JP5151821B2 - toner - Google Patents

Description

  The present invention relates to a toner used in an electrophotographic image forming method.

  Various additives (external additives) are used for the toner used in the electrophotographic image forming method in order to supplement the electrophotographic characteristics and durability, and a fluidizing agent such as silica is used for improving the fluidity. Externally added and mixed. However, when the conventional external additive is used, a phenomenon in which the external additive is embedded in the toner particles due to an increase in the number of copies (embedding of the external additive) occurs.

  When the external additive is buried, the effects such as fluidity and charge control imparted by the external additive are lost, and many problems occur as a toner.

  Also, disposal of collected toner is regarded as a problem from the viewpoint of environmental protection. In order to solve this problem, it is preferable to use an image forming apparatus with a toner recycling mechanism (with a recycling process) that does not generate waste toner at all. However, since the recycle toner is often subjected to stress in the image forming apparatus, the problem of image quality deterioration due to the burying of the external additive is more serious, and the conventional toner cannot withstand the recycle. there were.

For such problems,
(1) Examination of adhering silica particles in a partially aggregated state on the toner particle surface (for example, see Patent Document 1).
(2) Examination of adding silica particles having a primary particle diameter of 1 to 30 nm and inorganic oxide particles having a primary particle diameter of 150 nm to 5 μm (see, for example, Patent Document 2)
(3) Investigation of adding silica particles and polyvinylidene fluoride particles having a larger primary particle size (see, for example, Patent Document 3).
Has been.

However,
In the study of (1), the aggregate of silica particles is dispersed to the primary particle size by the pressing force applied to the toner particles in the developing unit or the like, and the silica particles are buried in the toner particles. In the study of (3), large-diameter inorganic oxide particles scratch the surface of the photoreceptor when it comes into contact with the surface of the photoreceptor, and in the study of (3), the polyvinylidene fluoride particles have a low glass transition point. In an image forming apparatus equipped with a recycle process having a long toner residence time in the developing device, there are problems such as fusing to the surface of the carrier and the photoconductor and causing aggregation of toner particles. It was.

  Therefore, studies are being made to prevent the external additive from being buried in the toner particles by using an external additive composed of silica particles and crosslinked organic fine particles having a primary particle size larger than that (for example, patents). Reference 4).

Examples of the crosslinked organic fine particles include fine particles composed of a silicone resin, a crosslinked styrene resin, a crosslinked acrylic resin, and a crosslinked polyester resin.
Japanese Patent Laid-Open No. 2-289859 Japanese Examined Patent Publication No. 2-45188 Japanese Patent Laid-Open No. 2-67567 JP-A-5-181304

  However, when an external additive composed of silica particles and crosslinked organic fine particles having a primary particle size larger than that is adhered to toner base particles having a small particle size suitable for high-speed processes and low-temperature fixing, the printing environment As a result, the charge amount fluctuates, causing problems such as fogging and image density reduction.

  According to the present invention, even if the printing environment changes from low temperature and low humidity (for example, 10 ° C., 20% RH) to high temperature and high humidity (for example, 30 ° C., 80% RH), the variation amount of the charge amount is small, and fog is continuously generated. It is an object of the present invention to provide a toner capable of obtaining a high-density print image without any problems.

  The present invention can be achieved by adopting the following configuration.

1. In a toner obtained by attaching an external additive to a toner base particle having a binder resin and a colorant,
A toner comprising a polymer obtained by polymerization using a monomer of (meth) acrylic acid ester having at least one of isobonyl group and adamantyl group as the external additive.

  2. 2. The toner according to 1 above, wherein the polymer is contained in an amount of 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the toner.

  3. 3. The toner according to 1 or 2, wherein the toner base particles are prepared by an emulsion polymerization association method.

  The toner of the present invention has a small variation in charge amount even if the printing environment changes from low temperature and low humidity (for example, 10 ° C., 20% RH) to high temperature and high humidity (for example, 30 ° C., 80% RH). In addition, there is an excellent effect that a high density printed image can be obtained without fog.

  In the field of electrophotographic image forming apparatuses such as copiers and printers, with the advancement of digital technology, high-resolution dot image reproduction of 1200 dpi (dpi: number of dots per inch: 2.54 cm) has recently been achieved. There is a growing demand for technology that realizes low-temperature fixing from the viewpoint of energy saving and high-speed printing. As means for accurately reproducing such a high-definition image, a toner having a small diameter and a low glass transition point has been studied. Specifically, a material having a low glass transition point is used, and the diameter can be reduced by a polymerized toner represented by an association type toner capable of forming particles while controlling the particle size and shape during the manufacturing process. I came.

  Such a toner has a small particle diameter of 3.0 to 8.0 μm and a shape factor of 0.935 to 0.990, and is almost spherical.

  Such a low-temperature fixing and a toner having a small particle size and a nearly spherical shape can be produced through an emulsion polymerization process or an association process.

