KR20120103388A - Flexible display device and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A flexible display device and a manufacturing method thereof are provided to prevent the mechanical and thermal damage of a thin film transistor and a light emitting element in a separation process by easily separating a flexible substrate for a short time. CONSTITUTION: A heating unit is formed on a carrier substrate(S10). A flexible substrate is formed on the heating unit(S20). A thin film transistor is formed on the flexible substrate(S30). A light emitting element connected with the thin film transistor is formed(S40). The flexible substrate is heated by the self heating of the heating unit to separate the flexible substrate from the heating unit(S50). [Reference numerals] (S10) Forming a heating unit on a carrier substrate; (S20) Forming a flexible substrate on the heating unit; (S30) Forming a thin film transistor on the flexible substrate; (S40) Forming a light emitting element and a plastic bag member; (S50) Separating the flexible substrate from the heating unit

Description

Flexible display device and manufacturing method thereof {FLEXIBLE DISPLAY DEVICE AND MANUFACTURING METHOD THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, and more particularly, to a flexible display device and a method of manufacturing the same.

Recently, the display device market is rapidly changing, especially for flat panel displays (FPDs), which are large in size, thin, and lightweight. Among the various flat panel displays, organic light emitting diode displays (OLEDs) are self-luminous types that do not require a separate light source, and thus are more advantageous for thinness and light weight.

Conventional flat panel display devices use glass substrates, and thus have poor flexibility, thereby limiting their application range. Therefore, recently, a flexible display device manufactured to be bent using a flexible substrate instead of a glass substrate has been developed.

Manufacturing and handling thin film transistors on flexible substrates is an important key process. However, there are many process difficulties in manufacturing a flexible display device by replacing a flexible substrate with a manufacturing facility set to be suitable for an existing glass substrate.

Therefore, as a method for manufacturing a flexible display device using existing manufacturing equipment, a flexible substrate is formed on a carrier substrate such as a glass substrate, a thin film transistor is formed on the flexible substrate, and the flexible substrate and The process of separating a carrier substrate is applied.

The present invention is to provide a method of manufacturing a flexible display device that prevents damage to the thin film transistor when separating the flexible substrate and the carrier substrate, lowers the processing cost, and can be separated in a short time even in a large area condition.

A method of manufacturing a flexible display device according to an exemplary embodiment of the present invention includes forming a heating unit on a carrier substrate, forming a flexible substrate on the heating unit, and forming a thin film transistor on the flexible substrate. And forming a light emitting device connected to the thin film transistor, and applying heat to the flexible substrate by self-heating of the heat generating unit to separate the flexible substrate from the heat generating unit.

The flexible substrate may be formed as a single layer on the heat generating portion. In the separating of the flexible substrate, the interface temperature between the heat generating unit and the flexible substrate may be higher than the melting point of the flexible substrate. On the other hand, the flexible substrate may include a sacrificial layer formed on the heat generating portion, a moisture barrier layer formed on the sacrificial layer, and a body layer formed on the moisture barrier layer. In the step of separating the flexible substrate, the interface temperature between the heating part and the sacrificial layer may be higher than the melting point of the sacrificial layer.

The display device according to the exemplary embodiment of the present invention is manufactured by the above method and includes a flexible substrate and a light emitting device. The outer surface of the flexible substrate has a root mean square roughness in the range of 1 nm to 15 nm.

In another aspect of the present invention, there is provided a method of manufacturing a display device, including: forming a heat generating part including a conductive material having a resistance on a carrier substrate, forming a flexible substrate on the heat generating part, and forming a flexible substrate. Forming a driving circuit unit including a thin film transistor on the substrate, forming a light emitting element and an encapsulation member on the driving circuit unit, and applying heat to the heat generating unit to generate Joule heat, thereby directly applying heat to the flexible substrate. Separating the flexible substrate from the heat generating portion.

The heat generating part may include at least one of a metal and a metal oxide, and may be formed to have a uniform thickness on the carrier substrate. The heat generating unit may generate Joule heat by receiving a voltage of a pulse waveform.

The flexible substrate may be formed as a single layer on the heat generating unit, and a portion of the region contacting the heat generating unit may be decomposed and separated from the heat generating unit by the joule heat of the heat generating unit.

The flexible substrate may comprise at least one of polyimide, polycarbonate, polyacrylate, polyetherimide, polyethersulfone, polyethylene terephthalate, and polyethylene naphthalate. The joule heat generation temperature of the heat generating unit may be in the range of 300 ° C to 900 ° C.

