JP2005234548A - Magnetic single component toner for electrostatic latent image development and method for forming image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic single component toner for electrostatic latent image development for stably forming a toner thin layer on a sleeve and giving stable image quality not only in the initial stage but in a long period in a developing system in which a magnetic single component development jumping system is employed and the ten-point roughness Rz of the sleeve surface of a developer carrier is relatively low. <P>SOLUTION: The magnetic single component toner for electrostatic latent image development is used in a developing system by a magnetic single component development jumping system in which an electrostatic latent image formed on a latent image holding body is developed by a developer carrier and the ten-point average roughness Rz of the sleeve surface of the developer carrier ranges from 2.0 μm to 6.0 μm. The toner contains magnetic powder having 1×10<SP>3</SP>Ω cm and 1×10<SP>7</SP>Ω cm volume specific resistance and an inorganic metal oxide having 10<SP>0</SP>to 10<SP>7</SP>Ω cm volume specific resistance added as an external additive. The charge amount of the toner on the sleeve is controlled to ≤8.0 μC/g. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a dry magnetic one-component toner for developing an electrostatic charge image (electrostatic latent image) formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method or the like.

  In general, in an electrophotographic method or an electrostatic recording method, it is formed by exposing a latent image carrier made of a photoconductive photosensitive member or a dielectric to a photosensitive member charged by corona charging or the like with a laser, an LED or the like. The electrostatic latent image is visualized using a developer such as toner, or the electrostatic latent image is visualized by reversal development to obtain a high quality image. In general, the toner applied to these development methods is obtained by mixing a thermoplastic resin as a binder with a dye, a pigment as a charge control agent, a wax as a release agent, and a magnetic material, and kneading, pulverizing, and classifying the average. Toner particles having a particle size of 5 to 15 μm are used. Then, inorganic fine powders such as silica and titanium oxide, and inorganic metal fine powders are externally added to the toner particles for the purpose of imparting fluidity to the toner, controlling charging of the toner, and improving cleaning properties.

  By the way, as dry development methods in various electrostatic copying methods currently in practical use, there are two-component development methods using a carrier such as toner and iron powder, and a magnetic material containing a magnetic substance inside the toner without using a carrier. A one-component development system is known.

  Many developing methods for electrostatic latent images have been developed and put into practical use. For example, a number of development methods such as a magnetic brush method described in Patent Document 1 below, a cascade development method and a powder cloud method, and a fur brush development method described in Patent Document 2 below are known. Among these, a magnetic brush method, a cascade method, and the like using a two-component developer mainly composed of toner and carrier are widely put into practical use. Initially, the methods using these two-component developers can provide a relatively stable and high-quality image. However, when used over a long period of time, carrier deterioration occurs, that is, the spent phenomenon occurs. There are common problems such as a problem that the charge imparting ability is deteriorated and a high-quality image cannot be obtained over a long period of time, and a long-term durability is lacking because the mixing ratio of the toner and the carrier is difficult to keep constant.

  In order to avoid such drawbacks, various development methods using a one-component developer composed only of toner have been proposed, and among them, a magnetic one-component development method employing a magnetic toner is generally well known and utilized.

  As a developing method using a one-component magnetic toner, a developing method using a conductive magnetic toner disclosed in Patent Document 3 below is known. In this method, a conductive magnetic toner is held on a cylindrical conductive developer carrier having magnetism inside, and is developed by bringing it into contact with an electrostatic latent image. At this time, in the developing unit, a conductive path is formed by toner particles between the surface of the latent image carrier and the surface of the sleeve, and electric charges are guided from the sleeve to the toner particles through this conductive path. The toner particles adhere to the image portion and are developed by the Coulomb force between the two. In this method, since the toner is conductive, it is difficult to electrostatically transfer the toner image on the latent image holding member to a printing medium (for example, plain paper) using an electric field, There are problems that it is difficult to obtain high image quality over a long period of time due to a trouble phenomenon derived from conductive toner in the process, and that there is a problem of electrical leakage destruction to the latent image carrier.

  Further, a method using an insulating toner has been proposed in Patent Document 4 below. This method is called a magnetic one-component jumping method, and a developer carrier is provided opposite to the electrostatic latent image carrier, and this developer carrier has a developing sleeve with a built-in magnet roller. The toner is transported by the rotation of the developing sleeve, is passed through the gap between the developing sleeve and the magnetic blade to form a thin toner layer, and the electrostatic latent image on the surface of the electrostatic latent image holding member is formed by the charged toner. Develop. This method has advantages such as prevention of background fogging, and an excellent image can be obtained.

  By using the magnetic one-component developing method in this way, the problem of lack of long-term durability with a two-component developer can be solved. Further, as a feature of the developing device used in such a developing method, it can be mentioned that it can have a very small and simple configuration.

  In addition, as a latent image holding body on which an electrostatic latent image is formed, in place of a selenium photoconductor or an organic photoconductive photoconductor, it is pollution-free and has high sensitivity, and Vickers strength is as high as 1500 to 2000. From the viewpoint of having characteristics such as being hard, an amorphous silicon photoreceptor (hereinafter referred to as a-Si photoreceptor) is used. In order to develop an electrostatic latent image formed on such a highly durable a-Si photosensitive member, it is desirable to use a toner having excellent charging properties and durability that can withstand long-term use. ing.

