JP2011232599A - Developer for electrophotography - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide developer for electrophotography capable of forming an image with high picture quality for long periods.SOLUTION: In this developer for electrophotography containing tonner and carrier, the tonner contains tonner base particles containing binding resin and coloring agent and external additive externally added to the tonner base particles, and the carrier contains core materials and coat resin covering the core materials, and the coat resin contains fluorine resin and amino silane coupling agent, and when the BET specific surface areas of the tonner, the carrier and the developer for electrophotography measured by a BET method are respectively set to Sm/g, Sm/g and Sm/g, and the contents of the tonner and the carrier with respect to 1 mass part of the developer for electrophotography are respectively set to a Cmass part and a Cmass part, the developer for electrophotography satisfying the following formula (1) is used, with the formula (1) being 0.8≤S/(S×C+S×C)≤0.95.

Description

  The present invention relates to an electrophotographic developer.

  An image forming apparatus using an electrophotographic system, such as a copying machine, a printer, a facsimile machine, and a composite machine of these, includes an image carrier, a charging device that uniformly charges the surface of the image carrier, and a charged image carrier. An exposure device for forming an electrostatic latent image on the surface of the image carrier by exposing the surface of the body; and supplying toner to the surface of the image carrier on which the electrostatic latent image is formed. A developing device that develops an electrostatic latent image as a toner image, a transfer device that transfers the toner image from the image carrier to a recording medium, and the transferred toner image is fixed to the recording medium by heating and pressing. A fixing device is provided. Such an image forming apparatus forms an image on a recording medium by transferring the toner image to the recording medium as described above by each of the above apparatuses and then fixing the toner image on the recording medium.

  As such an image forming apparatus, not only monochrome printing but also an apparatus having a color printing function for forming a color image has been used. Specifically, for example, a tandem color image forming apparatus and the like can be mentioned.

  Specifically, the tandem color image forming apparatus is, for example, for primary transfer of a toner image formed on an image carrier by electrophotography and then secondary transfer to a recording medium such as paper. Image formation that includes an intermediate transfer belt and forms a color image by superimposing toner images of multiple colors such as yellow (Y), magenta (M), cyan (C), and black (K) on the intermediate transfer belt Device. In such a color image forming apparatus, in order to superimpose a plurality of color toner images, image forming units corresponding to the respective colors are arranged in parallel along the intermediate transfer belt. On the intermediate transfer belt, YMCK four-color toner images from the respective photosensitive drums of the image forming unit are sequentially transferred (primary transfer) so as to overlap each other to form a color image. Then, the color image formed on the intermediate transfer belt is transferred (secondary transfer) onto a recording medium such as a sheet by a secondary transfer roller disposed opposite to the intermediate transfer belt. In this way, a toner image corresponding to each color is formed on each image carrier, and further, the color images are formed by superimposing the toner images. By doing so, the tandem color image forming apparatus achieves high-speed printing.

  Various image forming apparatuses using the electrophotographic method as described above have been studied as developers to be used in order to form high-quality images. Specifically, the thing of patent documents 1-4 is mentioned, for example.

  Patent Document 1 describes a developer comprising magnetic carrier particles made of ferrite particles having a spinel structure and having an average particle diameter of less than 30 μm.

  Further, in Patent Document 2, in a two-component developer composed of a toner and a carrier, the carrier has a fine surface crystal, and the proportion of particles having a particle size of 44 μm or less is 10 wt% or less, and 44 to 105 μm peaks. A developer using a small particle diameter carrier and a small particle diameter toner of 11 μm or less as a toner is described.

  Patent Document 3 discloses carrier particles for an electrophotographic developer comprising a core having an average diameter of about 30 microns to about 1000 microns, the core having negative frictional charging characteristics with respect to toner particles. Developers comprising carrier particles having an outer coating consisting of a polyblend of a first polymer having a second polymer with strong adhesive properties in addition to the core are described.

  Patent Document 4 discloses an electrophotographic carrier in which at least the surface of the core material is coated with a resin, and the coating resin includes a fluorine-modified silicone resin and an aminosilane coupling agent, and the aminosilane coupling agent includes: A developer containing an electrophotographic carrier that is contained in an amount of 5 to 40 parts by weight with respect to 100 parts by weight of the coating resin and charges the toner negatively is described.

JP 58-144839 A JP 61-204646 A JP-A-54-110839 International Publication No. 2004/031865

  The present inventor has developed a toner having a relatively small particle size (small particle size toner) as a developer toner used to form a high-quality image in an image forming apparatus using the electrophotographic method as described above. ). When such a small particle size toner is used, since the particle size of the toner is small, it can be expected that the formed image has high definition. Furthermore, not only can such high-quality images be formed, but the volume of toner forming one dot can be reduced because the toner particle diameter is small. That is, a reduction in toner consumption can be expected.

  However, when an image is formed using a developer containing such a small particle size toner, in practice, a defect such as fogging may occur in the formed image, and a suitable image may not be formed. The present inventors inferred that this is as follows. Specifically, first, the toner having a small particle diameter tends to increase the surface area of the whole toner, that is, the specific surface area of the toner. For this reason, the small particle size toner has a small contact area with the carrier, so that the toner is not sufficiently charged. Therefore, it was inferred that the toner was poorly charged.

  Therefore, it was considered that if the carrier used together with the toner is made smaller in particle size, the surface area of the carrier as a whole increases and the above problem can be solved. Specifically, a developer using a carrier having a relatively small particle diameter as described in Patent Document 1 and Patent Document 2 was examined.

  According to Patent Document 1, it is disclosed that an image quality with extremely good resolving power, denseness, black solid uniformity, gradation and the like can be obtained. Patent Document 2 discloses that a long life, little toner scattering, no smearing or fogging of characters, high image density stability, and high-definition image quality can be obtained. However, although Patent Document 1 and Patent Document 2 describe that a carrier having a relatively small particle diameter is used, there are cases where a suitable image is not actually formed. That is, there is a problem that it may not be sufficient to use only a carrier having a small particle diameter, that is, to simply define the particle diameter of the toner and the carrier.

  On the other hand, it is known that a core material coated with a coating resin is used as a carrier. The inventor has also studied the use of a carrier in which the core material is coated with such a coating resin. As the coating resin, styrene-methacrylate copolymer resin, silicone resin, fluorine resin, or the like is used. However, when a styrene-methacrylate copolymer resin is used, the obtained carrier is liable to generate so-called toner spent in which the toner component adheres to the surface of the carrier and decreases the performance of charging the carrier toner. Further, when a silicone resin was used, the obtained carrier was easily worn even if the toner spent resistance was good, and the coat resin was easily peeled off from the core material. Further, when the fluororesin is used, even if the obtained carrier has good wear resistance, the binding property between the core material and the coat resin covering the core material is insufficient, that is, Since the coating resin is easily peeled from the core material, the durability was not sufficiently satisfactory in practice.

  From the above, it is conceivable to use a resin in which a plurality of resins are mixed as the coating resin. Specifically, there are developers using carriers such as those described in Patent Document 3 and Patent Document 4. Can be mentioned.

  According to Patent Document 3, it is disclosed that it is possible to provide a developer having a carrier that has a long effective life and can exhibit negative frictional charging characteristics. However, when such a developer is actually used and low density printing is performed over a long period of time, it is difficult to continuously form an image having a suitable image density. This is achieved by coating a resin mixed with a polymer having a relatively good film forming property in order to make the carrier have the above properties, but if a polymer having a high film forming property is mixed, It is considered that the coated resin inevitably has a high resistance. That is, it is considered that the toner is easily overcharged when low density printing is performed for a long period of time.

  Further, according to Patent Document 4, there is no decrease in the charge amount under high temperature and high humidity and no extreme increase in the charge amount under low temperature and low humidity, preventing deterioration of the developer due to peeling of the coating layer of the carrier, and toner It is disclosed that a long-lasting carrier with high durability that does not deteriorate due to spent formation can be obtained. However, in reality, the durability is not sufficiently satisfactory. Specifically, when image formation is performed over a long period of time, the coating resin coated on the core material is scraped off and the durability is sufficiently high. I could not say.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an electrophotographic developer capable of forming a high-quality image over a long period of time.

  As described above, the present inventor may not be sufficient to form a high-quality image simply by defining the particle size of the toner and the carrier. Instead, focusing on the specific surface area of the toner, carrier and developer, the inventors have arrived at the present invention as follows.

