JP5101432B2 - Image forming apparatus, process cartridge, and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that shows replacing time of a latent image carrier before an abnormal image occurs, eliminates loss time, and continuously and stably provides a good image. <P>SOLUTION: The image forming apparatus includes a latent image carrier, a charging means, an electrostatic latent image forming means, a developing means, a cleaning means, and a protective agent supplying means. The image forming apparatus has a surface potential detection area for determining a latent image carrier replacing time outside an image area of the latent image carrier. In the surface potential detection area, similarly to the inside of the image area, at least charging, electrostatic latent image formation, development, cleaning, and protective agent supply are performed. The protective agent supplying means supplies a smaller amount of protective agent 3b than inside the image area, in the surface potential detection area of the latent image carrier. A surface potential detecting means is disposed in the surface potential detection area of the latent image carrier. A replacing time determining means of the latent image carrier is provided. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer. More specifically, the latent image carrier is predicted to wear before the latent image carrier becomes worn and the image becomes abnormal, and the latent image carrier is replaced. The present invention relates to an image forming apparatus capable of displaying time and obtaining a stable high-quality image.

In an image forming apparatus using an electrophotographic process, image formation is performed by subjecting a latent image carrier (hereinafter also referred to as an electrophotographic photosensitive member or a photosensitive member) to a charging step, an exposure step, a development step, and a transfer step. Is called. The discharge product generated in the charging process and remaining on the surface of the photoreceptor and the residual toner or toner component remaining on the surface of the photoreceptor after the transfer process are removed through a cleaning process.
Organic electrophotographic materials are widely used as electrophotographic photoreceptors used in electrophotographic methods widely used in copying machines, printers, and the like because of advantages such as low cost, mass productivity, and non-pollution. However, organic photoreceptors have lower abrasion resistance than inorganic photoreceptors.

  As a generally used cleaning method, a rubber blade that is inexpensive, has a simple mechanism, and has excellent cleaning properties is used. However, since the rubber blade is pressed against the photoconductor to remove the residue on the surface of the photoconductor, mechanical stress due to friction between the surface of the photoconductor and the cleaning blade is large. The wear of the photoconductor and the photoconductor cannot exhibit the predetermined performance when worn, so the life of the photoconductor and the cleaning blade is shortened. In recent years, miniaturization of electrophotographic systems has been desired, and the diameter of the photoreceptor has been inevitably reduced. The smaller the diameter of the photoreceptor, the shorter the lifetime.

In recent years, in the charging process, so-called AC charging using a charging roller or the like for charging by superimposing an AC voltage on a DC voltage has been used. This AC charging has excellent performance such as high uniformity of the charging potential of the photoconductor, less generation of oxidizing gas such as ozone and NOx, and miniaturization of the apparatus, but the applied AC voltage. Depending on the frequency, the positive and negative discharges of several hundred to several thousand times per second are repeated between the charging member and the photoconductor, so that the photoconductor is subjected to this large number of discharges and the deterioration of the surface layer is accelerated.
Therefore, in order to maintain high image quality over a long period of time, it is necessary to reduce deterioration of the photoconductor and cleaning blade due to friction and AC charging, extend the life of the organic photoconductor, and improve the cleaning property.

In response to this requirement, for example, a method shown in Patent Document 1 in which a brush or the like is pressed against a metal soap block such as zinc stearate to be pulverized and supplied to the photoreceptor is adopted. By using a metal soap such as zinc stearate, it functions as a protective agent, the lubricity of the photoreceptor surface is improved, and friction between the photoreceptor and the cleaning blade can be reduced. The toner cleaning property is also improved, which is very preferable.
Even when the photosensitive member is deteriorated by AC charging, if the protective agent is applied to the photosensitive member, the AC charging energy is first absorbed by the protective agent, and the photosensitive member becomes difficult to reach, so that the photosensitive member is protected.

On the other hand, there is an approach for improving the wear resistance of the organic photoreceptor. As a method for improving the wear resistance of an organic photoreceptor, there is a method of providing a protective layer on the surface of the photoreceptor. For example, a surface layer containing a filler such as titanium oxide or alumina has been studied and disclosed in Patent Document 2.
By forming a protective layer containing a filler on the surface of the photoconductor as described above, a photoconductor excellent in mechanical durability can be obtained. On the other hand, when the high wear resistance is too high, Discharge products accumulate on the surface of the photoreceptor over time, and abnormal images such as image flow may occur in a high temperature and high humidity environment. In view of this, the mainstream method is to suppress the above-described abnormalities by adjusting the amount and type of filler and appropriately wearing the surface of the photoreceptor.

  In the method of using the photoconductor as described above, the photoconductor is worn gradually, so that the photoconductor cannot exhibit a predetermined performance. That is, the photosensitive member film thickness is reduced, resulting in lower charging, lower resolution, background smudges, lower image density, and lower breakdown voltage, causing discharge and abnormal images. When it wears locally, it becomes a streak. When such an abnormal image is seen, the photoconductor is at the end of its life and the photoconductor is replaced. In some cases, the photosensitive unit is replaced. However, if the replacement is performed after seeing such an abnormal image, it may take several hours or several days until the serviceman arrives in the case of replacement by a serviceman, and printing may not be possible during that time. Even if the user can replace it, it is necessary to prepare a spare photoconductor or photoconductor unit in order to save downtime. It is useless from the aspect. In particular, in a printer with a high image quality, high speed, and high productivity area, stopping the apparatus for several hours can cause enormous damage, so there is a large loss in contacting a service person after the apparatus has stopped.

Therefore, a means for detecting wear on the surface of the photoconductor and giving a warning to the user of the life of the photoconductor before the wear reaches a level that causes an abnormal image is desired.
In conventional photoconductor life detection, the number of rotations of the drum is counted and a warning is issued when a certain number of rotations is reached, the current flowing from the charging device to the surface of the photoconductor and the change in film thickness of the photoconductor. Using the above correlation, a warning is issued when the inflow current reaches a reference value (Patent Document 3, etc.), or when the frictional resistance on the surface of the photoconductor is measured and the frictional resistance reaches a specified value A method of informing a photoconductor lifetime warning (Patent Document 4, etc.) has been used.

JP 2004-341480 A Japanese Patent No. 3734735 Japanese Patent Laid-Open No. 04-57068 Japanese Patent Laid-Open No. 08-044245

  However, the conventional drum life detection method has the following drawbacks. The system that counts the number of rotations of the photoconductor and issues a warning when it reaches a certain number of rotations is not a configuration that directly detects changes in the film thickness of the photoconductor, so accurate life detection could not be performed. . The method that detects the current flowing from the charging device to the surface of the photoconductor and issues a warning when the reference value is reached, and the method that measures the frictional resistance of the photoconductor surface, measures the current and frictional resistance in the image area. Therefore, when these measured values are determined to be abnormal, there are many cases where abnormalities have already occurred in the image, and there is a case where the resolution is deteriorated or the background is stained due to photoconductor wear. . As described above, in a printer in a high-quality, high-speed, high-productivity region, when the resolution is reduced or background contamination occurs, a huge number of prints may be wasted. Even if an attempt is made to predict the occurrence of an abnormality from experience, changes in current and frictional resistance due to photoconductor wear are small, and the changes are large when an abnormality occurs, and the prediction is difficult and inaccurate. In the case of a flowing-in current, since it is the total current in the axial direction, even if it is attempted to predict the occurrence of an abnormality, a large abnormality may occur in some cases. For this reason, there has been a demand for means for accurately informing the timing for replacing the photoconductor at the stage where normal image formation with high image quality can be performed.

  In view of the above-described conventional problems, the present invention uses a protective agent supply device that supplies a protective agent to the surface of a latent image carrier, and provides a portion with a small amount of protective agent supply in the surface potential detection region to forcibly carry a latent image. A part where the body thickness wears earlier than in the image area is formed, and the surface potential of the part where the film thickness wears earlier can be detected to determine the replacement time of the latent image carrier, thus producing an abnormal image. An object of the present invention is to provide an image forming apparatus capable of knowing the replacement time before the occurrence, having no loss time, and capable of continuously obtaining a good image.

That is, the present invention is as follows.
(1) a latent image carrier;
Charging means for charging the surface of the latent image carrier before formation of the latent image;
An electrostatic latent image forming unit that forms an electrostatic latent image on the surface of the latent image carrier charged by the charging unit based on image data;
Developing means for visualizing the formed electrostatic latent image;
Transfer means for transferring the visualized toner image to a non-transfer body;
Cleaning means for removing toner remaining on the surface of the latent image carrier after transfer;
A protective agent supply means for supplying a protective agent for the latent image carrier to the latent image carrier;
In an image forming apparatus comprising:
Outside the image area of the latent image carrier, it has a surface potential detection area for determining the latent image carrier replacement time,
In the surface potential detection region, as in the image region, at least charging, electrostatic latent image formation, development, cleaning, and supply of a protective agent are performed.
The protective agent supply means supplies a smaller amount of protective agent in the surface potential detection region of the latent image carrier than in the image region, and has surface potential detection means in the surface potential detection region of the latent image carrier, An image forming apparatus comprising: a latent image carrier replacement time determination unit.
(2) The image forming apparatus according to (1), wherein the surface potential detection means in the surface potential detection region of the latent image carrier detects the surface potential of the non-image portion (background portion).
(3) The image forming apparatus according to (1) or (2), wherein a protective layer is provided on the surface of the latent image carrier.
(4) Protection that the protective agent supply means includes a protective agent block and a brush that is positioned between and contacts the protective agent block and the latent image carrier, and that is in contact with the image area of the latent image carrier. The image formation according to any one of (1) to (3), wherein the height of the protective agent block contacting the latent image carrier surface potential detection region is lower than the height of the agent block. apparatus.
(5) A brush in which the protective agent supply means includes a protective agent block and a brush located between and in contact with the protective agent block and the latent image carrier, and in contact with the image area of the latent image carrier. Any one of the above (1) to (3), wherein the length of the bristle of the fiber of the brush contacting the latent image carrier surface potential detection region is shorter than the length of the bristle of the fiber of The image forming apparatus described.
(6) A brush in which the protective agent supply means includes a protective agent block and a brush located between and in contact with the protective agent block and the latent image carrier, and in contact with the image area of the latent image carrier. The image formation according to any one of (1) to (3), wherein the thickness of the fibers of the brush contacting the latent image carrier surface potential detection region is thinner than the thickness of the fibers of apparatus.
(7) A process cartridge including at least a latent image carrier, a charging unit, a cleaning unit, and a protective agent supply unit, wherein the image is formed according to any one of (1) to (6). A process cartridge for use in an apparatus.
(8) After charging the surface of the latent image carrier,
Forming an electrostatic latent image on the surface of the latent image carrier;
Supplying toner to the latent image on the surface of the latent image carrier to form a toner image;
Transfer the toner image formed on the surface of the latent image carrier to a non-transfer body,
Cleaning the toner remaining on the latent image carrier surface after transfer,
In an image forming method comprising a step of supplying a latent image carrier protective agent to the latent image carrier,
Outside the image area of the latent image carrier, it has a surface potential detection area for determining the latent image carrier replacement time,
In the surface potential detection area, as in the image area, at least charged, forming an electrostatic latent image, developing, cleaning, and supplying a protective agent,
Supply a smaller amount of protective agent to the surface potential detection area of the latent image carrier than in the image area, detect the surface potential of the surface potential detection area of the latent image carrier, and determine when to replace the latent image carrier An image forming method.

