KR102272048B1 - Exothermic sheet and Shape memory composite including the same - Google Patents

Abstract

The present invention includes a polymer binder, plate-shaped graphite, carbon nanotubes, and carbon black particles, wherein the graphite is arranged in a first direction, and the carbon nanotubes and the carbon black particles are disposed between the graphite It includes a heating sheet arranged in space, and the resistance of the heating sheet is reduced by packing carbon nanotubes and carbon black particles by graphite.
Therefore, it is possible to increase the response speed and recovery speed of the shape memory composite.

Description

Exothermic sheet and Shape memory composite including the same

The present invention relates to a shape memory composite, and more particularly, to a heating sheet having an improved temperature increase rate and a shape memory composite having a fast response time and recovery time including the same.

As society enters the information age in earnest, the field of display that processes and displays a large amount of information has developed rapidly, and in response to this, liquid crystal display device (LCD), plasma display device (Plasma Display) has developed rapidly. Various flat panel display devices such as a panel device: PDP), a field emission display device (FED), and an organic light emitting diode display device (OELD) have been developed and are in the spotlight.

Such a flat panel display device requires a display unit on which an image is displayed, and the size of the display unit is limited due to restrictions such as portability.

Recently, in order to overcome this size limitation, a flexible display device that can be folded and unfolded has been proposed.

For example, in a variable display device, a driving means such as a motor is used to make a flexible display panel have an appropriate curvature. However, the volume and thickness of the display device are increased by the motor, and there is a problem due to the noise of the motor.

In order to solve the above-described problem, a technology for changing a display device using a shape memory alloy instead of a motor method is being developed. In order to deform the shape memory alloy, self-heating is required, and for this purpose, nitinol (Ni-Ti) was mainly used as the shape memory alloy.

In the case of nitinol, since the resistance value is low (1.0 or less), it must be formed in a wire type for sufficient heat generation. However, a driving force for changing a display device cannot be obtained with a wire-type shape memory alloy.

That is, in the case of a conventional shape memory composite made of nitinol, there is a problem in that it does not generate sufficient heat to deform the shape of the shape memory alloy or obtain a driving force for changing the display device. In other words, in the conventional shape memory alloy, there is a trade-off relationship between the amount of heat generated and the driving force.

An object of the present invention is to provide a shape memory composite capable of generating a driving force for changing a display device while allowing sufficient heat to be generated for a shape change of a shape memory material.

In order to solve the above problems, the present invention includes a polymer binder, plate-shaped graphite, carbon nanotubes, and carbon black particles, wherein the graphite is arranged in a first direction, and the carbon nanotubes and The carbon black particles provide a heating sheet arranged in the space between the graphite.

In the heating sheet of the present invention, the graphite is arranged spaced apart from each other in a second direction perpendicular to the first direction.

The heating sheet of the present invention further includes first and second electrodes positioned at both ends in the first direction.

In the heating sheet of the present invention, the extending direction of the space formed by the graphite is parallel to the direction connecting the first and second electrodes.

In another aspect, the present invention provides a first heating sheet comprising a polymer binder, plate-shaped graphite, carbon nanotubes, and carbon black particles, and a shape memory sheet positioned on one side of the first heating sheet; a first insulating sheet positioned between the first heating sheet and a first surface of the shape memory sheet, wherein the graphite is arranged in a first direction, and the carbon nanotubes and the carbon black particles are disposed between the graphite A shape memory complex arranged in space is provided.

In the shape memory composite of the present invention, the graphite is arranged to be spaced apart from each other in a second direction perpendicular to the first direction.

The shape memory composite of the present invention further includes first and second electrodes positioned at both ends in the first direction.

In the shape memory composite of the present invention, the extending direction of the space formed by the graphite is parallel to the direction connecting the first and second electrodes.

In the shape memory composite of the present invention, the shape memory sheet includes at least one of a shape memory alloy or a shape memory polymer.

The shape memory composite of the present invention further includes a protective sheet positioned outside the first heat generating sheet and a heat diffusion sheet positioned on a second surface side of the shape memory sheet.

The shape memory composite of the present invention includes a second heating sheet positioned on the second surface side of the shape memory sheet and comprising a polymer binder, plate-shaped graphite, carbon nanotubes, and carbon black particles, and the shape memory It further includes a second insulating sheet positioned between the sheet and the second heating sheet.

