JPH03172853A - Laminate type electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance stability against repeated use by laminating on a conductive substrate an electric charge generating layer and a charge transfer layer comprising first and second charge transfer materials specified in ionization potential and content and a specified surfactant. CONSTITUTION:The laminate type electrophotographic sensitive body is formed by laminating on the conductive substrate the charge generating layer and the charge transfer layer containing the first and the second charge transfer materials lower and higher in the ionization potential than a charge generating material contained in the charge generating layer by + or -0.2eV, in a weight ratio 10:90 - 90:10, and the phenol type antioxidant, thus permitting the obtained photosensitive body to be enhanced in stability against repeated use.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a laminated electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer provided on a conductive substrate.

(Prior Art and its Problems) In general, the above-described laminated photoreceptor is conventionally known as a so-called functionally separated photoreceptor.

In such a laminated photoreceptor, in a structure in which a charge transport layer is formed on a charge generation layer, carriers are generated in the charge generation layer due to image exposure performed after a negative charge is evenly applied to the surface, for example. Based on this carrier, holes are injected and moved into the charge transport layer, and negative charges on the surface of the photoreceptor are neutralized to form an electrostatic latent image.

Therefore, in conventionally known laminated photoreceptors, a charge generating material having a higher ionization potential than the charge transporting material has been used so that holes can be easily injected into the charge transporting layer. However, when a charge-generating material and a charge-transporting material are used in combination as described above, there is a problem in that the stability of the surface potential is poor upon repeated use.

Therefore, in view of the above problems, in a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive substrate, a charge generation material used in the charge generation layer is added to the charge transport layer. A stacked electron material with excellent repeatability by containing a first charge transport material having an ionization potential smaller than the ionization potential and a second charge transport material having an ionization potential larger than the ionization potential of the charge generation material. Photographic photoreceptor (
(Japanese Patent Application No. 1-114308) was first proposed.

Furthermore, in order to prevent deterioration due to light, heat, etc. and improve repeatability stability, products in which an antioxidant is added to the charge transport layer have appeared in recent years.

(Problems to be Solved by the Invention) However, some of the various antioxidants used in the above-mentioned conventional electrophotographic photoreceptors do not show any significant additive effect, and some have a negative effect on the photosensitive properties. There are also things that affect. This is because the performance of antioxidants cannot be determined for sure until they are actually used.

The present invention has been made in view of the above circumstances, and
As a result of intensive research into various antioxidants by the present inventors in order to provide a photoreceptor with even better repeatability characteristics than the photoreceptor proposed in Japanese Patent Application No. 1-114308,
The photoreceptor of the present invention has been completed.

Accordingly, an object of the present invention is to provide a laminated electrophotographic photoreceptor that has better repeat stability.

(Means and effects for solving the problem) Therefore, in the present invention, in the laminated electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer provided on a conductive substrate, the charge transport layer is a first charge transport material having an ionization potential smaller than the ionization potential of the charge generation material used in the generation layer; a second charge transport material having an ionization potential larger than the ionization potential of the charge generation material; and a phenolic oxidation material. The above object was achieved by constructing a laminated electrophotographic photoreceptor comprising an inhibitor.

As a result of intensive research, the present inventors found that the charge transport layer contains a first charge transport material having an ionization potential smaller than that of the charge generation material as a charge transport material, and a first charge transport material having an ionization potential larger than the ionization potential of the charge generation material. In a photoconductor having a laminated photoconductor layer containing a second charge transporting material with ionization potential, repeated use of other antioxidants such as phosphorus or amine antioxidants will not provide repeated stability; Although the surface potential decreases significantly after repeated use, it has been found that the use of the phenolic antioxidant of the present invention provides the most favorable repeated stability.

(Preferred Embodiment of the Invention) The laminated photoreceptor of the present invention includes a 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, a metal foil or plate made of aluminum, copper, tin, tin, etc. is used in the form of a sheet or a drum.

In addition, the above metals can be applied to film substrates such as two-wheel stretched polyester films, glass, etc. by vacuum evaporation, sputtering,
Those applied by means such as electroless plating are also used. Paper treated to be conductive may also be used.

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.

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

For example, phthalocyanine pigments, perylene pigments, quinacridone pigments, pyranthrone pigments, disazo pigments,
Examples include polysazo pigments.

Such a charge generating material is generally finely dispersed in the binder resin so that the particle size is 5 μm or less, and is usually dispersed in the binder resin 1.
5 to 100 parts by weight per 00 parts by weight, especially IO to 5 parts by weight
Used in star proportions of 0 parts by weight.

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

Note that Table 1 below shows the structures and ionization potentials of main charge generating materials.

(Left below) 111 The charge transport layer formed on the charge generation layer is made by dispersing a charge transport material and a phenolic antioxidant in the same binder resin as described above. As the material, a combination of a first charge transporting material having a smaller ionization potential than the charge generating material used and a second charge transporting material having a larger ionization potential is used.

That is, although the charge transport materials used are known per se, according to the present invention, two types of charge transport materials as described above are used in combination.

Table 2 below shows the main charge transport materials and their ionization potentials.

