JPH0229665A - Carrier for developing electrostatic charge image, two-component developer and image forming method - Google Patents

Abstract

PURPOSE:To enhance developing efficiency and to increase image density by using carrier particles coated with a vinyl resin of 1-100 hydroxyl value contg. a hydroxyl group and fluoroplastic. CONSTITUTION:The carrier core material is a copolymer consisting of a styrene monomer, vinyl monomer such as acrylate or methacrylate, and a vinyl monomer contg. the hydroxyl group as constituting units and is coated with the resins having 1-100 hydroxyl value and the fluoroplastic. Since the fluoroplastic is exposed on the carrier coating surface in case of coating the carrier core material by using the mixture composed of the vinyl resin contg. the hydroxyl group and the fluoroplastic, the positive triboelectrostatic charge impartation power to the toner is high and the rise of the electrostatic charge is fast. The toner concn. is thus increased. The uniform and sufficient electrostatic charge of the toner is, therefore, possible even if the contact probability of the toner and the carrier decreases. The developing efficiency is extremely enhanced and the image density is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a carrier, a two-component developer, and an image forming method that constitute a developer for developing an electrostatic image together with a toner.

[Prior art]

As an electrophotographic method, US Pat.
Various methods are described in Publication No. 4748, etc., but in all of these methods, an electrostatic latent image is formed by irradiating a photoconductive layer with a light image corresponding to the document, and then the electrostatic latent image is The electrostatic latent image is developed by attaching colored fine powder called toner having the opposite polarity onto the image, and if necessary, after transferring the toner image to a transfer material such as paper, heat or pressure is applied. Alternatively, copies can be obtained by fixing with solvent vapor or the like.

In the process of developing the electrostatic latent image, toner particles charged to the opposite polarity to that of the latent image are attracted by electrostatic attraction and attached to the electrostatic latent image (in the case of reversal development, (using a toner with a triboelectric charge of the same polarity as the charge of the latent image).Generally speaking, methods for developing electrostatic latent images using toner can be roughly divided into so-called two-component methods in which a small amount of toner is dispersed in a medium called a carrier. There are two methods: a method using a one-component developer, and a method using a so-called one-component developer, which uses toner alone without using a carrier.

Generally, carriers constituting such two-component developers are broadly classified into conductive carriers and insulating carriers.

Oxidized or unoxidized iron powder is usually used as a conductive carrier, but in a developer containing this iron powder carrier, the triboelectricity of the toner is unstable, and the toner is formed by the developer. There is a problem that fog occurs in the visible image. In other words, with the use of developer,
As the toner particles adhere to the surface of the iron powder carrier particles, the electrical resistance of the carrier particles increases, the bias current decreases, and triboelectric charging becomes unstable, resulting in a decrease in the image density of the visible image formed. and fog increases.

Further, typical insulating carriers are carriers in which the surface of a carrier core material made of a ferromagnetic material such as iron, nickel, or ferrite is uniformly coated with an insulating resin. Developers using this carrier are significantly less likely to have toner particles fused onto the carrier surface than those using conductive carriers. It has the advantage of being suitable for

However, in this insulating carrier, the coating layer that covers the surface of the carrier core material has sufficient abrasion resistance and strong adhesion to the core material (durability), and the carrier surface has a toner film. The coating layer must have good anti-sticking properties to prevent the formation of particles (toner spent properties), and the desired charging state of charge and polarity can be obtained through friction with the specific toner used with the carrier (charging properties). is required. That is, the carrier is rubbed against other carrier particles and toner particles in the developing device, but when toner adheres to the surface of the carrier coating layer and a film is formed, the charging characteristics become unstable.

Conventionally, as a technique to solve this problem, a coated carrier coated with a fluorine-containing polymer or a fluorine-containing resin has been proposed in U.S. Pat. Such carriers have poor film-forming properties, can only partially cover the carrier surface, and have a very strong tendency for charging characteristics to become unstable. Also, JP-A-54-110839
In order to improve the film-forming properties of fluorine-containing polymers, US Pat. As the content ratio of the fluoropolymer decreases, the triboelectric charge of the toner slows down and the amount of triboelectric charge of the toner also decreases. As a result, if the toner concentration is small, i.e.
Unless the amount of toner is 5 parts by weight or less per Gearia 100 heavy-duty area, scattering and fogging occur, making it unsuitable for practical use.

On the other hand, in order to speed up the rise of triboelectric charging of toner,
As is conventionally known, there is a method of adding a charge control agent or a charge control resin to the toner, but this method alone cannot quickly increase the triboelectric charge of the toner; Under environmental conditions such as high humidity, low temperature and low humidity, there may be a considerable difference in the amount of triboelectric charge and the rise of charge, which leads to image fogging and poor density, and toner charge control (especially There are still points to be improved as a method for controlling positive charging.We also proposed a method to increase the triboelectrification of toner by adding fine particles to the toner that are located in the opposite direction of the toner on the triboelectrification series. (Unexamined Japanese Patent Publication No. 1986-
75551). However, this method alone is still insufficient to control the toner charge, and until the amount of frictional charge on the toner is sufficiently controlled, increasing the number of fine particles that charge in the opposite direction to the toner will cause the opposite effect. In this case, toner particles aggregate with each other and the fluidity of the toner deteriorates. As a result, the carrier and toner are not sufficiently mixed and it is necessary to provide a stronger and more uniform agitation device in the developer arrangement. Furthermore, if the fluidity of the toner deteriorates, it may cause an adverse effect on the cleaning device of the copying machine.

[Purpose of the invention]

An object of the present invention is to provide a carrier for development that has extremely high development efficiency and can achieve high image density.

An object of the present invention is to provide a developing carrier that provides an extremely stable image even under environmental changes.

SUMMARY OF THE INVENTION An object of the present invention is to provide a developing carrier in which toner chargeability is stable even when the toner concentration is high, and image quality does not deteriorate.

[Structure of the invention and explanation of each structure]

The present invention provides a copolymer in which the carrier core material is a vinyl monomer such as a styrene monomer, an acrylic ester monomer, or a methacrylic ester monomer, and a vinyl monomer containing a hydroxyl group. The present invention relates to a carrier for developing an electrostatic image, characterized in that the carrier is coated with a resin having a hydroxyl value of 1-100 and a fluorine-containing resin.

The present invention comprises a carrier for developing an electrostatic image whose carrier core material is coated with a vinyl copolymer having a hydroxyl value of 1 to 100 and a fluorine-containing resin, a toner, and positively charged hydrophobic colloidal silica. An object of the present invention is to provide a two-component developer characterized by the following.

The present invention provides an image forming method in which a toner image is formed by developing an electrostatic latent image held by an electrostatic latent image carrier with a two-component developer, in which the carrier core material is a vinyl-based toner image having a hydroxyl number of 1 to 100. An image characterized by developing an electrostatic latent image in the presence of an alternating electric field in a developing section using a two-component developer containing an electrostatic image developing carrier coated with a polymer and a fluorine-containing resin and a toner. The purpose is to provide a forming method.

As a result of extensive research, the present inventors found that vinyl resins containing hydroxyl groups have excellent binding properties with carrier core materials, and among blended resins of fluororesins and vinyl resins containing hydroxyl groups, Vinyl resins containing hydroxyl groups have a particularly strong tendency to selectively adhere to carrier core materials (fluororesins, which have poor binding properties with carrier core materials, have a particularly strong tendency to adhere to carrier core materials and vinyl resins containing hydroxyl groups). It is surmised that there is a tendency for it to be expelled from the interface and exposed to the carrier-coated surface.