The shape memory composite of the present invention further includes first and second protective sheets positioned outside each of the first and second heating sheets.

Since the heating sheet of the present invention includes carbon nanotubes, carbon black particles, and graphite, the rate of temperature increase by voltage application increases.

That is, the mixture of carbon nanotubes and carbon black particles has a structure in which the mixture is sandwiched by graphite, and the graphite serves as a current path, thereby reducing the resistance of the heating sheet. Accordingly, sufficient heat can be generated even by a low voltage.

In addition, since the shape memory composite of the present invention includes the heating sheet and the shape memory material layer, sufficient heat for driving the shape memory composite at a low voltage can be obtained. Accordingly, the shape memory composite can be manufactured in the form of a sheet, and sufficient driving force for changing the display device can be obtained, and the response speed and restoration speed of the shape memory composite can be improved.

That is, when the shape memory composite of the present invention is used, a variable display device capable of rapidly changing with a low voltage is provided.

1 is a schematic plan view of a heating sheet according to a first embodiment of the present invention.
2 is a schematic plan view of a heating sheet according to a second embodiment of the present invention.
3 is a photograph showing a heating sheet according to a second embodiment of the present invention.
4 is a schematic view for explaining the flow of electrons in the heating sheet according to the second embodiment of the present invention.
5 is a schematic diagram showing a shape memory composite according to a third embodiment of the present invention.
6 is a schematic view for explaining a driving principle of a shape memory alloy.
7 is a schematic diagram showing a shape memory composite according to a fourth embodiment of the present invention.

Hereinafter, the present invention capable of solving the above problems will be described in detail with reference to the drawings.

-First embodiment-

1 is a schematic plan view of a heating sheet according to a first embodiment of the present invention.

As shown in FIG. 1 , the heating sheet 100 according to the first embodiment of the present invention includes carbon nanotubes 120 dispersed in a polymer binder 110 .

The polymer binder (not shown) has non-conductive properties, and among polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), polyimide (PI), and cellulose-based binders. can be selected.

The carbon nanotubes 120 are dispersed in the polymer binder 110 to become a path of electrical flow. That is, when a voltage is applied to the first and second electrodes 130 and 132 , electrons from the first electrode 130 as a negative electrode 130 pass through the carbon nanotube 120 to the second electrode as an anode (+). Heat is generated from the heating sheet 100 while being transferred to (132).

Accordingly, heat is transferred to the shape-memory material layer (not shown) stacked on the heating sheet 100 and the shape of the shape-memory material layer (not shown) is changed. That is, as the temperature increases, the shape memory material layer is restored to its original state.

When the shape memory composite including the heating sheet and the shape memory material layer is used in a display device, the display device can be varied by changing the shape of the shape memory material layer.

Since the shape memory composite can be manufactured in the form of a sheet by using such a heating sheet, sufficient driving force can be obtained for variably changing the display device.

However, as in the first embodiment, since the resistance of the heat generating sheet 100 including the polymer binder 110 and the carbon nanotubes 120 is too high, the rate for sufficient heat generation, that is, the temperature increase rate is relatively low. In addition, since there is residual heat even when the voltage is removed by the high resistance, the temperature drop rate is also relatively low.

Therefore, since the response speed and recovery speed of the shape memory composite are low, the display device changes too slowly.

-Second embodiment-

2 is a schematic plan view of a heating sheet according to a second embodiment of the present invention.

As shown in FIG. 2 , the heating sheet 200 according to the first embodiment of the present invention includes a polymer binder (not shown), carbon nanotubes 220 , carbon black particles 230 , and graphite ( 240). The carbon nanotubes 220 , the carbon black particles 230 , and the graphite 240 are dispersed in the polymer binder (not shown).

The polymer binder (not shown) has non-conductive properties, and among polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), polyimide (PI), and cellulose-based binders. can be selected. The polymer binder may have a glass transition temperature of 80° C. or higher to withstand the heat of the heating sheet 200 .

The graphite 240 has a plate shape and is located at the edge of the heating sheet 200 , and the carbon nanotubes 220 and the carbon black particles 230 are located in an internal space provided by the graphite 240 . .

