JP3373073B2 - Electrophotographic toner and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner, and more particularly to an electrophotographic toner for a copying machine or printer which employs heat roll fixing.

[0002]

2. Description of the Related Art In recent years, electrophotographic copying machines and printers have been widely used in general households and the like. (Reduction of power consumption), high speed for the purpose of spreading to so-called gray area located at the boundary between printing machine and copying machine, or low roll pressure for simplification of fixing roll to reduce machine cost. Is desired. In addition, copiers equipped with a double-sided copy function and an automatic document feeder have become widespread with the sophistication of copiers, and therefore the fixing temperature of electrophotographic toner used in copiers and printers is low and There is a demand for a sheet having excellent offset properties and excellent fixing strength on a transfer sheet in order to prevent stains during double-sided copying and stains in the automatic document feeder.

In order to meet the above requirements, the prior art has proposed proposals for improving the molecular weight and molecular weight distribution of the binder resin. Specifically, attempts have been made to lower the fixing temperature by lowering the molecular weight of the binder resin. However, when the molecular weight is lowered, the melting point is lowered, but at the same time, the melt viscosity is also lowered, so that there is a problem that an offset phenomenon occurs on the fixing roll. In order to prevent this offset phenomenon, it has been proposed to widen the molecular weight distribution of the binder resin, and in the polyester resin, as a method for widening the molecular weight distribution, crosslinking is performed using a trivalent or higher polyfunctional monomer. Things were being done. However, in this method, although the offset phenomenon can be prevented by increasing the crosslink density, there is a problem that the melt viscosity increases and the fixability deteriorates. Further, in order to have sufficient fixability, the glass transition temperature (Tg) of the resin has to be lowered and it is unavoidable that the storability of the toner is impaired. Further, in order to prevent the offset phenomenon, there is a method of widening the overall molecular weight distribution by a method of mixing a high molecular weight polyester resin and a low molecular weight polyester at the time of melt-kneading to make the offset property and the fixing property compatible. Resins having different melt viscosities were kneaded and dispersed, and the resins could not be uniformly dispersed, and sufficient fixability and offset resistance could not be obtained.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to fix at a low fixing temperature, practically no problem occurs even in non-offset property, and excellent in fixing strength to transfer paper and image characteristics. It is to provide a toner for electrophotography.

[0005]

The present invention comprises a polyester resin and styrene acrylic gel fine particles having an average particle size of 1 μm or less and having a carboxyl group, and at least a part of the carboxyl groups of the styrene acrylic gel fine particle is contained.
It chemically reacts with the hydroxyl groups of the polyester resin
The toner for electrophotography is characterized in that a ter bond is formed to form a copolymer with the polyester resin. In the first method for producing an electrophotographic toner of the present invention, a polyester resin is formed by polymerizing an alcohol component and an acid component in the presence of styrene acrylic gel fine particles having an average particle size of 1 μm or less and having a carboxyl group. After that, the mixture obtained by mixing the polyester resin with at least a colorant is melt-kneaded, and then pulverized and classified, which is a method for producing an electrophotographic toner. Furthermore, the second production method of the present invention is a method in which an styrene acrylic gel fine particle having an average particle size of 1 μm or less and having a carboxyl group, a polyester resin having a hydroxyl value of 20 mgKOH / g or more, and a colorant are melt-kneaded. In the method for producing a toner for electrophotography, the styrene-acryl gel fine particles are reacted with the polyester resin during the melt-kneading, and then pulverized and classified.

