TWI503804B - Flexible display device and manufacturing method thereof - Google Patents

Description

Flexible display device and method of manufacturing same

The techniques are generally related to display devices. In particular, the techniques are generally directed to flexible display devices and methods of making the same.

The display device market has changed by introducing a flat panel display (FPD) that easily achieves a large area and exhibits reduced weight and thickness. For example, among a variety of FPDs, organic light emitting diode (OLED) displays exhibit reduced thickness and weight due to their self-illuminating properties (ie, no light source is required).

Since the conventional FPD may include a glass substrate, its flexibility is reduced and limited in application. Furthermore, conventional FPDs may include thin film transistors on their substrates for control.

The above information disclosed in this section is only for the purpose of promoting an understanding of the technology, and therefore this section may contain information that does not constitute a prior art known in the art to those of ordinary skill in the art.

Since the above-described technology has been made to provide a method of manufacturing a flexible display device, damage of the thin film transistor can be avoided when the flexible substrate and the carrier substrate are separated, and thus the processing cost can be reduced to allow a large-area situation. Do a quick break.

Exemplary embodiments provide a method of fabricating a flexible display device comprising: forming a thermal generator on a carrier substrate; forming a flexible substrate on the thermal generator; forming a thin film transistor on the flexible substrate; forming a light-emitting element coupled to the thin film transistor; and separating the flexible substrate from the heat generator by applying heat to the flexible substrate, wherein applying heat includes generating heat with a heat generator.

Forming the flexible substrate can include forming a single layer on the heat generator.

Separating the flexible substrate from the heat generator can include applying heat to provide an interface temperature between the heat generator and the flexible substrate that is greater than a melting point of the flexible substrate.

Forming the flexible substrate can include forming a flexible substrate having an initial thickness, and forming the heat generator includes forming a heat generator that transfers heat to the flexible substrate.

Forming the flexible substrate may include: forming a sacrificial layer on the heat generator; forming a water vapor permeable layer on the sacrificial layer; and forming the body layer on the water vapor permeable layer.

Separating the sacrificial layer from the heat generator can include applying heat to provide an interface temperature between the heat generator and the sacrificial layer that is greater than a melting point of the sacrificial layer.

The flexible display device can be manufactured by the above method, and the outer portion of the flexible substrate has a root mean square roughness ranging from about 1 nm to about 15 nm.

Exemplary Aspects Provided is another method of fabricating a flexible display device comprising: forming a heat generator on a carrier substrate, the heat generator comprising a conductive material having a predetermined electrical resistance; forming a flexible substrate in the heat generator Forming a driving circuit including a thin film transistor on the flexible substrate; forming a light emitting element and an encapsulating member on the driving circuit; generating Joule heat by applying a voltage to the heat generator, and generating the Joule heat The flexible substrate separates the flexible substrate from the heat generator.

Forming the heat generator can include depositing at least one of a metal and a metal oxide onto the carrier substrate to a uniform thickness.

Generating Joule heat can include applying a voltage having a pulse waveform to the heat generator.

Forming the flexible substrate can include forming a single layer on the heat generator such that a predetermined portion of the single layer contact heat generator is decomposed by the Joule heat of the heat generator.

The flexible substrate may include at least one of polyamine, polycarbonate, polyacrylate, polyether amide, polyether oxime, polyethylene terephthalate, and polybutylene naphthalate.

Producing Joule heat can include heating the heat generator to a temperature of from about 300 °C to about 900 °C.

Forming the flexible substrate can include forming a flexible substrate having an initial thickness, and forming the heat generator includes forming a heat generator that transfers heat to the flexible substrate.

Forming the flexible substrate may include: forming a sacrificial layer on the heat generator; forming a water vapor permeable layer on the sacrificial layer; and forming the body layer on the water vapor permeable layer.

The sacrificial layer may be formed thinner than the bulk layer, and at least a portion of the sacrificial layer is decomposed by the Joule heat of the heat generator, thus preventing the moisture vapor permeable layer and the body layer from separating from the heat generator.

