JPH0442234A - Conductive fine particle toner - Google Patents

Abstract

PURPOSE:To obtain the conductive fine particle toner having excellent fine line reproducibility, gradation characteristic, etc., for developing electrostatic charge image by grinding a compsn. formed by dispersing a carbon black in a thermoplastic resin with a grinding mill to form unshaped particles and specifying the average grain size based on weight and specific volume resistivity thereof. CONSTITUTION:This toner is formed of the unshaped particles obtd. by grinding the compsn. formed by dispersing at least the carbon black into the thermoplastic resin or the compsn. formed by dispersing coloring agents and conductive particles therein with the grinding mill utilizing mechanical impact forces. The average grain size based on weight thereof is specified to 0.5 to 5mum and the specific volume resistivity to about <= 1X10<10>OMEGAcm. The binder component preferably contains the thermoplastic resin having <= 1.5kgcm/cm<2> Izod impact value as its essential component. Printed matter having high fineness and high gradation is obtd. by using the toner having <= 5mum average grain size based on weight in this way.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Field of Application) The present invention provides improvements in fine line reproducibility, gradation, etc. for developing electrostatic images in electrophotography, electrostatic recording, etc. This invention relates to an excellent conductive fine particle toner.

(Prior Art) At present, dry development is the mainstream method for developing electrostatic images such as electrophotography and electrostatic recording, which are widely used in copying machines, printers, etc., and toner is used to develop them. is powder toner. There are two types of powder toner: insulating toner and conductive toner. Development with conductive toner has the following features.

■Since it does not utilize static charges caused by frictional charging, it can eliminate the effects of humidity.

2. Since the charge of the toner can be selected by the charge induced by the electrostatic latent image or by an arbitrary bias voltage, it is possible to perform more quantitative development than toner development using triboelectric charging, which improves halftone reproduction and solid areas. You can obtain images with excellent reproduction.

3. It becomes possible to select from a wider range of toner constituents such as resins, pigments, and additives.

4. Since a uniform charge can be applied to the toner, images with excellent resolution and less background smudge can be obtained.

5. Easy one-component development becomes possible.

6. Since a frictional charging mechanism is not required, the structure of the developing device is simplified and can be made smaller.

7. Both normal development and reverse development can be performed using the same toner.

8. Because the toner is conductive, it is easy to clean.

9. Since the conductive toner layer can be brought into contact with each other for a long time, development can be performed without toner scattering.

10 The toner has good fluidity and is less likely to cause agglomeration, freonking, or clogging of the toner replenishment unit inside the developing device.

On the other hand, toner is required to faithfully reproduce the electrostatic latent image, and for this purpose, the average particle size of toner is small (
It is also necessary that the particle size distribution be uniform.

Various methods have been proposed for obtaining powder toner, including suspension polymerization, emulsion polymerization, and spray drying.
There are many unresolved problems such as residual dispersion stabilizer and entrainment of solvents, so at present dyes, pigments, magnetic powders, etc. are melted in binder resin, dispersed by kneading, and then mechanically pulverized after cooling. A common method is to classify and obtain the pulverization method.

However, since the L-toner obtained by this pulverization method has an amorphous shape with many corners, when the obtained toner is an insulating toner, as the average particle size of the toner becomes smaller, the toner powder becomes smaller. liquidity deteriorated significantly,
When the average particle size is less than 5 μm, agglomeration and blocking occur inside the developing device, and clogging occurs during toner replenishment, making it practically unusable.

(Problem to be solved by the invention) The present invention uses fine particle toner of 5 μm or less, which could not be used conventionally due to its poor fluidity, to produce images with excellent fine line reproducibility, gradation, etc. This makes it possible to obtain

[Structure of the invention]

(Means for Solving the Problems) The present invention utilizes mechanical impact force to generate a composition in which at least carbon black is dispersed in a thermoplastic resin, or a composition in which a colorant and conductive particles are dispersed. Amorphous particles obtained by pulverizing with a pulverizer, having a weight-based average particle size of 0.5 μm to 5 μm, and
The present invention relates to a conductive fine particle toner having a volume resistivity of about 1X1010 Ωcm or less.

In the present invention, the binder component preferably contains as a main component a thermoplastic resin having an Izod impact value of 5 kg cm/cnf or less. Furthermore, the thermoplastic resin is contained in an amount of 70% by weight or more of all binder components, preferably 90% by weight of all binder components. If it is less than this, it is difficult to obtain fine particle toner by pulverization.

Izod impact value is a type of utility test that uses impact load to judge the toughness and brittleness of a material. Regarding the measurement principle and method of Izotsu impact value, please refer to J.
ISK 71. Complies with IO. In this test, a bending test piece of a certain shape is destroyed by a single impact, and the impact strength of the material is determined by the amount of energy absorbed by the test piece. At present, two types of tests are used, Charpy type and Izod type, but they are basically the same test, and either can be used as long as the unit of impact value is converted. To express the test results, the quotient obtained by dividing the absorbed energy of the test piece by the cross-sectional area of the test piece is expressed in kg-cm/cri, and this is taken as the Izod impact value. The Izot impact value test piece used in the present invention is a No. 2 test piece described in JIS K7110 without a notch.

The composition, molecular weight, etc. of the resin are not particularly limited as long as the thermoplastic resin has an Izod impact value of 5 kg-cm/cnr or less. Such thermoplastic resins include polystyrene, styrene-containing copolymers of styrene and acrylic esters or methacrylic esters, acrylonitrile or maleic esters, polyacrylic esters, polyamides, epoxies, and phenolics. Examples include hydrocarbon-based and petroleum-based resins, but more preferably resins with a weight average molecular weight of 20 selected from styrene resins, epoxy resins, rosin-modified polyester resins, and heat-melting phenolic resins.
．． 000 or less. The above thermoplastic resin may be a mixture of two or more types.

The above Izotsu impact value is 1.5 kg cm/co
? Other resins may be appropriately used in combination with the following thermoplastic resins to improve fixing properties and anti-offset properties. These resins include polystyrene, styrene and acrylic ester or methacrylic ester copolymer, acrylonitrile or maleic ester and styrene copolymer, polyacrylic ester, polymethacrylic ester, and polyester. , polyamide-based, polyvinyl acetate-based, hydrocarbon-based resin, petroleum-based resin, chlorinated paraffin, and various waxes.

The composition for I-ner of the present invention contains magnetic powders such as various magnetites, ferrites, and hematites, charge control agents and dispersion aids such as metal-containing dyes, nigronone dyes, and amine compounds, colorants, charge control agents, etc. It can also be kneaded into a thermoplastic resin.

In the present invention, carbon black is used as the colorant in the case of a black toner. When using a coloring agent other than carbon black, various metal oxides or simple metals such as tin oxide, zinc oxide, copper oxide, etc. are used in combination as the conductive substance. These conductive substances have an average primary particle diameter of 0.3
It is preferable that the thickness be about μm or less.

In addition to carbon black, colorants include zinc white, yellow iron oxide, Hansa yellow, disazo yellow, quinoline yellow, permanent yellow, permanent red, red iron, Lysol red, Wochan red calcium salt, Wochan red manganese salt, and pyrazolone ret. Pigments or oil-soluble dyes such as Lake Red C1, Lake Red D1, Brilliant Carmine 6B, Brilliant Carmine 3B, navy blue, phthalocyanine blue, and titanium oxide can be used.

In the present invention, the weight average particle diameter of fine particles 1 hener is 0.5 to 5.
μm, and substantially does not contain particles larger than 10 μm.

The fine particle toner of the present invention is produced by adding a coloring agent, conductive particles, and other necessary fine particles to the binder resin, dispersing these components in the binder by melt mixing, cooling, crushing, and classifying to obtain a desired particle size distribution. You can get it by preparing it.

Examples of the crusher that utilizes mechanical impact force to obtain the fine particles 1 to 3 of the present invention include an airflow suction type, an airflow collision type,
A jet mill that uses the pressure of compressed air, such as a collision plate collision type, is preferable, but other methods include a swing hammer mill, pin mill, turbo type mill, centrifugal classification mill, etc. that utilize impact, shearing, and grinding force. A high-speed rotating mill may also be used. When visually observed using a microscope, the toner particles obtained by such a crusher have an extremely irregular shape with many corners, and are different from those produced by other manufacturing methods such as suspension polymerization, emulsion polymerization, and spray drying. significantly different.

The toner of the present invention has a volume resistivity of approximately 1×10”9 cm or less.The method for measuring the volume resistivity is as follows:
Toner is pressurized with a strong pressure of 200 kg/cnr or more to produce pellets, a voltage is applied to both ends, and calculation is made from the current value. Volume resistivity of toner is approximately 1×1010
If it exceeds Ωcm, the fluidity of the toner may be insufficient, which is not preferable.

(Effects of the Invention) According to the present invention, it is now possible to use toner with a weight-based average particle diameter of 5 μm or less, which was previously unusable due to problems such as deterioration of the fluidity of the toner. It has become possible to obtain printed matter with high gradation.

(Example) The present invention will be explained below with reference to Examples. The middle part of the example shows parts by weight.

Example 1 After premixing raw materials according to the following recipe, they were melted and kneaded in a kneader, cooled, pulverized in a jet mill, and fine powder was cut in an air classifier to obtain a powder with an average particle size of 4.1 μm. Toner particles were obtained. The average particle size was measured using a Coulter Counter (trade name 2TΔ-■, manufactured by Coulter Electric Co.). Also, when we measured the volume resistivity, it was found that 6X1
It was 06Ωcm.

