JPS6145250A - Microencapsulated electrophotographic toner and its preparation - Google Patents

Abstract

PURPOSE:To prevent peeling of a coating layer and to secure superior fixability by binding a colorant and a soft resin both for forming a core material, and a thermoplastic resin for forming a coating layer with each other to form microparticles and allowing these microparticles to coexist in the boundary layer in a mixed state. CONSTITUTION:The colorant and the soft resin for forming the core material and the thermoplastic resin for forming the coating layer are bound with each other to for microparticles and they are allowed to coexist in the boundary layer between the core material and the coating layer in a mixed state. The microparticles of the colorant are dispersed in an aq. soln., the soft resin microparticles are dispersed into another aq. soln., and both dispersion solns. are mixed to be coagulate from the mixed solns. and to obtain the core material composed of the colorant and the soft resin, and this coagulated soln. is mixed with a dispersion soln. dispersing the microparticles of the thermoplastic resin, and the mixture of both dispersions are spray dried. The toner thus obtained is prevented from the coating layer because the boundary between the core material and the coating layer is in a continuous state, and since the total body is of a porous compsn., the coating layer does not hinder the fixability of the toner. In the figure, black circles are the soft resin, white circles are the soft resin, and the other ones are the thermoplastic resin.

Description

[Detailed Description of the Invention] Technical Field of Issue 1] The present invention relates to a microcapsule toner for electrophotography and a method for producing the same, and more specifically, a microcapsule toner for electrophotography with excellent pressure fixing properties and a method for producing the same. Regarding.

[Technical Background of the Invention and Its Problems J] The process of electrophotography involves the formation of a desired electrostatic Pl on the surface of a photoconductor.
An i-image is formed, and then this electrostatic latent image is developed with a colored powder (toner) having an opposite charge to form a visible image. This visible image is created by applying light to the toner.
It is fixed on paper, etc. by ripening or applying pressure.

Various methods have been used to fix this visible image, and among these, the pressure fixing method (1) does not require a heat source, so it contributes to energy saving. ■Preheating equipment is not required and can be carried out at the same time as the power is turned on, and research is active because it has characteristics such as excellent quick response.

Several proposals have already been made regarding the toner used in this pressure fixing method.

All of these toners have various drawbacks. For example,
Japanese Patent Publication No. 44-9880 discloses a toner composition comprising an aliphatic component of 08 to 25.
No. 033 and No. 48-789311 disclose electrostatic photographic toners made of soft polymers.

However, pressure fixing toner requires a soft toner in order to have good fixing properties, and from the viewpoint of stability during manufacturing and storage,
The toner itself is required to have contradictory characteristics such that it is better to have a higher mechanical strength. In this respect, all of the toners disclosed in the above-mentioned publications are insufficient to meet the required characteristics.

On the other hand, various microcapsule toners have been proposed in the field of pressure fixable toners in order to improve fixability.

For example, in Japanese Patent Publication No. 34-11581, a toner consisting of an encapsulated oil-based colorant is also disclosed in Japanese Patent Publication No. 48-11581.
No. 71848 discloses a capsule toner containing a solvent. Since these toners all have liquid cores, they are easily fixed by applying a small amount of pressure. However, on the other hand, the formed image tends to smear or flow after fixing, has low bleed resistance, and furthermore tends to cause offset during fixing. Moreover, since the core of these toners is a liquid, the toner itself has low mechanical strength, and therefore, it is necessary to prevent the capsule layer of the toner from being destroyed during its manufacture or storage. Countermeasures against this problem are technically extremely difficult. Therefore, the manufacturing cost also becomes extremely high.

To solve this problem, a toner in which the core is made of a soft resin has been proposed. The publication discloses such a toner.

However, since all of these toners use organic solvents during their manufacture, a solvent recovery device is naturally required as ancillary equipment, and the manufacturing cost thereof is also high.

