JP2578489B2 - Two-component dry developer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component developer containing a dry-type negatively chargeable color toner for developing an electrostatic latent image in electrophotography or electrostatic printing. . More specifically, in a developer comprising a negatively chargeable color toner and a carrier,
The present invention relates to a novel two-component dry developer capable of maintaining good chargeability even after repeated use.

(Prior art)

Conventionally, electrophotography has been described in U.S. Pat. No. 22,917,691 and Japanese Patent Publication No. 42-23910 (U.S. Pat. No. 3,666,363).
And Japanese Patent Publication No. 43-24748 (U.S. Pat.
Numerous methods are known as described in, for example, JP-A-71,361), and in general, an electric latent image is formed on a photoreceptor by various means using a photoconductive substance, and then the latent image is formed. The latent image is developed using a colored fine powder called a toner having an opposite charge and transferred to a transfer material such as paper as necessary, and then fixed by heating, pressure, heat pressure or solvent vapor, and copied. Get things.

In the development, as a toner to be used, generally, a colorant is mixed with a thermoplastic resin under heat melting, then finely pulverized, and classified if necessary, and a fluidity imparting agent such as silica fine powder is further used. The added one is used. As the thermoplastic resin, a styrene resin, a polyester resin, an epoxy resin, an acrylic resin, a urethane resin, or the like, or a styrene-acrylic copolymer and a styrene-methacrylic copolymer are widely used. As the colorant, various dyes and pigments are used. In the case of a magnetic toner, magnetic particles such as magnetite are used, and in the case of a color toner, a nonmagnetic toner containing only a chromatic dye and pigment is often used.

Further, in order to obtain a negatively charged toner, a negative charge control agent (for example, a thermoplastic resin having a negative polarity (for example, a polyester resin) is used as a binder resin or as a resin dispersed in the binder resin. When a metal-containing azo dye) is used, or when a fluidity-imparting agent having a negative polarity (for example, silica fine powder) is used as an external dye of the toner, the carrier particles are further charged to the positive polarity side than the toner particles on the charging series. There is a case where a material which is greatly separated (for example, an acrylic resin-coated carrier) is used, and a negatively chargeable toner is generally obtained by a combination thereof.

However, the conventional negatively chargeable toner as described above has the following serious problems because the chargeability of the toner is unstable or uneven.

(A) The development characteristics of the toner are largely dependent on the environment and humidity.

(B) The developing characteristics of the toner are deteriorated by repeated use. That is, the durability is poor.

(C) The toner characteristics deteriorate with time due to long-term storage.

(D) There is a large amount of toner scattering at the time of development, which may cause contamination in a copying machine or the like.

For example, depending on the dye or pigment selected as the colorant,
Alternatively, depending on the binder resin selected, poor dispersion of the colorant in the binder resin occurs, the content of the colorant differs between toner particles, or fine powder of only the colorant is generated by pulverization, The charging characteristics of the toner become non-uniform.

Further, since the color toner does not contain a low-resistance substance such as a magnetic powder and a carbon black, the charge amount of the toner tends to be excessive.

To address these problems, see, for example, JP-A-61-94059.
In the gazette, by using a binder resin crosslinked polymer,
Attempts have been made to improve the dispersion of the colorant,
Japanese Patent Application Laid-Open No. Sho 60-49344 discloses an attempt to disperse a resistance adjusting substance of 10 ¹³ Ω or less in a binder resin to prevent a toner from being charged.

However, according to the study by the present inventors, a large amount of a crosslinking agent having a polymerizable double bond is added (2% by weight based on resin).
), The pigment dispersion is rather deteriorated, the compatibility with other polymers is deteriorated, and the like, thereby deteriorating the charging characteristics of the toner when formed into a toner. Regardless of whether the binder resin has a crosslinked structure or not, the thermal melting characteristics of the binder resin in the kneading and dispersing step of the dye / pigment to the binder resin are rather important. It has been found that the method of imparting the characteristic is more preferable.

On the other hand, lowering the resistance of the toner by the resistance adjusting substance certainly has an effect on charging up of the toner in a low humidity environment, but the charge amount of the toner decreases for a long time in a high humidity environment or a normal humidity environment. Yes, (C),
The problem (D) remains. Also, when used for color toner,
There was a dullness in the image and it was disadvantageous to obtain clear chromatic colors.

Another important point for the toner charging behavior is that
It is a charging characteristic of an externally added toner when an external additive is added.
One of the important functions of the external additive is to impart fluidity to the toner, which makes it possible to smooth the frictional charging between the toner and the carrier particles and achieve good charging of the toner. Specifically, silica fine particles having a particle size of submicron or less are widely used. JP
Japanese Patent Application Laid-Open No. 62-174773 discloses that when the charge amount of the externally added toner becomes more than twice that of the non-externally added toner particles in frictional charging with the carrier, the charge amount does not decrease even after long-term repetition and the stable charging characteristics are maintained. I can do it. However, according to studies by the present inventors, in the case of a negatively chargeable toner, the charge amount of the externally added toner due to frictional charge with the carrier due to the fact that the silica fine particles are themselves negative polarity and the surface area is enormous. When the development is carried out in a low humidity environment or in continuous repetition, the developing ability is reduced.On the contrary, the external silica is easily affected by the moisture absorption of the externally added silica under high humidity and after long-term storage. There is a problem such as an increase in ground fog due to an extreme decrease in the charge amount of the attached toner, and the environmental stability is not necessarily improved.

Conventionally, studies have been made on the hydrophobization treatment and reduction of the resistance of silica, and on the study of fluidity-imparting agents other than silica. However, there are still points to be improved.

Moreover, recently, aiming at improving the image quality by full-color reproduction or multi-color reproduction, the developing method is to use a two-component developer using magnetic particles with high resistance as an insulating resin as carrier particles under the development area of 5 to 100 mg / mg. A method of developing an electrostatic latent image while applying an alternating electric field by arranging it with a small amount of cm ² has been put to practical use. And the development efficiency is greatly improved. Further, as a carrier used for such a developing method, a carrier obtained by coating an insulating resin on the surface of magnetic particles made of a ferromagnetic material such as iron, nickel, or ferrite is generally used.

