JPH0255365A - electrophotographic photoreceptor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and more specifically, an electrophotographic photoreceptor in which the surface layer contains fluorine-containing resin powder and the photosensitive layer below contains an antioxidant. Regarding photoreceptors.

[Conventional technology]

Electrophotographic photoreceptors are required to have predetermined sensitivity, electrical properties, and optical properties depending on the electrophotographic process to which they are applied. The surface layer of the photoreceptor, that is, the layer furthest from the support, is directly subjected to electrical and mechanical external forces such as corona charging, toner development, transfer to paper, and cleaning processing, so durability against these forces is required. be done.

Specifically, durability is required against surface abrasion and texture due to rubbing, and surface deterioration due to ozone generated during corona charging under high humidity conditions. Furthermore, there is a problem of toner adhesion to the surface layer due to repeated toner development and cleaning, and to solve this problem, it is desired to improve the cleaning properties of the surface layer. Various methods have been studied in order to satisfy the above-mentioned characteristics required for the surface layer, and among them, providing a resin layer in which fluorine-containing resin powder is dispersed is provided on the surface of the electrophotographic photoreceptor. is particularly effective.

By providing a resin layer in which fluorine-containing resin powder is dispersed on the surface of the electrophotographic photoreceptor, durability against scratches, surface cleaning, abrasion, etc. is improved, and water repellency and mold release of the surface of the electrophotographic photoreceptor are improved. It is also effective in preventing surface deterioration under high humidity conditions.

On the other hand, when an electrophotographic photoreceptor is used in accordance with the electrophotographic process to which it is applied, in addition to the physical shock it receives from the process, it is also subject to fatigue due to repeated exposure or due to corona discharge. Exposed to generated ozone and nitrogen oxides. In particular, ozone and nitrogen oxides directly chemically act on the charge transport material on the surface of the electrophotographic photoreceptor, lowering the resistance of the surface and affecting images. In order to prevent this, it is effective to use a charge transport material with a high oxidation potential to make it difficult to react with the ozone and nitrogen oxides.

However, especially regarding nitrogen oxides, in addition to acting on the electrophotographic photoreceptor in a gaseous state, it also acts on the electrophotographic photoreceptor in the form of nitric acid when combined with moisture in the air.

Especially near the corona charger, a large amount of nitric acid is generated.
This adheres to the corona charging machine, moves onto the electrophotographic photoreceptor while the machine is stopped for a long time, and then enters the electrophotographic photoreceptor and reaches the support. 'F! This caused a decrease in performance and a change in sensitivity, causing the phenomenon that the part had different characteristics from other parts.

In order to prevent these phenomena from occurring, studies have been made to add antioxidants to the surface layer to inactivate ozone, nitric acid, etc. that enter the electrophotographic photoreceptor. It has had good effects.

[Problem to be solved by the invention]

If the above two types of technologies are combined, mechanical properties,
An electrophotographic photoreceptor with excellent surface lubricity and moisture resistance should be completed. However, in reality, good things are not always possible. This is because the fluorine-containing resin powder discussed here has extremely poor dispersibility when dispersed in Guingoo resin, and in order to disperse it uniformly, it is necessary to use a surfactant as a dispersion aid. It can be said that it is almost indispensable.

However, when both a surfactant and an antioxidant coexist in the same layer of an electrophotographic photoreceptor, their interaction adversely affects the electrophotographic properties of the electrophotographic photoreceptor, resulting in, for example, decreased sensitivity. This causes a decrease in potential, an increase in residual potential, and an increase in potential fluctuation due to durability.

It is an object of the present invention to overcome the above-mentioned drawbacks, to have durability and moisture resistance against surface abrasion and scratches caused by rubbing during repeated use, and to provide moisture resistance to the parts caused by nitric acid, etc. An object of the present invention is to provide an electrophotographic photoreceptor that does not cause image unevenness due to uneven chargeability or uneven sensitivity.

Another object of the present invention is to provide an electrophotographic photoreceptor with high quality and particularly high sensitivity in repeated electrophotographic processes.

[Means to solve the problem]

In the present invention, as a result of repeated studies in accordance with these objectives, we have developed a surface layer containing fluororesin powder but no antioxidant, and a next layer containing a phosphorous antioxidant. By providing an electrophotographic photoreceptor having a laminated structure, it has become possible to solve the above problems.

That is, the present invention provides an electrophotographic photoreceptor having a conductive support, a photosensitive layer, and a surface layer, wherein the surface layer contains a binder and fluorine-containing resin powder dispersed therein, but does not contain an antioxidant; Further, the electrophotographic photoreceptor is one in which the layer on the side of the laminated photosensitive layer in contact with the surface layer or the single-layer photosensitive layer contains a phosphorus-based antioxidant.

In the present invention, the fluorine-containing resin powders include tetrafluoroethylene, trifluorochloride fV7, hexafluoropropylene, vinyl fluoride, vinylidene fluoride, ethylene dichloride dichloride, trifluoropropylmethyl Resin powder of a polymer such as dichlorosilane, a copolymer thereof, or a copolymer of these and vinyl chloride can be used as appropriate, and tetrafluoroethylene resin and vinylidene fluoride resin are particularly preferred. . The molecular weight of the resin and the particle size of the powder are selected within a range that does not affect the uniformity of the coating film formed. Specifically, the average particle diameter is 2μ or less, preferably 1μ
It is as follows.

The content of the dispersed fluororesin powder is suitably 1 to 50% by weight based on the total solid content of the surface layer.

If the content is less than 1 t, sufficient effect will not be obtained,
Moreover, if it exceeds 50 inches, the electrophotographic characteristics will be affected.

The binder resin used for dispersion may be any polymer that has film-forming properties, but polymethacrylic acid is preferred because it has a certain degree of hardness even when used alone and does not interfere with carrier transport. Estelle, Precar? nate, polyarylate, polyester, polysulfone,
Vinyl chloride/vinyl acetate copolymer, I-restyrene, etc. are preferred.

The surface layer in which the fluorine-containing resin powder is dispersed in the binder does not necessarily need to be treated only as a protective layer. That is, this surface layer may contain a charge transport material and function as part of the charge transport layer, or it may contain a charge generation material and function as part of the charge generation layer, and the surface layer may contain a charge transport material and function as part of the charge generation layer. The same charge transport material as the charge transport layer or charge generation layer of /
It can also be a binder ratio or a charge generating material/binder ratio. The amount of charge transporting material or charge generating material to be included can be appropriately selected depending on the performance of the electrophotographic photoreceptor. Even when the surface layer contains a charge transporting material or a charge generating material, the effect of the fluororesin powder is fully exhibited.

In the electrophotographic photoreceptor of the present invention, the photosensitive layer may be of a single-layer type, or may be of a laminated type with functions separated into a charge generation layer and a charge transport layer. In the case of a laminated type, the conductive support, the charge generation layer, the charge transport layer, and the surface layer may be laminated in this order, or the order of the charge generation layer and the charge transport layer may be reversed. .

In the present invention, the phosphorus-based antioxidant is contained in the entire photosensitive layer when the photosensitive layer is a single layer type, and in the layer in contact with the surface layer when the photosensitive layer is a laminated dust type, such as the conductive support and the charge generating layer. When a layer, a charge transport layer, and a surface layer are laminated in this order, it is contained in the charge transport layer. However, it may be contained in both the charge transport layer and the charge generation layer.

The amount of the oxidizing agent/based antioxidant added is preferably 0.1 to 10 molty based on the charge transport material in the layer to which it is added. When the amount is less than 0.1 molty, no sufficient effect can be obtained, and when it exceeds 10 molty, the electrophotographic properties are adversely affected.

Phosphorous antioxidants that can be used in the present invention include the following: When producing the electrophotographic photoreceptor of the present invention, any conductive support can be used as long as it has conductivity. For example, a cylindrical cylinder or film made of metal such as aluminum or stainless steel, or made of plastic, paper, etc., coated with a conductive material alone or together with a suitable binder resin to provide a conductive layer can be used. A subbing layer (adhesive layer) having a barrier function and a subbing function can also be provided on these conductive supports. The subbing layer is formed to improve adhesion of the photosensitive layer, protect the support for improving coating properties, cover defects on the support, improve charge injection from the substrate, protect the photosensitive layer from electrical breakdown, etc. be able to.

Materials for the undercoat layer include polyvinyl alcohol and polyvinyl alcohol.
N-vinylimidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, ethylene/acrylic acid copolymer casein, polyamide, copolymerized nylon, glue, gelatin, etc. are known. These are each dissolved in a suitable solvent and applied onto a support. The film thickness is about 0.2 to 2.0 μm.

Charge-generating materials include biryllium-based dyes, thiapyrylium-based dyes, phthalocyanine-based pigments, anthoanthrone pigments,
Z can be produced using dibenzpyrenequinone pigments, vilanthrone pigments, trisazo pigments, cis-sazo pigments, azo pigments, indigo pigments, quinacridone pigments, asymmetric quinocyanine, quinocyanine, and the like.

As the charge transport substance, pyrene, N-ethylcarbazole, N-isopropylcarbazole; N-methyl-N-phenylhydrazino-3-methylan-9-ethylcarbazole, N,N-diphenylhydrazino-3-methylan-9- Ethylcarbazole, N,N-diphenylhydrazino-3-methylan-10-ethylphenothiazine, N,N-diphenylhydrazino-3-methylan-10-ethylphenoxanone, p-diethylaminobenzaldehyde-N,N-diphenylhydra Gino, p-
Noethylaminopenzaldehyde N-α-naphthyl-
N-phenylhydrazone, p-virolidinobenzaldehyde-N,N-diphenylhydrazone, 1,3.3-
) 'J methylindolenine-α-aldehyde-N,N
-Hydrazone II such as diphenylhydrazone, p-diethylbenzaldehyde-3-methylbenzthiazolinone-2-hydrazone; 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole, 1-7
enyl-3-(p-diethylaminostyryl)-5-(
P-diethylaminophenyl)pyrazoline, 1-[quinolyl(2))-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline,
1-[pyrisol(2))-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, l-[6-medoxypyridyl(2)-3-
(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, 1-[pyridyl (3)
) -3-(p-diethylaminostyryl)-s-(p
-diethylaminophenyl)pyrazoline, 1-[lepidyl (2)) -3-(p-diethylaminostyryl)
-5-(p-diethylaminophenyl)pyrazoline, 1
-[pyridyl(2)) -3-(p-diethylaminostyryl)-4-methyl-5-(p-diethylaminophenyl)pyrazoline 1-[pyridyl(2)) -3
-(α-methyl-p-diethylaminostyryl)-5-
(p-diethylaminophenyl)pyrazoline, 1-phenyl-3-(p-diethylaminostyryl)-4-methyl-5-(p-diethylaminophenyl)pyrazoline,
1-7 enyl-3-(α-benzyl-p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, spiropyrazolines; 2(p-diethylaminosteryl)-6-ethylaminopenzoxazole, 2(p-diethylaminopenzoxazole) Oxazole compounds such as t2-(p-diethylaminostyryl)-6-dinithylaminopenzothiazole, etc. ; triarylmethane compounds such as bis(4-diethylamino-2-methylphenyl)-phenylmethane; 1.1-bis(4-N,N-
diethylamino-2-methylphenyl)hebutane, 1,
Polyarylalkanes such as 1,2,2-tetrakis(4-N,N-dimethylamine-2-methylphenyl)ethane and the like can be used.

In the present invention, methods for dispersing fluororesin powder in a resin solution include a homogenizer, ? - Lumir, vibration?
- Methods such as lumill, sand mill, attritor roll mill, etc. can be used.

The procedure is to dissolve the binder resin in an organic solvent, mix the fluorine-containing resin powder and the dispersion aid with it, disperse it using the above dispersion method, and add the charge transport material and charge generation material to the resulting dispersion. All you have to do is mix them. If the charge-generating material is a pigment, it is sufficient to separately prepare a dispersion of only the charge-generating material according to the dispersion conditions of the charge-generating material, and then mix it with a dispersion of fluorine-containing resin powder, as conditions permit. If so, this charge generating material may be dispersed simultaneously with the fluororesin powder.

When manufacturing the electrophotographic photoreceptor of the present invention, methods for coating each layer include, for example, a coach-in method such as a dip coating method, a spray coating method, a spinner coating method, a pea coating method, a blade coating method, and a curtain coating method. can be used. Especially when coating a surface layer in which fluororesin powder is dispersed, if the layer below and the binder are of the same type of resin, or even if they are not of the same type, the solvent used for one will dissolve the other. In such cases, there is a possibility that dip coating method etc. cannot be used, and in that case, press coating method etc. are suitable. The thickness of the surface layer after coating and drying can be adjusted to an appropriate thickness depending on the purpose. In particular, in systems containing a charge transport material or a charge generation material, the surface layer also functions as a charge transport layer or a charge generation layer, respectively, so electrophotographic properties can be maintained even if the coating is thicker than a general protective layer. It will not deteriorate.

Examples are shown below.

Example 1 A quaternary system of 6-6.6-6.10-1.2 was placed on an aluminum cylinder support with a diameter of 80 mφ and a length of 360 mm. A 0.5 μm thick undercoat layer was provided by applying a solution of lyamide copolymer resin in 5-timemethanol using a dipping method.

Next, the structural formula was scattered. 727,120 parts of tetrahydro were added to this dispersion and mixed, and this mixed solution was coated on the undercoat layer.
A charge generation layer of 2μ was formed.

Next, 12 parts of the charge-generating material of the formula, 6 parts of polyvinylpenzole resin, 60@f of cyclohexanone, 10 parts of the charge-transporting material shown in the formula and 10 parts of bisphenol type 2 polycarbonate in a sand mill apparatus using all 1 mφ glass beads were used for 20 hours. 10 parts of nate resin was dissolved in 70 parts of a mixed solvent of monochlorobenzene and dichloromethane, and 1 mole amount, based on the charge transporting material, of the phosphorus antioxidant 1 in No. 5 in the table above was added and dissolved therein.

This solution was applied onto the charge generation layer by dip coating, and 1
A charge transport layer having a thickness of 17 μm was formed by drying with hot air at 20° C.

Next, 5 parts of low molecular weight polytetrafluoroethylene powder with an average particle size of 0.3 μm, and 0.5 parts of a fluorine-based comb-shaped graft polymer having fluoroalkylate in the side chain as a dispersion aid.
and 5 parts of bisphenol type 2 polycarbonate having a number average molecular weight of 20,000 as a binder were mixed with 35 parts of monochlorobenceph, and dispersed in a Lumil for 50 hours. To this dispersion were added 52 parts of the above charge transport material, 50 parts of Polycar ($4-), 70ON of monochlorobenzene, and 100 parts of zochloromethane, and the resulting liquid was applied onto the charge transport layer using an air spray coating device. It was dried at 0.degree. C. to form a 5.mu.m surface layer.

This electrophotographic photoreceptor will be referred to as Sample 1.

In addition, sample 2 was prepared with a charge transport layer having a thickness of 22μ without coating the surface layer, and if added later when preparing the surface layer coating solution of sample 1, the amount of 6 agents was 300 parts of monochlorobenzene,
Prepared as 50 parts of dichloromethane, further added and dissolved 1 molar amount of the phosphorus-based antioxidant of &5 in the above table of the charge transport material added thereto, and coated this dispersion mixture on the charge generation layer, Sample 3 was obtained by drying at 120° C. to form a charge transport layer having a thickness of 22 μm, and sample 4 was obtained by adding no antioxidant to the charge transport layer in sample 3.

These samples 1 to 4 were installed in a dry plain paper copying machine, and conditions were set so that the dark area potential was 650 V and the bright area potential was 130 V. E-corona charging, image exposure, dry toner development, and toner transfer to plain paper were performed. - An electrophotographic process consisting of cleaning with a rubber blade was carried out, and images were evaluated after being used for 30,000 sheets. The results were as follows.

Next, after long-term use, these electrophotographic photoreceptors were left in a copying machine for 24 hours, and the images were evaluated again. In sample 1 and sample 4, the sensitivity of the portion facing the corona charger was apparently high, and when a halftone image was produced, that portion turned white in a band-like manner.

That is, Sample 1 was the only one in which no scratches, white capri, or band-like white spots occurred after running 30,000 sheets.

Example 2 In the method of Example 1, I-litz vinylidene powder was used as the fluororesin powder, and a fluorine-based pro-remer consisting of a tositeno-fluoroalkyl group moiety and an acrylic resin as a dispersion aid was used. Similar results were obtained when the phosphorus antioxidant No. 17 in the table above was used as the antioxidant.

Example 3 An aluminum cylinder of 80w+mφ
% methanol solution was dip coated to provide a 1 micron subbing layer.

Next, 1 part of the charge-generating material represented by the structural formula and 60 parts of bisphenol ZW polycarg+-)10t-monochlorobenzene were added, and this mixture was dispersed in a stainless steel one-lumen mill for 72 hours. Six parts of the charge transport material used was added and dissolved.

Further, to this solution was added 1.5 molt of a phosphorus-based antioxidant listed in Table 26, based on the charge transport material.

This solution was dip coated onto the undercoat layer to provide a 15 micron photosensitive layer.

Next, except that no antioxidant was added, the same method and the same ingredients as in the preparation of this photosensitive layer coating solution were used, and when dispersing in a stainless steel Gale mill, polytetrafluoroethylene resin powder was added. and 0.4 parts of a fluorine-based comb-shaped graft primer consisting of a perfluoroalkyl-based styrene resin as a dispersion aid, and dispersed.
A dispersion containing a charge transport material was prepared. Monochlorobenzene was further added to this dispersion liquid to make a solution with a solid content of 10%, and this was coated on the photosensitive layer using a Sugrey coating device,
It was dried at 120° C. to form a 5 μm surface layer. The electrophotographic photoreceptor thus produced is designated as sample 5.

Sample 6 is a photosensitive layer with a thickness of 20 μm and no surface layer is provided, and sample 7 is Sample 5 in which no antioxidant is added to the photosensitive layer. Further, Sample 8 is a sample in which both a polytetra7ethylene resin powder and an antioxidant are contained in the photosensitive layer when the photosensitive layer is provided.

These electrophotographic photoreceptors of Samples 5 to 8 were installed in a plain paper copying machine in the same manner as in Example 1, and subjected to one image exposure with e-corona charging, dry toner development, transfer to plain paper, and cleaning with rubber grade. An image formation durability test was conducted using a process of removing the optical surface potential by strong exposure. The image evaluation after 30,000 sheets is shown below.

The residual potential of these photoreceptors after strong exposure was measured and was as follows.

Furthermore, in the same manner as in Example 1, these electrophotographic photoreceptors were
When images were taken again after being left in the machine for a time, images similar to those before being left were obtained for samples 5 and 6.8, but for sample 7, the part corresponding to the corona charger was a halftone image. It was white and band-like.

Example 4 A 5-timemethanol solution of a quaternary polyamide copolymer resin of 6-6.6-6.10-1.2 was applied by dipping onto an aluminum cylinder support with a diameter of 80 m and a length of 360 ffilI. A subbing layer with a thickness of .5 μm was provided.

Next, a charge transport layer having a thickness of 18 microns was formed by dip coating on the undercoat layer of the above formula.

Next, 12 parts of a charge transport material represented by the formula, 10 parts of bisphenol 2 type polycargenate, and 1.5 parts based on the charge transport material.
The antioxidant shown by /1612 in the table above in the amount of malti was dissolved in monochlorobenzene, and 10 parts of the charge generating material shown by and 10 parts of bisphenol 2 type polycarmenate were dissolved in tetrahydro7rane/cyclohexanone = 17
In addition to 100 parts of the mixed solvent of No. 1, the charge generating material was dispersed in a sand mill until the average dispersed particle size of the charge generating material was 0.1 μm or less. In this dispersion, 5 parts of the charge transport material and 1.5 molti of the antioxidant of /1612 in the table above were dissolved, based on the charge transport material, and after dissolving, a charge transport layer was formed by spray coating. A charge generation layer having a thickness of 3 μm was formed by coating on top. In addition, 2 parts of polytetra7tethylene powder, 0.2 part of the fluorine-based graft polymer used in Example 1, and bisphenol 2 type polycarbonate? Mix 8 parts of analyte with 100 parts of a mixed solvent of monochlorobenzene/dichloromethane = 7/3? -Dispersed for 50 hours using Lumil. This dispersion was applied onto the charge generation layer by a spray coating method to form a 3 μm thick protective layer. The photoreceptor thus produced is designated as sample 9.

Furthermore, sample 10, which does not have the protective layer of sample 9,
Sample 11 was Sample 9 which contained no antioxidant in the charge transport layer or charge generation layer. These samples 9
For ~11, an electrophotographic process consisting of Φ corona charge 1 formation of a latent image by image exposure, development with dry toner, toner transfer to plain paper, urethane cleaning step 2 with urethane blade, removal of residual potential by strong exposure An image printing test was carried out for 10,000 sheets, and the image and potential after the test were evaluated.

Furthermore, after leaving samples 9 to 11 in the machine for 24 hours after being used for 10,000 sheets, images were taken again and the halftone images were compared. The corresponding part was a white band with approximately the same width as the charger. This is thought to be because the nitric acid adhering to the charger moved onto the photoreceptor and reached the support while it was left standing, resulting in a white band-like appearance.

From this result, it was found that Sample 9 had excellent durability.

〔Effect of the invention〕

Since the electrophotographic photoreceptor of the present invention is constructed as described above, it has excellent mechanical properties, surface lubricity, moisture resistance, and durability.

Agent Patent Attorney Johei Yamashita

Claims (1)

[Claims] 1. An electrophotographic photoreceptor having a conductive support, a photosensitive layer and a surface layer, the surface layer containing a binder and fluororesin powder dispersed therein, but containing no antioxidant;
Further, an electrophotographic photoreceptor characterized in that the layer on the side of the laminated photosensitive layer in contact with the surface layer or the single layer photosensitive layer contains a phosphorus-based antioxidant.