JPH0222662A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a photosensitive body little in change of initial acceptance potential before and after exposure to light by using 2 kinds of hydrazone compounds as an electric charge transfer material and a specified polymer as a binder resin in a charge transfer layer. CONSTITUTION:The charge transfer layer contains a mixture of 2 kinds of hydrazone compounds as the charge transfer materials represented by formulae A and B, respectively, in which each of R1-R5 is alkyl or the like; each of m and n is an integer of >=0; each of R6-R10 is aryl or the like. Said charge transfer layer is formed by combining said charge transfer material with the binder polymer which forms a film having an optical forbidden band width Egopt of >=2.78eV at the time of combining only with the compound A, on the contrary, a film having that of <2.78eV at the time of combining only with the compound of formula B, thus permitting the obtained photosensitive body to be very little in change of initial acceptance potential before and after exposure even if it is exposed to the light of a fluorescent light or the like, and good in sensitivity.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and more specifically to an electrophotographic copying machine, printer, etc., which are equipped with a charge generation layer and a charge transport layer containing an organic material. The present invention relates to a laminated electrophotographic photoreceptor used for.

[Conventional technology]

In recent years, research on organic photoconductive substances has been widely advanced as photosensitive materials for electrophotographic photoreceptors (hereinafter also referred to as photoreceptors). Photosensitive materials using organic photoconductive substances have greater flexibility, thermal stability, film-forming properties, and transparency than those using inorganic photoconductive substances such as selenium, which have been mainly used in the past. Although it has many advantages such as price, it has disadvantages such as poor dark resistance and light sensitivity. Taking advantage of the ease of film formation, the photosensitive layer of the photoreceptor functions as a layer that primarily contributes to charge generation, and a layer that primarily contributes to surface charge retention in the dark and charge transport during light reception. Practical progress is being made by laminating separate layers, selecting and using materials suitable for the functions of each layer, and improving the electrophotographic properties as a whole.

For example, the Carlson method is applied to image formation by electrophotography using these photoreceptors.

Image formation using this method involves charging a photoconductor in a dark place by corona discharge, forming electrostatic latent images such as letters and pictures on a document by exposing the surface of the charged photoconductor to light, and This is done by developing the image with toner, transferring the developed toner image to a support such as paper, and fixing it. After the toner image is transferred, the photoreceptor is charged.

After residual toner is removed and static electricity is removed, it is reused. Further, this image formation is classified into a positive charging method and a negative charging method depending on the charging polarity of the surface of the photoreceptor.

The above-mentioned laminated photoreceptor usually has a charge generation layer containing an organic charge generation substance and a charge transport layer containing an organic charge transport substance stacked one after another on a conductive substrate, and a negative charging method is applied to image formation. In some cases, a charge transport layer, a charge generation layer, and a coating layer are sequentially laminated on a conductive substrate, and a positive charging method is applied to image formation. In the case of a negative charging method, a charge generation layer is first formed on a conductive substrate such as aluminum, copper, or stainless steel. This charge generation layer is made of phthalocyanine compounds that have an absorption peak in the infrared region for printers, azo compounds that have an absorption peak in the visible region for copiers, and polyester, polymethyl methacrylate, etc. It is formed by applying a material mixed with a resin binder in an organic solvent by a dip method, a spray method, or the like. Next, by similarly applying a material in which an organic charge transporting substance such as a pyrazoline compound or a hydrazone compound and a resin binder such as polycarbonate are uniformly dissolved in an organic solvent,
A charge transport layer is formed to form a photoreceptor. In the case of a positive charging method, a charge transport layer and a charge generation layer are coated on a conductive substrate in this order, and finally, a coating layer is coated with an organic insulating material such as polyester or polyamide to protect this charge generation layer. It is used to form a photoreceptor. In the case of the positive charging method, the charge generation layer and the charge transporting layer are substantially the same as those in the negative charging method.

