Sheet material comprising at least one watermark having a colored shade

1. A sheet material, comprising:

at least one first fibrous layer having at least one first color; and

at least one second layer comprising at least one watermark having at least one second color,

wherein at least one of the first and second layers incorporates at least one dyeing agent in its mass, chosen so as to give said layer a colored shade appearing approximately continuous to the naked eye, and

wherein the first layer comprises at least one watermark, the at least one watermark of the first layer and the at least one watermark of the second layer comprising adjacent and/or superposed portions and being arranged in such a way as to cooperate when the material is observed in transmitted light to form a composite pattern chosen from at least one of an alphanumeric character, a symbol, a logo, and a drawing.

2. The material according to claim 1 , the second layer being a fibrous layer.

3. The material according to claim 1 , at least one of the first and second layers having a lightness L* greater than 70.

4. The material according to claim 1 , the second layer exhibiting a color having a saturation C* less than 50.

5. The material according to claim 1 , the first and/or the second layer incorporating in its mass at least one dyeing agent chosen from a direct dye, an acid dye, a basic dye, an organic or mineral pigment.

6. The material according to claim 1 , the two layers defining two opposite outer surfaces of the sheet material.

7. The material according to claim 1 , comprising a third coating layer comprising at least one dyeing agent, the three layers notably having different colors.

8. The material according to claim 1 , the second fibrous layer having a blue shade.

9. The material according to claim 1 , comprising two opposite outer surfaces having different colors in reflection.

10. The material according to claim 1 , wherein the watermarks are intaglio watermarks having shaded tones.

11. The material according to claim 1 , wherein the at least one watermark of the second layer is a watermark with a multitone effect comprising a series of light areas arranged to form a half-tone image with a multitone effect.

12. The material according to claim 1 , the first layer defining an outer surface of the sheet material.

13. The material according to claim 1 , the first and second colors having at least different saturations C* and/or hue angles.

14. A secure document and/or a value document comprising a sheet material according to claim 1 .

15. The material according to claim 2 , the second layer being cellulose-fiber based.

16. The material according to claim 3 , the lightness L* being greater than 80 or 90.

17. The material according to claim 4 , the saturation C* being less than 35 or 20.

18. The material according to claim 9 , the two opposite outer surfaces having different saturation C* and/or hue angles.