In the process of color box printing, we often encounter problems such as blurred outlines, corrugated crushing, ink filling in the gaps between prints, and poor quality of overprint / overprint. In addition, how to deal with low-weight base paper and how to print large corrugated colors The problem of boxes is also a technical problem that color box companies are very concerned about.

In view of the quality problems that often occur in the production process of color boxes and color boxes, here are some of the experiences and lessons accumulated by peers as follows:

Brushed or torn parts of paper

Due to the different materials, paper structures and production processes of white paper, coated paper and offset printing paper, when the temperature of the ink is low in winter and the viscosity of the ink is high, the surface of the white paper or the coating layer will often be covered with sticky hair or sticky ink. The phenomenon of breaking seriously affects the appearance quality of the color box.

1. Wetting powder and alcohol (5% ～ 20%) can be added to the fountain solution to reduce the tension on the edge of the inking part, or according to the different types of ink, choose the corresponding ink, degreaser or dilute. Agent to reduce the viscosity of the ink.

2. Control the printing shop and room temperature. Generally, it is advisable to control it at 19 ℃ ～ 28 ℃. In winter, it is best to heat the ink properly. This will help improve the fluidity of the ink and reduce the viscosity of the ink.

3. Use white paper with strong fuzz, and the printing pressure should not be too great.

4. Do not use too much backing paper under the blanket, and the pad cannot be soft. After using the blanket for a period of time, wipe it with a cleaning agent.

Color paper inks dry slowly

This phenomenon easily causes the printed matter to be damaged, and brings some difficulties to post-processing. This problem can be controlled from the following three aspects.

1. Use a base paper with slightly stronger ink absorption performance: if coated white paper is better than bleached white paper in this respect, it has better absorption performance.

2. Use fast-drying ink or add the appropriate amount of drying aid according to the characteristics of the ink, and reduce the amount of ink applied to the inking area.

3. Properly extend the post-processing interval time or spread the prints to dry.

4. Ink shades and differences in color appearance appear in the same batch of prints

You can get better results by controlling it as follows

1. The inks required for the same batch of products should preferably be prepared at one time. When preparing the inks, the necessary inks, as well as diluents, detackifiers, desiccants and other additives must be measured with an weighing instrument, otherwise multiple times Ink matching and random ink matching also cause differences in hue.

2. The absorption performance, whiteness, and thickness of the base paper (white paper) used in the same batch of products must be consistent. The thicker base paper will increase the printing pressure and cause heavy ink color. The uneven white background of the paper will also cause the dark color of the ink. And changes in color appearance.

3. It is necessary to control the ink and ink balance on the printing roller and strictly control empty cars, because after each empty car run, the ink color of the first dozen prints is obviously deeper and thicker. High, then there are naturally more prints with different shades of ink.

4. For products that need to be overprinted several times, the previous ink should be completely dry before the subsequent overprinting.

When printing a color box with white paper, if the moisture content of the paper is uneven, lotus leaf edges, wavy edges, or excessive drying due to the environment will cause more moisture to evaporate at the edges of the paper, and tight edges will occur. ; After repeated printing and wetting, the white paper will wrinkle during the color printing process.

Wrinkles when printing on white paper

To solve the wrinkles of white paper in the process of color box, we must first control the entry of the original paper moisture. And before printing on the white paper, it is best to put it in the offset printing workshop one to two weeks in advance, so that the moisture content of the paper and the humidity in the printing workshop are balanced. If the air humidity in the printing shop is dry, it is better to spray some water on the ground to adjust the air humidity to prevent the water from evaporating at the edges of the paper and causing wrinkles caused by tight edges. The other is to replace or remove uneven base paper.

Unevenness in color printing

The causes of color-printing veneers are the thickness of the paper, the direction of the silk flow, the solid content of the adhesive, the amount of glue on the corrugated peaks, the pressure after veneering, and the moisture content of the cardboard.

The problem of Lulu can be controlled by:

1. Properly increase the gram weight of color printing face paper, and make use of the characteristic that the horizontal expansion and contraction are greater than the vertical expansion after the base paper absorbs water, and the longitudinal silk flow of the color printing face paper and the corrugation form a "+" cross-lamination.

2. Increase the solid content of the adhesive, reduce the moisture in the adhesive, and adjust the gap between the sizing roller and the pressure roller of the veneer (or laminating machine) to ensure that the color printing paper and corrugation are bonded. In good cases, minimize the amount of sizing on the corrugated peaks.

3. Dry the surface after veneering, and control the moisture to 9 ± 2% to shrink the fiber of the color printing paper, which can also reduce dewring.

Delamination or corrugated collapse of the veneer

Veneer adhesives are currently mostly oxidized starch adhesives. If oxidized starch adhesives do not oxidize starch sufficiently during the formulation process, or starch is oxidized too deeply, the quality of the adhesive will be unstable, resulting in open glue. . In addition, if the sizing amount is adjusted too small, too little sizing on the corrugated peaks will also cause sizing. If it is veneered by hand laminating glue, each layer of tile paper or inner paper is not flattened, which will also lead to open glue.

Carry on the veneer; or mount the veneer by hand. If the amount of glue applied to the corrugated peak is too large, it will easily cause the corrugation to absorb too much water and then become soft. Corrugated collapse will occur after pressure is applied to the corrugated paper . In addition, if the sizing amount is too large, it will not only waste glue, but also make it difficult to dry the product after veneering. Therefore, the amount of sizing should be strictly controlled.

Color boxes fade during post processing and loading and unloading

From the surface phenomenon, the discoloration is mainly caused by the friction between the color boxes during post-processing and handling. In fact, this problem is also closely related to the method of mixing inks. During the production of color boxes, we often find that The viscosity of the ink is too large, causing the ink roller to emit uneven ink and the color box to be damaged by ink sticky hair. In order to solve this problem, a debinding agent is often added to the ink. If a debinding agent is used uniformly for inks with different characteristics, the phenomenon of discoloration will be very serious, because the characteristics of different types of inks are different. For example, type 05 and type 01 resin inks from Shanghai Ink Factory. If the debinding agent used in the ink adjustment is not proper, it will cause the ink to crystallize (the ink printed on the product has powdery features) and cause the product to fade. 05 type bright light fast-drying resin ink can only add 0592 type detackifier, and the amount of addition and control should be controlled within 3%, while 01 type resin ink can use 3% red dry oil and 6 # ink Adjust its viscosity, do not add detackifier under normal circumstances, otherwise the color box will also fade.

In addition to the deployment of the ink, attention should be paid to the control of products and products, as well as the discoloration caused by dry friction between products and equipment, products and tools during the post-processing and handling of color boxes, because the ink has not dried In the case of dry rubbing resistance, the new RMB has faded even if it is dried with rough paper.

If the color box is discolored, the remedy is to cover the color box with another layer of film or apply a bright paste to solve the problem.