CS198525B1 - Material for direct elektrography and elektrographic offset material - Google Patents

Description

The invention relates to a material for direct electrography and an electrographic offset material with improved properties and at the same time for high casting speeds.

Electrographic materials for direct electrographic copying on the throw of an inorganic semiconductor, most commonly zirconium oxide, are also commonly known as useful electrographic offset materials. This inorganic semiconductor in the form of a pigment having a size of 0.2 to 0.6 µm to be cleaned is finely dispersed in a carrier binder and deposited on a conductive substrate such as paper, metal and the like. The organic binder used can be described as a critical raw material component, because in many parameters it affects both the production process itself (especially according to pergolas and coatings) and the final properties of the prepared electrographic material, ie firstly receiving and surface stability of electrostatic charge (denzll damping). Thus, it is commonly used for this purpose to use synthetic or natural resins, or some combinations thereof, which usually allow to achieve and exploit most of the optimum properties of the original components. A wide variety of binders are currently described, including, for example, phenol-formaldehyde resins, maleic esters, oelulysis esters and esters, cellulose oetostearates, monohydrates, or substituted derivatives derived from vlaylkaxbazole, ethyl alkoxides, copolymers of woolen acetate with a phenylacetate 52 copolymers. vinyl esters of β vinyl alcohols, polyvinyl stearates, polyvinyl stearates, polyvinylbutyrates, polyvinylbutyrates, polyvinylbutyrates, polyvinylbutyrates, polyvinylbutyrates, polyvinylbutyrates, polyvinylbutyrates, polyvinylbutyrates, polyvinylbutyrates, polyvinylbutyrates, polyvinylbutyrates resins, abietic acid, pure, optionally modified, and various types of waxes and the like.

These binders or combinations thereof do not meet all of the requirements currently imposed on binders for these purposes. Usually, the relation between the application quality and the theology of processing or binder workability is not achieved.

Very often, cases occur. With an organic binder and good electrical and electrostatic properties, the pijpaent disperses so difficult. It is not possible to use it with good dispersing efficiency and on the other hand it provides low quality picture of many problems. Similar problems also arise with the use of offset printing presses from prepared matrices, if the material is used for offset printing, where the difficulty of the hydrophilization of the surface of the image surface is particularly difficult. Here, in the case of a high-quality electrostatic image, hydrophilization is usually too slow in terms of application. The attempt to increase the hydrophilic properties of the layer in hydrophilic aatrlee by using suitable binders then usually results in increased moisture expansion and increased penetration of water into the paper backing, or even tearing of the matrix at higher printing costs is not satisfactory. between the photoconductive layer and the substrate.

In all cases, the requirements and the binders used are increasing, not only in terms of perfect fllaotvomvll resilience in the area and good flowability of the dispersion at high application rates, as well as the requirements for rapid drying of the layer, which usually with barefoot creation of such phenomena as woe, lines, blisters and the like.

The above-mentioned drawbacks do not have the material for direct electrograph and the electrographic offset material according to the invention on the basis of zinc oxide on paper-plated aluminum-clad paper, characterized in that it contains as blend 30 to 95% by weight of polyesters, preferably alkyds. The advantage of using this binder mixture in the production of electrogression materials is, above all, the declining properties of the electrical application, which reflect the perfect quality of the finished materials, especially in the high values of blackening and sensitivity, reducing and possibly reducing glaze defects. In the case of electrographic effset materials, it is then possible to use single-layer coatings of the sensitive layer. Among the suitable technological properties, the high dispersing efficiency of the mixture is particularly suitable for high soups at speeds up to 140 xa / min and high drying speeds (min. 0.4 a). It is also a positive factor

190525 generally lower price β availability of all components, especially polyester (alkyl) component, The mentioned mixture is less demanding to maintain the standard quality of individual components, because the occurrence of one component is only slightly apparent in the oil quality (deviations of acidity, molecular weight, viscosity etc.) Another advantage of this binder mixture is the possibility of using aspartically weaker coatings of the photoconductive layer (about 10 to 20% compared to conventional methods), which is caused by generally higher charging potentials.

A copolymer of styrene alkyl acrylate with an acrylic acid with an acid number of 3 to 24 mg KOH / g binder, where the alkyl can be C 1 -C 4, can be used over a wide range of molecular weights depending on the desired properties. vinyl acetate contains, for example, vinyl chloride as an additional component, vinyl copolymers with crotons, acid, lauric, sebacic, palmitic, stearic or mixed copolymers and an acid number of 3 to 24 mg KOH / g binders are preferred. , its copolymers, terpolymers and modifications, for example, glycarinated alkyds with different acid numbers, optionally modified with vegetable oils, glycerin alkyds modified with dehydrated vegetable oils, glycerol polyesters modified with fatty acids of linseed and wood oil, optionally with rosin and alkylphenol-formaldehyde resin ad styrene-modified alkyd pentaerythritic polyesters, whether or not modified with vegetable oils

Exemplary embodiment

Mixture of composition

350 g of oxide or g of styrene methyl acrylate copolymer with acrylic acid (60% solution in toluene) g vinyl acetate acetate copolymer with aaleinanhydride (60% solution in toluene) g glycerylphthalic polyester (50% solution in toluene)

200 ml of toluene are thoroughly dispersed in a UXtra-Surrax mixer until a particle size of 20 to 35 µm, as measured by grindometre, is achieved. Dispersions can be made 1h4 with an aspen dose of binder, or with 15 g of styrene acrylic acid-acrylic acid copolymer and 5 g of vinyl acetate-aalein hydride copolymer (low-viscosity dlspergaoe), where the dlspergaoe is faster. Sensitize with the solution as follows. baxvivt ml fluoxesoelau (Ha-salj 1% solution in ethanol) ml breofenol blue (1% solution in ethanol)

0.4 ml of aurmaline (0.5% solution in ethanol)

198 525 and glazed with a spreading rate of 20 to 24 g / m ² on a conductive treated paper substrate.

TI of electrographic, offset materials are poured in a spreading rate of 29 to 32 g / m ² onto a paper substrate specially treated. After drying, a matrix is prepared by electrographic method, the surface of which is hydrophilic by coating with a solution containing ammonium acid phosphate and ammonium ferrocyanide. From the matrloe thus prepared, 200 to 500 copies are printed on a blank paper on an offset machine.

These electrographical materials can be used in a variety of industries, libraries and devices for output information systems.

Claims (1)

Material for direct electrography and electrographical offset material based on zinc oxide on paper or aluminum clad substrates, characterized in that the binder comprises a mixture of 30 to 95% by weight of styrene alkyl acrylate copolymers with acrylic acid, 3 to 45% by weight of vinyl oleate copolymers and 0.5 up to 35% by weight of polyester, preferably alkyl;