Coating method and coated product

• US 20020015796A1
• Filed: 06/22/2001
• Published: 02/07/2002
• Est. Priority Date: 06/26/2000
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Tomaru, Mikio, Mandai, Toshihiro, Takekuma, Hideaki
• Granted Patent: US 6,548,117 B2
• Time in Patent Office: Days
• US Class Current: 427/420
• CPC Class Codes: B05C 5/0254 Coating heads with slot-shaped outlet B05C5/0283 takes precedence
• CPC Class Codes: B05C 9/06 for applying two different liquids or other fluent materials, or the same liquid or other fluent material twice, to the same side of the work
• CPC Class Codes: B05D 1/265 Extrusion coatings
• CPC Class Codes: B05D 7/52 Two layers
• CPC Class Codes: B05D 7/56 Three layers or more
• CPC Class Codes: G11B 5/848 Coating a support with a magnetic layer by extrusion

Abstract

In a case to coat a web by using coating heads which have plural slits, the coating method coats the web by adjusting a running speed, an average high shear viscosity, and a surface tension of the coating liquid of the top layer so that the capillary number Ca, which is calculated by an equation Ca=Uμ/σ, satisfies an inequality 0.1<Ca<4, where U (m/s) is a running speed of the web, μ (Pa.s) is an average high shear viscosity of the coating liquids, and σ (N/m) is a surface tension of the coating liquid for the top layer.

Claims

1. A coating method in which a web which continuously runs is relatively pressed against an edge face of a coating head and a plurality of coating liquids are discharged from a plurality of slits formed in the edge face in a direction of width of said web so that layers of the coating liquids are formed on the web, wherein:

a capillary number Ca which is calculated by an equation Ca=Uμ

/σ

satisfies an inequality 0.1<

Ca<

4, where U (m/s) is a running speed of said web, μ

(Pa.s) is an average high shear viscosity of said coating liquids, and σ

(N/m) is a surface tension of the coating liquid for a top layer of said layers.

2. The coating method as defined in claim 1, wherein:

a gap is formed between said web and a front edge face of said coating head at an upper stream side in a running direction of said web; and

the coating liquid for a bottom layer of said layers is overflowed to the gap while the other coating liquids are applied on the bottom layer.

7. A coated product produced in accordance with the method as defined in one of claims 1 to 6.

8. The coated product as defined in claim 7, wherein a thickness of at least one layer of the layers except the bottom layer which contacts with said web is not more than 2 μ

m in a wet condition.

3. A coating method in which a coating liquid is oversupplied to a web which continuously runs to form a bottom layer and then the web is relatively pressed against an edge face of a coating head and a plurality of coating liquids are discharged from a plurality of slits formed in the edge face in a direction of width of said web while an upper stream side of the edge face removes a part of the bottom layer when the coating liquid of the bottom layer is wet so that a plurality of coating layers are formed on the bottom layer, wherein:

a capillary number Ca which is calculated by an equation Ca=Uμ

/σ

satisfies an inequality 0.1<

Ca<

4, where U (m/s) is a running speed of said web, μ

(Pa.s) is an average high shear viscosity of the plurality of coating liquids, and σ

(N/m) is a surface tension of the coating liquid for a top layer of said layers.

4. The coating method as defined in claim 3, wherein a coating head for the bottom layer and the coating head for the plurality of coating layers are integrated.

6. The coating method as defined in claim 3, wherein a coating head for the bottom layer and the coating head for the top coating layer are integrated.

5. A coating method in which a first coating liquid is oversupplied to a web which continuously runs to form a bottom layer and then the web is relatively pressed against an edge face of a coating head and a second coating liquid is discharged from a slit formed in the edge face in a direction of width of said web while an upper stream side of the edge face removes a part of the bottom layer when the first coating liquid of the bottom layer is wet so that a top coating layer is formed on the bottom layer, wherein:

a capillary number Ca which is calculated by an equation Ca=Uμ

/σ

satisfies an inequality 0.1<

Ca<

4, where U (m/s) is a running speed of said web, μ

(Pa.s) is a high shear viscosity of the second coating liquid, and σ

(N/m) is a surface tension of the second coating liquid.

