JPH03197959A - Positively chargeable toner - Google Patents

Abstract

PURPOSE:To obtain a toner superior in positive chargeability and in developing and coloring performances by incorporating a surface-treated specified carbon black so as to control its relative dielectric constant in a specified range. CONSTITUTION:The carbon black to be selected has a BET specific surface area of 240 - 1,500m<2>/g measured by the nitrogen adsorption method and adapted to adjustment of the relative dielectric constant of the toner and its surface is treated with an amino-modified silicone oil and the constant of the toner is regulated in the range of 8 - 30 by adding this carbon black. Such a carbon black is easily uniformly dispersed into the toner and its small content permits the distance between each carbon black particle to be reduced and the relative dielectric constant to be easily controlled in the range of 8 - 30, thus permitting the obtained toner to be controlled in the favorable range of the constant without impairing fixability, and superior in positive chargeability and in developing and coloring performances.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a positively chargeable toner containing carbon black.

[Conventional technology]

As toners containing carbon blanks, those listed in the conventional methods have been proposed.

(1) Surface area 275-800m2/g, oxygen content 3-10%, DBP oil absorption 70-250 cc/10
Toner (
JP-A No. 50-80137).

(2) - In component-based toner, BE by nitrogen adsorption method
T specific surface area is 850-1500m2/g, D B
Toner containing a porous carbon blank with a P oil absorption of 280 to 500 cc/LoOg
33264).

(3) A toner containing a magnetic material and a carbon blank hydrophobized with a titanium coupling agent, a silane coupling agent, etc., and produced by a suspension polymerization method (Japanese Patent Application Laid-open No. 117253/1983).

(4) Toner containing a carbon blank treated with a reaction product of a silane coupling agent and a specific compound and manufactured by a suspension polymerization method (Japanese Patent Application Laid-Open No. 63-158
566).

[Problem to be solved by the invention]

However, in the above toner (1), carbon black exhibits negative chargeability, so when used as a positively chargeable toner, the toner's triboelectricity rises poorly, and as the image forming process is repeated, the toner is There is a problem in that scattering occurs, contaminating charging electrodes, transfer electrodes, separation electrodes, etc., resulting in image defects and transfer defects. When the amount of toner scattering increases, there is a problem in that the back surface of the leading edge of the transfer material is smeared with toner.

The above toner (2) tends to have insufficient coloring properties, and therefore, in order to form high-density images, it is necessary to considerably increase the carbon black content.

However, when the content of carbon black increases, the resistance of the toner becomes low and the toner's triboelectric charging properties decrease, and when used in combination with a carrier as a two-component developer, the adhesion of the toner to the carrier surface becomes weak. , toner scattering, and fogging may occur. Furthermore, when the developing bias voltage is increased to prevent fogging, there is a problem in that carrier adhesion to the white background increases.

In the toners (3) and (4) above, when producing the toner by suspension polymerization, it is possible to improve the dispersibility of carbon black in the toner resin;
There is a problem that the triboelectric charging properties of the toner are still insufficient.

The object of the present invention is to exhibit excellent positive chargeability, a good rise in triboelectric chargeability, excellent developability and colorability, and to produce images of good image quality over many cycles without fogging or toner scattering. An object of the present invention is to provide a positively chargeable toner that can stably form a toner.

[Means to solve the problem]

In the present invention, the surface is treated with amino-modified silicone oil and has a BET specific surface area (hereinafter simply referred to as rBET specific surface area) of 240 to 1500 by nitrogen adsorption method.
A configuration is adopted in which carbon black is contained in m2/g and has a relative dielectric constant of 8 to 30.

That is, in the present invention, rather than simply hydrophobicizing carbon black, carbon black whose BET specific surface area is within a specific range and is suitable for adjusting the dielectric constant of the toner is selected, and this carbon black is By treating the surface, especially with amine-modified silicone oil, the chargeability of carbon black is controlled to a suitable positive chargeability, and by incorporating this surface-treated carbon black, it exhibits a specific dielectric constant within a specific range. , it is possible to obtain a toner with significantly superior positive chargeability.

Therefore, according to the toner of the present invention, excellent developability is exhibited, and the triboelectric chargeability rises steeply, thereby exhibiting excellent initial characteristics.

Furthermore, even when forming images at high line speeds of 300 mm/sec or more, toner scattering does not occur, and images with high image density, clarity, and excellent gradation and resolution can be formed. .

