JP3353168B2 - Magnetic toner for one-component development - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer for developing electrostatic images used in copying machines, printers and the like.

[0002]

2. Description of the Related Art A toner for developing an electrostatic image is usually manufactured, for example, as follows. First, a coloring agent for the binder resin,
If necessary, a release agent, a charge control agent, a magnetic substance, and other auxiliaries are added. After pre-mixing this blend, it is melt-kneaded. After cooling the obtained kneaded material, it is pulverized and classified to obtain colored particles. Further, toner is obtained by externally adding and mixing inorganic fine particles and other additives as necessary to the obtained colored particles.

The purpose of externally adding inorganic fine particles is to improve the fluidity of the toner and to control the chargeability. However, on the surface of the colored particles, a binder resin, a colorant,
Further, those having different physicochemical compositions such as a release agent and a charge control agent and having different charging properties are exposed. When inorganic fine particles are externally added to the mixture, they selectively adhere to portions that are likely to adhere electrostatically. As a result, non-uniform charging results in generation of weakly charged toner and oppositely charged toner. ,
And toner scattering. In particular, the colored particles immediately after the kneading, pulverizing, and classifying steps are extremely dry and in an electrostatically active state. Therefore, image fogging due to the non-uniformity of the charging property and toner scattering are likely to occur.

[0004] As a typical and well-known conventional example, a polystyrene surface abundance and a domain diameter of a compound having releasability, such as polypropylene, are specified to reduce toner particles, prevent filming and spent, and fix toner to a blade. A method of suppressing (JP-A-3-243956, JP-A-3-264961, JP-A-3-296067, JP-A-5-45925) or a method containing a metal-crosslinked styrene-acryl copolymer resin Regarding that toner, inorganic fine particles modified with ammonium salt-modified or inorganic fine particles treated with a nitrogen-containing coupling agent, and a developer comprising a fluororesin-coated carrier are excellent in low-temperature fixability, hot offset resistance, and storage stability. (JP-A-2-110473, JP-A-2-1104)
No. 74).

However, at present, fogging of images and toner scattering have not been sufficiently improved.

[0006]

SUMMARY OF THE INVENTION The present invention makes uniform the attachment of inorganic fine particles to toner particles, prevents generation of weakly charged and oppositely charged toner, and reduces image fogging and toner scattering.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems. That is, the present inventors
In the above-described kneading and pulverizing steps, it is necessary to make the chargeability of the surface of the colored particles uniform, specifically, to make the dispersion of the release agent that forms a domain with respect to the resin uniform on the toner surface of the external additive. They have found that it is important to improve the uniformity, and have completed the invention.

That is, in a one-component developing toner comprising at least colored particles comprising a resin, a magnetic substance and a release agent and inorganic fine particles, the ESC on the surface of the colored particles
The release agent surface abundance represented by the reciprocal of the amount of oxygen obtained in A is 0.1 to 0.3, and the release agent domain diameter in the colored particles is in the range of 0.1 to 1.0 μm. Achieved by one-component magnetic toner for development.

The domain diameter of the release agent refers to a circle-equivalent diameter (diameter) in a state where the release agent is dispersed as fine particles in the toner particles. In order to control the release agent domain diameter, in the kneader of the kneading step, the kneaded material average filling degree in the kneading zone is in the range of 240 to 400 (kg / m ³ ), and the fluctuation range is ± By controlling the content to be 10% or less, the additives, particularly the release agent, in the kneaded material can be uniformly dispersed. The amount of the surface release agent can be achieved by controlling the amount returned to the pulverizing step in the closed-circuit pulverizing system. By uniformly dispersing the negatively chargeable release agent in the colored particles, the negatively chargeable surface of the colored particles is made uniform and selected when the inorganic fine particles are externally added and mixed, where they are likely to adhere electrostatically. And the chargeability is uniform. As a result, the generation of weakly charged toner or toner of opposite polarity is reduced, and the problem of image fogging and toner scattering can be prevented. If the domain diameter of the release agent is less than 0.1 μm, inorganic fine particles are hardly adhered, and if it exceeds 1.0 μm, the dispersion of the release agent is insufficient and the adhesion of the inorganic fine particles becomes non-uniform, and the generation of weakly charged toner etc. increases. I do.

In the present invention, the release agent domain diameter was determined as follows.

The toner particles are embedded in a resin, and a section having a thickness of about 0.20 μm is formed by a microtome. The section was photographed with a transmission electron microscope at a negative magnification of 280 times and stretched to produce a 1200 times photograph. The domain diameter is measured using an image analyzer (SPICCA: Nippon Avionics). Here, the domain diameter was measured as a number average diameter.

