JPS61114247A - Preparation of encapsulation toner - Google Patents

Abstract

PURPOSE:To obtain an encapsulation toner small in secondary agglomeration, etc., and good in powder characteristics by dispersing a core material into an aq. medium contg. methyl cellulose adjusted at a temp. of 5-20 deg.C. CONSTITUTION:The core material contg. a display recording material and a binder is dispersed like emulsified fine oil drops into the aq. medium, then, outer shells are formed on the circumferences of the oily core material drops to form microcapsules, and they are separated from the aq. medium contg. a dispersion stabilizer of methyl cellulose as an essential component. In this process, at the time of forming the outer shells around the core material emulsified into fine oil drops in the aq. medium, the temp. of the aq. medium is adjusted within 5-20 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a method for manufacturing a capsule toner used for converting a latent image formed in an electrostatic recording method into a visible image.

[Background of the Invention] The electrostatic recording method, generally called electrophotography, transfers a toner image formed as a latent image onto a support medium such as transfer paper, and fixes it on the support medium to make it visible. This is a recording method consisting of: There are three known methods for fixing a toner image on a support medium: heat fixing, solvent fixing, and pressure fixing.

Since the pressure fixing method does not use heat or solvent, it does not suffer from the various problems associated with methods such as heat fixing or solvent fixing, and the access time is fast, making it possible to follow high-speed fixing methods. It inherently has various advantages.

However, the pressure fixing method has poor fixing properties compared to fixing methods such as heat fixing, and the fixed image easily peels off when rubbed, and requires considerably high pressure for fixing, so it is difficult to use a support like transfer paper. Fatigue of the media tends to occur due to destruction of media fibers, the surface of the supporting media tends to become excessively glossy, and there are limits to miniaturization of pressure rollers that apply high pressure. Therefore, there are various problems such as the fact that miniaturization of the entire reproduction stirrup is restricted.

In order to solve the above-mentioned problems associated with the pressure fixing method, capsule toner in which toner is contained in microcapsules has already been developed. Capsule toner is a toner in the form of microcapsules obtained by forming an outer shell around a core material containing a display recording material such as carbon black, which has the property of being destroyed by the application of pressure. Capsule toner is said to be a toner suitable for the pressure fixing method because it does not require high pressure for fixing and has excellent fixing properties.

[Prior Art and Problems] However, conventionally known capsule toners cannot necessarily be said to be satisfactory in terms of the characteristics originally required as toners for electrophotography.

That is, the toner used as an electrophotographic developer has good powder properties and excellent development performance.

It is necessary that the surface of the photoreceptor, which is the surface on which the latent image is formed, should not be contaminated, and in the case of two-component development, it is also necessary that the surface of the carrier particles used should not be contaminated. be done. In addition, the toner used in the pressure fixing method has good pressure fixing properties and is unlikely to cause offset phenomenon (a phenomenon in which toner adheres to the pressure roller surface and stains it) on the pressure roller used for pressure fixing. It becomes necessary.

Therefore, the toner used in the pressure fixing method depends on its powder properties, fixability to support media such as paper (including the shelf life of the fixed image), non-offset properties, and chargeability and However, hitherto known capsule toners are not necessarily satisfactory in terms of these properties.

For example, the general manufacturing method for capsule toner is as follows:
Microcapsules are prepared by forming an outer shell made of a resin material around a hydrophobic core material containing a display and recording material dispersed as microdroplets in an aqueous medium. A method of producing a powdered capsule toner by using a drying method is known.

However, the capsule toner obtained by the above manufacturing method does not have sufficient powder characteristics, and after drying, agglomerates due to secondary aggregation of a large number of capsule particles are formed, or Immediately after treatment, even if it is in powder form, it tends to agglomerate if it is placed in a high temperature environment, or left in the air at room temperature for an extended period of time. Furthermore, aggregation of capsule toner often occurs during the developing process in an actual developing device.

In such cases, problems occur such as a significant reduction in the resolution of the developed visible image.

