JPS63210849A - Electrostatic charge image developing toner and its manufacture - Google Patents

Abstract

PURPOSE:To enhance blackness, coloring power, and image density by selecting a carbon black having a comparatively small specific surface area and a pH of <=7.0 and adding an aluminum coupling agent to a polymerizable composition containing this. CONSTITUTION:The spherical toner particles containing a monomer capable of radical polymerization, the carbon black having a specific surface area of <=300m<2>/g and a pH of <=7.0, and the aluminum coupling agent are suspended in an aqueous medium, and polymerized in the presence of a radical polymerization initiator,and these toner particles have each a true sphericalicity of >=0.90 defined by the expression shown on the right, where r1 is the longer diameter of the toner particle and rs is its shorter one, thus permitting the blackness and the coloring power of the toner to be enhanced, an image high in density to be formed, and tendency of blocking during development to be hardly found.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a toner for developing electrostatic images and a method for producing the same. The present invention relates to a method for producing toner with good yield during a fixing resin polymerization step.

(Prior art) A toner for visualizing (developing) an electrostatic charge image using electrophotography or the like uses a fixing resin medium such as styrene resin, and carbon black etc. dispersed in this resin medium. A granulated composition containing a coloring agent is widely used.

The most typical manufacturing method for this toner is to melt and knead the aforementioned resin medium and colorant, cool and pulverize this kneaded composition, and
It consists of the process of classifying the pulverized material and aligning it within a certain particle size range. However, carbon black tends to form a chain structure even in the resin, making it difficult to uniformly atomize and disperse it in the resin.

As a solution to this drawback, Japanese Patent Application Laid-Open No. 60-9345
No. 2 describes that carbon black treated with an aluminum-based coupling agent is uniformly dispersed in a binder resin by melt-kneading, and then pulverized and classified to produce a toner.

(Problems to be Solved by the Invention) However, the yield of toner obtained by this pulverization and classification is low, and a large amount of equipment is required for these operations, which makes toner manufacturing cost extremely high. It is said that Further, since the shape of the obtained particles is irregular, the fluidity of the toner is generally low, and there is also a drawback that blocking is likely to occur.

Further, even if carbon black is surface-treated by melt-kneading with a fixing resin, complete atomization and dispersion is still difficult.

If the carbon black is not uniformly dispersed in the fixing resin medium, the degree of blackness and coloring power will be poor, leading to a decrease in image density. Furthermore, the effect of treating carbon black with a coupling agent does not simply depend on the type of coupling agent and the amount of treatment, but also greatly depends on the chemical and physical properties of the surface of the carbon black itself.
Since it is also affected by the mixing operation with the fixing resin, conventional means have not been able to achieve sufficiently satisfactory results.

(Means for Solving the Problems) The present inventors selected carbon black with a relatively small specific surface and a pH value of 7.0 or less as carbon black for toner; and a radically polymerizable monomer and suspended in an aqueous medium to polymerize into spherical particles; and adding an aluminum coupling agent to this polymerizable composition, It has been found that this is important in obtaining spherical toner particles in which carbon black is uniformly dispersed in a fixing resin medium.

According to the present invention, there is provided a toner for developing an electrostatic image comprising a composition of a fixing resin made of a radically polymerizable thermoplastic resin and carbon black dispersed in the fixing resin, in which the toner has the following formula: rl represents the long axis of the toner particle, and rs represents the short axis of the toner particle. Carbon black consists of spherical particles with a circularity of 0.90 or more defined as Provided is a toner characterized in that it is carbon black having a value of 7.0 or less, and an aluminum coupling agent is present in the toner.

According to the present invention, a composition containing a radically polymerizable monomer, a carbon black having a specific surface area of 300 rn''/g or less, a pi value of 7.0 or less, and an aluminum coupling agent is added to an aqueous medium. Production of a toner for developing electrostatic images, which comprises suspending the particles and polymerizing the suspended particles in the presence of a radical initiator to obtain spherical particles consisting of a fixing resin and carbon black dispersed in the resin. A method is provided.

