JPS61258260A - Production of dry process one-component type electrophotographic developer with less deposit on surface - Google Patents

Abstract

PURPOSE:To obtain a developer suitable for high-speed copying by dispersing a magnetic material which is the raw material for the developer into an aq. soln. contg. a surface active agent, emulsion polymn, preventive agent and emulsion dispersion stabilizer and adding the raw material for the developer thereto to form composite particles and washing the particles with a medium contg. alcohol. CONSTITUTION:The surface active agent, emulsion polymn. preventive agent and polymn. dispersion stabilizer are added into an aq. medium so as to co-exist therein at a certain ratio and thereafter the developer is produced by the special dispersion polymn. method to obtain the developer dispersed finely with the filler such as magnetic material into the developer particles while preventing the coalescence among the developer particles and emulsification polymn. and preventing eventually the contamination of the developer particle surface by the emulsion-polymerized substance. The particles are further washed with the solvent contg. alcohol after the polymn. by which the polymn. dispersion stabilizer, etc. sticking to the developer particle surface are removed. The production of the developer having the stable quality is thus made possible. The average grain size of the magnetic material is preferably 0.01-1mum and the content thereof is preferably about 30-70%. The developer which has excellent fluidity and is suitable for high speed copying is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a dry one-component electrophotographic developer with less surface deposits.

[Problems to be solved by conventional technology and invention]

Conventionally, dry one-component electrophotographic developers (hereinafter referred to as developers) are made by dispersing a magnetic material in a synthetic resin by heating, melting, and kneading, and then classifying it into a predetermined particle size using a pulverizer and a classifier. manufactured by the method.

Developers manufactured using conventional methods generally have the following drawbacks.

(1) Due to the pulverization process, the particle size distribution is wide, the yield that matches a predetermined particle size is low, and the manufacturing cost is high.

(Since the two steps are long and complicated, it is not suitable for high-mix, low-volume production.

(3) Since the shape is irregular, it is likely to be further crushed inside the copying machine to produce fine powder.

4) The generated fine powder tends to adhere to the white background, which tends to cause so-called fogging.

(Inorganic substances that are difficult to dissolve in the S resin are easily exposed, impairing the fluidity of the powder.

(6) Exposed inorganic substances make the electrical resistance value of the developer unstable.

(Due to the irregular shape of the sword particles, electrical polarization occurs inside the developer, which tends to cause trailing around the black solid areas.

(8) As a result of the above, the life of the developer is shortened.

To improve these drawbacks, Japanese Patent Application Laid-Open No. 53-17
A method for producing a developer using a polymerization method as disclosed in Japanese Patent No. 735 has been proposed.

According to this method, a well-shaped developer with a narrow particle size distribution can also be produced depending on the selection of conditions.

However, in order to meet the demand for reducing particle size to a practical range as quickly as possible, Japanese Patent Laid-Open No. 54-847
As a result of using a polymerized dispersion stabilizer such as that disclosed in Japanese Patent No. 31, a problem arises in that it remains adsorbed on the particle surface and contaminates the developer.

Furthermore, for the purpose of improving the wetting of magnetic materials, colorants, charge regulators, charge control agents, etc. that are difficult to finely disperse in polymerizable monomers, for example, "Modern Industrial Chemistry", Vol. 16, p. 65 (published by I! Shoten in the morning). Surfactants may also be used, as described in ). However, when a surfactant is used, an emulsion polymer is generated as a by-product, and the resulting emulsion polymer remains attached to the surface of particles purified by dispersion polymerization, contaminating the developer. When this contamination occurs, the following problems occur.

(1) Due to repeated use of the developer, the emulsion polymer adhering to the particle surface adheres to the photoreceptor, changing the surface potential characteristics.

(2) Decreases the blackness of the developer and, in turn, reduces the image density.

(3) Decreases the moisture resistance of the developer.

(4) It impairs the fluidity of the developer.

(5) As a result of the above, the life of the developer is reduced.

The present invention solves the problems of the conventional developer as described above, namely, it is a developer that has fillers sufficiently dispersed inside, has a smooth surface, has excellent fluidity, and is suitable for high-speed copying.
This was done in order to obtain a developer with an uncontaminated surface, a high degree of blackness, excellent moisture resistance, and a long life.

