JPH0774912B2 - Capsule toner - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a capsule toner used for making a latent image formed into a visible image in a recording method such as an electrophotographic method and an electrostatic recording method.

[Background of the Invention]

As a toner image fixing method in a recording method such as an electrophotographic method or an electrostatic recording method, three types of methods are known, which are heat fixing, solvent fixing and pressure fixing. Due to environmental problems and the like, a heat fixing method and a pressure fixing method which do not use a solvent are often used these days.

In the heat fixing method, a toner obtained by consolidating a coloring material with a binder made of at least a polymer has been conventionally used. The same type of toner is also used in the pressure fixing method, but recently, the use of capsule toner has been examined.

The capsule toner is a microcapsule form obtained by forming a resin outer shell having a property of being destroyed by applying pressure around a core substance containing a coloring material such as carbon black and a binder such as a polymer and an organic solvent. Toner.

[Prior art and its problems]

Conventionally known capsule toners are not always satisfactory in various properties originally required as toners.

For example, a toner used as a developer for electrophotography is required to have good powder properties, excellent developing performance, and not stain the surface of the photoreceptor on which a latent image is formed. In the case of the component developing method, it is necessary that the surface of the carrier particles used is not contaminated. The toner used in the pressure fixing method has good pressure fixing property, and an offset phenomenon to the pressure roller used for pressure fixing (a phenomenon in which the toner adheres to the surface of the pressure roller and is transferred and fixed again on the supporting medium). It is necessary to prevent the occurrence of

Therefore, the toner used in the pressure fixing method has powder characteristics, fixability on a supporting medium such as paper (including storability of a fixed image), anti-offset property, and charging property depending on the developing method used. And / or must have high levels of all properties such as conductivity. However, the toners known so far have not always been satisfactory in the above-mentioned various properties.

That is, in order to maintain good fixability on a support medium such as paper, it is necessary to break the capsule at a low pressure. On the other hand, when a capsule that breaks at a low pressure is used, the capsule is broken during the development and transfer processes. There was the problem of contaminating surfaces and other equipment. In particular, in the case of the two-component developing method, since it is mixed with the carrier, a force is applied during the mixing, the capsule is broken, and the surface of the carrier particles tends to be contaminated. In particular, when a large number of sheets are copied, that is, when they are mixed for a long time, the surface of the carrier particles, the surface of the photosensitive member and other devices are significantly contaminated, causing problems such as a decrease in image density and fog. Therefore, it is difficult to achieve both good fixing properties.

In recent years, with the downsizing of the entire copying machine, heat is likely to be accumulated in the copying machine. Therefore, the capsule toner stored in the developing machine tends to be exposed to high humidity and high temperature environmental conditions. In the encapsulated toner placed under such environmental conditions, the organic solvent which is a constituent component of the binder contained in the core substance of the encapsulated toner is not removed even after being stored in a powder state immediately after storage for a long time. There is a problem that, when the toner oozes out through the shell and is present in an adhered state on the surface of the encapsulated toner, agglomeration between toner particles remarkably occurs.

Further, when the organic solvent evaporates through the outer shell, there is a problem that the permeability of the adhesive component to the support such as paper is lowered in the fixing process, and the fixing property is lowered.

As a result of earnest research, the inventors of the present invention have conventionally been inactive,
The present invention has been reached by discovering that the pH of a magnetic material, which was considered not to affect the permeability of the capsule wall, greatly affects the permeability of the wall.

[Object of the Invention]

An object of the present invention is to provide an encapsulated toner having a good powder property with less secondary aggregation in the developing device or during storage.

It is another object of the present invention to provide a capsule toner that has little secondary aggregation even when stored for a long time or changes in environmental conditions, and has excellent fluidity, phenomenological property, fixability and offset prevention property.

[Summary of Invention]

The present invention provides an encapsulated toner in which a core substance containing at least a magnetic material, a polymer and an organic solvent is encapsulated by a resin shell, and the pH value of the magnetic material (in accordance with the pH measurement B method of JIS K-5101). (Measured) is 8.5 or less.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY The capsule toner of the present invention has a particularly high oil retention property (residual ratio of the organic solvent after the capsule toner is kept at 100 ° C. for 16 hours), and is not only immediately after preparation, but also after long-term storage and high temperature and high humidity Even after being stored under the above environmental conditions, secondary aggregation is small, and it is excellent in offset prevention property, powder property, fixing property, phenomenon property, and fluidity.

