JP4511332B2 - Full color image forming method - Google Patents

Description

  The present invention relates to a full-color image forming method that can be used in an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction machine using an electrophotographic system.

  As a full-color image forming method, toner on a photosensitive member (for example, a photosensitive drum) is temporarily transferred (primary transfer) to an intermediate transfer member, and then toners of four colors are collectively transferred onto a recording material such as paper (2 Next transfer) is used. In this method, if the transferability of each toner is different at the time of secondary transfer, there may be a large amount of transfer residue, resulting in missing characters or toner scattering due to overtransfer. Therefore, the four color toners must have the same transferability.

  Patent Document 1 below describes a method in which only black toner is used as magnetic toner. However, when this method is applied to the above-described full-color image forming method, the amount of charge is reduced because the magnetic powder is added to the black toner, and the pigment contained in the toner differs depending on the color. The charge amount may vary greatly. The charge amount of the toner affects the transferability of the toner. If the transferability of each toner varies greatly due to the difference in the charge amount, problems such as missing characters and scattered toner occur.

Patent Document 2 describes a method of adjusting the charge amount of toner by adding a charge control agent. However, this method has a problem that safety and cost increase because of the addition of the charge control agent. Furthermore, the addition of the charge control agent has a limit in charge control, and the charge amount may not be adjusted to a certain amount or more.
JP-A-5-249742 JP-A-11-174733

  An object of the present invention is to provide a full-color image capable of suppressing the occurrence of defects such as missing characters and toner scattering by making the transferability of each toner uniform even when the charge amount of the toner is different on the photoreceptor. It is to provide a forming method.

  As a result of intensive studies to solve the above problems, the present inventors have found that the transferability of the toner can be matched by providing a difference in the sphericity of the magnetic toner and the nonmagnetic toner. It came to complete.

  That is, in the full color image forming method of the present invention, each color toner image formed on the surface of the photoreceptor using non-magnetic toner and magnetic toner is transferred onto the intermediate transfer member in a superimposed manner, and then transferred onto the intermediate transfer member. The full-color image forming method of transferring the toner image onto a recording material, wherein the charge amount of the non-magnetic toner is related to the charge amount of the toner before the electrostatic latent image on the photosensitive member is developed and transferred to the intermediate transfer member. When the charge amount of the magnetic toner is 10 μC / g or more, the sphericity of the non-magnetic toner is made larger than the sphericity of the magnetic toner, and the difference between the sphericities is set to 0.03 or more.

  In addition to the above method, the full color image forming method of the present invention has a charge amount of the magnetic toner on the photoreceptor of 1 to 15 μC / g, and a charge amount of the nonmagnetic toner on the photoreceptor of 16 to 40 μC / g. It is characterized by.

  Further, the full color image forming method of the present invention is characterized in that, in addition to the above method, a polymerized toner is used as the non-magnetic toner, and a pulverized toner is used as the magnetic toner.

  According to the present invention, a nonmagnetic toner having a sphericity greater than that of a magnetic toner and a difference in sphericity of 0.03 or more is used. If toner having a difference in sphericity is used, even if the charge amount of the non-magnetic toner and the charge amount of the magnetic toner on the photoconductor are different, if the sphericity of the toner is increased, the toner and the photoconductor Since the contact is made at a point, the adhesive force becomes weak and the transferability becomes high. Therefore, even if the toner has a high charge amount and is in contact with the photoconductor with a strong electric force, the adhesion can be weakened by increasing the sphericity, so that the transferability of each toner can be made uniform. . As a result, it is possible to suppress the occurrence of problems such as missing characters and scattered toner.

  Further, by setting the charge amount of the magnetic toner on the photoconductor to 1 to 15 μC / g and the charge amount of the nonmagnetic toner on the photoconductor to 16 to 40 μC / g, the occurrence of toner scattering, thin layer unevenness and image It is possible to prevent a decrease in density and form a better image.

  Furthermore, when a polymerized toner is used as the nonmagnetic toner and a pulverized toner is used as the magnetic toner, the polymerized toner has a large sphericity, and therefore it becomes easy to make the sphericity of the nonmagnetic toner larger than the sphericity of the magnetic toner.

<Full color image forming method>
Hereinafter, an embodiment of the present invention will be described in detail. In the full color image forming method of the present invention, a non-magnetic toner and a magnetic toner are used. The magnetic toner here is a toner containing a magnetic material as a component, and is used as a black toner because the magnetic material has a dark color. When magnetic toner is used, a carrier is not used when it is used as a one-component developer. Therefore, a mechanism for stirring the carrier and the toner and a mechanism for controlling the toner density become unnecessary, and the cost of the developing unit can be reduced. it can.

  On the other hand, the non-magnetic toner is a toner that does not contain a magnetic material, and includes a two-component toner and a one-component toner. In the present invention, both a two-component toner and a one-component toner can be used as the non-magnetic toner, but it is preferably used as a one-component toner for the reasons described above. Further, since the non-magnetic toner does not contain a magnetic material, it is used as a color toner, that is, a magenta toner, a cyan toner, or a yellow toner.

