JP6192411B2 - Image forming method - Google Patents

Description

  The present invention relates to an electrophotographic image forming method used in a copying machine, a laser printer, and the like, and a toner used in the image forming method.

  In image forming apparatuses such as electrophotographic apparatuses (copiers, laser beam printers, etc.), electrostatic recording apparatuses, etc., as means for charging the surface of an image carrier as a charged body such as a photoreceptor or a dielectric, it has hitherto been used. Corona discharge devices are widely used. The corona discharge device is effective as a means for uniformly charging the surface of the photoreceptor to be charged at a predetermined potential, but requires a high current power source with a large amount of current and generates a large amount of ozone (especially during negative ion discharge). ) And other problems.

  A conductive charging member (roller-like, blade-like, belt-like, web-like, pad-like) to which a voltage (for example, a superimposed voltage of a DC voltage of about 1 to 2 kV and an AC voltage) is applied to such a corona discharge device. There are contact charging devices that transfer (inject) charges directly onto the surface of the object to be charged by bringing them into contact with a block, rod, brush, etc., and charge the surface of the object to be charged to a predetermined potential. This apparatus has features such that the pressure of the power source can be reduced, the amount of ozone generated is small, and the configuration is simple. For this reason, for example, image forming apparatuses have been proposed and put into practical use as charging means for image bearing members such as photoconductors and dielectrics, and other charged surfaces in place of conventional corona discharge devices.

  The surface of the photoconductor is worn by repeated discharge of the contact charging, rubbing by the contact charging means, and rubbing by the cleaning means in a configuration including the cleaning means. In recent years, it is necessary to reduce the wear of the photosensitive member in order to improve the image quality and the life of a device such as a printer, and it is effective to reduce the amount of discharge current by the contact charging unit.

  However, if the primary charging voltage becomes too small by reducing the amount of discharge current, the discharge becomes unstable and image defects may occur due to uneven charging.

  On the other hand, a toner used in a general electrophotographic method treats colored particle surfaces with a fluidity improver (external additive) to control desired fluidity and charging characteristics. As this external additive, what is generally widely used is fine particles made of inorganic or organic substances.

  If these external additives are continuously stirred in the image forming apparatus for a long time, they may be released from the toner particles due to the strong stress, and the released external additives are contacted by being conveyed by the image carrier that circulates and moves. In some cases, the surface of the charging member may be transferred.

  When the external additive is transferred to the surface of the contact charging member, if the amount is large, uniform charging by the contact charging member may be hindered to cause image defects.

  Specifically, this is a phenomenon that occurs when the electrical resistance of the contact charging member is different from the electrical resistance of the transferred external additive. Especially when the electrical resistance of the external additive is high, the phenomenon occurs in the region where the external additive has transferred. It may be difficult for the charging current to flow and cause uneven charging.

  Patent Document 1 discloses an image forming method in which a conductive particle is contained in a developer so that an insulating layer is not formed on the surface of the charging member even when the conductive particles are transferred to the charging member. Is disclosed.

  However, in the technique described in Patent Document 1, since a conductive layer is formed on the surface of the charging member, for example, when the charging of the photoreceptor is controlled at a constant voltage, the discharge current may increase. Alternatively, in the case where the charging of the photosensitive member is controlled at a constant current, the discharge may become unstable because the voltage of the discharge threshold is lowered.

Japanese Patent Laid-Open No. 5-150539

  An object of the present invention is to provide an image forming method and a toner for use in the image forming method in which the above problems are solved. That is, an object of the present invention is to provide an image forming method that makes it difficult to generate uneven charging of the photosensitive member even if the amount of discharge current by the contact charging means is set small.

  Another object of the present invention is to provide a toner that does not inhibit uniform charging even when fine particles used as an external additive are separated and transferred to the surface of the contact charging means.

  As a result of repeated studies, the present inventors have found that the above requirements can be satisfied by adopting the configuration of the present invention described below, and have reached the present invention.

That is, the present invention
A charging step of charging the image carrier negatively using a contact charging means that contacts the image carrier;
An electrostatic latent image forming step of forming an electrostatic latent image on the image carrier;
Developing the electrostatic latent image with a negatively charged toner to form a toner image;
A transfer step of transferring the toner image to a recording medium;
An image forming method comprising:
A charging bias in which an AC bias and a DC bias are superimposed is applied to the contact charging unit,
In the charging step, charging is performed in a state in which a negatively chargeable fine particle is interposed between the contact charging unit and the image carrier so as to cover 10% to 70% of the surface of the contact charging unit. And
In the image forming method, the fine particles have a volume resistivity of 1.0 × 10 ¹¹ Ω · cm or more and a relative dielectric constant at 1 kHz of 1.7 to 2.5.

A charging step of charging the image carrier negatively by applying a charging bias in which an AC bias and a DC bias are superposed using a contact charging means that contacts the image carrier;
An electrostatic latent image forming step of forming an electrostatic latent image on the image carrier;
A developing step of developing the electrostatic latent image with a negatively charged toner to form a toner image;
A transfer step of transferring the toner image to a recording medium;
An image forming how with,
The toner has toner base particles containing a binder resin and a colorant, and negatively charged fine particles are externally added to the surface.
The fine particles have a volume resistivity of 1.0 × 10 ¹¹ Ω · cm or more, a relative dielectric constant at 1 kHz of 1.7 or more and 2.5 or less, and a release rate of the fine particles from the toner of 10% or more. An image forming method is characterized in that there is an image forming method .

  According to the present invention, it is possible to provide an image forming method in which even if the amount of discharge current for charging is reduced in order to extend the life of the photosensitive member, uneven charging is unlikely to occur and uniform image output is possible.

  Furthermore, it is possible to provide a toner that does not hinder uniform charging even when fine particles used as an external additive are separated and transferred to the surface of the contact charging means.

1 is a schematic configuration diagram of an image forming apparatus to which the present invention is applied. It is a schematic block diagram of the charging means to which this invention is applied. It is explanatory drawing of a charging current characteristic. It is explanatory drawing of a discharge current characteristic.

  The present invention includes a charging step of negatively charging the image carrier using contact charging means that contacts the image carrier, an electrostatic latent image forming step of forming an electrostatic latent image on the image carrier, and the electrostatic latent image. This is an improvement of an image forming method including a developing step of developing an image with negative chargeable toner to form a toner image, and a transfer step of transferring the toner image to a recording medium. Hereinafter, preferred embodiments of the image forming method and the toner of the present invention will be described in detail.

[Image forming apparatus]
FIG. 1 is a schematic view of an image forming apparatus to which the present invention can be applied.

  The image forming apparatus 100 includes an image forming unit, a recording medium containing unit 200 such as a recording sheet, a recording medium conveying unit 210, and a control unit 300 for controlling them. The image forming means includes a photosensitive member 110 as an image carrier, a charging roller 120 as a contact charging means, a laser scanner 130 as an exposure means, a developing device 140 as a developing means, a transfer roller 150 as a transfer means, and a fixing means. A fixing device 170 is provided. You may provide the cleaner 160 as a cleaning means as needed.

[Contact charging means]
The contact charging means includes a charging roller 120 and a high voltage power source 124. The charging roller 120 is composed of a conductive shaft, a rubber or sponge roller whose electric resistance is adjusted, and has a surface layer whose electric resistance is adjusted as necessary. The resistance value when a voltage of 100 to 200 V is applied is 1. It is adjusted to 0 × 10 ⁴ Ω to 1.0 × 10 ⁶ Ω. The high-voltage power supply 124 supplies a charging bias in which an AC bias and a DC bias are superimposed, and is connected to a charging roller shaft.

