JP3254415B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method used in electrophotography, electrostatic printing, and the like.

[0002]

2. Description of the Related Art Conventionally, electrophotography generally uses a photoconductive substance, forms an electric latent image on a photoreceptor by various means, and then develops the latent image using toner.
After transferring the toner image to a transfer material such as paper as necessary,
The image is fixed by heating or pressure to obtain a copy. In this image forming process, even after the toner image is transferred to the transfer material, untransferred toner remains on the photoreceptor, so that the untransferred toner has been collected and discarded in the cleaning process.

In recent years, however, attention has been paid to the problem of environmental destruction, and waste regulations have become more stringent. Copiers, printers, facsimile machines, and the like using a recycling system that reuses conventionally discarded toner have been developed. Was.
The recycling system is a system in which the untransferred toner (collected toner) is collected and discarded by a blade, a fur brush, or the like of a cleaning unit, and is conveyed again to a replenishing hopper or a developing device to develop again. However, in a copying machine or the like using such a recycling system, the toner image density becomes unnecessarily high as a large number of copies are made, resulting in an increase in toner consumption, ground fogging and toner scattering. Had occurred.
It is considered that the cause of this problem is due to the deterioration of the triboelectric charging property of the collected toner. As a countermeasure, conventionally, silica or magnetic powder has been attached to the surface of the toner particles to improve the triboelectric charging property. Was. However, in this method, silica or magnetic powder is detached or buried from the toner surface due to heat or a physical load in the developing device, the cleaning unit, and the collected toner transporting unit, and the toner image density is required due to a decrease in triboelectricity. As described above, the density becomes higher, and as a result, the amount of toner consumption increases, and the problem of occurrence of ground fogging and toner scattering occurs. At present, it cannot be fundamentally solved.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method which solves the above-mentioned problems, and which can maintain a sufficient image density for a long period of time, An object of the present invention is to provide an image forming method that does not cause scattering.

[0005]

Specifically, the present invention uses a two-component developer containing a toner and a silicone-coated carrier, and recycles the toner to form an electrostatic latent image formed on a photoreceptor. An image forming method for developing an image, wherein the toner is particles obtained by adhering silica and magnetic powder to resin particles, has a glass transition temperature of 59 ° C. or more, and has a silica screen ratio of 0.97 or more, An image forming method, wherein the sieving ratio of the magnetic powder is 0.90 to 0.95 .

The details of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram for explaining the image forming method of the present invention. In FIG. 1, a photosensitive drum 1 rotates in the direction of the arrow shown in the figure, and a corona charger 2, an optical system 3, a developing device 4, a corona transfer device 5, and a cleaning member 9 are provided around the photosensitive drum 1.
And a static elimination means 10. First, the surface of the photosensitive drum 1 is uniformly charged by the corona charger 2 and then exposed by the optical system 3 to form an electrostatic latent image (not shown). Next, the electrostatic latent image is visualized by the developing device 4 to obtain a toner image 6. Transfer material 7 is placed on the obtained toner image 6
The toner image 6 is transferred onto a transfer material 7 by applying a transfer electric field from a back surface thereof by a corona transfer device 5 and then fixed by a fixing device 8 to obtain a final image. On the other hand, the toner image 6 remaining on the photosensitive drum 1 without being transferred to the transfer material 7 is cleaned by the cleaning member 9, transported to the developing device 4 again, and recycled. (The recycling path is indicated by a broken line in the figure.) Then, the charge on the surface of the photosensitive drum 1 is removed by the charge removing unit 10.

As the photosensitive drum 1, an organic optical semiconductor, a metal optical semiconductor, or the like can be used. As the optical system 3, an exposure method using visible light, a semiconductor laser, a liquid crystal shutter, a light emitting diode, or the like can be used.
Examples of the cleaning member 9 include an elastic blade, an elastic roller, wedge cleaning, fur brush cleaning, magnetic brush cleaning, and a cleaning method using a combination thereof. In the present invention, any method can be preferably used, but a cleaning method using an elastic blade can be more preferably used. The electrostatic latent image formed on the surface of the photoconductor drum 1 may be forward development or reverse development. As a method of recycling and using the untransferred toner that has been cleaned, the toner may be directly conveyed to the developing device as described above, or the cleaned toner may be returned to the hopper containing the toner for replenishment, stirred, and then stirred. May be transported.

