DE4025759A1 - ELECTROPHOTOGRAPHIC PHOTORE RECEPTOR - Google Patents

Description

The invention relates to an electrophotographic photoreceptor with an electrically conductive carrier, a damping layer and a photosensitive layer. In particular, it concerns the invention an electrophotographic photoreceptor with an improved cushioning layer.

In the current development of electrophotographic Photocopiers, increasing the number of copies of different sizes Speed is provided by the photoreceptors, used in these electrophotographic copying machines be required to have a higher photosensitivity and have a longer applicability.

There are many proposals for electrophotographic photoreceptors of various functional type have been made each several elements act as a photoreceptor to to improve various electrophotographic characteristics, for example, charge retention, stability at repeated use, response to light, spectral characteristics and mechanical strength.

These electrophotographic photoreceptors are known to have Disadvantages, for example, (1) unsatisfactory reproducibility the developed image contrast with repeated use or if the environment changes, (2) susceptibility to image defects, as white spots, black spots, roughness, Pinholes, etc. may be referred to or described  can and (3) unsatisfactory resistance to one low adhesion between the carrier and the photosensitive Layer goes back, so that it separates the photosensitive layer comes in use.

To overcome these disadvantages, it has been proposed Resin layer between the support and the photosensitive Provide layer. As resins, used for the resin layer are poly-p-xylene, casein, polyvinyl alcohol, Phenolic resins, polyvinylacetal resins, melamine resins, nitrocellulose, Ethylene / acrylic acid copolymers, polyamide (e.g. Nylon 6, nylon 66, nylon 610, copolymer nylon, alkoxy methylated nylon), polyurethane, gelatin, polyvinylpyrrolidone, Polyvinylpyridine and polyvinyl methyl ether known.

It has also been suggested to put an intermediate layer under Use of organozirconium compounds, for example zirconium chelate compounds and zirconium alkoxides, or silane coupling agents provide; see. JP-A-59 2 23 439, JP-A-61 94 057 and JP-A-62 2 73 549 (JP-A: Unexamined Published Japanese Patent application).

Characterized in that a resin layer as a damping layer or buffer layer is provided, the volume resistance or spec. Resistance can be regulated at such a low level that the electrophotographic properties are no longer impaired By essentially making a resin with one used relatively large proportion of polar groups. As the volume resistance a resin of ionic conductivity (ion conduction) It depends considerably on temperature and temperature Moisture affects. Therefore, if a photoreceptor of a low temperature and low humidity or exposed to high temperature and high humidity is, the resin layer shows a considerably increased resistance, causing an impairment of the electrophotographic Characteristics of the photosensitive layer,  or a considerably reduced resistance, what a Loss of expected properties means.

Thus, the known resin layers only partially mentioned Resolve disadvantages that occur in photoreceptors. When one considers the vulnerability to environmental influences, so the effects of the resin layer are reduced by half reduced. The known resin layers are therefore technical extremely unsatisfactory.

When organozirconium compounds, for example Zirkonchelatverbindungen and zirconium alkoxides, or silane coupling agents the problems mentioned become considerable tempered, but satisfy these compounds so far little, as they reduce the developed image contrast cause increased residual potential and cause image errors can, for example, white spots, black spots, roughness and pinholes.

Thus, the damping layers proposed in the prior art have for the elimination of the mentioned disadvantages, which at electrophotographic photoreceptors do not occur yet completely satisfied, so that the known photoreceptors unsatisfactory Have characteristics.

Object of the present invention is an electrophotographic Provide photoreceptor, the excellent electrostatic Characteristics with little loss of darkness or Dark decay possesses, almost no reduction of the developed Image contrast shows and in particular a low Residual potential supplies.

It is another object of the invention to provide an electrophotographic Provide photoreceptor, which is virtually no aberrations brings with it, such as white spots, black spots, roughness and pinholes.  

It is another object of the present invention to provide a To provide electrophotographic photoreceptor, which is practical not affected by environmental changes and extraordinary is durable.

