JP3387660B2 - Electrophotographic toner - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner, and more particularly to an electrophotographic toner produced by aggregating polymer particles obtained by a dispersion polymerization method.

[0002]

BACKGROUND OF THE INVENTION Toners for electrophotography have hitherto been produced by a so-called pulverization method, in which a thermoplastic resin, a colorant and other additives are melt-kneaded and then pulverized and classified. Has been done. However, since the toner obtained by such a pulverization method has a wide particle size distribution, it is difficult to uniformly charge the toner, and it is difficult to obtain an image with high resolution due to the large particle size.

Therefore, recently, as a method for producing toner particles, for example, a liquid monomer phase (oil phase) comprising a water-insoluble polymerizable monomer, a polymerization initiator soluble in the water-soluble monomer, and an additive such as a colorant is used. ) Is polymerized while being suspended and dispersed in an aqueous dispersion medium such as water (suspension polymerization method), or in a water-miscible solvent in which a polymerizable monomer is dissolved but the polymer is not dissolved. In addition, there is proposed a method (dispersion polymerization method) in which the above-mentioned monomer and an additive such as an oil-soluble dye (coloring agent) are dispersed and polymerized.

The toner obtained by these polymerizations is
Since the particle size distribution is narrow and the particle size can be reduced by changing the conditions of suspension and dispersion, there are advantages that the charging property is excellent and a high quality image can be obtained. However, according to this method, since the toner particles obtained have a spherical shape, it is difficult to remove the toner remaining on the photoconductor with a blade, and the blade cleaning property is poor.

On the other hand, a method for producing toner particles by aggregating fine polymer particles together with a colorant has also been proposed. For example, in JP-A-4-324868, as polymer particles, when the pH is high, ζ potential (zeta potential)
High (thus, high stability as a colloid in an aqueous medium) and low zeta potential at low pH (hence low stability as a colloid in an aqueous medium). After the polymer particles and the colorant are dispersed in an aqueous medium at a high pH, the pH of the obtained colloidal solution is lowered to agitate the polymer particles while vigorously stirring,
A method for producing toner particles by heat treatment of the obtained aggregate is disclosed.

In the method according to the above publication, it is possible to synthesize toner particles having an arbitrary shape from spherical particles to those having irregularities on the surface by changing heating conditions. Further, by using this method, it is possible to obtain toner particles having a narrow particle size distribution and a small particle size (7 μm or less). However, this method
Since the polymer particles are aggregated by lowering the temperature, the surface of the polymer particles has polar groups (hydrophilic functional groups) such that the ζ potential can be confirmed. The surfactant (hydrophilic substance) used for dispersion in the aqueous medium also remains. Therefore, the toner obtained by this method has a problem that the conductivity of the surface changes due to a change in humidity due to the presence of a hydrophilic functional group or a hydrophilic substance on the surface, and the charging characteristics become unstable.

An object of the present invention is to provide an electrophotographic toner having no hydrophilic functional group or hydrophilic substance on its surface and having stable charging characteristics against changes in humidity.

[0008]

MEANS FOR SOLVING THE PROBLEMS AND ACTION The electrophotographic toner of the present invention used for solving the above-mentioned problems comprises:
It is characterized in that it is composed of an agglomerate obtained by aggregating polymer particles together with a colorant, and the surface of the agglomerate is hydrophobic. As described above, since the toner of the present invention has a hydrophobic surface, it is possible to obtain stable charging characteristics against changes in humidity.

The polymer particles used in the toner are obtained by dispersion-polymerizing a polymerizable monomer in a non-aqueous medium containing a dispersion stabilizer having no hydrophilic functional group. As described above, since the dispersion stabilizer having no hydrophilic functional group is used, the surface of the aggregate obtained by aggregating the polymer particles can be made hydrophobic. In the present invention, the term “hydrophobic aggregates” means that they are not dispersed in water at all, or have a ζ potential of −2 to +2 mV when dispersed in water.
What is.

The electrophotographic toner of the present invention will be described in detail below. Synthesis of polymer particles Polymer particles are synthesized according to a dispersion polymerization method by using a polymerizable monomer, a dispersion stabilizer having no hydrophilic functional group (hereinafter referred to as a non-aqueous dispersion stabilizer) and an oil-soluble polymerization initiator. It is carried out in addition to the non-aqueous medium. The dispersion polymerization method in the present invention,
This is a method in which a polymerizable monomer, a non-aqueous dispersion stabilizer and a polymerization initiator are dissolved in a non-aqueous medium for polymerization, and the produced polymer particles are dispersed in the non-aqueous medium.

As the polymerizable monomer, a vinyl unsaturated monomer having radical polymerizability is used. Specifically, monovinyl aromatic monomers, acrylic monomers, vinyl ester monomers, vinyl ether monomers, diolefin monomers, monoolefin monomers, halogenated olefin monomers. Examples include a polymer. As the monovinyl aromatic monomer, the following general formula (1):

[0012]

[Chemical 1]

A monovinyl aromatic hydrocarbon represented by the formula: wherein R ¹ represents a hydrogen atom, a lower alkyl group or a halogen atom, and R ² represents a hydrogen atom, a lower alkyl group, a vinyl group or a halogen atom. Styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene,
Examples include o, m, p-chlorostyrene, p-ethylstyrene, divinylbenzene and the like.

The acrylic monomer has the following general formula
(2):

[0015]

[Chemical 2]

(In the formula, R ³ represents a hydrogen atom or a lower alkyl group, and R ⁴ represents a hydrocarbon group having 1 to 12 carbon atoms.)
An acrylic monomer represented by, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate, methacrylic acid-2 -Ethylhexyl, ethylene glycol dimethacrylic acid ester, tetraethylene glycol dimethacrylic acid ester and the like can be mentioned.

The vinyl ester-based monomer is represented by the following general formula (3):

[0018]

[Chemical 3]

(In the formula, R ⁵ represents a hydrogen atom or a lower alkyl group.) Vinyl ester monomers such as vinyl formate, vinyl acetate and vinyl propionate can be mentioned. The vinyl ether-based monomer has the following general formula (4):

[0020]

[Chemical 4]

(In the formula, R ⁶ represents a monovalent hydrocarbon group having 1 to 12 carbon atoms.) A vinyl ether monomer, for example, vinyl methyl ether, vinyl ethyl ether, vinyl-n- Butyl ether, vinyl phenyl ether, vinyl cyclohexyl ether and the like can be mentioned.
The diolefin-based monomer has the following general formula (5):

[0022]

[Chemical 5]

(In the formula, R ⁷ , R ⁸ and R ⁹ are the same or different and each represents a hydrogen atom, a lower alkyl group or a halogen atom.) A diolefin monomer represented by, for example, butadiene, isoprene, Examples include chloroprene and the like. As the mono-olefin compound, the following general formula (6)
:

[0024]

[Chemical 6]

(In the formula, R ¹⁰ and R ¹¹ are the same or different and each represents a hydrogen atom or a lower alkyl group.) A monoolefin monomer represented by, for example, ethylene, propylene, butene-1, pentene- 1,4-methylpentene-
1 etc. are mentioned. Examples of the halogenated olefin-based monomer include vinyl chloride and vinylidene chloride.

The above monomers can be used alone or in combination of two or more kinds. Among the above monomers, the monomer preferably used in the present invention is (meth) acrylic acid ester. Examples of the lower alkyl group include alkyl groups having 1 to 6 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, n-pentyl and n-hexyl.

Examples of the non-aqueous dispersion stabilizer include isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), butyl rubber (IIR),
Ethylene propylene rubber (EPM, EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), acrylic rubber (ACM, AEM) and the like can be mentioned.

As the oil-soluble polymerization initiator, for example, 2,
Examples include azo compounds having no coupling properties such as 2'-azobisisobutyronitrile and 2,2'-azobisvaleronitrile, and peroxides such as benzoyl peroxide, t-butyl peroxide and dicumyl peroxide. To be The weight ratio of the polymerizable monomer and the non-aqueous dispersion stabilizer to be blended is 5: 1 to 500: 1, preferably 10: 1 to 10: 1.
It is 0: 1. When the ratio of the non-aqueous dispersion stabilizer is lower than this range, the dispersion stability of the polymer particles is poor. on the other hand,
When the ratio of the non-aqueous dispersion stabilizer is higher than the above range,
It is not preferable because it has no corresponding effect and is economically disadvantageous.

The amount of the oil-soluble polymerization initiator blended is 0.01 to 20 parts by weight, based on 100 parts by weight of the polymerizable monomer.
It is preferably 0.1 to 10 parts by weight. As the non-aqueous medium in the dispersion polymerization, a solvent that dissolves the polymerizable monomer, the non-aqueous dispersion stabilizer, and the oil-soluble polymerization initiator, but does not dissolve the polymer particles is used. Specifically, the carbon number of n-hexane, n-heptane, n-octane or the like is 6 to 12
Alicyclic saturated hydrocarbons having 6 to 12 carbon atoms such as aliphatic saturated hydrocarbons, cyclohexane, cycloheptane, and cyclooctane; and petroleum fractions such as petroleum ether.