(Means for Solving Problem 1!1) The present invention involves coexisting a surfactant, an emulsion polymerization inhibitor, and a polymerization dispersion stabilizer in a certain proportion in an aqueous medium, and then using a special dispersion method. By manufacturing the developer, we can prevent coalescence between developer particles and emulsion polymerization, and as a result, prevent contamination of the developer particle surface with emulsion polymers while filling with magnetic materials, etc. It is possible to obtain a developer in which substances are uniformly and finely dispersed inside the developer particles, and furthermore, by washing with a solvent containing alcohol after polymerization, it is possible to remove polymerized dispersion stabilizers etc. that adhere to the surface of the developer particles. It was developed based on the discovery that a developer with stable quality can be produced and maintained in a sufficient amount, and contains 0.01 to 1% (by weight) surfactant (the same applies hereinafter) and 0 emulsion polymerization inhibitor. .1-10% and polymerization dispersion stabilizer 0.1-10%
A developer raw material (magnetic material) is dispersed in an aqueous liquid containing a developer material, and a developer raw material containing a polymerizable monomer and a polymerization initiator is added to produce composite particles by the dispersion 1 method, and then a medium containing alcohol is dispersed. The present invention relates to a method for producing a dry one-component electrophotographic developer that is cleaned with less surface deposits.

(Example) In the present invention, surfactant 0.01-1%, emulsion polymerization inhibitor 0.1-10% and polymerization dispersion stabilizer O61-1
An aqueous solution containing 0% is used.

Examples of the surfactant include anionic surfactants such as higher fatty acid salts, alkyl sulfate salts, and alkylbenzene sulfonates; nonionic surfactants such as polyoxyethylene alkyl ether and sorbitan fatty acid ester; and cationic surfactants such as polyoxyethylene alkyl ether and sorbitan fatty acid ester. Examples include alkylamine salts and quaternary ammonium salts that are culm surface active agents, and alkyl betaines that are amphoteric surfactants. These surfactants may be used alone, or two or more of the same type may be used in combination. When two or more different types of surfactants are used in combination, it is preferable to limit the combination to types that do not react when used together. The alkyl chain generally has 8 to 24 carbon atoms, more generally 12 to 18 carbon atoms.

The amount of surfactant used is 0.01 to 1% in the aqueous liquid, preferably 0.02 to 0.1%, and 0.01% for the core.
If it is less than 1%, it will not have a sufficient effect on wettability, which is the purpose of use, and if it exceeds 1%, the dispersion stability of the particles will deteriorate and agglomeration will occur between particles.

Examples of the emulsion polymerization inhibitor include metal salts from the royal family of the periodic table of elements, metal salts from group Ⅰ, specifically sodium, potassium, cadmium, magnesium, calcium,
Examples include hydrochlorides, sulfates, and nitrates of copper, zinc, etc. These may be used alone or in combination with 2fI or more. Among the emulsion polymerization inhibitors, sodium chloride and sodium sulfate are particularly preferred since they exhibit their effects upon reception.

The amount of emulsion polymerization inhibitor used is 0.1 to 10% in the aqueous liquid.
The amount is preferably 0.1 to 2%, and if it is used in excess of 10%, even the desired one-coat reaction may be suppressed, and the appropriate amount varies depending on the type of developer. On the other hand, if the amount used is less than 0.1%, the effect of preventing emulsion polymerization will not be sufficiently expressed.

Specific examples of the polymerization dispersion stabilizer include commonly used water-soluble polymers such as polyvinyl alcohol, polyethylene oxide, methyl cellulose, and droxyethyl cellulose. These may be used alone or in combination of two or more.

``Among the polymerization dispersion stabilizers, polyvinyl alcohol and incompletely saponified polyvinyl alcohol are preferred.

The amount of polymerization dispersion stabilizer used is 0.1 to 10% in the aqueous liquid.
The amount is preferably 1 to 5%, and when the amount used is less than 0.1%, the dispersion state of the particles decreases and aggregation occurs between particles.
If it exceeds 10%, the amount of polymerization dispersion stabilizer remaining on the particle surface increases, making it difficult to obtain stable quality products.

In the present invention, a magnetic material as a developer raw material is dispersed in the aqueous liquid, and a developer raw material containing a polymerizable monomer and a polymerization initiator is added, preferably at a stirring speed of 1.
Composite particles are produced by a dispersion polymerization method at 1000 rpm or more.

Representative examples of the magnetic material include triiron tetroxide, γ-ferric oxide, manganese ferrite, nickel ferrite, and cobalt ferrite. These magnetic materials may be used as they are, or may be surface-treated with a silane coupling agent, oleic acid, etc., if necessary. These may be used alone or in combination of two or more.

