JP2017198835A - Image forming apparatus and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus and an image forming method capable of continuously forming high-quality images while suppressing electrostatic offset and hot offset.SOLUTION: An image forming apparatus includes a fixing device 30. The fixing device 30 includes a first roller 31 and a second roller 32. The fixing device 30 is configured so as to sandwich a recording medium P so that the first roller 31 comes in contact with a toner image transferred on a front face (surface F1) and the second roller 32 comes in contact with a rear face (surface F2) out of the front and rear faces (surfaces F1 and F2) of the recording medium P, and thereby to fix the toner image onto the recording medium P. The first roller 31 has a coat layer which contains a fluorine resin and has surface resistivity of 1.0×10Ω or more, on its surface layer portion. A toner T substantially stored in a developing device 10 in an initial state contains a plurality of crystalline polyester resins having a volume resistivity of 7×10Ω cm or less and non-crystalline resins.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus and an image forming method for forming an image using toner.

  Patent Document 1 discloses a technique for improving the releasability of the surface of the fixing roller by providing a PFA resin tube (fluororesin tube) on the surface of the fixing roller.

JP 2015-210412 A

  In the image forming apparatus described in Patent Document 1, it is considered that hot offset (a phenomenon in which toner is fused to the fixing roller during high-temperature fixing) can be suppressed by improving the releasability of the surface of the fixing roller. However, fluororesins tend to have low electrical resistance and strong negative chargeability. Therefore, when the surface layer portion of the fixing roller contains a fluororesin, the positively charged toner easily adheres to the surface of the fixing roller with an electric force, and electrostatic offset (the toner is fixed with an electric force). Phenomenon).

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and an image forming method capable of continuously forming a high-quality image while suppressing electrostatic offset and hot offset. .

An image forming apparatus according to the present invention includes an image carrier, a developing device, a transfer unit, and a fixing device. The developing device is configured to store toner, develop an electrostatic latent image formed on the image carrier with the toner, and form a toner image on the image carrier. The transfer unit is configured to transfer a toner image on the image carrier to a recording medium. The fixing device is configured to fix the toner image transferred to the recording medium to the recording medium. The fixing device includes a first roller and a second roller. The fixing device sandwiches the recording medium such that the first roller is in contact with the toner image transferred to the front surface of the recording medium, and the second roller is in contact with the back surface. The toner image is fixed to the recording medium. The first roller includes a coat layer having a surface resistivity of 1.0 × 10 ¹⁰ Ω or more containing a fluororesin on a surface layer portion. The toner substantially accommodated in the developing device in an initial state includes a plurality of toner particles containing a crystalline polyester resin having a volume resistivity of 7 × 10 ⁹ Ω · cm or less and an amorphous resin. .

The image forming method according to the present invention includes a development step, a transfer step, and a fixing step. In the developing step, the developing device of the image forming apparatus develops the electrostatic latent image formed on the image carrier with toner to form a toner image on the image carrier. In the transfer step, the transfer unit of the image forming apparatus transfers the toner image on the image carrier to a recording medium. In the fixing step, the fixing device of the image forming apparatus causes the first roller of the fixing device to contact the toner image transferred to the front surface of the recording medium, and the back surface of the fixing device is The toner image is fixed to the recording medium by sandwiching the recording medium so that the two rollers are in contact with each other. The first roller includes a coat layer having a surface resistivity of 1.0 × 10 ¹⁰ Ω or more containing a fluororesin on a surface layer portion. The toner includes a plurality of toner particles containing a crystalline polyester resin having a volume resistivity of 7 × 10 ⁹ Ω · cm or less and an amorphous resin.

  According to the present invention, it is possible to provide an image forming apparatus and an image forming method capable of continuously forming high-quality images while suppressing electrostatic offset and hot offset.

1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a fixing device of the image forming apparatus illustrated in FIG. 1.

  An embodiment of the present invention will be described. It should be noted that the evaluation results (values indicating the shape or physical properties) of the powder (more specifically, toner base particles, magnetic powder, external additive, toner, etc.) are from the powder unless otherwise specified. A considerable number of average particles are selected and the number average of the values measured for each of the average particles.

The number average particle diameter of the powder is the number average value of the equivalent circle diameter of primary particles (diameter of a circle having the same area as the projected area of the particles) measured using a microscope unless otherwise specified. . Moreover, the measured value of the volume median diameter (D ₅₀ ) of the powder is measured using a laser diffraction / scattering particle size distribution measuring device (“LA-750” manufactured by Horiba, Ltd.) unless otherwise specified. It is the value. Moreover, the softening point (Tm) is a value measured using a Koka type flow tester (“CFT-500D” manufactured by Shimadzu Corporation) unless otherwise specified. In the S curve (horizontal axis: temperature, vertical axis: stroke) measured with the Koka type flow tester, the temperature that becomes "(baseline stroke value + maximum stroke value) / 2" is Tm (softening point). Equivalent to. Moreover, the measured value of the melting point (Mp) is an endothermic curve (vertical axis: heat flow (DSC) measured using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.), unless otherwise specified). Signal), horizontal axis: temperature) is the maximum endothermic peak temperature.

  The chargeability means the chargeability in frictional charging unless otherwise specified. The strength of positive chargeability (or strength of negative chargeability) in frictional charging can be confirmed by a known charge train or the like.

  Hereinafter, a compound and its derivatives may be generically named by adding “system” after the compound name. When the name of a polymer is expressed by adding “system” after the compound name, it means that the repeating unit of the polymer is derived from the compound or a derivative thereof. Acrylic and methacrylic are sometimes collectively referred to as “(meth) acrylic”. Further, acrylonitrile and methacrylonitrile may be collectively referred to as “(meth) acrylonitrile”.

  The image forming apparatus according to the present embodiment will be described below with reference to FIG. As shown in FIG. 1, the image forming apparatus according to the present embodiment includes a photosensitive drum 20 (image carrier), a developing device 10, and a charging device 21 (for example, a photosensitive layer of the photosensitive drum 20 by a contact charging method). Charging member), an exposure device 22 (for example, an LED head), a transfer roller 23 (transfer portion), a cleaning member 24 (for example, a cleaning blade), and a transport device 25 (for example, a belt transport system). A conveying device) and a fixing device 30. The developing device 10 contains toner and is configured to develop the electrostatic latent image formed on the photosensitive drum 20 with toner. The image forming apparatus may include a toner container for supplying toner to the developing device 10.

  The developing device 10 includes a developing roller 10a (toner carrier), a toner supply member 14 (for example, a toner supply roller), and a toner charging member 15 (for example, a doctor blade). The developing roller 10 a includes a shaft 11, a magnet roll 12, and a cylindrical sleeve 13. The magnet roll 12 is fixed to the shaft 11. The magnet roll 12 is located inside the sleeve 13 (inside the cylinder), and the sleeve 13 is located on the surface layer of the developing roller 10a. The sleeve 13 is supported so that it can rotate around the shaft 11 (fixed shaft). The developing roller 10 a is configured to attract the magnetic toner by the magnetic force of the magnet roll 12 and to carry the magnetic toner (one-component developer) on the surface. The shaft 11 and the sleeve 13 are connected via a flange portion so that the sleeve 13 can rotate around the non-rotating magnet roll 12. With such a structure, the sleeve 13 can rotate in the circumferential direction of the shaft 11 (for example, the direction of the arrow in FIG. 1).

