Information recording medium, label, card and method of authentication

1. An information recording medium formed by laminating a transparent protective layer and a base material having laser color-developing properties, comprising:

an intermediate layer that is disposed between the transparent protective layer and the base material, wherein

the intermediate layer includes a diffraction structure layer that has a diffraction structure, and a first reflective layer that reflects visible light and is destroyed when irradiated with a laser beam; wherein

light, when incident from a transparent protective layer side, causes a diffracted light pattern to appear in the diffraction structure layer so as to be observable from the transparent protective layer side; wherein

a laser beam, when applied from the transparent protective layer side, passes through the diffraction structure layer, destroys the first reflective layer, and develops color in the base material; and wherein

a colored layer is disposed between the base material and the intermediate layer, the colored layer transmitting visible light of a second wavelength range and reflecting visible light outside the second wavelength range.

2. The information recording medium of claim 1 , wherein the colored layer contains a color former that develops color when irradiated with a laser beam and changes color-development intensity depending on laser irradiation conditions.

3. The information recording medium of claim 2 , wherein

the colored layer is enclosed between the base material and the intermediate layer so that a shape of the colored layer is not observable from outside, the colored layer having an arbitrary shape; and

the laser beam, when applied from the transparent protective layer side, develops color in a region where the colored layer is present and develops no color in a region where the colored layer is not present to enable observation of a region that has been colored conforming to the shape of the colored layer.

4. The information recording medium of claim 1 , wherein the intermediate layer is completely encapsulated in the base material or the transparent protective layer to configure an integrated laminate.

5. The information recording medium of claim 1 , wherein the base material is permitted to develop color in a color development pattern conforming to personal verification information.

6. A label to which the information recording medium of claim 1 is affixed.

7. A card to which the information recording medium of claim 1 is affixed.

8. An information recording medium formed by laminating a transparent protective layer and a base material having laser color-developing properties, comprising:

an intermediate layer disposed at a part between the transparent protective layer and the base material, wherein

the intermediate layer includes a diffraction structure layer that has a diffraction structure, a first reflective layer that reflects visible light and is destroyed when irradiated with a laser beam, and a second reflective layer that is not destroyed when irradiated with the laser beam, transmits light of a first wavelength range, and reflects visible light outside the first wavelength range; and

when the laser beam is continuously applied while being moved, from a transparent protective layer side, to both a region where the intermediate layer is disposed and a region where the intermediate layer is not disposed, a first laser beam that has entered the intermediate layer via the transparent protective layer passes through the diffraction structure layer, destroys the first reflective layer, passes through the second reflective layer and develops color in the base material, the base material in which color has been developed by the first laser beam being shielded by the second reflective layer and not being observable from the transparent protective layer side; and a second laser beam that has entered the base material via the transparent protective layer but not via the intermediate layer develops color in the base material, the base material in which color has been developed by the second laser beam being observable from the transparent protective layer side, to achieve a color development pattern having a countermark whose shape is determined by an arrangement of the intermediate layer.

9. A method of authentication applied to an information recording medium that is formed by laminating a transparent protective layer and a base material having laser color-developing properties, wherein

the information recording medium includes an intermediate layer disposed between the transparent protective layer and the base material;

the intermediate layer includes a diffraction structure layer that has a diffraction structure, and a first reflective layer that reflects visible light and is destroyed when irradiated with a laser beam; and

the information recording medium further includes a colored layer at a part between the base material and the intermediate layer, the colored layer developing color when irradiated with a laser beam, the method comprising

determining the information recording medium as being authentic if a color development pattern achieved with application of a laser beam from a transparent protective layer side of the information recording medium matches an arrangement of the colored layer, and determining the information recording medium as not being authentic if the color development pattern does not match the arrangement of the colored layer.

10. A method of authentication applied to an information recording medium that is formed by laminating a transparent protective layer and a base material having laser color-developing properties, wherein

the information recording medium includes an intermediate layer that is disposed at a part between the transparent protective layer and the base material; and

the intermediate layer includes a diffraction structure layer that has a diffraction structure, a first reflective layer that reflects visible light and is destroyed when irradiated with a laser beam, and a second reflective layer that is not destroyed when irradiated with the laser beam, transmits light of a first wavelength range, and reflects visible light outside the first wavelength range, the method comprising

when the laser beam is continuously applied while being moved, from a transparent protective layer side, to both a region where the intermediate layer is disposed and a region where the intermediate layer is not disposed, determining the information recording medium as being authentic if a color development pattern having a countermark, whose shape is determined by an arrangement of the intermediate layer, is achieved by color development of the base material, and determining the information recording medium as not being authentic if the color development pattern is not achieved by color development of the base material.