JP3156882B2 - Toner for developing electrostatic images - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic image used in electrophotography, electrostatic recording and electrostatic printing.

[0002]

2. Description of the Related Art In the case of a dry method, an electrostatic image formed by an electrophotographic method, an electrostatic printing method, an electrostatic recording method or the like is generally developed with a dry toner containing a binder resin and a colorant as main components. The image is transferred and fixed on copy paper. There are various methods for fixing a toner image. Due to its high thermal efficiency and high-speed fixing, a hot roll fixing method is widely used, in which a toner image transferred to paper is fixed by passing it between hot rolls. Have been. However, in this fixing method, a so-called offset phenomenon in which the toner adheres to and transfers to the roll surface is likely to occur.

[0003] Therefore, in order to prevent the occurrence of the offset phenomenon, a method of applying a release oil such as silicone oil to the surface of the heat roll, or including a release agent such as low molecular weight polypropylene in the toner has been adopted. I have. However, in the former method, there is a problem that the cost is increased due to the provision of the oil application device in the fixing device, and further, an odor due to the release oil is generated at the time of fixing. Also,
The latter method has the disadvantage of adversely affecting the chargeability, fluidity, and blocking resistance of the toner, and furthermore, it is difficult to uniformly disperse and contain the release agent inside the small-sized toner particles. There are points.

In order to solve such problems, Japanese Patent Application Laid-Open No. Sho 56-144436 proposes a toner to which a release agent is externally added.
Japanese Patent No. 0245 proposes that a toner containing a fixing resin and a dye or pigment, or a charge control agent, and an emulsion wax are mixed to adhere waxes to the toner surface. The present applicant has also previously proposed a method in which release agent particles are adhered onto colored particles, and resin particles whose polarity is controlled are then immobilized.

However, the toner obtained by simply adhering a release agent or an emulsion wax to the toner surface is difficult to transfer the toner developed on the photoreceptor onto recording paper by electrostatic force.
There is a problem that the transferability is significantly deteriorated. In the case of the toner in which the release agent and the resin fine particles are adhered and fixed on the toner surface, the transferability is improved as compared with the toner in which only the release agent is adhered, but the resin fine particles adhere to the extent that the transferability is sufficiently satisfied. In such a case, the effect of the release agent is not sufficiently exhibited, and the effect of preventing offset in hot roll fixing may be insufficient.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and it is possible to prevent the offset phenomenon without using a release oil such as a silicone oil in the hot roll fixing, and to provide a static transfer roller having excellent transferability. An object of the present invention is to provide a toner for developing a charge image.

[0007]

According to the present invention, a release agent having at least a foaming agent present on the surface or inside is adhered to the surface of the colored resin particles, and the outer layer is covered with the release agent. There is provided a toner for developing an electrostatic image, which is provided with a coating layer. In addition, the present invention provides the electrostatic charge developing toner, in which the coating layer covering the release agent is mainly composed of resin fine particles and provided so as to have a lower layer exposed portion.

The toner of the present invention has a coating layer covering the release agent, so that the toner has excellent transferability. At the time of fixing, the foaming agent becomes gas by heating, and the molten release agent is pushed out of the coating layer to prevent offset. Excellent effect. In other words, in the toner before fixing, the releasing agent that deteriorates transferability is present in the inner layer, and the releasing agent is extruded to the outermost layer by the action of the foaming agent during fixing, thereby exhibiting the releasing effect and preventing the offset phenomenon. . Therefore, in order to sufficiently obtain the above effects, the decomposition temperature of the foaming agent must be higher than the melting point of the release agent, and the decomposition temperature of the foaming agent must be lower than the fixing roll temperature.
Further, by forming the thermoplastic resin into fine particles and coating the release agent to such an extent that the release agent is partially exposed, the release agent can be easily extruded due to foaming, and the effect of preventing offset can be further improved.

The colored resin particles which can be said to be core particles in the present invention are thermoplastic resin particles containing a colorant, and the method of forming the particles is the same as that of the conventional toner, that is, the steps of kneading, pulverizing, and classifying. How to make particles
Granulation methods such as spray drying and polymerization can also be used.