  In the image forming apparatus in the initial state (unused state), toner T (initial toner) is stored in the storage portion R of the developing device 10. However, the toner T (initial toner) may be automatically charged into the housing portion R of the developing device 10 by an initial setting (installation operation) when starting to use the image forming apparatus. The toner T is a one-component developer (a developer that does not include a carrier). The toner T is a powder containing a plurality of toner particles (specifically, particles defined by a “preferable toner configuration” described later).

  The developing roller 10a is configured to carry the toner T supplied from the storage portion R. The toner supply member 14 is configured to supply the toner T in the storage portion R to the developing roller 10a. The toner supply member 14 may play a role of stirring the toner T. The toner charging member 15 is configured to frictionally charge the toner T carried on the surface of the developing roller 10a. The toner charging member 15 may play a role of regulating the amount of toner T (the thickness of the toner layer) on the developing roller 10a. The toner supply member 14, the sleeve 13 of the developing roller 10a, and the photosensitive drum 20 are each rotated in the direction of the arrow in FIG. 1 to form an image.

  The image forming apparatus shown in FIG. 1 includes a photosensitive drum 20 (for example, an amorphous silicon photosensitive drum) in the vicinity of the developing roller 10a. The photosensitive drum 20 includes a photosensitive layer on a surface layer portion, for example. The charging device 21 is configured to uniformly charge the photosensitive layer of the photosensitive drum 20. The exposure device 22 is configured to perform exposure for forming an electrostatic latent image on the photosensitive layer of the photosensitive drum 20. The cleaning member 24 is configured to remove unnecessary deposits on the photosensitive drum 20 (for example, toner T that has not been transferred in the transfer step).

  The developing device 10 develops the electrostatic latent image formed on the photosensitive drum 20 with toner to form a toner image on the photosensitive drum 20. Specifically, the developing device 10 moves the toner carried on the developing roller 10a (specifically, the toner charged by the toner charging member 15) to the photosensitive layer of the photosensitive drum 20 by an electric force. The toner selectively adheres to the photosensitive drum 20 according to the potential distribution of the electrostatic latent image formed on the photosensitive drum 20. As a result, a toner image is formed on the photosensitive drum 20.

  The transfer roller 23 faces the photosensitive drum 20. A conveyance path for the recording medium P is provided between the transfer roller 23 and the photosensitive drum 20 so that the recording medium P passes between the transfer roller 23 and the photosensitive drum 20. A bias (voltage) is applied to the transfer roller 23 at a predetermined timing. By applying a bias (voltage), the transfer roller 23 applies a toner image on the photosensitive drum 20 to the recording medium P based on an electric force (specifically, a potential difference between the photosensitive drum 20 and the recording medium P). (In detail, it is configured to transfer to the recording medium P positioned between the photosensitive drum 20 and the transfer roller 23). The transport device 25 is configured to transport the recording medium P. The recording medium P to which the toner image has been transferred is conveyed to the fixing device 30 by the conveying device 25.

  The fixing device 30 includes a first roller 31 (for example, a heating roller having a heater) and a second roller 32 (for example, a non-heating roller without a heater). The fixing device 30 transfers the toner image (specifically, transferred to the recording medium P in the transfer step) on the front surface (the surface F1 on the photosensitive drum 20 side) of the front and back surfaces (surfaces F1 and F2) of the recording medium P. The toner image is fixed to the recording medium P by sandwiching the recording medium P so that the first roller 31 is in contact with the toner image) and the second roller 32 is in contact with the back surface (surface F2). . Specifically, the fixing device 30 records the toner image by heating the toner image on the recording medium P with the first roller 31 while pressing the recording medium P with the first roller 31 and the second roller 32. The medium P is configured to be fixed. FIG. 2 shows a schematic structure of the fixing device 30.

  As shown in FIG. 2, the first roller 31 includes a cylindrical cored bar 312. Examples of the core bar 312 include an aluminum pipe or a stainless steel pipe. The cored bar 312 includes a linear heater 311 (for example, a halogen heater). The heater 311 is located in the cored bar 312 (in the cylinder), and is configured to generate heat by energization, for example, to heat the cored bar 312. The amount of heat generated by the heater 311 can be electronically controlled by, for example, energization control (more specifically, control of power supplied to the heater 311 or the like). A primer layer 313 (undercoat paint) is formed on the surface of the cored bar 312. The surface of the cored bar 312 is covered with a coat layer 314 (top coat) via a primer layer 313. The primer layer 313 improves the adhesion between the surface of the core metal 312 and the coat layer 314. As a suitable example of the laminated structure of the first roller 31, a core metal 312 having an outer diameter of 25 mm to 45 mm and a thickness of 0.1 mm to 5.0 mm, a primer layer 313 having a thickness of 5 μm to 10 μm, and a thickness A laminated structure with a coating layer 314 having a thickness of 15 μm to 25 μm can be given.

  The coat layer 314 exists on the surface layer portion of the first roller 31. The coat layer 314 contains a fluororesin. Examples of fluororesins include polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene (PTFE), polytrifluoroethylene (more specifically, polychlorotrifluoroethylene, etc.), polyhexafluoropropylene, tetrafluoroethylene. -A hexafluoropropylene copolymer (FEP) or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) may be mentioned. In order to ensure sufficient releasability on the surface of the first roller 31, the coat layer 314 is made of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a polytetra It is preferable to contain at least one fluororesin selected from the group consisting of fluoroethylene.

In order to improve the electrostatic offset resistance of the image forming apparatus, the surface resistivity of the coat layer 314 is preferably 1.0 × 10 ¹⁰ Ω or more. In order to set the surface resistivity of the coat layer 314 to 1.0 × 10 ¹⁰ Ω or more, the coat layer 314 preferably does not contain a conductive material. However, even if the coat layer 314 contains a conductive material, the surface resistivity of the coat layer 314 can be 1.0 × 10 ¹⁰ Ω or more as long as the content of the conductive material is very small. It is. Examples of conductive materials include metals (more specifically, silver or copper), carbon materials (more specifically, carbon black, etc.), conductive metal oxides (more specifically, doped). Tin oxide or indium oxide), or a conductive polymer.

  The second roller 32 includes a cylindrical cored bar 321 and a coat layer 322. Examples of the core metal 321 include an aluminum pipe or a stainless steel pipe. The coat layer 322 is made of, for example, soft rubber (more specifically, urethane rubber or silicone rubber). The second roller 32 is not limited to a non-heated roller. If necessary, the second roller 32 may be provided with a heater.

  Next, an example of an image forming method by the image forming apparatus according to the present embodiment will be described with reference to FIG.

  First, the charging device 21 uniformly charges the photosensitive layer of the photosensitive drum 20. Next, the exposure device 22 irradiates light to the photosensitive layer of the photosensitive drum 20 based on, for example, image data input to the image forming apparatus, and electrostatic latent image (an image including a low potential portion and a high potential portion). Are formed on the photosensitive drum 20. Next, the developing device 10 develops the electrostatic latent image formed on the photosensitive drum 20 with the toner T, and forms a toner image on the photosensitive drum 20. Specifically, the toner T carried on the surface of the developing roller 10 a is charged by friction with the toner charging member 15. At this time, the positively chargeable toner is positively charged by friction. The negatively chargeable toner is negatively charged by friction. The developing device 10 attaches the charged toner T to the electrostatic latent image to form a toner image on the photosensitive layer. In the example shown in FIG. 1, the toner T held on the surface of the developing roller 10a is not brought into contact with the photosensitive drum 20, but is attracted to the photosensitive drum 20 by electric force, and the developing roller 10a. Flying toward the photosensitive drum 20. However, the present invention is not limited to this, and the toner T held on the surface of the developing roller 10 a may come into contact with the photosensitive drum 20.

