Thiophene derivative and use thereof

A compound represented by the following general formula (I):

• wherein:
• R1 is hydrogen or halogen;
• R in the number of m are each independently halogen, C1-6 alkyl, C1-6 hydroxyalkyl, C1-6 alkoxy optionally having a substituent, C1-6 alkoxycarbonyl, or C1-6 alkylcarbonyl, or
• two R on adjacent ring carbon atoms are bonded to each other to form, together with the two adjacent ring carbon atoms linked thereto, a 5- or 6-membered ring containing 1-2 oxygen atoms;
• and
• m is 0, 1, 2 or 3,
• or a salt thereof.