As the thermoplastic resin, all of those conventionally used as binder resins for toner are applied. Specifically, polystyrene, polychlorostyrene,
Styrene such as polyvinyltoluene and its substituted homopolymer; styrene / p-chlorostyrene copolymer, styrene / propylene copolymer, styrene / vinyltoluene copolymer, styrene / vinylnaphthalene copolymer, styrene / acryl Methyl acrylate copolymer, styrene / ethyl acrylate copolymer, styrene / butyl acrylate copolymer, styrene / octyl acrylate copolymer, styrene / methyl methacrylate copolymer, styrene / ethyl methacrylate copolymer Styrene / butyl methacrylate copolymer, styrene / α-chloromethyl methacrylate copolymer, styrene / acrylonitrile copolymer, styrene /
Vinyl methyl ether copolymer, styrene / vinyl ethyl ether copolymer, styrene / vinyl methyl ketone copolymer, styrene / butadiene copolymer, styrene / isoprene copolymer, styrene / acrylonitrile / indene copolymer, styrene / Styrene-based copolymers such as maleic copolymers and styrene / maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyvinyl butyl butyral, polyacrylic acid Resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin,
Examples thereof include paraffin waxes, which are used alone or in combination of two or more.

The coloring agents used in the present invention include carbon black, lamp black, iron black, ultramarine,
Nigrosine dye, aniline blue, phthalocyanine blue, phthalocyanine tree, Hansa Yellow G, Rhodamine 6G, lake, calco oil blue, chrome yellow, quinacridone, benzidine yellow, rose bengal, triallylmethane dye, monoazo dye, disazo dye, pigment Any conventionally known dyes and pigments may be used alone or in combination.

The release agent used in the present invention may be any substance that has an effect of assisting the release of the toner from the hot roll in fixing. Examples thereof include low molecular weight polyolefins and waxes. . in this case,
Specific examples of waxes include, for example, the following.

Mines such as carnauba wax, cotton wax, candelilla wax, sugar cane wax, beeswax, whale wax, shellac wax, wool wax; mineral or petroleum waxes such as montan wax, paraffin wax and microcrystalline wax; palmitic acid, stearic acid, Solid higher fatty acids having 6 to 22 carbon atoms such as hydroxystearic acid and behenic acid; oleamide, stearamide, palmitamide, N-hydroxyethyl-hydroxystearamide, N, N'-ethylene-bis-stearamide , N, N'-ethylene-bis-ricinoleamide, N, N'-ethylene-bis-hydroxystearylamide and the like having 6 to 22 carbon atoms (hereinafter, the term "higher" refers to the above-mentioned 6 to 22 carbon atoms). Amides of fatty acids). For example, metal salts of higher fatty acids such as calcium stearate, aluminum stearate, magnesium stearate and calcium palmitate, such as alkali metal salts, alkaline earth metal salts, zinc salts, and aluminum salts; and higher such as palmitic acid hydrazide and stearic acid hydrazide. Hydrazides of fatty acids; p-hydroxyanilide of higher fatty acids such as p-hydroxyanilide of myristic acid and p-hydroxyanilide of stearic acid; β-diethylaminoethyl ester hydrochloride of lauric acid; β-diethylaminoethyl ester hydrochloride of stearic acid Β-diethylaminoethyl ester hydrochloride of a higher fatty acid such as stearic acid amide-formaldehyde condensate and palmitic acid amide-formaldehyde condensate; Condensates; petroleum residues such as asphalt and Gilsonite; rubbers such as nitrile rubber and chlorinated rubber; synthetic hydrocarbons such as Fischer-Tropsch wax and derivatives; fatty acid esters and glycerides such as polyethylene glycol and sorbitol stearate; chlorinated paraffin And halogenated hydrocarbons such as chlorinated propylene; hydrogenated castor oil, hydrogenated tallow oil and the like. The release agent is used in an amount of about 0.2 to 20% by weight, preferably 0.5 to 10% by weight, based on the colored resin particles, depending on the type of the release agent.

Examples of the foaming agent include the following as an organic foaming agent. Azo system: azodicarbonamide, azobisisobutyronitrile, diazoaminobenzene nitroso system: N, N'-dimethyl N, N'-dinitrosoterephthalamide, N, N'-dinitrosopentamethylenetetramine sulfonyl hydrazide system : Benzenesulfonyl hydrazide, toluene 4-sulfonyl hydrazide, benzene 1,3-disulfonyl hydrazide, diphenylsulfone 3,3'-disulfonyl hydrazide, 4,
4'-oxybis (benzenesulfonyl hydrazide), sulfone hydrazide

These foaming agents may be contained inside the release agent or adhere to the surface, and 1 to 50% by weight of the release agent is used. As a method of adhering a release agent having a foaming agent present on the surface of the colored resin particles, for example, an emulsion of the release agent is formed in the presence of an emulsifier, and the foaming agent is separately dissolved in an organic solvent to form a solution. And, by adding to the emulsion of the release agent, an emulsion of the release agent containing a foaming agent is prepared, and then mixed with the colored resin slurry, and the dispersion system is destabilized by adjusting the pH and electrolyte concentration. A method in which release agent particles are attached to the surface of the colored resin particles in a so-called hetero-aggregated state, and then filtered and dried.

