JPH07199544A - Preparation of electrostatic toner - Google Patents

Abstract

PURPOSE: To obtain a novel electric charge stabilizer having favorable application characteristic by using metallic oxides as the electric charge stabilizer. CONSTITUTION: A metallic oxide pigment is used in an electrostatic toner as the electric charge stabilizer. This metallic oxide pigment is the metallic oxide itself and metallic oxide hydrate and a mixture of the metallic oxide and the metallic oxide hydrate, of course, mixed oxides and mixed oxide hydrates, namely various kinds of metallic oxides or oxide hydrates may be used too. In this case, the oxide pigments containing group VIII subgroup metals in a periodic table, especially Co or Ni and very preferably Fe are advantageous. Besides not only oxides formed of each of various metals in the group VIII subgroup but also oxides containing other metals are contained in the suitable mixed oxides.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to a novel use of metal oxide pigments as charge stabilizers in electrostatic toners.

[0002]

BACKGROUND OF THE INVENTION Electrophotography involves the selective exposure of an electrostatically charged photoconductor by the light reflected by the original to be copied to obtain an electrostatic latent image. In a laser printer this is done by means of a laser beam.

The electrostatic latent image is transferred through a magnetic brush, that is,
Development is achieved by transferring toner particles to the photoconductor through carrier particles arranged along the sector magnetic field lines. During the transfer of the electrostatically attached toner particles to the carrier particles and the magnetic field, friction causes the carrier particles to be electrostatically charged to it. Thus, the toner particles are transferred from the magnetic brush to the photoconductor drum to form a toner image, which is subsequently transferred to paper or film and fixed thereon.

To obtain a strong crisp image, the toner is mixed with a compound which stabilizes its electrostatic charge, known as a charge stabilizer or charge control agent.

Charge stabilizers should meet a number of requirements: they should be capable of developing electrostatic latent images into strong visible images; they are error-free, clear and It should be easily dispersed in the toner formulation in order to be able to produce a uniform image; at least it should be moisture impermeable and have high thermal stability.

These requirements are very difficult to meet at one time and at the same time. Therefore, the prior art charge stabilizers often have drawbacks in their property profile.

[0007]

One object of the present invention is to provide new charge stabilizers which have advantageous application properties.

[0008]

It has been found that this object is achieved by using metal oxide pigments as charge stabilizers in electrostatic toners.

Metal oxide pigments for the purposes of the present invention are
The metal oxide itself, the metal oxide hydrate, and the mixture of the metal oxide and the metal oxide hydrate. Of course, it is also possible to use mixed oxides and mixed oxide hydrates, ie oxides or oxide hydrates of various metals.

Preference is given to oxide pigments which contain a metal of group 8 of the periodic table, in particular cobalt or nickel and very preferably iron.

Suitable mixed oxides include not only oxides formed from various metals of Group 8 but also oxides containing these metals as well as other metals.

Examples of suitable metal oxides and oxide hydrates include: titanium dioxide, zinc oxide,
Antimony (III) oxide, chromium (III) oxide, chromium (III) oxide hydrate, cobalt oxide, cobalt (II, III) Co ₃ O ₄ , lead oxide (II, III)
Pb ₃ O ₄ and especially iron (III) oxide, especially α-Fe ₂ O ₃
(Hematite; CI Pigment Red 101;
C. I. 77491) and iron (III) oxide hydrate Fe
O (OH) .xH ₂ O (x is about 1 to 7; CI pigment yellow 42; CI 77492), especially α
-FeOH (goethite) and mixtures thereof.

Examples of suitable mixed oxides are of the rutile type, for example FeTiO ₃ and especially of the spinel type,
For example ZnCo ₂ O ₄ and especially CoAl ₂ O ₄ (cobalt spinel; CI Pigment Blue 28) and (C
o. Ni) Al ₂ O ₄ is included: of these, metal oxide pigments that are present in a transparent (highly transparent to translucent) form (eg finely ground α-Fe ₂ O ₃ and α-FeO ( O
H) .xH ₂ O) is particularly advantageous. These iron oxide pigments are generally well known. Information on their manufacture is
For example, "Roempps Chemie Lexiko
n ", 8th Edition, Volume 2, pages 1066-1067 (1981)
Year)).

The metal oxide pigments according to the invention are preferably 1-
And as a charge stabilizer during the production of electrostatic toners for 2-component developers. The average particle size of the pigments is generally ≦ 1 μm, preferably 0.005 to 0.1 μm, particularly preferably 0.01 to 0.05 μm. This listed value is
In the case of needle pigment particles, the diameter is perpendicular to the machine direction.

The most important components of electrostatic toners are generally:
0.01 to 10% by weight of binder and usually off-the-shelf toner
In particular, the charge stabilizer reaches 0.01 to 5% by weight.

