JP2005157019A - Full-color developer and full-color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a full-color developer with which a high-quality image can be obtained by suppressing the occurrence of filming and suppressing the contamination of a transferring object by inorganic oxides in image formation using a color image forming apparatus of a tandem system arrayed with a plurality of image carriers on the transferring object. <P>SOLUTION: The full-color developer contains a plurality of toners which are prepared by externally adding the inorganic oxides as polishing agents to a toner parent composed of at least a binder resin and a coloring agent and have different colors and when the amounts of addition of the inorganic oxides in the plurality of the toners are defined as D1, D2, D3 to Dn in order of toner image transfer (where (n) is an integer of 3 or over), these amounts of addition satisfy the following formulas (1) and (2). The formula (1) is expressed by D1>D2≥D3≥ to ≥Dn and the formula (2) is expressed by (D1xn)>(D1+D2+D3+ to +Dn)≥(D1xD2). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a full-color developer and a full-color image forming apparatus, and more particularly to a tandem-type full-color image forming apparatus in which a plurality of image carriers are arranged on a transfer body and a full-color developer suitable for this apparatus.

  Conventionally, in image forming methods used in copying machines, printers, etc., a toner composed of a binder resin, a colorant, etc. in order to prevent filming on the photosensitive drum (image carrier) and transfer defects. A developer in which an inorganic oxide is externally added to the base as an abrasive has been proposed (for example, Patent Document 1).

However, in a tandem color image forming apparatus in which a plurality of photosensitive drums are arranged on a transfer body such as an intermediate transfer belt or a transfer conveyance belt, the transfer body is contaminated with an inorganic oxide, resulting in a transfer failure, resulting in image quality. May cause problems such as vertical streaks on the transfer paper.
JP 2003-43733 A

  An object of the present invention is to suppress filming in image formation using a tandem color image forming apparatus in which a plurality of image carriers are arranged on a transfer body, and to contaminate the transfer body with an inorganic oxide. It is an object to provide a full color developer capable of obtaining a high quality image by suppressing the above, and a full color image forming apparatus using the developer.

  As a result of intensive studies to solve the above problems, the present inventors have determined the amount of inorganic oxide added to the toner first transferred to the transfer body (the toner supplied to the most upstream image carrier). In addition, the amount of inorganic oxide added to the toner is increased, and the total amount added is within a predetermined range (D1 × n> total added amount ≧ D1 × 2), thereby suppressing the occurrence of filming. The inventors have found a new fact that a high-quality image can be obtained by suppressing contamination of a transfer body with an inorganic oxide, and have completed the present invention.

That is, the full-color developer of the present invention is a full-color developer containing a plurality of toners of different colors in which an inorganic oxide is externally added as an abrasive to a toner base composed of at least a binder resin and a colorant. When the addition amount of each inorganic oxide in the plurality of toners is D1, D2, D3,..., Dn (where n is an integer of 3 or more) in the order of toner image transfer, these addition amounts are reduced. It is characterized by satisfying equations (1) and (2).

  The addition amount D1 is preferably 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the toner base.

  The full-color image forming apparatus of the present invention includes a transfer member, a plurality of image carriers that are arranged along the moving direction of the transfer member and sequentially transfer toner images onto the transfer member, and the full-color image on these image carriers. And a plurality of developer carrying members for supplying each toner of the developer to form a toner image.

  According to the present invention, the addition amount of each inorganic additive in the plurality of toners is set so as to satisfy the above-described conditions, so that the occurrence of filming is suppressed and the transfer body is contaminated with inorganic oxides. It is possible to obtain a high-quality image with suppression.

  Hereinafter, an embodiment of the present invention will be described in detail. The full-color developer according to the exemplary embodiment is used in a tandem color image forming apparatus in which a plurality of image carriers are arranged on a transfer body such as an intermediate transfer belt, an intermediate transfer drum, or a transfer conveyance belt, and at least a binder is used. A toner base material composed of a resin and a colorant contains a plurality of toners having different colors, to which an inorganic oxide is externally added as an abrasive.

