Toyo Soflantec
creates comfortable lifestyles.




Japan Urethan Industries Institute

Sleeping comfort

The SS curve is a graph that shows a relationship between vertical stress and vertical strain. The feeling of use can be measured by measuring this. Generally, as the inclination of the graph is gentle, the feeling of use and sleeping comfort is good. To provide comfortable sleep, the mattress should sink while touching the body softly when a person lies on the bed, and finally supports the body. Soft urethane is generally excellent in drape (performance that covers the body) and body pressure dispersion performance, but rollover is difficult compared with hard urethane and the body touches the bed board if it is thin. Urethane that surrounds the body softly and is excellent in body pressure dispersion performance and urethane that supports the body and makes rollover easy are laminated, and totally coordinated in consideration of the pressure that changes according to weight and the curve of the body to create well-balanced products that suit each person.

SS curve(Deflection curve)


Push the foam and

measure the resistance.


The zone (1) corresponds to when a person lies on the mattress, i.e., the beginning of sinking. The gentler the inclination of the graph, the softer the feeling. The mattress in the blue line of the graph has a soft feeling and the mattress in the red line has a hard feeling when you lie on it.


The zones (2) to (3) correspond to the stages in which the body sinks in the mattress and is held. The mattress is designed to deflect gradually according to the weight, and hold the body while maintaining elasticity like the mattress in the blue line which has good sleeping comfort. On the other hand, the mattress in the red line that is hard in the initial stage, but has low resistance, does not hold the body well so that it touches the bed board soon and does not have good sleeping comfort.