System and method of coating print media in an inkjet printer

A coating apparatus for applying a coating liquid to a printing substrate, comprising:

• a. a rotatable first roll;
• b. a rotatable second roll having a surface energy, the second roll positioned adjacent to the first roll and defining with the first roll a first nip through which the printing substrate passes;
• c. a rotatable third roll contacting the second roll and forming a second nip therebetween;
• and
• d. a doctor blade in contact with the third roll, the doctor blade applying a layer of coating liquid onto the third roll, the third roll transferring the coating liquid to the second roll, and the second roll in turn transferring the coating liquid to the printing substrate, wherein the hardness of the second roll is less than the hardness of the third roll

An ink jet printer comprising:

• a. a housing;
• b. an ink jet printing apparatus, located within the housing, having an ink jet printing device capable of ejecting ink droplets onto a first side of a printing substrate which moves through the housing;
• and
• c a coating apparatus spaced from the printing device, the coating apparatus applying a layer of coating liquid onto at least a portion of the first side of the printing substrate;
• wherein the coating apparatus is positioned before the ink jet printing device and comprises:
• a rotatable first roll having a surface energy;
• a rotatable second roll having a surface energy, the second roll positioned adjacent to the first roll and defining with the first roll a first nip through which the printing substrate passes;
• and a metering device for applying a layer of coating liquid onto the second roll, the second roll in turn transferring the coating liquid to the printing substrate, wherein the surface energy of the selected roll is greater than the surface energy of the coating liquid.

13 A coating apparatus for applying a coating liquid to a printing substrate, comprising:

• a. a rotatable first roll;
• b. a rotatable second roll, the second roll positioned adjacent to the first roll and defining with the first roll a first nip through which the printing substrate passes;
• and
• c. a metering device for applying a layer of coating liquid onto the second roll, which in turn transfers the coating liquid to the printing substrate, wherein the second roll has a surface roughness of about 0.5 micrometers Ra or less.

The coating apparatus of claim 13, wherein the metering device comprises:

• a a rotatable third roll contacting the second roll and forming a second nip therebetween;
• b. a supply of coating liquid in contact with the third roll;
• and
• c a doctor blade contacting the third roll and oriented at a contact angle relative to the third roll, the doctor blade having a longitudinal edge that contacts the third roll with a contact force so that a substantially uniform quantity of coating liquid is received by the third roll as the third roll is caused to rotate.

A metering device for providing a layer of coating liquid to a coating apparatus wherein the coating apparatus has a rotatable first roll and a rotatable second roll defining with the first roll a first nip through which a printing substrate passes, comprising:

• a. a rotatable third roll having a surface energy;
• b a supply of coating liquid having a surface energy, the supply of coating liquid being in contact with the third roll, and
• c. a doctor blade for metering a layer of coating liquid onto the third roll, the doctor blade having a distal edge with a surface energy that contacts the third roll,
• wherein the surface energy of at least a portion of the distal edge is less than the surface energy of the coating liquid.

36 A metering device for providing a layer of coating liquid to a coating apparatus wherein the coating apparatus has a rotatable first roll and a rotatable second roll defining with the first roll a first nip through which a printing substrate passes, comprising:

• a a rotatable third roll having a surface energy;
• b. a supply of coating liquid having a surface energy, the supply of coating liquid being in contact with the third roll, and
• c a doctor blade for metering a layer of coating liquid onto the third roll, the doctor blade having a distal edge with a surface energy that contacts the third roll,
• wherein the surface energy of at least a portion of the third roll is less than the surface energy of the coating liquid