JP2604586B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in an electrophotographic photoreceptor having a layer in which a charge generating substance is dispersed.

[Prior Art] Conventionally, there has been known an electrophotographic photoconductor provided with a charge generation layer in which various resins are blended together with a charge generation substance. Examples of such resins include polyvinyl butyral (JP-A-58-105154), fatty acid cellulose ester (JP-A-58-166353, acrylic resin having an Tg of 70 ° C. or less and an acid value of 10 to 40 (JP-A-58-165353). 58-192040), a mixture of a resin having a Tg of 70 ° C. or lower and a resin having a Tg of 75 ° C. or higher (JP-A-58-193)
No. 549), a resin-solvent system having a lower compatibility with the charge-generating material-resin-solvent system is added and redispersed (Japanese Patent Application Laid-Open No.
-12646), polyvinylpyrrolidone (JP-A-56-113140)
No.), polyvinyl formal resin (JP-A-61-235844)
No.) and the like.

However, conventionally known photoconductors have a problem that the sensitivity and the chargeability against pre-exposure fatigue vary depending on the mixing ratio of the charge generating substance and the binder resin.

That is, the conventional photoreceptor can increase the sensitivity by reducing the amount of the binder resin used for the charge generating substance, but the chargeability with respect to the pre-exposure fatigue becomes remarkable,
Conversely, if the amount of the binder resin used relative to the charge generating substance is increased, a decrease in the chargeability due to pre-exposure fatigue can be suppressed, but the problem that the sensitivity is significantly reduced is included.

Further, the conventional photoreceptor also has a drawback that the charging potential is significantly reduced when charging and exposure are repeated.

〔Purpose〕

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrophotographic photoreceptor which has high sensitivity, has a remarkably small reduction in chargeability due to pre-exposure fatigue, and has a charge potential which does not decrease even when charging and exposure are repeated.

〔Constitution〕

According to the present invention, in an electrophotographic photoreceptor having at least a layer in which a charge generating substance is dispersed on a conductive support, the layer in which the charge generating substance is dispersed is represented by the following general formulas (1) and (2). A photoreceptor for electrophotography, comprising a carboxylic acid amide to be obtained.

R ₁ CONHR ₂ (1) (Wherein R ₁ and R ₂ represent an alkyl group or cycloalkyl group having 1 to 24 carbon atoms, and R ₁ and R ₂ may be the same or different).

The electrophotographic photoreceptor of the present invention has a high sensitivity and a remarkably small reduction in chargeability due to pre-exposure fatigue because the carboxylic acid amide is contained in the layer in which the charge generating substance is dispersed. There is a remarkable effect that the charged potential does not decrease even in the repetition.

Generally, the chargeability of a highly sensitive photoreceptor is reduced due to pre-exposure fatigue. In this pre-exposure fatigue, the longer the charge generated by light absorption remains on the photoreceptor in a movable state, and the larger the number of the charges, the more the chargeability due to the pre-exposure fatigue becomes remarkable. That is, even if the charging operation is performed in a state where the charge generated by the light absorption remains, the surface charge is neutralized by the movement of the remaining carrier, so that the surface potential does not increase until the residual charge is consumed. Therefore, the rise of the surface potential is delayed by the amount of the pre-exposure fatigue, and the apparent charging potential is lowered.

The present inventors have intensively studied to improve this point. As a result, when the carboxylic acid amide represented by the general formulas (1) and (2) is contained in the layer in which the charge generating substance is dispersed, the above-mentioned disadvantage is solved. It was found that the present invention was completed.

The reason why the present invention has such a remarkable effect is not always clear at the local point, but since carboxylic acid amide is chemically adsorbed on the charge generating substance and becomes a recombination center of the charge generated by light absorption, the pre-exposure is performed. This is probably because the charge generated by the fatigue is quickly recombined and the charge disappears, thereby suppressing a decrease in the charged potential of the photoconductor.

Further, since the effect on the pre-exposure fatigue as described above also appears during actual use in which charging and exposure are repeated, the electrophotographic photoreceptor according to the present invention is more electrically charged than the conventional one. Even when the exposure is repeated, the decrease in the charged potential is remarkably small.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

FIGS. 1 to 4 are drawings for explaining a typical layer structure of the electrophotographic photoreceptor of the present invention.

FIG. 1 shows a structure in which a charge generation layer 1 and a charge transfer layer 2 are sequentially laminated on a conductive support 3, and FIG. 2 shows a structure in which the charge generation layer 1 and the charge transfer layer 2 are laminated in FIG. The charge generation layer 1 is formed by a coating method that does not disturb the charge transfer layer 2, such as a spray coating method.

