JPH0313958A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance sensitivity of a photosensitive body and to reduce deterioration of potential acceptance due to electrostatic fatigue by cross-link a specified copolymer to form an undercoat layer. CONSTITUTION:This photosensitive body is obtained by successively laminating on a conductive substrate the undercoat layer, an electric charge generating layer, and a charge transfer layer and the undercoat layer is made of a binder resin (A) of a copolymer of styrene-methylmethacrylate-acrylic acid-N- methylolacrylammide containing both of zirconium oxide and tin oxide particles, and this layer can be formed by coating the substrate with a coating fluid containing the resin A, heating it to a prescribed temperature or higher, and drying, cross-linking, and hardening it, thus permitting the layer to be insolubilized in the solvent to be used for forming the charge generating layer on the undercoat layer.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor comprising a photosensitive layer consisting of a substrate, an undercoat layer, a charge generation layer, and a charge transport layer, and particularly relates to This invention relates to an improved electrophotographic photoreceptor.

[Conventional technology]

Conventionally, photoreceptors used in electrophotography include those with a photoconductive layer mainly made of selenium or selenium alloys on a conductive support, and inorganic photoconductive materials such as zinc oxide and cadmium sulfide. Generally known are those that use organic photoconductive materials such as poly-N-vinylcarbazole and trinitrofluorenone or azo pigments, and those that use amorphous silicon-based materials. There is.

By the way, in general, the "electrophotographic method" means that a photoconductive photoreceptor is first charged in a dark place by, for example, corona discharge, and then imagewise exposed to selectively dissipate the charge only in the exposed area to create an electrostatic latent material. Image formation in which an image is obtained by obtaining an image, and developing and visualizing this latent image area with electrostatic fine particles (toner) made of coloring materials such as dyes and pigments and binders such as polymeric substances to form an image. It is one of the laws.

The basic characteristics required of the photoreceptor in such electrophotography are (1) the ability to be charged to an appropriate potential in a dark place;

(2) Less charge dissipation in the dark.

(3) Charge can be quickly dissipated by light irradiation.

Examples include.

In addition to these basic characteristics, each of the above-mentioned photoconductors has excellent features and disadvantages in practical use, but in recent years, photoconductors that have low manufacturing costs, little environmental pollution, and are relatively free have been developed. Organic photoreceptors are rapidly developing due to their ease of design.

In general, an organic photoreceptor is a material in which a charge-generating material and a charge-transporting material are dispersed or dissolved in a binder resin and coated on a conductive support. Single layer type with transport function, charge generation layer (CGL) with charge generation function, charge retention and CG
A charge transport layer having a function of transporting charges injected from L (
CTL), and a functionally separated type that has a laminated layer with functions such as blocking charge injection from the support or preventing light reflection on the support as necessary. It is being

Although these organic photoreceptors have excellent features as described above, they have the following drawbacks because they are organic materials.

(1) Low chargeability and charge retention.

(2) Residual charge causes fog and density unevenness on the image.

(3) Due to non-uniform chemical and physical 1-mechanical properties of the substrate, defects such as white spots and black spots occur on the image.

In particular, when a high-sensitivity photoreceptor is subjected to repeated charging and exposure, the characteristic (1) above appears as a significant deterioration due to so-called electrostatic fatigue. Such fatigue is said to occur mainly because positive and/or negative charges remain in a movable state in the photoreceptor. In other words, due to repeated charging exposure, residual charges are removed at the beginning of the primary charging operation.

Since it moves to the surface and neutralizes the charged charges, it is not possible to obtain the rapid rise in surface potential required at the initial stage of charging.

For this reason, a desired surface potential cannot be obtained within the time set in the charging process, which poses a serious problem particularly in high-speed copying processes.