[Adjustment of discharge current]
Evaluation in the present invention is performed while controlling the discharge current. The discharge current will be described with reference to FIGS.

  A charging bias voltage under a predetermined condition is applied to the charging roller 120. As a result, the surface of the rotating photoconductor 110 is contact-charged to a predetermined polarity / potential.

  In this embodiment, the charging bias voltage for the charging roller 120 is an oscillating voltage obtained by superimposing the DC voltage Vdc and the AC voltage Vac. More specifically, it is an oscillating voltage obtained by superimposing a DC voltage Vdc of −600 V and a sinusoidal AC voltage Vac set at a frequency of 1.7 kHz and a peak-to-peak voltage Vpp determined by control described later. is there. By this charging bias voltage, the surface of the rotating photoconductor 110 is uniformly contact-charged to −600 V (dark potential Vd) which is the same as the DC voltage applied to the charging roller 120.

  When the peak-to-peak voltage Vpp of the AC voltage Vac applied to the charging roller 120 is increased more than necessary, excessive discharge (discharge current) is generated between the charging roller 120 and the photoconductor 110.

  FIG. 3 shows the relationship between the peak voltage Vpp of the charging AC bias and the total current. FIG. 4 shows the relationship between the peak voltage Vpp of the charging AC bias and the discharge current.

  In FIG. 3, the region where the peak-to-peak voltage is low is the undischarged region, and the region where the peak-to-peak voltage is high is the discharge region. When the relationship between the peak-to-peak voltage and the current in the discharge region and the undischarge region is linearly approximated, the intersection is the discharge start point. In the discharge region, current flows with a larger slope than the approximate line using the slope of the undischarged region indicated by the dotted line, and the difference between the value indicated by the dotted line at a certain Vpp and the actually flowing current value is the discharge current.

  When the discharge current thus obtained is plotted, it can be seen that the discharge current flows at a peak-to-peak voltage above the discharge start point as shown in FIG.

  If the amount of discharge current is large, a large amount of charged products may adhere to the photoconductor 110, or wear of the photoconductor surface may be accelerated. This charged product induces deterioration of the surface of the photoconductor 110 and causes image quality deterioration such as image flow and filming. Therefore, it is preferable to reduce the amount of discharge current by suppressing the applied voltage to the minimum necessary peak-to-peak voltage that uniformly charges the surface of the photoconductor 110.

[Physical properties of fine particles]
When the absolute value of the peak-to-peak voltage is reduced by reducing the discharge current amount, it is observed that the discharge current flows macroscopically. However, microscopically, it is considered that a region where discharge occurs and a region where discharge does not occur are formed, and as a result, uneven charging occurs. Therefore, it is necessary to reduce the amount of discharge current without reducing the peak-to-peak voltage. It has been found that the effect can be obtained by allowing the fine particles of the present invention to be present on the surface of the charging roller 120.

  In order to reduce the discharge current amount, a method in which fine particles having a high volume resistivity are present on the surface of the charging roller 120 can be considered. However, if the volume resistivity is only high, when a large amount adheres to the surface of the charging roller 120, the amount of discharge current becomes too small and a high applied voltage is required, so there is a possibility that the capability of the high-voltage power supply may be insufficient.

  As a result of investigations by the inventors, it was found that the discharge current amount when applying the AC bias to the charging roller can be controlled by controlling the relative dielectric constant of the fine particles even for fine particles having a high volume resistivity.

If the electric volume resistance of the fine particles existing on the surface of the charging roller 120 is less than 1.0 × 10 ¹¹ Ω · cm, the surface resistance of the charging roller 120 is lowered and the discharge start voltage is lowered. According to the present invention, by setting the volume resistivity of the fine particles to 1.0 × 10 ¹¹ Ω · cm or more, even if the fine particles adhere to the surface of the charging roller 120, the surface resistance of the charging roller 120 is not reduced, so the discharge start voltage is reduced. do not do.

  In addition, the control of the relative dielectric constant of the fine particles is effective in order to allow a current to flow during AC charging even if high resistance fine particles adhere to the surface of the charging roller 120. The phenomenon that the charging current flows even when high-resistance fine particles adhere to the surface of the charging roller 120 occurs when the relative dielectric constant of the fine particles at 1 kHz is 1.7 or more and 2.5 or less. If the volume resistivity is high and the relative dielectric constant is higher than this range, the amount of current increases during AC charging, resulting in a low discharge start voltage. On the other hand, if the relative dielectric constant is lower than this range, the discharge start voltage becomes high, so it is necessary to prepare a high-output high-voltage power supply.

  It is preferable that charging is performed in a state where fine particles cover the surface of the charging roller 120 at 10% or more and 70% or less at the contact portion between the charging roller 120 and the photoreceptor 110. If it is less than 10%, that is, if there are few high-resistance fine particles, the discharge start voltage becomes low, and the amount of discharge current for avoiding discharge unevenness becomes large. Even if it exceeds 70%, the amount of fine particles having the above-mentioned relative permittivity is large, so that current flows easily, and the amount of discharge current is also increased.

  In the image forming process in which the photosensitive member is negatively charged, fine particles having negative charge are employed. Since the fine particles present at the contact portion between the charging roller 120 and the photosensitive member 110 are negatively charged, the fine particles are maintained on the surface of the charging roller without transferring the fine particles to the negatively charged photosensitive member surface. I think it can be done.

  Preferably, fine particles having a zeta potential ζ (A) of −40 mV to −10 mV, more preferably −35 mV to −15 mV can be applied.

  Therefore, in order to control the dielectric constant within the above range with a high-resistance material, the effect can be obtained in a structure in which a number of smaller particles are combined in one particle in the embodiment described later. I understood. For example, this can be achieved by forming fine particles in a state in which a large number of silica fine particles are present on and / or inside the organic particles. Or even if it is a silica single material, it can achieve by combining a some fine particle and forming a fine particle.

  The reason why the fine particles in the present invention exhibit such physical properties is not clear, but when a large number of fine particles are configured as a single body, it is considered that a large number of interfaces exist in one particle.

  When a voltage is applied to such fine particles, dielectric polarization occurs at each interface, so that the relative dielectric constant increases, and it is considered that an AC current flows easily even though the electric resistance is high.

  For example, this can be achieved by forming organic-inorganic composite fine particles in a state in which a large number of silica fine particles are present on and / or inside the organic particles.

  Specifically, the organic-inorganic composite fine particles have a structure in which inorganic fine particles are embedded in vinyl resin particles, and the inorganic fine particles are exposed on the surface of the organic-inorganic composite fine particles, and the convex portions derived from the inorganic fine particles are not present. It is an existing structure.

  Or even if it is a silica single material, it can achieve by forming the unification silica fine particle of the state which the several silica fine particle united.

  By adopting such a configuration, it is possible to allow an AC current to flow by exhibiting a suitable dielectric constant while having a high volume resistivity.

  The fine particles of the present invention preferably have a shape factor SF-2 of 103 or more and 220 or less measured using an enlarged image of the organic-inorganic composite fine particles photographed using a scanning electron microscope.

  The particle having a shape factor SF-2 of 103 or more and 220 or less indicates that the fine particle of the present invention has a convex portion, and is an index of the convex shape. When the shape factor SF-2 is in the above range, the number of contact points with the surface of the charging roller is increased, so that it is considered that the shape factor SF-2 tends to adhere to the surface of the charging roller. The value of SF-2 is more preferably 120 or less.

  The fine particles of the present invention preferably have a number average particle diameter of 70 nm to 500 nm. In the case where the number average particle diameter is in the above range, it is considered that a large number of interfaces are formed in the primary fine particles and the relative dielectric constant can be in a suitable range.

