JPH0683098A - Electrophotographic developer - Google Patents

Abstract

PURPOSE:To obtain excellent flowability and to reduce secular changes of an electrophotographic developer, and also to make it hardly influenced by environment by using organo polysiloxane having an epoxy group as a substituent together with polyalkyleneimine. CONSTITUTION:A powdery metal oxide is surface-treated by concurrently using organo-polysiloxane and polyalkyleneimine. At this time the powdery metal oxide is provided with high hydrophobic property by the organo-polysiloxane and also provided effectively with positive electrostatic chargeability by the polyalkyleneimne which is strongly bonded through the organo-polysiloxane having high physical adhesion, to the surface of the powdery metal oxide that is at the same time provided with hydrophobic property by the organo- polysiloxane. Preferably, the electrophotographic developer which features in containing the powdery metal oxide having a >=60% hydrophobicity determined by the transmissivity method, particularly that containing alumina or titania as the metal oxide, is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developer containing a hydrophobic metal oxide powder for the purpose of improving powder fluidity.

2. Description of the Related Art The so-called hydrophobic metal oxide powder obtained by hydrophobizing the surface of the metal oxide powder with an organic substance is used in electrophotography, electrostatic recording, etc.
It is widely used as an agent for improving cleaning properties.
In these applications, the triboelectrification property of the metal oxide powder itself to the carrier iron or iron oxide is one of the important properties, and its hydrophobicity and triboelectrification property are simultaneously controlled by various treatment agents. ing. Among them, as a method of reducing the negative chargeability or imparting the positive chargeability to the metal oxide powder, a method of treating the surface of the powder with an amine-based organic compound is generally used. It is used. However, when a low molecular weight compound such as a quaternary ammonium salt is used as the amine-based organic compound, the reproducibility of the obtained charge amount is low because the bondability with the surface is low, and the environment is particularly susceptible to moisture. Such problems are likely to occur. On the other hand, when treated with an amino group-substituted silane coupling agent or an amino-modified polysiloxane, these treatment agents chemically or physically bond strongly to the surface of the metal oxide powder, so that an effective positive The chargeability can be obtained. However, these treatment agents are relatively expensive and it is difficult to finely control the charge amount because there are few types of products on the market. On the other hand, polyalkyleneimine is an inexpensive organic compound having a high molecular weight and is expected to be a material for improving the above problems of the treating agent. However, when the metal oxide powder is actually treated only with polyalkyleneimine, it is difficult to perform uniform surface treatment because the polyalkyleneimine has a low affinity for the metal oxide surface, and the polyalkyleneimine itself is hydrophilic. Therefore, the metal oxide powder cannot be rendered hydrophobic. Therefore, the use of the metal oxide powder treated with polyalkyleneimine in an electrophotographic developer for the purpose of improving fluidity has not been practically made.

[0002]

It is an object of the present invention to contain a metal oxide powder having a controlled charge amount and a sufficient hydrophobicity by using polyalkyleneimine which is an inexpensive material.
An object is to provide an electrophotographic developer having stable chargeability and excellent fluidity.

[0003]

In order to solve the above problems and obtain an excellent hydrophobic metal oxide powder,
As a result of earnest research, a metal oxide powder having a controlled charge amount and sufficient hydrophobicity was obtained by surface-treating the metal oxide powder by using organopolysiloxane together with polyalkyleneimine. However, they have found that the fluidity of the developer is improved and the stable chargeability is obtained by containing this powder, and the object of the present invention has been achieved. That is, the organopolysiloxane imparts high hydrophobicity to the metal oxide powder, and at the same time, the polyalkyleneimine is firmly bonded to the metal oxide powder surface through the organopolysiloxane having high physical adhesiveness. The surface of the metal oxide powder was hydrophobized by the organopolysiloxane at the same time that the positively chargeable property was imparted, and the above preferable result was achieved. The feature of the present invention resides in that the metal oxide powder treated with the organopolysiloxane and the polyalkyleneimine is used as a fluidity improving agent for the electrophotographic developer. In a preferred embodiment, the electrophotographic developer is characterized in that it contains a metal oxide powder having a hydrophobicity of 60% or more by a transmittance method, particularly when the metal oxide is silica, alumina or titania. There is provided the above electrophotographic developer. The present invention will be described in more detail below.