As a method of adhering a release agent having a foaming agent present on the surface of the colored resin particles, for example, the affinity between the release agent and the foaming agent is low, and the foaming agent is contained inside the release agent. Is used when it cannot be impregnated, and includes a method of drying without performing filtration in the above method.

The material for forming the coating layer covering the release agent is required to be a solid and non-sticky material at a temperature of about 50 ° C. or lower in order to ensure the preservability of the toner. It can be used without any problem, but it is desirable that the layer be as thin as possible. Further, a charge control component is added as required. For example, inorganic fine particles, coupling agents, surfactants, charge control agents, various resins, and the like can be mentioned. In particular, a coating layer mainly composed of a thermoplastic resin having a softening temperature lower than the decomposition temperature of the blowing agent is used to prevent offset. Both the effect and the fixing property can be improved, and it is preferably used.
As the thermoplastic resin, the same as the thermoplastic resin used for the colored resin particles can be used. Further, such a thermoplastic resin is preferably copolymerized with a monomer having an anionic group in order to improve the chargeability. Examples of the monomer having an anionic group include (meth) acrylic acid and styrene. Sulfonic acid, (meth) acrylamido-2-methylpropanesulfonic acid and the like can be mentioned. The surfactant may be anionic, cationic, amphoteric or nonionic, but it is important to orient the hydrophobic group on the surface and to consider the chargeability. In the case of a negatively chargeable toner, a fluorine-based surfactant is used. In particular, the fluorine-containing quaternary ammonium salt can improve the chargeability even at high temperature and high humidity. Known coupling agents such as a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent can be used, and the use of a thin layer is preferred. Among the conventionally known inorganic fine particles and charge control agents, those having a particle size of 1 μm or less are used, and it is preferable to use them in combination with a resin or a coupling agent in order to prevent desorption during use.

As a method for forming the coating layer, for example, a method in which colored resin particles having a release agent attached thereto are added to a polymer solution for forming a coating layer, agitated, dispersed, and then dried. A method of polymerizing a polymerizable monomer for forming a coating layer in the presence of particles is exemplified. Further, as a method of providing the coating layer to the extent that the lower layer has an exposed portion, for example, a method of mixing, stirring, and adhering the colored resin particles to which the release agent is adhered and the resin particles for forming the coating layer, and the like are given. However, the proportion of the lower layer exposed portion can be adjusted by appropriately changing the proportion of the resin fine particles for forming the coating layer to be used. At this time, if the ratio of the lower exposed portion is large, the effect of the coating layer cannot be sufficiently exerted, and the ratio of the lower exposed portion to the total surface area is preferably about 5 to 50%.

It is preferable to externally add hydrophobized metal oxide fine particles conventionally known as a fluidity-imparting agent to the toner of the present invention, because this also has the effect of improving transferability. Excessive addition is not preferred from the viewpoint of reliability such as properties, and it is desirable to add a necessary minimum amount. As the fluidity-imparting agent, those obtained by hydrophobizing fine particles such as silica, titanium dioxide, and alumina with various hydrophobizing agents are used.
Usually, the addition amount is 2 to 3% by weight or less.

When the toner of the present invention is used as a two-component developer, it is used by mixing with a carrier powder. As the carrier in this case, all known carriers can be used, for example, iron powder, ferrite powder, magnetic powder such as nickel powder, glass beads and the like, and those obtained by treating these surfaces with a resin or the like. No.

Further, the toner of the present invention further contains a magnetic material and can be used as a magnetic toner. In this case, the magnetic material contained in the magnetic toner includes iron oxide such as magnetite, hematide, and ferrite, metals such as iron, cobalt, and nickel, or aluminum, cobalt, copper, lead, magnesium, tin, and zinc of these metals. ,
Examples include metal alloys such as antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, and vanadium, and mixtures thereof. These ferromagnetic materials have an average particle size of 0.1 to 2 μm.
And about 20 to 200 parts by weight per 100 parts by weight of the resin component.
Particularly preferably, about 40 to 1 to 100 parts by weight of the resin component is used.
50 parts by weight.

[0022]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited thereto. The percentages and parts shown below are all based on weight.

