Electrophotographic photosensitive member, process cartridge, and electrophotographic apparatus

Abstract

In order to solve the problem of providing an electrophotographic photosensitive member that improves durability by suppressing desorption of particles from a surface layer, while improving transferability by controlling a distance between particles of the surface layer and reducing an adhesive force of a toner, the following electrophotographic photosensitive member is provided. Namely, the electrophotographic photosensitive member according to the present invention is characterized in that: when a convex portion derived from a particle PAA and having a height in the range of 10-300 nm is defined as a convex portion CA, the convex portion CA is located on the surface of the surface layer; when the surface layer is viewed from above, the average value of the distances between the centers of gravity of the protrusions CA is 150-500 nm, and the standard deviation of the distances between the centers of gravity of the protrusions CA is 250 nm or less; and when the surface layer is viewed from above, when S1 represents an area occupied by the particles in the surface of the surface layer and S2 represents an area not occupied by the particles, S1 / (S1 + S2) is 0.70-1.00.

Description

Technical Field

[0001] The present invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus each including the electrophotographic photosensitive member. Background Art

[0002] In recent years, there has been a need to extend the life of an electrophotographic photosensitive member to be installed in an electrophotographic apparatus and to improve the image quality in the case of its repeated use, and an improvement in the mechanical durability of the surface layer of the electrophotographic photosensitive member has been required. Further, in an electrophotographic apparatus, there is a transfer step including, after developing an exposed latent image on the electrophotographic photosensitive member with toner, applying a predetermined transfer bias voltage to the toner to transfer the toner from the electrophotographic photosensitive member through an intermediate transfer member to a transfer material such as paper. In the transfer step, it is required to effectively transfer the toner developed on the surface of the electrophotographic photosensitive member to the intermediate transfer member or the transfer material such as paper without leaving too much toner on the surface of the electrophotographic photosensitive member. Therefore, a significant reduction in the adhesion force of the toner to the surface layer of the electrophotographic photosensitive member greatly contributes to reducing the residual toner. Further, a reduction in the untransferred residual toner enables omission of a cleaning device in a process cartridge of the electrophotographic apparatus and contributes to miniaturization of the electrophotographic apparatus.

[0003] A reduction in the adhesiveness between the toner and the surface layer of the electrophotographic photosensitive member reduces the transfer bias voltage to be applied in the transfer step, and thus space for a high-voltage power supply for applying a high transfer bias voltage can be saved in the electrophotographic apparatus. Further, scattering of the toner on the transfer material due to discharge caused by the high transfer bias voltage is suppressed, and the image quality can be improved. Two types of adhesion forces, non-electrostatic adhesion force and electrostatic adhesion force, greatly contribute to the adhesiveness between the toner and the surface layer of the electrophotographic photosensitive member in the transfer step. By imparting a shape to the surface of the surface layer of the electrophotographic photosensitive member to reduce the contact area with the toner so that the toner and the surface of the electrophotographic photosensitive member are in point contact with each other as much as possible, the non-electrostatic adhesion force can be reduced. Further, by causing the toner to roll or rotate in a toner layer sandwiched between the surface layer of the electrophotographic photosensitive member and the transfer material to reduce the image force caused by the surface charge of the toner, the electrostatic adhesion force can be reduced. There are several methods for imparting a shape to the surface of the surface layer of the electrophotographic photosensitive member, and as one of these methods, a method including introducing particles and a binder resin into the surface layer of the electrophotographic photosensitive member to form protrusions derived from the particles on the surface of the surface layer of the electrophotographic photosensitive member has been proposed so far.

[0004] In Patent Document 1, a technique is described that includes introducing conductive titanium oxide particles into a protective layer of an electrophotographic photosensitive member to improve cleanability and maintain stable potential characteristics even in a harsh environment.

[0005] In Patent Document 2, a technique is described that includes controlling the shape of protrusions on the surface of a toner and introducing an inorganic filler into the outermost layer of an electrophotographic photosensitive member to improve cleanability.

[0006] In Patent Document 3, a technique is described that includes causing conductive particles to exist near insulating particles in a protective layer of an electrophotographic photosensitive member to improve its abrasion resistance and suppress the potential rise in its exposed portion.

[0007] In Patent Document 4, a technique is described that includes introducing tin oxide and silica particles treated with a specific surface treatment agent into a protective layer of an electrophotographic photosensitive member to increase the surface hardness of the protective layer, thereby improving its abrasion resistance and flaw resistance.

[0008] [Citation List]

[0009] [Patent Document]

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-229495

[0011] Patent Document 2: Japanese Patent Application Laid-Open No. 2020-071423

[0012] Patent Document 3: Japanese Patent Application Laid-Open No. 2013-195707

[0013] Patent Document 4: Japanese Patent Application Laid-Open No. 2014-002364 Summary of the Invention

[0014] Problems to be Solved by the Invention

[0015] However, research conducted by the inventors of the present invention has found that in each of the electrophotographic photosensitive members described in Patent Documents 1 to 4, the contact area between the toner and the surface layer of the electrophotographic photosensitive member is reduced due to protrusions of particles in the surface layer of the electrophotographic photosensitive member, but it is difficult to suppress the detachment of particles from the surface layer by the closeness between the particles. In addition, it has been found that when the adhesion of the toner to the surface layer increases in the durability test of the electrophotographic photosensitive member, the transferability deteriorates.

[0016] Therefore, an object of the present invention is to provide an electrophotographic photosensitive member that has improved transferability by controlling the distance between particles in the surface layer to reduce the adhesion force of the toner, and that has improved durability by suppressing the detachment of particles from the surface layer.

[0017] Solution for solving problems

[0018] The above object is achieved by the present invention described hereinafter. That is, the present invention relates to an electrophotographic photosensitive member including a surface layer containing particles and a binder resin,

[0019] wherein the particles in the surface layer have multiple peaks in the particle size distribution on a number basis,

[0020] wherein, among the peaks with peak tops each being 20 nm or more in the multiple peaks, when the peak having the highest frequency at the peak top is defined as the first peak, and the peak having the second highest frequency at the peak top after the first peak is defined as the second peak, and

[0021] when, among the first peak and the second peak, the peak having a larger particle size value at the peak top is defined as peak PEA,

[0022] the particle size DA at the peak top of the peak PEA falls within the range of 80 nm or more and 300 nm or less,

[0023] wherein, among the particles in the surface layer, when the particles having particle sizes each within the range of DA ± 20 nm are defined as particles PAA, and the protrusions having heights each within the range of 10 nm or more and 300 nm or less derived from the particles PAA are defined as protrusions CA, the protrusions CA are disposed on the surface of the surface layer,

[0024] wherein, when the surface layer is observed from above, the average value of the center - to - center distances of the protrusions CA is 150 nm or more and 500 nm or less, and the standard deviation of the center - to - center distances of the protrusions CA is 250 nm or less, and

[0025] wherein, when the surface layer is observed from above, and when the area occupied by the particles on the surface of the surface layer is represented as S1 and the area occupied by the portion other than the particles is represented as S2, S1 / (S1 + S2) is 0.70 or more and 1.00 or less.

[0026] The present invention also relates to a processing cartridge including: the above - mentioned electrophotographic photosensitive member; and at least one device selected from the group consisting of: a charging device; a developing device; and a cleaning device, the processing cartridge integrally supports the electrophotographic photosensitive member and the at least one device, and is detachably mounted on the main body of an electrophotographic apparatus.

[0027] The present invention also relates to an electrophotographic apparatus including: the above - mentioned electrophotographic photosensitive member; and a charging device, an exposure device, a developing device, and a transfer device.

[0028] Effects of the Invention

[0029] The present invention can provide an electrophotographic photosensitive member having improved transferability by controlling the distance between particles in the surface layer to reduce the adhesion force of toner, and having improved durability by suppressing the detachment of particles from the surface layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a conceptual diagram for explaining an example of the layer structure of the electrophotographic photosensitive member according to the present invention.

[0031] Figure 2 is a conceptual diagram for explaining another example of the layer structure of the electrophotographic photosensitive member according to the present invention.

[0032] Figure 3 is a conceptual diagram obtained by observing the surface layer of the electrophotographic photosensitive member according to the present invention from above (surface observation).

[0033] Figure 4 is a conceptual diagram for explaining a method of observing the surface layer of the electrophotographic photosensitive member according to the present invention from above (surface observation) and calculating the inter-particle distance of particles PAA.

[0034] Figure 5 is a conceptual diagram of an example of observing the surface layer of the electrophotographic photosensitive member according to the present invention from the side (cross-sectional observation).

[0035] Figure 6 is a conceptual diagram of another example of observing the surface layer of the electrophotographic photosensitive member according to the present invention from the side (cross-sectional observation).

[0036] Figure 7 shows an example of a scanning probe microscope (SPM) image obtained by observing the surface layer of the electrophotographic photosensitive member according to the present invention.

[0037] Figure 8 shows an example of a STEM image of the conductive particles according to the present invention.

[0038] Figure 9 is for explaining Figure 8 of the STEM image.

[0039] Figure 10 is a diagram showing an example of the schematic structure of an electrophotographic apparatus including a process cartridge, the process cartridge including an electrophotographic photosensitive member and a charging device.

[0040] Figure 11A ​​​​​​​​​​​is a graph showing an example of the particle size distribution of particles in the surface layer of an electrophotographic photosensitive member according to the present invention.

[0041] Figure 11B is a graph showing another example of the particle size distribution of particles in the surface layer of an electrophotographic photosensitive member according to the present invention. DETAILED DESCRIPTION

[0042] The present invention will be described in detail below by preferred embodiments.

[0043] [Electrophotographic Photosensitive Member]

[0044] The electrophotographic photosensitive member of the present invention is characterized by including a surface layer containing particles and a binder resin.

[0045] As used herein, the term "surface layer" refers to the layer located on the outermost surface of the electrophotographic photosensitive member and means the layer that contacts the charging member or toner.

[0046] Figure 1 and Figure 2 are diagrams for explaining examples of the layer structure of the electrophotographic photosensitive member, respectively. In Figure 1 and Figure 2 , the support is denoted by reference numeral 101, the undercoat layer is denoted by reference numeral 102, the charge generation layer is denoted by reference numeral 103, and the charge transport layer is denoted by reference numeral 104. The surface layer according to the present invention is denoted by reference numeral 105, the particles PAA according to the present invention are each denoted by reference numeral 106, and the particles other than the particles PAA according to the present invention are each denoted by reference numeral 107.

[0047] The method for manufacturing the electrophotographic photosensitive member of the present invention is, for example, a method including the following steps: preparing coating liquids for the respective layers described later; applying the coating liquids in a desired layer sequence; and drying the coating liquids. In this case, examples of the method for applying the coating liquids include dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, loop coating, and dispense coating. Among them, dip coating is preferred from the viewpoints of efficiency and productivity.

[0048] Each layer will be described below.

[0049] [Surface Layer]

[0050] The electrophotographic photosensitive member of the present invention is an electrophotographic photosensitive member including a surface layer containing particles and a binder resin,

[0051] wherein the particles in the surface layer have multiple peaks in the particle size distribution on a number basis,

[0052] ​Among them, when among the peaks with peak tops each above 20 nm in multiple peaks, the peak with the highest frequency at the peak top is defined as the first peak, and the peak with the second highest frequency at the peak top after the first peak is defined as the second peak, and

[0053] when among the first peak and the second peak, the peak with a larger particle size value at the peak top is defined as peak PEA,

[0054] the particle size DA at the peak top of peak PEA falls within the range of 80 nm or more and 300 nm or less,

[0055] Among them, when among the particles in the surface layer, the particles with particle sizes each within the range of DA ± 20 nm are defined as particles PAA, and the protrusions with heights each within the range of 10 nm or more and 300 nm or less originating from particles PAA are defined as protrusions CA, the protrusions CA are arranged on the surface of the surface layer,

[0056] Among them, when observing the surface layer from above, the average value of the distances between the centers of gravity of the protrusions CA is 150 nm or more and 500 nm or less, and the standard deviation of the distances between the centers of gravity of the protrusions CA is 250 nm or less, and

[0057] Among them, when observing the surface layer from above, and when the area occupied by the particles on the surface of the surface layer is represented as S1 and the area occupied by the parts other than the particles is represented as S2, S1 / (S1 + S2) is 0.70 or more and 1.00 or less.

[0058] Although the reason for the effect of the present invention can be exerted under the above conditions has not been clearly explained, the inventors of the present invention speculate the reason as follows.

[0059] Meanwhile, in order to improve the transferability in an electrophotographic apparatus, it is necessary to reduce the adhesion force of the toner used for developing the electrostatic latent image on the electrophotographic photosensitive member. The adhesion force between the toner and the electrophotographic photosensitive member is roughly classified into an electrostatic adhesion force and a non-electrostatic adhesion force. The non-electrostatic adhesion force is caused by the van der Waals force based on the intermolecular force between objects. Therefore, imparting a shape to the surface of the surface layer of the electrophotographic photosensitive member results in a decrease in the contact area between the toner and the surface layer of the electrophotographic photosensitive member, and can greatly contribute to the reduction of the non-electrostatic adhesion force. The electrostatic adhesion force is mainly caused by the image force, and thus is greatly affected by the charge amount of the toner. The magnitude of the image force is proportional to the charge amount of the toner and inversely proportional to the square of the distance between the charge amount of the toner and the surface of the electrophotographic photosensitive member to which the toner adheres. Therefore, by appropriately setting the height of each convex portion derived from the particles on the surface of the electrophotographic photosensitive member, the distance between the electrophotographic photosensitive member and the toner can be ensured, and thus the image force can be reduced. In addition, imparting a surface profile to the surface layer promotes the rolling of the toner in the toner layer sandwiched between the surface of the surface layer of the electrophotographic photosensitive member and the intermediate transfer member or a transfer material such as paper. Therefore, the image force in the surface charge of the toner surface can also be reduced. As a result, the adhesion force of the toner is reduced, and the transferability of the toner to the transfer material is improved. Examples of the method of appropriately arranging the convex portions include: controlling the particle diameter of each introduced particle; and arranging the particles on the surface of the surface layer by increasing the ratio of the particles in the surface layer. Research conducted by the inventors of the present invention has found that by mixing a plurality of particles having different particle diameters in the surface layer, it is easy to control the height of each convex portion derived from the particles.

[0060] The electrophotographic photosensitive member of the present invention is an electrophotographic photosensitive member including a surface layer containing particles and a binder resin, and the particles have a plurality of peaks in the particle size distribution on a number basis. Among the plurality of peaks, in the peaks where each peak top is 20 nm or more, the peak having the highest frequency at the peak top is defined as the first peak, and further, among the peaks where each peak top is 20 nm or more in the plurality of peaks, the peak having the second highest frequency at the peak top after the first peak is defined as the second peak. When the first peak and the second peak are compared with each other, the peak having a larger particle diameter value at the peak top is defined as peak PEA. In the present invention, the particle diameter DA at the peak top of peak PEA preferably falls within the range of 80 nm to 300 nm, more preferably within the range of 85 nm to 250 nm, still more preferably within the range of 90 nm to 250 nm. When the particle diameter DA falls within the above range, it is easy to obtain the above-described effect of reducing the adhesion between the toner and the surface layer of the electrophotographic photosensitive member in the transfer step.

[0061] In this case, the particle diameter DA at the peak of the PEA represents the particle diameter of the particles having the highest particle diameter frequency in the surface layer. When the particle diameter DA is less than 80 nm, the height of each convex portion that contributes to the point contact between the toner and the convex portions of the particles in the surface layer of the electrophotographic photosensitive member decreases, and the contact area between the toner and the surface of the surface layer of the electrophotographic photosensitive member increases, thereby deteriorating the adhesiveness of the toner. As a result, the transferability decreases.

[0062] When the particle diameter DA is greater than 300 nm, the curvature of each convex portion derived from the particles decreases, and the contact area between the toner and the surface of the surface layer increases, thereby increasing the adhesive force between the toner and the surface of the electrophotographic photosensitive member. As a result, the transferability deteriorates.

