JPH0247669A - 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. metal oxides 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 metal oxide 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 [Field of Industrial Application] The present invention relates to electrophotographic copying, and more particularly 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 carrier provided with a photosensitive layer made of a photoconductive material is given a static charge of -, and then image exposure corresponding to the original image is applied to the surface of the latent image carrier. A corresponding electrostatic latent image is formed, 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 step, 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 an electrostatic 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 that uses a combination of negatively chargeable silica fine particles and a fluorine-based resin coated carrier with strong negative chargeability, the triboelectricity of the toner particles rises poorly, and the number of copies is As the amount 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 technique for improving offset properties, there is a technique for containing a low-resistance substance in the heating roll coating layer (Japanese Patent Publication No. 58
-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 blank into polytetrafluoroethylene used as a heating roll coating layer (Japanese Patent Application Laid-Open 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.

[Purpose of the invention]

Based on the above-mentioned circumstances, the present invention has been developed to provide a toner with good triboelectric charge build-up, stable positive triboelectrification over a long period of time, good transfer performance in a high temperature and high humidity environment, and a fixing roll. It is an object of the present invention to provide an image forming method in which the electrostatic adhesion of toner to the toner 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 device are long.

[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 having a pH of 7.0 or more, and a resin coating layer containing a dispersed metal oxide is provided as a surface layer of the roller used for the heat roller fixing, and the core layer is grounded. This is achieved by a characteristic electrophotographic image forming method.

Furthermore, the volume resistivity of the resin coating layer is 10' to 10''Ω・
Preferably it is Cl11.

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. 3A shows a cross section perpendicular to the axes of the heat roller 1 and the pressure roller 2, and FIG.

The heat roller 1 and the pressure roller 2 are pivotally attached to the copying machine housing so as to be in pressure 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 can freely rotate in dependence 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, the heat roller 1 is required to be grounded.
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 silylan 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 polyethylene tetrafluoride-perfluorinated alkyl vinyl ether copolymer (PFA resin), ethylene fluoride-hexafluoride resin, etc. At least one of polypropylene copolymer (FEP resin), polytetrafluoroethylene (PTFE resin)
Preferably, it consists of two.

Further, in the present invention, the volume resistivity of the release layer 13 is adjusted by dispersing and containing a metal oxide in the resin of the release layer 13. The volume resistivity is preferably in the range of 104 to 10th Ω·cIB. Volume resistivity is 1011Ω
・If it exceeds cLll, there is no problem in practicality, but the offset property tends to decrease, and 10'Ωcff
When less than l, transfer defects may occur in a high temperature and high humidity environment.

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

The metal oxides include SnO□, TiO□, T1
0□, -, (n#1), antimony oxide, and conductive zinc oxide are used, and commercially available products of 5noz/antimony oxide dope include T-1 (Mitsubishi Metal Industries), ELCOM
-TL-20 (Catalyst Chemical Industry Department), Ti0z/5n02
/ Commercial products of antimony oxide dope include W-L W
-10 (Mitsubishi Metal Industries Department), ECT-52, ECT-6
2, ECTT-1 (Titan Kogyo), Ti, J, -+
(n”; l) as a commercially available product, Teha, Titanium Black 1
Commercially available products of 2S, Titanium Black 20M (Mitsubishi Metal Industries), and conductive zinc oxide include 23-K (manufactured by Hakusui Chemical Co., Ltd.).

Examples of commercially available metal oxide fillers are listed in the table below, and the composition and film properties are also listed.

The conductivity of the metal oxide filler itself is thought to be derived from the contact resistance between the filler particles. Generally, the filler is placed in a container such as a cylinder, and a pressure of about 5 kg/cm is applied to reduce the electrical conductivity by 60 to 70%. Contact resistance is measured as the degree of filling using a digital multimeter or the like.

FIG. 2 shows the relationship between the wt% of the metal oxide dispersed in the PFA resin and the volume resistivity Ω·cm t:.

To measure the volume resistivity, gold was vacuum-deposited on the surface of a heated roller on which a 20 μm resin film was formed, and the area lc + mXlc was measured.
Measurements were made for 1 m using an electrometer (617 programmable electrometer manufactured by Kesley).

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, DuPont Tackware (A Primer) 459-8. ! 11
2. Mitsui 70 Rochemical M P 9028N etc. are used.

