KR101808985B1 - Complex with polymer and nano inorganic particle layer and method for preparing same - Google Patents

Abstract

A composite of polymer and nano-inorganic particles according to an embodiment of the present invention comprises: a substrate; a first adhesive layer having a first engraved surface on the substrate; a first nano-inorganic particle layer laminated along the first engraved surface on the first adhesive layer; a second adhesive layer with which an engraved space of the first engraved surface is filled, which has regular thickness and a second engraved surface on the first nano-inorganic particle layer; and a second nano-inorganic particle layer laminated along the second engraved surface on the second adhesive layer, wherein the first nano-inorganic particle layer and the second nano-inorganic particle layer are thermally or electrically connected in a vertical direction. The present invention can realize high thermal conductivity even at a low nano-inorganic particle ratio.

Description

TECHNICAL FIELD [0001] The present invention relates to a polymeric nano-inorganic particle composite and a method for manufacturing the same. BACKGROUND ART < RTI ID = 0.0 >

TECHNICAL FIELD The present invention relates to a polymer-nano-inorganic particle composite, and more particularly, to a polymer-nano-inorganic particle composite which is excellent in thermal and electrical conductivity and can be used as a heat sink and an electromagnetic wave shielding agent.

In order to effectively remove heat from a device having a heat generating property, to protect the product, or to maintain the performance of a device or the like, a high thermal conductive substrate is widely used.

In the case of the conventional polymer-nanoparticle complex having thermal conductivity, the nanoparticles were physically dispersed in the polymer. It has advantages of polymer and functional nanoparticles together, and is easy and simple to process, which is advantageous for mass production. However, since the nanoparticles are randomly located in the polymer, a high nanoparticle ratio is required in order to secure high thermal conductivity, which deteriorates the polymer properties such that the flexibility of the composite is lowered, fragility is lowered and the adhesion is lowered. There were disadvantages. It is also reported that it is difficult to control the effective nanoparticle array and the vertical heat transfer rate is about 10 times smaller than the horizontal heat transfer rate.

In addition, a method of aligning the nanoparticles in the polymer was also used to achieve a high thermal conductivity, despite the low proportion of the nanoparticles added. In this method, a method of aligning nanoparticles impregnated with metal in a fluid polymer and aligning them using a magnetic force, a method of filtering nanoparticles such as filtration using a filter paper, And the like.

In the case of aligning using magnetic force, since the nanoparticles were coated with metal ions or the like after being coated with metal ions or the like in order to allow the nanoparticles to react with magnetic force, the insulating property was poor, and the time required for the process was long depending on the viscosity of the polymer . In addition, it is possible to align only in one direction, and the thermal conductivity in the vertical direction is rather reduced.

Also in the case of filtration, alignment in the plane direction was possible, and the thermal conductivity in the axial direction was greatly reduced.

In addition, in the case of filling the polymer after the nanoparticles are aligned, such as filtration or freeze molding, the volume is increased and the alignment is disturbed in the process of injecting the polymer. In addition, the reproducibility is greatly reduced because it is not possible to precisely control the alignment interval or density in the alignment process. In addition, there was a drawback that the filling rate of the nanofiller could not be maximized.

Therefore, it has a similar thermal conductivity in the vertical and horizontal directions, is capable of transferring heat stably even in a high temperature environment due to accumulated heat, has excellent electrical insulation for preventing cross-talk in a highly integrated circuit, It is time to develop excellent composite manufacturing technology.

It is an object of the present invention to provide a polymer-nano-inorganic particle composite having excellent electrical and thermal conductivity in a vertical and horizontal direction, and a method for manufacturing the same.

According to one embodiment of the present invention, a polymeric nano-inorganic / inorganic particle composite includes a substrate, a first adhesive layer having a first intaglio surface on the substrate, a first adhesive layer on the first adhesive layer, A second nano-inorganic particle layer; a second adhesive layer having an intaglio space of the first intaglio surface with a very high constant thickness and a second intaglio surface on the first nano inorganic particle layer; and a second intaglio layer on the second adhesive layer, And a second nano inorganic particle layer laminated along the surface, wherein the first nano inorganic particle layer and the second nano inorganic particle layer are electrically or thermally connected in a vertical direction.

