JPS603179B2 - Method for manufacturing insulating magnetic toner for electrostatic charge development - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing magnetic toner for developing electrostatic latent images in electrophotography, electrostatic recording, electrostatic printing, etc.
Specifically, the present invention relates to a method for producing a transferable one-component insulating magnetic toner for electrostatic charge development, which does not contain a carrier and has only toner particles as its main component.

There are two main methods for developing electrostatic images: liquid development, which uses a developer in which various pigments and dyes are finely dispersed in an insulating organic liquid, and liquid development, which uses a developer containing a colorant such as carbon black dispersed in a natural or synthetic resin. A magnetic brush method or a cascade method using a developer in which a carrier made of iron powder, glass beads, etc. is mixed with finely powdered electrically inspected powder called toner, or a developer made only of the above-mentioned toner without mixing a carrier is used. There are dry developing methods such as the bristle brush method, impression method, powder cloud method, and open chamber method.

The present invention particularly relates to a method of manufacturing a developer of the latter dry development method, which uses a developer consisting only of toner without mixing carrier. Generally, in a two-component developer, when toner and carrier are mechanically mixed, frictional electricity is generated between the toner and carrier, the carrier is charged to a specific polarity, and the toner has a charge of the opposite polarity to the carrier. Electrostatic charge port images can be developed.

However, toner generally deteriorates after being developed several thousand times due to abrasion caused by shearing force, impact force, etc., which it receives during mechanical operations in a developing device. High relative humidity also adversely affects the triboelectric charging and flow characteristics of the developer. For example, the triboelectric charge value of certain developers varies with relative humidity. This is not preferable for use in electrophotographic devices. In order to eliminate these drawbacks, a one-component developer containing only toner and no carrier has been proposed. For example, U.S. Pat. No. 3, Shiji Shigeru No. 45 describes a so-called conductive magnetic toner which is a combination of fine particles of a ferromagnetic material such as triiron tetroxide, a thermoplastic resin such as an epoxy resin, and conductive carbon black. was disclosed. The magnetic toner
was able to eliminate the above-mentioned drawbacks of two-component developers, but on the other hand, since the magnetic toner is conductive, it is difficult to transfer onto plain paper using a corona discharger, which is the most common and easily controlled method. A powder image made of the same magnetic toner is partially or completely disturbed, making it impossible to obtain a good transferred image. The applicant is interested in a transferable magnetic toner.As a result of research, it has been found that the main components are a resin and a ferromagnetic material, and the ferromagnetic material is a fine particle that has a triboelectrostatic property with a polarity opposite to that of the resin. , the toner is made up of toner particles that are uniformly dispersed in a resin, and that are formed so that the magnetic fine powder is substantially exposed from the resin surface on the surface of each toner particle, and that is made entirely of electrically insulating toner. We have completed a new developer. This toner-only developer does not have the disadvantages of conventional two-component developers consisting of toner and carrier, and since the toner as a whole is electrically insulating, it can be used on plain paper, which was a disadvantage of conductive magnetic toner. made possible the transcription of The present invention aims to provide a novel method for producing transferable insulating magnetic toner for use in electrophotography. Conventionally, as general methods for manufacturing magnetic toner, a pulverization method, a mist drying granulation method, and the like are known.

When an insulating magnetic toner manufactured by a pulverization method for the purpose of transfer is used in a copying machine that repeatedly performs development and transfer, it contaminates the photoreceptor and the photoreceptor becomes unusable after a small number of copies.

That is, this causes a decrease in the sensitivity of the photoreceptor, a decrease in transfer efficiency, an increase in fog, and the occurrence of transfer blur. This is due to the fact that fine particles of one mountain or less generated during pulverization are mixed in the magnetic toner and therefore adhere to the photoreceptor during development. Fine particles of about 1r or less attached to the photoreceptor cannot be removed by cleaning using a bristle brush method or the like. Further, fine particles of 1 French or less size mixed in the magnetic toner adhere to the surface of the magnetic toner particles so strongly that they cannot be removed by a classification operation or the like. Furthermore, when magnetic toner is in a pulverized state, each particle is a powder with irregular shapes, and the magnetic material on the surface of each toner particle protrudes from the resin. , mutual frictional electrification between the magnetic toner particles occurs partially strongly and partially weakly.