[Object of the Invention] An object of the present invention is to provide a method for producing a capsule toner with good powder properties and less secondary aggregation in a developing device or during storage. More specifically, the present invention
It is an object of the present invention to provide a method for producing a capsule toner that has good waveability and less secondary aggregation even during long-term storage or fluctuations in environmental conditions by adjusting the oil retention rate of the capsule toner.

[Summary of the Invention] The present invention involves dispersing a core material containing a display recording material and a binder in the form of oil droplets in an aqueous medium, and then forming an outer shell around the oil droplet-like core material to form microcapsules. In a method of manufacturing a capsule toner comprising separating formed microcapsules from an aqueous medium, the core material is heated at 5°C.
A method for producing a capsule toner is characterized in that the capsule toner is dispersed in an aqueous medium containing methylcellulose whose temperature is adjusted to a temperature within the range of 20'O.

In the present invention, it is preferable to adjust the temperature of the water distributing medium to a range of 5 to 18°C. The temperature of the aqueous medium is more preferably adjusted to a range of 8 to 16°C, particularly preferably adjusted to a range of 10 to lδ°C.

[Effects of the Invention] The capsule toner obtained by the production method of the present invention has a particularly high oil retention rate, and has excellent powder properties such as agglomeration resistance not only immediately after preparation but also after long-term storage. Therefore, it exhibits excellent properties as a developer used for carrying out electrophotography.

[Detailed Description of the Invention] In a liquid medium such as water, surrounding an oil droplet-shaped core substance containing a display recording material dispersed in the medium and a binder that is an auxiliary material for fusing the display recording material to a support medium. As mentioned above, a method for preparing microcapsules by forming an outer shell is already known. The method for producing the capsule toner of the present invention can also be carried out basically in accordance with these methods.

In general, a capsule toner consists of a core material and an outer shell, and the core material usually includes a binder made of a polymer and an oily solvent, a display recording material, and the like.

When carrying out the method for producing a capsule toner of the present invention, there is no particular restriction on the polymer used as a binder component among the components constituting the core material.

Examples of polymers include polyolefins, olefin copolymers, styrene resins, styrene-butadiene copolymers, epoxy resins, polyesters, rubbers, polyvinylpyrrolidone, polyamides, coumaron-indene copolymers, methyl vinyl ether-maleic anhydride copolymers. , amine resins, polyurethanes, polyureas, homopolymers or copolymers of acrylic esters, homopolymers or copolymers of methacrylic esters, copolymer oligomers of acrylic acid and long-chain alkyl methacrylates, polyvinyl acetate, and polyvinyl chloride. These can be used alone or in combination.

Particularly preferred as the binder polymer are homopolymers or copolymers of acrylic esters, homopolymers or copolymers of methacrylic esters, and monostyrene-butadiene copolymers.

There is no particular restriction on the oil-based solvent used as a component of the binder, but usually a high boiling point solvent (hereinafter also referred to as high boiling point solvent) with a boiling point of 150 ° C. or higher that can dissolve or swell the polymer described in [2] is used. used. Examples of high-boiling solvents include phthalates (e.g., diethyl phthalate,
dibutyl phthalate); aliphatic dicarboxylic acid esters (e.g., diethyl malonate, dimethyl oxalate); phosphoric acid esters (e.g., tricresyl phosphate, tricresyl phosphate); citric acid esters (e.g., 0-7
cetyl triethyl citrate, tributyl citrate)
; Benzoic acid esters (e.g., butyl benzoate, hexyl benzoate); Aliphatic acid esters (e.g., hexadecyl myristate, dioctyl adipate); Alkylnaphthalenes (e.g., methylnaphthalene, dimethylnaphthalene, monoisopropylnaphthalene, diisopropylnaphthalene) ); Alkyldiphenyl ethers (e.g. o
-, m-1p-methyldiphenyl ether); amide compounds of higher fatty acids or aromatic sulfonic acids (e.g., N,
N-dimethyllauramide, N-butylbenzenesulfonamide); trimellitic acid esters (e.g. trioctyl trimellitate) and diarylalkanes (e.g. diarylmethane such as dimethylphenylphenylmethane, l-7enyl-1- Methylphenylethane, l-
diarylethanes such as dimethylphenyl-1-phenylethane and l-ethylphenyl-1-phenylethane)
These can be used alone or in combination.

In addition to the above-mentioned high-purity point solvents, the oil-based solvent used as a component of the binder is a 100-100% solvent that does not substantially dissolve or swell the polymer contained in the core material.
It is also possible to use organic liquids (hereinafter also referred to as organic liquids) having a boiling point in the range of 20°C (preferably 140-220°C). Examples of organic liquids include aliphatic saturated hydrocarbons, and it is also possible to use a mixture of aliphatic saturated hydrocarbons having different carbon numbers.

In the present invention, the binder is preferably a composition containing a polymer and a Takaura point solvent as an oily solvent.

Carbon black, grafted carbon black, etc. are commonly used as display recording materials for electrophotographic toners, but various chromatic colorants such as blue, red, and yellow are also used. . The capsule toner obtained by the production method of the present invention can also be used as a display and recording material, such as those known display and recording materials.

The core material of the capsule toner obtained by the manufacturing method of the present invention may contain magnetic particles. As the magnetic particles, known magnetic particles (magnetizable particulate matter) for magnetic toner can be used. Examples of such magnetic particles include magnetic particles made of elemental metals, alloys, or metal compounds such as cobalt, iron, or nickel. Note that when colored magnetic particles such as black magnetite are used as the magnetic particles, the colored magnetic particles such as magnetite can also be used as a component that functions as both the magnetic particles and the display recording material.

The resin forming the outer shell of the capsule toner obtained by the method of the present invention is not particularly limited as long as it can form an outer shell around the core material dispersed in the form of oil droplets in an aqueous medium. However, in consideration of the characteristics as a capsule toner, the outer shell resin is preferably polyurea, polyurethane, polyamide, or polyester. These resins can be used alone or as a mixture for forming the outer shell. The capsule toner obtained by the method of the present invention has a polyurea resin and/or a polyurethane resin, and has a strong outer shell.
In consideration of flexibility, etc., it is preferable, and furthermore, in consideration of the strength and flexibility of the outer shell, a composite wall containing a polyamide resin in addition to a polyurea resin and/or a polyurethane resin may also be used.

The method for manufacturing a capsule toner of the present invention can utilize a known method for manufacturing a capsule toner, which involves forming a resin shell around a core material by a polymerization reaction.

Next, we will take as an example a method for producing capsule toner made of a polyurethane resin or polyurea resin outer shell.
A method for manufacturing the capsule toner of the present invention will be explained.

In the present invention, when forming an outer shell around a core substance emulsified and dispersed in the form of oil droplets in an aqueous medium, the temperature of the aqueous medium in which the core substance is dispersed is adjusted to a range of 5°C or more and less than 20°C. It is necessary to disperse the core material in an aqueous medium. The temperature of this aqueous medium is preferably adjusted to a range of 5 to 18°C, more preferably adjusted to a range of 8 to 16°C, and more preferably adjusted to a range of 10 to 16°C. This is particularly preferred.

In addition, the aqueous medium used for manufacturing the capsule toner according to the manufacturing method of the present invention must contain methylcellulose as a dispersion stabilizer. - By performing an encapsulation reaction after melting the core substance within the range described above, the oil of the capsule toner obtained is more than that obtained when using a conventionally used dispersion stabilizer such as polyvinyl alcohol. It is possible to produce a capsule toner that has a high retention rate and does not lose its excellent powder properties even after long-term storage.

Although there is no particular restriction on the content of methylcellulose in the aqueous medium, it is usually used at a concentration in the range of 0.11 to 10% by weight, preferably in the range of 0.5 to 7% by weight based on the medium.

In addition to the above methyl cellulose, a polyfunctional amine may be added to the aqueous medium of the present invention as a dispersion stabilizer. There are no particular limitations on the polyfunctional amines that can be used. Examples of polyfunctional amines that can be used include diethylenetriamine, ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, p-phenylenediamine, m-phenylenediamine, 2-hydroxytrimethylenecyamine, triethylenetetra Examples include amines, diethylaminopropylamine, tetraethylenepentamine, adducts of epoxy compounds and amines, piperazine, 2-methylbiperazine, 2,5-dimethylpiperazine, and these can be used alone or in combination. can. Particularly in the present invention, it is preferable to use diethylenetriamine.

When using methylcellulose and polyfunctional amine, there is no particular restriction on the blending ratio of methylcellulose and polyfunctional amine, but generally it is in the range of 100:1 to 1:l, preferably in the range of 100:2 to 100:lO. blended into the medium.

By adjusting the temperature of the aqueous medium containing methylcellulose and a polyfunctional amine as a dispersion stabilizer to disperse the core material, and then carrying out the encapsulation reaction, the oil retention rate of the resulting capsule toner can be further improved. -1
- Also, the powder properties become even better after long-term storage.

Note that the oil retention rate refers to the component that constitutes the binder of the core material of the capsule toner, especially the oil-based solvent (e.g., high boiling point solvent), which is composed of the core material and the outer shell formed around the core material. This shows the percentage retained in the core material of the capsule toner. Therefore, a capsule toner with a high oil retention rate has a binder component in the core material,
In particular, this means that the proportion of oily solvents such as high boiling point solvents contained in the outer shell is small, and there is little deterioration in powder properties due to oozing of oily solvents from the surface of the outer shell. Since most of the binder, including the oil-based solvent, is retained as a core material by the tough outer shell, even if the capsule toner is stored for a long period of time, the oil-based solvent may ooze out onto the outer shell surface. There is almost no change in powder properties.

The method for producing a capsule toner of the present invention involves adding a display recording material and a binder (and After a core material containing, if desired, magnetic particles, etc., is dispersed in the form of oil droplets, an outer shell made of polyurea resin and/or polyurethane resin is formed around the core material.

The method of manufacturing microcapsules by forming an outer shell around the core substance dispersed in the form of oil droplets is as follows.

These methods are already known and can be used in the present invention.

As a method for forming an outer shell that can be used as a method for producing the capsule toner of the present invention, for example, an interfacial polymerization method can be mentioned. Further, other methods for forming the outer shell that can be used as a method for manufacturing the capsule toner of the present invention include an internal polymerization method and an external polymerization method.

The outer shell made of polyurea resin and/or polyurethane resin is made of polyisocyanate such as diisocyanate, triisocyanate, tetraisocyanate, polyisocyanate prepolymer, polyamine such as diamine, triamine, tetraamine, or diamine group. The outer shell of microcapsules can be easily formed by reacting a prepolymer, piperazine and its derivatives, a polyol, etc. containing at least 100 mol of silica in an aqueous solvent by an interfacial polymerization method.

Further, a composite wall made of polyurea resin and/or polyurethane and polyamide resin that can be used as the outer shell of the capsule toner of the present invention, such as a composite wall made of polyurea resin and polyamide resin, a composite wall made of polyurethane resin and polyamide resin, etc. Alternatively, a composite wall made of polyurea resin, polyurethane resin, and polyamide resin can be manufactured by the following method.

Composite walls made of polyurea resin and polyamide resin, composite walls made of polyurethane resin and polyamide resin, for example, use polyisocyanate, acid chloride, polyamine and polyol, and adjust the pH of the emulsifying medium that becomes the reaction liquid.
It can be prepared by an interfacial polymerization method consisting of conditioning and then heating. Further, a composite wall made of a polyurea resin and a polyamide resin can be prepared by using a polyisocyanate, an acid chloride, and a polyamine, adjusting the pH of an aqueous medium serving as a reaction solution, and then heating it. Details of the manufacturing method of these composite walls made of a polyurea resin and a polyamide resin, and the composite wall made of a polyurethane resin and a polyamide resin are described in JP-A-58-86948. Such composite-walled shells are particularly suitable for forming toner capsules containing magnetic particles within the core material.

The seven polymers involved in the polymerization reaction for forming the outer shell resin vary depending on the resin forming the outer shell, but two or more types of seven polymers are usually used in combination. Examples of such monomer combinations include at least one difunctional compound containing a group selected from the group consisting of an isocyanate group, a thioisocyanate group, a bischloroformate group, an acid chloride group, and a sulfonyl chloride group. Combinations of at least one compound selected from the group consisting of monohydric and dihydric acids, polyhydric amines, polyhydric alcohols, polyhydric thiols, polyhydric amines and polyhydric carboxylic acids can be mentioned.

After preparing microcapsules by forming an outer shell around a core material, the microcapsules are separated from the liquid phase and dried. This separation and drying operation is usually carried out by spray drying a dispersion containing microcapsules or heating and drying a slurry containing microcapsules.

Note that it is desirable that the separated and dried microcapsules are further subjected to heat treatment.This heat treatment particularly improves the powder characteristics of the capsule toner.

The heat treatment is preferably carried out at a temperature in the range of 50 to 300°C, and particularly preferably in the range of 80 to 150°C. The heating time depends on the heating temperature and the type of core material used. It can be determined as appropriate, but usually 10 minutes to 48 hours, preferably 2 to 2 hours.
Heat for 4 hours.

There are no particular limitations on the equipment and equipment used for the heat treatment, and examples of the equipment include an electric furnace, a matzuru furnace, a hot plate, an electric dryer, a fluidized bed dryer, an infrared dryer, and the like.

If desired, metal-containing dyes, charge control agents such as nigrosine, or other arbitrary additives can be added to the outer shell of the capsule toner obtained by the manufacturing method of the present invention. These additive substances can be incorporated into the outer shell of the capsule toner at any time, such as when the outer shell is formed or after the capsule toner is separated and dried.

Further, the method for manufacturing the capsule toner of the present invention is disclosed in Japanese Patent Application Laid-open No. 5
7-179860.58-21259.58-6894
8.5B-66949, 58-66950, 58-68
753,58-70236,58-91464,58-
95353, 58-100855, 58-100856
,58-100857,58-100858,58-1
11050, 58-144932, 58-145233
Publications such as No. 57-64673, 57-175404.57-
189139.58-41960.58-48418,
58-58419, 58-57421, 58-57
It is also possible to use the present invention in appropriate combination with the capsule toner and capsule toner manufacturing technology described in patent applications such as No. 422, 58-174898.

Next, Examples and Comparative Examples of the present invention will be shown. In the Examples and Comparative Examples, "%" means "% by weight" unless otherwise specified.

[Example 1] 40 g of a solution of l-isopropyl-phenyl-2-phenylethane containing 50% by weight of polyisobutyl methacrylate (trade name Niacrybase, MM-2002-2, manufactured by Fujikura Kasei) and magnetite magnetic particles were prepared. A dispersion liquid (magnetic ink) was prepared by cross-dispersing in an automatic mortar.

Separately, as a shell material, a solution was prepared in which 9.9 g of an addition compound of 3 moles of xylylene diisocyanate and 1 mole of trimethylolpropane (trade name: Takanate D-11ON, manufactured by Takeda Pharmaceutical ■) was dissolved in 20 g of ethyl acetate. This solution was mixed with the above dispersion (magnetic ink) to prepare an oily phase. However, the preparation of this oily phase mixed liquid (mixture of core material and outer shell forming material) was carried out while controlling the liquid temperature to 25° C. or lower.

An aqueous medium was prepared by adding 0.2 g of diethylenetriamine to 200 g of a 4% aqueous solution of methyl cellulose (methoxy group substitution fi: 1.8, average molecular weight: 15000), and the liquid temperature of this aqueous medium was cooled to 15°C.

The oily phase mixed liquid was emulsified and dispersed in this aqueous medium to obtain an oil-in-ice emulsion in which the average size of oil droplets in the emulsion was about 121 Lm.

Approximately 10 minutes after preparing the emulsion, 50 g of a 2.5% by weight aqueous solution of diethylenetriamine was gradually added dropwise to
Stir for 3 hours in a constant temperature bath at 0°C to complete encapsulation.
Next, this microcapsule dispersion liquid is centrifuged at 500 rpm to separate the generated microcapsules from the methylcellulose-containing aqueous solution (supernatant liquid), and the resulting microcapsule slurry is dispersed in water to prepare a 30% dispersion liquid. did. The resulting dispersion was centrifuged again, and the resulting microcapsule slurry was dispersed in water to again prepare a 30% by weight dispersion.

The water washing operation consisting of centrifugation and dispersion as described in -1- was performed one more time, and the microcapsule slurry obtained by centrifugation was dried in an oven to produce a powdered capsule toner.

This capsule toner had each capsule particle existing independently and exhibited very smooth fluidity.

In addition, after storing the obtained capsule toner in a sealed polyethylene container for six months, the powder characteristics were investigated.
Each capsule particle existed independently without any change from the time of preparation, and very smooth fluidity was maintained.

Furthermore, a part of the obtained capsule toner was fractionated.
After heating in an oven at 00°C for 16 hours and examining the weight loss due to heating, the oil retention rate was calculated from the following formula: 97
%Met.

Oil retention rate (weight) - (1 - [(Weight of capsule toner immediately after preparation) -
(Heavy weight after heating at 100°C for 16 hours) ÷ (weight of high boiling point solvent in weight of prepared capsule toner)]
)

[Example 21 The temperature of the aqueous medium in which the oily phase mixed liquid is emulsified and dispersed is set to 5 to 1
A capsule toner was produced in the same manner as in Example 1 except that the temperature was varied within a range of 9° C., and the oil retention rate of the obtained toner was measured. The results are shown in FIG.

[Comparative example 1] An oily phase mixed liquid was prepared in the same manner as in Example 1.

Methyl cellulose (methoxy group 11 degrees: t, a,
An aqueous medium was prepared by adding 0.2 g of diethylenetriamine to 200 g of a 4% aqueous solution of (average molecular weight: 15,000). The liquid temperature of this aqueous medium was 23°C.

The oily phase mixture liquid was emulsified and dispersed in this 23°C aqueous medium, and the average size of the oil droplet particles in the emulsion was about 12.
An oil-in-water emulsion of pLm was obtained.

Approximately 10 minutes after preparing the emulsion, 50 g of a 2.5% by weight aqueous solution of diethylenetriamine was gradually added dropwise to
The mixture was stirred in a constant temperature bath at ℃ for 3 hours to complete encapsulation.

Next, this microcapsule dispersion is centrifuged at 500 rpm to separate the generated microcapsules from a methylcellulose-containing aqueous solution (bi-clear solution), and the resulting microcapsule slurry is dispersed in water to form a 30% dispersion. was prepared. The resulting dispersion was centrifuged again, and the resulting microcapsule slurry was dispersed in water to prepare a 30% dispersion again. The water washing operation consisting of the above centrifugation and dispersion was carried out once more, and the microcapsule slurry obtained by centrifugation was dried in an oven to produce a powdered capsule toner.

In this capsule toner, each capsule particle existed independently, but the fluidity was slightly inferior to that of the capsule toner obtained in Example 1.

After the obtained capsule toner was stored in a polyethylene container in a sealed state, the powder properties were examined, and it was found that some of the capsule toner had aggregated into lumps.

In addition, the oil retention rate of the obtained capsule toner was 85%.
Met.

[Comparative Example 2] The temperature of the aqueous medium in which the oily phase mixed liquid is emulsified and dispersed is set at 20~20°C.
A capsule toner was produced in the same manner as in Example 1, except that the temperature was varied within a range of 25° C., and the oil retention rate of the obtained toner was measured. The results are also shown in FIG.

[Ratio 1 Example 3] In Example 1, an attempt was made to manufacture a capsule toner by setting the liquid temperature of the aqueous medium to 3°C, but the aqueous medium turned into a gel at the stage when the oily phase mixed liquid was put into the aqueous medium. Therefore, good emulsification and dispersion could not be performed. Therefore, it was not possible to carry out the microencapsulation reaction.

As shown in Figure 1, the manufacturing method of the present invention is used, in which the oily phase mixed liquid is emulsified and dispersed by adjusting the temperature of the aqueous medium containing methylcellulose in which the oily phase mixed liquid is dispersed to 5 degrees or more and less than 20 degrees Celsius. After that, the capsule toner obtained by forming an outer shell.

The oil retention rate is extremely high at over 90%.Compared to this, even when using a similar aqueous medium, the temperature is 2.
The oil retention rate of a capsule toner obtained by emulsifying and dispersing at 0° C. or higher and then forming an outer shell is low. This oil retention rate affects the powder properties of the toner, especially when the capsule toner is stored for a long period of time.

In other words, if the oil retention rate is lower than a certain level, for example, by storing the capsule toner in the hole for a month,
Part of it tends to agglomerate into lumps, resulting in particularly poor fluidity. Incidentally, FIG. 2 shows the relationship between the oil retention rate and the fluidity of the capsule toner after it has been stored in the hole for a month. In FIG. 2, A to E indicate the following states of the capsule toner.

A rank: No change is observed in the toner; B rank:
Agglomeration is observed in a very small portion of the toner, but the aggregation is released by slight movement; C rank: Aggregation is observed in a portion of the toner, but the aggregation is easily released by stirring; D rank: Toner Aggregation is observed in some parts of the toner, and the aggregation is not released even by stirring; E rank: Aggregation is observed throughout the toner, and the aggregation is not released even by stirring.

After storage, the capsule toner is in the A-rank, B-rank, and C-rank states suitable for actual use. The oil retention rate of A to C rank capsule toner is 90% or more,
Those with an oil retention rate of 90% or less, that is, those in which the encapsulation reaction was carried out by emulsifying and dispersing the oily phase mixed liquid at a temperature of 20°C or higher in the aqueous medium containing methylcellulose, as shown in Figure 1. The oil retention rate is so low that it is practically unusable after long-term storage, and as shown in Comparative Example 2, when the temperature of the aqueous medium does not reach 5°C, capsule toner is practically produced. Therefore, by adjusting the temperature of the aqueous medium to 5°C or more and less than 20°C when emulsifying and dispersing the oily phase mixture liquid in an aqueous medium containing methylcellulose, even after long-term storage. It becomes possible to produce a capsule toner that can actually be used.

Furthermore, since the dispersion stabilizer contained in the aqueous medium adjusted to the above temperature range is methylcellulose, preferably methylcellulose and a polyfunctional amine, for example,
It is possible to obtain a capsule toner with a higher oil retention rate and better powder characteristics than when conventionally used polyvinyl alcohol or the like is used.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the relationship between the temperature of an aqueous medium and the oil retention rate when emulsifying and dispersing an oily liquid. FIG. 2 is a diagram showing an example of the oil retention rate and the fluidity level of the capsule toner after storage. Patent applicant Fuji Photo Film Co., Ltd. Agent Patent attorney Yasushi Yanagikawa

Claims (1)

[Claims] 1. After dispersing a core material containing a display recording material and a binder in the form of oil droplets in an aqueous medium, an outer shell is formed around the oil droplet-like core material to form microcapsules. In the method for producing a capsule toner, the core material is heated at a temperature of 5° C. or higher and 2° C. or higher.
A method for producing a capsule toner, comprising dispersing the capsule toner in an aqueous medium containing methylcellulose whose temperature is adjusted to a temperature in a range of less than 0°C. 2. The method for producing a capsule toner according to claim 1, wherein the temperature of the aqueous medium is adjusted to a range of 5 to 18°C. 3. The method for producing a capsule toner according to claim 2, wherein the temperature of the aqueous medium is adjusted to a range of 8 to 16°C. 4. The method for producing a capsule toner according to claim 3, wherein the temperature of the aqueous medium is adjusted to a range of 10 to 16°C. 5. The method for producing a capsule toner according to claim 1, wherein the aqueous medium contains methyl cellulose and further contains a polyfunctional amine. 6. The blending ratio of methylcellulose and polyfunctional amine is 10
6. The method for producing a capsule toner according to claim 5, wherein the ratio is in the range of 0:1 to 1:1. 7. The method for producing a capsule toner according to claim 5, wherein the polyfunctional amine is diethylenetriamine. 8. The method for producing a capsule toner according to any one of claims 1 to 7, wherein the outer shell is made of polyurea resin and/or polyurethane resin.