Film shrinkage

Table VII. Glass Transition Temperatures and Film Shrinkage of UV-Hardened and Baked 7/3 NA-EBDMA Films...

Powder photographs were taken with a 57.3-mm radius Debye-Scherrer camera and nickel-filtered Cu Ka radiation (Xmean = 1.5418 A). For intensity work, the multiple-film technique was used. The lattice constant, derived from 23 reflections from 42.56° to 73.47° 20 and corrected for film shrinkage with a parallel film of a reference substance, was Oo = 15.02 A with an estimated standard deviation of 0.01 A. 

PSA Formulation and Properties. The formulations used in this study for the Hycar 2103-Prepolymer C and Hycar 2106-Prepolymer C PSA contain OH/NCO ratios of 1.7 and 1.3, respectively. Dibutyltin dilaurate catalyst is used at a 0.2 wt.% level based on the total adhesive solids. PSA samples are made from an 80% solids solution (by wt.) with a dry solvent system (27/73 by wt. of ethyl acetate-toluene) and cured at 150°C for 45 seconds. The samples are then evaluated by running 180° peel, static shear, rolling ball tack, and vinyl film shrinkage tests. 

These adhesive systems give an excellent combination of static shear (at both room temperature and 70°C) and rolling ball tack along with excellent vinyl film shrinkage resistance. The results of these tests are summarized in Table III. 

Knife-edges may also be used in this case as a basis for film-shrinkage corrections. 

The unsymmetrical, or Straumanis, method of film loading is shown in Fig. 6-5(c) and Fig. 3-12. Two holes are punched in the film so that it may be slipped over both the entrance collimator and the beam stop. Since it is possible to determine from measurements on the film where the incident beam entered the film circle and where the transmitted beam left it, no knife-edges are required to make the film-shrinkage correction. The point X (20 = 180°), where the incident beam entered, is halfway between the measured positions of lines 4,4 similarly, the point Y (20 = 0°), where the transmitted beam left, is halfway between lines 1,1. The difference between the positions of X and Y gives W, and 0 is found by proportion ... 

Unsymmetrical loading thus provides for the film-shrinkage correction without calibration of the camera or knowledge of any camera dimension. It is the most popular film arrangement. 

Thus, the overall error in 0 due to film shrinkage, radius error, centering error, and absorption, is given by the sum of Eqs. (11-5) and (11-8) ... 

Figure 11.50 Film shrinkage of PAR-700/A4 resist as a function of electron-beam dose. The nominal resist thickness was 400 nm.

These results point to two processes, premature radical chain termination and film shrinkage, which compete in determining the ultimate polymerization conversion efficient of multifunctional acrylates. It is obvious that critical attention must be paid to the pulse repetition rate, photoinitiator concentration, and acrylate functionality in developing any photopolymerizable system for laser-initiated polymerization. Future publications on laser-initiated polymerization of multifunctional acrylates will deal with monomer extraction of partially polymerized films, mechanical properties of laser polymerized films, and the Idnetics of single-pulsed systems. 

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