JPH01150153A - Production of capsule toner - Google Patents

Abstract

PURPOSE:To coat the surfaces of core particles with a shell material and to obtain a toner for low-temp. fixing having good fixability and offset resistance by dispersing the solid core particles into a soln. to an aq. medium set in the basic pH region of the shell material of the capsule toner and changing the pH of the liquid dispersion to the pH region where the shell material precipitates from the liquid dispersion. CONSTITUTION:The solid core particles having a prescribed grain size are dispersed into the soln. to the aq. medium set in the basic pH region of the core material of the capsule at the time of producing the capsule toner to be used for an electrophotographic method, electrostatic printing method, magnetic recording method, etc. The pH of the liquid dispersion dispersed with such solid core particles is changed until the shell material is precipitated from the liquid dispersion, by which the surfaces of the core particles are coated with the shell material. The greater part of the function of heat fixability is imparted to the core material. The use of materials having good toner characteristics such as developability and preservable property of the dry toner as the shell material is enabled. The toner for low-temp. fixing having the good fixability and excellent offset resistance is thus produced.

Description

DETAILED DESCRIPTION OF THE INVENTION 11 Light 1 The present invention relates to a method for producing a microcapsule type toner used in electrophotography, electrostatic printing, magnetic recording, and the like.

Toners that visualize latent electrical and magnetic images, etc., are used in various processes for forming and recording images.

In the electrophotographic method, which is one of such image forming processes, in order to obtain a copy image, an electrostatic latent image formed on a photoreceptor is generally converted into a powder ink called a toner. A toner image is formed by development, and this toner image is transferred to a recording medium (e.g. paper, OHP) through a transfer process.
A method is used in which the toner image is transferred onto a recording medium (paper, etc.), and then the toner image is fixed to the surface of the recording medium in a fixing step. Although the unfixed toner image formed on the recording medium is held on the recording medium, it is not fixed in a stable state, so generally, the above-mentioned toner image is The toner image is fixed to the recording medium.

Among these toner image fixing processes, the heat roll fixing method, in which a constant pressure is applied between two opposing rolls and at least one of the rolls is further heated, is particularly effective. be. This heat roll fixing method has the following advantages compared to other fixing methods such as flash fixing method and oven fixing method that do not involve pressure contact or conveyance using rolls.
It is the most commonly used method because it has various features such as low power consumption, high speed, and low risk of fire due to paper jams in the fixing device. The heating roll that makes up the heat roll fixing device uses a cylindrical metal core whose surface is coated with a heat-resistant resin such as fluororesin, while the opposing roll is used to form an effective nip width. As described above, a cylindrical metal core whose surface is coated with a heat-resistant elastic material such as silicone rubber or fluororubber is used.

However, when using a fixing device with such a configuration, the heat-resistant resin generally has poor thermal conductivity, so when a large amount of heat is rapidly lost from the heating roll surface during continuous copying, it is difficult to remove the heat from the heat source. The amount of heat supplied tends to be insufficient, the temperature of the heating roll surface decreases, and fixing failure tends to occur.

Therefore, the higher the fixing speed, the more heating energy is required to prevent poor fixing. On the other hand, especially in recent OA type equipment, there is a trend towards further speeding up the fixing process in order to improve the efficiency of copying operations.

In the conventional heat fixing method, in order to increase the fixing speed,
By lowering the softening point of the toner binder resin,
Attempts have been made to make the toner more easily heat-fixed, but lowering the softening point of the toner binder resin causes problems such as agglomeration of toner particles or blocking during use.

Thus, there is a strong desire for a toner that is suitable for faster hot roll fixing and has excellent toner properties such as no roller offset, no aggregation, no blocking, and the like.・Furthermore, during hot roll fixing, the roll and toner image come into contact, so some of the toner is transferred onto the roll surface, resulting in staining of the roll surface and staining the trailing edge of the recording medium or the next There is a problem in that the so-called offset phenomenon is likely to occur, in which the toner is retransferred and fixed onto the fed recording medium and further onto its backing. As a countermeasure to this offset phenomenon,
A mold release agent such as silicone oil is regularly or intermittently supplied and coated on the surface of at least one of two opposing rolls, but the mold release agent application device becomes complicated. This not only leads to an increase in the size of the fixing device, but also frequently causes problems such as paper being stained by the release agent and release agent spilling.

On the other hand, as described in Japanese Patent Publication No. 51-23354, such an offset phenomenon is likely to occur when a low molecular weight resin is used in the toner. It is thought that the offset phenomenon can be prevented to some extent by using a cross-linked resin, but of course, simply using a cross-linked resin will increase the fixing temperature and cause low-temperature offset in the unfixed area. problem occurs.

As mentioned above, when using the conventional simple pulverization method toner, it is difficult to meet the conflicting demands of high-speed fixing, toner blocking resistance, and caking resistance, so a certain degree of compromise is required. The current situation is that it is not possible.

As a method for solving many of the above-mentioned problems, microcapsule-type heat fixing toners aimed at high-speed heat fixing or low heat energy consumption have been proposed.

In this type of capsule toner, a low melting point component that is more easily melted by heat is used as the core material, and a component that has a higher melting point and has the necessary chargeability and electrification properties for the toner is used as the shell material.
Components having characteristics such as fluidity are used. For example, Japanese Patent Publication No. 1588/1988 discloses examples of polystyrene capsules with wax as the core material, or polystyrene capsules with an aqueous solution as the core material. ing.

However, to date, microcapsule toners in which core particles made of materials effective in low-temperature fixability and anti-offset effects are sufficiently coated with shell materials that contribute to development to the extent that they can withstand practical use have not been developed. One of the reasons for this is that materials that are easy to coat the core material do not always provide good charge control properties that contribute to toner properties, especially development properties. The range of choices is extremely narrow.

In addition, there are problems such as the wall material of the microcapsules peeling off due to the impact force received during the development process, and there are many issues that need to be resolved in order to put microcapsule toner into practical use, such as the completeness of the coating and the durability of the coating. The current situation is that there are still some things that need to be done.