The sacrificial layer may be formed of at least one of polyamine, polycarbonate, polyacrylate, polyether amide, polyether oxime, polyethylene terephthalate, and polybutylene naphthalate.

The Joule heating temperature of the heat generator may be in the range of about 300 ° C to about 900 ° C.

A flexible display device manufactured by the above method, the outer surface of the flexible substrate having a root mean square roughness of about 1 nm to about 15 nm.

21‧‧‧ sacrificial layer

22‧‧‧ Avoid water vapor permeability

23‧‧‧ body layer

25‧‧‧pixel electrode

26‧‧‧Organic emission layer

27‧‧‧Common electrode

30‧‧‧Switching thin film transistor

31‧‧‧Switching the semiconductor layer

32‧‧‧Switching gate

33‧‧‧Switching source

34‧‧‧Switching bungee

40‧‧‧Drive film transistor

41‧‧‧Drive semiconductor layer

42‧‧‧Drive gate

43‧‧‧Drive source

44‧‧‧Drive bungee

50‧‧‧ capacitor

51, 52‧‧‧ Capacitor plates

61‧‧‧ gate line

62‧‧‧Information line

63‧‧‧Common power line

64‧‧‧Interlayer insulation

110‧‧‧ Carrier substrate

120‧‧‧heat generator

130‧‧‧ cushion

200‧‧‧Flexible display device

201‧‧‧Flexible display device

210‧‧‧Flexible substrate

211‧‧‧Flexible substrate

220‧‧‧Barrier layer

230‧‧‧ drive circuit

240‧‧‧Lighting elements

250‧‧‧encapsulated components

S10~S50‧‧‧ operation

The above and other features and advantages will become more apparent to those of ordinary skill in the art in the <RTIgt; A flow chart of a method of manufacturing a flexible display device.

2A through 2E illustrate cross-sectional views of a method of fabricating a flexible display device in accordance with an exemplary embodiment.

Figure 2F illustrates a partial perspective view of Figure 2D.

3A through 3C illustrate phase cross-sectional views of a method of fabricating a flexible display device in accordance with another exemplary embodiment.

Figure 4 illustrates the simulation results of the heat distribution measured when a voltage is applied to the heat generator.

Figure 5 illustrates a photograph of a flexible display device that can be separated from the heat generator and the carrier substrate.

Figure 6 illustrates a scanning electron microscope (SEM) photograph of a flexible substrate surface of a flexible display device in accordance with an exemplary embodiment.

7 and 8 illustrate atomic force microscope (AFM) photographs of a flexible substrate surface of a flexible display device according to an exemplary embodiment.

Figure 9 illustrates an SEM photograph of a flexible substrate surface of a flexible display device to which a comparative example of a laser scanning process is applied.

Figure 10 illustrates an AFM photograph of a flexible substrate surface of a flexible display device using a comparative example of a laser scanning process.

Figure 11 illustrates a transfer characteristic pattern of a thin film transistor before/after a Joule heating induced lift-off (JILO) process.

Figure 12 is a graph showing the transfer characteristics of a thin film transistor after a JILO process according to a bias temperature stress (BTS) test.

Figure 13A illustrates a transfer pattern of a thin film transistor after a JILO process in accordance with a high threshold current (HDC) stress test.

Figure 13B illustrates a hysteresis pattern of a thin film transistor after the JILO process.

Figure 14 illustrates a pixel configuration layout of a flexible display device.

Figure 15 illustrates a cross-sectional view along line A-A of Figure 14.

The exemplary embodiments are described more fully hereinafter with reference to the accompanying drawings. Rather, these specific aspects are provided so that this disclosure will be thorough and complete, and will be <RTIgt;

In the drawings, the dimensions of layers and regions may be exaggerated for clarity. It will also be appreciated that when a layer (or component) is referred to as being "on" another layer or substrate, it can be directly on another layer or substrate, or an intervening layer. In addition, it will also be understood that when a layer refers to "between" layers, it can be the only layer between the two layers, or one or more intervening layers can exist. The same reference numerals are used throughout the drawings to refer to the same elements.

