JPH08262798A - Binder resin of electrophotographic toner and toner - Google Patents

Abstract

PURPOSE: To enhance each of fixability at low temperature, heat resistance, durability, impact strength, and offset resistance by containing a vinyl resin having a specified cross-linking structure. CONSTITUTION: The binder resin contains the vinyl resin having the cross-linking structure derived from a monomer represented by the formula having at least 2 ethylenically unsaturated groups and this binder resin has a THF-insoluble fraction in an amount of 1-50wt.%. In the formula, X is (CH2 )n -O or (CH2 CH2 O)m ; each of (n) and (m) is, independently, an integer of 1-15; and each of R1 is, independently, an H atom or a lower alkyl group. The use of this cross-linking structure permits the binder resin to begin to soften from a comparatively low temperature, and to obtain viscoelasticity in a wide temperature range. The use of it for the electrophotographic toner allows all of low temperature fixability, heat resistance, durability, impact strength, and offset resistance to be enhanced.

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 the toner image is re-fixed to the transfer material. In particular, due to the recent demand for high-speed copying in high-speed copying machines and demand for energy saving in copying machines, the substantial fixing temperature is lowered, and the offset phenomenon does not occur in a wide temperature range from low temperature to high temperature. A method of fixing toner is desired.

In order to prevent the offset phenomenon, the surface of the heat roller is made of a material having a good releasability for the toner, and a liquid for preventing offset such as silicone oil is supplied to the surface of the heat roller to heat the surface of the heat roller of the toner. 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 offset by adding wax such as low molecular weight polyethylene to the toner, but the toner containing wax has low heat resistance and poor aggregation due to increased cohesiveness. 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 fixing property is improved, but the polyester particles forming the discontinuous phase are more likely to fall off than the toner particles due to long-term use. The toner has a problem that it has poor durability.

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 above problems of the prior art, and provides a binder resin excellent in low-temperature fixing property, crushing property and offset resistance. Low temperature fixability used, charge stability,
It is an object of the present invention to provide a toner having excellent offset resistance and durability.

[0012]

The binder resin of the electrophotographic toner of the present invention contains a vinyl resin having a crosslinked structure, and the crosslinked structure is at least two ethylenic groups bonded via a carbon chain. It includes a structure derived from a monomer having an unsaturated group. Thereby, the above object is achieved.

In a preferred embodiment, the binder resin contains 1 to 50% by weight of THF insoluble matter.

In a preferred embodiment, the above monomers have the formula:

[0015]

Embedded image

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

Further, the toner of the present invention uses the above binder resin as the binder resin.

According to the present invention, the binder resin contains a vinyl resin having a crosslinked structure, and the crosslinked structure is derived from a monomer having at least two ethylenically unsaturated groups bonded via a carbon chain. By containing, the binder resin begins to soften from a relatively low temperature,
Moreover, it has viscoelasticity in a wide temperature range. By using this as a binder resin for toner, low-temperature fixability,
An electrophotographic toner having excellent heat resistance, durability, impact resistance, and offset resistance can be obtained. This achieves the above object.

The present invention will be described in more detail below.

In the present specification, the "toner component" means
Refers to components that compose the toner, such as binder resin and colorant.

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

(Crosslinking Structure) The crosslinking structure of the vinyl resin used in the present invention is derived from a monomer having at least two ethylenically unsaturated groups bonded via a carbon chain (hereinafter referred to as a crosslinking monomer). Including structure. Here, the carbon chain refers to a linear, branched or cyclic polyvalent saturated hydrocarbon having at least one hetero atom. Examples of the crosslinking monomer include diacrylate of glycol compound, pentaerythritol triacrylate, trimethylolethane triacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, oligoester acrylate, and methacrylate of the above compounds. In place of; a polyfunctional monomer such as triallyl cyanurate, triallyl trimellitate may be used.

Of these, diacrylate compounds represented by the following general formula are preferred:

[0024]

Embedded image

Here, X is (CH ₂ ) _n —O or (C
H ₂ CH ₂ O) _m , n and m are each independently 1-2.
0, preferably an integer of 4 to 15, and each R ¹ independently represents a hydrogen atom or a lower alkyl group.

Examples of such diacrylate compounds include ethylene glycol diacrylate, 1,
3-propylene glycol diacrylate, 1,4-butanediol diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 1,
9-nonanediol diacrylate, 1,10-decanediol diacrylate, and those obtained by replacing the acrylate of the above compound with methacrylate; diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, hexaethylene glycol diacrylate, Nano ethylene glycol diacrylate, polyethylene glycol #
400 diacrylate, polyethylene glycol # 60
0 diacrylate, dipropylene glycol diacrylate and the acrylates of the above compounds in place of methacrylate may be used.

