JPH0667471A - Dry two-component developer and image forming method - Google Patents

Abstract

PURPOSE:To obtain a dry two-component developer which can maintain good fixing property, offset property and excellent picture quality even repeatedly used for a long time. CONSTITUTION:The developer consists of ferrite carrier coated with acryl resin, and a toner containing styrene-acryl copolymer as a binder resin, carbon black as a pigment component, and magnetic powder. The ferrite carrier has 7.5X10<5>-6.7X10<7>OMEGA.cm electric resistivity. The binder resin has 8.3X10<3>-3.5X10<4> dyn/cm<2> storage elasticity and 9.2X10<3>-3.7X10<4>dyn/cm<2> loss elasticity and has a crosslinking component. The toner has -10 to -25muC/g charging amt. and 3.5X10<15>-8.7X10<15>OMEGA.cm electric resistivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry two-component developer used to visualize an electrostatic latent image formed on the surface of a photoconductor in reversal development such as electrophotography and electrostatic recording, and a dry two-component developer for the same. The present invention relates to an image forming method used, and more particularly to a dry two-component developer for reversal development applied to heat roll fixing and an image forming method using the same.

[0002]

2. Description of the Related Art In electrophotographic reversal development, a charge image induced on a non-image portion of an electrostatic latent image formed on a surface of a photoreceptor is developed to obtain a toner image, and the toner image is formed on a support such as paper. It is a method of forming a final visible image on a sheet by fixing it by heating, pressurizing, etc. A magnetic brush method is well known as a dry developing method for charged portions. The magnetic brush method uses a dry two-component developer composed of a mixture of magnetic carrier particles and toner particles formed of resin, carbon black, etc. to form a magnetic brush around a magnet roll for transport, and to rotate the magnetic brush. This is a method in which toner particles charged to a desired polarity by friction between magnetic carrier particles and toner particles in a brush are attracted to the latent image of the photoconductor to develop. As the magnetic carrier particles, Japanese Patent Publication Sho 56-
As disclosed in 11143, USP 4,126,454, etc., there are iron oxide powder carriers and ferrite carriers having various shapes such as spherical and flat shapes.
Many drawbacks are still recognized. That is, the iron oxide powder carrier is sensitive to humidity, and the developer performance may change due to the influence of humidity, or rust may be generated on itself, which limits the use environment. Also, the saturation magnetization is large,
The brushing of the magnetic brush is hard and trailing edges and vertical streaks are likely to occur on a solid black image. Further, the stress on the toner is large and there is a problem in terms of life. On the other hand, the ferrite carrier has a saturation magnetization of 50 to 60 emu / g and an iron oxide powder content of 200.
Since it is smaller than emu / g, the ears are soft and the trailing edge chipping and vertical stripes of a solid black image are small. Further, compared to iron oxide powder, it has less stress and is advantageous for long life. On the other hand, the ferrite carrier has a large electric resistance and has an edge effect (a phenomenon in which a larger amount of toner adheres to a boundary portion of an image than a solid image portion), and a uniform solid image quality cannot be obtained. Further, since the toner is consumed, it is necessary to replenish the developer with new toner commensurate with the toner consumption amount. At this time, the replenishment toner must be quickly and uniformly triboelectrically charged by frictional charging with the carrier, but the carrier is mixed and stirred to collide with each other or collide with the inner wall of the developing device, so that the toner is melted on the surface. When the carrier is deposited, the toner is contaminated with the toner. In such a state, the triboelectrification ability of the carrier decreases, the toner is not sufficiently triboelectrified to a desired polarity and the charging becomes unstable, and the image density decreases and toner adheres to the background portion, so-called fogging. Occur. In order to improve such a defect of the ferrite carrier, JP-A-61-110160 and JP-A-63.
-17222, JP-A-02-33159,
It has been proposed to coat the surface of a carrier with a resin as disclosed in Japanese Patent Application Laid-Open No. 02-46471.

By the way, as a fixing method in which a toner image is transferred onto a support such as paper and then fixed by heating, pressurizing, etc. to form a visible image, pressure fixing using only a pressure roll at room temperature and oven heating are used. A heat fixing method, a flash fixing method using a flash bulb such as a xenon lamp, and a heat roll fixing method using heat and pressure of a heat roll are used. Of these, formation of a visible image via an electrostatic latent image is, of course, preferably achieved at high speed,
Conventionally, a heat roll fixing method, which has high thermal efficiency in the fixing process and is advantageous over other methods, has been widely adopted. In this heat roll fixing method, a silicon rubber roll impregnated with silicon oil or a coating roll used while coating the surface of the silicone rubber roll with fluororesin and applying the silicone oil via a felt is used. In this heat roll fixing method, the image strength after fixing is high, and the offset phenomenon (a part of the toner adheres to the roll surface due to the contact of the toner on the heat roll surface in a heat-melted state, and the support such as paper is again used. It is required that there is no adhesion to the top and stain of the image). The former characteristic is fixability, and the latter characteristic is called offset resistance.