The heat roller according to the present invention using the above material is obtained by coating the solution type primer on the aluminum cylindrical base, and then mixing and dispersing powder such as PFA and metal oxide thereon. It is made by applying a dispersion, drying, and subjecting it to 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 Chromium, cerium oxide, red iron, antimony trioxide, magnesium oxide, zirconium oxide, barium WE acid, barium carbonate, calcium carbonate, silicon carbide,
Examples include silicon nitride, but fine silica powder is particularly preferred.

The inorganic fine particles used in the present invention are selected from those having a pH of 7.0 or higher.

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

Measurement of pi (value) Add 100 mQ of distilled water to 4 g of inorganic fine particles and stir vigorously for 5 minutes using a homomixer. Boil the distilled water to drive out CO2 and use water that shows at least a pH of 5.5. In any case, use an alkaline solution. In addition, the pH value is not increased.

When measuring, stop stirring and measure the pH value of the solution with a glass electrode pH 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 200J
(manufactured by Nippon Aerosil Co., Ltd.), etc.

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

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

Preferred examples of the amine-modified silicone compound include amino-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 3111 μm to 2 μm, particularly 5 to 500 μm. In addition, the specific surface area determined by the BET method is preferably 20 to 500 m''/g. If the average particle size is too small or the specific surface area is too large, for example, when cleaning with a blade-type cleaning device, inorganic Fine particles may easily slip through, resulting in poor cleaning.On the other hand, if the average particle size is too large or the specific surface area is too small, the fluidity of the developer decreases and the charging property becomes unstable, resulting in poor 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 pH of 7.0 or higher and whose surfaces are particularly treated with an amine-modified silicone compound become inorganic fine particles with excellent positive chargeability, and are also excellent in moisture resistance and durability, and are not affected by environmental conditions. The result is inorganic fine particles with stable positive triboelectric charging properties.

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

HzNCHzCH2CH2CH2Sl(OCHi)x)
bNcH2cH2cIhs+(OC2Hs)sHzNC
ONHCH2CH2CJSt(OC2Hs)sl(,N
CHtCll, NFICH□CH2CH, Si(OCH
3)! H2NCHzCH2NHCIhCHzNHC1(
2-CHzCHzSi(OClh)xH, C2OCOC
H□CH2NHCHzCHx-5i(OClh)sH5
C20COCHz012NHC)I2CHzNIl-C
HzCH2CHzSi (OCR3)3HsC20CO
CH2CH2NHCI(2CH2NH-CH2CH2N
HCH2CH2NHCH2--CH2CH2Si(OC
)ls)s tbCOCOCH2CH2NHCHzCHzNl(-C
HzCHzCH2Si(OCHs)x(H,C20)3
SiCH2CH2C112N)I ■ (H,C,0),5iC82C82C1(2IhCNH
C) 1zcFIicH2si(OCdls)sHzN(
CH2CHiNH)2cH2cH2cH2-3i(OC
HJtAlso, 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, for example, one represented by the following general formula (1) can be preferably used.

General formula [l] R11 represents an alkylene group, arylene group, aminoalkylene group, etc., R+2 and R13 each represent a hydrogen atom, a hydroquine group, an alkyl group, an aryl group, etc.,
X and y each represent an integer of 1 or more.

Commercially available amino-modified silicone oils that can be preferably used are listed in the table below, for example.The polysiloxane ammonium salt according to the present invention should be a dimethylpolysiloxane ammonium salt that has high positive chargeability and is less likely to cause cleaning defects. is preferred. Dimethylpolysiloxane ammonium salts generally include the following (A):
It is a dimethylsiloxane containing a structural unit represented by the formula, for example, represented by the structural formula of formula (B).

(A) Formula % Formula % Here, R+ is a hydrogen atom, a hydroxy group, an alkyl group,
An aryl group, an alkoxy group, or p.

Formula (B) where R6 and R each represent a hydrogen atom, a hydroxy group, an alkyl group, an aryl group or an alkoxy group,
These groups also include those having substituents. R1-R
6, X has the same meaning as R, -R5, and X in 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 any combination of these groups. ), or represents a simple bond, R3, R
4 and R6 each represent hydrogen, an atom, an alkyl group or an aryl group, and X represents a halogen atom.

Each group represented by Rl""'Rs includes those having a substituent.

Examples include those shown by the structural formula, but these include CzHt　NH2・C(2e CH3 CH.

