JPS59826B2 - Conductive toner for electrostatic printing - Google Patents

Description

Detailed Description of the Invention The present invention relates to a conductive toner for electrostatic printing, and more specifically, the present invention relates to a conductive toner for electrostatic printing, and more specifically, carbon black (conductive fine powder) having specific properties is attached or adsorbed to the surface of resin particles containing a colorant. This invention relates to a conductive toner for electrostatic printing.

Conventionally, as a developer powder (toner) for electrostatic printing, it is known that conductive fine powder such as carbon black is attached to the surface of a colored resin (U.S. Pat. No. 363
9245 specification).

In addition, "electrostatic printing" referred to here refers to a process of forming an electrostatic latent image and making it visible, such as electrophotography, electrostatic recording, and electrostatic printing, as well as U.S. Patent No. 3,879,737, This includes the electrostatic non-impact recording method proposed in the specification of the same No. 4,103,306, etc., in which toner is moved and recorded according to an electric signal.

By the way, the above-mentioned conventional toners are known to be of a heat-fusion type and a pressure-fixing type based on the fixing means.

However, since the former type of toner is inferior in speed and efficiency in the fixing process, the latter type of toner suitable for pressure fixing is currently attracting attention. For example, as a dry toner used in the pressure fixing method, microcapsule toner powder has been proposed in Japanese Patent Application Laid-open No. 48-71648 and Japanese Patent Application Laid-Open No. 48-75032. However, it has not yet become desirable due to restrictions from both the triboelectrification tendency between the carrier particles and the manufacturing technology. Further, Japanese Patent Application Laid-Open No. 50-50042 proposes a developer powder which is mainly composed of a resin, a wax component, a magnetic powder, and conductive particles. Similar to the heat fixing developer described in U.S. Pat. No. 3,639,245, this developer has conductive particles fixed to the resin constituting the powder matrix only on the surface portion thereof. Conductive toners in which conductive fine powder is adsorbed or adhered to the surface of such resin particles (which may also contain colorants, etc.) that have been put to practical use so far have poor fixability. Although the toner is satisfactory in this respect, it has drawbacks such as poor toner fluidity and poor storage stability, and when magnetic powder is mixed into the toner to make magnetic toner, the toner does not magnetically adhere to the counter electrode. Most of them also have defects such as insufficient image formation resulting in unclear image formation.

The purpose of the present invention is to eliminate all of these drawbacks, and to obtain high image density with excellent not only pressure fixing properties but also heat fixing properties.
Moreover, it is an object of the present invention to provide a conductive toner for electrostatic printing that can be usefully and safely applied to high-speed printing and exhibits good storage stability.

That is, the present invention provides a conductive toner for electrostatic printing in which conductive fine powder is adsorbed or adhered to the surface of resin particles containing a colorant, wherein the conductive fine powder has a number average particle diameter of 25 mμ or less and a volatile content. 2.5% by weight or less and DBP
The carbon black is characterized by having an oil absorption of 150 cc/100 y or less.

The term "volatile components" as used herein refers to hydroxyl groups, carboxyl groups, carbonyl groups, lactones, etc. on the surface of carbon black, which volatilize as CO2, H2O, etc. when heated at high temperatures. Also, “DBP oil absorption” is AS
It is defined by the TM test method. As a result of detailed study on conventional conductive toner for electrostatic printing, the inventor of the present invention found that
It has been found that carbon black is a good conductive fine powder that adheres (adsorbs or adheres) to the resin surface, and that a toner that covers the resin surface in as little amount as possible is good.
At the same time, we also learned that this coating is greatly affected by the volatile content and oil absorption of carbon black. The present invention has been made based on these findings. The present invention will be explained in more detail below.

Now, the resin particle core (base body) containing the colorant has a radius r1.
The carbon black particle attached to this core is a spherical particle with radius R2, and the volume of this core is V.
1. When the volume of carbon black particles is V2, and if this core is 100% covered with a single particle layer of carbon black particles, the volume ratio is expressed by the following formula.

If the radius r1 of the core is constant, the amount of carbon black required to coat the core decreases as the radius R2 of the carbon black particle decreases. Experiments have shown that it is extremely effective in practice when the number average particle diameter of carbon black is 25 mμ or less, preferably 17 mμ or less. However, as mentioned above, In fact, it is greatly influenced by the volatile content of carbon black and the DBP oil absorption.

Experiments using various types of commercially available carbon black have confirmed that this coating is effective when the volatile content is 2.5% by weight or less. The reasons for this are not fully understood, but include (1) experimental fact that the work function of carbon black changes greatly depending on the surface compounds of carbon black, (2) dissociation of functional groups on the surface of carbon black, and water adsorbed on the surface of carbon black. (3) The experimental fact that the dissociation of carbon black changes depending on the carbon black surface compound, and (3) the experimental fact that the contact resistance between carbon black particles increases due to the presence of carbon black surface compounds, etc., are intricately related to this coating mechanism. This is considered to be the result. Further, the coating of the resin particle core with carbon black is such that the DBP oil absorption amount of the carbon black is 150 CC/1007 or less, preferably 7
If it is 0CC/1007 or less, this carbon black coating can be performed efficiently.

Although the reason for this is still unclear, it may be as follows. DBP oil absorption is related to the chain structure of carbon black. Therefore, it is believed that carbon black, which has a small amount of DBP oil absorption, that is, does not have a well-developed chain structure, efficiently covers the core. The resins (thermoplastic resins) used in the present invention include petroleum resins, xylene resins, phenol resins, maleic acid resins, styrene resins, rosin modified resins, alkyd resins, phenol formaldehyde resins, ketone resins, and acrylic resins. Examples include resins such as vinyl resins, cellulose resins, and the like.

Furthermore, as the colorant (pigment, dye), any conventional colorant used in the technical field can be used, such as pigments such as carbon black, phthalocyanine blue,
Dyes such as Victoria Blue, Final Blue, Permanent Blue Toner, Nigrosine Base, and Oil Black can be cited.

The resin particles are the above-mentioned resin containing a coloring agent, and the size thereof is suitably about 2 to 20 μm in number average particle size.

The amount of colorant added is 10 to 100 parts by weight of resin.
The amount is approximately 150 parts by weight. Wax or magnetic powder may be added to the resin particles if necessary.

The wax component is effective in imparting good fixing properties to the toner, and therefore it is desirable that the wax component has a melting point in the range of about 35 to 160'C. To illustrate this, paraffin wax,
Natural or synthetic aliphatic waxes such as crystalline wax, carnauba wax, montan wax, ceresin wax and sugarcane wax,
Fatty acids such as stearic acid, palmitic acid and behenic acid, lithium stearate, aluminum stearate,
Fatty acid metal salts such as barium stearate and zinc palmitate; amidohydroxy such as N(β-hydroxyethyl)-ricinolamide, N-merethylenebisuricinolamide, and N-merethylenebis-1,2-hydroxystearylamide; These include wax, ethylene homopolymer, synchhexyl phthalate, diphenyl phthalate, hydroxystearic acid, and ethylene glycol monohydroxyethearate. The magnetic powder component is useful as a toner when a magnetic brush development method is employed as the developing means. Examples of magnetic powder include iron powder, triiron tetroxide powder,
Examples include iron sesquioxide powder, chromium powder, chromium dioxide powder, nickel powder, etc., and the average particle size is about 0.1 to 2.5
μm is appropriate. Furthermore, a suitable plasticizer such as octyl phthalate, dibutyl phthalate, etc. may be added to the resin particles containing this colorant.

On the other hand, it is essential that the conductive fine powder (power carbon black) that coats the resin particles has the above-mentioned certain characteristics.
Examples include NARCH-11001900 and 800 (all manufactured by Gearpot), and Printex-95, 85 and 75 (all manufactured by Degussa).

The amount of carbon black in the toner is suitably 10% by weight or less. As mentioned above, the conductive toner for electrostatic printing of the present invention has a specific carbon black coated on the surface of resin particles containing a colorant. Resin particles are prepared by kneading a resin and a colorant under heat and then pulverizing them, or by dissolving or dispersing these resins and colorants in a solvent and then spray drying them, and then using these resin particles as cores. (1) Mix the cores and carbon black at a certain ratio and shake, if necessary, further (Ii) At a temperature sufficient to melt at least the surface of the resin particle cores obtained in (1) above. The conductive powder toner may be subjected to heat treatment.

The conductive toner of the present invention thus obtained is of sufficient quality to achieve the intended purpose.

