Notebook printing covers several
main printing methods. In the plate making stage, different printing methods
are selected according to different product properties. Plate making process is
also different for different printing methods. Flexographic plate making
process is: manuscript film (negative) exposure - Development - drying -
post-processing.
1.
Original.
The
original design suitable for offset printing should have the following
characteristics: more colors but less overprint; no need to reproduce very
small details; the screen line is not too high, but can achieve color printing
effect; online packaging processing can be done.
2. Film
It meets the needs of
plate making, with clear picture and text, accurate size and specification for
the notebook printing;
with frosted film, it is required that the density of four corners of the film
is consistent; the use of film orthography; the white density is less than
0.06; the black density is more than 3.5.3.
3. Exposure includes back
exposure and main exposure.
Back
exposure.
The
supporting film of the photosensitive resin plate is upward and the protective
film is laid downward in the exposure drawer to receive exposure. UV light can
solidify the photosensitive adhesive layer through the supporting film to
establish a stable base. It can also control the plate washing depth and
strengthen the adhesion between the support film and the photosensitive resin
layer. The back exposure time is determined according to the thickness of the
substrate required.
Main
exposure.
Also
known as positive exposure, photosensitive resin plate support film down,
protective film up. The protective film is torn off continuously, and then the
film surface is pasted on the photosensitive resin plate. The ultraviolet ray
penetrates the vacuum film and the transparent part of the film to polymerize
and solidify the photosensitive part of the plate. The main exposure time is
determined by the plate type and light source strength. If the exposure time is
too short, the gradient of the text will be too straight in notebook
printing,
the lines will be bent, and the small characters and dots will be washed out.
Otherwise, if the exposure time is too long, the plate will be overlaid and the
handwriting will be blurred. If there are large, small, thick and thin lines on
the same plate, black film can be used to cover and expose separately. Small
parts will not be lost due to washing, so as to ensure the quality of the
plate.
4.
Rinse.
The
non photosensitive part is washed and dissolved to retain the light polymerized
relief. The washing time depends on the thickness of the plate and the depth of
the image. If the washing time is too short, the plate will leave non
photosensitive resin, which will affect the depth of plate making. If the
washing time is too long, the plate material will expand and the fine parts
will deform or fall off.
5.
Drying.
Remove
the washing solvent, so that the plate to restore the original size and
thickness of the notebook printing. The baking
temperature is between 50-60 ℃. Baking time depends on plate thickness and
plate washing time, generally two hours for thick plate and one hour for thin
plate. If the baking time is too long and the plate temperature is too high,
the printing plate will become brittle and affect the printing life. If the
baking temperature is too low, the drying time will be prolonged. If the baking
time is too short, the printing plate will be rotten.
6.
Post treatment.
That
is, debonding and post exposure. Make the photosensitive resin harden completely
(polymerize) to reach the required hardness index, and eliminate the printing
plate viscosity, in order to facilitate the ink transfer. The post-processing
time is obtained from the test to avoid cracking and adhesion.