JPH0685086B2 - Method for producing capsule toner having improved triboelectricity - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a capsule toner used for converting a latent image formed in a recording method such as an electrophotographic method into a visible image, and more specifically, particularly The present invention relates to a method for producing a capsule toner having improved triboelectricity.

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. Among these, the pressure fixing method does not use heat or solvent, so various obstacles associated with methods such as heat fixing and solvent fixing do not occur, the access time is fast, and it is possible to follow the high speed fixing method. It inherently has various advantages such as certain points. While the pressure fixing method has many advantages as described above, the fixing property is poor as compared with the fixing method such as the heat fixing method, the image after fixing is easily peeled off by rubbing, and a considerably high pressure is required for fixing. Therefore, fatigue of the medium is liable to occur due to breakage of fibers of the supporting medium such as transfer paper, and the surface of the supporting medium is apt to have excessive luster, and high pressure is applied. Since there is a limit to miniaturization of the pressure roller, there is a problem that the miniaturization of the entire copying apparatus is restricted.

In order to solve the above problems associated with the pressure fixing method, an encapsulated toner in which the toner is contained in a microcapsule has already been developed. The capsule toner is a microcapsule form obtained by forming a resin outer shell having a property of being destroyed by application of pressure around a core substance containing a coloring material such as carbon black and a binder such as a polymer and an oily solvent. Toner. The capsule toner is said to be a toner suitable for the pressure fixing method because it does not require a high pressure for fixing and has an excellent fixing property. However, the conventionally known capsule toner is originally a toner as a toner. It cannot be said that the required characteristics are always satisfactory.

For example, toner having an insulating surface has been generally used as a developer for electrophotography, but recently, a toner having an appropriate positive or negative triboelectric charging property on the toner surface has been developed. There is.

That is, a toner used in electrophotography of a system in which toner is charged by rubbing carrier particles such as iron powder or fur or the like with the toner, and the charged toner is attracted to a latent image has excellent triboelectric chargeability. Is desirable.

The triboelectrification property on the toner surface is conventionally generally applied by a method in which a powdery capsule toner and a charge control agent such as a nigrosine dye powder are brought into contact with each other to attach the charge control agent to the surface of the capsule toner. ing.

However, according to the study of the present inventor, in the capsule toner to which the charge control agent is added by the above-mentioned conventional method,
It has been found that it is difficult to achieve uniform attachment of the charge control agent, and the charge control agent attached to the toner surface is easily released during storage of the toner. The toner with such non-uniform adhesion of the charge control agent or the toner with a considerable amount of detachment of the charge control agent tends to have insufficient developing characteristics, resulting in image characteristics such as sharpness and density of the obtained visible image. It has an unfavorable effect.

[Object of the Invention] It is an object of the present invention to provide a method for producing a capsule toner having improved triboelectric chargeability.

The present invention particularly aims to provide a method for producing a capsule toner in which excellent triboelectricity is stably maintained.

SUMMARY OF THE INVENTION The present invention relates to an aqueous dispersion medium containing, in a dispersed state, a microcapsule composed of a core substance containing a coloring material and a binder and a resin shell formed around the core substance, and charge control. A method for producing a capsule toner having improved triboelectrification, which comprises depositing the charge control agent on the surface of the microcapsule by bringing it into contact with an organic solvent solution of the agent, and then drying.

EFFECTS OF THE INVENTION The capsule toner manufactured according to the present invention has a high level of triboelectrification because the charge control agent is uniformly and firmly attached to the surface of the capsule toner, and is suitable for performing recording methods such as electrophotography. It exhibits excellent properties as a developer used for. Further, the excellent triboelectric chargeability of the capsule toner obtained by the present invention hardly deteriorates even after long-term storage or physical impact.

Therefore, in particular, the capsule toner obtained by the present invention is
Particularly, it is advantageous as a capsule toner used in an electrophotographic method utilizing triboelectric charging.

[Detailed Description of the Invention] The method for producing a capsule toner having improved triboelectricity of the present invention comprises a step of bringing the formed capsule toner into contact with a charge control agent in a state of being dispersed in an aqueous dispersion medium, thereby forming microcapsules. It is characterized in that the charge control agent is selectively deposited on the surface of and is firmly attached.

