JPH08262795A - Electrophotographic toner - Google Patents

Abstract

PURPOSE: To obtain an electrophotographic toner having a low softening point, having viscoelasticity over a wide temp. range when melting and excellent in pulverizability, shock and heat resistances and durability. CONSTITUTION: This electrophotographic toner contains at least a resin binder and a colorant. The resin binder consists of high mol.wt. styrene-acrylic resin having a mol.wt. peak in a mol.wt. region of >=500,000 in its mol.wt. distribution measured by gel permeation chromatography, styrene-acrylic resin having a mol.wt. peak in the mol.wt. region of 50,000-500,000, styrene-acrylic resin having a crosslinked structure and polyester resin having a mol.wt. peak in a mol.wt. region of <=50,000.

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 used in an image forming apparatus to which an electrophotographic method such as an electrostatic copying machine or a laser beam printer is applied. .

[0002]

2. Description of the Related Art The electrophotographic method generally uses a photoconductive material to form an electric latent image on a photoconductor by various means, and then uses the electrophotographic toner with an electrophotographic toner. After being developed and visualized as a toner image, the toner image is transferred from the surface of the photoreceptor to a transfer material such as paper, and then heated,
This is a method of obtaining a copy by fixing with pressure, heat and pressure, or solvent vapor.

As the electrophotographic toner used for the image formation, a fixing resin is mixed with a colorant such as carbon black or a charge control agent, and the mixture is granulated to a predetermined particle size. Is used.

In the fixing step, heating and pressure fixing using a heat roller is generally used. In this method, the toner image on the transfer material is melted and pressure-bonded by the heat roller, so that the fixing efficiency is good and the fixing property is excellent.

However, in the above method, since the toner image and the heat roller are in direct contact with each other in a molten state, whether the fixing temperature is low,
Alternatively, when the temperature is very high, a part of the toner image is not fixed to the transfer material but adheres to the surface of the heat roller, and this is re-fixed on the transfer material. In particular, the substantial fixing temperature has been lowered due to the recent demand for high-speed fixing in a high-speed copying machine and demand for energy saving in the copying machine. Therefore, there is a demand for a method of fixing toner in a wide temperature range from a low temperature to a high temperature without causing an offset phenomenon.

In order to prevent the offset phenomenon, the surface of the heat roller is formed of a material having a good releasability for the toner, and a liquid for preventing offset such as silicone oil is supplied to the roller surface to heat the toner surface of the heat roller. There is known a method of preventing adhesion to the skin. However, although this method is extremely effective in preventing offset, there is a problem in that the fixing device becomes complicated because an apparatus for supplying the offset preventing liquid is required. Therefore, it has been attempted to prevent the offset by adding a wax such as low molecular weight polyethylene to the toner, but the toner containing the wax has poor heat resistance and increased cohesiveness, resulting in poor durability. Therefore, it is difficult to lower the fixing temperature (that is, improve the low temperature fixing property).

JP-A-60-260062 discloses a toner using a binder resin in which a polyester resin having a specific particle size forms a discontinuous phase in the resin. By using the polyester resin, the problems when the above wax is used are improved, and the low temperature fixability is improved. However, since the binder resin is a non-crosslinked polymer, it has a low elasticity when the toner is melted, and there is a problem that high temperature offset is likely to occur from a relatively low temperature.

Therefore, various attempts have been made to improve the binder resin constituting the toner. In order to improve the low-temperature fixability of the toner, it is generally effective that the toner melts at a low temperature and the contact area with the transfer material at the time of melting increases. For that purpose, it is effective to lower the Tg and the molecular weight of the binder resin used. On the other hand, in order to improve the offset resistance of the toner at high temperature, generally,
It is effective to increase the Tg and molecular weight of the binder resin to increase the viscoelasticity when the toner is melted. Therefore, in order to obtain a toner that can be fixed in a wide temperature range without causing an offset phenomenon (that is, a toner having excellent offset resistance), it is necessary to simultaneously satisfy the conflicting requirements.

JP-A-1-225965 and JP-A-5-6031 disclose binder resins having a crosslinked structure. By introducing a cross-linking structure into the binder resin, the offset resistance of the toner is improved, but since bulky groups exist between vinyl groups as the cross-linking agent or the spacing between vinyl groups is narrow, the polymer main chains are However, there is a problem in that the low temperature fixability is poor. If the cross-linking structure is further increased, the melt viscosity of the binder resin during heat kneading during toner preparation becomes extremely high, so it is necessary to perform heat kneading at a much higher temperature than usual, and as a result, the toner characteristics due to thermal decomposition of the additive There is also the problem that

JP-A-63-217358 and JP-A-2-110475 disclose binder resins having a crosslinked structure by ionic bonds. Crosslinking by an ionic bond improves the offset resistance of the toner and the softening fluidity in the low temperature range, but there is a problem in that the presence of ions lowers the chargeability and moisture resistance of the toner.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and provides a toner excellent in low-temperature fixing property, charging stability, offset resistance and durability. The purpose is to

[0012]

The present invention provides an electrophotographic toner containing at least a binder resin and a colorant, wherein the binder resin has a molecular weight distribution measured by gel permeation chromatography,
A high molecular weight styrene-acrylic resin having a molecular weight peak in the molecular weight range of 500,000 or more, a styrene-acrylic resin having a molecular weight peak in the molecular weight range of 50,000 to 500,000,
It is composed of a styrene-acrylic resin having a crosslinked structure and a polyester resin having a molecular weight peak in a region of a molecular weight of 50,000 or less. Thereby, the above object is achieved.

In a preferred embodiment of the present invention, the acrylic component constituting the high molecular weight styrene-acrylic resin is a monomer containing at least one acrylic acid or methacrylic acid ester monomer having a homopolymer Tg of 20 ° C. or lower. Formed from a mixture.