  However, since this toner has a low glass transition point, it is easy to embed external additives in the toner particles, and since many active agents and metal salts are used in the emulsion polymerization process and the associating process at the time of production, the toner is easily adapted to water. There is a problem that the charge amount is likely to vary depending on the printing environment.

  The present inventors do not embed external additives in the toner particles, and the printing environment changes from low temperature and low humidity (for example, 10 ° C., 20% RH) to high temperature and high humidity (for example, 30 ° C., 80% RH). However, the inventors examined toners that can obtain high-quality prints with little variation in charge amount and without fogging.

  As a result of various studies, polymer particles obtained by polymerization using a monomer of (meth) acrylic acid ester having either isobornyl group or adamantyl group as an external additive (hereinafter referred to as polycyclic polymer resin) It was also found that when the toner particles are used, the external additive is not buried in the toner particles, and the toner charge amount does not fluctuate even when the printing environment fluctuates.

  This is because the polycyclic polymer resin particles having a three-dimensional structure have a bulky and strong structure, and also have a high glass transition point, so that they have good stress resistance and are embedded in toner particles. It is presumed that it was possible to prevent this and ensure durability.

  In addition, the polycyclic polymer resin particles having a three-dimensional structure correspond to the moisture desorption of the toner base particles, and the moisture can be desorbed. We believe that it is small and the charge amount can be kept constant.

  Although the details of this action (moisture desorption) are unknown, the polycyclic polymer resin particles having a three-dimensional structure have voids at the molecular level suitable for desorption of water molecules. It is presumed that water molecules are desorbed in the voids at the level to reduce the fluctuation of the charge amount.

  In the present invention, toner is a generic term for toner particles, toner base is a generic term for toner base particles, and toner is obtained by attaching an external additive to the toner base.

  The toner of the present invention is obtained by attaching an external additive to a toner base having a binder resin and a colorant, and a monomer of (meth) acrylic acid ester having an isobornyl group as the external additive, And the resin particle formed by superposing | polymerizing using either of the monomer of the (meth) acrylic acid ester which has an adamantyl group is characterized by using.

  First, polycyclic polymer resin particles used as an external additive will be described.

<< Polycyclic polymer resin particles >>
The present invention relates to a three-dimensional polymer obtained by polymerization using either a (meth) acrylate monomer having an isobornyl group or a (meth) acrylate monomer having an adamantyl group as an external additive. Resin particles having a structure are used.

  Examples of the (meth) acrylic acid ester monomer having an isobornyl group include isobornyl acrylate and isobornyl methacrylate.

  Examples of the (meth) acrylic acid ester monomer having an adamantyl group include adamantyl acrylate, adamantyl methacrylate, and dimethyladamantyl methacrylate.

  Moreover, the resin obtained by copolymerizing the monomer of the (meth) acrylic acid ester which has either an isobornyl group and an adamantyl group, and the polymerizable monomer which can be copolymerized can also be used.

  As an example of the polymerizable monomer that can be copolymerized, a general (meth) acrylic monomer (for example, a chain-type methacrylic acid ester monomer) can be given.

  The polymerization ratio of the polymerizable monomer copolymerizable with the (meth) acrylic acid ester monomer having either an isobornyl group or an adamantyl group is any of the isobonyl group and the adamantyl group. The (meth) acrylic acid ester monomer having the above is 10 to 100 mol%, preferably 20 to 100 mol%.

  The effect of the present invention can be obtained by using a resin having a mass% within this range.

  Furthermore, in the present invention, resin particles formed by mixing polycyclic polymer resin particles and a known resin can be used as an external additive.

  Known resins include polyolefin resins such as polyethylene, polypropylene, chlorinated polyethylene and chlorosulfonated polyethylene; polyacrylate resins such as polystyrene resin and polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, and polychlorinated. Polyvinyl and polyvinylidene resins such as vinyl, polyvinyl carbazole, polyvinyl ether, and polybiliketones; copolymer resins such as vinyl chloride-vinyl acetate copolymers and styrene-acrylic acid copolymers; silicone resins composed of organosiloxane bonds Or a modified resin thereof (for example, modified resin by alkyd resin, polyester resin, epoxy resin, polyurethane, etc.); polytetrachloroethylene, polyvinyl fluoride Le, polyvinylidene fluoride, chloro tri full Lol ethylene and fluorine resin; polyamide resin; polyester resins; polyurethane resins; polycarbonate resins; - urea amino resins such as formaldehyde resins, epoxy resins and the like. Of these, polystyrene resins and polyacrylate resins are preferred.

  The mixing ratio of the polycyclic polymer resin particles in the resin particles prepared by mixing the polycyclic polymer resin particles and a known resin is preferably 20% by mass or more.

  By using resin particles in this range, the effect of the present invention can be obtained.

  The glass transition point of the polycyclic polymer resin particles is preferably 110 to 160 ° C.

  The glass transition temperature of the polycyclic polymer resin particles can be measured using a DSC-7 differential scanning calorimeter (manufactured by PerkinElmer) or a TAC7 / DX thermal analyzer controller (manufactured by PerkinElmer).

