JPH0685088B2 - Capsule toner - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a toner used for converting a latent image formed by a recording method such as electrophotography into a visible image.

BACKGROUND OF THE INVENTION As a fixing method of a toner image in a recording method such as an electrophotographic method, there are known three kinds of methods: 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 solidifying a display recording material with a binder 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 toner of a microcapsule type in which a resin outer shell having a property of being destroyed by application of pressure is formed around a core substance containing a display recording material such as carbon black and a binder.

[Prior Art and Problems] Conventionally known capsule toners are not always satisfactory in various properties originally required as electrophotographic toners.

That is, the 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 the latent image is formed. In the case of the component development 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 properties, and offset development on the pressure roller used for pressure fixing (a phenomenon in which toner adheres to the surface of the pressure roller and stains the roller) does not easily occur. Etc. are required.

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), non-offset property, and charging property depending on the developing method used. / Or have to be at a high level in all of their properties such as conductivity. However, the capsule toners known so far have not always been satisfactory with respect to the above-mentioned various properties.

For example, there is known a capsule toner in which a substance such as colloidal silica, aluminum silicate or calcium silicate is attached to the surface of the outer shell of the capsule toner in order to improve the fluidity of the capsule toner (JP-A-54). −7623
No. 3 bulletin). According to this, the fluidity of the capsule toner is improved due to the influence of colloidal silica and the like. However, the fixing property is not improved and is not sufficient.

Further, a capsule toner has been proposed in which a specific silicone is contained in the toner in order to improve the fixing property of the capsule toner (Japanese Patent Laid-Open No. 60-184259). That is,
In order to improve the fixability of the encapsulated toner, it is necessary to prevent the toner, which is transferred to paper or the like, is destroyed by pressure and is fixed, from peeling from the paper or the like. As a method for that purpose, a method of making the surface of a fixed image slip well is considered, and therefore silicone is added to the toner to impart a sliding effect to improve the fixability. However,
According to the study of the present inventors, when silicone is contained in the core substance, the silicone exudes to the surface of the outer shell, and as a result, the toner particles tend to aggregate. Further, the silicone exemplified in this publication is dissolved in the binder constituting the core substance, and the sliding effect of the silicone tends not to be sufficient.

[Object of the Invention] An object of the present invention is to provide an electrophotographic toner having improved fixability.

A further object of the present invention is to provide an electrophotographic toner having good powder characteristics, which is also excellent in offset prevention.

SUMMARY OF THE INVENTION The present invention relates to a capsule toner comprising a core substance containing a binder containing an oily solvent and a polymer and a display memory material, and an outer shell formed around the core substance. In the encapsulated toner, silicone is contained substantially insoluble in the binder, and hydrophobic silica is contained and / or attached to the inside and / or the surface of the outer shell.

[Advantages of the Invention] In the encapsulated toner of the present invention, silicone is contained in the core substance without being dissolved in the binder, and hydrophobic silica is contained and / or attached to the inside and / or the surface of the outer shell. Therefore, the fixability is excellent and the fluidity is good. Therefore, by using the capsule toner of the present invention, the resolution of the developed visible image is also improved.

Furthermore, the encapsulated toner of the present invention is an encapsulated toner having excellent anti-offset properties.

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 capsule toner of the present invention includes a binder composed of a polymer and an oily solvent, a display recording material, and silicone.

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 are polyolefin, olefin copolymer, styrene resin, styrene-butadiene copolymer, epoxy resin, polyester, rubbers, polyvinylpyrrolidone, polyamide, coumarone / indene 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 thereof include vinyl chloride, and these may be used alone or in a mixed state.

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

The oily solvent that can be used as a component of the binder of the present invention is a high-boiling solvent having a boiling point of 150 ° C. or higher (hereinafter, simply referred to as a high-boiling solvent, which does not substantially dissolve silicone and can dissolve or swell the polymer. Say).
Examples of such high boiling point solvents include phosphoric acid esters (eg, tricresyl phosphate, trixylyl phosphate); benzoic acid esters (eg, butylbenzoate, hexylbenzoate); alkylnaphthalenes (eg, methyl). Naphthalene, dimethylnaphthalene, monoisopropylnaphthalene, diisopropylnaphthalene); alkyldiphenyl ethers (eg, o-, m
-, P-methyldiphenyl ether) and diarylalkanes (eg, diarylmethane such as dimethylphenylmethane, 1-phenyl-1-methylphenylethane, 1-dimethylphenyl-1-phenylethane, 1-
Examples thereof include diarylethane such as ethylphenyl-1-phenylethane), and these may be used alone or in a mixed state.