In a preferred embodiment of the present invention, the high molecular weight styrene-acrylic resin has a glass transition point of 50 to 75 ° C.

In a preferred embodiment of the present invention, the acrylic component constituting the styrene-acrylic resin is a monomer mixture containing at least one acrylic acid or methacrylic acid ester monomer having a homopolymer Tg of 20 ° C. or lower. It is formed.

In a preferred embodiment of the present invention, the glass transition point of the styrene-acrylic resin having a molecular weight peak in the molecular weight range of 50,000 to 500,000 is 50 to 75 ° C.
Is.

In a preferred embodiment of the present invention, the glass transition point of the polyester resin is 50 to 75 ° C.

In a preferred embodiment of the present invention, the high molecular weight styrene-acrylic resin, the styrene-acrylic resin having a molecular weight peak in the region of the molecular weight of 50,000 to 500,000 and the styrene-acrylic resin having the crosslinked structure are preferred. 20-80% by weight of resin relative to binder resin
Contained.

In a preferred embodiment of the present invention, the THF insoluble content in the binder resin is 5% by weight or less.

In a preferred embodiment of the invention, the crosslinked structure comprises structures derived from monomers of the formula:

[0021]

Embedded image

Here, X is (CH ₂ ) _n —O or (C
H ₂ CH ₂ O) _m , n and m are each independently an integer of 1 to 15, and R ¹ is independently a hydrogen atom or a lower alkyl group.

The present invention will be described in more detail below.

In the present specification, "lower alkyl" refers to alkyl having 1 to 20 carbon atoms.

(Measurement of Molecular Weight Distribution) In the present invention, the molecular weight distribution of the resin is measured by gel permeation chromatography (hereinafter referred to as GPC) as follows.

1) Preparation of measurement sample 100 mg of sample and 20 ml of THF are mixed and stirred with a ball mill or the like until the resin components are uniformly dissolved. Then, it is passed through a treatment filter (pore size of 1 μm or less, for example, 0.5 μm can be preferably used), and the passing liquid is used as a sample of GPC. The resin concentration in the sample is 1 to
10 mg / ml is preferred.

The THF insoluble matter of the binder resin contained in the toner of the present invention is a resin component which remains as an insoluble matter in the above filter treatment.

2) Measurement of molecular weight In the measurement, THF was used as a solvent to stabilize the column of the GPC apparatus at 40 ° C., and then the column was allowed to flow at a flow rate of 1 ml / min and about 100 μl of the THF sample solution was injected. And measure. The molecular weight distribution of the sample is calculated from the relationship between the logarithmic value of the calibration curve prepared using several kinds of monodisperse polystyrene standard samples and the count number. As the standard polystyrene sample for preparing the calibration curve, for example, polystyrene having a molecular weight of 500 to 1,000,000 can be used. Examples of the column include a styrene-divinylbenzene polymer column.

(Binder Resin) Used in the present invention,
The high molecular weight styrene-acrylic resin having a molecular weight peak in the molecular weight range of 500,000 or more is composed of a polymer chain having no cross-linking structure or is a polymer chain in such a manner as not to form a network structure as a whole. It may have a structure in which the two are linked to each other by crosslinking.

When the high molecular weight styrene-acrylic resin is composed of a polymer chain having no crosslinked structure, the resin contains a polymer of a monomer mixture containing a styrene monomer and an acrylic monomer, a styrene monomer. It may be a mixture of a polymer of a monomer mixture and a polymer of a monomer mixture containing an acrylic monomer. It is preferably a polymer of a monomer mixture containing a styrene monomer and an acrylic monomer. In this case, the resulting polymer can be a random copolymer, a block copolymer or a graft copolymer. Furthermore, if necessary, other copolymerizable monomers may be copolymerized in addition to the styrene-based monomer and the acrylic-based monomer. The respective types of the styrene-based monomer, the acrylic-based monomer, and the other monomer to be copolymerized as necessary, and their copolymerization ratios are selected so that the Tg of the obtained resin is 50 ° C to 75 ° C. .

Polymerization of the monomer can be carried out by an ordinary solution polymerization method, suspension polymerization method or the like. The polymerization conditions are selected so that the obtained resin has a molecular weight peak in the region where the molecular weight is 500,000 or more. It is preferably selected so as to have a molecular weight peak in the region of molecular weight of 500,000 to 1,200,000. Suitable conditions are, for example, but not limited to, suspension polymerization of the monomer mixture with adibisisobutyronitrile as an initiator at 60 ° C. for 5 hours. When the high molecular weight styrene-acrylic resin has a structure in which polymer chains are linked by crosslinking, the resin is, for example, a polymer of a monomer mixture containing a styrene monomer, an acrylic monomer and a crosslinking agent, or a styrene resin. A mixture of a polymer of a monomer mixture containing a monomer and an acrylic monomer and a polymer of a monomer mixture containing a styrene monomer, an acrylic monomer and a crosslinking agent, or a polymer of a monomer mixture containing a styrene monomer and a crosslinking agent and acrylic It can be prepared by cutting a portion cross-linked by a polymer chain and / or a cross-linking agent by heating and kneading a mixture of a monomer mixture containing a system monomer and a cross-linking agent with a polymer. Preferably, a polymer of a monomer mixture containing a styrenic monomer, an acrylic monomer and a cross-linking agent is heated and kneaded while applying a shearing force to cut the polymer chain and / or the portion cross-linked by the cross-linking agent. Thus, the high molecular weight styrene-acrylic resin can be prepared. This preparation step can be carried out immediately after the preparation of the polymer of the monomer mixture containing the above-mentioned crosslinking agent, during the preparation of the binder resin, or in the step of melt-kneading the components constituting the toner to obtain a kneaded product.

