JPH07168391A - Magnetic toner for one component development - Google Patents

Abstract

PURPOSE:To uniformize the sticking of the inorganic fine particles to the colorant particles in the toner, to prevent the weakly charged or reversed-polarly charged toner particles from being generated and to reduce the generation of fogging in the image and scattering of the toner by specifying the amount of the releasing agent present on the surface of the colorant particles and the domain diameter of the releasing agent within the colorant particles respectively. CONSTITUTION:In this toner which consists of inorganic fine particles and colorant particles comprising a resin, a magnetic substance and a releasing agent, the amount of the releasing agent present on the surface of the colorant particles and the domain diameter of the releasing agent within the colorant particles are adjusted to 0.1 to 0.3 and 0.1 to 1.0mum respectively. At this time, the amount of the releasing agent present on the surface of the colorant particles can be adjusted by controlling the amount returned to the pulverizing process. The domain diameter of the releasing agent within the colorant particles can be controlled by adjusting the average degree of filling with the kneaded material of the kneader in the kneading process to a value within a prescribed range and controlling its width of variation to uniformize the dispersion of the releasing agent Thus, the uniform chargeability of the surface of the colorant particles can be attained to uniformize its chargeability at the time of adding the inorganic fine particles to it from outside and mixing them with each other.

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 an electrostatic charge image used in copying machines, printers and the like.

[0002]

2. Description of the Related Art Generally, a toner for developing an electrostatic image is manufactured as follows, for example. First, the binder resin and the colorant,
Then, if necessary, a release agent, a charge control agent, a magnetic material, and other auxiliary agents are added. After premixing this blend, it is melt-kneaded. The obtained kneaded product is cooled, then pulverized and classified to obtain colored particles. Further, a toner is obtained by externally mixing the obtained colored particles with inorganic fine particles and, if necessary, other additives.

The purpose of externally adding the inorganic fine particles is to improve the fluidity of the toner and to control the charging property. However, on the surface of the colored particles, a binder resin, a coloring agent,
Further, those having different physicochemical compositions such as release agents and charge control agents and different charging properties are exposed. When inorganic fine particles are externally added to and mixed with this, they selectively adhere to a portion that is easily electrostatically adhered. As a result, weakly charged toner and reverse polarity charged toner are generated due to uneven chargeability, and image fogging occurs. ,
It also causes toner scattering. In particular, the colored particles immediately after the kneading, pulverizing and classifying steps are very dry and in an electrostatically active state. Therefore, image fogging and toner scattering are likely to occur due to the non-uniformity of charging properties described above.

[0004] As a typical representative example of the prior art, the polystyrene surface abundance and domain size of a compound having releasability such as polypropylene are regulated to prevent toner particles from being pulverized, filming and spent are prevented, and toner is fixed to a blade. Suppressing method (JP-A-3-243956, JP-A-3-264961, JP-A-3-296067, JP-A-5-45925) and a metal-crosslinked styrene-acrylic copolymer resin Toner, ammonium salt-modified polysiloxane, or inorganic fine particles treated with a nitrogen-containing coupling agent, and a developer comprising a fluororesin-coated carrier have excellent low-temperature fixability, hot offset resistance, and storage stability. (Japanese Patent Laid-Open No. 2-110473, Japanese Patent Laid-Open No. 2-1104)
No. 74).

However, the present situation is that the fogging of images and the scattering of toner have not been sufficiently improved.

[0006]

The inorganic fine particles are uniformly adhered to the toner particles, the generation of weakly charged and oppositely charged toner is prevented, and image fog and toner scattering are reduced.

[0007]

The present invention has been made to solve the above problems. That is, the present inventors
In the aforementioned kneading and pulverizing steps, it is necessary to make the surface of the colored particles uniform in charge property, specifically, to uniformly disperse the release agent that forms the domain with the resin, on the toner surface of the external additive. They found that it is important to improve the uniformity, and completed the invention.

That is, in a one-component developing toner comprising colored particles consisting of at least a resin, a magnetic material and a releasing agent and inorganic fine particles, the amount of the releasing agent on the surface of the colored particles is 0.1 to 0.3, This is achieved by a magnetic toner for one-component development, wherein the release agent domain diameter in the colored particles is in the range of 0.1 to 1.0 μm.

The release agent domain diameter means 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 kneading machine of the kneading step, the kneaded material average filling degree of 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 in the kneaded material, particularly the release agent, can be uniformly dispersed. The amount of the surface release agent can be achieved by controlling the amount returned to the crushing process in the closed circuit crushing system. The negatively chargeable release agent is uniformly dispersed in the colored particles, so that the negatively charged property on the surface of the colored particles is made uniform, and it is selected in a portion where the inorganic fine particles are easily electrostatically adhered when externally mixed. Is less likely to adhere, and the chargeability becomes uniform. As a result, the generation of weakly charged toner or oppositely charged toner is reduced, and the problems of image fog and toner scattering can be prevented. If the release agent domain diameter is less than 0.1 μm, it is difficult for the inorganic fine particles to adhere, 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 increases. To 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 prepared with a microtome. This section was photographed with a transmission electron microscope at a negative magnification of 280 times and enlarged to produce a 1200 times photograph. The domain diameter is measured using an image analyzer (SPICCA: Nippon Avionics Co., Ltd.). Here, the domain diameter was measured by the number average diameter.

The amount of the surface release agent is, for example, when the resin containing oxygen such as styrene-acrylic polymer is used and the release agent is a hydrocarbon compound such as low molecular weight polyolefin. Can be defined by the amount of oxygen obtained by performing surface analysis on the toner surface by ESCA. The amount of surface release agent in the text is expressed by the reciprocal of the amount of oxygen obtained by ESCA.

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

ESCA measuring instruments include model 5400 series manufactured by ULVAC-PHI, Inc.

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

Measuring device: Perkin Elmer PHI model 560ESCA / SAM Measuring condition: X-ray output 15kV, 26.7mA Sample adjustment: Toner is sprinkled on a double-sided tape and fixed on the sample stand. Carbon C is used for quantitative calculation. A peak of _1S oxygen O _1S nitrogen N _1S was used, and each amount was obtained from the area of the peak. Using these peak areas, the intensity ratio was corrected by the sensitivity coefficient as the intensity correction by each element.

The sensitivity coefficient is "Hand" manufactured by Perkin Elmer.
"Book of Xray PHOTOELECTRON SPECTROS COPY". The amount of oxygen existing on the surface was calculated from the element ratio (AC) obtained as described above and expressed as the reciprocal.

If the amount of the oxygen release agent on the toner surface is less than 0.1, the inorganic fine particles are less likely to adhere, and if it exceeds 0.3, the negative chargeability of the release agent becomes a problem, and weakly charged toner and oppositely charged toner are generated. , Problems such as image fogging and toner scattering occur.

[0019]

As the raw material for 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. The number average primary particle diameter is the one observed by a transmission electron microscope. The addition amount of the magnetic substance is preferably 30 to 100 parts by weight with respect to 100 parts by weight of the resin. Also,
Magnetization at 1000 Oe when used as toner is 20-40emu /
It is preferable to adjust to about g. When the magnetization is low, the holding to the developing device becomes insufficient, so-called toner scattering occurs, and when the magnetization is high, the holding to the developing device becomes excessive, resulting in a problem that the developing property is deteriorated. The magnetization shows a value measured by applying a magnetic field of 1000 Oe by a BH meter.

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

As the charge control agent, a nigrosine dye, 4
An organic salt or complex containing a secondary ammonium salt compound, an alkylpyridinium compound and a divalent or higher valent metal can be used.

As the releasing agent, for example, low molecular weight polyethylene having a number average molecular weight (the number average molecular weight shows a polystyrene molecular weight conversion value in high temperature GPC) of 1500 to 5000, low molecular weight polypropylene, low molecular weight polyethylene-polypropylene copolymer weight Polyolefin wax such as coalesced,
High melting point paraffin wax such as microcrystalline wax and Fischer-Tropsch wax can be used.

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

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

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

Appropriately blending the above-mentioned raw materials, and mixing, melting, cooling, pulverizing, classifying and steps to obtain colored particles. At this time, the water content of the colored particles is usually 0.1% by weight or less, and the particles are in a state of being easily charged. (It is known that the particles just after crushing are actually charged with each other.) Next, the 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 property, an amino-modified silane coupling agent, amino-modified silicone oil, polysiloxane ammonium salt, organopolysiloxane and amine-modified silicon compound such as 3-aminopropyltriethoxysilane can be used. By the surface treatment, the chargeability can be adjusted. Particularly, it is preferable to use silica after the surface treatment.

As the inorganic fine particles, those having a number average particle diameter of primary average particle diameter of 0.005 to 0.5 μm are preferable, and particularly 0.0
It is preferably from 07 to 0.1 μm. The primary average particle of the inorganic fine particles means the number average particle diameter observed by a transmission electron microscope and measured by image analysis.

Inorganic fine particles 0.2 g and volume average particle diameter 100 μ
20g of iron powder carrier of m and 20 ° C, relative humidity of 50% 2
0 minute shaker (shaker: Yayoi YS-LD), blow-off powder charge amount measuring device "TB-200" (manufactured by Toshiba Chemical Co.) with a charge amount of +3 to 300 μc / g Is good. Particularly desirable is 10 to 150 μc / g.
When the charge amount exceeds 300 μc / g, the toner charge amount becomes too high and the developability is deteriorated. On the other hand, when the charge amount is less 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 inorganic fine particles used is 0.01
The range of 5 to 5% by weight is preferable, and the range of 0.05 to 2% by weight is particularly preferable. When the amount of the inorganic fine particles used exceeds 5% by weight, the inorganic fine particles are liberated and adhere to the photosensitive drum, causing scratches on the drum.

On the other hand, if the amount used is less than 0.05% by weight, the effect of adding the inorganic fine particles will not be exhibited.

The toner crushing method preferably used in the present invention includes a closed circuit crushing method, which is a method in which the separated coarse powder is directly returned to the crusher by a coarse powder classifier after crushing with a crusher. The basic process diagram is shown in FIG.

The pulverized raw material is fed from the pulverized raw material quantitative feeder 1 to
It is supplied to the crusher 2 and crushed. The crushed product is a coarse particle classifier 3
The coarse particles are classified by a classifier and then collected by a cyclone 4 to obtain a crushed product. Exhaust gas from the cyclone is discharged by a blower 6 after separating fine powder with a bag filter 5.

On the other hand, the coarse powder separated by the coarse-grain classifier 3 is returned to the crusher and circulated as return powder. Here, the coarse powder refers to particles that are coarser than the desired toner volume average particle diameter (DA), and when the volume average particle diameter is DB, 1.1 <DB / DA <1.3.

The magnetic toner of the present invention has improved chargeability uniformity, and is particularly suitable for a system in which a developer is conveyed in a thin layer to a developing area for 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. Therefore, the toner is required to have high charge rising characteristics. There is. In the toner of the present invention, since the inorganic fine particles are uniformly attached to the surface of the colored particles, the rise of charging is good, and therefore the toner can be used in the process by the thin layer forming method.

The thin layer forming method means a method of forming a toner layer of 20 to 500 μm on the surface of the developing sleeve in the developing area. When forming this thin layer, there is a method of regulating the toner layer on the surface of the magnetic blade or the developing sleeve using magnetic force. Further, there is also 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 regulation system, the pressing force of the pressure regulation member is preferably 1 to 15 gf / mm. When the pressing force is small, the regulation force is insufficient and the conveyance becomes unstable. 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 photoreceptor may be larger or smaller than the toner layer. Further, a system in which only the DC component is applied as the developing bias may be used,
Any method of applying an AC bias may be used.

[0040]

The present invention will be described in detail below with reference to examples, but the 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 The above components are mixed, melted and kneaded. -Coloring particles having a volume average particle size of 8.5 µm with different polypropylene surface abundance and domain diameter were obtained by changing the conditions of pulverization and classification. Toner was obtained by externally adding 0.8% by weight of the following four types of inorganic fine particles A to D to the colored particles. Five types of toners in the present invention (Examples 1 to 1)
5) and the contents of four toners (Comparative Examples 1 to 4) other than the present invention are shown in "Table 1" described later.

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

(Evaluation of actual machine) The evaluation was made by modifying the laser printer LP-3015 manufactured by Konica to a printing speed of A4 longitudinal feed of 20 sheets / min, and a diameter of 25 mm with a built-in 6-pole fixed magnet.
The development sleeve is made of magnetic stainless steel and has a development area gap: Dsd = 0.2 mm, and the toner layer on the surface of the developing device in the development area is 0.15 mm. The photosensitive member is a laminated organic photosensitive member and the developing portion potential is -500.
V, and the developing bias from peak to peak is -50 to -550.
An AC bias with a frequency of 2 kHz and a DC bias of -250 V was applied.

[0044]

[Table 1]

Evaluation Criteria Fog Toner Scraping Amount Correspondence on Image 10 g or less No image fogging and toner scattering 10 to 14 g There is no problem in practical use, but there is a tendency to fogging Image fogging and toner scattering occurrence results are shown in Example 1 In 5, the fog toner scraping amount is
The amount was 14 g or less, and good results with less image fog and toner scattering were obtained. On the other hand, in Comparative Examples 1 to 4, the amount of fogging toner scraped off was 14 g or more, and image fogging and toner scattering occurred.

(Evaluation of Durability in Actual Image) Using the toners of Examples 1 to 5 and Comparative Examples 1 to 4 and using the above evaluation machine, 20
When a long run of 50,000 copies was performed in an environment of 50 ° C. and a relative temperature of 50%, the amount of recovered 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, the dispersibility of the external additive in the developing toner particles can be improved and the chargeability can be made uniform. Therefore, it is possible to improve the background fog and the image quality, and it is also possible to improve the toner consumption amount, the collection amount, and the transfer rate.

[Brief description of drawings]

FIG. 1 is a process diagram of a closed circuit crushing device preferably used for carrying out the present invention.

[Explanation of symbols] 1 crushing raw material quantitative feeder 2 crushing machine 3 coarse particle classifier 4 cyclone 5 bag filter 6 blower 7 crushing raw material supply 8 return powder supply (circulating coarse powder)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kensuke Endo 2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica Stock Company

Claims (2)

[Claims] 1. In a one-component developing toner comprising colored particles comprising at least a resin, a magnetic material and a releasing agent and inorganic fine particles, the amount of the releasing agent on the surface of the colored particles is 0.1 to 0.3, A magnetic toner for one-component development, wherein the release agent domain diameter in the colored particles is in the range of 0.1 to 1.0 μm. 2. The charge amount of the inorganic fine particles is 3 to 300 μc /
2. The magnetic toner for one-component development according to claim 1, wherein g and the number average particle diameter are 0.005 to 0.5 μm in terms of primary average particle diameter.