The binder in the toner is, as is well known, usually a thermoplastic polymer having a softening point of 40 to 200 ° C., especially 50 to 130 ° C., particularly preferably 65 to 115 ° C.

Examples of suitable binders include: polystyrene, copolymers of styrene and acrylates or methacrylates, styrene and butadiene and / or
Or a copolymer with acrylonitrile, polyacrylate, polymethacrylate, copolymer of vinyl chloride or vinyl acetate with acrylate or methacrylate, polyvinyl chloride, copolymer of vinyl chloride with vinylitene chloride or vinyl acetate, polyester resin, epoxy resin,
Polyamide and polyurethane.

If desired, the electrostatic toner may contain other components such as waxes, flow control agents, colorants and magnetically attracting substances.

Coloring agents include organic dyes or pigments such as nigrosine, aniline blue, 2,9.
-Dimethylquinacridone, C.I. I. Disperse Red 51 (CI.60710), C.I. I. Solvent Red 19 (C.I. 26050), C.I. I. Pigment blue 15 (C.I. 74160), C.I. H. Pigment blue 22 (C.I. 69180) or C.I.
I. Solvent Yellow 16 (C.I. 12700)
Or it may be selected from inorganic pigments such as carbon black, lead red, yellow lead oxide or chrome yellow. Generally, the proportion of colorant present in the toner is
It does not exceed 15% by weight, based on the weight of the toner.

Magnetically attracting substances are, for example, iron, nickel, chromium oxide, iron oxide or ferrites of the formula MeFe ₂ O ₄ (where Me is a divalent metal such as iron, cobalt, zinc, nickel or manganese). May be

Toners can be prepared as follows: The charge stabilizers according to the invention are used in a conventional manner, for example, by mixing the components in solid form in a kneader and subsequently grinding or the remainder. Of the ingredients are dispersed in a melt binder using known mixing or kneading equipment and the melt is subsequently cooled to form a solid material which is ground to the desired size (generally 0.1 ~
50 μm).

It is also possible to dissolve the binder in a suitable solvent and finely disperse the charge stabilizer in this solution. The toner preparation thus obtained is directly subjected, for example in a xerographic image recording system, or first to a drying step, for example spray drying, freeze drying, or the solvent is evaporated and subsequently ground to the desired particles. Can be dimensioned.

The metal oxide pigments used according to the invention as charge stabilizers are notable for quite good application properties. They are impermeable to water, 180 ° C
It is heat stable up to temperatures of, in particular, provides a suitable electrostatic charging profile on toner formulations, ie the toner can be charged rapidly and to high levels. Furthermore, they have the effect that their charge is held constant at high levels.

[0024]

【Example】

I. Preparation of Electrostatic Toners Containing Charge Stabilizers According to the Invention The binders used were: Resin A: non-crosslinked styrene / butyl acrylate resin or Resin B: linear non-crosslinked polyester resin.

The toner preparation is: 100 ml of p-xylene by freeze-drying (method F).
0.2 g of the metal oxide pigment is dispersed in a solution of 10 g of each resin in, and the resulting suspension is freeze-dried or-by kneading (method k) 0.2 g of the metal oxide pigment and the respective Mix 10 g of resin thoroughly and knead at 120 ° C.
Extrusion and milling to produce toner particles having a mean particle size of 50μ.

The details of these toners and the metal oxide pigments used as the charge stabilizer are summarized in the table.

II. Developer Preparation and Testing For the developer preparation, the toners thus prepared were mixed with a steel carrier having a weight ratio of 1:99 each and an average particle size of 100 μ and activated on a roll stand.

Samples were taken after 10, 30, 60 and 120 minutes and measured for their electrostatic charge (q / m meter). (Epping, Neufahrn, Germ
from any).

For this purpose, 5 g of developer were weighed into a hard blow-molding cell, which in each case was connected to an electronic meter and which had a sieve with a mesh size of 63 μm. A high-velocity air stream (about 4000 cm ³ / min) was used at the same time as suction in order to almost completely remove from the carrier particles the toner particles with which they were held in the measuring cell by means of a sieve. The charge on the carrier, which is related to the charge on the toner particles except for the opposite sign, is read on an electronic counter; the weight of the blown toner is measured and the weight of the measuring cell is calculated back; Static charge q / m [μC /
g] was measured.

The measurement results obtained are summarized in the following table.

[0031]

[Table 1]

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Reiner Derrick-Brentzinger Weinheim Weinheimerstraße, Federal Republic of Germany 44 (72) Inventor Jörg Schroeder Weinheim Ampenfeld, Federal Republic of Germany 11

Claims (1)

[Claims] 1. A method for producing an electrostatic toner, which comprises using a metal oxide as a charge stabilizer.