For this reason, the magnetic toner has poor fluidity as a developer and often causes fogging, resulting in only unclear copies. In addition, when the relative humidity is high, the electric charge generated by mutual friction tends to leak, and the fluidity becomes poor, so the image obtained after transfer is a blurred image with low density overall. . In addition, a disadvantage of the mist drying granulation method is that when the droplets formed by mist dry, the liquid evaporates farther from the surface, and the resin solidifies from the surface of the droplet, resulting in the interior of the droplet becoming more likely to become hollow. However, the vapor that evaporates from inside tends to make the resin coating that has solidified first porous.

For this reason, the resulting powder has low mechanical strength, and when used in a developing machine in a copying machine, the particle size may change, causing trouble. Yet another drawback is that it is impossible to obtain a stable dispersion liquid using a conventional dispersion method for dispersing pigments, etc., resulting in a developer that is non-uniformly charged after drying. Furthermore, after a large number of copies have been made, development becomes impossible. In addition, in order to obtain a stable dispersion of pigments, it is necessary to use more or less ionic or nonionic surfactants, but the surfactants inevitably remain on the powder surface after drying. Become. For this reason, the particles tend to absorb moisture from the air, and the fluidity of the powder deteriorates significantly. This also causes the toner to not function properly in the developing machine. Yet another drawback is that large amounts of solvent must be completely evaporated, resulting in high energy consumption and very high costs associated with solvent recovery. Furthermore, since magnetic toner contains a filler (magnetic material) in its resin, its melt viscosity becomes relatively high, resulting in poor fixability. If a resin with a low softening point is used as a binder to improve this fixing property, the objective will be solved regarding the problem of fixing property, but on the other hand, blocking will occur during storage and toner filming will occur on the photoreceptor. This may cause problems such as causing problems. The present invention has been made to solve the disadvantages of two-component toners and one-component toners, as well as the various problems mentioned above.

It is therefore an object of the present invention to avoid the above-mentioned drawbacks and to develop a static latent image using a toner-based developer which does not require a carrier and which is transferred from a photoreceptor onto a transfer paper using a corona discharger. In this case, it is an object of the present invention to provide a method for producing a one-component developer capable of producing images without transfer bleeding on plain paper. Another object of the present invention is to provide a method for producing a transferable insulating magnetic toner with excellent electrophotographic properties in large quantities at low cost.

Another object of the present invention is to provide a method for producing a one-component developer that does not cause photoreceptor contamination.

Another object of the present invention is to provide a method for producing a one-component developer with good cleaning properties.

Another object of the present invention is to provide a method for producing a one-component developer with excellent durability.

Another object of the present invention is to provide a method for producing a one-component developer that does not cause blocking during storage. Another object of the present invention is to provide a method for producing a one-component developer with good fixing properties.

Another object of the present invention is to provide a method for producing a one-component developer that has excellent resolution and gradation and can produce clear copies without fogging.

Another object of the present invention is to provide a method for producing a one-component developer with good moisture resistance.

Another object of the present invention is to provide a method for producing a one-component developer with good fluidity.

Another object of the present invention is to provide a method for producing a one-component developer that is excellent in preventing toner filming on a photoreceptor.

As a result of research aimed at achieving these objectives, it was discovered that photoreceptor contamination caused by magnetic toner occurs when toner particles contain particles of about 1 µm or less in size.

For example, if this magnetic toner is treated in a hot air stream at a temperature higher than the softening point of the constituent resin, it is possible to substantially eliminate fine particles with a particle diameter of one peak or less that are electrically or physically attached to the toner surface. We were able to find out. Furthermore, when the magnetic toner contains at least one selected from higher fatty acids, metal soaps, higher alcohols, fatty acid amides, ester lubricants, and hydrocarbon lubricants (hereinafter collectively referred to as additives), heat treatment At this stage, the additive contained in the magnetic toner leaches out and coats the surface of the magnetic toner, and the fine particles with a particle size of 1 French or less easily fuse to the toner surface that has been softened by heat and are firmly fixed after cooling. be done. This eliminates photoconductor contamination, resulting in a developer with excellent durability. Furthermore, toner filming on the photoreceptor can be extremely prevented, and the photoreceptor can be used repeatedly for a longer period of time. Additionally, since the surface of the magnetic toner particles is covered with additives, it is possible to use a thermoplastic resin with a low softening point as the binder, providing a one-component magnetic toner with excellent fixing properties. I can do it. Moreover, it has been found that due to the above fact, it is possible to prevent blocking due to temperature inside the storage container or inside the copying machine. Furthermore, since the additives used in the present invention have suitable charging characteristics during development, they can easily provide clear images with excellent gradation, fogging, transfer, etc., and can be made into spherical shapes by heat treatment. It has been found that the toner particles prepared by the above method have excellent fluidity and cleaning properties.

