How to send IR data from Arduino to USB-TTL
You are transmitting data by encoding it using one of probably many Sony Consumer Remote Control formats and expecting to decode it using one of many possible RS232 like formats.  You will likely get something between nothing and random values. 

Instead, consider sending data using only the RS232 protocols.  This is what is done in this tutorial.  It is recommended you replicate the tutorial before moving on to using a TTL to USB dongle and a computer.  This should validate the transmitter is working.  Note in the tutorial transmitter code example no IR  remote control library is used.  Only the common serial libraries.

A word regarding the tutorial.  Consider using the second of the two examples in the tutorial.  The first does not modulate the IR transmitter and will not work with commonly available IR receivers.  The second does modulate the IR transmitter and discusses how to alter the modulation to accommodate different IR receivers.