JP5970891B2 - Electrophotographic photosensitive member, method for producing electrophotographic photosensitive member, process cartridge for image forming apparatus, and image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic photosensitive member, a method for manufacturing an electrophotographic photosensitive member, a process cartridge for an image forming apparatus, and an image forming apparatus. More specifically, the present invention relates to an electrophotographic photosensitive member for use in an image forming apparatus having a long life and a reduced printing cost, such as a copying machine, a facsimile, a laser printer, a direct digital plate making machine.

Electrophotographic photoconductors applied to copiers and laser printers used to be electrophotographic photoconductors made of inorganic materials such as selenium, zinc oxide, and cadmium sulfide. OPC photoreceptors (organic material-based electrophotographic photoreceptors) that are advantageous in terms of cost and high design freedom have become mainstream.
At present, the OPC photosensitive member is used at a rate of thinning to 100% of the total production amount of the electrophotographic photosensitive member. In recent years, OPC photoconductors have been required to change from disposable products to mechanical parts in response to the recent increase in global environmental conservation.

  Various attempts have been made to improve the durability of an OPC photoreceptor. At present, the formation of a crosslinked resin film on the surface of an electrophotographic photoreceptor (for example, Patent Document 1) and the formation of a sol-gel cured film on the surface of an electrophotographic photoreceptor (for example, Patent Document 2) are considered particularly advantageous. Has been.

  The former has the merit that even when a charge transporting component is blended, cracks and cracks hardly occur and the production yield can be reduced. Among these, radically polymerizable acrylic resins are particularly advantageous because they are easy to obtain an electrophotographic photoreceptor having toughness and good sensitivity characteristics.

  In these two types of measures taking a cross-linked structure, a coating film is formed by a plurality of chemical bonds. Therefore, even if the coating film is stressed and a part of the chemical bond is broken, it does not immediately progress to wear. At present, it can be said that the mechanical strength of the electrophotographic photosensitive member has reached its peak.

  Further, a method of applying a lubricant to the surface of an electrophotographic photosensitive member is used as a method for improving the cleaning property of the polymerized toner. This method also has a function of protecting the electrophotographic photosensitive member from a charging hazard, and contributes to a longer life of the photosensitive member.

  However, even if these technologies are combined, the actual situation is that the electrophotographic photosensitive member has a disposable performance. This is because the surface physical properties of the electrophotographic photosensitive member change due to durable use, and abnormal image generation and cleaning performance become unsatisfactory.

  In order to convert an electrophotographic photosensitive member into a non-disposable mechanical part, it is difficult to find an answer to the extension of the prior art. Therefore, new technology is required.

  The method of applying a lubricant to the surface of the photoconductor is an advantageous method for stabilizing the physical properties of the surface of the photoconductor, but because the input / output control of the lubricant is insufficient, the periphery of the electrophotographic photoconductor is contaminated with the lubricant. There are many cases. This is a cause of shortening the life of the photoreceptor.

  Recently, the present inventor and others have been developing technology for realizing the input / output control of the lubricant according to the surface shape of the photoreceptor. If the coating of the surface of the photoconductor with the lubricant is performed all over and the process of constantly coating and removing the surface of the photoconductor is realized, the surface of the photoconductor does not change permanently. The input / output of the lubricant affects the degree of rubbing between the surface of the photoreceptor and the coating of the lubricant or the member to be removed. Here, since the surface shape of the photoconductor changes the degree of rubbing, it is important to establish a method for controlling the surface shape of the photoconductor to realize such a process.

  For controlling the surface shape of the photoreceptor, it is convenient to use fillers in the surface layer of the photoreceptor and use the unevenness formed by the filler. However, since this method causes an increase in the potential of the exposed area, it is difficult to put the practical use of photoconductor surface shape control.

  In contrast, conventionally, the following techniques can be referred to as a measure for reducing the exposed portion potential of the electrophotographic photosensitive member.

  Patent Document 3 discloses a positively charged type in which a protective layer of an electrophotographic photosensitive member contains a cured film made of an organic pigment that generates charge and an electron-accepting carboxylic acid compound and / or an electron-accepting polycarboxylic acid anhydride. An electrophotographic photoreceptor has been proposed.

  In this technique, page 15, the electron acceptability of carboxylic acid and acid anhydride improves the injection of electrons from the charge generation layer to the protective layer, so that the increase in residual potential after light attenuation can be reduced. . However, the same effect cannot be expected when the charge responsible for light attenuation of the photoconductor is not an electron but a hole. In addition, even if a technique for increasing the injection of electrons between layers is used, the increase in the residual potential cannot be eliminated if impurities that become charge traps are included.

  Patent Document 4 proposes a technique in which a surface layer of an electrophotographic photoreceptor includes at least α-alumina particles and a binder resin, and a polymer material having a maleic acid derivative unit.

  According to the publication [0019], it is considered that the increase in the exposed portion potential of the electrophotographic photosensitive member is caused by charge trapping caused by hydroxyl groups present on the surface of the metal oxide filler. In view of this, it is a technique that assumes that a polymer material having a maleic acid derivative unit is adsorbed on the surface of α-alumina particles to suppress the exposure of the exposed portion by reducing exposure of charge traps.

  Although it is considered possible to use this polymer and a dispersant in combination, as long as the examples in the publication are seen, a polymer material having a maleic acid derivative unit is used as a kind of dispersant advantageous for the characteristics of the exposed portion potential. It is natural to interpret it as being. It is unclear whether an increase in the exposed portion potential can be suppressed when various dispersants are used in combination. Further, it cannot be said that the surface shape of the photoreceptor can be sufficiently controlled only by the disclosed polymer material group having a maleic acid derivative unit.

  Patent Document 5 discloses a technique using citric acid in the photosensitive layer. Patent Document 5 [0014] shows an effect that the image density is not lowered by repeated use by adding citric acid to the charge blocking layer.

  This is presumed to be a technique for controlling the resistance of the blocking layer by the organic acid from the configuration in which the organic acid is added to the N-alkoxymethylated nylon in the blocking layer. The improvement of the exposed portion potential caused by the surface layer of the photoreceptor needs to reduce not only the resistance design of the surface layer but also the amount of charge traps that prevent the accumulation of residual charges. It can be said that it is difficult to improve the potential of the exposed portion simply by designing the resistance of the photosensitive layer for the same reason as in Patent Document 3 above.

  When a metal oxide filler is contained in the surface layer of the electrophotographic photosensitive member, it is advantageous for suppressing wear of the photosensitive member. In this method, in order to uniformly disperse the metal oxide filler in the binder resin, a dispersant is usually used in combination. However, this method has a detrimental effect of increasing the exposed portion potential. Therefore, it is necessary to select a metal oxide filler and a dispersant that are balanced in terms of characteristics. This idea naturally eliminates the need for material selection because it is necessary to select the optimal material for the metal oxide filler and dispersant.

  On the other hand, the inventor has found that the metal oxide filler forms various aggregates depending on the dispersant and the surface shape of the photoreceptor changes accordingly. Using this property, the surface shape of the photoreceptor can be finished with a dispersant. When the rubbing degree of the photoconductor and the previous blade changes depending on the surface shape of the photoconductor, and the lubricant is circulated on the surface of the photoconductor, the input / output control of the lubricant is realized by the surface shape control of the photoconductor. As a result, the stability of the photoreceptor surface can be obtained. From these, the inventors have come up with the idea that the above photoreceptor can be improved in stability by the dispersant.

  Therefore, the present invention eliminates the increase in the potential of the exposed portion caused by the metal oxide filler and the dispersant, which hinders the degree of freedom in designing the surface layer of the photosensitive member, and provides a range of selection of these materials. An electrophotographic photosensitive member capable of controlling the surface shape of the photosensitive member, and further excellent in three characteristics of abrasion resistance, cleaning property, and exposed portion potential, a method for producing the electrophotographic photosensitive member, a process cartridge for an image forming apparatus, and image formation The purpose is to provide a device.

In order to achieve such an object, the electrophotographic photosensitive member according to the present invention is an electron in which a plurality of layers are formed on a support, of which a surface layer containing a metal oxide filler and a dispersant is formed as a surface layer. in photoreceptor der is, the organic acid which acid value containing the following organic acids 0.8gKOH / g or more 1.0gKOH / g to said surface layer is citric acid or maleic acid.

  According to the present invention, an increase in exposed portion potential due to the metal oxide filler and the dispersant is eliminated. The surface shape control of the photoconductor can be realized, and the selection of the material for the metal oxide filler and the dispersant can be widened with respect to the design of the photoconductor surface layer, and the design of the photoconductor surface layer can be facilitated. Accordingly, a commercially available dispersant can be used, and the manufacturing cost of the photoreceptor can be reduced. In addition, an electrophotographic photoreceptor excellent in the three characteristics of abrasion resistance, cleaning property, and exposed portion potential can be provided.

1 is a schematic cross-sectional view illustrating an example of an image forming apparatus. It is sectional drawing which shows an example of the layer structure of an electrophotographic photoreceptor. It is sectional drawing which shows the other example of a layer structure of an electrophotographic photoreceptor. FIG. 6 is a schematic cross-sectional view illustrating another example of an image forming apparatus. FIG. 6 is a schematic cross-sectional view illustrating another example of an image forming apparatus. It is a schematic cross section showing an example of a process cartridge. FIG. 6 is a schematic cross-sectional view illustrating another example of an image forming apparatus. FIG. 6 is a schematic cross-sectional view illustrating another example of an image forming apparatus. FIG. 6 is a schematic cross-sectional view illustrating another example of an image forming apparatus. It is a schematic cross section which shows an example of a lubricant supply means.

  Hereinafter, the configuration according to the present invention will be described in detail based on embodiments shown in the drawings.

  The present invention relates to the function of the dispersant in the surface layer of the photoreceptor (1) prevention of settling of the metal oxide filler in the paint, (2) control of the dispersion or aggregation state of the metal oxide filler in the surface layer of the photoreceptor, and (3) The present invention has been accomplished by separating the photosensitive member exposed portion potential and finding that the problem can be achieved by using a plurality of materials instead of a single dispersant according to the three functions.

That is, according to the present invention, in an electrophotographic photoreceptor in which a plurality of layers are formed on a support, and a surface layer containing a metal oxide filler and a dispersant is formed as a surface layer.
An electrophotographic photoreceptor is provided in which the surface layer contains an organic acid having an acid value of 0.8 gKOH / g or more and 1.0 gKOH / g or less.
According to the present invention, a metal oxide filler dispersion is prepared by dispersing a metal oxide filler in a solution not containing an organic acid having an acid value of 0.8 gKOH / g or more and 1.0 gKOH / g or less. The method for producing an electrophotographic photoreceptor according to claim 1, wherein the surface layer is formed using a coating for a surface layer formed by adding an organic acid having an acid value of 0.8 gKOH / g or more and 1.0 gKOH / g or less. Provided.

  In the present specification, the surface layer of the photoreceptor refers to a layer farthest from the support. When the protective layer is laminated, the surface layer refers to the protective layer, and when the outermost surface of the photoreceptor is the charge transport layer, the surface layer becomes the charge transport layer. However, what is coated with a lubricant or the like by the image forming apparatus is distinguished from the upper surface layer as a film.

  Based on the functional separation of the dispersant in the surface layer of the photoreceptor, the options for the dispersant can be expanded while ensuring a reduction in the exposed portion potential. The reduction of the exposed area potential is originally a function required only for the electrophotographic photosensitive member, and commercially available dispersants usually do not have this function. In the present invention, a substance that substantially expresses the functions (1) and (2) is defined as a dispersant, and the function (3) is expressed in a dispersant having the functions (1) and (2). Therefore, an organic acid having an acid value of 0.8 gKOH / g or more and 1.0 gKOH / g or less is used in combination. Therefore, what contains the organic acid which has only the function of (3) independently is not included in the concept of the present invention.

In the present invention, the acid value of the organic acid is defined as the mass of potassium hydroxide required to neutralize 1 gram of organic acid. The mass of potassium hydroxide usually uses milligram units, but in the present invention, gram units are used for convenience because of the size of the value defined.
In the present invention, the acid value of the organic acid is measured as follows.

That is, 100 ml of ethanol is added to 0.1 g of an organic acid and dissolved in a room temperature environment. Add 1.0 ml of phenolphthalein solution as an indicator to the organic acid solution, titrate with 0.1N isopropyl alcoholic potassium hydroxide solution, and continue titrating for 30 seconds to give a light red color. The acid value is calculated from the following formula (1).
Acid value (gKOH / g) = (56.11 × N × (s−b) × F) / S (1)
here,
N: Normality of KOH / isopropyl alcohol solution s: Titration volume (ml)
b: Blank titration (ml)
F: titer of titrant S: mass of organic acid (g)
It is.

  In the present invention, it has been found that for an organic acid having an acid value of 0.8 g or more and 1.0 g or less, an exposed portion potential can be reduced in accordance with the acid value.

  Since the effect is small when the acid value is 0.8 gKOH / g or less, it is not significant for the reduction of the exposed portion potential. For this reason, the minimum of the acid value of an organic acid shall be 0.8 gKOH / g. This effect is more strongly expressed as the acid value of the organic acid is larger, but the addition of a strong acid such as sulfuric acid is not suitable because it causes alteration of the material.

  In the present invention, it has been confirmed that the desired effect can be obtained without causing a problem until the acid value reaches 1.0 gKOH / g. Conventionally, the acid value of a dispersant has been used as an important physical property value that indicates characteristics of the dispersant. There are few examples of applying this to organic acids that deviate significantly from the conventional numerical range. This can be said to be one of the features of the present invention.

  The acid value of the dispersant is often disclosed as a catalog value of the dispersant manufacturer and can be said to be a general parameter. For example, as a component of the invention, Reference 1 (Patent No. 3802787) defines the acid value of the dispersant as 30 to 400 mg KOH / g, and Reference 2 (Patent No. 4425487) describes the dispersant. The acid value is specified as 10 to 400 mgKOH / g.

  Further, paragraphs [0038] to [0044] of Reference Document 3 (Japanese Patent Application Laid-Open No. 2011-13355) define 10 to 700 mgKOH / g from the residual potential characteristics of the photoreceptor, image characteristics, and dispersibility of the metal oxide filler. It can be seen.

  However, none of the specified ranges of acid values can be specified widely. Dispersant has multiple properties such as dispersibility of the dispersant, lowering the resistance of the photoreceptor, and charge trapping property of the dispersant itself. Therefore, it is difficult to satisfy multiple functions with one dispersant. . This seems to be the reason why there is a range in the regulation of acid value.

  On the other hand, in the present invention, by separating the function of the dispersant, an unprecedented large acid value is defined as an appropriate numerical range for the function of reducing the exposed portion potential of the photoreceptor, and depending on the acid value The inventors have succeeded in defining the range of acid values that can reduce the exposed area potential.

  Here, the organic acid used in the present invention is defined as a general term for acids of organic compounds. Examples of the organic acid include carboxylic acid, polycarboxylic acid, hydroxy acid, and sulfonic acid. These can be classified into organic acids of aliphatic compounds and aromatic compounds, saturated compounds and unsaturated compounds based on the characteristics of the molecular skeleton. Examples of organic acids include cyclohexanecarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, merit acid, mellitic acid, succinic acid, glycolic acid, maleic acid, citric acid, malonic acid, lactic acid, quinic acid, 2 -Hydroxybutyric acid, malic acid, glyceric acid, oxalic acid, tartaric acid, protocatechuic acid, gallic acid, p-toluenesulfonic acid and the like can be mentioned. These can be obtained from reagent manufacturers such as Tokyo Chemical Industry, Kanto Chemical, and Wako Pure Chemical Industries. Of the organic acids, it is particularly preferable to use either citric acid or maleic acid.

  These organic acids are preferably materials that can be dissolved in a coating solvent such as tetrahydrofuran described later and do not volatilize. In addition, organic acids with an unpleasant odor such as cyclohexanecarboxylic acid are difficult to handle and should not be used. Among these, maleic acid having an acid value of 1.0 gKOH / g is a preferable material that is soluble in a solvent, easily applied to a coating material, has no unpleasant odor, and has a large effect of reducing the potential of an exposed area.

  If the content of the organic acid contained in the surface layer of the photoreceptor is 0.5% by weight to 3% by weight with respect to the total solid content of the surface layer, the desired effect is easily exhibited. It cannot be said that the exposed portion potential is reduced depending on the content of the organic acid. It is considered that the organic acid itself has an action of accumulating charges. Citric acid is easy to handle, and is an advantageous material as a compound that can reduce the potential of the exposed area depending on the citric acid content.

  The present invention relates to an electrophotographic photosensitive member in which a surface layer containing at least a metal oxide filler and a dispersant is laminated. When an organic acid having an acid value of 0.8 gKOH / g to 1.0 gKOH / g is added, Since potential reduction is obtained, the options for metal oxide fillers and dispersants are expanded. An enormous amount of dispersing agents currently available on the market can be used for the coating of the surface layer of the photoreceptor.

  Further, when the dispersant used for the surface layer of the photoreceptor is a dispersant that does not dissolve in water, it is possible to further suppress an increase in the exposed portion potential. The details of this mechanism are unknown, but I think as follows.

  It is considered that the organic acid inactivates the hydrophilic part of the metal oxide filler because of the above effects due to the addition of the organic acid. According to this idea, it is considered that the hydrophilic dispersant increases the potential of the exposed portion under the same influence as the metal oxide filler. Therefore, it is considered that a part of the organic acid is consumed for deactivating the hydrophilicity of the dispersant, and the deactivation of the metal oxide filler is insufficient. If the amount of organic acid contained in the surface layer of the photoconductor is small, it can act on the deactivation of the metal oxide filler, so that the potential of the exposed area can be reduced. It is thought that the effect becomes stronger.

  In the present invention, it is preferable to prepare a surface layer coating material by pouring a vehicle into the dispersion of the metal oxide filler. The organic acid may be added afterwards or included in the vehicle.

  In the dispersion step of the metal oxide filler, the dispersion state of the metal oxide filler inherent to the dispersant is created by attaching the dispersant to the surface of the metal oxide filler in a state where no organic acid is present. When an organic acid is added after this, the characteristics of the dispersion state of the metal oxide filler are not destroyed. For this reason, a specific shape can be stably formed on the surface of the photoreceptor.

  An image forming process cartridge and an image forming apparatus equipped with the photosensitive member having the above-described features of the present invention are advantageous for forming an image having a low exposure portion potential and excellent contrast and gradation. In addition, since the optimum cleaning condition for the image forming apparatus can be realized from the surface shape of the photoreceptor, it is possible to realize an image forming process cartridge or an image forming apparatus that is advantageous in suppressing image noise and excellent in image quality consistency.

  An example of the image forming apparatus will be described with reference to FIG. In the apparatus shown in FIG. 1, the lubricant 3A is input to the surface of the electrophotographic photosensitive member by the application brush 3B, then smoothed by the application blade 3C, then removed by the cleaning blade 17, and goes back to the application brush 3B again. Since there is toner input / output in addition to the lubricant 3A on the surface of the electrophotographic photosensitive member 11, the lubricant 3A exists in a state of being mixed with the toner.

  Assuming that the loss component of the lubricant 3A is zero, at least the charging device 12, the application brush 3B, the application blade portion 3C, the mirror surface portion of the cleaning blade 17 and the surface of the electrophotographic photosensitive member 11 have toner, lubricant 3A and There is no stagnation of the mixture.

  Further, when using toner that does not include the lubricant 3A in the prescription, the toner concentration in the developing device becomes zero. That is, it is estimated that these stays and the lubricant component inside the developing device are the loss component of the lubricant. The charging device 12 is provided with a cleaner 12c for cleaning the charging device 12.

  Since the coating apparatus for coating the surface of the electrophotographic photosensitive member is built in the image forming apparatus, the electrophotographic photosensitive member is practically not worn. In the following description, the electrophotographic photoreceptor may be simply referred to as a photoreceptor. Conventionally, the electrophotographic photosensitive member has been frequently replaced and used as a consumable, but this is not necessary in the present invention. The electrophotographic photosensitive member does not need to be newly manufactured or collected, and the image forming apparatus of the present invention works extremely advantageously against a low environmental load due to resource saving. The method of recycling the electrophotographic photosensitive member, which is a conventional electrophotographic photosensitive member, after collecting it once cannot reach the advantage of the recycling cost per print with respect to the embodiment of the present invention.

  In the image forming apparatus of the present invention, the amount of coating for coating a material for forming a film (hereinafter referred to as a lubricant) on the surface layer of the electrophotographic photosensitive member is cleaned until the next coating is performed. It is a new process that makes it less than the amount to be removed. This is an important requirement for establishing the formation of a lubricant film on the outermost surface of the electrophotographic photosensitive member. By coating the lubricant according to the amount of lubricant removed, the mass balance of the lubricant entering and exiting the electrophotographic photosensitive member can be equivalent.

  At a glance, the above process is similar to the means for applying a lubricant to an existing electrophotographic photosensitive member, but the lubricant application is a lubricant to ensure the lubricating function of the surface of the electrophotographic photosensitive member, such as maintaining the cleaning property. Is designed to be thickly coated on the electrophotographic photosensitive member. The conventional method of applying the lubricant to the electrophotographic photosensitive member has no idea of laminating a lubricant film on the surface of the electrophotographic photosensitive member. For example, the surface of the electrophotographic photosensitive member is protected or the surface of the electrophotographic photosensitive member is rubbed. In order to keep the coefficient below a predetermined value, the lubricant is merely supplied to the surface of the electrophotographic photosensitive member. When observing the surface of the photoreceptor to which such a lubricant is supplied from the outside, it is possible to observe the appearance of the granular lubricant adhering to the surface of the photoreceptor. Such granular lubricant is a cause of contamination inside the apparatus.

  The amount (removed amount) removed by cleaning the lubricant in the image forming process cartridge and the image forming apparatus can be calculated from the lubricant concentration contained in the collected toner. This analysis can be performed by ICP (Inductively Coupled Plasma) analysis or XRF (X-ray Fluorescence) analysis described later. Thus, by calculating | requiring disappearance speed (total amount of consumption of a lubricant) previously, the relationship between the removal amount of a lubricant and the application amount can be materialized.

  Next, a method of determining the amount of lubricant applied per cycle to be equal to or less than the amount removed by cleaning will be described.

  The consumption amount of the lubricant is determined as a value obtained by multiplying the adhesion efficiency of the lubricant to the electrophotographic photosensitive member and the compensation for the loss caused by the image forming process. The loss caused by the image formation process is the amount of lubricant consumed by the powder, which is the amount of lubricant formed by the brush that could not be coated on the surface of the photoconductor due to scattering or dropping. It can be measured by collecting the powder.

  Further, the component from which the lubricant is removed from the surface of the photoreceptor can be measured by recovering the amount remaining in the path after the cleaning means and generally reaching the waste toner bottle. When toner is contained, the weight of all the collected powder is obtained, and the lubricant concentration of this powder is analyzed, whereby the mass of the lubricant removed from the surface of the photoreceptor can be obtained.

  If a difference between the loss due to the above process and the amount removed from the surface of the photoreceptor occurs with respect to the total consumption of the lubricant, it is considered as a contamination to other modules such as charging means. The adhesion efficiency of the lubricant on the surface of the electrophotographic photoreceptor is determined by the familiarity between the photoreceptor and the member to which the lubricant is applied, such as a coating blade.

  In the case of using an application blade, in order to coat the lubricant thinly, uniformly and without defects, it is inefficient if the application blade completely stops the lubricant during the rubbing between the photoreceptor and the application blade. It is important to form an appropriate gap and prevent chatter.

  When the lubricant is coated in parallel with an image forming process including various disturbances, the deposition efficiency needs to compensate for the loss due to the process and the loss due to the contamination of the underlying surface layer to be coated. The loss is calculated from the difference in lubricant adhesion efficiency depending on the presence or absence of disturbance.

  However, in the case of an image forming apparatus in which a lubricant film is formed, the amount of lubricant consumption is simply increased or decreased to evaluate the lubricant film defects and the degree of filming on the photoreceptor surface. The establishment point can be specified.

  This image forming apparatus is characterized in that a lubricant is coated on the surface layer of the electrophotographic photosensitive member in the electrophotographic apparatus, and in order to secure a good quality film formation, It is desirable that the coated surface is clean and the surface layer is not altered.

  In the former method, as a method of maximally eliminating the toner that destroys the cleanliness, it is important to dispose the lubricant coating device downstream of the cleaning device with respect to the electrophotographic photosensitive member surface movement direction. Furthermore, for the latter, it is necessary to prevent a change in the shape of the surface layer that causes modulation in conformity between members in contact with the electrophotographic photosensitive member. For this reason, in order to prevent the surface layer from being directly exposed to the charging hazard, the above coating device is disposed upstream of the charging device with respect to the electrophotographic photosensitive member surface moving direction to coat the lubricant film. This is very important.

  When mounted in the image forming process cartridge and the image forming apparatus described above, a circulation type film is formed on the surface layer of the electrophotographic photosensitive member of the present invention. Here, this film may be referred to as a circulating surface layer. The defects of this film are at least less than 10%, and the mass film thickness of the lubricant film is not less than one molecular layer and less than three molecular layers. The mass film thickness can be calculated by ICP analysis or simple XRF analysis.

  ICP analysis can be obtained according to Reference 4 (Japanese Patent Laid-Open No. 2008-122870), and XRF analysis calculates the amount of adhesion from a calibration curve based on the results of ICP analysis. The mass film thickness is calculated based on Reference 5 (Izumi Nakai, Actual X-ray fluorescence analysis, 154-161, Asakura Shoten, 2005).

Further, the defect of the coating film coated on the surface layer of the photoreceptor is calculated as a value obtained by subtracting the coverage from 100%. The coverage is a value obtained from the XPS analysis method according to the method described in Reference 4. The mass film thickness is obtained by dividing the surface density (g / cm ² ) described in Reference 5 by the density (g / cm ³ ), that is, the mass film thickness.

  The zinc stearate handled in the examples of the present invention uses the number of overlapping molecules as a unit of thickness, with the thickness of one molecule being 5 nm. This thickness is based on paragraph [0021] of Reference Document 6 (Japanese Patent Laid-Open No. 2006-91047), for example.

  In the electrophotographic photoreceptor of the present invention, the relationship between the amount of lubricant removed and the amount of adhesion is ignored only when a lubricant is provided on the surface of an unused photoreceptor. This is because the lubricant is not applied at all if the applied amount of the lubricant is less than or equal to the removed amount of the lubricant in the absence of the lubricant.

  The case where the lubricant is provided refers to an unsteady state until the photosensitive drum arrives at the image forming apparatus. Specifically, it refers to 1000 or less initial prints after a new photoconductor is mounted on the image forming apparatus. The means for providing the lubricant on the surface of the photosensitive member is to accumulate the lubricant on the surface of the photosensitive member by utilizing the property that the cleaning function of the image forming apparatus is insufficient because the lubricant coating on the surface of the photosensitive member is insufficient. Alternatively, it may be applied in advance using a setting powder or the like.

  The lubricant film on the surface of the electrophotographic photosensitive member is defined as described above, but it is not easy to form the lubricant film in the image forming apparatus or during the image forming process. This is because in the image forming process, the physical properties of the surface layer of the electrophotographic photosensitive member are constantly accumulated.

  In the course of the image forming process, not only the surface layer of the electrophotographic photosensitive member is coated with a lubricant but also an image is formed with toner. In this way, when coating of lubricant film and image formation are performed simultaneously, when the coating of lubricant is insufficient, the surface layer of the electrophotographic photosensitive member may be filmed with paper dust or toner components, or medaka-shaped filming. May occur.

  Such filming makes it difficult to coat the lubricant each time the image forming cycle is repeated. Further, if the coating function of the lubricant is weak and the film formation cannot keep up with the supply of the lubricant, the coating film of the lubricant may become grainy. In addition, the surface of the electrophotographic photosensitive member may be in a state of being coated with gravel due to the lubricant staying on or slipping through the member in contact with the electrophotographic photosensitive member.

  If this happens, the members around the electrophotographic photosensitive member (charging device, exposure device, developing device, transfer device) may be contaminated and the life may be shortened, or lubricant may be mixed into the developing device and toner charging may be disturbed. It becomes a problem when the image forming apparatus is used endured. Such a grain does not necessarily have to be 0%, but as a guide to avoid the problem, the area ratio of the grain is less than 0.05% when the surface of the electrophotographic photosensitive member is observed in the area of about 2 mm. More preferably, it is less than 0.03%. The area ratio of the grains can be calculated by image analysis software such as imageJ (manufactured by National Institutes of Health) or ImageProplus (manufactured by Media Cybernetics).

  Currently, when a general lubricant is applied in an image forming apparatus, the coverage of the lubricant is often about 85%, and the amount of adhesion is often about two to four molecular layers. Grain varies depending on the print pattern, but is often about 0.1% to 2.5%. For this reason, an abnormal image appears during durable use or the electrophotographic photosensitive member needs to be replaced, and it cannot be said that a lubricant film is formed.

  On the other hand, when the lubricant film is formed, the life of the surface layer of the electrophotographic photosensitive member is overcome, and the life of the electrophotographic photosensitive member is minimized. In addition, the coating device for coating the lubricant used in the image forming apparatus of the present invention can use existing lubricant coating means. For this reason, the image forming apparatus of the present invention can suppress a significant increase in cost.

  In the above image forming apparatus, by coating the lubricant on the surface layer of the electrophotographic photosensitive member with a coating amount smaller than the amount for removing the lubricant by cleaning up to the cleaning device, the film defect is less than 10%. In addition, in order to form a lubricant film having a mass film thickness of the lubricant film of one molecular layer or more and less than three molecular layers, is it possible to apply the lubricant all over the surface layer of the electrophotographic photoreceptor? Is the key.

  This enhancement of the coating function requires control of the rubbing state between the electrophotographic photosensitive member and the coating blade. More simply, a process to improve these familiarity is required.

  The inventor endured and used the image forming apparatus having the same configuration as the above-described image forming process cartridge and the image forming apparatus, and observed the rubbing portion of the coating blade with the electrophotographic photosensitive member. It was found that the roughness of the coating blade was different depending on the layer shape.

  In this observation, a field of view of 180 μm is observed from directly above the blade mirror surface with a confocal microscope having a 100 × objective lens. The coating blade is used in a trailing arrangement with respect to the electrophotographic photosensitive member. The roughness of the coating blade was measured from the surface roughness (Ra) in the vertical direction of 90 μm from the cut surface edge portion of the coating blade, the total length of the region of 180 μm, and the average interval (Sm) of the local peaks of the irregularities.

  When we try to classify the roughness by mapping the sizes of Ra and Sm, the surface curve of the surface layer of the electrophotographic photosensitive member has moderately high low-frequency component irregularities and moderately high frequency component irregularities. The characteristics with smaller roughness were obtained. Furthermore, it was found that the film particles tend to become stronger according to the roughness of the coating blade after durable use. The roughness of the coating blade was determined by observation with a confocal microscope OPTELICS H-1200 manufactured by Lasertec Co., Ltd. and the surface roughness Ra using the attached software LMeye, and a sample difference ranging from 0.3 μm to 0.6 μm was obtained. . Moreover, the average space | interval (Sm) of the local summit obtained the sample difference ranging from 2.5 micrometers to 5.5 micrometers. The roughness of the coating blade after durable use reflects the familiarity with the surface of the electrophotographic photosensitive member.

  Therefore, it is necessary to form the surface shape of the photoreceptor to suppress this roughness. As described above, the inventor has found that the metal oxide filler forms various aggregates depending on the dispersant, and the surface shape of the photoreceptor changes accordingly. Using this property, the surface shape of the photoreceptor can be finished with a dispersant. However, many of the dispersants have extremely increased the exposed portion potential, making it impossible to form the surface of the photoreceptor. As a technique for solving this problem, an organic acid is used in the present invention.

  For the formation of the film of the electrophotographic photosensitive member provided in the above image forming apparatus, it is desirable that the lubricant is a material that can be easily removed from the surface layer of the electrophotographic photosensitive member and can be easily coated. It is particularly preferable that the amount of material coated in one cycle and the amount of material removed by cleaning are equivalent in order to make the film made of the lubricant permanent. It is also necessary that the lubricant consumption rate is not excessive. The lubricant consumption rate is defined as the amount of lubricant input (mg / km) with respect to the travel distance of the electrophotographic photosensitive member generated in the image forming process.

  For the above requirements, wax or higher fatty acid metal salt is advantageous as a material used for the lubricant. As the wax, plant waxes such as goby wax, urushi wax, palm wax, carnauba wax, animal waxes such as beeswax, whale wax, ibota wax, wool wax, and mineral waxes such as montan wax and paraffin wax can be used.

  In particular, many of the higher fatty acid metal salts that have been generally used in the past are advantageous in terms of the properties of the material. This representative compound, zinc stearate, is a compound that can have a lamellar structure. A lamellar structure is a structure in which layers formed by regularly folding molecules are stacked and arranged. This lamellar structure has a layered structure in which amphiphilic molecules are self-organized, and when a shearing force is applied, the crystal is easily broken along the layers. This action is advantageous for establishing the circulation of the lubricant.

  The characteristic of the lamellar structure in which zinc stearate is subjected to a shearing force and uniformly covers the surface of the electrophotographic photosensitive member can be effectively covered with a small amount of lubricant. When applying a lubricant by this method, there are various methods for controlling the application state of the lubricant. For example, means for increasing the contact pressure between the solid lubricant and the application brush or controlling the rotation speed of the application brush can be considered. There is also an attempt to control the rotation speed of the application brush according to the image formation information.

  As the lubricant, a wax or a higher fatty acid metal salt may be used alone, but these can be used as a binder by mixing with other functional materials such as a charge transport material and an antioxidant.

  In order to identify materials that are easy to form and remove in the image forming apparatus using such a lubricant, it is possible to enjoy the effect of easily obtaining the equivalence of the amount of substances during the repeated steps of removing the lubricant and coating. it can. For this reason, the module responsible for applying and removing the lubricant can be simplified. In addition, the lubricant film can be formed for a long time. Furthermore, by combining with the shape of the surface layer described above, it is possible to achieve a particularly high covering capacity per cycle, and to enjoy a reduction in the consumption rate of the lubricant.

  Furthermore, as the lubricant in the present invention, the fatty acid metal salt capable of taking a lamellar structure contains at least one fatty acid of stearic acid, palmitic acid, myristic acid, oleic acid, and zinc, aluminum, calcium, Fatty acid metal salts containing at least one metal among magnesium and lithium are preferred.

  In particular, zinc stearate is the most preferable material in terms of cost, quality, stability, and reliability because it is produced on an industrial scale and has been used in many fields. In addition, there is an advantage that it is easy to apply abundant application techniques that have been accumulated as an effective application method of the lubricant. In addition, the higher fatty acid metal salt generally used industrially is not a compound simple substance composition of its name, but includes other more or less similar fatty acid metal salt, metal oxide, and free fatty acid, and the fatty acid of the present invention. Metal salts follow this convention.

  By using such a lubricant, high reliability and cost reduction can be enjoyed with respect to the formation of the lubricant film. In addition, it is possible to obtain the convenience of device development that facilitates application of accumulated coating technology as lubricant coating technology.

  By modeling the surface layer of the electrophotographic photosensitive member, it is possible to enjoy the effect of dramatically improving the applicability of the lubricant. In order to maintain this effect, it is advantageous to increase the strength of the surface layer. When the electrophotographic photoreceptor is worn during image formation by the electrophotographic process, the surface shape changes. The state can be seen from the change in the surface roughness, and the inventor has experimentally confirmed that the surface roughness tends to increase with the progress of wear of the electrophotographic photosensitive member.

  First, film formation by a wet process is advantageous for forming the above-described new shape. This is because it controls the surface shape from the micron to the millimeter scale, and is more advantageous in terms of technology and cost than mechanical processing. In film formation by a wet process, the lower the viscosity of the paint, the wider the range of shape control. Specifically, about 0.9 mPa · s to 10 mPa · s is preferable. The lower limit of the viscosity of the paint is determined from a value asymptotic to the solvent viscosity, and the upper limit is determined for the reason that shape control becomes difficult. In order for the viscosity of the paint to be low and for the surface layer after film formation to have a practically sufficient strength, a reactive resin monomer having a three-dimensional cross-linked structure is preferably selected as the main component.

  By using a resin having a three-dimensional crosslinked structure for the surface layer of the electrophotographic photoreceptor, a surface layer having excellent wear resistance can be obtained. The reason for this is considered to be that due to durability deterioration, even if a part of the chemical bond forming the resin film is broken, if a chemical bond at another site remains, it does not cause direct wear. Excellent wear resistance directly contributes to surface shape stabilization. As a result, when a resin having a three-dimensional cross-linked structure is used for the surface layer, the applicability of the lubricant can be stabilized.

  Among resins having a three-dimensional cross-linked structure, an acrylic resin has a merit that the influence of the uneven shape on the electrostatic property surface is small because the dielectric constant is larger than that of a solid solution of polycarbonate and a charge transport material. Furthermore, the combined use of the organic acid of the present invention is particularly advantageous because it has an effect of suppressing image blur.

  As described above, the use of a resin having a three-dimensional cross-linked structure in the surface layer has an effect of facilitating the modeling of the surface layer of the electrophotographic photosensitive member, and the applicability of the lubricant can be easily improved. Moreover, the effect of suppressing the special surface shape change of a surface layer and stabilizing the applicability | paintability of a lubricant can be enjoyed.

  When the metal oxide filler is added to the surface layer modeling based on a paint having a relatively low viscosity, an uneven shape can be imparted. Various uneven shapes can be obtained by controlling the aggregation state of the metal oxide filler. The technology of using a resin having a three-dimensional cross-linked structure for the surface layer of an electrophotographic photosensitive member and further incorporating a metal oxide filler has been known in the past, but many aim to focus on mechanical strength. Surprisingly, there have not been many techniques for using a metal oxide filler dispersant together.

  Furthermore, the concept of controlling the surface shape of the electrophotographic photosensitive member by changing the aggregation state of the metal oxide filler by the dispersant is a novel concept. . Among the metal oxide fillers, the metal oxide filler to be blended is preferably a metal oxide filler having a primary particle size of nano-order, and metal oxide metal such as α-alumina, tin oxide, titania, silica, ceria. Oxide fillers are useful.

  Some metal oxide fillers, such as organic fine particles and inorganic fine particles, are difficult to disperse and have a surface roughness of only micron order or more, and there are many thorn-like protrusions. Some metal oxide fillers do not have such problems. For the same reason, the content of the metal oxide is preferably 1 wt% or more and 20 wt% or less of the surface layer. The lower limit and the upper limit of the metal oxide content are specified because the shape control of the surface layer becomes difficult. The effect of improving the mechanical strength by the combined use of the metal oxide can also be enjoyed in the present invention.

  In the unlikely event that the lubricant coating is inadequate, paper powder or toner components may form on the surface layer of the electrophotographic photosensitive member, or medaka-shaped filming may occur. . At this time, the wettability of the surface layer may change and the intended circulation process of the lubricant may fail.

  In contrast, the addition of substantially spherical α-alumina fine particles to the surface layer of the electrophotographic photosensitive member has proved experimentally that the above filming can be greatly reduced, which is effective. The reason for this has not been clarified so far, but the high hardness of α-alumina is effective in preventing wounds on the underlying surface layer, and this effect makes it difficult to provide filming opportunities. This is considered to be because the unevenness of α-alumina has the effect of stabilizing the rubbing state between the electrophotographic photosensitive member and the coating blade or the cleaning blade to some extent even if it is insufficient. When the particle diameter of the metal oxide filler of the substantially spherical α-alumina is 0.1 μm or more and 2 μm or less, more preferably 0.3 μm or more and 1.5 μm or less, extreme irregularities such as thorns are formed during film formation. Therefore, it is easy to form an advantageous shape.

As described above, by containing α-alumina having an average primary particle size of 0.1 μm or more and 2 μm or less, it is possible to enjoy the effect of preventing the surface of the electrophotographic photosensitive member from being altered.
The effect of improving the mechanical strength by the combined use of the metal oxide can also be enjoyed in the present invention.

  When a metal oxide filler is added to the surface layer, a fine uneven shape can be imparted. Thereby, it is easy to obtain the effect of improving the circulation efficiency of the lubricant.

  In order to realize an image forming process cartridge and an image forming apparatus for forming a film having a predetermined defect or less on the surface of the photoconductor and the surface of the photoconductor, it is necessary to arbitrarily control the shape of the surface layer of the photoconductor. There is. This is because the surface shape of the photosensitive member needs to be finely adjusted according to the characteristics of the image forming apparatus.

  When individually dispersed (surface treatment) with a specific dispersant for a specific metal oxide filler, the metal oxide filler is subjected to a surface treatment specific to the dispersant. For this reason, the particle size distribution of the secondary particles inherent to the dispersant is formed in the surface layer after the solution and coating. When dispersing (surface treatment) metal oxides, adjust the mill base (or paint) for each type of dispersant rather than mixing multiple dispersants at once, and prepare multiple mill bases (or paints) at any ratio. Then, the additivity of shape control becomes clear and the efficiency of modeling is good.

  The metal oxide filler dispersant has a function of controlling the affinity between the metal oxide, the paint solvent, and the vehicle. The affinity with the former paint solvent is essential to prevent sedimentation. This is because reproducibility of the surface shape cannot be guaranteed in a state where the metal oxide filler does not settle. In addition to this essential condition, the affinity between the dispersant and the vehicle can be variously adjusted by the physicochemical affinity and steric hindrance between the dispersant and the vehicle. However, for the above reason, the dispersant needs to sufficiently treat the metal oxide filler.

  When such a variety of dispersants are used, the electrostatic characteristics of the photoreceptor deteriorate, and in extreme cases, the light attenuation characteristics of the photoreceptor disappear. Conventionally, it has been difficult to come up with the above idea because of such side effects. On the other hand, it is preferable to use an organic acid of 0.8 gKOH / g or more and 1.0 gKOH / g or less in combination. Further, in the case where an organic acid is added to the surface layer of the photoconductor, if the dispersant used for the surface layer of the photoconductor is a dispersant that does not dissolve in water, the increase in the exposed area potential can be further suppressed. The solubility of water can be determined by observing the visual phase separation when water and a dispersant are added.

  The addition amount of the organic acid is suitably 0.5% or more and 3% or less with respect to the total solid weight of the surface layer. The lower limit is determined from the magnitude of the effect of addition, and the upper limit is determined from the mechanical strength due to the weight loss of other components.

  Hereinafter, the electrophotographic photosensitive member of the present invention will be described in detail with reference to the drawings. FIG. 2 is a cross-sectional view schematically showing an example of an electrophotographic photosensitive member having the layer structure of the present invention. A charge generation layer 25, a charge transport layer 26, and a surface layer 28 are provided on a conductive support 21. Yes.

  FIG. 3 is a cross-sectional view schematically showing an example of an electrophotographic photoreceptor having still another layer structure of the present invention, in which an undercoat layer 24 is provided between the conductive support 21 and the charge generation layer 25. A charge transport layer 26 and a surface layer 28 are provided on the charge generation layer 25.

[Conductive support]
As the conductive support 21, a material having a volume resistance of 1010 Ω · cm or less, for example, aluminum, nickel, chromium, nichrome, copper, silver, gold, platinum, iron and other metals, tin oxide, indium oxide and the like An article coated with film or cylindrical plastic, paper, etc. by vapor deposition or sputtering, or a plate made of aluminum, aluminum alloy, nickel, stainless steel, etc., and these are drawn Ironing method, Impact Ironing method, Extruded Ironing method. It is possible to use a tube that has been surface-treated by cutting, super-finishing, polishing, or the like after being made into a raw tube by a method such as a method, an extruded drawing method, or a cutting method.

[Underlayer]
In the electrophotographic photoreceptor used in the present invention, an undercoat layer 24 can be provided between a conductive support and a photosensitive layer (a laminate of a charge generation layer 25 and a charge transport layer 26). The undercoat layer is provided for the purpose of improving adhesiveness, preventing moire, improving the coatability of the upper layer, and preventing charge injection from the conductive support.

  The undercoat layer 24 usually has a resin as a main component. Usually, since a photosensitive layer is applied on the undercoat layer 24, the resin used for the undercoat layer 24 is preferably a thermosetting resin that is hardly soluble in an organic solvent. In particular, polyurethane, melamine resin, and alkyd-melamine resin are particularly preferable materials because many of them sufficiently satisfy the above purpose. The resin can be used as a paint which is appropriately diluted with a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, butanone or the like.

  Further, in order to adjust conductivity and prevent moire, the undercoat layer 24 may contain fine particles such as metal or metal oxide, and titanium oxide is particularly preferably used.

  The fine particles are dispersed in a ball mill, attritor, sand mill, or the like using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, or butanone, and a coating material is obtained by mixing the dispersion and the resin component.

  The undercoat layer 24 is formed by depositing the above coating material on the conductive support by a dip coating method, a spray coating method, a bead coating method or the like. If necessary, it is formed by heat curing.

  In many cases, the thickness of the undercoat layer 24 is appropriately about 2 to 5 μm. When the accumulation of the residual potential of the electrophotographic photosensitive member becomes large, it is preferable to set it to less than 3 μm.

  The photosensitive layer in the present invention is preferably a laminated photosensitive layer in which a charge generation layer and a charge transport layer are sequentially laminated. However, the photosensitive layer in the present invention may be a single layer type photosensitive layer having both charge generation ability and charge transport ability.

[Charge generation layer]
Of the layers in the multilayer electrophotographic photoreceptor, the charge generation layer 25 will be described. The charge generation layer 25 indicates a part of the laminated photosensitive layer, and has a function of generating charges by exposure (charge generation ability). This layer is mainly composed of a charge generating substance among the contained compounds. The charge generation layer 25 may use a binder resin as necessary. As the charge generation material, inorganic materials and organic materials can be used.

  Examples of inorganic materials include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, selenium-arsenic compounds, and amorphous silicon. In amorphous silicon, dangling bonds that are terminated with hydrogen atoms or halogen atoms, or those that are doped with boron atoms, phosphorus atoms, or the like are preferably used.

  On the other hand, known materials can be used as organic materials, for example, metal phthalocyanines such as titanyl phthalocyanine and chlorogallium phthalocyanine, metal-free phthalocyanines, azulenium salt pigments, squaric acid methine pigments, symmetric types having a carbazole skeleton or Examples include an asymmetric azo pigment, a symmetric or asymmetric azo pigment having a triphenylamine skeleton, a symmetric or asymmetric azo pigment having a fluorenone skeleton, and a perylene pigment. Among these, metal phthalocyanines, symmetric or asymmetric azo pigments having a fluorenone skeleton, symmetric or asymmetric azo pigments having a triphenylamine skeleton, and perylene pigments have a high quantum efficiency of charge generation, and thus are suitable for the present invention. It is suitable as a material to be used. These charge generation materials may be used alone or as a mixture of two or more.

  The binder resin used as necessary for the charge generation layer 25 is polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, polyarylate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, poly-N-. Examples include vinyl carbazole and polyacrylamide. Moreover, the polymeric charge transport material mentioned later can also be used. Of these, polyvinyl butyral is often used and is useful. These binder resins may be used alone or as a mixture of two or more.

  Methods for forming the charge generation layer 25 are roughly classified into a vacuum thin film manufacturing method and a casting method from a solution dispersion system.

  The former method includes a vacuum deposition method, a glow discharge decomposition method, an ion plating method, a sputtering method, a reactive sputtering method, a CVD (Chemical Vapor Deposition) method, and the like, and is composed of the above-described inorganic materials and organic materials. A layer can be formed satisfactorily.

  Further, in order to provide the charge generation layer 25 by the casting method, the above-described inorganic or organic charge generation material is used together with a binder resin, if necessary, using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, butanone, ball mill, attritor. The dispersion may be dispersed by a sand mill or the like, and the dispersion may be diluted appropriately. Among these solvents, methyl ethyl ketone, tetrahydrofuran, and cyclohexanone are preferable because they have a lower environmental impact than chlorobenzene, dichloromethane, toluene, and xylene. The coating can be performed by a dip coating method, a spray coating method, a bead coating method, or the like.

  The film thickness of the charge generation layer 25 provided as described above is usually about 0.05 to 2.0 μm.

  When it is necessary to reduce the residual potential and increase the sensitivity, the charge generation layer 25 is often improved in its characteristics as the film thickness is increased. On the other hand, the chargeability often deteriorates, such as charge charge retention and space charge formation. From these balances, the thickness of the charge generation layer 25 is more preferably in the range of 0.05 to 2.0 μm.

  Further, if necessary, low molecular weight compounds such as antioxidants, plasticizers, lubricants, ultraviolet absorbers, and leveling agents that are conventionally well-known can be added to the charge generation layer. These compounds can be used alone or as a mixture of two or more. When a low molecular weight compound and a leveling agent are used in combination, sensitivity deterioration often occurs. For this reason, the amount of these used is generally 0.1 to 20 phr, preferably 0.1 to 10 phr, and the amount of the leveling agent used is suitably about 0.001 to 0.1 phr.

[Charge transport layer]
The charge transport layer 26 injects and transports the charge generated in the charge generation layer, and forms a part of the laminated photosensitive layer that has the function of neutralizing the surface charge of the electrophotographic photoreceptor provided by charging (charge transport ability). Point to. The main component of the charge transport layer 26 can be referred to as a charge transport component and a binder component that binds the charge transport component.

  Examples of materials that can be used for the charge transport material include low molecular weight electron transport materials, hole transport materials, and polymer charge transport materials.

  Examples of the electron transporting material include electron accepting materials such as asymmetric diphenoquinone derivatives, fluorene derivatives, naphthalimide derivatives and the like. These electron transport materials may be used alone or as a mixture of two or more.

  As the hole transport material, an electron donating material is preferably used. Examples include oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, butadiene derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl) propane, styryl. Anthracene, styrylpyrazoline, phenylhydrazones, α-phenylstilbene derivatives, thiazole derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, thiophene derivatives, and the like can be given. These hole transport materials may be used alone or as a mixture of two or more.

  Moreover, the polymeric charge transport material represented below can be used. For example, a polymer having a carbazole ring such as poly-N-vinylcarbazole, a polymer having a hydrazone structure exemplified in Reference 7 (JP 57-78402 A), Reference 8 (JP Examples thereof include polysilylene polymers exemplified in JP-A-63-285552, etc., and aromatic polycarbonates exemplified in general formula (1) to general formula (6) in Reference Document 9 (Japanese Patent Laid-Open No. 2001-330973). . These polymer charge transport materials can be used alone or as a mixture of two or more. In particular, the exemplified compound of Reference 9 is useful because of its good electrostatic characteristics.

  When the surface charge layer 28 is laminated, the polymer charge transport material has less oozing of the components constituting the charge transport layer 26 to the surface layer 28 than the low molecular weight charge transport material, and the surface layer 28 is hard to cure. It is a suitable material to prevent. Further, since the charge transport material has a high molecular weight, it is advantageous in that it is excellent in heat resistance and is less deteriorated by the heat of curing when the surface layer 28 is formed.

  Examples of the polymer compound that can be used as the binder component of the charge transport layer 26 include polystyrene, polyester, polyvinyl, polyarylate, polycarbonate, acrylic resin, silicone resin, fluorine resin, epoxy resin, melamine resin, urethane resin, and phenol resin. And thermoplastic or thermosetting resins such as alkyd resins. Of these, polystyrene, polyester, polyarylate, and polycarbonate are useful because many of them have good charge transfer characteristics when used as a binder component of a charge transport component. Further, since the surface layer 28 is laminated on the charge transport layer 26, the charge transport layer 26 does not require the mechanical strength of the conventional charge transport layer 26. For this reason, a material such as polystyrene, which is highly transparent but has a low mechanical strength and is difficult to apply in the prior art, can be effectively used as the binder component of the charge transport layer 26.

  These polymer compounds can be used alone or as a mixture of two or more kinds, or as a copolymer composed of two or more kinds of these raw material monomers and further copolymerized with a charge transport material.

  When an electrically inactive polymer compound is used for the modification of the charge transport layer 26, a cardo polymer type polyester having a bulky skeleton such as fluorene, a polyester such as polyethylene terephthalate or polyethylene naphthalate, or a C type polycarbonate is used. A polycarbonate in which the 3,3 ′ portion of the phenol component is alkyl-substituted with respect to such a bisphenol-type polycarbonate, a polycarbonate in which the geminal methyl group of bisphenol A is substituted with a long-chain alkyl group having 2 or more carbon atoms, biphenyl, Polycarbonate having a long-chain alkyl skeleton such as polycarbonate having a biphenyl ether skeleton, polycaprolactone, polycaprolactone (for example, Reference 10 (Japanese Patent Laid-Open No. 7-292095)), acrylic resin, polystyrene , Hydrogenated butadiene is effective.

  Here, it refers to a polymer compound that does not contain an electrically inactive polymer compound and a chemical structure that exhibits photoconductivity such as a triarylamine structure. When these resins are used in combination with a binder resin as an additive, the addition amount is preferably 50 wt% or less with respect to the total solid content of the charge transport layer 26 due to restrictions on light attenuation sensitivity.

  When a low molecular charge transport material is used, the amount used is 40 to 200 phr, preferably about 70 to 100 phr. When a polymer charge transport material is used, a material in which the resin component is copolymerized at a ratio of about 0 to 200 parts by weight, preferably about 80 to 150 parts by weight with respect to 100 parts by weight of the charge transport component is preferably used.

  When two or more kinds of charge transport materials are contained in the charge transport layer 26, it is preferable that the difference in ionization potential is small. Specifically, by setting the difference in ionization potential to be 0.10 eV or less, one charge transport is performed. The substance can be prevented from becoming a charge trap of the other charge transport substance.

  Regarding the relationship between the ionization potentials, the difference between the charge transporting material contained in the charge transporting layer 26 and the relationship between the curable charge transporting material described later is preferably 0.10 eV. In addition, the ionization potential value of the charge transport material in the present invention is a numerical value obtained by measuring by a general method using the atmospheric atmospheric ultraviolet photoelectron analyzer AC-1 manufactured by Riken Keiki Co., Ltd.

  In order to satisfy high sensitivity, the charge transport component is preferably added in an amount of 70 phr or more. In addition, α-phenyl stilbene compounds, benzidine compounds, butadiene compound monomers, dimers and polymer charge transport materials having these structures in the main chain or side chain are materials having high charge mobility. Many are useful.

  Examples of the dispersion solvent that can be used in preparing the charge transport layer paint include ketones such as methyl ethyl ketone, acetone, methyl isobutyl ketone, and cyclohexanone, ethers such as dioxane, tetrahydrofuran, and ethyl cellosolve, and aromatics such as toluene and xylene. , Halogens such as chlorobenzene and dichloromethane, and esters such as ethyl acetate and butyl acetate. Of these, methyl ethyl ketone, tetrahydrofuran, and cyclohexanone are preferable because they have a lower environmental impact than chlorobenzene, dichloromethane, toluene, and xylene. These solvents can be used alone or in combination.

  The charge transport layer 26 can be formed by dissolving or dispersing a mixture or copolymer mainly composed of a charge transport component and a binder component in an appropriate solvent, and applying and drying the mixture. As the coating method, a dipping method, a spray coating method, a ring coating method, a roll coater method, a gravure coating method, a nozzle coating method, a screen printing method, or the like is employed.

  Since the surface layer 28 is laminated on the upper layer of the charge transport layer 26, the thickness of the charge transport layer 26 in this configuration does not need to be designed to increase the thickness of the charge transport layer in consideration of wear in actual use. . The film thickness of the charge transport layer 26 is practically about 10 to 40 μm, more preferably about 15 to 30 μm for the purpose of ensuring the required sensitivity and charging ability.

  In addition, if necessary, low molecular weight compounds such as antioxidants, plasticizers, lubricants, ultraviolet absorbers and the like and leveling agents which are conventionally well-known can be added to the charge transport layer 26. These compounds can be used alone or as a mixture of two or more. When a low molecular weight compound and a leveling agent are used in combination, sensitivity deterioration often occurs. For this reason, the amount of these used is generally 0.1 to 20 phr, preferably 0.1 to 10 phr, and the amount of the leveling agent used is suitably about 0.001 to 0.1 phr.

  When the charge transport layer 26 contains a metal oxide filler, a dispersant, and an organic acid, those described above can be used.

[Protective layer]
After the protective layer 28 is coated with a paint containing a resin (monomer) component, a resin having a crosslinked structure is formed by a polycondensation reaction. Since the resin film has a crosslinked structure, it has the strongest wear resistance among the layers of the electrophotographic photoreceptor. In addition, since a cross-linked charge transporting structural unit is included, the charge transporting property is similar to that of the charge transporting layer.

(Roughening)
The surface of the electrophotographic photosensitive member may be formed with a surface shape that does not roughen the edge of the rubbing blade. For this reason, special roughening of the surface of the electrophotographic photosensitive member is required. As a concrete measure, an arbitrary surface shape is prepared by blending a mill base with one or more dispersants. As a side effect, electrostatic characteristics often deteriorate. However, this problem can be solved by adding the above organic acid separately from the dispersant. Dispersants that are commercially available from dispersant manufacturers such as Big Chemie, Enomoto Kasei, Kyoeisha Chemical, Takemoto Yushi, Kao, Ajinomoto Fine-Techno, Harima Kasei, etc. are used. Among these, a dispersant that does not dissolve in water has an advantageous effect on reducing the potential of the exposed area.

(Radical polymerizable material component)
In the present invention, when trimethylolpropane triacrylate is used on the surface of the electrophotographic photosensitive member, it is often advantageous to eliminate image blur. In addition, it is excellent in enhancing the abrasion resistance of the electrophotographic photoreceptor surface.

  The trifunctional or higher functional binder component may contain caprolactone-modified dipentaerythritol hexaacrylate or dipentaerythritol hexaacrylate. This often improves the wear resistance of the crosslinked film itself or increases the toughness.

  The trifunctional or higher functional radical polymerizable monomer having no charge transporting structure is preferably trimethylolpropane triacrylate, caprolactone-modified dipentaerythritol hexaacrylate, or dipentaerythritol hexaacrylate. These can be obtained from reagent manufacturers such as Tokyo Kasei Co., Ltd., Nippon Kayaku KAYARD DPCA series, DPHA series and the like.

  Moreover, in order to accelerate | stimulate hardening or to stabilize, you may add about 5-10 wt% with respect to the total solid which contains initiators, such as Ciba Specialty Chemicals Irgacure 184, in the coating material of a protective layer.

  Examples of the crosslinkable charge transport material include a chain polymerization compound having an acryloyloxy group and a styrene group, and a sequential polymerization compound having a hydroxyl group, an alkoxysilyl group and an isocyanate group, and includes a (meth) acryloyl having a charge transport structure. A compound having one or more oxy groups can be used. Alternatively, the composition may be combined with a monomer or oligomer having one or more (meth) acryloyloxy groups not including a charge transport structure. A protective layer can be formed by forming a protective layer by containing at least such a compound in the coating solution, and crosslinking and curing by applying energy by heat, light, or radiation such as an electron beam or γ-ray. Examples of the crosslinkable charge transporting material include charge transporting compounds represented by the following general formula 1.

(In General Formula 1, d, e and f are each an integer of 0 or 1, g and h are each an integer of 0 to 3. R ₁₃ is a hydrogen atom or a methyl group, and R ₁₄ and R ₁₅ are each Represents an alkyl group having 1 to 6 carbon atoms and may be different in a plurality of cases, Z represents a single bond, a methylene group, an ethylene group, or a divalent group represented by the following formulas (2) to (4). Represents.)

  As specific compounds, the structural formulas shown below: 1 to No. 26 are listed.

  The dispersion solvent used in preparing the protective layer coating is preferably one that sufficiently dissolves the monomer. In addition to the ethers, aromatics, halogens, esters described above, cellosolves such as ethoxyethanol, 1- Mention may be made of propylene glycols such as methoxy-2-propanol. Of these, methyl ethyl ketone, tetrahydrofuran, cyclohexanone, and 1-methoxy-2-propanol are preferable because they have a lower environmental impact than chlorobenzene, dichloromethane, toluene, and xylene. These solvents can be used alone or in combination.

  Examples of the coating for the protective layer paint include dipping method, spray coating method, ring coating method, roll coater method, gravure coating method, nozzle coating method, and screen printing method. In many cases, since the pot life of the paint is not long, a means capable of coating the required amount with a small amount of paint is advantageous in terms of environmental consideration and cost. Of these, the spray coating method and the ring coating method are preferred. Furthermore, an ink jet method may be used to give the special shape of the present invention.

When forming the protective layer, a UV irradiation light source such as a high-pressure mercury lamp or a metal halide lamp having a light emission wavelength mainly in ultraviolet light can be used. In addition, a visible light source can be selected in accordance with the absorption wavelength of the radical polymerizable substance or the photopolymerization initiator. Irradiation light amount is 50 mW / cm ² or more, preferably 1000 mW / cm ² or less, it takes time for the curing reaction is less than 50 mW / cm ^2. If it is higher than 1000 mW / cm ^2, the progress of the reaction becomes nonuniform, and local wrinkles are generated on the surface of the cross-linked charge transport layer, or many unreacted residues and reaction termination ends are generated. In addition, internal stress increases due to rapid crosslinking, causing cracks and film peeling.

  If necessary, conventionally known low-molecular compounds and leveling agents such as antioxidants, plasticizers, lubricants, ultraviolet absorbers and the like, and high-molecular compounds described in the charge transport layer can be added to the protective layer. These compounds can be used alone or as a mixture of two or more. When a low molecular weight compound and a leveling agent are used in combination, sensitivity deterioration often occurs. For this reason, the amount used is generally 0.1 to 20 wt%, preferably 0.1 to 10 wt%, and the leveling agent used is about 0.1 to 5 wt% in the total solid content of the paint.

  The thickness of the protective layer is suitably about 2 to 10 μm. More preferably, it is 3 μm to 5 μm. The lower limit is an advantageous condition for obtaining a homogeneous film without a coating film defect, and the upper limit is set from electrostatic characteristics such as charging stability and light attenuation sensitivity and film quality homogeneity.

(Image forming device)
Hereinafter, another configuration example of the image forming apparatus will be described with reference to the drawings. The image forming apparatus according to the present invention is provided with means for inputting a lubricant described later to the surface of the electrophotographic photosensitive member. This point will be described later.

  FIG. 4 is a schematic view showing an example of an image forming apparatus according to the present invention, and modifications as will be described later are also included in the present invention.

  In FIG. 4, an electrophotographic photosensitive member 11 is an electrophotographic photosensitive member in which a surface layer is laminated. The electrophotographic photosensitive member 11 has a drum shape, but may be a sheet shape or an endless belt shape.

  The charging device 12 is a means for uniformly charging the surface of the electrophotographic photosensitive member 11, and known means such as a corotron, a scorotron, a solid state charger (solid state charger), and a charging roller are used. The charging device 12 is preferably used in contact with or close to the electrophotographic photosensitive member 11 from the viewpoint of reducing power consumption. In particular, in order to prevent the charging device 12 from being contaminated, a charging mechanism disposed in the vicinity of the electrophotographic photosensitive member 11 having an appropriate clearance between the electrophotographic photosensitive member 11 and the surface of the charging device 12 is desirable. In general, the charger 16 can be used as the transfer device 16, but a combination of a transfer charger and a separation charger is effective.

  Light sources used in the exposure apparatus 13 and other forms of static eliminators (1A in FIG. 5) include fluorescent lamps, tungsten lamps, halogen lamps, mercury lamps, sodium lamps, light emitting diodes (LEDs), and semiconductor lasers (LDs). , And general luminescent materials such as electroluminescence (EL). Various types of filters such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter can be used to irradiate only light in a desired wavelength range.

  The toner 15 developed on the electrophotographic photosensitive member 11 by the developing device 14 is transferred to a printing medium 18 such as printing paper or an OHP slide, but not all is transferred and remains on the electrophotographic photosensitive member. Toner is also generated. Such toner is removed from the electrophotographic photosensitive member 11 by the cleaning device 17. The cleaning device 17 can be a rubber cleaning blade, a brush such as a fur brush, a mag fur brush, or the like.

  When the electrophotographic photosensitive member 11 is positively (negatively) charged by the charging device 12 and image exposure is performed by the exposure device 13, a positive (negative) electrostatic latent image is formed on the surface of the electrophotographic photosensitive member 11. . If this is developed with negative (positive) polarity toner (electrodetection fine particles) by the developing device 14, a positive image is obtained, and if developed with positive (negative) toner, a negative image is obtained. A known method is applied to the developing device 14, and a known method is also used for the static eliminator. The toner image developed on the print medium 18 is conveyed to a fixing device 19 from a position where the electrophotographic photosensitive member 11 and the transfer device 16 are opposed to each other, and is fixed on the print medium 18 by the fixing device 19.

  The lubricant 3A, the application brush 3B for applying the lubricant, and the application blade 3C are disposed downstream of the cleaning device 17 and upstream of the charging device 12 in the rotation direction of the electrophotographic photosensitive member 11. These arrangement relationships are the same in other embodiments described below.

  FIG. 5 shows another example of the image forming apparatus. In FIG. 5, an electrophotographic photoreceptor 11 is an electrophotographic photoreceptor 11 on which surface layers are laminated. The electrophotographic photosensitive member 11 has a belt shape, but may be a drum shape, a sheet shape, or an endless belt shape. The electrophotographic photosensitive member 11 is driven by the driving unit 1C, and is charged by the charging device 12, image exposure by the exposure device 13, development (not shown), transfer by the transfer device 16, exposure before cleaning by the exposure device 1B before cleaning, and cleaning. Cleaning by the device 17 and static elimination by the static elimination device 1A are repeatedly performed. The lubricant 3 </ b> A, the application brush 3 </ b> B for applying the lubricant, and the application blade 3 </ b> C are arranged between the cleaning device 17 and the charging device 12 as shown in the drawing with respect to the moving direction of the electrophotographic photoreceptor 11.

  In FIG. 5, light irradiation for pre-cleaning exposure is performed from the support side of the electrophotographic photoreceptor 11 (in this case, the support is translucent).

  The above-described electrophotographic process is an example. For example, in FIG. 5, the pre-cleaning exposure is performed from the support side, but this may be performed from the photosensitive layer side, or image exposure and neutralization light irradiation may be performed. You may carry out from the support body side. On the other hand, image exposure, pre-cleaning exposure, and static elimination exposure are illustrated in the light irradiation process. In addition, a pre-transfer pre-exposure, image exposure pre-exposure, and other known light irradiation processes are provided in the electrophotographic photoreceptor. Light irradiation can also be performed.

  The image forming means as described above may be fixedly incorporated in a copying machine, a facsimile machine, or a printer, but may be incorporated in these apparatuses in the form of a process cartridge. There are many types of process cartridges, but a typical example is shown in FIG. The electrophotographic photosensitive member 11 has a drum shape, but may be a sheet shape or an endless belt shape.

  FIG. 7 shows another example of the image forming apparatus. In this image forming apparatus, a developing device 14Bk, 14C for each of the charging device 12, the exposure device 13, black (Bk), cyan (C), magenta (M), and yellow (Y) around the electrophotographic photosensitive member 11 is provided. , 14M, 14Y, an intermediate transfer belt 1F as an intermediate transfer member, and a cleaning device 17 are arranged in this order.

  Note that the subscripts (Bk, C, M, Y) shown in FIG. 7 correspond to the color of the toner described above, and are omitted as appropriate. The electrophotographic photosensitive member 11 is an electrophotographic photosensitive member in which surface layers are laminated. Each color developing device 14Bk, 14C, 14M, 14Y can be controlled independently, and only the color developing device for image formation is driven. The toner image formed on the electrophotographic photosensitive member 11 is transferred onto the intermediate transfer belt 1F by the first transfer device 1D disposed inside the intermediate transfer belt 1F.

  The first transfer device 1D is disposed so as to be able to come into contact with and separate from the electrophotographic photosensitive member 11, and the intermediate transfer belt 1F is brought into contact with the electrophotographic photosensitive member 11 only during the transfer operation. Each color image is sequentially formed, and the toner images superimposed on the intermediate transfer belt 1F are collectively transferred to the print medium 18 by the second transfer device 1E, and then fixed by the fixing device 19 to form an image. . The second transfer device 1E is also arranged so as to be able to contact and separate from the intermediate transfer belt 1F, and contacts the intermediate transfer belt 1F only during the transfer operation.

  In the transfer drum type image forming apparatus, since the toner images of the respective colors are sequentially transferred to the print medium electrostatically attracted to the transfer drum, there is a limitation on the print medium that printing on thick paper is not possible, as shown in FIG. Such an intermediate transfer type image forming apparatus has an advantage that the toner images of the respective colors are superimposed on the intermediate transfer body 1F, and thus are not limited by the print media. Such an intermediate transfer method can be applied not only to the apparatus shown in FIG. 7, but also to the image forming apparatus as shown in FIGS. 4, 5, and 6 and FIGS.

  The lubricant 3 </ b> A, the application brush 3 </ b> B for applying the lubricant, and the application blade 3 </ b> C are arranged between the cleaning device 17 and the charging device 12 as shown in the figure with respect to the rotation direction of the electrophotographic photoreceptor 11.

  FIG. 8 shows another example of the image forming apparatus. This image forming apparatus is of a type that uses four colors of yellow (Y), magenta (M), cyan (C), and black (Bk) as toner, and an image forming unit is provided for each color. In addition, electrophotographic photoreceptors 11Y, 11M, 11C, and 11Bk for each color are provided. The electrophotographic photosensitive member 11 used in this image forming apparatus is an electrophotographic photosensitive member in which surface layers are laminated. Around each electrophotographic photosensitive member 11Y, 11M, 11C, 11Bk, charging devices 12Y, 12M, 12C, 12Bk, exposure devices 13Y, 13M, 13C, 13Bk, developing devices 14Y, 14M, 14C, 14Bk, cleaning devices 17Y, 17M, 17C, 17Bk, etc. are arranged.

  In addition, a transfer transfer belt 1G as a transfer material carrier that comes in contact with and separates from the transfer positions of the electrophotographic photosensitive members 11Y, 11M, 11C, and 11Bk arranged on a straight line is stretched by a driving unit 1C. . Transfer devices 16Y, 16M, 16C, and 16Bk are disposed at transfer positions facing the electrophotographic photoreceptors 11Y, 11M, 11C, and 11Bk with the conveyance transfer belt 1G interposed therebetween.

  The tandem type image forming apparatus shown in FIG. 8 has electrophotographic photoreceptors 11Y, 11M, 11C, and 11Bk for each color, and sequentially transfers the toner images of the respective colors onto the print medium 18 held on the transport transfer belt 1G. Compared to a full-color image forming apparatus having only one electrophotographic photosensitive member, it is possible to output a full-color image much faster. The toner image developed on the print medium 18 as a transfer material is conveyed to a fixing device 19 from a position where the electrophotographic photoreceptor 11Bk and the transfer device 16Bk are opposed to each other, and is fixed to the print medium 18 by the fixing device 19.

  Further, for example, the configuration in the embodiment as shown in FIG. 9 may be used. That is, instead of the direct transfer method using the transfer transfer belt 1G shown in FIG. 8, the intermediate transfer belt 1F can be used as shown in FIG.

  In the example shown in FIG. 9, the electrophotographic photoreceptors 11Y, 11M, 11C, and 11Bk are provided for each color, and toner images of the respective colors formed on these are placed on an intermediate transfer belt 1F that is driven and stretched by a roller 1C. Next transfer means 1D sequentially transfers and laminates to form a full color image.

  Next, the intermediate transfer belt 1F is further driven, and the full-color image carried on the intermediate transfer belt 1F is conveyed to a position where the secondary transfer unit 1E and the roller 1C arranged opposite to the secondary transfer unit 1E are opposed to each other. Then, the image is secondarily transferred to the transfer material 18 by the secondary transfer unit 1E, and a desired image is formed on the transfer material.

(Lubricant supply means)
As shown in FIG. 10, as a lubricant supply means for supplying the lubricant 3 </ b> A to the surface of the electrophotographic photosensitive member 11, the lubricant application device 3 is provided for all the image forming apparatuses described above. The lubricant application device 3 includes a fur brush 3B as an application member, a lubricant 3A, a pressure spring 3D for pressing the lubricant in the fur brush direction, and an application for applying or regulating the lubricant 3A. It has a blade 3C.

  The lubricant 3A is a lubricant molded into a bar shape. The fur brush 3B has a brush tip in contact with the surface of the electrophotographic photosensitive member. By rotating about the shaft, the lubricant 3A is once drawn into the brush, and the fur brush 3B is moved to the contact position with the surface of the electrophotographic photosensitive member 11 on the brush. And is applied to the surface of the electrophotographic photoreceptor 11.

  Further, even if the lubricant 3A is scraped by the fur brush 3B over time, the lubricant 3A is pressed against the fur brush 3B with a predetermined pressure by the pressurizing spring 3D so that the lubricant 3A does not come into contact with the fur brush 3B. Has been. As a result, even a small amount of the lubricant 3A is always uniformly drawn into the fur brush 3B.

  Further, a lubricant supply device for coating the surface of the electrophotographic photoreceptor 11 with the lubricant 3A may be provided. This means includes means for pressing a plate such as a cleaning blade against the electrophotographic photosensitive member 11 by a trailing method or a counter method.

  Lubricant 3A is, for example, fatty acid metal salts such as lead oleate, zinc oleate, copper oleate, zinc stearate, cobalt stearate, iron stearate, copper stearate, zinc palmitate, copper palmitate, zinc linolenate, etc. Fluorine series such as polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polytrifluorochloroethylene, dichlorodifluoroethylene, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-oxafluoropropylene copolymer Resin. In particular, a material having a lamellar structure has high circulation efficiency, and zinc stearate is advantageous in terms of cost.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

Example 1
By coating and drying the undercoat layer paint, charge generation layer paint, and charge transport layer paint in the following composition on an aluminum drum having a thickness of 1 mm, a length of 352 mm, and an outer diameter of 40 mm, A pulling layer, a 0.2 μm charge generation layer, and a 22.5 μm charge transport layer were formed.

On top of that, a protective layer coating was applied by spraying. Spray coating was performed using Olympus PC-WIDE308 as a spray gun at a position where the distance between the nozzle tip of the spray gun and the electrophotographic photosensitive member was 50 mm with an atomizing pressure of 2.5 kgf / cm ² . The discharge amount was 3cc-4cc. After coating the protective layer, UV curing was performed while rotating the drum at a distance of 120 mm from the drum and the UV curing lamp. The illuminance of the UV curing lamp at this position was 550 mW / cm ² (UV integrated light meter UIT-150, measured value by Ushio Inc.). The drum rotation speed was 25 rpm. When performing UV curing, UV curing was performed for 4 minutes continuously by circulating water at 30 ° C. in an aluminum drum. Then, it heat-dried at 130 degreeC for 30 minutes.

  As a result, an electrophotographic photosensitive member of Example 1 in which a protective layer of 3.5 μm was formed was obtained. The protective layer coating material was prepared by pouring a vehicle having a solid content concentration of 16 parts by mass into a mill base having a solid content concentration of 10% by weight comprising a metal oxide, a dispersant, and an organic solvent. The finally obtained surface layer paint has the composition described in the section of the following surface layer paint.

  Mill base is a UM sample bottle for 50 ml, charged with 100 g of φ2 mm YTZ ball (made by Nikkato Co., Ltd.) as a dispersion medium, a metal oxide with a solid content concentration of 10 parts by mass, one dispersant and tetrahydrofuran. For 2 hours. The dispersion strength was 1600 rpm. Three mill bases were prepared for each of the three dispersants. When preparing the protective layer coating material, three kinds of mill bases were mixed and immediately diluted with 16 parts by mass of a vehicle to prepare a protective layer coating material having a solid content concentration of 15 weight percent. Next, maleic acid, an organic acid, was added.

[Coating for undercoat layer]
-Alkyd resin solution 12 parts by mass (Beckolite M6401-50, manufactured by Dainippon Ink & Chemicals, Inc.)
Melamine resin solution 8.0 parts by mass (Super Becamine G-821-60, manufactured by Dainippon Ink & Chemicals, Inc.)
・ Titanium oxide (CR-EL manufactured by Ishihara Sangyo Co., Ltd.) 40 parts by mass ・ Methyl ethyl ketone 200 parts by mass

[Charge generation coating]
-5.0 parts by mass of bisazo pigment (made by Ricoh) having the following structure

・ Polyvinyl butyral (XYHL, manufactured by UCC) 1.0 part by mass ・ Cyclohexanone 200 part by mass ・ Methyl ethyl ketone 80 part by mass

[Charge transport layer coating]
-Z-type polycarbonate (Panlite TS-2050, manufactured by Teijin Chemicals Ltd.) 10 parts by mass-Charge transport material having the following structure 7.0 parts by mass

Tetrahydrofuran 100 parts by mass 1% silicone oil (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.)
Tetrahydrofuran solution 1 part by mass

[Protective layer paint]
・ 43 parts by mass of a cross-linked charge transport material having the following structure

・ 21 parts by mass of trimethylolpropane triacrylate (KAYARAD TMPTA, manufactured by Nippon Kayaku Co., Ltd.)
-21 parts by mass of caprolactone-modified dipentaerythritol hexaacrylate (KAYARAD DPCA-120, manufactured by Nippon Kayaku Co., Ltd.)
-Mixture of acrylic group-containing polyester-modified polydimethylsiloxane and propoxy-modified-2-neopentylglycol diacrylate 0.1 parts by mass (BYK-UV3570, manufactured by BYK Chemie)
・ 4 parts by mass of 1-hydroxycyclohexyl phenyl ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
・ Α-Alumina (Sumicorundum AA-03, manufactured by Sumitomo Chemical Co., Ltd.) 10 parts by mass ・ Phosphate-based wetting and dispersing agent (Superdyne V201, Takemoto Yushi Co., Ltd.) 0.33 parts by mass ・ Phosphate-based wetting and dispersing agent (HIPLAAD ED151, Enomoto Kasei Co., Ltd.) 0.33 parts by mass, acrylic copolymer dispersant (Floren WK-13E, Kyoeisha Chemical Co., Ltd.) 0.33 parts by mass, maleic acid (acid value; 1.0 gKOH / g, Tokyo Chemical Industry Co., Ltd.) 0 .5 parts by mass / tetrahydrofuran 566 parts by mass Of the dispersant used here, only WK-13E was dissolved in water. The remaining two dispersants do not dissolve in water.

(Comparative Example 1)
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the maleic acid coating material for the protective layer was removed from the electrophotographic photosensitive member of Example 1. The film thickness of the protective layer was 3.5 μm.

(Comparative Example 2)
For the electrophotographic photosensitive member of Example 1, the maleic acid of the protective layer coating was changed to 1,2,3,4-butanetetracarboxylic acid (acid value: 0.7 g KOH / g, Tokyo Chemical Industry Co., Ltd.). An electrophotographic photosensitive member was produced in the same manner as Example 1 except for the above. The film thickness of the protective layer was 3.5 μm.

(Comparative Example 3)
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the maleic acid of the protective layer coating material was changed to sulfuric acid (special grade, Kanto Chemical Co., Inc.) for the electrophotographic photosensitive member of Example 1. The film thickness of the protective layer was 3.5 μm.

(Example 2)
For the electrophotographic photoreceptor of Example 1, the same procedure as in Example 1 was conducted except that the maleic acid in the protective layer coating material was changed to citric acid (acid value: 0.8 g KOH / g, Tokyo Chemical Industry Co., Ltd.). A photographic photoreceptor was prepared. The film thickness of the protective layer was 3.5 μm.

(Example 3)
An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the amount of citric acid in the protective layer coating material of Example 2 was changed from 0.5 parts by mass to 1.0 part by mass. The protective layer thickness was 3.5 μm.

Example 4
The amount of maleic acid in the protective layer coating material of Example 1 was changed from 0.5 parts by mass to 1.0 part by mass, and the discharge amount was set to 2.0 cc to form a protective layer having a thickness of 2 μm. An electrophotographic photosensitive member was produced in the same manner as Example 1 except for the above.

(Example 5)
An electrophotographic photosensitive member was produced in the same manner as in Example 4 except that a protective layer having a thickness of 3.5 μm was formed by changing the discharge amount of the protective layer coating material of Example 4 to 3.5 cc.

(Example 6)
An electrophotographic photosensitive member was produced in the same manner as in Example 4 except that a protective layer having a thickness of 5 μm was formed by changing the discharge amount of the protective layer coating material of Example 4 to 5 cc.

(Example 7)
An electrophotographic photosensitive member was produced in the same manner as in Example 3 except that a protective layer having a thickness of 2 μm was formed by changing the discharge amount of the protective layer coating material of Example 3 to 2 cc.

(Example 8)
An electrophotographic photosensitive member was produced in the same manner as in Example 3 except that a protective layer having a thickness of 5 μm was formed by changing the discharge amount of the protective layer coating material of Example 3 to 5 cc.

(Examples 9 to 13)
In the production of the electrophotographic photoreceptor of Example 3, the electrophotographic photoreceptors of Examples 9 to 13 were produced in the same manner as in Example 3 except that the dispersant for the protective layer coating material was changed as shown in Table 1. did.

In addition, the coating material for surface layers of Examples 9 to 13 uses one or two kinds of dispersants. At this time, a metal oxide mill base was prepared in the same manner as in Example 3 for each type of dispersant. When preparing the surface layer paint, a maximum of two mill bases were mixed and immediately diluted with 16 parts by weight of a vehicle to prepare a 15% by weight surface layer paint. As the dispersant, HIPLAAD ED-151 (phosphate wet dispersant) manufactured by Enomoto Kasei Co., Ltd., Floren WK-13E manufactured by Kyoeisha Chemical Co., Ltd., and Superdyne V201 (phosphate wet dispersant) manufactured by Takemoto Yushi Co., Ltd. were used. . The protective layer was formed to a thickness of 3.5 μm.

(Example 14)
In the preparation of the electrophotographic photosensitive member of Example 3, in the preparation of the protective layer coating, the procedure of adding 1.0 part by mass of citric acid, which is an organic acid, was not added at the end of the coating preparation procedure, but was dispersed together with the filler. An electrophotographic photosensitive member was produced in the same manner as in Example 3 except that.

  After the photosensitive drums of Examples 1 to 14 and Comparative Examples 1 to 3 manufactured as described above were used for mounting, they were placed in the cyan developing station of the image forming apparatus (image MP C4500, manufactured by Ricoh). Equipped with a copy density of 100,000 sheets of paper on the condition that a halftone pattern and a blank paper pattern are printed alternately and continuously 5 sheets each with a pixel density of 600 dpi × 600 dpi and in an 8 × 8 matrix. (My Paper A4, manufactured by NBS Ricoh Co., Ltd.). As toner and developer, genuine cyan toner of imgio MP C4500 was used. The toner is a polymerized toner. The image forming apparatus has the same layout as in FIG.

  In the test, the following lubricant and lubricant application device were used. The consumption rate of the lubricant was set to a rate at which the solid lubricant decreased in weight at a rate of 120 mg / km with respect to the travel distance of the photosensitive drum.

  The photoconductor unit was a genuine product. As the voltage applied to the charging roller, a peak-to-peak voltage of 2.1 kV and a frequency of 1.7 kHz were selected as AC components. For the DC component, a bias was set so that the charged potential of the photosensitive member at the start of the test was −700 V, and the test was performed under this charging condition until the end of the test. The developing bias was −580V. In this apparatus, no static elimination means is provided.

After the test, the color test chart was copied and printed on PPC paper TYPE-6200A3. The test environment was 25 ° C./55% RH. In addition, using the same image forming apparatus, all solid patterns were written at the start of the test under the conditions that the linear velocity of the photosensitive drum was 205 mm / s, the writing light amount was 4.0 μJ / cm ² , and the charging potential was −800 V. The exposure part potential at the time was measured. The results are shown in Table 2.

  The lubricant used in the test was prepared as follows. Zinc stearate (manufactured by NOF Corporation, zinc stearate GF200) was placed in a glass container with a lid and melted with stirring by a hot stirrer whose temperature was controlled from 160 ° C to 250 ° C. The lubricant, which has been stirred and melted, is poured so that an aluminum mold having an inner dimension of 12 mm × 8 mm × 350 mm heated in advance to 150 ° C., and left to cool to 40 ° C. on a wooden table. Then, a weight was put on it to prevent warping and it was cooled to room temperature. After cooling, both ends in the longitudinal direction were cut and the bottom surface was cut to produce a 6 mm × 6 mm × 322 mm prismatic lubricant bar. Double-sided tape was attached to the bottom surface of the lubricant bar and fixed to the metal support.

  In addition, the lubricant application apparatus was attached to the image forming apparatus in combination with means for supplying the lubricant to the electrophotographic photosensitive member and means for coating the lubricant supplied to the electrophotographic photosensitive member. Lubricant supply means pressurizes solid zinc stearate shaped into a prismatic shape so as to be held by the support to the application brush with a spring spring having a spring constant that gives a predetermined consumption amount. A device for scraping zinc stearate by rotating to provide shaving powder on the electrophotographic photosensitive member was attached. An appropriate pressure spring was selected from the relationship between the spring constant and the amount of lubricant consumed.

  Here, a tension spring having a spring constant of 0.039 N / mm was used as a condition for the lubricant consumption rate to be 125 mg / km. A movable fin supported at one point was attached to both sides of the support, and a tension spring was turned around to adjust the contact pressure between the application brush and the lubricant by the tensile stress of the spring. The applicator brush used was a genuine product with a fur brush attached to a metal shaft. The coating brush was rotated in the counter direction with respect to the electrophotographic photosensitive member surface moving direction. The coating blade used was a polyurethane rubber (Shore A hardness: 84, rebound resilience: 52%, thickness: 1.3 mm) supported in a direction in which the electrophotographic photosensitive member was in contact with the electrophotographic photosensitive member at a blade holder of a steel plate at 19 ° .

  For image evaluation, test chart S-5Y (manufactured by Ricoh) was copied and printed, and the gradation of gray scale was evaluated.

5: All gray scales having an image density of 10% to 80% are clearly graduated.
4; A gray scale having an image density of 10% to 80% is sufficiently identified.
3: There is no problem in gray scale gradation with an image density of 10% to 80%.
2: The gradation of the low image density is slightly unclear, but acceptable for practical use.
1; A patch image having an image density of 10% is not sufficiently developed.

  The electrophotographic photosensitive member of Example 1 in which a surface layer containing a metal oxide filler and a dispersant is laminated contains the maleic acid having an acid value of 1.0 gKOH / g with respect to the same photosensitive member of Comparative Example 1. Have. Compared with Comparative Example 1, it is understood that the exposure portion potential is remarkably improved.

  Comparative Example 2 is characterized in that 1,2,3,4-butanetetracarboxylic acid having an acid value of 0.7 gKOH / g is contained in the surface layer as compared with Comparative Example 1. However, the increase in the exposed portion potential is not suppressed. Further, Comparative Example 3 containing sulfuric acid in the surface layer does not show the effect of reducing the exposed portion potential.

  Regarding Example 1, Comparative Example 2, and Example 2, when the relationship between the acid value of the organic acid contained in the surface layer and the exposed part potential is observed, a characteristic that the exposed part potential decreases according to the acid value is observed. From this tendency, it is judged that the acid value of the organic acid added to the surface layer is advantageously from 0.8 gKOH / g to 1.0 gKOH / g.

  The surface layer of Example 3 contains citric acid as in Example 2, but Example 3 has a high citric acid content. The effect of reducing the exposed portion potential of Example 3 having a high citric acid content is stronger than that of Example 2. It is understood that citric acid has a very advantageous effect on the reduction of the exposed area potential.

  In Examples 4 to 6, maleic acid is contained in the surface layer of the electrophotographic photosensitive member at an equal ratio, and the film thickness of the surface layer is different. There is a tendency that the potential of the exposed portion increases according to the film thickness. In Example 2, Example 7, and Example 8, the surface layer of the electrophotographic photosensitive member contains citric acid at an equal ratio, and the film thickness of the surface layer is different. Similar to the combinations of Examples 4 to 6, there is a tendency that the potential of the exposed portion increases according to the film thickness. However, the combination of Example 2 and Example 7 and Example 8 containing citric acid has a lower exposure portion potential. From this, it is judged that citric acid is extremely advantageous for reducing the potential of the exposed area.

  In addition, the combination of Example 2 and Examples 9 to 13 is one in which citric acid is contained in the surface layer of the electrophotographic photosensitive member in an equal proportion. Three types of dispersants used for these surface layers The mixing ratio is different. The higher the ratio of the dispersant that does not dissolve in water, the lower the exposed area potential. From this, it is understood that the use of a dispersant that does not dissolve in water under conditions where an organic acid is used in combination is advantageous in reducing the potential of the exposed area.

  The surface layer of the electrophotographic photoreceptor of Example 14 contains citric acid in the same proportion as in Example 3, but the procedure for adding citric acid in the preparation of the paint is different. In these photoreceptors, the effect of reducing the potential of the exposed area is expressed equally by the addition of citric acid. The difference in the image quality of the copied image can be attributed to the difference in the shape of the photoreceptor surface. Here, it is advantageous to add citric acid last in the preparation of the paint.

DESCRIPTION OF SYMBOLS 1A Static elimination apparatus 1B Exposure apparatus before cleaning 1C Drive means 1D 1st transfer apparatus 1E 2nd transfer apparatus 1F Intermediate transfer body 1G Conveyance transfer belt 3 Lubricant application apparatus 3A Lubricant 3B Application brush 3C Application blade 3D Pressure spring 11 , 11Bk, 11C, 11M, 11Y Electrophotographic photosensitive member 12, 12Y, 12M, 12C, 12Bk Charging device 13, 13Y, 13M, 13C, 13Bk Exposure device 14, 14Bk, 14C, 14M, 14Y Developing device 15 Toner 16, 16Y , 16M, 16C, 16Bk Transfer device 17, 17Y, 17M, 17C, 17Bk Cleaning device 18 Print media 19 Fixing device 21 Conductive support 24 Subbing layer 25 Charge generation layer 26 Charge transport layer 28 Surface layer

JP 2000-66424 A JP 2000-171990 A JP-A 63-261268 JP 2003-91083 A JP 2007-34274 A

Claims (5)

In the electrophotographic photosensitive member in which a plurality of layers are formed on a support, and a surface layer containing a metal oxide filler and a dispersant is formed as a surface layer,
The electrophotographic photoreceptor, wherein the surface layer contains an organic acid having an acid value of 0.8 gKOH / g or more and 1.0 gKOH / g or less, and the organic acid is citric acid or maleic acid . The electrophotographic photosensitive member according to claim 1, wherein the dispersant contained in the surface layer is a dispersant that does not dissolve in water. A method for producing an electrophotographic photosensitive member according to claim 1 or 2 ,
A metal oxide filler dispersion is prepared by dispersing a metal oxide filler in a solution not containing an organic acid having an acid value of 0.8 gKOH / g or more and 1.0 gKOH / g or less, and then an acid value of 0.8 gKOH / g. A method for producing an electrophotographic photosensitive member, wherein the surface layer is formed using a coating material for a surface layer to which an organic acid of g to 1.0 g KOH / g is added. A process cartridge for an image forming apparatus comprising the electrophotographic photosensitive member according to claim 1 . An image forming apparatus comprising the electrophotographic photosensitive member according to claim 1 .