Influencing Factors and Mathematical Description of Coating Uniformity of Holographic Coatings (II)

2 Evaluation of Coating Uniformity [6]

In the formula, the values ​​of i and j are determined by the determinants and random factors that affect the evaluation. According to equation (6), the total inhomogeneity ε of the coating film at a certain point at x can be characterized by the average value of the determined influence and the error caused by the random influence. The error bandwidth indicates the probability of a random event.

By integrating equation (6) over the entire coating width, a thickness non-uniformity curve can be obtained (see Figure 5). The width of the curve deviation band represents the random effect within the standard deviation range. The deviation band gives the theoretical limit of deviation within which an actual measured curve is given.

In order to more simply and intuitively represent the unevenness of the coating, the introduction of the parameter ε0 indicates the difference between the highest point and the lowest point of the deviation band. For example, in Figure 5, ε0 = 0.75 - ( - 1.02) = 1.77%.

By the same token, the coating optical density non-uniformity curve and unevenness can be obtained.

3 Conclusion

This paper, combined with the practical application of paper holographic printing technology, analyzes the influence of various factors on coating uniformity in the coating process of holographic coating, and classifies the influencing factors into deterministic and random factors. A mathematical model describing the uniformity of coating was established, two technical indexes for evaluating optical density variation and thickness variation of coating uniformity were determined, and a corresponding evaluation method was given. To further study the rheological behavior of the coating process and optimize the setting of coating process parameters, a certain theoretical basis is provided.

Author: Xie Yong, Peng Tao (Zhuzhou Institute of Technology)
Source: Packaging Engineering, Issue 3, 2005