These crosslinking monomers may be used alone or in combination of two or more.

(Binder Resin) The binder resin of the present invention contains a vinyl resin having a crosslinked structure. The vinyl resin having a crosslinked structure used in the present invention is a polymer of a monomer mixture containing an ethylenically unsaturated group and the above crosslinking monomer, a monomer mixture containing an ethylenically unsaturated group and the above crosslinking monomer. And polymers of these and other resins. It is preferably a polymer of a monomer mixture containing a monomer having an ethylenically unsaturated group and the crosslinking monomer. The resulting polymer can be a random copolymer, a block copolymer or a graft copolymer.

Examples of the monomer having an ethylenically unsaturated group 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-butylstyrene, p-tert-butylstyrene, p- Styrene-based monomers such as n-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene; methyl acrylate, ethyl acrylate, acrylic acid n- Butyl, isobutyl acrylate, propyl acrylate, acrylic acid n-
Octyl, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, methacrylic acid Isobutyl, cyclohexyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, β-hydroxyacrylate, γ- Acrylic monomers such as propyl hydroxyacrylate, δ-hydroxybutyl acrylate, β-hydroxyethyl methacrylate; ethylene, propylene, bromine Ren, ethylenically unsaturated mono-olefins such as isobutylene; unsaturated polyenes such as butadiene; vinyl chloride, vinylidene chloride, vinyl bromide,
Vinyl halides such as vinyl fluoride; vinyl acetate,
Vinyl esters such as vinyl propionate and vinyl benzoate; vinyl ethers such as vinyl methyl ether, 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-vinylcarbazole, N-vinylindole, N-vinylpyrrolidone and other N-vinyl compounds; vinylnaphthalenes; acrylonitrile, methacrylonitrile, acrylamide and other acrylic acid or methacrylic acid derivatives; and divinylbenzene, divinylnaphthalene and the like. Aromatic divinyl compounds can be used. These monomers may be used alone or in combination of two or more. The copolymerization ratio of the crosslinking monomer is
0.01 to 20 parts by weight, and preferably 0.05 to 20 parts by weight, based on 100 parts by weight of the monomer having an ethylenically unsaturated group.
5 parts by weight. If it is less than 0.01 part by weight, a high temperature offset phenomenon occurs. If the amount is more than 20 parts by weight, the toner cannot be sufficiently fixed.

In the vinyl resin used in the present invention,
Copolymerization of the styrene-based monomer can enhance the pulverizability of the toner component kneaded product. At that time, among the above acrylic monomers, the Tg of the homopolymer is 20.
Copolymerize ethyl acrylate, which has a temperature of ℃ or less, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, etc., with a styrene monomer. Thereby, the copolymerization ratio of the styrene-based 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. If the amount is less than 40 parts by weight, the pulverizability of the toner component kneaded product will be poor. If it is more than 90% by weight, the low temperature fixing property of the toner is deteriorated.

The vinyl resin having a cross-linked structure is usually 1 to 50% by weight, preferably 5 to 5% by weight of the binder resin.
50% by weight is contained. If it is less than 1% by weight, high temperature offset occurs. If it is more than 50% by weight, the pulverizability and the toner fixability are poor. The binder resin of the present invention,
In addition to the vinyl-based resin, if necessary, a vinyl-based resin,
Polyester, polyurethane, epoxy resin, polyamide, polyolefin, hydrocarbon resin, phenol resin,
Known resins such as 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 the above-mentioned monomer mixture in an aqueous phase and polymerizing.

The suspension polymerization is preferably carried out at 100 parts by weight or less, preferably 10 to 90 parts by weight, with respect to 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. These dispersants vary depending on the amount of monomers dispersed in the aqueous solvent, but generally 0.05 to 1 part by weight is added to 100 parts by weight of water or the aqueous solvent.

The polymerization temperature will differ depending on the initiator used and the target polymer, but is usually preferably 50 to 95 ° C. As the polymerization initiator, a water-insoluble or hardly soluble polymerization initiator can be used. For example, 2,2-azobis (2,4-dimethylvaleronitrile), 2,2-azobisisobutyronitrile, benzoyl peroxide, tert-butylperoxyhexanoate and the like can be used. The polymerization initiator is 0.5 to 100 parts by weight of the monomer mixture.
It can be used in 10 parts by weight.

(Preparation of Toner) The toner of the present invention contains the binder resin of the present invention as an essential component, and if necessary, further contains a compounding agent such as a colorant, a charge control agent, a release agent, and magnetic powder. May be included.

