JP2011099983A - Image forming apparatus and method for manufacturing photoreceptor used in the apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce image density unevenness due to periodical development unevenness caused by deflection of a photoreceptor surface at low cost, while suppressing an increase in power consumption or unnecessary consumption of a toner in an image forming apparatus. <P>SOLUTION: An image forming apparatus is provided, which uniformly charges the surface of a photoreceptor 1 by a charging means to a predetermined charge potential, and subsequently exposes the photoreceptor, generates charges in a charge generating layer in the photosensitive layer of the photoreceptor, attenuates the charge potential of the exposed area, thereby forming an electrostatic latent image in the exposed portion, and then develops the electrostatic latent image by depositing a developer on a developing roller onto the electrostatic latent image on the photoreceptor surface by a development electric field formed between the electrostatic latent image part on the photoreceptor surface and the surface part of the developing roller 51 opposing to each other across a developing gap 11. In the image forming apparatus, the thickness of the charge transport layer in the photoreceptor is controlled so that the layer becomes thinner in a portion where the amount of surface deflection of the photoreceptor is relatively large, when the photoreceptor is rotated around the rotation axis 14, than in a portion where the amount of surface deflection is small in a rotation direction of the photoreceptor. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a copying machine, a printer, and a printer that perform image formation using a photosensitive member having a photosensitive layer comprising a charge generating layer and a charge transporting layer located on the surface side of the charge generating layer on a cylindrical conductive support. The present invention relates to an image forming apparatus such as a facsimile and a method of manufacturing a photoreceptor used therefor.

  In general, this type of image forming apparatus forms an electrostatic latent image by an electrostatic charge on a photosensitive member having a photosensitive layer containing a photoconductive substance and the like, and a charged toner (developer) is applied to the electrostatic latent image. ) To form a visible image. This visible image is finally transferred to a recording material such as paper, and then fixed to the recording material with heat, pressure, solvent gas, or the like to obtain an output image. In such an image forming apparatus, a method of charging a toner for visualizing a toner, a two-component developing method using frictional charging by stirring and mixing the toner and a carrier, and a toner without using a carrier are used. It is roughly divided into those employing a one-component development system that applies charge to the substrate. The one-component development method is further classified into a magnetic one-component development method and a non-magnetic one-component development method depending on whether or not a magnetic force is used to hold toner by the developing roller. In general, image forming apparatuses such as copiers and multi-function machines that require high speed and image reproducibility often employ two-component development systems that are advantageous in terms of toner charging stability, start-up property, and long-term image quality. Is done. On the other hand, one-component development systems are often used in image forming apparatuses such as small printers and facsimiles that require space saving and cost reduction. In recent years, in any of the development methods, the colorization of the output image has progressed, and the demand for higher image quality and stabilization of the image quality has increased. In order to improve the image quality, the average particle size of the toner is reduced, and the particle shape has a more round shape with no angular portions.

In order to achieve high image quality in an image forming apparatus using a photoconductor, it is required to make the electrostatic latent image formed on the photoconductor visible without development unevenness and to reduce image density unevenness as much as possible. In order to meet this demand, conventionally, it has been considered important to maintain a constant development gap, which is the minimum distance between the surface of the photoreceptor and the surface of the developer carrying member, as described below.
That is, if there is a difference in the development gap, the development electric field formed between the electrostatic latent image on the surface of the photoreceptor and the surface of the developer carrying member changes due to the difference in the development gap. Specifically, the development electric field is smaller at a location where the development gap is wider than at a location where the development gap is narrow. When a difference occurs in the development gap, development unevenness occurs in which the toner adhesion amount (development amount) differs with respect to the same electrostatic latent image, and finally, image density unevenness occurs on the visible image. Therefore, conventionally, it has been considered important to keep the development gap constant so that the development gap does not change, which causes development unevenness.

  However, if the development gap is kept constant, the component cost and the manufacturing cost increase as will be described below. Therefore, in the current situation where there is a strong demand for cost reduction, it is practically difficult to keep the development gap constant.

  That is, due to demands for downsizing and cost reduction of the image forming apparatus, the cylindrical conductive support used for the photoreceptor tends to have a small diameter and a small thickness, and its dimensional accuracy is also to some extent. Has width (manufacturing tolerance). If the cross section orthogonal to the photoconductor axis direction of the photoconductor having the conductive support is not a perfect circle, or the rotation axis is deviated from the central axis even if the cross section is a perfect circle In the case of being decentered, shake occurs on the surface of the photoconductor when rotated about the rotation axis. Therefore, in a general configuration where the distance between the rotation axis of the photosensitive member and the rotation axis of the developer carrying member is constant, the development gap fluctuates in one rotation cycle of the photosensitive member due to the fluctuation of the surface of the photosensitive member. To do. Therefore, periodic development unevenness having one rotation cycle of the photosensitive member occurs due to the fluctuation of the development gap.

As an image forming apparatus capable of eliminating such development unevenness, for example, those described in Patent Document 1 and Patent Document 2 are known.
In the image forming apparatuses described in Patent Documents 1 and 2, the rotation shaft of the developer carrying member is configured to be displaceable with respect to the rotation shaft of the photosensitive member. Then, in a state where the abutting member provided on the developer carrier side is brought into contact with the non-image area existing outside in the axial direction of the image area (area where the electrostatic latent image can be formed) on the photoreceptor surface, The photoreceptor and the developer carrying member rotate. The abutting member maintains a separated state between the image area on the surface of the photoreceptor and the surface of the developer carrying member facing the image area, and a development gap is formed. According to this image forming apparatus, even if the cross section of the photoconductor is not a perfect circle or the rotation axis of the photoconductor is eccentric, the developing gap is maintained constant by the abutting member. Therefore, periodic development unevenness corresponding to one rotation cycle of the photosensitive member as described above does not occur.

  However, in these image forming apparatuses, it is necessary to give sufficient strength to the conductive support of the photosensitive member so that the photosensitive member is not deformed by the contact pressure of the abutting member. For this purpose, a measure for obtaining sufficient strength is required, such as increasing the thickness of the conductive support of the photosensitive member or performing processing for increasing the material strength of the conductive support. As a result, the parts cost and manufacturing cost of the photoreceptor increase.

  On the other hand, not the configuration using the abutting member as described above (the configuration in which the rotation shaft of the developer carrying member can be displaced with respect to the rotation shaft of the photosensitive member), but the rotation shaft of the photosensitive member and the rotation shaft of the developer carrying member. In the case of a general configuration in which the inter-axis distance is constant, the contact pressure by the abutting member is not applied to the photosensitive member. Therefore, the thickness of the conductive support of the photosensitive member can be reduced, and processing for obtaining an unnecessarily high strength is not necessary. Therefore, it is possible to prevent the cost of parts and manufacturing cost of the photosensitive member from rising, and to reduce the cost. Even in this case, if the photoconductor is manufactured so that the cross section of the photoconductor is almost a perfect circle and the rotation axis of the photoconductor is not decentered, the development gap can be made substantially constant, As will be described below, it is possible to sufficiently reduce the occurrence of the above-described development unevenness and reduce the image density unevenness.

FIG. 8 is a graph illustrating the relationship between the development electric field and the development amount (toner adhesion amount).
As shown in this graph, the development amount tends to increase as the development electric field strength increases in the region where the development electric field is weak, but in the region where the development electric field is strong, the toner attached to the electrostatic latent image becomes an obstacle. As a result, the toner becomes difficult to move to the electrostatic latent image side, and finally, the toner cannot move to the electrostatic latent image side, and the development amount becomes saturated. If the development amount is close to saturation, the toner image transferred onto the recording material is in a state where the toner layer is sufficiently overlapped. There is almost no difference in image density after fixing. Therefore, if image formation can be performed in a state where saturation development is always performed in this way, image density unevenness can be sufficiently suppressed. Hereinafter, the lower limit value of the developing electric field at which a developing amount within a range in which the image density hardly varies is obtained is a saturated developing electric field value A, and the developing electric field is equal to or higher than the saturated developing electric field value A [V / m]. The development performed is called “saturated development”.

  As described above, even when the development electric field fluctuates due to a change in the development gap, if the development electric field always fluctuates within the range of the saturation development electric field value A or more, image formation is always performed in a state where saturation development is performed. Image density unevenness can be sufficiently suppressed. Therefore, in a general configuration in which the distance between the rotation axis of the photosensitive member and the rotation axis of the developer carrying member is constant, the cross section of the photosensitive member is almost a perfect circle and the rotation axis of the photosensitive member is not decentered. In addition, if the photoreceptor is manufactured and the development gap can be made substantially constant, the development gap is set so that the development electric field is always within the range of the saturation development electric field value A or more, so that saturated development can be used. Image density unevenness can be sufficiently suppressed.

  However, in order to achieve high processing accuracy so that the cross section of the photoconductor is almost a perfect circle and the eccentricity of the rotation axis of the photoconductor is almost eliminated, the parts cost and manufacturing cost of the photoconductor are increased. Become. In addition, there is a concern that production efficiency may be reduced as a result of severe restrictions imposed on the handling of the photoconductor in the manufacturing process. Therefore, maintaining a constant development gap in a general configuration where the distance between the rotation axis of the photosensitive member and the rotation axis of the developer carrier is constant is realistic in the current situation where there is a strong demand for cost reduction. It is difficult to.

  On the other hand, in order to meet the demand for cost reduction, in this general configuration, if an inexpensive configuration in which the cross section of the photoconductor is not a perfect circle and the rotating shaft of the photoconductor is eccentric is adopted, A large shake occurs on the surface, and a large fluctuation occurs in the development gap. Even when the development gap fluctuates greatly as described above, it is possible to adjust the development electric field so that it constantly fluctuates within the saturation development electric field value A or more by setting the development bias sufficiently high. Therefore, even with such an inexpensive configuration, it is possible to sufficiently suppress the image density unevenness by utilizing the saturation development.

  However, in the case of adjusting the developing electric field so as to always fluctuate within the range of the saturated developing electric field value A or more with such an inexpensive configuration, the conventional general idea of adjusting the developing electric field with the developing bias is the developing bias. Must be set high. In this case, it is necessary to increase not only the developing bias but also the charging bias accordingly, leading to an increase in power consumption of the entire image forming apparatus, which is contrary to the recent demand for energy saving.

Moreover, the present inventors obtained the following knowledge as a result of research.
Generally, the shake amount on the surface of the photoconductor is not uniform and varies in the direction of the photoconductor rotation axis. That is, the photosensitive member has a portion with a relatively large shake amount and a small portion in the direction of the photosensitive member rotation axis. The reason for the difference in the shake amount in the direction of the photosensitive member rotation axis is mainly due to the manufacturing process of the photosensitive member and the handling of the photosensitive member during the manufacturing of the photosensitive member.
To explain with specific examples, when producing a photoreceptor, a charge generation layer, a charge transport layer, or other layers (protective layer, etc.) constituting the photosensitive layer are formed by ring coating, dip coating (dipping coating), spray coating. It is often formed by a coating method such as. Among them, dip coating is widely used because of its high productivity. In the case of forming a layer by this dip coating, for example, the conductive support that is the upper end side in the dipping posture in which the conductive support is erected so that the coating liquid does not enter the cylinder inside the cylindrical conductive support. The end is closed with an air chuck or the like so that the air inside the cylinder does not leak from the upper end side, and the conductive support in the dipping posture is immersed in the coating liquid to a predetermined depth. In such a multi-layered layer forming process, the conductive support is repeated in a plurality of coating and drying steps in a state where the conductive support is held only at the upper end side in the dipping posture. In such a multi-layer formation process, the conductive support in an immersion position is usually moved while holding its upper end side. Bending force is applied by deceleration. For this reason, roundness is easy to deteriorate at the upper end side of the electroconductive support body of immersion position compared with the lower end side. In particular, when the thickness of the conductive support is reduced for cost reduction or weight reduction, or when the diameter of the photoconductor is reduced for downsizing of the apparatus, the deterioration of roundness is significant. Become. As described above, when the photoreceptor layer is formed by dip coating, the roundness of the upper end side of the conductive support in the dipping posture tends to be worse than that of the lower end side. The amount of deflection on the side is larger than that on the other end.
For a reason different from this specific example, for example, the center region in the direction of the photosensitive drum rotation axis may have a greater shake amount than the end region, or may be smaller.

The present inventors have obtained the knowledge that the shake amount of the photoconductor is different in the direction of the rotation axis. When adjusting, not only the problem of increase in power consumption as described above, but also the problem that toner is wasted in a portion where the shake amount of the photosensitive member is small has occurred.
That is, in the conventional concept of trying to suppress the image density unevenness due to the change in the development gap due to the shake of the photosensitive member surface by adjusting the development bias, the development electric field is always equal to or higher than the saturated development electric field value A even in the portion where the shake amount is large. Therefore, it is necessary to set a high development bias. In this case, an excessive development electric field that greatly exceeds the saturation development electric field value A is formed in the portion where the shake amount is small even if the development electric field is the lowest value. For this reason, in a portion where the shake amount is small, there is always a situation where more toner than necessary is attached to the electrostatic latent image, and wasteful consumption of toner occurs regularly.

  The present invention has been made in view of the above background, and an object of the present invention is to provide periodic development unevenness due to fluctuations in the surface of the photoreceptor while suppressing an increase in power consumption and wasteful consumption of toner. It is an object to provide an image forming apparatus capable of reducing image density unevenness caused by the above-mentioned at low cost and a method of manufacturing a photoreceptor used therefor.

In order to achieve the above object, the invention of claim 1 comprises a photosensitive layer comprising a charge generation layer and a charge transport layer located on the surface side of the charge generation layer on a cylindrical conductive support, and a rotating shaft. A photosensitive member that can rotate in the center, and the surface of the photosensitive member is uniformly charged to a predetermined charging potential by a charging means and then exposed to light, thereby generating a charge in a charge generating layer in the photosensitive layer of the photosensitive member. An electrostatic latent image forming means for attenuating the charged potential of the exposed portion and forming the exposed portion as an electrostatic latent image, and a developer carrying member carrying the developer on the surface. The developer carrier is formed on the developer carrier by a developing electric field formed between the electrostatic latent image portion and the developer carrier surface portion on the surface of the photoreceptor facing each other through the development gap. The developer is attached to the electrostatic latent image on the surface of the photoreceptor to form the electrostatic latent image. An image for forming an image on the recording material by finally transferring the visible image on the surface of the photoreceptor obtained by developing the electrostatic latent image onto the recording material. In the forming apparatus, the thickness of the charge transport layer in the photoconductor is set to a portion larger than a portion in which the shake amount of the surface of the photoconductor when rotated about the rotation axis is relatively small in the direction of the photoconductor rotation axis. It is characterized in that it is made thinner.
According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the photoconductor has the deflection amount larger on the other end side than the one end side in the rotation axis direction, and the charge transport. The thickness of the layer is characterized in that the other end side is thinner than the one end side in the rotation axis direction.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the range of the shake amount of the photoconductor is 5 [μm] or more and 30 [μm] or less. is there.
According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the photosensitive member has a maximum thickness of the photosensitive layer of Dmax [μm] and a minimum thickness of the photosensitive layer of Dmin [μm]. ] So as to satisfy all of the following formulas (1) to (3).
3 [μm] ≦ Dmax−Dmin ≦ 10 [μm] (1)
20 [μm] ≦ Dmin (2)
Dmax ≦ 50 [μm] (3)
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the electrostatic latent image forming unit is configured to generate a static image per unit area in order to express the density of the image. An area gradation method for adjusting the area occupied by the electrostatic latent image is employed.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the electrostatic latent image forming unit is configured to bring the surface of the photoreceptor to a predetermined charging potential by a charging unit. Exposure is performed after uniform charging, and the exposed potential is attenuated to make the exposed portion an electrostatic latent image. As the charging means, a predetermined charging bias is applied to the surface of the photoreceptor. The charging roller to which is applied is charged by being brought into contact with or close to the charging roller.
According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the image forming apparatus further includes a cleaning unit that removes unnecessary deposits on the surface of the photoconductor with a cleaning brush. It is a feature.
According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, a protective material for supplying a protective material for protecting the surface of the photosensitive member to the surface of the photosensitive member. It has a supply means.
According to a ninth aspect of the present invention, a photosensitive layer comprising a charge generation layer and a charge transport layer positioned on the surface side of the charge generation layer is provided on a cylindrical conductive support, and the photosensitive layer is rotatable about a rotation axis. And a charge generation layer forming step of forming the charge generation layer on the conductive support, and a charge for forming the charge transport layer on the charge generation layer by an immersion method. A transport layer forming step, and in the charge transport layer forming step, the shake amount of the surface of the photoconductor when rotated about the rotation axis is larger than a relatively small portion in the photoconductor rotation axis direction. The charge transport layer is formed so that the portion is thinner.

