JPH02293854A - Laminate type electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To prevent accumulation of residual electric charge on a laminate type photosensitive body and to stabilize chargeability characteristics by incorporating in a charge transfer layer a charge generating material different in sensitive wavelength from the charge generating material used for a charge generating layer. CONSTITUTION:The charge transfer layer contains the charge generating material different in the sensitive wavelength from the charge generating material used for the charge generating layer. Therefore, charge can be generated only in the charge generating layer at the time of imagewise exposure, and charge can be generated only in the charge transfer layer at the time destaticization, and so, the charge accumulated at the interface between the charge generating layer and the charge transfer layer can be effectively eliminated, thus permitting the obtained laminate type photosensitive body to be prevented from the accumulation of residual charge, and to obtain stable chargeability characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a laminated photoreceptor for electrophotography that has stable electrophotographic properties upon repeated use.

(Prior Art and Problems Therewith) Laminated photoreceptors comprising a charge generation layer and a charge transport layer provided on a conductive substrate are widely used in the field of electrophotography such as copying machines.

This laminated photoreceptor has a problem in that, when used repeatedly, residual charges accumulate at the interface between the charge generation layer and the charge transport layer.

In order to solve this problem, a laminated photoreceptor in which a charge generating material is blended in the charge transport layer has been proposed (Japanese Patent Publication No. 6
3-42775).

Although the laminated photoreceptor of the prior art described above is relatively satisfactory in terms of preventing the accumulation of residual charges, carriers are injected from the charge generation layer to the charge transport layer even during static electricity removal, which causes charge generation. Since carriers accumulate at the interface between the layer and the charge transport layer, there is a problem in that the surface potential decreases when charged after repeated use.

Therefore, an object of the present invention is to prevent accumulation of residual charges in a laminated photoreceptor and to obtain stable charging characteristics.

(Means for Solving the Problems) That is, according to the present invention, in an electrophotographic laminated photoreceptor comprising a charge generation layer and a charge transport layer provided on a conductive substrate, the charge transport layer contains There is provided a laminated photoreceptor for electrophotography, which is characterized in that a charge generation material is blended therein, and the sensitivity wavelength of the charge generation material is different from the sensitivity wavelength of the charge generation material used in the charge generation layer.

Further, according to the present invention, there is provided an electrophotographic method in which the laminated photoreceptor is used and static electricity is removed by irradiating the photoreceptor with light in the sensitivity wavelength range of the charge generating material contained in the charge transport layer.

(Function) A remarkable feature of the present invention is that a charge-generating material having a sensitivity wavelength different from that of the charge-generating material used in the charge-generating layer is blended into the charge-transporting layer.

That is, incorporating a charge generating material into the charge transport layer means that
As seen in the prior art described above, this is a conventionally known technology.

According to such prior art means, residual charges accumulated at the interface between the charge generation layer and the charge transport layer due to repeated use of the photoreceptor are removed by carriers generated from the charge generation material in the charge transport layer by irradiation with static eliminating light. neutralized and erased.

However, in the laminated photoreceptor of the prior art, the same charge generation material as that used in the charge generation layer is used in the charge transport layer. Carrier injection from the layer into the charge transport layer will occur again. As a result, carriers are trapped again at the interface between the charge generation layer and the charge transport layer, resulting in a problem that stable charging characteristics cannot be obtained.

According to the present invention, the charge-generating material blended in the charge transport layer has a different sensitivity wavelength than the charge-generating material blended in the charge-generating layer. can be generated only in the charge generation layer, and can be generated only in the charge transport layer during static elimination, and as a result, the charges accumulated at the interface between the charge generation layer and the charge transport layer can be effectively removed. becomes possible.

That is, trapping of charges in the charge transport medium is effectively prevented during image exposure, and accumulated charges remaining at the interface with the charge generation layer during static elimination exposure are neutralized and erased, thereby maintaining stable repeated charging characteristics.

In this case, the ionization potential of the charge generation material used in the charge transport layer is higher than that of the charge generation material used in the charge generation layer. It is possible to improve the efficiency of carrier injection into the charge accumulated at the interface with the layer, and to reliably neutralize the accumulated charge.