The organopolysiloxane used in the present invention is not particularly limited except that it imparts sufficient hydrophobicity to the metal oxide surface, but in practice, those having a methyl group, a phenyl group or a hydro group as a substituent are used. From the viewpoint of processing operation, it is preferable to use one having a viscosity of about 10 to 1,000 cs. Currently commercially available materials are KF-96 and KF-9 manufactured by Shin-Etsu Silicone Co., Ltd.
9, KF-56; SH200, SH510, SH1107 and the like manufactured by Toray Dow Corning Silicone Co., Ltd. are exemplified.

The polyalkyleneimine used in the present invention may be polyethyleneimine, polypropyleneimine or the like which is generally used for industrial purposes (average molecular weight: about several hundreds to 100,000) and is practically used. Most preferably, a polyethyleneimine aqueous solution having a concentration of about 30% is used. The metal oxide powder used in the present invention can be selected according to the application, but silica, alumina or titania is particularly preferable for applications such as fluidity improvement. The particle size can also be selected according to the use, but those having a specific surface area of 50 m ² / g or more are particularly preferable for the above use. The metal oxide may be a complex oxide or a mixture.

The amount of the treatment agent suitable for obtaining the hydrophobic metal oxide powder constituting the present invention depends on the type of the metal oxide powder to be treated, the specific surface area and the type of the treatment agent and is not particularly limited. . However, since excessive use of polyalkyleneimine causes a decrease in hydrophobicity, polyalkyleneimine is usually not more than 20% by weight without water, and particularly preferably 12% with respect to the weight of the metal oxide powder to be treated. It is desirable to use an amount of less than or equal to%. Further, the amount of the organopolysiloxane used is 5 with respect to the weight of the polyalkyleneimine that does not contain water, for the purpose of fixing the polyalkyleneimine.
It is desirable to use an amount of ˜150%, particularly preferably 50-100%. The higher the degree of hydrophobicity of the metal oxide powder obtained as a result of such treatment, the lower the hygroscopicity of the metal oxide powder and the smaller the change in the charge amount of the toner with respect to humidity, and Although the effect of preventing aggregation is enhanced and the utility value is high, it is desirable that the value of the hydrophobicity measured by the transmittance method described later is 60% or more, preferably 70% or more in practical use.

The method for measuring the triboelectric charge amount on iron is specified in the literature, for example, "Coloring Material" 55 [9] 630-636.1982. The transmittance method is a method for experimentally obtaining the hydrophobicity of the treated metal oxide powder, and comprises the following steps. 1.0 g of the treated metal oxide powder and 100 ml of water are put in a separating funnel for extraction and shaken vigorously for 5 minutes. Then let stand for 1 minute and withdraw a small amount of suspension from the bottom of the separatory funnel. The transmittance of this liquid for light of 550 nm is represented by the transmittance of pure water as 100%, and the value is defined as the hydrophobicity of the metal oxide.

A conventionally known method is applied to the treatment of the metal oxide powder used in the present invention. That is, while mechanically and sufficiently stirring the metal oxide powder to be treated, an organopolysiloxane having an epoxy group as a substituent, a polyalkyleneimine, and an organopolysiloxane having an epoxy group as a substituent, if necessary, are added thereto. Other organopolysiloxanes are added dropwise or by spraying. It is also possible to use a solvent such as an alcohol, a ketone or a hydrocarbon as a diluent depending on the viscosity of the polyalkyleneimine and the organopolysiloxane used. After the treatment agent is added, the reaction is completed by heating under a nitrogen stream at a temperature in the range of 100 to 250 ° C., particularly preferably in the range of 130 to 170 ° C. to remove the solvent. Further, depending on the kind of the metal oxide powder, when the dry treatment as described above is difficult, it is possible to perform the treatment under a wet condition using a considerable amount of a solvent. The hydrophobic metal oxide obtained by such a method is added to the toner by a conventionally known method. The amount added is in the range of 0.1% to 20% with respect to the toner, and particularly 0.1% to 3%.
It is practically desirable to be in the range of%. The toner prepared in this manner is further mixed with iron powder or iron oxide powder to prepare a developer.

[0009]

INDUSTRIAL APPLICABILITY The hydrophobic metal oxide powder constituting the present invention can be made stronger by using the organopolysiloxane having an epoxy group as a substituent together with the polyalkyleneimine so that the polyalkyleneimine becomes stronger. It is fixed on the body surface. As a result, the developer containing the hydrophobic metal oxide has not only excellent fluidity, but also a characteristic that it exhibits little change with time and is stable and is not easily affected by environment such as humidity.

