JPH06103394B2 - Multilayer type photoconductor for electrophotography - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a laminated type electrophotographic photoreceptor comprising a conductive substrate on which a charge generation layer and a charge transport layer are provided.

(Prior Art and Problems Thereof) Generally, the above-described laminated photoreceptor is known as a so-called function-separated photoreceptor.

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

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

Therefore, in view of the above problems, in a laminated electrophotographic photosensitive member including a charge generation layer and a charge transport layer provided on a conductive substrate, in the charge transport layer, a charge generation material used for the charge generation layer is used. Stacked electron having excellent repeating characteristics 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 A photographic photoreceptor (Japanese Patent Application No. 1-114308 [see Japanese Patent Publication No. 5-6179]) was previously proposed.

In addition, in order to prevent deterioration due to light, heat, etc. and improve the repeated stability, a material in which an antioxidant is added to the charge transport layer has recently appeared.

(Problems to be Solved by the Invention) However, among the various antioxidants used in the above-mentioned conventional electrophotographic photoreceptors, those which do not show a significant addition effect, but adversely affect the photosensitive characteristics. There are things that affect them. This is because the performance of antioxidants cannot be ascertained unless they are actually used.

The present invention has been made in view of the above circumstances,
As compared with the photoreceptor of Japanese Patent Application No. 1-114308 previously proposed, the inventors of the present invention conducted various studies on various antioxidants in order to provide a photoreceptor having more excellent repeating characteristics. It came to completion.

Therefore, it is an object of the present invention to provide a laminated electrophotographic photosensitive member which is more excellent in repeated stability.

(Means and Actions for Solving Problems) Therefore, in the present invention, in the laminated electrophotographic photoreceptor comprising a charge generating layer and a charge transporting layer provided on a conductive substrate, the charge transporting layer is A first charge-transporting material having an ionization potential smaller than that of the charge-generating material used for the generation layer, a second charge-transporting material having ionization potential larger than that of the charge-generating material, and a phenol-based oxidation The above object was achieved by constructing a laminated type electrophotographic photoreceptor comprising an inhibitor.

As a result of earnest studies by the present inventors, the charge transport layer has a first charge transport material having an ionization potential smaller than that of the charge generation material as a charge transport material and a charge transport material having a larger ionization potential than that of the charge generation material. In a photoreceptor having a laminated type photosensitive layer containing a second charge transport material having an ionization potential, a phosphorus-based or amine-based antioxidant cannot be repeatedly used, and conversely it can be used repeatedly. It was found that although the surface potential after that is drastically reduced, repeated stability is most suitably obtained by using the phenolic antioxidant of the present invention.

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

Conductive Substrate As the conductive substrate, a sheet or drum of metal foil or metal plate of aluminum, copper, tin, tin plate or the like is used.

Further, on the film substrate such as biaxially stretched polyester film or glass, the above metal, vacuum deposition, sputtering,
Those applied by means such as electroless plating are also used. It is also possible to use conductively treated paper.

Charge Generation Layer The charge generation layer provided on the conductive substrate is one in which a charge generation material is dispersed in an electrically insulating binder resin.

The electrically insulating binder resin used is known per se, for example, polyester resin, acrylic resin, styrene resin, epoxy resin, silicone resin, alkyd resin,
Vinyl chloride-vinyl acetate copolymer resin or the like is used.

As the charge generating material, any material well known in the field of electrophotography can be used as long as it can receive charge and generate charge carriers.

For example, phthalocyanine pigments, perylene pigments, quinacridone pigments, pyranthrone pigments, disazo pigments,
Examples thereof include polyazo 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 the binder resin is usually used.
It is used in an amount ratio of 5 to 100 parts by weight, especially 10 to 50 parts by weight, per 0 parts by weight.

This charge generation layer is usually provided in a thickness of 0.05 to 3 μm, particularly 0.3 to 1 μm.

The structures and ionization potentials of the main charge generating materials are shown in Table 1 below.

Charge Transport Layer The charge transport layer formed on the charge generation layer is formed by dispersing the charge transport material and the phenolic antioxidant in the same binder resin as described above. A combination of a first charge transport material having a smaller ionization potential than the charge generating material used and a second charge transport material having a large ionization potential is used.

That is, although the charge transport material itself used is known per se, according to the present invention, the above-mentioned two kinds of charge transport materials are used in combination.

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

In the present invention, the ionization potentials of the first and second charge transport materials are both preferably within ± 0.2 eV of the ionization potential of the charge generation material.

