JP2009198899A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image forming apparatus which can enhance the recycle efficiency of black developer high in use frequency by recovering the black developer without being color-mixed in a color image forming process, and can shorten the reduce printing time in monochrome image formation. <P>SOLUTION: Toner images formed on YCM image carriers 1Y, 1C, and 1M are superposed and transferred to an intermediate transfer belt 6. A black toner image formed by an image carrier 1B is directly transferred to transfer paper conveyed by the transfer paper conveying belt 8 of a recording medium transfer means 15. Subsequently, the toner images superposed on the intermediate transfer belt 6 are transferred to the transfer paper by a secondary transfer roller 28. When a monochrome image is formed, the secondary transfer roller 28 is operated by a contact/separation mechanism, not shown, the transfer paper conveying belt 8 is separated from the intermediate transfer belt 6, and only the recording medium transfer means 15 is operated to transfer the black toner image. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, a plotter, or a multifunction machine provided with at least one of these, and more specifically, has an intermediate transfer member and recycles toner collected from an image carrier. The present invention relates to an image forming apparatus capable of forming a color image of a dry two-component development system.

In an electrophotographic image forming apparatus, an electrostatic latent image obtained by forming optical image information on a latent image carrier (image carrier) that is uniformly charged in advance is developed into a developing device (hereinafter referred to as a developing device). The image is formed by visualizing the toner with toner from a developing unit) and transferring and fixing the visible image on an intermediate transfer member or transfer paper.
In a color image forming apparatus, a toner image of a plurality of colors is formed on an image carrier, and this is overlaid on an intermediate transfer member or a transfer material (recording material) transported by a transfer belt (transfer material transport member). As a result, a full-color image is finally formed on the transfer material.
In this type of image forming apparatus, (1) one or two image carriers are sequentially formed with a plurality of color toner images, and (2) an image carrier and an image carrier for each of a plurality of colors. Some have a developing device that forms a toner image on the body and a cleaning device that cleans the toner on the image carrier (hereinafter also referred to as “cleaning means”).
The latter color image forming apparatus is usually of a so-called tandem type in which each color is arranged on a straight line along the running direction with respect to the intermediate transfer member or transfer belt.
The tandem method is excellent in speeding up because it can simultaneously form toner images of a plurality of colors.

By the way, a color image forming apparatus uses a larger number of toner colors than a monochrome one and outputs a document with a large image area ratio as in the case of a photographic document. From the viewpoints of space and running cost reduction, toner recycling is an important issue.
Regarding the toner recycling, in the electrophotographic color image forming apparatus as described above, the toner image on the image carrier corresponding to each color is directly or indirectly transferred onto the transfer material, and the color image is formed. Although formed, in each image carrier, a part of the toner (toner image) carried on the image carrier is unavoidably left on the image carrier without being transferred to the transfer material. The remaining toner is removed and collected by a cleaning means provided in each image carrier.

In practice, however, several problems have arisen with respect to the recycling of this toner. One of them is a problem of color mixing that occurs when an upstream color is mixed into a downstream color process.
In the case of a tandem system in which image carriers are provided in the number corresponding to the number of toner colors, each cleaning unit cleans toner of a color corresponding to the image carrier, so that the collected toner is returned to the developing device of that color for image formation. It is easy to reuse.
Furthermore, since the image forming systems for the respective colors are independent of each other, color mixing should ideally not occur in the tandem system, but in reality, this color mixing is unavoidable. This color mixture occurs in the transfer process of the toner image of each color from the image carrier to the transfer material.

The process in which the above color mixture occurs will be specifically described.
In the tandem system, for example, when a color image is formed on a transfer material by overlappingly transferring a toner image from an image carrier of each color onto a transfer material conveyed by a transfer belt, the second and subsequent color images are supported. When the toner (toner image) on the body is transferred to the transfer material, the color toner transferred on the upstream side in the transfer material moving direction is placed on the transfer material.
The upstream color toner on the transfer material is reversely transferred from the transfer material to the image carrier when the downstream color is transferred, and the reversely transferred toner is collected by the downstream color cleaning, and the toner collected by the downstream color cleaning unit. Is mixed with an upstream color (for example, the first color toner is reversely transferred to the second color image carrier and the first color toner is collected by the second color cleaning means). This color mixture also occurs in an intermediate transfer system using an intermediate transfer member.
As described above, in the conventional color image forming apparatus, when the toner is collected from the image carrier of each color and the collected toner is recycled as it is to the developing means corresponding to the image carrier of the collection source, as the image forming time elapses, There arises a problem that the hue of the toner in the developing means gradually changes from a state where there is no color mixing.

  In order to deal with such problems, in the intermediate transfer type tandem color arrangement so that color mixing does not occur, the recovered toner from the most upstream black image carrier that is not mixed is collected and reused in the black developing device. (Patent Document 1), or in the case of toner with mixed colors, all of this is mixed with black toner and reused (Patent Document 2), or the transport path of the collected toner can be switched, and reused or discarded as appropriate. (Patent Document 3) or a configuration in which a developing device dedicated to mixed-color toner is provided (Patent Documents 4 and 5) has been proposed.

JP 2002-357938 A Japanese Patent No. 3366969 JP 2002-36595 A JP 2000-35703 A JP 2006-30519 A

Looking at the operation status of color image forming apparatuses in the market, the proportion of monochrome images is about 70 to 80%, and considering that black toner is consumed even during full color image formation, black toner in waste toner It can be seen that the ratio is quite high.
For this reason, as in Patent Document 1, even if the collected toner is reused so that only the black toner is not mixed with the other color toner, it is practical because most of the collected toner does not have to be discarded.
However, in Patent Document 1, in each tandem color arrangement, as shown in FIG. 5, the image carrier 1 </ b> B corresponding to black and the developing device are arranged on the most upstream side, and therefore, from the transfer position S to the transfer paper. The farthest position. In FIG. 5, 1Y is an image carrier corresponding to yellow, 1M is an image carrier corresponding to magenta, 1C is an image carrier corresponding to cyan, and 50 is an intermediate transfer belt.
Therefore, when forming a monochrome image with the highest operating rate in the market, there is a problem that it takes a long time from the black toner being visualized to being transferred to the transfer paper.
Further, not only is the waiting time from when the operator executes printing to when the transfer paper is actually ejected, but also the idle time of each imaging device of other colors that is not required for monochrome image formation. Due to its long length, there is a problem that the wear speed of parts that are idly idle is increased and the life of the parts is shortened.

