JP2005345647A - Method for forming image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming an image by which toner remaining on the photoreceptor surface after a transfer step can be efficiently removed by using a cleaning blade even when a toner containing spherical and small particulate color resin particles is used, and an image with high definition and high picture quality can be formed under various environments. <P>SOLUTION: The method for forming an image includes a charging step 1, an exposure step 2, a developing step 3 using a developing roll, a transfer step 4, a fixing step 5 and a cleaning step 6 to remove the toner remaining on the photoreceptor surface after the transfer step by using a cleaning blade. The method is characterized in that: the developing roll has 30 to 220 surface brightness and 1 to 20 μm surface roughness Rz; the toner contains an external additive and color resin particles having 4 to 10 μm volume average particle diameter and 0.950 to 0.995 average circularity; and the absolute charge amount of the toner on the photoreceptor surface is 10 to 80 μC/g. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming method using an electrophotographic method, and more specifically, even when toner containing spherical and small colored resin particles and an external additive is used, the toner remains on the surface of the photoreceptor after transfer. The present invention relates to an image forming method capable of forming a high-quality image stably in various environments with excellent toner cleaning properties. The image forming method of the present invention is particularly suitable for a color image forming method using a color toner.

  In the present invention, the toner means a developer containing colored resin particles and an external additive. However, with respect to the colored resin particles that are the main component of the toner, those obtained by the pulverization method may be referred to as “pulverized toner”, and those obtained by the polymerization method may be referred to as “polymerized toner”.

  In an image forming method employing an electrophotographic method, generally, a charging step 1 for uniformly and uniformly charging the surface of a photoconductor (also referred to as an “image carrier”); image exposure (optical writing) on the charged photoconductor surface ) To form an electrostatic latent image 2; developing the electrostatic latent image on the surface of the photoreceptor with toner to form a toner image (visible image) 3; toner on the surface of the photoreceptor A transfer step 4 for transferring the image onto the transfer material; a fixing step 5 for fixing the toner image transferred onto the transfer material by heat or pressure; and a cleaning step 6 for removing the toner remaining on the surface of the photoreceptor after the transfer step. An image is formed. In order to prevent the occurrence of an afterimage, a charge eliminating process on the surface of the photoconductor may be arranged between the cleaning process and the exposure process.

  The photoreceptor has a photoconductive layer provided on a conductive substrate. In general, a function-separated type photosensitive drum in which a charge generation layer and a charge transfer layer are arranged in this order as a photosensitive layer on a cylindrical aluminum base material (conductive drum base material) as a photosensitive member is widely used. Yes. As the photoreceptor, various organic photoreceptors such as a single layer type and a reverse lamination type are known in addition to the function separation type. Also, the shape of the photoreceptor is not only a drum shape but also an endless belt shape.

  In the development process, a method is known in which a developing roll is disposed opposite to the surface of the photoreceptor, and a toner image is formed by contacting and developing the electrostatic latent image on the surface of the photoreceptor with toner supplied onto the development roll. Yes. More specifically, in the developing device, the toner is supplied onto the developing roll by the supply roll, the toner on the developing roll is formed into a thin layer by the layer thickness regulating member, and the surface of the photoreceptor on which the electrostatic latent image is formed In addition, the toner on the developing roll is contact-developed to form a toner image. As the toner, a developer containing colored resin particles and an external additive is used.

  A cleaning method using a cleaning blade is known as a cleaning method for removing toner remaining on the surface of the photoreceptor after the toner image on the surface of the photoreceptor is transferred onto a transfer material. However, as described in detail below, it has been found that toner containing colored resin particles having a spherical shape and a small particle size is inferior in cleaning properties when a cleaning method using a cleaning blade is applied.

  Electrophotographic image forming apparatuses such as electrophotographic copying machines and laser beam printers are required to form high-resolution images at high speed. In particular, with the advancement of high functionality and colorization in recent years, the required level for the formation of high-definition full-color images is increasing. In addition, with the worldwide spread of electrophotographic image forming apparatuses, image forming apparatuses are used not only under normal temperature and normal humidity environments but also under a wide range of environmental conditions from high temperature and high humidity to low temperature and low humidity. ing. Therefore, there is an increasing demand for an image forming method capable of forming a high-quality image corresponding to such a wide range of environmental conditions.

  In order to meet the above requirements, various improvements have been made mainly from both the image forming apparatus and the toner. In order to meet the demand for higher resolution, the colored resin particles constituting the toner have been reduced in size and sharpened in the particle size distribution. That is, the colored resin particles desirably have a small particle size and a sharp particle size distribution in order to form a high-definition and high-quality image. On the other hand, from the viewpoint of toner characteristics such as printing density, resolution, fogging, and cleaning properties, it is not preferable that a large amount of fine particles considerably smaller than a predetermined average particle diameter exist.

  The colored resin particles constituting the toner are roughly classified into a pulverized toner obtained by a pulverization method and a polymerized toner obtained by a polymerization method. In the pulverization method, a thermoplastic resin is melt-kneaded with additive components such as a colorant, a charge control agent, and a release agent, pulverized, and classified to obtain pulverized toner as colored resin particles. The pulverized toner has an irregular particle shape and a broad particle size distribution. The pulverized toner generates a large amount of fine powder by pulverization. Since the pulverized toner uses a thermoplastic resin having a property of being easily pulverized as a binder resin, the generation amount of excessively pulverized fine particles increases when the particle size is reduced. Further, in order to sharpen the particle size distribution of the pulverized toner, classification operation is required. In addition to the complicated operation, the amount of coarse particles and fine particles removed by classification is large, and the yield is high. bad.

  In contrast, a polymerization method such as a suspension polymerization method can provide colored resin particles (also referred to as “colored polymer particles”) having a desired average particle size and a sharp particle size distribution. it can. For example, in the suspension polymerization method, a polymerizable monomer composition containing a polymerizable monomer and various additive components such as a colorant and a charge control agent is dispersed in fine droplets in an aqueous dispersion medium. Then, a polymerized toner is obtained as colored polymer particles by a polymerization method.

  According to the polymerization method, colored polymer particles having a spherical shape and a sharp particle size distribution can be produced. Further, according to the polymerization method, after the polymerization, the polymerizable monomer for shell is further polymerized in the presence of the generated colored polymer particles, and the colored polymer particles having a core-shell structure (“core-shell type” Colored polymer particles ”). While lowering the glass transition temperature of the polymer component constituting the core particle and increasing the glass transition temperature of the polymer constituting the shell, a polymer toner having excellent storage stability (blocking resistance) and low-temperature fixability can be obtained. Can be manufactured.

  According to the polymerization method, colored polymer particles having a volume average particle diameter of 10 μm or less, preferably 4 to 10 μm, and a small particle diameter can be easily produced. Even when it is necessary to classify the polymerized toner in order to further sharpen the particle size distribution, it is not necessary to remove a large amount of fine powder as compared with the pulverized toner. Therefore, the polymerized toner can form a high-definition image and is suitable for speeding up printing and full color.

  As described above, the polymer toner having a small particle diameter plays an extremely important role in forming a high-resolution and high-definition image. However, various problems have arisen as the particle size of the polymerized toner is reduced. One such problem is inferior cleaning properties.

  It has been found that toner containing spherical colored resin particles having a small particle diameter is difficult to clean the toner remaining on the surface of the photoreceptor after the transfer process, and the image quality tends to deteriorate due to the residual toner. As a method for cleaning residual toner on the surface of the photoreceptor, a method is known in which an elastomer cleaning blade having elasticity is brought into contact with the surface of the photoreceptor to remove the residual toner. However, spherical colored resin particles having a small particle size (hereinafter sometimes abbreviated as “spherical and small particle size toner”) have a large adhesive force on the surface of the photosensitive member and are likely to slip through the cleaning blade. .

  In image formation using color toner, if the first color toner remains on the surface of the photoconductor after the transfer process, color mixing with the second and subsequent color toners will occur, so image formation with a single color using black toner will occur. More than the case, a cleaning process for removing the residual toner is important. However, in color toners, the chargeability of organic pigments used as colorants is generally higher than that of carbon black, so that the adsorptive power to the surface of the photoreceptor is increased.

  As a method for improving the cleaning property of the residual toner, there is a method of reducing the charge amount of the toner on the surface of the photoreceptor, but this method further increases the chargeability of the toner when used for a long time in a high temperature and high humidity environment. Therefore, it is easy to cause fogging and image density.

  2. Description of the Related Art Conventionally, there has been proposed a cleanerless type image forming method (also referred to as “development simultaneous cleaning method”) that performs cleaning at the same time as development without using a cleaning blade and a developer used in the image method (for example, Patent Documents 1-2). In the cleanerless system, the developing unit that develops the electrostatic latent image on the surface of the photoconductor to form a toner image also serves as a cleaning unit that collects residual toner on the surface of the photoconductor. However, when the cleanerless method is employed for forming a full-color image using color toner, color mixing between each color is likely to occur.

  For example, Patent Document 2 discloses a color image forming apparatus in which a plurality of cleanerless image forming units are arranged along a conveying belt. In a color image forming apparatus having such a configuration, color mixing due to retransfer tends to occur. The reason for this is that during the transfer of the second and subsequent toner images, the other color toner already transferred onto the transfer material is caused by the adhesive force between the toner and the photosensitive drum, or the polarity reversal of the toner by the transfer charger. Because of the repulsive force between the transfer material and the transfer material, the toner adheres to the surface of the photosensitive drum from the transfer material, and the toner attached to the surface of the photosensitive drum is collected in the developing device of other colors during the simultaneous development cleaning. is there.

In the image forming method corresponding to colorization, a method of cleaning and removing residual toner on the surface of the photoreceptor for each color is preferable. Therefore, a cleaning method using a cleaning blade has been reviewed. For example, an image forming method using a toner having a boron or phosphorus content of 0.1 to 100 ppm has been proposed in an image forming method having a cleaning step of removing residual toner with a cleaning blade (for example, Patent Document 3). There has been proposed a method of using a cleaning blade in which fine particles are adhered at an amount of 1 to 10 mg / cm ² per unit area on the surface of at least a portion of the cleaning blade that is in contact with the image carrier (photoconductor) (for example, Patent Document 4).

