You say "I have some ___ news" when you have news to tell someone. "News" is new information that you think they want to know.
You can use adjectives to say how you think the listener will feel about your information:
- good news
- bad news
- interesting news
When you say "I have some ___ news", it prepares the listener to pay attention to what you're going to say to them. If you don't use this phrase before telling someone important information, it can seem too sudden. The listener might not notice what you're telling them.