On the other hand, the flexible substrate may include a sacrificial layer formed on the heat generating portion, a moisture barrier layer formed on the sacrificial layer, and a body layer formed on the moisture barrier layer. The sacrificial layer is formed to have a thickness smaller than that of the main body layer, and at least a part of the sacrificial layer may be decomposed by the joule heat of the heat generating unit to separate the moisture barrier layer and the main body layer from the heat generating unit.

The sacrificial layer may comprise at least one of polyimide, polycarbonate, polyacrylate, polyetherimide, polyethersulfone, polyethylene terephthalate, and polyethylene naphthalate. The joule heat generation temperature of the heat generating unit may be in the range of 300 ° C to 900 ° C.

The light emitting device may include a plurality of organic light emitting devices, and the encapsulation member may be configured as a multilayer film including a plurality of organic films and a plurality of inorganic films.

A flexible display device according to another embodiment of the present invention is manufactured by the above-described method, and includes a flexible substrate and a light emitting device. The outer surface of the flexible substrate has a root mean square roughness in the range of 1 nm to 15 nm.

In the process of separating the carrier substrate and the flexible substrate, the flexible substrate can be easily separated in a short time of approximately several microseconds, and any thermal and mechanical damage to the thin film transistors and the light emitting device on the flexible substrate during the separation process is achieved. Do not leave either. This separation technique is suitable for mass production of large area flexible displays.

1 is a flowchart illustrating a manufacturing method of a flexible display device according to an exemplary embodiment of the present invention.
2A through 2E are cross-sectional views illustrating a first manufacturing method of the flexible display device illustrated in FIG. 1.
FIG. 2F is a perspective view of a portion of FIG. 2D. FIG.
3A to 3C are cross-sectional views illustrating a second manufacturing method of the flexible display shown in FIG. 1.
4 is a diagram illustrating a heat distribution simulation result measured when a voltage is applied to the heating unit.
5 is a photo illustrating a flexible display device separated from a heat generating unit and a carrier substrate.
FIG. 6 is a scanning electron microscope (SEM) photograph of the surface of the flexible substrate in the flexible display device according to the exemplary embodiment. FIG.
7 and 8 are atomic force microscope (AFM) photographs showing a surface of a flexible substrate in a flexible display device according to an exemplary embodiment of the present invention.
9 is a scanning electron microscope (SEM) photograph showing the surface of the flexible substrate in the flexible display device of the comparative example to which the laser scanning process is applied.
10 is an atomic force microscope (AFM) photograph showing the surface of a flexible substrate in the flexible display device of the comparative example to which the laser scanning process is applied.
FIG. 11 is a graph illustrating transfer characteristics of a thin film transistor before and after a Joule heating induced lift-off (JILO) process.
12 is a graph illustrating transfer characteristics of a thin film transistor after a JILO process according to a bias-temperature-stress (BTS) experiment.
FIG. 13A is a graph illustrating transfer characteristics of a thin film transistor after a JILO process according to a high drain current (HDC) stress experiment.
FIG. 13B is a graph showing hysteresis of a thin film transistor after a JILO process. FIG.
14 is a layout view illustrating a pixel structure of a flexible display device.
FIG. 15 is a cross-sectional view of the flexible display device taken along the line AA of FIG. 14.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. When a part of a layer, film, region, plate, etc. in the specification is said to be "on" or "on" another part, this includes not only the "right on" of the other part but also the other part in the middle. do. On the contrary, when a part is “just above” another part, there is no other part in the middle.

1 is a flowchart illustrating a manufacturing method of a flexible display device according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a method of manufacturing a flexible display device includes a first step S10 of forming a heating unit on a carrier substrate, a second step S20 of forming a flexible substrate on a heating unit, and a flexible substrate. A third step (S30) of forming a thin film transistor, a fourth step (S40) of forming a light emitting element and an encapsulation member, and a fifth of separating the flexible substrate from the heat generating portion and the carrier substrate by using self-heating of the heat generating portion Step S50 is included.

2A through 2E are cross-sectional views illustrating a first manufacturing method of the flexible display illustrated in FIG. 1, and FIG. 2F is a perspective view of a portion of FIG. 2D. A method of manufacturing the flexible display device according to the first exemplary embodiment of the present invention will be described in detail with reference to FIGS. 2A to 2F.

