checkbox field in editor

Hello,

I have the next checkbox with 2 posibles values "t" is checked and "f" is not checked:

         
{
                "label": "Login ST",
                "name": "login_status",
                "type": "checkbox",
                "ipOpts": [
                    {
                       "label": "",
                       "value": "t"
                    }
                ]
            },

When I save de form, in the database it save in blank. Why?

Than you!