JP3226104B2 - Positively chargeable magnetic toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to electrophotography, electrostatic printing,
The present invention relates to a positively chargeable magnetic toner used in magnetic recording and the like.

[0002]

2. Description of the Related Art In general, in electrophotography, a photoreceptor having a photosensitive layer made of a photoconductive material is provided with a uniform electrostatic charge, and is then subjected to image exposure, whereby an electrostatic charge is applied to the surface of the photoreceptor. A latent image is formed, and the electrostatic latent image is developed with a developer to form a toner image. The obtained toner image is transferred to a transfer material such as paper, and then fixed by heating or pressing to form a copied image. At this time, as the photoconductive material used for forming the photosensitive layer of the photoconductor, for example, an inorganic photoconductive material such as selenium, zinc oxide, cadmium sulfide, or a high molecular weight compound such as polyvinyl carbazole or a low molecular weight compound Organic photoconductive materials and the like are known. Of these, an organic photoreceptor having a photosensitive layer formed of a polymer-based photoconductive material, such as polyvinylcarbazole, has a better film-forming property than an inorganic photoconductive material, and is therefore less expensive. Photoreceptors can be manufactured, and they have the advantage that they are not toxic to the human body. However, on the other hand, inorganic materials are used because they have low sensitivity, easily deteriorate in the corona charging step or the exposure step, and have poor durability. It is still inferior to a photoreceptor having a photosensitive layer made of a photoconductive material, and development of a high-performance organic photoconductive material is desired. In order to overcome the above problems, it has been recently proposed to use a low molecular weight organic photoconductive material. That is, the low-molecular-weight organic photoconductive material generally has good dispersibility in a binder resin, and thus, the obtained photosensitive layer is one in which the organic photoconductive material is uniformly dispersed in fine particles. As a result, A photosensitive member having relatively high sensitivity can be obtained. Also, by dispersing the organic photoconductive material in a binder resin to form a photosensitive layer,
Since the film formability is improved, the photoreceptor can be manufactured with high productivity. Furthermore, since there are many types of low molecular weight photoconductive materials that can be used for forming the photosensitive layer, a photoconductor having better performance than before can be obtained by appropriately selecting and using a low molecular weight photoconductive material. It is possible. As described above, an organic photoreceptor having a photosensitive layer formed of a low molecular weight organic photoconductive material is more preferable than a conventional photoreceptor. By the way, organic photoconductive materials are usually
Since the positive charge moves to show photoconductivity, the polarity of the electrostatic latent image formed on the photoreceptor surface having the photosensitive layer formed of the organic photoconductive material is negative. Is preferred. Further, in order to develop a negative electrostatic latent image, it is necessary to use a developer containing a positively chargeable toner. On the other hand, in the case of a photosensitive member having a photosensitive layer made of an inorganic photoconductive material such as selenium, which has been widely used in the related art, the electrostatic latent image formed on the surface thereof has a positive polarity. A developer having a negatively charged toner is used for developing the latent image. For this reason, research and development of a developer containing a negatively-charged toner have been performed considerably.

[0003]

However, research and development of a developer containing a positively chargeable toner used for developing an electrostatic latent image formed on the surface of the organic photoreceptor has been delayed. In fact, a developer containing a sufficiently positively charged toner has not been obtained. On the other hand, as a method of developing an electrostatic latent image, a wet development method and a dry development method are known. However, in the former wet development method, since a liquid developer is used, there is a problem that it emits a bad smell. In addition, there is a problem that high energy is required for drying the transfer material and high-speed copying is difficult. On the other hand, the latter dry developing method does not have such a problem and can be preferably used as a developing method of an electrostatic latent image. Further, as a developer used in the dry developing method, a so-called one-component developer composed of only a magnetic toner containing a magnetic material and a so-called two-component developer composed of a non-magnetic toner containing no magnetic material and a magnetic carrier are used. Component developers are known.
Among them, the one-component developing system is an excellent method in that the two-component developing system including the carrier and the toner can solve the problems of the change in the mixing ratio of the carrier and the toner and the problem of the spent carrier. It is. Accordingly, an object of the present invention is to provide a novel positively-chargeable magnetic toner having excellent development characteristics, which constitutes a one-component developer used in a dry development method and solves the above-mentioned problems of the prior art. It is in.