FIG. 3 is different from the laminated photosensitive layer of FIGS.
1 shows a photoconductor composed of a single-layer type photosensitive layer having a charge generation function and a charge transfer function in one layer.

FIG. 4 shows a structure in which an undercoat layer 5 is provided between the conductive support 3 and the charge generation layer 1 in FIG. Such an undercoat layer 5 can be similarly applied to the structure shown in FIGS. 2 and 3.

When the undercoat layer is intended to prevent light interference in a photoreceptor for a laser printer, a light-scattering undercoat layer or a light-absorbing undercoat layer is used. A resin undercoat layer such as polyamide, polyester, vinyl chloride-vinyl acetate copolymer, or polyvinyl butyral having good properties is used.

Next, each constituent material used in the present invention will be described.

The conductive support is intended to supply a charge having a polarity opposite to that of the charged charge to the substrate side, and has an electric resistance of
A material having a resistivity of 10 ⁸ Ωcm or less and capable of withstanding the conditions for forming the charge generation layer, the charge transfer layer, and the undercoat layer can be used. Examples of such materials include electrically conductive metals and alloys such as Al, Ni, Cr, Zn, and stainless steel; inorganic insulating materials such as glass and ceramics; and organic insulating materials such as polyester, polyimide, phenolic resin, nylon resin, and paper. The surface of the material is vacuum-evaporated, sputtered, spray-painted, etc., using Al, Ni, Cr, Zn, stainless steel, carbon,
Examples thereof include those obtained by coating an electrically conductive substance such as SnO ₂ or In ₂ O ₃ and performing a conductive treatment.

The layer in which the charge generating substance is dispersed is constituted as a charge generating layer in the laminated photosensitive layer as shown in FIGS. 1, 2 and 4, and a single layer type as shown in FIG. In the photosensitive layer, it is formed in the photosensitive layer.

In the multilayer photosensitive layer, the charge generation layer is composed of a charge generation substance and a binder.

In the present invention, carboxylic acid amides represented by the following general formulas (I) and (II) are used as the binder.

R ₁ CONHR ₂ (I) (In the formula, R ₁ and R ₂ represent an alkyl group or a cycloalkyl group having 1 to 24 carbon atoms, and R ₁ and R ₂ may be the same or different.) The general formula (I) used in the present invention. Specific examples of the compound represented by, acetic acid, propionic acid, butyric acid, caproic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, petadecanoic acid, palmitic acid,
N-substituted fatty acid amides having 1 to 24 carbon atoms such as margaric acid, stearic acid, nonadecanoic acid, arachinic acid, bevenic acid and oleic acid, and especially N-substituted higher fatty acid amides having 11 to 18 carbon atoms. Substitutes, for example, lauric amide, stearic amide, oleic amide, palmitic acid ethylamide, stearic acid methylamide, stearic acid dimethylamide, stearic acid ethylamide, stearic acid butylamide, stearic acid stearinamide, etc. and higher having 18 to 21 carbon atoms Amido acids derived from aliphatic amines, such as stearyl acetamide, stearyl pyropionamide, stearyl butyramide, benenyl acetamide, benenyl propionamide and the like are preferably used.

Further, specific examples of the compound represented by the general formula (II) include the following.

(In the formula, R ₁ and R ₂ are the same as described above.) The layer in which the charge generating substance of the present invention is dispersed contains carboxylic acid amide as a binder. Other resin binders can be used in combination.

Such resin binders include polystyrene,
Styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer,
Polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyacrylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly- Thermoplastic or thermosetting resins such as N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol resin, and alkyd resin.

The total amount of the binder resin is 100
It is suitably used in an amount of 0.01 to 200 parts by weight, preferably 1 to 50 parts by weight based on parts by weight. Further, the carboxylic acid amide is at least 0.0
It is necessary to contain 1 part by weight, preferably 1 part by weight or more.