In one embodiment, the substrate may be a flexible transparent substrate.

In one embodiment, the coating on the adhesive layer of the first and second nano inorganic particles may be located on the surface of the adhesive layer, or all or a portion of the nano inorganic particles may be impregnated into the adhesive layer.

In one embodiment, the adhesive may comprise a bisphenol A based acrylate compound and an alkoxysilyl based acrylate compound.

In one embodiment, the bisphenol A-based diacrylate compound may comprise bisphenol A glycerolate (1 glycerol / phenol) diacrylate of Formula 1 below.

Formula 1

In one embodiment, the alkoxysilyl acrylate compound may comprise 3- (trimethoxysilyl) propyl methacrylate of Formula 2 below.

(2)

In one embodiment, the adhesive may comprise a photoinitiator.

In one embodiment, the photoinitiator is selected from the group consisting of 2-benzyl-2- (dimethylamino) -4-morpholinobutyrophenone of formula 3: Polymer Nano Inorganic Particle Complex:

(3)

In one embodiment, the adhesive may comprise poly (methyl silsesquioxane) (poly (methyl silsesquioxane)).

In one embodiment, the thickness of the adhesive layer may be less than the thickness of the engraved surface.

In one embodiment, the nanoparticulate particles may comprise at least one of graphene, a metallic grid, a carbon nanotube, a silver nanowire, and boron nitride.

The heat sink, which is another embodiment of the present invention, may include any one of the above-described polymeric nano-inorganic particle composites.

The electromagnetic wave shielding agent according to another embodiment of the present invention may include any one of the above-mentioned polymeric nano-inorganic particle composites.

In another embodiment of the present invention, there is provided a method of preparing a polymer nanomolecular inorganic particle composite, comprising the steps of: preparing a substrate; forming a first adhesive layer on the substrate; forming a stamp having nano- A third step of forming a first intaglio surface on one side of the first adhesive layer and laminating a nano-inorganic particle layer along the first intaglio surface, using a first intaglio surface formed by the nano- A fourth step of forming a second adhesive layer so as to have a predetermined thickness and a fifth step of forming a second indentation surface on one surface of the second adhesive layer using a stamp on which nano- The first nano inorganic particle layer and the second nano inorganic particle layer adjacent to the first nano inorganic particle layer are electrically or thermally connected in the vertical direction.

In one embodiment, the adhesive is a thermosetting or light-curable adhesive, and in the third step, it is cured by irradiation with heat or light.

According to one embodiment of the present invention, high thermal conductivity can be realized even when a low content of nano inorganic particles is included, and flexibility, adhesiveness, etc., which are characteristics of a polymer, can be maintained. In addition, since it is manufactured using a mold, high reliability can be maintained even in mass production, and the heat conduction characteristics can be controlled effectively by controlling the size and the aspect ratio of the structure. The present invention can be applied to various fields such as a TIM, a heat dissipation board and the like in the future.

Specifically, high thermal conductivity can be realized even at a low nanoparticle ratio. By controlling the size and the aspect ratio of the mold structure, 3D structures of various densities can be manufactured, and the selective thermal conductivity of the axial direction (vertical) and the plane direction (horizontal) can be controlled. Further, by using the adhesive polymer, the device can be easily transferred to the substrate without a separate process. By using the photo-curable polymer, it is possible to easily remove the adhesiveness of the portion where the element is not transferred. In addition, it can be applied to a bending device using a polymer having high flexibility.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a method of manufacturing a composite according to an embodiment of the present invention. FIG.
2 is a schematic diagram of a cross-section of a composite according to another embodiment of the present invention.
3 is a schematic diagram of a cross-section of a composite according to another embodiment of the present invention.
4 is a schematic diagram of a heat sink and an IC chip including a composite according to another embodiment of the present invention.
5 (a) and 5 (b) are electron micrographs of cross-sections of a composite according to another embodiment of the present invention.
FIG. 6 is an electron micrograph and a graph of energy dispersive spectroscopy (EDS) of the composite part shown in FIG. 5 and a result table.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the term "comprises" or "having" is intended to designate the presence of stated features, elements, etc., and not one or more other features, It does not mean that there is none.

The terms " first "and" second "and the like used in the present application are not intended to limit the elements of the present invention, but merely set to distinguish the elements.

