How to improve the wear resistance and adhesion of UV varnish?
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
UV glazing is a surface finishing process commonly seen in the packaging and printing industry. Color box printing companies (especially color box printing companies with export business in Japan, Europe and the United States and other countries) often encounter such troubles: after UV varnishing of printed products, the wear resistance of UV varnish layer and Poor adhesion, especially when the print is printed with metallic ink (gold or silver) and UV glazing is used.
In general, color box printing companies often solve this problem by replacing UV varnish. In fact, we should not limit our thinking to replacing UV varnish. Instead, we should diversify our thinking and change our thinking to change the production process of the color box or adjust the relevant process parameters.
Solutions
The conventional corrugated box production process route is: plate making and paper cutting → ordinary printing → over UV bottom oil → over UV surface oil → 裱 楞 楞 → die cutting → paste box. After many trials, the author summarizes the methods for improving the production process of corrugated box.
(1) Plate making and paper cutting → UV ink printing + online UV glazing. Tests have shown that this production process can greatly improve the abrasion resistance and adhesion of UV varnish on metal UV inks, but metal UV inks are rare on the market, require special customization, are expensive, and must be UV-coated. Printing press. Generally, most small-color box printing enterprises do not have UV printing machines, so this production process is only applicable to some color box printing enterprises, and the general promotion is of little significance.
(2) Plate making and paper cutting → ordinary printing → screen printing UV glazing. This production process can also solve the problem of poor wear resistance and adhesion of UV varnish on metal ink, but the cost of screen printing UV varnish is higher, and the environmental performance is not as good as that of waterborne UV varnish. In addition, very colorful box printing companies do not have automatic screen printing machines, only semi-automatic screen printing machines with low production efficiency, so this production process can only be applied to some color box printing enterprises, and it is not worth popularizing.
Finally, after repeated verification, we have clarified the idea of solving this problem: using high abrasion resistance UV surface oil to improve wear resistance, and ensuring the adhesion of UV primer by adjusting process parameters or replacing materials. Due to the two glazing, the varnish film is thicker, which makes the wear resistance of the high abrasion resistant UV surface oil more secure. The next step is to solve the key factors affecting the adhesion of UV varnish - printing ink and UV base oil.
Solution
Before solving the problem, you first need to understand the customer's requirements for the color box and how to detect it.
(1) Detecting the wear resistance of the color box UV varnish, the method is as follows: 1 If the color box needs to be shipped by sea, the actual product can be installed in the carton used in the actual customs declaration, or the weight specification of one box is consistent with the actual product. The product model is placed on the simulated transportation test machine (vibration test bench) for more than 2 hours, and the surface of the color box has no obvious UV varnish film layer or ink layer falling. 2 The color box sample is placed on the friction resistance tester. On the top, use a 22N weight to rub back and forth 80 times (weight and number can be determined according to customer requirements), with no obvious UV varnish or ink drop as qualified.
(2) Check the adhesion of the UV varnish of the color box. The method is as follows: 1 Apply 3M transparent tape to the surface of the color box, and then tear the tape quickly and forcefully at a 45-degree angle to prevent the UV film from sticking. The layer or the ink layer is qualified; 2 using the HB pencil lead to force back and forth on the surface of the color box UV varnish film layer so as not to cross the UV varnish film layer or the ink layer.
There are two main types of silver powder contained in silver inks currently on the market: one is a nearly circular granular structure; the other is a sheet-like structure similar to "fish scales". The former is more conducive to the adsorption of UV base oil, while the latter is more able to show the metallic luster and texture of the ink. However, there is only one type of gold powder contained in the gold ink currently on the market: a sheet-like structure similar to "fish scales". Therefore, the adhesion of the UV base oil to the gold ink is much worse than that of the silver ink, and it is also troublesome to solve. The author also learned that the oily UV primer has better adhesion to metallic inks than aqueous UV primers. However, the oily UV base oil was also used in the improved process, but the problem of adhesion on the metal ink was still not solved, so we had to shift the focus to the improvement of the metal ink.
In detecting the adhesion of the problem box UV varnish, we found that not only the UV varnish layer but also a part of the ink layer was adhered by the 3M scotch tape. In addition, we have found that after the conventional printing process is completed and the metal ink is completely dried, a thin layer of metal powder is left on the finger when it is gently swept across the surface of the print with a finger. From this we judge: It may be that the binder in the metal ink is not enough. So we added some transparent inks to the metal ink. Once again, we found that the adhesion of the UV primer to the metal ink has been significantly improved, but it still does not meet the customer's requirements. In this regard, we replaced the transparent ink with quick-drying varnish, so that the adhesion of the UV primer to the metal ink was basically solved. However, the addition of fast-drying varnish dilutes the color of the metallic ink, causing a slight change in the color of the printed product. Therefore, a small amount of four-color ink must be added to the metallic ink for re-dispensing. In addition, in the three processes after UV glazing, mainly the water content of the color box affects the abrasion resistance of the UV varnish, and therefore it is necessary to control it.
Program summary
Finally, the author summarizes the technical points of the wear resistance and adhesion of UV varnish on metal ink.
(1) Production process route: plate making and paper cutting → ordinary printing → over UV bottom oil → over UV surface oil.
(2) Select high abrasion resistant UV surface oil and oily UV base oil.
(3) Add 10% to 20% of fast-drying varnish to the metal ink (the specific ratio is completely dried after the metal ink is dried, the finger gently strokes the surface of the printed product, and the metal powder on the finger is basically left, if the metal ink The color is diluted and can be blended by adding four-color ink). It should be emphasized that the UV ink must be passed after the metal ink is completely dried.
(4) The quick-drying varnish contains ink drier. If the metal ink is still difficult to dry after adding fast-drying varnish, the drier with the same drying property as white dry oil can be added appropriately (addition ≤ 3%) ), do not add red dry oil, because red dry oil can only accelerate the drying speed of the ink layer surface, but can not accelerate the drying speed inside the ink layer.
(5) In the process after glazing, the moisture content of the color box must be controlled to be 16% or less.
(6) The brand of various materials in the fixed production process route, and the various process parameters of the ordinary printing, UV base oil and UV surface oil processing should be kept stable, and relevant records should be made.