JPH02219064A - Developer for electrostatic photography - Google Patents

Abstract

PURPOSE:To provide the stabilization of the electrostatic chargeability of a toner and the improvement in the flowability which are compatible with each other and to obtain stable image quality by using additives in which the electrostatic chargeability on the triboelectrification series exists on the side nearer the friction material to charge the toner than the toner and hydrophobic silica to the toner. CONSTITUTION:The additives in which the electrostatic chargeability on the triboelectrification series exists on the side nearer the friction material to charge the toner than the toner and the hydrophobic silica are added in combination to the toner. Ethylenic unsatd. carboxylates, such as xylene formaldehyde resin and polymethyl methacrylate, are used a the additives in which the electrostatic chargeability exists on the side nearer the friction material to charge the toner than the toner. Silica imparted with hydrophobicity by methyl group and trimethylsillyl group in used to the hydrophobic silica powder. Since the negative charge of the hydrophobic silica is adequately neutralized in this way, the improved flowability of the toner and the stabilized electrostatic chargeability of the toner are obtained and the stable image quantity is obtd.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a dry developer for electrostatography.

(Prior Art) Conventionally, development methods using electrostatic photographic developers include a one-component development method and a two-component development method.

Particle size 10J made by dispersing magnetic powder 9 colorant and charge control agent in binder resin! This is a method in which the electrostatic latent image is developed by rubbing the toner with the blade or sleeve in the developing device, and then sprinkling it onto the electrostatic latent image. A toner with a particle size of about 107 m to 12 m, which is made by dispersing a charge control agent in a binder resin,
This is a method in which the toner is mixed with iron powder or ferrite powder (hereinafter referred to as carrier) having a particle size of 50 to 150Q and stirred at a certain ratio to charge the toner and develop an electrostatic latent image.

An important property common to both types of toners mentioned above is the amount of toner charge due to friction (microcoulomb/gram μC/g
) and fluidity, and these characteristics determine the quality of the copy image.

For one-component development type toner, the ease with which it charges when it rubs against the blade or sleeve, as well as the amount and stability of the charge, are important. Among the physical properties that affect these charging characteristics, the most important are: It is fluid. If the fluidity is poor, the replenished toner will have difficulty entering the gap between the sleeve and the blade, resulting in unstable charging properties.In severe cases, the toner may clog the gap or cause damage to the sleeve or blade. Causes friction. Moreover, not only does the charging property become unstable, but also the developing power of the electrostatic latent image on the photoreceptor decreases, resulting in a decrease in image quality.

Even in the two-component development method, it is ideal for the toner to contact the carrier and be charged uniformly and stably, but if the fluidity is poor, the toner replenished from the hopper may come into contact with the carrier evenly in a short period of time. It becomes difficult to charge the film, and the film is used for development while being non-uniformly charged, resulting in fogging. It also causes the toner to scatter and prevent smooth replenishment from the hopper. Furthermore, in order to control the most important toner concentration, a magnetic permeability sensor is used to measure the magnetic permeability of the developer, but in addition to the toner concentration, the magnetic permeability of the developer has a large effect on its charge amount and fluidity. Therefore, if the charged amount of the replenished toner does not rise well and is unstable, or if the fluidity is poor, the control of toner density will not be stable, which may cause a decrease in print density or the occurrence of fogging. .

As mentioned above, Japanese Patent Publication No. 54-16219 discloses a method for controlling the charge amount of toner and improving fluidity, which is an important characteristic that determines image quality, regardless of the development method.
JP-A-59-133560 and JP-A-58-1
As shown in Japanese Patent No. 157, a method of adding hydrophobic silica, titanium oxide, alumina, etc. is widely used.

In addition, as a method for stabilizing negative charging, JP-A No. 48-4
As shown in Japanese Patent No. 7346, a method is proposed in which a metal salt of stearic acid is added together with silica.

(Problem to be Solved by the Invention) However, while adding hydrophobic silica, titanium oxide, alumina, etc. improves fluidity, especially in the case of negatively charged toner, on the other hand, due to the strong negative charging characteristics of these additives, Another problem is that the absolute value of the charge amount of the toner increases, resulting in a decrease in developability.

Furthermore, when a metal salt of stearic acid is added together with silica in order to stabilize negative charging, there is a problem in that fluidity also decreases at the same time.

The present invention solves the above-mentioned problems, and provides an electrostatographic developer that is particularly suitable for negatively chargeable toners and is capable of stabilizing toner chargeability and improving fluidity, thereby providing stable image quality. It is something to do.

(Means for Solving Problem 111) In order to solve the above problems, 1 the present invention provides a friction material (1
Additives located on the side of the blade and sleeve material in the component development method, iron powder and ferrite powder in the two-component development method,
Hydrophobic silica is also added.

