JPH06250413A - Electrophotographic sensitive body and electrophotographic device having the same - Google Patents

Abstract

PURPOSE:To provide the electrophotographic sensitive body capable of greatly ameliorating the drop-out of a toner image in a direct electrostatic charge transfer system and the electrophotographic device having the same. CONSTITUTION:This electrophotographic sensitive body is used for the electrophotographic device having a transfer means for transferring the toner image to a transfer material by direct electrostatic charge and has >=110 deg. contact angle of the surface of the photosensitive body with water. This electrophotographic device has such electrophotographic sensitive body. The electrophotographic sensitive body which provides the images of high quality with the decreased drop-outs in the direct electrostatic charge transfer system and the electrophotographic device having such photosensitive body are obtd.

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 capable of obtaining a high quality image in an electrophotographic apparatus having a direct charging transfer means.

The present invention also relates to an electrophotographic apparatus having the above electrophotographic photosensitive member.

[0003]

2. Description of the Related Art As a charging member in an electrophotographic apparatus,
Conventionally commonly used corona chargers have the problem of deterioration of the photoconductor due to ozone generated during discharge, and an electrophotographic device adopting the direct charging method as a means to replace it will be put to practical use. Has become. This is for charging by applying a voltage to a low resistance member that is in contact with the electrophotographic photosensitive member.

When transfer charging is performed by direct charging, there is a problem that the central portion of the toner image to be transferred tends to remain on the photosensitive member. This is a so-called “blank image” in the toner image, which causes deterioration in image quality.

It is considered that this hollow portion occurs because the charging member has a shape in which the toner image formed on the surface of the photoconductor is pressed against the photoconductor via the transfer material. As means for improving this, studies have been made in terms of toner prescription and transfer process, but they are not always sufficient and adverse effects cannot be avoided.

[0006]

That is, the present invention provides an electrophotographic photosensitive member and an electrophotographic apparatus which are capable of improving the above-mentioned drawbacks and greatly improving the phenomenon of hollowing out of a toner image in a direct charging transfer system. To aim.

[0007]

That is, the present invention provides an electrophotographic photosensitive member used in an electrophotographic apparatus having a transfer means for transferring a toner image onto a transfer material by direct charging.
The electrophotographic photosensitive member is characterized in that a contact angle of water on the surface of the photosensitive member is 110 ° or more.

The present invention is also an electrophotographic apparatus having the above electrophotographic photosensitive member.

In order to reduce the dropout of the toner image, it is necessary to optimize the thickness of the developed toner layer, the fluidity of the toner, and the like in terms of the development process. Further, in terms of the transfer process, there are factors such as the contact pressure of the charging member with respect to the photoconductor, the plunge angle of the transfer material, and the peripheral speed difference between the charging member and the photoconductor. However, as described above, there are problems that the effect is insufficient and adverse effects cannot be avoided only with these conditions.

On the other hand, from the viewpoint of the photosensitive member, the inventors of the present invention have found that the releasability of the surface on which a toner image is formed has a particularly large effect in the case of direct charge transfer. That is, it was found that when the releasability of the surface of the photoconductor is 110 ° or more at the contact angle with water, excellent transfer characteristics are exhibited and a great effect is exerted on voids.

The present invention is effective when the surface of the photoconductor is mainly composed of a polymer binder. For example, when a protective layer mainly composed of a resin is provided on an inorganic optical semiconductor such as selenium or amorphous silicon, or when a photosensitive layer containing an organic photoconductive material and a resin is provided, the above-mentioned photosensitive layer is further formed on the photosensitive layer. Such a protective layer may be provided.

As means for imparting releasability to such a surface layer, a resin having a low surface energy is used for the resin itself constituting the film, and an additive for imparting water / oil repellency is added. For example, a material having releasability may be made into a powder form and dispersed.

As an example of the above, it is achieved by introducing a fluorine-containing group, a silicon-containing group or the like into the structure of the resin. For this, a surfactant or the like may be used as an additive.
However, this means that the additive easily migrates to the outermost surface,
The effect of the present invention may be poor in sustainability. As the above, it is preferable to disperse a fluorine-containing polymer, for example, powder of polytetrafluoroethylene, polyvinylidene fluoride or the like.

Next, an example of a specific embodiment of the electrophotographic photosensitive member will be described.

