Point light source drying flexographic resin version of the exposure test II

Exposure test

We used a point light source exposure machine and a general exposure machine to perform a series of exposure tests to answer this question: What effects can a point exposure device use for exposure of flexo plates and after exposure processing in a certain environment?

The test material was selected from a multi-spinning equipment supplier and a flexo plate using a 1.14 mm thin flexo plate material recommended by the customer for use with a point light source printing machine. We use the graphic depth of drying out between 0.6 and 0.7mm for this printing requirement.

To realize the main exposure of the idea on the printing machine, we tested the adjustment step by step in the following order:

brightness

Scattered light

The length of exposure time

Firmness of outlets (based on 1% of 120 lines and 2% outlets? basis)

Robustness and independent presence width 0.1mm line or diameter 0.1mm dot reproduction

Width ? 0.08mm reverse line depth reproduction

Evaluation of test results

Imprint shape and its firmness

To ensure that all the tested factors can be clearly printed, the point light source exposure machine is required to expose the printing plate with the highest light intensity and at least astigmatism over 50%. The visual evaluation of the exposure results by eye alone, especially the evaluation of sharp dots is extremely unscientific. Because of the limited ability of the human eye to discriminate, if the tiny dots are not enlarged, we cannot see its shape at all. In fact, the printing plate's Internet access point should form a firm bond with the foundation from the beginning, but it will cause the screen to tilt and the ruggedness of the edge of the screen to be reduced. These phenomena can only be clearly seen under the electron microscope.

It is an important means to evaluate the pros and cons of the printing plate that printing on the flexographic plate independently exists. People often use a width of 0.1mm Yangxian to evaluate. For a high-sensitivity printing plate, the main exposure time is about 20 minutes, that is, the undulation of the ray is not generated, and for the printing plate with the low sensitivity, the wavy line shape cannot be removed even if the exposure time is 45 minutes. The stability of a fine masculine imprint on a general stencil depends on the type and location of the adjacent elements. At the edge of the plate, if there are other imprints, it is stronger. But if there is only a single existence, then it will lose some of its solidity. For the dots or threads in the middle of the printing plate, their firmness with the foundation is stronger.

Exposure latitude

In the field of flexographic platemaking, it is stipulated that the lower limit of the exposure latitude: the number of screen lines and the 120 line network.

2% of the dots in the dot area can be sun-dried, that is, the width of the positive line of 0.1mm can be dried out. Its upper limit is the width of 0.08mm anti-white line can reach the depth defined in advance. Although this is a previously established standard, it is still being used on light source printers to evaluate the latitude of exposure latitude. The purpose of our test in this way is to prove that we can guarantee the perfect reproduction of the thin lines while also ensuring that the reproduction quality of the original anti-white lines is not lost.

During the printing process of the point light source, it was clearly shown that the soft exposure latitude is small and there is not even a forgiving exposure. They usually show a straight line with a width of 0.1 mm with strong enough solidity, but the depth of the depression is not enough or the clarity of the line is lacking. Instability of the plate material, the complexity of the plate layout image, and the instability of the film quality can have an important influence on the exposure process and exposure latitude. As we all know, the sharp dots that exist on the printing plate alone are higher than the surrounding full plates. This may be due to material expansion due to incomplete exposure of the sharp dots and the substrate. The sharp dots can be significantly strengthened by increasing the amount of scattered light or extending the exposure time.

To make the exposure latitude work well, we have tried to use UV filters to filter out the unwanted UV components that exist in the emission spectrum of point light sources. However, it is regrettable that the luminous intensity of the light source is also reduced while removing the UV component. Therefore, this idea does not work.

Plate edge

The presence of dot dips at the edge of the plate is a common headache for spot light exposure machines, and this tilt angle is surprisingly consistent with the incident angle of incident light. When the exposure is insufficient, the inclination angle of the printing plate internet point is disorderly, and when the exposure is normal or overexposed, the inclination direction of the printing plate internet point points to the light source. This phenomenon occurs because the light emitted by the point light source is obliquely irradiated to the edge of the printing plate instead of being vertically irradiated. People can use mirrors to correct this phenomenon, but the cost is relatively high, so it is not used in actual production.

Total

Although the point light source exposure apparatus can photosensitize most of the flexographic resin plates, it has the following obvious deficiencies with respect to conventional exposure equipment:

The exposure machine has a certain significance for a small-format, relatively thin-thickness flexo plate. For deep

The drying requirement of degree greater than 0.6mm (with longer exposure time, but we find the middle depth is relatively poor), taking into account that to reach a steep enough dot, we accepted the recommendation of the dot exposure equipment provider, using 40% Astigmatism ingredients. However, unfortunately found: the depth can not exceed 0.5mm.

Insufficient resolution of the plate (because the dots have a certain tilt angle and the thin lines are wave-like, so the lack of stability in reproducing fine dots).

Copy results are not ideal and format restrictions. In point exposure equipment, the quality of the film, the layout image on the film, and the photosensitivity of the printing plate material have a great influence on the printing and copying results. The position of the light source relative to the plate material sometimes affects the shape of the dot.

Long Chen Printing Technology Network