In order to eliminate the drawbacks associated with the use of organic solvents, Japanese Patent Laid-Open Nos. 51-104829 and 51-1224411 have been proposed.
In the publication, an aqueous suspension or aqueous latex of a soft resin such as microcrystalline wax emulsion is sequentially coated with a hydrophilic film-forming polymer such as gum arabic or gelatin and a hard resin such as polycarbonate. A toner is disclosed.

However, since these toners have no affinity between the core and its outer skin, and between the outer skins, they tend to peel off at their respective interfaces, and during use, the peeled off film layer is attached to the surface of the photoconductor. Otherwise, phenomena such as fusion on the developing sleeve occur, and the core naturally becomes stuck to other members, so in severe cases, the developing device and the photoreceptor must all be replaced. Furthermore, in this manufacturing method, since the surface of the core body is sequentially coated in double layers, the number of manufacturing steps increases, resulting in an increase in manufacturing costs.

[Objective of R1 Ming] An object of the present invention is to provide a microcapsule toner that solves the above-mentioned problems and a method for producing the same.

[Summary of the Invention g11 The microcapsule toner for electrophotography of the present invention is a microcapsule for electrophotography comprising a core containing at least a coloring material and a soft resin, and a thermoplastic resin coating covering the core. In the toner, the colorant, the soft resin, and the thermoplastic resin all exist as fine particles bound to each other.

Further, at the interface between the core body and the coating layer, fine particles of the coloring material, the soft resin, and the thermoplastic resin are mixed with each other, and the manufacturing method is characterized in that fine particles of the coloring material are mixed with each other. A dispersion liquid dispersed in an aqueous solution and a dispersion liquid in which fine particles of a soft resin are dispersed in an aqueous solution are mixed, and a coloring material and a soft resin are aggregated from the obtained mixed solution to form a core body, Next, a dispersion liquid in which fine particles of a thermoplastic resin are dispersed is mixed with the agglomerated liquid, and the resulting mixed liquid is subjected to a spray drying treatment.

First, the core of the uninvented toner contains at least a coloring material and a soft resin. All of these particles are bonded to each other and mixed together in the form of fine particles. The average particle size of each particle is preferably 2 L or less, particularly 500 L or less.

Soft resins include 1, for example, polyethylene wax, polypropylene wax, ethylene-acrylic ester copolymer, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polyamide, epoxy resin, polyvinyl butyral, polybutadiene, liquid polybutadiene, oligoester 7 Examples include acrylate, urethane acrylate, epoxy 7-acrylate, phenolic resin, unsaturated polyester resin, alkyd resin, urethane resin, styrene-butadiene copolymer, silicone resin, drying oil such as linseed oil, boiled oil, and various modified products thereof. be able to.

In addition, the coloring material is not particularly limited and may be any commonly used pigment.These coloring materials may be used as they are, or the surface may be treated with a silane coupling agent or the like to make it hydrophobic. It may be used after applying.

The average particle size of the core is preferably in the range of 3 to 15 J & intestines, and if it is smaller than 3 J & intestines, the mechanical strength of the resulting toner increases due to the dense coating layer described below, making it difficult to fix. requires high pressure, and 15p
If it is larger than m, the particle size of the entire toner also increases, leading to a decrease in image resolution, which is not preferable.

A thermoplastic resin coating layer is formed on the surface of this core.

This coating layer is also composed of fine particles of the thermoplastic resin. As mentioned above, the particle size of the seventh particle is 2 mm or less, preferably 5 mm.
00s 4 layers or less.

Examples of thermoplastic resins include polystyrene, polyacrylic ester, polymethacrylic ester, polyester, polyamide, polyethylene, polypropylene,
Polyvinylidene fluoride.

Polyvinylidene chloride, polyvinyl chloride, ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer, styrene-acrylic ester copolymer, styrene-methacrylic ester copolymer, styrene-butadiene copolymer, Styrene-vinylidene chloride copolymer, styrene-vinylidene chloride copolymer, styrene-vinylidene fluoride copolymer, styrene-acrylonitrile copolymer, epoxy resin, modified rosin, polyethylene wax, alkyd resin, esterified epoxy resin, or these Examples include various modified products of.