(Preferred Embodiment of the Invention) The laminated photoreceptor of the present invention comprises an electrically conductive substrate, a charge generation layer provided on the substrate, and a charge transport layer provided on the charge generation layer.

As the conductive substrate and conductive gas, a sheet or drum-shaped metal foil or plate of aluminum, copper, tin, tin, etc. is used.

Also used is a film substrate such as a biaxially stretched polyester film, glass, or the like in which the above-mentioned metal is applied by vacuum deposition, sputtering, electroless plating, or the like. Paper treated to be conductive may also be used.

2m layer The charge generation layer provided on the conductive substrate is made by dispersing a charge generation material in an electrically insulating binder resin. The electrically insulating binder resin used is known per se, such as polyester resin, acrylic resin, styrene resin, epoxy resin, silicone resin, alkyd resin,
Vinyl chloride-vinyl acetate copolymer resin and the like are used.

As the charge-generating material, any material known in the field of electrophotography can be used as long as it generates charge carriers upon receiving light.

For example, cyanine pigments, berylene pigments, quinacridone pigments, lanthrone pigments, disazo pigments,
Examples include borisazo pigments.

Such a charge generating material is generally finely dispersed in the binder resin so that the particle size is 5 microns or less, and is usually contained in an amount of 5 to 100 parts by weight, particularly 1 to 50 parts by weight, per 100 parts by weight of the binder resin. Used in quantitative proportions.

This charge generation layer usually has a thickness of 0.05 to 3 μm, in particular 0.05 μm to 3 μm.
It is provided with a thickness of only 3 to 1 μm.

The charge transport layer formed on the charge generation layer is made by dispersing a charge transport material in the same binder resin as described above, but in the present invention, it further contains a charge generation material.

As this charge generation material, any material that can be used in the charge generation layer can be used, but as mentioned above, in the present invention, the charge generation material is more ionized than the charge generation material used in the charge generation layer. Those with a large potential and sensitivity to different wavelengths are used.

Table 1 below shows the main charge generating materials, their structural sensitivity wavelengths and ionization potentials.

All known charge transport materials can be used as the charge transport material, but the ionization potential of the charge transport material must be greater than the ionization potential of the charge generation material in the charge generation layer. is desirable,
In particular, it is most preferable that the difference between the two is within 0.2 eV. That is, by using a charge transport material having the above-mentioned ionization potential, injection of charge from the charge generation layer into the charge transport material during charging is effectively suppressed, and excellent charging characteristics are maintained.

On the other hand, if the difference in ionization potential between the two exceeds the above range, it becomes difficult for hole carriers generated in the CGM to be injected into the CTM, resulting in a disadvantage that the sensitivity of the photoreceptor is significantly reduced. Table 2 below shows the main charge transport materials and their ionization potentials.

The above-mentioned charge transport material is used in a proportion of 10 to 200 parts by weight, particularly 70 to 100 parts by weight, per ioom parts of the binder resin.

The charge generating material to be incorporated into the charge transport layer is used in an amount of 10 to 1000 parts by weight, particularly 30 to 700 parts by weight, per 100 parts by weight of the charge transport material.

Such a charge transport layer usually has a thickness of 10 to 30 μm, especially 15 μm.
It is provided with a thickness of 20 μm to 20 μm.

Electrophotographic method In the present invention, the laminated photoreceptor described above is used, and after being charged, image exposure is performed by irradiation with light in the sensitivity wavelength range of the charge generation material in the charge generation layer to generate electrostatic charges on the surface of the photoreceptor. Forms a latent image. According to the present invention, the sensitivity wavelength range of the charge generating material in the charge transport layer is different from that of the charge generating material in the charge derivation layer, so that carriers can be effectively generated in the charge transport layer during image exposure. Since charge trapping is prevented, a stable electrostatic latent image is always formed.

Further, the photoreceptor on which the electrostatic latent image has been formed is subjected to development and transfer steps, which are known per se, to form an image on a predetermined sheet of paper or the like. This transferred image is supplied to a fixing process such as thermal fixing, and the image is fixed.

