Discussion on the most popular factors affecting t

2022-08-13
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Discussion on the relevant factors affecting the quality of UV printing (Part 2)

VI. introduction of surface treatment methods

because the way of UV ink printing is surface adhesion rather than oxidation or penetration, the amount of surface tension is very important. Because the plastic surface is a non-polar and insoluble interface, even solvent based inks are difficult to adhere. We can understand the relationship between surface tension and cohesion from the water droplets on the lotus leaf. In addition, because the additives in plastics often float out of the surface, it will also happen that they cannot be physically connected. There are three kinds of surface treatment methods:

1. Corona treatment

it is a kind of electric shock treatment, which uses the way of generating high-voltage and high-frequency waves to ground and induce electric shock from the air nozzle respectively, and there is no current between them until the voltage reaches volts/square centimeter, and the electric shock molecules eject from the air nozzle, speeding up to the positive pole with high-energy free electrons, This is to change the polarity of the material and increase the roughness of the surface

the dyne value of the printed material after corona treatment is not the higher the better. The difference between the normal dyne value and the ink is about 10, which is more suitable. It is often asked that the dyne value is already very high, why is it still unable to print smoothly? One reason is that many printed materials contain many additives, which will float out of the surface of the material due to high temperature and cause printing failure. The surface tension of materials treated in this way will gradually decay with the increase of days. Therefore, it is recommended to test with dyne pen before printing to understand the relevant information. In addition, not all materials are suitable for surface treatment in this way, such as PP

2. Primer priming treatment

a thin film is used as the medium between the ink and the printed material. It is normally used for materials that cannot be corona treated, such as PP. The processing methods are divided into online primer and offline primer processing

the thickness of this film is closely related to whether the printing is smooth or not. Too thick is easy to cause waste, and too thin is easy to cause printing failure

3. Flame treatment

is carried out in the form of flame, which is generally applicable to the treatment of adhesive film with irregular shape or high speed (1000 m/min), and is generally used in the bumper

VI. UV printing related test methods and projects

in UV printing related tests, there are about five methods, including 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 condition on the right side of Figure 7 appears, it means that the dyne value of the printed material surface is below 38. If the condition on the left side of Figure 7 appears, it means that the dyne value of the printed material surface is above 38. Then test with a higher number until the condition on the right appears

2. Tightness test

this test is mainly to understand the adhesion between the ink and the printed material. 3M 610 tape is the main testing tool

3. Dryness test

whether the ink is dry or not has a great relationship with whether it can be post processed. Because UV printing does not belong to surface infiltration drying, if it is not completely dry, its scratch resistance and friction resistance performance are not ideal. In terms of ink drying, in addition to the following items, the opacity of the ink will also have a great impact. The higher the opacity of the ink, the worse its dryness

the factors that affect the dryness are as follows:

(1) the thickness of UV ink

(2) different types of materials to be printed

(3) the speed of the machine

(4) the type of UV reflector

(5) the intensity of UV lamp

VII. Conclusion

this article makes a simple introduction to the relevant technologies of UV printing technology. The economic benefits that UV printing can bring, such as increasing output, shortening delivery time, saving space Improving the working environment, increasing the accuracy of products, solvent resistance, scratch resistance, saving electricity, waste of ink without scaling, etc., will help the industry to reduce damage; The package shall be printed with the product name, manufacturer name and address, production date, product grade (excellent product, first-class product, qualified product), adopted standard number, implemented sanitary standard number and other information to improve quality, and meet the needs of environmental protection at the same time. Due to the high entry threshold, the following suggestions are provided for manufacturers who want to transform

1. Collection of relevant information:

there are many things to consider before you want to engage in UV printing, including the selection of factories, locations, machines, personnel technology, future positioning, etc. These are all information that needs to be collected in advance. Information collection can be obtained from domestic or foreign agents, or through the use of peers through channels, or through road search. It is suggested that the company should have a special person in charge or set up a research and development team

2. Investment considerations in the initial stage, medium and long term of planning:

every investment needs to be carefully evaluated with spring washers. If investment planning is not done in advance, there will be a lot of things missing in the real operation. Generally, the scale of investment will vary greatly depending on the financial resources of each company, such as whether it needs to have prepress equipment or auxiliary equipment, because UV printing will produce ozone, and the planning of its ventilation system, in addition, Some basic equipment, such as illuminance meter, intensity meter, concentration meter, tank pH meter, conductivity meter, dyne pen, small UV drying equipment, color developing machine, etc., will be ignored by many bosses because they do not know its importance

3. Confirm the positioning and attributes of products:

this paper focuses on lithographic UV printing. Lithographic UV printing can print a wide range of prints. At present, domestic manufacturers need to face the competition of the same industry, but also need to worry about the low-cost competition in the mainland. It is very important to have a good development, improve the company's image, and do a good job in product differentiation and positioning. If we still maintain the company's operation in the way of low-cost competition, I believe this is not a long-term plan for the future development of the company

reference:

1 Xiaoyaohui (1986): lithography, Wuzhou publishing house

2. Cailiren (1991): quality control of color printing, Journal of printing and design, No. 55

3. Li xingcai and Luo Fulin (1992): introduction to printing industry, publishing department of China Culture University

4. Lin Qichang, Wang Xun (1984): printing ink manufacturing and use, Wuzhou publishing house

5. Industrial Bureau of the Ministry of Economic Affairs (1991): A Study on the characterization of sheet lithography inks in Taiwan

6. Tian Suying (1991): on the viscosity of ink, Taipei: printing technology bimonthly, 36 issues

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9. China Printing Technology annual report, China Printing Technology Association

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16. Translated by Guo Lansheng (1991): water based ink printing of non porous packaging films, Taipei: printing people change monthly, No. 85

17. Pei Yu Jian, et al. Study on the comparison of weathering color variation between UV ink and inkjet printing, Huagang Journal of printing and communication, No. 33

18. Zhang Renshu (1993): application and global market analysis of UV/eb dry solid coatings, printing technology, Vol. 10, No. 2

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