JP2006154313A - Toner for image forming device, and image forming method using this toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single magnetic component toner of an image forming device which does not make trails in a magnetic jumping developing system without defective images due to low density when repeating intermittent printing and low density printing, and provide an image forming method using this toner. <P>SOLUTION: This toner is obtained by making it contain at least binder resin, magnetic powder, and charge control resin. The magnetic powder has the electric resistance 1.0×10<SP>3</SP>to 1.0×10<SP>5</SP>Ωcm when 1,000 V is applied and is contained 30-50 pts.wt. in the toner, and the charge control resin has the same polarity as the photoconductor and is contained 4-9 pts.wt. in the toner. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a toner for an image forming apparatus such as a copying machine, a printer, a facsimile, and a composite machine using the electrophotographic method, and an image forming method using the toner, and more particularly, an image forming using a magnetic jumping system. The present invention relates to a toner for an image forming apparatus and an image forming method using the toner, which can prevent image defects such as a trailing in the apparatus and a decrease in image density caused by intermittently printing at a low density. It is.

  As a developing method in an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic method, there is a one-component developing method using a one-component developer and a two-component developing method using a two-component developer. However, in the two-component development method, it is difficult to reduce the size and the weight because a carrier is used and a mechanism for controlling the mixing ratio of the toner and the carrier is required. The one-component development method seems to be suitable for the demands for small size, light weight, and low power consumption.

  Among these one-component developing systems, the magnetic toner is supported on the developing sleeve by the magnetic force of a fixed magnet disposed inside, and the developing sleeve is formed into a thin layer while the toner is frictionally charged by the developer layer thickness regulating member. A magnetic jumping system that performs development by a potential difference between the electrostatic latent image on the photosensitive drum and the developing sleeve by applying a developing bias voltage composed of an AC component and a DC component in a state of being very close to the photosensitive drum. This is a system that can increase the chance of contact between the developing sleeve and the toner to enable sufficient frictional charging, and can obtain an excellent image without aggregation between the toner particles.

  In this developing system, the charged state of the developer on the developing sleeve is very important. For example, if the developer is not sufficiently charged, the developer cannot fly to the photosensitive drum, and the image density decreases. In addition, if the developer is not uniformly charged, image unevenness in which the density is locally reduced on the image occurs.

  In this method, when high-speed printing (for example, A4 at 50 sheets / min or more) is performed, if the adhesion between the toner transferred from the photosensitive drum to the recording paper and the recording paper is weak, the recording paper is As the moisture evaporates, the transferred toner scatters, causing a problem called tailing on the image.

  Furthermore, in this system, when low density printing is intermittently repeated, the toner in the developing device (mainly on the developing sleeve) is charged up due to repeated friction, and the adhesion to the developing sleeve is increased due to overcharging. As a result, the developability of the photosensitive drum is lowered, and there is a problem that the image density is lowered.

  Of these, for tailing, for example, a pre-transfer charger as shown in Patent Document 1 can be used to charge the toner on the photosensitive drum before transfer, thereby enhancing the adhesion to the recording paper. know.

  Patent Document 2 includes a vinyl resin, a polyester resin, and a hybrid resin component having these polymer units as a binder resin, and a styrene / acrylic monomer sulfonic acid-containing acrylamide monomer as a charge control agent. Development that uses a toner using a copolymer with a toner and develops it by applying a rectangular wave with a duty of 20% as a development alternating voltage, thereby preventing image density reduction and fogging phenomenon due to charging changes due to environmental fluctuations. The device is shown.

  Further, Patent Document 3 is a toner containing a binder resin, wax, and magnetic powder, having an average circularity of 0.960 or more, and the magnetic powder is not substantially exposed on the toner particle surface, and the wax is at least Magnetic toner containing at least two types of waxes that are soluble in monomers and insoluble waxes that are constituents of the binder resin. An image forming method and magnetic toner aiming at preventing a decrease in image density in use are shown.

JP-A-11-338250 JP 2003-202736 A JP 2002-202627 A

  However, even if the pre-transfer charger as shown in Patent Document 1 is used, if the magnetic toner itself is weakly charged with respect to the discharge applied by the pre-transfer charger, the pre-transfer charger tries to charge it. However, sufficient charging cannot be obtained and tailing occurs.

  In the technique disclosed in Patent Document 2, aiming at prevention of image density reduction and fogging at high temperature and high humidity and low temperature and low humidity by setting properties of toner resin and charge control material and development alternating voltage conditions. However, particularly in the case of high-speed printing, if intermittent printing is repeated over a long period of time, a decrease in density occurs due to overcharging of the developer.

  In addition, the technique disclosed in Patent Document 3 is intended to prevent the image density from being lowered over a long period of use in consideration of the average circularity of the toner and the compatibility between the resin and the wax. Even if the pre-transfer charger is used, the adhesion between the toner after the transfer process and the transfer paper is weak, so that a trailing phenomenon occurs in the fixing process, resulting in an image defect.

  Therefore, in the present invention, a magnetic one-component toner for an image forming apparatus that does not cause image defects due to density reduction in the case of repeating the trailing in the magnetic jumping development method, intermittent printing, and low density printing, and the toner It is an object to provide an image forming method using the above.