On the other hand, after the photoreceptor passes through each process of development and transfer, it is subjected to static elimination in the sensitive wavelength range of the charge generating material in the charge transport layer. In this case, since the ionization potential of the charge generating material in the charge generating layer is smaller than that of the charge generating material in the charge transporting layer, the carriers generated in the charge transporting layer by the static elimination are efficiently transferred to the charge generating layer. It is injected into the interface between the charge transport layer and the charge generation layer to neutralize and erase the remaining charge accumulated at the interface between the charge transport layer and the generation layer.

Image formation is performed using the above cycle as one process.

(Effects of the Invention) According to the present invention, it is possible to erase the charges accumulated at the interface between the charge generation layer and the charge transport layer in the laminated photoreceptor without impairing the charging characteristics. It has become possible to obtain stable images at all times.

The invention is illustrated by the following example.

(Example) Hereinafter, the present invention will be explained in more detail based on examples.

[Preparation of electrophotographic photoreceptor]

Example 1 100 parts by weight of polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., trade name Slec BLI) as a binder, 200 parts by weight of metal-free lid cyanine as a charge generating material, and a predetermined amount of tetrahydrofuran were charged in a ball mill. 2
A coating solution for the charge generation layer was prepared by stirring and mixing for 4 hours, and this prepared solution was applied to an aluminum drum by the dipping method.
A charge generation layer having a thickness of 0.5 μm was formed by drying and curing with hot air at 10° C. for 30 minutes.

Next, 100 parts by weight of polycarbonate resin (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name: Iupilon) was used as a binder, and N,N'-(0,P-dimethylphenyl)-N,N' was used as a charge transport material. -(diphenyl)benzidine (hereinafter 4M
e-TPD) 100 parts by weight, N,N'-di(3.5-dimethylphenyl)berylene as a charge generating material
A coating solution for a charge transport layer was prepared by stirring and mixing 0.2 parts by weight of 3.4,9.10-tetracarboxydiimide and a predetermined amount of toluene using a homomixer. This coating solution was applied to the surface of the charge generation layer by dipping, and
A charge transport layer having a thickness of about 20 μm was formed by drying with hot air for 1 minute, thereby producing an electrophotographic photoreceptor.

The charge generating material used in the charge transport layer is N,N'' (3.5
An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that 0.4 parts by weight of -dimethylphenyl)berylene-3.4,9.10-tetracarboxydiimide was used. The charge generating material used in the XJu charge transport layer is N,N' di(3.5
-dimethylphenyl)perylene-3. An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that 0.6 parts by weight of 4.9,10-tetracarboxydiimide was used.

Example 4 The charge generating material used in the charge transport layer was N,N'di(3.5
-dimethylphenyl)perylene-3.4,9.10-tetracarboxydiimide 0.8 3! An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the amounts were changed.

The charge generating material used in the charge transport layer of Tue J1 is N,N'di(3.5
An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that 1.0 parts by weight of -dimethylphenyl)berylene-3.4,9.10-tetracarboxydiimide was used.

J1 student 1 N,N' di(3,5
An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that 2.0 parts by weight of -dimethylphenyl)berylene-3.4,9.10-tetracarboxydiimide was used.

The charge generating material used in the charge transport layer is N, N'di (3.5
An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that 3.0 parts by weight of -dimethylphenyl)berylene-3.4,9.10-tetracarboxydiimide was used.

fire! {+II The charge generating material used in the mutual charge transport layer is N,N' di(3.5
-dimethylphenyl)berylene-3.4,9.10-tetracarboxydiimide An electrophotographic photoreceptor was prepared using the same cherry blossoms as in Example 1, except that 4.0 parts by weight of berylene-3.4,9.10-tetracarboxydiimide was used. N,N' di(3,5
An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that 5.0 parts by weight of -dimethylphenyl)berylene-3.4,9.10-tetracarboxydiimide was used.

N, N' di(3.5
-Dimethylphenyl)berylene-3.4,9.10-tetracarboxydiimide An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that 6.0 1 i parts of the tetracarboxydiimide was used.

1 mouthful of eggplant.” The charge generating material used in the charge transport layer is N,N'
．． 5-dimethylphenyl)berylene-3.4,9.10
- An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that 7.0 parts by weight of tetracarboxydiimide was used.

