Method for manufacturing a multilayer data medium with security marking which can be marked by laser

1. A method for manufacturing a multi-layer data medium by hot rolling a stack of a plurality of superimposed layers under pressure, the stack of plurality of superimposed layers comprising at least one layer made of at least one thermoplastic material able to be marked by laser radiation applied to at least one outer surface of said data medium, the method comprising:

providing at least one covering layer which is transparent to marking laser radiation, the at least one covering layer extending between said outer surface and a laser marking sub-layer sensitive to the laser radiation so as to permit production of a marking in the marking sub-layer when the laser radiation passes through each covering layer;

incorporating at least one marking with an optically variable effect disposed with respect to the laser marking sub-layer so that said outer surface has a portion with optically variable effect optically superimposed on at least one part of the laser marking sub-layer and a portion without marking with optically variable effect optically superimposed on at least one part of the laser marking sub-layer, wherein

said at least one covering layer also incorporates at least one marking agent which is sensitive to said laser radiation so as to permit production of a marking in said at least one covering layer when subject to the laser radiation, and wherein said portion without marking with optically variable effect and said portion with optically variable effect are produced with at least one marking agent which is sensitive to said laser radiation, between said outer surface of the medium and said laser marking sub-layer, and

wherein said portion without marking with optically variable effect and said portion with optically variable effect are different from one another, and

wherein said portion without marking with optically variable effect is without any marking agent which is sensitive to said laser radiation, at least one marking agent which is sensitive to said laser radiation being incorporated into at least one covering layer only in said portion with optically variable effect.

2. The method according to claim 1 , wherein each marking with optically variable effect is disposed with respect to the laser marking sub-layer so that said laser marking sub-layer extends facing at least one separation between the portion with optically variable effect and the portion without marking with optically variable effect.

3. The method according to claim 1 , wherein said contents of at least one marking agent which is sensitive to said laser radiation are selected so that the laser marking obtained when subject to said laser radiation, as seen from said outer surface, is at least substantially homogeneous.

4. The method according to claim 1 , wherein at least one covering layer incorporating at least one marking agent which is sensitive to said laser radiation and at least one covering layer comprising at least one marking with optically variable effect are optically superimposed.

5. The method according to claim 1 , wherein at least one marking agent which is sensitive to said laser radiation is incorporated in at least one covering layer comprising at least one marking with optically variable effect.

6. The method according to claim 1 , wherein each covering layer and the laser marking sub-layer are hot rolled under pressure after production of each marking with optically variable effect.

7. The method according to claim 2 , wherein said contents of at least one marking agent which is sensitive to said laser radiation are selected so that the laser marking obtained when subject to said laser radiation, as seen from said outer surface, is at least substantially homogeneous.

8. The method according to claim 1 , wherein at least one covering layer incorporating at least one marking agent which is sensitive to said laser radiation and at least one covering layer comprising at least one marking with optically variable effect are optically superimposed.

9. An official document comprising a multi-layer data medium comprising at least one layer made of at least one thermoplastic material, able to be marked when subject to laser radiation applied to at least one outer surface, comprising:

at least one covering layer

which is transparent to marking laser radiation,

said covering layer extending between said outer surface and placed covering a laser marking sub-layer, the laser marking sub-layer sensitive to laser radiation so as to permit production of a marking in the marking sub-layer by laser radiation through each covering layer,

the multi-layer data medium further including at least one marking with an optically variable effect disposed with respect to the laser marking sub-layer so that said outer surface has a portion with an optically variable effect optically superimposed on at least one part of the laser marking sub-layer and a portion without marking with the optically variable effect optically superimposed on at least one part of the laser marking sub-layer, wherein

said at least one covering layer further includes at least one marking agent which is sensitive to said laser radiation so as to permit production of a marking in said at least one covering layer when subject to the laser radiation, said portion without marking with optically variable effect and said portion with optically variable effect have contents of at least one marking agent which is sensitive to said laser radiation, between said outer surface of the medium and said laser marking sub-layer, and wherein said portion without marking with optically variable effect and said portion with optically variable effect are different from one another, and wherein at least one outer surface has at least one laser marking, and

wherein at least one laser marking is optically superimposed on at least one separation between at least one marking with optically variable effect and the portion without marking with optically variable effect, and wherein said laser marking is at least substantially homogeneous as seen from said outer surface.

10. A method for manufacturing a multi-layer data medium by hot rolling a stack of a plurality of superimposed layers under pressure, the stack of plurality of superimposed layers comprising at least one layer made of at least one thermoplastic material able to be marked by laser radiation applied to at least one outer surface of said data medium, the method comprising:

providing at least one covering layer which is transparent to marking laser radiation, the at least one covering layer extending between said outer surface and a laser marking sub-layer sensitive to the laser radiation so as to permit production of a marking in the marking sub-layer when the laser radiation passes through each covering layer;

incorporating at least one marking with an optically variable effect disposed with respect to the laser marking sub-layer so that said outer surface has a portion with optically variable effect optically superimposed on at least one part of the laser marking sub-layer and a portion without marking with optically variable effect optically superimposed on at least one part of the laser marking sub-layer,

wherein said at least one covering layer also incorporates at least one marking agent which is sensitive to said laser radiation so as to permit production of a marking in said at least one covering layer when subject to the laser radiation,

wherein said portion without marking with optically variable effect and said portion with optically variable effect are produced with at least one marking agent which is sensitive to said laser radiation, between said outer surface of the medium and said laser marking sub-layer,

wherein said portion without marking with optically variable effect and said portion with optically variable effect are different from one another,

wherein each marking with optically variable effect is disposed with respect to the laser marking sub-layer so that said laser marking sub-layer extends facing at least one separation between the portion with optically variable effect and the portion without marking with optically variable effect, and

wherein said portion without marking with optically variable effect is without any marking agent which is sensitive to said laser radiation, at least one marking agent which is sensitive to said laser radiation being incorporated into at least one covering layer only in said portion with optically variable effect.

11. A method for manufacturing a multi-layer data medium by hot rolling a stack of a plurality of superimposed layers under pressure, the stack of plurality of superimposed layers comprising at least one layer made of at least one thermoplastic material able to be marked by laser radiation applied to at least one outer surface of said data medium, the method comprising:

providing at least one covering layer which is transparent to marking laser radiation, the at least one covering layer extending between said outer surface and a laser marking sub-layer sensitive to the laser radiation so as to permit production of a marking in the marking sub-layer when the laser radiation passes through each covering layer;

incorporating at least one marking with an optically variable effect disposed with respect to the laser marking sub-layer so that said outer surface has a portion with optically variable effect optically superimposed on at least one part of the laser marking sub-layer and a portion without marking with optically variable effect optically superimposed on at least one part of the laser marking sub-layer,

wherein said at least one covering layer also incorporates at least one marking agent which is sensitive to said laser radiation so as to permit production of a marking in said at least one covering layer when subject to the laser radiation,

wherein said portion without marking with optically variable effect and said portion with optically variable effect are produced with at least one marking agent which is sensitive to said laser radiation, between said outer surface of the medium and said laser marking sub-layer,

wherein said portion without marking with optically variable effect and said portion with optically variable effect are different from one another,

wherein said contents of at least one marking agent which is sensitive to said laser radiation are selected so that the laser marking obtained when subject to said laser radiation, as seen from said outer surface, is at least substantially homogeneous,

wherein said portion without marking with optically variable effect is without any marking agent which is sensitive to said laser radiation, at least one marking agent which is sensitive to said laser radiation being incorporated into at least one covering layer only in said portion with optically variable effect.