JP2002031913A - Toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide toner which hardly causes fog, fading, filming or the like for long-term printing in various environments and with which images with high print density can be obtained even when recycled paper is used as a transfer material. SOLUTION: The toner is obtained by adding as external additives, attapulgite having 0.1 μm number average particle size and 53% hydrophobicity, silica having 12 nm number average particle size and 64% hydrophobicity, and organic fine particles having 0.39 μm number average particle size and 1.16 sphericity to color particles having 1.0 to 1.3 sphericity.

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 latent image formed by an electrophotographic method, an electrostatic recording method, or the like. In particular, the present invention relates to a toner free from fogging, blurring and filming even when recycled paper is used as a transfer material.

[0002]

2. Description of the Related Art Conventionally, an electrostatic latent image formed in an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus is first developed with toner, and then the formed toner image is used as required. After being transferred onto a transfer material such as paper, it is fixed by various methods such as heating, pressing, and solvent vapor.
As a toner, generally, a colorant, a charge control agent, a release agent, and the like are melt-mixed and uniformly dispersed in a thermoplastic resin serving as a binder resin component to form a composition, and then the composition is pulverized. ,
A pulverized toner that obtains colored particles by classification, a colorant in a polymerizable monomer that is a binder resin material, a charge control agent,
Dissolve or disperse the release agent, etc., after adding the polymerization initiator, suspended in an aqueous dispersion medium containing a dispersion stabilizer,
The polymer is heated to a predetermined temperature to start the polymerization, and after the polymerization is completed, the polymer is subjected to filtration, washing, dehydration, and drying to obtain colored particles, and a suspension-polymerized toner or a polar resin-containing binder resin particle obtained by emulsion polymerization. And particles containing a colorant and a charge control agent, and stirred at a temperature higher than the glass transition temperature of the binder resin. After a hydrophilic group-containing resin is used as a binder resin, a colorant or the like is added thereto and dissolved in an organic solvent, and then the resin is neutralized, phase inversion is performed, and then color particles are obtained by drying. For example, normal toner is used.

In recent years, there has been a growing demand for higher image quality, such as higher image quality, and stable image quality even in poor environments such as high temperature, high humidity, and low temperature, low humidity. ing. In response to such requirements, in addition to the design of a binder resin and a proposal to include a functional component such as a charge control agent or a release agent, the obtained colored particles include organic or inorganic fine particles. There is also a proposal to improve the image quality of the toner by adding an external additive. For example,
JP-A-6-194864 discloses that by using silica fine particles and organic fine particles together as an external additive, it is possible to ensure sufficient fluidity and chargeability of the polymerized toner and obtain good image quality. are doing. JP-A-4-18625
No. 1 discloses a flow improver such as titanium oxide or alumina, organic fine particles, and a weight average particle diameter of 0.2 as external additives.
It has been proposed to use silicon-containing compounds of up to 2.5 μm. A two-component developer obtained by adding the three-component external additive to a pulverized polyester toner may damage the photoconductor when an electrophotographic method using an organic photoconductor (OPC) is used to obtain a color image. It has been shown to enable continuous printing of sharp images without any problems. Also, JP-A-11-32
No. 7194, a spherical inorganic oxide particle selected from silica or titanium oxide having a particle diameter of 20 to 50 nm as an external additive to a non-magnetic pulverized toner, and a particle diameter of 50 to 300 nm
It has been reported that when used in combination with spherical inorganic oxide particles selected from silica, titanium oxide and the like, good image quality can be formed even when there is a change in temperature or humidity.

Recently, from the viewpoint of environmental protection, recycled paper has been widely used mainly in offices. In offices, there are many opportunities for continuous printing, and there is a tendency to use a machine with a high printing speed. Good image quality is required even when printing continuously on recycled paper with a high-speed machine.

[0005]

SUMMARY OF THE INVENTION The present inventors have found that when conventional toner is applied to recycled paper, fogging is likely to occur in printing during durability. An object of the present invention is to provide a toner capable of obtaining an image having a high print density without fogging, blurring, filming, etc., even when using recycled paper as a transfer material and in various environments, even when printing for a long time. Is to provide.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve this object, and as a result, the above object has been achieved by using an external additive containing specific inorganic fine particles. And completed the present invention based on this finding. Thus, according to the present invention, there is provided a toner containing colored particles and fine particles of magnesium silicate minerals.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The toner of the present invention contains colored particles and an external additive. The external additive used in the present invention contains at least fine particles of magnesium silicate minerals.

