JP2817059B2 - Toner and method for producing toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention is a toner composition for electrostatic charge development used in electrophotography, electrostatic recording and electrostatic printing which can be pressure-fixed or heat-fixed at a low temperature. And its manufacturing method.

(Prior Art) As a copying method using electrophotography, an electrostatic latent image is formed by various means on a photoreceptor using a photoconductive substance, and then an external latent image is developed using toner, and paper In general, a method of obtaining a copy by transferring the image onto a sheet and fixing the image is performed.

In this copying method, as a fixing method of the toner image, there are a heating fixing method using an oven or a hot roll, a pressure fixing method for fixing by pressing, and the like.

At present, with the speeding up of copying, power saving, miniaturization, and the spread of terminal printers using electrophotography, advantages such as being able to copy without waiting time when the power is turned on and the simplicity of the fixing device are available. Heat roller fixing and pressure fixing at low temperatures are becoming widespread.

In these fixing systems, sufficient fixing properties cannot be obtained with conventional toners. Because, in order to obtain a sufficient fixing property at a low temperature, it is necessary to use a material having a low Tg or a low melting point as a binder resin, which not only has a problem in the storability of the toner but also causes contamination of a carrier during development, There are also problems such as fusion to the photoreceptor surface.

As the toner used in the pressure fixing method, those which cause plastic deformation under a predetermined pressure (about 3 to 300 kg / cm ² ), specifically, waxes such as polyethylene wax, polyolefin wax and polyamide wax are used. However, among the above waxes, those having a low softening point have a low compression yield value and good fixability, but have problems in pulverizability at the time of toner production, toner storage stability, and the like.

It is not possible to solve these problems with a toner obtained by a conventional pulverization method.

Therefore, recently, a so-called capsule type toner comprising a core material of a soft component and an outer shell of a hard component has been studied.

As a method for producing a toner using a microencapsulation method, an interfacial polymerization method using a polymer synthesis reaction, in
-Situ polymerization method (JP-A-55-70851), encapsulation by spray drying using a polymer emulsion (JP-A-51-124435, JP-A-52-108134), and spray drying method (JP-A-52-108134). 48-90977), a curing coating method in liquid using a method of changing the properties of a polymer, a coacervation method in which phase separation is performed from an organic solution or an aqueous solution (Japanese Patent Application Laid-Open No. 48-90977).
80478), but the conventional methods have limitations on the materials selected as the core material and the shell material, making it difficult to form a uniform shell film and making toner with a uniform particle size difficult. In addition, there is a problem that there is a risk of fire due to the use of a flammable solvent.

In order to fix at a low temperature or at a relatively low pressure, and to maintain fluidity as a powder without causing thermal aggregation during storage or in a developing machine, it is extremely important to control the uniform capsule structure and shell film. In the conventional method, the above structure,
It is impossible to produce a toner having high performance, and a practically satisfactory capsule toner has not yet been obtained.

(Problems to be Solved by the Invention) An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to show good fixability at low temperatures and / or low pressures, and to have good storage stability at high temperatures, and An object of the present invention is to provide a novel toner manufacturing method capable of controlling a uniform capsule structure, a shell film, and a toner particle size to achieve the object.

(Means for Solving the Problems) The object of the present invention is achieved by the following (1), (2) and (3).

(1) A toner comprising particles having a soft component as a main component, in which a vinyl polymer is present as a plurality of spherical bodies, and the outer shell of the particles is a film of a vinyl polymer. A toner characterized by being formed.

(2) An aqueous suspension or emulsion of a vinyl monomer containing an oil-soluble initiator is mixed with an aqueous dispersion of particles mainly composed of a soft component, and the particles are mixed with the vinyl monomer. After swelling, the temperature is raised to a temperature equal to or higher than the decomposition temperature of the oil-soluble initiator, and then the vinyl-based monomer is continuously converted into a water suspension in the form of droplets having a size equal to or less than the average particle size of the swelled particles. The method for producing a toner according to the above (1), wherein the polymerization is carried out by adding the toner.

(3) An aqueous suspension or emulsion of a vinyl monomer containing an oil-soluble initiator is mixed with an aqueous dispersion of particles mainly composed of a soft component, and the particles are mixed with the vinyl monomer. The above item (1), wherein after swelling, the temperature is raised to a temperature not lower than the decomposition temperature of the oil-soluble initiator, and then an emulsion of a vinyl monomer is continuously added to advance the polymerization. A method for producing the toner described in the above.

As a soft substance that is a main component of a core portion of a particle (hereinafter, sometimes referred to as a core particle), a resin that softens at a relatively low temperature (preferably 100 ° C. or lower) and has a low melt viscosity, or A resin that undergoes plastic deformation under pressure (about 3 to 300 kg / cm ² ) is used. Styrene resin, acrylic resin, styrene acrylic resin, styrene diene resin, epoxy resin, polyester resin, polyamide resin, natural wax , Synthetic waxes, higher fatty acids and their derivatives, polyolefins and the like, and these are used alone or in combination.

There is no particular limitation on the preparation of the core particles, and a method of pulverizing by melt kneading and then pulverizing, a method of pulverizing in a polymerization process, a method of pulverizing by a phase separation using a solvent for solubilizing a resin, and the like can be mentioned. .

In the present invention, examples of the vinyl monomer which is a precursor of a vinyl polymer which is a spherical body present in the core particle and an outer shell of the core particle include styrene, vinyl toluene, α
Styrene monomers such as methylstyrene; acrylic acid;
Methacrylic acid, methyl acrylate, ethyl acrylate,
Propyl acrylate, butyl acrylate, acrylic acid 2
-Derivatives of acrylic acid or methacrylic acid such as ethylhexyl, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, dimethylaminoethyl methacrylate, acrylonitrile, acrylamide; ethylenic properties such as ethylene, propylene and butylene Unsaturated monoolefin; vinyl chloride,
Vinyl halides such as vinylidene chloride and virfluoride; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone and methyl isopropenyl ketone; 2-vinylpyridine And nitrogen-containing vinyl compounds such as 4-vinylpyridine and N-vinylpyrrolidone. These vinyl monomers may be used alone, or a plurality of monomers may be used in combination for copolymerization. In addition, any crosslinking agent together with these monomers, for example, divinylbenzene, aromatic divinyl compounds such as divinylnaphthalene and derivatives thereof; ethylene glycol dimethacrylate, diethylenically unsaturated carboxylic acid esters such as diethylene glycol dimethacrylate; Divinyl compounds such as N-divinylaniline and divinyl ether and compounds having three or more vinyl groups can be used alone or in combination of two or more.

The vinyl polymer forms the outer shell of the core particles mainly composed of a soft substance and exists as a spherical body inside the core particles, and prevents thermal aggregation during storage of the toner and in the developing machine, and as a powder. It is necessary to maintain the fluidity of the resin and to have a destructible strength after fixing. Therefore, the glass transition temperature of the vinyl polymer is preferably 40 ° C. or higher, and the above monomer composition and molecular weight are preferably set so that the glass transition temperature of the obtained polymer is 40 ° C. or higher.

The ratio between the core particles and the vinyl polymer constituting the shell film is set to a desired value based on the relationship between the size and specific gravity of the core particles and the thickness and specific gravity of the shell film, but a uniform shell film and fixability are obtained. In order to
The ratio of the core particles to the vinyl polymer constituting the shell film is 1: 0.
The ratio is preferably 5 to 1: 2.

Furthermore, another function of the shell film is that the capsule must be easily broken under the pressure of the fixing roll, and in view of this point, a styrene monomer is preferable among the above monomers.

It is effective to use an appropriate emulsifier when preparing an emulsion of a vinyl monomer. Examples of the emulsifier include sodium dodecylbenzenesulfonate, sodium lauryl sulfate, dialkyl sulfosuccinate, potassium oleate and the like. These are used alone or in combination.

The amount of the emulsifier used is 0.0 per 100 parts by weight of the vinyl monomer.
The amount is from 0.01 to 20 parts by weight, preferably from 0.01 to 10 parts by weight. If an emulsifier is used more than necessary, emulsified droplets are independently present in water, and uniform encapsulation by subsequent polymerization cannot be achieved.

It is effective to use a suitable water-soluble polymer dispersant when preparing a suspension of a vinyl monomer. Examples of the water-soluble polymer dispersant include alkyl cellulose, polyvinyl alcohol, gelatin, starch, carboxymethyl cellulose, polyacrylic acid, polymethacrylic acid, styrene-maleic acid copolymer, polyacrylamide, polyvinyl acetate, and the like. Used alone or in combination. The suspension droplet of the vinyl monomer in the suspension is preferably smaller than the average particle size of the particles serving as the core material. If the average particle size is larger than this, the encapsulation by polymerization is not uniform, and the object cannot be achieved.

