JPH07128905A - Production of electrophotographic toner - Google Patents

Abstract

PURPOSE:To produce an electrophotographic toner having a narrow grain size distribution, capable of pulverization. excellent in cleanability by a cleaning blade and capable of preventing offsetting by heating the toner grain contg. a foaming agent in the fixing resin above the glass transition temp. of the resin and above the foaming temp. of the agent. CONSTITUTION:A spherical toner grain 2 contg. a foaming agent is heated above the glass transition temp. of a fixing resin contg. the grain 2 and above the foaming temp. of the agent to foam the agent. When the heating temp. is higher than the foaming temp. but lower than the glass transition temp., the grain is not sufficiently deformed or cracked to generate a fine grain deteriorating the formed picture, and the grain size distribution is widened. Consequently, since the agent is foamed, many bubbles 1 are generated in the globular grain 2, the surface of the grain 2 is pushed up, and the grain is deformed.

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 an electrophotographic toner used in an image forming apparatus to which a so-called electrophotographic method is applied, such as an electrostatic copying machine and a laser beam printer.

[0002]

2. Description of the Related Art Conventional toner for electrophotography is styrene-
It is manufactured by melt-kneading a fixing resin such as an acrylic copolymer and carbon black as a colorant and other additives, and then pulverizing and classifying. However, since such a pulverized toner has a wide particle size distribution, it is difficult to make charging uniform, and since the particle size is large,
It was difficult to obtain a high-resolution image. Further, since the shape of the obtained particles is irregular, the fluidity of the toner is generally low and there is a problem that blocking or the like is likely to occur.

Therefore, recently, as a method for producing an electrophotographic toner replacing the above-mentioned pulverization method, a method for producing a toner utilizing the production of resin particles by a suspension polymerization method, a dispersion polymerization method or a spray drying method has been proposed. Among them, the method for producing a toner using the suspension polymerization method is a water-insoluble polymerizable monomer that is a base of the fixing resin, a polymerization initiator soluble in the monomer, and a colorant and other additives. Is a method of polymerizing a polymerizable monomer by preparing a liquid monomer phase (oil phase) containing the above and heating it while suspending and dispersing it in an aqueous dispersion medium such as water in the form of droplets.

Further, in the method for producing a toner using the dispersion polymerization method, the polymerizable monomer which is the base of the fixing resin and the colorant and other additives are dissolved in the polymerizable monomer. This is a method in which the polymer is dissolved together with the dispersion stabilizer in a medium in which it is not dissolved, and is polymerized under stirring. Further, a method for producing a toner using a spray drying method is a spray drying liquid obtained by dissolving or dispersing the fixing resin and a colorant and other additives in an appropriate solvent using a spraying device. It is a method of drying and removing the solvent while spraying in a mist state.

All of the electrophotographic toners produced by these methods have a narrow particle size distribution and can be made smaller by changing the conditions, so that they have excellent charging characteristics and high quality. There is an advantage that an image can be obtained. It also has excellent productivity because it does not require classification. However, since the toner particles for electrophotography obtained by these methods have almost spherical particles, there is a problem that they are excellent in fluidity but poor in cleaning property. That is, as described above, when the spherical toner remains on the surface of the photoconductor after image formation, it is difficult to remove it with the cleaning blade that is brought into pressure contact with the surface of the photoconductor.

Therefore, when the toner particles are manufactured by the suspension polymerization method among the above-mentioned manufacturing methods, an azo type initiator is used as an initiator for initiating the polymerization of the polymerizable monomer. A method has been proposed in which nitrogen gas is generated by decomposition and the toner particles are deformed by the bubbles of the gas (Japanese Patent Laid-Open No. SHO 6-96).
No. 2-297855). Specifically, an azo-based initiator is added to the droplets of the monomer phase of the suspension polymerization, and the polymerization reaction is initially performed at a temperature not higher than the decomposition temperature of the azo-based initiator. When the polymerization reaction proceeds and the unreacted monomer reaches 5 to 15% by weight, the polymerization temperature is raised to decompose the azo-based initiator, and the nitrogen gas bubbles generated by the decomposition generate liquid. The surface of the droplet is pushed up, and the toner particles are deformed.

[0007]

However, in the above method, when the azo-based initiator is decomposed, the residual amount in the droplet is 5 to 5.
Since 15% by weight of the monomer is polymerized at once by a large amount of radicals generated by the decomposition of the azo-based initiator, the manufactured toner particles contain a large amount of a relatively low molecular weight component that lowers the melting temperature. Therefore, there is a problem that an offset is likely to occur.

The present invention has been made in view of the above circumstances, and retains the advantage of spherical toner particles that the particle size distribution is narrow and the particle size can be reduced, and is also modified. Therefore, it is an object of the present invention to provide a method for producing a toner for electrophotography, which has excellent cleaning properties with a cleaning blade, and does not contain a low-molecular weight component and thus does not cause offset.

[0009]

In order to solve the above-mentioned problems, the method for producing an electrophotographic toner of the present invention is to fix substantially spherical toner particles in which a foaming agent is internally added to a fixing resin. It is characterized in that it is heated above the glass transition temperature of the resin for use and above the foaming temperature of the foaming agent to foam the foaming agent and deform it.

