KR102393781B1 - Flexible device - Google Patents

Abstract

The present invention provides a flexible element applied to a flexible display device. According to an embodiment of the present invention, the flexible element, a substrate including a first surface and a second surface opposite to the first surface, the first surface is provided with a plurality of grooves; and a metal layer positioned on the second surface of the substrate.

Description

Flexible device

The technical idea of the present invention relates to an electronic device, and more particularly, to a flexible element applied to a flexible display device.

Recently, a demand for mechanical mobility is greatly increased in order to improve the ease of storage by changing the size of a foldable portable device or a rollable display device, or to increase the degree of freedom in the shape of the device. The flexible display device used in these devices is required to secure a fatigue life of about 200,000 cycles. However, it is difficult to secure a sufficient lifespan due to a mechanical reliability problem occurring in the current bending portion.

Various studies have been conducted to impart mechanical mobility to electronic devices, and according to the flow of such developments, electronic devices must be able to accommodate greater mechanical stress. Accordingly, it is necessary to develop a core technology that can secure mechanical reliability in flexible electronic devices. In conventional electronic devices, high temperature, current density, voltage, etc. were the main factors causing reliability problems such as thermal stress, metal ion migration (electromigration), and dielectric breakdown. However, in the case of a flexible electronic device, since mechanical deformation such as bending, curling, and torsion is repeatedly applied, mechanical reliability problems such as peeling, breaking, and fatigue occur especially in the metal wiring portion occupying a large area inside the product. To solve this reliability problem, more than 200,000 long-term life evaluations are required.

Typically, industrialized technology has been researched in the form of providing mechanical mobility by replacing parts with a low influence on electrical performance, such as wiring or substrates, with deformable materials, rather than deforming devices that are susceptible to deformation. As one of them, in the case of the applied technology used in the existing flexible device, deformability is given to the metal wiring through a pattern of a folded structure in the form of a horse shoe, and the hard device is placed on it like an island to mechanically deform it. not to be affected by This causes the following problems. Since a space is required around the device to place a pattern of deformable wiring on the substrate, the degree of integration is inevitably reduced, and since deformation occurring in the patterned wiring is still present, fatigue occurring in the wiring causes a decrease in performance. point.

Our research team has studied various factors for bending deformation, and has the know-how on various fatigue phenomena that occur in materials when repetitive bending deformation occurs. Based on the above study, when bending deformation occurs, the stress change in the thickness direction has the greatest effect on the deformation of the element located on the surface, It was predicted that it would be possible to suppress and improve reliability.

Korean Patent Application No. 201300977979

The technical problem to be achieved by the technical idea of the present invention is to provide a flexible device having excellent fatigue resistance due to mechanical deformation.

However, these tasks are exemplary, and the technical spirit of the present invention is not limited thereto.

According to one aspect of the present invention, there is provided a flexible element having excellent fatigue resistance due to mechanical deformation.

According to an embodiment of the present invention, the flexible element, a substrate including a first surface and a second surface opposite to the first surface, the first surface is provided with a plurality of grooves; and a metal layer positioned on the second surface of the substrate.

According to an embodiment of the present invention, the plurality of grooves may extend at a predetermined angle with respect to the bending direction of the flexible element.

According to an embodiment of the present invention, the plurality of grooves may extend vertically with respect to a thickness direction of the substrate.

According to an embodiment of the present invention, the plurality of grooves may have a repeating pattern.

According to an embodiment of the present invention, the plurality of grooves may be spaced apart at the same interval.

According to an embodiment of the present invention, the plurality of grooves may be spaced apart from each other by an interval in the range of 0.1 mm to 2 mm.

According to an embodiment of the present invention, the plurality of grooves may have the same depth.

According to an embodiment of the present invention, the plurality of grooves may have a depth in the range of 50% to 80% of the thickness of the substrate.

According to an embodiment of the present invention, the plurality of grooves may have the same width.