That is, the present invention provides a magnetic toner mainly composed of a thermoplastic resin and ferromagnetic fine particles, which contains a higher fatty acid, a metal soap, a fatty acid amide, a higher alcohol, an ester thickener, and a hydrocarbon flooring agent. For example, the magnetic toner contains at least one selected from the following in an amount of 0.1 to 65% by weight, preferably 0.2 to 20% by weight, based on the weight of the magnetic toner. A transferable insulating property characterized in that the surface of the toner particles is leached and coated with the additive by heat treatment at a temperature higher than the softening point, particularly preferably at a temperature 30° C. or higher higher than the softening point. The present invention relates to a method for producing magnetic toner.

Next, the manufacturing process of the insulating magnetic toner of the present invention will be described. First, the thermoplastic resin, magnetic powder, additives used in the present invention, and if necessary, the beam pigment are thoroughly mixed, and then heated, melted, and kneaded. , pulverize so that the average particle size is 10 to 20 particles.

Next, the pulverized fine particles are atomized using an air jet nozzle into a device that generates a hot air stream heated to a temperature equal to or higher than the softening point of the thermoplastic resin.

The obtained sample is classified and made into a product. An example of a device for forming the hot air flow is shown in FIG.

By operating the blower 1, outside air enters through the air inlet 2, passes through the heater 3, is heated to a temperature equal to or higher than the softening point of the thermoplastic resin, and is introduced into the hot air flow forming device 6. Similarly, a sample 5 is introduced into the hot air flow forming device 6 from the air jet nozzle 4 and is instantaneously heat-treated by the hot air flow 7.
The heat-treated toner particles and air are separated in the collector 8, and the product 10 is collected in the pot 9. On the other hand, air enters the back filter 11 through the blower. In the manufacturing method of the present invention, any device can be used as long as it forms a hot air flow. The temperature condition for the heat treatment may be a temperature equal to or higher than the softening point of the thermoplastic resin, and particularly preferably, good results can be obtained by heat treatment at a temperature 3000 or more higher than the softening point. In the present invention, a hot air flow refers to a state in which gas heated to a certain temperature moves at a certain speed, and heat treatment in the present invention refers to a state in which a sample to be treated moves randomly in the hot air flow. , refers to the form in which the entire system moves together with the hot air current.

Also, although the softening point of the resin cannot be clearly defined, as a guideline, in the present invention, the softening point JI measured by the ring and ball method is used.
Defined by S-K2531. The magnetic substance used in the present invention is a substance that is strongly magnetized in the direction of a magnetic field, preferably black in color, well dispersed in a resin, chemically stable, and having a particle size of 1. Magnetite (triiron tetroxide) is the most preferable because it is desirable to easily obtain fine particles with a size smaller than 100 yen. Representative magnetic or magnetizable materials include metals such as cobalt, iron, nickel and their alloys, ferrites and mixtures thereof, and the like. These ferromagnetic materials preferably have an average particle size of about 0.1 to 1 peak, and are contained in the toner in an amount of about 50 to 16 parts by weight based on 10 parts by weight of the resin component. Particularly preferably resin component 1
0 parts by weight to 80 to 13 parts by weight. The thermoplastic resin used in the present invention has a softening point of 50°C to 2000°C.
0 resin is good, particularly preferably 70oo to 15
It is a resin having a softening point of 0qo.

