Using thermally transferred invisible ink detectable by exposure to invisible light of specific wavelength

A secrecy-protected facsimile machine comprising:

• receiving means for receiving transmit data based on an original which is transmitted from a facsimile transmission machine;
• recording means for recording an image of said original on a recording paper using invisible ink based on the transmit data received by the receiving means;
• and
• visual observation means for converting the image recorded in the invisible ink into a visible image and for displaying the visible image,
• wherein said visual observation means comprises:
• converting means for converting the image recorded in the invisible ink to an image of invisible light by irradiating the invisible ink with light of a predetermined wavelength,
• a sensor for detecting the invisible light of the image which is converted by the converting means, and
• displaying means for displaying an image in the invisible ink as a visible image based on the invisible light which is detected by the sensor.

A facsimile machine with a secrecy protection function comprising:

• receiving means for receiving transmit data based on an original which is transmitted from a facsimile transmission machine;
• recording means for recording an image of said original on a recording paper based on the transmit data received by said receiving means, said image being recorded by using one of visible ink and invisible ink,
• determining means for determining whether said transmit data indicates secret data or non-secret data;
• and
• control means for controlling said recording means to record said image using said visible ink if said determining means has determined said non-secrecy of data and for controlling said recording means to record said image with said invisible ink if said determining means has determined secrecy of data.