The terms "above" or "over," as used in this application include not only that other components are located directly on one component but also that a third component is inserted and positioned between the two components do.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic view of a method of manufacturing a composite according to an embodiment of the present invention. As shown in FIG. 1, a substrate is transferred onto an adhesive layer laminated on a substrate with a stamp (PDMS (polydimethylsiloxane) mold coated with a nano-inorganic particle) to form an embossed layer A corresponding engraved is formed, and along the engraved surface, a nano-inorganic particle layer is laminated. Then, the composite can be produced by alternately repeating the step of applying the adhesive layer and forming the engraved surface on the adhesive layer with a stamp. Here, heat or light may be irradiated during stamping to transfer the nano-inorganic particle layer more well and to cure the adhesive layer. However, in the present invention, the order disclosed in Fig. 1 is only one example, and the specific manufacturing method thereof is not limited to Fig.

(1) Step 1

In a method of manufacturing a composite according to an embodiment of the present invention, a substrate is first prepared as a first step. The substrate is not particularly limited, but may be a polymer substrate, preferably a flexible transparent polymer such as PET.

(2) Step 2

As a second step, a first adhesive layer is formed on the substrate. The first adhesive layer may be placed on the substrate by various methods in accordance with the object of the present invention.

The adhesive is a thermosetting or light-curable adhesive, and can be cured by irradiation with heat or light in the third step.

The adhesive may include a transparent adhesive including a bisphenol A-based acrylate compound and an alkoxysilyl acrylate compound.

The bisphenol A based diacrylate compound may be Bisphenol A glycerolate (1 glycerol / phenol) diacrylate having the following formula (1).

The alkoxysilyl acrylate compound may be 3- (trimethoxysilyl) propyl methacrylate having the following general formula (2).

In addition, the adhesive may include a photoinitiator.

The photoinitiator may be 2-benzyl-2- (dimethylamino) -4-morpholinobutyrophenone of the following Chemical Formula 3.

The adhesive may comprise poly (methyl silsesquioxane) (poly (methyl silsesquioxane)).

The adhesive of the present invention can provide sufficient adhesion to nano-inorganic particles while forming a thin layer, and facilitates percolation between nano-inorganic particles. This percolation maximizes conduction and heat dissipation characteristics.

The thickness of the adhesive layer of the present invention is 100 nm to 150 nm, and when the thickness is 100 nm or less, process defects may occur. A thickness of 150 nm or more may degrade the mechanical stability.

(3) Step 3

As a third step, a first intaglio surface is formed on one surface of the first adhesive layer using a stamp on which nano-inorganic particles are placed on the embossed surface, and a nano-inorganic particle layer is laminated along the first intaglio surface .

Here, the coating on the adhesive layer of the nano-inorganic particles may be located on the surface of the adhesive layer, or some or all of the nano-inorganic particles may be impregnated into the interfacial layer.

For the stamping, a stamp can be used. The stamp may use a polymethylsiloxane (PMDS) mold having a structure such as a line, a space, a pillar, or a prism. In the present invention, the mold is only one example of performing the stamping process, but is not limited thereto.

In this method using a mold, firstly, boron nitride particles dispersed in ethanol are uniformly coated on the PDMS structure. At this time, when the PDMS is coated in a state of applying heat, the solvent is blown off immediately after passing the bar coater with the solution, Boron is coated on the PDMS in the direction of the plane, increasing the contact between the nanoparticles and increasing the thermal conductivity. The thickness of the coating may be controlled by adjusting the concentration of the boron nitride dispersion, the coating speed, and the temperature.

Since the 3D structure of the nanoparticles in the polymer is achieved by the multi-layer transfer method of the nanoparticles through the PDMS mold, the nanoparticle structure can be easily deformed according to the size and the aspect ratio of the mold. In addition, in the case of transfer using a mold, since it has high reproducibility, it is possible to manufacture a large area using roll-to-roll.

In addition, the nano-inorganic particles may include at least one of graphene, a metallic grid, a carbon nanotube, a silver nanowire, and boron nitride.