The oily solvent, in addition to the high-boiling solvent, does not substantially dissolve the silicone contained in the core substance, and has a boiling point of 100 to 250 ° C that does not substantially dissolve or swell the polymer. An organic solvent within the range (hereinafter, also simply referred to as a low boiling point solvent) can be used. Examples of the low boiling point solvent include saturated or unsaturated paraffin oil having a carbon number of 5 to 20.

The low boiling point solvent can be mixed with the above high boiling point solvent at an arbitrary ratio, but generally, it is mixed at a weight ratio of high boiling point solvent / low boiling point solvent of 9/1 to 1/9. Is desirable.

The binder is preferably a composition containing a polymer and a high boiling point solvent. Also preferred is a composition containing a polymer, a high boiling solvent and a low boiling solvent.

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

Black toners such as carbon black and grafted carbon black are generally used as display recording materials for electrophotographic toners, but blue, red,
Various chromatic colorants such as yellow are also used. The capsule toner of the present invention can also use those known display recording materials as the display recording material.

The encapsulated toner of the present invention is characterized by containing silicone as a core substance. Furthermore, the encapsulated toner of the present invention is characterized in that the silicone contained in the core substance is not substantially dissolved in the oily solvent used as a component of the above-mentioned binder. Silicones that can be used in the present invention include silicone oils, silicone rubbers and silicone resins.

Examples of the silicone oil include dimethyl silicone oil, methylphenyl silicone oil, chlorophenylmethyl silicone oil and fluoropropylmethyl silicone oil.

Examples of the silicone rubber include dimethyl silicone raw rubber, methylphenyl silicone raw rubber, methyl vinyl silicone raw rubber and methylphenyl vinyl silicone raw rubber.

Among these, silicone oil is preferable, and silicone oil having a dimethylsiloxane structure is more preferable.

Specific examples of the silicone oil having a dimethylsiloxane structure include hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, dodecamethylpentasiloxane, tetradecamethylhexasiloxane, hexadecamethylheptasiloxane, octadecamethyloctasiloxane. And decosamethyldecasiloxane.

Further, the viscosity of the silicone oil is 300 cs (25 ° C.) or higher, preferably 500 cs (25 ° C.) or higher.

The content of silicone is 0 based on the weight of the capsule toner.
It is in the range of 5 to 8% by weight, preferably 1 to 4% by weight.
If the silicone content is less than 0.5% by weight, the fixability may not be improved to the extent intended by the present invention, while if it exceeds 8% by weight, the effect is often not so improved.

Magnetic particles may be contained in the core substance of the encapsulated toner. As the magnetic particles, known magnetic particles for magnetic toner (magnetizable particles) 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. When colored magnetic particles such as black magnetite are used as the magnetic particles, the colored magnetic particles such as magnetite can be used as a component that serves both as the magnetic particles and the coloring material.

The type of resin forming the outer shell of the capsule toner is not particularly limited, but considering the characteristics as the capsule toner, the outer shell resin is preferably polyurethane, polyurea, polyamide or epoxy resin. These resins can be used alone or as a mixture as a resin for forming an outer shell.

The capsule toner of the present invention is characterized in that hydrophobic silica is contained and / or attached to the inside and / or the surface of the outer shell. The hydrophobic silica contained and / or attached to the inside and / or the surface of the outer shell of the capsule toner has an action of absorbing the silicone exuded to the outer shell or the surface of the outer shell, and particularly improves the fluidity of the capsule toner. Can be made.

The average particle size of the primary particles of the hydrophobic silica is preferably 5 μm to 17 μm. Even if the average particle size of the primary particles is smaller than 5 mμ or larger than 17 mμ, the effect as intended by the present invention may not be obtained.

Furthermore, it is preferable that such ultrafine powder silica is subjected to a hydrophobic treatment. The powder characteristics and fluidity of the capsule toner using silica not subjected to the hydrophobic treatment deteriorates with time.

Examples of hydrophobically treated silica include dimethyldichlorosilane treated silica, hexamethyldisilazane treated silica, octyltrimethoxysilane treated silica and silicone oil treated silica.

