JPS6343744B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic latent image developing method, specifically, an electrostatic latent image developing method in which an electrostatic latent image is developed using a magnetic developer made of a mixture of magnetic toner and non-magnetic toner. The present invention relates to an image developing method.

Conventionally, as electrostatic latent image developing methods, methods using a two-component developer formed by mixing an insulating non-magnetic toner and a carrier, such as a cascade development method and a magnetic brush development method, have been put into practical use. ing. The carrier in this type of development method is involved in transporting and charging the non-magnetic toner, and in some cases functions as a development electrode, but since it is not consumed during development, its function gradually decreases. In addition, there has been a problem in that the mixing ratio of the carrier and the non-magnetic toner changes, resulting in a deterioration in the quality of the developed image. As a way to solve this problem, the applicant prepared a magnetic developer by mixing magnetic toner, which has both the functions of a carrier and a toner, with a non-magnetic toner, and used this magnetic developer to generate electrostatic charges. A new developing method for developing latent images was proposed in Japanese Patent Application No. 158110/1983. In this method, a magnetic developer is prepared by mixing a magnetic toner whose main components are magnetic powder and resin, and an insulating non-magnetic toner whose main components are resin. The non-magnetic toner is conveyed to the development position by the toner, where the electrostatic latent image is developed with both toners, and then the toner image is transferred to the transfer paper by the corona charger.
It is here to stay. In this developing method, the magnetic toner itself is also consumed during development, so there is no problem of deterioration as with conventional carriers.
Even when the same resin is used as a component of magnetic toner and non-magnetic toner, in order for the magnetic toner to maintain its transport function, it is necessary to contain a large amount of magnetic powder in the magnetic toner. It has become clear that as the proportion of resin in the magnetic toner decreases, the fixing properties of the magnetic toner inevitably deteriorate, making it difficult to reproduce halftones and causing problems such as rough area images.

On the other hand, in order to improve the fixing properties of magnetic toner,
It is conceivable to use a resin with a lower softening point than the constituent resin of the non-magnetic toner, but
In this case, new problems arise such as deterioration of the developer over time and aggregation of toner on the sleeve. That is, in the above-mentioned developing method, a magnetic brush developing device is usually used in which the developing sleeve is fixed and a magnet inside the developing sleeve is rotated. must be at a certain high speed, and as a result, eddy currents due to the high-speed changes in the magnetic field are generated in the conductive material such as the developing sleeve, causing heat generation. Therefore, when a resin with a low softening point is used as the constituent resin of the magnetic toner, there are disadvantages in that the toner aggregates on the developing sleeve due to the heat generated by the developing sleeve, or the developer deteriorates significantly over time. There is.

The present invention has been made in view of the problems and drawbacks described above, and is an electrostatic latent material that can simultaneously improve fixing performance, solve problems such as developer deterioration over time, and toner aggregation. It is an object of the present invention to provide an image developing method. The electrostatic latent image developing method according to the present invention includes a magnetic powder, a first resin, and a second resin having a softening point higher than that of the first resin.
A magnetic toner having a resin as a main component, in which a part of the magnetic powder is exposed on the surface of the magnetic toner, a non-exposed part of the magnetic powder is covered with the first resin, and a part of the magnetic powder is covered with the first resin. A magnetic toner bound by the second resin via a resin, and a non-magnetic toner whose main component is a third resin having substantially the same softening point as the second resin. This method is characterized by developing an electrostatic latent image using a magnetic developer.

The magnetic toner used in the electrostatic latent image developing method according to the present invention is mainly composed of magnetic powder, a first resin, and a second resin having a higher softening point than the first resin. In order to ensure that the magnetic powder is exposed on the surface, it is preferable that the surface of the magnetic powder is coated with a first resin (hereinafter referred to as magnetic powder exposed toner). be.

Specifically, the exposed magnetic powder toner having the structure described above is manufactured by the following method. That is, first, magnetic powder is kneaded with a first resin, then kneaded with a second resin having a higher softening point than the first resin at a temperature equal to or higher than the softening point of the second resin, solidified, and then pulverized. It can be manufactured by.