When an emulsion or suspension of a vinyl monomer is added to form a shell film, the added vinyl monomer is polymerized while diffusing into core particles containing an initiator to form a shell film. It is necessary to strictly select the polymerization conditions so that the polymerization occurs in the surface layer of the core particles. Therefore, it is preferable to continuously add the emulsion or suspension of the vinyl monomer so as not to diffuse into the core particles faster than the polymerization rate.

Examples of the initiator used in the polymerization include persulfates such as potassium persulfate, hydroperoxides such as cumene hydroperoxide and paramenthane hydroperoxide, water-soluble initiators such as a redox initiator, and lauryl peroxide. And oil-soluble initiators such as peroxides such as benzoyl peroxide, azobisisobutyronitrile, and azo-based compounds such as azobisisovaleronitrile.

When the vinyl monomer containing an oil-soluble initiator is introduced into the core particles, if the amount of the vinyl monomer containing the oil-soluble initiator to be used is too small, the initiator cannot be uniformly introduced into all the core particles. Also, if the amount is too large, the amount of the shell material particles formed in the core particles increases or becomes large, which adversely affects the fixing property. Therefore, the vinyl monomer containing the oil-soluble initiator is 5 to 5 parts of the core particles. 20% by weight is preferred. The vinyl monomer containing an oil-soluble initiator can be easily introduced into the core particles by adding a fine particle obtained by using an emulsifier or a water-soluble polymer dispersant to an aqueous dispersion of the core particles.

Various pigments can be used in the capsule toner according to the present invention. As the pigment, for example, titanium oxide, zinc oxide, carbon black, and other various coloring materials can be used to form a black toner and a color toner. Further, by incorporating magnetic powder, it can be used as a magnetic toner.

The pigment is contained in the capsule toner, inside the core particles,
It may be present at the interface of the outer shell or anywhere in the outer shell.

Further, the capsule toner according to the present invention may contain or be externally added an additive for controlling chargeability, conductivity, fluidity, or adhesion to a photoreceptor or a fixing roll. Additives include metal-containing dyes, dyes such as nigrosine dyes, inorganic fine powders such as carbon black, silica, cerium oxide and zinc oxide, long-chain fatty acids and derivatives thereof such as stearic acid, and fine resin powders such as fluororesins. There is.

(Effect of the Invention) Thus, according to the toner and the method for producing the toner of the present invention, a soft polymer having properties sufficient to maintain the fixability to a support under low-temperature or low-pressure fixing conditions can be obtained. A structure in which the surface of the core particles as the main component is uniformly covered with a shell material having a high glass transition temperature or a high melting point, and the film thickness of the shell is uniformly controlled, and of the same material as the film. A capsule toner having a matrix structure containing a plurality of polymer particles inside can be manufactured.

The toner having such a structure exhibits good fixability at low temperature and / or low pressure, and has good fluidity as a powder without causing thermal aggregation during storage and in a developing machine.

Further, since the soft component of the core particles and the soft component of the outer shell form a matrix structure, the strength after fixing is high.

(Examples) Next, the present invention will be specifically described with reference to examples. The number of copies is based on weight.

Example 1 25 parts of crystalline polyester having a melting point of 40 ° C., magnetite
Fifty parts were melt-dispersed at a temperature of 60 ° C., and further stirred at high shear to disperse the magnetite agglomeration to form a uniform dispersion.

Thereafter, the melt dispersion was added to an aqueous solution of polyvinyl alcohol at 60 ° C., and cooled to room temperature with high shear stirring to obtain core particles having magnetite dispersed in the particles and having an average particle diameter of 7 μm and a sharp distribution. Obtained.

Subsequently, 2.5 parts of styrene monomer and benzoyl peroxide (B
PO) 0.5 part in a 0.2% aqueous solution of polyvinyl alcohol 100
The suspension was mixed under a high shear to obtain a suspension droplet having an average of 3 μm.
This suspension was mixed with the core particle dispersion at 20 ° C., and the mixture was stirred for 60 minutes. After the styrene monomer and BPO were absorbed by the core particles, the temperature was raised to 70 ° C. Subsequently, 25 parts of a styrene monomer were mixed with 1 in a 0.2% aqueous solution of polyvinyl alcohol to form suspension droplets having an average of 3 μm under high shear, and these were sequentially added over 4 hours to carry out polymerization. Thereafter, the temperature of the dispersion was raised to 80 ° C., polymerization was completed under ordinary stirring conditions for 2 hours, and after cooling, dehydration and washing were repeated, followed by drying. The average particle size of the obtained particles was 8.4 μm, and the particle size distribution was the same as that of the core particles. The obtained particles were cut and observed with a transmission electron microscope (TEM). As shown in FIG. 1, spherical particles of a styrene polymer of 0.1 to 0.3 μm were present in the core particles. It was found that a uniform film of about 1 μm of styrene polymer was observed, and that complete capsule particles were obtained. The black mass is magnetite, and the white portion is polyester.