Further, in recent years, from the viewpoint of environmental protection, in the transfer step, there has been a strong demand to reduce the amount of waste toner collected from the photoreceptor by a cleaner without being transferred. There is a demand for a toner having a high transfer rate. The present inventors have made intensive studies to solve this problem and as a result, have found that the transferability of the toner can be enhanced by further increasing the electrical resistance of the toner particles. On the other hand, one method of increasing the electrical resistance of toner particles is to make the magnetic powder to be contained in the toner hydrophobic. The conventionally well-known magnetic powder that has been subjected to a hydrophobic treatment with a fatty acid, TTS or the like is used. In the case of a positively chargeable toner containing, there is a problem that the toner is excessively charged in a low humidity environment, and the image density is reduced. Accordingly, another object of the present invention is to provide a novel positively chargeable magnetic toner having high transferability.

[0005]

The above objects are achieved by the present invention described below. That is, in the present invention, the toner is transferred.
From the photoconductor surface to the cleaner without being transferred in the process
Recovered magnetic toner used in electrophotography
The magnetic toner is a positively chargeable magnetic toner manufactured through a process of hot-kneading and pulverizing magnetic powder surface-treated with a binder resin, a positive charge control agent and a coupling agent having a mercapto group or a chlorine atom. The coupling agent is a silane coupling agent in which a mercapto group or a chlorine atom does not constitute a hydrolysis group directly bonded to a silicon atom, but is bonded to a silicon atom through an organic group. Yes,
The surface treatment amount of the silane coupling agent with respect to the magnetic powder is 0.3 to 5% by weight, and the ratio of the major axis diameter to the minor axis diameter of the magnetic powder (major axis diameter / minor axis diameter) Is 1.0 to 1.1
5 is a positively chargeable magnetic toner.

[0006]

The positively-chargeable magnetic toner containing a magnetic powder surface-treated with a coupling agent having a mercapto group or a halogen group has a higher electric resistance and therefore has better transferability. Furthermore, even in a low-humidity environment, the charge amount does not become excessive, so that a high-density image can be stably obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Mercapto group used to treat magnetic powder
Or for silane coupling agents containing chlorine atoms:
This is described below. First, a silane cap having a mercapto group is used.
The pulling agent will be described. For example, in the present invention
As a silane coupling agent with a mercapto group
Is the HS (CH₂)₂Si (OCH₃)₃  HS (CH₂)₃Si (OCH₃)₃  HS (CH₂)₄Si (OCH₃)₃  [HS (CH₂)₃]₂Si (OCH₃)₂  HSC₆H₄Si (OCH₃)₃  (HSC₃H₆)₂CHCH₂Si (OCH₃)₃  And the like.

Next, the present invention is applied to the positively chargeable magnetic toner of the present invention.
Of silane coupling agent containing chlorine atom
I will tell. As shown in the following exemplary compounds, a chlorine atom
As a decomposing group, it is not directly bonded to a Si atom,
Those bonded to an organic group that is a hydrophobic group are particularly preferred.
No. For example, having a chlorine atom with such a structure
As the silane coupling agent, Cl (C₃H₆) Si (OCH₃)₃  Cl (C₂H₄) Si (OCH₃)₃  Cl (C₄H₈) Si (OCH₃)₃  (ClC₃H₆)₂CHCH₂Si (OCH₃)₃  ClC₆H₄Si (OCH₃)₃  (ClC₃H₆)₂Si (OCH₃)₂  And the like.