According to an embodiment of the present invention, the plurality of grooves may have a width in a range of 10 μm to 80 μm.

According to an embodiment of the present invention, an interval between the plurality of grooves may be in the range of 1/10 to 5 times the thickness of the substrate.

According to an embodiment of the present invention, the strain rate of the substrate may satisfy the following relational expression (1).

<Relational Expression 1>

(where ε is the strain, g is the spacing between grooves, d is the depth of the grooves, h is the thickness of the substrate, and w is the width of the grooves)

According to an embodiment of the present invention, the substrate is made of polyimide, polyethylene terephthalate (PET), polyurethane, polydimethylsiloxane (PDMS), polyether block amides (PEBA), ethylene-vinyl acetate (EVA), Ecoflex, Dragon skin, silicon rubber, or micro-thin silicon wafers may be included.

According to an embodiment of the present invention, the substrate may have a thickness in the range of 10 μm to 1000 μm.

According to an embodiment of the present invention, the metal layer is copper (Cu), aluminum (Al), chromium (Cr), nickel (Ni), palladium (Pd), molybdenum (Mo), titanium (Ti), gold (Au) ), silver (Ag), platinum (Pt), or an alloy thereof.

According to an embodiment of the present invention, the metal layer may include at least one of metal nanowires, metal-carbon nanofibers, metal-carbon nanostructures, and graphene.

According to an embodiment of the present invention, the metal layer may have a thickness in the range of 10 nm to 1000 nm.

According to an embodiment of the present invention, the flexible element, a substrate including a first surface and a second surface opposite to the first surface, the first surface is provided with a plurality of grooves; and a metal layer positioned on the second surface of the substrate, wherein the metal layer has a carbon nanomaterial as a base material, and a rapid material may be coated on the surface of the carbon nanomaterial.

According to an embodiment of the present invention, the carbon nanomaterial may include carbon nanofibers, and the metal material may include copper.

According to the technical idea of the present invention, the flexible element is by processing the rear surface of the substrate on which the element is disposed to have a plurality of grooves in order to overcome the material deformation limit while maintaining the electrical performance of the existing element as it is. It can overcome the mechanical deformation limit and improve reliability.

The flexible element may form a plurality of grooves extending in a direction perpendicular to the bending direction on the rear surface of the substrate, thereby relieving the surface stress against deformation of bending the substrate on which the electronic element or wiring is formed inward, and maintaining reliability. . The grooves formed on the rear surface of the substrate may be linearly arranged at regular intervals. However, this is exemplary and the technical spirit of the present invention is not limited thereto. Therefore, it is possible to greatly improve the reliability by significantly lowering the stress generated on the surface, and there is an advantage that the degree of integration of the elements on the surface is not affected. There is an advantage in that a separate complicated process or device is not required for this purpose.

The above-described effects of the present invention have been described by way of example, and the scope of the present invention is not limited by these effects.

1 is a rear view showing a flexible device according to an embodiment of the present invention.
Figure 2 is a cross-sectional view taken along line AA of the flexible element of Figure 1 according to an embodiment of the present invention.
3 is a view showing the relationship between the dimensions and strain of the grooves provided in the flexible element according to an embodiment of the present invention.
4 shows a simulation model for analyzing the bending deformation behavior of a flexible element according to an embodiment of the present invention.
5 shows the formation of grooves of various dimensions applied to a simulation model for the analysis of bending deformation behavior of a flexible element according to an embodiment of the present invention.
6 to 13 show simulation results for the analysis of bending deformation behavior of a flexible element according to an embodiment of the present invention.
14 is a real photograph of a flexible device according to an embodiment of the present invention.
15 to 17 are graphs showing the resistance change with respect to the bending deformation cycle of the flexible element according to an embodiment of the present invention.
18 is a schematic diagram illustrating a case in which copper/carbon nanofibers are applied as a metal layer in a flexible device according to an embodiment of the present invention.
19 is a graph showing the resistance change with respect to the bending deformation cycle of the flexible element of FIG. 18 according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments of the present invention are provided to more completely explain the technical idea of the present invention to those of ordinary skill in the art, and the following examples may be modified in various other forms, The scope of the technical idea is not limited to the following examples. Rather, these embodiments are provided so as to more fully and complete the present disclosure, and to fully convey the technical spirit of the present invention to those skilled in the art. In this specification, the same reference numerals refer to the same elements throughout. Furthermore, various elements and regions in the drawings are schematically drawn. Accordingly, the technical spirit of the present invention is not limited by the relative size or spacing drawn in the accompanying drawings.

