The UV equipment + UV glazing process let you print charming
Time:2016-04-20 09:13Source:sankunClick: Number
The UV equipment + UV glazing process let you print charming
Glazing, is a process with the post-press processing, is one of the printing surface finishing processing technology. Colloquially, glazing is in the printing surface coating a layer of colorless transparent coating, after flow leveling, drying, pressure light, can be in print form a thin and uniform transparent shiny surface layer.
Polishing not only increases the surface smoothness of printed matter, printed products brings out the more luster, but also to protect printing graphic, and therefore is widely used in packaging decoration, book covers, picture album, trademark, advertising decoration, poster, calendar, sharp printing surface finishing processing. Glazing technology as an extension of the printing process and the important means of print finishing, has been widely used in many printing factories, has become an important means to realize and improve the grade of printed matter.
The principle of UV glazing is not complicated, under the irradiation of UV light, UV glazing oil after light initiator absorb radiant energy in the formation of free radicals or cation, monomer and prepolymer polymerization and crosslinking reaction, in a very short time to a three dimensional network structure of polymer. Most of them are radical polymerization system at present.
The advantages of UV glazing
Glazing process according to the glazing oil way of drying, can be divided into oxidative polymerization glazing, solvent evaporation glazing, UV glazing and thermal curing polishing, etc. UV glazing or UV curing glazing, it is with UV glazing oil, is coated on the surface of printed after UV irradiation light oil, can be cured within a short period of time. Compared with other polishing method, UV glazing has the following advantages:
(1) oil polish for the solid content of 100%, without solvent volatilization. To be both safe and environmentally friendly.
(2) the fast drying speed, high production efficiency. General drying speed can reach 100-300 m/min, the fastest of over 500 m/min.
(3) is not restricted by class printing species, can not only in the paper, aluminum, plastic materials such as surface polishing, but also can be used for the polymerization, furniture, metal materials, such as wireless material surface polishing.
(4) low energy consumption, save energy.
(5) work under low temperature and can be used for thermal type printing, such as plastic substrates.
(6) are of good quality. The printing after UV glazing surface flat light, without become warped edge, the phenomenon such as wrinkling, foaming, and high surface hardness, friction resistance, not easy to scratch, chemical corrosion resistance.
(7) after glazing substrates, can be processed immediately, no hardening, in such aspects as cutting, molding and folding have higher adaptability.
Therefore, UV glazing as an important way of glazing, more and more widely applied.
The components of UV light oil
UV glazing oil is mainly composed of oligomers, active diluents. Light initiator and other additives.
1. The oligomer
Oligomer is also called the prepolymer, UV glazing oil is the most basic components. It is a film forming substance, its performance on the nature of the curing process and curing film plays an important role. Structurally, oligomer to contain unsaturated C = C double bond of low molecular resin, mostly for the acrylic resin.
There is often used in UV glazing oil oligomer epoxy acrylic resin, acrylic and polyester polyurethane acrylic resin, etc. Epoxy acrylic resin has many characteristics, such as fast curing speed, price cheap, made of glazing oil coating on the paper or paperboard, make it has good chemical resistance and high mechanical strength.
Polyurethane acrylic resin has good flexibility, strong flexibility, high gloss, etc, but the price is more expensive, often mixed with epoxy acrylic resin. Lower polyester acrylic resin viscosity and good flexibility, the price is cheaper. Because of its non absorbent substrates such as plastic, metal, good adhesion, so commonly used for this kind of material of glazing oil, mixed with other resin used commonly, can sometimes be gloss oil thinners, used to adjust the viscosity of epoxy acrylate resin and polyurethane acrylic resin.
Polyurethane acrylic resin has good flexibility, strong flexibility, high gloss, etc, but the price is more expensive, often mixed with epoxy acrylic resin. Lower polyester acrylic resin viscosity and good flexibility, the price is cheaper. Because of its non absorbent substrates such as plastic, metal, good adhesion, so commonly used for this kind of material of glazing oil, mixed with other resin used commonly, can sometimes be gloss oil thinners, used to adjust the viscosity of epoxy acrylate resin and polyurethane acrylic resin.
3. Light initiator
Light initiator can absorb radiant energy is, through chemical change of reactive intermediates substance capable of polymerization, is anything that need to be the main component of the UV curing system.
Light initiator can be divided into take hydrogen and cracking - take type hydrogen light initiator and containing active hydrogen compounds (commonly called help initiator, usually for amine compounds) coordinates, through hydrogen radicals formed in the reaction. It is a double light initiator molecules, there are two commonly used in the oil polish benzophenone old P), etc. After cracking type light initiator by light excitation, intramolecular decomposition of free radicals, is a single molecule light initiator. Commonly used in the oil polish have. A hydroxyl isopropyl benzene ketone and. A ring of hydroxyl has benzophenone, etc.
4. The additives
Fertilizer is mainly used to improve the performance of the ink, that is commonly used in UV glazing oil additives have stable agent, flow ping agent, defoaming agent, etc.