The stamp coated with the nano-inorganic particles is physically contacted to the adhesive layer, and as the pressure is applied, the relief surface is formed on the adhesive layer so as to correspond to the relief formed on the stamp. In addition, the nano-inorganic particle layer coated on the surface of the stamp is transferred and positioned along the relief surface of the adhesive layer.

Here, the embossed or engraved surface means a surface shape such as a concavo-convex shape or a saw-tooth shape formed on the surface of the adhesive layer, although the specific surface shape is not particularly limited.

Further, in the third step, it is possible to irradiate further heat or light. When the stamp is removed by irradiating heat or light to partially cure the adhesive layer, the structure of the embossed surface is made to correspond to the embossing formed on the stamping surface in the adhesive layer, and at the same time, The nano-inorganic particle layer can be easily transferred to the adhesive layer. In addition, by using heat or partial curing through light during transfer, separation between the layers can be prevented. As described later, a sheet having nanoparticle 3D structure in the adhesive layer can be manufactured by coating the adhesive layer on the adhesive layer and transferring the nano-inorganic particles several times.

(4) Step 4

As a fourth step, a second adhesive layer is formed so that the first intaglio face formed by the nano-inorganic particle layer has a very thick thickness.

The description of the second adhesive layer used here is the same as that described in the first adhesive layer, and thus is not specifically described. However, the second adhesive layer and the first adhesive layer may be the same composition or may be different. In addition, the shape of the engraved surface may be the same or different.

(5) Step 5

As a fifth step, a second intaglio surface is formed on one surface of the second adhesive layer using a stamp on which nano-inorganic particles are placed on the embossed surface.

The stamp used here may be the same as the stamp described in the third step. However, it is not limited thereto.

In addition, the second step and the third step may be carried out two or more times to form a composite in which the adhesive layer coated with the nano-inorganic particle layer is alternately laminated.

Hereinafter, using the first and second modifiers, an adhesive layer in which a nanoparticle layer formed in a primary direction and an adhesive layer in which a nanoparticle layer formed in a secondary direction are laminated will be described.

Specifically, first, a first adhesive layer in which the first nano inorganic particle layer is laminated on the substrate and the substrate, which is laminated on the substrate, is formed through the first through third steps. An additional adhesive is applied on the engraved surface to laminate the second adhesive layer. The second adhesive layer also forms the engraved surface through the third step, and the second nano inorganic particle layer is laminated. Such a process can be repeatedly carried out in accordance with the purpose of the present invention.

However, at this time, the first nano inorganic particle layer and the first adhesive layer, and the second nano inorganic particle layer and the second adhesive layer may alternately be laminated. Means that the first layer and the second layer stacked on the first layer are not stacked in a superimposed manner so that they are stacked at an intersection or obliquely stacked Is used herein in its entirety.

In the present invention, through the lamination structure, the first nano inorganic particle layer and the second nano inorganic particle layer adjacent to the first nano inorganic particle layer among the plurality of nano inorganic particle layers in the composite can be electrically or thermally connected in the vertical direction have. As used herein, the term " connected "means that some or all of the first nano inorganic particle layer is in physical contact with the second nano inorganic particle layer.

Further, in order to connect the first nano inorganic particle layer and the second nano inorganic particle layer in such a vertical direction, the thickness of the second adhesive layer is preferably set such that the depth of the second adhesive layer Is preferably smaller than the thickness of the surface.

If the first nano inorganic particle layer and the neighboring second nano inorganic particle layer can be vertically connected, the concave surface of the first composite layer and the concave surface of the second composite layer may have the same pattern, direction, depth, It may be different.

A composite according to another embodiment of the present invention comprises a substrate, a first adhesive layer having a first intaglio surface on the substrate, a first adhesive layer on the first adhesive layer, A second adhesive layer on the first nano inorganic particle layer having a depressed space of a first intaglio surface with a very high constant thickness and a second intaglio surface, and a second adhesive layer on the second adhesive layer along the second intaglio surface And the second nano inorganic particle layer is laminated, and the first nano inorganic particle layer and the second nano inorganic particle layer are electrically or thermally connected to each other in the vertical direction.

In the description of this embodiment, the components described in the above-described manufacturing method are omitted.