  In the full-color image forming method of the present invention, the sphericity of the non-magnetic toner is made larger than the sphericity of the magnetic toner, and the difference between the sphericities is 0.03 or more. Is preferably 1 to 15 μC / g, and the charge amount of the nonmagnetic toner on the photoreceptor is preferably 16 to 40 μC / g.

  The magnetic toner is restrained mainly on the developing sleeve by a magnetic force and an electric force. When the charge amount of the magnetic toner on the photoconductor is less than 1 μC / g, the amount of uncharged toner becomes excessive and toner scattering occurs. On the other hand, when the charge amount of the magnetic toner on the photoconductor is larger than 15 μC / g, the charge amount of the developing portion also becomes high, causing thin layer unevenness and image density reduction. Accordingly, the charge amount of the magnetic toner on the photoreceptor is preferably 1 to 15 μC / g.

  The nonmagnetic toner is mainly restrained on the developing sleeve by an electric force. When the charge amount of the non-magnetic toner on the photoreceptor is less than 16 μC / g, toner scattering occurs. On the other hand, when the charge amount of the non-magnetic toner on the photoconductor is larger than 40 μC / g, the charge amount of the developing portion also becomes high, causing thin layer unevenness and image density reduction. Therefore, the charge amount of the nonmagnetic toner on the photoreceptor is preferably 16 to 40 μC / g.

The charge amount of toner on the photoconductor (the charge amount of toner before the electrostatic latent image on the photoconductor is developed and transferred to the intermediate transfer member) is black, cyan, magenta, yellow, etc. in the mono color mode. For each of these colors, a solid patch (2.5 cm × 2.5 cm) with a toner amount of 0.2 to 0.4 mg / cm ² is output, and the toner charge amount of the solid patch on the photoreceptor is measured. It is done.

  Regarding the sphericity of the toner, it is necessary to make the sphericity of the non-magnetic toner larger than the sphericity of the magnetic toner so that the difference in sphericity is 0.03 or more. The non-magnetic toner preferably has a sphericity of 0.93 to 0.99. Note that the sphericity of a toner that is put into practical use is 0.90 or more due to being close to a spherical shape through a pulverization and classification process even when manufactured by a pulverization method, and is often about 0.93. Note that the sphericity of the toner can be increased by, for example, spheroidizing with a surffusion system or the like. The sphericity of the toner can be measured using a measuring device such as FPIA-2100 (manufactured by Sysmex Corporation). The sphericity is an average sphericity measured by a flow type particle image analyzer FPIA-2100 manufactured by Sysmex Corporation, and the circularity of a two-dimensional projection image of toner (perimeter of a circle having the same area as the projection image / projection image) The perimeter of

<Manufacture of toner>
The magnetic toner and non-magnetic toner used in the present invention are produced using a release agent and a charge control agent together with a binder resin. The magnetic toner is manufactured using magnetic powder, and the non-magnetic toner is manufactured using a colorant.

(Binder resin)
The type of the binder resin is not particularly limited. For example, polystyrene resin, polyacrylic resin, styrene-acrylic copolymer, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide And thermoplastic resins such as styrene resins, polyurethane resins, polyvinyl alcohol resins, vinyl ether resins, N-vinyl resins, and styrene-butadiene resins.

  The polystyrene resin may be a styrene homopolymer or a copolymer with another copolymerizable monomer copolymerizable with styrene. As copolymerizable monomers, p-chlorostyrene; vinyl naphthalene; ethylene unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl halides such as vinyl chloride, vinyl bromide, and vinyl fluoride; vinyl acetate, propion Vinyl esters such as vinyl acrylate, vinyl benzoate, vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, acrylic (Meth) acrylic acid esters such as phenyl acid, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate; other acrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide; Vinyl ethers such as nylmethyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidene, etc. N-vinyl compounds of One of these copolymerization monomers can be copolymerized alone with the styrene monomer, or two or more of these copolymerization monomers can be copolymerized with the styrene monomer. The polystyrene resin preferably has two weight average molecular weight peaks (low molecular weight peak and high molecular weight peak). Specifically, the low molecular weight peak is preferably in the range of 3000 to 20000, and the other high molecular weight peak is preferably in the range of 300000 to 1500,000. Furthermore, it is preferable that Mw / Mn is 10 or more for the weight average molecular weight (Mw) and the number average molecular weight (Mn). If the weight average molecular weight peak is within such a range, the toner can be easily fixed, and offset resistance can be improved.

  Examples of the polyester-based resin include resins obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component. Examples of the alcohol component include divalent or trivalent or higher alcohol components, and specific examples include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4- Butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol Diols such as bisphenol A, hydrogenated bisphenol A, bisphenols such as polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; sorbitol, 1,2,3,6- Xanthetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, Examples include trivalent or higher alcohols such as 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5, -trihydroxymethylbenzene.

