Disc four-color printing - offset printing fault

Sixth, offset printing easy cause and processing:

1, ghost: The color image of the disc on the ghost and its ghosting nature, can be used about 10 times magnifying glass inspection. In offset printing, the ink on the printing plate is first transferred to a roller colored by a blanket, and then the ink on the image on the roller blanket is transferred to the printing surface of the optical disc, so if a double image is produced in the offset printing, then Ghosts appear in the longitudinal ghosts perpendicular to the axial direction of the blanket cylinder and the lateral ghosts in the direction parallel to the axis of the blanket cylinder.

1) When longitudinal ghosting occurs, check:

a) The rubber blanket on the rubber roller is tightly stretched? If it is not tight, it will shift and deform under the printing pressure to produce ghosting;

b) The blanket on the blanket cylinder is skewed when it is cut or when it is installed and not in place when the iron plate is installed, resulting in inconsistent elasticity. A version of Changbai pays poor power, "The upper part of the map asks double-images." The wear of the Huo-Xian M2' in the tenth of the H Chuan and the bearing transmission make the meshing clearance between the gears exceed the control of the olM. Ten years of printing in the printing industry led to a drop in the shadow:

c) L is always thinking about the kidneys, and the scalp between the two drums is suitable. When the tune is large, it will produce ghost images. In one case, the printing plate J For O wide 0 Bu;;;;;;, Rubber drum') pressure between the impression cylinder is 0 / O calendar; nn;. In addition, the blanket maintenance and repair of the blanket cylinder are related to the copying and reproduction of the original and the printing resistance of the printing plate, and at the same time, the ink transfer effect and the printing quality are determined. This should be noted! Not only that, the thickness is even and uniform. The ink transfer effect is good. The factory applies UV ink blanket (such as ethylene propylene rubber) to the machine. At the same time, it often does not regularly clean the blanket table n in printing, restores its good elasticity and ink absorption. Prevents the appearance of cracking and crystallization of the conjunctiva on the rubber blanket surface.

2) When a lateral ghost appears, check:

a) Check the wear condition of the shaft end sliding bearing of the roller. If the wear is serious, the transverse clearance ghost will be generated if the clearance is too large;

b) The loosening of the nut of the sliding bearing causes axial turbulence and causes horizontal ghosting. Therefore, the phenomenon of ghosting occurring in offset printing—a corresponding solution

Decision.

2. After UV ink printing, the main problems are:

a) Check if the lamp is aging (usually the lamp life is about 1000 hours) should be replaced;

b) The surface of UV lamps and reflectors should be dirty and should be cleaned with absolute ethanol at certain intervals. After every 1/4 of the life of the lamps used, the UV lamps should be rotated 90 degrees in a certain direction to avoid the inside of the lamps. The metal particles evaporating on the glass wall are blocked by the metal particles and affect the light illumination efficiency of the UV ink. The monomers in the composition of the C several V ink penetrate into the blanket cylinder and interact with the eraser, so that the monomer in the UV ink is reduced to make the curing composition insufficient. , causing UV curing bad; mountain rubber roller and printing roller printing pressure is not good, and poor results; affect the UV ink leveling bad;

e) When the UV ink is poorly cured, the wear resistance of the ink is deteriorated, and the adhesion to the protective layer of the optical disc is also affected at the same time;

f) Select a suitable curing UV ink to adapt to rapid offset, or adjust the print speed appropriately so that the UV illumination of the UV ink is extended to reach the cure.

3. UV ink on the machine:

a) The rubber roller does not match with the UV ink. You can use the rubber blanket roller specially designed for UV ink, or increase the hardness of the blanket.

b) The new blanket cylinder absorbs a large amount of monomers in the UV ink during the initial period, so that the UV ink is dried and sticky, so that it can be improved after the rubber absorbent monomer is saturated and printed normally;

c) The special cleaning solution that does not use the UV ink to remove the UV ink must not be cleaned with a solvent-based ink cleaning agent, because the blanket is only UV-resistant and not resistant to common solvents. The photosensitive layer on the bovine plate is damaged: Only the PS plate should be suitable for UV ink, and the non-UV special cleaning solution is not used to clean the PS plate.

4. Gold, silver UV ink gloss deterioration:

a) Gold and silver UV inks should be stored in dark places around 10°C;

b) After the gold and silver UV ink tanks are opened, they can be mixed evenly, and the lids of the cans can be sealed immediately to prevent contact with the outside air and moisture to promote premature oxidation and discoloration. If gold or silver ink is used with gold or silver powder, how much is it used?

5. UV ink adhesion between layers is not good:

a) The main overprinted UV ink over-cured (crystallized) phenomenon, making the surface wettability and surface tension of the ink layer become smaller, so that the latter printing ink can not wet the previous ink layer, so the previous ink The layer should only reach 50%~90% of full cure when cured. UV inks have the property of polymerization after secondary polymerization. Therefore, when printing UV inks, the thickness of the ink layer should be thinner and the UV energy should be minimized. The polymerized photopolymerization should not be too complete, especially the first layer (front layer), that is, the final printing is also controlled to be hardened on the surface and slightly less solidified in the interior because of its secondary and post-polymerization properties.

Pay attention to the thickness of the ink layer in the printing, in the offset printing plate printing and graphics production, printing pressure and so on. In screen printing, about 50% is related to screen materials, about 20% is related to screen making techniques such as stretch nets, screen templates, etc. About 30% is related to the rheological characteristics of inks, type of presses, pressure angle of squeegees , Squeegee hardness and ink blade angle, pressure and so on.


Source: CD production network