Note that this toner has similar effects not only in pressure fixing but also in heat fixing. Examples are shown below, in which all parts are by weight. Example 1 First, 34 parts of Picolastic A-75, 50 parts of Picolastic D-125 (both manufactured by Esso Standard Oil Co., Ltd.), 19 parts of magnetite fine powder M32 (manufactured by Toda Kogyo Co., Ltd.), and Oil Black HBB (manufactured by Orient Chemical Co., Ltd.) were prepared. made)
70 parts of the mixture were dissolved and dispersed in 600 parts of methylene chloride, spray-dried with a spray dryer at a temperature of 30 to 35°C and a pressure of 5K9/Cd, and then classified to obtain resin particles with an average particle size of 5 μm.

Carbon black in an amount of 1 to 3% by weight was added to and mixed with the resin particles, and the mixture was thoroughly shaken to produce toner particles. The carbon black used here was MONARCHl
lOO (number average particle diameter 14 mμ, volatile content 2.0% by weight,
Oil absorption amount 65CC/1007), MONARCH9OO(
Number average particle diameter 15 mμ, volatile content 2.0% by weight, oil absorption 7
0CC/1007), Printex 95 (number average particle diameter 15 mμ, volatile content 2.5% by weight, oil absorption 50CC/1
007), Printex85 (number average particle diameter 16 mμ
, volatile content 1.8% by weight, oil absorption 50CC/1007),
and Printex 75 (number average particle diameter 17 mμ, volatile content 1.5% by weight, oil absorption 50 CC/100y), and the specific resistance of the five types of toner particles obtained using these carbon blacks is 102 to 103 Ω. ? It was within the range of These toners are
When subjected to the non-impact printing method proposed in Publication No. 9, a large number of good copies (high density, high clarity) were successively obtained.

This fixed image did not come off even when rubbed with fingers. It was also found that this toner had good magnetic adhesion to the counter electrode. Incidentally, the measurement results of the image density, etc. of the copies were as shown in Table 1. For comparison, carbon black that does not satisfy at least one of the above three conditions, namely Denka Black manufactured by Asahi Denka Kogyo KK (number average particle diameter 42 mμ, volatile content 0.2% by weight) was used.
, oil absorption 115CC/1007), Gearpot VU
LCAN-XC-72 (number average particle diameter 30 mμ, volatile content 1.5% by weight, oil absorption 185 CC/1007), MONARCH-1300 manufactured by Cabonet (number average particle diameter 1
3mμ, volatile content 9.5% by weight, oil absorption 121CC/10
07), SPECIAL BLACK 5 manufactured by Degussa (number average particle diameter 20 mμ, volatile content 15.0% by weight, oil absorption 12
Comparative toners were used in the same manner except that 5CC/1007) was used (however, the inherent resistance of these toners was 105 to 101).
4Ω? When a similar test was conducted using the same method, no good copies were obtained, and it was observed that when the fixed image was rubbed with a finger, the finger became stained.

Incidentally, the measurement results of the image density etc. of the copies were as shown in Table 1. 1 example
As a 2 channel black, FW2 made by West German Degussa
(Number average particle diameter 13 mμ, volatile content 16% by weight, oil absorption 1
45ec/100V), FW2V (number average particle diameter 13m
μ, volatile content 16% by weight, oil absorption 2140CC/100
7), FW2OO (number average particle diameter 13 mμ, volatile content 21
Weight%, oil absorption 14CC/*finished 1007), FWl (number average particle diameter 13mmμ, volatile content 6 weight Hiroshi oil absorption 165CC)
/100y), FWl8 (number average particle diameter 15mμ, volatile content 6 weight oil absorption 150CC/1007) were each pulverized in a ball mill for 24 hours, then 1000°C, 1
High-temperature deaeration treatment under 0-3 mmHg conditions for 7 hours yields a number average particle diameter of 13-15 mμ and oil absorption of 100-150 CC/1.
Printing was carried out in the same manner as in Example 1, except that 00y and the volatile content was changed to 2.5% by weight or less, and good printed copies were obtained.

Claims (1)

[Claims] 1. In a conductive toner in which conductive fine powder is adsorbed or adhered to the surface of resin particles containing a colorant, the conductive fine powder has a number average particle diameter of 25 mμ or less, a volatile content of 2.5% by weight or less, and DBP oil absorption is 150cc
A conductive toner for electrostatic printing, characterized in that carbon black having a property of /100g or less is used.