For fixing a heat roll, Japanese Patent Application Laid-Open No. 61-1986
As disclosed in Japanese Unexamined Patent Publication No. 110160, a release agent composed of a polyolefin wax such as polypropylene wax or polyethylene wax is contained in the toner particles in a large amount of 5 to 20% by weight based on the binder resin to obtain non-offset properties. Toners aiming to achieve the above are known. Such a toner does not have a release agent in itself, and does not require a silicone coating mechanism as compared with a means for fixing while applying a release agent such as silicone oil on the surface of the heat roll. It is easy to use and does not require maintenance such as replenishment of silicone oil. However, on the other hand, the fluidity of the toner is lowered, and eventually the developer characteristics and the transfer efficiency are lowered, and a good visible image cannot be obtained. It also tends to have secondary aggregation, especially in recycling systems,
That is, even in a system in which the toner remaining on the photoconductor is recovered again and returned to the developing machine for re-development, there is a drawback that toner flakes and the like are likely to occur. In the case where the toner contains a large amount of the releasing agent as described above, it is difficult to obtain sufficient releasing property and non-aggregating property. Therefore, a crosslinking type styrene-acrylic copolymer has been proposed.

[0005]

However, when the degree of crosslinking of the conventionally known styrene-acrylic copolymer is increased, the offset resistance is improved,
There was a problem that the fixability was not sufficient. Further, even in the case of a two-component developer consisting of a resin-coated ferrite carrier and a high electric resistance toner, compatibility of fogging, fine lines and solid images,
Improvements in image quality such as stability of image density have been desired. The present invention provides a two-component developer suitable for heat roll fixing, which has good fixing properties and offset properties and is capable of obtaining stable image quality without fog.

[0006]

That is, according to the present invention, an acrylic resin-coated ferrite carrier having an electric resistance in the range of 7.5 × 10 ^{5 to} 6.7 × 10 ⁷ Ω · cm and a storage elastic modulus of 8 are used. .3 × 10 ^{3 to} 3.5 × 10 ⁴ dyn / cm ² ,
Loss elastic modulus is 9.2 × 10 ^{3 to} 3.7 × 10 ⁴ dyn / c
m ^{2 in} the range of styrene-acrylic copolymer having a crosslinking component as a binder resin, containing carbon black and magnetic powder as a pigment component, and having a charge amount of -10 to -25.
μC / g, electric resistance 3.5 × 10 ^{15 to} 8.7 × 10 ¹⁵
The present invention relates to a dry two-component developer containing a toner in the range of Ω · cm and an image forming method using the same. The electrophotographic apparatus preferably applied in the present invention is a driving and rotating metal drum having an organic photoconductor film wound on its surface, an image exposure mechanism including a charging corotron charger and an optical system around the drum, and a toner. A developing mechanism having a belt, a belt-shaped transfer mechanism, a charge eliminating lamp, and a cleaning mechanism are provided in this order. The fixing unit is composed of a Teflon-coated aluminum roll controlled at 190 ° C. and a silicon rubber-coated aluminum heat roll pressed at a nip pressure of 5 kgf / cm ² .

In the image forming method of the present invention, first, the surface of the organic photoconductor (photoreceptor) is charged with a charging corotron charger. Then, through image exposure, an electrostatic latent image is formed on the surface of the organic photoconductor. This electrostatic latent image is developed with a dry two-component developer (developing mechanism) of the present invention having toner to visualize the toner image, and the toner image is transferred to a support such as paper and then fixed by a fixing unit, preferably a heat roll. It is fixed. Next, the charge removal lamp erases the residual charge, then the organic photoconductor is discharged and the cleaning mechanism removes the residual toner.

[0008] Electrical resistance of the carrier used in the present invention is a ^{7.5 × 10 5 ~6.7 × 10 7} Ω · cm, the electric resistance is higher than 6.7 × 10 ⁷ Ω · cm The voltage drop between the magnetic brush tip and the latent image surface is large, and a sufficient electric field does not act between the magnetic brush tip and the latent image surface. On the other hand, when the electric resistance of the carrier is lower than 7.5 × 10 ⁵ Ω · cm, the carrier becomes conductive and the latent image on the photoconductor disappears, and also the photoconductor is damaged by discharging the bias voltage. Therefore, the present invention has an electric resistance of 7.5 × 10 ^{5 to} 6.7 × 10 ⁷ Ω · c.
in the range of m, more preferably 8 × 10 ^{5 to} 3 × 10 ^6.
An acrylic resin-coated ferrite carrier in the range of Ω · cm is used. In the present invention, the electric resistance of the carrier means a diameter of 6 which is provided with a sleeve which is magnetized in a fixed multi-pole and which is rotatable around the magnet roll in the clockwise direction.
1 kg of the carrier is put into a developing machine having a 0 mm developing roll and a counter electrode with a gap of 4.5 mm to form a magnetic brush, and the magnetic brush is rubbed against the counter electrode while rotating at 235 rpm to develop a developing sleeve. Between the counter electrode and the counter electrode
Apply a DC voltage of 200V through a load resistor of kΩ,
It is represented by the volume resistivity obtained from the contact area between the closed circuit current and the counter electrode of the magnetic brush and the developing gap.