  In the transfer process subsequent to the development process, the transfer roller 23 transfers the toner image on the photosensitive drum 20 to the recording medium P. Specifically, when the recording medium P passes between the transfer roller 23 and the photosensitive drum 20, a bias (voltage) is applied to the transfer roller 23, and the photosensitive member is based on the potential difference between the photosensitive drum 20 and the recording medium P. The toner image formed on the drum 20 is transferred to the recording medium P. Thereafter, the recording medium P on which the toner image is placed is transported to the fixing device 30 by the transport device 25.

  In the fixing step subsequent to the above-described transfer step, the fixing device 30 (fixing method: nip fixing with a heating roller and a pressure roller) transfers to the front surface (surface F1) of the front and back surfaces (surfaces F1 and F2) of the recording medium P. The recording medium P is sandwiched so that the first roller 31 of the fixing device 30 comes into contact with the toner image thus formed, and the second roller 32 of the fixing device 30 comes into contact with the back surface (surface F2). The toner image is fixed on the recording medium P by heating and pressing. As a result, an image (specifically, an image fixed on the recording medium P) is formed on the recording medium P.

  The image forming apparatus according to the present embodiment has a “preferred apparatus configuration” described below.

(Preferred apparatus configuration)
The image forming apparatus includes an image carrier (for example, the photosensitive drum 20 shown in FIG. 1), a developing device (for example, the developing device 10 shown in FIG. 1), and a transfer unit (for example, the transfer shown in FIG. 1). Roller 23) and a fixing device (for example, fixing device 30 shown in FIG. 1). The developing device is configured to store toner, develop the electrostatic latent image formed on the image carrier with toner, and form a toner image on the image carrier. The transfer unit is configured to transfer the toner image formed on the image carrier to a recording medium. The fixing device is configured to fix the toner image transferred to the recording medium to the recording medium. The fixing device includes a first roller (for example, the first roller 31 shown in FIG. 2) and a second roller (for example, the second roller 32 shown in FIG. 2). The fixing device sandwiches the recording medium such that the first roller contacts the toner image transferred to the front surface of the recording medium, and the second roller contacts the back surface, whereby the toner image is recorded on the recording medium. Configured to be fixed to. The first roller includes a coat layer (for example, the coat layer 314 shown in FIG. 2) having a surface resistivity of 1.0 × 10 ¹⁰ Ω or more containing a fluororesin on the surface layer portion. The toner (initial toner) that is substantially accommodated in the developing device in the initial state has a “preferable toner configuration” described below. The initial state means an unused state (for example, at the time of product sales). The initial toner is toner that is substantially contained in the developing device in an initial state. The initial toner includes not only the toner stored in the developing device storage unit in the initial state of the image forming apparatus, but also the initial setting (installation operation) at the start of use of the image forming apparatus. In addition, the toner to be charged automatically is also included. The initial toner is distinguished from the replenishing toner. The replenishment toner is toner that is replenished to the housing portion of the developing device after the start of use of the initial toner.

(Preferable toner configuration)
The toner includes a plurality of toner particles containing a crystalline polyester resin having a volume resistivity of 7 × 10 ⁹ Ω · cm or less and an amorphous resin. The volume resistivity measurement method is the same method as in the examples described later or an alternative method thereof.

  The toner particles may include an external additive. When the toner particles include an external additive, the toner particles include a toner base particle and an external additive. The external additive adheres to the surface of the toner base particles. The toner base particles contain a binder resin. The image forming apparatus shown in FIG. 1 uses magnetic toner. In the magnetic toner, the toner base particles contain magnetic powder. However, the present invention is not limited to this, and the toner base particles may not contain magnetic powder. The nonmagnetic toner can be used, for example, in an image forming apparatus for a two-component developer. A two-component developer can be prepared by mixing a non-magnetic toner with a carrier. The toner base particles may contain an internal additive other than the magnetic powder (for example, at least one of a release agent, a colorant, and a charge control agent) as necessary. The toner base particles may be toner base particles without a shell layer (hereinafter referred to as non-capsule toner particles), or toner base particles with a shell layer (hereinafter referred to as capsule toner particles). May be. The capsule toner particle includes a core and a shell layer that covers the surface of the core. The shell layer is substantially composed of a resin. For example, by covering a core that melts at a low temperature with a shell layer having excellent heat resistance, it is possible to achieve both heat-resistant storage stability and low-temperature fixability of the toner. Additives may be dispersed in the resin constituting the shell layer. The shell layer may cover the entire surface of the core, or may partially cover the surface of the core. Capsule toner particles may be produced using non-capsule toner particles described below as a core.

  Of the first roller and the second roller that presses with the recording medium sandwiched in the fixing device, the surface layer portion of the first roller on the side in contact with the toner image is made to contain a fluororesin, thereby releasing the surface of the first roller. Can be improved. However, fluororesins tend to have low electrical resistance and strong negative chargeability. Therefore, when the surface layer portion of the first roller of the fixing device contains a fluororesin, the positively chargeable toner easily adheres to the surface of the first roller with an electric force, and electrostatic offset (the toner is electrically Phenomenon of fixing to the fixing roller with a strong force).

  In order to suppress electrostatic offset, it is also conceivable to add a conductive material (for example, carbon black) into the surface layer portion of the first roller containing a fluororesin. However, when there is too much quantity of the electroconductive material in the surface layer part of a 1st roller, there exists a tendency for the mold release property of the surface of a 1st roller to become inadequate. If the releasability of the surface of the first roller becomes insufficient, hot offset (a phenomenon in which toner is fused to the fixing roller during high-temperature fixing) tends to occur. Moreover, there exists a tendency for the surface resistivity of the surface layer part of a 1st roller to become small, so that the quantity of the electroconductive material in the surface layer part of a 1st roller increases.

The inventor has found that electrostatic offset can be suppressed while ensuring sufficient releasability of the surface of the first roller by using the toner having the above-mentioned “preferable toner configuration”. Specifically, in the toner having the above-mentioned “preferable toner configuration”, the toner particles contain a crystalline polyester resin having a volume resistivity of 7 × 10 ⁹ Ω · cm or less. At the time of fixing, the crystalline polyester resin is easily dissolved from the toner particles. Further, the melted crystalline polyester resin tends to exist between the toner particles and the first roller. The presence of the crystalline polyester resin having a low electrical resistance between the toner particles and the first roller is considered to reduce the negative charging effect on the surface of the first roller. For this reason, electrostatic offset can be suppressed by using the toner having the “preferable toner configuration” described above.

In order to stably form a high-quality image, the surface resistivity of the coat layer present on the surface layer of the first roller is 1.0 × 10 ¹⁰ Ω or more and 1.0 × 10 ¹⁴ Ω or less, and the toner The volume resistivity of the crystalline polyester resin in the particles is preferably 2 × 10 ⁹ Ω · cm or more and 7 × 10 ⁹ Ω · cm or less.

