Thermally expandable sheet and thermally expandable sheet production method
A thermally expandable sheet includes: a first thermally expansive layer that is formed on one side of a base and contains a first thermally expandable material; and a second thermally expansive layer that is formed on the first thermally expansive layer and contains a second thermally expandable material, wherein the second thermally expandable material further contains white pigment.
1. A thermally expandable sheet comprising:
a base;
a first thermally expansive layer formed on the base and comprising a first thermally expandable material; and
a second thermally expansive layer formed on the first thermally expansive layer and comprising:
a second thermally expandable material; and
white pigment,
wherein the first thermally expansive layer does not comprise white pigment.
2. The thermally expandable sheet according to claim 1 ,
wherein the white pigment comprises a material selected from titanium oxide, barium sulfate, and zinc oxide.
3. The thermally expandable sheet according to claim 1 , further comprising:
an ink reception layer formed on the second thermally expansive layer and configured to receive ink.
4. The thermally expandable sheet according to claim 3 ,
wherein the ink reception layer comprises porous silica.
5. The thermally expandable sheet according to claim 4 ,
wherein a thickness of the second thermally expansive layer is thinner than a thickness of the first thermally expansive layer.
6. The thermally expandable sheet according to claim 5 ,
wherein the first thermally expandable material and the second thermally expandable material are the same material.
7. The thermally expandable sheet according to claim 6 ,
wherein each of the first thermally expandable material and the second thermally expandable material comprise microcapsules, wherein each of the microcapsules comprises a shell and a vaporizing substance in the shell, and
wherein a thickness of the second thermally expansive layer corresponds to a combined thickness of one to ten times the average particle size of the microcapsules.
8. The thermally expandable sheet according to claim 4 ,
wherein each of the first thermally expandable material and the second thermally expandable material comprise microcapsules, wherein each of the microcapsules comprises a shell and a vaporizing substance in the shell, and
wherein a thickness of the second thermally expansive layer corresponds to a combined thickness of one to ten times the average particle size of the microcapsules.
9. The thermally expandable sheet according to claim 1 ,
wherein a thickness of the second thermally expansive layer is thinner than a thickness of the first thermally expansive layer.
10. The thermally expandable sheet according to claim 1 ,
wherein the first thermally expandable material and the second thermally expandable material are the same material.
11. The thermally expandable sheet according to claim 1 ,
wherein the first thermally expansive layer further comprises a first binder, wherein the first thermally expandable material is dispersed in the first binder,
wherein the second thermally expansive layer further comprises a second binder, wherein the second thermally expandable material and the white pigment are dispersed in the second binder,
wherein the thermally expandable sheet further comprises a third thermally expansive layer provided between the base and the first thermally expansive layer and comprising a third binder and a third thermally expandable material dispersed in the third binder,
wherein a ratio, defined by volume, weight or density, at which the third thermally expandable material is contained in the third binder is lower than a ratio, defined by volume, weight or density, at which the first thermally expandable material is contained in the first binder.