JPH03197961A - 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 a fluorinated silane coupling agent 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 black, those listed in the conventional methods have been proposed.

(1) Surface area is 275-800 m"/g, oxygen content is 3-10%, DBP oil absorption is 70-250 cc/10
A toner containing 5 to 20 parts by weight of furnace carbon black having a particle diameter of 5 to 75 mμ (Japanese Patent Application Laid-open No. 80137/1983).

(2) - In component-based toner, BE by nitrogen adsorption method
T specific surface area is 850 to 1500 m”/, g, D B
Toner containing porous carbon black with a P oil absorption of 280 to 500 cc/100g
33264).

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

(4) Toner containing carbon black treated with a reaction product of a silane coupling agent and a specific compound and produced by a suspension polymerization method (Japanese Patent Laid-Open No. 63-1585
Publication No. 66).

[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 a high-density image, 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 an amino-modified silane coupling agent and has a BET specific surface area (hereinafter simply referred to as rBET specific surface area) measured by nitrogen adsorption method of 240 to 1.
A structure containing 500 m2/g of carbon black and having a dielectric constant of 8 to 30 is adopted.

That is, in the present invention, carbon black is not simply subjected to hydrophobization treatment (but rather, a carbon black whose BET specific surface area is within a specific range and suitable for adjusting the dielectric constant of the toner is selected, and this carbon black is By treating the surface of carbon black with an amino-modified silane coupling agent in particular, the chargeability of carbon black can be controlled to a suitable positive chargeability, and by incorporating this surface-treated carbon black, a specific dielectric constant within a specific range can be achieved. showing the rate;
This makes it 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. .

Furthermore, even when subjected to an image forming process that employs a toner recycling system, the initial excellent properties are stably exhibited over a long period of time, and hydrophobic silica fine 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 an amino-modified silane coupling agent and has a BET specific surface area of 240 to 1500 m''/g.Such carbon black easily forms so-called stractures and has a low 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. In this way, the content of carbon black can be reduced to a small amount. A toner with a suitable dielectric constant can be obtained without impairing the fixability of the toner.

As the amino-modified silane coupling agent, for example, the following compounds can be preferably used.

H2N CH2CH2CH2CH2S l (OCH3
) yH2NCH2CH2CH2Si(○C2H3)3
(5) 'H2NC0NHCH2CH2CH25l(
OCzHs)s(6) H2NCH2CH2NHCH
2CH2CH25l(OCH3)3(7) H2N
CH2CH2N HCH2CH2N HCH2CH2C
H2-5l(OCH3) 3 (8) Hs C20COCH2CH2N HCH2
CH2S l (OCH3) 3(9) Hs C2
0COCH2CH2N HCH2CH2N HCH2C
H2-CH25l(OCH3)3 (10) H5C20COCH, CH2NHCH2C
H,NHCH2CH2-N HCH2CH2N HCH
a CH2CH2S i (OCH3) 5(11)
H3COCOCH2CH2NHCH2CH2NHCH
2CH2-CH2S1 (OCH3) 5 (12) H5C2\-5i(OCH3).

(18) HOC82CH.

\ (20) (H5C20)3SiCH2CH2CH
2(21) H3CNHCHzCH2CHzSi(O
C2Hs)a(22) HzN('CH2CH2NH
)2CH2CH2CHzSi(OCH3)s and 3tis
+1 (lJshiHsh) In addition, in the above compound, the alkoxy group may be substituted with a chlorine atom.These amino-modified silane coupling agents may be used alone or in combination of multiple ones. May be used.

The method for surface treating carbon black using the above amino-modified silane coupling agent is as follows: (1) carbon black is dispersed in a solution of the amino-modified silane coupling agent dissolved in a solvent, and then filtered or spray-dried. (2) Spraying a solution of an amino-modified silane coupling agent dissolved in a solvent onto carbon black using a fluidized bed granulator. Then, the solvent can be removed by heating and drying to harden the surface film.

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 m”/
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, with carbon black having a BET specific surface area in the range of 800 to 1500 m2/g, a toner having a dielectric constant of 8 to 30 can be obtained with an even smaller amount of 2 to 10 parts by weight.

However, the BET specific surface area is particularly preferably in the range of 240 to 1200 m'/g since the specific dielectric constant becomes sensitive to the carbon black content.

Examples of carbon black with a BET specific surface area of 240 to 1200 m'/g include Condagtex 40-220 manufactured by Columbia Carbon Co., Ltd., and a BET specific surface area of 80 m'/g.
Examples of carbon black having a density of 0 to 1500 m2/g include Black Burls 2000 manufactured by Cabrac Co., Ltd.

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, 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 dielectric constant is too small, the development performance will not be improved sufficiently, and conversely, if it is too large, the charge retention ability of the toner will be small, the amount of charge will be small, and transfer defects will occur. .

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 circular plate with a diameter of 7 mm and a thickness of 1.5 mm. Electrodes were formed by vapor-depositing gold, and R manufactured by Yokogawa Hewlett-Packard Co.
F network analyzer model HP 875
The dielectric constant of the disc plate was measured at 915 MHz under appropriate conditions using 3 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.

Examples of such inorganic fine particles include hydrophobic silica fine particles R-972, R-974, and R-811 manufactured by Nippon Aerosil Co., Ltd. from the viewpoint of improving charge controllability and fluidity.

R-812, R-805, RA-200H, etc. can be used. Among these, RA-2008 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, "part" represents "part by weight".

Production of carbon black (1) Carbon black A Carbon black with a BET specific surface area of 1066 m2/g is placed in a fluidized bed granulator, and 5 of the amino-modified silane coupling agent represented by the following structural formula (■) is added to the carbon black. The weight percent solution was sprayed onto the carbon black to give a 7% solution.

Next, it was heated to 160° C. to harden the carbon black surface coating. This is called carbon black A.

Structural formula■ H2NCH2CH2CH25l(OC2H5)3(2)
Carbon Black B Carbon black B 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 1475 m''/g.

(3) Carbon Black C Carbon black C 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 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 m''/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 m''/g) Carbon black E was obtained in the same manner except that the carbon black E was changed to (BET specific surface area: 138 m''/g).

(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 an amino-modified silane coupling agent, that is, carbon black with a BET specific surface area of 1066 m''/g, is referred to as carbon black G.

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

Example 1 100 parts of toner resin A, 10 parts of carbon black, and 10 parts of carbon black E. After mixing 40 parts or more of the materials in a ball mill, a powder with an average particle size of 11 μm was obtained through the steps of cross-mixing, crushing, and classification. Ta. In addition to this powder, hydrophobic Nlica fine particles R manufactured by Nippon Aerosil Co., Ltd.
Toner 1 having a dielectric constant of 22 was obtained by adding and mixing A-200H in a proportion of 0.3% by weight.

Example 2 In the same manner as in Example 1, except that carbon black 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 12 parts of carbon black D was used instead of carbon black A.

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 Same as Example 1, carbon black A was changed to 3 parts of carbon black F, and the blending amount of carbon black E was changed to 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 5 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 6 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 with an average particle diameter of 80 μm, which was formed by providing a resin coating layer of fluororesin with a thickness of 1.0 μm on the surface of ferrite particles.

Konica's electrophotographic copying machine U-8 is equipped with a toner recycling system using each of the above two-component developers.
ix 1017 modified machine, line speed 350m
A test was conducted to form a copy image at a high speed of m/sec,
The following items were evaluated. 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. .65m
It was set to m.

(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) The relative density of the white background area was measured and evaluated using a Sakura densitometer 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 smaller the change in toner density, the better the developability.

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

The results are shown in Table 1.

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, comparative toner 1 is carbon black FO
Since the BET specific surface area is too large, the carbon black F is insufficiently dispersed in the toner resin, resulting in contamination of the carrier surface during actual photography tests, significantly reducing chargeability, and causing fogging and toner scattering.

Comparative toner 2 has carbon black G that has not been surface-treated with an amino-modified silane coupling agent, so it has poor instantaneous charging performance, poor development efficiency, high toner density changes, and a high level of toner density before reaching 100,000 cycles. Toner scattering occurs and fogging is slightly reduced.

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 contamination of the carrier surface with carbon black E, resulting in fogging. , toner scattering occurs.

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

Comparative toner 5 has an excessive relative dielectric constant, so the amount of charge becomes too low, causing 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 formed many times without toner scattering.

Claims (1)

[Claims] The surface is treated with an amino-modified silane coupling agent and has a BET specific surface area of 240 to 1500 by nitrogen adsorption method.
A positively chargeable toner containing carbon black having a specific dielectric constant of m^2/g and a relative dielectric constant of 8 to 30.