Pen input device sheet with elastic layer having recessed protruding pattern facing a position detecting device

A pen input device sheet for a position detection region of a position detecting sensor, the pen input device sheet comprising:

• an elastic material layer that has elasticity and is composed of a plurality of layer portions stacked in a thickness direction of the pen input device sheet,
• wherein, in operation, a side opposite of a side of the position detecting sensor in the elastic material layer is a writing input surface to which writing input with an electronic pen is made,
• wherein the pen input device sheet is configured such that a vibration frequency characteristic of a kinetic friction coefficient when the electronic pen is moved at a predetermined speed on the writing input surface of the pen input device sheet matches the vibration frequency characteristic of the kinetic friction coefficient when a predetermined writing material is moved at the predetermined speed on a predetermined writing medium,
• wherein the pen input device sheet is configured such that a frequency that exhibits a peak magnitude of vibration of the kinetic friction coefficient defined by regarding, as a maximum value, an apex of a waveform of frequency distribution of magnitudes of the vibration in the vibration frequency characteristic of the kinetic friction coefficient when the electronic pen is moved at the predetermined speed on the writing input surface of the pen input device sheet in a state in which a predetermined writing pressure is applied is in a predetermined frequency range,
• wherein a hardness of a tip part of the predetermined writing material that comes into contact with the predetermined writing medium is one of a plurality of predetermined hardnesses, and
• wherein the frequency that exhibits the peak magnitude of the vibration of the kinetic friction coefficient is set according to the hardness of the tip part of the predetermined writing material.