JPH11153879A - Dry toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dry toner which always has a stable charge amt. without producing a toner with the opposite polarity. SOLUTION: This toner contains a polyimide powder having about <=6 μm average particle size and about 1×10<10> to 1×10<13> Ωcm electric resistance which is internally added. Since the average particle size (about <=6 μm) is smaller than the average particle size (about 5 to 20 μm) of the dry toner, the polyimide powder which is highly electrified into negative charges can be uniformly dispersed in the dry toner and prevents generation of a toner with the opposite polarity. Thereby, no fog is produced, uniform electrification is obtd, and stable image density is obtd. Since the electric resistance is large as about 1×10<10> to 1×10<13> Ωcm, the charge amt. can be always stabilized without depending on environmental conditions such as temp. and humidity, and therefore, gradation in the image density is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry toner used for forming an image in an electrophotographic method, an electrostatic printing method, a toner jet method or the like.

[0002]

2. Description of the Related Art Conventionally, electrophotography has been disclosed in U.S. Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910.
No. (corresponding US Pat. No. 3,666,363)
As described in JP-B-43-24748 (corresponding to U.S. Pat. No. 4,071,361) and the like, a number of methods are known, but in general, a photosensitive method utilizing a photoconductive substance is used. An electrostatic latent image is formed on the body by various means, and then the latent image is developed using toner, and if necessary, a toner image is transferred to a transfer material such as paper.
The image is fixed by pressure or solvent vapor to obtain a copy.

[0003] Various developing methods for visualizing an electrostatic latent image using toner are also known. For example, the magnetic brush method described in U.S. Pat. No. 2,874,063, the cascade developing method described in U.S. Pat. No. 2,618,552, and the U.S. Pat. No. 2,221,776. Numerous development methods are known, such as the powder cloud method and the fur brush development method described.

As a toner used in these developing methods, a fine powder in which a dye or a pigment is dispersed in a natural or synthetic resin is conventionally used. Further, it is also known to use a finely developed powder to which a third substance is added for various purposes.

[0005] The developed toner image is transferred and fixed to a transfer support such as paper as necessary. As a fixing method of the toner image, a method in which the toner is heated and melted by a heater or a heat roller to fix the toner image to the support, a method in which the binder resin of the toner is softened or dissolved with an organic solvent and fixed to the support, A method of fixing toner to a support is known.

[0006]

However, in the image forming apparatus, the toner having the opposite polarity is charged in the image forming apparatus with a polarity opposite to the original charge polarity of the toner. It was developed where there was no electrostatic latent image above, causing fogging.
In addition, even if the toner is not charged to the opposite polarity, the charge amount of the toner becomes unstable due to environmental conditions such as temperature and humidity, and the image density may be varied.

The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a dry toner which does not generate reverse polarity toner and has a stable charge amount at all times.

[0008]

In order to achieve this object, the dry toner according to the first aspect of the present invention has an average particle diameter of about 6 μm or less and an electric resistance of about 1 × 10 ^10.
ポ リ イ ミ ド 1 × 10 ¹³ Ωcm polyimide powder internally added.

As a result, the average particle diameter of the dry toner (about 5
２０20 μm) than the average particle diameter of polyimide powder (about 6 μm).
μm or less), the strongly negatively charged polyimide powder is uniformly dispersed in the dry toner to prevent the generation of toner of the opposite polarity, and the electric resistance is about 1 × 10 ¹⁰ to 1 × 10 Since it is as large as ¹³ Ωcm, the temperature,
The charge amount can always be stabilized irrespective of environmental conditions such as humidity.

The dry toner according to claim 2 has an average particle diameter of about 6 μm or less and a charge amount of about −10.
A polyimide powder of μC / g to −50 μC / g is internally added. As a result, since the average particle diameter of the polyimide powder (about 6 μm or less) is smaller than the average particle diameter of the dry toner (about 5 to 20 μm), the strongly negatively charged polyimide powder is uniformly dispersed in the dry toner, The generation of the opposite polarity toner can be prevented, and the charge amount can be set to a value suitable for electrophotographic development.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the dry toner of the present invention will be described.

The toner of the present embodiment is a dry toner in which polyimide powder obtained by polycondensation of an acid anhydride and a diamine is internally added.