  Here, the “shake amount” of the surface of the photoconductor means that on the virtual plane perpendicular to the rotation axis of the photoconductor, the rotation axis center of the photoconductor and one imaginary line drawn from the rotation axis center are the photoconductor. This is the difference between the maximum value and the minimum value when the distance from the surface intersecting with the surface is measured for the entire circumference of the photoreceptor.

In the present invention, the thickness of the charge transport layer of the photoconductor is thinner at the portion where the shake amount on the surface of the photoconductor is larger than the portion where the shake amount is relatively small in the photoconductor rotation axis direction. As the thickness of the charge transport layer in the photosensitive layer decreases, the electrostatic capacity of the photosensitive body (capacitance between the conductive support and the surface of the photosensitive body) increases. When the exposure amount to the photoconductor is the same, the charge amount generated in the charge generation layer by the exposure is the same, but the surface potential of the photoconductor in the exposed portion (that is, the potential of the electrostatic latent image) is , And varies depending on the electrostatic capacity of the photosensitive member in the exposed portion. Specifically, the absolute value of the potential of the electrostatic latent image decreases as the electrostatic capacity of the photoreceptor increases. Therefore, even if the developing bias is constant, increasing the electrostatic capacity of the photosensitive member partially increases the potential difference between the electrostatic latent image potential and the developer carrier surface potential in the direction of the photosensitive member rotation axis. The developing electric field can be partially strengthened. The present invention makes use of this knowledge, and by thinning the charge transport layer in the larger portion than the portion with the small amount of shake on the surface of the photoconductor, the developing electric field in the portion with the large amount of shake is less than the portion with the small amount of shake. Is also trying to be relatively strong.
When the developing bias is set low so that the developing electric field is always equal to or greater than the saturated developing electric field value A with reference to the portion where the shake amount is small in the photosensitive member rotating axis direction, the thickness of the charge transport layer is uniform in the photosensitive member rotating axis direction. In the conventional photoconductor, the electrostatic capacity of the photoconductor is uniform in the direction of the photoconductor rotation axis, so that a situation in which the developing electric field falls below the saturation developing electric field value A occurs in a portion where the shake amount is large.
According to the present invention, even when the developing bias is set to be low in this way, the thickness of the charge transport layer in the portion where the shake amount is large is reduced, and the electrostatic capacity of the photoconductor in this portion is smaller than the portion where the shake amount is small. Can also be increased. As a result, the development electric field of the portion with a large amount of shake can be made stronger than the portion with a small amount of shake, so even if the development bias is set lower with reference to the portion with a small amount of shake, A situation in which the developing electric field falls below the saturation developing electric field value A can be suppressed. As a result, image density unevenness can be suppressed over the entire photosensitive member.
In addition, according to the present invention, it is possible to set the developing bias at a low level based on the portion where the shake amount is small as described above, so that an excessive developing electric field can be formed in the portion where the shake amount is small. Therefore, increase in power consumption and wasteful consumption of toner are suppressed.

  As described above, according to the present invention, even if the development bias is set low with respect to a portion where the shake amount is small, image density unevenness in a portion with a large shake amount can be suppressed. Compared to a higher setting, it is possible to reduce the image density unevenness due to the periodic development unevenness due to the shake of the surface of the photoconductor at low cost while suppressing the increase in power consumption and wasteful toner consumption. can get.

1 is a schematic diagram illustrating a schematic configuration of a printer according to an embodiment. FIG. 3 is a schematic diagram for explaining a schematic configuration of one of four image forming units constituting the printer. FIG. 4 is an explanatory diagram illustrating a peripheral configuration of a development area where a photoconductor and a development roller face each other. 4 is a graph showing a profile of a photosensitive layer thickness of the photoreceptor in Example 1. 3 is a graph showing a profile of a shake amount of a photoconductor in Example 1. It is a table | surface which shows the experimental condition and evaluation result in an Example, a comparative example, and a reference example. It is the figure which arranged the 2by2 visual image evaluation result of Example 1, 6-18 and Comparative Examples 1-4 by matching with a photosensitive layer thickness. 6 is a graph illustrating the relationship between a development electric field and a development amount (toner adhesion amount). FIG. 6 is a model diagram illustrating development gap fluctuation corresponding to one rotation of the photoreceptor. FIG. 6 is a model diagram illustrating development electric field intensity fluctuation corresponding to one rotation of the photoreceptor. FIG. 6 is a model diagram illustrating development amount fluctuations for one rotation of the photoconductor corresponding to the photoconductor. FIG. 6 is a model diagram illustrating an optical density (image density) variation for one rotation of the photoconductor corresponding to the photoconductor. FIG. 11 is a model diagram illustrating development electric field intensity fluctuations corresponding to one rotation of the photoreceptor when the photosensitive layer is made thinner than in the case of FIG. 10. FIG. 6 is a model diagram illustrating development amount fluctuations for one rotation of the photoconductor corresponding to the photoconductor. FIG. 6 is a model diagram illustrating an optical density (image density) variation for one rotation of the photoconductor corresponding to the photoconductor.

Hereinafter, an embodiment in which the present invention is applied to a printer as an image forming apparatus that forms an image by an electrophotographic method will be described.
In addition, since embodiment described below is a suitable embodiment of this invention, various technically preferable restrictions are attached | subjected. However, the present invention is not limited to these embodiments unless otherwise described in the following description. In particular, the image forming process by the printer 100 is a negative / positive process, but is not limited thereto.

FIG. 1 is a schematic diagram illustrating a schematic configuration of a printer 100 according to the present embodiment.
FIG. 2 is a schematic diagram for explaining a schematic configuration of one of the four image forming units constituting the printer 100.
The printer 100 includes a protective material coating device 2 serving as a protective material supply unit, a charging device 3 constituting an electrostatic latent image forming unit, and an exposure device 30 around the drum-shaped photoconductors 1Y, 1C, 1M, and 1K. A developing device 5 as an developing means, an intermediate transfer belt 60, and a cleaning device 4 are disposed. Y, C, M, and K added after the reference numerals are color classification codes indicating that the members are for yellow, cyan, magenta, and black, respectively. The code may be omitted.

  The charging device 3 is preferably a charging device in which the charging roller 31 is disposed in contact with or close to the surface of the photoreceptor, and is different from a corona discharge device called a corotron or a scorotron using a discharge wire. Thus, the amount of ozone generated during charging can be greatly suppressed. A photoreceptor having a photosensitive layer such as an organic photoconductive layer is neutralized by a neutralizing lamp (not shown) or the like, and is uniformly negatively charged by a charging device 3 having a charging roller 31. When charging the photosensitive member 1 by the charging device 3, an appropriate voltage suitable for charging the photosensitive member 1 to a desired potential (background potential) from a voltage application mechanism (not shown) to the charging roller 31. A large voltage or a charging voltage obtained by superimposing an AC voltage thereon is applied. On each of the charged photoreceptors 1Y, 1C, 1M, and 1K, an electrostatic latent image is formed by the laser light L irradiated by the exposure device 30 such as a laser optical system. As a result, the charged portion of the photosensitive member irradiated with the laser light L is dropped by the plus charge generated in the charge generation layer, which will be described later, and becomes a potential closer to 0 V (exposure portion potential) than the background portion potential. Laser light L is emitted from a semiconductor laser and scans the surface of each photoconductor 1Y, 1C, 1M, 1K in the direction of the rotation axis of the photoconductor by a polygonal polygonal mirror (polygon) that rotates at high speed.

  The electrostatic latent image formed in this way is developed with a developer made of toner or a mixture of toner and carrier particles carried on a developing roller, which is a developer carrying member provided in the developing device 5, and can be developed. A visual image (toner image) is formed. In the present embodiment, a two-component development system using a developer composed of a mixture of toner and carrier particles is employed. The toners used in each process cartridge are of different colors, and are yellow, cyan, magenta, and black. At the time of development, a voltage of an appropriate magnitude positioned between the exposure portion potential (electrostatic latent image potential) of the photoreceptor 1 and the background portion potential from the voltage application mechanism (not shown) to the developing roller A developing bias with an alternating voltage superimposed thereon is applied. As a result, a developing electric field is formed between the exposed portion (electrostatic latent image portion) on the photoreceptor 1 and the developing roller to move the negatively charged toner toward the exposed portion, and the background portion on the photoreceptor 1 is formed. An electric field for moving the toner toward the developing roller is formed between the (non-electrostatic latent image portion) and the developing roller. As a result, the toner can be attached only to the exposed portion on the photoreceptor 1, and the electrostatic latent image can be used as a toner image.

The color toner images formed on the photoconductors 1Y, 1C, 1M, and 1K are transferred onto the intermediate transfer belt 60 by the transfer device 6 so as to overlap each other, and become color toner images. At this time, it is preferable that a potential having a polarity opposite to the charging polarity of the toner is applied to the transfer device 6 as a transfer bias.
On the surface portion of the photoreceptor 1 after the transfer, partially deteriorated protective material for the photoreceptor, transfer residual toner, and the like remain, but are cleaned and cleaned by the cleaning member 41. The cleaning member 41 is a cleaning brush that rubs in the direction opposite to the rotation direction of the photosensitive member.
The protective material coating device 2 disposed facing the photoconductor 1 includes a protective material 21 as a photoconductor protective material, a protective material supply member 22, a pressing force applying member 23, a protective layer forming member 24, and the like. The The photosensitive member protective member 21 is supplied from the protective member supply member 22 to the surface of the photosensitive member from which the residual toner on the surface and the deteriorated protective member for the photosensitive member have been removed from the cleaning device 4. A protective layer is formed. At this time, the photosensitive member protective material has a better adsorptivity to the portion of the surface of the photosensitive member that is highly hydrophilic due to electrical stress. Even if the surface of the photoreceptor starts to deteriorate partially, the progress of deterioration of the photoreceptor itself can be prevented by adsorption of the protective material.

  The color toner image on the intermediate transfer belt 60 is transferred onto a recording material such as paper fed from the paper feed mechanism 200 in the secondary transfer unit. The recording material onto which the color toner image has been transferred is then subjected to a fixing process by a fixing device and then discharged outside the apparatus.

  As this printer, a plurality of developing devices are used, and a plurality of toner images of different colors sequentially produced by the plurality of developing devices are sequentially transferred onto a transfer material, then sent to a fixing mechanism, and heated by heat or the like. Or a plurality of similarly produced toner images are sequentially transferred onto an intermediate transfer belt and then transferred to a recording material such as paper and fixed in the same manner. It may be a device that performs.

  In the present embodiment, the photosensitive member 1 and the protective material coating device 2, the charging device 3, the developing device 5, the cleaning device 4, the device arranged around the photosensitive member, such as a static eliminator, or the like. Two or more devices can be configured to be detachable from the printer main body integrally as a process cartridge.

[Photoreceptor]
Next, the photoreceptor 1 used in this embodiment will be described.
The photosensitive member 1 has a photosensitive layer comprising a charge generation layer and a charge transport layer positioned on the surface side of a cylindrical conductive support on a cylindrical conductive support, and is rotatable about a rotation axis. If it is, there will be no restriction | limiting in particular, According to the objective, it can select suitably.

The conductive support is not particularly limited as long as it exhibits conductivity having a volume resistivity of 1.0 × 10 ¹⁰ [Ω · cm] or less, and can be appropriately selected according to the purpose. , Metal such as aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum, metal oxide such as tin oxide, indium oxide, etc. coated on cylindrical plastic, tempered glass, etc. by vapor deposition or sputtering, Alternatively, pipes that have been subjected to surface treatment such as cutting, finishing, and polishing after aluminum, aluminum alloy, nickel, stainless steel, and the like are formed into a drum shape by a method such as extrusion or drawing. These are drum-shaped (cylindrical).

  There is no restriction | limiting in particular as a diameter of an electroconductive support body, Although it can select suitably according to the objective, 20 [mm]-150 [mm] are preferable, and 24 [mm]-100 [mm] are more preferable. 28 [mm] to 70 [mm] are particularly preferable. When the diameter is less than 20 [mm], it may be physically difficult to arrange the charging, exposure, development, transfer, and cleaning steps around the photoreceptor, and when the diameter exceeds 150 [mm]. The printer may become large. In particular, since the printer is a tandem type, it is necessary to mount a plurality of photoconductors, and the diameter is preferably 70 [mm] or less, and more preferably 60 [mm] or less.

The photosensitive layer is not particularly limited as long as it is a normal layer type having a charge transport layer containing a charge transport material on a charge generation layer containing a charge generation material, and can be appropriately selected according to the purpose.
In order to improve the mechanical strength, abrasion resistance, gas resistance, cleaning property, etc. of the photoreceptor, an outermost surface layer can be provided on the photosensitive layer.
An undercoat layer may be provided between the photosensitive layer and the conductive support.
Further, a blocking layer for more reliably performing the charge injection inhibiting function of the undercoat layer may be provided.
Moreover, an appropriate amount of a plasticizer, an antioxidant, a leveling agent or the like can be added to each layer as necessary.

As for the thickness of the photosensitive layer, it is preferable that the maximum value Dmax [μm] of the photosensitive layer thickness and the minimum value Dmin [μm] of the photosensitive layer thickness satisfy all of the following formulas (1) to (3).
3 [μm] ≦ Dmax−Dmin ≦ 10 [μm] (1)
20 [μm] ≦ Dmin (2)
Dmax ≦ 50 [μm] (3)
When these relationships are satisfied, uniform visible image formation can be reliably and stably realized over a long period of time, so that a stable image forming function with little variation with time can be provided. When the difference in the photosensitive layer thickness is less than 3 [μm], depending on the dielectric constant of the material used for the photosensitive layer, variation in electric field strength may not be sufficiently suppressed. On the other hand, when the difference in the photosensitive layer thickness exceeds 10 [μm], the electrostatic latent image contrast between the exposed portion and the non-exposed portion (background portion) may not be sufficiently large. Further, when the thickness of the photosensitive layer is less than 20 [μm] or exceeds 50 [μm], the durability may be lowered and the electrostatic latent image resolution may be lowered.

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

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

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

Examples of the antioxidant in the photosensitive layer include phenolic compounds, paraphenylenediamines, hydroquinones, organic sulfur compounds, and organic phosphorus compounds.
Examples of phenolic compounds include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearyl-β- (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate, 2,2'-methylene-bis- (4-methyl-6-t-butylphenol), 2,2'-methylene-bis- (4-ethyl-6) -T-butylphenol), 4,4'-thiobis- (3-methyl-6-t-butylphenol), 4,4'-butylidenebis- (3-methyl-6-t-butylphenol), 1,1,3- Tris- (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl Benzene, tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, bis [3,3′-bis (4′-hydroxy-3′-t) -Butylphenyl) butyric acid] cricol ester, tocopherols and the like.
Examples of paraphenylenediamines include N-phenyl-N′-isopropyl-p-phenylenediamine, N, N′-di-sec-butyl-p-phenylenediamine, and N-phenyl-N-sec-butyl-p. -Phenylenediamine, N, N'-di-isopropyl-p-phenylenediamine, N, N'-dimethyl-N, N'-di-t-butyl-p-phenylenediamine and the like.
Examples of hydroquinones include 2,5-di-t-octyl hydroquinone, 2,6-didodecyl hydroquinone, 2-dodecyl hydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t-octyl-5-methyl hydroquinone. , 2- (2-octadecenyl) -5-methylhydroquinone and the like.
Examples of organic sulfur compounds include dilauryl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, ditetradecyl-3,3′-thiodipropionate, and the like.
Examples of the organic phosphorus compounds include triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine, and the like.

These compounds are known as antioxidants such as rubbers, plastics and fats and oils, and commercially available products can be easily obtained.
As addition amount of antioxidant, 0.01 mass%-10 mass% are preferable with respect to the total mass of the layer to add.

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

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

The undercoat layer is not particularly limited and may be a single layer or a plurality of layers. For example, (1) a resin as a main component, (2) a white pigment and a resin as a main component. And (3) a metal oxide film obtained by chemically or electrochemically oxidizing the surface of a conductive support. Among these, those containing a white pigment and a resin as main components are preferable.
The white pigment is not particularly limited, and examples thereof include metal oxides such as titanium oxide, aluminum oxide, zirconium oxide, and zinc oxide. Among these, oxidation that is excellent in preventing injection of charges from the conductive support. Titanium is particularly preferred.
The resin is not particularly limited, and examples thereof include thermoplastic resins such as polyamide, polyvinyl alcohol, casein, and methyl cellulose; thermosetting resins such as acrylic, phenol, melamine, alkyd, unsaturated polyester, and epoxy. These may be used individually by 1 type and may use 2 or more types together.
The thickness of the undercoat layer is not particularly limited and may be appropriately selected according to the purpose. .