The present invention will be described in detail below. Examples of the alcohol component of the polyester resin used in the present invention include polyoxypropylene 2,2-2,2-bis (4-hydroxyphenyl) propane and polyoxypropylene (3,3) -2,2- Bis (4-hydroxyphenyl) propane, polyoxyethylene (2,0) 2,2
-Bis (4-hydroxyphenyl) propane, polyoxypropylene (2,0) -polyoxyethylene (2,
0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (6) -2,2-bis (4-)
Hydroxyphenyl) propane, ethylene glycol,
1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, or trivalent or higher Examples of polyhydric alcohols include sorbitol, 1,
2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol,
Tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol,
2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-
Trihydroxybenzene etc. can be raised. Further, as the acid component, fumaric acid, maleic acid, phthalic acid, isophthalic acid, itaconic acid, glutaconic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid, alkenylsuccinic acid, or trivalent or more 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4.
4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2
-Methylene carboxy propane, tetra (methylene carboxylic) methane, 1,2,7,8-octane tetracarboxylic acid and the like.

In the present invention, a polyester resin obtained by appropriately combining the alcohol component and the acid component as described above is used and is not particularly limited, but it melts at a low melting point as a toner and contributes to the improvement of fixing strength. Therefore, it is desirable that the crosslinked structure is as small as possible, and a polyester resin composed of a divalent alcohol component and a divalent acid component is preferable.

The styrene acrylic gel fine particles used in the present invention are copolymers having a cross-linking structure containing at least a styrene monomer and an acrylic monomer as a copolymerization component, and have an average fine particle diameter of 1 μm. It is necessary that it be below, and preferably 0.05 to 1 μm. Further, the glass transition point is 60 to 110 ° C., the softening point (flow tester method, 1/2 raising point) is 150 to 250 ° C., and the crosslink density is 5
Those having 0 to 95% are preferably used. There is no particular limitation as long as it is a fine particle of such a copolymer, but in the present invention, (a) a styrene-based monomer / acrylic acid ester monomer /
Carboxyl group-containing vinyl monomer (b) Styrene monomer / methacrylic acid ester monomer / Carboxyl group-containing vinyl monomer (c) Styrene monomer / acrylic ester monomer /
Those having a composition of methacrylic acid ester monomer / carboxyl group-containing vinyl monomer are preferable. Specific examples of the styrene-based monomer include o-methylstyrene and m-, in addition to styrene.
Methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-ter-butylstyrene, pn-hexylstyrene, pn- Octyl styrene, pn-dodecyl styrene, p-phenyl styrene, p-chloro styrene, etc. are mentioned.

Specific examples of the acrylic acid ester and methacrylic acid ester monomers include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, and n-acrylate.
Octyl, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, methacrylic acid. In addition to alkyl esters of acrylic acid or methacrylic acid such as stearyl, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxy acrylate. Butyl, glycidyl acrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate Pills, 2-hydroxybutyl methacrylate, glycidyl methacrylate, bisglycidyl methacrylate, polyethylene glycol dimethacrylate, methacryloxy ethyl phosphate, and the like. Further, acrylic acid such as acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid and the like α- or β-alkyl derivative as a carboxyl group-containing vinyl monomer; fumaric acid, maleic acid, citraconic acid, itacone Unsaturated dicarboxylic acids such as acids and monoester derivatives thereof; succinic acid monoacryloyloxyethyl ester, succinic acid monomethacryloyloxyethyl ester and the like. In addition to the above ingredients,
For example, an acrylic monomer such as acrylonitrile, methacrylonitrile, or acryloamide, or other vinyl monomer can be used as a copolymerization component as required.

In the present invention, gel fine particles having an average particle diameter of 1 μm or less of a styrene-acrylic copolymer having a crosslinked structure composed of the above-mentioned constituents are used. Here, from the viewpoints of dispersibility of gel fine particles, reactivity with polyester resin, handleability during production, cost, etc., fine particles having an average particle size of about 0.05 to 0.8 μm are preferable, and an average particle size of more than 1 μm. And it is difficult to disperse in the toner, the gel particles are detached at the time of pulverization, and the high temperature non-offset property is lowered. The average particle size of the gel particles is measured by electron microscopy. Further, the ratio of each of the above-mentioned monomer components constituting the styrene acrylic gel fine particles is not particularly limited, but in consideration of the fixability as a toner and the reactivity with a polyester resin, a styrene-based monomer is used. 95% by weight or less, particularly 60 to 95% by weight, acrylic and methacrylic acid ester monomers are 40% by weight or less, particularly 5 to 40% by weight, and vinyl monomers having a carboxyl group are 0.2 to 10% by weight. It is preferably in the weight%.