  Inorganic metal fine powders such as alumina, titanium oxide, and magnesium oxide that are externally added to the toner are very hydrophilic due to the hydroxyl groups present on the surface, and as a result, the fluidity of the toner when added to the toner. And the rising characteristics of charging change due to the influence of humidity, causing adverse effects such as printing durability and a decrease in image density.

  In order to prevent the influence of such environmental conditions as humidity, the surface of these inorganic metal fine powders is treated with a hydrophobizing agent or a polar group is introduced. For example, Patent Document 5 below proposes to use a metal oxide treated with aminosilane as a polar group introduction. Patent Document 6 below proposes using a titanium compound treated with a silane coupling agent.

  Patent Document 7 listed below discloses an electrostatic latent image developer in which abrasive fine particles such as alumina and zirconia are fixed on the surface of toner base particles, and the ratio of the particle size of the toner base particles to the particle size of the abrasive fine particles is controlled. Has been proposed. According to this method, it is possible to obtain an excellent polishing effect on the surface of the photosensitive member, it is not necessary to incorporate a large system such as a cleaning brush, the apparatus can be miniaturized, and it is effective for image flow, image density, fog, and the like. There is.

  By the way, in recent years, in the market of copying machines and printers using electrophotography and electrostatic printing, the speed of printing and the size of machines have been remarkably advanced. As the printing speed increases, the image characteristics that match the printing speed, that is, the charging characteristics, must be more stable. Further, medium- and low-speed machines, which are becoming smaller in size, are required to have good initial charging and stable charging characteristics over a long period of time since the warm-up time after turning on the power is short. That is, it is required to form a uniform toner thin layer on the developing sleeve stably for a long period of time.

  In addition, as office equipment such as printers and copiers are moving toward higher speed and smaller size, high resolution, high image quality, and high durability are required as natural performance. Needless to say, the formation of a thin toner layer on the sleeve is the key to high resolution, high image quality, high durability, and response to environmental fluctuations. In a developer carrier system with a relatively small Rz, it is no exaggeration to say that the toner thin layer determines high image quality and high durability.

  However, in high-speed machines and small machines using such a system, ensuring long-term stability of the toner thin layer formation on the sleeve is a long-term use, environmental fluctuations (especially in low-temperature and low-humidity environments), and quick warming. Deterioration and long-term stability of the image, that is, high resolution, due to problems such as disturbance of the toner thin layer on the sleeve and occurrence of vertical streaky toner thin layer loss due to factors such as uptime As a result, there arises a problem that high image quality and high durability cannot be realized.

US Pat. No. 2,874,063 US Pat. No. 2,618,552 U.S. Pat. No. 3,909,258 Japanese Patent Laid-Open No. 55-18656 JP-A-52-135739 Japanese Patent Laid-Open No. 10-3177 JP-A-5-181306

  Accordingly, an object of the present invention is to stably form a thin toner layer on a sleeve in a developing system that uses a magnetic one-component development jumping method and that has a relatively small ten-point average roughness Rz on the sleeve surface of the developer carrier. It is an object of the present invention to provide a magnetic one-component toner for developing an electrostatic latent image and an image forming method capable of obtaining stable image quality over a long period of time as well as in the initial stage.

  As a result of diligent research to solve the above problems, the present inventors have found that in the above developing system, in the developing method using a magnetic one-component developing jumping method using a sleeve having a predetermined surface roughness, a specific volume specific By using a magnetic one-component toner to which a magnetic powder having a resistance value and an inorganic metal oxide having a predetermined volume specific resistance value are added as an external additive, a toner thin layer is stably formed on the sleeve. The present inventors have found a new fact that it is possible to complete the present invention.

That is, the magnetic one-component toner for developing an electrostatic latent image and the image forming method of the present invention have the following characteristics.
(1) Magnetic 1 for electrostatic latent image development used in a development system based on a magnetic one-component development jumping system using a developer carrier having a ten-point average roughness Rz of 2.0 μm or more and 6.0 μm or less on the sleeve surface. The toner contains a magnetic powder having a volume resistivity of 1 × 10 ³ Ω · cm to 1 × 10 ⁷ Ω · cm, and has a volume resistivity of 10 ⁰ as an external additive. A magnetic single component for developing an electrostatic latent image, characterized in that an inorganic metal oxide in the range of -10 ⁷ Ω · cm is added and the toner charge amount on the sleeve is 8.0 μC / g or less. toner.
(2) The magnetic one-component toner for developing an electrostatic latent image according to (1), wherein the inorganic metal oxide is added in a range of 0.5 to 5.0% by mass with respect to the toner.
(3) An image forming method by a magnetic one-component development jumping method using a developer carrying member having a ten-point average roughness Rz of 2.0 μm or more and 6.0 μm or less on the sleeve surface, and the toner to be used is ( An image forming method comprising the magnetic monocomponent toner for developing an electrostatic latent image according to 1) or (2).
(4) The image forming method according to (3), wherein the latent image holding member is an amorphous silicon drum.
(5) The image forming method according to (3) or (4), wherein the sleeve is made of stainless steel.