Furthermore, this phenomenon is related to the compatibility between the vinyl resin having hydroxyl groups and the fluororesin,
It is thought that the fluororesin is separated from the vinyl resin containing hydroxyl groups and easily appears on the surface. When a carrier core material is coated with a mixture of a vinyl resin containing a hydroxyl group and a fluororesin, the fluororesin is exposed on the surface of the carrier coating, and due to the strong negative chargeability of the fluororesin, it is difficult to charge toner. Due to its high positive triboelectric charging ability and rapid charging rise, the toner concentration is high (this makes it possible to uniformly and sufficiently charge the toner even if the probability of contact between the toner and the carrier is low).
As a result, development efficiency is extremely high and image density is high (
Furthermore, it has the effect of providing an extremely stable image even under environmental fluctuations, and there is little fog in the toner image even in high-speed copying machines where the developing sleeve rotates at high speed. It has the effect of extremely little scattering into the main body.

The hydroxyl group-containing vinyl resin used in the present invention is a copolymer of a hydroxyl group-containing vinyl monomer and another vinyl monomer. Vinyl monomers having hydroxyl groups include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxylbutyl acrylate, and 2-hydroxy-acrylate.
3-phenyloxypropyl, 2-hydroxyethyl methacrylate.

2-hydroxypropyl methacrylate, 2-hydroxypropyl methacrylate
-Hydroxybutyl, 2-hydroxy-3 methacrylate
-Phenyloxypropyl, etc. These monomers have a copolymer hydroxyl value of 1 to 100 (K O
Hm g/g), more preferably 5 to 701, and even more preferably 10 to 50 (KOH mg〆g). If this value is small, the adhesion between the carrier core material and the coating layer will be insufficient, and the coating will be easily destroyed by impact, friction, etc., and furthermore, the exposure of the fluorine-containing resin to the carrier surface, which is the main objective of the present invention, will be reduced. The effect is insufficient and the ability of the carrier to impart positive charge is reduced. Moreover, if it is too large, hygroscopicity will increase and charging stability will be lost under high temperature and high humidity conditions.

Other vinyl monomers to be copolymerized with these vinyl monomers having hydroxyl groups include styrene, α-
Styrene derivatives such as methylstyrene, p-methylstyrene, p-t-butylstyrene, p-chlorostyrene;
Methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, hebutyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, undecyl methacrylate, dodecyl methacrylate, methacrylate Glycidyl acid, methoxyethyl methacrylate, propoxyethyl methacrylate, butoxyethyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate.

Mention may be made of hexyl acrylate, hebutyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, and vinyl monomers.

Among these other vinyl monomers, vinyl monomers having one vinyl group in one molecule include styrene, styrene derivatives, and methacrylic acid esters.

Acrylic esters are preferred, especially those containing 1 in the alkyl group.
Alkyl esters of methacrylic acid or acrylic acid having ~5 carbon atoms are preferred.

Among these vinyl monomers, vinyl monomers having a hydroxyl group have a copolymer with a hydroxyl value of 1 to 1.
100 (KOHm g/g). These vinyl monomers are copolymerized by methods such as suspension polymerization, emulsion polymerization, and solution polymerization. These copolymers have a weight average molecular weight of 10.000 to 70,
000 is preferred. Weight average molecular weight is 10,
If it is less than 70,000, the impact resistance tends to be insufficient.
If it exceeds 000, it becomes difficult to coat the carrier core material and aggregates are formed, which is not preferable. Further, this copolymer may be crosslinked with melamine aldehyde or isocyanate. In addition, in the present invention,
The hydroxyl value refers to a value measured based on JIS-KOO70.

On the other hand, examples of the fluororesin to be mixed with the vinyl resin containing hydroxyl groups include polyvinyl fluoride, polyvinylidene fluoride, polytrifluoroethylene, halofluoropolymers such as polytrifluorochloroethylene, polytetrafluoroethylene, Polyvar fluoropropylene,
Copolymer of vinylidene fluoride and acrylic monomer, copolymer of vinylidene fluoride and trifluorochloroethylene,
Copolymers of tetrafluoroethylene and hexafluoropropylene, copolymers of vinyl fluoride and vinylidene fluoride, copolymers of vinylidene fluoride and tetrafluoroethylene, copolymers of vinylidene fluoride and hexafluoropropylene Copolymers, fluoroterpolymers such as terpolymers of tetrafluoroethylene and vinylidene fluoride and non-fluorinated monomers, etc. are preferably used.

The mixing ratio of these fluororesins and vinyl resins having hydroxyl groups can be applied within a wide range due to the above-mentioned characteristic effects of the vinyl resins having hydroxyl groups. Specifically, the ratio (weight ratio) of the fluororesin to the vinyl resin having hydroxyl groups is 3:97.
95:5 to 95:5, more preferably 5:95 to 90':1
0, more preferably 80:20 to 20:8
0 is good. When the content of fluororesin is less than 3% by weight,
The effect of adding fluororesin tends to be insufficient. On the other hand, when the content of fluororesin exceeds 95% by weight, the amount of vinyl resin having hydroxyl groups decreases, so that the core material There is a tendency for the adhesiveness of the resin coating layer to decrease.

Further, the weight average molecular weight of the fluororesin is preferably 5
0,000 to 400,000, more preferably 100.
000 to 250,000 is good. If it is less than 50,000, the friction resistance tends to be insufficient;
If it exceeds 100%, it becomes difficult to uniformly coat the carrier material. Note that the weight average molecular weight in the present invention refers to a value determined by gel permeation chromatography against a calibration curve obtained using standard monodisperse polystyrene. Examples of measurement methods will be described below.

1. Measurement conditions ■ Temperature 25°C ■ Solvent Tetrahydrofuran ■ Flow rate 1mj! 1m1n ■ Sample concentration 8mg 1mj! Tetrahydrofuran solution ■ Sample injection volume: 0.5 mf 2, column: 10" to 2 x 10' In order to properly measure the molecular weight range, the column used is a combination of multiple commercially available polystyrene gel columns. , in the present invention, μm Styragel manufactured by WATERS
500. 10", 10'.

1O6 combination Showa Denko 5hodex A-802, 803, 8
A combination of 04°805 is suitable.

3. Calibration curve When creating a calibration curve, standard polystyrene is used. As the standard polystyrene, for example, Pressure
Chemical Co., or Toyo Tsudani Gyoi ■, with a molecular weight of 6X1O", 2.1X103, 4X1
O”.

1.75X10', 5. lX10', 1. lX10
6.3.9X10'.

It is appropriate to use standard polystyrene with dimensions of 8.6 x 10', 2 x 10', and 4.4 s x 10', and at least about 10 points.

4. Detector An RI (refractive index) detector is used as the detector.

Examples of the carrier core material used in the present invention include surface oxidized or unoxidized iron, copper, and zinc.

Metals such as nickel, cobalt, manganese, chromium, rare earths, and their alloys or oxides can be used, but metal oxides are preferably used, and iron-based ferrite particles are more preferably used.