The magnesium silicate minerals include, for example, palygorskite (general name of all the minerals belonging to the seiolite-paramonmonillonite system), attapulgite, sepiolite and the like. Of these, attapulgite is preferred.

The fine particles of these magnesium silicate minerals have a hydrophobicity of 20 to 80 as measured by a methanol method.
% Is preferred. Fine particles of magnesium silicate minerals having such a degree of hydrophobicity are generally commercially available, but can also be obtained by subjecting them to a hydrophobic treatment with a silane coupling agent, silicone oil, or the like. As a method of the hydrophobic treatment, a method of dropping or spraying a processing agent such as silicone oil while stirring the fine particles at a high speed, and a method of dissolving the processing agent and adding the fine particles to the stirred organic solvent. And the like. In the former case, the treating agent may be diluted with an organic solvent or the like.

The number average particle size of the fine particles of the magnesium silicate mineral is not particularly limited, but is usually from 0.02 to 0.5.
μm, preferably 0.05 to 0.3 μm. If the number average particle size is small, the photoreceptor tends to cause filming, while if it is large, the flowability is reduced and the photoreceptor is liable to be blurred.

The addition amount of the fine particles of the magnesium silicate mineral is not particularly limited, but is usually 0.05 to 1 part by weight, preferably 0.1 to 0.1 part by weight, per 100 parts by weight of the colored particles.
5 parts by weight. If the amount is small, filming may not be improved, and if the amount is large, fluidity may be reduced and scumming may occur.

The toner of the present invention preferably contains fine particles other than fine particles of magnesium silicate minerals as an external additive. In this case, when the inorganic fine particles are used, the fluidity of the toner is improved and the blur is reduced, and when the organic fine particles are used, the filming can be suppressed.

Examples of the inorganic fine particles include silica, titanium oxide, aluminum oxide, zinc oxide, tin oxide, barium titanate, and strontium titanate. Of these, silica is preferable because of low fog during printing. . These inorganic fine particles preferably have a hydrophobicity of 30 to 90% as measured by a methanol method. The number average particle size of the inorganic fine particles is not particularly limited,
It is usually 5 to 40 nm, preferably 10 to 30 nm.
If the number average particle diameter is small, the print density decreases due to charge-up at low temperature and low humidity. Conversely, if the number average particle diameter is large, the fluidity is reduced, and there is a possibility that blurring is likely to occur. The amount of the inorganic fine particles is not particularly limited, but is usually 0.1 to 2 parts by weight, preferably 0.3 to 1.5 parts by weight, per 100 parts by weight of the colored particles. If this amount is small, the fluidity decreases and it is easy to lose,
Conversely, when the amount is increased, the fluidity becomes too good and fog may be easily caused.

The organic fine particles are not particularly limited, but the compound constituting the fine particles usually has a glass transition temperature or melting point of 80 to 80 from the viewpoint of suppressing blocking between the particles.
The temperature is 250 ° C, preferably 90 to 200 ° C. Examples of the compound constituting the organic fine particles include a methyl methacrylate polymer and a styrene-methyl methacrylate copolymer. The number average particle size of the organic fine particles is not particularly limited, but is usually 0.1 to 1 μm, preferably 0.1 to 0.8 μm.
m. The sphericity is also not particularly limited, but is usually 1.0 to 1.3, preferably 1.0 to 1.2.
If the number average particle size is too small, filming may not be prevented, whereas if it is too large, the fluidity may be reduced. Further, when the sphericity is large, the transferability may be reduced. The sphericity (Sc / Sr) in the present invention is a value obtained by dividing the area (Sc) of a circle having the diameter of the absolute maximum length of a particle by the substantial projected area (Sr) of the particle. The amount of the organic fine particles is not particularly limited, but is usually 0.05 to 1 part by weight, preferably 0.1 to 0.1 part by weight, per 100 parts by weight of the colored particles.
5 parts by weight. If the amount is small, filming is likely to occur, and if it is large, the fluidity may be poor and the film may be easily worn.