The acrylic resin used as the coating material for the carrier used in the present invention includes styrene, o-methylstyrene, and m.
-Methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, pt-butylstyrene, pn-hexylstyrene, pn-octylstyrene, p Styrene-based monofunctional monomer such as -n-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, n-methoxystyrene, p-phenylstyrene, p-chlorostyrene and 3,4-dichlorostyrene Body, ethylene, propylene,
Ethylene unsaturated monoolefins such as butylene and isobutylene, vinyl chloride, vinylidene chloride, vinyl bromide,
Vinyl halides such as vinyl fluoride, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl esters such as vinyl butyrate, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, N-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate ,
Isobutyl methacrylate, n-octyl methacrylate,
Dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate,
Α-methylene aliphatic monocarboxylic acid esters such as dimethylaminoethyl acrylate and diethylaminoethyl methacrylate, acrylonitrile, methacrylonitrile,
Acrylamide, methacrylamide, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and fumaric acid, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether, 2-hydroxyethyl acrylate and methacryl in some cases. Hydroxy group-containing derivatives of acrylic acid or methacrylic acid such as 2-hydroxyethyl acid and 2-hydroxypropyl methacrylate, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone, N-vinyl pyrrole, N-vinyl. N-vinyl compounds such as carbazole, N-vinylindole and N-vinylpyrrolidone, vinylnaphthalene salts, etc., aromatic divinylation such as divinylbenzene, divinylnaphthalene and their derivatives. Things, allyl methacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol triacrylate, trimethylolpropane triacrylate,
It means a copolymer of 1,6-hexanediol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, N, N-divinylaniline, divinyl ether, divinylsulfite, etc., but especially styrene monomer and acrylic acid. Alternatively, a copolymer containing an alkyl ester of methacrylic acid as a main component is preferable.

Further, in the present invention, if necessary, a reactive functional group may be provided in the acrylic resin and crosslinked with a melamine resin to enhance the toughness of the coating. The melamine resin is 2,4,6-triamino-1,3,5-
Triazine (melamine), 2,4-diamino-1,3
It is an addition product or addition condensation product of 5-triazine (guanamine) or a substitution product thereof with formaldehyde, and an alkyl ether compound of this addition product or addition condensation product. The alkyl ether compound can be obtained by reacting the above addition product or addition condensation product with a lower alcohol such as methanol or butanol. In addition, it is preferable to adjust the electric resistance of the carrier by adding a powder that imparts conductivity to the acrylic resin for coating the carrier. The powder which imparts such conductivity has a specific surface area (low temperature nitrogen adsorption method) 85 to 25.
Carbon black having 0 m ² / g and an oil absorption of 53 to 150 ml / g, particularly furnace black, can be preferably used.

The core material of the carrier has a particle size of 30 to 3
00 μm of iron or a metal mixture containing iron as a main component such as cobalt, nickel, titanium, vanadium, chromium, manganese, zinc, molybdenum, and copper, and oxides thereof that are conventionally used as ferrite powders are used. be able to. These can be manufactured, for example, as follows. An appropriate amount of ferric oxide (Fe ₂ O ₃ ) and a metal oxide containing CuO and ZnO as essential components are blended, pulverized and mixed in a wet ball mill or a wet vibration mill, and the resulting slurry is dried. After crushing, calcination is performed at 700 to 1000 ° C. After calcination, it is further pulverized by a wet ball mill, a wet vibration mill or the like to have a particle size of 20 μm or less, and then granulated.
Hold at 00 ° C for 2-24 hours. The fired product is crushed and classified. If necessary, reduction is performed to further oxidize the surface. The production of the core material of the carrier is not limited to the above example.

As a method of forming a coating layer of an acrylic resin on the core material, there is, for example, the following method. An acrylic resin and, if necessary, a melamine resin or the like are dissolved in an organic solvent such as methylene chloride, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, ethyl acetate, butyl acetate or toluene to form a varnish. Furthermore, if necessary, conductive fine particles such as carbon black are dispersed to adjust the electric resistance. The magnetic carrier core material is put into a circulating fluidized bed dryer, and a thin spray is applied so as to wrap the surface of the magnetic carrier core material with the varnish prepared above. After coating, a high temperature gas is blown into the circulation type fluidized bed dryer to dry and cure the varnish, and if necessary, classification is performed.