[0063] In addition, the first peak and the second peak are selected from the range where the particle diameter corresponding to the peak top is 20 nm or more. That is, among the peaks where the peak tops are each 20 nm or more in a plurality of peaks, the peak having the highest frequency at the peak top is defined as the first peak, and the peak having the second highest frequency at the peak top after the first peak is defined as the second peak. Figure 11A It is a graph showing an example of the particle size distribution indicating the number standard of the particles in the surface layer of the electrophotographic photosensitive member, where the first peak 201 exists at a particle diameter of 50 nm and the second peak 202 exists at a particle diameter of 170 nm. In this case, the second peak 202 at the large particle diameter becomes the peak PEA, and its particle diameter DA is 170 nm. Therefore, the condition of 80 nm ≤ DA is satisfied. In addition, since the first peak 201 exists at a particle diameter of 50 nm, the condition that the particle diameter at the peak top is 20 nm or more is satisfied.

[0064] Figure 11B It is a graph showing another example of the particle size distribution of the particles in the surface layer of the electrophotographic photosensitive member. Although there is a peak at a particle diameter of 5 nm, since the particle diameter at the peak top is less than 20 nm, this peak is not included in the first peak or the second peak. Thus, in the same manner as in Figure 11A the case, the peak at a particle diameter of 50 nm becomes the first peak 201, and the peak at a particle diameter of 170 nm becomes the second peak 202. The peaks are selected in this way. Here, even in the electrophotographic photosensitive member 1 in which a large number of significantly small particles are included in the surface layer 105, the effects of the present invention described later can be obtained. In view of the above, as described with reference to Figure 11A and Figure 11B by selecting the first peak 201 and the second peak 202 from the peaks where the particle diameter is 20 nm or more, the effects of the present invention can be stably obtained.

[0065] Next, particles with particle diameters each within the range of DA ± 20 nm in the surface layer of the electrophotographic photosensitive member of the present invention are defined as particles PAA. Further, in the present invention, when protrusions CA with heights each of 10 nm or more and 300 nm or less derived from particles PAA are defined, the protrusions CA exist on the surface of the surface layer. When the height of each protrusion CA is less than 10 nm, the height of each protrusion CA becomes too low. Therefore, in the contact between the electrophotographic photosensitive member and the toner, the rotation of the toner cannot be promoted, and the electrostatic adhesion force between the toner and the surface layer of the electrophotographic photosensitive member does not decrease, resulting in deteriorated transferability. When the height of each protrusion CA is greater than 300 nm, the recesses in the surface layer of the electrophotographic photosensitive member expand, and as a result of the progress of the accumulation of external additives for toner, the contact area between the surface of the surface layer of the electrophotographic photosensitive member and the toner increases, and the transferability deteriorates.

[0066] Next, in the electrophotographic photosensitive member of the present invention, when observing the surface layer of the electrophotographic photosensitive member from above, the average value of the distances between the centers of gravity of the protrusions CA is 150 nm or more and 500 nm or less.

[0067] When the average value of the distances between the centers of gravity of the protrusions CA on the surface layer of the electrophotographic photosensitive member is greater than 500 nm and the interval between the protrusions CA derived from the particles becomes too large, the possibility of contact between the toner and the surface of the surface layer of the electrophotographic photosensitive member increases. As a result, the distance between the toner and the surface of the surface layer cannot be maintained, and the toner and the recesses of the surface layer are likely to come into contact with each other, deteriorating the transferability. The Coulomb force does not decrease, so the electrostatic adhesion force increases, and as a result, the transferability cannot be improved.

[0068] At the same time, when the average value of the distances between the centers of gravity of the protrusions CA is less than 150 nm and the distance between the centers of gravity of the protrusions CA in the surface layer of the electrophotographic photosensitive member decreases, the surface layer is filled with the protrusions CA, and the number of contact points between the toner base particles and the surface layer increases. Therefore, the contact area between the toner and the surface layer of the electrophotographic photosensitive member increases, increasing the non-electrostatic adhesion force, and as a result, the transferability deteriorates.

[0069] The distances between the centers of gravity of the protrusions CA on the surface of the surface layer of the electrophotographic photosensitive member of the present invention are each more preferably 150 nm or more and 450 nm or less, and still more preferably 150 nm or more and 400 nm or less.

[0070] In addition, in the electrophotographic photosensitive member of the present invention, the standard deviation of the distance between the centers of gravity of the convex portions CA is 250 nm or less. When the standard deviation of the distance between the centers of gravity of the convex portions CA is greater than 250 nm, there is a wide variation in the distribution of the convex portions CA in the surface layer, and this variation causes uneven adhesion between the toner and the surface of the electrophotographic photosensitive member. This uneven adhesion causes uneven transferability, and roughness becomes obvious in halftone images. The standard deviation of the average value of the distance between the centers of gravity is preferably 200 nm or less, and more preferably 175 nm or less.

[0071] Similarly, the coefficient of variation obtained by dividing the standard deviation of the distance between the centers of gravity of the convex portions CA by the average value of the distance between the centers of gravity is preferably 50% or less. When the coefficient of variation of the average value of the distance between the centers of gravity is greater than 50%, there is a large variation in the distribution of the surface layer in the convex portions CA, and this variation causes uneven adhesion between the toner and the surface of the electrophotographic photosensitive member. This uneven adhesion causes uneven transferability, and roughness becomes obvious in halftone images. The coefficient of variation of the average value of the distance between the centers of gravity is more preferably 40% or less, and still more preferably 35% or less.

[0072] Research conducted by the inventors of the present invention has found that when regions between the particles PAA are further filled with particles other than the particles PAA in a state close to a close-packed state in the surface direction of the drum (electrophotographic photosensitive member), the closeness between the particles increases. The reason is as follows. When the particles PAA are impacted in the tangential direction of the drum surface, by controlling the distance between the particles PAA within the above range, the restraint of the binder resin between the particles and the movement of the particles in the direction of the drum surface are restrained by the particles other than the particles PAA, and thus the movement of the particles PAA is suppressed. As a result, even with respect to the friction between the electrophotographic photosensitive member and the charging member, developing member, and transfer member that are in contact with the electrophotographic photosensitive member, an effect of suppressing the detachment of the particles PAA from the surface layer of the electrophotographic photosensitive member is obtained. Therefore, in the present invention, it is possible to maintain the surface profile of the surface layer of the electrophotographic photosensitive member with excellent transferability throughout the durability test. With this configuration, it is easy to impart the surface profile of the surface of the surface layer of the electrophotographic photosensitive member, so the contact area with the toner is reduced, thereby reducing the adhesion to the toner. As a result, a state with improved transferability can be maintained. In addition, the surface of the surface layer of the electrophotographic photosensitive member is less likely to be contaminated, so it is possible to easily avoid the situation where the latent image is disturbed and it is difficult to obtain a density.

[0073] In addition, in the surface of the surface layer of the electrophotographic photosensitive member of the present invention, the particles refer to all particles, such as particle A, particle B, and other particles described later, etc. And when the area occupied by the particles is represented as S1 and the area occupied by the part other than the particles is represented as S2, S1 / (S1 + S2) is 0.70 or more and 1.00 or less. When S1 / (S1 + S2) is less than 0.70, the part without particles cannot form a convex portion. In the present invention, under the setting that the acceleration voltage is 5 kV or more, the surface of the surface layer of the electrophotographic photosensitive member of the present invention is observed from above using a scanning electron microscope (SEM). The area of the image in which the particles are identified in the backscattered electron image of the surface layer is added to the area S1 occupied by the particles.

[0074] Theoretically, the upper limit of S1 / (S1 + S2) is 1.00. S1 / (S1 + S2) is more preferably 0.80 or more and 1.00 or less, and still more preferably 0.85 or more and 0.95 or less.

[0075] In the electrophotographic photosensitive member of the present invention, in the cross-section of the surface layer, when the particles are stacked in a single layer as shown, when the average value of the thickness of the surface layer at the part where PAA particles are not contained in the cross-section of the surface layer is represented as T, it is preferable that DA and T satisfy the following formula (1). Figure 5 Shown particles are stacked in a single layer, when the average value of the thickness of the surface layer at the part where PAA particles are not contained in the cross-section of the surface layer is represented as T, it is preferable that DA and T satisfy the following formula (1).

[0076] DA > T … Formula (1)

[0077] In the case where the particles are stacked in multiple layers as shown, when the average value of the thickness of the surface layer at the part where PAA particles are not contained in the cross-section of the surface layer is represented as T, it is preferable that DA and T satisfy the following formula (1)'. Figure 6 Shown particles are stacked in multiple layers, when the average value of the thickness of the surface layer at the part where PAA particles are not contained in the cross-section of the surface layer is represented as T, it is preferable that DA and T satisfy the following formula (1)'.

[0078] DA × 2 > T … Formula (1)'

[0079] When DA is less than the average value T of the thickness, as described above, it becomes difficult to form such a convex portion CA, and the reduction in the adhesiveness between the toner mother particles and the electrophotographic photosensitive member becomes insufficient, and as a result, the risk of deterioration of the transferability increases. The average value T of the thickness is preferably 50 nm or more and 500 nm or less, more preferably 70 nm or more and 450 nm or less, and still more preferably 80 nm or more and 400 nm or less, as long as the particles are stacked in a manner that satisfies formula (1) as shown in and. Figure 1 And Figure 2 Shown stacked in a manner that satisfies formula (1).

[0080] Further, in the cross-section of the surface layer in the electrophotographic photosensitive member of the present invention, the particles in the surface layer have multiple peaks in the particle size distribution based on the number. Among the multiple peaks, for the peaks with peak tops each of 20 nm or more, the peak with the highest frequency at the peak top is defined as the first peak, and the peak with the second highest frequency at the peak top after the first peak is defined as the second peak. Further, when comparing the first peak and the second peak with each other, the peak with a smaller particle size value at the peak top is defined as peak PEB, the particle size at the peak top of peak PEB is represented as DB, and the average value of the thickness of the surface layer at the portion where particles PAA are not contained in the cross-section of the surface layer is represented as T. Preferably, DB and T satisfy the following formula (2).

[0081] DB < T … Formula (2)

[0082] In the case where the particles with particle sizes each within the range of DB ± 20 nm among all the particles in the surface layer are defined as particles PAB, when DB is less than or equal to the average value T of the thickness, the tightness between the particles PAA for forming the convex portions CA and the particles PAB arranged between the convex portions CA increases, and clear concave portions are formed in the surface layer. Therefore, the detachment of the particles is suppressed. When DB is greater than the average value T of the thickness, the particles PAB are likely to be exposed from the surface layer, and the detachment of the particles is likely to occur.

[0083] Further, in the cross-section of the surface layer in the electrophotographic photosensitive member of the present invention, preferably DA and DB satisfy the following formula (3).

[0084] DB / DA > 1 / 10 … Formula (3)

[0085] When the particles PAA form the convex portions CA and the regions between the particles PAA are filled with the particles PAB, the average value and the standard deviation of the distance between the centers of gravity of the convex portions CA can be controlled. Further, when the particle sizes of the particles PAA and the particles PAB satisfy the formula (3), while sufficiently maintaining the height of each convex portion CA, the detachment of the particles can be suppressed with respect to the friction in the tangential direction of the surface layer of the electrophotographic photosensitive member. DB / DA in the formula (3) is preferably greater than 1 / 3, and more preferably greater than 1 / 2.

[0086] Next, in the electrophotographic photosensitive member of the present invention, the ratio of the number of the convex portions CA to the total number of the convex portions present on the surface of the surface layer is preferably 90% or more by number. When the ratio of the number of the convex portions CA is less than 90% by number, due to the friction in the developing portion in the electrophotographic apparatus, the convex portions not derived from the particles PAA have weak mechanical strength and are worn with respect to the friction in the tangential direction of the electrophotographic photosensitive member. In this case, it becomes difficult to maintain the transferability in a satisfactory state for long-term use.

[0087] In addition, the half-value width of the peak PEA in the surface layer of the electrophotographic photosensitive member of the present invention is preferably 20 nm or more and 50 nm or less. Since the height of each convex portion CA is controlled according to the particle size, it is preferable that the half-value width of the peak PEA falls within a certain range as much as possible. When the half-value width of the PEA is greater than 50 nm, the height of the convex portion CA also varies greatly, resulting in variations in the point contact between the toner mother particles and the surface of the surface layer of the electrophotographic photosensitive member. As a result, the rotation of the toner cannot be promoted, and it becomes difficult to reduce the electrostatic adhesion force between the surfaces. By promoting the point contact between the toner and the electrophotographic photosensitive member, the adhesion force of the toner to the electrophotographic photosensitive member is reduced, so that the transfer property can be improved.

[0088] The maximum height difference Rz of the surface of the surface layer in the electrophotographic photosensitive member of the present invention is preferably 100 nm or more and 400 nm or less. When the maximum height difference Rz of the surface of the surface layer is less than 100 nm, the rotation of the toner cannot be appropriately promoted, and the transfer property is not improved. When the maximum height difference Rz of the surface of the surface layer is greater than 400 nm, the external additives continue to accumulate in the concave portions, so that the surface of the surface layer of the electrophotographic photosensitive member is contaminated. As a result, the latent image may be disturbed and it is difficult to obtain a density. In addition, it is difficult to impart a surface profile to the surface of the surface layer of the electrophotographic photosensitive member, so that the contact area between the surface and the toner increases, thereby deteriorating the transfer property. Further, discharge is likely to occur in the transfer step, and roughness due to density unevenness occurs in the halftone image. The maximum height difference Rz is more preferably 125 nm or more and 375 nm or less, and still more preferably 150 nm or more and 350 nm or less. Regarding the measurement method of the maximum height difference Rz, using a scanning probe microscope (SPM "JSPM-5200", manufactured by JEOL Ltd.) described later, at a total of 12 positions at one position in each of the specimens of the photosensitive member, the surface profile of the surface of the electrophotographic photosensitive member having a size of 3 μm × 3 μm is measured. In the analysis image of the surface profile to which a flattening process for correcting the first-order linear slope of the entire image is applied, the difference between the maximum value Zmax and the minimum value Zmin of the height "z" is defined as the maximum height difference Rz.

[0089] The roundness of each particle PAA in the surface layer in the electrophotographic photosensitive member of the present invention is preferably 0.950 or more. When the roundness of each particle PAA is less than 0.950, the contact area between the toner mother particles and the surface of the surface layer of the electrophotographic photosensitive member increases. As a result, an increase in non-electrostatic adhesion force is observed, and the transfer property of the toner is likely to deteriorate with long-term use.

[0090] As described below, the circularity of the particles was determined using a scanning electron microscope. The particles to be measured were observed using a scanning electron microscope (“JSM-7800F”, manufactured by JEOL Ltd.), and the respective particle diameters of 100 particles were measured from the images obtained by the observation. For each particle, the longest side “a” and the shortest side “b” of the particle were measured once, and the ratio “b / a” was adopted as the circularity. The circularities of the 100 particles were averaged to calculate the circularity of the particles.

[0091] As the particles in the surface layer of the electrophotographic photosensitive member of the present invention, it is preferable that the surface layer contains at least the above-described particles PAA and particles PAB. Since particle A contributes to the contact with the toner, in order to reduce the electrostatic adhesion force, it is effective to reduce the specific dielectric constant. The relative dielectric constant ε(A) of particle A is preferably 5 or less, more preferably 4 or less, and still more preferably 3 or less.

[0092] Examples of particle A used in the present invention include: organic resin particles such as acrylic resin particles; and inorganic particles such as silica.

[0093] Each of the acrylic particles contains a polymer of acrylate or methacrylate. Among them, styrene-acrylic particles are more preferable. There is no particular limitation on the degree of polymerization of the acrylic resin or styrene-acrylic resin, or whether the resin is thermoplastic or thermosetting. Examples of the organic resin particles include crosslinked polystyrene, crosslinked acrylic resin, phenolic resin, melamine resin, polyethylene, polypropylene, acrylic particles, polytetrafluoroethylene particles, and silicone particles.