In the above recycling copying system,
As a result of various studies conducted by the present inventors, the use of a toner in which specific silica and magnetic powder are adhered to resin particles and a silicone coat carrier allows the toner particles to exhibit excellent triboelectric charging properties even when recycled. It was confirmed that a sufficient image density was obtained and that there was no background fog and toner scattering. The resin particles are fine particles containing a binder resin, a colorant, and a charge control agent, and may contain other additives as necessary. The resin particles are
After the above materials are mixed and then melt-kneaded using a kneading machine such as a heating roll, a kneader, an extruder or the like, the mixture can be pulverized by a pulverizer such as a jet mill and classified by an airflow classifier or the like. Further, it may be obtained by a polymerization method such as a suspension polymerization method or an emulsion polymerization method. Examples of the binder resin include polystyrene, poly-p-chlorostyrene, polymers of styrene such as polyvinyltoluene and substituted products thereof, styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene. Copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, stalene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, Styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-isoprene copolymer, styrene-acrylonitrile-indene copolymer, etc. Styrenic Polymer,
Polyvinyl chloride, phenolic resin, natural modified phenolic resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, epoxy resin, xylene resin, polyvinyl butyral, petroleum A resin or the like can be used.

[0009] Coloring agents include any suitable pigments or dyes. For example, carbon black, aniline black, acetylene black, naphthol yellow,
Hansa Yellow, Rhodamine Lake, Alizarin Lake, Bengala, Phthalocyanine Blue, Indanthrene Blue and the like. These are used in an amount of 0.1 to 20 parts by weight, preferably 2 to 10 parts by weight, based on 100 parts by weight of the binder resin in order to obtain a sufficient image density.

The charge controlling agent may be incorporated into the resin particles or may be attached to the surface of the resin particles. Examples of positively chargeable charge control agents include denatured products such as nigrosine and fatty acid metal salts, tributylbenzylammonium-1-hydroxy-4-naphthosulfonate,
Quaternary ammonium salts such as tetrabutylammonium tetrafluoroborate, diorganotin oxides such as dibutyltin oxide, dioctyltin oxide and dicyclohexyltin oxide, diorganotin borate such as dibutyltin borate, dioctyltin borate and dicyclohexyltin borate alone or Two or more types can be used in combination. Of these, particularly preferred are nigrosine compounds and quaternary ammonium salts. As the negatively chargeable charge control agent, for example, an acetylacetone metal complex, a monoazo metal complex, an organic metal compound such as a naphthoic acid or salicylic acid-based metal complex or a salt, a chelate compound or the like can be used alone or in combination of two or more kinds. . Of these, salicylic acid-based metal complexes and monoazo metal complexes are particularly preferably used. The charge control agent is used in an amount of 0.1 to 20 parts by weight, preferably 0.2 to 10 parts by weight, based on 100 parts by weight of the binder resin. Other additives include synthetic waxes such as low-molecular-weight polypropylene wax, low-molecular-weight polyethylene wax, and paraffin wax, hardened castor oil, natural waxes such as carnauba wax, Fischer-Tropsch wax, magnetic powders, and metal oxides.

As the silica, both hydrophobic silica fine particles and hydrophilic silica fine particles can be used, but hydrophobic silica fine particles are preferable in consideration of environmental resistance. Silica may be used, if necessary, for the purpose of hydrophobization, charge control, etc., silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane coupling agents, silane coupling agents having functional groups, and other organic compounds. It may be treated with a treating agent such as a silicon compound or various treating agents. Silica is preferably used in an amount of 0.01 to 8 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the resin particles.

Examples of the magnetic powder include metals such as magnetite, hematite, and ferrite, such as iron oxide, iron, cobalt, and nickel, or aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, and the like of these metals.
Examples include alloys of metals such as beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, and vanadium, and mixtures thereof. The magnetic powder has an average particle diameter of 0.1 to 2 μm, and further 0.1 to 0.5 μm.
μm is preferred. The magnetic powder is preferably used in an amount of 0.01 to 8 parts by weight, more preferably 0.1 to 5 parts by weight based on 100 parts by weight of the resin particles.