In order to solve the above problems, the toner for an image forming apparatus according to the present invention is:
An alternating electric field for development is applied with a magnet inside, and the latent image formed on the photoconductor is developed by an electrophotographic method held on a sleeve arranged in the vicinity of the photoconductor, A toner for an image forming apparatus, comprising a resin and a magnetic powder and a charge control resin,
The magnetic powder has an electric resistance of 1.0 × 10 ^{3 to} 1.0 × 10 ⁵ Ω · cm when 1000 V is applied, and the magnetic powder is contained in an amount of 30 to 50 parts by weight with respect to the toner. The charge control resin has the same polarity as that of the photosensitive member and is contained in 4 to 9 parts by weight with respect to the toner.

By including the charge control resin having the same polarity as the photoconductor in the toner for the image forming apparatus in this way, the toner can be improved in chargeability and improved in adhesion to the recording paper, and the occurrence of tailing can be prevented. In addition, the overcharged charge can be removed by setting the electric resistance of the magnetic powder to 1.0 × 10 ^{3 to} 1.0 × 10 ⁵ Ω · cm, and even when intermittent printing and low density printing are repeated. Excessive charging is prevented, and the phenomenon that the image density is lowered can be prevented.

  In a preferred embodiment, the binder resin is a polyester, and the charge control resin contains a styrene-acrylic copolymer and a quaternary ammonium salt.

Furthermore, in order to solve the above problems, an image forming method according to the present invention includes:
An alternating electric field for development is applied with a magnet inside, and the latent image formed on the photoconductor is developed by an electrophotographic method held on a sleeve arranged in the vicinity of the photoconductor, An image forming method using a toner for an image forming apparatus comprising a resin, a magnetic powder, and a charge control resin,
The image forming apparatus includes a pre-transfer charger that charges a toner image formed on the photoconductor before being transferred to a recording paper, and the peripheral speed of the photoconductor is 300 mm / sec or more,
The magnetic powder has an electric resistance of 1.0 × 10 ^{3 to} 1.0 × 10 ⁵ Ω · cm when 1000 V is applied, and is contained in an amount of 30 to 50 parts by weight with respect to the toner. The latent image formed on the photosensitive member having the same polarity as that of the body and contained in 4 to 9 parts by weight with respect to the toner is developed, and the pre-transfer charging is performed before the formed toner image is transferred to the recording paper. It is characterized by being charged with a container.

As described above, by providing the pre-transfer charger, the toner on the photosensitive member can be transferred with good adhesion to the recording paper, and the electric resistance of the magnetic powder is 1.0 × 10 ^{3 to} 1.0 × 10 ^5. By including a charge control resin having the same polarity as that of the photoreceptor, the formed toner image can be quickly charged with the pre-transfer charger before being transferred to the recording paper. In addition, since it is possible to remove excessive charge, overcharge due to continuing trailing and intermittent low density printing can be prevented, and an image forming method capable of obtaining a good image can be provided.

  As described above, according to the present invention, when the trailing in the magnetic jumping development method, intermittent printing, and low density printing are repeated, the magnetic material 1 that does not cause an image defect due to density reduction can be obtained. Component toner for an image forming apparatus and an image forming method using the toner can be provided.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

First, the present invention will be briefly described. In the present invention, a binder resin composed of polyester and a magnetic material having an electric resistance of 1.0 × 10 ^{3 to} 1.0 × 10 ⁵ Ω · cm when 1000 V is applied. 30 to 50 parts by weight of the powder with respect to the toner, and 4 to 9 parts by weight of the charge control resin having the same polarity as the photoreceptor and containing a styrene-acrylic copolymer and a quaternary ammonium salt. The toner is constituted.

  When the toner is configured in this way, the charge control resin is first included, so that the rising of the charge of the toner is improved. For example, a pre-transfer charger that charges a toner image formed on a photoconductor before it is transferred to a recording sheet, although tailing is likely to occur when the peripheral speed of the photoconductor is 300 mm / sec or higher. Even if the toner is provided, the transfer is performed before the toner is sufficiently charged due to the increase in the peripheral speed of the photosensitive member, and tailing occurs. However, the addition amount of the conventional charge control resin to the toner is 2 to 3 parts by weight, but if the charge control resin is added in an amount of 4 to 9 parts by weight exceeding that amount, the rise of the toner charge becomes faster. The toner is charged, the adhesion between the toner and the recording paper is ensured, and tailing hardly occurs.

However, when a large amount of charge control resin is added in this way, the toner in the developing machine (mainly on the developing sleeve) becomes the developer when the low density printing such as the printing rate of 1% or less is repeated intermittently by the magnetic jumping method. Charging up by repeatedly passing between the regulating member and the developing sleeve and being rubbed, overcharging and increasing the adhesion to the developing sleeve, the developability to the photosensitive drum is lowered, and the image density is lowered. It will cause. However, by including magnetic powder having an electric resistance of 1.0 × 10 ^{3 to} 1.0 × 10 ⁵ Ω · cm when 1000 V is applied, the charge of the toner can be obtained even when intermittent printing and low density printing are repeated. Can be prevented from being excessively charged and the image density can be reduced.