[0094] Examples of the inorganic particles include silica particles, metal oxide particles, and metal particles. As the particles in the surface layer of the electrophotographic photosensitive member of the present invention, inorganic particles having low elasticity and being advantageous for promoting point contact between the toner and the electrophotographic photosensitive member are preferably used.

[0095] When inorganic particles are used, silica particles are preferably used in the particles. Since silica particles have a lower elastic modulus and a larger average circularity than other insulating particles, it is expected that silica particles exhibit the following effects: the particles promote point contact between the toner and the electrophotographic photosensitive member and reduce the adhesion force of the toner.

[0096] As the silica particles, known fine silica particles can be used, and dry-process fine silica particles and wet-process fine silica particles can be used respectively. Among them, fine particles of wet-process silica obtained by the sol-gel method (hereinafter also referred to as “sol-gel silica”) are preferred.

[0097] The sol-gel silica used as the particles in the surface layer of the electrophotographic photosensitive member of the present invention may be hydrophilic, or its surface may be hydrophobized.

[0098] Examples of the hydrophobization method include a method that includes removing a solvent from a silica sol suspension in the sol-gel method to dry the suspension and then treating the dried product with a hydrophobizing agent, or a method that includes directly adding a hydrophobizing agent to the silica sol suspension and simultaneously drying and treating the suspension. Among them, from the viewpoints of controlling the half-value width of the particle size distribution of the sol-gel silica and controlling its saturated water adsorption amount, a method that includes directly adding a hydrophobizing agent to the silica sol suspension is preferred.

[0099] Examples of the hydrophobizing agent include the following:

[0100] Chlorosilanes, such as methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tert-butyldimethylchlorosilane, and vinyltrichlorosilane;

[0101] Alkoxysilanes, such as tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltriethoxysilane, decyltriethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, and γ-(2-aminoethyl)aminopropylmethyldimethoxysilane;

[0102] Silazanes, such as hexamethyldisilazane, hexaethyldisilazane, hexapropyldisilazane, hexabutyldisilazane, hexapentyldisilazane, hexahyldisilazane, hexacyclohexyldisilazane, hexaphenyldisilazane, divinyltetramethyldisilazane, and dimethyltetravinyldisilazane;

[0103] Silicone oils, such as dimethyl silicone oil, methylhydrogen silicone oil, methylphenyl silicone oil, alkyl-modified silicone oil, chloroalkyl-modified silicone oil, chlorophenyl-modified silicone oil, fatty acid-modified silicone oil, polyether-modified silicone oil, alkoxy-modified silicone oil, methanol-modified silicone oil, amino-modified silicone oil, fluorine-modified silicone oil, and terminal-reactive silicone oil;

[0104] Siloxanes such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldisiloxane, and octamethyltrisiloxane; and

[0105] As fatty acids and their metal salts, long-chain fatty acids such as undecanoic acid, lauric acid, tridecanoic acid, dodecanoic acid, myristic acid, palmitic acid, pentadecanoic acid, stearic acid, heptadecanoic acid, arachidic acid, montanic acid, oleic acid, linoleic acid, and arachidonic acid, etc., and salts of these fatty acids and metals such as zinc, iron, magnesium, aluminum, calcium, sodium, and lithium.

[0106] Among them, alkoxysilanes, silazanes, and silicone oils are preferably used because the hydrophobization treatment is easy to perform. These hydrophobization treatment agents can be used alone or in combination.

[0107] The surface layer in the present invention may contain additives such as antioxidants, UV absorbers, plasticizers, leveling agents, slipperiness imparting agents, or abrasion resistance improvers. Specific examples of the additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, silicone-modified resins, and silicone oils, etc.

[0108] The surface layer of the present invention can be formed by: preparing a coating liquid for the surface layer containing the above-mentioned various materials and a solvent; forming a coating film of the coating liquid; and drying and / or curing the coating film. Examples of the solvent used in the coating liquid include alcohol solvents, ketone solvents, ether solvents, sulfoxide solvents, ester solvents, and aromatic hydrocarbon solvents, etc.

[0109] In the surface layer of the electrophotographic photosensitive member of the present invention, the ratio of the volume of the particles to the total volume of the surface layer is preferably 40% by volume or more and 90% by volume or less, more preferably 45% by volume or more and 85% by volume or less, still more preferably 50% by volume or more and 80% by volume or less. When the ratio falls within the above range, the formation of the convex portions in the surface layer as described above can be reliably achieved. When the ratio is 40% by volume or less, the height of each convex portion decreases, so the transferability is not improved. When the ratio is 90% by volume or more, the detachment of the particles accelerates. Therefore, when a durability test is performed, the transferability deteriorates to reduce the image density.

[0110] Among the particles in the surface layer of the electrophotographic photosensitive member of the present invention, each particle other than particle A preferably has a relative dielectric constant ε(NA) that is more than 5 greater than ε(A). As described above, as particle A, particles with a relative dielectric constant of 5 or less are used. Therefore, when only particle A is used, the capacitance of the surface layer decreases, and when the electrophotographic photosensitive member is charged in the charging step, the charge amount per unit area decreases.

[0111] When increasing the relative dielectric constant of particles other than particle A, the electrostatic capacitance of the surface layer can be increased, and when the electrophotographic photosensitive member is charged in the charging step, a large charge amount per unit area can be maintained. Therefore, a latent image with higher definition can be formed. As a result, a reduction in roughness and the like can be achieved in a halftone image.

[0112] In order to increase the relative dielectric constant of particles other than particle A, conductive particles can be used. When inorganic particles are used as the conductive particles, it is desirable to use metal oxide particles. Examples of the metal oxide include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, bismuth oxide, and the like. Examples of the metal include aluminum, nickel, iron, nickel-chromium alloy, copper, zinc, silver, and the like.

[0113] Among them, it is particularly more preferable to use titanium oxide, tin oxide, and zinc oxide.

[0114] The surface of the metal oxide can be treated with a silane coupling agent or the like, or the metal oxide can be doped with elements such as phosphorus, aluminum, niobium, or their oxides. Doping can control the relative dielectric constant of the metal oxide.

[0115] Therefore, in the electrophotographic photosensitive member of the present invention, it is preferable that the particles other than particle PAA in the surface layer are conductive particles obtained by treating the surface of metal oxide particles with a Si-containing compound, and in the X-ray photoelectron spectroscopy analysis of the surface layer, when the total of the carbon atom concentration d(C), oxygen atom concentration d(O), Ti atom concentration d(Ti), and Si atom concentration d(Si) is defined as 100.0 atomic%, d(Ti) (atomic%) and d(Si) (atomic%) satisfy the following formulas (4) to (6).

[0116] 0 < d(Ti) ≤ 2.0 … Formula (4)

[0117] d(Si) ≤ 15.0 … Formula (5)

[0118] 0.01 ≤ d(Ti) / d(Si) ≤ 1.0 … Formula (6)

[0119] When d(Ti) is 2.0 atomic% or less, titanium oxide particles in the surface of the surface layer of the electrophotographic photosensitive member are sufficiently present. As a result, the electrostatic capacitance of the surface layer can be increased, and when the electrophotographic photosensitive member is charged in the charging step, a high charge amount per unit area that can be held can be maintained. Therefore, a latent image with higher definition can be formed, and thus a reduction in roughness and the like can be achieved in the output of a halftone image.

[0120] In addition, it is preferable that the surface of each titanium oxide particle in the surface layer of the electrophotographic photosensitive member of the present invention is treated with a silane coupling agent. Depending on the degree of this treatment, the dispersion state of the titanium oxide particles in the surface layer changes, and the electrostatic capacitance of the surface layer changes.

[0121] When d(Si) is 15.0 atomic % or less and d(Ti) / d(Si) is 0.01 or more and 1.0 or less, there is a high possibility that the surface of each titanium oxide particle is sufficiently treated with a silane coupling agent, and the titanium oxide particles in the surface layer of the electrophotographic photosensitive member are dispersed in the surface layer. As a result, the electrostatic capacitance of the surface layer can be increased.

[0122] In addition, when the electrophotographic photosensitive member has a drum shape, uneven dispersion of the titanium dioxide particles in the longitudinal direction of the electrophotographic photosensitive member is suppressed. Therefore, when the electrophotographic photosensitive member is charged in the charging step, a large amount of electric charge per unit area can be maintained. As a result, a latent image with higher definition can be formed. As a result, reduction of roughness etc. can be achieved in a halftone image.

[0123] Examples of the conductive particles in the surface layer include particles of metal oxides such as titanium oxide, zinc oxide, tin oxide, and indium oxide. Among them, titanium oxide is preferable. In particular, in the case of anatase-type titanium oxide, charge transfer in the protective layer becomes smooth, and charge injection becomes satisfactory. The anatase formation degree of the anatase-type titanium oxide is preferably 90% or more. The metal oxide particles may be doped with atoms such as niobium, phosphorus, and aluminum or their oxides, and titanium oxide particles each containing niobium and having a structure in which niobium is unevenly distributed near the surface of each particle are particularly preferable. The uneven distribution of niobium near the surface enables effective charge transfer.

[0124] Examples of the conductive particles include particles formed of metal oxides such as titanium oxide, zinc oxide, tin oxide, and indium oxide, and having a metal oxide containing titanium atoms and niobium atoms on their surfaces. Specific examples thereof include particles formed of a metal oxide containing titanium atoms doped with niobium atoms or niobium oxides.

[0125] The conductive particles are particularly preferably titanium oxide particles each containing niobium atoms and having a structure in which niobium is unevenly distributed near the surface of the particle. This is because the uneven distribution of niobium atoms near the surface enables efficient charge transfer. More specifically, in each titanium oxide particle, the concentration ratio calculated as "niobium atom concentration / titanium atom concentration" inside the particle at 5% of the maximum diameter of the particle from the particle surface is greater than 2.0 relative to the concentration ratio calculated as "niobium atom concentration / titanium atom concentration" at the center of the particle. The niobium atom concentration and the titanium atom concentration are obtained by using a scanning transmission electron microscope (STEM) connected to an energy dispersive X-ray spectrometer (EDS analyzer). A TEM image of an example (X1) of titanium oxide particles used in an embodiment of the present invention is shown in Figure 8 In addition, for schematic illustration Figure 8 The STEM image is shown in Figure 9 As described in detail later, the niobium-containing titanium oxide particles used in the examples according to the present invention are produced by coating titanium oxide particles with niobium-containing titanium oxide and then firing. Therefore, it is assumed that the coated niobium-containing titanium oxide grows as a crystal of niobium-doped titanium oxide along the crystal of titanium oxide as the core by so-called epitaxial growth. Figure 9 As shown, the niobium-containing titanium oxide thus produced has a lower density near the surface than in the center of the particle, and is therefore controlled to have a core-shell morphology.

[0126] In such Figure 9 In each of the niobium-containing titanium oxide particles shown, the niobium / titanium atom concentration ratio near the particle surface 32 is higher than the niobium / titanium atom concentration ratio in the center portion 31 of the particle, and the niobium atoms are unevenly distributed near the particle surface. Specifically, the ratio of the niobium / titanium atom concentration ratio inside the particle at 5% of the maximum diameter of the particle from the particle surface to the niobium / titanium atom concentration ratio in the center portion 31 of the particle (hereinafter also referred to as "the ratio between the niobium / titanium atom concentration ratios") is 2.0 or more. In the electrophotographic photosensitive member of the present invention, in each of the conductive particles, in the energy dispersive X-ray analysis (EDS analysis) connected to the scanning transmission electron microscope (STEM), the ratio of the niobium atom / titanium atom concentration ratio inside the conductive particle at 5% of the maximum diameter of the conductive particle from the conductive particle surface to the niobium atom / titanium atom concentration ratio in the center portion of the conductive particle is preferably 2.0 or more. When the ratio between the above-mentioned niobium / titanium atom concentration ratios is set to 2.0 or more, charges can easily move in the protective layer, and charge injection properties can be improved. When the ratio between the niobium / titanium atomic concentration ratios is less than 2.0, charge transfer does not easily proceed.

[0127] The EDS analysis with STEM involves observing with a transmission electron microscope and measuring the niobium / titanium atomic concentration ratio by EDS analysis. The electron beam 33 at the central part of the analyzed particle can measure the niobium / titanium atomic concentration ratio at the central part 31 of the particle. In addition, the electron beam 34 inside the particle at 5% of the primary particle size starting from the particle surface can measure the niobium / titanium atomic concentration ratio inside the particle at 5% of the maximum diameter of the particle starting from the particle surface. Furthermore, the niobium / titanium atomic concentration ratio can be directly measured from the electrophotographic photosensitive member by slicing the electrophotographic photosensitive member by methods such as a microtome, Ar polishing, or FIB.

[0128] Examples of the conductive particles in the surface layer of the present invention include particles of metal oxides such as titanium oxide, zinc oxide, tin oxide, and indium oxide, among which titanium oxide is preferred. In particular, in the case of anatase-type titanium oxide, charge transfer within the surface layer becomes smooth and charge injection becomes satisfactory. The anatase formation degree of the anatase-type titanium oxide is preferably 90% or more. The metal oxide particles may be doped with atoms such as niobium, phosphorus, and aluminum or their oxides, and titanium oxide particles containing niobium and having a structure in which niobium is unevenly distributed near the surface of each particle are particularly preferred. The uneven distribution of niobium near the surface enables effective charge transfer. By using such conductive particles, charge is easily injected from the charging member in contact with the surface of each conductive particle, and the charge easily moves within the surface layer. Therefore, the inhibitory effect on the reduction of the surface resistivity of the electrophotographic photosensitive member can be highly obtained.

[0129] When using a metal oxide as the conductive particle, its average primary particle size is preferably 20 nm or more and 200 nm or less, more preferably 25 nm or more and 150 nm or less.

[0130] The average primary particle size D1 of the metal oxide particles is obtained as described below using a scanning electron microscope. The particles to be measured are observed using a scanning electron microscope JSM-7800 manufactured by JEOL Ltd. The respective particle sizes of 100 particles are measured from the image obtained by the observation, and their arithmetic mean is calculated to provide the average primary particle size D1. Each primary particle size is obtained by (a + b) / 2, where "a" and "b" represent the longest side and the shortest side of the primary particle, respectively. In the case of needle-shaped metal oxide particles or flaky titanium oxide particles, the average particle size is calculated for the major axis diameter and the minor axis diameter respectively to obtain the average primary particle size.

[0131] When controlling the relative dielectric constant of each of the particle A and the particles other than the particle A and performing the surface treatment of the particles as described above, it is possible to sufficiently maintain the surface charge amount in the surface layer of the electrophotographic photosensitive member during charging while maintaining the transferability.

[0132] In addition, for the purpose of improving the charge transport ability of the surface layer, a charge transport material can be added to the coating liquid for the surface layer. In addition, for the purpose of improving various functions of the layer, additives can be added. Examples of the additives include antioxidants, UV absorbers, plasticizers, and leveling agents, etc.

[0133] The binder resin according to the present invention can be in the following form. In this case, the surface layer preferably contains a charge transport material.

[0134] Examples of the binder resin include polyester resins, acrylic resins, phenoxy resins, polycarbonate resins, polystyrene resins, phenolic resins, melamine resins, and epoxy resins, etc. Among them, polycarbonate resins, polyester resins, and acrylic resins are preferred. In addition, the surface layer of the present invention can be formed into a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. The reaction in this case is, for example, a thermal polymerization reaction, a photopolymerization reaction, or a radiation polymerization reaction. Examples of the polymerizable functional group of the monomer having a polymerizable functional group include an acrylic group and a methacrylic group, etc. As the monomer having a polymerizable functional group, a material having a charge transport ability can be used.

[0135] The compound having a polymerizable functional group can have a charge transport structure and a chain polymerizable functional group. From the viewpoint of charge transport, as the charge transport structure, a triarylamine structure is preferred. As the chain polymerizable functional group, an acryloyl group or a methacryloyl group is preferred. The compound can have one or more functional groups. In particular, it is preferable to form a cured film containing a compound having multiple functional groups and a compound having one functional group, because it is easy to eliminate the strain caused by the polymerization between multiple functional groups.

