JPH0251176B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developer used in electrophotography, electrostatic printing, etc., and particularly to a dry developer suitable for heat fixing.

Conventionally, as an electrophotographic method, U.S. Patent No. 2297691
Specification of No. 42-23910 and Special Publication No. 1973
Although a number of methods are known, such as those described in Japanese Patent Application No. 24748, in general, a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, and then the latent image is The toner image is developed using toner, the toner image is transferred to a transfer material such as paper as required, and then fixed by heat or pressure to obtain a copy.

Furthermore, various developing methods are known in which an electrical latent image is visualized using toner.

For example, the magnetic brush method described in U.S. Pat. No. 2,874,063, the cascade development method described in U.S. Pat. A number of development methods are known, such as the development method. As toners used in these developing methods, fine powders in which dyes and pigments are dispersed in natural or synthetic resins have conventionally been used. Furthermore,
It is also known to use fine developing powders to which third substances are added for various purposes.

The developed toner image is transferred and fixed onto a transfer material such as paper, if necessary.

Methods for fixing toner images include heating and melting the toner using a heater or heated roller to fuse and solidify it to the support, softening or dissolving the binder resin of the toner with an organic solvent, and fixing it to the support, and applying pressure. A method of fixing toner on a support by using a method is known.

Toner materials are selected to be suitable for each fixing method, and toners used for a particular fixing method generally cannot be used for other fixing methods. especially,
It is almost impossible to transfer the toner used in the conventionally widely used heat fusion fixing method using a heater to a hot roller fixing method, a solvent fixing method, a pressure fixing method, or the like. Therefore, toners suitable for each fixing method are being researched and developed.

Various magnetic recording methods are also known in which a magnetic latent image is formed and developed with magnetic toner.

Various methods and devices have been developed for the process of fixing toner images on paper, etc., but the most common method currently is the so-called hot roll fixing method, which applies heat and pressure at the same time. In this method, the toner image is fixed on the image-receiving sheet by bringing the image-receiving sheet carrying the toner image into contact with a heated roller. However, when such a fixing method is used, problems such as so-called offset occur with conventional toner. Offset is an undesirable phenomenon in which a portion of the toner carried on the image receiving sheet is transferred to the roller surface.

As described in Japanese Patent Publication No. 51-23354, such an offset phenomenon tends to occur when low molecular weight resins are used. It is thought that by using such a resin, the offset phenomenon can be prevented to some extent, but of course, simply using a cross-linked resin increases the fixing temperature, causing the problem of low-temperature offset in the unfixed area.

The roller that comes into contact with the toner image usually has at least a surface layer formed of silicone rubber or fluororesin, which has good releasability, and is used to prevent offset and fatigue of the roller surface. For this reason, there is also a method of applying mold release oil such as silicone oil. However, the method of applying oil has problems such as the provision of an oil application system which complicates the fixing device and the evaporation of the oil causing discomfort to the user.

Therefore, it is not desirable to try to prevent offset by coating with oil, but rather the development of a toner with good offset resistance over a wide fixing temperature range is currently desired. It goes without saying that in addition to fixing properties, toners also need to have excellent blocking resistance, developing properties, transferability, cleaning properties, etc., but conventional toners must have the following defects: had one or more. That is, many toners that are easily melted by heating tend to cake or aggregate during storage or in a copying machine. Many toners exhibit poor triboelectric properties and flow properties due to environmental temperature changes. In addition, with many toners, the image density obtained changes due to mutual deterioration of the toner, carrier particles, and photosensitive plate due to collisions between the toner particles and carrier particles and their contact with the photosensitive plate surface due to repeated development due to continuous use. , or the background density increases, reducing the quality of the copy. Therefore, there is a need for a toner that has excellent toner properties and is suitable for hot roller fixing.

More recently, high-speed fixing has been sought to improve the efficiency of copying operations. In order to increase the fixing speed in conventional heat fixing methods, attempts have been made to lower the softening point of the toner binder resin to facilitate heat fixing. Troubles such as agglomeration and blocking occur.

In this way, it is suitable for faster heat roller fusing,
Moreover, there is a strong desire for a toner that is free from roller offset and has excellent toner properties such as agglomeration and blocking.