1 illustrates a flow chart of a method of fabricating a flexible display device in accordance with an exemplary embodiment. Referring to FIG. 1, a method of manufacturing a flexible display device may include: forming a heat generator on a carrier substrate (operation S10); forming a flexible substrate on the heat generator (operation S20); forming a thin film transistor (thin film) a transistor (TFT) on the flexible substrate (operation S30); forming a light-emitting element and an encapsulation member (operation S40); and separating the flexibility from the heat generator and the carrier substrate by using heat generated by the heat generator Substrate (operation S50).

2A through 2E illustrate a first method stage cross-sectional view of the manufacture of the flexible display device of FIG. 1, and FIG. 2F illustrates a partial perspective view of FIG. 2D. A method of manufacturing a flexible display device according to a first exemplary embodiment will now be described with reference to FIGS. 1 and 2A to 2F.

Referring to FIG. 2A, a carrier substrate 110 may be prepared in operation S10, and a heat generator 120 may be formed on the carrier substrate 110. The carrier substrate 110 may be a glass substrate as a hard insulating substrate. The heat generator 120 generates heat under predetermined conditions. The heat generator 120 may be formed on the carrier substrate 110 to function as a surface heating member.

Referring to FIG. 2B, the flexible substrate 210 may be formed on (eg, directly from) the heat generator 120 in operation S20. For example, the flexible substrate 210 can be a plastic film and can be fabricated by coating a liquid polymeric material on (eg, directly on) the heat generator 120 and then thermally hardening the coated liquid polymeric material. For example, the flexible substrate 210 may be at least one of polytheneamine, polycarbonate, polyacrylate, polyether amide, polyether oxime, polyethylene terephthalate, and polybutyl naphthalate. Formed by the people. For example, polymethyleneamine can be used at process temperatures greater than 450 ° C, thereby minimizing degradation of the thin film transistor on the flexible substrate 210 during fabrication.

Note that the flexible substrate 210 is made of a plastic film and may be bent or extended by heat, but may be difficult to form on the flexible substrate 210 by a thin film transistor, a light-emitting element, and/or a wire. Precise film pattern. Therefore, since the flexible substrate 210 can be formed on the carrier substrate 110, the carrier substrate 110 can provide sufficient support for the flexible substrate 210 during subsequent processes, such as during formation of the thin film transistor on the flexible substrate 210. .

The flexible substrate 210 may be constructed in a single layer and may be formed on the heat generator 120 to contact the heat generator 120. For example, because the flexible substrate 210 can be smaller than the heat generator 120, the edges of the heat generator 120 can extend beyond the flexible substrate 210, such as along the entire perimeter of the flexible substrate 210.

Referring to FIG. 2C, a barrier layer 220 may be formed on the flexible substrate 210, and a driving circuit 230 including a thin film transistor may be formed on the barrier layer 220. For example, the barrier layer 220 may be flexible. Between the substrate 210 and the driving circuit 230. For ease of demonstration, the driver circuit 230 is shown as a single layer in FIG. 2C, such as a true driver circuit that may include a plurality of thin film transistors and a plurality of capacitors. A plurality of wires may be formed on the flexible substrate 210.

As further illustrated in FIG. 2C, in operation S40, the light emitting element 240 may be formed on the driving circuit 230, and the encapsulation member 250 may be formed on the light emitting element 240. The light emitting element 240 may include a plurality of organic light emitting elements. The light emitting element 240 can be controlled by the driving circuit 230, and can display an image by emitting light according to the driving signal. For ease of description, FIG. 2C simplifies the light-emitting element 240 into a single layer.

The barrier layer 220 may be formed of an inorganic layer and/or an organic layer, or may be formed of stacked inorganic and organic layers. The barrier layer 220 suppresses unwanted elements (such as moisture or oxygen) from penetrating into the light emitting element 240 via the flexible substrate 210 because moisture or oxygen can degrade the light emitting element 240 and reduce the life of the light emitting element 240.