[0010]

DETAILED DESCRIPTION OF THE INVENTION Examples and comparative examples are shown below for the purpose of facilitating the understanding of the present invention, but these do not limit the present invention at all.

[Example 1] Heat-dried silica powder ("Aerosil # 130" manufactured by Nippon Aerosil Co., Ltd. specific surface area 13)
0 m ² / g) 10 g was placed in a stainless steel container, and a treating agent having the following composition was sprayed while stirring at room temperature under a nitrogen atmosphere. Treatment agent Polyethyleneimine (30% aqueous solution) 2.00 g Dimethyl polysiloxane (Shin-Etsu Chemical Co., Ltd. "KF-96" (50cs)) 1.00 g n-propanol 5.0 ml After spraying, stir for 5 minutes at room temperature. After that, external heating was performed under a nitrogen stream. The temperature was raised to 150 ° C. over 40 minutes, held at this temperature for 60 minutes, and then allowed to cool to room temperature. The hydrophobicity of the obtained powder by the transmittance method and the amount of triboelectrification on iron were 92% and +109 μC /
It was g.

Next, 18% carbon and 5% nigrosine were dispersed in a styrene-acrylic resin material, and after pulverization, 10 to 10
A toner was prepared by mixing 1 g of the above metal oxide particles with 100 g of the resin powder obtained by classification into 20 μm. Further, 30 g of this toner was added to 1000 g of iron oxide powder to prepare a developer. The triboelectric charge of this developer is + 17μ
It was C / g. When this developer was put into a commercially available copying machine and a life test was conducted, no fog occurred on the image even after copying about 20,000 sheets or more. Further, a good image was shown even in an environment of high temperature and high humidity (28 ° C., 85% RH). The triboelectric charge amount of the developer prepared without adding the metal oxide powder was +16 μC / g.

Comparative Example 1 Silica powder dried by heating (“Aerosil # 130” manufactured by Nippon Aerosil Co., Ltd. specific surface area 13)
0 m ² / g) 10 g was placed in a stainless steel container, and a treating agent having the following composition was sprayed while stirring at room temperature under a nitrogen atmosphere. Treating agent Polyethyleneimine (30% aqueous solution) 2.00 g n-Propanol 5.0 ml After spraying was completed, the mixture was further stirred at room temperature for 30 minutes, and then externally heated under a nitrogen stream. The temperature was raised to 150 ° C. over 40 minutes, held at this temperature for 30 minutes, and then allowed to cool to room temperature. The obtained powder was hydrophilic, and the triboelectric charge amount on iron was 14 μC / g.

Next, 18% carbon and 5% nigrosine were dispersed in a styrene-acrylic resin material, and after pulverization, 10 to 10
A toner was prepared by mixing 1 g of the above metal oxide particles with 100 g of the resin powder obtained by classification into 20 μm. Further, 30 g of this toner was added to 1000 g of iron oxide powder to prepare a developer. The triboelectric charge of this developer is + 16μ
It was C / g.

When this developer was put into a commercially available copying machine and a life test was conducted, fog occurred on the image after about 2,000 sheets. The triboelectric charge amount of the developer prepared without adding the metal oxide powder was +17 μC / g.

Example 2 Heat-dried alumina powder ("Aluminum oxide C" manufactured by Nippon Aerosil Co., Ltd.)
10 g of a specific surface area of 90 m ² / g) was placed in a stainless steel container, and a treating agent having the following composition was sprayed while stirring at room temperature under a nitrogen atmosphere. Treatment agent Polyethyleneimine (30% aqueous solution) 2.00 g Dimethyl polysiloxane (Shin-Etsu Chemical Co., Ltd. "KF-96" (50cs)) 1.00 g n-propanol 5.0 ml After spraying, stir for 5 minutes at room temperature. After that, external heating was performed under a nitrogen stream. The temperature was raised to 150 ° C. over 40 minutes, held at this temperature for 60 minutes, and then allowed to cool to room temperature. The hydrophobicity of this powder by the transmittance method and the amount of triboelectrification against iron were 75% and 86 μC / g, respectively. Next, carbon 1 in styrene-acrylic resin material
Toner was prepared by dispersing 1% of the metal oxide particles in 100 g of the resin powder obtained by dispersing and pulverizing 8% and 5% of nigrosine in 10 to 20 μm. Further, 30 g of this toner was added to 1000 g of iron oxide powder to prepare a developer. The triboelectric charge of this developer was +16 μC / g. When this developer was put in a commercially available copying machine and a life test was conducted, no fog occurred on the image even after copying about 17,000 sheets. Higher temperature and humidity (28
Good images were shown even under the environment of 85 ° C. and 85% RH. The triboelectric charge amount of the developer prepared without adding the metal oxide powder was +16 μC / g.