(Hereinafter, blank spaces) In the present invention, it is preferable that the ionization potentials of the first and second charge transport materials are both within a range of ±0.2e■ compared to the ionization potential of the charge generation material.

That is, if the ionization potential of the first charge transport material is too small, the surface potential will decrease significantly, and the ionization potential of the second charge transport material (
(hereinafter sometimes abbreviated as ip) is too large, it is difficult for holes to be injected, and residual charges tend to accumulate significantly.

Furthermore, it is preferred that the first charge transport material and the second charge transport material are used in a ratio of 10:90 to 90:IOl, particularly 30 nia 0 to 70:30 flt, on a weight basis. The above-mentioned charge transport materials are used in a total amount of 50 to 300 parts by weight, particularly 70 to 100 parts by weight, per 100 parts by weight of binder resin.
Used in parts by weight.

As the phenolic antioxidant in the present invention, 2.
6-t-butyl-p-cresol, triethylene glycol bis(3-(3-t-7'+ru-5-methyl-4
-hydroxyphenyl)propionate, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2-(3,5-di-L-butyl-4-hydroxybenzyl)-2-n-butylmalone Examples include acid bis(1,2,2,6-bentamethyl-4-piperidyl L4,4°-thiobis(3-methyl-6-tert-butylphenol)).The above phenolic antioxidants may be used alone or in combination with Several types of fM can be used in combination, among which octadecyl-3-(3,5-di-monobutyl-4-hydroxyphenyl)propionate,
2-(3,5-di-t-7'' thyl-4-hydroxyhensyl)-2n-butylmalonate bis(1,2,26-bentamethyl-4-piperidyl) is preferably used.

The above-mentioned phenolic antioxidant is used in an amount of 5 to 50 parts by weight per 100 parts by weight of the binder resin. If the amount used exceeds 50 parts by weight, sensitivity will deteriorate and residual potential will increase during repeated use. Moreover, if it is less than 5 parts by weight, sufficient stability of the surface potential cannot be obtained during repeated use.

Such a charge transport layer typically has an IO to 30 pm, especially 15
It is provided with a thickness of 20 μm to 20 μm.

(Effects of the Invention) According to the present invention, in a so-called functionally separated laminated photoconductor, the problem of a decrease in surface potential during repeated use can be more effectively solved, and the accumulation of residual charges can also be effectively avoided. It became possible to do so.

The invention is illustrated by the following example.

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

[Adjustment of electrophotographic photoreceptor]

Example 1 Polyvinyl butyral (manufactured by Block Chemical Co., Ltd.,
100 parts by weight of the product name Kosuretsuku BLI), 200 parts by weight of metal-free phthalocyanine as a charge-generating material, and a predetermined amount of tetrahydrofuran were placed in a ball mill.
A coating solution for the charge generation layer was prepared by stirring and mixing for 24 hours, and this prepared solution was applied to an aluminum drum by a dipping method.
By drying and curing with hot air at 110° C. for 30 minutes, a charge generation layer having a thickness of 11% and 0.5 μm was formed.

Next, 100 parts by weight of polycarbonate resin (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name: Niepiron) was used as a binder resin, and N, N.-(o, p-dimethylphenyl)-N, N=-(diphenyl) was used as a charge transport material. Benzidine (IP=5
．． 70 parts by weight of 1.1-bis(p-diethylaminophenyl)-4,4-diphenyl-1°3-butadiene (IP=5.32; hereinafter referred to as compound B) , 5 parts by weight of 2.6-di-L-butyl-p-cresol (manufactured by Kawaguchi Chemical Co., Ltd., trade name: BHT) as a phenolic antioxidant, and a predetermined amount of toluene were stirred and mixed with a homomixer to prepare a charge transport layer. The coating solution was prepared. This coating solution was applied to the surface of the charge generation layer by a dipping method, and then dried with hot air at 110° C. for 30 minutes to form a charge transport layer having a thickness of 20 μm, thereby producing an electrophotographic photoreceptor.

Example 2 2.6-di-butyl- as a phenolic antioxidant
25 p-cresol (manufactured by Kawaguchi Chemical Co., Ltd., trade name BIT)
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that parts by weight were used.

Example 3 2.6-sheet t-butyl as a phenolic antioxidant
50 p-cresol (manufactured by Kawaguchi Chemical Co., Ltd., trade name BIT)
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that parts by weight were used.

Example 4 Except for using 5 parts by weight of triethylene glycol bis(3-(3-t-butyl-5methyl 4-hydroxyphenyl)propionate) (manufactured by Ciba Geigy, trade name IRGANOX 245) as a phenolic antioxidant. An electrophotographic photoreceptor was prepared in the same manner as in Example 1.

Example 5 Except for using 25 parts by weight of triethylene glycol bis(3-(3-t-butyl-5methyl 4-hydroxyphenyl)propionate) (manufactured by Ciba Geigy, trade name IRGANOX 245) as a phenolic antioxidant. An electrophotographic photoreceptor was prepared in the same manner as in Example 1.

