JPH04155348A - Electrophotography photosensitive body - Google Patents

Abstract

PURPOSE:To obtain a photosensitive body high in sensitivity and excellent in stability by containing specified enamine derivatives in an electric charge transport layer. CONSTITUTION:As electric charge generating material to be contained in an electric charge generating layer 1, the various kinds of dye stuff and pigments in an azo series and a phthalocyanine series shall be used. An electric charge transport layer 2 is formed in such a way that enamine derivates 5 indicated by a formula (I) are dissolved into solvent medium together with binder while being coated over the layer 1 so as to be dried. When enamine derivatives 5 indicated by the structural formula (I) is contained in the layer 2, the level of energy involved in electron hole transportation comes close to the level of energy of electron holes generated within electric charge generating material, so that high sensitivity is thereby exhibited. In addition, since remaining potential is low, characteristic are not deteriorated at all regardless of repeated use, excellent stability can thereby be secured continuously.

Description

[Detailed Description of the Invention] [Summary] An object of the present invention is to provide an electrophotographic photoreceptor having high sensitivity and excellent continuous stability, which is widely used in copying machines, printers, etc. that apply an electrophotographic method. An electrophotographic photoreceptor having at least a charge generation layer and a charge transport layer on a conductive support, wherein the charge transport layer contains an enamine derivative represented by the following structural formula (I). do.

(I) (Ar represents a phenyl group which may be substituted with lower alkyl or lower alkoxy, or a naphthyl group, R,,R
2 represents a lower alkyl group, or a phenyl group which may be substituted with a lower alkyl group, dialkylamino group, or lower alkoxy group. ) [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor that is widely used in copying machines, printers, etc. that apply an electrophotographic method.

As an example of electrophotography, a common method is to obtain a printed matter by repeating the steps of charging, exposing, developing, transferring, and fixing.

Charging applies a uniform positive or negative electrostatic charge to the surface of a photoconductive photoreceptor. 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 called toner, thereby forming a visible image of the toner on the photoreceptor. Finally, this toner image is electrostatically transferred onto recording paper and fused using heat, light, pressure, etc. to obtain a printed matter.

[Prior Art] Inorganic photoreceptors typified by selenium-based photoreceptors have been widely used as photoreceptors having photoconductivity.

This inorganic photoreceptor has high sensitivity and is resistant to mechanical wear.
Although it has the advantage of being suitable for high-speed, large-scale machines, it is expensive because it must be manufactured using a vacuum evaporation method, and it must be recovered because it is harmful to the human body. The problem was that it was difficult to apply to low-cost machines.

Organic photoreceptors were developed as an alternative to inorganic photoreceptors. This material can be manufactured by a coating method, so it is easy to reduce costs through mass production, it has a wider range of material selection than inorganic photoreceptors that use inorganic substances such as selenium, so it is possible to select non-hazardous compounds, and it is easy to reduce the cost of mass production. It has the advantage of being maintenance-free.

In particular, as shown in FIG. 2, a functionally separated laminated photoreceptor in which a charge generation layer 1 and a charge transport layer 2 are laminated has attracted attention. Here, the charge generation layer 1 has a function of absorbing incident light and generating electron-hole pairs (carrier pairs), and the charge transport layer 2 retains a charge on its surface, and the charge generation layer 1 has a function of generating electron-hole pairs (carrier pairs). It has the function of transporting one of the generated carriers to the surface of the photoreceptor to form an electrostatic latent image.

The charge generation layer 1 is formed by forming a charge generation substance that absorbs light and generates carrier pairs into a vapor deposited film or 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 2 is formed by dissolving a charge transport material having a carrier transport function in a binder resin. As charge transport substances, electron transport charge transport substances such as trinitrofluorenone and chloranil, which have the property of transporting electrons,
There are hole-transporting charge-transporting substances such as hydrazone and pyrazoline that have the property of transporting holes, and polycarbonate, styrene-acrylic, and the like are used as the binder resin.

By separating the functions of the photoreceptor into two layers in this way, it is possible to select the optimal compound for each function almost independently, improving various properties such as sensitivity, spectral characteristics, and mechanical abrasion resistance. can be done.

In FIG. 2, 3 is a photosensitive layer, and the photosensitive layer 3 is composed of a charge generation layer 1 and a charge transport layer 2.

A photosensitive layer 3 is formed on a conductive support 4 .

[Problems to be Solved by the Invention] However, such organic photoreceptors have a problem in that their sensitivity is still lower than that of inorganic photoreceptors such as selenium, making it difficult to apply them to high-speed printers.

In addition, as the charging-exposure process is repeated, the charge transport material deteriorates due to the ozone generated during charging and the laser irradiated with high brightness, resulting in a decrease in the charging potential and an increase in the residual potential, resulting in a decrease in continuous stability. There was a problem with this.