  As a measuring procedure, 4.5 mg to 5.0 mg of polycyclic polymer resin particles are precisely weighed to two digits after the decimal point, sealed in an aluminum pan (KIT No. 0219-0041), and set in a DSC-7 sample holder. The reference used an empty aluminum pan. The measurement conditions were a measurement temperature of 0 ° C. to 200 ° C., a temperature increase rate of 10 ° C./min, a temperature decrease rate of 10 ° C./min, and heat-cool-heat temperature control. Analysis is performed based on the data in Heat.

  The glass transition temperature draws an extension of the baseline before the rise of the first endothermic peak and a tangent line indicating the maximum slope between the rise of the first peak and the peak apex, and the intersection is taken as the glass transition point. Show.

  The number average particle diameter of the external additive used in the present invention is preferably 50 to 500 nm.

  The number average particle diameter is measured by the following method.

  A 30,000 times photograph of the toner is taken with a scanning electron microscope, and the photograph image is captured by a scanner. The image processing analyzer LUZEX AP (manufactured by Nireco) binarizes the external additive present on the toner surface of the photographic image, and calculates the horizontal ferret diameter for 100 external additives. The average value is the number average particle size.

  Further, the content of the polycyclic polymer resin particles with respect to the toner is preferably from 0.1 part by weight to 5.0 parts by weight. When the amount is larger than the portion, the chargeability of the toner is affected, causing fogging and the like.

  Next, preparation of toner base particles according to the present invention will be described.

<Production of toner base particles>
The toner base particles according to the present invention preferably have a small particle size and a narrow particle size distribution. Further, the toner base particles according to the present invention are preferably those produced by a chemical method capable of controlling the particle size distribution with a small particle size.

  Examples of the method for preparing toner base particles by chemical method include suspension polymerization method, emulsion association method, dispersion polymerization method, dissolution suspension method, etc. Among them, the particle size distribution is narrowly controlled with a small particle size. An emulsification association method that is easy to perform is preferred.

  Hereinafter, the emulsion association method will be described.

<Emulsion association method>
The emulsion association method is a method in which resin particles are prepared by salting out / fusion in an aqueous medium. The method is not particularly limited, and examples thereof include methods disclosed in JP-A-5-265252, JP-A-6-329947, and JP-A-9-15904. That is, dispersed particles of constituent materials such as resin particles and a colorant, or a method of salting out, agglomerating and fusing a plurality of particles composed of a resin and a colorant, etc., particularly in water using an emulsifier Then, a coagulant with a critical coagulation concentration or higher is added for salting out, and at the same time, the formed polymer is heated and fused at a temperature higher than the glass transition temperature of the polymer itself to gradually grow the particle size while forming fused particles. When the desired particle size is reached, a large amount of water is added to stop particle size growth, and the shape is controlled by smoothing the particle surface while heating and stirring, and the particles are heated in a fluidized state while containing water. By drying, the toner according to the present invention can be formed.

  In the method for producing a toner according to the present invention, a release agent is dissolved or dispersed in a polymerizable monomer, and then finely dispersed in an aqueous medium, and the polymerizable monomer is polymerized by a miniemulsion polymerization method. A method of salting out / fusion-bonding the composite resin particles formed through the step of causing the colorant particles and the colorant particles is preferably used.

  In addition, as a method for producing the toner base particles according to the present invention, a step of salting out / fusing the composite resin particles obtained by the multistage polymerization method and the colorant particles is preferably used.

  Next, an example of a preferable method for producing toner base particles (emulsion polymerization association method) will be described in detail.

This manufacturing method includes
(1) Dissolution / dispersion step for dissolving or dispersing the release agent in the radical polymerizable monomer (2) Polymerization step for preparing a dispersion of resin particles (3) Resin particles and colorant particles in an aqueous medium (4) Cooling step for cooling the dispersion of the toner base particles (5) Cooling the dispersion of the toner base particles to fix the toner base particles from the cooled dispersion of the toner base particles Liquid Separation and Cleaning Step for Removing Surfactant from the Toner Base Particles (6) Drying Step for Drying Washed Toner Base Particles Each step will be described below.

[Dissolution / dispersion process]
This step is a step of preparing a radical polymerizable monomer solution of the release agent by dissolving or dispersing the release agent in the radical polymerizable monomer.

[Polymerization process]
In a preferred example of this polymerization step, a radical polymerizable monomer solution in which the release agent is dissolved or dispersed is added to an aqueous medium containing a surfactant, and mechanical energy is applied to form droplets. Then, the polymerization reaction is allowed to proceed in the droplets by radicals from the water-soluble radical polymerization initiator. In addition, you may add the resin particle as a core particle in the said aqueous medium.

  By this polymerization step, resin particles containing a release agent and a binder resin are obtained. Such resin particles may be colored particles or non-colored particles. The colored resin particles can be obtained by polymerizing a monomer composition containing a colorant. In addition, when using uncolored resin particles, a dispersion of colorant particles is added to a dispersion of resin particles in a fusing step described later, and the resin particles and the colorant particles are fused. Thus, toner base particles can be obtained.