The encapsulation member 250 may be formed of a plurality of layers. The encapsulation member 250 may be formed of a plurality of organic layers, a plurality of inorganic layers, and/or a plurality of alternately stacked organic and inorganic layers. The inorganic layer may, for example, comprise aluminum oxide and/or cerium oxide, and the organic layer may, for example, comprise an epoxy resin, an acrylate and/or an ethyl urethane acrylate.

The inorganic layer prevents the outside moisture and oxygen from penetrating into the light emitting element 240. The organic layer weakens the internal stress of the inorganic layer or the micro-cracks and pinholes filled with the inorganic layer. The materials of the inorganic layer and the organic layer are exemplary and not limited to the materials, and various inorganic layers and organic layers known to those skilled in the art may be used.

The encapsulation member 250 may surround the side of the driving circuit 230 and the side of the light emitting element 240 such that the sides of the driving circuit 230 and the light emitting element 240 may not be exposed to the outside. In other words, the package The sealing member 250 can contact (e.g., directly contact) the barrier layer 220 with the driver circuit 230 and the light emitting element 240 therebetween.

Referring to FIG. 2D, in operation S50, the heat generator 120 may generate heat and apply the generated heat to the flexible substrate 210. As a result of the application of heat, since the flexible substrate 210 contacts a predetermined region of the heat generator 120 (that is, the bottom region in the drawing) can be decomposed by thermal energy, the flexible substrate 210 can be from the heat generator 120 and the carrier substrate. 110 is separated (Fig. 2E). That is, since the heat generator 120 can function as a source of thermal energy to contact the flexible substrate 210, such as directly contacting the flexible substrate 210 facing the entire bottom surface of the heat generator 120, the heat energy of the heat generator 120 can Transfer directly to the flexible substrate 210 without using a medium.

In contrast, if the flexible substrate on the carrier substrate is heated by a laser source, such as with respect to the heat generator 120 of the exemplary embodiment, the laser beam (such as a quasi-molecular laser beam) can The region outside the carrier substrate is irradiated toward the flexible substrate via the carrier substrate to transfer thermal energy to the flexible substrate. That is, since the laser source may be positioned externally with respect to the carrier substrate, such as beyond the bottom surface of the carrier substrate facing away from the flexible substrate, the laser beam output of the laser source will pass through the thickness of the carrier substrate to reach and Focusing on the flexible substrate thereby transferring thermal energy to the flexible substrate. Accordingly, the laser source outside the carrier substrate requires the medium relative to the heat generator 120 (ie, the heat source contacting the flexible substrate 210 and located within the structure of the carrier substrate 110 and the flexible substrate 210). That is, the carrier substrate) to transfer energy.

For example, the heat generator 120 can be constructed with a conductive layer, such as a conductive layer, to cause Joule heating under voltage application conditions. However, the configuration of the heat generator 120 and its heat generation principle are not limited to the above examples, and other configurations may be applied to immediately generate the heat and thermal decomposition portions of the flexible substrate 210.

Heat generator 120 can include a metal or metal oxide. For example, the heat generator 120 may include at least one of molybdenum (Mo), titanium (Ti), copper (Cu), silver (Ag), and chromium (Cr) as the metal and / or at least one of indium tin oxide (ITO), indium zinc oxide (IZO) as a metal oxide.

Referring to FIG. 2F, the carrier substrate 110 and the heat generator 120 may be formed to have an area larger than that of the flexible substrate 210, such that the end of the heat generator 120 (eg, the heat generator 120 faces the upper surface of the flexible substrate 210) Portions of the opposite edges of the heat generator 120 may be exposed to the outside of the flexible substrate 210. A second pad 130 connected to an external power supply (not shown) may contact the exposed end of the heat generator 120 to apply a voltage (such as a voltage having a pulsed waveform) to the heat generator 120.