The toner can be obtained by stirring the above resin particles, silica and magnetic powder with a stirrer such as a turbine type stirrer, a Henshal mixer, a super mixer, or the like. In this case, the silica and the magnetic powder may be in a state where the silica and the magnetic powder are simply dusted and adhered to the surface of the resin particle, or the silica and the magnetic powder are partially fixed and buried inside the resin particle. You may. The glass transition temperature of the toner having silica and magnetic powder adhered to the surface of the resin particles is determined by a thermal analyzer (DSC) RDS-
The midpoint value measured for the second time is defined as the glass transition temperature in the present invention. The glass transition temperature of the toner must be 59 ° C. or higher, preferably 63 ° C. to 68 ° C. When the glass transition temperature of the toner is less than 59 ° C., when the collected toner is conveyed to the developing device or the hopper, heat is applied due to the internal temperature of the device, heat of the fixing device, or the pressure of the screw in the developing device. The particle surface softens, and silica and magnetic powder are buried more than necessary. As a result, the silica and the magnetic powder do not contribute to the triboelectrification property with the silicone-coated carrier, and a charge amount value required for the triboelectrification amount of the collected toner cannot be obtained. .

The sieve ratio of silica and magnetic powder can be determined as follows. That is, the amounts of silica and magnetic powder in the toner are measured in advance with a fluorescent X-ray measuring device (trade name: JSX-3201, manufactured by JEOL Ltd.). Specifically, the method of measuring with a fluorescent X-ray measuring device is as follows.
First, a toner containing silica and magnetic powder was
A sample is obtained by molding into a pellet at a pressure of gf / cm ² . Then, the pellets are measured with a fluorescent X-ray measuring device, the tube voltage is 12 KV, the tube current is automatically controlled (optimum value), and the amounts of silica and magnetic powder are measured under the measurement conditions of 300 seconds. Next, the above-mentioned toner is sieved under the following conditions by using a powder characteristics comprehensive measuring device (PT-E) manufactured by Hosokawa Micron Corporation. Measurement Condition of Powder Tester 20 g of the toner is sieved for 15 seconds at an amplitude of 1 using a standard 300 mesh sieve. The amount of silica and magnetic powder is measured using a fluorescent X-ray measuring apparatus and measuring conditions using toner passed through a 300-mesh standard sieve. The sieving ratio of silica and magnetic powder can be determined by the following equation. The sieving rate of silica = the above silica amount / the above silica amount The sieving rate of the magnetic powder = the above magnetic powder amount / the above magnetic powder amount

The sieve ratio of silica obtained by the above measurement method is not a Banara was cry at least 0.97, preferably 0.98 to 1.00. The sieving ratio of silica is 0.
If it is smaller than 97, the amount of silica in the recovered toner is small, so that the triboelectric charge with the silicone-coated carrier is low, and the background fog and toner scattering to the non-image area occur. Further, sieve ratio of the magnetic powder obtained by the above measurement method only Re shall be the 0.90 to 0.95. When the sieving ratio of the magnetic powder is larger than 0.95, the magnetic powder on the surface of the toner particles is buried more than necessary, and the magnetic powder does not contribute to the triboelectric charging property with the silicone-coated carrier, and the friction of the collected toner is reduced. Since a charge amount value required for the charge amount cannot be obtained, ground fogging and toner scattering to a non-image portion occur.

The silicone-coated carrier is obtained by treating the surface of magnetic core powder such as iron powder, ferrite powder, nickel powder and magnetite powder with a silicone resin or a silicone compound. As a silicone resin or a silicone-based compound for forming a carrier coating layer, polysiloxane, for example, dimethylpolysiloxane, phenylmethylpolysiloxane, or the like is used. Further, modified resins such as alkyd-modified silicone, epoxy-modified silicone, polyester-modified silicone, urethane-modified silicone, and acryl-modified silicone can also be used. The average particle size of the silicone-coated carrier is preferably 30 to 130 μm, more preferably 40 to 120 μm, and still more preferably 50 to 110 μm. When applying the magnetic particles to the surface of the core magnetic particles, the silicone resin is varnished, such as solid methyl silicone varnish, solid phenyl silicone varnish, solid methyl phenyl silicone varnish, solid ethyl silicone varnish, and various modified silicone varnishes. A method of dispersing the varnish into the inside, a method of spraying a varnish onto the core magnetic particles, and the like can be used.

