JP3034707B2 - Method for producing toner for developing electrostatic images - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a toner for developing an electrostatic image in an electrophotographic method, an electrostatic recording method, and an electrostatic printing method. The present invention relates to an improvement in a method for producing a toner for electrostatic image development by a suspension polymerization method for obtaining toner particles having a sharp distribution.

[0002]

2. Description of the Related Art
In order to obtain a dry toner containing a colorant and a resin as main components, a thermoplastic resin is melted, and a colorant such as a dye or a pigment is added thereto, and if necessary, a magnetic substance, a triboelectric charge controlling agent, an offset preventing agent, and a lubricant. After adding and mixing well, solidify by cooling,
After pulverization, a method of performing classification to obtain a required particle size has been implemented.

[0003] However, such a method has various disadvantages. Firstly, polymerization equipment for resin production,
Many devices such as a kneading device, a crusher, and a classifier are required, the number of steps is large, the energy consumption is large, and the cost is high. Secondly, it is difficult to obtain a uniform mixture in the kneading step, and the conditions for uniformly dispersing are particularly delicate and difficult to control. Thirdly, in the pulverization step, not only a fine powder having a particle size range appropriate for obtaining a clear and fog-free image is obtained, but also fine powder and coarse powder are classified and removed because they are by-products. That is, the process becomes complicated, the yield for obtaining the desired particle size range is low, and this leads to an increase in cost. Fourth, the resulting powder has an irregular shape due to the pulverization, causing poor flowability of the fine powder, and the fine powder is easily generated by the pulverization by stirring at the time of triboelectric charging. There are drawbacks such as causing image fogging.

On the other hand, JP-B-36-10231, JP-B-47-51830, JP-B-51-14895 and the like disclose a method for producing a toner by a suspension polymerization method. This suspension polymerization method does not require pulverization, simplifies the production process, and can be said to have improved the above-mentioned disadvantages.

[0005] The suspension polymerization method is generally a method in which a polymerizable monomer composition containing a charge controlling agent, a colorant and the like is suspended in an aqueous medium and polymerized. A water-soluble polymer substance or a poorly water-soluble inorganic salt powder such as calcium phosphate or calcium carbonate is present in a medium as a dispersion stabilizer, and polymerization is performed after the monomer droplets are refined by mechanical shearing force. . However, even in this suspension polymerization method, a toner having a particle size distribution actually required by a usual synthesis method and dispersion formulation cannot be obtained.

Here, a coefficient of variation y is defined by the following equation (1) as a scale indicating the spread of the particle size distribution of the toner, and will be described below. y = s / x × 100 (%) (1) where x is a volume average particle diameter (μm) determined by a particle size measuring instrument such as a Coulter counter, and s is a particle diameter determined similarly. The standard deviation (μm) of the volume distribution is shown.
The larger the coefficient of variation y is, the larger the particle size distribution becomes, and the smaller the value, the narrower the particle size distribution becomes.

More specifically, a toner obtained by classification by a conventional pulverization method generally has a coefficient of variation of 27 to 35% when the average particle diameter is about 11 μm, for example. If the particle size distribution is further narrowed by the classification, the recovery rate of the toner is remarkably reduced, but the improvement in image quality and other performances is hardly expected. On the other hand, in the suspension polymerization method, when particles having an average particle size of about 11 μm are synthesized, the coefficient of variation usually has a value of 40 to 70% or more, which is far higher than that of the classification method toner by the pulverization method. Shows a wide distribution.

For example, when polyvinyl alcohol is used as the dispersion stabilizer, a monomer solution having a toner composition is suspended in water using a homomixer or the like, and the average particle size is 10 to 12 μm.
m, and the toner obtained by polymerization contains a large amount of fine toner of 3 μm or less or coarse toner of 20 μm or more,
The coefficient of variation shows a wide particle size distribution of 55 to 70%.
Further, even when a poorly water-soluble inorganic dispersion stabilizer capable of relatively narrowing the particle size distribution, for example, a tricalcium phosphate powder and an anionic activator is used in combination as a dispersion stabilizing aid, the coefficient of variation is about 40 to 50%. Can only be obtained.

[0009] Such a state of particle size distribution includes toner having a particle size range not consumed during copying, so that printing durability and
Very bad effect on image quality, chargeability, etc. According to the knowledge obtained by the present inventors, the toner obtained by suspension polymerization has a spherical shape or a quasi-spherical shape without an acute angle portion, but in this case, an irregular toner obtained by a usual pulverization method. The effect on the performance by the particle size distribution is significantly greater than that of That is, in the spherical toner, the adhesive force (Van der Walls force) with the carrier or the photoreceptor is much larger than that of the pulverized toner. It tends to be large, and it cannot be ignored.

