Image formation apparatus

1. An image formation apparatus for forming a stereoscopic image by applying heat to a printing medium having a surface evenly coated with foaming capsules which foam when heated, comprising:

a plurality of conveyance rollers that feed the printing medium into the apparatus and convey the printing medium;

a conveyance guide that is formed into a convex shape whose apex is an image formation position where heat is applied to the printing medium, and regulates a position of the conveyed printing medium;

a thermal head that is installed such that a distal end portion contacts with a printing medium conveyed by the plurality of conveyance rollers from below the image formation position, and forms a stereoscopic image by applying heat to the printing medium; and

a tension unit that is positioned on an upstream side of the image formation position in a conveying direction of a printing medium, and pushes the conveyed printing medium toward the distal end portion of the thermal head by giving tension to the printing medium.

2. The apparatus according to claim 1 , further comprising a control unit that controls the tension unit to contact with and give load to the printing medium, when the printing medium is conveyed to the image formation position by the plurality of conveyance rollers.

3. The apparatus according to claim 2 , wherein

the tension unit is a tension roller that conveys the printing medium to the image formation position, and

when the printing medium is conveyed to the image formation position by the plurality of conveyance rollers, the control unit performs control to give torque to the tension roller such that the printing medium is pulled in a direction opposite to the conveying direction.

4. The apparatus according to claim 3 , wherein the tension roller is positioned below a distal end portion of the thermal head.

5. The apparatus according to claim 1 , further comprising a support roller that is placed in a position facing a distal end portion of the thermal head and contacts with the conveyed printing medium and pushes the printing medium toward the distal end portion of the thermal head, a portion of the support roller which contacts with the printing medium being formed by a material which does not crush a foaming portion of the printing medium.

6. The apparatus according to claim 5 , wherein the material is sponge.

7. The apparatus according to claim 2 , wherein in synchronism with a timing at which the printing medium is conveyed to the image formation position, the control unit calculates a heating time corresponding to a foaming height of each pixel in image formation data to be famed, and performs heating control on a plurality of micro heating elements formed in the thermal head in accordance with the calculated heating time.

8. The apparatus according to claim 7 , wherein the control unit fans an image by performing heating control on the plurality of micro heating elements for each line in a main scanning direction.

9. The apparatus according to claim 7 , further comprising a plurality of temperature sensors that sense heat storage states of the plurality of micro heating elements of the thermal head,

wherein the control unit corrects a heating control time corresponding to the image formation data based on sensing results from the plurality of temperature sensors.

10. The apparatus according to claim 1 , wherein the conveyance roller of the plurality of conveyance rollers, which is positioned on a downstream side of the image formation position in the conveying direction, conveys the printing medium by contacting with two end portions of the printing medium in a sub-scanning direction without contacting with a foamed portion where an image is formed.