That is, when the ionization potential of the first charge transport material is too small, the surface potential lowering tendency becomes large, and the ionization potential of the second charge transport material (hereinafter sometimes abbreviated as Ip) is too large. In this case, since it is difficult to inject holes, residual charge tends to be accumulated. Furthermore, the first charge transport material and the second charge transport material are 10:90 to 90:10, especially 30:70 to 7 by weight.
It is preferably used in a 0:30 volume ratio. The charge transport material described above is 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 the binder resin.

The phenolic antioxidant in the present invention includes 2,6
-T-butyl-p-cresol, triethylene glycol bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate, octadecyl-3-
(3.5-di-t-butyl-4-hydroxyphenyl) propionate, 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid bis (1,2,
2,6-pentamethyl-4-piperidyl), 4,4'-thiobis (3-methyl-6-tert-butylphenol) and the like. The said phenolic antioxidant can be used individually or in combination of multiple types, Among them, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2- (3, Bis (1,2,2,6-pentamethyl-4-piperidyl) 5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonate is preferably used.

The above-mentioned phenolic antioxidant is used in a proportion of 5 to 50 parts by weight per 100 parts by weight of the binder resin. When the amount used exceeds 50 parts by weight, the sensitivity is deteriorated and the residual potential increases even after repeated use. Also, 5
If it is less than the weight part, sufficient stability of the surface potential cannot be obtained during repeated use.

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

(Effects of the Invention) According to the present invention, in the so-called function-separated type laminated photoreceptor, the problem of decrease in surface potential during repeated use is more effectively solved, and residual charge accumulation is also effectively avoided. It became possible to do.

The invention is illustrated by the following example.

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

[Adjustment of electrophotographic photoreceptor]

Example 1 Polyvinyl butyral as a binder resin (manufactured by Sekisui Chemical Co., Ltd.,
Product name S-REC BL1) 100 parts by weight, 200 parts by weight of metal-free phthalocyanine as a charge generating material, and a predetermined amount of tetrahydrofuran are charged in a ball mill and mixed by stirring for 24 hours to prepare a coating solution for the charge generating layer. Is applied to an aluminum drum by the dipping method, and is heated at 110 ° C for 30
A charge generation layer having a film thickness of 0.5 μm was formed by drying with hot air for curing for minutes.

Next, 100 parts by weight of a polycarbonate resin (trade name: Iupilon manufactured by Mitsubishi Gas Chemical Co., Inc.) as a binder resin, and N, N '-(o, p-dimethylphenyl) -N, N'- as a charge transport material.
70 parts by weight of (diphenyl) benzidine (IP = 5.43; hereinafter referred to as compound A) and 1,1-bis (p-diethylaminophenyl) -4,4-diphenyl-1,3-butadiene (IP = 5.3
2; hereinafter referred to as B compound) 30 parts by weight, 5 parts by weight of 2,6-di-t-butyl-p-cresol (manufactured by Kawaguchi Chemical Co., Ltd., trade name BHT) as a phenolic antioxidant, and a predetermined amount of toluene Was stirred and mixed with a homomixer to prepare a charge transport layer coating solution. This coating solution was applied on 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 film thickness of about 20 μm, thereby preparing an electrophotographic photoreceptor.

Example 2 2,6-di-t-butyl-as a phenolic antioxidant
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that 25 parts by weight of p-cresol (BHT manufactured by Kawaguchi Chemical Co., Ltd.) was used.

Example 3 2,6-di-t-butyl-as a phenolic antioxidant
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that 50 parts by weight of p-cresol (BHT manufactured by Kawaguchi Chemical Co., Ltd.) was used.

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

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

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. An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except for the above.

Example 7 As a phenolic antioxidant, octadecyl-3- (3,
5-di-t-butyl-4-hydroxyphenyl) propioneketo (Ciba-Geigy, trade name IRGANOX 1076)
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that 5 parts by weight of was used.

Example 8 Octadecyl-3- (3, as a phenolic antioxidant
5-di-t-butyl-4-hydroxyphenyl) propioneketo (Ciba-Geigy, trade name IRGANOX 1076)
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that 25 parts by weight of was used.

Example 9 Octadecyl-3- (3, as a phenolic antioxidant
5-di-t-butyl-4-hydroxyphenyl) propioneketo (Ciba-Geigy, trade name IRGANOX 1076)
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that 50 parts by weight of was used.

