Do not go around defaming your company, it will give a bad impression about you.

Give reasons such as:

☛ Professional Growth

☛ New challenges

☛ Change in profile

☛ Planning to relocate (if applicable)

☛ With time I found my job was becoming monotonous and I didn't want this to have any impact on the job I was doing for my employer

☛ I am not actively looking for a job change but, I saw this opening and it looked interesting.