(Function) In the present invention, carbon black for toner has a relatively small specific surface area, that is, a specific surface area (BET) of 30
The first characteristic is to use carbon black with a pH value of 7.0 or less at a temperature of 0 m''/g or less.The pH value of carbon black is
The pH of an aqueous suspension of carbon black, p
Carbon black with a low H value is characterized by containing carbon, hydrogen, and a considerable amount of oxygen (generally 2 to 12% by weight) due to its manufacturing and processing methods. It is recognized that this oxygen exists as a polar group on the surface of the carbon black particles, but the existence of these polar groups causes the carbon black particles to be integrated into the fixing resin monomer due to the cooperative action with the aluminum coupling agent. It is said to be a method of atomization and dispersion.

It is also important that this carbon black has a specific surface area of 300 m'/g or less, and if the specific surface area exceeds this range, even if it is used in combination with an aluminum coupling agent, It becomes difficult to uniformly atomize and disperse the monomer, and the conversion rate of monomer to polymer and polymerization rate also tend to decrease. This seems to be related to the fact that the larger the specific surface area, the greater the surface activity and the greater the tendency for particles to aggregate with each other, and the less effective the aluminum coupling agent is.

Channel type carbon blacks suitable for the purpose of the present invention include Special Black 4, Special Black 5,
It is available as MA-100, but is of course not limited to these.

In the present invention, a composition containing the channel carbon black, a fixing resin monomer, and an aluminum coupling agent is suspended in an aqueous medium, and the suspended particles are polymerized in the presence of a radical initiator. is the second characteristic.

That is, by adopting this method, not only can spherical particles of the resin-carbon black composition with a particle size suitable for the toner be produced all at once in the polymerization process of the fixing resin, but also carbon black particles can be produced at once. It has the advantage that the dispersion in the resin becomes extremely fine. Also,
According to the present invention, the aluminum coupling agent does not require surface treatment of individual carbon black particles, and can be made into uniform fine particles by simply adding the aluminum coupling agent into the monomer. This makes it possible to perform chemical dispersion.

Generally, when carbon black is added to a fixing resin monomer, its polymerization rate tends to decrease, and the conversion rate to a polymer also tends to decrease. This is thought to be due to the presence of quinoidal oxygen on the surface of carbon black, which exhibits a polymerization inhibiting effect. According to the present invention, by using carbon black with a relatively small specific surface area as the carbon black and also containing an aluminum coupling agent in the polymerization composition, the polymerization rate and conversion rate to a polymer can be increased to a high level. This makes it possible to maintain the

As coupling agents, many silane-based and titanium-based coupling agents other than aluminum-based coupling agents are known, and are also widely used in various fields. However, according to the research conducted by the present inventors, the use of silane coupling agents and titanium coupling agents for this purpose has little effect, and that the various effects described above are caused by the use of aluminum coupling agents. It is unique to A suitable example of an aluminum-based coupling agent is, but is not limited to, acetalkoxyaluminum diisopropylate.

In the present invention, the channel type carbon black is preferably used in an amount of 1 to 20% by weight, particularly 2 to 10% by weight, based on the monomer, while the aluminum coupling agent is used in an amount of 0.1 to 30% by weight, based on the carbon black.
, especially in an amount of 10 to 30% by weight.

In the present invention, the monomers used are radically polymerizable, and the resulting polymer has the fixing properties and electrodetection properties required for toners. One type or a combination of two or more types may be used subject to the above-mentioned limitations. Suitable examples of such monomers are:
These include monovinyl aromatic monomers, acrylic monomers, vinyl ester monomers, vinyl ether monomers, diolefin monomers, monoolefin monomers, and the like.

As a monovinyl aromatic carmer, R1 is a hydrogen atom, a lower alkyl group, or a halogen atom, and R2 is a hydrogen atom, a lower alkyl group, a halogen atom, an alkoxy group, an amino group, a nitro group, or a vinyl group. or a monovinyl aromatic hydrocarbon which is a carboxyl group, such as styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene,
o +, m +, p-chlorostyrene, p-ethylstyrene, sodium styrene sulfonate, divinylbenzene alone or in combination of 2fff1 or more, and furthermore, the other monomers mentioned above include the following: Each can be mentioned.

