UV (ultraviolet) curing technology has been widely used since the invention in the 1960s until the end of the 20th century. In China, UV printing and UV coating have been widely used in aluminum foil and aluminum foil paperboard printing, magnetic card printing, commercial printing, metal printing, food packaging and printing (beverage cups, fast food boxes, etc.), adhesive printing, etc. Especially in the screen printing (glass, wood products, plastic film and other non-absorbable materials) field is even more significant. UV printing products are increasing at a rate of more than 10% per year, and the application prospects of UV printing and UV polishing are very broad.
UV printing and UV glazing use UV light to irradiate UV inks or UV varnishes to decompose the binders in UV inks and photoactive materials in UV lacquers to form highly activated atoms or highly activated radicals; these highly activated atoms Or the atomic group will induce the UV ink and the unsaturated compound in the UV varnish to produce cross-linking polymerization to quickly cure and dry, complete the printing and polishing.
First, UV printing and UV polishing characteristics Curing speed UV ink and UV coating can be fully cured in 1 second to several seconds. It is especially suitable for the printing of non-absorbent printing materials, and is especially suitable for high-speed multi-color printing. When printing aluminum foil (or aluminum foil jam), if you use ordinary ink, it will take several hours or even 24 hours to dry completely after printing, so that you can go to the next process; instead, you can use UV ink to print it. Can cure dry, improve production efficiency.
2. UV printing is green printing Since UV inks and UV coating oils do not contain solvents and there is no problem of solvent evaporation, they will not cause pollution to the atmosphere. At the same time, due to the elimination of powder spraying, the working environment is greatly improved and the number is reduced. Machine abrasion caused by dusting; In addition, the use of UV printing and UV polishing paper can be completely recycled after paper recycling, reducing the waste of resources.
3. High efficiency, good quality UV printing production cycle is short, the production capacity is high, the printing network is clear, the ink resistance of printing ink is good, the corrosion resistance is good, the glossiness is high, it is very difficult for common ordinary ink to reach the effect of UV printing. For example, the use of UV imitation metal etching ink for screen printing, its print three-dimensional effect is good, strong metal texture, it looks elegant and beautiful.
The quality of UV coating is also better than that of solvent-based coating. It is more difficult to compare with coating.
4. UV printing and UV coating Low energy consumption and moderate price UV inks and UV coatings are solvent-free, do not require heat during curing, and require only solvent-based inks and solvent-based coating oils for curing. %about. Although UV inks and UV coatings are expensive. However, due to the low energy consumption and high utilization required for curing, its use price is still acceptable.
Second, several problems in the application 1. UV Ink and UV Varnish (1) UV inks and UV Varnish should be stored at low temperatures as much as possible, stored in a ventilated cool place or in a refrigerator, and their shelf life is usually 1 year; if stored at a higher temperature, It is easy to degenerate or harden.
(2) The ink layer or coating of UV printing and UV coating should not be too thick, otherwise the UV ink and UV coating do not solidify on the substrate.
(3) UV inks and UV coatings cannot be mixed with ordinary inks and ordinary coating oils. When converting from ordinary ink printing to UV ink printing, the ink fountain and ink roller should be thoroughly cleaned before printing. In addition, adjuvants can only be used with UV printing aids.
(4) UV inks and UV coatings need to be cleaned with special cleaning agents or ethyl acetate, while gasoline and kerosene are not washable.
(5)UV ink and UV coating oil stick to the skin for a long time, it will produce itching, redness, pimples and even peeling. Therefore, once UV ink or UV coating oil adheres to the skin, wash it off with soap as quickly as possible. .
(6) The adhesion fastness of UV ink differs depending on the type of substrate. When replacing a new printing material, it is necessary to confirm its adhesion properties before proceeding with printing.
(7) The black ink in UV ink has strong UV absorption ability, and it is slower than other color UV inks. The colorless or highly transparent UV ink has faster curing speed. Therefore, when printing UV black ink, it is appropriate to slow down the printing speed so as to increase the irradiation time of ultraviolet light so that it can be completely cured.