The types of the styrene-based monomer, the acrylic-based monomer, the cross-linking agent, and other monomers to be copolymerized as necessary, and their copolymerization ratios are determined by cutting the polymer chain and / or the cross-linked portion. The resin thus obtained has a Tg of 50 ° C. to 75 ° C. and a molecular weight of 5
Region of 0,000 or more, more preferably molecular weight of 500,000 to 120
Selected to have a molecular weight peak in the tens of thousands of regions. In particular, the copolymerization amount of the cross-linking agent is 0.
01 to 20% by weight is preferable, and more preferably 0.1 to 20% by weight.
It is 10% by weight. If it is less than 0.01% by weight, the molecular weight of the obtained resin will not be sufficiently high. If it is more than 20% by weight, the polymer chain and / or the cross-linked portion will not be sufficiently cut, and the molecular weight of the obtained resin will not be sufficiently high.

The preparation conditions in the above preparation step differ depending on the degree of crosslinking of the resin. For example, a resin obtained by suspension polymerization of azobisisobutyronitrile for 5 hours at 60 ° C. using a monomer mixture containing 0.5% by weight of a crosslinking agent as an initiator was kneaded using a three-roll mill. In this case, the preparation conditions are 120 ° C. to 140 ° C. for about 5 minutes to 30 minutes.
It can be adjusted while looking at it on a PC.

The above-mentioned polymer may be a random copolymer, a block copolymer or a graft copolymer, and, in addition to the styrene-based monomer and the acrylic-based monomer, if necessary, other copolymerizable with them. The monomer may be copolymerized.

The styrene-acrylic resin having a molecular weight peak in the molecular weight range of 50,000 to 500,000 used in the present invention is a polymer of a monomer mixture containing a styrene monomer and an acrylic monomer, a monomer mixture containing a styrene monomer. And a polymer of a monomer mixture containing an acrylic monomer. It is preferably a polymer of a monomer mixture containing a styrene monomer and an acrylic monomer. In this case, the resulting polymer may be a random copolymer, a block copolymer or a graft copolymer, and, in addition to the styrene-based monomer and the acrylic-based monomer, may be copolymerized with them, if necessary. Other monomers may be copolymerized.

The kinds of the styrene-based monomer, the acrylic-based monomer, and the other monomer to be copolymerized as necessary, and their copolymerization ratios are selected so that the Tg of the obtained resin is 50 ° C. to 75 ° C. To be done.

The polymerization of the monomer can be carried out by a usual solution polymerization method, suspension polymerization method or the like, but the polymerization conditions are selected so that the obtained resin has a molecular weight peak in the region of 50,000 to 500,000 or more. , More preferably a molecular weight of 50,000-
It is selected to have a molecular weight peak in the 300,000 region. Suitable conditions are, for example, without limitation, suspension polymerization of the monomer mixture with azobisisobutyronitrile as an initiator at 80 ° C. for 5 hours.

In any of the above styrene-acrylic resins, when the Tg of the resin is lower than 50 ° C., the storage stability of the toner is lowered. If it is higher than 75 ° C., the low temperature heat fixing property of the toner is deteriorated.

The styrene-acrylic resin having a crosslinked structure used in the present invention is a polymer of a monomer mixture containing a styrene monomer, an acrylic monomer and a crosslinking agent, and a polymer of a monomer mixture containing a styrene monomer and an acrylic monomer. A mixture of the polymer and a polymer of a monomer mixture containing a styrenic monomer, an acrylic monomer and a crosslinking agent, or a polymer of a monomer mixture containing a styrene monomer and a crosslinking agent and a monomer mixture containing an acrylic monomer and a crosslinking agent. It may be a mixture with a combination, and is preferably a polymer of a monomer mixture containing a styrene monomer, an acrylic monomer and a crosslinking agent. The resulting polymer may be a random copolymer, a block copolymer or a graft copolymer, and further, in addition to a styrene-based monomer, an acrylic-based monomer and a cross-linking agent, if necessary, in addition to these. Other copolymerizable monomers may be copolymerized.

The kinds of the styrene-based monomer, the acrylic-based monomer, the cross-linking agent, and the other monomer to be copolymerized as necessary, and their copolymerization ratios are not particularly limited, but the THF-insoluble matter contained in the resin is not limited. It is selected to be 0.1 to 5% by weight of the resin weight. Alternatively, in the high molecular weight styrene-acrylic resin having a structure in which the polymer chains are linked by crosslinking,
This may be the case where the crosslinked portion remains uncut.

In any of the above styrene-acrylic resins, the styrene monomer represented by the following general formula (I) can be preferably used:

[0042]

Embedded image

Here, R ² is a hydrogen atom, a lower alkyl group or a halogen atom, R ³ is a hydrogen atom, a lower alkyl group, a halogen atom, an alkoxy group, an amino group, a nitro group or the like, and Φ is a phenylene group. Is.

Styrene-based monomers include styrene,
α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-chlorostyrene,
o-, m-, or p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrene, p-methoxystyrene, p-phenylstyrene, 2,4-dimethylstyrene,
pn-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, etc. Can be used. These monomers may be used alone or in combination of two or more.

In any of the above styrene-acrylic resins, the acrylic monomer represented by the following general formula (II) can be preferably used:

[0046]

[Chemical 4]

Here, R ⁴ is a hydrogen atom or a lower alkyl group, and R ⁵ is an alkyl group having 12 or less carbon atoms or a hydroxyalkyl group having 12 or less carbon atoms.