  The type of the binder resin is not particularly limited. For example, a polystyrene resin, an acrylic resin, a styrene-acrylic copolymer, a polyethylene resin, a polypropylene resin, a polyvinyl chloride resin, and a polyester resin. It is preferable to use thermoplastic resins such as resins, polyamide resins, polyurethane resins, polyvinyl alcohol resins, vinyl ether resins, N-vinyl resins, styrene-butadiene resins.

  Specifically, the polystyrene resin may be a homopolymer of styrene 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 These may be used alone or in combination of two or more with a styrene monomer.

  The polystyrene resin preferably has two mass average molecular weight peaks (a low molecular weight peak and a high molecular weight peak). Specifically, the low molecular weight peak is in the range of 3,000 to 20,000, the high molecular weight peak is in the range of 300,000 to 1,500,000, and the mass average molecular weight (Mw) and number average The ratio (Mw / Mn) to the molecular weight (Mn) is preferably 10 or more. If the mass average molecular weight peak is within such a range, the toner can be easily fixed, and offset resistance can be improved. The mass average molecular weight and number average molecular weight of the binder resin are measured with a molecular weight measuring device (GPC) and the elution time from the column is measured, and compared with a calibration curve prepared in advance using a standard polystyrene resin. It can be determined by combining them.

  As the polyester resin, those obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component can be used. The following are mentioned as a component used when synthesize | combining a polyester-type resin.

  Examples of the divalent or trivalent or higher alcohol component include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4- Diols such as butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol; bisphenol A, hydrogenated bisphenol Bisphenols such as A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, penta Lithritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butane Examples include trivalent or higher alcohols such as triol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

  As the divalent or trivalent or higher carboxylic acid component, a divalent or trivalent carboxylic acid, an acid anhydride or a lower alkyl ester thereof is used. Maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalate Acid, isophthalic acid, terephthalic 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- Divalent carboxylic acids such as alkyl or alkenyl succinic acid such as octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid and isododecenyl succinic acid; -Benzenetricarboxylic acid (trimellitic acid), 1,2,5-ben Tricarboxylic 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 Examples thereof include trivalent or higher carboxylic acids and the like.

  The softening point of the polyester resin measured with the Koka flow tester is preferably 110 to 150 ° C, more preferably 120 to 140 ° C.

  The binder resin is preferably a thermoplastic resin from the viewpoint of good fixability, but the amount of cross-linked portion (gel amount) measured using a Soxhlet extractor is 10% by mass or less, preferably 0.1. A thermosetting resin may be used as long as the value is within a range of 10 mass% to 10 mass%. By introducing a partially crosslinked structure in this way, the storage stability, form retention, or durability of the developer can be further improved without deteriorating the fixability. Therefore, it is not necessary to use 100% by mass of the thermoplastic resin as the binder resin for the toner base, and it is possible to add a crosslinking agent or to partially use a thermosetting resin.

  As the thermosetting resin, an epoxy resin, a cyanate resin, or the like can be used. Specifically, one or a combination of two 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. Is mentioned.

  Further, as the binder resin, 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 is included in the molecule. It is preferable to use the resin which has. Whether or not these functional groups are present can be confirmed using a Fourier transform infrared spectrometer (FT-IR apparatus) and further quantified using a titration method.

  The glass transition point (Tg) of the binder resin is preferably set to a value within 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 may be lowered. On the other hand, if the glass transition point of the binder resin exceeds 70 ° C., the toner fixing ability may 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).

  Colorants include black pigments such as acetylene black, lanblack, and aniline black; yellow pigments such as yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, and navel yellow , Naphthol Yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake; orange pigments such as reddish yellow lead, molybten orange, permanent orange GTR, pyrazolone Orange, Vulcan orange, Indanthrene brilliant orange RK, Benzidine orange G, Indanthrene brilliant orange GK; As red pigment, Bengala, Cadmium red , Lead cadmium, mercury cadmium sulfide, permanent red 4R, risor red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B; , Manganese Purple, Fast Violet B, Methyl Violet Lake; As Blue Pigment, Bitumen, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Metal-free Phthalocyanine Blue, Phthalocyanine Blue Partial Chlorides, Fast Sky Blue, Induslen Blue BC: As a green pigment, chrome green, chromium oxide, pigment green B, malachite green lake, fanal yellow green G; white pigment To, zinc oxide, titanium oxide, antimony white, zinc sulfide; as a white pigment, baryta powder, barium carbonate, clay, silica, white carbon, talc, alumina white can be used. These colorants are preferably used in the range of 2 to 20 parts by mass, particularly 5 to 15 parts by mass per 100 parts by mass of the binder resin.