[Problem to be solved by the invention]

However, such a laminated organic photoreceptor has a capacity of 1500 fu.
By exposing the photoreceptor to a fluorescent lamp of about x, the characteristics of the photoreceptor after exposure change significantly. Table 1 lists p-diethylaminobenzaldehyde-diphenylhydrazone and 1-phenyl to 3-(p-diethylaminostyryl)
-5-(varadiethylaminophenyl)-2-pyrazoline was used as a charge transport material and polycarbonate was used as a resin binder to form a charge transport layer. This figure shows the initial charging potential changes on the surface of the photoreceptor immediately after corona discharge at -4.5 kV before and after exposure to a fluorescent lamp. The charge generation layer of these laminated organic photoreceptors contains X-type phthalocyanine as a charge generation substance and Vylon as a resin binder (as shown in Table 1 of Toyobo Co., Ltd., the photoreceptor is The initial charging potential of the photoreceptor varies greatly. Therefore, when this type of laminated organic photoreceptor is incorporated into an actual printer or copier, the photoreceptor will be turned off by the room light when replacing the photoreceptor or clearing paper jams. As a result of being exposed to When diethylaminobenzaldehyde-diphenylhydrazone is used, the charged potential after exposure to a increases compared to before exposure, whereas 1-phenyl-3-(
A decrease is observed when p-diethylaminostyryl)-5-(para-diethylaminophenyl)-2-pyrazoline is used.

Therefore,! ! In order to stabilize the charging potential before and after exposure, we investigated using a mixed system of both of these charge-transporting substances, and as shown in Table 2, the charging potential change was resolved, but the initial photoreceptor characteristics This causes a decrease in sensitivity, that is, an increase in half-attenuation exposure, which poses a practical problem. Note that the half-attenuation exposure amount is when the photoreceptor is exposed to 16 kV in a dark place.
After being charged by corona discharge for 0 seconds, a wavelength of 78
It was determined as the exposure amount (μJ/cut) until the charged potential was halved by irradiating monochromatic light of 1 μW at 0 nm.

Table 2 This invention has been made in view of the above points, and includes:
In a laminated photoconductor equipped with a charge generation layer and a charge transport layer containing an organic material, even when irradiated with light such as a fluorescent lamp,
The initial charging potential hardly changes before and after exposure to light, and
An object of the present invention is to provide an electrophotographic photoreceptor for use in copying machines and printers, which has excellent electrophotographic properties and good sensitivity.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an electrophotographic photoreceptor comprising a charge generation layer containing an organic material and a charge transport layer on a conductive substrate, wherein the charge transport layer has a charge transport property. At least one first compound of the hydrazone compounds having the following Funabashi formula (Δ) that acts as a substance and at least one second compound of the hydrazone compounds having the Funabashi formula (B) below. and a resin binder that binds these charge transporting substances to each other to form a charge transport layer, and the resin binder is such that the optical bandgap width of the layer formed in combination with only the first compound is 2. For electrophotography using an organic polymer resin that satisfies both the conditions that the voltage is .78 eV or more, and the optical band gap of the layer formed in combination with only the second compound is less than 2.78 eV. Use as a photoreceptor.

[In formula (A), R and R3 represent any of the following optionally substituted alkyl groups, alkenyl groups, and aralkyl groups, and Ro and R9 are alkyl groups, alkenyl groups, aralkyl groups, and aryl groups. R5 is a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, or an aryl group.

It represents any of the hydroxy groups, and m represents an integer of 0 or more. ] RlA [In formula (B), Rg and R7 represent any of the following optionally substituted aryl groups and heterocyclic groups, fL
a and R3 are an alkyl group or an alkenyl group.

Represents either an aralkyl group or an aryl group.
Rlo is a hydrogen atom, a halogen atom, or an alkyl group.

It represents any one of an alkoxy group, an aryl group, and a hydroquine group, and n represents an integer of 0 or more. [Function] A mixture of two types of hydrazone compounds having the above-mentioned -shell structural formulas (A) and (B) is used as a charge transporting substance in the charge transport layer of the photosensitive layer of the laminated photoreceptor. When used as a resin binder in combination with only the hydrazone compound having the shell structural formula (A) above, a resin film having an optical band gap E g (opt) of 2.78 eV or more can be formed, and the - By using a specific polymer resin that can form a resin film with an optical band gap Eg (opt) of less than 2.78 eV when used in combination with only a hydrazone compound having the shell structure formula (B), sensitivity can be improved. It is possible to obtain a photoreceptor which has good characteristics and further shows almost no change in initial charging potential before and after exposure to light even when the surface of the photoreceptor is irradiated with light.