The toner obtained by the above method was applied to a selenium photoreceptor PPC copier to perform copying, and was fixed at room temperature under a pressure of 200 kg / cm ² . The fixability of the obtained image was good, no offset was observed, and the image was good without gloss. Further, this toner did not undergo any aggregation after storage at 50 ° C. overnight.

Example 2 Core particles having an average of 8 μm and a monodispersed particle diameter, containing 20 parts of carbon black in 80 parts of a styrene-butyl acrylate resin having a Tg of 20 ° C. and a molecular weight of 5,000, were obtained by suspension polymerization. Subsequently, 5 parts of a styrene monomer and 2 parts of BPO are emulsified in 200 parts of water in which 1.5 parts of sodium lauryl sulfate and 0.2 part of sodium carbonate are dissolved, and added to an aqueous dispersion of the fine particles (solid concentration: 40%). Then, the mixture was stirred at a temperature of 20 ° C. for 1 hour, and was absorbed by the core particles.

Next, 2 parts of a chromium dye is dissolved in 80 parts of a styrene monomer, and 3.0 parts of sodium lauryl sulfate and sodium carbonate are dissolved.
An emulsion was prepared by emulsification in 400 parts of water in which 0.4 part was dissolved.

The temperature was raised to 70 ° C. in an aqueous dispersion of the core particles having absorbed the styrene monomer and BPO, and the polymerization was carried out while adding the emulsion little by little over 4 hours with stirring. After that, the dispersion is heated to 80 ° C.
, And the polymerization was completed under ordinary stirring conditions for 2 hours. After cooling, dehydration and washing were repeated, followed by drying.

The average particle size of the obtained particles was 10 μm, and the particle size distribution was sharp as in the state of the core particles.
Further, the obtained particles were cut and observed with a TEM.
As shown in the figure, spherical particles of the styrene polymer were present in the core particles, and a uniform film of the styrene polymer was observed around the core particles, indicating that the particles were complete capsule particles.

The toner obtained by the above method was applied to a selenium photoreceptor PPC copier, copied, and fixed with a fixing roller at 150 ° C., whereby sufficient fixing property was obtained. Further, the toner was stored at 50 ° C. for 24 hours, and the aggregation was measured. As a result, no aggregation was found.

Comparative Example 1 The core particles obtained in Example 1 were filtered, dried at 30 ° C., and taken out as a toner. This toner is applied to a selenium photoreceptor PPC copier to make a copy, and the pressure is 200 kg / c at room temperature.
When fixing was performed with a weight of m ² , the obtained image was brittle and the fixing property was inferior to that of Example 1.

In addition, in addition to agglomeration during storage at 50 ° C, agglomeration and filming occurred in a PPC copier.

[Brief description of the drawings]

FIGS. 1 and 2 are photographs of the toner particles obtained in Examples 1 and 2 observed by TEM, respectively.

Claims (3)

(57) [Claims] 1. A toner comprising particles having a soft component as a main component, wherein a vinyl polymer is present as a plurality of spheres in the particles, and the outer shell of the particles is a vinyl polymer. A toner comprising a film. 2. An aqueous dispersion or emulsion of a vinyl monomer containing an oil-soluble initiator is mixed with an aqueous dispersion of particles mainly composed of a soft component, and the particles are mixed with the vinyl monomer. After swelling in the body, the temperature is raised to a temperature not lower than the decomposition temperature of the oil-soluble initiator, and then the vinyl-based monomer is continuously converted into a water suspension in the form of droplets having an average particle diameter of the swelled particles or less. The method according to claim 1, wherein the polymerization is carried out by the addition of an organic solvent. 3. An aqueous suspension or emulsion of a vinyl monomer containing an oil-soluble initiator is mixed with an aqueous dispersion of particles mainly composed of a soft component, and the particles are mixed with the vinyl monomer. After swelling with a body, the temperature is raised to the decomposition temperature of the oil-soluble initiator or higher, and then an emulsion of a vinyl monomer is continuously added to promote polymerization. Item 1) The method for producing a toner according to Item 1.