  However, the above method is not yet sufficient in terms of reducing the adhesion between the spherical and small particle size toner and the photoreceptor surface, and in particular, the cleaning performance is insufficient in a low temperature and low humidity environment. When an image is formed over a long period of time in an environment, the charge amount of the toner is reduced, and the image density is likely to be lowered or fogged.

  On the other hand, polyurethane elastomer cleaning blades have been proposed as cleaning blades for small particle size toners (for example, Patent Documents 5 to 6). However, simply using a cleaning blade made of polyurethane elastomer is insufficient for cleaning spherical and small toner particles in a low temperature and low humidity environment.

  When forming a color image using a latent image carrier (photoreceptor) composed of an organic photoreceptor containing a fluororesin powder, a flow improver and a weight average particle diameter as an external additive are added to the colored resin particles. A method using a color developer containing spherical fine particles of 0.2 to 2.5 μm has been proposed (for example, Patent Document 7). However, when a fluororesin powder is contained in the organic photoreceptor, the coefficient of friction of the photoreceptor tends to be too low, so that developability is reduced and it is difficult to obtain a high print density. .

Japanese Patent Laid-Open No. 5-188737 Japanese Patent Laid-Open No. Hei 8-146652 JP 2002-31634 A JP 2003-280474 A JP 2001-255801 A JP 2003-12752 A Japanese Patent No. 3114020

  An object of the present invention is to efficiently remove toner remaining on the surface of a photoreceptor after a transfer process using a cleaning blade even when toner containing spherical resin particles having a small particle diameter is used. Another object of the present invention is to provide an image forming method capable of forming a high-definition and high-quality image not only in an environment of normal temperature and humidity but also in an environment of low temperature and low humidity and high temperature and high humidity.

  As a result of intensive studies to solve the above problems, the present inventors have found that an image forming method having a charging process, an exposure process, a development process, a transfer process, a fixing process, and a cleaning process by an electrophotographic method on a developing roll. A developing method in which an electrostatic latent image on the surface of the photoreceptor is contact-developed with the supplied toner to form a toner image, and the surface property of the developing roll is controlled at that time, and a cleaning method using a cleaning blade Can effectively clean residual toner containing colored resin particles that are spherical and have a small particle size, and with high definition and high image quality such as print density and durability under various environments. It has been found that an image of an image quality can be formed.

  Specifically, it has been found that the above-mentioned problem can be achieved by using a developing roll having a surface brightness adjusted within a range of 30 to 220 and a surface roughness Rz adjusted within a range of 1 to 20 μm. It was. Conventionally, in order to improve the cleaning property, attention has been paid mainly to the change of the cleaning method and the improvement of the cleaning blade. By modifying the surface of the developing roll, the cleaning property is remarkably improved and high The ability to form a fine and high-quality image has not been easily conceived even by those skilled in the art.

  On the other hand, even when a developing roll with modified surface characteristics is used, if the absolute value of the charge amount on the photoreceptor surface of a spherical and small-diameter toner is excessively increased, the cleaning property is reduced and the print density is reduced. Was also found to decline. Even if the absolute value of the charge amount of the toner on the surface of the photoreceptor is too small, fog is likely to occur. Therefore, by using the developing roll and further controlling the absolute value of the charge amount of the spherical and small-diameter toner on the surface of the photoreceptor within a specific range, the cleaning property and the image quality characteristic are highly balanced. be able to. The present invention has been completed based on these findings.

Thus, according to the present invention, the following steps 1-6:
(1) Charging step 1 for charging the surface of the photoreceptor;
(2) an exposure step 2 in which an electrostatic latent image is formed by performing image exposure on the surface of the charged photoreceptor;
(3) A developing step 3 in which the electrostatic latent image on the surface of the photoreceptor is contact-developed with toner supplied on the developing roll to form a toner image;
(4) Transfer process 4 for transferring the toner image on the surface of the photoreceptor onto a transfer material;
(5) a fixing step 5 for fixing the toner image transferred onto the transfer material; and (6) a cleaning step 6 for removing toner remaining on the surface of the photoconductor with a cleaning blade in contact with the surface of the photoconductor.
In an image forming method including:
(I) The developing roll has a surface brightness of 30 to 220 and a surface roughness Rz of 1 to 20 μm,
(II) The toner contains colored resin particles having a volume average particle diameter of 4 to 10 μm and an average circularity of 0.950 to 0.995 and an external additive, and
(III) An image forming method is provided wherein the absolute value of the charge amount of the toner on the surface of the photoreceptor is 10 to 80 μC / g.

  According to the present invention, in an electrophotographic image forming method, even when a spherical and small-diameter toner is used in order to form a high-definition and high-definition image, transfer is performed using a cleaning blade. The toner remaining on the surface of the photoreceptor after the process can be efficiently removed, and a high-definition and high-quality image can be formed not only in a normal temperature and normal humidity environment but also in a low temperature and low humidity and high temperature and high humidity environment. An image forming method is provided.

  According to the image forming method of the present invention, the absolute value of the charge amount of the toner on the surface of the photosensitive member is controlled at the same time by modifying the surface characteristics of the developing roll even when the toner is spherical and has a small particle diameter. Thus, cleaning can be performed effectively, and a high-definition and high-quality image can be formed.

  In the image forming method of the present invention, (1) a charging step 1 for uniformly and uniformly charging the surface of the photoreceptor; (2) an electrostatic latent image is formed by performing image exposure on the charged photoreceptor surface. Exposure process 2; (3) Development process 3 in which the electrostatic latent image on the surface of the photoconductor is contact-developed with toner supplied on the developing roll to form a toner image; (4) Transfer of the toner image on the surface of the photoconductor Transfer step 4 for transferring onto the material; (5) Fixing step 5 for fixing the toner image transferred onto the transfer material; and (6) Toner remaining on the surface of the photoconductor after the transfer step is brought into contact with the surface of the photoconductor. A cleaning step 6 to be removed by a cleaning blade. In addition to these steps, other steps such as a static elimination step may be additionally arranged.

  The image forming method employed in the present invention will be described with reference to FIG. FIG. 1 is an explanatory diagram showing an example of an image forming apparatus to which the image forming method employed in the present invention can be applied. As shown in FIG. 1, a photosensitive drum 1 as a photosensitive member is mounted in the image forming apparatus so as to be rotatable in the direction of arrow A. The photoreceptor is obtained by forming a photoconductive layer on a conductive substrate. The photosensitive drum 1 is obtained by providing a photoconductive layer on a conductive drum base material. The photoconductive layer is composed of, for example, an organic photoreceptor, a selenium photoreceptor, a zinc oxide photoreceptor, an amorphous silicon photoreceptor, or the like. Among these, organic photoconductor (OPC) is a typical one.

  Examples of the resin that binds the photoconductive layer to a conductive substrate such as a conductive drum substrate include polyester resin, acrylic resin, polycarbonate resin, phenol resin, and epoxy resin.

  Around the photosensitive drum 1, a charging roll 2 as a charging member, a laser beam irradiation device 3 as an exposure device, a developing device 9, a transfer roll 10, and a cleaning blade 12 are arranged along the circumferential direction. The charging step is a step of uniformly charging the surface of the photosensitive drum 1 positively or negatively by the charging member. In addition to the charging roll 2 shown in FIG. 1, there are a charging method using a charging member, a contact charging method for charging with a fur brush, a magnetic brush, a blade or the like, and a non-contact charging method using corona discharge. It is also possible to replace 2 with these.

  In the exposure process, the surface of the photosensitive drum 1 is irradiated with light corresponding to an image signal by a laser beam irradiation device 3 as shown in FIG. This is a step of forming an electrostatic latent image. The laser beam irradiation device 3 includes, for example, a laser irradiation device and an optical system lens. In addition to the laser beam irradiation apparatus, there is an LED irradiation apparatus as an exposure apparatus, for example.

  The development process is a process in which toner (developer) is attached to the electrostatic latent image formed on the surface of the photosensitive drum 1 by the exposure process by the developing device 9. In the reverse development, a bias voltage is applied between the developing roll 4 and the photosensitive drum 1 so that the toner is attached only to the light irradiation portion, and in the normal development, the toner is attached only to the light non-irradiation portion. .

  A developing device 9 shown in FIG. 1 is a developing device used in a one-component contact developing method using a one-component developer (toner). A developing roll 4 and a supply roll 6 are arranged in a casing 7 that contains toner 8. The developing roll 4 is arranged so as to be opposed to the photosensitive drum 1 and partially in contact with the photosensitive drum 1, and rotates in the direction B opposite to the photosensitive drum 1. The supply roll 6 comes into contact with the development roll 4 and rotates in the same direction C as the development roll 4, and supplies the toner 8 to the outer periphery of the development roll 4. Other development methods include a one-component non-contact development method, a two-component contact development method, and a two-component non-contact development method.

  A developing roll blade 5 as a toner layer thickness regulating member is disposed around the developing roll 4 at a position between the contact point with the supply roll 6 and the contact point with the photosensitive drum 1. The blade 5 is made of, for example, a conductive rubber elastic body or metal.

  The transfer process is a process of transferring the toner image on the surface of the photosensitive drum 1 formed in the developing process onto a transfer material 11 such as paper. In the transfer step, transfer is usually performed using a transfer roll 10 as shown in FIG. 1, but there are also belt transfer and corona transfer. The cleaning process is a process for cleaning the toner remaining on the surface of the photosensitive drum 1 after the transfer process. In the cleaning process, a cleaning blade 12 as shown in FIG. 1 is generally used. Also in the present invention, cleaning is performed using the cleaning blade 12. After the transfer process, the transfer material 11 having the toner image is transferred to the fixing process. In the fixing step, for example, the transfer material is passed between the fixing roll 13 and the pressure roll 14 and heated and pressed to fix the toner image on the transfer material.