For example, when a magnetic powder-exposed toner is manufactured according to the above method, unlike the case where a magnetic toner is manufactured by kneading the first and second resins at the same time as magnetic powder, the first and second resins are not homogenized. First, magnetic powder is the first
Because the resin is coated with the first resin and dispersed in the second resin with a high softening point, the first
It is easy to break at the resin part, and there is a very high probability that the magnetic powder in that part will be exposed on the surface of the magnetic toner particles. In addition, since the first resin with a low softening point exists in a state attached to the surface of the magnetic powder, it does not lower the softening point (melting point) of the entire magnetic toner, and can prevent the deterioration of the developer over time and the toner. It is also possible to improve fixing properties without causing problems such as aggregation.

The second resin of the magnetic toner and the third resin of the non-magnetic toner may be the same, in short, as long as the third resin has substantially the same softening point as the second resin. good.

As these second and third resins, resins having a relatively high softening point may be used, and usually 80 to 80
Those having a softening point of 180°C, preferably 90 to 140°C are suitable, such as polystyrene resin,
Examples include styrene resins such as styrene/acrylic acid ester copolymers and styrene/acrylonitrile copolymers, and thermoplastic resins such as alicyclic saturated hydrocarbons.

The reason why the softening point of the second resin is set to the above range is that when the softening point of the second resin is less than 80℃, it is 10
Because the magnetic powder is coated with the first resin, which has a low softening point of ℃ or more, the magnetic particles tend to coagulate and solidify due to heat, depending on the mixing ratio with the first resin. If the temperature exceeds 180°C, the magnetic particles must be kneaded at a high temperature during production, and in some cases, the first resin may deteriorate in quality.

Further, as the first resin, a resin having a softening point lower by 10°C or more than the second and third resins may be used, and is usually 50 to 100°C, preferably 50 to 100°C.
Those having a softening point of 85°C are suitable, for example,
Hydrogenated rosin, fatty acid amide, styrene resin,
Examples include thermoplastic resins such as vinyl chloride resin and vinyl acetate resin.

The reason why the softening point of the first resin is set in the above range is that the first resin is used to make it easier to expose the magnetic powder and to improve fixing properties. If the difference from the softening point is less than 10℃,
This is because the effect of exposing the magnetic powder cannot be expected to be sufficient. In addition, if the softening point of the first resin is less than 50°C, the magnetic particles will tend to aggregate and solidify on the sleeve due to heat, and if it exceeds 100°C, the fixing properties will deteriorate due to the relationship with the second resin. It is.

Magnetic powders include iron, cobalt, nickel, chromium, manganese, and their compounds or alloys, such as their metal powders, triiron tetroxide, gamma ferric oxide, chromium dioxide, manganese oxide, ferrite, manganese/copper-based Examples include alloys.

Incidentally, in order to impart a desired color to the magnetic toner or non-magnetic toner, a coloring agent such as carbon black, an inorganic pigment, an organic pigment, etc. may be added, if necessary.

The ratio of the first resin and the second resin in the magnetic toner can be arbitrarily set depending on the resin used and the usage conditions of the magnetic toner, but usually,
The first resin is mixed in an amount of 10 to 90% by weight, preferably 20 to 60% by weight based on the total resin. This means that if the content of the first resin is less than 10% by weight,
Individual powder particles of magnetic powder cannot be sufficiently coated, and the probability that the magnetic powder will be exposed during crushing becomes low, and at the same time, fixing properties become poor. The probability that the magnetic powder will be exposed increases as the first resin part becomes easier to break, but the amount of the first resin exposed on the surface of the charged particles becomes too large and the heat received during storage and use increases. This is because it becomes easy to coagulate and solidify. Also,
The average particle size of both toners is 5 to 50 μm, preferably 10 μm.
~30 μm is suitable.

Next, examples of the electrostatic latent image developing method according to the present invention will be described together with comparative examples thereof.

