JP2785176B2 - 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 a printer which employs heat roll fixing.

[0002]

2. Description of the Related Art In recent years, with the spread of copying machines and printers using an electrophotographic system including general households and the like, the energy consumption of the copying machines and printers has been reduced mainly for the purpose of multifunctionalization ( (Reduction in power consumption), speeding up to spread into the so-called gray area located at the boundary between the printing machine and copying machine, or lowering the roll pressure to simplify the fixing roll to reduce machine cost. Is desired. In addition, as copiers have become more sophisticated, since copiers equipped with a two-sided copy function and an automatic document feeder have become widespread, the fixing temperature of electrophotographic toner used in copiers and printers is low, and the There is a demand for an electrophotographic toner that has excellent offset properties and has excellent fixing strength to transfer paper in order to prevent the occurrence of stains during duplex copying and the occurrence of stains in an automatic document feeder.

[0003] In response to the above demands, in the prior art, there have been proposed, for example, ones in which the molecular weight and molecular weight distribution of the binder resin are improved as follows. Specifically, attempts have been made to lower the fixing temperature by lowering the molecular weight of the binder resin. However, the lowering of the molecular weight lowers the melting point but also lowers the viscosity at the same time, so that there has been a problem that an offset phenomenon to the fixing roll occurs. In order to prevent this offset phenomenon, a method of widening a low molecular weight region and a high molecular weight region of the molecular weight distribution of the binder resin, or a method of cross-linking a polymer portion has been performed. However, in this method, the glass transition temperature (hereinafter, abbreviated as Tg) of the resin must be lowered in order to have sufficient fixability, and it is inevitable that the storage stability of the toner is impaired.

Conventionally, as a means for securing the storage stability, a method of adhering inorganic fine particles such as silica, titanium, and alumina, resin fine particles, and the like to the toner surface has been used. However, it is difficult to completely cover the toner surface with these fine particles, and the toner having a low Tg could not sufficiently maintain the storage stability. Further, in order to completely cover the toner surface, a large amount of fine particles must be added, and as a result, the fixing property and the offset property have been reduced.
Further, there has been a problem that a large amount of fine particles adversely affect the charging characteristics and shorten the service life of the developer.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to fix at a low fixing temperature, to cause no practical problem in non-offset property, and to improve the fixing strength and the storability to transfer paper. An object of the present invention is to provide an electrophotographic toner having excellent image characteristics.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and an outline of the invention is a toner particle containing at least a resin having a carboxyl group and a resin having a glycidyl group. The toner for electrophotography is cured such that the crosslink density increases stepwise toward the particle surface. Further, the present invention provides a method in which a mixture mainly composed of a resin containing at least a carboxyl group and a resin containing a glycidyl group is melted and kneaded, and then pulverized and classified to prepare toner particles. Or applying a mechanical impact force,
An object of the present invention is to provide a method for producing an electrophotographic toner, characterized in that the toner is cured so that the crosslink density increases stepwise toward the surface of the toner particles.

Hereinafter, the present invention will be described in detail. The resin containing a carboxyl group applied to the present invention is styrene-
An acrylic resin or a polyester resin may, for example, be mentioned.
Styrene containing a carboxyl group applicable to the present invention-
Acrylic resins are prepared by suspension polymerization, emulsion polymerization, solution polymerization, and bulk polymerization of monomers containing a carboxyl group such as acrylic acid, methacrylic acid, and maleic acid, and other copolymer components shown below. And the like. Examples of the copolymer component include styrenes such as styrene, α-methylstyrene and chlorostyrene, and acrylic esters such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, and alkyl acrylate. And methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, octyl methacrylate, stearyl methacrylate, glycidyl methacrylate, and alkyl methacrylate. In addition, acrylonitrile, maleic acid ester, vinyl chloride, vinyl acetate,
A vinyl monomer such as vinyl benzoate, vinyl methyl ketone, vinyl hexyl ketone, vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether may be contained at 30% by weight or less based on the polymer. Examples of the styrene-acrylic resin containing a carboxyl group in the present invention are shown below. In the following general formula, Ph is a phenyl group, R is a hydrogen or alkyl group, and n is 10 to 10.
⁷ , m is 10 to 10 ⁷ , l is 10 to 10 ⁷ , M is 10 ³
Indicating the 10 ^7.