In the method for producing the electrophotographic toner of the present invention having the above-mentioned constitution, the toner is contained in the substantially spherical toner particles produced by the suspension polymerization method, the dispersion polymerization method, the spray drying method or the like. Since the foaming agent internally added during the production of the particles is foamed by the subsequent heating to deform the toner particles, the obtained electrophotographic toner is generated by the decomposition of the azo initiator. The nitrogen gas bubbles do not contain a low-molecular weight component that causes an offset, as in the case of deforming a droplet during polymerization.

The present invention will be described below. As described above, the point of the present invention is to heat spherical toner particles to which a foaming agent is internally added in advance to a temperature not lower than the glass transition temperature of the fixing resin constituting the toner particles and not lower than the foaming temperature of the foaming agent. To foam the foaming agent. Even if the heating temperature is equal to or higher than the foaming temperature of the foaming agent, if the temperature is equal to or lower than the glass transition temperature of the fixing resin, not only the toner particles are not properly deformed, but also the toner particles are cracked and the formed image is Fine particles that deteriorate the image quality are generated, and the particle size distribution is widened.

The method for heating and foaming the toner particles is not particularly limited, but in order to prevent the toner particles from being fused and to be deformed, the toner particles are dispersed in a medium such as water and then autoclaved. It is desirable to heat by using such as. When the toner particles are produced by the suspension polymerization method or the dispersion polymerization method, the toner particles are obtained in a state of being dispersed in an aqueous dispersion medium or medium, and therefore, they are directly used in the heating and foaming steps of the next step. You can also do it.

In the electrophotographic toner T of the present invention thus obtained, as shown in FIG. 1, a large number of air bubbles 1 are generated inside the originally spherical toner particles 2 due to the foaming of the internally added foaming agent. Then, the surface of the toner particle 2 is pushed up by this, and it is made to be deformed. The particle size of the electrophotographic toner of the present invention is not particularly limited, but in order to obtain a high resolution image, the central particle size is 10 μm.
Before and after, the particle size dispersion is preferably within a range of 1.50 or less.

The spherical toner particles that are the basis of the electrophotographic toner are obtained by adding a foaming agent in spherical particles made of a fixing resin.
It is a mixture of various additives necessary for electrophotographic toner in predetermined amounts. The above spherical toner particles can be produced by various production methods, including a water-insoluble polymerizable monomer which is a base of the fixing resin,
A liquid monomer phase (oil phase) containing a polymerization initiator soluble in this, a foaming agent, and various additives is prepared, and it is suspended and dispersed in a droplet form in an aqueous dispersion medium such as water. While heating,
A suspension polymerization method of polymerizing a polymerizable monomer, a polymerizable monomer that is a base of a fixing resin, a polymerization initiator, a foaming agent, and various additives, A dispersion polymerization method in which a polymer that dissolves but does not dissolve the polymer is dissolved together with a dispersion stabilizer and polymerized under stirring, the fixing resin, a foaming agent, and various additives,
A spray-dried method in which a spray-dried solution obtained by dissolving or dispersing in a suitable solvent is sprayed in a mist using a spraying device, and the solvent is dried and removed, is produced. , Is preferably adopted. All of the spherical toner particles produced by these three methods have a narrow particle size distribution and can be made smaller by changing the conditions, so that they have excellent charging characteristics and high quality images can be obtained. The advantage is that It also has excellent productivity because it does not require classification.

When the toner particles produced by the above method are used, the polymerization rate is 95% or more in order to prevent the generation of a large amount of low molecular weight components that cause offset and the like. It is preferable to use a polymer that has been polymerized. As the polymerizable monomer used as the base of the fixing resin used in the above method, various radically polymerizable polymerizable monomers can be used. As the fixing resin used in the other method, a polymer of the above polymerizable monomer is used.

Examples of such polymerizable monomers include monovinyl aromatic monomers, acrylic monomers, vinyl ester monomers, vinyl ether monomers, diolefin monomers and monoolefin monomers. Various conventionally known compounds such as a monomer, a halogenated olefin-based monomer and a polyvinyl-based monomer can be used. As the monovinyl aromatic monomer, the following general formula (1):

[0017]

[Chemical 1]

(In the formula, R ¹ is a hydrogen atom, a lower alkyl group or a halogen atom, R ² is a hydrogen atom, a lower alkyl group, a halogen atom, an alkoxy group, an amino group, a nitro group, a vinyl group, a sulfo group or sodium sulfo group. A monovinyl aromatic hydrocarbon represented by a nato group, a potassium sulfonato group or a carboxyl group), such as styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene, o, m, p-chlorostyrene, p. -Ethyl styrene, sodium styrene sulfonate, divinyl benzene and the like.

