JP2001051456A - Electrostatic latent image developing carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrostatic charge image developing carrier excellent in the environmental stability and aging stability of electrostatic charge and not causing the lowering of image density and the occurrence of fog and to obtain a developer. SOLUTION: Fine inorganic oxide particles are dispersed in a resin coating layer on each of magnetic core particles to obtain the objective electrostatic latent image developing carrier. The work function of the inorganic oxide is 4.30-4.60 eV and the electric resistance of the coated carrier is 108-1013 Ωm. The developer contains a toner containing a colorant and a bonding resin and the electrostatic latent image developing carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image developing carrier and a developer used for developing an electrostatic latent image in electrophotography and electrostatic recording.

[0002]

2. Description of the Related Art Electrophotography generally includes a charging step of charging a photoreceptor, an exposure step of forming an electrostatic latent image on the photoreceptor, a developing step of developing the electrostatic latent image with a developer, and a process of developing the developed image. The method includes a transfer step of transferring the image onto a support such as paper, a fixing step of fixing the transferred image on the paper, and a cleaning step of removing the toner remaining on the photoconductor.

There are two types of developers used in the electrophotography, a one-component developer composed of only a toner and a two-component developer composed of a toner and a carrier. Among them, a two-component developer which is easy to control the charging property and has high reliability is widely used. The role of the carrier used in the two-component developer is to apply electric charge to the toner by frictional charging and to convey the toner to the photoreceptor. Particularly, the application of electric charge to the toner is an important role.

By the way, electrophotographic devices such as copiers and printers are required to have higher reliability than before, irrespective of black and white or color. In particular, in the development step, in order to meet reliability, a developer that has a fast charging rise, has stable charging properties for a long period of time, and can provide high image quality has been demanded. In particular, with respect to carriers, further improvement in charging characteristics and electrical characteristics is desired.

[0005] Carriers are generally broadly classified into coated carriers having a resin coating layer on the surface of magnetic core particles and non-coated carriers having no coating layer. The coated carrier is superior from the viewpoints of prolonging the life of the developer and controlling the charge of the toner. On the other hand, in a developing method using a two-component developer, the peripheral speed of the developing sleeve is generally set to be higher than the peripheral speed of the photoconductor in order to secure a sufficient image density. However, in this developing method, a developing defect caused by a relative speed difference between the developing sleeve and the photoconductor, for example, a trailing edge of a solid image, or a boundary between a solid image front end and a halftone when a halftone and a solid image are mixed. It is known that a trailing edge of a halftone image in a portion may be missing.

[0006] In these image omissions, the amount of potential change of the developer layer due to the movement of the toner in the developing nip region in the developing process appears depending on the latent image structure, and further, the speed difference between the developing sleeve and the photosensitive member. When developing with
Since the developer retains the electric field history immediately before, defects appear remarkably at discontinuous points of the latent image structure, for example, at a boundary between a solid image portion and a non-image portion, or at a boundary between a halftone portion and a solid image portion. It is supposed to be. In particular, in the case of a full-color image in which various kinds of latent image levels are frequently mixed continuously, the above-mentioned defect cannot be sufficiently solved at present.

[0007] Control of the resistance value of the developer is considered to be effective in solving these defects. In order to properly control the resistance value of the developer layer, it is necessary to precisely control the resistance value of the carrier and stabilize the toner concentration in the developer. In particular, stabilization of the toner density requires an image forming system that controls the amount of charge of the developer to keep the image density constant.

Various types of coated carriers having a resin coating layer have been studied so far in order to ensure the stability over time of charging. However, in general, the electrical resistance of the coated type carrier is high, Due to the net charge, the image quality of the solid portion tends to deteriorate, and it is difficult to control the electric resistance of the coated carrier. In order to improve the defect, there is a method of reducing the electric resistance of the carrier by reducing the thickness of the resin coating layer of the carrier. However, when the thickness is too small, the effective electrode of the developer is extremely close to the photoconductor. As a result, the ability to supply the toner to the photoconductor is reduced, and a so-called brush mark is generated due to the occurrence of a latent image leak. In addition, the external additive or the toner easily adheres to the uncoated portion of the carrier, and the charge tends to decrease.

In order to improve the drawbacks of the above-mentioned coated carrier, various studies have been made on optimizing the electric resistance by including a conductive powder or an inorganic powder in the resin coating layer. For example, JP-A-62-2877
JP-A-3-27 discloses a carrier containing amorphous and spherical titanium oxide fine particles in a resin coating layer.
No. 66 proposes a carrier in which conductive carbon and titanium oxide are added to a silicone resin. However, the conductive powder and the inorganic powder cannot be said to have sufficient adhesiveness or dispersibility with the coating resin, and particularly when repeatedly colliding with a toner having an external additive having a large specific gravity in a developing machine,
The charging property significantly decreases with time, and fogging and toner scattering tend to occur.

In order to solve the above problem, Japanese Patent Application Laid-Open
No. 80268 proposes adding titanium black treated with a silicone oil or a silane coupling agent to a silicone resin coating layer. However, depending on the type of the silane coupling agent, the charge imparting ability and dispersibility are different, and it is difficult to obtain a desired charge amount.
Depending on the material, the charging stability is degraded, or the charging distribution is broadened, and the problem has not yet been sufficiently solved.

