Export Data to Excel export as incorrect format. Dataset uses to_char to convert number column (4226316)

When running a query, data results are returned as a string with the command TO_CHAR(). In the datagrid it displays the full number correctly as a string/text. But if right click | Export dataset | export format set to Excel Instance, the data in the newly created Excel displays as a number, not as a string and not as displayed in the editor.

EX:CREATE TABLE SYSTEM.test_tbl
(
  PRIM_KEY   NUMBER(19),
  COL_DESC   CHAR(4 BYTE),
  TEST_DATE  DATE
);

Insert into test_tbl
   (prim_key, col_desc, test_date)
 Values
   (1.00003013000539E18, 'Test', TO_DATE('02/07/2011 15:16:25', 'MM/DD/YYYY HH24:MI:SS'));

Run the following using F9, to display in data grid:

select to_char(prim_key),col_desc,test_date from test_tbl;

Right click | Export Dataset | save this as "Excel Instance". What is exported is the number itself 1.00003013000539E18, instead of the the expected full number as a string, 1000030130005390000.