Therefore, not only resins conventionally used as binder resins for electrophotographic toners can be used, but also all kinds of natural and synthetic resins having thermoplasticity can be used. For example, the styrene resin may be a homopolymer of styrene, or a copolymer of vinyl monomer and styrene. Similarly, phenolic resins, eboxy resins, polyester resins, acrylic resins, polycarbonate resins, and many other thermoplastic resins can be used. Typical examples of higher fatty acids that can be used in the present invention include the following.

Mention may be made of lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, ceracoleic acid, etc., and mixtures thereof.

Representative examples of metal soaps that can be used in the present invention include the following.

Stearic acid and zinc, cadmium, barium, lead, iron,
Metal salts of nickel, cobalt, steel, aluminum, magnesium, etc. Similarly, metal salts obtained from oleic acid, palmitic acid, caprylic acid, caproic acid, linoleic acid, ricinoleic acid, ricinoleic acid, etc. and the various metals mentioned above, and mixtures thereof can be mentioned.

The fatty acid amide that can be used in the present invention is preferably a fatty acid amide compound having a melting point of 60 oo or higher. Examples include compounds of the aforementioned fatty acids and amides such as myristic acid, palmitic acid, and stearic acid, and alkylene bis fatty acid amides. The higher alcohols added to the present invention may be monohydric alcohols or polyhydric alcohols, and typical examples include lauryl alcohol, myristyl alcohol, palmyl alcohol, stearyl alcohol, arachyl alcohol, and behenyl alcohol. I can list many. As fatty acid esters that can be used in the present invention, esters of fatty acids and -hydric alcohols, esters of fatty acids and polyhydric alcohols, partial esters of fatty acids and polyhydric alcohols, etc. can be used. In the present invention, these fatty acid esters or partially saponified products thereof may be used alone, or a mixture consisting of a mixture of various fatty acid esters, or fatty acid esters and partially saponified products thereof may be used. It can also be used as a mixture consisting of a mixture of the following. Hydrocarbon lubricants that can be used in the present invention include natural paraffin, microwax, synthetic paraffin, and chlorinated hydrocarbons.

The mixing ratio of these additives that can be used in the present invention is 0.1 to 65% by weight, particularly preferably 0.2 to 20% by weight, based on the total weight of the toner. If it is too large, it will be difficult to obtain a good image and suitable conditions for development, and if it is too small, the initial purpose will not be achieved and it will be noisy. Any suitable pigment or dye can be used as a colorant and charge control agent in the one-component toner of the present invention. For example, carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue,
Chloride phthalocyanine blue, malachite green oxalate, lamp black, rose bengal and mixtures thereof are used and are included in the magnetic toner in such amounts that upon development a sharp visible image is produced. Toner is obtained by heating and mixing a mixture of magnetic material, resin, additives, and dyes and pigments using two rolls, and then pulverizing and heat-treating the mixture. This pulverization and granulation method has very excellent advantages such as low manufacturing cost, very easy powder processing, and very advantageous in terms of pollution problems. Since the surface of the insulating magnetic toner of the present invention requires that the magnetic particles be exposed from the resin surface,
It is necessary to take this point into consideration when manufacturing it.
The conditions depend on the types of magnetic material and resin used and the content of the magnetic material, but are also influenced by the manufacturing conditions. If the degree of surface exposure of the magnetic particles becomes excessive, a good transferred image will not be obtained, and the amount of triboelectric charge of each toner particle will not be appropriate, so care must be taken.

The magnetic toner obtained in this way is a one-component type developer that does not use a carrier, so it does not have the drawbacks of conventional two-component type developers, and since the magnetic toner particles as a whole are electrically insulating, it is easy to transfer. Clear copies can be obtained on paper, and there is no blocking during toner storage. There is no contamination of the photoreceptor, there is no fogging, and a stable developing action can be guaranteed just by replenishing toner. This is an insulating magnetic toner for electrostatic development with excellent durability.

Next, Examples and Comparative Examples of the present invention will be given, and their effects will be explained.

