In the Blu-ray settings, turn off "Match TV Power State." You can also turn off HDMI CEC so that the TV cannot control the Blu-ray player. The last thing you can try is, in your TV settings, set the TV to default to an input of your choice, the last used, or none at all during power-up. If it's set to the past input and you were using your Blu-ray player, it will keep turning it on until you are on a different input when you power it off.
