Print glazing question and answer
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In modern packaging printing, the surface finishing of printed materials is becoming more and more important in the later stage. The most widely used one is coating and glazing, and glazing is more unique because of its unique advantages (environmental protection, short production cycle, production cost). Low), and gradually show stronger momentum, playing an irreplaceable role in the field of post-press processing.
Why is it on the surface of the print?
Firstly, the glazing on the surface of the printed matter can greatly increase the surface gloss of the printed matter, and the surface smoothness of the printed matter is also improved, thereby improving the design grade of the printed matter; secondly, the wear resistance of the printed surface can be improved. Protect the graphic of the printed matter. Therefore, the glazing process can be widely applied in the fields of packaging decoration, book cover, trademark, advertisement, calendar and the like.
What are the processes of glazing?
The glazing process of printed matter generally consists of two steps of coating and calendering of the glazing coating. The classification of glazing coating can be divided into ordinary printing equipment glazing, special glazing glazing (with online and offline); according to the type of glazing coating, oxidative polymerization coating Polishing, solvent volatilization coating glazing, photocurable coating glazing, thermosetting coating glazing; according to the coated product form, it can be divided into whole glazing, partial glazing, extinction, artistic glazing, etc. .
Is glazing and calendering the same thing?
If it is not according to the more general term, we generally refer to the process of coating the glazing paint as glazing in production. Calendering is a subsequent process of glazing coating, which is generally processed according to customer requirements. It is a special production process carried out on a special glazing equipment after the glazing coating is dried. Calendering is mainly through the high temperature and pressure provided by the calender, which makes the surface smoother and the visual feeling is brighter.
What are the most popular glazing paints in printing houses? Introduce the process characteristics.
Nowadays, relatively popular glazing coatings have UV glazing and water varnish glazing, while solvent glazing coatings are gradually eliminating due to their environmental and hazardous effects. The following describes the characteristics of each UV and water varnish.
UV glazing
UV glazing is ultraviolet light curing glazing, which is a kind of light curing glazing. The varnish is mainly composed of a photosensitive resin prepolymer, a reactive solvent, a photoinitiator and other auxiliary agents. The reaction mechanism is that the unsaturated double bond in the prepolymer absorbs the energy of the ultraviolet light emission, and then opens the double bond. Under the action of the initiator, the monomer is crosslinked and polymerized to form a film. Due to the instant curing, the UV varnish has a fast glazing speed and a full gloss, and the surface resistance after film formation is considerably improved. In addition, UV varnish has a good adsorption performance on different surfaces and has little influence on the environment, so it is generally favored.
UV glazing equipment conditions
Rubber roller: ink roller that can resist UV varnish corrosion, such as EPDM, nitrile rubber, etc.
Light source: UV lamps with a power range of 80 to 120 W/cm and a wavelength spectrum of 200 to 450 nm are selected. If you need to increase the glazing speed, the power of the UV lamp needs to be increased accordingly (or increase the number of lamps).
Mirrors: It is important to keep the mirror clean and intact. If it is not clean or damaged, it will affect the curing speed of the glazing.
Use of UV varnish
1 UV varnish must be stored in the room at 15 ~ 20 ° C
2 Stir before use and make necessary tests (there will be some differences in the adsorption capacity of different UV varnish for different print surfaces)
3 During the glazing process, a reasonable film thickness should be emphasized. Although it is UV-light-solid, it may cause problems such as incomplete curing, residual odor, and deformation of the substrate for an excessively thick film.
4 For papers with different surface smoothness, pay attention to the choice of varnish with different viscosity and leveling. For paper with rough surface, choose varnish with low viscosity and good leveling.
5 UV varnish for special products must consider the corresponding varnish performance. If it is used for the outer packaging of detergents, then UV varnish must choose chemical resistance, especially alkali resistance.
6 In the printing production, we should also pay attention to the change of ink color of UV varnish. For sensitive ink pigments (light blue, gold light red, etc.), it should be applied cautiously.
Waterborne varnish
The water-based varnish is mainly composed of water-soluble polymer resin and a small amount of additives. Its main solvent is water, which has high solid content, colorless, odorless, good transparency, and is non-toxic and free of organic volatiles.
