DD159416A1 - COMPOSITE DESIGN OF A SCREEN PRINT - Google Patents

Abstract

In the novel doctor blade design described in the invention recesses are incorporated in the doctor blade compared to the conventional doctor blade design with a continuous pressure edge. The basic doctor blade thus consists of several partial doctor blades. This squeegee design is preferably used in applications where strip-like coatings are to be applied by means of large-format printing screens. In a staggered arrangement of two novel doctor blade executions at a small distance one behind the other, the printing of all occurring geometries is possible. The advantages of the novel doctor blade design described in the invention are that a better printability of thixotropic pastes is possible. Furthermore, a minimization of the tolerances of the printed layer thicknesses could be achieved. Because of. Flexibility of the squeegee design could increase the service life of the sieves.

Description

23056

1st title of the invention

Comb-shaped design of a screen printing squeegee

2, Field of application of the invention _:. , .. ...

The comb-shaped design of a screen printing squeegee described in the invention is used in the field of screen printing technology, especially in screen printing machines. These special screen squeegees are preferably used where in large-format printing row-shaped screen printing geometries are to be applied to large-sized carrier materials.

3 »Characteristic of the known technical solutions

Known technical solutions use depending on the application Siebdruckrakel different widths with a rectangular rigid mold made of polyurethane or similar, with a continuous screen printing edge, the width of the doctor blade is adapted to the surface to be printed.

When printing Z ₄ B _{4 of} electrically conductive layers, measurements of the printed resistive layers resulted in a relatively large scattering range, which is reflected even after the subsequent curing of the layers in a large variation of the resistance values and relatively low yield.

Strong thixotropo pastes have insufficient turbidity. The paste remains partly on the doctor blade and then the screen geometries were not completely wetted by the return squeegee. This manifests itself in an unsatisfactory quality of the surface and in variations in the layer thickness.

Large-format printing screens made of canvas fabrics are stretched very taut «

-.- 230568

Due to the rigidity of the screen squeegee, a greater squeegee pressure is exerted on the screen fabric at the edge zones of the screen squeegee during the printing process than in the middle of the squeegee. This can lead to an incomplete printing of the Viderstandsbahnen in the peripheral zones. Due to the necessary large squeegee pressure on the screen, the fabric wears very quickly, especially at the substrate edges, the result is a reduction in the service life of the sieves.

A reduction of the sieve distance to the substrate does not bring the desired success, since heavy noble metal-containing screen printing pastes leads to a relatively large sagging of the fabric in the middle of the screen. This leads to smearing of the printed layers. '·

4 «Aim of the invention

The caramel-like embodiment of a screen-printing squeegee for preferably strip-shaped screen-printing geometries described in the invention has the following advantages over the known technical solutions:

- Due to the caramel-like design of the screen squeegee is a better adaptation to the large-scale screen production

, inevitably resulting Siebspannunterschiede. Schichtdickenschv / annulations on the printing material are thus largely eliminated.

- Due to the better flexibility of the comb-like screen squeegee, the screen fabric is spared and the life of the production relatively expensive printing screens is increased.

"'- By the free spaces -der described in the invention

Screening squeegee remains next to the geometries to be printed • screen printing paste · during printing process · · '' ··· "

As a result, complete wetting of the screen contours on the screen is achieved with the aid of the return squeegee. This ensures better printability, even of very thixotropic pastes.

23056

5 "Explanation of the nature of the invention

With the described in the invention novel design of ßiebdruckrakel described in Pkt. 3 disadvantages are largely eliminated.

The screen squeegee consists of a base doctor, which is clamped consistently at the upper end in a clamping device. In the lower part of the screen printing squeegee, which takes over the printing function, recesses are provided with a non-printable area between the screen contours corresponding length and width ratio «(Figure 1)

Angled sheets are attached to the screen-printing squeegee, which recirculate screen printing paste which is not printed during the printing process. (FIG. 3)

6 «embodiment

It was the object of the invention to print a large number of identical resistance webs with a constant layer thickness onto a large card paper carrier body.

The arrangement of the resistance paths took place in a row with the same distance between the rows »

In the series, the resistance paths were offset and placed twice against each other. Between two rows are the contacts for each resistor track.

The Siebdruckrakel for printing the resistor tracks was designed so that a partial blade according to Figure 1 is slightly wider than the row-shaped contour in the printing screen.

The partial doctor blade width and the length of the recesses according to the figure has been chosen to be constant so that no differences in the flexibility of the partial doctor blade occur

 Angled sheets were attached to the side of the squeegee to prevent screen printing paste escaping from the space between the squeegee and the squeegee. In practical use of this novel screen printing squeegee, the following results were achieved:. ·

.a) Boira large-format surface screen printing was able to achieve complete wetting of the screen contours with the return squeegee, especially with strongly thixotropic paston.

b) The variations in the layer thickness could be minimized as far as possible.

In the present example, on a hard paper substrate in the dimensions (100 × 4-60) mm, the thickness fluctuations of the printed layer could be reduced from previously (20 + 7) / im to (20 + 2) ^ . The yield after curing of the resistance paths could be increased considerably

c) The novel design of the screen squeegee greater flexibility of the individual partial blade is achieved. As a result, a better adaptation of the individual partial doctor blade to the differences in the screen tension occurring in the case of screen production occurs in the case of large-format printing screens. There is a protection of the screen mesh and associated with a significant increase in the service life of printing screens.

The technology described in the embodiment allows only the printing of strip-shaped screen contours.

Assigning a second similar doctor blade offset at kuraem distance behind the first squeegee, so the printing of all occurring screen contours is possible.

Claims (3)

7. Claims 1. Comb-shaped design of a screen-printing squeegee, characterized in that is divided into strip-like contours to be printed on substrates, the screen printing squeegee in a plurality of the number and the width of the contours corresponding partial blade (according to Figure 1). 2. Comb-shaped design of a screen squeegee, characterized in that the width of a partial blade is greater than the width of the screen contours. 3f Kajamförmige design of a screen printing blade, gekannzeichnet that in addition to the doctor side angled sheets are arranged (according to Figure 2 and 3) 4-, comb-shaped design of screen printing squeegee, characterized in that two novel squeegee versions are arranged offset at a small distance, so that the printing of all possible screen contours is possible _o J, For this purpose vL pages drawings-