〔Example〕

FIG. 1 is a schematic cross-sectional view of an embodiment of the photoreceptor of the present invention, in which a photosensitive layer 2a is formed by sequentially laminating a charge generation layer 3 and a charge transport layer 4 on a conductive substrate l such as an aluminum alloy. This figure shows a negative charging type laminated photoreceptor for printers. This charge transport layer 4 is made of a hydrazone compound having the following shell structural formula (A1), which further specifies a part of the shell structural formula (A), and the following structural formula (B), which specifies the shell structural formula (B).
A mixture system with a hydrazone compound having Bl) is used as a charge transporting substance, and polycarbonate is used as a resin binder.

[In formula (A1), R1 and R2 each represent any of the following optionally substituted alkyl groups, alkenyl groups, and aralkyl groups. ] When polycarbonate is used in combination with a hydrazone compound having the above-mentioned -shell structural formula (AI), a resin film having an optical bandgap E g (opt) of 2.78 eV or more is formed, and the polycarbonate has the above-mentioned structural formula (AI). When used in combination with a hydrazone compound having (B1), the optical band gap E g (opt) is less than 2.78 eV)
This resin is known from measurement results to form a sealing film. The optical band gap E g of the resin film described here
(opt) is the absorption coefficient α(λ) of the film [λ: wavelength]
It is calculated using the following equation at the absorption edge in the wavelength range of 350 nm to 500 nm in the spectrum.

α(λ) ” ((h-C)/λ) −E g (ap
t) However, in the above formula, h is a blank constant and C is the speed of light.

The charge generation layer 3 was formed using a coating liquid in which X-type phthalocyanine as a charge generation substance was dispersed in Vylon (polyester resin manufactured by Toyobo Co., Ltd.) as a resin binder.

As the charge transporting substance, the general structural formula (A1
) with the leftmost R, and R2 changed as shown in Table 3 below (each of the hydrazone compounds of L A 1-1 to NαA1-4 and the hydrazone compound of the above structural formula (B1) Four types of photoreceptors were prepared by mixing these at a weight mixing ratio of 2:8, and these were used to fabricate the photoreceptors of Examples Nα1 to Nα4 as described above.

The initial surface charging potential of the photoreceptor was measured immediately after discharge.

The results of these measurements are shown in Table 4.

Table 4 Also, for comparison, compounds as charge transporting substances? i
Photoreceptors of Comparative Examples No. 1 to "Ao" and "4" were prepared in the same manner as in the Examples except that NαAl-1 to No. and Al-4 were used alone.

For these photoconductors, turn the photoconductor to -5kV10 in a dark place.
After being charged by corona discharge for seconds, monochromatic light of 1 μW at a wavelength of 780 nm was irradiated to measure the half-attenuation exposure amount. In addition, as shown in Table 4, the photoconductor surface was irradiated with a fluorescent lamp of 1500 Ilux for 5 minutes at -4.5kV around Ni1, in the photoconductor of the example using a mixed charge transport material. The change in the initial surface charging potential at around 148 rays of light is significantly reduced compared to the comparative photoreceptor using a single charge transporting substance. In addition, the aforementioned p-
Diethylarnobenzaldehyde diphenylhydrazone and 1-phenyl-3-(p-diethylaminostyryl)
There was no initial deterioration in sensitivity due to the mixing, as was observed in the mixed system with -5-(varadiethylaminophenyl)-2-pyrazone.

As a result of more detailed experiments, it was found that if the mixing ratio of the hydrazone compound having the structural formula (B1) to the total charge transporting substance is within the range of 10% to 90%,
It was found that the change in charging potential due to light exposure could be suppressed to within 20 V, and there was no problem in practical use.