FIGS. 2 and 3 are schematic diagrams of a cross-section of a composite according to an embodiment of the present invention. The structures shown in Figs. 2 and 3 are only examples of the present invention, and the present invention is not limited to these structures. As shown in Figs. 2 and 3, the first nano inorganic particle layer 22 and the second nano inorganic particle layer 32 are connected vertically, so that thermal or electrical conduction can be performed rapidly.

Specifically, the composite 1 of the present invention includes a substrate 10 and a composite layer 20, 30 laminated on the substrate 10. The composite layers 20 and 30 are composed of adhesive layers 21 and 31 and nano-inorganic particle layers 22 and 32. The adhesive layer has a depressed surface on a surface that does not face the substrate and a nano inorganic particle layer is laminated along the depressed surface. Each of the multiple layers may alternatively be laminated alternately. The number of the multiple layers to be laminated can be variously applied according to the purpose of the present invention.

However, the nano-inorganic particle layer should be in contact with the layer of the nano-inorganic particles partially or entirely adjacent to the layers to be laminated and electrically or thermally connected thereto.

Another embodiment of the present invention is a heat sink comprising any one of the various composites described above.

FIG. 4 is a schematic view of a heat sink and an IC chip including a composite according to another embodiment of the present invention. In Fig. 4, the h-BN & polymer composite refers to a composite in which the nano inorganic particle layer and the adhesive layer are alternately laminated. The enlarged view of the insert shows a composite overlying the heat sink and layers of adhesive and nano-inorganic particles (H-BN) alternately laminated. Since the nano inorganic particle layer is vertically thermally or electrically connected inside the composite, the heat generated by the electronic device including the IC chip by the heat sink easily escapes to the heat sink.

The electromagnetic wave shielding agent according to another embodiment of the present invention includes any one of the various composites described above.

Hereinafter, the present invention will be described in detail with reference to specific examples.

(1 glycerol / phenol) diacrylate, 3- (trimethoxysilyl) propyl methacrylate, spin-on-glass (SOG 500F), and the like were used as the ultra- 2-benzyl-2- (dimethylamino) -4, and anhydrous ethanol in a mass ratio of 200: 100: 100: 9: 1700. The PET film was prepared as a substrate, treated with oxygen plasma, and then the adhesive prepared on the substrate was spin-coated at 3000 rpm for 30 seconds to form an adhesive layer having a thickness of 100-120 nm.

In order to transfer the nano-inorganic particles onto the adhesive layer by the stamping method, PDMS was prepared as a stamping material. PDMS stamps were prepared using the SYLGARD 184 silicone elastomer kit (Dow Corning Inc.). In SYLGARD 184, the PDMS precursor and hardener are mixed at a ratio of 10: 1 and poured into Petri dishes. The bubbles were removed and cured at 70 ° C for 1 hour. The PDMS mold was coated with boron nitride to form a nano-inorganic particle layer. A stamping process was performed using a PDMS mold coated with boron nitride to form a depressed surface on the adhesive layer, and the nano inorganic particle layer was transferred onto the depressed surface. This process was repeated five or more times.

5 (a) and 5 (b) show electron micrographs of cross-sections of the examples prepared under the experimental conditions described above. As shown in Figs. 5 (a) and 5 (b), it was confirmed that the nano-inorganic particle layers were vertically connected.

FIG. 6 shows electron microscopic photographs of a part of the complex shown in FIG. 5, a graph of energy dispersive spectroscopy (EDS), and a result table. As shown in Fig. 6, it was confirmed that a large amount of nitrogen and boron existed at the portion where the nano-inorganic particle layer is connected.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. It can be understood that it is possible.

Claims (25)

Board;
A first adhesive layer having a first intaglio surface on the substrate;
A first nano-inorganic particle layer laminated on the first adhesive layer along the first intaglio surface;
A second adhesive layer on the first nano inorganic particle layer, the second adhesive layer having an intaglio space of the first intaglio surface with a very high constant thickness and a second intaglio surface; And
And a second nano inorganic particle layer laminated on the second adhesive layer along the second intaglio surface,
Wherein the first nano inorganic particle layer and the second nano inorganic particle layer are electrically or thermally connected to each other by a physical contact of a part of each layer. The method according to claim 1,
Wherein the substrate is a flexible transparent substrate. The method according to claim 1,
Wherein the coating on the adhesive layer of the first and second nano-inorganic particles comprises a part or all of the nano-inorganic particles being impregnated into the adhesive layer or on the surface of the adhesive layer. The method according to claim 1,
Wherein the adhesive comprises a transparent adhesive comprising a bisphenol A acrylate compound and an alkoxysilyl acrylate compound. 5. The method of claim 4,
Wherein the bisphenol A-based acrylate compound comprises bisphenol A glycerolate (1 glycerol / phenol) diacrylate having the following Formula 1:
Formula 1

