The application of ink in the hottest stereo print

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The application of ink in stereoscopic printing

stereoscopic printing is a branch of printing technology. It is the product of the combination of grating stereoscopic imaging technology and special printing technology, which makes the planar printing image show the unique visual feeling of stereoscopic vision and variant animation. The company where the author works is also engaged in stereoscopic printing, so I would like to talk about my own experience combined with my own production experience. Printing methods of stereoscopic printing

there are two common printing methods of stereoscopic printing

the first is to use ordinary machines to print on the surface of paper or synthetic paper. After the ink on the surface of the paper is dried, use the grating matched with the image to frame the paper. Usually, when solvent based ink is used for printing on paper, the ink is dried by penetrating and oxidizing the conjunctiva. Stereo printing requires a high number of additional lines. Generally speaking, the point expansion is inversely proportional to the perimeter of the point. That is to say, the higher the number of additional lines, the smaller the point. The more serious the point expansion in the printing process and drying process. Therefore, when using high-line printing on paper, the dark part of the image is easy to appear pasted, resulting in the loss of the dark level of the image. At the same time, grating mounting is generally manual. Because stereo printing requires high matching degree of materials and images, if the process control is not appropriate, the product scrap rate is very high

the second method Anhui Lishi Power Technology Co., Ltd. was approved by Anhui Industrial Design Center; Four new invention patents are directly printed on the back of the grating. Because the grating is made of polymer material, which is a non absorbent surface, and ordinary ink will not be infiltrated and dried on the grating material, we use UV ink printer to directly print on the back of the grating, and use the principle of UV drying to make the ink produce light. He is more willing to seek the expansion of the range of chemical reactions under stable conditions. Instant drying. At the same time, it should be noted that when the film is released, the direction of the film surface is upward, which is opposite to the film surface of the first method

uv curing refers to that under the irradiation of ultraviolet light, the photoinitiator absorbs the radiation of ultraviolet light and splits into free radicals. The prepolymer is initiated to undergo polymerization, cross-linking and grafting reactions. It is solidified into a three-dimensional polymer in a very short time to obtain a hardened film. The essence is to realize chemical drying by forming chemical bonds. Stereoscopic printing adopts the technology of direct printing on the back of the grating. UV curing can effectively control the loss of fine dots and improve the ink transfer rate of chromatic overprint

precautions for stereoscopic printing with UV offset printing

(1) different inks should be selected for substrates with different properties. The light transmittance, curing rate, covering property of inks and gloss of print surface should be comprehensively considered. Water ink balance is a well-known principle, specifically: the pH value of water should be equal to the pH value of ink, otherwise it is either water color oil or oil color water (here for offset printing), forming ink emulsification, resulting in the opacity of UV ink film, which directly affects the passing rate of ultraviolet radiation. This will slow down the drying time of the film. Even though the light is fixed, there is still water in the ink film. Once the text is firmly fastened by friction or adhesive tape, the ink film will be found to be pulled off. At the same time, the temperature and humidity of UV ink warehouse and printing workshop should be strictly controlled. Prevent the ink from being exposed to natural light for a long time. Because ultraviolet light contains a small amount of ultraviolet light, if exposed for a long time, the surface of UV ink will dry and peel, affecting the use, and even causing printing accidents. At the same time, the impurities in the ink and the falling of dust splashes in the production process will weaken the light intensity effect of the UV region, thus greatly reducing the drying time of the UV curing ink. Generally, it is required to clean the dust in time and often and cover the ink tank (bucket). When printing grating products, the company where the author works uses Gao's rap series inks, which have good printability

(2) UV curable inks generally strictly stipulate the sequence of printing, that is, color sequence. UV printing ink is strictly in accordance with its wavelength. Otherwise, it is difficult to achieve consistent drying after UV curing, especially the gray balance of hue. In color printing, the ability of various pigments to absorb UV photons is different, and the transmittance from high to low is magenta cyan and black (M Y C, K). Therefore, the curing degree of various inks is also different. The transmittance directly affects the excitation energy of photons to photoinitiators. Because yellow (y) has the weakest visual stimulation to human eyes, it is appropriate to arrange the printing color sequence as black blue, magenta, yellow (k avoids contact with dust and other external influences C M, y), so that the ink with poor light transmittance can absorb photons as much as possible and enhance its curing effect

(3) the use of alcohol fountain system can reduce the surface tension of the ink and promote the curing effect. In the printing process, the fountain solution can be used to strengthen the oil drainage area (blank part) of the printing plate to ensure that the lipophilic area is fully ink friendly and the hydrophilic area is not inked

improving the ink formula and adding corresponding additives can increase the hydrophobicity of the ink. However, too strong hydrophobicity will lead to the shrinkage of the ink at the edge of the image, the loss of fine layers, and the unclear point boundary, which will affect the print quality. Photosensitizers and initiator crosslinkers are involved in UV ink and catalytic drying (curing). Usually people only pay attention to the wavelength of pigments and ignore printing inks with different viscosity and purity. We should scientifically choose different photosensitive initiators or crosslinkers. For example, benzoin is different from benzophenone because it is both a photosensitizer and an initiator

(4) stereo printing requires high surface strength of grating, and the surface strength is not enough, which is prone to printing accidents with poor bending force. Due to the smooth surface of the grating, the affinity for ink is small, and the ink of the first color is easy to be pulled out when overprinting the second color. Therefore, in stereo printing, we should choose grating materials with large surface tension, arrange the color sequence reasonably, and adjust the relevant process parameters of many such information processes in the printing market, so as to avoid and reduce the occurrence of the above phenomena

(5) different types of inks have different drying characteristics. To fully dry UV inks, it is necessary to choose a UV light source that matches the ink. There are three kinds of commonly used UV light sources: high pressure mercury lamp, ozone free lamp, metal halogen lamp, and the lamp tube cooling methods include ventilation cooling and water cooling. When selecting UV light source, it should be determined according to the drying conditions of UV ink and UV light oil. The irradiation efficiency of UV lamp should also be compared. The irradiation efficiency of various UV lamps is different

30% of the UV light absorbed by the ink during drying comes from the direct light source and 70% from the reflection of the reflector. At present, aluminum reflectors are widely used. Due to different processing technologies, the reflectance of reflectors varies greatly. Therefore, when detecting UV light energy, it is necessary to not only detect the lamp, but also measure all UV light, including reflected light. In stereoscopic printing, it is necessary to use a cold reflection plate, which only reflects ultraviolet light and transmits infrared light, so that the surface temperature of the printed matter decreases by 10 ℃. In addition, the general service life of UV lamp is about 1000 hours, which is very limited. This also directly affects the drying and curing time of UV ink

(6) except for the positive PS version for UV ink, if other positive PS versions have not been baked, their printing resistance is low. Therefore, they need to be baked. The baking condition is 250 ℃, 6 ~ 8 minutes. For negative PS version, try to choose high printing resistance version. At the same time, there is no special fountain solution for UV ink. When printing with UV ink, avoid adding excessive Arabic gum to the fountain solution, because Arabic gum will react with UV ink, causing the failure of ink stacking and rubber blanket stacking

(7) due to the fact that domestic UV offset printing is not very common and the number of technical operators of the equipment is also small, enterprises need to invest considerable funds in the training of operators, which is also the top priority in the stereo printing process, which is difficult to control

reprinted from: printing quality and standardization

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