Discussion on Factors Affecting UV Printing Quality (3)
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Six. Introduction to surface treatment methods
Since the way UV inks are printed is by surface attachment rather than by oxidation or penetration, the amount of surface tension is very important. Since the plastic surface is a non-polar and incompatible interface, even solvent-based inks are difficult to adhere to. The principle is that we can know the relationship between surface tension and cohesion by the water droplets on the lotus leaf. In addition, since the additives in the plastic often come out of the surface, there is also a case where it is impossible to actually connect. There are three types of surface treatments:
1. Corona treatment
It is an electric shock treatment, which uses a method of generating a high voltage and a high frequency, respectively, and grounds and an electric air nozzle to generate an electric shock, no current flows between them until the voltage reaches 3000-5000 volts/cm 2 , and the electric shock molecules are ejected from the air nozzle. The high energy free electrons are accelerated toward the positive electrode, in addition to changing the polarity of the material and increasing the roughness of the surface.
The dyne value of the printed material after corona treatment is not as high as possible, and the difference between the normal dyne value and the ink is suitable at about 10. It is often asked that the value of Dyne is already high. Why is it still impossible to print? One of the reasons is that many of the materials contained in the printing materials contain many additives, and these additives may cause printing failure due to high temperature and floating on the surface of the material. For materials treated in this way, the surface tension value will gradually decrease with the increase of the number of days. Therefore, before printing, it is recommended to test with Dyne pen to understand the relevant information. In addition, not all materials are suitable for surface treatment in this way.
2.Primer bottoming treatment
A film is used as a medium between the ink and the material to be printed, and is normally used for materials that cannot be corona treated, such as PP. The processing method is divided into on-board connection PRIMER and offline PRIMER processing.
The thickness of the film has a great relationship with the smoothness of printing. Too thick is easy to cause waste, and too thin is easy to cause printing failure.
3. Flame treatment
It is flame-proof and generally suitable for irregular shape or high speed (1000 m/min) film treatment, generally used in bumpers.
Seven. UV printing related test methods and projects
In the UV printing related tests, there are about five types of surface tension test, adhesion test, dryness test, UV energy test and ink film hardness test.
1.Surface tension test
First test with Dyne pen 38. If the situation on the right side of Figure 7 appears, it means that the surface value of the printed material is below 38. If the condition on the left side of Figure 7 appears, it means that the surface value of the printed material is above 38. , you must test with a higher number until the right condition occurs.
2. Adhesion test
This test is mainly to understand the adhesion of the ink to the printed material. 3M 610 tape is the main test tool.
3. Dryness test
Whether the degree of drying of the ink is related to whether it can be post-processed or not, since UV printing is not a surface permeation drying, if it is not completely dried, its scratch resistance and rubbing resistance are not satisfactory. In terms of ink drying, the dryness of the ink will have a great influence on the opacity of the ink, and the ink with higher opacity will have poorer drying properties.
The factors affecting the dryness are as follows
(1) Thickness of UV ink
(2) Different types of materials to be printed
(3) The speed of the machine
(4) UV reflector type
(5) UV lamp strength
Conclusion
This article introduces the related technologies of UV printing technology. The economic benefits brought by UV printing, such as increasing production, shortening delivery time, saving space, improving working environment, increasing product accuracy, solvent resistance and resistance Scratches, electricity savings, waste of paper without skinning, etc., help the industry to reduce costs and improve quality, while at the same time meeting environmental needs. Due to the higher barriers to entry, the following suggestions are provided for the vendors that want to transform.
1. Collection of relevant information:
There are many things to consider before you want to switch to UV printing, including the plant, location, machine purchase, personnel technology, future positioning, etc., which are collected beforehand. Information collection can be obtained from domestic or foreign agents. Or, through the pipeline to obtain the situation of peer use, or through the Internet search, it is recommended that the company should have a dedicated person or set up a research and development team.
2. Early and medium- and long-term investment considerations:
Every investment needs to be carefully evaluated. Without prior investment planning, there will be a lot of things in the real operation. The general investment scale will vary greatly depending on each financial strength, such as whether you need to have prepress equipment. Or auxiliary equipment, due to the ozone generated by UV printing, the planning of the ventilation system, in addition, some basic equipment will ignore the purchase because many bosses do not know the importance, such as illuminance meter, intensity meter, concentration meter, sink PH value Equipment, conductivity meter, Dyne pen, small UV drying equipment, color machine, etc.
3. Confirm product positioning and attributes:
This article focuses on lithographic UV printing. The lithographic UV printing can print a wide range of printing. At present, domestic manufacturers have to face the competition of the same industry, but also need to worry about low-cost competition in the mainland. How to develop and enhance the company's image It is very important to make product separation and positioning. If the company's operation is still maintained at a low price, it is not a long-term solution for the company's future development.