For the above-mentioned drawbacks, for example, Japanese Patent Application Laid-Open No. 47-6341.
Nos. 48-3544 and 48-12034 have cellulose nitrate resin intermediate layers, as disclosed in JP-A No. 48-47344.52.
-25638.58-30757.58-63945.
58-95351.58-98739 and 60-66
No. 258 has a nylon resin intermediate layer, which is disclosed in Japanese Patent Application Laid-Open No. 49-6
Nos. 9332 and 52-10138 disclose a maleic acid resin intermediate layer, and JP-A-58-105155 discloses a polyvinyl alcohol resin intermediate layer.
do. Further, in order to control the electrical resistance of the intermediate layer, an intermediate layer in which various conductive additives are contained in the resin has been proposed. The intermediate layer dispersed in a synthetic resin is
JP-A-52-82238 discloses a thermal polymer intermediate layer using an isocyanate curing agent with the addition of a quaternary ammonium salt, and JP-A-55-1180451 discloses a resin intermediate layer containing a resistance modifier. , JP-A-58-58556 discloses a resin intermediate layer in which aluminum or tin oxide is dispersed, and JP-A-58-93062 discloses a resin intermediate layer in which an organometallic compound is added. .60-9
Nos. 7363 and 60-111255 have a resin intermediate layer in which conductive particles are dispersed, and JP-A-59-17557 has a layer in which magnetite is dispersed in a resin.
9-84257.59-93453 and 60-320
No. 54 discloses a resin intermediate layer in which Tie, SnO, and powder are dispersed.

However, conventionally known electrophotographic photoreceptors are still insufficient in terms of deterioration in chargeability due to repeated use, particularly in terms of delay in the rise of the 4th charge, and furthermore, residual potential changes are large, which is still a major problem. Furthermore, many of the resins, inorganic particles, dyes, and other organic substances used in the intermediate layer are easily affected by temperature and humidity, to varying degrees, and as a result, the resistance value of the intermediate layer changes widely. . Even if an intermediate layer of a certain suitable material and film thickness is provided at room temperature, the electrostatic properties of the photoreceptor change significantly at low temperature and low humidity or high temperature and high temperature.

[Problem to be solved by the invention]

The present invention provides electrophotography that is highly sensitive, has a significantly small decrease in chargeability due to electrostatic fatigue, and has a fast rise in charging potential and small change in residual potential even after repeated charging and exposure. Another object of the present invention is to provide an electrophotographic photoreceptor that has good charging properties and does not change its residual potential even under high temperature and low temperature conditions and low humidity.

[Means to solve the problem]

According to the present invention, on a conductive substrate, a subbing layer, a charge generation layer,
and an electrophotographic photoreceptor in which a charge transport layer is sequentially laminated, the undercoat layer is made of a binder resin containing zirconium oxide particles and tin oxide particles at the same time, and the binder resin is made of styrene/methyl methacrylate/acrylic acid IN. - An electrophotographic photoreceptor characterized by being a cured product of a copolymer of methylol acrylamide is provided.

The present inventor focused on the subbing layer of an electrophotographic photoreceptor, which is formed by sequentially laminating a subbing layer, a charge generation layer, and a charge transport layer on a conductive substrate, and conducted extensive studies to eliminate the above-mentioned drawbacks. result,
By making the components of the undercoat layer have the above-mentioned specific composition, an electrophotographic photoreceptor is provided that has a small delay in the rise of the 4th charge after repeated use, a small change in residual potential, and a small change in characteristics with respect to temperature and humidity. The present inventors have discovered that the following can be obtained, and have completed the present invention.

The present invention will be explained in detail below.

Zirconium oxide to be contained in the undercoat layer.

Usually with a purity of 90% or higher, preferably 99.5%
% or more purity is used. Similarly, the tin oxide has a purity of 90% or more, preferably 99.5%.
% or more purity is used.

The average particle diameter of the primary particles of zirconium oxide and tin oxide is preferably 0.5 μm or less, preferably 0.3 μm or less. If it is 0.5 μm or more, rough letters, stains, etc. may occur on the image. It is conspicuous, and its electrostatic properties have large variations in sensitivity and poor quality stability.

As the binder resin, a copolymer of styrene (a), methyl methacrylate (b), acrylic acid (C) and N-methylolacrylamide (d) is used. In this copolymer, the monomers (a) to (d) have the following weight relationship.

(a) + (b) + (c) ÷ (d) ((d) / (c)) Q≧1.0 In this copolymer resin, the constituent monomer N-methylolacrylamide (d) component is It is said that the acrylic acid (C) component contributes to crosslinking, and is presumed to have a catalytic effect.

That is, if the undercoat layer is heated and dried at a temperature of 100°C or higher, the undercoat layer will be cured by a curing reaction.

It is made insoluble in the solvent of the charge generation layer that is then applied.