The acrylic monomers include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate. , Acrylic acid 2-
Chlorethyl, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate,
Propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, methacrylic acid. Diethylaminoethyl, β-hydroxyethyl acrylate, γ-hydroxypropyl acrylate, δ-hydroxybutyl acrylate, β-hydroxymethacrylic acid ethyl and the like can be used. These monomers may be used alone or in combination of two or more.

Examples of the cross-linking agent include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene;
And the following diacrylate compounds of general formula (III) can be used:

[0050]

Embedded image

Here, X is (CH ₂ ) _n —O or (CH
A ₂ CH ₂ O) _m, n and m are from 1 to 20 independently, preferably an integer of 4 to 15, R ⁶ are each independently a hydrogen atom or a lower alkyl group.

Examples of the cross-linking agent include ethylene glycol diacrylate, 1,3-propylene glycol diacrylate, 1,4-putanediol diacrylate, 1,5-pentanediol diacrylate and 1,6.
-Hexanediol diacrylate, neopentyl glycol diacrylate, 1,9-nonanediol diacrylate, 1,10-decanediol diacrylate, or these acrylates replaced by methacrylates; diethylene glycol diacrylate, triethylene glycol diacrylate , Tetraethylene glycol diacrylate, hexaethylene glycol diacrylate, nanoethylene glycol diacrylate, polyethylene glycol # 400 diacrylate, polyethylene glycol # 600 diacrylate, dipropylene glycol diacrylate, or those in which these acrylates are replaced by methacrylate Can be used.

Further, for example, pentaerythritol triacrylate, trimethylol ethane triacrylate, trimethylol propane triacrylate, tetramethylol methane tetraacrylate, oligoester acrylate, or these acrylates replaced by methacrylates; triallyl cyanurate, Multifunctional crosslinkers such as triallyl trimellitate may also be used. These cross-linking agents may be used alone or in combination of two or more.

Other monomers which are optionally polymerized are:
The resulting polymer is selected to have the low temperature fixability, chargeability, grindability and anti-offset properties required of the toner, and one or more combinations of monomers having ethylenically unsaturated bonds are used. . Examples of such monomers include ethylenically unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene; unsaturated polyenes such as butadiene; vinyl halides such as vinyl chloride, vinyl chloride, vinyl bromide and vinyl fluoride. Vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate; vinyl methyl ether,
Vinyl ethers such as vinyl ethyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone and the like Examples thereof include N-vinyl compounds; vinylnaphthalene compounds; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide. These monomers may be used alone or in combination of two or more.

By increasing the copolymerization ratio of the styrene-based monomer in the kind and the copolymerization ratio of each monomer that achieves the conditions required for each resin, the pulverizability of the kneaded product of the components constituting the toner can be improved. At that time, among the above acrylic-based monomers, Tg when it is a homopolymer
Acrylic acid, acrylic acid n-
Butyl, isobutyl acrylate, propyl acrylate,
By copolymerizing n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate and the like with the styrene monomer, the copolymerization ratio of the styrene monomer can be further increased.

The copolymerization ratio of the styrene-based monomer varies depending on the type of other monomer such as the acrylic-based monomer to be copolymerized, but is usually 40 to 90% by weight, preferably 50 to 80% by weight of the monomer mixture. 40% by weight
If the amount is less, the pulverizability of the kneaded product will be poor. If it is more than 90% by weight, the low temperature fixing property of the toner is deteriorated.

The polyester resin used in the present invention is
It is preferably a saturated or unsaturated polyester synthesized from at least one diol and at least one dicarboxylic acid, and the obtained polyester is a homopolymer,
It may be a copolymer, a mixture of two or more homopolymers, a mixture of two or more copolymers, or a mixture of a mixture of at least one homopolymer and at least one copolymer.

As the diol, ethylene glycol,
Propylene glycol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,
6-hexanediol, decamethylene glycol, 1,
4-dihydroxyhexane, 1,4-dihydroxymethylcyclohexane, hydroquinone, p-xylylene glycol, 2,5-dichloro-p-xylylene glycol, 1,3-bis (hydroxyalkyl) benzimidazolone, 1,1- Methylene-bis [3- (2'-hydroxyethyl) -5,5-dimethylhydantoin] and the like can be used. These may be used alone or in combination of two or more. Examples of the dicarboxylic acid include malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, 1,3-cyclopentanedicarboxylic acid, 1,
3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1-carboxymethyl-4-cyclohexanecarboxylic acid, terephthalic acid, isophthalic acid,
2,5-dibromoterephthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 4,
4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 1,2-bis (4'-carboxyphenoxy) ethane, bis (p-carboxyphenyl) methane, 4,4'-sulfone-diphenyldicarboxylic acid, etc. Can be used. These may be used alone or in combination of two or more. Further, if necessary, a polyfunctional alcohol such as glycerin, trimethylolpropane, pentaerythritol and the like, and a polyfunctional carboxylic acid such as tricarparic acid, trimesic acid and trimellitic acid may be further copolymerized.

The combination of the above diol and dicarboxylic acid is not particularly limited, but the Tg of the obtained resin is from 50 ° C to
Selected to be 75 ° C. When the Tg of the resin is lower than 50 ° C., the storage stability of the toner is lowered. If it is higher than 75 ° C, the low temperature heat fixing property of the toner is adversely affected.

The polyester resin used in the present invention is
The molecular weight by GPC method is 2000-50000, preferably 3000-30000. If the molecular weight is less than 2000, toner fusion and blocking occur. When the molecular weight is more than 50,000, the pulverizability and the toner fixability are poor.

Each styrene used in the toner of the present invention
The mixing ratio of the acrylic resin and the polyester resin is as follows.