  Other additives may be added to the developer of the present invention as long as the effects of the present invention are not impaired. Examples of such additives include waxes and charge control agents.

  The wax is not particularly limited. For example, plant waxes such as carnauba wax, sugar wax, and wood wax; animal waxes such as beeswax, insect wax, whale wax, wool wax; Fischer-Tropsch wax having ester in the side chain (FT wax), synthetic hydrocarbon waxes such as polyethylene wax and polypropylene wax. Among these, from the viewpoint of dispersibility, it is preferable to use FT wax or polyethylene wax having ester in the side chain.

  The wax preferably has an endothermic main peak in a range of 70 to 100 ° C. in an endothermic curve obtained by a differential scanning calorimeter. When the endothermic main peak is less than 70 ° C., toner blocking and hot offset may occur, and when the endothermic main peak exceeds 100 ° C., low-temperature fixability may not be obtained.

  Furthermore, the addition amount of the wax is preferably in the range of 0.1 to 20 parts by mass with respect to 100 parts by mass of the binder resin. If the added amount of the wax is less than 0.1 parts by mass, it may be difficult to obtain a sufficient effect of the wax. If the added amount exceeds 20 parts by mass, the anti-blocking property is reduced, and the amount of the wax from the toner base material is reduced. Desorption may occur.

  As the charge control agent, conventionally known charge control agents can be used. For example, as the positively chargeable charge control agent, nigrosine dye, fatty acid modified nigrosine dye, carboxyl group-containing fatty acid modified nigrosine dye, quaternary ammonium salt, amine series A compound, an organometallic compound, or the like can be used. As the negatively chargeable charge control agent, a metal complex of oxycarboxylic acid, a metal complex of azo compound, a metal complex dye, a salicylic acid derivative, or the like can be used.

  As the inorganic oxide externally added as a polishing agent to the toner base, alumina, titanium oxide, zinc oxide, magnesium oxide, strontium titanate, or the like can be used. The volume average diameter of the inorganic oxide is 0.02 to 1.0 μm, preferably 0.1 to 0.3 μm. When the volume average diameter of the inorganic oxide is less than 0.02 μm, the ability to polish the surface of the photoreceptor may be reduced and aggregation may easily occur. On the other hand, if the volume average diameter exceeds 1.0 μm, the inorganic oxide may be easily detached from the toner base.

In the present invention, the amount of inorganic oxide added to the toner base is set in the order of toner image transfer (the toner image transferred first is referred to as the upstream side) D1, D2, D3,. When an integer of 3 or more), it is important that these addition amounts satisfy the following expressions (1) and (2).

  Here, the reason why the respective addition amounts of the inorganic additives are set as in the formulas (1) and (2) is based on the following reasons. That is, filming in the image carrier is likely to occur in the upstream image carrier, particularly the most upstream image carrier, due to the influence of paper dust or the like of the transfer paper. Therefore, by increasing the addition amount D1, In particular, the occurrence of filming in the most upstream image carrier is suppressed, and the other addition amounts D2, D3,..., Dn are made smaller than D1 within a range satisfying the expressions (1) and (2). As a result, contamination of the transfer body by the inorganic oxide is suppressed.

Further, the addition amount D1 is set according to the added inorganic oxide so that filming does not occur in the most upstream image carrier and the inorganic oxide is detached from the toner base surface and does not contaminate the transfer body. Although not particularly limited, it is 0.1 to 3.0 parts by weight, preferably 0.5 to 1.5 parts by weight, based on 100 parts by weight of the toner base. The determination as to whether or not the most upstream image carrier can suppress the occurrence of filming and contamination of the transfer member can be made, for example, by actually performing a printing durability test and evaluating the output image.
D2 is preferably set to 50 to 90% of D1, D3 to 10 to 100% of D1, and D4 to 10 to 100% of D1. n is preferably 3 or 4. When D1, D2, D3, and D4 are below the above range, filming tends to occur on the surface of the photoreceptor (especially, the most upstream side and the photoreceptor surface located downstream thereof), and D1, D2, D3, and D4 are If it exceeds the above range, the inorganic oxide tends to be detached from the toner surface, and the transfer body tends to be contaminated by the inorganic oxide, and both image defects are likely to occur.