(8) After printing UV white ink on a metal substrate, the ink layer will turn yellow after a long time. This should be noted.
2. UV curing device (1) UV printing and UV coating must use a special UV irradiation device. Ultraviolet rays are very harmful to the human eye, so do not let ultraviolet rays shine on the substrate.
(2) The surface temperature of the UV lamp can be up to 700°C. Therefore, users must install the air cooling device in the light box when they modify the UV irradiation device (standard UV curing devices are equipped with air cooling device).
(3) UV lamp life is generally about 8000 hours, more than this time, the curing efficiency will be reduced, so the use of the lamp must be recorded in order to replace the lamp.
(4) In order to reflect ultraviolet light, a reflector is installed behind the UV lamp so that the ultraviolet light can be focused on the substrate. However, the use of a long time, the mirror will inevitably be dirty, causing part of the UV light scattered, reducing the curing efficiency. Therefore, it is often necessary to clean the mirror with a UV ink cleaner to keep the mirror clean.
3. PS version and blanket (1) UV printing should use a dedicated PS version, but suppliers are generally not stocked, need to book, the time is 3 to 4 months, very inconvenient.
In actual work, if there is no PS plate for UV printing, the developed normal PS plate can be heated for 15 minutes at 150°C.
(2) Blanket (including ink roller) should also be used for special purpose. Ordinary blanket and UV printing blanket cannot replace each other. If a device needs to use UV inks and regular inks, it is recommended to use blankets that use both UV inks and common inks.
4. Printing Environment (1) In the printing area, try not to let the sun shine directly on the printing press. If the print shop site is small, an ultraviolet shielding film can be applied to the window glass of the workshop.
(2) It is best not to use lamps, such as fluorescent lamps and mercury lamps, which are usually installed above the printing press. Instead, use safety lamps that block ultraviolet rays. If it is difficult to replace at one time, please set the light fixture 1.5 to 2 meters away from the printing press and turn it off at rest or when it is stopped for a long time.
(3) Do not spray ordinary ink anti-drying agent around the printing machine that is engaged in UV printing so as not to delay the curing of the UV ink.
UV printing and UV glazing use UV light to irradiate UV inks or UV varnishes to decompose the binders in UV inks and photoactive materials in UV lacquers to form highly activated atoms or highly activated radicals; these highly activated atoms Or the atomic group will induce the UV ink and the unsaturated compound in the UV varnish to produce cross-linking polymerization to quickly cure and dry, complete the printing and polishing.
First, UV printing and UV polishing characteristics Curing speed UV ink and UV coating can be fully cured in 1 second to several seconds. It is especially suitable for the printing of non-absorbent printing materials, and is especially suitable for high-speed multi-color printing. When printing aluminum foil (or aluminum foil jam), if you use ordinary ink, it will take several hours or even 24 hours to dry completely after printing, so that you can go to the next process; instead, you can use UV ink to print it. Can cure dry, improve production efficiency.
2. UV printing is green printing Since UV inks and UV coating oils do not contain solvents and there is no problem of solvent evaporation, they will not cause pollution to the atmosphere. At the same time, due to the elimination of powder spraying, the working environment is greatly improved and the number is reduced. Machine abrasion caused by dusting; In addition, the use of UV printing and UV polishing paper can be completely recycled after paper recycling, reducing the waste of resources.
3. High efficiency, good quality UV printing production cycle is short, the production capacity is high, the printing network is clear, the ink resistance of printing ink is good, the corrosion resistance is good, the glossiness is high, it is very difficult for common ordinary ink to reach the effect of UV printing. For example, the use of UV imitation metal etching ink for screen printing, its print three-dimensional effect is good, strong metal texture, it looks elegant and beautiful.
The quality of UV coating is also better than that of solvent-based coating. It is more difficult to compare with coating.