Toner formulation Made of polystyrene resin (product name: REGIT 5-94, Sanyo Chemical Industries @): Izod impact value 0.5 kgcm, /
cnf or less) 47.5
1 part carbon black (product name: MA-8, manufactured by Mitsubishi Chemical Industries ■) 12.5 parts triiron tetroxide (product name: MG-WMK, manufactured by Mitsui Kinzoku Industries ■)
40 parts The toner particles thus obtained had an irregular shape with many corners when visually observed using an electron microscope. When this conductive toner was transferred onto electrostatic recording paper using a modified copying machine that uses a commercially available one-component magnetic toner, a good image was obtained.

The volume resistivity was measured as follows.

In a commercially available tablet molding machine for infrared absorption spectrum measurement (inner cross section of molding or circle with a diameter of 20 mm), preheat the tablet at 23°C and 500°C.
Approximately 0.0.
Put 8g and use a hydraulic press to produce 400kg/cn? By applying pressure with
A cylindrical pellet with a circular diameter of 0 mm was made. A main electrode having a diameter of 10 mm was applied to the center of both circular end surfaces of this pellet by applying silver paste, and one end was set to the ground.

Next, a guard electrode with one end grounded was provided along the outer periphery of the pellet. A DC voltage of 100 V was applied to the main electrodes, the current flowing between the main electrodes was directly read using an ammeter, and the volume resistivity was calculated from the stable value using the following formula.

Volume resistivity = (resistance value
A toner having a weight-based average particle diameter of 4.7 μm was obtained.

Toner formulation: Made of epoxy resin (product name: Epicote 1004, Yuka Shell Epoxy@): Izod impact value 1.4 kgcm/
cnr) 80 parts carbon black (Product 82M△-8, manufactured by Mitsubishi Chemical Corporation)
15 parts triiron tetroxide (product name: MG-WM
K, made by Mitsui Kinzoku Kogyo)
The 5-part volume resistivity was 6×10 7 Ωcm. Colloidal Silica (Product name: R-972, Nippon Aerosil@
) was added to 100 parts of toner and thoroughly mixed. When this was used in a copying machine using a commercially available one-component toner and transferred to electrostatic recording paper, an extremely good image was obtained. .

Example 3 A premix of the following formulation was kneaded in a kneader, and then ground in a jet mill in the same manner as in Example 1 to obtain an average particle size of 3.
Black magnetic particles of 6 μm were obtained.

Rosin modified polyester resin (product name: KR445, manufactured by Arayo Chemical Industry Co., Ltd.: Izod impact value 1°4 kgcm/
ci) 60 parts magnetic powder (product name: E
PT-500, manufactured by Toda Kogyo ■)
40 parts 56 parts of carbon black (same as in Example 1) were added to 95 parts of the magnetic particles, introduced into a test medium stirring mill, and processed at 400 rpm for 20 minutes. The toner thus obtained had an average particle size of 4.5 μm and a volume resistivity of 6×10 6 Ωam. When this conductive toner was transferred onto electrostatic recording paper using a modified copying machine that uses a commercially available one-component magnetic toner, a good image was obtained.

Comparative Example 1 A toner was produced in the same manner as in Example 1 using the following formulation.

Epoxy resin (same as Example 2) 93 parts Carbon black (same as Example 2) 2 parts Triiron tetroxide (same as Example 2) 5 parts The toner particles thus obtained had an average particle size of 4.5 μm. Yes, the volume resistivity is 1
015 or higher. This insulating toner had extremely poor fluidity and could not be used as a toner.

Comparative Example 2 A toner was experimentally produced in the same manner as in Example 3 except that the amount of carbon black was 2 parts. Volume resistivity is 2X1
013 Ωcm, and as it was, the fluidity was extremely poor and it could not be used as a toner.

Example 4 A toner was experimentally produced in the same manner as in Example 1 according to the following recipe to obtain a blue conductive toner having a weight-based average particle size of 4.1 μm.

Polystyrene resin (same as Example 1) 78 parts Phthalocyanine blue (trade name: Rionol Blue SM, manufactured by Toyo Ink Mfg. ■) 15 parts Triiron tetroxide (same as Example 1)
7 parts Tin oxide (Product 82T-1, manufactured by Mitsubishi Metals Co., Ltd.) 10 parts The obtained toner was slightly dark blue and had a volume resistivity of 7 x 10
It was 7Ωcm. When this toner was used for transfer in the same manner as in Example 1, an extremely good image was obtained.

Patent applicant: Toyo Ink Manufacturing Co., Ltd.

Claims (1)

[Scope of Claims] 1. Amorphous particles obtained by pulverizing a composition in which at least carbon black is dispersed in a thermoplastic resin as a binder component using a pulverizer that uses mechanical impact force. , weight-based average particle size 0.5-5μ
1. A conductive fine particle toner having a volume resistivity of approximately 1×10^1^0 Ωcm or less. 2. Amorphous particles obtained by pulverizing a composition in which at least a colorant and conductive particles are dispersed in a thermoplastic resin as a binder component using a pulverizer that uses mechanical impact force, and the weight Standard average particle size 0.5-5
.mu.m, and a volume resistivity of about 1×10^1^0 Ωcm or less.