In Patent Document 2, in order to reuse the mixed color toner in the black developing device, the amount of the collected toner is limited to a predetermined mixing amount or less. However, the black color tone is inevitably caused by mixing of the mixed color toner. It is inevitable that the image quality will deteriorate due to changes.
In Patent Document 3, reused and discarded toner is collected by switching the rotation direction of the toner conveying screw. However, mixed-color toner is stored inside the cleaning device 4 and is used for each image by pixel count. Even if the amount of toner used can be ascertained, the integrated value is actually handled, so it is difficult to accurately estimate the degree of color mixing in the collected toner.
In Patent Documents 4 and 5, since it is necessary to install a developing device dedicated to mixed color toner, an image carrier, etc. and install more units than the normal number of image forming units, the size of the machine increases and the manufacturing cost increases. There was a defect that would cause an increase in

  The present invention has been made in view of such a situation. In the image forming process of a color image, the black developer is collected in a state where it is not mixed to improve the recycling efficiency of the black developer that is frequently used. The main object of the present invention is to provide a color image forming apparatus capable of shortening the printing time during image formation.

  To achieve the above object, according to the first aspect of the present invention, a plurality of image carriers corresponding to each color including black and a developer for developing a latent image on each image carrier are accommodated. A plurality of developing devices and an intermediate transfer body for transferring a visualized toner image, and the black toner recovered from the image carrier corresponding to black after the transfer, corresponding to black In the image forming apparatus which is returned to and reused, the image carrier corresponding to a color other than black and the developing device are arranged to transfer the toner image to the intermediate transfer member, and the image carrier corresponding to black. And the developing device is provided independently of the intermediate transfer member upstream of the intermediate transfer member in the conveyance direction of the recording medium, and after transferring the toner image on the image carrier corresponding to the black to the recording medium Above It characterized in that it has a transferable recording medium transfer means superimposed toner images on between transcript.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the recording medium transfer unit directly transfers the toner image on the image carrier corresponding to the black to the recording medium. It is characterized by that.
According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the recording medium transfer unit includes an endless transfer conveyance belt and a secondary that makes the transfer conveyance belt contact and separate from the intermediate transfer member. And a transfer means.

According to a fourth aspect of the invention, there is provided the image forming apparatus according to the first or second aspect, further comprising means for bringing the intermediate transfer member into contact with or separating from the recording medium transfer means.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, an image carrier corresponding to a color other than the black is in contact with the intermediate transfer body. To do.

According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the intermediate transfer member has an endless belt shape.
According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the plurality of image carriers and developing devices corresponding to the respective colors are integrally supported by individual process cartridges detachably attached to the main body of the image forming apparatus. It is characterized by being.
According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the toner has a circularity of 0.92 or more.

According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the toner has a shape factor SF-1 in the range of 100 to 180, and the shape factor SF-2. It is characterized by being in the range of 100-180.
According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to ninth aspects, the toner has a volume average particle diameter (Dv) in a range of 3 to 8 μm, and a volume average particle diameter. The degree of dispersion defined by the ratio (Dv / Dn) of (Dv) to the number average particle diameter (Dn) is in the range of 1.05-1.40.

According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the first to tenth aspects, the toner has a major axis / minor axis ratio (r2 / r1) of 0.5 to 1. In the range of 0, the ratio of the thickness to the minor axis (r3 / r2) is in the range of 0.7 to 1.0, and the relationship of major axis r1 ≧ minor axis r2 ≧ thickness r3 is satisfied. And
According to a twelfth aspect of the present invention, in the image forming apparatus according to any one of the first to eleventh aspects, the toner includes a polyester prepolymer having a functional group containing a nitrogen atom, a polyester, a colorant, and a release agent. The toner composition is a toner that causes at least one of crosslinking and elongation to react in an aqueous medium in the presence of resin fine particles.

According to the present invention, in the image forming process of a color image, since the black developer can be recycled without any color mixture, it is possible to increase the recycling efficiency of the frequently used black developer without causing deterioration in image quality. , It can contribute to shortening the waiting time and reducing the cost.
Further, if the direct transfer method is adopted in the black image transfer device (recording medium transfer means), the number of components can be reduced, and further, the black image laser writing image exposed from the exposure device can be converted into a YCM image laser. Writing can be performed in the same direction as the writing image, and the writing control is not complicated, which can further contribute to cost reduction.
In addition, since there is no tension fluctuation of the intermediate transfer belt, color misregistration during full color image formation can be suppressed with high accuracy.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a color digital multifunction peripheral as an image forming apparatus according to the present embodiment. As shown in FIG. 1, the color digital multi-function peripheral has three image forming units 12Y, 12C, and 12M of yellow, cyan, and magenta (hereinafter abbreviated as Y, C, and M) arranged in a loop and substantially horizontally. This is a tandem system arranged in series in the belt moving direction along an intermediate transfer belt 6 as an extended intermediate transfer body.
The black image forming unit 12B is provided independently upstream of the tandem arrangement in the transfer paper (recording medium) moving direction so that the toner image of the black image forming unit 12B is directly transferred to the transfer paper. Has been placed.
The black (B) image forming unit 12B is independent of the Y, C, and M transfer configurations for the intermediate transfer belt 6, and the black toner image created there is a recording medium transfer unit different from the intermediate transfer belt 6. 15 is directly transferred to the transfer paper.
The recording medium transfer means 15 is arranged so as to intersect the intermediate transfer belt 6 extending substantially horizontally substantially vertically.
More specifically, the black image forming unit 12B is arranged in the vicinity of the substantially vertical conveyance path of the transfer paper, and the recording medium transfer unit 15 is located upstream of the fixing device 10 in the substantially vertical conveyance path. Arranged using space.

Each of the image forming units 12Y, 12C, 12M, and 12B is a process cartridge that is detachable from the main body of the image forming apparatus.
Each image forming unit 12 includes a photoreceptor 1 as an image carrier, a charging device 2, a developing device 3 for supplying toner to a latent image to form a toner image, a cleaning device 4 and the like. Each image forming unit 12 is arranged such that each photoreceptor 1 is in contact with the lower extending surface of the intermediate transfer belt 6.
An electrostatic latent image is formed on each photoconductor by the exposure device 5 that forms a latent image with a laser.
In the present embodiment, a blade type device is used as the cleaning device 4. However, the present invention is not limited to this, and a fur brush roller or a magnetic brush cleaning method may be used. Further, the exposure apparatus 5 is not limited to the laser system, but may be a system such as an LED system.

Received data such as a document or facsimile read by the scanner 16 or color image information transmitted from a computer is color-separated into yellow, cyan, magenta, and black colors to form plate data for each color. It is sent to the exposure device 5 of the image forming unit.
The uniformly charged photosensitive member 1 is exposed on the image portion by exposure light for each color from the exposure device 5, and a toner image is formed by the developing device 3. The color toner images formed on the photoconductors 1Y, 1C, and 1M are transferred to the intermediate transfer belt 6 at the same timing, and a color-superposed toner image is formed.

