Frictional hinge device and a portable business machine into which the frictional hinge device is incorporated

A frictional hinge device comprising:

• a shaft member having a rotational axis as a rotational center;
• a support member which rotatably supports said shaft member;
• said support member being arranged so that said support member is rotatable relative to said shaft member, said support member being formed by a synthetic resin molded around said shaft member substantially in integral therewith to produce a surface frictional resistance between said support member and said shaft member due to a residual stress caused from a shrinkage allowance appeared when said synthetic resin is solidified;
• and
• an inequable strain distribution degree within said synthetic resin being 15% or less in order to equalize a strain distribution within said synthetic resin under the condition that a strain within said synthetic resin corresponds to 80% or less of a yield point when said synthetic resin is subjected to a tensile experimental test, wherein said inequable strain distribution degree (%) is expressed by (|maximum strain (minimum strain)−average strain|)×100/(average strain) in which a greater one is selected when compared said absolute value |maximum strain| with said absolute value |minimum strain|.