JPH0584898B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a toner for dry developing electrostatic latent images such as electrophotography.

(Prior Art) Conventionally, dry development methods include a method using a two-component developer in which toner particles are mixed with carrier particles, that is, glass beads or iron powder, and a method in which a two-component developer is used in which toner particles are mixed with carrier particles, and a developer in which the toner particles themselves are made magnetic. There are methods using component toners, and more recently, methods using non-magnetic one-component toners with excellent environmental resistance have been proposed.

The conventional method for producing these toners is to heat and melt thermoplastic resins, colorants such as pigments and dyes, and additives such as wax, plasticizers, and charge control agents, and then to remove the secondary agglomerated pigments. Most of the methods involved kneading by applying strong shearing force, heating and melting magnetic powder as necessary to obtain a uniform composition, cooling this, pulverizing it, and classifying it.

However, the quality of the toner obtained by this pulverization method is limited by the size of the toner particles.
Because they have different shapes and are generally irregular, they have different frictional charging characteristics, which can cause background smudges or scattering inside the machine, and the toner has poor fluidity and is difficult to replenish, which can cause trouble. There are some drawbacks, and improvements are desired. In addition, in terms of the manufacturing process, there are problems such as the kneading process requires a large amount of energy and the need for classification, which requires a large number of man-hours.

To this end, attempts have been made to obtain spherical toner by spray drying and suspension polymerization. However, in the former case, it is necessary to select a resin with good solubility in the solution, and problems remain in the offset phenomenon to the fixing drum, and in the latter, problems in blocking and offset phenomena remain. It has not been industrialized.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned problems, eliminates the need for a toner classification step, and has particles with a rounded (angular) shape compared to conventional toners. It is an object of the present invention to provide a toner having a relatively uniform particle size, excellent flowability, and triboelectric charging properties.

[Structure of the invention]

(Means for Solving the Problem) As a result of extensive research, the present inventors have found that an electrophotographic toner with an average particle size of 5 to 15 μ and containing fine particles of 5 μ or less has an average particle size of 5 to 20 μ. , substantially 5μ
The purpose of the present invention is to provide an electrophotographic toner which is mixed by applying mechanical strain under conditions such that the following fine particles are not present. In addition, in this specification,
The particle size was measured using a Coulter Counter TA model (manufactured by Coulter Electronics), and is expressed on a volume basis.

The toner used in the present invention may be obtained by conventional methods, such as a pulverization method or a spray method, and may be used as it is, but it is preferable that there are no coarse particles of 25μ or more, but fine particles of 5μ or less are preferable. As will be explained later,
The present invention has the advantage that the particles can be sized through the mixing process.

Examples of toner resins include polystyrene, copolymers containing styrene with styrene and acrylic esters, methacrylic esters, acrylonitriles, maleic esters, etc., polyacrylic esters, polymethacrylic esters, polyesters, Examples of binder resins known per se include polyamide-based, polyvinyl acetate-based, epoxy-based resins, phenolic resins, hydrocarbon-based resins, petroleum-based resins, and chlorinated paraffin.
These can be used alone or in combination. As other additives, in addition to coloring agents such as pigments and dyes, charge control agents, and magnetic powder, lubricants such as wax, fluidity agents such as colloidal silica, and low molecular weight polyolefins may be used in combination depending on the purpose. I can do it.

Coloring agents include zinc yellow, yellow iron oxide, Hansa Yellow, Disazo Yellow, Quinoline Yellow, Permanent Yellow, Permanent Red, Red Garla, Resole Red, Watch Yan Red Ca salt,
Watchyan Red Mn Salt, Pyrazolone Red,
Lake Red C, Lake Red D, Brilliant Carmine 6B, Brilliant Carmine 3B, Dark Blue,
Phthalocyanine blue, metal-free phthalocyanine,
In addition, colored pigments such as orange, purple, and green, white pigments such as titanium oxide, and oil black, and black pigments or dyes may be used if necessary.

In the present invention, the electrophotographic toner containing the aforementioned fine particles of 5 μm or less and having an average particle size of 5 to 15 μm is machined under conditions such that the average particle size is 5 to 20 μm and substantially no fine particles of 5 μm or less are present. The method of mixing by applying a certain strain force is such that the toner does not fuse into large lumps, or conversely, the strain force is too large and the toner is not pulverized into fine particles, and the toner surface is The conditions are such that at least a portion of the charge control agent is embedded in the charge control agent. As a specific method that satisfies both of these conditions, a mortar is used in the laboratory. Industrially, conditions such as operating conditions, throughput, dispersion medium, etc. of dispersing machines such as attritors, ball mills, and sand mills, which exhibit effects similar to those of mortar, may be changed so as to achieve the above objectives.