Example 1 125 parts by weight of triiron tetroxide (average particle size: 0.3 μm),
As a low softening point resin, Picolastic A-75 (manufactured by Etsuo Chemical, styrene resin, softening point: 75℃)25
After mixing and pulverizing the weight parts in a ball mill, they were melt-kneaded in a heating kneader at 120°C, and then separately mixed and pulverized in a ball mill to prepare a high softening point resin called Priorite ACL (Guddoyer). Add a mixture of 100 parts by weight of styrene/acrylic acid ester copolymer (manufactured by Chemical Co., Ltd., softening point: 160°C) and 4 parts by weight of carbon black (average particle size: 0.3 μm), and knead at 170°C for 10 minutes. After cooling and solidifying, the mixture was coarsely pulverized in a hammer mill, finely pulverized in a jet mill, and then classified to produce a magnetic toner having an average particle size of 20 μm.

In addition, 100 parts by weight of Pryolite ACL, 10 parts by weight of carbon black (average particle size: 0.3 μm)
Part by weight and 1 part by weight of oil black were mixed and pulverized in a ball mill, kneaded for 30 minutes at 170°C in a heating kneader, cooled and solidified, and then pulverized and classified in the same manner as magnetic toner. A magnetic toner was produced.

A magnetic developer is prepared by thoroughly mixing 100 parts by weight of the magnetic toner and 50 parts by weight of the non-magnetic toner produced as described above in a V-type stirrer, and this developer is used in a powder image transfer type electrophotographic copying machine. When loaded into the magnetic brush developing device of
Clear, fog-free, high-density, and well-fixed copied images were obtained from the first copy, and toner aggregation did not occur on the developing sleeve even when the magnet rotation speed was increased to 2000 rpm. Further, no deterioration of the developer over time was observed. The magnetic brush developing device has a fixed developing sleeve and a rotating internal magnet, and the magnet rotation speed is
The moving speed of the photoreceptor, which is the surface to be developed, is 1200 rpm.
8.7cm/sec, its highest surface potential is -750V,
Transfer of the toner image on the photoreceptor to plain paper was performed by corona discharge, and fixing was performed using a heat roller method, and the fixing temperature was 180°C.

In addition, when we measured the amount of magnetic toner consumed per 100 mg of total toner consumption using a line image chart and an area image chart as copy documents, we found that each
mg, 20mg.

Comparative Example 1 In Example 1, Pryolite ACL (25 parts by weight), which is the same as the resin added in the next step, was used in place of Picolastick A-75 added in the initial mixing step, and the average particle size was adjusted in the same manner. A 20 μm magnetic toner was produced.

A magnetic developer was prepared by sufficiently mixing this low softening point resin-free magnetic toner (100 parts by weight) with the non-magnetic toner (50 parts by weight) of Example 1, and the developer was continuously produced in the same manner as in Example 1. When we conducted a photo-copying test, we found that some fogging occurred from the first 10 copies, the fixation of the copied images was insufficient and the density was low, and when we increased the developing bias voltage to remove the fogging, the density of the copied images also decreased. It has declined.

Comparative Example 2 In Example 1, all the components of the magnetic toner were simultaneously mixed and pulverized in a ball mill, then melted and kneaded in a heating kneader at 170°C for 30 minutes, and after cooling and solidifying,
It was crushed and classified to produce a magnetic toner with an average particle size of 20 μm.

A magnetic developer was prepared by sufficiently mixing this magnetic toner (100 parts by weight) with the non-magnetic toner (50 parts by weight) of Example 1, and a continuous printing test was conducted in the same manner as in Example 1. The copied image is Comparative Example 1
Although it was better than the original, there was some fogging, and although the fixing performance was good, the number of rotations of the magnet was
When the speed was increased to 2000 rpm, some toner agglomeration was observed on the developing sleeve. Further, when a line image chart and an area image chart were used as original documents, the amount of magnetic toner consumed per 100 mg of total toner consumption was 40 mg and 20 mg, respectively. Although this magnetic toner is slightly inferior to that of Example 1, it can be said that it has sufficiently improved fixing properties and the like compared to Comparative Example 1.

Example 2 Picolastic D-125 (styrene resin manufactured by Etsu Chemical, softening point: 125°C) 100 parts by weight Epicoat 1002 (manufactured by Ciel Chemical, epoxy resin, softening point: 82°C) 50 parts by weight CDX-660 (Toda Industrially manufactured, γ-Fe ₂ O ₃ ) 300 parts by weight Ketsuen Black EC (manufactured by Lion Oil)
10 parts by weight A magnetic toner having an average particle size of 12 μm was produced in the same manner as in Example 1 using the above composition.