Formula % Formula % (2) In the formula, R3 is a hydrogen atom or a lower alkyl group, and R4 is a hydrogen atom, a hydrocarbon group having up to 12 carbon atoms, a hydroxyalkyl group, a vinyl ester group, or an aminoalkyl group. Monomers such as acrylic acid, methacrylic acid,
Methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, β-hydroxyethyl acrylate, γ -Propyl hydroxyacrylate, δ-butyl hydroxyacrylate, β-ethyl hydroxymethacrylate, γ-aminopropyl acrylate, γ-N-N-diethylaminopropyl acrylate, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate acid esters, etc.

Vinyl esters of formula % formula % where R6 is a hydrogen atom or a lower alkyl group, such as vinyl formate, vinyl acetate, vinyl propionate, etc.

Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl-〇-butyl ether, vinyl phenyl ether, vinyl cyclohexyl ether, etc., where R6 is a monovalent hydrocarbon group having up to 12 carbon atoms.

Diolefins of the formula, in which each of R7%ResR9 is a hydrogen atom, a lower alkyl group, or a halogen atom, particularly butadiene, isoprene, chlorobrene, and the like.

Monoolefins of the formula, IG CH2=C-R11 (6), in which each of R3゜ and R11 is a hydrogen atom or a lower alkyl group, especially ethylene, Propylene, isophthylene, phthene-1, pentene-1,4-methylpentene-1, etc.

In the present invention, in addition to the above-mentioned essential components, additive components that are desirable to be included in the toner can be blended into the polymerization system prior to polymerization.

For example, for use as a two-component pigment, charge control agents known per se, such as nigrosine base (C15045
), Oil Black (CI26150), Spiron Black, and other oil-soluble dyes, naphthenic acid metal salts, fatty metal soaps, resin acid soaps, etc. can be blended. , low molecular weight polyethylene, low molecular weight polypropylene, various waxes,
A mold release agent such as silicone oil can be included.

In the method of the present invention, the above-mentioned raw materials are suspended in water. Organic or inorganic dispersants are generally used to stabilize the suspension in water.

Examples of organic dispersants include gelatin, starch, water-soluble starch conductors, water-soluble cellulose conductors such as carboxymethylcellulose and etocel, water-soluble polymers such as polyvinyl alcohol, water-soluble acrylic resins, vinyl ether-maleic acid copolymers, etc. , anionic, nonionic, cationic or amphoteric surfactants.

Examples of the inorganic dispersant include poorly soluble inorganic fine particles such as various clays such as calcium carbonate, magnesium carbonate, magnesium phosphate, barium sulfate, silica, alumina, talc, and bentonite, diatomaceous clay, and the like.

These inorganic or organic dispersants can be used alone or in combination of two or more.

In the case of the present invention, if desired, although generally not necessary,
In addition to the above-mentioned dispersant, water-soluble salts such as NaCl, C1, Na2SO4, etc. can also be used for the purpose of adjusting the specific gravity, surface tension, viscosity, etc. of the medium.

As the polymerization initiator, azo compounds such as azobisisobutyronitrile, and peroxides such as cumene hydroperoxide, t-butyl hydroperoxide, benzoyl peroxide, and lauroyl peroxide, which are soluble in the polymer, are used. used.

The ratio of monomer to water can vary quite widely, but is generally from 1=99 to 50:50, especially from 5:95 to 3.
It is preferable to use a weight ratio of 0:70. The amount of dispersant used varies depending on the type, but for water-soluble polymer dispersants,
0.1 to 10% by weight, especially 0.5 to 51% by weight
It is best to use an inorganic dispersant at a concentration of 0.0 per monomer.
It is preferred to use amounts of 1 to 10% by weight, especially 0.1 to 5% by weight. If surfactants are used, they should not be used in amounts such that the suspended particles become emulsion sized. The amount of the radical polymerization initiator is 0.1 to 0.1 per monomer.

It is preferred to use an amount of 10% by weight, especially 0.5 to 5% by weight.

The polymerization temperature is generally 40 to 100°C, particularly 50 to 90°C.
The temperature range is suitable, and although the polymerization time varies depending on the type of monomer, it is preferable to select a time for completing the polymerization from a range of 2 to 20 hours.

According to the invention, the roundness (
True spherical particles having D) in a range of 0.9 or more, particularly 0.95 or more are obtained. Further, according to the present invention, by carrying out polymerization under the above conditions, the particle size of the produced polymer particles, that is, toner particles, can be adjusted to 1 to 30 μm, particularly 5 to 20 μm.
It is easy to control the particle size within this range, and its particle size distribution is extremely sharp, and its standard deviation is generally within 3. The generated particles are separated from the reaction medium, subjected to purification operations such as washing if necessary, and dried to produce a toner product.

