Ink jet recording device

An ink-jet printing apparatus comprising:

• a web roll heating/supporting mechanism for supporting and heating a web roll formed by winding a sheet-like resin printing medium into a roll shape;
• a plurality of ink-jet printing heads which eject a plurality of water-based inks onto the printing medium that is wound off from the web roll and transported in a feeding direction thereof;
• a plurality of under heaters which each heat the printing medium from a rear side surface of the printing medium opposed to a front side surface thereof which faces to the respective ink-jet printing heads;
• a take-up mechanism for winding the printing medium around a take-up roll;
• a tension mechanism for applying a tension force to a portion of the printing medium which is located between the web roll heating/supporting mechanism and the take-up mechanism such that the portion of the printing medium is maintained in a uniform state without any deflection in the feeding direction;
• a plurality of temperature measuring devices which each measure a temperature of a surface of the printing medium;
• and
• a heating amount control device for controlling a heating amount of the web roll heating/supporting mechanism and heating amounts of the plurality of under heaters,
• in which when setting a plurality of measuring positions of the printing medium comprising a position of the printing medium at which the printing medium is wound into the web roll in the web roll heating/supporting mechanism and positions of the printing medium which are respectively located just below the plurality of ink-jet printing heads, the plurality of temperature measuring devices measure the temperatures of the surface of the printing medium at the plurality of measuring positions, respectively;
• and
• the heating amount control device controls the heating amount of the web roll heating/supporting mechanism and the heating amounts of the plurality of under heaters on the basis of the temperatures measured by the plurality of temperature measuring devices such that a difference between the temperatures measured at the measuring positions in the portion of the printing medium to which a tension force is applied falls within the range of 10° C.