  FIG. 1 shows an example of an image forming apparatus 10 that uses the toner for an image forming apparatus according to the present invention and performs the image forming method of the present invention. The illustrated image forming apparatus 10 includes a photosensitive drum 11 that is an image carrier. Around the photosensitive drum 11, a main charger 12, a developing device 13, a pre-transfer charger 14, and a cleaning unit. 15 is arranged. The photosensitive drum 11 is in contact with a transfer belt 16 as transfer means at the transfer position.

  The developing device 13 is provided with a developing roller (developing sleeve) 13a having a magnet (not shown) inside, and a toner layer on the developing roller 13a by a developer layer thickness regulating member (not shown). The thickness is regulated and the toner is triboelectrically charged. A partition wall 131 is provided so as to partition the developing device housing 13b. A recovery roller 13c is disposed in the lower portion of the developing device housing 13b separated by the partition wall 131. Are facing each other. A sealing member 17 is disposed between the pre-transfer charger 14 and the developing unit 13. The sealing member 17 is insulated from the shield 14a of the pre-transfer charger 14 and is grounded. It should be noted that the sealing member 17 may be disposed at the approximate center between the opposed surfaces of the shield 14a and the developing device housing 13b of the pre-transfer charger 14 or at a position slightly closer to the developing device housing 13b. desirable.

  If it is not arranged in this way, that is, if the sealing member 17 is too close to the shield 14a, the effect of the sealing member 17 is impaired due to the influence of the electric field due to the voltage applied to the shield 14a. . When there is a sufficient space between the shield 14a and the developing device housing 13b, the sealing member 17 may be disposed so as to be not affected by the electric field of the shield 14a. The sealing member 17 is made of a metal plate such as stainless steel. By disposing the sealing member 17 in this manner, it is possible to prevent the shield 14a, in particular, the outer side facing the developing unit 13 from directly facing the developing unit and being contaminated by sucking the reversely charged toner. Further, the sealing member 17 is not contaminated by the toner scattered from the developing device 13.

  A bias voltage having the same polarity as the toner charging polarity (hereinafter referred to as a collecting roller bias voltage) 21 is applied to the collecting roller 13c, and a bias voltage (having the same polarity as the toner charging polarity) is applied to the shield 14a of the pre-transfer charger 14. (Hereinafter referred to as shield bias voltage) 22 is applied. In the illustrated example, since the toner is positively charged, both the recovery roller bias voltage 21 and the shield bias voltage 22 are positive voltages. The shield bias voltage 22 is controlled by, for example, a control device (not shown), and when printing is started by the image forming apparatus 10, the shield bias voltage 22 is applied to the shield 14a. When the image forming apparatus 10 is stopped, the application of the shield bias voltage 22 is stopped.

  When forming an image, the surface of the photosensitive drum 11 is uniformly charged by the main charger 12 (plus charging), and the photosensitive drum 11 is exposed by an exposure unit (not shown) according to the image data. Thus, an electrostatic latent image is formed on the photosensitive drum 11. Then, the electrostatic latent image is developed by the developing roller 13a to form a toner image on the photosensitive drum 11 (the toner is positively charged). Since the collection roller bias voltage 21 has the same polarity as the toner charging polarity, the positive toner is applied in accordance with the action of the electric field formed between the photosensitive drum 11 and the collection roller 13c by the application of the collection roller bias voltage 21. It receives an electrostatic force pushed back to the photosensitive drum 11 side.

  On the other hand, negative polarity toner of opposite polarity is unavoidably present in the toner. The negative polarity toner receives an electrostatic force toward the collection roller 13c due to the action of the electric field, and is attracted to the surface of the collection roller 13c and collected in the developing device housing 13b.

  Thereafter, a charge is applied to the toner image on the photosensitive drum 11 by the pre-transfer charger 14 to adjust the toner charge amount, and then the toner is applied to the recording paper (transfer medium) by the transfer belt 16 at the transfer position. The image is transferred. Then, the recording paper is conveyed to a fixing unit (not shown), where the toner image on the recording paper is fixed and then discharged. The residual toner remaining on the photosensitive drum 11 is cleaned by the cleaning unit 15.

  The magnetic powder to be internally added to the toner of the present invention used in the image forming apparatus configured as described above is manufactured as follows. First, in a ferrous sulfate aqueous solution, 1.1 to 1.2 equivalents of a caustic soda solution with respect to iron element, and 2.0 mass% sodium silicate in terms of silicon element with respect to iron element are mixed. An aqueous solution containing 1 iron was prepared. Then, air was blown in while maintaining the aqueous solution at pH 8, and an oxidation reaction was performed at 80 to 90 ° C. for 1 hour to prepare a slurry liquid. After filtering and washing it, the produced hydrophobic magnetic powder was washed, filtered and dried, and the resulting particles were subjected to charge / decomposition treatment to obtain a magnetic powder 1 having an average particle size of 0.20 μm. In addition, magnetic powders 2 and 3 were obtained by changing the amount of sodium silicate mixed and the reaction time during the preparation of the aqueous solution containing ferrous hydroxide. In addition, when preparing an aqueous solution containing ferrous hydroxide, the production of the magnetic powder was repeated until an appropriate amount of magnesium sulfate was added to obtain a magnetic powder having a desired resistance value, whereby a magnetic powder 4 was obtained.

