JPH0247672A - Electrophotographic image forming method - Google Patents

Abstract

PURPOSE:To prolong the life of a developer and the maintenance cycle of a fixing device by incorporating fine inorg. particles having pH >=7.0 into the developer and providing a resin coating layer dispersedly contg. graphite as the surface layer of a heat roller, then grounding this layer. CONSTITUTION:The fine inorg. particles having pH >=7.0 are incorporated into the developer and the resin coating layer 13 dispersedly contg. the graphite is provided as the surface layer of the roller 1 used for fixing with the heat roller; in addition, the layer 13 is grounded. The rise of the triboelectrostatic charge of the toner is improved in this way and the stable positive triboelectrostatic charge over a long period of time and the good transfer characteristic in high-temp. high-moisture environment are maintained. The electrostatic adhesive power of the toner to the fixing rolls 1, 2 is decreased and the exchange cycle of the fixing cleaning roll is prolonged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to electrophotographic copying, and further relates to a developer for forming a copied image and fixing of the copied image.

[Prior art]

As a method for forming an image from information to be visualized, methods using electrostatic latent images, such as electrophotography, electrostatic recording, and electrostatic printing, are widely used.

For example, in electrophotography, a latent image bearing member provided with a photosensitive layer made of a photoconductive material is given an electrostatic charge of -, and then image exposure is applied to the latent image bearing member corresponding to the original image. A corresponding electrostatic latent image is formed on the surface, and this electrostatic latent image is developed with a developer to form a toner image. This toner image is transferred to a recording material such as paper and then fixed by heating, pressure, etc. to form a copy image. On the other hand, after the transfer process, the latent image carrier is neutralized, and then the toner remaining on the latent image carrier without being transferred is cleaned, and the toner is used for forming the next copy image.

Furthermore, in order to stably form high-quality, fog-free copied images over a large number of times, it is required that the triboelectric charging properties of the toner be maintained stably.

An example of a developer used in electrophotography is a Suzuden image developer composed of toner particles containing polyester as a binder resin, inorganic fine particles made of negatively charged silica fine particles, and a fluororesin-coated carrier. (Unexamined Japanese Patent Publication No. 6
0-176052), or toner particles containing polyester as a binder resin, positively chargeable inorganic fine particles such as alumina fine particles, titanium oxide fine particles, nitrogen-containing silica fine particles, and a fluororesin-coated carrier. Electrostatic image developer (Japanese Patent Application Laid-Open No. 62-229158
No.) etc. are known.

However, in the technique disclosed in JP-A-60-176052, which uses a combination of negatively chargeable silica fine particles and a strongly negatively chargeable fluorine-based resin-coated carrier, the triboelectricity of the toner particles does not rise well, resulting in copying problems. As the number of cycles increases, toner scatters in the developing section, contaminating the charging electrode, transfer electrode, separation electrode, etc., resulting in image defects or transfer defects. Furthermore, when the amount of toner scattering increases, backside staining occurs in which the backside of the leading edge of the transfer material is stained with toner.

In addition, fluorine-based resins such as polytetrafluoroethylene and fluoroethylene propylene used as the coating layer of the fixing roll have good electrical insulation properties and are easily negatively charged.
In the technology using positively chargeable inorganic fine particles disclosed in JP-A No. 62-229158, the triboelectricity of the toner particles rises well and image defects due to toner scattering are reduced. Due to the charging property of the toner, electrostatic adhesion to the negatively charged fixing roll increases, resulting in poor offset properties and shortening of the fixing cleaning roll replacement cycle.

On the other hand, as a technology to improve offset properties, there is a technology to include a low-resistance substance in the heating roll coating layer (Tokuko Showa 5g
-23626), or technology for containing a conductive substance in the primer layer, JP-A-57-150869, JP-A-57-150869, JP-A-57-150869;
No. 83181, No. 59-111177, or a technique for incorporating oxobenzoyl polyether and carbon black into polytetrafluoroethylene used as a heating roll coating layer (Japanese Unexamined Patent Publication No. 100777/1983). There is.

These technologies improve the offset properties and paper wrapping properties around the fixing roll by making the heating roll coating layer conductive. When the resistance of the transfer paper decreases due to moisture absorption, transfer current leaks from the heating roller, resulting in defective transfer and a decrease in transfer efficiency. Furthermore, if the fixing process is repeated many times, the separating claw or the surface of the heat roller that contacts the temperature sensor will be worn or scratched, resulting in a decrease in mold releasability and the occurrence of image offset failures.