  The value of the number average particle diameter is more preferably 70 nm or more and 350 nm or less.

  The inorganic fine particles used for the organic / inorganic composite fine particles are not particularly limited, but in the present invention, at least one inorganic oxide selected from the group consisting of silica and titanium oxide is used in terms of adhesion to the surface of the charging roller. It is preferable that it is a physical particle.

  The fine particles of the present invention can be used by external addition to toner. Since the fine particles of the present invention are present on the surface of the photoreceptor together with the transfer residual toner and fog toner, the above-mentioned effects can be obtained.

  Even when externally added to the toner, fine particles having a negative charge are used for the above-mentioned reasons.

  Further, the effect of the present invention is obtained when the release rate of the fine particles from the toner is 10% or more, and the effect is obtained stably when the release rate is 40% or more.

  In order to be suitably applied to each process in the image forming process, the absolute value | ζ of the difference between the zeta potential ζ (T) of the toner base particles and the zeta potential ζ (A) of the fine particles from the viewpoint of negative chargeability of the toner (T) −ζ (A) | is set to 50 mV or less. That is, in order to make the charge amount of the negatively chargeable toner within a suitable range, it is preferable that the zeta potential of the fine particles is in the range of plus 50 mV to minus 50 mV with respect to the zeta potential of the toner base particles. Furthermore, it is more preferable to set it in a range of plus 40 mV to minus 40 mV.

[Evaluation of uneven charging]
Evaluation of charging unevenness is performed as follows using an image forming apparatus such as a multifunction peripheral.

  The charge amount of the photosensitive member is set by adjusting the discharge current amount of primary charging and adjusting the DC bias. The image exposure is turned off or a solid image is output, and the development DC bias is adjusted so that the image reflection density on the paper when an analog halftone image is formed is 0.3 to 0.6. When the output image is visually observed, it is confirmed whether there is a spot-like image defect, and the charging unevenness is evaluated for each discharge current setting.

[Binder resin]
Examples of the binder resin used in the present invention include polyester resins, vinyl resins, epoxy resins, and polyurethane resins.

[Magnetic material]
When the present invention is applied to a magnetic toner, the magnetic material contained in the magnetic toner includes iron oxides such as magnetite, hematite and ferrite, metals such as iron, cobalt and nickel, and these metals and aluminum and cobalt. And alloys of metals such as copper, lead, magnesium, tin, zinc, antimony, bismuth, calcium, manganese, titanium, tungsten, vanadium and mixtures thereof.

  These magnetic materials have an average particle diameter of 2 μm or less, preferably 0.05 μm or more and 0.5 μm or less. The amount contained in the toner is preferably 40 parts by mass or more and 95 parts by mass or less with respect to 100 parts by mass of the resin component.

[wax]
The toner of the present invention may contain a wax.

  The waxes used in the present invention include the following. For example, low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, aliphatic hydrocarbon wax such as Fischer-Tropsch wax; oxide of aliphatic hydrocarbon wax such as oxidized polyethylene wax Or block copolymers thereof; plant waxes such as candelilla wax, carnauba wax, waxy wax, jojoba wax; animal waxes such as beeswax, lanolin, spermaceti; mineral systems such as ozokerite, ceresin, petrolactam; Waxes; waxes mainly composed of aliphatic esters such as montanic acid ester wax and castor wax; those obtained by partially or fully deoxidizing aliphatic esters such as deoxidized carnauba wax . Further, saturated linear fatty acids such as palmitic acid, stearic acid, montanic acid, or long-chain alkyl carboxylic acids having a long-chain alkyl group; unsaturated fatty acids such as brassic acid, eleostearic acid, and valinal acid; stearyl alcohol Saturated alcohol such as eicosyl alcohol, behenyl alcohol, cannavir alcohol, seryl alcohol, melyl alcohol, or alkyl alcohol having a long chain alkyl group; polyhydric alcohol such as sorbitol; linoleic acid amide, oleic acid amide, lauric acid Aliphatic amides such as acid amides; saturated aliphatic bisamides such as methylene bisstearic acid amide, ethylene biscapric acid amides, ethylene bislauric acid amides, hexamethylene bisstearic acid amides; Unsaturated fatty acid amides such as inamide, hexamethylenebisoleic acid amide, N, N′-dioleyl adipic acid amide, N, N′-dioleyl sebacic acid amide; m-xylene bisstearic acid amide, N, Aromatic bisamides such as N'-distearylisophthalamide; aliphatic metal salts such as calcium stearate, calcium laurate, zinc stearate and magnesium stearate (commonly referred to as metal soap); aliphatic hydrocarbons Wax grafted with a vinyl monomer such as styrene or acrylic acid; partially esterified product of fatty acid and polyhydric alcohol such as behenic acid monoglyceride; hydroxyl group obtained by hydrogenating vegetable oil Methyl ester compounds It is.

  In addition, these waxes have a sharp molecular weight distribution using a press sweating method, a solvent method, a recrystallization method, a vacuum distillation method, a supercritical gas extraction method or a melt liquid crystal deposition method, a low molecular weight solid fatty acid, a low molecular weight A solid alcohol, a low molecular weight solid compound, and other impurities are preferably used.

  Specific examples of the wax that can be used as a release agent include Biscol (registered trademark) 330-P, 550-P, 660-P, TS-200 (Sanyo Chemical Industries), high wax 400P, 200P, 100P, 410P, 420P, 320P, 220P, 210P, 110P (Mitsui Chemicals), Sazol H1, H2, C80, C105, C77 (Schumann Sazol), HNP-1, HNP-3, HNP-9, HNP-10, HNP-11, HNP-12 (Nippon Seiwa Co., Ltd.), Unilin (registered trademark) 350, 425, 550, 700, Unicid (registered trademark), Unicid (registered trademark) 350, 425, 550, 700 (Toyo Petrolite) ), Wax, beeswax, rice wax, candelilla wax, carnauba wax (Serari Co., Ltd.) Available at NODA possible), and the like.

[Charge control agent]
In the toner used in the present invention, in order to control the charge amount and charge amount distribution of the toner particles, a charge control agent is blended into the toner particles (internal addition) or mixed with the toner particles (external addition). Is preferred.

  Examples of the negative charge control agent for controlling the toner to be negatively charged include organometallic complexes and chelate compounds. Examples of the organometallic complex include a monoazo metal complex, an acetylacetone metal complex, an aromatic hydroxycarboxylic acid metal complex, and an aromatic dicarboxylic acid metal complex. Further, the negative charge control agent includes aromatic hydroxycarboxylic acid, aromatic monocarboxylic acid and aromatic polycarboxylic acid and metal salts thereof; anhydrous hydroxycarboxylic acid, aromatic monocarboxylic acid and aromatic polycarboxylic acid anhydride. Things. Furthermore, ester compounds of aromatic hydroxycarboxylic acid, aromatic monocarboxylic acid and aromatic polycarboxylic acid, and phenol derivatives such as bisphenol are included.

  Preferred for negative charging are, for example, Spiron Black TRH, T-77, T-95 (Hodogaya Chemical), BONTRON (registered trademark) S-34, S-44, S-54, E-84, E- 88, E-89 (Orient Chemical).

  These charge control agents can be used alone or in combination of two or more. Moreover, charge control resin can also be used and can also be used together with said charge control agent.

  The above charge control agent is preferably used in the form of fine particles. When these charge control agents are internally added to the toner particles, it is preferable to add 0.1 parts by mass or more and 20.0 parts by mass or less to the toner particles with respect to 100.0 parts by mass of the binder resin.