Conventionally, it has been considered to make toner into a capsule type simply to increase the heat fixing speed, or to keep the speed constant and reduce the heat source energy. Fusing toners have been proposed. This type of capsule toner uses a low melting point component that is more easily melted by heat as the core material, and a component that has a high melting point and has properties such as chargeability and fluidity required for a toner as the shell material. For example, Japanese Patent Publication No. 49-1588 provides examples of polystyrene capsules using wax as the core material or polystyrene capsules using an aqueous solution as the core material. However, none of these methods takes into account the recent high-speed fixing with hot rolls, and therefore suffers from severe roller offset, and is therefore impractical. As described above, conventional heat-fixing capsule toners cannot avoid the problem of roller offset.

As a result of our investigation into materials that have good high-speed hot roll fixing properties and excellent offset resistance, we discovered that a combination of amorphous polyester resin and a polyvalent metal compound satisfies these requirements. did. It is presumed that the polyvalent metal compound mixed in the polyester causes a thermal reaction during heat treatment such as kneading, which is thought to be due to the effect of the free metal, and therefore promotes the formation of a crosslinked structure in the polyester. As a result, the offset resistance of the polyester is improved without impairing its fixing properties. However, these characteristics of a mixture of polyester and a polyvalent metal compound alone are not sufficient to make a toner, and there is still a barrier to blocking in achieving better low-temperature fixability.

As a result of intensive study to take advantage of the characteristics of these resins and overcome the toner blocking and caking factors that are disadvantageous when achieving high-speed fixing with conventional simply pulverized toner, we have developed this type of resin. We have found that it is essential to create a capsule structure using a material as a core material.

In other words, low-temperature fixing properties and offset resistance are achieved by a reaction product of amorphous polyester with a low softening point and a polyvalent metal salt, and the slight drawback of blocking properties of this material is compensated for by creating a capsule structure. It has been found that this makes it possible to satisfy various toner properties such as hot roll high-speed fixing properties, offset resistance, blocking resistance, caking resistance, developability, and durability, which led to the present invention.

An object of the present invention is to provide a heat fixable toner that solves the above-mentioned problems. A further object of the present invention is to provide a toner for hot roller fixing which has particularly good fixing properties and good offset resistance.

A further object of the present invention is to provide a toner for hot roller fixing that has good chargeability and always exhibits stable chargeability during use, and provides clear and fog-free images.

A further object of the present invention is to provide a toner for hot roller fixing that has excellent fluidity, does not cause aggregation, and has excellent impact resistance.

A further object of the present invention is to provide a toner for thermal roller fixing that has less deposits on the surface of a toner holding member or photoreceptor.

A further object of the present invention is to provide a magnetic toner which, when used as a magnetic developer, exhibits good and uniform magnetism and can be fixed by a hot roller.

The above object of the present invention is achieved by providing a toner with a capsule structure in which the core material is a material having high-speed heat fixing properties and offset prevention properties.

Specifically, the present invention relates to an electrostatic image developer used for heat fixing that contains a capsule toner in which the core particle surface of a heat fixable material whose main components are a binder resin and a colorant is coated with a thermoplastic resin. In the developer for
The binder resin has a glass transition temperature of 60°C or less, and a glass transition temperature of 50°C or less.
Amorphous polyester with a softening point of ~110°C and an acid value of 10 to 150, and 1/50 to the polyester
The thermoplastic resin contains 1/4 weight of a polyvalent metal salt, and the thermoplastic resin is selected from the group consisting of 0.2 to 10 mol% of an organic acid monomer, styrene or its derivatives, acrylic esters, methacrylic esters, and maleic esters. A vinyl copolymer resin with two or more selected monomers, and 55℃
Glass transition temperature over 100~150℃, softening point 15
The present invention relates to a developer for developing electrostatic images, which is a vinyl copolymer resin having an Mw of 10,000 or more and a Mw/Mn of 5 or more.

In other words, the present invention is characterized by achieving high-speed heat fixing properties and offset resistance using a special core material.
At the same time, the shell material has a heat-fixable toner structure with a capsule structure that achieves general toner properties such as cohesiveness, blocking properties, and developability.