  The amount of inorganic oxide added can be confirmed, for example, as follows. That is, the toner is pressed at a pressure of about 20 t and formed into a disk shape to prepare a measurement sample, and this measurement sample is quantitatively analyzed using a fluorescent X-ray analyzer (for example, Model 3270 manufactured by Rigaku Corporation).

  The inorganic oxide and the toner base can be mixed using, for example, a Henschel mixer, a V-type mixer, a turbula mixer, a hybridizer, or the like. The inorganic oxide may be subjected to a known surface treatment such as silicone oil treatment or coupling treatment. Furthermore, carbonates, such as calcium carbonate, can also be used as an abrasive | polishing agent with said inorganic oxide.

  As a surface treatment agent externally added to the toner base, in order to adjust the charge controllability and bulk density (fluidity) of the toner, inorganic fine powder such as silica; organic fine powder such as polymethyl methacrylate; zinc stearate The fatty acid metal salt etc., such as these, can be mentioned, These 1 type (s) or 2 or more types can be used together. The addition amount of the surface treatment agent is preferably in the range of 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the toner base. The surface treatment agent and the toner particles can be mixed using, for example, a Henschel mixer, a V-type mixer, a turbula mixer, a hybridizer, or the like.

  Hereinafter, a method for producing toner in the full color developer of the present invention will be described. First, the binder resin, a predetermined amount of colorant, and additives such as wax and charge suppressant, if necessary, are charged into a mixing device such as a Henschel mixer and mixed. Next, the mixture is melt-kneaded with a twin screw extruder or the like, then cooled with a drum flaker or the like, and coarsely pulverized with a pulverizer such as a hammer mill. Then, after finely pulverizing with a pulverizer such as a mechanical mill, classification is performed using an air classifier or the like to obtain a toner base having a volume average diameter in the above range.

  Next, a predetermined amount of an inorganic oxide and, if necessary, a surface treatment agent such as silica are externally added to the obtained toner base, and agitated and mixed with a mixing device such as a Henschel mixer to obtain a toner.

  The obtained toner may be used as a one-component full-color developer, or may be mixed with a carrier and used as a two-component full-color developer.

  The carrier used for the two-component developer is not particularly limited, and examples thereof include magnetic metals such as iron, nickel, cobalt, and alloys thereof, alloys containing rare earths, hematite, magnetite, manganese-zinc ferrite, By sintering and atomizing magnetic materials such as nickel-zinc ferrite, manganese-magnesium ferrite, soft ferrite such as lithium ferrite, iron-based oxides such as copper-zinc ferrite, and mixtures thereof The produced magnetic particles and those obtained by coating the surfaces of the magnetic particles with a resin can be used.

  In addition, a magnetic material dispersed resin can be used as the carrier. In this case, the above magnetic material can be used as the magnetic material, and examples of the binder resin include vinyl resins, polyester resins, epoxy resins, phenol resins, urea resins, polyurethane resins, polyimide resins, cellulose resins, and polyethers. Resins or mixtures thereof can be mentioned.

The particle diameter of the carrier is generally 20 to 200 μm, particularly preferably 30 to 150 μm, expressed in terms of particle diameter by electron microscopy. Further, the apparent density of the carrier is preferably in the range of 2.4 to 3.0 g / cm ³ , although it varies depending on the composition of the magnetic material, the surface structure and the like when the magnetic material is mainly used.

  The toner concentration in the two-component developer is 1 to 20% by mass, preferably 3 to 15% by mass. When the toner concentration is less than 1% by mass, the image density may be too thin. On the other hand, when the toner concentration exceeds 20% by mass, the toner scatters in the developing device, which may cause a problem that the toner adheres to background portions such as in-machine dirt and transfer paper.