The magnetic one-component toner for developing an electrostatic latent image and the image forming method of the present invention comprise a magnetic powder having a volume resistivity of 1 × 10 ³ Ω · cm to 1 × 10 ⁷ Ω · cm and a volume as an external additive. By adding an inorganic metal oxide having a specific resistance value in the range of 10 ⁰ to 10 ⁷ Ω · cm to the toner, the toner thin layer formation on the sleeve peculiar to the magnetic one-component development jumping method can be stably provided. As a result, it is possible to obtain a stable image quality over a long period of time as well as the initial stage, and to be resistant to environmental fluctuations.

  In the development process of the present invention, a developer carrying member having a developing sleeve surface that is provided facing the latent image holding member and includes a magnet roller therein, conveys toner by rotation of the developing sleeve, It is a magnetic one-component development jumping method in which a toner thin layer is formed on the surface of the developing sleeve by passing between the magnetic blade and the developing sleeve, and the electrostatic latent image formed on the latent image holding member is developed. In the developing system, the ten-point average roughness Rz of the sleeve surface of the developer holder is 2.0 μm or more and 6.0 μm or less.

Here, if the ten-point average roughness Rz is less than 2.0 μm, the image density is not satisfied due to a decrease in the toner conveying force. On the other hand, if the thickness exceeds 6.0 μm, the image quality deteriorates, and a leak from the protrusion on the surface of the sleeve to the photosensitive drum occurs, resulting in an image black spot, which impairs the image quality.
These ten-point average roughness Rz can be measured using a surface roughness measuring instrument “Surfcoder SE-30D” manufactured by Kosaka Laboratory.

  Further, as a material used for the developing sleeve, for example, aluminum, stainless steel (SUS) or the like can be used. When considering high durability, it is preferable to use SUS as a sleeve material, and for example, SUS303, SUS304, SUS305, SUS316, or the like can be used. Moreover, it is more preferable to use SUS305 which has weak magnetism and is easy to process.

  In the present invention, any photosensitive member can be used as the latent image carrier, but it is preferable to use an amorphous silicon drum from the viewpoint of high durability. This is because of the high hardness unique to amorphous silicon drums, so it has a very long durability compared to organic photoreceptors, etc., as in the case of using organic photoreceptors for the mechanical life of printers, copiers, etc. Since there is no need to replace the latent image carrier, and it can be said that the photosensitive layer is not worn like an organic photoreceptor, there is an advantage that image characteristics are stabilized over a long period of time.

  The magnetic monocomponent toner for developing an electrostatic latent image of the present invention can be obtained by dispersing various toner compounding agents such as a colorant in a binder resin. The type of the binder resin used in the toner of the present invention is not particularly limited. For example, styrene resin, acrylic resin, styrene-acrylic copolymer, polyethylene resin, polypropylene resin, vinyl chloride. It is preferable to use thermoplastic resins such as resin, polyester resin, polyamide resin, polyurethane resin, polyvinyl alcohol resin, vinyl ether resin, N-vinyl resin, styrene-butadiene resin.

  More 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.

  Moreover, as the polyester resin, any resin 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. First, dihydric or trihydric or higher alcohol components include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1, Diols such as 4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol; bisphenol A, hydrogen Bisphenols such as added bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tri Pentaellis Ritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylol Examples are trihydric or higher alcohols such as propane and 1,3,5-trihydroxymethylbenzene.

  Further, as the divalent or trivalent or higher carboxylic acid component, divalent or trivalent carboxylic acid, this acid anhydride or this lower alkyl ester is used, 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, or n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, Divalent carboxylic acids such as alkyl or alkenyl succinic acid such as n-octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid, isododecenyl succinic acid; , 4-Benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalene Recarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, Examples include trivalent or higher carboxylic acids such as 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empole trimer acid. Is done. Moreover, it is preferable that the softening point of a polyester-type resin is 80-150 degreeC, More preferably, it is 90-140 degreeC.

  Further, the binder resin may be a thermosetting resin. 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 parts by mass of the thermoplastic resin as the binder resin for the toner, and it is also preferable to add a crosslinking agent or to partially use a thermosetting resin.

  Therefore, an epoxy resin, a cyanate resin, or the like can be used as the thermosetting resin. 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.

  Moreover, in this invention, it is preferable that the glass transition point (Tg) of binder resin is 50-65 degreeC, More preferably, it is 50-60 degreeC. When the glass transition point is lower than the above range, the obtained toners are fused with each other in the developing device, and the storage stability is lowered. Further, since the resin strength is low, there is a tendency that toner adheres to the photoreceptor. Further, when the glass transition point is higher than the above range, the low-temperature fixability of the toner is lowered. The glass transition point of the binder resin can be determined from the change point of the specific heat using a differential scanning calorimeter (DSC). More specifically, it was determined by measuring an endothermic curve using a differential scanning calorimeter DSC-6200 manufactured by Seiko Instruments Inc. as a measuring device. Put 10 mg of measurement sample in an aluminum pan, use an empty aluminum pan as a reference, measure at a measurement temperature range of 25 to 200 ° C, and a temperature increase rate of 10 ° C / min. The glass transition point was determined from the curve.

  In the toner of the present invention, a pigment such as carbon black or a dye such as Acid Violet can be dispersed in the binder resin as a colorant in order to adjust the color tone, as in the known toner. Such a colorant is usually blended in an amount of 1 to 10 parts by mass per 100 parts by mass of the binder resin.

