Use strict escaping.
Source position: fpjson.pp line 420
| public TJSONString.StrictEscaping : Boolean; | 
StrictEscaping indicates that only the absolutely necessary characters will be escaped (when set to True) when convering string values to JSON If set to False/ will also be escaped, although this is strictly speaking not necessary.
| 
 | Convert a string to a JSON-escaped string. |