  Hereinafter, a color image forming apparatus that can suitably use the full color developer of the present invention will be described. FIG. 1 is a schematic sectional view showing an example of a tandem (direct transfer tandem type) color image forming apparatus in which four photosensitive drums (image carriers) are arranged on a transfer conveyance belt (transfer body).

  As shown in FIG. 1, a transfer conveyance belt 11 is provided in a housing 10 of the image forming apparatus and travels while being stretched between a pair of rollers 12 and 12 ′. Four image forming units 101, 102, 103, and 104 are arranged in order of toner image transfer (in order from the upstream side).

  In the image forming units 101, 102, 103, and 104, a charging unit 1, an exposing unit 2, a developing unit 3, and a cleaning unit 5 are arranged around the photosensitive drums (image bearing members) 61, 62, 63, and 64, respectively. Have a structure. These photosensitive drums 61, 62, 63, 64 are arranged in order along the moving direction of the transfer conveyance belt 11.

  FIG. 2 is an enlarged sectional view in which the developing unit 3 in the image forming unit 101 is enlarged. The developing means 3 includes a developing sleeve (developer carrier) 31 in which a magnet 31a is fixed and incorporated in a sleeve 31b, and a spiral stirring member 32. The developing sleeve 31 is conveyed to the developing portion at the upper right portion of the developing sleeve 31. A blade 33 that regulates the amount of developer to be applied and applies frictional charging is disposed at a predetermined distance from the developing sleeve 31. A toner hopper 34 is provided above the stirring member 32. The toner hopper 34 contains toner T1 (Black toner).

The configuration of the other image forming units 102, 103, and 104 is the same as that of the image forming unit 101. In the toner hoppers 34 in the image forming units 102, 103, and 104, toners T2 (Yellow toner), T3 (Cyan toner), and T4 (Magenta toner) are accommodated, respectively. In the toners T1, T2, T3, and T4, the inorganic oxide is externally added to the toner base in the amounts of D1, D2, D3, and D4. These addition amounts D1, D2, D3 and D4 satisfy the following expressions (1) ′ and (2) ′.

  FIG. 3 is an enlarged cross-sectional view of the fixing unit 7 in the image forming apparatus. The fixing unit 7 has a basic structure in which a lower fixing roller 72 is brought into contact with an upper fixing roller 71. No oil applicator is provided on the outer periphery of the upper fixing roller 71. Each of the upper and lower fixing rollers 71 and 72 has a structure in which rubber layers 712 and 722 are formed on the outer periphery of cylindrical cores 711 and 721, and heaters 713 and 723 are disposed at the centers of the cores 711 and 721. The thermistors 714 and 724 arranged so as to be in contact with the surfaces of the upper and lower fixing rollers 71 and 72 are on / off controlled to a predetermined temperature. The set temperature is appropriately determined depending on the type of toner to be used, but is generally in the range of 160 to 210 ° C. On the outer periphery of the upper fixing roller 71, a cleaning blade 715 for removing attached toner is disposed, and a separation claw 716 for preventing paper from being wound is disposed.

  Next, an image forming process of the image forming apparatus will be outlined. Taking the image forming unit 101 as an example, first, the surface of the photosensitive drum 61 is uniformly charged positively 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 3, when the toner sensor 35 installed on the right side wall of the stirring member 32 detects that the toner amount in the developing unit 3 is insufficient, the replenishing roller 36 rotates to move from the toner hopper 34 to the developing unit 3. Toner T1 is supplied. The supplied toner T1 is agitated and mixed with the carrier by the agitating member 32 and sequentially supplied to the developing sleeve 31. The supplied toner T1 and carrier form a developer layer on the developing sleeve 31. The developer in the developing sleeve 31 is sent to the position facing the photosensitive drum 61 (developing unit) by the counterclockwise rotation of the developing sleeve 31. At this time, the amount of developer sent to the developing unit is controlled by the blade 33, and triboelectric charging is applied to the toner T1. The charged toner T1 adheres to the electrostatic latent image on the photosensitive drum 61, and the electrostatic latent image is visualized (developed) to form a toner image. In the other image forming units 102, 103, and 104, the electrostatic latent images on the photosensitive drums 62, 63, and 64 are visualized and toner images are formed in the same flow as described above.