[Purpose of the invention]

Based on the above-mentioned circumstances, the present invention provides toner with good triboelectric charge build-up, positive triboelectrification that is stable over a long period of time, and good transfer t! in a high temperature and high humidity environment. J:
The purpose of the present invention is to provide an image forming method in which the performance of the image forming apparatus is maintained, the electrostatic adhesion of toner to the fixing roll is small, the replacement cycle of the fixing cleaning roll is long, and the life of the developer and the maintenance cycle of the fixing unit are long. do.

[Structure of the invention]

The object of the present invention described above is to provide an image forming method in which an electrostatic latent image is formed on a latent image carrier, developed with a developer, and the generated toner image is transferred to a recording material and fixed with a heated roller. The developer contains inorganic fine particles with a pH of 7.0 or more, and a resin coating layer containing dispersed graphite is provided as a surface layer of a roller used for hot roller fixing, and the core layer is grounded. This is accomplished by an electrophotographic image forming method.

Furthermore, the volume resistivity of the resin coating layer is 10' to 10Ωc.
It is preferable that it is m.

Next, the present invention will be explained in detail.

A typical embodiment of the fixing roller according to the present invention is shown in FIG. FIG. 2A shows a cross section of the heat roller I and the pressure roller 2 at right angles to the axis J, and FIG.

The heat roller 1 and the pressure roller 2 are pivotally attached to the copying machine housing so as to be in contact with each other at a predetermined pressure, and generally, a rotation drive mechanism is connected to the heat roller so that the heat roller 1 and the pressure roller 2 rotate freely depending on the pressure roller. provided.

It is preferable to use a conductive material for the bearing used for shaft attachment, and in particular in the present invention, since it is necessary to ground the heat roller l.
It is essential that the bearing 3 is made of a conductive material.

The pressure roller 2 has an elastic layer 22 made of an elastic resin material such as silicone rubber on a cylindrical base 21 made of aluminum or the like.

The heat roller l according to the present invention has a cylindrical base 1 made of aluminum or the like.
A release layer 13 is provided on the surface of 1 with a primer layer 12 for adhesion interposed therebetween. Further, a heating heat source, for example, a halogen heater 14, is inserted into the hollow space of the cylindrical base 11. Note that the heat source 14 is not shown in FIG. 1(b).

The surface temperature of the heat roller 1 is detected by a thermistor 4, which is connected to a temperature control means to turn on and off the heat source to maintain the temperature in an appropriate temperature range for fixing without causing offset failure.

The mold release layer 13 is preferably made of a fluorine-based resin with good mold release properties, and in particular, the composition of the resin is tetrafluoroethylene-perfluorinated alkyl vinyl ether copolymer (PFImM resin), fluoroethylene-hexafluoroethylene, etc. It is preferable that the material is made of at least one of a polypropylene copolymer (FEP resin) and a polytetrafluoroethylene (PTFE resin).

Further, in the present invention, the volume resistivity of the release layer 13 is adjusted by dispersing graphite in the resin of the release layer 13. The volume resistivity is 10' to 10
A range of 11Ω・C11 is preferable.9 If the volume resistivity exceeds 10Ω・clI, there is no problem with practicality, but the offset property tends to decrease, and 10′Ω・Cm
If this is not achieved, transfer defects may occur in high temperature and high humidity environments.

In addition, in the case of the present invention, there are signs that mold releasability deteriorates due to excessive graphite content, and the offset resistance tends to decrease.

Graphite consists of a layer of carbon atoms connected in a ring shape, and has a large anisotropy and a remarkable ability to open its arms. The electrical resistance is small in the a-axis direction parallel to the arm opening plane, and large in the c-axis direction perpendicular to the arm opening plane.
1000 times as large as in the axial direction. The overall resistivity is 0.
2-4. OX 10-30 am.

Its characteristics include good electrical and thermal conductivity, and heat resistance.
It has corrosion resistance and excellent lubricity.

In general, significant differences in physical properties occur depending on whether the single crystal, polycrystalline aggregate, powder, or crystal structure is imperfect.

Graphite includes natural graphite and artificial graphite. Natural graphite includes mud graphite and scale graphite, with scale graphite having high conductivity being preferred.