The constitution of the photoreceptor of the present invention takes several forms as described above, but it has a charge generating layer containing a charge generating material and a charge transporting layer containing a charge transporting material, and is provided from the support side. An example of a photoreceptor in which a charge generation layer and a charge transport layer are laminated in this order and a protective layer is further provided thereon will be described.

As the conductive support, aluminum,
Examples thereof include metals such as stainless steel, plastic provided with a conductive layer, paper and the like, and examples of the shape include a cylindrical shape and a film shape.

An undercoat layer having a barrier function and an adhesive function can be provided between the support and the photosensitive layer. The undercoat layer is for improving adhesion of the photosensitive layer, improving coatability, protecting the support, covering defects on the support, improving charge injection from the support, protecting the photosensitive layer against electrical breakdown, etc. Form. Examples of the material of the undercoat layer include polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide,
Ethyl cellulose, polyamide, copolymerized nylon, ethylene-acrylic acid copolymer and the like are known. Each of these is dissolved in a suitable solvent and coated on a support.
The film thickness is about 0.1 to 2.0 μm.

Further, it is preferable to provide a conductive layer between the support and the subbing layer for the purpose of covering unevenness and defects of the support and, in the case of laser image input, for preventing interference fringes due to scattering. is there. This is carbon black, metal particles,
It can be formed by dispersing conductive powder such as metal oxide in a binder resin. The thickness of the conductive layer is 5-40 μ
m, preferably 10 to 30 μm.

The charge generation layer is provided on the undercoat layer. Examples of the charge generation layer include those formed by coating an inorganic photoconductor such as amorphous silicon or selenium with a binder, if necessary, by coating, or by vacuum deposition. In the case of an organic material, one or more kinds of charge generating materials such as azo pigments, quinone pigments, perylene pigments and phthalocyanine pigments may be vapor-deposited or dispersed with an appropriate binder to form by coating. .

The charge transport layer is formed by dissolving the charge transport material in a solvent together with a binder. Examples of organic charge transport materials include hydrazone compounds, stilbene compounds,
Examples include pyrazoline-based compounds, oxazole-based compounds, triarylamine-based compounds and the like. These charge transport materials can be used alone or in combination of two or more.

When the surface layer of the present invention is provided on the charge transport layer, the binder resin of the charge transport layer can be selected from a relatively wide range of insulating resins or organic photoconductive polymers. For example, examples of the insulating resin include polycarbonate, polyarylate, polyester, polyacrylic acid ester, polyurethane and the like. Examples of organic photoconductive polymers include polyvinylcarbazole, polyvinylanthracene, and polyvinylpyrene.

The thickness of the charge transport layer is 5 to 50 μm, preferably 10 to 30 μm, and the weight ratio of the charge transport material to the binder is 5: 1 to 1: 5, preferably 3: 1 to 1. : 3
It is a degree.

On the charge transport layer, the contact angle to water is 1
A surface layer of 10 ° or more is provided. As a constitution, powder of polytetrafluoroethylene, for example, is dispersed in the above insulating resin. The amount of such a low surface energy imparting agent added to the entire surface layer is 10 to 100% by weight, preferably 20 to 50% by weight. If the addition amount is less than 10% by weight, the effect of the present invention may be insufficient, and if it exceeds 100% by weight, the film strength of the surface layer tends to decrease, and the durability upon repeated use may decrease. is there. Further, if necessary, a charge transport material may be added to improve potential characteristics.

The contact angle was measured with a contact angle meter CA-DS type manufactured by Kyowa Interface Science Co., Ltd.

FIG. 1 shows a schematic constitutional example of an electrophotographic apparatus using the electrophotographic photosensitive member of the present invention.

In the figure, reference numeral 1 denotes a drum type photosensitive member of the present invention as an image bearing member, which is rotationally driven around an axis 1a in a direction of an arrow at a predetermined peripheral speed. The photosensitive member 1 is uniformly charged at its peripheral surface by a charging unit 2 at a predetermined positive or negative potential in the course of its rotation, and then at an exposure unit 3 an optical image exposure L (slit exposure Laser beam scanning exposure). As a result, electrostatic latent images corresponding to the exposed image are sequentially formed on the peripheral surface of the photoconductor.

The electrostatic latent image is then toner-developed by the developing means 4, and the toner-developed image is rotated by the transfer means 5 between the photoconductor 1 and the transfer means 5 from a paper feeding portion (not shown). The images are sequentially transferred onto the surface of the transfer material P that is synchronously taken out and fed.