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

[0020]

[Chemical 2]

(Wherein R ³ is a hydrogen atom or a lower alkyl group, R ⁴ is a hydrogen atom, a hydrocarbon group having up to 12 carbon atoms,
It represents a hydroxyalkyl group, a vinyl ester group or an aminoalkyl group. ) An acrylic monomer represented by, for example, acrylic acid, methacrylic acid, methyl acrylate,
Ethyl acrylate, butyl acrylate, acrylic acid-2
-Ethylhexyl, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, butyl γ-hydroxyacrylate, butyl δ-hydroxyacrylate, β-hydroxy Ethyl methacrylate, γ-aminopropyl acrylate,
Examples include γ-N, N-diethylaminoacrylic acid propyl ester, ethylene glycol dimethacrylic acid ester, and tetraethylene glycol dimethacrylic acid ester.

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

[0023]

[Chemical 3]

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

[0025]

[Chemical 4]

(In the formula, R ⁶ represents a monovalent hydrocarbon group having up to 12 carbon atoms.) Examples thereof include vinyl ether type monomers such as vinyl methyl ether, vinyl ethyl ether and vinyl-n. -Butyl ether, vinyl phenyl ether, vinyl cyclohexyl ether and the like. The diolefin-based monomer has the following general formula (5):

[0027]

[Chemical 5]

(Wherein 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), and examples thereof include a diolefin monomer. , Isoprene, chloroprene and the like. As a mono-olefin monomer,
The following general formula (6):

[0029]

[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 the formula (I) is exemplified, such as ethylene, propylene and butene-1. , Pentene-1, 4-methylpentene-1 and the like. Examples of the halogenated olefin-based monomer include vinyl chloride and vinylidene chloride.

Further, examples of the polyvinyl monomer include divinylbenzene, diallyl phthalate and tricyanurate. These can be used alone or in combination of two or more. For example, when a toner containing the most common styrene-acrylic fixing resin is produced, styrene and an acrylic monomer may be used in combination as the polymerizable monomer.

In the method (1), examples of the polymerization initiator for initiating the polymerization of the polymerizable monomer include azobisisobutyronitrile and 2,2'-azobis- (2,4).
-Dimethylvaleronitrile), 2,2'-azobis-
(4-methoxy-2,4-dimethylvaleronitrile),
2,2'-azobis- (2-cyclopropylpropionitrile), 2,2'-azobis- (2-methylpropionitrile), 2,2'-azobis- (2-methylbutyronitrile), 1 , 1'-azobis- (cyclohexane-
1-carbonitrile), 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, dimethyl-2,
Azo compounds such as 2'-azobis (2-methylpropionate); cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, di-t-butyl peroxide, benzoyl peroxide, lauroyl peroxide and other peroxides In addition to the above, a conventionally known photopolymerization initiator can be used when the polymerization is carried out by irradiation with ultraviolet rays or visible rays. These are used alone,
Two or more kinds can be used in combination. As the polymerization initiator used in the suspension polymerization method, those that are insoluble in the aqueous dispersion medium and compatible with the polymerizable monomer are preferably adopted from the above.

The amount of the polymerization initiator used is the polymerizable monomer 10
The amount is 0.001 to 10 parts by weight, preferably 0.01 to 0.5 parts by weight, relative to 0 parts by weight. It is also possible to initiate the polymerization using γ rays, accelerated electron beams, etc.
In this case, the polymerization initiator may not be used. Also,
The polymerization may be initiated by combining ultraviolet rays and various photosensitizers.

As the foaming agent internally added to the toner particles, various conventionally known foaming agents can be used, but a foaming agent satisfying the following conditions is particularly preferably used. First, when the toner particles are produced by the suspension polymerization method, a foaming agent which is not deteriorated or decomposed by various components constituting the monomer phase and the aqueous dispersion medium and which does not foam depending on the polymerization temperature during the suspension polymerization is preferable. Further, in particular, in order to efficiently internally add the foaming agent to the toner particles, it is preferable to use a foaming agent having a higher affinity for the monomer phase than the aqueous dispersion medium. Further, in the case of producing toner particles by the suspension polymerization method, in order to prevent a large amount of low molecular weight components that cause offset and the like from being generated, a foaming agent that does not generate radicals during foaming is used. Is preferred.

When the toner particles are produced by the dispersion polymerization method, a foaming agent which is not deteriorated or decomposed by various components constituting the dispersion system such as a medium and which does not foam at the polymerization temperature during the dispersion polymerization is preferably used. It Further, a foaming agent having a better affinity with the polymerizable monomer than the medium is particularly preferable. Such a foaming agent transfers from the medium to the polymer when the amount of the monomer decreases due to the progress of the polymerization, so that the foaming agent is efficiently internally added to the toner particles. Further, in the case of producing toner particles by the dispersion polymerization method, in order to prevent a large amount of low molecular weight components causing offset and the like,
It is preferable to use a foaming agent that does not generate radicals during foaming.

Further, when the toner particles are manufactured by the spray dry method, a foaming agent which is not deteriorated or decomposed by various components constituting the spray dry liquid is used. Further, it is particularly preferable to use a foaming agent having a better affinity for the fixing resin than the solvent. Such a foaming agent is efficiently internally added to the toner particles when the solvent is evaporated.