  The toner particles used in the present invention may be produced by any method such as a pulverization method or a polymerization method, but a production method by a pulverization method is preferable in terms of shape control.

  Further, after sufficiently mixing the toner constituent materials as described above with a ball mill or other mixer, the mixture is thoroughly kneaded using a heat kneader such as a hot roll, kneader or extruder, cooled, solidified, and then finely pulverized. A method of performing surface modification of toner particles using a surface modification device after pulverization and classification is more preferable.

  For example, as a mixer, Henschel mixer (made by Mitsui Mining); Super mixer (made by Kawata); Ribocorn (made by Okawara Seisakusho); Nauter mixer, turbulizer, cyclomix (made by Hosokawa Micron); Spiral pin mixer (Manufactured by Taiheiyo Kiko Co., Ltd.);

  As a pulverizer, a counter jet mill, a micron jet, an inomizer (manufactured by Hosokawa Micron); an IDS type mill, a PJM jet pulverizer (manufactured by Nippon Pneumatic Industry Co., Ltd.); a cross jet mill (manufactured by Kurimoto Iron Works Co., Ltd.); SK Jet Oh Mill (manufactured by Seishin Enterprise Co., Ltd.); Kryptron (manufactured by Kawasaki Heavy Industries, Ltd.); Turbo Mill (manufactured by Turbo Industry Co., Ltd.); Super Rotor (manufactured by Nissin Engineering Co., Ltd.).

Classifiers include: Classy, Micron Classifier, Spedic Classifier (manufactured by Seishin Enterprise); Turbo Classifier (manufactured by Nissin Engineering); Micron Separator, Turbo Flex (ATP), TSP Separator (manufactured by Hosokawa Micron) Elbow Jet (manufactured by Nippon Steel & Mining Co., Ltd.), Dispersion Separator (manufactured by Nippon Pneumatic Industrial Co., Ltd.); YM Microcut (manufactured by Yaskawa Shoji Co., Ltd.).
Examples of the surface modification apparatus include faculty (manufactured by Hosokawa Micron), mechanofusion (manufactured by Hosokawa Micron), nobilta (manufactured by Hosokawa Micron), hybridizer (manufactured by Nara Machinery), inomizer (manufactured by Hosokawa Micron), and theta composer. (Made by Tokuju Kogakusha Co., Ltd.) and Mechanomyl (Made by Okada Seiko Co., Ltd.)

  As a sieving device used to screen coarse particles, Ultrasonic (manufactured by Sakae Sangyo Co., Ltd.); Resonator Sheave, Gyroshifter (Deoksugaku Kojo Co., Ltd.); Vibrasonic System (Dalton Co., Ltd.); Soniclean (Shinto) (Industry company); Turbo screener (Turbo industry company); Micro shifter (Ogino industry company); Circular vibration sieve, etc.

  The toner particles of the present invention are preferably sufficient when the weight average particle size is 2.5 μm or more and 10.0 μm or less, preferably 5.0 μm or more and 9.0 μm or less, more preferably 6.0 μm or more and 8.0 μm or less. Is effective and preferable.

  Further, the toner according to the present invention can be manufactured by sufficiently mixing the above-described desired external additives with a mixer such as a Henschel mixer.

  A method for measuring physical properties of the toner of the present invention is as follows. Examples described later are also based on this method.

[Production of toner]
An example of a toner manufacturing method using the toner processing apparatus of the present invention will be described.

  The method for producing the toner is not particularly limited, and a conventionally known production method can be used. Here, a toner manufacturing procedure using a pulverization method will be described.

  In the raw material mixing step, as a material constituting the toner particles, a binder resin, a colorant, a wax, and, if necessary, other components such as a charge control agent are weighed and mixed in a predetermined amount and mixed. Examples of the mixing apparatus include a super mixer (manufactured by Kawata Co., Ltd.), a Henschel mixer, a mechano hybrid (manufactured by Nippon Coke Industries, Ltd.), a nauter mixer (manufactured by Hosokawa Micron Co., Ltd.), and the like.

  Next, the mixed material is melt-kneaded to disperse wax or the like in the binder resin. In the melt-kneading step, a batch kneader such as a pressure kneader or a Banbury mixer, or a continuous kneader can be used. Due to the advantage of continuous production, single-screw or twin-screw extruders are the mainstream. For example, KTK type twin screw extruder (manufactured by Kobe Steel Co., Ltd.), TEM type twin screw extruder (manufactured by Toshiba Machine Co., Ltd.), PCM kneader (manufactured by Ikekai Co., Ltd.), Needex (manufactured by Nippon Coke Industries, Ltd.) ).

  Furthermore, the resin composition obtained by melt-kneading may be rolled with two rolls or the like and cooled with water or the like in the cooling step.

  Next, the cooled product of the resin composition is pulverized to a desired particle size in the pulverization step. In the pulverization process, after coarse pulverization with a pulverizer such as a crusher or hammer mill, the pulverizer is further finely pulverized with a pulverizer such as a kryptron system (Earth Technica Co., Ltd.) or a turbo mill (Freunde Turbo Co., Ltd.). Smash.

  After that, if necessary, classification is performed using a classifier or sieving machine such as an inertia class elbow jet (manufactured by Nippon Steel Mining), centrifugal force class TSP separator (manufactured by Hosokawa Micron), or Faculty (manufactured by Hosokawa Micron). Then, toner particles are obtained.

[External additive]
In the toner suitably used in the present invention, an external additive that is fine particles is fixed to the surface of the toner particles. By fixing the fine particles, the fluidity and transferability of the toner particles can be improved.

  The external additive fixed to the toner particle surface preferably contains fine particles of any one of titanium oxide, alumina oxide, and silica fine particles.

  The surface of the fine particles contained in the external additive is preferably subjected to a hydrophobic treatment. The hydrophobizing treatment is preferably performed by a coupling agent such as various titanium coupling agents and silane coupling agents; fatty acids and metal salts thereof; silicone oils; or a combination thereof.

  Among various combinations, it is preferable to add a large particle size external additive having a number average particle size of 80 nm to 300 nm as one of the fine particles. This is because it has a function as a spacer particle and mainly improves transferability. Examples of the material include silica, alumina, titanium oxide, cerium oxide and the like.

  In the case of the silica, any silica produced using a conventionally known technique such as a gas phase decomposition method, a combustion method, or a deflagration method can be used. Among these, silica particles obtained by a sol-gel method capable of sharpening the particle size distribution are preferable.

  The content of the external additive in the toner is preferably 0.1% by mass or more and 10.0% by mass or less, and more preferably 0.5% by mass or more and 8.0% by mass or less. The external additive may be a combination of a plurality of types of fine particles.

  Hereinafter, methods for measuring various physical properties of the toner and the like in the present invention will be described.

[Measurement method of relative permittivity]
The relative dielectric constant of the fine particles is measured as follows.

  As measuring devices, ARES manufactured by TA Instruments and 4284A Precision LCR meter manufactured by Hewlett-Packard Company are used.

  When a dielectric constant measuring electrode having a diameter of 25 mm is mounted on the ARES and a sample fine particle is placed between the electrodes and a load of 0.49 to 1.96 N (50 to 200 g) is applied, the distance between the electrodes is 0.5 to 3 Adjust to 0.0 mm.

The electrostatic capacity at an applied voltage of 1.0 V and a frequency of 1.0 kHz is measured using 4284A, and the relative dielectric constant is calculated using the following equation.
ε _r = (L × C) ÷ (S × ε ₀ )
ε _r : relative dielectric constant L: distance between electrodes (m)
S: Electrode area (square m)
C: Capacitance (F / m)
Dielectric constant of vacuum = 5.854 × 10 ⁻¹² (F / m)

[Measurement method of volume resistivity]
The volume resistivity of the fine particles is measured as follows.

  As a device, a Keithley Instruments 6517 type electrometer / high resistance system is used. An electrode having a diameter of 25 mm is connected to 6517, and 0.1 to 0.5 g of sample fine particles are placed between the electrodes, and a load of 1.0 to 2.0 N (102 to 204 g) is applied. taking measurement.

In 6517, the resistance value when a voltage of 1,000 V is applied to the sample for 1 minute is measured, and the volume resistivity is calculated using the following equation.
Volume resistivity (Ω · cm) = R ÷ L
R: Resistance value (Ω)
L: Distance between electrodes (cm)

[Measurement method of zeta potential]
The zeta potential (ζ (T)) of the toner particles and the zeta potential (ζ (A)) of the toner particles when dispersed in water are measured using a Zetasizer Nano-Zs (manufactured by Sysmex Corporation). It was. ζ (T) is measured by the following procedure.

  As a dispersion, 0.1 g of toner particles is added to 9.9 g of methanol, and the mixture is dispersed for 5 minutes with an ultrasonic disperser (manufactured by Nihon Riken Kikai Co., Ltd.) to prepare a dispersion.

  This dispersion is put with a dropper so that bubbles do not enter the DTS1060C-Clear Disposable Zeta Cell attached to the apparatus.

  This cell was attached to a measuring instrument, and the zeta potential was measured at 25 ° C. This measurement is performed, and the arithmetic average value of three times is defined as ζ (T) in the present invention.

  Subsequently, ζ (A) is measured by the following procedure.

  As a dispersion, 0.1 g of fine particles is added to 9.9 g of methanol, and the mixture is dispersed for 5 minutes with an ultrasonic disperser (manufactured by Nihon Riken Kikai Co., Ltd.) to prepare a dispersion.

  However, when the first external additive white precipitate and suspended matter are present in the dispersion, the amount of the Triton X-100 aqueous solution added is appropriately adjusted. This dispersion is put with a dropper so that bubbles do not enter the DTS1060C-Clear Disposable Zeta Cell attached to the apparatus.

  This cell was attached to a measuring instrument, and the zeta potential was measured at 25 ° C. This measurement is performed, and the arithmetic average value of three times is defined as ζ (A) in the present invention.

  For example, when measuring the zeta potential of magnetic toner particles and fine particles from magnetic toner to which fine particles are externally added, the magnetic toner particles and fine particles can be measured separately from the magnetic toner. The magnetic toner is ultrasonically dispersed in methanol to remove the external additive, and left to stand for 24 hours. The magnetic toner particles that have settled and the fine particles dispersed in the supernatant can be separated and recovered and sufficiently dried to be isolated. When a plurality of fine particles and external additives are externally added to the magnetic toner, the measurement can also be performed by separating and isolating the supernatant liquid by a centrifugal separation method.

[Method for Measuring Weight Average Particle Size (D4) of Toner]
The weight average particle diameter (D4) is calculated as follows.

  As a measuring device, a precise particle size distribution measuring device “Coulter Counter Multisizer 3” (registered trademark, manufactured by Beckman Coulter, Inc.) using a pore electrical resistance method equipped with a 100 μm aperture tube is used. For setting the measurement conditions and analyzing the measurement data, the attached dedicated software “Beckman Coulter Multisizer 3 Version 3.51” (manufactured by Beckman Coulter, Inc.) is used. The measurement is performed with 25,000 effective measurement channels. As the electrolytic aqueous solution used for the measurement, a solution obtained by dissolving special grade sodium chloride in ion-exchanged water so as to have a concentration of 1% by mass, for example, “ISOTON II” (manufactured by Beckman Coulter, Inc.) can be used.

  Prior to measurement and analysis, the dedicated software is set as follows.

  On the “Change Standard Measurement Method (SOM)” screen of the dedicated software, set the total count in the control mode to 50000 particles, set the number of measurements once, and set the Kd value to “standard particles 10.0 μm” (Beckman Coulter, Inc.) Set the value obtained using

  By pressing the “Threshold / Noise Level Measurement Button”, the threshold and noise level are automatically set. In addition, the current is set to 1600 μA, the gain is set to 2, the electrolyte is set to ISOTON II, and the “aperture tube flush after measurement” is checked.

  In the “Pulse to particle size conversion setting” screen of the dedicated software, the bin interval is set to logarithmic particle size, the particle size bin is set to 256 particle size bin, and the particle size range is set to 2 μm to 60 μm.

  The specific measurement method is as follows.

  (1) Put 200 ml of the aqueous electrolytic solution into a glass 250 ml round bottom beaker for exclusive use of Multisizer 3, set it on a sample stand, and stir the stirrer rod counterclockwise at 24 rpm. Then, the dirt and bubbles in the aperture tube are removed by the “aperture flush” function of the dedicated software.

  (2) 30 ml of the electrolytic aqueous solution is placed in a glass 100 ml flat bottom beaker. As a dispersant, "" Contaminone N "(a nonionic surfactant, an anionic surfactant, a 10% by weight aqueous solution of a neutral detergent for washing a pH7 precision measuring instrument comprising an organic builder, Wako Pure Chemical Industries, Ltd. 0.3 ml of a diluted solution obtained by diluting the product 3) with ion-exchanged water.

  (3) Two oscillators with an oscillation frequency of 50 kHz are incorporated with the phase shifted by 180 degrees, and an ultrasonic disperser “Ultrasonic Dispersion System Tetora 150” (manufactured by Nikka Ki Bios) having an electrical output of 120 W is prepared. Into the water tank of the ultrasonic disperser, 3.3 l of ion-exchanged water is added, and 2 ml of Contaminone N is added to the water tank.

  (4) The beaker of (2) is set in the beaker fixing hole of the ultrasonic disperser, and the ultrasonic disperser is operated. And the height position of a beaker is adjusted so that the resonance state of the electrolyte solution liquid surface in a beaker may become the maximum.

  (5) In a state where the electrolytic aqueous solution in the beaker of (4) is irradiated with ultrasonic waves, 10 mg of the object to be measured is added to the electrolytic aqueous solution little by little and dispersed. Then, the ultrasonic dispersion process is continued for another 60 seconds.

  In the ultrasonic dispersion, the temperature of the water tank is appropriately adjusted so as to be 10 ° C. or higher and 40 ° C. or lower.

  (6) To the round bottom beaker of (1) installed in the sample stand, the electrolyte aqueous solution of (5) in which the measurement object is dispersed is dropped using a pipette, and the measurement concentration is adjusted to 5%. To do. Measurement is performed until the number of measured particles reaches 50,000.

  (7) The measurement data is analyzed with the dedicated software attached to the apparatus, and the weight average particle diameter (D4) is calculated. The “average diameter” on the “analysis / volume statistics (arithmetic average)” screen when the graph / volume% is set in the dedicated software is the weight average particle diameter (D4).

[Measurement method of number average particle diameter of fine particles]
Measurement of the number average particle diameter of the fine particles adhered to the charging roller surface or the toner surface is performed using a scanning electron microscope “S-4800” (trade name; manufactured by Hitachi, Ltd.). The charging roller or toner to which the fine particles are adhered is observed, and the major axis of 100 fine particles is randomly measured in the field of view enlarged up to 200,000 times to obtain the number average particle size. The observation magnification is appropriately adjusted according to the size of the external additive.