Japanese Patent Application Laid-Open No. Hei 5-232740 discloses a carrier obtained by adding an alkoxysilane coupling agent having a chlorine group and a conductive fine powder to a silicone resin coating layer. There has been proposed a carrier in which the charging ability during friction is adjusted in the thickness direction of the coating layer by changing the amount of the aminosilane coupling agent in the thickness direction of the resin coating layer. The addition of a silane coupling agent improves the dispersibility of a conductive substance represented by carbon black, and enables suppression of toner spent to some extent.However, when the silane coupling agent itself is exposed to moisture or moisture, hydrolysis occurs. Occurs, and the surface composition of the carrier coating layer tends to change. For this reason, the humidity dependency of the charge amount and the electric resistance or the stability over time deteriorated, and sufficient carrier characteristics could not be obtained.

When the charge carrier is an electron, the charge amount of the toner is generally the amount of electrons that move from a material having a small work function to a material having a large work function due to the work function difference between the toner and the carrier. Will be discussed. That is, a substance having a small work function is positively charged by the movement of electrons, and a substance having a large work function is negatively charged by receiving electrons.

In JP-A-9-179353, a coating resin having a work function of 4.5 or less is provided with a work function of 4.6 to 5.2.
There has been proposed a carrier in which the charge rising property of the toner is increased by adding a conductive fine powder of eV. In the carrier described in the above publication, the work function of the coating resin is lower than that of the conductive fine powder, and the positive charging property of the carrier basically has a structure that the coating resin plays, and the chargeability of the carrier is fast. Is effective, but development of a carrier capable of imparting more stable chargeability to the toner is desired. Such long-life carriers meet the demand for waste reduction in markets such as copiers and printers.

[0014]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and is excellent in the environmental stability of charging and the stability with time, and does not reduce the image density and does not cause fogging. An object is to provide a carrier and a developer.
The present invention also provides an electrostatic latent image that can suppress the trailing edge of a solid image and suppress the trailing edge of a halftone image at the boundary between the leading edge of the solid image and the halftone when the halftone and the solid image are mixed and approached. An object is to provide a carrier for image development. More specifically, an object of the present invention is to provide a carrier for developing an electrostatic latent image, which can prevent a brush mark caused by a reduction in toner supply capability to an electrostatic latent image carrier and a leak of a latent image.

[0015]

Means for Solving the Problems The present inventors have conducted intensive studies on a carrier for developing an electrostatic latent image in which inorganic oxide fine particles are dispersed in a resin coating layer on magnetic core particles, and as a result, the work function is determined. By using inorganic oxide fine particles having a high charge-imparting ability of 4.30 or more and 4.60 eV or less and by setting the electric resistance of the coated carrier in the range of 10 ⁸ to 10 ¹³ Ωm, the chargeability of the toner can be maintained for a long time. The inventors have found that the present invention can be stably maintained, and completed the present invention. The configuration of the present invention is as follows.

(1) In a carrier for developing an electrostatic latent image in which inorganic oxide fine particles are dispersed in a resin coating layer on magnetic core particles, the work function of the inorganic oxide is not less than 4.30 eV and 4.60 eV. An electrostatic latent image developing carrier, wherein the carrier after coating has an electric resistance of 10 ⁸ to 10 ¹³ Ωm. (2) The work function of the coating resin is 4.50 eV or more.
The carrier for developing an electrostatic latent image according to the above (1), wherein the carrier is 90 eV or less. (3) The carrier for developing an electrostatic latent image according to (2), wherein the work function of the coating resin is larger than the work function of the inorganic oxide.

(4) The inorganic oxide fine particles are characterized in that the fine particles are surface-treated and the work function is adjusted to be from 4.30 eV to 4.60 eV, in any one of the above (1) to (3). The carrier for developing an electrostatic latent image according to any one of the preceding claims.

(5) In a developer containing a toner containing a colorant and a binder resin and a carrier, the carrier may be:
An electrostatic latent image developer comprising the carrier for developing an electrostatic latent image according to any one of the above (1) to (4).

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has a work function of 4.30 e.
A carrier in which inorganic oxide fine particles of not less than V and not more than 4.60 eV are dispersed in a matrix resin to form a resin coating layer on magnetic core particles, and the coated carrier has an electric resistance of 10 ⁸ to 10 ¹³ Ωm. By adjusting to the range of
It has excellent charge retention, does not cause fogging, and can provide a stable image for a long time regardless of the environment. The reason is considered that the inorganic oxide fine particles having the work function described above function effectively in providing charging sites in the resin coating layer. As the coating resin, one having a work function of 4.50 eV or more and 4.90 eV was used.
When the work function of the coating resin is made larger than the work function of the inorganic oxide fine particles, the above effect can be further enhanced.

