JP3352305B2 - Electrophotographic photoreceptor, process cartridge having the electrophotographic photoreceptor, and electrophotographic apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member, and more particularly, to an electrophotographic photosensitive member having a protective layer containing a specific resin and a photosensitive layer containing a specific resin, a process cartridge having the same, and an electronic device. Related to photographic equipment.

[0002]

2. Description of the Related Art An electrophotographic method is disclosed in U.S. Pat.
As shown in the specification, a photoconductive material which is insulative in a dark place, but whose electric resistance changes according to the irradiation amount received during image exposure is used. The basic characteristics required for an electrophotographic photoreceptor using this photoconductive material include:
(1) It is possible to charge to an appropriate potential in a dark place, (2) There is little dissipation of the potential in a dark place, and (3) The charge is quickly dissipated by light irradiation.

In particular, since various electrical and mechanical external forces such as charging means, exposing means, developing means, transferring means and cleaning means are directly applied to the surface of an electrophotographic photosensitive member which is repeatedly used, the durability against these is remarkable. Is also required.

[0004] More specifically, durability against electrical deterioration due to ozone or nitrogen oxides generated during charging, or mechanical deterioration such that the surface is worn or scratched due to discharge during charging or rubbing by various members. Sex is required.
In particular, an electrophotographic photosensitive member using an organic photoconductive material has relatively low mechanical durability, and its improvement is particularly desired.

Attempts have been made to provide a surface protective layer containing a resin as a main component on the surface of the photosensitive layer in order to satisfy the durability characteristics required for the photosensitive member as described above. For example, JP-A-56-42863 and JP-A-53-10374.
No. 1 discloses that hardness and abrasion resistance are improved by using a protective layer containing a curable resin as a main component.

However, when a curable resin is used as the surface protective layer, especially when the lower photosensitive layer is a photosensitive layer containing a resin as a main component, the protective layer or the protective layer is formed due to volume shrinkage that occurs when the curable resin is cured. In some cases, the photosensitive layer was cracked, resulting in defects in the obtained image.

As a countermeasure against the cracks, Japanese Patent Laid-Open No. 5-1
No. 00464 discloses a protective layer containing a photocurable resin using an acrylic monomer having a relatively small volume shrinkage. However, the protective layer has better characteristics in terms of residual potential and photo memory. Photoreceptors are being considered.

In recent years, in particular, organic photoconductors have been used up to a high-speed process for printing at least 10 sheets per minute, and there is a strong demand for improvement in durability during repeated use, particularly reduction in residual potential.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrophotographic photoreceptor having excellent characteristics in which residual potential hardly accumulates even when used repeatedly and image deterioration hardly occurs.

It is another object of the present invention to provide an electrophotographic photoreceptor in which a photo memory hardly occurs.

It is a further object of the present invention to provide a process cartridge having the above electrophotographic photosensitive member and an electrophotographic apparatus.

[0012]

That is, the present invention relates to an electrophotographic photosensitive member having a conductive support, a photosensitive layer on the conductive support, and a protective layer on the photosensitive layer, wherein the protective layer is formed of an acrylic resin.
To contain Le resin monomer or an acrylic resin oligomer
Solution is applied to the photosensitive layer and then cured.
It is, port of said photosensitive layer has a glass transition temperature above 170 ° C.
An electrophotographic photosensitive member containing a carbonate .

Further, the present invention is a process cartridge and an electrophotographic apparatus having the above electrophotographic photosensitive member.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a protective layer will be described.
The protective layer used in the present invention includes a monomer or an oligomer,
Further, if necessary, the solution containing the polymerization initiator is cured by applying heat or irradiating light .
Ri Ru is formed. That is, the protective layer of the present invention is formed by applying the solution on the photosensitive layer and then curing.

The resin contained in the protective layer used in the present invention is an acrylic resin in terms of curability, coating properties and paint stability.
It is . Preferred examples of the acrylic monomer are shown below, but are not limited thereto.

[0016]

[Outside 1]

[0017]

[Outside 2]

[0018]

[Outside 3]

[0019]

[Outside 4]

[0020]

[Outside 5] However, R and R 'in the above formula are each represented by the following formula.