Examples of commercially available flaky graphite include cssp
(manufactured by Nippon Graphite Industries), etc.

Examples of commercially available products are listed in the table below.

FIG. 2 shows the relationship between W% and volume resistivity Ω·C11 of the graphite filler dispersed in the PFA resin.

To measure the volume resistivity, gold was vacuum-deposited on the surface of a heat roller on which a 20 μl resin film was formed, and the area lc+*X l was measured.
There are two electrometers (Kesley 617)
Measured using a programmable electrometer);
.

As the release resin primer used for the primer layer 12, a commercially available solution type primer mainly composed of fluororesin is used as an adhesive undercoat for the metal material such as iron alloy or aluminum alloy. Specifically, Tackware (A Primer) 459-882 manufactured by DuPont, M P 9028N manufactured by Mitsui 70 Rochemical, etc. are used.

The heat roller according to the present invention using the above-mentioned material is a dispersion obtained by coating the solution-type primer on the aluminum cylindrical base and then mixing and dispersing powder such as PFA and graphite filler thereon. Apply the liquid,
Made by drying and heat treatment if necessary.

The developer according to the present invention is mixed with inorganic fine particles. Examples of such inorganic fine powder include fine silica powder, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand, clay, mica, wollastonite, diatomaceous earth, and oxide Examples include chromium, cerium oxide, red iron oxide, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride, with silica fine powder being particularly preferred.

As the inorganic fine particles used in the present invention, those having a pH of 7.0 or more are selected.

Incidentally, the pH was measured according to the following method.

Measurement of pH value 100a+12 of distilled water is added to 4g of inorganic fine particles and stirred vigorously for 5 minutes using a homomixer. Distilled water is boiled to reduce CO7
A pH of at least 5.5 is used. Under no circumstances should an alkaline solution be added to increase the pH value.

When measuring, stop stirring and measure the pH value of the solution with a glass electrode p)I meter. The device is calibrated with a buffer solution before measurements.

Commercially available silica particles with a pH of 7.0 or higher include
Aerosil R812J, rAerosil RX 200
J (manufactured by Nippon Aerosil Co., Ltd.) and the like.

Furthermore, it is preferable that these inorganic fine particles have a pH of 7.0 or more even after being surface-treated with an amine-modified silicone compound.

The amines include primary, secondary and tertiary amines,
Also included are ammonium salts derived from tertiary amines.

Preferred examples of amine-modified silicone compounds include amine-modified silane coupling agents, amino-modified silicone oils, and polysiloxanes containing ammonium salts (polysiloxane ammonium salts).

A known technique can be used to treat the surface of the inorganic fine particles with the amine-modified silicone compound. Specifically, for example, after dispersing the inorganic fine particles in a solution in which the silicone compound is dissolved in a solvent, , removing the solvent by filtration or spray drying, followed by drying and curing by heating, or using a fluidizing bed device, spraying a solution of the silicone compound dissolved in a solvent to coat the inorganic fine particles; A method may be used in which the solvent is removed by heating and drying to form a film.

Regarding the particle size of the inorganic fine particles according to the present invention, it is preferable that the average particle size of the primary particles is within the range of 3f11μ to 2μm, particularly 5 to 500mμ. Moreover, the specific surface area according to the BET method is 20 to 500 m! /g is preferable. If the average particle diameter is too small or the specific surface area is too large, the inorganic particles may easily slip through during cleaning using a blade-type cleaning device, resulting in poor cleaning. On the other hand, when the average particle size is too large or the specific surface area is too small, the fluidity of the developer decreases, making the charging property unstable, and as a result, durability may decrease.

When forming a developer using the above-mentioned inorganic fine particles,
The above-mentioned inorganic fine particles are added to and mixed with the toner particles from the outside, so that they are contained in a state attached to the surface of the toner particles, and a carrier and the like are further mixed therein.

The content ratio of the inorganic fine particles is 0.1 to 5v of the toner.
It is preferably t%, particularly preferably 0.1 to 2vt%. When the content ratio of the inorganic fine particles is too small, the fluidity of the developer may decrease, resulting in poor triboelectric charging properties of the toner, making it difficult to impart an appropriate amount of positive charge to the toner. This may cause fogging.