The toner used in the present invention uses a styrene-acrylic copolymer having a crosslinking component as a binder resin. Examples of the monofunctional monomer as a raw material include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene and pt. -Butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, n-methoxy styrene, p-phenyl styrene, p -Chlorostyrene,
Styrene monofunctional monomers such as 3,4-dichlorostyrene, ethylenically unsaturated monoolefins such as ethylene, propylene and butylene isobutylene, halogenated vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride, etc. Vinyls, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, and other vinyl esters, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-acrylate.
Octyl, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, ethyl methacrylate, propyl methacrylate,
Α-methylene fats such as n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl acrylate and diethylaminoethyl methacrylate. Group monocarboxylic acid esters, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, and in some cases acrylic acid, methacrylic acid,
Unsaturated carboxylic acids such as maleic acid and fumaric acid, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,
Hydroxyl group-containing derivatives of acrylic acid or methacrylic acid such as 2-hydroxypropyl methacrylate, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone, N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole ,
Examples thereof include N-vinyl compounds such as N-vinylpyrrolidone and vinylnaphthalene salts.

As the cross-linking component, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene and their derivatives, allyl methacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol triacrylate, trimethylolpropane triacrylate. , 1,
2 in the molecule of 6-hexanediol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, N, N-divinylaniline, divinyl ether, divinylsulfite, etc.
Examples thereof include monomers having one or more ethylenically unsaturated bonds. It is preferable to use a styrene-based monofunctional monomer, a methacrylic acid derivative, or an acrylic acid derivative as the monofunctional monomer and an aromatic divinyl compound as the crosslinking component. Particularly, the styrene-based monofunctional monomer is 60-
95 parts by weight, 5 to 40 parts by weight of methacrylic acid derivative or acrylic acid derivative (total of 100 parts by weight as a monofunctional monomer), and 0.1 to 3.1 of divinylbenzene as an aromatic divinyl compound as a cross-linking component. Copolymers that are parts by weight are especially useful. If the molecule does not contain a cross-linking component, thermal motion of the main chain segment is facilitated, the storage elastic modulus has a large temperature dependency, and the offset property decreases.

The binder resin is preferably contained in the toner in an amount of 85 to 95% by weight. Further, the styrene-acrylic copolymer used as the binder resin has a storage elastic modulus of 8.3 × 10 ³ to
3.5 × 10 ⁴ dyn / cm ² , loss elastic modulus of 9.2 × 1
It is necessary to be in the range of 0 ^{3 to} 3.7 × 10 ⁴ dyn / cm ² . When the storage elastic modulus or the loss elastic modulus is larger than the above range, the fixability is poor, and when the storage elastic modulus or the loss elastic modulus is smaller than the above range, the offset property is deteriorated. The storage elastic modulus and loss elastic modulus were measured by using a Rheopex Analyzer RPX-705 manufactured by Iwamoto Seisakusho Co., Ltd., and a parallel plate with a diameter of 1.5 cm was measured by a forced sinusoidal vibration method.
The measurement was performed under the conditions of a gap of 0.8 mm, a frequency of 1 Hz, a displacement angle of 1 degree, and a sample temperature of 175 ° C.

The magnetic powder used as the pigment component may be an alloy or compound containing an element exhibiting a ferromagnetic substance such as iron, cobalt and nickel, including ferrite and magnetite. It is preferable that the specific surface area is in the range of 1.6 to 12.3 m ³ / g and the oil absorption is about 25 ml / 100 g. It is suitable that the compounding amount is in the range of 1 to 10% by weight based on the toner. If it is less than 1% by weight, the rise of charging tends to be poor, and if it exceeds 10% by weight, the fixing property tends to be lowered. Further, since carbon black used as the other pigment component tends to lower the electric resistance of the toner, it is used within the range of 3 to 15% by weight in the toner in order to bring the electric resistance into the above range. Is preferable, and it is particularly preferable to use in the range of 5 to 10% by weight.

In addition to the binder resin, carbon black and magnetic powder, the toner used in the present invention includes a fluidity modifier such as hydrophobic silica, a nigrosine dye, and a metal-containing Cr.
One or more known additives such as a charge control agent such as an azo dye and a polyolefin wax may be added to the inside and / or the surface of the toner. The addition amount may be adjusted according to the charge amount of the toner, but is preferably less than 4% by weight.