The exposed end of the heat generator 120 and the two pads 130 thereon may face each other along the direction of the carrier substrate 110 (such as along the x-axis in the drawing), and may be formed into a long rod shape in the cross-sectional direction, such as The liner 130 can extend along the y-axis along the entire length of the heat generator 120 and its exposed ends. Accordingly, since the pad 130 contacts the opposite ends of the heat generator 120, a uniform current flows in one direction (e.g., along the x-axis direction in the drawing) through the heat generator 120 of the carrier substrate 110, thereby causing the heat generator Joule heat is generated in 120.

The heat generator 120 generates heat at a plurality of temperatures depending on the resistance value and the pulse condition, for example, the heat generator 120 can generate heat of more than 1000 °C. The temperature of the heat generator 120 may be set to a range suitable for controlling heat to quickly pass through a predetermined portion of the flexible substrate 210, and immediately decomposing the predetermined portion to a predetermined heat penetration depth without affecting formation on the flexible substrate The drive circuit 230 and the light-emitting element 240 on 210.

For example, the heating temperature of the heat generator 120 at operation S50 can be set in the range of about 300 ° C to about 900 ° C. When the heating temperature of the heat generator 120 is lower than 300 ° C, thermal decomposition in the bottom region of the flexible substrate 210 may be uneven, such as a material that may be decomposed, thereby making the flexible substrate 210 difficult to decompose. When the heating temperature of the heat generator 120 is higher than 900 ° C, the flexible substrate 210 may be overheated, thereby causing deterioration of the thin film transistor formed on the flexible substrate 210.

The heat generator 120 can form a uniform thickness on the carrier substrate 110 to produce uniform Joule heat across the heat generator 120.

The pulse time of the voltage applied to the heat generator 120 can be controlled in consideration of the heat penetration depth of the flexible substrate 210. When the thickness of the flexible substrate 210 is about 10 microns, the thermal penetration depth can be less than about 1 micron. In this case, deterioration of the drive circuit 230 and the light-emitting element 240 caused by the supply of heat to the flexible substrate 210 can be substantially minimized.

The separation process according to the exemplary embodiment described above may be referred to as a Joule heating induced lift-off (JILO) process. In this exemplary aspect of using the JILO process, Joule heat is generated by applying a voltage to the heat generator 120. Since the heat generator 120 contacts a predetermined area of the flexible substrate 210, the Joule heat transferred from the heat generator 120 to a predetermined area of the flexible substrate 210 penetrates the flexible substrate 210 to a predetermined depth, such as before As discussed, this is based on the voltage pulse time. Since the portion of the flexible substrate 210 that is thermally penetrated (for example, the entire contact surface between the flexible substrate 210 and the heat generator 120) is decomposed, the flexible substrate 210 is separated from the heat generator 120. The separation process can also be performed over a few microseconds (μs) on a wide and/or large substrate with little or no thermal and/or mechanical damage to the driver circuit 230 and the light-emitting elements 240 on the flexible substrate 210. .

In contrast, when a laser beam is used in the separation process, the driving circuit and the light-emitting element may be damaged due to the intensity of the laser, since the flexible substrate and the layers formed thereon are very thin, although the laser beam is controlled. The intensity and depth of focus are also the same. Furthermore, the use of lasers may increase costs due to the expense of the laser system and may increase manufacturing time due to the limited number of laser beams available and the necessity to scan the laser beam.

3A to 3C are cross-sectional views showing a second method stage of manufacturing the flexible display device shown in Fig. 1. A method of manufacturing a flexible display device according to a second exemplary embodiment will now be described with reference to FIGS. 1 and 3A to 3C.

Referring to FIG. 3A, a carrier substrate 110 may be prepared in operation S10, and the heat generator 120 may be formed on the carrier substrate 110 in a manner similar to the first exemplary embodiment (FIG. 2A). In operation S20, the flexible substrate 211 can be formed on the heat generator 120 by sequentially depositing the sacrificial layer 21, avoiding the water vapor permeation layer 22, and the body layer 23 on (eg, directly) the heat generator 120. In other words, the flexible substrate 211 may include a plurality of layers, that is, the flexible substrate 211 may include the sacrificial layer 21, the moisture barrier layer 22, and the body layer 23. A sacrificial layer 21 may be formed (eg, directly) to the heat generator 120 to contact the heat generator 120.