Referring to FIG. 2A, the carrier substrate 110 is prepared in the first step S10, and the heat generating unit 120 is formed on the carrier substrate 110. The carrier substrate 110 may be a glass substrate as a rigid insulating substrate. The heat generating unit 120 is a member that generates self heat under a set condition. The heat generating unit 120 is formed on the carrier substrate 110 as a whole to function as a surface heating element.

Referring to FIG. 2B, in operation S20, the flexible substrate 210 is formed on the heat generating part 120. The flexible substrate 210 may be a plastic film, and may be manufactured by applying a liquid polymer material on the heat generating part 120 and then thermally curing the same.

As the flexible substrate 210, polyimide, polycarbonate, polyacrylate, polyetherimide, polyethersulfone, polyethylene terephthalate, polyethylene naphthalate, or the like can be used. Among them, polyimide can be used at a high process temperature of 450 ° C. or more, thereby minimizing the deterioration of characteristics of the thin film transistor.

Since the flexible substrate 210 made of a plastic film has a property of being bent or stretched by heat, it is difficult to precisely form a thin film pattern such as a thin film transistor, a light emitting device, and a conductive wiring thereon. Therefore, the subsequent process is performed while the flexible substrate 210 is positioned on the carrier substrate 110.

In the first embodiment, the flexible substrate 210 is formed of a single layer and is formed directly on the heat generating part 120 to contact the heat generating part 120.

Referring to FIG. 2C, in the third step S30, the barrier layer 220 is formed on the flexible substrate 210, and the driving circuit unit 230 including the thin film transistor is formed on the barrier layer 220. In FIG. 2C, the driving circuit unit 230 is schematically illustrated as one layer for convenience, but the actual driving circuit unit 230 includes a plurality of thin film transistors and a plurality of power storage elements. In addition, a plurality of conductive wires are formed on the flexible substrate 210.

In the fourth step S40, the light emitting device 240 is formed on the driving circuit unit 230, and the encapsulation member 250 is formed on the light emitting device 240. The light emitting device 240 may include a plurality of organic light emitting devices. The operation of the light emitting device 240 is controlled by the driving circuit unit 230, and emits light according to the driving signal to display an image. In FIG. 2C, the light emitting device 240 is schematically illustrated as one layer for convenience.

The barrier film 220 may be formed of any one of an inorganic film and an organic film or a laminated film of an inorganic film and an organic film. The barrier layer 220 suppresses unnecessary components such as moisture or oxygen from penetrating the flexible substrate 210 and penetrating into the light emitting device 240. Moisture and oxygen penetrated into the light emitting device 240 deteriorate the light emitting device 240 and shorten the life of the light emitting device 240.

The encapsulation member 250 may be formed of a multilayer film. The encapsulation member 250 may be formed of a plurality of inorganic layers, or may have a structure in which a plurality of inorganic layers and a plurality of organic layers are alternately stacked one by one. The inorganic film may include aluminum oxide or silicon oxide, and the organic film may include epoxy, acrylate, urethane acrylate, or the like.

The inorganic layer prevents external moisture and oxygen from penetrating into the light emitting device 240. The organic film serves to relieve internal stress of the inorganic film or to fill fine cracks and pinholes of the inorganic film. The constituent materials of the inorganic film and the organic film described above are merely examples, and are not limited to the above materials, and various kinds of inorganic films and organic films known to those skilled in the art may be used.

The encapsulation member 250 surrounds the side surface of the driving circuit unit 230 and the side surface of the light emitting device 240 to prevent the side surfaces of the driving circuit 230 and the light emitting device 240 from being exposed to the outside.

2D and 2E, in the fifth step S50, heat is directly supplied to the flexible substrate 210 by using self-heating of the heat generating unit 120. Then, a portion of the flexible substrate 210 which contacts the heat generating portion 120 (the lower region based on the drawing) is decomposed by the thermal energy, and thus the flexible substrate 210 is formed of the heat generating portion 120 and the carrier substrate. Separated from 110.

The method of the present embodiment using the heat generating unit 120 is significantly different from the conventional method of transferring heat energy to the flexible substrate by irradiating a laser beam (typically an excimer laser beam) from the outside of the carrier substrate toward the flexible substrate. .

That is, in the conventional method, a laser source, which is a heat energy source, is located outside the carrier substrate, and a laser beam emitted from the laser source passes through the carrier substrate and is focused on the flexible substrate, thereby transferring heat energy to the flexible substrate. On the other hand, in the method of the present embodiment, the heat generating unit 120, which is a heat energy source, is in contact with the flexible substrate 210 and is located inside the carrier substrate 110, and the heat generating unit 120 receives the thermal energy of the heat generating unit 120 without an intermediate medium. ) Directly.