1 is a rear view showing a flexible element 100 according to an embodiment of the present invention.

2 is a cross-sectional view taken along the line A-A of the flexible element 100 of FIG. 1 according to an embodiment of the present invention.

1 and 2 , the flexible device 100 includes a substrate 110 and a metal layer 120 . The substrate 110 includes a first side 112 and a second side 114 opposite the first side 112 . A plurality of grooves 130 may be provided on the first surface 112 of the substrate 110 . The metal layer 120 may be positioned on the second surface 114 of the substrate 110 .

The substrate 110 may include various insulating materials. In addition, the substrate 110 may include a material having various flexible characteristics. The substrate 110 is, for example, polyimide, polyethylene terephthalate (PET), polyurethane, polydimethylsiloxane (PDMS), polyether block amides (PEBA), ethylene-vinyl acetate (EVA), Ecoflex, Dragon. It may include skin, silicon rubber, or a micro-thin thin silicon wafer. The substrate 110 may have a thickness ranging from 10 μm to 1000 μm.

The metal layer 120 may include various conductive materials, for example, a metal, for example, copper (Cu), aluminum (Al), chromium (Cr), nickel (Ni), palladium (Pd). ), molybdenum (Mo), titanium (Ti), gold (Au), silver (Ag), platinum (Pt), or an alloy thereof. The metal layer 120 may include at least one of metal nanowires, metal-carbon nanofibers, metal-carbon nanostructures, and graphene. The metal layer 120 may have a thickness in the range of 10 nm to 1000 nm. In the metal layer 120 , wirings or electronic devices may be disposed.

The flexible element 100 may be bent in a downward direction (or upward direction) that is a thickness direction of the substrate 110 . The plurality of grooves 130 may extend at a predetermined angle with respect to the direction in which the flexible element 100 is bent, that is, with respect to the bending direction of the flexible element 100 . For example, the plurality of grooves 130 may extend perpendicular to the thickness direction of the substrate 110 .

The plurality of grooves 130 may have a repeating pattern. The plurality of grooves 130 may be spaced apart from each other at the same interval. The plurality of grooves 130 may have the same depth. The plurality of grooves 130 may have the same width. However, this is an example, and cases in which the plurality of grooves 130 have different depths, different widths, or the plurality of grooves 130 are spaced apart from each other at different intervals are also included in the technical spirit of the present invention. do.

The plurality of grooves 130 may be spaced apart from each other at intervals ranging from 0.1 mm to 2 mm, for example. The plurality of grooves 130 may have, for example, a depth ranging from 50% to 80% of the thickness of the substrate 110 . For example, when the substrate 110 has a thickness of 125 μm, the plurality of grooves 130 may have a depth ranging from 62.5 μm to 100 μm. The plurality of grooves 130 may have, for example, a width ranging from 10 μm to 80 μm. An interval between the plurality of grooves 130 may be in the range of 1/10 to 5 times the thickness of the substrate.

Since the plurality of grooves 130 are formed by removing a partial region of the substrate 110 , the method of forming the plurality of grooves 130 includes a physical method using a blade or the like, a chemical method such as etching, and a laser method. This may be performed using various methods such as a light source method. In addition, the plurality of grooves 130 may be formed in various pattern shapes as well as straight lines as shown, and in this case, an additional effect of improving deformability in a specific direction may be provided.