The volume average particle size of the carrier core material is generally 30 to 150μ.
It is preferable that it is m, and it is more preferable that it is 35-100 micrometers. If the average particle diameter is less than 30 μm, the carrier is likely to be developed (transferred together with the toner) onto the latent image carrier, the carrier will adhere to the surface of the latent image carrier, and the latent image carrier or cleaning blade will be likely to be damaged. Furthermore, the toner image may be transferred to the transfer material and deteriorate the image quality of the toner image.

On the other hand, if the average particle size of the carrier is larger than 150 μm, the toner retention ability of the carrier will be reduced, making it difficult to obtain uniform and high-resolution images, and causing uneven solid images, toner scattering, fogging, etc. ( Furthermore, as the toner concentration in the carrier increases, toner scattering increases.Such a carrier core material may be composed only of magnetic material (or may be composed of magnetic material and non-magnetic material). It may be composed of a combination of magnetic particles, or it may be a mixture of two or more types of magnetic particles.

A carrier having a sharp particle size distribution is preferable in terms of development characteristics, and a carrier having a volume average particle diameter of ±20 μm in an amount of 75% by weight or more, more preferably 80% by weight or more is preferable. Further, the shape of the carrier is preferably spherical, and the sphericity (major axis/minor axis) is 2 or less, more preferably 1.
2 or less is preferable from the viewpoint of fluidity.

As a method for coating the surface of the carrier core material with the coating resin, the resin is dissolved or suspended in a solvent and applied to the surface of the core material, and the resin is adhered to the core material made of magnetic particles or the like. The method is preferred.

The amount of the above-mentioned coating resin to be treated is generally 0.1 to 30% by weight based on the carrier core material in total, considering the film formability and durability of the coating material.
(preferably 0.5 to 20% by weight).

If the coating amount is less than 0.1% by weight, the effect of coating tends to be insufficient, and if it exceeds 30% by weight, it becomes difficult to form a coating layer with a uniform thickness.

When the carrier for developing an electrostatic image of the present invention is used in a developing method in which an alternating electric field is applied between a developing device and a photoreceptor, as will be described later, the electrical resistance of the carrier becomes an important parameter. 1X10”ohm-
cm, more preferably 5X 10"ohm*cm~7
A coated carrier with x10'30hm-Cm is preferred. In the present invention, the method of measuring electrical resistance is exemplified by the method shown in FIG.

A suitable electrical resistance of the carrier of the present invention is furthermore 0.1 μA to 5 μA at a current value measured from the apparatus shown in FIG.
A1 is particularly preferably 0.2 μA to 2.0 μA.

In other words, - To determine the electrical resistance of a carrier when fishing on a boat, apply a voltage using the device shown in Figure 1, measure the minute current flowing at that time, and calculate the specific resistance ρ (Ohm-Cm) from this. Since it is a powder, it may change depending on the filling rate, so care must be taken. Since the object to be measured is a carrier for developing an electrostatic image, it is also preferable to use an apparatus for measuring the current value shown in FIG. 2, which is adapted to a resistance measuring method suitable for an actual developing system.

In FIG. 2, a carrier magnetic brush is formed at 9, a voltage of 200 V is applied, and the value of the current flowing through the system is measured with an ammeter 11. At that time, the closest gap between the magnetic sleeve 9 and the aluminum drum 10 is set to approximately 1 mm, and the height of the ears formed by the carrier magnetic poles is 1.5 mm.
The length should be ~3.5 mm. Note that this measurement is performed at a temperature of 22° C. to 23° C. and a humidity of 50% to 60%.

Here, the method for measuring the amount of triboelectric charge of toner on carrier according to the present invention will be described in detail with reference to FIG.

FIG. 3 is an explanatory diagram of the frictional charge amount measuring device. 40 on the bottom
A magnetic brush (toner and magnetic particles) on a developer carrier to measure the amount of triboelectric charge is placed in a metal measurement container 32 with a conductive screen 33 of 0 mesh (can be changed as appropriate to a size that does not allow carrier particles to pass through). mixture) and cover with a metal lid 34. The weight of the entire measuring container 32 at this time is measured as W+(g). Next, with the suction device 31 (the portion in contact with the measurement container 32 is small (both are insulators), suction is performed from the suction port 37, the air volume control valve 36 is adjusted, and the vacuum gauge is
The pressure in step 5 is 70 mm Hg. In this state, suction is applied sufficiently (for about 1 minute) to remove the toner. The potential of the electrometer 39 at this time is assumed to be V (volt). here 3
8 is a capacitor whose capacity is C (μF).

In addition, the weight of the entire measurement container after suction is measured and is defined as W2 (g). This triboelectric charge amount Q (μC/g) is calculated as shown in the following formula.

However, the measurement conditions are 23° C. and 65% RH.

The binder resin of the toner used in the two-component developer in combination with the carrier of the present invention includes monomers of styrene and its substituted products such as polystyrene and polyvinyltoluene; styrene-propylene copolymers, styrene-vinyltoluene; copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer.

Styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-acrylic-aminoacrylic copolymer, styrene-aminoacrylic copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer,
Styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer.

Styrenic copolymers such as styrene-maleic acid ester copolymers; polymethyl methacrylate.

Polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane,
Polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, paraffin wax, etc., singly or in combination of two or more as necessary It can be used as

Any suitable pigment or dye can be used as a colorant in the above toner. For example, carbon black,
Dyes or pigments such as iron black, phthalocyanine blue, ultramarine blue, quinacridone, and benzidine yellow are used.

In addition, as positive charge control agents, amino compounds, quaternary ammonium compounds, organic dyes, especially basic dyes and their salts, benzyldimethyl-hexadecyl ammonium chloride, decyl-trimethylammonium chloride,
Nigrosine base, nigrosine hydrochloride, safranin γ, crystal violet, etc. may be added.

In combination with the carrier of the present invention, a positively charged toner is preferable in that a good triboelectric charge is imparted to the toner.

The toner structure described above may be used in a toner produced by a commonly used mixing-pulverization method, or may be used as a wall material or a core material, or both, of a microcapsule toner. In the present invention, the toner may mean colored resin particles to which colloidal silica is externally added, or may mean the colored resin particles themselves.

The carrier of the present invention exhibits more preferable development characteristics in combination with a positively charged toner and positively charged hydrophobic colloidal silica.

Among colloidal silica fine powders, the specific surface area due to nitrogen adsorption measured by BET method is 30 d/g or more (especially 50 d/g or more).
~400%/g) gives good results. In the case of positively charged toner, it is better to use positively charged colloidal silica fine powder rather than negatively charged colloidal silica fine powder, which is added to prevent friction of the toner and prevent staining of the sleeve surface. does not impair charging stability (preferably).

As a method for obtaining positively charged colloidal silica or silica fine powder, the above-mentioned untreated fine silica powder is treated with a silicone oil having an organo group having at least one nitrogen atom in its side chain, or There is a method of treatment with a silane coupling agent, or a method of treatment with both.

In the present invention, positively charged silica refers to silica that has a positive triboelectric charge relative to an iron powder carrier or a stainless steel carrier when measured by a blow-off method.

As the silicone oil having a nitrogen atom in the side chain used in the treatment of silica fine powder, a silicone oil having at least a partial structure represented by the following formula can be used.

(In the formula, R1 represents hydrogen, an alkyl group, an aryl group, or an alkoxy group, R2 represents an alkylene group or a phenylene group, R3 and R4 represent hydrogen, an alkyl group, or an aryl group, and R5 represents a nitrogen-containing heterocyclic ring. The above alkyl group, aryl group, alkylene group, and phenylene group may have an organo group having a nitrogen atom, or may have a substituent such as a halogen within a range that does not impair chargeability. It's okay.