The work function in the present invention was measured as follows. The work function is the difference between the Fermi level and the vacuum level,
It is a physical quantity measured by the Kelvin method using the change in vibration capacity based on the principle of the contact potential difference. FIG. 1 is a conceptual diagram of a contact potential difference measuring device by the Kelvin method. The reference electrode 1 and the base 2 are made of brass plated with gold, and the sample 3 is applied on the base 2. The reference electrode 1 and the sample 3 form a kind of capacitor, and a contact potential difference generated between the sample 3 and the reference electrode 1 during this period is added. When the reference electrode is vibrated, the capacitance of the capacitor changes and a current flows through the circuit, which is measured by the ammeter 4. At this time, a potential in a direction to cancel the contact potential difference is applied by the external power supply 5, a potential when the current becomes zero is obtained, and the potential of the external power supply 5 at that time is defined as a contact potential difference.

When measuring the work function of a sample of the coating resin or the inorganic oxide fine particles, a sample dissolved or dispersed in a solvent is applied on the substrate 2 in a thin layer of 0.5 to 1 mm, and the sample is applied to the substrate 2. After drying under vacuum at 100 ° C. for 5 hours, drying at 20 ± 2 ° C. in an environment of 50 ± 5% RH%, and then leaving for 2 hours, measurement was carried out using the above-mentioned contact potential difference measuring apparatus. Since the value of the contact potential difference measured in this way is a difference from the work function of the reference electrode, the contact potential difference is converted from the work function of the reference electrode in order to convert it to the work function of the coating resin or the inorganic oxide fine particles. Draw and ask.

The contact potential difference becomes a positive value when the work function of the sample is smaller than the work function of the reference electrode. The work function of the reference electrode is the photoelectron spectrometer AC-1.
(Manufactured by Riken Keiki Co., Ltd.). What can measure the work function with this photoelectron spectrometer is a substance having a metallic electronic state such as a reference electrode. Using the above device, the photoelectron emission of an insulator or a semiconductor is measured, and the value determined by plotting the power of the photoelectron yield against the energy of incident light is the ionization potential or the threshold of photoemission. It is to be called a value, not a work function of the present invention.

As the inorganic oxide fine particles used in the present invention, any known inorganic oxide fine particles may be used as long as the work function is in the range of 4.30 eV to 4.60 eV.
It is more preferable that the work function is not less than 4.40 eV and not more than 4.50 eV. Specifically, inorganic oxide fine particles such as silica, titanium oxide, magnesium oxide, zinc oxide, aluminum oxide, calcium carbonate, aluminum borate, potassium titanate, calcium titanate, titanium oxide, zinc oxide, barium sulfate, Examples include fine particles of aluminum borate, potassium titanate powder, and the like whose surfaces are coated with tin oxide, carbon black, and metal.

Even inorganic oxide fine particles having a work function exceeding 4.6 eV or less than 4.30 eV can be used if surface treatment is performed to adjust the work function to 4.30 eV to 4.60 eV. it can. The inorganic oxide fine particles subjected to such a surface treatment are effective in optimizing the adhesion to the resin coating layer, the charge controllability, and the environmental stability of the charge. The surface treatment method may be any method as long as the work function of the inorganic oxide fine particles can be adjusted to 4.30 eV to 4.60 eV. Specifically, chemical treatment,
Coupling agent treatment, solvent treatment, surface grafting, low-temperature plasma treatment, plasma jet treatment, surfactant treatment, ion implantation, sputtering, reactive vapor deposition, ion plating, CVD, and the like. In particular, when the inorganic oxide fine particles are treated with an amino-based coupling agent, the work function can be easily increased to 4.30 eV to 4.60.
eV or less, charge amount control is easy,
The carrier surface composition does not deteriorate due to unreacted coupling agents or the like, and the environmental stability of charging does not decrease.

Among them, in particular, when titanium oxide treated with an amino-based coupling agent is used, uniform treatment can be easily performed, and variation in the surface composition between fine particles is small. Therefore, the dispersibility in the carrier coating layer is excellent, the charge distribution of the toner is sharp, and the environmental stability of the charge is good. The average particle size of the inorganic oxide fine particles is 10 nm to 1 mm, preferably 10 to 500 nm. The amount of the inorganic oxide fine particles in the resin coating layer is 1 to 80% by volume, preferably 5 to 5% by volume.
0% by volume.

The amino coupling agent used in the present invention may be of any type as long as the work function of the fine particles after treating the surface of the inorganic oxide fine particles can be adjusted to 4.30 eV to 4.60 eV. Specifically, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane,
N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, (N, N-dimethylamino) Dimethylchlorosilane, dimethylaminomethylethoxysilane, 3-dimethylaminopropyldiethoxymethylsilane, (N, N-
Dimethylaminopropyl) trimethoxysilane, (N, N-
Dimethylamino) triethylsilane, (N, N-dimethylamino) trimethylsilane, (3,3-dimethylbutyl) dimethylchlorosilane, 3-aminopropyldiisopropylethoxysilane, etc. can be used. γ-aminopropyltriethoxysilane is optimal.