However, as conventionally studied, the coating material has to have a releasing property to the toner in order to suppress the toner from being spent while maintaining the adhesiveness and the coating property to the core material particles. Have. In recent years, in order to further improve image quality, toners and carriers have tended to be reduced in particle size. In particular, when the toner is subjected to the above-described developing method, the carrier adheres (the carrier particles adhere to the image portion and the non-image portion of the latent image carrier). This itself causes the transfer of the magnetic restraining force of the development carrier to move and adheres thereto, and the like, and the problem of unstable charging of the carrier to the toner (especially charging up).

[Object of the invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a specific negatively chargeable color toner in which the charging characteristics of the externally added toner are less affected by the external additive, and An object of the present invention is to provide a two-component developer having at least an agent and a specific carrier.

Further, an object of the present invention is to have at least a specific negatively-chargeable color toner, a fluidizing agent, and a specific carrier, which are less dependent on the environment for developing characteristics of the toner and can maintain initial developing characteristics even when used repeatedly. An object of the present invention is to provide a two-component developer.

It is a further object of the present invention to provide a two-component type developer having a negatively chargeable color toner which causes little aging and deterioration of the toner under long-term storage or high humidity, that is, has a small attenuation of the charge amount of the toner. .

It is a further object of the present invention to provide a two-component developer having a chromatic, negatively-chargeable color toner with a clear tint.

Further, an object of the present invention is to provide a resin-coated carrier which exhibits excellent adhesiveness to a carrier core material, and at the same time exhibits excellent release properties to a toner, and is improved with respect to release of a coating material and spent toner. To provide a two-component developer having the following formula:

It is a further object of the present invention to provide a two-component developer having a resin-coated carrier with improved carrier adhesion to the latent image holding layer.

It is a further object of the present invention to provide a two-component developer having a resin-coated carrier which is stable in quality and has little rotting.

[Summary of the Invention]

The present invention provides: (i) a negatively-chargeable binder resin; a metal complex of salicylic acid, alkylsalicylic acid or dialkylsalicylic acid; and a positively-chargeable colorant treated with a homopolymer or copolymer of a nitrogen-containing vinyl monomer. (Ii) a fluidizing agent, and (iii) the carrier core material has a critical surface tension of 30 dyn / cm.
Is a two-component dry developer containing a resin-coated carrier coated with an electrically insulating resin having a critical surface tension of 30 dyn / cm or more and a carrier core material having a critical surface tension of 30 dyn / cm or more. An externally added color toner having a particle size distribution in which the content of carrier core particles having a particle size of less than 1/10 of the average particle size is 2% by weight or less, and the fluidizing agent is externally added. The ratio [A] / [B] of the triboelectric charge amount [B] to the resin-coated carrier and the triboelectric charge amount [A] to the resin-coated carrier of an unexternally added color toner not externally added with a fluidizing agent is: The present invention relates to a two-component dry developer, which is larger than 0.5 when mixed for 30 seconds under the same mixing conditions.

The two-component dry developer of the present invention is a developer composed of a specific negatively chargeable color toner and a specific carrier, wherein the toner is obtained by externally adding a fluidizing agent to toner fine powder, and The ratio [A] / [B] of the triboelectric charge [B] to the toner and the triboelectric charge [A] to the carrier of the toner fine powder without externally adding a fluidizing agent is [A] / [B] by mixing for 30 seconds under the same mixing conditions. It is a value larger than 0.5, characterized in that the rise of the charge amount of the non-externally added toner is made as close as possible to the rise of the charge amount of the externally added toner.

That is, by increasing the frictional charging ability between the unexternally added toner and the carrier relative to the frictional charging ability between the fluidizing agent and the carrier, the fluidizing agent mainly composed of silica having a strong negative polarity is externally added. Even in the negatively charged toner, the fluidizer is preferentially adsorbed on the carrier surface, so that the toner can be smoothly taken in and released from the carrier particles, and good and stable development characteristics can be achieved. You.
Further, the charge amount of the once charged toner is not reduced, and good development characteristics with little fog can be maintained even when the toner is left for a long period of time and under high humidity.

[Specific description of the invention]

As the configuration of the negatively chargeable color toner according to the present invention,
In a thermoplastic resin that is electrically negatively charged as a binder resin,
A salicylic acid, an alkylsalicylic acid or a di-alkylsalicylic acid in which a negative charge control agent and an electrically positive colorant are dispersed, and the negative charge control agent ionically crosslinks the binder resin during hot kneading with the binder resin. Wherein the colorant is a pigment which is coated with a homopolymer or copolymer of a nitrogen-containing vinyl monomer and is electrically positively charge-enhanced. The dispersion of the control agent becomes good.

As the usable binder resin, those having an electron-withdrawing functional group or a polar functional group in the main chain or side chain in the molecule can be used. Particularly, those having a carbonyl group and a carboxylic acid group are preferred, and polyester is most preferred.

The charge amount of the binder resin is in the range of −10 to −100 μc / g, preferably −20 to −60 μc / g. When the number of electron-withdrawing functional groups or polar functional units is extremely small, the charge amount of the resin is substantially −10 μc / g or less, and one of them impairs the dispersibility of the positively charge-enhanced colorant of the present invention. One is that the charge control agent of the present invention impairs the ionic crosslinking property of the binder resin due to heat, and similarly, the dispersibility of the colorant and the compatibility of the charge control agent with the binder resin are reduced, and the toner is charged. The characteristics will be degraded.

More specifically, polyesters composed of at least an etherified diphenol monomer and a dicarboxylic acid monomer are mentioned. In consideration of fixing property and offset property, a polycarboxylic acid or a polyhydric alcohol is added to obtain a non-linear polyester. A succinic acid or an anhydride thereof substituted with an alkyl or alkenyl group having 6 to 18 carbon atoms may be added as a soft segment.

Examples of the etherified diphenol monomer include polyoxinpropyne (2.2) -2,2-bis (4-hydroxyphenylpropane; polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) ) Propane; polyoxypropylene (6) -2,2-bis (4-hydroxyphenyl)
Propane; polyoxyetalene (6) -2,2-bis (4
-Hydroxyphenyl) propane; polyoxypropylene (1.3) -2,2-bis (4-hydroxyphenyl) propane; polyoxyethylene (1.3) -2,2-bis (4-hydroxyphenyl) propane and the like. Is exemplified.