  In the image forming apparatus shown in FIG. 1, the surface of the photosensitive drum 1 is uniformly charged negatively by the charging roll 2, and then an electrostatic latent image is formed by the laser light irradiation device 3. The toner image is formed by development by the apparatus 9. The toner image on the photosensitive drum 1 is transferred onto a transfer material such as paper by the transfer roll 10, and the toner (transfer residual toner) remaining on the surface of the photosensitive drum 1 is cleaned by the cleaning blade 12. . After the cleaning process, the next image forming cycle starts.

  FIG. 2 shows an enlarged schematic diagram of the photosensitive drum 1 and the cleaning blade 12. As shown in FIG. 2, the cleaning blade 12 used in the image forming apparatus shown in FIG. 1 is in contact with the surface of the photosensitive drum 1 from the direction opposite to the rotation direction (that is, in the counter direction), and has a predetermined penetration amount d. Thus, the contact is made at a predetermined set angle θ. Here, the penetration amount d is the penetration amount in the direction perpendicular to the cleaning blade axis when it is assumed that the tip of the cleaning blade 12 has not been deformed and has entered the photosensitive drum 1 as it is. The setting angle θ of the cleaning blade is an angle formed by the tangent line at the point where the front end surface of the cleaning blade 12 and the photosensitive drum 1 intersect with the axis of the cleaning blade 12.

   Said penetration | invasion amount d is 0.7-1.5 mm normally, Preferably it is 0.9-1.5 mm. When the intrusion amount d is within this range, the cleaning blade 12 is prevented from rolling due to the rotation of the photosensitive drum, and the cleaning performance is improved. Said setting angle (theta) is 10-30 degrees normally, Preferably it is 15-30 degrees. When the set angle θ is within this range, the cleaning blade is prevented from rolling and the cleaning property is improved.

  The thickness of the tip of the cleaning blade 12 is usually 1 to 2.5 mm, preferably 1.2 to 2.3 mm, more preferably 1.4 to 2.1 mm. When the thickness of the tip of the cleaning blade is within this range, the wear on the surface of the photosensitive drum and the phenomenon of the cleaning blade being curled are suppressed. The hardness of the cleaning blade is Shore A, and is usually 60 to 90, preferably 65 to 80. When the hardness of the cleaning blade is in this range, the abrasion of the photosensitive drum surface and the phenomenon of the cleaning blade being curled are suppressed.

  The cleaning blade is made of, for example, a rubber elastic body such as polyurethane or acrylonitrile-butadiene copolymer. The rebound resilience of the cleaning blade is preferably 30 to 70%, more preferably 40 to 70%. When the rebound resilience of the cleaning blade is within this range, the cleaning property when used for a long time is improved. The measurement of the resilience elastic modulus of the cleaning blade can be performed, for example, by the Rüpke method (specified in JIS K6255). The rebound resilience of the cleaning blade can be adjusted, for example, by selecting vulcanization conditions such as the amount of vulcanizing agent contained in the rubber elastic body (elastomer).

   The image forming apparatus shown in FIG. 1 is for monochrome use, but the image forming method of the present invention can also be applied to a color image forming apparatus such as a copying machine or a printer that forms a color image. As a color image forming apparatus, a multi-development system in which a multi-color toner image is developed on a photoconductor and transferred onto a transfer material at once; after developing only a monochromatic toner image on the photoconductor, the transfer material There is a multiple transfer method in which the transfer process is repeated for the number of colors of the color toner. In the multiple transfer method, a transfer drum method in which a transfer material is wound around a transfer drum and transferred for each color; primary transfer is performed for each color on an intermediate transfer member, and a multicolor image is formed on the intermediate transfer member. Intermediate transfer system that performs secondary transfer in a batch; tandem system that arranges the photoconductors for each color in tandem, adsorbs and conveys the transfer material by a transfer conveyance belt, and sequentially transfers each color to the transfer material There is. Among these transfer systems, the tandem system is preferable because the image forming speed can be increased.

  The first feature of the image forming method of the present invention is that, in the electrophotographic image forming method as described above, the developing roll has a surface brightness of 30 to 220 and a surface roughness Rz of 1 to 20 μm. The point is to use the one adjusted to the range.

  Below, the manufacturing method of a developing roll is demonstrated. As shown in FIG. 3, the developing roll includes a columnar conductive shaft body 41 and a cylindrical elastic layer 42 covering the surface of the conductive shaft body 41. The surface brightness value of the developing roll is set in the range of 30 to 220, and the surface roughness Rz of the developing roll is set in the range of 1 to 20 μm.

  The material of the conductive shaft 41 is not limited, but a metal core made of iron, aluminum, SUS (stainless steel), or brass; a metal film on the surface of a thermoplastic resin or thermosetting resin core A shaft body in which a metal film is deposited on the surface of a thermoplastic resin or thermosetting resin core; carbon black or metal powder as a conductivity-imparting agent in the thermoplastic resin or thermosetting resin Etc. and a core; etc. are used.

  The elastic layer 42 is made of silicone rubber, ethylene-propylene-diene rubber, polyurethane, chloroprene rubber, natural rubber, butyl rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber, nitrile rubber, ethylene-propylene rubber, acrylic rubber, and these It is composed of rubber (elastomer) such as a mixture.

  These rubbers include fillers such as fumed silica, precipitated silica and reinforcing carbon black; conductive carbon black; metal powders such as nickel, aluminum and copper; metal oxides such as zinc oxide and tin oxide; sulfuric acid Conductive filler with tin oxide coated on core material such as barium, titanium oxide, potassium titanate, etc., etc., with peroxide, hydrogen siloxane in the presence of platinum catalyst, vulcanizing agent such as isocyanate A kneaded product is used.

  The surface of the developing roll may be an elastic layer, but a surface layer may be provided on the elastic layer. The material for forming the surface layer is not particularly limited, but alkyd resin, modified alkyd resin such as phenol modification and silicone modification, oil-free alkyd resin, acrylic resin, silicone resin, epoxy resin, fluororesin, Examples include phenolic resins, polyamide resins, urethane resins, and mixtures thereof.

  The surface brightness of the developing roll is adjusted to a range of 30 to 220. The surface brightness of the developing roll is preferably 50 to 200, more preferably 60 to 140. If the surface brightness of the developing roll is too low, the image density of the black solid print sample becomes higher than necessary, density unevenness occurs in the intermediate tone print sample, and dot reproducibility decreases. If the surface brightness of the developing roll is too high, the image density of the black solid print sample is low, and the paper as the print medium is seen through, making it difficult to obtain a good image. If the surface brightness of the developing roll is too high, the dot reproducibility of the intermediate tone print sample also decreases. By setting the surface brightness of the developing roll within the above range, a good image can be obtained. The surface brightness of the developing roll is a value measured by the surface brightness measuring apparatus shown in FIG. 4, and a specific measuring method is described in the examples.

  The developing roll has a surface roughness Rz (10-point average roughness Rz) of 1 to 20 μm, preferably 3 to 10 μm, more preferably 3 to 8 μm. If the surface roughness Rz of the developing roll is too low, the image density becomes low, and if it is too high, the image density becomes too high, fogging is likely to occur, and the resolution is also lowered. The surface roughness Rz of the developing roll is a value measured by the measuring method described in the examples.

  By adjusting the surface brightness and the surface roughness Rz of the developing roll within the above ranges, the cleaning performance using the cleaning blade is remarkably improved, and high-definition and high-quality images can be formed under various environments. . In order to adjust the surface brightness of the developing roll within the above range, a method of controlling by using a resin having a high brightness in the surface layer and dispersing fine inorganic particles having a small particle diameter in order to lower the surface layer can be mentioned. In order to adjust the surface roughness Rz to the above range, the thickness of the resin coating layer having a small surface roughness and a method of polishing the surface layer can be mentioned.

The electric resistance between the core of the developing roll and the surface of the developing roll is usually in the range of 10 ⁵ to 10 ⁹ Ω, preferably in the range of 10 ⁶ to 10 ⁸ Ω. If this electric resistance is too lower than the above range, a developing bias is applied too much and fogging is likely to occur. If this electrical resistance becomes too high, a developing bias is not applied, and developability is lowered and image density is lowered.

  The second feature of the image forming method of the present invention is that in the electrophotographic image forming method as described above, the developing roll has a surface brightness of 30 to 220 and a surface roughness Rz of 1 to 20 μm. In addition, the specific toner is used, and the absolute value of the charge amount of the toner on the surface of the photoreceptor is controlled within a specific range.

  The toner used in the image forming method of the present invention is a developer containing colored resin particles and an external additive. The toner used in the present invention is preferably a one-component developer, and more preferably a non-magnetic one-component developer.

  The volume average particle diameter dv of the colored resin particles as the main component of the toner is 4 to 10 μm, preferably 4 to 9 μm, more preferably 5 to 8 μm. The volume average particle diameter is a value measured by the method described in Examples. When the volume average particle diameter of the colored resin particles is within the above range, a high-resolution and high-definition image can be formed. When the volume average particle diameter dv of the colored resin particles is in the above range, it is possible to obtain a toner having high fluidity, good transferability, no blurring, high printing density, and high image resolution.

  In the particle size distribution of the colored resin particles, the ratio of the colored resin particles having a particle size of 3 μm or less is preferably 20% by number or less, more preferably 10% by number or less, and further preferably 5% by number or less. When the proportion of the colored resin particles having a particle size of 3 μm or less is within the above range, the cleaning property is improved, which is preferable.

  The colored resin particles preferably have a particle size distribution represented by a ratio dv / dp between the volume average particle size dv and the number average particle size dp of 1.0 to 1.3, more preferably 1.0 to 1. .2. When the particle size distribution dv / dp of the colored resin particles is in the above range, there is no occurrence of blur, a transfer property is good, and a toner with high print density and resolution can be obtained. The volume average particle diameter and the number average particle diameter of the colored resin particles can be measured using, for example, Multisizer (manufactured by Beckman Coulter, Inc.).