Parts in Examples and Comparative Examples are by weight unless otherwise specified. Comparative example 1/・Immer SBM-73 (styrenic resin manufactured by Sanyo Chemical Co., Ltd.) 5 and Mapico Black B
Mix 50 parts of L-500 (triiron tetroxide manufactured by Titan Kogyo Co., Ltd.), 2.5 parts of Peerless 155 (carbon black manufactured by Columbia Carbon Co., Ltd.), and 1 part of Oil Black BS (dye manufactured by Orient Chemical Co., Ltd.). The mixture was milled in a ball mill for about 2 hours, kneaded using hot rolls, cooled, pulverized, and classified to have an average particle size of about 15 mm to prepare a toner.

A sample was prepared by adding 0.2% by weight of silica powder (R-972 manufactured by Nippon Aerosil Co., Ltd.) as a flow agent to the obtained toner. The developing device described in the specification of Tokusei Sho 51-26 No. 6 was attached to a U-Bix800 type electrophotographic copying machine manufactured by Konishiroku Photo Industry Co., Ltd., and the sample was filled and transferred onto a zinc oxide photoreceptor. Development and transfer were performed repeatedly. As a result, high-density fogging occurred, and even after copying about 1q of copies, no image appeared and significant staining occurred on the master. Similar results were also obtained when 2% by weight of zinc stearate was added to the above toner and kneaded and ground. Comparative example 2heimer SBM-735
Foundation County, Mapico Plaque BL-5005$ Department, Peerless-
After mixing 1,552.5 parts of oil black BSI and applying a ball mill for about 2 hours, the mixture was kneaded using hot rolls, cooled, and then pulverized.

Next, the powdered toner was blown into a commercially available experimental spray dryer (Mobil Miner, manufactured by Niro Corporation) using an air jet nozzle and instantaneously heat-treated with hot air at 25,000 yen to produce a toner. The toner was classified using a classification stone to obtain a toner having an average particle size of 154, and 0.2% by weight of silica powder was added as a flow agent to the obtained toner to prepare a sample. When this toner was filled into the developing device described in Comparative Example 1 and development and transfer was performed repeatedly,
Although the initial image was clear with no transfer bleeding,
Capri occurred after the actual shooting of 200 women, and the sharpness decreased compared to the initial image. Also, the surface of the zinc oxide photoreceptor was slightly stained. Comparative Example 3 4 parts of Epikot 1004 (epoxy resin manufactured by Shell Chemical Co.) and 6 parts of Mapico Black (triiron tetroxide manufactured by Columbia Carbon) were mixed in a mixed solvent of 7 parts of toluene and 3 parts of acetone. After dispersing in a porcelain ball mill for 3 hours to make the solid content 60%, the above-mentioned strained solvent was further added to adjust the solid content to 20%, and the product was produced by a rotating disk type mist drying method. It was grainy.

When the thus obtained black toner particles having an average particle diameter of about 10 mm were developed and transferred using the apparatus described in Comparative Example 1, the image developed on the photosensitive plate was an extremely good gradation image. A large blurring occurred in the transferred image of the object. In addition, the zinc oxide photoreceptor was significantly contaminated. Example 1 Heimer S
333 parts of BM-7, 1552.5 parts of Mapico Black BL-Arc 05 Hobe, 1552.5 parts of Peerless, 1 part of zinc stearate, and 1 part of behenyl alcohol were thoroughly kneaded using a pressure kneader.

After cooling, this was crushed, and further finely crushed using a jet mill. Next, the pulverized toner was blown into the experimental spray dryer using an air jet nozzle for 100 pm and 1 pm.
25℃, 150 pm, 175qC, 200 pm, 250
Each sample was instantaneously heat-treated at each hot air temperature of qo to produce an insulating magnetic toner. Each of the prepared toners was classified using a classifier to obtain a toner with an average particle size of 15 mm, and 0.2% by weight of silica powder was added as a fluidizing agent to the resulting toner. Samples 1 to 6 were used. Separately, the heat treatment using the spray dryer was instantaneous at 400qC. Comparative sample M similar to samples 1 to 6
．． 7 was created. The only one that was not heat treated was the ship. 1
Comparative sample No. 6 similar to sample No. 8 was created. The content of fine particles of 1 μm or less in these samples was measured using a light transmission particle size distribution analyzer (manufactured by Seishin Enterprise Co., Ltd.), and the sample was measured using a U-BIX200 dish-type electrophotographic copying machine manufactured by Konishiroku Photo Industry Co., Ltd. The number of copies that can be made when filled with
Table 1 shows the image evaluation values classified into three grades: - excellent, × - poor, and △ - somewhat poor. Example 2 / Imar-ST-95 (Polystyrene manufactured by Sanyo Chemical Co., Ltd.) 5
0 parts, part of Mapico Black BL-5005, 1552.5 parts of Peerless, 1 part of matearyl alcohol, 1500 parts
When a formulation of 2 parts of microparaffin (manufactured by Nippon Oil Co., Ltd.) was treated in the same manner as in Comparative Example 2 and development and transfer was repeated, a clear image that was the same as the initial image was obtained even after copying 20,000 copies.