Hydrophobic silica is 0.1 based on the total weight of the encapsulated toner.
It is preferably contained or attached in the range of 5 to 5% by weight, and particularly preferably contained or attached in the range of 0.5 to 3% by weight. If it is less than 0.1% by weight, the desired effect of the present invention may not be obtained, while if it exceeds 5% by weight, the hydrophobic silica may be detached from the surface of the outer shell. In the present invention, the state in which the hydrophobic silica is attached to the surface of the outer shell of the capsule toner means that most of the hydrophobic silica is in contact with the surface of the outer shell of the toner. The state that the hydrophobic silica is contained in the outer shell surface means that most of the hydrophobic silica is at least partially embedded in the outer shell surface. The state of being present in a state is referred to as a state, and the state of being attached or contained includes the above-mentioned attached state and buried state, and also includes an intermediate state between the two.

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 polyurethane resin, polyurea resin or polyamide resin will be described as an example.

In the production of the capsule toner, an outer shell was formed around the core substance by utilizing a microcapsule production method such as an interfacial polymerization method or an external polymerization method in an aqueous liquid, particularly a microcapsule production method based on a polymerization reaction. After that, a known method such as a method of washing with water can be used.

An example of a method for forming a sparse shell that can be used as a method for producing a capsule toner composed of an outer shell of a polyurethane resin or a polyurea resin is an interfacial polymerization method.

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

In addition, a composite wall made of a polyurethane resin and / or a polyurea resin, and a polyamide resin, for example,
A composite wall composed of a polyurethane resin and a polyamide resin, a composite wall composed of a polyurea resin and a polyamide resin, or a composite wall composed of a polyurethane resin, a polyurea resin and a polyamide resin can be manufactured by the following method.

The composite wall made of polyurethane resin and polyamide resin is
For example, using polyisocyanate, acid chloride, polyamine and polyol,
It can be prepared by an interfacial polymerization method which comprises adjusting pH and then heating. Further, 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 emulsifying medium to be the reaction solution and then heating. Details of the method for producing the composite wall made of the polyurethane resin and the polyamide resin and the composite wall made of the polyurea resin and the polyamide resin are described in JP-A-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 resin differ depending on the resin forming the outer shell, but usually two or more kinds of monomers are used in combination. An example of such a combination of monomers is at least one of difunctional compounds containing a group selected from the group consisting of an isocyanate group, a bischloroformate group, an acid chloride group and a sulfonyl chloride group, and water. , A polyvalent amine, a polyhydric alcohol and a polycarboxylic acid, in combination with at least one compound selected from the group consisting of polycarboxylic acids.

One raw material compound of the core substance and outer shell forming substance containing the display recording material, the binder and silicone (and optionally magnetic particles etc.) in the form of oil droplets in an aqueous medium (including the other raw material compound of the outer shell forming substance). After the dispersion, the outer shell made of polyurethane resin or pariurea resin is formed around the core substance to produce microcapsules. At this time, the hydrophobic silica can be contained in the outer shell of the capsule toner by dispersing the hydrophobic silica in the aqueous medium and performing the encapsulation reaction. The method itself for producing microcapsules by forming an outer shell around the core substance dispersed in the form of oil drops is already known as described above, and can be produced by utilizing these known methods. .

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

The hydrophobic silica can be attached by a method of mixing a predetermined amount of metal oxide particles with a slurry containing microcapsules separated from the liquid phase and then drying.

The mixing method is not particularly limited, and a commonly used mixer, V-type mixer, or the like can be used. Also,
There is also no particular limitation on the device and equipment used for drying, and examples of the device include an electric furnace, a muffle furnace, a hot plate, an electric dryer, a fluidized bed dryer, and an infrared dryer.

If desired, a metal-containing dye, a charge control agent such as nigrosine, or any other additive substance can 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.

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

Example 1 40 g of a solution of 1-isopropyl-phenyl-2-phenylethane containing 50% by weight of polyisobutyl methacrylate (trade name: Acrybase, MM-2002-2: manufactured by Fujikura Kasei Co., Ltd.) and magnetite 40 g of magnetic particles were kneaded and dispersed in an automatic mortar to prepare a dispersion liquid (magnetic ink).

