Talking about the Development and Characteristics of UV Curable Ink

In 1969, for the first time in the United States, UV curing inks were used for cardboard (carton) printing, and the practical first step was achieved. Japan began applying it to metal printing and label printing two years later in 1971. Since then, UV curable inks have been quickly cured, solvent-free, and dust-free. The advantages of UV inks at the printing site (improvement of the operating environment, short delivery time, inventory reduction, space saving, etc.) have been recognized and they are used rapidly. expand.

1, LED ink development

In 1969, for the first time in the United States, UV curing inks were used for cardboard (carton) printing, and the practical first step was achieved. Japan began applying it to metal printing and label printing two years later in 1971. Since then, UV curable inks have been quickly cured, solvent-free, and dust-free. The advantages of UV inks at the printing site (improvement of the operating environment, short delivery time, inventory reduction, space saving, etc.) have been recognized and they are used rapidly. expand.

However, in the past, ultraviolet light sources used in the printing industry generally used light sources such as high-pressure mercury lamps and metal halide lamps. Due to the enlargement of lamps and power supply devices, users were worried that the power consumption and heat generation caused damage to the printing presses and substrates. Problems such as ozone generation during use. However, in recent years, a light emitting diode (LED) capable of emitting ultraviolet light has been developed, and a special offset ink (FDLED series) that is instantaneously cured under LED ultraviolet light is used by Toyo Ink Manufacturing Co., Ltd. of Japan.

This article compares the difference between the traditional lamp-type light source and the LED light source from the environment of the UV-curable ink, and introduces the principle and characteristics of the LED-curable ink.

2. Environmental harmonization of UV ink

1) Non-VOCS ink

The so-called VOCS "Volatile Organic Compounds", which is the generic name of volatile organic compounds. VOCS, which is diffused in the atmosphere, has a stronger greenhouse effect than carbon dioxide, which is the material of global warming listed in the article. In addition, VOCS can react in sunlight to become an oxidant (caused by the photochemical smoke screen). Therefore, the world’s nations, led by developed countries, have established strict regulations on their emissions worldwide.

Typical offset inks are classified as heat-fixing rubber roller inks and sheet-fed offset inks, both of which contain petroleum-based solvents. Drying process of sheet-fed offset printing ink: When the ink is transferred to the paper, the solvent separates from the paper to precipitate the resin component, and at the same time, the vegetable oil component in the ink undergoes an oxidative polymerization reaction with the oxygen in the air to form a hardened ink film. The drying process of the rubber wheel ink: after printing, the solvent in the ink is evaporated and the resin component is precipitated, thereby forming an ink film.

About VOCS emissions. Sheetfed offset inks have the advantage of no energy consumption when dry, but due to the need for a longer drying time, strictly speaking, in this drying process, the VOCS component in the ink is either left on the substrate or gradually Released to the atmosphere. Rotary offset inks are heated to evaporate and dry to release VOCS components. These VOCS gases pass through the drying oven and are then treated in the re-combustion chamber to decompose into water and carbon dioxide. Therefore, there is a countermeasure from the viewpoint of VOCS.

On the other hand, UV curable inks activate photopolymerization initiators by irradiating ultraviolet light, thereby promoting the combination of monomers and oligomers (low molecular components) contained in inks through chemical reactions to form a hardened ink film. Since there is no VOCS-generating solvent in the UV ink, of course, no VOCS will be discharged into the atmosphere, so it can be said that the UV ink is an environment-friendly ink system.

2) Earth ring warming

With regard to carbon dioxide, which has just been discussed, it is illustrated here again from the point of view of becoming one of the substances that cause the ring to warm. In the dry process of rubber wheel printing, carbon dioxide is generated due to the combustion of gaseous fuels. In particular, the cost of not discharging VOCS from the ink to the atmosphere is to use a device such as a recombustion chamber to burn volatile VOCS. When you lose, carbon dioxide will be produced.

Since the UV curable ink contains no solvent and does not need to be equipped with the hot air drying device as described above, the energy efficiency required for ink curing can be said to be more than five times that of the rubber wheel printing. Therefore, the total amount of carbon dioxide generated when using the UV ink is small. From the perspective of global warming, it can be said that it is also an environment-friendly system.

3) dusting

Sheet-fed offset printing In order to prevent the back from sticking, the corn powder is evenly sprayed on the printed sheet by dusting. As a result, the printer and the printed matter are contaminated, and the printing environment is also contaminated, causing annoyance to the operator on the spot. .

UV printing does not require dusting because it cures instantaneously. From the perspective of the operating environment, UV inks are a better ink system than sheet-fed offset inks.

As described above, the UV ink printing system has the advantages of energy saving, space saving, and short-time curing compared with a printing system using a conventional sheet-fed oil ink and a web-fed offset ink, and its use has rapidly expanded in recent years.