In order to effectively suppress both electrostatic offset and hot offset, in the “preferred toner configuration”, the toner base particles are made of a crystalline polyester resin having a volume resistivity of 7 × 10 ⁹ Ω · cm or less. It is preferable that the non-crystalline resin is included, and the external additive includes particles (hereinafter referred to as conductive inorganic particles) including an inorganic base material and a conductive layer covering the inorganic base material. Examples of the inorganic substrate include particles of silica particles or metal oxides (more specifically, alumina, zirconia, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, or barium titanate). . The conductive layer is, for example, a metal oxide film (hereinafter, referred to as a doped metal oxide) provided with conductivity by doping (specifically, an Sb-doped SnO ₂ film). The conductive layer may be a layer containing a conductive material other than the doped metal oxide (more specifically, a metal, a carbon material, a conductive polymer, or the like).

  When the toner particles are provided with conductive inorganic particles as external additives, the conductive inorganic particles are present between the toner particles and the first roller during fixing, and the negatively charged surface of the first roller is negatively charged. Impact is weakened. For this reason, electrostatic offset can be suppressed by providing the toner particles with conductive inorganic particles as external additives.

  In order to effectively suppress both electrostatic offset and hot offset, it is preferable that the inorganic base material of the conductive inorganic particles is titanium oxide particles. In general, titanium oxide particles have high abrasiveness. For this reason, it is thought that the contamination of the first roller can be effectively suppressed by using conductive inorganic particles (conductive titanium oxide particles) containing titanium oxide particles as the inorganic base material.

  In order to suppress electrostatic offset and hot offset, the amount of the conductive inorganic particles is preferably 0.5 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the toner base particles.

  In addition to the above-described “preferred apparatus configuration”, an image forming apparatus (hereinafter, referred to as a preferable apparatus example) further including the following configuration is positively charged while suppressing electrostatic offset and hot offset. It is possible to continuously form high-quality images using a magnetic toner.

(Configuration of preferred apparatus example)
A developing device stores a toner (for example, a storage portion R shown in FIG. 1) that contains toner, and a toner carrier (for example, the developing roller 10a shown in FIG. 1) that carries toner supplied from the storage portion. And a toner charging member (for example, toner charging member 15 shown in FIG. 1) for frictionally charging the toner carried on the surface of the toner carrying member. The initial toner is a positively chargeable toner that is positively charged by friction with the toner charging member. The toner particles further contain magnetic powder in a proportion of 30% by mass or more.

  In order to stably form a high-quality image, in the above “preferred apparatus example”, it is preferable that the toner particles contain magnetic powder in a proportion of 30% by mass to 60% by mass. For example, if the toner particles have a mass of 100 g, the toner particles preferably contain 30 g or more and 60 g or less of magnetic powder.

  In order to ensure a sufficient charge amount and transport amount of the toner, the amount of the amorphous resin contained in the toner base particles is 40 parts by weight or more with respect to 40 parts by weight of the magnetic powder contained in the toner base particles. The amount of the crystalline polyester resin contained in the toner base particles is preferably 0.5 parts by mass or more and 10 parts by mass or less.

In order to obtain a toner suitable for image formation, the toner median particle preferably has a volume median diameter (D ₅₀ ) of 4 μm or more and 9 μm or less.

  Hereinafter, a preferred example of the configuration of the non-capsule toner particles will be described. The toner base particles and the external additive will be described in order. However, unnecessary components may be omitted depending on the use of the toner.

[Toner mother particles]
(Binder resin)
In the toner base particles, generally, the binder resin occupies most of the components (for example, 85% by mass or more). For this reason, it is considered that the properties of the binder resin greatly affect the properties of the entire toner base particles. By using a combination of a plurality of types of resins as the binder resin, the properties of the binder resin (more specifically, the hydroxyl value, acid value, Tg, Tm, etc.) can be adjusted. When the binder resin has an ester group, a hydroxyl group, an ether group, an acid group, or a methyl group, the toner base particles tend to be anionic, and when the binder resin has an amino group or an amide group. The toner base particles tend to be cationic. In order to improve the charging stability of the toner, the acid value of the amorphous resin contained in the toner base particles is preferably 6 mgKOH / g or more and 15 mgKOH / g or less.

In the toner having the “preferable toner configuration” described above, the toner base particles contain a crystalline polyester resin and an amorphous resin as a binder resin. The volume resistivity of the crystalline polyester resin is 7 × 10 ⁹ Ω · cm or less, and more preferably 2 × 10 ⁹ Ω · cm or more and 7 × 10 ⁹ Ω · cm or less. In order to make the volume resistivity of the crystalline polyester resin appropriate, the melting point of the crystalline polyester resin is preferably 80 ° C. or higher and 100 ° C. or lower. As the melting point of the crystalline polyester resin increases, the volume resistivity of the crystalline polyester resin tends to increase. The lower the melting point of the crystalline polyester resin, the smaller the volume resistivity of the crystalline polyester resin tends to be.

  In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, the toner base particles preferably contain a crystalline polyester resin having a crystallinity index of 0.90 or more and 1.50 or less as the crystalline resin. A crystalline polyester resin having such a crystallinity index is excellent in sharp melt property. The crystallinity index is the ratio of the softening point (Tm) to the melting point (Mp) (= Tm / Mp). For amorphous resins, it is often impossible to measure a clear Mp. The crystallinity index of the polyester resin can be adjusted by changing the type or amount of a material (for example, alcohol and / or carboxylic acid) for synthesizing the polyester resin.

  In order to make the volume resistivity of the crystalline polyester resin appropriate, the crystalline polyester resin is one or more aliphatic diols having 3 to 9 carbon atoms (more specifically, having 9 or more carbon atoms). α, ω-alkanediol such as 1,9-nonanediol) and one or more aliphatic dicarboxylic acids having 10 to 15 carbon atoms (more specifically, α, ω-alkanedicarboxylic having 12 carbon atoms). More preferably, it is a copolymer of 1,10-decanedicarboxylic acid or the like that is an acid) and one or more aromatic dicarboxylic acids (more specifically, terephthalic acid or the like).

  Examples of the amorphous resin include a styrene resin, an acrylic resin (more specifically, an acrylic ester polymer or a methacrylic ester polymer), an olefin resin (more specifically, a polyethylene resin). Or a thermoplastic resin such as a vinyl chloride resin, a polyvinyl alcohol, a vinyl ether resin, an N-vinyl resin, a polyester resin, a polyamide resin, or a urethane resin. Further, copolymers of these resins, that is, copolymers in which arbitrary repeating units are introduced into the resin (more specifically, styrene-acrylic acid resin or styrene-butadiene resin, etc.) are also non- It can be suitably used as a crystalline resin.

  In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, the toner base particles preferably contain a polyester resin and / or a styrene-acrylic acid resin as an amorphous resin, and contain a polyester resin. It is particularly preferable to do this.

  The polyester resin is composed of one or more polyhydric alcohols (more specifically, aliphatic diols, bisphenols, trihydric or higher alcohols, etc. as shown below) and one or more polyhydric carboxylic acids ( More specifically, it can be obtained by polycondensation with a divalent carboxylic acid or a trivalent or higher carboxylic acid as shown below.

  Preferred examples of the aliphatic diols include ethylene glycol, diethylene glycol, triethylene glycol, neopentyl glycol, 1,2-propanediol, α, ω-alkanediol (more specifically, 1,3-propanediol. 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, or 1,12-dodecanediol Etc.), 2-butene-1,4-diol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol.

  Preferable examples of the bisphenol include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, or bisphenol A propylene oxide adduct.

  Preferable examples of trihydric or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butane. Triol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, or 1,3,5- Trihydroxymethylbenzene is mentioned.