The electrophotographic developer according to an aspect of the present invention is an electrophotographic developer containing a toner and a carrier, and the toner includes toner base particles containing a binder resin and a colorant, and the toner. An external additive externally added to the base particles, the carrier includes a core material and a coating resin that coats the core material, the coating resin includes a fluorine-based resin, and an amino group in the molecule. A BET specific surface area measured by a BET method of the toner, the carrier, and the electrophotographic developer, respectively, including S _T m ² / g, S _C m ² / g, and and S D _{m 2} / ^g, the relative electrophotographic developer 1 part by weight, the toner and the amount of the carrier, respectively, if the C _T parts by mass C _C parts by weight, satisfying the following formula (1) Features to do To.

_{0.8 ≦ S D / (S C} × C C + S T × C T) ≦ 0.95 (1)
According to such a configuration, an electrophotographic developer capable of forming a high-quality image over a long period of time can be provided.

  This is considered to be due to the following.

S _D / (S _C × C _C + S _T × C _T ) in the above formula (1) is assumed when it is assumed that the toner and the carrier are maintained as they were before mixing each other. This is considered to indicate the ratio of the specific surface area of the actual developer to the specific surface area of the developer. Actually, when the toner and the carrier are mixed, it is considered that the external additive is buried to some extent in the toner base particles constituting the toner. Therefore, S _D / (S _C × C _C + S _T × C _T ) in the above formula (1) indicates how much the external additive of the toner is buried in the toner base particles by mixing the toner and the carrier. It is considered to be an indicator to show.

Then, when S _D / (S _C × C _C + S _T × C _T ) in the above formula (1) is within the above range, it is considered that the amount of the external additive embedded in the toner base particles is appropriate. Therefore, the adhesion of the toner to the carrier becomes suitable, the occurrence of toner spent on the carrier can be suppressed, and further, the external additive added to the toner from the toner can be prevented from being detached. Therefore, even if image formation is performed over a long period of time, it is considered that the occurrence of toner scattering, toner spent on the carrier, and the like generated when the external additive is detached from the toner can be suppressed.

  Further, as a carrier coating resin, by using a fluororesin and a silane coupling agent containing an amino group in the molecule, that is, an aminosilane coupling agent, the charging stability and durability of the toner, etc. It is thought that a career with improved

  First, the fluorine-based resin is excellent in wear resistance and improves durability. On the other hand, fluororesin can impart positive chargeability to the toner, but when printing over a long period of time with little toner replacement, such as printing an image with a low density printing rate, the toner is excessive. It is considered that the toner is electrically charged and the electric attractive force between the toner and the carrier becomes excessively high, so that the toner is difficult to be separated from the carrier and the density of the formed image may be lowered. In the present invention, the coating resin contains a fluororesin, but such a problem is unlikely to occur. This is considered to be due to the fact that the coating resin contains not only a fluorine-based resin but also an aminosilane coupling agent. That is, it is thought that generation | occurrence | production of said malfunction can be suppressed when an aminosilane coupling agent is contained. This is considered to be due to the fact that the excessively charged toner comes into contact with the aminosilane coupling agent to reduce the charge amount of the toner, thereby suppressing the occurrence of a decrease in image density of the formed image.

  Furthermore, when an aminosilane coupling agent is contained, peeling of the coating resin from the core material can be suppressed, and a carrier having excellent durability can be obtained. This is considered to be because if the aminosilane coupling agent is contained, the binding property between the coating resin and the core material of the carrier can be improved.

  From the above, it is considered that an electrophotographic developer capable of forming a high-quality image over a long period of time can be provided by using the above-described configuration.

  In the electrophotographic developer, the content of the silane coupling agent is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the resin component of the coat resin.

  According to such a configuration, a higher quality image can be formed over a long period of time. This is considered to be due to the fact that the binding property between the coat resin of the carrier and the core material can be further improved and the occurrence of a decrease in the image density of the formed image can be further suppressed.

  In the electrophotographic developer, the fluororesin is selected from the group consisting of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and polytetrafluoroethylene. It is preferable that there is at least one.

  According to such a configuration, a higher quality image can be formed over a long period of time. This is considered to be due to the fact that the toner is more excellent in wear resistance and can positively charge the toner stably and suitably, so that the charging stability of the toner can be further improved.

  In the electrophotographic developer, it is preferable that the coating resin further includes at least one selected from the group consisting of a polyamide resin, a polyimide resin, and a polyamideimide resin.

  According to such a configuration, a higher quality image can be formed over a long period of time. This is considered to be because the hardness of the coating resin is high and the coating is not scraped even after repeated use.

  In the electrophotographic developer, the coating amount of the coating resin is preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the core material.

  According to such a configuration, a higher quality image can be formed over a long period of time. This is considered to be because the coating resin can be prevented from being scraped or peeled off from the core material of the carrier, and further, the charging stability to the toner can be improved.

  In the electrophotographic developer, the content of the fluororesin is preferably 20 to 90 parts by mass with respect to 100 parts by mass of the resin component of the coat resin.

  According to such a configuration, a higher quality image can be formed over a long period of time. This is considered to be because the above-mentioned effects of the fluororesin can be sufficiently exhibited.

  According to the present invention, an electrophotographic developer capable of forming a high-quality image over a long period of time can be provided.

1 is a schematic cross-sectional view illustrating an example of an overall configuration of an image forming apparatus that uses an electrophotographic developer according to an exemplary embodiment.

  Hereinafter, although the embodiment concerning the present invention is described, the present invention is not limited to these.

The electrophotographic developer according to the exemplary embodiment is an electrophotographic developer containing a toner and a carrier, and the toner includes toner base particles containing a binder resin and a colorant, and the toner base particles. The carrier includes a core material and a coating resin that coats the core material, and the coating resin contains a fluorine-based resin and an amino group in the molecule. BET specific surface areas of the toner, the carrier, and the electrophotographic developer, as measured by the BET method, are S _T m ² / g, S _C m ² / g, and S _{D, respectively.} and m 2 ^{/ g,} for the electrophotographic developer 1 part by weight, the toner and the amount of the carrier, respectively, if the C _T parts by mass C _C parts by weight, satisfying the following formula (1) Features .

_{0.8 ≦ S D / (S C} × C C + S T × C T) ≦ 0.95 (1)
Such an electrophotographic developer can form a high-quality image over a long period of time.

First, as described above, S _D / (S _C × C _C + S _T × C _T ) in the above formula (1) is maintained as it was before the toner and the carrier were mixed. It is considered that the ratio of the specific surface area of the actual developer to the specific surface area of the developer assumed is shown. In practice, it is considered that when the toner and the carrier are mixed, the external additive is buried to some extent in the toner base particles constituting the toner. Therefore, S _D / (S _C × C _C + S _T × C _T ) in the above formula (1) indicates how much the external additive of the toner is buried in the toner base particles by mixing the toner and the carrier. It is thought that it becomes the indicator (burial level) shown.

Each specific surface area is a BET specific surface area measured by the BET method (nitrogen adsorption specific surface area method), and specifically, liquid nitrogen adsorbed on the surface of each sample of toner, carrier, and developer. It is calculated | required from the adsorption amount of. More specifically, for example, by using an automatic specific surface area measuring apparatus (Macsorb model 1208 manufactured by Mountec Co., Ltd.) or the like, nitrogen is adsorbed on the sample surface, and the BET specific surface area (BET single-point type) of the sample is m ² / g) can be measured.

  A specific measurement procedure is, for example, as follows.

  First, the weight of the empty cell is measured. Next, a predetermined amount of a sample as a measurement object is weighed, and the weighed sample is filled so as not to adhere to the inner wall surface of the cell. When the object to be measured is a toner, about 0.8 g is weighed. When the object to be measured is a carrier, about 9 g is weighed. When the object to be measured is a developer, about 7 g is weighed. To do. Then, nitrogen is flowed into the cell filled with the sample with a flow meter so that the flow rate becomes 25 ml / min. Then, nitrogen is passed through the cell for 30 minutes under the condition of a temperature of 45 ° C. By doing so, the sample (sample) is deaerated. Then, after cooling for 2 minutes, zero point adjustment of a measuring device, for example, an automatic specific surface area measuring device (Macsorb model 1208 manufactured by Mountec Co., Ltd.) is performed, and then measurement is started. After the measurement is started, the cell is immersed in liquid nitrogen in a dewar bottle to perform an adsorption process, and then the cell is returned to the atmosphere from the dewar bottle to perform a desorption process. The actual surface area of the sample is measured by automatic measurement during the previous process. Then, the specific surface area of the sample can be calculated by dividing the measured actual surface area by the sample weight.

Further, S _D / (S _C × C _C + S _T × C _T ) in the above formula (1) may satisfy the above formula (1), but more preferably satisfies the following formula (2).

