JPH07209906A - Electrostatic charge image developing toner - Google Patents

Abstract

PURPOSE:To obtain a toner high in the dispersibility of a colorant and good in fixability by specifying the surface energy of the resin to be used and the weight average particle diameter of the secondary particle diameter of the colorant. CONSTITUTION:The toner comprises the resin having a surface energy of 30-50 dyn/cm measured by the Willhelm surface tension measuring method and the colorant having a weight average secondary particle diameter D550 of 0.2-1mm measured by a sieving and weighing method. The resin having such a surface energy is obtained by selecting a suitable monomer, and a polyester resin is especially preferable. It is preferred to use a monomer of a comparatively small molecular weight in order to obtain the polyester resin of such a surface energy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic latent image which has a good dispersion of a colorant and a good fixing property.

[0002]

A conventional toner for black and white development comprises at least a resin and a colorant, and the toner components thereof are obtained by the steps of dry mixing, melt kneading, pulverizing / classifying, and external additive mixing.

At this time, the dispersion of the colorant in the resin has a great influence on the triboelectric charging characteristics and the image density of the toner. Further, the dispersion of the colorant in the toner has a great influence on the fixing performance. This is because the presence of colorant aggregates in the toner easily causes breakage at the interface between the resin and the colorant, which makes the fixed image brittle.

[0004]

As a conventional technique for making the dispersion of the colorant uniform, there is disclosed in JP-A-5-72811 and JP-A-63-
As described in No. 146047, it is known to secondary-aggregate the colorant to be used, but the resin to be used is not specified, which may cause a problem in fixing performance.
In particular, in the case of fine toner in recent years, the fixing property has become more and more severe, and the deterioration of the fixing property due to poor dispersion of the colorant has become a serious problem. The secondary aggregation referred to here is to aggregate primary particles.

In order to solve such a problem, the present invention pursues an interrelationship by specifying the surface energy of the resin and the secondary particle diameter of the colorant in the toner composed of at least the resin and the colorant, and dispersing the colorant. It is an object of the present invention to provide a toner for developing an electrostatic charge image which is excellent in fixing property and excellent in fixing property.

[0006]

The object of the present invention is to provide a toner comprising at least a resin and a colorant, in which the surface energy of the resin used is 30 to 50 dyn / cm, and the weight of the secondary particle diameter of the colorant. This is solved by an electrostatic charge image developing toner characterized by having an average particle diameter D50 of 0.2 to 1 mm.

Here, the surface energy of the resin is Willhe
The value is obtained by the lmy surface tension measurement method, and the secondary particle diameter of the colorant is the value obtained by the sieve weight method.

Here, a method for measuring the surface energy of the resin,
That is, Willhelmy's surface tension measurement method
After the solution is saturated and dissolved in K, the cover glass is immersed in this solution and pulled up to coat the surface of the cover glass with resin thinly (about 100 μm), and this is used as a sample. Using the dynamic contact angle measuring device DCA-20 (manufactured by Orientec Co., Ltd.), it is immersed in pure water and pulled up at a speed of 20 mm / min, and the contact angle of the surface tension film is measured to obtain the surface energy. Is the way.

The method for measuring the secondary particle diameter of the colorant is as follows:
Set the sieves with 1000, 710, 500, 300, 180, 37 μm openings and set them on a powder tester (made by Hosokawa Micron), add 10 g of colorant, set the vibrator strength scale to 2 and sieve for 1 minute, The weight of the colorant remaining on each sieve was measured, the ratio was determined, and D50 which is the particle diameter when the weight average becomes 50% was calculated and defined as the weight average particle diameter D50.

The resin used in the present invention has a surface energy
30 to 50 dyn / cm, which is obtained by appropriate selection of the raw material monomers for the resin. Any resin having a surface energy of 30 to 50 dyn / cm can be used in the resin of the present invention, but a polyester resin is particularly preferable. In order to obtain a polyester resin having a surface energy of 30 to 50 dyn / cm, it is preferable to use a monomer having a relatively small molecular weight. It is more desirable that the acid / alcohol molar ratio of the monomers used is 1.01 or more. Further, the secondary aggregate of the colorant is obtained by a compression granulation method using a compression molding machine or the like.

The toner is manufactured by using a Henschel mixer, V, and a raw material composed of at least a binder resin and a colorant.
After dry-mixing using a mold mixer, melt-kneading with a single-screw or twin-screw continuous extruder, or batch-type kneader, then air flow type
Grind with a mechanical grinder. Further, after classification with an air classifier or the like to obtain a desired particle size distribution, an external additive or the like is added in some cases and dry mixing is performed to obtain a toner.

[0012]

[Function] The surface energy of the resin used is 30 to 50 dyn / c
The resin of m has a value close to the surface energy of cellulose, which is the main component of paper, and therefore has good adhesion to paper and good fixability. Also, if a resin having a high surface energy is used, the interaction with the polar group on the surface of the colorant causes
It has been found that the dispersion of the colorant is good.

Further, we pay attention to the toner component mixing process in the toner manufacturing process, and secondarily aggregate the colorant, and when the weight average particle diameter D50 is 0.2 to 1 mm, the dispersion of the colorant in the toner is It has been found to be good. It is considered that this is because the shearing force applied to the colorant becomes larger when the colorant is secondarily aggregated in the toner component mixing step. If the D50 of the secondary particles of the colorant is 0.2 mm or less, the colorant will be re-aggregated during the mixing process and easily adhere to the wall surface in the mixing container, and the adhered colorant will be agglomerated into the toner. It falls into the component mixture and causes poor dispersion.

If D50 is 1 mm or more, the toner cannot be completely loosened during the mixing process, and aggregates remain in the toner.

As described above, according to the present invention, by using a resin having a surface energy of 30 to 50 dyn / cm and a colorant having a weight average particle diameter D50 of secondary particles of 0.2 to 1 mm, Since the adhesive strength to paper is good and the colorant is well dispersed, a fixed image having high mechanical strength can be obtained.

[0016]

[Examples] The following toner components were dry-mixed for 5 minutes with a Henschel mixer, melt-kneaded with a twin-screw extruder, cooled, coarsely crushed with a hammer mill, crushed with an air-flow crusher, and air-classified. And set the volume average particle size to about 8 μm,
Further, 0.6 part by weight of hydrophobic silica was added and mixed to obtain the following toners 1 to 4 as examples of the present invention.

Each of the polyester resins 1, 2 and 3 is obtained by polymerizing the raw material monomers shown in Table 1 by the following method. That is, each of the dialcohol monomer, the dicarboxylic acid monomer and the tricarboxylic acid monomer was mixed with a thermometer, a stainless steel stirrer, a glass nitrogen introduction tube and a flow-down condenser, and a capacity of 2 liters.
Put the flask in a two-necked flask, set this flask in a mantle heater, and introduce nitrogen gas from a glass nitrogen gas introduction tube to raise the temperature to 220 ° C. while maintaining an inert atmosphere in the reactor and stir in this state. While carrying out the polymerization reaction. When the amount of the monomer decreased due to scattering, sublimation, etc., the amount of the monomer corresponding to the decreased amount was replenished in the flask. The reaction system is appropriately sampled to stop the reaction at an appropriate time, the reaction product is taken out from the flask into a vat, and cooled to room temperature to cool each polyester 1, 2, 3
Got As the carbon black as a colorant, a commercially available powdery one was granulated with a compression granulator and then a sieve was used to obtain carbon black having a desired particle size.

[0018]

[Table 1]

Toner 1 Polyester resin 1 (surface energy: 43 dyn / cm) 100 parts by weight Carbon black 1 (secondary particle diameter D50: 450 μm) 10 parts by weight Polypropylene 3 parts by weight Toner 2 Polyester resin 2 (surface energy: 33 dyn / cm) ) 100 parts by weight Carbon black 1 (secondary particle size D50: 450 μm) 10 parts by weight Polypropylene 3 parts by weight Toner 3 Polyester resin 2 (surface energy: 33 dyn / cm) 100 parts by weight Carbon black 2 (secondary particle size D50: 860 μm) ) 10 parts by weight Polypropylene 3 parts by weight Toner 4 Polyester resin 1 (surface energy: 43 dyn / cm) 100 parts by weight Carbon black 3 (secondary particle diameter D50: 220 μm) 10 parts by weight Polypropylene 3 parts by weight-Comparative Example-Example and By the same process, the following toners 5 to 8 were obtained from the following toner components as comparative examples.