The intermediate transfer belt 6 is supported by a driving roller 17, a driven roller 18, and tension rollers 19 and 20. The intermediate transfer belt 6 faces the respective photoreceptors 1 inside the intermediate transfer belt 6 and serves as a primary transfer unit. Transfer rollers 21Y, 21C, and 21M are provided.
A cleaning means 7 for removing residual toner on the intermediate transfer belt 6 is provided outside the intermediate transfer belt 6 so as to face the driven roller 18.
The black toner image formed on the photoreceptor 1B is directly transferred to a transfer sheet conveyed by a transfer sheet conveying belt 8 as a transfer conveying belt, and then a YCM toner image superimposed on the intermediate transfer belt 6 is color-transferred. Transferred onto transfer paper.
Therefore, the transfer paper conveyance belt 8 functions as a direct transfer belt in the transfer portion of the black toner image, and functions as a secondary transfer belt in the transfer portion of the YCM toner image on the intermediate transfer belt 6.

Paper feed trays 22 and 23 having different transfer paper sizes are provided in the lower part of the image forming apparatus main body. Transfer paper P fed from each paper feed tray by a paper feed unit (not shown) is transferred by a transport unit (not shown). It is conveyed and reaches the registration roller pair 24, and after the skew is corrected here, it is conveyed by the registration roller pair 24 to the transfer portion of the photosensitive member 1 </ b> B and the transfer paper conveyance belt 8 at a predetermined timing.
The transfer paper onto which the black toner image and the YCM toner image are transferred is fixed by the fixing device 10 to form a color image. After the fixing, the transfer paper is transported along the transport path R1, and is discharged and stacked on the paper discharge tray 31 by the paper discharge roller pair 30 in a face-down state. In the duplex mode, the sheet is guided to the transport path R2 by a switching claw (not shown), reversed by the duplex unit 33, and then transported to the registration roller pair 24 to follow the same paper discharge path as that for single-sided copying.

The recording medium transfer unit 15 includes a transfer paper transport belt 8, a driving roller 25 that supports the transfer paper transport belt 8, a driven roller 21B that also serves as a transfer unit, a tension roller 27, and a secondary transfer roller as a secondary transfer unit. 28 and a cleaning means 9 for cleaning the transfer paper conveyance belt 8 and the like.
The secondary transfer roller 28 is disposed to face the driving roller 17 of the intermediate transfer belt 6 and can be brought into contact with and separated from the intermediate transfer belt 6 by a contact / separation mechanism (not shown).
At the time of creating a monochrome image, the image unit on the photoreceptor 1B is exposed by the exposure device 5 based on the black image data, and a toner image is formed by the developing device 3B.
The created black toner image is directly transferred onto the transfer paper transported by the transfer paper transport belt 8 and is fixed by the fixing device 10 to form a monochrome image.
At the time of monochrome image formation, as shown in FIG. 2, the contact portion of the intermediate transfer belt 6 and the transfer paper transport belt 8 is released by the contact / separation mechanism (not shown) and is separated to the position indicated by the alternate long and short dash line. Each image forming unit 12 and the intermediate transfer belt 6 do not operate.
For this reason, there is a secondary merit that the life of each YCM image forming unit 12 and the intermediate transfer belt 6 can be extended.

In this embodiment, the secondary transfer roller 28 is displaced. However, the entire transfer paper conveying belt 8 may be displaced with the driven roller 21B as a fulcrum.
Since the transfer paper conveyance belt 8 side, which has a significantly shorter circumference than the intermediate transfer belt 6, is brought into contact with and separated from the intermediate transfer belt 6, the intermediate transfer belt 6 can be stationary (not linked to the transfer paper conveyance belt 8), and therefore the tension fluctuation of the intermediate transfer belt 6 can be changed. There is no.
That is, the intermediate transfer belt 6 having a large number of color matching can be configured to be in contact with or separated from the transfer paper transport belt 8, but in this case, the positional accuracy for color matching may be deteriorated with time. . On the other hand, in the present embodiment, the intermediate transfer belt 6 can be configured to remain in contact with the YCM photoreceptors 1.
For this reason, since the positioning accuracy between the rollers of the intermediate transfer belt 6 can be set high, the margin with respect to the belt shift is improved. Further, by stabilizing the belt running, it is possible to improve the margin with respect to the color shift at the time of full color.
Conventionally, a configuration is also known in which an intermediate transfer belt is separated from an image carrier of a color other than black during monochrome image formation. In this method, it is not necessary to drive only the intermediate transfer belt and drive (idle) an image forming unit of a color other than black. However, since the intermediate transfer belt is displaced, the above problem of fluctuation in tension is unavoidable.

The drive roller 17 that supports the intermediate transfer belt 6 may be displaced by means (not shown) so that the intermediate transfer belt 6 contacts and separates from the transfer paper transport belt 8.
In this case, since the transfer paper transport posture does not change, the behavior of the transfer paper between the transfer paper transport belt 8 and the fixing device 10 does not become unstable. For this reason, it is possible to prevent the transfer paper after being discharged from the fixing device 10 from being wrinkled or disturbed.

Since the black image forming unit 12B is arranged independently of the YCM image forming unit, the YCM reverse transfer toner is not mixed in the black image forming process.
Therefore, the toner collected from the photoreceptor 1B is conveyed to the black developing device 3B through a black toner collection path (not shown) and reused.
In the middle of the black toner collection path, an apparatus for removing paper dust or an apparatus capable of switching to a path for discarding toner may be provided.
A toner bank 32 is provided above the intermediate transfer belt 6. The toner bank 32 includes toner tanks 32B, 32Y, 32, C, and 32M, and these toner tanks are connected to the developing devices 3 by toner supply pipes 33B, 33Y, 33C, and 33M.

In the present embodiment, the type in which the black toner image is directly transferred onto the transfer paper is shown, but this is because the number of components is reduced and the laser writing image of the black image exposed from the exposure device 5 is YCM. This is because there is a merit that writing can be performed in the same direction as the laser writing image.
The present invention is not limited to this, and may be a method of transferring a toner image formed on the photosensitive member 1 corresponding to black onto a transfer sheet via an intermediate transfer belt and an intermediate transfer roller. However, in this case, the laser writing image of the black image exposed from the exposure device 5 becomes a mirror image of the laser writing image of the YCM image, and the writing control becomes complicated.

The toner is composed of at least a binder resin and a colorant, and a lubricant for reducing friction is externally added to the toner surface. In addition, a charge control agent for controlling the chargeability of the toner and releasability to the fixing device. It may contain an external additive that contains a release agent or the like that improves fluidity and imparts fluidity.
The binder resin is an ester resin, a vinyl resin, an amide resin, an epoxy resin, a silicone resin, or the like, and a vinyl resin is particularly preferable. Specifically, styrene such as polystyrene, poly P-chlorostyrene, polyvinyltoluene, and the like Homopolymer of the substituted product, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate Copolymer, styrene-ethyl acrylate copolymer, styrene-butyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-butadiene copolymer, styrene-meta Use methyl acrylate-butyl acrylate copolymer, etc. Rukoto can.