_{0.85 ≦ S D / (S C} × C C + S T × C T) ≦ 0.90 (2)
If the degree of burying is too small, the external additive is too embedded in the toner base particles, and the effect of externally adding the external additive tends to decrease. For example, toner tends to adhere to the carrier and toner spent on the carrier tends to occur.

  On the other hand, when the degree of burying is too large, the external additive is not sufficiently embedded in the toner base particles, and the external additive tends to be insufficiently fixed to the toner base particles. For example, there is a tendency that the external additive is detached from the toner and the toner is likely to be scattered due to this.

  Therefore, it is considered that the burying amount of the external additive in the toner base particles is appropriate when the burying degree is within the above range. Therefore, adhesion of the toner to the carrier becomes suitable, generation of toner spent on the carrier can be suppressed, and further, the external additive can be prevented from detaching from the toner. Therefore, even if image formation is performed over a long period of time, it is considered that the occurrence of toner scattering, toner spent on the carrier, and the like generated when the external additive is detached from the toner can be suppressed.

  Further, the coating resin will be described later, but by using a resin containing a fluorine-based resin and a silane coupling agent containing an amino group in the molecule, that is, an aminosilane coupling agent, charging stability to the toner is achieved. It is considered that a carrier having improved durability and durability can be obtained.

  First, the fluororesin is excellent in wear resistance and improves the durability of the carrier. On the other hand, fluororesin can impart positive chargeability to the toner, but when printing over a long period of time with little toner replacement, such as printing an image with a low density printing rate, the toner is excessive. It is considered that the toner is charged and the toner is difficult to be separated from the carrier, which may cause a decrease in image density. In this embodiment, the coating resin contains a fluororesin, but such a problem is unlikely to occur. This is considered to be due to the fact that the coating resin contains not only a fluorine-based resin but also an aminosilane coupling agent. That is, it is thought that generation | occurrence | production of said malfunction can be suppressed when an aminosilane coupling agent is contained. This is considered to be because the excessively charged toner is brought into contact with the aminosilane coupling agent contained in the coating resin, thereby reducing the charge amount of the toner and thereby suppressing the occurrence of image density reduction or the like. .

  Furthermore, when an aminosilane coupling agent is contained, peeling of the coating resin from the core material can be suppressed, and a carrier having excellent durability can be obtained. This is considered to be due to the fact that when the aminosilane coupling agent is contained, the binding property between the coating resin and the core material can be enhanced.

  From the above, it is considered that an electrophotographic developer capable of forming a high-quality image over a long period of time can be provided by using the above-described configuration.

[toner]
As described above, the toner includes toner base particles containing a binder resin and a colorant, and an external additive externally added to the toner base particles, and can satisfy the above formula (1). If it is a specific surface area, it will not specifically limit.

Further, BET specific surface area S _T of the toner, as described above, if the BET specific surface area that can satisfy the above formula (1) is not particularly limited. It Specifically, the varies depending _{S D} etc. BET specific surface area _{S C} and the electrophotographic developer carrier, for example, if the toner 7 [mu] m, a 2.0~2.8m ² / g Is preferred.

  Further, the particle diameter of the toner is preferably 4.5 to 9.0 μm in volume average particle diameter. If such a toner having a relatively small particle size (small particle size toner) is used, an image to be formed is considered to have high definition. In general, when such a small particle size toner is used, fogging or the like may occur and a suitable image may not be formed. However, the electrophotographic developer according to this embodiment has such a problem. Is suppressed. Therefore, a higher quality image can be formed. Here, the volume average particle diameter can be measured, for example, by measurement using a laser diffraction scattering method or the like, or measurement using a general particle size meter.

<Toner base particles>
The toner base particles are not particularly limited as long as they contain a binder resin and a colorant and can be used as toner base particles. Further, the particle diameter is substantially the same as the particle diameter of the toner, and specifically, for example, the volume average particle diameter is preferably 4.5 to 9.0 μm.

(Binder resin)
The binder resin can be used without particular limitation as long as it is conventionally used as a binder resin for toner base particles. Specifically, for example, polystyrene resins such as styrene-acrylic resins and styrene-butadiene resins; acrylic resins; olefin resins such as polyethylene resins and polypropylene resins; vinyl chloride resins; polyester resins; polyamides Polyurethane resin; polyvinyl alcohol resin; vinyl ether resin; N-vinyl resin and the like. Among these, polyester resins are preferably used because they have a relatively low softening point, excellent low-temperature fixability, and a wide non-offset temperature range. Moreover, as said binder resin, each said binder resin may be used independently, and may be used in combination of 2 or more type.

  Examples of the polyester-based resin include those obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component. Moreover, the following are mentioned as a component used when synthesize | combining a polyester-type resin.

  The alcohol component is not particularly limited as long as it can be used as an alcohol for synthesizing a polyester resin. In addition, the alcohol component needs to contain an alcohol having 2 or more hydroxyl groups (divalent or higher alcohol) in the molecule. Specific examples of the divalent alcohol among those used as the alcohol component include, for example, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4- Butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol Diols such as bisphenol A, hydrogenated bisphenol A, bisphenols such as polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A, and the like. Further, among the alcohols used as the alcohol component, as the trivalent or higher alcohol, specifically, for example, sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dithiol Pentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, tri Examples include methylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene and the like. Moreover, as said alcohol component, said each component may be used independently and may be used in combination of 2 or more type.

  The carboxylic acid component is not particularly limited as long as it can be used as a carboxylic acid for synthesizing a polyester resin. The carboxylic acid component includes not only carboxylic acids but also acid anhydrides and lower alkyl esters of carboxylic acids. And as said carboxylic acid component, it is necessary to contain the carboxylic acid (divalent or more carboxylic acid) which has 2 or more of hydroxyl groups in the molecule | numerator of carboxylic acid. Specific examples of the divalent carboxylic acid used as the carboxylic acid include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and cyclohexanedicarboxylic acid. Examples include acids, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, alkyl succinic acid, and alkenyl succinic acid. Examples of the alkyl succinic acid include n-butyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid, isododecyl succinic acid, and the like. Examples of the alkenyl succinic acid include n-butenyl succinic acid and isobutyl succinic acid. , Isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, isododecenyl succinic acid and the like. Further, among the carboxylic acids used as the carboxylic acid, the trivalent or higher carboxylic acid specifically includes, for example, 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid. Acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2 -Methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empole trimer acid, etc. Can be mentioned. Moreover, as said carboxylic acid component, said each component may be used independently and may be used in combination of 2 or more type.

  The polystyrene resin may be a styrene homopolymer or a copolymer with another copolymerizable monomer copolymerizable with styrene. Examples of the copolymerizable monomer include p-chlorostyrene; vinyl naphthalene; olefinic hydrocarbons (alkene) such as ethylene, propylene, butylene, and isobutylene; vinyl halides such as vinyl chloride, vinyl bromide, and vinyl fluoride; vinyl acetate. Vinyl esters such as vinyl propionate, vinyl benzoate, vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate Acrylic esters such as phenyl acrylate and methyl α-chloroacrylate; methacrylic esters such as methyl methacrylate, ethyl methacrylate and butyl methacrylate; acrylics such as acrylonitrile, methacrylonitrile and acrylamide Derivatives; Vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrole N-vinyl compounds, such as den, etc. are mentioned. Moreover, as said copolymerization monomer, said each monomer may be used independently and may be used in combination of 2 or more type.

  As the binder resin, it is preferable to use the thermoplastic resin as described above from the viewpoint of fixability, but it is not necessary to use only the thermoplastic resin, and a crosslinking agent or a thermosetting resin is combined with the thermoplastic resin. May be used. By introducing a partially crosslinked structure into the binder resin as described above, it is possible to improve the offset resistance while suppressing a decrease in fixability at the time of fixing the toner onto the paper.

  Specific examples of the thermosetting resin include bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, novolac type epoxy resins, polyalkylene ether type epoxy resins, and cyclic aliphatic type epoxy resins. And cyanate resins such as cyanate resins and cyanate resins. These may be used alone or in combination of two or more.