(1) stabilizer
Stabilizing agent used to reduce storage occurs when thermal polymerization, improve the UV glazing oil storage stability. Commonly used stabilizers have hydroquinone, the methoxy phenol, benzoquinone, 2, 6 December uncle Ding Jijia phenol, etc.
(2) flow ping agent
Flows in my life. At the same time also increased the glazing coating gloss.
(3) the defoaming agent
Defoaming agent is used to prevent and eliminate the glazing oil produced in the process of manufacture and use of bubbles.
Ordinary UV glazing oil does not contain solvents, but due to large oligomer viscosity are commonly used for coating needs, must add low molecular reactive diluent, they generally have a certain volatile or irritating, there is still a hazard to the environment. , therefore, has now developed water-borne UV glazing oil, it does not have to use reactive diluent to adjust viscosity, but water or thickening agent to control the rheological properties of glazing oil, and can solve the problem of volatile and stimulating, is an ideal environmental protection product, is the development direction of glazing oil in the future.
UV glazing wayUV glazing way
UV glazing way has a lot of, the classification method also has a lot of kinds, basically has the following several kinds of classification methods:
1. According to the glazing machine and printing machine classification relationship
Press polishing machine and the relationship between the printing press, glazing can be divided into offline glazing and online glazing in two ways.
Offline glazing of the print by special glazing machine polishing, namely, printing, polishing, respectively in their own special equipment. This way of polishing is more flexible, convenient and lustering hair for investment is small, suitable for professional postpress manufacturers use. But this way of glazing increased transportation transfer between printing and polishing process, the production efficiency is low.
Online glazing is the glazing unit directly connected to the printing unit, namely printing, glazing on the same machine speed, high efficiency, low processing cost, reduces the handling of printed matter, to overcome the various quality faults caused by powder injection, is the development direction in the future. But online glazing Liu Shangguang technology, glazing oil. Is very tall to the requirement of drying equipment and polishing equipment.
2. Classified by polishing method
Press polishing method, glazing can be divided into two kinds of, roller coated gloss and print gloss.
Roller coated with light is the most common way of polishing by the applicator roll will be whole wide gloss oil on the surface of printed evenly coated.
Printing glazing glazing oil through the glazing coating on the print, so local glazing can be performed. There is often used in gravure polishing, flexible glazing, offset printing, glazing and silk screen version glazing.
3. According to the polishing product type classification
By polishing product type, glazing can be divided into the wide glazing glazing, local glazing, polishing, and art, etc.
The wide glazing for printed matter is the main purpose of protection, and improve the surface gloss of printed matter. The wide glazing generally adopt the method of roller glazing.
Local glazing is usually important to emphasize on printed matter by polishing the part. Use polishing parts images of high gloss with no glazing low gloss frame, wonders of artistic effect. Adopt the method of printing glaze for local glazing, which USES the way of silk screen printing glaze of thick film, other ways effect is obvious, and the cost is low, at present in domestic use morer, but its production efficiency is low.
Extinction glazing is UV matte oil, with ordinary polishing effect is the opposite. It is to reduce printing surface gloss, which, in turn, produce a kind of special effects. Due to high gloss to the human eye has a certain degree of stimulation, and so on extinction light is now more popular a kind of polishing method.
Art glazing effect, to make the glazing products for special artistic effects, such as using UV glazing bead light oil in the surface gloss of print, printing surface causes pearl effect, make the print appears gorgeous, noble and elegant.
UV glazing problems should be paid attention to
To ensure the quality of UV glazing, polishing, attention should be paid to the following main problems:
1. Polishing oil selection
Glazing oil first should undertake choosing according to polishing way, different methods of glazing glazing oil performance requirement is different, therefore need a different performance glazing oil and its matching. Offline glazing and online glazing glazing oil roller used for different polishing and the printing glaze should adopt different gloss oil when printing glaze, glazing oil used in the different ways of printing are also different.
Second, glazing oil should also match the print on the surface of the ink. Requires glazing oil surface tension must be less than the surface tension of ink, so that the glazing oil well wetting, adhesion and penetration in print graphic on the surface of the part. Otherwise, the coating after glazing reservoir will produce certain shrinkage, uneven, and even in some places such as sand holes of failure.
If also has been hot stamping or glazing products after processing such as pasting, should choose relatively stable chemical performance glazing oil.
2. The choice of uv curing light source
As a result of UV glazing oil curing depend on to absorb ultraviolet light initiator of radiant energy after the formation of free radicals, triggering monomer and prepolymer polymerization and crosslinking reaction. So the UV curing light source selection on UV glazing oil have great effect on the drying speed. Select uv curing light should consider the following factors:
(1) the absorption spectra of light initiator as far as possible match the output spectrum of light source, so as to maximize the use of the light source of radiant energy, produce more free radicals, so as to improve the curing rate of UV glazing oil.
(2) electrical energy converted into uv energy efficiency should be higher.
(3) the intensity should be appropriate, the light is too strong, free radicals produce too fast, high concentration of termination reaction speed increases, the adverse effects of crosslinking reaction; Strength is too low, free radicals produce too slow, oxygen polymerization effect will be very strong. These will make UV glazing oil drying too slowly.