[0010] Therefore, in such a spherical toner, during development, the smaller the particle size of the toner, the more difficult it is to separate from the carrier, and the tendency to be consumed from the larger particle size toner becomes abnormally strong. As a result of the accumulation of the diameter toner, the balance of the particle size distribution is lost when copying a large number of sheets, and the performance such as image quality and charge amount cannot be maintained in a favorable state. Further, even if the toner is once developed on the photoreceptor, the toner having a relatively small particle diameter is difficult to be transferred onto the copy paper due to such an adhesive force, and is also difficult to be scraped off by the blade in the cleaning process. ,
This causes a decrease in transfer efficiency and a significant deterioration in image quality.

On the other hand, a toner having a particle size larger than necessary has a poor chargeability and is easily accumulated in a developer, and when copying a large number of sheets, remarkable image quality deterioration such as reduction in resolution and deterioration in gradation reproducibility is caused. cause.

In order to make the particle size distribution of the suspension polymerization method sharper as described above, proposals have been made for improving the dispersion step of the polymerizable monomer composition. JP
63-113561, JP-A-2-69969, JP-A-4-195153
Each of the publications discloses a method for obtaining a toner having a sharp particle size distribution by improving the dispersion step, but in these methods, a monomer having a drastic change in physical properties during polymerization is disclosed. In the case of a composition, aggregation occurs during polymerization, and toner particles having a sharp particle size distribution cannot be obtained. In order to solve this problem, Japanese Patent Application Laid-Open Nos.
No. 179650 discloses a method of improving by adding a dispersion stabilizer during polymerization or after the end of granulation, but these methods are because the dispersion stabilizer is added at an elevated temperature. It is added under polymerization. For this reason, it is not possible to cope with a case where a sudden change in physical properties occurs, and aggregation also occurs.

Accordingly, an object of the present invention is to solve the above-mentioned drawbacks of the prior art and to make it possible to produce a toner having a sharp particle size distribution having a coefficient of variation of 30% or less. An object of the present invention is to provide a method for producing a toner.

[0014]

The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, a part of the dispersion stabilizer was added at the start of dispersion, and the remaining dispersion stabilizer was dispersed during or after dispersion. By adding it after completion, it has been found that the dispersion of the polymerizable monomer in the dispersion medium is stabilized, and that toner particles having a sharp particle size distribution with an average particle size of 3 to 50 μm can be obtained, thereby completing the present invention. Reached.

That is, the present invention relates to a toner for developing an electrostatic image by dispersing a polymerizable monomer composition containing a charge controlling agent and a colorant in an aqueous medium using a dispersion stabilizer and then subjecting the polymer to a suspension polymerization. In the method of producing, using a poorly water-soluble inorganic compound powder as a dispersion stabilizer, a surfactant as a dispersion stabilizing aid,
At the start of dispersion, part of the poorly water-soluble inorganic compound powder and part or all of the surfactant are added, and the remaining poorly water-soluble inorganic compound powder and the remaining surfactant or the remaining poorly water-soluble inorganic compound powder are dispersed. It is an object of the present invention to provide a method for producing a toner for developing an electrostatic image, which is added during or after the completion of dispersion.

The liquid temperature in the dispersion step of the present invention is 0 to 40.
° C, preferably 0 to 30 ° C, more preferably 0 to 20 ° C. Since the liquid temperature uses an aqueous medium, it is not possible to freeze water at 0 ° C. or lower because of the occurrence of freezing. At 40 ° C. or higher, the reaction proceeds, so that a uniform particle size distribution cannot be obtained.

Hereinafter, the method for producing the toner of the present invention will be specifically described. First, a colorant such as carbon black, a charge controlling agent, a wax, and other toner property improvers as needed are added to the polymerizable monomer, and these are mixed and dispersed by a known solid-liquid disperser. A monomer composition obtained by dissolving a polymerization initiator in this dispersion is dispersed in an aqueous medium in the presence of a poorly water-soluble inorganic compound powder and a surfactant to a particle size suitable for a toner.

The poorly water-soluble inorganic compound powder which is a dispersion stabilizer used in the present invention includes salts of alkaline earth metals,
For example, barium sulfate, calcium sulfate, barium carbonate,
Examples include poorly water-soluble inorganic compound powders such as calcium carbonate, magnesium carbonate, and calcium phosphate. In the present invention, the calcium phosphate preferably used as the poorly water-soluble inorganic compound powder refers to tricalcium phosphate (Ca ₃ (P
O _{4) 2),} hydroxyapatite _{(mCa 3 (PO 4) 2} · nCa (OH) 2)
, Dibasic calcium phosphate, calcium pyrophosphate, etc., with hydroxyapatite and tribasic calcium phosphate being most preferred.