Example 10 Bis (1,2,2,6,6-pentamethyl-4) -2- (3,5-di-t-putyl-4-hydroxybenzyl) -2-n-butylmalonate as a phenolic antioxidant An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that 5 parts by weight of piperidyl (manufactured by Ciba Geigy, trade name TINUVIN 144) was used.

Example 11 Bis (1,2,2,6,6-pentamethyl-4) -2- (3,5-di-t-putyl-4-hydroxybenzyl) -2-n-butylmalonate as a phenolic antioxidant An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that 25 parts by weight of piperidyl (manufactured by Ciba Geigy, trade name TINUVIN 144) was used.

Example 12 Bis (1,2,2,6,6-pentamethyl-4) 2- (3,5-di-t-putyl-4-hydroxybenzyl) -2-n-butylmalonate as a phenolic antioxidant An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that 50 parts by weight of piperidyl (manufactured by Ciba Geigy, trade name TINUVIN 144) was used.

Comparative Example 1 phosphorus-based antioxidant 4,4'-isopropylidene - diphenol alkyl (C ₁₂ -C ₁₅₎ phosphite (Adeka Argus Co., Ltd., trade name MARK1500) except for using 10 parts by weight, performed An electrophotographic photosensitive member was prepared in the same manner as in Example 1.

Comparative Example 2 Diisodecyl pentaerythritol diphosphite (manufactured by Sanko Chemical Co., Ltd., trade name HIMO) was used as a phosphorus-based antioxidant.
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that the parts by weight were used.

Comparative Example 3 Example 1 was repeated except that 10 parts by weight of 1,3-bis (dimethylaminopropyl-2-thiourea (manufactured by Ouchi Shinko Chemical Co., Ltd., trade name Norax NS10) was used as an amine-based antioxidant.
An electrophotographic photoreceptor was prepared in the same manner as in.

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

[Evaluation of electrophotographic photoreceptor]

Electrophotographic characteristics such as charging ability and residual potential were measured by the apparatus shown in FIG.

While rotating the electrophotographic photosensitive member 5 obtained in each example, the corotron 1 was used to perform corona discharge under the condition of −6 KV to be negatively charged, and the surface potential V _sp (V) was arranged at the position 7. It was measured with a surface potential meter.

Next, semiconductor laser 2 (λ = 780 nm, exposure intensity = 0.7
mW / cm ² , exposure time = 260 μsec), the photoconductor is exposed, and the surface potential after 400 msec has passed is the residual potential V
_rp (v).

Then, after performing corona discharge using Corotron 3 under the condition of +4 KV, the photosensitive member was exposed by using LED (λ = 630 nm), and a charge eliminating step 4 was performed.

Surface potential V after 100 cycles of the electrophotographic process
_{Measure 100sp} (V) and measure the initial surface potential V of the photoconductor
the difference between the _sp (V), calculated as [Delta] V _sp (V) The results are shown in Table.

As is clear from Table 3, all of the electrophotographic photoreceptors of Examples 1 to 12 have a low residual potential and have excellent electrophotographic characteristics with stability of surface potential due to repeated use. There was found.

On the other hand, the electrophotographic photoconductors of Comparative Examples 1, 3, and 4 had a high residual potential, and the electrophotographic photoconductors of Comparative Example 2 had poor surface potential stability due to repeated use.

[Brief description of drawings]

FIG. 1 is a diagram showing an apparatus for measuring electrophotographic characteristics of a photoconductor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Sakuma 1-22-28 Tamatsukuri, Chuo-ku, Osaka-shi, Osaka Mita Industry Co., Ltd. Mitsuo Suma (56) Reference JP-A-58-58550 (JP, 58-58550) A) JP 58-123546 (JP, A)

Claims (3)

[Claims] 1. A laminated electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer provided on a conductive substrate, wherein the charge transport layer is higher than an ionization potential of a charge generation material used for the charge generation layer. Laminated electrophotography comprising a first charge transport material having a small ionization potential, a second charge transport material having an ionization potential larger than that of the charge generating material, and a phenolic antioxidant Photoconductor. 2. The laminated electrophotographic photosensitive material according to claim 1, wherein the ionization potentials of the first and second charge transport materials are within ± 0.2 eV with respect to the ionization potential of the charge generation material. body. 3. The laminated type electrophotographic photosensitive material according to claim 1, wherein the first charge transport material and the second charge transport material are used in a ratio of 10:90 to 90:10 on a weight basis. body.