[0136] Examples of the above-mentioned compound having one functional group are represented by formulas (2-1) to (2-6).

[0137]

[0138] Examples of the above-mentioned compound having multiple functional groups are represented by formulas (3-1) to (3-5).

[0139]

[0140] <Support body>

[0141] In the present invention, the electrophotographic photosensitive member preferably includes a support body. In the present invention, the support body is preferably a conductive support body having conductivity. In addition, examples of the shape of the support body include a cylindrical shape, a belt shape, and a sheet shape, etc. Among these shapes, a support body having a cylindrical shape is preferred. In addition, the surface of the support body can be subjected to an electrochemical treatment such as anodic oxidation, a sandblasting treatment, or a cutting treatment.

[0142] As the material of the support, metals, resins, glass, etc. are preferred. Examples of metals include aluminum, iron, nickel, copper, gold, stainless steel, and their alloys, etc. Among these metals, an aluminum support made of aluminum is preferably used.

[0143] In addition, resins or glasses can be made conductive by treatments such as mixing with or covering with a conductive material.

[0144] <Conductive layer>

[0145] In the present invention, the conductive layer can be disposed on the support. The disposition of the conductive layer can cover defects and irregularities on the surface of the support, and can control light reflection on the surface of the support. The conductive layer preferably contains conductive particles and a resin.

[0146] The material of the conductive particles is, for example, a metal oxide, a metal, or carbon black.

[0147] Examples of the metal oxide include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, and bismuth oxide, etc. Examples of the metal include aluminum, nickel, iron, nichrome, copper, zinc, and silver, etc.

[0148] Among them, as the conductive particles, metal oxides are preferably used, and titanium oxide, tin oxide, and zinc oxide are particularly more preferably used.

[0149] When using a metal oxide as the conductive particles, the surface of the metal oxide can be treated with a silane coupling agent, etc., or the metal oxide can be doped with elements such as phosphorus or aluminum or their oxides.

[0150] In addition, the conductive particles can have a laminated structure in which particles before being covered such as titanium oxide, barium sulfate, or zinc oxide are covered with a metal oxide having a different composition from that of the particles before being covered. Examples of the covering are metal oxides such as tin oxide, etc.

[0151] In addition, when using a metal oxide as the conductive particles, its average primary particle size is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less.

[0152] Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenolic resin, and alkyd resin, etc.

[0153] In addition, the conductive layer can further contain, for example, silicone oil, resin particles, or a concealing agent such as titanium oxide, etc.

[0154] The average thickness of the conductive layer is preferably 1 μm or more and 50 μm or less, and particularly preferably 3 μm or more and 40 μm or less.

[0155] The conductive layer can be formed by: preparing a coating liquid for the conductive layer containing the above-mentioned respective materials and a solvent; forming a coating film of the coating liquid; and drying the coating film. Examples of the solvent used in the coating liquid include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. The dispersion method for dispersing the conductive particles in the coating liquid for the conductive layer is, for example, a method including using a paint stirrer, a sand mill, a ball mill, or a liquid collision type high-speed disperser.

[0156] <Base coating>

[0157] In the present invention, the base coating can be disposed on the support or the conductive layer.

[0158] The average thickness of the base coating is preferably 0.1 μm or more and 50 μm or less, more preferably 0.2 μm or more and 40 μm or less, and particularly preferably 0.3 μm or more and 30 μm or less.

[0159] Examples of the resin for the base coating are polyacrylic resin, polyvinyl alcohol resin, polyvinyl acetal resin, polyethylene oxide resin, polypropylene oxide resin, ethyl cellulose resin, methyl cellulose resin, polyamide resin, polyamic acid resin, polyurethane resin, polyimide resin, polyamide-imide resin, polyvinylphenol resin, melamine resin, phenol resin, epoxy resin, and alkyd resin.

[0160] In addition, a resin having a structure in which a resin having a polymerizable functional group and a monomer having a polymerizable functional group are crosslinked with each other is also allowed.

[0161] In addition to the resin, the base coating may further contain an inorganic compound or an organic compound.

[0162] Examples of the inorganic compound include metals, oxides, and salts.

[0163] Examples of the metal include gold, silver, and aluminum. Examples of the oxide include zinc oxide, white lead, alumina, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, bismuth oxide, indium oxide, tin oxide, and zirconium oxide. Examples of the salt include barium sulfate and strontium titanate.

[0164] These inorganic compounds can each exist as particles in the film used as the base coating.

[0165] The number average particle diameter of the particles of the inorganic compound is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less.

[0166] These inorganic compounds may each have a laminated structure including a core particle and a coating layer covering the particle.

[0167] The surfaces of these inorganic compounds may each be treated with, for example, silicone oil, silane compounds, silane coupling agents, or any other organosilicon compounds or organotitanium compounds. In addition, these inorganic compounds may each be doped with elements such as tin, phosphorus, aluminum, or niobium.

[0168] Examples of the organic compounds include electron transporting materials and conductive polymers.

[0169] Examples of the conductive polymers include polythiophene, polyaniline, polyacetylene, polyphenylene, and poly(ethylenedioxythiophene), etc.

[0170] Examples of the electron transporting materials include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylidene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyano vinyl compounds, halogenated aryl compounds, silole compounds, and boron-containing compounds, etc.

[0171] The electron transporting material may have a polymerizable functional group and may be crosslinked with a resin having a functional group capable of reacting with the functional group. Examples of the polymerizable functional group include a hydroxyl group, a thiol group, an amino group, a carboxyl group, a vinyl group, an acryloyl group, a methacryloyl group, and an epoxy group, etc.

[0172] These organic compounds may each exist as particles in the film, or their surfaces may be treated.

[0173] Various additives including a leveling agent such as silicone oil, a plasticizer, and a thickener may be added to the undercoat.

[0174] The undercoat is obtained by: preparing a coating solution for the undercoat containing the above materials; then applying the coating solution to a support or a conductive layer; and then drying or curing the coating film.

[0175] Solvents in the manufacture of the coating solution are, for example, alcohol solvents, ketone solvents, ether solvents, ester solvents, or aromatic hydrocarbon solvents, etc.

[0176] A dispersion method for dispersing particles of the material in the coating solution is, for example, a method including using a paint stirrer, a sand mill, a ball mill, or a liquid collision type high-speed disperser.

[0177] <Photoresist layer>

[0178] The photosensitive layer of the electrophotographic photosensitive member is mainly classified into (1) a laminated photosensitive layer and (2) a single-layer photosensitive layer. (1) The laminated photosensitive layer is a photosensitive layer having a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material. (2) The single-layer photosensitive layer is a photosensitive layer containing both a charge generation material and a charge transport material.

[0179] (1) Laminated photosensitive layer

[0180] The laminated photosensitive layer has a charge generation layer and a charge transport layer.

[0181] (1-1) Charge generation layer

[0182] The charge generation layer preferably contains a charge generation material and a resin.

[0183] Examples of the charge generation material include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments, etc. Among them, azo pigments and phthalocyanine pigments are preferred. Among the phthalocyanine pigments, titanium oxyphthalocyanine pigment, gallium chloride phthalocyanine pigment, and gallium hydroxide phthalocyanine pigment are preferred.

[0184] The content of the charge generation material in the charge generation layer is preferably 40% by mass or more and 85% by mass or less, more preferably 60% by mass or more and 80% by mass or less, relative to the total mass of the charge generation layer.

[0185] Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, polyvinyl butyral resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenolic resin, polyvinyl alcohol resin, cellulose resin, polystyrene resin, polyvinyl acetate resin, and polyvinyl chloride resin, etc. Among them, polyvinyl butyral resin is more preferred.

[0186] In addition, the charge generation layer may further contain additives such as an antioxidant or a UV absorber. Specific examples thereof include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.

[0187] The charge generation layer can be formed by: preparing a coating liquid for the charge generation layer containing the above-mentioned various materials and a solvent; forming a coating film of the coating liquid on the undercoat layer; and drying the coating film. Examples of the solvent used in the coating liquid include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents, etc.

[0188] The thickness of the charge generation layer is preferably 0.1 μm or more and 1.5 μm or less, more preferably 0.15 μm or more and 1.0 μm or less.

[0189] (1-2) Charge transport layer

[0190] The charge transport layer preferably contains a charge transport material and a resin.

[0191] Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from each of these materials. Among them, triarylamine compounds and benzidine compounds are preferred.

[0192] The content of the charge transport material in the charge transport layer is preferably 25% by mass or more and 70% by mass or less, more preferably 30% by mass or more and 55% by mass or less, relative to the total mass of the charge transport layer.

[0193] Examples of the resin include polyester resins, polycarbonate resins, acrylic resins, and polystyrene resins. Among them, polycarbonate resins and polyester resins are preferred. As the polyester resin, polyarylate resin is particularly preferred.

[0194] The content ratio (mass ratio) between the charge transport material and the resin is preferably 4:10 to 20:10, more preferably 5:10 to 12:10.

[0195] In addition, the charge transport layer may contain additives such as antioxidants, UV absorbers, plasticizers, leveling agents, slip property imparting agents, or abrasion resistance improvers. Specific examples thereof include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, silicone-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles.

[0196] The charge transport layer can be formed by: preparing a coating liquid for the charge transport layer containing the above-mentioned respective materials and a solvent; forming a coating film of the coating liquid on the charge generation layer; and drying the coating film. Examples of the solvent used in the coating liquid include alcohol solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. Among these solvents, ether solvents or aromatic hydrocarbon solvents are preferred.

[0197] The thickness of the charge transport layer is 3 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less, and particularly preferably 10 μm or more and 30 μm or less.

[0198] (2) Single-layer type photosensitive layer

[0199] The single-layer type photosensitive layer can be formed by: preparing a coating liquid for the photosensitive layer containing a charge generation material, a charge transport material, a resin, and a solvent; forming a coating film of the coating liquid on the undercoat layer; and drying the coating film. Examples of the charge generation material, charge transport material, and resin are the same as the materials in the section of "(1) Laminated type photosensitive layer".

[0200] The thickness of the single-layer photosensitive layer is preferably 10 μm or more and 45 μm or less, more preferably 25 μm or more and 35 μm or less.

[0201] [Processing Cartridge and Electrophotographic Apparatus]

[0202] The processing cartridge of the present invention can integrally support the electrophotographic photosensitive member and at least one device selected from the group consisting of: a charging device; a developing device; and a cleaning device. The processing cartridge is characterized in that it is detachably mounted on the main body of the electrophotographic apparatus.

[0203] In Figure 10 an example of the schematic configuration of an electrophotographic apparatus including a processing cartridge containing the electrophotographic photosensitive member of the present invention is shown.

[0204] [Configuration of Electrophotographic Apparatus]

[0205] The electrophotographic apparatus of the present invention may include: the electrophotographic photosensitive member; and a charging device, an exposure device, a developing device, and a transfer device.

[0206] The electrophotographic apparatus of the present embodiment is a so-called tandem type electrophotographic apparatus including a plurality of image forming units "a" to "d". The first image forming unit "a" forms an image with a yellow (Y) toner. The second image forming unit "b" forms an image with a magenta (M) toner. The third image forming unit "c" forms an image with a cyan (C) toner. The fourth image forming unit "d" forms an image with a black (Bk) toner. These four image forming units are arranged in a row at a constant interval, and the configurations of the respective image forming units are substantially the same in many aspects except for the color of the toner to be stored. Therefore, the electrophotographic apparatus of the present embodiment will be described below by using the first image forming unit "a".

[0207] The first image forming unit "a" includes a photosensitive drum 1a as a drum-shaped electrophotographic photosensitive member, a charging roller 2a as a charging member, a developing device 4a, and a charge removing device 5a.

[0208] The photosensitive drum 1a is an image bearing member that bears a toner image and is rotationally driven in the direction shown by the arrow in the figure at a prescribed circumferential speed (processing speed). The developing device 4a stores yellow toner and develops the yellow toner on the photosensitive drum 1a by using a developing roller 41a.

[0209] When a control device (not shown) such as a controller receives an image signal, an image forming operation starts, and the photosensitive drum 1a is rotationally driven. During the rotation, the photosensitive drum 1a is uniformly charged to a predetermined voltage (charging voltage) with a predetermined polarity (negative polarity in this embodiment) by the charging roller 2a, and is exposed by the exposure device 3a according to the image signal. Thus, an electrostatic latent image corresponding to the yellow component image of the target color image is formed on the photosensitive drum 1a. Then, the electrostatic latent image is developed at the developing position by the developing device 4a and visualized as a yellow toner image on the photosensitive drum 1a. Here, the normal charging polarity of the toner stored in the developing device 4a is negative polarity, and the electrostatic latent image is reversely developed using the toner charged to the same polarity as the charging polarity of the photosensitive drum 1a by the charging roller 2a. However, the present invention is not limited thereto, and the present invention can also be applied to an electrophotographic apparatus in which the electrostatic latent image is positively developed using the toner charged to the opposite polarity to the charging polarity of the photosensitive drum 1a. Additionally, many particle-derived protrusions can be arranged on the surface layer of the charging roller 2a. The protrusions arranged on the surface layer of the charging roller 2a each function as a spacer between the charging roller 2a and the photosensitive drum 1a at the charging portion. The function is as follows: when the transfer residual toner, which is the toner remaining on the photosensitive drum 1a without being transferred in the primary transfer portion described later, enters the charging portion, contamination of the charging roller 2a by the transfer residual toner due to contact between the transfer residual toner and the portion other than the protrusions is suppressed.

[0210] The pre-exposure unit 5a serving as a charge removal device exposes the surface of the photosensitive drum 1a to remove charge therefrom before the surface of the photosensitive drum 1a is charged by the charging roller 2a. This unit removes charge from the surface of the photosensitive drum 1a, functions to make the surface potential formed on the photosensitive drum uniform, and functions to control the amount of charge released by discharge occurring in the charging portion.

[0211] The annular and movable intermediate transfer belt 10 has conductivity, contacts the photosensitive drum 1a to form a primary transfer portion, and rotates at substantially the same circumferential speed as the photosensitive drum 1a. Additionally, the intermediate transfer belt 10 is tensioned by the opposing roller 13 as an opposing member, the driving roller 11 and the tension roller 12 each as a tensioning member, and the metal roller 14a, and is tensioned by the tension roller 12 under a total pressure of 60 N. When the driving roller 11 is rotationally driven in the direction shown by the arrow in the figure, the intermediate transfer belt 10 can move.

[0212] The yellow toner image formed on the photosensitive drum 1a is primarily transferred from the photosensitive drum 1a to the intermediate transfer belt 10 during the process of passing through the primary transfer portion.

[0213] Figure 2The second, third, and fourth image forming sections therein respectively include photosensitive drums 1b, 1c, and 1d, charging rollers 2b, 2c, and 2d, exposure devices 3b, 3c, and 3d, developing devices 4b, 4c, and 4d, charge removing devices 5b, 5c, and 5d, metal rollers 14b, 14c, and 14d, and developing rollers 41b, 41c, and 41d.

[0214] Subsequently, a magenta toner image of the second color, a cyan toner image of the third color, and a black toner image of the fourth color are formed in the same manner and sequentially transferred onto the intermediate transfer belt 10 in a superposed manner. Thus, toner images of four colors corresponding to the target color image are formed on the intermediate transfer belt 10. Thereafter, the toner images of four colors carried on the intermediate transfer belt 10 are batchwise secondarily transferred onto the surface of a transfer material P such as a sheet of paper or an OHP sheet fed by a paper feeding device 50 during the process of passing through a secondary transfer portion formed by the contact between the secondary transfer roller 15 and the intermediate transfer belt 10. Then, the transfer material P having the toner images of four colors transferred thereto by secondary transfer is heated and pressurized in a fixing device 30, and the toner of four colors melts and mixes to be fixed onto the transfer material P. The toner remaining on the intermediate transfer belt 10 after secondary transfer is cleaned and removed by a belt cleaning device 17 disposed opposite to the opposing roller 13 with the intermediate transfer belt 10 interposed therebetween.