4. UV printing and UV coating Low energy consumption and moderate price UV inks and UV coatings are solvent-free, do not require heat during curing, and require only solvent-based inks and solvent-based coating oils for curing. %about. Although UV inks and UV coatings are expensive. However, due to the low energy consumption and high utilization required for curing, its use price is still acceptable.
Second, several problems in the application 1. UV Ink and UV Varnish (1) UV inks and UV Varnish should be stored at low temperatures as much as possible, stored in a ventilated cool place or in a refrigerator, and their shelf life is usually 1 year; if stored at a higher temperature, It is easy to degenerate or harden.
(2) The ink layer or coating of UV printing and UV coating should not be too thick, otherwise the UV ink and UV coating do not solidify on the substrate.
(3) UV inks and UV coatings cannot be mixed with ordinary inks and ordinary coating oils. When converting from ordinary ink printing to UV ink printing, the ink fountain and ink roller should be thoroughly cleaned before printing. In addition, adjuvants can only be used with UV printing aids.
(4) UV inks and UV coatings need to be cleaned with special cleaning agents or ethyl acetate, while gasoline and kerosene are not washable.
(5)UV ink and UV coating oil stick to the skin for a long time, it will produce itching, redness, pimples and even peeling. Therefore, once UV ink or UV coating oil adheres to the skin, wash it off with soap as quickly as possible. .
(6) The adhesion fastness of UV ink differs depending on the type of substrate. When replacing a new printing material, it is necessary to confirm its adhesion properties before proceeding with printing.
(7) The black ink in UV ink has strong UV absorption ability, and it is slower than other color UV inks. The colorless or highly transparent UV ink has faster curing speed. Therefore, when printing UV black ink, it is appropriate to slow down the printing speed so as to increase the irradiation time of ultraviolet light so that it can be completely cured.
(8) After printing UV white ink on a metal substrate, the ink layer will turn yellow after a long time. This should be noted.
2. UV curing device (1) UV printing and UV coating must use a special UV irradiation device. Ultraviolet rays are very harmful to the human eye, so do not let ultraviolet rays shine on the substrate.
(2) The surface temperature of the UV lamp can be up to 700°C. Therefore, users must install the air cooling device in the light box when they modify the UV irradiation device (standard UV curing devices are equipped with air cooling device).
(3) UV lamp life is generally about 8000 hours, more than this time, the curing efficiency will be reduced, so the use of the lamp must be recorded in order to replace the lamp.
(4) In order to reflect ultraviolet light, a reflector is installed behind the UV lamp so that the ultraviolet light can be focused on the substrate. However, the use of a long time, the mirror will inevitably be dirty, causing part of the UV light scattered, reducing the curing efficiency. Therefore, it is often necessary to clean the mirror with a UV ink cleaner to keep the mirror clean.
3. PS version and blanket (1) UV printing should use a dedicated PS version, but suppliers are generally not stocked, need to book, the time is 3 to 4 months, very inconvenient.
In actual work, if there is no PS plate for UV printing, the developed normal PS plate can be heated for 15 minutes at 150°C.
(2) Blanket (including ink roller) should also be used for special purpose. Ordinary blanket and UV printing blanket cannot replace each other. If a device needs to use UV inks and regular inks, it is recommended to use blankets that use both UV inks and common inks.
4. Printing Environment (1) In the printing area, try not to let the sun shine directly on the printing press. If the print shop site is small, an ultraviolet shielding film can be applied to the window glass of the workshop.
(2) It is best not to use lamps, such as fluorescent lamps and mercury lamps, which are usually installed above the printing press. Instead, use safety lamps that block ultraviolet rays. If it is difficult to replace at one time, please set the light fixture 1.5 to 2 meters away from the printing press and turn it off at rest or when it is stopped for a long time.
(3) Do not spray ordinary ink anti-drying agent around the printing machine that is engaged in UV printing so as not to delay the curing of the UV ink.
Linkand Co., Ltd. , http://www.csceramics.com