Analysis of the most popular printing ink gloss I

Analysis of printing ink gloss (I)

gloss and color are collectively referred to as color. Because color is more intuitive and has a direct impact on people's mental state, emotion and many other mental factors, people started to study color earlier. This research work has been basically mature and has been widely used in daily life. Gloss, like color, can also have a corresponding response to people's psychology, especially in the evaluation of print quality

the so-called gloss of a printed product refers to the brightness on the surface of a printed product under certain background and lighting conditions and the contrast relationship with the brightness distribution in all directions. Optical properties related to gloss mainly include surface reflected light and internal reflected light

1. The surface reflected light is composed of the surface reflected light and the surface diffuse light

positive and negative reflected light: the light that conforms to the reflection law is called positive and negative reflected light. The intensity of the positive and reflected light is mainly related to the state of the object's light receiving surface besides the reflectivity of the material. Generally speaking, the smoother the surface, the stronger the reflected light. The positive and negative reflected light is a special information in the reflected light of an object, which is of special significance to the study of gloss. In the past, the gloss research has protective devices such as over-current, over-voltage, overload, etc., which attach great importance to the forward and reflected light. For example, for the gloss measurement of general smooth surface objects, the mirror gloss directly related to the forward and reflected light is mostly used in the Japanese and American Industrial standards. The positive and reflected light is basically reflected on the surface of the object, so the object has little selective absorption of this part of light, and its spectral composition is basically the same as that of the original incident light

surface diffuse light: the actual mirror surface is not an ideal mirror surface, so the light will diffuse. At this time, it can be considered as the superposition of light intensity reflected by many small mirrors. When the brightness of the diffusion surface is a constant, it is called cosine diffuser

2. Internal reflected light: after the light is refracted into the object, it is reflected from the object and re enters the original medium. This part of light is called internal reflected light. The internal reflected light will be selectively absorbed by the substance, making its spectral composition change. If the incident light is white, the internal reflected light will change into colored light and show the fluctuation of the object, which means that the oil pressure inside the hydraulic servo testing machine (which can be used for power loading) may take a high-frequency wave action to control the color

whether the imprint is glossy or not is one of the quality signs of the printed matter. If it is glossy, the imprint color of the printed matter can increase the brightness; Enhance the stereoscopic sense of the image, especially the reproduction of physical photos, which has a luster and is more realistic. There are many factors affecting the gloss of imprinting, which can be summarized as follows

I. properties of paper

the structural state of paper has a decisive impact on the imprinting gloss, which is the most basic condition. The surface smoothness, gloss and ink absorption of paper will affect the gloss of printed products

1. The influence of paper surface smoothness on the gloss of printed matter. In order to make the printing products form specular reflection, bright colors and good gloss, smooth paper must be used for printing. The paper with rough surface is difficult to make the imprint glossy. Even if the flatness is good, the coating particles of the paper form pores, and the permeability of the binder is large, so high luminosity products are still not available. The surface smoothness of various papers is different, and the smoothness has a great impact on the gloss of finished products. The paper with high smoothness has good contact speed with ink, which can ensure the complete reproduction of points and make the finished product have better luster. Because the gloss of the ink film on the paper depends on whether the incident light can be specular reflected. Only the paper with high smoothness can produce specular reflection after the ink film is leveled. On the contrary, for the paper with poor smoothness and rough surface, the imprinted ink film will not be thick and uneven, which can only form diffuse reflection to light, and the finished product will have no luster. Therefore, for exquisite and high-grade products, in order to obtain better finished product luster, we must first select paper with high smoothness for printing

2. The effect of ink absorption on gloss of paper. The ink absorption of paper actually refers to the paper's absorption of ink binder. The paper's absorption is one of the main conditions that determine the penetration. If the nature of ink is certain, the paper's absorption is large, the ink layer pigments overlap thick, and the imprinting gloss will be reduced or even dull. The coarser the paper, the larger the fiber gap, and the stronger the absorption capacity of the binder. When the binder is not dry, most of it is absorbed by the fiber, and the rest of the binder and ink particles are attached to the surface of the paper, losing their due leveling performance and unable to form a smooth ink film, making the product dull. For coated paper (coated paper), there are two main reasons that affect the ink absorption: one is the variety and material of the tablets used in the coating. The lower the ratio of adhesive to pigment, the higher the absorption of paper to ink. If the coating concentration is low, the adhesive and water in the coating are easy to penetrate into the thick paper, reducing the amount of adhesive in the coating, thereby increasing the absorption of ink. Second, the pigment variety and particle fineness in the paint are also related to ink absorption. The finer the pigment particles, the harder it is to transfer the glue in the coating to the paper base. The pigment particles are coarse and the particle gap is large, so it is difficult to obtain the desired gloss effect for the finished product due to the business improvement of ink absorption

3. The influence of paper gloss on the gloss of printed matter. The gloss of the paper itself plays a considerable role in the gloss of the finished product. The gloss of coated paper mainly depends on the brightening materials used in papermaking and the processing accuracy of the paper. Brightening materials include aluminum stearate, paraffin wax, insect wax, etc. the finishing method is super calendering. The paper processed by the above method has a smooth plane, and has the property of specular reflection (unidirectional reflection) of light. If the ink with high transparency is printed, the gloss effect of the finished product will be better

4. The influence of paper strength on the gloss of printed matter. The paper strength is low, and the phenomenon of powder and hair loss is serious. When printing, the binding force between the ink and the paper is not high, and the gloss of the printed product is low or even dull

5. The influence of pH of paper on the gloss of printed matter. The pH of paper affects the drying speed of ink film, and the drying speed of ink film affects the gloss of printed matter. Alkaline paper can speed up the drying of ink film, thus relatively reducing the penetration time and the penetration of binder, so the printing gloss is better; Acid paper followed