JPH0629980B2 - Toner for electrostatic image development - Google Patents

Description

The present invention relates to a toner for developing an electrostatic image, and more specifically, a sphericity, preferably produced by a suspension polymerization method,
The present invention relates to a toner for developing an electrostatic charge image, which has excellent particle characteristics such as particle size distribution and in which developing characteristics and fixing characteristics are harmonized.

Conventionally, a toner used for developing an electrostatic image is generally prepared by melting and mixing a colorant and other additives in a thermoplastic resin,
After being uniformly dispersed, the solidified product was finely pulverized and classified to produce colored fine particles having a desired particle size. Although this manufacturing method can produce fairly good toners, it has certain limitations.

That is, the toner obtained using the crushing method must have brittleness so that the material is crushed to some extent. However, if it is too brittle,
In order to obtain a toner having an appropriate particle size distribution after being pulverized too much, it is necessary to cut fine powder which does not match the cost, resulting in an increase in cost. Further, in the developing device of the copying machine, it is sometimes further pulverized. Further, when a material having a low melting point is used to improve the heat fixing property or a material having a pressure fixing property is used, a fusion phenomenon may occur in the crushing device or the classifying device, and continuous production may not be possible.

Other requirements for toners are that they have triboelectric charging properties suitable for development, that they form excellent images, that they do not change in performance when left standing and do not coagulate (blocking, etc.), and that they do not undergo substantial heat or pressure fixing. It has characteristics and does not contaminate the surface of the photoreceptor. Especially in fixing, the offset phenomenon in which toner adheres to the fixing roller and is retransferred to the next copy paper is always a problem.To prevent this, a release agent such as silicone oil is applied to the fixing roller. Things have been done. However, in recent years, a method has been generally used in which the toner contains a polyolefin such as polypropylene or polyethylene and the offset is prevented without applying a release agent to the fixing roller. However, in this method, since the fixing roller itself does not exhibit sufficient effect for preventing offset, an auxiliary fixing roller cleaning device is required,
There was a problem that a large number of copies could not be made without maintenance. Therefore, it was attempted to add a larger amount of polyolefin or to use a polyolefin having a lower melting point, but fusion occurred with a pulverizer or a classifier, or blocking due to exposure of the low melting polyolefin on the toner surface. Or the fluidity is deteriorated and the developability is remarkably lowered.

Therefore, in order to overcome the drawbacks of such a pulverization method, a method of obtaining colored polymer fine particles of a size that can be used as a toner as it is by suspension polymerization, that is, a method of producing a toner by a suspension polymerization method has been proposed. According to this method
Since the pulverization step is not included at all, the toner does not need to be brittle, and since the obtained toner shape is spherical, it has excellent fluidity, and therefore various advantages such as uniform triboelectrification can be obtained.

However, it is not always technically easy to carry out the polymerization in a stable suspension system without coalescence, and to obtain fine polymer particles having a uniform particle size distribution by the polymerization. Therefore, in the polymerizable monomer, a cationic polymerizable monomer or a poorly water-soluble organic amine compound is added,
A method has been proposed in which the interface of polymerizable monomer particles is charged with cations and suspension polymerization is performed in the presence of an anionic dispersant. That is, the anionic dispersant is thereby ionically bound to the surface of the polymerizable monomer particles to prevent coalescence.

However, even by this method, a toner having a sufficiently narrow particle size distribution has not been obtained. The reason is not bound by theory, but in the above-mentioned method, when a cationically polymerizable monomer or a poorly water-soluble organic amine compound is added to the monomer system, these substances become suspended particles on the surface. , The particles are slightly distributed from the monomer system to the dispersion medium system, the interface between the particles and the dispersion medium becomes uncertain, and the suspended particles are slightly unstable, resulting in a sufficiently narrow particle size distribution. It is thought to disappear.

Furthermore, it is difficult for the toner obtained by this method to satisfy the contradictory properties of offset property, fixing property, blocking property and developing property. In the toner obtained by this method, cationic groups are gathered on the particle surface, but since the whole is an almost homogeneous aggregate, it is necessary to reduce the molecular weight and Tg (glass transition point) to improve the heat fixing property. However, the blocking property is deteriorated, and it is reflected in the development, and the image quality is deteriorated. On the contrary, if the polymer is made to have a high molecular weight or is crosslinked in order to improve the blocking property, this causes a vicious cycle that the heat fixing property is deteriorated.

An object of the present invention is to solve the above-mentioned problems, to provide an electrostatic charge image developing toner having excellent particle characteristics such as fluidity and abrasion resistance, and having excellent developing characteristics and fixing characteristics including offset resistance. To provide.