. 5. The method of claim 4,
Wherein the alkoxysilyl acrylate compound comprises 3- (trimethoxysilyl) propyl methacrylate represented by the following formula (2): < EMI ID =
(2)

. 5. The method of claim 4,
Wherein the adhesive comprises a photoinitiator. 8. The method of claim 7,
The photoinitiator is a polymeric nano-inorganic particle composite material comprising 2-benzyl-2- (dimethylamino) -4-morpholinobutyrophenone of the following formula (3) :
(3)

. 5. The method of claim 4,
Wherein the adhesive comprises poly (methyl silsesquioxane) (poly (methyl silsesquioxane)). The method according to claim 1,
Wherein the thickness of the first and second adhesive layers is smaller than the thickness of the first and second intaglio surfaces, respectively. The method according to claim 1,
Wherein the nano-inorganic particle comprises at least one of graphene, a metallic grid, a carbon nanotube, a silver nanowire, and boron nitride. 12. A heat sink comprising the polymer nanomolecular particle composite according to any one of claims 1 to 11. 11. An electromagnetic wave shielding material comprising a multilayer thin film of a polymeric nano-inorganic particle composite according to any one of claims 1 to 11. A first step of preparing a substrate;
A second step of forming a first adhesive layer on the substrate; And
A third step of forming a first intaglio surface on one surface of the first adhesive layer using a stamp on which nano-inorganic particles are placed on the embossed surface, and laminating the nano inorganic particle layer along the first intaglio surface;
A fourth step of forming a second adhesive layer on the first intaglio face formed by the nano inorganic particle layer so as to have a very thick thickness; And
And a fifth step of forming a second indentation surface on one surface of the second adhesive layer using a stamp on which nano-inorganic particles are placed on the embossed surface,
Wherein the first nano inorganic particle layer and the second nano inorganic particle layer adjacent to the first nano inorganic particle layer are electrically or thermally connected in the vertical direction. 15. The method of claim 14,
The adhesive is a thermosetting or light curable adhesive,
In the third step, irradiating with heat or light to cure the polymer nanofiber composite particles. 15. The method of claim 14,
Wherein the substrate is a flexible transparent substrate. 15. The method of claim 14,
Wherein the coating on the adhesive layer of the nano-inorganic particles comprises a step of impregnating all or a part of the nano-inorganic particles in the adhesive layer or on the surface of the adhesive layer. 15. The method of claim 14,
Wherein the adhesive comprises a transparent adhesive comprising a bisphenol A acrylate compound and an alkoxysilyl acrylate compound. 19. The method of claim 18,
Wherein the bisphenol A-based acrylate compound comprises bisphenol A glycerolate (1 glycerol / phenol) diacrylate represented by the following Formula 1:
Formula 1

. 19. The method of claim 18,
Wherein the alkoxysilyl acrylate compound comprises 3- (trimethoxysilyl) propyl methacrylate represented by the following formula (2): < EMI ID =
(2)

. 19. The method of claim 18,
Wherein the adhesive comprises a photoinitiator. 22. The method of claim 21,
The photoinitiator is a polymeric nano-inorganic particle composite material comprising 2-benzyl-2- (dimethylamino) -4-morpholinobutyrophenone of the following formula (3) : ≪
(3)

. 19. The method of claim 18,
Wherein the adhesive comprises poly (methyl silsesquioxane) (poly (methyl silsesquioxane)). 15. The method of claim 14,
Wherein the thickness of the first and second adhesive layers is smaller than the thickness of the first and second intaglio surfaces, respectively. 15. The method of claim 14,
Wherein the nano-inorganic particle comprises at least one of graphene, a metallic grid, a carbon nanotube, a silver nanowire, and boron nitride.

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