Fifth, the test method to determine the markings
IGT, a Dutch company, used the printability instrument it produced to develop methods to determine the markings. Stripping and Wet-stretching The wet-resistance marking test was performed on an AIG2-5 printability tester. The peel-off speckle test was also performed on a CI-type printability tester. Wet pull resistance temperature test has been discussed in another article.
principle
The paper to be measured is printed with a special spectrophotometer. With the first method of measurement, the ink on the printed test strip is transferred to a clean printing plate. The test was transferred four times, each time using a clean printing plate.
Due to the irregularity of the ink absorbed by the paper, ink that has not been fully absorbed is transferred to the printing plate. With this method, the effect of markings has been strengthened, making assessment of results easier.
The second method is to print an inked printing plate onto five clean papers respectively, during which the printing plate does not need to be inked again. This method is faster but the test accuracy is poor.
the first method
The 50 mm blanket printing disc was inked with a speckle marking ink using conventional methods. The test strip was printed on AIC2-5. No padding is used for printing. The speed is 0.2m/s and the pressure is 500N. After printing for 10 seconds, the plate was printed again with 500N using another clean 50mm blanket printing plate. The ink on the paper is transferred to the printing plate. Every 10 seconds, print on the next clean print plate. A total of four stripping.
The test can also be carried out on C1 with a printing plate width of 35 mm and a pressure of 450 N. Volume is not all types of paper and paperboard suitable for testing on C1, the results can not be compared with the results obtained on AIC2-5. Please note.
The amount of ink used is based on the type of paper and board, but it is generally recommended to use 1cm3 for AIC2-5 and 0.3cm3 for C1.
The second method inked the 50mm print disc and then printed it on the AIC2-5 at 0.2m/s, 625N. After 10 seconds, change a piece of paper and print it again. Use a clean strip of paper and print it 5 times, 10 seconds apart. If the type C1 is used, the pressure is set to 450N, and a printing cloth like a leather cloth is used. The ink is 0.3 cm3 on AIC2-5 and 0.5 cm3 on C1.
Test result evaluation
The method of assessment generally uses prefabricated, splined strips that represent a certain print quality.
This assessment method can only be used by the user. Unless comparison proofs can unify or use a speckle index table, they cannot exchange data with other units.
The zebra index is based on two conditions that influence the evaluation of zebra patterns: the perimeter of bright and dark spots and their density contrast. Larger areas and contrasts are easier to observe. Using a scanner, it is possible to measure and express the effective perimeter of bright and dark spots (Specific
Perimeter), Density change can be calculated as Coefficient, Of Variables.
With the above two variables, the speckle index is obtained:
In the high-variable coefficient (large contrast) and small effective circumference (large spots), the speckle index increased, which is consistent with the results of visual assessment.
The relationship between printing quality and parameters related to the marking index can be expressed by the following table:
MI=COV/(SP)1/2
COV SP MI
Good print quality Less speckles Smaller size General print quality Large spots Low contrast Low contrast Spots Some small prints Common print quality Spots High contrast High marks Some prints are poor Medium print quality Spots High contrast High graffiti size
Table 1 Expected marking index
Speckle analysis is not a blind test on only a few samples. It is very important to clearly set goals and how to achieve them.