Specifically, the present invention uses an aqueous dispersion medium system containing an anionic inorganic fine powder dispersant and a monomer system containing at least a polymerizable monomer, a cationic polymer and a silicone oil. A toner produced by a suspension polymerization method, wherein the toner has a Wader practical sphericity of 0.95.
A toner having a substantially spherical shape of ˜1.00 and a number average diameter of 5˜25 μm, a cationic polymer is present on the surface of the toner particles, and silicone oil is encapsulated inside the toner particles. The present invention relates to a toner for developing an electrostatic image.

That is, in order to eliminate the above-mentioned drawbacks of the toner for developing an electrostatic image by the conventional method, it is desirable to use a spherical toner having a uniform particle diameter obtained by the suspension polymerization method. According to the present inventors, such a spherical toner is satisfied by having a Wader practical sphericity of 0.95 to 1.00 and a number average diameter of 5 to 25 μm. Therefore, in the present invention, such a spherical toner is obtained by incorporating a cationic polymer and a silicone oil into a polymerizable monomer during suspension polymerization. The reason why a toner having excellent characteristics can be obtained by including such a cationic polymer is not necessarily clear, but is presumed as follows. That is, such a cationic polymer tends to collect on the surface of the suspension particles during suspension polymerization, and pseudo capsule particles are formed by using this as a kind of shell. Therefore, if a material having a relatively low molecular weight and excellent fixing properties is included inside by adjusting the polymerization conditions or selecting other materials, it is possible to fix at a low fixing temperature, as well as offset resistance and blocking resistance. In addition, it is possible to obtain a toner having good abrasion resistance. Furthermore, even if the cationic polymer collects on the surface of the suspended particles, it is not distributed from the monomer system to the dispersion medium system. Therefore, the surface of the suspended particles is stable and the particle size is spherical and uniform. Toner can be obtained. On the other hand, since silicone oil is hydrophobic and has a low molecular weight, it has a polar group and is hard to mix with a cationic polymer having a large molecular weight, and is pushed into the toner, not on the surface where the cationic polymer gathers. Form. Then, the toner comes out of the inside at the time of fixing and remarkably improves the fixability and the offset resistance. Further, the silicone oil is included in the toner without being copolymerized with the monomer and acts as a good plasticizer, release agent or lubricant. As a result of the above-mentioned effects, the toner of the present invention is considered to be an electrostatic image developing toner having excellent properties as a whole.

Hereinafter, the present invention will be described in more detail. In the following description, “%” and “part” representing the quantitative ratio are based on weight unless otherwise specified.

The toner for developing an electrostatic image of the present invention is generally obtained by a suspension polymerization method. More specifically, a cationic polymer, a silicone oil, a colorant, other additives, and a suitable polymerization initiator are mixed or dispersed in the monomer, and the resulting polymerizable mixture is dispersed in an aqueous dispersion medium. , Suspension polymerization.

The following are used as the monomer. That is, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p
-Phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene , Pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene and the like styrene and derivatives thereof; ethylene, propylene, butylene,
Ethylenically unsaturated monoolefins such as isobutylene;
Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate and vinyl benzoate.
Methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethyl methacrylate. Α-Methylene aliphatic monocarboxylic acid esters such as aminoethyl and diethylaminoethyl methacrylate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, acrylic acid Dodecyl, 2-ethylhexyl acrylate, stearyl acrylate,
Acrylic esters such as 2-chloroethyl acrylate and phenyl acrylate; Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N -Vinylpyrrole, N-vinylcarbazole,
N such as N-vinylindole and N-vinylpyrrolidone
-Vinyl compounds; vinyl naphthalenes; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide.

Examples of the cationic polymer used in the present invention include dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl acrylate, Nn-butoxyacrylamide, diacetone acrylamide, acrylamide, N-vinylcarbazole, vinylpyridine, 2-
In addition to vinyl imidazole, 2-hydroxy-3-methacryloxypropyltrimethylammonium chloride and the like, or homopolymers of monomers containing a nitrogen atom in the molecule such as those obtained by quaternizing these nitrogens, these monomers and the above A copolymer with the above monomer is used.

It is preferable to use these cationic polymers in a ratio of 2 to 30 parts with respect to 100 parts of the above-mentioned monomer.

Further, as the silicone oil, oil-soluble silicone oil such as methyl silicone oil, methylphenyl silicone oil, methylchlorinated phenyl silicone oil and the like are used. These silicone oils are preferably used in a ratio of 1 to 15 parts with respect to 100 parts of the above-mentioned monomer. Further, it is preferable to use one having a viscosity of 100 to 300,000 cSt (centistokes).

Further, in addition to the above-mentioned cationic polymer, a homopolymer or copolymer of the above-mentioned monomers or waxes can be further added to the polymerizable mixture.

The polymerizable mixture may be polymerized in the presence of the following crosslinking agent to give a crosslinked polymer.

Divinylbenzene, divinylnaphthalene, divinyl ether, divinyl sulfone, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol dimethacrylate ,
1,6-hexane glycol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2'-bis (4-methacryloxydiethoxyphenyl) propane, 2,2'-bis ( 4-
A general cross-linking agent such as acryloxydiethoxyphenyl) propane, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, dibromoneopentyl glycol dimethacrylate, diallyl phthalate can be appropriately used.

If these crosslinking agents are used in a large amount, they will not dissolve and the fixability will be poor. If the amount used is small, properties such as blocking resistance and durability required as a toner deteriorate, and during heat roll fixing, part of the toner adheres to the roller surface without completely sticking to the paper, It becomes difficult to prevent the offset phenomenon of transfer. Therefore, the amount of these crosslinking agents used is 0.001 to 15% by weight (more preferably 0.1 to 10% by weight) based on the polymerizable mixture.
It is better to use it by weight%.

Further, a colorant such as carbon black, dye or pigment, or a magnetic powder for giving a magnetic toner can be appropriately mixed in the polymerizable mixture.

As the polymerization initiator, any suitable polymerization initiator, for example, azobisisobutyronitrile (AIBN), benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxy carbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide is used. , Lauroyl peroxide, etc. can be used to polymerize the monomers. Generally about 0.1 to 10% of the total weight of the monomers (more preferably 0.5 to 5).
%) Of the initiator is sufficient.

In the toner of the present invention, generally, the polymerizable mixture obtained by mixing the above components is put into an aqueous dispersion medium containing, for example, about 0.1 to 10% of a suitable dispersant, and stirred, It is generally obtained by suspending so as to have a particle size of 25 μm or less and polymerizing at a temperature of 50 ° C. or higher, preferably 70 to 90 ° C.

In the present invention, it is particularly preferable to use an anionic dispersant because it stabilizes the polymerization system and gives a toner having a uniform particle size distribution. This is because the anionic dispersant ionically binds to the cationic polymer and covers the surface of the suspended particles to form a stable system without coalescence. As such an anionic dispersant, fine powder such as colloidal silica such as Aerosil # 200 or # 300 (manufactured by Nippon Aerozil), Nipseal E-220A (manufactured by Nihon Silica), and Fineseal T-32 (manufactured by Tokuyama Soda). Inorganic compounds and the like can be mentioned.

Further, in order to finely disperse the inorganic fine powder dispersant as described above, a surfactant in the range of 0.001 to 0.1% by weight may be used. This is to promote the desired action of the above-mentioned dispersant, and specific examples thereof include sodium dodecylbenzenesulfonate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, and allyl-alkyl-polyether sulfone. Sodium acid salt, sodium oleate, sodium laurate, sodium caprate, sodium caprylate, sodium caproate, potassium stearate, calcium oleate, 3,3-disulfonediphenylurea-4,4-diazo-bis-amino- 8-naphthol-
Sodium 6-sulfonate, ortho-carboxybenzene-azo-dimethylaniline, 2,2,5,5-tetramethyl-triphenylmethane-4,4-diazo-bis-
Examples include β-naphthol-sodium disulfonate and the like.

A toner is obtained by treating the fine particulate polymer obtained by the suspension polymerization as described above by washing, filtering, decanting, centrifuging, etc., collecting and drying.

In this way, the electrostatic image developing toner of the present invention is obtained as a substantially spherical toner having a Wadell practical sphericity of 0.95 to 1.00 and a number average diameter of 5 to 25 μm.
Here, the Wadell's practical sphericity is a value represented by the ratio of the diameter of a circle having an area equal to the projected area of the target particle and the diameter of the smallest circle circumscribing the projected image of the particle, and more specifically Specifically, it was measured by the following method. That is, an appropriate amount of toner is placed on a slide glass and dispersed so that individual toner particles do not come into contact with each other or overlap each other. These toner particles are
0 (manufactured by Nippon Regulator) is used to project a microscope with a magnification of 500x on the CRT screen. Luzex 4 here
As for 50, if individual particles exist separately, any one can be freely selected and its projected area can be measured, so that the diameter of a circle having an equal area can be calculated. On the other hand, take a picture of this CRT screen as it is,
"The diameter of the smallest circle circumscribing the projected image of the particle is determined by drawing. Here, the above ratio is calculated for 100 randomly selected toner particles, and the average value thereof is calculated to obtain the" Practical sphericity of Wader ". did.