In order to solve these problems, many encapsulation production methods have been proposed (Tasushi Kondo, "Microcapsules", Sankyo Publishing, 1977), such as the spray dryer method, electrostatic coalescence method, and submerged drying method. , an interfacial polymerization method, a phase separation method, an 1n-situ polymerization method, and a method combining these methods.

In the encapsulation process, the core particles are dispersed in a solution in which the shell material is dissolved or dispersed, and the dispersion liquid is discharged using a two-fluid nozzle or a disc atomizer to coat the surface of the core particles with the shell material. When a spraying method is adopted, a capsule toner having a coarse particle size in which the particles coalesce may be obtained, and particles called free shells consisting only of shell material may also be produced as a by-product.

Furthermore, when an interfacial polymerization method is used in the encapsulation process, the polymerization reaction generally takes a long time and the toners coalesce, resulting in an unavoidable drop in productivity. Furthermore, since the range of materials that can be used in this interfacial polymerization method is very narrow, it is necessary to appropriately control the characteristics of the capsule toner obtained using the interfacial polymerization method, such as triboelectric charging characteristics. This becomes extremely difficult.

Furthermore, even when a phase separation method is used in the encapsulation process, there are various problems. By adding a non-solvent that cannot substantially dissolve the shell material into the solution in which the shell material has been dissolved using a solvent, the shell material that has been dispersed or dissolved in a good solvent can be coated on the surface of the core particle. This is a method of forcing them.

In this phase separation method, it is essential that the binder constituting the core particles does not dissolve in the good solvent during the process of dispersing the core particles in the good solvent. If part of the core material is dissolved in the good solvent, the core material will be mixed into the resulting shell film, leading to destabilization of the triboelectric charging characteristics of the toner and contamination of the sleeve, which is the toner carrier. Furthermore, when the once-dissolved core material is precipitated by the action of a non-solvent, a capsule toner that does not contain a colorant and has extremely high triboelectric charging properties is produced as a by-product, causing ground force blur in the developing process and toner particles on the sleeve. This tends to cause so-called sleeve unevenness, in which the material is applied unevenly.

In such an encapsulation method using a phase separation method, selection of a good solvent and non-solvent for the shell material and temperature control are extremely important. In other words, if these selections are made incorrectly, the precipitation point of the shell material will be too early, resulting in poor product stability and reproducibility.On the other hand, if the precipitation point is too late, the manufacturing equipment will become large and the solvent will be too small for the core particles. Since the amount increases, productivity decreases.

An object of the present invention is to provide a method for producing a heat-fixable toner that solves the above-mentioned problems.

An object of the present invention is to provide a method for producing a toner for low-temperature fixing that has particularly good fixing properties and good anti-offset properties.

A further object of the present invention is to provide a method for producing a low-temperature fixing toner that has good chargeability and always exhibits stable chargeability during use, giving clear and fog-free images.

Furthermore, the object of the present invention is to have excellent fluidity, not cause agglomeration,
It is an object of the present invention to provide a method for producing a toner for low temperature fixing that also has excellent impact resistance.

A further object of the present invention is to provide a method for producing toner for low-temperature fixing with less deposits on the surface of a toner holding member or photoreceptor.

Another object of the present invention is to provide a method for producing a microcapsule toner that does not coalesce or aggregate, has high coating integrity, and has excellent functional separation.

and Ell (7011) As a result of intensive research, the present inventors have found that using an aqueous medium solution of the shell material in a certain equilibrium state between the dissociated type and the non-dissociated type of the shell material, and further utilizing the above equilibrium, the surface of the core particle is It has been found that precipitating the shell material in the process is not only extremely effective in achieving the above objectives, but also provides a capsule toner with excellent environmental stability.

The method for producing a heat-fixable negatively charged capsule toner of the present invention is based on the above-mentioned knowledge. and the pH of the dispersion obtained in the above dispersion step to the pH at which the shell material precipitates from the dispersion.
This method is characterized by comprising a step of coating the surface of the core particle with a shell material by changing the material to the H range.

In the manufacturing method of the present invention having the above configuration, a material having excellent agglomeration resistance, blocking resistance, and charge controllability is used as the shell material, and solid core particles are sufficiently formed in a manner that no free shell by-product is produced. It becomes possible to coat the

Therefore, according to the production method of the present invention, the core particles have excellent low-temperature heat fixing properties and anti-offset properties. It becomes possible to use a material with low (Tg). That is, according to the manufacturing method of the present invention, most of the functions of heat fixability are shared by this core material,
Moreover, it becomes possible to use a material having better toner characteristics such as developability and storage stability of a dry toner than ever before as the shell material, and as a result, a capsule toner with excellent functional separation properties can be obtained.

Hereinafter, the present invention will be explained in more detail. In the following description, "1%" and "part" representing a quantitative ratio are based on weight unless otherwise specified.

Core materials used in the present invention include, for example, waxes such as polyethylene wax, oxidized polyethylene, paraffin wax, higher fatty acids, higher fatty acid esters, higher fatty acid amides, higher fatty acid metal salts, and higher alcohols; ethylene-acetic acid. vinyl copolymer, polyester resin,
Resins such as epoxy resin, styrene-acrylic acid copolymer, styrene-acrylic ester copolymer, styrene-butadiene copolymer, cyclized rubber; Oils such as silicone oil and fluorocarbon oil; etc. They can be used alone or in combination or in a mixture of two or more.

The core particles used in the present invention can be manufactured by various manufacturing methods using the core material as described above. As a method for manufacturing such core particles, for example, a known dry toner manufacturing method can be applied as is.For example, various compounds are mixed in advance into fine particles, uniformly mixed by hot melt mixing, and then air jet pulverization. , a method for obtaining core particles of a constant particle size using a wind classifier, etc., applying DC voltage and discharging core material from a disk atomizer, JP-A-58-216
Electrostatic exposure method using the method described in No. 736, JP-A-59-1202, in which core particles are formed using a two-fluid nozzle
The melt spray method described in Japanese Patent Publication No. 63, and the suspension granulation method described in Japanese Patent Application Laid-Open No. 127062/1983, which involves granulation in an aqueous medium, are preferably used.