Waterborne varnish equipment conditions
Plate: Water-based glazing is usually made of flexographic glazing, so you can use a variety of flexographic resin plates, but you can't use a water-washed resin plate. Various glazing rolls can also be used for coating.
Use of waterborne varnish
1 Store at 15～20°C, especially avoid storing or transporting below 0°C.
2 The use of water-based varnish is basically the same as that of water-based ink. The pH value of the glazing process should be stably controlled between 8.5 and 9.5, otherwise the glazing intensity will be affected.
3 In the coating process, ensure that the viscosity is in the range of 25 ~ 35S, otherwise there will be quality problems.
Which is more advantageous for water-based varnish and UV varnish?
In terms of quality and production efficiency, UV varnish has obvious advantages, mainly in the surface of the product with high gloss, good surface resistance and short production cycle.
From the perspective of cost and environmental protection, water-based varnish has great advantages. The coating of water-based varnish does not require special equipment such as UV varnish coating (special ink roller, special drying system, etc.), and it is free to use. Larger, water-based varnish itself is cheaper than UV varnish without any environmental pollution.
From the above point of view, UV and water-based varnish which is more advantageous, and can not arbitrarily draw conclusions, but we also found that with the continuous improvement of water-based varnish itself, the development of water-based varnish is a good trend. And UV varnish is also firmly in the market because of its unique irreplaceable characteristics.
What are the more common glazing devices?
Above we mentioned that there are several kinds of glazing coating equipment, including glazing of the glazing machine, glazing with the printing unit, and online glazing.
How to use the unit glazing?
There are generally two ways to use the unit to glaze, one is to use the wetting device to glaze, and the other is to use the inking portion of the printing press to glaze through the plate or blanket. Below we introduce:
Lubricating with a wetting device
This kind of glazing method is more typical of KBA's RAPIDA sheet-fed lithographic multi-color printing machine, which can be equipped with a wetting and glazing conversion device. The operator can quickly wet the operation with a simple manual operation. The state transitions to the glazing job state. When the wetting and glazing functions are switched, the dampening fluid is converted into a glazing liquid, in which case the wetting and glazing device can be set to run in the forward direction.
1. Plate cylinder 2. Metering roller; 3. Liquid (water) roller; 4. Liquid transfer (water) roller; 5. Liquid (water) bucket roller; 6. Liquid (water) roller; 7. Rubber roller
The state of the graph a can also be selected in the transition. As shown in the above figure a, the rotation speed of the water fountain roller is operated at a rotation speed of 1/3 to 2/3 of the rotation speed of the water transfer roller, so that the pre-glazing is formed by the rotation speed difference, and the true glazing is still passed through the water fountain roller. Speed is adjusted.
If it is adjusted as shown in Figure b, it can achieve better glazing effect and better eliminate ghosting.
Using inking unit glazing
The operation of using the printing machine to inject glazing is the same as using ordinary ink printing, except that the offset printing machine water roller does not work when the full glazing is performed. In addition, screen printing machines, flexographic printing machines, gravure printing machines, and resin printing machines can be used for glazing, and these types of machines are commonly used for partial glazing. In addition, for partial glazing products that require less precision, lithographic offset printing machines can also be used to directly engrave the blankets. In particular, sheetfed presses (whether flat, concave, convex, or stencil) are often used for off-line glazing of various products, which is very practical and practical for small print shops that cannot be made large and large. of.
How many online glazing? What is the characteristics of the organization? What are the advantages?
More common on-line glazing, roller glazing and blade glazing. The following is a separate introduction to the two forms of online glazing:
Roller glazing
The Heidelberg Speedmaster 102-4 CD, ROLAND700, Mitsubishi DIAMOND 3000, and Komori Lithrone 40 are all roller glazing units.