CH3 C3H6NH Co-Nl(3-C4 C3HI N (CHi)s ・CQ"srs -N
Hs・CI2 (I5) CI2 \ C, H, OH Polysiloxane ammonium salts can be obtained by using organohalogenated silanes having an ammonium salt as a functional group and especially organohalogenated silanes having no ammonium base. It can be obtained by a method in which it is introduced by copolymerization in the polymerization step, 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, and the like. Here, organoalkoxysilane may be used instead of organohalogenated silane. 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 polyester resin, styrene-acrylic resin, etc. Depending on the case, the resin may contain a magnetic material and a property improver.

Examples of the coloring agent include carbon black, nigrosine dye (C, 1, No. 504158), aniline blue (C, 1, No. 50405), and calco oil blue (C, I.

Noazoic Blue 3), Chrome Yellow (Jin 1
No. 14090), Ultramarine Blue (C, I
, No. 77103), DuPont Oil Red (C, 1
, No. 26105), quinoline yellow (C, I, N
o47005), methylene blue chloride (C,I
.

No. 52015), Phthalocyanine Blue (C, 1, N
o74160), malachite green oxalate (C
, 1, No. 42000), lamp black (C, I
, No. 77266), Rose Bengal (C, 1, No. 4)
5435) and mixtures thereof can be used. The amount of the colorant used is preferably 0.1 to 20 parts by weight per 100 parts by weight of the toner.

Examples of the magnetic material include metals or alloys exhibiting ferromagnetism such as ferrite and magnetite, compounds containing these elements, and the like.

These magnetic substances are uniformly dispersed in the resin in the form of fine powder with an average particle size of 0.01-1μ, for example, and the content thereof is 1002! The amount is 20 to 80 parts by weight.

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

As the fixing property improver, 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 K2
531) is preferably 60 to 180°C.

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. A toner having a desired particle size can be obtained by pulverizing the toner particles by pulverizing the particles by pulverizing the particles by pulverizing the granules, etc., and classifying the pulverized particles.

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 transfer paper and fixed by an upper heating port-ra fixing device. A duplicate 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 a 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 silicone resin or a fluorine resin, especially since it has excellent performance in imparting positive chargeability to the toner. A fluorine-based resin-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.

Metals or alloys that exhibit ferromagnetism, such as magnetite, iron, nickel, and cobalt, or compounds containing these elements, and alloys that do not contain ferromagnetic elements but become ferromagnetic through appropriate heat treatment. 1. For example, particles of an alloy called Heusler alloy such as manganese-copper-aluminum or manganese-copper-tin or chromium dioxide can be used.

(Example) (1) Developer An example of a preferred electrostatic latent image developer of the present invention will be described below.

(Manufacture of binder resin) Dicarboxylic acids and dialcohols shown in Table 1 below were prepared in a 4-hole round bottom flask with a capacity of 112 equipped with a thermometer, a stainless steel stirrer, a glass nitrogen gas introduction tube, and a flowing 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, then add 0.05 g of dibutyltin oxide. temperature 200
After reacting while maintaining the temperature at °C, polyvalent monomers of trivalent or higher valence shown in Table 1 were added and further reacted.

Table 1 (Manufacture of toner) Binder resin 100 parts by weight Carbon black "Mogulshi" (manufactured by Capot) 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 Sanyo Chemical Co., Ltd.)] Manufactured by Hoechst)
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 1 (for example) Silica fine particles [Aerosil 200J (manufactured by Nippon Aerosil Co., Ltd.) were placed in a mixer, and the amino-modified silane coupling agent was added at 5 wt% to the silica fine particles. γ-aminopropyltriethoxysilane diluted with alcohol was added and stirred at high speed. The obtained fine powder was
After drying at 0°C, the silica was placed in a mixer again and stirred until the viscosity at 25°C was 100.
Dimethyl'y IJ cone, which is cps, was sprayed at a concentration of 2 wt%. Stir at high speed for 2 hours at room temperature, and then stir for 16 hours.
After stirring at 0°C for 15 hours, 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 m2/9.