The electric resistance of the obtained toner is 3.5.
It is set to x10 ^{15 to} 8.7 x 10 ¹⁵ Ω · cm, but outside this range, a good image cannot be obtained. The electrical resistance of the toner is a disk-shaped sample having a diameter of 15 mm and a thickness of 1 mm, which is molded at a pressure of 400 kgf / cm ² , and has a surface of 1 mm.
A main electrode of 0 mmφ and a guard electrode are arranged on the outside of the main electrode, a counter electrode is provided on the back surface, and a DC voltage 1 is applied between the main electrode and the counter electrode.
It is a value obtained as a volume resistivity by measuring the current value after applying KV for 1 minute. The toner charge amount is -10 to
-25 μC / g. Outside this range, good images cannot be obtained. The charge amount of the toner is obtained by using a developer collected from a developing machine and using a particle charge amount distribution measuring device E-SPART1 of Hosokawa Micron Co., Ltd. to calculate the charge q of the toner particles and the aerodynamic particle size. The electric charge amount was converted to μC. For the fogging, LAB D25A-2 manufactured by Hunter was used.

The dry two-component developer of the present invention can be obtained by mixing the carrier and the toner, and the mixing ratio of the toner is preferably 1.5 to 7% by weight of the carrier. If the blending amount of the toner is less than 1.5% by weight, the spent increases, the life of the carrier tends to be shortened, and carrier adhesion tends to occur. When the blending amount of the toner exceeds 7% by weight, the toner tends to scatter.

[0020]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Preparation of Styrene-Acrylic Resin Containing Crosslinking Component to Become Binder Resin of Toner Synthetic Example 1 Apatite (Super Tight 10, manufactured by Nippon Kagaku Co., Ltd.)
10 parts by weight, 3,000 parts by weight of deionized water, agitator,
A reaction vessel equipped with a nitrogen blowing tube, a temperature control thermocouple and a cooling tube was charged, and then a mixture of 492 parts by weight of styrene in which 18 parts by weight of benzoyl peroxide was dissolved and 108 parts by weight of butyl acrylate was added, and stirred to obtain 87 ~
The reaction was carried out at 90 ° C for 5 hours. Then, once the temperature is 40 ℃
After cooling to 1,3-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane 4 parts by weight dissolved 314 parts by weight styrene, butyl acrylate 8
A mixture of 6 parts by weight, 2 parts by weight of butyl maleate and 2 parts by weight of divinylbenzene was charged, and 87 to 9 with stirring.
The reaction was completed by holding at 0 ° C for 4 hours and further at 96 ° C or more for 10 hours. After cooling, it was washed with a hydrochloric acid aqueous solution and dried with hot air to obtain a styrene-acrylic resin containing a cross-linking component.

Synthesis Example 2 10 parts by weight of apatite (Supertite 10) and 3,000 parts by weight of ion-exchanged water were charged in a reaction vessel equipped with a stirrer, a nitrogen blowing tube, a temperature control thermocouple and a cooling tube, and then benzoylper. 574 parts by weight of styrene in which 48 parts by weight of oxide was dissolved, 106 parts by weight of butyl acrylate,
A mixture of 20 parts by weight of butyl methacrylate was added, and the mixture was reacted at 87 to 90 ° C for 5 hours while stirring. Then, the temperature was once cooled to 40 ° C., and then 198 parts by weight of styrene in which 9.6 parts by weight of 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane were dissolved, and butyl acrylate 51 was added. 6 parts by weight and butyl maleate 1.
Charge 2 parts by weight of the mixture and stir at 87-90 ° C.
The temperature was maintained for 4 hours and then at 96 ° C. or higher for 10 hours to complete the reaction. After cooling, it was washed with an aqueous solution of hydrochloric acid and dried with hot air to obtain a styrene-acrylic resin.

Synthesis Example 3 10 parts by weight of apatite (Supertite 10) and 3,000 parts by weight of ion-exchanged water were charged into a reaction vessel equipped with a stirrer, a nitrogen blowing tube, a temperature control thermocouple and a cooling tube, and then benzoylper. A mixture of 410 parts by weight of styrene in which 5 parts by weight of oxide was dissolved and 90 parts by weight of butyl methacrylate was added, and the mixture was reacted at 87 to 90 ° C. for 5 hours while stirring. Then, after cooling the temperature to 40 ° C,
Styrene 39 in which 4 parts by weight of 1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane was dissolved
A mixture of 3 parts by weight, butyl acrylate 108 parts by weight, butyl maleate 2.5 parts by weight and divinylbenzene 3 parts by weight was charged, and the mixture was maintained at 87 to 90 ° C for 4 hours while stirring, and further at 96 ° C or higher for 10 hours. Hold to complete the reaction.
After cooling, it was washed with a hydrochloric acid aqueous solution and dried with hot air to obtain a styrene-acrylic resin containing a cross-linking component.

