JP5244545B2 - Toner for electrophotography and image forming method using the same - Google Patents

Description

  The present invention is used for developing an electrostatic latent image formed by, for example, electrophotography, electrostatic recording method, electrostatic printing method, etc., and suitable for non-magnetic toner or magnetic toner, The present invention relates to the image forming method used.

  In general, in electrophotography, electrostatic recording method, electrostatic printing method, etc., the surface of a latent image carrier (photoreceptor) made of a photoconductive photoreceptor or dielectric is charged by corona charging or the like, Furthermore, the electrostatic latent image formed by exposing the surface of the photoreceptor by irradiating a laser or LED is visualized using a developer containing toner, or the electrostatic latent image is visualized by reversal development. A high-quality image is obtained by forming a thin toner layer on the photoreceptor and transferring it to a transfer target.

Organic photoreceptors and selenium photoreceptors are known as photoreceptors, but in recent years, with the enhancement of durability of image forming apparatuses, amorphous silicon having an amorphous silicon-based photosensitive layer on the surface of a conductive substrate. Photoconductors (hereinafter referred to as “a-Si photoconductors”) have come to be used.
The lifetime of the organic photoreceptor is approximately 50,000 in terms of the number of printed sheets, whereas the a-Si photoreceptor has an extremely high surface hardness (for example, Vickers hardness of 1500 to 2000 HV). ), Its lifetime reaches 500,000 or more, and it has excellent durability.
When an image is formed using a photoreceptor such as an organic photoreceptor or an a-Si photoreceptor, an image is formed by sequentially performing each process such as charging, exposure, development (reversal development), transfer, cleaning, and charge removal. .

  Since the a-Si photoconductor described above is excellent in durability, it is not necessary to replace the photoconductor until the lifetime of the image forming apparatus, and it is possible to reduce man-hours and downtime for replacing members constituting the image forming apparatus. However, due to the influence of discharge products generated in processes such as charging due to repeated use, the resistance of the surface of the photoreceptor is lowered in an H / H environment, and a phenomenon called image flow is likely to occur. In addition, a toner component and a paper powder component such as paper used as a transfer target may adhere firmly to the surface of the photoreceptor, resulting in an image defect in the attached portion.

Therefore, the surface of the photoconductor is polished using the toner collected in the cleaning process to remove the photoconductor adhering material such as a discharge product, a toner component, and a paper powder component adhering to the surface of the photoconductor. Occurrence of image defects is suppressed.
However, if the surface of the photosensitive member is excessively polished, the photosensitive layer is excessively shaved, and the photosensitive layer may be insufficiently thick due to repeated use over a long period of time, thereby causing image defects. Therefore, the toner used in the image forming apparatus provided with the a-Si photosensitive member is required to have chargeability and durability that can withstand long-term use corresponding to the lifetime of the photosensitive member. In many cases, it is necessary to have an appropriate polishing property that prevents adhesion of a photoreceptor adhering to the surface of the photoreceptor that causes image defects and that can be polished to such an extent that the surface of the photoreceptor is not excessively shaved.

  As the toner, usually, a thermoplastic resin as a binder (binder resin) is mixed with a colorant, a dye or pigment as a charge control agent, a wax as a release agent, and the resulting toner is used as a magnetic toner. When used, a magnetic material is added, kneaded, pulverized, and classified to obtain particles (toner base particles) having an average particle size of 5 to 15 μm. Then, for the purpose of imparting fluidity to the toner, controlling charging of the toner, or improving the cleaning property, an inorganic fine powder such as silica or an inorganic metal fine powder such as titanium oxide is added to the toner base particles. Often externally added.

In recent years, the toner has been required to have a small particle size due to the increase in image quality. By making the toner have a small particle size, there is a tendency for the letter scattering and fine line reproducibility to be improved. However, particularly in the pulverized toner, the ultra fine particles having a particle diameter of 3 μm or less generated when pulverized to a small particle diameter may contaminate the carrier and the developing roller. For example, since the ultrafine powder particles have a strong adhesive force, if the ultrafine powder particles adhere to the developing roller, they are not developed on the photoconductor during development and are likely to remain on the developing roller. If this is repeated, ultra fine particles having strong adhesion force are unevenly distributed on the developing roller. As a result, the toner thin layer is not sufficiently formed on the developing roller, the developability is lowered, and the image density is lowered. .
On the other hand, when the toner adheres to the carrier, it is easy to cause fogging or toner scattering due to long-term use.

  As a countermeasure against toner adhesion to the developing roller, for example, Patent Document 1 discloses a developing device that controls the bias voltage between the developing roller and the supply roller. According to the developing device described in Patent Document 1, toner adhesion to the developing roller can be suppressed, but this is a countermeasure on the apparatus side, and no countermeasure on the toner side is taken.

  In addition, since the ultrafine powder particles have a larger specific surface area than those of other particle sizes, they tend to adsorb moisture particularly in a high temperature and high humidity environment (H / H environment). As a result, the charge amount of the toner decreases, and fog is likely to occur when an image is formed.

By the way, as a dry development method currently in practical use, a two-component development method using a two-component developer composed of a carrier such as toner (non-magnetic toner) and iron powder, and a magnetic material without using a carrier. A magnetic one-component development system using a toner (magnetic toner) contained therein as a developer is known.
As a method for developing an electrostatic latent image, a number of development methods such as the magnetic brush method described in Patent Document 2, the cascade method described in Patent Document 3, the powder cloud method, and the fur brush development method are known. ing. Among these, a magnetic brush method using a two-component developer, a cascade method, and the like have been widely put into practical use.

In a color copying machine using a two-component developer, a magnetic roller for holding the developer, and a developing roller for transferring only the toner from the developer held on the magnetic roller to form a thin toner layer on the surface, And an image forming apparatus including a photoconductor provided at a predetermined interval from the developing roller, and the toner is ejected from the toner thin layer formed on the surface of the developing roller to the photoconductor A so-called touch-down development method (hybrid development method) is known in which an electrostatic latent image is developed as a toner image.
In the touch-down development method, a one-drum color superposition method in which a plurality of color images are sequentially formed on a photoreceptor has been studied as a high-speed image forming method. In this method, it is possible to form a color image with little color misregistration by accurately superimposing toner on the photoconductor, and it is possible to cope with high image quality of color.

Furthermore, in recent years, attention has been paid to a tandem method in which a plurality of photoconductors corresponding to the color of toner are used to form a color image in synchronization with the feeding of the transfer member and to superimpose colors on the transfer member. Although this method has an advantage of high speed, there is a problem that the image forming apparatus becomes large because the electrophotographic process members corresponding to the respective colors have to be arranged side by side.
Therefore, as a countermeasure against this problem, there has been proposed a small tandem image forming apparatus in which a compact image forming unit is arranged by narrowing the interval between the photosensitive members.

In a small tandem image forming apparatus, it is advantageous to make the developing device a vertical type in order to minimize the size of the image forming unit in the width direction. That is, it is desirable to arrange the developing device in the upper direction of the photosensitive member.
As such an image forming apparatus, for example, an image forming apparatus in which a developing device, a transfer device, and the like are efficiently arranged inside the apparatus is known, but such an image forming apparatus can be downsized, It was necessary to slide the developing device and the transfer device, and it was easy to make the structure complicated.

  Among small tandem image forming apparatuses, an image forming apparatus that employs a touch-down developing method is a non-contact type because the photosensitive member is provided at a certain distance from the developing roller on which the toner thin layer is formed. For this reason, compared to the contact type, there is less adhesion of toner components, carriers, etc. to the photoconductor, and damage to the photoconductor by a magnetic brush or the like, and high image quality is possible. Further, as a charging method in the developing device, a two-component method by mixing with a carrier is adopted, and the toner can be quickly charged to a desired charge amount particularly in high density printing or continuous printing. Therefore, it is particularly effective in a model in which the volume of the developing device is small due to downsizing.

  However, when the touch-down development method is employed, the developing roller is often disposed below the magnetic roller in order to achieve downsizing, and the developer is easily stressed. As a result, there has been a problem that the external additive is buried in the surface of the toner base particles due to long-term printing (printing durability), the toner is charged up, and the toner adheres to the developing roller. When toner adheres to the developing roller, the developability deteriorates, and as a result, the image density tends to decrease. Such a phenomenon is considered to be caused by the following.

  That is, for example, in the case of a small tandem page printer that employs a touch-down development method, a toner charged to a desired charge amount is supplied from the magnetic roller to the developing roller between the magnetic roller and the developing roller, and at the same time, the developing roller The toner remaining on the developing roller without flying to the photosensitive member is collected by the magnetic roller, and fresh toner is always supplied to the developing roller. However, in order to reduce the size of the apparatus, the developing roller is disposed below the magnetic roller, so that the toner remaining on the developing roller is collected on the magnetic roller against gravity, and the collection is likely to be difficult. . Further, when the toner is charged up, the mirror image force on the developing roller is increased, so that the toner is easily attached, and the toner is more difficult to collect. As a result, the same toner always stays on the developing roller, the charge-up is further accelerated, and the toner adheres firmly to the developing roller. As described above, due to the recent increase in image quality, there is a tendency to reduce the particle diameter of toner, and the smaller the particle diameter, the more noticeable adhesion to the developing roller.

  As a countermeasure against toner adhesion to the developing roller, a method of controlling the bias voltage between the developing roller and the supply roller (magnetic roller) as described in Patent Document 1 is known. Since it is provided so as to be in pressure contact with the developing roller, and a one-component developer using toner as a developer is used, it is difficult to apply to an image forming apparatus employing a touch-down developing method.

  As described above, in the case of the two-component development method using a two-component developer, it is possible to form a relatively stable and high-quality image in the initial stage. As a result, the image density decreases, or the toner adheres to the carrier and fogging occurs, which may make it difficult to obtain a high-quality image.

On the other hand, as a magnetic one-component developing system, for example, Patent Document 4 discloses a developing method using conductive magnetic toner. In the developing method described in Patent Document 4, a conductive magnetic toner is held on a cylindrical conductive developing roller having magnetism inside, and the conductive magnetic toner is applied to an electrostatic latent image formed on the surface of a photoreceptor. This is a method of developing a toner image by bringing it into contact. During development, a conductive path is formed by the toner between the surface of the photosensitive member and the surface of the developing roller, and the charge is guided to the toner from the developing roller through the conductive path, and between the image portion of the electrostatic latent image. Due to the Coulomb force, the toner adheres to the image portion and forms a toner image.
In the method described in Patent Document 4, since the toner is conductive, it is difficult to electrostatically transfer the toner image formed on the photosensitive member to the transfer target (for example, paper) using an electric field. there were. In addition, in each step of image formation, defects derived from conductive toner are likely to occur, and it has been difficult to form high-quality images over a long period of time. In addition, the photoconductor may be leak-destructed electrically.