(Coloring agent)
As the colorant, a known pigment or dye can be used so as to obtain a desired color as the toner. Specifically, for example, the following colorants may be mentioned depending on the color. Examples of the black pigment include carbon black such as acetylene black, lamp black, and aniline black. Examples of yellow pigments include yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, and Benzidine Yellow. GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C.I. I. And CI Pigment Yellow 180. Examples of the orange pigment include reddish yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK and the like. Red pigments include Bengala, cadmium red, red lead, mercury cadmium sulfide, permanent red 4R, risor red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, Brilliant Carmine 3B, C.I. I. Pigment red 238 and the like. Examples of purple pigments include manganese purple, fast violet B, and methyl violet lake. Examples of blue pigments include bitumen, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, induslen blue BC, C.I. I. And CI Pigment Blue 15: 3 (copper phthalocyanine blue pigment). Examples of the green pigment include chrome green, chromium oxide, pigment green B, malachite green lake, and final yellow green G. Examples of white pigments include zinc white, titanium oxide, antimony white, zinc sulfide, barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white. Among these, for example, the following colorants are preferable. Carbon black is preferred as the colorant for the black toner. Examples of the colorant for yellow toner include C.I. I. Pigment Yellow 180 is preferable. Examples of the colorant for cyan toner include C.I. I. Pigment Blue 15: 3 (copper phthalocyanine blue pigment) is preferred. Examples of the colorant for magenta toner include C.I. I. Pigment Red 238 is preferred.

  The content of the colorant varies depending on the type of the colorant, but in order to achieve a suitable image density, for example, it is 1 to 10 parts by mass with respect to 100 parts by mass of the binder resin. Preferably, it is 2-5 mass parts.

(Charge control agent)
The toner base particles generally contain a charge control agent in order to control chargeability such as frictional chargeability of the toner. A positive charge control agent and a negative charge control agent are used in combination as necessary according to the charging polarity of the toner. The charge control agent is not particularly limited as long as it is conventionally used as a charge control agent for toner base particles.

  Specific examples of the positive charge control agent include pyridazine, pyrimidine, pyrazine, orthooxazine, metaoxazine, paraoxazine, orthothiazine, metathiazine, parathiazine, 1,2,3-triazine, 1,2,4- Triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine, 1,3,4-thiadiazine, 1,3,5-thiadiazine, 1,2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6-oxatriazine, 1,3,4,5-oxa Azine compounds such as triazine, phthalazine, quinazoline, quinoxaline; Azin Fast Red FC, Azin Fast Red 12BK, Azine Violet BO Direct dyes comprising azine compounds such as azine brown 3G, azine light brown GR, azine dark green BH / C, azine deep black EW, azine deep black 3RL; nigrosine compounds such as nigrosine, nigrosine salt, nigrosine derivatives; nigrosine BK, nigrosine Acid dyes comprising nigrosine compounds such as NB and nigrosine Z; metal salts of naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; quaternary ammonium salts such as benzylmethylhexyldecylammonium and decyltrimethylammonium chlorids; Resin or oligomer having quaternary ammonium salt; resin or oligomer having carboxylate in molecule; resin or oligomer having carboxyl group in molecule

  Specific examples of the negative charge control agent include organometallic complexes, salts thereof, and chelate compounds. Specific examples of the organometallic complex and salts thereof include acetylacetone metal complexes, salicylic acid metal complexes, and salts thereof. Specific examples of the chelate compound include aluminum acetylacetonate, iron (II) acetylacetonate, and 3,5-di-tert-butyl salicylate chromium.

  Moreover, as content of the said charge control agent, it is preferable that it is 0.1-10 mass parts with respect to 100 mass parts of binder resin, and it is more preferable that it is 0.5-5 mass parts. When the content of the charge control agent is too small, it is difficult to stably charge the toner to a predetermined polarity, and fog may easily occur in the formed image. Further, when the content of the charge control agent is too large, the toner is likely to be charged up and the density of the formed image may be lowered.

(wax)
The toner base particles generally contain a wax in order to improve fixability and offset property. The wax is not particularly limited as long as it is conventionally used as a wax for toner base particles. Specific examples include, for example, plant waxes such as carnauba wax, sugarcane wax, and wood wax; animal waxes such as beeswax, insect wax, whale wax, and wool wax; Fischer-Tropsch (hereinafter referred to as “FT”) And synthetic hydrocarbon waxes such as wax, polyethylene wax and polypropylene wax. Among these, synthetic hydrocarbon waxes such as FT wax and polyethylene wax are preferable, and FT wax is more preferable because of excellent dispersibility in the binder resin. The added amount of the wax is preferably 0.1 to 20 parts by mass with respect to 100 parts by mass of the binder resin. If the amount added is too small, the effect of adding wax may not be obtained. If the amount added is too large, the blocking resistance of the toner will be reduced, and the wax will be removed from the toner. Separation may occur.

(Production method)
The method for producing the toner base particles is not particularly limited, but can be produced, for example, as follows.

  First, the components constituting the toner base particles such as the binder resin and the colorant are mixed with a mixer or the like. As the mixer, a known one can be used, and examples thereof include a Henschel type mixing device such as a Henschel mixer, a super mixer, and a mechano mill, an ang mill, a hybridization system, and a cosmo system. Among these, a Henschel mixer is preferable.

  Next, the obtained mixture is melt-kneaded with a kneader or the like. A well-known thing can be used as said kneading machine, For example, extruders, such as a twin-screw extruder, a 3 roll mill, a lab blast mill, etc. are mentioned, An extruder is used suitably. Further, the temperature at the time of melt kneading is preferably a temperature that is not lower than the softening point of the binder resin and lower than the thermal decomposition temperature of the binder resin.

  Next, the obtained melt-kneaded product is cooled to form a solid, and the solid is pulverized by a pulverizer or the like. As the pulverizer, known pulverizers can be used. For example, an air pulverizer such as a jet pulverizer (jet mill) that pulverizes using a supersonic jet stream, a mechanical pulverizer such as a turbo mill, or an impact pulverizer. Examples thereof include a pulverizer, and an airflow pulverizer is preferably used.

  Finally, the obtained pulverized product is classified with a classifier or the like. By classification, excessively pulverized material and coarse powder can be removed, and desired toner base particles can be obtained. As the classifier, known ones can be used, and examples thereof include a wind classifier such as a swirling wind classifier (rotary wind classifier) such as an elbow jet classifier, a centrifugal classifier, and the like. A machine is preferably used.

<External additive>
The toner is obtained by externally adding an external additive to the toner base particles. That is, it is obtained by subjecting the toner base particles to an external addition process.

  As the external addition step, any conventionally known external addition step can be used without limitation. Specifically, for example, a step of adding or fixing the external additive to the surface of the toner base particles by adding the external additive to the toner base particles and stirring the mixture with a stirrer or the like.

  The external additive is not particularly limited as long as it can be used as an external additive for toner. Specifically, for example, metal soap particles such as silica particles, titanium oxide particles, alumina particles, zinc oxide particles, and magnetite particles, zinc stearate particles, magnesium stearate particles, calcium stearate particles, Resin particles, resin particles surface-treated with the metal oxide particles and the metal soap particles, and the like. Among these, the combination of silica particles and titanium oxide particles is preferable from the viewpoint of excellent fluidity, chargeability, and polishing properties. Moreover, as said external additive, the said external additive may be used independently, and may be used in combination of 2 or more type.

  Further, the content of the external additive is preferably 0.2 to 3 parts by mass with respect to 100 parts by mass of the toner base particles.

  As the stirrer, a conventionally known stirrer can be used without limitation. Specifically, for example, a general stirrer such as a turbine-type stirrer, a Henschel mixer, a supermixer or the like can be used, and a Henschel mixer is preferably used.

[Career]
As described above, the carrier is not particularly limited as long as it includes a core material and a coating resin that coats the core material and has a BET specific surface area that satisfies the above formula (1).

Further, BET specific surface area S _C of the carrier, as described above, if the BET specific surface area that can satisfy the above formula (1) is not particularly limited. Specifically, the varies depending _{S D,} etc. of BET specific surface area _{S T} and the developer for electrophotography toner, for example, when the volume center diameter of 35μm carriers, 0.05～0.08M ² / G is preferable.

  The core material can be used without particular limitation as long as it is conventionally used as a carrier for an electrophotographic developer (two-component developer). Specific examples include magnetic particles such as metals such as iron, nickel, and cobalt, alloys containing the metals, iron-based oxides such as ferrite and magnetite, and mixtures thereof. Examples of the magnetic particles include magnetic particles produced by sintering and atomizing the magnetic material. Among these, particles made of ferrite and magnetite are preferable.

  In addition, the particle diameter of the core material is preferably 20 to 50 μm, more preferably 25 to 45 μm in terms of the volume center diameter. Here, the volume center diameter can be measured by, for example, measurement using an electron microscope, measurement using a laser diffraction scattering method, or measurement using a general particle size meter.

  The coating resin is not particularly limited as long as it contains a fluorine-based resin and a silane coupling agent containing an amino group in the molecule, that is, an aminosilane coupling agent.