In the electrophotographic toner of the present invention, the polyester resin used as a binder reacts with at least a part of the styrene acrylic gel fine particles to form a copolymer. The reaction referred to here is that a hydrogen group of the polyester resin and a carboxyl group of the styrene-acryl gel particles chemically react to form an ester bond, and such reaction causes grafting of the polyester resin and styrene-acryl gel particles. A copolymer or a block copolymer is produced.
By forming such a copolymer, the compatibility between the two is improved, and the styrene-acryl gel fine particles are prevented from being detached in the pulverization step during toner production. Therefore, excellent non-offset properties can be achieved by using a low melting point polyester resin without impairing its good fixing property. As a method for forming the above-mentioned copolymer, not only simply reacting the two, but more effectively, as in the toner production method of the present invention, the styrene-acryl gel fine particles during the polyester resin condensation polymerization The reaction may be carried out by allowing them to coexist, or both may be allowed to react at the time of hot melt kneading during toner preparation.

The toner for electrophotography of the present invention contains a colorant in addition to the above components, and if necessary, a binder resin other than polyester, a magnetic material, a charge control agent, an anti-offset agent, a fluidizing agent. Characteristic improvers such as can be used.
In the present invention, as a resin that can be used in addition to the polyester resin, a resin such as a styrene acrylic resin, a polyethylene resin, an epoxy resin, a silicone resin, a polyamide resin, or a polyurethane resin may be blended. As the colorant, carbon black, nigrosine dye,
Examples include aniline blue, chalco oil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, and mixtures thereof. It is necessary that these colorants are contained in a sufficient ratio to form a visible image having a sufficient density, and usually 1 to 2 relative to 100 parts by weight of the binder resin.
The ratio is about 0 parts by weight.

As the magnetic substance, a metal or alloy exhibiting ferromagnetism such as ferrite, magnetite and other iron, cobalt, nickel, etc., or a compound containing these elements, or an appropriate heat treatment without containing ferromagnetic elements. An alloy which exhibits ferromagnetism when applied, for example, a type of alloy called a Heusler alloy containing manganese and copper, such as manganese-copper-aluminum, manganese-copper-tin, or chromium dioxide, or the like can be given. .
These magnetic materials are uniformly dispersed in the binder resin in the form of fine powder having an average particle size of 0.1 to 1 micron. The content is 20 to 70 parts by weight, preferably 40 to 70 parts by weight, per 100 parts by weight of the toner. Examples of the charge control agent include a nigrosine dye, a quaternary ammonium salt, a pyridinium salt, a triphenylmethane-based compound, a carexarene compound, a resin-based control agent, and a monoazo-based metal complex dye.

The electrophotographic toner of the present invention has the composition as described above, and in order to improve the fixability at a lower temperature and achieve excellent fixing strength, the melting start temperature is 60 ° C. It is desirable that the temperature is 100 ° C. or lower. If the melting start temperature is higher than 100 ° C, the fixability will be insufficient,
If the temperature is lower than 60 ° C, the blocking property may be deteriorated and the storability may be deteriorated. The melting start temperature referred to in the present invention refers to the falling start temperature of the plunger under the following measuring machine and measuring conditions. Measuring instrument; Shimadzu's advanced flow tester CFT-
500 Measuring conditions; Plunger: 1 cm2 Die diameter: 1 mm Die length: 1 mm Load: 20 KgF Preheating temperature: 50-80 ° C Preheating time: 300 sec Temperature rising rate: 6 ° C / min

The electrophotographic toner of the present invention is mixed with a carrier composed of ferrite powder, iron powder or the like to form a two-component developer. When a magnetic substance is contained, it may be used as it is as a one-component developer for developing an electrostatic image without mixing with a carrier, or may be mixed with a carrier and used as a two-component developer. Furthermore non-magnetic 1
It is also applicable to the developing method of the components.