The average particle diameter of the magnetic material is preferably approximately 0.01 to 1 mm in order to finally obtain developer particles of 1 to 30 m+. Also, the content in the final developer is as follows:
In order to obtain a developer with good deviations in magnetic properties and fixing properties, it is preferably about 30 to 70%, more preferably about 40 to 60%.

The amount of magnetic material dispersed in the aqueous solution is usually 15
The content is about 35%, and preferably about 20 to 30% in order to obtain a developer with good magnetic properties and fixing properties.

As the polymerizable monomer that can be used in the present invention, any monomer that can produce a thermoplastic resin by polymerization can be used, but vinyl spinning wheel Q is a typical example, and examples include styrene, General-purpose polymerizable monomers such as butyl acrylate, butyl methacrylate, and methyl methacrylate are inexpensive and easy to use industrially. These polymerizable monomers may be used alone or in combination of two or more at the same time or sequentially, but from the viewpoint of easy control of the charging performance and fixing performance of the resulting developer, the combination It is common to use

The polymerization initiator may be any commonly used oil-soluble polymerization initiator without any particular limitation, but depending on the type of carbon black that is generally used as a coloring agent or an electrical resistance control agent, it may be more suitable than a peroxide-based polymerization initiator. In some cases, an azo-based initiator is preferable.

In addition to these components, the developer raw material containing the polymerizable monomer and polymerization initiator may also contain a chain transfer agent such as lauryl mercaptan, a coloring agent, a plasticizer, a crosslinking agent, a charge control agent, an electrical resistance control agent, etc. may be added.

In addition to the magnetic material, polymerizable monomer, and polymerization initiator used as developer raw materials, other components used as necessary (chain transfer agent, colorant, plasticizer, crosslinking agent, charge control agent, electrical resistance agent) etc.), the chain transfer agent is preferably 0.1 to 15% to the polymerizable monomer,
More preferably 1 to 10%, and preferably 0.1 to 20% of the plasticizer and crosslinking agent to the polymerizable l$ monomer.
, more preferably 1 to 10%, a colorant, a charge control agent,
The content of the nitrogen resistance control agent is preferably 0.1 to 10%, more preferably 1 to 5%, based on the developer. To obtain the above composition, the magnetic material is first dispersed in an aqueous liquid using developer raw materials, and the remaining components are added while stirring and the gas phase of the reaction vessel is replaced with nitrogen gas. By carrying out dispersion polymerization, composite particles that serve as a developer in which the filler is sufficiently dispersed inside the particles are manufactured.

The polymerization temperature is generally 40 to 100°C, but from the viewpoint of controlling the polymerization rate, 55 to 85°C is more preferable.

About 20 to 80% of the composite particles obtained in this way,
After separating the composite particles from a dispersion containing preferably about 40 to 60% by a method such as centrifugation or vacuum filtration, the composite particles are washed with an alcohol-containing medium to form a dry one-component electronic material with less deposits on the surface of the present invention. A photographic developer is manufactured.

The alcohol-containing medium is one or more alcohols that can dissolve polyvinyl alcohol, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, 1-propyl alcohol, butanol, and can be removed by washing with water. It refers to an alcohol solution containing two or more types and having a concentration of 10% or more, preferably 30% or more.

There are no particular limitations on the method of cleaning composite particles with a medium containing alcohol, and as long as a small amount of emulsion polymer, polyvinyl alcohol, etc. attached to the composite particles is removed and the composite particles are not destroyed, any method can be used. method can also be adopted. Specific examples of such methods include, for example, a method of washing composite particles by immersing them in a medium containing alcohol;
Examples include a method of washing under stirring. If necessary, such cleaning methods may be combined, or the same method may be applied repeatedly.

In this way, it is possible to obtain a developer according to the present invention with less deposits on the surface of the composite particles, that is, the surface is not contaminated.

Since the surface of the developer according to the present invention obtained as described above has almost no dispersion stabilizer attached to it, the developer can be used as a developer having excellent moisture resistance, excellent fluidity, and long life.

Although it has not been clearly elucidated what mechanism is responsible for the characteristics of the developer according to the present invention, the present inventors believe as follows.