As a magnetic one-component development system, for example, Patent Document 5 discloses a development method using an insulating toner. The developing method described in Patent Document 5 is generally called a magnetic one-component jumping developing method, and is provided with a developing roller facing the photoconductor and at a predetermined interval. The developing roller has a sleeve with a built-in magnet roller, conveys toner by rotation of the sleeve, and passes through a gap between the sleeve and the magnetic blade, thereby forming a thin toner layer on the surface of the developing roller. Then, the charged toner flies to the electrostatic latent image formed on the surface of the photoreceptor to develop the toner image.
The magnetic one-component jumping development system can suppress the occurrence of fog even when used for a long period of time, so that a high-quality image can be formed over a long period of time. Further, by adopting the developing system, the developing device provided in the image forming apparatus can be downsized, and a simple configuration can be achieved.

  In recent years, in the market of copying machines, printers, and the like based on electrophotography and electrostatic printing, printing speed and apparatus size have been remarkably advanced. As the printing speed increases, it is desirable that the image characteristics matched to the printing speed, that is, the charging characteristics are more stabilized. In addition, medium- and low-speed machines that are becoming smaller in size are required to have good initial charging and stable charging characteristics over a long period of time because the warm-up time after turning on the power is short. That is, it is required to form a uniform toner thin layer on the developing roller stably for a long period of time.

  In addition, as office equipment such as printers and copiers are moving toward higher speeds and miniaturization, high resolution, high image quality, and high durability have come to be required. Formation of a thin toner layer on the developing roller is important for high resolution, high image quality, high durability, and response to environmental fluctuations. In particular, in a developing roller that employs a magnetic one-component jumping development method and has a relatively small ten-point average roughness (Rz) of the sleeve, toner thin layer formation affects high image quality and high durability.

However, in high-speed machines and small machines that adopt the magnetic one-component jumping development method, ensuring long-term stability of the toner thin layer formation on the developing roller is long-term use, environmental fluctuations (especially low temperature and low humidity environment), It was difficult due to factors such as quick warm-up time. As a result, the toner thin layer on the developing roller may be disturbed or the toner thin layer may be missing in the form of vertical streaks, and a stable image can be formed over a long period of time. There was a problem that image quality and high durability could not be realized.
For example, Patent Document 6 discloses a toner capable of forming a stable image over a long period of time, but it is not always satisfactory.
JP 2001-109242 A U.S. Pat. No. 2,874,063 US Pat. No. 2,618,552 U.S. Pat. No. 3,909,258 Japanese Patent Laid-Open No. 55-18656 JP 2006-184748 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to realize an electrophotographic toner that can suppress a decrease in image density over a long period of time and can stably form a high-quality image, and an image forming method using the same. And

  As a result of intensive studies, the present inventors specify the number distribution ratio of particles having a particle diameter of 4.0 μm or less, the ratio of particles having a particle diameter of 3.0 μm or less, and the standard deviation of the volume distribution. As a result, it has been found that the developability of the toner is improved and that moisture adsorption can be suppressed even at high temperature and high humidity. Such a toner can be suitably used as a one-component developer or a two-component developer, and adopts a one-component jumping development method or a touch-down development method, and an image forming apparatus that meets the demands for speeding up and downsizing. The present invention has been completed by finding that a high-quality image can be stably formed over a long period of time.

  That is, the electrophotographic toner of the present invention is used in an image forming apparatus having an amorphous silicon photoreceptor, and the electrophotographic toner in which an external additive is added to toner base particles containing at least a binder resin. The ratio of the number distribution of particles having a particle diameter of 4.0 μm or less in all particles contained in the photographic toner is 8.0% or less, and the standard deviation (SD) of the volume distribution is 1.25 or less. In the externally added toner, the ratio of particles having a particle size of 3.0 μm or less is 5.0% or less, and the average circularity of particles having a particle size of 3 to 10 μm is 0.945 or more. It is characterized by.

  In addition, the electrophotographic toner of the present invention comprises a magnetic roller that stirs a developer composed of a non-magnetic toner and a magnetic carrier and forms a spike of the developer on the surface; A developing roller for forming a thin layer of non-magnetic toner, and an amorphous silicon photoconductor provided on the surface of the developing roller at a certain distance from the developing roller. Image formation in which non-magnetic toner is ejected from the thin layer formed on the surface of the developing roller onto the surface of the formed amorphous silicon photoconductor to develop the electrostatic latent image on the surface of the amorphous silicon photoconductor as a toner image. It is suitable as the non-magnetic toner in the apparatus.

The electrophotographic toner of the present invention is provided with a developing roller that stirs a developer composed of a non-magnetic toner and a magnetic carrier and forms a spike of the developer on the surface, and is opposed to the developing roller. An amorphous silicon photoconductor having an electrostatic latent image formed on the surface, and the amorphous silicon photoconductor is brought into contact with a developer spike formed on the surface of the developing roller so that the surface of the amorphous silicon photoconductor is static. It is suitable as the non-magnetic toner in an image forming apparatus that develops an electrostatic latent image as a toner image.
Further, the content of the nonmagnetic toner in 100% by mass of the developer is preferably 1 to 20% by mass.

  Further, the electrophotographic toner of the present invention includes a developing roller for forming a thin layer of magnetic toner on the surface, and amorphous silicon on which an electrostatic latent image is formed at a certain distance from the developing roller. A magnetic toner is allowed to fly from the thin layer formed on the surface of the developing roller onto the surface of the amorphous silicon photosensitive member on which the electrostatic latent image is formed. It is suitable as the magnetic toner in an image forming apparatus that develops a latent image as a toner image.

  The image forming method of the present invention also includes a charging step for charging the surface of the amorphous silicon photoconductor, an exposure step for exposing the surface of the amorphous silicon photoconductor to form an electrostatic latent image, a non-magnetic toner and a magnetic carrier. The developer consisting of the above is agitated to form developer spikes on the surface of the magnetic roller, and a thin layer of nonmagnetic toner is formed on the surface of the developer roller in contact with the spiked developer. A development step of developing non-magnetic toner on the surface of the silicon photoconductor to develop the electrostatic latent image as a toner image, and a transfer step of transferring the toner image from the amorphous silicon photoconductor to the transfer body, The electrophotographic toner of the present invention is used as the nonmagnetic toner.

  The image forming method of the present invention also includes a charging step for charging the surface of the amorphous silicon photoconductor, an exposure step for exposing the surface of the amorphous silicon photoconductor to form an electrostatic latent image, a non-magnetic toner and a magnetic carrier. A developing step of stirring the developer to form developer spikes on the surface of the developing roller, and contacting the amorphous silicon photoreceptor with the developer spikes to develop the electrostatic latent image as a toner image; And a transfer step of transferring the toner image from the amorphous silicon photosensitive member to the transfer target, and the electrophotographic toner of the present invention is used as the nonmagnetic toner.

Further, the image forming method of the present invention includes a charging step for charging the surface of the amorphous silicon photoconductor, an exposure step for exposing the surface of the amorphous silicon photoconductor to form an electrostatic latent image, and a surface formed on the surface of the developing roller. The magnetic toner is ejected from the thin layer of the magnetic toner onto the surface of the amorphous silicon photoconductor to develop the electrostatic latent image as a toner image, and the toner image is transferred from the amorphous silicon photoconductor to the transferred material. The electrophotographic toner of the present invention is used as the magnetic toner.
The developing roller has a sleeve having a ten-point average roughness (Rz) of 2.0 to 8.0 μm on the surface, and the sleeve is preferably made of stainless steel.

According to the electrophotographic toner of the present invention and the image forming method using the same, it is possible to suppress a decrease in image density over a long period of time and to stably form a high-quality image.
Further, the electrophotographic toner of the present invention can be suitably used as a one-component developer or a two-component developer.

Hereinafter, the present invention will be described in detail.
[Electrophotographic toner]
The electrophotographic toner of the present invention (hereinafter simply referred to as “toner”) is used in an image forming apparatus having an amorphous silicon photoreceptor (a-Si photoreceptor). The toner includes toner mother particles, which will be described later, particles having an external additive attached to the toner mother particles, and external additives that are free without being attached to the toner mother particles. In the present invention, “externally added toner” is a generic term for particles having an external additive attached to toner base particles and particles having no external additive (toner base particles).

  In the toner of the present invention, the ratio of the number distribution of particles having a particle diameter of 4.0 μm or less (hereinafter referred to as “fine powder particles”) among all particles contained in the toner is 8.0% or less. .5% or less is preferable. If the ratio of the number distribution of fine powder particles is 8.0% or less, it is possible to suppress the toner charge amount distribution from being broad, maintain good developability even during long-term printing (printing durability), and image density. Can be suppressed.

  The toner of the present invention has a standard deviation (SD) of volume distribution of 1.25 or less, preferably 1.24 or less. When SD is 1.25 or less, it is possible to suppress the toner particle size distribution and charge amount distribution from becoming broad, maintain good developability even in printing durability, and suppress the decrease in image density.

The ratio of the number distribution of fine particles and the SD of the toner can be obtained as follows.
Using a particle size distribution measuring device “Coulter Counter Multimizer 3” manufactured by Beckman Coulter, using Isoton II manufactured by Beckman Coulter as an electrolytic solution, using a 100 μm aperture as an aperture diameter, a toner particle size distribution (number distribution) Or volume distribution).
Specifically, 10 mg of a measurement sample (toner) is added to a solution obtained by adding a small amount of a surfactant to the electrolytic solution, and dispersion processing is performed with an ultrasonic disperser, and the particle size distribution measurement is performed on the solution in which the measurement sample is dispersed. The number distribution or volume distribution of the sample particle diameter is obtained by measuring with an apparatus. The ratio of particles having a particle size of 4.0 μm or less is determined from the obtained number distribution. On the other hand, the toner SD is obtained from the volume distribution.

In the toner of the present invention, the ratio of particles having a particle size of 3.0 μm or less (hereinafter referred to as “ultra fine particles”) in the externally added toner is 5.0% or less, and is 4.0% or less. Preferably there is. When the ratio of the ultrafine particles is 5.0% or less, the influence of the ultrafine particles can be reduced, so that the charge-up phenomenon of the toner can be suppressed and the toner can be prevented from being charged and aggregated on the developing roller. Accordingly, the toner thin layer can be satisfactorily formed on the developing roller, and as a result, image unevenness that is likely to occur particularly when printing a solid image can be reduced, and image defects can be suppressed.
In addition, since the ultrafine powder particle has a large specific surface area as compared with particles having other particle sizes, it is easily adsorbed with moisture present in the air. In particular, in a high-temperature and high-humidity environment, it is easy to adsorb moisture, and as a result, the charge amount of the toner decreases and the charge amount distribution tends to become broad, causing fogging and decreasing the image density. Prone to defects. However, in the case of the toner of the present invention, since the ratio of the ultrafine particles is 5.0% or less, the amount of moisture adsorbed in the entire toner can be reduced. Therefore, a decrease in toner charge amount can be suppressed even in a high-temperature and high-humidity environment, thereby preventing fogging and a decrease in image density.