Specific examples of the above foaming agent include, but are not limited to, oxybisbenzenesulfonylhydrazine (foaming temperature 140 ° C.), p
-Toluenesulfonyl hydrazide (foaming temperature 106
℃), dinitrosopentamethylenetetramine (foaming temperature 200 ℃), azodicarbonamide (foaming temperature 120 ~
220 ° C.) and the like. These foaming agents can be used alone or in combination of two or more.

The amount of the foaming agent internally added to the toner particles is not particularly limited in the present invention, but is preferably 0.01 to 100 parts by weight, and 0.1 to 100 parts by weight of the polymerizable monomer.
-30 parts by weight is more preferred. Among the additives, various conventionally known colorants can be used as the colorant for imparting color to the toner.

The colorant may be blended in a predetermined amount in advance when the toner particles are produced by any of the above-described methods, and the non-colored toner particles are produced by the above-mentioned methods. However, it may be dyed later with a colorant (either before or after the modification). In the suspension polymerization method of, the colorant to be preliminarily blended in the monomer phase is not limited to this,
For example, <black> carbon black, nigrosine dye (C.I.
No. 50415B), Lamp Black (C.I. No. 7)
7266), oil black, azo oil black, <red> DuPont oil red (CI. No. 2610)
5), Rose Bengal (CI. No. 45435), Orient Oil Red # 330 (CI. No. 605)
0), <yellow> chrome yellow (CI. No. 1409)
0), quinoline yellow (C.I.O. 47005), <green> malachite green oxalate (C.I.N.
o. 42000), <blue> chalco oil blue (CI No. azoec
Blue 3), aniline blue (C.I. No. 5040)
5), methylene blue chloride (C.I. No. 520)
1), phthalocyanine blue (C.I. No. 7416)
0), Ultramarine Blue (C.I. No. 7710)
3), etc. These may be used alone or in combination of two or more. The colorant is a polymerizable monomer 1
It is preferable to use 1 to 20 parts by weight per 00 parts by weight.

Among the above colorants, in the case of a black toner, carbon black, particularly carbon black which has been subjected to a surface treatment to improve its affinity with a polymerizable monomer, is most preferable. Examples of the surface treatment for improving the affinity of carbon black with the polymerizable monomer include a coupling treatment with a coupling agent and a grafting treatment with a polymerizable monomer.

In the dispersion polymerization method (1), a dye that is more soluble in the polymerizable monomer than the medium is preferably used as the colorant to be preliminarily blended in the reaction system. Examples of the dye include oil-soluble dyes. The oil-soluble dye is transferred from the medium to the polymer when the amount of the monomer is reduced due to the progress of polymerization, so that efficient dyeing can be performed. Specific examples of oil-soluble dyes are shown below. <Black dye> Black FS-Special A, Black S, Black # 103, Black # 107, Black #
215, Black # 141 (all are trade names manufactured by Chuo Gosei Kagaku Co., Ltd.), OPLAS Black HZ, Oplas Black # 836, and Oplas Black # 838 (all trade names manufactured by Orient Chemical Industry Co., Ltd.). <Red dye> MACROLEX red 5B,
Macrolex Red Violet R (all are trade names manufactured by Bayer), Sumiplast Red AS, Samiplast Tread B-2, Samiplast Red HLG-Z (all trade names manufactured by Sumitomo Chemical Co., Ltd.), Oprah Thread RR, Oprah Thread # 330 (all are trade names manufactured by Orient Chemical Industry Co., Ltd.), Red 6B, Red T
R-71 (all are trade names of Chuo Gosei Kagaku KK). <Orange dye> Macrolex Orange 3G, Macrolex Orange R (all are brand names manufactured by Bayer), Orange S, Orange R, Orange # 826N (all are brand names manufactured by Chuo Synthetic Chemicals), Oplas Orange PS , Oplas Orange RR (trade name of Orient Chemical Industry Co., Ltd.), Samiplast Orange HRP (trade name of Sumitomo Chemical Industry 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 ,
Samiplast Yellow R (all are trade names of Sumitomo Chemical Co., Ltd.), Oplus Yellow 3G, Oplus Yellow # 1
30 (all are trade names manufactured by Orient Chemical Industry Co., Ltd.). <Purple dye> Macrolex Violet 3R, Macrolex Violet B (both trade names manufactured by Bayer), Violet MVB (trade name manufactured by Chuo Gosei Kagaku), Samiplast Violet RR, Samiplast Violet B (all Sumitomo) (Chemical Industry Co., Ltd.), Oplus Violet # 370, Oplus Violet #
732 (all are trade names manufactured by Orient Chemical Industry Co., Ltd.). <Blue Dye> Macrolex Blue RR (trade name of Bayer), Blue BO, Blue # 8B (all are trade names of 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, and Oplas Blue # 630 (all are trade names manufactured by Orient Chemical Co., Ltd.). <Green dye> Macrolex Green 5B, Macrolex Green G (all are trade names manufactured by Bayer), Green # 550, Green # 201 (all are trade names manufactured by Chuo Synthetic Chemicals), Samiplast Green G (Sumitomo) Chemical Industry Co., Ltd. product name), Oplus Green # 502, Oplus Green # 503 (all are product names of Orient Chemical Industry Co., Ltd.). <Brown Dye> Brown PB, Brown SG (all are trade names of Chuo Gosei Kagaku), Oplas Brown # 430,
Oplas Brown # 431 (all are trade names manufactured by Orient Chemical Industry Co., Ltd.).

