Serial.println("Opening the file: " + String(file_name1) + " done.");
Pissing away resources on the String class to save having to use three Serial.print() calls is the height of laziness.
ibuffer = File1.read();
The read() method that takes no arguments returns ONE character. You can NOT assign one character to an entire array. There is another version of the read() method that takes two arguments - an array to store data in and a number that defines the amount of data to read. RTFM.