The outermost surface layer is provided to improve the mechanical strength, abrasion resistance, gas resistance, cleaning properties, etc. of the photoreceptor.
Although there is no restriction | limiting in particular as an outermost surface layer, For example, what disperse | distributed the inorganic filler to the polymer | macromolecule higher in mechanical strength than a photosensitive layer is preferable.
The resin used for the outermost layer is not particularly limited and may be either a thermoplastic resin or a thermosetting resin, but has high mechanical strength and the ability to suppress wear due to friction with the cleaning blade. Very high thermosetting resins are preferred.
If the outermost surface layer is thin, there is no problem even if it does not have the charge transport capability, but if the outermost layer without the charge transport capability is formed thick, the sensitivity of the photoreceptor decreases, the potential increases after exposure, Since the residual potential is likely to increase, it is preferable to include the aforementioned charge transport material in the outermost surface layer, or to use a polymer having charge transporting capability as the polymer used in the outermost surface layer.

Since the mechanical strength of the photosensitive layer and the outermost surface layer is generally greatly different, the outermost surface layer is worn away due to friction with the cleaning member. When provided, it is important that the outermost surface layer has a sufficient thickness.
From such a viewpoint, the thickness of the outermost surface layer is preferably 0.1 [μm] to 12 [μm], more preferably 1 [μm] to 10 [μm], and 2 [μm] to 8 [μm]. When the thickness is less than 0.1 [μm], it is so thin that it tends to disappear partially due to friction with the cleaning member, and the photosensitive layer may be worn away from the disappeared portion. If it exceeds [μm], the sensitivity is lowered, the potential after exposure is increased, and the residual potential is likely to increase. In particular, when a polymer having charge transport capability is used, the cost of the polymer having charge transport capability increases. Sometimes.

The resin used for the outermost surface layer is preferably one that is transparent to the writing light during image formation and excellent in insulation, mechanical strength, and adhesiveness. For example, ABS resin, ACS resin, olefin-vinyl monomer copolymer Polymer, chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallylsulfone, polybutylene, polybutylene terephthalate, polycarbonate, polyethersulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic resin, Polymethylbenten, polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS resin, butadiene-styrene copolymer, polyurethane, polyvinyl chloride, polyvinylidene chloride, epoxy resin, etc. It is below.
These polymers are not particularly limited and may be thermoplastic resins, but in order to increase the mechanical strength of the polymer, crosslinks having a polyfunctional acryloyl group, carboxyl group, hydroxyl group, amino group, etc. It is preferable to crosslink with an agent to form a thermosetting resin. In this way, the mechanical strength of the outermost surface layer increases, and wear due to friction with the cleaning member can be greatly reduced.

The outermost surface layer preferably has a charge transport capability.
The method for giving the outermost surface layer a charge transporting ability is not particularly limited, and a method of using a mixture of a polymer used for the outermost surface layer and a charge transporting substance, a polymer having a charge transporting ability being used for the outermost surface layer. Although there is a method, the latter method is preferred because a photoconductor with high sensitivity and little increase in potential after exposure and little increase in residual potential can be obtained.

The polymer having the charge transport layer ability is not particularly limited and may be appropriately selected depending on the intended purpose. For example, as a group having the charge transport ability in the polymer, Those having a group to be used are preferred.

  However, Ar1 represents the arylene group which may have a substituent in structural formula (i). Ar2 and Ar3 may be the same as or different from each other, and each represents an aryl group that may have a substituent.

Such a group having a charge transporting ability is preferably added to a side chain of a polymer having high mechanical strength such as polycarbonate resin and acrylic resin, so that the production of the monomer is easy and the coatability and curability are improved. It is more preferable to use an acrylic resin that is also excellent.
As an acrylic resin having such a charge transport capability, a surface layer having high mechanical strength, excellent transparency, and high charge transport capability by polymerizing an unsaturated carboxylic acid having a group of the structural formula (i) Can be formed.
Moreover, the acrylic resin forms a crosslinked structure by mixing a polyfunctional unsaturated carboxylic acid, preferably a tri- or higher functional unsaturated carboxylic acid, with an unsaturated carboxylic acid having a monofunctional structural formula (i) group. However, it becomes a thermosetting polymer, and the mechanical strength of the surface layer becomes extremely high.
The group of the structural formula (i) may be added to the polyfunctional unsaturated carboxylic acid. However, since the production cost of the monomer increases, the polyfunctional unsaturated carboxylic acid includes the structural formula (i It is preferable to use a photocurable polyfunctional monomer without adding a group of

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

In Structural Formula (ii) and Structural Formula (iii), R ₁ represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. An aryl group which may have, a cyano group, a nitro group, an alkoxy group which may have a substituent, -COOR ₇ (wherein R ₇ is a hydrogen atom, an alkyl group which may have a substituent) Represents an aralkyl group which may have a substituent, or an aryl group which may have a substituent, a carbonyl halide group, CONR ₈ R ₉ (wherein R ₈ and R ₉ are the same as each other) It may be different or may have a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. Represents an aryl group which may be
In Structural Formula (ii) and Structural Formula (iii), Ar1 and Ar2 may be the same as or different from each other, and represent an arylene group that may have a substituent.
In Structural Formula (ii) and Structural Formula (iii), Ar3 and Ar4 may be the same as or different from each other, and each represents an aryl group that may have a substituent.
In Structural Formula (ii) and Structural Formula (iii), X has a single bond, an alkylene group that may have a substituent, a cycloalkylene group that may have a substituent, or a substituent. An alkylene ether group, an oxygen atom, a sulfur atom, or a vinylene group that may be present.
In Structural Formula (ii) and Structural Formula (iii), Z has an alkylene group which may have a substituent, an alkylene ether divalent group which may have a substituent, or a substituent. The alkyleneoxycarbonyl divalent group which may be sufficient.
In Structural Formula (ii) and Structural Formula (iii), m and n each represents an integer of 0 to 3.

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

Examples of the aryl group for Ar3 and Ar4 include a condensed polycyclic hydrocarbon group, a non-condensed cyclic hydrocarbon group, and a heterocyclic group.
As the condensed polycyclic hydrocarbon group, those having 18 or less carbon atoms forming a ring are preferable. For example, a pentanyl group, an indenyl group, a naphthyl group, an azulenyl group, a heptaenyl group, a biphenylenyl group, an as-indacenyl group, s -Indacenyl group, fluorenyl group, acenaphthylenyl group, preadenyl group, acenaphthenyl group, phenalenyl group, phenanthryl group, anthryl group, fluoranthenyl group, acephenanthrenyl group, aseantrilenyl group, triphenylyl group, pyrenyl group, chrysenyl group Group, naphthacenyl group and the like.
Examples of the non-condensed cyclic hydrocarbon group include monovalent groups of monocyclic hydrocarbon compounds such as benzene, diphenyl ether, polyethylene diphenyl ether, diphenyl thioether, diphenyl sulfone; biphenyl, polyphenyl, diphenylalkane, diphenylalkene, diphenylalkyne, Monovalent groups of non-condensed polycyclic hydrocarbon compounds such as triphenylmethane, distyrylbenzene, 1,1-diphenylcycloalkane, polyphenylalkane and polyphenylalkene; ring-assembled hydrocarbons such as 9,9-diphenylfluorene And monovalent groups of the compound.
Examples of the heterocyclic group include monovalent groups such as carbazole, dibenzofuran, dibenzothiophene, oxadiazole, and thiadiazole.

  As content of polyfunctional unsaturated carboxylic acid, 5 mass%-75 mass% of the whole outermost surface layer are preferable, 10 mass%-70 mass% are more preferable, 20 mass%-60 mass% are especially preferable. When the content is less than 5% by mass, the mechanical strength of the outermost surface layer is insufficient, and when it exceeds 75% by mass, cracks are likely to occur when a strong force is applied to the outermost surface layer, resulting in sensitivity deterioration. May also occur.

  When an acrylic resin is used for the outermost surface layer, an unsaturated carboxylic acid is applied to the photoconductor, followed by irradiation with an electron beam or active light such as ultraviolet rays to cause radical polymerization to form a surface layer. Can do. When performing radical polymerization with actinic rays, a solution obtained by dissolving a photopolymerization initiator in an unsaturated carboxylic acid is used. As the photopolymerization initiator, materials used for photocurable paints can be used.

In order to increase the mechanical strength of the outermost surface layer, the outermost surface layer preferably contains metal fine particles, metal oxide fine particles, and other fine particles.
Examples of the metal oxide include titanium oxide, tin oxide, potassium titanate, TiO, TiN, zinc oxide, indium oxide, and antimony oxide. Examples of the other fine particles include fluorine resins such as polytetrafluoroethylene, silicone resins, or those obtained by dispersing inorganic materials in these resins for the purpose of improving wear resistance.

  The thickness of the photosensitive layer of the photoreceptor 1 produced using these compositions can be measured using an electromagnetic or eddy current film thickness meter depending on the material of the conductive support.

[Measurement method of runout]
Next, a method for measuring the shake amount of the surface of the photoreceptor 1 will be described.
In this embodiment, since the photoreceptor manufacturing process described later is performed, the amount of shake of the photoreceptor increases from one end to the other end in the rotation axis direction. The difference in the axial direction of the shake amount on the surface of the photoreceptor can be generally known as follows.
First, the photosensitive member 1 whose rotation axis is fixed is slowly rotated around the rotation axis, and the surface of the photosensitive member is scanned in the circumferential direction with a contact or non-contact position fixed position. Then, a displacement amount profile is obtained. The surface displacement data for one rotation of the photosensitive member is acquired from this profile, and the minimum value is subtracted from the maximum value to obtain the amount of shake. The shake amount obtained in this way is obtained at a plurality of points, preferably 10 points or more, at substantially equal intervals in the image area in the rotation axis direction (area where an electrostatic latent image can be formed). Check the axial difference and the amount of runout.

[Electrostatic latent image forming means]
Next, the electrostatic latent image forming unit will be described.
The electrostatic latent image forming means is one that generates an electric charge in the charge generation layer in the photosensitive layer of the photosensitive member by exposing the surface of the photosensitive member 1 and forms the exposed portion as an electrostatic latent image. If there is no restriction | limiting in particular, according to the objective, it can select suitably. The electrostatic latent image forming unit of the present embodiment includes a charging device 3 that uniformly charges the surface of the photoconductor 1 and an exposure device 30 that exposes the surface of the photoconductor 1 imagewise.

The charging method can be performed by applying a voltage to the surface of the photoreceptor 1 using the following charging device 3. The charging device 3 is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include non-contact charging devices using corona discharge such as devices, corotrons, and scorotrons. Among these, for the reasons described above, a charging device having a charging roller that performs either contact charging or proximity charging on the photosensitive member 1 with a conductive or semiconductive roll is preferable. In addition, when using a charging means having a charging roller of either contact charging or proximity charging, use a soft contact charging roller or arrange a pressure member so that a large pressing force is not applied to the contact portion. It is more preferable to adopt a charging means configuration that is not provided.
The charging device 3 preferably has a voltage applying means for applying a voltage having an AC component.

  The exposure device 30 is not particularly limited as long as the surface of the photoreceptor 1 charged by the charging device 3 can be exposed like an image to be formed, and can be appropriately selected according to the purpose. Examples thereof include various exposure apparatuses such as a copying optical system, a rod lens array system, a laser optical system, a liquid crystal shutter optical system, and an LED optical system. In addition, you may employ | adopt the light back system which performs imagewise exposure from the back surface side of the photoreceptor 1. FIG.

[Development means]
The developing unit is a unit that develops the electrostatic latent image formed on the photoreceptor 1 using a developer to form a visible image. More specifically, a developing roller as a developer carrying member having a developer carried on the surface thereof is opposed to the surface of the photoconductor through a development gap, and the electrostatic latent image on the surface of the photoconductor facing through the development gap is used. The electrostatic latent image is developed by causing the developer (toner) on the developing roller to adhere to the electrostatic latent image on the surface of the photosensitive member by the developing electric field formed between the image portion and the developing roller surface portion. If there is, there is no particular limitation.

FIG. 3 is an explanatory diagram showing a peripheral configuration of the developing area where the photosensitive member 1 and the developing roller face each other.
The developing roller carries the developer and conveys it to a position facing the photoreceptor 1. A gap is formed between the photoreceptor 1 and the developing roller, and this is the developing gap 11. The development gap 11 is a substantially uniform gap in consideration of the pumping amount of the developer, the strength of the magnetic field for holding the developer on the developing roller, the magnetization of the carrier in the developer, the rotation speed of the developing roller, and the like. However, the average value is preferably about 0.2 to 0.4 [mm].

  Since the development gap 11 is adjusted substantially uniformly as described above, the amount of change in the development gap 11 increases from the side where the shake amount of the photosensitive member 1 is small to the side where the shake is large. For this reason, in the photoconductor 1 having a photosensitive layer with a uniform thickness, it is not possible to absorb fluctuations in the development electric field due to the change in the development gap, and fluctuations in the development amount during one rotation of the photoconductor 1 occur in the image. It appears as density unevenness, degrading image quality. In this embodiment, as will be described in detail later, the exposed portion of the photoconductor 1 is compared with a portion where the shake amount of the photoconductor 1 is small by thinning the charge transport layer in a portion where the shake amount of the photoconductor 1 is large. Since the potential (the potential of the electrostatic latent image) is close to 0 V, the potential difference between the constant surface potential of the developing roller to which a constant developing bias is applied and the exposed portion potential of the photoreceptor 1 is widened, and the developing electric field is increased. Becomes stronger. As a result, a sufficiently large developing electric field can be obtained even in a portion where the developing gap 11 is maximized due to the shake of the photosensitive member 1, and saturation development can be realized. As a result, the image density is not lowered at the portion where the development gap 11 is maximized due to the shake of the photosensitive member 1, so that there is no difference in image density from other portions, and image density unevenness occurs. It will be resolved.

  The developing roller is driven to rotate counterclockwise in FIG. 2 by a driving means (not shown). In order to form a magnetic brush made of carrier particles, the developing roller is provided with a magnet (not shown) as a magnetic field generating means disposed inside the developing roller magnetic pole fixed shaft 56 so as not to change relative position to the developing device 5. ). The developer is supplied to the surface of the developing roller by the rotation of the developing roller and the developer supply screw 52 of the agitating and conveying mechanism, and is regulated by a regulating member 54 (doctor blade) that maintains a certain clearance from the outer peripheral surface of the developing roller. A predetermined amount of developer on the developing roller is held and conveyed to a developing area where the photoreceptor 1 and the developing roller face each other. As a material of the sleeve 51 of the developing roller 50 for holding the developer, a nonmagnetic metal such as aluminum can be preferably used. Moreover, it is preferable that the surface has unevenness | corrugation by blasting etc.

As shown in FIG. 3, the photosensitive member 1 includes a conductive support 10 having a photosensitive layer 12 in a body portion, and is rotatably supported by a rotating shaft 14 via a bearing 13.
The developing roller 50 has a sleeve 51 at the body portion thereof, and the sleeve 51 is rotatably supported by the rotating shaft 55 via the bearing 13, while the developing roller magnetic pole fixing shaft 56 is pivotally supported.

(Developer)
There is no restriction | limiting in particular as a developing agent, According to the objective, it can select suitably, It is a two-component developing agent which consists of a toner and a carrier.

The toner is not particularly limited and can be appropriately selected according to the purpose. Is preferable, and 0.95-0.99 is more preferable.
This average circularity is an index of the degree of unevenness of toner particles, and indicates 1.00 when the toner is a perfect sphere, and the average circularity becomes smaller as the surface shape becomes more complicated.

  Circularity SR = (perimeter of circle having the same area as the projected area of toner particles) / (perimeter of projected image of toner particles) (4)

  When the average circularity is in the range of 0.93 to 1.00, the surface of the toner particles is smooth, and the contact area between the toner particles and between the toner particles and the photosensitive member is small, so that the transferability is excellent. Further, since the toner particles have no corners, the developer agitation torque in the developing device is small, and the agitation drive is stabilized, so that no abnormal image is generated. Further, since there are no angular toner particles in the toner forming dots, the pressure is uniformly applied to the entire toner forming the dots when pressed against the recording material during transfer, and the transfer is not easily lost. Further, since the toner particles are not angular, the abrasive power of the toner particles themselves is small, and the surface of the photoreceptor 1 is not damaged or worn.

The circularity SR can be measured using, for example, a flow type particle image analyzer (manufactured by Toa Medical Electronics Co., Ltd., FPIA-1000).
First, a surfactant (preferably alkylbenzene sulfonate) as a dispersant is added in 0.1 [mL] to 0.5 [0.5] to 100 [mL] to 150 [mL] of water from which impure solids have been removed in advance. Add [mL], and further add about 0.1 [g] to 0.5 [g] of the measurement sample. Next, the suspension in which the sample is dispersed is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the dispersion concentration is set to 3,000 [pieces / μL] to 10,000 [pieces / μL] by an apparatus. Measure the shape and particle size of the toner.