[0215] The electrophotographic photosensitive member of the present invention can be used in, for example, a laser beam printer, an LED printer, or a copying machine.

[0216] [Examples]

[0217] A method for measuring various physical properties of the electrophotographic photosensitive member and the conductive particles according to the present invention is described below. The present invention is in no way limited by the following examples within the scope not departing from the gist of the present invention. In the following examples, the term "parts" is by mass unless otherwise specified.

[0218] [Measurement of Physical Properties of Electrophotographic Photosensitive Member]

[0219] <Method for Measuring Average Primary Particle Diameter Based on the Number of Particles of the Present Invention>

[0220] The number-average particle size was measured using a Zetasizer Nano-ZS (manufactured by Malvern Panalytical Ltd.). This device can measure the particle size by dynamic light scattering method. First, a sample to be measured was prepared by dilution at a solid-liquid ratio of 0.10 mass% (±0.02 mass%), collected in a quartz cell, and placed in the measurement section. As the dispersion medium, when the sample is inorganic fine particles, water or a mixed solvent of methyl ethyl ketone and methanol is used, and when the sample is resin particles or an external additive for toner, water is used. As the measurement conditions, the refractive index of the sample, the refractive index, viscosity, and temperature of the dispersion solvent were input into the control software Zetasizer Software 6.30 for measurement. The average primary particle size based on the number was adopted as Dn.

[0221] The refractive index of the particles was taken from "Refractive indices of solids" recorded on page 517 of Volume II of the revised 4th edition of "Handbook of Chemistry: Fundamentals" (edited by The Chemical Society of Japan, Maruzen Co., Ltd.). As the refractive index of the resin particles, the refractive index of the resin used in the resin particles introduced into the control software was adopted. However, when the refractive index was not introduced, the value recorded in the polymer database of the National Institute for Materials Science was used. The refractive index of the external additive for toner was calculated by taking the weight average of the refractive index of the inorganic fine particles and the refractive index of the resin used in the resin particles. As the refractive index, viscosity, and temperature of the dispersion solvent, the values introduced into the control software were selected. In the case of a mixed solvent, the weight average of the dispersion media to be mixed was used.

[0222] <Method for measuring the maximum height difference Rz on the surface of the surface layer of the electrophotographic photosensitive member>

[0223] The surface of each electrophotographic photosensitive member manufactured in the examples was observed. As specimens for surface observation, the electrophotographic photosensitive member was divided into four equal parts in its longitudinal direction, and specimen pieces with dimensions of 5 mm × 5 mm were cut out from the electrophotographic photosensitive member at positions corresponding to 1 / 4, 1 / 2, and 3 / 4 of the length from the end at intervals of 120° in its circumferential direction. Each specimen piece was fixed to a specimen holder so that the surface layer of the electrophotographic photosensitive member could be observed. For each specimen piece fixed to the specimen holder, the surface profile with dimensions of 3 μm × 3 μm on the surface of the surface layer of the electrophotographic photosensitive member was measured at one point of each specimen using a scanning probe microscope SPM. This measurement was performed for each of the 9 specimen pieces, and the average value of the maximum height differences Rz at 9 positions was defined as the maximum height difference Rz of the electrophotographic photosensitive member of the present invention.

[0224] As the SPM, a scanning probe microscope "JSPM-5200" (manufactured by JEOL Ltd.), a scanning probe microscope "E-sweep" (manufactured by Hitachi High-Tech Corporation), or a medium-sized probe microscope system AFM5500M (manufactured by Hitachi High-Tech Corporation) can be used.

[0225] The measurement method including using the scanning probe microscope "JSPM-5200" (manufactured by JEOL Ltd.) is as follows. The scanning operation is performed by WinSPM scanning, and the data analysis image of the surface profile is output. The maximum height difference Rz on the surface of the surface layer of the electrophotographic photosensitive member of the present invention is measured under the observation conditions of the "JSPM-5200" described below. An example of the SPM observation result is shown in Figure 7 in. Figure 7 The surface profile is shown.

[0226] After the measurement, the measurement positions of the specimens are marked, and the specimens are subjected to the measurement of "calculation of the particle size distribution of particles in the surface layer of the electrophotographic photosensitive member and the height of each convex portion" described below.

[0227] Observation conditions of "JSPM-5200"

[0228] Scanner: 4

[0229] SPM scan: All SPM modes

[0230] Cantilever: SI-DF3P2 (manufactured by Hitachi High-Tech Fielding Corporation)

[0231] Resonance frequency detection:

[0232] (Start) 1.00 kHz

[0233] (Stop) 100 kHz (depending on the type of cantilever when f = 67 kHz)

[0234] Cantilever auto - tuning: Normal method

[0235] Aquisition: 2 inputs (512)

[0236] Scan mode: Normal

[0237] STM / AFM: AC - AFM

[0238] Clock: 833.33 μs

[0239] Scan size: 3,000 nm

[0240] Offset: 0

[0241] Bias [V]: 0

[0242] Reference / V: Constant (calibration value already input)

[0243] Filter: 1.4 Hz

[0244] Loop gain: 16

[0245] The image of the surface profile and the surface height data included in the image are analyzed by scanning with WinSPM, and the difference between the maximum value Zmax and the minimum value Zmin of the height "z" is determined as the maximum height difference Rz in the flattened image.

[0246] In addition, the measurement method using the scanning probe microscope "E - sweep" (manufactured by Hitachi High - Tech Corporation) is as follows. The measurement is performed by a scanning operation, and an analysis image of the surface profile of the electrophotographic photosensitive member can be output.

[0247] · Observation conditions of "E - sweep"

[0248] Cantilever: SI - DF20 (back is AL) K - A102002771 (manufactured by Hitachi High - Tech Fielding Corporation)

[0249] Scanning probe microscope: Hitachi High - Tech Science Corporation

[0250] Measurement unit: E - sweep

[0251] Measurement mode: DFM (resonance mode) shape image

[0252] Resolution: 512 data points in the X direction and 512 data points in the Y direction

[0253] Measurement frequency: 127 Hz

[0254] Adjust the Q-curve measurement magnification, excitation voltage, low-pass filter, high-pass filter, etc. to optimize the resonance state of the cantilever.

[0255] By using the attached software to analyze the surface profile image and the surface height data included in the image, the difference between the maximum value Zmax and the minimum value Zmin of the height "z" is determined as the maximum height difference (maximum height) Rz based on JIS B0601:2001 in the flattened image.

[0256] <Observation of the stacking state of particles in the surface layer of the electrophotographic photosensitive member, ratio of the volume of particles to the total volume of the surface layer, particle size distribution, and calculation of the height of each convex portion CA>

[0257] Calculate the ratio of the volume of particles to the total volume of the surface layer from the addition amount, density, and true specific gravity of the monomer having a polymerizable functional group and the particles used in the coating liquid for the surface layer. For the specific gravity of the polymerization product obtained after polymerizing the monomer having a polymerizable functional group and the particles, the values publicly available in the database "POLYINFO" of the manufacturer of each material and the National Institute for Materials Science can be referred to.

[0258] In addition, when calculating this ratio from the electrophotographic photosensitive member, for example, the following method can be adopted. Observe the cross-section of each electrophotographic photosensitive member manufactured in the examples. Determine whether the particles are stacked in a single layer in the surface layer as shown in Figure 1 or Figure 5 or whether the particles are stacked in multiple layers as shown in Figure 2 or Figure 6 Collect specimens for cross-section observation from the positions determined as follows: When the electrophotographic photosensitive member is divided into four equal parts in its length direction, select the positions corresponding to 1 / 4, 1 / 2, and 3 / 4 of the length of the electrophotographic photosensitive member from its end, and offset them by 120° from each other in the circumferential direction. Cut out specimen pieces of 5 mm square from each electrophotographic photosensitive member, and use the Slice&View function of FIB-SEM to reconstruct their surface layers into three-dimensional objects with dimensions of 2 μm × 2 μm × 2 μm respectively.

[0259] Set the conditions for the Slice&View function as described below.

[0260] Treatment of the specimen for analysis: FIB method

[0261] Treatment and observation apparatus: NVision 40, manufactured by SII / Zeiss

[0262] Slice interval: 10 nm

[0263] (Observation conditions)

[0264] Acceleration voltage: 1.0 kV

[0265] Specimen tilt: 54°

[0266] WD: 5 mm

[0267] Detector: BSE detector

[0268] Aperture: 60 μm, high current

[0269] ABC: ON

[0270] Image resolution: 1.25 nm / pixel

[0271] In addition, the temperature of the measurement environment is 23 °C and the pressure is 1×10 -4 Pa. Strata400S (specimen tilt: 52°) manufactured by FEI can also be used as the treatment and observation apparatus.

[0272] Analysis is performed in a region with dimensions of 2 μm in length × 2 μm in width, and the information segments of each cross-section are integrated to obtain the volume V per unit volume in the surface layer with dimensions of 2 μm in length × 2 μm in width × 2 μm in thickness (8 μm 3 ). In addition, the images of each cross-section are analyzed using the image processing software "Image-Pro Plus" manufactured by Media Cybernetics, Inc.

[0273] The particle content in the total volume of the surface layer is calculated from the contrast difference between the layers and the particles obtained through the Slice&View function of FIB-SEM. In addition, based on the information obtained from the image analysis, the volume V of the particles of the present invention in the volume with dimensions of 2 μm × 2 μm × 2 μm (unit volume: 8 μm 3 ) is obtained for each of the 4 specimen pieces, and the particle content [volume%] (= V μm 3 / 8 μm 3×100). As the content [volume%] of each particle of the present invention in the surface layer with respect to the total volume of the surface layer, the average value of the content of the particles in each specimen piece was adopted. The composition of the particles was determined by using the SEM-EDX function of SEM.

[0274] From the results of FIB-SEM, in the particle size distribution A where the particle size of each particle on the surface of the surface layer was plotted on the horizontal axis and the number-based frequency at each particle size was plotted on the vertical axis, the presence of multiple peaks was confirmed.

[0275] In the particle distribution A, among the multiple peaks where the peak tops are each 20 nm or more, the peak having the highest frequency at the peak top was defined as the first peak. Next, in the particle distribution A, among the multiple peaks where the peak tops are each 20 nm or more, the peak having the second highest frequency at the peak top after the first peak was defined as the second peak. In addition, when comparing the first peak and the second peak with each other, the peak having a larger particle size value at the peak top was defined as peak PEA.

[0276] Then, the particle size at the peak top of peak PEA in the particle size distribution A was represented as DA. Among all the particles in the surface layer, the particles with particle sizes each within the range of DA ± 20 nm were defined as particles PAA. When the protrusions with heights each of 10 nm or more and 300 nm or less derived from particles PAA were defined as protrusions CA, the height L of each protrusion CA was shown in Figure 5 and Figure 6 As shown in Figure 5 and Figure 6 The height of each protrusion CA measured from the surface without particles PAA was defined as the height L of each protrusion CA. When there are particles with different compositions, these particles are distinguished by using the mapping image of EDS. In addition, the protrusions were measured at 100 points, and the ratio of the protrusions CA derived from particles PAA to all the protrusions was calculated. In addition, regarding the height L, the average value LV was calculated.

[0277] Next, in the particle size distribution A, the peak having the highest frequency at the peak top was defined as the first peak, and the peak having the second highest frequency at the peak top after the first peak was defined as the second peak. When comparing the first peak and the second peak with each other, the peak having a smaller particle size value at the peak top was defined as peak PEB. The particle size DB at the peak top of peak PEB was calculated.

[0278] In addition, in the cross-sectional image of the surface layer, as shown in Figure 5 and Figure 6 the average value of the thickness of the surface layer at the part without particles PAA was defined as the average thickness T.

[0279] <Method for Measuring the Average Distance and Standard Deviation between the Centers of Gravity of Particles on the Surface of the Surface Layer of an Electrophotographic Sensitive Member>

[0280] In the electrophotographic photosensitive member of the present invention, when the surface layer is observed from above, the average value and standard deviation of the distances between the centers of gravity of the convex portions CA derived from the particles PAA can be calculated as described below.

[0281] The surface of the surface layer of the electrophotographic photosensitive member is photographed using a scanning electron microscope (SEM) (“S-4800”, manufactured by JEOL Ltd.) at an acceleration voltage of 10 kV. Photographic images of the surface layer of the electrophotographic photosensitive member of the present invention with a magnification of 30,000 are captured at a total of 12 positions using a scanner: three positions including positions 50 mm from each end of the electrophotographic photosensitive member in the longitudinal direction and the center position; and four positions at 90° intervals in the circumferential direction. The particles PAA in the electrophotographic image are binarized using an image processing analysis device (“LUZEX AP”, manufactured by NIRECO CORPORATION).

[0282] In the pattern of the distances between the centers of gravity of adjacent particles PAA, as Figure 4 shown, the distances between the centers of gravity of adjacent particles PAA are measured, and the average value of the distances between the centers of gravity is calculated. In this case, the distance between the centers of gravity is calculated by Voronoi division of the respective centers of gravity of the particles PAA. The distances between the centers of gravity and the standard deviation are calculated in a total of 10 fields of view, and the average value and standard deviation of the distances between the centers of gravity of the particles in the surface layer of the electrophotographic photosensitive member are respectively defined as such.

[0283] <Method for measuring the coverage ratio S1 / (S1 + S2) of particles on the surface of the surface layer of the electrophotographic photosensitive member>

[0284] In the electrophotographic photosensitive member of the present invention, when the surface layer is observed from above, when the particles are defined as, for example, particle A, particle B, and other particles as shown in Table 4, and the area of the particles is represented as S1 and the total area of the portions other than the particles is represented as S2, the coverage ratio S1 / (S1 + S2) can be calculated as described below. In the present invention, under the setting of an acceleration voltage of 5 kV or more, the surface of the surface layer of the electrophotographic photosensitive member of the present invention is observed from above using a scanning electron microscope (SEM). The area of the image in which the particles are identified in the backscattered electron image of the surface layer is added to the area S1 occupied by the particles.

[0285] The surface of the surface layer of the electrophotographic photosensitive member was photographed using a scanning electron microscope (SEM) (“S-4800”, manufactured by JEOL Ltd.) at an acceleration voltage of 5 kV. Photographic images with a magnification of 30,000 of the surface layer of the electrophotographic photosensitive member of the present invention were captured at a total of 12 positions using a scanner: three positions including positions 50 mm from each end in the longitudinal direction of the electrophotographic photosensitive member and the central position; and four positions at 90° intervals in the circumferential direction. The particles in the electrophotographic image were binarized using an image processing analysis device (“LUZEX AP”, manufactured by NIRECO CORPORATION).

[0286] The area of the particles in the photographic image is expressed as S1, and the total area of the portions other than the particles is expressed as S2. Then, the coverage rate S1 / (S1 + S2) (%) is calculated. The coverage rate is calculated in a total of 10 fields of view, and the average value of the obtained coverage rates is defined as the coverage rate of the particles in the surface layer of the electrophotographic photosensitive member.

[0287] <Method for measuring the circularity of particle PAA of particles on the surface of the surface layer of the electrophotographic photosensitive member>

[0288] The surface of the surface layer of the electrophotographic photosensitive member was photographed using a scanning electron microscope (SEM) (“S-4800”, manufactured by JEOL Ltd.) at an acceleration voltage of 10 kV. Photographic images with a magnification of 30,000 of the surface layer of the electrophotographic photosensitive member were captured at a total of 12 positions using a scanner: three positions including positions 50 mm from each end in the longitudinal direction of the electrophotographic photosensitive member and the central position; and four positions at 90° intervals in the circumferential direction. In addition, image processing was performed on the particle PAA in the photographic image using an image processing analysis device (“LUZEX AP”, manufactured by NIRECO CORPORATION), and the average value of the circularity in a total of 10 fields of view was calculated and defined as the circularity of the particle PAA.