Example 12 The charge generating material used in the charge transport layer was N,N'di(3.5
An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that 8.0 parts by weight of -dimethylphenyl)berylene-3.4,9.10-tetracarboxydiimide was used. Example 13 The charge generating material used in the charge transport layer was N,N'di(3.5
An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that 9.0 parts by weight of -dimethylphenyl)berylene-3,4,9.10-tetracarboxydiimide was used.

Fugoni 11 The charge generating material used in the charge transport layer is N,N'di(3,5
-dimethylphenyl)berylene-3.4,9.10-tetracarboxydiimide 10 parts by weight,
An electrophotographic photoreceptor was produced in the same manner as in Example 1.

leather! ± An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that no charge generating material was used in the charge transport layer. [Method for evaluating electrophotographic photoreceptors] Electrophotographic properties such as charging ability and residual potential were measured using the apparatus shown in Figure 1. While rotating the electrophotographic photoreceptors 5 obtained in Examples 1 to 14 and Comparative Example 1, using a corotron 1, -
Corona discharge was performed under conditions of 6 KV to negatively charge the sample, and the surface potential was measured using a surface potentiometer placed at position 7.

Next, a semiconductor laser 2 (λ = 780 nm, exposure intensity wO.7 mW/cm', exposure time = 260 μsec
) to expose the photoreceptor to light for 400 msec after exposure.
The surface potential after passage was defined as the residual potential.

Next, after performing corona discharge under +4KV conditions using Corotron 3, the photoreceptor was exposed to light using a λ = 550 nm LED (green light) or a λ = 630 nm LED (red light), and 4 static elimination steps were performed. Ta.

Surface potential V. after performing one cycle of the above electrophotographic process.
, (V), residual potential vr+=(v), and surface potential V1 after 100 cycles. . Measure at(V) and residual potential VIOOrP(V), and calculate the difference as △V,,
．． (V) and Δvrp(v), and the results are shown in Table 1.

As is clear from Table 3, the electrophotographic photoreceptors of Examples 1 to 14, in which the charge generation materials contained in the charge generation layer and the charge transport layer had different sensitivity wavelengths, = 550 nm LED (green light) has a low initial residual potential, and furthermore, the stability of the residual potential after retraction use is very good. It was found that by increasing the amount of perylene added, the decrease in surface potential due to repeated use was improved. On the other hand, when the static elimination light is an LED (red light) with λ = 630 nm, the initial residual potential is high, and furthermore, the stability of the residual potential after repeated use is poor. Even when the amount of charge-generating material and berylene added to the material was increased, the surface potential decreased significantly. The electrophotographic photoreceptor of Comparative Example 1, in which no charge generating material was added to the charge transport layer, had a high initial residence potential and also had poor stability of residual potential and surface potential after repeated use.

The charge generating material used in the charge transport layer was N,N'-di(3
．． 5-dimethylphenyl)berylene-3.4,9.10
- An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that 0.2 parts by weight of metal-free lid cyanine was used instead of 0.2 parts by weight of tetracarboxydiimide.

Comparative Example 3 An electrophotographic photoreceptor was prepared in the same manner as Comparative Example 2, except that 0.4 parts by weight of metal-free lid cyanine was used as the charge-generating material in the charge transport layer.

Comparative Example 4 An electrophotographic photoreceptor was prepared in the same manner as Comparative Example 2, except that the charge generating material used in the charge transport layer was 0.6 fii parts of metal free lid cyanine.

Comparative Example 5 Comparative Example 2 except that the charge generating material used in the charge transport layer was 0.8 g 9 parts of metal free lid cyanine.
At the same time, he created an electrophotographic photoreceptor.

An electrophotographic photoreceptor was prepared in the same manner as in Comparative Example 2, except that the charge generating material used in the charge transport layer was 1.0 parts by weight of metal-free lid cyanine.

An electrophotographic photoreceptor was prepared in the same manner as in Comparative Example 2, except that the charge-generating material used in the charge transport layer was 1.2 parts by weight of metal-free lid cyanine.

(Evaluation method of electrophotographic photoreceptor) Electrophotographic properties such as charging ability and residual potential were measured using the apparatus shown in FIG.