These poorly water-soluble inorganic compound powders are used in a total amount of 0.2 to 400 parts by weight per 100 parts by weight of the polymerizable monomer composition.
Add parts by weight in parts. The addition amount in the case of divided addition is 0.1 to 300 parts by weight at the start of dispersion, during or after dispersion.
0.1 to 300 parts by weight, preferably 0.5 to 150 at the start of dispersion
Parts by weight, 0.5 to 150 parts by weight during or after dispersion. If the addition amount of the poorly water-soluble inorganic compound powder is less than 0.2 parts by weight, the dispersing effect is insufficient, and aggregated particles are formed, which is not preferable. If it exceeds 400 parts by weight, the viscosity rises, and the stirring becomes non-uniform.

The surfactant used in the present invention includes:
Anionic, cationic, amphoteric or nonionic ones are used. Examples of the anionic surfactant include higher fatty acid salts such as sodium oleate and sodium stearate, higher alcohol sulfates such as sodium lauryl sulfate and ammonium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, and alkylnaphthalene sulfone. Sodium acid, β-
Naphthalene sulfonic acid derivatives such as sodium salt of naphthalene sulfonic acid formalin condensate, sodium dialkyl sulfosuccinate, sulfosuccinic acid derivatives such as phenoxyethyl allyl sulfosuccinate ammonium salt, dialkyl phosphate, polyoxyethylene alkyl ether sulfate, Examples thereof include polyoxyethylene alkylphenol ether sulfate and alkylethanol triethanolamine. Of these, sodium dodecylbenzenesulfonate and sulfosuccinic acid derivatives are particularly preferred.

Examples of the cationic surfactant include stearylamine hydrochloride, alkylamine salts such as dioleylamine sulfate, quaternary alkylammonium salts such as stearyltrimethylammonium chloride, and amine oxides such as lauryldimethylamine oxide. Examples of amphoteric surfactants include alkyl betaines such as lauryl betaine, and nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene alkyl aryl such as polyoxyethylene nonyl phenyl ether. And sorbitan fatty acid esters such as ether and sorbitan monolaurate.

These surfactants are used in an amount of 0.01 to 10% by weight, preferably 0.1 to 5% by weight, based on the poorly water-soluble inorganic compound powder. These may be used in combination of two or more. These surfactants may be partially added at the start of dispersion and the remainder may be added during or after dispersion, or may be added at the start of dispersion.

In the present invention, a combination using calcium phosphate as the poorly water-soluble inorganic compound powder and using an anionic surfactant as the surfactant is particularly preferable.

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, the charge control agent may be negatively charged. When a positively-chargeable toner such as nigrosine is used, a positively-chargeable toner is obtained and can be used as needed. The charge control agent is added in an amount of 0.1 to 5 based on 100 parts by weight of the polymerizable monomer.
It is preferably from 0.5 to 3 parts by weight, more preferably from 0.5 to 3 parts by weight.

As the polymerizable monomer used in the present invention, a polymerizable monomer having 3 to 25 carbon atoms can be used. Examples thereof include styrene, p-chlorostyrene, p-methylstyrene, vinyl acetate and propion. Vinyl acid, vinyl benzoate, methyl acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl Methacrylate, diethylaminoethyl methacrylate, t-butylaminomethyl methacrylate, acrylonitrile, 2-vinylpyridine, 4-vinylpyridine and the like are used alone or in combination.

Further, in the present invention, by adding a polyfunctional monomer such as divinylbenzene, ethylene glycol dimethacrylate, trimethylolpropane triacrylate, glycidyl methacrylate or glycidyl acrylate as a crosslinking agent to the above-mentioned monomer, the durability can be further improved. Excellent toner can be manufactured. The amount of the polyfunctional monomer to be added is 0.05 to 20 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the polymerizable monomer.

As the colorant used in the present invention, in the case of a black toner, various carbon blacks produced by thermal black method, acetylene black method, channel black method, furnace black method, lamp black method, etc. In the case, copper phthalocyanine, monoazo pigment (CIPigment Red 5, CIPigment Orange3
6, CIPigment Red 22), disazo pigments (CIPigmen
t Yellow 83), anthraquinone pigment (CIPigment Bl
ue 60), disazo dyes (Solvent Red 19), rhodamine dyes (Solvent Red 49) and the like.