  On the other hand, transfer paper (not shown) conveyed from a paper feed cassette 13 provided in the lower part of the housing 10 moves on the transfer conveyance belt 11 in the conveyance direction (from right to left in FIG. 1). At this time, a bias paper having a polarity opposite to the charging polarity of the toner is applied to a transfer roller (transfer means) 4 provided on the lower side of the transfer conveyance belt 11 to transfer the transfer paper (on the transfer conveyance belt 11). The toner images of the respective colors formed on the photosensitive drums 61, 62, 63, and 64 are sequentially transferred from the upstream photosensitive drum 61 (not shown).

  The toner that has not been transferred onto the photosensitive drums 61, 62, 63, 64 is removed by the cleaning means 5, respectively. As shown in FIG. 3, the full color image T transferred onto the transfer paper P is melted and fixed on the transfer paper P by applying heat and pressure in a fixing means 7 having a fixing roller 71 and a lower fixing roller 72. Then, the transfer paper P is discharged above the housing 10.

  The full color developer of the present invention can be suitably used in the image forming apparatus shown in FIG. FIG. 4 is a schematic cross-sectional view showing a tandem (indirect transfer tandem system) full-color image forming apparatus in which four photosensitive drums are arranged on an intermediate transfer belt (transfer body). The image forming apparatus includes an intermediate transfer belt 45 that runs while being stretched around rollers 41, 42, and 43, and a photosensitive drum on the intermediate transfer belt 45 in order of toner image transfer (in order from the upstream side). 61, 62, 63, 64 are arranged.

  In this image forming apparatus, toner images visualized on the photosensitive drums 61, 62, 63, 64 are sequentially transferred from the upstream photosensitive drum 61 onto the surface of the intermediate transfer belt 45. Then, the full-color image transferred onto the intermediate transfer belt 45 is transferred to transfer paper (not shown) conveyed from the paper feed cassette 13 between the roll 41 and the transfer roll 44. The toner that has not been transferred onto the intermediate transfer belt 45 is removed by the cleaning means 46. The full color image transferred onto the transfer paper is melted and fixed on the transfer paper by applying heat and pressure in a fixing means 7 ′ having a fixing roller 73 and a fixing roller 74. To be discharged. Other portions are denoted by the same reference numerals as those in FIG.

  The method for developing the electrostatic latent image on each photosensitive drum may be either a normal developing method or a reversal developing method. As a developing method, a contact developing method in which the developer layer and the photosensitive drum are in contact with each other, or both are used. Any of the jumping development methods that do not contact may be used. The reversal development method is preferable from the viewpoint of obtaining a high-quality image. In this case, the photosensitive drum is charged with the same polarity as the toner, and the latent image portion is removed by exposure. Then, by applying an alternating voltage, in which an alternating current is superimposed on a direct current, as a developing bias between the developing sleeve and the photosensitive drum in the developing unit, the electrostatic latent image on the photosensitive drum from which the electric charge has been removed is added to the developer. The toner is transferred and attached to the electrostatic latent image to be visualized as a toner image.

  The material of the photosensitive drum that can be used in the present invention is not particularly limited, and conventionally known materials can be used. For example, photoconductors such as an amorphous silicon photoconductor, an organic photoconductor, a Se photoconductor, a ZnO photoconductor, and a CdS photoconductor can be used. Among these, an amorphous silicon photoreceptor is preferable from the viewpoint of durability.

  Furthermore, in the above-described embodiment, the magnet 31a built in the developing sleeve 31 is fixed and the sleeve 31b on the cylinder rotates, but the structure in which the sleeve 31b is fixed by rotating the built-in magnet 31a, Alternatively, a structure in which both the internal magnet 31a and the sleeve 31b are rotated (the rotation direction may be either the same direction or the reverse direction) may be used.

  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.

[Examples 1-7, Comparative Examples 1-6]
100 parts by weight of polyester resin (manufactured by Kao) as binder resin, 5 parts by weight of carbana wax (manufactured by Toa Kasei) as wax, 5 parts by weight of colorant, quaternary ammonium salt compound (manufactured by Orient Chemical) 3 parts by mass into a Henschel mixer, and then melted and kneaded with a twin screw extruder, cooled with a drum flaker, and coarsely pulverized with a hammer mill. Next, it is finely pulverized by a mechanical mill, classified using an air classifier, and a toner base of four colors having a volume average diameter of 9.0 μm (Black toner: BK, Yellow toner: Y, Cyan toner: C, Magenta toner: M) was prepared. The black pigment for BK is carbon black, and the yellow pigment for Y is C.I. I. pigment yellow 17, and magenta pigments for M include C.I. I. pigment Red122 was used.