Example 3 Heat-dried titania powder (“Titanium oxide P2” manufactured by Nippon Aerosil Co., Ltd.)
10 g of 5 "specific surface area 80 m ² / g) was charged into a stainless steel container, and a treating agent having the following composition was sprayed while stirring at room temperature under a nitrogen atmosphere. Treatment agent Polyethyleneimine (30% aqueous solution) 2.00 g Dimethyl polysiloxane (Shin-Etsu Chemical Co., Ltd. "KF-96" (50cs)) 1.00 g Acetone 5.0 ml After spraying was completed, the mixture was stirred at room temperature for 5 minutes, and then nitrogen. External heating was performed under a stream of air. The temperature was raised to 150 ° C. over 40 minutes, held at this temperature for 60 minutes, and then allowed to cool to room temperature. The hydrophobicity of this powder by the transmittance method and the amount of triboelectricity with respect to iron were 68% and 47 μC / g, respectively. Next, carbon 1 in styrene-acrylic resin material
Toner was prepared by mixing 1 g of the above metal oxide particles with 100 g of resin powder obtained by dispersing 8% and nigrosine 5%, pulverizing, and then classifying to 10 to 20 μm. Further, 30 g of this toner was added to 1000 g of iron oxide powder to prepare a developer. The triboelectric charge of this developer was +17 μC / g. When this developer was put into a commercially available copying machine and a life test was conducted, no fog occurred on the image even after copying about 18,000 sheets. Higher temperature and humidity (28
Good images were shown even under the environment of 85 ° C. and 85% RH. The triboelectric charge amount of the developer prepared without adding the metal oxide powder was +16 μC / g.

[Example 4] Heat-dried silica powder ("Aerosil # 130" manufactured by Nippon Aerosil Co., Ltd. specific surface area 13)
0 m ² / g) 10 g was placed in a stainless steel container, and a treating agent having the following composition was sprayed while stirring at room temperature under a nitrogen atmosphere. Treatment agent Polyethyleneimine (30% aqueous solution) 0.40 g Methylhydropolysiloxane ("KF-99" (20CS) manufactured by Shin-Etsu Chemical Co., Ltd.) 1.00 g n-Propanol 5.0 ml After spraying, it is 5 minutes at room temperature. After stirring, external heating was performed under a nitrogen stream. The temperature was raised to 150 ° C. over 40 minutes, held at this temperature for 60 minutes, and then allowed to cool to room temperature. The hydrophobicity of the obtained powder by the transmittance method and the amount of triboelectricity with respect to iron were 98% and -123 μC /, respectively.
It was g. Next, 18% carbon and 5% nigrosine were dispersed in a styrene-acrylic resin material, pulverized, and then 10-
A toner was prepared by mixing 1 g of the above metal oxide particles with 100 g of the resin powder obtained by classification into 20 μm. Further, 30 g of this toner was added to 1000 g of iron oxide powder to prepare a developer. The triboelectric charge of this developer is -15μ.
It was C / g. When this developer was put into a commercially available copying machine and subjected to a life test, no fog occurred on the image even after copying about 13,000 sheets. Further, a good image was shown even in an environment of high temperature and high humidity (28 ° C., 85% RH). The triboelectric charge of the developer prepared without adding the metal oxide powder was -14 μC / g.

Claims (3)

[Claims] 1. A developer for electrophotography containing a metal oxide powder having a coating of organopolysiloxane and polyalkyleneimine. 2. The electrophotographic developer according to claim 1, wherein the metal oxide powder has a hydrophobicity of 60% or more as measured by a transmittance method. 3. The electrophotographic developer according to claim 1, wherein the metal oxide is silica, alumina or titania.