RU88606U1 - ELASTIC PRINTING FORM FOR FLEXOGRAPHY - Google Patents

Abstract

1. An elastic printing plate for flexography, having protrusions and spaces on its surface, characterized in that to improve the transfer of the ink layer by increasing local pressure in the microcells, the working surface of the protrusions has outwardly open microcells that are smaller than the width of the flexoform lines. ! 2. The elastic printing form according to claim 1, characterized in that the cells have a round, hexagonal or arbitrary shape, open towards the substrate and do not go beyond the line width of the flexoform.

Description

The invention relates to flexography, which is a variant of the printing method, in which elastic printing forms (flexoforms) of various hardness are used, having working protrusions and white space elements. This fact, combined with the use of liquid low-viscosity inks, allows this method to be printed on a wide variety of materials (paper, cardboard, foil, polymer films, etc.) in the manufacture of packaging. Thus, flexographic printing sections are part of the line in this kind of in-line production simultaneously with packaging and finishing processes and, in particular, for marking packaging tape.

The convenience of embedding the printing process in the line for the production of various products is a great advantage over other printing methods, but it also has its drawback because the printing process has the same requirements as the entire line as a whole. Thus, increasing productivity by increasing line speed requires the ability of the printing form to perceive and transfer ink from the anilox roller to the printed material (substrate) in a shorter time and to dry as soon as possible. Ink transfer depends on many factors, including the thickness of the ink layer on the printing plate, contact time, and specific print pressure. This amount can be approximately determined by the Walker-Fecko formula, which takes into account the estimated amount of ink penetrating into the printed material and the splitting coefficient of the remaining layer.

With increasing printing speed on absorbent and non-absorbent printed materials, the contact time of the mold and substrate becomes less and the amount of ink transferred decreases. But an increase in the pressure and thickness of the ink film between the flat working surface of the flexoform protrusions and the substrate does not compensate for this decrease in the amount of ink transferred, since the ink is squeezed out to the outside of the working surface, thereby reducing print quality, see RF patent 2314926.

Therefore, the task is to select such conditions for the transfer of the ink film to the substrate in order to reproduce the necessary optical density and uniformity of the given pattern with the smallest amount.

In accordance with the invention, the problem is solved in that the flexible flexographic printing form has protrusions and spaces on its surface, and the working surface of the protrusions has microcells that are open to the outside, the size of which is less than the width of the flexoform lines to transfer the ink layer by increasing local pressure in the microcells.

Microcells on a flat working surface of an elastic printing form are open outward towards the substrate and are made of round, hexagonal or arbitrary shape, the size of which is more than half the width of the flexoform lines. The width of the walls between the cells is minimal so that they can deform to change the volume of the cells during work and thereby create in the place of contact increased pressure on the printed material, but would prevent it from spreading beyond the width of the line of the picture, choosing their profile and dimensions for each In a particular case, it is possible to adjust the thickness of the paint layer transferred to the substrate on a wide variety of materials and in a wide speed range, thereby ensuring the required quality of the picture. We get the greatest effect when the cell contour is closed and the wall thickness between the cells is minimal.

The invention is illustrated by drawings, which depict:

figure 1 - transfer of paint to a substrate in a known device;

figure 2 - the disadvantages of the known device;

figure 3 - transfer of paint to a substrate in the claimed invention;

4 to 9 show an example embodiment of the invention by engraving the matrix with a profile diamond engraver.

Let us explain the essence of the claimed technical solution by the example of printing alphanumeric information on a packing tape of a packaging conveyor line. Known flexoform 1 (figure 1) has white space 2 and protruding 3 elements, the working surface 4 of which is flat (more precisely, "smooth"). In the process, the initial thickness of the ink layer 5 in the interaction of the protrusions 3 and the printed material 6 is divided into absorbable part 7 and non-absorbable, which is divided approximately equally into 8 and 9. The amount of absorbed ink 7 depends on the properties of the material 6 and the pressure with which the ink pressed into the material. And this pressure, which can be applied without loss of quality, in turn, depends on the ability of the paint 10 (FIG. 2) to spread to the sides from the gap between the working surface 4 and the material 6 under the influence of the force between these surfaces at a given thickness of the paint film. Figure 3 shows the execution of an elastic printing form in accordance with the invention, where 11, 12, 13 and 14 are the different positions of the cells on the working surface of the form, the parameters of which are selected experimentally.