Example 6 50 parts by weight of triethylene glycol bis(3-(3-t-butyl-5methyl-4-hydroxyphenyl)propionate) (manufactured by Ciba Geigy, trade name IRGANOX 245) was used as a phenolic antioxidant. Except for this, an electrophotographic photoreceptor was produced in the same manner as in Example 1.

Example 7 Octadecyl-3-(3
,5-di-t-butyl-4-hydroxyphenyl) propionekide (manufactured by Ciba Geigy, trade name IRGANO)
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that 5 parts by weight of X 1076) was used.

Example 8 Octadecyl 3-(3,
5-dibutyl-4-hydroxyphenyl) propionekide (manufactured by Ciba Geigy, trade name IRGANOX)
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that 25 parts by weight of 1076) was used.

Example 9 Octadecyl-3-(3
,5-di-t-butyl-4-hydroxyphenyl) propionekide (manufactured by Ciba Geigy, trade name IRGANO)
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that 50 parts by weight of X 1076) was used.

Example 10 2-(3,5-di=
butyl-4-hydroxybenzyl)-2-〇nibutylmalonate bis(1,2,2,,6,6-bentamethyl-4
- Piperidyl (manufactured by Ciba Geigy, trade name TINUVI)
Example 1 except that 5 parts by weight of N144) was used.
An electrophotographic photoreceptor was prepared in the same manner as described above.

Example 11 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonic acid bis(1,2,2,6,6-bentamethyl-4-piperidyl( Manufactured by Ciba Geigy, product name: TINUVIN
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that 25 parts by weight of 144) was used.

Example 12 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonate bis(1,2,2,6,6pentamethyl-4-piperidyl) as a phenolic antioxidant (Ciba Geigy) Manufactured by company, product name: TINUVIN
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that 50 parts by weight of 144) was used.

Comparative Example 1 4,4''-isopropylidene- as a phosphorus antioxidant
Diphenolalkyl (CI□~C1,) phosphite (manufactured by Adeka Argus, trade name MARK1500) was added to
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that 0 parts by weight was used.

Comparative Example 2 Diisodecylpentaerythol diphosphite (manufactured by Sangen Kagaku Co., Ltd., trade name HIMO) as a phosphorus antioxidant
An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that 10 parts by weight of the following were used.

Comparative Example 3 Except for using 10 parts by weight of 1,3-bis(dimethylaminopropyl-2-thiourea (manufactured by Iriuchi Shinko Kagaku Co., Ltd., trade name Norax N5IO) as an amine antioxidant,
An electrophotographic photoreceptor was produced in the same manner as in Example 1.

Comparative Example 4 Example except that 10 parts by weight of bis(2,2,6°6-tetramethyl-4-piperidyl) sebacate (manufactured by Sankyo Kagaku Co., Ltd., trade name Sanol 770) was used as the amine antioxidant. An electrophotographic photoreceptor was prepared in the same manner as in Example 1.

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

While rotating the electrophotographic photoreceptor 5 obtained in each example, corona discharge was performed using a corotron 1 under the condition of -6 KV to negatively charge the electrophotographic photoreceptor 5 and increase the surface potential V, , (V) to 7
It was measured with a surface electrometer placed at the position.

Next, the photoreceptor was exposed to light using a semiconductor laser 2 (λ-780 nm, exposure intensity = 0.7 mW/cIa, exposure time -260 μ5 ec), and the surface potential after 400 m5 ec of exposure was determined as the residual potential V, (v ).

Next, after performing corona discharge under +4KV conditions using Corotron 3, using LED (λ-6300m),
The photoreceptor was exposed to light, and static elimination step 4 was performed.

Surface potential (2) after performing the above electrophotographic process for 100 cycles. . , p(V) were measured, and the difference between the initial surface potential V of the photoreceptor and p(V) was calculated as ΔV, , (V), and the results are shown in the table.

(Leaving space below) Table 3 Table 3 (Continued) As is clear from Table 3, the electrophotographic photoreceptors of Examples 1 to 12 all have low residual potentials and have stable surface potentials even after repeated use. It was found that it had excellent electrophotographic properties.

On the other hand, the electrophotographic photoreceptors of Comparative Examples 1, 3, and 4 had high residual potentials, and the electrophotographic photoreceptors of Comparative Example 2 had poor stability of surface potential after repeated use.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an apparatus for measuring electrophotographic characteristics of a photoreceptor. Patent distributor: Mita Kogyo Co., Ltd. Figure 1 [τ] L”

Claims (3)

[Claims] (1) In a laminated electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer provided on a conductive substrate, the charge transport layer has an ionization potential lower than the ionization potential of the charge generation material used in the charge generation layer. A multilayer electrophotographic photosensitive material comprising a first charge transporting material having a potential, a second charge transporting material having an ionization potential greater than the ionization potential of the charge generating material, and a phenolic antioxidant. body. (2) The laminated electrophotographic photoreceptor according to claim 1, wherein the ionization potential of the first and second charge transport materials is within a range of ±0.2 eV with respect to the ionization potential of the charge generation material. . (3) The first charge transport material and the second charge transport material are:
The laminated electrophotographic photoreceptor according to claim 1, wherein the photoreceptor is used in a ratio of 10:90 to 90:10 on a weight basis.