Embedded image

As the carboxyl group-containing polyester resin applied to the present invention, those having a carboxylic acid at the terminal are used, and are obtained by polycondensation of the following components. That is, examples of the diol component of the polyester resin include polyoxypropylene 2,2-2,2
-Bis (4-hydroxyphenyl) propane, 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, Examples thereof include 1,5-pentanediol, 1,6-hexanediol, 1,4-butenediol, and 1,6-hexenediol. Examples of trihydric or higher 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-
Examples thereof include 1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxybenzene. The acid components include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, malonic acid, fumaric acid, maleic acid, maleic anhydride, human laconic acid, itaconic acid, and succinic acid. , Dodecenylsuccinic acid, alkenylsuccinic acid, pentenedicarboxylic acid and the like. Alternatively, examples of the trivalent or higher polycarboxylic acid include 1,2,4-benzenetricarboxylic acid,
2,5,7-naphthalenetricarboxylic acid, 1,2,4-
Naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid,
Examples include 3-dicarboxyl-2-methyl-2-methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, and the like.

The glycidyl group-containing resin used in the present invention includes glycidyl group-containing acrylic resins and epoxy resins. Examples of the glycidyl group-containing acrylic resin include a homopolymer obtained by homopolymerizing a glycidyl methacrylate monomer and a copolymer obtained by copolymerizing with a vinyl monomer. Examples of the acrylic resin containing a glycidyl group are shown below. In the following general formula, R is a hydrogen or an alkyl group, p is 10 to 10 ⁷ , q is 10 to 10 ⁷ , N is 10
³ shows the 10 ^7.

Embedded image An example of synthesizing such an acrylic resin containing a glycidyl group is shown below. First, a homopolymer of glycidyl methacrylate (GMA) is synthesized by the following method.
That is, 253 g of methyl ethyl ketone (MEK) is placed in a flask and heated to 80 ° C. GMA1 under nitrogen flow
42 g and benzoyl peroxide (BPO) 2.11
g of the mixture are added dropwise at a constant rate over 3 hours. After the dropwise addition, the reaction is continued at 80 ° C. for 2 hours. MEK31g and BP
A solution of 0.31 g of O is added. Further, the polymerization reaction is performed at 80 ° C. for 5 hours. After cooling, the product was treated with 2414 g of MEK
insert. This solution is slowly dropped into 14,200 g of vigorously stirred methanol. The precipitated polymer is separated by filtration and dried under reduced pressure to produce a glycidyl methacrylate (GMA) homopolymer having the following structure.

Embedded image

Next, GMA and methyl methacrylate (MM
An example of the synthesis of the copolymer (A) is shown below. That is, a mixture of xylene-MEK and 1 mol% of BPO are charged into a flask and heated to 80 ° C. GMA 25 mol%, MMA
The 75 mol% mixture is added dropwise over 3 hours. The reaction is continued for 2 hours after the addition. 0.15 mol% of BPO is charged as a 10% solution of the above solvent. The polymerization is continued for another 5 hours. After cooling, the product is placed in MEK. This solution is slowly dropped into vigorously stirred methanol. The precipitated polymer is separated by filtration and dried under reduced pressure to produce an acrylic resin containing a glycidyl group having the following structure.

Embedded image

As the epoxy resin containing a glycidyl group applied to the present invention, commercially available epoxy resins can be used, but a typical type is a bisphenol A type epoxy resin produced by a condensation reaction of bisphenol A and epichlorohydrin. Resin can be used. Examples of such an epoxy resin are those manufactured by Yuka Shell Epoxy Co., Ltd., trade names: Epicoat 1001, 1002, 1003, 10
04, 1007, 1009, and 1010.
Further, a novolak type epoxy resin (trade name: Epicoat 157S70, 157H7, manufactured by Yuka Shell Epoxy Co., Ltd.)
0), brominated epoxy resin, glycidyl ester type epoxy resin and the like can also be used.