The heat generating unit 120 may be formed of a conductive layer that generates Joule heating under voltage application conditions. However, the structure and the principle of heat generation of the heat generating unit 120 is not limited to the above-described example, and any configuration may be applied as long as it generates heat instantly and thermally decomposes a part of the flexible substrate 210.

The heat generating part 120 includes a metal or a metal oxide. The heat generating unit 120 may include at least one of molybdenum (Mo), titanium (Ti), copper (Cu), silver (Ag), and chromium (Cr) as a metal, and indium tin oxide (Indium) as a metal oxide. Tin Oxide) and at least one of indium zinc oxide.

Referring to FIG. 2F, the carrier substrate 110 and the heat generating part 120 may be formed to have a larger area than the flexible substrate 210 so that both ends of the heat generating part 120 are exposed to the outside of the flexible substrate 210. Can be. Two pad parts 130 provided in an external power supply device (not shown) contact the exposed end of the heat generating part 120 to apply a pulse waveform voltage to the heat generating part 120.

The exposed end of the heat generating part 120 and the two pad parts 130 contacting with each other face each other along one direction (the x-axis direction of the drawing) of the carrier substrate 110, and the direction perpendicular thereto (y in the drawing). Along the axial direction). As a result, a uniform current flow occurs in one direction (the x-axis direction of the drawing) of the carrier substrate 110 in the heat generating part 120, thereby causing Joule heat generation.

The heat generating unit 120 generates heat at various temperatures according to resistance and pulse conditions, and may generate heat of approximately 1,000 ° C. or more. The heat generation temperature of the heat generating part 120 rapidly penetrates heat into a part of the flexible substrate 210 without affecting the driving circuit 230 and the light emitting device 240 formed on the flexible substrate 210. Only an area as deep as the penetration depth is set in a range suitable for instantaneous decomposition.

In consideration of this, the exothermic temperature of the exothermic part 120 in the fifth step S50 may be in a range of about 300 ° C. to 900 ° C. If the heat generation temperature of the heat generating unit 120 is less than 300 ° C., thermal decomposition of the lower region of the flexible substrate 210 may be uneven, and separation of the flexible substrate 210 may be difficult. When the heat generating temperature of the heat generating part 120 exceeds 900 ° C., the characteristics of the thin film transistor formed on the flexible substrate 210 may be degraded.

The heat generating unit 120 is formed to have a uniform thickness on the carrier substrate 110 to cause uniform Joule heat generation in the entire heat generating unit 120. In addition, the pulse period of the voltage applied to the heat generator 120 is adjusted in consideration of the heat penetration depth of the flexible substrate 210. When the thickness of the flexible substrate 210 is 10 μm, the heat penetration depth may be, for example, 1 μm or less. In this case, deterioration of the driving circuit 230 and the light emitting device 240 due to heat provided to the flexible substrate 210 may be minimized.

The above-described separation process of this embodiment may be referred to as a Joule heating Induced Liff-Off (JILO) process. Hereinafter, the joule heating induction lift-off process is referred to as a JILO process.

In the present exemplary embodiment using the JILO process, as a joule heat is generated by applying a voltage to the heat generating unit 120, the flexible substrate 210 may thermally decompose an area as much as the depth of heat penetration from the heat generating unit 120. Are separated. This separation process is performed in a short time of approximately several microseconds even in a large area substrate, and does not leave thermal and mechanical damages to the driving circuit unit 230 and the light emitting device 240.

On the other hand, the conventional method using the laser beam requires an expensive laser system, and even if the intensity and focus depth of the laser beam are precisely adjusted, the flexible substrate and the films formed thereon are extremely thin, which damages the driving circuit unit and the light emitting device. May cause In addition, since the size of the available laser beam is limited and the laser beam needs to be scanned, the large-area display device takes a long time to separate the carrier substrate.

The flexible substrate 210, the barrier layer 220, the driving circuit unit 230, the light emitting device 240, and the encapsulation member 250 may be formed through the above-described first to fifth steps S10 to S50. The flexible display device 200 according to the first embodiment is completed.

3A to 3C are cross-sectional views illustrating a second manufacturing method of the flexible display shown in FIG. 1. A method of manufacturing the flexible display device according to the second exemplary embodiment of the present invention will be described with reference to FIGS. 3A to 3C.