That is, in the heating sheet 200 according to the second embodiment of the present invention, the carbon nanotubes 220 and the carbon black particles 230 are dispersed in the polymer binder (not shown), and the graphite 240 is It has a shape surrounding the carbon nanotubes 220 and the carbon black particles 230 .

Referring to FIG. 3, which is a photograph showing a heating sheet according to the second embodiment of the present invention, plate-shaped graphite is positioned with a wall, and carbon nanotubes (CNT) and carbon black particles (CB) are attached to the graphite wall. It can be seen that they are mixed in the space by

Since the graphite 240 traps carbon nanotubes (CNTs) and carbon black particles (CB) in a predetermined space and serves as an electron movement space, an electron movement path is shortened and electron movement occurs smoothly.

Accordingly, the resistance of the heating sheet 200 is lowered and the amount of heat is increased.

Referring to FIG. 4, which is a schematic diagram for explaining the flow of electrons in the heating sheet according to the second embodiment of the present invention, carbon nanotubes 220, carbon black particles 230 and Graphite 240 is dispersed. The graphite 240 forms a wall-like shape and surrounds the carbon nanotubes 220 and the carbon black particles 230 .

In addition, first and second electrodes 252 and 254 are formed at opposite ends of the heating sheet 200 .

When a voltage is applied to the first and second electrodes 252 and 254, electrons (e-) from the first electrode 252 that are negative (-) are positive (+) of the second electrode 254 Heat is generated while moving to the , and electrons (e-) move smoothly through the carbon nanotubes 220 and the carbon black particles 230 packed by the graphite 240 .

That is, when only the carbon nanotubes 220 are formed, since there is a space between the carbon nanotubes 220 , the movement of electrons e- is prevented, thereby increasing the resistance of the heating sheet. However, when the carbon nanotubes 220 and the carbon black particles 230 are mixed as in the second embodiment of the present invention, since the carbon black particles 230 fill the space between the carbon nanotubes 220, the electron (e) -) moves smoothly, so that the resistance of the heating sheet 200 is reduced.

In this case, the graphite 240 is arranged parallel to the direction in which the first and second electrodes 252 and 254 are connected. That is, the extending direction of the space provided by the graphite 240 is parallel to the direction connecting the first and second electrodes 252 and 254 , and serves as a movement path of the electrons e-.

In other words, in the heating sheet 200 according to the second embodiment of the present invention, the graphite 240 provides a movement space for electrons (e-) and carbon nanotubes 220 in the space defined by the graphite 240 . ) and the carbon black particles 230 are mixed, the resistance of the heating sheet 200 is reduced.

Accordingly, the temperature increase and temperature decrease time of the heating sheet 200 are reduced.

[Production of heating sheet]

Table 1 shows the composition for forming the heating sheet, and the resistance of the heating sheet prepared by coating and drying the composition. In this case, PET was used as the binder, ethanol was used as the solvent, and the thickness of the prepared heating sheet was about 40 μm.

Table 2 shows the results of the temperature increase test in the heating sheet prepared using the composition of Table 1. While changing the applied voltage, the temperature after 10 seconds was measured.

As shown in Tables 1 and 2, the heating sheet of the present invention comprising carbon nanotubes (CNT), carbon black particles (CB) and graphite (GP) has low resistance and has a high temperature increase rate. Therefore, when the heating sheet of the present invention is used for a shape memory composite, the response speed and restoration speed of the shape memory composite can be increased. As can be seen from Tables 1 and 2, when the weight ratio of graphite (GP) and carbon black particles (CB) is greater than the weight ratio of carbon nanotubes (CNT) (Ex3, Ex4), the resistance of the heating sheet is greatly reduced and the temperature increase rate is greatly increased.

-Third embodiment-

5 is a schematic diagram showing a shape memory composite according to a third embodiment of the present invention.

As shown in FIG. 5 , the shape memory composite 300 according to the third embodiment of the present invention includes a heating sheet 330 including a heating material layer 310 and first and second electrodes 322 and 324 . ), a shape memory sheet 340 positioned to correspond to one surface of the heating sheet 310 , and an insulating sheet 350 positioned between the heating sheet 330 and the shape memory sheet 340 . .

The heating sheet 330 may be the heating sheets 100 and 200 according to the first and second embodiments of the present invention.

