If you want to see more details about the ubuntu boot process or just want to turn off the splash screen, you can try the following ways:
1. Edit the grub.
$ sudo gedit /etc/default/grub
Then find the following lines:
delete the words quiet splash
So that later will become like this:
Once finished save and exit immediately.
2. The second step is to update grub.
$ Sudo update-grub
Please restart your computer ..