The magnetic powder to be treated with the above-described coupling agent used in the positively chargeable magnetic toner of the present invention includes:
Alloys and compounds containing ferromagnetic elements, such as magnetite, maghemite, and other iron, zinc, cobalt, nickel,
Conventionally known magnetic materials such as alloys and compounds such as manganese and other ferromagnetic alloys are preferably used. The shape of the magnetic powder is preferably spherical or nearly spherical. In the ratio of the major axis diameter to the minor axis diameter, 1.
Use those in the range of 0 to 1.15. At this time, the shape of the magnetic powder was measured with a transmission electron microscope at 20,000.
At times, take a photograph of the magnetic powder, the longest length of each particle as the long axis diameter, the shortest length as the short axis diameter,
(Long axis diameter) / (short axis diameter) is defined as the ratio of the diameter of the long axis to the short axis.
The amount of the coupling agent for treating the surface of the magnetic powder is preferably from 0.1 to 10% by weight, more preferably from 0.2 to 7% by weight, and still more preferably from the magnetic powder. 0.3 to 5% by weight. Further, as a method of surface treatment of the magnetic powder with the coupling agent, the magnetic powder and the coupling agent are mixed together by a stirrer or the like,
It is processed by stirring.

Examples of the binder resin of the toner used as the binder resin used in the positively chargeable magnetic toner of the present invention include styrene such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene, and monomers of substituted styrene. ;
Styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-
Methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer Coalesce, styrene-butyl methacrylate copolymer,
Styrene-acryl-aminoacrylic copolymer, styrene-aminoacrylic 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-butadiene copolymer, styrene-isobrene copolymer, styrene-acrylonitrile-indene copolymer, styrene-
Styrene-based copolymers such as maleic acid copolymer and styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin , Polyvinyl butyral, polyacrylic acid resin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin,
Aromatic petroleum resins, chlorinated paraffins, paraffin waxes and the like can be used alone or in combination of two or more as needed.

The positively chargeable magnetic toner of the present invention may optionally contain a charge control agent and a fluidity modifier, and the charge control agent and the fluidity modifier are mixed with the toner particles. (External addition). Nigrosine dyes, quaternary ammonium salts, triphenylmethane dyes and the like are used as charge control agents. Among these, a nigrosine dye is particularly preferable because it exhibits particularly excellent transferability when used in the positively chargeable magnetic toner of the present invention. Examples of the fluidity modifier include colloidal silica and metal salts of fatty acids. Also, for the purpose of increasing the amount of filler such as calcium carbonate, finely divided silica,
It can be blended in the toner in the range of 0.1 to 20% by weight. Further, a fluidity improver such as Teflon fine powder may be blended in order to prevent agglomeration of the toner particles and to improve the fluidity thereof, and to improve the releasability at the time of hot roll fixing. For the purpose, low-molecular-weight polyethylene, low-molecular-weight polypropylene, microcrystalline wax, carnauba wax, wax-like substance such as
About 5% by weight can be added.

[0012]

Next, the present invention will be described in more detail with reference to examples of the present invention. Note that the present invention is not limited to the examples given here.

Example 1 100 parts by weight of styrene-butyl acrylate copolymer (copolymerization weight ratio = 75:25) Spherical treated with 2% by weight of HS (C ₃ H ₆ ) Si (OCH ₃ ) ₃ 80 parts by weight of magnetite (long / short axis ratio = 1.05) 2 parts by weight of nigrosine dye 4 parts by weight of low molecular weight polypropylene After the above materials were premixed with a Henschel mixer, 15 parts by weight were added.
The mixture was kneaded with a two-roll mill heated to 0 ° C. for 20 minutes. After allowing the kneaded material to cool, coarsely pulverized by a cutter mill, pulverized by a fine pulverizer using a jet stream, and further classified by an air classifier, the black fine powder having a volume average particle size of 8.7 μm. I got a body. 0.6 part of colloidal silica fine powder was dry-mixed with 100 parts of the black fine powder thus obtained to obtain a positively-chargeable magnetic toner (developer) of the present invention.

This toner is used in a copying machine manufactured by Canon Inc.
This was applied to P-1215 to evaluate development characteristics and transferability. The evaluation of the developability was performed in a low temperature and low humidity environment (15 ° C. /
10%). As a result, the image density is 1.
There were 40 images, and even after 500 images were continuously output, the image density was also 1.40, and a stable image was obtained. There was also no fog. Regarding the evaluation of the transferability, under normal environment (23 ° C.
/ 60%). Transfer rate is to copy solid black image,
The amount of toner developed on the photoreceptor (g / cm ² ) and the amount of toner transferred on the transfer material (g / cm ² ) were measured and determined. As a result, the transfer rate was 92%, indicating good transferability.

