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UV Ink Usage Points And Applications Waterless Printing UV Ink Usage Points And Innovative Applications
- May 28, 2018 -

Waterless offset UV inks are a type of UV-curable offset inks. In addition to the characteristics that UV inks do not emit VOCs during use, no fountain solution is needed during the printing process, and large amounts of volatile isopropanol can be avoided. In line with the requirements of the green trend of the printing industry in the future, it is worth promoting. The author engaged in UV ink research and development and application for many years, in this case, to give an introduction, on the use of waterless offset UV ink points and waterless offset printing technology in recent years, the latest market applications are briefly described.

The use of waterless offset UV ink points

1. Ink itself

The formula of the waterless offset UV ink is basically the same as that of a traditional water-based offset UV ink, and consists of a resin or a binder, an initiator, an additive, a filler, a pigment, and the like. Since HJ 2542-2016 “Technical Requirements for Offset Printing of Technical Labels for Environmental Labeling Products” was formally implemented on January 1, 2017, ink manufacturers are required to conform their respective waterless offset UV inks to this standard and must strictly control the ink formulation. To ensure the green environmental protection requirements for waterless offset UV inks.

Since waterless offset UV inks do not require the use of fountain solution during the printing process, they all rely on their own cohesion to achieve the purpose of anti-dirt in the ink transfer process, which requires that it has a better than traditional approach on the basis of maintaining good fluidity. There is a higher viscoelasticity of a water-based offset UV ink to ensure that the ink layer can be completely peeled off from the plate.

In addition, although the waterless offset UV ink at room temperature is more viscous and harder than the traditional water-based offset UV ink, it is still convenient to use when the machine is under proper temperature control. It is hoped that the press operator will not misunderstand. .

2. Waterless offset CTP plate and plate making process

The waterless offset CTP plate is composed of an aluminum base layer, a primer layer, a photosensitive layer, a silicone layer, and a surface film layer. Silica gel is used instead of a fountain solution to utilize its low surface energy to repel ink. At present, waterless offset CTP plates are available in both positive and negative patterns, with the former being used more. After the waterless offset CTP plate is exposed to light, a chemical reaction occurs, and the adhesive force with the silicone layer becomes smaller. After development, the weak adhesive portion of the silicone layer is brushed off to expose the photosensitive layer. The exposed photosensitive layer absorbs ink during printing to form a graphic portion. The remaining silicone layer repels the ink and forms a non-graphical portion. Specifically, the plate-making process of the waterless offset CTP plate can be mainly divided into exposure, development, and drying.

(1) Exposure. The waterless offset CTP plate exposure can be performed directly in an ordinary CTP platesetter. It should be noted that the exposure time should be reasonably controlled during exposure.

(2) Development. The development process is divided into pre-treatment, water washing, post-treatment and re-washing steps. Plates should be placed in a dedicated waterless automatic plate processor for stencil printing. In the pretreatment, the pretreatment liquid should be used to break the interface between the photosensitive layer and the silicone layer of the photosensitive portion; when washing, the surface of the printing plate should be brushed with a brush, the silicone layer of the photosensitive portion should be peeled off, and the residual pretreatment liquid should be rinsed cleanly. During post-processing, the exposed graphic part should be colored to improve the inspection effect of the printing plate; finally, the printing plate should be washed again to remove excess dyeing substances.

(3) Drying. After water washing, waterless offset CTP plate can't be heated and dried like traditional water offset CTP plate, but it must be cooled by cold air.

Unlike the traditional water-based offset CTP plate, the waterless offset CTP plate does not require protective glue, otherwise dirt will appear. In addition, the waterless offset CTP plate is particularly prone to scratching. Therefore, if the waterless offset CTP plate that is to be plated is to be placed in an overlapping position, it should be protected with a release paper. The long-term preservation of the waterless offset CTP plate will result in a decline in the ink repellency of the graphic part. Therefore, it must be cleaned with a cleaning solution before printing.

3. Waterless UV offset printing equipment and parameter setting

In recent years, domestic printing companies use waterless UV offset printing equipment both domestic brands and imported brands. The domestic brand of waterless UV offset printing equipment is basically an intermittent rotary printing press. The printing speed is basically 5500 to 6,000 sheets/hour. The temperature control system controls the entire printing process by means of a sealed cover over the ink tank to allow the corresponding temperature to cool. The temperature inside each printing unit. The imported brand of waterless UV offset printing equipment is based on a waterless UV offset printing machine manufactured by Codig, a French label printing machine manufacturer. It uses a laser-engraved anilox roller with a closed squeegee and a closed-loop water cooling system. The machine is quite simplified structure.

In addition, waterless offset printing can also be realized on existing conventional water-based UV offset printing presses by only detaching the relevant water rollers from the printing plate cylinder, and installing cooling tubes in the ink supply rollers of the ink supply system, using conventional water-based UV offset printing presses. The original temperature control system can control the temperature. The internal temperature of the ink roller is basically 20 to 25°C; the platen temperature of the waterless offset CTP plate varies depending on the waterless offset UV ink used, and generally should be controlled at 25 to 30°C.

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