FIG. 2 shows a different embodiment, which includes a photosensitive layer 2b having a layer structure opposite to that of FIG. 1, in which a charge generation layer 3 is laminated on a charge transport layer 4. In this case, a coating layer 5 is generally provided to protect the charge generation layer, and the layer is used for positive charging. The embodiment shown in Fig. 2 also has a charge transport layer and a charge generation layer similar to those of the embodiment shown in Fig. 1, so that it has good sensitivity and almost no change in charging potential even when exposed to light. It becomes a charging type laminated photoconductor.

As a result of further detailed studies on various hydrazone compounds, it was found that by using a charge transporting substance as a mixture of two types of hydrazone compounds having the above-mentioned membrane structural formulas (A) and (B), good sensitivity and It is possible to obtain a photoreceptor whose initial charging potential changes little when exposed to light.

On the other hand, as a resin binder for the charge transport layer, as a result of experiments with various polymers, optical inhibition of resin films formed in combination with only hydrazone compounds having the above-mentioned film structural formula (A), such as polycarbonate, was found. Band width Eg
(opt) is 2.78 eV or more, and the optical band gap Eg(opt) of the resin film formed in combination only with the hydrazone compound having the above-mentioned film structural formula (B)
is less than 2.78 eV, the above 2.
It has become clear that a photoreceptor that is stable against light exposure can be obtained by using it in combination with a mixed system of different types of compounds.

In this way, a photosensitive layer is constructed by laminating a charge transport layer made of a charge transporting substance and a resin binder according to the present invention and a charge generation layer containing an appropriately selected charge generation substance. Alternatively, it is possible to obtain a laminated photoreceptor that can be used in a positive charging or negative charging system and is suitable for various electrophotographic devices such as copying machines and printers that use monochromatic light of various wavelengths as an exposure light source.

〔Effect of the invention〕

According to the present invention, in the laminated photoreceptor, at least one mixed system of two types of hydrazone compounds having the above-mentioned -Funabashi formula (A) and (B) is used as a charge transporting substance, and the -Funabashi structure Hydrazone compound having formula (A>)
Any combination of these will result in a film with an optical band gap Eg (apt) of 2.73 eV or more, and when combined only with the hydrazone compound having -formation (B), the optical band gap Eg (apt) will be 2.78 eV. A charge transport layer is formed by using an organic polymer resin that forms a film with a resin binder as a resin binder. By providing such a charge transport layer, even when irradiated with light such as a fluorescent lamp, the initial charging potential hardly changes before and after exposure to the light, and the copy has excellent electrophotographic characteristics with good sensitivity. Photoreceptors for electrophotographic devices such as machines and printers can be obtained.

[Brief explanation of the drawing]

1 and 2 are schematic cross-sectional views of photoreceptors of different embodiments of the present invention. 1 conductive substrate, 2a, 2b-photosensitive layer, 3 charge generation layer, 4 charge transport layer, 5 coating layer.

Claims (1)

[Scope of Claims] 1) In an electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer containing an organic material on a conductive substrate, the charge transport layer functions as a charge transport substance and has the following general structural formula: (A) and at least one second compound of the hydrazone compounds having the following general structural formula (B); Equipped with a resin binder that binds substances together to form a charge transport layer,
In addition, as this resin binder, the optical bandgap width of the layer consisting of a combination only with the first compound is 2.78e.
V or more, and the optical bandgap width of the layer formed by the combination of only the second compound is 2.78 eV
1. An electrophotographic photoreceptor characterized by using an organic polymer resin that satisfies the following conditions: ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・・・・
...(A) [In formula (A), R_1 and R_2 represent any of the following optionally substituted alkyl groups, alkenyl groups, and aralkyl groups, R_3 and R_4 are alkyl groups,
Represents any one of an alkenyl group, an aralkyl group, and an aryl group, R_5 represents any one of a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryl group, and a hydroxy group, and m represents an integer of 0 or more. represent. ] ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・・・・
...(B) [In formula (B), R_6 and R_7 represent any of the following optionally substituted aryl groups and heterocyclic groups,
R_8 and R_9 represent any one of an alkyl group, an alkenyl group, an aralkyl group, and an aryl group, and R_1
_0 represents any one of a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryl group, and a hydroxy group, and n represents an integer of 0 or more. ]