Decorative paper is a kind of paper that is printed with various tree patterns on the decor base paper and gives the natural wood fell to the furniture or laminate flooring product. It is generally packed in paper rolls and used for decoration. The color shading of decor paper refers to the difference between the finished decorative paper products and the standard sample in the patterns and colors. This chromatic aberration of decorative paper is mainly produced in the printing process. Due to the influence of raw materials, production equipment, and the skills of production personnel, the color shading is difficult to control and may cause many customer complaints. Therefore, how to control the color difference is a topic that many decorative paper printing companies are eager to discuss. As a member of the decorative paper enterprise, today let’s talk about some of our ideas.
What’s the classification of decorative paper color shading?
It is unrealistic for the decorative paper to be 100% free of color shading. The color shading we usually talk about refers to the obvious color difference that human eyes can distinguish.
According to different classification bases, there are several classification methods as follows:
1. Classify by Batch
1) Same Roll Color Shading: It refers to the color difference between a certain part and other parts of in a certain decorative paper roll
2) Same batch color shading: It refers to the color difference between the roll and roll of the same batch décor paper.
3) Color shading between batches: It refers to the color difference between a batch of decorative paper and previous batches of decor paper products.
2. Classify by severity
1) Slight color shading: It refers to the color difference that can be distinguished by people who are sensitive to colors at a distance of 250cm and a field of view of 10 degrees, while others cannot.
2) General color shading: It refers to the color difference that most people can distinguish at a distance of 250cm and a field of view of 10 degrees.
3) Obvious color shading: It refers to the color difference that most people can distinguish wherever they can see the layout.
What’s the purpose to control the printed decorative paper color shading?
Decorative paper is used for decoration, so the pattern and color are required to be unified and harmonious. The existence of color difference will cause the product to change in color, then lead to the downstream customers’ products being inconsistent in color. This will inevitably fail to be recognized by the market and satisfied with the end consumers. For example, if there are color differences in the same roll, the flooring factory will have a color difference when the same batch of products leaves the factory. Once the floors with the color difference are assembled together, it will bring strong dissatisfaction and complaints from the final consumer. So the purpose and significance of controlling color shading lie in:
1. Protect the decor paper product with good consistency, and ensure the color and pattern consistency within each batch or between batches.
2. Effectively improve the ratio of downstream customers’ satisfaction and reduce customer problems and complaints in other areas
3. Effectively enhance the company’s reputation and position in the industry. Because color shading is a common problem in the decor paper industry at present, whoever controls the color difference well will stay ahead of the curve.
4. Good control of color shading can also help the printed paper factory to save costs. At present, most factories also need to make samples before mass production, so the waste caused by color shading is also a serious phenomenon.
What caused the decorative paper color shading?
The color shading of decorative paper is at the bottom a quality problem, so it is the same as quality problem, the reasons are not more than personnel, equipment, raw material, technology, etc.
Personal skills can affect the furniture decor paper product quality. A good color colorist can make the colors most like the standard sample paper; A good printing operator can control the machine stably to maintain the color consistency; and a good standard sample paper manager can prevent or find the sample paper problem like moisture absorption, color fading in time, so as to avoid color difference. A good raw material inspector can accurately detect the problems of raw materials, thereby reducing the color difference.
The overprint accuracy of the printing machine, the control accuracy of various printing accessories, the stability of the squeegee and the printing plate, all of them will affect the color difference of the decorative paper.
1) Overprint Accuracy
The decorative color is realized by the principle of the color subtractive method. Therefore, in the multi-color overprinting process, the final color of the product depends on the color presented after each color overprinting. When the printing machine does not register correctly, the different color blocks of two or more colors that should be stacked together will be staggered or stacked with other colors. At this time, the decor color seen by the human eyes will not be the color that should have appeared, so color shading occurs.
