JP2004184908A - Developer and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developer which ensures little variation of electrostatic properties even after passage of time and can stably produce images of high image quality, and to provide a high reliability process cartridge using the developer and free of toner scattering. <P>SOLUTION: The developer fed to a developing device 4 for developing an electrostatic latent image and consisting of a toner and a magnetic carrier has a peak value/half-width value not less than 0.5 in the charge amount distribution of the toner and ensures a toner concentration change less than 1% when the developing device 4 is turned with no load. The process cartridge 1 comprises at least a photoreceptor 2 and the developing device 4 using the developer and is constructed in one. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a developer for developing an electrostatic latent image formed in an electrophotographic method, an electrostatic recording method, and an electrostatic printing method, and a process cartridge having a developing unit.
[0002]
[Prior art]
In recent years, demand for full-color images has increased, and as for output devices, full-color machines have been used more frequently than conventional monochrome machines. In a full-color printer, monochrome and full-color printers are often used in combination, so that the image area ratio may vary greatly depending on the document to be printed. For example, an image based on only text information has an image area ratio of about 7%, while an image such as a photograph or a material used for a presentation may have an image area ratio of 80% or more. As described above, the image area ratio greatly differs depending on the output image, and therefore, the amount of toner used greatly changes depending on the image.
When the amount of toner used at one time in the developing device changes as described above, the time during which the toner stays on the developer carrying member is not constant. Therefore, if the toner stays on the developer carrier for a long time, it changes the surface structure of the toner. This change is a change in the state and amount of the additive, the shape of the toner, and the like, and affects the toner characteristics, particularly the charging characteristics.
[0003]
In order to prevent the charging characteristics of the toner from changing significantly with time, there are some conventional techniques for treating the additives of the toner. In Patent Document 1, the adhesion of the additive to the developer carrier is prevented from the charging performance of the additive and the toner, but the adhesion to the magnetic carrier is not clear.
Patent Literature 2 describes that an additive is immobilized on a toner surface by mixing the additive with the toner at a temperature higher than room temperature. In this method, some toner particles can fix the additive by a temperature effect, but it is impossible to make the additive presence state identical in all toners.
Patent Literature 3 attempts to immobilize an additive using ultrasonic waves. Also in this case, it is difficult to keep all additives in the same state to prevent the transfer of the additives to the magnetic carrier.
Further, in Patent Documents 4 and 5, there are a toner in which half the additive is buried and a toner in which the half additive is not buried, so that sufficient durability cannot be obtained.
[0004]
Further, since a change in the shape of the toner also affects the toner charging characteristics, it is desirable that a change in the shape hardly occurs.
Further, changes in the magnetic carrier due to peeling or detachment of the coating material on the surface of the magnetic carrier, adhesion of the toner to the surface of the magnetic carrier, and transfer of silica present on the surface of the toner to the magnetic carrier, etc., are also factors that change the charging characteristics of the toner. It has become.
[0005]
In addition, when outputting a full-color image, it is desired that a high-quality image be output stably. Further, there is a demand in the market for machines having high durability and high reliability. In order to stably output a high quality image, one dot needs to be reproduced stably. Therefore, it has been found that it is necessary to reduce the writing beam diameter, the average particle diameter of the toner, and the average particle diameter of the magnetic carrier. However, in the past, the image characteristics often deteriorated over time even though the granularity and sharpness of the initial image were good. As for reliability, there are problems such as toner scattering and background contamination, but these also have a significant effect on image characteristics, but no remarkable approaches have been seen so far.
[0006]
[Patent Document 1]
JP-A-9-274368 [Patent Document 2]
JP 2000-267354 A [Patent Document 3]
JP 2000-267333 A [Patent Document 4]
JP-A-3-76035 [Patent Document 5]
JP-A-7-92727
[Problems to be solved by the invention]
In view of the above problems, the present invention provides a developer having a small change in charging characteristics, outputs a high-quality image stably over time using the developer, and has reliability without toner scattering. It is an object to provide a process cartridge having high performance.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 is a developer comprising a toner and a magnetic carrier, which is provided to a developing unit for developing an electrostatic latent image, wherein the developer is charged with a toner. The developer has a peak value / half value width value of 0.5 or more in the amount distribution and a toner density change of 1% or less when the developing unit is idled.