In addition, when the content ratio is excessive, some of the inorganic fine particles may exist in a free state from the toner particles, and as a result, the free inorganic fine particles may adhere to and transfer to the carrier particles, or the inner wall of the developing device, the developing When the toner adheres and accumulates on the sleeve, regulating blade, etc., and eventually the triboelectricity of the toner becomes poor, making it difficult to apply an appropriate amount of positive charge to the toner, resulting in fogging and a decrease in image density. There is.

Such inorganic fine particles with a pF of 17.0 or more and whose surfaces are particularly treated with an amine-modified silicone compound become inorganic fine particles with excellent positive chargeability, and also have excellent moisture resistance and durability, and are resistant to environmental conditions. The result is inorganic fine particles that have stable positive triboelectric charging properties that are not affected by the electrostatic charge.

As the amino-modified silane coupling agent according to the present invention, for example, the following compounds can be preferably used.

)+2NcH2cH2cH2cH,5i(OCH3)s
H2NCH2CH2CHzSi(OC2H1).

CH.

1(2NCH2CH2CH2St(OcHJxHzN+
5I (OCHs)! σN1 (CH, CB, CH, 5i (QC) 1.)
2NCONHCH2C4CHzS+(OCzHs)xH
zNCH2CHzNHCHzCHzCHzSI(OCH
t) xH2NCH□CHtNHCHHzCHxNHCHz
-CHxCHxSLCOCHl>sH,C2OCOCH
2CH2N)ICFI2CH2-5i(OClh)3H
jc 20COCR,CI! NHCH, CI (2NH
-CH,CHICH,S i (OCH,') 3! (
2NCI4. Ocu! co2S1(OCHs)sH5c
OcOcHtcHzN)IC)lzc)IzNH-C
ToCHzcHzsi (OCRs).

(HsCzO)isicH2cTocHzH (HxC20)zsicHtc)IzCHt83CNH
CHIC)l, CH,5i(QC,H,).

HzN(CHzCHJH)zcHzcHxcIh-3i
(OCH3)s Commercially available amino-modified silicone oils that can be preferably used include, for example, those listed in the table below.

Further, in the above compound, the alkoxy group may be substituted with a chlorine atom. These compounds may be used alone or in combination.

As the amino-modified silicone oil according to the present invention, those represented by the following general formula (1) can be preferably used.

General formula [1] R represents an alkylene group, arylene group, aminoalkylene group, etc., and RI! and B I 1 each represent a hydrogen atom, a hydroxyl group, an alkyl group, an aryl group, etc., and x and y each represent an integer of 1 or more.

The boryloxacyanmonium salt according to the present invention includes:
Dimethylpolysiloxane ammonium salt, which has high positive chargeability and is less likely to cause cleaning defects, is preferred. The dimethylpolysiloxane ammonium salt is generally a dimethylsiloxane containing a structural unit represented by the following formula (A), for example, represented by the structural formula (B).

(A) Formula % Formula % The 6 groups represented by R1-R3 include those containing substituents.

Formula (B) where R1 is a hydrogen atom, a hydroxy group, an alkyl group,
an aryl group, an alkoxy group, or where R6 and R7
represent a hydrogen atom, a hydroquine group, an alkyl group, an aryl group, or an alkokyne group, respectively, and are these groups substituents?
It also includes those who have. R3-R1 and X have the same meanings as R-R6 and X in the formula (A) above. m and n each represent an integer of 1 or more.

Kylene group, arylene group, aralkylene group, -NH--
Examples include NHCO-, or a group obtained by arbitrarily combining these groups. ), or just a bonding hand, ! 23,
R1 and R5 each represent a hydrogen atom, an alkyl group or an aryl group, and X represents a halogen atom.

Examples include those shown by the structural formula, but these include -C,l(,-NH,・Cα C2)1.0)1 -C2H, -NH, ・Cffe H3 -C21(4-NH(C1(Jz・Cl2C,H.

CH.

A method for obtaining a polyrinloxane ammonium salt is a method in which an organohalogenated silane having an ammonium salt as a functional group and an organohalogenated silane that does not have an ammonium base are copolymerized in the polymerization step. It can be obtained by a method in which a polysiloxane obtained by polymerization using an organohalogenated silane is partially modified with an organic group having an ammonium salt as a functional group. Here, organoalkoxysilane may be used instead of the organohalogenated 7rane. Moreover, some compounds can also be obtained as commercial products.