In the present invention, the suspension granulation method is used, that is, the core material is granulated in an aqueous medium in the presence of a dispersant under normal pressure or under pressure,
It is preferable to use a method for producing core particles because the particle size distribution of the core particles becomes sharp.

More specifically, for example, when using a method of granulating core particles by using a poorly water-soluble dispersant in an aqueous medium, the charge induced by dissociation of the dispersant in the aqueous medium and the opposite charge. When obtaining core particles in the presence of a poorly water-soluble dispersant in an aqueous medium, it is best to combine a cationic or anionic compound that induces It is common to use a dispersant having a diameter. In other words, when the particle size of the dispersant is very small, the surface of the dispersant particles is significantly activated energetically, which increases the selective adhesion of the dispersant particles onto the surface of the core particle.

In the present invention, when a polar solvent such as water is used as a decomposition medium for the core particles, it is advantageous to provide the dispersant with a highly polar functional group, and these dispersants are By occupying , due to ionic ability interaction,
Furthermore, it becomes possible to make the core particles as desired. Furthermore, by making effective use of such functional groups, it is expected that, for example, the dispersant can be removed when it is not needed. In other words, if it is desired to obtain a desired particle size, it can be achieved by arbitrarily selecting the amount of the slightly water-soluble dispersant added.

However, simply using a dispersant selected in this way does not necessarily ensure that the dispersant selectively and uniformly adheres only to the surface of the core particle, and is still insufficient to obtain uniform particles. There are cases.

In order to uniformly adhere the dispersant to the surface of the core particles, it is necessary to add a cationic material that induces a charge opposite to the charge induced by dissociation of the dispersant in the aqueous medium in the core material to be atomized. It is preferable to combine a compound imparting anionic properties or a compound imparting anionic properties.

For example, typical examples of dispersants that dissociate as anions in water include silica, titanium oxide, iron oxide, bentonite, etc., and hydrophobic amines are generally used as compounds imparting cationic properties to these dispersants. Particularly preferably, a long-chain aliphatic amine or a graft compound produced from polyethylene and a mercury containing an amino group is particularly preferable as a cationic property-imparting compound that is sufficiently compatible with other components contained in the core material. be.

Specifically, Deeomin C (melting temperature 18-26°C), Duomin O (melting temperature 20-26°C), Duomin S (
Melting temperature 32-40℃), Duomin T (melting temperature 35℃)
~42℃), Duomiso CD1 Duomine TX (Lion Akzo); Primary amines such as octylamine, dodecylamine, hexadecylamine, octadecylamine, oleylamine, nidodecylmethylamine, tetradecylmethylamine, hexadecylmethyl amine,
Secondary amines such as octadecylmethylamine; aliphatic amines such as tertiary amines such as dodecyldimethylamine, tetradecyldimethylamine, hexadecyldimethylamine, and octadecyldimethylamine; and polybutenylsuccinic anhydride obtained by maleating polybutene. A succinimide compound made by reacting a polyamine with a succinimide compound; Furthermore, after heating and dissolving polyethylene wax, adding an aprotic polar solvent in which an amino group-containing vinyl monomer and a radical initiator are dissolved, and heating again. There are amino-modified waxes obtained by.

On the other hand, examples of dispersants that can be dissociated as cations in water include aluminum oxide, magnesium oxide, zinc oxide, and cadmium oxide.

Compounds imparting anionic properties include hydrophobic long-chain aliphatic carboxylic acids such as stearic acid and oleic acid. Also included are long-chain aliphatic dicarboxylic acids, carboxylic anhydrides, such as reaction products of C6 α-olefins and maleic anhydride, or half esters thereof.

The average particle size of the core particles used in the present invention is preferably 0.5 to 30 μm, more preferably 4 to 15 μI, as a volume average particle size.

In the present invention, when magnetic particles are contained in the core substance, ferromagnetic elements such as iron, cobalt, nickel, or manganese, and alloys and compounds such as magnetite and ferrite containing these elements are used as the magnetic substance. be able to. This magnetic substance may also serve as all or part of the colorant. Furthermore, each particle of this magnetic substance has an f!
The content of this magnetic substance, which may be treated with a hydrophobizing agent (for example, a silane coupling agent, a titanium coupling agent, an aluminum coupling agent, a zircoaluminum coupling agent), a surfactant, etc. 15 to 150 parts (and even 50 to 150 parts) are preferred for every 100 parts of total resin in the material.

In the core material of the present invention, a coloring agent can be used alone or in combination with the above-mentioned magnetic substance. Such colorants include, for example, various carbon blacks, aniline black, naphthol yellow, molybdenum orange,
Known dyes and pigments include rhodamine lake, alizarin lake, methyl violet lake, phthalocyanine blue, nigrosine methylene blue, rose bengal, and quinoline yellow.

The amount of colorant added is based on 100 parts of the binder resin of the core particles.
0.5 to 20 parts is preferred.

In the method of melting and mixing this core material, it is poured into an aqueous medium and granulated by applying strong shearing force using a homomixer or the like in the presence of a dispersant or emulsifier. , the apparent viscosity of the core material decreases, improving granulation properties.On the other hand, after shearing, the apparent viscosity increases, which causes particles to coalesce and colorants, magnetic substances, etc. inside the particles to Aggregation and bias are suppressed.

In addition, core materials that generally have good fixing properties have a relatively low melt viscosity, so during melt mixing, shearing force between pigments such as colorants and magnetic materials and binder resin does not work. Therefore, the pigment tends to be insufficiently dispersed in the binder resin. As a result, particles with no coloring material present inside the toner particles,
Alternatively, a large number of particles in which the coloring material in the toner particles is unevenly distributed is generated, which tends to deteriorate the performance as a toner and, in turn, adversely affect the image quality, durability, stability, etc. of the toner.