[0289] <Measurement of the thickness of each layer>

[0290] The thicknesses of the layers other than the surface layer and the charge generation layer of each electrophotographic photosensitive member in the examples and comparative examples were determined by a method including using an eddy current type thickness gauge (Fischerscope, manufactured by Fischer Instruments K.K.) or a method including converting the mass of the layer per unit area into specific gravity. The thickness of the charge generation layer was measured by converting the Macbeth concentration value of the electrophotographic photosensitive member using a calibration curve obtained in advance from: the Macbeth concentration value measured by pressing a spectro-concentration meter (product name: X-Rite504 / 508, manufactured by X-Rite, Inc.) against the surface of the electrophotographic photosensitive member; and the value of the thickness of the layer measured by observing its cross-sectional SEM image.

[0291] <Measurement of the relative concentration of each atom on the surface of the surface layer>

[0292] X-ray photoelectron spectroscopy analysis on the surface of the surface layer can be carried out as specifically described below.

[0293] First, five specimens for observation, each with a size of 5 mm × 5 mm, were cut out from randomly selected positions on the surface of the electrophotographic photosensitive member to prepare five specimens for observation. Subsequently, X-ray photoelectron spectroscopy (XPS) analysis was performed on the surface layer of each specimen for observation. The equipment and measurement conditions of XPS are as described below.

[0294] Equipment used: Quantum 2000, manufactured by ULVAC-PHI, Inc.

[0295] Analysis method: Narrow analysis

[0296] X-ray source: Al-Kα

[0297] X-ray conditions: 100 μm, 25 W, 15 kV

[0298] Photoelectron acceptance angle: 45°

[0299] Pass energy: 58.70 eV

[0300] Measurement range:

[0301] Under the above conditions, the peak of the C-C bond derived from the carbon 1s orbital was corrected to 285 eV. Subsequently, the relative sensitivity factors provided by ULVAC-PHI, Inc. were applied to the peak areas of the atoms whose peaks were detected at 100 eV to 103 eV. The results obtained from 5 observation specimen pieces were averaged, and the respective spectral peaks of carbon atoms, oxygen atoms, titanium atoms, and silicon atoms were integrated and converted. When the sum of the relative concentrations d(C) of carbon atoms, d(O) of oxygen atoms, d(Ti) of titanium atoms, and d(Si) of silicon atoms was defined as 100.0 atomic %, the relative concentrations d(C) of carbon atoms, d(O) of oxygen atoms, d(Ti) of titanium atoms, and d(Si) of silicon atoms were determined. The atomic concentration ratios d(Ti) (atomic %), d(Si) (atomic %), and d(Ti) / d(Si) in the metal oxide were calculated.

[0302] <Calculation of the niobium atom / titanium atom concentration ratio in the conductive particles in the surface layer of the electrophotographic photosensitive member>

[0303] A specimen piece with a size of 5 mm square was cut out from the electrophotographic photosensitive member and cut into a thickness of 200 nm at a cutting speed of 0.6 mm / s using an ultrasonic ultramicrotome (Leica, UC7) to produce a section specimen. The section specimen was observed in the STEM mode of a scanning transmission electron microscope (JEOL Ltd., JEM2800) connected to an energy dispersive X-ray spectroscopic analyzer (EDS analyzer) at a magnification of 500,000 to 1,200,000.

[0304] In the cross-section of the observed conductive particles, cross-sections of conductive particles having a maximum diameter of about 0.9 times or more and about 1.1 times or less of the above-calculated primary particle diameter were selected by visual observation. Subsequently, the spectra of the constituent elements of the selected cross-section of the conductive particles were collected using the EDS analyzer to generate an EDS mapping image. The collection and analysis of the spectra were performed using NSS (Thermo Fischer Scientific). The collection conditions were set as an acceleration voltage of 200 kV, a probe size of 1.0 nm or 1.5 nm appropriately selected to achieve a dead time of 15 or more and 30 or less, a mapping resolution of 256×256, and a number of frames of 300. EDS mapping images of 100 cross-sections of the conductive particles were obtained.

[0305] Analyze each of the obtained EDS mapping images to calculate the ratio between the internal niobium atom concentration (atomic %) and the titanium atom concentration (atomic %) at the 5% of the maximum diameter of the measured particle at the center and surface of the particle, respectively (atomic %; the same unit as the above-mentioned atomic %). Specifically, first, press the "line extraction" button of the NSS to draw a straight line in a manner consistent with the maximum diameter of the particle, and obtain the information of the atomic concentration (atomic %) on the straight line extending from one surface through the interior of the particle to the other surface. When the maximum diameter of the particle obtained by this analysis falls within a range less than 0.9 times or greater than 1.1 times the primary particle size calculated above, the particle is excluded from the subsequent analysis. (Only the particles having a maximum diameter within the range of more than 0.9 times and less than 1.1 times the primary particle size are subjected to the following analysis.) Next, on the surfaces on both sides of the particle, read the niobium atom concentration (atomic %) at the interior at 5% of the maximum diameter of the measured particle from the particle surface. Similarly, obtain the "titanium atom concentration (atomic %) at the interior at 5% of the maximum diameter of the measured particle from the particle surface". Then, by using these values, obtain the "concentration ratio between niobium atoms and titanium atoms at the interior at 5% of the maximum diameter of the measured particle from the particle surface" on each surface on both sides of the particle from the following formula.

[0306] The concentration ratio between niobium atoms and titanium atoms at the interior at 5% of the maximum diameter of the measured particle from the particle surface is (niobium atom concentration (atomic %) at the interior at 5% of the maximum diameter of the measured particle from the particle surface) / (titanium atom concentration (atomic %) at the interior at 5% of the maximum diameter of the measured particle from the particle surface).

[0307] In the present invention, the smaller value of the two obtained concentration ratios is adopted as the "concentration ratio between niobium atoms and titanium atoms at the interior at 5% of the maximum diameter of the measured particle from the particle surface".

[0308] In addition, read the niobium atom concentration (atomic %) and the titanium atom concentration (atomic %) at the position on the above-mentioned straight line that coincides with the midpoint of the maximum diameter. By using these values, obtain the "concentration ratio between niobium atoms and titanium atoms at the center of the particle" from the following formula.

[0309] The concentration ratio between niobium atoms and titanium atoms at the center of the particle is (niobium atom concentration (atomic %) at the center of the particle) / (titanium atom concentration (atomic %) at the center of the particle).

[0310] The "ratio of the concentration ratio calculated from the niobium atom concentration / titanium atom concentration inside the particle at 5% of the maximum diameter of the particle measured from the particle surface to the concentration ratio calculated from the niobium atom concentration / titanium atom concentration at the center of the particle" is (the concentration ratio between niobium atoms and titanium atoms inside the particle at 5% of the maximum diameter of the particle measured from the particle surface) / (the concentration ratio between niobium atoms and titanium atoms at the center of the particle).

[0311] <Method for Measuring the Relative Dielectric Constants ε(A) and ε(NA) of Particle A and Particles Other than Particle A>

[0312] The dielectric properties of particle A and particles other than particle A in the present invention are measured by the following method.

[0313] Weigh 0.1 g each of particle A and particles other than particle A in the present invention, and apply a load of 20 kPa to them for 1 minute to form specimens to be measured in a disk shape with a diameter of 25 mm and a thickness of 0.15 ± 0.01 mm. For particles other than particle A, particle B and other particles in the examples are pre-mixed in an input ratio and weighed.

[0314] Mount each specimen to be measured on an ARES (manufactured by TA Instruments) including a dielectric constant measurement fixture (electrode) with a diameter of 25 mm. The relative dielectric constant ε(A) and the relative dielectric constant ε(NA) are calculated respectively by the following formula (7): Under the state of applying a load of 250 g / cm 2 at a measurement temperature of 40 °C, using a 4284A precision LCR meter (manufactured by Hewlett-Packard Co., Ltd.), calculate the dielectric constant ε from the measured values of the retention dielectric constant ε′ and the loss dielectric constant ε″ of the complex dielectric constant at 100 kHz and a temperature of 40 °C, and divide the obtained value by the dielectric constant in vacuum.

[0315] ε = (ε′ 2 + ε″ 2 ) 1 / 2 … Formula (7)

[0316] [Manufacture of Electrophotographic Sensitive Member]

[0317] Manufacture a support, a conductive layer, a bottom coating layer, a charge generation layer, a charge transport layer, and a surface layer by the following method.

[0318] <Preparation of Coating Liquid 1 for Conductive Layer>

[0319] Use anatase titanium oxide with an average primary particle size of 200 nm as the substrate, and prepare a solution containing TiO 2Titanium counted as 33.7 parts and niobium counted as 2.9 parts of a sulfuric acid solution of titanium and niobium. 100 parts of the substrate were dispersed in pure water to provide 1,000 parts of a suspension, and the suspension was heated to 60 °C. The sulfuric acid solution of titanium and niobium and 10 mol / l sodium hydroxide were added dropwise over 3 hours to bring the pH of the suspension to 2 to 3. After adding all of the solution, the pH was adjusted to near the neutral value, and a polyacrylamide-based flocculant was added to precipitate the solid components. The supernatant was removed, the residue was filtered and washed, and then dried at 110 °C. Thus, an intermediate containing 0.1 wt% of the organic matter derived from the flocculant in terms of C was obtained. The intermediate was calcined in nitrogen at 750 °C for 1 hour and then in air at 450 °C to produce titanium oxide particles 1. The average primary particle size of the obtained particles measured by the above method of measuring the particle size with a scanning electron microscope was 220 nm. 2 O 5 Subsequently, 50 parts of a phenolic resin as a binder (monomer / oligomer of the phenolic resin) (product name: PLYOPHEN J-325, manufactured by DIC Corporation, resin solid content: 60%, density after curing: 1.3 g / cm

[0320] 2 ) were dissolved in 35 parts of 1-methoxy-2-propanol as a solvent to provide a solution. 2

[0321] 60 parts of titanium oxide particles 1 were added to the solution, and the mixture was charged into a vertical sand mill using 120 parts of glass beads having a number average primary particle size of 1.0 mm as a dispersion medium, and a dispersion treatment was carried out for 4 hours under the conditions of a dispersion liquid temperature of 23 °C ± 3 °C and a rotation speed of 1,500 rpm (circumferential speed 5.5 m / s). Thus, a dispersion liquid was obtained. The glass beads were removed from the dispersion liquid using a sieve. 0.01 part of silicone oil as a leveling agent (product name: SH28PAINT ADDITIVE, manufactured by Dow Corning Toray Co., Ltd.) and 8 parts of silicone resin particles as a surface roughness imparting material (product name: KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd., average primary particle size: 2 μm, density 1.3 g / cm 3 3

[0322] <Preparation of coating liquid 1 for the undercoat>

[0323] 100 parts of rutile titanium oxide particles (average primary particle size: 50 nm, manufactured by Tayca Corporation) were stirred and mixed with 500 parts of toluene. 3.5 parts of vinyltrimethoxysilane (product name: KBM-1003, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the mixture, and then the mixture was subjected to a dispersion treatment for 8 hours in a vertical sand mill using glass beads each having a diameter of 1.0 mm. After removing the glass beads, toluene was evaporated by vacuum distillation, and the residue was dried at 120 °C for 3 hours to provide rutile titanium oxide particles whose surfaces had been treated with a silicone compound. When the volume of the obtained titanium oxide particles is expressed as "a", and the average primary particle size of the titanium oxide particles is expressed as "b" [μm], the ratio "a / b" is 15.6. The value of "a" was determined from a micrograph obtained by observing a cross-section of the electrophotographic photosensitive member using a field emission scanning electron microscope (FE-SEM, product name: S-4800, manufactured by Hitachi High-Technologies Corporation) after the manufacture of the electrophotographic photosensitive member.

[0324] To a mixed solvent of 90 parts of methanol and 60 parts of 1-butanol, 18.0 parts of rutile titanium oxide particles whose surfaces had been treated with a silicone compound, 4.5 parts of N-methoxymethylated nylon (product name: TORESIN (trademark) EF-30T, manufactured by Nagase ChemteX Corporation), and 1.5 parts of a copolyamide resin (product name: AMILAN (trademark) CM8000, manufactured by Toray Industries, Inc.) were added to prepare a dispersion.

[0325] The dispersion was subjected to a dispersion treatment for 5 hours in a vertical sand mill using glass beads each having a diameter of 1.0 mm, and the glass beads were removed. Thus, a coating liquid 1 for an undercoat was prepared.

[0326] <Synthesis of phthalocyanine pigment>

[0327] (Synthesis Example 1)

[0328] Under a nitrogen flow atmosphere, 100 g of gallium trichloride and 291 g of phthalonitrile were added to 1,000 ml of α-chloronaphthalene, and the mixture was reacted at a temperature of 200 °C for 24 hours, and then the product was filtered. The obtained wet filter cake was heated and stirred in N,N-dimethylformamide at a temperature of 150 °C for 30 minutes, and then filtered. The obtained filter residue was washed with methanol and then dried to provide a chlorogallium phthalocyanine pigment with a yield of 83%.

[0329] Dissolve 20 g of the chloro-gallium phthalocyanine pigment obtained by the above method in 500 ml of concentrated sulfuric acid, and stir the solution for 2 hours. Then, drop the solution into a mixed solution of 1700 ml of distilled water and 660 ml of concentrated ammonia water that has been cooled with ice to cause the pigment to reprecipitate. Wash the precipitate thoroughly with distilled water and dry it to provide the hydroxy-gallium phthalocyanine pigment.

[0330] <Preparation of Coating Liquid 1 for Charge Generation Layer>

[0331] Mix 0.5 part of the hydroxy-gallium phthalocyanine pigment obtained in Synthesis Example 1, 7.5 parts of N,N-dimethylformamide (product code: D0722, manufactured by Tokyo Chemical Industry Co., Ltd.), and 29 parts of glass beads each with a diameter of 0.9 mm, and perform a grinding treatment at a temperature of 25 °C for 24 hours using a sand mill (BSG-20, manufactured by AIMEX Co., Ltd.). At this time, the treatment is carried out under the condition that the disk of the sand mill rotates 1,500 times in 1 minute. Filter the liquid thus treated using a filter (product number: N-NO.125T, pore size: 133 μm, manufactured by NBC Meshtec Inc.) to remove the glass beads. Add 30 parts of N,N-dimethylformamide to the liquid, then filter the mixture, and then thoroughly wash the residue on the filter with n-butyl acetate. Then, vacuum-dry the washed residue to provide 0.45 part of the hydroxy-gallium phthalocyanine pigment. The resulting pigment contains N,N-dimethylformamide.

[0332] Subsequently, mix 20 parts of the hydroxy-gallium phthalocyanine pigment obtained by the grinding treatment, 10 parts of polyvinyl butyral (product name: S-LEC (trademark) BX-1, manufactured by Sekisui Chemical Co., Ltd.), 190 parts of cyclohexanone, and 482 parts of glass beads each with a diameter of 0.9 mm, and perform a dispersion treatment at a cooling water temperature of 18 °C for 4 hours using a sand mill (K-800, manufactured by Igarashi Machine Production Co., Ltd. (now AIMEX Co., Ltd.), disk diameter: 70 mm, number of disks: 5). At this time, the treatment is carried out under the condition that each disk rotates 1,800 times in 1 minute. Remove the glass beads from the dispersion, add 444 parts of cyclohexanone and 634 parts of ethyl acetate to the residue to prepare Coating Liquid 1 for the charge generation layer.

[0333] <Preparation of Coating Liquid 1 for Charge Transport Layer>

[0334] Next, prepare the following materials to prepare a mixed solvent.

[0335] · 25 parts by mass of o-xylene

[0336] · 25 parts by mass of methyl benzoate

[0337] · 25 parts by mass of dimethoxymethane

[0338] In addition, the following materials are dissolved in a mixed solvent to prepare a coating liquid 1 for a charge transport layer.