The invention according to claim 2 is the developer according to claim 1, wherein the toner has an average particle diameter of 3 to 7 μm, and the carrier has an average particle diameter of 20 to 50 μm.
According to a third aspect of the present invention, in the developer according to the first or second aspect, a peak value of an adhesive force between the toner and the carrier is 1.0 × 10 ^{−8 to} 1.0 × 10 ⁻⁷ N. A certain developer.
[0009]
According to a fourth aspect of the present invention, in the developer according to any one of the first to third aspects, the toner is obtained by adding a fluorine-based compound as a charge control agent.
According to a fifth aspect of the present invention, in the developer according to any one of the first to fourth aspects, the toner is obtained by externally adding silica and titania, and after mixing the toner with silica, the toner is mixed with titania. And then mixed again with silica.
According to a sixth aspect of the present invention, in the developer according to any one of the first to fifth aspects, the charge amount distribution of the toner is −1fC / 10 μm or less, and the ratio is 10% or less.
The invention according to claim 7 is the developer according to any one of claims 1 to 6, wherein the toner contains a compound having a melting point in the range of 60 to 90 ° C as a release agent.
[0010]
The invention according to claim 8 is a process cartridge in which a photoreceptor and a developing unit, and at least one unit selected from a charging unit and a cleaning unit are integrally supported, and are detachably formed in an image forming apparatus main body. A process cartridge in which the developing means uses the developer according to any one of claims 1 to 7.
According to a ninth aspect of the present invention, in the process cartridge according to the eighth aspect, the toner is supplied to the developing unit by an impact type toner supply device.
According to a tenth aspect of the present invention, in the process cartridge according to the eighth or ninth aspect, the coefficient of friction of the surface of the photoconductor is 0.5 or less.
According to an eleventh aspect of the present invention, there is provided the process cartridge according to any one of the eighth to tenth aspects, wherein a surface of the photosensitive member contains a filler.
[0011]
According to a twelfth aspect of the present invention, in the process cartridge according to any one of the eighth to eleventh aspects, the granularity of an image formed using the process cartridge is 0.4 or less.
According to a thirteenth aspect, in the process cartridge according to any one of the eighth to eleventh aspects, the sharpness of an image formed by using the process cartridge is 0.6 or less.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described.
The developer of the present invention is a two-component developer composed of a toner and a magnetic carrier. Generally, the image quality of an image is evaluated based on graininess, sharpness, and gradation. For example, the graininess is deteriorated by background stains in development, dot thickening, dust in transfer, and dot thickening in fixing. Here, it has been found that the background dirt in development, dot thickening, and dust in transfer greatly affect the charge amount distribution of the toner. Therefore, if the charge amount distribution of the toner can be controlled to be constant over time, these adverse effects on image quality can be suppressed. As a result of investigations by the present inventors, the distribution of the charge amount of the toner is such that the value of the peak value / half-value width is 0.5 or more from the initial stage when the developer is in the developing unit, and this distribution even with time. Has been found to be desirable. If the value of the peak value / half width in the charge amount distribution becomes less than 0.5 over time, the charge amount distribution is widened, causing background smearing in development, dot thickening, and dust in transfer.
In addition, the developer including the toner having the above-described charge amount distribution and the magnetic carrier has a toner concentration change of 1% or less when the developer is idled in the developing unit. This is because if the toner density change exceeds 1%, toner scattering or the like occurs and adversely affects the image.
[0013]
Further, in order to improve the granularity, it is preferable that the particle size of the toner is small, and the average particle size is 3 to 7 μm, more preferably 3 to 5 μm. The magnetic carrier for charging the toner also preferably has a small diameter because it affects the granularity, and has an average particle diameter of 20 to 50 μm, and more preferably 20 to 40 μm.