While rotating the electrophotographic photoreceptors 5 obtained in Comparative Examples 2 to 7, corona discharge was performed using Coroton 1 under the condition of -6κV to negatively charge the electrophotographic photoreceptors 5, and the surface potential was placed at position 7. It was measured with a meter. ? Then, semiconductor laser 2 (λ = 780 nm, exposure intensity = 0.7 mW/cm", exposure time = 260 μsec
) to expose the photoreceptor to light for 400 msec after exposure.
The surface potential after the elapsed time was taken as the residual potential. Next, after performing corona discharge under +4KV conditions using Corotron 3, λ
The photoreceptor was exposed to light using a =630 nm LED (red light), and static elimination step 4 was performed. Residual potential V after performing one cycle of the above electrophotographic process
(V) was measured and the results are shown in Table 4.

Table 4 As is clear from Table 4, the electrophotographic photoreceptors of Comparative Examples 2 to 7, in which the same charge generation material was used in the charge generation layer and the charge transport layer, all had high residual potentials. Ta. 1.1-bis(P-jethylaminophenyl) was used instead of 4Me-TPD as the charge transport material used in the charge transport layer.
-4,4-diphenyl-1,3-butadiene (hereinafter T-
An electrophotographic photoreceptor was produced in the same manner as in Example 5, except that the sample was abbreviated as 405). An electrophotographic photoreceptor was prepared in the same manner as in Example 6, except that the charge transport material used in the charge transport layer was D-405 instead of 4Me-TPD. An electrophotographic photoreceptor was prepared in the same manner as in Example 7, except that T-405 was used instead of 4Me-TPO as the charge transport material used in the charge transport layer.

An electrophotographic photoreceptor was prepared in the same manner as in Example 8, except that T-405 was used instead of 4Me-TPO as the charge transport material used in the Togokou 1 charge transport layer. Cold 11 Yu 1 An electrophotographic photoreceptor was prepared in the same manner as in Example 9, except that the charge transport material used in the charge transport layer was T-405 instead of 4Me-TPD. (Method for evaluating electrophotographic photoreceptors) Electrophotographic properties such as chargeability and residual potential were measured using the apparatus shown in Figure 1. Electrophotographic photoreceptor 5 obtained in Examples 15 to 19
While rotating, corona discharge was performed under the condition of -6κV using Corotron 1 to negatively charge the sample, and the surface potential was measured with a surface potentiometer placed at position 7. Next, a semiconductor laser 2 (λ = 780 nm, exposure intensity = 0.7 mW/cm', exposure time = 260 μsec
) to expose the photoreceptor to light for 400'mse after exposure.
The surface potential after c elapsed was defined as the residual potential.

Next, corona discharge was performed using a corotron 3 under the condition of +4 KV, and then the photoreceptor was exposed to light using a λ=550 nm LED (green light), and a static elimination step 4 was performed.

Residual potential vr after performing one cycle of the above electrophotographic process
p(■) was measured and the results are shown in Table 5.

Table 5 Examples 15 to 19 in which the ionization potential was higher than that of the charge transport material used in the charge transport layer
Although all of the electrophotographic photoreceptors had low residual potentials, there was a tendency for the residual potentials to increase as the amount of berylene added increased.

[Brief explanation of drawings]

FIG. 1 shows an apparatus in which the electrophotographic photoreceptor was evaluated. 1, 3... Corotron, 2... Semi-unit laser, 4... LED, 5... Electrophotographic photoreceptor, 7... Surface electrometer.

Claims (3)

[Claims] (1) In an electrophotographic laminated photoreceptor comprising a charge generation layer and a charge transport layer provided on a conductive substrate, a charge generation material is blended in the charge transport layer,
A laminated photoreceptor for electrophotography, wherein a sensitivity wavelength of the charge generation material is different from a sensitivity wavelength of the charge generation material used in the charge generation layer. (2) The laminated photoreceptor according to claim 1, wherein the ionization potential of the charge generation material used in the charge transport layer is greater than the ionization potential of the charge generation material used in the charge generation layer. (3) In an electrophotographic method in which each step of image exposure, development, transfer, and static elimination is performed using the laminated photoreceptor according to claim (1), the sensitivity wavelength range of the charge generation material blended in the charge transport layer is provided. An electrophotographic method characterized in that static electricity is removed by irradiation with a light beam.