Referring to FIG. 3A, the process of preparing the carrier substrate 110 and forming the heating unit 120 on the carrier substrate 110 is the same as the first embodiment described above. In the second step S20, the sacrificial layer 21, the moisture barrier layer 22, and the main body layer 23 are sequentially formed on the heat generating part 120 to form the flexible substrate 211. The sacrificial layer 21 is formed directly on the heat generating part 120 to contact the heat generating part 120. The flexible substrate 211 has a three-layer structure of the sacrificial layer 21, the moisture barrier layer 22, and the main body layer 23.

The sacrificial layer 21 and the main body layer 23 may be made of a plastic film such as the flexible substrate 210 of the first embodiment, and may be manufactured by a method of thermally curing the liquid polymer material after coating. In this case, the sacrificial layer 21 is formed to have a thickness smaller than that of the body layer 23. The sacrificial layer 21 may be formed to have a thickness equal to or greater than the heat penetration depth of the flexible substrate 210 described in the first embodiment. The body layer 23 may be formed to the same thickness as the flexible substrate 210 of the first embodiment.

The moisture barrier layer 22 may include, for example, at least one of aluminum (Al), molybdenum (Mo), titanium (Ti), copper (Cu), silver (Ag), and chromium (Cr). , Sputtering or the like. The moisture barrier layer 22 prevents external moisture from penetrating the flexible substrate 211 and penetrating into the light emitting device 240. That is, in the second embodiment, as the barrier layer 220 and the moisture barrier layer 22 are positioned, the penetration of moisture into the light emitting device 240 may be more effectively suppressed.

Forming the barrier layer 220 and the driving circuit unit 230 on the flexible substrate 211 in the third step S30, and the light emitting device 240 and the driving circuit unit 230 on the fourth step S40. The process of forming the sealing member 250 is the same as the first embodiment described above.

3B and 3C, Joule heat is generated by applying a voltage to the heat generating unit 120 in a fifth step. Then, a part or all of the sacrificial layer 21 in contact with the heat generating part 120 is thermally decomposed by Joule heat and the moisture barrier layer 22 of the flexible substrate 211 is separated from the heat generating part 120. A portion of the sacrificial layer 21 that is not thermally decomposed may or may not remain on the surface of the moisture barrier layer 22. The resistance, the heating temperature, the pulse condition, and the like of the heat generator 120 are the same as those of the first embodiment described above.

Through the first to fifth steps S10 to S50 described above, the flexible substrate 211 including the moisture barrier layer 22 and the main body layer 23, the barrier film 220, the driving circuit unit 230, and the light emitting device are provided. The flexible display device 201 according to the second embodiment including the 240 and the sealing member 250 is completed.

Next, an actual manufacturing process and a heat conduction simulation result of the flexible display device according to the first embodiment will be described.

A glass substrate was used as the carrier substrate 110, and a heat generating part 120 formed of a molybdenum (Mo) single layer was formed on the glass substrate. A polyimide film was used as the flexible substrate 210. The polyimide film had a thickness of approximately 10 μm and was cured at a high temperature of 350 ° C. or higher. The process after the polyimide film formation is the same as a conventional organic light emitting display device. Subsequently, a thermal waveform simulation was performed by applying a voltage of a pulse waveform to the heat generator 120.

4 is a diagram illustrating a heat distribution simulation result measured when a voltage is applied to the heating unit. In FIG. 4, 'PI substrate' represents a polyimide film, 'conductive layer' represents a heating portion, and 'Glass' represents a glass substrate as a carrier substrate.

Referring to FIG. 4, the maximum temperature of the heat generating part reaches 600 ° C., and the interface temperature between the polyimide film and the heat generating part reaches 450 ° C. higher than 360 ° C., which is the melting point of the polyimide film. As a result, part of the polyimide film is decomposed by heat to separate the polyimide film from the heat generating portion.

5 is a photo illustrating a flexible display device separated from a heat generating unit and a carrier substrate. The heat penetration depth of the polyimide film measured in this process is smaller than 0.5 mu m. Due to the very small percentage of heat penetration depth in the entire polyimide film, even if the Joule heating temperature is high enough to melt the flexible substrate, no thermal or mechanical damage is left to the drive circuitry and the light emitting device.