The amount of the amino-based coupling agent to be treated is such that the work function of the inorganic oxide fine particles is not less than 4.30 eV and 4.60.
It is appropriately selected within a range adjusted to eV or less. Usually, the range of 1 to 50% by weight, preferably 2 to 20% by weight, based on the total weight of the inorganic oxide fine particles is suitable. If the amount is less than 1% by weight, the aggregation of the metal oxide fine particles becomes remarkable, and the time-dependent decrease in charging becomes sharp. If it exceeds 50% by weight, the resistance of the inorganic oxide fine particles increases, leading to an increase in the carrier resistance, which causes a decrease in the image quality of the solid portion and the occurrence of uneven image density.

As the coating resin used in the present invention, any known resin may be used. Among them, those having a work function of 4.50 eV to 4.90 eV are preferable.
In particular, it is preferable to select a material having a work function larger than that of the inorganic oxide fine particles because the function as a charging site of the inorganic oxide fine particles can be more effectively used. Specifically, polyolefin-based resins such as polyethylene and polypropylene; polyvinyl and polyvinylidene-based resins such as polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyvinyl carbazole, polyvinyl ether and polyvinyl Ketones; vinyl chloride-vinyl acetate copolymers; styrene-acrylic acid copolymers; straight silicone resins comprising organosiloxane bonds or modified products thereof; polyesters; polyurethanes; polycarbonates; phenolic resins; amino resins such as urea-formaldehyde resins;
Melamine resin, benzoguanamine resin, urea resin,
Polyamide resin; epoxy resin and the like.

In the present invention, when a coating resin having a critical surface tension of 30 dyne / cm or less is used for part or all of the coating resin, the charge amount and the resistance due to toner contamination on the surface of the electrostatic latent image developing carrier are reduced. There is an advantage that the change in the value can be minimized. As the coating resin having a critical surface tension of 30 dyne / cm or less, for example, polyvinyl fluoride (28 d
yne / cm), polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, etc.
Homopolymers and copolymers of fluorinated alkyl (meth) acrylic acid are preferred.

The coating amount of the coating resin is preferably 1.0 to 10% by weight based on the total weight of the carrier. 1.
If it is less than 0% by weight, the core particles are likely to be exposed on the carrier surface. In particular, the toner is likely to adhere to the uncoated portion, and the charge amount is significantly reduced with time, which is not preferable. Meanwhile, 1
If it exceeds 0% by weight, it is difficult to uniformly charge the toner because the fluidity of the carrier is significantly reduced.

In the resin coating layer of the present invention, carbon black may be added in addition to the metal oxide fine particles. Carbon black can obtain an appropriate electric resistance independently of the charge amount. As the carbon black, any known carbon black such as channel black, furnace black, thermal black, and lamp black may be used. Average particle size of carbon black is 10 to 100
nm, especially in the range of 20 to 80 nm. The amount of carbon black added to the resin coating layer is suitably in the range of 1 to 80% by volume, preferably 5 to 50% by volume.

Further, when resin fine particles are added to the resin coating layer together with carbon black, the charging stability can be further improved. As the material of the resin fine particles, any of a thermoplastic resin and a thermosetting resin can be used. Examples of the thermoplastic resin include polyolefin resins, for example, polyethylene and polypropylene; polyvinyl and polyvinylidene resins, for example, polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether and Polyvinyl ketone; vinyl chloride / vinyl acetate copolymer;
Styrene / acrylic acid copolymer; straight silicone resin comprising organosiloxane bond or modified product thereof;
Fluororesins, for example, polytetrafluoroethylene; polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene; polyester; polyurethane;

Examples of the thermosetting resin include amino resins such as urea-formaldehyde resin, melamine resin, silicone resin, benzoguanamine resin, urea resin, polyamide resin, and epoxy resin. Among these resin fine particles, thermosetting resin fine particles are preferable because of their excellent dispersibility in the resin coating layer, and crosslinked resin fine particles are particularly preferable.

The average particle size of the resin fine particles is 0.1 to 2 mm,
Preferably, the range of 0.2 to 1 mm is suitable. 0.1
If it is less than 2 mm, dispersion in the resin coating layer is very poor, and if it is more than 2 mm, it tends to drop off from the coating layer, and stable charging properties cannot be obtained. The addition amount of the resin fine particles is 1 to 50% by volume, preferably 5 to 30% by volume, more preferably 5 to 20% by volume in the resin coating layer.

The electric resistance of the coated carrier in the present invention is in the range of 10 ⁸ to 10 ¹³ Ωm, preferably 10 ⁹ to 1 Ωm.
A range of 0 ¹¹ Ωm is suitable. Electric resistance of carrier is 1
If it is less than 0 ⁸ Ωm, carrier adhesion due to charge injection will occur. If it is more than 10 ¹³ Ωm, the image quality of the solid portion will be reduced. In addition, the above-mentioned electric resistance is obtained by placing the carrier particles at a temperature of about 1 mm in a container having a cross-sectional area of 8 × 10 ⁻³ m ² under normal temperature and normal humidity, and tapping, and then placing a metal member on the particles. 5 × 10 ^-1 (kg / m ² ), apply a voltage that generates an electric field of 5 × 10 ⁵ V / m between the metal member and the bottom electrode, and read the current value at that time. This is a value obtained from voltage and current.