  As the colorant, all dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher, yellow Lead, titanium yellow, polyazo yellow, bengara, red lead, lead vermilion, cadmium red, cadmium mercurial red, antimony vermilion, permanent red 4R, para red, phise red, parachlor ortho nitroaniline red, risor fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmine BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Per Nent Red F5R, Brilliant Carmine 6B, Pigment Scarlet 3B, Thioindigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red, Polyazo Red, Chrome Vermilion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean blue, alkali blue rake, peacock blue rake, Victoria blue rake, metal-free phthalocyanine blue, phthalocyanine blue, indigo, ultramarine blue, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone Violet, Chrome Green, Zinc Green, Pigment Green B, Naphthol Green B, G Ngorudo, titanium oxide, zinc white, lithopone and mixtures thereof can be used. The content of the colorant is usually 1 to 15%, preferably 3 to 10%, based on the toner.

As the charge control agent, for example, a salicylic acid compound, a nigrosine dye, a quaternary ammonium salt compound, an alkylpyridinium compound, or the like can be used. The content is usually from 0.1 to 5%, preferably from 1 to 3%, based on the toner.
As the release agent, for example, polyolefin wax such as low molecular weight polyethylene, low molecular weight polypropylene, low molecular weight polyethylene-polypropylene copolymer, ester wax such as fatty acid lower alcohol ester, fatty acid higher alcohol ester, fatty acid polyhydric alcohol ester, An amide wax or the like can be used. The content is usually 0.5 to 10%, preferably 1 to 5%, based on the toner.

The toner preferably has a circularity of 0.92 or more. Circularity SR = (peripheral length of a circle having the same area as the particle projection area / perimeter length of the particle projection image) × 100%. The closer the toner is to a true sphere, the closer to 100%. When such a toner is used in a conventional image forming apparatus, there is a case where the toner cannot be sufficiently scraped by contact with a cleaning member such as a cleaning blade of the cleaning device 4. This is because the toner easily rolls on the photoreceptor 1. In this case, it can be considered that the cleaning blade is brought into contact with the photoconductor 1 with a stronger force, but this affects the rotation or movement accuracy of the photoconductor 1 and causes banding.
On the other hand, a lubricant is applied to the surface of the photoconductor 1 from both the application means and the toner (not shown) to reduce the friction coefficient of the surface of the photoconductor 1, thereby increasing the transfer rate at the time of transfer and remaining toner. It is possible to reduce the burden of cleaning by the cleaning blade and to perform cleaning without banding even if the cleaning blade comes into contact with a strong force.

This degree of circularity is thermally or mechanically spheroidized with toner produced by dry grinding. Thermally, for example, the spheronization treatment can be performed by spraying toner base particles together with a hot air stream on an atomizer or the like. In addition, a spheroidizing treatment can be performed by mechanically charging the mixture into a mixer such as a ball mill together with a mixed medium such as glass having a low specific gravity and stirring. However, in the thermal spheronization process, toner base particles that are aggregated and have a large particle size or fine particles are generated in the mechanical spheronization process, and thus a second classification step is required. In addition, in a toner manufactured in an aqueous solvent, the shape can be controlled by applying strong stirring in the process of removing the solvent.
Furthermore, a fluidity imparting agent may be added to the toner. Examples of the fluidity-imparting agent include fine particles of metal oxides such as silica, titania, alumina, magnesia, zirconia, ferrite, and magnetite, and metal oxides obtained by treating these fine particles with a silane coupling agent, titanate coupling agent, or zircoaluminate. Fine particles. Silica and titania hydrophobized with a coupling agent are preferred. Since the primary particle diameter of silica is small, the effect of imparting fluidity is large. Further, titania can control the toner charge amount. It is more preferable to add these in combination.
Further, the amount of lubricant added externally to the toner is preferably in the range of 0.1 to 2.0%. If the addition amount of the lubricant is less than 0.1%, the amount supplied to the photoreceptor 1 is small and it is difficult to reduce the friction coefficient of the photoreceptor 1. If it exceeds 2.0%, the photoreceptor 1 is charged with the charging roller. 14a or the like may cause an abnormal image.

Further, since the toner having a smaller volume average particle diameter Dv can improve the reproducibility of fine lines, a toner having a maximum particle size of 8 μm or less is used. However, since the developing property and the cleaning property are lowered when the particle size is small, at least 3 μm is preferable. Further, if the particle size is less than 3 μm, the toner having a small particle diameter that is difficult to be developed on the surface of the carrier or the developing roller increases. This is not preferable because an abnormal image such as fogging is formed.
Moreover, it is preferable that the particle size distribution represented by ratio (Dv / Dn) of volume average particle diameter Dv and number average particle diameter Dn is the range of 1.05-1.40. By sharpening the particle size distribution, the toner charge amount distribution can be made uniform. When Dv / Dn exceeds 1.40, the toner charge amount distribution is wide and the amount of the reversely charged toner T1 increases, making it difficult to obtain a high-quality image. If Dv / Dn is less than 1.05, it is difficult to produce and it is not practical. The particle size of the toner is 50,000 by using a Coulter Counter Multisizer (manufactured by Coulter Co., Ltd.) and selecting an aperture having a measurement hole size of 50 μm corresponding to the particle size of the toner to be measured. It is obtained by measuring the average particle size of the particles.

The toner preferably has a shape factor SF-1 in the range of 100 or more and 180 or less and a shape factor SF-2 in the range of 100 or more and 180 or less in the circularity.
3A and 3B are diagrams schematically illustrating the shape of the toner. FIG. 3A is a diagram for explaining the shape factor SF-1, and FIG. 3B is a diagram for explaining the shape factor SF-2. The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) 2 / AREA} × (100π / 4) (1)
When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.
The shape factor SF-2 indicates the ratio of the unevenness of the toner shape, and is represented by the following formula (2). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner on the two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-2 = {(PERI) 2 / AREA} × (100π / 4) (2)
When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent.
Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), introducing it into an image analyzer (LUSEX 3: manufactured by Nireco) and analyzing it. Calculated.

When the shape of the toner is close to a sphere, the contact between the toner and the toner or the photoreceptor 1 becomes a point contact, so that the adsorbing force between the toners is weakened, resulting in an increase in fluidity. 1 is weakened, the transfer rate is increased, and the reversely charged toner T1 is easily collected by the temporary holding device 40.
The shape factors SF-1 and SF-2 of the toner are preferably 100 or more. Further, when SF-1 and SF-2 are increased, the amount of the reversely charged toner T1 is increased, the toner charge amount distribution is broadened, and the load on the temporary holding device 40 is increased. For this reason, SF-1 preferably does not exceed 180, and SF-2 preferably does not exceed 180.