The carbon content of the silicone-coated carrier is preferably 1% by weight or less, particularly preferably 0.2 to 1.0% by weight.
When the amount is more than 1% by weight, the ground fogging and toner scattering to a non-image portion are liable to occur due to poor triboelectricity with the toner. The amount of carbon of the silicone-coated carrier was determined by calcining the silicone-coated carrier at 1250 ° C. until the amount of carbon dioxide disappeared using a carbon analyzer EMIA-110 manufactured by HORIBA, Ltd., measuring the amount of carbon, and measuring the amount of carbon by sample weight. Can be obtained by expressing the value divided by as a percentage. The two-component developer is preferably used in an amount of 1 to 40 parts by weight of the toner based on 100 parts by weight of the silicone-coated carrier.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described below with reference to examples. In the examples, parts are parts by weight. Example 1 After the above materials were melt-kneaded, they were pulverized and classified to obtain resin particles having an average particle diameter of 10 μm. Next, the following two-stage mixing process was performed. (First Mixing Step) Using a Henschel mixer, 100 parts of the above resin particles and 0.1 part of silica (trade name: R-972, manufactured by Nippon Aerosil Co., Ltd.) were used, and the number of revolutions of the stirring blade was 2,000 r.
The mixture was mixed at pm for 5 minutes, and the rotation of the stirring blade was stopped. (Second mixing step) Further, ferrite-based magnetic powder (trade name: EPT-1 manufactured by Toda Kogyo Co., Ltd.) is placed in the Henschel mixer.
000) 0.3 part, and the stirring blade is set to 1 at 2000 rpm.
The toner was rotated for 1 minute to obtain a toner in which silica and magnetic powder were adhered to resin particles. The characteristics of the toner were as follows. <Carrier> 100 parts of ferrite particles (trade name: FL-1025) manufactured by Powder Tech Co., Ltd. were placed in a stainless steel container, and a silicone obtained by diluting 20 parts of dimethyl silicone with 200 parts of toluene was added thereto, followed by sufficient stirring. Then, the ferrite particles were taken out, and the silicone was cured at room temperature to obtain a silicone-coated carrier. The carbon content of this silicone-coated carrier was 0.6% by weight. <Two-Component Developer> A three-component developer was prepared by mixing 3 parts of the toner and 100 parts of a silicone-coated carrier.

Example 2 A two-component developer was prepared in the same manner as in Example 1 except that the following carrier was used. <Carrier> A silicone-coated carrier was obtained in the same manner as in Example 1 except that the amount of dimethyl silicone was changed to 30 parts. The carbon content of this silicone coated carrier is 1.0
% By weight.

Example 3 A two-component developer was prepared in the same manner as in Example 1 except that the following toner and carrier were used. <Toner> A toner was obtained in the same manner as in Example 1, except that the number of revolutions of the stirring blade in the first mixing step was 2,000 rpm for 7 minutes. The characteristics of the toner were as follows. <Carrier> A silicone-coated carrier was obtained in the same manner as in Example 1 except that the amount of dimethyl silicone was changed to 10 parts. The carbon content of this silicone coated carrier is 0.4
% By weight.

Example 4 A two-component developer was prepared in the same manner as in Example 1 except that the following toner was used. <Toner> A toner was obtained in the same manner as in Example 1, except that the styrene-acrylic resin was changed to a styrene-acrylic resin (trade name: FS-5001, manufactured by Seiko Chemical Co., Ltd.). The characteristics of the toner were as follows.

Example 5 A two-component developer was prepared in the same manner as in Example 1 except that the following toner was used. <Toner> A toner was obtained in the same manner as in Example 1, except that the styrene-acrylic resin was changed to a styrene-acrylic resin (trade name: T-6980, manufactured by Sekisui Chemical Co., Ltd.). The characteristics of the toner were as follows.