In addition, since the ratio of the ultrafine powder particles is as extremely low as 5.0% or less, an increase in the mirror image force of the developing roller can be suppressed when used in an image forming apparatus. Therefore, toner adhesion to the developing roller can be reduced. In particular, when the toner is mixed with a carrier to form a two-component developer and used in a miniaturized tandem image forming apparatus employing a touch-down development method, the residual toner on the developing roller can be efficiently collected on the magnetic roller. Further, toner adhesion to the developing roller can be suppressed, and a decrease in image density can be suppressed.
Furthermore, the adhesion of the toner to the carrier can be reduced because the ratio of the ultra fine particles is as low as 5.0% or less. Therefore, fogging and toner scattering can be suppressed over a long period of time.

The ratio of ultrafine particles can be determined as follows.
Contrast the photograph of the toner magnified by the scanning electron microscope with the photograph of the toner mapped by elemental analysis such as X-ray microanalyzer (XMA) attached to the scanning electron microscope. The number of externally added toners to be measured is measured, and the number of ultrafine particles whose particle diameter is measured to be 3.0 μm or less is counted. Observation is performed on 1000 randomly selected externally added toners, and the number of ultrafine particles having a particle size of 3.0 μm or less is counted to determine the ratio of the ultrafine particles.
In the mapped toner, particles that are considered to be external additives are not counted.

  In the toner of the present invention, the average circularity of particles having a particle diameter of 3 to 10 μm is 0.945 or more, and preferably 0.947 or more. If the average circularity is 0.945 or more, the shape of the toner approaches a true sphere, so that an increase in the coefficient of contact friction with the a-Si photoreceptor can be suppressed. Accordingly, when the toner is peeled off from the a-Si photosensitive member at the time of transferring the toner image, the toner can be easily peeled off, occurrence of a transfer omission or the like can be suppressed, and transfer efficiency can be improved.

  By the way, since the a-Si photoreceptor is likely to adhere to the surface of the photoreceptor, such as discharge products and toner components, the surface of the photoreceptor is usually polished with toner to remove the photoreceptor deposit. Since the surface hardness is high as described above, the toner is required to be excellent in abrasiveness. However, if the surface of the photoconductor is excessively polished, the surface may be excessively shaved and image defects may be caused. Therefore, it is desirable that the toner has an appropriate polishing property that can prevent the adhesion of the photoreceptor adhering material to the surface of the photoreceptor and can be polished to such an extent that the surface of the photoreceptor is not excessively scraped.

  If the average circularity of particles having a particle diameter of 3 to 10 μm is 0.945 or more, an increase in the contact friction coefficient with the a-Si photosensitive member can be suppressed while exhibiting an appropriate polishing property. It is possible to suppress excessive shaving. Accordingly, it is possible to suppress the adhesion of the photoreceptor adhering material without causing an image defect due to excessive shaving of the photoreceptor.

The average circularity of particles having a particle diameter of 3 to 10 μm can be determined as follows.
Using a flow-type particle image analyzer “FPIA-3000” manufactured by Sysmex Corporation, measurement is performed on particles having a circle-equivalent diameter of 0.60 to 400 μm in an environment of a temperature of 23 ° C. and a humidity of 60 RH%. And the circularity of the measured particle | grain is calculated | required from following formula (1), and also the value which remove | divided the sum total of circularity by the total number of particles in particle | grains with a circle equivalent diameter of 3-10 micrometers is made into circularity. Measurement is performed on 1000 to 1500 particles, and the calculated value is defined as the average circularity.
Circularity = perimeter of a circle having the same projected area as the particle image / perimeter of the projected image of the particle (1)

In order to obtain such a toner, the type and amount of each component, manufacturing conditions, etc. may be adjusted. Hereinafter, each component will be described.
The toner of the present invention is obtained by adding an external additive to toner base particles. The toner base particles contain at least a binder resin. Moreover, a coloring agent, a charge control agent, a mold release agent, etc. are contained as needed.

<Toner base particles>
(Binder resin)
Examples of the binder resin include polystyrene resin, acrylic resin, styrene-acrylic copolymer, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, and polyvinyl alcohol. And thermoplastic resins such as vinyl resins, vinyl ether resins, N-vinyl resins, and styrene-butadiene resins. Of these, polystyrene resins and polyester resins are preferable.

  The polystyrene resin may be a styrene homopolymer or a copolymer with another copolymerizable monomer copolymerizable with styrene. Other copolymerization monomers include p-chlorostyrene; vinyl naphthalene; ethylene unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl halides such as vinyl chloride, vinyl bromide, and vinyl fluoride; vinyl acetate , Vinyl esters such as vinyl propionate, vinyl benzoate, vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate , (Meth) acrylic esters such as phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate; other acrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide Vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidene N-vinyl compounds such as These may be used alone or in combination of two or more with a styrene monomer.

Examples of the polyester resin include those obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component. The following are mentioned as a component used when synthesize | combining a polyester-type resin.
As the alcohol component, a bivalent or trivalent or higher alcohol component is preferable. Specifically, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butane. Diol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. Diols; bisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; sorbitol, 1,2,3,6-hexane Trol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2- Trivalent or higher alcohols such as methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene can be exemplified.

  On the other hand, the carboxylic acid component is preferably a divalent or trivalent or higher carboxylic acid component, and specific examples thereof include a divalent or trivalent carboxylic acid, an acid anhydride thereof, or a lower alkyl ester thereof. Examples of such carboxylic acids include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malon Acid, or n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid, Divalent carboxylic acids such as alkyl or alkenyl succinic acids such as isododecenyl succinic acid; 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid, 2,5,7 -Naphthalenetricarboxylic acid, 1,2,4-naphthalenetricar Acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, Examples thereof include trivalent or higher carboxylic acids such as tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empole trimer acid.

  Moreover, it is preferable that the softening point of a polyester-type resin is 80-150 degreeC, More preferably, it is 90-140 degreeC.

Further, a thermosetting resin may be used as the binder resin. The thermosetting resin partially has a cross-linked structure, but by introducing the cross-linked structure, the storage stability, shape retention, or durability of the toner can be further improved without deteriorating the toner fixability. Can be improved. Therefore, it is not necessary to use 100 parts by mass of the thermoplastic resin as the binder resin, and a crosslinking agent may be added, or a part of the thermosetting resin may be used in combination.
Examples of the thermosetting resin include epoxy resins and cyanate resins, and specifically, bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, novolac type epoxy resins, polyalkylene ether type epoxy resins. , Cycloaliphatic epoxy resins, cyanate resins and the like. These may be used individually by 1 type, or may be used in combination of 2 or more type.

The glass transition point (Tg) of the binder resin is preferably 50 to 65 ° C, more preferably 50 to 60 ° C. When Tg is 50 ° C. or higher, the obtained toner can be prevented from fusing with each other in the developing device, so that the storage stability can be maintained. Further, since the resin strength can be maintained, toner adhesion to the photoreceptor can be suppressed. On the other hand, when Tg is 65 ° C. or lower, it is possible to suppress a decrease in low-temperature fixability of the toner.
In addition, Tg of binder resin can be calculated | required from the change point of specific heat using a differential scanning calorimeter (DSC). More specifically, it is obtained by measuring an endothermic curve using a differential scanning calorimeter “DSC-6200” manufactured by Seiko Instruments Inc. as a measuring device. 10 mg of a measurement sample was put in an aluminum pan, an empty aluminum pan was used as a reference, and the measurement temperature range was 25 to 200 ° C. and the temperature increase rate was 10 ° C./min. Tg is obtained from the endothermic curve.

(Coloring agent)
The colorant adjusts the color tone of the toner, and a known colorant such as a pigment such as carbon black and a dye such as acid violet can be used. As the colorant, a known pigment for color toner can be used.
The content of the colorant is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the binder resin.

(Charge control agent)
The charge control agent remarkably improves the toner charge level and charge rise characteristics (an index of whether or not the toner is charged to a constant charge level in a short time), and imparts characteristics such as excellent durability and stability to the toner. It is formulated for this purpose.
When the toner is positively charged for development, a positively chargeable charge control agent may be added. When the toner is negatively charged for development, a negatively chargeable charge control agent may be added.

  Examples of positively chargeable charge control agents include pyridazine, pyrimidine, pyrazine, orthooxazine, metaoxazine, paraoxazine, orthothiazine, metathiazine, parathiazine, 1,2,3-triazine, 1,2,4-triazine, 1, 3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine, 1,3,4-thiadiazine, 1,3,5-thiadiazine, 1,2, 3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6-oxatriazine, 1,3,4,5-oxatriazine, phthalazine, Azine compounds such as quinazoline and quinoxaline; azine fast red FC, azine fast red 12BK, azine violet BO, azine Direct dyes composed of azine compounds such as Raun 3G, azine light brown GR, azine dark green BH / C, azine deep black EW and azine deep black 3RL; nigrosine compounds such as nigrosine, nigrosine salt, nigrosine derivatives; nigrosine BK, nigrosine NB Examples include acidic dyes composed of nigrosine compounds such as Nigrosine Z; metal salts of naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; quaternary ammonium salts such as benzylmethylhexyldecylammonium and decyltrimethylammonium chloride. These may be used individually by 1 type, or may be used in combination of 2 or more type. In particular, the nigrosine compound is suitable as a positively chargeable charge control agent from the viewpoint of obtaining a quicker start-up property.

  Further, as a positively chargeable charge control agent, a quaternary ammonium salt, a carboxylate, or a resin or oligomer having a carboxyl group as a functional group can be used. Specifically, a styrene resin having a quaternary ammonium salt, an acrylic resin having a quaternary ammonium salt, a styrene-acrylic resin having a quaternary ammonium salt, a polyester resin having a quaternary ammonium salt, and a carboxylate Styrene resin having carboxylate, acrylic resin having carboxylate, styrene-acrylic resin having carboxylate, polyester resin having carboxylate, polystyrene resin having carboxyl group, acrylic resin having carboxyl group , A styrene-acrylic resin having a carboxyl group, a polyester resin having a carboxyl group, and the like. These may be used individually by 1 type, or may be used in combination of 2 or more type.

In particular, a styrene-acrylic resin having a quaternary ammonium salt as a functional group is optimal as a positively chargeable charge control agent from the viewpoint that the charge amount can be easily adjusted to a value within a desired range. In this case, preferred acrylic comonomers copolymerized with styrene units include, for example, methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, Examples include (meth) acrylic acid alkyl esters such as 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and iso-butyl methacrylate.
As the quaternary ammonium salt, a unit derived from a dialkylaminoalkyl (meth) acrylate through a quaternization step is used. Examples of the derived dialkylaminoalkyl (meth) acrylate include di (lower) such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, and dibutylaminoethyl (meth) acrylate. Alkyl) aminoethyl (meth) acrylate; dimethylmethacrylamide, dimethylaminopropylmethacrylamide are preferred. Further, hydroxy group-containing polymerizable monomers such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and N-methylol (meth) acrylamide can be used in combination during polymerization.