Therefore, in order to effectively use this resin, (C
The content rates of component ) and component (d) are important.

The content of these components is determined mainly from the above-mentioned aspects of dissolution resistance and life as a dispersion.

That is, from the dissolution resistance of the crosslinked resin, the total copolymerization ratio (weight ratio) of components (C) and (d) is 10 to 30 wt%, preferably 15 to 20 wt%, based on the entire resin.
Contains t%.

And for the component (d) that mainly contributes to crosslinking, (C
) in the molar ratio to the component ((d)/(c))wo
Expressed as Q, ((d)/(c))moQ=10/1
~171. Preferably it is 671-271. If the monomer composition is within this range, sufficient solvent resistance and a long life of the coating solution of the undercoat layer can be ensured.

In addition, styrene (,) component and methyl methacrylate (b)
The copolymerization ratio of the components can be set within a relatively wide range with respect to other components. The main setting conditions are determined by the solvent involved in dispersing the zirconium oxide particles and tin oxide particles of this resin.

For example, if the weight ratio of toluene-butanol is set to 8=1 to 9=1 as a solvent during dispersion, component (a),
The copolymerization ratio for component (b) is usually set as follows.

It is also possible to change the copolymerization ratio of styrene and acrylic acid by changing the dispersion conditions or coating conditions, such as adding xylene instead of toluene.

The total ratio of the zirconium oxide particles and the tin oxide particles to the binder resin is 1/1 to 19/1, preferably 371 to 10/1, by weight. If the ratio is less than 18, the effect will be small, and if it exceeds 19/1, air bubbles will remain in the undercoat layer and defects will occur in the charge generation layer and charge transfer layer coatings, which is not preferred.

The ratio of zirconium oxide particles to tin oxide particles is 40/SnO, where the weight ratio is expressed as ZrO,/SnO.
1 to 1/1, preferably 1571 to 5/1. If the usage ratio exceeds 4071, residual charge will cause fogging on the image, and if it is less than 1/1, it will be difficult to ensure chargeability and the desired image density will not be obtained.

The thickness of the undercoat layer is 0.3 to 10 .mu.m, preferably 0.5 to 5.0 .mu.m. If the thickness of the undercoat layer is less than 0.3 μm, the effect will be poor, and if it is more than 10 μm, residual potential will accumulate, which is not desirable.

In the present invention, to form the undercoat layer.

A solution in which the above components are dissolved or dispersed is applied onto a conductive substrate and dried. Drying conditions are usually 80-150℃
, 20 minutes to 10 hours.

As the conductive substrate, one having a conductivity of 1 volume resistivity of 1010 Ωcm or less, for example, 1. aluminum, nickel,
Metals such as chromium, nichrome, copper, silver, gold, and platinum, and metal oxides such as tin oxide and indium oxide are coated on film or cylindrical plastics, paper, etc. by vapor deposition or sputtering, or aluminum. , plates of aluminum alloy, nickel, stainless steel, etc., and their adhesives; 1. ．． 1.1. It is possible to use pipes that have been made into blank pipes by methods such as , extrusion, and drawing, and then surface-treated by cutting, superfinishing, polishing, and the like.

Next, the charge generation layer will be explained.

The charge generation layer is a layer mainly composed of a charge generation substance, and a binder resin may be used as necessary.

Binder resins include polyamide, polyurethane,
Polyester, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone,
Polystyrene, boryl N-vinylcarbazole, polyacrylamide, etc. are used.

As the charge generating substance, for example, C.I. Pigment Blue 25 [Color Index X ((J) 211803,
CI Pigment Red 41 (CI 21200),
C.I. Acid Red 52 (CI 45100), C.I. Basic Red 3 (CI 45210), and a butalocyanine pigment having a porphyrin skeleton,
Azulenium salt pigments, squalic salt pigments, azo pigments with a carbazole skeleton (described in JP-A-53-95033), azo pigments with a stilstilbene skeleton (
(described in JP-A No. 53-138229), azo pigments having a triphenylamine skeleton (described in JP-A-53-1325)
47), azo pigments having a dibenzothiophene skeleton (described in JP-A No. 54-21728), azo pigments having an oxadiazole skeleton (described in JP-A-54-1
2742), azo pigments having a fluorenone skeleton (described in JP-A-54-22834), azo pigments having a bisstilbene skeleton (described in JP-A-54-177)
33), an azo pigment having a distyryloxadiazole skeleton (described in JP-A No. 54-2129), an azo pigment having a distyrylcarbazole skeleton (described in JP-A-54-17734) , triazo pigments having a carbazole skeleton (described in JP-A-57-195767 and JP-A-57-195768), and CI Pigment Blue 16 (CI 74100).
Phthalocyanine pigments such as Sea Eye Butt Brown 5
((:I 73410), CI Bat Die (CI
73030), Argo Scarlet 8 (manufactured by Violet), Indus Thread Scarlet R
Organic pigments such as perylene pigments such as (manufactured by Bayer) can be used.