The colored particles which can be used in the present invention usually contain a binder resin, a colorant and other additives. The colored particles are (1) a colorant, a charge control agent, a release agent, and the like, melted and mixed in a thermoplastic resin to be a binder resin component to uniformly disperse the composition. Colored particles obtained by crushing and classifying the product,
(2) An aqueous dispersion medium containing a dispersion stabilizer after dissolving or suspending a colorant, a charge control agent, a release agent, and the like in a polymerizable monomer as a binder resin raw material, adding a polymerization initiator, and The suspension is heated to a predetermined temperature to initiate suspension polymerization, and after completion of the polymerization, contains colored particles obtained by filtration, washing, dehydration and drying, and (3) contains a polar group obtained by emulsion polymerization. The primary particles of the binder resin are aggregated into a secondary particle by adding a colorant and a charge control agent, and the particles that are associated by stirring at a temperature higher than the glass transition temperature of the binder resin are further filtered and dried. (4) A hydrophilic resin containing a hydrophilic group is used as a binder resin, a coloring agent and the like are added thereto and dissolved in an organic solvent. Colored particles are obtained by summing and inverting the phases, followed by drying. A phase inversion emulsification method toner and the like that,
Any of them can be used, but substantially spherical colored particles obtained by the suspension polymerization method (2) are preferred from the viewpoint of obtaining a toner that gives good image quality on recycled paper.

The colored particles preferably have a sphericity (Sc / Sr) of 1.0 to 1.3.
More preferably, the ratio is 1.0 to 1.2. When the sphericity is increased, the fluidity is reduced, and the spheroidity may be easily reduced.

As specific examples of the binder resin, resins widely used in conventional toners such as polystyrene, styrene-butyl acrylate copolymer, polyester resin and epoxy resin can be used.

The color particles are not particularly limited, but have a volume average particle size (dv) of usually 3 to 12 μm, preferably 4 to 1 μm.
0 μm. Moreover, it is desirable that the ratio (dv / dn) of the volume average particle diameter (dv) to the number average particle diameter (dn) is in the range of 1.0 to 1.3.

The colored particles may be particles having a structure obtained by combining two different polymers inside (core layer) and outside (shell layer) of the particles, so-called core-shell structure (also called capsule structure). In the core-shell structure particles, the balance between the lowering of the fixing temperature and the prevention of agglomeration during storage can be achieved by encapsulating the material having a lower softening point inside (core layer) with a material having a higher softening point. It is preferred. The colored particles having a core-shell structure may be obtained by a pulverization method, or may be obtained by a suspension polymerization method or an emulsion polymerization method.

In the case of core-shell particles, the volume average particle size of the core particles is not particularly limited, but is usually 2 to 10 μm, preferably 2 to 9 μm, more preferably 3 to 8 μm.
The volume average particle diameter (dv) / number average particle diameter (dp) is not particularly limited either, but is usually 1.7 or less, preferably 1.
5 or less, more preferably 1.3 or less.

The weight ratio between the core layer and the shell layer of the core-shell particles is not particularly limited, but is usually 80/20 to 99.
Used at 9 / 0.1. When the ratio of the shell layer is smaller than the above ratio, the storage stability is deteriorated.

The average thickness of the shell layer of the core-shell particles is as follows:
Usually 0.001 to 1.0 μm, preferably 0.003 to
It is considered to be 0.5 μm, more preferably 0.005 to 0.2 μm. When the thickness is large, the fixability is reduced, and when the thickness is small, the storability may be reduced. In addition,
It is not necessary that the entire surface of the core particle forming the colored particle having the core-shell structure is covered with the shell layer, and it is sufficient that a part of the surface of the core particle is covered with the shell layer. When the core particle diameter of the core-shell particles and the thickness of the shell layer can be observed by an electron microscope, it can be obtained by directly measuring the size and the shell thickness of the particles randomly selected from the observation photograph. When it is difficult to observe the core and the shell, it can be calculated from the particle size of the core particles and the amount of the monomer forming the shell used in producing the toner.

The method for producing the core-shell particles is as follows.
Methods such as a spray drying method, an interface reaction method, an in situ polymerization method, and a phase separation method can be adopted. In particular, an in situ polymerization method or a phase separation method is preferable from the viewpoint of production efficiency.

The toner of the present invention comprises colored particles and an external additive,
It is obtained by mixing with a high-speed stirrer such as a Henschel mixer.

[0025]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples below, but the present invention is not limited to these examples. In addition, parts and%
Are by weight unless otherwise specified. In the present example, evaluation was made by the following method.

[Evaluation Method] (Volume Average Particle Size and Particle Size Distribution) The volume average particle size (dv) of the colored particles and the particle size distribution, ie, the ratio (dv / d) of the volume average particle size to the number average particle size (dp). dp) was measured with a Multisizer (manufactured by Beckman Coulter). The measurement with this multisizer was performed with an aperture diameter of 100 μm.
m, medium: Isoton II, concentration 10%, number of measured particles:
The test was performed under the condition of 100,000 pieces. (Number average particle size) The number average particle size of attapulgite, silica and organic fine particles is determined by taking an electron micrograph of each particle and using the photograph by an image processing / analysis apparatus Luzex IID.
[Equipment made by Nireco Co., Ltd.] was used to calculate the equivalent circle diameter under the conditions that the area ratio of the particles to the frame area was 2% at the maximum and the total number of particles processed was 100, and the average value was calculated. In the case of attapulgite, since the fine particle shape is fibrous, the major axis is defined as the particle size of the fine particles.

(Sphericity) The sphericity (Sc / Sr) of the value obtained by dividing the area (Sc) of a circle whose diameter is the absolute maximum length of a particle by the substantial projected area (Sr) of the particle is represented by an electron microscope. A photograph is taken, and the photograph is taken by an image processing / analysis apparatus Luzex IID (manufactured by Nireco Co., Ltd.).
It is an average value of 100 measured and calculated on 0 conditions. (Degree of hydrophobicity) The degree of hydrophobicity by the methanol method is determined according to the following measuring method. 0.2 g of the hydrophobized inorganic fine particles were weighed into a 500 ml beaker, and 50 m of pure water was used.
l and stirring with a magnetic stirrer,
Methanol is added below the liquid level to gradually settle the inorganic fine particles. The point at which no inorganic fine particles are observed on the liquid surface is defined as the end point, and the degree of hydrophobicity is calculated by the following equation. Degree of hydrophobicity (%) = (X / (50 + X)) × 100 X; Methanol usage (ml)

(Fog) Recycled paper is set in a commercially available non-magnetic one-component developing type printer (12-sheet machine), and a developer to be evaluated is put in a developing device of the printer.
℃, humidity 50% (N / N) environment, temperature 35 ℃, humidity 80
% (H / H) environment and temperature 10 ° C., humidity 20% (L / H
L) Continuously print at 5% printing density after standing overnight in each environment of the environment, printing is temporarily stopped at the initial printing (at the time of printing 10 sheets) and after printing 10,000 sheets, and on the photoreceptor after development Was adhered to an adhesive tape (Scotch Mending Tape 810-3-18 manufactured by Sumitomo 3M Limited). It was attached to a printing paper, and its whiteness (B) was measured with a whiteness meter (manufactured by Nippon Denshoku). Similarly, only the adhesive tape was affixed to the printing paper, the whiteness (A) thereof was measured, and the fog value was calculated by the following formula: fog (%) = (AB). A smaller value indicates less fog.

(Removal) A recycled paper is set in a commercially available non-magnetic one-component developing system printer (12-sheet machine), and a developer to be evaluated is put in a developing device of the printer.
℃, humidity 50% (N / N) environment-5% after standing overnight
Continuous printing was performed at the printing density, and black solid printing was performed every 500 sheets, and the number of occurrences of blurring was counted. The final number of printed sheets is 10,000. Those without a number in the table indicate that no blurring occurred even after continuous printing of 10,000 sheets. (Filming) Recycled paper is set in a commercially available non-magnetic one-component developing system printer (12-sheet machine), and a developer to be evaluated is put in a developing device of this printer. The temperature is 23 ° C., the humidity is 50% (N / N). N) Under an environment-After standing for 24 hours a day, continuous printing was performed at 5% printing density, halftone printing was performed every 500 sheets, and the number of sheets where white blurring occurred was counted. The final number of printed sheets is 10,000. Those without numbers in the table indicate that filming did not occur even after continuous printing of 10,000 sheets.

(Example 1) 83 parts of styrene, 17 parts of n-butyl acrylate, carbon black (trade name "# 2")
5B ", manufactured by Mitsubishi Chemical Corporation; 6 parts of primary particle size; styrene / 2-ethylhexyl acrylate / 2-acryloylamino-2-methyl-1-propanesulfonic acid copolymer (trade name" FCA ") as a charge control resin -1001-N
S ", manufactured by Fujikura Kasei) 1 part, divinylbenzene 0.6 part,
One part of t-dodecyl mercaptan and 10 parts of dipentaerythritol hexamyristate were dispersed in a bead mill at room temperature to obtain a uniform mixed solution. While stirring the mixture, 5 parts of a polymerization initiator t-butyl peroxy 2-ethylhexanoate (trade name: “Perbutyl O”, manufactured by NOF CORPORATION) was added, and the mixture was stirred until the droplets became uniform. Continued.

On the other hand, in an aqueous solution obtained by dissolving 9.5 parts of magnesium chloride (water-soluble polyvalent metal salt) in 250 parts of ion-exchanged water, 4.8 parts of sodium hydroxide (alkali metal hydroxide) is added to 50 parts of ion-exchanged water. The aqueous solution in which was dissolved was gradually added under stirring to prepare a magnesium hydroxide colloid (poorly water-soluble metal hydroxide colloid) dispersion. The polymerizable monomer composition was charged into the colloid, and the mixture was subjected to high shear stirring at a rotation speed of 12000 rpm using an Ebara Milder to granulate droplets of the polymerizable monomer mixture. The aqueous dispersion of the granulated polymerizable monomer mixture is put into a reactor equipped with a stirring blade, a polymerization reaction is started at 90 ° C., polymerization is performed for 8 hours, and then cooling is performed. I got

While stirring the aqueous dispersion of the polymer particles obtained above, sulfuric acid was added to adjust the pH to 4 or less, acid washing was performed, water was separated by filtration, and 500 parts of ion-exchanged water was newly added. In addition, the slurry was reslurried and washed with water. After that, dehydration and washing with water were repeated several times again, and the solid content was separated by filtration, followed by drying at 45 ° C. for 2 days and night with a drier to obtain colored particles. The volume average particle size of the colored particles is 7.5.
μm, the volume average particle diameter (dv) / number average particle diameter (dp), which is an index of the particle diameter distribution, was 1.21, and the sphericity was 1.12.

The obtained colored particles (100 parts) and attapulgite (trade name “Atagel 50”, manufactured by Engelhardt Co., Ltd.) having a volume average particle diameter of 0.1 μm and a hydrophobicity of 53% were used.
5 parts, silica having a number average particle diameter of 12 nm and a hydrophobicity of 64% (trade name "RX-200", manufactured by Nippon Aerosil Co., Ltd.)
2.0 parts, number average particle size 0.39 μm, sphericity 1.1
And 0.2 parts of organic fine particles (styrene-methyl methacrylate copolymer having a core-shell structure having a core of styrene and a shell of methyl methacrylate: a glass transition temperature of 100 ° C.) of 10 parts by a Henschel mixer for 10 minutes at a rotation speed of 1400 rpm.
pm to obtain a toner. Printing evaluation was performed on the obtained toner. Table 1 shows the results.

[0034]

[Table 1]

(Examples 2 and 3, Comparative Examples 1 to 3) Evaluations were made in the same manner as in Example 1 except that the external additives were changed as shown in Table 1. Table 1 shows the results.

From the evaluation results of the toners in Table 1, the following can be understood. The toners of Comparative Examples 1 to 3 in which the external additive does not contain the fine particles of the magnesium silicate minerals are liable to cause any of filming, fogging and blurring during continuous printing. On the other hand, it can be seen that the toners of Examples 1 to 4 of the present invention hardly cause fogging, blurring and filming.

[0037]

According to the present invention, even if recycled paper is used as a transfer material, fog, blurring, filming, etc. are unlikely to occur in long-term durability printing under various environments.
A toner capable of obtaining an image having a high print density is provided.

Claims (1)

[Claims] 1. A toner containing colored particles and fine particles of magnesium silicate minerals.