[Fusion process]
As a method of fusing in the fusing step, a salting out / fusing method using resin particles (colored or non-colored resin particles) obtained in the polymerization step is preferable. In the fusing step, resin particles and colorant particles can be fused together with internal additive particles such as release agent particles and charge control agents.

  The colorant particles can be prepared by dispersing the colorant in an aqueous medium. The dispersion treatment of the colorant is performed in a state where the surfactant concentration is set to a critical micelle concentration (CMC) or more in water. The disperser used for the dispersion treatment of the colorant is not particularly limited, but preferably an ultrasonic disperser, a mechanical homogenizer, a pressure disperser such as a manton gorin or a pressure homogenizer, a sand grinder, a Getzmann mill, a diamond fine mill, or the like. Examples thereof include a medium type disperser.

  The colorant (particles) may be surface-modified. In the surface modification method of the colorant, the colorant is dispersed in a solvent, the surface modifier is added to the molecular weight solution, and the system is reacted by raising the temperature. After completion of the reaction, the colorant is separated by filtration, washed and filtered with the same solvent, and dried to obtain a colorant (pigment) treated with the surface modifier.

  The salting-out / fusion method, which is a preferred fusing method, is a method in which a salting-out agent composed of an alkali metal salt, an alkaline earth metal salt, or the like is added to water having resin particles and colorant particles in excess of the critical aggregation concentration. Adding as a flocculant, and then proceeding to salting out by heating to a temperature above the glass transition point of the resin particles and above the melting peak temperature (° C.) of the release agent, and at the same time, fusing It is a process to be performed.

[Cooling process]
This step is a step of cooling (rapid cooling) the dispersion of toner base particles. As a cooling treatment condition, cooling is performed at a cooling rate of 1 to 20 ° C./min. The cooling treatment method is not particularly limited, and examples thereof include a method of cooling by introducing a refrigerant from the outside of the reaction vessel, and a method of cooling by directly introducing cold water into the reaction system.

[Solid-liquid separation and washing process]
In this solid-liquid separation / washing step, a solid-liquid separation process for solid-liquid separation of the toner base particles from the dispersion of the toner base particles cooled to a predetermined temperature in the above-described step, and a solid-liquid separated toner cake (wet) A cleaning process is performed to remove deposits such as a surfactant and a salting-out agent from an aggregate of toner base particles in a state of aggregation in a cake form. Here, the filtration method is not particularly limited, such as a centrifugal separation method, a vacuum filtration method using Nutsche or the like, a filtration method using a filter press or the like.

[Drying process]
In this step, the washed toner cake is dried to obtain dried toner base particles. Examples of dryers used in this process include spray dryers, vacuum freeze dryers, vacuum dryers, etc., stationary shelf dryers, mobile shelf dryers, fluidized bed dryers, rotary dryers It is preferable to use a stirring dryer or the like. The moisture content of the dried toner base particles is preferably 5% by mass or less, and more preferably 2% by mass or less. When the toner base particles that have been dried are aggregated with weak interparticle attractive forces, the aggregate may be crushed. Here, as the crushing treatment apparatus, a mechanical crushing apparatus such as a jet mill, a Henschel mixer, a coffee mill, or a food processor can be used.

  Next, compounds constituting the toner base particles (binder resin, colorant, release agent, charge control agent, external additive, lubricant) will be described.

(Binder resin)
As the polymerizable monomer constituting the binder resin, known monomers can be used. Specifically, it is preferable to use a combination of styrene, acrylic acid or methacrylic acid derivatives, and those having an ionic dissociation group.

(Coloring agent)
As the colorant used in the present invention, a known inorganic or organic colorant can be used. These colorants may be used alone or in combination of two or more as required. The addition amount of the colorant is set in the range of 1 to 30% by mass, preferably 2 to 20% by mass with respect to the whole toner.

(Release agent)
A known compound can be used as the release agent used in the present invention. When the release agent is contained in an amount of 1 to 15% by mass, preferably 3 to 12% by mass, based on the whole toner, good results can be obtained.

(Charge control agent)
In the present invention, a charge control agent can be added as necessary. A known compound can be used as the charge control agent.

<Production of toner>
The toner of the present invention can be produced by attaching an external additive containing a polycyclic polymer resin to the surface of toner base particles.

  Examples of the method for attaching the external additive to the surface of the toner base particles include a method using a mechanical mixing device such as a Henschel mixer and a coffee mill. Among these, the Henschel mixer can be uniformly attached. preferable.

(External additive)
In the present invention, in addition to the external additive containing polycyclic polymer resin particles, a known external additive can be mixed as necessary. Known external additives are not particularly limited, and various inorganic particles, organic particles, and lubricants can be used.

  As the known external additive, various inorganic fine particles, organic fine particles and lubricants can be used.

  As inorganic fine particles, silica fine particles, titania fine particles, alumina fine particles and the like can be preferably used. These inorganic particles are preferably hydrophobic.