A magnetic developer was prepared by sufficiently mixing this magnetic toner (100 parts by weight) with the non-magnetic toner (30 parts by weight) of Example 1, and a continuous printing test was conducted in the same manner as in Example 1. A clear copy image with good fixability and no fog was obtained from one sheet, and toner aggregation did not occur on the developing sleeve even when the rotational speed of the magnet was increased.

Comparative example 3 Picolastick D-125 (softening point: 125°C)
150 parts by weight CDX-660 300 parts by weight Kettchen Black 10 parts by weight After mixing and pulverizing the above composition in a ball mill,
The mixture was sufficiently kneaded at 150° C. in a heating kneader, cooled and solidified, and then crushed and classified in the same manner as in Example 1 to produce a magnetic toner having an average particle size of 12 μm.

A magnetic developer was prepared by sufficiently mixing this magnetic toner (100 parts by weight) with the non-magnetic toner (30 parts by weight) of Example 1, and a continuous printing test was conducted. In addition to causing fogging, the fixing properties of the copied images were also insufficient.

Example 3 Hymer UP110 (manufactured by Sanyo Chemical Co., Ltd., styrene-acrylic copolymer, softening point: 104°C) 100 parts by weight Ester Gum H (manufactured by Arakawa Forestry Chemical Co., Ltd., hydrogenated rosin,
Softening point: 70℃) 40 parts by weight RB-BL (manufactured by Titanium Industries, magnetite)
200 parts by weight Carbon black 10 parts by weight A magnetic toner having an average particle size of 13 μm was produced in the same manner as in Example 1 using the above composition.

A magnetic developer was prepared by sufficiently mixing this magnetic toner (100 parts by weight) with the non-magnetic toner (25 parts by weight) of Example 1, and a continuous printing test was conducted in the same manner as in Example 1, and the same results were obtained. I got good results.

Example 4 Hyma SBM73 (manufactured by Sanyo Kasei, styrene-acrylic copolymer, softening point: 94°C) 80 parts by weight Ester Gum H (softening point: 70°C) 30 parts by weight Triiron tetroxide 100 parts by weight Using the above composition After kneading Estem Gum H and magnetic powder in a heating kneader at 120°C for 30 minutes, Hymer SBM73 was added and kneaded for an additional 30 minutes, cooled and solidified, and crushed and classified in the same manner as in Example 1. A magnetic toner having an average particle size of 14 μm was produced.

In addition, apart from this, Pikorastic D-125
(Softening point: 125℃) 100 parts by weight, carbon black
After kneading 10 parts by weight of Oil Black BS (manufactured by Orient Chemical) in a heating kneader at 130°C for 10 minutes,
The mixture was kneaded at .degree. C. for 5 minutes, cooled and solidified, then pulverized and classified to produce a non-magnetic toner having an average particle size of 15 .mu.m.

A magnetic developer was prepared by sufficiently mixing the above magnetic toner (100 parts by weight) and non-magnetic toner (20 parts by weight), and a continuous printing test was conducted in the same manner as in Example 1. As a result, there was no fog from the beginning. Clear copies were obtained and the fixing properties were also good. In addition, when we investigated the acceptable range for obtaining a copy image with no fog and good fixing properties by varying the toner mixing ratio, we found that the ratio of magnetic toner to non-magnetic toner was 10:0.3~
It was until 10:11.

Example 5 Ferrite (Mn・Zn)O・Fe ₂ O ₃ (manufactured by TDK)
100 parts by weight Amide C (manufactured by Kao Soap, fatty acid amide, softening point: 70°C) 20 parts by weight Priorite AC (styrene-acrylic copolymer, manufactured by Gutdeyer Chemical, softening point: 160°C)
40 parts by weight A magnetic toner having an average particle size of 16 μm was produced in the same manner as in Example 1 using the above composition.