  The mass average particle diameter (D4) of the toner is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 3 [μm] to 10 [μm], and 4 [μm] to 8 [μm]. Is more preferable. In this range, since the toner particles have a sufficiently small particle size with respect to the minute latent image dots, the dot reproducibility is excellent. If the mass average particle diameter (D4) is less than 3 [μm], phenomena such as a decrease in transfer efficiency and a decrease in blade cleaning properties may occur, and if it exceeds 10 [μm], scattering of characters and lines is suppressed. It can be difficult.

  Further, the ratio (D4 / D1) of the mass average particle diameter (D4) and the number average particle diameter (D1) in the toner is preferably 1.00 to 1.40, more preferably 1.00 to 1.30. The closer the ratio (D4 / D1) is to 1, the sharper the particle size distribution of the toner. In the range of (D4 / D1) from 1.00 to 1.40, selective development by the toner particle size is performed. Since it does not occur, it has excellent image quality stability. In addition, since the toner particle size distribution is sharp, the triboelectric charge amount distribution is also sharp and the occurrence of fog is suppressed. Further, when the toner particle diameter is uniform, the latent image dots are developed so as to be arranged densely and orderly, so that the dot reproducibility is excellent.

Here, as a measuring method of the mass average particle diameter (D4) and the particle size distribution of the toner, for example, a Coulter counter method may be mentioned.
As an apparatus for measuring the particle size distribution of toner particles by the Coulter counter method, there are Coulter Counter TA-II and Coulter Multisizer II (both manufactured by Coulter).

Specifically, it can be measured as follows.
First, 0.1 [mL] to 5 [mL] of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to the electrolytic aqueous solution 100 [mL] to 150 [mL]. Here, the electrolytic solution is prepared by preparing an about 1% NaCl aqueous solution using primary sodium chloride, and for example, ISOTON-II (manufactured by Coulter) can be used. Here, 2 [mg] to 20 [mg] of the measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 minute to 3 minutes, and a measuring device is used to measure the volume and number of toner particles or toner using a 100 μm aperture as an aperture. Volume distribution and number distribution are calculated. From the obtained distribution, the mass average particle diameter (D4) and the number average particle diameter (D1) of the toner can be obtained.

  As a channel in the measuring apparatus, 2.00 [μm] to less than 2.52 [μm]; 2.52 [μm] to less than 3.17 [μm]; 3.17 [μm] to 4.00 [μm] Less than 4.00 [μm] to less than 5.04 [μm]; 5.04 [μm] to less than 6.35 [μm]; 6.35 [μm] to less than 8.00 [μm]; [Μm] to less than 10.08 [μm]; 10.08 [μm] to less than 12.70 [μm]; 12.70 [μm] to less than 16.00 [μm]; 16.00 [μm] to 20 Less than 20 [μm]; 20.20 [μm] to less than 25.40 [μm]; 25.40 [μm] to less than 32.00 [μm]; 32.00 [μm] to 40.30 [μm] The target is particles having a particle size of 2.00 [μm] or more and less than 40.30 [μm], using less than 13 channels.

  As the toner having such a substantially spherical shape, a toner composition containing a polyester prepolymer having a functional group containing a nitrogen atom, a polyester, a colorant, and a release agent is crosslinked in the presence of resin fine particles in an aqueous medium. It can be prepared by an extension reaction. The toner produced by this reaction can reduce the hot offset by curing the toner surface, and can prevent the fixing device from becoming dirty and appearing on the image.

  Examples of the prepolymer made of the modified polyester resin include a polyester prepolymer (A) having an isocyanate group, and examples of the compound that extends or crosslinks with the prepolymer include amines (B).

  Examples of the polyester prepolymer (A) having an isocyanate group include a polycondensate of a polyol (1) and a polycarboxylic acid (2) and a polyester having an active hydrogen group, which is further reacted with a polyisocyanate (3). Can be mentioned. Examples of active hydrogen groups possessed by polyester include hydroxyl groups (alcoholic hydroxyl groups and phenolic hydroxyl groups), amino groups, carboxyl groups, mercapto groups, and the like. Among these, alcoholic hydroxyl groups are particularly preferable.

  Examples of the polyol (1) include a diol (1-1) and a trivalent or higher polyol (1-2), but the diol (1-1) alone or the diol (1-1) and a small amount of a trivalent or higher valence. A mixture of polyol (1-2) is preferred.

  Examples of the diol (1-1) include alkylene glycol (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, etc.); alkylene ether glycol (Diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc.); Alicyclic diols (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.); Bisphenols (bisphenol A) Bisphenol F, bisphenol S, etc.); alicyclic diol alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) adduct; bis Alkylene oxide phenol compound (ethylene oxide, propylene oxide, butylene oxide, etc.), etc. adducts. Among these, alkylene glycols having 2 to 12 carbon atoms and alkylene oxide adducts of bisphenols are preferable, and combined use of alkylene oxide adducts of bisphenols and alkylene glycols having 2 to 12 carbon atoms is particularly preferable.

  Examples of the trivalent or higher polyol (1-2) include 3 to 8 or higher polyhydric aliphatic alcohols (glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, etc.); (Trisphenol PA, phenol novolak, cresol novolak, etc.); Examples thereof include alkylene oxide adducts of trivalent or higher polyphenols.

  Examples of the polycarboxylic acid (2) include dicarboxylic acid (2-1) and trivalent or higher polycarboxylic acid (2-2). Among these, (2-1) alone and (2-1) And a small amount of (2-2) are preferred.

  Examples of the dicarboxylic acid (2-1) include alkylene dicarboxylic acids (succinic acid, adipic acid, sebacic acid, etc.); alkenylene dicarboxylic acids (maleic acid, fumaric acid, etc.); aromatic dicarboxylic acids (phthalic acid, isophthalic acid, Terephthalic acid, naphthalenedicarboxylic acid, etc.). Among these, alkenylene dicarboxylic acid having 4 to 20 carbon atoms and aromatic dicarboxylic acid having 8 to 20 carbon atoms are particularly preferable.

  Examples of the trivalent or higher polycarboxylic acid (2-2) include aromatic polycarboxylic acids having 9 to 20 carbon atoms (trimellitic acid, pyromellitic acid, and the like). In addition, as polycarboxylic acid (2), you may make it react with polyol (1) using the acid anhydride or lower alkyl ester (methyl ester, ethyl ester, isopropyl ester, etc.) of the above-mentioned thing.

  The ratio of the polyol (1) to the polycarboxylic acid (2) is preferably 2/1 to 1/1 with respect to the equivalent ratio [OH] / [COOH] of the hydroxyl group [OH] and the carboxyl group [COOH]. 5/1 to 1/1 is more preferable, and 1.3 / 1 to 1.02 / 1 is particularly preferable.

  Examples of the polyisocyanate (3) include aliphatic polyisocyanates (tetramethylene diisocyanate, hexamethylene diisocyanate, 2,6-diisocyanatomethylcaproate, etc.); alicyclic polyisocyanates (isophorone diisocyanate, cyclohexylmethane diisocyanate, etc.) Aromatic diisocyanates (tolylene diisocyanate, diphenylmethane diisocyanate, etc.); araliphatic diisocyanates (α, α, α ′, α′-tetramethylxylylene diisocyanate, etc.); isocyanurates; polyisocyanates to phenol derivatives, oximes, caprolactam And the like blocked. These may be used individually by 1 type and may use 2 or more types together.

  The ratio of the polyisocyanate (3) is preferably 5/1 to 1/1 in the equivalent ratio [NCO] / [OH] of the isocyanate group [NCO] and the hydroxyl group [OH] of the polyester having a hydroxyl group. 1 to 1.2 / 1 is more preferable, and 2.5 / 1 to 1.5 / 1 is particularly preferable. When [NCO] / [OH] exceeds 5, the low-temperature fixability may be deteriorated. When the molar ratio of [NCO] is less than 1, the urea content in the modified polyester is lowered and the hot offset resistance is reduced. Gets worse.

  The content of the polyisocyanate (3) component in the prepolymer (A) having an isocyanate group at the terminal is preferably 0.5% by mass to 40% by mass, more preferably 1% by mass to 30% by mass. A mass% to 20 mass% is particularly preferred. When the content is less than 0.5% by mass, the hot offset resistance deteriorates, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability. When the content exceeds 40% by mass, the low-temperature fixability deteriorates. There are things to do.

  As an isocyanate group contained per molecule in the prepolymer (A) having an isocyanate group, an average of 1 or more is preferable, an average of 1.5 to 3 is more preferable, and an average of 1.8 to 2.5 is preferable. Individual is particularly preferred. When the number is less than 1 per molecule, the molecular weight of the urea-modified polyester is lowered, and the hot offset resistance may be deteriorated.

As amines (B), diamine (B1), trivalent or higher polyamine (B2), aminoalcohol (B3), aminomercaptan (B4), amino acid (B5), and amino acids B1 to B5 blocked (B6) etc. are mentioned.
Examples of the diamine (B1) include aromatic diamines (phenylenediamine, diethyltoluenediamine, 4,4′diaminodiphenylmethane, etc.); alicyclic diamines (4,4′-diamino-3,3′dimethyldicyclohexylmethane, diaminecyclohexane, Isophorone diamine etc.); and aliphatic diamines (ethylene diamine, tetramethylene diamine, hexamethylene diamine etc.) and the like.
Examples of the trivalent or higher polyamine (B2) include diethylenetriamine and triethylenetetramine.
Examples of amino alcohol (B3) include ethanolamine and hydroxyethylaniline. Examples of amino mercaptan (B4) include aminoethyl mercaptan and aminopropyl mercaptan.
Examples of the amino acid (B5) include aminopropionic acid and aminocaproic acid.
Examples of B1 to B5 blocked amino groups (B6) include ketimine compounds and oxazoline compounds obtained from B1 to B5 amines and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.).
Among these amines (B), preferred are B1 and a mixture of B1 and a small amount of B2.

Furthermore, if necessary, the molecular weight of the urea-modified polyester can be adjusted using an elongation terminator.
Examples of the elongation terminator include monoamines (diethylamine, dibutylamine, butylamine, laurylamine, etc.), or those obtained by blocking them (ketimine compounds).

  The ratio of amines (B) is equivalent ratio [NCO] / [NHx] of isocyanate groups [NCO] in prepolymer (A) having isocyanate groups and amino groups [NHx] in amines (B). Is preferably 1/2 to 2/1, more preferably 1.5 / 1 to 1 / 1.5, and particularly preferably 1.2 / 1 to 1 / 1.2. If [NCO] / [NHx] is more than 2 or less than 1/2, the molecular weight of the urea-modified polyester (i) becomes low, and the hot offset resistance deteriorates.

  The polyester (i) modified with a urea bond may contain a urethane bond together with a urea bond. The molar ratio between the urea bond content and the urethane bond content is preferably 100/0 to 10/90, more preferably 80/20 to 20/80, and particularly preferably 60/40 to 30/70. When the molar ratio of the urea bond is less than 10%, the hot offset resistance may be deteriorated.

  By these reactions, the modified polyester used in the toner, particularly urea-modified polyester (i) can be produced. These urea-modified polyesters (i) are produced by a one-shot method or a prepolymer method. The mass average molecular weight of the urea-modified polyester (i) is preferably 10,000 or more, more preferably 20,000 to 10,000,000, and particularly preferably 30,000 to 1,000,000. When the mass average molecular weight is less than 10,000, the hot offset resistance may be deteriorated.

  The number average molecular weight of the urea-modified polyester is not particularly limited when the unmodified polyester (ii) described later is used, and may be a number average molecular weight that can be easily obtained to obtain a mass average molecular weight. (I) When used alone, the number average molecular weight is preferably 20,000 or less, more preferably 1,000 to 10,000, and particularly preferably 2,000 to 8,000. When the number average molecular weight exceeds 20,000, the low-temperature fixability and the gloss when used in a full-color printer may be deteriorated.

Not only the polyester (i) modified with a urea bond can be used alone, but also the polyester (ii) not modified can be contained as a binder resin component together with this (i). By using (ii) in combination, the low-temperature fixability and the gloss when used in a full-color apparatus are improved, and therefore, it is preferable to use alone.
Examples of (ii) include the same polycondensates of polyol (1) and polycarboxylic acid (2) as in the polyester component of (i), and preferred ones are also the same as (i).
(Ii) is not limited to unmodified polyester, but may be modified with a chemical bond other than a urea bond, and may be modified with a urethane bond, for example.
It is preferable that (i) and (ii) are at least partially compatible with each other in terms of low-temperature fixability and hot offset resistance.

  Accordingly, the polyester component (i) and (ii) preferably have similar compositions. In the case of containing (ii), the mass ratio of (i) and (ii) is preferably 5/95 to 80/20, more preferably 5/95 to 30/70, and further preferably 5/95 to 25/75. 7/93 to 20/80 is particularly preferable. When the mass ratio of (i) is less than 5% by mass, the hot offset resistance is deteriorated, and it may be disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability.

The peak molecular weight of (ii) is preferably 1,000 to 30,000, more preferably 1,500 to 10,000, and particularly preferably 2,000 to 8,000. When the peak molecular weight is less than 1,000, the heat resistant storage stability may be deteriorated, and when it exceeds 10,000, the low-temperature fixability may be deteriorated.
The hydroxyl value of (ii) is preferably 5 or more, more preferably 10 to 120, and particularly preferably 20 to 80. If the hydroxyl value is less than 5, it may be disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability.
As an acid value of (ii), 1-30 are preferable and 5-20 are more preferable. By having an acid value, it tends to be negatively charged.

The glass transition temperature (Tg) of the binder resin is preferably 50 [° C.] to 70 [° C.], and more preferably 55 [° C.] to 65 [° C.]. When the glass transition temperature is less than 50 [° C.], the blocking of the toner during high-temperature storage may deteriorate, and when it exceeds 70 [° C.], the low-temperature fixability becomes insufficient. Due to the coexistence of the urea-modified polyester resin, the heat resistant storage stability tends to be good even if the glass transition point is low, as compared with known polyester toners.
As the storage elastic modulus of the binder resin, the temperature (TG ′) at which the measurement frequency is 20 [Hz] is 10,000 [dyne / cm ² ] is preferably 100 [° C.] or higher, and 110 [° C.] to 200 [° C.]. ° C] is more preferable. When the temperature (TG ′) is less than 100 [° C.], the hot offset resistance may be deteriorated.

  As the viscosity of the binder resin, the temperature (Tη) at 1,000 [poise] at a measurement frequency of 20 [Hz] is preferably 180 [° C.] or less, and more preferably 90 [° C.] to 160 [° C.]. When the temperature (Tη) exceeds 180 [° C.], the low-temperature fixability deteriorates. That is, TG ′ is preferably higher than Tη from the viewpoint of achieving both low-temperature fixability and hot offset resistance. In other words, the difference between TG ′ and Tη (TG′−Tη) is preferably 0 [° C.] or higher, more preferably 10 [° C.] or higher, and particularly preferably 20 [° C.] or higher. The upper limit of the difference is not particularly limited. In addition, from the viewpoint of achieving both heat-resistant storage stability and low-temperature fixability, the difference between Tη and Tg is preferably 0 [° C.] to 100 [° C.], more preferably 10 [° C.] to 90 [° C.], and 20 [° C.]. ˜80 [° C.] is particularly preferable.

The binder resin can be produced by the following method.
First, the polyol (1) and the polycarboxylic acid (2) are heated to 150 [° C.] to 280 [° C.] in the presence of a known esterification catalyst such as tetrabutoxy titanate or dibutyltin oxide, and the pressure is reduced as necessary. The produced water is distilled off to obtain a polyester having a hydroxyl group. Next, the polyisocyanate (3) is reacted at 40 [° C.] to 140 [° C.] to obtain a prepolymer (A) having an isocyanate group. Further, (A) is reacted with amines (B) at 0 [° C.] to 140 [° C.] to obtain a polyester modified with a urea bond. When reacting (3) and reacting (A) and (B), a solvent may be used as necessary.

Examples of solvents that can be used in the reaction include aromatic solvents (toluene, xylene, etc.); ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.); esters (ethyl acetate, etc.); amides (dimethylformamide, dimethylacetamide) Etc.) and ethers (tetrahydrofuran etc.) and the like, and those inert to the isocyanate (3).
In the case where the polyester (ii) not modified with a urea bond is used in combination, (ii) is produced in the same manner as the polyester having a hydroxyl group, and this is dissolved in the solution after completion of the reaction of (i), Mix.