The toner for developing electrostatic latent images according to the present invention contains a coloring agent in a binder made of a commonly used toner resin such as a polyester resin, a styrene-acrylic resin, etc. magnetic material in the resin,
It may also contain a property improver.

Examples of the coloring agent include carbon black, nigrosine dye (C,l, No. 504158), aniline blue (C,l, No. 50405), calco oil blue (Noazoic Blue 3), chrome yellow (
C. 1. No. 14090), Ultramarine Blue (
C. 1. No. 77103), DuPont Oil Red (
C. 1. No.26105), quinoline yellow (C.I.
1. No. 47005), methylene blue chloride (
C. I.

No. 52015), Phthalocyanine Blue (C.1.
No. 74160), malachite green oxalate (
C. ! , No. 42000), lamp black (
C. 1. No.77266), Rose Bengal (C.1
．． No. 45435) and mixtures thereof. It is preferable that the amount of the colorant used is generally 0.1 to 20 parts by weight per 100 parts by weight of the toner.

Examples of the magnetic substance include metals or alloys exhibiting ferromagnetism such as ferrite and magnetite; compounds containing these elements; and others.

These magnetic substances are uniformly dispersed in the resin in the form of fine powder with an average particle size of 0.01 to 1 μm, and the content thereof is preferably 20 to 80 parts by weight per 100 parts by weight of toner.
It is 0 to 100 parts by weight.

The property improver includes a fixability improver, a charge control agent,
There are others.

As the fixing property improving agent, for example, polyolefin, fatty acid metal salt, fatty acid ester wax, paraffin wax, polyamide wax, silicone wax, etc. can be used. Especially the softening point (ring and ball method JIS K25
31) Wax having a temperature of 60 to 180°C is preferable.

As the charge control agent, conventionally known ones can be used, and examples thereof include nigrosine dyes, metal-containing dyes, and the like.

To give an example of a preferred method for manufacturing the toner of the present invention, first, a resin material for the binder or a toner component such as a colorant is added thereto as necessary is melt-kneaded using, for example, an extruder, cooled, and then jet-milled. The powder is finely pulverized by a method such as the like, and then classified to obtain a toner having a desired particle size.

The toner of the present invention is used to develop an electrostatic latent image formed in, for example, an electrophotographic copying machine, and the obtained toner image is electrostatically transferred onto a transfer paper and fixed by an upper heating roller fixing device to produce a copied image. is obtained.

In the present invention, the effects of the present invention can be obtained with either a one-component developer consisting only of non-magnetic toner or a toner containing a magnetic substance, or a two-component developer using a toner and a carrier. can. - Layer In order to maintain excellent charge rise and charge stability and obtain good image quality even after multiple uses, it is preferable to use a two-component developer that uses carrier particles, and furthermore, the carrier particles are toner particles. In order to prevent contamination caused by the like, it is preferable to use a resin-coated carrier coated with a low surface energy resin such as a fluoricone resin or a fluorine-based resin, which has particularly excellent performance in imparting positive chargeability to the toner. From this point of view, a fluororesin-coated carrier is preferred.

The magnetic particles include materials that are strongly magnetized in the direction of a magnetic field, such as iron and ferrite.

Ferromagnetic metals such as magnetite, iron, nickel, and cobalt, alloys, or compounds containing these elements; alloys that do not contain ferromagnetic elements but can become ferromagnetic through appropriate heat treatment. For example, particles of an alloy called a Heusler alloy such as manganese-copper-aluminum or manganese-copper-tin, or chromium dioxide can be used.

[Example] r. Developer An example of a preferred electrostatic latent image developer of the present invention will be described below.

(Manufacture of binder resin) A 4-hole round bottom flask with a capacity of IQ equipped with dicarboxylic acids and dialcohols shown in Table 1 below, a thermometer, a stainless steel stirrer, a glass nitrogen gas introduction tube, and a flow-down condenser. Set the flask on a mantle heater, introduce nitrogen gas from the nitrogen gas inlet tube to raise the temperature while keeping the inside of the flask in an inert atmosphere, and then add O-05g of dibutyltin oxide. Temperature 200℃
After the mixture was reacted while maintaining the temperature, a polyvalent monomer of trivalent or higher valence shown in Table 1 was added and further reacted.