  The fluororesin is not particularly limited, and examples thereof include a fluororesin generally used as a carrier coating resin. Specific examples include tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyvinylidene fluoride, polytetrafluoroethylene (PTFE), and the like. It is done. Among these, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) is preferable. It is considered that the fluororesin not only has excellent wear resistance but also can impart positive chargeability to the toner. Therefore, it is considered that the wear resistance of the carrier can be improved and the charging stability can be further improved by including the fluororesin in the coat resin.

The silane coupling agent is not particularly limited as long as it is a silane coupling agent containing an amino group in the molecule. That is, it is not particularly limited as long as it is a silane coupling agent containing a hydrolyzable group such as an alkoxy group or a halogen group and an amino group in the molecule. Specifically, for example, H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si (OCH ₃ ) ₃ , H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si (CH ₃ ) (OCH ₃ ) ) ₂ , H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si (OCH ₃ ) ₃ , H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si (OCH ₃ ) ₃ , H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ , C ₆ H ₅ NH (CH ₂ ) ₃ Si (OCH ₃ ) _{3, and the} like. Moreover, as said silane coupling agent, said each silane coupling agent may be used independently, and may be used in combination of 2 or more type.

  In addition to the fluorine resin and the aminosilane coupling agent, the coat resin may contain other components. Specifically, for example, a polyamide resin, a polyimide resin, and a polyamideimide resin may be contained.

  It is preferable that content of the said silane coupling agent is 0.1-10 mass parts with respect to 100 mass parts of resin components of the said coat resin. When the amount of the silane coupling agent is too small, the effect of containing a silane coupling agent such as suppressing the occurrence of a decrease in image density of the formed image and improving the binding property between the coating resin and the core material is sufficiently obtained. There is a possibility that it cannot be demonstrated. Further, when the amount of the silane coupling agent is too much, there is a possibility that poor dispersion occurs in the coating resin, and it is detached from the core material to cause toner charging failure. Therefore, it is considered that the content of the silane coupling agent is within the above range, whereby the occurrence of a decrease in concentration can be further suppressed, and the binding property between the coating resin and the core material can be further increased. A higher quality image can be formed over a long period of time.

  Moreover, it is preferable that content of the said fluororesin is 20-90 mass parts with respect to 100 mass parts of resin components of the said coating resin. If the amount of the fluororesin is too small, the effect of adding the fluororesin to the coating resin, such as improving the wear resistance of the carrier and improving the charging stability of the toner, may not be sufficiently exhibited. Moreover, when there is too much said fluorine-type resin, there exists a possibility that the adhesion failure of coat resin to a core material will be caused and it may peel from a core material. Therefore, it is considered that the content of the fluororesin is within the above range, so that the effect of the fluororesin can be sufficiently exhibited, and a higher quality image can be formed over a long period of time. .

  Further, the coating amount of the coating resin on the core material is not particularly limited. Specifically, it is preferable that it is 0.5-10 mass parts with respect to 100 mass parts of said core materials, for example. If the coating amount of the coating resin is too small, there is a possibility that charging stability and durability cannot be sufficiently improved by the coating resin. Further, if the coating amount of the coating resin is too large, the magnetism of the carrier core material is shielded by the thick coating layer, and it is difficult for the carrier to be magnetically supported on the developing roller, and the phenomenon of the carrier flying on the photosensitive member is likely to occur. . Therefore, it can be considered that the coating amount of the coating resin is within the above range, so that the coating resin can be prevented from being scraped or peeled off, and further, the charging stability can be improved. It can be formed over a long period of time.

(Production method)
Moreover, the manufacturing method of the carrier is not particularly limited as long as the coating resin is coated on the core material. Specifically, for example, a method of solidifying the coating resin by coating the liquid coating resin on the core material and then heat-treating it can be mentioned. Examples of the coating method include a fluid coating method and a dipping method. The heat treatment varies depending on the composition of the coat resin.

As described above, the toner concentration in the electrophotographic developer is not particularly limited as long as it is a toner concentration that can satisfy the above formula (1). Specifically, the toner of S _T, wherein varies depending S _D etc. BET specific surface area S _C and the electrophotographic developer carrier, for example, the inclusion of the toner to the electrophotographic developer 1 part by weight the amount _{C T} is preferably a concentration such that 0.03 to 0.15 parts by weight. The content _{C C} of the carrier for the electrophotographic developer 1 part by mass is preferably a 0.85 to 0.97 parts by weight. If the toner density is too low, the image density of the formed image may be too low. On the other hand, if the toner concentration is too high, the toner scatters from the inside of the developing device, and there is a tendency that the toner adheres to the in-machine dirt or the transfer paper. Therefore, by setting the toner density within the above range, a high image density is obtained, and further, toner scattering occurs in the developing device, and the problem that the toner adheres to background portions such as in-machine dirt and transfer paper is suppressed. Can do.

  The electrophotographic developer according to the exemplary embodiment is a two-component developer obtained by mixing the toner with the carrier at an appropriate ratio, and can be used, for example, in an image forming apparatus described later.

[Image forming apparatus]
The image forming apparatus using the electrophotographic developer is not particularly limited as long as it is an electrophotographic image forming apparatus. Further, a tandem type color image forming apparatus using a plurality of colors of toner as described later is preferable. Specifically, for example, a tandem color image forming apparatus using a plurality of colors of toner as described later can be given. Here, a tandem color image forming apparatus will be described. Note that the image forming apparatus using the electrophotographic developer according to the present embodiment has a plurality of image carriers arranged in parallel in a predetermined direction in order to form toner images with different colors of toner on each surface. A plurality of developing units each having a developing roller disposed opposite to the image carrier and each image carrier, carrying and transporting toner on the surface, and supplying the conveyed toner to the surface of each image carrier And an electrophotographic developer as the developer.

  FIG. 1 is a schematic cross-sectional view showing the overall configuration of the image forming apparatus 1. As shown in FIG. 1, the image forming apparatus 1 has a box-shaped device body 1a. In the apparatus main body 1a, a toner image based on image data and the like is transferred to the paper P while feeding the paper P fed from the paper feeding unit 2 and the paper P fed from the paper feeding unit 2. An image forming unit 3 and a fixing unit 4 for performing a fixing process for fixing the unfixed toner image transferred to the paper P by the image forming unit 3 to the paper P are provided. Further, on the upper surface of the apparatus main body 1a, a paper discharge unit 5 for discharging the paper P subjected to the fixing process by the fixing unit 4 is provided.

  The paper feed unit 2 includes a paper feed cassette 21, a pickup roller 22, paper feed rollers 23, 24 and 25, and a registration roller pair 26. The paper feed cassette 21 is provided so as to be detachable from the apparatus main body 1a, and stores paper P of each size. The pickup roller 22 is provided at the upper right position of the paper feed cassette 21 shown in FIG. 1 and takes out the paper P stored in the paper feed cassette 21 one by one. The paper feed rollers 23, 24, and 25 send out the paper P taken out by the pickup roller 22 to the paper transport path. The registration roller pair 26 temporarily waits for the paper P sent to the paper transport path by the paper feed rollers 23, 24, 25, and then supplies the paper P to the image forming unit 3 at a predetermined timing. Specifically, the toner is supplied to a secondary transfer nip between a secondary transfer roller 12 and a backup roller 15 described later.

  The paper feeding unit 2 further includes a manual feed tray (not shown) and a pickup roller 27 that are attached to the right side surface of the device main body 1a shown in FIG. The pickup roller 27 takes out the paper P placed on the manual feed tray. The paper P taken out by the pickup roller 27 is sent out to the paper transport path by the paper feed rollers 23 and 25, temporarily held by the registration roller pair 26, and then sent to the image forming unit 3 at a predetermined timing. Supplied. Specifically, the toner is supplied to a secondary transfer nip between a secondary transfer roller 12 and a backup roller 15 described later.

  The image forming unit 3 includes an image forming unit 7, an intermediate transfer belt 11 on which a toner image based on image data transmitted from a computer or the like to the surface (contact surface) of the image forming unit 7 is primarily transferred, A secondary transfer roller 12 is provided for secondary transfer of the toner image on the intermediate transfer belt 11 onto the paper P fed from the paper feed cassette 21.

  The image forming unit 7 includes a magenta unit 7M, a cyan unit 7C, and a yellow unit 7Y, which are sequentially arranged from the upstream side (left side in FIG. 1) to the downstream side in the rotation direction of the intermediate transfer belt 11. And a black unit 7K. In each of the units 7M, 7C, 7Y and 7K, a photosensitive drum 71 as an image carrier is arranged at the center position so as to be rotatable in the direction of an arrow (counterclockwise). Around each photosensitive drum 71, a charger 75, an exposure device 76, a developing device 72, a cleaning device 73, a static eliminator 74, and the like are sequentially arranged from the upstream side in the rotation direction of the photosensitive drum 71. .

  The charger 75 uniformly charges the peripheral surface of the photosensitive drum 71 rotated in the direction of the arrow. Examples of the charger 75 include a non-contact discharge type corotron and scorotron type charger, a contact type charging roller, a charging brush, and the like.

  The exposure device 76 is a so-called laser scanning unit, which irradiates the peripheral surface of the photosensitive drum 71 uniformly charged by the charger 75 with laser light based on image data input from an image reading device or the like. An electrostatic latent image based on image data is formed on the photosensitive drum 71. The developing device 72 includes a developer accommodating portion that accommodates a developer composed of the carrier and toner. Then, the developing device 72 supplies toner based on the image data by supplying the toner of the developer stored in the developer storage portion to the peripheral surface of the photosensitive drum 71 on which the electrostatic latent image is formed. Form an image. The toner image is primarily transferred to the intermediate transfer belt 11 by the action of a primary transfer roller 16 described later. Note that the developer containing portion of the developing device 72 contains developers containing different color toners for each image forming unit 7. The cleaning device 73 cleans the toner remaining on the peripheral surface of the photosensitive drum 71 after the primary transfer of the toner image to the intermediate transfer belt 11 is completed. The neutralizer 74 neutralizes the peripheral surface of the photosensitive drum 71 after the cleaning of the residual toner is completed. The peripheral surface of the photosensitive drum 71 cleaned by the cleaning device 73 and the static eliminator 74 is directed to the charger 75 for a new charging process, and is newly charged.

  The intermediate transfer belt 11 is an endless belt-like rotating body, and includes a driving roller 13, a belt support roller 14, and a backup roller 15 so that the surface (contact surface) side is in contact with the peripheral surface of each photosensitive drum 71. And a plurality of rollers such as the primary transfer roller 16. Further, the intermediate transfer belt 11 is configured to rotate endlessly by the driving roller 13 while being pressed against the photosensitive drum 71 by a primary transfer roller 16 disposed to face each photosensitive drum 71. .

  The driving roller 13 is rotationally driven by a driving source such as a stepping motor, and provides a driving force for rotating the intermediate transfer belt 11 endlessly. The belt support roller 14 and the backup roller 15 are driven rollers that are rotatably provided and rotate with the endless rotation of the intermediate transfer belt 11 by the drive roller 13. These driven rollers 14 and 15 are driven to rotate via the intermediate transfer belt 11 according to the main rotation of the drive roller 13 and support the intermediate transfer belt 11.

  The primary transfer roller 16 applies a primary transfer bias (a polarity opposite to the charging polarity of toner) to the intermediate transfer belt 11. By doing so, the toner image formed on each photosensitive drum 71 is moved in the direction of the arrow (clockwise) by driving the driving roller 13 between each photosensitive drum 71 and the primary transfer roller 16. Are sequentially transferred (primary transfer) in an overcoated state to the intermediate transfer belt 11 that circulates. The primary transfer roller 16 rotates by obtaining a driving force from a driving motor that rotates the photosensitive drum 71.

  The secondary transfer roller 12 applies a secondary transfer bias having a reverse polarity to the toner image to the paper P. By doing so, the toner image primarily transferred onto the intermediate transfer belt 11 is transferred onto the paper P between the secondary transfer roller 12 and the backup roller 15, and thereby the color of the toner image is transferred onto the paper P. The transferred image (unfixed toner image) is transferred.

  The fixing unit 4 performs a fixing process on the transfer image transferred to the paper P at the secondary transfer nip, and is disposed opposite to the heating roller 41 heated by the energized heating element, And a pressure roller 42 having a peripheral surface pressed against and in contact with the peripheral surface of the heating roller 41.

  Then, the transferred image transferred onto the paper P by the secondary transfer roller 12 at the secondary transfer nip is heated and heated when the paper P passes between the heating roller 41 and the pressure roller 42. It is fixed on the paper P by a fixing process using pressure. Then, the paper P subjected to the fixing process is discharged to the paper discharge unit 5. In the image forming apparatus 1, a pair of conveying rollers 6 is disposed at an appropriate position between the fixing unit 4 and the paper discharge unit 5.

  The paper discharge unit 5 is formed by recessing the top of the apparatus main body 1a of the image forming apparatus 1, and a paper discharge tray for receiving the discharged paper P is formed at the bottom of the recess. ing.

  The image forming apparatus 1 forms an image on the paper P by the image forming operation as described above. In the tandem image forming apparatus as described above, since the electrophotographic developer is used, a high-quality image can be formed over a long period of time.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by the Example.

[Example 1]
(Manufacture of black toner)
First, 100 parts by mass of a polyester resin (Tafton NE-1110 manufactured by Kao Corporation) obtained by polycondensation of bisphenol A and fumaric acid as a binder resin, and carbon black (manufactured by Mitsubishi Chemical Corporation) as a colorant. MA-100) 4 parts by mass, as a wax, 3 parts by mass of Fischer-Tropsch wax (FT-100 manufactured by Nippon Seiwa Co., Ltd.), and as a charge control agent, a quaternary ammonium salt compound (P manufactured by Orient Chemical Co., Ltd.) -51) 2 parts by mass were mixed for 2 minutes with a Henschel mixer (manufactured by Nippon Coke Kogyo Co., Ltd.). Then, the obtained mixture was melt-kneaded with a twin screw extruder (PCM-30 manufactured by Ikegai Co., Ltd.). The obtained melt-kneaded product was finely pulverized with an airflow type pulverizer (jet mill IDS-2 manufactured by Nippon Pneumatic Kogyo Co., Ltd.) and classified with an air classifier (TPS classifier manufactured by Hosokawa Micron Corporation). . By doing so, toner mother particles having a volume average particle diameter of 7 μm were obtained. The volume average particle diameter of the toner base particles was measured with a particle size meter (Multisizer 3 manufactured by Beckman Coulter, Inc.).

  Next, 2 parts by mass of silica particles (TG-820 manufactured by Cabot) and titanium oxide particles (JR-405 manufactured by Teika Co., Ltd.) 1 are used as external additives with respect to 100 parts by mass of the obtained toner base particles. .5 parts by mass was added and mixed with the same Henschel mixer at 3000 rpm for 10 minutes. By doing so, black toner (toner mother particles to which an external additive was externally added) was obtained.

Using the obtained black toner as a sample, the BET specific surface area (m ² / g) was measured. Specifically, using an automatic specific surface area measuring apparatus (Macsorb model 1208 manufactured by Mountec Co., Ltd.), nitrogen is adsorbed on the sample surface, and the BET specific surface area (m ² / g of the sample) is obtained by a flow method (BET single point type) ) Was measured. BET specific surface area _{S T} of measured toner was 2.44 m ² / g. Further, the volume average particle diameter of the toner was measured in the same manner as the volume average particle diameter of the toner base particles, and as a result, it was 7 μm.

(Manufacture of yellow toner)
The black toner was manufactured in the same manner as the black toner except that 2 parts by weight of yellow pigment (CI Pigment Yellow 180) was added instead of 4 parts by weight of carbon black.

Then, the BET specific surface area and volume average particle diameter of the obtained yellow toner were measured by the same method as that for the black toner. BET specific surface area _{S T} of measured toner was 2.44 m ² / g. The volume average particle size of the toner was 7 μm.

(Manufacture of cyan toner)
The black toner was produced in the same manner as the black toner except that 3 parts by mass of a cyan pigment (CI Pigment Blue 15-3) was added instead of 4 parts by mass of carbon black.

Then, the BET specific surface area and volume average particle diameter of the obtained yellow toner were measured by the same method as that for the black toner. BET specific surface area _{S T} of measured toner was 2.44 m ² / g. The volume average particle size of the toner was 7 μm.

(Manufacture of magenta toner)
The black toner was manufactured in the same manner as the above black toner except that 3 parts by mass of magenta pigment (CI Pigment Red 238) was added instead of 4 parts by mass of carbon black.

Then, the BET specific surface area and volume average particle diameter of the obtained yellow toner were measured by the same method as that for the black toner. BET specific surface area _{S T} of measured toner was 2.44 m ² / g. The volume average particle size of the toner was 7 μm.

