New glazing pattern - reverse matte process
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The reverse sanding process is a new printing process that has appeared in the past one or two years. It needs to be processed by several special base oils or varnishes. Some people call it the reverse-light process, which is regarded as a partial A new process of light. The process is to print the printed matter in the normal color sequence, and on the basis of the complete drying or solidification of the ink, the offset line (or offline) is used to print a special base oil on a local area that does not need to highlight high brightness. After the base oil is completely dried, the UV varnish is applied to the entire print surface in a full version. Thus, a cohesive reaction occurs in the region where the varnish and the base oil are in contact with U V to form a small particle-shaped ink film to form a matte or matte matte surface; and a U V glazing region in which the primer is not printed forms a high-gloss mirror surface. Finally, the surface of the print forms a local high gloss and a partially frosted low gloss area. Two completely different gloss effects achieve high contrast of the partial image, embellishing and highlighting the graphic with glossy mirror.
First, the reverse frosting process
The reverse sanding process can be realized in two ways, namely, a reverse line frosting process and an offline reverse sanding process.
1. Offset line reverse frosting process
Process flow: According to the requirements of the substrate and product effect, the white ink is printed on the first unit; the U V light source of the first unit is also turned on, and the white ink is dried. In the second to fifth units, normal U V colors are printed, and it is generally not necessary to turn on the U V light source. In the sixth unit, the U V spot color can be printed (can be left when there is no spot color), and the special base oil with graphic and graphic printing is printed on the seventh unit. At this time, the U V light source can be turned on or off as needed. The on-line glazing unit coats the varnish on the base oil in a coating manner. After the final U V drying (at least 3 tubes), you can get a beautiful reverse-frosting product. The above process is completed in one time, with high speed, high efficiency and good quality. The corresponding equipment cost is high, as shown in Figure 1.
2. Offline reverse sanding process
Process: First printing, white ink base (colorful, bar code and other graphic parts required); second printing, normal UV four or more colors; third printing base oil, online glazing; For glazing on-line, it is necessary to apply glazing to the coater. In general, it must be printed at least 2 or 3 times. It is time-consuming, slightly poor in quality, low in efficiency, and relatively low in equipment cost. It is suitable for proofing or trial production.
Second, the realization of high quality reverse matte process products
In order to obtain a high quality reverse matte product, the following elements are required to support it.
1. Understand the principle of reverse matte process
It is based on U V offset printing. The core is that the special base oil and the coated varnish are polymerized under U V light, and the particles are fine and evenly distributed. The screen sanding process is that some substances in the sanding ink are bulk polymerized under U V light to form particles, which are slightly larger than the reverse-sanded particles, and the distribution is slightly uneven.
2. Equipment requirements
Ideally, the “7-color + 1 U V” printing equipment and the C T P plate-making system ensure that the 5-color product is completed at one time; the C T P plate-making can produce high-precision screens of various colors, including the printing plate for printing special base oil. The ink path in the press is preferably equipped with a full U V rubber roller to minimize the conversion between normal printing and U V printing. Conditional printers can designate special machines and personnel for U V printing to improve the production efficiency and quality of reverse matte.
3. Special base oil and coating varnish requirements
Here we introduce the mature practices of practice and the experience of peers to share with you.
1 Donghua Ink's U V H J K base oil series and U V coated varnish H T A – W. The following tables mainly describe the characteristics of some manufacturers of reverse-frost varnish.
2 Manroland's Prudential varnish series.
First, Pu Dekang S 8 1 2 U (oily O P oil, base oil) is combined with Pu Dekang S 7 0 2 U (U V varnish) to achieve the combination of local U V and matte. No need for flexographic printing, it can print complex graphics and texts, and it can also produce high-precision printing products.
Second, Pu Dekang S 8 2 2 U (oily O P oil, base oil) is combined with Pu Dekang S 4 1 2 U (high gloss water-based varnish) to achieve a combination of local water glazing and matte.
Matters needing attention: First, after the special base oil is dried, the coated varnish with concave and convex parts may fall off easily when scratching, and the ink adhesion test must be carried out frequently during the printing process. Second, the special base oil and the coated varnish exhibit a mutually exclusive effect, so that a local high gloss and a local frosted low gloss area can be formed on the surface of the printed product, and the concentration of the base oil can be finely adjusted according to actual conditions.
4. Substrate requirements
The substrate for the reverse matte process generally uses a composite paper composed of a cardboard (substrate), an adhesive layer, a non-absorbent material film, an aluminized layer, a varnish, etc., as shown in FIG.
Figure 2 Schematic diagram of the substrate structure
Cardboard: Generally, it is a white card and a white card with a gray bottom. The printed surface is smooth and smooth, and the printing adaptability is good.