That is, the adhesion of the charge control agent to the surface of the microcapsules of the present invention is such that the charge control agent dissolved in an organic solvent in the microcapsules is present in the presence of an aqueous dispersion medium, such as microcapsules dispersed in an aqueous medium. The feature is that the agent is contacted.

First, a method for forming microcapsules will be described.

A method for producing a capsule toner by forming a resin outer shell having a property of being destroyed by application of pressure around a core material containing a coloring material such as carbon black, and a binder such as a polymer and an oily solvent is described above. As already known.

In the production of the encapsulated toner of the present invention, an outer shell is 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 forming, the well-known method such as a method of separating it from a liquid and drying it can be used.

Examples of the polymer that can be used as the component of the binder in the encapsulated toner of the present invention include the following compounds.

Polyolefin, olefin copolymer, styrene resin, styrene-butadiene copolymer, epoxy resin,
Polyester, rubber, polyvinylpyrrolidone, polyamide, coumarone / indene copolymer, methyl vinyl ether / maleic anhydride copolymer, amino resin, polyurethane, polyurea, homopolymer or copolymer of acrylic ester, homopolymer of methacrylic ester or Copolymers, copolymers of acrylic acid and long-chain alkyl methacrylates, polyvinyl acetate, polyvinyl chloride.

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.

Examples of the oily 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 polymer. An example of this high boiling point solvent is described below.

Phthalates (eg, diethyl phthalate, dibutyl phthalate); Aliphatic dicarboxylic esters (eg,
Diethyl malonate, dimethyl oxalate); phosphoric acid esters (eg, tricresyl phosphate, trixylyl phosphate); citric acid esters (eg, o-acetyl triethyl citrate, tributyl citrate); benzoic acid esters (Eg, butyl benzoate, hexyl benzoate); Aliphatic acid esters (eg, hexadecyl myristate, dioctyl adipate); Alkyl naphthalenes (eg, methyl naphthalene, dimethyl naphthalene, monoisopropyl naphthalene, diisopropyl naphthalene); Alkyl diphenyl ethers (Eg, o-,
m-, p-methyldiphenyl ether); amide compounds of higher fatty acid or aromatic sulfonic acid (eg, N, N-dimethyllauroamide, N-butylbenzenesulfonamide); trimellitic acid esters (eg, trioctyltri) Melitate); Diarylalkanes (eg, diarylmethane such as dimethylphenylphenylmethane, 1-
Phenyl-1-methylphenylethane, 1-dimethylphenyl-1-phenylethane, 1-ethylphenyl-1
-Diarylethanes such as phenylethane).

In the present invention, the binder is preferably a composition containing both a polymer and a high boiling point solvent.

Black toners such as carbon black and grafted carbon black are generally used as coloring materials for electrophotographic toners, but various chromatic colorants such as blue, red and yellow are also used. ing. These coloring materials can also be used in the capsule toner of the present invention. The core substance of the capsule toner of the present invention may contain magnetic particles. 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 of the present invention is not particularly limited, but in consideration of the characteristics as the capsule toner, the outer shell resin is polyurea, polyurethane, polyamide, polyester or epoxy resin. Is preferred. These resins alone,
Also, it can be used as a mixture as a resin for forming an outer shell. The capsule toner of the present invention is particularly preferably composed of a composite wall containing at least one of a polyurea resin, a polyurethane resin, and a polyamide resin in consideration of the strength and flexibility of the outer shell.

Next, taking as an example a method for producing a capsule toner comprising an outer shell of a polyurethane resin or a polyurea resin,
A method for producing the encapsulated toner having improved triboelectricity according to the present invention will be described.

By forming an outer shell made of a polyurea resin and / or a polyurethane 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, as a method for producing microcapsules utilizing a polymerization reaction that can be used for producing the encapsulated toner of the present invention, an interfacial polymerization method can be mentioned. Further, as another example of the method for producing a microcapsule utilizing a polymerization reaction that can be used in the present invention, an internal polymerization method and an external polymerization method can be mentioned.

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

Further, a composite wall composed of a polyurea resin and / or polyurethane and a polyamide resin which are preferable as the outer shell of the capsule toner of the present invention, for example, a composite wall composed of a polyurea resin and a polyamide resin, a composite wall composed of a polyurethane resin and a polyamide resin, or A composite wall made of polyurea resin, polyurethane resin and polyamide resin can be manufactured by the following method.