In addition, even when the toner is subjected to an image forming process that employs a toner adhesive cycle stem, the initial excellent properties are stably exhibited over a long period of time, and hydrophobic silica particles, etc., which are usually added as external additives, are released or incorporated into the toner. It is possible to sufficiently compensate for the deterioration of triboelectric charging properties over time even if the material is buried in water.

The configuration of the present invention will be specifically explained below.

The carbon black used in the present invention is surface-treated with amino-modified silicone oil and has a BET specific surface area of 240 to 1500 m''/g.

Such carbon black easily forms so-called stractures, and with a small content, the distance between particles of carbon black becomes small, and the dielectric constant of the toner can be sufficiently controlled within the range of 8 to 30. Since the content of carbon black can be reduced in this way, a toner with a suitable dielectric constant can be obtained without impairing the fixing properties of the toner.

As the amine-modified silicone oil, for example, those represented by the following general formula [1] can be preferably used.

General formula [1] In the above general formula [1], R1 represents an alkylene group, an arylene group, an aminoalkylene group, etc., and R2 and R3 each represent a hydrogen atom, a hydroxyl group, an alkyl group, an aryl group, etc. X and y each represent an integer of 1 or more.

In addition, the amino-modified silicone oil has an amine equivalent value within the range of 200 to 22.500, and 25
Preferably, the viscosity at °C is within the range of 10 to 10.000 cps.

Commercially available amine-modified silicone oils include SF8417 manufactured by Toray Silicone, KF393, KF857, KF860, KF861 manufactured by Shin-Etsu Chemical Co., Ltd.
KF862, KF864, KF865, KF369, K
F383, X-22-3680, X-22-380DS
X-22-3801C.

X-22-3810B etc.

The method for surface-treating a carbon blank using the above amino-modified silicone oil is as follows: (1) Carbon black is dispersed in a solution of amino-modified silicone oil dissolved in a solvent, and then the solvent is removed by filtration or spray drying. (2) A solution of amino-modified silicone oil dissolved in a solvent is sprayed onto carbon black using a fluidized bed granulator, and then heated and dried. A method of curing the surface film by removing the solvent by removing the solvent can be adopted.

In the present invention, the BET specific surface area of carbon black is required to be in the range of 240 to 1500 m'/g. Here, the BET specific surface area is a value measured under appropriate conditions using Micromeritic Model 2200.

In this way, the BET specific surface area is 240 to 1500 m2/
According to the carbon black of No.g, a toner having a dielectric constant of 8 to 30 can be obtained with a precious small amount of 10 to 20 parts by weight per 100 parts by weight of the toner resin.

In particular, if carbon black has a BET specific surface area in the range of 800 to 1500 m''/g, a toner with a dielectric constant of 8 to 30 can be obtained with an even smaller amount of 2 to 10 parts by weight.

However, as the BET specific surface area increases, the relative permittivity becomes sensitive to the carbon black content, so the BET specific surface area is particularly preferably in the range of 240 to 1200 m2/g.

Examples of carbon black having a BET specific surface area of 240 to 1200 m2/g include Condagtex 40-220 manufactured by Columbia Carbon Co., Ltd. Further, examples of carbon black having a BET specific surface area of 800 to 1500 m''/H include Black Pearls 2000 manufactured by CABLACK.

The content of carbon black is preferably in the range of 2 to 25 parts by weight based on 100 parts by weight of the toner resin from the viewpoint of improving coloring properties and triboelectric charging properties without impairing fixing properties. If the content of carbon black is too small, the dielectric constant of the toner tends to be too small, and conversely, if the content is too large, the fixing properties of the toner tend to deteriorate.

In the present invention, two or more types of carbon black may be used in combination, and in this case, at least one type may be the above-mentioned specific carbon black.

In the present invention, it is necessary that the relative dielectric constant of the toner is within the range of 8 to 30. That is, if the dielectric constant of the toner is in the range of 8 to 30, the effective value of the developing electric field will be large, and the developability of the toner will be significantly improved. On the other hand, if the relative permittivity is too small, the development performance will not be improved sufficiently, and if the relative permittivity is too large, the charge retention ability of the toner will be small, resulting in a small amount of charge, resulting in poor transfer. occurs.

Here, the relative permittivity of the toner is a value measured as follows. That is, a toner (containing external additives such as hydrophobic silica fine particles) was heated and melted at 200°C for 10 minutes to prepare a disc plate with a diameter of 7 mm, a thickness of l, and 5 mm, and both sides of this disc plate were RF network analyzer model HP 8 manufactured by Yokogawa Hewlett-Buckard Co., Ltd.
The dielectric constant of the disc plate was measured at 915 MHz under appropriate conditions using a 753 A, and this value was taken as the dielectric constant of the toner. Note that the measurements were performed in an environment with a temperature of 20° C. and a relative humidity of 65%.

The dielectric constant of the toner can be adjusted by the type and degree of polymerization of the toner resin, the type and content of carbon black, and the type and amount of other additives used as necessary.

Polyester resins, styrene resins are used as toner resins.
Acrylic copolymer resin or the like can be used.

The toner of the present invention may contain internal additives such as wax and charge control agents, if necessary. Further, external additives such as inorganic fine particles may be used.

Such inorganic fine particles include hydrophobic/liquid fine particles R-972, R-974, R-811, R-812, and R manufactured by Nippon Aerosil Co., Ltd. from the viewpoint of high charge controllability and fluidity.
-805, RA-200H, etc. Among these, RA-200H exhibits positive chargeability, so it can be preferably used in the present invention.

In one example of the method for manufacturing the toner of the present invention, after mixing toner resin, specific carbon black, and internal additives used as necessary using a ball mill or the like,
Powder is obtained through the steps of kneading, grinding, and classification. This powder may be used as a toner as it is, or a toner may be obtained by adding external additives such as inorganic fine particles to this powder and mixing with a turbular mixer or the like.

The carrier used in combination with the toner of the present invention is preferably a coated carrier in which the surface of magnetic particles made of ferrite or the like is coated with a negatively chargeable resin such as a silicone resin or a fluorine resin.

〔Example〕

Examples of the present invention will be described below along with comparative examples, but the embodiments of the present invention are not limited thereto.

In addition, in the following, "parts" represent "parts by weight".

<Manufacture of carbon black> (1) Carbon blank A Carbon black with a BET specific surface area of 1066 m''/g was placed in a fluidized bed granulator, and this carbon black was
A bexane solution containing 10% by weight of amino-modified silicone oil r S F8417J (manufactured by Toray Silicone Co., Ltd.) and 8% by weight of hexamethyldisilazane rsZ6079J (Torre Silicone Co., Ltd.) was made into a 5% solution with respect to carbon black. I sprayed it like this. Next, it was heated to 150° C. to harden the carbon black surface coating. This is called carbon black A.

(2) Carbon Black B Carbon black B was obtained in the same manner as in the production of carbon black, except that the carbon black was changed to carbon black with a BET specific surface area of 1475+++2/g.

(3) Carbon Black C Carbon blank C was obtained in the same manner as in the production of carbon black A, except that the carbon blank was changed to a carbon blank with a BET specific surface area of 800 m''/g.

(4) Carbon Black D Carbon black D was obtained in the same manner as in the production of carbon black A, except that the carbon black was changed to carbon black with a BET specific surface area of 254 m2/g.

(5) Carbon Black E In the production of carbon black, carbon black is manufactured by CABLACK Co., Ltd.'s carbon black "Mogal".
(BET specific surface area: 138 m2/g), carbon black E was obtained in the same manner.

(6) Carbon Black F Carbon black F was obtained in the same manner as in the production of carbon black A, except that the carbon black was changed to carbon black with a BET specific surface area of 1700 m2/g.

(7) Carbon black G In the production of carbon black, carbon black before surface treatment with amino-modified silicone oil,
That is, carbon black having a BET specific surface area of 1066 m2/g is referred to as carbon black G.

Resin for toner> A styrene-acrylic copolymer resin is used as resin A for toner.

Example 1 Toner resin A 100 parts Carbon black A 10 parts Carbon black E 10 parts or more of the materials were mixed in a ball mill, and then subjected to the steps of kneading, pulverization, and classification to form a powder with an average particle size of 11 μm. Obtained. In addition to this powder, hydrophobic bending force fine particles RA-2 manufactured by Nippon Aerosil Co., Ltd.
Toner 1 having a dielectric constant of 22 was obtained by adding and mixing 008 in a proportion of 0.3% by weight.

Example 2 In the same manner as in Example 1, except that carbon blank A was changed to 6 parts of carbon black B, the relative permittivity was 2.
6 toner 2 was obtained.

Example 3 The same procedure was used as in Example 1 except that carbon black A was changed to 5 parts of carbon black C.
4 toner 3 was obtained.

Example 4 Toner 4 having a dielectric constant of 8 was obtained in the same manner as in Example 1 except that 8 parts of carbon black was replaced with 12 parts of carbon black D.

Example 5 Toner 5 having a dielectric constant of 29 was obtained in the same manner as in Example 1 except that carbon blacks A and E were changed to only 14 parts of carbon black A.