  Charge control agents are blended to remarkably improve the charge level and charge rise characteristics (an indicator of whether to charge to a constant charge level in a short time), and to obtain characteristics such as durability and stability. It is. That is, when the toner is positively charged for development, a positively chargeable charge control agent is added. When the toner is negatively charged for development, a negatively chargeable charge control agent can be added. .

  The charge control agent is not particularly limited. For example, specific examples of the positively chargeable charge control agent 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, Azine compounds such as 2,4,6-oxatriazine, 1,3,4,5-oxatriazine, phthalazine, quinazoline, quinoxaline; azine fast red FC, azine fast red 12BK, azine violet BO, azine brown 3G, azinelite Brown GR, Azindauk Direct dyes comprising azine compounds such as lean BH / C, azine dip black EW, and azine black 3RL; nigrosine compounds such as nigrosine, nigrosine salt and nigrosine derivatives; nigrosine compounds such as nigrosine BK, nigrosine NB and nigrosine Z Quaternary ammonium salts such as benzylmethylhexyldecylammonium and decyltrimethylammonium chloride can be exemplified, and these can be used alone. May be used in combination, or two or more may be used in combination. In particular, the nigrosine compound is optimal for use as a positively chargeable toner from the viewpoint of obtaining a quicker start-up property.

  Further, a quaternary ammonium salt, a carboxylate, or a resin or 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 Examples thereof include one or more of a resin, a styrene-acrylic resin having a carboxyl group, and a polyester resin having a carboxyl group.

  In particular, a styrene-acrylic copolymer resin having a quaternary ammonium salt as a functional group is optimal from the viewpoint that the charge amount can be easily adjusted to a value within a desired range. In this case, preferred acrylic comonomers to be copolymerized with the styrene unit include methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, Examples include (meth) acrylic acid alkyl esters such as 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and iso-butyl methacrylate. As the quaternary ammonium salt, 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) acrylate; 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.

  For example, organometallic complexes and chelate compounds are effective as charge control agents exhibiting negative chargeability, such as aluminum acetylacetonate, iron (II) acetylacetonate, chromium 3,5-di-tert-butylsalicylate. 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 aforementioned positively or negatively chargeable charge control agent is generally contained in 1.5 to 15 parts by mass, preferably 2.0 to 8.0 parts by mass, more preferably 3.0 to 7.0 parts by mass of toner (toner Of 100 parts by mass). If the amount of the charge control agent added is less than the above range, it tends to be difficult to stably charge the toner to a predetermined polarity. When forming, the image density tends to decrease or the durability of the image density tends to decrease. In addition, the charge control agent tends to be poorly dispersed, causing so-called fogging, and the contamination of the photoconductor tends to be severe. On the other hand, when the charge control agent is used in a larger amount than the above range, it tends to cause defects such as environmental resistance, particularly poor charging under high temperature and high humidity and defective images, and contamination of the photoreceptor.

  The waxes used for improving the fixing property and offset property are not particularly limited. For example, polyethylene wax, polypropylene wax, Teflon (registered trademark) wax, Fischer-Tropsch wax, paraffin wax, It is preferable to use ester wax, montan wax, rice wax or the like. Two or more of these waxes may be used in combination. By adding such wax, offset property and image smearing can be more efficiently prevented.

  The waxes described above are not particularly limited, but generally, the wax is preferably blended in an amount of 1 to 5 parts by mass in the toner (the total amount of the toner is 100 parts by mass). If the addition amount of the wax is less than 1 part by mass, there is a tendency that the offset property, image smearing, etc. cannot be effectively prevented, while if it exceeds 5 parts by mass, the toners are fused together, Storage stability tends to decrease.

  In the magnetic one-component toner for developing an electrostatic latent image of the present invention, a magnetic powder is blended in a binder resin to form a one-component developer. Examples of such magnetic powder include those known per se, for example, ferrite, magnetite and other iron, cobalt, nickel and other ferromagnetic metals, alloys, compounds containing these elements, or ferromagnetic materials. An alloy that does not contain an element but becomes ferromagnetic when subjected to an appropriate heat treatment, chromium dioxide, or the like can be given.

  These magnetic powders are uniformly dispersed in the above-described binder resin in the form of fine powders having an average particle size in the range of 0.1 to 1 μm, particularly 0.1 to 0.5 μm. The magnetic powder can also be used after being subjected to a surface treatment with a surface treatment agent such as a titanium coupling agent or a silane coupling agent.

  The magnetic powder is contained in the toner in an amount of 35 to 60 parts by mass, preferably 40 to 60 parts by mass. When the magnetic powder is used in a larger amount than the above range, the durability of the image density is deteriorated, and the fixability tends to be extremely lowered. When the amount is smaller than the above range, the fog in the image density durability is deteriorated. End up.

The magnetic powder has a volume-specific low-efficiency value in the range of 1 × 10 ³ Ω · cm to 1 × 10 ⁷ Ω · cm, preferably 1 × 10 ³ Ω · cm to 1 × 10 ⁶ Ω · cm. It is good to be. When the volume resistivity value of the magnetic powder is less than 1 × 10 ³ Ω · cm, sufficient chargeability cannot be imparted to the toner, causing a decrease in image density. On the other hand, if it exceeds 1 × 10 ⁷ Ω · cm, the charge amount becomes excessively high, and the durability is also charged up, causing a decrease in image density, deterioration in durability, and the like. Furthermore, excessive charge-up of the toner causes discharge breakdown to the amorphous silicon photoconductor, which causes black spots on the image.