  According to the present invention, a protective agent supply device that supplies a protective agent to the surface of the photosensitive member is used, and a portion where the protective agent supply amount is small is provided in the surface potential detection region, so that the photosensitive member film thickness is forcibly faster than in the image region. By detecting the surface potential of the part that wears out and the part where the film thickness wears quickly, and predicting the replacement time of the photoconductor, resolution failure due to charge reduction, ground contamination, abnormal images due to discharge destruction, etc. Before leaving, it is possible to know the replacement time of the photoconductor, and it is not necessary to produce a non-high quality image. When replacing the photoconductor, even when the serviceman replaces the photoconductor, it is possible to eliminate a time loss of several hours or days until the serviceman arrives. Even when the user can replace the photoconductor or the process unit, it is not necessary to prepare a spare photoconductor or process unit even though it is not time to replace the photoconductor or the process unit, and waste of space and cost can be saved.

In addition, the surface potential detection means in the surface potential detection region has a better contrast with the image and more accurate than detecting the surface potential of other parts by detecting the surface potential of the non-image part (background part). In addition, the photoreceptor replacement time can be predicted.
By having the protective layer on the surface of the photoconductor, the replacement time is determined by setting the time when the protective layer in the image area predicted from the time when the protective layer in the surface potential detection area is worn to be worn. Becomes easy.

The protective agent supply means comprises a protective agent block, and a brush located between and in contact with the protective agent block and the latent image carrier, and is higher than the height of the protective agent block in contact with the image area of the photoreceptor. The height of the protective agent block in contact with the photosensitive member surface potential detection region makes it possible to wear the photosensitive member earlier in the surface potential detection region than in the image region. Can be predicted.
In addition, since the length of the bristles of the brush fibers that contact the photoconductor surface potential detection area is shorter than the length of the bristles of the fibers of the brush that contacts the image area of the photoconductor, The photoconductor can be worn earlier than in the area, and the photoconductor wear time in the image area can be predicted.
In addition, the thickness of the brush fibers in contact with the photoconductor surface potential detection area is smaller than the thickness of the brush fibers in contact with the image area of the photoconductor. The photoconductor can be worn quickly, and the photoconductor wear time in the image area can be predicted.

  By using a process cartridge including at least a photosensitive member, a charging unit, a cleaning unit, and a protective agent supply unit in the image forming apparatus of the present invention, the wear in the image region is predicted due to the wear in the surface potential detection region. However, when the photoconductor is replaced, the replacement becomes easier, and even in the case of replacement by a serviceman, it is possible to omit a time loss of several hours or several days until arrival of the serviceman. Further, even when the user can replace the photoconductor or the process unit, it becomes easier to replace the photoconductor or the process unit, and it is not necessary to prepare a spare photoconductor or process unit even when it is not time to replace the photoconductor or the process unit. be able to.

  The surface potential detection area is subjected to the same image formation process as in the image area, and a smaller amount of protective agent is supplied to the surface potential detection area of the photoconductor than in the image area, so that the surface potential of the surface potential detection area of the photoconductor is supplied. By detecting the photosensitive member and determining the replacement time of the photoconductor, the wear in the image area is predicted due to the wear of the surface potential detection region. When replacing the photoconductor, the replacement becomes easier. However, it can save time loss for several hours or days until arrival of the service person. Further, even when the user can replace the photoconductor or the process unit, it becomes easier to replace the photoconductor or the process unit, and it is not necessary to prepare a spare photoconductor or process unit even when it is not time to replace the photoconductor or the process unit. be able to.

Embodiments of the present invention will be described below with reference to the drawings.
The drum-shaped photoconductor is described below, but the present invention is not limited to this, and a sheet-shaped or endless belt-shaped photoconductor may be used.

FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus to which the present invention is applied.
In the figure, reference numeral 1 is a photosensitive member, 9 is an exposure device, 51 is a primary transfer roller, 52, 53 and 54 are rollers, 56 is an intermediate transfer belt, 57 is an intermediate transfer belt cleaning device, 61 is a secondary transfer roller, 71 Denotes a fixing belt, 72 denotes a heating roller, 73 denotes a fixing roller, and 74 denotes a pressure roller. Y, M, C, and K are subscripts indicating colors.

  The image forming apparatus includes an intermediate transfer belt 56 in the approximate center of the inside thereof. The intermediate transfer belt 56 is an endless belt made of a heat-resistant material such as polyimide or polyamide, and a base body adjusted to a medium resistance. The intermediate transfer belt 56 is supported by being wound around four rollers 52, 53, and 54. It is rotationally driven in the direction. Above the intermediate transfer belt 56, four image forming units corresponding to yellow (Y), magenta (M), cyan (C), and black (K) toners are arranged along the belt surface of the intermediate transfer belt 56. It is out.

FIG. 2 is an enlarged view showing one of the four image forming units.
In the figure, reference numeral 2 denotes a charging device, 3 denotes a protective agent coating device, 4 denotes a developing device, 8 denotes a cleaning device, and S denotes a surface potential inspection sensor which is a surface potential inspection means.
Since any image forming unit has the same configuration, Y, M, C, and K indicating color distinction are omitted in this figure. Each image forming unit has a photoreceptor 1, and around each photoreceptor 1, a charging device 2 that applies a charge to the surface of the photoreceptor 1, and a latent image formed on the surface of the photoreceptor 1 is developed with each color toner. A developing device 4 for forming a toner image, a protective agent coating device 3 for applying a protective agent to the surface of the photoconductor 1, and a cleaning device 8 for cleaning the surface of the photoconductor 1 after transferring the toner image are arranged.

This image forming unit is called a process cartridge. If an abnormality occurs in any part of the process cartridge, for example, if the photoconductor wears out and an abnormal image appears, the component itself that becomes the abnormal part, such as a photosensitive Only the body may be replaced, or the entire process cartridge may be replaced.
Referring to FIG. 1, an exposure device 9 is provided above the four image forming units to expose the surface of each charged photoconductor based on the image data of each color to form a latent image. .
A primary transfer roller 51 that primarily transfers a toner image formed on the photoconductor 1 onto the intermediate transfer belt 56 is disposed at a position facing each photoconductor 1 with the intermediate transfer belt 56 interposed therebetween. The primary transfer roller 51 is connected to a power source (not shown) and is applied with a predetermined voltage.

A secondary transfer roller 61 is pressed against the outside of the portion of the intermediate transfer belt 56 supported by the roller 52. The secondary transfer roller 61 is connected to a power source (not shown) and is applied with a predetermined voltage. A contact portion between the secondary transfer roller 61 and the intermediate transfer belt 56 is a secondary transfer portion, and the toner image on the intermediate transfer belt 56 is transferred onto a transfer sheet.
An intermediate transfer belt cleaning device 57 for cleaning the surface of the intermediate transfer belt 56 after the secondary transfer is provided outside the portion of the intermediate transfer belt 56 supported by the roller 53.

  A fixing device 70 for fixing the toner image on the transfer paper to the transfer paper semi-permanently is provided downstream of the secondary transfer unit. The fixing device 70 includes a heating roller 72 having a halogen heater therein and an endless fixing belt 71 wound around the fixing roller 73, and a pressurization disposed so as to face and contact the fixing roller 73 via the fixing belt 71. And a roller 74.

Hereinafter, the features of the image forming apparatus will be described in more detail.
4 and 5 are schematic cross-sectional views of a multilayer electrophotographic photosensitive member used in the image forming apparatus of the present invention.
In FIG. 4, 101 is a conductive support, 102 is a photosensitive layer, and is formed by laminating a charge generation layer 103 mainly composed of a charge generation material and a charge transport layer 104 mainly composed of a charge transport material. is there.
There are no particular restrictions on the material, shape, structure, size, etc. of the photoconductor, and it can be appropriately selected from known ones, but the shape is preferably a drum shape, Examples thereof include inorganic photoreceptors such as amorphous silicon and selenium, and organic photoreceptors such as polysilane and phthalopolymethine. The photoreceptor (photoreceptor) used in the image forming apparatus of the present invention has a conductive support and at least a photosensitive layer on the conductive support, and further has other layers as necessary. Become.