In the heat fixable toner with a capsule structure related to the present invention, Tg, which could not be used alone as a core material due to its properties such as blocking and cohesive properties, is used as a core material.
A material with low oxidation and good offset resistance is used to share most of the functions of heat roller fixing, and as a shell material, toner characteristics such as developability and storage stability of dry toner can be maintained as before or even better. By using the materials described above and creating a so-called functionally separated type, the various objects of the present invention could be achieved.

It is essential that the binder resin for the core particles used in the present invention contains a thermally reacted product of a specific polyester resin and a polyvalent metal compound that meets the purpose of the present invention. In other words, the glass transition temperature is 60℃ or less, and the softening point is 50~
110℃, molecular weight preferably 2000 to 20,000, acid value 10
~150% amorphous polyester resin 98~80% by weight;
It is desirable that the mixture contains 2 to 20% by weight of a polyvalent metal compound, and that these are appropriately crosslinked by thermal reaction.

Terephthalic acid, isophthalic acid, phthalic acid,
Aromatic polycarboxylic acids such as naphthalene dicarboxylic acid, trimellitic acid, pyromellitic acid; P-(2
Aromatic oxycarboxylic acids such as -hydroxyethoxy)benzoic acid; maleic acid, maleic anhydride, fumaric acid, succinic acid, adipic acid, azelaic acid,
Aliphatic polycarboxylic acids such as sebacic acid; 1,3-
Examples include alicyclic polycarboxylic acids such as cyclohexanedicarboxylic acid, hexahydrophthalic acid, and tetrahydrophthalic acid.

In addition, alcohol components include ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, glycerin, trimethylolethane. , trimethylolpropane, pentaerythritol, sorbitol and other aliphatic polyols; 1,4-cyclohexanediol, 1,4-
Alicyclic polyols such as cyclohexanedimethanol; etherified diphenols such as ethylene oxide adducts of bisphenol A and propylene adducts of bisphenol A;

The polyester used in the present invention is amorphous,
Both the acid component and the alcohol component can be selected arbitrarily as long as the combination satisfies the glass transition temperature conditions, but generally it is necessary to include an asymmetric component in order to have amorphousness and a certain low softening point. There is. Further, for the purpose of offset resistance, it is preferable to include a polycarboxylic acid of trivalent or higher valence and/or a polyol as a component to give the polyester a suitable network structure.

The polyester used in the present invention has a glass transition temperature of 60°C or less and a softening point of 50 to 110°C. If the glass transition temperature exceeds 60°C or the softening point exceeds 130°C, the softening point will become even higher when taking into account the thermal reaction with the polyvalent metal salt of the present invention, and excessive thermal energy will be required during heat fixing. is required, and high-speed heat fixing performance deteriorates. If the softening point is less than 50°C, the offset resistance during fixing may be poor depending on the degree of reaction with the polyvalent metal salt.

Similarly, if the molecular weight is less than 2000, the hot roller releasability will be poor and the offset phenomenon will easily occur.
On the other hand, if it exceeds 20,000, the softening point increases and the heat fixability decreases.

The polyvalent metal compound used in combination with the polyester is one that can react with the carboxyl group in the polyester, and includes, for example, oxides such as zinc oxide, magnesium oxide, and aluminum oxide; magnesium acetate, calcium acetate, and basic aluminum acetate. , salts such as calcium stearate and zinc stearate; alkoxides such as aluminum isopropoxide, aluminum-n-butoxide and aluminum methoxide; hydroxides such as aluminum hydroxide and ferric hydroxide; aluminum acetylacetonate, iron acetyl There are chelate compounds such as acetonate.

In the present invention, the mixing ratio of polyester and polyvalent metal compound is 98 to 80% by weight of polyester;
The polyvalent metal compound is 2 to 20% by weight, that is, the ratio of the polyvalent metal compound to the polyester is 1/50 to 1/50.
4 weight ratio, and if the metal compound content is less than 1/50, the thermal reaction will be insufficient and the releasability of the toner from the heated roll will deteriorate, making it easy to cause an offset phenomenon.

Furthermore, if the amount of the metal compound exceeds 1/4, the thermal fluidity of the toner is adversely affected, resulting in poor fixing such as increased fixing temperature.

As the binder resin of the core particles, other known binder resins such as polyester resins, epoxy resins, styrene-acrylic resins, butyral resins, and ethylene resins other than those of the present invention may be used as the binder resin of the core particles.
Ethyl acrylate resin, styrene-butadiene resin, etc. can be mixed and used.

As the thermoplastic resin as the wall material used in the present invention, those conventionally used as binders for toners can basically be used, but they are limited to some extent due to constraints in manufacturing the capsules of the present invention. Within this range, for example, those that can be used as aqueous suspensions, those that can be used as alkali-soluble aqueous solutions, those that can form a coating layer on core particles by known microencapsulation methods, or those that can be used during encapsulation. There are some that can be formed by reaction.

As an aqueous suspension resin, the suspension must have a minimum film-forming temperature near the softening point of the core particle, or preferably at least 30°C lower than that, and have wettability and adhesion to the core particle. In order to maintain the durability of the toner when forming the outer wall, it is necessary to have a uniform coating and not be brittle or sticky, and to maintain the image forming ability, it has characteristics such as appropriate electrical resistance (insulating property) and triboelectric charging properties. is required.

As such resin components, acrylic ester,
Two or more monomers arbitrarily selected from monomers such as methacrylic acid ester, styrene or its derivatives, vinyl acetate, maleic acid ester, etc., and 0.2 to 10 mol% of acrylic acid or methacrylic acid. , those mainly composed of copolymer resins obtained by emulsion polymerization with organic acid monomers such as maleic acid, itaconic acid, and crotonic acid, that is, containing 60 mol% or more of this copolymer component in the resin content. Things can be given.

In addition, as a type of resin that can be used as an alkali-soluble aqueous solution, two or more monomers arbitrarily selected from monomers such as styrene or its derivatives, acrylic esters, methacrylic esters, maleic esters, etc. On the other hand, the acid value after polymerization is
Acrylic acid, maleic acid in an amount of about 40 to 200,
Some are copolymerized with organic acid monomers such as itaconic acid and crotonic acid.

These thermoplastic resins have a glass transition temperature of 55°C or higher and a softening point of 100 to 150°C. If the glass transition temperature is less than 55° C., the resulting toner will cause blocking during storage, rendering it impractical.
Furthermore, if the softening point is below 100°C, offset will easily occur during heat fixing. Furthermore, if the softening point exceeds 150°C, the heat fixability of the core material will be significantly inhibited.

The weight average molecular weight Mw needs to be 150,000 or more from the point of view of preventing thermal roller offset, and from the same point of view
It is desirable that Mw/Mn is 5 or more. When Mw is less than 150,000 and Mw/Mn is less than 5, the heat-molten vinyl polymer has poor offset resistance.

In the capsule toner of the present invention, a charge control agent, a coloring agent, and a fluidity modifier may be added to one or both of the core material and the outer shell, as necessary. The agent may be used by being mixed with the toner (externally added). Examples of this charge control agent include metal-containing dyes and nigrosine, and conventionally known dyes and pigments can be used as colorants.
Examples of fluidity modifiers include colloidal silica and fatty acid metal salts.

Furthermore, if it is desired to obtain a magnetic toner, magnetic fine particles may be added to the toner. The magnetic substance may be any material that exhibits magnetism or can be magnetized, such as fine metal powders such as iron, manganese, nickel, cobalt, and chromium, various ferrites, alloys and compounds of manganese, and other ferromagnetic alloys. Conventionally known magnetic materials can be used. These magnetic fine particles may be added to either the core material or the shell material, but in the case of obtaining an insulating toner, it is preferable to add them to the core material.

Furthermore, polyolefins such as low molecular weight polyethylene and low molecular weight polypropylene may be added to the core material and/or shell material in order to improve the releasability from the heat fixing roll.

In the present invention, the method for obtaining core particles is as follows:
A known dry toner manufacturing method can be applied as is.
For example, the most common method is to pre-mix polyester resin and other compounds into fine particles, mix them uniformly by kneading with a hot melt, and then obtain core particles of a constant particle size using air jet pulverization, wind classifier, etc. It is. In the case of the present invention, the thermal reaction between the polyester resin and the polyvalent metal compound is an important point in terms of toner properties.
Therefore, care must be taken to control the temperature and time during hot kneading.

In the present invention, the spray drying method is preferred as the encapsulation method, but other phase separation methods, air suspension coating methods, etc. can be used depending on the material used as the wall material.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but these are not intended to limit the present invention. Further, all parts in the examples are parts by weight.
In addition, each physical property of the resin was measured by the following method.

Glass transition temperature - heating rate 16 by differential scanning calorimeter (PerkinElmer Model DSC-1B)
Measured in °C/min.

Softening point - Based on JISK2531. Ring and ball softening point test.

number average molecular weight Weight average molecular weight - Polystyrene determined by GPC measurement Measured using Ren standard product standards.

Production Example 1 Put 700 parts of polyethylene oxide adduct of bisphenol A and 7 parts of glycerin into a four-necked flask, set a stirrer, condenser, thermometer, and gas inlet tube, and place it in a mantle heater. After purging the inside of the reaction vessel with nitrogen gas, when the temperature of the contents reached 50-60℃, 270 parts of fumaric acid and hydroquinone were added.
Add 0.4 part and heat to 210°C with stirring. After about 5 hours have passed while continuously removing the reaction water, the reaction is monitored by measuring the acid value every hour to check the end point of the reaction.

After continuing the reaction until the acid number is approximately 25, the resin is cooled to room temperature. The resin thus obtained had a Tg of 52°C, a softening point of 110°C, and an acid value of 45.

Production example 2 650 parts of terephthalic acid, 200 parts of sebacic acid, 140 parts of isophthalic acid, 650 parts of ethylene glycol, and 350 parts of neopentyl glycol were placed in a flask and the mixture was heated to 180 parts.
The reaction was carried out at 220°C for 4 hours, and then the system was reduced in pressure and the reaction was further carried out at 230°C for 1 hour. The obtained resin had a Tg of 30°C, a softening point of 100°C, and an acid value of 73.

Production Example 3 After charging 490 parts of terephthalic acid, 180 parts of trimellitic acid, 640 parts of propylene glycol, 220 parts of neopentyl glycol, and 25 parts of trimethylolpropane into a flask and carrying out an esterification reaction at 210°C to 230°C for 5 hours, 266 parts of isophthalic acid was added, and the reaction was carried out at 230°C for 6 hours in a nitrogen stream.

The obtained polyester has a Tg of 46℃, a softening point of 57℃,
The acid value was 140.

Production example 4 500 parts of terephthalic acid, 100 parts of ethylene glycol
1 part, 420 parts of neopentyl glycol, 50 parts of trimethylolpropane, and 270 parts of isophthalic acid were placed in a flask and heated to 50°C with stirring.

Next, add 0.6 parts of dibutyltin oxide and heat at 220°C.
The reaction was carried out for about 6 hours. The obtained polyester had a Tg of 50°C, a softening point of 86°C, and an acid value of 96.

Production Example 5 According to the same method as Production Example 1, terephthalic acid
400 parts, isophthalic acid 100 parts, ethylene glycol
Put 280 parts and 120 parts of neopentyl glycol into a flask, and heat and stir at 60°C.

Next, the mixture is heated to about 220°C and the reaction is carried out for about 6 hours. After the reaction is completed, the resulting polyester is left to cool.
The Tg was 65°C and the softening point was 135°C.

Production Example 6 580 parts of dimethyl terephthalate, 300 parts of 1,2-propanediol, and 4 parts of trimethylolpropane are placed in a flask. After heating the mixture to about 80 °C and adding 1.5 parts of tetrabutyl titanate,
Gradually heat to about 200°C over about 6 hours.

After reducing the pressure of the system and removing the distillate, the system was further heated under reduced pressure for 6 hours to complete the reaction. The obtained polyester had a Tg of about 80°C and a softening point of about 95°C.

Example 1 A mixture consisting of 100 parts of polyester (Production Example 1), 2 parts of basic aluminum acetate, 70 parts of magnetic powder (Magnetite EPT-1000 manufactured by Toda Industries), and 5 parts of low molecular weight polypropylene (Viscol 660P manufactured by Sanyo Chemical Industries) was prepared. The mixture was heated and kneaded using a roll. During heating and kneading, it was confirmed that the viscosity of the kneaded product gradually increased. After cooling this, it is crushed into pieces of 1 to 2 mm.
Further, fine pulverization using a jet mill and classification using an air classifier were performed to obtain core material particles with an average size of about 12 μm.

Separately, a styrene/butyl methacrylate/butyl acrylate/acrylic acid copolymer emulsion (acrylic acid 3 mol%, solid content 40%) was prepared. The glass transition temperature of the constituent resin of this emulsion is 70
℃, the softening point was 140℃, Mw was 230,000, and Mw/Mn was 6.3.

58 parts of the core material for 20 parts of this emulsion.
1 part, 0.4 part of metal complex salt (Orient Chemical, Bontron E-81), and 240 parts of water were mixed and dispersed well while avoiding foaming, and then sprayed with a spray dryer at an inlet temperature of 160°C and an outlet temperature of 90°C. After drying, a crosslinked resin coating layer mainly composed of the emulsion-constituting copolymer was provided around the core material particles.

Colloidal silica (Aerosil R-972) was added to the capsule toner thus obtained, and a one-component development type electrophotographic copying machine (manufactured by Canon Co., Ltd.) was used.
NP-400RE) and a copying test was conducted, and sufficient image density and development durability were obtained.

In addition, in order to examine the thermal fixability in detail, we prepared a separate fixing unit for the copying machine and used this separate fixing unit to fix an unfixed image on a separately prepared transfer paper, and no offset phenomenon occurred over a wide temperature range. The fixing properties were also excellent.

Further, this capsule toner was left in an atmosphere at 50° C. for a long time, but no blocking or caking was observed.

Example 2 A capsule toner was obtained in the same manner as in Example 1 except that the polyester of Example 1 was replaced with that of Production Example 2 and the basic aluminum acetate was replaced with aluminum isopropoxide. The performance of this magnetic toner was the same as in Example 1, with no problems in developability, fixability, offset, and blocking.

Example 3 Example 1 except that the polyester of Example 1 was replaced with that of Preparation Example 3 and aluminum isopropoxide was used as the polyvalent metal compound.
A capsule toner was obtained in the same manner as above. The performance of this magnetic capsule toner is similar to that of Example 1, such as developability,
Fixability, offset, and blocking were all good.

Example 4 A capsule magnetic toner was obtained in the same manner as in Example 1, except that the polyester of Production Example 4 was used and iron acetylacetonate was used as the polyvalent metal compound.

The performance of this toner was also good in terms of developability, fixing power, offset, and blocking, as in each of the Examples.

Comparative Example 1 A capsule magnetic toner was obtained in the same manner as in Example 1 except that the polyester of Production Example 5 was used and aluminum isopropoxide was used as the polyvalent metal compound.

When this toner was subjected to the same test as in Example 1, the fixing temperature was high and unfixed offset caused by poor fixing occurred.

Example 5 A mixture consisting of 100 parts of polyester (Production Example 1), 2 parts of basic aluminum acetate, 70 parts of magnetic powder (Magnetite BL-120 manufactured by Titan Industries), and 5 parts of low molecular weight polypropylene (Viscol 660P manufactured by Sanyo Chemical Industries) was prepared. The mixture was heated and kneaded using a roll. After allowing this to cool, it was crushed to a size of 1 to 2 mm, and further finely pulverized using a jet mill and classified using an air classifier to obtain core material particles with an average size of about 12 μm.

Separately, a styrene/butyl methacrylate/ethyl acrylate/2-ethylhexyl acrylate/itaconic acid copolymer emulsion (2 mol% itaconic acid, 42% solid content) was prepared. The glass transition temperature of the constituent resin of this emulsion is 65℃, the softening point is 135℃,
Mw was 280,000, and Mw/Mn was 8.5.

Further, an acrylic copolymer resin (Seiko Kagaku, Hylos X-316, Oxidation 60) was dissolved in ammonia alkaline water to make a 25% aqueous solution.

8 parts of the above resin aqueous solution are mixed with 20 parts of the above emulsion, and 50 parts of the above core material particles and water are mixed.
After adding 200 parts and thoroughly mixing and dispersing, spray drying was performed using a spray dryer at an inlet temperature of 160°C and an outlet temperature of 80°C to coat the emulsion-constituting copolymer and alkali-soluble resin around the core material particles. A resin coating layer was provided as the main body.

Colloidal silica (Aerosil R-972) was added to the capsule toner thus obtained, and a copying test was conducted in the same manner as in Example 1. As a result, the developability, fixability, and offset were all good, and there was no problem with blocking when left at 45°C.

Example 6 A capsule toner was obtained in the same manner as in Example 5 except that the polyester used in Production Example 3 was used and aluminum acetylacetonate was used as the polyvalent metal salt. This product was subjected to the same tests as in Example 1, and as a result, all of the developability, fixability, and offset were good, and there was no problem with blocking even when left at 45° C. for 24 hours.

Comparative Example 2 A capsule magnetic toner was obtained in the same manner as in Example 5 except that the polyester of Production Example 6 was used.

When this toner was subjected to the same test as in Example 1, the fixing temperature was high and unfixed offset caused by poor fixing occurred.

Comparative Example 3 A mixture consisting of 100 parts of the polyester of Production Example 2, 2 parts of aluminum isopropoxide, 70 parts of magnetic powder (Magnetite EPT-1000 manufactured by Toda Industries), and 5 parts of low molecular weight polyethylene was heated and mixed with a roll,
After cooling, it was pulverized using a speed mill and a jet mill, and then classified to obtain a magnetic toner with an average size of about 12 μm.

Colloidal silica (Aerosil R-
972) was added and supplied to a one-component development type electrophotographic copying machine (a modified Canon NP-201), and a copying test was conducted, and satisfactory images were obtained. Further, the results of tests using a separately prepared hot roll fixing tester showed that no offset phenomenon occurred over a wide temperature range, and the fixing properties were excellent. However, this toner easily caused blocking when left in an atmosphere at 45°C.

Reference Example 1 Core material particles were prepared in the same manner as in Example 1 except that basic aluminum acetate was not used. The viscosity of the kneaded product did not substantially increase during heating and kneading of the core material. Furthermore, a coating layer was provided around the core material particles in the same manner as in Example 1 to prepare a capsule toner.

Example 1 Using the prepared capsule toner
A copying test was conducted in the same manner as in Example 1, and a heat fixing test was conducted in the same manner as in Example 1. The fixing temperature was the same as that of the capsule toner of Example 1, but the high temperature offset temperature was lower than that of Example 1. The temperature was about 15°C lower than that of No. 1 capsule toner.

Reference Example 2 Core material particles were prepared in the same manner as in Example 1, except that 0.1 part of basic aluminum acetate was used. During heating and kneading of the core material, the viscosity of the kneaded material is
rose slightly.

Furthermore, a coating layer was provided around the core material particles in the same manner as in Example 1 to prepare a capsule toner.

Example 1 Using the prepared capsule toner
A copying test was conducted in the same manner as in Example 1, and a heat fixing test was conducted in the same manner as in Example 1. The fixing temperature was the same as that of the capsule toner of Example 1, but the high temperature offset temperature was lower than that of Example 1. The temperature was about 13°C lower than that of No. 1 capsule toner.

Reference Example 3 Core material particles were prepared in the same manner as in Example 1 except for using 30 parts of basic aluminum acetate. During heating and kneading of the core material, the viscosity of the kneaded material increased significantly.

Furthermore, a coating layer was provided around the core material particles in the same manner as in Example 1 to prepare a capsule toner.

Example 1 Using the prepared capsule toner
A copying test was conducted in the same manner as in Example 1, and a heat fixing test was also conducted in the same manner as in Example 1. The fixing temperature was 12°C higher than that of the capsule toner of Example 1. The heat fixability was decreased.

Claims (1)

[Scope of Claims] 1. A developer for developing an electrostatic image used for heat fixing, which contains a capsule toner in which the surface of the core particle of a heat fixable material containing a binder resin and a colorant as main components is coated with a thermoplastic resin. In the agent, the binder resin is heated to 60°C.
Glass transition temperature below, softening point of 50~110℃, 10
An amorphous polyester having an acid value of ~150 and a polyvalent metal compound in an amount of 1/50 to 1/4 of the weight of the polyester, the thermoplastic resin containing an organic acid monomer of 0.2 to 10 mol%; A vinyl copolymer resin with two or more monomers selected from the group consisting of styrene or its derivatives, acrylic esters, methacrylic esters, and maleic esters, and at 55°C
Glass transition temperature over 100~150℃, softening point 15
A developer for electrostatic image development, characterized in that it is a vinyl copolymer resin having Mw of 10,000 or more and Mw/Mn of 5 or more.