Preparation of Acrylic Resin for Carrier Coating (Synthesis Example 4) 5 parts by weight of polyvinyl alcohol, 10 parts by weight of aqueous solution and 300 parts by weight of deionized water were provided with a stirrer, a nitrogen blowing tube, a temperature control thermocouple and a cooling tube. The reaction vessel was charged. Then, a mixture of 30 parts by weight of -n-butyl acrylate in which 5 parts by weight of benzoyl peroxide was dissolved, 40 parts by weight of methyl methacrylate and 30 parts by weight of styrene was added, and the mixture was reacted at 90 ° C for 5 hours while stirring. After cooling, filtration, drying and crushing to obtain a weight average molecular weight of 135,000
An acrylic resin having a glass transition temperature of 0 and a glass transition temperature of 66 ° C. was obtained. The weight average molecular weight was determined by gel permeation chromatography method using standard polystyrene (Waters) conversion. The glass transition temperature was measured by a differential scanning calorimeter.

Example 1 The above acrylic resin (synthesis example 4) and carbon black (BLACK PEARLS 700 furnace black manufactured by Cabot Co., specific surface area 200 m ² / g, oil absorption 1)
20 ml / g) toluene varnish 3 with a solid content of 5%
Using a circulation type fluidized bed dryer, a ferrite core mainly composed of spherical FeO and Fe ₂ O ₃ having a particle size of an apparent density of 2.5 g / cm ³ , a saturation magnetization of 60 emu / g and an average particle size of 100 μm. 10 kg of material (Kanto Denka Kogyo Co., Ltd.) was spray-coated at a temperature of 70 ° C., and then the temperature was raised to 100 ° C.
After drying for 0 minutes, an acrylic resin-coated ferrite carrier having an electric resistance of 8.3 × 10 ⁵ Ω · cm was obtained. This carrier was a non-agglomerating, non-agglomerating and good-flowing product. The storage elastic modulus of Synthesis Example 1 is 2.5 × 10 ⁴ dyn /
cm ² and 90% by weight of styrene-acrylic resin containing a cross-linking component having a loss elastic modulus of 1.9 × 10 ⁴ dyn / cm ² , carbon black Black Pearls L (manufactured by Cabot Corporation) 8% by weight, and magnetite MG -RF (Mitsui Metal Industry Co., Ltd.) 2% by weight, charge control agent Eisenspiron Black TRH (Hodogaya Chemical Co., Ltd.) 1.0% by weight, low molecular weight polypropylene Hymer TP-32
(Manufactured by Sanyo Chemical Industry Co., Ltd.) 0.3% of hydrophobic silica fine powder R972 (manufactured by Nippon Aerosil Co., Ltd.) was added to the toner powder having an average particle diameter of 12 μm consisting of 1.0% by weight.
%, Magnetite powder having an average particle diameter of 0.6 μm (manufactured by Mitsui Metal Industry Co., Ltd.) 0.4% by weight and zinc stearate (NOF CORPORATION) 0.02% by weight to add electric resistance. To obtain a T-1 toner of 7.5 × 10 ¹⁵ Ω · cm.
Mixing with the above acrylic resin-coated ferrite carrier, first, an organic photoconductor rotating at a peripheral speed of about 25.4 cm / sec is uniformly charged to negative 630 V by a charging corotron charger, and then a 680 nm semiconductor laser is used to print characters. Information is written, an electrostatic latent image is formed on the organic photoconductor, the electrostatic latent image is reversely developed by the magnetic brush method using the above-mentioned developer, transferred to a sheet, and then Teflon controlled at 190 ° C. Coated aluminum roll and nip pressure 5kgf / c
An image was obtained by fixing with a fixing unit composed of a silicon rubber-coated aluminum heat roll pressed by m ² . As a result, both the fixability and the offset property were good, the initial charge amount was -15.3 μC / g, and the charge amount was −20.5 μC / g even after printing 100,000 pages, which showed little fluctuation and the image density of 1 An excellent image quality of 0.4 and a fog of 0.3 could be obtained.

Comparative Example 1 The storage elastic modulus of Synthesis Example 2 was 6.3 × 10 ³ dyn / cm ² ,
A T-2 toner was obtained under the same conditions as in Example 1 except that a styrene-acrylic copolymer having a loss elastic modulus of 5.2 × 10 ³ dyn / cm ^{2 and} no crosslinking component was used as the binder resin. .
An organic photoconductor rotating at a peripheral speed of about 25.4 cm / sec was uniformly charged with a charging corotron charger to negative 630 V by mixing with the acrylic resin-coated ferrite carrier of Example 1, and then with a 680 nm semiconductor laser. Character information was written, an electrostatic latent image was formed on the organic photoconductor, the electrostatic latent image was reverse-developed by the magnetic brush method using the above-mentioned developer, transferred to paper, and then controlled at 190 ° C. Teflon coated aluminum roll and nip pressure 5kgf / cm
^An image was obtained by fixing with a fixing unit composed of a silicon rubber-coated aluminum heat roll pressed in step ² .
As a result, the fixability was good, but offset occurred. The charge amount in the initial stage is -13.8 μC / g,
After printing 100,000 pages, the charge amount was −36.5 μC / g, the fluctuation was large, the image density was 1.0, and the fog was 0.8, which was a poor image quality.