The polymerization reaction is carried out at a temperature of 10 to 90 ° C., preferably 30 to 70 ° C. for 30 minutes to 10 hours while stirring the non-aqueous medium containing each of the above components. Also,
In order to control the termination reaction of the polymerization due to oxygen, it is preferable to carry out the reaction under an atmosphere of an inert gas such as argon or nitrogen. The polymer particles thus obtained are spherical particles having an average particle size of usually 0.1 to 1.0 μm. Toner Synthesis The electrophotographic toner of the present invention is prepared by mixing the above-obtained dispersion of polymer particles with a colorant and, if necessary, other additives to prepare a mixed solution, It can be obtained by adding a solvent that is compatible with the aqueous medium but does not dissolve the non-aqueous dispersion stabilizer to cause aggregation, and heat-treat the obtained aggregate.

The mechanism of aggregation of the polymer particles is considered as follows. That is, as shown in FIG. 1 (a), since the molecular chain of the non-aqueous dispersion stabilizer 2 extends on the surface of the polymer particle 1, it is dispersed as a stable colloid in the non-aqueous medium. However, when the above-mentioned solvent in which the non-aqueous dispersion stabilizer is not dissolved is added to this, the molecular chain of the non-aqueous dispersion stabilizer 2 shrinks into a string as shown in Fig. 1 (b),
The polymer particles 1 are aggregated with each other to form aggregates. The colorant dispersed in the above non-aqueous medium also aggregates as polymer particles by the same operation as above.

As the colorant, those having a hydrophobic surface may be used, and particularly those having excellent dispersibility in a non-aqueous medium and insoluble in a solvent which does not dissolve the non-aqueous dispersion stabilizer are preferable. Specific examples include the pigments and oil-soluble dyes shown below. Pigment carbon black, lamp black, chrome yellow,
Hansa Yellow, Benzidine Yellow, Bethlen Yellow, Quinoline Yellow, Permanent Orange GTR,
Pyrazolone Orange, Vulcan Orange, Watchtang Red, Permanent Red, Brilliant Carmine 3B, Brilliant Carmine 6B, DuPont Oil Red, Pyrazolone Red, Resole Red, Rhodamine B
Lake, Lake Red C, Rose Bengal, Aniline Blue, Ultramarine Blue, Calco Oil Blue, Methylene Blue Chloride, Phthalocyanine Blue, Phthalocyanine Green, Malachite Green Oxalate. Black dye Black FS-Special A, Black S, Black #
103, Black # 107, Black # 215, Black # 141 (all are trade names of Chuo Gosei Kagaku KK), OPLAS Black HZ, Oplas Black # 83
6, Oplas Black # 838 (all are trade names manufactured by Orient Chemical Industry Co., Ltd.). Red dye Macrolex (MACROLEX) Red 5B, Macrolex Red-Violet R (all are trade names manufactured by Bayer Co., Ltd.), Sumiplast (AS), Samiplast tread B-2, Samiplast tread HLG-Z (all Product name manufactured by Sumitomo Chemical Co., Ltd., Oprah Red R
R, Oprah Red # 330 (both are trade names manufactured by Orient Chemical Industry Co., Ltd.), Red 6B, Red TR-71
(All are trade names of Chuo Gosei Kagaku). Orange dyes Macrolex Orange 3G, Macrolex Orange R (all are trade names manufactured by Bayer), Orange S, Orange R, orange # 826N (all are trade names manufactured by Chuo Gosei Kagaku), Oplus Orange PS, Oh Plus Orange RR (both are trade names manufactured by Orient Chemical Industry Co., Ltd.) and Samiplast Orange HRP (trade name manufactured by Sumitomo Chemical Co., Ltd.). Yellow dye Macrolex Yellow 6G, Macrolex Yellow R (all are trade names manufactured by Bayer), Yellow D, yellow GE, yellow # 189 (all are trade names manufactured by Chuo Synthetic Chemicals), Samiplast Yellow GC, Sami Plast Yellow R (both are trade names of Sumitomo Chemical Co., Ltd.), Oplus Yellow 3G, Oplus Yellow # 13
0 (all are trade names manufactured by Orient Chemical Industry Co., Ltd.). Purple dye Macrolex Violet 3R, Macrolex Violet B (both are trade names manufactured by Bayer), Violet MVB (trade name manufactured by Chuo Gosei Kagaku), Samiplast Violet RR, Samiplast Violet B
(All are trade names manufactured by Sumitomo Chemical Co., Ltd.), Oplus Violet # 370, Oplus Violet # 732 (all are trade names manufactured by Orient Chemical Co., Ltd.). Blue dye Macrolex Blue RR (Bayer brand name),
Blue BO, Blue # 8B (all are trade names manufactured by Chuo Gosei Kagaku), Samiplast Blue OR, Samiplast Blue GP, Samiplast Blue S (all are trade names manufactured by Sumitomo Chemical Co., Ltd.), Oplus Blue IIN , Oplas Blue # 630 (all are trade names manufactured by Orient Chemical Industry Co., Ltd.). Green dye Macrolex Green 5B, Macrolex Green G (all are trade names manufactured by Bayer), Green # 55
0, Green # 201 (all are trade names of Chuo Gosei Kagaku), Samiplast Green G (trade name of Sumitomo Chemical Co., Ltd.), Oplus Green # 502, Oplus Green # 503 (all are Orient Chemical Co., Ltd. Product name made by the company). Brown dye Brown PB, Brown SG (all are trade names manufactured by Chuo Synthetic Chemical Industry Co., Ltd.), Oplus Brown # 430, and Oplas Brown # 431 (all trade names manufactured by Orient Chemical Industry Co., Ltd.).