Therefore, it is desirable to disperse the pigment particles (used to include magnetic particles) in the toner particles so that the particle size is 5 μm or less, preferably 2 μm or less. Compared to the two-roll, two-wheeled extruder kneader used to melt and disperse ingredients,
It is desirable to melt and mix and disperse for a sufficiently long time using an attritor, ball mill, or sand mill using media.

In order to check the degree of dispersion of pigment substances, it is possible to determine the degree of dispersion of the toner by dispersing the toner in an embedding resin such as an epoxy resin, curing it, cutting it into ultrathin sections using a microtome, etc., and observing it with a transmission electron microscope. can. In addition, a particle size gauge (
For example, the dispersibility of the pigment substance can also be determined by using a grind gauge (type 2, manufactured by Yoshimitsu Seiki Co., Ltd.).

Above, the core material used in the microcapsule toner manufacturing method of the present invention has been mainly explained.

On the other hand, the shell material used in the present invention mainly has good mechanical properties and thermal properties, and also has a film-forming property function (^) that gives sufficient film-forming property, and is mainly salt-resistant in an aqueous medium. Preferably used is a resin that has both the function (B) of forming a dissociated body with a curing agent and controlling the charge as a toner, and the solubilization function (C) of mainly solubilizing it in an aqueous medium. It will be done.

As for the resin properties, the number average molecular weight is s, ooo~so,
ooo, and more preferably a resin having a ratio of 10.000 to 30.000, and a ratio of number average molecular weight (Mn) to weight average molecular weight (Mw) showing monodispersity of molecular weight distribution (M
w/M n ) is in the range of 1.5 to 4.5, the glass transition temperature (Tg) is 40°C or higher, preferably 60 to 120°C, and cross-linking (cross-11n
Thermostable resins having excellent moisture absorption properties, having no bond (King) and having an acid value of 5 to 200, particularly preferably 10 to 100, can be preferably used.

However, it is difficult for a resin synthesized from a single type of cypress to satisfy all of the functions (^) (B) and (C) above; Polymers are preferably used. Specifically, a resin composed of a type of cypress resin having the following various functions is used.

Styrene (st
), halogen-substituted styrene monomers such as brominated styrene, chlorinated styrene, iodinated styrene, fluorinated styrene; dodecylstyrene, decylstyrene, ethoxystyrene, ethylstyrene, hexylstyrene, isopropylstyrene, phenoxystyrene, phenylstyrene, etc. Monoalkyl or allyl substituted styrene monomer!
Ii: Polysubstituted alkyl or allyl substituted styrene monomers such as dimethylstyrene, trimethylstyrene, diethylstyrene, etc. are mainly used.

As the monomer having function (B), acrylic acid (A
A); Methacrylic acid; maleic anhydride monomethyl ester, maleic anhydride dimethyl ester, maleic anhydride monoethyl ester, maleic anhydride diethyl ester, maleic anhydride n-propyl monoester (PMA)
, maleic anhydride n-propyl diester, maleic anhydride 1so-propyl monoester (IPMA), maleic anhydride 1so-propyl diester, maleic anhydride butyl monoester, maleic anhydride butyl diester, etc. is mainly used.

Examples of the polymer having function (C) include methyl acrylate (MA), ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, 5ec-butyl acrylate, tert-butyl acrylate, hexyl acrylate, heptyl acrylate, 2- Ethylhexyl acrylate (2・EH
A) Acrylic acid esters such as fluorinated methyl acrylate, cyclohexyl acrylate, phenyl acrylate; methyl methacrylate (MMA), ethyl methacrylate, isopropyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate , benzyl methacrylate, hexyl methacrylate, heptyl methacrylate, 2-ethylhexyl methacrylate (2・EHM), and other methacrylic acid esters; maleic anhydride dimethyl ester, maleic anhydride diethyl ester, maleic anhydride diisopropyl ester, maleic anhydride Maleic anhydride diesters such as di-n-propyl ester; acrylonitrile; ・Halogenated ethylene: vinyl acetate;
Mainly used are ethylenically unsaturated monoolefins such as ethylene, propylene, isoprene (IP), butadiene (BD), butylene, and isobutylene; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride; etc. It will be done.

In the present invention, it is generally preferable that functions (A), (B), and (C) are composed of different monomer types;
) sometimes has the function (C'), and furthermore, a ternary or more multi-component copolymer formed by configuring a single function from multiple thousand molecules is used. It is also possible.

The shell material used in the present invention is not limited to resins composed of monomers having functions (A), (B), or (C) as described above, but may also include polyester, polycarbonate, polysulfonate, Polyamide, polyurethane, polyurea, epoxy resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, melamine resin, polyether resin such as polyphenylene oxide, or thioether It is also possible to use a homopolymer or a copolymer such as a resin.

More preferable examples of the shell material used in the present invention include S t-I PMA-MMA copolymer, S t-A
A-MMA copolymer, terpolymer such as St-PMA-2/EHA copolymer, St-IPMA-MMA-IP
Copolymer, St-AA-MMA-2/EHA copolymer,
Examples include quaternary copolymers such as S t-AA-I PMA-MMA copolymers.

The composition ratio of the monomers having functions (A), (B), and (C) is expressed as a molar ratio (^) : (B) : (C) = taking the total monomers constituting the copolymer as 100.
(30-90): (5-65): (5-30
) (mol%).

When the ratio of the monomer having the function (^) is less than 30 mol%, toner is formed on the surface of the sleeve (which is the toner carrier in the developing device) that rotates facing the photosensitive drum which is the latent image carrier. The layer collapses due to the force applied to the toner between the regulating blade mosleeve, which is a toner layer thickness regulating means, and the force applied to the toner between the sleeve surface layer rotating against the external magnetic force, and as a result, This can easily cause sleeve fusion and non-uniformity in the toner coating layer formed on the sleeve surface.Also, some of the toner developed on the photoreceptor surface may be absorbed by the cleaner during the cleaning process. External force between the member and the photoreceptor surface layer tends to cause toner fusion on the photoreceptor drum surface, resulting in harmful effects.

