Patterned birefringent product
A product comprising a patterned optically anisotropic layer having two or more regions of different birefringence in the form of a pattern, which further comprises a semi-transmissive-half-reflective layer having a transmittance of 30% or higher and a reflectance of 30% or higher is provided. The product permits visualization of a latent image in the product through a polarizing plate as well as visualization of the information on the side opposite to the side to be viewed from.
1. A patterned birefringent product comprising a patterned optically anisotropic layer having two or more regions of different birefringence in the form of a pattern, which further comprises a semi-transmissive-half-reflective layer having a transmittance of 30% or higher and a reflectance of 30% or higher, and a protective layer with a refractive index of 1.4 to 1.7,
wherein the product comprises the semi-transmissive-half-reflective layer, the patterned optically anisotropic layer, and the protective layer in this order,
wherein the regions of different birefringence are regions of different retardation,
wherein the thickness of the protective layer is in the range from 40 to 200 micrometers,
wherein the semi-transmissive-half-reflective layer which has the transmittance of 30% or higher and the reflectance of 30% or higher is disposed only at one side of the patterned optically anisotropic layer, and
wherein the patterned birefringent product permits the visual recognition of the birefringence pattern, through a polarizing plate or another device used for observation of the pattern, from the side of the protective layer.
2. The product according to claim 1 , wherein the patterned optically anisotropic layer has a region imparted with a retardation within a range of 30 to 1000 nm and a region imparted with a retardation within a range of less than 30 nm.
3. The product according to claim 2 , which is embrittled.
4. The product according to claim 2 , wherein the protective layer is a transparent polymer material.
5. The product according to claim 2 , comprising an adhesive layer between the patterned optically anisotropic layer and the protective layer, wherein the refractive index of the adhesive layer is in the range from 1.4 to 1.7.
6. The product according to claim 1 , wherein the patterned optically anisotropic layer is a layer that is formed of a composition comprising a liquid-crystal compound having at least one reactive group.
7. The product according to claim 6 , wherein the patterned optically anisotropic layer is formed by a method comprising steps below:
irradiating with heat or light a layer formed of a composition comprising a liquid-crystal compound;
subjecting the layer to patterned light exposure; and
heating the layer obtained to 50° C. or higher but not higher than 400° C.
8. The product according to claim 7 , wherein the patterned light exposure is scanning exposure.
9. The product according to claim 6 , wherein the liquid-crystal compound has at least one reactive group for radical polymerization and at least one reactive group for cationic polymerization.
10. The product according to claim 9 , wherein the reactive group for radical polymerization is acrylic group or methacrylic group, and the reactive group for cationic polymerization is vinyl ether group, oxetanyl group, or epoxy group.
11. The product according to claim 10 , which is embrittled.
12. The product according to claim 10 , wherein the two or more regions of different birefringence are in the form of a pattern which becomes visible when viewed through a polarizing plate.
13. The product according to claim 10 , wherein the protective layer is a transparent polymer material.
14. The product according to claim 10 , comprising an adhesive layer between the patterned optically anisotropic layer and the protective layer, wherein the refractive index of the adhesive layer is in the range from 1.4 to 1.7.
15. The product according to claim 1 , which is embrittled.
16. The product according to claim 1 , wherein the two or more regions of different birefringence are in the form of a pattern which becomes visible when viewed through a polarizing plate.
17. The product according to claim 1 , wherein the protective layer is a transparent polymer material.
18. The product according to claim 1 , comprising an adhesive layer between the patterned optically anisotropic layer and the protective layer, wherein the refractive index of the adhesive layer is in the range from 1.4 to 1.7.