6 illustrates a scanning electron microscopy (SEM) photograph of the surface of the flexible substrate 210 for the flexible display device 200 according to the first embodiment completed through the above-described fabrication process. Atomic force microscopy (AFM) images are shown in FIGS. 7 and 8.

The surface of the flexible substrate illustrated in FIGS. 6 to 8 is an outer surface of the flexible substrate separated from the heat generation unit 120 by Joule heat generation after contact with the heat generation unit 120. In the flexible display device 201 of the second embodiment, the surface of the sacrificial layer 21 also has the same characteristics as those of FIGS. 6 and 7. The magnification of FIG. 6 is 130,000 times.

A flexible display device of a comparative example in which a laser scanning process was applied instead of a JILO process was prepared, and scanning electron microscopy (SEM) and atomic force of the surface of the flexible substrate in the flexible display device according to the comparative example in FIGS. 9 and 10, respectively. Microscopic (AFM) pictures are shown. The surface of the flexible substrate shown in FIGS. 9 and 10 is an outer surface of the flexible substrate separated from the carrier substrate by a laser beam after contacting the carrier substrate. The enlargement ratio of FIG. 9 is 130,000 times.

The flexible display device of the comparative example was formed on the carrier substrate instead of the heat generating portion, and the present invention was carried out except that the carrier substrate and the flexible substrate were separated by scanning a laser beam toward the flexible substrate from the outside of the carrier substrate. It is manufactured by the same process as the flexible display device of the example.

First, referring to FIGS. 6 to 8, in the flexible display device of the first embodiment using the JILO process, it can be seen that the flexible substrate realizes a very uniform surface having extremely low roughness. These surface properties are due to the JILO process characteristics, which simultaneously separate the entire surface of the flexible substrate from the carrier substrate by instantaneous thermal decomposition.

In the flexible display device of this embodiment, the root mean square (RMS) roughness of the surface of the flexible substrate is in a range of 1 nm to 15 nm. The root mean square (RMS) roughness of the flexible substrate may vary depending on various factors such as the type of the flexible substrate, the resistance of the heating portion, the heating temperature, and the pulse period of the voltage applied to the heating portion, but are generally larger than 1 nm and exceed 15 nm. I never do that. The root mean square (RMS) roughness of the flexible substrate surface measured by the atomic force microscope (AFM) analysis of FIG. 7 is approximately 2.5 nm, and the surface of the flexible substrate measured by the atomic force microscope (AFM) analysis of FIG. 8. The root mean square (RMS) roughness is approximately 7.5 nm.

9 and 10, in the flexible display device of the comparative example using the laser scanning process, the flexible substrate has a root mean square (RMS) roughness of 20 nm or more, and the surface roughness is larger and not uniform than the flexible substrate of the present embodiment. You can see that we are implementing a surface. The root mean square (RMS) roughness of the flexible substrate surface measured by the atomic force microscope (AFM) analysis of FIG. 10 is approximately 30 nm.

The surface characteristics of the flexible substrate according to the comparative example are not accurate because of the laser scanning characteristics, that is, the accuracy of the laser beam intensity and the depth of focus are limited, and the surface of the flexible substrate is not constant. This is due to the characteristic of thermal decomposition in succession (ie, partially) along the laser scanning direction.

Next, changes in thin film transistor characteristics before and after the JILO process in the flexible display device according to the present embodiment will be described.

Table 1 is a table showing the characteristics of the thin film transistor measured before the JILO process, Figure 11 is a graph showing the transfer characteristics of the thin film transistor before and after the JILO process.

Prior to the JILO process, the thin film transistor's charge mobility (μFET) was measured at 90.4 cm ² / Vsec, threshold voltage at -2.9V, and s-slope (sub-threshold slope) at 0.32V / decade. After the JILO process, as shown in FIG. 11, there is no change in the threshold voltage and the S-slope of the thin film transistor. This result means that the JILO process does not cause significant performance damage to thin film transistors.

12 is a graph showing the transfer characteristics of the thin film transistor after the JILO process, and shows the results of a bias-temperature-stress (BTS) experiment. BTS experiments were conducted under Vg = 15V, 600 seconds, 85 ℃ bias stress conditions.

Referring to FIG. 12, a threshold voltage shift of 0.1V was observed under a bias stress condition of Vds = 5.1V and 0.1V compared to pre-stress. This value is similar to that of a typical low temperature poly-silicon (LTPS) thin film transistor formed on a glass substrate. From these results, it can be seen that the JILO process has little effect on the reliability of the thin film transistor.