The magnetic core particles used in the present invention include ferrite powder, iron powder, magnetite powder, Ni—Fe alloy, Co
All known carrier core particles such as -Fe alloys, Al-Fe alloys, or composite particles obtained by dispersing magnetic powder in a resin can be used. The particle size distribution of the carrier of the present invention can be adjusted to a desired particle size distribution by a centrifugal classifier, an inertial classifier or a sieve.
The average particle size of the carrier of the present invention is suitably in the range of 10 to 100 mm, preferably 20 to 50 mm. When the average particle diameter of the carrier is smaller than 10 mm, the adhesive force between the toner and the carrier increases, and the toner development amount decreases. On the other hand, if it is larger than 100 mm, the magnetic brush becomes rough,
It is difficult to form a fine image.

To form a resin coating layer on the surface of the carrier core particles, a coating resin, inorganic oxide fine particles, and if necessary, resin fine particles and carbon black are added to a solvent to prepare a resin coating layer forming solution. A typical method is to use this. Specifically, the carrier nucleus particles are immersed in a solution for forming a resin coating layer, the dipping method is performed by spraying the solution for forming a coating layer onto the surface of the carrier nucleus particles, and the carrier nucleus particles are suspended in flowing air. Fluidized bed method in which a coating layer forming solution is sprayed in a heated state, a kneader coater method in which carrier nucleus particles are mixed with a coating layer forming solution in a kneader coater, and the solvent is removed. Among them, the kneader coater method is particularly preferably used.

The carrier of the present invention is mixed with a toner and used as a two-component developer. The toner is obtained by dispersing a colorant in a binder resin. Examples of the binder resin used in the toner include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene, and isobutylene; Vinyl esters such as vinyl and vinyl benzoate; methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, dodecyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate Α-methylene aliphatic monocarboxylic esters such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone. It can be exemplified a homopolymer or a copolymer thereof. Further, polyester, polyurethane, epoxy resin, silicone resin, polyamide resin, modified rosin, paraffin wax and the like can be mentioned.

Colorants used in the toner include carbon black, aniline black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, and lamp black. , Rose Bengal and the like can be exemplified as typical ones.

The toner components other than the colorant include charge control agents such as salicylic acid metal salts, metal-containing azo compounds, nigrosine and quaternary ammonium salts, and anti-offset agents such as low molecular weight polypropylene, low molecular weight polyethylene and wax. Known additives can be mentioned. Among them, low molecular weight polypropylene having a weight average molecular weight of 500 to 5000 is particularly effective.

For the production of the toner, the above-mentioned toner materials are blended, mixed using a Banbury mixer, a kneader coater, a CM mixer extruder, etc., melt-kneaded, and pulverized and classified. The average particle size of the toner is suitably 30 μm or less, preferably 3 to 20 μm.

Further, a fluidizing agent such as silica, titania and alumina, an external additive such as a cleaning aid or a transfer aid such as polystyrene fine particles, polymethyl methacrylate fine particles and polyvinylidene fluoride fine particles can be used. Among them, the primary average particle size is 5 to 30 nm.
Is particularly effective.

[0043]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 (Preparation of γ-aminosilane-treated oxide fine particles A) Titanium oxide (rutile type titanium oxide; average particle size 0.015 μm,
Work function 4.71 eV) 8.5 parts by weight of toluene 100
Parts by weight, and the solution was stirred and dispersed by an ultrasonic disperser, and then γ-aminopropyltriethoxysilane 1.5 was added.
The mixture was stirred at room temperature for 1 hour, toluene was distilled off, dried, and heated at 110 ° C. for 10 minutes to complete the reaction of the γ-aminopropyltriethoxysilane polymer.
-Aminosilane-treated titanium oxide fine particles A (titanium oxide:
(γ-aminosilane weight ratio = 8.5: 1.5) was obtained. The work function of the titanium oxide fine particles A treated with γ-aminosilane was 4.45 eV.

(Manufacture of Carrier) Toluene 15 parts by weight Styrene / methyl methacrylate copolymer 1.5 parts by weight (copolymerization ratio of styrene: methyl methacrylate = 25: 75, Mw: 80,000, work function: 4.67 eV) 0.4 parts by weight of γ-aminosilane-treated titanium oxide fine particles A (volume average particle size: 0.015 μm, work function: 4.45 eV) The above components were stirred and dispersed with an ultrasonic disperser for 10 minutes to obtain a coating layer forming solution. Obtained. 16.9 parts by weight of this solution for forming a coating layer and 100 parts by weight of ferrite having an average particle size of 40 μm were put into a vacuum degassing kneader, stirred at a temperature of 60 ° C. for 10 minutes, and then toluene was distilled off under reduced pressure. A resin coating layer was formed on the ferrite surface to obtain the carrier of Example 1. The electric resistance of this carrier was 10 ^9.5 Ωm.

