The poles of Padé approximants to $_1F_1(1;c;z)$

We construct some regions without zeros of the confluent hypergeometric function $_1F_1(-n;d;z)$ ($n\in\mathbf N, d\in\mathbf C$). The main result is as follows. If
$$ -n+\frac7{16}\geq\operatorname{Re}(d),\quad_1F_1(-n;d;z)=0, $$
then
$$ -\operatorname{Re}(d)-\operatorname{Im}(d)\operatorname{tg}\biggl(\frac{\arg(z)}2\biggr) \geq|z|>\operatorname{Re}(z)+2\biggl(-n+\frac7{16}- \operatorname{Re}(d)\biggr). $$