3 is a view showing the relationship between the dimensions of the grooves and the strain provided in the flexible element according to an embodiment of the present invention.

Referring to FIG. 3 , (a) is a case in which a groove is not formed in the substrate, and the strain (ε) of the substrate is proportional to the thickness (h) of the substrate and inversely proportional to the radius of curvature (r ₀ ). On the other hand, (b) shows a case in which a groove is formed in the substrate, and the strain (ε) of the substrate is determined by the spacing between the grooves (g), the depth of the grooves (d), the thickness of the substrate (h), and the width of the grooves (w). It can be seen that it is related to and can be represented by the following Relational Expression 1.

<Relational Expression 1>

(where ε is the strain, g is the spacing between grooves, d is the depth of the grooves, h is the thickness of the substrate, and w is the width of the grooves)

Therefore, when the groove is formed in the substrate, the strain rate of bending deformation increases in proportion to the thickness, and the groove causes a local thickness reduction effect. The strain occurring on the substrate surface increases as the distance between the grooves increases, and decreases as the depth and width of the grooves increase.

Hereinafter, simulation results for the analysis of bending deformation behavior of the flexible element will be described.

4 shows a simulation model for analyzing the bending deformation behavior of a flexible element according to an embodiment of the present invention.

Referring to FIG. 4 , a simulation was performed to analyze the bending deformation behavior of the flexible element. As the simulation conditions, an elastic model was calculated, and the Young's modulus was 3.7 GPa, and the Poisson's ratio was 0.43, so a numerical value representative of flexible substrates such as PET and PI was selected. The length of the flexible element was set to 20 mm, width 1 mm, and thickness 100 μm. The bending deformation behavior was simulated by the U-shaped bending deformation model. The bending radius was 2.5 mm, and the condition of 2% strain was selected.

5 shows the formation of grooves of various dimensions applied to a simulation model for the analysis of bending deformation behavior of a flexible element according to an embodiment of the present invention.

Referring to FIG. 5 , cases in which the depth of the groove is 20%, 50%, and 80% of the total thickness of the substrate are illustrated. In addition, cases in which the widths of the grooves are 10 μm, 20 μm, and 80 μm are shown. Also, the cases in which the intervals between the grooves are 0.1 mm, 0.5 mm and 2.0 mm are shown.

6 to 13 show simulation results for analyzing bending deformation behavior of a flexible element according to an embodiment of the present invention.

Referring to (a) of FIG. 6 , when a bending force is applied to the region in which the groove is formed in the substrate and the substrate is bent, tensile deformation is induced, which is a deformation affecting the destruction of the substrate. The strain in this region will be referred to as the outside strain. On the other hand, in the region on the opposite side of the substrate where the groove is not formed, compressive deformation is induced and the electronic device is deformed. The strain in this region will be referred to as the inner strain.

Referring to FIG. 6B , as a result of analyzing the strain according to the depth of the groove with respect to the thickness of the substrate, the inner strain increased as the depth of the groove with respect to the thickness of the substrate increased. The slope of the linear regression of the inner strain was about 0.019. On the other hand, the outer strain increased initially when the depth of the groove with respect to the thickness of the substrate was increased, and then decreased. The linear regression slope of the outer strain was about -0.047. In the case of having an outer strain equal to or less than the breaking strain of the substrate, a condition for securing a minimum inner strain may be grasped.