(Carrier production)
First, trimet acid anhydride and 4,4′-diphenylmethane diisocyanate were added to water and stirred at 80 ° C. for 2 hours. By doing so, a polyamideimide solution was obtained. Next, in this polyamideimide solution, tetrafluoroethylene-hexafluoropropylene is used as a fluororesin (second coat resin) with respect to 50 parts by mass of the solid content (resin content: first coat resin) of the polyamideimide solution. 50 parts by mass of a copolymer (FEP) (120-J manufactured by DuPont) and 3 parts by mass of an aminosilane coupling agent (Z-6011 manufactured by Toray Dow Corning Co., Ltd.) were mixed as a silane coupling agent. By doing so, a liquid coat resin was obtained.

  Next, as a core material, a ferrite core carrier (EF-35B manufactured by Powder Tech Co., Ltd., volume center diameter 35 μm, mass magnetization intensity 68 emu / g) is used. 5 parts by mass of the resin was coated using a fluidized coating apparatus (MP-1 manufactured by Paulec Co., Ltd.). Thereafter, heat treatment was performed at 280 ° C. for 1 hour. By doing so, the coating resin coated on the core material was solidified, and a carrier (core material coated with the coating resin) was obtained.

The BET specific surface area of the obtained carrier was measured by the same method as that for the black toner. BET specific surface area _{S C} of the measured carrier was 0.066m ² / g.

  In addition, the coating amount of the coating resin of the obtained carrier was 5 parts by mass with respect to 100 parts by mass of the core material. And content of the fluororesin of the obtained carrier was 50 mass parts with respect to 100 mass parts of resin components of coat resin. Moreover, content of the silane coupling agent of the obtained carrier was 3 mass parts with respect to 100 mass parts of resin components of coat resin.

(Manufacture of developer)
100 g of each color toner obtained as described above and 1 kg of the carrier were mixed by stirring for 20 minutes with a mixing device manufactured by Kyocera Mita Co., Ltd., which was adjusted to 40 ° C. By doing so, an electrophotographic developer (two-component developer) was obtained. Specifically, the mixing device includes a plastic cylindrical container, and rotates the cylindrical container at a rotation speed of about 100 rpm. That is, it is an apparatus that mixes the material in the cylindrical container by rotating the cylindrical container in a state where each material that is a mixing object is accommodated.

Then, the developer was set in a color MFP (KM-C3232) manufactured by Kyocera Mita Co., Ltd., and the evaluation machine was turned on and stabilized. The BET specific surface area of the electrophotographic developer in this state was measured by the same method as that for the black toner. The BET specific surface area _SD of the measured electrophotographic developer was 0.242 m ² / g.

Note that, as described above, 1100 g of the electrophotographic developer is manufactured by mixing 100 g of toner and 1 kg (1000 g) of carrier as described above. That is, the toner is manufactured so that the toner concentration (T / C) with respect to the carrier is 10 mass%. Thus, the content C _T of the toner to the electrophotographic developer 1 part by weight was about 0.0909 parts by weight. The content C _C of the carrier for the electrophotographic developer 1 part by weight was about 0.909 parts by weight.

[Example 2]
The same as Example 1, except that the stirring time during the production of the developer was changed from 20 minutes to 7 minutes. The BET specific surface area _SD of the electrophotographic developer measured by the same method as in Example 1 was 0.267 m ² / g.

[Example 3]
The same as Example 1, except that the stirring time during the production of the developer was changed from 20 minutes to 40 minutes. The BET specific surface area _SD of the electrophotographic developer measured by the same method as in Example 1 was 0.229 m ² / g.

[Example 4]
In the production of the toner, the same as Example 1 except that the mixing time of the toner base particles and the external additive was changed from 10 minutes to 3 minutes.

Then, was measured in the same manner as in Example 1, BET specific surface area _{S T} of the toner is 2.56m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.276m ² / g Met.

[Example 5]
In the production of the toner, the same as Example 1 except that the mixing time of the toner base particles and the external additive was changed from 10 minutes to 30 minutes.

Then, was measured in the same manner as in Example 1, BET specific surface area _{S T} of the toner is 2.31m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.220m ² / g Met.

Then, was measured in the same manner as in Example 1, the BET specific surface area _{S T} of the toner, a 2.31m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.220m ² / g.

[Example 6]
In manufacture of a carrier, it is the same as that of Example 1 except having changed the addition amount of the aminosilane coupling agent (Toray Dow Corning Co., Ltd. Z-6011) from 3 mass parts to 1 mass part. In addition, content of the silane coupling agent of the obtained carrier was 1 mass part with respect to 100 mass parts of resin components of coat resin.

Then, was measured in the same manner as in Example 1, BET specific surface area _{S C} of the carrier is 0.064 m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.242m ² / g Met.

[Example 7]
In manufacture of a carrier, it is the same as that of Example 1 except having changed the addition amount of the aminosilane coupling agent (Toray Dow Corning Co., Ltd. Z-6011) from 3 mass parts to 10 mass parts. In addition, content of the silane coupling agent of the obtained carrier was 10 mass parts with respect to 100 mass parts of resin components of coat resin.

Then, was measured in the same manner as in Example 1, BET specific surface area _{S C} of the carrier is 0.072m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.243m ² / g Met.

[Example 8]
In the production of the carrier, instead of tetrafluoroethylene-hexafluoropropylene copolymer (FEP) (120-J made by DuPont), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) (made by DuPont) The same as Example 1 except that MP-102) was used.

Then, was measured in the same manner as in Example 1, BET specific surface area _{S C} of the carrier is 0.066m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.242m ² / g Met.

[Example 9]
In the production of the carrier, polytetrafluoroethylene (PTFE) (31-JR manufactured by DuPont) was used instead of tetrafluoroethylene-hexafluoropropylene copolymer (FEP) (120-J manufactured by DuPont). Except for this, this is the same as Example 1.

Then, was measured in the same manner as in Example 1, BET specific surface area _{S C} of the carrier is 0.066m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.242m ² / g Met.

[Example 10]
The production of the carrier is the same as that of Example 1 except that a polyamide resin (SP-500 manufactured by Toray Industries, Inc.) was used instead of the polyamideimide resin.

Then, was measured in the same manner as in Example 1, BET specific surface area _{S C} of the carrier is 0.069m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.242m ² / g Met.

[Example 11]
In manufacture of a carrier, it is the same as that of Example 1 except having used the polyimide resin (Ube Industries, Ltd. VIP-S) instead of the polyamide-imide resin.

Then, was measured in the same manner as in Example 1, BET specific surface area _{S C} of the carrier is 0.068m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.242m ² / g Met.

[Example 12]
In the production of the carrier, it was carried out except that an aminosilane coupling agent (Z-6020 manufactured by Toray Dow Corning Co., Ltd.) was used instead of an aminosilane coupling agent (Z-6011 manufactured by Toray Dow Corning Co., Ltd.). Similar to Example 1.

Then, was measured in the same manner as in Example 1, BET specific surface area _{S C} of the carrier is 0.066m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.242m ² / g Met.

[Example 13]
In manufacture of a carrier, it is the same as that of Example 1 except having changed the addition amount of the aminosilane coupling agent (Toray Dow Corning Co., Ltd. Z-6011) from 3 mass parts to 12 mass parts. In addition, content of the silane coupling agent of the obtained carrier was 12 mass parts with respect to 100 mass parts of resin components of coat resin.

Then, was measured in the same manner as in Example 1, BET specific surface area _{S C} of the carrier is 0.075 m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.244m ² / g Met.

[Example 14]
In the production of the carrier, the same procedure as in Example 1 was performed except that a silicone resin (methyl-dimethyl silicone resin, SR2400 manufactured by Toray Dow Corning Co., Ltd.) was used instead of the polyamideimide resin.

Then, was measured in the same manner as in Example 1, BET specific surface area _{S C} of the carrier is 0.068m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.242m ² / g Met.

[Comparative Example 1]
In the production of the developer, instead of stirring and mixing in the mixing container for 20 minutes, the toner 100 g and the carrier 1 kg are put into a 2 L plastic container, covered, and then turned upside down three times. The same as Example 1 except that the developer is manufactured. The BET specific surface area _SD of the electrophotographic developer measured by the same method as in Example 1 was 0.281 m ² / g.

[Comparative Example 2]
The same as Example 1, except that the stirring time during the production of the developer was changed from 20 minutes to 60 minutes. The BET specific surface area _SD of the electrophotographic developer measured by the same method as in Example 1 was 0.220 m ² / g.

[Comparative Example 3]
In the production of the developer, it is the same as Example 1 except that the temperature control temperature of the mixing container was changed from 40 ° C to 25 ° C. The BET specific surface area _SD of the electrophotographic developer measured by the same method as in Example 1 was 0.277 m ² / g.

[Comparative Example 4]
In the production of the toner, the same as Example 1 except that the mixing time of the toner base particles and the external additive was changed from 10 minutes to 1 minute.