Generally, a polymeric dispersion stabilizer is used to control the particle size of the composite particles to a particle size that is practical for use as a developer. The polymeric dispersion stabilizer used adsorbs around the oil droplets generated by shearing force and prevents the oil droplets from coalescing. Cough oil droplets polymerize into polymerized particles. However, the polymer dispersion stabilizer adsorbed on the polymer particles cannot be easily removed by simple washing with water. However, when washed with a suitable alcohol-containing solvent, the compatibility of the polymerization dispersion stabilizer changes and it is removed from the polymer particles.

On the other hand, if a surfactant that improves the wettability of the surface of the filler is used to suspend a developer in which filler such as a magnetic material is sufficiently dispersed inside the polymer particles, emulsion-polymerized micelles in an aqueous medium will have an effect other than the above-mentioned effect. is also formed, and the surfaces of the composite particles are contaminated by the resulting emulsion polymer. However, when surfactants and emulsification inhibitors are used at appropriate concentrations, the emulsion polymerization inhibitor has the effect of destroying the emulsion polymerization micelles in the aqueous medium without sacrificing the wettability of the filler surface. This suppresses the formation of emulsion polymers and prevents contamination.

Next, the method of the present invention will be explained based on Examples, but the present invention is not limited thereto.

Example 1 In a 500 m separable flask, 230 parts of ion-exchanged water, amphoteric surfactant (Amphitol 86B manufactured by Kao Soap Co., Ltd.)
) 0.192 parts, 10% polyvinyl alcohol (Gohsenol KP-08 manufactured by Nippon Gosei Kagaku Kogyo) aqueous solution 1
00 parts and 1.12 parts of sodium sulfate were added, and after thorough stirring, triiron tetroxide (KN-320 manufactured by Toda Kogyo ■) was added.
72 parts were added and dispersed under stirring.

Apart from this, 57.6 parts of styrene monomer, 19.2 parts of lobethyl methacrylate, 1.6 parts of diethylaminoethyl methacrylate, and 1 part of glycidyl methacrylate.
．． 6 parts, 2-hydroxyethyl methacrylate 1
．． 6 parts, dye (Bontron N01 manufactured by Orient Chemical ■
), 3.2 parts of carbon black (furnace black #44 manufactured by Mitsubishi Chemical Corporation), 4 parts of lauryl mercaptan, and 6 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) were uniformly added. A mixed monomer mixture was prepared.

After replacing the gas phase of the separable flask with nitrogen gas, the above monomer mixture was added and dispersed using a turbine spatula at a rotation speed of 1200 rpm, followed by stirring at 65°C.
The temperature was raised to 1, and the mixture was allowed to react for 2 hours. Thereafter, the temperature was further raised to 80°C and treated for 3 hours to complete the polymerization reaction.

After cooling the polymerization liquid, the generated particles were separated by vacuum filtration, thoroughly washed with water, and then mixed with ethanol:water at a volume ratio of 1:1.
It was washed several times with a mixed solvent of No. 1 and then washed again with water to replace the residual ethanol. After dehydration by filtration, the developer was air-dried to obtain a developer.

The particle size of the obtained developer was 15 mm as measured by Coulter Counter, the shape was substantially spherical and it had excellent fluidity, and the value of the angle of repose test was 38.2''. In addition, SEW (Scan in Q Electr
1 on the surface with HiCrO3COpe! Upon inspection, the surface was smooth and no contaminants were observed. No blocking of the powder occurred even after being left for 10 days at 38° C. and 80% RH. Furthermore, the image characteristics were examined using a Sharp 5F-730 copying machine, and both were excellent in terms of contrast, with an image density of 1.2B and a white background density of 0.01.

Example 2 A developer was produced and evaluated in the same manner as in Example 1, except that 24 parts of sodium chloride was used instead of 1.12 parts of sodium sulfate used in Example 1.

The average particle size of the obtained developer was 25AlI11, the shape was substantially spherical, the fluidity was excellent, and the value of the angle of repose test was 3.
It was 8.8°. When the surface was observed with SEN,
Similar to that obtained in Example 1, the surface was smooth and no contaminants were observed. Further 30℃, 80℃
No blocking of the powder occurred even after standing for 10 days under conditions of %RH.

Example 3 In a 500 m bulk flask, 284 parts of ion exchange water, 0.016 parts of sodium dodecylbenzenesulfonate, 1
40 parts of 0% polyvinyl alcohol (Gohsenol KP-08 manufactured by Nippon Gosei Kagaku Kogyo n) and 1 part of sodium sulfate
After stirring thoroughly, 72 parts of triiron tetroxide (N-320 manufactured by Toda Kogyo ■) was added and dispersed with stirring.