  Examples of the carboxylic acid component include divalent or trivalent carboxylic acids, acid anhydrides or lower alkyl esters thereof, and include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid. Acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, or n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n- Divalent carboxylic acids such as alkyl succinic acid or alkenyl succinic acid such as octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid and isododecenyl succinic acid; 1,2,4-benzenetricarboxylic acid (Trimellitic acid), 1,2,5-benzene Carboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl- 2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empole trimer acid, etc. And trivalent or higher carboxylic acids.

  The binder resin is preferably a thermoplastic resin from the viewpoint of good fixability, but the cross-linked portion amount (gel amount) measured using a Soxhlet extractor is 10% by weight or less, more preferably 0.1 to 10%. A thermosetting resin may be used as long as the value is within the range of% by weight. By introducing a partially crosslinked structure in this way, it is possible to further improve the storage stability, form retention, and durability of the toner without deteriorating the fixability. Therefore, it is not necessary to use 100% by weight of the thermoplastic resin as the binder resin for the toner, and a crosslinking agent may be added or a part of the thermosetting resin may be used. As the thermosetting resin, for example, an epoxy resin or a cyanate resin can be used. More specifically, one or more of bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, novolac type epoxy resin, polyalkylene ether type epoxy resin, cycloaliphatic type epoxy resin, cyanate resin, etc. Combinations are listed.

  When the binder resin is used in the production of a magnetic toner, in order to improve the dispersibility of the magnetic powder, at least one functional group selected from a hydroxyloxy (hydroxy acid) group, a carboxyl group, an amino group, and a glycidoxy (epoxy) group It is preferable to use a binder resin having in the molecule. In addition, it can be confirmed using an FT-IR apparatus whether it has these functional groups, and also can be quantified using a titration method.

  In the binder resin, the glass transition point (Tg) is preferably set to a value in the range of 55 to 70 ° C. When the glass transition point of the binder resin is less than 55 ° C., the obtained toners are fused with each other, and the storage stability tends to be lowered. On the other hand, when the glass transition point of the binder resin exceeds 70 ° C., the fixability of the toner tends to be poor. In addition, the glass transition point of binder resin can be calculated | required from the change point of specific heat using a differential scanning calorimeter (DSC).

(Release agent)
Examples of mold release agents include plant waxes such as carnauba wax, sugar wax, and wood wax; animal waxes such as beeswax, insect wax, whale wax, and wool wax; Fischer-Tropsch wax and polyethylene wax having ester in the side chain And synthetic hydrocarbon waxes such as polypropylene wax. Further, the release agent preferably has an endothermic main peak in a range of 70 to 135 ° C. in an endothermic curve by a differential scanning calorimeter. This is because when the endothermic main peak is less than 70 ° C., toner blocking and hot offset may occur, and when the endothermic main peak exceeds 135 ° C., low-temperature fixability may not be obtained. The amount of the wax added is preferably in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the binder resin. If the addition amount of the wax is less than 0.1 parts by weight, it is difficult to obtain a sufficient effect of the wax. On the other hand, if the addition amount is more than 20 parts by weight, the anti-blocking property is lowered and the toner may be detached. is there.

(Charge control agent)
Examples of the charge control agent include positively chargeable charge control agents, and specific examples include pyridazine, pyrimidine, pyrazine, orthooxazine, metaoxazine, paraoxazine, orthothiazine, metathiazine, parathiazine, 1,2,3-triazine. 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine, 1,3,4-thiadiazine, , 3,5-thiadiazine, 1,2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6-oxatriazine, 1, Azine compounds such as 3,4,5-oxatriazine, phthalazine, quinazoline, quinoxaline; azine fast red FC, azine fast red 12 Direct dyes composed of azine compounds such as K, azine violet BO, azine brown 3G, azine light brown GR, Azinda-Kugrain BH / C, azine dip black EW and azine black 3RL; nigrosine, nigrosine salt, nigrosine derivative Nigrosine compounds such as: nigrosine BK, nigrosine NB, nigrosine compounds such as nigrosine Z; acid dyes; metal salts of naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; benzylmethylhexyldecylammonium, decyltrimethylammonium chloride, etc. Quaternary ammonium salts can be exemplified, and these can be used alone or in combination of two or more.

  Further, a quaternary ammonium salt, a carboxylate, or a resin or an oligomer having a carboxyl group as a functional group can also be used as a positively chargeable charge control agent. More specifically, a styrene resin having a quaternary ammonium salt, an acrylic resin having a quaternary ammonium salt, a styrene-acrylic resin having a quaternary ammonium salt, a polyester resin having a quaternary ammonium salt, a carboxylic acid Styrene resin with salt, acrylic resin with carboxylate, styrene-acrylic resin with carboxylate, polyester resin with carboxylate, polystyrene resin with carboxyl group, acrylic with carboxyl group 1 type, or 2 or more types, such as resin, the styrene-acrylic resin which has a carboxyl group, and the polyester-type resin which has a carboxyl group, are mentioned.