  As the negatively chargeable charge control agent, for example, an organometallic complex and a chelate compound are suitable. Specifically, aluminum acetylacetonate, iron (II) acetylacetonate, 3,5-di-tert-butylsalicylic acid Examples thereof include chromium and the like, and acetylacetone metal complexes, salicylic acid metal complexes or salts thereof are particularly preferable, and salicylic acid metal complexes or salicylic acid metal salts are particularly preferable.

  The content of the charge control agent is preferably 0.5 to 15.0% by mass, more preferably 0.5 to 8.0% by mass, and more preferably 0.5 to 7.0% by mass in 100% by mass of the toner base particles. Is particularly preferred. When the content of the charge control agent is 0.5% by mass or more, a toner having a predetermined polarity can be stably charged, and the image density is determined when an image is formed by developing an electrostatic latent image. And deterioration of durability of image density can be suppressed. In addition, since poor dispersion of the charge control agent can be prevented, generation of fog and contamination of the photoreceptor can be suppressed. On the other hand, if the content of the charge control agent is 15.0% by mass or less, it is possible to prevent environmental resistance, in particular, charging failure and image failure in a high-temperature and high-humidity environment, and to suppress photoreceptor contamination.

(Release agent)
The release agent is blended in order to improve the fixing property and offset property of the toner. As the release agent, waxes are suitable, and specific examples include polyethylene wax, polypropylene wax, polytetrafluoroethylene wax, Fischer-Tropsch wax, paraffin wax, ester wax, montan wax, rice wax and the like. It is done. These may be used individually by 1 type, or may be used in combination of 2 or more type. By blending the waxes described above, offset properties and image smearing can be more efficiently prevented.

  The content of the release agent is preferably 1.0 to 5.0% by mass in 100% by mass of the toner base particles. If the content of the release agent is 1.0% by mass or more, offset property and image smearing can be efficiently prevented. On the other hand, when the content of the release agent is 5.0% by mass or less, fusion between the toners can be prevented, and a decrease in storage stability of the toner can be suppressed.

(Magnetic powder)
When the toner of the present invention is used as a magnetic one-component developer, the toner base particles contain magnetic powder in addition to the components described above. When the magnetic powder is included, the toner is colored by the magnetic powder, and thus the above-described colorant may not be included.
As the magnetic powder, known powders can be used, for example, iron, cobalt, nickel and other ferromagnetic metals such as ferrite and magnetite, alloys, compounds containing these elements, or ferromagnetic elements. An alloy that exhibits ferromagnetism by applying an appropriate heat treatment, chromium dioxide, or the like can be given.

The magnetic powder is preferably uniformly dispersed in the above-described binder resin in the form of fine powder having an average particle size of 0.1 to 1.0 μm, particularly 0.1 to 0.5 μm. The magnetic powder can also be used after being subjected to a surface treatment with a surface treatment agent such as a titanium coupling agent or a silane coupling agent.
The content of the magnetic powder is preferably 35 to 60% by mass and more preferably 40 to 60% by mass in 100% by mass of the toner base particles. If the content of the magnetic powder is 35% by mass or more, the durability of the image density can be maintained and the occurrence of fog can be suppressed. On the other hand, when the content of the magnetic powder is 60% by mass or less, it is possible to maintain the durability of the image density and to suppress the deterioration of the fixability.

The magnetic powder preferably has a volume specific resistance value of 1 × 10 ³ to 1 × 10 ⁷ Ω · cm, and more preferably 1 × 10 ³ to 1 × 10 ⁶ Ω · cm. If the resistance value of the magnetic powder is 1 × 10 ³ Ω · cm or more, sufficient positive chargeability can be imparted to the toner, and the image density can be maintained. On the other hand, if the resistance value of the magnetic powder is 1 × 10 ⁷ Ω · cm or less, it is possible to suppress the toner charge amount from becoming higher than necessary and to suppress toner charge-up in terms of durability. In addition to preventing a decrease in density and deterioration in durability, it is possible to suppress discharge breakdown of the a-Si photosensitive member, prevent black spots from being generated, and maintain image quality.

The volume specific resistance value of magnetic powder changes the shape of the magnetic powder (spherical, hexahedral, octahedral, etc.), and includes titanium coupling agents, silane coupling agents, aluminum coupling agents, various fatty acids, etc. It can be adjusted by changing the type and amount of the surface treatment agent or by forming a conductive coating layer made of tin / antimony, francium or the like on the surface of the magnetic powder.
In addition, the volume specific resistance value of magnetic powder can be calculated | required with the applied voltage DC10V, applying 1 kg load using the microammeter "R8340A ULTRA HIGH RESISTANCE METER" made from an Advantest company.

(Preparation of toner base particles)
The toner base particles are obtained by mixing the binder resin and, if necessary, the above-described components, melt-kneading using a kneader such as an extruder, cooling, pulverizing and classifying. At this time, it is common to use a mechanical pulverizer in the pulverization process and an airflow classifier in the classification process, but by adjusting the setting conditions of these pulverizers and classifiers, the number distribution of fine powder particles Ratio, SD, ultrafine particle ratio, and average circularity can be controlled. For example, in the classifying process, the particle size distribution can be adjusted by changing the classifying edge angle of a classifier (manufactured by Nippon Steel & Mining Co., Ltd., “Elbow Jet”). Specifically, the zone (classified to the fine powder side of the classifier ( By adjusting the particle size distribution by adjusting the fine powder zone, zone width: ΔF) and the zone classified to the coarse side (coarse zone, zone width: ΔM), the ratio of the number distribution of fine particles, SD, Controls the ratio of ultrafine particles and average circularity. More specifically, when ΔF is increased, the ratio of the number distribution of fine powder particles is decreased and the value of SD tends to be decreased.
The toner base particles are usually classified and adjusted in size so that the average particle size is about 5 to 10 μm.

<External additive>
In the toner of the present invention, an external additive is added to the toner base particles described above. By adding an external additive, charged products and the like attached to the surface of the photoreceptor can be removed by polishing.
Examples of the external additive include inorganic metal oxides. Specific examples include alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate. Among these, titanium oxide is preferable. The average particle diameter of these inorganic metal oxides is preferably 0.01 to 1.0 μm.
When an inorganic metal oxide is added as an external additive, the addition amount is preferably 0.5 to 5.0 parts by mass with respect to 100 parts by mass of toner base particles. When the added amount of the inorganic metal oxide is 0.5 parts by mass or more, the photoreceptor can be polished sufficiently, and the occurrence of image flow can be suppressed particularly in a high temperature and high humidity environment, thereby preventing image defects. On the other hand, if the added amount of the inorganic metal oxide is 5.0 parts by mass or less, the fluidity of the toner can be maintained, so that it is possible to prevent a decrease in image density and a deterioration in durability.

  The volume-specific resistance value of the inorganic metal oxide is determined by forming a coating layer made of tin oxide and antimony oxide on the surface of the inorganic metal oxide and changing the thickness of the formed coating layer, It can be adjusted by changing the content ratio of antimony.

Further, for the purpose of maintaining the fluidity, storage stability, cleaning properties, etc. of the toner, an external additive other than the above-described inorganic metal oxide may be added to the toner base particles to treat the surface of the toner base particles. . Examples of such external additives include colloidal silica, hydrophobic silica, and silicon carbide. These external additives may be added to the toner base particles after surface treatment with aminosilane, chicone oil, hexamethyldisilazane, titanate coupling agent, silane coupling agent, etc., if necessary. You can also. These external additives may be used in combination with the inorganic metal oxides described above.
The average particle diameter of these external additives is preferably 1.0 μm or less. Further, the addition amount is preferably 0.2 to 10.0 parts by mass with respect to 100 parts by mass of the toner base particles.

<Preparation of toner>
The toner of the present invention can be obtained by mixing the above-described toner base particles and the external additive in a dry manner. The stirring and mixing is preferably performed using a Henschel mixer or a Nauter mixer so that the external additive is not embedded in the toner base particles.

The toner of the present invention thus obtained defines the number distribution ratio of particles having a particle diameter of 4.0 μm or less, the ratio of particles having a particle diameter of 3.0 μm or less, and the standard deviation of volume distribution. Therefore, the developability of the toner is improved, and moisture adsorption can be suppressed even in a high temperature and high humidity environment.
Further, since the toner of the present invention has a very low ratio of ultrafine particles of 5.0% or less, an increase in the image power of the developing roller can be suppressed when used in an image forming apparatus. Therefore, toner adhesion to the developing roller can be reduced. Further, since the toner can be prevented from being charged and aggregated on the developing roller, the toner thin layer can be favorably formed on the developing roller. Furthermore, since the ratio of the ultrafine powder particles is as low as 5.0% or less, the adhesion force of the toner to the carrier can be reduced, so that fogging and toner scattering can be suppressed over a long period of time.
In the toner of the present invention, since the average circularity of particles having a particle diameter of 3 to 10 μm is 0.945 or more, an increase in the coefficient of contact friction with the photoreceptor can be suppressed, so that the transfer efficiency is improved. It is possible to suppress excessively shaving the surface of the photoreceptor. Accordingly, it is possible to suppress the adhesion of the photoreceptor adhering material without causing an image defect due to excessive shaving of the photoreceptor.

The toner of the present invention can be used as it is as a one-component developer. In particular, a magnetic toner can be obtained if the toner base particles contain magnetic powder, and therefore can be used as a magnetic one-component developer.
Further, the toner of the present invention and a carrier can be mixed and used as a two-component developer. In particular, a toner using toner base particles that do not contain magnetic powder is a non-magnetic toner and can therefore be used as a non-magnetic two-component developer. At that time, it is preferable to use a magnetic carrier as the carrier.

Examples of the magnetic carrier include a carrier core material whose surface is treated with a surface coating agent.
Carrier core materials include, for example, magnetic metals such as iron, nickel, cobalt and their alloys, or alloys containing rare earths, hematite, magnetite, manganese-zinc ferrite, nickel-zinc ferrite, manganese-magnesium Resin the surface of magnetic particles produced by sintering and atomizing magnetic materials such as ferrite, soft ferrites such as lithium ferrite, iron-based oxides such as copper-zinc ferrite, and mixtures thereof. The thing etc. which were coat | covered are mentioned.
On the other hand, the surface coating agent is preferably a fluorine-based binder resin, and specific examples thereof include polytetrafluoroethylene, polychlorotrifluoroethylene, and polyvinylidene fluoride.

The particle diameter of the carrier is usually 20 to 200 μm, more preferably 30 to 150 μm, expressed as a particle diameter by electron microscopy.
Further, the apparent density of the carrier is preferably 2.4 to 3.0 g / cm ^{3 in} general when it is mainly composed of a magnetic material, although it varies depending on the composition of the magnetic material and the surface structure.