[0021]

[Outside 6] In the present invention, two or more types of curable resins can be used, and can be mixed with other resins such as polyester, polycarbonate, polyurethane, silicone resin and alkyd resin and vinyl chloride-vinyl acetate copolymer. Can also be used.

In the present invention, a polymerization initiator may or may not be used, but the technical problem of the present invention is more remarkable when a polymerization initiator is used. The addition amount of the polymerization initiator is preferably from 0.1 to 80%, more preferably from 0.5 to 50%, based on the total weight of the monomers and oligomers. In addition, since photocuring usually causes smaller volume shrinkage during curing than thermal curing, it is preferable to use a photopolymerization initiator in the present invention. Preferred examples of the photopolymerization initiator that can be used are shown below, but are not limited thereto.

[0023]

[Outside 7] In the present invention, for the purpose of controlling resistance,
It is preferable to disperse conductive particles such as metal oxide particles in the protective layer. As conductive metal oxides, zinc oxide,
Tin oxide, titanium oxide, antimony oxide, indium oxide, bismuth oxide, tin oxide doped with indium,
Examples include tin oxide and zirconium oxide doped with antimony. One or two of these metal oxides are used.
Mix and use seeds. The content of the metal oxide particles is
It is preferably 5 to 90% of the total solid weight of the protective layer,
90% is more preferred. If the content of the metal oxide is less than 5%, the resistance as the protective layer may be too high, and if it exceeds 90%, the resistance as the surface layer of the photoreceptor is liable to be low, and the chargeability may be reduced or the pinhole may be reduced. May cause.

In the present invention, for the purpose of improving surface lubricity and environmental stability, it is preferable to disperse lubricating particles such as tetrafluoroethylene in the protective layer.

Further, in the present invention, various kinds of coupling agents and antioxidants can be added to the protective layer for the purpose of improving dispersibility, adhesiveness, environmental stability and the like.

The protective layer used in the present invention has a thickness of 0.1
It is preferably from 10 to 10 μm, more preferably from 0.5 to 7 μm.

The coating method of the protective layer may be any general coating method, but a dip coating method is preferred from the viewpoint of productivity.

Next, the photosensitive layer will be described. Under the protective layer, a photosensitive layer, preferably, a charge transport layer having a charge transport material and a binder resin is formed. As mentioned above,
It is necessary to reduce the residual potential of the photoconductor. To simply lower the resistance of the protective layer, the protective layer may be made to contain conductive particles, but the residual potential alone cannot be sufficiently reduced.

As a result of intensive studies, the present inventors have found a correlation between the resin of the photosensitive layer in contact with the protective layer and the residual potential or photo memory, and have reached the present invention. That is, by using a resin having a glass transition point (hereinafter, abbreviated as Tg) of 170 ° C. or more as a binder resin of the photosensitive layer in contact with the protective layer, the residual potential can be reduced, and the residual potential is accumulated due to durability. Can be avoided.

Although the mechanism of the present invention is not clear, it can be considered as follows. When a curable resin is used as the protective layer, the monomer or oligomer itself of the resin acts as an organic solvent, and erodes the photosensitive layer to be coated. The binder resin in the photosensitive layer does not completely dissolve in the monomer or oligomer, and the photosensitive layer swells only near the interface between the photosensitive layer and the protective layer. As a result, the charge transporting material and the polymerization initiator migrate and form an electric trap. Therefore, it is considered that the residual potential does not decrease only by lowering the resistance of the protective layer. Since the charge transporting material and the polymerization initiator have a low molecular weight, some migration is considered to occur without fail. Therefore, by using a binder resin having a high Tg, the swelling of the photosensitive layer is prevented by increasing the crystallinity of the resin, and by imparting steric hindrance to the photosensitive layer, the movement of the charge transport material and the polymerization initiator is prevented. The present invention was conceived to prevent such a situation. This does not simply add a bulky group to the structure of the monomer constituting the binder resin to impart steric hindrance, but increases the easily crystallized portion in the molecule at the time of film formation to form a coating film. It is intended to impart steric hindrance.

In the present invention, Tg is preferably 240 ° C. or lower. If the temperature exceeds 240 ° C., cracks tend to easily occur in the photosensitive layer. In addition, Tg in the present invention can be measured by a general method from a DTA curve of the resin.

The molecular weight is preferably from 5,000 to 1,000,000, more preferably from 15,000 to 100,000 in terms of weight average molecular weight from the viewpoint of coatability.

In the present invention, the resin contained in the photosensitive layer is
Polycarbonate in terms of solvent resistance and hardness. The polycarbonate used in the present invention is a resin having a carbonate bond in the main chain, and is preferably a resin obtained by polymerizing a bisphenol compound by a phosgene method or a transesterification method. Thermoplastic resins such as polyester and polystyrene are sometimes insufficient in hardness, and thermosetting resins such as phenolic resins and urethane resins have many polar groups and may adversely affect sensitivity.

In the present invention, the resin may be used alone, or may be used by blending with another resin. However, when the Tg of the other resin is less than 170 ° C., the proportion of the resin having a Tg of 170 ° C. or more is preferably 50% by weight or more based on the total weight of the resin in the contained layer. .

As the charge transporting material used together with the binder resin, various triarylamine compounds,
Examples include hydrazone compounds, stilbene compounds, pyrazoline compounds, oxazole compounds, triallylmethane compounds, and thiazole compounds.

The thickness of the charge transport layer in the present invention is 4 to 3
It is preferably 0 μm, and particularly preferably 5 to 20 μm. Further, the ratio of the charge transport material to the resin is preferably 1/10 to 20/10 by weight,
Particularly, the ratio is preferably 5/10 to 10/10.

When the photosensitive layer in contact with the protective layer is a charge transport layer, the lower layer is a charge generation layer. The charge generation layer is preferably formed by applying a solution in which the charge generation material is dispersed in a binder resin and drying the solution. Alternatively, the charge generation layer may be formed by depositing only the charge generation material.

Examples of the charge generating material include phthalocyanine pigments, azo pigments and anthantrone pigments, and examples of the binder resin include polyester, polyacryl, polyvinyl carbazole, phenoxy resin, polycarbonate, polystyrene, polyvinyl acetate, and the like.
Polysulfone, polyarylate, vinylidene chloride / acrylonitrile copolymer, polyvinyl benzal, and the like. The weight ratio of the binder resin to the charge generating material is preferably 1/5 to 5/1, and particularly preferably 1/2 to 3/1.

When the photosensitive layer is a single layer, it is formed by applying and drying a solution obtained by dispersing and dissolving the above-mentioned charge generation material and charge transport material in a resin having a Tg of 170 ° C. or less. be able to.

In the present invention, an intermediate layer having a barrier function and an adhesive function can be provided below the photosensitive layer. Examples of the material for the intermediate layer include polyamide, polyvinyl alcohol, polyethylene oxide, ethyl cellulose, casein, polyurethane, and polyether urethane. This layer can be formed by applying a solution in which these are dissolved in an appropriate solvent and drying the solution. The thickness of the intermediate layer is preferably from 0.01 to 5 μm, and particularly preferably from 0.1 to 1 μm.

In the present invention, a conductive layer having a function of preventing interference fringes and covering defects of the support can be provided below the intermediate layer. This layer can be formed by applying a solution in which conductive powders such as carbon black and metal particles are dispersed in various binder resins, and drying. The thickness of the conductive layer is preferably from 5 to 40 μm, particularly preferably from 5 to 30 μm.

Examples of the method for applying each of these layers include dipping, spray coating, spinner coating, bead coating, blade coating, and beam coating.

The conductive support for forming each of the layers may be a conductive support, and may be a metal such as aluminum, or a metal provided with a conductive layer, plastic, paper, or the like. Film-like and the like.

The electrophotographic photosensitive member of the present invention can be used not only for an electrophotographic copying machine but also for a laser beam printer,
It can be widely used in electrophotographic applications such as RT printers, LED printers, liquid crystal printers, and laser plate making.

FIG. 1 shows a schematic configuration of an electrophotographic apparatus having a process cartridge having the electrophotographic photosensitive member of the present invention.

In FIG. 1, reference numeral 1 denotes a drum-shaped electrophotographic photosensitive member of the present invention, which is driven to rotate around an axis 2 at a predetermined peripheral speed in a direction indicated by an arrow. The photoreceptor 1 rotates during the rotation process.
The peripheral surface thereof is uniformly charged with a predetermined positive or negative potential by the primary charging unit 3 and then receives image exposure light 4 from an image exposure unit (not shown) such as slit exposure or laser beam scanning exposure. Thus, an electrostatic latent image is sequentially formed on the peripheral surface of the photoconductor 1.

The formed electrostatic latent image is then transferred to developing means 5
The toner-developed image developed by the toner image is transferred from a paper supply unit (not shown) between the photoconductor 1 and the transfer unit 6 in synchronization with the rotation of the photoconductor 1 and fed to a transfer material 7 fed therefrom. The image is sequentially transferred by the transfer unit 6.

The transfer material 7 having undergone the image transfer is separated from the photoreceptor surface, introduced into the image fixing means 8 and subjected to image fixing, thereby being printed out of the apparatus as a copy.

The surface of the photoreceptor 1 after the image is transferred is cleaned by removing the untransferred toner by the cleaning means 9, and is further cleaned by a pre-exposure light 10 from a pre-exposure means (not shown).
Is used for image formation repeatedly after the charge removal processing. When the primary charging unit 3 is a contact charging unit using a charging roller or the like, pre-exposure is not necessarily required.

In the present invention, a plurality of components such as the above-described electrophotographic photosensitive member 1, primary charging means 3, developing means 5, and cleaning means 9 are integrally connected as a process cartridge. The process cartridge may be configured to be detachable from a main body of an electrophotographic apparatus such as a copying machine or a laser beam printer. For example, at least one of the primary charging unit 3, the developing unit 5, and the cleaning unit 9 is integrally supported together with the photoreceptor 1 to form a cartridge, which can be attached to and detached from the apparatus main body using a guide unit such as a rail 12 of the apparatus main body. The process cartridge 11 can be used.

When the electrophotographic apparatus is a copying machine or a printer, the image exposure light 4 is reflected or transmitted from the original, or the original is read by a sensor and converted into a signal, and the exposure is performed according to the signal. Laser beam scanning,
Light emitted by driving the LED array, driving the liquid crystal shutter array, and the like.

On the other hand, when used as a facsimile printer, the image exposure light 4 becomes exposure light for printing received data. FIG. 2 is a block diagram showing an example of this case.

The controller 14 controls the image reading unit 13 and the printer 22. The entire controller 14 is controlled by the CPU 20. The read data from the image reading unit 13 is transmitted to the partner station through the transmission circuit 16. Data received from the partner station is sent to the printer 22 through the receiving circuit 15. Predetermined image data is stored in the image memory. The printer controller 21 controls the printer 22. 17 is a telephone.

The image received from the line 18 (image information from a remote terminal connected via the line) is demodulated by the receiving circuit 15 and then decoded by the CPU 20 to be sequentially stored in the image memory 19. Is done. When the image of at least one page is stored in the memory 19, the CPU 20 performs image recording of the page. The CPU 20 reads out the image information of one page from the image memory 19, and Sends out image information. The printer controller 21
When receiving one page of image information from the CPU 20, the printer 22 is controlled to record image information of the page. The CPU 20 is receiving the next page during recording by the printer 22.

Thus, the reception and recording of the image are performed.

[0056]

The present invention will be described in detail below with reference to examples. (Example 1) A paint composed of the following materials was applied on an aluminum cylinder of 30φ × 260 mm by a dip coating method, and thermally cured at 140 ° C. for 30 minutes to form a conductive layer having a thickness of 15 μm.

Conductive pigment: tin oxide-coated titanium oxide 10 parts (parts by weight, the same applies hereinafter) Resistance adjusting pigment: titanium oxide 10 parts Binder resin: phenol resin 10 parts Leveling agent: silicone oil 0.001 part Solvent: methanol / methyl cellosolve = 1/1 ... 20 parts

Next, on this layer, 3 parts of N-methoxymethylated nylon and 3 parts of copolymerized nylon were added.
A solution dissolved in a mixed solvent of 5 parts and 30 parts of n-butanol was applied by a dip coating method and dried to form a 0.5 μm intermediate layer.

Next, the Bragg angles 2θ ± 0.2 ° in the CuKα characteristic X-ray diffraction are 9.0 °, 14.2 °, 23.
A solution obtained by mixing 4 parts of oxytitanium phthalocyanine having strong peaks at 9 ° and 27.1 °, 2 parts of polyvinyl butyral (trade name: Eslec BM-2, manufactured by Sekisui Chemical Co., Ltd.), and 80 parts of cyclohexanone was mixed with φ1 mm glass beads. After dispersing for 4 hours in a sand mill using
115 parts of methyl ethyl ketone was added to obtain a dispersion for charge generation layer. This was applied on the intermediate layer by a dip coating method and dried to form a 0.3 μm charge generation layer.

Next, 10 parts of an amine compound having the following structural formula

[0061]

[Outside 8] And polycarbonate 10 of sample number 1 in Table 1
Parts were 30 parts of monochlorobenzene and 30 parts of dichloromethane.
Of the mixed solvent. This paint was applied on the above-mentioned charge generation layer by a dip coating method, and dried at 110 ° C. for 1 hour to form a charge transport layer having a thickness of 20 μm.

Next, a preparation solution for the protective layer was prepared according to the following procedure. Antimony-containing tin oxide fine particles having an average particle size of 0.02 μm (trade name: T-1, Mitsubishi Materials Corporation)
100 parts, (3,3,3-trifluoropropyl)
30 parts and 9 of trimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.)
A solution obtained by dispersing a solution obtained by mixing 300 parts of a 5% ethanol-5% aqueous solution with a milling device for 1 hour was filtered.
After washing with ethanol, drying and heating at 120 ° C. for 1 hour, the surface of the tin oxide fine particles was treated. Next, an acrylic monomer exemplified compound No. 1 was used as a binder resin. 23, 25 parts of 2-methylthioxanthone as a photopolymerization initiator, and 35 parts of the surface-treated antimony-containing tin oxide particles and 300 parts of toluene were mixed and dispersed in a sand mill for 96 hours. To
Polytetrafluoroethylene resin particles (trade name: Lubron L-2,
A solution prepared by mixing 25 parts of Daikin Industries, Ltd.) was dispersed in a sand mill for 8 hours to obtain a dispersion for a protective layer.

This dispersion was spray-coated on the charge transport layer, dried, and irradiated with ultraviolet light at a light intensity of 800 mW / cm ² for 15 seconds using a high-pressure mercury lamp to form a film having a thickness of 4 μm.
m of protective layers were formed.

[0064]

[Outside 9]

[0065]

[Outside 10]

[0066]

[Outside 11]

[0067]

[Outside 12]

(Examples 2 to 9) As binder resins for the charge transport layer, sample numbers 2, 3, 5, 6,
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that the polycarbonates of 8, 9, 11 and 12 were used.

The prepared electrophotographic photosensitive member was heated at 23 ° C. and 30%
After being left overnight under RH, it was mounted on a modified machine of Canon Laser Beam Printer LBP-NX to measure the residual potential. That is, remove the developing unit and cleaner, prepare a cartridge with a potential sensor attached to the position of the developing unit,
After removing the transfer roller from the main body, the potential of the photoreceptor surface after performing an electrophotographic process for printing five A4 sheets in the whole black image mode (entire light irradiation) is set to V1, and then the laser is irradiated. The primary charge was turned off, and the surface potential when the photoconductor rotated 5 times was defined as the residual potential.

Further, 15,000 sheets were passed, and Vl and the residual potential of the photosensitive member immediately after the durability were measured in the same manner as described above.

Further, another photoreceptor prepared in the same manner as above was irradiated with light for 6 minutes by a fluorescent lamp having an illuminance of 2000 lux, left in a dark place for 2 minutes after irradiation, and V1 was measured in the same manner as described above. What is obtained by subtracting V1 of the portion irradiated with light from V1 of the portion not irradiated with light is shown as a photo memory.

Further, an image in which a black line having a width of one dot was repeated at intervals of two dots was formed using the photosensitive member evaluated for the photo memory, and the obtained image was visually evaluated.

[0073]

(Comparative Examples 1 to 6) Sample numbers 4, 7, 10, 1 in Table 1 were used as binder resins for the charge transport layer.
An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1, except that the polycarbonates of Nos. 3, 14 and 15 were used. Table 3 shows the results.

[0075]

Examples 10 to 18 Electrophotographic photosensitive members were prepared and evaluated in the same manner as in Examples 1 to 9 except that the acrylic monomer exemplified compound No. 22 was used as a binder resin for the protective layer.

Table 4 shows the results.

[0078]

(Examples 19 and 20) The same procedures as in Example 1 were carried out except that the charge transporting material having the following structure was used.
An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Examples 2 and 3. Table 5 shows the results.

[0080]

[Outside 13]

[0081]

(Comparative Examples 7 and 8) An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Comparative Examples 1 and 2, except that the charge transporting material having the following structure was used. Table 6 shows the results.

[0083]

[Outside 14]

[0084]

(Examples 21 to 23) As the binder resin for the charge transporting layer, the polycarbonates of Sample No. 2 and Sample No. 13 in Table 1 were used in a weight ratio of 7 respectively.
An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 2, except that 0/30, 60/40 and 50/50 were used. Table 7 shows the results.

[0086]

(Comparative Examples 9 and 10) Electrophotographic photosensitive members were prepared and evaluated in the same manner as in Example 1 and Comparative Example 1, respectively, except that the thickness of the charge transport layer was 24 μm and the protective layer was not applied. . Table 8 shows the results.

[0088]

[0089]

As described above, according to the electrophotographic photoreceptor of the present invention, the process cartridge having the electrophotographic photoreceptor, and the electrophotographic apparatus, the residual potential is maintained while maintaining excellent mechanical durability by the protective layer. Can be reduced, image deterioration due to an increase in residual potential due to durability can be prevented, and electrical sensitivity can be increased and photo memory can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a schematic configuration of an electrophotographic apparatus having a process cartridge having an electrophotographic photosensitive member of the present invention.

FIG. 2 is a diagram illustrating an example of a block diagram of a facsimile having the electrophotographic photosensitive member of the present invention.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-214408 (JP, A) JP-A-6-214412 (JP, A) JP-A-6-282092 (JP, A) JP-A-6-214209 35220 (JP, A) JP-A-6-308756 (JP, A) JP-A-6-39221 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 5/00

Claims (7)

(57) [Claims] 1. An electrophotographic photosensitive member having a conductive support, a photosensitive layer on the conductive support, and a protective layer on the photosensitive layer, wherein the protective layer is formed of an acrylic resin monomer or an acrylic resin.
After applying the solution containing the resin oligomer on the photosensitive layer, it is cured
It is formed by an electrophotographic photosensitive member the photosensitive layer is characterized by containing a polycarbonate having a glass transition temperature of greater than or equal to 170 ° C.. 2. The electrophotographic photosensitive member according to claim 1, wherein the glass transition point is 240 ° C. or lower. 3. The composition according to claim 1, wherein the proportion of the polycarbonate is at least 50% by weight based on the total weight of the resin in the layer containing the polycarbonate.
Or the electrophotographic photosensitive member according to 2. 4. An acrylic resin monomer or an acrylic resin
The electrophotographic photoreceptor according to any one of claims 1 to 3 , wherein the fat oligomer is cured by light irradiation. 5. An acrylic resin monomer or acrylic resin
The electrophotographic photoreceptor according to any one of claims 1 to 4 , wherein the solution containing a fat oligomer contains a photopolymerization initiator. 6. The electrophotographic photosensitive member according to any one of claims 1 to 5, and charging means, at least one means selected from the group consisting of the developing means and cleaning means integrally supported, the electrophotographic apparatus body A process cartridge which is detachably attached to the cartridge. 7. The electrophotographic photosensitive member according to claim 1 to 5, a charging means, an exposure means, the electrophotographic apparatus, characterized in that it comprises a developing means and a transfer means.