Further, the nitrogen-containing silane coupling agent used in the present invention generally has a structure represented by the following formula.

Rm-si-yn (R represents an alkoxy group or a halogen, Y represents an amino group or an organo group having one or more nitrogen atoms, m and n are integers of 1 to 3, and m +
n = 4. ) Examples of the organo group having at least one nitrogen atom include an amino group having an organic group as a substituent, a nitrogen-containing heterocyclic group, or a group having a nitrogen-containing heterocyclic group. Examples of the nitrogen-containing heterocyclic group include unsaturated heterocyclic groups and saturated heterocyclic groups, and known ones can be used. Examples of the unsaturated heterocyclic group include the following.

Examples of the saturated heterocyclic group include the following.

The heterocyclic group used in the present invention is preferably a five-membered ring or a six-membered ring in consideration of stability.

Examples of such treatment agents include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, mono- Butylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyldimethoxysilane.

Dibutylaminopropyl monomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-γ-propylphenylamine.

trimethoxysilyl-γ-propylbenzylamine, and the nitrogen-containing heterocyclic group having the structure described above can be used; examples of such compounds include trimethoxysilyl-γ-propylpiperidine, trimethoxysilyl-γ-propylpiperidine, Examples include silyl-γ-propylmorpholine, trimethoxycysyl-γ-propylimidazole, and the like.

The application amount of these treated positively charged silica fine powders is
The effect is exhibited when the amount is o, oi to 8 parts by weight, particularly preferably 0,1 to 5 parts by weight, relative to 100 parts by weight of the positively charged toner.
It exhibits positive chargeability with excellent stability when added in parts by weight. As for the preferred form of addition, it is preferable that 0.1 to 3 parts by weight of the treated silica fine powder be attached to the surface of the toner particles per 100 parts by weight of the positively charged toner. .

Furthermore, the silica fine powder used in the present invention may be treated with a treatment agent such as a silane coupling agent or an organosilicon compound for the purpose of hydrophobization, if necessary, to react with or physically adsorb to the silica fine powder. Treated with the above-mentioned processing agent.

Examples of such treatment agents include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane,
Allyl phenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane.

β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilyl mercaptan,
Trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyljethoxysilane, hexamethyldisiloxane, 1
．． 3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and siloxane units having 2 to 12 siloxane units per molecule, each having one Si-bonded hydroxyl group in the unit located at the end. Contains dimethylpolysiloxane, etc. These can be used alone or in a mixture of two or more.

A commonly used mixing method can be used to mix the carrier and toner (and silica fine powder) of the present invention, but the toner concentration is 3 to 3 to 30 parts by weight (more preferably 6 to
25 parts by weight). As mentioned above, when using the carrier of the present invention, the T/C+T ratio (weight of toner present/weight of carrier present + amount of toner present)
Even if T/C+T ratio is set high, it is possible to form an image without fogging or darkening, and the T/C+T ratio can be set high.

Within this range, the characteristics of the carrier of the present invention are well exhibited, and high image density (and sharp images can be obtained).

The developing method using the carrier of the present invention is applicable to a general two-component developing method, but is particularly effective in a developing method that applies an alternating electric field between a developing device and a photoreceptor (Japanese Patent Laid-Open No. 62-63970). be.

The reason for this is that the developing method that applies alternating electric fields between the developing device and the photoreceptor causes the toner to fly alternately between the latent image and the carrier at high speed due to the alternating electric fields, which reduces the durability of the carrier, especially the toner spent. Although sufficient performance is desired for
The carrier according to the present invention has good adhesion of the vinyl copolymer core material containing OH groups and low specific critical surface tension (friction coefficient) of the fluororesin, which causes the carrier to become spent and wear out. It is particularly suitable because it can withstand peeling from the core material of the coating resin and has a suitable electrical resistance value or current value. For example, when using a laminated organic photoconductive photoreceptor, the dark potential is -600v+toov, the bright potential is -200+1OOV (7), and a DC voltage of -300v±100V is applied to the electrostatic latent image. 300~2000Vpp, frequency 200~3000
Development conditions include applying an alternating Hz voltage to a developer carrier such as a sleeve, holding the photoreceptor at ground potential, and generating an alternating electric field in the developing section.

A developing device to which the carrier of the present invention is preferably applicable will be described below with reference to FIG.

FIG. 4 shows a sectional view of the developing device, and in FIG. 4, 4]
is an electrostatic latent image carrier that carries an electrostatic latent image to be imaged; specifically, it is an endlessly movable photosensitive drum or belt, or a dielectric drum or belt. In this apparatus, the electrostatic latent image carrier is, for example, a photosensitive drum on which an electrostatic latent image is formed by electrophotography, and is rotatable in the direction of arrow a.

This device controls a developer container 62, a developing sleeve 42 (hereinafter simply referred to as a sleeve) which is a developer holding member, a magnet 43 which is a magnetic field generating means, and the amount of developer conveyed to the developing section on the sleeve 42. It includes a regulating blade 44 (hereinafter simply referred to as a blade), a power source 54 which is an alternating electric field forming means, and the like. Each configuration will be explained below.

Container 62 contains a developer having a mixture of magnetic carrier particles 47 and toner particles 48 . The toner particles are
For example, non-magnetic toner particles. Although the toner particles and magnetic particles are stored so that the concentration of magnetic particles is high near the sleeve 42 and low at a distance from the sleeve 42, they may be stored in the container 62 as a uniform mixture. The container 62 has an opening at the lower left in FIG.

The sleeve 42 is made of a non-magnetic material such as aluminum, and is provided at the opening of the container 62 so that a part of its surface is exposed and the other surface protrudes into the container 62. The sleeve 42 is rotatably supported about an axis perpendicular to the drawing and is rotationally driven in the direction indicated by the arrow. Although the sleeve 22 is a cylindrical sleeve, it may also be an endless belt.

The sleeve 42 opposes the photosensitive drum 41 with a small gap therebetween and constitutes a developing section. Toner and magnetic carrier particles are conveyed to this developing section by a sleeve 42, and the magnetic carrier particles exist here in a volume ratio of, for example, 1.5 to 30%.

The magnet 43 is fixed statically inside the sleeve 42 and remains stationary even when the sleeve 42 rotates. The magnet 43 includes an N magnetic pole 43a1 that controls the amount of developer applied onto the sleeve 42 in cooperation with a blade 44 to be described later, and an S magnetic pole 43b1 that is a developing magnetic pole.
N magnetic pole 4 that transports the developer after passing through the developing section into the container 62
3c and an S magnetic pole 43d.

The south pole and north pole may be reversed. This magnet is a permanent magnet, but an electromagnet may be used instead.