Toner 5 Styrene-butyl acrylate copolymer (80/20) resin 1 (surface energy: 23 dyn / cm) 100 parts by weight Carbon black 1 (secondary particle diameter D50: 450 μm) 10 parts by weight Polypropylene 3 parts by weight Toner 6 Polyester resin 1 (Surface energy: 43 dyn / cm) 100 parts by weight Carbon black 4 (Secondary particle diameter D50: 150 μm) 10 parts by weight Polypropylene 3 parts by weight Toner 7 Polyester 3 (Surface energy: 28 dyn / cm) 100 parts by weight Carbon Black 4 (Secondary particle size D50: 150 μm) 10 parts by weight Polypropylene 3 parts by weight Toner 8 Polyester resin 1 (Surface energy: 43 dyn / cm) 100 parts by weight Carbon black 5 (Secondary particle size D50: 1200 μm) 10 parts by weight Polypropylene 3 parts by weight For these Examples and Comparative Examples, the carbon black dispersion evaluation and toner Results were obtained in the fixing property evaluation and fog evaluation performed and Table 2 over.

(Evaluation of dispersion of carbon black in toner)
Regarding the toners obtained in Examples and Comparative Examples, the dispersion of carbon black in the kneaded material obtained after the melt-kneading step was observed by an optical microscope. For evaluation, the kneaded product was sliced to a thickness of 0.5 μm with a microtome, photographed at a magnification of 300 times, and then, in an image analyzer (SPICCA: Nippon Avionics), out of 5 fields of view (1 field of view was 0.4 × 0.3).
mm), the number of carbon black aggregates of 1 μm or more was determined.

(Evaluation of Fixability of Toner) The toners obtained in Examples and Comparative Examples had an acrylic resin-coated ferrite (volume average particle size 80 μm) and a toner concentration of 6%.
And mixed so that each developer was prepared.

By using the obtained developer, the fixing heat roller temperature is increased from 140 to 200 ° C. in an electrophotographic copying machine KONICA5082.
A copy image is formed by gradually increasing in increments of ° C, and the fixing ratio measured by the following method is applied to this copy image.
The lowest setting temperature when the value exceeded 70% was evaluated as the lowest fixing temperature.

The fixing rate was measured as follows.

The fixing toner was rubbed by reciprocating a load of 1 kg / cm ² wrapped with a bleaching cloth 15 times on the solid black part (image density 1.0) of the copied image, and the image density before and after rubbing was calculated based on the following formula. The fixing rate was calculated. The concentration was measured with a "Sakura densitometer" (manufactured by Konica Corporation).

Fixing ratio (%) = image density after rubbing / image density before rubbing × 100 (image fog evaluation) After 100,000 actual copies were made with the electrophotographic copying machine KONICA5082 using the above developer. , The original density is
The relative density of the 0.000 white background portion with respect to the copied image was measured with a "Sakura densitometer" (manufactured by Konica Corp.), and defined as the fog density.

[0027]

[Table 2]

[0028]

EFFECT OF THE INVENTION At least the surface energy is 30 to 50 dy.
Resin with n / cm and weight average particle diameter D50 of secondary particle diameter is 0.2
With the toner of the present invention composed of a colorant of 1 mm or less, a toner having a high dispersibility of the colorant and a good fixing performance can be obtained. Therefore, it is possible to keep the fixing temperature low, and a toner having a low fog density can be obtained. I was able to get it.

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Claims (1)

[Claims] 1. A toner comprising at least a resin and a colorant, wherein the resin used has a surface energy of 30 to 50 dy.
A toner for developing an electrostatic image, characterized in that the weight average particle diameter D50 of the secondary particle diameter of the colorant is 0.2 to 1 mm.