  Preferable examples of the divalent carboxylic acid include aromatic dicarboxylic acid (more specifically, phthalic acid, terephthalic acid, or isophthalic acid), α, ω-alkanedicarboxylic acid (more specifically, malonic acid). Succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, or 1,10-decanedicarboxylic acid), alkyl succinic acid (more specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid) Acid, n-dodecyl succinic acid, or isododecyl succinic acid), alkenyl succinic acid (more specifically, n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, or isodode Senylsuccinic acid, etc.), maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, or cyclohexanedicarboxylic acid Examples include acids.

  Preferred examples of the trivalent or higher carboxylic acid include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) Examples include methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, or empole trimer acid.

  The styrene-acrylic acid resin is a copolymer of one or more styrene monomers and one or more acrylic monomers. In order to synthesize a styrene-acrylic acid resin, for example, a styrene monomer and an acrylic acid monomer as shown below can be suitably used.

  Preferable examples of the styrene monomer include styrene, alkyl styrene (more specifically, α-methyl styrene, p-ethyl styrene, 4-tert-butyl styrene, etc.), p-hydroxy styrene, m-hydroxy styrene. , Vinyl toluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, or p-chlorostyrene.

  Preferable examples of the acrylic acid monomer include (meth) acrylic acid, (meth) acrylonitrile, (meth) acrylic acid alkyl ester, or (meth) acrylic acid hydroxyalkyl ester. Suitable examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, and (meth) acrylic. Examples include n-butyl acid, iso-butyl (meth) acrylate, or 2-ethylhexyl (meth) acrylate. Suitable examples of the (meth) acrylic acid hydroxyalkyl ester include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, or (meth) acrylic. The acid 4-hydroxybutyl is mentioned.

(Coloring agent)
The toner base particles may contain a colorant (for example, a black colorant). Examples of black colorants include carbon black, oil furnace black, channel black, lamp black, acetylene black, or aniline black. You may use the magnetic powder mentioned later as a black coloring agent.

  The amount of the black colorant is preferably 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin.

(Release agent)
The toner base particles may contain a release agent. The release agent is used, for example, for the purpose of improving the fixing property or offset resistance of the toner. In order to improve the fixing property or offset resistance of the toner, the amount of the release agent is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin.

  Examples of the release agent include low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, or aliphatic hydrocarbon wax such as Fischer-Tropsch wax; oxidized polyethylene wax or a block thereof Oxides of aliphatic hydrocarbon waxes such as copolymers; plant waxes such as candelilla wax, carnauba wax, wood wax, jojoba wax, or rice wax; animal properties such as beeswax, lanolin, or whale wax Waxes; mineral waxes such as ozokerite, ceresin, or petrolatum; waxes based on fatty acid esters such as montanate ester wax or castor wax; fats such as deoxidized carnauba wax The wax portion of the ester or the whole was deoxygenated can be suitably used. One type of release agent may be used alone, or multiple types of release agents may be used in combination.

(Charge control agent)
The toner base particles may contain a charge control agent. The charge control agent is used, for example, for the purpose of improving the charge stability or charge rising property of the toner. The charge rising characteristic of the toner is an index as to whether or not the toner can be charged to a predetermined charge level in a short time.

  By adding a negatively chargeable charge control agent (more specifically, an organometallic complex or a chelate compound) to the toner base particles, the anionicity of the toner base particles can be enhanced. Further, by adding a positively chargeable charge control agent (more specifically, pyridine, nigrosine, quaternary ammonium salt, or the like) to the toner base particles, the cationicity of the toner base particles can be increased. In order to increase the cationicity of the toner base particles, the toner base particles may contain two or more positively chargeable charge control agents. However, if sufficient chargeability is ensured in the toner, it is not necessary to add a charge control agent to the toner base particles.

(Magnetic powder)
The toner base particles may contain magnetic powder. Examples of magnetic powder materials include ferromagnetic metals (more specifically, iron, cobalt, nickel, or alloys containing one or more of these metals), ferromagnetic metal oxides (more specifically, Ferrite, magnetite, chromium dioxide, or the like) or a material subjected to ferromagnetization treatment (more specifically, a carbon material or the like imparted with ferromagnetism by heat treatment) can be suitably used. One type of magnetic powder may be used alone, or a plurality of types of magnetic powder may be used in combination.

[External additive]
An external additive (specifically, a powder containing a plurality of external additive particles) may adhere to the surface of the toner base particles. For example, the toner base particles (powder) and the external additive (powder) are stirred together, so that the external additive adheres (physically bonds) to the surface of the toner base particles with a physical force. The external additive is used, for example, to improve the fluidity or handleability of the toner.

  In order to effectively suppress both electrostatic offset and hot offset, the toner particles preferably include conductive inorganic particles as external additives. The toner particles may include external additive particles other than the conductive inorganic particles (hereinafter referred to as other external additive particles).

  Other external additive particles are preferably inorganic particles, silica particles, or metal oxides (more specifically, alumina, zirconia, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, etc. ) Is particularly preferred. However, as other external additive particles, particles of an organic acid compound such as a fatty acid metal salt (more specifically, zinc stearate) or resin particles may be used. Moreover, you may use the composite particle which is a composite of a multiple types of material as another external additive particle.

[Toner Production Method]
In order to easily and suitably manufacture the toner having the above-mentioned “preferable toner configuration”, for example, a toner manufacturing method including the following melt-kneading step, pulverizing step, classification step, and external addition step is preferable.

(Melting and kneading process)
Hereinafter, an example of the melt-kneading process will be described. In the melt-kneading step, a toner material containing a crystalline polyester resin, an amorphous resin, and magnetic powder (for example, a crystalline polyester resin, an amorphous resin, a colorant, a release agent, a charge control agent, and magnetic powder) Are mixed to obtain a mixture. For mixing the toner material, a mixing device (for example, FM mixer) can be suitably used.

  Subsequently, the obtained mixture is melt-kneaded to obtain a melt-kneaded product. For melt kneading of the mixture, a twin-screw extruder, a three-roll kneader, or a two-roll kneader can be suitably used. As the toner material, a master batch containing a binder resin and a colorant may be used.

(Crushing process and classification process)
Hereinafter, an example of the pulverization step and the classification step will be described. First, the melt-kneaded product is solidified by cooling using a cooling and solidifying device such as a drum flaker. Subsequently, the obtained solidified product is roughly pulverized using the first pulverizer. Thereafter, the obtained coarsely pulverized product is further pulverized using a second pulverizer. Subsequently, the obtained pulverized product is classified using a classifier (for example, an air classifier). Thereby, toner mother particles having a desired particle diameter are obtained.

(External addition process)
In the external addition step, an external additive is attached to the surface of the toner base particles. By using a mixer, the toner base particles and the external additive are mixed under conditions that prevent the external additive from being embedded in the toner base particles, thereby allowing the external additive to adhere to the surface of the toner base particles. .

  Through the above process, a toner containing a large number of toner particles can be produced. Note that unnecessary steps may be omitted. For example, when a commercially available product can be used as a material as it is, the step of preparing the material can be omitted by using a commercially available product. If an external additive is unnecessary, the external addition process may be omitted. When the external additive is not attached to the surface of the toner base particles (the step of external addition is omitted), the toner base particles correspond to the toner particles. In order to obtain a predetermined compound, a salt, ester, hydrate, or anhydride of the compound may be used as a raw material. In order to produce the toner efficiently, it is preferable to form a large number of toner particles simultaneously. The toner particles produced at the same time are considered to have substantially the same configuration.