The colored particles for toner are sprinkled with carbon black, hydrophobic silica, etc., if necessary, to form a final toner.

(Effects of the Invention) According to the present invention, by completely and uniformly atomizing and dispersing carbon black in a fixing resin medium, it is possible to increase the degree of blackness and coloring of a toner and form a high-density image. Can be done. Furthermore, since this toner is perfectly spherical and contains no residual particles, it has excellent fluidity and has almost no blocking tendency during development.

Further, it has the advantage that spherical toner particles of a predetermined particle size can be obtained all at once in the polymerization process of the fixing resin, resulting in a high yield and high productivity.

Examples of the present invention are shown below, but the present invention is not limited thereto.

Example-1 Carbon black: MA-Zoo (specific surface area 134rr
? 20 weight parts of toluene in which 5 parts by weight of the aluminum coupling agent AL-M (acetalkoxydiisopropylate) (manufactured by Ajinomoto ■) was dissolved in 5 parts by weight of the aluminum coupling agent AL-M (acetalkoxydiisopropylate) (manufactured by Ajinomoto ■) After drying under reduced pressure, carbon black treated with an aluminum coupling agent was obtained.70 parts by weight of styrene and 30 parts by weight of n-butyl methacrylate were added to 5 parts by weight of this AL-M treated carbon black. A carbon black dispersion was obtained by stirring for 5 minutes at 3000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo).The obtained carbon black dispersion was examined under an optical microscope t(xs
When observed at oo), no carbon black aggregates were observed, and the dispersibility was good.

To this carbon black dispersion, 2 parts by weight of charge control agent Bontron S-34 (manufactured by Orient Kagaku ■), 2 parts by weight of mold release agent Viscol 550P (manufactured by Sanyo Chemical ■), and 2 parts by weight of polymerization initiator 2'-azobis-( 2-4 dimethylvaleronitrile) was added and thoroughly dispersed.Next, the above dispersion was added to a 2% by weight polyvinyl alcohol aqueous solution, and mixed at 6000 rpm using a TK homomixer.
After stirring for 0 minutes, oil droplets were obtained. These oil droplets are very stable;
As a result of observation with an optical microscope, the property imparting agent such as carbon black was uniformly dispersed in the oil droplets. Thereafter, the stirrer was stirred at a stirring speed of 60 rpm for 70 min under a nitrogen stream.
The polymerization reaction was completed at ℃ for 5 hours.

After the polymerization reaction was completed, dehydration and washing were repeated and dried to obtain a toner of the present invention having an average particle size of 12 μm.

When an image was formed using the toner obtained as described above in an electrophotographic copying machine DC-1001 (manufactured by Sanda Kogyo ■), an image with little fog and a high degree of blackening was obtained. . Further, when this was measured with a reflection densitometer, good results were obtained, with a fog density of 0.003 and an image density of a solid black area of 1.4.

Example-2 Carbon black: Special black 5 (specific surface area 1
34rr? /g, pH value 2.7) (manufactured by Degussa)
5 parts were treated with aluminum coupling agent AL-M in the same manner as in Example-1 to form oil droplets. As a result,
The dispersibility of carbon black in the oil droplets was good. A toner was synthesized from the obtained oil droplets in the same manner as in Example 1 to obtain a toner of the present invention having an average particle size of 12 μm. When this toner was used to form an image using DC-1001, a good image having a fog density of 0.003 and an image density of 1.4 was obtained.

Comparative example-1 Carbon black FW200 (specific surface area 460 m2/
g, p) l value 2.5) (manufactured by Degussa) was treated with aluminum coupling agent AL-M in the same manner as in Example-1 to form oil droplets. , carbon black aggregates of approximately 1 to 2 μm in size were observed in the oil droplets. This suspension was synthesized into a toner using the same method as in Example 1 to obtain the toner of the present invention with an average particle size of 12 μm. When an image was formed with DC-1001 using this toner, fogging occurred with a fogging density of 0.007 and an image density of 1.1, and an image with a low density was obtained.

