JPH11153880A - 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 <=4 μm average particle size and-about 1×10<10> to 1×10<13> Ωcm electric resistance which is externally coated. Since the average particle size (about <=4 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 in 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 the environmental conditions such as temp. and humidity, and therefore, irregularity 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 present invention has an average particle diameter of about 4 μm or less and an electric resistance of about 1 × 10 ^10.
A polyimide powder of about 1 × 10 ¹³ Ωcm is externally added.

As a result, the average particle diameter of the toner (about 5 to 2
0 μm) than the average particle size of polyimide powder (about 4 μm).
), The strongly negatively charged polyimide powder is uniformly dispersed in the toner, and the generation of the opposite polarity toner can be prevented, and the electric resistance is about 1 × 10
Since it is as large as ¹⁰ to 1 × 10 ¹³ Ωcm, the charge amount can always be stabilized regardless of environmental conditions such as temperature and humidity.

The dry toner according to claim 2 has an average particle size of about 4 μm or less and a charge amount of about −10.
It is obtained by externally adding polyimide powder of μC / g to −50 μC / g.

As a result, the average particle size of the toner (about 5 to 2
0 μm) than the average particle size of polyimide powder (about 4 μm).
Since the following is small, the strongly negatively charged polyimide powder is uniformly dispersed in the toner, thereby preventing the generation of toner of the opposite polarity and having a charge amount suitable for development by electrophotography. Can be.

Further, in the dry toner according to the third aspect, the polyimide powder is added in an amount of 0.1 to 100 parts by weight of the toner.
~ 5 parts by weight externally added.

As a result, the average particle diameter of the toner (about 5 to 2
0 μm) than the average particle size of polyimide powder (about 4 μm).
The following is small, the polyimide powder that is strongly negatively charged is uniformly dispersed in the toner, preventing the generation of toner of the opposite polarity, and at the same time, obtaining a sufficient image density and enabling transfer to a transfer material such as paper. Fixing can be facilitated.

[0014]

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 to which polyimide powder obtained by condensation polymerization of an acid anhydride and a diamine is externally 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 4 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 4 μm or less. Therefore, since the average particle diameter of the polyimide powder is smaller than the average particle diameter of the toner (about 5 to 20 μm), the strongly negatively charged polyimide powder is uniformly dispersed in the toner,
Generation of reverse polarity toner can be prevented. 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 4 μm or more is used, the proportion of the polyimide in the toner becomes excessively large, and toner particles that cannot be fixed may be generated, resulting in insufficient fixing strength.

The binder for the dry toner may be a homopolymer of styrene or a substituted styrene such as polystyrene, poly (P-chlorostyrene) or polyvinyltoluene; a styrene-P-chlorostyrene copolymer, 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 this embodiment, 0.1 to 5 parts by weight of the polyimide powder is externally added to 100 parts by weight of the toner.

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 2 μm was prepared using a pulverizer.

First, 100 parts by weight of polyester resin (manufactured by Mitsui Toatsu) 13 parts by weight of carbon black (manufactured by Mitsubishi Chemical) 5 parts by weight of polypropylene wax (manufactured by Sanyo Chemical) 2 parts by weight of charge control material (manufactured by Orient Chemical) The polyester resin, carbon black, polypropylene wax, and a charge control material are dispersed while heating with a kneading extruder, and the heated and kneaded material is cooled. A dry toner having a thickness of 10 μm was obtained. 1 part by weight of the polyimide powder and 0.5 part of silica as a fluidity-imparting material were added to this dry toner.
By weight, toner A was obtained.

As described above, the above-mentioned various materials are heated and kneaded,
By pulverizing to form a dry toner and then externally adding a polyimide powder, various materials are heated and kneaded in advance after the polyimide powder is mixed and pulverized to form a dry toner (this is referred to as “internal addition”). ), Sufficient effects can be obtained with a smaller amount of the polyimide powder added. This is because in the case of internal addition, a polyimide powder which is buried inside the toner particles and cannot exert a sufficient effect is generated, but in the case of external addition, this does not occur.

Then, 30 g of the toner A was charged into a developing device of a laser printer, and an image output experiment was performed.
This image output experiment was performed by developing an image on a photoconductor with a developing device, transferring the image to a recording medium with a transfer roller, and fixing the toner A with a heat fixing roller. As a recording medium, 4024 20-pound paper manufactured by XEROX was used.