2) Squeegee Stability
The connect position, angle, and pressure of the squeegee and the printing plate cylinder will also have a greater impact on the ink color of the decorative paper, especially the ink color of the shallow parts, so the ideal state is that the squeegee is in the same position from beginning to end. However, due to various reasons, the squeegee cannot always maintain the same position during the printing process. The connect position of the squeegee and the printing plate cylinder determines the distance between the knife, the plate connects point, and the imprinting point. The longer the distance, the greater the degree of ink drying in the cell and the lower the ink transfer rate, which is equal to the ink color withdrawal and becomes light. On the contrary, when the distance is shorter, the ink transfer rate is higher, some fine lines on the layout will be transferred to the decorative paper. The angle of the squeegee is increased, it is easy to scrape the ink on the layout so that the graphics and text are clear, the ink layer is thinner, and the gloss of the ink film is reduced. When the angle of the squeegee decreases, the ink layer becomes thicker and the ink film has good gloss, but the edges and corners of the graphics and text are easy to blur. Therefore, the angle of the doctor blade, the pressure, and the contact position of the plate roller, all of them can be the reason to cause the color shading.
3) Printing Plate Stability
The printing plate will also affect the color difference. For example, the blockage caused by the solidification and high viscosity of the ink, or the insoluble foreign matter will reduce the amount of ink transfer, thereby affecting the hue. Secondly, when the volume of the printed product is large, the printing plate will wear and tear, so the ink volume will be reduced. This matter will cause the printing ink to become lighter. In addition, if the influence of printing and post-press processing technology is not fully considered when the printing plate is designed, it will also cause color shading. For example, the colors of some dot areas are prone to gradation and gradation, resulting in color differences.
3. Raw Material
The color difference, the ink absorption and the smoothness of the base paper, the color shift and the stability of the ink during the printing process will all affect the color difference of the printed decorative products.
Ink is one of the main factors that determine the color consistency of printed decorative papers. The ink itself has the problem of color difference in the same batch or between different batches. In addition, during the printing process, if the ink cannot be stirred sufficiently in the circulating ink tank, the viscosity and solid content will make the ink feeding unstable, then result in color difference.
The quality of the decorative base paper is also one of the main reasons for the color shading. For example:
1) The Color shading of the base paper itself
The base paper itself also has the problem of color difference. If the color shading of the plain paper is too large, no matter it becomes darker or lighter, it cannot be corrected by subsequent printing. Because decorative paper is multi-layer printing, most of the patterns cannot completely cover the plain base paper. Almost the color of all the decorative paper designs has the base paper color. Base paper color is an indispensable part to the color of the final decorative paper patterns.
2) The opacity of the base paper
The opacity of the paper affects the color difference of the final product. Opacity refers to that the graphics and text do not pass through the other side after printing. If the opacity of the solid base paper itself is not good, the opacity of the printed product will not be good. Because the decorative paper is finally used to press on the high-density or medium-density fiberboard, particleboard, plywood, HPL, etc., if the opacity is not good, the color of the substrate will show through after pressing, then make the color difference.
3) The Ink absorption of base paper
The ink absorption refers to the acceptability of the base paper to ink and the absorbency of the base paper to the printing ink link material. The ink absorption is affected by the free energy of the paper surface, the smoothness of printing, the ink absorption performance, and the curing form of the ink. The base paper with good ink absorption absorbs more ink during the printing, which makes the thickness of the ink layer thicker. On the contrary, it absorbs less ink, which makes the thickness of the ink layer thinner, resulting in color differences.
Therefore, the decorative paper factory should strengthen the control of suppliers and the inspection of incoming raw materials, try to ensure that the color difference of the base paper, the color shift of the ink is minimized, and the various physical and chemical performance indicators are as stable as possible, so as to avoid the color difference caused by the problem of the printing material itself.
The standardization of process technology, the accuracy of standard samples, and the standardization of control methods are also some of the reasons for the color difference. At present, there are still many decorative paper printing companies on the market that do not have a complete process technology management system and have not regulated the relevant process parameters in the printing process. For example, the printing speed, drying temperature, squeegee pressure, squeegee position, printing pressure, ink formula, etc. are not regulated.
How to control the color difference of decorative printed paper?
After knowing the main reasons for color shading, it is relatively easier to take measures to control the color difference. However, even though we know the reasons, we cannot take measures because the measures are not feasible or don’t have economic significance. Below we will talk about some feasible and economically meaningful measures that can be taken against the color difference.
1. Method to the problem caused by personnel
For personnel issues, if one wants to effectively control the color difference, the factory needs to strengthen the training to the personnel of some key positions and carry out long-term training. At the same time, the factory needs to use a lot of practice to improve the skills of relevant personnel. In particular, the skills of color matching operators (colorists) and printing operators (start-up workers) should be trained. At the same time, the sample management personnel and raw material inspection personnel must be strictly required to avoid color differences due to their slack work.
2. Method to the problem caused by Equipment
1) Using medium and high-end decorative paper printing line. At present, both China and foreign medium and high-end printing presses are equipped with automatic overprinting systems, which can effectively solve the problem of inaccurate overprinting and ensure the accuracy of overprinting.
2) Properly adjust the production speed and adjust it to a suitable speed. The specific speed needs to be determined according to different printing machines and let the operator find an exact number through production practices.
3) Well-controlled the base paper to ensure that the vertical and horizontal expansion rate of the base paper is stable. The instability of the vertical and horizontal expansion rate of the base paper is the main cause of inaccurate overprinting.
4) Well control the squeegee to keep the angle and pressure of the contact position stable. The printing paper factory can record the contact position, angle and pressure of the squeegee for each product during sample production. And when it is produced each time, transfer the squeegee to the same position. What’s more, pay attention to the wear of the scraper blade and replace it in time.
5) When the production is completed, clean the printing plate with solvent or special cleaning agent, then pack it for storage, and check again before use, which can effectively prevent plate blocking. What’s more, regularly repair the printing plate or repair after a fixed output is one of the effective methods to prevent the color difference caused by the abrasion of the printing plate. If the color shading is caused by the problem of plate design, then the best way is to re-design the printing plate.
3. Method to the problem caused by Raw Material
1) Implement the incoming color inspection and physical and chemical index inspection of the printing ink to ensure the consistency and stability of the incoming ink color. Physical and chemical indicators refer to the inspection of ink viscosity, PH value, and solid content, etc. Physical and chemical indicators will eventually affect the stability of the ink. To maintain the stability of the ink, it must be measured
2) In the production process, use the method of stirring and circulation to maintain the uniformity of the ink. The factory can control the number of print inks each time to ensure that the ink does not change due to long-term use. The decor printing companies can also control ink stability through physical and chemical analysis of online inks.
3) Well control the use of remaining ink. The remaining ink is a resource that has to be used. If it is not used, except for increasing the cost, it will not be allowed from the perspective of environmental protection. However, when using the old pulp, it is better to observe the principle of” first-in, first-out”. New remaining ink must not be added to the unused bucket blindly.
4) Strengthen the control when raw base paper enters the factory. Pay attention to whether the color difference and various physical and chemical indicators reach the standard.
5) Match color for each base paper roll individually. This requires color matching personnel to have high skills and be able to adjust colors in the production process
6) Classify to use the base decor paper, such as use it alone for base paper with a color difference or with similar smoothness and air permeability.
4. Method to the problem caused by Technology
Generally speaking, there is no one-size-fits-all method to ensure that every company can effectively control the color difference of the product. Therefore, the technical problem must be addressed to specific enterprises. However, the principles adopted are nothing more than the following points:
1) Establish a complete technical management system, such as stipulating the most basic process parameters, process technical standards, and management methods, and stipulating who has the right to change these data, when to change, which steps to change, and what is the principle of change, etc.
2) Lay down a management plan for the standard sample paper and archive materials. Because the color difference of decorative paper is a special product index that cannot be digitized at present, it can only be determined by the standard sample, then the management of this standard sample should not make mistakes, and it should be kept well. In addition, some samples or sample paper from customers are also production standards and should be managed well.
3) Train an enterprise’s executive power to ensure that all regulations can be effectively implemented.
All in all, in the actual printing production process, there are many reasons that can cause the color difference of decorative paper, but no matter how the cause changes, we only need to control the main factors such as people, machines, raw materials, and technology. We believe that we will be able to produce high-quality products if we pay much attention to these factors. As a professional manufacturer of decorative paper, VIIKAN DECOR has always attached great importance to the control of color shading. Our production engineers are all with more than ten years of decor paper printing experience. The equipment we use is modern high-end automatic overprinting equipment. The raw materials are strictly controlled from entering the factory to the final production. The process technology is implemented according to strict standards. If you are very concerned about the color difference and want to find a reliable decorative paper supplier, please contact us as soon as possible.