However, in a mortar, it takes several hours to several tens of days, and in a ball mill or sand mill, it takes a long time, so industrially, powder is mixed in a fluidized bed state, with a mixer in which the powder moves at high speed with air current, or in an impact mill. An example of such a mixer is the SI mill (manufactured by Toyo Ink Mfg. Co., Ltd.; see Japanese Patent Publication No. 57-43051 for an overview). , an atomizer, a Jiyu crusher (Nara Kikai Seisakusho Co., Ltd.), a crusher manufactured by Kawasaki Heavy Industries, Ltd. (KTM-1), etc., and these devices can be used as they are or modified as appropriate for the purpose of the present invention. It can be modified and used. If possible, a closed system with a circulation system is preferable.

This mixing process eliminates the presence of fine toner particles and produces the effect of particle size regulation, because toner particles collide with each other or with dispersion media such as walls, blades, and beads. It is thought that a phenomenon similar to a mechanochemical reaction in the field of inorganic chemistry occurs, where the temperature instantaneously and locally becomes quite high, and the air flow temperature in the system rises to near the Tg of the resin. , it may also be necessary to cool the system. The above phenomenon is
This can be understood by observing electron micrographs before and after pre-mixing. In other words, before the mixing process, relatively angular, large toner particles and fine toner particles are partially aggregated, and after the process, the surface of the toner is smooth and almost no fine toner particles can be seen. Moreover, the particles are resistant to breakage even during running tests in copying machines. Furthermore, according to the measurement of particle size distribution, it is recognized that the average particle size has increased by about 10% after the mixing treatment.

Further, it is observed that the toner after the treatment has a uniform particle size and the corners of the particles are rounded. That is, it is considered that toner particles having a small particle size are sized into particles of a constant size by the mixing process.

Various factors can be considered to obtain the above effects, but according to research by the present inventors, the speed of airflow is the highest, and is preferably from several tens of meters/second to several hundred meters/second.

The particle size of the toner according to the present invention is preferably in the range of several microns to 20 microns in average particle diameter, and substantially does not contain toner with a particle size of 5 microns or less and 25 microns or more.
When the amount of toner with a particle size of 5μ or less increases, fluidity deteriorates and background smudges occur. Furthermore, if the amount of toner with a size of 25 μm or more increases, the image becomes distorted and the commercial value decreases, but in the toner of the present invention, the particles of 5 μm or less are sized, so no special classification is required.

In the present invention, when a one-component magnetic toner is used, a known toner containing magnetic powder may be used, and the magnetic powder may include various types of ferrite, magnetite, hematite, iron, zinc, etc.
Known magnetic powders such as alloys or compounds of cobalt, nickel, manganese, etc. can be used. Depending on the purpose, these magnetic powders may be classified or may be subjected to surface treatments known per se, such as hydrophobic. It may be treated with a silane coupling agent or the like.

The charge control agent used in the present invention is known per se, for example,
HBN, Nigrosine Base, Brilliant Spirit, Pomegranate X, Ceres Cucumber
There are dyes such as RG, copper phthalocyanine dyes, and metal-containing dyes, as well as CI solvent black 1,
2, 3, 5, 7, CI Assisted Black 123, 22,
23, 28, 42, 43, oil black (CI26150),
Examples include dyes such as spiro black, quaternary ammonium salts, naphthenic acid metal salts, fatty acid or resin acid metal soaps, and colloidal silica.

The present invention will be explained below using specific examples. The middle part of the example shows parts by weight.

Example 1 Styrene-acrylic resin (manufactured by Sanyo Kasei Co., Ltd., trade name Hymer SBM-73) 88 parts, charge control agent (manufactured by Orient Chemical Co., Ltd., trade name Bontron S-34) 4 parts
1 part, 5 parts of carbon black and low molecular weight polypropylene (manufactured by Sanyo Kasei Co., Ltd., trade name Vinicol)
550P) were premixed in a Henschel mixer, melted and kneaded in a twin-screw extruder, allowed to cool, and coarsely crushed this kneaded product in an I-type jet mill to a powder with an upper limit particle size of 25μ. A toner having an average particle size of about 10 μm was prepared below. This toner contained approximately 3% of fine particles of 5 μm or less.

This toner was premixed for 1 minute at a rotational speed of 2500 rpm using a super mixer, and then introduced into a free mill M-3 with an internal rotational speed of 5000 rpm. The airflow velocity in the free mill at this time is approximately 90m/
The average residence time of the introduced mixture in the system was about 3 seconds, and the mixture discharged to the collector was passed through the free mill seven times in total to obtain the desired toner.