Further, the toner used in this image forming apparatus may be substantially spherical. 4A and 4B are schematic views showing the outer shape of the toner, FIG. 4A is an appearance of the toner, and FIG. 4B is a cross-sectional view of the toner. In FIG. 4A, the X axis represents the longest axis r1 of the longest axis of the toner, the Y axis represents the shortest axis r2 of the next longest axis, and the Z axis represents the thickness r3 of the shortest axis. ≧ Short axis r2 ≧ Thickness r3
The toner has a major axis / minor axis ratio (r2 / r1) of 0.5 to 1.0 and a thickness / minor axis ratio (r3 / r2) of 0.7 to 1.0. It has a substantially spherical shape. When the ratio of the major axis to the minor axis (r2 / r1) is less than 0.5, the charge amount distribution becomes wide because it approaches an indefinite shape.
When the ratio of the thickness to the short axis (r3 / r2) is less than 0.7, the charge amount distribution becomes wide because the shape approaches an indefinite shape. In particular, when the ratio of the thickness to the short axis (r3 / r2) is 1.0, the charge amount distribution becomes narrow because of the substantially spherical shape.
The size of the toner so far was measured with a scanning electron microscope (SEM) while changing the angle of the field of view and observing in situ.
The shape of the toner can be controlled by the manufacturing method. For example, the toner by the dry pulverization method has an irregular shape in which the toner surface is uneven and the toner shape is not constant. Even this dry pulverized toner can be made into a nearly spherical toner by applying mechanical or thermal treatment. In many cases, a toner produced by forming droplets by a suspension polymerization method or an emulsion polymerization method has a smooth surface and a nearly spherical shape. Moreover, it can be made into an ellipse by stirring in the middle of the reaction in a solvent and applying a shearing force.

In addition, as the toner having such a substantially spherical shape, a toner composition containing a polyester prepolymer having a functional group containing a nitrogen atom, a polyester, a colorant, and a release agent in an aqueous medium in the presence of fine resin particles. A toner that undergoes crosslinking and / or elongation reaction is preferred.
Hereinafter, the constituent material of the toner and a suitable manufacturing method will be described.
(polyester)
The polyester is obtained by a polycondensation reaction between a polyhydric alcohol compound and a polycarboxylic acid compound.
Examples of the polyhydric alcohol compound (PO) include dihydric alcohol (DIO) and trihydric or higher polyhydric alcohol (TO). (DIO) alone or a mixture of (DIO) and a small amount of (TO) preferable. Examples of the dihydric alcohol (DIO) include alkylene glycol (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, etc.); alkylene ether glycol (diethylene glycol) , Triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc.); alicyclic diols (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.); bisphenols (bisphenol A, bisphenol) F, bisphenol S, etc.); alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) adduct of the above alicyclic diol; Alkylene oxide bisphenol (ethylene oxide, propylene oxide, butylene oxide, etc.), etc. adducts. Among them, preferred are alkylene glycols having 2 to 12 carbon atoms and alkylene oxide adducts of bisphenols, and particularly preferred are alkylene oxide adducts of bisphenols and alkylene glycols having 2 to 12 carbon atoms. It is a combined use. The trihydric or higher polyhydric alcohol (TO) includes 3 to 8 or higher polyhydric aliphatic alcohols (glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, etc.); trihydric or higher phenols (Trisphenol PA, phenol novolak, cresol novolak, etc.); and alkylene oxide adducts of the above trivalent or higher polyphenols.

  Examples of the polyvalent carboxylic acid (PC) include divalent carboxylic acid (DIC) and trivalent or higher polyvalent carboxylic acid (TC). (DIC) alone and (DIC) with a small amount of (TC) Mixtures are preferred. Divalent carboxylic acids (DIC) include alkylene dicarboxylic acids (succinic acid, adipic acid, sebacic acid, etc.); alkenylene dicarboxylic acids (maleic acid, fumaric acid, etc.); aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid) And naphthalenedicarboxylic acid). Of these, preferred are alkenylene dicarboxylic acids having 4 to 20 carbon atoms and aromatic dicarboxylic acids having 8 to 20 carbon atoms. Examples of the trivalent or higher polyvalent carboxylic acid (TC) include aromatic polycarboxylic acids having 9 to 20 carbon atoms (such as trimellitic acid and pyromellitic acid). In addition, as polyhydric carboxylic acid (PC), you may make it react with polyhydric alcohol (PO) using the above-mentioned acid anhydride or lower alkyl ester (Methyl ester, ethyl ester, isopropyl ester, etc.).

The ratio of the polyhydric alcohol (PO) to the polycarboxylic acid (PC) is usually 2/1 to 1/1, preferably as the equivalent ratio [OH] / [COOH] of the hydroxyl group [OH] and the carboxyl group [COOH]. Is 1.5 / 1 to 1/1, more preferably 1.3 / 1 to 1.02 / 1.
The polycondensation reaction between a polyhydric alcohol (PO) and a polycarboxylic acid (PC) is carried out in the presence of a known esterification catalyst such as tetrabutoxytitanate or dibutyltin oxide, and heated to 150 to 280 ° C. while reducing the pressure as necessary. The produced water is distilled off to obtain a polyester having a hydroxyl group. The hydroxyl value of the polyester is preferably 5 or more, and the acid value of the polyester is usually 1 to 30, preferably 5 to 20. By giving an acid value, it tends to be negatively charged, and furthermore, when fixing to a recording paper, the affinity between the recording paper and the toner is good and the low-temperature fixability is improved. However, when the acid value exceeds 30, there is a tendency to deteriorate with respect to the stability of charging, particularly environmental fluctuation.
The weight average molecular weight is 10,000 to 400,000, preferably 20,000 to 200,000. A weight average molecular weight of less than 10,000 is not preferable because offset resistance deteriorates. On the other hand, if it exceeds 400,000, the low-temperature fixability is deteriorated.

In addition to the unmodified polyester obtained by the above polycondensation reaction, the polyester preferably contains a urea-modified polyester. The urea-modified polyester is obtained by reacting a terminal carboxyl group or hydroxyl group of the polyester obtained by the above polycondensation reaction with a polyvalent isocyanate compound (PIC) to obtain a polyester prepolymer (A) having an isocyanate group. It is obtained by cross-linking and / or extending the molecular chain by the reaction of the amine with amines.
Examples of the polyvalent isocyanate compound (PIC) include aliphatic polyisocyanates (tetramethylene diisocyanate, hexamethylene diisocyanate, 2,6-diisocyanatomethylcaproate, etc.); alicyclic polyisocyanates (isophorone diisocyanate, cyclohexylmethane diisocyanate, etc.) Aromatic diisocyanates (tolylene diisocyanate, diphenylmethane diisocyanate, etc.); araliphatic diisocyanates (α, α, α ′, α′-tetramethylxylylene diisocyanate, etc.); isocyanates; Those blocked with caprolactam or the like; and combinations of two or more of these.
The ratio of the polyvalent isocyanate compound (PIC) is usually 5/1 to 1/1, preferably as an equivalent ratio [NCO] / [OH] of the isocyanate group [NCO] and the hydroxyl group [OH] of the polyester having a hydroxyl group. 4/1 to 1.2 / 1, more preferably 2.5 / 1 to 1.5 / 1. When [NCO] / [OH] exceeds 5, low-temperature fixability deteriorates. When the molar ratio of [NCO] is less than 1, when a urea-modified polyester is used, the urea content in the ester is lowered and hot offset resistance is deteriorated.
The content of the polyvalent isocyanate compound (PIC) component in the polyester prepolymer (A) having an isocyanate group is usually 0.5 to 40 wt%, preferably 1 to 30 wt%, more preferably 2 to 20 wt%. . If it is less than 0.5 wt%, the hot offset resistance deteriorates, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability. On the other hand, if it exceeds 40 wt%, the low-temperature fixability deteriorates.
The number of isocyanate groups contained per molecule in the polyester prepolymer (A) having an isocyanate group is usually 1 or more, preferably 1.5 to 3 on average, more preferably 1.8 to 2 on average. Five. If it is less than 1 per molecule, the molecular weight of the urea-modified polyester will be low, and the hot offset resistance will deteriorate.