[0012] The surface release agent amount, tree butter styrene - If a compound of hydrocarbon as of yet release agent using those containing oxygen as an acrylic polymer a low molecular weight polyolefin The surface of the toner can be analyzed by ESCA and defined by the amount of oxygen obtained.
The amount of the surface release agent in the text is represented by the reciprocal of the amount of oxygen obtained by ESCA.

The surface in the present invention is generally from the outermost surface.
Defined to a depth of 0.1 μm. That is, the effective depth from the surface which can contribute to the charging property of the toner surface is determined to be approximately 0.1 μm. When measuring the existence ratio of the surface, the depth as a measured value differs depending on the measurement method, but in ESCA, the measurement depth can be controlled by a method such as surface etching.

As the ESCA measuring instrument, there is a model 5400 series manufactured by ULVAC-PHI, Inc.

In the present invention, the measurement conditions for the ESCA analysis are as follows.

Measuring device: PHI model 56 manufactured by PerkinElmer
0ESCA / SAM Measurement conditions: X-ray output 15kV, 26.7 mA sample adjustment made with assay: toner measured quantitatively calculated by fixing the sample stage scattered on double-sided tape, the carbon C _1S oxygen O _1S nitrogen N _1S Each amount was determined from the area of the peak using the peak of (1). Using these peak areas, the intensity was corrected by the sensitivity coefficient as the intensity correction by each element, and the intensity ratio was obtained.

[0017] The sensitivity coefficient is calculated by using "Ha" manufactured by PerkinElmer.
ndbook of Xray PHOTOELECT
RON SPECTROCOPY ”. The amount of oxygen present on the surface was calculated from the element ratio (AC) obtained as described above, and represented by the reciprocal. Measure the amount of oxygen,
The reciprocal is shown for the following reason. For example low
In release agents such as high molecular weight polypropylene, oxygen
Although the binder content ratio is 0 or a small value, the binder resin (binder)
-) Etc., for example, acrylate resin, polyester
The value is much larger than that of a release agent such as a tellurium resin. Follow
Measure the oxygen content ratio on the surface of the colored particles (toner particles)
When the reciprocal is taken, that value indicates a specific value
That is, the amount ratio of the release agent on the particle surface becomes a specific amount ratio.
It represents that it is.

If the amount of the oxygen releasing agent on the toner surface is less than 0.1, the inorganic fine particles are hardly adhered, and if it exceeds 0.3, the negative charging property of the releasing agent becomes a problem. This causes problems such as image fogging and toner scattering.

[0019]

As the raw material of the toner used in the present invention, all known materials can be used.

As the magnetic material used in the present invention, a magnetic material such as ferrite or magnetite having a number average primary particle diameter of 0.1 to 2.0 μm, preferably 0.1 to 0.5 μm can be used. In addition, the number average primary particle diameter indicates that observed by a transmission electron microscope. The addition amount of the magnetic substance is preferably 30 to 100 parts by weight based on 100 parts by weight of the resin. Also,
The magnetization at 1000 Oe in the case of toner is 20 to 40 emu /
It is preferably adjusted to about g. When the magnetization is low, the toner is not sufficiently retained in the developing device, so-called toner scattering occurs. When the magnetization is high, the toner is excessively retained in the developing device, and there is a problem that the developability is reduced. The magnetization indicates a value measured by applying a magnetic field of 1000 Oe with a BH meter.

Examples of the binder resin include polyester resin, styrene-acrylic resin, styrene-methacrylic resin, styrene-butadiene resin, styrene-acrylonitrile resin, styrene-acryl-polyester resin, and styrene-acrylic crystalline polyester. Examples include a graft resin, a polyurethane resin, an epoxy resin, a silicone resin, polyvinyl chloride, polyamide, polyvinyl butyral, rosin, modified rosin, phenol resin, and xylene resin. Examples of the coloring material include carbon black, chrome yellow, Dupont oil red, quinoline yellow, phthalocyanine blue and the like.

Nigrosine dyes, 4
Organic salts or complexes containing a quaternary ammonium salt compound, an alkylpyridinium compound and a divalent or higher valent metal can be used.

Examples of the release agent include low molecular weight polyethylene, low molecular weight polypropylene, and low molecular weight polyethylene-polypropylene copolymer having a number average molecular weight (the number average molecular weight is a value converted to polystyrene molecular weight by high-temperature GPC) of 1500 to 5000. Polyolefin wax such as coalescence,
High melting point paraffin wax such as microcrystalline wax and Fischer-Tropsch wax can be used.

The release agent is preferably added and mixed in the toner in an amount of 0.1 to 5% by weight. If the amount is too small, the offset property with respect to the fixing roller is reduced. If the amount is too large, the adhesiveness with respect to the paper is reduced.

Further, the toner of the present invention may contain additives such as a colorant and a charge control agent.

When the magnetic material is black, the coloring material can also serve as the coloring material.

The above-mentioned raw materials are appropriately blended, and colored particles are obtained through mixing, melting, cooling, pulverization, classification, and steps. Usually, at this time, the water content of the colored particles is 0.1% by weight or less, and it is very easily charged. (It is known that the particles immediately after the pulverization are actually mutually charged.) Next, inorganic fine particles and other substances as necessary are mixed as an external additive. Examples thereof include silica, alumina, titania, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, cerium oxide, antimony trioxide, zirconium oxide, silicon carbide, and silicon nitride.

In order to obtain inorganic fine particles having an appropriate charging characteristic range, an amino-modified silane coupling agent, an amino-modified silicone oil, a polysiloxane ammonium salt, an amine-modified silicon compound such as an organopolysiloxane and 3-aminopropyltriethoxysilane, etc. By applying a surface treatment, the chargeability can be adjusted. In particular, it is preferable to use silica after surface treatment.

The inorganic fine particles preferably have a number average particle diameter of a primary average particle diameter of 0.005 to 0.5 μm, particularly
It is preferably from 07 to 0.1 μm. In addition, the primary average particle of the inorganic fine particles refers to a number average particle diameter measured by image analysis while observing with a transmission electron microscope.

Further, 0.2 g of inorganic fine particles and 100 μm
20g iron powder carrier 20g at 20 ℃, relative humidity 50%
0 minute shaker (shaking machine: Yayoi YS-LD), with a charge of 3 to 300 μc / g when measured with a blow-off powder charge meter “TB-200” (manufactured by Toshiba Chemical Corporation) Is good. Particularly desirable is 10 to 150 μc / g.
When the charge amount exceeds 300 μc / g, the charge amount of the toner becomes too high, and the developability deteriorates. On the other hand, when the charge amount is lower than the lower limit of 3 μc / g, the charge amount becomes too low,
Image fogging and toner scattering occur.

Other external additives include lubricants such as zinc stearate and polyvinylidene fluoride, and fixing aids such as low molecular weight polypropylene.

The amount of the inorganic fine particles used is 0.01% of the whole toner.
The range is preferably from 5 to 5% by weight, particularly preferably from 0.05 to 2% by weight. If the use amount of the inorganic fine particles exceeds 5% by weight, release of the inorganic fine particles occurs, and the inorganic fine particles adhere to the photosensitive drum and cause a scratch on the drum.

On the other hand, when the amount is 0.05% by weight or less, the effect of adding the inorganic fine particles is not exhibited.

As a method of pulverizing the toner preferably used in the present invention, there is a closed-circuit pulverization method, which is a method of pulverizing with a pulverizer and then returning the separated coarse powder directly to a pulverizer by a coarse powder classifier. The basic process diagram is shown in FIG.

The pulverized raw material is supplied from the pulverized raw material quantitative feeder 1
It is supplied to the crusher 2 and crushed. The pulverized product is a coarse classifier 3
After the coarse particles are classified by a classifier, they are collected by a cyclone 4 to obtain a pulverized product. The exhaust gas from the cyclone is discharged by a blower 6 after fine powder is separated by a bag filter 5.

On the other hand, the coarse powder separated by the coarse classifier 3 is returned to the pulverizer and returned and circulated as powder. Here, the coarse powder refers to particles larger than a desired toner volume average particle diameter (DA), and is 1.1 <DB / DA <1.3 when the volume average particle diameter is DB.

The magnetic toner of the present invention has improved uniformity in chargeability, and is particularly suitable for a system in which a thin layer of a developer is conveyed to a development area to perform development. That is, in the case of the thin-layer forming developing method, the toner needs to be charged by frictional charging with the surface of the developing device, that is, the sleeve and the toner layer regulating member. I have. The toner of the present invention can be used in a process by a thin-layer forming method because the fine particles have uniform rising on the surface of the colored particles and thus have a good charge rising.

The thin layer forming method refers to a method of forming a toner layer of 20 to 500 μm in the developing area on the surface of the developing sleeve. When this thin layer is formed, there is a method of regulating the toner layer on the surface of a magnetic blade or a developing sleeve using magnetic force. Further, there is a method in which a urethane blade, a phosphor bronze plate or the like is brought into contact with the surface of the developing sleeve to regulate the toner layer. In the case of the pressure control method, the pressing force of the pressure control member is preferably set to 1 to 15 gf / mm. When the pressing force is small, the conveyance becomes unstable due to insufficient regulation force. On the other hand, when the pressing force is large, the stress on the developer increases, so that the durability of the developer decreases. The preferred range is 3 to 10 gf / mm.

The gap between the developing sleeve and the surface of the photosensitive member may be larger or smaller than the toner layer. Further, a method of applying only a DC component as a developing bias may be used,
Any method of applying an AC bias may be used.

[0040]

EXAMPLES The present invention will be described below in detail with reference to examples, but embodiments of the present invention are not limited thereto.

Examples and Comparative Examples Binder resin Styrene-acrylic resin 100 parts by weight Colorant magnetite (0.18 μm) 60 parts by weight Release agent Low molecular weight polypropylene (Mn = 2500) 3 parts by weight Mixing, melting and kneading the above components Coloring particles having a volume average particle diameter of 8.5 μm having different polypropylene abundance and domain diameter were obtained by changing the conditions of pulverization and classification. The coloring particles were externally treated with the following four types of inorganic fine particles A to D by 0.8% by weight to obtain a toner. These five toners in the present invention (Examples 1 to 5)
5) The contents of the four toners (Comparative Examples 1 to 4) outside the present invention are described in Table 1 below.

Inorganic fine particles Charge amount μc / g A Hydrophobized silica 98 B surface-treated with an amino-modified silane coupling agent having a primary average particle size of 0.012 μm Surface treatment with an amino-modified silicone oil having a primary average particle size of 0.012 μm Hydrophobized silica 70 C Hydrophobized silica surface treated with an organopolysiloxane having a primary average particle size of 0.012 μm 112 D Hydrophobized silica surface treated with an organopolysiloxane having a primary average particle size of 0.05 μm 42 Image fogging evaluation The following tests were performed to quantify the fog on the image.

(Evaluation of the actual machine) The evaluation was carried out by modifying a laser printer LP-3015 made by Konica so that the printing speed in A4 vertical feed was 20 sheets / min and the diameter was 25 mm with a built-in 6 pole fixed magnet.
The development sleeve was modified to a non-contact type in which the development area gap: Dsd = 0.2 mm, and the toner layer on the surface of the developing device in the development area was 0.15 mm. The photoreceptor uses a stacked organic photoreceptor and the developing section potential is -500.
V, and the developing bias is -50 to -550 from peak to peak.
At V, an AC bias having a frequency of 2 kHz and a DC bias of -250 V were applied.

[0044]

[Table 1]

Evaluation criteria Fogging toner scraping amount Correspondence with image 10 g or less No image fogging and toner scattering 10 to 14 g No practical problem, but fogging 14 g or more Image fogging and toner scattering occurred. In 5, the fog toner scraping amount is
It was 14 g or less, and good results with little image fogging and toner scattering were obtained. On the other hand, in Comparative Examples 1 to 4, the fog toner scraping amount was 14 g or more, and image fogging and toner scattering occurred.

(Evaluation of Actual Photographic Durability) Using the toners of Examples 1 to 5 and Comparative Examples 1 to 4, 20
When a long run of 50,000 copies was performed in an environment at 50 ° C. and a relative temperature of 50%, the amount of collected toner was as follows, and the toner of the present invention was able to obtain good results.

[0047]

[Table 2]

[0048]

According to the present invention, it is possible to improve the dispersibility of the external additive in the developed toner particles and to make the chargeability uniform. Therefore, it is possible to improve the ground fogging and the image quality, and it is also possible to achieve an improvement in the toner consumption and the recovery amount and an increase in the transfer rate.

[Brief description of the drawings]

FIG. 1 is a process diagram of a closed-circuit pulverizer preferably used in the practice of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pulverized raw material fixed feeder 2 Pulverizer 3 Coarse particle classifier 4 Cyclone 5 Bag filter 6 Blower 7 Pulverized raw material supply amount 8 Return powder supply amount (circulated coarse powder amount)

 ────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Kensuke Endo 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation (56) References JP-A-5-197199 (JP, A) JP-A-2-87159 ( JP, A) JP-A-3-296067 (JP, A) JP-A-3-26461 (JP, A) JP-A-3-288863 (JP, A) JP-A-4-255865 (JP, A)

Claims (2)

(57) [Claims] 1. A one-component developing toner comprising at least colored particles comprising a resin, a magnetic substance and a release agent and inorganic fine particles, wherein the toner is obtained by ESCA on the surface of the colored particles .
Release agent surface abundance expressed as the reciprocal of the
~ 0.3, the release agent domain diameter in the colored particles is 0.1 ~
A magnetic toner for one-component development, which has a range of 1.0 μm. 2. The charge amount of the inorganic fine particles is 3 to 300 μc /
2. The magnetic toner according to claim 1, wherein the number average particle diameter is 0.005 to 0.5 [mu] m.