  When the toner of the present invention is used as a two-component developer, the toner content is preferably 1 to 20% by mass and more preferably 3 to 15% by mass in 100% by mass of the two-component developer. When the toner content is 1% by mass or more, an appropriate image density can be maintained. On the other hand, when the toner content is 20% by mass or less, the occurrence of toner scattering in the developing device can be suppressed, and the toner can be prevented from adhering to background portions such as dirt in the apparatus and transfer paper.

As described above, the toner of the present invention can be suitably used as a one-component developer or a two-component developer. The toner of the present invention can be suitably used in a general image forming apparatus equipped with an a-Si photosensitive member as a photosensitive member.
Here, the a-Si photosensitive member will be described.

The a-Si photosensitive member has a high surface hardness and has a long-term durability as compared with an organic photosensitive member or the like. Therefore, there is almost no need to replace the photoconductor during the life of the image forming apparatus. In addition, since it is harder to wear than an organic photoreceptor, image characteristics are likely to be stable over a long period of time.
As such an a-Si photosensitive member, for example, a conventionally well-known one having an amorphous silicon photosensitive layer (a-Si photosensitive layer) on the surface of a conductive substrate formed in a predetermined shape such as a drum shape. Photoconductors having various structures can be used.
The a-Si photosensitive layer can be formed, for example, by a vapor phase growth method such as a glow discharge decomposition method, a sputtering method, an ECR method, or an evaporation method. In forming the a-Si type photosensitive layer, H or a halogen element may be included. it can. Furthermore, in order to adjust the characteristics of the photoreceptor, elements such as C, N, and O may be included, or a group 13 element or a group 15 element in the periodic table (long period type) may be included.

Specifically, the a-Si photosensitive layer is formed of various photoconductive materials such as a-Si, amorphous silicon such as a-SiC, a-SiO, and a-SiON. Is preferred. In particular, it is preferable to use a-SiC. In this case, when Si _1-x C _x is set, the value of x is preferably set to 0 <x ≦ 0.5, more preferably 0.05 ≦ x. ≦ 0.45. If x is in the above range, the photosensitive layer made of a-SiC has higher resistance than the photosensitive layer made of a-Si while maintaining good carrier transport, and the photosensitivity characteristics of the photoreceptor can be improved. .
As the group 13 element or the group 15 element, B and P are preferable, respectively, because they are excellent in covalent bonding property, can change the semiconductor characteristics sensitively, and can obtain excellent photosensitivity.

Further, the a-Si-based photosensitive layer may have a laminated structure in which a layer region (photoexcitation layer) having an enhanced function of generating photocarriers and a layer region (carrier transporting layer) having a function of transporting carriers are laminated. By adopting such a laminated structure, it is possible to improve both the photosensitivity and withstand voltage characteristics of the photoreceptor.
In order to increase the generation efficiency of photocarriers in the photoexcitation layer, among the film formation conditions, (1) the film formation rate is set low, (2) the dilution ratio of the film formation component is increased by H ₂ or He, (3 It is preferable to form the film while taking measures such as increasing the amount of the element to be doped to be larger than that of the carrier transport layer region.
On the other hand, the carrier transport layer mainly has a role of increasing the withstand voltage of the a-Si photosensitive layer and smoothly transporting the carriers injected from the photoexcitation layer to the conductive substrate. Carrier generation is performed by the transmitted light, which contributes to an improvement in photosensitivity of the photoreceptor.
The thickness of the a-Si photosensitive layer is preferably a thickness obtained by adding 0.1 to 2.0 μm to the depth of light absorption obtained from the absorption coefficient of the photosensitive layer with respect to light having an exposure wavelength.
Further, when the a-Si photosensitive layer has a laminated structure in which the photoexcitation layer and the carrier transport layer are laminated as described above, the thickness of the photoexcitation layer is set to be approximately equal to the depth of light absorption. Is preferred.

It is preferable to interpose a carrier blocking layer between the a-Si type photosensitive layer and the conductive substrate. By interposing the carrier blocking layer, when the surface of the photoreceptor is in contact with the toner while a bias voltage is applied during development, the carrier injection from the conductive substrate to the a-Si photosensitive layer is blocked. The electrostatic contrast between the exposed portion and the non-exposed portion can be increased to improve the image density, and the fogging of the blank portion can be reduced.
As the carrier blocking layer, inorganic insulating layers formed of a-SiC, a-SiO, a-SiN, a-SiON, a-SiCON, etc., which are insulating, polyethylene terephthalate, Parylene (registered trademark), poly-tetra It is preferable to use an organic insulating layer formed of fluorinated ethylene, polyimide, polyfluorinated ethylene propylene, polyurethane, epoxy resin, polyester, polycarbonate, cellulose acetate cellulose resin, or the like.

In addition, the carrier blocking layer has good insulating properties and adhesion to the conductive substrate and the a-Si photosensitive layer, and does not cause significant alteration in heating during the formation of the a-Si photosensitive layer. Such characteristics are required. In consideration of such characteristics, the carrier blocking layer is preferably formed of a-SiC. In order to make the a-SiC forming the carrier blocking layer insulative, for example, the amount of C contained in the carrier blocking layer may be increased as compared with the case of the a-Si photosensitive layer.
The thickness of the carrier blocking layer is preferably from 0.01 to 5 μm, more preferably from 0.1 to 3 μm.

The surface of the a-Si photosensitive layer is preferably covered and protected by a surface protective layer made of an organic or inorganic insulating material. As a result, it is possible to prevent the surface of the a-Si photosensitive layer from being oxidized during discharge by a charging member or the like that charges the photosensitive member, thereby forming an oxide film that easily adsorbs ion products or water molecules. . Furthermore, it is possible to improve the withstand voltage or improve the wear resistance when repeatedly used.
As the surface protective layer, a layer made of an a-Si insulating material such as a-SiC, a-SiN, a-SiO, a-SiCO, or a-SiNO is preferably used. It can be formed by the same thin film forming method as the layer. In particular, it is preferable to form a surface protective layer using a-SiC.

When a-SiC is used for the surface protective layer, the amount of C contained in the surface protective layer may be increased as compared with the a-Si type photosensitive layer in the same manner as the carrier blocking layer.
Specifically, when Si _1-x C _x is set, the value of x is preferably set to 0.3 ≦ x <1.0, and more preferably 0.5 ≦ x ≦ 0.95. .
Moreover, it is preferable to adjust the value of x so that the dark resistivity of the surface protective layer is 1 × 10 ¹³ Ω · cm or more. When the dark resistivity is 1 × 10 ¹³ Ω · cm or more, the potential flow in the surface direction of the surface protective layer is reduced, the electrostatic latent image maintaining ability is excellent, and the moisture resistance is excellent. It is easy to obtain a photoconductor that can suppress the occurrence of.
Thus, if the surface protective layer has a high resistance, it is possible to prevent the injection of electric charges due to the bias through the toner, and to increase the potential contrast between the exposed portion and the non-exposed portion. A function of attracting a large amount of toner to increase the density of the toner image and sufficiently increase the image density can be provided. Further, it is possible to suppress the fogging of the blank portion and increase the withstand voltage of the photoreceptor.

Note that a surface protective layer formed of an insulating material other than a-SiC may continue to trap optical carriers even after image formation, and there is a possibility that the residual potential cannot be erased reliably in a normal charge removal step.
However, if the surface protective layer is formed using a-SiC, positive charges from the surface are effectively blocked, but negative charges from the conductive substrate are relatively easy to pass. The residual potential can be effectively erased by a normal static elimination process, and image formation can be performed continuously. In addition, the surface protective layer formed using a-SiC has good adhesion with an a-Si photosensitive layer such as a-SiC, and is excellent in wear resistance, environmental resistance, etc. Stable image formation can be performed over a long period of time.
The surface protective layer formed using a-SiC may form a gradient in the thickness direction in the amount of C within the layer. Further, elements such as N, O, and Ge can be contained together with C to further improve the moisture resistance.

  The thickness of the surface protective layer is preferably 0.05 to 5 μm, more preferably 0.1 to 3 μm. If the thickness of the surface protective layer is 0.05 μm or more, the effect of preventing the above-mentioned oxide film formation, the effect of improving the withstand voltage, the effect of improving the wear resistance when repeatedly used, etc. are sufficiently obtained. It is done. Further, it is possible to effectively trap the optical carrier and contribute to the formation of the toner image. On the other hand, if the thickness of the surface protective layer is 5 μm or less, the resolution is maintained since the electric field (electric field lines) is prevented from spreading in the film surface direction in the surface protective layer when forming a fine charge pattern. And sufficient resolution can be easily obtained. Further, since the increase in the charge remaining on the surface is suppressed, the residual potential is not increased more than necessary, and the image density is lowered, the blank portion is fogged, and the image density is not easily changed in repeated use.

As described above, the a-Si photosensitive member is liable to adhere to photosensitive member deposits such as discharge products and toner components. Therefore, it is usually necessary to remove the photosensitive member deposit by polishing the surface with toner. is there. At this time, if the surface is excessively polished, the a-Si type photosensitive layer may be excessively shaved to cause image defects.
However, according to the toner of the present invention, since the average circularity of particles having a particle diameter of 3 to 10 μm is 0.945 or more, the a-Si type photosensitive layer can be appropriately polished without excessively scraping. Accordingly, the toner of the present invention is suitable for use in an image forming apparatus having an a-Si photoreceptor, but due to its characteristics, a contact-type development method is employed when used as a non-magnetic two-component developer. In addition to the image forming apparatus described above, the image forming apparatus is particularly suitable for use in an image forming apparatus that employs a touch-down developing method that is a non-contact developing method. Further, when used as a magnetic one-component developer, it is particularly suitable for use in an image forming apparatus employing a one-component jumping development method which is a non-contact type development method.

An image forming apparatus that employs a touch-down development method includes a magnetic roller that stirs a non-magnetic two-component developer to form spikes of the non-magnetic two-component developer on the surface, and a spiked non-magnetic two-component developer. A developing roller that forms a thin layer of non-magnetic toner on the surface, and an a-Si photosensitive member that is provided at a certain distance from the developing roller and forms an electrostatic latent image on the surface. Yes.
The touch-down development method means that “only the non-magnetic toner is transferred from the magnetic roller to the surface of the developing roller by contacting the spikes of the non-magnetic two-component developer formed on the surface of the magnetic roller. A thin layer of non-magnetic toner is formed on the surface of the developing roller, and the non-magnetic toner is allowed to fly from the thin layer onto the surface of the a-Si photosensitive member on which the electrostatic latent image is formed. It is a method of developing as an image.

  Since the toner of the present invention has a very low ratio of ultrafine particles of 5.0% or less, an increase in the image power of the developing roller can be suppressed when used in an image forming apparatus. Therefore, toner adhesion to the developing roller can be reduced. Therefore, according to the present invention, in the image forming apparatus adopting the touch-down development method, the residual toner on the developing roller can be efficiently collected on the magnetic roller, so that the toner adhesion to the developing roller can be suppressed and the image density is lowered. Can be suppressed. The present invention can also be applied to a downsized image forming apparatus.

