How to search for “OR” word inside a Field on ElasticSearch?

I´m having a problem when I try to search into a field that stores the states acronyms.

I have the next query:

"query": {
"query_string": {
"query": "field_state:'OR' AND type:incentive"
And the problem comes when i try to get the results for the Oregon State (OR). For all the other states works but with this particular one is like the Elasticsearch takes the "OR" as a condition an retrieves all.

Is there a way to make this work????, i have try it with terms, prefix filters, and all with the same results.