9. A coating method in which a web which continuously runs is relatively pressed against an edge face of a coating head and a plurality of shear thinning coating liquids are discharged from a plurality of slits formed in the edge face in a direction of width of said web so that layers of the plurality of coating liquids are applied on the web in a wet-on-wet condition, wherein:

viscosities of the plurality of coating liquids are adjusted so that a following inequality is satisfied,

−

15×

10<sup>−

3</sup><

μ

_n-1−

μ

_n<

5×

10<sup>−

3</sup>,

where μ

_n (Pa.s) is a high shear viscosity of the coating liquid forming an n-th (n≧

2) layer from said web and μ

_n-1 (Pa.s) is a high shear viscosity of the coating liquid forming an (n−

1)-th layer that is adjacent to the n-th layer.

10. The coating method as defined in claim 9, wherein a viscosity of the coating liquid for the bottom layer is adjusted so that a following inequality is satisfied,

μ

₁<

20×

10<sup>−

3</sup>,

where μ

₁ (Pa.s) is a high shear viscosity of the coating liquid forming the bottom layer that contacts with said web.

15. A coated product produced in accordance with the method as defined in one of claims 9 to 14.

11. A coating method in which a shear thinning coating liquid is oversupplied to a web which continuously runs to form a bottom layer and then the web is relatively pressed against an edge face of a coating head and a plurality of shear thinning coating liquids are discharged from a plurality of slits formed in the edge face in a direction of width of said web while an upper stream side of the edge face removes a part of the bottom layer when the coating liquid of the bottom layer is wet so that a plurality of coating layers are formed on the bottom layer in a wet-on-wet condition, wherein:

viscosities of the coating liquids are adjusted so that a following inequality is satisfied,

−

15×

10<sup>−

3</sup><

μ

_n-1−

μ

_n<

5×

10<sup>−

3</sup>,

where μ

_n (Pa.s) is a high shear viscosity of the coating liquid forming an n-th (n≧

2) layer from said web and μ

_n-1 (Pa.s) is a high shear viscosity of the coating liquid forming an (n−

1)-th layer that is adjacent to the n-th layer.

12. The coating method as defined in claim 11, wherein a viscosity of the coating liquid for the bottom layer is adjusted so that a following inequality is satisfied,

μ

₁<

20×

10<sup>−

3</sup>,

where μ

₁ (Pa.s) is a high shear viscosity of the coating liquid forming the bottom layer that contacts with said web.

14. The coating method as defined in claim 13, wherein a viscosity of the coating liquid for the bottom layer is adjusted so that a following inequality is satisfied,

μ

₁<

20×

10<sup>−

3</sup>,

where μ

₁ (Pa.s) is a high shear viscosity of the coating liquid forming the bottom layer that contacts with said web.

16. The coated product as defined in claim 15, wherein a thickness of at least one layer of the layers except the bottom layer which contacts with said web is not more than 1 μ

m in a wet condition.

13. A coating method in which a first shear thinning coating liquid is oversupplied to a web which continuously runs to form a bottom layer and then the web is relatively pressed against an edge face of a coating head and a second shear thinning coating liquid is discharged from a slit formed in the edge face in a direction of width of said web while an upper stream side of the edge face removes a part of the bottom layer when the first coating liquid of the bottom layer is wet so that a top coating layer is formed on the bottom layer in a wet-on-wet condition, wherein:

viscosities of the first and second coating liquids are adjusted so that a following inequality is satisfied,

−

15×

10<sup>−

3</sup><

μ

₁−

μ

₂<

5×

10<sup>−

3</sup>,

where μ

₁ (Pa.s) is a high shear viscosity of the first coating liquid and μ

₂ (Pa.s) is a high shear viscosity of the second coating liquid.