A Brief Analysis of Low Gloss Coated Paper (I)

Low-gloss coated paper has a lower gloss and can obtain higher print gloss and print quality. It is used for graphic printing and the product is easier to read, and therefore it is increasingly favored by readers. In particular, matt coated paper and low-weight coated paper (LWC for short) have been widely used in printing advanced magazines, book inserts, catalogs, advertisements, and high-end art due to their excellent printability, operability, and exquisite appearance characteristics. Products and other aspects. In Europe, low glossy coated papers account for about 60% of the coated paper market, and U.S. matte coated papers account for 2% of coated papers, and this trend continues to grow and has become coated paper. An important part of the market.

At present, there is no strict definition for low-gloss coated paper. In Europe and North America, according to the 75 degree gloss classification, the coated paper with a glossiness of less than 4D% is referred to as the “Shenzhen” glossy coated paper, which is divided into matt coating. Paper and matte coated paper, see Table 1. It can be seen that the most important criterion for measuring low gloss coated paper is mainly glossiness. This article mainly introduces the principle of light extinction, coating structure, production method and its development status at home and abroad for low gloss coated paper.

The principle of extinction of coated paper

Although high-gloss coated paper or low-quantity coated paper can obtain high printing t quality and print quality, its high gloss will produce a strong glare effect, which will affect reading easily. Therefore, the current graphic combined with printed publications, page toward the use of low-gloss paper. However, some low-gloss papers (such as non-energized, etc.) have a lower gloss, but the rough surface will reduce the printing quality, and the prints will be dull.

The most important feature of low-gloss coated paper reflected in the quality of printed matter is the difference between paper glossiness and printing glossiness. The lower paper gloss does not produce strong glare and interferes with people's perception of printed gloss. This effect is determined by the surface structure of the low-gloss coated paper.

Glossiness as a property of the paper surface depends on the mirror reflection ability of the paper surface. Theoretically, the glossiness is defined as the degree of closeness between the paper mirror-reflected light and the completely mirror-reflected light. For example, the cast paper is very smooth and almost mirror-like. On the other hand, the "non-glossy surface" has reflections at any angle, such as frosted glass. Therefore, in order to obtain a perfect matte or matt coated paper, the surface of the paper should have a light scattering coefficient that is as high as possible to achieve the lowest possible paper gloss.

Low gloss coated paper is not only low gloss, it must also meet the requirements of high print gloss and print quality after printing. The quality of printed matter is mainly reflected in the optical properties of the ink film, that is, the state, quality and sensory effect of the film after the ink is dried and filmed. Such as film gloss (print gloss), film transparency and film color characteristics. The fundamental factor that determines the optical properties of the ink film is the ability of the ink film to reflect, scatter, and absorb light that is incident on its surface. Among them, the mirror reflection ability of the ink film is an important indicator reflecting the gloss of the film (printing gloss).

Paper gloss depends on the surface roughness, the rougher the paper surface, the stronger the light scattering, the lower the gloss. Printing gloss depends on the paper surface roughness and porosity (paper surface pore size distribution), because the paper roughness can be mapped to the ink film surface, if the paper surface roughness is greater than or equal to the ink film thickness, will cause ink density Uneven; and porosity can restrict the amount of ink in the coating surface fixation and fixation rate, a direct impact on the print gloss and print quality.

In order to meet the printing quality requirements, for low-gloss coated paper, it is required that the surface of the paper has a certain degree of roughness, has a high scattering capacity, so that the paper surface has a lower gloss; at the same time, the roughness is not required after printing. And porosity is too large to damage the film gloss and print quality. Obviously, this is a contradiction. It is difficult to obtain high gloss and good printing quality under low paper gloss. Therefore, the production of matte coated paper and matte coated paper is to be Solve this conflict and bring it to a balance.

Structure of coated surface

There are two kinds of roughness on the coated paper surface that affect paper gloss and print gloss—macro roughness and micro roughness.

The fiber arrangement and uniformity of the base paper determine the macroscopic roughness, while the view roughness mainly depends on the shape, size, orientation and adhesive distribution of the pigment particles on the coating surface. True matte or matt paper must have both macro-roughness and micro-roughness. Figure 1 shows the relationship between paper gloss and paper surface smoothness.

Low-gloss coated paper is one of the pigment-coated printing papers and also has the coating structure characteristics of FIG. 1 , and the low-gloss coated papers produced using different production methods have different coating structures.