Referring to FIG. 7 , simulation results for a case where the bending radius is 2.5 mm, the width of the grooves is 20 μm, and the spacing between the grooves is 0.1 mm are shown in different colors with respect to the strain. If there is no groove, the central part is marked with a dark color, and the deformation occurs greatly due to stress concentration, and thus the deformation rate is large. On the other hand, it is analyzed that the strain is reduced as it changes to a dull color as it goes away from the center. On the other hand, when the groove is formed, as the depth of the groove increases, the overall color changes from a dark color to a dull color may be obtained. It is analyzed that the deformation as a whole is reduced, and it can be seen that the difference between the strain at the center and the outside is also reduced. For example, when the depth of the groove is 80% of the thickness of the substrate, it is analyzed that the overall strain becomes almost uniform as a whole. Accordingly, the inner strain generated on the surface of the substrate decreases as the depth of the groove increases, and may, for example, decrease linearly.

In FIGS. 8 to 13 , (a) is a simulation result, and strain when the depth of the groove is 50% is shown in color, and (b) is a graph showing the strain according to the depth of the groove with respect to the thickness of the substrate.

Referring to FIG. 8 , simulation results are shown when the bending radius is 2.5 mm, the width of the grooves is 20 μm, and the spacing between the grooves is 0.1 mm. When the depth of the grooves was 50%, the maximum outer strain was 3.90%, and the inner strain was -1.83%. In the bending deformation behavior analyzed using color, the deformation rate was slightly higher corresponding to the region where the grooves were formed. The inner strain gradually increased as the depth of the grooves with respect to the thickness of the substrate increased. The linear regression slope of the inner strain was about 0.019. On the other hand, the outer strain increased initially when the depth of the grooves with respect to the thickness of the substrate increased, and then decreased. The linear regression slope of the outer strain was about -0.047.

Referring to FIG. 9 , simulation results are shown when the bending radius is 2.5 mm, the width of the grooves is 20 μm, and the spacing between the grooves is 0.5 mm. When the depth of the grooves was 50%, the maximum outer strain was 8.37%, and the inner strain was -4.10%. In the deformation behavior analyzed using color, the deformation rate was higher in the region in which the grooves were formed, compared to the case of FIG. 8 . The inner strain showed a tendency to decrease as the depth of the grooves with respect to the thickness of the substrate increased, and increased again at 70% or more. The linear regression slope of the inner strain was about -0.018. On the other hand, the outer strain increased when the depth of the grooves with respect to the thickness of the substrate was increased, and then decreased again after showing a maximum value at 60%. The linear regression slope of the outer strain was about 0.015. Compared with FIG. 8 , the result of FIG. 9 shows a different aspect as a case in which the distance between the grooves is increased. Specifically, when the depth of the grooves with respect to the thickness of the substrate was in the range of about 50% to 80%, the outer strain was maximum and the inner strain was the minimum.

Referring to FIG. 10 , simulation results are shown when the bending radius is 2.5 mm, the width of the grooves is 20 μm, and the distance between the grooves is 2.0 mm. When the depth of the grooves was 50%, the maximum outer strain was 11.57%, and the inner strain was -5.86%. In the deformation behavior analyzed using color, the deformation rate was higher in correspondence with the region in which the grooves were formed, as compared to the case of FIGS. 8 and 9 . The inner strain decreased relatively rapidly as the depth of the grooves with respect to the thickness of the substrate increased. The linear regression slope of the inner strain was about -0.102. On the other hand, the outer strain increased relatively rapidly as the depth of the grooves with respect to the thickness of the substrate increased. The linear regression slope of the outer strain was about 0.177.

From the results of FIGS. 8 to 10 , when the interval between the grooves becomes larger than a certain level, a stress concentration portion occurs, and accordingly, the change in strain with respect to the depth of the grooves increases, so that the grooves are formed at a predetermined interval or less. it is preferable Compared with the case where the spacing between the grooves is 0.1 mm, it can be seen that the stress concentration is greatly generated when the spacing between the grooves is 2 mm, and thus the change in strain is increased. The spacing between the grooves is preferably controlled to be 5 times or less the thickness of the substrate. For example, an interval between the plurality of grooves may be in a range of 1/10 to 5 times the thickness of the substrate.

