CS231469B1 - cleaning solution for oxidized aluminum offset plates - Google Patents

Abstract

The cleaning solution is intended for cleaning printing areas on an aluminum printing plate to increase the adhesion of the printing varnish. The essence of the solution consists of sodium hydroxide, disodium salt of ethylenediaminetetraacetic acid and water.

Description

BACKGROUND OF THE INVENTION The present invention relates to a cleaning solution for an oxidized surface aluminum offset plate for a positive printing process.

The printing plates serve as a support to which the sensitive layer is applied, the sensitive layer is illuminated over the positive original that we want to reproduce by printing, and is invoked after exposure. This produces a negative template which, after painting, serves as a printing form.

When using aluminum large-format plates for offset printing, the surface of the plate is treated by electrochemical roughening followed by anodic oxidation. In this way, a layer of aluminum oxide having a capillary structure of 1 to 2 µm thickness is formed on the surface of the plate. The optimum board roughness is about 0.6 to 1 µm. The plate is then coated with a sensitive solution having a negative photochemical character, lighted over the desired positive pattern and developed. Development is carried out with water. At non-illuminated layers the water is washed away. A light-cured, cured sensitive layer remains in the illuminated areas. The printing points are rubbed with printing varnish and inverted from negative to positive.

In order for the printing varnish to adhere well to the aluminum base of the printing plate, the printing areas must be absolutely clean before applying the varnish. The printing varnish receives ink when printing. The remaining hardened layer in the non-printing areas is removed chemically, resulting in a printing form.

The cleaning solutions used hitherto to clean the printing areas before applying the printing varnish are not sufficiently reliable. This is reflected in the reduced adhesion of the printing varnish to the aluminum substrate and the consequent low durability of the printing mold during printing. Practice has faced this by additionally rubbing the printing form with a solution of anhydrous alcohol denatured by gasoline, which is uneconomical.

These drawbacks are overcome by the cleaning solution according to the invention, which consists of 1 to 6 wt. parts by weight of sodium hydroxide, 1 to 15 wt. parts by weight of disodium ethylene amine tetraacetic acid and 500 to 1000 wt. parts of room temperature water.

Example

While stirring, 4 g of sodium hydroxide are added to 1 liter of water, and after dissolution, 12.5 g of disodium ethylene amine tetraacetic acid are added. After all components had dissolved, the solution was filtered and diluted with water 1: 9.

The cleaning solution according to the invention perfectly cleans the aluminum plate at the printing points to which the printing lacquer is to adhere. The printing varnish adheres perfectly to the mat and in increased quantities. The durability of the printing form is stabilized and substantially increased. It also removes the veil of the artwork when printing.

Claims (1)

Cleaning solution for aluminum offset plates with an oxidized surface, characterized in that it consists of 1 to 6 wt. parts by weight of sodium hydroxide, 1 to 15 wt. parts by weight of disodium ethylene amine tetraacetic acid and 500 to 1000 wt. parts of water.