5 g of the magnetic powders 1 to 4 thus obtained were weighed, put into a measurement cell, molded at a molding pressure of 300 kg / cm ² with a hydraulic cylinder, and with a pressure of 150 kg / cm ² applied, the lower end of the measurement cell and A super insulation resistance meter was connected to the upper end, and 1000 V was applied to read the value after 5 seconds. Further, the thickness (cm) of the molded product was measured with a caliper, and the electrical resistance (Ω · cm) was calculated by the following formula.
Electrical resistance (Ω · cm) = Measured resistance value (Ω) × cross-sectional area (cm ² ) / molded product thickness (cm)

The resistance values of the obtained magnetic powders 1 to 4 when 1000 V is applied are as follows.
Magnetic powder 1 4.0 × 10 ³ (Ω · cm)
Magnetic powder 2 6.8 × 10 ² (Ω · cm)
Magnetic powder 3 8.6 × 10 ⁴ (Ω · cm)
Magnetic powder 4 5.4 × 10 ⁵ (Ω · cm)

  In consideration of the good dispersion of the magnetic powder in the binder resin, surface treatment with a surface treatment agent such as a titanium coupling agent, a silane coupling agent, an aluminum coupling agent, or various fatty acids may be performed. Good. Of these, silane coupling agents are preferred, and specific compounds thereof include, for example, hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allyl Phenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilyl mercaptan, trimethylsilyl mercaptan, triorganosilyl acrylate, vinyl Dimethylacetoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, diphenylethoxysilane, hexamethyldisiloxane 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and the like. Further, dimethylpolysiloxane having 2 to 12 siloxane units in one molecule and having one hydroxyl group bonded to a silicon atom, one for each siloxane unit located at the terminal, can also be used.

<Binder resin>
Examples of the binder resin include polystyrene resin, acrylic resin, polyethylene resin, polypropylene resin, polyvinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, polyvinyl alcohol resin, vinyl ether resin, Examples thereof include N-vinyl resins and styrene-butadiene resins. Among toners used in 50 or more high-speed image forming apparatuses, polyester resins are particularly preferable from the viewpoint of charging stability and fixing at low temperatures.

Examples of the polyester resin include various polyester resins obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component. Among these, as the alcohol component, for example, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, Diols such as 1,5-pentanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, 1,6-hexanediol, 1,8-octanediol ;
Bisphenols such as bisphenol A, hydrogenated bisphenol A, propylene oxide bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A;
Sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentane Triol, glycerin, diglycerin, 2-methylprovantriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene Examples include alcohols.
The carboxylic acid component includes oxalic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid , Malonic acid, alkyl succinic acid (n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid, isododecyl succinic acid, etc.), alkenyl succinic acid (n-butenyl succinic acid, isobutenyl succinic acid) Divalent carboxylic acids such as n-octenyl succinic acid, n-dodecenyl succinic acid, isododecenyl succinic acid, etc.];
1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic 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) And trivalent or higher carboxylic acids such as methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empole trimer acid.

  Considering that the surface of a printed material such as paper is satisfactorily fixed by a heat fixing unit used in a normal image forming apparatus, the softening point of the polyester resin is preferably 80 to 150 ° C., and preferably 90 to 140. More preferably, it is ° C.

A part of the binder resin preferably has a crosslinked structure. By introducing a cross-linked structure in part, the storage stability, form retention, durability, etc. of the magnetic toner can be improved without deteriorating the fixability. In order to make a part of the binder resin have a crosslinked structure, a crosslinking agent may be added to crosslink the resin, or a thermosetting resin may be blended.
Examples of the thermosetting resin include epoxy resins such as bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, novolac type epoxy resin, polyalkylene ether type epoxy resin, cycloaliphatic type epoxy resin, and cyanate resin. 1 type, or 2 or more types.

The glass transition temperature Tg of the binder resin is preferably 50 to 65 ° C, and more preferably 50 to 60 ° C. If the glass transition temperature is less than this range, the toner particles are likely to be fused with each other, and the storage stability may be lowered. Further, since the strength of the resin is low, there is a possibility that the toner adheres to the surface of the latent image holding member and does not leave. On the other hand, when the glass transition temperature exceeds this range, the fixability to the surface of the substrate such as paper may be lowered.
In addition, the glass transition temperature of binder resin can be calculated | required from the change point of specific heat in the endothermic curve measured, for example using the differential scanning calorimeter (DSC). Specifically, for example, a differential scanning calorimeter DSC-6200 manufactured by Seiko Instruments Inc. is used, and 10 mg of a measurement sample is put in an aluminum pan, and an empty aluminum pan is used as a reference, and a measurement temperature range of 25 to 200 ° C. The glass transition temperature of the binder resin can be determined from the change point of specific heat in the endothermic curve obtained by measuring at a temperature increase rate of 10 ° C./min and at normal temperature and normal pressure.

  The magnetic toner of the present invention may contain various conventionally known additives such as a colorant, a charge control agent, and a wax. Among these, examples of the colorant include pigments such as carbon black and dyes such as acid violet in order to adjust the color tone. The proportion of the colorant in the toner is preferably about 0.5 to 5% by weight.