Next, as amines (B) to be reacted with the polyester prepolymer (A), a divalent amine compound (B1), a trivalent or higher polyvalent amine compound (B2), an amino alcohol (B3), an amino mercaptan (B4) ), Amino acid (B5), and amino acid block of B1 to B5 (B6).
Examples of the divalent amine compound (B1) include aromatic diamines (phenylenediamine, diethyltoluenediamine, 4,4′-diaminodiphenylmethane, etc.); alicyclic diamines (4,4′-diamino-3,3′-dimethyldicyclohexyl). Methane, diamine cyclohexane, isophorone diamine, etc.); and aliphatic diamines (ethylene diamine, tetramethylene diamine, hexamethylene diamine, etc.) and the like. Examples of the trivalent or higher polyvalent amine compound (B2) include diethylenetriamine and triethylenetetramine. Examples of amino alcohol (B3) include ethanolamine and hydroxyethylaniline. Examples of amino mercaptan (B4) include aminoethyl mercaptan and aminopropyl mercaptan. Examples of the amino acid (B5) include aminopropionic acid and aminocaproic acid. Examples of the compound (B6) obtained by blocking the amino group of B1 to B5 include ketimine compounds and oxazolidine compounds obtained from the amines of B1 to B5 and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.). Among these amines (B), preferred are B1 and a mixture of B1 and a small amount of B2.

The ratio of amines (B) is equivalent to the equivalent ratio [NCO] / [NHx] of isocyanate groups [NCO] in the polyester prepolymer (A) having isocyanate groups and amino groups [NHx] in amines (B). Is usually 1/2 to 2/1, preferably 1.5 / 1 to 1 / 1.5, more preferably 1.2 / 1 to 1 / 1.2. When [NCO] / [NHx] is more than 2 or less than 1/2, the molecular weight of the urea-modified polyester is lowered, and the hot offset resistance is deteriorated.
The urea-modified polyester may contain a urethane bond together with a urea bond. The molar ratio of the urea bond content to the urethane bond content is usually 100/0 to 10/90, preferably 80/20 to 20/80, and more preferably 60/40 to 30/70. When the molar ratio of the urea bond is less than 10%, the hot offset resistance is deteriorated.

The urea-modified polyester is produced by a one-shot method or the like. Polyhydric alcohol (PO) and polyvalent carboxylic acid (PC) are heated to 150-280 ° C. in the presence of a known esterification catalyst such as tetrabutoxytitanate, dibutyltin oxide, etc., and water generated while reducing the pressure as necessary. Distill off to obtain a polyester having a hydroxyl group. Subsequently, at 40-140 degreeC, this is made to react with polyvalent isocyanate (PIC), and the polyester prepolymer (A) which has an isocyanate group is obtained. Further, this (A) is reacted with amines (B) at 0 to 140 ° C. to obtain a urea-modified polyester.
When reacting (PIC) and when reacting (A) and (B), a solvent may be used if necessary. Usable solvents include aromatic solvents (toluene, xylene, etc.); ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.); esters (ethyl acetate, etc.); amides (dimethylformamide, dimethylacetamide, etc.) and ethers And those inert to isocyanates (PIC), such as tetrahydrofuran (such as tetrahydrofuran).

In addition, in the crosslinking and / or extension reaction between the polyester prepolymer (A) and the amines (B), a reaction terminator can be used as necessary to adjust the molecular weight of the resulting urea-modified polyester. Examples of the reaction terminator include monoamines (diethylamine, dibutylamine, butylamine, laurylamine, etc.), and those obtained by blocking them (ketimine compounds).
The weight average molecular weight of the urea-modified polyester is usually 10,000 or more, preferably 20,000 to 10,000,000, and more preferably 30,000 to 1,000,000. If it is less than 10,000, the hot offset resistance deteriorates. The number average molecular weight of the urea-modified polyester or the like is not particularly limited when the above-mentioned unmodified polyester is used, and may be a number average molecular weight that can be easily obtained to obtain the weight average molecular weight. When the urea-modified polyester is used alone, its number average molecular weight is usually 2000-15000, preferably 2000-10000, more preferably 2000-8000. When it exceeds 20000, the low-temperature fixability and the glossiness when used in a full-color apparatus are deteriorated.

By using the unmodified polyester and the urea-modified polyester in combination, the low-temperature fixability and the gloss when used in the full-color image forming apparatus 100 are improved. Therefore, it is preferable to use the urea-modified polyester alone. The unmodified polyester may include a polyester modified with a chemical bond other than a urea bond.
The unmodified polyester and the urea-modified polyester are preferably at least partially compatible with each other in terms of low-temperature fixability and hot offset resistance. Therefore, it is preferable that the unmodified polyester and the urea-modified polyester have a similar composition.
The weight ratio of unmodified polyester to urea-modified polyester is usually 20/80 to 95/5, preferably 70/30 to 95/5, more preferably 75/25 to 95/5, and particularly preferably 80 /. 20-93 / 7. When the weight ratio of the urea-modified polyester is less than 5%, the hot offset resistance is deteriorated, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability.
The glass transition point (Tg) of the binder resin containing unmodified polyester and urea-modified polyester is usually 45 to 65 ° C, preferably 45 to 60 ° C. If it is less than 45 ° C., the heat resistance of the toner deteriorates, and if it exceeds 65 ° C., the low-temperature fixability becomes insufficient.
In addition, since the urea-modified polyester is likely to be present on the surface of the obtained toner base particles, the heat-resistant storage stability tends to be good even when the glass transition point is low as compared with known polyester-based toners.

  Here, the aforementioned substances can be used for the colorant, charge control agent, release agent, external additive and the like.

Next, a toner manufacturing method will be described. Here, although a preferable manufacturing method is shown, it is not limited to this.
(Toner production method)
1) A toner material solution is prepared by dispersing a colorant, unmodified polyester, a polyester prepolymer having an isocyanate group, and a release agent in an organic solvent.
The organic solvent is preferably volatile with a boiling point of less than 100 ° C. from the viewpoint of easy removal after toner base particle formation. Specifically, toluene, xylene, benzene, carbon tetrachloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, dichloroethylidene, methyl acetate, ethyl acetate, methyl ethyl ketone, Methyl isobutyl ketone and the like can be used alone or in combination of two or more. In particular, aromatic solvents such as toluene and xylene and halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, chloroform, and carbon tetrachloride are preferable. The usage-amount of an organic solvent is 0-300 weight part normally with respect to 100 weight part of polyester prepolymers, Preferably it is 0-100 weight part, More preferably, it is 25-70 weight part.