Examples of the dicarboxylic acid monomer include aromatic dicarboxylic acids such as terephthalic acid, inphthalic acid, phthalic acid, diphenyl-p, p'-dicarboxylic acid, and maleic acid, malonic acid, citraconic acid, itaconic acid, and maleic anhydride. And aliphatic unsaturated dicarboxylic acids such as succinic acid, adipic acid and sebacic acid. Examples of the polycarboxylic acid monomer include trimellitic acid, pyromellitic acid, cyclohexanetricarboxylic acids, and 2,5,7-naphthalenetricarboxylic acid. As polyhydric alcohol monomers, sorbitol, 1,2,3,6-hexanetetol, pentaerythritol of 1,4-sorbitan,
Glycerin and the like can be exemplified.

Examples of the succinic acid substituted with an alkyl or alkenyl group having 6 to 18 carbon atoms as a soft segment include succinic acid having an n-dodecyl group, an n-dodecenyl group, an isododecyl group, an isododecenyl group, or an n-octyl group. Etc. can be exemplified.

In addition, as those containing a carbonyl group and a carboxylic acid group,
Styrene-based or styrene-acrylic resins can also be used, and monomers such as n-butyl acrylate, methyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate are used in combination with monomers such as styrene, vinyl styrene, and chlorostyrene. Polymerized products, furthermore, those obtained by copolymerizing an acid containing a vinyl group such as maleic acid, microconic acid, microconic acid, itaconic acid, acrylic acid, or a partially esterified product thereof can be used.

As the colorant that can be used in the present invention, a chromatic pigment or dye which is coated with a homopolymer or a copolymer of a nitrogen-containing vinyl monomer and has a positively charged property can be used. The dye or pigment to be treated, BET specific surface area by nitrogen adsorption method 0.1m ² / g~300m ² / g, preferably
Was 1.0m ² / g~100m ² / g, conventionally known pigments, for example anthraquinone, quinacridone, phthalocyanine, perylene-based, perinone-based, various organic pigments and chrome azo such as ultramarine, etc. Prussian Various inorganic pigments can be used.

Further, the charge amount of the colorant obtained by the above treatment is preferably at least +5 μc / g or more, more preferably +10 μc / g or more (more preferably +15 to +60 μc / g) than that of the binder resin. Are particularly preferred.

The coloring agent having the same or stronger negative polarity as the negative binder resin used in the present invention causes poor dispersion, poor color when formed into toner, and further rises in the charge amount of the externally added toner. Supposedly, when the toner is externally added, the toner is easily affected by silica, and the charge amount of the externally added toner becomes excessive.

Some dyes and pigments have a negative polarity due to their chemical structure and the like.In such cases, coating treatment with a homopolymer of a nitrogen-containing vinyl monomer or a copolymer of a nitrogen-containing vinyl monomer is performed to obtain a positive polarity. It is necessary to enhance the charge.

Specific examples of the nitrogen-containing vinyl monomer include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate,
Examples thereof include n-propylaminoethyl methacrylate, diethylelaminoethyl acrylate, monomethylaminoethyl methacrylate, monomethylaminoethyl methacrylate, monophenylaminoethyl methacrylate, diphenylaminoethyl methacrylate, and the like. Copolymers such as an acrylic monomer, a still monomer, and a butadiene monomer are exemplified, and a homopolymer of diethylaminoethyl methacrylate and a copolymer of diethylaminoethyl methacrylate-methyl methacrylate are particularly preferable in terms of chargeability.

As a specific treatment method, for example, in an aqueous solution containing a surfactant, a polymer emulsion obtained by adding the above monomer and emulsion polymerization is added to an aqueous chiller of a dye / pigment, or subjected to a heat treatment, or A method in which the pH of an aqueous chiller of a dye / pigment is made acidic, a polymer emulsion is added, the pH is shifted to an alkaline side, and the polymer or copolymer is precipitated on the surface of the dye / pigment, or a method combining the both. However, the deposition coating method using pH is more preferable because it can perform a more robust treatment and does not cause separation of the treated material. Although the treatment amount cannot be specified unconditionally due to the difference in the surface area of the dye / pigment, it is preferably 0.5 to 20% by weight based on the dye / pigment.

The charge control agent usable in the present invention has a charge amount of −20 μc / g or less (more preferably, −30 to −8).
0 μc / g), and those which are ionically cross-linked during hot kneading with a resin having an acid group, and are metal complexes of salicylic acid, alkyl salicylic acid or di-alkylsalicylic acid, and the metal species is Cr, Al , Zn, Fe, Co, Cu, Mn, etc.
In particular, a Cr complex is preferable. The amount of addition can be 0.5 to 10 parts by weight to the binder resin, more preferably 2 to 10 parts by weight.
5 parts by weight. If the amount is less than 0.5 part by weight, the crosslinking of the binder resin is insufficient at the time of hot kneading, resulting in poor kneading and poor dispersion of the colorant.If the amount is more than 10 parts by weight, the crosslinking density becomes too high and the rubber elasticity of the toner melt becomes too high. Is lost, resulting in poor dispersion of the colorant, which further deteriorates the fixability of the toner.

As the constitution of the resin-coated carrier according to the present invention, the core particles are substances that are strongly magnetized in the direction by a magnetic field as described later, and particles having a weight-average particle diameter aμ of less than 1/10 are included in the entire core material. Insulating resin that has been removed to less than 2% by weight and the coating resin has a critical surface tension of less than 30 dyn / cm
It is a mixture of R ₁ and an insulating resin R ₂ of 30 dyn / cm or more, and the mixture ratio is R ₂ / (R ₁ + R ₂ ) = 0.5 to 0.9 in weight ratio.
It is preferred that

That is, according to the study of the present inventors, the carrier core material itself is granulated with 0.1 to 10 μm carrier particles and fired,
Inevitably, a grain boundary is formed, and the generation of fine core particles less than 1/10 of the weight average particle diameter aμ cannot be avoided by crushing and sieving for adjusting the particle size thereafter. The presence of such a core material hinders uniform coating properties of the coating resin, and as a result, there are carrier particles having an excessively large charging ability and a small magnetization force, thereby deteriorating the charging characteristics of the toner ( According to the findings of the present inventors, A / B is reduced) and carrier adhesion is increased.