On the other hand, the percentage of thousands of people with functions (^) is 90%.
If it exceeds 100%, the blending ratio of 1,000 ml having functions (B) and (C) becomes relatively small, and it becomes difficult to solubilize the shell material in an aqueous medium by adding a basifying agent.

If the proportion of the toner having the function (B) is less than 5 mol %, solubilization in an aqueous medium is prevented, and furthermore, the triboelectric charging properties of the toner become poor.

On the other hand, if the ratio exceeds 65 mol%, the stability of the toner at high temperatures deteriorates, resulting in the
It becomes difficult to satisfy the g value.

When the ratio of 1,000 mol % having the function (C) is less than 5 mol %, the dissociated product of the shell material produced by the action of the basifying agent,
On the other hand, if the ratio exceeds 30%, the solubility of the dissociated product in the aqueous medium becomes sufficiently high, but on the other hand, the shell on the surface of the core particle becomes difficult to solubilize in the aqueous medium. The film formability of the material becomes insufficient.

Although the amount of the shell material added to cover the surface of the core particle cannot be determined uniquely depending on the surface shape of the core particle, the density of the core material and shell material, the particle diameter of the core particle, etc., in the present invention. It is preferable to determine the amount of the shell material to be added by calculating the amount of the film material based on the set film thickness of the shell material from the viewpoint of toner characteristics.

That is, it is preferable to calculate the amount of the shell material added using the following formula.

Here, δ: set film thickness (μ■), amount of Wail material charged, ρ: density of shell material, G: density of core particles, S: amount of prepared core particles, D: volume average of core particles Particle size (μ).

The volume average particle size of the core particles is determined as follows. That is, by putting about 115 ml of 1% saline in a beaker, adding a small amount of core particles, and dispersing the core particles in an ultrasonic cleaning volume for about 60 seconds, further adding 1% saline,
Adjust the core particle concentration to 5 to 10%, and then increase the concentration to about 6% again.
Disperse with ultrasonic waves for 0 seconds to prepare a sample. This sample is measured using Coulter Counter TA-II (manufactured by Coulter Electronics).

The set film thickness δ in the present invention is 0.01 to 2°0 μm
(more preferably 0.05 to 1.0μ). If this set film thickness is less than 0.01μ1, the shell material cannot completely cover the surface of the core particle, resulting in the formation of a so-called defective film. In the development below, stable triboelectric charging is not performed, and furthermore,
Toner tends to cause drum fusion, on the other hand, when the set film thickness is 2
．． If 0μ is exceeded, the resistance of the toner becomes too high, and uneven coating of the toner on the sleeve is likely to occur during development under low humidity.

Further, in the present invention, the average particle size (volume average particle size) of the encapsulated toner is usually 0.5 to 100 μm, preferably 5 to 20 μm.

In the present invention, the above-mentioned shell material is subjected to the step of coating the core particles in the state of a solution dissolved in an aqueous medium set in a basic pH range.

The method for obtaining such a shell material solution is not particularly limited. For example, it is possible to obtain the solution via a solution polymerization method, but from the viewpoint of improving the environmental stability of the capsule toner, Preferably, the shell material described above is solubilized in an aqueous medium with the aid of a salinizing agent to form a shell material solution.

Using such a shell material solution, the core particles are dispersed in an aqueous medium in advance, and by changing the DH of the dispersion to a predetermined pH range in which the shell material becomes insoluble, the surface of the dispersed core particles is dispersed. The shell material can be precipitated to sufficiently cover the dispersed core particles.

As the aqueous medium used in the present invention, a solvent that satisfies one or more of the following conditions (1) to (4) is preferably used.

l) The shell material is preferably a solvent that can stably form a dissociated product in the presence of a basifying agent.

In other words, it is preferable to use a highly polar solvent that can completely solubilize the shell material in the aqueous medium by adding a basifying agent.

In the present invention, a highly polar solvent is defined as one that is sufficiently miscible with water and has a solubility parameter (according to "Polymer Handbook").
(described on pages 337 to 359 of the second edition) means a solvent with a value of 11.0 or more.

2) It is preferable that the solvent is a solvent that does not substantially increase the viscosity of the solution when the shell material is insolubilized.In a system using a solvent that increases the viscosity when the shell material is precipitated, the system should be sufficiently agitated. As a result, the precipitated shell material particles do not selectively coagulate and precipitate on the surface of the core particle, and many free shells consisting only of shell material particles are generated as by-products, and the capsule toner particles that have aggregated and coalesced. The proportion increases.

3) From the viewpoint of recovering and reusing the solvent, a low boiling point solvent is preferable.

4) It is preferable that the solvent is a solvent that does not substantially dissolve the core material.

In other words, when the core material is dissolved when the core particles are dispersed in an aqueous medium, when the shell material is precipitated in the next step, the core material containing no magnetic particles (or colorant, etc.) is encapsulated as a core. Free shells that do not contain core particles are likely to be produced as by-products because toner is produced as a by-product or the dissolved core material destabilizes minute oil droplets that are generated at the initial stage of precipitation of the shell material.

Specific examples of solvents preferably used in the present invention are shown in the table below.In the present invention, it is most preferable to encapsulate using a single solvent consisting only of water, but in order to satisfy the above conditions, Usually, a mixed solvent system composed of water and a lower alcohol is particularly preferably used. In this case, the mixing ratio of water and lower alcohol greatly depends on the characteristics of the shell material used, but in general, the weight ratio of lower alcohol to water (weight of lower alcohol/weight of water) is E, and the ratio of water to lower alcohol is If the value obtained by dividing the number average molecular weight by 10,000 is N, then the blending ratio (D) of these is D=E/N=0. It is preferable that D=0.05 to D=0.6, and more preferably D=0.1 to D=4.