The amount of the oil-soluble dye used varies depending on the desired degree of color density, but is usually 1 to 10 ^-9 times, especially 10 ^-6 times the weight of the reaction solution 1. It is preferable. Further, in the spray-drying method, as the colorant to be preliminarily mixed in the solution, any of the above-exemplified colorants can be used.

On the other hand, in order to dye the uncolored toner particles later, for example, the uncolored toner particles may be dispersed together with a dye such as a dispersible dye in an aqueous medium and stirred at a predetermined temperature for a predetermined time. Examples of dispersible dyes used for dyeing include azo dyes, anthraquinone dyes, indigoid dyes, sulfur dyes and phthalocyanine dyes. The dispersible dye preferably has a high affinity for the polymer constituting the toner particles and can dye the toner particles firmly. The amount of the dispersible dye used varies depending on the desired degree of coloring density, but is usually preferably 2% by weight or more, and more preferably 4% by weight or more, relative to the toner particles. Water is usually used as the aqueous medium, but when the dispersibility of the toner particles and the dye is poor, a suitable organic solvent may be added in a small amount. The amount of the aqueous medium used is preferably 500 parts by weight or more based on 100 parts by weight of the toner particles.

Typical additives other than the above colorants include a charge control agent and an offset preventive agent. The charge control agent is blended to control the triboelectric chargeability of the toner, and there are two types, one for controlling the positive charge and one for controlling the negative charge. As the charge control agent for controlling the positive charge, an organic compound having a basic nitrogen atom, such as a basic dye, an aminopyrine, a pyrimidine compound, a polynuclear polyamino compound, an aminosilane, or the like, a filler surface-treated with each of the above compounds, or the like Can be given.

Charge control agents for controlling the negative charge include nigrosine base (CI5045) and oil black (CI26150).
), An oil-soluble dye such as Bontron S or Spiron Black; a charge control resin such as a styrene-styrene sulfonic acid copolymer; a compound containing a carboxy group (for example, a metal chelate of alkylsalicylic acid), a metal complex dye, a fatty acid metal Examples thereof include soap, resin acid soap, and metal salt of naphthenic acid.

The charge control agent is used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the polymerizable monomer. The offset preventing agent is blended in order to impart an offset preventing effect to the toner. Examples of the anti-offset agent include aliphatic hydrocarbons, aliphatic metal salts, higher fatty acids, fatty acid esters or partially saponified products thereof, silicone oil, and various waxes. Among them, the weight average molecular weight is 1000 to 100
An aliphatic hydrocarbon of about 00 is preferable. In particular,
One or a combination of two or more of low molecular weight polypropylene, low molecular weight polyethylene, paraffin wax, low molecular weight olefin polymer composed of olefin units having 4 or more carbon atoms, silicone oil and the like is suitable.

The offset preventing agent is a polymerizable monomer 100.
0.1 to 10 parts by weight, preferably 0.5
Used at a rate of ~ 8 parts by weight. In addition to the above components, examples of components that can be added to the monomer phase include magnetic powder and a crosslinking agent. When magnetic powder is added, a magnetic toner as a one-component developer can be obtained.

The magnetic substance is a substance that is strongly magnetized in that direction by a magnetic field, and is preferably chemically stable, and is a fine powder having a particle size of 1 μm or less, particularly about 0.01 to 1 μm. Good. Typical magnetic materials include iron oxides such as magnetite, hematite, and ferrite,
Metals such as iron, cobalt and nickel, or with these metals, aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth,
Cadmium, calcium, manganese, selenium, titanium,
Examples thereof include alloys with tungsten and vanadium, and mixtures thereof.

The amount of the magnetic powder blended is 10
20 to 300 parts by weight, preferably 50 to 0 parts by weight
It is preferable to use it in a proportion of 150 parts by weight. The cross-linking agent is
It is added to crosslink the fixing resin to improve the mechanical or thermal characteristics of the electrophotographic toner. For example, divinyl compounds such as divinylbenzene; diallyl phthalate, diallyl isophthalate, diallyl adipate, diallyl glyco. Rate, diallyl maleate, diallyl sebacate and other diallyl compounds; triallyl phosphate, triallyl aconitate, triallyl cyanurate, trimellitic acid allyl ester, pyromellitic acid allyl ester and other triallyl compounds; 1,6-hexanediol Diacrylate, neopentyl glycol diacrylate, ethylene glycol diacrylate,
Diacrylate compounds such as diethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, butylene glycol diacrylate, pentaerythritol diacrylate, 1,4-butanediol diacrylate; trimethylolpropane triacrylate, pentaerythritol triacrylate, etc. Triacrylate compound;
Dimethacrylate compounds such as 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, butylene glycol dimethacrylate;
Trimethacrylate compounds such as trimethylolpropane trimethacrylate; poly (meth) acrylates such as dipentaerythritol hexaacrylate, tetramethylolmethane tetraacrylate, N, N, N ′, N′-tetrakis (β-hydroxyethyl) ethylenediamine, etc. ) Acrylate compounds; allyl acrylate,
Allyl-acrylic compounds such as allyl methacrylate;
Examples thereof include acrylamide compounds such as N, N'-methylenebisacrylamide and N, N'-methylenebismethacrylamide, and prepolymers such as polyurethane acrylate, epoxy acrylate, polyether acrylate and polyester acrylate.