The blade 44 is made of a non-magnetic material such as aluminum at least at its tip, extends in the longitudinal direction of the sleeve 42 near the top of the opening of the container 62, has a base fixed to the container 62, and has a distal end attached to the sleeve. It faces the surface of 42 with a gap. The gap between the tip of the blade 44 and the surface of the sleeve 42 is 50 to 500 μm1, preferably 1
00 to 350 μm. If this gap is smaller than 50 μm, magnetic carrier particles are likely to clog this gap (,5
If it exceeds 00 μm, a large amount of magnetic carrier particles and toner will pass through the gap, making it impossible to form a developer layer with an appropriate thickness on the sleeve 42. The thickness of the developer layer is smaller than the gap between the photosensitive drum 41 and the sleeve 42 in the developing section (however, the thickness of the developer is the thickness on the sleeve 42 when no magnetic force is applied). ). In order to create a developer layer with such a thickness, it is preferable that the gap between the blade tip and the sleeve surface be equal to or smaller than the gap between the sleeve surface and the photosensitive drum surface, but it is also possible to make it larger. .

A magnetic carrier particle circulation limiting member 46 is provided on the inside of the container 62 of the blade 44, and this restricts the circulation area of the magnetic carrier particles within the container 62.

The power supply 54 applies a voltage between the photosensitive drum 41 and the sleeve 42 to form an alternating electric field in the gap between them.
Toner is transferred from the developer on the sleeve 42 to the photosensitive drum 41. The voltage from the power supply 54 may be a symmetrical alternating voltage in which the peak voltages on the positive side and the negative side are the same, or an asymmetrical alternating voltage in which a DC voltage is superimposed on such an alternating voltage. As a specific voltage value, for example, dark potential -600V
For example, a DC voltage of -300V is superimposed on an electrostatic latent image with a bright area potential of -200V, so that the peak-to-peak voltage is 300 to 2000 Vpp1, and the frequency is 200 to 3000 H.
z alternating voltage is applied to the sleeve 42 side, and the photosensitive drum 41
is held at ground potential.

The lower part of the container 62 extends in the direction of the photosensitive drum 41 to form an extension, and prevents the developer (particularly toner particles) from leaking to the outside. In order to further ensure the prevention of such leakage, a member 49 is provided on the upper surface of the extension portion to receive and restrain the leaked toner.

Further, a scattering prevention member is fixed to the tip of the extension along the longitudinal direction of the sleeve 42. A voltage having the same polarity as the toner particles may be applied to this member. As a result, the toner scattered from the development area can be pushed toward the photosensitive drum by the electric field, thereby preventing the toner from scattering.

Developer blocking members are provided at both ends of the sleeve 42 in the longitudinal direction to prevent application of developer at both ends of the sleeve 42 .

Next, the operation of the developing device will be explained. First, container 6
2, magnetic carrier particles 47 are introduced. The charged magnetic carrier particles are held on the sleeve 42 by the magnetic poles 43a and 43d, and the sleeve 42 facing into the container 62
The magnetic carrier particles adhere to the entire surface of the magnetic carrier particles and form a layer of magnetic carrier particles. In the portion of the magnetic carrier particle layer near the magnetic poles 43a and 43d, the magnetic carrier particles 47 constitute a magnetic brush. Thereafter, the toner 48 is placed into the container 62 to form a toner layer outside the magnetic carrier particle layer. It is preferable that the magnetic carrier particles 47 initially introduced include toner in an amount of 2 to 70% (by weight) based on the magnetic carrier particles, but may be composed of only magnetic carrier particles. The magnetic carrier particles 47 are partially attached to the sleeve 42
If it is adsorbed and held as a layer of magnetic carrier particles on the surface,
Vibrations or significant tilting of the device will not cause substantial flow or tilting, and the surface of the sleeve 42 will remain covered.

Next, when the sleeve 42 is rotated in the direction of the arrow, the magnetic carrier particles rise from the bottom of the container 62 in a direction along the surface of the sleeve 42 and reach the vicinity of the blade 44 . Therefore, a part of the magnetic carrier particles passes through the gap between the tip of the blade 44 and the surface of the sleeve 42 together with the toner, and the other part collides with the member 46 and then reverses and moves outside the ascending path of the magnetic carrier particles due to gravity. It descends to reach the lower part of the container 62, rises again near the sleeve 42, and repeats the above operation. Note that some of the magnetic carrier particles 47 rising from the lower part of the container 62 toward the blade 44 turn around and fall before reaching the vicinity of the blade 44 . This is particularly noticeable in the magnetic carrier particles far from the surface of the sleeve 42.

In this way, the magnetic carrier particles that turn around and fall near or in front of the blade 44 pick up toner particles from the outer toner layer.

By circulating in this manner with the rotation of the sleeve 42, the toner 48 is charged by friction between the magnetic carrier particles 47 and the surface of the sleeve 42.

Near the front of the blade 44, the magnetic carrier particles 47 near the surface of the sleeve 42 are attracted to the surface of the sleeve 42 by the magnetic pole 43a, and as the sleeve 42 rotates, they pass below the blade 44 and exit the container 62. At this time, the magnetic carrier particles 47 carry out the toner attached to their surfaces together. Further, some of the charged toner particles 48 leave the container on the sleeve 42 while remaining attached to the surface of the sleeve 42 due to the reflection force. Blade 44 regulates the amount of developer applied onto sleeve 42.

The developer layer (mixture of magnetic carrier particles 47 and toner 48) thus formed on the surface of the sleeve 42
As the sleeve 42 rotates, it reaches the developing section facing the photosensitive drum 41. Here, toner is transferred from the surface of the sleeve 42 and the surface of the magnetic carrier particles onto the latent image by an alternating electric field applied between the photosensitive drum 41 and the sleeve 42, and the latent image is developed. The volume ratio of magnetic particles in the developing area is preferably 1.5 to 30%.

As the sleeve 42 rotates, the toner particles and magnetic carrier particles that have not been consumed for development are transferred to the container 6.
2 and applied again onto the sleeve 42 by the circulation action described above in the container 62, and the process is repeated. During this recirculation, the magnetic carrier particles take in toner from the toner layer on the upper part of the container 62, and are supplied with the amount of toner consumed in development.

FIG. 5 is an enlarged sectional view for explaining the behavior in the developing section. The photosensitive drum 41 carries charges constituting a latent image, and the charges constituting the electrostatic latent image have a negative polarity, and the toner is charged to a positive polarity. Further, the photosensitive drum 41 and the sleeve 42 rotate in the direction of the arrow so as to move in the same circumferential direction.The above-mentioned alternating voltage is applied to the space between them by the power supply 54, and an alternating electric field is formed. On the other hand, there is a magnetic pole 43b of the magnet 43 inside the sleeve 42 corresponding to the closest portion between the photosensitive drum 41 and the sleeve 42.

In this space, there is a developer, which is a mixture of magnetic carrier particles 47 and toner 48, which have been conveyed by the rotation of the sleeve 42 as described above. In the case of the development method using the so-called one-component non-magnetic developer thin layer (Japanese Patent Laid-Open No. 58-143), magnetic carrier particles 47 are present here.
No. 360 and No. 59-101680). In addition, due to the volume ratio of magnetic carrier particles in this area (described later), the amount of magnetic carrier particles present is much smaller than in the normal so-called magnetic brush development method (in this respect, the magnetic brush development method This small number of magnetic carrier particles 47 forms a chain of ears 6 due to the action of the magnetic pole 43a.
1 is formed in a rough state, that is, in a sparse state.

The behavior of the magnetic carrier particles 47 in the developing section is special because the degree of freedom is increased.

In other words, these sparse ears of magnetic carrier particles can form a uniform distribution in the direction of the magnetic field lines, and can open both the sleeve surface and the magnetic carrier particle surface.
The toner adhering to the surface of the magnetic carrier particles can be supplied to the photosensitive drum without being obstructed by the spikes, and by forming a uniform open surface on the sleeve surface, the toner adhering to the sleeve surface is blown from the sleeve surface to the photosensitive drum surface by an alternating electric field. can.