Specific examples of polar solvents When the above blending ratio (D) is less than 0.05, the shell material that can be solubilized in an aqueous medium is restricted, and high molecular weight resins cannot be used particularly from the viewpoint of solubility. - When the shell material, which has been solubilized with the aid of a basicizing agent, precipitates (preferably with the aid of an acidifying agent), the viscosity of the shell material solution becomes extremely high, and sufficient stirring is not carried out, resulting in free shells and Coalesced toner is more likely to be generated.

On the other hand, when the blending ratio (D) is greater than 6, the viscosity of the solution when the shell material precipitates becomes low and the load on stirring is reduced, but on the contrary, the shell material swells and some solubilizes. This causes the shell material to be difficult to solidify even after encapsulation, making the post-processing process extremely complicated. Furthermore, the stability of the precipitated shell material emulsion particles is poor, making it difficult to selectively adsorb onto the surface of the core particles, making it easy for the shell material to mechanically adhere to containers and the like.

The smaller the amount of solvent used for the core particles containing the magnetic substance or colorant, the better from the viewpoint of productivity.
It is preferable that the encapsulation is carried out in a range of usually 10 to 50 parts of the core particles to 0 parts of the core particles.

In the present invention, it is also possible to further add another polar solvent to the aqueous medium in order to smooth the shell film. Such other polar solvents include, for example, ethylene glycol diacetate, ethylene glycol dimethyl ether, ethylene glycol monoacetate, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monomethyl ether, ethylene Cellosolves such as glycol monomethyl ether acetate; polar aproton-donating solvents such as acetonitrile, dioxane, dimethylformamide, dimethyl sulfoxide, dimethylacetamide, dimethylurea, etc. can be used.

In the present invention, the concentration of the shell resin solubilized in the aqueous medium with the aid of a basifying agent is usually 0.5 to 20 parts (particularly preferably 1.0 to 10 parts) per 100 parts of the aqueous medium. )
It is preferable to use it at a concentration of .

When the concentration of the shell material is less than 0.5 parts, the manufacturing equipment becomes large and furthermore, a large burden is placed on solvent recovery. On the other hand, if the concentration of the shell material exceeds 20 parts, the viscosity of the solution increases when the shell material precipitates, making it impossible to stir sufficiently, resulting in not only an increase in free shells but also a large amount of coalesced toner. do.

The occurrence of free shells causes sleeve contamination, a decrease in image density, and further causes ground braking. In addition, the coalesced toner has poor triboelectric charging characteristics, and image density gradually decreases during the process of continuous copying, and development characteristics, particularly under high temperature and high humidity conditions, become extremely poor.

In the present invention, it is preferable to add a basifying agent to the aqueous medium and set the pH to a basic pH range to solubilize the shell material to form a shell material solution. In this case, The pH value at which the shell material can be solubilized depends on the type of aqueous medium,
Blend ratio, film-forming properties (^), solubilization properties (
Although it depends somewhat on the type, molecular weight, ionic strength, etc. of C), the pK of the dissociative fluorine (B) used in the present invention
In general, the pH value of the aqueous medium is 8±2 in order to make the ionization rate of 1,000 yen (B) 99.99% or more, which is defined by the zero-order equation having a value of 4±2. It is preferable to adjust it with a basifying agent so that it becomes 1.

In order to precipitate the 1 + anti log (pH-pKa) shell material, it is preferable to change the DH up to the precipitation range using a normal acidifying agent. As the acidifying agent to be used, in addition to the usual organic/inorganic acids, it is also possible to use a p)I buffer.

Encapsulation in the present invention can be carried out under the above p)I conditions by heating or at room temperature, but it is important to completely cover the surface of the core particle with the shell material or to suppress mechanical adhesion of the shell material. Furthermore, in order to prevent elution of the core material, it is preferable to carry out encapsulation at a temperature of -10 to +30°C. If the encapsulation temperature is lower than -110°C, the equipment will be complicated and running costs will increase. invite

On the other hand, if the encapsulation temperature exceeds +30°C, mechanical adhesion of the shell material and elution of the core material tend to increase, which is not preferable.

In the present invention, as the basifying agent, inorganic bases such as sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia gas, and aqueous ammonia; and organic bases such as ethylenediamine, diethylenetriamine, and triethylenediamine are preferably used. However, aqueous ammonia is particularly preferably used.

On the other hand, in the present invention, the acidifying agent includes hydrochloric acid, sulfuric acid,
Inorganic acids such as phosphoric acid; and organic acids such as formic acid, acetic acid, and succinic acid are preferably used, and acetic acid is particularly preferably used.

In the present invention, the rate of addition of the acidifying agent used is determined by the following formula: F: Concentration of shell material in aqueous medium (g#) G: Amount of aqueous medium (1) H: 'el & rate of addition of acidifying agent It is preferable to set the speed to satisfy (m days/minute), and it is more preferable to control the speed as described above.

It takes time to convert, and production efficiency drops significantly.

In addition, since the shell material resin precipitated by the production method of the present invention first precipitates in the state of viscous oil droplets and undergoes a step of successive solidification, if the dropping speed of the acidifying agent is slow, the precipitated shell resin On the other hand, the 932 particles cannot be completely adsorbed onto the surface of the core particles, leading to the generation of free shells and causing the coalescence of the shell material emulsion particles. have a tendency to occur.

As described above, according to the present invention, by controlling the pH of the dissociated-non-dissociated equilibrium of the shell material, the shell material dissolved in the aqueous medium is suitably insolubilized, and the shell material dissolved in the aqueous medium is insoluble. Provided is a method for producing a capsule toner that satisfactorily coats a shell material on the surface of core particles dispersed in a medium.

According to the production method of the present invention, aggregation of the produced capsules,
A microcapsule toner that suppresses coalescence, does not generate free shells, and has excellent functional separation can be produced at low cost and with good reproducibility.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples.