[0339] · 5 parts by mass of a charge transport material (hole transport material) represented by the following structural formula (C-1)

[0340] · 5 parts by mass of a charge transport material (hole transport material) represented by the following structural formula (C-2)

[0341] · 10 parts by mass of polycarbonate (product name: Iupilon (trademark) Z400, manufactured by Mitsubishi Engineering-Plastics Corporation)

[0342]

[0343] (Manufacturing Example 1 of a surface layer containing particles)

[0344] Prepare the materials shown in Table 1 as particles A and particles B.

[0345] [Table 1]

[0346] Table 1

[0347]

[0348] (Manufacturing Example of Anatase Titanium Oxide Particles 1 to 3)

[0349] Anatase titanium oxide particles can be manufactured by a known sulfuric acid method. In the manufacture of titanium oxide, a solution containing titanium sulfate and titanyl sulfate as titanium compounds is hydrolyzed by heating to manufacture a hydrated titanium dioxide slurry, and the titanium dioxide slurry is dehydrated and calcined. Thus, anatase titanium oxide with an anatase degree close to 100% is obtained.

[0350] By controlling the solution concentration of titanyl sulfate in the above method, anatase titanium oxide particles 1 to 3 are manufactured respectively. Their particle sizes are shown in Table 2.

[0351] (Manufacturing Example of Anatase Titanium Oxide Particles 4)

[0352] Add niobium sulfate (water-soluble niobium compound) to the hydrated titanium dioxide slurry obtained by hydrolyzing an aqueous solution of titanyl sulfate. For the addition amount, niobium sulfate is added at a ratio of 1.8% by mass in terms of niobium ions with respect to the amount of titanium in the slurry (calculated as titanium dioxide).

[0353] Hydrolyze an aqueous solution of titanium oxysulfate added with niobium sulfate at a ratio of 1.8% by mass in terms of niobium ions to provide an aqueous titanium dioxide slurry. Next, dehydrate the aqueous titanium dioxide slurry containing niobium ions and other components, and calcine it at a calcination temperature of 1,000 °C. Thus, anatase-type titanium dioxide particles 4 containing 1.8% by mass of niobium element are obtained. Their particle sizes are shown in Table 2.

[0354] [Table 2]

[0355] Table 2

[0356] Titanium oxide particles Average primary particle size [nm] Anatase-type titanium oxide particle 1 55 Anatase-type titanium oxide particle 2 22 Anatase-type titanium oxide particle 3 220 Anatase-type titanium oxide particle 4 150

[0357] <Manufacture of Conductive Particles>

[0358] (Manufacture of Conductive Particle 1)

[0359] Dissolve niobium(V) hydroxide in concentrated sulfuric acid, and mix the solution with an aqueous solution of titanium sulfate to prepare an acidic mixed solution of niobium salt and titanium salt (hereinafter referred to as "titanium-niobium mixed solution").

[0360] Measure 100 parts of anatase-type titanium dioxide particles 1, disperse them in water as particles before coating to provide a suspension, and heat the 1,000-part water suspension to 67 °C with stirring.

[0361] While maintaining the pH of the suspension at 2.5, simultaneously add to the suspension a titanium-niobium mixed solution containing 337 g / kg Ti and 10.3 g / kg Nb based on the weight of anatase-type titanium dioxide particles 1 and an aqueous sodium hydroxide solution.

[0362] In addition, a titanium-niobium acid solution (the weight ratio between niobium atoms and titanium atoms in the solution is 1.0 / 20.0) obtained by mixing a niobium solution prepared by dissolving 3 parts of niobium pentachloride (NbCl 5 ) in 100 parts of 11.4 mol / l hydrochloric acid and 200 parts of a titanium sulfate solution containing 12.0 parts of titanium is prepared. The titanium-niobium acid solution and a 10.7 mol / l aqueous sodium hydroxide solution are simultaneously added dropwise to the above water suspension within 3 hours so that the pH of the water suspension is 2 to 3 (parallel addition). After the dropwise addition is completed, filter and wash the suspension, and dry it at 110 °C for 8 hours. The dried product is calcined in a nitrogen atmosphere at 725 °C for 1 hour together with an organic substance to provide niobium atom-containing titanium dioxide particles 1 in which niobium atoms are unevenly distributed near the surface.

[0363] Next, prepare the following materials.

[0364] · 100.0 parts of niobium atom-containing titanium dioxide particles 1

[0365] · Surface treatment agent 1 (compound represented by the following formula (S-1)) (product name: trimethoxypropylsilane, manufactured by Tokyo Chemical Industry Co., Ltd.) 6.0 parts

[0366]

[0367] · Toluene 200.0 parts

[0368] These materials were mixed and stirred with a stirring device for 4 hours, then filtered and washed. After that, the washed product was further heat-treated at 130 °C for 3 hours to provide conductive particles 1. Various physical property values are shown in Table 3.

[0369] <Manufacture of Conductive Particles 2 to 6>

[0370] Except that in the manufacture of conductive particles 1, as shown in Table 3, the type of core particles used and the weight ratio between niobium atoms and titanium atoms in the titanium-niobium mixed solution relative to the core were changed, conductive particles 2 to 6 were each manufactured in the same manner as the manufacture of conductive particles 1. Various physical property values of the obtained conductive particles 2 to 6 are shown in Table 3.

[0371] [Table 3]

[0372] Table 3

[0373]

[0374] Surface treatment agent 1: Trimethoxy(propyl)silane (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0375] Surface treatment agent 2: Dimethoxy(methyl)-n-octylsilane (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0376] Surface treatment agent 3: Decyltrimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0377] In the table, C represents "the concentration ratio between niobium atoms and titanium atoms inside the particle at 5% of the maximum diameter of the measured particle on the particle surface", and D represents "the concentration ratio between niobium atoms and titanium atoms at the center of the particle". That is, C / D is "the ratio of the concentration ratio calculated as the niobium atom concentration / titanium atom concentration at 5% of the maximum diameter of the measured particle on the particle surface to the concentration ratio calculated as the niobium atom concentration / titanium atom concentration at the center of the particle".

[0378] <Preparation of Coating Liquid 1 for Surface Layer>

[0379]

[0380] Mix the above components and stir for 6 hours using a stirring device to prepare Coating Liquid 1 for the surface layer.

[0381] <Preparation of Coating Liquids 2 to 68 for the surface layer>

[0382] Except for changing the types and addition amounts of Particle A, Particle B, and other particles as shown in Table 4, prepare Coating Liquids 2 to 68 for the surface layer in the same manner as the preparation of Coating Liquid 1 for the surface layer, respectively.

[0383] <Preparation of Coating Liquid 69 for the surface layer>

[0384]

[0385]

[0386] Mix the above components and stir for 6 hours using a stirring device to prepare Coating Liquid 69 for the surface layer.

[0387] <Preparation of Coating Liquid 70 for the surface layer>

[0388]

[0389] Mix the above components and disperse for 2 hours using a sand mill to prepare Coating Liquid 70 for the surface layer.

[0390] <Preparation of Coating Liquid 71 for the surface layer>

[0391] Methanol 10 parts by mass

[0392] Tin oxide (number-average primary particle size: 100 nm) 5 parts by mass

[0393] Disperse the above materials using a US homogenizer at room temperature for 30 minutes.

[0394] Next, add the following materials to the above dispersion and stir the mixture at room temperature for 60 minutes.

[0395] 3-Methacryloxypropyltrimethoxysilane (“KBM-503”, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.25 parts by mass

[0396] Toluene 10 parts by mass

[0397] After removing the solvent using an evaporator, heat the mixture at 120 °C for 60 minutes to provide tin oxide particles 1 surface-treated with a reactive surface treatment agent.

[0398] Subsequently, the following materials were mixed and dispersed for 60 minutes at room temperature using a US homogenizer.

[0399] 15 parts by mass of surface-treated tin oxide particles 1

[0400] 40 parts by mass of 2-butanol

[0401] Next, 0.15 g of a linear silicone surfactant (“KF-9908”, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the dispersion product, and it was further dispersed for 60 minutes at room temperature using a US homogenizer. After dispersion, the solvent was volatilized at room temperature, and the residue was dried at 120 °C for 60 minutes to produce surface-treated particles 1.

[0402]

[0403] The above components were mixed to prepare coating liquid 71 for the surface layer.

[0404] [Preparation of Coating Liquid 72 for Surface Layer]

[0405]

[0406] The above components were mixed to prepare coating liquid 72 for the surface layer.

[0407] [Preparation of Coating Liquid 73 for Surface Layer]

[0408]

[0409]

[0410] The above components were mixed and stirred at 40 °C and a rotation speed of 1500 rpm using a sand mill. The tin oxide particles were surface-treated with a surfactant having a reactive organic group.

[0411] In addition, the above-treated mixture was taken out and charged into a Henschel mixer, and then stirred at a rotation speed of 1500 rpm for 15 minutes. After that, the obtained product was dried at 120 °C for 3 hours to provide surface-treated tin oxide particles 2.

[0412]

[0413] Next, the above components were mixed and dispersed at a rotation speed of 1500 rpm using a sand mill to provide coating liquid 73 for the surface layer.

[0414] [Table 4]

[0415]

[0416]

[0417]

[0418] <Manufacturing Example of Electrophotographic Sensitive Member 1>

[0419] (Support)

[0420] An aluminum cylinder with a diameter of 24 mm and a length of 257 mm is used as the support (cylindrical support).

[0421] (Conductive Layer)

[0422] The conductive layer coating liquid 1 is applied to the above-mentioned support by dip coating to form a coating film, and the coating film is cured by heating at 150 °C for 30 minutes. Thus, a conductive layer with a thickness of 22 μm is formed.

[0423] (Undercoat)

[0424] The undercoat coating liquid 1 is applied to the above-mentioned conductive layer by dip coating to form a coating film, and the coating film is cured by heating at 100 °C for 10 minutes. Thus, an undercoat with a thickness of 1.8 μm is formed.

[0425] (Charge Generation Layer)

[0426] The charge generation layer coating liquid 1 is applied to the above-mentioned undercoat by dip coating to form a coating film, and the coating film is dried by heating at a temperature of 100 °C for 10 minutes. Thus, a charge generation layer with a thickness of 0.20 μm is formed.

[0427] (Charge Transport Layer)

[0428] The charge transport layer coating liquid 1 is applied to the above-mentioned charge generation layer by dip coating to form a coating film, and the coating film is dried by heating at a temperature of 120 °C for 30 minutes. Thus, a charge transport layer with a thickness of 21 μm is formed.

[0429] (Surface Layer)

[0430] The surface layer coating liquid 1 is applied to the above-mentioned charge transport layer by dip coating to form a coating film, and the temperature of the coating film is raised by 5 minutes at a temperature of 50 °C. Then, in a nitrogen atmosphere, under the conditions of an acceleration voltage of 65 kV and a beam current of 5.0 mA, the coating film is irradiated with an electron beam for 2.0 seconds, while the support (the irradiated object) is rotated at a speed of 300 rpm. The dose of the electron beam is 15 kGy. Then, in a nitrogen atmosphere, the temperature of the coating film is raised to 120 °C. The oxygen concentration in the atmosphere during the period from electron beam irradiation to subsequent heat treatment is 10 ppm.

[0431] Next, in air, the coated film was naturally cooled until its temperature reached 25°C, and then heat treatment was carried out for 30 minutes under the condition that the temperature of the coated film reached 120°C. Thus, a surface layer with a thickness of 1.0 μm was formed. The physical properties of the obtained electrophotographic photosensitive member are shown in Table 5.

[0432] <Manufacturing Examples of Electrophotographic Photosensitive Members 2 to 68>

[0433] Except that in the manufacture of the electrophotographic photosensitive member 1, the coating liquid 1 for the surface layer was changed as shown in the conditions in Table 5, electrophotographic photosensitive members 2 to 68 were each manufactured in the same manner as in the manufacture of the electrophotographic photosensitive member 1. The physical properties of the obtained electrophotographic photosensitive members 1 to 68 are shown in Table 5.

[0434] <Manufacturing Example of Electrophotographic Photosensitive Member 69>

[0435] Except that in the manufacture of the electrophotographic photosensitive member 1, the coating liquid 1 for the surface layer was changed to the coating liquid 69 for the surface layer, the electrophotographic photosensitive member 69 was manufactured in the same manner as in the manufacture of the electrophotographic photosensitive member 1. The physical properties of the obtained electrophotographic photosensitive member are shown in Table 5.

[0436] <Manufacturing Example of Electrophotographic Photosensitive Member 70>

[0437] In the manufacture of the electrophotographic photosensitive member 1, the same manufacture as that of the electrophotographic photosensitive member 1 was carried out until the charge transport layer was formed. After that, the coating liquid 70 for the surface layer was applied to the charge transport layer, and then UV light was irradiated for 1 minute (cumulative light amount: 960 mJ / cm 2 ) by using a metal halide lamp to manufacture the electrophotographic photosensitive member 70. The physical properties of the obtained electrophotographic photosensitive member 70 are shown in Table 5. 2

[0438] <Manufacturing Example of Electrophotographic Photosensitive Member 71>

[0439] In the manufacture of the electrophotographic photosensitive member 1, the same manufacture as that of the electrophotographic photosensitive member 1 was carried out until the charge transport layer was formed. After that, the coating liquid 71 for the surface layer was applied to the charge transport layer, and then UV light was irradiated for 1 minute (irradiation intensity: 15 mW / cm 2 ) by using a metal halide lamp, and then dried at 80°C for 120 minutes to manufacture the electrophotographic photosensitive member 71. The physical properties of the obtained electrophotographic photosensitive member 71 are shown in Table 5.

[0440] <Manufacturing Example of Electrophotographic Photosensitive Member 72>

[0441] In the manufacture of the electrophotographic photosensitive member 1, the same manufacturing process as that of the electrophotographic photosensitive member 1 is carried out until the charge transport layer is formed. Thereafter, the surface layer coating liquid 72 is applied to the charge transport layer, and then UV light is irradiated for 20 seconds by using a metal halide lamp at an irradiation intensity of 500 mW / cm 2 , and then dried at 130 °C for 30 minutes to manufacture the electrophotographic photosensitive member 72. The physical properties of the obtained electrophotographic photosensitive member 72 are shown in Table 5.

[0442] <Manufacturing Example of Electrophotographic Photosensitive Member 73>

[0443] In the manufacture of the electrophotographic photosensitive member 1, the same manufacturing process as that of the electrophotographic photosensitive member 1 is carried out until the charge transport layer is formed. Thereafter, the surface layer coating liquid 73 is applied to the charge transport layer, and then UV light is irradiated for 1 minute (cumulative light amount: 960 mJ / cm 2 ) by using a metal halide lamp at an irradiation intensity of 16 mW / cm to manufacture the electrophotographic photosensitive member 73. The physical properties of the obtained electrophotographic photosensitive member 73 are shown in Table 5. 2

[0444] [Table 5-1]

[0445]

[0446]

[0447]

[0448] [Table 5-2]

[0449] Table 5 (continued)

[0450]

[0451]

[0452] In the table, C represents "the concentration ratio between niobium atoms and titanium atoms inside the particle at 5% of the maximum diameter of the measured particle on the particle surface", and D represents "the concentration ratio between niobium atoms and titanium atoms at the center of the particle". That is, C / D is the "ratio of the concentration ratio calculated as the niobium atom concentration / titanium atom concentration at 5% of the maximum diameter of the measured particle on the particle surface to the concentration ratio calculated as the niobium atom concentration / titanium atom concentration at the center of the particle".

[0453] <Manufacturing Example of Toner Particle 1>

[0454] (Preparation of Aqueous Medium 1)

[0455] ​Charge 650.0 parts of ion-exchanged water and 14.0 parts of sodium phosphate (manufactured by RASA Industries, Ltd., dodecahydrate) into a reaction vessel equipped with a stirrer, a thermometer, and a reflux pipe. Maintain the temperature of the mixture at 65°C for 1.0 hour while purging the vessel with nitrogen.