  The volume resistivity of magnetic powder can be changed by changing the shape (spherical, hexahedral, octahedral, etc.) of magnetic powder, titanium coupling agent, silane coupling agent, aluminum coupling agent, various fatty acids, etc. It is adjusted by changing the type and amount of the surface treatment agent, or by forming a conductive coating layer made of tin / antimony, francium or the like on the surface of the magnetic powder.

  The volume specific resistance value of the magnetic powder can be obtained at an applied voltage of DC 10 V by applying a load of 1 kg using “R8340A ULTRA HIGH RESISTANCE METER” manufactured by Advantest Corporation.

  In the magnetic monocomponent toner for developing an electrostatic latent image of the present invention, the toner charge amount on the sleeve is 8.0 μC / g or less, preferably 3.0 μC / g or more and 8.0 μC / g or less. . If the toner charge amount is greater than 8.0 μC / g, image fogging may occur, image density may be reduced due to toner charge-up, and toner durability may be reduced. It may cause discharge breakdown on the surface. The toner charge amount on the sleeve can be measured using a charge amount measuring device (Q / M Meter 210HS) manufactured by TREC. The toner charge amount can be adjusted by changing the addition amount of the magnetic powder, the particle diameter of the magnetic powder, the volume resistivity value of the magnetic powder, the type and addition amount of the charge control agent.

  The magnetic one-component toner for developing an electrostatic latent image of the present invention is prepared by mixing a binder resin and various toner compounding agents such as a charge control agent, melt-kneading using a kneader such as an extruder, and cooling the mixture. Obtained by pulverization and classification. In general, the toner is preferably classified and adjusted to have an average particle size of about 5 to 10 μm.

In addition, the magnetic one-component toner for developing an electrostatic latent image of the present invention is added with an inorganic metal oxide as an external additive in order to polish and remove charged organisms and the like attached to the surface of the latent image carrier. As the inorganic metal oxide, for example, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate and the like are preferable, and titanium oxide is particularly preferable. The inorganic metal oxide has a volume resistivity value of 10 ⁰ to 10 ⁷ Ω · cm, preferably 10 ¹ to 10 ⁶ Ω · cm. When the volume resistivity value of the inorganic metal oxide is less than 10 ⁰ Ω · cm, sufficient positive chargeability cannot be imparted to the toner, causing a decrease in image density. On the other hand, if it exceeds 10 ⁷ Ω · cm, the charge amount is too high and the durability is also increased, resulting in a decrease in image density and deterioration in durability. Furthermore, excessive charge-up of the toner causes discharge breakdown to the amorphous silicon photoconductor, which causes black spots on the image.

  In addition, the volume specific resistance value of the inorganic metal oxide can be obtained at an applied voltage of DC 10 V by applying a load of 1 kg using “R8340A ULTRA HIGH RESISTANCE METER” manufactured by Advantest Corporation.

  The inorganic metal oxide is preferably added in the range of 0.5 to 5% by mass with respect to the toner. When the addition amount is less than 0.5% by mass, the latent image carrier cannot be polished sufficiently, and image flow occurs at high temperature and high humidity, resulting in image defects. On the other hand, if the amount exceeds 5% by mass, the fluidity of the toner is extremely deteriorated, resulting in a problem that the image density is lowered and the durability is deteriorated. The inorganic metal oxide preferably has an average particle size of 0.01 to 1 μm.

  The volume resistivity value of the inorganic metal oxide is changed in the thickness of the coating layer formed by forming a coating layer made of tin oxide and antimony oxide on the surface of the inorganic metal oxide, as will be described later in the examples. Or by changing the content ratio of tin oxide and antimony oxide.

  The external addition treatment of the inorganic metal oxide is performed by stirring and mixing the magnetic toner in a dry manner. This stirring and mixing is performed so that the inorganic metal oxide fine particles are not embedded in the toner. It is better to use a mixer or the like.

  The magnetic one-component toner for developing an electrostatic latent image of the present invention is prepared by mixing a binder resin and various toner compounding agents such as a charge control agent, melt-kneading using a kneader such as an extruder, and cooling the mixture. Obtained by pulverization and classification. In general, the toner is preferably classified and adjusted to have an average particle size of about 5 to 10 μm.

  In addition, the magnetic one-component toner for developing an electrostatic latent image of the present invention treats the surface of toner particles with an external additive such as colloidal silica or hydrophobic silica for the purpose of improving fluidity, storage stability, cleaning properties, and the like. can do. Usually, these external additives are used in an amount of 0.2 to 10.0 parts by mass per toner. In addition, these external additive fine particles are externally added by stirring and mixing with a magnetic toner. This stirring and mixing is performed using a Henschel mixer or a Nauta mixer so that the fine particles are not embedded in the toner. It is good to use.

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

[Examples 1-5, Comparative Examples 1-3]
<Preparation of titanium oxide>
A colloidal titanium compound obtained by neutralizing and precipitating a titanium tetrachloride solution with sodium hydroxide was aged, calcined at 575 ° C., and pulverized with a hammer mill to obtain titanium dioxide having an average particle diameter of 0.25 μm. This titanium dioxide was dispersed in water, sodium pyrophosphate was further added, and wet grinding was performed with a sand mill to obtain a water-soluble slurry having a titanium dioxide concentration of 50 g / l.