[Detailed description of the invention]

The encapsulated toner of the present invention has a basic structure composed of a core substance and an outer shell formed around the core substance.

The core material of the encapsulated toner of the present invention contains a binder composed of at least an organic solvent and a polymer, and a magnetic material.

Of the components constituting the core substance of the capsule toner of the present invention, the polymer which is the component of the binder is not particularly limited. Examples of the polymer contained as the core substance include polyolefin, olefin copolymer, styrene resin, styrene / butadiene copolymer, epoxy resin, polyester, rubbers, polyvinylpyrrolidone, polyamide, coumarone / intene copolymer, methyl vinyl ether / anhydrous. Maleic acid copolymer, amino resin, polyurethane, polyurea, homopolymer or copolymer of acrylic acid ester, homopolymer or copolymer of methacrylic acid ester, copolymer oligomer of acrylic acid and long chain alkyl methacrylate, polyvinyl acetate and poly Examples of the core substance of the capsule toner of the present invention may include vinyl chloride and the like, and these may be contained alone or in a mixed state.

Particularly preferable as the above-mentioned binder polymer is a homopolymer or copolymer of an allyl acid ester, a homopolymer or copolymer of a methacrylic acid ester, or a styrene-butadiene copolymer.

Examples of the organic solvent that can be used as the component of the binder include a high boiling point solvent having a boiling point of 150 ° C. or higher (hereinafter, also simply referred to as a high boiling point solvent) capable of dissolving or swelling the above-mentioned polymer. Examples of high boiling point solubilization include phthalic acid esters (eg, diethyl phthalate, dibutyl phthalate); aliphatic dicarboxylic acid esters (eg,
Diethyl malonate, dimethyl oxalate); Phosphate esters (eg, tricresyl phosphate, trixylyl phosphate); Citric acid esters (eg, o-acetyl triethyl citrate, tributyl citrate); Benzoic acid Esters (eg, butylbenzoate, hexylbenzoate); Esters of fatty acids (eg, hexadecylmyristate, dioctyl adipate); Alkylnaphthalenes (eg, methylnaphthalene, dimethylnaphthalene, monoisopropylnaphthalene, diisopropylnaphthalene); Alkyldiph Phenyl ethers (eg, o-,
m-, p-methyldiphenyl ether); amide compounds of higher fatty acid or aromatic sulfonic acid (eg, N, N-dimethyllauroamide, N-butylbenzenesulfonamide); trimellitate esters (eg, trioctyl) Trimellitate); diarylalkanes (eg, diarylmethane such as dimethylphenylphenylmethane, 1-
Phenyl-1-methylphenylethane, 1-dimethylphenyl-1-phenylethane, 1-ethylphenyl-1
-Phenylethane, diarylethane such as 1-isopropylphenyl-2-phenylethane); 8 carbon atoms
To 30 and a chlorination degree of 10 to 40% by weight. Examples of the core substance of the capsule toner of the present invention include those singly and in a mixed state. May be.

The capsule toner of the present invention, as an organic solvent that is a component of the binder, in the range of 100 to 250 ° C., which does not substantially dissolve or swell the polymer contained in the core substance in addition to the high boiling point solvent. It is also possible to contain an organic solvent having a boiling point (hereinafter, also simply referred to as a non-soluble organic liquid). Examples of non-soluble organic liquids include aliphatic saturated hydrocarbons, and the aliphatic saturated hydrocarbons may be a mixture of different carbon numbers.

The non-soluble organic liquid can be mixed with the above high boiling point solvent in any ratio, but generally, the weight ratio of the high boiling point solvent / non-soluble organic liquid is 9/1 to 1/9. Mixing within the range is preferable.

The binder is preferably a composition containing a polymer and a high boiling point solvent. Also preferred is a composition comprising a polymer, a high boiling solvent and a non-soluble organic liquid.

The mixing ratio of the polymer and the high-boiling point solvent is preferably the polymer / high-boiling point solvent polymerization ratio and is in the range of 0.1 to 100. Also, the mixing ratio of [polymer + high boiling solvent] and non-soluble organic liquid is preferably in the range of 0.1 to 100 in terms of [polymer + high boiling solvent] / non-soluble organic liquid weight ratio.

As the magnetic particles of the capsule toner of the present invention, known magnetic particles for magnetic toner (magnetizable particulate matter) can be used. Examples of such magnetic particles include magnetic particles made of a simple metal such as cobalt, iron or nickel, an alloy or a metal compound.