The composite wall composed of a polyurea resin and a polyamide resin, the composite wall composed of a polyurethane resin and a polyamide resin, for example, polyisocyanate, acid chloride, and polyamine and a polyol are used to adjust the pH of the emulsifying medium to be the reaction liquid, and then perform heating. It can be prepared by the interfacial polymerization method. 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 a composite wall made of these polyurea resin and polyamide resin, and a composite wall made of a polyurethane resin and polyamide resin are described in JP-A No.
There is a description in 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. Examples of such a combination of monomers include a difunctional group 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. A combination of at least one and at least one of compounds selected from the group consisting of water, polyhydric amines, polyhydric alcohols, polyhydric thiols, polyhydric amines and polycarboxylic acids can be mentioned.

According to the present invention, the uniform and firm adhesion of the charge control agent to the surface of the capsule toner is obtained by contacting the charge control agent dissolved in an organic solvent in the presence of an aqueous dispersion medium with the microcapsule after the formation of the microcapsules. Can be achieved.

That is, a method of adding a charge control agent to the reaction liquid generated by the microcapsules, a method of separating the microcapsules from the reaction liquid and adding to the dispersion liquid in a state of being dispersed in water for washing, or drying once. A method in which the microcapsules are dispersed in water to prepare a dispersion and a charge control agent is added to the dispersion can be used.

Various types of charge control agents that have been attached to the surface of the toner are already known, and these known charge control agents can also be used in the production of the encapsulated toner of the present invention. Examples of the charge control agent for positively shifting the triboelectric charging property of the toner include electron-donating dyes such as nigrosine and various cationic substances. Examples of the charge control agent for negatively shifting the triboelectricity of the toner include monoazo metal complex salts, electron-accepting organic complexes such as copper phthalocyanine compounds, titanates of metals such as calcium and barium, and chlorinated paraffin. be able to.

In the present invention, in a state where the charge control agent is dissolved in an organic solvent,
It is added to an aqueous dispersion medium containing microcapsules, and by contact with the aqueous dispersion medium, a fine powder of the charge control agent is deposited on the surface of the microcapsules in the dispersion system. The organic solvent used above is a highly miscible organic solvent with water, examples of which include dimethylformamide, dimethylacetamide, dimethylsulfoxide, ketones,
(Eg, acetone, methyl ethyl ketone, tetrahydrofuran), alcohols (eg, methanol, ethanol,
Isopropanol) and N-methylpyrrolidone.

After the charge control agent is added to the microcapsule dispersion liquid to obtain microcapsules having the charge control agent attached to the surface thereof, 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, a method of filtering a slurry containing microcapsules, or a method of heating and drying as it is.

It is desirable that the microcapsules separated and dried by the above-mentioned method are then 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 varies depending on the heating temperature and the type of core substance used, but it is usually selected from the range of 10 minutes to 48 hours, and more generally 2 to 24 hours.

There is no particular limitation on the device and equipment used for the heat treatment, for example, an electric furnace, a muffle furnace, a hot plate,
Any heat dryer and heat dryer such as an electric dryer, a fluidized bed dryer and an infrared dryer can be used.

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 (binder) containing 50% of polyisobutyl methacrylate and magnetite magnetic particles were kneaded and dispersed in an automatic mortar to give a dispersion (magnetic ink). Prepared.

Separately, 9.9 g of an addition compound of 3 mol of xylylene diisocyanate and 1 mol of trimethylolpropane in 20 g of ethyl acetate.
Was prepared, and this solution was mixed with the above-mentioned dispersion liquid (magnetic ink) to prepare an oily phase. However, the preparation of this oily phase mixed liquid was carried out while adjusting the liquid temperature to 25 ° C or lower.

Methylcellulose (Methoxy group substitution degree 1.8, average molecular weight:
15000) 4% aqueous solution 200g diethylenetriamine 0.2g
Was added to prepare an aqueous liquid, and the liquid temperature of this aqueous liquid was cooled to 15 ° C.