The toner can be produced by the following method, but is not limited to these.
The toner may be formed by reacting a dispersion composed of a prepolymer (A) having an isocyanate group in an aqueous medium with (B), or a urea-modified polyester (i) produced in advance may be used. . As a method for stably forming a dispersion comprising urea-modified polyester (i) or prepolymer (A) in an aqueous medium, a toner raw material comprising urea-modified polyester (i) or prepolymer (A) in an aqueous medium is used. And a method of dispersing by shearing force.

  The prepolymer (A) and other toner compositions (hereinafter also referred to as toner raw materials), colorants, colorant master batches, mold release agents, charge control agents, unmodified polyester resins, etc. are aqueous media. However, it is more preferable to mix the toner raw materials in advance and then add and disperse the mixture in the aqueous medium. In the present invention, other toner raw materials such as a colorant, a release agent, and a charge control agent do not necessarily have to be mixed when forming particles in an aqueous medium. It may be added later. For example, after forming particles not containing a colorant, the colorant can be added by a known dyeing method.

  As an aqueous medium, water alone may be used, but a solvent miscible with water may be used in combination. Examples of miscible solvents include alcohol (methanol, isopropanol, ethylene glycol, etc.), dimethylformamide, tetrahydrofuran, cellosolves (methyl cellosolve, etc.), lower ketones (acetone, methyl ethyl ketone, etc.) and the like.

  The amount of the aqueous medium used relative to 100 parts by mass of the toner composition containing the urea-modified polyester (i) and the prepolymer (A) is preferably 50 parts by mass to 2,000 parts by mass, and 100 parts by mass to 1,000 parts by mass. Is more preferable. When the amount used is less than 50 parts by mass, the dispersion state of the toner composition is poor, and toner particles having a predetermined particle size may not be obtained, and when it exceeds 2,000 parts by mass, it is not economical.

  Moreover, a dispersing agent can also be used as needed. It is preferable to use a dispersant because the particle size distribution becomes sharp and the dispersion is stable.

The dispersion method is not particularly limited and may be appropriately selected depending on the intended purpose. For example, known equipment such as a low-speed shear method, a high-speed shear method, a friction method, a high-pressure jet method, and an ultrasonic wave can be applied.
In order to make the particle size of the dispersion 2 [μm] to 20 [μm], a high-speed shearing method is preferable.
When a high-speed shearing disperser is used, the rotational speed is not particularly limited, but is preferably 1,000 [rpm] to 30,000 [rpm], and is preferably 5,000 [rpm] to 20,000 [rpm]. Is more preferable. The dispersion time is not particularly limited, but in the case of a batch method, it is usually 0.1 minutes to 5 minutes. The temperature at the time of dispersion is usually preferably 0 [° C.] to 150 [° C.], more preferably 40 [° C.] to 98 [° C.]. Higher temperatures are preferred in that the dispersion made of urea-modified polyester (i) or prepolymer (A) has a low viscosity and is easy to disperse.

  In the step of synthesizing the urea-modified polyester (i) from the prepolymer (A), the amine (B) may be added and reacted before the toner composition is dispersed in the aqueous medium, or may be dispersed in the aqueous medium. An amine (B) may be added later to cause a reaction from the particle interface. In this case, urea-modified polyester is preferentially produced on the surface of the manufactured toner, and a concentration gradient can be provided inside the particles.

In the reaction, it is preferable to use a dispersant as required.
There is no restriction | limiting in particular as a dispersing agent, According to the objective, it can select suitably, For example, surfactant, a sparingly water-soluble inorganic compound dispersing agent, a polymeric protective colloid, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together. Among these, surfactants are preferable.

  Examples of the surfactant include an anionic surfactant, a cationic surfactant, a nonionic surfactant, and an amphoteric surfactant.

  Examples of the anionic surfactant include alkylbenzene sulfonates, α-olefin sulfonates, phosphate esters, and the like. Among these, those having a fluoroalkyl group are preferable. Examples of the anionic surfactant having a fluoroalkyl group include a fluoroalkylcarboxylic acid having 2 to 10 carbon atoms or a metal salt thereof, perfluorooctanesulfonyl glutamate disodium, 3- [omega-fluoroalkyl (6 to 6 carbon atoms). 11) Sodium oxy] -1-alkyl (3 to 4 carbon atoms) sulfonate, sodium 3- [omega-fluoroalkanoyl (6 to 8 carbon atoms) -N-ethylamino] -1-propanesulfonate, fluoroalkyl ( Carbon number 11-20) carboxylic acid or metal salt thereof, perfluoroalkyl carboxylic acid (carbon number 7-13) or metal salt thereof, perfluoroalkyl (carbon number 4-12) sulfonic acid or metal salt thereof, perfluorooctane Sulfonic acid diethanolamide, N-propyl-N- (2-hydroxy Chill) perfluorooctanesulfonamide, perfluoroalkyl (carbon number 6-10) sulfonamidopropyltrimethylammonium salt, perfluoroalkyl (carbon number 6-10) -N-ethylsulfonylglycine salt, monoperfluoroalkyl (carbon number) 6-16) Ethyl phosphate and the like. Commercially available surfactants having a fluoroalkyl group include, for example, Surflon S-111, S-112, S-113 (Asahi Glass Co., Ltd.); Fluorard FC-93, FC-95, FC-98, FC-129 (Manufactured by Sumitomo 3M); Unidyne DS-101, DS-102 (manufactured by Daikin Industries); Megafac F-110, F-120, F-113, F-191, F-812, F-833 (Dainippon) Ink Chemical Industries Ltd.); Xtop EF-102, 103, 104, 105, 112, 123A, 123B, 306A, 501, 201, 204 (manufactured by Tochem Products); Etc.).

  Examples of the cationic surfactant include amine salt type surfactants and quaternary ammonium salt type cationic surfactants. Examples of amine salt type surfactants include alkylamine salts, aminoalcohol fatty acid derivatives, polyamine fatty acid derivatives, imidazolines, and the like. Examples of the quaternary ammonium salt type cationic surfactant include alkyltrimethylammonium salt, dialkyldimethylammonium salt, alkyldimethylbenzylammonium salt, pyridinium salt, alkylisoquinolinium salt, benzethonium chloride and the like. Among cationic surfactants, aliphatic quaternary ammonium salts such as aliphatic primary, secondary or tertiary amine acids having a fluoroalkyl group, and perfluoroalkyl (6 to 10 carbon atoms) sulfonamidopropyltrimethylammonium salt Benzalkonium salt, benzethonium chloride, pyridinium salt, imidazolinium salt, and the like. Commercially available cationic surfactants include, for example, Surflon S-121 (Asahi Glass Co., Ltd.); Florard FC-135 (Sumitomo 3M Co., Ltd.); Unidyne DS-202 (Daikin Kogyo Co., Ltd.), MegaFuck F-150, F-824 (manufactured by Dainippon Ink & Chemicals, Inc.); Xtop EF-132 (manufactured by Tochem Products);

Examples of nonionic surfactants include fatty acid amide derivatives and polyhydric alcohol derivatives.
Examples of the amphoteric surfactant include alanine, dodecyldi (aminoethyl) glycine, di (octylaminoethyl) glycine, N-alkyl-N, N-dimethylammonium betaine and the like.

  Examples of the hardly water-soluble inorganic compound dispersant include tricalcium phosphate, calcium carbonate, titanium oxide, colloidal silica, and hydroxyapatite.

  Examples of the polymeric protective colloid include acids, (meth) acrylic monomers containing hydroxyl groups, vinyl alcohol or ethers of vinyl alcohol, esters of vinyl alcohol and a compound containing a carboxyl group, amide compounds Alternatively, homopolymers or copolymers such as those having methylol compounds, chlorides, nitrogen atoms or heterocyclic rings thereof, polyoxyethylenes, celluloses, and the like can be given.

Examples of the acids include acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid, maleic anhydride, and the like.
Examples of the (meth) acrylic monomer containing a hydroxyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, and γ-acrylate. Hydroxypropyl, γ-hydroxypropyl methacrylate, 3-chloro-2-hydroxypropyl acrylate, 3-chloro-2-hydroxypropyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerin monoacrylate, Examples include glycerin monomethacrylate, N-methylol acrylamide, N-methylol methacrylamide and the like.
Examples of vinyl alcohol or ethers with vinyl alcohol include vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, and the like.
Examples of esters of a compound containing vinyl alcohol and a carboxyl group include vinyl acetate, vinyl propionate, vinyl butyrate and the like.
Examples of the amide compound or these methylol compounds include acrylamide, methacrylamide, diacetone acrylamide acid, or these methylol compounds. Examples of chlorides include acrylic acid chloride and methacrylic acid chloride.
Examples of homopolymers or copolymers such as those having a nitrogen atom or a heterocyclic ring thereof include vinyl pyridine, vinyl pyrrolidone, vinyl imidazole, and ethylene imine.
Examples of the polyoxyethylene type include polyoxyethylene, polyoxypropylene, polyoxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonylphenyl ether, polyoxyethylene Examples include ethylene lauryl phenyl ether, polyoxyethylene stearyl phenyl ester, and polyoxyethylene nonyl phenyl ester.
Examples of celluloses include methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and the like.

In preparing the dispersion, a dispersion stabilizer can be used as necessary. Examples of the dispersion stabilizer include acids that can be dissolved in acids and alkalis such as calcium phosphate salts.
When a dispersion stabilizer is used, the calcium phosphate salt can be removed from the fine particles by a method of dissolving the calcium phosphate salt with an acid such as hydrochloric acid and then washing with water or a method of decomposing with an enzyme.

  In preparation of the dispersion, a catalyst for elongation reaction or crosslinking reaction can be used. Examples of the catalyst include dibutyltin laurate and dioctyltin laurate.

  Furthermore, in order to lower the viscosity of the toner composition, a solvent in which the urea-modified polyester (i) or the prepolymer (A) is soluble can be used. The use of a solvent is preferable in that the particle size distribution becomes sharp. The solvent is preferably volatile from the viewpoint of easy removal.

Examples of the solvent include toluene, xylene, benzene, carbon tetrachloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, dichloroethylidene, methyl acetate, ethyl acetate, methyl ethyl ketone. And methyl isobutyl ketone. These may be used individually by 1 type and may use 2 or more types together. Among these, aromatic solvents such as toluene and xylene; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, chloroform and carbon tetrachloride are preferable, and aromatic solvents such as toluene and xylene are more preferable.
0 mass parts-300 mass parts are preferable, as for the usage-amount of the solvent with respect to 100 mass parts of prepolymers (A), 0 mass parts-100 mass parts are more preferable, and 25 mass parts-70 mass parts are especially preferable. When a solvent is used, it is removed by heating under normal pressure or reduced pressure after the elongation and / or crosslinking reaction.

The elongation and / or cross-linking reaction time is selected depending on the reactivity depending on the combination of the isocyanate group structure of the prepolymer (A) and the amines (B). Is more preferable.
The reaction temperature is preferably 0 [° C.] to 150 [° C.], more preferably 40 [° C.] to 98 [° C.]. Furthermore, a known catalyst can be used as necessary. Specific examples include dibutyltin laurate and dioctyltin laurate.

In order to remove the organic solvent from the obtained emulsified dispersion, a method in which the temperature of the entire system is gradually raised to completely evaporate and remove the organic solvent in the droplets can be employed. It is also possible to spray the emulsified dispersion in a dry atmosphere to completely remove the water-insoluble organic solvent in the droplets to form toner fine particles, and also remove the aqueous dispersant by evaporating it. is there.
As a dry atmosphere in which the emulsified dispersion is sprayed, a gas obtained by heating air, nitrogen, carbon dioxide gas, combustion gas, or the like, in particular, various air currents heated to a temperature equal to or higher than the boiling point of the highest boiling solvent used is generally used. Sufficient quality can be obtained with a short treatment such as spray dryer, belt dryer or rotary kiln.

When the particle size distribution at the time of emulsification dispersion is wide and washing and drying processes are performed while maintaining the particle size distribution, the particle size distribution can be adjusted by classifying into a desired particle size distribution.
In the classification operation, the fine particle portion can be removed in the liquid by a cyclone, a decanter, centrifugation, or the like. Although classification operation may be performed after obtaining as powder after drying, it is preferable in terms of efficiency to be performed in a liquid. The unnecessary fine particles or coarse particles obtained can be returned to the kneading step and used for the formation of particles. At that time, unnecessary fine particles or coarse particles may be wet.
The dispersant used is preferably removed from the obtained dispersion as much as possible, but it is preferable to carry out it simultaneously with the classification operation described above.

  The resulting dried toner powder is mixed with dissimilar particles such as release agent fine particles, charge control fine particles, fluidizing agent fine particles, and colorant fine particles, or mechanical impact force is applied to the mixed powder. As a result, it is possible to prevent the dissociation of the foreign particles from the surface of the composite particle obtained by immobilizing and fusing on the surface.

  As specific means, (1) a method of applying an impact force to the mixture by blades rotating at high speed, (2) the mixture is injected into a high-speed air stream, accelerated, and particles or composite particles are mixed with an appropriate collision plate. There is a method of making it collide. As equipment, Ong mill (manufactured by Hosokawa Micron Corporation), I-type mill (manufactured by Nippon Pneumatic Co., Ltd.), with reduced pulverization air pressure, hybridization system (manufactured by Nara Machinery Co., Ltd.), kryptron system ( Kawasaki Heavy Industries, Ltd.) and automatic mortar.

  As the colorant used in the toner, pigments and dyes that have been conventionally used as toner colorants can be used. Specifically, carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline Blue, phthalocyanine blue, phthalocyanine green, Hansa yellow G, rhodamine 6C lake, calco oil blue, chrome yellow, quinacridone red, benzidine yellow, rose bengal and the like can be used alone or in combination.

  Furthermore, if necessary, in order to give the toner particles magnetic properties, for example, iron oxides such as ferrite, magnetite and maghemite; metals such as iron, cobalt and nickel, or alloys of these with other metals The magnetic components such as these may be contained in the toner particles alone or in combination. These components can also be used as a colorant component.

The number average particle size of the colorant in the toner is preferably 0.5 [μm] or less, more preferably 0.4 [μm] or less, and particularly preferably 0.3 [μm] or less. When the number average particle diameter exceeds 0.5 [μm], the dispersibility of the pigment does not reach a sufficient level, and preferable transparency may not be obtained. On the other hand, a colorant having a fine particle diameter smaller than 0.1 [μm] is sufficiently smaller than a half wavelength of visible light, and thus is considered not to adversely affect light reflection and absorption characteristics.
Therefore, the colorant particles having a number average particle size of less than 0.1 [μm] contribute to good color reproducibility and transparency of the OHP sheet having a fixed image.
On the other hand, when there are many colorants having a number average particle size larger than 0.5 [μm], the transmission of incident light is hindered or scattered, and the projected image of the OHP sheet becomes bright. There is a tendency to decrease the color and color.
Further, when a large amount of colorant having a particle size larger than 0.5 [μm] is present, the colorant is detached from the surface of the toner particles, which may cause various problems such as fogging, drum contamination, and poor cleaning.
The colorant having a number average particle diameter larger than 0.7 [μm] is preferably 10% by number or less, more preferably 5% by number or less of the total colorant.

  Also, by mixing the colorant together with part or all of the binder resin in advance after adding a wetting liquid, the binder resin and the colorant are initially sufficiently adhered, In this toner production process, the colorant is dispersed more effectively in the toner particles, the dispersed particle diameter of the colorant is reduced, and better transparency can be obtained.

  As the binder resin used for kneading in advance, the resins exemplified as the binder resin for toner can be used as they are, but are not limited thereto.

  As a specific method for kneading the mixture of the binder resin and the colorant with the wetting liquid in advance, for example, the mixture obtained by mixing the binder resin, the colorant and the wetting liquid with a blender such as a Henschel mixer. Is kneaded at a temperature lower than the melting temperature of the binder resin with a kneader such as a two-roll or three-roll roll to obtain a sample.

Further, as the wetting liquid, a general one can be used in consideration of the solubility of the binder resin and the paintability with the colorant, but an organic solvent such as acetone, toluene, butanone, and water are used as the colorant. It is preferable from the viewpoint of dispersibility. Among these, the use of water is particularly preferable from the viewpoint of environmental considerations and maintaining the dispersion stability of the colorant in the subsequent toner production process.
According to this production method, not only the particle size of the colorant particles contained in the toner obtained is reduced, but also the uniformity of the dispersed state of the particles is increased, so the color reproducibility of the projected image by OHP is further improved. .

The toner preferably contains a release agent together with the binder resin and the colorant.
The release agent is not particularly limited and may be appropriately selected from known ones according to the purpose. For example, polyolefin wax (polyethylene wax, polypropylene wax, etc.); long chain hydrocarbon (paraffin wax) And waxes containing carbonyl groups. Among these, a carbonyl group-containing wax is particularly preferable.

  Examples of the carbonyl group-containing wax include polyalkanoic acid esters (carnauba wax, montan wax, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1 , 18-octadecanediol distearate, etc.); polyalkanol esters (tristearyl trimellitic acid, distearyl maleate, etc.); polyalkanoic acid amides (ethylenediamine dibehenyl amide, etc.); polyalkylamides (trimellitic acid tristearyl amide) Etc.); dialkyl ketones (distearyl ketone, etc.) and the like. Among these, polyalkanoic acid esters are particularly preferable.

The melting point of the release agent is preferably 40 [° C.] to 160 [° C.], more preferably 50 [° C.] to 120 [° C.], and particularly preferably 60 [° C.] to 90 [° C.]. If the melting point is less than 40 [° C.], the heat resistant storage stability may be adversely affected. If the melting point exceeds 160 [° C.], cold offset may easily occur during fixing at a low temperature.
The melt viscosity of the release agent is preferably 5 [cps] to 1,000 [cps] at a temperature 20 [° C.] higher than the melting point, and more preferably 10 [cps] to 100 [cps]. When the melt viscosity exceeds 1,000 [cps], the effect of improving hot offset resistance and low-temperature fixability may be poor.
The content of the release agent in the toner is preferably 0% by mass to 40% by mass, and more preferably 3% by mass to 30% by mass.

  Further, in order to accelerate the toner charge amount and its rise, a charge control agent may be contained in the toner as necessary. Since a color change occurs when a colored material is used as the charge control agent, a colorless or nearly white material is preferable.

  The charge control agent is not particularly limited and may be appropriately selected from known ones according to the purpose. For example, triphenylmethane dyes, molybdate chelate pigments, rhodamine dyes, alkoxyamines, 4 Examples include quaternary ammonium salts (including fluorine-modified quaternary ammonium salts), alkylamides, phosphorus simple substances or compounds, tungsten simple substances or compounds, fluorine-based activators, salicylic acid metal salts, and metal salts of salicylic acid derivatives.

  Commercially available products can be used as the charge control agent. Examples of commercially available products include quaternary ammonium salt Bontron P-51, oxynaphthoic acid metal complex E-82, and salicylic acid metal complex E-. 84, E-89 of a phenol-based condensate (both manufactured by Orient Chemical Co., Ltd.); TP-302 and TP-415 of quaternary ammonium salt molybdenum complexes (both manufactured by Hodogaya Chemical Co., Ltd.); Copy charge PSY VP2038 of quaternary ammonium salt, copy blue PR of triphenylmethane derivative, copy charge of quaternary ammonium salt NEG VP2036, copy charge NX VP434 (both manufactured by Hoechst); LRA-901, boron complex LR-147 (all manufactured by Nippon Carlit Co., Ltd.), quinacridone, azo pigments, Other examples include high molecular compounds having a functional group such as a sulfonic acid group, a carboxyl group, and a quaternary ammonium salt.

  The addition amount of the charge control agent varies depending on the type of the binder resin, the presence or absence of the additive, the toner production method including the dispersion method, and the like, and cannot be uniquely defined, but is 0 for 100 parts by mass of the binder resin. 1 mass part-10 mass parts are preferable, and 0.2 mass part-5 mass parts are more preferable. When the addition amount exceeds 10 parts by mass, the chargeability of the toner is too high, the effect of the charge control agent is reduced, the electrostatic attractive force with the developing roller is increased, the flowability of the developer is reduced, and the image density May be reduced. These charge control agents can be melted and kneaded together with a masterbatch and resin and then dissolved and dispersed, or they can be added directly when dissolved and dispersed in an organic solvent, or fixed after the toner particles are prepared on the toner surface. You may let them.

Further, when the toner composition is dispersed in the aqueous medium during the toner production process, resin fine particles mainly for stabilizing the dispersion may be added.
The resin fine particle is not particularly limited as long as it is a resin capable of forming an aqueous dispersion, and may be a thermoplastic resin or a thermosetting resin. For example, vinyl resin, polyurethane resin, epoxy resin, polyester resin, polyamide Examples thereof include resins, polyimide resins, silicon resins, phenol resins, melamine resins, urea resins, aniline resins, ionomer resins, and polycarbonate resins. These may be used individually by 1 type and may use 2 or more types together. Among these, a vinyl resin, a polyurethane resin, an epoxy resin, a polyester resin, or a combination thereof is preferable because an aqueous dispersion of fine spherical resin particles can be easily obtained.

  As the vinyl resin, a polymer obtained by homopolymerization or copolymerization of a vinyl monomer is used. For example, a styrene- (meth) acrylate resin, a styrene-butadiene copolymer, a (meth) acrylic acid-acrylate polymer Examples thereof include styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer, and styrene- (meth) acrylic acid copolymer.

As an external additive for assisting fluidity, developability and chargeability of toner particles, inorganic fine particles are preferable.
Examples of the inorganic fine particles include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, quartz sand, clay, mica, wollastonite, diatomaceous earth, Examples thereof include chromium oxide, cerium oxide, pengala, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride.

The primary particle diameter of the inorganic fine particles is preferably 5 [nm] to 2 [μm], more preferably 5 [nm] to 500 [nm]. Further, the specific surface area of the inorganic fine particles by the BET method is preferably 20 [m ² / g] to 500 [m ² / g].
The addition amount of the inorganic fine particles in the toner is preferably 0.01% by mass to 5% by mass, and more preferably 0.01% by mass to 2.0% by mass.

  Examples of other polymer fine particles include, for example, polystyrene obtained by soap-free emulsion polymerization, suspension polymerization, and dispersion polymerization, polycondensation systems such as methacrylic acid ester and acrylic acid ester copolymer, silicone, benzoguanamine, and nylon, heat Examples thereof include polymer particles made of a curable resin.

A fluidizing agent can also be added to the toner.
The fluidizing agent performs surface treatment to increase hydrophobicity, and can prevent deterioration of flow characteristics and charging characteristics even under high humidity.
Examples of the fluidizing agent include silane coupling agents, silylating agents, silane coupling agents having a fluorinated alkyl group, organic titanate coupling agents, aluminum coupling agents, silicone oils, and modified silicone oils. It is done.

  Examples of cleaning improvers for removing the developer after transfer remaining on the photoreceptor and the intermediate transfer belt include fatty acid metal salts such as zinc stearate, calcium stearate and stearic acid; polymethyl methacrylate fine particles, polystyrene Examples thereof include polymer fine particles produced by soap-free emulsion polymerization of fine particles and the like. The polymer fine particles preferably have a relatively narrow particle size distribution and a volume average particle size of 0.01 [μm] to 1 [μm].

  By using such a toner, as described above, it is possible to form a high-quality toner image having excellent development stability.

  The printer of the present invention can be applied not only to the above-described polymerization toner having a configuration suitable for obtaining a high-quality image, but also to an irregular shaped toner by a pulverization method. Even in this case, the life of the apparatus can be greatly extended. As a material constituting such a pulverized toner, those usually used as an electrophotographic toner can be applied without particular limitation.

  Examples of the binder resin used in the pulverized toner include a homopolymer of styrene such as polystyrene, poly p-chlorostyrene, polyvinyltoluene, or the like; a styrene / p-chlorostyrene copolymer, and a styrene / propylene copolymer. Polymer, styrene / vinyl toluene copolymer, styrene / vinyl naphthalene copolymer, styrene / methyl acrylate copolymer, styrene / ethyl acrylate copolymer, styrene / butyl acrylate copolymer, styrene / acrylic acid Octyl copolymer, styrene / methyl methacrylate copolymer, styrene / ethyl methacrylate copolymer, styrene / butyl methacrylate copolymer, styrene / α-chloromethyl methacrylate copolymer, styrene / acrylonitrile copolymer , Styrene / vinyl methyl ketone copolymer, steel Styrene copolymers such as ethylene / butadiene copolymer, styrene / isoprene copolymer, styrene / maleic acid copolymer; polymethyl acrylate, polybutyl acrylate, polymethyl methacrylate, polybutyl methacrylate, etc. Acrylic ester-based homopolymers or copolymers thereof; polyvinyl derivatives such as polyvinyl chloride and polyvinyl acetate; polyester-based polymers, polyurethane-based polymers, polyamide-based polymers, polyimide-based polymers, polyol-based polymers, Examples thereof include epoxy polymers, terpene polymers, aliphatic or alicyclic hydrocarbon resins, and aromatic petroleum resins. These may be used individually by 1 type and may use 2 or more types together. Among these, a styrene-acrylic copolymer resin, a polyester resin, and a polyol resin are preferable from the viewpoint of electrical characteristics, cost, and the like, and further, polyester resins and polyol resins are preferable as those having good fixing characteristics. Particularly preferred.

  In the pulverized toner, the colorant component, the wax component, the charge control component, etc., as described above, together with these resin components are premixed if necessary, and then kneaded at a temperature close to the melting temperature of the resin component, and then cooled. The toner may be prepared through a pulverizing and classifying step, and an external additive component may be appropriately added and mixed as necessary.

  The developing unit may be of a dry development type, may be of a wet development type, may be a single color developer, or may be a multicolor developer. For example, a toner or a developer having a stirrer for charging a toner or a developer by frictional stirring and a rotatable magnet roller can be preferably used.

  In the developing device, for example, the toner and the carrier are mixed and stirred, and the toner is charged by friction at that time, and held on the surface of the rotating magnet roller in a raised state, thereby forming a magnetic brush. Since the magnet roller is disposed in the vicinity of the photoreceptor 1 (photoreceptor), a part of the toner constituting the magnetic brush formed on the surface of the magnet roller is electrically attracted to the photoreceptor 1 (photoreceptor). ) Move to the surface. As a result, the electrostatic latent image is developed with toner, and a visible image with toner is formed on the surface of the photoreceptor 1 (photoreceptor).

[Cleaning means]
The cleaning means is not particularly limited as long as it is a means for cleaning the surface of the photoreceptor 1 and can be appropriately selected according to the purpose. Among them, a cleaning brush for cleaning the surface of the photoreceptor 1 is provided. Is preferred.
In general, as a cleaning method of the photosensitive member 1, in addition to a method using a cleaning blade, there is an electrostatic cleaning method using a brush to which a voltage is applied so as to be opposite in polarity to the toner remaining on the photosensitive member 1. Can be mentioned.
In the cleaning means using the cleaning member, the cleaning member is generally brought into contact with the rotation direction of the photosensitive member 1 in the trailing direction (counter direction), and the remaining components mainly composed of toner remaining on the photosensitive member 1 are removed. At this time, since the cleaning member comes into relatively strong contact with the photosensitive member 1, the conductive support member of the photosensitive member 1 may be partially deformed when the thickness of the conductive supporting member becomes thin.

On the other hand, the cleaning means having the cleaning brush is preferable when the thickness of the conductive support of the photosensitive member 1 is thin because the load on the photosensitive member 1 is relatively small.
As a cleaning brush, it is preferable that the brush fibers have flexibility in order to suppress mechanical stress on the surface of the photoreceptor 1. The material for the flexible brush fiber is not particularly limited and may be appropriately selected depending on the intended purpose. For example, polyolefin resin (for example, polyethylene, polypropylene); polyvinyl resin or polyvinylidene resin (for example, polystyrene) , Acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polyvinyl ketone); vinyl chloride-vinyl acetate copolymer; styrene-acrylic acid copolymer; styrene-butadiene Resin; Fluorine resin (eg, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene); polyester; nylon; acrylic; rayon; Polycarbonate; phenolic resins; amino resins (e.g. urea - formaldehyde resins, melamine resins, benzoguanamine resins, urea resins, polyamide resins).
In order to adjust the degree of bending, for example, diene rubber, styrene-butadiene rubber (SBR), ethylene propylene rubber, isoprene rubber, nitrile rubber, urethane rubber, silicone rubber, hydrin rubber, norbornene rubber, etc. may be combined. .

  Examples of the roll-shaped cleaning brush include a roll brush obtained by winding a tape having brush fibers in a pile ground around a metal core bar in a spiral shape. The brush fiber has a fiber diameter of about 10 [μm] to 500 [μm], the length of the brush fiber is 1 [mm] to 15 [mm], and the brush density is 10,000 to 300,000 per square inch (1 1.5 × 10 7 to 4.5 × 10 8) per square meter are suitable.

  The cleaning brush preferably has a high brush density from the viewpoint of cleaning stability accompanying the uniformity of the brush fibers, and one fiber is produced from several to several hundreds of fine fibers. Is preferred. For example, bundling 50 fine fibers of 6.7 decitex (6 denier), such as 333 decitex = 6.7 decitex × 50 filament (300 denier = 6 denier × 50 filament), and implanting as one fiber Is preferred.

  Moreover, you may provide a coating layer in the brush surface for the purpose of stabilizing the surface shape, environmental stability, etc. of a brush as needed. As a component constituting the coating layer, it is preferable to use a coating layer component that can be deformed according to the bending of the brush fiber. The coating layer component is not particularly limited as long as it is a material that can maintain flexibility, and can be appropriately selected according to the purpose. For example, polyolefin such as polyethylene, polypropylene, chlorinated polyethylene, and chlorosulfonated polyethylene Resins such as polystyrene, acrylic (for example, polymethyl methacrylate), polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polybiliketones, and the like, or polyvinylidene resins such as polyvinyl chloride-vinyl acetate Copolymer; Silicone resin composed of organosiloxane bond or modified product thereof (for example, modified product by alkyd resin, polyester resin, epoxy resin, polyurethane resin, etc.); Fluorine resins such as alkyl ether, polyfluorovinyl, polyfluorovinylidene and polychlorotrifluoroethylene; polyamides; polyesters; polyurethanes; polycarbonates; amino resins such as urea-formaldehyde resins; epoxy resins or composite resins thereof .

[Protective material supply means]
The protective material supply means is not particularly limited as long as it is a means for supplying a protective material for protecting the surface of the photoreceptor, and can be appropriately selected according to the purpose. In this embodiment, the protective material coating apparatus 2 is used. Is used.
By providing the protective material supply means, not only can the surface of the photoconductor be maintained by cleaning, but also deterioration of the photoconductor surface due to electrical stress during charging can be suppressed by the protective material.

  The protective material coating device 2 disposed facing the photoconductor 1 is mainly composed of a photoconductor protective material 21, a protective material supply member 22, a pressing force applying member 23, a protective layer forming member 24, and the like. The photoconductor protective material 21 is brought into contact with, for example, a brush-like protective material supply member 22 by the pressing force from the pressing force applying member 23. The protective material supply member 22 rotates and rubs with the photosensitive member 1 with a linear velocity difference. At this time, the protective material for the photosensitive member held on the surface of the protective material supply member is supplied to the surface of the photosensitive member 1. Since the protective material for the photosensitive member supplied to the surface of the photosensitive member 1 may not be a sufficient protective layer upon supply depending on the selection of the material type, for example, one rotation of the photosensitive member is performed to form a more uniform protective layer. The protective layer forming member 24 having a blade-like member gently abutting in the trailing direction with respect to the direction becomes a protective layer.

  For example, a charging roller 31 to which a DC voltage or a voltage in which an AC voltage is superimposed is applied by a high voltage power supply (not shown) is brought into contact with or brought close to the photosensitive member 1 on which the protective layer is formed. The photosensitive member 1 is charged by the discharge at. At this time, a part of the protective layer is decomposed or oxidized due to electrical stress, and air discharge products adhere to the surface of the protective layer, resulting in a deteriorated product. The deteriorated protective material for the photoconductor is removed by the cleaning device together with components such as toner remaining on the photoconductor 1 by the cleaning device. Such a cleaning device may be used also as a protective material application member, but the function of removing the residue on the surface of the photoreceptor 1 and the function of forming the protective layer differ in the rubbing state of an appropriate member. Therefore, the functions are separated, and as shown in FIG. 2, a cleaning device 4 including a cleaning member 41, a flicker 42, a waste toner conveying member 43, and the like is provided on the upstream side of the photosensitive member supply unit. preferable.

  The material of the blade used for the protective layer forming member is not particularly limited and can be appropriately selected from known materials used for the cleaning member or the like according to the purpose. For example, urethane rubber, hydrin rubber, silicone rubber And fluororubber. These may be used individually by 1 type and may use 2 or more types together. In these blades, the contact portion with the photoreceptor 1 may be coated or impregnated with a low coefficient of friction material. Moreover, in order to adjust the hardness of an elastic body, you may disperse fillers, such as an organic filler and an inorganic filler.

  The blade for forming the protective layer is fixed to the blade support by an arbitrary method such as adhesion or fusion so that the tip can be pressed against the surface of the photoreceptor 1. The thickness of the protective layer-forming blade is not uniquely defined in consideration of the force applied by pressing, but is preferably 0.5 [mm] to 5 [mm], and preferably 1 [mm] to 2 [mm]. ] Is more preferable. Further, the length of the blade that protrudes from the support and can be deflected, that is, the so-called free length, is not unambiguously defined in consideration of the force applied by pressing in the same manner, but 1 [mm] to 15 [Mm] is preferable, and 2 [mm] to 10 [mm] is more preferable.

  As another configuration of the protective layer forming blade member, the surface of the elastic metal blade such as a spring plate is coated with a coating layer of resin, rubber, elastomer or the like via a coupling agent or a primer component as necessary. It may be formed by a method such as dipping, heat-cured or the like if necessary, and further subjected to surface polishing if necessary.

The coating layer contains at least a binder resin and a filler, and further contains other components as necessary.
The binder resin is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include fluorine resins such as PFA, PTFE, FEP and PVdF; silicone elastomers such as fluorine rubber and methylphenyl silicone elastomer; Can be mentioned.

  The thickness of the elastic metal blade is preferably 0.05 [mm] to 3 [mm], more preferably 0.1 [mm] to 0.5 [mm]. In an elastic metal blade, in order to suppress twisting of the blade, a process such as bending may be performed in a direction substantially parallel to the support shaft after attachment.

  The force that presses the photosensitive member 1 with the protective layer forming member is sufficient as the protective material for the photosensitive member extends to form a protective layer, and the linear pressure is 5 [gf / cm] to 70 [gf / cm]. Is preferable, and 10 [gf / cm] to 30 [gf / cm] is more preferable.

  As described above, the protective material supply member may be used also as a cleaning brush, or may be separately provided immediately after the cleaning brush. Moreover, as a material used for the protective material supply member, a material equivalent to the material used for the cleaning brush can be used.

  The components constituting the photoconductor protective material are not particularly limited and may be appropriately selected depending on the intended purpose. For example, fatty acid metal salts and saturated hydrocarbon waxes are preferred.

  Examples of fatty acid metal salts include long chain alkyl carboxylates such as laurate, myristic acid, palmitate, stearate, behenate, lignocerate, cellotate, montanate, melinate, etc. An anion (anion) at the end of a hydrophobic site such as, alkali metal ions such as sodium and potassium, alkaline earth metal ions such as magnesium and calcium, metal ions such as aluminum and zinc, etc. Bound compounds are mentioned. Specific examples include zinc stearate, calcium stearate, magnesium stearate, zinc laurate, calcium laurate, magnesium laurate and the like. These fatty acid metal salts may be used in combination.

  The saturated hydrocarbon wax is not particularly limited and may be appropriately selected depending on the intended purpose. However, the saturated hydrocarbon wax has a sharp peak of heat of fusion in the range of 80 [° C.] to 130 [° C.], and the melt after melting A thing with a low viscosity is preferable.

Examples of saturated hydrocarbon waxes include aliphatic saturated hydrocarbons, aliphatic unsaturated hydrocarbons, alicyclic saturated hydrocarbons, hydrocarbons classified as alicyclic unsaturated hydrocarbons and aromatic hydrocarbons, carnauba wax, Examples include plant natural waxes such as rice bran wax and candelilla wax, and animal natural waxes such as beeswax and snow wax.
In particular, aliphatic saturated hydrocarbons and alicyclic saturated hydrocarbons, in which the bonds in the molecule consist only of low-reactivity and stable saturated bonds, are preferred, among which hydrocarbon waxes such as normal paraffins, isoparaffins and cycloparaffins are added. The reaction is difficult to occur and is chemically stable, and it is difficult to cause an oxidation reaction in the actual air.

  Further, since the durability of the protective layer itself can be increased by using a hydrocarbon wax containing at least one of Fischer-Tropsch wax and polyethylene wax as a relatively hard saturated hydrocarbon wax, the surface of the photoreceptor 1 is improved. It is more preferable because protection of the photoreceptor 1 can be realized without making the thickness of the protective layer formed excessively.

In addition to this, an amphiphilic organic compound such as a surfactant is used as an additive as a formulation for enhancing the affinity between the protective material for the photosensitive member and the surface of the photosensitive member 1 and assisting the formation of the protective material layer. You may use together.
Since the amphiphilic organic compound may greatly change the surface characteristics of the main material, the addition amount thereof is 0.01% by mass to 3% by mass with respect to the total mass of the protective material for the photoreceptor. Is preferably about 0.05% by mass to 2% by mass.

  In order to mold the protective material for the photoreceptor into a certain shape, for example, a prismatic shape or a cylindrical shape, a dry molding method, which is one of powder molding methods, can be used in addition to the hot melt molding method.

As a typical example of the dry molding method, the uniaxial pressure molding method can be generally performed by the following procedure.
1. The raw material powders of the various photoconductor protective materials whose specific gravity is measured in advance are sufficiently mixed at a desired ratio, and the weight at which a desired filling rate is obtained is measured.
2. The weighed powder of the protective material for the photoreceptor is put into a mold having a predetermined shape.
3. While pressurizing the powder thrown in by the pressing mold, it is heated as necessary to prepare a protective material molded body. The molded body is removed from the mold to obtain a protective material for the photoreceptor.
4). Thereafter, the shape of the photoconductor protective material may be adjusted by cutting or the like.

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

[Transfer means]
The transfer means is a means for transferring a visible image onto a recording material. As in the present embodiment, the intermediate transfer belt 60 is used to primarily transfer the visible image onto the intermediate transfer belt, and then the visible image is transferred. A mode of secondary transfer onto a recording material is preferable, and a primary transfer step of forming a composite transfer image by transferring a visible image onto an intermediate transfer belt using two or more colors, preferably a full color toner as a toner, A mode including a secondary transfer step of transferring the composite transfer image onto the recording material is more preferable.

As the intermediate transfer belt 60, a material exhibiting conductivity having a volume resistivity of 1.0 × 10 ⁵ [Ω · cm] to 1.0 × 10 ¹¹ [Ω · cm] is preferable. When the volume resistivity is less than 1.0 × 10 ⁵ [Ω · cm], when the toner image is transferred from the photoreceptor 1 onto the intermediate transfer belt, the toner image is disturbed due to discharge, so-called transfer dust. If the toner image exceeds 1.0 × 10 ¹¹ [Ω · cm], the toner image is transferred from the intermediate transfer belt 60 to a recording material such as paper, and then the toner image is countered onto the intermediate transfer belt. Charge may remain and appear as an afterimage on the next image.

  The material of the intermediate transfer belt 60 is, for example, a metal oxide such as tin oxide or indium oxide, conductive particles such as carbon black, or a conductive polymer, either alone or in combination, and kneaded with a thermoplastic resin, and then extrusion molding. A belt-like or cylindrical plastic can be used. In addition, it is also possible to obtain an intermediate transfer belt on an endless belt by adding conductive particles or a conductive polymer to a resin solution containing a thermal crosslinking reactive monomer or oligomer, if necessary, and performing centrifugal molding while heating. it can. When a surface layer is provided on the intermediate transfer belt, the resistance is adjusted by appropriately using a conductive material in combination with the composition excluding the charge transport material among the surface layer materials used for the photoreceptor surface layer. be able to.

The transfer means (primary transfer means, secondary transfer means) preferably has at least a transfer device that peels and charges the visible image formed on the photoreceptor 1 to the recording material side. There may be one transfer means, or two or more transfer means. Examples of the transfer device include a corona transfer device using corona discharge, a transfer belt, a transfer roller, a pressure transfer roller, and an adhesive transfer device.
The recording material is not particularly limited and can be appropriately selected from known recording materials (recording paper).

[Fixing means]
The fixing means is a means for fixing the visible image transferred to the recording material, and may be performed each time the toner of each color is transferred to the recording material, or once in a state in which the toner of each color is laminated. May be performed simultaneously.
The fixing unit is not particularly limited and may be appropriately selected depending on the intended purpose. However, a known heating and pressing unit is preferable.
Examples of the heating and pressing means include a combination of a heating roller and a pressure roller, a combination of a heating roller, a pressure roller, and an endless belt.
The heating temperature in the heating and pressurizing means is usually preferably 80 [° C.] to 200 [° C.].
Depending on the purpose, for example, a known optical fixing device may be used together with or instead of the fixing unit.

Next, examples will be described.
However, the present invention is not limited to the examples described below. Note that “parts” used in the examples all represent parts by mass.

[Example 1]
In the photoreceptor 1 used in Example 1, an aluminum cylinder having an outer diameter of 40 [mm] and a wall thickness of 0.8 [mm] was used as a conductive support. On this aluminum cylinder, an undercoat layer coating solution, a charge generation layer coating solution, and a charge transport layer coating solution having the following composition are successively applied by dip coating and drying to obtain 3.5 [μm]. A photosensitive layer having an undercoat layer, a charge generation layer of 0.2 [μm], a charge transport layer of about 30 [μm] at the thinnest portion and about 35 [μm] at the thickest portion 1 was obtained.

[Coating liquid for undercoat layer]
An undercoat layer coating solution having the following composition was dip-coated on an aluminum cylinder, and then heated and dried at 120 [° C.] for 25 minutes to form an undercoat layer of 3.5 [μm].

<Coating liquid composition for undercoat layer>
Alkyd resin 6 parts (Beccosol 1307-60-EL, manufactured by Dainippon Ink & Chemicals, Inc.)
Melamine resin 4 parts (Super Becamine G-821-60, manufactured by Dainippon Ink & Chemicals, Inc.)
Titanium oxide (CR-EL, manufactured by Ishihara Sangyo Co., Ltd.) 40 parts Methyl ethyl ketone 200 parts

[Coating liquid for charge generation layer]
A coating solution for charge generation layer having the following composition was dip-coated on the undercoat layer and then heated and dried at 120 [° C.] for 20 minutes to form a 0.2 [μm] charge generation layer.

<Coating solution composition for charge generation layer>
Oxotitanium phthalocyanine pigment 2 parts Polyvinyl butyral 0.2 part (S-REC BM-S, manufactured by Sekisui Chemical Co., Ltd.)
50 parts of tetrahydrofuran

[Coating liquid for charge transport layer]
A charge transport layer coating solution having the following composition was dip coated on the charge generation layer and then dried by heating at 135 [° C.] for 20 minutes to form a charge transport layer. In the dip coating process, the speed was adjusted so that the amount of adhesion of the coating liquid was increased at the lower end by gradually increasing the pulling speed and gradually increasing it.
<Coating liquid composition for charge transport layer>
10 parts of a charge transport material (D-1) represented by the structural formula shown in Chemical Formula 4 below

Bisphenol Z polycarbonate 10 parts (Panlite TS-2050: manufactured by Teijin Chemicals Ltd.)
0.002 part of silicone oil (KF-50, manufactured by Shin-Etsu Chemical Co., Ltd.)
Tetrahydrofuran 100 parts

  Subsequently, the thickness of the photosensitive layer of the obtained photoreceptor 1 (the total of the undercoat layer, the charge generation layer, and the charge transport layer) was determined using an eddy current film thickness meter (universal film thickness meter LZ-200 (stock) ) Using a LHP-20 (NFe) type probe manufactured by Kett Science Laboratory, 15 points were measured along the photosensitive member rotation axis direction. The measurement results are as shown in FIG. These measurement results were divided into an upper end side and a lower end side with respect to the central part in the axial direction of the photoconductor, and averaged. As a result, the thickness of the photosensitive layer was 30.0 [μm] on the upper end side and 35 on the lower end side. It was 2 [μm].

  The photoreceptor 1 was provided with flanges at both ends. Subsequently, in order to measure the shake amount of the photosensitive member 1 with the flange, the optical fiber displacement meter (rocks) was obtained by preliminarily collecting the relationship between the distance and the voltage while rotating at a constant speed so that the rotation center does not shake. A distance profile from the tip of the measurement probe to the surface of the photoreceptor was collected using ST 3711, probe type 0702R, front slope measurement (manufactured by Tsutsukaku Co., Ltd.). For the profile of the entire circumference of the photoconductor, the difference between the maximum value (position where the probe tip and the surface of the photoconductor 1 are farthest apart) and the minimum value (position where the probe tip and the surface of the photoconductor 1 are closest) is taken. A shake amount of 1 was calculated. The same measurement was performed at intervals of 20 mm in the direction of the rotation axis from the center of the image area of the photoreceptor 1 toward both ends (a total of 15 points, 7 on each of the center and both sides), and the side with the larger shake amount was identified. Thereby, it was confirmed that the runout amount on the side to which the air chuck was applied during dip coating (the upper end side during coating) was large. The shake amount of the photosensitive member 1 was 5.2 [μm] to 17.7 [μm]. The measurement result of this shake amount is shown in FIG.

  This flanged photoreceptor 1 was supported by the printer 100. Next, the photoreceptor 1 was incorporated into an image forming unit for Ricoh's imgio MPC 4500, and the developing gap was adjusted to 280 [μm] to prepare an image forming unit. Here, as the development gap, an average value obtained when the photoreceptor 1 is rotated once is used. The image forming unit was modified using a cyan image forming unit.

Further, this image forming unit was assembled in an Ricoh imagio MPC4500 to produce the printer of Example 1, and image evaluation was performed.
In order to confirm the uniformity of the visible image, the evaluation image is an A4 size print image of 600 [dpi] and 2by2 full tone with a pixel density of 25%, and a full solid image of 600 [dpi] and 100% pixel density. A4 size printed image was obtained. The uniformity of the initial image was confirmed visually, and the uniformity of the dots was observed with a magnifying glass of 25 times to evaluate the rank.

Here, the 2by2 full-surface tone with a pixel density of 25% means that in a square area formed by 4 × 4 pixels, 2 × 2 pixels are defined as a rectangular image area and other than the rectangular image area as a non-image area. This means that an image having a pixel density of 4/16 = 25% is formed by forming an image over the entire surface.
Further, a full image with a pixel density of 100% means that an image is formed on the entire surface.

As a result, it was confirmed that an extremely uniform tone image was formed. The evaluation results are shown in FIG.
As evaluation criteria for image uniformity, each of the following cases was evaluated for visual observation (2 by 2 image, full-color solid image) and enlarged observation (2 by 2 image).
Note that, when magnifying and observing, the maximum value Rmax of the average value at each measurement point of the dot diameters (area reference circle equivalent diameters) measured at the three positions at both ends and the center in the image width direction (developing roller axial direction). A ratio Rr (Rr = Rmin / Rmax) between [μm] and the minimum value Rmin [μm] was taken and evaluated according to the following criteria.

<Evaluation criteria for visual uniformity 2 by 2 image>
A: Excellent (level at which unevenness cannot be detected over the entire surface)
○: Level that does not cause any problem in practical use (a level at which periodic unevenness can be detected slightly when viewed alongside ◎)
Δ: acceptable level for practical use (level at which periodic unevenness can be detected when viewed alongside ◎)
×: Cannot be used (periodic unevenness can be clearly detected by itself)

<Evaluation Criteria for Visual Uniformity Full Image>
A: Excellent (level at which unevenness cannot be detected over the entire surface)
○: Level that does not cause any practical problems (level that can detect slight unevenness when viewed side by side with ◎)
△: Practically acceptable level (level that can detect unevenness when viewed side by side with ◎)
×: Cannot be used (can clearly detect unevenness by itself)

<Evaluation Criteria for Uniformity with Enlarged Image Only 2by2 images>
A: Extremely excellent (dots are very uniform; Rr is 0.9 or more)
○: Level where there is no problem in practical use (there are a few places where there is a difference in dot size for each field of view; Rr is 0.8 or more and less than 0.9)
Δ: Practically acceptable level (there is a place where there is a difference in dot size for each field of view; Rr is 0.6 or more and less than 0.8)
×: Unusable (sizes of dots in a plurality of areas are clearly different; Rr is less than 0.6)

In addition, when the printer of Example 1 was subjected to the A4 size 5% chart 10000 sheet passing test and then evaluated in the same manner as described above, a tone image having extremely high uniformity similar to the initial time point was obtained. It was confirmed that the image was formed.
Note that the A4 version 5% chart means that an A4 version chart composed of text images (character images) so as to have a pixel density of 5% on the entire surface is output.

[Examples 2 to 18, Comparative Examples 1 to 4]
For Examples 2 to 18 and Comparative Examples 1 to 4, coating of the charge transport layer was performed in order to confirm the shake amount of the photoreceptor 1 and the magnitude relationship between the thickness of the photosensitive layer and a more preferable range of the photosensitive layer thickness. Except for adjusting the conditions (dipping and pulling speed conditions and acceleration / deceleration conditions during horizontal movement of the photosensitive member) to obtain the film thickness shown in FIG. 6, it is the same as in Example 1. These were also evaluated in the same way as in Example 1. The evaluation results are also shown in FIG.

<Comparison between Examples 1 to 3 and Example 4>
As in Example 1, when the maximum shake amount of the photoreceptor 1 is less than a certain value by comparing Examples 2 and 3 which are better ranges of the shake amount and Example 4 which is out of this range, It was confirmed to have a more remarkable effect.

<Comparison between Examples 1 and 5-13 and Examples 14-18>
As in Example 1, the upper and lower limits of the photosensitive layer thickness and the difference between Examples 5 to 13 which are better ranges of the photosensitive layer thickness and Examples 14 to 18 which are outside this range are more It was confirmed that there is a preferable range in which an image with high image quality can be stably obtained.

<Comparison between Examples and Comparative Examples>
From the comparison between the example and the comparative example, when the photosensitive layer thickness (the thickness of the charge transport layer) corresponding to the shake amount of the photoconductor 1 having a difference in shake amount was not set, a remarkable image It was confirmed that a defect occurred and the image was unsuitable for quality. This is because the developing bias is set low with reference to the lower end side where the shake amount is small. That is, the developing electric field is always equal to or higher than the saturated developing electric field value A on the lower end side, and the saturated developing is always realized. However, when the developing electric field shows a minimum value on the upper end side where the shake amount is large, This is because the density was lowered and this appeared as image density unevenness.
As described above, if the developing bias is set higher with the upper end side having a large shake amount as a reference, the developing electric field is always equal to or higher than the saturated developing electric field value A even on the upper end side, and it is always possible to realize saturated development. It is possible. However, in this case, power consumption is increased and toner is wasted, which is a more serious problem than image density unevenness.

  From the above, the superiority of the printer according to the embodiment of the present invention over the comparative example is shown in terms of image quality related to image density unevenness, increase in power consumption, and wasteful consumption of toner. In the embodiment of the present invention, there is a deviation in the shake amount of the surface of the photoreceptor 1, and even if the maximum value of the shake amount exceeds the conventional allowable range, the thickness of the charge transport layer is adjusted. Since uniform images without uneven image density can be obtained, the production process can be simplified and the cost can be reduced.

FIG. 7 is a diagram in which the 2-by2 visual image evaluation results of Examples 1 and 6 to 18 and Comparative Examples 1 to 4 are placed in association with the photosensitive layer thickness.
A straight line indicated by a broken line in the drawing connects points where the thickness of the photosensitive layer on the side where the shake amount is large and the side where the shake amount is small is the same. In all the examples, the thickness of the photosensitive layer on the side with a large amount of shake is formed thinner than the side with a small amount of shake, so all the examples are placed above the broken line in the figure. On the other hand, in the comparative examples, the thickness of the photosensitive layer on the side with a large amount of shake is formed to be the same as or thicker than that on the side with a small amount of shake. In addition, in the figure, only Example 1, 6-18 is described for convenience.
In FIG. 7, it can be seen that the examples in which the evaluation result is “◯” or more are concentrated in the range surrounded by the straight line B in the drawing.

[Reference Examples 1-2]
In the photoreceptor 1 of this embodiment, the thickness of the charge transport layer is given a deviation so that the thickness of the photosensitive layer is biased in the axial direction of the photoreceptor. The reference example is for confirming that such a thickness deviation of the photosensitive layer does not affect the image quality.
In this reference example, in order to confirm the influence on the image quality of the left and right difference of the photosensitive layer thickness when there is no deviation in the shake amount of the photosensitive member 1, the photosensitive member 1 with no deviation in the shake amount is used. Except for the set values shown, the printers of Reference Examples 1 and 2 were produced in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. Specifically, in the photoconductors according to Reference Examples 1 and 2, when the layer formation is performed so that the photoconductor layer thickness is the same as that of the photoconductor of Example 1, the photoconductor is placed sideways in a state where only the upper end is held. Each time dip coating is completed without moving in the direction, repeatedly moving to the next process after supporting the upper and lower ends of the photoconductor so that the lateral force on the photoconductor holder is not applied as much as possible. In addition, the coating and drying processes were repeated. The evaluation results are shown in FIG.

From the results of Reference Example 1, it was shown that even when there is no deviation in the shake amount of the photoreceptor, saturation development can be realized with the same low developing bias as in Example 1 and image density unevenness is not caused.
Further, from the result of Reference Example 2, when the development gap was adjusted to be wide to prevent saturation development, the image density was slightly low on the side where the photosensitive layer was thick, and the image quality was lowered.
Note that the yield of the photoreceptor 1 having no deviation in the shake amount was 50% or less even when produced under exactly the same conditions.

As described above, the printer according to the present embodiment includes the photosensitive layer including the charge generation layer and the charge transport layer positioned on the surface side of the charge generation layer on the cylindrical conductive support, and is rotatable about the rotation axis. As electrostatic latent image forming means for generating a charge in the charge generation layer in the photosensitive layer of the photosensitive member 1 by exposing the photosensitive member 1 and the surface of the photosensitive member 1, and forming the exposed portion as an electrostatic latent image. The charging device 3 and the exposure device 30 of this embodiment and the developing roller 50 as a developer carrying member carrying the developer on the surface thereof are opposed to the surface of the photosensitive member via the developing gap 11 and opposed to each other via the developing gap 11. The developer on the developing roller is caused to adhere to the electrostatic latent image on the surface of the photosensitive member by a developing electric field formed between the electrostatic latent image portion (exposed portion) on the surface of the photosensitive member and the surface portion of the developing roller. Developing device as developing means for developing an electrostatic latent image And forming an image on the recording material by finally transferring the visible image (toner image) on the surface of the photoreceptor obtained by developing the electrostatic latent image onto the recording material. Device. The photosensitive member 1 has a maximum deviation of the developing electric field between a portion where the shake amount of the surface of the photosensitive member when the photosensitive member 1 is rotated around the rotational axis is relatively large and small in the direction of the photosensitive member rotational axis. The thickness of the charge transport layer in the photosensitive layer is different so as to decrease.
More specifically, the electrostatic latent image forming unit uniformly charges the surface of the photoreceptor 1 to a predetermined charging potential by the charging device 3 and then exposes the exposure device 30 to attenuate the charging potential of the exposed portion. As a result, the exposed portion is made into an electrostatic latent image, and the photosensitive member 1 has a thinner charge transport layer than a charge transport layer with a relatively small shake amount.
In particular, in the present embodiment, the layer is formed while repeatedly moving and stopping while holding one end of the photoreceptor in the manufacturing process, and thus the roundness on the end is poor. Therefore, the photoconductor 1 has a deflection amount that increases from one end side in the rotation axis direction to the other end side (upper end side during coating). Therefore, in the photoreceptor 1 of the present embodiment, the thickness of the charge transport layer decreases from one end side in the rotation axis direction to the other end side (upper end side during coating).

  In this embodiment, the charge transport layer in the portion where the shake amount of the photoconductor 1 is large is thinned, so that the exposed portion potential (electrostatic latent image) of the photoconductor 1 is compared with the portion where the shake amount of the photoconductor 1 is small. Potential) is close to 0V. Therefore, the potential difference between the constant surface potential of the developing roller to which a constant developing bias is applied and the exposed portion potential of the photoreceptor 1 is widened, and the developing electric field becomes strong. As a result, a sufficiently large developing electric field can be obtained even in a portion where the developing gap 11 is maximized due to the shake of the photosensitive member 1, and saturation development can be realized. As a result, the image density is not lowered at the portion where the development gap 11 is maximized due to the shake of the photosensitive member 1, so that there is no difference in image density from other portions, and image density unevenness occurs. It will be resolved.

Hereinafter, the relationship between the variation in the development gap and the image density unevenness caused by the uneven development will be described with reference to the graphs shown in FIGS.
In the following description, it is assumed that the development gap periodically fluctuates greatly as in the end-side development gap where the shake amount of the photoconductor of the present embodiment is large. It is assumed that Further, it is assumed that development is performed by applying a DC developing bias to the developing roller, and the potential of the electrostatic latent image (exposure portion potential) and the developing roller surface potential (developing bias potential) due to the developing bias do not vary.

  When the development gap periodically changes as shown in FIG. 9, the distance between the electrostatic latent image on the surface of the photosensitive member and the surface of the developing roller changes, so that the electrostatic latent image on the surface of the photosensitive member and the surface of the developer carrying member are changed. The developing electric field formed therebetween periodically varies as shown in FIG. At this time, when the thickness of the photosensitive layer (that is, the thickness of the charge transport layer) is relatively thick like the thickness of the photosensitive layer on the side of the end portion where the shake amount in the photosensitive member of the present embodiment is small, As shown in FIG. 10, when the development gap is widened and the development electric field is lowered, a situation where the saturation development electric field value A shown in FIG. If the saturation development electric field value A is less than the saturation development electric field value A, the saturated development cannot be realized. Therefore, as shown in FIG. As a result, as shown in FIG. 12, when the saturation development cannot be realized below the saturation development electric field value A, the image density (optical density) is compared with that when the saturation development can be realized at the saturation development electric field value A or more. Decreases, resulting in uneven image density.

  In the present embodiment, the thickness of the charge transport layer on the upper end side (the end side where the shake amount is large) of the photoconductor that causes such image density unevenness is reduced to reduce the thickness of the photosensitive layer (charge). The thickness of the generation layer is constant). As the thickness of the charge transport layer in the photosensitive layer decreases, the electrostatic capacity of the photosensitive body (capacitance between the conductive support and the surface of the photosensitive body) increases. When the exposure amount to the photoconductor is the same, the charge amount generated in the charge generation layer by the exposure is the same, but the surface potential of the photoconductor in the exposed portion (that is, the potential of the electrostatic latent image) is , And varies depending on the electrostatic capacity of the photosensitive member in the exposed portion. Therefore, by reducing the thickness of the charge transport layer of the photoreceptor, the absolute value of the potential of the electrostatic latent image can be reduced, that is, the potential of the electrostatic latent image can be made closer to zero. Thereby, even if the developing bias is constant, the potential difference between the potential of the electrostatic latent image and the surface potential of the developer carrier is widened, and the developing electric field can be increased. As a result, by reducing the thickness of the photosensitive layer in this way, the developing electric field becomes larger as shown in FIG. 13, and even when the developing gap becomes wider and the developing electric field becomes lower, the saturated developing electric field value A is set. The situation below does not occur. Therefore, saturation development can always be realized, the development amount is maintained constant as shown in FIG. 14, the image density (optical density) is also constant as shown in FIG. 15, and image density unevenness does not occur.

Further, in this embodiment, even when the range of the shake amount of the photoconductor is a wide range of 5 [μm] or more and 30 [μm] or less, the image density unevenness can be sufficiently suppressed as described above. Easy.
In this embodiment, the photosensitive member 1 has the following formulas (1) to (1) when the maximum value of the photosensitive layer thickness is Dmax [μm] and the minimum thickness of the photosensitive layer is Dmin [μm]. It is desirable to satisfy all of 3) as shown in FIG. By satisfying this condition, a high-quality image without image density unevenness can be formed.
3 [μm] ≦ Dmax−Dmin ≦ 10 [μm] (1)
20 [μm] ≦ Dmin (2)
Dmax ≦ 50 [μm] (3)

  Further, the exposure apparatus 30 in the present embodiment employs an area gradation method that adjusts the area occupied by the electrostatic latent image per unit area in order to express the density of the image. As a result, even if the development is performed so that the saturation development is always performed, it is possible to form an image that appropriately expresses the multi-tone density. In other words, as a technique for expressing the density of an image in multiple stages, there are a density gradation method in which the potential of an electrostatic latent image (exposure portion potential) is adjusted in multiple stages according to the density of an image, and a technique according to the density of an image. There is an area gradation method for adjusting the area occupied by the electrostatic latent image per unit area. In the case of the density gradation method, the amount of toner attached to the electrostatic latent image is adjusted according to the potential of the electrostatic latent image, so the relationship between the potential of the electrostatic latent image and the amount of toner attached (development amount) changes. As a result, the shading of the image cannot be expressed properly. For this reason, when development unevenness occurs in which the toner adhesion amount differs with respect to the electrostatic latent image having the same potential, the effect directly appears in the difference in the density of the image, and is directly connected to the image density unevenness. On the other hand, in the case of the area gradation method, since the potential of the electrostatic latent image is usually constant regardless of the density of the image, development unevenness occurs if saturation development can always be maintained for the electrostatic latent image. Therefore, image density unevenness can be sufficiently suppressed.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Protection material coating device 3 Charging device 4 Cleaning device 5 Developing device 6 Transfer device 10 Conductive support 11 Development gap 12 Photosensitive layer 14 Rotating shaft 30 Exposure device 50 Developing roller 60 Intermediate transfer belt 100 Printer 200 Paper feed mechanism

JP-A-9-211975 JP 2000-194191 A

Claims (9)

A photosensitive layer comprising a charge generating layer and a charge transport layer located on the surface side of the charge generating layer on a cylindrical conductive support, and a photosensitive member rotatable about a rotation axis;
The surface of the photoconductor is uniformly charged to a predetermined charging potential by a charging means and then exposed, whereby charges are generated in the charge generation layer in the photosensitive layer of the photoconductor to thereby increase the charging potential of the exposed portion. An electrostatic latent image forming unit that attenuates and forms the exposed portion as an electrostatic latent image;
A developer carrying member carrying a developer on the surface is opposed to the surface of the photoreceptor through a development gap, and an electrostatic latent image portion on the surface of the photoreceptor facing the development gap and the developer carrying member. Development means for developing the electrostatic latent image by causing the developer on the developer carrying member to adhere to the electrostatic latent image on the surface of the photosensitive member by a developing electric field formed between the surface and the surface portion. And
In the image forming apparatus for forming an image on the recording material by finally transferring the visible image on the surface of the photoreceptor obtained by developing the electrostatic latent image onto the recording material,
When the thickness of the charge transport layer in the photoconductor is rotated about the rotation axis, the portion where the shake amount of the surface of the photoconductor is relatively small in the direction of the photoconductor rotation axis is thinner than the portion. An image forming apparatus characterized by being configured as described above. The image forming apparatus according to claim 1.
In the photoconductor, the shake amount is larger on the other end side than one end side in the rotation axis direction, and the thickness of the charge transport layer is thinner on the other end side than one end side in the rotation axis direction. An image forming apparatus. The image forming apparatus according to claim 1 or 2,
The image forming apparatus is characterized in that a range of a shake amount of the photosensitive member is 5 [μm] or more and 30 [μm] or less. The image forming apparatus according to claim 3.
In the photoreceptor, when the maximum value of the thickness of the photosensitive layer is Dmax [μm] and the minimum value of the thickness of the photosensitive layer is Dmin [μm], all of the following formulas (1) to (3) are satisfied. An image forming apparatus characterized by satisfying the requirements.
3 [μm] ≦ Dmax−Dmin ≦ 10 [μm] (1)
20 [μm] ≦ Dmin (2)
Dmax ≦ 50 [μm] (3) The image forming apparatus according to any one of claims 1 to 4, wherein:
The electrostatic latent image forming means employs an area gradation method for adjusting the area occupied by the electrostatic latent image per unit area in order to express the density of the image. . The image forming apparatus according to any one of claims 1 to 5,
The electrostatic latent image forming means exposes the surface of the photoreceptor uniformly after charging it to a predetermined charging potential by a charging means, and attenuates the charging potential of the exposed portion, thereby electrostatically exposing the exposed portion. A latent image,
An image forming apparatus according to claim 1, wherein the charging means is a device in which a charging roller, to which a predetermined charging bias is applied, is brought into contact with or in proximity to the surface of the photoconductor. The image forming apparatus according to any one of claims 1 to 6,
An image forming apparatus comprising: a cleaning unit that removes unnecessary deposits on the surface of the photosensitive member with a cleaning brush. The image forming apparatus according to any one of claims 1 to 7,
An image forming apparatus comprising: a protective material supplying unit that supplies a protective material for protecting the surface of the photoconductor to the surface of the photoconductor. A method for producing a photoreceptor, comprising: a photosensitive layer comprising a charge generation layer and a charge transport layer positioned on the surface side of the charge generation layer on a cylindrical conductive support, wherein the photoreceptor is rotatable about a rotation axis. In
A charge generation layer forming step of forming the charge generation layer on the conductive support;
A charge transport layer forming step of forming the charge transport layer on the charge generation layer by a dipping method,
In the charge transport layer forming step, the shake amount of the surface of the photoconductor when rotated about the rotation axis is thinner in the larger portion than the relatively small portion in the photoconductor rotation axis direction. A method for producing a photoreceptor, wherein the charge transport layer is formed.

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