In addition, since the depth of the groove and the relaxation of strain are proportional, the surface deformation may be relieved as the depth of the groove increases. However, when the depth of the groove is very large, for example, exceeding 80% of the thickness of the substrate, the substrate may be rather destroyed. The depth of the groove with respect to the thickness of the substrate may be, for example, in the range of 50% to 80%. Preferably, it may be about 60%.

In the simulation results described above, the smaller the gap between the grooves, the lower the strain, and thus the reliability can be improved. However, in reality, it is analyzed that the desired reliability is achieved only when the interval between the grooves is greater than a certain level. The reason is that stress concentration is induced in the grooves and reliability is deteriorated. As the gap between the grooves is smaller, the area of the stress concentration part is widened, and thus the deformation area is increased, and as a result, reliability may be lowered. However, when the gap between the grooves exceeds a certain level, for example, when the gap exceeds 2 mm, the substrate may be damaged. Accordingly, the plurality of grooves may be spaced apart from each other at an interval in the range of 0.1 mm to 2 mm. Preferably, it may be 0.5 mm apart.

Referring to FIG. 11 , simulation results are shown when the bending radius is 2.5 mm, the spacing between the grooves is 0.1 mm, and the width of the grooves is 10 μm. When the depth of the grooves was 50%, the maximum outer strain was 4.26%, and the inner strain was -1.66%. In the bending deformation behavior analyzed using color, the deformation rate was slightly higher corresponding to the region where the grooves were formed. The inner strain increased as the depth of the grooves with respect to the thickness of the substrate increased. The linear regression slope of the inner strain was about 0.021. On the other hand, the outer strain decreased relatively rapidly as the depth of the grooves with respect to the thickness of the substrate increased. The linear regression slope of the inner strain was about -0.058.

Referring to FIG. 12 , simulation results are shown when the bending radius is 2.5 mm, the interval between the grooves is 0.1 mm, and the width of the grooves is 20 μm. When the depth of the grooves was 50%, the maximum outer strain was 3.56%, and the inner strain was -1.64%. In the bending deformation behavior analyzed using color, the strain was slightly higher in correspondence to the region where the grooves were formed, but the influence was smaller than in FIG. 11 . The inner strain gradually increased as the depth of the grooves with respect to the thickness of the substrate increased. The linear regression slope of the inner strain was about 0.019. On the other hand, the outer strain increased initially when the depth of the grooves with respect to the thickness of the substrate increased, and then decreased. The linear regression slope of the outer strain was about -0.047. For reference, it should be noted that the result of FIG. 11 is the same as the result of FIG. 8 .

Referring to FIG. 13 , simulation results are shown when the bending radius is 2.5 mm, the interval between the grooves is 0.1 mm, and the width of the grooves is 80 μm. When the depth of the grooves was 50%, the maximum outer strain was 2.11%, and the inner strain was -1.47%. In the bending deformation behavior analyzed using color, the influence of the region in which the grooves were formed was hardly observed. The inner strain increased as the depth of the grooves with respect to the thickness of the substrate increased. The linear regression slope of the inner strain was about 0.022. On the other hand, the outer strain increased as the depth of the grooves with respect to the thickness of the substrate increased. The linear regression slope of the outer strain was about -0.030.

From the results of FIGS. 11 to 13 , as the width of the grooves increases, the overall strain decreases, and in particular, it can be seen that the strain in the region where the grooves are disposed is greatly reduced by about half.

14 is a real photograph of a flexible device according to an embodiment of the present invention.

Referring to FIG. 14 , a transparent substrate made of polyimide and a metal layer made of copper positioned on the substrate are shown. It is a photograph of a state in which the metal layer is disposed on the lower side and the substrate is disposed on the upper side. The indicated wrinkle shape is formed in the grooves formed in the substrate, and is not the shape of the metal layer.

15 to 17 are graphs showing the resistance change with respect to the bending deformation cycle of the flexible element according to an embodiment of the present invention.