The crosslinking agent is used in an amount of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the polymerizable monomer. In addition, various additives such as a stabilizer may be blended in an appropriate ratio. In the suspension polymerization method, the aqueous dispersion medium for dispersing the monomer phase containing each of the above components in the form of droplets includes water, or a mixed solvent containing water as a main component and incompatible with the monomer phase, Water is most preferably adopted.

A dispersion stabilizer is preferably added to the above aqueous dispersion medium for the purpose of stabilizing the dispersibility of the monomer phase droplets. Examples of the dispersion stabilizer include water-soluble polymers such as polyvinyl alcohol and the above-mentioned poorly water-soluble inorganic fine particles. Considering the environmental stability, fluidity, charging characteristics, etc. of the toner, the surface of the toner particles Inorganic fine particles that are poorly water-soluble are preferably used, rather than water-soluble polymers that may be taken up by and become hygroscopic on the surface. The addition amount of the dispersion stabilizer may be similar to the conventional amount.

Further, it is preferable to add a surfactant to the aqueous dispersion medium in order to obtain a good dispersed state of the monomer phase. The surfactant is preferably added after addition of the monomer phase in order to prevent bubbles from being caught. As the surfactant, various conventionally known anionic, cationic or nonionic surfactants can be used. However, considering that the intended toner particle size is 10 μm or less, the suspension-dispersing ability is improved. It must be excellent, and it is desirable that it be easily removed from the toner in order not to affect the characteristics of the toner after manufacturing. The surfactant is added in an appropriate ratio according to the ratio of the monomer phase and the aqueous dispersion medium.

In the dispersion polymerization method, the polymerizable monomer is dissolved but the polymer is not dissolved. Examples of the medium include water; lower alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol; ethylene glycol and propylene. Polyhydric alcohols such as glycol, butanediol, diethylene glycol and triethylene glycol; cellosolves such as methyl cellosolve and ethyl cellosolve; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran; esters such as ethyl acetate. .

These media can be used alone or in combination of two or more. The medium preferably used in the present invention includes lower alcohols such as ethanol, water or a mixed medium of water and lower alcohol. In the above mixed medium, the weight ratio of water to lower alcohol is 40:60 to 5:95, and particularly 30:70 to.
It is preferably within the range of 10:90. The amount of the medium used is 50 to 50 per 100 parts by weight of the polymerizable monomer.
It is preferably in the range of 00 parts by weight, particularly 500 to 2500 parts by weight.

As the dispersion stabilizer for stabilizing the dispersibility of the polymer in the medium, for example, polyacrylic acid, polyacrylic acid salt, polymethacrylic acid, polymethacrylic acid salt,
(Meth) acrylic acid- (meth) acrylic acid ester copolymer, acrylic acid-vinyl ether copolymer, methacrylic acid-styrene copolymer, carboxymethyl cellulose, poly (hydroxystearic acid-g-methyl methacrylate-co- (Methacrylic acid) copolymer, poly (ethylene oxide), polyacrylamide, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose,
Examples thereof include polyvinyl alcohol. Further, nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants and the like can also be used. The amount of the dispersion stabilizer used is 0.
It is in the range of 1 to 30% by weight, preferably 1 to 10% by weight.

In the further spray-drying method, as the solvent for dissolving each of the above-mentioned components, a solvent capable of dissolving the fixing resin is preferably adopted from among various conventionally known organic solvents. The solid content concentration of the spray-dried solution may be similar to the conventional one.

[0057]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples. Example 1 <Production of Spherical Toner> 100 g of grafted carbon black (styrene content 40% by weight) produced by treating carbon black with a styrene monomer was mixed with each of the following components in a high-speed stirrer (Tokuki Kika Kogyo Co., Ltd.). Made of TK
With a homomixer), the monomer phase was prepared by stirring for 10 minutes at a rotation speed of 1000 rpm.

Component (g) -Polymerizable monomer Styrene 400 Propyl acrylate 120-Crosslinking agent Divinylbenzene 1-Polymerization initiator benzoyl peroxide 12-Polymerization regulator t-dodecyl mercaptan 1-Charge control agent Bontron S- 34 5 ・ Foaming agent oxybisbenzenesulfonylhydrazine 10 Next, the above-mentioned monomer phase was used as an aqueous dispersion medium 1500
g of ion-exchanged water and 10 g of polyvinyl alcohol as a dispersion stabilizer, and the mixture is stirred for 30 minutes at a rotation speed of 10,000 rpm with the above-mentioned high-speed stirrer so that the average particle diameter of the droplets is 10 μm. A suspension of was prepared.