The sacrificial layer 21 and the main body layer 23 may be made of the same plastic film as the flexible substrate 210 of the first exemplary embodiment, and the plastic film may be fabricated by reheating and hardening the liquid polymer material. For example, the sacrificial layer 21 may be formed to be less thick than the body layer 23, such as the thickness of the sacrificial layer 21 may be equal to or greater than the thermal penetration depth of the flexible substrate 210. The body layer 23 may be formed to have the same thickness as the flexible substrate 210 of the first exemplary embodiment.

The water vapor permeable layer 22 may include at least one of aluminum (Al), molybdenum (Mo), titanium (Ti), copper (Cu), silver (Ag), and chromium (Cr) as a metal layer, and it may be via Formed by sputtering. The moisture permeation layer 22 is prevented from controlling the outside moisture to permeate into the light-emitting element 240 through the flexible substrate 211. That is, in the second exemplary embodiment, the barrier layer 220 and the water vapor barrier layer 22 are both inhibited from infiltrating moisture and oxygen into the light-emitting element 240, thereby increasing the efficiency of blocking moisture and oxygen.

As previously described with reference to FIG. 2C, the barrier layer 220 and the driving circuit 230 may be formed on the flexible substrate 211 in operation S30. In operation S40, the light emitting element 240 and the encapsulation member 250 may be formed on the driving circuit 230, which corresponds to the first exemplary embodiment.

Referring to FIGS. 3B and 3C, at operation S50, a voltage is applied to the heat generator 120 to generate Joule heat. The sacrificial layer 21 of some or all of the contact heat generator 120 may be thermally decomposed by Joule heat, and the moisture barrier layer 22 of the flexible substrate 211 may be separated from the heat generator 120 to complete the flexible display device 201. The portion of the sacrificial layer 21 that is not thermally decomposed may or may not remain in the water vapor permeable layer 22 On the surface. The resistance, heating temperature, and pulse conditions of the heat generator 120 correspond to (i.e., are identical to) the first exemplary embodiment.

example:

An exemplary process for manufacturing a flexible display device according to the first exemplary embodiment and a simulation result of thermal conductivity will now be described.

A glass substrate is used for the carrier substrate 110, and a heat generator 120 constructed of a single layer of molybdenum (Mo) is formed on the glass substrate. A polyimide film is used for the flexible substrate 210. The polyimide film is about 10 microns thick and hardens at temperatures above 350 °C. The process after the formation of the polyimide film corresponds to the process of a general OLED display. A voltage having a pulse waveform is applied to the heat generator 120 for thermal conductivity simulation.

Figure 4 shows the simulation results of the heat distribution measured when a voltage is applied to the heat generator. In Fig. 4, the "PI substrate" is a polyimide film (that is, a flexible substrate), the "conductive layer" is a heat generator, and the "glass" is a glass substrate as a carrier substrate.

Referring to Fig. 4, the maximum temperature of the heat generator is 600 ° C, and the interface temperature between the polyimide film and the heat generator is 450 ° C, which is higher than the melting point (360 ° C) of the polyimide film. Therefore, since a part of the polyimide film is decomposed by heat, the polyimide film (that is, the flexible substrate) is separated from the heat generator.

Figure 5 shows a photograph of a flexible display device that can be separated from the heat generator and the carrier substrate. The depth of thermal penetration measured by the polyimide film during this process is less than 0.5 microns. Since the ratio of the heat penetration depth to the entire polyimide film is very small, when the Joule heating temperature is high enough to melt the flexible substrate, the driving circuit and the light-emitting element are not thermally or mechanically damaged.

6 shows a scanning electron microscope (scanning electron microscope) on the surface of the flexible substrate 210 of the flexible display device 200 according to the above first exemplary embodiment. Microscopy, SEM) photos, and Figures 7-8 show their atomic force microscopy (AFM) photos.