In the present invention, generally used oil-soluble peroxide-based or azo-based initiators can be used as the polymerization initiator. For example, benzoyl peroxide, lauroyl peroxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis- (2,4-dimethylvaleronitrile), orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide and the like Is mentioned. These are used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the polymerizable monomer.

Further, the toner obtained in the present invention can contain a low molecular weight olefin polymer known as a so-called release agent for the purpose of preventing offset, improving fluidity, and improving fixability. This low molecular weight olefin polymer is preferably present during the polymerization of the monomer together with the colorant used in the present invention. Examples of the low molecular weight olefin polymer used in the toner of the present invention include polyethylene, polypropylene, ethylene vinyl acetate copolymer, and chlorinated polyethylene wax. The amount of the low molecular weight olefin polymer used is 1 to 20 parts by weight, preferably 3 to 15 parts by weight, per 100 parts by weight of the resin component of the toner.
If it is less than 1 part by weight, it may not have a sufficient offset preventing effect, and if it exceeds 20 parts by weight, gelation may occur during polymerization, which is not preferable.

Further, the toner obtained in the present invention can contain a magnetic substance and can be used as a one-component toner. When a magnetic material is contained, it is preferable to use it by dispersing it in a polymerizable monomer, like the colorant. The content of the magnetic substance is based on 100 parts by weight of the polymerizable monomer.
It is preferably 20 to 200 parts by weight, more preferably 50 to 150 parts by weight. Further, the present invention can be applied to a capsule toner produced by an interfacial polymerization method or an in situ polymerization method, in which a change in physical properties is particularly severe.

To form an image using the toner of the present invention by, for example, electrophotography, a selenium photoreceptor or an inorganic material such as zinc oxide, cadmium sulfide, cadmium selenide, cadmium sulfate selenide, lead oxide, and mercury sulfide. A photoconductor in which a photosensitive layer in which a photoconductive material is dispersed and contained in a binder resin is provided on a conductive support, or an organic photoconductive material such as anthracene, polyvinyl carbazole, etc. A photosensitive member in which a photosensitive layer contained therein is provided on a conductive support is used. The entire surface of the photosensitive layer of such a photoreceptor is 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 image. Next, the electrostatic image is developed by, for example, a cascade method or a magnetic brush method with a developer composed of a mixture of the toner of the present invention and glass balls or iron powder carriers to form a toner image. This toner image is pressed against the transfer paper under corona discharge, for example, and is transferred onto the transfer paper. The toner image transferred onto the transfer paper is heated and fixed by a hot roll fixing device coated with a fluororesin or silicone rubber having releasability.

Next, a specific example of the process for producing the toner for developing an electrostatic image according to the present invention will be described. After mixing and stirring the polymerizable monomer, the colorant, the charge control agent, the release agent and, if necessary, the magnetic substance, the polymerization initiator is dissolved. Next, this mixture is added to water, and then a part of the poorly water-soluble inorganic compound powder and a part or all of the surfactant are added at the start of dispersion. The remaining poorly water-soluble inorganic compound powder and the remaining surfactant, or the remaining poorly water-soluble inorganic compound powder are added during or after the dispersion. Thereafter, the polymer is subjected to suspension polymerization by raising the temperature, and the polymer is washed, filtered, and dried, and then subjected to a surface treatment such as attaching fine powder such as silica to the surface to obtain a toner. Here, the start of dispersion indicates the time immediately before or immediately after the start of the dispersion, and the middle of the dispersion or after the end of the dispersion is the time after the start of the dispersion and before the start of the temperature rise for performing the polymerization. Indicates the time.

For dispersing the polymerizable monomer composition in the aqueous medium in the present invention, the following disperser can be used. High-speed rotating dispersing machines include TK Homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), CLEARMIX (manufactured by M-Technic Co., Ltd.), Slasher (manufactured by Mitsui Miike Works), and Milder (manufactured by Mitsui Miike Works). Ebara Corporation), TK
High Line Mill (made by Tokushu Kika Kogyo Co., Ltd.), TK Homomic Line Flow (made by Tokushu Kika Kogyo Co., Ltd.), TK Pipeline Homomixer (made by Tokushu Kika Kogyo Co., Ltd.), TK
Homomic line mill (made by Tokushu Kika Kogyo Co., Ltd.), TK
Hibis line mixer (made by Tokushu Kika Kogyo Co., Ltd.), DI
SHO (manufactured by Colma), etc., and as a dispersing machine depending on the shape of the stationary blade or the inside of the tank, ALM homogenizer (manufactured by Gorin), static mixer PSM (manufactured by Pezhold), sulzer mixer (manufactured by Sulzer Brothers Co., Ltd.)
), High Mixer (manufactured by Toray Industries, Inc.), Noritake Static Mixer (manufactured by Noritake Co., Ltd.), TK Fiscarin (manufactured by Tokushu Kika Kogyo Co., Ltd.), TK-ROSS LPD Mixer (tokushu Kika Kogyo Co., Ltd.) )), TK-ROSS ISG Mixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) and Cause Majellar (manufactured by Chugoku Explosives Co., Ltd.). Manufactured).

