DE3137547A1 - Printing process - Google Patents

Abstract

The printing process according to the invention allows glossy or photograph-like prints to be produced. As in the production of transferable prints, a single- or multicolour, in particular screened, print is applied to a substrate provided with a thermoplastic coating, preferably by the offset method, using a transfer printing ink which contains a conventional liquid vehicle (binding medium) and, distributed therein, pigments, which are in turn composed of a solid, thermoplastic binder and a dye. The printed substrate is heated briefly, at least on the surface, to a temperature at which the thermoplastic coating and the thermoplastic binder melt and flow together to form a glossy surface.

Description

Technical area

The invention relates to a printing process for producing glossy ones or photo-like prints.

State of the art

Prints that are faintly glossy are usually made glossier by printing Papers made with glossy drying inks. In this way, however, only a weak gloss can be produced. So-called "heat-set" inks, which, like a stoving varnish, condense by heating after printing, produce a higher gloss will. The gloss is then limited to the printed areas and differs from the gloss of the unprinted surface. A uniform high gloss cannot be achieved in this way either. High-gloss prints are therefore predominantly through Varnishing or laminating non-glossy prints produced. These subsequent operations are too expensive for many purposes.

A high gloss generally promotes the photo-like appearance of the print, but there remains a considerable difference in effectiveness a real photograph with all known printing processes. This difference is essentially due to the sharp limited halftone dot, which never allows the uniformity of a photographic halftone to be fully achieved.

Task and solution

The invention is based on the object of an improved method for the production of glossy or photo-like prints find that can be carried out in one operation. The ·: according to the invention The solution to this task is based on the so-called "transfer printing process" ο It is used to print from paper to others Transferring substrates that are difficult to print on themselves. For the production of glossy or photo-like prints it has not yet been applied. The principle of the transfer printing process consists in applying a transfer printing ink to a paper that has been provided with a thermoplastic coating to print a reversed image. The transfer printing ■ * · paint consists of a common liquid binder and in it

Printing process

Claims

i! Printing process "in which one is on a substrate, which with. a thermoplastic coating that melts at 50 "to 25O C stranding is j, applies a single or multi-colored print, wherein the printing ink contains a liquid binder and coloring matter and the coloring matter contains a coloring matter and a thermoplastic3 binder that melts at 50 to 250 ° C contain,

characterized,

that the printed substrate is at least superficially heated briefly to a temperature at which the thermo = the plastic coating and the thermoplastic binder melt =,

2 ο Method according to claim 1, characterized in that the print is applied to the substrate using the offset method.

3 "Method according to claims 1 or 2, characterized in that a screened print - preferably applied in multiple colors" is _o

4 * method according to claims 1 to 5s characterized that the printed substrate was heated immediately after printing

5 = method according to claims 1 to 49, characterized in that that the .Druck is heated by means of a radiant heater.

Fabric foil prints for making cans, tubes, toys and the like called.

Printable substrates

All substrates can be printed which can also be printed in the conventional way. Paper and cardboard are available as most important to mention. Cardboard, plastic films, wood veneers or sheet metal can also be used. A smooth, pore and A scar-free surface is an advantage, but not an essential requirement. A light carbene structure can be used in special cases be desirable for the production of effect prints.

The substrate to be printed is provided with a thermoplastic coating. This is understood to mean a coating that melts on heating and - if it was not shiny beforehand - melts with the formation of a shiny surface. When it cools, the coating solidifies and the gloss is retained. If required, coatings? are used that form special surface structures, e.g. a matt gloss »Thermoplastic coatings can generally be melted several times, although for the process the invention a unique meltability is sufficient.