  As the organic fine particles, spherical fine particles having a number average primary particle size of about 10 to 2000 nm can be used. Examples of the constituent material of the organic fine particles include polystyrene, polymethyl methacrylate, styrene-methyl methacrylate copolymer, and the like.

  The addition amount of the external additive is preferably 0.1 to 10.0% by mass with respect to the whole toner.

<Production of developer>
The toner of the present invention can be used as a one-component developer or a two-component developer for forming a mono black toner image or a color toner image.

  Examples of the one-component developer include a non-magnetic one-component developer or a magnetic one-component developer containing about 0.1 to 0.5 μm of magnetic particles in the toner. Can do.

  As the two-component developer, one prepared by mixing a carrier and a toner can be used. As the carrier, conventionally known magnetic particles such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead can be used. Ferrite particles are particularly preferable. The particle diameter of the carrier is preferably 20 to 100 μm, and more preferably 25 to 80 μm.

  The mixing ratio of the carrier and the toner is preferably carrier: toner = 100: 10 to 100: 2 in terms of mass ratio.

  For mixing the carrier and the toner, various known mixing devices such as a Turbuler mixer, a Henschel mixer, a Nauter mixer, and a V-type mixer can be used.

  The toner of the present invention can be used by being loaded into an image forming apparatus employing a one-component developing unit or a two-component developing unit.

  Hereinafter, an image forming apparatus employing a two-component developing unit will be described.

<Image forming apparatus>
FIG. 1 is a schematic view showing an example of an image forming apparatus according to the present invention.

  An image forming apparatus 1 shown in FIG. 1 is a digital image forming apparatus, and includes an image forming unit including an image reading unit A, an image processing unit B, and an image forming unit C, and a recording material conveying unit that conveys a recording material. And a fixing device 500.

  An automatic document feeder that automatically conveys the document is provided above the image reading unit A, and the document placed on the document table 11 is separated and conveyed by the document conveying roller 12 to the reading position 13a. The image is read at. The document after the document reading is completed is discharged onto the document discharge tray 14 by the document transport roller 12.

  On the other hand, the image of the original when placed on the platen glass 13 is positioned in a V-shape and the reading operation at the speed v of the first mirror unit 15 including the illumination lamp and the first mirror constituting the scanning optical system. Reading is performed by moving the second mirror unit 16 including the second mirror and the third mirror in the same direction at a speed v / 2.

  The read image is formed on the light receiving surface of the image sensor CCD, which is a line sensor, through the projection lens 17. The line-shaped optical image formed on the image sensor CCD is sequentially photoelectrically converted into an electric signal (luminance signal) and then A / D converted, and the image processing unit B performs processing such as density conversion and filter processing. Then, the image data is temporarily stored in the memory.

  In the image forming unit C, as an image forming unit, a drum-shaped photoconductor 21 as an image carrier, a charging unit 22 for charging the photoconductor 21 on the outer periphery thereof, and a potential for detecting the surface potential of the charged photoconductor. A detecting means 220 and a developing means 23 are arranged. Further, a transfer electrode 24 and a separation electrode 25 as transfer separation means, a cleaning device 190 for the photosensitive member 21, and a PCL (precharge lamp) 27 as an optical charge removal means are arranged in order of operation. Further, on the downstream side of the developing means 23, a reflection density detecting means 222 for measuring the reflection density of the patch image developed on the photosensitive member 21 is provided. The photoconductor 21 is formed by coating a photoconductive compound on a drum base. For example, an organic photoconductor (OPC) is preferably used and is driven to rotate in the clockwise direction shown in the drawing.

  After the rotating photosensitive member 21 is uniformly charged by the charging unit 22, image exposure based on an image signal called from the memory of the image processing unit B is performed by an exposure optical system 30 as an image exposure unit. An exposure optical system 30 serving as an image exposure unit serving as a writing unit uses a laser diode (not shown) as a light source, and a light path is bent by a reflection mirror 32 through a rotating polygon mirror 31, an fθ lens 34, and a cylindrical lens 35. Is to be made. By this scanning, image exposure is performed on the photosensitive member 21 at the line Ao, and a latent image is formed by rotation (sub-scanning) of the photosensitive member 21. In one example of the present embodiment, the character portion is exposed to form a latent image.

  The latent image on the photoreceptor 21 is subjected to reversal development by the developing unit 23, and a visible toner image is formed on the surface of the photoreceptor 21. In the recording material transport unit D, paper feeding units 41 (A), 41 (B), and 41 (C) as recording material storage means in which recording materials P as recording papers of different sizes are stored below the image forming unit. And a conveyance roller 43D, and a manual paper feed unit 42 for performing manual paper feed is provided on the side. The recording material P selected from any one of them is fed along the conveyance path 40 by the guide roller 43, and the recording material P is fed by the registration roller pair 44 that corrects the inclination and the deviation of the fed recording material P. After the temporary stop, the paper is fed again. Then, the toner image on the photoreceptor 21 is guided onto the recording material P by the transfer pole 24 and the separation pole 25 at the transfer position Bo, guided by the transport path 40, the pre-transfer roller 43a, the paper feed path 46, and the entry guide plate 47. The The recording material P is separated from the surface of the photosensitive member 21 while being placed and conveyed on the conveyance belt 454 of the conveyance belt device 45, and is conveyed by the conveyance belt device 45 to, for example, an induction heating type fixing device 500 as a fixing unit.