For example, as shown in FIGS. 2 to 4 , the heating material layer 310 includes a polymer binder 210 , carbon nanotubes 220 dispersed in the polymer binder 210 , and carbon Black particles 230 and graphite 240 are included.

At this time, the graphite 240 has a plate shape and is arranged to form a wall, thereby providing a space. In addition, the carbon nanotubes 220 and the carbon black particles 230 are mixed with each other in the space provided by the graphite 240 .

According to this arrangement, since the graphite 240 traps the carbon nanotubes (CNTs) and the carbon black particles (CB) in a predetermined space and serves as an electron transfer path, the electron transfer path is shortened and the electron transfer path is shortened. This happens smoothly. Accordingly, the resistance of the heating material layer 310 is lowered.

Referring back to FIG. 5 , the first and second electrodes 322 and 324 are positioned at both ends of the heating material layer 310 . One of the first and second electrodes 322 and 324 is an anode and the other is a cathode. Each of the first and second electrodes 322 and 324 may be formed of a low-resistance metal material, for example, copper (Cu), gold (Au), or silver (Ag).

In FIG. 5 , it is shown that the first and second electrodes 322 and 324 are formed on the upper surface of the heating material layer 310 . Alternatively, the first and second electrodes 322 and 324 may be formed on the lower surface of the heating material layer 310 or formed on the side surface of the heating material layer 310 .

At this time, the graphite (240 in FIG. 4 ) is arranged parallel to the direction in which the first and second electrodes 322 and 324 are connected. That is, the extending direction of the space provided by the graphite (240 in FIG. 4 ) is parallel to the direction connecting the first and second electrodes 322 and 324 . In other words, graphite (240 in FIG. 4) is arranged along the first direction and spaced apart in the second direction perpendicular to the first direction in the heating sheet 330 to provide a space extending along the first direction, , first and second electrodes 322 and 324 are positioned at both ends in the first direction.

As described above, when a voltage is applied to the first and second electrodes 322 and 324 , electrons (e−) from the first electrode 322 that are negative (−) are positive (+) of the first electrode (+). Heat is generated while moving to the second electrode 324. The graphite (240 in FIG. 4) provides a movement space for electrons (e-) and is packed by the graphite (240 in FIG. 4). Since the movement of electrons (e-) is facilitated through the carbon nanotubes (220 in FIG. 4 ) and the carbon black particles ( 230 in FIG. 4 ), the amount of heat generated by the heating sheet 330 is increased and the temperature is increased rising) and temperature-falling rates increase.

The shape memory sheet 340 is positioned on one side of the heating sheet 330 and includes a shape memory material. That is, the shape memory sheet 340 is manufactured to have a memory shape or an original shape, and has a deformed shape at a temperature lower than the transition temperature. On the other hand, when the heat is provided from the heating sheet 330 and is above the transition temperature, the memory shape is restored. Also, when the heat is removed and the temperature is lower than the transition temperature, the shape is deformed again.

The shape memory material is at least one of a shape memory alloy (SMA) or a shape memory polymer (SMP).

A shape memory alloy is a metal alloy having a property of being deformed below a transition temperature and returning to a shape before deformation when above a transition temperature.

For example, the shape memory alloy is formed to have a curved memory shape, maintains a flat shape, and is restored to a curved memory shape when heat is applied and the temperature is higher than a certain temperature.

6 is a schematic view for explaining a driving principle of a shape memory alloy.

Referring to FIG. 6 , the shape memory alloy has an austenite structure in a memory state that stores a flat or curved shape. When the shape memory alloy is cooled, it transforms into a martensite structure in a random state, and returns to the original austenite structure when heated again. That is, the shape of the memory state is restored by heat.

That is, when heat is applied after deformation occurs, it has a shape memory effect due to thermoelastic martensitic transformation that returns to an original shape.

On the other hand, the shape memory polymer is formed in a form in which various phases such as a fixed (hard) phase and a reversible (soft) phase exist together.

The stationary phase acts like a thermally stable crosslinking point. In general, the 'crosslinking point' may be a crystalline phase, a glassy phase, or an entangled polymer chain that prevents the free movement of at least one part of the material. On the other hand, the reversible phase is a major part of shape memory polymers and plays an elastic role in deformation or recovery. Above a certain temperature, the reversible phase becomes a 'fluid' and has the property of being able to move freely. Conversely, below a certain temperature, the reversible phase may form a glassy or crystalline structure.