The coating can be applied in any conventional manner, for example by spraying, brushing or rolling a solution of the coating agent in an organic solvent or an aqueous dispersion of the coating agent. The coating does not need to be closed after the substrate has been coated and to be shiny, but should merge at the latest when heated to the melting temperature. The thickness of the coating must be sufficient to compensate for unevenness in the surface of the substrate. As a rule, one layer thickness is between 5 and 100 ^ im satisfactory. Lower layer thicknesses result no satisfactory gloss; greater layer thicknesses have no advantages. The melting temperature depends on the chemical nature of the coating agent and should not be below 50 or above 25O C. The majority of suitable coating

by means of transfer printing varnishes which are also customary, melt at 80 "to 180 ⁰ Co

Printing process

Transfer prints are mainly produced using the offset process ^ which is also best suited for the method of the invention »In principle, letterpress, gravure or Screen printing process under consideration »It can be printed in one or more colors. The best results are in halftone printing because the photo-like effect comes into its own. «The special features of the transfer printing process can be used in the method of the invention in the known manner »

Printing inks

This also applies to the printing inks used. Usual transfer printing inks are suitable »They contain a liquid binding agent that is preferably slow-drying oxidatively. UV curing |

bare or solvent-based, physically drying bandages j

I medium are also suitable. A small amount of connective tissue is sufficient ^:

Medium amount that is needed to fix the color bodies on the I

Substrate is sufficient until it fuses with the thermoplastic coating »

The color bodies contained in the printing ink are made from the color pigment and a thermoplastic binder which is solid under printing conditions. In principle, a soluble Dye be homogeneously distributed in the thermoplastic binder. The amount of thermoplastic binder in the color bodies must be at least so large that they soften at the melting temperature until they begin to flow and can fuse with the thermoplastic coating.

JC The melting temperature of the binder should be the same as that of the Coating in the range from 50 to 250 °, preferably 80 to 180 C, lie «It is an advantage if the melting temperatures of the coating and the binding agent are roughly the same. That is especially the case when both have the same chemical

% - ■

Have structure. This also has a positive effect on the miscibility. At least the coating agent and the binder should be compatible in the molten state to such an extent that they flow together and can form a continuous surface at their point of contact.

Implementation of the procedure

As is the case with the production of transferable prints, it is possible to first apply in a conventional manner in a first step print, creating a non-glossy print. To prevent blocking, powder can be applied after each print run. The heating to fuse the print with the thermoplastic The coating can be done in a second, separate operation. However, this is not the preferred embodiment the invention.

This is the direct consequence of the printing and fusing process. Immediately after the last print run, the printed substrate is passed through to the printing machine connected heating zone run in which the pressure is heated and is fused to the underlying coating. The hardening of the liquid binder takes place when entering the heating zone has not yet been completed if it is completed in the heating zone at the same time as the melting process will.

When heated, the printed surface must be exposed. As soon as the print and the underlying coating or at least its top layer have melted sufficiently, they flow together, which is usually associated with a deepening of the color tones. The gloss and the photo-like effect develop faster and better the higher the surface temperature. However, temperatures at which the substrate, the coating or the color bodies _r example, by yellowing - are damaged, to absolutely avoid comparable ·. When the temperature is high enough, the flow process

Completed after a very short time »Depending on the nature the processed materials and the desired gloss, the heating time can be from a fraction of a second "up to take several seconds. If the substrate itself does not need to be heated, it is sometimes even harmful, one leaves

preferably the heating on the exposed surface \

act. It is particularly useful to use radiant heaters ^:

in particular so-called infrared heating rods. Instead, you can also blow hot air or apply a flame to the surface or the back of the printed substrate via a heated one Let the orphan run »As a rule, the printed substrate is run through a fixed heating zone. However can one also moves the heat source across the substrate

After fusing and before stacking or rolling up the treated substrate, the surface is left under the Cool the melting temperature, which can be accelerated by blowing cold air on it. The cooled print is glossy and does not require any further treatment of the surface. . ·

Claims (1)

Printing process Claims ii printing method applies a single or multi-color printing "which comprises applying to a substrate a thermoplastic with. at 50" is provided to 250 C fusible coating _9, wherein the ink comprises a liquid vehicle and color bodies and color body a dye and contain a thermoplastic binder that melts at 50 to 250 C, characterized, that the printed substrate is at least superficially heated briefly to a temperature at which the thermoplastic Coating and the thermoplastic binder schmelzeηο 2ο Method according to claim 1 _9, characterized in that the print is applied to the substrate in an offset process. 3ο Method according to claims 1 or 2, characterized in that a screened print - preferably applied in multiple colors -will" 4. The method according to claims 1 to 3 »characterized in that the printed substrate immediately after Printing heated « 5 = method according to claims 1 to 4 »characterized in that that the .Druck is heated by means of a radiant heater.