[Measurement of particle coverage on charging roller surface]
The surface of the charging roller is photographed 500 to 1000 times using an optical microscope, and the photographed image is binarized so that the area where the fine particles are attached can be identified.

  The binarization processing of the photographed image uses Image-Pro Plus manufactured by Media Cybernetics as image analysis software, and calculates the area ratio from the image binarized with a threshold of 50% to obtain the coverage ratio.

[Developer preparation method and toner triboelectric charge measurement method]
A magnetic carrier (standard carrier N-01 prepared by the Imaging Society of Japan) and toner are weighed in a 50 ml polybin so that the total amount is 5.0 g, and the magnetic carrier and toner are laminated in a room temperature and humidity environment. Humidify to (23 ° C., 60%) for 24 hours. After humidity control, the lid of the polybin was closed, and it was rotated 15 times at a speed of 1 rotation per second by a roll mill. Subsequently, the sample together with the plastic bottle was attached to a shaker, shaken at a stroke of 150 times per minute, and a developer for measurement was prepared by mixing the toner and the magnetic carrier for 5 minutes. In this operation, the developer was prepared such that the toner was 3% by mass, 5% by mass, and 7% by mass with respect to the total amount of the developer (for example, if 3% by mass, the magnetic carrier was 4.85 g and the toner was 0.15 g. Become).

  As a device for measuring the triboelectric charge amount, a suction separation type charge amount measuring device Sepasoft STC-1-C1 type (manufactured by Sankyo Piotech) was used. A 20 μm mesh (metal mesh) with an opening of 20 μm is placed on the bottom of the sample folder (Faraday cage), and 0.20 g of developer is placed on the mesh and covered. The mass of the entire sample folder at this time is weighed and is defined as W1 (g). Next, the sample folder is installed in the main body, and the air volume control valve is adjusted so that the suction pressure is 6 kPa. In this state, suction is performed for 1 minute to remove the toner by suction. The charge at this time is q (mC). Further, the mass of the entire sample folder after suction is weighed and is defined as W2 (g). Since q obtained at this time is measuring the charge of the carrier, the toner triboelectric charge amount has the opposite polarity. The absolute value of the triboelectric charge amount Q (mC / kg) of the developer is calculated as follows: The measurement was also performed in a normal temperature and humidity environment (23 ° C., 60%). Triboelectric charge Q (mC / kg; μC / g) = q / (W1-W2)

[Measurement method of fine particle release rate from toner]
In belt donor plurality of external additive is externally added, when measuring the liberation percentage of fine particles of the present invention to remove the fine particles and the external additive from the preparative toner particles, further isolating a plurality of types of external additives・ It needs to be collected.

Specific examples of the method include the following methods.
(1) placed bets toner 5g sample bottle, methanol is added 200 ml.
(2) The sample is dispersed for 5 minutes with an ultrasonic cleaner to separate the external additive.
(3) suction filtration (10 [mu] m membrane filter) and separates the door toner particles and external additive. In the case of magnetic toner , a neodymium magnet may be applied to the bottom of the sample bottle to fix the magnetic toner particles and only the supernatant liquid may be separated.
(4) Perform the above (2) and (3) three times.

By the operation, externally added particulates and the external additive is isolated from preparative toner particles. The collected aqueous solution is centrifuged to separate and collect the silica fine particles and the fine particles of the present invention. Next, the solvent is removed, the film is sufficiently dried with a vacuum drier, and the weight is measured to obtain the free amount of fine particles.

<Measuring Method of Shape Factor SF-2 of Fine Particle>
The shape factor SF-2 of the fine particles was calculated as follows by observing the fine particles using a scanning electron microscope “S-4800” (trade name; manufactured by Hitachi, Ltd.).

Although the observation magnification was appropriately adjusted according to the size of the fine particles, the image processing software “Image-Pro Plus 5.1J” (manufactured by Media Cybernetics) was used in the field of view enlarged to 100,000 to 200,000 times. The perimeter and area of the particles were calculated. The shape factor SF-2 was calculated by the following formula, and the average value was defined as the shape factor SF-2 of the fine particles.
SF-2 = (perimeter of particle) ² / area of particle × 100 / 4π

  Hereinafter, the present invention will be described with respect to specific image forming methods, fine particle manufacturing methods, and toner manufacturing methods with examples and comparative examples, but the present invention is not limited to these examples.

[Organic inorganic composite fine particles 1 to 4]
The organic-inorganic composite fine particles can be produced according to the description in the examples of WO 2013/063291.

  As the organic-inorganic composite fine particles used in Examples described later, those prepared according to Example 1 of WO 2013/066291 using silica shown in Table 1 were prepared. Table 1 shows the physical properties of the organic-inorganic composite fine particles 1 to 4.

[Inorganic fine particles 1]
After supplying oxygen gas to the burner at 30 Nm ³ / h and igniting the ignition burner, hydrogen gas is supplied to the burner at 50 Nm ³ / h to form a flame. The raw material silicon tetrachloride is charged at 100 kg / h for gasification, the residence time is set to 0.010 sec, the flame hydrolysis reaction is performed, and the generated silica powder is recovered. Thereafter, the obtained silica powder is transferred to an electric furnace and spread in a thin layer, and then subjected to heat treatment at 700 ° C. to sinter and agglomerate to obtain coalesced fine particles. The physical properties are shown in Table 1.

[Inorganic fine particles 2]
As the inorganic fine particles 2, a base BET100 obtained by a fumed method and silica having a primary particle diameter of 25 nm are used.

[Inorganic fine particles 3]
The inorganic fine particles 3 are obtained by a general sol-gel method using a wet method.

  In a glass reactor equipped with a stirrer, a dropping funnel and a thermometer, 693.0 g of methanol, 46.0 g of water and 55.3 g of 5.4 mass% aqueous ammonia solution were added as alcohol solvents, and methanol, water and ammonia were added. Prepare a mixed solution. The obtained mixed solution is adjusted to a reaction temperature of 45 ° C., stirred while maintaining the reaction temperature, and the dropwise addition time of tetramethoxysilane is dropped for 8 hours. The ammonia water is adjusted so that dropping is completed one hour earlier than tetramethoxysilane. After completion of the dropwise addition, the mixture is stirred for 1 hour to cause a hydrolysis reaction to obtain a methanol-water dispersion of sol-gel silica fine particles.

  The dispersion is then heated to 75 ° C. to distill off 1320 g of methanol and then add 1320 g of water. Then, the dispersion is heated to 90 ° C. to distill off 532.4 g of methanol to obtain an aqueous dispersion of sol-gel silica fine particles.

  After adding 1584 g of methyl isobutyl ketone to the aqueous dispersion, methanol and water are distilled off at 100 ° C./15 hours.

After cooling the obtained methyl isobutyl ketone dispersion of sol-gel silica to 25 ° C., 322 g of hexamethyldisilazane was added as a surface treating agent (0.24 mol relative to 1 mol of SiO ₂ unit), and 110 ° C./5 Surface treatment is performed by reacting for a time.

  The inorganic fine particles 3 are obtained by distilling off the solvent from the dispersion at 80 ° C. under reduced pressure. The physical properties are shown in Table 1.

[Inorganic fine particles 4]
As the inorganic fine particles 4, titanium oxide having a primary particle diameter of 270 nm and physical properties shown in Table 1 is used.

[Inorganic fine particles 5]
The inorganic fine particles 5 use alumina having a primary particle diameter of 200 nm and physical properties shown in Table 1.

[Particle supply method]
The contact charging means applied to the present invention includes a fine particle supply means 400 shown in FIG.