15 to 17, in the flexible device, a copper thin film having a thickness of 100 nm is deposited on a polyimide substrate having a thickness of 125 μm. The interval between the grooves formed in the substrate was 0.2 mm. The bending radius was 4.16 mm (under 2% strain condition), and sliding bending deformation was performed up to 200,000 cycles. A change in resistance indicates a change in resistance of the copper thin film.

Referring to FIG. 15 , resistance changes are shown with respect to the depth of various grooves with respect to the thickness of the substrate. The depths of the grooves were 5%, 24%, 47%, 62%, and 80% without grooves (0%). Based on the case of no groove, in 5%, 24%, and 47% cases, the increase in resistance according to the increase in the number of bending deformation cycles was larger. On the other hand, in 62% and 80%, the increase in resistance according to the increase in the number of bending deformation cycles was smaller. A larger increase in resistance means that damage is applied to a copper layer capable of forming wiring, and thus it can be seen that the smaller the increase in resistance is, the higher the reliability is. Accordingly, it is preferable that the depth of the grooves with respect to the thickness of the substrate be 50% or more.

Referring to FIG. 16 , it is an experimental result for a case where the depth of the grooves with respect to the thickness of the substrate is 80%. Of the total of 5 samples, 3 failed at about 100,000 bending cycles, and the remaining two did not fail until 200,000 bending cycles. In the photo below, the red circle indicates the flexible element that is destroyed according to the bending deformation cycle. Accordingly, it is preferable that the depth of the grooves with respect to the thickness of the substrate be at least 80% or less. In particular, in order to improve reliability, it is preferable that the depth of the grooves with respect to the thickness of the substrate be about 60%.

Referring to FIG. 17 , the depth of the grooves with respect to the thickness of the substrate was 62%. The spacing between the grooves was changed to 0.2 mm, 0.5 mm, and 2 mm. When the gap between the grooves was 0.2 mm, the increase in resistance according to the increase in the number of bending deformation cycles was small compared to the case where there was no groove, but it showed a large increase in resistance compared to 0.5 mm and 2 mm. It is analyzed that the effect of improving reliability is reduced because stress concentration due to the grooves overlaps in the case of a 0.2 mm gap. On the other hand, in the case of 2 mm, it was fractured at about 100,000 bending deformation cycles. Accordingly, the interval between the grooves may be in the range of 0.1 mm to 2 mm, and in particular, the 0.5 mm interval has the greatest reliability improvement effect.

18 is a schematic diagram illustrating a case in which copper/carbon nanofibers are applied as a metal layer in a flexible device according to an embodiment of the present invention.

Referring to FIG. 18 , a case in which copper/carbon nanofibers (Cu/CNF) is applied as a metal layer 120a on a substrate made of PET. The copper/carbon nanofiber is a form in which copper (Cu) is coated on the surface of carbon nanofiber (CNF). The copper may cover the entire surface of the carbon nanofiber. In addition, the copper may be inserted as a plurality of particles on the surface of the carbon nanofiber.

The copper/carbon nanofibers may be, for example, at a temperature in the range of about 400° C. to about 600° C., for example at a temperature of about 500° C., and also at a pressure in the range of, for example, about 10 mTorr to about 100 mTorr, e.g. For example, it can be formed at pressures in the range of about 50 mTorr. In the lower right corner, the real object of the flexible element is shown.

The copper/carbon nanofibers are exemplary, and a case in which various metal materials are applied instead of copper and a case in which various carbon nanomaterials are applied instead of carbon nanofibers are included in the technical concept of the present invention. That is, the metal layer may have a carbon nanomaterial as a base material, and a rapid material may be coated on the surface of the carbon nanomaterial.

19 is a graph showing the resistance change with respect to the bending deformation cycle of the flexible element of FIG. 18 according to an embodiment of the present invention.