(Manufacture of toner) Binder resin 100 parts by weight Carbon black "Mogulshi" (manufactured by Capot Co., Ltd.) 100 parts by weight low molecular weight polypropylene [Viscol 660PJ (manufactured by Sanyo Chemical Co., Ltd.) 2 parts by weight Alkylene bis fatty acid amide "Hoechst WaxCJ (manufactured by Hoechst Co., Ltd.) made)
2 parts by weight or more of the substances are mixed, melted and kneaded with heated rolls, cooled, coarsely pulverized, further finely pulverized with a supersonic jet mill, and classified with an air classifier to obtain toner powder with an average particle size of 11.0 μm. I got it.

(Manufacture of inorganic fine particles) (1) Inorganic fine particles l (for examples) Put silica fine particles "Aerosil 200J (manufactured by Nippon Aerosil Co., Ltd.) into a mixer, and add the silica fine particles to the silica fine particles.
γ-Aminopropyltriethoxysilane diluted with alcohol so that the amino-modified silane coupling agent was 5% by volume was added and stirred at high speed. The obtained fine powder is 1
After drying at 20°C, the silica was placed in a mixer again and stirred until the viscosity at 25°C was 100.
Dimethyl silicone oil (cps) was sprayed at a concentration of 2 wt%. Stir at high speed for 2 hours at room temperature, and then
The mixture was stirred at 60°C for 15 hours, and then the mixture was further stirred at atmospheric pressure and room temperature for 3 hours to produce inorganic fine particles 1 treated with a nitrogen-containing substance.

These inorganic fine particles l have an average primary particle diameter of 12 mμBE.
The T specific surface area was 130 m''/9.

(2) Inorganic fine particles 2 (for examples) Average particle size is 12 mμ, BET specific surface area is 200+s”/
100 parts by weight of silica fine particles "Aerosil 200J (manufactured by Nippon Aerosil Co., Ltd.) of
0 cps amino modified silicone oil rS F 84
A treatment solution prepared by dissolving 10 parts by weight of Hexamethyldisilazane r S Z 6079J (manufactured by Toren Ricon Co., Ltd.) in 100 parts by weight of hexane was added dropwise to the high-speed rotating mixer. After surface treatment, the contents of the mixer were transferred to a flask and heated to a temperature of 100 to 150°C under an inert gas atmosphere.
By heating for 5 hours while stirring at
The hexane solvent was removed and the reaction proceeded to produce inorganic fine particles 2 treated with a nitrogen-containing substance.

The inorganic fine particles 2 have an average primary particle diameter of 13 mμ, and B
The ET specific surface area was 180 m''/g.

(3) Inorganic Fine Particles 3 (for Examples) Polysiloxane ammonium salt shown below was dissolved in xylene to prepare a treatment liquid.

(X is an integer) Next, silica fine particles [Aerosil 200J (manufactured by Nippon Aerosil Co., Ltd.) are placed in a mixer, and the above-mentioned polysiloxane is sprayed on the silica fine particles at a ratio of 5 wt%. The mixture was placed in a flask, and the solvent xylene was removed at a temperature of 200° C. for 5 hours with stirring to obtain inorganic fine particles whose surface was treated with a polysiloxane ammonium salt (nitrogen-containing substance). This will be referred to as "inorganic fine particles 3."

The inorganic fine particles 3 have an average primary particle diameter of 12111
μ,.

The specific surface area determined by the BET method was 115 m''/g.

(4) Inorganic fine particles 4 (for examples) Silica fine particles treated with hexamethyldisilazane [Aerosil R812J (manufactured by Nippon Aerosil Co., Ltd.) are used as inorganic fine particles 4 for examples of the present invention.

The inorganic fine particles 4 have an average primary particle diameter of 7111μ,
The BET specific surface area was 200 m2/g.

(5) Inorganic fine particles 5 (for examples) Alumina fine particles "Aerosil RX-Cl (manufactured by Nippon Aerosil Co., Ltd.) treated with hexamethyldisilazane are used as inorganic fine particles 5 for examples of the present invention.

The average particle diameter of the primary particles of the inorganic fine particles 5 is 20Illμ
, the BET specific surface area was 70+a2/9.