The resin forming the outer shell of the encapsulated toner of the present invention is not particularly limited as long as it is a resin capable of forming the outer shell around the core substance dispersed in the form of oil droplets in an aqueous solvent. Considering the characteristics of the toner, the outer shell resin is preferably polyurea, polyurethane, polyamide or polyester. These resins may form the outer shell alone, or may form the outer shell as a mixture. The outer shell of the encapsulated toner of the present invention is preferably a polyurea resin and / or a polyurethane resin in consideration of strength and flexibility of the outer shell, and further considering strength and flexibility of the outer shell. Then, a composite wall containing a polyamide resin in addition to the polyurea resin and / or the polyurethane resin can be used.

The capsule toner of the present invention has a pH value (pH value according to JIS K-5101).
It is necessary to include a magnetic material whose measurement) is 8.5 or less according to the measurement method B).

The magnetic material as described above has excellent adhesion to the outer shell even at the interface between the core substance and the outer shell, inside the outer shell, and even when a part of the magnetic material is present protruding from the surface of the outer shell. As a result, it forms a highly dense outer layer, exhibits a high oil retention of 90% or more (remaining rate of the organic solvent), and the organic solvent in the core substance rarely exudes through the outer shell. According to the research conducted by the present inventor, an encapsulated toner having an oil retention of less than 90% oozes out through an outer shell of an organic solvent during long-term storage, and when it is present by adhering to the toner surface, aggregation between toner particles occurs. Has been found to occur significantly. Therefore, the pH value
Capsule toners containing 8.5 or less magnetic substance have high oil retention of 90% or more and little secondary aggregation, so long-term stable powder properties, fluidity, fixability, phenomenological property, and offset prevention property are obtained. be able to.

Therefore, stable powder characteristics, fluidity, fixability, phenomenological property, and offset prevention property can be obtained for a long period of time.

The pH value of the magnetic material is more preferably 7.5 or less.

When the pH value of the magnetic material exceeds 8.5, the oil retention of the capsule toner is low.

Next, regarding the method for producing the encapsulated toner of the present invention,
A method for producing an encapsulated toner having an outer shell of a polyurethane resin and / or a polyurea resin or a composite toner having a composite wall of a polyurethane resin and / or a polyurea resin and a polyamide resin will be described as an example.

By forming an outer shell made of a polyurethane resin and / or a polyurea resin around an oil-drop dispersed core substance containing a coloring material and a binder (and optionally magnetic particles) in an aqueous liquid, a micro shell is formed. Methods for producing capsules are already known, and these known methods can also be used for producing the encapsulated toner of the present invention.

For example, an interfacial polymerization method can be mentioned as a method for producing microcapsules utilizing a polymerization reaction that can be used for producing a capsule toner. Also,
Another example of the method for producing microcapsules utilizing a polymerization reaction that can be used in the present invention is an internal polymerization method and an external polymerization method.

The outer shell made of polyurea resin and / or polyurethane resin is composed of polyisocyanate such as diisocyanate, triisocyanate, tetraisocyanate and polyisocyanate prepolymer and polyamine such as diamine, triamine and tetraamine, and two amino groups. It is known that the prepolymer, piperazine and its derivative, polyol, etc. containing the above can be easily formed as the outer shell of a microcapsule by reacting them in an aqueous solvent by an interfacial polymerization method.

Further, a polyurea resin and / or polyurethane resin which is preferable as the outer shell of the capsule toner, and a composite wall made of a polyamide resin, for example, a composite wall made of a polyurea resin and a polyamide resin or a composite wall made of a polyurethane resin and a polyamide resin can be prepared by the following method. Can be manufactured by.

The composite wall made of polyurethane resin and polyamide resin is
For example, using polyisocyanate, acid chloride, polyamine and polyol, the pH of the emulsifying medium used as the reaction liquid
It can be prepared by an interfacial polymerization method which comprises adjustment and then heating. The composite wall composed of polyurea resin and polyamide resin can be prepared by using polyisocyanate, acid chloride and polyamine to adjust the pH of the aqueous medium serving as the reaction solution and then heating. For details of the method for producing the composite wall made of these polyurea resin and polyamide resin, and the composite wall made of polyurethane resin and polyamide resin, see
58-66948. The outer shell composed of such a composite wall is particularly suitable for forming an encapsulated toner containing magnetic particles in a core substance. The monomers involved in the polymerization reaction for forming the outer shell differ depending on the resin forming the outer shell, but two or more kinds of monomers can be used in combination. Examples of such a combination of monomers include an isocyanate group, a bischloroformate group, at least one bifunctional compound containing a group selected from the group consisting of an acid chloride group and a sulfonyl chloride group, and water, A combination with at least one compound selected from the group consisting of polyvalent amines, polyhydric alcohols, polyvalent amines and polycarboxylic acids can be mentioned.

