I don't think CD4050 is a good choice to drive anything; it is just a buffer (typical application includes CMOS to TLL or CMOS at a Lower VDD), and, to increase the output current, what you need is a driver ..
Forgive me if I ask this question, but are you aware that in CD4050 the Vdd pin is pin nr 1 , not 14?
Maybe this is the reason the display goes off?
However, if you don't want to use discrete transistors, or transistor arrays, then the other option is to employ typical drivers, such as, for example,7407 (open collector output - good for sinking current), or for both, sinking and sourcing, consider 74HCTXX, 74ACQ (or similar) buffers/drivers (CD/SN74HCT241: h**p://focus.ti.com/lit/ds/symlink/cd74hct241.pdf ), and even paralleling them to increase output current(s) capability ..
Regards,
IanP