The number average diameter is Coulter Counter Type II,
The measurement was performed by calibrating with a polystyrene standard sample with an aperture diameter of 100 μm.

Since the toner obtained by the suspension polymerization method according to the present invention is obtained without any pulverization step, brittleness is not required, and the shape is generally spherical and the particle size distribution is narrow. In particular, a toner having a Wadell practical sphericity of 0.95 to 1.00 and a number average diameter of 5 to 25μ is excellent in fluidity, and is particularly close to a true sphere, and has little fine powder and coarse powder.
An image with uniform triboelectrification and free from fog and black spots can be obtained. Actually, if the sphericity is less than 0.95, fog is conspicuous in the obtained image, and if the particle size is less than 5μ, there are many fine powders and fog is conspicuous. However, it is difficult to say a high-quality image.

A charge control agent and a fluidity modifier may be further mixed (externally added) to the toner of the present invention, if necessary.

The obtained toner can be applied to all known electrostatic image development methods. For example, two-component developing method such as cascade method, magnetic brush method, microtoning method; one-component developing method using magnetic toner such as conductive one-component developing method, insulating one-component developing method, jumping developing method; powder cloud Method and fur brush method; used in a non-magnetic one-component developing method in which the toner is carried on a toner carrier by electrostatic force and conveyed to a developing section for development.

Hereinafter, the present invention will be described more specifically with reference to Examples.

Example 1 Each of the above components is heated to 70 ° C., a copolymer, silicone oil (BI-3000), an initiator and the like are dissolved in a styrene monomer, and TK homomixer (manufactured by Tokushu Kika Kogyo)
Mix for about 5 minutes while heating to about 60 ° C. in a vessel equipped with a high shear mixing device such as.

Separately, 4 g of colloidal silica (Aerogel # 200), which is an inorganic fine powder dispersant that is anionically charged in water, is dispersed in 1000 cc of water, heated to about 60 ° C., and the above monomer system is stirred under stirring by a TK homomixer. Input, 4000r
Stir at pm for about 1 hour. After that, the mixed system was stirred with a paddle stirring blade to complete the polymerization. After that, the dispersant was removed, followed by washing with water, drying and drying to obtain a toner.

The obtained toner has a number average diameter of 9.1 μm (Coulter counter, aperture 100 μ), the styrene-dimethylaminoethyl methacrylate copolymer is unevenly distributed on the surface of the toner particles, and the silicone oil is good inside the toner particles. Was included in.

Image output is mixed iron powder carrier EFV ^250/400 (the Japan iron powder) toner as a toner concentration of 10 wt%,
Reversal development was performed with a copying machine NP5500 as a developer. Further, the fixing property test was carried out by using a fixing device of PC-10 to which a releasing agent such as silicone oil was not applied. The fluidity was judged by visual inspection in the actual developing device.

As a result, a sharp fog-free image was obtained. At a fixing temperature of 150 ° C., both offset property and fixability were good.

Example 2 A toner was obtained from the above materials in the same manner as in Example 1.
The obtained toner had a number average diameter of 9μ.

Images were printed by PC-10 copying, and the fixing property of the same machine was used.

As a result, a good image without sharp fog was obtained, and the offset development was not observed even when the fixing temperature was set to 150 ° C. and 2000 images were continuously printed. A toner was obtained from the above components in the same manner as in Example 1.

Using the toner thus obtained, image formation was carried out in the same manner as in Example 1. As a result, a sharp and good image free from fog was similarly obtained.

Continuation of the front page (56) Reference JP-A-56-110945 (JP, A) JP-A-54-54039 (JP, A) JP-A-57-11354 (JP, A) JP-A-59-50450 (JP , A) JP 54-48243 (JP, A) JP 55-135856 (JP, A) JP 47-57830 (JP, B1) JP 55-50964 (JP, B2)

Claims (1)

[Claims] 1. A suspension polymerization method using an aqueous dispersion medium system containing an anionic inorganic fine powder dispersant and a monomer system containing at least a polymerizable monomer, a cationic polymer and a silicone oil. The toner having a practical sphericity of Wader of 0.95 to 1.00.
Of the toner having a substantially spherical shape and a number average diameter of 5 to 25 μm, a cationic polymer is present on the surface of the toner particles, and a silicone oil is encapsulated inside the toner particles. Toner for charge image development.