<Charge control agent>
The charge control agent is blended in order to improve the charge level and charge rising characteristics of the magnetic toner (an index indicating whether the charge is charged to a constant charge level in a short time) and to improve durability and stability. There are two types of charge control agents, one that is positively charged and the other that is negatively charged, and either one is blended in accordance with the charging polarity of the magnetic toner.

  Examples of positively chargeable charge control agents 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, 1,3,5-thiadiazine, 1,2, 3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6-oxatriazine, 1,3,4,5-oxatriazine, phthalazine, Azine compounds such as quinazoline and quinoxaline; Azin Fast Red FC, Azin Fast Red 12BK, Azin Violet BO, Azine Direct dyes composed of sub-zine compounds such as Raun 3G, Azin Light Brown GR, Azin Dark Green BH / C, Azin Deep Black EW, Azin Deep Black 3RL; Nigrosine Compounds such as Nigrosine, Nigrosine Salt, Nigrosine Derivatives; Nigrosine BK , Nigrosine NB, nigrosine Z and other acid dyes; metal salts of naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; quaternary ammonium salts such as benzylmethylhexyldecylammonium and decyltrimethylammonium chloride 1 type, or 2 or more types. In particular, a nigrosine compound is suitable as a positively chargeable toner because it can obtain a quicker charge rising characteristic.

  In addition, as the positively chargeable charge control agent, a resin or oligomer having a quaternary ammonium salt called a so-called charge control resin to assist the action of the charge control agent, a resin or oligomer having a carboxylate, Resins or oligomers having a carboxyl group can also be used. Specifically, polystyrene resin having quaternary ammonium salt, acrylic resin having quaternary ammonium salt, styrene-acrylic resin having quaternary ammonium salt, polyester resin having quaternary ammonium salt, carboxylate Polystyrene resin having carboxylate, acrylic resin having carboxylate, styrene-acrylic resin having carboxylate, polyester resin having carboxylate, polystyrene resin having carboxyl group, acrylic resin having carboxyl group 1 type, or 2 or more types, such as a styrene-acrylic resin having a carboxyl group and a polyester resin having a carboxyl group.

  In particular, a styrene-acrylic resin (styrene-acrylic copolymer) having a quaternary ammonium salt, carboxylate or carboxyl group as a functional group can easily adjust the charge amount to a value within a desired range. It is preferable in that it can be performed. Further, acrylic monomers constituting styrene-acrylic resin together with styrene are methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, acrylic acid 2 Examples include (meth) acrylic acid alkyl esters such as ethylhexyl, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate.

  Furthermore, as the quaternary ammonium salt compound, a unit derived from a dialkylaminoalkyl (meth) acrylate through a quaternization step is used. Examples of the derived dialkylaminoalkyl (meth) acrylate include di (amino) ethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dibutylaminoethyl (meth) acrylate and the like ( Lower alkyl) aminoethyl (meth) acrylates; dimethylmethacrylamide; dimethylaminopropylmethacrylamide are preferred. Further, hydroxy group-containing polymerizable monomers such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and N-methylol (meth) acrylamide can be used in combination during polymerization.

  As the negatively chargeable charge control agent, for example, organometallic complexes and chelate compounds are effective, and among them, acetylacetone metal complexes, salicylic acid metal complexes or salts are preferable, and salicylic acid metal complexes or salts are particularly preferable. Among these, examples of the acetylacetone metal complex include aluminum acetylacetonate and iron (II) acetylacetonate. Examples of the salicylic acid-based metal complex or salt include chromium 3,5-di-tert-butylsalicylate. As the negatively chargeable charge control resin, those disclosed in JP-A-2002-040717 can be used.

  The proportion of the charge control agent in the toner is preferably 4 to 15% by weight, and more preferably 5 to 10.0% by weight. When the ratio of the charge control agent is less than this range, it is difficult to impart stable charging characteristics to the magnetic toner, and there is a possibility that the image density is lowered or the durability is lowered. In addition, since poor dispersion with respect to the binder resin is likely to occur, there is a risk that background fogging may occur, or the charge control agent aggregated without being dispersed may contaminate the photoreceptor. On the other hand, if the above range is exceeded, the magnetic toner tends to have environmental resistance, particularly charging failure and image failure under high temperature and high humidity. Further, since poor dispersion with respect to the binder resin is likely to occur, there is a possibility that background fogging may occur, or the charge control agent aggregated without being dispersed may contaminate the photoreceptor.

<wax>
Wax improves the anti-offset property by improving the fixability of the magnetic toner to the surface of the printed material such as paper, or preventing the magnetic toner during fixing from adhering to the fixing roller of the image forming apparatus. The magnetic toner adhering to the fixing roller or the like is added to improve or prevent the image smearing from being reattached to the surface of the printing material and soiling the image.

  Examples of the wax include olefin waxes such as polyethylene wax and polypropylene wax; plant waxes such as carnauba wax, rice wax and candelilla wax; mineral waxes such as montan wax; Fischer-Tropsch wax produced by the Tropsch method; Petroleum wax such as paraffin wax and microcrystalline wax; Ester wax; Teflon (registered trademark) wax selected from one or more Can be used.