560 parts of glycidyl ether of bisphenol A on the large JLIu were placed in a four-way flask equipped with a stirrer, a condenser, a thermometer, and a gas inlet tube, and placed in a heating mantle. After replacing the inside of the flask (reaction vessel) with nitrogen gas,
When the contents of the flask were heated to 50 to 60°C, 190 parts of fumaric acid and 0.4 parts of hydroquinone were added to the contents, and the water produced by the reaction was heated to 210°C and stirred. After heating and stirring for about 5 hours with continuous removal, the reaction was monitored by acid value measurement every hour to check the end point of the reaction. When the acid value reached approximately 50, 0.3 part of sorbitol was added to the reaction mixture, and the reaction was continued by heating and stirring until the acid value reached approximately 25. The resin was cooled to room temperature. The polyester resin thus obtained had a glass transition point (Tg) of 55°C and a softening point of 95°C by the ring and ball method.

1 Using 100 parts of the polyester resin obtained above,
The mixture was heated and kneaded at 130°C for 60 minutes. After cooling this kneaded material, it is crushed into coarse particles with a particle size of 1 to 2 cm using a cutter mill,
After further pulverization using a jet mill and classification using a thermal classifier, the particle size distribution (measured using a Coulter counter) was determined to be 9.1 μm in number average particle size and 1 volume average particle size in
Core particles having a volume average particle size variation coefficient of 18.7% were obtained.

On the other hand, 320 g of isopropyl alcohol and 80 g of water were collected in an IJ2 flask equipped with an autohomo mixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), a thermometer, and a pH meter, and 5t-I PMA as a shell material was collected. -MMA copolymer (copolymerization molar ratio 60:15:25, number average molecular weight Mn=
18,000, weight average molecular weight Mw = 42,000, M w /
Mn=2.

3, acid value 70) to 8g (set film thickness δ=0.20μff1
)added. Furthermore, 11 Bg of 28% aqueous ammonia was accurately weighed and added to solubilize the copolymer resin. p at this time
H was 9.0.

While maintaining the temperature of the system at 0° C., 100 g of the core particles were added to the solubilized shell material solution obtained above, and the rotation speed was 4000 r.
The mixture was stirred at pm for 5 minutes to sufficiently disperse the core particles.

Glacial acetic acid was gradually added dropwise to this dispersion, and the addition was continued until the pH of the system reached 4 (approximately 40 minutes) to perform encapsulation. At this time, the dispersion liquid was centrifuged using a small centrifugal separator and was further thoroughly washed with water 21 to obtain a capsule toner with a yield of 9%.

At this time, after concentrating the filtrate obtained from the centrifuge using a rotary evaporator, xylene was added,
When the xylene layer was separated using a separating funnel and the solvent (xylene) was removed again, it was found that the charged shell material was effectively utilized for encapsulation at a rate of 95%.

The particle size distribution of the obtained capsule toner had a number average particle size of 10.0 μm, a volume average particle size of 11.2 μm, and a variation coefficient of the volume average particle size of 22.0%. This particle size distribution suggests encapsulation with less free shell and less coalescence. Further, when the triboelectric charge amount of this capsule toner was measured by the method described in U.S. Pat. No. 4,302,201, it was found to be -15.5μ couJ.
It was 2/g. From observation using a scanning electron microscope,
It was found that the shell material sufficiently covered the core particles.

To 100 parts of the capsule toner obtained above, add 0% of negatively charged hydrophobic silica (Nibseal E, manufactured by Nippon Silica Kogyo Co., Ltd.).
．． 4 parts were added and stirred in a coffee grinder to obtain an externally added capsule toner.

The obtained externally added capsule toner was applied to an NP120 (copying machine manufactured by Canon Inc.) with the fixing unit removed, and an image formation test was conducted.

For fixing, a fixing test was also conducted at the same time by using a separate fixing device that can arbitrarily change the roller surface temperature, and fixing the unfixed image on the transfer paper.

As a result, in a durability test of up to 5,000 sheets, no problems related to fixing were observed, and the image density remained at a constant value (approximately 1.2 to 1.
4) was recommended. The fixing point, which is the lowest temperature at which fixing is practically sufficient, was also low (roller surface temperature of about 130°C), and no offset phenomenon occurred over a wide temperature range (roller surface temperature of about 100 to 180°C).

Further, this toner was left in an atmosphere of 50° C. and 85% RH for a long time (30 days), but no blocking, caking, etc. were observed.

Further, image formation was carried out in the same manner as described above under a high temperature and high temperature atmosphere (32.5° C., 85% RH), but no difference was observed between the image characteristics and those at room temperature.

E1 ■U commercially available carnauba wax (manufactured by Noda Wax Co., Ltd.) 1 to 2 g
The mixture was placed in a four-bottle flask, and the pressure inside the container was reduced to 1 to 2 mlHg in a nitrogen atmosphere. While maintaining this reduced pressure state, the inside of the container was heated to 250'e and reacted for 8 hours. The acid value of the carnauba wax obtained at this time was 0.
It was 5.

Carnauba wax obtained above (Vickers hardness Hv
= 3.6) 400 g and polywax 655 (manufactured by Petrolite: critical surface tension γC = 31 dyne/cm
) and 400 g of 5PO145 (manufactured by Nippon Seiro Co., Ltd., compressive elastic modulus E-15 g/III2) into a 21 four-lobe flask, and then n-butyl-
Add 4,4-bis-tert-butyl peroxypareate (Perhexa V1 manufactured by NOF Corporation, temperature 105°C to obtain a half-life of 10 hours) Ig, and heat the inside of the container to 150'e for 2 hours. Heat treated.

Further, the mixture of the above formulation was kneaded at 120° C. using an attritor at 200 rpm for 3 hours to obtain a core material.

The crosstalk (core material) has a sliding rate of 10 at 120°C.
5ec-' apparent viscosity is 600 cps, shear rate 0
．． The apparent viscosity at 5 sec' was 6500 cps.

In addition, the particle size of magnetite particles in the kneaded material is at most 1.5
It was μm.

On the other hand, in a 201 Ajihomo mixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), 18 liters of water and wood-philic silica that is negatively ionized in water (Aeroseal #200, manufactured by Nippon Aerosil Co., Ltd.) were added in advance.
20g was collected and heated to 90°C to use as a dispersion medium. In the dispersion medium thus obtained, the above kneaded material (core material) 1
g, and the circumferential speed of the above Ajihomo mixer is 20 m/
Pelletization was carried out for 1 hour under the conditions of sec and 6.9 baths/+in.

