Abstract: A label (1) of this invention includes an optical function layer (13) configured to pass light of a certain wavelength, a light absorption layer (15) facing the optical function layer (13) and configured to absorb the light of the wavelength, and a light scattering layer (12) intervening between the optical function layer (13) and the light absorption layer (15) and including hollow bodies configured to scatter the light of the wavelength. The light scattering layer (12) is configured to raise a transmittance at the wavelength upon receiving external heat.

Abstract: A label (1) of this invention includes an optical function layer (13) configured to pass light of a certain wavelength, a light absorption layer (15) facing the optical function layer (13) and configured to absorb the light of the wavelength, and a light scattering layer (12) intervening between the optical function layer (13) and the light absorption layer (15) and including hollow bodies configured to scatter the light of the wavelength. The light scattering layer (12) is configured to raise a transmittance at the wavelength upon receiving external heat.

Abstract: An ink cartridge has a label portion on a wall surface of one periphery of a case forming an ink accommodating unit. The label unit has an optical functional layer that allows a predetermined wavelength of light to pass, an optical dispersion layer that includes hollow bodies, and an optical absorptive layer that absorbs the first wavelength of light, which are laminated in this order, and the optical absorptive layer is a surface side of the case. When the optical reflective layer is heated from a heating unit directed to the label portion at a temperature of damaging the hollow bodies, the dispersion of the light is suppressed by the damage to the hollow bodies, and the transmittance of the wavelength of light is irreversibly raised.