The polyimide powder used in the present invention includes:
For example, biphenyltetracarboxylic acids such as 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic dianhydride, and lower alkyl esters thereof Ingredients and 4,4'-
Diamines such as diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminodiphenyl ether, omp-phenylenediamine, benzophenone diamine, diphenylphosphine diamine, and diphenylmethane diamine And polycondensation of The average particle size of the polyimide powder is about 6 μm or less, and a desired size can be obtained depending on the reaction conditions. Further, the bulk polycondensate can be pulverized to obtain a powder having a desired particle diameter.

The physical properties of the polyimide powder used in the present invention are shown below.

1. Electric resistance is about 1 × 10 ¹⁰ to 1 × 10 ¹³
Ωcm. Since the toner has such a high electric resistance value, a stable charge amount can always be given to the toner regardless of environmental conditions such as temperature and humidity.

2. The triboelectric charge polarity is negative, and the charge amount is extremely large. 0.2 g of polyimide powder of 10 μm or less
And 4.8 g of carrier (FC-6 manufactured by TDK) for 30
The mixture obtained by stirring and mixing for one minute was measured by a blow-off type charge amount measuring device (manufactured by Toshiba Chemical Co., Ltd.). Such a charge amount is suitable for imaging by an electrophotographic method. Of course, the charging polarity of the polyimide powder is opposite to the polarity generated on the carrier.

3. There is no environmental dependency. 15 ° C, 10% RH
Even in an atmosphere of ~ 35 ° C and 90% RH, the amount of triboelectric charge hardly changes.

4. The average particle size is about 6 μm or less. Accordingly, since the average particle size of the polyimide powder is smaller than the average particle size of the toner (about 5 to 20 μm), the strongly negatively charged polyimide powder is uniformly dispersed in the toner, thereby preventing the generation of the opposite polarity toner. be able to. Further, polyimide is a thermosetting resin and cannot be melted by heating, so that it is not fixed on a support such as paper. Therefore, when a polyimide powder having an average particle diameter of 6 μm or more is used, the proportion of the polyimide in the toner becomes excessive, and toner particles that cannot be fixed may be generated, and the fixing strength may be insufficient.

The binder of the dry toner includes a homopolymer of styrene such as polystyrene, poly-P-chlorostyrene and polyvinyltoluene and a substituted product thereof; a styrene-P-chlorostyrene copolymer, and a styrene-propylene copolymer. Coalesce, 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 Polymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene- Vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer, etc. Styrene-based copolymer, etc. It can be.

Further, polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic resin, rosin, modified rosin,
Terpene resins, phenolic resins, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, paraffin waxes and the like can also be used.

A coloring agent such as a dye or a pigment, a fixing aid,
An additive such as a caking inhibitor may be added, but any known material can be used. When used as a magnetic toner, for example, iron tetroxide powder, iron sesquioxide powder,
Cobalt-γ-iron sesquioxide powder (Co-γ-Fe ₂ O ₃ ),
Materials conventionally known as magnetic materials, such as chromium oxide powder, iron powder, chromium powder, nickel powder, and alloys and compounds such as iron, cobalt, nickel, manganese, and chromium, and other ferromagnetic alloys can be used. .

In the present embodiment, 0.1 to 10 parts by weight (preferably 0.5 to 5 parts by weight) of polyimide powder is added to 100 parts by weight of the binder.

The present invention is not limited to a dry toner used in an electrophotographic method, but can be applied to a dry toner used in an electrostatic printing method or a toner jet method described in JP-A-6-155798.

Next, an embodiment of the present invention will be described.

(Example) A lump of polyimide was shaved with a plane, and a polyimide powder having an average particle diameter of 3 μm was prepared with a pulverizer. Using this polyimide powder, 100 parts by weight of a polyester resin (manufactured by Mitsui Toatsu) was used. Carbon black (manufactured by Mitsubishi Chemical) 5 parts by weight Polypropylene wax (manufactured by Sanyo Chemical) 5 parts by weight Charge control material (manufactured by Orient Chemical) 2 parts by weight Polyimide powder 2 parts by weight are mixed in a powder state, and then mixed and extruded with a kneading extruder The polyester resin and carbon black, polypropylene wax, charge control material, and polyimide powder are dispersed while heating, and the heated and kneaded material is cooled, and then coarsely ground and finely ground to obtain a dry toner having a particle size of 9 to 10 μm. Obtained.

The dry toner thus prepared was charged as toner A into a developing device of a laser printer in an amount of 30 g, and an image was output. In this image output, after the image was developed on the photosensitive member by the developing device, the image was transferred to the recording medium by the transfer roller, and the toner A was fixed by the heat fixing roller. As a recording medium, 4024 20 pound paper manufactured by XEROX was used.

Under the above conditions, the density of the image of the black solid print portion formed on the recording medium was measured with a Macbeth transmission densitometer, and an image density of 2.2 was obtained. The printing density of 2.0 was satisfied. Also,
The non-printed portion was measured with a reflection densitometer TC-6MC manufactured by Tokyo Denshoku Co., Ltd., and the difference from new paper was compared.

Further, a polyimide powder having an average particle diameter of 5 μm was prepared, and using this, a toner B was obtained by the same manufacturing method as described above. When an image output experiment similar to the above was performed on this toner B, the image density was 2.1 and the fog was 0.78.

Further, a polyimide powder having an average particle diameter of 1 μm was prepared, and using this, a toner C was obtained by the same manufacturing method as described above. When an image output experiment similar to the above was performed on this toner C, the image density was 2.3 and the fog was 0.43.

Further, a polyimide powder having an average particle diameter of 0.5 μm was prepared, and using this, a toner D was obtained by the same manufacturing method as described above. When an image output experiment similar to the above was performed on this toner D, the image density was 2.4 and the fog was 0.31.

Further, a polyimide powder having an average particle diameter of 0.1 μm was prepared, and using this, a toner E was obtained by the same manufacturing method as described above. When an image output experiment similar to the above was performed on this toner E, the image density was 2.4 and the fog was 0.20.

(Comparative Example) A polyimide powder having an average particle diameter of 6.5 μm was prepared, and using this, a toner F was obtained by the same manufacturing method as described above. When an image output experiment similar to the above was performed on this toner F, the image density was 2.
0, fog was 1.2.

Further, a polyimide powder having an average particle diameter of 8 μm was prepared, and using this, a toner G was obtained by the same manufacturing method as described above. When an image output experiment similar to the above was performed on this toner G, the image density was 1.5 and the fog was 2.8.

Further, the toner H was prepared by the same method as described above without internally adding polyimide powder.
I got When an image output experiment similar to the above was performed on this toner H, the image density was 2.3 and the fog was 1.2.

[0035]

As is apparent from the above description,
According to the dry toner according to claim 1 of the present invention, in particular,
Since polyimide powder having an average particle diameter of about 6 μm or less is internally added, the average particle diameter of the dry toner (about 5 to about 5 μm) is used.
20 μm) than the average particle size of the polyimide powder (about 6 μm).
m or less), the strongly negatively charged polyimide powder is uniformly dispersed in the dry toner, preventing the generation of toner of the opposite polarity without causing fogging, and the electric resistance is about 1 × Since it is as large as 10 ¹⁰ to 1 × 10 ¹³ Ωcm, charging is made uniform, so that a stable image density can be obtained, and the charging amount can always be stabilized regardless of environmental conditions such as temperature and humidity. There is no shading in the image density.

According to the dry toner of the present invention, particularly, a polyimide powder having an average particle diameter of about 6 μm or less and a charge amount of about −10 μC / g to −50 μC / g is used. Since the average particle size (about 6 μm or less) of the polyimide powder is smaller than the average particle diameter (about 5 to 20 μm) of the dry toner, the strongly negatively charged polyimide powder is contained in the dry toner. The toner is uniformly dispersed, prevents generation of toner of the opposite polarity, does not cause fogging, and has a charge amount suitable for image formation by an electrophotographic method.

Claims (2)

[Claims] 1. A dry toner containing a polyimide powder having an average particle diameter of about 6 μm or less and an electric resistance of about 1 × 10 ¹⁰ to 1 × 10 ¹³ Ωcm. 2. A dry toner comprising a polyimide powder having an average particle size of about 6 μm or less and a charge amount of about −10 μC / g to −50 μC / g.