Next, this suspension was transferred to a 3 liter separable flask equipped with a stirrer, a nitrogen introducing tube and a condenser, and heated to 80 ° C. while stirring under a nitrogen atmosphere to carry out a polymerization reaction for 5 hours. . When the suspension after polymerization was observed with an optical microscope, it was confirmed that the toner particles were substantially spherical black particles.

<Modification of Toner Particles> The above suspension was transferred to an autoclave and heat-treated at 140 ° C. for 3 hours.
It was cooled to room temperature, further filtered, washed with ion-exchanged water, and dried to obtain a deformed electrophotographic toner. When the obtained electrophotographic toner T was observed with an electron microscope, it was confirmed that the toner was deformed as shown in FIG. 2 (a). Further, when the electrophotographic toner T was crushed with a mortar and a pestle and then observed with an electron microscope in the same manner, as shown in FIG. 2B, a large number of bubbles 1 were observed therein.

Example 2 <Production of Spherical Toner> 100 g of grafted carbon black (styrene content 40% by weight) produced by treating carbon black with a styrene monomer, together with the following components, was mixed with a high-speed stirrer (special machine). TK manufactured by Chemical Industry
With a homomixer), the monomer phase was prepared by stirring for 10 minutes at a rotation speed of 1000 rpm.

Component (g) -Polymerizable monomer Styrene 400 Butyl acrylate 120-Crosslinker 2-ethylene glycol dimethacrylate 1-Polymerization initiator benzoyl peroxide 12-Polymerization regulator t-dodecyl mercaptan 1-Charge control Agent Bontron S-34 5 Foaming agent p-toluenesulfonyl hydrazide 10 Next, the above-mentioned monomer phase is 1500 as an aqueous dispersion medium.
g of ion-exchanged water and 10 g of tricalcium phosphate as a dispersion stabilizer, and the mixture was stirred for 30 minutes at a rotation speed of 10000 rpm with the above-mentioned high-speed stirrer so that the average particle diameter of the droplets was A 10 μm suspension was made.

Then, this suspension was polymerized under the same conditions as in Example 1. When the suspension after polymerization was observed with an optical microscope, it was confirmed that the toner particles were substantially spherical black particles. <Transformation of Toner Particles> The above suspension was transferred to an autoclave, heat-treated at 120 ° C. for 3 hours, cooled to room temperature, filtered, washed with ion-exchanged water, and dried to be transformed. An electrophotographic toner was obtained.

When the obtained electrophotographic toner was observed with an electron microscope, it was confirmed that the toner was deformed by the bubbles generated inside, as in Example 1. Example 3 <Production of Spherical Toner> 8 g of polyacrylic acid as a dispersion stabilizer was dissolved in 800 ml of methanol as a dispersion medium for dispersion polymerization, and then 5 g of carbon black.
And the following components were dissolved.

Component (g) Polymerizable monomer Styrene 20 Methacrylic acid-n-butyl 5 Polymerization initiator Azobisisobutyronitrile 1 Blowing agent Oxybisbenzenesulfonylhydrazine 5 Next, the above solution is stirred. Transfer to a 1 liter separable flask equipped with a vessel, nitrogen inlet tube and condenser, and stir at a rotation speed of 150 rpm under a nitrogen atmosphere for 8 hours.
Heated to 0 ° C. Then, 2 hours, 4 hours, and 6 hours after the start of the reaction, a polymerization reaction was carried out for 15 hours while additionally adding 20 g of styrene and 5 g of -n-butyl methacrylate, respectively.

When the dispersion after polymerization was observed with an optical microscope, it was confirmed that the toner particles were substantially spherical black particles having a uniform particle size of about 10 μm. <Modification of Toner Particles> The above dispersion liquid was transferred to an autoclave, heated under the same conditions as in Example 1, cooled to room temperature, further filtered, washed with ion-exchanged water, and dried to obtain a modified shape. An electrophotographic toner was obtained.

When the obtained electrophotographic toner was observed with an electron microscope, it was confirmed that the toner was deformed by the air bubbles generated inside, as in Example 1. Comparative Example 1 Instead of benzoyl peroxide, 0.6 g of azobisisobutyronitrile was used as a polymerization initiator which generates nitrogen gas and also functions as a foaming agent, and oxybisbenzenesulfonylhydrazine as a foaming agent. A suspension having an average particle diameter of droplets of 10 μm was prepared in the same manner as in Example 1 except that the above was not used.

Next, this suspension was transferred to a 3 liter separable flask equipped with a stirrer, a nitrogen introducing tube and a condenser, and heated to 80 ° C. with stirring under a nitrogen atmosphere to carry out a polymerization reaction for 3 hours. . At this time, the polymerization rate of the monomer was 95%. Next, the heating temperature was raised to 95 ° C. and stirring was continued for another 2 hours, whereby azobisisobutyronitrile was decomposed and foamed, and the polymerization of the monomer was completed. At this time, the polymerization rate of the monomer is 99.5%
Met.

