CS199799B1 - Electrographic negative liquid developer - Google Patents

Description

(54) Electrographic negative liquid developer

The present invention relates to an electrographic negative liquid developer based on isoparaffinic petroleum hydrocarbons with high mechanical and electrical stability of the dispersion system and with the possibility of using an electrophoretic-induced image for offset printing.

Electrographic fluid developers, possibly also toners, are commonly used for electrophoretic development of latent electrostatic images produced by a known process on photodet conductive layers. The most widespread is the process whereby a paper substrate coated with zinc oxide with suitable binder and other additives is surface-charged, exposed and a latent electrostatic image is induced immediately thereafter.

Positive electrographic developer is usually used for direct copying of originals. In the case of copying negative originals, but especially in reverse reproductions from negative microfilms or microfiche, a negative developer is used to produce the image, allowing the resultant copy to be obtained in positive.

Negative liquid developers are subject to considerable demands. In particular, high stability of the solid dispersed phase in the carrier medium regardless of concentration, coagulation and sedimentation resistance, suitable electrophoretic properties, i.e., the highest charge stability during aging, small changes in the particle and / or part of the potonoial, respectively, are required. changes

199 799

199,799 diffuse electric bilayers in outer field trams and the like. From the point of view of the image production, it is in the case of negative electrolytic toners to achieve an indirect dependence of the image densities on the potential amount of electroetatlograph recording on the surface of the photoconductor, resulting in a low boundary contrast at the interface induced and not developed. Meeting these requirements is usually difficult because, for example, the formation of a negative charge of a part in an environment with a lower dielectric constant than its own part is relatively unnatural and has to be generated by a number of special components. This problem is serious since only about 15 to 20% of the pigments meet the requirements for negative developer pigments from a wide variety of well known electro-developer pitments. Only some types of carbon black are then commonly used for this purpose, for example oil soot with a medium to small particle size. Suitable pigments are used alone, since tinting (e.g., blue) by the addition of additional pitments deteriorates strongly the electrical and meohaniotic properties of the dispersion syetam.

Of the other admixtures, organic binders are usually used for the purpose of forming a diffuse electric bilayer, eventually ensuring the stability of the part in the system, as well as securing the pigment fixation on the surface of the photovoltaic conductor after electrolysis of the induction. For this purpose, resins which are fully or partially soluble in the dispersion medium (isoparaffinic and paraffinic hydrocarbons) are used. These include polyterpone resin, various types of alkyd and modified, polyester resin, vegetable oils, silicone resin, mineral oils, petrolatum, natural and artificial waxes, paraffin, low molecular weight polyethylene. The latter group of components can already be considered as surfactants which facilitate dispersion and also play a significant role in the formation of a diffuse electrical bilayer of a mioellar character. These may be higher fatty acids, such as oleic acid, linoleic acid, and also naphthenates, octoates, or manganese, cobalt and lead stearates. Further preferred is the use of abitetic acid, its derivatives or copolymers.

The actual preparation of the negative electrographic developer (concentrate) consists in an intensive dispersion of a mixture of pigment, binder, surfactant and other components in a nonpolar environment of isoparaffinic and paraffinic hydrocarbons. The resulting achieved particle size is 8.10 ** ^ to 1.5.10 “- ^ mm depending on the technology used.

The disadvantages of the currently produced negative electrographic developers are, as has already been said, in the narrow selection of the raw-wool raw materials and in particular the pigments, and the corresponding components of the binder and the surface active. The limited combination possibilities make it difficult to regulate the suitable properties of the negative developers being manufactured, particularly when it is necessary to adapt these developers to the respective instrumentation systems.

One of the negative properties of negative developers (toners) is its low physico-manganese stability of the dispersion system, which can be easily disturbed by, for example, heat, light or even movement, which makes it difficult to transport, store and

199 799 use of these toners * A defect and in this case will result in complete solid phase coagulation, and the spreading is no longer possible, since in this case the adsorbed layers will be severely damaged, keeping the particles floating and giving them a negative charge.

The above-mentioned disadvantages have no electrographic negative liquid developer based on paraffinic and isoparaffinic petroleum hydrocarbons according to the invention, characterized in that it contains a binder mixture of 4 to 70% by weight of a terpolymer of ethyl acrylate, butadiene and vinyltoluene, 20 to 95% by weight of pentaerythrite up to 15% by weight of leoithine. The preparation technology employed consists in the dlspergaol pigment in the above binder mixture, which is usually diluted with paraffinic and isoparaffinocarbons 0 to 12. The pontaerythrlt polyester can be modified, for example, with linseed, soybean, coconut, castor oil or other vegetable oil. Leoithin is used in normal toohnloká quality.

The advantage of the above described electrographical negative liquid developer is, in particular, the possibility of using a large number of different pigments, in particular different types of carbon black, ranging from colloidal types to structurally largest particle types, and also allows the use of organiocyte pigments, e.g. well-usable different types of carbon blacks give a negative developer with said mixture of binders, which is extremely etable in terms of meohanieká and electric. The developer in concentrated and diluted state is insensitive to shocks and shocks, thermal stresses that are common in transportation, storage and processing. For example, it allows processing in the temperature range from -20 ° C to + 50 ° C. The advantage was the possibility of using this developer for developing images that could be used as an offset matrix. Thus, for example, it is useful when used in a negative microfilm system - reverse electrographic enlargement (matrioe) - offset printing on blank paper.

Example

In a 500 ml bead disperser, glass ballotini of 3 mm diameter disperses to smooth the mixture

160 ml Iseparafine and praffinine oil phrases with a distillation range of 140 to 180 ° C, g of medium-sized oil of the SS 5 type, g of ethyl acrylate, butadione and vinyltoluene terpolymer, g of soybean-modified pentaerythrite polyester and g of leelthine.

It is dispersed to a particle size of 0.2 to 1.2 microns. The disporgaoi is poured

199 799 zr. the glass balletins for use are diluted with the above-mentioned petroleum fraction in a ratio of 8 ml of developer kenoentrate to 1000 ml of petroleum fraction. It is used to produce electrographic reproductions from negative microfilms, and microfiche. For offset printing, the prepared offset matrioe is smeared with a solution containing ammonium ferrocyanide and ammonium phosphate (conversion solution), clamped in an offset machine and the necessary number of prints is made on plain paper.

The described negative electrographic liquid developer is important for securing the operation of micrographic systems in industry and libraries.

Claims (1)

OBJECT OF THE INVENTION Electrographic negative liquid developer based on paraffinic and isoparaffinic petroleum hydrocarbons, characterized in that it contains a binder mixture of 4 to 70% by weight of a terpolymer of ethyl acrylate, butadiene and wool-toluene, 20 to 95% by weight of a vegetable oil modified pentaerythritic polyester and 1 to 15% by weight .