Non-absorbent materials: such as polyethylene (P E ) film, polyvinyl chloride ( P V C ) film, polypropylene (P P) film, metal foil and non-absorbent special materials. These printing materials require a certain drying time if they are printed with ordinary solvent-based inks. Usually, it is necessary to use dusting, drying equipment or other additives in the ink, and U V inks have no such troubles. But do the necessary surface treatment:
1 Corona treatment. It is a kind of electric shock treatment, which uses a method of generating high voltage and high frequency, respectively, to ground and the electric air nozzle to generate electric shock, no current flows between, until the voltage reaches 3 0 0 0 0 0 0 volts / square centimeter, the electric shock molecule Ejected from the air nozzle, with high energy free electrons accelerating toward the positive electrode, in addition to changing the polarity of the material and increasing the roughness of the surface. The dyne value of the printed material after corona treatment is not as high as possible. The normal dyne value of 3 8 (available with Dyne pen test) and ink difference will be suitable around 10%.
2 varnish base treatment. A layer of varnish film is used as a medium between the ink and the substrate, and is often used for materials that cannot be corona treated, such as P P. From a microscopic point of view, the ink is actually printed on this layer of varnish. The thickness of the film has a great relationship with the smoothness of printing. Too thick is easy to cause waste, and too thin is easy to cause printing failure. 3 Flame treatment. It is flame-proof and is generally suitable for film processing with irregular shapes or high speed (100 m/min). Aluminized layer: The aluminum plating method includes vacuum aluminum plating, aluminum spray coating, etc. The aluminum plating layer is divided into an aluminum layer upward and an aluminum layer downward.
5. Light source requirements, U V light source equipment
Including lamps, reflectors, energy control devices, temperature control devices (or cooling devices).
1 Lamp: U V The lamp used in the light source. The most common type is mercury lamp with internal mercury filling. Sometimes other metals such as gallium are added. In addition, metal halide tubes and quartz tubes are also commonly used.
2 Reflector: The main function of the reflector is to reflect the U V electromagnetic wave to increase the efficiency of the U V light source. Another important function is to maintain the operating temperature of the lamp. The surface of the reflector is usually made of aluminum, and the reflectivity requirement is usually as high as 90%.
3 Energy control device: The main function of this device is to control the U V energy emitted by the U V lamp to be stable to maintain the efficiency and stability of the hardening to meet the needs of different printing speeds. There are electronic designs and there are also microcomputer controls.
4 Cooling device: Since the UV lamp emits UV electromagnetic waves, it also emits IR (infrared wave), which makes the UV device operate at high temperatures (for example, the temperature of the quartz lamp can reach 600-800 °C). In addition to shortening the life of the equipment, the printed matter is also prone to expansion and contraction, which results in the inability to register the printing.
Matters needing attention: In actual operation, it is not necessary to open all lamps at full power. Generally, dark ink and white ink have higher opening power, which is convenient for quick drying; special base oil and coated varnish open power is 80% - 9 5 %. The more suitable ratio should be explored in combination with the actual situation.
6. Additives added
In the entire reverse sanding process, it is necessary to add U V enhancer, U V photosensitizer, etc. in some aspects.
U V enhancer produces a certain degree of slip on the surface after drying the ink, which is used to increase the scratch resistance (wear resistance) and surface adhesion of the printed surface. According to the product requirements and materials, choose the appropriate amount, usually add 1% - 2%. Note: If the product has a post-process, please try the production. The addition of the reinforcing agent may cause the post-process to be difficult to process, and the laminating film may be poor, and the bronzing may be poor. If the amount is too large, it may be difficult to print; In the ink fountain of the printing machine, it cannot be directly added to the ink fountain to avoid bad phenomena.
U V photosensitizers produce photochemical reactions with U V light to accelerate ink drying. According to the product requirements and materials, choose the appropriate amount, generally add 1% ~ 10%, it is recommended to control between 1% ~ 3%. Note: Adding photosensitizer may cause the adhesion of the ink to decrease. Please do the adhesion test after printing. After adding the photosensitizer, the UV ink viscosity will decrease, and the ink emulsification will occur easily. The ink and water balance should be controlled in time. Stir well (manually stir for more than 15 minutes) to be added to the ink fountain of the press and not directly to the fountain.
7. Ink adhesion detection method
Use a blade to draw a “× ” shape with a diameter of about 5 mm on the surface of the print. Use a scotch tape (width 15 mm, adhesive force about 3 to 4 N / 2 0 mm). If the print is faded when peeling off the scotch tape More than 10%, indicating that the ink adhesion is poor and needs to be solved.
Third, the conclusion
The reverse matte (glazing) process uses a unique combination of integral matte and partial bright light to achieve high registration accuracy of the local image portion, which can meet the local glazing needs of complex edges and images. The text has a stronger stereo effect and more expressiveness. It also enhances the decorative effect of the printed surface while highlighting the theme of the layout. Although the equipment cost is high, as the market demand increases, this process will inevitably have a broader development space.