JPH01100562A - Production of toner for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To obtain a toner which is sharp is grain size distribution and is unshaped while maintaining the dispersion stability at the time of suspension polymn. and to prevent defective cleaning by executing a specific method in a production consisting in dispersing a coloring agent and charge control agent into a polymerizable monomer, then executing the suspension polymn. CONSTITUTION:This production process contains the stage for excuting the polymn. by incorporating a polymn.-inert solvent into the polymerizable monomer or absorbing the polymn.-inert solvent in the polymerizable monomer after the polymn. of said monomer, then removing the polymn.-inert solvent. The toner obtd. in such a manner is the so-called unshaped toner having the undulations as if the surfaces are depressed and, therefore, the toner has the excellent cleanability. Since the toner has no sharply pointed parts as with the toner obtd. by a grinding method, the generation of the fine powder by friction with a carrier, etc., is obviated and the excellent printing resistance is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a dry toner for developing electrostatic images in electrophotography, electrostatic recording, and electrostatic printing.

A developing method using a dry toner whose main components are a colorant and a resin is as follows: (1) The dry toner is mixed with a carrier whose particle size is larger than that of the toner, and the toner is charged by friction with a polarity opposite to that of the electrostatic latent image. A method using a two-component developer in which an electrostatic latent image is developed by applying a charge and bringing a developer, which is a mixture of toner and carrier, into contact with the electrostatic latent image. There is a method using a one-component developer that is developed in contact with or in close proximity to.

[Conventional technology and problems]

Conventionally, in order to obtain these toners, thermoplastic resin was melted, coloring agents such as dyes and pigments, and if necessary magnetic materials, tribostatic charge control agents, anti-offset agents, lubricants, etc. were added and thoroughly mixed. After that, it is cooled and solidified, and then finely pulverized.
Methods of classification have been implemented to obtain the required particle size.

However, the methods described above have various drawbacks. First, equipment for many processes is required, such as polymerization equipment for resin production, equipment for kneading, crushers, classifiers, etc., and the number of steps is large and energy consumption is large, which increases costs. It is the cause. The second reason is that it is difficult to obtain a uniform mixture in the kneading process, and the conditions for uniform dispersion are particularly delicate. Thirdly, the grinding process does not only yield fine powder in the appropriate particle size range to obtain clear, capri-free images; fine and coarse particles are produced as by-products that must be classified and removed. There are disadvantages that lead to increased costs, such as the complexity of the process and poor yield for obtaining a desired particle size range.

Fourth, the resulting powder has an angular and amorphous shape due to the pulverization, and the fluidity of the fine powder is poor, and the image fogging is caused by the fine powder generated by both pulverization due to stirring during frictional charging. can be mentioned.

In contrast, Special Publication No. 36-10231, Special Publication No. 47
Publications such as Japanese Patent Publication No. 518305 and Japanese Patent Publication No. 14895/1989 describe methods for producing toners by suspension polymerization. This suspension polymerization method does not require pulverization, the manufacturing process is simplified, and it can be said that the above-mentioned drawbacks have been improved.

In the method for manufacturing toner using suspension polymerization, a mixture consisting of a colorant, a charge control agent, etc. dispersed in a polymerizable monomer is formed into desired particles by mechanical force in an aqueous medium in the presence of a dispersion stabilizer. This is a method in which toner particles are atomized to a fine diameter and then polymerized, and a toner having a substantially spherical shape is obtained.

Although the spherical toner compensates for the drawbacks of the pulverized toner as described above, it has been found that the spherical shape also causes new drawbacks. That is, although the fluidity is excellent, the problem is that the adhesion to the photoreceptor becomes strong.

For this reason, in the cleaning process, the toner on the photoreceptor is not sufficiently removed by the cleaning blade, and a negative image or a positive image is formed on the photoreceptor during continuous copying, resulting in development called a cleaning failure.

In order to solve this problem, a method using a toner consisting of a mixture of spherical particles and irregularly shaped particles (Japanese Patent Laid-Open No. 60-123
No. 857), however, such a method does not completely solve the above-mentioned drawbacks associated with the pulverized toner, and furthermore, the mixing ratio of spherical particles and irregularly shaped particles is 10:1. 100-60:100, which is a higher proportion of amorphous particles, and the cost advantage of using the suspension polymerization method is also halved. In addition, there is a method of obtaining an amorphous toner by using a suspension polymerization method by adjusting the mixing ratio of a surfactant and a dispersant to a specific ratio (Japanese Patent Laid-Open No. 61-67039,
However, this method requires classification because the dispersion stability during polymerization is poor, there are many aggregates, and the particle size distribution of the toner is not relatively wide. There are many problems, such as:

An object of the present invention is to provide a method for producing a toner for developing electrostatic images using a suspension polymerization method, which provides an amorphous toner having excellent cleaning properties.