The following can be preferably used as the colorant.

Black pigment: carbon black such as furnace black, channel black, thermal, gas black, oil black, acetylene black, lamp black, aniline black; white pigment: zinc white, titanium oxide, antimony white, zinc sulfide; red pigment : 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 (for example, a metal chelate of alkylsalicylic acid), a metal complex salt dye, a fatty acid soap, a 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 or a combination of two or more 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 can be preferably used.

The release 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 may be used.

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

The toner of the present invention can be manufactured by a well-known method for manufacturing 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 raw toner powder is made into a toner by adding an external additive as required. 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 stearic acid metal salt 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 may be mixed with a magnetic carrier such as ferrite or iron powder and used as a two-component developer in an image forming apparatus.

As the magnetic carrier, a ferrite type magnetic carrier can be preferably used. Fe and C
Soft ferrite containing at least one metal component selected from the group consisting of u, Mg, Mn, and Ni, preferably two or more, can be preferably used. For example, copper
Particles of sintered ferrite of 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 to the toner is generally 98: 2 to 90:10 by weight, and particularly 97: 3 to 9.
A weight ratio of 4: 6 is preferred.

[0055]

The binder resin of the present invention contains a vinyl-based resin having a crosslinked structure to enhance the viscoelasticity of the resin when melted. Furthermore, since the crosslinked structure includes a structure derived from a monomer having at least two ethylenically unsaturated groups bonded via an aliphatic hydrocarbon, there are few constraints between crosslinked polymer chains and the crosslinked structure is Have flexibility. As a result, the binder resin begins to soften at low temperatures,
In addition, it has a predetermined viscoelasticity.

Therefore, when such a binder resin is used for the toner, the toner can be softened from a low temperature and has a predetermined viscoelasticity even when melted, so that the fixing property of the toner at a low temperature is improved and the toner is widely spread. Offset resistance of the toner is improved in the temperature range. Further, the crosslinked structure improves the mechanical strength and heat resistance of the toner, and as a result, the durability of the toner is improved.

[0057]

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

In the following examples, unless otherwise specified, all parts are parts by weight, and all contents are expressed in% by weight.

(Preparation of Binder Resin) (Preparation of Low Molecular Weight Resin) 70 parts by weight of styrene, 30 parts by weight of n-butyl methacrylate, 2,2-azobis (2,2)
4-Dimethylvaleronitrile) (2.5 parts by weight) and toluene (400 parts by weight) were placed in a glass reaction vessel equipped with a nitrogen inlet tube, degassed with nitrogen, and then polymerized while refluxing at 80 ° C. for 5 hours. The low molecular weight resin was obtained by removing the solvent by deaeration heating and drying the reaction product. The molecular weight of this low molecular weight resin by the GPC method was 9,000.

(Preparation 1 of Binder Resin) 50 parts by weight of the low molecular weight resin obtained by the above process, 70 parts by weight of styrene as a monomer, 30 parts by weight of n-butyl methacrylate, 1 part by weight of tetradecaethylene glycol dimethacrylate as a cross-linking agent. Then, a mixture of 1.1 parts by weight of 2,2-azobisisobutyronitrile as an initiator was suspended in 450 parts by weight of water containing 12 parts by weight of tricalcium phosphate using a homomixer (manufactured by Tokushu Kiki). After turbidity, a binder resin was obtained by carrying out suspension polymerization at 80 ° C. for 6 hours while stirring using a stirrer. The molecular weight distribution of this resin was wide, the molecular weight peak by the GPC method was 9000, and the THF insoluble content was 21%.

(Preparation 2 of Binder Resin) A binder resin was obtained in the same manner as in Preparation 1 of the binder resin described above except that 0.7 part by weight of nanoethylene glycol dimethacrylate was used as a crosslinking agent.

(Preparation 3 of Binder Resin) A binder resin was obtained in the same manner as in Preparation 1 of the binder resin described above except that 0.25 part by weight of divinylbenzene was used as the crosslinking agent.

Example 1 (Preparation of Toner) Toner raw powder was prepared according to the formulation shown in Table 1.

[0064]

[Table 1]

After the components shown in Table 1 were mixed using the binder resin obtained in Preparation 1 of the above resin and melt-kneaded at a temperature 5 ° C. higher than the softening temperature of the above resin using a twin-screw extruder. , Cooled, crushed, classified, average particle size 10 μm
Toner raw powder of

Hydrophobic silica fine particles having an average particle diameter of 0.015 μm are added to the obtained toner raw powder as a fluidity improver in a ratio of 0.3 part by weight to 100 parts by weight of the raw toner powder (external addition). And mixed with a Henschel mixer for 2 minutes to obtain a toner.

(Preparation of Developer) The toner and the average particle size 1
A two-component developer having a toner concentration of 3.5% was obtained by mixing with a ferrite carrier of 00 μm.

Example 2 A toner and a developer were obtained in the same manner as in Example 1 except that the binder resin obtained in Preparation 2 of the above resin was used.

Comparative Example 1 Next, a toner and a developer were obtained in the same manner as in Example 1 except that the binder resin obtained in Preparation 3 of the above resin was used.

(Evaluation of Binder Resin and Toner) The binder resin and toner obtained in the above Examples and Comparative Examples were evaluated for the following items. The toner was evaluated by mixing the toners obtained in the following examples and comparative examples with a ferrite carrier to prepare a two-component developer, which was used as an electrophotographic copying machine (manufactured by Mita Industry Co., Ltd., model number "DC").
-1755 ", heating pressure roll fixing method, using OPC drum).

(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 resins prepared in the examples and comparative examples.

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

(C) THF-insoluble matter A part of the resin prepared in the examples and comparative examples was taken and its weight W ₀ was measured. Then, it was dissolved in THF at 25 ° C., centrifuged, the weight W _{1 of the} residue was measured, and the content of the THF insoluble content was calculated by the following formula.

[0074]

[Equation 1]

(D) Grindability A predetermined amount of the toner component kneaded product prepared in the examples and comparative examples was crushed using a jet crusher (manufactured by Nippon Pneumatic Co., Ltd., model number "ID-2"), and averaged. Particle size is 10 μm
Speed (process weight per unit time (g /
Min)) was measured. Here, the pulverization speed of the toner component kneaded material produced in Example 1 is represented as 100.

(E) Toner Fixing Rate The heating roller temperature of the copying machine is set to 150 ° C. and 180 ° C.
C., and at each temperature, the transfer paper on which the toner image corresponding to the black solid document is formed is passed through the transfer roller to fix the image, and the image density _C.sub.0 of the obtained copy image is set to the reflection density. It was measured using a meter (manufactured by Tokyo Denshoku Co., Ltd., model number "TC-6D"). Next, the adhesive tape was pressure-bonded and then peeled off, the image density C ₁ was measured again, and the toner fixing ratio was calculated by the following formula.

[0077]

[Equation 2]

(F) Offset Phenomenon Occurrence Temperature The temperature of the heating roller of the copying machine is changed from 180 ° C. by 10 ° C. in the vertical direction, and at each temperature, a predetermined original is passed and 500 continuous copies are made. went. The offset phenomenon and stain of the non-image portion of the 500th copy image at each temperature were visually determined, and the temperature at which the fixing offset phenomenon began to occur was recorded on both the low temperature side and the high temperature side.

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

The evaluation results are shown in Table 2.

[0081]

[Table 2]

As can be seen from Table 2, the resins having wide-chain cross-links with aliphatic straight chains obtained in Resin Preparations 1 and 2 were rigid and closely spaced with divinylbenzene obtained in Resin Preparation 3. It began to soften at a lower temperature than the resin with crosslinks. Further, the toners obtained in Examples 1 and 2 are
It had excellent fixability at low temperatures and a wide offset resistance range. Further, it was excellent in both toner pulverizability and durability.

[0083]

According to the present invention, the binder resin contains a vinyl resin having a crosslinked structure, and the crosslinked structure is derived from a monomer having at least two ethylenically unsaturated groups bonded via a carbon chain. By including the structure, the binder resin begins to soften at a relatively low temperature,
Moreover, it has viscoelasticity in a wide temperature range. By using this as a binder resin for toner, low-temperature fixability,
An electrophotographic toner having excellent heat resistance, durability, impact resistance, and offset resistance can be obtained. This enables high quality electrophotographic image formation with low power consumption.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomokei Wada 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Industrial Co., Ltd.

Claims (4)

[Claims] 1. A binder resin for an electrophotographic toner, comprising a vinyl-based resin having a crosslinked structure, wherein the crosslinked structure has at least two ethylenically unsaturated groups bonded via a carbon chain. A binder resin containing a structure derived from a monomer. 2. The binder resin according to claim 1, which contains 1 to 50% by weight of THF insoluble matter. 3. The binder resin according to claim 1, wherein the monomer is represented by the following formula: Here, X is (CH ₂ ) _n —O or (CH ₂ CH
₂ O) _m , 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. 4. A toner comprising the binder resin according to claim 1.