2) The toner material liquid is emulsified in an aqueous medium in the presence of a surfactant and resin fine particles.
The aqueous medium may be water alone or an organic solvent such as alcohol (methanol, isopropyl alcohol, ethylene glycol, etc.), dimethylformamide, tetrahydrofuran, cellosolves (methyl cellosolve, etc.), lower ketones (acetone, methyl ethyl ketone, etc.). It may be included.
The amount of the aqueous medium used relative to 100 parts by weight of the toner material liquid is usually 50 to 2000 parts by weight, preferably 100 to 1000 parts by weight. If the amount is less than 50 parts by weight, the dispersion state of the toner material liquid is poor and toner particles having a predetermined particle diameter cannot be obtained. If it exceeds 20000 parts by weight, it is not economical.

Further, in order to improve the dispersion in the aqueous medium, a dispersant such as a surfactant and resin fine particles is appropriately added.
As surfactants, anionic surfactants such as alkylbenzene sulfonates, α-olefin sulfonates, phosphate esters, alkylamine salts, amino alcohol fatty acid derivatives, polyamine fatty acid derivatives, amine salt types such as imidazoline, Quaternary ammonium salt type cationic surfactants such as alkyltrimethylammonium salt, dialkyldimethylammonium salt, alkyldimethylbenzylammonium salt, pyridinium salt, alkylisoquinolinium salt, benzethonium chloride, fatty acid amide derivative, polyhydric alcohol Nonionic surfactants such as derivatives, for example, amphoteric surfactants such as alanine, dodecyldi (aminoethyl) glycine, di (octylaminoethyl) glycine and N-alkyl-N, N-dimethylammonium betaine And the like.

Further, by using a surfactant having a fluoroalkyl group, the effect can be obtained in a very small amount. Preferred anionic surfactants having a fluoroalkyl group include fluoroalkyl carboxylic acids having 2 to 10 carbon atoms and metal salts thereof, disodium perfluorooctanesulfonyl glutamate, 3- [ω-fluoroalkyl (C6-C11 ) Oxy] -1-alkyl (C3-C4) sodium sulfonate, 3- [ω-fluoroalkanoyl (C6-C8) -N-ethylamino] -1-propanesulfonic acid sodium, fluoroalkyl (C11-C20) carvone Acids and metal salts, perfluoroalkylcarboxylic acids (C7 to C13) and metal salts thereof, perfluoroalkyl (C4 to C12) sulfonic acids and metal salts thereof, perfluorooctanesulfonic acid diethanolamide, N-propyl-N- ( 2-Hydroxyethyl) Perful Olooctanesulfonamide, perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salt, perfluoroalkyl (C6-C10) -N-ethylsulfonylglycine salt, monoperfluoroalkyl (C6-C16) ethyl phosphate, etc. Can be mentioned.
Product names include Surflon S-111, S-112, S-113 (Asahi Glass Co., Ltd.), Florard FC-93, FC-95, FC-98, FC-129 (Sumitomo 3M Co., Ltd.), Unidyne DS-101. DS-102 (manufactured by Daikin Industries, Ltd.), Megafac F-110, F-120, F-113, F-191, F-812, F-833 (manufactured by Dainippon Ink, Inc.), Xtop EF-102, 103, 104, 105, 112, 123A, 123B, 306A, 501, 201, 204 (manufactured by Tochem Products), and Fgentent F-100, F150 (manufactured by Neos).

  Further, as the cationic surfactant, aliphatic quaternary ammonium salts such as aliphatic primary, secondary or secondary amine acids having a fluoroalkyl group, and perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salts. , Benzalkonium salt, benzethonium chloride, pyridinium salt, imidazolinium salt, trade names include Surflon S-121 (manufactured by Asahi Glass), Florard FC-135 (manufactured by Sumitomo 3M), Unidyne DS-202 (Daikin Industries) Manufactured), MegaFuck F-150, F-824 (Dainippon Ink Co., Ltd.), Xtop EF-132 (Tochem Products), Footgent F-300 (Neos), and the like.

The resin fine particles are added to stabilize the toner base particles formed in the aqueous medium. For this reason, it is preferable to add so that the coverage existing on the surface of the toner base particles is in the range of 10 to 90%. For example, polymethyl methacrylate fine particles 1 μm and 3 μm, polystyrene fine particles 0.5 μm and 2 μm, poly (styrene-acrylonitrile) fine particles 1 μm, trade names are PB-200H (manufactured by Kao), SGP (manufactured by Soken), Techno Examples include polymer SB (manufactured by Sekisui Chemical Co., Ltd.), SGP-3G (manufactured by Sokensha), and micropearl (manufactured by Sekisui Fine Chemical Co., Ltd.).
In addition, inorganic compound dispersants such as tricalcium phosphate, calcium carbonate, titanium oxide, colloidal silica, and hydroxyapatite can also be used.

  As a dispersant that can be used in combination with the above resin fine particles and inorganic compound dispersant, the dispersed droplets may be stabilized by a polymer protective colloid. For example, acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid or maleic anhydride and other (meth) acrylic monomers containing hydroxyl groups Such as acrylic acid-β-hydroxyethyl, methacrylic acid-β-hydroxyethyl, acrylic acid-β-hydroxypropyl, methacrylic acid-β-hydroxypropyl, acrylic acid-γ-hydroxypropyl, methacrylic acid-γ-hydroxy Propyl, acrylic acid-3-chloro-2-hydroxypropyl, methacrylic acid-3-chloro-2-hydroxypropyl, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerol monoacrylate, glycerol monomethacrylate Luric acid esters, N-methylol acrylamide, N-methylol methacrylamide, etc., vinyl alcohol or ethers with vinyl alcohol, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, or compounds containing vinyl alcohol and a carboxyl group Esters such as vinyl acetate, vinyl propionate, vinyl butyrate, acrylamide, methacrylamide, diacetone acrylamide or their methylol compounds, acid chlorides such as acrylic acid chloride, methacrylic acid chloride, vinyl pyridine, vinyl pyrrolidone, vinyl Nitrogen compounds such as imidazole and ethyleneimine, or homopolymers or copolymers such as those having a heterocyclic ring thereof, polyoxyethylene, poly Xylpropylene, polyoxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonylphenyl ether, polyoxyethylene, lauryl phenyl ether, polyoxyethylene stearyl phenyl ester, poly Polyoxyethylenes such as oxyethylene nonylphenyl ester, celluloses such as methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose can be used.