Comparative example-2 Carbon black Niblintex specific surface area 150
(manufactured by Degussa) was treated with aluminum coupling agent AL-M in the same manner as in Example 1 to form oil droplets. Carbon black aggregates of about 2 to 3 μm in size were observed in the droplets. This suspension was synthesized into a toner using the same method as in Example 1 to obtain a toner with an average particle size of 12 μm. When an image was formed using DC-1001, fog density G, Q12, image density 0.9, and sufficient image density could not be obtained.

Comparative Example-3 Carbon black: MA-100 (specific surface area 134 d/g) not treated with an aluminum coupling agent
, p) I value 3.0) (manufactured by Mitsubishi Chemical Industries, Ltd.) was used to form oil droplets in the same manner as in Example-1. As a result,
Carbon black aggregates of about 5 to 10 μm were observed in the oil droplets. A toner was synthesized from this suspension in the same manner as in Example 1 to obtain a toner having an average particle size of 13 μm. When an image was formed with DC-1001 using this toner, the fog density was 0.02 and the image density was 0.75.

Comparative Example-4 Carbon black not treated with aluminum coupling agent: Special Black 5 (specific surface area 13
4 m'/g, pu value 2.7) (manufactured by Degussa) to form oil droplets in the same manner as in Example-1. Aggregates of carbon black were observed.This suspension was synthesized into a toner using the same method as in Example 1 to obtain a toner with an average particle size of 14 μm.Using this toner, an image was produced using DC-1001. When formed, the fog density was 0.02 and the image density was 0.78.

Comparative Example-5 No treatment with aluminum coupling agent. Carbon black: FW200 (specific surface area 460rn”/
(g, pH value 2.5) (manufactured by Degussa) to form oil droplets in the same manner as in Example 1. As a result, carbon black of about 2 to 10 μm was found in the oil droplets. Aggregates were observed. A toner was synthesized from this suspension in the same manner as in Example 1 to obtain a toner having an average particle size of 14 μm. When an image was formed using this toner using DC-1001, the fog density was 0.02 and the image density was 0.69.

Comparative Example-6 Carbon black not treated with aluminum coupling agent: Printex has a specific surface area of 15 or
n”/g, pH value 8.5) (manufactured by Degussa) at 5
As a result of forming oil droplets in the same manner as in Example 1, carbon black aggregates of about 5 to 10 μm in size were observed in the oil droplets. A toner was synthesized from this suspension in the same manner as in Example 1, and an image was formed using DC-1001, resulting in a fog density of 0.03 and an image density of 0.72.

Table 1 summarizes the results of Example 1.2 and Comparative Examples 1 to 6 above.
It was shown to.

In each of the above-described embodiments, the classified toner particles are sieved using a mesh with square openings of a predetermined size, and the separated toner particles are passed through a sieve with the same square openings again. By repeating this several times, a toner with high roundness was obtained.

Further, as the toner of the comparative example, the toner after normal classification was used as it was.

The values of roundness (D) are shown below.

Toner - Sue 1 Example 1 0.93 Example 2 0.92 Comparative example to,a a Comparative example 2 0.87 Comparative example 3 0.88 Comparative example 4 0.86 Comparative example 5 0.87 Comparison Example 6 0.86 The roundness was measured by observing the toner particles under an electron microscope, measuring the major axis and minor axis, and calculating by the diameter method.

Claims (2)

[Claims] (1) In an electrostatic image developing toner comprising a composition of a fixing resin made of a radically polymerizable thermoplastic resin and carbon black dispersed in the fixing resin, the toner has the following formula D=√(r_l・r_s)/r_l In the formula, r_l represents the major axis of the toner particle, and r_s represents the minor axis of the toner particle. Carbon black consists of spherical particles with a circularity of 0.90 or more, defined as A toner comprising carbon black having a carbon black of 300 m^2/g or less and a pH value of 7.0 or less, and in which an aluminum coupling agent is present. (2) Radical polymerizable monomer, specific surface area is 300m^2
/g or less and a composition containing carbon black and an aluminum coupling agent with a pH value of 7.0 or less in an aqueous medium, and the suspended particles are polymerized in the presence of a radical initiator for fixing. A method for producing a toner for developing electrostatic images, which comprises obtaining spherical particles consisting of a resin and carbon black dispersed in the resin.