In addition, by applying a polymer blend of a resin having a different critical surface tension as a coating resin, in the process of removing the solvent, a phase separation of the polymer occurs, and in the vicinity of the carrier core material, the critical surface tension is large, that is, the carrier core material is removed. A polymer with good wettability is present in the lith, while a polymer with a low critical surface tension is likely to be present in the lith near the carrier surface. Carriers that are difficult to perform and have a strong film are achieved. Carrier polymer blends of R ₂ / R ₁ + R ₂ = 0.5 to 0.9 in the critical surface tension mixing ratio by weight of 30 dyn / cm ² less than the resin R ₁ and 30dym / cm ² or more resins R ₂ in the present invention 1/10 of the weight average particle size of the core material
Particularly preferred results are obtained by coating less than 2% by weight of the fine powder of the entire carrier core material. When R ₂ / R ₁ + R ₂ = 0.5 or less, the adhesion to the carrier core material is reduced, the resin coating is defective, the charging characteristics for the toner are deteriorated, and the carrier has a low resistance. It is easy to occur. Conversely, R ₂
If / R ₁ + R ₂ = 0.9 or more, spent is likely to occur.

Specifically, in the present invention, the magnetic carrier core particles have a weight average particle diameter aμ, and the content of the magnetic carrier core particles having a particle diameter of less than a / 10 μm is 2% by weight or less, the critical surface tension rising magnetic carrier core particle is coated with a mixed composition of 30 dyn / cm less than the electrical insulating resin R ₁ and critical surface tension 30 dyn / cm or more electrically insulating resin R _2, the resin
R ₁ and the resin R ₂ and the mixing weight ratio of 5: 5 to 1: a is that it is preferable to use a resin Kotokiyaria electrostatic image developer 9.

The resin-coated carrier of the present invention is obtained by classifying a magnetic carrier core material and has a weight average particle size of aμ and a content of magnetic carrier core material particles having a particle size of less than a / 10 μm is 2% by weight.
The magnetic carrier core particles or less prepared, prepared magnetic carrier core material particles critical surface tension electrically insulating resin R ₁ and critical surface tension of less than 30 dyn / cm 30 dyn / cm or more electrically insulating resin R ₂ mixture composition (mixing weight ratio 5: 5 to 1: 9)
It is preferable to adjust by coating treatment.

In the method for producing a carrier according to the present invention, the carrier core is preferably calcined, crushed, and sieved (removal of coarse and fine powders with a mesh filter), and then fines and ultrafines of the carrier are removed by air classification.

That is, according to the study by the present inventors, fine powder and ultrafine powder having a particle diameter of less than 1/10 of the weight average particle diameter aμ are generated during firing-crushing of the carrier core material. These fine powders and ultrafine powders themselves have high cohesive strength and cannot be completely removed by the usual sieving, and are mixed in 3% by weight or more (usually 3 to 6% by weight) of the total amount. . The mixture of the fine powder and the ultrafine powder in the carrier core material causes a coating failure of the insulating resin and further hinders the increase in the resistance of the carrier.

In other words, the ability to provide a triboelectric charge on the toner is reduced, and a good charge state cannot be provided to the toner particles.

Further, when a latent image is formed, adverse effects such as the above-described adhesion of the carrier occur.

On the other hand, by removing such ultrafine powder, the resin coat of the carrier core material is made uniform, and production and quality can be stabilized.

As a means for removing ultrafine powder, air classification is the most efficient and can be performed at low cost.

In the present invention, the weight average particle diameter and the particle size distribution of the carrier core particles refer to values measured using, for example, a microtrack (model 7995) manufactured by Nikkiso Co., Ltd.

The weight average particle size of the magnetic carrier core particles is 25 to 100 μm.
m, preferably 30 to 80 μm. 25μ weight average particle size
If it is less than m, the carrier easily adheres to the electrostatic image carrier such as the photosensitive drum. When the weight average particle size exceeds 100 μm, it is difficult to uniformly apply a triboelectric charge to the toner, the amount of the toner taken in decreases, the development efficiency decreases, and the image quality (resolution) decreases. In the present invention, the carrier core particles after classification have a weight average particle diameter aμ.
The content of fine or ultrafine core particles having a particle size smaller than 1/10 is 2% by weight or less, preferably 1% by weight
The following is good.

Further, it is preferable that the core material particles have a particle size distribution of 60% by weight or more, preferably 65% by weight or more in a range of ± 10 μm of the weight average particle diameter aμ, and have a sharp particle size distribution. Weight average particle size aμ
When the core material particles are less than 60% by weight in the range of ± 10 μm, the two-component developer prepared by mixing the coarse carrier and the small carrier with the toner has a triboelectric charge to the toner. , The charge amount of the toner becomes non-uniform, and the developing characteristics, fine line reproducibility and durability are reduced.
Further, the content of the carrier core particles having a particle diameter of +30 μm or more of the weight average particle diameter aμ is preferably less than 5% by weight. When the content of the coarse particles is 5% by weight or more, the ability to impart triboelectric charge to the toner becomes non-uniform, and the occurrence of fogging and adhesion of the carrier are liable to occur.

As the material of the carrier core material used in the present invention, a substance which is strongly magnetized in its direction by a magnetic field, for example, a ferromagnetic metal such as ferrite, magnetite, iron, cobalt, nickel or the like, or a metal having such ferromagnetism Alloys that do not contain a compound or a ferromagnetic element, but exhibit ferromagnetism when appropriately heat-treated. The carrier core particles preferably have a spherical shape in terms of developing characteristics and fluidity.

As a method for removing the ultrafine powder from the carrier core material, an ordinary air classifier can be used after sieving. More preferably, it is preferable to use a DS classifier which has good productivity and can easily change the classification point.

Using the above air classifier, fine powder or ultra fine powder of 1/10 or less of the weight average particle size of the carrier core material is 2% by weight of the total amount.
Or less, more preferably 1% by weight or less.

The second feature of the present invention is that the insulating resin coating the classified carrier core particles has a critical surface tension.
Consist of a mixture of 30 dyn / cm less than the insulating resin R ₁ and 30 dyn / cm or more insulating resin R _2, preferably, the ratio of the resin R ₁ and _{R 2 (R 1: R 2} ) is 5: 5 : 9.
By selecting the above-mentioned carrier coating material, the adhesive force to the carrier core material, the mechanical strength, the coating property are increased, and it is possible to have the releasability of the carrier particles and the toner particles.

That is, by the resin R ₁ below critical surface tension 30 dyn / cm is present in the carrier surface, keeping the releasability of the toner, the toner adheres to the carrier surface, the deterioration prevention of the charge-imparting ability to toner carrier plays and a critical surface tension 30 dyn / cm or more resins R ₂ provides a carrier having a mechanical strength having adhesion to the carrier core particles.

In general, in the process of applying the resin mixture of the present invention to the carrier core particles and removing the solvent, polymer phase separation occurs, and near the carrier core, the critical surface tension is large, that is, the carrier core is wetted. there sex good resin R ₂ is Ritsuchi, whereas the carrier surface vicinity, the critical surface tension small resin R ₁ is likely to exist in Ritsuchi.

The present invention is characterized by easily providing a resin-coated carrier having the above-described carrier characteristics by selecting a material based on a measure of the wettability of the resin, namely, the critical surface tension of the carrier-coating material.

Resin R ₁ below critical surface tension 30 dyn / cm is reduced adhesion between the carrier core particles exceeds 50 wt%, from defects in the coating property is lowered carrier coating carrier, the frictional charging characteristics of the carrier particles Adversely affect

On the other hand, resin R _{1 having} a critical surface tension of less than 30 dyn / cm, 10% by weight
If it is less than the above, the resin-coated carrier surface does not become a low-energy surface, and toner adheres and fuses on the carrier surface,
The ability to impart charge to the toner is reduced, causing a reduction in image density and fogging.

As described above, the present invention is to provide a carrier without rotting which is excellent in carrier covering property by combining ultra-fine powder removal of the carrier core material and mixing and using at least two kinds of coating resins having different wettability. Features.

The carrier core particles obtained by removing the fine powder and ultrafine powder obtained as described above are then coated with an insulating resin.

In the present invention, the insulating resin has a volume resistance value of 10 ¹² Ω.
Cm or more, preferably 10 ¹³ Ω · cm or more. Insulating resin for coating the carrier core particles consist of a mixture of the resin R ₁ and 30 dyn / cm or more resins R ₂ less than the critical surface tension of 30 dyn / cm, more preferably the critical surface tension of the resin R ₁ is 28dyn / cm or less.

The resin R ₁ below critical surface tension 30 dyn / cm to provide a low energy surface, it is preferable to use the following such a fluorine-based resin, or silicon resin.

As the fluorine resin, polyvinyl fluoride (critical surface tension γ
c = 28dyn / cm), polyvinylidene fluoride (γc = 25dyn / c)
m), polytrifluoroethylene (γc = 22 dyn / cm),
Those having a critical surface tension of 30 dyn / cm or less such as polytetrafluoroethylene (γc = 18 dyn / cm) and polyhexafluoropropylene (γc = 16.2 dyn / cm) can be used. In addition, copolymers of vinylidene fluoride and acrylic monomer, copolymers of vinylidene fluoride and vinyl fluoride, copolymers of vinylidene fluoride and tetrafluoroethylene, vinylidene fluoride and hexafluoro Resins having a critical surface tension of less than 30 dyn / cm such as copolymers with propylene, fluoroterpolymers such as terpolymers of tetrafluoroethylene with vinylidene fluoride and non-fluorinated monomers can be used. These resins, if it is less than the critical surface tension of 30 dyn / cm, can be used as the resin R ₁ individually or in combination.

The resin R ₂ larger than the critical surface tension of 30 dyn / cm combined with the resin R ₁ below critical surface tension 30 dyn / cm, there is a resin synthesized from the following such monomers. For example, styrene, p
Styrene such as chlorostyrene, p-dimethylamino-styrene and its substituted products; acrylic acid or methacrylic acid such as methyl acrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, NN-dimethylaminoethyl methacrylate; Esters; maleic anhydride half-esters, half-amides; nitrogen-containing vinyls such as diesteroid vinylpyridine and N-vinylimidazole; vinyl chloride; vinyl monomers such as acrylonitrile and vinyl acetate; vinylidene monomers such as vinylidene chloride; ethylene and propylene Olefin monomer.

To partially exemplify the critical surface tension of the resin composed of the above monomer, polystyrene has γc = 33 dyn / cm, polymethyl methacrylate has γc = 39 dyn / cm, polyvinyl chloride has γc = 39 dyn / cm, Polyvinylidene chloride is γ
c = 40 dyn / cm, and polyethylene has γc = 31 dyn / cm.

In addition, polyesters, polysulfonates, polyamides, polyurethanes, polycarbonates, polyureas, epoxy resins, rosins, modified rosins, terpene resins, phenolic resins, fatty acid or alicyclic hydrocarbon resins, aromatic petroleum resins, melamine resins, A homopolymer or copolymer such as a polyether resin such as polyphenylene oxide or a thioether resin, or a mixture thereof as long as the critical surface tension is 30 dyn / cm or more, can be used as the resin B.

Wire carrier ratio of the rear quotes queuing resin R ₁ and the resin R ₂ is preferably 5: 5 to 3: 7 in the range of.

The carrier coating method of the present invention includes an immersion method,
Spray method and fluidized bed method are preferred. The organic solvent used here is not particularly limited as long as it can dissolve the resin, but a mixed solvent obtained by combining a good solvent and a poor solvent can also be used.

The carrier of the present invention is manufactured through a resin coating, followed by a heat drying or curing step.

The coating amount of the insulating resin on the carrier core particles of the present invention is sufficient to form at least a substantially continuous resin film on the surface of the carrier core particles. % By weight, preferably 0.5 to 3% by weight.

 Hereinafter, the present invention will be described in detail with reference to Production Examples and Examples.

[Production Example 1] Method for producing polyester A The mixture was placed in a two-container, four-necked, round-bottomed flask equipped with a thermometer, a stirrer made of stainless steel, a nitrogen inlet tube made of glass, and a falling ondenser. Next, the flask was placed in a mantle heater, nitrogen gas was introduced from a glass introduction tube, and the inside of the reactor was heated to an inert atmosphere. Then add 0.10 g of dibutyltin oxide and keep at 210 ° C
A co-condensation polymerization reaction was performed for 12 hours to obtain a polyester resin. The charge amount was -42 μc / g.

[Production Example 2] Production method of styrene-acrylic resin A 2,4 equipped with thermometer, glass nitrogen inlet tube, stainless steel stirrer and water-cooled Jimroth type condenser
420 g of xylene was placed in a round-bottomed one-necked flask, and the temperature was raised to the xylene reflux temperature using an oil lot with a heater. The above mixture was added dropwise thereto under reflux over 3.5 hours. After dripping 4
The polymerization reaction was carried out for a period of time, and then the solvent was removed by ordinary vacuum distillation to obtain a polymer. The charge amount of the obtained polymer is -31 μ
c / g.

[Production Example 3] Production method of styrene-acrylic resin B A polymer was produced in the same manner as in Production Example 2 except that monobutyl maleate was removed. The charge amount of the polymer is -5
A μc / g polymer was obtained.

[Production Example 4] Method for producing blue pigment A A polymer emulsion emulsion-polymerized in an aqueous solution of diethylaminoethyl methacrylate was mixed with a copper phthalocyanine pigment classified into CI74160 and contained in an aqueous slurry adjusted to pH about 4.0 by weight of solid content. The mixture was added in a ratio of 3: 100, and then heated to 80 ° C. with stirring, the pH was further raised to about 10.5, and the coating was performed with washing, drying, and disintegration, followed by coating with a diethylaminoethyl methacrylate polymer. A blue pigment A was obtained. Its BET specific surface area was 50 m ² / g, and the charge amount was +45 μc / g. Incidentally, the untreated pigment had a BET specific surface area of 59 m ² / g and a charge amount of +12 μc / g.

[Production Example 5] Production method of red pigment B A red pigment having the following structural formula classified into CI12370 was coated with a diethylaminoethyl methacrylate-methyl methacrylate copolymer in the same manner as in Production Example 4 to obtain a red pigment. B was obtained.

 However, the treatment amount was 10% by weight based on the pigment.

The BET specific surface area of the treated red pigment B was 40 m ² / g, and the charge amount was +20 μc / g. Incidentally, the untreated pigment had a BET specific surface area of 65 m ₂ / g, and the charge amount was −23 μc / g.

[Production Example 6] Production method of Chiaria A Ferrite raw material containing Fe ₂ O ₃ and ZnO as main components was granulated.
After drying and firing, a spherical magnetic ferrite carrier core material was produced. The agglomerates of the carrier core material are crushed and knotted, containing 67% by weight of particles having a weight average particle size of 52 μm, having a weight average particle size of 52 ± 10 μm, and containing 1.2% by weight of particles having a particle size of 82 μm or more. To obtain a carrier core material.

However, as can be seen in the SEM photograph, the ferrite fragments less than 1/10 of the weight average particle size (fine and ultrafine)
Existed.

This fine powder and ultrafine powder are 4% by weight of the total amount of the carrier core material.
Existed.

The above carrier core was subjected to air classification using a DS classifier to obtain spherical magnetic ferrite carrier core particles having a weight average particle diameter of 53 μm. The core material particles have a content of particles of less than 5.3 μm of 0.3% by weight, 68% by weight of particles in the range of 43 to 63 μm, and a content of particles of 83 μm or more of 1.1%.
% By weight. When the spherical magnetic ferrite carrier core particles obtained by the classification were observed with an electron microscope, they did not substantially contain fine powder and ultrafine powder.

A critical surface tension of 30 dy is applied to the carrier core material thus obtained.
Resin R ₁ of less than n / cm is a copolymer of vinylidene fluoride and tetrafluoroethylene (γc = 21.5 dyn / cm, volume resistivity = 10 ¹⁶ Ω · cm), resin with a critical surface tension of 30 dyn / cm or more As a styrene-methyl methacrylate resin (γc =
35.8 dyn / cm, volume resistivity = 10 ¹⁵ Ω · cm) were mixed at a weight ratio of 4: 6, and a coating solution dispersed and dissolved in methyl ethyl ketone was sprayed and coated with the carrier core particles in a fluidized bed state. After coating, a heat treatment was performed at an ambient temperature of 150 ° C. for 3 hours to obtain a resin-coated carrier A.

By spraying and coating the coating solution, the carrier core material was coated with 1 wt% of resin solid content to obtain Carrier A.

[Production Example 7] Method for producing carrier B Carrier B was obtained in the same manner as in Production Example 6, except that the core of the carrier was not subjected to wind classification.

[Production Example 8] In Production Example 6, a copolymer of vinylidene fluoride and tetrafluoroethylene as a resin having a critical surface tension of less than 30 dyn / cm ² and styrene-methyl methacrylate as a resin having a critical surface tension of 30 dyn / cm ² or more were used. Carrier C was obtained in the same manner except that the mixing weight ratio with the polymer was 7: 3.

[Production Example 9] Carrier D was obtained in the same manner as in Production Example 6, except that only a resin styrene-methyl methacrylate copolymer having a critical surface tension of 30 dyn / cm ² or more was coated.

[Example 1] The mixture was hot-kneaded with a twin-screw extruder kneader, cooled, and pulverized and classified to obtain an externally added toner having a volume average of 11.0 μm. To this was externally added 0.5% by weight of hydrophobic negatively chargeable silica powder (Taranox 500) to obtain an externally added toner.

Next, the charge amount B of the externally added toner was −25 μc / g after mixing for 30 seconds using the resin coat carrier A of Production Example 6, and the charge amount A of the externally added toner was −21 μc. / g, and [A] / [B] = 0.84.

Further, the above-mentioned externally added toner and the above-mentioned carrier are combined with a toner having a toner concentration of 8
% And a starting agent was prepared. The Canon NP5000 copier (with OPC photoreceptor) was improved for reversal development, and the actual machine was subjected to endurance. Tone with high image density without fog, ghost, and carrier adhesion A clear red image with good properties and sharpness was obtained.