Under the above conditions, the image density 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.
2.0, which is a practical print density, was satisfied. In addition, the non-printed part was measured with a Tokyo Denshoku reflection densitometer TC-6MC,
When the difference from new paper was compared, it was 0.57, which satisfies 1 or less, which is a practical reference value of fog.

Toner B was obtained by externally adding 2 parts by weight of a polyimide powder to the toner prepared in the same manner 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 toner C was obtained by externally adding 5 parts by weight of a polyimide powder to the toner prepared in the same manner as described above. When an image output experiment similar to the above was performed on this toner C, the image density was 2.1 and the fog was 0.63.

Toner D was obtained by externally adding 0.5 parts by weight of polyimide powder to the toner prepared in the same manner as described above.
When an image output experiment similar to the above was performed on this toner D, the image density was 2.3 and the fog was 0.81.

Further, a toner E was obtained by externally adding 0.1 parts by weight of a polyimide powder to the toner prepared in the same manner 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 0.72.

(Comparative Example) Toner F obtained without externally adding polyimide powder to a toner prepared in the same manner as described above.
When the same image output experiment as described above was performed with respect to, the image density was 2.3 and the fog was 1.2.

Toner G was obtained by externally adding 0.05 parts by weight of polyimide powder to the toner prepared in the same manner as described above. When an image output experiment similar to the above was performed on this toner G, the image density was 2.3 and the fog was 1.2.
It became.

Toner H was obtained by externally adding 6 parts by weight of a polyimide powder to the toner prepared in the same manner as described above. When an image output experiment similar to the above was performed on this toner H, the image density was 1.7 and the fog was 0.93.

Further, 7 parts by weight of a polyimide powder was externally added to the toner prepared in the same manner as above to obtain a toner I. When an image output experiment similar to the above was performed on this toner I, the image density was 1.5 and the fog was 0.51.

Further, 11 parts by weight of a polyimide powder was externally added to the toner prepared in the same manner as above to obtain a toner J. When an image output experiment similar to the above was performed on this toner J, the fixing strength was insufficient and the image could not be held, and the image density and fog could not be measured.

[0042]

As is apparent from the above description, according to the dry toner according to the first aspect of the present invention, particularly, a dry toner having an average particle diameter of about 4 μm or less is externally added. It is. Accordingly, since the average particle diameter of the polyimide powder (about 4 μm or less) is smaller than the average particle diameter of the toner (about 5 to 20 μm), the strongly negatively charged polyimide powder is uniformly dispersed in the toner, No fogging is caused by preventing the occurrence of fog, and since the electric resistance is as large as about 1 × 10 ¹⁰ to 1 × 10 ¹³ Ωcm, a stable image density can be obtained by uniform charging. The charge amount can always be stabilized irrespective of environmental conditions such as temperature, humidity, etc., and the image density does not vary.

According to the dry toner of the present invention, the polyimide powder having an average particle diameter of about 4 μm or less and a charge amount of about −10 μC / g to −50 μC / g is particularly removed. It is attached. Accordingly, since the average particle diameter of the polyimide powder (about 4 μm or less) is smaller than the average particle diameter of the toner (about 5 to 20 μm), the strongly negatively charged polyimide powder is uniformly dispersed in the toner, The generation of fogging is prevented by preventing the occurrence of fogging, and the charge amount can be set to a value suitable for image formation by an electrophotographic method.

According to the dry toner according to the third aspect, in particular, since 0.1 to 5 parts by weight of the polyimide powder is externally added to 100 parts by weight of the toner, generation of the opposite polarity toner is generated. Can be prevented, a sufficient image density can be obtained, and fixing to a transfer material such as paper can be facilitated.

Claims (3)

[Claims] 1. A dry toner to which a polyimide powder having an average particle diameter of about 4 μm or less and an electric resistance of about 1 × 10 ¹⁰ to 1 × 10 ¹³ Ωcm is externally added. 2. A dry toner comprising an externally added polyimide powder having an average particle size of about 4 μm or less and a charge amount of about −10 μC / g to −50 μC / g. 3. The dry toner according to claim 1, wherein 0.1 to 5 parts by weight of the polyimide powder is externally added to 100 parts by weight of the toner.