[0014]
To prevent toner scattering, it is necessary to control the adhesion between the toner and the magnetic carrier. This is because toner easily scatters when the toner is easily detached from the magnetic carrier on the developing sleeve that supplies the toner onto the photoconductor. Therefore, it is desirable that the peak value of the adhesive force between the toner and the magnetic carrier is 1.0 × 10 ^{−8 to} 1.0 × 10 ⁻⁷ N. If the value is smaller than this value, a large amount of toner is scattered, and if the value is larger than this value, the developing ability is reduced and the image density is reduced.
[0015]
It is preferable to use a fluorine compound as the charge control agent of the toner. The fluorine-based compound, general ^{_{formula: Rf-X-NH 4 +}} Y - compounds represented by the like. Here, Rf is a perfluoroalkyl group, X is a group such as amide, urea, urethane, methylene, phenyl and bisphenol, and Y is halogen. The charge control of the toner is controlled by controlling the ζ potential of the toner surface in a polymerization process in which a toner composition in which a toner binder, a colorant, etc. are dissolved or dispersed in an organic solvent is dispersed in an aqueous medium to produce a toner. Then, the above-mentioned fluorine-based compound can be attached to the surface of the toner. This makes it easy to control the charge amount distribution and minimizes the change in the toner charge amount distribution over time.
[0016]
The toner contains silica and titania as an external additive, and the toner and the external additive are mixed with the silica, then mixed with the titania, and then mixed with the silica again. It is preferable that the processing is divided into three. The toner into which the external additive has been injected by this method can obtain a stable charge amount distribution without exchanging additives between the toner in the developing means and the replenishment toner. Therefore, it is possible to minimize the generation of a low charge component in the charge distribution of the toner, thereby achieving high image quality.
As for the charge amount distribution of the toner in the developing means, the ratio of -1fC / 10 m or less is set to 10% or less. As a result, toner scattering is greatly reduced, and at the same time, background toner is also reduced, thereby achieving high image quality.
[0017]
Further, the toner preferably contains a compound having a melting point in the range of 60 to 90 ° C. as a release agent. Specific examples include higher fatty acid esters, carnauba wax, rice wax, polyethylene, polypropylene and the like. By containing the above compound, oil-less fixing of the toner on the recording material becomes possible, and it becomes possible to obtain a low gloss image with controlled gloss.
[0018]
Next, the process cartridge of the present invention will be described.
FIG. 1 is a diagram showing a schematic configuration of a process cartridge according to the present invention. Photoreceptor 2, charging roller 3 as a charging unit for charging the surface of photoreceptor 2, developing unit 4 for developing a latent image formed on the surface of photoreceptor 2, cleaning for cleaning the surface of photoreceptor 2 after image formation The process cartridge 1 is formed by integrally supporting the means 7. The process cartridge of the present invention is not limited to the configuration shown in FIG. 1 and may include at least the photoconductor 2 and the developing unit 4. In addition, a plurality of components such as the charging unit 3 and the cleaning unit 7 may be used. May be included.
The process cartridge 1 is configured to be detachable from a main body of an image forming apparatus such as a copying machine or a printer. The developer described above is used for the developing means 4.
[0019]
The photoconductor 1 has a configuration in which toner filming is prevented by setting the surface friction coefficient to 0.5 or less and suppressing the surface roughness to submicron or less. Further, by providing a top coat layer containing a filler on the surface, the wear rate of the photoconductor can be suppressed.
The charging of the photoconductor 1 is non-contact charging by the charging roller 3. With this charging method, the surface of the photoconductor 1 can be uniformly charged without uneven charging.
Further, with the above configuration, the durability of the photoreceptor 1 can be improved, and a high durability and high quality image can be obtained up to 300K sheets.