The high molecular weight styrene-acrylic resin may be contained in 20 to 80% by weight, preferably 20 to 50% by weight based on the total weight of the binder resin. If it is less than 20% by weight, fusion blocking occurs, which is not preferable. 8
If it is more than 0% by weight, sufficient fixing of the toner cannot be obtained, which is not preferable.

The styrene-acrylic resin having a molecular weight peak in the above-mentioned molecular weight range of 50,000 to 500,000 is 1 to 30% by weight, preferably 1 to 1 of the total weight of the binder resin.
It may be contained at 0% by weight. If it is less than 1% by weight, a high temperature offset phenomenon occurs, which is not preferable. If it is more than 30% by weight, sufficient fixing of the toner cannot be obtained, which is not preferable. The styrene-acrylic resin having the crosslinked structure may be included in an amount of 0.5 to 5% by weight based on the total weight of the binder resin.
If it is less than 0.5% by weight, offset is likely to occur, which is not preferable. If it exceeds 5% by weight, sufficient fixing property cannot be obtained, which is not preferable.

The mixing weight ratio of the above three kinds of styrene-acrylic resin and polyester resin is 20: 80-8.
It is 0:20, preferably 30:50 to 50:30.

In the present invention, the polyester resin can be uniformly mixed in the styrene-acrylic resin, or the dispersed phase of the polyester resin in the styrene-acrylic resin is 1 μm or less, preferably 0.05 μm to 1 μm. Can be formed.

When the dispersed phase is formed, if it is larger than 1 μm, desorption, drum filming, poor fluidity, etc. occur, and if it is smaller than 0.05 μm, the effect of the dispersed phase disappears.

The diameter of the dispersed phase can be adjusted by the kinds of the diol component and the dicarboxylic acid component constituting the polyester resin and the kneading conditions at the time of kneading the components constituting the toner. Preferred combinations of the diol component and the dicarboxylic acid component for achieving the dispersed phase of 1 μm or less are, for example, bisphenol A and ethanedicarboxylic acid, bisphenol A derivative and ethanedicarboxylic acid, butanediol and ethanedicarboxylic acid. Is not limited. Further, preferable kneading conditions vary depending on the type of polyester resin, for example, 110 ° C to 15 ° C.
It is 0 ° C., but is not limited thereto.

The diameter of the dispersed phase can be measured by cutting a kneaded material of the components constituting the toner with a microtome and observing the flakes with a transmission microscope.

In the binder resin of the present invention, in addition to the above-mentioned styrene-acrylic resin and polyester resin,
If necessary, known resins such as vinyl resins, polyesters, polyurethanes, epoxy resins, polyamides, polyolefins, hydrocarbon resins, phenol resins and aromatic resins may be included.

(Preferably used for preparing binder resin) The styrene-acrylic resin used in the present invention is produced by any of bulk polymerization method, solution polymerization method, suspension polymerization method and emulsion polymerization method. However, the suspension polymerization method is preferred.

In the suspension polymerization method, a desired polymer can be obtained by suspending and polymerizing the above-mentioned monomer mixture in an aqueous phase.

The suspension polymerization is preferably carried out in an amount of 100 parts by weight or less, preferably 10 to 90 parts by weight, based on 100 parts by weight of water or an aqueous solvent. As the dispersant, polyvinyl alcohol, partially saponified polyvinyl alcohol, calcium phosphate and the like can be used. The amount of the dispersant varies depending on the amount of the monomer dispersed in the water-based solvent, but is generally 0.1% with respect to 100 parts by weight of water or the water-based solvent.
05-1 parts by weight are added. The polymerization temperature varies depending on the initiator used and the target polymer, but usually,
50-95 degreeC is preferable. Any kind of polymerization initiator may be used as long as it is insoluble or hardly soluble in water. For example, benzoyl peroxide, tert-butyl peroxyhexanoate, 2,2-azobis (2,4-dimethylvaleronitrile) and the like can be used. The polymerization initiator may be used in an amount of 0.5 to 10 parts by weight based on 100 parts by weight of the monomer mixture.

The polyester resin used in the present invention can be produced by a conventional direct esterification method or transesterification method, and the reaction temperature is 80 ° C to 280 ° C, preferably 150 ° C to 250 ° C. The reaction time varies depending on the reaction temperature and is usually selected in the range of 10 minutes to 48 hours.

The binder resin is a polyester resin,
It can be prepared from a polymer obtained by suspension polymerization of a mixture containing a monomer mixture and a polymerization initiator, a mixture containing a polyester resin and a polymer of a monomer mixture, or a heat-kneaded product thereof. (Preparation of Toner) The toner contains a binder resin as an essential component, and may further contain a compounding agent such as a colorant, a charge control agent, a release agent, and a magnetic powder, if necessary.

The following are preferably used as the colorant.

Black pigments: carbon black such as furnace black, channel black, thermal, gas black, oil black, acetylene black, lamp black, aniline black; white pigments: zinc white, titanium oxide, antimony white, zinc sulfide; red pigments : Bengal, cadmium red, red lead, mercury sulfide, permanent red 4R, resole red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B; orange color Pigment: Red lead yellow lead, molybdenum orange, permanent orange GTR, pyrazolo orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, Andrenslen Brilliant Orange GK; Yellow pigments: yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, Naples yellow, naphthol yellow S, hunter yellow G, hunter yellow 10G, benzidine. Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake; Green Pigment: Chrome Green, Chromium Oxide, Pigment Green B, Malachite Green Lake, Fanal Yellow Green G; Blue Pigment: Navy Blue, Cobalt Blue, Alkali Blue Lake, Victoria Blue Lake, Phthalocyanine Blue Partial Chloride, Fast Sky Blue, Indanthrene Blue BC; Purple Pigment: Manganese Purple, Fast Bio B, methyl violet lake; extender pigment: barite powder, barium carbonate, clay, silica, white carbon, talc, alumina white; conductive pigment: conductive carbon book, aluminum powder; photoconductive pigment: zinc oxide, selenium , Cadmium sulfide, cadmium selenide.

The colorant may be used in an amount of 1 to 30 parts by weight, preferably 2 to 20 parts by weight, based on 100 parts by weight of the binder resin.

As the charge control agent, a positive charge control agent or a negative charge control agent can be used depending on the polarity of the toner.

Examples of the positive charge control agent include organic compounds having a basic nitrogen atom, such as basic dyes, aminopyridines, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, and fillers surface-treated with these compounds. Can be used.

As the negative charge control agent, a compound containing a carboxy group (eg, metal chelate of alkylsalicylic acid), metal complex salt dye, fatty acid soap, metal salt of naphthenic acid and the like can be used.

The charge control agent is 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the binder resin.
It may be used in a proportion of parts by weight.

Examples of the releasing 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-
About 10,000 aliphatic hydrocarbons are preferred. Specifically, one kind or a combination of two or more kinds of low molecular weight polypropylene, low molecular weight polyethylene, paraffin wax, a low molecular weight olefin polymer composed of olefin units having 4 or more carbon atoms is preferable.

The releasing 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 binder resin.

As the magnetic powder, various ferrites such as ferric tetroxide (Fe ₃ O ₄ ) and ferric sesquioxide (γ-Fe _2).
O ₃ ), iron oxide zinc (ZnFe ₂ O ₄ ), iron yttrium oxide (Y ₃ Fe ₅ O ₁₂ ), iron cadmium oxide (CdFe _2).
O ₄ ), iron gadolinium oxide (GdFe ₅ O ₄ ), iron oxide copper (CuFe ₂ O ₄ ), lead iron oxide (PbFe ₁₂ O ₁₉ ), neodymium iron oxide (NdFeO ₃ ), barium iron oxide (Ba)
Fe ₁₂ O ₁₉ ), magnesium iron oxide (MgFe ₂ O ₄ ),
Iron manganese oxide (MnFe ₂ O ₄ ), lanthanum iron oxide (L
aFeO ₃ ), iron powder, cobalt powder, nickel powder and the like.

The toner of the present invention can be prepared by the following method.

The toner of the present invention can be manufactured by a known method for manufacturing a toner. For example, the components constituting the toner are homogeneously pre-kneaded by a dry blender, a Henschel mixer, a ball mill or the like to obtain a mixture.
The obtained mixture is uniformly melt-kneaded by using a kneading device such as a Panbury mixer, a roll, a uniaxial or biaxial extrusion kneader and the like. The obtained kneaded product may be cooled, pulverized, and classified as necessary to produce a raw toner powder.
Raw toner powder can also be produced by a suspension polymerization method or the like. The toner has a volume average particle diameter (median diameter by Coulter counter) of 5 to 25 μm.
It is preferably 5 to 15 μm, and particularly preferably 7 to 12 μm.

The above toner raw powder is made into a toner by adding an external additive, if necessary. The external additive can improve the fluidity and chargeability of the toner.

As the external additive, various conventionally known materials such as inorganic fine particles, resin fine particles and metal stearate can be used. In particular, silica-based surface treatment agents containing hydrophobic or hydrophilic silica fine particles, for example, hydrophobic or hydrophilic silica fine particles such as ultrafine particulate anhydrous silica and colloidal silica are preferably used. The external additive is added in an amount of 0.1 to 2.0% by weight based on the total weight of the toner, that is, the total weight of the raw toner powder and the external additive.

The toner of the present invention can be mixed with a magnetic carrier such as ferrite or iron powder to be used as a two-component developer in an image forming apparatus.

As the magnetic carrier, a ferrite type magnetic carrier is preferably used. Fe and Cu,
Soft ferrite containing at least one, preferably two or more metal components selected from the group consisting of Mg, Mn, and Ni can be suitably used. For example, particles of sintered ferrite of copper-zinc-magnesium ferrite, especially spherical particles, can be used as soft ferrites. The surface of the magnetic carrier may not be coated, but it is preferable that it is coated with a silicone resin, a fluorine resin, an epoxy resin, an amino resin, a urethane resin or the like. The particle size of the magnetic carrier is 30 to 200
It is desirable that the thickness is in the range of 50 μm, particularly 50 to 150 μm. The saturation magnetization of the carrier is preferably 30 to 70 emu / g, particularly 45 to 65 emu / g.

The mixing ratio of the magnetic carrier and the toner is generally 98: 2 to 90:10 by weight, particularly 97: 3 to 9.
A weight ratio of 4: 6 is preferred.

[0092]

The binder resin used in the toner of the present invention is a high molecular weight styrene-acrylic resin having a molecular weight peak in the molecular weight range of 500,000 or more, and a styrene-acrylic resin having a molecular weight peak in the molecular weight range of 50,000 to 500,000. And a styrene-acrylic resin having a cross-linking structure, and a polyester resin having a molecular weight peak in a region having a molecular weight of 50,000 or less.

The high molecular weight styrene-acrylic resin has an appropriate mechanical strength, but has an appropriate viscoelasticity when melted. This improves the mechanical strength of the toner,
Offset resistance at high temperature is improved. Molecular weight 50,000-50
The styrene-acrylic resin having a molecular weight peak in the range of 10,000 improves the compatibility of the high molecular weight styrene-acrylic resin with other resins and further improves the dispersibility of the colorant and the like. Further, when melted, it contributes to the improvement of the fixing property of the toner. The styrene-acrylic resin having a crosslinked structure imparts rubber elasticity to the toner and thus improves the offset resistance of the toner. Since the styrene-acrylic resin contains a styrene component, it has excellent pulverizability. Since the polyester resin melts at a relatively low temperature and has a low viscosity when melted, it easily penetrates into other resins around it. As a result, the other resin in which the polyester resin has permeated is in a plasticized state and is softened at a temperature lower than the softening point of the resin. Therefore, the low temperature fixability of the toner is improved. Further, since the charge control agent or the like normally contained in the toner is a polar substance, it is difficult to disperse it in a styrene-acrylic resin having a low polarity, and therefore, it is easily detached from the resin. On the other hand, since polyester resin has polarity,
Charge control agents are easy to disperse, and it is difficult to remove them. Therefore, when the toner further contains the charge control agent and the like, the charge control agent is easily dispersed in the resin by the polyester resin and is also difficult to be detached, so that the charging performance of the toner is stabilized for a long period of time.

[0094]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto.

In the present specification, all parts are parts by weight and all contents are represented by weight% unless otherwise specified.

Example 1 Preparation of Binder Resin 50 parts by weight of 2,2-bis (4-oxyphenyl) propane, 20 parts by weight of 1,4-butanediol, 70 parts by weight of p-benzenedicarboxylic acid,
15 parts by weight of 1,2-ethanedicarboxylic acid and dibutyltin as a catalyst were placed in a glass reaction vessel equipped with a nitrogen introducing tube. After degassing the vessel and replacing with nitrogen, the reaction vessel was heated to remove water as a by-product, and polymerization was performed at 180 ° C. for 5 hours. The polyester was obtained by removing the monomer by heating under reduced pressure and then drying. The weight average molecular weight of this polyester by GPC method is 7,000, the softening temperature is 97 ° C., and the glass transition point T _g
Was 68 ° C.

Then, 30 parts by weight of the polyester obtained by the above process, 70 parts by weight of styrene, 30 parts by weight of n-butyl methacrylate, 1 part by weight of tetradecaethylene glycol dimethacrylate and 2,2-azobisisobutyronitrile 2 0.5 parts by weight of the mixture was suspended in 450 parts by weight of water containing 12 parts by weight of tricalcium phosphate under a nitrogen stream using a homomixer (made by Tokushu Kika), and then stirred with a stirrer. A binder resin was obtained by suspension polymerization at 80 ° C. for 6 hours.

Then, 30 parts by weight of the polyester resin obtained by the above process, 80 parts by weight of styrene, 20 parts by weight of 2-ethylhexyl methacrylate, 1 part by weight of tetradecaethylene glycol dimethacrylate, 2,2-azobis (2,4- Dimethylvaleronitrile) 2.5 parts by weight and 2,2-azobisisobutyronitrile 1.1
After being suspended in 450 parts of water containing 12 parts by weight of a mixture of tricalcium phosphate using a homomixer,
A resin was obtained by suspension polymerization at 80 ° C. for 6 hours while stirring using a stirrer. The THF-soluble component of this resin has a molecular weight peak by GPC of 85,000, a softening temperature of 118 ° C. and a glass transition point of 64 ° C.
The insoluble content was 23%.

(Preparation of Toner) Using the resin obtained above, a toner was prepared according to the formulation shown in Table 1.

[0100]

[Table 1]

The respective components shown in Table 1 were mixed, the above resin was melt-kneaded at 130 ° C. to 140 ° C. using a twin-screw extrusion kneader, then cooled, pulverized and classified to obtain an average particle size of 10
Raw toner powder of μm was obtained. In the obtained toner raw powder, a part of the cross-linking of the resin is cut by the shear during kneading, and TH
The F insoluble content was reduced to 4%, and the molecular weight peak of the newly dissolved THF-dissolved component as a result of cross-linking was 580000.
Appeared in. Hydrophobic silica fine particles having an average particle size of 0.015 μm are added (externally added) to the obtained toner raw powder at a ratio of 0.3 parts by weight to 100 parts by weight of the toner raw powder, as a fluidity improving agent. The toner was obtained by mixing for 2 minutes with a Henschel mixer.

(Example 2) (Preparation of binder resin and toner) 70 parts by weight of styrene and 3 parts of 2-ethylhexyl methacrylate were used.
A binder resin was obtained in the same manner as in Example 1 except that 0 parts by weight and 0.7 parts by weight of nanoethylene glycol dimethacrylate were used instead of tetradeca ethylene glycol dimethacrylate.

Next, Example 1 was repeated except that the above resin was used.
A toner similar to that of was obtained.

Comparative Example 1 (Preparation of Binder Resin and Preparation of Toner) Except that nanoethylene glycol dimethacrylate was changed to divinylbenzene and 1.9 parts by weight of 2,2-azobisisobutyronitrile was used as an initiator. In the same manner as in Example 1, a binder resin was obtained.

A toner was obtained in the same manner as in Example 1 except that the above resin was used.

Table 2 shows the resin compositions of Examples 1 and 2 and Comparative Example 1 described above.

[0107]

[Table 2]

(Evaluation of Toner) The toners produced in the above Examples and Comparative Examples were evaluated for the following items. The toners were evaluated by mixing the toners obtained in the above Examples and Comparative Examples with a ferrite carrier having an average particle size of 100 μm to obtain a two-component developer having a toner concentration of 3.5%, which was used as an electrophotographic copying machine. (Model number "DC, manufactured by Mita Industry Co., Ltd.
-1755 ", heating pressure roll fixing method, using organic photoconductor drum). The evaluation items and evaluation methods are as follows.

(A) Softening start temperature Flow tester (manufactured by Shimadzu Corporation, model number "CFT-5"
00A ”) was used to measure the softening start temperature of the toners produced in the examples and comparative examples.

(B) Softening Temperature Using the above flow tester, the softening temperatures of the toners produced in the examples and comparative examples were measured.

(C) THF-insoluble matter The toners produced in Examples and Comparative Examples were taken and their weight W ₀ was measured. Then dissolve in THF at 25 ° C,
By centrifuging, measure the weight W ₁ of the residue,
The content of the THF insoluble matter was calculated by the following formula.

[0112]

[Equation 1]

(D) Glass transition point Differential scanning calorimeter (manufactured by Rigaku, model number "TAS-200")
Thus, the glass transition points of the toners produced in the examples and comparative examples were measured.

(E) Low molecular weight peak The toners prepared in Examples and Comparative Examples were dissolved in THF, the resulting THF-soluble component was applied to GPC, and the molecular weight of the obtained molecular weight peak was read.

(F) Medium molecular weight peak The molecular weight of the medium molecular weight peak was read in the same manner as in the evaluation item (e).

(G) Peak due to molecular chain scission The same treatment as in the evaluation item (e) was performed and subjected to GPC to read the molecular weight of the peak on the high molecular weight side.

(H) Toner Fixing Rate The temperature of the heating roller of the copying machine is set to 150 ° C. and 180 ° C., and at each temperature, the transfer paper on which the toner image corresponding to the black solid original is formed is used as the transfer roller. The paper was passed through to fix the image, and the image density C ₀ of the obtained copied image was measured using a reflection densitometer (manufactured by Tokyo Denshoku Co., Ltd., model number “TC-6D”). Then, an adhesive tape was pressed onto the copied image to peel it off, the image density C ₁ was measured again, and the toner fixing ratio was calculated by the following formula.

[0118]

[Equation 2]

(I) Offset Phenomenon Occurrence Temperature The temperature of the heating roller of the copying machine was changed from 180 ° C. by 10 ° C. in the vertical direction, and 500 sheets of a predetermined document were continuously copied at each temperature. Visually judge the offset phenomenon and stain of the non-image part of the 500th copy image,
The temperature at which the offset phenomenon started to occur was recorded on both the low temperature side and the high temperature side.

(J) Grindability The kneaded products of the components constituting the predetermined amount of toner prepared in the examples and comparative examples were jetted using a jet grinder (manufactured by Nippon Pneumatic Co., Ltd., model number "ID-2"). After crushing, the speed (processing weight per unit time (g / min)) when the average particle diameter was 10 μm was measured. Here, the kneading speed of the kneaded material of the components constituting the toner manufactured in Example 1 was set to 100.
Express as.

(K) Durability Continuous copying was performed using a predetermined document, and durability was defined as the number of copies at which image quality began to deteriorate.

Table 3 shows the evaluation results.

[0123]

[Table 3]

As can be seen from Table 3, Examples 1 and 2
Compared with the toner of Comparative Example 1,
The softening start temperature was low, the offset resistance was excellent over a wide temperature range, and the fixability at low temperatures was good. Furthermore, it was also excellent in durability. In addition, the pulverizability of the kneaded product of the components constituting the toner was excellent.

[0125]

According to the present invention, the binder resin is a high molecular weight styrene-acrylic resin having a molecular weight peak in the molecular weight range of 500,000 or more, and a styrene-acrylic resin having a molecular weight peak in the molecular weight range of 50,000 to 500,000. Since the resin comprises a styrene-acrylic resin having a crosslinked structure and a polyester resin having a molecular weight peak in the molecular weight range of 50,000 or less, the toner has viscoelasticity in a wide temperature range when melted at a low softening point. Excellent low-temperature fixing property and offset resistance over a wide temperature range, and excellent crushability, impact resistance, heat resistance, and durability.

Claims (9)

[Claims] 1. An electrophotographic toner containing at least a binder resin and a colorant, wherein the binder resin has a molecular weight peak in a region of a molecular weight of 500,000 or more in a molecular weight distribution measured by gel permeation chromatography. High molecular weight styrene-acrylic resin, styrene-acrylic resin having a molecular weight peak in the molecular weight range of 50,000 to 500,000, styrene-acrylic resin having a crosslinked structure, and molecular weight 5
A toner comprising a polyester resin having a molecular weight peak in the range of 10,000 or less. 2. The homopolymer Tg of the acrylic component constituting the high molecular weight styrene-acrylic resin is 20.
The toner according to claim 1, which is formed from a monomer mixture containing at least one acrylic acid or methacrylic acid ester monomer having a temperature of not higher than 0 ° C. 3. The toner according to claim 1, wherein the high molecular weight styrene-acrylic resin has a glass transition point of 50 to 75 ° C. 4. The acrylic component constituting the styrene-acrylic resin is formed from a monomer mixture containing at least one acrylic acid or methacrylic acid ester monomer having a homopolymer Tg of 20 ° C. or lower. The toner according to. 5. The toner according to claim 1, wherein the glass transition point of the styrene-acrylic resin having a molecular weight peak in the molecular weight range of 50,000 to 500,000 is 50 to 75 ° C. 6. The toner according to claim 1, wherein the polyester resin has a glass transition point of 50 to 75 ° C. 7. The binder resin comprises the high molecular weight styrene-acrylic resin, the styrene-acrylic resin having a molecular weight peak in the region of 50,000 to 500,000 and the styrene-acrylic resin having the crosslinked structure. The toner according to claim 1, wherein the toner is contained in an amount of 20 to 80% by weight. 8. The toner according to claim 1, wherein the THF insoluble content in the binder resin is 5% by weight or less. 9. The toner of claim 1, wherein the crosslinked structure comprises a structure derived from a monomer of the formula: Here, X is _(CH 2) _n -O or (CH ₂ CH ₂ O) _m
And n and m are each independently an integer of 1 to 15, and R ¹ is each independently a hydrogen atom or a lower alkyl group.