The first method for producing an electrophotographic toner of the present invention is a styrene-acryl gel fine particle having an average particle size of 1 μm or less and a carboxyl group when a polyester resin used as a binder is polymerized in the toner. In the presence, the above-mentioned alcohol component and acid component are preferably polymerized with a monomer composition such that the molar ratio thereof is 1.0 or more. The resin obtained by such a polymerization method has a good fixing property and an excellent non-offset property because the polyester resin and at least a part of the styrene acrylic gel fine particles as described above form a graft or block copolymer. Is achieved. In the above toner production method, it is preferable that the mixing ratio of the alcohol component and the acid component constituting the polyester resin is 1.0 or more in a molar ratio, that is, the alcohol component is used more than the acid component in a molar ratio. Is more preferable, and more preferably, the molar ratio of the alcohol component to the acid component is 1.1 to 2.0. In the above production method, the ratio of the polyester resin component consisting of the alcohol component and the acid component and the styrene acrylic gel fine particles is preferably 2 to 25 parts by weight of the styrene acrylic gel fine particles with respect to 100 parts by weight of the polyester resin component. If the amount is less than 2 parts by weight, the effect of the present invention cannot be sufficiently obtained. If the amount is more than 25 parts by weight, the low temperature fixability may be deteriorated, or detachment may easily occur during the crushing process during production, which may adversely affect the image characteristics. is there. When the polyester resin is polymerized in the above production method, a catalyst such as dibutyltin laurate or tin octylate, and other commonly used additives can be used if necessary.

Next, in the second production method of the present invention, the polyester resin as the binder and the styrene acrylic gel fine particles are reacted with each other during the melt-kneading to increase the molecular weight, and the styrene acrylic gel fine particles are uniformly distributed in the toner. It is possible to obtain a toner dispersed in the toner, and to achieve excellent non-offset properties without impairing the fixing property of the polyester resin. In the method for producing such a toner, first, at least the polyester resin, the styrene acrylic gel fine particles as described above, and the colorant are mixed as a mixture using a mixer such as a super mixer or a Henschel mixer, and the mixture is melt-kneaded.
A roll mill, a pressure kneader, a Hanbury mixer, an extruder and the like can be used as the melt kneader. The melt-kneading conditions are appropriately set according to the composition and are not particularly limited, but for example, a pressure kneader is used,
A preferable copolymer can be obtained by kneading at a resin temperature of 100 to 200 ° C. for 5 to 30 minutes. The obtained kneaded mixture is pulverized using a pulverizer such as a jet mill or a turbo mill, and then adjusted to have a desired particle size distribution using an air classifier. The polyester resin used in the above-mentioned method for producing a toner needs to have a hydroxyl value of 20 mgKOH / g or more in order to obtain good reactivity with styrene acrylic gel fine particles under the kneading conditions which are usually used. Is. Further, the mixing ratio of the polyester resin and the styrene acrylic gel fine particles is preferably 2 to 25 parts by weight of the styrene acrylic gel fine particles with respect to 100 parts by weight of the polyester resin, as in the case of the first manufacturing method. A catalyst such as dibutyltin laurate or tin octylate may be used to accelerate the esterification reaction during melt-kneading.

[0018]

EXAMPLES The present invention will be described below based on examples. In the examples, “parts” means “parts by weight”. First, as Synthesis Examples 1 to 3 below, polyester resins A to C according to the first method for producing a toner of the present invention were produced. Also, as Synthesis Examples 4 to 5, comparative polyester resins D and E were produced. Synthesis Example 1 55 mol% of bisphenol A ethylene oxide adduct as an alcohol component and 45 terephthalic acid as an acid component
80 parts of a mixture of mol% and styrene acrylic gel fine particles (FA-1250 manufactured by Nippon Paint Co., Ltd. average particle size 0.1
20 parts of μm maleic acid content 2%) is put into a reactor equipped with a thermometer, a stainless stirrer, and a flow-down condenser, and the stirring speed is 2 at an internal temperature of 220 ° C. under a nitrogen gas atmosphere.
The reaction was carried out at 00 rpm. The melting start temperature of the obtained polyester resin A was 87 ° C. Synthetic Example 2 80 parts of a mixture of 55 mol% of bisphenol A ethylene oxide adduct and 45 mol% of terephthalic acid and styrene acrylic gel fine particles (CA-2250 manufactured by Nippon Paint Co., Ltd.).
Average particle size 0.5 μm Maleic acid content 2%) 20
Part into a reactor equipped with a thermometer, a stainless stirrer, and a flow-down condenser, and set the internal temperature to 220 under a nitrogen gas atmosphere.
The reaction was carried out at a stirring speed of 200 rpm at 0 ° C. The melting start temperature of the obtained polyester resin B was 88 ° C.

Synthesis Example 3 80 parts of a mixture of 55 mol% of bisphenol A ethylene oxide adduct and 45 mol% of terephthalic acid and styrene acrylic gel fine particles (S-069 manufactured by Nippon Paint Co., Ltd. average particle size 0.1 μm maleic acid content of 0. 5%) 20
Part into a reactor equipped with a thermometer, a stainless stirrer, and a flow-down condenser, and set the internal temperature to 220 under a nitrogen gas atmosphere.
The reaction was carried out at a stirring speed of 200 rpm at 0 ° C. The melting start temperature of the obtained polyester resin C was 87 ° C. Synthesis Example 4 The same procedure as in Synthesis Example 1 was repeated except that styrene acrylic gel fine particles containing no acid component (XA-1310, Nippon Paint Co., average particle size 0.1 μm) were used instead of the styrene acrylic gel fine particles of Synthesis Example 1. A polyester resin D (melting start temperature 87 ° C.) for comparison was obtained. Synthesis Example 5 A polyester resin E (melting start temperature) for comparison was prepared in the same manner as in Synthesis Example 1 except that styrene acrylic gel fine particles having an average particle diameter of 3 μm (prototype) were used in place of the styrene acrylic gel fine particles of Synthesis Example 1. 87 ° C.) was obtained.

Next, examples and comparative examples of the present invention using the above-prepared resin, and examples and comparative examples of the method for producing the toner of the present invention will be described. Example 1 Polyester resin A 100 parts Chromium metal dye 1.5 parts (Orient Chemical Co., Ltd. trade name: Bontron S-34) Carbon black 6.5 parts (Mitsubishi Kasei Co. Ltd. trade name: MA-100) Polypropylene 3 parts (Sanyo Kasei Co., Ltd. trade name: Viscole 330P) The raw materials having the above mixing ratios are mixed with a super mixer, and after hot melt kneading with a biaxial kneader (kneading temperature 120 ° C.),
It was pulverized with a jet mill and then classified with a dry airflow classifier to obtain particles having an average particle size of 11 μm. Then, 100 parts of the particles and 0.3 part of hydrophobic silica (trade name: Cabosil TS-530 manufactured by Cabot Corporation) are stirred for 1 minute in a Henschel mixer to adhere the hydrophobic silica to the surface of the particles. To obtain a toner for electrophotography.

Example 2 Polyester resin B 100 parts Chromium-containing metal dye 1.5 parts (Orient Chemical Co., Ltd. product name: Bontron S-34) Carbon black 6.5 parts (Mitsubishi Kasei Co. product name: MA- 100) Polypropylene 3 parts (manufactured by Sanyo Chemical Industry Co., Ltd .; Viscole 330P) The raw materials having the above mixing ratios are mixed in a super mixer, and after hot melt kneading in a twin-screw kneader (kneading temperature 120 ° C.),
It was pulverized with a jet mill and then classified with a dry airflow classifier to obtain particles having an average particle size of 11 μm. Then, 100 parts of the particles and 0.3 part of hydrophobic silica (trade name: Cabosil TS-530 manufactured by Cabot Corporation) are stirred for 1 minute in a Henschel mixer to adhere the hydrophobic silica to the surface of the particles. To obtain a toner for electrophotography.

Example 3 Polyester resin C 100 parts Chromium-containing metal dye 1.5 parts (Orient Chemical Co., Ltd. trade name: Bontron S-34) Carbon black 6.5 parts (Mitsubishi Kasei Co. Ltd. trade name: MA- 100) Polypropylene 3 parts (manufactured by Sanyo Chemical Industry Co., Ltd .; Viscole 330P) The raw materials having the above mixing ratios are mixed in a super mixer, and after hot melt kneading in a twin-screw kneader (kneading temperature 120 ° C.),
It was pulverized with a jet mill and then classified with a dry airflow classifier to obtain particles having an average particle size of 11 μm. Then, 100 parts of the particles and 0.3 part of hydrophobic silica (trade name: Cabosil TS-530 manufactured by Cabot Corporation) are stirred for 1 minute in a Henschel mixer to adhere the hydrophobic silica to the surface of the particles. To obtain a toner for electrophotography.

Example 4 Polyester resin NCP-002 80 parts Styrene acrylic gel fine particles 20 parts (Nihon Paint Co. FA-1250 average particle diameter 0.5 μm maleic acid content 2%) Chromium-containing metal dye 1.5 parts (Orient Chemistry) Industrial Co., Ltd. product name: Bontron S-34) Carbon black 6.5 parts (Mitsubishi Chemical Co., Ltd. product name: MA-100) Polypropylene 3 parts (Sanyo Chemical Co., Ltd. product name; Viscole 330P) Polyester resin is Japan Carbide Company product name: NCP
-002 (number average molecular weight 8000, weight average molecular weight 18
000, acid value 1, hydroxyl value 14, melting start temperature (96
℃) is used to mix the raw materials with the above blending ratio in a super mixer, and the mixture is melted and kneaded by a batch type pressure kneader (kneading temperature 180 ° C.), pulverized by a jet mill, and then classified by a dry air stream classifier. Thus, particles having an average particle diameter of 11 μm were obtained. Then, 100 parts of the particles and hydrophobic silica (Cabosil TS-530 manufactured by Cabot Corporation) 0.3
The resulting mixture was stirred for 1 minute in a Henschel mixer, and hydrophobic silica was attached to the surface of the particles to obtain the electrophotographic toner of the present invention.

Comparative Example 1 A comparative electrophotographic toner was obtained in the same manner as in Example 4, except that the styrene-acryl gel fine particles of Example 4 were not used and 100 parts of the polyester resin NCP-002 was used. Comparative Example 2 A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that the polyester resin D was used in place of the polyester resin A in Example 1. Comparative Example 3 A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that the polyester resin E was used in place of the polyester resin A of Example 1.

[0025]

Next, the following items were evaluated for the above Examples and Comparative Examples. (1) Non-Offset Temperature Region First, 4 parts of each electrophotographic toner obtained in the above-mentioned Examples and Comparative Examples and 96 parts of a ferrite carrier (product name: FL-1020 manufactured by Powdertech Co., Ltd.) not coated with a resin are prepared. A two-component developer was prepared by mixing. Next, a commercially available copying machine (trade name: SF-9, manufactured by Sharp Corporation) is used using the developer.
800), a plurality of belt-shaped unfixed images having a length of 2 cm and a width of 5 cm were formed on an A4 transfer paper. Then, a heat fixing roll having a surface layer made of Teflon and a pressure fixing roll having a surface layer made of silicone rubber are paired and rotated, and a fixing device is rotated at a roll pressure of 1 Kg / cm ² and a roll speed of 50.
The surface temperature of the heat fixing roll was changed stepwise so as to fix the toner image on the transfer paper having the unfixed image at each surface temperature. At this time, it was observed whether or not the toner was smeared in the blank area, and the temperature range in which the smear did not occur was defined as the non-offset temperature range. (2) Non-offset temperature width The difference between the maximum value and the minimum value in the above non-offset temperature region was defined as the non-offset temperature width.

(3) Fixing Strength The surface temperature of the heat fixing roll of the fixing machine was set to 140 ° C., and the toner image on the transfer paper on which the unfixed image was formed was fixed. Then, the formed fixed image was rubbed with a cotton pad, and the fixing strength was calculated by the following formula to be used as an index of low energy fixing property. As the image density, a reflection densitometer RD-914 manufactured by Macbeth was used. Fixing strength (%) = image density of fixed image after rubbing / image density of fixed image before rubbing × 100 (4) Melting start temperature According to the above-mentioned measuring machine and measuring conditions. The evaluation results of the above items are shown in Table 1.

[0028]

[Table 1]

As is clear from the test results of Table 1, the non-offset temperature range of the electrophotographic toner of the present invention is 75-9.
It was confirmed that a practically sufficient range of 0 ° C. was maintained. The fixing strength at a fixing temperature of 140 ° C is 8
It was confirmed that the content was 0% or more and the fixing strength was practically sufficient. On the other hand, in Comparative Example 1, the non-offset width was not obtained. In Comparative Examples 2 to 3 , the non-offset temperature width was as narrow as 30 to 35 ° C. and there was a problem in practical use.
In Comparative Example 3, more fine particles (particle diameter: 5 μm or less), which are considered to be desorption of styrene-acryl gel fine particles, were generated during pulverization, and the non-offset temperature on the high temperature side was also low.

Further, a commercially available copying machine (trade name: manufactured by Toshiba Corp.) using each of the developers of Examples 1 to 4 in the above item (1) is used.
Table 2 shows the results of a continuous copy test of up to 10,000 sheets using BD-3801). Examples 1 to 4
In all of the above, the triboelectric charge amount was changed from -20 μc / g to -25 μc / g from the initial stage to 10,000 sheets, and the image density was 1.4 from the initial stage to 10,000 sheets.
It was confirmed that there is no problem in practical use because the value changes from 3 to 1.38. The copied original was A4 with a black portion of 6%, the triboelectric charge amount was measured using a blow-off triboelectric charge amount measuring device manufactured by Toshiba Chemical Co., and the image density was measured by a Macbeth reflection densitometer RD-914. For the fog, a color difference meter Z-1001DP manufactured by Nippon Denshoku Co., Ltd. was used.

[0031]

[Table 2]

[0032]

The electrophotographic toner of the present invention is capable of fixing at a low temperature while maintaining a sufficient non-offset temperature region, is excellent in fixing strength, and is capable of obtaining a sufficient number of image densities. It has the effect of being able to.

Claims (3)

(57) [Claims] 1. A polyester resin having an average particle size of 1 μm.
containing styrene acrylic gel particles having the following carboxyl group m, the styrene-acrylic gel particles of Cal
At least a part of the boxyl group of the polyester resin
A toner for electrophotography, which chemically reacts with a hydroxyl group to form an ester bond and forms a copolymer with the polyester resin. 2. A polyester resin is formed by polymerizing an alcohol component and an acid component in the presence of styrene acrylic gel fine particles having an average particle diameter of 1 μm or less and having a carboxyl group, and then the polyester resin is mixed with at least a colorant. A method for producing a toner for electrophotography, which comprises melt-kneading a mixture obtained by pulverizing and classifying. 3. The method for producing an electrophotographic toner according to claim 2, wherein the molar ratio of the alcohol component to the acid component is 1.0 or more.