  The recording material P after the fixing of the toner image is discharged onto a paper discharge tray 81 of the recording material stacking means 80.

  The above describes the state in which image formation is performed on one side of the recording material P. However, in the case of double-sided copying, the paper discharge switching member 170 is switched, the recording material guide portion 177 is opened, and the transfer material or recording paper is The recording material P called is conveyed in the direction of the broken line arrow.

  Further, the recording material P is conveyed downward by the conveying mechanism 178 and switched back by the recording material reversing unit 179, and the rear end portion of the recording material P so far becomes the leading end portion in the double-sided copying paper feeding unit 130. It is conveyed to.

  The recording material P moves a conveyance guide 131 provided in the duplex copying paper supply unit 130 in the paper supply direction, refeeds the recording material P by the paper supply roller 132, and guides the recording material P to the conveyance path 40. .

  Again, as described above, the recording material P is conveyed in the direction of the photosensitive member 21, the toner image is transferred to the back surface of the recording material P, fixed by the fixing device 500, and then discharged onto the discharge tray 81 of the sheet stacking means 80. Make paper.

  The above is the description of the image forming apparatus 1 for obtaining a monochrome image. The image carrier is a photosensitive drum. However, the present invention can be applied not only to such a monochrome image but also to a color image forming apparatus. .

  This color image forming apparatus is called, for example, a tandem type color image forming apparatus, and has an image forming unit that forms yellow, magenta, cyan, and black color toner images along the moving direction of the intermediate transfer member. It is. Then, the color toner images formed on the respective photosensitive drums as the image carriers of the respective image forming units are superimposed on the intermediate transfer member as the image carrier by multiple transfer, and then superimposed on the recording material P. A batch transfer is performed as a secondary transfer.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the embodiment of the present invention is not limited thereto.

<Production of toner>
First, polycyclic polymer resin particles were prepared.

<Preparation of polycyclic polymer resin particles 1>
A copolymer of isobornyl acrylate / methyl methacrylate (copolymerization ratio 20/80) was synthesized by an emulsion polymerization method in an aqueous medium containing 0.3 part by mass of sodium dodecylbenzenesulfonate as a surfactant. It was washed with water using an external filtration device and then dried with a spray dryer to prepare “polycyclic polymer resin particles 1” having a glass transition point (Tg) of 120 ° C. and a number average primary particle size of 20 nm.

<Preparation of polycyclic polymer resin particles 2>
A copolymer of isobornyl acrylate / methyl methacrylate (copolymerization ratio 50/50) was synthesized by an emulsion polymerization method in an aqueous medium containing 0.3 part by mass of sodium dodecylbenzenesulfonate as a surfactant. It was washed with water using an external filtration device and then dried with a spray dryer to produce “polycyclic polymer resin particles 2” having a Tg of 123 ° C. and a number average primary particle size of 60 nm.

<Preparation of polycyclic polymer resin particles 3>
A copolymer of isobornyl acrylate / methyl methacrylate (copolymerization ratio 70/30) was synthesized by an emulsion polymerization method in an aqueous medium containing 0.3 part by mass of sodium dodecylbenzenesulfonate as a surfactant. It was washed with water using an external filtration device and then dried with a spray dryer to produce “polycyclic polymer resin particles 3” having a Tg of 158 ° C. and a number average primary particle size of 80 nm.

<Preparation of polycyclic polymer resin particles 4>
A copolymer of adamantyl acrylate / methyl methacrylate (copolymerization ratio 90/10) was synthesized by an emulsion polymerization method in an aqueous medium containing 0.3 part by mass of sodium dodecylbenzenesulfonate as a surfactant. It was washed with water using a filtration device and then dried with a spray dryer to produce “polycyclic polymer resin particles 4” having a Tg of 137 ° C. and a number average primary particle size of 150 nm.

<Preparation of polycyclic polymer resin particles 5>
Isobornyl acrylate / adamantyl acrylate / methyl methacrylate (copolymerization ratio 30/30/40) by an emulsion polymerization method in an aqueous medium containing 0.3 part by mass of sodium dodecylbenzenesulfonate as a surfactant. The copolymer was washed with water using an ultrafiltration device, and then dried with a spray dryer to produce “polycyclic polymer resin particles 5” having a Tg of 138 ° C. and a number average primary particle size of 490 nm. .

<Preparation of polycyclic polymer resin particles 6>
A copolymer of isobornyl acrylate / methyl methacrylate (copolymerization ratio 10/90) was synthesized by an emulsion polymerization method in an aqueous medium containing 0.3 part by mass of sodium dodecylbenzenesulfonate as a surfactant. It was washed with water using an external filtration device and then dried with a spray dryer to prepare “polycyclic polymer resin particles 6” having a Tg of 113 ° C. and a number average primary particle size of 120 nm.