  As the charge control agent exhibiting negative chargeability, for example, organometallic complexes and chelate compounds are effective. Examples thereof include aluminum acetylacetonate, iron (II) acetylacetonate, and 3,5-di-tert-butylsalicylate chromium. In particular, acetylacetone metal complexes, salicylic acid metal complexes or salts are preferable, and salicylic acid metal complexes or salicylic acid metal salts are particularly preferable.

  The addition amount of the charge control agent is 1 to 15.0 parts by weight, preferably 1.5 to 8.0 parts by weight with respect to 100 parts by weight of the binder resin. If the amount of the charge control agent added is less than the above range, it may be difficult to stably charge the toner, and the electrostatic latent image was developed using the toner to form an image. In some cases, a decrease in image density may occur. On the other hand, when the amount of the charge control agent is larger than the above range, there may be disadvantages such as environmental resistance, particularly charging failure or image failure under high temperature and high humidity, and contamination of the photoreceptor.

(Magnetic powder)
Magnetic powders include, for example, ferrite, magnetite and other iron, cobalt, nickel and other metals that exhibit ferromagnetism, alloys of these metal elements, compounds containing these metal elements, and those that do not contain ferromagnetic elements but are subjected to appropriate heat treatment. Examples thereof include alloys that exhibit ferromagnetism and chromium dioxide. As these magnetic powders, fine powders having an average particle diameter of 0.1 to 1 μm, preferably 0.1 to 0.5 μm, may be used. Moreover, you may use the magnetic powder surface-treated with surface treatment agents, such as a titanium coupling agent and a silane coupling agent. The addition amount of the magnetic powder is 30 to 60 parts by weight, preferably 40 to 60 parts by weight with respect to 100 parts by weight of the binder resin. If the magnetic powder is added in a larger amount than the above range, the durability of the image density is lowered and the fixability tends to be extremely lowered. If the amount is less than the above range, fogging in image density durability tends to occur. In the black toner, carbon black may be further added together with the magnetic powder.

(Coloring agent)
The colorant is not particularly limited, and examples thereof include magenta, cyan and yellow colorants. These colorants are added in an amount of 2 to 20 parts by weight, preferably 4 to 15 parts by weight, based on 100 parts by weight of the binder binder resin.

  As the magenta colorant, for example, C.I. I. Pigment red 81, C.I. I. Pigment red 122, C.I. I. Pigment red 57, C.I. Pigment Red 49, C.I. I. Solvent Red 49, C.I. I. Solvent Red 19, C.I. I. Solvent Red 52, C.I. I. Basic Red 10, C.I. I. Disperse Red 15 etc. are mentioned.

  As the cyan colorant, for example, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15-1, C.I. Pigment blue 16, C.I. I. Solvent Blue 55, C.I. I. Solvent Blue 70, C.I. I. Direct Blue 86, C.I. I. Direct Blue 25 etc. are mentioned.

  Examples of yellow colorants include nitro pigments such as naphthol yellow S, azo pigments such as Hansa Yellow 5G, Hansa Yellow 3G, Hansa Yellow G, Benzidine Yellow G, and Vulcan Fast Yellow 5G, or yellow iron oxide and ocher. And inorganic pigments. In addition, C.C. I. Pigment yellow 12, C.I. I. Pigment yellow 180, C.I. I. Solvent Yellow 2, C.I. I. Solvent Yellow 6, C.I. I. Solvent Yellow 14, C.I. I. Solvent Yellow 15, C.I. I. Solvent Yellow 16, C.I. I. Solvent Yellow 19, C.I. I. Solvent yellow 21 etc. are mentioned.

(Other ingredients)
As other components, silica powder may be added to the toner. Examples of the silica powder include Aerosil R972, R974, Silica D-17, T-805, R-812, RA200, HRX-C manufactured by Nippon Aerosil Co., Ltd. Taranox 500 manufactured by Tarco Co., Ltd., Cab-o- manufactured by Cabot Corporation. Examples include SilM-5, MS-7, MS-75, HS-5, EH-5, S-17, TS-72, and the like. When these silica powders are used, the content is preferably 3% by weight or less based on the total weight of the toner.

(Production method)
A predetermined amount of a binder resin, a release agent, a charge control agent, and a colorant (in the case of magnetic toner, magnetic powder instead of the colorant) are added, and the mixture is stirred and mixed by a mixing device such as a Henschel mixer. Next, the mixture is melt-kneaded with a twin screw extruder or the like, cooled, and then pulverized with a pulverizer such as a hammer mill or a jet mill. Next, toner particles having a predetermined particle diameter are obtained using a classifier such as an air classifier. Next, when it is necessary to adjust the sphericity of the toner, for example, a spheroidization process of the toner is performed using a surffusion system or the like. Furthermore, a predetermined amount of an external additive (for example, silica powder) is added to the obtained toner particles, and the toner is manufactured by stirring and mixing with a mixing device such as a Henschel mixer.

(Dissolution suspension method)
In the present invention, a non-magnetic toner may be processed by a method such as a dissolution suspension method to obtain a toner. In the dissolution suspension method, for example, 150 parts by weight of ethyl acetate is dispersed in a ball mill for 48 hours with respect to 100 parts by weight of the toner to form Liquid A.

  On the other hand, 60 parts by weight of calcium carbonate (average particle size 80 nm) and 40 parts by weight of water were dispersed with a ball mill for 48 hours, and then 7 parts by weight of calcium carbonate dispersion and carboxymethylcellulose (trade name “Serogen BS-H”: Daiichi Kogyo Seiyaku Co., Ltd. 100 parts by weight of a 2% aqueous solution (manufactured) was stirred.

  Next, 100 parts by weight of Liquid B is stirred with an emulsifier (trade name “Auto Homo Mixer”: manufactured by Tokushu Kika Kogyo Co., Ltd.), and 50 parts by weight of Liquid A is slowly added to suspend the mixed liquid. Thereafter, the solvent is removed under reduced pressure, and then 100 parts by weight of 6N hydrochloric acid is added to remove calcium carbonate, followed by washing with water, drying and classification, whereby a toner treated by the dissolution suspension method can be obtained. By performing such processing, the sphericity of the toner can be increased.

(Polymerized toner)
In the present invention, a polymerized toner, for example, a polymerized toner obtained by a known suspension polymerization method may be used as the nonmagnetic toner. Specifically, a composition containing a polymerizable monomer, a colorant, a polymerization initiator, a charge control agent and the like is added to an aqueous phase with stirring, and granulated. After the polymerization reaction, the particles are filtered and dried. By doing so, a polymerized toner can be obtained. Examples of the polymerizable monomer include a monovinyl aromatic monomer, an acrylic monomer, a vinyl ester monomer, a vinyl ether monomer, a diolefin monomer, and a monoolefin monomer. Can be mentioned. As the colorant, the same colorant as described above can be used. Examples of the polymerization initiator include benzoyl peroxide, lauroyl peroxide, isopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichloroylbenzoyl peroxide, methyl ethyl ketone peroxide, and the like. As the charge control agent, the same charge control agent as described above can be used.

<Image forming apparatus>
An image forming apparatus that can suitably use the image forming method of the present invention will be described with reference to FIG. In the full-color image forming apparatus 10 shown in FIG. 1, developing sleeves 31, 32, 33, and 34 corresponding to the toners T 1, T 2, T 3, and T 4 are arranged around the photosensitive drum 61 in the housing 11. A full-color toner image is formed on one photosensitive drum, and the toner images of the respective colors are transferred onto the intermediate transfer drum 45 (intermediate transfer body), and then the toner image on the intermediate transfer drum 45 is transferred to a sheet of paper. This is a full-color image forming apparatus for transferring onto a (recording material). Further, not only the developing sleeves 31, 32, 33, and 34 but also a charging unit 1, an exposure unit 2, and a cleaning unit 5 are provided around the photosensitive drum 61.

  A known material can be used as the photosensitive drum 61. For example, a photosensitive member such as an amorphous silicon photosensitive member, an organic photosensitive member, a Se photosensitive member, a ZnO photosensitive member, or a CdS photosensitive member is used. it can.

  The charging unit 1 is configured to obtain a predetermined surface potential on the surface of the photosensitive drum 61. The exposure unit 2 irradiates the charged surface of the photosensitive drum 61 with image information from an external terminal as laser light to form a latent image. In the exposure means 2, LED light may be used instead of laser light. The cleaning unit 5 removes the toner that has not been transferred by the intermediate transfer drum 45 from the photosensitive drum 61.

  The full-color image forming apparatus 10 is provided with four developing means 38. In the toner container of these developing means 38, toner T1 (black toner) as magnetic toner and toner T2 (yellow toner) as non-magnetic toner are provided. ), Toner T3 (magenta toner) and toner T4 (cyan toner) are stored. The full-color image forming apparatus 10 includes a toner in which the sphericity of the toners T2, T3, and T4 is larger than the sphericity of the toner T1, and the difference in sphericity is 0.03 or more. The sphericity of the toner is 0.90 to 0.95 for the toner T1, and 0.93 to 0.99 for the toners T2 to T4.

  The toners T1, T2, T3, and T4 are used to form a toner image on the surface of the photosensitive drum 61. Specifically, first, the toner T1 is conveyed to the developing sleeve 31 via a conveyance path (not shown), the toner T2 is conveyed to the developing sleeve 32, the toner T3 is conveyed to the developing sleeve 33, and the toner T4 is conveyed to the developing sleeve 34. .