Example 1 Production of Colored Resin Particles First, base particles were produced by a dispersion polymerization method as described below. That is, 320 parts of methanol was placed in a three-necked flask equipped with a stirring blade and a condenser, and 6.4 parts of polyvinylpyrrolidone (average molecular weight: 40,000) was added little by little while stirring to completely dissolve. Further, the following composition was added and completely dissolved. Styrene 25.6 parts n-butyl methacrylate 6.4 parts 2,2'-azobisisobutyronitrile 0.2 parts Then, the inside of the flask is purged with nitrogen gas and polymerized at 60 ° C for 20 hours while stirring at 200 rpm. Styrene / n-butyl methacrylate copolymer particles having a volume average particle size of 7.4 μm were obtained. Oil black 8 in this slurry
03 (manufactured by Orient Chemical Co., Ltd.) was added, and the mixture was heated and stirred at 50 ° C. for 1 hour to color the resin particles. After the colored resin slurry was centrifuged down and the supernatant was removed, the operation of adding 300 parts of ion-exchanged water was repeated 5 times to carry out washing to obtain a colored resin slurry A.

Adhesion of release agent Next, an emulsion was prepared using carnauba wax as a release agent. In 24.0 parts of carnauba wax, 6 parts of a nonionic activator as an emulsifier were melted, and stirred while stirring.
70.0 parts of hot water at ℃ was gradually added to prepare an emulsion of carnauba wax having an average particle size of 0.1 μm. 3 parts of azobisisobutyronitrile as a foaming agent was dissolved in 70 parts of methanol, and this solution was added to the emulsion wax prepared above, and stirred at room temperature for 5 hours to obtain Carnauba was emulsion B containing the foaming agent. The colored resin slurry A and the emulsion B are mixed in such an amount that the solid resin content: the wax solid content becomes 97: 3, the wax fine particles containing a foaming agent are adhered to the surface of the colored resin, and the mixture is filtered and dried to obtain a foamed agent-containing material. Colored particles C having carnauba wax fine particles adhered to the surface were obtained.

Formation of Coating Layer Ethyl methacrylate and the following (formula 1) monomer 93:
0.3 part of 7 copolymer is methanol

Embedded image The resultant was dissolved in 70 parts, the colored particles C were added to the solution, and the mixture was stirred and dispersed. 99.5 parts of the coated layer forming particles and 0.5 part of hydrophobic silica R-972 (manufactured by Nippon Aerosil Co., Ltd.) were stirred and mixed with a mixer for 20 seconds to obtain the toner of the present invention.

Two parts of the toner obtained above were mixed with 98 parts of a carrier obtained by coating ferrite particles having an average particle diameter of 70 μm with a silicon resin, and the mixture was used as a two-component developer. The offset property and the transfer property were evaluated with an experimental machine modified so that the apparatus could be removed and the fixing temperature could be changed. The offset property was examined at a fixing roller temperature of 180 to 230 ° C.
There was no occurrence of offset in the range of 80 to 225 ° C., indicating good offset resistance. The transferability was determined as (transfer toner weight-transfer residual toner weight) / developed toner amount.times.100 (%) three times. The transferability was 90 to 93%, indicating good transferability.

Example 2 Production of Colored Resin Particles 90 parts of a styrene / butyl acrylate copolymer having a weight average particle amount of 100,000 and Tg of 63 ° C. and 10 parts of carbon black were melt-kneaded by a two-roll mill, cooled, and coarsely ground by a stamp mill. Then, the mixture was finely pulverized with a jet mill, and black colored particles D having a volume average particle size of 9.0 μm were obtained by air classification.

Next, an emulsion was prepared using microcrystalline wax as a release agent. In 45 parts of microcrystalline wax, 5 parts of a nonionic activator as an emulsifier were melted, and 50 parts of hot water at 90 ° C. was added with stirring to add an average particle diameter of 0.1 part.
A 2 μm wax emulsion was obtained. Methanol 48
2 parts of p-toluenesulfonyl hydrazide as a foaming agent was dissolved in 100 parts of the mixture, and the solution was added to 100 parts of the microcrystalline wax emulsion prepared above and stirred at room temperature for 5 hours to obtain a microcrystalline wax emulsion E containing a foaming agent. 50 parts of the coloring particles D are dispersed in 50 parts of a 50% aqueous methanol solution, 6.7 parts of wax emulsion E is added, and 0.2 parts of a fluorinated quaternary ammonium salt of the following (Chem. 2) is added to the surface of the coloring particles D. Microcrystalline wax emulsion E containing a blowing agent was applied.

Embedded image

Formation of Coating Layer Further, 0.2 part of methyltrimethoxysilane as a silane coupling agent was added, and the mixture was stirred for 10 minutes, transferred to a stainless steel vat and dried at room temperature under reduced pressure. A coating layer of methyltrimethoxysilane containing a quaternary ammonium salt was formed. 99.5 parts of the coating layer forming particles and 0.5 part of hydrophobic silica R.972 were stirred and mixed with a mixer for 20 seconds to obtain the toner of the present invention.