An image forming apparatus that employs a contact-type developing system is provided with a developing roller that stirs a non-magnetic two-component developer and forms a spike of the developer on the surface, and is opposed to the developing roller. And an amorphous silicon photoconductor on which an electrostatic latent image is formed.
The contact-type development method is “an amorphous silicon photoconductor in which an electrostatic latent image is formed in contact with a head of a nonmagnetic two-component developer formed on the surface of a developing roller. A system in which non-magnetic toner is transferred to the surface and an electrostatic latent image is developed as a toner image ”.

  In the case of the contact-type development method, there are cases where adhesion of toner components, carriers, etc. to the photoreceptor and damage to the photoreceptor due to a magnetic brush, etc. may be a problem, but the toner of the present invention has a particle diameter of 3-10 μm. Since the average circularity of the particles is 0.945 or more, an appropriate polishing property can be exhibited. Therefore, when recovering non-magnetic toner that remains without being transferred from the photosensitive member to the transfer target, the surface of the photosensitive member is polished by using the recovered toner, and toner components, carriers, etc. attached to the photosensitive member Can be easily removed.

An image forming apparatus adopting a magnetic one-component jumping development system has a sleeve having a magnet roller built in on the surface thereof, a developing roller for forming a thin layer of magnetic toner on the surface, and a constant distance from the developing roller. An a-Si photoconductor provided on the surface and having an electrostatic latent image formed thereon.
The magnetic one-component jumping development method is “a thin layer of magnetic toner is formed on the surface of a developing roller having magnetic force, and the thin layer is formed on the surface of an a-Si photosensitive member on which an electrostatic latent image is formed. In other words, the magnetic latent image is developed as a toner image by flying magnetic toner from the toner.

  In the toner of the present invention, the ratio of the ultrafine particles is as low as 5.0% or less, so the influence of the ultrafine particles can be reduced, the charge-up phenomenon of the toner can be suppressed, and the toner is charged and aggregated on the developing roller. Can be prevented. Therefore, a thin toner layer can be satisfactorily formed on the developing roller. Therefore, according to the present invention, since the long-term stability of the toner thin layer formation can be secured in the image forming apparatus adopting the magnetic one-component jumping development system, a stable image can be formed over a long period of time, and the high resolution, high image quality, It can satisfy the demand for high durability. The present invention can also be applied to a downsized image forming apparatus.

[Image forming method]
The image forming method of the present invention is characterized in that an image is formed by a touch-down developing method, a contact developing method, or a magnetic one-component jumping developing method. In these image forming methods, as the image forming apparatus, an image forming apparatus adopting the above-described touch-down developing method, contact-type developing method, or magnetic one-component jumping developing method is used.

<Touchdown development method>
The image forming method using the touch-down development method includes a charging process, an exposure process, a development process, and a transfer process. In this image forming method, a nonmagnetic two-component developer composed of a nonmagnetic toner and a magnetic carrier is used as the developer, and the toner of the present invention is used as the nonmagnetic toner. Moreover, the carrier mentioned above is mentioned as a magnetic carrier.
The charging step is a step of charging the surface of the a-Si photosensitive member.
The exposure step is a step of exposing the surface of the a-Si photoreceptor to form an electrostatic latent image.
In the developing process, a developer consisting of a non-magnetic toner and a magnetic carrier is agitated to form developer spikes on the surface of the magnetic roller, and in contact with the spiked developer, a non-magnetic toner thin film is formed on the surface of the developer roller. In this step, a non-magnetic toner is ejected from the thin layer onto the surface of the a-Si photoreceptor to develop the electrostatic latent image as a toner image.
The transfer step is a step of transferring the toner image from the a-Si photosensitive member to the transfer target.

  Conventionally, in the case of a two-component developing method using a two-component developer, it is possible to form a relatively high-quality image at a relatively early stage, but as a result of long-term use, toner adheres to the developing roller. As a result, the image density may decrease, or the toner may adhere to the carrier and fogging may occur, making it difficult to obtain a high-quality image. In particular, in the case of the touch-down development method, it is difficult to collect the toner remaining on the developing roller to the magnetic roller.

  However, according to the present invention, a toner having a fine powder particle number distribution ratio of 8.0% or less and an SD of 1.25 or less can be used. The decrease in concentration can be suppressed. Further, since the toner having the ultrafine particle ratio of 5.0% or less is used, an increase in the mirror image force of the developing roller can be suppressed, and the adhesion of the toner to the developing roller can be reduced. Therefore, since the residual toner on the developing roller can be efficiently collected on the magnetic roller, toner adhesion to the developing roller can be suppressed, and a decrease in image density can be suppressed. Further, since the adhesion of the toner to the carrier can be reduced, the occurrence of fog can be suppressed.

<Contact development system>
An image forming method using a contact-type development method includes a charging step, an exposure step, a development step, and a transfer step. In this image forming method, a nonmagnetic two-component developer composed of a nonmagnetic toner and a magnetic carrier is used as the developer, and the toner of the present invention is used as the nonmagnetic toner. Moreover, the carrier mentioned above is mentioned as a magnetic carrier.
The charging process, the exposure process, and the transfer process are the same as those in the image forming method using the touch-down development method.
In the developing process, a developer consisting of a non-magnetic toner and a magnetic carrier is agitated to form developer spikes on the surface of the developing roller, and an a-Si photosensitive member is brought into contact with the developer spikes to cause electrostatic latent. This is a step of developing an image as a toner image.

In the case of the contact-type development method, adhesion of toner components and carriers to the photoconductor and damage to the photoconductor due to a magnetic brush or the like may be a problem.
However, according to the present invention, toner having an average circularity of 0.945 or more for particles having a particle diameter of 3 to 10 μm is used, so that the nonmagnetic toner remaining without being transferred from the photosensitive member to the transfer target is recovered. At this time, the surface of the photoconductor is polished using the collected toner, and the toner component, carrier, and the like attached to the photoconductor can be easily removed.

<Magnetic single component jumping development method>
An image forming method using a magnetic one-component jumping development method includes a charging step, an exposure step, a development step, and a transfer step. In this image forming method, a magnetic one-component developer composed of a magnetic toner is used as a developer, and the toner of the present invention is used as a magnetic toner.
The charging process, the exposure process, and the transfer process are the same as those in the image forming method using the touch-down development method.
The developing process is a process in which a thin layer of magnetic toner is formed on the surface of the developing roller, the magnetic toner is ejected from the thin layer to the surface of the a-Si photosensitive member, and the electrostatic latent image is developed as a toner image. .

In the image forming method using the magnetic one-component jumping development method, it is preferable to use a developing roller having a sleeve having a ten-point average roughness (Rz) of 2.0 to 8.0 μm on the surface as the developing roller. If Rz is 2.0 μm or more, a decrease in toner conveying force can be suppressed, and an appropriate image density can be maintained. On the other hand, if Rz is 8.0 μm or less, a high-quality image can be formed and leakage from the protrusion on the sleeve surface to the a-Si photosensitive member can be suppressed. Can be maintained.
Rz can be measured using a surface roughness measuring instrument “Surfcoder SE-30D” manufactured by Kosaka Laboratory.

  As a material used for the sleeve, for example, aluminum, stainless steel (SUS), or the like can be used. In consideration of high durability, it is preferable to use SUS as a sleeve material, and specifically, “SUS303”, “SUS304”, “SUS305”, “SUS316”, and the like can be given. In addition, it is more preferable to use “SUS305” because it is weak in magnetism and easy to process.

  Conventionally, in the case of the magnetic one-component jumping development method, it has been difficult to ensure long-term stability of the toner thin layer formation on the developing roller, particularly in a high-speed machine or a small machine. For this reason, problems such as disturbance of the toner thin layer on the developing roller and occurrence of toner thin layer omission in the form of vertical streaks occur, making it difficult to obtain a stable image over a long period of time.

  However, according to the present invention, a toner having a fine powder particle number distribution ratio of 8.0% or less and an SD of 1.25 or less can be used. The decrease in concentration can be suppressed. In addition, since the toner having a ratio of the ultrafine particles of 5.0% or less is used, the influence of the ultrafine particles can be reduced, the toner charge-up phenomenon can be suppressed, and the toner can be prevented from being charged and aggregated on the developing roller. . Therefore, a thin toner layer can be satisfactorily formed on the developing roller. Therefore, since long-term stability of toner thin layer formation can be ensured, a stable image can be formed over a long period of time, and the requirements for high resolution, high image quality, and high durability can be satisfied.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to a following example.

[Example 1-1]
<Preparation of polyester resin>
1,960 g of propylene oxide adduct of bisphenol A, 780 g of ethylene oxide adduct of bisphenol A, 257 g of dodecenyl succinic anhydride, 770 g of terephthalic acid, and 4 g of dibutyltin oxide in a nitrogen atmosphere at 235 ° C. over 8 hours After reacting, it was further reacted at 8.3 kPa for 1 hour. Furthermore, trimellitic anhydride was added to the reaction system at 180 ° C. so as to have a desired acid value, and the temperature was raised to 210 ° C. at a rate of 10 ° C./hour to cause reaction to obtain a polyester resin.

<Manufacture of non-magnetic toner>
100 parts by mass of a polyester resin prepared as a binder resin, 5 parts by mass of carbon black (manufactured by Mitsubishi Chemical Corporation, “MA100”) as a colorant, and a quaternary ammonium salt (manufactured by Orient Chemical Industries, Ltd.) as a charge control agent , "Bontron P-51") and 2 parts by mass of Carnauba wax (manufactured by Kato Yoko Co., "Carnauba wax No. 1") as a release agent were mixed with a Henschel mixer (Mitsui Mining Co., Ltd.) The mixture was melt kneaded with a twin-screw kneader (manufactured by Toshiba Machine Co., Ltd.), cooled, and coarsely pulverized with a hammer mill (manufactured by Hosokawa Micron Corporation). Thereafter, the finely pulverized product by a mechanical pulverizer (Turbo Kogyo Co., “Turbo Mill”) is classified by an airflow classifier (Nittetsu Mining Co., “Elbow Jet”), and the volume average particle size (D50 ) Toner mother particles of 6.8 μm were obtained.
Hydrophobic silica (“REA200” manufactured by Nippon Aerosil Co., Ltd.) and titanium oxide (“EC-100” manufactured by Titanium Industry Co., Ltd.) as external additives are added to the obtained toner base particles, and a Henschel mixer (Mitsui Mining Co., Ltd.) is added. The mixture was stirred and mixed under the conditions of a rotational speed of 30 m / sec and a mixing time of 5 minutes to obtain a black toner (non-magnetic toner). The amount of each external additive added was 1.8% by mass for hydrophobic silica and 1.0% by mass for titanium oxide in 100% by mass of the toner.