Comparative Example 1 In Example 1, carbon black A was 3 parts of carbon black F, and the amount of carbon black E was 14 parts.
Comparative toner 1 having a dielectric constant of 26 was obtained in the same manner except that the dielectric constant was changed to 1.

Comparative Example 2 Comparative toner 2 having a dielectric constant of 22 was obtained in the same manner as in Example 1 except that carbon black A was changed to 10 parts of carbon black G.

Comparative Example 3 Comparative toner 3 having a dielectric constant of 8 was obtained in the same manner as in Example 1 except that carbon black A and E were changed to only 30 parts of carbon black E.

Comparative Example 4 Comparative toner 4 having a dielectric constant of 7 was obtained in the same manner as in Example 1, except that the amount of carbon black A was changed to 3 parts.

Comparative Example 5 In Example 1, the blending amount of carbon black A was 15
Comparative toner 5 having a dielectric constant of 32 was obtained in the same manner except that the dielectric constant was changed to 3.

Evaluation> Each of the toners obtained in the above Examples and Comparative Examples and a carrier were mixed to prepare two-component developers. In addition,
The carrier used was a coated carrier having an average particle diameter of 80 μm and having a resin coating layer of 1.0 μm in thickness made of a fluororesin on the surface of ferrite particles.

Using each of the above two-component developers, the Konica ■ electrophotographic copying machine U-Bi is equipped with a toner recycling system.
x 1017 modified machine, line speed 350mn
A test was conducted to form a copy image at a high speed of +/sec,
The following items were evaluated. The results are shown in Table 1.

The surface potential of the photoreceptor is -650 (V), the minimum gap Dsd between the photoreceptor and the developing sleeve is 0.75 mm, and the gap Hcut between the thickness regulating member that regulates the thickness of the developer and the developing sleeve is 0. It was set to .65mm.

(1) Triboelectricity of toner The amount of charge on the toner was measured by a known blow-off method.

The toner concentration in the developer was adjusted to 5% by weight both at the initial stage and after 100,000 cycles.

(2) Relative density of the white background area was measured and evaluated using a Sakuraten cytometer manufactured by Cabrikonica@.

(3) Toner scattering The inside of the electrophotographic copying machine was visually observed and evaluated based on the degree of toner staining on the transfer electrode and charging electrode.

(4) Developability Image density control Judgment was made based on the change in toner density when a real photo test was conducted using the control method.

The lower the toner density transition, the better the developability.

(5) Coloring property (toner blackening degree) Toner particles were uniformly applied in one layer on a white Maitatsu label (manufactured by Chiban ■), and the reflection density was measured using a Sakura densitometer manufactured by Konica ■. .

As is clear from Table 1, toners 1 to 5 of the present invention have good positive chargeability, good rise in triboelectric chargeability, and can be used many times without fogging or toner scattering. Good copy images can be stably formed over a long period of time. In addition, it has excellent developability and sufficient colorability.

On the other hand, in Comparative Toner 1, since the BET specific surface area of carbon black F is too large, the dispersion of carbon black F into the toner resin is insufficient, and the carrier surface is contaminated during running, resulting in significant The amount of charge decreases, causing fogging and toner scattering.

Comparative toner 2 has carbon black G that has not been surface-treated with amine-modified silicone oil, so it has poor instant charging performance, poor development efficiency, high toner concentration transition, and toner scattering is tolerated up to 10,000 times. Can not. Also, some fogging occurs.

Comparative Toner 3 has a small BET specific surface area of carbon black E, so it is necessary to add a considerable amount to improve developability, and repeated use causes carbon black contamination on the carrier surface, causing fogging and Toner scattering occurs.

Comparative Toner 4 has a too low relative dielectric constant, so it has poor developability and a high toner density transition, resulting in toner scattering and fogging.

Comparative toner 5 has an excessive relative dielectric constant, so the amount of charge becomes too low, resulting in fogging and toner scattering. Furthermore, the transfer rate is low and the density of the transferred image is not sufficient.

〔Effect of the invention〕

As explained in detail above, the positively chargeable toner of the present invention exhibits good positive chargeability, has a good rise in triboelectric chargeability, has excellent developability, has sufficient colorability, and has no fogging property. Also, good images can be stably formed many times without toner scattering.

Claims (1)

[Claims] Surface treated with amino-modified silicone oil and has a BET specific surface area of 240 to 1500 m^ by nitrogen adsorption method.
1. A positively chargeable toner containing carbon black with a specific dielectric constant of 8 to 30.