Referring to FIG. 19 , the flexible device is composed of a metal layer of copper/carbon nanofibers. In addition, in the flexible device, the depth of the grooves with respect to the thickness of the substrate was 50%, the width of the groove was 20 μm, the interval between the grooves was 2 mm. When the flexible element does not have a groove, the resistance is continuously increased as the number of bending deformation cycles is increased. On the other hand, when the flexible element has a groove, resistance change hardly appeared even up to the number of 500,000 bending deformation cycles. As described above, it is analyzed that carbon nanofibers can absorb bending deformation to a certain level along with an increase in reliability due to the provision of grooves, and consequently, the flexible element has a reinforcing effect on bending deformation. do.

The technical spirit of the present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is the technical spirit of the present invention that various substitutions, modifications and changes are possible without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in the art to which this belongs.

Claims (19)

a substrate including a first surface and a second surface opposite to the first surface, the substrate having a plurality of grooves on the first surface; and
Including; a metal layer located on the second surface of the substrate;
The plurality of grooves are spaced apart at intervals in the range of 0.1 mm to 2 mm,
The spacing between the plurality of grooves ranges from 1/10 times to 5 times the thickness of the substrate,
wherein the plurality of grooves have a depth in the range of 50% to 80% of the thickness of the substrate;
flexible element. The method of claim 1,
The plurality of grooves extend at a predetermined angle with respect to the bending direction of the flexible element,
flexible element. The method of claim 1,
The plurality of grooves extend perpendicular to the thickness direction of the substrate,
flexible element. The method of claim 1,
The plurality of grooves have a repeating pattern,
flexible element. The method of claim 1,
The plurality of grooves are spaced apart at equal intervals,
flexible element. delete The method of claim 1,
The plurality of grooves have the same depth,
flexible element. delete The method of claim 1,
The plurality of grooves have the same width,
flexible element. The method of claim 1,
wherein the plurality of grooves have a width ranging from 10 μm to 80 μm,
flexible element. delete The method of claim 1,
The strain rate of the substrate satisfies the following relation 1,
flexible element.
<Relational Expression 1>

(where ε is the strain, g is the spacing between grooves, d is the depth of the grooves, h is the thickness of the substrate, and w is the width of the grooves) The method of claim 1,
The substrate is polyimide, PET (polyethylene terephthalate), polyurethane, PDMS (Polydimethylsiloxane), PEBA (polyether block amides), EVA (ethylene-vinyl acetate), Ecoflex, Dragon skin, silicone rubber rubber), or including a micro-thin thin silicon wafer,
flexible element. The method of claim 1,
wherein the substrate has a thickness ranging from 10 μm to 1000 μm;
flexible element. The method of claim 1,
The metal layer is copper (Cu), aluminum (Al), chromium (Cr), nickel (Ni), palladium (Pd), molybdenum (Mo), titanium (Ti), gold (Au), silver (Ag), platinum ( Pt) or an alloy thereof,
flexible element. The method of claim 1,
The metal layer includes at least one of metal nanowires, metal-carbon nanofibers, metal-carbon nanostructures, and graphene,
flexible element. The method of claim 1,
The metal layer has a thickness in the range of 10 nm to 1000 nm,
flexible element. a substrate including a first surface and a second surface opposite to the first surface, the substrate having a plurality of grooves on the first surface; and
a metal layer positioned on the second surface of the substrate; and
The metal layer is a carbon nano material as a base material, a metal material is coated on the surface of the carbon nano material,
The plurality of grooves are spaced apart at intervals in the range of 0.1 mm to 2 mm,
The spacing between the plurality of grooves ranges from 1/10 times to 5 times the thickness of the substrate,
wherein the plurality of grooves have a depth in the range of 50% to 80% of the thickness of the substrate;
flexible element. 19. The method of claim 18,
The carbon nanomaterial includes carbon nanofibers,
wherein the metallic material comprises copper;
flexible element.

Images