Examples of additives other than the colorant include a charge control agent and an offset preventive agent (release agent). The charge control agent is added when the toner is used as a two-component developer, for example, nigrosine base (CI5045), oil black (CI2615).
0), oil-soluble dyes such as spirone black, and the like.

Examples of the anti-offset agent include low molecular weight polyethylene, low molecular weight polypropylene, various waxes, and silicone oil. The colorant and other additives may be dispersed in the non-aqueous medium together with the polymer particles, or may be mixed with the dispersion liquid of the polymer particles obtained by dispersion polymerization. At this time, it is preferable to disperse the non-aqueous dispersion stabilizer together with the polymer particles in another non-aqueous medium in advance.

The non-aqueous medium and the non-aqueous dispersion stabilizer used here are preferably the same as those used in the dispersion polymerization, but as long as they are compatible with the non-aqueous medium used in the dispersion polymerization, other Non-aqueous media may be used. The mixing ratio of the polymer particles and the colorant varies depending on the desired coloring concentration, but is usually 0.5: 20 by weight, preferably 1:10.

The amount of the other additives to be added is not particularly limited, but is usually 0 to 20 parts by weight with respect to 100 parts by weight of the polymer particles, and the amount of the charge control agent (CCA) to be added is
0 to 5 parts by weight. Examples of the solvent which is compatible with the non-aqueous medium but does not dissolve the non-aqueous dispersion stabilizer include, for example, alcohols having a relatively large alkyl group having 6 to 12 carbon atoms such as n-hexanol, n-heptanol and n-octanol. Is mentioned.

In the toner of the present invention, the above-mentioned mixed solution is put in a homogenizer or the like and stirred at a rotation speed of 100 to 20000 rpm, preferably 1000 to 10000 rpm, and a solvent that does not dissolve the non-aqueous dispersion stabilizer is added to cause aggregation. The temperature at which the coalesced particles soften, that is, around the glass transition temperature of the polymer particles (usually 30 to 120 ° C., preferably 5
It is obtained by heating at 0 to 90 ° C.) for 10 minutes to 1 hour to obtain an aggregate, further cooling, filtering and drying.

The amount of the solvent that does not dissolve the non-aqueous dispersion stabilizer is 100 parts by weight or more based on 100 parts by weight of the polymer particles. If the addition amount is less than 10 parts by weight, aggregates are not sufficiently formed, which is not preferable. The toner thus obtained usually has an average particle size of 4 to 7 μm, and its particle size distribution is relatively small. Further, the particle size and shape of the toner particles change depending on the type and amount of the aggregating agent, the temperature and time of heat treatment, the stirring speed, and the like. Specifically, by increasing the heating time or raising the heating temperature, the shape of the toner particles approaches a spherical shape. Therefore, the optimum conditions may be set according to the desired particle size and shape.

