Coated board of wood-based material

1. A coated board of wood-based material, comprising a board of wood-based material having a front side and a rear side, and a polymer coating on the front side of the board of wood-based material, wherein the polymer coating has an inner area predominantly formed of a first polymer having a first hardness in a cured state, an outer area predominantly formed of a second polymer having a second hardness in a cured state that is greater than the first hardness, the first polymer being different than the second polymer, and an intermediate area between the inner and outer areas, the intermediate area having a concentration gradient of the first and second polymers, the concentration of the first polymer in the intermediate area continuously decreasing going from the inner area toward the outer area and the concentration of the second polymer in the intermediate area continuously decreasing going from the outer area toward the inner area, such that the hardness of the polymer coating continuously decreases with increasing depth viewed from an outer surface of the polymer coating.

2. The coated board of wood-based material according to claim 1 , wherein the polymer coating has a hardness gradient that corresponds to the following formula:

(−3,0* x )+ C<=Y ( x )<=(−0,2* x )+ C

wherein:

x is the absolute value of the depth in μm of the coating viewed from the surface of the coating;

Y(x) is the absolute value of the hardness in N/mm 2 at a certain depth x; and

C is the absolute value of the initial hardness in N/mm 2 of the coating at a depth of approximately x≈0-5 μm.

3. The coated board of wood-based material according to claim 1 , wherein the polymer coating has a hardness gradient that corresponds to the following formula:

(−2,5* x )+ C<=Y ( x )<=(−0,4* x )+ C

wherein:

x is the absolute value of the depth in μm of the coating viewed from the surface of the coating;

Y(x) is the absolute value of the hardness in N/mm 2 at a certain depth x; and

C is the absolute value of the initial hardness in N/mm 2 of the coating at a depth of approximately x≈0-5 μm.

4. The coated board of wood-based material according to claim 1 , wherein the polymer coating has a hardness gradient that corresponds to the following formula:

(−2,0* x )+ C<=Y ( x )<=(−0,6* x )+ C

wherein:

x is the absolute value of the depth in μm of the coating viewed from the surface of the coating;

Y(x) is the absolute value of the hardness in N/mm 2 at a certain depth x; and

C is the absolute value of the initial hardness in N/mm 2 of the coating at a depth of approximately x≈0-5 μm.

5. The coated board of wood-based material according to claim 1 , wherein the board of wood-based material is a chip board, MDF board, HDF board, OSB board or real wood board.

6. The coated board of wood-based material according to claim 1 , wherein the polymer coating consists of polymers which are curable by means of radiation.

7. The coated board of wood-based material according to claim 1 , wherein the polymer coating has an initial Martens hardness at a depth of approximately 0-5 μm from 120 N/mm 2 to 250 N/mm 2 measured according to DIN ISO 14577.

8. The coated board of wood-based material according to claim 1 , wherein the polymer coating has an initial Martens hardness at a depth of approximately 0-5 μm from 130 N/mm 2 to 200 N/mm 2 measured according to DIN ISO 14577.

9. The coated board of wood-based material according to claim 1 , wherein the polymer layer includes abrasion-resistant particles.

10. The coated board of wood-based material according to claim 9 , wherein the abrasion-resistant particles include corundum particles.

11. A floor covering comprising a plurality of the coated boards of wood-based material according to claim 1 .

12. A floor panel made by a method comprising the following steps:

a) providing a board of wood-based material having a front side and a back side;

b) applying a first liquid coating to the front side of the board of wood-based material, the first liquid coating being formed of a first polymer composition that has a first hardness in a cured state;

c) applying a second liquid coating onto the still wet first liquid coating, so that a partial mixing of the first and second liquid coatings takes place, the second liquid coating being formed of a second polymer composition having a second hardness in a cured state that is greater than the first hardness, the first polymer composition being a different polymer composition than the second polymer composition;

d) exposing the first and second liquid coatings to radiation to effect curing of the first and second liquid coatings to form a polymer coating on the board of wood-based material; and

wherein the partial mixing of the first and second polymer compositions forms a concentration gradient of the first and second polymer compositions in an intermediate area of the polymer coating disposed between an inner area of the polymer coating predominantly formed of the first polymer composition and an outer area of the polymer coating predominantly formed of the second polymer composition, the concentration of the first composition in the intermediate area continuously decreasing going from the inner area toward the outer area and the concentration of the second composition in the intermediate area continuously decreasing going from the outer area toward the inner area, such the hardness of the polymer coating when cured decreases with increasing depth viewed from an outer surface of the polymer coating.

13. The floor panel according to claim 12 , wherein the polymer coating has a hardness gradient that corresponds to the following formula:

(−3,0* x )+ C<=Y ( x )<=(−0,2* x )+ C

wherein:

x is the absolute value of the depth in μm of the coating viewed from the surface of the coating;

Y(x) is the absolute value of the hardness in N/mm 2 at a certain depth x; and

C is the absolute value of the initial hardness in N/mm 2 of the coating at a depth of approximately x≈0-5 μm.

14. The floor panel according to claim 12 , wherein the polymer coating has a hardness gradient that corresponds to the following formula:

(−2,5* x )+ C<=Y ( x )<=(−0,4* x )+ C

wherein:

x is the absolute value of the depth in μm of the coating viewed from the surface of the coating;

Y(x) is the absolute value of the hardness in N/mm 2 at a certain depth x; and

C is the absolute value of the initial hardness in N/mm 2 of the coating at a depth of approximately x≈0-5 μm.

15. The floor panel according to claim 12 , wherein the polymer coating has a hardness gradient that corresponds to the following formula:

(−2,0* x )+ C<=Y ( x )<=(−0,6* x )+ C

wherein:

x is the absolute value of the depth in μm of the coating viewed from the surface of the coating;

Y(x) is the absolute value of the hardness in N/mm 2 at a certain depth x; and

C is the absolute value of the initial hardness in N/mm 2 of the coating at a depth of approximately x≈0-5 μm.

16. A coated board of wood-based material, comprising a board of wood-based material having a front side and a rear side, and a polymer coating on the front side of the board of wood-based material, wherein the polymer coating has an inner area predominantly formed of a first polymer having a first hardness in a cured state, an outer area predominantly formed of a second polymer having a second hardness in a cured state that is greater than the first hardness, the second polymer comprising more C—C double bonds than the first polymer, and an intermediate area between the inner and outer areas, the intermediate area having a concentration gradient of the first and second polymers, the concentration of the first polymer in the intermediate area continuously decreasing going from the inner area toward the outer area and the concentration of the second polymer in the intermediate area continuously decreasing going from the outer area toward the inner area, such that the hardness of the polymer coating continuously decreases with increasing depth viewed from an outer surface of the polymer coating.