(6) Inorganic fine particles (1) (for comparative example) Negatively chargeable phosphor fine particles treated with dimethyldichlorane [Aerosil R-972J (manufactured by Nippon Aerosil Co., Ltd.)]
is referred to as Comparative Example Inorganic Fine Particles (1).

Table 2 lists the pH of each inorganic fine particle.

*1 Value when dispersed at 4% in 1:1 solution of methanol and water *2 HMDS: Hexamethyldisilazane (manufacturing of carrier) Vinylidene fluoride-ethylene tetrafluoride copolymer "vT-10"
0J (copolymerization molar ratio -80+20, intrinsic viscosity -0.95
dQ/g, manufactured by Daikin Industries, Ltd.) and 6 g of the methyl methacrylate copolymer "Acrivet MF" (manufactured by Mitsubishi Rayo Corporation) in a mixed solvent of acetone and methyl ethyl ketone (mixed volume ratio -1: l). A coating solution was prepared by dissolving it in 500ml. Using a fluidizing bed device, the coating solution was coated onto Ikg of spherical copper-zinc ferrite particles (manufactured by Nippon Tetsuko Kogyo Co., Ltd.), and then 2 kg.
After heat treatment at 00'C for 5 hours, the agglomerate was then sieved to produce a carrier with a resin coating layer having a thickness of about 2 μm. The average particle size of this carrier is 82 μm
Met.

(Production of developer) 5 parts by weight of a composite toner obtained by mixing 100 parts by weight of the toner produced by the above method with 0.8 parts by weight of the inorganic fine particles using a Henschel mixer and 100 parts by weight of the carrier were mixed using a V-type mixer. and mixed to prepare a developer.

(2) Heat Roller Table 3 lists the specifications of the fixing rolls A to G of the present invention and the comparative fixing roll H.

The graphite filler was added using the method described above.

139ml 1/5ee) was used. Copying evaluation was performed in advance with sufficient paper passing and with the temperature of the heat roller and backup roller stabilized.

(2) Evaluation of Offset Properties Table 4 shows the temperatures at which offset occurs when the developer containing each inorganic fine particle produced by the above method is combined with each heat roller.

The evaluation was made using a modified U-Bix 1550 machine manufactured by Konica Corporation (linear speed ○; no occurrence at 230°C; no occurrence at 01240°C). Also, no offset was observed even when the heat roller temperature reached 230°C.
In the case of C, A and B of the present invention.

Occurrence of offset was observed in heat rollers F and G in 5 cases.

On the other hand, in the heat roller of the comparative example, offset occurs at 210° C. even when the developer containing inorganic fine particles according to the present invention is used in combination, and the roller does not meet the practical level.

Further, in the combination of the heat roller of the comparative example and the developer containing inorganic fine particles of the comparative example, offset may occur at 210°C, and occurrence of offset is definitely observed at 220°C.

■Comprehensive evaluation: Konica (
Co., Ltd. U-Bix1550 modified machine (linear speed 139m+i
Table 5 shows the results of live-action comprehensive performance evaluation.

Note that the fixing temperature was 200°C.

With the combination of the heat roller of the present invention and the developer containing inorganic fine particles of the present invention, (Examples 1 to 8) all had good charging start-up, good initial images, and even after 60 Kc. The image was good.

Among them, the developer containing inorganic fine particles 1 and 2.3 surface-treated with a nitrogen-containing substance according to the present invention had a very stable toner charge amount, so we further evaluated Examples 2 to 5. , the image was good up to 100KC.

On the other hand, in the developer containing inorganic fine particles of the comparative example, stains at the leading edge of the image due to toner scattering occurred by 15KC in any combination with the heat roller.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a heat roller according to the present invention. FIG. 2 is a graph showing the relationship between the amount of graphite filler dispersed in the PFA resin and the volume resistivity (0 cm). ■ Heat roller 2 Pressure roller +1 Cylindrical base 12 Primer layer 13 Release layer I4 Heat source 21 Cylindrical base 22 Elasticity Layer 1 Figure 1

Claims (1)

[Claims] In an image forming method in which an electrostatic latent image is formed on a latent image carrier, developed with a developer, and the generated toner image is transferred to a recording material and fixed with a heated roller, the developer contains an inorganic material with a pH of 7.0 or more. An electrophotographic image forming method, characterized in that a resin coating layer containing fine particles and dispersed graphite is provided as a surface layer of the roller used for the heat roller fixing, and the layer is grounded.