10,000 sheets at room temperature and normal temperature while replenishing replenisher (external toner) periodically 50,000 sheets at low temperature and low humidity (15 ° C, 10% RH)
Under high temperature and high humidity (32.5 ° C, 85% RH), 50,000 sheets were subjected to a total of 110,000 sheets. The image density showed 1.2 to 1.3 under low temperature and low humidity, and 1.3 to 1.4 under high temperature and high humidity. The environmental dependence of the developing characteristics was good without any practical problems.

The toner density setting during running was varied from 7 to 20% by weight, but no substantial change in image quality was observed, and the toner scattered inside the apparatus was very good.

The surface of the carrier after the endurance was observed with a scanning electron microscope, but was not spent, and there was no difference from an unused carrier surface.

In addition, where the starting agent is left for a long time under high temperature and high humidity,
The charge amount of the start agent was -23 μc / g, -20 μc / g, and -21 μc / g in two weeks, one month, and three months, respectively, and did not fall below the charge amount immediately after mixing the carrier and the non-externally added toner. No change in image quality such as an increase in fog after standing was observed.

[Example 2] The above mixture was converted into a toner in the same manner as in Example 1, and the charging characteristics were measured using the resin-coated carrier of Production Example 6. The charge B of the externally added toner was −26.0 μc / g, and the The amount A was −20.5 μc / g, and the result was that A / B = 0.79.

When the external additive toner was used in the same manner as in Example 1, and the characteristics of the actual device were observed, the same good results as in Example 1 were obtained.

Comparative Example 1 A toner was prepared in the same manner as in Example 1, except that the chromium 1,3-di-tert-butylbutyrate was not used. The charge amount B of the attached toner is −23.0 μc / g,
The charge amount A of the non-externally added toner is −5.7 μc / g, and A / B = 0.2
A result of 5 was obtained.

Using the externally added toner, the actual machine characteristics were examined in the same manner as in Example 1. As a result, the image density under normal temperature and normal humidity was 1.4 at the start and 1.0 at the end of 10,000 sheets. Below, at the start of 1.05,10,000 sheets, the value was below 0.8, and the problem of low image density under low humidity occurred.

Also, as in the first embodiment, the toner concentration during the running is set to 7 to 20.
When the toner concentration was increased up to 10% by weight, the fog also increased when the toner concentration exceeded 10% by weight.

Further, when the start agent (toner concentration 8% by weight) was left for a long time under high temperature and high humidity, the chargeability of the start agent was 2%.
−15 μc / g, −10 μc / g, −7 for weekly, monthly, and monthly
μc / g, and the fog at the start of copying was inferior in the actual characteristics of the starting agent after standing for one month.

[Comparative Example 2] In Example 2, the negative chargeability of Production Example 3 was changed without using the chromium complex of 1,3-di-tert-butyl-salicylic acid and instead of the styrene-acrylic resin A of Production Example 2. A toner was prepared in the same manner as in Example 2 except that a low styrene-acrylic resin B was used.
Is -24.5 μc / g, and the charge amount A of the externally added toner is -4.8
μc / g, [A] / [B] = 0.20, and the actual device characteristics were not satisfactory as in Comparative Example 1.

[Comparative Example 3] A toner was prepared in the same manner as in Example 1 except that the untreated pigment was used instead of the red pigment B of Production Example 5, and the charge amount B of the externally added toner was -29 µc. / g, and the charge amount A of the non-externally added toner is −10.5 μc / g.
/B=0.36, and the actual device characteristics were not satisfactory as in Comparative Examples 1 and 2.

[Comparative Example 4] The toner prepared in the same manner as in Example 1 was used, and the carrier of Production Example 7 was used.
Is −35 μc / g, and the charge amount A of the non-externally added toner is −14.2.
μc / g, and A / B = 0.40. Regarding the characteristics of the actual machine, adhesion of minute carriers was observed in the solid and non-image areas of the image. With the progress of the durability, the OPC photosensitive member and the cleaning member were scratched, the drum was damaged by the damage, and the cleaning was poor.

Further, the image density, durability, leaving characteristics, etc. were determined in Examples 1 and 2.
And Comparative Examples 2, 3 and 4.

Comparative Example 5 Production Example 8 was performed using the toner prepared in the same manner as in Example 1.
When the carrier was used, the charge amount B of the externally added toner was-
30 μc / g, and the charge amount A of the non-externally added toner is −10.2 μc / g.
And A / B = 0.34. Regarding the characteristics of the actual machine, slight carrier adhesion was observed, and spot marks of the leak were observed on the image.

Also, the image density, durability characteristics and the like are shown in Comparative Examples 1, 2 and 3.
It was not satisfactory as well.

Comparative Example 6 Production Example 9 using a toner prepared in the same manner as in Example 1
When the carrier was used, the charge amount B of the externally added toner was-
40 μc / g, the charge amount A of the unexternally added toner was −18 μc / g, and A / B = 0.45.

When the characteristics of the actual machine were examined using the externally added toner, the image quality was acceptable in practical use up to 10,000 sheets. However, fog gradually increased thereafter, and fog was remarkable at 20,000 sheets, resulting in poor image quality. It became. When the charge amount of the toner at that time was measured, it was -15 μc / g. Most of the carrier surface was covered with the fused toner, and carrier deterioration due to spent was observed.

The experimental results of the above Examples and Comparative Examples will be considered with reference to FIGS. 1 and 2 attached.

FIG. 1 shows the rise of the charge amount of the unexternally added toner of Example 1 and the externally added toner obtained by externally adding 0.5% by weight of hydrophobic silica powder (Taranox T-500). FIG. 2 shows that of Comparative Example 3. In Example 1, the rise characteristics of the charge amount of the non-externally added toner and the externally added toner are close to each other. In Comparative Example 3, the rise of the charge amount of the externally added toner is slower than the rise of the charge amount of the externally added toner. In addition, the charge amount of the externally added toner is higher than that in Example 1 even though the charge amount of the non-externally added toner is small. From these, the toner according to the present invention is not affected by the externally added silica. Good charging characteristics,
That is, it is suggested that it has good development characteristics.

The same can be said for the other examples and comparative examples, although the absolute value of the charge amount of the toner slightly fluctuates depending on the presence or absence of the charge control agent, the carrier coating resin, and the like.

The measurement of the charge amounts of the various materials of the present invention was carried out as follows using the apparatus shown in FIG.

FIG. 3 is an explanatory view of an apparatus for measuring a triboelectric charge amount of a toner (or another sample). First, 10 g of a mixture of a test object and a carrier having a predetermined weight ratio, which is to be measured for triboelectric charge, is placed in a polyethylene bottle of a 50 ml container in a metal measuring container having a screen 3 of 500 mesh at the bottom, and the tar is charged. The mixture is fixed on a shaking part of a brush aker / mixer T2C type (manufactured by WAB), shaken for 30 seconds, and 0.7 ± 0.03 g of the mixture (developer) is precisely weighed, and the metal lid 4 is closed. At this time, the weight of the entire measurement container 2 is weighed and defined as W ₁ (g). Next, the suction machine 1
In the portion (at least the portion in contact with the measuring container 2 which is an insulator), the pressure of the vacuum gauge 5 is adjusted to 250 mmAq by adjusting the air volume control valve 6 by suctioning from the suction port 7. In this state enough, exactly 1
The toner is sucked and removed for a minute. The potential of the electrometer 9 at this time is set to V (volt). Here, reference numeral 8 denotes a capacitor, whose capacity is C (μF). Further, the weight of the whole measurement container after suction is weighed to be W ₂ (g). The triboelectric charge (μc / g) of this toner is calculated as in the following equation.

(However, the measurement environment is 23 ° C and 60% RH.) The carrier used for the measurement is a charge control agent, colorant, resin powder (pulverized and cut coarse powder by classification, and the volume average diameter is 5μ or less). For the measurement of the charge amount of (I), an iron powder carrier (EFV200 / 300 manufactured by Nippon Iron Powder Co., Ltd.) was used. The weight ratio of the coloring agent and the charge control agent to the carrier was 0.2: 9.8, and that of the resin powder was 0.8: 9.2.

Regarding the charge amounts of the externally added toner and the non-externally added toner, the toner: carrier mixture ratio using the carrier in Examples and Comparative Examples was 0.8: 9.2 by weight.

〔The invention's effect〕

According to the two-component developer of the present invention, as described above, the negatively chargeable color toner is a positively chargeable resin treated with a polymer of a negatively chargeable binder resin, a salicylic acid-based metal complex and a nitrogen-containing vinyl monomer. By containing at least a coloring agent, the dispersion of the pigment and the charge control agent is improved, and the resin-coated carrier coats the surface of the carrier core material with a different electrically insulating resin having a specific critical surface tension. As a result, phase separation occurs in the process of removing the solvent after coating (coating), so that a resin having a large critical surface tension exists rich near the carrier core material and a resin having a small critical surface tension exists near the carrier surface. Is rich in the carrier, the carrier has a releasability from the toner and the resin film becomes a tough carrier, and the band for the toner due to the defect of the resin film is formed. It is difficult to deteriorate the characteristics, and the carrier core material has a small amount of fine powder and ultrafine powder which may cause a coating failure or prevent the carrier from having a high resistance, so that the triboelectric charging ability to the toner is good. In addition, carrier adhesion due to a decrease in magnetic force is unlikely to occur. The two-component developer using the specific negatively chargeable color toner of the present invention in combination with the specific resin-coated carrier has a triboelectric charge amount with respect to the carrier of the toner without externally adding a fluidizing agent. [A] and triboelectric charge amount of toner externally added with a fluidizing agent to carrier [B]
The ratio [A] / [B] is larger than 0.5 in the mixing for 30 seconds under the same mixing condition, that is, the rising of the charge of the non-externally added toner is closer to the rising of the charge of the non-externally added toner. Therefore, the frictional charging ability between the toner and the carrier not externally added with the fluidizing agent is relatively higher than the frictional charging ability between the fluidizing agent and the carrier, and the fluidizing agent is preferentially attached to the carrier surface. Since the adsorption is reduced, the incorporation of the toner into the carrier particles,
Detachment is carried out smoothly, good and stable developing characteristics are achieved, and furthermore, there is little decrease in the amount of charge of the toner once charged, and it is possible to maintain good developing characteristics with little fog even when left for a long time and under high humidity. It is excellent in terms of development characteristics, durability, and standing characteristics, and can suppress generation of scratches on the photosensitive member and the cleaning member due to carrier adhesion.

[Brief description of the drawings]

FIG. 1 is a graph showing the change over time in the charge amounts of the externally added toner and the non-externally added toner of Example 1, and FIG. It is a graph which shows a temporal change. FIG. 3 is a diagram schematically showing an apparatus for measuring the charge amount of the toner. DESCRIPTION OF SYMBOLS 1 ... Suction machine, 2 ... Measuring container 3 ... Screen, 4 ... Metal lid 5 ... Vacuum gauge, 6 ... Air flow control valve 7 ... Suction port, 8 ... Condenser 9 ... Electrometer

Continuation of front page (56) References JP-A-61-59347 (JP, A) JP-A-63-2074 (JP, A) JP-A-61-27761 (JP, A) JP-A-59-83171 (JP, A) JP-A-61-149969 (JP, A) JP-A-54-110839 (JP, A) JP-A-63-80267 (JP, A) JP-A-62-39879 (JP, A) 62-39880 (JP, A)

Claims (1)

(57) [Claims] (1) (i) a negatively chargeable binder resin; salicylic acid,
A dry negatively-chargeable color toner containing at least a positively-chargeable colorant treated with a metal complex of an alkylsalicylic acid or a dialkylsalicylic acid; and a homopolymer or copolymer of a nitrogen-containing vinyl monomer; And (iii) the surface of the carrier core material has a critical surface tension of 30 dyn / cm.
A two-component dry developer containing a resin-coated carrier coated with an electrically insulating resin having a critical surface tension of less than 30 dyn / cm and an electrically insulating resin having a critical surface tension of 30 dyn / cm or more, wherein the carrier core material has a weight of the carrier core material. An externally added color toner having a particle size distribution in which the content of carrier core particles having a particle size of less than 1/10 of the average particle size is 2% by weight or less, and the fluidizing agent is externally added. Triboelectric charge [B] for the resin-coated carrier
The ratio [A] / [B] of the triboelectric charge [A] to the resin-coated carrier of the non-externally added color toner not externally added with a fluidizing agent is the same for 30 seconds under the same mixing conditions. , A two-component dry developer, which is larger than 0.5.