Postpress Technology 1000 Questions (110-115)

110. What is the effect of ink layer thickness on the film quality?

When the printed ink layer is thick and the graphic area is large, the ink changes the porous surface characteristics of the paper and closes the pores of many paper fibers, hindering the penetration and diffusion of the adhesive, making the EEI, U products and plastic films very Difficult to bond, prone to delamination, blistering and other failures. Therefore, during process selection, offset printing should be used to print products that will be film-coated because the ink layer of offset products is thin (approximately 1 to 2 um).

111 What is the effect of the dryness of the printed ink on the film quality?

When the ink is not completely dried, the high boiling point solvent contained in the ink can easily cause the plastic film to expand and elongate. This is the main reason for blistering and delamination of the product after the film is covered. The sufficient drying of the ink layer is the primary condition for guaranteeing the quality of the coating film. For products whose imprints are not dried and are eagerly coated, they can be dried in an oven.

112. What is the impact of gold and silver ink on the printed film?

Gold and silver inks are formulated with metal powders and binders. The distribution and homogeneity of the metal powders in the binder are extremely poor, and the ink layers are easily separated during the drying process. These separated metal powders form a barrier between the ink layer and the adhesive layer that will affect the effective bonding of the two interfaces. After such a product is left for a period of time, wrinkling and blistering may occur. Therefore, the coating of gold and silver ink prints should be avoided.

113. What is the effect of the humidity of the film shop on the quality of the film products?

The environmental humidity of the film coating shop affects the quality of the coating film, mainly because the water content changes with the relative humidity in the air between the adhesive and the plastic film and the printed matter, and the humidity-sensitive printed product changes with the size. And generate internal stress. For example, the longitudinal stretch rate of the print is o. 5%, BOPP film thermal shrinkage of 4% in the longitudinal direction, if the print water absorption is too large and stretch, and the film heat shrinkage caused by the internal stress, can cause film products curl, wrinkling, bonding is not strong. In addition, in a relatively high humidity environment, the balance of moisture in the printed matter will also change, absorbing large amounts of moisture from the air medium, releasing it from the surface during hot pressing and compounding, stagnating at the adhesive interface, and locally forming non- Adhesion phenomenon. Moreover, changes in the balance of moisture in the printed matter (absorbing moisture from the air medium or releasing moisture into the air medium) often occur at the edge of the print, making it a scalloped edge or a tight edge, and it is not easy to form a film with the film during hot press compounding. Good adhesion produces wrinkles, making production unsuccessful.

114. What are the main reasons for the failure of film adhesion failure and how to troubleshoot it?

(1) Improper selection of adhesives, improper setting of glue amount, and incorrect ratio measurement. The adhesive brand and coating amount should be re-selected and accurately formulated.

(2) The diluent contains a hydroxyl-consuming alcohol and water so that the hydroxyl group of the main agent does not react. High purity (99 5%) ethyl butyrate should be used.

(3) The surface of the printed matter is dusted. Wipe gently with a dry cloth.
(4) The printed ink layer is too thick. Should increase the amount of adhesive coating, increase the pressure.

(5) The ink layer of the printed matter is not dry or completely dry. Should be hot-pressed again and then gluing; choose a high solid content (6) adhesive; increase the adhesive coating thickness; increase the drying temperature and so on. The adhesive is absorbed by the printing ink and paper, and the amount of coating is insufficient. The formula and coating amount should be reset.

(7) The surface treatment of the plastic film is insufficient or exceeds the pot life, rendering the treated surface ineffective. Plastic film should be replaced.

(8) The pressure is small, the speed is fast, and the temperature is low. The film temperature and pressure should be increased and the vehicle speed should be appropriately reduced.

115. What are the main reasons for the film bubble failure? How to troubleshoot?

(1) The printing ink layer is dried. Should be hot-pressed again and then glue; delay filming time, make it completely dry.
(2) The ink layer is too thick. The amount of adhesive applied should be increased to increase the pressure and the composite temperature.

(3) The drying temperature is too high and the adhesive surface is crusted. Should dry humidity.

(4) The surface temperature of the composite roll is too high. The composite roll temperature should be reduced.

(5) The film is wrinkled or loose, and the film is uneven or curled. Replace the qualified film and adjust the tension.

(6) Wrap dust and impurities on the surface of the film. Dust and impurities should be removed.

(7) The adhesive is unevenly coated and used in small amounts. Should increase the amount of coating and uniformity.

(8) High binder concentration, high viscosity, and uneven coating. Apply Diluent's binder concentration.

Source: "Guangdong Printing" (author / Jin Yinhe: Beizhuang Institute of Graphic Communication)