  Next, an image forming process of the full-color image forming apparatus 10 will be outlined. First, the surface of the photosensitive drum 61 is uniformly charged by the charging unit 1. Next, an electrostatic latent image is formed on the surface of the photosensitive drum 61 by the exposure unit 2. In the developing unit 38, the toners T1 to T4 are sequentially supplied to the developing sleeves 31 to 34. The supplied toners T1 to T4 form a developer layer on the developing sleeves 31 to 34. A predetermined amount of triboelectric charge is applied to the toners T1 to T4 of the developer layer, and the charged toners T1 to T4 corresponding to the respective colors on the photosensitive drum 61 adhere to the photosensitive drum 61. A toner image is formed on the surface. At this time, in the full-color image forming apparatus 10, the difference between the charge amount of the toners T2 to T4 and the charge amount of the toner T1 on the photosensitive drum 61 is 10 μC / g or more. However, since there is a difference in the sphericity of the toner as described above, the full-color image forming apparatus 10 does not suffer from defects such as missing characters and scattered toner.

  The toner image formed on the surface of the photosensitive drum 61 is transferred onto the intermediate transfer drum 45. In the intermediate transfer drum 45, color transfer is performed by repeating the transfer of the toner image on the photosensitive drum 61 for each of the toners T1 to T4.

  On the other hand, a sheet (not shown) conveyed from a sheet feeding cassette 13 provided in the lower part of the full-color image forming apparatus 10 is conveyed to registration rollers 50 and 51, and after the leading edge alignment and timing, a secondary transfer roller. 44. Then, the full color image transferred onto the intermediate transfer drum 45 is transferred to a sheet conveyed between the intermediate transfer drum 45 and the transfer roller 44. After the transfer, the sheet is conveyed to a fixing unit 7 having a pair of rollers 73 and 74 having a built-in heat source such as a heater. The toner is melted and fixed on the sheet conveyed to the fixing unit 7 by heat and pressure. Thereafter, the paper is conveyed to the paper discharge unit 78. The toner remaining on the intermediate transfer drum 45 without being transferred to the paper is removed by the cleaning means 46.

  The full-color image forming method of the present invention can also be suitably used for the image forming apparatus shown in FIG. In FIG. 2, four image forming units 101, 102, 103, and 104 are provided, and four photosensitive drums 61, 62, 63, and 64 are arranged on an intermediate transfer belt (intermediate transfer member). 1 illustrates a transfer tandem type full-color image forming apparatus. The full-color image forming apparatus 10 includes an intermediate transfer belt 47 that runs while being stretched around rollers 41, 42, and 43. The toner image is transferred onto the intermediate transfer belt 47 in order of toner image transfer (in order from the upstream side). Body drums 61, 62, 63, 64 are arranged. In the full-color image forming apparatus 10, the toner images visualized on the photosensitive drums 61, 62, 63, 64 are sequentially transferred from the upstream photosensitive drum 61 to the surface of the intermediate transfer belt 47. . Then, the full color image transferred onto the intermediate transfer belt 47 is transferred to a sheet (not shown) conveyed from the paper feed cassette 13 between the roller 41 and the transfer roller 44. The toner that has not been transferred onto the intermediate transfer belt 47 is removed by the cleaning means 46. Other portions are denoted by the same reference numerals as those in FIG.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited to a following example.

[Example]
In accordance with the following formulation, the materials are mixed and stirred with a mixing stirrer (Henschel mixer), then melt kneaded with a twin screw extruder, pulverized with a jet mill, and air-classified with a classifier to obtain toner particles having an average particle size of 8 μm. Got. In addition, in order to obtain a sphericity that cannot be obtained only by the pulverization method of 0.95 or more, the toner particles are spheroidized by a surffusion system (manufactured by Nippon Pneumatic Industry Co., Ltd.) to obtain a toner raw material. It was. Next, 0.6 parts by weight of silica fine particles (RA200, manufactured by Aerosil Co., Ltd.) was added to 100 parts by weight of the toner raw material, and the final toner was prepared by spraying in the mixing stirrer.

