the denominator if the same spd film formulation also uses less matrix polymer it will also result in a lower phase ratio particle number because the value for the matrix capsule ratio is in the numerator therefore an spd film formulation made by increasing the particles in the capsule and de creasing the amount of matrix polymer relative to the capsule phase will yield a dark low off state t spd film that will be represented by low phase ratio particle number on the other hand an spd film made by decreasing the particles in the capsule phase and increasing the amount of matrix polymer will yield lighter high off state t spd film in this case a high value for the matrix capsule in the numerator and a low value for the particles in the denominator will be represented by a high value for the ratio particle the following table includes non limiting examples of spd emulsion formulations to achieve spd films with dark off state transmittances lt 0 5 t and other spd films with very clear on state transmittances gt 70 t the table also includes other examples where the transmittance requirements of the invention were not met for illustrative and comparative purposes all of the examples in the table were prepared in the same manner 0 3 irgacure 819 photoinitiator was dissolved in the matrix polymer prior to mixing said matrix polymer with the capsule phase to form the spd emulsion a 4 mil thick layer of spd emulsion was sandwiched between two 7 mil thick ito pet substrates and identical uv irradiation conditions were employed to cure the samples analyzing the.