Brief Analysis of Low Gloss Coated Paper (2)

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Low gloss coated paper manufacturing features

At present, low gloss coated papers mainly have the following production methods.

Fine (or ultrafine) pigments are not calendered or light calendered to form a microscopically smooth, macroscopically rough coating surface; coarse pigmented calendering methods produce microscopically rough, macroscopically smooth coating surfaces; thick and thin pigments The method and adhesive wrinkling method can form a smooth and rough surface coating effect.

1. Manufacturing process

(1) Fine (or ultra-fine) pigments are not calendered or light calendered

Using fine or ultra-fine pigment particles without pressure or light calendering technology, pigment particles are scattered on the surface of the coating, poor orderliness, the ability to scatter light is greatly improved, the paper gloss is significantly reduced, can be achieved without light or Glossy paper requires gloss. And because the coating uses fine or ultra-fine pigment particles, the printing friction is small (refers to the degree of abrasion of the printing paper or ink to the printing plate in the printing process), the ink film can evenly cover the rough surface of the coating after printing, and the ink filming property, The gloss of the film has little effect, the printing gloss is high, and the printing quality is better.

However, the surface of a rough coating obtained by using fine or ultra-fine pigment non-pressing or light calendering technology can rapidly increase the gloss of the paper after calendering, and the matt or matte paper produced by this method can easily produce a scratch. Traces, especially occasional local force or wrinkles in product handling and packaging, can cause uneven gloss on the paper surface, affecting print quality.

(2) Crude pigment calendering

The coating obtained by the crude pigment calendering method can be formed into a macroscopically smooth and microscopically rough surface after calendering. The use of large particle size pigments breaks the orderliness of particle arrangement on the coating surface after calendering, and can also obtain relatively low. Paper gloss, and will not scratch due to local force. However, the roughness of the pigment itself will cause problems such as reduced print gloss and increased printing friction, which reduces print quality and printability.

2. Manufacturing requirements and methods for low gloss coated paper

(1) The relationship between surface gloss of paper and each index

Through experiments, it can be seen that the paper roughness, glossiness, printing gloss and printing friction are interrelated and contradictory. The PPS value is an important indicator of the roughness of the paper. As the gloss of the paper increases, the PPS value (roughness) decreases rapidly and the coating surface gradually becomes smooth. The print gloss rises with the gloss of the paper and the smoothness of the paper, and the printing friction decreases accordingly.

(2) Method for producing low-gloss coated paper

Low gloss coated paper production must achieve a certain balance of roughness, paper gloss, print gloss, and print friction. In order to solve the drawbacks of the first two manufacturing methods and improve the quality of low-gloss coated paper, a method of matching coarse and fine pigments is now used, and it is hoped that a suitable coating structure can be produced through the combination of coarse and fine pigment particles. Need to use fine (ultrafine) pigments to make the paper have a high printing gloss and low printing friction, but also need to use coarse pigment particles to make the coating has a certain degree of rigidity, after calendering will not improve the paper and the appropriate degree of gloss Scratches can be avoided. Figure 2 shows the structure of this coating.

As shown in Figure 2, a rigid coating of large particle size, bulk pigment particles reduces both paper gloss and calendering, and fine (ultra-fine) pigment particles fill the middle of these coarse particles. During the process, the presence of coarse particles protects the fine particles from excessive calendering and causes the gloss to rise rapidly. This not only reduces the macroscopic roughness but does not produce excessive microscopic smoothness, it also avoids the occurrence of scratches and is therefore widely used.


However, this kind of pigment matching system imposes severe requirements on the ratio of the two components of the coarse and fine pigments, and it is very easy to adversely affect the quality of the low-gloss coated paper. Especially in the current situation where the pigment production quality is unstable and the particle size distribution is not easily controlled, this effect is even more pronounced. Excessive coarse particles, the pores between the coarse particles can not be fully filled with fine particles, resulting in increased paper printing friction and printing gloss decreased; coarse particles will cause the fine particles to be pressed and cause the paper gloss is too high.

In recent years, a new method for producing a low-gloss coated paper has been proposed, and it is proposed to first apply a primer to the surface of the base paper so as to obtain a primer surface having a relatively smooth and certain porosity, and then use a specific paint for micro-coating, and The surface roughness of the coating is controlled below 1 μm. This roughness allows the 75° gloss of the paper to be kept within 30% to obtain a very high print gloss and excellent print quality. However, in order to obtain such a coating surface, and the surface coating roughness is controlled below 1 μm, there are certain difficulties in the implementation, and it is still in the research stage. In addition, a special adhesive for matt coated paper has also been synthesized abroad, and the wrinkling reaction of the adhesive in the drying process achieves the purpose of extinction.

In foreign countries, low gloss coated paper has become a very important product in the coated paper market. In order to further improve the quality of low-gloss coated papers, new production methods are still being explored to develop special pigments and adhesives. Relatively speaking, there are few manufacturers engaged in the research and production of low-gloss coated papers, and the prices are relatively high. However, with the continuous growth of China's low-gloss coated paper market, there should be a lot of room for development.


Changsha University of Science and Technology Liu Yanxin

Tianjin University of Science and Technology Wang Yuxi

Source: Printing Technology

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