  The fine particle supply means 400 is attached by modifying a developing device for one-component development generally used in an electrophotographic printer. The container includes a container 402 for storing fine particles, a supply roller 403 for supplying fine particles, a regulating blade 404 for restricting the amount of fine particles supplied to the supply roller, and a coating brush 401 for applying fine particles on the supply roller to the charging roller 120.

  Fine particles are stored in the storage container 402, and the supply roller 403 in contact with the regulating blade 404 is rotated so that the application brush 401 rotates while being in contact with the supply roller 403 and the charging roller 120.

  With this configuration, a certain amount of fine particles can be supplied to the surface of the supply roller 403 via the application brush 401.

  The amount of fine particles supplied to the surface of the charging roller 120 is adjusted by the number of rotations of the supply roller 403. When the rotational speed is reduced, the supply amount is small, and when the rotational speed is increased, the supply amount can be increased.

[Image evaluation]
Image evaluation is performed as follows.

  Laser beam printer manufactured by Hewlett-Packard Company: HP LaserJet M455 modified so that the process speed can be arbitrarily set is used, and the process speed is set to 350 mm / sec. GF-C081 sold by Canon Marketing Japan is used as the printer paper in a temperature 23 ° C. and humidity 50% RH environment. Image evaluation is performed by changing the primary charging current from 10 to 100 μA every 10 μA, and a current value at which a spot image due to charging unevenness does not occur is evaluated as a lower limit of the discharge current.

[Evaluation of discharge current]
A discharge current amount of primary charging is changed from −10 μA to −100 μA every 10 μA, and a halftone image having an image density of 0.3 to 0.6 is output to perform image evaluation. The current value that does not occur is evaluated as the discharge current lower limit value.

  After evaluating this in the initial state of the printer, it is evaluated again after a print endurance test for 10,000 sheets.

[Evaluation of image density]
A 10 × 10 mm test pattern is output on the printer paper, the maximum density of the test pattern portion is measured with an optical densitometer, and the following determination is made.
A: Reflection density of 10th sheet is 1.4 or more B: Reflection density of 10th sheet is 1.3 or more and less than 1.4 C: Reflection density of 10th sheet is 1.2 or more and less than 1.3 (Actual usable level)
D: The reflection density of the tenth sheet is less than 1.2

  An optical densitometer uses a spectral densitometer 504 manufactured by X-Rite Corporation.

[Manufacture of magnetic toner base particles]
-Polyester resin 100 parts by mass-Magnetic iron oxide particles 60 parts by mass-Polyethylene wax (PW2000: manufactured by Toyo Petrolite, melting point 120 ° C)
4 parts by mass / charge control agent (T-77: manufactured by Hodogaya Chemical Co., Ltd.) 2 parts by mass After the above materials were premixed with a Henschel mixer, the mixture was melt-kneaded with a biaxial extruder heated to 110 ° C. and cooled. Coarsely pulverize with a hammer mill to obtain a coarsely pulverized toner. The obtained coarsely pulverized product was coated with a mechanical pulverizer turbo mill (manufactured by Turbo Kogyo Co., Ltd .; coated with chromium alloy plating containing chromium carbide on the rotor and stator surfaces (plating thickness 150 μm, surface hardness HV1050)). And then pulverize by mechanical pulverization.

  The finely pulverized product obtained is classified and removed at the same time by a multi-division classifier (Elbow Jet Classifier manufactured by Nittetsu Mining Co., Ltd.) using the Coanda effect.

  After classification, the surface of the magnetic toner particles is treated using a surface modification device Faculty F-600 (manufactured by Hosokawa Micron) to perform surface modification and fine powder removal.

  Through the above steps, magnetic toner base particles having a weight average particle diameter (D4) of 7.2 μm, an average circularity of 0.957, and an average surface roughness (Ra) of 23.9 nm are obtained as shown in Table 3.

[Production of toner]
[Magnetic toner particles 1]
1.1 parts by mass of the organic / inorganic composite fine particles 1 as the first external additive and 0.5 parts by mass of the inorganic fine particles 2 as the second external additive are added to 100 parts by mass of the magnetic toner base particles. Externally mixed for 15 minutes with a Henschel mixer (FM10C type, manufactured by Nippon Coke Kogyo Co., Ltd.), and sieved with a mesh having an opening of 100 μm to obtain negative triboelectrically magnetic toner particles 1. Table 2 shows various physical properties of the obtained magnetic toner particles 1.

[Magnetic toner particles 2]
The negative triboelectric magnetic toner particles 2 are obtained under the same configuration and conditions as the magnetic toner particles 1 except that the external addition time is 10 minutes. Table 2 shows various physical properties of the obtained magnetic toner particles 2.

[Magnetic toner particles 3]
Magnetic toner particles 3 having negative tribocharging properties are obtained under the same configuration and conditions as the magnetic toner particles 1 except that the external addition mixing time is 5 minutes. Table 2 shows various physical properties of the obtained magnetic toner particles 3.

[Magnetic toner particles 4]
Magnetic toner particles 4 having negative triboelectric charging properties are obtained with the same configuration and conditions as magnetic toner particles 1 except that the external mixing time is 30 minutes. Table 2 shows various physical properties of the obtained magnetic toner particles 4.

[Magnetic toner particles 5]
Instead of the organic / inorganic composite fine particles 1, 1.1 parts by mass of the inorganic fine particles 1 is added as a first external additive. Other than that, negatively triboelectrically magnetic toner particles 5 are obtained under the same configuration and conditions as the magnetic toner particles 2. Table 2 shows various physical properties of the magnetic toner particles 5 thus obtained.

[Magnetic toner particles 6]
0.5 part by mass of the inorganic fine particles 2 is added without adding the organic / inorganic composite fine particles 1.

  Other than that, negatively triboelectrically magnetic toner particles 6 are obtained under the same configuration and conditions as the magnetic toner particles 2. Table 2 shows various physical properties of the magnetic toner particles 6 thus obtained.

<Example 1>
In this embodiment, the organic / inorganic composite fine particles 1 are placed in the fine particle supply means 400, and the supply amount is adjusted so that the coverage of the fine particles on the surface of the charging roller 120 is about 30%. The developing device 140 is filled with magnetic toner particles 6 to evaluate charging unevenness. Table 3 shows the evaluation results of the coverage of the organic-inorganic composite fine particles 1 on the surface of the charging roller 120, the evaluation of the release rate of fine particles from the toner, and the image evaluation results.

<Example 2>
In this embodiment, the supply amount is adjusted so that the coverage of fine particles on the surface of the charging roller 120 is about 15%. Other than that, the charging unevenness is evaluated as the same configuration and conditions as in the first embodiment. The evaluation results are shown in Table 3.

<Example 3>
In this embodiment, the supply amount is adjusted so that the coverage of fine particles on the surface of the charging roller 120 is about 65%. Other than that, the charging unevenness is evaluated as the same configuration and conditions as in the first embodiment. The evaluation results are shown in Table 3.

<Example 4>
In this embodiment, the organic / inorganic composite fine particles 2 are placed in the fine particle supply means 400, and the supply amount is adjusted so that the coverage of the fine particles on the surface of the charging roller 120 is about 30%. Other than that, the charging unevenness is evaluated as the same configuration and conditions as in the first embodiment. The evaluation results are shown in Table 3.

<Example 5>
In this embodiment, the organic / inorganic composite fine particles 3 are placed in the fine particle supply means 400, and the supply amount is adjusted so that the coverage of the fine particles on the surface of the charging roller 120 is about 30%. Other than that, the charging unevenness is evaluated as the same configuration and conditions as in the first embodiment. The evaluation results are shown in Table 3.