After completion of the reaction, the reaction solution was cooled to room temperature, further filtered, washed with ion-exchanged water, and dried to obtain a modified electrophotographic toner. When the obtained electrophotographic toner was observed with an electron microscope, it was confirmed that the toner was deformed by the air bubbles generated inside, as in Example 1. Comparative Example 2 The spherical toner particles obtained in the production of the spherical toner of Example 1 were used as Comparative Example 2 without being subjected to the foaming treatment.

The electrophotographic toners prepared in the above Examples and Comparative Examples were mixed with a ferrite carrier,
A two-component developer having a toner concentration of 3% by weight is prepared, and the two-component developer is used as an electrostatic copying machine [model number D manufactured by Mita Industry Co., Ltd.
C-1205], the cleaning property of the electrophotographic toner was evaluated by the following test method. Cleaning test As shown in FIG. 3, a sheet of A3 size paper 3 to which a strip 4 having a width of 30 mm and a Munsell value of N2.0 is pasted is used as a document, and the transfer paper is supplied to the electrostatic copying machine. The copying operation was performed without doing so, and before the cleaning process was completed, the copying machine was turned off to stop the copying machine, and the photosensitive drum was taken out.

Next, as shown in FIG. 4, the photosensitive drum 5
In the toner image corresponding to the original on the surface of the sheet, the rotation direction of the photosensitive drum 5 (indicated by a white arrow in the figure) from the cleaning blade contact position indicated by the dashed line in the figure in the portion 6 corresponding to the strip 4. The cellophane adhesive tape was attached to the surface of the portion 6a (indicated by a broken line) that was cleaned by the cleaning blade on the downstream side of FIG.

Next, after the above-mentioned cellophane adhesive tape was peeled from the surface of the photosensitive drum 5 and attached to the surface of a white paper, its density was measured by a reflection densitometer (TC-6 manufactured by Tokyo Denshoku Co., Ltd.).
The cleaning property was evaluated by measuring using D). The density is 0.10 to 0.14 when no toner remains on the surface of the photosensitive drum, and the density is 0.2.
When the above is reached, it is determined that the toner remains.

The results are shown in Table 1.

[0074]

[Table 1]

As is clear from the results shown in Table 1, the electrophotographic toner of Comparative Example 2 which was not modified had a very poor cleaning property and a large amount remained on the surface of the photosensitive drum. . On the other hand, it was found that the electrophotographic toners of Examples 1 to 3 and Comparative Example 1 were excellent in cleaning property and hardly remained on the surface of the photosensitive drum.

Offset Resistance Test For the electrophotographic toners of Example 1 and Comparative Example 1,
In order to examine the offset resistance, a paper for transfer was supplied to the above electrostatic copying machine to perform continuous copying. As a result, when the electrophotographic toner of Example 1 was used, problems such as fixing offset did not occur even after continuous copying of 100,000 sheets, and the copied image was good, but Comparative Example 1 When the toner for electrophotography of No. 1 was used, fixing offset occurred on 1000 sheets.

Then, in order to investigate the cause of the above-mentioned fixing offset, the molecular weight distributions of the electrophotographic toners of Example 1 and Comparative Example 1 were measured by the gel permeation method, and as shown in FIG. It was found that the electrophotographic toner of Example 1 contained a large amount of low molecular weight components which are considered to be the cause of offset.

[0078]

As described above in detail, according to the present invention,
The substantially spherical toner particles have a foaming agent that has been internally added when the toner particles are manufactured, and are foamed by subsequent heating to deform the toner particles, so that the particle size distribution is narrow and the particle size is small. The spherical toner particles have the advantage that they can be made into the same shape, and because they are shaped differently, they have excellent cleaning properties with a cleaning blade,
Moreover, since no low molecular weight component is contained, it is possible to manufacture an electrophotographic toner in which offset does not occur.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an electrophotographic toner produced by a method for producing an electrophotographic toner of the present invention and having a modified shape due to internal bubbles.

2 (a) is a front view showing the appearance of the electrophotographic toner prepared in Example 1 of the present invention, and FIG. 2 (b) is a crushed view of the electrophotographic toner prepared in Example 1; It is the front view which showed the inside.

FIG. 3 is a front view of an original image used in an electrostatic copying machine to evaluate the cleaning properties of the electrophotographic toners manufactured in Examples and Comparative Examples of the present invention.

FIG. 4 is a perspective view showing a photosensitive drum taken out from an electrostatic copying machine in order to evaluate the cleaning property of the electrophotographic toner using the original image.

FIG. 5 is a graph showing the molecular weight distribution of the electrophotographic toners produced in Example 1 and Comparative Example 1 of the present invention.

[Explanation of sign]

 T Electrophotographic toner 1 Bubble 2 Toner particle

Claims (1)

[Claims] 1. A substantially spherical toner particle in which a foaming agent is internally added to a fixing resin is heated above the glass transition temperature of the fixing resin and above the foaming temperature of the foaming agent to foam the foaming agent. A method for producing a toner for electrophotography, which comprises: