JPH01101557A - Toner for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To obtain good images even if many sheet of copies are formed by using the title toner to a nonmagnetic one-component developing method by forming the toner of the toner particles added with hydrophobic silica and fine resin particles having <=1mum average grain size on the surface of nonmagnetic particles contg. a binder resin, coloring agent and fine particles of a polishing agent and specifying the grain size of the toner particles. CONSTITUTION:The toner 8 contains the fine particles of the polishing agent in the toner particles. The surface of a sleeve 1 is polished by the parts exposed on the surfaces of the toner particles among the fine particles of the polishing agent and the surface of the sleeve 1 is polished by the fine silica particles added to the surfaces of the toner particles, by which the sticking of the toner 8 is prevented. The flowability and fixability of the toner are improved by adding the fine resin particles to the surfaces of the toner particles. The grain size distribution of the toner is adjusted to the average grain sizes ranging 8-10mum and is so adjusted that the particles having >=20mum grain size are not incorporated into the toner particles. The high-quality images having the good fixability are thereby obtd. even if many sheets of copies are formed.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to toners used to develop electrostatic images in electrophotography, electrostatic printing, etc., and particularly to one-component nonmagnetic toners. Regarding.

[Conventional technology]

In electrophotography, electrostatic printing, etc., an electrostatic charge image is formed on the surface of a photoreceptor by various means, this electrostatic charge image is developed with toner, and the developed toner image is printed on plain paper, etc. Generally, the image is transferred and then fixed to obtain the final image.

A common method for developing electrostatic images is the magnetic brush method, which uses a mixed powder of a carrier such as iron powder or ferrite powder and a toner mainly containing a resin colorant. Two-component repellents have been widely used. The disadvantages of using a two-component developer are that the image quality is unstable unless the mixing ratio of toner and carrier (toner concentration) is strictly controlled, so a means of controlling the toner concentration is required, and it can be used for a long time. When using the carrier, the surface of the carrier becomes contaminated with toner, and the triboelectric charging ability of the carrier decreases.

In order to overcome these drawbacks, a one-component developing method using a magnetic toner mainly composed of resin and magnetic powder has been developed and put into practical use. In the one-component development method, an insulating magnetic toner is often used to obtain good transferability (see, for example, Japanese Patent Laid-Open No. 31136/1983). Although various developing methods have been proposed, a method in which the toner is triboelectrically charged by friction between the toners or between the toner and a sleeve or the like is often used.

However, the developing method using triboelectric charging of toner has drawbacks in that the toner tends to aggregate and the image quality tends to change depending on environmental conditions. Further, since magnetic toner contains about 20 to 70% by weight of magnetic powder such as magnetite, it has a disadvantage that it has poorer fixing properties than two-component developers.

For these reasons, a developing method using a non-magnetic one-component toner that does not contain magnetic powder is attracting attention.

As the nonmagnetic one-component development method, an impression development method, a touchdown development method, or a jumping development method is well known. However, in the impression development method and the touchdown development method, since the toner carrier and the photoreceptor come into contact with each other, caps occur. In addition, in the jumping development method, in order to increase development efficiency, it is necessary to narrow the gap between the toner-carrying body and the photoreceptor, and to bind a thin layer of toner in this gap. difficult to form.

Therefore, in order to eliminate these drawbacks, it has been considered to use a sleeve having a plurality of floating electrodes on its surface as a toner carrier. As shown in FIGS. 1 and 2, the sleeve 1 includes a dielectric layer 3 formed on a base 2 made of a non-magnetic and conductive material such as aluminum or stainless steel, and a dielectric layer 3 formed on the surface of the dielectric layer 3. It has a structure in which a large number of dielectric particles forming the microelectrodes 4 are kept electrically insulated from each other. A sleeve having such a structure is disclosed in, for example, Japanese Patent Application Laid-Open No. 1986-
No. 225179. According to the apparatus shown in FIG. 1, the sleeve l is rotated while the toner 8 housed in the container 5 is triboelectrically charged by an appropriate means (not shown), and along with the rotation, a doctor is used to regulate the thickness of the sleeve and the toner layer. By connecting a bias voltage source 7 between one member 6 and applying a bias voltage between the two, the photoreceptor 10
An electrostatic charge image (not shown) formed on the surface is developed. According to this developing method, it is possible to stably exhibit a sufficient edge effect, so that it is possible to obtain both good surface images and line images.

[Problem that the invention seeks to solve]

The above-mentioned non-magnetic one-component toner is mainly composed of a binder resin and a colorant, so when used for a long period of time, the toner adheres to the surface of the developing roll (for example, a sleeve with a microelectrode), causing the toner to deteriorate. A thin layer will be formed. As a result, even if a bias voltage is applied to the sleeve, the electric field strength between the microelectrode and the photoreceptor decreases, resulting in a problem that the image density decreases.

Therefore, an object of the present invention is to provide a toner for developing electrostatic images that can be applied to a non-magnetic one-component developing method and that can produce good images even when a large number of copies are made.

Means for Solving Problems] The toner for developing electrostatic images of the present invention has hydrophobic silica on the surface of nonmagnetic particles containing a binder resin, a colorant, and fine abrasive particles, and an average particle size of 1 μm or less. The toner particles have an average particle size of 8 to 1.
It is characterized by having a particle size distribution in the range of 0 μm and substantially free of particles with a particle size of 20 μm or more.

The toner of the present invention contains fine abrasive particles inside the toner particles, and the part exposed on the surface of the toner particles inside the fine abrasive particles polishes the sleeve surface, and fine silica powder added to the surface of the toner particles. By polishing the sleeve surface, toner adhesion is prevented, and furthermore, by adding resin fine particles to the surface of the toner particles, fluidity and fixing properties are improved.

Each material constituting the present invention will be described.

Examples of binder resins include polystyrene, styrene, etc.
Known toner resins such as butadiene copolymers, styrene resins such as styrene/acrylic acid esters, epoxy resins, and polyester resins can be used alone or in combination.

Colorants include carbon blank, chrome yellow,
Hansa Yellow, Benzine Yellow, Rose Bengal,
Known pigments or dyes such as aniline red, phthalocyanine blue, aniline blue, nigrosine dye, and aniline black can be used. The amount added is 3-10%
Good weight range.

As the abrasive particles, materials such as nitride-based or carbide-based ceramics, and ceramics that are a mixture thereof can be used. Examples of such ceramics include B, C5TtC% StC5TiN -.

5iJa. The size of the abrasive fine particles is desirably 3 μm or less in average particle size in order to ensure uniform dispersion in the toner and to prevent damage to the roll surface.

The amount added should be 0.5 to 3. The range is preferably 5% by weight, more preferably 0.7 to 2.0% by weight.

The above ceramics can be made by known methods. For example, a method (see JP-A-59-227765) of heating ceramics or a mixture of ceramics and metal or carbon using an arc or plasma jet generated in hydrogen or nitrogen gas alone or in a mixed gas can be applied.

The toner particles according to the present invention can contain additives such as a charge control agent, a mold release agent, and a filler in addition to the above-mentioned components. Charge control agents include nigrosine dyes, reaction products of nigrosine dyes and carboxyl group-containing resins, triphenylmethane dyes, metal-containing (Cr) azo dyes, etc. Release agents include polypropylene, polyethylene, paraffin wax, carnauba, etc. wax, amide wax, etc.
As the filler, inorganic fine powder such as calcium carbonate, talc, clay, etc. can be used. These contents are determined as appropriate depending on the characteristics required of the toner, but generally the charge control agent is 1 to 5, the release agent is 1 to 5, and the filler is 1 to 10% by weight. Range is preferred.

Next, fine powder silica is added to the surface of the above toner particles in order to prevent the toner from adhering to the surface of the developing sleeve, and the amount of addition is 0.5 to 100 parts by weight of the toner particles. The range of 2 parts by weight is preferable; if the amount added is less than 0.5 parts by weight, the fluidity will decrease and the abrasive action on the sleeve surface will be small, and if it exceeds 2 parts by weight, the fixing properties will deteriorate, which is not preferable. As this fine powder silica, commercially available hydrophobic colloidal silica may be used as is, but from the viewpoint of toner fluidity and humidity resistance stability, one with a hydrophobicity index of 50 or more (Japanese Patent Application Laid-open No. 58-81650 ) is preferred. Furthermore, when hydrophobic colloidal silica having an average particle size of 14 nm or more is used, fluidity is further improved.

In addition, in the present invention, fine resin particles are added to the surface of the toner particles in order to improve fluidity and fixing properties, but if the particle size is too large, they will easily separate from the toner particles and stain the image. Fine particles with a diameter of 1 μl or less should be used. The amount added is preferably in the range of 1 to 5 parts by weight per 100 parts by weight of toner particles.

If the amount added is less than 1 part by weight, there is no effect, and if it exceeds 5 parts by weight, the chargeability of the toner becomes unstable due to the presence of excess resin particles liberated from the surface of the toner particles. Such fine resin particles preferably have a glass transition temperature of 50° C. or higher in order to prevent toner agglomeration.

As the resin constituting such resin particles, known thermoplastic resins can be used, such as acrylic resins or copolymers of acrylic-vinyl monomers such as polymethyl methacrylate and poly-n-butyl methacrylate copolymers. It will be done.

The toner of the present invention can be manufactured by a known method such as a pulverization method or a spray drying method. In the case of the pulverization method, the raw materials are premixed using a ball mill, dry mixer, etc., heated and kneaded using a kneader and rolls, cooled, pulverized using a jet mill, and then classified to obtain toner particles. Thereafter, hydrophobic silica and fine resin particles are added to the toner particles and mixed to retain them on the surface of the toner particles. From the viewpoint of image quality, the particle size distribution of the toner is such that the average particle size is in the range of 8 to 10 μm, and the particle size is 2.
It is preferable to adjust the composition so that it does not substantially contain particles of 0 μm or more, for the following reason. Average particle size is 8μm
If it is less than 10 μm, the fluidity will be extremely reduced and the toner will easily scatter, and if it exceeds 10 μm, the toner adhering to the literature area will be noticeable on the printed image, the resolution will decrease, and particles with a particle size of 20 μm or more will This is because if a large amount of .