  With respect to 100 parts by mass of these toner bases, the addition amounts (D1, D2, D3, D4) shown in Table 1 of titanium oxide (volume average diameter 0.25 μm) and hydrophobic silica (volume average diameter 0.012 μm) 0.8 parts by mass were added and mixed with high agitation with a Henschel mixer to prepare four-color positively chargeable toners. Next, 7 parts by mass of the produced toner and 93 parts by mass of ferrite carrier (Powder Tech Co., Ltd.) were mixed to obtain four color developers.

Using the tandem color image forming apparatus “FS-C5016N” manufactured by Kyocera Mita Co., Ltd. having a structure having an intermediate transfer belt as shown in FIG. 4, the performance of the developer obtained above was evaluated. The results are shown in Table 2.
In the evaluation test, a predetermined full-color original is used to perform a 10,000-sheet printing test, and whether or not a spot-like grayscale image due to filming or a streaky grayscale image due to transfer belt contamination is generated. It was observed visually. As a full-color original, a halftone image printed in A4 size and each color of cyan, magenta, yellow, and black at 25% density was used.

  From Table 2, since D1 = D2, it does not satisfy the formula (1), and the total addition amount (D1 + D2 + D3 + D4) is the same value as (D1 × 4), so the comparative example 1 and the comparison that do not satisfy the formula (2) In Example 4, the intermediate transfer belt was contaminated with titanium oxide, and vertical stripes were generated on the transfer paper. In Comparative Example 2, Comparative Example 3, Comparative Example 5, and Comparative Example 6 that do not satisfy Expression (2) because the total addition amount is smaller than (D1 × 2), filming occurred on the photosensitive drum.

  On the other hand, in Examples 1 to 6 in which the amount of the inorganic additive in each developer satisfies the expressions (1) and (2), the intermediate transfer belt is not contaminated and filming is also observed. I couldn't.

1 is a schematic cross-sectional view showing an example of a tandem color image forming apparatus that can suitably use a full color developer of the present invention. FIG. 2 is an enlarged cross-sectional view in which a developing device in the image forming apparatus shown in FIG. 1 is enlarged. FIG. 2 is an enlarged cross-sectional view in which a fixing unit in the image forming apparatus shown in FIG. 1 is enlarged. It is a schematic sectional drawing which shows the other example of the tandem type color image forming apparatus which can use the full color developer of this invention suitably.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charging means 2 Exposure means 3 Developing means 4 Transfer roller 5 Cleaning means 7, 7 'Fixing means 10 Housing 11 Transfer conveyance belt (transfer body)
12, 12 'roller 13 paper feed cassette 31 developing sleeve (developer carrier)
32 Stirring members 41, 42, 43 Roller 44 Transfer roller 45 Intermediate transfer belt (transfer body)
46 Cleaning means 61, 62, 63, 64 Photosensitive drum (image carrier)
71 Upper fixing roller 72 Lower fixing rollers 73 and 74 Fixing rollers 101, 102, 103, and 104 Image forming unit

Claims (3)

A full-color developer comprising a plurality of toners having different colors, wherein an inorganic oxide is externally added as an abrasive to a toner base comprising at least a binder resin and a colorant,
When the addition amount of each inorganic oxide in the plurality of toners is D1, D2, D3,..., Dn (where n is an integer of 3 or more) in the order of toner image transfer, these addition amounts are expressed by the following formulas. A full-color developer satisfying (1) and (2).

  The full color developer according to claim 1, wherein the addition amount D1 is 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the toner base. A transfer body, a plurality of image carriers that are arranged along the moving direction of the transfer body and that sequentially transfer toner images onto the transfer body, and the full-color developer according to claim 1 or 2 on the image carriers. A full-color image forming apparatus comprising a plurality of developer carriers for supplying each toner to form a toner image.

Images