  The average circularity of the colored resin particles is 0.950 to 0.995, preferably 0.960 to 0.995, more preferably 0.970 to 0.990. When the average circularity of the colored resin particles is within the above range, fine line reproducibility can be improved.

  The circularity of the colored resin particles is defined as the ratio between the circumference of a circle having the same projected area as the particle image and the circumference of the projected image of the particles. The average circularity is one method for quantitatively expressing the shape of the particles, and is an index indicating the degree of unevenness of the colored resin particles. The average circularity is 1 when the colored resin particles are completely spherical, and becomes smaller as the surface shape of the colored resin particles becomes uneven. The average circularity (Ca) is a value obtained by the following equation (1).

  In the above formula (1), n is the number of particles for which the circularity Ci is obtained. The circularity Ci is the circularity of each particle calculated by the following equation (2) based on the circumferential length measured for each particle of a particle group having a circle-equivalent diameter of 0.6 to 400 μm.

Ci = perimeter of circle equal to projected area of particle / perimeter of projected particle image (2)
In the above formula (1), fi is the frequency of particles having a circularity Ci. The circularity and the average circularity can be measured using, for example, a flow type particle image analyzer “FPIA-2100” or “FPIA-2000” manufactured by Sysmex Corporation.

  In the image forming method of the present invention, the charge amount of the toner developed on the photoreceptor is 10 to 80 μC / g, preferably 20 to 80 μC / g, in absolute value (absolute value of plus or minus charge amount). More preferably, it is 20 to 70 μC / g. Since the absolute value of the charge amount of the toner on the surface of the photoreceptor is within the above range, the cleaning property and the image quality can be highly balanced. If the absolute value of the charge amount of the toner on the surface of the photoreceptor is too large, the cleaning property is lowered and fogging is likely to occur. If the absolute value of the charge amount of the toner on the surface of the photoreceptor is too small, the cleaning property is good, but the print density in a low-temperature, low-humidity or high-temperature, high-humidity environment is lowered, and fogging is likely to occur.

  The absolute value | Q | (μC / g) of the charge amount of the toner on the surface of the photoconductor is solid-printed in a normal temperature and normal humidity (N / N) environment at a temperature of 23 ° C. and a humidity of 50%, and the photoconductor The toner developed on the surface is sucked by a suction-type charge amount measuring device (manufactured by Trek Japan, model name “210HS-2A”). Based on the suction amount (g) and the measured value (μC) of the toner, It was measured by a method of calculating the charge amount Q (μC / g) per unit weight. Since the toner includes a positively chargeable toner and a negatively chargeable toner, the charge amount per unit weight of the toner is represented by an absolute value | Q | of a plus or minus charge amount. Details of the method of measuring the absolute value of the charge amount are as described in the examples.

The developing amount M / A of the toner on the surface of the photosensitive member (the amount of toner on the photosensitive member after development) is preferably in the range of 0.3 to 0.8 mg / cm ² . This development amount is a value measured by the measurement method described in Examples. That is, the toner developed on the photoreceptor is sucked by the suction-type charge amount measuring device. A filter whose weight has been accurately measured in advance is attached to the Faraday gauge of this measuring device, and the filter area A (cm ² ) of the portion sucked after suction is measured. The measured value A and the weight increase of the Faraday gauge [ie, suction The development amount M / A (mg / cm ² ) is calculated from the amount M (mg)]. If the toner amount (development amount) on the photoconductor after development is too small, the print density tends to decrease. When the development amount is in the above range, the print density can be set to an appropriate range.

  The absolute value of the charge amount of the toner on the surface of the photoconductor is the type and amount of the charge control agent contained in the colored resin particles described later, the type and amount of the external additive, the configuration of the photoconductor, the configuration of the developing roll, the photosensitivity. By adjusting the bias voltage or the like between the body and the developing roll, it can be within the above range.

  The colored resin particles constituting the toner used in the present invention are colored resin particles containing at least a binder resin and a colorant. In addition to the colorant, a release agent and a charge control agent are preferably contained. Specific examples of the binder resin include conventionally used binder resins such as polystyrene, styrene-butyl acrylate copolymer, polyester resin, and epoxy resin.

  As the colorant, various pigments and dyes can be used in addition to carbon black, titanium black, magnetic powder, oil black, and titanium white. Black carbon black having a primary particle number average particle size of 20 to 40 nm is preferably used. When the average particle diameter is in this range, carbon black can be uniformly dispersed in the toner and fogging is reduced, which is preferable. In order to obtain a full color toner, generally, a yellow colorant, a magenta colorant, and a cyan colorant are used as the colorant.

  Examples of the yellow colorant include compounds such as an azo colorant and a condensed polycyclic colorant. Specific examples of the yellow colorant include C.I. I. Pigment yellow 3, 12, 13, 14, 15, 17, 62, 65, 73, 74, 83, 90, 93, 97, 120, 138, 155, 180, 181, 185, 186 and the like.

  Examples of the magenta colorant include compounds such as azo colorants and condensed polycyclic colorants. Specific examples of the magenta colorant include C.I. I. Pigment Red 31, 48, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 144, 146, 149, 150, 163, 170, 184, 185, 187, 202, 206, 207, 209, 251; I. Pigment violet 19 and the like.

  Examples of cyan colorants include copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, and the like. Specific examples of the cyan colorant include C.I. I. Pigment blue 2, 3, 6, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, 17, 60, and the like. The use ratio of the colorant is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  Examples of the release agent include polyolefin waxes such as low molecular weight polyethylene, low molecular weight polypropylene, and low molecular weight polybutylene; plant-based natural waxes such as candelilla, carnauba, rice, wood wax, jojoba; paraffin, microcrystalline, petrolatum, etc. Petroleum waxes and modified waxes thereof; synthetic waxes such as Fischer-Tropsch wax; polyfunctional ester compounds such as pentaerythritol tetrastearate, pentaerythritol tetrapalmitate, dipentaerythritol hexamyristate; and the like.

  The release agents can be used alone or in combination of two or more. Of the release agents, synthetic waxes and polyfunctional ester compounds are preferred. Further, among the release agents, in the DSC curve measured by a differential scanning calorimeter, the endothermic peak temperature at the time of temperature rise is preferably 30 to 150 ° C, more preferably 40 to 100 ° C, and further preferably 50 to 80 ° C. A polyfunctional ester compound in the range is preferred because a toner having an excellent fixing-peeling balance at the time of fixing can be obtained. A mold release agent having a molecular weight of 1000 or more, dissolving at least 5 parts by weight with respect to 100 parts by weight of styrene at 25 ° C., and having an acid value of 10 mgKOH / g or less is particularly preferable because it exhibits a remarkable effect on lowering the fixing temperature. . As such a polyfunctional ester compound, dipentaerythritol hexamyristate and pentaerythritol tetrastearate are preferable. Endothermic peak temperature means a value measured by ASTM D3418-82. The compounding ratio of the release agent is usually 3 to 20 parts by weight, preferably 5 to 15 parts by weight with respect to 100 parts by weight of the binder resin.

  The colored resin particles constituting the toner used in the image forming method of the present invention preferably contains a charge control agent. The charge control agent is not particularly limited as long as it is conventionally used in the technical field of toner. Among charge control agents, a charge control resin is preferably contained. The reason is that the charge control resin has high compatibility with the binder resin, is colorless, and a toner having stable chargeability can be obtained even in color continuous printing at high speed. The charge control resin is manufactured as a positive charge control resin according to the descriptions in JP-A-63-60458, JP-A-3-175456, JP-A-3-243594, JP-A-11-15192, and the like. Positive charge control resins such as secondary ammonium (salt) group-containing copolymers; sulfonic acid (salt) group-containing copolymers produced according to the description of JP-A-1-217464, JP-A-3-15858, etc. Negative charge control resin.

  The ratio of the monomer unit having a functional group such as a quaternary ammonium (salt) group or a sulfonic acid (salt) group contained in these copolymers is preferably 0.5% based on the weight of the charge control resin. -12% by weight, more preferably 1-8% by weight. When the ratio of the monomer unit containing a functional group is in the above range, the charge amount of the toner can be easily controlled and the occurrence of fogging can be reduced.

  The weight average molecular weight of the charge control resin is preferably 2000 to 50000, more preferably 4000 to 40000, and particularly preferably 6000 to 35000. When the weight average molecular weight of the charge control resin is within the above range, it is possible to suppress the occurrence of offset and the deterioration of fixability.

  The glass transition temperature of the charge control resin is preferably 40 to 80 ° C, more preferably 45 to 75 ° C, and particularly preferably 45 to 70 ° C. When the glass transition temperature of the charge control resin is within the above range, the storage stability and fixing ability of the toner can be improved in a well-balanced manner. The blending ratio of the charge control agent is usually 0.1 to 10 parts by weight, preferably 1 to 6 parts by weight with respect to 100 parts by weight of the binder resin.

  The colored resin particles are preferably core-shell type (also referred to as “capsule type”) colored resin particles obtained by combining two different polymers inside (core layer) and outside (shell layer) of the particles. . In the core-shell type colored resin particles, the low softening point material in the core (core layer) is coated with a material having a higher softening point to balance the lowering of the fixing temperature and the prevention of aggregation during storage. This is preferable. The core layer of the core-shell type colored resin particles is composed of the binder resin and the colorant, and if necessary, various additives such as a charge control agent and a release agent are contained. Consists only of resin.

  The weight ratio between the core layer and the shell layer of the core-shell type colored resin particles is not particularly limited, but is usually selected from the range of 80/20 to 99.9 / 0.1. By setting the ratio of the shell layer to the above ratio, both the storage stability of the toner and the fixing property at a low temperature can be achieved.