(Function) With the above configuration, the negative charge of the hydrophobic silica is moderately neutralized by the additive whose chargeability is closer to the friction material than the toner, which improves the fluidity of the toner and stabilizes the chargeability. can be obtained.

(Example) First, an ethylenically unsaturated carboxylic acid ester such as xylene formaldehyde resin, polymethyl methacrylate, or polyethyl methacrylate is used as an additive whose charging property is closer to the friction material than the toner. Its usage is as follows: 1. It is usually used as a binder resin for toner, and is mixed with a styrene-acrylic copolymer or polyester resin that exhibits strong negative chargeability against the above-mentioned friction materials. What is its usage?

The amount is 10 to 50 parts by weight, preferably 20 to 30 parts by weight, based on 100 parts by weight of the binder resin.

If the amount added is more than the above upper limit, the fixing properties such as the offset resistance of the binder resin will be impaired, and if it is less than the lower limit, stability of charging property will not be obtained.6 Hydrophobic silica powder has methyl groups and trimethylsilyl groups. A method of adding 0.1 part to 0.5 part by weight to 100 parts by weight of toner powder using known silica hydrophobized with a group, etc., and stirring and mixing the toner powder using a Henschel mixer or the like is as follows: Same as before A.

The thus obtained toner had improved fluidity and at the same time had appropriate chargeability without an increase in the amount of negative charge, and stable image quality was obtained.

Next, two embodiments according to the present invention will be described in detail.

15-kan upper styrene-acrylic copolymer (Bryolide ACL,
100 parts by weight of carbon black (manufactured by Gutdeyer),
MAloo, manufactured by Mitsubishi Chemical Corporation) 6 parts by weight, chromium-containing oil-soluble dye (Bontron 5-34. manufactured by Orient Chemical Industries)
2 parts by weight and 20 parts by weight of xylene formaldehyde resin (Rig Tool R-70, manufactured by Lignite) were stirred and mixed in a Henschel mixer, further melted and kneaded in a heating mixer, cooled and solidified, and then processed into a jet pulverizer and an air classifier. The particle size is 5 to 30.
With a particle size distribution of 12I! I got the I@ toner. To 100 parts by weight of the obtained toner, 0.2 parts by weight of hydrophobic silica powder (Erosil R972, manufactured by Nippon Aerosil Industries Co., Ltd.) as a fluidity improver was added, and the mixture was rotated with a Henschel mixer at a circumferential speed of the blades of 25 m/s. 2 minutes at speed,
The toner was subjected to surface treatment by stirring and mixing.

3 parts by weight of the obtained toner was transferred to a ferrite carrier (LC
In addition to 100 parts by weight of OO2 (manufactured by TDK Co., Ltd., $1), the mixture was stirred and mixed using a V-type blender to obtain a two-component developer.

Example 1 In Example 1, polymethyl methacrylate polymer fine powder (M
2 in the same manner as in Example 1 except that v45000) was used.
A component developer was obtained.

In order to compare with the above-mentioned example, a two-component developer (hereinafter referred to as a comparative example) was obtained in the same manner as in Example 1 without adding the xylene formaldehyde resin.

Regarding the developers of the above examples and comparative examples, 10 chargeability Ss
A continuous copying test was conducted using a copying machine equipped with a photoreceptor, and changes in the number of copies, toner charge amount, and copy density (measured with a Macbeth densitometer) were investigated.

The above-mentioned copying machine consists of a photoreceptor, a sleeve containing a magnetic roller placed opposite to the photoreceptor, and a packet that stirs the developer and charges the toner. was 60 sheets/min for A4 size paper.

The test results are shown in Tables 1 and 2.

Table 1. Table 21: Ground inspection of toner friction charge amount (unit: μC/g) Table 21: Image density inspection (using Macbeth densitometer) (Effects of the invention) As explained above, according to the present invention, the absolute value of toner charge amount The increase in image quality can be reduced and the image quality can be improved.

It goes without saying that the present invention is not limited to the above-mentioned two-component toner, but can also be broadly applied to one-component toner.

Patent applicant: Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] (1) An electrostatic photographic developer characterized in that an additive whose charging property is located closer to the friction material that charges the toner than the toner on the triboelectrification array and hydrophobic silica are added. (2) The electrostatic photographic developer according to claim (1), wherein the toner is a negatively chargeable toner. (3) The electrostatic photographic developer according to claim 1, wherein the additive is xylene formaldehyde resin. (4) The electrostatic photographic developer according to claim 1, wherein when the toner is negatively chargeable, the additive is an ethylenically unsaturated monocarboxylic acid ester polymer.