The Tg of the resin containing a carboxyl group or the resin containing a glycidyl group applied to the present invention is 30 ° C.
It is preferably at least 60 ° C. In the case where other binder resins are contained in addition to these resins, it is also preferable that the other binder resin components have a low Tg similarly, since fixing can be performed at a low temperature. In addition, if it comprises only the binder resin whose Tg is higher than 60 ° C., sufficient fixing strength may not be obtained. Tg is measured by DSC. Examples of the measuring device include a differential scanning calorimeter SSC-5200 manufactured by Seiko Denshi Kogyo. As measurement conditions, about 10 mg of the resin was weighed, placed in an aluminum cell, placed on a DSC, and charged at 50 minutes per minute.
Blow in milliliter of N ₂ gas. Then, the process of raising the temperature between 20 ° C. and 150 ° C. at a rate of 10 ° C. per minute and then rapidly cooling from 150 ° C. to 20 ° C. is repeated twice to measure the heat absorption at that time. Tg here
Indicates the temperature at the intersection of the baseline at the time of the second measurement and the tangent line indicating the maximum slope from the start to end point of endotherm.

In the present invention, it is considered that the carboxyl group and the glycidyl group react by heating to generate a hydroxyl group, and the hydroxyl group and the glycidyl group further react to form a crosslinked structure. By forming a crosslinked structure on the surface of the toner particles, Tg is improved and blocking resistance is improved. Further, it is considered that the high-temperature offset is improved by increasing the melt viscosity. The reaction mechanism of the resin is shown below.

Embedded image

In the electrophotographic toner of the present invention, in addition to the above components, other binder resins, coloring agents, magnetic substances, charge control agents, offset preventing agents, lubricants for improving fluidity, and other property improving agents can be used. It is. Other binder resins applied to the electrophotographic toner of the present invention include styrene resin, styrene-acrylic copolymer resin containing no carboxyl group,
Polyethylene resin, silicone resin, polyamide resin,
A resin such as a polyurethane resin may be blended. Colorants include carbon black, nigrosine dye, aniline blue, coco oil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, and the like. , And others. These colorants need to be contained in a sufficient ratio to form a visible image having a sufficient concentration, and usually a ratio of about 1 to 20 parts by weight based on 100 parts by weight of the binder resin. Is done.

The magnetic material may be a ferromagnetic metal or alloy such as ferrite or magnetite, cobalt, nickel, or a compound containing these elements, or a compound containing these elements, or a suitable heat treatment. Alloys that become ferromagnetic when applied, such as manganese-copper-aluminum, manganese-copper-tin, and other alloys of the type called Heusler alloys containing manganese and copper, or chromium dioxide, and the like. .
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 per 100 parts by weight of the toner particles,
Preferably it is 40 to 70 parts by weight.

The toner for electrophotography according to the present invention is mixed with a carrier made 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 without mixing with a carrier for developing an electrostatic image, or may be mixed with a carrier and used as a two-component developer. Further, the present invention can be applied to a non-magnetic one-component developing method.

The method for producing an electrophotographic toner according to the present invention comprises:
First, a resin containing at least a carboxyl group, a resin containing a glycidyl group, and other additional components such as a colorant are mixed using a Henschel mixer or the like to obtain a mixture, and the mixture is melted and kneaded. In this case, a roll mill, a pressure kneader, a Banbury mixer, an extruder, or the like can be used as the hot melt kneader. After kneading, the mixture is pulverized using a pulverizer such as a jet mill or a turbo mill, and then adjusted to a desired particle size distribution using an air classifier to obtain toner particles. Thereafter, the toner particles for electrophotography of the present invention can be produced by gradually increasing the crosslinking density toward the surface of the toner particles by applying a heat treatment or a mechanical impact force to the toner particles. As the means for the heat treatment or the mechanical impact force, mixers giving a high-speed shearing force, for example, a super mixer, a Henschel mixer, a turbulizer and the like can be used. By stirring with these mixers, frictional heat is generated on the toner surface, and a crosslinking reaction proceeds. If it is desired to further promote cross-linking, means such as heating with hot water or blowing hot air into the jacket of the mixer may be added. In addition to the methods described above, a hybridizer (manufactured by Nara Machinery Co., Ltd.) and Angmill (manufactured by Hosokawa Micron Co., Ltd.), which are commercially available with toner particles as a surface modifier, can also be used. Further, heat treatment or mechanical impact may be applied by using a heat fluidized bed, for example, a surfing system (manufactured by Nippon Pneumatic Co., Ltd.), a swirling fluidized bed dryer (manufactured by Okawara Seisakusho), or the like.

