JPH0312662A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To suppress the degradation in electrostatic chargeability and the change in residual potential by constituting an under coating layer of a binder resin in which zirconium oxide particles and indium oxide particle are simultaneously incorporated and consisting of the binder resin of the cured matter of a copolymer of styrene/methyl methacrylate/acrylic acid/glycidyl acrylate. CONSTITUTION:The under coating layer of the electrophotographic sensitive body constituted by successively laminating the under coating layer, charge generating layer and charge transfer layer on a conductive base body consists of the binder resin in which the zirconium oxide particles and indium oxide particle are simultaneously incorporated. In addition, the binder resin consists of the cured matter of the copolymer of the styrene/methyl methacrylate/acrylic acid/glycidyl acrylate. The delay in the rise of the potential by electrification after repetitive use is lessened in this way and the change in the residual potential is lessened.

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 sulfate. Generally known are those using organic photoconductive materials such as poly-N-vinylcarbasol and trinitrofluorenone or azo pigments, and those using amorphous silicon-based materials. ing.

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 at the tip of the S. An image that is created by obtaining a latent image and visualizing the latent image area by developing it with electrostatic fine particles (toner) consisting of a coloring material such as a dye or pigment and a binder such as a polymeric substance to form an image. This is one of the formation methods.

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 CGL
A charge transport layer (CTL) has the function of transporting charges injected from the GL, and further has functions such as blocking injection of charges from the support or preventing reflection of light on the support as necessary. A functionally separated type, which has a structure in which layers such as

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) Due to the residual ffi load, fogging and density unevenness occur 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, the remaining charges move to the surface at the start of the next charging operation and neutralize the charged charges.
The required rapid rise in surface potential at the initial stage of charging cannot be achieved.

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.
5g-95351, 5g-98739 and 60-66
No. 258 has a nylon resin intermediate layer, which was published in JP-A-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. In addition, intermediate layers have been proposed in which various conductive additives are contained in a resin in order to control the electrical resistance of the intermediate layer.

For example, JP-A No. 51-65942 uses an intermediate layer in which carbon or chalcogen-based substances are dispersed in a curable resin, and JP-A No. 52-82238 uses an isocyanate-based curing agent with the addition of a quaternary ammonium salt. JP-A-55-1180451 discloses a resin intermediate layer containing a resistance modifier, and JP-A-58-58556 discloses a resin intermediate layer in which aluminum or tin oxide is dispersed. ,
JP-A No. 58-93062 discloses a resin intermediate layer containing an organometallic compound;
Nos. 363 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.
-84257.59-93453 and 60-3205
No. 4 discloses a resin intermediate layer in which TiO□ and SnO□ 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 has high sensitivity, has a significantly small decrease in chargeability due to electrostatic fatigue, and even after repeated charging and exposure, the charging potential rises quickly and the residual potential changes little. For the purpose of providing photographic photoreceptors,
Another object of the present invention is to provide an electrophotographic photoreceptor with good charging properties and no change in residual potential even at high temperatures and low temperatures 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 Electrotransport JfltI - An electrophotographic photoreceptor in which the undercoat layer is made of a binder resin containing zirconium oxide particles and indium oxide particles at the same time, and
There is provided an electrophotographic photoreceptor characterized in that the binder resin is a cured product of a copolymer of styrene/methyl methacrylate/acrylic acid/glycidyl acrylate.

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 setting the components of the undercoat layer to the above-mentioned specific composition, an electrophotographic photoreceptor is provided that has little delay in the rise of charge potential after repeated use, has little change in residual potential, and has little 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.

The zirconium oxide contained in the undercoat layer usually has a purity of 90% or more, preferably 99.5% or more. Similarly, the indium oxide has a purity of 90% or more, preferably 99.8%.
Those with a purity higher than that are used.

The average particle diameter of the primary particles of zirconium oxide and indium oxide is preferably 0.5μ or less, preferably 0.3μ or less.If it is 0.5μ or more, the characters may become rough, 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 glycidyl methacrylate (d) is used. In this copolymer resin, the heptamer components (a) to (d) have the following weight relationship.

and the molar ratio (d)/(e) of (c) and (d) is (d)/(C
)≦1.0 It is said that the glycidyl methacrylate (d) component, which is a constituent monomer of this copolymer resin, contributes to crosslinking, and the acrylic acid (c) component 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 insolubilized in the solvent of the charge generation layer to be first coated due to a curing reaction.

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, in view of the solvent resistance of the crosslinked resin, the total copolymerization ratio (weight ratio) of component (C) and component (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
) component to ((d)/(c month ■ o
Expressed as Q, ((d)/(c))moQ210/1
-1/1, preferably 6/1 to 2/l. If the monomer composition is within this range, sufficient dissolution resistance and a long life of the coating solution of the undercoat layer can be ensured.

In addition, styrene (a) component and methyl methacrylate (b)
The copolymerization ratio of components is relative to other components.

Can be set over a relatively wide range. The main setting conditions are determined by the solvent involved in dispersing the zirconium oxide and indium oxide particles of this resin.

For example, if toluene-butanol is used as a solvent for dispersion in a weight ratio of 8:1 to 9:1, the copolymerization ratios of components a and b are 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 zirconium oxide and indium oxide particles to the binder resin is 1/1 to 1971, preferably 3/1 to 10/1, in terms of weight ratio. If the ratio is less than 1/1, 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.

Also, the usage ratio of zirconium oxide and indium oxide is
The weight ratio is expressed as ZrO,/In,Os, and is 4
071 to 1/1, preferably 15/1 to 571. 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.