Implement the claimed technical solution in several ways.

a) in the classical method of producing a rubber mold — metal patricia — matrix — rubber flexoform, where the mold is the third generation of the image, in accordance with the invention, it is proposed to use metal (zinc plate, magnesium, etc.) for the manufacture of metal patricia, with advance patterned cells.

b) in a method for producing a mold from plastic obtained by exposing a polymer followed by washing out an undecreased layer, in accordance with the invention, it is proposed to use a polymer with a pre-printed cell pattern;

c) in a method for producing a mold from plastic obtained by exposing a polymer followed by washing out an undecreased layer, in accordance with the invention, it is proposed to apply a pattern of cells simultaneously with drawing a mold by sequential or simultaneous exposure of the polymer, depending on the specific flexoform requirement;

g) in the method for producing a mold from rubber by laser engraving, in accordance with the invention, it is proposed to use a rubber blank with a pre-patterned cell;

e) in the method for producing a mold from rubber by laser engraving, in accordance with the invention, it is proposed to apply a pattern of cells simultaneously or sequentially with a pattern of a mold, depending on the particular flexoform requirement;

f) the method of producing flexoform, in accordance with the invention, involves engraving to a certain depth with an engraver of a certain matrix profile, followed by filling the engraved volume with a rubber mixture and subsequent vulcanization; g) the method of producing flexoform, in accordance with the invention, involves using pressed material in the matrix based on plant or synthetic fibers or granules bonded with phenol-formaldehyde, urea or other resins, to which during engraving are destroyed, forming an irregular pattern of cells on the working surface of the form.

The most universal is the method of obtaining flexoform with the required qualities according to paragraph e). The method can be implemented by engraving the matrix on a three- or five-coordinate CNC machine. On a three-coordinate machine, we have the largest volume of cells if we select the feed per revolution (feed pitch) of a single-pen engraver that is a multiple of an integer fraction of the diameter of the circle described by its vertex, then the trace of its vertex on a horizontal plane will take the form of FIG. 4, the frontal section of this surface will look like FIG. .5. On a five-coordinate machine, where the spindle has an inclination towards the direction of movement or in the opposite direction, we have a trace of the engraver top as in Fig.6 or Fig.7, respectively, and the scan of each groove will take the form of Fig. Choosing the pitch of the feed and the geometrical parameters of the engraver (Fig. 9), namely: the rake angle in plan 15 from 4 degrees to 60 and the trailing corner in plan 16 from 4 degrees to 90 degrees, in each case, you can get the cell depth from maximum to zero respectively.

Let us show the interaction of the claimed flexoform and the printed material on the example of marking packaging materials for small-scale products where fonts with the height of letters and numbers 2-5 mm are most often used. and a line width of 0.05-0.3 mm.

The claimed device operates as follows (figure 3).

When interacting with a substrate, each flexoform microcell passes a series of positions in which it is in one of the states: 11) a free state similar to the known one; 12) touching one of the sides of the cell and the beginning of the free flow of paint from one cell to another;

13) sealing the cell, the beginning of the increase in pressure, squeezing the paint through leaks of the walls and rubbing under pressure the excess paint between the flexoform and the substrate; 14) maximum pressure to absorb paint.

In addition, at high speeds of relative displacement of flexoform and substrate, we observe a phenomenon similar to water hammer, i.e. an increase in local pressure with a decrease in the volume of incompressible fluid in the confined space of the microcell. This is confirmed by the fact that the greatest effect is manifested at high speeds on hard rubber (more than 70 units on Shore)

On non-absorbable materials, the paint transfer process is also improved by rubbing the paint in section 13 under pressure.

Claims (2)

1. An elastic printing plate for flexography having protrusions and spaces on its surface, characterized in that in order to improve the transfer of the ink layer by increasing local pressure in the microcells, the working surface of the protrusions has outwardly open microcells whose size is less than the width of the flexoform lines. 2. The elastic printing form according to claim 1, characterized in that the cells have a round, hexagonal or arbitrary shape, open towards the substrate and do not go beyond the line width of the flexoform.