Comparative Example 2 The storage elastic modulus of Synthesis Example 3 was 4.1 × 10 ⁴ dyn / cm ² ,
90% by weight of styrene-acrylic resin containing a crosslinking component having a loss elastic modulus of 4.5 × 10 ⁴ dyn / cm ² , carbon black Black Pearls L (Cabot Corporation)
8% by weight, magnetite MG-RF (manufactured by Mitsui Kinzoku Kogyo KK) 2% by weight, charge control agent Eisenspiron Black TRH (manufactured by Hodogaya Kagaku KK) 1.0% by weight, low molecular weight polypropylene hymer TP-32 (manufactured by Sanyo Chemical Industry Co., Ltd.) 1.0% by weight, average particle diameter 12 μm
Toner powder of hydrophobic silica fine powder R9
0.3% by weight of 72 (manufactured by Nippon Aerosil Co., Ltd.), 0.4% by weight of magnetite powder having an average particle size of 0.6 μm (manufactured by Mitsui Metal Industry Co., Ltd.), and zinc stearate (NOF CORPORATION). ) 0.03% by weight of T-3 toner having an electric resistance of 7.5 × 10 ¹⁵ Ω · cm was obtained. By mixing with the acrylic resin-coated ferrite carrier of Example 1, first, an organic photoconductor rotating at a peripheral speed of about 25.4 cm / sec was uniformly charged with a charging corotron charger to negative 630 V, and then a 680 nm semiconductor. Character information is written with a laser to form an electrostatic latent image on an organic photoconductor, and the electrostatic latent image is reverse-developed by the magnetic brush method using the above-mentioned developer, transferred to paper and controlled at 190 ° C. Teflon coated aluminum roll and nip pressure 5kgf / c
An image was obtained by fixing with a fixing unit composed of a silicon rubber-coated aluminum heat roll pressed by m ² . As a result, the offset property was good, but the fixability was poor. Initial charge amount is -21.5μC
/ G, and the charge amount is -19.8 μC even after printing 100,000 pages.
However, the image density was 1.2 and the fog was 0.3, and the image density was light and the image quality was poor.

Comparative Example 3 3 kg of a toluene varnish having a solid content of 5% made of the acrylic resin of Synthesis Example 4 and carbon black (BLACKPEARLS 700 manufactured by Cabot Corporation) was used in a circulation type fluidized bed drier to obtain an apparent density of particles. 2.5 g / cm ³ ,
Spherical FeO having a saturation magnetization of 60 emu / g and an average particle size of 100 μm, 10 kg of a ferrite core material (Kanto Denka Kogyo Co., Ltd.) containing Fe ₂ O ₃ as a main component was spray coated at a temperature of 70 ° C., and then the temperature was raised to 100 ° C. The temperature was raised and dried for 30 minutes to obtain an acrylic resin-coated ferrite carrier having an electric resistance of 6.3 × 10 ⁵ Ω · cm. This carrier was a non-agglomerating, non-agglomerating and good-flowing product. The storage elastic modulus of Synthesis Example 1 is 2.5 × 10 ⁴ dyn / cm ² , and the loss elastic modulus is 1.
90% by weight of styrene-acrylic resin containing 9 × 10 ⁴ dyn / cm ² of cross-linking component, 8% by weight of carbon black Black Pearls L (manufactured by Cabot Corp.), magnetite MG-RF (Mitsui Metal Industry Co., Ltd.) 2% by weight, charge control agent Eisenspirone Black TRH (manufactured by Hodogaya Chemical Co., Ltd.) 1.0% by weight, low molecular weight polypropylene Hymer TP-32 (manufactured by Sanyo Kasei Co., Ltd.) 1.
Toner powder having an average particle diameter of 12 μm consisting of 0% by weight,
0.3% by weight of hydrophobic silica fine powder R972 (manufactured by Nippon Aerosil Co., Ltd.) with an average particle diameter of 0.6μ
m magnetite powder (Mitsui Metal Industry Co., Ltd.) 0.4% by weight and zinc stearate (NOF Corporation) 0.02
Electric resistance of 7.5% × 10 ¹⁵ Ω ・ c
m of T-4 toner was obtained. Mixing with the above acrylic resin-coated ferrite carrier, first, the peripheral speed is about 25.4 cm /
The organic photoconductor rotating in seconds is uniformly charged with a negative charge of 630 V by a charging corotron charger, and then character information is written by a 680 nm semiconductor laser to form an electrostatic latent image on the organic photoconductor. The latent image is subjected to reversal development by the magnetic brush method using the above-mentioned developer, and transferred to a sheet.
An image was obtained by fixing with a fixing unit composed of a Teflon-coated aluminum roll controlled at 0 ° C. and a silicon rubber-coated aluminum heat roll pressed at a nip pressure of 5 kgf / cm ² . As a result, both the fixability and the offset property were good, and the initial charge amount was -16.4 μC.
/ G, and the charge amount is -14.2 μC even after printing 100,000 pages.
/ G reduces the charge amount, image density is 1.3, and fog is 1.
The image was 1 and poor.