[0456] When the mixture is stirred at 15,000 rpm using a T.K. HOMOMIXER (manufactured by Tokushu Kika Kogyo Co., Ltd.), a calcium chloride aqueous solution obtained by dissolving 9.2 parts of calcium chloride (dihydrate) in 10.0 parts of ion-exchanged water is added to the mixture all at once to prepare an aqueous medium containing a dispersion stabilizer. Additionally, 10 mass% hydrochloric acid is added to the aqueous medium to adjust its pH to 5.0. Thus, aqueous medium 1 is obtained.

[0457] (Preparation of Polymerizable Monomer Composition)

[0458] · Styrene 60.0 mass parts

[0459] · C.I. Pigment Blue 15:3 6.5 mass parts

[0460] Charge this material into a grinder (manufactured by Mitsui Miike Kakoki K.K.), disperse it with zirconia particles each having a diameter of 1.7 mm at 220 rpm for 5.0 hours, and then remove the zirconia particles. Thus, a colorant dispersion is prepared.

[0461]

[0462] (Condensate of propylene oxide-modified bisphenol A (2 mol adduct) and terephthalic acid (molar ratio 10:12), glass transition temperature (Tg): 68°C, weight-average molecular weight (Mw): 10,000, molecular weight distribution (Mw / Mn): 5.12)

[0463] · Fischer-Tropsch wax (melting point: 78°C) 7.0 mass parts

[0464] Meanwhile, add this material to the above colorant dispersion and heat the mixture to 65°C. Thereafter, dissolve and disperse the material uniformly in the dispersion at 500 rpm using a T.K. HOMOMIXER (manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare a polymerizable monomer composition.

[0465] (Granulation Step)

[0466] When the temperature of the aqueous medium 1 is adjusted to 70 °C and the rotation speed of the T.K.HOMOMIXER is maintained at 15,000 rpm, the polymerizable monomer composition is put into the aqueous medium 1, and 10.0 parts by mass of tert-butyl peroxyneodecanoate as a polymerization initiator is added thereto. The mixture is granulated as it is for 10 minutes using a stirring device while maintaining the rotation speed at 15,000 rpm.

[0467] (Polymerization step and distillation step)

[0468] After the granulation step, the stirrer is changed to a propeller-type stirring blade, and polymerization is carried out for 5.0 hours by maintaining the temperature of the granulated material at 70 °C while stirring the granulated material at 150 rpm. In addition, polymerization is carried out by raising the temperature to 85 °C and maintaining it at this temperature for 2.0 hours. After that, the reflux pipe of the reaction vessel is replaced with a cooling pipe, and distillation is carried out for 6 hours by heating the obtained slurry to 100 °C, thereby evaporating the unreacted polymerizable monomer. Thus, the toner particle dispersion liquid 1 is obtained.

[0469] (Filtration step, washing step, drying step, classification step)

[0470] Hydrochloric acid is added to the obtained toner particle dispersion liquid 1 to set the pH to 1.4 or less, the above-mentioned dispersion stabilizer is dissolved in this liquid, and then it is filtered, washed, dried, and classified. Thus, the toner particles 1 are obtained. The number average particle diameter (D1) of the toner particles 1 is 6.2 μm, and the weight average particle diameter (D4) is 6.7 μm.

[0471] <Manufacturing example of toner 1>

[0472] 100.0 parts by mass of the obtained toner particles 1 and 1.0 part by mass of fine silica particles (hydrophobized with hexamethyldisilazane, number average particle diameter of primary particles: 8 nm, BET specific surface area: 160 m 2 / g) are mixed in a Henschel mixer (manufactured by Mitsui Miike Kakoki K.K.). The obtained mixture is sieved through a sieve with a mesh size of 75 μm to provide toner 1.

[0473] [Evaluation method]

[0474] Examples and comparative examples are evaluated by the following evaluation methods.

[0475] <Evaluation of transferability (Evaluation method 1)>

[0476] A modified machine of a commercially available laser beam printer "i-SENSYS LBP 673Cdw" manufactured by Canon Inc. is used. The printer is modified as follows: The main body and software of the evaluation machine are changed so that the bias voltage applied in the transfer step can be changed.

[0477] Take out the toner in the cyan cartridge of the evaluation machine "i-SENSYS LBP 673Cdw" and load 1 an appropriate amount of toner into it. Place the cyan toner cartridge with the reloaded toner in a normal temperature and normal humidity environment (25°C, 50% RH; hereinafter also referred to as "in the N / N environment") for 24 hours. Install the cyan toner cartridge placed in this environment on the above-mentioned evaluation machine, and output an image with a printing rate of 2.0% on up to 30 sheets of A4 paper as follows in the N / N environment: Configure margins with a width of 50 mm on both the left and right sides of the paper, and output the image at the center of the horizontal direction of the paper. Use plain paper CS-680 (68 g / m 2 )(Canon Marketing Japan Inc.) as the paper.

[0478] Next, output an overall solid image with a width of 30 mm in the vertical direction of the plain paper CS-680. Stop the output when forming the solid image, and collect the transfer residual toner on the electrophotographic photosensitive member using a transparent tape (polyester tape 5511, manufactured by NICHIBAN Co., Ltd.) made of transparent polyester.

[0479] The concentration of the transfer residual toner is measured by the following method. Paste the transparent tape that has been peeled off from the surface of the electrophotographic photosensitive member and has collected the transfer residual toner and a brand-new transparent tape onto high white paper (GF-C081, Canon Inc.) respectively. Then, measure the concentration D1 of the transparent tape in the part that has collected the transfer residual toner and the concentration D0 of the brand-new transparent tape part using an X-Rite color reflection densitometer (manufactured by X-Rite, Inc., X-Rite 500 series) respectively.

[0480] As the concentration of the transfer residual toner (transfer residual concentration), the difference "D1 - D0" obtained by measurement is adopted. The smaller the value of the transfer residual toner concentration (transfer residual concentration), the less the amount of the transfer residual toner means.

[0481] Judge the transferability as follows. Based on the following criteria, classify the obtained transfer residual concentration into 5 grades from A to E. Consider grades A to D in the grades as the grades showing the effects of the present invention. The evaluation results are shown in Table 6.

[0482] (Evaluation criteria)

[0483] A: The transfer residual concentration is less than 0.02.

[0484] B: The transfer residual concentration is 0.02 or more and less than 0.05.

[0485] C: The transfer residue concentration is 0.05 or more and less than 0.10.

[0486] D: The transfer residue concentration is 0.10 or more.

[0487] <Evaluation of Transferability during Durability (Evaluation Method 2)>

[0488] As one of the durability evaluations, after evaluating the transfer residue toner with tape, an image with a print rate of 2.0% is output on up to 5,000 sheets of A4 paper in an N / N environment as follows: Margins with a width of 50 mm each are arranged on the left and right sides of the paper, and the image is output at the center of the horizontal direction of the paper. Then, in the same manner as in the <Evaluation of Transferability> above in the <Evaluation of Transferability (Evaluation Method 1)>, the transfer residue toner is evaluated by tape. Judgment is made based on the same evaluation criteria.

[0489] <Evaluation of Roughness (Evaluation Method 3)>

[0490] As one of the durability evaluations, after outputting a character image with a print rate of 1% on 10,000 sheets of paper using a modified machine placed in an environment of 30°C and 80% RH, a halftone (20H) image is formed, and the roughness (concentration uniformity) of the image is evaluated based on the following criteria. Use ordinary paper CS-680 (68 g / m 2 )(Canon Marketing Japan Inc.) as the paper. The 20H image is a halftone image using values representing 256 gray levels expressed in hexadecimal format, where 00H is solid white (non-image) and FFH is solid black (full image).

[0491] As the evaluation criteria for roughness, the roughness is evaluated based on the following criteria. Concentration measurements are taken at 20 positions, and judgment is made as follows based on the value of the concentration difference between the maximum and minimum values (concentration uniformity). Use an X-Rite color reflection densitometer (manufactured by X-Rite, Inc., X-Rite 500 series) to measure the concentration.

[0492] (Evaluation Criteria)

[0493] A: The concentration uniformity is less than 0.04.

[0494] B: The concentration uniformity is 0.04 or more and less than 0.06.

[0495] C: The concentration uniformity is 0.06 or more and less than 0.08.

[0496] D: The concentration uniformity is 0.08 or more.

[0497] <Evaluation of Durability Concentration Change (Evaluation Method 4)>

[0498] As one of the durability evaluations, the concentration change during the durability test is evaluated using a modified machine placed in an environment of 30 °C and 80% RH. An original image with solid black patches each having a size of 20 mm × 20 mm is output at five positions in the developing area, and the developing bias is set so that the initial reflection concentration is 1.3. Next, a durability test of outputting text images with a printing rate of 1% on 10,000 sheets of paper is performed. Ordinary paper CS-680 (68 g / m 2 )(Canon Marketing Japan Inc.) is used as the paper. The durability is evaluated by comparing the concentration difference between the image concentration after the durability test and the initial image concentration, based on the average concentration of the five points of the solid black patches.

[0499] The image concentration is obtained by measuring the concentration with respect to the white background blank part of the original image using a "Macbeth Reflection Densitometer RD918" (manufactured by Macbeth).

[0500] (Evaluation Criteria)

[0501] A: The concentration difference is less than 0.10.

[0502] B: The concentration difference is 0.10 or more and less than 0.15.

[0503] C: The concentration difference is 0.15 or more and less than 0.20.

[0504] D: The concentration difference is 0.20 or more.

[0505] The results are shown in Table 6 below.

[0506] [Table 6]

[0507]

[0508]

[0509]

[0510] The present invention is not limited to the above-described embodiments, and various changes and improvements can be made without departing from the gist and scope of the present invention. In order to disclose the scope of the present invention, the claims are appended herein.

[0511] This application claims priority based on Japanese Patent Application No. 2022-167788 filed on October 19, 2022, and Japanese Patent Application No. 2023-072647 filed on April 26, 2023, the entire contents of which are incorporated herein by reference.

[0512] Description of Reference Numerals

[0513] 100 Electro-photographic apparatus

[0514] a, b, c, d Image forming section

[0515] 1a, 1b, 1c, 1d Electro-photographic photosensitive member

[0516] 2a, 2b, 2c, 2d Charging roller

[0517] 3a, 3b, 3c, 3d Exposure device

[0518] 4a, 4b, 4c, 4d Developing device

[0519] 5a, 5b, 5c, 5d Static eliminator

[0520] 41a, 41b, 41c, 41d Developing device

[0521] 10 Intermediate transfer belt

[0522] 11 Driving roller

[0523] 12 Tension roller

[0524] 13 Opposing roller

[0525] 14a, 14b, 14c, 14d Metal roller

[0526] 15 Secondary transfer roller

[0527] 17 Belt cleaning device

[0528] 30 Fixing device

[0529] 50 Paper feeding device

[0530] P Transfer material

[0531] 101 Support

[0532] 102 Undercoat layer

[0533] 103 Charge generation layer

[0534] 104 Charge transport layer

[0535] 105 Surface layer

[0536] 106 Insulating particle

[0537] 107 Conductive particle

[0538] 108 Binder resin

[0539] 31 Center part of the conductive particle

[0540] 32 Near the surface of the conductive particle

[0541] 33 Electron beam analyzing the center part of the conductive particle

[0542] 34 Electron beam analyzing the inside at 5% of the primary particle diameter on the surface of the conductive particle

[0543] 201 First peak

[0544] 202 Second peak

Claims

1. An electrophotographic photosensitive member comprising a surface layer containing particles and a binder resin, wherein the particles in the surface layer have multiple peaks in the particle size distribution on a number basis, wherein, when among the peaks where the peak tops are each 20 nm or more in the multiple peaks, the peak having the highest frequency at the peak top is defined as the first peak, and the peak having the second highest frequency at the peak top after the first peak is defined as the second peak, and when among the first peak and the second peak, the peak having a larger particle size value at the peak top is defined as peak PEA, the particle size DA at the peak top of the peak PEA falls within the range of 80 nm or more and 300 nm or less, wherein, when among the particles in the surface layer, the particles having particle sizes each within the range of DA ± 20 nm are defined as particles PAA, and the protrusions having heights each within the range of 10 nm or more and 300 nm or less and originating from the particles PAA are defined as protrusions CA, the protrusions CA are disposed on the surface of the surface layer, wherein, when the surface layer is observed from above, the average value of the distances between the centers of gravity of the protrusions CA is 150 nm or more and 500 nm or less, and the standard deviation of the distances between the centers of gravity of the protrusions CA is 250 nm or less, and wherein, when the surface layer is observed from above, and when the area occupied by the particles on the surface of the surface layer is represented by S1 and the area occupied by the portions other than the particles is represented by S2, S1 / (S1 + S2) is 0.70 or more and 1.00 or less.

2. The electrophotographic photosensitive member according to claim 1, wherein, when the average value of the thickness of the surface layer at the portion not containing the particles PAA in the cross section of the surface layer is represented by T, the DA and the T satisfy the following formula (1):

3. The electrophotographic photosensitive member according to claim 1 or 2, wherein, when among the first peak and the second peak, the peak having a smaller particle size value at the peak top is defined as peak PEB, the particle size at the peak top of the peak PEB is represented by DB, and in the cross section of the surface layer, the average value of the thickness of the surface layer at the portion not containing the particles PAA is represented by T, the DB and the T satisfy the following formula (2):

4. The electrophotographic photosensitive member according to claim 3, wherein the DA and the DB satisfy the following formula (3): DB / DA > 1 / 10... Formula (3).

5. The electrophotographic photosensitive member according to any one of claims 1 to 4, wherein the ratio of the number of the protrusions CA to the total number of the protrusions present on the surface of the surface layer is 90 number % or more.

6. The electrophotographic photosensitive member according to any one of claims 1 to 5, wherein the half-value width of the peak PEA is 20 nm or more and 50 nm or less.

7. The electrophotographic photosensitive member according to any one of claims 1 to 6, wherein the maximum height difference Rz of the surface of the surface layer is 100 nm or more and 400 nm or less.

8. The electrophotographic photosensitive member according to any one of claims 1 to 7, wherein each of the particles PAA has a circularity of 0.950 or more.

9. The electrophotographic photosensitive member according to any one of claims 1 to 8, wherein the relative dielectric constant ε(A) of each of the particles A in the surface layer is 5 or less, and the relative dielectric constant ε(NA) of each of the particles other than the particles A introduced into the surface layer is 5 or more greater than the ε(A).

10. The electrophotographic photosensitive member according to claim 9, wherein the particles other than the particles PAA in the surface layer are conductive particles obtained by treating the surface of metal oxide particles with a Si-containing compound, and wherein, in the X-ray photoelectron spectroscopy analysis of the surface layer, when the sum of the relative concentrations d(C), d(O), d(Ti), and d(Si) of carbon atoms, oxygen atoms, titanium atoms, and silicon atoms determined by the X-ray photoelectron spectroscopy analysis is defined as 100.0 atomic%, the d(Ti) (atomic%) and the d(Si) (atomic%) satisfy the following formulas (4) to (6): 0 < d(Ti) ≤ 2.0 … Formula (4) 0.01 ≤ d(Ti) / d(Si) ≤ 1.0 … Formula (6).

11. The electrophotographic photosensitive member according to claim 10, wherein, in each of the conductive particles, in the energy dispersive X-ray analysis (EDS analysis) connected to a scanning transmission electron microscope (STEM), the ratio of the niobium atom / titanium atom concentration in the interior at 5% of the maximum diameter of the conductive particle from the surface of the conductive particle to the niobium atom / titanium atom concentration in the central portion of the conductive particle is 2.0 or more.

12. A processing cartridge, which comprises: the electrophotographic photosensitive member according to any one of claims 1 to 11; and at least one device selected from the group consisting of a charging device; a developing device; and a cleaning device, the processing cartridge integrally supports the electrophotographic photosensitive member and the at least one device, and is detachably mounted on the main body of an electrophotographic apparatus.

13. An electrophotographic apparatus, which comprises: the electrophotographic photosensitive member according to any one of claims 1 to 11; and a charging device, an exposure device, a developing device, and a transfer device.

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