This constant temperature is generally called a triggered temperature and corresponds to the glass transition temperature (Tg) or the melting point (Tm). When deformation is applied to the shape memory polymer, such as pulling at a temperature higher than the induced temperature, the polymer chains are aligned, which in turn leads to a decrease in structural entropy. This state can be referred to as an entropy unstable or unfavorable state. This alignment can be maintained by rapidly cooling to the induced temperature in the strained state, except for the fine recovery performance.

Looking at the shape restoration process of the shape memory polymer, first, the shape memory polymer material exhibiting elastic rubber properties at a temperature higher than the transition temperature is changed by applying a specific strain. At this time, the polymer chains are aligned according to the deformation. When a force capable of sustaining deformation is continuously applied and the material is cooled below the transition temperature ( ) at which the material can be hardened, the chains constituting the polymer become immobile and change in the form of potential deformation energy to remain fixed. do. When the force given at the transition temperature is removed, a slight temporary recovery occurs. Shape recovery generally occurs without any external force by heating the temperature above the transition temperature, and the stored strain energy is released by allowing the polymer chain to move again.

Referring back to FIG. 5 , the shape memory sheet 340 is bent or flattened by the heat transferred from the heating sheet 330 . The shape memory sheet 340 is made of a shape memory material such as a shape memory alloy or a shape memory polymer.

The shape memory alloy may be at least one of a nickel (Ni) alloy, a copper (Cu) alloy, or an iron (Fe) alloy. For example, the shape memory sheet 340 may include at least one selected from Cu-Zn-Ni, Cu-Al-Ni, Ag-Ni, Au-Cd, and Ni-Ti.

When the shape memory sheet 340 includes the shape memory polymer, the shape memory polymer may be selected from polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, ethylene propylene rubber, chloroprene rubber, styrene butadiene rubber, nitrile butadiene rubber, and Teflon. It may be any one or more.

The insulating sheet 350 is positioned between the heating sheet 330 and the shape memory sheet 340 , insulates them, and transfers heat from the heating sheet 330 to the shape memory sheet 340 . The material constituting the insulating sheet 350 preferably has high heat transfer properties.

The insulating sheet 350 may be formed of an organic material, an inorganic material, or an organic-inorganic hybrid material.

For example, the insulating sheet 350 may include polycarbonate (PC), polyethylene terephthalate (PET), polyimide (PI), polyethylstyrene (PES) and An organic-inorganic hybrid material in which the same organic material, an inorganic material such as silicon oxide or silicon nitride, and a material of silica or a low-k metal-based material is mixed with an organic material may be formed.

The shape memory composite 300 according to the third embodiment of the present invention may further include a protection sheet 360 positioned on the heating sheet 330 . That is, the heating sheet 330 is positioned between the protective sheet 360 and the insulating sheet 350 .

The protective sheet 360 serves to protect the heating sheet 330 and may be made of an organic material such as polycarbonate, polyethylene terephthalate, polyimide, or polyethylstyrene.

In addition, the shape memory composite 300 according to the third embodiment of the present invention may further include a heat diffusion sheet 370 positioned under the shape memory sheet 340 . That is, the shape memory sheet 340 is positioned between the insulating sheet 350 and the heat diffusion sheet 370 .

The heat diffusion sheet 370 serves to dissipate heat so that the heat of the shape memory sheet 340 is easily discharged. Accordingly, the heat diffusion sheet 150 is in contact with the entire lower surface of the shape memory sheet 340 and is made of a material having excellent thermal conductivity. For example, the heat diffusion sheet 150 may be made of carbon nanotubes, graphite, aluminum (Al), copper, tungsten (W), or the like.

As described above, the shape memory composite 300 according to the third embodiment of the present invention includes a heating sheet 330 and a shape memory sheet 340 stacked with an insulating sheet 350 interposed therebetween, and the heating sheet It may further include a protective sheet 360 and a heat diffusion sheet 370 attached to the outer surface of each of the 330 and the shape memory sheet 340 .