(4) long service life. Ultraviolet light gradually aging, expired UV lamp light intensity will reduce a lot, UV glazing oil drying too slowly.
(5) should have good chimney condenser, also the stand or fall of a lamp shade, can make the efficiency is more than a dozen times.
(6) the shape right, can make the light uniform distribution on the printed matter, and is easy to install, cheap, safe and reliable. General use tube lamp.
(7) with under uv light, can have generation of ozone in the air, so should have ventilation equipment.
Commonly used uv light source is medium pressure mercury lamp (in China) to be included in the high pressure mercury lamp, mainly launch the following wavelengths of light: 405 nm (42), 365-366 nm (100), 312-313 nm (49), 302-303 nm {24}, 297 nm (16, 6), 265 nm (15, 3), 254 (16, 6), 248 (8, 6), the Numbers in brackets their relative energy. In addition to this, and visible light and infrared light. Infrared light not have triggered effect, but have a synergistic effect to chain growth. Commonly used medium pressure mercury lamp power line density of 80 w/cm, light from a few cm to 200 cm long, 15 to 25 cm in diameter. The application temperature is higher, need air cooling, the service life of the general about 1000 hours.
Mercury lamp need to have a preheating time after moving, so that the mercury evaporate, in the preheating time can not be ultraviolet light. Mercury lamp closed after, can't restart, cooling needed - a period of time, use less convenient. Now appeared a kind of infinite mercury lamp, can the instantaneous switch, and long service life, the UV effect. Used for UV curing electrodeless mercury lamp light spectrum is different from medium pressure mercury lamp is - a continuous spectrum, and can be used for the curing of thick film.
3. Control of polish oil viscosity
Glazing oil viscosity on the printing and the wettability of ink flowing property of coated eligibility has important influence, will ultimately affect the polishing glossiness of the product. Glazing oil viscosity control should consider to print absorbent and coating thickness, and so on and so forth. Glazing oil viscosity also affect the print gloss oil absorbent, glazing oil viscosity is smaller. The more absorbed by print. So if print absorbent strong, can be appropriately increased gloss oil viscosity, shortening the time of its flow flat, or in a long time to flow leveling process, glazing oil is absorbed by a lot, it is difficult to form a smooth film layer in the surface of printed matter, easy to form a film with a similar print surface concave and convex state. Glazing oil viscosity has a great influence on the thickness of the coating, glazing oil of low viscosity, thin coating layer. To reduce the viscosity of ordinary uv glazing oil, alcohol can be added, but it can't add too much, otherwise will affect the curing speed of uv glazing oil.
4. Oil glazing coating weight control
Glazing oil coating weight is appropriate, uniform coating.
Even a moderate amount of coating surface smooth degree is high, high gloss. If the coating quantity too little, glazing oil not evenly spread out, to print on the surface of the optical defects (smoothness) can reduce the offset function of coating surface smoothness is poor; If the coating weight too much, although is advantageous to the glazing oil flow, also enhanced the offset effect of the surface defect of printed matter, but dry occur is difficult, and high cost.
Glazing coating weight determination of species, the condition of the surface of printed matter with coating. Coating conditions, to balance each other, determine the overall arrangement, should not only meet the polishing quality requirements, and is suitable for all kinds of craft.
Coating, can control institutions or changed by adjusting the glazing coater coating machine speed to achieve the change of the coating weight. Change in hours, but can be by changing glazing oil viscosity.
5. Polishing speed control
Polishing speed, that is, coating machine speed, should be based on the curing speed and coating of the glazing oil quantity. Glazing oil curing speed, the coating machine speed can be improved, when the coating flow flat time is short, relatively thick coating, on the other hand, on the other hand. Coating machine speed also with coater curing light condition, the condition of printed matter and other factors.
6. Polishing effect on the color print
Using UV glazing print, can appear sometimes yellowing phenomenon, its main reason has two: one is the yellow UV glazing oil; The second is in the process of polishing, polishing oil only in the print surface curing. And internal is not completely cured.
Glazing oil yellow, instead of the oligomer and reactive diluent with some yellow, so should choose colorless oligomer and reactive diluent to make oil polish. In addition, the influence of light initiator is big, there are some yellow light initiator can make the system after curing, such as benzoin methyl ether, so should avoid to use these light initiator preparation glazing oil.
In the process of polishing, polishing oil inside there is no completely curing, its internal oil polish thinner gradually absorbed by the ink, paper, at the same time can produce effect of ink in the link, cause fat loss, pigment can not get adequate protection, free pigment particles, the paper coating and ink layer surface smoothness will reduce. Rough surface can produce diffuse light, so add factory some white in color composition, raising the lightness, saturation decline, give a person with the feeling of whole yellowing, color lighter. Therefore, we should improve the curing speed of UV glazing oil or choose efficient UV curing light source. In addition, the waterborne UV glazing oil, can avoid thinner, ink and paper coating layer of chemistry, liu can avoid yellowing phenomenon in print.
On the UV light is a means to provide value-added services to the customers. If haven't the processing capacity of your workshop, might as well give it a try.
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UV equipment(10)