FIG. 13A is a graph illustrating transfer characteristics of a thin film transistor after a JILO process, and illustrates a result of a high drain current (HDC) stress test. FIG. FIG. 13B is a graph showing hysteresis of a thin film transistor after a JILO process. FIG.

The HDC stress conditions in FIG. 13A are Vgs = (-15V), Vds = (-20V), and 60 seconds. It can be seen from the results of FIG. 13A that the electrical characteristics of the thin film transistor did not change after the HDC stress. In addition, in FIG. 13B, the threshold voltage shift after the JILO process is approximately 0.2 V, which is almost similar to that of a typical LTPS thin film transistor.

From the above experimental results, it can be seen that the JILO technology according to the present embodiment does not affect the performance and reliability of the thin film transistor and is suitable for mass production. Hereinafter, the flexible display device will be described with reference to FIGS. 14 and 15. The internal structure of the will be described in detail.

14 is a layout view illustrating a pixel structure of the flexible display device, and FIG. 15 is a cross-sectional view of the flexible display device taken along the line A-A of FIG. 14. 14 and 15 illustrate an organic light emitting diode display as a specific example of the flexible display.

14 and 15, the flexible display device 200 includes a plurality of pixels, and the driving circuit unit 230 and the organic light emitting element 240 are positioned in each pixel. The driving circuit unit 230 includes a switching thin film transistor 30, a driving thin film transistor 40, and a power storage device 50. The gate line 61 is positioned along one direction of the flexible substrate 210, and the data line 62 and the common power line 63 are insulated from and cross the gate line 61.

In FIG. 14, a structure in which two thin film transistors 30 and 40 and one power storage element 50 are positioned in one pixel is illustrated as an example. However, the flexible display device 200 may include three or more thin film transistors and two or more capacitors in one pixel, and may have various structures by further providing separate wirings.

The switching thin film transistor 30 includes a switching semiconductor layer 31, a switching gate electrode 32, a switching source electrode 33, and a switching drain electrode 34. The driving thin film transistor 40 includes a driving semiconductor layer 41, a driving gate electrode 42, a driving source electrode 43, and a driving drain electrode 44. As the thin film transistor, a thin gate transistor having a bottom gate structure may be used in addition to the top gate structure shown in FIG. 15.

The power storage element 50 includes a pair of power storage plates 51 and 52 arranged with an interlayer insulating film 64 therebetween. At this time, the interlayer insulating film 64 is formed of a dielectric. The electrical storage capacity is determined by the electric charges accumulated in the electrical storage element 50 and the voltage between the two electrical storage plates 51 and 52.

The organic light emitting element 240 includes a pixel electrode 25, an organic emission layer 26 formed on the pixel electrode 25, and a common electrode 27 formed on the organic emission layer 26. The pixel electrode 25 may be a hole injection electrode, and the common electrode 27 may be an electron injection electrode. The reverse case is also possible depending on the driving method of the flexible display device 200. Holes and electrons are respectively injected into the organic emission layer 26 from the pixel electrode 25 and the common electrode 27. When the exciton, which is a combination of the injected hole and the electron, falls from the excited state to the ground state, light emission occurs.

A reflective electrode may be used as the pixel electrode 25, and a transmissive or semi-transmissive electrode may be used as the common electrode 27. In this case, the organic light emitting element 240 emits light toward the encapsulation member 250. A transmissive or semi-transmissive electrode may be used as the pixel electrode 25, and a reflective electrode may be used as the common electrode 27. In this case, the organic light emitting element 240 emits light toward the flexible substrate 210.

The switching thin film transistor 30 is used as a switching element for selecting a pixel to emit light. The switching gate electrode 32 is connected to the gate line 61. The switching source electrode 33 is connected to the data line 62. The switching drain electrode 34 is spaced apart from the switching source electrode 33 and is connected to any one capacitor plate 51.

The driving thin film transistor 40 applies driving power to the pixel electrode 25 to emit the organic light emitting layer 26 of the organic light emitting element 240 in the selected pixel. The driving gate electrode 42 is connected to the capacitor plate 51 connected to the switching drain electrode 34. The driving source electrode 43 and the other capacitor plate 52 are connected to the common power line 63, respectively. The driving drain electrode 44 is connected to the pixel electrode 25 of the organic light emitting element 240 through the contact hole.