After the granulation was completed, the dispersion was cooled to 30° C. using a heat exchanger, and then 50 g of sodium hydroxide was added to the dispersion, and stirring was continued for 5 hours to obtain core particles.

When the obtained spherical core particles were analyzed by fluorescent X-ray analysis, no residual silica was observed.

Furthermore, the core particles were filtered using a centrifuge and washed with water to determine the particle size distribution (measured using a Coulter counter).
Number average particle size 9.2μm, volume average particle size 10.7μm1
Core particles with a volume average particle diameter variation coefficient of 19.8% were obtained.

Using Fubusco, each component of the above formulation was treated in the same manner as in Example 1 to form a solution in which the shell material was solubilized (set film thickness: 0.
2μ11) was obtained.

In the shell material solution thus obtained, the core particles 1 obtained above are added.
After adding 00 g, the core particles were sufficiently dispersed in the same manner as in Example 1 by rotating the autohomogen mixer at 5000 rpm for 5 minutes while maintaining the temperature of the system at 5°C.

Glacial acetic acid was gradually added to this dispersion at a dropwise rate of 1 cc/min until the pH change rate of the system reached saturation to perform encapsulation. This dispersion was centrifuged using a small centrifuge, and then thoroughly washed with water at 2°C to obtain a capsule toner.

When the particle size distribution of the obtained capsule toner was measured using a Coulter counter, the number average particle size was 10.3μ.
m, and the volume average particle diameter was 11°5 μm. or,
When the triboelectric charge amount of the capsule toner was measured in the same manner as in Example 1, it was -18°2 μ couu /g.

Using this toner, an image reproduction test was conducted using NP-120 in the same manner as in Example 1, and the fixing roller temperature was 8.
Sufficient fixing properties were obtained at 0° C., and the offset phenomenon was slight.

This toner was stored in an atmosphere of 45°C and 85% RH for a long time (
Although the toner was left for 30 days, no toner blocking or caking phenomenon was observed.

A solution in which the shell material was solubilized (set film thickness δ = 0.2 μm) was obtained.

After adding 100 g of core particles produced by the method described in Example 1 into the shell material solution obtained in this way, the rotation speed of the autohomogen mixer was set to 5000 rpm while maintaining the system temperature at 5°C. The core particles were sufficiently dispersed for 5 minutes in the same manner as in Example 1.

Glacial acetic acid was added dropwise to this dispersion at a speed of Icc/min.
Encapsulation was carried out by gradually adding the solution until the pH change rate of the system reached saturation. This dispersion was centrifuged using a small centrifuge, and then thoroughly washed with water 21 to obtain a capsule toner.

When the particle size distribution of the obtained capsule toner was measured using a Coulter Counter, the number average particle size was 10.3 μm.
The volume average particle diameter was 11.2 μm. Further, when the triboelectric charge amount of the capsule toner was measured in the same manner as in Example 1, it was -19°5μ couJ2/g. Furthermore, when image formation was performed using NP120 in the same manner as in Example 1, Example 1 Similarly, sufficient image density and fixing properties were obtained.

After spraying, cooling and solidifying using a two-fluid nozzle with the air temperature set at 120°C, the mixture was classified to obtain core particles.

When the particle size distribution of the obtained core particles was measured using a Coulter Counter, the number average particle diameter was 8.7 .mu.m, and the volume average particle diameter was 11.0 .mu.m.

The same method as in Example 1 was used, except that 100 g of the above core particles were used and a mixed solvent system consisting of 300 g of isopropyl alcohol, 10 g of 15N aqueous sodium hydroxide solution, and 100 g of water was used as the solvent for solubilizing the shell material. Encapsulation was performed at

The particle size distribution of the obtained capsule toner had a number average particle size of 9.8 μm and a volume average particle size of 12.0 μm. Moreover, the amount of triboelectric charge of this capsule toner is -16,
It was 5 μc ou 1/g.

When this toner was used to produce an image using NP120 in the same manner as in Example 1, sufficient image density and fixability were obtained. Furthermore, although it was left in an atmosphere of 50° C. and 85% RH for a long time (30 days), no blocking or caking was observed.

Example 2 was carried out in the same manner as in Example 2, except that a mixed solvent system consisting of 330 g of methanol, 50 g of water, 10 g of glycerin, and 8 g of a 15N hydrium hydroxide aqueous solution was used as the solvent for solubilizing the East 1st Motor Co., Ltd. encapsulation was performed.

The particle size distribution of the obtained capsule toner had a number average particle size of 10.2 μm and a volume average particle size of 11.0 μm. The amount of triboelectric charge of the toner is -15.2 μcouj!
/g, and image printing was carried out using a modified NP-120 machine as in Example 1, and as in Example 2, sufficient image density and fixability were obtained.

After spraying, cooling, and solidifying using a two-fluid nozzle with the air temperature set at 120° C., the mixture was classified to obtain a toner. The particle size distribution of the obtained toner was such that the number average particle diameter was 9.9 μm and the volume average particle diameter was 12°2 μm. Also, this toner's friction zone i! The amount is -9.8 μc ou 1
/g. Image printing was performed using NP120 in the same manner as in Example 1, but the image density was lower than in Example 4, and furthermore, toner fusion occurred on the sleeve surface during continuous image printing. , it was not possible to maintain stable image density.

Furthermore, when the toner obtained above was left at 50° C. and 85% RH for a long time (30 days), toner blocking occurred.

Claims (1)

[Claims] A dispersion step of dispersing the solid core particles in a solution of the shell material in an aqueous medium set to a basic pH range, and adjusting the pH of the dispersion obtained in the above dispersion step. A method for producing a heat-fixable negatively charged capsule toner, comprising the step of coating the surface of a core particle with a shell material by changing the pH of the liquid to a pH range in which the shell material precipitates.