Among these charge-generating substances, azo pigments are particularly preferred, and among azo pigments, disazo pigments and trisazo pigments shown below are most preferred.

Specific examples of azo pigments are shown below.

These charge generating substances may be used alone or in combination of two or more.

The binder resin is suitably used in an amount of 0 to 100 parts by weight, preferably 0 to 100 parts by weight, based on 100 parts by weight of the charge generating substance.
-50 parts by weight.

The charge generation layer contains a charge generation substance, along with a binder resin if necessary, tetrahydrofuran, cyclohexanone,
It can be formed by dispersing using a ball mill, attritor, sand mill, etc. using a solvent such as dioxane or dichloroethane, diluting the dispersion liquid appropriately, and applying the dispersion. Application can be performed using a dip coating method, a spray coating method, a bead coating method, or the like.

The thickness of the charge generation layer is suitably about 0.01 to 5 tones, preferably about 0.1 to 2 tones.

The charge transport layer consists of a charge transport substance and a binder resin used as necessary.

A charge transport layer can be formed by dissolving or dispersing the above-mentioned substances in a suitable solvent and applying and drying the solution.

Charge transport materials include hole transport materials and electron transport materials.

As hole transport substances, poly-N-vinylcarbazole and its derivatives, poly-γ-carbazolylethyl glutamate 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.

Examples include electron-donating substances such as styryl anthracene, styryl pyrazoline, phenylhydrazones, and α-phenylstilbene derivatives.

Examples of electron transport substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinone dimethane, 2,4.7-trinitro-9-fluorenone, 2,4,5.7-tetranitro-9-fluorenone, 2, 4,5.7-tetranitroxanthone, 2,
4゜8-Trinidrothioxanthone, 2,6.8-trinitro-4H-indeno(1,2-b)thiophene-
Examples include electron-accepting substances such as 4-one, 1,3.7-dolinitrodibenzothiophenone-5.5-dioxide.

These charge transport substances may be used alone or in a mixture of two or more.

Binder resins that may be used as necessary in the present invention include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride- Vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate resin,
Phenoxy resin, polycarbonate, cellulose acetate resin.

Ethyl cellulose resin, polyvinyl butyral.

Polyvinyl formal, polyvinyltoluene, poly-N
- Thermoplastic or thermosetting resins such as vinyl carbazole, acrylic resins, silicone resins, epoxy resins, melamine resins, urethane resins, phenolic resins, and alkyd resins.

As the solvent, tetrahydrofuran, dioxane, toluene, monochlorobenzene, dichloroethane, methylene chloride, etc. are used.

The appropriate thickness of the charge transport layer is about 5 to 100 mm.

In addition, in the present invention, a plasticizer or a leveling agent may be added to the charge transport layer.As the plasticizer, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are. The appropriate amount to be used is about O to 30X by weight based on the binder resin. As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil are used, and the appropriate amount thereof is about 0 to 1% by weight based on the binder resin.

In the present invention, it is also possible to further provide an insulating layer or a protective layer on the photosensitive layer.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Examples 1 to 4 The following subbing layer coating solution was dip-coated on an An plate at 130°C.
This was dried for 30 minutes to form an undercoat layer containing zirconium oxide and tin oxide and having a thickness of 3.0 μm.

(Undercoat layer coating liquid) Components (a), (b), (e), and (d) are 4 kinds of styrene/methyl methacrylate/acrylic acid/
An N-methylol acrylamide resin was synthesized.

Next, a solution of each resin U-1, 2, 3, 4 (toluene/
Butanol = 971, solid content 8.0 wt%), zirconium oxide (TZO3N manufactured by Toyo Soda Kogyo Co., Ltd.), and tin oxide (manufactured by Mitsubishi Metals Co., Ltd. 5-1) in a weight ratio of 10.0/4.5.
The mixture was mixed at a ratio of 10.5, put into a glass ball mill pot, and ball milled for 120 hours.

Add an appropriate amount of the above solvent to this subbing layer dispersion to dilute it,
This was used as an undercoat layer coating solution.

Next, the charge generation layer coating solution shown below was applied by clipping coating on the undercoat layer, and after drying at 120° C. for 10 minutes, a charge generation layer having a thickness of 0.7 μm was formed.

(Charge generation layer coating liquid) Place the psz ball in a 15φ1 hardened glass pot.

Add about half of the content, then add the azo pigment Nα39.
25 g and 415 g of cyclohexanone were added. 50
After ball milling for an hour, further cyclohexanone 560
g was added and ball milled for 24 hours. Cyclohexanone was added to this mill base to dilute it to about 2.0 wt % to prepare a charge generation layer coating solution.

Next, on this undercoat layer, the following charge generation layer coating solution was applied by dipping coating, and after drying at 120° C. for 10 minutes, a charge generation layer having a thickness of 0.5 μm was formed.

Next, the charge transfer layer coating solution shown below was coated on the charge generation layer by dipping, and dried at 120°C for 20 minutes to form a film with a thickness of 20°C.
．． A charge transport layer was provided to obtain an electrophotographic photoreceptor of the present invention.

(Charge transport layer coating liquid) Charge transfer material having the following structural formula: 20 g Tetrahydrofuran 160 g Example 5 In Example 3, the ratio of zirconium oxide to tin oxide was changed to 15/1, and an azo pigment as a charge generating material was used. An electrophotographic photoreceptor was produced in the same manner as in Example 3 except that -1 was used.

Example 6 An electrophotographic photoreceptor was produced in the same manner as in Example 4, except that the ratio of zirconium oxide and tin oxide used was changed to 371, and the azo pigment, which was a charge generating material, was replaced with NQI. did.

The electrophotographic photoreceptor produced in the manner described above was charged using a commercially available electrostatic copying paper tester I (Kawaguchi Electric Seisakusho 5P-428) by performing corona discharge at -6 V for 20 seconds, and then The surface potential V* (V) was measured 2 seconds after the start of charging. Also, after 20 seconds of charging, the surface potential V
After measuring the R (residual potential) and charging it again to the surface potential of -aoov, the exposure amount S required to attenuate the surface potential to -aoov by exposing it to the tungsten lamp is:
was measured.

Furthermore, in order to know the repeated fatigue characteristics, #Ali
! Charging at 17 KV and exposure at 301 ux were alternately repeated for 1 hour, and y/2, y/R and S' after fatigue were measured. The results are shown in Table-1.

Further, the drum-shaped electrophotographic photoreceptors of Examples 2 and 3 were attached to a laser beam printer (25° C., 60% RH), (10° C., 15% RH).
The image quality was evaluated by repeatedly subjecting the electrophotographic photoreceptor to fatigue by repeatedly printing 5,000 sheets in an environment of (30° C., 90% RH). After continuous printing,
A clear image with little deterioration equivalent to the initial image was obtained.

〔effect〕

The electrophotographic photoreceptor of the present invention has a thermosetting styrene/methyl methacrylate/acrylic acid/N-
By adopting the structure of a functionally separated laminated photoreceptor with an undercoat layer made of methylol acrylamide copolymer, it has high sensitivity and even after repeated charging and exposure.
It has the remarkable characteristics that the rise of the charge at the 4th position is fast, the residual potential is small, and there is little deterioration even with changes in temperature and humidity.

Therefore, according to the electrophotographic photoreceptor of the present invention, it is possible to obtain a high-quality image output without abnormal images due to light interference even in exposure using coherent light such as a laser printer.

Claims (1)

[Claims] (1) In an electrophotographic photoreceptor in which an undercoat layer, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive substrate, the undercoat layer is made of a binder resin containing zirconium oxide particles and tin oxide particles at the same time. An electrophotographic photoreceptor, wherein the binder resin is a cured product of a copolymer of styrene/methyl methacrylate/acrylic acid/N-methylolacrylamide.