In order to increase the overall effect of packaging, many customers will design a larger spot color when designing packaging. If they cannot control well in the printing process, the grade of the product will be greatly reduced, thus affecting the product in the market. The competitiveness. Therefore, from the quality control of the raw materials and the technical quality of the operator during printing, strict requirements are imposed.

1. Inconsistent hue of each batch or lot

(1) At the first proofing, it is necessary to make a detailed record of the angle of the doctor blade and the ratio of the ink.

(2) Control before printing, because the spot color ink is generally self-distribution, so we must ensure that the ink used in the deviation, the matching ratio is accurate, ink tray. Inker, ink pump to clean. The previous use of the remaining ink should be added to the new ink in an appropriate amount, and the viscosity of the ink should be recorded according to the record.

(3) The viscosity of the ink must be controlled during printing. It is recommended to increase the number of manual measurements or to automatically adjust the gauge by measuring the amount of stain.

2. Inhomogeneous ink transfer

(1) The color of the ink should be reduced as much as possible, and the two colors can be used without the three colors. The inks of different manufacturers cannot be mixed. After the blending is completed, stir well and add the appropriate methyl ethyl ketone. Dissolved. When adding the solution, it should be slowly added and stirred evenly so as not to cause the solubility to deteriorate due to the impact with the solution, destroying the ink structure, thereby causing poor transfer.

(2) Reduce the blade angle and the blade pressure (more applies to transitional spot colors).

(3) Watermarks

Increase the viscosity of the ink, because the spot color version is deeper and is generally 30-35um, so the ink stain is too low and there will be water marks. It is recommended that the speed of 120-150m/min be used for 22 seconds-20 seconds (Zahn 3 cup)

3. Indented twill

(1) Reduce the pressure of the creasing roller.

(2) The embossing roll has a softer gel, and the replaced embossing roll has a hardness of 75 Shore.

4. Insufficient peel strength and adhesion.

Because = spot color generally accounts for 40%-60% of the entire package, or even more. Therefore, the peel strength of spot colors must be better and can be controlled from the following aspects.

(1) The substrate surface tension must meet the requirements and must not be less than 38 dyne/cm.

(2) Select the ink that is suitable for the substrate model.

(3) Use a solvent with a lower surface tension to reduce the surface tension of the entire ink system, thereby improving the wetting of the substrate.

(4) Increase the heat of the oven, air volume, if the oven heat, air volume is small, the amount of ink on the spot color is large, it will cause adhesion and peeling is not enough.

In short, to control the printing of spot colors, it is also necessary to concisely sum up and improve the awareness of operators on product quality, earnestly improve each gate, and strive for excellence.

Source: Xin Shida Packaging Equipment Co., Ltd.

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