<Prescription of Toner A>
(Magenta toner A)
Binder resin: SE-0040 (manufactured by Sekisui Chemical Co., Ltd.) 100 parts by weight Colorant: Toner Magenta E02 (manufactured by Clariant Japan) 5.0 parts by weight Charge control agent: N-07 (manufactured by Orient Chemical Co., Ltd.) 2.0 weights Part release agent: Carnauba wax (manufactured by Toa Kasei Co., Ltd.) 5.0 parts by weight (Cyan Toner A)
Binder resin: SE-0040 (manufactured by Sekisui Chemical Co., Ltd.) 100 parts by weight Colorant: Toner Cyan BG (manufactured by Clariant Japan) 5.0 parts by weight Charge control agent: N-07 (manufactured by Orient Chemical Co., Ltd.) 2.0 weights Part release agent: Carnauba wax (manufactured by Toa Kasei Co., Ltd.) 5.0 parts by weight (yellow toner A)
Binder resin: SE-0040 (manufactured by Sekisui Chemical Co., Ltd.) 100 parts by weight Colorant: Toner Yellow HG (manufactured by Clariant Japan) 5.0 parts by weight Charge control agent: N-07 (manufactured by Orient Chemical Co., Ltd.) 2.0 weights Part release agent: Carnauba wax (manufactured by Toa Kasei Co., Ltd.) 5.0 parts by weight (Black Toner A)
Binder resin: SE-0040 (manufactured by Sekisui Chemical Co., Ltd.) 100 parts by weight Magnetic powder: MTS-106 (manufactured by Toda Kogyo Co., Ltd.) 45.0 parts by weight Charge control agent: N-07 (manufactured by Orient Chemical Co., Ltd.) 2.0 weights Part release agent: Carnauba wax (manufactured by Toa Kasei) 5.0 parts by weight

<Prescription of Toner B>
(Magenta toner B)
The formulation was the same as that of the magenta toner A except that the weight of the charge control agent was changed to 5 parts by weight.
(Cyan Toner B)
The formulation was the same as that of the cyan toner A except that the charge control agent was changed to 5 parts by weight.
(Yellow Toner B)
The formulation was the same as that of the yellow toner A, except that the weight of the charge control agent was changed to 5 parts by weight.
(Black Toner B)
The formulation was the same as that of the black toner A except that the charge control agent was changed to 0.5 parts by weight.

<Toner C prescription>
(Magenta toner C)
The formulation was the same as that of the magenta toner A except that the weight of the charge control agent was changed to 1 part by weight.
(Cyan Toner C)
The formulation was the same as that of Cyan Toner A except that the weight of the charge control agent was changed to 1 part by weight.
(Yellow Toner C)
The formulation was the same as that of the yellow toner A except that the weight of the charge control agent was changed to 1 part by weight.
(Black Toner C)
The formulation was the same as that of the black toner A, except that the weight of the charge control agent was changed to 4.0 parts by weight.
(Black toner C ')
The formulation was the same as that of the black toner A, except that the weight of the charge control agent was changed to 6.0 parts by weight.

[Examples 1-2]
Using each of the above toners, spheronization treatment was performed as necessary to obtain the full color toners shown in Tables 1 to 3. Thereafter, an image output test and a toner charge amount measurement were performed.

(Image output test)
The black developer of the image forming apparatus KM-C850 (manufactured by Kyocera Mita) is converted to a magnetic one-component developing system, and the color developer is converted to a non-magnetic one-component developing system, and each toner manufactured by the above method is used as an image forming apparatus. I set it. Next, a full-color image was output on a sheet, and it was visually confirmed whether or not voids and dust were generated in the character portion of each of the four colors (magenta, yellow, cyan, and black). The results are shown in Tables 1 to 3 below. The image forming apparatus uses an amorphous silicon photosensitive drum as the photosensitive member.

(Measurement of toner charge)
Using the same image forming apparatus as in the above image output test, a solid patch (2.Pg) in which the toner amount is 0.2 to 0.4 mg / cm ² for each color of cyan, magenta, yellow, and black in the mono color mode. The front cover of the machine body was opened during the output of each solid patch, and the toner charge amount of the solid patch on the photosensitive drum was measured with a q / m meter (made by MODEL 210HS Trek). . The results are shown in Tables 1 to 3 below.

  As shown in Table 1, in Example 1, the charge amount of the nonmagnetic toner on the photosensitive drum is larger than the charge amount of the magnetic toner, and the difference in charge amount is 20 μC / g or more. However, for the non-magnetic toner, a toner that has been spheroidized is used. If the sphericity of the nonmagnetic toner is increased in this way and a difference of 0.03 or more is provided between the sphericity of the nonmagnetic toner and the sphericity of the magnetic toner, it can be seen that image defects do not occur. . The same applies to Example 2 shown in Table 2.

  In Example 3 shown in Table 3, as compared with Examples 1 and 2, black toner C ′ to which a larger amount of charge control agent was added was used. Therefore, the charge amount of the non-magnetic toner on the photosensitive drum is larger than the charge amount of the magnetic toner, but the difference in charge amount is a relatively small value (10.4 to 17.1). However, as in the first and second embodiments, the sphericity of the nonmagnetic toner is increased so that a difference of 0.03 or more is provided between the sphericity of the nonmagnetic toner and the sphericity of the magnetic toner. It can be seen that no image defects have occurred.

[Comparative Examples 1-3]
Using each of the full color toners having the formulations shown in Tables 4 to 6, an image output test and a toner charge amount measurement were performed in the same manner as in the above examples. The results are shown in Tables 4-6.

  As shown in Table 4, when a non-magnetic toner that has not been spheroidized is used when the charge amount of the non-magnetic toner is larger than the charge amount of the magnetic toner and the difference is 20 μC / g or more, There was an image defect such as missing text.