Another object of the present invention is to provide a method for producing a toner for developing electrostatic images, which maintains good dispersion stability during suspension polymerization and provides a toner with a sharp particle size distribution and an amorphous shape. be.

[Means for solving problems]

In order to solve the above-mentioned problems, the present inventors have made extensive studies and have discovered that electrostatic image development involves dispersing a colorant and a charge control agent in a polymerizable monomer and then carrying out suspension polymerization. By applying a specific method to the production of toner for commercial use, it is possible to obtain a toner with a sharp particle size distribution and an amorphous shape while maintaining dispersion stability during suspension polymerization, thereby solving the problem of poor cleaning. This discovery led to the completion of the present invention.

That is, the present invention provides a method for producing a toner for developing an electrostatic image by a suspension polymerization method after dispersing a colorant and an antistatic agent in a polymerizable monomer. It is characterized by comprising a step of carrying out polymerization by containing a polymerization-inactive solvent, or absorbing a polymerization-inactive solvent after polymerizing the polymerizable monomer, and then removing the polymerization-inactive solvent. The present invention relates to a method for producing a toner for developing an electrostatic image.

The toner obtained in the present invention has excellent cleaning properties because it is a so-called amorphous toner having a concave-like undulation on the surface. Furthermore, unlike toner obtained by a pulverization method, there are no sharp points, so there is no generation of fine powder due to friction with carriers, etc., and therefore, it has excellent rigidity resistance. Furthermore, in the present invention, since polymerization is carried out under a stable suspension state, there are almost no aggregates, and the particle size distribution of the toner does not change in any way compared to when a normal suspension polymerization method is used. Therefore, a toner with a sharp particle size distribution can be obtained.

As described above, the present invention has the cost advantage of using the suspension polymerization method, and also makes it possible to obtain an amorphous toner with excellent cleaning properties, good fluidity, and a sharp particle size distribution. The present invention relates to a method for producing a toner for developing electrostatic images.

The specific method will be explained in detail below.

First, a colorant such as carbon black, a charge control agent, wax, and other toner property improvers are added to the polymerizable monomer, and a polymerization-inactive solvent is further added, and these are mixed and dispersed.

The toner composition thus obtained is used as an oil phase, and suspension polymerization is carried out in the presence of a dispersion stabilizer.

An example of a suspension polymerization method is to add a dispersion of the oil phase to an aqueous phase in which a dispersion stabilizer such as a water-soluble polymer compound or a poorly water-soluble inorganic compound is uniformly dissolved or dispersed, and then add the dispersion liquid of the oil phase to the aqueous phase in which a dispersion stabilizer such as a water-soluble polymer compound or a poorly water-soluble inorganic compound is uniformly dissolved or dispersed. It is dispersed into oil droplets of 5 to 30 μm using a dispersing means such as the above. The weight ratio of oil phase to water phase is 1:2 to 1:1
It is set within a range of 0 so that coalescence of particles does not occur during polymerization. The dispersion liquid in which the oil phase is uniformly dispersed in the water phase is transferred to a polymerization reaction tank equipped with a stirring device, a condenser, a thermometer, a nitrogen introduction pipe, and a dehydration pipe, and the temperature is raised to a temperature at which the polymerization initiator decomposes. Polymerization is carried out under atmosphere.

Next, the temperature is raised to the boiling point of the added polymerization-inactive solvent or the azeotrope point with water, and the polymerization-inactive solvent is distilled out under normal pressure or by reducing the pressure as necessary. By removing it from the toner particles, it is made into an amorphous shape. After removing the solvent, the aqueous phase is removed by filtration and treated with water or dilute acid as required.

Further, after suspension polymerization of a polymerizable monomer in which a colorant such as carbon black, a charge control agent, etc. is dispersed, a polymerization-inactive solvent is added to the suspension and absorbed into toner particles.
Amorphousization can be carried out by distillation, or these methods may be used in combination.

The polymerization-inactive solvent used in the present invention has a solubility parameter of 6.5 to 10.0 (cal/cm3) 1
/2 and whose boiling point at normal pressure is in the range of 10°C to 150°C.