After the slurry was heated to 80 ° C., a solution prepared by dissolving appropriate amounts of tin chloride (SnCl ₄ .5H ₂ O) and antimony chloride (SbCl ₃ ) in 300 cc of 2N hydrochloric acid solution and a 10% sodium hydroxide solution were added. While maintaining the pH of the system at 6 to 9, it was added over 60 minutes to form a coating layer composed of tin oxide and antimony oxide on the surface of the titanium oxide particles. Thereafter, the pH of the slurry was finally adjusted to 8, followed by filtration and washing, and drying (120 ° C.).

  The titanium dioxide dried material thus obtained was calcined in an electric furnace at 500 ° C. for 60 minutes, then crushed with a jet mill, and the thickness of the coating layer composed of tin oxide and antimony oxide was changed to Table 1. Titanium oxide having various volume resistivity values shown was obtained.

<Manufacture of binder resin>
In a reactor equipped with a thermometer, a stirrer, and a nitrogen introduction tube, 300 parts by mass of xylene was placed, and under a nitrogen stream, 845 parts by mass of styrene and 155 parts by mass of n-butyl acrylate and di-tert-butyl were mixed. Using a mixed solution of 8.5 parts by mass of peroxide (polymerization initiator) and 125 parts by mass of xylene, it was added dropwise at 170 ° C. over 3 hours. After dripping, it was made to react at 170 degreeC for 1 hour, and superposition | polymerization was completed. Thereafter, the solvent was removed to obtain a binder resin.

<Preparation of toner and developer>
49 parts by mass of the binder resin thus produced had a magnetic powder (retention force of 5.0 kA / m when 796 kA / m was applied, saturation magnetization of 82 Am ² / kg, residual magnetization of 11 Am ² / kg, number average particle diameter 0.25 μm, volume specific resistance value 3.6 × 10 ⁵ Ω · cm) 45 parts by mass, wax (Sazol Wax H1, manufactured by Sazol) 3 parts by mass, quaternary ammonium salt (Bontron P-51, Orient Chemical Co., Ltd.) 3 parts by mass were mixed with a Henschel mixer, melt-kneaded with a twin screw extruder, cooled, and coarsely pulverized with a hammer mill. Further finely pulverized by a mechanical pulverizer was classified by an airflow classifier to obtain a magnetic toner having a volume average particle size of 8.0 μm.

  To the toner powder (magnetic one-component toner) obtained above, 1.0 part by mass of silica (RA-200H: manufactured by Nippon Aerosil Co., Ltd.) and 1.0 part by mass of titanium oxide prepared as described above were added to a Henschel mixer. Was added to the surface of the magnetic toner powder to prepare a magnetic one-component positively charged developer.

<Evaluation test>
Using this developer, a page printer (FS-3800) manufactured by Kyocera Corporation equipped with an amorphous silicon photoreceptor was used to evaluate the initial image characteristics and durability, and the state of the toner thin layer on the developing sleeve. Was visually confirmed and the charging characteristics were measured. SUS305 having a 10-point average roughness Rz of 5.0 μm was used for the developing sleeve. Table 1 shows the volume resistivity values of the titanium oxides used, and Table 2 shows the evaluation results.
In addition, the volume specific resistance value of the titanium oxide was measured using "R8340A ULTRA HIGH RESISTANCE METER" manufactured by Advantest Corporation. The measurement was performed by weighing about 5 g of titanium oxide, putting it in a measurement cell, applying a load of 1 kg, connecting electrodes, and applying voltage of DC 10V. When the load is applied, the titanium oxide sample has a diameter of about 35 mm and a thickness of about 5 mm.

The evaluation method of each characteristic is as follows.
(1) Charging characteristics 4 parts by mass of the above magnetic toner and 100 parts by mass of ferrite carrier (FK-150, manufactured by Powdertech) were mixed, and the charge amount (μC / g) was defined as the initial charge amount. Further, the above-described page printer was used to form an image with the developer, and the toner charge amount when 100,000 sheets were continuously passed (printing rate 5%) was defined as the charge amount after durability. The results are shown in Table 2.
Details of the measurement are as follows.
The magnetic toner and the ferrite carrier are mixed in a normal temperature and humidity environment, and are then triboelectrically charged by stirring for 60 minutes in a ball mill. Of these, a charge amount of about 100 mg was measured using a charge amount measuring device (Q / M Meter 210HS) manufactured by TREK, and the charge amount μC / g per gram of the developer was determined from the mass change at that time.

(2) Image characteristics An image evaluation pattern is printed by the above page printer at the initial stage in a normal temperature and humidity environment (20 ° C, 65% RH) to obtain an initial image, and then 100,000 sheets are continuously passed through to evaluate the image again. Patterns were printed to obtain post-endurance images. Each solid image was measured using a Macbeth reflection densitometer (RD914), and image characteristics were evaluated by visually observing fog. The image density was 1.30 or higher. The following criteria were used for fog evaluation.
○: Fog is not seen.
Δ: Slight fogging occurs.
X: The fog is terrible.

(3) Toner thin layer state The toner thin layer state on the developing sleeve was visually confirmed, and the following criteria were used for evaluation.
○: A thin layer is uniformly formed and there is no unevenness.
(Triangle | delta): There exists a part with thick layer thickness.
X: Unevenness occurs.

(4) The toner charge amount on the sleeve The toner charge amount was measured using a charge amount measuring device (Q / M Meer210HS) manufactured by TREC immediately after the toner was put into the developing device. The results are shown in Table 1.

From Tables 1 and 2, etc., in Examples 1 to 6 in which the volume resistivity values of titanium oxide and magnetic powder are within a predetermined range and the toner charge amount on the sleeve is 8.0 μC / g or less, before printing, It can also be seen that there was no problem after printing 100,000 sheets. However, in Comparative Example 1 in which the volume resistivity value of titanium oxide was smaller than 10 ⁰ Ω · cm, the toner charge amount and the image density were low, fogging occurred, and the toner thin layer state was poor. Further, in Comparative Examples 2 and 3 in which the volume resistivity of titanium oxide was larger than 10 ⁷ Ω · cm, the toner charge amount was high, fogging occurred, and the toner thin layer state was also poor.

[Examples 7 to 12, Comparative Examples 4 to 8]
<Preparation of toner and developer>
In 49 parts by mass of the same binder resin in Examples 1 to 6, 45 parts by mass of magnetic powder (particle size: 0.21 μm, type: magnetite), 3 parts by mass of wax (Sazol Wax H1, manufactured by Sazol), 3 parts by mass of a quaternary ammonium salt (Bontron P-51, manufactured by Orient Chemical Co., Ltd.) was mixed with a Henschel mixer, melted and kneaded with a twin-screw extruder, cooled, and finely pulverized with a hammer mill. Further finely pulverized by a mechanical pulverizer was classified by an airflow classifier to obtain a magnetic toner having a volume average particle size of 8.0 μm. In addition, the used magnetic powder was prepared to the volume specific resistance value shown in Table 3 by carrying out the surface treatment with a titanate coupling agent (Ajinomoto Co., Ltd. pre-act KR TTS). However, in the toner formulation, in Example 12 (using the same magnetic powder as in Example 8) and Comparative Example 7 (using the same magnetic powder as in Example 9), the amount of magnetic powder was 40 parts by mass, and Comparative Example 8 (implementing). In the same magnetic powder as in Example 8, the amount of magnetic powder was 55 parts by mass.

To the toner powder (magnetic one-component toner) obtained above, 1.0 part by mass of silica (RA-200H: manufactured by Nippon Aerosil Co., Ltd.) and 1.0 part by mass of titanium oxide used in Example 3 ( A magnetic one-component positively charged developer was prepared by externally adding a volume resistivity value of 3.2 × 10 ⁴ Ω · cm) to the surface of the magnetic toner powder using a Henschel mixer.

<Evaluation test>
Using this magnetic toner, a page printer (FS-3800) manufactured by Kyocera Corporation equipped with an amorphous silicon photoconductor was used to evaluate the initial image characteristics and durability, and the state of the toner thin layer on the developing sleeve. Was visually confirmed to measure the charging characteristics. As the developing sleeve, SUS305 having a ten-point average roughness Rz of 5.0 μm was used.
Table 3 shows the volume resistivity value of the magnetic powder used and the toner charge amount on the sleeve.
In addition, the volume specific resistance value of the magnetic powder was measured by using “R8340A ULTRA HIGH RESISTANCE METER” manufactured by Advantest Corporation. The measurement was performed by applying magnetic powder in a measurement cell, applying a load of 1 kg, connecting the electrodes, and applying voltage DC10V. When a load is applied, the magnetic powder sample has a diameter of about 35 mm and a thickness of about 5 mm. Further, the toner charge amount was measured by using a charge amount measuring device (Q / M Meer210HS) manufactured by TREC, immediately after the toner was put into the developing device. The measurement results are shown in Table 3.

Using the toners obtained in Examples 7 to 12 and Comparative Examples 4 to 8, the following printing / image quality evaluation and evaluation of the toner thin layer state on the sleeve were performed. The results are shown in Table 4.
In addition, the evaluation method of each characteristic is as follows.

(1) Image characteristics An image evaluation pattern is printed by the above page printer at the initial time in a normal temperature and humidity environment (20 ° C., 65% RH) to obtain an initial image, and then 100,000 sheets are continuously passed and image evaluation is performed again. A pattern was printed to obtain a post-endurance image. Each solid image was measured using a Macbeth reflection densitometer (RD914), and at the same time, the image characteristics were evaluated by visually observing the toner thin layer state and fog. An image density of 1.30 or more was determined to be OK (when the toner thin layer state is poor, only a measurable location was measured). The following criteria were used for fog evaluation.
-Toner thin layer state ○: The thin layer is uniformly formed and there is no unevenness.
(Triangle | delta): There exists a part with thick layer thickness.
X: Unevenness occurs.
・ Evaluation of fog ○: Fog is not seen.
Δ: Slight fogging occurs.
X: The fog is terrible.