  The proportion of the wax in the toner is preferably 1 to 5% by weight. If the wax ratio is less than this range, the effect of improving the offset property of the magnetic toner or preventing image smearing may be insufficient. May be easily fused and storage stability may be reduced.

<Manufacture of toner>
In the magnetic toner of the present invention, the above components are mixed using a stirring mixer such as a Henschel mixer, then kneaded using a kneader such as an extruder, cooled, further pulverized, Manufactured by classification as necessary. Moreover, you may wet-mix said each component. The magnetic toner of the present invention thus produced preferably has a volume-based center particle size of 5 to 10 μm.

  In addition, the manufactured magnetic toner improves the flowability, storage stability, cleaning properties indicating the ease of cleaning removal from the surface of the latent image holding member, etc. Surface treatment may be performed with fine particles (external additive, usually having an average particle size of 1.0 μm or less) such as silica, hydrophobic silica, alumina, titanium oxide and the like. For the surface treatment, it is preferable to dry-mix the toner and the external additive. In particular, in order to prevent the external additive from being embedded in the surface of the toner particles, the toner is mixed using a Henschel mixer or a Nauter mixer. Is preferred. The addition amount of the external additive is preferably 0.2 to 10.0% by weight with respect to the toner. The external additive may be surface-treated with aminosilane, silicone oil, silane coupling agent (hexamethyldisilazane, etc.), titanium coupling agent, or the like, if necessary.

  Using this magnetic powder, a toner was produced by the following method. First, 100 parts by weight of a polyester resin (alcohol component; bisphenol A propion oxide adduct, acid component; terephthalic acid, softening point 150 ° C., acid value 7.0), 90 parts by weight of the magnetic powder 1 produced above, 3 parts by weight of CCA (trade name; Bontron No. 1, manufactured by Orient Chemical) as a charge control component, 12 parts by weight of charge control resin (quaternary ammonium salt-added styrene / acrylic copolymer; FCA196 manufactured by Fujikura Kasei), as a wax component 3 parts by weight of ester wax (trade name: WEP · 5, manufactured by NOF Corporation) is mixed with a Henschel mixer, kneaded with a twin screw extruder (cylinder setting temperature 100 ° C.), coarsely pulverized with a feather mill, and then a jet mill Was pulverized and classified by an airflow classifier to obtain a toner classified product having an average particle size of 8.0 μm. Next, 0.5 parts by weight of silica (trade name: RA200HS, manufactured by Nippon Aerosil Co., Ltd.) and 1.0 part by weight of titanium oxide (trade name: EC100T1, manufactured by Titanium Industry Co., Ltd.) are added to 100 parts by weight of the toner classified product. The magnetic toner A was obtained by mixing with a Henschel mixer.

Then, similarly to the magnetic toner A, only the kind of magnetic powder and the number of mixing parts were changed to obtain magnetic toners B to D. In addition, magnetic toners E to L were obtained by changing the addition amount of the magnetic powder and the charge control resin. The magnetic powder to toner ratio and the electrification control resin to toner ratio in each magnetic toner are as follows.
Magnetic powder Magnetic powder to toner ratio Charge control resin to toner ratio A Magnetic powder 1 43.3% 5.8%
B Magnetic powder 2 ↑ ↑
C Magnetic powder 3 ↑ ↑
D Magnetic powder 4 ↑ ↑
E Magnetic powder 1 48.2% 5.3%
F ↑ 50.4% 5.0%
G ↑ 33.7% 6.7%
H ↑ 29.8% 7.1%
I ↑ 33.0% 8.8%
J ↑ 32.6% 9.8%
K ↑ 44.1% 4.4%
L ↑ 44.3% 3.4%

Using the magnetic toner obtained above and the image forming apparatus LS-9500 modified by Kyocera Mita shown below, at a normal temperature and normal humidity (temperature 20 ° C./humidity 65%), according to data with a printing rate of 0.2%. 3000 sheets of intermittent printing were performed, and the image tailing, image density, and fog density in the initial image and after 3000 sheets of intermittent printing were evaluated.
Specification of evaluation experiment machine, Kyocera Mita image forming device LS-9500 remodeled machine.
[Development conditions]
Development method: dry-one-component jumping development Photosensitive drum peripheral speed: 440 mm / sec (80 sheets / min in terms of A4 paper)
Gap between photoconductor and developing sleeve: 0.30 mm
Development sleeve / photosensitive member peripheral speed ratio: 1.4
Blade gap: 0.25mm
Photoconductor potential: 400V
Development DC bias: 300V
Development AC peak to peak: 1.5KV
Development AC frequency: 2.5 kHz
Number of magnetic rolls of developing sleeve: 4 poles S1 pole (developing pole) Magnetic flux density: 800 × 10 ⁻⁴ T
[Fixing conditions]
Heat roll fixing method Fixing pressure: 350N
Fixing nip width: 6.5 mm
Fixing temperature: 210 ° C
[Charger conditions before transfer]
Corotron system AC / V _PP : 4.0KV
DC: 1.5KV

As a result of the evaluation, the magnetic toner that was satisfactory was shown in FIG. 2A as Examples 1 to 6, and the defective magnetic toner was shown in FIG. 2B as Comparative Examples 1 to 6. The determination criteria are as follows.
Status Judgment Image tailing not occurred ○
Occurrence ×
Image density 1.3 or higher ○ (Good)
Less than 1.3 1.1 or more △ (somewhat good)
Less than 1.1 × (Poor)
Fog density 0.006 or less ○ (Good)
0.007 to 0.012 △ (slightly good)
0.013 or more × (Poor)
Image tailing is an image density measuring device for visually observing the fixed image to determine the presence or absence, image density is the image density of the solid part of the image, and fog density is the image density of the non-printing part of the paper. (Measured by Gretag Macbeth: RD-914).

