Problem with offset value with IR transmitter

I am trying to drive 3 ir leds from an ic using the following schematic :

This seemed to work for a while but at my receiver i am getting a strange offset value as if the transistor cant turn the led"s truly off at any time. Any ideas ?

I tried with another trasmitter and the receiver works fine

it mite help to have a 1k resistor in the base cct of the transistor :)

Dave