Separately, xylylene diisocyanate 3 in 20 g of ethyl acetate
Mole and an addition compound of trimethylolpropane 1 mole (trade name: Takenate D-110N: Takeda Pharmaceutical Co., Ltd.) 9.9
After preparing a solution in which g is dissolved and mixing this solution with the above-mentioned dispersion liquid (magnetic ink), silicone oil (trade name: Shin-Etsu Silicone Oil KF-96, viscosity 1000cs (25
(° C): 3 g of Shin-Etsu Chemical Co., Ltd.) was added to prepare an oily phase. However, this oily phase mixed liquid (mixture of core substance and outer shell forming material) was prepared while adjusting the liquid temperature to 25 ° C or lower.

0.2 g of diethylenetriamine was added to 200 g of a 4% aqueous solution of methylcellulose (methoxy group substitution degree: 1.8, average molecular weight: 15000).
Prepare an aqueous medium by adding 2 g, and adjust the liquid temperature of this aqueous medium.
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 in which the average size of the oil droplet particles in the emulsion was about 12 μm.

About 10 minutes after the preparation of the emulsion, 50 g of a 2.5 wt% aqueous solution of diethylenetriamine was gradually added dropwise, and the mixture was stirred in a constant temperature bath at 60 ° C. for 3 hours to complete the encapsulation. Next, this microcapsule dispersion is subjected to a centrifugation operation at 5000 rpm to separate the generated microcapsules from the methylcellulose-containing aqueous solution (supernatant), and the resulting microcapsule slurry is dispersed in water to prepare a 30% dispersion. did.
The obtained dispersion liquid was centrifuged again, and the obtained microcapsule slurry was dispersed in water to prepare a 30% by weight dispersion liquid again. The above-mentioned centrifugation, washing operation consisting of dispersion is further performed once, and the microcapsule slurry obtained by centrifugation is subjected to colloidal silica (trade name: R-97
4, average particle size 12mμ: Nippon Aerosil Co., Ltd.) 5% dispersion liquid 20g (dispersion method, 5g colloidal silica 5g to 95g water and stir vigorously with a mixer) Add well and dry using an oven Now, a powdery capsule toner is manufactured.

This capsule toner was in a state in which each capsule particle existed independently and showed extremely smooth fluidity.

Also, after the obtained encapsulated toner was stored in a polyethylene container in a sealed state for 6 months, the separation 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 pressure fixing property of the capsule toner obtained above was evaluated by the following method.

An electrostatic latent image formed by a usual electrophotographic method was developed with the above-mentioned capsule toner to form a toner image, and then the toner image was transferred to a transfer paper to obtain a visible image. When this visible image was pressure-fixed with a pressure fixing roller at a pressure of 250 kg / cm ^2, a copy image with good fixability and high sharpness was obtained. Then, almost no toner adhered to the roller. Further, even if the copy image fixed on the transfer paper under pressure was rubbed with a finger, the toner was not peeled off and the copy image was not affected. Further, even after storage for a long time, toner aggregation was not observed and it was stable.

Table 1 shows the results of the evaluation of the fixability, fluidity, anti-offset property, and stability after long-term storage of the obtained capsule toner. Judgment methods are related to each other and visually observed. A is particularly good, B is
Was evaluated as being good, C being somewhat inferior, and D being poor.

Example 2 40 g of a solution of 1-isopropyl-phenyl-2-phenylethane containing 50% by weight of polyisobutyl methacrylate (trade name: Acrybase, MM-2002-2: manufactured by Fujikura Kasei Co., Ltd.) and magnetite A dispersion liquid (magnetic ink) was prepared by kneading and dispersing 40 g of magnetic particles and 20 g of colloidal silica 5% dispersion liquid (the same as that used in Example 1) in an automatic mortar.

Hereinafter, a capsule toner was manufactured in the same manner as in Example 1 except that Shin-Etsu Silicone Oil KF-96 manufactured by Shin-Etsu Chemical Co., Ltd. and a viscosity of 300 sc (25 ° C.) were used as the silicone oil.

With respect to the obtained capsule toner, the powder characteristics and the like were evaluated in the same manner as in Example 1. The results of evaluation are shown in Table 1.

[Example 3] A capsule toner was manufactured in the same manner as in Example 1 except that colloidal silica manufactured by Nippon Aerosil Co., Ltd. (trade name: R-976, average particle size 16 mμ) was used as the colloidal silica. .