First, the magnetic toners A, C, E, G, I, and K of Examples 1 to 6 in which the results shown in FIG. The toners are 0 × 10 ³ (Ω · cm) and 8.6 × 10 ⁴ (Ω · cm), and the magnetic powder to toner ratio is 33.0% of I at the lowest and 48 of E at the highest. Further, the charge control resin to toner ratio is 6.8% for E at the lowest and 13.8% for I at the highest.

That is, the electric resistance of the magnetic powder is about 1.0 × 10 ^{3 to} 1.0 × 10 ⁵ (Ω · cm), the toner ratio of the magnetic powder is about 30 to 50%, and the charge control resin pair It is considered that good results can be obtained when the toner ratio is about 4 to 9%.

On the other hand, in the magnetic toners B, D, F, H, J, and L of Comparative Examples 1 to 6 in which the result shown in FIG. 0.8 × 10 ² (Ω · cm) and 5.4 × 10 ⁵ (Ω · cm), and the toner ratio of magnetic powder is 29.8% of H at the lowest and 50.50 of F at the highest. Further, the charge control resin to toner ratio is 3.4% for L at the lowest and 9.8% for J at the highest.

When the defects of the respective toners are closely observed, in the toner B of Comparative Example 1, the image tailing is generated from the initial stage, and the image density is slightly good from the initial stage. The toner B of Comparative Example 1 uses a magnetic powder having a resistance of 6.8 × 10 ² (Ω · cm) with a magnetic powder of 2, and the toner ratio of the magnetic powder to the toner of the charge control resin is According to this result, the magnetic powder 2 has a toner resistance value that is too low, the charge amount is insufficient, and the adhesion of the toner transferred to the recording paper is insufficient, and the tailing is not good. In addition, it is considered that the image density is satisfactory and the image density is not satisfactory due to insufficient charge amount.

In the toner D of Comparative Example 2 below, the image tailing is good, but the image density is good at the initial stage, but worse after printing, and the fog density is slightly good for Δ both at the initial stage and after printing. It has become. As the toner D of Comparative Example 2, a magnetic powder having a resistance value of 5.4 × 10 ⁵ (Ω · cm) with a magnetic powder of 4 is used, and the toner ratio of the magnetic powder to the toner of the charge control resin is the same as that of the toner A. According to this result, the toner using the magnetic powder 4 has a toner resistance value that is too high, and the toner that has been transferred to the recording paper due to the excessive charge amount has good adhesion to the recording paper. However, it is considered that after intermittent printing based on the low printing rate data, the toner is charged up and overcharged, the image density is lowered, and fogging has occurred from the initial state.

In the toner F of Comparative Example 3 below, image tailing occurs from the beginning, and the image density is slightly good from the beginning. The toner F of Comparative Example 3 uses 4.0 × 10 ³ (Ω · cm) of the same magnetic powder as that of A, and the magnetic powder to toner ratio is 50.4% higher than that of the toner A. The charge control resin to toner ratio is 5.0%, which is lower than that of toner A. From this result, the toner resistance value is low due to the high magnetic powder to toner ratio, and the charge rise is poor due to the small amount of charge control resin, so that the charge amount is insufficient and transferred to the recording paper. It is thought that tailing occurred due to insufficient adhesion of the toner to the recording paper, and it was considered that satisfactory image density could not be obtained due to insufficient charge amount.

In the toner H of Comparative Example 4 below, the image tailing is good, but the image density is good at the initial stage, but becomes worse after printing, and the fog density is slightly good at Δ at the beginning and worse after printing. Yes. The toner H of Comparative Example 4 uses a magnetic powder having the same electric resistance as that of A, 4.0 × 10 ³ (Ω · cm), and the magnetic powder to toner ratio is 29.8% lower than that of the toner A. The charge control resin to toner ratio is 7.1%, which is higher than that of the toner A. According to this result, the toner resistance value is high due to the low magnetic powder to toner ratio, and the charge rise is improved due to the large amount of charge control resin, resulting in excessive charge. Although the adhesion to the recording paper is improved and tailing does not occur, after intermittent printing with low printing rate data, the toner is charged up and overcharged, the image density decreases and the initial state is reduced. It is considered that fogging occurred and the amount of charge was further increased as compared with Comparative Example 2, and the fogging after printing was also deteriorated.

In Toner J of Comparative Example 5 below, the image tailing is good, but the image density is good at the initial stage, but slightly better after printing, and the fog density becomes worse both at the initial stage and after printing. ing. The toner J of Comparative Example 5 uses a magnetic powder having the same electric resistance as that of A, 4.0 × 10 ³ (Ω · cm), and the magnetic powder to toner ratio is lower than that of Toner A. Comparative Example 4 32.6%, which is higher than that of Toner H, and the ratio of the charge control resin to toner is 9.8%, which is higher than that of Toner H of Comparative Example 4. From this result, since the magnetic powder to toner ratio is lower than that of toner A and higher than that of toner H of comparative example 4, the resistance value of the toner is lower than that of toner H of comparative example 4 but higher than that of toner A. Further, since the amount of charge control resin is larger than that of the toner H of Comparative Example 4, it is considered that the rising of the charge is improved and the charge is excessive, although not as high as that of the toner H of Comparative Example 4. As a result, the adhesion of the toner transferred to the recording paper to the recording paper is improved and tailing does not occur. However, after intermittent printing with low printing rate data, the toner is charged up and the image density is Δ. Slightly better, but since there are many overcharged toner particles from the beginning, the fog seems to have deteriorated from the initial state.

In the last toner L of Comparative Example 6, image tailing occurred from the beginning, the image density was slightly good from the beginning to after printing, and the fog density was good at the beginning but slightly good after printing. It has become. The toner L of Comparative Example 6 uses 4.0 × 10 ³ (Ω · cm) of the same magnetic powder as that of A, and the magnetic powder to toner ratio is slightly higher than that of the toner A, 44.3%. The charge control resin to toner ratio is 3.4%, which is considerably lower than that of the toner A. From this result, it is considered that the resistance value of the toner is slightly lower than that of the toner A, but the amount of charge control resin is significantly less, the rise of charging is poor, and tailing has occurred from the beginning. Further, the image density is not sufficiently satisfactory due to insufficient charge amount, and the fogging is considered to be somewhat deteriorated after printing.

Therefore, as described above, the electrical resistance of the magnetic powder is about 1.0 × 10 ^{3 to} 1.0 × 10 ⁵ (Ω · cm), and the magnetic powder to toner ratio is about 30 to 50%. It can be seen that good results can be obtained if the charge control resin to toner ratio is approximately 4-9%.

  According to the present invention, magnetic single-component image formation that does not cause image defects due to density reduction when the trailing in the magnetic jumping development system, intermittent printing, and low density printing is repeated can be obtained. An apparatus toner and an image forming method using the toner can be provided.

It is an example of an image forming apparatus that uses the toner for an image forming apparatus according to the present invention and performs the image forming method of the present invention. Magnetic powder and charge control resin to be internally added to the toner are prepared by changing the resistance value of the magnetic powder, and a plurality of toners are manufactured by changing the amount of addition of the charge control resin. As a result of evaluation of tailing, image density, and fog density, the magnetic toner that was satisfactory was designated as Examples 1 to 6 in (A), and the defective magnetic toner was designated as Comparative Examples 1 to 6 in (B). It is the table shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Photoconductor drum 12 Main charging device 13 Developing device 13a Developing roller 13b Developing device housing 13c Collection roller 131 Partition wall 14 Pre-transfer charging device 14a Pre-transfer charging device shield 15 Cleaning unit 16 Transfer belt 17 Sealing Member 21 Recovery roller bias voltage 22 Shield bias voltage

Claims (4)

An alternating electric field for development is applied with a magnet inside, and the latent image formed on the photoconductor is developed by an electrophotographic method held on a sleeve arranged in the vicinity of the photoconductor, A toner for an image forming apparatus, comprising a resin and a magnetic powder and a charge control resin,
The magnetic powder has an electric resistance of 1.0 × 10 ^{3 to} 1.0 × 10 ⁵ Ω · cm when 1000 V is applied, and the magnetic powder is contained in an amount of 30 to 50 parts by weight with respect to the toner. The toner for an image forming apparatus, wherein the charge control resin has the same polarity as that of the photoreceptor and is contained in an amount of 4 to 9 parts by weight with respect to the toner.   The toner for an image forming apparatus according to claim 1, wherein the binder resin is polyester.   The toner for an image forming apparatus according to claim 1, wherein the charge control resin contains a styrene-acrylic copolymer and a quaternary ammonium salt. An alternating electric field for development is applied with a magnet inside, and the latent image formed on the photoconductor is developed by an electrophotographic method held on a sleeve arranged in the vicinity of the photoconductor, An image forming method using a toner for an image forming apparatus comprising a resin, a magnetic powder, and a charge control resin,
The image forming apparatus includes a pre-transfer charger that charges a toner image formed on the photoconductor before being transferred to a recording paper, and the peripheral speed of the photoconductor is 300 mm / sec or more,
The magnetic powder has an electric resistance of 1.0 × 10 ^{3 to} 1.0 × 10 ⁵ Ω · cm when 1000 V is applied, and is contained in an amount of 30 to 50 parts by weight with respect to the toner. The latent image formed on the photosensitive member having the same polarity as that of the body and contained in 4 to 9 parts by weight with respect to the toner is developed, and the pre-transfer charging is performed before the formed toner image is transferred to the recording paper. An image forming method characterized by charging with a container.

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