<Preparation of polycyclic polymer resin particles 7>
In an aqueous medium containing 0.3 parts by mass of sodium dodecylbenzenesulfonate as a surfactant, isobornyl acrylate is synthesized by an emulsion polymerization method, washed with water using an ultrafiltration device, and then dried with a spray dryer. “Polycyclic polymer resin particles 7” having a Tg of 180 ° C. and a number average primary particle size of 120 nm were produced.

<Preparation of polycyclic polymer resin particles 8>
A copolymer of isobornyl acrylate / methyl methacrylate (copolymerization ratio 8/92) was synthesized by an emulsion polymerization method in an aqueous medium containing 0.3 part by mass of sodium dodecylbenzenesulfonate as a surfactant. It was washed with water using an external filtration device and then dried with a spray dryer to prepare “polycyclic polymer resin particles 8” having isobonyl acrylate having a Tg of 110 ° C. and a number average primary particle size of 120 nm.

<Preparation of polycyclic polymer resin particles 9>
In an aqueous medium containing 0.3 part by mass of sodium dodecylbenzenesulfonate as a surfactant, a polymer of methyl methacrylate is synthesized by emulsion polymerization, washed with water using an ultrafiltration device, and then spray sprayed. This was dried to prepare “polycyclic polymer resin particles 9” having methyl acrylate having a Tg of 105 ° C. and a number average primary particle size of 120 nm.

  Table 1 shows the monomers used for preparing the polycyclic polymer resin particles, their copolymerization ratio, glass transition point, and average particle diameter.

  The glass transition point and the average particle diameter are values measured by the above methods.

  The toner was prepared as follows.

<Preparation of Toner 1>
(Preparation of toner base particle A)
First stage polymerization (mini emulsion polymerization)
Styrene 175 parts by weight n-butyl acrylate 60 parts by weight Methacrylic acid 15 parts by weight n-octyl-3-mercaptopropionate 7 parts by weight of monomer mixture is put into a reaction vessel equipped with a stirrer, and there 100 parts by mass of pentaerythritol tetrabehenate was added, heated to 70 ° C. and dissolved to prepare a monomer solution.

  On the other hand, a surfactant solution in which 2 parts by mass of sodium polyoxyethylene (2) dodecyl ether sulfate was dissolved in 1350 parts by mass of ion-exchanged water was heated to 70 ° C., added to and mixed with the monomer solution, and then circulated. Dispersion was carried out at 70 ° C. for 30 minutes using a mechanical disperser “Clearmix” (manufactured by M. Tennicnic Co., Ltd.) having a path to prepare an emulsified dispersion.

  Next, an initiator solution in which 7.5 parts by mass of potassium persulfate was dissolved in 150 parts by mass of ion-exchanged water was added to this dispersion, and this system was heated and stirred at 78 ° C. for 1.5 hours. Polymerization was performed to obtain a dispersion of resin particles. This is referred to as “dispersion of resin particles 1”.

Second stage polymerization (formation of outer layer)
An initiator solution in which 12 parts by mass of potassium persulfate is dissolved in 220 parts by mass of ion-exchanged water is added to the “dispersion of resin particles 1” obtained as described above, and styrene 320 is added at a temperature of 80 ° C. Mass part n-Butyl acrylate 100 parts by mass Methacrylic acid 35 parts by mass n-Octyl-3-mercaptopropionate A monomer mixture consisting of 7.5 parts by mass was added dropwise over 1 hour. After completion of the dropping, polymerization was carried out by heating and stirring for 2 hours. Then, it cooled to 28 degreeC and obtained "the dispersion liquid of the resin particle 2."

(Colorant particle dispersion)
A solution was prepared by stirring and dissolving 90 parts by mass of sodium dodecyl sulfate in 1600 parts by mass of ion-exchanged water. While stirring this solution, 400.0 parts by mass of carbon black “Regal 330R” (Cabot) is gradually added, and then dispersed using a mechanical disperser “Clearmix” (M Technique). A colorant particle dispersion was prepared by treatment. The particle diameter of the colorant particles in this dispersion was measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.) and found to be 110 nm.

(Meeting process)
Dispersion liquid of resin particles 2 2000 parts by weight Ion exchange water 670 parts by weight Colorant particle dispersion 400 parts by weight The above liquid is placed in a 5 L reaction vessel equipped with a temperature sensor, a cooling tube, a nitrogen introducing device, and a stirring device, and stirred. After adjusting the liquid temperature to 30 ° C., 5N aqueous sodium hydroxide solution was added to this solution to adjust the pH to 10.

  Next, an aqueous solution in which 60 parts by mass of magnesium chloride hexahydrate was dissolved in 60 parts by mass of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After standing for 3 minutes, the temperature was started to rise, and the temperature of the system was raised to 90 ° C. over 60 minutes to grow the particle size and perform an association reaction. In this state, the particle size of the associated particles was measured with “Coulter Multisizer 3” (manufactured by Beckman Coulter), and when the median particle size on a volume basis reached 5.0 μm, 8.5 mass of sodium chloride was obtained. An aqueous solution in which 35 parts by mass of ion-exchanged water was dissolved was added to stop particle growth, and then heating and stirring were continued for 3 hours for fusion.