(2) Inorganic fine particles 2 (for examples) Average particle size is 12fflμ, BET specific surface area is 200m"
/g of silica fine particles [Aerosil 200J (manufactured by Nippon Aerosil Co., Ltd.)] were placed in a high-speed rotating mixer, and then the amine equivalent was 3500.The viscosity at 25°C was 1.
200cps amino-modified silicone oil rS F
10 parts by weight of 8417J (manufactured by Tomu Nricorn Co., Ltd.) and hexamethyldisilazane r S Z 6079J (
A treatment solution prepared by dissolving 8 parts by weight of (manufactured by Toray Silicone Co., Ltd.) in 100 parts by weight of hexane was added dropwise to the high-speed rotating mixer for surface treatment.The contents of the mixer were then transferred to a flask and heated with an inert gas. Temperature 100-1 in atmosphere
By heating at 50 ° C. for 5 hours while stirring, the solvent hexane is removed and the reaction is proceeded.
Inorganic fine particles 2 treated with a nitrogen-containing substance were produced.

The inorganic fine particles 2 have an average primary particle diameter of 13 mμ, and B
The ET specific surface area was 180 m2/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 at a ratio of 5 vt% to the silica fine particles; These were placed in a flask, and the solvent xylene was removed at a temperature of 200'O while stirring for 5 hours to obtain inorganic fine particles whose surface was treated with a polysiloxane ammonium salt (nitrogen-containing substance). this"
No *fine particles 3".

The inorganic fine particles 3 have an average primary particle diameter of 12+aμ
The specific surface area as determined by the BET method was 115 m''/g.

(4) Inorganic fine particles 4 (for examples) Silica fine particles "Aerosil R-812J (manufactured by Nippon Aerosil Co., Ltd.) treated with hexamethyldisilazane are used as inorganic fine particles 4 for examples of the present invention. These inorganic fine particles 4 are 1 The average particle size of the secondary particles was 7111μ, and the specific surface area by BET method was 2001f12/g.

(5) Inorganic fine particles 5 (for examples) Alumina fine particles treated with hexamethyldisilazane [Aerosil RX-CJ (manufactured by Nippon Aerosil Co., Ltd.) are referred to 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 20 mμ.

The BET specific surface area was 70 m''/g.

(6) Inorganic fine particles (1) (for comparative example) Negatively charged silica fine particles treated with dimethyldichlorosilane "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 rVT-10
0J (copolymerization molar ratio -80:20, intrinsic viscosity -〇, 95
dQ/g, manufactured by Daikin Industries, Ltd.) and 6 g of methyl methacrylate copolymer [Acrypela l-MFJ (manufactured by Mitsubishi Rayon), in a mixed solvent of acetone and methyl ethyl ketone (mixed volume ratio -1: 1) 500 mff A coating liquid was prepared by dissolving it in the liquid. Using a fluidizing bed device, the coating solution was applied onto I kg of spherical copper-zinc ferrite magnetic particles (manufactured by Nippon Tetsuko Kogyo Co., Ltd.), and then heat-treated at 200°C for 5 hours. The aggregate was then sieved to produce a carrier having a resin coating layer with 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.

Addition of metal oxides is carried out using the method described above.
.

139mm/5ec) is 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 Offcentity Table 4 shows the temperature at which offset occurs when the developer containing each inorganic fine particle prepared by the above method is combined with each heat roller.

The evaluation was conducted using a modified U-Bix 1550 machine manufactured by Konica Corporation (linear speed ○: no occurrence occurred at 230°C, no occurrence occurred at 01240°C, and the heat roller of the present invention did not react with any developer containing inorganic fine particles. Even in combination, the heat roller temperature is 230
No offset is observed even when the temperature reaches °C. 2 more
When the temperature is 40° C., offset may occur in the heat rollers A and G of the present invention.

On the other hand, in the heat roller of the comparative example, even when the developer containing the inorganic fine particles according to the present invention is combined, an offset occurs at 210° C., 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 Under high temperature and high humidity environment (33°080%), Konica (
Co., Ltd. U-Bix1550 modified machine (linear speed 139111
Table 5 shows the results of the 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, in all cases (Examples 1 to 8), the charging start-up and the initial image were good, and even after finishing at 60', the image remained unchanged. In good condition.

Among them, the developer containing the inorganic fine particles 1.2.3 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 LOOK'.

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 up to 15 KC 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 metal oxide dispersed in the PFA resin and the volume resistivity (00m). ■ Heat roller 2 Pressure roller 11 Cylindrical base 12 Primer layer 13 Release layer 14 Heat source 21 Cylindrical base 22 Elasticity Layer 1 ■ Figure

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 containing a metal oxide dispersed therein is provided as a surface layer of the roller used for the heat roller fixing, and the layer is grounded.