At this time, the heating sheet 330 is a polymer binder 210 , carbon nanotubes 220 dispersed in the polymer binder 210 , and heat generated including carbon black particles 230 and graphite 240 . The material layer 310 and the first and second electrodes 322 and 324 are included, and the graphite 240 traps carbon nanotubes (CNTs) and carbon black particles (CB) in a predetermined space, and electron transfer paths (paths). ) or as an electron movement space, the electron movement path is shortened and the electron movement becomes smooth, so that the resistance of the heating material layer 310 is lowered.

That is, since the temperature increase or decrease speed of the heating sheet 330 is increased, the response speed and the restoration speed of the shape memory composite 300 are increased. Therefore, when such a shape memory composite 300 is used in a display device, a change in the shape of the display device can be easily obtained.

-Fourth embodiment-

7 is a schematic diagram showing a shape memory composite according to a fourth embodiment of the present invention.

As shown in FIG. 7 , the shape memory composite 400 according to the fourth embodiment of the present invention includes a first heating material layer 412 and first and second electrodes 414 and 416 . A heating sheet 410, a second heating sheet 420 including a second heating material layer 422, and third and fourth electrodes 424 and 426, and the first and second heating sheets 410, The shape memory sheet 430 positioned between the 420, the first insulating sheet 432 positioned between the first heating sheet 410 and the shape memory sheet 430, and the second heating sheet 420 ) and a second insulating sheet 434 positioned between the shape memory sheet 430 .

Each of the first and second heating sheets 410 and 420 may be the heating sheets 100 and 200 according to the first and second embodiments of the present invention.

For example, as shown in FIGS. 2 to 4 , each of the first and second heating material layers 412 and 422 includes a polymer binder 210 and carbon dispersed in the polymer binder 210 . It includes the nanotubes 220 , carbon black particles 230 and graphite 240 .

At this time, the graphite 240 has a plate shape and is arranged to form a wall, thereby providing a space. In addition, the carbon nanotubes 220 and the carbon black particles 230 are mixed with each other in the space provided by the graphite 240 .

According to this arrangement, since the graphite 240 traps carbon nanotubes (CNTs) and carbon black particles (CB) in a predetermined space and serves as an electron transfer path or an electron transfer space, the electron transfer path is shortened and Electron transfer occurs smoothly. Accordingly, the resistance of the first and second heating material layers 412 and 422 is lowered.

Referring back to FIG. 7 , the first and second electrodes 414 and 416 are located at both ends of the first heating material layer 412 , and the third and fourth electrodes 424 and 426 are the first It is located at both ends of the heating material layer 422 . One of the first and second electrodes 414 and 416 is an anode and the other is a cathode. Also, one of the third and fourth electrodes 424 and 426 is an anode and the other is a cathode. Each of the first to fourth electrodes 414 , 416 , 424 , and 426 may be formed of a low-resistance metal material, for example, copper (Cu), gold (Au), or silver (Ag).

In FIG. 5 , first and second electrodes 414 and 416 are formed on the upper surface of the first heating material layer 412 , and third and fourth electrodes 424 and 426 are formed on the second heating material layer 422 . ) is shown on the upper surface. Alternatively, the first and second electrodes 414 and 416 may be formed on the lower surface of the first heating material layer 412 or formed on the side surface of the first heating material layer 412 . In addition, the third and fourth electrodes 424 and 426 may be formed on the lower surface of the second heating material layer 422 or formed on the side surface of the second heating material layer 422 .

At this time, the graphite (240 in FIG. 4 ) of the first heating material layer 412 is arranged parallel to the direction in which the first and second electrodes 414 and 416 are connected. That is, the extending direction of the space provided by the graphite (240 in FIG. 4 ) is parallel to the connecting direction of the first and second electrodes 414 and 416 . In addition, the graphite (240 in FIG. 4 ) of the second heating material layer 422 is arranged parallel to a direction in which the third and fourth electrodes 424 and 426 are connected. That is, the extending direction of the space provided by the graphite (240 in FIG. 4 ) is parallel to the direction connecting the third and fourth electrodes 424 and 426 .

In other words, graphite (240 in FIG. 4 ) is arranged along the first direction and spaced apart in a second direction perpendicular to the first direction in the first and second heating sheets 410 and 420 to form the first direction. A space extending along the line is provided, and the first to fourth electrodes 414 , 416 , 424 , 426 are positioned at both ends in the first direction.