Here, the behavior of magnetic particles and the flight of toner particles will be explained.

As shown in FIG. 5, since the electrostatic latent image is composed of negative charges (dark parts of the image), the electric field due to the electrostatic latent image is in the direction indicated by arrow a. The direction of the electric field due to the alternating electric field changes alternately, but in the phase where the positive component is applied to the sleeve 42 side, the direction of the electric field due to this matches the direction of the electric field due to the latent image. At this time, the electric field causes the panicle 6 to
The amount of charge injected into the photosensitive drum 41 becomes maximum, and therefore, the ears 61 are in the maximum standing state as shown in the figure, and the long ears extend onto the surface of the photosensitive drum 41.

On the other hand, as described above, the toner 48 on the surfaces of the sleeve 42 and the magnetic carrier particles 47 is transferred to the photosensitive drum 41 by the electric field formed in this space. Since the sleeve 42 is standing upright in a rough state, the surface of the sleeve 42 is exposed, and the toner 48 separates from both the sleeve 42 surface and the surface of the spike 61. In addition, the spike 61 has a material having the same polarity as the toner 48. Because of the presence of electric charges, the toner 48 on the surface of the ears 61 is more likely to move due to electrical repulsion.

In the phase in which the negative component of the alternating voltage component is applied to the sleeve 42, the electric field due to the alternating voltage (arrow b) is in the opposite direction to the electric field due to the electrostatic latent image (arrow a). Therefore, the electric field in this space becomes strong in the opposite direction, and the amount of charge injected becomes relatively small (ie, the ears 51 are brought into a contact state in which they are shrunk in accordance with the amount of charge injected).

On the other hand, since the toner 48 on the photosensitive drum 41 is positively charged as described above, the electric field formed in this space causes the sleeve 42 or the magnetic carrier particles 47 to
countertransfer to. In this way, the toner 48 reciprocates between the photosensitive drum 41 and the surface of the sleeve 42 or the surface of the toner 48, and as the space between them expands due to the rotation of the photosensitive drum 41 and sleeve 22, the electric field weakens (becomes more At the same time, the developing action is completed.

There are charges injected into the spikes 61 by frictional charges or mirror charges with the toner 48, electrostatic latent image charges on the photosensitive drum 41, and alternating electric fields between the photosensitive drum 41 and the sleeve 42. The state is magnetic carrier particle 47
It changes depending on the charging/discharging time constant of the charge, which is determined by the material and other factors.

As described above, the spikes 61 of the magnetic carrier particles 47 are brought into a state of slight but intense vibration due to the above-mentioned alternating electric field.

Here, the volume ratio of magnetic carrier particles in the developing section will be explained. The "developing section" is a section to which toner is transferred or supplied from the sleeve 42 to the photosensitive drum 41. The term "volume ratio" refers to the percentage of the volume occupied by the magnetic carrier particles present in the developing section. In the above-mentioned developing device, this volume ratio has an important influence, and it is 1.5 to 30%, especially 2.
It has been found that a range of 6 to 26% is extremely preferable.

If it is less than 1.5%, a decrease in the density of the developed image will be observed, a sleeve ghost will occur, a noticeable difference in density will occur between the area where the ears 61 are present and the area where the ears 61 are not present, and the surface of the sleeve 42 will be This is undesirable in that the thickness of the developer layer formed is non-uniform throughout.

If it exceeds 30%, the degree of closure of the sleeve surface increases, which is undesirable because fogging may occur.

In particular, the present invention prevents the image quality from monotonically deteriorating or increasing as the volume ratio increases or decreases (,1,5
Sufficient image density is obtained in the range of ~30%, image quality deteriorates even if it is less than 1.5% or exceeds 30%, and sleeve ghost and fogging occur in the range of the above values where image quality is sufficient. do not.

The former image quality deterioration is thought to be due to negative characteristics, while the latter is caused by an increase in the amount of magnetic carrier particles present in the sleeve 42.
This is thought to occur because the surface cannot be opened and the amount of toner supplied from the surface of the sleeve 42 is significantly reduced.

Furthermore, the developer using the carrier according to the present invention has stable charging characteristics even when the toner concentration reaches a certain level, and the developer moves uniformly even in a developing device without a complicated developer stirring mechanism. Therefore, the fluctuation of the T/C+T ratio is small and the tribo value is stable, and the T/C + T ratio is small.
Even when the ratio changes, the rise of the tribo is quick, so the toner can be charged uniformly and sufficiently.
This is particularly effective in a developing method using a simple developing device without an R mechanism (such as Japanese Patent Laid-Open No. 63-4280).

Hereinafter, the present invention will be explained in more detail with reference to Examples. "Parts" shown in the following examples are parts by weight.

Practical JE Example 2 The volume average particle size is 65 μm, the content of particles with a particle size of less than 45 μm is 8.2% by weight, and the content of particles with a particle size of more than 85 μm is 6.3% by weight, Particle size 45 to 8
Spherical magnetic ferrite particles (sphericity of about 1.03) containing 85.5% by weight of 5 μm particles were used as the carrier core material. On the other hand, the following copolymer was used as a coating resin for the carrier core material.

The carrier was used to form spikes similar to the carrier spikes in an actual developing device, and the current value flowing through the carrier spikes was measured and found to be 0.6 μA.

The above copolymer (10 parts by weight in total) was mixed with a mixed solvent of acetone and methyl ethyl ketone (mixed weight ratio = 1:1)90
Prepare a coating solution with a concentration of 10% by dissolving it in parts by weight, and apply the prepared coating solution using a coating machine (Spira Coater manufactured by Okada Seiko Co., Ltd.)
was applied to the ferrite particles.

After removing the solvent, it was dried at a temperature of 90° C. for 1 hour to produce a resin coated carrier A1. Calculated from the weight change before and after coating, the ferrite particles contain approximately 0.8% by weight.
was coated with a copolymer of

It was Ωcm. Further, in the apparatus shown in FIG. 2, the above composition was mixed, melt-kneaded, pulverized, and classified to produce cyan resin fine particles having a volume average particle diameter of 11 μm. A cyan toner was prepared by mixing 100 parts by weight of cyan resin particles and 0.8% by weight of positively charged hydrophobic colloidal silica treated with amino-modified silicone oil using a Henschel mixer.

The toner and the carrier A1 were mixed at a weight ratio of 15:85 using a V-blender to obtain a two-component developer. Canon high-speed copying machine applying an alternating electric field between an organic photoconductive photosensitive drum and a developing sleeve [sleeve peripheral speed = 270 mm/sec; alternating electric field components (peak-to-peak voltage = 1300 V, frequency = 1800 Hz)
When applying the obtained two-component developer to the DC voltage (-220 V) applied to the 2-component (-220V) and performing image formation tests (image production) in various environments, the image reflection density was found to be at room temperature and humidity ( 1.30 at 23°C, 60% RH), 1.30 at low temperature and low humidity (15
1.40 under high temperature and high humidity (35℃,
90% RH), which was as high as 1.30, and a clear image without fogging was obtained. The amount of charge on the toner at this time (
(Measured using the charge measuring device shown in Figure 3) is +21.5μC/g under normal temperature and normal humidity conditions, and +21.0μ under low temperature and low humidity conditions.
C/g, +19.8 μC/g under high temperature conditions,
It was stable and virtually independent of environmental differences.