  As the photosensitive layer, a known photosensitive layer can be used, a single layer type in which a charge generation material and a charge transport material are mixed, a forward layer type in which a charge transport layer is provided on the charge generation layer, or charge transport. There is a reverse layer type in which a charge generation layer is provided on the layer. Further, in order to improve the mechanical strength, abrasion resistance, gas resistance, cleaning property, etc. of the photoreceptor, a protective layer 105 can be provided on the photosensitive layer 102 as shown in FIG. An undercoat layer 106 may be provided between the photosensitive layer and the conductive support. Moreover, an appropriate amount of a plasticizer, an antioxidant, a leveling agent or the like can be added to each layer as necessary.

The conductive support is not particularly limited as long as it has a volume resistance of 1.0 × 10 ¹⁰ Ω · cm or less, and can be appropriately selected according to the purpose. Metals such as nickel, chromium, nichrome, copper, gold, silver and platinum, metal oxides such as tin oxide and indium oxide, film or cylindrical plastic, paper coated or aluminum by vapor deposition or sputtering A plate made of aluminum alloy, nickel, stainless steel or the like, and a tube processed into a drum shape by a method such as extrusion or drawing, and then subjected to surface treatment such as cutting, superfinishing, or polishing can be used.

The drum-shaped support preferably has a diameter of 20 to 150 mm, more preferably 24 to 100 mm, and still more preferably 28 to 70 mm. When the diameter of the drum-shaped support is less than 20 mm, it may be physically difficult to arrange each step of charging, exposure, development, transfer, and cleaning around the drum. When the diameter exceeds 150 mm, The image forming apparatus may become large. In particular, when the image forming apparatus is a tandem type, since it is necessary to mount a plurality of photoconductors, the diameter is preferably 70 mm or less, and more preferably 60 mm or less.
Further, an endless nickel belt or an endless stainless steel belt as disclosed in JP-A-52-36016 can also be used as the conductive support.

  The undercoat layer of the photoconductor may be composed of a single layer or a plurality of layers. For example, (1) the resin is the main component, and (2) the white pigment and the resin are the main components. And (3) a metal oxide film obtained by chemically or electrochemically oxidizing the surface of a conductive substrate. Among these, those containing a white pigment and a resin as main components are preferable.

Examples of the white pigment include metal oxides such as titanium oxide, aluminum oxide, zirconium oxide, and zinc oxide. Among these, titanium oxide is particularly preferable because it is excellent in preventing injection of charges from the conductive support.
Examples of the resin include thermoplastic resins such as polyamide, polyvinyl alcohol, casein, and methyl cellulose; thermosetting resins such as acrylic, phenol, melamine, alkyd, unsaturated polyester, and epoxy. These may be used individually by 1 type and may use 2 or more types together.
There is no restriction | limiting in particular in the thickness of the said undercoat layer, According to the objective, it can select suitably, 0.1-10 micrometers is preferable and 1-5 micrometers is more preferable.

  Examples of the charge generation material in the photosensitive layer include monoazo pigments, bisazo pigments, trisazo pigments, tetrakisazo pigments and other azo pigments, triarylmethane dyes, thiazine dyes, oxazine dyes, xanthene dyes, Cyanine dyes, styryl dyes, pyrylium dyes, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, bisbenzimidazole pigments, indanthrone pigments, squarylium pigments, phthalocyanine pigments, etc. Organic pigments or dyes; selenium, selenium-arsenic, selenium-tellurium, cadmium sulfide, zinc oxide, titanium oxide, amorphous silicon, and other inorganic materials. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the charge transport material in the photosensitive layer include anthracene derivatives, pyrene derivatives, carbazole derivatives, tetrazole derivatives, metallocene derivatives, phenothiazine derivatives, pyrazoline compounds, hydrazone compounds, styryl compounds, styryl hydrazone compounds, enamine compounds, butadiene compounds, distyryl. Examples thereof include compounds, oxazole compounds, oxadiazole compounds, thiazole compounds, imidazole compounds, triphenylamine derivatives, phenylenediamine derivatives, aminostilbene derivatives, and triphenylmethane derivatives. These may be used individually by 1 type and may use 2 or more types together.

  As the binder resin used to form the photosensitive layer, it is electrically insulating and may be a known thermoplastic resin, thermosetting resin, photocurable resin, photoconductive resin, or the like. it can. Examples of the binder resin include polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, ethylene-vinyl acetate copolymer, polyvinyl butyral, Polyvinyl acetal, polyester, phenoxy resin, (meth) acrylic resin, polystyrene, polycarbonate, polyarylate, polysulfone, polyethersulfone, ABS resin and other thermoplastic resins, phenol resin, epoxy resin, urethane resin, melamine resin, isocyanate Examples thereof include thermosetting resins such as resins, alkyd resins, silicone resins, thermosetting acrylic resins, polyvinyl carbazole, polyvinyl anthracene, and polyvinyl pyrene. These may be used individually by 1 type and may use 2 or more types together.

Examples of the antioxidant include phenolic compounds, paraphenylenediamines, hydroquinones, organic sulfur compounds, and organic phosphorus compounds.
Examples of the phenol compound include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearyl-β- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate, 2,2'-methylene-bis- (4-methyl-6-t-butylphenol), 2,2'-methylene-bis- (4-ethyl- 6-t-butylphenol), 4,4′-thiobis- (3-methyl-6-tert-butylphenol), 4,4′-butylidenebis- (3-methyl-6-tert-butylphenol), 1,1,3 -Tris- (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxy Ben ) Benzene, tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, bis [3,3′-bis (4′-hydroxy-3 ′) -T-butylphenyl) butyric acid] cricol ester, tocopherols and the like.

  Examples of the paraphenylenediamines include N-phenyl-N′-isopropyl-p-phenylenediamine, N, N′-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl- Examples include p-phenylenediamine, N, N′-di-isopropyl-p-phenylenediamine, N, N′-dimethyl-N, N′-di-t-butyl-p-phenylenediamine, and the like.

  Examples of the hydroquinones include 2,5-di-t-octyl hydroquinone, 2,6-didodecyl hydroquinone, 2-dodecyl hydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t-octyl-5-methyl. Examples include hydroquinone and 2- (2-octadecenyl) -5-methylhydroquinone.

Examples of the organic sulfur compounds include dilauryl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, ditetradecyl-3,3′-thiodipropionate, and the like. .
Examples of the organic phosphorus compounds include triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine, and the like.

These compounds are known as antioxidants such as rubbers, plastics and fats and oils, and commercially available products can be easily obtained.
The addition amount of the antioxidant is preferably 0.01 to 10% by mass with respect to the total mass of the layer to be added.

  As the plasticizer, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount used is about 0 to 30 parts by mass with respect to 100 parts by mass of the binder resin. Is appropriate.

  Further, a leveling agent may be added to the photosensitive layer. Examples of the leveling agent include silicone oils such as dimethyl silicone oil and methylphenyl silicone oil; polymers having a perfluoroalkyl group in the chain or oligomers. As for the usage-amount of the said leveling agent, 0-1 mass part is preferable with respect to 100 mass parts of said binder resins.

  The protective layer of the photoreceptor is provided to improve the mechanical strength, abrasion resistance, gas resistance, cleaning property, etc. of the photoreceptor. As the protective layer, a polymer having a mechanical strength higher than that of the photosensitive layer and a material in which an inorganic filler is dispersed in the polymer are suitable. The resin used for the protective layer may be either a thermoplastic resin or a thermosetting resin, but the thermosetting resin has high mechanical strength and the ability to suppress wear due to friction with the cleaning blade. Is particularly preferable since it is extremely high. If the protective layer has a small thickness, there is no problem even if it does not have a charge transporting capability. However, if a protective layer having no charge transporting capability is formed thick, the sensitivity of the photoreceptor decreases, the potential increases after exposure, and the residual layer remains. Since the potential rise is likely to occur, it is preferable to use a protective layer containing the above-described charge transporting substance or a polymer used for the protective layer containing charge transporting ability.

  When the protective layer is provided, the mechanical strength of the photosensitive layer and the protective layer is generally greatly different, so the protective layer is worn away by friction with the cleaning blade, and the photosensitive layer is worn away as soon as it disappears. For this, it is important that the protective layer has a sufficient thickness, preferably 0.1 to 12 μm, more preferably 1 to 10 μm, and still more preferably 2 to 8 μm. When the thickness is less than 0.1 μm, it is too thin and easily disappears due to friction with the cleaning blade, and wear of the photosensitive layer may proceed from the disappeared portion. In the case of using a polymer having a charge transport ability, the cost of the polymer having a charge transport ability may be increased.

  The resin used for the protective layer is preferably one that is transparent to the writing light at the time of image formation and excellent in insulation, mechanical strength, and adhesiveness. For example, ABS resin, ACS resin, olefin-vinyl monomer copolymer are used. Polymer, chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallylsulfone, polybutylene, polybutylene terephthalate, polycarbonate, polyethersulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic resin, Polymethylbenten, polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS resin, butadiene-styrene copolymer, polyurethane, polyvinyl chloride, polyvinylidene chloride, epoxy resin, etc. It is below. These polymers may be thermoplastic resins, but in order to increase the mechanical strength of the polymers, they are crosslinked with a crosslinking agent having a polyfunctional acryloyl group, carboxyl group, hydroxyl group, amino group, etc. By using a functional resin, the mechanical strength of the protective layer increases, and wear due to friction with the cleaning blade can be greatly reduced.

  The protective layer preferably has a charge transporting capability. In order to give the protective layer a charge transporting capability, a method of using a mixture of the polymer used for the protective layer and the above-described charge transporting substance, A method of using a polymer having a transport capability for the protective layer is conceivable, and the latter method is preferable because a photosensitive member having high sensitivity and a small increase in potential after exposure and a small increase in residual potential can be obtained.

ただし、前記構造式（ｉ）中、Ａｒ₁は置換基を有していてもよいアリーレン基を表す。Ａｒ₂、及びＡｒ₃は、互いに同一であってもよいし、異なっていてもよく、置換基を有していてもよいアリール基を表す。 Preferred examples of the polymer having the charge transport layer ability include those having a group represented by the following structural formula (i) as a group having a charge transport ability in the polymer.

However, in the structural formula (i), Ar ₁ represents an arylene group which may have a substituent. Ar ₂ and Ar ₃ may be the same as or different from each other, and each represents an aryl group that may have a substituent.

Such a group having a charge transporting ability is preferably added to a side chain of a polymer having high mechanical strength such as a polycarbonate resin and an acrylic resin, and the monomer can be easily produced, and the coating property and curability are also improved. It is particularly preferable to use an excellent acrylic resin.
The acrylic resin having such a charge transport capability is a protective layer having high mechanical strength, excellent transparency, and high charge transport capability by polymerizing the unsaturated carboxylic acid having the group of the structural formula (i). Can be formed. Further, the acrylic resin has a crosslinked structure by mixing a polyfunctional unsaturated carboxylic acid, preferably a tri- or higher functional unsaturated carboxylic acid, with the monofunctional unsaturated carboxylic acid having the group of the structural formula (i). When formed, it becomes a thermosetting polymer, and the mechanical strength of the protective layer is extremely high. The polyfunctional unsaturated carboxylic acid may be added with the group of the structural formula (i). However, since the production cost of the monomer is increased, the polyfunctional unsaturated carboxylic acid has the above structure. It is preferable to use a photocurable polyfunctional monomer without adding the group of the formula (i).

Examples of the monofunctional unsaturated carboxylic acid having a group represented by the structural formula (i) include the following structural formula (ii) or structural formula (iii).

In the structural formula (ii) and the structural formula (iii), R ₁ represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. An aryl group which may have a cyano group, a nitro group, an alkoxy group which may have a substituent, -COOR ₇ (wherein R ₇ is a hydrogen atom, an alkyl which may have a substituent) Group, an aralkyl group which may have a substituent, or an aryl group which may have a substituent, a carbonyl halide group, CONR ₈ R ₉ (where R ₈ and R ₉ are It may be the same or different, and has a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. Represents an optionally substituted aryl group).

In Structural Formula (ii) and Structural Formula (iii), Ar ₁ and Ar ₂ may be the same as or different from each other, and represent an arylene group that may have a substituent.
In Structural Formula (ii) and Structural Formula (iii), Ar ₃ and Ar ₄ may be the same as or different from each other, and each represents an aryl group that may have a substituent.
In the structural formula (ii), X represents a single bond, an alkylene group which may have a substituent, a cycloalkylene group which may have a substituent, or an alkylene which may have a substituent. Represents an ether group, an oxygen atom, a sulfur atom, or a vinylene group;
In the structural formula (ii) and the structural formula (iii), Z has an alkylene group which may have a substituent, an alkylene ether divalent group which may have a substituent, or a substituent. Represents an optionally substituted alkyleneoxycarbonyl divalent group.
m and n each represent an integer of 0 to 3.

In the structural formula (ii) and the structural formula (iii), examples of the alkyl group in the substituent of R ₁ include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the aryl group include a phenyl group and a naphthyl group. Examples of the aralkyl group include a benzyl group, a phenethyl group, and a naphthylmethyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, and a propoxy group. These include halogen atoms, nitro groups, cyano groups; alkyl groups such as methyl groups and ethyl groups; alkoxy groups such as methoxy groups and ethoxy groups; aryloxy groups such as phenoxy groups; aryl groups such as phenyl groups and naphthyl groups; It may be substituted with an aralkyl group such as a benzyl group or a phenethyl group. Of these R ₁ substituents, a hydrogen atom or a methyl group is particularly preferred.

The aryl group of Ar ₃ and Ar ₄ includes a condensed polycyclic hydrocarbon group, a non-condensed cyclic hydrocarbon group, or a heterocyclic group.
As the condensed polycyclic hydrocarbon group, those having 18 or less carbon atoms forming a ring are preferable. s-indacenyl group, fluorenyl group, acenaphthylenyl group, preadenyl group, acenaphthenyl group, phenalenyl group, phenanthryl group, anthryl group, fluoranthenyl group, acephenanthrenyl group, aceanthrylenyl group, triphenylyl group, pyrenyl group, Examples include a chrycenyl group and a naphthacenyl group.

Examples of the non-condensed cyclic hydrocarbon group include monovalent groups of monocyclic hydrocarbon compounds such as benzene, diphenyl ether, polyethylene diphenyl ether, diphenyl thioether, diphenyl sulfone; biphenyl, polyphenyl, diphenylalkane, diphenylalkene, diphenylalkyne , Monovalent groups of non-condensed polycyclic hydrocarbon compounds such as triphenylmethane, distyrylbenzene, 1,1-diphenylcycloalkane, polyphenylalkane, and polyphenylalkene; ring assembly carbonization such as 9,9-diphenylfluorene And monovalent groups of hydrogen compounds.
Examples of the heterocyclic group include monovalent groups such as carbazole, dibenzofuran, dibenzothiophene, oxadiazole, and thiadiazole.

  The content of the polyfunctional unsaturated carboxylic acid is preferably 5 to 75% by mass, more preferably 10 to 70% by mass, and still more preferably 20 to 60% by mass of the entire protective layer. When the content is less than 5% by mass, the mechanical strength of the protective layer is insufficient, and when it exceeds 75% by mass, cracks are likely to occur when a strong force is applied to the protective layer, and the sensitivity deteriorates. May be more likely to occur.

  When an acrylic resin is used for the protective layer, after applying the unsaturated carboxylic acid to the photoreceptor, irradiation with an electron beam or actinic rays such as ultraviolet rays causes radical polymerization to form a protective layer. be able to. When performing radical polymerization with actinic rays, a solution obtained by dissolving a photopolymerization initiator in an unsaturated carboxylic acid is used. As the photopolymerization initiator, materials used for photocurable paints can be used.

The protective layer preferably contains metal fine particles, metal oxide fine particles, and other fine particles in order to increase the mechanical strength of the protective layer. Examples of the metal oxide include titanium oxide, tin oxide, potassium titanate, TiO, TiN, zinc oxide, indium oxide, and antimony oxide. Examples of the other fine particles include fluorine resins such as polytetrafluoroethylene, silicone resins, or those obtained by dispersing inorganic materials in these resins for the purpose of improving wear resistance.
In general, when the protective layer is used, the wear rate of the photosensitive member is significantly reduced as compared with the case where the protective layer is not used. Therefore, when the protective layer is worn out, the wear rate at that portion increases rapidly, and the surface potential of the photoconductor also changes rapidly.

The charging device 2 includes a charging roller 2a configured by covering a conductive cored bar with a medium resistance elastic layer as a charging member. The charging roller 2a is preferably disposed with a small gap with respect to the photoreceptor 1. The minute gap is set by, for example, winding a spacer member having a certain thickness around the non-image forming regions at both ends of the charging roller 2a to bring the surface of the spacer member into contact with the surface of the photoreceptor 1. can do. Further, the charging roller 2a is provided with a charging cleaning member 2b for cleaning in contact with the surface of the charging roller 2a.
In the present invention, the charging roller 2a charges the surface potential detection area outside the image area as well as within the image area of the photoreceptor.
The charging member is not particularly limited and may be appropriately selected according to the purpose. In addition to the charging roller, a known contact charger including a brush, a film, a rubber blade, etc., a corotron, A non-contact charger using a corona discharge such as a scorotron can be used.

The charging roller 2a used in the present invention is of a type in which the surface of the photosensitive member is charged by causing proximity discharge by being placed in contact or non-contact proximity to the photosensitive member.
In the above, contact means that the charging roller is in direct contact with the photosensitive member, and non-contact proximity means that a gap of 200 μm or less exists between the photosensitive member and the charging roller. The non-contact proximity method has an advantage that the surface of the charging member is hardly contaminated by toner remaining on the surface of the photosensitive member.

The charging roller is made of, for example, epichlorohydrin rubber on the outer periphery of a metal core that is, for example, a metal shaft having an outer diameter of 8 mm formed by SUM-Ni plating (steel surface is nickel-plated), and has a volume resistivity of 1 × 10 ^3. An elastic roller portion having a thickness of ˜1 × 10 ⁸ Ω · cm is formed as a layer having a thickness of 1.5 mm, for example. Furthermore, the elastic roller part uses that whose test piece hardness of rubber itself is 60 degrees, for example. Further, specific examples of the charging roller 2a having a hard surface include, for example, a thermoplastic resin composition (polyethylene, polypropylene, polymethyl methacrylate, polystyrene, and their co-polymers) in which a polymer ion conductive agent is dispersed in a resistance adjustment layer. And the like, and the surface of the resistance adjustment layer is subjected to a cured film treatment with a curing agent.

  The cured film treatment is performed, for example, by immersing the resistance adjustment layer in a treatment solution containing an isocyanate-containing compound, but may be performed by forming a cured treatment film layer on the surface of the resistance adjustment layer. In addition, a gap can be created between the photosensitive member and the charging roller by sticking an adhesive sheet having one side made of polyester or polyethylene terephthalate, for example, to each end of the charging roller unit. A contact proximity method can be realized. Then, by applying a DC voltage or a voltage obtained by superimposing an AC voltage and a DC voltage to the charging roller mandrel, the surface of the photoreceptor can be charged by causing a proximity discharge. This makes it possible to significantly suppress the amount of ozone generated during charging as compared to a so-called corotron or scorotron using a discharge wire.

An electrostatic latent image is formed on the uniformly charged photoreceptor 1 by exposure L corresponding to image information emitted from an exposure unit (not shown). As the exposure means, a laser diode (LD), a light emitting diode (LED) or the like can be used.
Outside the image area of the photoreceptor, exposure is performed by exposure L so that the entire surface is always solid.

The electrostatic latent image formed on the photoreceptor 1 is developed by the developing device 4 to form a toner image.
The developing device 4 includes a developing roller 4a facing the photoconductor 1, a first conveying screw 4b1 that is adjacent to the developing roller 4a and conveys the developer from the front surface to the back surface, and from the back surface to the front surface. Second transport screws 4b2 for transporting the developer are provided in parallel to each other. Although not shown, the developing roller 4 is composed of a rotatable sleeve on the outer peripheral side and a magnet fixed inside. A toner replenishing port is provided on the upstream side of the second conveying screw 4b2 in the conveying direction, and a toner replenishing device (not shown) is provided according to the output of the toner concentration sensor provided on the downstream side of the second conveying screw 4c in the conveying direction. Toner is replenished. The toner to be replenished from the toner replenishing device to the screw 4b2 is mixed with the developer, and stirred up to the developing sleeve 4a through the screw 4b1.

The developer composed of toner and magnetic carrier pumped up by the developing sleeve 4a is regulated to a predetermined developer layer thickness by the doctor blade 4c and is carried on the developing sleeve 4a. The developing sleeve 4a carries and carries the developer while moving in the same direction or in the opposite direction at the position facing the photoconductor 1, and supplies the toner to the latent image surface of the photoconductor 1.
In FIG. 1, the configuration of the two-component developing type developing device 4 is shown, but the present invention is not limited to this, and a one-component developing type developing device can also be applied.
Further, the developing device develops the electrostatic latent image in the surface potential detection area outside the image area as well as the electrostatic latent image in the image area of the photoconductor to form a toner image.

  The developer is a two-component developer composed of a toner and a carrier. The carrier is a surface of a magnetic material such as ferrite, magnetite, iron, etc. having a particle size of about 50 μm and surface-treated by a method such as spraying a resin such as a silicone resin. use. The toner is obtained by kneading and pulverizing a binder resin such as ester resin, acrylic resin or styrene resin, a pigment and a charge control agent, and adding an external additive such as silica or titania to a particle size of 7 μm. Degree.

  In some cases, the toner may be internally added with a fixing aid such as wax or oil, or may be externally added with a powder of a lubricant such as zinc stearate or a fluororesin. By adding a fixing aid, it is possible to prevent fixing offset without applying fixing oil such as silicone oil to the fixing roller forming the fixing device, which can reduce costs and spill the fixing oil to stain the floor. You don't have to worry about The lubricant acts to reduce the surface energy of the photoconductor, to prevent photoconductor filming due to paper dust and toner, and to prevent the occurrence of abnormal images such as omission in transfer.

  The protective agent application device 3 as a protective agent supply means includes a solid protective agent 3b housed in a fixed case, a brush roller 3a that contacts the solid protective agent 3b, scrapes off the protective agent, and applies it to the photoreceptor 1. Is provided. The solid protective agent 3b is formed in a block shape and is urged toward the brush roller 3a by the pressure member 3c. The pressurizing member 3c is preferably a spring such as a leaf spring or a compression spring, and a compression spring can be preferably used as shown in the drawing. The solid protective agent 3b is scraped off and consumed by the brush roller 3a, and the thickness of the solid protective agent 3b decreases with time. However, the solid protective agent 3b is always in contact with the brush roller 3a because it is pressurized by the pressure member 3c. The brush roller 3a applies the protective agent scraped off while rotating to the surface of the photoreceptor 1.

In the image forming unit shown in FIG. 2, a cleaning device 8 is installed downstream of the protective agent coating device 3.
The cleaning device 8 includes a cleaning blade 8a, a support member 8b, a toner recovery coil 8c, and a blade pressure spring 8d. The cleaning blade 8a is formed by forming a rubber such as urethane rubber or silicone rubber into a plate shape, and the edge of the cleaning blade 8a is in contact with the surface of the photoconductor 1 to remove the toner on the photoconductor 1 remaining after transfer. To do. The cleaning blade 8 a is attached to and supported by a support member 8 b made of metal, plastic, ceramic, or the like, and is installed at a predetermined angle with respect to the surface of the photoreceptor 1. Further, the blade pressing spring 8d is brought into contact with the surface of the photosensitive member 1 with a predetermined contact pressure and a biting amount.
The cleaning blade 8a removes the toner on the photosensitive member 1 and also serves as a coating blade that extends the protective agent applied on the photosensitive member by the protective agent applying device 3 into a thin film.
Further, the toner image formed in the surface potential detection area remains without being transferred, and is removed together with the transfer residual toner in the image area.

FIG. 3 is a view showing another embodiment of the protective agent coating apparatus.
The protective agent coating device 3 includes a solid protective agent 3 b housed in a fixed case, and a brush roller 3 a that contacts the solid protective agent 3 b to scrape off the protective agent and apply it to the photoreceptor 1. The solid protective agent 3b is formed in a block shape and is urged toward the brush roller 3a by the pressure member 3c. The pressurizing member 3c is preferably a spring such as a leaf spring or a compression spring, and a compression spring can be preferably used as shown in the drawing. The solid protective agent 3b is scraped off and consumed by the brush roller 3a, and the thickness of the solid protective agent 3b decreases with time. However, the solid protective agent 3b is always in contact with the brush roller 3a because it is pressurized by the pressure member 3c. The brush roller 3a applies the protective agent scraped off while rotating to the surface of the photoreceptor 1. Further, a leveling blade 3d, a support member 3e, and a pressure spring 3f are installed on the downstream side of the brush roller 3a. The granular protective agent applied on the photoconductor by the brush roller 3a is formed into a uniform film on the photoconductor by the leveling blade 3d.

A cleaning device 8 described below is installed upstream of the protective agent coating device 3.
Since the protective lubricant is applied after removing the transfer residual toner on the photosensitive member 1 by the cleaning device, the protective agent can be uniformly applied on the photosensitive member regardless of the toner input.
The cleaning device 8 includes a cleaning blade 8a, a support member 8b, a toner recovery coil 8c, and a blade pressure spring 8d. The cleaning blade 8a is formed by forming a rubber such as urethane rubber or silicone rubber into a plate shape, and the edge of the cleaning blade 8a is in contact with the surface of the photoconductor 1 to remove the toner on the photoconductor 1 remaining after transfer. To do. The cleaning blade 8 a is attached to and supported by a support member 8 b made of metal, plastic, ceramic, or the like, and is installed at a predetermined angle with respect to the surface of the photoreceptor 1. Further, the blade pressing spring 8d is brought into contact with the surface of the photosensitive member 1 with a predetermined contact pressure and a biting amount.
Further, the toner image formed in the surface potential detection area remains without being transferred, and is removed together with the transfer residual toner in the image area.

The protective agent coating device 3 will be described in more detail.
As the solid protective agent 3b, a fatty acid metal salt (metal soap), a fluorine resin, or the like can be used, but a fatty acid metal salt is particularly preferable. Examples of the fatty acid metal salt include fatty acid metal salts of linear hydrocarbons such as myristic acid, palmitic acid, stearic acid, and oleic acid. Examples of the metal include lithium, magnesium, calcium, strontium, zinc, cadmium, Examples include aluminum, cerium, titanium, and iron. Among these, zinc stearate, magnesium stearate, aluminum stearate, iron stearate, etc. are preferable. In particular, zinc stearate, zinc palmitate, or a mixture of zinc stearate and zinc palmitate is effective for protecting the photoreceptor. Is high and preferable.

Moreover, the following structures are also suitable as the protective agent.
What contains hydrophobic organic compound (A) and amphiphilic organic compound (B) as an essential component.
Examples of the hydrophobic organic compound (A) include aliphatic saturated hydrocarbons, aliphatic unsaturated hydrocarbons, alicyclic saturated hydrocarbons, alicyclic unsaturated hydrocarbons and aromatic hydrocarbons as described above. In addition to the classified hydrocarbons, polytetrafluoroethylene (PTFE), polyperfluoroalkyl ether (PFA), perfluoroethylene-perfluoropropylene copolymer (FEP), polyvinylidene fluoride (PVdF), ethylene -Examples include, but are not limited to, fluorine resins such as tetrafluoroethylene copolymer (ETFE) and fluorine waxes, silicone resins such as polymethyl silicone and polymethyl phenyl silicone, and silicone waxes. .

On the other hand, examples of the amphiphilic organic compound (B) include an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant as described above.
Examples of anionic surfactants include alkylbenzene sulfonate, α-olefin sulfonate, alkane sulfonate, alkyl sulfate, alkyl polyoxyethylene sulfate, alkyl phosphate, long chain fatty acid salt, α -Having an anion (anion) at the end of the hydrophobic site, such as sulfo fatty acid ester salt and alkyl ether sulfate, and sodium,
Examples include compounds in which alkali metal ions such as potassium, alkaline earth metal ions such as magnesium and calcium, metal ions such as aluminum and zinc, ammonium ions, and the like are bonded.

  Examples of cationic surfactants include a cation (cation) at the end of a hydrophobic site, such as alkyltrimethylammonium salt, dialkylmethylammonium salt, alkyldimethylbenzylammonium salt, etc., and chlorine, fluorine , Bromine and the like, and compounds in which phosphate ions, nitrate ions, sulfate ions, thiosulfate ions, carbonate ions, hydroxide ions, and the like are bonded.

Examples of amphoteric surfactants include dimethylalkylamine oxide, N-alkylbetaines, imidazoline derivatives, alkyl amino acids and the like.
Examples of nonionic surfactants include alcohol compounds such as long-chain alkyl alcohols, alkyl polyoxyethylene ethers, polyoxyethylene alkyl phenyl ethers, fatty acid diethanolamides, alkyl polyglucooxides, polyoxyethylene sorbitan alkyl esters, ethers Examples thereof include compounds and amide compounds. In addition, long-chain alkyl carboxylic acids such as lauric acid, palmitic acid, stearic acid, behenic acid, lignoceric acid, serotic acid, montanic acid, and melicic acid, and polyhydric alcohols such as ethylene glycol, propylene glycol, glycerin, erythritol, and hexitol And ester compounds with these partial anhydrides are also preferred.

More specific examples of ester compounds include glyceryl monostearate, glyceryl distearate, glyceryl monopartic acid, glyceryl dilaurate, glyceryl trilaurate, glyceryl dipartimate, glyceryl tripartinate, glyceryl dimyristate, trimyristate Glyceryl palmitate, glyceryl stearate, glyceryl monoarachidate, glyceryl diarachidate, glyceryl monobehenate, glyceryl stearate, glyceryl stearate, glyceryl monomontanate, and glyceryl monomelinate Sorbitan monostearate, sorbitan tristearate, sorbitan monopartitic acid, sorbitan dipartitic acid, Sorbitan lipartinate, sorbitan dimyristate, sorbitan trimyristate, sorbitan palmitate stearate, sorbitan monoarachidate, sorbitan diarachidate, sorbitan monobehenate, sorbitan behenate stearate, sorbitan stearate sorbitan monomontanate, monomelicine Examples of the alkyl carboxylic acid sorbitan such as sorbitan acid and the substitution thereof are not limited thereto.
These amphiphilic organic compounds may be used in combination.

  The protective effect of the protective agent basically depends on the supply amount of the protective agent. The larger the supply amount of the protective agent, the more the photoreceptor is protected and the wear rate is reduced. Therefore, as in the present invention, the wear rate is relatively fast in the surface potential detection region where the supply amount of the protective agent is small, and the wear rate is relatively slow in the image region where the supply amount of the protective agent is large.

As a method for molding the photoconductor protective agent of the present invention into a block having a certain shape, for example, a prismatic shape or a cylindrical shape, a method known as a solid material molding method can be used.
Examples include, but are not limited to, melt molding, powder molding, hot press molding, cold isostatic pressing (CIP), hot isostatic pressing (HIP), etc. Absent.

Taking a melt molding method as an example, a specific method for molding a protective agent will be described.
A predetermined amount of heat-melted glyceryl alkylcarboxylate is poured into a mold having a predetermined shape that has been heated above the melting temperature of the protective agent in advance, and if necessary, maintained at a temperature above the melting point for a certain period of time, and then allowed to cool or gradually. A molded body can be obtained by cooling with cooling. In addition, in order to remove internal distortion of the molded body, after cooling proceeds to a temperature lower than the phase transition temperature of the protective agent component in the middle of cooling, it is gradually reheated to a temperature equal to or higher than the phase transition temperature again. Also good.
After cooling to a temperature close to room temperature, the molded body is removed from the mold to obtain a molded body of the protective agent.
After that, the shape of the protective agent may be further adjusted by cutting or the like.

  As the above-mentioned formwork, metal formwork such as steel, stainless steel, and aluminum is preferable because of good thermal conductivity and good dimensional accuracy. The inner wall surface of the mold is preferably coated with a release agent such as a fluororesin or a silicone resin in order to improve the releasability.

  The solid protective agent 3b obtained by molding the fatty acid metal salt as described above into a rectangular parallelepiped shape is fixed to a protective agent holding member (not shown). In the case that accommodates the solid protective agent 3b, a plurality of pressure members 3c that are biased toward the brush roller 3a are provided side by side in the longitudinal direction.

  The pressure applied to the brush roller 3a by the solid protective agent 3b is set to be in the range of 200 to 1000 mN in terms of the total pressure applied by the plurality of pressure members 3c. If the total pressure is less than 200 mN, the brush roller 3a does not sufficiently scrape off the solid protective agent 3b, and the amount of the protective agent applied to the surface of the photoreceptor 1 is insufficient. As a result, abrasion of the cleaning blade 8a and the surface of the photosensitive member 1 is promoted, and cleaning defects such as transfer residual toner are likely to occur. If the total pressure exceeds 1000 mN, the amount of the protective agent applied to the surface of the photoreceptor 1 becomes excessive. This is because not only the solid protective agent 3b is consumed earlier, but also the surface of the photoreceptor 1 is affected by humidity due to excessive application of a protective agent made of a hygroscopic fatty acid metal salt, etc. This causes a problem that an image flows and image blur occurs. Therefore, the solid protective agent 3b is preferably pressed against the brush roller 3a at a total pressure of 200 to 1000 mN.

In the brush roller, a sheet made of fiber is bonded to a cored bar made of stainless steel or iron. In the example of FIG. 3, the outer diameter of the metal core is 6 mm, and the outer diameter of the brush roller is 14 mm.
As a specific material of the brush fiber, one or more kinds selected from generally known materials can be selected and used. Specifically, polyolefin resins (for example, polyethylene, polypropylene); polyvinyl and polyvinylidene resins (for example, polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether and Polyvinyl chloride); vinyl chloride-vinyl acetate copolymer; styrene-acrylic acid copolymer; styrene-butadiene resin; fluorine resin (for example, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene); Polyester; Nylon; Acrylic; Rayon; Polyurethane; Polycarbonate; Phenol resin; Amino resin (eg urea-formaldehyde resin, mela Down resins, benzoguanamine resins, urea resins, polyamide resins); Among such, it may be a resin having flexibility.
Also, in order to adjust the degree of bending, diene rubber, styrene-butadiene rubber (SBR), ethylene propylene rubber, isoprene rubber, nitrile rubber, urethane rubber, silicone rubber, hydrin rubber, norbornene rubber, etc. are used in combination. Also good.

  Moreover, you may provide a coating layer in the brush surface for the purpose of stabilizing the surface shape of a brush, environmental stability, etc. as needed. As a component constituting the coating layer, it is preferable to use a coating layer component that can be deformed according to the bending of the brush fiber, and these are not limited as long as the material can maintain flexibility. Polyolefin resins such as polyethylene, polypropylene, chlorinated polyethylene, chlorosulfonated polyethylene, etc .; polystyrene, acrylic (for example, polymethyl methacrylate), polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, Polyvinyl and polyvinylidene resins such as polyvinyl carbazole, polyvinyl ether, and polyvinyl ketone; vinyl chloride-vinyl acetate copolymer; silicone resin composed of an organosiloxane bond or a modified product thereof (for example, alkyd) Modified products with oils, polyester resins, epoxy resins, polyurethane, etc.); Fluorine resins such as perfluoroalkyl ether, polyfluorovinyl, polyfluorovinylidene, polychlorotrifluoroethylene; polyamides; polyesters; polyurethanes; polycarbonates; urea-formaldehyde resins An amino resin such as an epoxy resin or a composite resin thereof.

  In order to detect photoconductor wear before an abnormal image appears due to wear of the photoconductor, a surface potential detection region is provided outside the image region, and a portion of the surface potential detection region that wears out earlier than in the image region, Intentionally formed. The term “inside the image area” usually refers to an area that forms an image, such as A3 or A4, that matches the paper size. It is not a non-image portion of the background portion such as so-called character spacing. Outside the image area refers to an area other than the inside of the image area.

  In order to prevent abrasion of the photoreceptor, as described above, a method is adopted in which a brush or the like is pressed against a metal soap block such as zinc stearate to be finely powdered and supplied to the photoreceptor as a protective agent. By using a metal soap such as zinc stearate, the lubricity of the surface of the photoreceptor is improved, and friction between the photoreceptor and the cleaning blade can be reduced. As described above, the wear of the photoconductor can be reduced by supplying the protective agent to the photoconductor, and the photoconductor is worn if the protective agent is not supplied. It is also known that the wear state of the photoreceptor varies depending on the amount of the protective agent (see Japanese Patent No. 3732109, paragraph [0029]). That is, the more the protective agent, the less the wear, and the less, the more the wear.

  In order to form a portion that wears faster in the surface potential detection region than in the image region, the height of the protective agent block may be changed between the corresponding portion in the image region of the photoconductor and the corresponding portion of the surface potential detection region. Compared with the normal protective agent block height (H_in) in the image area, the surface potential detection area corresponding part lowers the height of the protective agent block (H_out). In the case of FIG. 6, since the protective agent block does not come into contact with the brush roller in the surface potential detection region in the initial stage after the use of the photoconductor or process cartridge which is a replacement part when printing with the image forming apparatus, A protective agent is not applied to the surface potential detection region. By overlapping the prints, the protective agent block is gradually scraped by the brush roller. Even if the protective agent block is shaved and lowered, the protective agent block is pressed against the brush roller by the pressurizing member 3c so that the protective agent block continues to contact the brush roller. When the height of the protective agent block corresponding to the image area of the photoconductor and the surface potential detection area becomes substantially equal, the protective agent starts to be applied to the surface potential detection area. As the life of the photoreceptor, the period during which the protective agent is applied differs between the image area and the surface potential detection area. Therefore, in the surface potential detection region of the photoconductor, a smaller amount of protective agent is supplied than in the image region, and a certain degree of wear is earlier than in the image region.

  In the above, the height of the protective agent block was changed in order to intentionally form a portion that wears faster than in the image area in the surface potential detection area, but the length of the bristle of the brush roller 3a was changed. Also good. The brush roller is composed of two types of fibers having different bristle lengths. Long fibers (H_B_in) in the image area and short fibers (H_B_out) in the surface potential detection area are brought into contact with the photoconductor and the protective agent block.

The longer fiber of the brush roller, for example, has a bristle length of 5 mm and bites into the protective agent block relatively deeply and makes strong contact, whereas the shorter fiber of the brush roller has, for example, a bristle length of 3 mm. is there. The position of the shaft of the brush with respect to the photosensitive member and the contact pressure of the solid lubricant with respect to the brush are adjusted so that the shorter fiber bites into the protective agent block relatively shallowly and weakly contacts. In the surface potential detection region, the contact of the brush roller with the protective agent black is weaker than that in the image region, and the supplied protective agent is smaller than in the image region, and a certain degree of wear is earlier than in the image region.
The thickness of the brush fiber is preferably 0.5 to 3 denier, and the density of the brush fiber is preferably 100,000 to 600,000 / inch ² .
As shown in FIG. 7, the brush roller is arranged so that the brush fibers with long bristles abut on the corresponding part in the image region, and the brush fibers with short bristles abut on the surface potential detection region corresponding part. Make it. In FIG. 7, for the sake of convenience, the brush roller and the photoconductor, and the brush roller and the protective agent block are illustrated separately.

In order to intentionally form a portion that wears faster than in the image area in the surface potential detection area, the thickness of the bristle of the brush roller 3a may be changed. The brush roller is composed of two types of fibers having different bristle thicknesses. Thick fibers in the image area and short fibers in the surface potential detection area are brought into contact with the photoconductor and the protective agent block.
The thicker fibers of the brush roller are preferably 6 to 20 denier, and the density of the brush fibers is preferably 10,000 to 50,000 fibers / inch ² . Since the fiber is thick, it is relatively strong in contact with the protective agent block, whereas the thin fiber of the brush roller is preferably 0.5 to 3 denier, and the density of the brush fiber is preferably 100,000 to 600,000 / inch ² Weakly contact the protective agent block. In the surface potential detection region, the contact of the brush roller with the protective agent black is weaker than that in the image region, and the supplied protective agent is smaller than in the image region, and a certain degree of wear is earlier than in the image region.
The length of the bristle feet of the brush roller is 4 mm, for example.
As shown in FIG. 8, the brush roller is manufactured so that thick brush fibers contact the corresponding part in the image region, and thin brush fibers contact the surface potential detection region corresponding part. . In FIG. 8, for the sake of convenience, the brush roller and the photoconductor, and the brush roller and the protective agent block are illustrated separately.

In order to detect the degree of wear, the surface potential of the photoreceptor is measured. S in FIG. 2 indicates a surface potential sensor. In order to detect wear, a surface potential sensor as surface potential detection means is installed in the surface potential detection region of the photoreceptor, and the surface potential of the surface potential detection region is measured.
At this time, the normal image forming process similar to that in the image area is performed in the surface potential detection area. However, the intermediate transfer belt, the intermediate transfer drum, the transfer charger, the transfer roller, the transfer material, and the like may be provided only in the image area. Since the wear is detected by detecting the surface potential, the development process is not directly required, but the wear of the photoreceptor is greatly affected by the presence of toner during cleaning. It is desirable to apply the same process as in the above.

  A case where a charging potential (surface potential after charging and before writing) is detected as the photoreceptor surface potential will be described. As the photoconductor wears, the charging potential (surface potential after charging and before writing) becomes lower than normal. In some cases, the wear proceeds locally. If the wear is locally, the electric field concentrates on the locally worn portion during charging, resulting in discharge breakdown, and the partially charged potential becomes abnormally low.

In order to determine the photosensitive member replacement timing by detecting the photosensitive member charging potential, the following method is used.
First, the case where the height of the protective agent block is changed between the corresponding part in the image area of the photoconductor and the corresponding part in the surface potential detection area, and a part that wears faster than in the image area is formed in the surface potential detection area will be described. To do.
First, the relationship between the number of prints and the wear amount of the protective agent block in the image area (FIG. 9A) is grasped. Furthermore, with respect to the relationship between the number of printed sheets and the amount of wear of the photoconductor (FIG. 9B), with or without a protective agent block (when the protective agent is supplied as in the image area or when the protective agent is not supplied). Keep track of. How long do you want to detect an abnormality in the image area of the photoconductor, and how much you want to determine when to replace the photoconductor (= Image area after printing after an abnormality occurs in the surface potential detection area) The level difference between the corresponding part in the photoreceptor image area and the corresponding part in the surface potential detection area of the protective agent block is determined depending on whether or not an abnormality occurs in the protective agent block (FIG. 9C).
On the other hand, the relationship between the photoconductor wear amount and the photoconductor charge potential (FIG. 9D is grasped. Further, the photoconductor charge potential and, for example, a non-image portion (background portion) OD (optical image density) of the image on paper. 9) (see FIG. 9E) The allowable value T of the non-image portion OD is determined, and the non-image portion OD exceeds the allowable value T and has a charged potential indicating abnormality. From the relationship between the amount of photoconductor wear at this time and the number of printed sheets and the amount of photoconductor wear, the amount of wear (K) ) To determine whether or not to detect an abnormality or to determine the photosensitive member replacement time (= after an abnormality occurs in the surface potential detection area, how many sheets are abnormal in the image area after printing).

  For example, from FIG. 9 (e), the non-image portion OD is unacceptable = photoreceptor charging potential when it is higher than T, and the photoreceptor wear amount at which the photoreceptor charging potential is 500V from FIG. 9 (d). Is about 5 μm, and the wear amount of the photosensitive member is about 5 μm from FIG. 9B when about 50,000 sheets are printed in the presence of the protective agent. In FIG. 9C, the amount of wear in the image area (with a protective agent) is plotted (line in the image area) as in FIG. 9B, and the image area of the photoconductor is worn and abnormal. When it is desired to detect anomalies before 5,000 sheets (= K), it is shifted by 5,000 sheets from the line in the image area and parallel to the wear amount line in the image area as the wear amount line in the surface potential detection area. Draw a straight line. However, the amount of wear in the surface potential detection region is steeply inclined with respect to the number of printed sheets because there is no protective agent at the start of printing (initial stage). Is also plotted in FIG. In the surface potential detection region, the combination of the presence of the protective agent (a) and the absence of the protective agent (b) is the amount of wear. That is, when the number of prints is 10,000 when the intersection, the photoreceptor wear amount is about 1.5 μm, the protective agent block begins to contact the photoreceptor even in the surface potential detection region. From FIG. 9A, when the number of printed sheets is 10,000, the wear amount of the protective agent block is about 1 mm. Therefore, if the protective agent block in the surface potential detection region is 1 mm lower than the protective agent block in the image region, the surface potential detection region is worn and the surface potential detection means detects a charged potential of 500V (non- It can be predicted that an abnormal image will appear in the image area after about 5,000 sheets from the time when the image portion OD is in an unacceptable range.

A method of detecting the photosensitive member charging potential and determining the photosensitive member replacement time will be described in the case of changing the brush length. The relationship between the photosensitive member charging potential and the non-image portion (background portion) OD of the on-paper image is grasped in advance (FIG. 9E). On the other hand, the relationship between the photosensitive member wear amount and the photosensitive member charging potential (see FIG. 9D) is determined. The allowable value T of the non-image portion OD is determined, and the non-image portion OD exceeds the allowable value T. Know the amount of photoconductor wear, which is a charging potential that indicates an anomaly, and understand the relationship between the number of prints and the amount of photoconductor wear (Fig. 9 (f)) for multiple brushes with different brush lengths. At this time, the brush a has the longest length in the order of brush a> brush b> brush c.
For example, from FIG. 9 (e), the non-image portion OD is unacceptable = photoreceptor charging potential when it is higher than T, and the photoreceptor wear amount at which the photoreceptor charging potential is 500V from FIG. 9 (d). Is about 5 μm, and the photosensitive member wear amount is about 5 μm from FIG. 9 (f). About 50,000 sheets for the brush a, about 45,000 sheets for the brush b, and about 40,000 for the brush c. This is when a sheet is printed. When the brush a is used for the inside of the image area (FIG. 7H_B_in) and the brush b is used for the surface potential detection area outside the image area (FIG. 7H_B_out), the surface potential detecting area is worn and the surface potential detecting means is charged to 500V. It can be predicted that an abnormal image will appear in the image area after about 5,000 sheets from the time when the image is detected (when the non-image portion OD is in an unacceptable range).

A method of detecting the photosensitive member charging potential and determining the photosensitive member replacement time will be described in the case of changing the thickness of the brush. The relationship between the photosensitive member charging potential and the non-image portion (background portion) OD of the on-paper image is grasped in advance (FIG. 9E). On the other hand, the relationship between the photosensitive member wear amount and the photosensitive member charging potential (see FIG. 9D) is determined. The allowable value T of the non-image portion OD is determined, and the non-image portion OD exceeds the allowable value T. Know the amount of photoconductor wear that is an abnormal charging potential, and understand the relationship between the number of prints and the amount of photoconductor wear (Fig. 10 (b)) for multiple brushes with different brush thicknesses. At this time, the brush a is thickest in the order of brush x> brush y> brush z.
For example, as shown in FIG. 9E, the non-image portion OD is unacceptable = the photosensitive member charging potential is 500 V when T is higher than T. From FIG. 9 (d), the photoreceptor wear amount at which the photoreceptor charge potential is 500V is about 5 μm. From FIG. 10 (a), the photoreceptor wear amount is about 5 μm. About 50,000 sheets for the brush x, about 45,000 sheets for the brush y, and about 40,000 sheets for the brush z are printed. It's time. When the brush x is used for the inside of the image area and the brush y is used for the surface potential detection area outside the image area, the surface potential detecting area is worn and the surface potential detecting means detects the charged potential 500V (non-image portion) It can be predicted that an abnormal image appears in the image area after about 5,000 sheets from the time when the OD is in an unacceptable range.

The potential measurement in the surface potential detection region may always be performed, but even if a potential abnormality is recognized in the surface potential detection region, the abnormality does not immediately occur in the image region. Therefore, for example, the surface potential may be detected every 10 to 1000 sheets, preferably 50 to 500 sheets. In addition, when a potential abnormality is detected once, it may be immediately determined as a photoconductor replacement time. However, when abnormality is continuously recognized, it may be determined as a photoconductor replacement time. . These settings are determined by the requested image.
The surface potential detection means may detect a charging potential after writing and before writing, or may detect a surface potential of a non-image portion (background portion) after writing. After writing, the image is closer to the developing portion, and the correlation with the image is better. In the surface potential detection area outside the image area, 100% exposure is performed at the time of image formation and a solid image is formed. Therefore, when detecting the surface potential after writing, exposure is not performed in accordance with the timing of surface potential detection. It is preferable to provide time and detect the surface potential of the non-image area.

The image forming apparatus of the present invention has a replacement time determining means for the latent image carrier. For example, when the surface potential detection means generates a signal exceeding a predetermined set value, the latent image carrier replacement time determination means determines that this is the replacement time and sends this signal to an appropriate warning means. Means for generating a warning signal.
A warning about the replacement timing of the photosensitive member or the process cartridge is displayed on a display unit such as a liquid crystal of the main body of the image forming apparatus, or is reported to the user by turning on a warning lamp, an LED, or a buzzer. It is more convenient to connect the potential information to the service call system so as to notify the service person directly.
Further, when an extra photoconductor, process cartridge, or the like is mounted as in a high-speed and high-production device, it may be set so that it is automatically replaced.

If the surface of the latent image carrier has a protective layer, it is easy to see that it is worn.
In the electrophotographic photoreceptor of the present invention, a protective layer 105 containing a filler may be formed on the photosensitive layer 102 as shown in FIG. 5 in order to protect the photosensitive layer 102 and improve durability. As shown in FIG. 11A, when there is a protective layer, when the protective layer is worn away and the protective layer disappears, the wear rate changes rapidly. Therefore, as shown in FIG. 11B, the relationship between the number of printed sheets and the charged potential changes when the protective layer is removed, compared to the case where the protective layer is provided, and when the protective layer is removed, the charged potential changes rapidly. So it is easy to detect the wear of the protective layer.
Therefore, in the case of a photoconductor provided with a protective layer, the number of prints, the photoconductor protective layer wear amount, the photoconductor charging potential, It is preferable to grasp the relationship in advance and select the film thickness of the photoconductor protective layer.

  The tandem type color image forming apparatus imagio MP C3500 is modified, and the protective agent block 3b shown in FIG. 6 is arranged so that the overall configuration is as shown in FIG. Was 280 mm / s. The photosensitive member 1 is not provided with a surface protective layer, and is provided with a surface potential detection region (H_out portion of the protective agent block 3b) for detecting the degree of wear. The width of the protective agent block 3b was 5 mm, the height was 8 mm for the H_in portion, 7 mm for the H_out portion, and the length was 305 mm for the H_in portion and 15 mm for the H_out portion. The pressure applied to the brush roller by the solid protective agent was 400 mN as the total pressure of the pressure members. In addition, charging was modified so that a charging roller applied a -600 V DC voltage and an amplitude of 1.2 kV and an AC frequency of 2 kHz to the photosensitive member.

  In order to detect the degree of wear, the surface potential of the photoreceptor 1 is measured. In order to detect wear, a surface potential sensor, which is a surface potential detection means, is installed in the surface potential detection region of the photoreceptor 1 and the surface potential of the surface potential detection region is measured. A normal image forming process similar to that in the image area is performed in the surface potential detection area. However, here, the transfer process was excluded, and charging, exposure, development, and cleaning were performed. Since the developed toner is not transferred, all was collected by cleaning. The surface potential sensor was installed after exposure, and the surface potential was measured for every 100 sheets of image formation. In the surface potential detection region, a solid image is formed by 100% exposure at the time of image formation, but in accordance with the timing of surface potential detection, a time during which exposure is not performed is provided to detect the surface potential of the non-image portion. The time during which exposure is not performed for detecting the surface potential depends on the specifications of the surface potentiometer, but one second is sufficient.

  Using the photoreceptor 1 and the protective agent block 3b, four process cartridges are manufactured and mounted on the modified tandem type image forming apparatus. A test chart with an image density of 7% is obtained at 22 ° C. and 40% environment. Thus, continuous image formation was performed. FIG. 9F shows the measurement result of the surface potential of the surface potential detection region that is outside the black image region among the four colors. The surface potential, which was about 600 V at the beginning of image formation, is about 570 V when 10,000 images are formed. Thereafter, as the image formation is continued, the surface potential decreases, and image formation when the image potential reaches about 500 V is about 45. , 000. When the image at that time was evaluated, the non-image portion OD of the on-paper image was about 0.09, and although it was within the allowable range, the background dirt was slightly noticeable even visually. The non-image area OD at the beginning of image formation was about 0.05, and the background stain was not noticed visually. At this point, it is time to warn about the replacement timing of the process cartridge. When continuous image formation is continued for confirmation, the surface potential of the surface potential detection area is about 490 V and the non-image portion OD is about 50,000 at about 50,000 sheets. 1.0.

In order to warn of the replacement timing of the process cartridge, a message of replacement timing is displayed on the liquid crystal display unit of the image forming apparatus main body.
Although this mechanism can reliably predict the replacement timing of each color process cartridge when it is mounted on all color photoconductors, it is generally used only on black where the photoconductor is consumed at an early stage. The color process cartridge may be replaced. Further, since colors tend to have the same tendency as four colors, they may be mounted on one of the colors in addition to black.

1 is a schematic configuration diagram of an example of an image forming apparatus of the present invention. It is a schematic block diagram of an example of an image forming unit of the image forming apparatus of the present invention. It is a schematic block diagram of the other example of the image formation unit of the image forming apparatus of this invention. 1 is a schematic cross-sectional view of an example of a laminated electrophotographic photosensitive member used in an image forming apparatus of the present invention. FIG. 6 is a schematic cross-sectional view of another example of a multilayer electrophotographic photosensitive member used in the image forming apparatus of the present invention. It is explanatory drawing of the method of changing the height of a protective agent block, and making the supply amount of the protective agent of a surface potential detection area | region small amount rather than an image area | region. It is explanatory drawing of the method of changing the length of a brush and making the supply amount of the protective agent of a surface potential detection area | region small amount from an image area | region. It is explanatory drawing of the method of changing the thickness of the fiber of a brush and making the supply amount of the protective agent of a surface potential detection area | region small amount rather than an image area | region. (A) is a graph showing the relationship between the number of printed sheets and the amount of wear of the protective agent block, and (b) is the case of the number of printed sheets and the presence or absence of the protective agent block (when the protective agent is supplied as in the image area, (C) is a graph showing the relationship between the number of prints in the image area and the surface potential detection region and the amount of photoconductor wear. d) is a graph showing the relationship between the photoconductor wear amount and the photoconductor charging potential, and (e) is a graph showing the relationship between the non-image OD and the photoconductor charging potential. (A) is a graph showing the relationship between the brush length, the number of printed sheets and the photoreceptor wear amount, (b) is a graph showing the relationship between the brush thickness, the number of printed sheets and the photoreceptor wear amount, (A) is a graph showing a change in wear of a photoconductor having a protective layer, and (b) is a graph showing a relationship between the number of prints of the photoconductor having a protective layer and a charging potential.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 9 Exposure apparatus 51 Primary transfer roller 52, 53, 54 Roller 56 Intermediate transfer belt 57 Intermediate transfer belt cleaning apparatus 61 Secondary transfer roller 71 Fixing belt 72 Heating roller 73 Fixing roller 74 Pressure roller 101 Conductive support body 102 Photosensitive layer 103 Charge generation layer 104 Charge transport layer 105 Protective layer 106 Undercoat layer

Claims (8)

A latent image carrier;
Charging means for charging the surface of the latent image carrier before formation of the latent image;
An electrostatic latent image forming unit that forms an electrostatic latent image on the surface of the latent image carrier charged by the charging unit based on image data;
Developing means for visualizing the formed electrostatic latent image;
Transfer means for transferring the visualized toner image to a non-transfer body;
Cleaning means for removing toner remaining on the surface of the latent image carrier after transfer;
A protective agent supply means for supplying a protective agent for the latent image carrier to the latent image carrier;
In an image forming apparatus comprising:
Outside the image area of the latent image carrier, it has a surface potential detection area for determining the latent image carrier replacement time,
In the surface potential detection region, as in the image region, at least charging, electrostatic latent image formation, development, cleaning, and supply of a protective agent are performed.
The protective agent supply means supplies a smaller amount of protective agent in the surface potential detection region of the latent image carrier than in the image region, and has surface potential detection means in the surface potential detection region of the latent image carrier, An image forming apparatus comprising: a latent image carrier replacement time determination unit.   2. The image forming apparatus according to claim 1, wherein the surface potential detection means in the surface potential detection region of the latent image carrier detects the surface potential of the non-image portion (background portion).   3. The image forming apparatus according to claim 1, further comprising a protective layer on the surface of the latent image carrier.   The protective agent supply means comprises a protective agent block and a brush positioned between and in contact with the protective agent block and the latent image carrier, and the protective agent block contacting the image area of the latent image carrier. The image forming apparatus according to claim 1, wherein the height of the protective agent block that contacts the latent image carrier surface potential detection region is lower than the height.   The protective agent supply means comprises a protective agent block, and a brush located between and in contact with the protective agent block and the latent image carrier, and the fibers of the brushes in contact with the image area of the latent image carrier. The image forming apparatus according to any one of claims 1 to 3, wherein the length of a bristle of a brush fiber contacting the latent image carrier surface potential detection region is shorter than the length of the bristle.   The protective agent supply means comprises a protective agent block, and a brush located between and in contact with the protective agent block and the latent image carrier, and the fibers of the brushes in contact with the image area of the latent image carrier. The image forming apparatus according to claim 1, wherein the thickness of the fibers of the brush contacting the latent image carrier surface potential detection region is smaller than the thickness.   7. A process cartridge including at least a latent image carrier, a charging unit, a cleaning unit, and a protective agent supply unit, and used in the image forming apparatus according to claim 1. Feature process cartridge. After charging the latent image carrier surface,
Forming an electrostatic latent image on the surface of the latent image carrier;
Supplying toner to the latent image on the surface of the latent image carrier to form a toner image;
Transfer the toner image formed on the surface of the latent image carrier to a non-transfer body,
Cleaning the toner remaining on the latent image carrier surface after transfer,
In an image forming method comprising a step of supplying a latent image carrier protective agent to the latent image carrier,
Outside the image area of the latent image carrier, it has a surface potential detection area for determining the latent image carrier replacement time,
In the surface potential detection area, as in the image area, at least charged, forming an electrostatic latent image, developing, cleaning, and supplying a protective agent,
Supply a smaller amount of protective agent to the surface potential detection area of the latent image carrier than in the image area, detect the surface potential of the surface potential detection area of the latent image carrier, and determine when to replace the latent image carrier An image forming method.

Images