The greatest feature of the toner of the present invention is that the interface between the core and the coating material covering its surface does not form a clear boundary, but each fine particle of the core and the fine particles of the coating layer interact with each other. It is a mixed state. The situation is illustrated in the figure.

In the figure, 0 indicates fine particles of soft resin, and 0 indicates fine particles of coloring material.The core body is constituted by a mixture of both. On the outside of the core there is a layer of fine particles of thermoplastic resin shown in pores. At the interface between the core body and the coating layer, the three components coexist, and as you move toward the outside, the WI target is composed only of thermoplastic resin, that is, 1
In the toner of the present invention, the transition from the core to the coating layer is continuous.

In this way, the phenomenon of the Wi layer peeling off from the core is basically suppressed.

The toner of the present invention is manufactured as follows.

First, three types of dispersion liquids in which fine particles of a coloring material, a soft resin, and a thermoplastic resin are dispersed in an aqueous solution are separately prepared. Hereinafter, the respective dispersions will be referred to as dispersion (1), dispersion (2), and dispersion (3).

The aqueous solution used serves as a dispersion medium, which contains water at 50%
It is a dispersion medium containing 11X amount % or more, preferably 80 weight % or more. That is, it is characterized by being mostly composed of water. In this aqueous solution, in order to stabilize the dispersion of the above-mentioned fine particles and prevent their agglomeration, various well-known dispersants, antisettling agents, thixotropic agents, slip agents, leveling agents, and wet dispersants are added to this aqueous solution. In addition, in order to suppress the foaming phenomenon during the fine particle dispersion operation described below, various antifoaming agents or alcohol to lower the surface tension may be added. , Furthermore, a dispersion liquid (dispersion liquid (
For 3), it is effective to add a small amount of a film forming aid such as higher glycol or its ether or a plasticizer such as dibutyl heptalate in order to increase the film strength of the coating layer.

Since this aqueous solution does not have the conventionally commonly used organic solvent as its main component, a solvent recovery device is not required in the subsequent spray drying process.

It also eliminates dangers such as dust explosions and ignition of organic solvents, and contributes to reforming the working environment.

Dispersion liquid! The important thing when making Il is the coloring agent.

This is to make soft resins and thermoplastic resins into fine particles.

For example, as a method for converting soft resins and thermoplastic resins into a-particles, it is preferable to carry out emulsion polymerization or aFRffi polymerization of monomers or oligomers of these resins in the above-mentioned aqueous solution. Also applicable is a method in which these resins are stirred and emulsified in an aqueous solution containing a surfactant in the presence of an alkali or acid while being heated to a predetermined temperature.

Furthermore, it is also possible to prepare a colorant dispersion by pulverizing (cured products of) these resins using a pulverizer, sand mill, ball mill, colloid mill, homogenizer, etc., and dispersing the resulting fine powder in an aqueous solution. This can be done in almost the same way.

After preparing each of the above dispersions, first, the dispersion (
1) (liquid for dispersing coloring material particles) and dispersion liquid (2) (liquid for dispersing soft resin particles) are mixed. Then, from this mixed solution, a core body containing a mixture of colorant fine particles and soft resin fine particles is agglomerated.

The aggregation of the core takes advantage of the fact that a dispersion is an inherently unstable system, and that the aggregation phenomenon of the dispersed phase occurs due to external stimulation (e.g., thermal, mechanical, or electrical stimulation). For example, adding an electrolytic agent such as acid, alkali or hard water to the mixed solution to give it an electric charge, adding various polymeric surfactants and polymeric flocculants as demulsifiers, or adding a mixed solution to the mixed solution. Methods such as cooling or heating, adding alcohol, etc. to the 8-mix solution, or mixing the mixed solution in a ball mill and applying a mechanical #Y blow, each alone or in combination as appropriate. This can be achieved by

If each dispersed phase is selected to be stable due to opposite charges, aggregation of the core proceeds simultaneously with mixing of dispersion <1) and dispersion (2).

Next, 1 dispersion liquid (3) (liquid for dispersing fine particles of F!I plastic resin) is mixed with the above mixed solution in which the agglomeration process has been completed and the cores have been dispersed. In this process, the aggregated cores are partially loosened by the dispersion liquid (3) and suspended in the dispersion liquid (3) while maintaining an appropriate particle size.

If this mixed solution is spray-dried in a hot air stream, fine particles of thermoplastic resin 1M colorant and soft resin will be mixed on the surface of the core, and will continuously form a thermoplastic resin layer outward. A progressive coating layer is formed. At this time, particles made only of the thermoplastic resin are also produced, but since the particle size after drying is smaller than that of the toner of the present invention, these particles can be easily removed by a classification operation.

Spray drying is carried out using a normal spray dryer method, and the inlet temperature is 2, although it varies depending on the type of each component.
The temperature may be in the range of 00 to 300°C, and the outlet temperature may be in the range of 80 to 150°C.

[Examples of the invention] Example 1 (1) Preparation of dispersion of R coloring agent 5 parts by weight of carbon black (MAloo, manufactured by Mitsubishi Kasei ■), 55 ff of magnetic powder (BLloo, manufactured by Titanium Industries ■)
i quantity part, impropa tool 40ff [! Nibu, water 4GO
jl portion was subjected to a dispersion treatment for 50 hours using a ball mill dispersion method.

This is referred to as dispersion liquid (1).

(2) Preparation of soft resin dispersion 50 parts of polyethylene wax (Sunwax!-300° manufactured by Sanyo Kasei ■) and 5 parts of stearylamine. I
! parts were melt-mixed at 120°C. While stirring this melt, add t1 parts of glacial acetic acid, and further add 95 to 99°
450 parts by weight of heated water was gradually added to C and emulsified. This is referred to as dispersion liquid (2).

(3)! Preparation of plastic resin dispersion 5 parts by weight of surfactant (Emar 0 (manufactured by Kao Soap), 300 parts by weight of methanol, silicone antifoaming agent (TSA)
730, manufactured by Toshiba Silicone ■) 0.2 parts by weight, water 15
00! I! An aqueous solution consisting of 150 parts of n-butyl methacrylate was heated to 80° C. llff
1 part, 450 parts by weight of styrene monomer, 20 parts by weight of carbon tetrachloride
First, 1/4 ik of the composition consisting of parts by weight was added to the above aqueous solution and stirred to form an emulsified state. Then, while adding the remaining composition dropwise over 2 hours, a polymerization initiator consisting of 100 parts by weight of a 4% aqueous potassium persulfate solution and 100 parts by weight of 4% sodium acid sulfate was divided into 10 portions of 1710 parts, and 2 Added over time.

After the addition, the mixture was further heated to 60° C. for 2 hours and then cooled. This is referred to as dispersion liquid (3).

(4) Production of toner 100 parts by weight of dispersion (1) and 100 parts by weight of dispersion (2) were mixed in a ball mill. Agglomeration occurred. 25 ffii parts of dispersion liquid (3) was added to this and mixed again.

The mixed liquid was heated to an inlet temperature of 200°C using a spray dryer.
Spray drying was carried out under the condition that the first outlet temperature was 120°C. The obtained powder was classified to have an average particle size of 13. ■I obtained toner.

(5) Fixability of toner This toner was used to develop an electrostatic latent image and its pressure was applied. The fixability was evaluated using a friction fastness tester manufactured by Daiei Scientific Co., Ltd. (a model corresponding to the friction tester type H specified in JIS L 0823). In other words, a solid black area whose density is 1.2 when measured with a Macbeth reflection densitometer is rubbed with a friction piece covered with cotton cloth. ! IIL(
At this time, the bleeding property is evaluated based on the concentration of toner adhering to the cotton cloth. Result is,
The adhesion density of the toner was 0.3, and the fixability was good.

Comparative Example 1 5 parts by weight of carbon black CMAIGO), magnetic powder (B
LIGO) 55 parts by weight, Sunwax E-30040
Parts of fi were melt-mixed at 120° C., coarsely crushed, and then finely pulverized using a type 1 jet mill (manufactured by Nippon Pneumatic Co., Ltd.) after the middle frame. At this time, toner adhered to the collision plate of the jet mill, and the nozzle became clogged.

When this toner was used to develop an electrostatic latent image, the toner stuck to the doctor blade in the developing device, and a layer of the toner on the developing sleeve remained in the stuck portion, making it impossible to obtain a good quality image.

Comparative Example 2 Only the solid content of the dispersion liquid (3) of Example 1 was separated and dissolved in toluene to obtain a 5% by weight resin liquid. 20 parts by weight of the toner of Comparative Example 1 was dispersed in 100 parts by weight of this resin liquid, and spray-dried under the same conditions as in Example 1. The resulting toner having an average particle size of 13 gm was subjected to the same stability test as in Example 1. The i density of the toner is 0.4,
Its stickiness is somewhat difficult.

Example 2 A soft resin dispersion was prepared using 250 g of old wax 4202E (polyethylene wax, manufactured by Mitsui Petrochemicals), 250 parts of boiling oil, and 5 ff of cobalt naphthenate.
1 part of stearylamine and 1 part of stearylamine
Except that it is a dispersion obtained by melting and mixing at 0°C, adding 10 parts by weight of glacial acetic acid to this melt under stirring, and then gradually adding 4,500 parts by weight of water at 35 to 89°C to emulsify. A toner having an average particle size of 13 tons was produced in the same manner as in Example 1. The adhesion density of this toner was 0.35, which was good.

[Effects of the Invention] As is clear from explanation 1 above, the toner of the present invention has
Since the boundary between the core and the coating layer is continuous, peeling of the coating layer is greatly suppressed. ■Core body.

All toner particles are essentially porous because they are composed of fine particles bound together, so when pressure is applied to the toner during pressure fixing, the soft resin of the core penetrates between the particles of the coating layer. The coating layer easily flows through the toner to the outside of the toner, which eliminates the problem of conventional toners in which the coating layer inhibits fixing performance. In addition, the manufacturing method (1) does not use organic solvents that cause environmental pollution problems, so it is safe and does not require a solvent recovery device. ■The core is manufactured by coagulating it in an aqueous solution, so it is extremely easy to manufacture.In addition, materials that could not be used in the core due to their inability to be crushed can be used as the core, and the pressure The range of applicable materials can also be expanded from the viewpoint of improving fixing properties. It has the following effects and its industrial value is extremely large.

[Brief explanation of the drawing]

Figure 0 is a diagram for explaining the internal structure of the toner of the present invention. In Figure 0, Q marks represent fine particles of soft resin, fists represent fine particles of coloring material, and 0 represents fine particles of thermoplastic resin.

Claims (1)

[Claims] 1. A core containing at least a coloring material and a soft resin;
In an electrophotographic microcapsule toner comprising a thermoplastic resin coating layer covering the core, the colorant, the soft resin, and the thermoplastic resin all exist as fine particles bound to each other, and A microcapsule toner for electrophotography, characterized in that fine particles of the coloring material, the soft resin, and the thermoplastic resin are mixed with each other at the interface between the core and the coating layer. 2. Mix a dispersion liquid in which colorant particles are dispersed in an aqueous solution and a dispersion liquid in which soft resin particles are dispersed in an aqueous solution, and aggregate the colorant and soft resin from the obtained mixed solution. Microcapsules for electrophotography, characterized in that a core body is formed using the agglomerated liquid, and then a dispersion liquid in which fine particles of a thermoplastic resin are dispersed is mixed with the agglomerated liquid, and the resulting mixed liquid is subjected to a spray drying process. Toner manufacturing method.