Further, after leaving the two-component developer in each of the above environments for one month, images were produced in the same manner, and no abnormalities were observed in the initial images.

Furthermore, adhesion of carrier onto the latent image holder and toner scattering from the developing device were hardly observed during continuous copying of 100,000 sheets under the above three conditions.

Ratio 1: 1 Instead of the mixed resin of Example 1 (mixing ratio = 1: 1),
An average particle size of 65 μm was obtained in the same manner as in Example 1 except that only ethyl methacrylate polymer (hydroxyl value 0.1 or less; weight average molecular weight 39,000) was used as the coating resin.
The ferrite particles were coated with the above ethyl methacrylate polymer to obtain resin-coated carrier particles (carrier B1).

The toner used in Example 1 and the carrier B1 obtained above were mixed at a weight ratio of 15:85 to form a two-component developer, and image formation was carried out in the same manner as in Example 1. Fog and toner scattering were noticeable at the bottom. The charge amount of toner on carrier B under low temperature and low humidity is +3.7
It was μC/g.

"Comparison 1" Instead of the mixed resin used in Example 1 (mixing ratio = 1:1), vinylidene fluoride-tetrafluoroethylene copolymer resin (monomer composition weight ratio 75:25, weight average molecular weight 210,000) was used. ) was used as the coating resin.
Ferrite particles with an average particle size of 65 μm were coated in the same manner as in Example 1 to obtain resin-coated carrier particles (carrier B2).
I got it. The resin coating amount of the obtained carrier B2 was about 0.
2% by weight, and when Carrier B2 was observed under an electron microscope, it was found that the vinylidene fluoride-tetrafluoroethylene copolymer resin coating was not sufficient and the core material was exposed in some places. When the current value of carrier B2 was measured using the measuring device shown in FIG. 2 in the same manner as in Example 1, it was 12.0 μA, which was lower resistance than carrier A1 of Example 1.

The toner used in Example 1 and the above carrier B2 were
:85 to form a two-component developer, and when images were produced in the same manner as in Example 1, the image density was low even at room temperature and humidity, and solid black areas were rough, making it unsuitable for practical use. Toner carrier B under room temperature and humidity
The amount of charge against 2 was +12.5 μC/g.

Placement 1” Instead of the mixed resin of Example 1 (mixing ratio = 1:1),
Styrene-2-hydroxyethyl methacrylate-methyl methacrylate copolymer (monomer composition ratio 35:8:
57. Hydroxyl number 30; Weight average molecular weight 5
Example 1 except that only 2.000) was used as the coating resin.
In the same manner as above, ferrite particles having an average particle size of 65 μm were coated with the above styrene-2-hydroxyethyl methacrylate-methyl methacrylate copolymer to obtain resin-coated carrier particles (carrier B2).

The toner used in Example 1 and the carrier B3 obtained above were mixed at a weight ratio of 15:85 to form a developer, and images were produced in the same manner as in Example 1. Similar to No. 1, fogging and toner scattering were noticeable.

The amount of charge of toner on carrier B3 under low temperature and low humidity is +
It was 3.4 μC/g.

"Comparison 1" Instead of the mixed resin used in Example 1 (mixing ratio = 1: 1), styrene-ethyl methacrylate copolymer resin (monomer composition weight ratio = 65: 35. Hydroxyl value =
O, l, weight average molecular weight = 59,000) and vinylidene fluoride-tetrafluoroethylene copolymer resin (monomer composition weight ratio = 75: 25. Weight average molecular weight = 21
0,000) at a mixing ratio of 1:1 to coat the ferrite core material in the same manner as in Example 1,
A coated carrier B4 was produced.

The toner used in Example 1 and the carrier B4 obtained above were mixed at a weight ratio of 15:85 to form a two-component developer, and image development was carried out in the same manner as in Example 1. Slight fogging and slight toner scattering were observed near the image output area of more than 10,000 images. The amount of charge of the toner on carrier B3 under low temperature and low humidity was +13.5 μC/g.

In addition, the concentration was slightly low at 1.08 under high temperature and high humidity conditions.

"Support main" Instead of the mixed resin of Example 1 (mixing ratio = 1: 1),
Styrene - 2-hydroxymethyl methacrylate - methyl methacrylate - ethyl methacrylate (monomer composition weight ratio = 57: 20: 13: 10. Hydroxyl number = 409 Weight average molecular weight = 54,000) 3.5
1.5 parts by weight of methyl etherified melamine formaldehyde resin and 5 parts by weight of vinylidene fluoride-tetrafluoroethylene copolymer (monomer composition weight ratio = 75 = 25, weight average molecular weight = 210,000) were added to a methyl ethyl ketone solution. Dissolved in 500 m j7, Example 1
Ferrite particles having an average particle size of 65 μm (the same core material used in Example 1) were coated with the above resin in the same manner as above to obtain a resin-coated carrier A2.

The resin coating amount of carrier A2 is 0.75% by weight, the electrical resistance value is 7×10”Ω・cm, and the electrical value is 0.
．． It was 45μA. The toner used in Example 1 and the carrier A2 obtained above were mixed at a weight ratio of 15:85 to prepare a two-component developer, and image formation was carried out in the same manner as in Example 1. Similar to 1, good results were obtained under each environment.

Comparison 1" Styrene-2-hydroxymethyl methacrylate methyl methacrylate (monomer composition weight ratio = 70:15: 15.
Hydroxyl number = 352 Weight average molecular weight = 52,00
0) 7 parts by weight and 3 parts by weight of methyl etherified melamine-formaldehyde resin were dissolved in acetone-methyl ethyl ketone mixed solvent (mixing ratio = 1:1), and ferrite particles with an average particle size of 65 μm were prepared in the same manner as in Example 1. were coated with the above resin to obtain resin-coated carrier particles B5.

Toner used in Example 1 and carrier B obtained above
, and were mixed at a weight ratio of 15:85 to form a two-component developer, and when image formation was carried out in the same manner as in Example 1, fog appeared on the toner image under low temperature and low humidity, and toner scattering was noticeable. Therefore, the image was poorer than that of Example 1. The amount of charge of the toner on the carrier B5 under low temperature and low humidity was +4.3 μC/g.

Example 1. The results of Comparative Examples 2 and Comparative Examples 1 to 5 are shown in Table 1 below.

Positively charged hydrophobic colloidal silica 1 prepared from the above composition in the same manner as in Example 1 and treated with amino-modified silicone oil to black fine powder with a volume average particle diameter of 11.5 μm
．． A toner was prepared by externally adding 0% by weight.

Separately, styrene-2-hydroxyethyl acrylate-2-hydroxypropyl methacrylate-methyl methacrylate copolymer (monomer composition ratio = 70:5:5:2
0. Weight average molecular weight = 64,000. Hydroxyl number=
A coating solution was prepared by dissolving 8 parts by weight of 40 (KOHmg/g)) and 2 parts by weight of polyvinylidene fluoride (weight average molecular weight 230,000) in a mixed solvent of acetone and methyl ethyl ketone. Diameter 6
0 μm (88.7% by weight of 40 μm to 80 μm, 4
A resin-coated carrier A3 was obtained by coating IKg of ferrite particles (9.0% by weight less than 0μ and 2.3% by weight more than 80μ) using a fluidized bed device in the same manner as in Example 1. Calculating the resin coating amount of carrier A3 is 0.8
It was wt%. Also, the resistance of carrier A3 is 6.5X
The resistance was 10''Ω·cm, and the current value was 0.45 μA.