  Examples of the present invention will be described. Table 1 shows devices D-1 to D-7 (respectively image forming devices) according to examples or comparative examples. Table 2 shows the toner used in each apparatus. Table 3 shows fixing rollers (heating rollers) used in each apparatus.

  Hereinafter, a manufacturing method, an evaluation method, and an evaluation result of the devices D-1 to D-7 will be described in order. In the evaluation in which an error occurs, a considerable number of measurement values with sufficiently small errors are obtained, and the arithmetic average of the obtained measurement values is used as the evaluation value.

[Preparation of materials]
(Synthesis of crystalline polyester resin A)
1,9-nonanediol 50 was placed in a 2 L four-necked flask equipped with a thermometer, a glass nitrogen inlet tube, a stirrer (agitating blade made of stainless steel), and a flow-down condenser (heat exchanger). A mole part, 45 mole part of 1,10-decanedicarboxylic acid, 5 mole part of terephthalic acid, and 0.05 mole part of catalyst (tetra-n-butoxy titanium) were added. Subsequently, the flask was placed on a mantle heater, nitrogen gas was introduced into the flask through a nitrogen introduction tube, and the atmosphere in the flask was changed to a nitrogen atmosphere (inert atmosphere). Subsequently, while stirring the flask contents in a nitrogen atmosphere, the temperature is raised to a predetermined reaction temperature (200 ° C.), and the reaction is performed while stirring the flask contents in a nitrogen atmosphere and at a temperature of 200 ° C. (reaction temperature). (Condensation polymerization reaction). Thereafter, the contents of the flask were taken out into a stainless steel container (bat) and cooled to a temperature of 25 ° C. in a room temperature environment to obtain a crystalline polyester resin A.

(Synthesis of crystalline polyester resin B)
The synthesis method of the crystalline polyester resin B is crystal except that 50 mol parts of 1,12-dodecanediol is used instead of 50 mol parts of 1,9-nonanediol and the reaction temperature is changed from 200 ° C. to 220 ° C. This was the same as the synthesis method of the conductive polyester resin A.

(Synthesis of crystalline polyester resin C)
The method for synthesizing the crystalline polyester resin C is the same as the above-described monomer composition (1,12-dodecanediol: 50 mol parts, 1,10-decanedicarboxylic acid: 45 mol parts, terephthalic acid: 5 mol parts). -It was the same as the synthesis method of the crystalline polyester resin B, except that it was changed to 50 mol parts of propanediol, 40 mol parts of 1,10-decanedicarboxylic acid, and 10 mol parts of terephthalic acid.

With respect to the crystalline polyester resins A to C obtained as described above, the measurement results of the volume resistivity and the melting point were as shown in Table 2. For example, regarding the crystalline polyester resin A, the melting point was 97 ° C. and the volume resistivity was 7 × 10 ⁹ Ω · cm. Further, regarding the crystalline polyester resin C, the melting point was 91 ° C. and the volume resistivity was 2 × 10 ⁹ Ω · cm. In any of the crystalline polyester resins A to C, the crystallinity index was 0.90 or more and 1.50 or less. Specifically, the crystalline polyester resin A has a crystallinity index of 1.10, the crystalline polyester resin B has a crystallinity index of 1.00, and the crystalline polyester resin C has a crystallinity index of 1.20. It was. Each measuring method of volume resistivity and melting point was as follows.

<Measurement method of volume resistivity>
A sample (crystalline polyester resin) was molded into a disc to prepare a test piece having a diameter of 100 mm and a thickness of 2 mm. Resistance meter ("SM-8213" manufactured by Hioki Electric Co., Ltd.) and plate sample electrode ("SM-8411" manufactured by Hioki Electric Co., Ltd.), main electrode: circular electrode with a diameter of 19.6 mm, guard electrode: inner diameter of 24.1 mm / Using a ring electrode having an outer diameter of 28.8 mm, the volume resistivity of the test piece was measured in accordance with JIS (Japanese Industrial Standard) K 6911-2006 under the conditions of an applied voltage of 1000 V and a voltage application time of 60 seconds. The volume resistance is a numerical value obtained by dividing a DC voltage applied between two electrodes by a current passing through a unit volume of a test piece sandwiched between the electrodes. The volume resistivity is a numerical value obtained by dividing the potential gradient in the direction parallel to the current flowing inside the test piece by the current density. This numerical value is equal to the volume resistance between two electrodes having two opposing surfaces of a cube of 1 cm on each side as electrodes.

<Measuring method of melting point>
A differential scanning calorimeter (“DSC 8000” manufactured by PerkinElmer, Inc., measurement principle: input compensation type, furnace type: double furnace) was used as a measuring apparatus. An endothermic curve (vertical axis: heat flow (DSC signal), horizontal axis: temperature) of a sample (crystalline polyester resin) was measured using a measuring apparatus. The Mp (melting point) of the sample was read from the obtained endothermic curve. In the endothermic curve, the maximum peak temperature due to the heat of fusion corresponds to the Mp (melting point) of the sample.

(Synthesis of non-crystalline polyester resin)
In a 4-liter flask having a capacity of 2 L equipped with a thermometer, a glass nitrogen inlet tube, a stirring device (stainless blade made of stainless steel), and a flow-down condenser (heat exchanger), 43 mol parts of ethylene glycol; 42 mol parts of terephthalic acid and 5 mol parts of 1,2,4-benzenetricarboxylic acid anhydride were added. Subsequently, the flask was placed on a mantle heater, nitrogen gas was introduced into the flask through a nitrogen introduction tube, and the atmosphere in the flask was changed to a nitrogen atmosphere (inert atmosphere). Subsequently, the flask contents were heated to 230 ° C. while stirring the flask contents in a nitrogen atmosphere, and the flask contents were reacted (condensation polymerization reaction) while stirring under the conditions of a nitrogen atmosphere and a temperature of 230 ° C. A small amount of the resin in the flask was collected during the polymerization reaction, the acid value was measured, and the polymerization reaction was stopped when the acid value of the resin in the flask reached 12 mgKOH / g. Thereafter, the contents of the flask were taken out into a stainless steel container (bat) and cooled to a temperature of 25 ° C. in a room temperature environment to obtain an amorphous polyester resin.

(Manufacture of magnetic powder)
30 L of a ferrous sulfate aqueous solution containing Fe ²⁺ at a concentration of 2.0 mol / L and 28 L of a 4.5 N (normality) sodium hydroxide aqueous solution were added to a reaction vessel and mixed. Subsequently, after the container contents were heated to 90 ° C., the pH of the container contents was adjusted to 10.5 using an aqueous sodium hydroxide solution. Subsequently, air was blown into the container for 100 minutes at a speed of 80 L / min under the conditions of pH 10.5 and a temperature of 90 ° C. to advance the oxidation reaction of the ferrous salt in the container. Subsequently, an aqueous sulfuric acid solution was added to the container to adjust the pH of the container contents to 7. And the temperature of the container contents was maintained at 90 ° C., and air was blown into the container at a speed of 80 L / min for 10 minutes. As a result, magnetite particles were generated in the liquid, and a suspension containing magnetite particles was obtained. Thereafter, magnetite particles (powder) were filtered off from the obtained suspension. Subsequently, the obtained magnetite particles (powder) were washed with water and dried to obtain an aggregate of magnetite particles. Subsequently, the obtained aggregate was pulverized to obtain a magnetic powder containing a large number of octahedral magnetite particles. The obtained magnetic powder has a number average primary particle diameter of 0.2 μm, an external magnetic field of 796 kA / m, a coercive force of 8.5 kA / m, a saturation magnetization of 82 Am ² / kg, and a residual magnetization of 5. It was 0 Am ² / kg.