Examples 2 to 5 and Comparative Examples 1 to 4 The same procedures as in Example 1 were carried out except that the magnetic material treated with a coupling agent having a mercapto group shown in Table 1 was used. A positively-chargeable magnetic toner was prepared, and the developing property and the transfer property were evaluated using the same method as in Example 1. Table 2 shows the results.

[Table 1]

[Table 2]

Example 6 100 parts by weight of styrene-butyl acrylate copolymer (copolymer weight ratio = 78: 22) Spherical treated with 2% by weight of Cl (C ₃ H ₆ ) Si (OCH ₃ ) ₃ 80 parts by weight of magnetite (long / short axis ratio = 1.05) 2 parts by weight of nigrosine dye 4 parts by weight of low molecular weight polypropylene The above materials were premixed with a Henschel mixer as in Example 1, and then heated to 150 ° C. The mixture was kneaded with a heated two-roll mill for 20 minutes. After allowing the kneaded material to cool, coarsely pulverized with a cutter mill, then pulverized using a fine pulverizer using a jet stream,
Further, the particles were classified using an air classifier to have a volume average particle size of 8.7.
A black fine powder of μm was obtained. 0.4 part of colloidal silica fine powder was dry-mixed with 100 parts of the black fine powder thus obtained to obtain a positively chargeable magnetic toner (developer) of the present invention.

The toner is used in a copying machine manufactured by Canon Inc.
This was applied to P-1215 to evaluate development characteristics and transferability. In addition, the evaluation of the developability was performed under a low temperature and low humidity environment (15 ° C./10
%). As a result, the image density was 1.40 from the beginning.
It was also 1.40 even after continuous output of 500 sheets. There was also no fog. The transferability was evaluated under a normal environment (23 ° C./60%). The transfer rate was determined by copying the amount of toner (g / cm ² ) developed on the photoreceptor by copying a solid black image and the amount of toner (g) transferred onto the transfer material.
/ Cm ² ). As a result, the transfer rate was 93%, showing good transferability.

Examples 7 to 12 and Comparative Examples 5 to 8 The same procedure as in Example 6 was repeated except that the magnetic material treated with a coupling agent having a chlorine atom shown in Table 3 was used. Forming a positively chargeable magnetic toner,
Evaluation of development characteristics and transferability was performed in the same manner as in Example 6. Table 4 shows the results.

[Table 3]

[Table 4]

[0019]

As described above, according to the positively chargeable magnetic toner of the present invention, even in a low humidity environment, the charge amount does not become excessive, the developing property is excellent, and the image density is high. Image can be obtained stably. Further, the positively-chargeable magnetic toner of the present invention has high electric resistance, so that excellent transferability is realized, and the amount of so-called waste toner that is collected by the cleaner from the photoconductor without being transferred in the transfer step is reduced. I can do it.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaji Fujiwara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masashi Jimbo 3-30-2 Shimomaruko, Ota-ku, Tokyo JP-A-63-250660 (JP, A) JP-A-54-127329 (JP, A) JP-A-60-254054 (JP, A) JP-A-1-259372 (JP) JP-A-58-87559 (JP, A) JP-A-2-146557 (JP, A) JP-A-3-1160 (JP, A) JP-A-62-168163 (JP, A)

Claims (1)

(57) [Claims] (1) In a transfer step, a residue is left without being transferred.
An electronic image in which toner is collected from the photoreceptor surface by a cleaner
In the magnetic toner used in the true method, the magnetic toner is manufactured through a process of heat-kneading and pulverizing magnetic powder surface-treated with a binder resin, a positive charge control agent and a coupling agent having a mercapto group or a chlorine atom. The coupling agent is a mercapto group or a chlorine atom,
A silane coupling agent that is not bonded to a hydrolyzable group directly bonded to a silicon atom but is bonded to a silicon atom via an organic group, and a surface treatment amount of the silane coupling agent with respect to the magnetic powder is: 0.3 to 5% by weight, and the ratio of the major axis diameter to the minor axis diameter (major axis diameter / minor axis diameter) of the magnetic powder is 1.0 to 1.15. Positively chargeable magnetic toner.