As described above, when a voltage is applied to the first to fourth electrodes 414 , 416 , 424 , 426 , electrons (e−) from the first and third electrodes 414 and 424 that are negative (−) ) moves to the second and fourth electrodes 416 and 426 that are positive (+), and heat is generated, and the graphite (240 in FIG. 4 ) provides a space for electrons (e-) to move and the graphite Since the movement of electrons (e-) is facilitated through the carbon nanotubes (220 in FIG. 4) and the carbon black particles (230 in FIG. 4) packed by (240 in FIG. 4), the The calorific value of the first and second heat generating sheets 410 and 420 increases, and the temperature rise and fall rates increase.

The shape memory sheet 430 is positioned between the first and second heating sheets 410 and 420 and includes a shape memory material. That is, the shape memory sheet 430 is manufactured to have a memory shape or an original shape, and has a deformed shape at a temperature lower than the transition temperature. Meanwhile, when heat is supplied from the first and second heat generating sheets 410 and 420 and the transition temperature is higher than the transition temperature, the memory shape is restored. Also, when the heat is removed and the temperature is lower than the transition temperature, the shape is deformed again.

The shape memory material includes at least one of a shape memory alloy (SMA) and a shape memory polymer (SMP).

For example, the shape memory sheet 430 may include at least one selected from a shape memory alloy such as Cu-Zn-Ni, Cu-Al-Ni, Ag-Ni, Au-Cd, Ni-Ti, or Polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, ethylene propylene rubber, chloroprene rubber, styrene butadiene rubber, nitrile butadiene rubber, and may be made of any one or more selected from shape memory polymers such as Teflon.

The first and second insulating sheets 432 and 434, respectively, are positioned between the first and second heat generating sheets 410 and 420 and the shape memory sheet 430, insulate them and the first and second heat generating sheets 410 and 420, respectively. Heat from the heating sheets 410 and 420 is transferred to the shape memory sheet 430 . The material constituting the first and second insulating sheets 432 and 434 preferably has high heat transfer properties.

Each of the first and second insulating sheets 432 and 434 may be formed of an organic material, an inorganic material, or an organic-inorganic hybrid material. For example, each of the first and second insulating sheets 432 and 434 may include polycarbonate (PC), polyethylene terephthalate (PET), polyimide (PI), and polyethylstyrene. An organic material such as (poly ether sulfone, PES), an inorganic material such as silicon oxide or silicon nitride, and a silica or a low-k metal-based material may be formed of an organic-inorganic hybrid material mixed with an organic material.

The shape memory composite 400 according to the fourth embodiment of the present invention includes a first protective sheet 442 positioned above the first heating sheet 410 and a second protective sheet 442 positioned below the second heating sheet 420 . A protective sheet 444 may be further included. That is, the first heating sheet 410 is positioned between the first protective sheet 442 and the first insulating sheet 432 , and the second heating sheet 420 is formed between the second protective sheet 444 and the second protective sheet 444 . It is positioned between the second insulating sheets 434 .

Each of the first and second protective sheets 442 and 444 is for protecting the first and second heat generating sheets 410 and 420, and includes organic materials such as polycarbonate, polyethylene terephthalate, polyimide, and polyethylstyrene. It can be made of material.

As described above, in the shape memory composite 400 according to the fourth embodiment of the present invention, the first heating sheet 410 , the first insulating sheet 432 , the shape memory sheet 430 , and the second insulating sheet are sequentially stacked. First and second protective sheets 442 and 444, each including a sheet 434 and a second heating sheet 420, attached to the outer surfaces of the first and second heating sheets 410 and 420, are further added. may include

In this case, the first and second heating sheets 410 and 420 include a polymer binder 210 , carbon nanotubes 220 dispersed in the polymer binder 210 , carbon black particles 230 , and graphite. The first and second heating material layers 412 and 422 including 240 and electrodes 414, 416, 424 and 426 are respectively included, and graphite 240 is carbon nanotube (CNT) and carbon black particles. Since (CB) is confined in a certain space and serves as an electron transport path, the electron transport path is shortened and the electron transport becomes smooth, thereby reducing the resistance of the first and second heating material layers 412 and 422 .

That is, since the temperature increase or decrease rate of the first and second heating sheets 410 and 420 is increased, the response speed and restoration speed of the shape memory composite 400 are increased. In addition, since the first and second heat generating sheets 410 and 420 are respectively positioned on both sides of the shape memory sheet 430 having a sandwich structure, the response speed and the recovery speed are further increased. Accordingly, when such a shape memory composite 400 is used in a display device, a change in the shape of the display device can be easily obtained.

For example, the variable display device may include a display panel such as a liquid crystal panel or an organic light emitting diode, a frame covering the rear surface of the display panel, and the shape memory complexes 300 and 400 attached to the rear surface of the frame.

When heat from the heating sheets 330 , 410 , 420 of the shape memory composites 300 and 400 is transferred to the shape memory sheets 340 and 430 , the shape of the shape memory sheets 340 and 430 is changed and used as a variable display device. can be

Although the above has been described with reference to the preferred embodiment of the present invention, those skilled in the art can variously modify and change the present invention within the scope without departing from the spirit and scope of the present invention described in the claims below. You will understand that it can be done.

100, 200, 330, 410, 420: heating sheet
110, 210: polymer binder 120, 220: carbon nanotube
130, 230: carbon black particles 140, 240: graphite
340, 430: shape memory sheet 350, 432, 434: insulating sheet
360, 442, 444: protective sheet 370: heat diffusion sheet

Claims (15)

a polymer binder; plate-shaped graphite; carbon nanotubes; It includes a heating film containing carbon black particles,
The graphite is arranged in a first direction and positioned at both ends of the heating film in a second direction perpendicular to the first direction to have a structure for packing the carbon nanotubes and the carbon black particles, the carbon nanotubes and The carbon black particles are arranged in the space between the graphite,
In the heating film, the graphite serves as a current path to reduce the resistance of the heating sheet,
The carbon nanotubes, the carbon black particles, and the graphite have 4% by weight, 10% by weight, 10% by weight, or 4% by weight, 13% by weight, 13% by weight of the heating sheet.

delete The method of claim 1,
A heating sheet further comprising first and second electrodes positioned at both ends of the heating film in the first direction.
4. The method of claim 3,
An extension direction of the space formed by the graphite is parallel to a direction connecting the first and second electrodes.
a first heating sheet comprising a polymer binder, plate-shaped graphite, carbon nanotubes, and a heating film including carbon black particles;
a shape memory sheet positioned on one side of the first heating sheet;
a first insulating sheet positioned between the first heating sheet and the first surface of the shape memory sheet;
The graphite is arranged in a first direction and positioned at both ends of the heating film in a second direction perpendicular to the first direction to have a structure for packing the carbon nanotubes and the carbon black particles, the carbon nanotubes and The carbon black particles are arranged in the space between the graphite,
In the heating film, the graphite serves as a current path to reduce the resistance of the first heating sheet,
The shape memory composite, characterized in that the carbon nanotubes, the carbon black particles, and the graphite have 4 wt%, 10 wt%, 10 wt%, or 4 wt%, 13 wt%, 13 wt%.


delete 6. The method of claim 5,
The shape memory composite further comprising first and second electrodes positioned at both ends of the heating film in the first direction.
8. The method of claim 7,
An extension direction of the space formed by the graphite is parallel to a direction connecting the first and second electrodes.
6. The method of claim 5,
The shape memory sheet is a shape memory composite including at least one of a shape memory alloy or a shape memory polymer.
6. The method of claim 5,
The shape memory composite further comprising: a protective sheet positioned outside the first heat generating sheet; and a heat diffusion sheet positioned on a second surface side of the shape memory sheet.
6. The method of claim 5,
a second heating sheet positioned on the second surface side of the shape memory sheet and including a polymer binder, plate-shaped graphite, carbon nanotubes, and carbon black particles;
The shape memory composite further comprising a second insulating sheet positioned between the shape memory sheet and the second heating sheet.
12. The method of claim 11,
The shape memory composite further comprising: first and second protective sheets positioned outside each of the first heating sheet and the second heating sheet.
delete delete a display panel;
a frame covering a rear surface of the display panel;
A variable display device comprising the shape memory complex of any one of claims 5 and 7 to 12 attached to a rear surface of the frame.

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