[Manufacture of toner TA]
(Preparation of toner base particles)
46 parts by mass of an amorphous resin (amorphous polyester resin synthesized by the aforementioned procedure), 5 parts by mass of a crystalline resin (crystalline polyester resin A synthesized by the aforementioned procedure), and magnetic powder (magnetite particles: the aforementioned 42 parts by mass of magnetic powder produced by the above procedure, 1 part by mass of first charge control agent (azine compound: “BONTRON (registered trademark) N-77” manufactured by Orient Chemical Industries, Ltd.), and second charge control agent ( "Acrybase (registered trademark) FCA-207P" manufactured by Fujikura Kasei Co., Ltd., 3 parts by mass of styrene-acrylic acid resin containing a repeating unit derived from a quaternary ammonium salt, and ester wax (manufactured by NOF Corporation) "Nissan Electol (registered trademark) WEP-3") 3 parts by mass using an FM mixer ("FM-20" manufactured by Nippon Coke Industries Co., Ltd.) In were mixed for 4 minutes.

Subsequently, the obtained mixture was melt melt kneaded at a temperature of 120 ° C., rotated at a speed of 150 rpm, and processed at a rate of 100 g / min using a twin screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.). Melt kneaded. Thereafter, the obtained kneaded material was cooled. Subsequently, the obtained kneaded material was coarsely pulverized with a set particle diameter of 2 mm using a pulverizer ("Rohtoplex (registered trademark)" manufactured by Hosokawa Micron Corporation). Subsequently, the obtained coarsely pulverized product was finely pulverized using a mechanical pulverizer (“Turbo Mill T250” manufactured by Freund Turbo Inc.). Subsequently, the obtained finely pulverized product was classified using a classifier (wind classifier using the Coanda effect: “Elbow Jet EJ-LABO type” manufactured by Nittetsu Mining Co., Ltd.). As a result, toner mother particles having a volume median diameter (D ₅₀ ) of 8 μm were obtained.

(External addition process)
Using an FM mixer (“FM-20” manufactured by Nippon Coke Kogyo Co., Ltd.) under the conditions of a rotational speed of 2000 rpm, 100 parts by mass of the toner base particles obtained as described above and positively charged silica particles (Nippon Aerosil Co., Ltd.) “AEROSIL (registered trademark) RA200” manufactured by the company, contents: dry silica particles imparted with hydrophobicity and positive charge by surface treatment, surface treatment agents: hexamethyldisilazane (HMDS) and aminosilane, number average primary particle size : about 12 nm) and 0.8 parts by weight, conductive titanium oxide particles (manufactured by Titan Kogyo, Ltd. "EC-100", base: TiO _2, coating layer: Sb doped SnO ₂ film, the number average primary particle diameter: About 0.35 μm) 0.8 part by mass was mixed for 5 minutes. As a result, external additives (positively charged silica particles and conductive titanium oxide particles) adhered to the surface of the toner base particles. Then, sieving was performed using a 300 mesh sieve (aperture 48 μm). As a result, a toner TA (magnetic toner) containing a large number of magnetic toner particles was obtained.

[Manufacture of toner TB]
In the toner TB manufacturing method, the addition amount of the amorphous resin (non-crystalline polyester resin) is changed from 46 parts by mass to 50 parts by mass, and the addition amount of the crystalline resin (crystalline polyester resin A) is 5 parts by mass. The production method of Toner TA was the same as that of Toner TA except that the amount was changed from 1 to 1 part by mass.

[Production of Toner TC]
The production method of the toner TC was the same as the production method of the toner TA except that the crystalline polyester resin C (addition amount: 5 parts by mass) was used as the crystalline resin instead of the crystalline polyester resin A.

[Production of Toner TD]
The production method of the toner TD is that the crystalline resin (crystalline polyester resin A) is not used and the addition amount of the amorphous resin (noncrystalline polyester resin) is changed from 46 parts by mass to 51 parts by mass. This was the same as the production method of the toner TA.

[Manufacture of toner TE]
The production method of the toner TE was the same as the production method of the toner TA except that the crystalline polyester resin B (addition amount: 5 parts by mass) was used as the crystalline resin instead of the crystalline polyester resin A.

[Method for Manufacturing Image Forming Apparatus]
(Manufacture of fixing roller RA)
Foreign matter on the surface of the core metal (a stainless steel pipe having a wall thickness of 0.7 mm and an outer diameter of 35 mm) was removed. Subsequently, a primer (PFA primer: “PJ-YL910” manufactured by Mitsui DuPont Fluoro Chemical Co., Ltd.) with a thickness of about 7.5 μm was uniformly applied to the surface of the core bar by electrostatic coating and dried. . Subsequently, a liquid containing a top coat (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA)) is formed on the surface of the core metal covered with the primer (that is, the surface of the primer layer) by electrostatic coating: “EJ-CL700” manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was uniformly applied at a thickness of about 20 μm and dried. Subsequently, by baking at a temperature of about 400 ° C., a laminated structure of a primer layer (lower layer) and a coat layer (upper layer) was obtained on the surface of the core metal. The coat layer contained a fluororesin. Thereafter, the surface of the coating layer was polished to obtain a fixing roller RA (heating roller).

(Manufacture of fixing roller RB)
The manufacturing method of the fixing roller RB is carbon black (manufactured by Mitsubishi Chemical Corporation) at a ratio of 7.0 parts by mass with respect to 100 parts by mass of PFA in the top coat (EJ-CL700) instead of the top coat (EJ-CL700). The method was the same as the method for manufacturing the fixing roller RA, except that a liquid added with “# 3030B” (particle size: 55 nm) was used.

(Manufacture of fixing roller RC)
The fixing roller RC is manufactured by using carbon black (manufactured by Mitsubishi Chemical Corporation) at a ratio of 7.5 parts by mass with respect to 100 parts by mass of PFA in the top coat (EJ-CL700) instead of the top coat (EJ-CL700). The method was the same as the method for manufacturing the fixing roller RA, except that a liquid added with “# 3030B” (particle size: 55 nm) was used.

With respect to the fixing rollers RA to RC obtained as described above, the measurement results of the surface resistivity are as shown in Table 3. For example, regarding the fixing roller RA, the surface resistivity was 2.0 × 10 ¹² Ω (measurement limit) or more. Further, regarding the fixing roller RB, the surface resistivity was 2.0 × 10 ¹⁰ Ω. The method for measuring the surface resistivity was as follows.

<Measurement method of surface resistivity>
Using an ohmmeter ("SM-8213" manufactured by Hioki Electric Co., Ltd.) and an electrode for surface resistance measurement ("SM-8302" manufactured by Hioki Electric Co., Ltd .: 4 mm), an applied voltage of 1000 V and a voltage application time of 60 seconds The surface resistivity of the fixing roller was measured according to JIS (Japanese Industrial Standard) K 6911-2006. The surface resistance is a numerical value obtained by dividing a DC voltage applied between two electrodes on the surface of the test piece by a current flowing through the surface layer. The surface resistivity is a numerical value obtained by dividing the potential gradient in the direction parallel to the current flowing along the surface of the test piece by the current per unit width of the surface. This numerical value is equal to the surface resistance between two electrodes having the opposite sides of a square of 1 cm on each side as electrodes.