Further, the thickness of the undercoat layer is 0.3 to 10μ, preferably O1
It is 5 to 5.0μ. If the thickness of one copy of the undercoat Jfl 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, in order to form the undercoat layer, a liquid in which the above components are dissolved or dispersed is applied onto the conductive substrate,
dry. Drying conditions are usually 80 to 150°C and 20 minutes to 10 hours.

Conductive substrates include those exhibiting conductivity with a volume resistance of 10"00 m or less, such as metals such as aluminum, nickel, chromium, nichrome, copper, silver, gold, and platinum, and metal oxides such as tin oxide and indium oxide. coated on a film or cylindrical plastic, 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, poly-N-vinylcarbazole, polyacrylamide, etc. are used.

Examples of the charge generating substance include CI Pigment Blue 25 (Color Index (CI) 21180),
CI Pigment Red 41 (CI 21200),
C.I. Acid Red 52 (CI 45100), C.I. Basic Red 3 (CI 45210), and a phthalocyanine 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
(CI 73410), Sea Eye Bat Die (CI 7
3030), etc., Argo Scarlet 8
(manufactured by Violet), Indus Thread Scarlet R (
Organic pigments such as perylene pigments such as those manufactured by Bayer AG11) 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.

It is appropriate to use the binder resin in an amount of 0-0 parts by weight based on 100 parts by weight of the charge-generating substance, preferably 0 parts by weight.
~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 with 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 pm, preferably 0.1-2.

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-(dodiethylaminostyryl)anthracene, 1.1-bis-(4-dibenzylaminophenyl)propane, styrylanthracene, styrylpyrazoline, phenylhydrazones, α-phenylstilbene Examples include electron-donating substances such as derivatives.

Examples of electron transport substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinone dimethane, 2,4,7-)-dinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4,5.7-titranitroxanthone, 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-trinitrodibenzothiophenone-5.5-dioxide.

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

Binder resins 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, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone Examples include thermoplastic or thermosetting resins such as 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 1100p.

Further, 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, and the appropriate amount to be used is about 0 to 30% 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 applied on the AQ root plate by dip coating at 130°C.
Dry for 30 minutes to reduce the film thickness to 3. An undercoat layer containing zirconium oxide and indium oxide of θμ was formed.

(Undercoat layer coating liquid) Four types of styrene/methyl methacrylate/acrylic acid/glycidyl methacrylate resins having the following compositions were synthesized.

Next, a solution of each resin U-1, 2, 3, 4 (toluene/
Butanol = 9/l, solid content 8. Ott%), zirconium oxide (TZO3N manufactured by Toyo Soda Kogyo Co., Ltd.), and indium oxide (Mitsubishi Metals Co., Ltd. 11) in a weight ratio of 12.5/4.
The mixture was mixed at a ratio of 510.5, put into a glass ball mill pot, and ball milled for 120 hours.

An appropriate amount of the above solvent was added to the undercoat layer dispersion to dilute it to obtain an undercoat layer coating liquid.

Next, on this undercoat layer, the following charge generation layer coating solution was applied by dipping coating, and after drying at 120 DEG C. for 10 minutes, a charge generation layer having a thickness of 0.7 .mu.m was formed.

(Charge generation layer coating liquid) Psz balls were placed in a 15φ1 hardened glass pot to about half of the content, and then the azo pigment-3925 was added to the pot.
g and 415 g of cyclohexanone were charged. After ball milling for 50 hours, 560 g of cyclohexanone was further added and ball milling was carried out 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 generating MfJ1 working solution was applied by dipping coating, and after drying at 120°C for 10 minutes, the film thickness was 0.5 μm.
A charge generation layer 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 and indium 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 &l was replaced with &l.

Example 6 An electrophotographic photoreceptor was produced in the same manner as in Example 4, except that the ratio of zirconium oxide to indium oxide was changed to 4/l, and the azo pigment, which was a charge generating material, was replaced with at. was created.

The electrophotographic photoreceptor prepared as above was charged by performing -6KV corona discharge for 20 seconds using a commercially available electrostatic copying paper tester (Kawaguchi Electric Seisakusho 5P-428), and after 2 seconds Surface potential VX (V) and maximum potential Vm (V)
After measuring and leaving it in the dark for 20 seconds, the surface potential V,
(V) was measured.1 Next, tungsten lamp light was irradiated so that the illuminance of the photoreceptor surface was 4.5 Qux, and the exposure amount El/2 (j
! ux-sec) and residual potential VR (V) after 30 seconds
was measured.

In addition, in order to know the repeated fatigue characteristics, -7,5
KV's? Exposure with iF light and 30 Qux was repeated for one hour to obtain the above measured values after fatigue. The results are shown in Table-1.

Also, the electrophotographic photoreceptors of Example 2 and Example 3.

Attach the drum shape to a laser beam printer, 25℃/60%RH110℃/15%R1 and 3
In an environment of 0°C/90% R1, the electrophotographic photoreceptor was subjected to repeated printing operations for 5,000 sheets to repeatedly fatigue the image quality, and the image quality was evaluated. Clear images with no deterioration were obtained.

〔effect〕

The electrophotographic photoreceptor of the present invention has an undercoat layer made of a thermosetting styrene/methyl methacrylate/acrylic acid/glycidyl methacrylate copolymer containing zirconium oxide and indium oxide particles simultaneously on a conductive substrate. By adopting the structure of the function-separated laminated photoreceptor provided, it has high sensitivity, and even after repeated charging and exposure, it has remarkable characteristics such that the charge at position 4 rises quickly and the residual potential is small.

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

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 indium 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/glycidyl acrylate.