The surface of the flexible substrate shown in FIGS. 6 to 8 indicates the outer surface of the flexible substrate separated from the heat generator 120 by the generation of Joule heat after contacting the heat generator 120. In the case of the flexible display device 201 according to the second exemplary embodiment, the surface of the sacrificial layer 21 also has the same characteristics as those of FIGS. 6 and 7. Figure 6 is an enlargement of 130,000 times.

A flexible display device according to a comparative example is prepared, that is, a laser scanning process is applied to heat the flexible substrate, and FIGS. 9 and 10 respectively show a flexible substrate surface of the flexible display device according to the comparative example. SEM photos and AFM photos. The surface of the flexible substrate shown in Figures 9 and 10 represents the outer surface of the flexible substrate separated from the carrier substrate by the laser beam after contacting the carrier substrate. Figure 9 is enlarged by 130,000 times.

The flexible display device according to the comparative example is manufactured in the same process as the flexible display device according to the present exemplary embodiment, with the exception that a flexible substrate is formed on the carrier substrate instead of heat generation. And scanning the laser beam from the outside of the carrier substrate toward the flexible substrate to separate the carrier substrate and the flexible substrate.

Referring to FIGS. 6 through 8, with respect to the flexible display device using the JILO process according to the first exemplary embodiment, the flexible substrate is realized to have a very uniform surface with a much smaller roughness. This surface property is caused by the JILO process characteristics in which the entire surface of the flexible substrate is simultaneously separated from the carrier substrate by instantaneous thermal decomposition.

With respect to the flexible display device according to the present exemplary embodiment, the root mean squared (RMS) roughness of the surface of the flexible substrate (such as the exterior of the flexible substrate 210) is from 1 nm to 15 In the nano range. The RMS roughness of a flexible substrate varies by many factors, such as the type of flexible substrate, heat generator resistance, heating temperature, voltage pulse time applied to the heat generator, and is typically greater than about 1 nm and less. About 15 nm. Flexible substrate measured by AFM analysis of Figure 7 The RMS roughness is substantially about 2.5 nm, while the RMS roughness of the flexible substrate measured by the AFM analysis of Figure 8 is substantially about 7.5 nm.

Referring to FIG. 9 and FIG. 10, in the flexible display device using the laser scanning process according to the comparative example, the flexible substrate has an RMS roughness of more than 20 nm, and the surface achieved is compared with the example according to the present example. The flexible substrate of the specific aspect is rougher and less uniform. The RMS roughness of the surface of the flexible substrate measured on the AFM surface shown in Figure 10 is substantially about 30 nm.

The surface characteristics of the flexible substrate according to the comparative example are dependent on the laser scanning characteristics, wherein the thermal decomposition depth of the flexible substrate is not fixed, because the precision of the laser beam intensity and the depth of focus is controlled. The degree is limited, and the surface of the flexible substrate is thermally decomposed sequentially (i.e., partially) in the direction of the laser scanning.

The change in film crystal characteristics of the flexible display device according to this exemplary embodiment before and after the JILO process will now be described. Table 1 shows the film transistor characteristics measured before the JILO process was carried out, and the graph shown in Fig. 11 indicates the transfer characteristics of the film transistor before and after the JILO process.

Prior to the JILO process, the charge mobility (μFET) of the thin film transistor was measured to be 90.4 cm ^ 2 / volt second, the threshold voltage was measured to be -2.9 volts, and the s slope (ie, the secondary threshold slope) was measured to be 0.32 volts / tens (V / Decade). After the JILO process, as shown in FIG. 11, it was found that the threshold voltage and s slope of the thin film transistor did not change. The above results show that the JILO process does not cause significant damage to the performance of the thin film transistor.

The graph shown in Figure 12 is a bias temperature stress (BTS) test result indicating the transfer characteristics of the thin film transistor after the JILO process. The BTS test was carried out under bias stress conditions of Vg = 15 volts, 600 seconds, and 85 °C.