After preparing microcapsules by forming an outer shell around the core material, the microcapsules are separated from the liquid phase, washed with water and dried. The operation for separating and drying is usually performed by a method of heating and drying a slurry containing microcapsules.

The separated and dried microcapsules can be 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, more preferably at a temperature in the range of 80 to 150 ° C. The heating time can be appropriately determined depending on the heating temperature and the type of core substance used, but is usually 10 minutes to 48 hours, preferably 2 to 24 hours.

There is no particular limitation on the device and equipment used for the heat treatment, and examples of the device include an electric furnace, a pine oven, a hot plate, an electric dryer, a fluidized bed dryer, an infrared dryer and the like.

If desired, a metal-containing dye, a charge control agent such as nigrosine, or any other additive substance may be added to the outer shell of the capsule toner of the present invention. These additive substances can be contained in 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.

The obtained toner exhibits excellent powder characteristics, and its fluidity is particularly good. In Examples and Comparative Examples, "%" means "% by weight" unless otherwise specified.

Hereinafter, the present invention will be described in detail by way of Examples and Comparative Examples, but these do not limit the present invention in any way.

[Example 1] Chlorinated paraffin (trade name: Toyo Palax 120: manufactured by Toyo Soda Co., Ltd.) containing 40% by weight of polyisobutyl methacrylate (trade name: Acrybase, MM-2002-2; manufactured by Fujikura Kasei Co., Ltd.) ) 20g and pH value 6.55, specific surface area 5.9m ² / g, bulk density 0.59g / m ³ , wetting speed (chlorinated paraffin) 2.60 ×
A dispersion liquid (magnetic ink) was prepared by kneading and dispersing 40 g of magnetic particles (Fe ₃ O ₄ ) of 10 ⁻³ cm ² / s in an automatic mortar.

Separately, polyisobutyl methacrylate (trade name: Acrybase, MM-2002-2: Fujikura Kasei Co., Ltd.) 4 g, polyisobutyl methacrylate (trade name: Acrybase, MM-2002)
1, Fujikura Kasei Co., Ltd. 8 g, an addition compound of 3 moles of xylylene diisocyanate and 1 mole of trimethylolpropane (trade name: Takenate D-110N: Takeda Pharmaceutical Co., Ltd.)
21.0 g) was dissolved in a mixed solution of 32.5 g of ethyl acetate and 12.0 g of Isopar · H (saturated aliphatic hydrocarbon mixture: manufactured by Exxon Chemical Co., Ltd.), and this solution was dispersed (magnetic ink). To prepare an oily phase. However, the preparation of this oily phase mixed liquid (mixture of core substance and outer shell forming material)
The liquid temperature was adjusted to 25 ° C or lower.

Diethylenetriamine (0.1 g) was added to 180 g of a 4% aqueous solution of methylcellulose (methoxy group substitution: 1.8, average molecular weight: 15000).
An aqueous medium was prepared by adding 2 g, and the aqueous medium was cooled to 15 ° C.

The above oily phase mixed liquid was emulsified and dispersed in this aqueous medium to obtain an oil-in-water emulsion having an average size of oil droplet particles in the emulsion of about 10 μm.

About 10 minutes after the preparation of emulsion, 104 g of a 2.5 wt% aqueous solution of diethylenetriamine was gradually added dropwise, and the mixture was stirred for 3 hours in a constant temperature bath at 60 ° C. to complete the encapsulation.

The obtained microcapsule dispersion was allowed to stand naturally to allow the microcapsules to settle, the upper aqueous layer was discarded, washing water was added instead, and the mixture was allowed to stand naturally. This washing operation was repeated 7 times to remove methylcellulose and the like adhering to the surface of the microcapsules. Next, Al ₂ O ₃ (Aluminum Oxide C manufactured by Nippon Aerosil Co., Ltd.) was surface-treated with a titanium coupling agent (Planeact KR-44 manufactured by Ajinomoto Co., Inc.), and an aqueous dispersion of Al ₂ O ₃ was added to the toner. 0.7% by weight
And added in an oven to obtain a capsule toner. This capsule toner was in a state in which each capsule particle existed independently and showed a very smooth fluidity.

Further, after the obtained encapsulated toner was stored in a polyethylene container in a sealed state for 6 months, the powder characteristics were examined,
Each capsule particle was independently present without any change from the time of preparation, and the fluidity was kept very smooth.

Furthermore, a part of the obtained capsule toner is collected and
After heating for 16 hours in an oven at 0 ° C., the weight loss due to heating was examined, and the oil retention determined by the following equation was 98%.

Oil retention (%) = {1- [weight of capsule toner immediately after preparation]-
(Weight after heating at 100 ° C. for 16 hours) / ÷ (weight of organic solvent ^{* 1} in weight of prepared capsule toner)} × 100 Note) In Example 1, * 1 is an organic solvent Isop
er · H and chlorinated paraffin.

[Example 2] A capsule toner was obtained in the same manner as in Example 1 except that 1-isopropylphenyl-2-phenylethane was used instead of chlorinated paraffin. This capsule toner was in a state in which each capsule particle existed independently and showed a very smooth fluidity.

Further, after the obtained encapsulated toner was stored in a polyethylene container in a sealed state for 6 months, the powder characteristics were examined,
Each capsule particle was independently present without any change from the time of preparation, and the fluidity was kept very smooth.

The oil retention was also measured and found to be 98%.

Example 3 Instead of the magnetic particles used in Example 1, a pH value of 8.25, a specific surface area of 6.0 m ² / g, a bulk density of 0.63 g / cm ³ , and a wetting rate (chlorinated paraffin) 2.50 × 10 ⁻³ Capsule toner was obtained in the same manner as in Example 1 except that the magnetic particles with cm ² / s were used.
This capsule toner was in a state in which each capsule particle existed independently and showed a very smooth fluidity.

Further, after the obtained encapsulated toner was stored in a polyethylene container in a sealed state for 6 months, the powder characteristics were examined,
Each capsule particle was independently present without any change from the time of preparation, and the fluidity was kept very smooth.

The oil retention was measured and found to be 93%.

[Comparative Example 1] Example 1 except that magnetite magnetic particles having a pH value of 9.18 (trade name: EPT-1000, manufactured by Toda Kogyo Co., Ltd.) were used in place of the magnetic particles used in Example 1. Made in the same way.
In this capsule toner, each capsule particle was independently present, but the fluidity was slightly inferior to the capsule toner obtained in Example 1.

The obtained capsule toner was stored in a polyethylene container in a sealed state for 6 months, and the powder characteristics were examined. As a result, a part of the capsule toner was aggregated into a lump.

The oil retention of the obtained capsule toner was 82%.

Comparative Example 2 Instead of the magnetic particles used in Example 1, pH value 10.1, specific surface area 6.8 m ² / g, bulk density 0.67 g / cm ³ , wetting rate (chlorinated paraffin) 1.41 × 10 ^-3 It was manufactured in the same manner as in Example 1 except that magnetic particles having a size of cm ² / s were used. In this capsule toner, each capsule particle was independently present, but the fluidity was considerably inferior to the capsule toner obtained in Example 1.

The obtained capsule toner was stored in a polyethylene container in a sealed state for 6 months, and the powder characteristics were examined. As a result, a part of the capsule toner was aggregated into a lump.

The oil retention of the obtained capsule toner was 50%.

Claims (6)

[Claims] 1. A microcapsule-shaped encapsulated toner in which a core substance containing at least a magnetic material, a polymer and an organic solvent is encapsulated in a resin outer shell, which is a JI of the magnetic material.
A capsule toner having a pH value of 8.5 or less as measured by the pH measurement method B of S K5101. 2. The resin outer shell is formed around the core substance by a polymerization method selected from the group consisting of an interfacial polymerization method, an internal polymerization method and an external polymerization method. The capsule toner according to claim 1. 3. The encapsulated toner according to claim 1, wherein the organic solvent is an organic solvent having a boiling point of 150 ° C. or higher which can dissolve or swell the polymer. 4. The composition according to claim 1, wherein the viscosity of the mixture of the polymer and the organic solvent is in the range of 1000 to 100000 cp (25 ° C.). Capsule toner. 5. The toner according to claim 1, wherein the magnetic material is contained in the toner in an amount of 0.1 to 70 parts by weight with respect to 100 parts by weight of the toner. Third
Item, and the capsule toner according to Item 4. 6. The capsule toner according to claim 1, wherein the resin outer shell is made of a polyurea resin and / or a polyurethane resin.