How to do digital post-printing of special paper

How to do digital post-printing of special paper?

In the field of digital printing, people no longer only demand product personalization, but also the pursuit of aesthetics. In order to meet this demand, more and more special papers have begun to be used in digital printing products, especially after laminating, hot stamping, embossing, embossing, embossing, flocking, oiling, local UV varnishing and other digital post-press surface finishing processes, so that the already colorful, fast and flexible digital printed products shine more brilliantly.

Characteristics of special paper

Common types of specialty paper and their characteristics are as follows.

01

Embossed paper

Embossed paper refers to the use of mechanical embossing or pleating to form a concave and convex pattern on the surface of the paper, making the paper textured. There are many types of embossing, such as leather pattern, cloth pattern, plaid pattern, eggshell pattern, straight stripe, curved pattern, etc. This paper is beautiful and elegant, has a strong decorative effect, and is commonly used in the printing and packaging industry.

02

Patterned paper

Patterned paper is different from embossed paper, although some patterned paper also has textures on the surface, but its formation occurs in the papermaking process rather than mechanical forced pressing in the later stage. This type of paper is soft to the touch, not easy to lose powder, and has a gorgeous appearance, and its finished products are more noble. There are many types of patterned paper, each with its own characteristics, such as Nissan, cloud, embroidered Leni, water stripe, bamboo silk pattern and other surfaces are as textured as embossed paper, but more delicate. In addition, there are some patterned papers with other ingredients on the surface, such as floating silver, floating gold, etc., with gold and silver sand spots on the surface but very flat, the paper is tight and has high toughness.

03

Coated paper

Coated paper refers to the paper obtained by coating the surface of the base paper with various coatings, with smooth and bright surface, good optical properties and printability, and waterproof, oil-proof, wear resistance, and corrosion resistance. Therefore, this paper is widely used in imaging products and high-end printed materials, such as making photo books, albums, invitations, etc. Commonly used coated special papers include star illusion, ordinary photo paper, metal photo paper, silk soft silver, silk soft ice white, etc.

04

Sulfuric acid paper

Sulfuric acid paper is a kind of translucent paper formed after being soaked in 72% sulfuric acid during processing and washed with water made of plant fibers. Its paper is tight and solid, highly transparent, non-breathable, and has the characteristics of waterproof, oil-proof, and moisture-proof. This paper is suitable for use in book ring linings or title pages, which is not only in line with the trend of the times, but also can effectively improve the grade of printed materials.

Key points for post-printing application of special paper

In recent years, specialty paper has become more and more widely used in digital printing due to its high added value. Although the application is widespread, due to the wide variety of special paper and different characteristics, coupled with the combination of digital printing and many post-press processing processes, its uncertainty in the digital printing process is multiplied compared with ordinary paper.

For example, due to the uneven surface of the paper, the printing is inaccurate; Due to the background color of the paper itself, there is obvious color difference in the bright skin tone; Due to the thickness of the paper, the line burst after folding; Due to the poor ink absorption of the paper, it is difficult to dry and becomes dirty during post-processing; It may also cause slippage during cutting because the surface of the paper is too slippery; or because the surface of the paper itself is coated, the friction resistance after processing is poor.

Therefore, it is particularly important to understand the paper characteristics of special paper and the key points of process and quality control after combining special paper with special technology. The following mainly analyzes several process links that may have problems in the digital post-press finishing processing of special paper.

01

Lamination

Generally speaking, because the surface of special paper has been specially treated, or has some textures, it is inevitable that there will be some unevenness, or it has been coated or covered with some special substances, such as gold and silver cardboard, etc., so it is rare to laminate on special paper in digital printing. If the customer has this need, it is necessary to communicate with the customer in time, it is recommended to cancel the lamination process, because special paper and ordinary paper can show some texture effects or texture differences, and these effects will be offset accordingly after lamination, and the surface of special paper is generally tighter, which is not conducive to the penetration of glue, and is not conducive to the adhesion between the film and the paper, and the firmness will be very poor after lamination.

It is worth mentioning that there are now some special films that can make special effects on ordinary paper, such as leather film, cloth pattern film, diamond film, etc., so that the laminated ordinary paper looks very similar to special paper. This method is worth promoting in digital prints, because there are many types of special paper, it is generally difficult to stock, and it requires a certain ordering cycle. while the film with special effect compounded on ordinary paper is much simpler, and it is more water-resistant and wear-resistant than ordinary special paper.

Of course, in the process of recommending this process, it is also necessary to respect the opinions and choices of customers, after all, the type, texture and color of special paper are very distinctive and personal.

02

Hot stamping

Generally speaking, in the digital post-press processing process related to special paper, hot stamping is a relatively difficult link. Due to the particularity of the surface of special paper, it is not easy to print or color, so the use of hot stamping and UV varnishing is more common, in contrast, electrochemical aluminum after gold printing can achieve some metallic texture effect, and there are a variety of laser or refractive effects to choose from, and the characteristics of the special paper itself can be complemented by each other, which makes people shine.

In the process of using hot stamping process on imitation leather paper and PVC materials, the technical difficulty is mainly reflected in the use of some special papers with deep grains and special papers with low quantitative ratio. The former due to the uneven surface of the paper causes a relatively large pressure to be stamped on the paper completely during hot stamping, and excessive pressure will lead to some fine text or pattern paste, on the contrary, reducing the pressure will cause the local hot stamping to be unfirm and easy to fall off, which can be described as a dilemma.

For some special papers with low quantification, due to the relatively thin paper, when the hot stamping pressure is slightly larger, it often leads to indentations on the back of the paper, and the hot stamping effect is mostly presented on the cover of digital prints, the back of which is the second cover, generally the most important content or advertising, if the indentation will affect the aesthetics, customers with higher requirements are often difficult to accept such an effect.

In this case, because the number of digital prints is generally not large, it is recommended to choose electrochemical aluminum with better quality and high brand awareness. Secondly, it is necessary to make necessary adjustments and trade-offs in pressure and temperature, and optimize the ratio, which requires operators to have a certain experience accumulation and technical level.

02

UV varnishing

When applying the UV varnishing process to special paper, the problems that are easy to arise are: the surface of some special paper has undergone special processing, resulting in the UV varnish on the coating being quickly absorbed in large quantities, and a thick and flat varnish coating cannot be formed on the surface of the paper, resulting in a weak unevenness, not flat and bright enough.

In this case, we can generally use the following methods to solve this problem:

The primer treatment of special paper is to change the absorption capacity of the paper to UV varnish by applying a layer of primer before UV varnishing.
UV inks with higher viscosity are used to reduce the amount of penetration before curing into a film, and improve the effect of UV polishing.

To sum up, special paper will be more difficult than ordinary paper when decorating its digital post-printing surface due to its special texture and different paper characteristics. By understanding the paper characteristics of special paper and grasping the key points of process and quality control brought about by the combination of special paper and special technology, you can use special paper freely, better display the design theme, and make the digital print that best meets customer requirements.