〔Example〕

The present invention will be specifically explained with reference to the following examples.

Styrene/acrylic copolymer (Himer S manufactured by Sanyo Chemical Co., Ltd.
BM600) 77 parts by weight, carbon black (Mitsubishi Kasei #50) 10 parts by weight, low molecular weight polypropylene (Sanyo Kasei Viscole 550 P) 3 parts by weight, charge control agent (
Orient Chemical Bontron 554) 2 parts by weight, silicon carbide fine powder (Showa Denko DU-AI, average particle size 0.45)
．． um) 1 part by weight, CaC03 (Nitto Funka Kogyo NS#
2500, average particle size 0.89 μm) were dry mixed in a ball mill, heated and kneaded in a kneader, cooled and crushed in a jet mill, and classified to produce one particle of 5 toner.

Next, fine powder of hydrophobic colloidal silica (hydrophobicity index 60, average particle size 16 nm) and polymethyl methacrylate (hereinafter referred to as PMMA, average particle size 0.4 μm, glass transition temperature 53° C.) was added to the above toner particles. , and mixed in a Henschel mixer to produce a toner. Here silica and P
Seven types of toners shown in Table 1 were manufactured by varying the amount of MMA fine particles added. The average particle size of each toner is 9 μm,
In addition, the content of particles of 20 μm or more in each toner is 2% by weight.
Met.

Note that the above colloidal silica was created by the following procedure. First, 10 parts of commercially available colloidal silica (Aerosil #130 manufactured by Nippon Aerosil) were placed in a high-speed rotating mixer, and while rotating at 8000 r, p, m, 1 part by weight of hexamethyldisilazane was diluted with 8 parts by weight of hexane. The solution was added dropwise and dispersed.

Next, the obtained powder liquid was heated and stirred at 150° C. for 4 hours to obtain hydrophobized colloidal silica.

Further, PMMA fine particles were created according to the following procedure.

I equipped with a stirrer, thermometer, nitrogen inlet tube, and reflux condenser
100 parts by weight of methyl nucleate and 300 parts by weight of distilled water were placed in a four-bottle flask (E), and a redox catalyst consisting of potassium persulfate and sodium thiosulfate was added as an initiator at 5 x 10-'won! The mixture was added at a ratio of e/l, and the reaction was carried out at 60° C. for 2 hours in a nitrogen stream. Thereafter, the solution was cooled to a temperature of 20° C., and PMMA fine particles were obtained using a filtration device and a hot air dryer.

The electrostatic charge image on the OPC photoreceptor is developed using each of the above toners, the resulting toner image is transferred to plain paper, and then heat roll fixing (fixing temperature 165°C, fixing pressure 1 kg/a
m) was carried out. The development is performed using sleeve 1 in FIG.
was rotated at a speed of 65 tm/sec, the doctor gap was set to 0.05 mm, and the photoreceptor 10 and sleeve l were
The test was carried out by placing the sleeve 1 and the doctor member 6 in a substantially contact state, and applying a DC bias voltage of -80 V between the sleeve 1 and the doctor member 6.

The evaluation results of the obtained images are also shown in Table 1.

From the results in the table above, it can be seen that when a toner (Magnetic 1) to which neither silica nor PMMA is added is used, the fixing performance is good, but the toner adheres to the sleeve surface. In addition, when using toner containing only silica (Magnetic 2 to 4),
It can be seen that although toner adhesion to the sleeve surface can be prevented, the fixing performance is reduced.

On the other hand, when the toners of the present invention (!lh5-7) were used, it was found that the toner did not adhere to the sleeve surface and had good fixing properties. However, if the amount of PMMA added is too large (m8), burr will occur, and if the amount of silica added is too large (9), the fixing performance will be reduced.

Since the main purpose of the present invention is to prevent toner from adhering to the toner conveying body, the toner of the present invention can provide the same effects as described above even when applied to devices other than those shown in FIGS. 1 and 2. Of course, it is possible to obtain

〔Effect of the invention〕

As described above, the toner of the present invention has hydrophobic silica and resin particles added to the surface of the toner particles including abrasive particles, so it can be applied to, for example, a non-magnetic one-component system using a dielectric sleeve with an electrode. This effectively prevents toner from adhering to the sleeve surface even when a large number of copies are made, and it is possible to obtain high-quality images with good fixing properties.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an example of a developing device using the toner of the present invention, and FIG. 2 is a diagram schematically showing the sleeve in FIG. 1. 1 sleeve, 2: substrate, 3: dielectric layer, 4: microelectrode

Claims (1)

[Claims] (1) Toner particles are made of non-magnetic particles containing a binder resin, a colorant, and abrasive particles, and hydrophobic silica and resin particles with an average particle size of 1 μm or less are added to the surface of the toner particles, and the toner particles are average particles. The diameter is in the range of 8 to 10 μm, and
A toner for developing an electrostatic image, characterized by having a particle size distribution that substantially does not contain particles with a particle size of 20 μm or more.