Example 2 (Manufacture of Carrier) Toluene 15 parts by weight Styrene / methyl methacrylate copolymer 1.5 parts by weight (styrene: methyl methacrylate copolymerization ratio = 25: 75, Mw: 80,000, work function) : 4.67 eV) 0.4 parts by weight of γ-aminosilane-treated titanium oxide fine particles A (volume average particle size: 0.015 μm, work function: 4.45 eV) Carbon black (REGAL33, manufactured by Cabot Corporation)
0) 0.2 parts by weight The above components were used in the same manner as in Example 1 to obtain a carrier of Example 2. The electric resistance of this carrier was 10 ^8.1 Ωm.

Example 3 (Preparation of γ-aminosilane-treated silica fine particles B) Untreated silica (average particle size: 0.04 μm, work function: 4.8 eV)
9.5 parts by weight was added to 100 parts by weight of toluene, and the solution was stirred and dispersed by an ultrasonic disperser, and then 0.5 part by weight of γ-aminopropyltriethoxysilane was added.
After stirring for 1 hour, the toluene was distilled off and dried.
The mixture was heated for 0 minutes to complete the reaction of the γ-aminopropyltriethoxysilane polymer, and the γ-aminosilane-treated silica fine particles B (silica: γ-aminosilane weight ratio = 9.
5: 0.5). The work function of the γ-aminosilane-treated silica fine particles B was 4.50 eV.

(Manufacture of Carrier) Toluene 15 parts by weight Styrene / methyl methacrylate copolymer 1.5 parts by weight (copolymerization ratio of styrene: methyl methacrylate = 25: 75, Mw: 80,000, work function: 4.67 eV) 0.4 parts by weight of γ-aminosilane-treated silica fine particles B (volume average particle size: 0.04 μm, work function: 4.50 eV) 0.2 parts by weight of carbon black (REGAL330, manufactured by Cabot Corporation) In the same manner, the carrier of Example 3 was obtained. The electrical resistance of the carrier was 10 ^8.4 Ωm.

Example 4 (Production of Carrier) Toluene 15 parts by weight Polymethyl methacrylate 1.5 parts by weight (Mw: 70,000, work function: 4.57 eV) γ-aminosilane-treated titanium oxide fine particles A 0.4 part by weight Part (volume average particle size: 0.015 μm, work function: 4.45 eV) The above components were used in the same manner as in Example 1 to obtain a carrier of Example 4. Electrical resistance of the carrier was 10 ^9.8 [Omega] m.

Example 5 (Preparation of aminosilane-treated aluminum oxide fine particles C)
8.5 parts by weight of untreated aluminum oxide (average particle size: 0.3 μm, work function: 4.64 eV) was added to 100 parts by weight of toluene, and the solution was dispersed by stirring with an ultrasonic disperser. Add 1.5 parts by weight of propyldiethoxymethylsilane, stir at room temperature for 1 hour to distill off toluene, dry and heat at 110 ° C for 10 minutes to react the 3-dimethylaminopropyldiethoxymethylsilane polymer. Completed, aminosilane-treated aluminum oxide fine particles C (weight ratio of aluminum oxide: aminosilane = 8.
5: 1.5). The work function of the aminosilane-treated aluminum oxide fine particles C was 4.53 eV.

(Manufacture of Carrier) Toluene 15 parts by weight Styrene / methyl methacrylate copolymer 1.5 parts by weight (copolymerization ratio of styrene: methyl methacrylate = 25: 75, Mw: 80,000, work function: 4.67 eV) Aminosilane-treated aluminum oxide fine particles C 0.4 parts by weight (volume average particle size: 0.3 μm, work function: 4.53 eV) The above components were used in the same manner as in Example 1 to obtain a carrier of Example 5. The electric resistance of this carrier was 10 ^9.6 Ωm.

Example 6 (Manufacture of carrier) Toluene 15 parts by weight Styrene / methyl methacrylate copolymer 1.5 parts by weight (copolymerization ratio of styrene: methyl methacrylate = 25: 75, Mw: 80,000, work function) : 4.67 eV) Untreated magnesium oxide fine particles 0.4 parts by weight (volume average particle size: 0.4 μm, work function: 4.55 eV) The above components were used in the same manner as in Example 1 to obtain a carrier of Example 6. . Electrical resistance of the carrier was 10 ^8.9 [Omega] m.

Example 7 (Production of Carrier) Toluene 15 parts by weight Methyl methacrylate / perfluorooctyl methacrylate copolymer 1.5 parts by weight (copolymerization ratio of methyl methacrylate / perfluorooctyl methacrylate = 80: 20) , Mw: 50,000, work function: 4.75 eV) γ-aminosilane-treated titanium oxide fine particles A 0.4 part by weight (volume average particle size: 0.015 μm, work function: 4.45 eV) carbon black (manufactured by Cabot Corporation) REGAL330) 0.2 parts by weight The above components were used in the same manner as in Example 1 to obtain a carrier of Example 7. The electrical resistance of the carrier was 10 ^8.2 Ωm.

Example 8 (Preparation of γ-aminosilane-treated titanium oxide fine particles D) Titanium oxide (rutile type titanium oxide; average particle size 0.015 μm)
m, work function 4.71 eV) 5.5 parts by weight of toluene 1
To 100 parts by weight, and the resulting solution was dispersed by stirring with an ultrasonic disperser. Then, 4.5 parts by weight of γ-aminopropyltriethoxysilane was added, and the mixture was stirred at room temperature for 1 hour, and toluene was distilled off and dried. Then, the mixture was heated at 110 ° C. for 10 minutes to complete the reaction of the γ-aminopropyltriethoxysilane polymer, and the γ-aminosilane-treated titanium oxide fine particles D (titanium oxide: γ-aminosilane weight ratio = 5.5: 4.5) I got The work function of the titanium oxide fine particles D treated with γ-aminosilane was 4.38 eV.

(Manufacture of Carrier) Toluene 15 parts by weight Styrene / methyl methacrylate copolymer 1.5 parts by weight (copolymerization ratio of styrene: methyl methacrylate = 25: 75, Mw: 80,000, work function: 4.67 eV) 0.4 parts by weight of γ-aminosilane-treated titanium oxide fine particles D (volume average particle size: 0.015 μm, work function: 4.38 eV) The above components were used in the same manner as in Example 1 to obtain a carrier of Example 8. The electric resistance of this carrier was 10 ^10.4 Ωm.

Comparative Example 1 Toluene 15 parts by weight Polymethyl methacrylate 1.5 parts by weight (Mw: 70,000, work function: 4.57 eV) Untreated strontium titanate fine particles 0.4 part by weight (volume average particle diameter: (0.3 μm, work function: 4.69 eV) The carrier of Comparative Example 1 was obtained in the same manner as in Example 1 with the above components. The electrical resistance of the carrier was 10 ^8.7 Ωm.

[Comparative Example 2] (Production of silane-treated titanium oxide fine particles E) 8.5 parts by weight of titanium oxide (rutile-type titanium oxide; average particle size: 0.015 µm, work function: 4.71 eV) was added to 100 parts by weight of toluene. In addition, the solution was stirred and dispersed by an ultrasonic disperser, and 1.5 parts by weight of trifluoropropyltrimethoxysilane was added. The mixture was stirred at room temperature for 1 hour, toluene was distilled off, and dried. The reaction of trifluoropropyltrimethoxysilane was completed by heating for 10 minutes to obtain silane-treated titanium oxide fine particles E (titanium oxide: trifluoropropyltrimethoxysilane weight ratio = 8.5: 1.5). The work function of the silane-treated titanium oxide fine particles E was 5.21 eV.

(Manufacture of Carrier) Toluene 15 parts by weight Polymethyl methacrylate 1.5 parts by weight (Mw: 70,000, work function: 4.57 eV) Silane-treated titanium oxide fine particles E 0.4 parts by weight (volume average particle size: (0.015 μm, work function: 5.21 eV) A carrier of Comparative Example 2 was obtained by using the above components in the same manner as in Example 1. The electric resistance of this carrier was 10 ^9.2 Ωm.

Comparative Example 3 Production of Carrier Toluene 15 parts by weight Methyl methacrylate / perfluorooctyl methacrylate copolymer 1.5 parts by weight (copolymerization ratio of methyl methacrylate / perfluorooctyl methacrylate = 80: 20) , Mw: 50,000, work function: 4.75 eV) Silane-treated titanium oxide fine particles 0.4 parts by weight (volume average particle size: 0.015 μm, work function: 5.21 eV) carbon black (REGAL 330, manufactured by Cabot Corporation) 0.2 parts by weight The above components were used in the same manner as in Example 1 to obtain a carrier of Comparative Example 3. The electrical resistance of the carrier was 10 ^8.6 Ωm.

Comparative Example 4 (Production of Titanium Black Fine Particles Treated with γ-Aminosilane) 8.5 parts by weight of titanium black (average particle size 0.050 μm, work function 4.82 eV) was added to 100 parts by weight of toluene. After stirring and dispersing the solution with an ultrasonic disperser, 1.5 parts by weight of γ-aminopropyltriethoxysilane was added, the mixture was stirred at room temperature for 1 hour, toluene was distilled off, and the mixture was dried at 110 ° C. for 10 minutes. The reaction of the γ-aminopropyltriethoxysilane polymer was completed by heating to obtain γ-aminosilane-treated titanium black fine particles F (weight ratio of titanium black: γ-aminosilane = 8.5: 1.5). These γ-aminosilane-treated titanium black fine particles F
Had a work function of 4.46 eV.

(Manufacture of Carrier) Toluene 15 parts by weight Straight silicone (Mw: 90,000, work function 4.83 eV) 1.5 parts by weight γ-aminosilane-treated titanium black fine particles F 0.4 parts by weight (volume average particle size: 0.050 μm, work function: 4.46 eV) The above components were used in the same manner as in Example 1 to obtain a carrier of Comparative Example 4. The electrical resistance of the carrier was 10 ^7.2 Ωm.

Comparative Example 5 (Production of Carrier) Toluene 15 parts by weight Styrene / methyl methacrylate copolymer 3.0 parts by weight (copolymerization ratio of styrene: methyl methacrylate = 25: 75, Mw: 80,000, work function) : 4.67 eV) 0.4 parts by weight of γ-aminosilane-treated titanium oxide fine particles A (volume average particle size: 0.015 μm, work function: 4.45 eV) The above components were used in the same manner as in Example 1, and the carrier of Comparative Example 5 was used. I got The electric resistance of this carrier was 10 ^13.5 Ωm.

Comparative Example 6 (Production of Carrier) Toluene 15 parts by weight Dimethylaminoethyl methacrylate / methyl methacrylate copolymer 1.5 parts by weight (copolymerization ratio of dimethylaminoethyl methacrylate: methyl methacrylate = 5: 95, Mw) : 90,000, work function: 4.42 eV) Silane-treated titanium oxide fine particles 0.4 parts by weight (volume average particle size: 0.015 μm, work function: 5.21 eV) The above components were compared in the same manner as in Example 1. The carrier of Example 6 was obtained. The electrical resistance of the carrier was 10 ^9.7 Ωm.

(Production of Toner) 87 parts by weight of polyester resin (synthesized from bisphenol A-ethylene oxide diadduct, bisphenol A-propylene oxide diadduct, terephthalic acid and trimellitic acid, Mw = 14000, Tg = 62 ° C., THF insolubles 25%) Cyanine blue (manufactured by Dainichi Seika, 4933M) 3 parts by weight Polypropylene wax (manufactured by Sanyo Chemical Industries, Inc., Viscol 660P) 6 parts by weight After melt-kneading while maintaining the temperature at 110 ° C. with a machine, the mixture was rolled, cooled and preliminarily pulverized with a hammer mill. Thereafter, the mixture was finely pulverized by a jet mill, and fine and coarse powders were cut by an air classifier to produce negatively chargeable polyester cyan toner particles having a weight average particle diameter of 7 μm. The particle size was measured with a Coulter Counter TA-II (aperture diameter 100 μm). To 100 parts by weight of the toner particles, 0.2 parts by weight of silica treated with silicone oil and 1.2 parts by weight of titanium oxide treated with hexamethyldisilazane were added as external additives, and mixed with a Henschel mixer. A negatively charged cyan toner having silica fine particles and titanium oxide fine particles adhered to the surface was obtained.

(Preparation of Developer) 100 parts by weight of each of the carriers of Examples 1 to 8 and Comparative Examples 1 to 6 were prepared and mixed with 6 parts by weight of the toner to prepare 11 types of developers. These developers were used with Fuji Xerox's Acolor
630, modified to normal temperature and normal humidity (22 ° C, 55%
RH), the charge amount of the toner was measured by a blow-off method after copying 100 sheets and after copying 50,000 sheets.
The fog after 50,000 copies and the image density were visually evaluated.

(Evaluation of fogging) The evaluation criteria for fogging are as follows. ：: No fog △: Some fog, but no practical problem ×: Fog is noticeable

(Evaluation of Image Density) Evaluation criteria for image density are as follows. ：: no problem in image density Δ: slight decrease in density but no practical problem ×: noticeable decrease in density

(Evaluation of Environment Ratio) The environment ratio of the charging was determined by heating the carrier of Example and Comparative Example and the toner at a high temperature and a high humidity (28 ° C.,
85% RH) and low temperature and low humidity (10 ° C., 15% RH) for 24 hours, and then measure the amount of charge when adjusting the developer by the blow-off method, and charge under low temperature and low humidity. It is a value obtained as the ratio of the charge amount under high temperature and high humidity to the charge amount. The closer to 1, the better. When this value was less than 0.5, it was evaluated as x, when it was 0.5 to 0.7, it was evaluated as △, and when it exceeded 0.7 and was 1 or less, it was evaluated as ○.

(Comprehensive evaluation) In the comprehensive evaluation, the evaluation items having no x in the above evaluation items were evaluated as ○.
And The evaluation results are as shown in Table 2.

[0070]

[Table 1]

[0071]

[Table 2]

[0072]

[Table 3]

[0073]

According to the present invention, by adopting the above-mentioned structure, a stable chargeability can be given to the toner for a long time, and a good image without fog can be stably obtained. .

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a contact potential difference measuring device by the Kelvin method.

[Explanation of symbols]

 1. Reference electrode 2. 2. A base that ensures electrical contact with the sample Sample 4. Current detector 5. Power supply

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Sugizaki 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Tsutomu Kubo 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. Inventor Hiroyoshi Okuno 1600 Takematsu, Minami Ashigara, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Akira Matsumoto 1600 Takematsu, Minami Ashigara City, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Masahiro Okita Minami Ashigara, Kanagawa 1600 Takematsu Fuji Xerox Co., Ltd. F-term (reference) 2H005 BA06 BA07 CA26 CA28 CB07 EA01 FA01

Claims (2)

[Claims] 1. In a carrier for developing an electrostatic latent image in which inorganic oxide fine particles are dispersed in a resin coating layer on magnetic core particles, the work function of the inorganic oxide is from 4.30 eV to 4.60 eV. Wherein the carrier after coating has an electrical resistance of 10 ⁸ to 10 ¹³ Ωm. 2. A toner containing a colorant and a binder resin,
2. An electrostatic latent image developer according to claim 1, wherein said carrier is a carrier for developing an electrostatic latent image according to claim 1.