(Fixing roller installation)
Fixing roller of black-and-white printer (“ECOSYS (registered trademark) FS-4200DN” manufactured by Kyocera Document Solutions Co., Ltd.)) Instead of the first roller on the contact side, a fixing roller (any of the fixing rollers RA to RC shown in Table 1 defined in each device) manufactured in the above-described procedure was attached. A heater (halogen heater) was installed in the core (in the cylinder) of the fixing roller (first roller). The heater was held by an electrode inside the fixing device. Then, in the monochrome printer installation mode, toner (any of toners TA to TE shown in Table 1 defined in each device) was set in the housing of the developing device. As a result, image forming apparatuses (devices D-1 to D-7) were obtained. For example, in the manufacture of the device D-1, the fixing roller RA is mounted on a monochrome printer (ECOSYS FS-4200DN), and the toner TA is set in the housing portion of the developing device. Each of the fixing devices of the devices D-1 to D-7 sandwiches the recording medium (printing paper) between the first roller (heating roller: any of the fixing rollers RA to RC) and the second roller (non-heating roller). The toner image on the recording medium is heated by the first roller while being pressed with the pressure, so that the toner image is fixed on the recording medium.

[Evaluation method]
The evaluation methods of the devices D-1 to D-7 (hereinafter referred to as target devices) are as follows.

(Electrostatic offset resistance)
Surface temperature of first roller (heating roller: any of fixing rollers RA to RC) of the fixing device of the target device (any of devices D-1 to D-7) in an environment of a temperature of 23 ° C. and a humidity of 50% RH Was set to 180 ° C., and a solid image having a size of 25 mm × 25 mm was output to 10 evaluation sheets using the target apparatus. Specifically, a solid image (specifically, an unfixed toner image) was formed at a position 20 mm from the tip of each evaluation sheet. Thereafter, the paper on which the image (unfixed toner image) was formed was passed through the fixing device (fixing temperature: 180 ° C.) of the target device. The evaluation sheet passed through the fixing device was visually checked to determine whether or not an offset occurred. Specifically, it was determined that an offset had occurred if there was dirt on the evaluation paper due to toner adhering to the fixing roller. In the output of 10 sheets of evaluation paper, if no offset occurred at all, it was evaluated as “good”, and if an offset occurred even once, it was evaluated as “poor” (not good).

(Hot offset resistance)
Except for changing the set temperature of the first roller (heating roller: any of fixing rollers RA to RC) of the fixing device of the target device (any of devices D-1 to D-7) from 180 ° C to 200 ° C, The hot offset resistance of the target device was evaluated in the same manner as the electrostatic offset resistance evaluation. In the output of 10 sheets of evaluation paper, if no offset occurred at all, it was evaluated as “good”, and if an offset occurred even once, it was evaluated as “poor” (not good).

[Evaluation results]
Table 4 shows the evaluation results of the electrostatic offset resistance and the hot offset resistance for the devices D-1 to D-7.

The apparatuses D-1 to D-4 (image forming apparatuses according to Examples 1 to 4) each had the above-described “preferred apparatus configuration”. Specifically, the fixing device generally has the structure shown in FIG. The first roller of the fixing device was provided with a coat layer having a surface resistivity of 1.0 × 10 ¹⁰ Ω or more containing a fluororesin on the surface layer portion (see Tables 1 and 3). Further, the initial toner had the above-mentioned “preferable toner configuration”. The toner particles contained a crystalline polyester resin having a volume resistivity of 7 × 10 ⁹ Ω · cm or less and an amorphous resin (see Tables 1 and 2).

  As shown in Table 4, each of the devices D-1 to D-4 was able to continuously form high-quality images while suppressing electrostatic offset and hot offset.

  The image forming apparatus and the image forming method according to the present invention can be used to form an image in, for example, a copying machine, a printer, or a multifunction peripheral.

DESCRIPTION OF SYMBOLS 10 Developing device 10a Developing roller 14 Toner supply member 15 Toner charging member 20 Photoconductor drum 21 Charging device 22 Exposure device 23 Transfer roller 24 Cleaning member 25 Conveying device 30 Fixing device 31 First roller 32 Second roller P Recording medium R Storage unit T Toner F1, F2 side

Claims (8)

An image carrier;
A developing device configured to store toner, develop an electrostatic latent image formed on the image carrier with the toner, and form a toner image on the image carrier;
A transfer portion for transferring the toner image on the image carrier to a recording medium;
A fixing device for fixing the toner image transferred to the recording medium to the recording medium;
With
The fixing device includes a first roller and a second roller, and the first roller contacts the toner image transferred to the front surface of the recording medium, and the second roller is on the back surface. The toner image is fixed on the recording medium by sandwiching the recording medium so as to come into contact with the recording medium.
The first roller includes a coat layer having a surface resistivity of 1.0 × 10 ¹⁰ Ω or more containing a fluororesin on a surface layer portion,
The toner substantially accommodated in the developing device in an initial state includes a plurality of toner particles containing a crystalline polyester resin having a volume resistivity of 7 × 10 ⁹ Ω · cm or less and an amorphous resin. , Image forming apparatus.   The image forming apparatus according to claim 1, wherein the crystalline polyester resin has a melting point of 80 ° C. or higher and 100 ° C. or lower.   The crystalline polyester resin comprises one or more aliphatic diols having 3 to 9 carbon atoms, one or more aliphatic dicarboxylic acids having 10 to 15 carbon atoms, and one or more aromatic dicarboxylic acids. The image forming apparatus according to claim 1, wherein the image forming apparatus is a copolymer. The developing device includes:
An accommodating portion for accommodating the toner;
A toner carrier for carrying the toner supplied from the container;
A toner charging member that frictionally charges the toner carried on the surface of the toner carrier;
With
The toner particles further contain magnetic powder in a proportion of 30% by mass or more,
The image forming apparatus according to claim 1, wherein the toner is a positively chargeable toner that is positively charged by friction with the toner charging member. The toner particles are
Toner base particles containing the crystalline polyester resin having a volume resistivity of 7 × 10 ⁹ Ω · cm or less and the amorphous resin;
An external additive attached to the surface of the toner base particles;
With
The image forming apparatus according to claim 1, wherein the external additive includes conductive inorganic particles including an inorganic base material and a conductive layer that covers the inorganic base material.   The image forming apparatus according to claim 5, wherein the inorganic base material is titanium oxide particles. The surface resistivity of the coat layer is 1.0 × 10 ¹⁰ Ω or more and 1.0 × 10 ¹⁴ Ω or less, and the volume resistivity of the crystalline polyester resin is 2 × 10 ⁹ Ω · cm or more and 7 × 10 ⁹ Ω. The image forming apparatus according to claim 1, wherein the image forming apparatus is cm or less. A developing device of the image forming apparatus develops the electrostatic latent image formed on the image carrier with toner to form a toner image on the image carrier;
A transfer unit of the image forming apparatus transfers the toner image on the image carrier to a recording medium;
In the fixing device of the image forming apparatus, the first roller of the fixing device contacts the toner image transferred to the front surface of the recording medium, and the second roller of the fixing device contacts the back surface. Fixing the toner image on the recording medium with the recording medium interposed therebetween,
Including
The first roller includes a coat layer having a surface resistivity of 1.0 × 10 ¹⁰ Ω or more containing a fluororesin on a surface layer portion,
The image forming method, wherein the toner includes a plurality of toner particles containing a crystalline polyester resin having a volume resistivity of 7 × 10 ⁹ Ω · cm or less and an amorphous resin.

Images