The present invention has been made in view of these conventional problems, and an object of the present invention is to provide an electrophotographic photoreceptor having high sensitivity and excellent continuous stability.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an electrophotographic photoreceptor having at least a charge generation layer and a charge transport layer on a conductive support, comprising: It contains an enamine derivative represented by structural formula (I).

Hereinafter, the present invention will be explained in further detail with reference to FIG. 1 as necessary.

In FIG. 1, 1 is a charge generation layer, 2 is a charge transport layer, and 3 is a charge generation layer.
is a photosensitive layer consisting of a charge generation layer 1 and a charge transport layer 2; 4 is a conductive support; and 5 is an enamine derivative represented by the structural formula (I).

First, the conductive support 4 may be anything that can ground the photoreceptor, such as various metal cylinders, cylinders made of conductive resin or paper, insulating cylinders with metal vapor-deposited or laminated on the surface, An insulating cylinder coated with a conductive organic thin film, a film having the same structure as above, etc. can be used.

As the charge generating substance constituting or contained in the charge generating layer 1, various dyes and pigments such as azo, phthalocyanine, indigo, perylene, squarylium, and quinone can be used. However, particularly when phthalocyanine pigments are used, good sensitivity can be obtained. As the phthalocyanine, metal-free phthalocyanine,
Copper phthalocyanine, aluminum chloride phthalocyanine,
Various metal phthalocyanines such as titanyl phthalocyanine, vanadyl phthalocyanine, and indium phthalocyanine can be used. The charge generation layer 1 is a conductive support 4
It is formed by vapor depositing these charge generating substances thereon, or by coating and drying a mixture dispersed in a solvent together with a binder resin. Binder resins include various resins such as polyester, polyvinyl alcohol, polyvinyl acetal, polyamide, epoxy, and silicone.
Alternatively, various organic compounds having film-forming properties such as casein can be used, and are selected in consideration of adhesion to the base, dispersibility of the charge generating substance, etc.

The solvent is selected according to 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,
Various organic solvents such as ethyl acetate can be used alone or in combination. Methods for coating the support 4 include dip coating, spray coating, wire barcode coating, and doctor blade coating. Film thickness is 0.01~3μm
It is desirable that the thickness be 1 μm or less.

The charge transport layer 2 is formed by dissolving the compound represented by the structural formula I in a solvent together with a binder resin, coating the solution on the charge generation layer 1, and drying the solution. The structural formula I
The compound represented by can be synthesized from dialkylamine (1) and dialdehyde (m) represented by the following structural formulas, respectively, by a known dehydration condensation reaction. Examples of compounds are shown in Table 1.

R, -N-H (II) OHCH2CARr CH2CHO (m) (Ar represents a phenyl group that may be substituted with lower alkyl or lower alkoxy, or a naphthyl group, R,, R
2 represents a lower alkyl group, or a phenyl group which may be substituted with a lower alkyl group, dialkylamino group, or lower alkoxy group. ) In general, in the case of a laminated photoreceptor such as the one of the present invention, the sensitivity is determined by: (1) carrier generation efficiency in the charge generation layer 1, (2) carrier injection efficiency from the charge generation layer 1 to the charge transport layer 2, and (2) charge transport layer 2. It is said that the higher the carrier transport efficiency and the closer the product of these efficiencies to 1, the higher the sensitivity.

Carrier injection from the charge generation layer 1 to the charge transport layer 2 involves separation of electron-hole pairs generated in the charge generation material in the charge generation layer 1, and the isolated holes are transferred from the charge generation material by electric field energy. It is believed that this is achieved by migration to the charge transport material in the transport layer 2. At this time, the closer the respective energy levels involved in the movement of holes, the more
The transfer efficiency (ie, carrier injection efficiency) is said to be high.

In the present invention, since the enamine derivative represented by the structural formula (I) is contained in the charge transport layer 2, the energy level involved in hole transport is equal to the energy level of holes generated in the charge generating substance. This is considered to be the reason for the high sensitivity. In addition, the sensitivity is particularly good with phthalocyanine, probably because the energy levels of phthalocyanine and enamine derivatives are close to each other.

It is believed that hole transport in the charge transport layer 2 is achieved by the holes injected from the charge generation layer 1 hopping and conducting charge transport particles toward the surface.

Therefore, it can be said that the easier hole hopping occurs, the higher the carrier transport efficiency. The enamine derivative of the present invention has a longer resonance structure than a hydrazone compound, and its electron orbits are large and extend outward. Therefore, the molecular orbitals of the charge transport materials uniformly distributed in the charge transport layer 2 have a large overlap, which makes it easier for hole hopping to occur, and it is considered that the carrier transport efficiency is high.

For the above reasons, it is believed that the photoreceptor of the present invention exhibits higher sensitivity than those using conventional charge transport materials.