  Then, it cooled to 30 degreeC, hydrochloric acid was added, pH was adjusted to 2.0, and stirring was stopped. The grown associated particles were filtered, washed repeatedly with ion exchange water at 35 ° C., and then dried with hot air at 40 ° C. to obtain “toner base particles A”.

(External additive mixing process)
0.2 parts by weight of “polycyclic polymer resin particle 1” and 1.0 part by weight of hydrophobic silica (number average primary particle size = 12 nm) are added to “toner base particle A” obtained above, “Henschel mixer” (manufactured by Mitsui Miike Chemical Co., Ltd.) was mixed for 10 minutes to prepare “Toner 1”.

<Preparation of Toners 2 to 13>
“Toners 2 to 13” were prepared in the same manner except that the polycyclic polymer resin particles 1 and the hydrophobic silica used in the preparation of the toner 1 were changed as shown in Table 2.

《Career preparation》
A “carrier” in which the surface of Cu—Zn ferrite particles having a volume average primary particle size of 60 μm and a saturation magnetization of 63 emu / g was coated with a silicone resin was prepared.

<< Preparation of two-component developer >>
Each toner prepared above and the carrier prepared above were mixed using a low speed mixer so that the toner concentration was 5% by mass to prepare “two-component developers 1 to 13”.

<Evaluation>
As the image forming apparatus for evaluation, “bizhub 750” (manufactured by Konica Minolta Business Technologies) was prepared.

"Toners 1-13" and "Developers 1-13" are sequentially loaded into this evaluation image forming apparatus, and 50,000 sheets of a document with a printing rate of 5% are printed in a low-temperature, low-humidity (10 ° C, 20% RH) printing environment. After printing, 50,000 sheets were printed in a high temperature and high humidity (30 ° C., 80% RH) printing environment. A4 high-quality paper (64 g / m ² ) was used as print paper (transfer material).

(Fog)
Fog prints 50,000 sheets in a low-temperature, low-humidity (10 ° C, 20% RH) printing environment, and measures the image density of 20 unprinted print paper (white paper) when printing 50,000 sheets. The average value is defined as the white paper density. Next, the white density of the printed paper on which the plain image is printed is similarly measured at 20 locations, the image density is measured to calculate the average density, and the white paper density is subtracted from the average density. The value was evaluated as fog density. The measurement was performed using a reflection densitometer “RD-918” (manufactured by Macbeth). The image fog is determined to be 0.010 or less.

(Image density)
The image density is 50,000 sheets printed in a printing environment of low temperature and low humidity (10 ° C., 20% RH) and then 50,000 sheets in a printing environment of high temperature and high humidity (30 ° C., 80% RH). The evaluation was based on the image density when printing 10,000 sheets. The image density was measured at 12 points using a reflection densitometer “RD-918 (manufactured by Macbeth)”, and the average value was evaluated as the image density. The image density is 1.35 or higher.

(Charge variation)
The fluctuation of the charge amount is 50,000 sheets printed at low temperature and low humidity (10 ° C, 20% RH) and then 50,000 sheets printed at high temperature and high humidity (30 ° C, 80% RH). After completion of printing at high temperature and high humidity, the charge amount of the toner in the developer was measured and evaluated by the change in the charge amount depending on the environment.

  The charge amount was measured using a blow-off charge amount measuring device “TB-200” (manufactured by Toshiba Chemical Corporation).

  The developer to be measured was set in the charge amount measuring device equipped with a 400 mesh stainless steel screen, and blown with nitrogen gas for 10 seconds under the condition of a blow pressure of 50 kPa, and the charge was measured. The charge amount (−μC / g) was calculated by dividing the measured charge by the flying toner mass. In addition, the variation in charge amount is 4.0 μC / g or less.

  Table 3 shows the evaluation results.

  As shown in Table 3, “Examples 1 to 11” corresponding to the present invention obtained good results for any of the evaluation items. On the other hand, “Comparative Examples 1 and 2” outside the present invention had a problem in any of these evaluation items, and it was confirmed that the effects of the present invention were not expressed.

1 is a schematic diagram illustrating an example of an image forming method and an image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Document mounting stand 12 Document conveyance roller 500 Fixing device A Image reading part B Image processing part C Image forming part D Recording material conveyance part P Transfer material

Claims (3)

In a toner obtained by attaching an external additive to a toner base particle having a binder resin and a colorant,
A toner comprising a polymer obtained by polymerization using a monomer of (meth) acrylic acid ester having at least one of isobonyl group and adamantyl group as the external additive. The toner according to claim 1, wherein the polymer is contained in an amount of 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the toner. The toner according to claim 1, wherein the toner base particles are produced by an emulsion polymerization association method.

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