<Example 6>
In this embodiment, the organic / inorganic composite fine particles 4 are placed in the fine particle supply means 400, and the supply amount is adjusted so that the coverage of the fine particles on the surface of the charging roller 120 is about 30%. Other than that, the charging unevenness is evaluated as the same configuration and conditions as in the first embodiment. The evaluation results are shown in Table 3.

<Example 7>
In this embodiment, the inorganic fine particles 1 are put in the fine particle supply means 400, and the supply amount is adjusted so that the coverage of the fine particles on the surface of the charging roller 120 is about 30%. Other than that, the charging unevenness is evaluated as the same configuration and conditions as in the first embodiment. The evaluation results are shown in Table 3.

<Example 8>
In this embodiment, the fine particle supply means 400 is not provided, and the developing device 140 is filled with the magnetic toner particles 1 instead. Other than that, the charging unevenness is evaluated as the same configuration and conditions as in the first embodiment. The evaluation results are shown in Table 3.

<Example 9>
In this embodiment, instead of the magnetic toner particles 1, the developing device 140 is filled with the magnetic toner particles 2. Otherwise, the charging unevenness is evaluated as the same configuration and conditions as in Example 8 . The evaluation results are shown in Table 3.

<Example 10>
In this embodiment, instead of the magnetic toner particles 1, the developing device 140 is filled with the magnetic toner particles 3. Otherwise, the charging unevenness is evaluated as the same configuration and conditions as in Example 8 . The evaluation results are shown in Table 3.

[Example 11]
In this embodiment, the organic / inorganic composite fine particles 1 are placed in the fine particle supply means 400, and the supply amount is adjusted so that the coverage of the fine particles on the surface of the charging roller 120 is about 15%. The developing device 140 is filled with magnetic toner particles 2. Other than that, the charging unevenness is evaluated as the same configuration and conditions as in the first embodiment. The evaluation results are shown in Table 3.

<Example 12>
In this embodiment, the charging unevenness is evaluated under the same configuration and conditions as in Embodiment 8 except that the developing device 140 is filled with the magnetic toner particles 5. The evaluation results are shown in Table 3.

<Comparative Example 1>
This comparative example evaluates uneven charging as the same configuration and conditions as in Example 1 except that the fine particle supply unit 400 is not provided. The evaluation results are shown in Table 3.

<Comparative example 2>
In this comparative example, the supply amount is adjusted so that the coverage of the organic-inorganic composite fine particles 1 on the surface of the charging roller 120 is about 5%. Other than that, the charging unevenness is evaluated as the same configuration and conditions as in the first embodiment. The evaluation results are shown in Table 3.

<Comparative Example 3>
In this comparative example, the supply amount is adjusted so that the coverage of the organic-inorganic composite fine particles 1 on the surface of the charging roller 120 is about 80%. Other than that, the charging unevenness is evaluated as the same configuration and conditions as in the first embodiment. The evaluation results are shown in Table 3.

<Comparative Example 4>
In this comparative example, the inorganic fine particles 2 are put in the fine particle supply means 400, and the supply amount is adjusted so that the coverage of the fine particles on the surface of the charging roller 120 is about 30%. Other than that, the charging unevenness is evaluated as the same configuration and conditions as in the first embodiment. The evaluation results are shown in Table 3.

<Comparative Example 5>
In this comparative example, the inorganic fine particles 3 are put in the fine particle supply means 400, and the supply amount is adjusted so that the coverage of the fine particles on the surface of the charging roller 120 is about 30%. Other than that, the charging unevenness is evaluated as the same configuration and conditions as in the first embodiment. The evaluation results are shown in Table 3.

<Comparative Example 6>
In this comparative example, the inorganic fine particles 4 are placed in the fine particle supply means 400, and the supply amount is adjusted so that the coverage of the fine particles on the surface of the charging roller 120 is about 30%. Other than that, the charging unevenness is evaluated as the same configuration and conditions as in the first embodiment. The evaluation results are shown in Table 3.

<Comparative Example 7>
In this comparative example, the inorganic fine particles 5 are placed in the fine particle supply means 400, and the supply amount is adjusted so that the coverage of the fine particles on the surface of the charging roller 120 is about 30%. Other than that, the charging unevenness is evaluated as the same configuration and conditions as in the first embodiment. The evaluation results are shown in Table 3.

<Comparative Example 8>
In this comparative example, the developing device 140 is filled with magnetic toner particles 4. Other than that, the charging unevenness is evaluated as the same configuration and conditions as in Comparative Example 1. The evaluation results are shown in Table 3.

  From the results of Table 3, in the configurations of Examples 1 to 7 in which the fine particles of the present invention are applied to the surface of the charging roller, there are no adverse effects such as uneven charging and defective images at a 100 μA discharge current setting that is normally used for primary charging. Further, even if the amount of discharge current is reduced, uneven charging is less likely to occur, so that it is possible to form an image with a lower discharge current setting than in the prior art.

  In the configurations of Examples 1 to 6, the performance is maintained because the fine particles stably adhere to the surface of the charging roller even after the endurance.

  The same effects can be obtained in the structures of Examples 8 to 10 and 12 in which the fine particles of the present invention are externally added to the toner particles. Since it adheres, performance is maintained.

  In Example 11, the same effect can be obtained even when the fine particles are applied to the surface of the charging roller and externally added to the toner particles.

  In the configurations of Comparative Examples 1 to 8 that do not employ the configuration of the present invention, a spot image due to uneven charging is generated when the amount of discharge current is reduced to less than 100 μA, so the effect of reducing the amount of discharge current is small.

  As described above, by applying the present invention, it is possible to provide an image forming method in which image defects are unlikely to occur even when the discharge current in the contact charging method is reduced, and a toner used in the image forming method.

  DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus, 110 ... Photoconductor (image carrier), 120 ... Charging roller (contact charging means), 124 ... High voltage power supply, 130 ... Laser scanner, 140 ... Developer, 150 ... Transfer roller, 160... Cleaner, 170... Fixer, 200... Recording medium accommodation means, 210... Recording medium transport means, 300... Control means, 400. ··· Container, 403 ··· Feed roller, 404 · · · Restricting blade

Claims (2)

A charging step of charging the image carrier negatively using a contact charging means that contacts the image carrier;
An electrostatic latent image forming step of forming an electrostatic latent image on the image carrier;
Developing the electrostatic latent image with a negatively charged toner to form a toner image;
A transfer step of transferring the toner image to a recording medium;
An image forming method comprising:
A charging bias in which an AC bias and a DC bias are superimposed is applied to the contact charging unit,
In the charging step, charging is performed in a state in which negatively chargeable fine particles are interposed between the contact charging unit and the image carrier so that the surface of the contact charging unit covers 10% or more and 70% or less. Is performed,
The fine particle has a volume resistivity of 1.0 × 10 ¹¹ Ω · cm or more and a relative dielectric constant at 1 kHz of 1.7 or more and 2.5 or less. A charging step of charging the image carrier negatively by applying a charging bias in which an AC bias and a DC bias are superposed using a contact charging means that contacts the image carrier;
An electrostatic latent image forming step of forming an electrostatic latent image on the image carrier;
A developing step of developing the electrostatic latent image with a negatively charged toner to form a toner image;
A transfer step of transferring the toner image to a recording medium;
An image forming method comprising:
The toner has toner base particles containing a binder resin and a colorant, and negatively charged fine particles are externally added to the surface.
The fine particles have a volume resistivity of 1.0 × 10 ¹¹ Ω · cm or more, a relative dielectric constant at 1 kHz of 1.7 or more and 2.5 or less, and a release rate of the fine particles from the toner of 10% or more. There is provided an image forming method.

Images