Examples of the charge generating substance include C.I. Pigment Blue 25 (Color Index (CI) 21180), C.I. Pigment Red 41 (CI 21200), C.I. Red 52 (CI. 45100), and C.I.
45210), a phthalocyanine pigment having a porphyrin skeleton, an azulenium salt pigment, a squaric salt pigment, and an azo pigment having a carbazole skeleton (JP-A-53-950).
No. 33), azo pigments having a stilstilbene skeleton (described in JP-A-53-138229), azo pigments having a triphenylamine skeleton (described in JP-A-53-132547), dibenzothiophene Azo pigments having a skeleton (described in JP-A-54-21728), azo pigments having an oxadiazole skeleton (described in JP-A-54-12742),
Azo pigments having a fluorenone skeleton (described in JP-A-54-22834), azo pigments having a bis-stilbene skeleton (described in JP-A-54-17733), and azo pigments having a distyryloxadiazole skeleton ( JP-A-54-2129), azo pigments having a distyrylcarbazole skeleton (described in JP-A-54-17734), and triazo pigments having a carbazole skeleton (JP-A-57-195767; 57-
Phthalocyanine pigments such as C.I. Pigment Blue 16 (CI 74100), indigo pigments such as C.I.Bat Brown 5 (CI 73410) and C.I.Bat Die (CI 73030), and Argoscarlet Organic pigments such as perylene pigments such as B (manufactured by Violet) and Induration Scarlet R (manufactured by Bayer) can be used.

Among these charge generating substances, azo pigments are particularly preferred, and among the azo pigments, the following disazo pigments or trisazo pigments are most preferred.

 Specific examples of the azo pigment are shown below.

The thickness of the charge generation layer 1 is suitably about 0.05 to 2 μm, and preferably 0.1 to 1 μm.

The charge generation layer 1 can be formed by dissolving or dispersing a resin binder and a charge generation substance in an appropriate solvent, and applying and drying this. As a solvent, benzene, toluene, xylene, methylene chloride, dichloroethane, monochlorobenzene, dichlorobenzene, ethyl acetate, butyl acetate, methyl ethyl ketone, dioxane, tetrahydrofuran, cyclohexanone, methyl cellosolve, ethyl cellosolve, etc. may be used alone or in combination. it can.

The charge transfer layer 2 is formed by dissolving or dispersing a charge transfer material and a resin binder in an appropriate solvent,
It can be formed by coating and drying on the top. If necessary, a plasticizer or a leveling agent can be added.

Examples of the charge transfer material include poly-N-vinyl carbazole and its derivatives, poly-γ-caubazolylethyl daltamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, Oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyryl) anthracene, 1,1-bis- (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazolin, phenylhydrazones, An electron donating substance such as an α-phenylstilbene derivative may be used.

Examples of the resin binder include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, and vinyl chloride-vinyl acetate copolymer used in the charge generation layer. Coalescence, polyvinyl acetate, polyvinylidene chloride, polyacrylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin And a thermoplastic or thermosetting resin such as melamine resin, urethane resin, phenol resin and alkyd resin.

As the solvent at this time, tetrahydrofuran, dioxane, toluene, monochlorobenzene, dichloroethane, methylene chloride and the like can be used.

The thickness of the charge transfer layer 2 is suitably about 5 to 100 μm.

In the case where the layer in which the charge-generating substance is dispersed is a single-layer photosensitive layer as shown in FIG. 3, the charge-generating substance used in the charge-generating layer, the carboxylic acid amide, the resin binder and, if necessary, It can be formed by mixing the charge transfer substances used in the charge transfer layer and applying and drying these coating solutions on a conductive support or the like.

Further, in the present invention, as described above, an undercoat layer can be provided between the conductive support and the photosensitive layer, if necessary.

The light-scattering subbing layer and the light-absorbing subbing layer are layers for preventing light interference in the photoreceptor for a printer as described above. The light-scattering undercoat layer is formed by dispersing a conductive powder such as tin oxide and antimony oxide and a white pigment such as zinc oxide, zinc sulfide and titanium oxide in the following thermosetting resin. The light-absorbing undercoat layer is formed by dispersing a conductive light-absorbing pigment such as carbon or various metals and / or a light-absorbing inducing pigment in a similar thermosetting resin. The thermosetting resin used here is, for example, active hydrogen (-OH group,-
It is obtained by thermally polymerizing a compound containing a plurality of hydrogens such as NH ₂ groups and —NH groups) with a compound containing a plurality of isocyanate groups and / or a compound containing a plurality of epoxy groups. Examples of the compound containing a plurality of active hydrogens include, for example, acrylic resins containing active hydrogens such as polyvinyl butyral, phenoxy resin, phenol resin, polyamide, polyester, polyethylene glycol, polypropylene glycol, polybutylene glycol, and hydroxyethyl methacrylate groups. And the like. As the compound containing a plurality of isocyanate groups, for example,
Examples include tolylene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, and prepolymers thereof, and examples of the compound having a plurality of epoxy groups include bisphenol A epoxy resin.

