Differences and Similarities between Digital Flexible Platemaking and Traditional Pattern Making (I)

After more than 20 years of hard and winding development in China, traditional flexo printing has finally ushered in a new period of development—the CDI digital laser engraving machine. In March 2001, it first entered the Xinhua Precision Plate (Shanghai). ) Ltd.

CDI is a flexo direct platemaking system developed by Barco and DuPont in the process of summarizing the problems encountered in the development of traditional flexographic printing. While the quality improvement and development of flexo printing is a relatively complicated system project, the quality of platemaking is undoubtedly a key link! Therefore, recognizing the similarities, differences, and disadvantages between CDI and traditional plate making will promote Chinese flexographic technology. The development has a very important role. CDI laser flexography has digital high quality and high stability detectability; while traditional flexography has many uncontrollable factors.

From micro viewing, CDI does not use film. Therefore, in order to avoid the well-known disadvantages of the traditional version, such as film folding and dusting, the process and structure of dot formation have also undergone qualitative changes.

First, the difference between the quality of the traditional flexographic printing plate diffusion diffused UV light tube and the CDI laser plated YAG laser beam: the diffusion of scattered light through the network point light hole, will produce a large number of diffraction phenomenon to make the edge of the virtual, and multiple YAG laser To ablate a network point directly, the realities of its edges can be imagined.

Second, the traditional flexographic negative film is output from the offset plateetter. The maximum density of the general film is about 35～40, but under the high-net point traditional flexible version of the UV light tube, the exposure is less, and the finer points of the sun do not come out; the exposure time is long and the fine ideas appear. But there are fine dirt spots. The amount of laser light must be increased to allow the laser to be used extraordinarily. The density of the film output must be greater than 42 and close to 4  5 in order to be used. This shows that the requirements for the density value of offset printing film are different from the requirements for the density of flexo printing high-line counts. The CDI version does not have this phenomenon.

Third, the traditional version in the exposure, in order to prevent the VU lamp arrangement after the striped light and dark uneven, so the light pipe and film will be added between a matte flashing film. In this way, the original diffused UV light passes through the frosted glittering film, on the one hand, the light of the strip-shaped light pipe becomes more uniform, and on the other hand, a large amount of light scattering phenomenon is inevitably generated, so that a large amount of expansion of the exposed dot edges occurs. And blur.

Fourth, since the flexible plate material is soft and not completely flat, there may be problems in the airtightness of the film and the plate material. Therefore, for high-precision net products, a matte-layered film output is often used to improve the degree of adhesion during printing. In this way, due to the presence of the matte layer between the plate and the film, the diffuse scattering of the UV light source and the uniform scattering of the matte glitter sheet further exacerbates the light diffraction phenomenon when the film dots are exposed to the surface of the plate material, resulting in the film. It is difficult to control the phenomenon of light penetration in the process of transfer to the plate.
5. The phenomenon of uncontrollable optical permeation enlargement in such a network transfer is manifested on the one hand by the proportion of different perimeters with the percentage of the network points when making a flexographic plate, which results in different percentages of the optical permeation enlargement value. On the other hand, due to the phenomenon of light scattering, the sensitivity around the dots is different, and the steepness of the edge of the corresponding dot is reduced to form a “buntou” shape. In this way, the area and the shape of the top portion of the dots do not have a practical effect under the transfer of the flexographic pressure, but the size of the dot on the print is changed by the actual amount of the depressed portion after passing through the pressure. This is also the point at which it is difficult to control the changes in the amount of dots between a computer's display and the actual print when the traditional flexible platemaking is performed.

Sixth, the traditional flexographic printing UV light tube, with the extension of the use of time, there is a decay curve from the new to the aging. This shows that in the new light tube, the photosensitivity is strong, the exposure time is relatively short, and the light penetration is relatively small; but with the gradual aging of the UV light tube, the light efficiency is weakened, the exposure time is gradually extended, the fine dots are not easy to come out, but the light of the deep point The osmotic expansion is becoming more and more severe, resulting in the traditional version even if the same sub-film is on the same stencil. After a certain period of time, the flexible version of the sun-dried flexible stencil will change from a deep web to a shallow web. Different curves will also change! This light decay physics is also one of the reasons why traditional flexible platemaking cannot be controlled.