■ Settings of this command affect multilingual characters and user-defined characters.
■ The underline has the same color as the characters.
■ Even if Kanji underline mode is specified, 90 clockwise-rotation characters,
white/black reverse characters, and spaces skipped by HT, ESC $, or ESC \ are not
underlined.
■ When a character size is changed, an underline width is not changed.
■ When underline mode is canceled, the following characters are not underlined;
however, an underline width set right before the mode is canceled remains.
■ Settings of this command are effective until FS ! is executed, ESC @ is executed, the
printer is reset, or the power is turned off.