Photopolymerizable composition containing a photosensitive donor and photoinitiating acceptor

DETAILED DESCRIPTION OF THE INVENTION An important feature of the photoabsorbers used in the present invention is their lack of photoinitiating groups.
A donor or combination of donors are sequentially activated to excited states but such excited states do not generate free radicals.
Rather, upon application of the second selected wavelenghts of energy, the donor molecules are transformed to a sufficiently high energy state so that transfer of energy to the acceptor molecule can occur.
The acceptor molecules bear the photoinitiating reactivity which via conventional free-radical intermediate generation results in the photopolymerization of the photopolymerizable vehicle.
Without the presence of the second selective wavelength of energy, the excited state or states of the donor molecules will not result in any generation of photo-initiating functionality.
Thus, the clarity and resolution of the vehicle is preserved which resolution permits precise control over the photopolymerization process for ensuring the generation of a three-dimensional figure within the vehicle which is of precise dimensions and surface configuration.
Of course, it will be appreciated that a series of donor molecules may be excited one after the other prior to ultimate generation of an acceptor in an excited state.
Thus, the use of three or more wavelengths of energy is comprehended within the broad teachings of the present invention.
A variety of relationships between the excited states of the donor and acceptor molecules must be maintained in order for the present invention to operate effectively and efficiently as described herein.
In order to explore these relationships more fully, reference is made to FIG.
1 which sets forth the energy transformation relationships between the donor and acceptor molecules.
The donor molecule initially is excited by the application of energy (h.
nu.
.
sub.
1) to a high S.
sub.
1 state which can then intersystem cross to a lower T.
sub.
1 state.
This process may or may not occur through radiationless transition from the S