Furthermore, since a low residual potential is obtained, excellent continuous stability is obtained without deterioration of characteristics even after repeated use.

Next, as the binder resin for the charge transport layer 2, 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 1, depending on the binder resin used. A coating method similar to that for the charge generation layer 1 can be used. The film thickness is 5 to 50 μm, preferably 10 to 30 μm.

In addition to the enamine derivative, the charge transport layer 2 contains:
Other hole-transporting charge-transporting substances such as hydrazone derivatives and pyrazoline derivatives may also be added. At that time, the mixing ratio of other charge transport substances to enamine derivatives is 1
A range of 00.1 to 100:500 is desirable.

Further, the stacking order of the charge transport layer 2 of the charge generation layer 1 may be reversed.

Between the conductive support 4 and the charge-generating layer 1, there are various steps such as improving adhesion, flattening the surface of the support, covering defects on the surface of the support, controlling the injection of hot carriers, and improving charge acceptance and charge retention. A subbing layer may be provided for this purpose. The constituent material of the undercoat layer may be a film-forming material such as various binder resins or casein used in the charge generation layer 1 or the charge transport layer 2, or a material containing a conductive substance therein. A material whose resistance value is adjusted to 1014 Ω·cm or less can be used. Conductive substances for adjusting the resistance value of the undercoat layer include various metal powders, conductive metal oxide powders,
Any conductive material such as carbon may be used.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 1 part (by weight) of titanium oxide phthalocyanine, 1 part of polyester, 9 parts of dichloromethane, and 9 parts of dichloroethane were dispersed and mixed for 24 hours using a hard glass pole and a hard glass pot, and a mixture was mixed on the aluminum surface of an aluminum vapor-deposited polyester film. The charge generating layer was coated with a doctor blade and dried at 100° C. for 1 hour to form a charge generation layer with a thickness of 0.3 μm.

Next, 1 part of the enamine derivative N11l shown in Table 1 and 1 part of polycarbonate were dissolved in 10 parts of tetrahydrofuran, and the solution was applied onto the charge generation layer using a doctor blade.
The photoreceptor of Example 1 was obtained by drying at 70° C. for 2 hours to form a charge transport layer with a thickness of about 17 μm.

Comparative Example A photoreceptor of a comparative example was obtained in the same manner as in Example 1 except that a hydrazone derivative represented by the following structural formula was used instead of the enamine derivative as a charge transport substance.

The following measurements were performed on the above two types of photoreceptors. First, -5
Corona charging is performed at 1 V, and the surface potential after 1 second is V o (V
). From that moment, exposure is performed with incident light of 780 nm, and the time t1/2 until the surface potential becomes half of Vo is determined to calculate the half-reduced exposure amount El/2 (μJ7'caf).

Furthermore, the surface potential V r at 10 t 1/2 after the start of exposure
(V) is recorded, and finally the process is completed by eliminating the charge using a 6Hnm LED. Table 2 shows the results of repeating this process 5000 times.

As can be seen from Table 2, the photoreceptor of Example 1 has an E1/2 value 40 to 50% smaller than that of the comparative example, and therefore has high sensitivity. Further, even after 5000 consecutive tests, there was no decrease in sensitivity or increase in residual potential Vr, and it is considered that there is no deterioration in characteristics. On the other hand, although the photoreceptor of the comparative example shows relatively good characteristics at the initial stage, after continuous testing, the photoreceptor deteriorates with a decrease in sensitivity and an increase in residual potential.
or fatigue).

Examples 2 to 4 Example 2 was carried out in exactly the same manner as in Example 1 except that the enamine derivatives shown in Table 1 were used as the enamine derivatives in the charge transport layer.
- 4 photoreceptors were prototyped.

This photoreceptor was subjected to the same tests as in Example 1, and the results are shown in Table 2.

M] Compound of Example! 12 [Effects of the Invention] As explained above, according to the present invention, since the charge transport layer contains the enamine derivative represented by the structural formula (I), high sensitivity and excellent continuous stability can be achieved. It is possible to obtain a photoreceptor having the following properties.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of the present invention, FIG. 2 is a configuration diagram of a conventional example. In the figure, 1... Charge generation layer, 2...charge transport layer, 3...photosensitive layer, 4... Conductive support, Death: Enamine derivative.

Claims (1)

[Scope of Claims] An electrophotographic photoreceptor having at least a charge generation layer and a charge transport layer on a conductive support, wherein the charge transport layer contains an enamine derivative represented by the following structural formula (I). An electrophotographic photoreceptor featuring: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (Ar represents a phenyl group that may be substituted with lower alkyl or lower alkoxy, or a naphthyl group, and R_1
, R_2 is a lower alkyl group or a lower alkyl group,
Represents a phenyl group which may be substituted with a dialkylamino group or a lower alkoxy group. )