[0034]

The present invention will be described in detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples. All parts in the examples are on a weight basis.

Example 1 85 parts of styrene, 15 parts of 2-ethylhexyl acrylate
A mixture of 6 parts of carbon black (manufactured by Mitsubishi Kasei Co., Ltd., # 44) and 1.5 parts of a charge control agent (manufactured by Hodogaya Chemical Co., Ltd., Aizen Spiron Black TRH) was used as a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). ), And mixed for 10 minutes. After dissolving 10 parts of 2,2'-azobisisovaleronitrile in this mixed solution, this solution was added to a hydroxyapatite slurry [manufactured by Nippon Chemical Industry Co., Ltd., super tight (100 parts by weight of hydroxyapatite and water 900 parts by weight). Part) and 180 parts of an aqueous solution of 0.025 part of sodium dodecylbenzenesulfonate, and mixed and stirred at 3,000 rpm at 3,000 rpm at a liquid temperature of 15 ° C. for 3 minutes. The polymerizable monomer composition was suspended and dispersed. To this suspension was added 80 parts of hydroxyapatite slurry and 0.025 parts of sodium dodecylbenzenesulfonate,
In a separable flask, a polymerization reaction was carried out at 75 ° C. for 8 hours under a nitrogen atmosphere at a stirring speed of 100 rpm with a usual stirrer. After further washing with hydrochloric acid and washing with water, it was dried at 40 ° C. for 10 hours with a vacuum dryer. The particle size and the particle size distribution of the obtained toner were measured with a Coulter counter (TA-II type, aperture diameter 50 μm). The average particle size of the obtained toner was 9.3 μm, and the coefficient of variation was 25%.

Example 2 A toner was prepared in the same manner as in Example 1 except that the amount of sodium dodecylbenzenesulfonate added before the suspension dispersion was 0.05 parts, and sodium dodecylbenzenesulfonate was not added after or during the dispersion. Was manufactured. The average particle size of the obtained toner was 9.5 μm, and the coefficient of variation was 29%.

Comparative Example 1 The amount of hydroxyapatite slurry added before suspension dispersion was 180 parts, and the amount of sodium dodecylbenzenesulfonate was adjusted to 180 parts.
The toner was manufactured in the same manner as in Example 1 except that the hydroxyapatite slurry and sodium dodecylbenzenesulfonate were not added after the dispersion was completed or during the dispersion. The average particle size of the obtained toner is 8.1.
μm, and the coefficient of variation was 73%.

Comparative Example 2 The amount of the hydroxyapatite slurry added before the suspension dispersion was 100 parts, after the dispersion was completed, the hydroxyapatite slurry was 80 parts, and the sodium dodecylbenzenesulfonate was dispersed at the start of the dispersion, after the dispersion was completed, or after the dispersion. A toner was manufactured in the same manner as in Example 1 except that the toner was not added to any of the portions. The average particle size of the obtained toner was 13.7 μm, and the coefficient of variation was 49%.

[0039]

According to the present invention, toner particles having a sharp particle size distribution can be obtained since aggregation of toner particles in a dispersion medium during polymerization can be prevented and dispersion can be stabilized.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Miho Sasaki 6-6-17 Komatsubara, Wakayama-shi (56) References JP-A-2-179650 (JP, A) JP-A-2-1-111967 (JP, A) JP-A-64-86160 (JP, A) JP-A-59-174851 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (1)

(57) [Claims] 1. A toner for developing an electrostatic image is produced by dispersing a polymerizable monomer composition containing a charge control agent and a colorant in an aqueous medium using a dispersion stabilizer, and then subjecting it to suspension polymerization. In the method, a poorly water-soluble inorganic compound powder as a dispersion stabilizer, a surfactant as a dispersion stabilizing aid, a part of the poorly water-soluble inorganic compound powder and part or all of the surfactant are added at the start of dispersion, and the remaining A method for producing a toner for developing an electrostatic image, comprising adding the poorly water-soluble inorganic compound powder and the remaining surfactant or the remaining poorly water-soluble inorganic compound powder during or after dispersion.