In any case, the light-scattering or light-absorbing undercoat layer is applied on a substrate with a solution obtained by dissolving or dispersing the above components on a substrate.
It is formed by thermal polymerization at 200 ° C. The thickness of the undercoat layer is suitably from 1 to 10 μm. The weight ratio of the conductive powder, the white pigment, and the thermosetting resin is suitably 2 to 6/1 to 5/2 to 6, and the weight ratio of the light-absorbing pigment to the thermosetting resin is 4 to 9/1 to 6 / is suitable.

〔effect〕

The electrophotographic photoreceptor of the present invention has a high sensitivity and a remarkably small reduction in chargeability due to pre-exposure fatigue because the carboxylic acid amide is contained in the layer in which the charge generating substance is dispersed. There is a remarkable effect that the charged potential does not decrease even in the repetition.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to examples.

Example 1 [Coating solution for charge generation layer] 5 parts by weight of azo pigment ((Pigment No. 1) and 0.78% by weight of carboxylic acid amide (C ₁₇ H ₃₅ CONHC ₆ H ₄ NHCOC ₁₇ H ₃₅ ) shown in Table 1 cyclohexanone 160 parts by weight of the solution and a ball mill for 72 hours to obtain a pigment dispersion.
While stirring, 90 parts by weight of methyl ethyl ketone was additionally mixed with 0 parts by weight to obtain a charge generating layer coating liquid.

(Coating liquid for charge transfer layer)

α-phenylstilbene-based charge transfer material (mixture below) 100 parts by weight Polycarbonate (trade name, Panlite C 1400: Teijin Limited) 100 parts by weight Silicone oil (trade name, KF 50: Shin-Etsu Silicone Co., Ltd.)
0.1 part by weight Tetrahydrofuran 800 parts by weight Next, the above-mentioned coating solution for a charge generation layer is coated on a 75 μm polyester film substrate on which Al has been vacuum-deposited, and dried by heating at 120 ° C. for 10 minutes to about 0.2 μm. A charge generation layer was formed. Next, a coating liquid for a charge transfer layer having the above composition was coated on the charge generation layer with a blade, and dried by heating at 120 ° C. for 20 minutes to form a charge transfer layer having a thickness of about 20 μm.

Example 2 A photoconductor was prepared in the same manner as in Example 1, except that the azo pigment of the coating solution for the charge generation layer was changed to Pigment No. 39.

Example 3 A coating solution for a chlorinated transfer layer used in Example 1 was applied to a 75 μm polyester film substrate on which Al was vacuum-deposited.
Coated with blade in the same manner as above, then dried to about 20μm
Was formed. Then, the coating liquid for a charge generation layer used in Example 1 was spray-coated on the charge transfer layer, and dried by heating at 120 ° C. for 30 minutes to form a charge generation layer of about 0.2 μm. Created.

Example 4 A photoconductor was prepared by the same way as that of Example 1 except that the α-phenylstilbene compound in the coating solution for the charge transfer layer was changed to a compound having the following structure.

Example 5 A 0.78% by weight cyclohexanone solution of the carboxylic amide used for preparing the coating solution for the charge generating layer was added to the carboxylic amide. A photoconductor was prepared in the same manner as in Example 2 except that a 0.156% by weight cyclohexanone solution was used.

Example 6 90 parts by weight of methyl ethyl ketone used for preparing a coating solution for a charge generation layer was polyvinyl butyral (trade name: XYHL,
A photoconductor was prepared in the same manner as in Example 5, except that a 0.43 wt% methyl ethyl ketone solution (manufactured by Union Carbide Plastics Co., Ltd.) was 90 parts by weight.

Example 7 Fine powder of tin oxide containing 10% by weight of antimony oxide 8
Parts by weight, 5 parts by weight of titanium oxide white pigment powder and 68 parts by weight of a 12% by weight solution of polyvinyl butyral (trade name: BL-1, manufactured by Sekisui Chemical Co., Ltd.) in a methyl ethyl ketone were treated in a ball mill for 72 hours, and then methyl ethyl ketone 47 Additional parts by weight were processed again in the ball mill for 48 hours. Next, while stirring 80 parts by weight of the pigment dispersion, 8 parts by weight of a 20% by weight solution of tolylene diisocyanate in methyl ethyl ketone was added and mixed to obtain an undercoat layer coating liquid for light scattering.

Next, the above-mentioned undercoat layer coating solution for light scattering was coated on a 75 μm polyester film substrate on which Al was vacuum-deposited with a blade, and heated and cured at 120 ° C. for 30 minutes to form an undercoat layer for light scattering of about 2.5 μm. Was formed.