Then, was measured in the same manner as in Example 1, BET specific surface area _{S T} of the toner is 2.60m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.289m ² / g Met.

[Comparative Example 5]
In the production of the toner, the same as Example 1 except that the mixing time of the toner base particles and the external additive was changed from 10 minutes to 60 minutes.

Then, was measured in the same manner as in Example 1, BET specific surface area _{S T} of the toner is 2.22m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.206m ² / g Met.

[Comparative Example 6]
In the production of the carrier, the same as Example 1 except that the aminosilane coupling agent (Z-6011 manufactured by Toray Dow Corning Co., Ltd.) was not added. In addition, content of the silane coupling agent of the obtained carrier was 0 mass part with respect to 100 mass parts of coating resin.

Then, was measured in the same manner as in Example 1, BET specific surface area _{S C} of the carrier is 0.060m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.241m ² / g Met.

[Comparative Example 7]
In the production of the carrier, instead of containing 50 parts by mass of the polyamideimide resin, 100 parts by mass of silicone resin (methyl-dimethyl silicone resin, SR2400 manufactured by Toray Dow Corning Co., Ltd.) is contained, and tetrafluoroethylene-hexafluoropropylene is contained. Same as Example 1 except that no copolymer (FEP) was added. In addition, content of the fluororesin of the obtained carrier was 0 mass part with respect to 100 mass parts of resin components of coat resin.

Then, was measured in the same manner as in Example 1, BET specific surface area _{S C} of the carrier is 0.070m ² / g, BET specific surface area _{S D} of the electrophotographic developer, 0.243m ² / g Met.

  Including the above, it summarizes in Table 1.

[Evaluation]
The obtained electrophotographic developer was evaluated by the following method.

  First, a color MFP (KM-C3232) manufactured by Kyocera Mita Co., Ltd. was used as an evaluation machine, each developer obtained was used as a start developer, and each toner was used as a replenishing toner, and the temperature was set to 20 to Images were formed in a normal temperature and humidity environment at 23 ° C. and a relative humidity of 50 to 65% RH, and the following evaluation was performed.

  Specifically, first, the start developer was set in the evaluator, and the evaluator was turned on and stabilized. Thereafter, an image was output. This image was used as the initial image (first image). Next, 3000 sheets of images with a printing rate of 0.1% were printed while replenishing toner. The 3000th image was a low density printed image. Thereafter, while supplying the replenishing toner, 1000 images with a printing rate of 10% and a printing ratio of 25% for each color were printed. The 1000th image (4000th image from the initial image) was a high-density print image.

(Image density)
In each of the initial image, the low density print image, and the high density print image, a 2 × 2 cm solid image has a position in the vicinity of the left end, a center portion, and a right end in the paper transport direction. It is formed at three locations.

  About each solid image of the formed image, the reflection density was measured using a reflection densitometer (RD-19A: SpectroEyeLT manufactured by Gretag Macbeth). The average value was taken as the image density of the obtained image.

  If the measured lower limit of the image density is 1.2 or more, it is evaluated as “◯”, if it is 1 or more and less than 1.2, it is evaluated as “Δ”, and if it is less than 1, “x”. evaluated.

(Cover)
In the obtained image, the fog density was obtained by subtracting the image density value of the base paper (that is, the white paper before image output) from the image density value of the blank paper equivalent measured by the reflection densitometer. Then, the fog density was measured every predetermined number of sheets, and the fog was evaluated with the maximum value.

  When the maximum value of the fog density is 0.007 or less, it is evaluated as “◎”, and when it exceeds 0.007 and is 0.010 or less, it is evaluated as “◯”, exceeds 0.010, and is equal to 0.0. If it was 020 or less, it was evaluated as “Δ”, and if it exceeded 0.020, it was evaluated as “x”.

(Charge amount)
The developer immediately after printing the initial image, the low density printed image, and the high density printed image was taken out, and each charge amount was measured by the same method as described above.

  The evaluation results are shown in Table 2.

  The obtained electrophotographic developer was further evaluated by the following method.

  First, apart from the image formation, a color MFP (KM-C3232) manufactured by Kyocera Mita Co., Ltd. is used as an evaluation machine, each developer obtained is used as a start developer, and each toner is used as a replenishment toner. As a result, an image was formed in a normal temperature and humidity environment at a temperature of 20 to 23 ° C. and a relative humidity of 50 to 65% RH.

  Specifically, first, the start developer was set in a developer container corresponding to each color of the evaluation machine, and the evaluation machine was turned on and stabilized. Thereafter, a sample image including a 100% solid portion, a 50% halftone portion, a character portion, and a fine line portion was output under a normal temperature and humidity environment. Thereafter, a standard pattern with a printing rate of 5% was printed in a normal temperature and humidity environment (300,000 durable printing).

  As a result, when the developer according to Comparative Example 1 was used, it was visually confirmed that toner unrelated to the image was dropped (attached) on the image obtained by printing 150,000th sheet. Further, when the developer according to Comparative Example 3 was used, it was visually confirmed that toner unrelated to the image was dropped (attached) on the image obtained by printing on the 200,000th sheet.

  When a developer other than these was used, no particular problem occurred even with an image obtained by printing on the 300,000th sheet. Specifically, it was impossible to visually confirm that toner unrelated to the image was dropped (attached) on the formed image.

As can be seen from the results of Table 1, Table 2 and 300,000 sheets of durable printing, it includes a core material and a coat resin that coats the core material, and the coat resin contains a fluorine-based resin and an amino group in the molecule. An electrophotographic developer containing a carrier containing a silane coupling agent (aminosilane coupling agent), wherein the BET specific surface area of the toner, the carrier and the electrophotographic developer is measured by a BET method. _{respectively,} and _{^{S T m 2 / g, S}} C m 2 / g and _S D ^m 2 / g, for the electrophotographic developer 1 part by weight, the toner and the amount of the carrier, respectively, _{C T} parts by and if the C _C parts by weight, when using an electrophotographic developer satisfies the following formula (1) (examples 1-14), compared to other cases (Comparative examples 1 to 7), Image density High, low fog density, further, the charging property of the toner was found to be stable.

_{0.8 ≦ S D / (S C} × C C + S T × C T) ≦ 0.95 (1)
Furthermore, it was found that when the electrophotographic developer according to Examples 1 to 14 was used, a suitable image could be obtained even after 300,000 durable printing.

  From these facts, it was found that the electrophotographic developers according to Examples 1 to 14 can form high-quality images over a long period of time.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Paper feed part 3 Image forming part 4 Fixing part 5 Paper discharge part 6 Conveyance roller 7 Image forming unit 11 Intermediate transfer belt 12 Secondary transfer roller 13 Drive roller 14 Belt support roller 15 Backup roller 16 Primary transfer roller DESCRIPTION OF SYMBOLS 21 Paper feed cassette 22 Pickup roller 23, 24, 25 Paper feed roller 26 Registration roller pair 27 Pickup roller 41 Heating roller 42 Pressure roller 71 Photosensitive drum 72 Developing device 73 Cleaning device 74 Charger 75 Charger 76 Exposure device

Claims (6)

An electrophotographic developer containing a toner and a carrier,
The toner includes toner base particles containing a binder resin and a colorant; and an external additive externally added to the toner base particles;
The carrier includes a core material and a coating resin that covers the core material,
The coating resin includes a fluorine resin and a silane coupling agent containing an amino group in the molecule,
The BET specific surface areas measured by the BET method of the toner, the carrier and the electrophotographic developer are S _T m ² / g, S _C m ² / g and S _D m ² / g, respectively. for photographic developer 1 part by weight, the toner and the amount of the carrier, respectively, if the C _T parts by mass C _C parts by weight, development for electrophotography which satisfies the following formula (1) Agent.
_{0.8 ≦ S D / (S C} × C C + S T × C T) ≦ 0.95 (1)   The electrophotographic developer according to claim 1, wherein the content of the silane coupling agent is 0.1 to 10 parts by mass with respect to 100 parts by mass of the resin component of the coat resin.   The fluororesin is at least one selected from the group consisting of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and polytetrafluoroethylene. Item 3. The electrophotographic developer according to Item 2.   The electrophotographic developer according to claim 1, wherein the coating resin further includes at least one selected from the group consisting of a polyamide resin, a polyimide resin, and a polyamideimide resin.   The electrophotographic developer according to any one of claims 1 to 4, wherein a coating amount of the coating resin is 0.5 to 10 parts by mass with respect to 100 parts by mass of the core material.   6. The electrophotographic developer according to claim 1, wherein the content of the fluororesin is 20 to 90 parts by mass with respect to 100 parts by mass of the resin component of the coat resin.

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