Example 3 Chemitylene PEB-4 (polyester resin manufactured by Sanyo Kasei Co., Ltd.) 5 sparse parts, Mapicoplak BL-50050 parts, Peerless 1552 parts, stearic acid amide 1.5 parts, Lytol (manufactured by Sanwa Yushi Co., Ltd.) 1 part were used in Example 1 shame. The same treatment as for sample 4 was carried out, and a selenium photoreceptor was installed in place of the zinc oxide photoreceptor in a U-BIX200 dish-type copying machine made by Konishiroku Photo Industry Co., Ltd., and development and transfer was performed repeatedly. A clear image was obtained, just like the original image.

It was also predicted that after 50,000 copies, hundreds of thousands of copies could be guaranteed. Example 4 25 parts of Himer UP-110 (polyester resin manufactured by Sanyo Chemical Co., Ltd.), 25 parts of Picolastic E-100 (polystyrene manufactured by Esso Standard Co., Ltd.), Mapico Black BL-
50050 copies, Peerless 1552.5 copies, NAA-
Two parts of Zone (manufactured by Nippon Oil & Fats Co., Ltd.) and a toner with the formulation of Oil Black BSI were added to the vessel of Example 1. The same processing as for sample 5 was performed, and repeated development and transfer was performed using a U-BIX 200 dish-type copying machine manufactured by Nishiroku Photo Industry Co., Ltd. Even after 20,000 copies, a clear image that was the same as the initial image was obtained. .

Example 5 Epikote 1004 (epoxy resin 4 manufactured by Shell Chemical Co., Ltd.)
5 parts of Mapico Black BL-5005, 2.5 parts of Peerless-155, 3 parts of Bisamide (manufactured by Nippon Hydrogen Industry Co., Ltd.), and 1 part of Rikemar B-100 (manufactured by Riken Vitamin Oil Co., Ltd.). is the gunwale of Example 1. The same processing as Sample 6 was carried out, and development and transfer were repeated using a U-BIX200 pig-shaped copying machine manufactured by Roku Konishi Photo Industries Co., Ltd. Even after copying 30,000 copies, a clear image that was the same as the initial image was obtained.

Example 6 Epicort 100440 parts, Mapico Black BL-10
06 Ikaribe, 2 parts of Oil Black BS, 6 parts of zinc stearate, and 2 parts of stearic acid were heated to a temperature of 30,000.
The sample was processed in the same manner as the sample of Comparative Example 2 except that the sample was developed and transferred repeatedly, and no change in the image was observed even after copying 10,000 copies.

[Brief explanation of drawings]

The figure is a schematic diagram of the number of roots showing an example of the insulating magnetic toner manufacturing apparatus of the present invention. In the figure, 1 is a blower, 2 is an air inlet, 3 is a heater,
4 is an air jet nozzle, 5 is a sample, 6 is a hot air flow forming device, 7 is a hot air flow, 8 is a collector, 9 is a pot, 10
indicates the product, and 11 indicates the back filter.

Claims (1)

[Claims] 1. In a method for producing magnetic toner containing thermoplastic resin and ferromagnetic powder as main components, a compound selected from metal soaps, higher fatty acids, fatty acid amides, higher alcohols, hydrocarbon lubricants, and ester lubricants is used. One-component insulation characterized by containing at least one kind of toner component as a toner component and heat-treating mixed, kneaded, and pulverized toner fine particles using hot air flow in a temperature range higher than the softening point of the thermoplastic resin. Method for manufacturing magnetic toner.