Comparative Example 1 A two-component developer was prepared in the same manner as in Example 1 except that the following toner was used. <Toner> A toner was obtained in the same manner as in Example 1, except that the number of revolutions of the stirring blade in the second mixing step was 2,000 rpm for 3 minutes. The characteristics of the toner were as follows.

Comparative Example 2 A two-component developer was prepared in the same manner as in Example 1 except that the following toner was used. <Toner> A toner was obtained in the same manner as in Example 1, except that the number of rotations of the stirring blade in the first mixing step was 2000 rpm for 1 minute. The characteristics of the toner were as follows.

Comparative Example 3 A two-component developer was prepared in the same manner as in Example 1 except that the following toner was used. <Toner> In Example 1, the rotation speed of the stirring blade in the first mixing step was 2,000 rpm for 30 seconds, and the rotation speed of the stirring blade in the second mixing step was 2,000 rpm.
m for 2 minutes to obtain a toner in the same manner.
The characteristics of the toner were as follows.

Comparative Example 4 A two-component developer was prepared in the same manner as in Example 1 except that the following toner was used. <Toner> A toner was obtained in the same manner as in Example 1, except that the styrene-acrylic resin was changed to a styrene-acrylic resin (trade name: FS-5002, manufactured by Seiko Chemical Co., Ltd.). The characteristics of the toner were as follows.

Next, a copying machine (trade name: PD-301, manufactured by Matsushita Electric Industrial Co., Ltd.) having the recycling system shown in FIG.
Table 1 shows the results of 10,000 copies made in 8). In Table 1, "recycle toner replenishment" indicates the characteristics immediately after recycle toner is supplied to the developer for the first time. The triboelectric charge was measured by measuring the triboelectric charge of the toner with a blow-off triboelectric charge measuring device manufactured by Toshiba Chemical Corporation.
The non-image area was measured with a side color difference meter MODELZ1001DP manufactured by Nippon Denshoku Industries Co., Ltd. Regarding toner scattering, toner stains around the developing device were visually observed. A mark with extremely much toner stain was indicated by x, and a mark with almost no toner stain was indicated by ○.

[0028]

[Table 1]

In the image forming methods of Examples 1 to 5 using a two-component developer according to the present invention, the triboelectric charge amount is 10,000.
It was confirmed that the image density was stable up to the sheet and that there was no problem with ground fog and toner scattering. On the other hand, in Comparative Examples 1 to 4, the image density was higher than necessary due to a decrease in the triboelectric charge amount, and ground fog and toner scattering also occurred.

[0030]

According to the present invention, it is possible to provide an image forming method using a recycling system which can maintain a sufficient image density for a long period of time and does not cause ground fog or toner scattering.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining an image forming method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoreceptor drum 2 Corona charger 3 Optical system 4 Developing device 5 Corona transfer device 6 Toner image 7 Transfer material 8 Fixing device 9 Cleaning member 10 Static elimination means

Continuation of the front page (56) References JP-A-8-254851 (JP, A) JP-A-8-262785 (JP, A) JP-A-9-244292 (JP, A) JP-A-7-261464 (JP) JP-A-7-311477 (JP, A) JP-A-4-68359 (JP, A) JP-A-7-92727 (JP, A) JP-A-6-83100 (JP, A) 7-43931 (JP, A) JP-A-7-84400 (JP, A) JP-A 8-69131 (JP, A) JP-A 9-244298 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/08 G03G 9/10

Claims (2)

(57) [Claims] 1. An image forming method for developing an electrostatic latent image formed on a photoreceptor by using a two-component developer containing a toner and a silicone-coated carrier, and recycling the toner. Are particles obtained by adhering silica and magnetic powder to resin particles, having a glass transition temperature of 59 ° C. or higher, a silica screen ratio of 0.97 or higher, and a magnetic powder screen ratio of 0.90 to 0.3%. 95. An image forming method, comprising: 2. The silicone coated carrier having a carbon content of 1
2. The image forming method according to claim 1, wherein the content is not more than% by weight.