<Measurement / Evaluation>
(Measurement of volume average particle diameter of toner base particles)
Using a Beckman Coulter particle size distribution measuring device “Coulter Counter Multimizer 3”, using Beckman Coulter's Isoton II as the electrolyte, and using a 100 μm aperture as the aperture diameter, the particle size distribution of the toner base particles ( Volume distribution) was measured.
Specifically, 10 mg of a measurement sample (toner mother particles) is added to a solution obtained by adding 10 g of a surfactant (7 mass% sodium alkyl ether sulfate) to 100 g of an electrolytic solution, and the dispersion treatment is performed using an ultrasonic disperser. The solution in which the measurement sample was dispersed was measured with a particle size distribution measuring device to obtain a volume distribution of the sample particle size. From the obtained volume distribution, the volume average particle diameter (D50) of the toner base particles was determined. The results are shown in Table 1.

(Measurement of the number distribution ratio of fine particles)
In the same manner as the measurement of the volume average particle diameter of the toner base particles, the particle size distribution (number distribution) of the black toner was measured using a particle size distribution measuring apparatus and using 10 mg of black toner as a measurement sample. The ratio of particles having a particle size of 4.0 μm or less was determined from the obtained number distribution. The results are shown in Table 1.

(Measurement of SD)
In the same manner as the measurement of the volume average particle diameter of the toner base particles, the particle size distribution (volume distribution) of the black toner was measured using a particle size distribution measuring apparatus and using 10 mg of black toner as a measurement sample. The SD of the black toner was determined from the obtained volume distribution. The results are shown in Table 1.

(Measurement of the ratio of ultrafine particles)
One field of view comparing a black toner photograph magnified by a scanning electron microscope with a black toner photograph mapped by elemental analysis such as an X-ray microanalyzer (XMA) attached to the scanning electron microscope. The number of externally treated toner observed in the above was measured, and the number of ultrafine particles measured with a particle size of 3.0 μm or less was counted. Observation was conducted on 1000 randomly selected externally added toners, and the number of ultrafine particles having a particle size of 3.0 μm or less was counted to determine the ratio of the ultrafine particles. It is assumed that particles that are considered to be external additives among the mapped black toner are not counted. The results are shown in Table 1.

(Measurement of average circularity)
Using a flow particle image analyzer “FPIA-3000” manufactured by Sysmex Corporation, measurement was performed on particles in a range of an equivalent circle diameter of 0.60 to 400 μm in an environment of a temperature of 23 ° C. and a humidity of 60 RH%. Next, the circularity of the measured particles was obtained from the following formula (1), and the value obtained by dividing the sum of the circularity by the total number of particles in the particles having an equivalent circle diameter of 3 to 10 μm was defined as the circularity. Measurement was performed on 1000 particles, and the calculated value was defined as the average circularity. The results are shown in Table 1.
Circularity = perimeter of a circle having the same projected area as the particle image / perimeter of the projected image of the particle (1)

(Measurement of image density)
A black toner and a carrier (“Ferrite Carrier”, manufactured by Powdertech Co., Ltd., average particle size: 35 μm) were mixed to prepare a nonmagnetic two-component developer. The mass ratio of the toner (T) and the carrier (C) was T: C = 1: 10.
The obtained non-magnetic two-component developer is set in an evaluation machine adopting a touch-down development method (a modified machine in which an organic photoconductor is replaced with an a-Si photoconductor in “FS-C5016” manufactured by Kyocera Mita). Then, the evaluation machine was turned on and a solid image immediately after stabilization (solid image with a printing rate of 100%) was output, which was used as the initial image.
Next, a solid image (solid image with a printing rate of 100%) after outputting 5000 sheets of a document with a printing rate of 4% was output, and this was used as a printing-resistant image.
The image density (ID) of each of the initial image and the solid image of the printing durability image was measured using a Macbeth reflection densitometer (manufactured by Gretag Macbeth, “RD-914”). The results are shown in Table 2.

(Evaluation of transferability)
In the same manner as the measurement of image density, the obtained non-magnetic two-component developer was set in an evaluation machine, the evaluation machine was turned on, and an image immediately after stabilization (thin line image) was output.
The obtained thin line image was visually observed with a magnifying glass for the void in the thin line and evaluated according to the following evaluation criteria. The results are shown in Table 2.
5: No void has occurred.
4: The void is very slight.
3: Many voids occur.
2: The void is remarkably generated.
1: The void is remarkably generated over a wide range.

(Evaluation of fog in high temperature and high humidity environment (H / H environment))
The obtained non-magnetic two-component developer is set in the evaluation machine in the same manner as the image density measurement except that the evaluation machine is left in a high temperature and high humidity environment (temperature: 35 ° C., humidity: 85 RH%) overnight. The evaluation machine was turned on and a solid image immediately after stabilization (solid image with a printing rate of 100%) was output.
The resulting solid image was visually observed for occurrence of fog and evaluated according to the following evaluation criteria. The results are shown in Table 2.
5: No fog occurs and the image quality is good.
4: Fog is very slight, but the image quality is good.
3: A lot of fog occurs and the image quality is affected.
2: Fog is noticeably generated and the image quality is affected, which is a problem level.
1: Fog is remarkably generated over a wide range, which is a problem level as image quality, and cannot be used in actual use.

(Evaluation of image quality)
In the same manner as the measurement of image density, the obtained non-magnetic two-component developer was set in an evaluation machine, and after outputting 5000 sheets of a 4% printing original, a solid image and a 50% half image were output. Thereafter, the state of the developing roller and the solid image / 50% half image were visually observed and evaluated according to the following evaluation criteria. The results are shown in Table 2.
5: No toner adheres to the developing roller, and both solid images and 50% half images are good.
4: Toner is slightly adhered on the developing roller, but both solid image and 50% half image are good.
3: A lot of toner adheres on the developing roller, and an image defect (sleeve layer unevenness) occurs due to the sleeve roller pitch in the solid image and 50% half image.
2: A large amount of toner adheres to the developing roller, a large amount of image defects (sleeve layer unevenness) occur due to the sleeve roller pitch in the solid image and 50% half image, and the toner on the developing roller during printing durability This is a problem level.
1: A large amount of toner adheres to the developing roller, and image defects (sleeve layer unevenness) occur due to the sleeve roller pitch in the solid image and 50% half image, and the toner on the developing roller from the initial stage of printing durability This is a problem level and cannot withstand actual use.

(Evaluation of abrasiveness)
In the same manner as the image density measurement, the obtained non-magnetic two-component developer is set in an evaluation machine, and immediately after the evaluation machine is turned on in a normal temperature and humidity environment (temperature: 20 ° C., humidity: 65 RH%). The image evaluation pattern was output as an initial image.
Next, an image evaluation pattern after outputting 300,000 sheets with a 5% printing rate document was output and used as a durable image.
The a-Si photoreceptor after outputting the durable image was visually observed and evaluated according to the following evaluation criteria. The results are shown in Table 2.
○: No deposits are observed on the photoreceptor surface.
Δ: Deposits are observed on the surface of the photoreceptor, but they are not fixed and do not affect the durable image.
X: Deposits are observed on the surface of the photoconductor and are completely fixed.

[Examples 1-2 to 1-5, Comparative Examples 1-1 to 1-4]
A mechanical pulverizer in the pulverizing step so that the volume average particle diameter (D50) of toner base particles, the number distribution ratio of fine particles, SD, the ratio of ultrafine particles, and the average circularity are the values shown in Table 1. A black toner was produced in the same manner as in Example 1-1 except that the conditions of the airflow classifier in the classification step were changed, and each measurement and evaluation were performed. The results are shown in Table 2.

As is apparent from Table 2, the black toner obtained in each example hardly changed the image density even after printing 5000 sheets (printing durability), and the decrease in the image density could be suppressed. Further, the results of transferability, fog and image quality were also good. Further, the black toner obtained in each example had an appropriate polishing property, and could be polished without excessively scraping the surface of the photoconductor, thereby suppressing the adhesion of the photoconductor.
On the other hand, since the average circularity of the black toner obtained in Comparative Example 1-1 was as small as 0.944, the contact friction coefficient with the photoconductor increased, and the transferability and the abrasiveness were inferior to those of the examples. It was.
Since the black toner obtained in Comparative Example 1-2 had a large SD of 1.29, the image density was liable to decrease, and the image quality was inferior to those of the Examples.
The black toner obtained in Comparative Example 1-3 had a fine powder particle number distribution ratio as high as 9.6%, so that the image density was likely to be lowered, and the image quality was inferior to those of the Examples.
The black toner obtained in Comparative Example 1-4 has a fine powder particle number distribution ratio of 8.1% and a super fine powder particle ratio of 5.6%, so that the image density tends to decrease and the image quality is low. It was inferior to each Example. Also, fog was likely to occur.

[Example 2-1]
As a binder resin, 100 parts by mass of the polyester resin prepared in Example 1-1, 5 parts by mass of carbon black (manufactured by Mitsubishi Chemical Corporation, “MA100”) as a colorant, and a quaternary ammonium salt ( Henschel Mixer (manufactured by Mitsui Mining Co., Ltd.) 2 parts by mass of “Bontron P-51” manufactured by Orient Chemical Co., Ltd. and 5 parts by mass of carnauba wax (manufactured by Hiroyuki Kato, “Carnauba Wax No. 1”) as a release agent Then, the mixture was melt-kneaded with a twin-screw kneader (manufactured by Toshiba Machine Co., Ltd.), cooled, and coarsely pulverized with a hammer mill (manufactured by Hosokawa Micron Corporation). Thereafter, the finely pulverized product by a mechanical pulverizer (Turbo Kogyo Co., “Turbo Mill”) is classified by an airflow classifier (Nittetsu Mining Co., “Elbow Jet”), and the volume average particle size (D50 ) Toner mother particles of 6.8 μm were obtained.
To the obtained toner base particles, hydrophobic silica (“REA90” manufactured by Nippon Aerosil Co., Ltd.) and titanium oxide (“MPT240” manufactured by Ishihara Sangyo Co., Ltd.) are added as external additives, and Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) is added. The mixture was stirred and mixed at a rotational speed of 30 m / sec and a mixing time of 2 minutes to obtain a black toner (non-magnetic toner). The amount of each external additive added was 1.8% by mass for hydrophobic silica and 1.0% by mass for titanium oxide in 100% by mass of the toner.

<Measurement / Evaluation>
For the obtained magnetic toner, the number distribution ratio of fine particles, SD, the ratio of ultrafine particles, and the average circularity were measured in the same manner as in Example 1-1. The results are shown in Table 3.
Further, the obtained black toner and carrier (“Ferrite Carrier”, manufactured by Powdertech Co., Ltd., average particle size: 75 μm), the mass ratio of toner (T) and carrier (C) is T: C = 1: 19. Other than using a non-magnetic two-component developer prepared by mixing in such a manner and using an a-Si photoconductor-equipped evaluation machine (“DC-7085” manufactured by Kyocera Mita Co., Ltd.) employing a contact-type development method. In the same manner as in Example 1-1, the image density of the initial image and the printing durability image was measured, and the transferability, fogging in a high-temperature and high-humidity environment, image quality, and abrasiveness were evaluated. The results are shown in Table 4.