Specific examples of polymerization-inactive solvents used in the present invention include isopropyl ether, pentane, amyl ether,
Hexane, heptane, octane, dodecane, diisopropyl ketone, lauryl alcohol, cyclohexane, diethyl benzoate, anisole, butyl acetate,
Examples include carbon tetrachloride, diethyl ketone, xylene, toluene, ethyl acetate, benzene, chloroform, methyl ethyl ketone, chlorobenzene, 1,2-dichloroethane, dimethyl carbonate, isoamyl alcohol, 1,4-dioxane, nitrobenzene, etc. These can be used alone or in combination of two or more. Among these, those that are azeotropic with water are particularly preferred.

The amount of the polymerization-inactive solvent used in the present invention is preferably 5 to 100 parts by weight, more preferably 10 to 50 parts by weight, based on 100 parts by weight of the polymerizable monomer. If it is less than 5 parts by weight, the toner will not be sufficiently shaped, and if it is more than 100 parts by weight,
This is not preferable because it adversely affects the polymerization, leading to a decrease in molecular weight and polymerization rate, and furthermore, the dispersion stability during polymerization deteriorates.

In the present invention, amorphization occurs. Although the reason is not clear, it is thought that by removing the solvent contained in the toner particles, the volume of the particles decreases, resulting in the appearance of depression-like undulations on the surface.

The charge control agent used in the present invention may be either positively chargeable or negatively chargeable. For example, when a negatively chargeable charge control agent such as an azo complex dye is used, it may be negatively chargeable. When a positively chargeable charge control agent such as nigrosine is used in the toner, a positively chargeable toner can be obtained and can be used as desired. The amount of the charge control agent added is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the polymerizable monomer.

As the polymerizable monomer used in the present invention, a polymerizable monomer having 3 to 25 carbon atoms can be used, such as styrene, p-chlorostyrene, p-methylstyrene, vinyl acetate, hinyl propionate, Vinyl benzoate, methyl acrylate, ethyl acrylate, n-butyl acrylate, 1so-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, n-octyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 1so-butyl methacrylate , diethylaminoethyl methacrylate, t-butylaminomethyl methacrylate, acrylonitrile, 2-vinylpyridine, 4-vinylpyridine, etc. may be used alone or in combination of two or more.

Furthermore, in the present invention, durability can be further improved by adding polyfunctional monomers such as divinylbenzene, ethylene glycol dimethacrylate, trimethylolpropane triacrylate, glycidyl methacrylate, and glycidyl acrylate to the above polymerizable monomers as a crosslinking agent. can produce excellent toner. The content of the polyfunctional monomer is 0.05 to 2 parts by weight per 100 parts by weight of the polymerizable monomer.
The amount is preferably 0 parts by weight, more preferably 0.5 to 5 parts by weight.

In the present invention, commonly used oil-soluble peroxide-based or azo-based initiators can be used as the polymerization initiator. For example, benzoyl peroxide, lauroyl peroxide, 2,
Examples include 2'-azobisisobutyronitrile, 2,2'-azobis-(2,4-dimethylvaleronitrile), orthochlorohendyl peroxide, and orthomethoxybenzoyl peroxide. The amount used is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the polymerizable monomer.

Dispersion stabilizers used in the present invention include water-soluble polymer compounds such as gelatin, starch, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl pyrrolidone, polyvinyl alkyl ether, and polyvinyl alcohol, barium sulfate, calcium sulfate, barium carbonate,
Examples include poorly water-soluble inorganic compounds such as calcium carbonate, magnesium carbonate, and calcium phosphate. The amount of these dispersants used is 0 to 100 parts by weight of the polymerizable monomer.
．． It is preferably 5 to 20 parts by weight, more preferably 2 to 10 parts by weight.
Parts by weight.

Further, the toner obtained in the present invention may contain a low molecular weight olefin polymer known as a so-called mold release agent for the purpose of preventing offset, improving fluidity, improving fixing properties, etc.

This low molecular weight olefin polymer is preferably dispersed in the monomer together with the colorant used in the present invention.

The low molecular weight olefin polymers used in the toner obtained in the present invention include polyethylene, polypropylene, ethylene vinyl acetate copolymer, chlorinated polyethylene wax, polyamide, polyester, polyurethane, polyvinyl butyral, butylene rubber, phenolic resin, epoxy Examples include resins, rosin-modified resins, silicone oils, and silicone waxes.