  The dispersion method is not particularly limited, and known equipment such as a low-speed shear method, a high-speed shear method, a friction method, a high-pressure jet method, and an ultrasonic wave can be applied. Among these, the high-speed shearing method is preferable in order to make the particle size of the dispersion 2 to 20 μm. When a high-speed shearing disperser is used, the rotational speed is not particularly limited, but is usually 1000 to 30000 rpm, preferably 5000 to 20000 rpm. The dispersion time is not particularly limited, but in the case of a batch method, it is usually 0.1 to 5 minutes. The temperature during dispersion is usually 0 to 150 ° C. (under pressure), preferably 40 to 98 ° C.

3) At the same time as the preparation of the emulsion, the amines (B) are added to cause a reaction with the polyester prepolymer (A) having an isocyanate group.
This reaction involves molecular chain crosslinking and / or elongation. The reaction time is selected depending on the reactivity between the isocyanate group structure of the polyester prepolymer (A) and the amines (B), but is usually 10 minutes to 40 hours, preferably 2 to 24 hours. The reaction temperature is generally 0 to 150 ° C, preferably 40 to 98 ° C. Moreover, a well-known catalyst can be used as needed. Specific examples include dibutyltin laurate and dioctyltin laurate.

4) After completion of the reaction, the organic solvent is removed from the emulsified dispersion (reactant), washed and dried to obtain toner base particles.
In order to remove the organic solvent, the temperature of the entire system is gradually raised in a laminar stirring state, and after giving strong stirring in a certain temperature range, the solvent base is removed to produce spindle-shaped toner base particles. . Further, when an acid such as calcium phosphate salt or an alkali-soluble material is used as the dispersion stabilizer, the calcium phosphate salt is dissolved from the toner base particles by a method such as dissolving the calcium phosphate salt with an acid such as hydrochloric acid and washing with water. Remove. It can also be removed by operations such as enzymatic degradation.

5) A charge control agent is injected into the toner base particles obtained above, and then inorganic fine particles such as silica fine particles and titanium oxide fine particles are externally added to obtain a toner.
When preparing a developer by adding external additives and lubricants, these may be added simultaneously or separately and mixed. For mixing external additives and the like, a general powder mixer is used, but it is preferable to equip a jacket or the like to adjust the internal temperature. Examples of the mixing equipment that can be used include a V-type mixer, a rocking mixer, a Ladige mixer, a Nauter mixer, a Henschel mixer, and the like. It is preferable to prevent the embedding of the external additive and the formation of a thin film on the toner surface of the lubricant by changing the mixing conditions such as the rotation speed, rolling speed, time, and temperature.
Thereby, a toner having a small particle size and a sharp particle size distribution can be easily obtained. Furthermore, by giving strong agitation in the process of removing the organic solvent, the shape between the spherical shape and the spindle shape can be controlled, and the surface morphology is also controlled between the smooth shape and the umeboshi shape. Can do.

The toner of the present invention can be mixed with a magnetic carrier and used as a two-component developer. In this case, the toner concentration of the carrier and the toner in the developer is preferably 1 to 10 parts by weight of the toner with respect to 100 parts by weight of the carrier. The toner of the present invention can also be used as a one-component magnetic toner that does not use a carrier or a non-magnetic toner.
Further, the photosensitive member 1 for forming a latent image and one or more devices selected from the charging device 2, the developing device 3, and the cleaning device 4 are integrally supported, and the process cartridge is detachable from the image forming device. Since it is an (image forming unit), when maintenance is required, the process cartridge can be replaced, and convenience is improved.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a diagram illustrating an approach / separation operation of a recording medium transfer unit. 4A and 4B are diagrams schematically illustrating the shape of a toner. FIG. 5A is a diagram for explaining a shape factor SF-1, and FIG. 5B is a diagram for explaining a shape factor SF-2. 2A and 2B are schematic diagrams illustrating an outer shape of a toner used in the present invention, in which FIG. 3A is an external view of the toner, and FIG. It is the schematic which shows the structure of the conventional tandem system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor as image carrier 3 Developing device 6 Intermediate transfer belt as intermediate transfer body 8 Transfer paper conveyance belt as transfer conveyance belt 12 Process cartridge 15 Recording medium transfer means 28 Secondary transfer roller as secondary transfer means

Claims (12)

A plurality of image bearing members corresponding to each color including black, a plurality of developing devices that store a developer for visualizing a latent image on each image bearing member, and a transferred toner image In the image forming apparatus, the black toner recovered from the image carrier corresponding to black after the transfer is returned to the developing device corresponding to black and reused.
An image carrier and a developing device corresponding to colors other than black are arranged to transfer a toner image to the intermediate transfer member,
The image carrier and the developing device corresponding to black are provided independently of the intermediate transfer member on the upstream side of the intermediate transfer member in the conveyance direction of the recording medium,
An image forming apparatus comprising: a recording medium transfer unit capable of transferring a toner image on the image transfer member corresponding to the black onto a recording medium and transferring the toner image on the intermediate transfer member in a superimposed manner. . The image forming apparatus according to claim 1.
An image forming apparatus, wherein the recording medium transfer unit directly transfers a toner image on an image carrier corresponding to the black to a recording medium. The image forming apparatus according to claim 2.
The image forming apparatus, wherein the recording medium transfer unit includes an endless transfer conveyance belt and a secondary transfer unit that contacts and separates the transfer conveyance belt from the intermediate transfer member. The image forming apparatus according to claim 1 or 2,
An image forming apparatus comprising: a means for bringing the intermediate transfer member into and out of contact with the recording medium transfer means. The image forming apparatus according to any one of claims 1 to 4,
An image forming apparatus, wherein an image carrier corresponding to a color other than black is in contact with the intermediate transfer member. The image forming apparatus according to claim 5.
An image forming apparatus, wherein the intermediate transfer member has an endless belt shape. The image forming apparatus according to claim 6.
An image forming apparatus, wherein the plurality of image carriers and developing devices corresponding to the respective colors are integrally supported by individual process cartridges detachably attached to the image forming apparatus main body. The image forming apparatus according to any one of claims 1 to 7,
An image forming apparatus, wherein the toner has a circularity of 0.92 or more. The image forming apparatus according to any one of claims 1 to 8,
The image forming apparatus according to claim 1, wherein the toner has a shape factor SF-1 in a range of 100 to 180 and a shape factor SF-2 in a range of 100 to 180. The image forming apparatus according to any one of claims 1 to 9,
The toner has a volume average particle diameter (Dv) in the range of 3 to 8 μm, and has a dispersity defined by a ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn). An image forming apparatus having a range of 1.05 to 1.40. The image forming apparatus according to claim 1,
The toner has a major axis / minor axis ratio (r2 / r1) in the range of 0.5 to 1.0 and a thickness / minor axis ratio (r3 / r2) of 0.7 to 1.0. An image forming apparatus having a range satisfying a relationship of major axis r1 ≧ minor axis r2 ≧ thickness r3. The image forming apparatus according to claim 1,
In the toner, a toner composition containing a polyester prepolymer having a functional group containing a nitrogen atom, polyester, a colorant, and a release agent is subjected to at least one reaction of crosslinking and elongation in the presence of resin fine particles in an aqueous medium. An image forming apparatus characterized by being a toner to be used.

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