[Examples 2-2 to 2-5, Comparative examples 2-1 to 2-4]
A mechanical pulverizer in the pulverization step so that the volume average particle diameter (D50) of toner base particles, the number distribution ratio of fine particles, SD, the ratio of ultrafine particles, and the average circularity are the values shown in Table 3. A black toner was produced in the same manner as in Example 2-1, except that the conditions of the airflow classifier in the classification process were changed, and each measurement and evaluation were performed. The results are shown in Table 4.

As is clear from Table 4, the black toner obtained in each example hardly changed the image density even after printing 5000 sheets (printing durability), and the decrease in the image density could be suppressed. Further, the results of transferability, fog and image quality were also good. Further, the black toner obtained in each example had an appropriate polishing property, and could be polished without excessively scraping the surface of the photoconductor, thereby suppressing the adhesion of the photoconductor.
On the other hand, since the average circularity of the black toner obtained in Comparative Example 2-1 was as small as 0.944, the coefficient of contact friction with the photoconductor increased, and the transferability and abrasiveness were inferior to those of the Examples. It was.
Since the black toner obtained in Comparative Example 2-2 had a large SD of 1.29, the image density was likely to be lowered, and the image quality was inferior to those of the Examples.
The black toner obtained in Comparative Example 2-3 had a fine powder particle number distribution ratio as high as 9.6%, so that the image density was likely to be lowered, and the image quality was inferior to those of the Examples.
The black toner obtained in Comparative Example 2-4 has a fine powder particle number distribution ratio of 8.1% and a super fine powder particle ratio of 5.6%, so the image density tends to decrease and the image quality is low. It was inferior to each Example. Also, fog was likely to occur.

[Example 3-1]
<Preparation of binder resin>
In a reactor equipped with a thermometer, a stirrer, and a nitrogen introduction tube, 300 parts by mass of xylene was placed, and under a nitrogen stream, 845 parts by mass of styrene and 155 parts by mass of n-butyl acrylate and di-tert- It dropped at 170 degreeC over 3 hours using 8.5 mass parts of butyl peroxide (polymerization initiator) and 125 mass parts of xylene. After dripping, it was made to react at 170 degreeC for 1 hour, and superposition | polymerization was completed. Thereafter, the solvent was removed to obtain a binder resin.

<Manufacture of magnetic toner>
49 parts by mass of the binder resin thus obtained, magnetic powder (magnetite, holding power 4.5 kA / m when 796 kA / m applied, saturation magnetization 82 Am ² / kg, residual magnetization 4.5 Am ² / kg , Number average particle size 0.25 μm) 45 parts by mass, 3 parts by mass of a quaternary ammonium salt (manufactured by Orient Chemical Co., Ltd., “Bontron P-51”) as a charge control agent, and wax (manufactured by Sasol) , “Sazol Wax H1”) was mixed with 3 parts by mass with a Henschel mixer (Mitsui Mining Co., Ltd.), melted and kneaded with a twin-screw kneader (Toshiba Machine Co., Ltd.), cooled, and a hammer mill (Hosokawa Micron). Coarsely pulverized. Thereafter, the finely pulverized product by a mechanical pulverizer (Turbo Kogyo Co., “Turbo Mill”) is classified by an airflow classifier (Nittetsu Mining Co., “Elbow Jet”), and the volume average particle size (D50 ) Toner mother particles of 6.8 μm were obtained.
To 100 parts by mass of the obtained toner base particles, 1 part by mass of silica (“RA200-H” manufactured by Nippon Aerosil Co., Ltd.) as an external additive and 2 parts by mass of titanium oxide (“EC-100” manufactured by Titanium Industry Co., Ltd.) And stirring and mixing with a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) under the conditions of a rotational speed of 30 m / second and a mixing time of 5 minutes, to obtain a magnetic toner.

<Measurement / Evaluation>
For the obtained magnetic toner, the number distribution ratio of fine particles, SD, the ratio of ultrafine particles, and the average circularity were measured in the same manner as in Example 1-1. The results are shown in Table 5.
Further, the obtained magnetic toner was used as a magnetic one-component developer, and an a-Si photoconductor-equipped page printer (“FS-4000”, 45 ppm, manufactured by Kyocera Corporation) adopting a magnetic one-component jumping development system as an evaluation machine. ) Was used in the same manner as in Example 1-1, and the image density of the initial image and the printing durability image was measured, and the transferability, fog in a high-temperature and high-humidity environment, image quality, and abrasiveness were evaluated. It was. The results are shown in Table 6.

[Examples 3-2 to 3-5, Comparative examples 3-1 to 3-4]
A mechanical pulverizer in the pulverization step so that the volume average particle diameter (D50) of toner base particles, the number distribution ratio of fine particles, SD, the ratio of ultrafine particles, and the average circularity are the values shown in Table 5. A magnetic toner was produced in the same manner as in Example 3-1, except that the conditions of the airflow classifier in the classification step were changed, and each measurement and evaluation were performed. The results are shown in Table 6.

As is apparent from Table 6, the magnetic toner obtained in each example hardly changed the image density even after printing 5000 sheets (printing durability), and the decrease in the image density could be suppressed. Further, the results of transferability, fog and image quality were also good. Furthermore, the magnetic toner obtained in each example had an appropriate polishing property, and could be polished without excessively scraping the surface of the photoreceptor, thereby suppressing adhesion of the photoreceptor deposits.
On the other hand, the magnetic toner obtained in Comparative Example 3-1 had a small average circularity of 0.944, so that the coefficient of contact friction with the photoreceptor increased, and the transferability and abrasiveness were inferior to those of the Examples. It was.
The magnetic toner obtained in Comparative Example 3-2 had a large SD of 1.28, so that the image density was likely to be lowered, and the image quality was inferior to each of the examples.
The magnetic toner obtained in Comparative Example 3-3 had a fine powder particle number distribution ratio as high as 9.8%. Therefore, the image density was likely to be lowered, and the image quality was inferior to those of the Examples.
In the magnetic toner obtained in Comparative Example 3-4, since the ratio of ultrafine particles was as high as 5.5%, the image density was likely to be lowered, and the image quality was inferior to those of the Examples. Also, fog was likely to occur.

Claims (9)

In an electrophotographic toner obtained by a pulverization method in which an external additive is added to toner base particles containing at least a binder resin, which is used in an image forming apparatus including an amorphous silicon photoreceptor,
The ratio of the number distribution of particles having a particle diameter of 4.0 μm or less in all particles contained in the electrophotographic toner is 8.0% or less,
The standard deviation (SD) of the volume distribution is 1.21 or more and 1.25 or less,
In the externally added toner, the ratio of particles having a particle size of 3.0 μm or less is 2.8% or more and 5.0% or less, and the average circularity of particles having a particle size of 3 to 10 μm is 0.945. The toner for electrophotography characterized by the above.   Development that stirs a developer composed of a non-magnetic toner and a magnetic carrier and forms a thin layer of non-magnetic toner on the surface by contacting the magnetic roller that forms the spike of the developer on the surface and the developer that spiked. An amorphous silicon photoconductor provided with a roller and a constant interval from the developing roller, and an electrostatic latent image is formed on the surface, on the surface of the amorphous silicon photoconductor on which the electrostatic latent image is formed, The non-magnetic toner in an image forming apparatus that develops an electrostatic latent image on the surface of an amorphous silicon photosensitive member as a toner image by flying non-magnetic toner from the thin layer formed on the surface of the developing roller. The toner for electrophotography according to claim 1.   A developing roller that stirs a developer composed of a non-magnetic toner and a magnetic carrier to form a spike of the developer on the surface, and an amorphous that is provided opposite the developing roller and forms an electrostatic latent image on the surface. An image forming apparatus comprising: a silicon photoconductor, wherein the amorphous silicon photoconductor is brought into contact with a spike of developer formed on the surface of the developing roller, and an electrostatic latent image on the surface of the amorphous silicon photoconductor is developed as a toner image. The electrophotographic toner according to claim 1, wherein the toner is the non-magnetic toner in the apparatus.   The electrophotographic toner according to claim 2, wherein the content of the nonmagnetic toner in 100% by mass of the developer is 1 to 20% by mass.   A developing roller that forms a thin layer of magnetic toner on the surface, and an amorphous silicon photoconductor that is provided at a certain distance from the developing roller and forms an electrostatic latent image on the surface. An image forming apparatus for developing an electrostatic latent image on the surface of the amorphous silicon photosensitive member as a toner image by causing magnetic toner to fly from the thin layer formed on the surface of the developing roller onto the surface of the formed amorphous silicon photosensitive member. The toner for electrophotography according to claim 1, wherein the toner is a magnetic toner. A charging process for charging the surface of the amorphous silicon photoreceptor;
Exposing the surface of the amorphous silicon photoreceptor to form an electrostatic latent image; and
A developer consisting of a non-magnetic toner and a magnetic carrier is agitated to form developer spikes on the surface of the magnetic roller, and a thin layer of non-magnetic toner is formed on the surface of the developer roller in contact with the spiked developer. A developing step of causing the non-magnetic toner to fly from the thin layer to the surface of the amorphous silicon photoreceptor and developing the electrostatic latent image as a toner image;
A transfer step of transferring the toner image from the amorphous silicon photosensitive member to the transfer target,
An image forming method using the electrophotographic toner according to claim 1 as the nonmagnetic toner. A charging process for charging the surface of the amorphous silicon photoreceptor;
Exposing the surface of the amorphous silicon photoreceptor to form an electrostatic latent image; and
A developer consisting of a non-magnetic toner and a magnetic carrier is agitated to form developer spikes on the surface of the developing roller, and an amorphous silicon photoreceptor is brought into contact with the developer spikes to form an electrostatic latent image as a toner image. A development process to develop;
A transfer step of transferring the toner image from the amorphous silicon photosensitive member to the transfer target,
An image forming method using the electrophotographic toner according to claim 1 as the nonmagnetic toner. A charging process for charging the surface of the amorphous silicon photoreceptor;
Exposing the surface of the amorphous silicon photoreceptor to form an electrostatic latent image; and
A developing step of developing the electrostatic latent image as a toner image by causing magnetic toner to fly from the thin layer of magnetic toner formed on the surface of the developing roller to the surface of the amorphous silicon photoreceptor;
A transfer step of transferring the toner image from the amorphous silicon photosensitive member to the transfer target,
An image forming method using the toner for electrophotography according to claim 1 as the magnetic toner.   9. The image according to claim 8, wherein the developing roller has a sleeve having a ten-point average roughness (Rz) of 2.0 to 8.0 [mu] m on the surface, and the sleeve is made of stainless steel. Forming method.