With respect to the obtained capsule toner, the powder characteristics and the like were evaluated in the same manner as in Example 1. The results of evaluation are shown in Table 1.

[Example 4] The same operation as in Example 1 was performed except that a mixture of diisopropylnaphthalene and paraffin oil having 10 to 12 carbon atoms in a weight ratio of 3: 2 was used as an oil for dissolving polyisobutyl methacrylate. To produce a capsule toner.

With respect to the obtained capsule toner, the powder characteristics and the like were evaluated in the same manner as in Example 1. The results of evaluation are shown in Table 1.

[Comparative Example 1] A capsule toner was manufactured in the same manner as in Example 1 except that silicone oil was not used.

With respect to the obtained capsule toner, the powder characteristics and the like were evaluated in the same manner as in Example 1. The results of evaluation are shown in Table 1.

[Comparative Example 2] A capsule toner was produced in the same manner as in Example 1 except that colloidal silica was not used.

With respect to the obtained capsule toner, the powder characteristics and the like were evaluated in the same manner as in Example 1. The results of evaluation are shown in Table 1.

[Comparative Example 3] A capsule toner was produced in the same manner as in Example 1 except that isopropyl laurate was used as the oil in which polyisobutyl methacrylate was dissolved.

With respect to the obtained capsule toner, the powder characteristics and the like were evaluated in the same manner as in Example 1. The results of evaluation are shown in Table 1.

[Comparative Example 4] In Example 1, instead of 20 g of the colloidal silica 5% dispersion, a carbon black water-acid solution containing 19.0 g of water, 1.0 g of carbon black and 0.2 g of a surfactant (sodium dodecylbenzenesulfonate) was used. Example 1 except that
A capsule toner was manufactured in the same manner as described above.

With respect to the obtained capsule toner, the powder characteristics and the like were evaluated in the same manner as in Example 1. The results of evaluation are shown in Table 1.

[Comparative Example 5] A capsule toner was manufactured in the same manner as in Example 1, except that 20 g of the colloidal silica 5% dispersion liquid was used in place of the colloidal silica 5% dispersion liquid of 20 g.

With respect to the obtained capsule toner, the powder characteristics and the like were evaluated in the same manner as in Example 1. The results of evaluation are shown in Table 1.

As is clear from the results shown in Table 1, silicone oil was contained in the core substance without being substantially dissolved in the oily solvent constituting the binder, and colloidal silica was contained or adhered to the inside or the surface of the outer wall. Further, the encapsulated toner of the present invention is excellent in fixability and fluidity, and is also excellent in offset prevention property and storage stability.

Claims (9)

[Claims] 1. A capsule toner comprising a core substance containing a binder containing an oily solvent and a polymer and a display recording material, and an outer shell formed around the core substance, wherein the core substance is substantially silicone. Capsule toner characterized in that it is contained without being dissolved in the binder, and hydrophobic silica is contained and / or attached to the inside and / or the surface of the outer shell. 2. The capsule toner according to claim 1, wherein the amount of silicone contained in the core substance is in the range of 0.5 to 8% by weight based on the total weight of the capsule toner. 3. The encapsulated toner according to claim 1, wherein the silicone is selected from the group consisting of silicone oil, silicone rubber and silicone resin. 4. The capsule toner according to claim 3, wherein the silicone is a silicone oil having a dimethylsiloxane structure. 5. The encapsulated toner according to claim 4, wherein the silicone is a silicone oil having a dimethylsiloxane structure having a viscosity of 300 cs (25 ° C.) or higher. 6. The encapsulated toner according to claim 1, wherein the hydrophobic silica is contained in the range of 0.1 to 5% by weight based on the total weight of the encapsulated toner. 7. The hydrophobic silica has an average particle diameter of 5 mμ to 17 mμ.
The encapsulated toner according to claim 1, which is a hydrophobically-treated silica within the range. 8. The encapsulated toner according to claim 1, wherein the oily solvent does not substantially dissolve silicone and dissolves a polymer. 9. The oily solvent is a phosphoric acid ester, a benzoic acid ester, an alkylnaphthalene, an alkyldiphenyl ether, a diallyl alkane, and a carbon number of 5 to 5.
The encapsulated toner according to claim 1, which is selected from the group consisting of saturated or unsaturated paraffin oil in the range of 20.