Comparative Example 4 3 kg of a toluene varnish having a solid content of 5% made of the acrylic resin of Synthesis Example 4 and carbon black (BLACKPEARLS 700 manufactured by Cabot Corporation) was used in a circulating fluidized bed drier to obtain an apparent density of particles. 2.5 g / cm ³ ,
10 g of ferrite core material (Kanto Denka Kogyo Co., Ltd.) containing spherical Fe ₂ O ₃ having a saturation magnetization of 60 emu / g and an average particle diameter of 100 μm as a main component was spray-applied at a temperature of 70 ° C., and then the temperature was raised to 100 ° C. Then, it is dried for 30 minutes and the electric resistance is 8.
A 1 × 10 ⁷ Ω · cm acrylic resin-coated ferrite carrier was obtained. This carrier was a non-agglomerating, non-agglomerating and good-flowing product. The storage elastic modulus of Synthesis Example 1 is 2.5 × 10 ⁴ dyn / cm ² , and the loss elastic modulus is 1.9 × 1.
90% by weight of styrene-acrylic resin containing a cross-linking component of 0 ⁴ dyn / cm ² , carbon black Black Pearls L (manufactured by Cabot Co., Ltd.) 8% by weight, magnetite MG-RF (manufactured by Mitsui Metal Industry Co., Ltd.) 2% by weight, 1.0% by weight of charge control agent Eisenspiron Black TRH (manufactured by Hodogaya Chemical Co., Ltd.), and 1.0% by weight of low molecular weight polypropylene Hymer TP-32 (manufactured by Sanyo Chemical Industry Co., Ltd.) 0.3% by weight of hydrophobic silica fine powder R972 (manufactured by Nippon Aerosil Co., Ltd.) to the toner powder having an average particle diameter of 12 μm, and magnetite powder having an average particle diameter of 0.6 μm (Mitsui Metal Industry Co., Ltd.) Made) 0.4% by weight
Further, a T-5 toner having an electric resistance of 7.5 × 10 ¹⁵ Ω · cm was obtained by adding 0.02% by weight of zinc stearate (NOF CORPORATION). By mixing with the acrylic resin-coated ferrite carrier, an organic photoconductor rotating at a peripheral speed of about 25.4 cm / sec was uniformly charged with negative 630 V by a charging corotron charger, and then 680 nm semiconductor laser. To write character information to form an electrostatic latent image on the organic photoconductor. The electrostatic latent image is reverse-developed by the magnetic brush method using the above-mentioned developer, and transferred to paper.
An image was obtained by fixing with a fixing unit composed of a Teflon-coated aluminum roll controlled at 0 ° C. and a silicon rubber-coated aluminum heat roll pressed at a nip pressure of 5 kgf / cm ² . As a result, both the fixability and the offset property are good, and the initial charge amount is -20.3 μC /
g, and the amount of charge was -32.4 μC / even after printing 100,000 pages.
The fluctuation is large at g, and the image density is 0.9 and the fog is 0.3.
And the image quality was poor.

[0029]

The dry two-component developer of the present invention has good fixability and offset property and maintains excellent image quality even after repeated use over a long period of time.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location G03G 9/113 15/20 102 G03G 9/08 325 9/10 351 (72) Inventor Tetsuya Fujii Ibaraki 4-13-1, Higashi-machi, Hitachi, Japan Inside the Yamazaki factory of Hitachi Chemical Co., Ltd.

Claims (2)

[Claims] 1. An electric resistance of 7.5 × 10 ^{5 to} 6.7 × 1.
Acrylic resin-coated ferrite carrier in the range of 0 ⁷ Ω · cm and a storage elastic modulus of 8.3 × 10 ^{3 to} 3.5 ×
10 ⁴ dyn / cm ² , loss elastic modulus 9.2 × 10 ³ ~
Styrene-acrylic copolymer having a crosslinking component in the range of 3.7 × 10 ⁴ dyn / cm ² as a binder resin,
Contains carbon black and magnetic powder as a pigment component,
Charge amount is -10 to -25 μC / g, electric resistance is 3.5x
A dry two-component developer containing a toner in the range of 10 ^{15 to} 8.7 × 10 ¹⁵ Ω · cm. 2. The dry two-component developer according to claim 1, wherein the electrostatic latent image formed on the surface of the photoconductor is visualized, transferred to a support, and heat-roll fixed. Image forming method.