The solvent-based ink refers to an ink system formed by dispersing a pigment or a dye in a carrier using an organic solvent or a solvent-based polymer film-forming agent as a carrier. Solvent-based inks have a huge market for large-format and wide-format applications due to their long-lasting print image quality and low raw material cost. Although solvent evaporation is likely to cause environmental pollution, its development in the European and American markets has been limited, but in the Chinese ink market, solvent-based inks are still booming. In response to environmental pollution problems, a new type of ink, ECO-solvent ink, has begun to develop rapidly. This kind of ink with less environmental pollution will be the development direction of solvent-based inks in the future. This paper will discuss its current situation and development trend from the aspects of market positioning, composition characteristics and emerging products of solvent-based inks.
Market positioning of solvent-based inks
Based on printing speed, solvent-based inks are mainly used for classic wide-format printing and industrial wide-format printing for medium-speed printing. Water-based inks are mainly used in homes and offices where printing speed is not high. High-speed inkjet printing The market is firmly occupied by UV ink.
In general, solvent-based inks are popular in the field of outdoor advertising printing. Compared with water-based inks, solvent-based inks have the characteristics of bright color, good color reproduction, less lateral diffusion on the substrate, and fast drying speed. Therefore, special treatments for the printing materials are not required, such as paper and plastic film. Direct printing on uncoated materials such as self-adhesive films and mesh fabrics. If the solvent-based ink is made of high-quality pigment, it will have good UV resistance without the use of a film, and the volatility of the ink can make the ink film after drying thinner. Solvent-based inks can be adapted to a wide range of substrates, and printed images have better durability and are less expensive than aqueous inks. As a result, solvent-based inkjet printers have opened up billboards, body advertising and many areas where traditional printing was not possible.
The disadvantage of solvent-based inks is that during the drying process, harmful substances are emitted into the air by the volatilization of the solvent, which affects the indoor and outdoor air quality. Therefore, it is necessary to pay attention to some problems such as routine maintenance of the nozzle and solvent evaporation, and it must be used in a well-ventilated environment. These shortcomings have limited the growth trend in the ink market in the US and Europe. Only by strengthening the use of non-hazardous substances or environmentally friendly solvents can the application of solvent-based inks grow even more. In fact, high-quality UV inks are becoming competitors for solvent-based inks due to technological advances and rigorous R&D testing. UV inks outperform solvent-based inks in terms of drying speed, substrate suitability, and application range. At the same time, UV inks do not contain volatile organic compounds (VOCs) and have very good environmental benefits. Therefore, UV inks are likely to become the main ink for industrial inkjet printing in the future.
Although solvent-based inks have been challenged by UV inks in some areas, their inherent advantages have increased their share of the domestic market for a longer period of time. At present, related ink manufacturers are also improving their ink formulations, introducing environmentally friendly solvent-based inks that are free of harmful substances and environmentally friendly solvent-based inkjet printers. The new generation of solvent-based inks will be more perfect and the environment will be harmed. It will get smaller and smaller.
Solvent-based ink composition and characteristics
Inkjet inks are distinguished by ink base and can be classified into aqueous inks, solvent inks, and UV inks. The solvent-based ink uses a water-insoluble solvent as a main component of the dissolved colorant, and the colorant herein may be either a pigment or a dye. Solvent-based inks are typically composed of components such as colorants, solvents, surfactants, humectants, pH adjusters, driers, metal ion chelators, preservatives, and other additives. The following is a brief introduction to the main components of the ink, colorants and solvents.
Colorant
Colorants commonly used in the preparation of inkjet inks are of the two types of dyes (Dye) and pigments (Pigment). The amount of the colorant generally ranges from 0.5% to 10% of the total amount of the ink, and a suitable range is from 0.5% to 5%. Both dyes and pigments can be nonionic, cationic, anionic or a mixture thereof.
From a chemical point of view, the dye exists in the state of a single molecule in the ink, and the pigment is composed of a floc composed of a myriad of pigment molecules. The use of dyes as colorants has the advantages of convenient preparation, low cost, bright color, complete chromatogram and difficulty in clogging nozzles. Dye inks have better color performance or color gamut than pigment inks. When printing on better quality substrates, dye inks can achieve the same quality as silver salt photos. However, dye inks have poor stability, especially poor light resistance, dark storage stability, moisture resistance and water resistance, because the chemical properties of individual dye molecules are not high under light, moisture and oxidation conditions. Stable, it is easy to chemical reaction, causing the print to fade. In addition, dye inks are also very picky on print media and often require specialized media support. When printing on ordinary copy paper, since the copy paper is composed of paper fibers which are criss-crossed, it is filled with a gelatinous substance, and the hydrophilic factor in the general dye ink accounts for a large proportion, due to these hydrophilic factors. The role of the dye ink is easy to penetrate along the paper fiber, resulting in blooming on ordinary copy paper, seriously affecting the final printing effect.
Pigment inks have been developed for the above disadvantages of dye inks. Unlike dyes, pigments in pigment inks are present in a state of flocculation where numerous pigment molecules are aggregated, so their environmental impact is better. The pigment is used as a coloring agent, and the ink is excellent in light resistance, water resistance, heat resistance, and oxidation resistance, and is not easily affected by the weather. However, pigment inks have poor liquid stability, and in long-term storage, the dispersibility of the pigment may cause nozzle clogging.
According to the above advantages and disadvantages, it can be seen that the dye ink has strong performance, bright and uniform color, high brightness level and easy to express color tone, so it is especially suitable for indoor printing; and pigment ink stability and durability are good. Suitable for outdoor printing. At present, solvent-based inks mostly use pigments as colorants, which are determined by the characteristics of the pigments and the market positioning of the solvent-based inks, and less solvent-based inks using dyes as colorants.
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