  As shown in Table 5, when all the toners are spheroidized and no difference in sphericity is provided (the sphericity is made uniform), there is a problem in that dust is generated in the character portion of the black toner image. There has occurred.

  Table 6 shows the results of Comparative Example 3 using toner C. In Comparative Example 3, the difference between the charge amount of the non-magnetic toner and the charge amount of the magnetic toner was made smaller than in Examples 1-2 and Comparative Examples 1-2. However, in the image with cyan toner C, the text portion was missing.

[Example 4: Production of polymerized toner by suspension polymerization method and image output test]
A polymerized toner was produced according to the following formulation. Styrene 80 parts by weight, 2-ethylhexyl methacrylate 20 parts by weight, Toner Magenta E02 (manufactured by Clariant Japan) 5 parts by weight, low molecular weight polypropylene 3 parts, charge control agent (P-53) 2 parts, divinylbenzene (crosslinking agent) 1 2 parts by weight of the polymerization initiator 2,2-azobis (2,4-dimethylvaleronitrile) was added after sufficiently dispersing the mixed solution in a ball mill, added to 400 parts by weight of ion-exchanged water, and further suspended. Add 5 parts by weight of tribasic calcium phosphate and 0.1 part by weight of sodium dodecylbenzenesulfonate as a turbid stabilizer, and stir at 7000 rpm for 20 minutes using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) under a nitrogen atmosphere. The polymerization reaction was carried out at 70 ° C. and 100 rpm for 10 hours. Thereafter, acid washing was performed to obtain a toner base particle dispersion having a volume average particle size of 8 μm from which tricalcium phosphate has been removed. This dispersion was filtered, washed and dried to obtain a toner raw powder. Next, 0.6 part by weight of silica fine particles (RA200, manufactured by Aerosil) is added to 100 parts by weight of the toner raw material, and the mixture is stirred in the mixing stirrer to form a polymerized toner (magenta toner D, which is the final toner). )

  The yellow polymer toner (yellow toner D) was produced in the same manner as the magenta toner D, except that Toner Yellow HG (manufactured by Clariant Japan) was used instead of Toner Magenta E02. A cyan polymerized toner (cyan toner D) was produced in the same manner as the magenta toner D, except that Toner Cyan BG (manufactured by Clariant Japan) was used instead of Toner Magenta E02.

  Next, using the produced polymer toner and the black toner A, an image output test and a toner charge amount measurement similar to those described above were performed. The results are shown in Table 7.

  As shown in Table 7, in Example 4, the charge amount of the non-magnetic toner on the photosensitive drum is larger than the charge amount of the magnetic toner, and the difference in charge amount is 20 μC / g or more. However, polymerized toner was used for the non-magnetic toner. Even when the sphericity is increased by using the non-magnetic toner as a polymerized toner and a difference of 0.03 or more is provided between the sphericity of the non-magnetic toner and the sphericity of the magnetic toner, It can be seen that no malfunction occurs. When a polymerized toner is used as the nonmagnetic toner, a difference of 0.03 or more can be provided between the sphericity of the nonmagnetic toner and the sphericity of the magnetic toner without performing the spheroidizing treatment.

It is a schematic sectional drawing which shows an example of the full-color image formation apparatus which can use the full-color image formation method of this invention suitably. It is a schematic sectional drawing which shows the other example of the full-color image formation apparatus which can use the full-color image formation method of this invention suitably.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charging means 2 Exposure means 5 Cleaning means 7 Fixing means 10 Full-color image forming apparatus 45 Intermediate transfer drum (intermediate transfer body)
47 Intermediate transfer belt (intermediate transfer member)
61-64 photoconductor drum (photoconductor)
T1 black toner (magnetic toner)
T2 Yellow toner (non-magnetic toner)
T3 Magenta toner (non-magnetic toner)
T4 cyan toner (non-magnetic toner)

Claims (3)

A full color image in which each color toner image formed on the surface of the photoreceptor using non-magnetic toner and magnetic toner is transferred onto the intermediate transfer member, and then transferred onto the recording material. An image forming method comprising:
When the charge amount of the non-magnetic toner is 10 μC / g or more larger than the charge amount of the magnetic toner before the electrostatic latent image on the photosensitive member is developed and transferred to the intermediate transfer member, the non-magnetic toner An image forming method, wherein the sphericity is larger than the sphericity of the magnetic toner, and the difference between the sphericities is 0.03 or more.   2. The image forming method according to claim 1, wherein the charge amount of the magnetic toner on the photoconductor is 1 to 15 [mu] C / g, and the charge amount of the non-magnetic toner on the photoconductor is 16 to 40 [mu] C / g. 3. The image forming method according to claim 1, wherein a polymerized toner is used as the non-magnetic toner, and a pulverized toner is used as the magnetic toner.

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