The amount of the low molecular weight olefin polymer used is preferably 1 to 20 parts by weight per 100 parts by weight of the resin component of the toner.
More preferably, it is 3 to 15 parts by weight. If it is less than 1 part by weight, it may not have a sufficient offset prevention effect, and if it is more than 20 parts by weight, it may gel during polymerization, which is not preferable.

Furthermore, the toner obtained in the present invention can contain a magnetic material and can also be used as a -component toner. When a magnetic substance is contained, it is preferable to disperse it in a polymerizable monomer and use it, similarly to a coloring agent. The content of the magnetic material is 20 parts by weight per 100 parts by weight of the polymerizable monomer.
-200 parts by weight is preferred, more preferably 50-15 parts by weight.
It is 0 parts by weight.

To form an image using the toner obtained in the present invention, for example, by electrophotography, use a selenium photoreceptor or an inorganic light source such as zinc oxide, cadmium sulfide, cadmium selenide, cadmium selenide sulfide, lead oxide, or mercury sulfide. A photoreceptor in which a photosensitive layer containing a conductive material dispersed in a binder resin is provided on a conductive support, or an organic photoconductive material such as anthracene or polyvinylcarbazole is contained in the binder resin as necessary. A photoreceptor in which a photosensitive layer is provided on a conductive support is used. The surface of the photosensitive layer of such a photoreceptor is entirely charged by corona discharge using, for example, a corotron or scorotron charger, and then imagewise exposed to light or the like to form an electrostatic charge image. Next, this electrostatic charge image is developed, for example, by a cascade method or a magnetic brush method, with a developer consisting of a mixture of the toner obtained in the present invention and a glass beads or iron powder carrier to form a toner image. This toner image is transferred onto the transfer paper by being pressed against the transfer paper under, for example, corona discharge. The toner image transferred onto the transfer paper is heat-fixed by a hot roll fixing device coated with a fluororesin or silicone rubber that has releasable properties.

〔Effect of the invention〕

As explained above in detail, the method for producing the toner for developing electrostatic images of the present invention involves mixing and dispersing a colorant, a charge control agent, and other necessary toner property improving agents in a polymerizable monomer. By adding a polymerization-inactive solvent to the toner particles and carrying out suspension polymerization, or by absorbing a polymerization-inactive solvent after polymerizing the polymerizable monomer and further distilling the solvent out from within the toner particles, This is a method of obtaining toner having a so-called amorphous shape, the surface of which has depressions and undulations. As a result, the present inventors were able to significantly improve the poor cleaning properties of spherical toners normally obtained through suspension polymerization due to their shape, while also maintaining the cost advantages of using the suspension polymerization method. In addition, for the first time, it has become possible to maintain the characteristics of the conventional suspension polymerization method, which is that a toner with good fluidity and a sharp particle size distribution can be obtained.

〔Example〕

Examples of the present invention are shown below, but the present invention is not limited thereto. Note that parts in the examples are parts by weight.

Example 1 Styrene 85 parts, n-butyl acrylate 15 parts, divinylbenzene 0.5 parts, carbon black (Mitsubishi Kasei ■
7 parts of low molecular weight polyethylene (manufactured by Mitsui Petrochemical Industries Ltd., #44), 2 parts of low molecular weight polyethylene (Mitsui Hiwax 210P, manufactured by Mitsui Petrochemical Industries Ltd.), and 1.5 parts of a charge control agent (manufactured by Hodogaya Chemical Corporation Ltd., Eisenspiron Black TRI) in a ball mill. After 5 hours of dispersion, 30 parts of toluene and 2 parts of 2,2°-azobisisobutyronitrile were added to tricalcium phosphate (Katayama Chemical).
(manufactured by Kao ■) 10 parts, Perex 0T-P (manufactured by Kao ■) 0.1
and 300 parts of water, and the mixture was stirred for 3 minutes at 6000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo ■).

This suspension was subjected to a polymerization reaction at 75°C for 8 hours in a nitrogen atmosphere at a stirring speed of 1100 rpm in a separable flask equipped with a dehydration tube, a condenser, and a stirring device, and then the temperature was raised to 90"C. Toluene was distilled out.9
After keeping it at 0°C for 1 hour to completely remove toluene, it was filtered, washed with hydrochloric acid, and washed with water, and dried under reduced pressure at 40°C overnight to obtain an average particle size of 11.5μ and a coefficient of variation of 25.
Amorphous toner particles having undulations on the surface of No. 3 were obtained. Here, the coefficient of variation is the standard deviation of the volume distribution of particle sizes divided by the volume average diameter, expressed in %.