Investigations preceding the invention have found that one of a solution of the above task thereby it may come close to having a cushioning or buffering layer therethrough produces an organozirconium compound and a Silane coupling agent applies and the coating up to a certain Hardening degree hardens.

Thus, the present invention relates to an electrophotographic Photoreceptor with an electrically conductive support, the a cushioning layer and a photosensitive layer Wearing layer, wherein the damping layer is a Layer with a degree of cure of 3.0 or more, the obtained by mixing a mixed solution of zirconium chelate compound or zirconium alkoxide compound (hereinafter sometimes commonly referred to as Organozirkonverbindung Apply) and a silane coupling agent, after which one hardened.

The term "degree of cure" as used herein refers to a ratio of

• (A) Intensity of the peak in the IR absorption spectrum of Si-O-Zr at 940 cm ^{-1 of} the cushioning layer after application of the above-mentioned mixed solution and after hardening
• (B) Intensity of the peak in the IR absorption spectrum of a silane coupling agent with or -Si-OR (wherein R represents an alkyl group) at 1090 cm ^-1 before coating, ie, the ratio A / B. The IR absorption spectrum can be measured by a standard potassium bromide tablet method.

The degree of cure of the cushioning layer is preferably 3.0 to 6.0, and especially 3.0 to 4.0, in terms of  Curing time and production efficiency, for example, the energy required for curing.

Fig. 1 is a schematic sectional view of an example of an electrophotographic photoreceptor according to the invention, wherein numerals 1 to 4 denote an electroconductive support, a cushion layer, a charge generation layer and a charge transport layer;

Fig. 2 is a graph of the drying time versus the degree of cure of the cushioning layers of Examples 1 and 2.

It may be the known electrically conductive support for the invention be used. Examples of suitable materials of Carriers are aluminum and stainless steel.

On the conductive support, a damping layer is applied. The damping layer according to the invention is a coating layer, which is formed by mixing a mixed solution a zirconium chelate compound or zirconium alkoxide and a Apply silane coupling agent, which is followed to a degree of cure of 3.0 or more hardens. When the degree of cure achieved is less than 3.0, the resulting photoreceptor in terms of its electrophotographic properties due to environmental changes and changes of the copying process vary, whereby also easily picture errors occur can, for example, white spots, black spots and roughness.

The organozirconium compound and the silane coupling agent are preferably in a Zr / Si molar ratio in the range of 1/1 to 8/1, in particular 2/1 to 4/1 mixed.

Since a damping layer containing no silane coupling agent apart from the fact that it can be provided, very unsatisfactory Film forming properties and adhesion properties  has the simultaneous use of a silane coupling agent essential to the present invention.

Organozirconium compounds which are used according to the invention can be represented by the following formula:

(R * O) _n Zr-R ' _m

wherein R represents an alkyl group having 1 to 5 carbon atoms; R 'is an acetylacetone, a ketoester, a glycol or hydroxy acid residue; and n and m are each 0 or one integer from 1 to 4, where the sum of n and m is 4 is.

Typical examples of organozirconium compounds are tetrakisacetylacetonatozircon, Zirconium tetrabutoxide and acetylacetonatotributoxyzircon.

Silane coupling agents which can be used according to the invention include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, Vinyltris (2-methoxyethoxy) silane, vinyltriacetoxysilane, gamma-glycidoxypropyltrimethoxysilane, gamma Methacryloxypropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, gamma-chloropropyltrimethoxysilane, gamma-2-aminoethylaminopropyltrimethoxysilane, gamma-mercaptopropyltrimethoxysilane, gamma-ureidopropyltriethoxysilane and β- (3,4-epoxycyclohexyl) - ethyltrimethoxysilane.

The damping layer according to the invention has a thickness of generally 0.01 to 5 μm, and preferably 0.2 to 2 μm.

The mixed solution for coating the cushioning layer becomes thereby prepared by reacting the organozirconium compound and the Silane coupling agent in a solvent, for example an alcohol such as ethanol, methanol, propanol and butanol; an aromatic hydrocarbon such as toluene; an ester,  such as ethyl acetate and cellosolve acetate; or a mixture of these Solvent dissolves.

The mixed solution is coated, for example by immersion, Spray coating, coating with a knife, spinning coating, Bead coating or curtain coating applied. The coating will be in a stream of air or in motion Air at a temperature in the range of 110 to 250 ° C and preferably 170 to 200 ° C over 5 minutes to 6 hours and preferably dried for 10 min to 2 h. drying temperature and drying time should be chosen so that the desired Achieved degree of cure.

The thermosetting of the coating can be done immediately after the Overshadding or achieving that during training the photosensitive layer arranged above heats.

Thereafter, the photosensitive layer on the on this Way formed formed damping layer. The photosensitive Layer can be either a single layer structure or have a laminate structure. The photosensitive layer single-layer structure comprises a dye-sensitized Photosensitive ZnO layer or photosensitive CdS Layer and a photosensitive layer with a charge Transport substance in which a charge-generating substance is dispersed.

The photosensitive laminate-structured layer comprises a Combination of charge generation layer and charge transport layer, each of which performs the respective function. The Order of order of these layers is arbitrary.

The charge generation layer is provided with Help formed a charge generating substance, possibly in a suitable binder is dispersed. Examples of suitable Charge generating substances are selenium and selenium alloys; inorganic photoconductive substances, such as Cds, CdSe,  CdSSe, ZnO and ZnS; metallized or metal-free phthalocyanine pigments; Azo pigments, such as bisazo pigments and trisazo pigments; squarylium compounds; azulenium; perylene; Indigo pigments; quinacridone; polycyclic Quinone pigments; cyanine; xanthene; charge Transfer complexes of, for example, poly-N-vinylcarbazole and trinitrofluorenone; and eutectic complexes for example, pyrylium salt dye and polycarbonate resin.

Binder resins used in the charge generation layer are known and include polycarbonate, polystyrene, Polyester, polyvinyl butyral, methacrylic ester homopolymers or mixed polymers, vinyl acetate homopolymers or mixed polymers, Cellulose esters or cellulose ethers, polybutadiene, Polyurethane and epoxy resins.

The charge transport layer is mainly using a Charge transport substance formed. In the selection of the charge transport substance there are no special restrictions as long as it is transparent to visible light and electrical Can transport cargoes. Specific examples are imidazole, pyrazoline, thiazole, oxadiazole, oxazole, hydrazone, Ketazine, azine, carbazole, polyvinylcarbazole and their derivatives; Triphenylamine derivatives, stilbene derivatives and benzidine derivatives. Optionally, a binder resin may be used in combination be used. Examples of suitable binder resins are Polycarbonate, polyacrylate, polyester, polystyrene, styrene / acrylonitrile Mischpolymere, polysulfone, polymethacrylate and Styrene / methacrylic acid copolymers.

The invention will be explained in more detail by way of examples. All parts, percentages and ratios are on Weight basis unless otherwise stated.  

Example 1

Tetrakisacetylacetonatozircon (ZC 150 from Matsumoto Kosho K.K.) 10 parts gamma-methacryloxypropyltrimethoxysilane (KBM 503 from Shin-etsu Chemical Industry Co., Ltd.) 20 parts methyl alcohol 400 parts n-butyl alcohol 100 parts n-amyl alcohol 200 parts

The above components were stirred by means of a stirrer to prepare a coating composition for a cushioning layer. The composition was applied to the surface of an aluminum cylinder about 85 mm in diameter by immersion coating to a dry thickness of about 0.2 μm, air-dried for about 5 minutes, and then heat-cured at a drying temperature in the range of 135 to 170 ° C and dried for a drying time of 7.5 to 360 minutes to obtain damping layers of different degrees of hardness. The resulting samples were numbered 1-8. The relationship between drying conditions and the degree of cure achieved are shown in FIG .

It became a solution of 87 parts of a granular trigonal Selenium and 13 parts of a vinyl chloride-vinyl acetate copolymer (Solution vinyl VMCH from Union Carbide Inc.) in 200 parts n- Butyl acetate dispersed in an attritor for 24 h. To 30 parts The resulting dispersion was added 57 parts of n-butyl acetate for dilution to a dip coating composition manufacture.

The damping layer on the aluminum cylinder was then with of the coating composition by dipping and at 100 ° C Dried for 5 minutes, with an approximately 0.1 micron thick Charge generation layer received.  

10 parts of N, N'-diphenyl-N, N'-bis (3-methylphenyl) - [1,1'-biphenyl] - 4,4'-diamine and 10 parts polycarbonate Z resin were incorporated in 80 parts monochlorobenzene dissolved to a coating composition for a charge transport layer. The composition was applied to a charge generation layer and dried in hot air at 100 ° C for 60 minutes, wherein to obtain a 25 μm thick charge transport layer.

The electrophotographic photoreceptor thus obtained was based on an electrostatic principle Working dry copying machine brought (FX 2700 Modified Model of Fuji Xerox Co., Ltd.). After seeing the dark potential VD set to -800 V, became the photoreceptor Exposed to an exposure amount of 2 erg / cm², wherein the light potential VL was measured. After that became one Running test, which received 10 000 copies and the Changes of VD and VL were determined. Also, the Image quality of the copies after the running test rated by Sample artwork copies (white paper) and fixed images optical density of 0.2 and 1.0 used.

It became an electrophotographic photoreceptor found in the at 40 ° C and 85% (RH (relative humidity)) for one month, after which an image quality test was performed.

The results of these reviews are in the following table 1 compiled.

example 2

Acetylacetonatotributoxyzircon (ZC 540 from Matsumoto Kosho K.K.) 100 parts gamma-aminopropyltrimethoxysilane (A 1110 from Nippon Unicar Co., Ltd.) 11 parts ethyl alcohol 600 parts n-butyl alcohol 150 parts

The above components were stirred with a stirrer to prepare a coating composition for a cushioning layer. The composition was coated on an aluminum support in the same manner as in Example 1 and dried in the air for about 8 minutes, and thereafter dried in the heat at various temperatures and for various times in the same manner as in Example 1 to obtain damping layers having various thicknesses To obtain degrees of cure. The accrued samples were designated with the numbers 9 to 15. The relationship between the drying conditions and the degree of cure achieved is shown in FIG .

There was a charge transport layer and a charge generation layer as laminates in the same way as in Example 1 applied to an electrophotographic photoreceptor to obtain; Each photoreceptor was in the same way as tested in Example 1. The results obtained are in Table 1 given.  

Table 1

The electrophotographic photoreceptor of the invention, the has a damping layer of said training has excellent electrostatic characteristics low dark loss and low residual potential; it comes hardly to a reduction of the developed picture contrast. Furthermore, the photoreceptor of the invention is less susceptible against environmental influences, giving it an excellent resistance has. Therefore, when the photoreceptor of the invention is used is used to continuously receive a large number of copies deliver, one obtains stable electrophotographic properties and constantly excellent images without defects, like white ones Stains, black spots, roughness and pinholes.

Claims (5)

1. Electrophotographic photoreceptor with an electric conductive support, on which a damping layer and a photosensitive Layer are provided, wherein the damping layer is a layer that has a degree of cure of 3.0 or having more obtained by mixing a mixed solution a zirconium chelate compound or a zirconium alkoxide and a silane coupling agent and then cured. 2. An electrophotographic photoreceptor according to claim 1, at the degree of cure of the damping layer is 3.0 to 6.0. 3. An electrophotographic photoreceptor according to claim 2, at the degree of cure of the damping layer is 3.0 to 4.0. 4. An electrophotographic photoreceptor according to claim 1, at the zirconium chelate compound or zirconium alkoxide and the Silane coupling agent in a molar ratio Zr / Si im Range from 1/1 to 8/1. 5. An electrophotographic photoreceptor according to claim 4, at the zirconium chelate compound or zirconium alkoxide and the Silane coupling agent in a molar ratio Zr / Si im Range from 2/1 to 4/1.