The lamination effect is not only related
to the film covering raw materials and the film covering operation methods, but
also to the ink layer status of the pasted printed matter. The ink layer
condition of printed matter is mainly determined by the properties of paper,
ink performance, ink layer thickness, image and text area and integrated
density of printed image and text. These factors affect the forming conditions
of mechanical binding force and physical-chemical binding force of adhesion, so
as to cause the change of surface adhesion of printed matter.
1. Ink layer thickness of printed
matter of printing books in china
The thick ink layer of the field printed
matter is often difficult to bond with the plastic film, and will soon be
delaminating and foaming. This is because the thick ink layer changes the
porous surface characteristics of the paper, making the paper fiber pores
closed, seriously hindering the penetration and diffusion of the adhesive. The
penetration of adhesive in a certain extent is beneficial to the lamination
bonding.
In addition, if the ink layer and the area
of the ink layer on the surface of the printed matter are different, the
adhesion and wettability are also different. The results show that the surface
tension decreases with the increase of ink thickness or image area. Therefore,
both monochrome printing and superimposed color printing should strive to
control the ink layer in a thinner degree.
The thickness of the printing ink
layer is also directly related to the printing method. The thickness of the ink
layer varies with the printing method. For example, the thickness of the ink
layer of the lithographic product is about 1-2 μ m, 2-5 μ m for the convex
printing, and 10 μ m for the gravure printing. From the perspective of film
covering, flat printing is ideal, its ink layer is very thin.
2. Type of printing ink of printing books in china
The printing materials to be coated shall
be fast fixing bright offset printing ink. The binder of the ink is composed of
synthetic resin, dry vegetable oil, high boiling point kerosene and a small
amount of gum. There are polar groups in the synthetic resin molecules, which
are easy to diffuse and permeate with the polar groups in the adhesive
molecules, produce cross-linking, and form a physical and chemical binding
force, which is conducive to film covering; fast fixation of the photo offset
ink also has the advantage of rapid drying of the ink layer after printing,
which is also very beneficial to film covering. However, it is not suitable to
add too much drying agent, otherwise, the surface of the ink layer will produce
crystallization, which will affect the film covering effect.
3. Use of ink diluent of printing books in
china
Ink diluent is a kind of substance that can
make the ink color lighter. The common ink diluents include white ink, villi
oil and gloss oil.
White ink is a kind of ink, which is
composed of white ink pigment, binder and auxiliary materials. It is commonly
used in light color field printing, spot color printing and trademark pattern
printing. Poor white ink has obvious powder particles, which are not tightly
combined with the binder. After printing, the binder will soon penetrate into
the paper, while the pigment floating on the paper surface will hinder the
adhesion, which is the reason why some light color field printing products are
easy to be covered with lamination.
Before printing, we should carefully choose
self ink, try to choose even and fine self ink without obvious particles as
diluent.
Villi oil is a kind of paste transparent
body made of aluminum hydroxide and dry vegetable oil binder, which can
increase the gloss of the surface of printing products and has excellent
printing performance. However, aluminum hydroxide is light and floats on the
surface of the ink layer after printing. When the film is covered, an
imperceptible separation layer is formed between the adhesive and the ink
layer, resulting in poor adhesion or foaming. Its own slow drying, but also has
the characteristics of inhibiting ink drying, which is also difficult to adapt
to film.
Glossy
oil is a kind of fast drying diluent from inside to outside. It is a kind of
gelatinous transparent material made of resin, flat vegetable oil, drier and so
on. It has fine texture, bright conjunctiva, good affinity, and can firmly
absorb polypropylene film on the surface of ink layer. At the same time, glossy
oil can make the imprint shiny and dry faster, and the printing performance is
good. Therefore, it is an ideal ink diluent in printing books in china.