Roller glazing device 1. liquid bucket; 2. liquid bucket; 3. liquid roller; 4. glazing coating roller; 5. embossing roller;
The roller glazing mechanism of these types of machines basically has the same principle. As shown in the above figure, the amount of glazing and pressure of the on-line glazing unit of such a printing machine are controlled by the printing machine control center, such as the Heidelberg printing machine glazing device. The glazing supply mechanism controls the entire process of glazing. The glazing liquid is pumped from the liquid storage tank through the hose to the glazing liquid pan. The liquid level and the circulation of the glazing liquid are monitored by the potentiometer cycle to ensure uniform supply of the glazing liquid. Ultrasonic monitoring can be performed at any time. Monitor the amount of glazing of the coating.
KBA KBA Rapida 105 machine roller glazing unit
The KBA Rapida 105 can be used as a two-roller system for forward operation or as a three-roller system for reverse operation. As shown in (b) and (c) above, when the two-roller is operated in the forward direction, the metering roller 6 is disengaged, and the coating liquid is passed through the pressure adjustment between the coating roller 2 and the liquidizing roller 3 at this time. The amount of light is simple. When the three-roller reverse operation is performed, the polishing roller and the liquid roller are reversely operated to obtain a good gloss, and at the same time, it is not necessary to excessively increase the pressure between the rollers to achieve a thin and uniform coating when using a high-viscosity coating liquid. purpose.
The benefits of this type of roller glazing are:
The transfer route of the polishing liquid from the liquid pan to the buffing roller is very short, and the contact point is relatively small, and is directly transmitted from the liquid bucket roller to the coating roller, so that the polishing liquid is not easily dried inside the coating unit, Use a quick drying polish.
Even if the contact point is small, the thick coating liquid can be evenly transferred. The thickest wet film can reach 8g/m2, and the thickness of the glazing liquid can reach 3~4g/m2.
The operation of replacing the work or changing the liquid liquid is simple and convenient.
Scraper glazing
Scraper-type glazing devices are becoming more and more widely used in modern printing equipment. It is usually made up of two glazing scrapers
The closed blade box is composed of a ceramic anilox roller which acts as a metering roller. The upper and lower scrapers and the anilox roller form a closed “glazing box”, and the glazing liquid is input through the pipeline. The Heidelberg SM102-4CD, ROLAND700, KBA RAPIDA105, Mitsubishi DIAMOND 3000, Komori Lithrone 40, etc. all have a scraper type glazing device. Their institutions are basically the same, as shown in the figure below, the Heidelberg SM102-4 machine scraper type glazing device.
Heidelberg SM102-4 scraper glazing device 1. glazing coating roller 2. anilox roller 3. upper scraper 4. lower scraper
This type of glazing device has many irreplaceable advantages:
1 Stable, excellent glazing quality. The upper and lower blades in the blade-type glazing structure are pneumatically clutched with the anilox roller. Due to the action of the upper scraper, the coating amount of the coating liquid can be uniform and uniform, and is not affected by the change of the printing speed. Even in the continuous printing operation for many days, the glazing effect can be kept constant. In the conventional light structure, the change in color tone due to the change in the thickness of the coating does not exist in this mechanism.
2 Conducive to environmental protection. The structure of the blade-type glazing is a closed structure, requiring only a small amount of phosgene circulation, and there is no problem of odor emission, and the waste to be cleaned is also minimized.
3 The glazing economy is stronger. Generally, during the plate changing operation, the polishing liquid can be directly cleaned with a cleaning agent, and the manual cleaning of the blade system is required only when converting from ordinary glazing to gold or silver glazing. If a plurality of such blade type glazing devices are used instead, the plate changing and cleaning operation time can be further shortened. The use of qualified automatic cleaning devices can also greatly improve work efficiency.
4 This structure is a closed system that allows glazing at high speeds even with very low viscosity coatings.
5 It is precisely because of the use of the anilox roller that the thickness of the coating liquid layer can be set accurately over the entire width of the paper for glazing, ensuring a stable glazing effect on the printed matter, especially for glazing when thinning the paper. The coating amount is the lowest range while being evenly coated. Changing the thickness of the coating is determined by the density of the screen of the anilox roll.
Polished gold. The glazing device can be adapted to gold and silver glazing with different elemental compositions to achieve a relatively high wear resistance.