By the above-described structure, the switching thin film transistor 30 is operated by the gate voltage applied to the gate line 61 to transfer the data voltage applied to the data line 62 to the driving thin film transistor 40. The voltage corresponding to the difference between the common voltage applied to the driving thin film transistor 40 from the common power supply line 63 and the data voltage transmitted from the switching thin film transistor 30 is stored in the power storage element 50 and stored in the power storage element. A current corresponding to the voltage flows to the organic light emitting element 240 and the organic light emitting element 240 emits light.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Of course.

30: switching thin film transistor 40: driving thin film transistor
50: power storage element 61: gate line
62: data line 63: common power line
110: carrier substrate 120: heat generating portion
210, 211: flexible substrate 220: barrier film
230: driving circuit portion 240: light emitting element
250: sealing member 200, 201: flexible display device

Claims (19)

Forming a heat generating portion on the carrier substrate;
Forming a flexible substrate on the heat generating unit;
Forming a thin film transistor on the flexible substrate;
Forming a light emitting device connected to the thin film transistor; And
Separating heat from the heat generating part by applying heat to the flexible substrate by self-heating of the heat generating part
Method of manufacturing a flexible display device comprising a. The method of claim 1,
The flexible substrate may be formed as a single layer on the heat generating part. The method of claim 2,
The method of claim 1, wherein an interface temperature between the heat generating part and the flexible substrate is higher than a melting point of the flexible substrate in the separating of the flexible substrate. The method of claim 1,
The flexible substrate includes a sacrificial layer formed on the heat generating part, a moisture barrier layer formed on the sacrificial layer, and a body layer formed on the moisture barrier layer. The method of claim 4, wherein
The method of claim 1, wherein an interface temperature between the heat generating part and the sacrificial layer is higher than a melting point of the sacrificial layer in the separating of the flexible substrate. A flexible display manufactured by the method of any one of claims 1 to 5, comprising the flexible substrate and the light emitting element, wherein an outer surface of the flexible substrate has a root mean square roughness in the range of 1 nm to 15 nm. Device. Forming a heat generating part including a conductive material having a resistance on the carrier substrate;
Forming a flexible substrate on the heat generating unit;
Forming a driving circuit unit including a thin film transistor on the flexible substrate;
Forming a light emitting element and an encapsulation member on the driving circuit portion;
Separating the flexible substrate from the heat generating portion by applying heat directly to the flexible substrate by applying a voltage to the heat generating portion to generate joule heat
Method of manufacturing a flexible display device comprising a. The method of claim 7, wherein
The heat generating part includes at least one of a metal and a metal oxide, and is formed on the carrier substrate with a uniform thickness. The method of claim 8,
And the heat generating part generates Joule heat by receiving a voltage of a pulse waveform. The method of claim 7, wherein
The flexible substrate may be formed as a single layer on the heat generating part, and a portion of the region contacting the heat generating part may be decomposed and separated from the heat generating part by Joule heat of the heat generating part. The method of claim 10,
The flexible substrate includes at least one of polyimide, polycarbonate, polyacrylate, polyetherimide, polyethersulfone, polyethylene terephthalate, and polyethylene naphthalate. The method of claim 11,
Joule heat generation temperature of the heat generating unit is in the range of 300 ℃ to 900 ℃ manufacturing method of a flexible display device. The method of claim 7, wherein
The flexible substrate includes a sacrificial layer formed on the heat generating part, a moisture barrier layer formed on the sacrificial layer, and a body layer formed on the moisture barrier layer. The method of claim 13,
The sacrificial layer is formed to have a thickness smaller than that of the main body layer, and at least a portion of the sacrificial layer is decomposed by the joule heat of the heat generating part so that the moisture barrier layer and the main body layer are separated from the heat generating part. 15. The method of claim 14,
The sacrificial layer includes at least one of polyimide, polycarbonate, polyacrylate, polyetherimide, polyethersulfone, polyethylene terephthalate, and polyethylene naphthalate. 16. The method of claim 15,
Joule heat generation temperature of the heat generating unit is in the range of 300 ℃ to 900 ℃ manufacturing method of a flexible display device. The method of claim 7, wherein
The light emitting device includes a plurality of organic light emitting devices. 18. The method of claim 17,
The encapsulation member is a manufacturing method of a flexible display device comprising a multilayer film including a plurality of organic films and a plurality of inorganic films. 19. A flexible display made by the method of any one of claims 7 to 18, comprising the flexible substrate and the light emitting element, wherein an outer surface of the flexible substrate has a root mean square roughness in the range of 1 nm to 15 nm. Device.

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