A magnetic developer was prepared by sufficiently mixing this magnetic toner (100 parts by weight) with the non-magnetic toner (50 parts by weight) of Example 4, and a continuous printing test was conducted in the same manner as in Example 1. As in Example 1, a clear copy image with good fixability and no fogging was obtained, and no aggregation of toner on the developing sleeve occurred even when the rotational speed of the magnet was set to 2000 rpm. Also, the upper limit of the mixing ratio of magnetic toner and non-magnetic toner is 10:12.
Magnetic toner consumption for line image chart and area image chart is per 100 mg of toner consumption, respectively.
The doses were 30mg and 25mg.

Example 6 Triiron tetroxide 100 parts by weight Picolastic D-125 (softening point: 125°C)
40 parts by weight Picolastick A-75 (softening point: 75°C) 10 parts by weight Carbon black 4 parts by weight Using the above composition, triiron tetroxide, Picolastick A-75 and a part (10 parts by weight) of Picolastick D-125 were added. After kneading for 10 minutes at 170℃ in a heating kneader,
The remaining Picolastic D-125 and carbon black were added and kneaded for a further 10 minutes. After cooling, a magnetic toner having an average particle size of 22 μm was produced in the same manner as in Example 1.

A magnetic developer was prepared by sufficiently mixing this magnetic toner (100 parts by weight) with the non-magnetic toner (10 parts by weight) produced in Example 4, and a continuous printing test was conducted in the same manner as in Example 1. A clear copy image with good fixability and no fogging was obtained from the beginning, and toner aggregation did not occur on the developing sleeve even when the rotation speed of the magnet was set to 2000 rpm. Also, the upper limit of the mixing ratio of magnetic toner and non-magnetic toner is 10:12.5.
The amount of magnetic toner consumed for the line image chart and the area image chart was 30 mg and 20 mg, respectively.

Example 7 Iron powder (average particle size 5 μm) 100 parts by weight Alcon P-100 (manufactured by Arakawa Forestry Chemical, alicyclic saturated hydrocarbon, softening point: 100°C) 50 parts by weight Picolastic A-50 (softening point: 50°C) ) 30 parts by weight Using the above composition, Picolastic A-50 and iron powder were kneaded in a roll mill at 120°C for 15 minutes, then Alcon P-100 was gradually added, kneaded for 10 minutes, and solidified by cooling. The powder was crushed and classified in the same manner as in 1 to produce a magnetic toner having an average particle size of 50 μm.

This magnetic toner (100 parts by weight) was prepared in the same manner as the non-magnetic toner of Example 4 with the same composition and average particle size.
A magnetic developer was prepared by mixing it with 6 μm non-magnetic toner (30 parts by weight), and a continuous copying test was conducted in the same manner as in Example 1. Clear copied images with good fixability and no fogging from the beginning were obtained. Even when the magnet rotation speed was increased to 2000 rpm, toner aggregation did not occur on the developing sleeve.

As is clear from the above results, according to the electrostatic latent image developing method according to the present invention, it is possible to obtain a clear developed image with no fog and good fixability, and there is no deterioration of the developer over time. In addition, there is no big difference in the amount of magnetic toner consumed for line images and area images, and there is also a wide tolerance range for the mixing ratio of magnetic toner and non-magnetic toner, making stable development possible over a long period of time. Since the toner does not aggregate on the developing sleeve or the like, the developing device can be easily maintained.

Claims (1)

[Scope of Claims] 1. A magnetic toner mainly composed of magnetic powder, a first resin, and a second resin having a higher softening point than the first resin, wherein one of the magnetic powders a magnetic toner in which a portion of the magnetic powder is exposed on the surface of the magnetic toner, and a non-exposed portion of the magnetic powder is covered with the first resin and bonded with the second resin via the first resin; The electrostatic latent image is developed using a magnetic developer mixed with a non-magnetic toner whose main component is a third resin having substantially the same softening point as the second resin. Electrostatic latent image development method. 2. The electrostatic latent image developing method according to claim 1, wherein the second resin and the third resin are the same resin. 3. The electrostatic latent image developing method according to claim 1 or 2, wherein the softening point of the second resin is 10° C. or more higher than the softening point of the first resin.