Ink performance detection method
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
The ink management mainly controls the color quality parameters of the ink by detecting the hue, tinting strength and light fastness of the ink, and eliminates the color shift from the source.
The quality of the ink directly affects the correctness and stability of the color of the printed product. The water-based ink used in flexographic printing has the characteristics of low viscosity and low pollution. The ink management mainly controls the color quality parameters of the ink by detecting the hue, tinting strength and light fastness of the ink, and eliminates the color shift from the source. Ink testing and related information can be provided by the supplier or by the printing company.
1, ink hue, tinting strength detection
Hue, tinting strength is a basic item of ink detection, and they have a great influence on the color of the ink. Hue is a specific feature of the color of the ink, and optically corresponds to light of a certain wavelength and frequency, such as: red, yellow, and blue refers to the hue of the ink. Tinting strength refers to the extent to which one ink affects the degree of color change of another ink. When the spot color ink is dispensed, when the hue of one of the original inks changes, the color of the spot color ink that is called out changes. For example, when the hue of the original ink is yellowish than before, the spot color ink blended has an effect of increasing yellow color; if the tinting power of the red original ink is strong, there is an effect of increasing red color. When this color deviation exceeds a certain range, visual inspection can be found, resulting in customer complaints. Therefore, it is very important to control the color of the printed matter to ensure the correctness of the hue of the printing ink and the stability of the coloring power.
2, hue detection
For the newly provided ink, it is generally necessary to adjust the viscosity to the viscosity of the machine, use the printing machine to proof, print the color sample of the ink in the solid version, or drop the ink on the color wheel with the pressure adjusted. Drag on the surface of the substrate with a certain pressure and speed, and display a ribbon as a color sample. Observe the effect of these samples. If the ink layer is even and smooth, the coloring is good, there is a certain gloss, the ink color is thick, and the standard color card provided by the same supplier (which can be provided by the ink factory) is basically the same, indicating the hue of the ink. Meet the requirements. Finally, a certain amount of ink for this test can be sealed and stored as a reference wet color sample for the next hue detection.
For inks that have been used, adjust the viscosity of the ink to a suitable value, and use the color wheel to make a good sample. In contrast to the qualified color samples or standard color samples retained in the previous pattern, the color can be initially detected. Another method is to compare the wet color of the ink to be tested with the ink that has passed the last test, and drop a few drops on the color wheel at a distance of about 1 cm.
At this time, two adjacent ribbons will be left on the printing paper, and the two ribbons can be used to judge whether the hue is the same or not.
3, tinting strength detection
Ink coloring force detection uses white ink as a reference color sample, and the degree of influence of the coloring power of a certain ink on the white ink is judged. The coloring power is detected by adding the ink to be tested and the standard color ink in a small beaker, stirring it evenly, then playing the plate, and then comparing and judging the strength of the ink tinting strength against the standard tinting strength color sample. The specific practices are as follows:
Add 10g of ink to be tested and 100g of standard white ink to the small beaker. Stir well and use the color wheel to make a plate. The color sample is compared with the standard ink coloring force card provided by the supplier. If the ink color is light, the ink coloring is indicated. It is weak, if the ink color is too deep, it means that the ink coloring power is too strong, and if it is basically the same, the coloring power is acceptable.
In addition, the degree of strength of the change in the coloring power can be detected by increasing the weight of the ink to be tested or the standard white ink. The lighter color of the ink can increase the weight of the ink to be tested. For example, add 2g of the ink to be tested in a small beaker. After mixing evenly, use the color wheel to make an excellent sample. If it is consistent with the standard color sample, press (10+2):100= 10:x calculation, can be launched x = 100 × 10 ÷ 12 = 83.3 (g), indicating that the color ink of this color ink is only 83.3% of the standard color ink, it can be said that the weak 16.7g.
The darkness of the ink can be adjusted to the weight of the white ink. If 10g of standard white ink is added to the small beaker and the pattern color is the same as the standard color card, then 10:(100+10)=10:x is pushed out =10 (g). It indicates that the tinting strength of the ink to be tested is 110% of the standard ink, and it can be said to be 10g strong.
The above x represents the weight of the white ink when the standard coloring force color card is added after adding a certain amount of white ink to the ink to be tested, that is, the strength of the coloring power is measured by the amount of white ink.
In addition, there is a wet color comparison comparison method, that is, the coloring power detection wet color sample of the ink to be tested is combined with the coloring force detection wet color sample of the previously qualified ink on the color wheel, and the wet color is performed after playing the excellent sample. Sample control. This detection method eliminates the disadvantage that the wet color sample and the dry color sample have a color shift and has an adverse effect on the evaluation of the real result. Since the samples are wet and adjacent, the contrast color is convenient and the accuracy is high.
After finishing the tinting strength and hue detection, remember to keep the wet and dry samples at the time of the test. In particular, the wet and dry samples of the standard ink must be sealed and stored for identification. When used. Since the color requirement of the spot color is stable, the hue of the ink is required to be correct, and the tinting strength is required to be stable. The general standard is: within ±10%, it is acceptable, within ±5%, it is acceptable, not high, nor low.
4, the detection of ink viscosity
Liquid ink has low viscosity and good fluidity. The method of detecting viscosity is also very simple. Only one viscosity cup and one stopwatch can complete the ink viscosity detection.
The specific operation method is: firstly stir the ink evenly, then immerse the viscosity cup in the ink, and then put the viscosity cup at a constant speed. When the viscosity cup just pulls out the ink surface, press the stopwatch to watch the ink outflow; when the ink just has a break point, press the stopwatch immediately. At this time, the time value on the stopwatch represents the viscosity of the ink, the viscosity is high, the number of seconds is large; the viscosity is low, and the number of seconds is small. The viscosity of the ink also changes due to the difference in temperature. Therefore, the general detection temperature is fixed at 25 °C.
It is worth mentioning that there is no obvious correlation between the temperature and the color of the ink, but it has some influence on the performance of the ink when printing on the machine.
5, ink light resistance test
The light fastness of the ink refers to a property in which the ink maintains a stable color after seeing light. The ink with poor light resistance will fade after a period of illumination. Some printed products meet the requirements when printed in the printing house, and the color shift phenomenon occurs after being used for a period of time at the customer. This is mostly due to this.
Here is a method for roughly detecting the light fastness of ink: the solid color sample after printing or patterning is divided into two parts, one part is placed in sunlight for about 4 hours, and the other part is placed in dark and dark place; or the color sample is folded in half. After being placed in daylight, a part of the printing surface is placed on the surface to allow sunlight to be irradiated, and a part of the printing surface is placed facing the backlight. After 4 hours, the color deviation of the two parts of the color samples was compared. If there was a significant color shift, the light resistance of the ink was unacceptable.
When purchasing inks, printers should require ink suppliers to provide products with accurate hue and stable tinting strength, and to maintain a certain amount of safety stock, and do not break the material.