Next, a photoreceptor having a charge generation layer and a charge transfer layer formed on the light scattering subbing layer in the same manner as in Example 2 was prepared.

Comparative Examples 1 and 2 Photoconductors were prepared in the same manner as in Examples 1 and 2, except that the carboxylic acid amide of the coating solution for the charge generation layer was changed to polyvinyl butyral (trade name: XYHL, manufactured by Union Carbide Plastics). .

Comparative Example 3 A photoconductor was prepared in the same manner as in Example 3, except that the carboxylic acid amide of the coating solution for the charge generation layer was changed to polyvinyl butyral (trade name: XYHL, manufactured by Union Carbide Plastics).

Comparative Example 4 A photoconductor was prepared in the same manner as in Example 4, except that the carboxylic acid amide of the coating solution for the charge generation layer was changed to polyvinyl butyral (trade name: XYHL, manufactured by Union Carbide Plastics).

Comparative Example 5 A photoconductor was prepared in the same manner as in Example 2, except that the carboxylic acid amide of the coating solution for the charge generation layer was changed to polyester (trade name: Byron 200, manufactured by Toyobo Co., Ltd.).

Comparative Example 6 The carboxylic acid amide at the time of preparing the coating solution for the charge generation layer was 0.78
A photoreceptor was prepared in the same manner as in Example 1, except that the weight% cyclohexanone solution was changed to a 5.88% by weight cyclohexanone solution of polyvinyl butyral (trade name: XYHL, manufactured by Union Carbide Plastics).

Comparative Example 7 An azo pigment (pigment No. 1) shown on page 12 and a structural formula (Compound described in JP-A-61-11752)
The photoreceptor was prepared in the same manner as in Example 1, except that a pigment dispersion having a weight ratio of 4/1 was used.

Comparative Example 8 Using a pigment dispersion in which the weight ratio of the azo pigment (pigment No. 1) shown on page 12 and myristic acid diethanolamide (described in JP-A-58-68750) was 4/1. A photoreceptor was prepared in the same manner as in Example 1 except for the above.

The electrophotographic photoreceptor prepared as described above was evaluated for electrophotographic characteristics as follows using an electrostatic copying paper test apparatus (Kawaguchi Electric Mfg. Co., Ltd., Model SP 428). First, a -6 KV corona discharge was applied to each photoconductor for 20 seconds, during which a charge potential V ₂ (volt) 2 seconds after the start of corona discharge was measured.
Thereafter, when the device was left in a dark place and the surface potential became -800 V, it was irradiated with tungsten light, and an exposure amount S (lux sec) required for light attenuation of the surface potential to -400 V was obtained. Then, after irradiating 100000 lux sec with tungsten light having a color temperature of 2856 ° K, the charging potential V ₂ ′ (vo
lt) and the exposure amount S ′ (lux sec). Table 1 shows the above results.

In addition, the type photoreceptor shown in FIG.
The charging was performed for 0 seconds, during which time the charged potential V ₂ was measured 2 seconds after the start of corona discharge, and then left in a dark place to increase the surface potential to +80.
When the voltage reached 0 V, the substrate was irradiated with tungsten light, and an exposure amount S required for the surface potential to attenuate to +400 V was obtained. Thereafter, in the same manner as described above, the charged potential V ₂ ′ and the exposure amount S ′ after the light fatigue after the irradiation of 100,000 lux sec were determined.

[Brief description of the drawings]

1 to 4 are schematic sectional views of various electrophotographic photosensitive members according to the present invention. 1; charge generation layer 2; charge transfer layer 3; conductive support 4; single-layer photosensitive layer 5; undercoat layer

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor: Shu Taniguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor: Minoru Umeda 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (56) References JP-A-58-68750 (JP, A) JP-A-61-11752 (JP, A) JP-A-63-44662 (JP, A) JP-A-63-210935 (JP) JP, A)

Claims (1)

(57) [Claims] 1. An electrophotographic photoreceptor having at least a layer in which a charge generating substance is dispersed on a conductive support, wherein the layer in which the charge generating substance is dispersed is represented by the following general formula (1) or (2). A photoreceptor for electrophotography, comprising a carboxylic acid amide. R ₁ CONHR ₂ (1) (In the formula, R ₁ and R ₂ represent an alkyl group or a cycloalkyl group having 1 to 24 carbon atoms, and R ₁ and R ₂ may be the same or different.)