  The average thickness of the shell layer of the core-shell type colored resin particles is usually 0.001 to 0.1 μm, preferably 0.003 to 0.08 μm, and more preferably 0.005 to 0.05 μm. If the thickness of the shell layer is too large, the fixing property is lowered, and if it is too small, the storage property is lowered. The core particles forming the core-shell type colored resin particles do not need to be entirely covered with the shell layer, and only a part of the surface of the core particles may be covered with the shell layer.

  If the core particle diameter and the thickness of the shell layer of the core-shell type colored resin particles can be observed with an electron microscope, they can be obtained by directly measuring the size and shell thickness of particles randomly selected from the observation photograph. . When it is difficult to observe the core and shell clearly by observation with an electron microscope, the thickness of the shell layer is determined based on the particle size of the core particle and the amount of monomer that forms the shell used in the toner production. Can be calculated.

  The colored resin particles used in the present invention are not particularly limited as long as the colored resin particles can be obtained with predetermined characteristics, but are preferably produced by a polymerization method. Therefore, a method for producing colored resin particles constituting the toner by a polymerization method will be described below.

  In order to produce colored resin particles by the polymerization method, first, a polymerizable monomer that is a raw material of the binder resin is dissolved or dispersed in a colorant, a charge control agent, and other additives. A body composition is prepared. The polymerizable monomer composition is dispersed as fine droplets in an aqueous dispersion medium containing a dispersion stabilizer, and a polymerization reaction is performed using a polymerization initiator. After the polymerization, the colored resin particles are recovered by filtration, washing, dehydration, and drying.

  Examples of the polymerizable monomer include a monovinyl monomer, a crosslinkable monomer, and a macromonomer. This polymerizable monomer is polymerized to become a binder resin component.

  Monovinyl monomers include aromatic vinyl monomers such as styrene, vinyltoluene and α-methylstyrene; (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylic acid (Meth) acrylic monomers such as propyl, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, and isobornyl (meth) acrylate; monomers such as ethylene, propylene and butylene Olefin monomer; and the like. Monovinyl monomers may be used alone or in combination of a plurality of monomers. Among these monovinyl monomers, aromatic vinyl monomers alone, combinations of aromatic vinyl monomers and (meth) acrylic monomers, and the like are preferably used.

  When a crosslinkable monomer is used together with a monovinyl monomer, hot offset is effectively improved. A crosslinkable monomer is a monomer having two or more vinyl groups. Specific examples include divinylbenzene, divinylnaphthalene, ethylene glycol dimethacrylate, pentaerythritol triallyl ether, trimethylolpropane triacrylate, and the like. These crosslinkable monomers can be used alone or in combination of two or more. The use ratio of the crosslinkable monomer is usually 10 parts by weight or less, preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of the monovinyl monomer.

  It is preferable to use a macromonomer together with a monovinyl monomer because the balance between the storage stability of the toner and the fixing property at low temperature is improved. The macromonomer has a polymerizable carbon-carbon unsaturated double bond at the end of the molecular chain, and is an oligomer or polymer having a number average molecular weight of usually 1000 to 30000.

  The macromonomer is preferably one that gives a polymer having a glass transition temperature higher than that of a polymer obtained by polymerizing a monovinyl monomer. The proportion of the macromonomer used is usually 0.01 to 10 parts by weight, preferably 0.03 to 5 parts by weight, and more preferably 0.05 to 1 part by weight with respect to 100 parts by weight of the monovinyl monomer.

  Examples of the polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate; 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-methyl-N- (2 -Hydroxyethyl) propionamide, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, etc. Di-t-butyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butylperoxypivalate, Such as di-isopropyl peroxydicarbonate, di-t-butyl peroxyisophthalate, t-butyl peroxyisobutyrate Oxides and the like. May be used a redox initiator in combination with a reducing agent and the polymerization initiator.

  The proportion of the polymerization initiator used is preferably 0.1 to 20 parts by weight, more preferably 0.3 to 15 parts by weight, and particularly preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the polymerizable monomer. Part. The polymerization initiator may be added in advance to the polymerizable monomer composition, but in order to suppress undesired early polymerization, during or after the formation of droplets of the polymerizable monomer composition. You may add in an aqueous dispersion medium.

  The aqueous dispersion medium contains a dispersion stabilizer. Examples of the dispersion stabilizer include inorganic salts such as barium sulfate, calcium sulfate, calcium carbonate, magnesium carbonate, and calcium phosphate; inorganic oxides such as aluminum oxide and titanium oxide; aluminum hydroxide, magnesium hydroxide, and second hydroxide And inorganic compounds such as inorganic hydroxides such as iron. As the dispersion stabilizer, water-soluble polymers such as polyvinyl alcohol, methylcellulose, and gelatin; anionic surfactants, nonionic surfactants, and amphoteric surfactants can also be used. The dispersion stabilizers can be used alone or in combination of two or more.

  Among dispersion stabilizers, dispersion stabilizers containing colloids of inorganic compounds, particularly poorly water-soluble inorganic hydroxides, can narrow the particle size distribution of the colored resin particles, and the dispersion stabilizer can be washed. This is preferable because a toner that can be reproduced in a clear manner can be obtained with a small remaining amount.

  The amount of the dispersion stabilizer used is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the polymerizable monomer. When the amount of the dispersion stabilizer used is in the above range, it is preferable because sufficient polymerization stability can be obtained and formation of polymerization aggregates is suppressed.

  In the polymerization, a molecular weight modifier is preferably used. Examples of the molecular weight modifier include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, 2,2,4,6,6-pentamethylheptane-4-thiol, and the like. The molecular weight modifier can be added to the polymerizable monomer composition before or during the polymerization. The usage-amount of a molecular weight modifier is 0.01-10 weight part normally with respect to 100 weight part of polymerizable monomers, Preferably it is 0.1-5 weight part.

There is no restriction | limiting in particular as a method of manufacturing a core-shell type colored resin particle, It can manufacture by a conventionally well-known method. For example, a spray drying method, an interfacial reaction method, an in situ polymerization method, a phase separation method and the like can be mentioned. More specifically, colored resin particles obtained by a pulverization method, a polymerization method, an association method, or a phase inversion emulsification method are used as core particles, and the core particles are coated with a shell layer, whereby core-shell type colored resin particles are obtained. Can be obtained. Among these production methods, the in situ polymerization method and the phase separation method are preferable from the viewpoint of production efficiency.

Hereinafter, a method for producing colored resin particles having a core / shell structure by an in situ polymerization method will be described. In an aqueous dispersion medium in which core particles (colored resin particles) are dispersed, a polymerizable monomer (shell polymerizable monomer) and a polymerization initiator for forming a shell are added and polymerized. Colored resin particles having a core-shell structure can be obtained.

  As a specific method for forming the shell, a method of continuously polymerizing by adding a polymerizable monomer for shell to a reaction system of a polymerization reaction performed to obtain core particles; obtained by another reaction system Examples thereof include a method in which core particles are charged and a shell polymerizable monomer is added thereto for polymerization. The polymerizable monomer for shell may be added all at once in the reaction system, or may be added continuously or intermittently using a pump such as a plunger pump.

  As the polymerizable monomer for the shell, monomers that form a polymer having a glass transition temperature exceeding 80 ° C., such as styrene, acrylonitrile, and methyl methacrylate, may be used alone or in combination of two or more. Can do.

  When adding the polymerizable monomer for shell, it is preferable to add a water-soluble polymerization initiator because colored resin particles having a core-shell structure can be easily obtained. When a water-soluble polymerization initiator is added during the addition of the shell polymerizable monomer, the water-soluble polymerization initiator moves to the vicinity of the outer surface of the core particle to which the shell polymerizable monomer has migrated, and the core particle surface It is considered that a polymer layer (shell) is easily formed.

  Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate; 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis [ An azo initiator such as 2-methyl-N- [1,1-bis (hydroxymethyl) 2-hydroxyethyl] propionamide] can be used. The usage-amount of a water-soluble polymerization initiator is 0.1-30 weight part normally with respect to 100 weight part of polymerizable monomers for shells, Preferably it is 1-20 weight part.

  The polymerization temperature is preferably 50 ° C. or higher, more preferably 60 to 95 ° C. The reaction time is preferably 1 to 20 hours, more preferably 2 to 10 hours. After the polymerization is completed, filtration, washing, dehydration, and drying are performed according to a conventional method, and this operation is preferably repeated several times.

  In the case of using an inorganic compound such as an inorganic hydroxide as a dispersion stabilizer, an aqueous dispersion containing colored resin particles (colored polymer particles) obtained by polymerization is stabilized by adding an acid or an alkali. The agent is preferably dissolved in water and removed by filtration and washing. When a colloid of a poorly water-soluble inorganic hydroxide is used as the dispersion stabilizer, it is preferable to adjust the pH of the aqueous dispersion to 6.5 or less by adding an acid. As the acid to be added, inorganic acids such as sulfuric acid, hydrochloric acid and nitric acid, and organic acids such as formic acid and acetic acid can be used, but sulfuric acid is particularly preferable because of its high removal efficiency and low burden on production equipment. It is.

  The method for filtering and dewatering the colored resin particles from the aqueous dispersion medium is not particularly limited. Examples thereof include a centrifugal filtration method, a vacuum filtration method, and a pressure filtration method. Among these, the centrifugal filtration method is preferable.

  The toner used in the present invention is a developer containing colored resin particles and an external additive. If necessary, other fine particles may be added. Colored resin particles (including core / shell type colored resin particles) prepared by a polymerization method can be used as a main component of various developers, but are preferably used as a one-component developer. More preferably, it is used as a component developer. Examples of the external additive include inorganic fine particles and organic resin fine particles that act as a fluidizing agent and an abrasive.

  Examples of the inorganic fine particles include silicon dioxide (silica), aluminum oxide (alumina), titanium oxide, zinc oxide, tin oxide, barium titanate, and strontium titanate. As organic resin fine particles, methacrylic acid ester polymer particles, acrylic acid ester polymer particles, styrene-methacrylic acid ester copolymer particles, styrene-acrylic acid ester copolymer particles, a core is a styrene polymer, and a shell is methacrylic acid. Examples thereof include core-shell type particles formed of an ester copolymer.

  Among these, inorganic oxide fine particles are preferable, and silica fine particles are particularly preferable. The surface of the inorganic fine particles can be hydrophobized, and silica particles that have been hydrophobized are particularly suitable. Two or more types of external additives may be used in combination. When external additives are used in combination, a method in which inorganic fine particles having different average particle diameters or inorganic fine particles and organic resin fine particles are combined is suitable. .

  Inorganic fine particles such as silica are preferably subjected to a hydrophobic treatment. Hydrophobized inorganic fine particles are generally commercially available, but can also be obtained by hydrophobizing with a silane coupling agent or silicone oil. As a method of hydrophobizing treatment, a method of dripping or spraying silicone oil as a treatment agent while stirring the fine particles at a high speed, and adding and mixing fine particles in an organic solvent which is dissolved by stirring the treatment agent Thereafter, a heat treatment method and the like can be mentioned. In the former case, the treatment agent may be diluted with an organic solvent or the like.

  The degree of hydrophobicity is preferably 20 to 90%, more preferably 40 to 80%, as measured by the methanol method. When the degree of hydrophobicity is within this range, it is difficult to absorb moisture under high temperature and high humidity, and sufficient polishing properties can be obtained.

  The use ratio of the external additive (single or total use ratio) is not particularly limited, but is usually 0.1 to 6 parts by weight with respect to 100 parts by weight of the colored resin particles. In order to attach the external additive to the colored resin particles, the colored resin particles and the external additive are usually placed in a mixer such as a Henschel mixer and stirred.

  As the external additive, a combination of silica fine particles (A) having a number average particle diameter of 5 to 20 nm, preferably 7 to 15 nm of primary particles and spherical silica fine particles (B) having a volume average particle diameter of 0.1 to 0.5 μm. It is more preferable to combine silica fine particles (C) in which the number average particle size of primary particles is 25 to 80 nm, preferably 30 to 60 nm. By using these fine particles together, it is possible to suppress toner filming on the surface of the photoreceptor and image blurring.

  The spherical silica fine particles (B) have a sphericity measured by the method described later of 1 to 1.5, preferably 1 to 1.3, and more preferably 1 to 1.2. Environmental stability can be made favorable by setting it as the said range of sphericity.

  In the case of spherical silica fine particles (B), in the particle size distribution, when the particle size corresponding to 10% of the volume particle size calculated from the small particle size side is Dv10 and the particle size corresponding to 50% is Dv50, The ratio of Dv50 to Dv10 (Dv50 / Dv10) is preferably 1.8 or more, and more preferably 2.0 or more. When spherical silica fine particles having a Dv50 / Dv10 greater than 1.8 are used, toner blocking and toner filming on the photoreceptor can be effectively suppressed.

  The bulk density of the spherical silica fine particles (B) is preferably 50 to 250 g / l, and more preferably 80 to 200 g / l. By setting the bulk density within this range, it is possible to suppress toner filming and fogging on the photosensitive member, and deterioration in cleaning properties.

  The blending ratio of the silica fine particles (A) is preferably 0.1 to 3 parts by weight, more preferably 0.3 to 2 parts by weight with respect to 100 parts by weight of the colored resin particles. By making the blending ratio of the silica fine particles (A) in the above range, it is possible to effectively suppress the deterioration of the cleaning property, the occurrence of printing stains and poor fixing under low temperature and low humidity.

  The blending ratio of the spherical silica fine particles (B) is usually 0.3 to 3 parts by weight, preferably 0.5 to 2 parts by weight with respect to 100 parts by weight of the colored resin particles. By making the blending ratio of the spherical silica fine particles (B) in the above range, it is possible to suppress the deterioration of the cleaning property and the occurrence of scumming.

  The blending ratio of the silica fine particles (C) is preferably 0.1 to 3 parts by weight, more preferably 0.3 to 2 parts by weight with respect to 100 parts by weight of the colored resin particles. By making the blending ratio of the silica fine particles (C) in the above range, it is possible to effectively suppress the deterioration of the cleaning property, the occurrence of printing stains and poor fixing under low temperature and low humidity.

The coverage of the colored resin particles with the external additive is preferably 60 to 140% from the viewpoint of cleaning properties. The coverage of the external additive is as follows: (i) all of the added external additive is attached to the surface of the colored resin particles, (ii) the external additive is spherical, (iii) silica fine particles The specific gravity is assumed to be 2.2. (Iv) The calculation is made on the assumption that the shape of the toner is a true sphere.
The coverage f is expressed by the following formula 2:

Can be calculated. Here, Ds is the particle size of the silica fine particles, Dt is the particle size of the colored resin particles, ρt and ρs are the true specific gravity of the colored resin particles and the silica fine particles, and C is the weight ratio of the resin particles to silica. Respectively. However, when silica fine particles are added to the colored resin particles, some of the silica fine particles adhere to the surface of the colored resin particles in an aggregated state. For this reason, the actual coverage is lower than the value calculated from the above formula.

  Hereinafter, the present invention will be described more specifically with reference to production examples, examples and comparative examples. In the following production examples, examples and comparative examples, “parts” and “%” are based on weight unless otherwise specified. The evaluation method of characteristics and physical properties in the present invention is as follows.

(1) Volume particle size and particle size distribution of colored resin particles:
The volume average particle size dv of the colored resin particles and the particle size distribution represented by the ratio dv / dp of the volume average particle size dv and the number average particle size dp were measured by Multisizer (manufactured by Beckman Coulter, Inc.). The measurement with this multisizer was performed under the conditions of an aperture diameter of 100 μm, a medium isotone, a sample concentration of 10%, and a measurement particle number of 100,000.

(2) Average circularity:
In a container, 10 ml of ion-exchanged water is put in advance, 0.02 g of a surfactant (alkyl benzene sulfonic acid) as a dispersant is added, 0.02 g of colored resin particles are further added, and 60 W is added using an ultrasonic disperser. The dispersion treatment was performed for 3 minutes. The concentration of the colored resin particles at the time of measurement was adjusted to 3000 to 10000 / μL, and a flow type particle image analyzer “FPIA-2100” manufactured by Sysmex Corporation for 1000 to 10000 colored resin particles having an equivalent circle diameter of 1 μm or more. It measured using. The average circularity was determined from the measured value.

(3) Volume average particle size and particle size distribution (Dv50 / Dv10) of spherical silica fine particles:
Place 0.5 g of silica fine particles in a 100 ml beaker, drop several drops of surfactant, add 50 ml of ion-exchanged water, disperse for 5 minutes using an ultrasonic homogenizer US-150T, and then microtrack UPA150 (Nikkiso Volume average particle size and particle size distribution.

(4) Number average particle diameter of silica fine particles:
The number average particle diameter of the silica fine particles is obtained by taking an electron micrograph of each particle, and using the image processing analysis device Luzex IID (manufactured by Nireco Corporation), the area ratio of the particles to the frame area: maximum 2%, total Number of treated particles: The equivalent circle diameter was calculated under the condition of 100 particles, and the average value was obtained.

(5) Sphericality:
The sphericity Sc / Sr, which is the value obtained by dividing the area Sc of the spherical silica fine particle with the absolute maximum length as the major axis divided by the actual projected area Sr of the particle, is obtained by taking an electron micrograph of each particle and analyzing the photograph by image processing analysis. Using an apparatus Luzex IID (manufactured by Nireco Co., Ltd.), the particle area ratio with respect to the frame area was 2% at maximum and the total number of processed particles was 100. The average value of the calculated 100 particles was defined as the sphericity. .

(6) Hydrophobization degree:
The degree of hydrophobicity of the spherical silica fine particles was determined by the methanol method. 0.2 g of silica fine particles were put into a 500 ml beaker, 50 ml of pure water was added, and subsurface hemethanol was added while stirring with a magnetic stirrer. The point at which fine particles were not observed on the liquid surface was taken as the end point, and the degree of hydrophobicity was calculated by the following formula.
Hydrophobicity (%) = [X / (50 + X)] × 100
In the above formula, X is the amount of methanol used (ml).

(7) Bulk density:
The spherical silica fine particles to be measured were gradually added to a 100 ml graduated cylinder weighed in advance without applying vibration. When 100 ml is reached, the weight of the mescillator is measured, the difference between the weight before and after adding the silica fine particles is calculated, and the value is multiplied by 10 to obtain the bulk density (g / l) of the spherical silica fine particles (B). did.

(8) Surface brightness:
The surface brightness of the developing roll was measured with a surface brightness value measuring apparatus shown in FIG. This surface luminance value measuring apparatus includes an objective lens 406 (trade name “CF IC BD Plan20X” manufactured by Nikon Corporation), a CCD camera 401 (trade name “XC-003” manufactured by Sony Corporation), and an illumination lamp 402 (Philips). 77241) having a microscope main body 403 (trade name “EPI-U”, manufactured by Nikon Corporation), a developing roll 4 is set below the microscope main body 403, and the voltage supplied to the illumination lamp 402 is The developing roller 4 is illuminated by the vertical irradiation method with the voltage adjuster 404 adjusted to DC 10V.

  The CCD camera 401 is connected to a computer 405 in which image processing software (manufactured by Oji Scientific Instruments Co., Ltd., product name “DA-6000”) is installed. The captured image is taken into the computer 405 and the captured image is captured. Analyze with image processing software and measure the surface brightness value. In the measurement, the surface luminance values at three locations were measured for each developing roll, and the average value was used.

(9) Surface roughness Rz:
A developing roll is set on a surface roughness meter (trade name “590A”, manufactured by Tokyo Seimitsu Co., Ltd.) equipped with a measurement probe having a tip radius of 2 μm, a measurement length of 2.4 mm, a cutoff wavelength of 0.8 mm, and a cutoff type Gaussian. Was used to measure the surface roughness Rz. The surface roughness at three locations was measured for each developing roll, and the average value was used.

(10) Electric resistance:
Using an electric resistance meter manufactured by Advantest and trade name “ULTRA HIGH RESISTANCE METER R8340A”, the developing roll is placed horizontally, and the thickness of the roller rubber is 5 mm, the width is 30 mm, and the length can be placed on the entire roller rubber part. An aluminum plate was used as an electrode, a load of 500 g was applied to both ends of the developing roll mandrel, a current of 100 V was passed between the mandrel and the electrode as a direct current, and the value after 1 second was read to obtain an electric resistance value.

(11) Charge amount of toner on the photoreceptor:
The charge amount of the toner on the photoreceptor is a value measured by the following method. A printer in which a developing roll of a commercially available non-magnetic one-component color printer (Oki Data Corporation, model name “Microline 5300”) was modified was used.
The cartridge filled with the toner prepared in the production example was mounted at the position of the black toner cartridge of the modified printer. After printing for a day and night in an N / N environment at a temperature of 23 ° C. and a humidity of 50%, solid printing is performed, and then the second solid printing is stopped halfway, and then the toner developed on the photoreceptor is sucked. The amount of charge was measured by suction using a type charge amount measuring device (manufactured by Trek Japan, model name “210HS-2A”). The charge amount Q (μC / g) per unit weight of the toner was calculated based on the toner suction amount (g) and the measured value (μC). The charge amount Q is represented by an absolute value | Q |.

(12) Development amount of toner on photoconductor (M / A):
In the same manner as in (11), solid printing is performed, and then the second solid printing is stopped halfway, and then the toner developed on the photoconductor is charged with the suction-type charging used in (11). Aspiration was performed using a quantity measuring device. A filter whose weight has been accurately measured in advance is attached to the Faraday gauge of this measuring device, and the filter area A (cm ² ) of the portion sucked after suction is measured. The measured value A and the weight increase of the Faraday gauge [ie, suction The development amount M / A (mg / cm ² ) was calculated from the amount M (mg)].

(13) Print density:
Using the modified printer used in the above (11), a cartridge filled with magenta toner is mounted at the position of the black toner cartridge, in an L / L environment at a temperature of 10 ° C. and a humidity of 20%, and at a temperature of 35 ° C. and a humidity of 80%. In the H / H environment, printing was performed at 5% printing density for a whole day and night, solid printing was performed at the 500th and 5000th sheets, and the printing density was measured using a Macbeth reflection type image density measuring machine. However, those that caused problems in the cleaning and fog evaluation described below were not evaluated.

(14) Cleanability:
Using the printer used in (11) above, after standing overnight in an L / L environment at a temperature of 10 ° C. and a humidity of 20% and in an N / N environment of a temperature of 23 ° C. and a humidity of 50%, each continuously at a concentration of 5%. Printing was performed, and after every 500th sheet, the cleaning blade was passed through, and it was visually evaluated whether toner was attached to the charging roll. Evaluation was performed up to 10,000 sheets. “10000 ≦” in the table indicates that the toner did not adhere to the charging roll even when 10000 sheets were continuously printed.

(15) Durability Using the printer used in (11) above, after standing overnight in an N / N environment at a temperature of 23 ° C. and a humidity of 50% and an H / H environment of a temperature of 35 ° C. and a humidity of 80%, Continuous printing was performed at 5% density, and solid white printing was performed every 500th sheet. The toner remaining on the developed photoreceptor was peeled off with an adhesive tape (manufactured by Sumitomo 3M, Scotch Mending Tape 810-3-18), and the adhesive tape was attached to a new printing paper. Next, the color tone D of the printing paper pasted with the adhesive tape is measured with the spectral color difference meter used in the above (9), and the color tone B of the printing paper pasted with only the adhesive tape described above, From this, a color difference ΔE was calculated, and the number of continuously printed sheets that can maintain this value of 1 or less was examined up to 10,000 sheets. Note that “10000 ≦” in the table indicates that the color difference ΔE was 1 or less even after continuous printing of 10,000 sheets.

[Production Example 1] Production Example of Developing Roll A A SUM22 electroless nickel-plated shaft having a diameter of 10 mm and a length of 275 mm was used as the conductive shaft, and a silicone primer (manufactured by Shin-Etsu Chemical Co., Ltd., product) Name “Primer No. 16”) was applied and baked in a gear oven at 150 ° C. for 10 minutes.

  100 parts of methyl vinyl silicone raw rubber (Shin-Etsu Chemical Co., Ltd., trade name “KE-78VBS”), 20 parts of dimethyl silicone raw rubber (Shin-Etsu Chemical Co., Ltd., trade name “KE-76VBS”) and carbon black (Asahi) Carbon Co., Ltd., trade name “Asahi Thermal”) 10 parts, Fumed Silica-based filler (Nippon Aerosil Co., Ltd., trade name “AEROSIL 200”) 15 parts, Platinum catalyst (Shin-Etsu Chemical Co., Ltd., trade name) "C-19A") 0.5 part and hydrogen siloxane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "C-19B") 2 parts were added and kneaded with a pressure kneader to prepare a silicone rubber composition. .

  Next, the silicone rubber composition was integrated and dispensed through a cross head with an extruder, and vulcanized by heating at 250 ° C. for 30 minutes in a gear oven, and vulcanized and bonded to a conductive shaft body comprising a shaft at φ 18 mm. Then, secondary vulcanization was performed in a gear oven at 200 ° C. for 4 hours to form an elastic layer. After vulcanization, the outer peripheral surface of the elastic layer was polished with a cylindrical grinder equipped with a GC # 400 grindstone to produce a roll base having a diameter of 16 mm and a rubber part length of 230 mm. The sample had a surface luminance of 32 and a surface roughness Rz of 25 μm.

  On the surface of this roll elastic layer, 100 parts of urethane-based paint (trade name “Nipporan 5196”, manufactured by Nippon Polyurethane Co., Ltd., 30% non-volatile content) and fumed silica filler (made by Nippon Aerosil Co., Ltd., trade name “AEROSIL 200”). ")" And 10 parts of a polyisocyanate-based cross-linking agent (product name "Coronate-L" manufactured by Nippon Polyurethane Co., Ltd.) are added, and spray coating is applied once and heated at 150 ° C for 30 minutes. Curing was performed to produce a developing roll A having a surface luminance value of 83 and a surface roughness Rz of 6 μm.

[Production Example 2] Production Example of Developing Roll B By the same method as in Production Example 1, a conductive shaft and an elastic layer were produced, respectively, and urethane-based paint (manufactured by Nippon Polyurethane Co., Ltd., product) on the surface of this elastic layer Name "Nipporan 5196", 30% non-volatile) 100 parts fumed silica filler (Nippon Aerosil Co., Ltd., trade name "AEROSIL 200") and polyisocyanate cross-linking agent (Nippon Polyurethane Co., Ltd., commodity A coating solution to which 10 parts of the name “Coronate-L”) was added was applied once by spray coating, and heat-cured at 150 ° C. for 30 minutes to prepare a developing roll B. The developing roll B had a surface brightness of 121 and a surface roughness Rz of 6.0 μm.

[Production Example 3] Production Example of Developing Roll C A conductive shaft and an elastic layer were produced in the same manner as in Production Example 1, and the surface of the elastic layer was polished. 10 parts of a polyisocyanate crosslinking agent (trade name “Coronate-L”, manufactured by Nippon Polyurethane Co., Ltd.) is added to 100 parts of urethane-based paint (manufactured by Nippon Polyurethane Co., Ltd., trade name “Nipporan 5196”, nonvolatile content 30%). At the same time, spray coating was applied twice, and heat development was performed at 150 ° C. for 30 minutes to prepare a developing roll C. The developing roll C had a surface luminance of 230 and a surface roughness Rz of 0.7 μm.

[Production Example 4] Production Example of Developing Roll D A conductive shaft and an elastic layer were produced in the same manner as in Production Example 1, and a cylindrical grinding machine equipped with a GC # 120 grindstone was used for the surface of the elastic layer. Then, the roller surface was polished to prepare a developing roll D. The developing roll D had a surface brightness of 20 and a surface roughness Rz of 25 μm.

[Production Example 5] Production Example of Spherical Silica Fine Particles 1.0 mol of SiO _{2 of} silica powder (average particle size 2 μm, maximum particle size 60 μm) and metal silicon powder (average particle size 10 μm, maximum particle size 100 μm) 100 parts of mixed powder consisting of 8 moles and 50 parts of pure water were mixed, placed in a thin container, and continuously fed to a 2000 ° C. electric furnace. Hydrogen gas is introduced from the same direction as the feed of the mixed raw material, the hydrogen gas and the generated gas are sucked with an exhaust blower provided at the upper part in the opposite direction, further brought into contact with 400 Nm ³ / hr of air, and cooled with a bag filter. Silica fine particles were collected. The silica fine particles were classified with an air classifier. The obtained silica fine particles had Dv50 / Dv10 = 2.54, the volume average particle diameter of primary particles was 0.2 μm, and the sphericity was 1.12.

  To this silica fine particle, hexamethyldisilazane diluted with alcohol was added dropwise so that hexamethyldisilazane was 1% with respect to the silica fine particle, and heated at 70 ° C. for 30 minutes with vigorous stirring, then 140 ° C. Then, the solvent was removed and heat treatment was performed with vigorous stirring at 210 ° C. for 4 hours to obtain spherical silica fine particles 1 subjected to hydrophobic treatment. The obtained spherical silica fine particles 1 had a hydrophobicity of 70% and a bulk density of 110 g / l.

[Production Example 6] Production Example of Toner Containing Colored Resin Particles 1 Styrene 80.5 parts, n-butyl acrylate 19.5 parts, polymethacrylic acid ester macromonomer (trade name “AA6” manufactured by Toagosei Co., Ltd.) 0.5 parts, divinylbenzene 0.6 parts, t-dodecyl mercaptan 1.2 parts, and magenta pigment (trade name “CI Pigment Red 122” manufactured by Client Corporation) 5 parts, Charge-controlling resin (number average molecular weight = 7000, polymerized by 2-acrylamido-2-methylpropanesulfonic acid 2-acrylamide-2 part) by wet pulverization using Asada Iron Works, trade name “Picomil”) Weight average molecular weight = 22000, Mw / Mn = 3.1, manufactured by Fujikura Kasei Co., Ltd., trade name “FCAS748”) 3 parts, and ester compound (dipentaerythrito 10 parts) was added, mixed and dissolved to obtain a polymerizable monomer composition for the core.

  On the other hand, an aqueous solution of sodium hydroxide in which 6.2 parts of sodium hydroxide is dissolved in 50 parts of ion-exchanged water is gradually added with stirring to an aqueous solution of magnesium chloride in which 10.2 parts of magnesium chloride are dissolved in 250 parts of ion-exchanged water. A magnesium hydroxide colloidal dispersion was prepared.

  On the other hand, 2.0 parts of methyl methacrylate and 65 parts of water were mixed to obtain an aqueous dispersion of a polymerizable monomer for shell.

  To the magnesium hydroxide colloidal dispersion obtained as described above, the polymerizable monomer composition for core obtained as described above was charged at room temperature and stirred until the droplets became stable. . After the droplet was stabilized, 6 parts of t-butyl peroxy-isobutyrate (Nippon Yushi Co., Ltd., trade name “Perbutyl IB”) was added, and Ebara Milder (Ebara Seisakusho, model number “MDN303V type”) was used. Then, high shear stirring was performed for 30 minutes at a rotational speed of 15000 rpm to form smaller droplets of the polymerizable monomer mixture for the core.

  Magnesium hydroxide colloidal dispersion, in which droplets of the polymerizable monomer composition for the core are dispersed, is placed in a reactor equipped with a stirring blade, temperature rise is started, and the temperature is controlled to be constant at 95 ° C. did. After reaching a polymerization conversion rate of almost 100%, the water-soluble initiator (trade name “VA-086” = 2,2′-azobis, manufactured by Wako Pure Chemical Industries, Ltd.) was added to the aqueous dispersion of the polymerizable monomer for shell. [2-Methyl-N- (2-hydroxyethyl) -propionamide]) 0.3 parts was dissolved and added to the reactor. After the polymerization was continued for 4 hours, the reaction was stopped to obtain an aqueous dispersion of core-shell type colored polymer particles.

  The aqueous dispersion of the obtained colored polymer particles was washed with sulfuric acid (25 ° C., 10 minutes) while stirring at room temperature to adjust the pH of the system to 4.5. After the aqueous dispersion was filtered and dehydrated, 250 parts of ion exchanged water at 40 ° C. was added to obtain an aqueous dispersion, the aqueous dispersion was filtered and dehydrated, and then washed with ion exchanged water at 40 ° C. again. went.

  By drying, colored resin particles 1 were obtained. To 100 parts of the obtained colored resin particles, 1 part of spherical silica fine particles having a volume average particle size of 0.2 μm obtained in Production Example 5 (sphericity = 1.12, degree of hydrophobicity = 70%) as an external additive And stirring with a Henschel mixer for 5 minutes at a rotational speed of 1200 rpm (peripheral speed = 34.5 m / s). Further, while cooling the stirrer jacket with water, silica having a number average particle size of 12 nm of primary particles (Japan) Part 1 of Aerosil, trade name “R-104”, degree of hydrophobicity = 45%), silica fine particles with a primary particle number average particle size of 50 nm (made by Clariant, trade name “HDK-H05TX”, degree of hydrophobicity = 80%) 0.5 part was added and stirred at 1400 rpm for 10 minutes to prepare a toner having an external additive coverage of 90.8%. Table 1 shows the characteristics of the obtained toner (magenta toner).

[Production Example 7] Production Example of Toner Containing Colored Resin Particles 2 In Production Example 6, a charge control resin obtained by polymerizing 7% 2-acrylamido-2-methylpropanesulfonic acid (number average molecular weight = 8000, weight average molecular weight) = 24000, Mw / Mn = 3.0, manufactured by Fujikura Kasei Co., Ltd., trade name “FCA626N”), and the others were carried out in the same manner as in Production Example 6. In this manner, a toner containing the colored resin particles 2 and having an external additive coverage of 93.7% was prepared.

[Production Example 8] Production Example of Toner Containing Colored Resin Particles 3 In Production Example 6, the same procedure as in Production Example 6 was carried out except that 3 parts of the charge control resin was changed to 1 part. In this way, a toner containing the colored resin particles 3 and having an external additive coverage of 92.3% was prepared.

[Production Example 9] Production Example of Toner Containing Colored Resin Particles 4 Production Example 6 was carried out in the same manner as in Production Example 6 except that 3 parts of the charge control resin was changed to 7 parts. In this way, a toner containing the colored resin particles 4 and having an external additive coverage of 95.1% was prepared.

[Example 1]
Using a commercially available non-magnetic one-component printer (Oki Data Corporation, model name “Microline 5300”), the black toner cartridge is filled with the magenta toner containing the colored resin particles 1 prepared in Production Example 6, and Then, the developing roll A of Production Example 1 was mounted on a cartridge and evaluated by the above method. The results are shown in Table 1.

[Example 2]
Using the same non-magnetic one-component printer as in Example 1, the black toner cartridge is filled with the toner containing the colored resin particles 2 prepared in Production Example 7, and the developing roll B produced in Production Example 2 is used as the cartridge. And evaluated by the above method. The results are shown in Table 1.

[Comparative Example 1]
Using the same non-magnetic one-component printer as in Example 1, the position of the black toner cartridge is filled with the toner containing the colored resin particles 3 prepared in Production Example 8, and the developing roll A produced in Production Example 1 is used as the cartridge. And evaluated by the above method. The results are shown in Table 1.

[Comparative Example 2]
Using the same non-magnetic one-component printer as in Example 1, the black toner cartridge is filled with the toner containing the colored resin particles 4 prepared in Production Example 9, and the developing roll B produced in Production Example 2 is used as the cartridge. And evaluated by the method described above. The results are shown in Table 1.

[Comparative Example 3]
Using the same non-magnetic one-component printer as in Example 1, the black toner cartridge is filled with the toner containing the colored resin particles 1 prepared in Production Example 6, and the developing roll C produced in Production Example 3 is used as the cartridge. And evaluated by the above method. The results are shown in Table 1.

[Comparative Example 4]
Using the same non-magnetic one-component printer as in Example 1, the black toner cartridge is filled with the toner containing the colored resin particles 2 prepared in Production Example 7, and the developing roll D produced in Production Example 4 is used as the cartridge. And evaluated by the above method. The results are shown in Table 1.

  From the results in Table 1, the following can be understood. Comparative Examples 1 and 2 in which the absolute value of the charge amount of the toner on the photoreceptor is outside the range of the present invention are inferior in cleaning property and durability, and in particular, Comparative Example 1 has a low print density. Further, Comparative Examples 3 and 4 in which the surface brightness and the surface roughness Rz of the developing roll are outside the scope of the present invention are inferior in cleaning properties and durability.

  On the other hand, the surface brightness of the developing roll is 30 to 220, the surface roughness Rz is 1 to 20 μm, and the colored resin particles have a volume average particle diameter of 4 to 10 μm and an average circularity of 0.950 to 0.995. Examples 1 and 2 in which the toner containing the toner and the external additive is used, and the absolute value of the charge amount of the toner on the surface of the photoreceptor is 10 to 80 μC / g, the print density is high, the cleaning property and It has good durability.

  The image forming method of the present invention can be used for forming an image using an image forming apparatus such as an electrophotographic copying machine or a laser beam printer.

It is explanatory drawing which shows an example of the image forming apparatus with which the image forming method of this invention is applied. It is an enlarged schematic diagram of a photosensitive drum and a cleaning blade. It is sectional drawing of a developing roll. It is explanatory drawing which shows a surface luminance value measuring apparatus.

Explanation of symbols

1: photosensitive drum, 2: charging roll, 3: laser light irradiation device,
4: development roll, 5: toner layer thickness regulating member, 6: supply roll,
7: casing, 8: toner, 9: developing device,
10: transfer roll, 11: transfer material, 12: cleaning blade,
13: fixing roll, 14: pressure roll,
41: conductive shaft, 42: elastic layer,
401: CCD camera, 402: illumination lamp, 403: microscope main body,
404: Voltage regulator, 405: Computer, 406: Objective lens.

Claims (4)

Following steps 1-6:
(1) Charging step 1 for charging the surface of the photoreceptor;
(2) an exposure step 2 in which an electrostatic latent image is formed by performing image exposure on the surface of the charged photoreceptor;
(3) A developing step 3 in which the electrostatic latent image on the surface of the photoreceptor is contact-developed with toner supplied on the developing roll to form a toner image;
(4) Transfer process 4 for transferring the toner image on the surface of the photoreceptor onto a transfer material;
(5) a fixing step 5 for fixing the toner image transferred onto the transfer material; and (6) a cleaning step 6 for removing toner remaining on the surface of the photoconductor with a cleaning blade in contact with the surface of the photoconductor.
In an image forming method including:
(I) The developing roll has a surface brightness of 30 to 220 and a surface roughness Rz of 1 to 20 μm,
(II) The toner contains colored resin particles having a volume average particle diameter of 4 to 10 μm and an average circularity of 0.950 to 0.995 and an external additive, and
(III) An image forming method, wherein the absolute value of the charge amount of the toner on the surface of the photoreceptor is 10 to 80 μC / g.   2. The image forming method according to claim 1, wherein the developing roll has a surface brightness of 60 to 140 and a surface roughness Rz of 3 to 8 [mu] m. ^2. The image forming method according to claim 1, wherein the amount of toner on the surface of the photoconductor after development is 0.3 to 0.8 mg / cm < ² >.   The image forming method according to claim 1, wherein the toner has a covering ratio of 60 to 140% with the external additive of the colored resin particles.

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