Analysis of Influencing Factors on Printing Quality of Whiteboard (I)

Abstract : With the continuous growth of China's economy, China's packaging carton, carton industry has been rapid development, packaging whiteboard paper gradually replace yellow paper, from monochrome printing to white color development, the more the carton carton packaging The higher the printing requirements, the paper discusses the factors affecting the printing quality of whiteboard.

Keywords: white cardboard; print quality; printability

White paperboard is divided into double-sided white paperboard and single-side white paperboard. Double-sided white paperboard is mainly used for packing high-end goods. In general, the paperboard carton is mostly made of single-side white paperboard, such as packaging boxes for cigarettes, cosmetics, medicines, food, stationery and other goods. Packing box.

With the rapid development of China's economy, the demand for packaging cartons and cartons is increasing in the society, and the requirements for printing quality are also getting higher and higher. The printing development trend is reflected in three aspects: First, cartons are gradually packed into packages for transportation. Development, packaging carton printing text pattern requirements clear, beautiful, bright, multi-color, dot, three-dimensional sense of strong; Second, the packaging carton carton printing will gradually develop from monochrome, two-color to three-color, six-color and other multi-color printing, requirements Accurate dyeing, dot network from the current 150 lines / cm to 200 lines / cm, while the packaging and printing machinery precision requirements are quite high; Third, the gradual replacement of yellow cardboard packaging white paper, development of white color printing, water-based ink alternative Solvent-based ink, so that the carton carton printing surface beautiful and clear, bright, high-tech printing, increase the added value of goods, and meet environmental requirements. Whiteboard printing often uses lithographic offset printing and flexographic printing. Exquisite high-end carton cartons are required to be offset-printed. General carton cartons are mostly made of flexographic printing. Their quality requirements should meet the industry standards for related printing methods. This article discusses the main factors that affect the printing quality of whiteboard paper.

1 Cardboard Brightness

The whiteness of paperboard refers to the degree of whiteness of the paperboard, which is the total reflection of visible light uniformly diffused in all wavelength ranges. The factors affecting the whiteness are mainly the lignin content and the degree of bleaching in the pulp. Since the lignin has a chromophoric group, it is necessary to minimize the lignin content in the paper in order to obtain a high brightness paper. The whiteness of the white paperboard has a greater influence on the color rendering range of the final print. The higher the whiteness of the paper, the more the true color of the ink can be reproduced. The more vivid the color of the printed matter is, the wider the color gamut is. Assume now that a solid red color is printed on white paperboard, first printed in yellow and then in magenta, as shown in Figure 1 below. The solid red (R) is formed by laminating a yellow (Y) ink layer and a magenta (M) ink printed on white cardboard. The white light (w) first absorbs green light in the white light through the upper magenta ink layer. The light (G) is then irradiated to the yellow ink layer to absorb red light and blue light (B) in the blue light, so that only red light is irradiated on the white paper, reflected by the white paper, then transmitted through the Y and M ink layers, and filtered again. Blu-ray and green light are removed to make red more pure, but if the whiteness of the white paper is not high, the amount of red light reflected on it is less, and finally less red light is emitted, so that the color saturation of red is reduced. . In packaging carton printing, color is a very important quality indicator, and customers are also more sensitive to it.

In addition, the printed image is generally printed in the brightly adjusted region of 3% to 5% and in the darkened region of 95% or more, that is, the highlight portion of the print is formed by the color of the paper. If the whiteness of the white paperboard is different, it will affect the brightness and saturation of the colors on the screen, thereby affecting the color contrast of the screen.

2 Gloss of white cardboard

Gloss is the degree of closeness of the cardboard surface to the ability to reflect incident light with full specular reflectance, expressed as the ratio of the specular reflectance of the cardboard at a certain angle to the specular reflectance of the standard black glass at the same angle. When paper gloss is high, the color of its prints becomes more vivid.
A very obvious feature of box printing is the vivid and full color of the printing. To make the printing colorful, the glossiness of the cardboard is an indicator that must be considered. The higher the paperboard light penetration, the stronger the reflection ability to the light and the brighter the color.

3 Smoothness of cardboard surface

The so-called smoothness refers to the time in seconds required for a certain volume of air to pass through the gap between the surface of the sample and the glass surface under a certain pressure and a certain area under a certain degree of vacuum. The smoothness of the paperboard surface has a direct effect on printing, and paperboards with high smoothness are easily covered by the ink film when printing. The higher the smoothness of the paper, can be used for more precise printing screens to produce higher quality prints. On the other hand, printing on the surface of cardboard with low smoothness must increase the pressure of printing in order to ensure the transfer of the ink layer, which leads to the expansion of printing dots and the loss of the subtle levels of the graphic and text; The number of network cables is getting higher and higher, from the original 150 lines/cm gradually to 200 lines/cm, and the requirements for the reproduction of network points are getting higher and higher.

In printing, we first require that the smoothness of the whiteboard paper used is uniform, and that the expanded printing dots are within the permissible range. Lithographic offset general products, yellow ink (Y), magenta ink (M), and blue ink (C), Black ink (BK) 50% outlet expansion value controlled at 10% to 25%, fine product Y, M control at 8% to 20%, C control at 10% to 20%, BK control at 10% to 25%, flexible 70% printing of dot printing Paper Science & Technology 2005 Vo1.24 No. The value of 3 is less than 21%. Followed by high-smooth cardboard.

(to be continued)