(2) Toner thin-layer state in low-temperature and low-humidity environment In a low-temperature and low-humidity environment (10 ° C, 20% RH), an image evaluation pattern is printed immediately after installation, and then 100,000 sheets are continuously passed, and the image is printed again. An evaluation pattern was printed and after endurance, and the toner thin layer state on the developing sleeve was visually confirmed, and the following criteria were used for evaluation.
○: A thin layer is uniformly formed and there is no unevenness.
(Triangle | delta): There exists a part with thick layer thickness.
X: Unevenness occurs.

  From Tables 3 and 4, etc., Examples 7 to 12 in which the volume resistivity values of titanium oxide and magnetic powder are within a predetermined range and the toner charge amount on the sleeve is 8.0 μC / g or less are all clean. It can be seen that a clear image and a thin toner layer were obtained, and the same clear image and a thin toner layer as in the initial stage were maintained even after printing 100,000 sheets. Also, no abnormal toner thin layer formation was observed even under low temperature and low humidity (10 ° C / 20% RH) environmental conditions. In Comparative Examples 4 and 6, since the volume resistivity value of the magnetic powder is too high, the toner is overcharged, the thin layer is not formed cleanly on the sleeve, the occurrence of fog is increased, and the image quality is extremely deteriorated. . In Comparative Example 5, since the volume specific resistance value of the magnetic powder was too low, the charge amount of the toner was remarkably reduced, and a thin layer was not clearly formed on the sleeve as in Comparative Examples 4 and 6. In Comparative Example 7, the volume resistivity of the magnetic powder was within the specified range, but the amount of use was small, and the charge charge of the toner through the magnetic powder was reduced, so the charge amount of the toner was too high. The thin layer was not formed cleanly on the sleeve, the occurrence of fog increased, and the image quality was extremely lowered. In Comparative Example 8, the volume resistivity of the magnetic powder was within the specified range. However, since the amount of the magnetic powder used was too large, the amount of charged charge of the toner passing through the magnetic powder was excessive, and the charge amount of the toner was low. Too thin a thin layer was not formed on the sleeve.

[Examples 13 to 15, Comparative Examples 9 to 10]
A developer was prepared according to the toner formulation of Example 9, and the toner image characteristics and the like were evaluated when the ten-point average roughness Rz of the developing sleeve surface was changed. Table 5 shows the ten-point average roughness Rz of the developing sleeve surface, the volume specific resistance value of the magnetic powder, and the toner charge amount on the sleeve used in each example and comparative example. Rz was measured using a surface roughness measuring device manufactured by Kosaka Laboratory Ltd., Surfcoder SE-30D.

  Using the developing sleeve of 10-point average roughness Rz obtained in Examples 13 to 15 and Comparative Examples 9 to 10, the following printing and image quality evaluation and toner thin layer state on the sleeve were the same as in Examples 7 to 12 Was evaluated. The results are shown in Table 6, respectively.

Furthermore, in this evaluation test, leakage black spots were also evaluated. Regarding leaked black spots, white images were output by the page printer at the initial stage in a normal temperature and humidity environment (20 ° C., 65% RH), and the number of black spots with a diameter of 0.1 mm or more present on the white images was evaluated. For evaluation, the following criteria were used. The results are shown in Table 6.
○: The number of black spots is zero.
Δ: The number of black spots is less than 5.
X: The number of black spots is 5 or more.

According to Table 6, in all of Examples 13 to 15, a clear and clear image and toner thin layer formation were obtained, and even after printing after 100,000 sheets, the same clear image and toner thin layer formation as in the initial stage were formed. Was maintained. Also, no abnormal toner thin layer formation was observed even under environmental conditions of low temperature and low humidity (10 ° C./20% RH). In Comparative Example 9, the image density continued to decrease as Rz was too small and the durable printing progressed. In Comparative Example 10, contrary to Comparative Example 9, Rz was too large, and image black spots occurred due to leakage from the developing sleeve to the photosensitive drum during durable printing, and thus durable printing was interrupted. Further, as shown in Table 5 and Table 6, in Comparative Example 10, the sleeve thin layer state deteriorates if the value of the ten-point average roughness Rz is smaller than the predetermined range, and if it is larger than the predetermined value, the cause of the leak is Black spots are generated.

Claims (5)

A magnetic one-component toner for electrostatic latent image development used in a development system based on a magnetic one-component development jumping system using a developer carrier having a 10-point average roughness Rz of 2.0 μm or more and 6.0 μm or less on the sleeve surface. There,
The toner contains magnetic powder having a volume resistivity of 1 × 10 ³ Ω · cm to 1 × 10 ⁷ Ω · cm, and has a volume resistivity of 10 ⁰ to 10 ⁷ Ω · cm as an external additive. An inorganic metal oxide that is within the range of
A magnetic one-component toner for developing an electrostatic latent image, wherein the toner charge amount on the sleeve is 8.0 μC / g or less.   The magnetic one-component toner for developing an electrostatic latent image according to claim 1, wherein the inorganic metal oxide is added in a range of 0.5 to 5.0 mass% with respect to the toner.   An image forming method by a magnetic one-component development jumping method using a developer carrier having a 10-point average roughness Rz of 2.0 μm or more and 6.0 μm or less on a sleeve surface, wherein the toner used is claim 1 or 3. An image forming method comprising the magnetic one-component toner for developing an electrostatic latent image according to 2.   4. The image forming method according to claim 3, wherein the latent image holding member is an amorphous silicon drum. 5. The image forming method according to claim 3, wherein the sleeve is made of stainless steel.