When this toner was used for image evaluation using a Sharp 5F8600, no cleaning defects were observed even during continuous copying, and clear images without fog were obtained. Further, even after copying 10,000 copies, the amount of charge did not decrease, and a clear image without fogging was obtained, which was the same as the initial image.

Example 2 In Example 1, toluene was changed to benzene, 2.2゛-
Azobisisobutyronitrile is 2.2”-azobis-(
Suspension polymerization was carried out in the same manner as in Example 1, except that the polymerization temperature was changed to 65° C. (2,4-dimethylvaleronitrile). Then, benzene was distilled off at 75°C for 1 hour.
Benzene is removed from toner particles and the average particle size is 11.8.
Amorphous toner particles having a surface with a depression-like undulation and a coefficient of variation of 26.5 were obtained.

When image evaluation was performed using this toner in the same manner as in Example 1, no cleaning defects were observed and a clear image without fogging was obtained.

Example 3 Suspension polymerization was carried out in the same manner as in Example 2, except that benzene was replaced with cyclohexane. then 7
The pressure was reduced to 100 Torr at 0°C, and cyclohexane was distilled out over 1 hour to remove cyclohexane from the toner particles. Amorphous toner particles were obtained.

When image evaluation was performed using this toner in the same manner as in Example 1, no cleaning defects were observed, and a clear image without fogging was obtained.

Comparative Example 1 A toner was synthesized in exactly the same manner as in Example 1, except that toluene was not added and the solvent removal step was not performed. The obtained toner had an average particle size of 11.8μ and a coefficient of variation of 26.1.
It was a spherical toner.

When this toner was used for image evaluation using a Sharp 5F-8600, poor cleaning occurred during continuous copying.

Example 4 87 parts of styrene, 13 parts of 2-ethylhexyl acrylate
part, 0.2 part of divinylhenzene, carbon black (manufactured by Columbian Carbon Japan, RAVEN2100)
After dispersing 7 parts, low molecular weight polyethylene (manufactured by Mitsui Petrochemical Industries, Ltd., 210P), 2 parts, and 2 parts of a charge control agent (manufactured by Orient Chemical Company, Ltd., S-34) for 8 hours in a ball mill,
2. To which 2 parts of 2'-azobisisobutyronitrile was added, 5 parts of tricalcium phosphate (manufactured by Katayama Kagaku ■), 0.05 part of Demol N (manufactured by Kao ■), and 300 parts of water were mixed. In addition to those, TK homo mixer (manufactured by Tokushu Kika Kogyo ■)
At, soo.

Stir for 2 minutes at rpm.

This suspension was placed in a separable flask equipped with a dehydration tube, a condenser, and a stirring device, and a polymerization reaction was carried out at 65°C for 6 hours in a nitrogen atmosphere at a stirring speed of 1100 rpm, and then at this temperature for 2 hours. , 30 parts of toluene was added dropwise to allow the toner particles to absorb the toluene. After that, 85
Toluene was distilled out at ℃ for 1 hour to remove toluene from inside the toner particles, followed by filtration, washing with hydrochloric acid, and washing with water.
By drying under reduced pressure overnight at 0°C, the average particle size was reduced to 11.
Amorphous toner particles having a surface of 5 μm and a coefficient of variation of 23.8 had depression-like undulations were obtained.

Ta.

When image evaluation was performed using this toner in the same manner as in Example 1, no cleaning defects were observed and a clear image without fogging was obtained.

Claims (1)

[Scope of Claims] 1. In a method for producing a toner for developing an electrostatic image by a suspension polymerization method after dispersing a colorant and a charge control agent in a polymerizable monomer, It is characterized by comprising a step of carrying out polymerization by adding a polymerization-inactive solvent to the monomer, or absorbing a polymerization-inactive solvent after polymerizing the polymerizable monomer, and then removing the polymerization-inactive solvent. A method for producing a toner for developing an electrostatic image. 2. Solubility parameter of polymerization inactive solvent is 6.5-1
0.0 (cal/cm^3)^1^/^2, and the boiling point at normal pressure is in the range of 10°C to 150°C. The method for producing the electrostatic image developing toner described above. 3. The electrostatic image according to claim 1 or 2, wherein the amount of the polymerization-inactive solvent added is 5 to 100 parts by weight per 100 parts by weight of the polymerizable monomer. A method for manufacturing toner for development.