The toner and carrier A3 were mixed at a weight ratio of 15:85 using a V-blender to obtain a two-component developer. The obtained two-component developer was applied to a Canon medium-speed copying machine [sleeve circumferential speed = 180 mm/sec, alternating electric field (peak/peak voltage = 1300 V).

Applying a DC voltage of -220 V to a frequency of 1900 Hz] and performing image formation tests (image production) in various environments, the image reflection density was 1.3 at room temperature and humidity.
5. The image quality was high at 1.40 under low temperature and low humidity and 1.21 under high temperature and high humidity, and a clear image without fogging was obtained.

The amount of charge on the toner at this time (measured with the above charge amount measuring device)
is +18.5μ under normal temperature and humidity conditions in each environment.
C/g, +17.0 μC/g under low temperature and low humidity conditions, and +16.5 μC/g under high temperature and high humidity conditions, and was stable, substantially independent of environmental differences.

Further, after leaving the two-component developer in each of the above environments for one month, images were produced in the same manner, and no abnormalities were observed in the initial images.

Furthermore, adhesion of carrier onto the latent image holder and toner scattering from the developing device were hardly observed during continuous copying of 100,000 sheets under the above three conditions.

In place of the carrier coating resin used in Example 3, a styrene-butyl methacrylate copolymer resin (monomer composition weight ratio = 70:30. Weight average molecular weight 48,000) was used.
8 parts by weight and polyvinylidene fluoride (weight average molecular weight 15
0.000) was coated on carrier particles in the same manner as in Example 3 to obtain carrier B6.

When the toner used in Example 3 was mixed with the above carrier B6 at a weight ratio of 10:90 to form a two-component developer, and an image was produced in the same manner as in Example 3, the image density was low at room temperature and humidity. It was low.

From the above composition, a volume particle size of 12.5 was prepared in the same manner as in Example 1.
A toner was prepared by externally adding 0.8% by weight of positively charged hydrophobic colloidal silica treated with amino-modified silicone oil to micrometer red fine powder.

Next, styrene - 2-hydroxymethyl methacrylate - methyl methacrylate - butyl methacrylate (monomer composition weight ratio = 55:35:5:5. Weight average molecular weight = sa,
ooo; Hydroxyl number 60 (K OHm g /
g) 6 parts by weight and polyvinylidene fluoride-tetrafluoroethylene copolymer (monomer composition weight ratio = 85 = 1
5; weight average molecular weight 180,000) was dissolved in a methyl ethyl ketone solvent to prepare a coating solution, and this coating solution had a volume average particle size of 55 μm (35 to 75 μm).
In the same manner as in Example 1, resin-coated carrier particles (Carrier A 4) was obtained.

The resin coating amount of carrier A4 is 1.2% by weight,
Also, the resistance value is 9XIO”Ω・cm, and the current value is 0.
．． It was 8μ8.

The toner and carrier A4 were mixed at a weight ratio of 20:80 using a narrator to obtain a two-component developer. Applied to a Canon personal copying machine (alternating electric field: peak-to-peak voltage = 1200V, frequency = 1800Hz) that does not have an ATR mechanism or a strong developer stirring mechanism, image formation tests (image output) were performed in various environments. As a result, the image reflection density was as high as 1.30 at room temperature and humidity, 1.35 at low temperature and low humidity, and 1.20 at high temperature and high humidity, and a clear image without fogging was obtained. The charge amount of the toner at this time (measured with the above charge amount measuring device) was +15.7 μC/g under normal temperature and normal humidity conditions, +13.0 μC/g under low temperature and low humidity conditions, and +13.0 μC/g under high temperature and high humidity conditions. It was stable at +14.5 μC/g, substantially independent of environmental differences.

Further, after leaving the two-component developer in each of the above environments for one month, image reproduction was performed in the same manner, but the initial image was also fixed (no abnormality was observed).

Furthermore, as in Example 1, adhesion of carrier onto the latent image holder and toner scattering from the developing device were hardly observed during continuous copying of 1,500 sheets under the above three conditions. There wasn't. T/C+T ratio (%) is 20.
0%, 21.8% at 500 sheets, 18 at 1000 sheets.
．． 5%, and it was found that the variation in T/C ratio was small.

Lid 1'' The toner concentration (toner weight/carrier weight + toner weight) of the two-component developer used in Example 1 was changed as shown in Table 2, and the test was carried out at room temperature and humidity using a Canon medium-speed copying machine. (2
Continuous copying of 1% sheets was carried out at 2.5° C./60%) and the state of toner scattering inside the copying machine was investigated. As a comparative example, a similar experiment was conducted using the developer of Comparative Example 4. From the experimental results, it was found that in the case of the carrier of the present invention, there was little toner scattering even when the toner concentration was high.

Table 2 Evaluation rank 20: Good with no problems), ○Δ: Average.

Δ: Practical, ×: Bad. The amount of toner scattering is the amount of toner accumulated in the toner scattering tray at the bottom of the developing device after 10,000 sheets have been produced.

〔Effect of the invention〕

As described above, according to the present invention, by using carrier particles coated with a vinyl resin containing a hydroxyl group and having a hydroxyl value of 1 to 100 and a fluorine-containing resin, development efficiency is extremely high and image density can be increased. Furthermore, a developer carrier having excellent charging properties is provided. The carrier of the present invention has stable charging characteristics even at high toner concentrations, and provides a developer with stable charging characteristics even under various environments. Furthermore, according to the present invention, it is possible to produce a developer that can produce better images with better reproducibility than before,
In particular, even in a developing device without an ATR mechanism or a developer stirring mechanism, good images without fog, density unevenness, or fading can now be obtained using this developer.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram schematically showing a device for measuring the electrical resistance value of a carrier, and FIG. 2 is a schematic diagram schematically showing a device for measuring the current value flowing through the carrier. FIG. 3 is a schematic diagram schematically showing an apparatus for measuring the triboelectric charge of toner of a two-component developer. FIG. 4 is a diagram schematically showing a developing device to which the carrier of the present invention can be applied, and FIG. 5 is a diagram schematically showing a developing device in which the carrier of the present invention can be applied. Cell magnetic sleeve aluminum drum ammeter resistance (IM ohm) constant voltage device (DC200V)

Claims (3)

[Claims] (1) A carrier for developing electrostatic images, characterized in that the carrier core material is coated with a vinyl copolymer having a hydroxyl value of 1 to 100 and a fluorine-containing resin. (2) The carrier core material contains a carrier for electrostatic image development coated with a vinyl copolymer having a hydroxyl value of 1 to 100 and a fluorine-containing resin, a toner, and positively charged hydrophobic colloidal silica. A two-component developer characterized by: (3) In an image forming method in which a toner image is formed by developing an electrostatic latent image possessed by an electrostatic latent image carrier with a two-component developer, the carrier core material is a vinyl copolymer having a hydroxyl value of 1 to 100. Image formation characterized by developing an electrostatic latent image in the presence of an alternating electric field in a developing section using a two-component developer containing an electrostatic image developing carrier and a toner that have been combined and coated with a fluorine-containing resin. Method.