The definition and composition of high gloss offset printing ink

The glossiness of the printed matter is the essence of the printed matter, and it is also an important aspect to measure the appearance quality of the printed matter. It not only increases the vividness of the printed matter's color, makes the screen bright and has a sense of texture, but also improves the aesthetic appearance of the printed matter and enhances the dimensionality of the printed matter. .

In the case of limited ink conditions, the use of post-press processing methods to improve the print gloss, such as laminating, plastic coating, printing varnish, etc., but this is only limited to improve the gloss of the cover, and increased printing costs . To fully improve the luster and color of printed matter, it is necessary to improve the gloss of the printed material itself. Increasing the gloss of ink has become an important part of ink production.

High-gloss ink is a high-gloss ink that can increase the brightness of prints. Its gloss is higher than that of ordinary offset inks, and its saturation is also high. The pictures printed with high-gloss inks are exquisite, rich in texture, and good in texture, and they overcome the feeling of floating colors in prints.

I have done some targeted experiments on high-gloss inks. I hope that through the analysis of the basic composition and printability of inks, I can put forward some meaningful suggestions and references for the application of high-gloss inks in practice.

First, the definition of high light offset ink

The glossiness of offset printing ink refers to the ability of the ink on the surface of the printed matter to be concentrated and reflected in the same direction after being dried by the oxidized conjunctiva. It reflects the brightness of the ink after drying on the surface of the substrate.

So what is a high gloss ink? In "National Standard of the People's Republic of China - Ink Terminology" it is defined that "high gloss offset ink" is a "high gloss offset ink". "People's Republic of Industry Standards - Offset Bright Ink" stipulates that Offset Bright Ink is a colloidal body made of synthetic resin, dry vegetable oil, high-boiling-point paraffin oil, high-quality pigments, and auxiliary agents. The glossiness index of offset four-color bright ink is shown in Table 1.

High-gloss inks also belong to the category of offset inks, but their gloss is higher than that of glossy inks. According to experimental data, the gloss of high-gloss inks should be above 60%, and the gloss on substrates should be above 35%.

The high-gloss ink AGH produced by DIC ink company (hereinafter referred to as "DIC high light") and the famous German brand BASF high-gloss ink (hereinafter referred to as "BASF") are excellent high-gloss offset printing inks. The ordinary light fast-drying ink (hereinafter referred to as "DIC") produced by the company is also a high-grade offset ink in ordinary light fast-drying inks, and has a very good reputation in the printing industry. This article intends to conduct a superficial comparison and analysis of the above products to discuss the practical application of high brightness ink.

The data mentioned in this article were all tested and tested at 25°C and 60% humidity.

Second, the composition of high light offset ink

High-gloss offset inks, like general offset inks, are also composed of binders, pigments, fillers and additives.

1. Binder

The binder is an adhesive fluid. Its role is to mix powdery pigments and other substances together, so that after grinding and dispersing, they form a pastelike glue with a certain degree of fluidity. The binder is a fluid component in the ink.

The quality of the binder material directly affects the performance of the ink. Because the pigment is generally a solid powder, and the binder is a liquid with a certain viscosity, the pigment relies on its wetting and adhesion to complete transfer in the printing press. In printed matter, the binder also plays a role of protecting the ink film and exhibits the necessary gloss.

The binder material largely determines the viscosity, viscosity, drying and flow properties of the ink. To obtain high quality inks, high quality binders must be used. If the linking material is improperly prepared or there is a problem in the production process, not only will colorful and glossy prints not be obtained, but it will also result in a series of printing without inking, stencil stencils, scratching, squeegeeing, squeegeeing, and drying. Failure, even make the printing can not proceed smoothly. Therefore, the binder is a critical component of the ink.

High-gloss inks require fast drying speed, good film-forming properties on the substrate, and the ink film has an ideal mirror reflection effect and high gloss. Since the gloss of the ink is mainly determined by the binder, the binder of the high-gloss ink is particularly important. It directly affects the gloss of the high-gloss ink. The high brightness ink binder consists of the following components.

1) Resin

Resin is a type of amorphous material. In general, resins are all organic compounds with relatively large molecular masses and complex structures. Its form is both hard and brittle solids and viscous liquids. Different solid resins can be dissolved in different organic solvents and oils and dissolved into resin solutions. As the solvent evaporates from the resin solution, the concentration of the resin solution gradually increases, the solution becomes more and more viscous, and eventually the resin molecules are tightly bound together to form a solidified gel that can form a transparent thin film layer, which is also the ink Reasons for film formation on prints.

As a high gloss ink resin, in addition to the need to be able to make the offset ink meet the printability of the printing process, such as rheology and other requirements, it must also have good mutual solubility with the oil, solvent or other resin in the link material. It should also enable the prints to have a high gloss, and have a strong adhesion and a certain hardness on the surface of the substrate, as well as a good film forming performance.

Resins can be divided into natural resins and synthetic resins. Due to various problems with natural resins, the quality stability of the ink is affected, and therefore, natural resins are replaced soon after the appearance of the synthetic resin.

Synthetic resin is usually a polymer compound synthesized by a chemical plant or a laboratory without molding, such as polyethylene resin, polyvinyl chloride resin, polypropylene resin, polyacrylate resin, phenolic resin, polyester resin, polyamide resin and many more.

Synthetic resins differ from natural resins and their simple processing products. There are two main differences: one is that the synthetic resin molecules are obtained through complex artificial synthesis; the other is that the molecular weight of the synthetic resin is very large, and can even be as large as tens or even several million. Although their molecular weight is large, the composition is not complicated. They are macromolecules formed by the chemical polymerization of millions of small molecules of the same species or different species. Therefore, polymer compounds are also called polymers or polymers.

Synthetic resins and common polymer compounds commonly used in the ink industry are also different. Since the ink industry is developed on the basis of vegetable oil as the linking material, the synthetic resins used must firstly consider their oil-solubility. Therefore, rosin-modified phenolic resins, vegetable oil-modified alkyd resins and the like are often used.

Phenolic resin is a product of condensation of phenol and aldehyde under the action of a catalyst. Due to the different raw materials, catalysts, and reaction conditions used, a variety of resins with different properties can be obtained. The main used in ink is modified phenolic resin. These resins have good oil solubility. The ink formulated with rosin-processed resin has the advantages of fast fixation, high gloss, and strong water resistance. Modified phenolic resins used in inks include rosin modified diphenol propane resin, rosin modified p-tert-butyl phenol resin, and rosin modified other alkyl phenol resin.

The resin used in the high gloss ink is mainly a rosin modified phenolic resin, and its production process is relatively complicated. The refining temperature is different, ie, the range of temperature increase and temperature drop is different, and the measures adopted in the middle are different. The structure of the obtained resin is different. The molecular weight is different and thus directly affects the gloss, drying properties, water resistance, viscosity, rheological properties and printing properties of the ink. In this regard, it is precisely the key technology for the manufacture of high-gloss ink binders. (to be continued)