[0020]
In the process cartridge 1, in order to make the toner charge amount distribution appropriate, the method of replenishing the developing unit 4 with the toner is preferably an impact type toner supply device. FIG. 2 is a diagram showing a schematic configuration of the impact type toner supply device. When the toner density sensor provided in the developing means 4 of FIG. 1 detects a decrease in the toner density in the developing means 4, it sends a replenishment signal to the impact type toner supply device 5 of FIG. When the toner container 5a is received, the toner container 5a moves in the direction of arrow A in the figure and collides with the damper 5b. Due to this collision, the toner in the toner container 5a vibrates, falls in the direction of arrow C in the figure, and is supplied to the developing means 4. As described above, the toner is supplied by the vibration, so that the charge amount distribution of the toner can be appropriately maintained. It was also found that the durability of the image forming apparatus was improved and the quality of the image was stabilized by using the process cartridge together.
[0021]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples. Note that these examples are only one aspect of the present invention, and the present invention is not limited to these.
[0022]
[Example 1]
100 parts by weight of a low-molecular-weight polyester resin, 6 parts by weight of carbon black, 5 parts by weight of a synthetic ester wax, and 1 part by weight of a polymer charge controlling agent are kneaded by a usual screw kneader kneading method, followed by rolling and cooling followed by coarse pulverization. The obtained toner was pulverized by a jet mill, and finally, a toner having a volume average particle size of 4.8 μm and a number average particle size of 4.5 μm was obtained by an airflow classifier.
Similarly, for magenta, cyan, and yellow, color toners were obtained by changing the pigment.
Next, 0.3 parts by weight of silica was added to 100 parts by weight of the obtained toners of each color, and mixed for 1 minute using a Henschel mixer. Subsequently, 0.3 part by weight of titania was added and mixed for 1 minute, and then 1.0 part by weight of silica was added and mixed for 1 minute.
5 parts by weight of the obtained toner was mixed with a magnetic carrier having an average particle diameter of 38 μm to prepare a developer. When the charge amount distribution of the toner was measured using E-Spart manufactured by Hosokawa Micron Corporation, the value of the peak value / half value width over time from the initial stage was 0.4, and the ratio of −1fc / 10 μm or less in the charge amount distribution was found. 4%. In addition, when the Ricoh color printer Ipsio8000 developing unit alone was idle, the toner density change in the unit was 0.6%. Further, the adhesive force of the toner was 3.0E-08N.
[0023]
Next, the developer was placed in a developing unit of a color printer Ipsio8000 manufactured by Ricoh, and an image was formed. The photoreceptor used had a top coat layer containing a filler provided on the surface. As the toner supply device for the developing unit, an impact type toner supply device shown in FIG. 2 was used. The obtained image was a high-quality image with a granularity of 0.12 and a sharpness of 0.44. When 100K sheets were printed using this developer and the image was evaluated, a high-quality image with a granularity of 0.19 and a sharpness of 0.94 was obtained.
[0024]
[Example 2]
A toner was produced in the same manner as in Example 1, except that the same material as in Example 1 was used and the toner particle diameter was changed to 3.7 μm in volume average particle diameter and 3.3 μm in number average particle diameter. Mixing of additives was performed in the same manner as in Example 1.
5 parts by weight of the obtained toner was mixed with a magnetic carrier having an average particle diameter of 38 μm to prepare a developer. When the charge amount distribution of the toner was measured using E-Spart manufactured by Hosokawa Micron Corporation, the value of the peak value / half-width from the beginning to the lapse of time was 0.43, and the ratio of −1fc / 10 μm or less in the charge amount distribution was found. 7%. Further, when the Ricoh color printer Ipsio8000 developing unit alone was idle, the toner density change in the unit was 0.3%. Further, the adhesion of the toner was 9.2E-08N.
Next, the developer was placed in a developing unit of a color printer Ipsio8000 manufactured by Ricoh, and an image was formed. The photoreceptor used had a top coat layer containing a filler provided on the surface. As the toner supply device for the developing unit, an impact type toner supply device shown in FIG. 2 was used. The obtained image was a high-quality image with a granularity of 0.08 and a sharpness of 0.41.
[0025]
[Comparative Example 1]
Using the same materials as in Example 1, a toner was produced in the same manner. The method of mixing the additives was different from that of Example 1 and was performed by mixing silica and titania at once.
5 parts by weight of the obtained toner was mixed with a magnetic carrier having an average particle diameter of 38 μm to prepare a developer. When the charge amount distribution of the toner was measured using E-Spart manufactured by Hosokawa Micron Corporation, the value of the peak value / half-value width over time from the initial stage was 1.33, and the ratio of −1fc / 10 μm or less in the charge amount distribution was found. It was 12%. The toner density change in the Ricoh color printer Ipsio8000 developing unit when the single developing unit was idle was 2.2%. Further, the adhesive force of the toner was 9.5E-09N.
Next, the developer was placed in a developing unit of a color printer Ipsio8000 manufactured by Ricoh, and an image was formed. Incidentally, as a toner supply device for the developing unit, an impact type toner supply device shown in FIG. 2 was used. The obtained image was an image in which the image quality was deteriorated with a granularity of 0.55 and a sharpness of 0.64.
[0026]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a developer with little change in charging characteristics even with time, and it is possible to stably output a high-quality image with time. Further, according to the present invention, it is possible to provide a highly reliable process cartridge without toner scattering.
[Brief description of the drawings]
FIG. 1 is a view showing a schematic configuration of a process cartridge according to the present invention.
FIG. 2 is a diagram illustrating a schematic configuration of an impact type toner supply device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Process cartridge 2 Photoconductor 3 Charging roller 4 Developing means 5 Impact type toner supply device 7 Cleaning means

Claims (13)

In a developer comprising a toner and a magnetic carrier to be provided to a developing unit for developing an electrostatic latent image,
The developer has a peak value / half value width value of 0.5 or more in a toner charge amount distribution,
A developer, wherein a change in toner concentration when the developing unit is idle is within 1%. The developer according to claim 1,
The developer is characterized in that the toner has an average particle diameter of 3 to 7 μm, and the carrier has an average particle diameter of 20 to 50 μm. The developer according to claim 1, wherein
The developer, wherein a peak value of an adhesive force between the toner and the carrier is 1.0 × 10 ^{−8 to} 1.0 × 10 ⁻⁷ N. The developer according to any one of claims 1 to 3,
The developer, wherein the toner is obtained by adding a fluorine compound as a charge control agent. The developer according to any one of claims 1 to 4,
The developer is obtained by externally adding silica and titania to the toner, mixing the toner with silica, mixing with titania, and then mixing with silica again. The developer according to any one of claims 1 to 5,
The developer according to claim 1, wherein the toner has a charge amount distribution of -1fC / 10 m or less and a ratio of 10% or less. The developer according to any one of claims 1 to 6,
The developer according to claim 1, wherein the toner contains a compound having a melting point in the range of 60 to 90C as a release agent. A process cartridge integrally supporting a photoreceptor and a developing unit, and at least one unit selected from a charging unit and a cleaning unit, and detachably formed in the image forming apparatus main body;
8. A process cartridge, wherein the developing means uses the developer according to claim 1. The process cartridge according to claim 8, wherein
The developing unit is supplied with the toner by an impact type toner supply device. The process cartridge according to claim 8, wherein
A process cartridge according to claim 1, wherein said photosensitive member has a surface friction coefficient of 0.5 or less. The process cartridge according to claim 8, wherein
A process cartridge wherein the photosensitive member contains a filler on the surface. The process cartridge according to any one of claims 8 to 11,
An image formed using the process cartridge has a granularity of 0.4 or less. The process cartridge according to any one of claims 8 to 11,
A process cartridge wherein the sharpness of an image formed using the process cartridge is 0.6 or less.

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