Hereinafter, a developer was prepared in the same manner as in Example 1 using the same carrier, and the offset property and the transfer property were evaluated in the same manner as in Example 1. Offset property is fixing roller temperature 1
There was no occurrence of offset in the range of 50 to 225 ° C., indicating good offset resistance. The transfer rate was 91 to 92%, indicating good transferability.

Example 3 The following thermoplastic resin fine particles (8 parts) were mixed with the foaming agent-containing carnauba wax fine particles obtained in Example 1 and the following thermoplastic resin fine particles (8 parts) mixed with 92 parts of the colored particles C adhered to the surface. After stirring for 20 minutes in a ball mill with the zirconia balls removed by a sieve, R-972 was removed.
The toner of the present invention was obtained by mixing 0.5% with a mixer. S
Observation of the toner surface by EM confirmed that the resin fine particles were slightly crushed spheres and exposed lower layers. Thermoplastic resin fine particles Potassium persulfate is used as a polymerization initiator, styrene and butyl acrylate are polymerized by soap-free emulsion polymerization, and after polymerization, a copolymer powder obtained by drying by freeze-drying method, Tg 61 ° C, weight average molecular weight 1
20,000, average particle size 0.2 μm.

Thereafter, a developer was prepared in the same manner as in Example 1,
The results of the same evaluation are shown. As for the offset property, no offset occurred in the fixing roller temperature range of 180 to 230 ° C., and even better offset resistance was shown as compared with Examples 1 and 2. The transfer rate was 89 to 91%, indicating good transferability.

Comparative Example 1 The colored resin slurry A obtained in Example 1 was filtered and dried, and then 0.5% of hydrophobic silica R-972 was mixed with a mixer to obtain Comparative Toner 1. As a result of preparing and evaluating the developer in the same manner as in Example 1, the transferability was as good as 91 to 93%, but the offset occurred even at 180 ° C.

COMPARATIVE EXAMPLE 2 Carnauba emulsion containing no foaming agent and no coating layer was formed in Example 1, that is, after the carnauba wax emulsion containing no foaming agent was attached to the colored slurry A, The filtered and dried particles were mixed with 0.5% of hydrophobic silica R-972 by a mixer to obtain Comparative Toner 2. As a result of preparing and evaluating the developer in the same manner as in Example 1, the offset was 180 to 230.
Although no good results were obtained in the temperature range of ℃, the transferability was 3
The image after transfer was as poor as 8%, and the image after transfer was also very poor with uneven density.

Comparative Example 3 Colored particles C having the foaming agent-containing fine particles of carnauba wax obtained in Example 1 adhered to the surface thereof were filtered and dried, and then 0.5% of hydrophobic silica R-972 was mixed with a mixer. Thus, Comparative Toner 3 was obtained. Comparative toner 3 is the same toner as in Example 1 except that it does not have a coating film covering the release agent. A developer was prepared and evaluated in the same manner as in Example 1. As a result, good results were obtained without offset occurring in the range of 180 to 230, but the transferability was poor at 42%, and the image was a comparative example. It was as poor as 2.

Comparative Example 4 A toner was prepared in the same manner as in Example 1 except that the foaming agent was not contained in the carnauba wax emulsion, and Comparative toner 4 was obtained. When a developer was prepared and evaluated in the same manner as in Example 1, no hot offset occurred from 180 to 200 ° C., but from 205 ° C. to 23 ° C.
Hot offset occurred at 0 ° C., and although there was offset resistance, it could not be said that there was sufficient margin. The transferability was a good result of 91 to 93%.

[0037]

According to the toner for developing an electrostatic image of the present invention, at least a releasing agent having a foaming agent present on the surface or inside thereof is attached to the surface of the colored resin particles, and a coating layer is further provided on the outer layer. Thus, the toner has excellent offset resistance in hot roll fixing and excellent transferability. In particular, when the coating layer is provided so as to have the lower layer exposed portion, the offset resistance is further improved.

Claims (2)

(57) [Claims] The present invention is characterized in that a release agent having at least a foaming agent present on the surface or inside thereof is attached to the surface of the colored resin particles, and a coating layer is provided on the outer layer so as to cover the release agent. An electrostatic image developing toner. 2. The electrostatic image developing toner according to claim 1, wherein the coating layer covering the release agent is mainly composed of resin fine particles and provided so as to have a lower layer exposed portion.