In the present invention, as the technical means for increasing the crosslink density stepwise toward the surface of the toner particles, a set temperature and time of a mixer or a surface reformer as a heat treatment means can be controlled by controlling. For example, a hybridizer manufactured by Nara Machinery Co., Ltd.
m for 10 minutes. In order to determine whether the crosslink density of the toner particles gradually increased toward the surface, 20 g of the toner particles were placed in a 200 cc bottle of polyethylene, and left in a thermostat kept at 50 ° C. for 16 hours. By not blocking between particles, it is an indication that the surface of the toner particles has started to be cured, and this is one of the judgments that the toner particles have been crosslinked. On the other hand, when the heat curing progresses and the entire inside of the toner particles is cured, the melting start temperature by the curable flow tester becomes 100 ° C. or more, so that the criterion of excessive heat treatment or mechanical impact force is applied. can do.

In the present invention, in order to further promote the crosslink density on the surface of the toner particles, a curing catalyst such as dodecane diacid, dibutyltin dilaurate, salicylic acid or the like is adhered to the toner surface and then subjected to heat treatment or mechanical impact force. Is also possible. In this case, the toner particles after classification and the curing catalyst are simultaneously charged into a stirrer and mixed with stirring to uniformly adhere the toner particles to the toner surface. Further, the surface of the toner particles is heated and cured by a heat treatment or a mechanical impact force in the same manner as described above.

In the present invention, the melting start temperature of the electrophotographic toner is preferably from 60 ° C. to 100 ° C. in order to improve the fixability at a lower temperature. 10
If the temperature is higher than 0 ° C., the fixability is not sufficient. The melting start temperature refers to the temperature at which the plunger starts to fall when measured by the following measuring instrument and measuring conditions. Measuring machine; Koka type flow tester CF-500 manufactured by Shimadzu Corporation Measurement conditions; Plunger: 1 cm ² Die diameter: 1 mm Die length: 1 mm Load: 20 kgF Preheating temperature: 50 to 80 ° C Preheating time: 300 sec Speed: 6 ° C / min

[0021]

The present invention will be described below with reference to examples. In the examples, parts are parts by weight. Example 1 Weight average molecular weight 9 × 10 ⁵ and number average molecular weight 3.9 × 1
0 ⁵ of styrene - butyl acrylate - acrylic acid copolymer (A) and 10 parts of styrene having a weight average molecular weight 8 × 10 ³ and a number average molecular weight 2.7 × 10 ³ - butyl acrylate - acrylic acid copolymer (B) 90 parts with GPC
In the chromatogram, the molecular weights are 7.5 × 10 ⁵ and 4.5.
A styrene-acrylic resin having a peak position at × 10 ³ was obtained. The amount of acrylic acid in the resin was 10% by weight. This resin has a Tg of 59 ° C. and a melting start temperature of 99.8.
° C, the acid value was 12 mgKOH / g. The raw materials having the above mixing ratios are mixed by a super mixer, hot-melt kneaded by a twin-screw kneader, pulverized by a jet mill, and then classified by a dry air classifier to have an average particle diameter of 10
μm toner particles were obtained. Then, the toner particles are subjected to 6000 RPM and 2 μm with a hybridizer (manufactured by Nara Machinery Co., Ltd.).
Treated for 0 minutes. Further, 100 parts of the treated toner particles and hydrophobic silica (trade name: Cabosil T, manufactured by Cabot Corporation)
S-530) was stirred in a Henschel mixer for 1 minute, and hydrophobic silica was attached to the surface of the particles to obtain an electrophotographic toner of the present invention. The melting start temperature of this electrophotographic toner was 95.3 ° C.

Example 2 Synthesis of carboxyl group-containing polyester resin Polyoxyethylene (2,0) as alcohol component
2,2-bis (4-hydroxyphenyl) propane 85
Mol%, trimethylolpropane 15 mol%, trimellitic acid 5 mol% as an acid component, dodecenyl succinic acid 30
The polycondensation is carried out using 70% by mole of terephthalic acid and a number average molecular weight of 7000 and a weight average molecular weight of 3600.
A polyester resin having 0, an acid value of 30 mg KOH / g, a Tg of 57 ° C., and a melting start temperature of 91.7 ° C. was obtained. The raw materials having the above mixing ratios are mixed by a super mixer, hot-melt kneaded by a twin-screw kneader, pulverized by a jet mill, and then classified by a dry air classifier to have an average particle diameter of 10
μm toner particles were obtained. Then, the toner particles are subjected to 6000 RPM and 2 μm with a hybridizer (manufactured by Nara Machinery Co., Ltd.).
Treated for 0 minutes. Further, 100 parts of the treated toner particles and hydrophobic silica (trade name: Cabosil T, manufactured by Cabot Corporation)
S-530) was stirred in a Henschel mixer for 1 minute, and hydrophobic silica was attached to the surface of the particles to obtain an electrophotographic toner of the present invention. The melting start temperature of this electrophotographic toner was 92.3 ° C.

Embodiment 3 The raw materials having the above mixing ratios are mixed by a super mixer, hot-melt kneaded by a twin-screw kneader, pulverized by a jet mill, and then classified by a dry air classifier to have an average particle diameter of 10
μm toner particles were obtained. Then, the toner particles are subjected to 6000 RPM and 2 μm with a hybridizer (manufactured by Nara Machinery Co., Ltd.).
Treated for 0 minutes. Further, 100 parts of the treated toner particles and hydrophobic silica (trade name: Cabosil T, manufactured by Cabot Corporation)
S-530) was stirred in a Henschel mixer for 1 minute, and hydrophobic silica was attached to the surface of the particles to obtain an electrophotographic toner of the present invention. The melting start temperature of this electrophotographic toner was 89.5 ° C.

Example 4 In Example 1, before performing the step of heating the toner particles with a hybridizer (manufactured by Nara Machinery Co., Ltd.),
Dodecane diacid is added in an amount of 0.1 to 100 parts by weight of toner particles.
The toner for electrophotography of the present invention was obtained in the same manner as above except that a step of adding the mixture and mixing with a Henschel mixer was added. The melting start temperature of this electrophotographic toner was 95.3 ° C.

Example 5 In Example 2, before performing the step of heating the toner particles with a hybridizer (manufactured by Nara Machinery Co., Ltd.),
Dodecane diacid is added in an amount of 0.1 to 100 parts by weight of toner particles.
The toner for electrophotography of the present invention was obtained in the same manner as above except that a step of adding the mixture and mixing with a Henschel mixer was added. The melting start temperature of this electrophotographic toner was 92.3 ° C.

Example 6 In Example 3, before performing the step of heating the toner particles with a hybridizer (manufactured by Nara Machinery Co., Ltd.),
Dodecane diacid is added in an amount of 0.1 to 100 parts by weight of toner particles.
The toner for electrophotography of the present invention was obtained in the same manner as above except that a step of adding the mixture and mixing with a Henschel mixer was added. The melting start temperature of this electrophotographic toner was 89.5 ° C.

Comparative Example 1 A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that the acrylic resin containing a glycidyl group was not used. The melting start temperature of this electrophotographic toner is 100.
2 ° C.

Comparative Example 2 Instead of the styrene-acrylic resin of Example 1, a commercially available styrene-acrylic resin containing no carboxyl group, Hymer TB-1000F (trade name, manufactured by Sanyo Chemical Industries, Ltd.) Tg 58 ° C., melting start temperature An electrophotographic toner for comparison was obtained in the same manner as in Example 1 except that 115 ° C. was used. The melting start temperature of this electrophotographic toner was 112 ° C.

Comparative Example 3 In Example 1, a hybridizer (manufactured by Nara Machinery Co., Ltd.)
A comparative electrophotographic toner was obtained in the same manner except that the step of heat treatment was omitted. The melting start temperature of this electrophotographic toner was 92.1 ° C.

Comparative Example 4 In Example 1, before performing the step of heating the toner particles with a hybridizer (manufactured by Nara Machinery Co., Ltd.),
An electrophotographic toner for comparison was obtained in the same manner except that a step of treating the toner particles with a swirling fluidized bed drier (trade name: FBS-3) manufactured by Okawara Seisakusho at 150 ° C. for 20 minutes was added. The melting start temperature of this electrophotographic toner is 1
21 ° C.

Next, the following tests were conducted for the above-mentioned Examples and Comparative Examples. (1) Fixing Strength First, 4 parts of each electrophotographic toner obtained in the above Examples and Comparative Examples were mixed with 96 parts of a ferrite carrier without a resin coating (trade name: FL-1020 manufactured by Powder Tech). Thus, a two-component developer was prepared. Next, a commercially available copying machine (trade name: BD-281 manufactured by Toshiba Corporation) is used by using the developer.
In 0), a plurality of belt-shaped unfixed images each having a length of 2 cm and a width of 5 cm were formed on A4 transfer paper. Next, a heat fixing roll having a surface layer formed of Teflon and a pressure fixing roll having a surface layer formed of silicone rubber rotate as a pair. A fixing device having a roll pressure of 1 kg / cm ² and a roll speed of 50 mm was used.
/ Sec, the surface temperature of the heat fixing roll was set to 120 ° 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 according to the following equation, which was used as an index of low energy fixing property. The image density is a reflection density meter RD-91 manufactured by Macbeth.
4 was used. Fixing strength (%) = Image density of fixed image after rubbing / Image density of fixed image before rubbing × 100 (2) Preservability First, 20 g of each electrophotographic toner obtained in the above Examples and Comparative Examples was polyethylene. Into a 200 cc bottle of 50
It was left for 16 hours in a thermostat kept at an atmosphere of ° C., and cooled to room temperature. The toner after being left was taken out, and the blocking state of the toner was visually observed. Evaluation is based on the following criteria. ◎ No fusion between toners and no change from before standing. ○ Fluidity was slightly deteriorated, but coarse aggregates were not found. Δ: Aggregation of toner was observed, but it was loosened quickly by lightly pressing with a finger. X: A state in which coarse particles that do not collapse even when pressed with a finger are generated due to fusion of toners. Table 1 shows the test results of the above items.

[0032]

[Table 1]

As is evident from the test results in Table 1, the electrophotographic toner of the present invention has a fixing strength at a fixing temperature of 120 ° C. of 90% or more, has a practically sufficient fixing strength, and has no problem in storage stability. It was confirmed that. On the other hand, it was confirmed that Comparative Examples 1 and 3 had poor storability, and Comparative Examples 2 and 4 had low fixing strength and had practical problems. Further, a commercially available copying machine (trade name: BD-281, manufactured by Toshiba Corporation) is used by using each developer in the above item (1).
0), a continuous copy test was performed on up to 5000 sheets. As a result, in all of Examples 1 to 6, the triboelectric charge amount was 15 μc / g to 20 μm between the initial and 5000 sheets.
c / g, and the image density also changed from 1.45 to 1.40 from the initial stage to 5000 sheets, and it was confirmed that there was no practical problem. The copied original was A4 having a black portion of 6%, the frictional charge was measured using a blow-off frictional charge measuring device manufactured by Toshiba Chemical Co., and the image density was measured using a reflection densitometer RD-9 manufactured by Macbeth.
14 were used.

[0034]

The toner for electrophotography according to the present invention has an effect that it can be fixed at a low temperature, is excellent in storability, and can obtain a sufficient number of images with sufficient image density.

Claims (8)

(57) [Claims] 1. A toner particle containing at least a resin containing a carboxyl group and a resin containing a glycidyl group, which is cured so that the crosslink density increases stepwise toward the particle surface. For electrophotography. 2. The electrophotographic toner according to claim 1, wherein the resin having a carboxyl group is a styrene-acrylic resin or a polyester resin. 3. The electrophotographic toner according to claim 1, wherein the resin containing a glycidyl group is an acrylic resin or an epoxy resin. 4. The electrophotographic toner according to claim 3, wherein the glycidyl group-containing acrylic resin is a homopolymer or a copolymer of glycidyl methacrylate. 5. The electrophotographic toner according to claim 1, wherein the glass transition temperature of the resin containing a carboxyl group or the resin containing a glycidyl group is 30 ° C. or more and 60 ° C. or less. 6. The melting start temperature of the toner for electrophotography is 60.
2. The electrophotographic toner according to claim 1, wherein the temperature is not lower than 100 ° C. and not higher than 100 ° C. 7. A hot melt-kneading mixture comprising a resin containing at least a carboxyl group and a resin containing a glycidyl group, followed by pulverization and classification to prepare toner particles,
Thereafter, the toner particles are subjected to a heat treatment or a mechanical impact force to cure the toner particles so as to gradually increase the crosslink density toward the surface of the toner particles. . 8. The method for producing an electrophotographic toner according to claim 7, wherein after the curing catalyst is attached to the surface of the toner particles, heat treatment or mechanical impact is applied.