The transfer material P which has received the image transfer is separated from the surface of the photoconductor and is introduced into the image fixing means 8 where it is subjected to the image fixing and printed out as a copy.

After the image transfer, the surface of the photosensitive member 1 is cleaned by the cleaning means 6 to remove residual toner after transfer, and is further discharged by the pre-exposure means 7 to be repeatedly used for image formation.

As the uniform charging means 2 for the photoconductor 1, a corona charging device is generally widely used, but as described above, a direct charging device in which a charging member is in contact is also used. Further, since the transfer device 5 is a direct charging type in the present invention,
Here, a conductive roller is pressed against the photoconductor. The electrophotographic apparatus is configured by integrally combining a plurality of constituent elements such as the photoconductor, the developing unit, and the cleaning unit described above as an apparatus unit, and the unit is configured to be detachable from the apparatus body. May be. For example, the photosensitive member 1 and the cleaning unit 6 may be integrated into one device unit, and the device unit may be detachably configured by using a guide unit such as a rail. At this time, the above device unit may be provided with a charging unit and / or a developing unit.

When the electrophotographic apparatus is used as a copying machine or a printer, the light image exposure L is reflected light from a document or transmitted light, or a document is read and converted into a signal, and a laser beam is scanned based on this signal. Or driving an LED array or a liquid crystal shutter array.

When used as a facsimile printer, the optical image exposure L becomes an exposure for printing the received data. FIG. 2 is a block diagram showing an example of this case.

The controller 11 controls the image reading section 10 and the printer 19. The entire controller 11 is CP
It is controlled by U17. The read data from the image reading unit 10 is transmitted to the partner station through the transmission circuit 13. The data received from the partner station is sent to the printer 19 through the receiving circuit 12. The image memory 16 stores predetermined image data. The printer controller 18 controls the printer 19. 14 is a telephone.

The image information received from the line 15 (image information from a remote terminal connected via the line) is demodulated by the receiving circuit 12, then decoded by the CPU 17, and sequentially stored in the image memory 16. Is stored. When the image information of at least one page is stored in the memory 16, the image recording of that page is performed. The CPU 17 reads out one page of image information from the memory 16 and sends the decoded one page of image information to the printer controller 18. Upon receiving the image information of one page from the CPU 17, the printer controller 18 controls the printer 19 to record the image information of the page.

The CPU 17 is receiving the next page while the printer 19 is recording.

Images are received and recorded as described above.

The electrophotographic photoreceptor of the present invention can be used not only in electrophotographic copying machines, but also in laser beam printers, C
RT printer, LED printer, liquid crystal printer,
It can be widely used in electrophotographic application fields such as laser plate making.

[0038]

EXAMPLES Next, the present invention will be explained according to examples.

Example 1 A coating composed of the following materials was applied by a dipping method onto a support of an Al cylinder of 30φ and 260 mm, and 140
The film was heat cured at 30 ° C. for 30 minutes to form a conductive layer of 18 μm.

Conductive pigment: tin oxide / antimony oxide coating Titanium oxide: 10 parts (weight part, hereinafter the same) Resistance adjusting pigment: Titanium oxide: 10 parts Binder resin: Phenol resin: 10 parts Leveling agent: Silicon oil ... 0.001 part Solvent: methanol / methyl cellosolve = 1/1 ... 20 parts Next, on this, 3 parts of N-methoxymethylated nylon and 3 parts of copolymerized nylon, 65 parts of methanol and 30 parts of n-butanol were added. 0.5μ by applying the solution dissolved in
m undercoat layer was formed.

Next, 4 parts of an azo pigment having the following structural formula,

[0042]

[Chemical 1]

2 parts of polyvinyl butyral resin and 80 parts of cyclohexanone were dispersed in a sand mill using φ1 mm glass beads for 6 hours, and then 100 parts of THF was added to obtain a dispersion liquid for a charge generation layer. This was applied onto the undercoat layer by a dipping method to form a 0.2 μm charge generation layer.

Next, 10 parts of the following charge-transporting material,

[0045]

[Chemical 2]

10 parts of polycarbonate Z resin was dissolved in 50 parts of monochlorobenzene and 10 parts of dichloromethane.
This paint is applied onto the above-mentioned charge generation layer by a dipping method,
A 0 μm charge transport layer was formed.

Next, 2.5 parts of polytetrafluoroethylene powder and 5.5 parts of polycarbonate Z resin were dispersed in monochlorobenzene, and 2 parts of the above charge transport material was dissolved therein. This was applied onto the charge transport layer by a spray method to form a surface layer of 3 μm.

The photoconductor thus obtained was mounted on a laser beam printer LBP-NX (manufactured by Canon Inc.), and images were evaluated. This printer performs transfer by bringing a conductive rubber roller into contact with a photoconductor at a total pressure of 1400 g and applying a DC bias of 2 KV between the roller and the photoconductor.

Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1 except that the thickness of the charge transport layer was 23 μm and no surface layer was provided. Images were similarly evaluated for the obtained photoreceptors.
The results are shown in Table 1.

The evaluation of the voids was performed by measuring the toner hiding ratio in the character image (alphabet). As is clear from this result, the photoconductor of the present invention is remarkably effective in preventing hollow defects.

Example 2 A conductive layer and an undercoat layer were provided in the same manner as in Example 1 on the support of an Al cylinder of 30φ and 346 mm. Next, 4 parts of an azo pigment having the following structural formula,

[0052]

[Chemical 3]

2 parts of polyvinyl butyral resin and 80 parts of cyclohexanone were dispersed for 6 hours in a sand mill using φ1 mm glass beads, and then 100 parts of THF was added to obtain a charge generation layer dispersion liquid. This was applied onto the undercoat layer by a dipping method to form a 0.2 μm charge generation layer.

Next, 10 parts of the following charge-transporting material,

[0055]

[Chemical 4]

10 parts of polycarbonate Z resin was dissolved in 50 parts of monochlorobenzene and 10 parts of dichloromethane.
This paint is applied onto the above-mentioned charge generation layer by a dipping method,
A 2 μm charge transport layer was formed.

Next, 3 parts of polytetrafluoroethylene powder and 5 parts of polycarbonate Z resin were dispersed in monochlorobenzene, and 2 parts of the above charge transport material was dissolved therein. This is applied onto the charge transport layer by a spray method, and 3
A μm surface layer was formed.

The obtained photoreceptor is used as a plain paper copying machine NP-2.
The transfer mechanism of 020 was mounted on a roller transfer system similar to the printer used in Example 1 and evaluated. The results are shown in Table 1.

Example 3 Up to the charge transport layer was prepared in the same manner as in Example 1.

Next, a polymer 1 having the following structure was formed as a surface layer.
Copy 0

[0061]

[Chemical 5]

Was dissolved in 100 parts of monochlorobenzene,
This is applied onto the charge transport layer by a spray method to form 3 μm
The surface layer of was formed.

The same test as in Example 1 was conducted on the obtained photoreceptor. The results are shown in Table 1.

Example 4 Up to the charge generation layer was prepared in the same manner as in Example 1. Next, 8.5 parts of polytetrafluoroethylene powder was added to Polycarbonate Z.
This was dispersed in monochlorobenzene together with 10 parts of the resin, and 10 parts of the charge transport material having the following structural formula was dissolved therein.

[0065]

[Chemical 6]

This was applied onto the charge generation layer by a dipping method to form a 25 μm charge transport layer. In this example, the charge transport layer was the surface layer.

The same test as in Example 1 was conducted on the obtained photoreceptor. The results are shown in Table 1.

[0068] The rank of void is such that the toner image hiding rate is 90% or more: ○ 60% or more and less than 90%: △ less than 60%: ×

[0069]

As described above, the photoconductor of the present invention can provide a high-quality image with few voids as a photoconductor used in a direct charge transfer type electrophotographic apparatus.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus of the present invention.

FIG. 2 is a block diagram of a facsimile using the electrophotographic apparatus as a printer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging means 3 Exposure part 4 Developing means 5 Transfer means 6 Cleaning means 7 Pre-exposure means 8 Image fixing means

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hideyuki Ainoya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Hidetoshi Hirano 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (2)

[Claims] 1. An electrophotographic photosensitive member used in an electrophotographic apparatus having a transfer means for transferring a toner image onto a transfer material by direct charging, wherein a contact angle of water on the surface of the photosensitive member is 1.
An electrophotographic photosensitive member characterized by having an angle of 10 ° or more. 2. An electrophotographic apparatus comprising a transfer means for transferring a toner image onto a transfer material by direct charging, and the electrophotographic photosensitive member according to claim 1.