Spot UV, or spot varnish in the packaging industry ruled over decades. However, manufacturers and consumers realized the many benefits of spot UV, or spot varnish, in the packaging industry.
According to the needs of product glazing, local glazing coating is carried out on the prominent parts of
trademarks and packaging printed materials. Compared with the surrounding patterns, the glazing pattern isbright,
bright, and has a strong three-dimensional effect, which can produce unique artistic effects. Therefore, it is
favored by Chinese and foreign merchants.
overview
As an important surface finishing process, UV glazing process has become an important means to realize the value
-added of cartons. The so-called UV varnish refers to coating a layer of UV varnish on the surface of the paper
through a specific glazing equipment, and the surface of the printed product can reach a certain gloss after curing.
Most of the traditional glazing equipment is full-page glazing equipment, that is, it can only glazing the entire
printed product surface, which can protect the printing surface, beautify the carton, and improve the product
grade.
The local UV varnishing process is to varnish some parts or specific patterns of the printed matter, so that these
parts or patterns can have a clear contrast effect with the surrounding graphics, thereby highlighting the focus or
theme of the packaging, reflecting the characteristics of the product, and achieving The purpose of attracting
customers' attention and making purchases. Full-screen UV glazing is more environmentally friendly due to no
solvent volatilization, and it is an alternative to the lamination process; partial UV glazing process highlights the
effect of appealing to product characteristics.
Now, many cosmetics, electrical appliances, food, health care products, etc. have applied partial UV glazing
process on the packaging cartons, which has achieved good publicity and promotional effects.
UV effect
At present, the common partial UV effects are: partial bright light, partial extinction, partial frosting, partial colorful
partial refraction, partial wrinkles and partial ice flowers, etc.
Partial UV can be implemented after lamination, or directly on the printed matter, but in order to highlight the
effect of partial glazing. Generally, it is carried out after the printed matter is coated with a film, and most of them
are covered with a matt film, accounting for about 80% of the local UV coating products. The biggest difference
between partial glazing and full-plate glazing is that one needs to make printing plates and the other is that there
are certain registration requirements for glazing equipment. There are three major elements in local UV glazing,
namely glazing plate, equipment registration and curing equipment. In order to ensure that the local UV glazing
part is consistent with the size of the printed graphic, the photosensitive imaging method should be used when
making the glazing plate.
Classification
1. Partial glazing for screen printing
Screen printing has the characteristics of high ink transfer, thick ink layer and strong three-dimensional effect.
Generally, 200-300-mesh screen should be used for the screen plate for glazing (for glazing effects such as partial
frosting and local colorful, the mesh number is lower), and the tension of the stretching net is 20-25N/cm. Due to
the small investment in equipment. Many books, periodicals and packaging factories prefer screen printing when
increasing local glazing business. Some professional printing and glazing companies improve glazing precision
and production efficiency. Fully automatic roller screen printing machines are already in use. The production speed
can reach 3000 sheets/hour. However, the local glazing of screen printing basically adopts the offline production
mode. On-line rotary screen printing units are rarely used.
2. Partial glazing of flexographic plate
Flexographic printing is characterized by the ability to form thicker coatings with a simpler process.
Therefore, it is quite popular in UV glazing. Flexographic printing local glazing is divided into ordinary flexographic
printing glazing and special flexographic printing glazing, and some simple graphics are still using engraved
rubber letterpress. Flexographic printing local glazing is suitable for off-line glazing and can also realize online
glazing. Using flexographic printing glazing method, combined with anilox roller and cavity scraper, can accurately
control the amount of varnish, and the glazing quality is stable.
3. Partial glazing for gravure printing
Gravure printing also has advantages in local UV glazing due to its thick printing ink layer and high printing
resistance of the gravure cylinder, especially the emergence of sheet-fed gravure printing machines has played a
role in fueling the development of gravure local glazing. However, due to its high plate-making costs, it is mainly
used for long-run glazing business.
4. Other partial glazing methods
Before the emergence of UV varnish, no one would use offset printing for varnish because its printing ink layer is
too thin. Due to the thicker film layer, higher gloss and high overprint accuracy, UV varnish has some applications
in local UV glazing, but it is mainly used for online glazing.
In terms of production methods, local UV glazing machines can also be divided into offline glazing and online
glazing.Off-line glazing refers to printing, and glazing is carried out on special equipment respectively, requiring
the use of special glazing machines or calenders. When off-line varnishing, because the printed matter can be
fully dried, a higher gloss can be obtained than on-line varnishing. In addition, the off-line glazing production has
great flexibility. Equipment investment is small. In-line glazing means that printing and glazing are completed on
one production line, that is, glazing and UV curing devices are added to the printing machine. Allows the print to
be varnished directly after printing.
Partial UV New School Technology
1. Mixed ink technology
Since UV printing or UV glazing is not suitable for application on the surface of highly absorbent printing materials,
and the surface adhesion of printing ink is not good, so most of them need to carry out on-line UV glazing. If all
of them are printed with UV ink, the cost will inevitably increase : If ordinary ink is used for printing, lamination or
full glazing is carried out before glazing, which undoubtedly hinders the application of offset printing on-line
glazing.
The mixed ink technology effectively solves this bottleneck problem. In terms of performance, it combines the
advantages of UV ink and traditional ink, that is, the advantages of photocuring and oxidative polymerization
drying,which improves the synergistic effect of ink surface and UV varnish, and paves the way for online glazing of
offset printing.
2. Reverse glazing
Reverse glazing (Pro-Cure) is relative to traditional local glazing. The traditional glazing method (flexographic
printing, screen printing or gravure printing) is used for partial glazing, and finally partial glazing plate printing
must be used to achieve a high contrast effect of partial graphics. Therefore, the overprint accuracy of glazing and
printing becomes glazing. The key to craftsmanship. The reverse glazing process breaks through the above laws
and solves the registration problem.
3. On-line UV coating
This is the advantage of Hongxin Technology. We have a German manroland 8+1UV in-line coating printing
machine.
In-line coating is not a new technology for flexographic printing and gravure printing, but for offset printing,
which has a wide range of applications, high printing accuracy and high speed, it is launched under the voice of
differentiation and value-added services The glazing technology with innovative ideas. There are four main forms
of online UV glazing methods that have been applied: ordinary ink + double glazing (water-based glazing + UV
glazing); mixed ink + UV glazing; UV ink + UV glazing; UV ink + OP oil + UV glazing (reverse glazing).
