LAMINATE FOR REDUCING FLOW RESISTANCE AND MANUFACTURING METHOD THEREFOR

Abstract

There is provided a flow-resistance reducing laminate comprising: a substrate; and a flow-resistance reducing layer formed on the substrate, wherein the flow-resistance reducing layer has a surface portion facing a liquid, wherein a flow interface is formed between the liquid and the laminate upon relative movement between the liquid and the laminate, wherein the flow-resistance reducing layer is configured such that an air layer defines the flow interface.

Claims

1. A flow-resistance reducing laminate comprising: a substrate; and a flow-resistance reducing layer formed on the substrate, wherein the flow-resistance reducing layer has a surface portion facing a liquid, wherein a flow interface is formed between the liquid and the laminate upon relative movement between the liquid and the laminate, wherein the flow-resistance reducing layer is configured such that an air layer defines the flow interface.

2. The flow-resistance reducing laminate of claim 1, wherein the surface portion of the flow-resistance reducing layer has a plurality of cavities defined therein, wherein when the surface portion faces the liquid, the air is filled in the cavities, wherein the shape of each of the cavities is configured such that when the flow interface is formed, the air filled in each cavity is kept trapped therein.

3. The flow-resistance reducing laminate of claim 2, wherein each cavity has a spherical shape having an open portion defined therein toward the liquid, wherein a length of the open portion of the cavity toward the liquid is smaller than a radius of the spherical cavity so that the air filled in the cavity is kept trapped therein.

4. The flow-resistance reducing laminate of claim 2, wherein each cavity has a cylindrical shape having a rounded edge and having a first depth and having an opened portion; or each cavity has a rectangular cross-section shape having rounded corners and edges and having the first depth and an opened portion, wherein a relationship between a length of the open portion of the cavity toward the liquid and the first depth is defined so that the air filled in the cavity is kept trapped therein.

5. The flow-resistance reducing laminate of claim 1, wherein the flow-resistance reducing layer includes a support layer in contact with the substrate, wherein a plurality of hollow micro-capsules is dispersed in the support layer or in a surface portion of the support layer, wherein each hollow micro-capsule is partially open to define a corresponding cavity.

6. The flow-resistance reducing laminate of claim 2 or 5, wherein an inner face of each cavity surface is water repellent to form the air layer.

7. The flow-resistance reducing laminate of claim 6, wherein a shell of each hollow micro-capsule has gas-blocking property to allow expansion; or the shell is brittle to enable rupture thereof at a notch point thereof by expansion.

8. A method of manufacturing a sheet having a plurality of cavities defined in a surface portion thereof, the method comprising: providing a plurality of micro-capsules carrying a thermally expandable material therein, wherein each capsule has a shell surrounding the thermally expandable material; dispersing the plurality of micro-capsules in a support layer; floating at least some of the hollow micro-capsules upwardly into a surface portion of the support layer such that said at least some of the micro-capsules are exposed upwardly; expanding the thermally expandable material contained in the shells by heating the exposed micro-capsules; and rupturing an exposed portion of the shell of each micro-capsule by the expansion to hollow each capsule to form a corresponding cavity.

9. The method of claim 8, wherein when the micro-capsules are dispersed in the support layer, the micro-capsules are in close contact with each other, such that each of the capsule has a cylindrical shape having a rounded edge or a rectangular cross-section shape having rounded corners and edges.

10. The method of claim 8, wherein the support layer includes a liquid-phase or gel-phase support layer precursor, wherein dispersing the plurality of micro-capsules in the support layer includes dispersing the plurality of micro-capsules in the liquid-phase or gel-phase support layer precursor, wherein heating the exposed micro-capsules includes curing the liquid-phase or gel-phase support layer precursor.

11. The method of claim 8, wherein the support layer includes a liquid-phase or gel-phase support layer precursor, wherein dispersing the plurality of micro-capsules in the support layer includes dispersing the plurality of micro-capsules in the liquid-phase or gel-phase support layer precursor, wherein heating the exposed micro-capsules includes curing the liquid-phase or gel-phase support layer precursor, wherein the method further comprises applying the liquid-phase or gel-phase support layer precursor having the plurality of micro-capsules dispersed therein onto a surface of a substrate.

12. The method of claim 8, wherein the shell of each micro-capsule is water-repellent.

13. The method of claim 8, wherein the thermally expandable material is un-permeable through the shell of the micro-capsule such that the shell is ruptured by the thermal expansion of the thermally expandable material.

14. The method of claim 8, wherein the shell of the micro-capsule is brittle such that the shell is ruptured by the thermal expansion of the thermally expandable material.

15. The method of claim 8 or 10, wherein the shell of the micro-capsule is non-dissolved into the support layer or the support layer precursor.

16. The method of claim 8, wherein the thermally expandable material surrounded by the shell includes a thermally expandable gas, oil and/or liquid.

17. The method of claim 8, wherein the thermally expandable material surrounded by the shell has a lower specific gravity than a material of the support layer.

18. A self-cleaning sheet comprising the flow-resistance reducing laminate of claim 1.

19. A soundproof sheet comprising the flow-resistance reducing laminate of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 is a schematic view showing a cross-section of a laminate for flow-resistance reduction according to the present invention.

[0035] FIG. 2 is a schematic diagram illustrating that the cavity inner surface is spherical.