The average particle size of the toner particles was 11μ, and there were substantially no particles smaller than 5μ and particles larger than 25μ, and no classification was required.

80 parts of this toner and iron powder carrier (Dowa Iron Powder Co., Ltd.)
720 parts of DSP 128B (trade name: DSP 128B) were mixed in a ball mill for 1 hour to prepare a two-component developer.
This is a commercially available copying machine (manufactured by Sanda Kogyo Co., Ltd., product name: DC).
-232) and made continuous copies on plain paper using a test chart.

In this copying, the toner's fixability, charging stability, blocking resistance, and offset resistance were extremely good, and in a running image test in which the toner of the present invention was put into the toner supply hopper in the copying machine, 60,000 sheets were printed. An image equivalent to the initial image was maintained over the period of time, and toner replenishment performance was also good.

Example 2 A toner was obtained in the same manner as in Example 1, except that a red organic pigment (No. 28 Lionol Red, trade name manufactured by Toyo Ink Mfg. Co., Ltd.) was used instead of carbon black, and the same test was carried out. When I did that,
Again, it shows an excellent effect, and there was no filming phenomenon of the pigment on the photoreceptor, which is often a problem when using a toner using an organic pigment as a coloring agent by the conventional method.

Comparative Example 1 When the same test as in Example 1 was carried out using fine particles of 5μ or less cut from the toner before the mixing process of Example 2, some fading was observed in the solid areas when compared with the toner of the present invention. According to a running test, a decrease in image density was observed after approximately 5,000 copies, a filming phenomenon of red pigment occurred on the photoreceptor, and a bridging phenomenon was observed in the replenishment hopper.

Example 3 Styrene-acrylic resin (Nippon Carbide Industries)
(manufactured by Sanyo Chemical Co., Ltd., trade name: Nicalite-NC-6100), 53 parts of carbon black, 3 parts of low molecular weight polypropylene (manufactured by Sanyo Kasei Co., Ltd., trade name: Vinicol 550P), and a charge control agent (manufactured by Orient Chemical Co., Ltd.). A toner having an average particle size of about 10 μm was prepared by using 4 parts of 4 parts (trade name: Bontron E-81) and 40 parts of magnetite (manufactured by Toda Kogyo Co., Ltd., trade name EPT-500) in the same manner as in Example 1. . This toner contained approximately 3% of fine particles of 5 μm or less.

This toner was premixed for 1 minute at a rotation speed of 280 rpm using a super mixer, and then introduced into a closed system atomizer, and the rotation speed of the internal rotating blade was set to 4500 rpm. The airflow velocity at this time is 80m/
The introduced mixture remained for 30 seconds and was then discharged to the Sunclone collector to obtain toner.

The average particle size of this toner was 12.5μ, and no particles smaller than 5μ or larger than 25μ were measured.

Apply 200g of this magnetic toner to a commercially available copier (Canon).
The test chart was set in a developing machine (NP-500 (trade name, manufactured by Canon Inc.)) and a clear image was obtained by copying the test chart onto plain paper.

The fixing properties, charging stability, blocking resistance, and offset resistance of the toner are extremely good.When we conducted a running test while adding toner, images equivalent to the initial image were obtained over 50,000 sheets, and the toner No bridging phenomenon was observed.

Comparative Example 2 When the same test as in Example 2 was conducted using the toner from which fine particles of 5 μm or less were cut from the toner before the mixing process of Example 3, the image density decreased after approximately 10,000 copies, and background smear occurred. A bridging phenomenon was observed within the hopper.

Example 5 In Example 1, instead of the styrene-acrylic resin, polyester resin (manufactured by Kao Corporation, trade name
A toner obtained in the same manner except that KTR-2500) was used showed similar good suitability.

(Effects of the Invention) The toner for electrophotography according to the present invention is a particle without corners, has an unbreakable surface, and has a relatively uniform particle size, so it has good fluidity and charge stability. Excellent, and shows good characteristics even in long-term running tests. Due to this characteristic, it is also suitable for developing devices that use non-magnetic one-component toners, such as the one shown in Japanese Patent Application Laid-Open No. 60-22150, where conventional toners had various problems. It's Tona.

Claims (1)

[Claims] 1. Electrophotographic toner having an average particle size of 5 to 15 μ and containing fine particles of 5 μ or less is mixed by applying mechanical strain to the toner, which has an average particle size of 5 to 20 μ and is substantially 5 μ.
The following method for producing an electrophotographic toner that does not contain fine particles. 2. A method for producing a one-component magnetic toner according to claim 1, characterized in that a toner containing magnetic powder is used. 3. The method for producing a non-magnetic one-component magnetic toner according to claim 1, characterized in that a toner containing no magnetic powder is used.