The above oily phase mixture was emulsified and dispersed in this aqueous liquid to obtain an oil-in-water emulsion in which the average size of 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% 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. After the encapsulation reaction was completed, decantation was performed and the supernatant was removed to obtain a capsule slurry. Water was added to this slurry, the mixture was stirred, and then the same decantation was repeated for 20 times to remove methylcellulose.

A dispersion of microcapsules that had been washed with water was dispersed in water while stirring vigorously, and a separately prepared nigrosine dye (trade name: Spirit Black No850, Sumitomo Chemical Co., Ltd.) acetone solution (nigrosine dye
2 g / 100 cc acetone) 100 cc was dropped. When the nigrosine dye was brought into contact with the microcapsule dispersion medium, it immediately precipitated and adhered to the surface of the microcapsules. Then, the microcapsules were separated from the dispersion by filtration, and an oven was used.
It was dried at 60 ° C. for 3 hours to obtain a powdery capsule toner (average particle diameter 18 μm). When the surface of this capsule toner was observed with a scanning electron microscope, it was confirmed that the nigrosine dye was uniformly attached to the toner surface in the form of fine particles having a particle size of 1 μm or less.

0.1 g of the above capsule toner was mixed with 5 g of an iron powder carrier coated with a mixture of ethyl cellulose and nitrocellulose (1: 1) and stirred, and the triboelectric charge amount was measured by a blow-off powder charge amount measuring device (TB-200 : Toshiba Chemical Co., Ltd.
(+) 10μC / g
Met.

Using this capsule toner as a developer, a repeated copying test by an electrophotographic copying machine was conducted on 5000 sheets of paper to examine the change in density of the toner image. The decrease in the density of the toner image after copying 5,000 sheets was small, and there was practically no problem.

[Comparative Example 1] A powdery capsule toner was obtained in the same manner as in Example 1 except that the nigrosine dye dispersion liquid was not added to the microcapsule dispersion liquid.

Nigrosine dye 0.02 per 1 g of the obtained capsule toner
g was mixed by trituration.

When the surface of this capsule toner was observed with a scanning electron microscope, some of the nigrosine dye was present without adhering to the toner surface.

When the same charging test as in Example 1 was performed on this capsule toner, the amount of charge was (+) 12 μC / g.

Using this capsule toner as a developer, a repeated copying test by an electrophotographic copying machine was conducted on 5000 sheets of paper to examine the change in density of the toner image. The decrease in the density of the toner image after copying 5000 sheets was remarkable. It was also observed that a considerable amount of the nigrosine dye had been released from the toner inside the developing machine.

Comparative Example 2 A powdery capsule toner was obtained in the same manner as in Example 1 except that the nigrosine dye dispersion liquid was not added to the microcapsule dispersion liquid.

When this capsule toner was subjected to the same charging test as in Example 1, the charge amount was (+) 1 μC / g, which was remarkably low.

Example 2 Instead of an acetone solution of a nigrosine dye, a monoazo metal complex salt type charge control agent (trade name: Spiron Black TRH, Hodogaya Chemical Co., Ltd.) in dimethylformamide (charge control agent: 2 g / 100 g dimethyl) A powdery capsule toner was obtained in the same manner as in Example 1 except that the same amount of formamide was used.

When the surface of this encapsulated toner was observed with a scanning electron microscope, it was confirmed that the charge control agent was uniformly attached to the toner surface in the form of fine particles having a particle size of 1 μm or less.

When the same charging test as in Example 1 was performed on this capsule toner, the amount of charge was (−) 8 μC / g.

Using this capsule toner as a developer, a repeated copying test by an electrophotographic copying machine was conducted on 5000 sheets of paper to examine the change in density of the toner image. The decrease in the density of the toner image after copying 5,000 sheets was small, and there was practically no problem.

Claims (3)

[Claims] 1. An aqueous dispersion medium containing in a dispersed state microcapsules composed of a core substance containing a coloring material and a binder, and a resin shell formed around the core substance, and an organic solvent for a charge control agent. A method for producing a capsule toner having improved triboelectric chargeability, which comprises depositing the charge control agent on the surface of a microcapsule by bringing it into contact with a solution and then drying. 2. The method for producing a capsule toner according to claim 1, wherein the charge control agent is an electron-donating dye or an electron-accepting organic complex. 3. The method for producing a capsule toner according to claim 2, wherein the charge control agent is a nigrosine-based electron donating dye.