Apart from this, 51.6 parts of styrene monomer, 19.2 parts of n-butyl methacrylate, 3.2 parts of aniline blue,
A liquid was prepared by uniformly mixing 3.2 parts of carbon black (furnace black #50 manufactured by Mitsubishi Chemical Corporation), 4 parts of lauryl mercaptan, and 8 parts of 2,2'-azobisisobutyronitrile.

'After replacing the gas phase of the separable flask with nitrogen gas, the above monomer mixture was added and dispersed at a rotation speed of 130 rpm using a turbine propeller, and then stirred at 65°C.
The temperature was raised to ℃ and allowed to react for 2 hours.

The generated particles were washed with an ethanol-water mixed solvent in the same manner as in Example 1 to obtain a developer.

The average particle size of the obtained developer was 18 Is, the shape was substantially spherical, the fluidity was excellent, and the value of the angle of repose test was 38.0.
It was °. In addition, when the surface was observed using SEW,
The surface was smooth and no contaminants were observed. When the image characteristics were examined using a Sharp O-730 copying machine in the same manner as in Example 1, the image density was 1.17, and the image quality was excellent with particularly little fog.

Comparative Example 1 A developer was produced and evaluated in the same manner as in Example 1, except that the particles produced after polymerization were washed using only water. The surface was sticky, and when it was air-dried, a cake-like lump appeared in some parts. When the strongly solidified particles were loosened and observed under SEN, residual gelatinous polyvinyl alcohol was confirmed.

When the fluidity of the obtained developer was measured, it was found to be extremely poor, and blocking occurred between the magnetic roller and the doctor sleeve, to the extent that it could not be transported. In the angle of repose test method, the funnel became clogged and measurement was impossible.

Comparative Example 2 An attempt was made to produce a developer in the same manner as in Example 2, except that polyvinyl alcohol, which is the polymerization dispersion stabilizer used in Example 2, was not added, but after raising the temperature to 65°C, the developer was produced for 1.5 hours. As time passed, the dispersion stability of the entire polymerization system deteriorated, resulting in lumps, making it impossible to proceed with the reaction any further.

Comparative Example 3 A developer was produced in the same manner as in Example 1 except that the surfactant used in Example 1 was not added.

Although the polymerization reaction itself was carried out without any problems, the shape of the particles produced was amorphous, and when observed with SEN, fillers were found exposed on the surface of the developer. In addition, free fine magnetic substances were confirmed. When the image characteristics of the roughened developer were examined, it was found that the image had a significant amount of fog, and the white background density increased to 0.13. The value of the angle of repose test was 41.2°, and the powder flowability was also inferior to that of Example 1. Moreover, when it was left under conditions of 30° C. and 80% RH, blocking was observed after 3 days.

Comparative Example 4 A developer was produced in the same manner as in Example 3, except that sodium sulfate, the emulsion polymerization inhibitor used in Example 3, was not added. The aqueous phase after polymerization was extremely cloudy.

Use the obtained developer at SEN! When I put it in the dormitory, deposits were observed on the surface, and the color tone of the dried particles did not have sufficient blackness, probably because it was affected by the color tone of the emulsion polymer.
It was grayish. The value of the angle of repose test method is 42.
2°, which was also inferior to that of Example 3 in terms of powder fluidity.

Moreover, when it was left under conditions of 30° C. and 80% R), blocking already occurred after one day and the powder lost its fluidity.

〔Effect of the invention〕

When a developer is produced by the method of the present invention, 0 a developer with an uncontaminated surface can be obtained; 2 a developer with a smooth surface and fillers sufficiently dispersed inside can be obtained; a developer with high blackness can be obtained; The following effects can be obtained: ■ A developer with excellent moisture resistance can be obtained. ■ A developer with excellent fluidity and suitable for high-speed copying can be obtained. ■ A developer with a long life can be replaced.

Claims (1)

[Claims] 1 Surfactant 0.01-1% by weight, emulsifier 0.1
~10% by weight and polymerization dispersion stabilizer 0.1-10% by weight
A magnetic material, which is a developer raw material, is dispersed in an aqueous liquid containing a polymer, and a developer raw material containing a polymerizable monomer and a polymerization initiator is added to produce composite particles by a dispersion polymerization method. A method for producing a dry one-component electrophotographic developer with less surface deposits to be cleaned.