Analysis of Influencing Factors on UV Solid Drying Speed

Known as the first ink, and excessive exaggeration of "pollution-free, solid fast, energy-efficient" UV-curable ink - referred to as UV ink. The ink has been in existence for 30 years. When people talk about their characteristics, they will always beautify their advantages and seldom blame them (such as cleaning, removing ink, and not reusing multiplexing). After focusing on this issue, the author visited several packaging printers in the north and south of the country, and summarized them as the top ten factors that affect the UV ink drying speed. It is very necessary for the packaging and printing industry colleagues to re-discuss and re-communicate to compensate for the printing process. Ten major flaws. Uncovering the “red hijab” of light-curing packaging printing inks, let us analyze it one by one.

1 ink inhaled moisture

Naturally inhaled moisture, mostly caused by environmental humidity during storage and use, especially in workshops and warehouses. There are also people, such as the use of screen printing, offset printing ink, and then forget to cover it or intentionally injected water to prevent dry crust and added. The purpose is to use the water to separate the oxygen in the air and prevent the crust from drying out. Do you not know that this product is almost never cured and dried without ultraviolet radiation.

2 Imbalance of ink and wash

The balance of water and ink is well known. However, the specific point is that: the PH value of water is the same as the PH of the ink, that is, the abbreviation: ink and water balance. Otherwise, it is not a water-colored oil, that is, oil-colored water (in this case, offset printing) forms an ink emulsification phenomenon, which causes the UV ink film to be opaque and directly affects the passing rate of ultraviolet radiation light energy. This slows down the film formation and drying time. Even though the film is cured, there is still moisture in the ink film. After the ink film is formed, the ink film is pulled off once it has been rubbed or stuck in the image with an adhesive tape. phenomenon.

3 lamp maintenance

We have known for a long time that the general service life of UV lamps is about 1,000 hours, which means that they are limited. This not only affects the light intensity and directly affects the drying and curing time of the UV ink. In addition, the impurities of the ink and the deposition of the dust during the production process will weaken the effect of the light intensity in the ultraviolet region, thereby greatly reducing the photocurable ink. The drying time is generally required to clean the dust and cover the ink tank (bucket) frequently and timely.

4 Photosensitizers and initiators

Participation in UV inks and catalytic drying (curing) are photosensitizers and initiator crosslinkers. Generally, people only pay attention to the pigment wavelength and ignore different viscosity, different purity printing inks and scientifically choose different photoinitiators or crosslinking agents. For example, benzoin is different from benzophenone because it is both a photosensitizer and an initiator. I recently used the 16IS ink of Zhejiang Songhua Ink Co., Ltd. in Qingdao, Shandong Province, ideal science and printing company can not be cured after drying on the static PVC film and firmly attached. When 1% benzoin or 13% of the 907 photosensitizer was added, the dry speed was almost doubled.

5 Temperature and Substrate Tension

People seem to have little communication around this issue. Often ignore its harmfulness. The author's feedback from Mr. Ye Jianxing at Xiamen verified this point—low ​​temperature, slow photo-curing, high humidity, and low substrate tension. The ink sucks in water molecules and causes the ink film to mix and bleed, which greatly hinders the radiation. The frequency of energy, and will gradually consume the exposure and affect the ink and substrate binding energy.

6 Color purity and amount of ink system

With fluctuations in the balance of pigment grayscale, especially the decrease in color purity, the increase in the amount of use, and the increase in fineness of grinding and dispersion, they did not grasp the essentials of the chromatics of printing inks. After the pursuit of "color juxtaposition," they were not red. It tends to purple, yellow to green; not yellow to orange, and green to blue.... We artificially set a barrier for the drying of photocurable inks. Although printing operators even design and sample the person only to pursue "color juxtaposition," and ignore the adjacent color (ring) phase juxtaposed to impede or weaken the influence of the color color relative to the light curing, that is to say, although it can form a A new kind of color feels, but from the eyes of human retina nerves. Only when we understand this law of colorization can we design the color juxtaposition to be just right. Otherwise, it is impossible to control the purity of the color and the thickness of the ink film to achieve a uniform drying of the entire multicolor version.

7 Substrates and Printing Inks

The three types of substrates that absorb light or light transmitted or reflected by light energy are light-transmitting materials that are superior to light-absorbing materials, and materials that reflect light energy are inferior. In addition, there is a transparency of the ink, especially by the viscosity, and sometimes also to distinguish the transparency of the substrate, opaque or high viscosity ink due to light energy, sometimes due to low voltage, light intensity will be directly affected Light curing speed.

8 Mechanical or manual printing speed

Different mechanical printing or manual screen printing speeds all have a light-cured best operating method. We have different printing runs at 2500 rpm, 3000 rpm, 3500 rpm and 8000 rpm, and pass through the UV irradiation zone. However, at the same lamp surface temperature of 800°C, the drying speed is also different. Although there is a distance between the lamp and the substrate, it directly affects the formation of the ink film of the photo-curing ink.

9 ink printing color sequence

Light-curable inks generally strictly regulate the order of printing, that is, the color sequence. Scientific color ordering is based on the wavelength in the ink system. Unlike printing inks such as lead printing and offset printing, printing inks are arranged according to three primary colors, and light-curing printing inks are strictly according to their wavelengths. Otherwise it is difficult to achieve consistent drying after photocuring, in particular the gray balance of the hue.

10 Resins in Ink Systems

Whether we use binary resin, or ternary or quaternary resin for unsaturated synthesis. In general, acrylic resins with cross-linking monomers have the same photo-curing time as epoxy resins under the same conditions. We don’t explore why, and often it’s easy to give people an illusion—the same content, the same viscosity, the same printing method, the same number of UV lamps, the same light intensity, the same light energy, but it should also face With crosslinker ingredients? Is the transparency of the resin the same? Whether or not it is so, at the same time, the ink film is hardened. For example, different glycols, only neopentyl glycol as an unsaturated photocuring binder (resin), will greatly increase the speed of light curing by about three times. Also in this system, the addition of tetrahydric alcohols (such as pentaerythritol) will increase the gloss of UV-curable printing inks, increase the hardness of the ink film, etc., and have long attracted attention.

In a device that typically passes three ultraviolet light tubes, the electrical energy is converted into high-intensity ultraviolet light, and the coating is irradiated for photo-curing to form a film. In addition to the above ten factors, the ultraviolet wavelength and light intensity emitted by the UV lamp are also important factors affecting the speed and quality of curing. For this reason, we need to understand in practice, in the understanding of transformation, so that the curing speed of light-curable ink further increase, is the packaging and printing industry pray for the goal.