[0036] FIG. 3 is a schematic diagram illustrating that the cavity inner surface has a square shape with rounded corners or rounded cylindrical shape;

[0037] FIG. 4 illustrates an example in which a laminate for flow-resistance reduction according to the present invention contacts a liquid, for example, when the laminate moves relative to the liquid, air filled in the cavity forms the air layer.

[0038] FIG. 5 is a schematic view showing a method of manufacturing a laminate for flow-resistance reducing according to the present invention.

[0039] FIG. 6 is an enlarged view of a micro-capsule dispersed support layer prepared according to an embodiment of the present invention.

[0040] FIG. 6 is an enlarged view of a hollow micro-capsule prepared according to an embodiment of the present invention in which a surface exposed shell thereof is ruptured and a cavity is defined on the surface.

DETAILED DESCRIPTIONS

[0041] Examples of various embodiments are illustrated and described further below. It will be understood that the description herein is not intended to limit the claims to the specific embodiments described. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the present disclosure as defined by the appended claims. The same reference numbers in different figures denote the same or similar elements, and as such perform similar functionality.

[0042] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms a and an are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms comprises, comprising, includes, and including when used in this specification, specify the presence of the stated features, integers, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, operations, elements, components, and/or portions thereof.

[0043] Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0044] FIG. 1 is a schematic view showing a cross-section of a laminate for flow-resistance reduction according to the present invention. A laminate for flow-resistance reduction according to the present invention comprises a substrate 110; and a flow-resistance reducing layer 100 formed on the substrate 110, wherein the flow-resistance reducing layer 100 includes a support layer 120 in contact with the substrate, and the support layer 120 has a cavity 130 defined in a surface portion thereof.

[0045] The cavity 130 in accordance with the present invention may be configured to define the recessed space having a circular shape (see FIG. 2) or a rectangular surface (see FIG. 3) having a rounded corner in the surface portion of the support layer. The recessed space contains air therein; when the flow-resistance reducing laminate according to the present invention is in contact with the liquid, air is retained in the cavity, and the air layer is formed by fluid movement or laminate movement. Thus, the length of the open portion of the cavity is defined such that the air layer remains within the cavity as the fluid moves or the laminate moves.

[0046] As seen from FIG. 2, the inner surface of the cavity may be spherical or cylindrical with the rounded corners; in this case, the length of the open portion of the cavity (designated by reference A in FIG. 2) may be less than the radius of the spherical cavity (R in FIG. 2) so that the air filled in the cavity is trapped therein. In this connection, limiting the length A to a specific numerical value limits the scope of the invention too much. Accordingly, those skilled in the art will be able to set the length A so that the air in the cavity can be trapped therein at various flow interfaces that are generated, in accordance with the application of the present invention.

[0047] Further, as illustrated in FIG. 3, the cavity inner surface may be a rounded rectangle having the rounded corners. The depth of the cavity (H in FIG. 3) and the length of the open portion of the cavity (A in FIG. 3) may be defined so that the air filled in the cavity is trapped therein. It will be appreciated that the limitation of the length A to a specific value overrides the scope of the present invention. Accordingly, those skilled in the art will be able to set the length A so that the air in the cavity can be trapped therein at various flow interfaces that are generated, in accordance with the application of the present invention.

[0048] In particular, it is desirable that the surface forming this cavity may be water repellent so that the cavity maintains air therein and the air layer forms well as the fluid moves.

[0049] FIG. 4 is a cross-sectional view of a laminate for flow-resistance reduction according to the present invention in which, when, the air in the cavity is in contact with a liquid, in particular, when the laminate moves relative to the liquid, the air filled in in the cavity (shown as hollow in FIG. 4) forms the air layer thereon.

[0050] The flow-resistance reducing layer, having a support layer 120 designated as paint in FIG. 4 and a cavity 130 defined in the surface portion of the support layer 120, faces the liquid 140. Air is trapped in the cavity (as shown in 150. When the flow-resistance reducing layer moves to the right in the drawing, an air film 160 is formed. That is, the air film 160, which is a flow interface, is defined between the air layer and the liquid 140, thereby rapidly reducing the flow resistance.

[0051] FIG. 5 is a schematic view showing a method of manufacturing a laminate for flow-resistance reducing according to the present invention.

[0052] FIG. 5A shows preparing for a hollow micro-capsule in which a thermally expandable material (e.g., oil) is contained therein; further, FIG. 5A illustrates the step of dispersing the hollow micro-capsules in a liquid support layer precursor (e.g., a coatable liquid paint). FIG. 5D shows the hollow oil-carrying micro-capsule floated toward the paint surface portion, wherein the support layer precursor (e.g., paint) is cured and heat is applied to the surface portion thereof. FIG. 5c illustrates the expansion of the oil carried in the micro-capsule by heat; FIG. 5D illustrates a step in which a rupture occurs in a notch at which the shell of the micro-capsule starts to be exposed from the support layer, thereby starting the hollow process in the support layer surface portion.

Example 1

[0053] The oil-contained micro-capsule and PVA (polyvinyl alcohol) were dispersed at a ratio of 1:1. The micro-capsules were well dispersed in the PVA. This capsule-dispersed PVA was spin-coated onto the silicon surface. The specific gravity of the oil was smaller than the specific gravity of the PVA, so that the micro-capsule floated toward the PVA surface, and the PVA was cured after a certain time. See the SEM picture of FIG. 6. As shown in the SEM photograph of FIG. 7, the shell of the micro-capsule was ruptured and a surface portion of the PVA having the partially opened micro-cavities was formed.

[0054] While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims.