Flexo Printing Answers Collection (1-15)

1. What kind of flexible version?

According to the different materials used, the flexographic plate can be divided into two major categories: rubber plate and photosensitive resin plate. The rubber plate can be divided into natural rubber plate, synthetic rubber plate, 50% natural rubber and 50% synthetic rubber plate. Photosensitive resin plate can be divided into two types of liquid photosensitive resin plate and solid photosensitive resin plate.

2. What is a photosensitive resin plate?

The photosensitive resin plate is a photopolymerization type relief plate made of a photosensitive resin and exposed to light and washed.

3. What is a photosensitive resin?

Photosensitive resin, also known as photosensitive polymer or photosensitive resin, usually refers to the chemical change in a short time under the action of light, which causes the solvent in the solvent, coloring ability, hardening and adhesion and Other properties change. Polymer material. Its photochemical reactions mainly include photolysis, photocrosslinking and photopolymerization.

4. How is photopolymer resin polymerization developed?

Photopolymerization of photosensitive resins has been used by humans as early as in Egypt (about 1500 BC) as part of the mummification process. Modern technology has gradually emerged from 1820 onwards. Natural resins are applied to metal plates and exposed to sunlight to form rough images. In the 20th century, DuPont's Louis PlamBeck pointed out that photopolymer resin can be applied to image technology. In 1590, he obtained the first profit in this field. Hundreds of patented technologies are now widely used in everything from electronic materials to printing. In the past 30 years, photographic printing plates have made great strides in printing quality and have promoted the development of the flexographic printing industry.

5. What are the advantages of the photosensitive resin plate compared to the rubber plate?

(1) The shrinkage of the photosensitive resin plate is small, and no stretching deformation occurs during the plate making process. A precise plate can be produced with good dimensional stability.

(2) The photosensitive resin plate making process is simple, and the reproduction accuracy of the original is high.

(3) The side of the photosensitive resin plate is flat, and the compensation problem can be considered in the making of the bottom plate. It is not necessary to grind the plate back. Even if it is thinner than the plate, the plate can be made with high precision.

6. What is the composition of the solid photosensitive resin plate and how is its specific composition?

The solid photosensitive resin plate consists of a polyester film substrate, a photosensitive resin layer, and a polyester protective film. Unexposed raw materials contain several key components: binders, monomers, and photoinitiators.

7. Why do solid photographic plates have wider applications than liquid photographic plates?

The solid photosensitive resin plate uses a polyester base as a base material, a solid resin binder, a liquid monomer and a photoinitiator can be rolled on the base material, and the use of a solid binder to bind the liquid component provides a wider control range. Liquid plates are more limited in composition because solid plates have a wider range of applications than liquid plates.

8. What is the role of solid binders?

The solid binder has many uses, the most important being that it provides the resin monomer and the photoinitiator before the exposure of the carrier.

9. What is a photoinitiator?

Photoinitiators are molecules that initiate photopolymerization chain reactions under the action of light.

10. What is photopolymerization chain reaction?

Photopolymerization chain reaction refers to the polymerization process of the monomer molecules and the resin binder under the irradiation of UV light to form a three-dimensional network.

11. What is the typical plate making process?

Usually, the process of making the photosensitive resin plate is: back exposure - main exposure - development - rinse - drying - detackification - post-exposure.

12. How to prepare film and plate?

Films used in the production of flexo plates are to be selected as negative film with a density of 40 (after light treatment), and the dimensions of the flexographic plate should be appropriate. Note that in order to avoid waste of the plate when cutting the plate, the size of the negative film should be measured first, and then the plate is placed on the platen, and the plate is cut facedown, leaving a margin of 12mm on the plate edge. can.

13. What is the effect of back exposure? What is the relationship between back exposure time and plate thickness?

The photopolymer resin is polymerized by back exposure in order to increase the thickness of the substrate to support the relief graphic. The length of the back exposure time determines the thickness of the plate base. The longer the exposure time, the thicker the plate base and the thicker the printing plate; conversely, the thinner the plate base, the smaller the printing plate thickness.

14. How to back exposure?

The specific operation of the back exposure is as follows: the light source is warmed up for 5 minutes, the plate is placed face down on a print rack, the exposure timer is adjusted, and the full exposure of the depth of the relief is determined.

15. How to do a back exposure ladder test to determine the right back exposure?

In order to control the thickness of the substrate, which is to control the height of the relief, the platemaker often relies on experience (such as the data of the previous batch of plates) to determine the back exposure time and obtain a certain amount of plate thickness. However, depending on the previous batch of exposure parameters, there is a certain risk. With a precise approach, you can achieve the desired value, the back exposure step test. A series of back exposures at different times on the same plate were performed and rinsed without any positive exposure. The depth of the relief or the thickness of the substrate was measured for each of the different exposed areas to obtain the optimum back exposure time. In this test, the plate-making staff used time control. However, UV lamps will gradually age, and in a certain period of time, the ultraviolet light output of the UV lamp is not the same. In this way, using exposure energy units to measure is more scientific than using time units. According to the use conditions, monitoring the status of the UV lamp at a certain period of time can make the plate-making personnel make corresponding adjustments according to the lamp life. When using a precision-corrected UVA illuminometer to check the working condition of the lamp, the illumination wavelength of the illuminometer and the lamp should be consistent. Plate-making equipment manufacturers should recommend suitable illuminometers. At the same time, the back exposure ladder test should also be performed when replacing the plate supplier.

(to be continued)