[0039]

EXAMPLES The electrophotographic toner of the present invention will be described in more detail below with reference to examples. Example 1 (Synthesis of polymer particles) 4 g of butadiene rubber was dissolved in 800 g of n-heptane, and 1 ml of methyl methacrylate was added to this solution.
40 g, 60 g of butyl acrylate, 1.5 g of ethylene glycol dimethacrylate and 4 g of 2,2'-azobisisobutyronitrile were added, and the mixture was stirred in a 1 liter separable flask under a nitrogen stream at a rotation speed of 50 rpm. The reaction was carried out at 60 ° C. for 12 hours to complete the polymerization.
The average particle size of the obtained polymer particles was measured by a Coulter counter and found to be 1.0 μm. (Synthesis of Toner) 4 g of butadiene rubber and 10 g of carbon black were sufficiently kneaded using a two-roll mill, and then n
-Adding to 1 liter of heptane to dissolve and disperse. This was mixed with the dispersion liquid of the above polymer particles, 100 g of n-hexanol was added while stirring at 4000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), and further heated to 70 ° C., Aggregates were obtained by heating at temperature for 30 minutes.

The produced agglomerates had irregularities on the surface, and the average particle size was 7.3 μm as measured by a Coulter counter. This aggregate is filtered and dried,
About 200 g of toner was obtained. Example 2 A toner was synthesized in the same manner as in Example 1 except that the temperature of the heat treatment was 80 ° C. As a result, the obtained aggregate was substantially spherical, and the average particle size was 7.1 μm when measured with a Coulter counter. Comparative Example Synthesis of Polymer Particles 2 g of a nonionic surfactant (Tween 80) and 1.0 g of potassium persulfate were dissolved in 500 g of water. Next, 140 g of methyl methacrylate, 60 g of butyl acrylate, 1.5 g of ethylene glycol dimethacrylate and 5 g of acrylic acid were added to this solution, and the mixture was stirred at 80 ° C. for 8 hours to carry out emulsion polymerization. The average particle size of the obtained polymer particles was measured with a Coulter counter to be 0.6μ.
It was m. (Synthesis of Toner) 1 g of an anionic surfactant (sodium dodecylbenzenesulfonate) was dissolved in 500 g of water, 40 g of carbon black was further added, and sufficiently dispersed with a TK homomixer. This dispersion and the dispersion of the above polymer particles were mixed with TK homomixer (Tokushu Kika Kogyo Co., Ltd.)
PH) to 4 with dilute hydrochloric acid while stirring at
After heating to, the pH was adjusted to 7 by adding aqueous ammonia. Furthermore, it heated up to 70 degreeC, stirring, and heated at this temperature for 2 hours. The average particle size of the produced aggregate was measured with a Coulter counter and found to be 7.0 μm.

The aggregate was filtered and dried to obtain about 200 g of toner. Measurement of ζ potential (Measurement method) Since the toners obtained in Examples 1 and 2 are not dispersed in water, the toner is dispersed in water using a nonionic surfactant (Tween 80) that hardly affects the ζ potential. Then, the pH of the dispersion was adjusted to 9 with aqueous ammonia.

Since the toner of the comparative example is dispersed in water, it is dispersed in water as it is and the pH of the dispersion is adjusted to 9 with ammonia water.
Adjusted to. Next, the ζ potential of each of the above dispersions was measured using a laser rotating prism type colloidal particle ζ potential measuring device (manufactured by Nozaki Sangyo Co., Ltd.). The measurement results are shown in Table 1.

[0043]

[Table 1]

Evaluation of Printing Properties (Preparation of Developer) The toner obtained in each of the above Examples and Comparative Examples was mixed with a ferrite carrier having a particle diameter of 80 μm, and each developer (toner concentration: 4.5% by weight) was added. It was made. (Evaluation method) The above developer was used as an electrophotographic copying machine DC-609.
0 (manufactured by Mita Kogyo Co., Ltd.) and installed in a high temperature and high humidity environment (3
A printing test was conducted at 5 ° C. and 85% RH). (Evaluation Results) With the toners obtained in Examples 1 and 2,
Good images were maintained from the beginning of printing to after printing 2.4 million sheets. In addition, toner scattering and fog did not occur.

On the other hand, with the toners obtained in the comparative examples, toner scattering, fog and the like occurred.

[0046]

Since the electrophotographic toner of the present invention comprises an aggregate of polymer particles whose surface is completely hydrophobic,
Very little change in charging characteristics due to changes in humidity,
Therefore, it has excellent stability against environmental changes.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the aggregation mechanism of polymer particles in the present invention.

[Explanation of symbols]

1 polymer particles 2 Non-aqueous dispersion stabilizer

Claims (2)

(57) [Claims] 1. An electrophotographic toner comprising an aggregate formed by aggregating polymer particles together with a colorant, and the surface of the aggregate being hydrophobic. 2. The polymer particles are obtained by dispersion-polymerizing a polymerizable monomer in a non-aqueous medium containing a dispersion stabilizer having no hydrophilic functional group. Toner for electrophotography.