene, and polysulfone can be used. The solvent is appropriately selected from the same solvents as those used for coating the charge generation layer, depending on the binder resin used.

As for the coating method, the same method as in the case of the charge generation layer can be used. The film thickness is approximately 5 to 50-1, especially 10 to 30 tr.
It is desirable to set it to m.

In addition to the triarylamine derivative (I), other hole-transporting charge-transporting substances such as hydrazone derivatives and pyrazoline derivatives may be added to the charge-transporting layer. At that time, the mixing ratio of the other charge transport substance to the triarylamine derivative is 100:1 to 100:
A range of 500 is desirable.

Furthermore, improvements in adhesion, flattening of the surface of the support, covering of defects on the surface of the support, control of hot carrier injection, and improvement of charge acceptance and charge retention between the conductive support and the charge generation layer are provided. A subbing layer may be provided for purposes such as the following. The constituent material of the undercoat layer may be a film-forming material alone such as various binder resins or casein used in the charge generation layer or charge transport layer, or a conductive material may be added therein to increase the resistance value. It is possible to use a material whose resistance is adjusted to 10'4 Ω·cm or less. As the conductive substance for adjusting the resistance value of the undercoat layer, any substance having conductivity may be used, such as various metal powders, conductive metal oxide powders, and carbon.

[For production]

As a result of using a specific triarylamine derivative as a charge transport material, the electrophotographic photoreceptor according to the present invention has high sensitivity and excellent continuous stability (the sensitivity changes over time), as will be made clear in the following examples. (no deterioration) is obtained.

〔Example〕

Next, the present invention will be explained in more detail by describing examples and comparative examples of the present invention. In addition, in the examples, "parts" means "parts by weight" unless otherwise specified.

1 part of pan-earth oxidized titanium phthalocyanine, 1 part of polyester, 9 parts of dichloromethane, and 9 parts of dichloroethane were dispersed and mixed for 24 hours using hard glass beads and a hard glass pot. The resulting mixture was applied onto the aluminum surface of an aluminized polyester film using a doctor blade and dried at 100° C. for 1 hour to form a charge generation layer having a thickness of about 0.3 −.

Next, a triarylamine derivative (
1 part of the compound 2) and 1 part of polycarbonate were dissolved in 10 parts of tetracarbonate, coated on the charge generation layer with a doctor blade, and dried at 70°C for 2 hours to form a charge transport layer with a film thickness of about 17 cm. formed a layer. An electrophotographic photoreceptor as shown in FIG. 1 was obtained.

The following measurements were carried out on the obtained photoreceptor: First, 5k
Corona charging is performed with V, and the surface potential after 1 second is Vo (V). From that moment, exposure is performed with 780 nm incident light,
The time tl/Z until the surface potential becomes half of Vo is determined, and the half-reduction exposure amount El/□ (μJ/cni) is calculated.

Furthermore, the surface potential of 10 jl/□ after the start of exposure, that is, the residual potential, Vr (V), is recorded. Finally, 630n
The process is completed by eliminating static electricity using the LED m. The results of repeating this process 10,000 times are shown below.
Shown in the table.

MA91 The procedure described in Example 1 above was repeated. However, in this example, a hydrazone derivative (a known substance) represented by the following structural formula was used as the charge transport substance instead of the triarylamine derivative.

2: The procedure described in Example 1 above was repeated for 11 pairs. However, in this example, the triarylamine derivative of Example 1 (compound number 2)
Instead, the compounds listed in Table 2 below (compounds 8, 10, 18 and 22 in Table 1) were used. As shown in the results in Table 2 below, satisfactory results were obtained.

The results obtained are shown in Table 2 below.

As can be seen from the results of Example 1 and Comparative Example 1 shown in Table 2, the photoreceptor of the present invention has a smaller value of El/□ than the Comparative Example, and therefore has high sensitivity.

Furthermore, even after 10,000 continuous tests, there was no decrease in sensitivity or increase in residual potential Vr, and it is considered that there is almost no deterioration in characteristics. On the other hand, the photoreceptor of the comparative example
Despite exhibiting relatively good characteristics initially, after continuous testing, sensitivity decreased and residual potential increased, indicating that the photoreceptor had deteriorated (or become fatigued).

〔Effect of the invention〕

According to the present invention, by containing a specific triarylamine derivative in the charge transport layer, an electrophotographic photoreceptor is obtained which provides high sensitivity and low residual potential and does not cause deterioration of characteristics even after repeated use. be able to.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a preferred example of the layer structure of the electrophotographic photoreceptor according to the present invention. In the figure, ■ is a support, 2 is a charge generation layer, 3 is a charge transport layer,
4 is a photosensitive layer, and 5 is a photoreceptor. 1...Support 2...Charge generation layer...Charge transport layer 4...Photosensitive layer 5...Photoreceptor

Claims (1)

[Claims] 1. Triarylamine derivative represented by the following general formula (I): ▲There are numerical formulas, chemical formulas, tables, etc.▼(I) (In the above formula, X_1 and X_2 are the same or different from each other. each represents hydrogen or a lower alkyl group, and Ar_1, Ar_2, Ar_3 and Ar_4 may be the same or different from each other and each represents a substituted or unsubstituted aryl group) as a charge transport substance. A functionally separated laminated electrophotographic photoreceptor characterized by: