JP6417816B2 - Image forming apparatus, process cartridge, and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus, a process cartridge, and an image forming method.

  In recent years, from the viewpoints of saving office space and expanding business opportunities, image forming apparatuses are desired to be faster, smaller, more colored, particularly higher in image quality, and easier to maintain. These are related to improvement of electrical characteristics and durability of the electrophotographic photosensitive member, and are positioned as problems to be solved by improving the electrophotographic photosensitive member.

  From the viewpoint of improving ease of maintenance, there is a reduction in the replacement frequency of the electrophotographic photosensitive member. This is to reduce image defects derived from the electrophotographic photosensitive member as much as possible over a long period of time, and this is nothing but a longer life of the electrophotographic photosensitive member. It is also related to high quality output images over a long period of time. In order to solve the above-mentioned problems in the electrophotographic photosensitive member, attempts have been made to reduce image defects derived from the electrophotographic photosensitive member during long-term use, and many developments relating to extending the life of the electrophotographic photosensitive member have been reported. ing. In order to achieve a long life of the electrophotographic photosensitive member, it is necessary to improve the wear durability of the electrophotographic photosensitive member against various hazards received by the electrophotographic photosensitive member during image formation and the surface maintenance of the electrophotographic photosensitive member. is there.

In addition, from the viewpoint of miniaturization as described above, a charging method using proximity discharge tends to be frequently used as a charging process of recent image forming apparatuses. This is a system in which a charging member is brought into contact with the surface of an object to be charged or a charging member is arranged in the vicinity without contact so as to generate a proximity discharge and charge the surface of the object to be charged. If this method is used, a large-scale charging device is not required, and thus it is very effective for downsizing the device.
However, it is known that the charging method using proximity discharge causes chemical changes such as decomposition and oxidation of the surface of the object to be charged because the discharge concentrates near the surface of the object to be charged (Non-Patent Documents 1 and 2). In particular, this tendency is significant when an AC voltage is superimposed on a DC voltage and applied to a charging member, and these deteriorations are known to have an adverse effect on the wear durability and surface maintenance of the electrophotographic photosensitive member. .

  Many technical means for improving wear durability against such chemical hazards have been reported. For example, Patent Documents 1 to 6 describe techniques for providing a crosslinkable protective layer on the outermost surface of an electrophotographic photosensitive member. If these techniques are used, chemical hazards such as discharge hazards and mechanical hazards such as cleaning blades that are in contact with the contact member with the electrophotographic photosensitive member and the mechanical hazard represented by the electrophotographic photosensitive member It is effective for.

On the other hand, there are not many reports on the improvement of the surface maintainability of the electrophotographic photosensitive member. Surface maintainability refers to the fact that toner components (toner particles, toner-added fine particles, etc.) adhere to the surface of an electrophotographic photosensitive member when an image is repeatedly output using an image forming apparatus. In order not to cause the phenomenon that the charging function, the light attenuation function, the latent image maintaining function, etc., which should be present, are impaired, it refers to maintaining a clean surface without adhesion of foreign matters such as toner to the surface of the electrophotographic photosensitive member. As the technical means for maintaining the surface of the electrophotographic photosensitive member, for example, it is presumed from the same literature that the technique of providing the above-mentioned crosslinkable protective layer exhibits the same function.
However, if this technology is used, it is considered that high surface maintenance is exhibited. However, since the constitution layer of the electrophotographic photosensitive member is increased by one, the electrophotographic photosensitive member itself is expensive, so that a high-end image is obtained. There is a problem that application is limited to the forming apparatus.

In addition, as a means for improving the surface maintainability of the electrophotographic photosensitive member by means other than the crosslinkable protective layer, there is a technique in which an electrophotographic photosensitive member provided with arbitrary irregularities on the surface of the electrophotographic photosensitive member and a blade cleaning method are used together. It is reported in patent documents 7 to 10. By using these techniques, it is considered that the toner cleaning property is improved and the surface contamination property of the electrophotographic photosensitive member is improved accordingly.
However, it is known that the surface of the electrophotographic photosensitive member is in contact with various rubbing members inside the image forming apparatus, and the surface gradually wears with each image output. Therefore, there is a problem that it is difficult to maintain any surface irregularities formed in the initial stage and the function does not continue.

Patent Documents 11 to 15 disclose a technique in which a layer constituting the outermost surface of the electrophotographic photosensitive member contains a lubricant made of an organic material such as PTFE (polytetrafluoroethylene). By using this technique, the toner cleaning property is improved, and it is considered that the surface contamination of the electrophotographic photosensitive member is improved as in the above technique.
However, surface degradation of the electrophotographic photosensitive member due to proximity discharge, especially when using a method in which an AC voltage is superimposed on a DC voltage and applied to a charging member, the organic lubricant itself also deteriorates due to oxidation, decomposition, etc. There is a problem that it is difficult to maintain the lubricity of the organic lubricant.

  As described above, there are reports on the surface maintenance of the electrophotographic photosensitive member, but there are still many problems to satisfy the quality. In addition, there are few reports on versatile technologies, such as having a cost handicap, in the technology that shows high maintainability, and there is a strong demand for technological development that shows high effects on the surface maintenance of electrophotographic photoreceptors. This is the current situation.

  The present invention has been made in view of the above-mentioned problems of the prior art, and can maintain a clean state without surface contamination such as toner adhesion to the surface of the electrophotographic photosensitive member. An object of the present invention is to provide an image forming apparatus capable of maintaining a charging function, a light attenuation function, and a latent image maintenance for a long period of time and maintaining an excellent image quality.

In order to solve the above problems, an image forming apparatus of the present invention forms at least an electrophotographic photosensitive member, a charging unit for charging the surface of the electrophotographic photosensitive member, and an electrostatic latent image on the electrophotographic photosensitive member. A latent image forming unit; a developing unit that attaches a developer to the electrostatic latent image to form a visible image; a transfer unit that transfers the visible image to a recording medium; and a surface of the electrophotographic photosensitive member. A cleaning means for removing the adhered developer,
The electrophotographic photoreceptor contains at least a polycarbonate resin or a polyarylate resin in the outermost layer in the thickness direction, and the discharge frequency of the alternating current component of the charging means is 7.5 times the linear velocity of the electrophotographic photoreceptor. Then, before and after applying a discharge charge of 100 μC / mm ^{2 to} the electrophotographic photosensitive member using the charging means, the average adhesive force fluctuation between the surface of the electrophotographic photosensitive member and the probe of the silicon cantilever is 0 nN. The cleaning means is composed of a blade member having a rubber material, and the surface of the electrophotographic photosensitive member is cleaned by bringing the leading edge portion of the blade member into contact with the electrophotographic photosensitive member. Yes, the vicinity of the tip ridge line portion of the blade member is made of the rubber material, and the blade member is positioned near the tip ridge line portion. Wherein the Martens hardness of 1.0 N / mm ² or more 7.0 N / mm ² or less.

  According to the present invention, it is possible to maintain a clean state without surface contamination such as toner adhesion to the surface of the electrophotographic photosensitive member, and to prolong the initial charging function, light attenuation function, and latent image maintenance of the electrophotographic photosensitive member. An image forming apparatus capable of maintaining a period and maintaining excellent image quality can be provided.

It is a schematic diagram for explaining an example of how to obtain the adhesion force between the surface of the electrophotographic photosensitive member and the probe of the cantilever. It is a figure which shows an example of the change of the adhesive force with respect to the distance of the electrophotographic photoreceptor surface and the probe of a cantilever. It is a schematic diagram showing an example of the configuration of the electrophotographic photosensitive member according to the present invention. It is a schematic diagram which shows the other example of a structure of the electrophotographic photoreceptor which concerns on this invention. It is a schematic diagram which shows the other example of a structure of the electrophotographic photoreceptor which concerns on this invention. It is a schematic diagram which shows the other example of a structure of the electrophotographic photoreceptor which concerns on this invention. It is a schematic diagram which shows the other example of a structure of the electrophotographic photoreceptor which concerns on this invention. 1 is a schematic diagram illustrating an example of an image forming apparatus according to the present invention. It is a schematic diagram which shows the structural example of a charging means. It is a schematic diagram which shows an example of a cleaning blade. It is a schematic diagram which shows the principal part expansion in an example of a cleaning blade. FIG. 6 is a schematic diagram illustrating a case where the cleaning blade is in contact with an electrophotographic photosensitive member. It is a schematic diagram which shows the other example of a cleaning blade. It is a schematic diagram which shows an example of the process cartridge which concerns on this invention.

  Hereinafter, an image forming apparatus, a process cartridge, and an image forming method according to the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, and other embodiments, additions, modifications, deletions, and the like can be changed within a range that can be conceived by those skilled in the art, and any aspect is possible. As long as the functions and effects of the present invention are exhibited, the scope of the present invention is included.

The image forming apparatus of the present invention includes at least an electrophotographic photosensitive member, a charging unit that charges the surface of the electrophotographic photosensitive member, a latent image forming unit that forms an electrostatic latent image on the electrophotographic photosensitive member, and the static image forming unit. Developing means for attaching a developer to the electrostatic latent image to form a visible image; Transfer means for transferring the visible image to a recording medium; Cleaning for removing the developer attached to the surface of the electrophotographic photosensitive member Means. The electrophotographic photoreceptor contains at least a polyester resin in the outermost layer in the thickness direction. And when the discharge frequency of the alternating current component of the charging means is 7.5 times or more the linear velocity of the electrophotographic photosensitive member, a discharge charge of 100 μC / mm ² is applied to the electrophotographic photosensitive member using the charging means. Before and after, the variation in average adhesion between the surface of the electrophotographic photosensitive member and the probe of the silicon cantilever is greater than 0 nN and not greater than 5 nN.

  Moreover, the measuring method of average adhesion force fluctuation | variation is performed as follows. Before the electrophotographic photosensitive member is charged by the charging means, a probe of a silicon cantilever is brought into contact with the surface of the electrophotographic photosensitive member, and the amount of deflection of the silicon cantilever when separated is measured, The value obtained by multiplying the amount of deflection by the spring constant of the silicon cantilever is defined as the adhesive force, and the arithmetic average of the adhesive force measured at a plurality of locations on the electrophotographic photosensitive member is defined as the average adhesive force before charging. Similarly, after the electrophotographic photosensitive member is charged by the charging means, the average adhesive force is obtained, and the value obtained by subtracting the average adhesive force before charging from the average adhesive force after charging is the surface of the electrophotographic photosensitive member and silicon. Change in average adhesion force with the cantilever probe.

Hereinafter, the present invention will be described in detail.
(Surface maintenance)
<Requirements for surface maintenance>
As described above, the surface maintenance means, “When an image is repeatedly output using an image forming apparatus, toner components (toner particles, toner-added fine particles, etc.) adhere to the surface of the electrophotographic photosensitive member. The surface of the electrophotographic photosensitive member is kept free of foreign matters such as toner to maintain a clean surface so that the charging function, light attenuation function, latent image maintenance function, etc. that the body should have are not impaired. Refers to that.

  The main cause of toner components adhering to the surface of the electrophotographic photosensitive member is considered to be poor cleaning that removes toner remaining after the transfer process from the electrophotographic photosensitive member. ”And“ Toner external additive particle cleaning failure ”. “Toner particle cleaning failure” is considered to be mainly caused by a defect in the cleaning method, for example, wear or chipping of the cleaning blade. On the other hand, “poor toner externally added particle cleaning” means that the silica fine particles used as an external additive of toner rub against the electrophotographic photosensitive member strongly by the cleaning blade when it is scraped between the electrophotographic photosensitive member and the cleaning blade. Crimping due to being attached is considered to be the main factor. It is necessary to suppress both phenomena for maintaining the surface of the electrophotographic photosensitive member, but especially for the latter “poor toner externally added particle cleaning”, the cause particle is very small, tens of nanometers, and cleaning It is difficult to dampen with a cleaning member such as a blade. Therefore, it is difficult to take countermeasures with an electrophotographic photosensitive member or a cleaning blade, which is likely to be an obvious problem.

As a means for suppressing this "toner externally added particle cleaning failure" in the electrophotographic photosensitive member, even when the toner externally added fine particles are pressed against the electrophotographic photosensitive member with a member such as a cleaning blade, it is difficult to press-bond. The surface is considered to be most effective.
The inventors of the present invention have made extensive studies to achieve the above object. As a result, the surface that is difficult to press is electrophotographic even when the electrophotographic photosensitive member is repeatedly charged using a charging member of a proximity charging type rather than increasing the hardness near the surface of the electrophotographic photosensitive member. It has been found that it is most effective not to increase the viscosity of the photoreceptor surface. That is, it is important not to increase the viscosity of the surface of the electrophotographic photosensitive member regardless of the usage history of the electrophotographic photosensitive member in the image forming apparatus. The present inventors have found that this is nothing but an increase in the adhesive force with similar members.

<< Surface maintenance expression means >>
The requirement that the viscosity of the surface of the electrophotographic photosensitive member hardly increases even when the discharge hazard is repeatedly applied by the charging means of the proximity discharge method is that (i) the binder resin as a constituent component on the outermost surface of the electrophotographic photosensitive member The present inventor has found that a high molecular weight polyester resin is used as a component, and (ii) the content of the low molecular charge transporting component of the constituent component on the outermost surface of the electrophotographic photosensitive member is reduced. Satisfying these requirements makes it difficult to increase the viscosity of the surface of the electrophotographic photosensitive member even when a discharge hazard is repeatedly applied by the charging means of the proximity discharge method. The following can be considered as this factor.

(I) When a discharge hazard is applied using a proximity discharge type charging means, the organic material on the outermost surface of the electrophotographic photosensitive member is considered to break the bond due to the collision of the discharge charge. The viscosity of the material is considered to be less likely to increase in viscosity because the higher the raw material, the easier it is to remove the polymer after cutting.
(Ii) When a discharge hazard is applied to an electrophotographic photosensitive member having a large amount of low molecular weight organic material on the outermost surface using a proximity discharge type charging means, the organic material caused by collision of discharge charges is the same as the phenomenon of (i) above. Oxidation / decomposition occurs. Since low-molecular charge transport materials are likely to change to highly viscous materials during oxidation / decomposition, it is unlikely that viscosity increases will occur even when discharge hazards are repeatedly applied if the material content is low. It is done.

  These requirements (i) and (ii) may be applied for the purpose of improving the surface maintenance function separately from the material group described later as long as the basic functions (charging function, light attenuation function, etc.) of the electrophotographic photosensitive member are not impaired. good. Among them, the use of a material type obtained by copolymerizing a charge transporting functional unit in the binder function as a binder material shows a high effect on prevention of pressure bonding of silica or the like.

  The binding material is not particularly limited as long as it is a polyester-based resin, and can be appropriately selected according to the purpose. Further, two or more kinds of polyester-based resins or non-polyester-based resins can be mixed depending on the purpose. Also good. Details will be described later.

Further, as described above, a polymer charge transport material having both the function of the binder resin and the function of the charge transport material may be used.
A known material can be used as the polymer charge transport material, but at least one polymer selected from polycarbonate, polyurethane, polyester, and polyether is preferable. In particular, a polycarbonate containing a triarylamine structure in the main chain and / or side chain is preferable. Among these, polymer charge transport materials represented by the following general formulas (1) to (10) are preferably used.

In general formula (1), R ₁ , R ₂ and R ₃ are each independently a substituted or unsubstituted alkyl group or halogen atom, R ₄ is a hydrogen atom or a substituted or unsubstituted alkyl group, R ₅ and R ₆ Is a substituted or unsubstituted aryl group, o, p, q are each independently an integer of 0-4, k, j are compositions, 0.1 ≦ k ≦ 1, 0 ≦ j ≦ 0.9, n Represents the number of repeating units and is an integer of 5 to 5000. X represents an aliphatic divalent group, a cycloaliphatic divalent group, or a divalent group represented by the following general formula (I) or general formula (II).

In general formula (I), R ₁₀₁ and R ₁₀₂ each independently represents a substituted or unsubstituted alkyl group, aryl group or halogen atom. l and m are integers of 0 to 4, Y is a single bond, a linear, branched or cyclic alkylene group having 1 to 12 carbon atoms, —O—, —S—, —SO—, —SO ₂ —. , -CO-, -CO-O-Z-O-CO- (wherein Z represents an aliphatic divalent group).

In general formula (II), a represents an integer of 1 to 20, b represents an integer of 1 to 2000, and R ₁₀₃ and R ₁₀₄ represent a substituted or unsubstituted alkyl group or aryl group. Here, R ₁₀₁ and R ₁₀₂ , and R ₁₀₃ and R ₁₀₄ may be the same or different.

In the general formula (2), R ₇ and R ₈ represent a substituted or unsubstituted aryl group, and Ar ₁ , Ar ₂ , and Ar ₃ represent the same or different arylene groups. X, k, j, and n are the same as in the general formula (1).

In general formula (3), R ₉ and R ₁₀ represent a substituted or unsubstituted aryl group, and Ar ₄ , Ar ₅ and Ar ₆ represent the same or different arylene groups. X, k, j, and n are the same as in the general formula (1).

In General Formula (4), R ₁₁ and R ₁₂ represent a substituted or unsubstituted aryl group, and Ar ₇ , Ar ₈ , and Ar ₉ represent the same or different arylene groups. X, k, j, and n are the same as in the general formula (1).

In the general formula (5), R ₁₃ and R ₁₄ are substituted or unsubstituted aryl groups, Ar ₁₀ , Ar ₁₁ and Ar ₁₂ are the same or different arylene groups, X ₁ and X ₂ are substituted or unsubstituted ethylene groups, Or a substituted or unsubstituted vinylene group. X, k, j, and n are the same as in the general formula (1).

In the general formula (6), R ₁₅ , R ₁₆ , R ₁₇ and R ₁₈ are substituted or unsubstituted aryl groups, Ar ₁₃ , Ar ₁₄ , Ar ₁₅ and Ar ₁₆ are the same or different arylene groups, Y ₁ and Y _2. Y ₃ represents a single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted cycloalkylene group, a substituted or unsubstituted alkylene ether group, an oxygen atom, a sulfur atom, or a vinylene group, which may be the same or different. May be. X, k, j, and n are the same as in the general formula (1).

In the general formula (7), R ₁₉ and R ₂₀ represent a hydrogen atom or a substituted or unsubstituted aryl group, and R ₁₉ and R ₂₀ may form a ring. Ar ₁₇ , Ar ₁₈ and Ar ₁₉ represent the same or different arylene groups. X, k, j, and n are the same as in the general formula (1).

In the general formula (8), R ₂₁ represents a substituted or unsubstituted aryl group, and Ar ₂₀ , Ar ₂₁ , Ar ₂₂ , Ar ₂₃ represent the same or different arylene groups. X, k, j, and n are the same as in the general formula (1).

In the general formula (9), R ₂₂ , R ₂₃ , R ₂₄ and R ₂₅ represent a substituted or unsubstituted aryl group, and Ar ₂₄ , Ar ₂₅ , Ar ₂₆ , Ar ₂₇ and Ar ₂₈ represent the same or different arylene groups. X, k, j, and n are the same as in the general formula (1).

In General Formula (10), R ₂₆ and R ₂₇ represent a substituted or unsubstituted aryl group, and Ar ₂₉ , Ar ₃₀ , and Ar ₃₁ represent the same or different arylene groups. X, k, j, and n are the same as in the general formula (1).

  These polymer charge transport materials may be used alone, or two or more kinds of polymer charge transport materials may be used in combination.

(Adhesion measurement method)
<< Characteristic value and measurement method >>
Next, a method for measuring the adhesion force on the surface of the electrophotographic photosensitive member will be described as the viscosity characteristic value of the outermost surface of the electrophotographic photosensitive member.
In the present invention, the cantilever of the scanning probe microscope is used to measure the adhesion force acting between the surface of the electrophotographic photosensitive member and the cantilever made of a material similar to the material adhering to the surface of the electrophotographic photosensitive member. As described above, since silica is the main component of the toner external additive adhering to the surface of the electrophotographic photosensitive member, the value measured using a silicon cantilever is applied as the adhesive force in the present invention. In addition, as a measuring apparatus used for the adhesive force measuring method, a commonly used apparatus can be used, and measurement can be performed with an atomic force microscope, a scanning tunneling microscope, or the like.

In the present invention, the silicon cantilever is not particularly limited as long as it contains silicon, and includes a cantilever made of a material such as silicon nitride.
Examples of commercially available products include SI-AF, SN-AF, and SN-FF manufactured by Hitachi High-Tech Science.
The size of the cantilever is not particularly limited, and can be changed as appropriate according to the purpose. In addition, the spring constant of the cantilever described later is not particularly limited and can be appropriately changed according to the purpose, but can be set to 0.05 to 50 N / m, for example.

  In the present invention, the scanning probe microscope used for measuring the adhesion force scans the sample surface with a probe called a cantilever provided with a probe at one end of the cantilever, and quantitatively evaluates the shape and height difference of the sample surface. Use a microscope. Among them, an atomic force microscope is most preferable for the measurement of the present invention, but it can also be used in another microscope called a cantilever type scanning probe microscope such as a scanning tunneling microscope.

Next, a specific measurement principle / method will be described with reference to FIG. As shown in FIGS. 1A and 1B, a microprobe 41 provided on the cantilever 40 is brought close to and slowly brought into contact with the surface of the electrophotographic photosensitive member. 1A and 1C conceptually show the moving direction of the probe 41.
Thereafter, as shown in FIG. 1C, when the cantilever 40 is gradually pulled away from the surface of the electrophotographic photosensitive member, it is affected by the adhesive force between the surface of the electrophotographic photosensitive member and the probe 41 of the cantilever 40. The cantilever 40 will bend. When the cantilever 40 is further pulled away, the cantilever 40 is further bent, and thus the cantilever 40 performs the same function as a spring. As a result, the amount of deflection of the cantilever 40 is measured, and the adhesion force between the surface of the electrophotographic photosensitive member and the cantilever probe can be measured by multiplying the spring constant of the cantilever 40. The surface of the electrophotographic photosensitive member and the probe 41 of the cantilever 40 are separated from each other until they are in a peeled state, and a value obtained by multiplying the detected maximum deflection amount by the spring constant of the cantilever and the surface of the electrophotographic photosensitive member and the cantilever probe. The adhesion force between the needles.

  Here, when the horizontal axis is the distance between the surface of the electrophotographic photosensitive member and the probe 41, and the vertical axis is the deflection amount of the cantilever 40 × the spring constant of the cantilever 40, the change in adhesion force (both the force curve and the force distance curve). FIG. 2 shows an example. In FIG. 2, the surface of the electrophotographic photosensitive member in a state where nothing is performed is set to 0 on the horizontal axis, a negative value indicates a state in which the probe 41 is pushed into the electrophotographic photosensitive member, and a positive value indicates an electron. This means that the probe 41 is away from the photoconductor. In FIG. 2, the spring constant of the cantilever 40 is 0.38 N / m.

Referring to FIG. 2, when the cantilever 40 is pulled away from the state in which the probe 41 is pushed into the electrophotographic photosensitive member, and the probe 41 is located on the surface of the electrophotographic photosensitive member (the horizontal axis is 0), the cantilever is 40 is not bent and the amount of deflection is represented by zero. However, when the cantilever 40 is further separated, the probe 41 does not move away from the electrophotographic photosensitive member as shown in FIG. 1C, and the deflection amount (reference numeral 42) of the cantilever 40 is observed. When further apart, the probe 41 is separated from the electrophotographic photosensitive member at a certain point in time, the amount of deflection disappears, and the adhesion force becomes zero.
At this time, as described above, a value obtained by multiplying the maximum deflection amount, that is, the deflection amount immediately before the probe 41 is separated from the electrophotographic photosensitive member by the spring constant of the cantilever, is assigned between the surface of the electrophotographic photosensitive member and the cantilever probe. It is assumed to be strong. Note that the amount of deflection is not particularly limited, and can be measured with an atomic force microscope, a scanning tunneling microscope, or the like.

  Next, the average adhesion force will be described. The adhesion is measured at a plurality of locations on the electrophotographic photosensitive member, and an average value is obtained. The setting of the measurement point is not particularly limited. For example, an area of 10 μm × 10 μm is set on the surface of the electrophotographic photosensitive member, and the area is set at eight locations in the rotation direction of the electrophotographic photosensitive member and eight in the axial direction. A total of 64 places are set as measurement points. The adhesion force is measured at each measurement point, and the same measurement is performed for a total of five regions, and a total of about 340 measurements are performed. By calculating the arithmetic average of the obtained measured values, the average adhesion force between the electrophotographic photosensitive member surface and the cantilever probe can be determined.

  The average adhesion force is measured before and after charging by the charging means of the image forming apparatus of the present invention. After obtaining the average adhesion before charging, the electrophotographic photosensitive member is charged by the charging means, and then the average adhesion after charging is further obtained. A value obtained by subtracting the average adhesive force before charging from the average adhesive force after charging is defined as the average adhesive force fluctuation between the surface of the electrophotographic photosensitive member and the silicon cantilever.

In the present invention, when the discharge frequency of the alternating current component of the charging means is 7.5 times or more the linear velocity of the electrophotographic photosensitive member, a discharging charge of 100 μC / mm ² is applied to the electrophotographic photosensitive member using the charging means. Before and after the application, the average adhesive force variation is greater than 0 nN (nanonewton) and 5 nN or less. By being 5 nN or less, it becomes difficult for a developer or an external additive of the developer to adhere to the surface of the electrophotographic photosensitive member, and the surface contamination can be suppressed and a clean state can be maintained. On the other hand, if it exceeds 5 nN, the toner base or the toner external additive tends to adhere to the surface of the electrophotographic photosensitive member, and a high-quality image cannot be obtained.
In order to make the average adhesive force fluctuation a desired value, it is not particularly limited, but examples include controlling the material used for the outermost layer of the electrophotographic photosensitive member.

  By setting the discharge frequency of the AC component of the charging means to 7.5 times or more the linear velocity of the electrophotographic photosensitive member, the surface of the electrophotographic photosensitive member can be sufficiently charged, and the image quality can be improved. On the other hand, if it is less than 7.5 times, the surface of the electrophotographic photosensitive member cannot be sufficiently charged, image unevenness or the like occurs, and a good image cannot be obtained.

In the charging means of the present invention, the surface property of the electrophotographic photosensitive member changes due to charging by an alternating current component, and the average adhesion force between the electrophotographic photosensitive member and the probe 41 of the cantilever 40 changes before and after charging. Therefore, merely setting the discharge frequency of the alternating current component of the charging means to 7.5 times or more of the linear speed of the electrophotographic photosensitive member is not sufficient to continuously develop a good image, satisfying various requirements, It is necessary to have an appropriate configuration.
When comparing the discharge frequency of the AC component of the charging means with the linear velocity of the electrophotographic photosensitive member, the unit of the discharge frequency of the AC component is Hz, and the unit of the linear velocity of the electrophotographic photosensitive member is mm / sec. Compare the values of both. For example, when the discharge frequency of the AC component is 1500 Hz and the linear speed of the electrophotographic photosensitive member is 200 mm / sec, the relationship between the two becomes 7.5 times.

(Electrophotographic photoreceptor)
Hereinafter, structural examples of the electrophotographic photosensitive member of the present invention will be described with reference to FIGS.
FIG. 3 is a diagram showing a layer configuration of an electrophotographic photosensitive member having a single-layer type photosensitive layer, in which a single-layer type photosensitive layer 36 is formed on a conductive support 31. FIG. 4 is a diagram showing a layer structure of an electrophotographic photosensitive member having a laminated type photosensitive layer in which a charge generation layer 33 and a charge transport layer 34 are sequentially laminated on a conductive support 31. The charge generation layer 33 and the charge transport layer 34 correspond to the photosensitive layer. 5 has a configuration in which an undercoat layer 32 is further provided on the electrophotographic photosensitive member having the configuration of FIG.
FIG. 6 is a diagram showing a layer structure of an electrophotographic photosensitive member in which an undercoat layer 32, a charge generation layer 33, a charge transport layer 34, and a surface layer 35 are sequentially laminated on a conductive support 31. FIG. 7 is a diagram showing a layer structure of an electrophotographic photosensitive member in which a charge generation layer 33, a charge transport layer 34, an intermediate layer 37, and a surface layer 35 are sequentially laminated on a conductive support 31. The charge generation layer 33, the charge transport layer 34, and the surface layer 35 correspond to the photosensitive layer.

<Polyester resin>
The electrophotographic photoreceptor of the present invention contains at least a polyester resin in the outermost layer in the thickness direction. Depending on the purpose, two or more polyester resins may be included, or a non-polyester resin may be mixed.
Examples of polyester resins include polyester resins, polycarbonate resins, and polyarylate resins. Examples of resins other than polyester resins include methacrylic resins, acrylic resins, polyethylene resins, polyvinyl chloride resins, polyvinyl acetate resins, Examples include polystyrene resin, phenol resin, epoxy resin, polyurethane resin, polyvinylidene chloride resin, alkyd resin, silicone resin, polyvinyl carbazole resin, polyvinyl butyral resin, polyvinyl formal resin, polyacrylate resin, polyacrylamide resin, and phenoxy resin.
Among these, polycarbonate resin or polyarylate resin is preferable.

The viscosity average molecular weight (Mv) of the polyester resin is preferably 50,000 or more. It is preferable for the viscosity average molecular weight to be 50,000 or more because the average adhesion force fluctuation can be kept small.
For the purpose of imparting a charge transport function, the outermost layer may further contain a donor. Examples of the donor in the present invention include a low molecular charge transport material described later. In addition, a low molecular charge transport material having a structural unit of the above-described polymer charge transport material can also be used.
When the donor is contained, the donor content with respect to the polyester resin is preferably 60 parts by weight or less with respect to 100 parts by weight of the polyester resin. When the amount is 60 parts by weight or less, fluctuations in the adhesion force between the surface of the electrophotographic photosensitive member and the probe of the silicon cantilever can be suppressed.

<Conductive support>
The conductive support 31 is not particularly limited as long as it has a volume resistance of 1 × 10 ¹⁰ Ω · cm or less, and can be appropriately selected according to the purpose. An endless belt (such as an endless nickel belt or an endless stainless steel belt) disclosed in Japanese Patent Laid-Open No. 52-36016 may be used.

  There is no restriction | limiting in particular as a formation method of the electroconductive support body 31, According to the objective, it can select suitably. For example, metal (aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum, etc.) or metal oxide (tin oxide, indium oxide, etc.) is deposited or sputtered to form a support (film, cylindrical, etc.) Forming method by coating plastic, paper, etc .; Extruding a metal (aluminum, aluminum alloy, nickel, stainless steel, etc.) plate, drawing, etc., surface treatment (cutting, superfinishing, polishing after forming a blank) Etc.) and the like.

The conductive support 31 may have a configuration in which a conductive layer is provided on the conductive support 31.
There is no restriction | limiting in particular as a formation method of the said electroconductive layer, According to the objective, it can select suitably. For example, a method for forming a conductive powder and a binder resin by applying a coating liquid obtained by dispersing or dissolving the conductive powder and a binder resin in a solvent on a conductive support 31, polyvinyl chloride, polypropylene, Examples thereof include a method of forming using a heat-shrinkable tube in which the conductive powder is contained in a material such as polyester, polystyrene, polyvinylidene chloride, polyethylene, rubber chloride, and Teflon (registered trademark).

  There is no restriction | limiting in particular as said electroconductive powder, According to the objective, it can select suitably. Examples thereof include carbon fine particles such as carbon black and acetylene black; metal powders such as aluminum, nickel, iron, nichrome, copper, zinc and silver; metal oxide powders such as conductive tin oxide and ITO.

There is no restriction | limiting in particular as binder resin used for the said electroconductive layer, According to the objective, it can select suitably. For example, a thermoplastic resin, a thermosetting resin, a photocurable resin, and the like can be mentioned. Specifically, a polystyrene resin, a styrene-acrylonitrile copolymer, a styrene-butadiene copolymer, a styrene-maleic anhydride copolymer. , Polyester resin, polyvinyl chloride resin, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate resin, polyvinylidene chloride resin, polyarylate resin, phenoxy resin, polycarbonate resin, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral resin, polyvinyl Formal resin, polyvinyl toluene resin, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol resin, alkyd resin, and the like can be given.
There is no restriction | limiting in particular as a solvent used for the said electroconductive layer, According to the objective, it can select suitably, For example, tetrahydrofuran, a dichloromethane, methyl ethyl ketone, toluene etc. are mentioned.

<Photosensitive layer>
As described above, the photosensitive layer may be a laminated photosensitive layer or a single-layer photosensitive layer.
<< Laminated Photosensitive Layer >>
The laminated photosensitive layer has at least a charge generation layer 33 and a charge transport layer 34 because independent layers have a charge generation function and a charge transport function. Many charge generating materials have poor chemical stability, and exposure to acidic gases such as discharge products around chargers in the electrophotographic imaging process can lead to reduced charge generation efficiency. It is preferable to stack the charge transport layer 34 on the generation layer 33. As the charge generation layer 33 and the charge transport layer 34, conventionally known ones can be used.

-Charge generation layer-
The charge generation layer 33 includes a charge generation material, preferably includes a binder resin, and may further include other components such as an antioxidant as necessary.

-Charge generation material-
There is no restriction | limiting in particular as said charge generation substance, According to the objective, it can select suitably, For example, an inorganic material, an organic material, etc. are mentioned.

---- Inorganic material ---
The inorganic material is not particularly limited and may be appropriately selected depending on the intended purpose. For example, crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, selenium-arsenic compound, amorphous silicon (For example, a dangling bond that is terminated with a hydrogen atom, a halogen atom, or the like; a boron atom, a phosphorus atom, or the like is preferred).

---- Organic materials ---
There is no restriction | limiting in particular as said organic type material, According to the objective, it can select suitably. For example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine; azulenium salt pigments, squaric acid methine pigments, azo pigments having a carbazole skeleton, azo pigments having a triphenylamine skeleton, azo pigments having a diphenylamine skeleton, dibenzothiophene skeleton Azo pigments having a fluorenone skeleton, azo pigments having an oxadiazole skeleton, azo pigments having a bis-stilbene skeleton, azo pigments having a distyryl oxadiazole skeleton, azo pigments having a distyrylcarbazole skeleton, perylene Pigments, anthraquinone or polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, indigo Id based pigments, and bisbenzimidazole pigments. These may be used individually by 1 type and may use 2 or more types together.

--Binder resin--
There is no restriction | limiting in particular as said binder resin, According to the objective, it can select suitably. For example, polyamide resin, polyurethane resin, epoxy resin, polyketone resin, polycarbonate resin, silicone resin, acrylic resin, polyvinyl butyral resin, polyvinyl formal resin, polyvinyl ketone resin, polystyrene resin, poly-N-vinyl carbazole resin, polyacrylamide resin, etc. Is mentioned. These may be used individually by 1 type and may use 2 or more types together.
The binder resin may include a charge transporting polymer material having a charge transport function in addition to the above-described binder resin. For example, a polymer material having an arylamine skeleton, a benzidine skeleton, a hydrazone skeleton, a carbazole skeleton, a stilbene skeleton, a pyrazoline skeleton, or the like, a polymer material such as a polycarbonate, polyester, polyurethane, polyether, polysiloxane, or acrylic resin, or a polymer having a polysilane skeleton A material etc. can be used.

-Other ingredients-
There is no restriction | limiting in particular as said other component, According to the objective, it can select suitably, For example, a low molecular charge transport material, a solvent, a leveling agent etc. are mentioned, You may contain the above-mentioned antioxidant.
There is no restriction | limiting in particular as content of the said other component, Although it can select suitably according to the objective, 0.01 mass%-10 mass% are preferable with respect to the total mass of the layer to add.

--- Low molecular charge transport material ---
There is no restriction | limiting in particular as said low molecular charge transport material, According to the objective, it can select suitably, For example, an electron transport material, a hole transport material, etc. are mentioned.
The electron transport material is not particularly limited and may be appropriately selected depending on the intended purpose. For example, chloroanil, bromilyl, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone 2,4,5,7-tetranitro-9-fluorenone, 2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1 , 2-b] thiophen-4-one, 1,3,7-trinitrodibenzothiophene-5,5-dioxide, diphenoquinone derivatives and the like. These may be used individually by 1 type and may use 2 or more types together.
The hole transport material is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include oxazole derivatives, oxadiazole derivatives, imidazole derivatives, monoarylamine derivatives, diarylamine derivatives, and triarylamine derivatives. , Stilbene derivatives, α-phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9-styrylanthracene derivatives, pyrazoline derivatives, divinylbenzene derivatives, hydrazone derivatives, indene derivatives, butadiene derivatives, pyrene derivatives, etc. Derivatives, enamine derivatives and the like. These may be used individually by 1 type and may use 2 or more types together.

--- Solvent ---
There is no restriction | limiting in particular as said solvent, According to the objective, it can select suitably. For example, tetrahydrofuran, dioxane, dioxolane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexanone, cyclopentanone, anisole, xylene, methyl ethyl ketone, acetone, ethyl acetate, butyl acetate and the like can be mentioned. These may be used individually by 1 type and may use 2 or more types together.

--- Leveling agent ---
There is no restriction | limiting in particular as said leveling agent, According to the objective, it can select suitably, For example, silicone oils, such as dimethyl silicone oil and methylphenyl silicone oil, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.

--Method of forming charge generation layer--
There is no restriction | limiting in particular as a formation method of the electric charge generation layer 33, According to the objective, it can select suitably. For example, a coating liquid obtained by dissolving or dispersing the charge generating material and the binder resin in the other components such as the solvent is applied on the conductive support 31 and dried. The method etc. are mentioned. In addition, the said coating liquid can be apply | coated by the casting method etc.
There is no restriction | limiting in particular as thickness of the electric charge generation layer 33, Although it can select suitably according to the objective, 0.01 micrometer-5 micrometers are preferable, and 0.05 micrometer-2 micrometers are more preferable.

-Charge transport layer-
The charge transport layer 34 is a layer intended to hold a charged charge and to couple the charge generated and separated in the charge generation layer 33 by exposure to the charged charge held by movement. In order to achieve the purpose of holding the charged charge, it is required that the electric resistance is high. Further, in order to achieve the purpose of obtaining a high surface potential with the charged charge held, it is preferable that the dielectric constant is small and the charge mobility is good.
The charge transport layer 34 includes a charge transport material, preferably includes the binder material, and further includes other components as necessary.

-Charge transport material-
The charge transport material is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include an electron transport material and a hole transport material. In addition, the above-described polymer charge transport material can be used.
There is no restriction | limiting in particular as content in the charge transport layer whole quantity of the said charge transport substance, According to the objective, it can select suitably. In order to suppress adhesion between the surface of the electrophotographic photosensitive member and the toner externally added particles, the content of the charge transport material is preferably 20% by mass to 60% by mass with respect to the binder material, preferably 30% by mass to More preferably, it is 50 mass%. If the content of the charge transport material is less than 20% by mass, the charge transport property of the charge transport layer may be reduced, and desired light attenuation characteristics may not be obtained. If it exceeds 60% by mass, it will be worn more than necessary due to various hazards received by the electrophotographic photosensitive member during image formation, and toner particles or toner externally added particles will easily adhere to the surface of the electrophotographic photosensitive member. This is not preferable because image formation cannot be achieved. On the other hand, when the content of the charge transport material in the charge transport layer is within the preferable range, desired light attenuating properties can be obtained.

  Further, the amount of wear is small even when used, and the toner particles and the toner external additive particles are less likely to adhere to the surface of the electrophotographic photosensitive member, which is advantageous in that an excellent image can be output over a long period of time. In addition, when a polymer charge transport material is used as the binder material, the content of the charge transport material in the binder resin varies depending on the type of material applied, but the content of the charge transport material can be further reduced. It is.

---- Electron transport material ---
There is no restriction | limiting in particular as said electron transport substance (electron-accepting substance), According to the objective, it can select suitably. For example, chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4,5,7- Tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophene-4-one, 1,3,7-trinitrodibenzothiophene-5 5-Dioxide etc. are mentioned. These may be used alone or in combination of two or more.

--- Hole transport material ---
The hole transport material (electron donating material) is not particularly limited and may be appropriately selected depending on the intended purpose. For example, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazoline , Phenylhydrazones, α-phenylstilbene derivatives, thiazole derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, thiophene derivatives, and the like. These may be used alone or in combination of two or more.

-Other ingredients-
There is no restriction | limiting in particular as said other component, According to the objective, it can select suitably, For example, a solvent, a plasticizer, a leveling agent, etc. are mentioned, You may contain antioxidant mentioned above.
There is no restriction | limiting in particular as content of the said other component, Although it can select suitably according to the objective, 0.01 mass%-10 mass% are preferable with respect to the total mass of the layer to add.

--- Solvent ---
The solvent is not particularly limited and may be appropriately selected depending on the intended purpose. The same solvent as the charge generation layer 33 can be used, but a solvent that dissolves the charge transport material and the binder resin satisfactorily. preferable. These may be used singly or in combination of two or more.

---- Plasticizer ---
The plasticizer is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate.

--- Leveling agent ---
There is no restriction | limiting in particular as said leveling agent, According to the objective, it can select suitably. Examples thereof include silicone oils such as dimethyl silicone oil and methylphenyl silicone oil; polymers or oligomers having a perfluoroalkyl group in the side chain.

--Method of forming charge transport layer--
There is no restriction | limiting in particular as a formation method of the electric charge transport layer 34, According to the objective, it can select suitably. For example, a coating liquid obtained by dissolving or dispersing the charge transport material and the binder resin in the other components such as the solvent is applied on the charge generation layer 33 and heated or dried. The method of doing is mentioned.
There is no restriction | limiting in particular as a coating method of the said coating liquid used in the case of formation of the charge transport layer 34, According to the objectives, such as the viscosity of a coating liquid and the thickness of a desired charge transport layer, it selects suitably. Can do. Examples include dip coating, spray coating, bead coating, ring coating, and the like.

From the viewpoint of electrophotographic characteristics and film viscosity, the charge transport layer 34 needs to be heated using some means to remove the solvent from the charge transport layer 34.
Examples of the heating method include a method of heating heat energy such as air, nitrogen and other gases, steam, various heat media, infrared rays, and electromagnetic waves from the coated surface side or the support side.
There is no restriction | limiting in particular as temperature at the time of the said heating, Although it can select suitably according to the objective, 100 to 170 degreeC is preferable. When the temperature is less than 100 ° C., the organic solvent in the film cannot be sufficiently removed, and electrophotographic characteristics and wear durability may be deteriorated. On the other hand, when the temperature exceeds 170 ° C., not only the surface of the surface is distorted and cracks are generated, peeling occurs at the interface with the adjacent layer, etc., but volatile components in the photosensitive layer are scattered outside. In this case, desired electrical characteristics may not be obtained.

  The thickness of the charge transport layer 34 is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 50 μm or less and more preferably 45 μm or less from the viewpoint of resolution or responsiveness. The lower limit varies depending on the system to be used (particularly charging potential), but is preferably 5 μm or more.

<< Other layers >>
There is no restriction | limiting in particular as said other layer, According to the objective, it can select suitably, For example, the undercoat layer 32, the intermediate | middle layer 37, the surface layer 35, etc. are mentioned.
-Undercoat layer-
The undercoat layer 32 can be provided between the conductive support 31 and the photosensitive layer.
The undercoat layer 32 includes a resin, and further includes other components such as the above-described antioxidant, fine powder pigment, and coupling agent as necessary.
There is no restriction | limiting in particular as resin contained in the undercoat layer 32, According to the objective, it can select suitably. For example, water-soluble resins such as polyvinyl alcohol, casein, sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine resin, phenol resin, alkyd-melamine resin, epoxy resin, etc. Examples thereof include a curable resin that forms a network structure.
Among these, a resin having a high solvent resistance with respect to a general organic solvent is preferable in that a photosensitive layer is coated on the resin with a solvent.

  The fine powder pigment contained in the undercoat layer 32 is not particularly limited as long as it is a pigment capable of preventing moire and reducing the residual potential, and can be appropriately selected according to the purpose. Examples thereof include metal oxides such as titanium oxide, silica, alumina, zirconium oxide, tin oxide, and indium oxide.

  There is no restriction | limiting in particular as a coupling agent contained in the undercoat layer 32, According to the objective, it can select suitably, For example, a silane coupling agent, a titanium coupling agent, a chromium coupling agent etc. are mentioned.

There is no restriction | limiting in particular as the undercoat layer 32, According to the objective, it can select suitably, For example, a single layer may be sufficient and the lamination | stacking of two or more layers may be sufficient.
There is no restriction | limiting in particular as a formation method of the undercoat layer 32, It can form using a suitable solvent and a coating method. For example, a method in which Al ₂ O ₃ is formed by anodic oxidation, an organic substance such as polyparaxylylene (parylene); an inorganic substance such as SiO ₂ , SnO ₂ , TiO ₂ , ITO, or CeO ₂ ; The method of forming etc. are mentioned.
There is no restriction | limiting in particular as thickness of the undercoat layer 32, Although it can select suitably according to the objective, 1 micrometer-5 micrometers are preferable.

-Intermediate layer-
The intermediate layer 37 can be provided between the charge transport layer 34 and the surface layer 35 for the purpose of suppressing the mixing of charge transport layer components into the surface layer 35 or improving the adhesion between the two layers. The intermediate layer 37 includes a binder resin, and further includes other components such as the above-described antioxidant as necessary. The intermediate layer coating solution is preferably insoluble or sparingly soluble in the surface layer coating solution.
There is no restriction | limiting in particular as binder resin contained in the intermediate | middle layer 37, According to the objective, it can select suitably, For example, polyamide, alcohol soluble nylon, polyvinyl butyral, polyvinyl alcohol, etc. are mentioned.
There is no restriction | limiting in particular as a formation method of the intermediate | middle layer 37, According to the objective, it can select suitably, For example, the method etc. which form using the suitable solvent and coating method similar to the said photosensitive layer are mentioned.
There is no restriction | limiting in particular as thickness of the intermediate | middle layer 37, Although it can select suitably according to the objective, 0.05 micrometer-2 micrometers are preferable.

-Surface layer-
The surface layer 35 can be provided for the purpose of improving wear resistance, scratch resistance, and electrostatic stability. The surface layer 35 contains at least the aforementioned polyester-based resin, and may contain the aforementioned donor in some cases, and may further contain other components such as the aforementioned antioxidant as necessary. Good.
There is no restriction | limiting in particular as a formation method of the surface layer 35, According to the objective, it can select suitably, For example, the method of forming using the suitable solvent and coating method similar to the said photosensitive layer is mentioned.
There is no restriction | limiting in particular as thickness of the surface layer 35, Although it can select suitably according to the objective, 3 micrometers-5 micrometers are preferable.

<< Single-layer type photosensitive layer >>
The single-layer type photosensitive layer 36 is a layer having a charge generation function and a charge transport function at the same time. The single-layer type photosensitive layer 36 contains a charge generation material, a charge transport material, and a binder resin, and further contains other components as necessary.

-Charge generation material-
The charge generation material is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include the same materials as those used in the above-described laminated photosensitive layer. There is no restriction | limiting in particular as content of the said charge generation substance, Although it can select suitably according to the objective, 5 mass parts-40 mass parts are preferable with respect to 100 mass parts of said binder resins.

-Charge transport material-
There is no restriction | limiting in particular as said charge transport substance, According to the objective, it can select suitably, For example, the same substance etc. as what is used with the above-mentioned lamination type photosensitive layer are mentioned. There is no restriction | limiting in particular as content of the said charge transport material, Although it can select suitably according to the objective, 190 mass parts or less are preferable with respect to 100 mass parts of said binder resin, and 50 mass parts-150 masses. Part is more preferred.

-Binder resin-
The binder resin is not particularly limited as long as it is a polyester resin, and can be appropriately selected according to the purpose. For example, the exemplified compounds include those described above.

-Other ingredients-
The other components are not particularly limited and may be appropriately selected depending on the purpose. For example, the same low molecular charge transport material, the same solvent, and the same as those used in the above-mentioned laminated photosensitive layer A leveling agent, the above-mentioned antioxidant, etc. are mentioned.

-Method for forming a single-layer type photosensitive layer-
There is no restriction | limiting in particular as a formation method of the single layer type photosensitive layer 36, According to the objective, it can select suitably. For example, a coating obtained by dissolving or dispersing a charge generating material, a charge transporting material, a binder resin, and other components in an appropriate solvent (eg, tetrahydrofuran, dioxane, dichloroethane, cyclohexane, etc.) using a disperser. Examples thereof include a method of forming a liquid by coating or drying.
There is no restriction | limiting in particular as a method to apply the said coating liquid, According to the objective, it can select suitably, For example, a dip coating method, a spray coat, a bead coat, a ring coat etc. are mentioned. Moreover, you may add a plasticizer, a leveling agent, antioxidant, etc. as needed.
There is no restriction | limiting in particular as thickness of the single layer type photosensitive layer 36, Although it can select suitably according to the objective, 5 micrometers-25 micrometers are preferable.

(Image forming device)
The image forming apparatus of the present invention includes at least the electrophotographic photosensitive member, a charging unit that charges the surface of the electrophotographic photosensitive member, a latent image forming unit that forms an electrostatic latent image on the electrophotographic photosensitive member, A developing unit that attaches a developer to the electrostatic latent image to form a visible image, a transfer unit that transfers the visible image to a recording medium, and a developer that adheres to the surface of the electrophotographic photosensitive member are removed. And a cleaning means. Furthermore, you may have another means as needed. The charging unit and the exposure unit may be collectively referred to as a latent image forming unit.
Details will be described below.

A configuration example of the image forming apparatus of the present invention is shown in FIG. In FIG. 8, around the electrophotographic photosensitive member 1, a charging unit 3, an exposing unit 5, a developing unit 6, a transfer unit 10, a cleaning unit 15, and the like are illustrated.
The outline of image formation will be described. First, the electrophotographic photosensitive member 1 is averagely charged by the charging means 3. Next, an electrostatic latent image is formed on the uniformly charged electrophotographic photosensitive member 1 by the exposure unit 5, and the electrostatic latent image formed on the electrophotographic photosensitive member 1 is visualized by the developing unit 6. The Then, a visible image visualized on the electrophotographic photosensitive member 1 is transferred onto the recording medium 9 by the transfer means 10 with respect to the recording medium 9 transferred by the transfer roller 8. Note that a pre-transfer charger 7 may be used for better transfer. Thereafter, the developer remaining on the surface of the electrophotographic photosensitive member is cleaned by the cleaning unit 15.
Details of each means will be described below.

<Charging means>
The charging unit 3 in the present invention is not particularly limited, and examples thereof include a charging unit comprising an AC / DC superposed charging roller that uniformly charges the surface of the electrophotographic photosensitive member. The charging means 3 by the charging roller is a conductive roller (hereinafter referred to as a charging roller) disposed in the vicinity of the electrophotographic photosensitive member, and an electric field is applied to the charging roller so that the charging roller and the electrophotographic photosensitive member are close to each other. In this method, the electrophotographic photosensitive member is charged by causing discharge.

  A schematic diagram of the charging roller is shown in FIG. FIG. 9 shows a charging roller 21 including a shaft portion 21a and a roller portion 21b, a spacer 22, a pressure spring 25, and a power source 16. The charging means by the charging roller 21 includes a contact charging system in which a rotatable roller-like conductive roller is disposed in contact with the electrophotographic photosensitive member, and a non-contact charging in which the charging roller is disposed in a non-contact manner on the electrophotographic photosensitive member. There is a method. In the present invention, any method may be selected, and a means capable of uniformly charging the surface of the electrophotographic photosensitive member may be selected. FIG. 9 is a schematic view of a non-contact charging method. The only difference from the contact charging method is whether or not the charging roller 21 is in contact with the surface of the electrophotographic photosensitive member (there is no spacer 22 described later).

  The charging roller 21 includes a shaft portion 21a and a roller portion 21b. The roller portion 21 b can be rotated by the rotation of the shaft portion 21 a, and a portion of the surface of the electrophotographic photosensitive member 1 that faces the image forming region 26 where an image is formed is in contact with or not in contact with the electrophotographic photosensitive member 1. is there. The charging roller 21 is generally set to have a length in the longitudinal direction (axial direction) slightly longer than the image forming area, and a non-image forming area 27 is provided. In the case of the non-contact charging method, spacers 22 are provided at both ends in the longitudinal direction, and a gap 24 is formed between the charging roller 21 and the electrophotographic photosensitive member 1 by contacting the non-image forming region 27. Will be formed.

  Further, the shaft portion 21a is pressed against the electrophotographic photosensitive member 1 by a pressure spring 25 made of a spring, and the charging roller 21 rotates along with the surface of the electrophotographic photosensitive member 1. As a result, a fine nip or a fine gap between the electrophotographic photosensitive member 1 and the charging roller 21 can be maintained with high accuracy in either the contact charging method or the non-contact charging method.

  A charging power source 16 is connected to the charging roller 21, and the electrophotographic photosensitive member is caused by proximity discharge in a minute gap (gap 24) between the surface of the electrophotographic photosensitive member 1 and the surface of the charging roller 21. 1 surface is uniformly charged. As the applied voltage, a DC voltage or an AC voltage may be used alone. However, if an alternating voltage obtained by superimposing the AC voltage on the DC voltage is used as the applied voltage, the charged potential varies due to a change in a minute nip or a minute gap. Can be uniformly charged. For this reason, it is preferable to use a DC voltage and an AC voltage superimposed on each other. In the present invention, an alternating voltage obtained by superimposing an AC voltage that is an AC component on a DC voltage that is a DC component is preferably used.

Next, a method for calculating the discharge charge amount to the electrophotographic photosensitive member will be described. As described above, the current (alternating current) flowing through the charging roller 21 in a state where an alternating voltage in which a DC voltage that is a DC component and an AC voltage that is an AC component are applied to the charging roller 21 is A (A). . A value obtained by dividing A [A] by the effective discharge width W [mm] of the charging roller 21 is the current density of the charging roller. On the other hand, the linear velocity of the electrophotographic photosensitive member is S [mm / sec], and the amount of charge discharged from the charging roller 21 to the electrophotographic photosensitive member per rotation of the electrophotographic photosensitive member is A / (S × W) [C / Mm ² ]. In general, the discharge charge of the direct current component is very small as compared with the alternating current component. Therefore, in the present invention, the discharge charge is calculated based on the current value of the alternating current component.

  In addition, there is no restriction | limiting in particular in the positive / negative of the electric charge charged to the electrophotographic photoreceptor 1. When the electrophotographic photosensitive member 1 is positively (negatively) charged and image exposure is performed, a positive (negative) electrostatic latent image is formed on the surface of the electrophotographic photosensitive member. A positive image can be obtained by developing this with negative (positive) toner (electrodetection fine particles), and a negative image can be obtained by developing with positive (negative) toner.

<Exposure means>
The exposure means 5 is not particularly limited as long as it can expose the surface of the electrophotographic photosensitive member charged by the charging means 3 like an image to be formed, and can be appropriately selected according to the purpose. Examples include various exposure devices such as a copying optical system, a rod lens array system, a laser optical system, a liquid crystal shutter optical system, and an LED optical system.
As the light source in the exposure device, it is possible to use all luminescent materials such as a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, a light emitting diode (LED), a semiconductor laser (LD), and an electroluminescence (EL).
In addition, 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. In the present invention, an optical backside system that performs imagewise exposure from the backside of the electrophotographic photosensitive member may be employed.

<Developing means>
The developing unit 6 is not particularly limited and may be appropriately selected depending on the purpose. For example, as long as development can be performed using the toner or developer, there is no particular limitation, and the developing unit 6 is appropriately selected according to the purpose. can do. Among these, it is preferable to have at least a developing device that accommodates the developer and can apply the developer to the electrostatic latent image in a contact or non-contact manner.

  The developing unit may be a dry developing type, a wet developing type, a single color developing unit, or a multicolor developing unit. Also good. For example, a developer having a stirrer that charges the developer by frictional stirring and a rotatable magnet roller is preferable. Further, a one-component development method using a dry toner, a two-component development method, a wet development method using a wet toner, or the like may be used.

  In the developing device, for example, the toner and the carrier are mixed and agitated, and the toner is charged by friction at that time, and held on the surface of the rotating magnet roller in a spiked state to form a magnetic brush. . Since the magnet roller is disposed in the vicinity of the electrophotographic photosensitive member, a part of the toner constituting the magnetic brush formed on the surface of the magnetic roller is part of the electrophotographic photosensitive member by an electric attractive force. Move to the surface. As a result, the electrostatic latent image is developed with the toner to form a visible image with the toner on the surface of the electrophotographic photosensitive member.

<Transfer means>
The transfer means 10 is a means for transferring the visible image to a recording medium. The transfer means 10 directly transfers the visible image from the surface of the electrophotographic photosensitive member to the recording medium, and an intermediate transfer member. There is a method in which a visible image is primarily transferred and then the visible image is secondarily transferred onto a recording medium 9. Either aspect can be used satisfactorily, but the former method (direct transfer) with a small number of transfers is preferred when the adverse effect of transfer increases when the image quality is improved. The transfer can be performed, for example, by charging the electrophotographic photosensitive member using a transfer charger and transferring the visible image to the recording medium 9.
As the transfer means 10, an electrostatic transfer method using a transfer charger, a bias roller, or the like; a mechanical transfer method such as an adhesive transfer method or a pressure transfer method; a magnetic transfer method, or the like can be used.

<Cleaning means>
The cleaning means 15 removes the developer remaining on the electrophotographic photosensitive member. The cleaning means 15 is not particularly limited. However, since the purpose is to remove the developer remaining on the surface of the electrophotographic photosensitive member, a method of placing it in contact with the electrophotographic photosensitive member is preferable. It can be suitably selected from the inside. Examples thereof include a magnetic brush cleaner, an electrostatic brush cleaner, a magnetic roller cleaner, a blade cleaner (cleaning blade), a brush cleaner, a web cleaner, and the like. Among these, a cleaning blade is particularly preferable.
As the cleaning unit 15, a method suitable for removing the residual developer from the electrophotographic photosensitive member may be selected from among the transfer methods described above, and a single method or a plurality of methods may be used together as necessary. .

The cleaning means preferably used in the present invention is composed of a blade member having a rubber material, and cleans the surface of the electrophotographic photosensitive member by bringing the tip ridge portion of the blade member into contact with the electrophotographic photosensitive member. . In addition, it does not restrict | limit especially as a rubber material, A well-known thing can be used.
And the vicinity of the front-end ridgeline part of the said blade member consists of said rubber materials, and the Martens hardness in the vicinity of the front-end | tip ridgeline part of the said blade member is 1.0 N / mm < ² > or more. Details will be described below.

  FIG. 10 shows an example of the cleaning blade in contact with the electrophotographic photosensitive member. FIG. 11 shows an enlarged view of the vicinity of the edge portion of an example of the cleaning blade. FIG. 12 shows an example of cleaning by the cleaning blade. 10 to 12, the cleaning blade 200 includes an edge portion 201 including a tip edge line portion, a blade facing surface 202, a blade facing surface 202, and a blade tip surface 203.

First, the behavior of the cleaning blade in the electrophotographic process will be described.
FIG. 11A shows a state where the edge portion 201 of the cleaning blade 200 is not in contact with the surface of the electrophotographic photosensitive member 210. The strip-shaped cleaning blade 200 has a blade facing surface 202 and a blade tip surface 203 which are adjacent to each other with a right-angled edge portion 201 interposed therebetween. The blade facing surface 202 faces the surface of the electrophotographic photoreceptor 210.
FIG. 11B shows a state in which the edge portion 201 of the cleaning blade 200 is in contact with the surface of the electrophotographic photosensitive member 210. The electrophotographic photosensitive member 210 is moved in a moving direction 220 indicated by an arrow, and the blade tip surface 203 forming the edge portion 201 of the cleaning blade 200 is downstream of the moving direction 220 as the electrophotographic photosensitive member 210 moves. The behavior drawn into Due to this pull-in behavior, the edge portion 201 is greatly deformed to form a wedge-shaped portion 204 at the edge portion 201, the wedge-shaped portion 204 contacts the surface of the electrophotographic photosensitive member 210, and the electrophotographic photosensitive member 210 is moved. Slide relatively. At this time, the blade facing surface 202 is not in contact with the surface of the electrophotographic photoreceptor 210.

A cleaning blade which is generally used is a plate-like structure made of polyurethane rubber of low hardness, Martens hardness in the vicinity of the front edge portion is 0.5N ^/ mm ² ~0.7N / mm 2 and relatively low, FIG. In many cases, the shape (wedge shape) shown in FIG. In such a state, the contact area between the cleaning blade 200 and the electrophotographic photosensitive member 210 increases, and the pressure (so-called contact surface pressure) applied to the electrophotographic photosensitive member 210 by the cleaning blade 200 decreases.

  For this reason, as shown in FIG. 12B, the toner 300 and the external additive (silica, etc.) 310 remaining on the surface of the electrophotographic photosensitive member 210 are easily rubbed out from the cleaning blade 200. Further, since the toner 300 and the external additive 310 are pressed against the surface of the electrophotographic photosensitive member 210 when it is rubbed through, foreign matter adheres to the electrophotographic photosensitive member 210 and surface contamination in the electrophotographic photosensitive member 210 is caused. It will occur.

  On the other hand, when one having a higher Martens hardness than a commonly used cleaning blade is used, the shape (wedge shape) as shown in FIG. And the contact surface pressure between the electrophotographic photosensitive member 210 and the electrophotographic photosensitive member 210 increase. For this reason, as shown in FIG. 12 (a), the toner 300 remaining on the surface of the electrophotographic photosensitive member 210 tends to be easily removed. However, with respect to relatively small particles (external additives such as silica), Although less frequent, a slip-through behavior can occur. By being pressed against the electrophotographic photosensitive member 210 at the time of the rubbing, foreign matter adheres to the surface of the electrophotographic photosensitive member 210.

  On the other hand, in the present invention, by controlling the hardness of the cleaning blade 200, the wedge-shaped portion 204 tends to be small, and the contact surface pressure between the cleaning blade 200 and the electrophotographic photosensitive member 210 is reduced. Can be bigger. This facilitates removal of the toner 300, the external additive 310, and the like remaining on the surface of the electrophotographic photoreceptor 210.

  Furthermore, when the electrophotographic photosensitive member of the present invention is used, the adhesion of external additives such as silica can be reduced as described above, and surface contamination can be suppressed. The cleaning blade 200 of the present invention has a large contact surface pressure, and therefore can remove deposits on the surface of the electrophotographic photoreceptor 210 in a very short time. Therefore, the combination of the electrophotographic photosensitive member and the cleaning blade in the present invention is preferable because the function of maintaining the surface of the electrophotographic photosensitive member can be made extremely high.

As a structure of the cleaning blade in the present invention, for example, a single layer structure as shown in FIG. The cleaning blade 200 shown in FIG. 10 is a strip-shaped blade member, and is held on one end surface of the blade holder.
Next, another example of the cleaning blade in the present invention is shown in FIG. The present invention is not limited to the single layer structure as shown in FIG. 10, but also includes a double layer structure as shown in FIG. The cleaning blade 200 shown in FIG. 13 is a two-layer blade including an edge layer 216 including an edge portion 201 and a backup layer 217, and is manufactured by sequentially superimposing each layer by a circular center molding method. In this case, the edge layer 216 is preferably made of a rubber material.
The cleaning blade in the present invention may be applied with a single layer structure or a laminated structure in accordance with the applied electrophotographic image forming system, and is not particularly limited.

  In FIG. 13, as in FIG. 10, 201 indicates an edge portion including a tip edge line portion, 202 indicates a blade facing surface, and 203 indicates a blade tip surface including an edge portion. The backup layer 217 preferably has a lower hardness than the edge layer 216 from the viewpoint of durability.

In the present invention, the cleaning blade 200 may have a single layer structure or a laminated structure having a Martens hardness of 1.0 N / mm ² or more in the following (a) or (b). In addition, the following A1, A2, B1, and B21 indicate symbols in FIGS.
(A) A1 or B1 in the vicinity of the tip ridge line portion of the blade facing surface 202
(B) A2 or B21 in the vicinity of the tip ridge line portion of the blade tip surface 203 (B21 indicates a portion made of the edge layer 216 in the blade tip surface 203)
In the present invention, the requirement that the Martens hardness is 1.0 N / mm ² or more may satisfy at least one of A1, B1, A2, and B21.

In the present invention, in order to enhance further the surface retention properties of the electrophotographic photosensitive member 210, the Martens hardness is good when used as a 1.0 N / mm ² or more, and used as a 1.5 N / mm ² or more above It is further preferable from the viewpoint of the mechanism. At this time, the upper limit value of the Martens hardness is not particularly limited. However, if it is larger than 7.0 N / mm ^2, the cleaning blade may be chipped in a low temperature environment, so 7.0 N / mm ² or less is preferable.

As a method for measuring the Martens hardness, a known method can be used, and any apparatus that can simultaneously measure the amount of indenter movement and the indenter load when pressing the diamond indenter against the object to be measured can be used. For example, Fischer Scope H-100 and Fischer Scope HM2000 commercially available from Fisher Instruments, and a dynamic micro hardness tester DUH-211 commercially available from SHIMAZU are listed.
Although it depends on the measurement conditions, the measurement is easily affected by the lower layer (in the present invention, the conductive support 31 and the charge generation layer 33 in the electrophotographic photosensitive member 210). . Specifically, the amount of displacement of the diamond indenter is preferably 1/6 or less, more preferably 1/10 or less of the film thickness of the object to be measured.

  The method of controlling the Martens hardness value to a predetermined value is not particularly limited, but can be performed by appropriately changing the material used for the cleaning blade.

<Other means>
The other means is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include a fixing means, a static elimination means, a recycling means, a control means, and a separation means.

-Fixing means-
The fixing unit is not particularly limited and may be appropriately selected depending on the intended purpose. However, a known heating and pressing unit is preferable. Examples of the heating and pressing unit include a combination of a heating roller and a pressing roller, a combination of a heating roller, a pressing roller, and an endless belt. The heating in the heating and pressing unit is usually 80 ° C. to 200 ° C. ° C is preferred. The fixing may be performed, for example, every time the toner of each color is transferred to the recording medium, or may be performed simultaneously in a state where the toner of each color is stacked.

-Static elimination means-
In order to remove the latent image on the electrophotographic photosensitive member 1, the charge eliminating unit 13 may be used.
The neutralization means 13 is not particularly limited as long as it can apply a neutralization bias to the electrophotographic photosensitive member, and can be appropriately selected from known neutralizers. For example, a neutralization lamp, a neutralization charger, etc. Preferably mentioned.

-Recycling means-
Developer collecting means 14 for recycling the developer attached to the electrophotographic photosensitive member may be used as the recycling means.
There is no restriction | limiting in particular as said recycling means, A well-known conveyance means etc. are mentioned.

-Control means-
The control means is not particularly limited as long as the movement of each means can be controlled, and can be appropriately selected according to the purpose. Examples thereof include devices such as sequencers and computers.

-Separation means-
A separation charger 11 and a separation claw 12 may be used as means for separating the recording medium 9 from the electrophotographic photosensitive member 1. As other separation means, electrostatic adsorption induction separation, side end belt separation, tip grip conveyance, curvature separation, and the like can be used.

(Process cartridge)
The process cartridge of the present invention is a process cartridge provided in the image forming apparatus of the present invention, and includes at least the electrophotographic photosensitive member, and the charging unit, the latent image forming unit, the developing unit, the transfer unit, and the like. It has at least one means selected from the group consisting of the cleaning means, and is detachable from the image forming apparatus of the present invention. And you may have other means as needed.

  An example of the process cartridge of the present invention is shown in FIG. In FIG. 14, an electrophotographic photosensitive member 101, a charging unit 102, a developing unit 104, a transfer unit 106, and a cleaning unit 107 are illustrated. As the electrophotographic photosensitive member 101 rotates in the direction of the arrow, an electrostatic latent image corresponding to the exposure image is formed on the surface by charging by the charging unit 102 and exposure by the exposure unit 103. The electrostatic latent image is developed with a developer by the developing unit 104 to form a visible image (toner image). The toner development is transferred to the recording medium 105 by the transfer unit 106 and printed out. Next, the surface of the electrophotographic photosensitive member after the image transfer is cleaned by the cleaning unit 107 and further neutralized by a neutralizing unit (not shown), and the above operation is repeated again.

(Image forming method)
The image forming method of the present invention comprises a charging step for charging the surface of an electrophotographic photosensitive member with a charging means, a latent image forming step for forming an electrostatic latent image on the electrophotographic photosensitive member, and development on the electrostatic latent image. A developing process for attaching a developer to form a visible image, a transfer process for transferring the visible image to a recording medium, and a cleaning process for removing the developer attached to the surface of the electrophotographic photosensitive member. The electrophotographic photoreceptor contains at least a polyester resin in the outermost surface layer in the thickness direction, and the discharge frequency of the AC component of the charging means is 7.5 times or more the linear velocity of the electrophotographic photoreceptor. Before and after applying a discharge charge of 100 μC / mm ^{2 to} the electrophotographic photoreceptor using the charging means, the surface of the electrophotographic photoreceptor and the probe of the silicon cantilever obtained by the following measurement method The average adhesive force variation is greater than 0 nN and 5 nN or less.

  Moreover, the measuring method of average adhesion force fluctuation | variation is performed as follows. Before the electrophotographic photosensitive member is charged by the charging means, a probe of a silicon cantilever is brought into contact with the surface of the electrophotographic photosensitive member, and the amount of deflection of the silicon cantilever when separated is measured, The value obtained by multiplying the amount of deflection by the spring constant of the silicon cantilever is defined as the adhesive force, and the arithmetic average of the adhesive force measured at a plurality of locations on the electrophotographic photosensitive member is defined as the average adhesive force before charging. Similarly, after the electrophotographic photosensitive member is charged by the charging means, the average adhesive force is obtained, and the value obtained by subtracting the average adhesive force before charging from the average adhesive force after charging is the surface of the electrophotographic photosensitive member and silicon. Change in average adhesion force with the cantilever probe.

  Hereinafter, the present invention will be described with reference to examples and comparative examples. In addition, this invention is not limited to the Example illustrated here. Further, hereinafter, “Mv” means the viscosity average molecular weight.

<Example 1>
By coating and drying an undercoat layer coating solution, a charge generation layer coating solution, and a charge transport layer coating solution in the following composition on a φ40 mm aluminum cylinder in sequence, an undercoat layer of 3.5 μm A 0.2 μm charge generation layer and a 32 μm charge transport layer were formed.

[Coating liquid for undercoat layer]
・ Alkyd resin 12 parts by weight (Beckosol 1307-60-EL, manufactured by Dainippon Ink & Chemicals, Inc.)
・ 8 parts by weight of melamine resin (Super Becamine G-821-60, manufactured by Dainippon Ink & Chemicals, Inc.)
・ Titanium oxide (CR-EL, manufactured by Ishihara Sangyo Co., Ltd.) 80 parts by weight ・ Methyl ethyl ketone 250 parts by weight

[Coating liquid for charge generation layer]
-2.5 parts by weight of a bisazo pigment pigment of the following structural formula (1)-0.5 parts by weight of polyvinyl butyral (XYHL, manufactured by UCC)-200 parts by weight of cyclohexanone-80 parts by weight of methyl ethyl ketone

[Coating liquid for charge transport layer]
-Polymer charge transport material (Mv62,000) of the following structural formula (2) 10 parts by weight-Charge transport compound of the following structural formula (3) 2 parts by weight-Tetrahydrofuran 58.6 parts by weight-Tetrahydrofuran of 1% silicone oil 1 part by weight of solution (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.)

<Example 2>
An electrophotographic photoreceptor was produced in the same manner as in Example 1 except that the charge transport layer coating solution in Example 1 was changed to the following.
[Coating liquid for charge transport layer]
-10 parts by weight of the polymer charge transport material (Mv 62,000) of the above structural formula (2)-4 parts by weight of the charge transporting compound of the above structural formula (3)-68.4 parts by weight of tetrahydrofuran-Tetrahydrofuran of 1% silicone oil 1 part by weight of solution (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.)

<Example 3>
An electrophotographic photoreceptor was produced in the same manner as in Example 1 except that the charge transport layer coating solution in Example 1 was changed to the following.
[Coating liquid for charge transport layer]
-10 parts by weight of the polymer charge transporting material (Mv 62,000) of the above structural formula (2)-6 parts by weight of the charge transporting compound of the above structural formula (3)-78.1 parts by weight of tetrahydrofuran-Tetrahydrofuran of 1% silicone oil 1 part by weight of solution (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.)

<Examples 4 to 6>
Except that the viscosity average molecular weight Mv of the polymeric charge transport material of the above structural formula (2) used in the coating liquid for charge transport layer of Examples 1 to 3 is 81000, it is the same as in Examples 1 to 3. An electrophotographic photosensitive member was produced.

<Examples 7 to 9>
The polymer charge transport material of the above structural formula (2) used in the coating liquid for charge transport layer of Examples 1 to 3 is changed to the polymer charge transport material of the following structural formula (4), and the viscosity average molecular weight is changed. An electrophotographic photosensitive member was produced in the same manner as in Examples 1 to 3, except that Mv was changed to 65500.

<Examples 10 to 12>
Example except that the polymer charge transport material of the above structural formula (2) used in the charge transport layer coating liquids of Examples 1 to 3 was changed to bisphenol Z polycarbonate having a viscosity average molecular weight Mv of 50,000. An electrophotographic photosensitive member was produced in the same manner as in 1-3.

<Examples 13 to 15>
The polymer charge transport material of the above structural formula (2) used in the charge transport layer coating liquids of Examples 1 to 3 is represented by the following structural formula (5) having a viscosity average molecular weight Mv of 53,000. An electrophotographic photosensitive member was produced in the same manner as in Examples 1 to 3 except that the polyarylate was used.

<Example 16>
By coating and drying an undercoat layer coating solution, a charge generation layer coating solution, and a charge transport layer coating solution in the following composition on a φ40 mm aluminum cylinder in sequence, an undercoat layer of 3.5 μm A 0.2 μm charge generation layer and a 32 μm charge transport layer were formed.
[Coating liquid for undercoat layer]
・ Alkyd resin 12 parts by weight (Beckosol 1307-60-EL, manufactured by Dainippon Ink & Chemicals, Inc.)
・ 8 parts by weight of melamine resin (Super Becamine G-821-60, manufactured by Dainippon Ink & Chemicals, Inc.)
・ Titanium oxide (CR-EL, manufactured by Ishihara Sangyo Co., Ltd.) 80 parts by weight ・ Methyl ethyl ketone 250 parts by weight

[Coating liquid for charge generation layer]
-2.5 parts by weight of the bisazo pigment of the above structural formula (1)-0.5 parts by weight of polyvinyl butyral (XYHL, manufactured by UCC)-200 parts by weight of cyclohexanone-80 parts by weight of methyl ethyl ketone

[Coating liquid for charge transport layer]
-10 parts by weight of bisphenol Z polycarbonate (Panlite TS-2050, manufactured by Teijin Chemicals Ltd.)
-7 parts by weight of charge transporting compound of the structural formula (3)-83 parts by weight of tetrahydrofuran-1 part by weight of tetrahydrofuran solution of 1% silicone oil (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.)

  Next, a surface layer coating solution having the following composition is applied onto the laminate comprising the conductive support 31 / undercoat layer 32 / charge generation layer 33 / charge transport layer 34 using a spray coating method, and then 150 ° C. and 20 ° C. A surface layer 35 having a thickness of 5 μm was formed by performing a drying process for 5 minutes. As a result, an electrophotographic photosensitive member comprising the conductive support 31 / undercoat layer 32 / charge generation layer 33 / charge transport layer 34 / surface layer 35 was obtained.

[Coating liquid for surface layer]
-5.8 parts by weight of the polymer charge transport material (Mv 62,000) of the structural formula (2)-1.2 parts by weight of the charge transport compound of the structural formula (3)-Alumina fine particles (AA03, manufactured by Sumitomo Chemical Co., Ltd.) 3 parts by weight ・ 170 parts by weight of tetrahydrofuran ・ 50 parts by weight of cyclohexanone

<Example 17>
An electrophotographic photosensitive member was produced in the same manner as in Example 16 except that the surface layer coating solution of Example 16 was changed to the following.
[Coating liquid for surface layer]
-5 parts by weight of the polymer charge transport material (Mv 62,000) of the structural formula (2)-2 parts by weight of the charge transport compound of the structural formula (3)-3 parts by weight of alumina fine particles (AA03, manufactured by Sumitomo Chemical Co., Ltd.)・ 170 parts by weight of tetrahydrofuran ・ 50 parts by weight of cyclohexanone

<Example 18>
An electrophotographic photosensitive member was produced in the same manner as in Example 16 except that the surface layer coating solution of Example 16 was changed to the following.
[Coating liquid for surface layer]
-4.4 parts by weight of the polymer charge transport material (Mv 62,000) of the structural formula (2)-2.6 parts by weight of the charge transport compound of the structural formula (3)-Alumina fine particles (AA03, manufactured by Sumitomo Chemical Co., Ltd.) 3 parts by weight ・ 170 parts by weight of tetrahydrofuran ・ 50 parts by weight of cyclohexanone

<Examples 19 to 21>
Examples 16 to 18 except that the polymer charge transport material of the above structural formula (2) used in the surface layer coating solutions of Examples 16 to 18 was changed to bisphenol Z polycarbonate having a viscosity average molecular weight Mv of 50,000. In the same manner as in Example 18, an electrophotographic photosensitive member was produced.

<Comparative Example 1>
An electrophotographic photoreceptor was produced in the same manner as in Example 1 except that the charge transport layer coating solution in Example 1 was changed to the following.
[Coating liquid for charge transport layer]
-10 parts by weight of the polymer charge transport material (Mv 62,000) of the structural formula (2)-8 parts by weight of the charge transporting compound of the structural formula (3)-87.9 parts by weight of tetrahydrofuran-Tetrahydrofuran of 1% silicone oil 1 part by weight of solution (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.)

<Comparative example 2>
An electrophotographic photosensitive member was produced in the same manner as in Example 7 except that the charge transport layer coating solution in Example 7 was changed to the following.
[Coating liquid for charge transport layer]
-10 parts by weight of the polymer charge transport material (Mv65,500) of the structural formula (4)-8 parts by weight of the charge transporting compound of the structural formula (3)-87.9 parts by weight of tetrahydrofuran-Tetrahydrofuran of 1% silicone oil 1 part by weight of solution (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.)

<Comparative Example 3>
An electrophotographic photoreceptor was produced in the same manner as in Example 10 except that the charge transport layer coating solution in Example 10 was changed to the following.
[Coating liquid for charge transport layer]
-10 parts by weight of bisphenol Z polycarbonate (Mv 50,000)-8 parts by weight of the charge transporting compound of the above structural formula (3)-87.9 parts by weight of tetrahydrofuran-1 part by weight of tetrahydrofuran solution of 1% silicone oil (KF50-100CS, (Shin-Etsu Chemical Co., Ltd.)

<Comparative example 4>
An electrophotographic photosensitive member was produced in the same manner as in Example 13, except that the charge transport layer coating solution in Example 13 was changed to the following.
[Coating liquid for charge transport layer]
-10 parts by weight of the polyarylate (Mv53,000) of the above structural formula (5)-8 parts by weight of the charge transporting compound of the above structural formula (3)-87.9 parts by weight of tetrahydrofuran-1% by weight of a tetrahydrofuran solution of 1% silicone oil (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.)

<Comparative Example 5>
An electrophotographic photosensitive member was produced in the same manner as in Example 16 except that the surface layer coating solution of Example 16 was changed to the following.
[Coating liquid for surface layer]
-3.9 parts by weight of the polymer charge transport material (Mv 62,000) of the structural formula (2)-3.1 parts by weight of the charge transport compound of the structural formula (3)-Alumina fine particles (AA03, manufactured by Sumitomo Chemical Co., Ltd.) 3 parts by weight ・ 170 parts by weight of tetrahydrofuran ・ 50 parts by weight of cyclohexanone

<Comparative Example 6>
An electrophotographic photosensitive member was produced in the same manner as in Example 16 except that the surface layer coating solution of Example 16 was changed to the following.
[Coating liquid for surface layer]
-Bisphenol Z polycarbonate (Mv50,000) 3.9 parts by weight-Charge transporting compound of the above structural formula (3) 3.1 parts by weight-Alumina fine particles (AA03, manufactured by Sumitomo Chemical Co., Ltd.) 3 parts by weight-Tetrahydrofuran 170 parts by weight・ Cyclohexanone 50 parts by weight

<Comparative Examples 7-9>
Example except that the polymer charge transport material of the above structural formula (2) used in the coating liquid for charge transport layer of Examples 1 to 3 was changed to bisphenol Z polycarbonate having a viscosity average molecular weight Mv = 40,000. An electrophotographic photosensitive member was produced in the same manner as in 1-3.

<Comparative Example 10>
An electrophotographic photoreceptor was prepared in the same manner as in Comparative Example 3 except that the viscosity average molecular weight of the bisphenol Z polycarbonate used in the charge transport layer coating solution of Comparative Example 3 was changed to bisphenol Z polycarbonate having Mv = 40,000. Produced.

<Comparative Examples 11-13>
The same as in Examples 1 to 3 except that the viscosity average molecular weight Mv of the polymer charge transport material of the above structural formula (2) used in the coating liquid for charge transport layer in Examples 1 to 3 was set to 42,500. Thus, an electrophotographic photosensitive member was produced.

<Comparative example 14>
Electrophotography as in Comparative Example 1 except that the viscosity average molecular weight Mv of the polymeric charge transport material of the structural formula (2) used in the coating liquid for charge transport layer of Comparative Example 1 is 42,500. A photoconductor was prepared.

<Comparative Examples 15-17>
The same as in Examples 16 to 18 except that the viscosity average molecular weight Mv of the polymeric charge transport material of the above structural formula (2) used in the charge transport layer coating solutions of Examples 16 to 18 was set to 42,500. Thus, an electrophotographic photosensitive member was produced.

<Comparative Example 18>
An electrophotographic photoreceptor in the same manner as in Comparative Example 5 except that the viscosity average molecular weight Mv of the polymeric charge transport material of the above structural formula (2) used in the surface layer coating solution of Comparative Example 5 is 42,500. Was made.

<Comparative Examples 19-21>
Electrophotographic photosensitivity in the same manner as in Examples 16 to 18 except that the viscosity average molecular weight of the bisphenol Z polycarbonate used in the surface layer coating solutions of Examples 19 to 21 was changed to bisphenol Z polycarbonate having an Mv of 40,000. The body was made.

<Comparative Example 22>
An electrophotographic photosensitive member was prepared in the same manner as in Comparative Example 5 except that the viscosity average molecular weight of the bisphenol Z polycarbonate used in the charge transport layer coating solution of Comparative Example 5 was changed to bisphenol Z polycarbonate having an Mv of 40,000. Produced.

  Table 1 shows the formulations of Examples and Comparative Examples.

(Evaluation)
The following tests were carried out on the electrophotographic photoreceptors produced in Examples 1 to 21 and Comparative Examples 1 to 22.
<< Measurement of in-flight potential >>
The process cartridge unit of Imagio MPC5000 manufactured by Ricoh Co., Ltd. was changed to a process cartridge unit that was modified so that the surface potential meter was attached to the developing unit and the surface potential of the electrophotographic photosensitive member in the image forming apparatus could be measured. The electrophotographic photoreceptors obtained in 1-21 and Comparative Examples 1-22 were attached. Charging conditions were set so that the surface potential in the 0% chart (dark part potential) was −650 V, and the 100% chart (exposed part potential) was measured. The obtained results are shown in Table 2.

  In Examples 1, 4, 7, 10, 11, 13, 14, and 19, since the charge transport material content ratio of the charge transport layer 34 of the electrophotographic photosensitive member is low, the exposed portion potential is obtained in the other examples. Although a tendency to be higher than that of the obtained electrophotographic photosensitive member was observed, there was no problem in actual use, and a good image was obtained. In addition, when the electrophotographic photoreceptors of Examples other than the above Examples were used, the exposed area potential was sufficiently low, and similarly good images were obtained.

<< Measurement of Adhesive Force Between Electrophotographic Photoreceptor Surface and Cantilever Probe and Adhesion of Foreign Objects on Image Surface of Electrophotographic Photoreceptor After Image Output >>
A product obtained by removing the lubricant application mechanism (metal soap and application brush / application blade) from the process cartridge unit of Imagio MPC5000 manufactured by Ricoh was prepared, and the process cartridge unit was obtained in Examples 1-21 and Comparative Examples 1-22. An electrophotographic photoreceptor was attached. With respect to this, the average adhesion force between the surface of the electrophotographic photosensitive member and the cantilever probe was measured under the following adhesion force measurement conditions.

-Measurement conditions for average adhesion force-
In the measurement of the average adhesive force, SN-FF01 (having a spring constant of 0.38) manufactured by Hitachi High-Tech Science Co., Ltd. was used as the cantilever, and the measurement frequency was 1 Hz. On the surface of the electrophotographic photosensitive member, an area of 10 μm × 10 μm was set, and the area was provided at 8 points in the rotation direction of the electrophotographic photosensitive member and 8 points in the axial direction, for a total of 64 points. The adhesion force was measured at each measurement point, and the same measurement was performed for a total of five regions, and a total of about 340 measurements were performed. The average adhesion force between the surface of the electrophotographic photosensitive member and the cantilever probe was determined by calculating the arithmetic average of the obtained measured values.

Next, the surface of the electrophotographic photosensitive member was charged by the charging means shown in FIG. 9 with the linear velocity of the electrophotographic photosensitive member at the time of image output being set at 200 mm / sec and the AC component frequency in charging being 1500 Hz. By this charging means, a discharge charge of 100 μC / mm ² was applied to the electrophotographic photosensitive member, and a charging process was performed.

Next, a 5% density image (about 2800 sheets) to which a discharge charge of 100 μC / mm ² was applied was output. The cleaning blade used in this evaluation has a single layer structure shown in FIG. 10 and is made of urethane rubber. The Martens hardness was measured at the location A1 of the cleaning blade, and the measured Martens hardness was 0.60 N / mm ² . Here, the Martens hardness was measured using a Fischer scope HM-2000 manufactured by Fischer Instruments. The measurement conditions are shown below.

<Elastic power measurement conditions>
・ Measurement device: HM2000 manufactured by Fischerscope
・ Measurement environment: 23 ° C, 50% Rh
Measurement mode: dF / dt = const
・ Maximum load: 1N
・ Loading / unloading time: 10 sec each
・ Creep time: 5 sec

A 100% chart was output using the electrophotographic photoreceptor after image output obtained here, and the image quality was evaluated. In the evaluation of the image quality, the surface of the electrophotographic photosensitive member was observed with a microscope, and the presence or absence of a deposit on the surface of the electrophotographic photosensitive member was evaluated to evaluate the presence or absence of a blank image. For the evaluation of image quality, an image rank according to the following criteria was obtained.
-Image quality evaluation criteria-
Image rank 5: No abnormality Image rank 4: Slightly blank images Image rank 3: Partially blank images Image rank 2: Blank images on the entire surface Image rank 1: Streaky image abnormalities on the entire surface

Further, the average adhesion force between the electrophotographic photosensitive member and the cantilever after outputting an image was measured under the same conditions as before charging the electrophotographic photosensitive member. A value obtained by subtracting the average adhesive force before charging from the average adhesive force after charging was determined, and the average adhesive force fluctuation between the surface of the electrophotographic photosensitive member and the cantilever was determined.
The obtained evaluation results are shown in Table 3.

  In any of Examples 1 to 21, no abnormality is seen in the output image before and after the sheet passing, and it is understood that good image quality is maintained. Further, there is no significant variation in the adhesion force between the outermost surface of the electrophotographic photosensitive member and the silicon cantilever probe. Further, as a result of observing the surface of the electrophotographic photoreceptor after image output with a microscope, no adhesion of foreign matter was observed on the surface of the electrophotographic photoreceptor. From this, it can be seen that the electrophotographic photoreceptors having the configurations of Examples 1 to 21 have extremely high surface maintainability. In Examples 4 to 6, a binder material made of a polymer charge transport material having a relatively high molecular weight is used. However, the increase in adhesion is very small, and the surface property is maintained by image output. You can see that

  On the other hand, in the electrophotographic photoreceptor obtained in the comparative example, the output image quality is deteriorated before and after the paper is passed. In particular, it can be seen that large image quality deterioration is likely to occur in Comparative Examples 7 to 22 in the case where the molecular weight of the binder material is reduced as compared with Comparative Examples 1 to 6 in which a large amount of the low molecular charge transport material is contained. In addition, the adhesive force variation between the surface of the electrophotographic photosensitive member obtained in the comparative example and the silicon cantilever tends to increase as the image quality decreases greatly. The electrophotographic photosensitive member obtained in the comparative example It can be seen that the surface maintainability is inferior to the electrophotographic photoreceptor obtained in the examples.

Next, using the electrophotographic photoreceptors of Examples 1 to 15, the Martens hardness of the cleaning blade was 0.60 N / mm ² (Blade 1), 1.06 N / mm ² (Blade 2), 1.97 N / mm ^2. (Blade 3) is used, except that the number of output sheets is changed and the number of output sheets is changed in the same manner as described above, 15000 sheets of 5% density images are output in total, and 100% chart is output after output. Evaluated. In addition, the surface of the electrophotographic photosensitive member used for running was observed using a microscope (200 times) to evaluate the degree of foreign matter adhesion on the surface. Evaluation criteria for image quality and evaluation criteria for the degree of adhesion on the surface of the electrophotographic photosensitive member are shown below.
As for the Martens hardness here, the location A1 in the cleaning blade having a single-layer structure shown in FIG. 10 was measured in the same manner as described above.

-Image quality evaluation criteria-
Image rank 5: No abnormality Image rank 4: Slightly blank images Image rank 3: Partially blank images Image rank 2: Blank images on the entire surface Image rank 1: Streaky image abnormality on the entire surface- Evaluation criteria for foreign matter adhesion-
Adhesion rank 5: No foreign matter adherence Adhesion rank 4: Slightly foreign matter adherence Adhesion rank 3: Small area foreign matter adhering part Adhesion rank 2: Large area foreign matter adherence Adhesion rank 1: Foreign matter adheres to the entire surface

  The obtained evaluation results are shown in Table 4.

  As in the previous experimental results, it can be seen that the electrophotographic photoreceptors of Examples 1 to 15 maintain good image quality even after running. However, in the electrophotographic photoreceptors of Examples 9, 12, and 15 in which the average adhesive force variation between the outermost surface of the electrophotographic photoreceptor and the silicon cantilever probe is relatively large, the image rank is slightly lowered in the blade 1 ( Evaluation result “4” in Table 4). However, compared to Comparative Examples 1, 2, and 15 in which the image rank is “4” in Table 3, good image quality is obtained, and it can be said that there is no problem in actual use.

When the surface of the electrophotographic photosensitive member is observed with a microscope and the foreign matter adhesion rank is evaluated, when the Martens hardness of the cleaning blade is relatively low (0.60 N / mm ² , blade 1), the electrophotographic photosensitive member is Adherence of foreign substances thought to be derived from the toner component was observed on the surface.

  The results of the evaluation of image quality and the evaluation of adhesion of foreign matter are all phenomena in electrophotographic photosensitive members with relatively large fluctuations in average adhesion force, so the validity of the physical parameters in the present invention is clear. It is thought that it became. On the other hand, when the blade 2 and the blade 3 having a high Martens hardness of the cleaning blade are used, no adhesion of foreign matters is observed on the surface of the electrophotographic photosensitive member, and an extremely clean surface of the electrophotographic photosensitive member is maintained. As a result, it has been clarified that a clean state can be maintained with no surface contamination of the electrophotographic photosensitive member by combination with a cleaning blade having a high Martens hardness.

  From the above results, the electrophotographic photosensitive member of the present invention has excellent charge transportability and surface maintenance, maintains extremely high image quality even when running for a long time, and produces images with few defects. It was found to be an electrophotographic photoreceptor capable of outputting.

DESCRIPTION OF SYMBOLS 1,210 Electrophotographic photosensitive member 3 Charging means 5 Exposure means 6 Developing means 7 Charger before transfer 8 Transfer roller 10 Transfer means 11 Separation charger 12 Separation claw 13 Electric discharge means 14 Developer recovery means 15 Cleaning blade 16 Power supply 21 Charging roller 21a Shaft Portion 21b roller portion 22 spacer 24 gap 25 pressure spring 26 image forming region 27 non-image forming region 31 conductive support 32 subbing layer 33 charge generation layer 34 charge transport layer 35 surface layer 36 single layer type photosensitive layer 37 intermediate layer 40 Cantilever 41 Probe 42 Deflection amount 200 Cleaning blade 201 Edge portion 202 Blade facing surface 203 Blade tip surface 204 Wedge shape portion 220 Moving direction 300 Toner 310 External additive

JP-A-5-181299 JP 2002-6526 A JP 2002-82465 A JP 2000-284514 A JP 2001-194413 A JP 2013-109297 A JP 2012-108487 A JP 2012-247749 A JP 2013-142734 A JP, 2014-026149, A JP 2002-196516 A Japanese Patent No. 3927930 JP 2010-151894 A JP 2011-053689 A JP 2011-186308 A

KONICA Technology Report Vol. 13 (2000) Journal of Imaging Science 32: 205-210 (1988)

Claims (5)

At least an electrophotographic photoreceptor,
Charging means for charging the surface of the electrophotographic photosensitive member;
Latent image forming means for forming an electrostatic latent image on the electrophotographic photosensitive member;
Developing means for attaching a developer to the electrostatic latent image to form a visible image;
Transfer means for transferring the visible image to a recording medium;
Cleaning means for removing the developer attached to the surface of the electrophotographic photosensitive member,
The electrophotographic photoreceptor contains at least a polycarbonate resin or a polyarylate resin in the outermost layer in the thickness direction,
When the discharge frequency of the AC component of the charging means is 7.5 times the linear velocity of the electrophotographic photosensitive member, a discharge charge of 100 μC / mm ² is applied to the electrophotographic photosensitive member using the charging means. Before and after, the average adhesion fluctuation, which is a value obtained by subtracting the average adhesion before charging from the average adhesion after charging determined by the probe of the surface of the electrophotographic photosensitive member and the silicon cantilever, is greater than 0 nN and not more than 5 nN. With
The cleaning means is composed of a blade member having a rubber material, and the tip ridge line portion of the blade member is brought into contact with the electrophotographic photosensitive member to clean the surface of the electrophotographic photosensitive member.
The vicinity of the tip ridge line portion of the blade member is made of the rubber material,
The image forming apparatus Martens hardness in the vicinity of the front edge portion of the blade member and wherein the at 1.0 N / mm ² or more 7.0 N / mm ² or less. The outermost layer in the thickness direction may further contain a low molecular charge transport material ,
2. The image formation according to claim 1, wherein a content ratio of the low-molecular charge transporting material to the polycarbonate resin or the polyarylate resin is 60 parts by weight or less with respect to 100 parts by weight of the polycarbonate resin or the polyarylate resin. apparatus. The image forming apparatus according to claim 1, wherein the polycarbonate resin or the polyarylate resin has a viscosity average molecular weight (Mv) of 50,000 or more. A process cartridge provided in the image forming apparatus according to any one of claims 1 to 3,
Having at least the electrophotographic photoreceptor, and at least one means selected from the group consisting of the charging means, the latent image forming means, the developing means, the transfer means, and the cleaning means,
A process cartridge which is detachable from the image forming apparatus. A charging step of charging the surface of the electrophotographic photosensitive member with a charging means;
A latent image forming step of forming an electrostatic latent image on the electrophotographic photosensitive member;
A developing step of attaching a developer to the electrostatic latent image to form a visible image;
A transfer step of transferring the visible image to a recording medium;
A cleaning step of removing a developer attached to the surface of the electrophotographic photosensitive member,
The electrophotographic photoreceptor contains at least a polycarbonate resin or a polyarylate resin in the outermost layer in the thickness direction,
When the discharge frequency of the AC component of the charging means is 7.5 times the linear velocity of the electrophotographic photosensitive member, a discharge charge of 100 μC / mm ² is applied to the electrophotographic photosensitive member using the charging means. Before and after, the average adhesion fluctuation, which is a value obtained by subtracting the average adhesion before charging from the average adhesion after charging determined by the probe of the surface of the electrophotographic photosensitive member and the silicon cantilever, is greater than 0 nN and not more than 5 nN. With
The cleaning step is performed using a cleaning unit, and the cleaning unit is configured by a blade member having a rubber material, and the edge of the blade member is brought into contact with the electrophotographic photosensitive member to clean the surface of the electrophotographic photosensitive member. Is what
The vicinity of the tip ridge line portion of the blade member is made of the rubber material,
Image forming method, wherein the Martens hardness in the vicinity of the front edge portion of the blade member is 1.0 N / mm ² or more 7.0 N / mm ² or less.

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