Referring to Fig. 12, a threshold voltage shift of 0.1 volt was observed under bias stress conditions of Vds = 5.1 volts and 0.1 volts as compared to the case before stress. This value is similar to a low temperature poly-silicon (LTPS) thin film transistor generally formed on a glass substrate. The JILO process has minimal impact on the reliability of the thin film transistor.

The graph shown in Figure 13A indicates the transfer characteristics of the thin film transistor after the JILO process, which shows the high drain current (HDC) stress test results. Figure 13B shows a graph indicating the hysteresis of the thin film transistor after the JILO process.

In Figure 13A, the HDC stress conditions are Vgs = -15 volts, Vds = -20 volts, 60 seconds. From the results of Fig. 13A, it was judged that the electrical characteristics of the thin film transistor did not change after the HDC stress. Meanwhile, in FIG. 13B, the threshold voltage shift after the JILO process is substantially 0.2 volts, which is very similar to a general LTPS thin film transistor.

From the above test results, it was found that the JILO technique according to this exemplary embodiment does not affect the performance and reliability of the thin film transistor, and it is suitable for mass production. Referring to Figures 14 and 15, the internal configuration of the flexible display device will now be described.

Figure 14 shows a pixel configuration layout of the flexible display device, and Figure 15 shows a cross-sectional view of the flexible display device with respect to line A-A of Figure 14. 14 and 15 show a detailed example of an OLED display as a flexible display device.

Referring to FIGS. 14 and 15, the flexible display device 200 formed according to the first exemplary method may include a plurality of pixels each having a driving circuit 230 and an organic light emitting element 240. The driving circuit 230 includes a switching thin film transistor 30, a driving thin film transistor 40, and a capacitor 50. The gate line 61 is provided in one direction of the flexible substrate 210, and the data line 62 and the common power line 63 are insulated across the gate line 61.

The pixel illustrated in FIG. 14 has two thin film transistors 30 and 40 and a capacitor 50. Furthermore, each pixel of the flexible display device 200 may have three or more thin film transistors and two or more capacitors, and may further have additional wires for various configurations. .

Switching the thin film transistor 30 includes switching the semiconductor layer 31, switching the gate 32, switching the source 33, and switching the drain 34. The driving thin film transistor 40 includes a driving semiconductor layer 41, a driving gate 42, a driving source 43, and a driving drain 44. Both the thin film transistor of the bottom gate structure and the thin film transistor of the top gate structure shown in Fig. 15 can be used for the thin film transistor.

The capacitor 50 includes a pair of capacitor plates 51 and 52 with an interlayer insulating layer 64 disposed therebetween. In this example, the interlayer insulating layer 64 is formed of a dielectric material. The capacitance is determined by the charge charged in the capacitor 50 and the voltage between the capacitor 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. Depending on the method of driving the flexible display device 200, the reverse is also permissible. The holes and electrons are injected from the pixel electrode 25 and the common electrode 27 into the organic emission layer 26. When an exciton (ie, an injected hole and an electron combines) enters the ground state from an excited state, luminescence is emitted.

A reflective electrode is used for the pixel electrode 25, and a transparent or semi-transparent electrode is used for the common electrode 27; in this case, the organic light emitting element 240 emits light to the encapsulation member 250. A transparent or semi-transparent electrode is used for the pixel electrode 25, and a reflective electrode is used for the common electrode 27; in this case, the organic light-emitting element 240 sends light to the flexible substrate 210.

The switching thin film transistor 30 is used as a switch for selecting illuminating pixels. The switching gate 32 is connected to the gate line 61. The switching source 33 is connected to the data line 62. The switching gate 34 is configured to be separated from the switching source 33 and connected to a capacitor plate 51.

The driving film transistor 40 applies driving power for the organic emission layer 26 of the selected pixel of the organic light emitting element 240 to the pixel electrode 25. The drive gate 42 is connected to a capacitor plate 51 which is connected to the switching gate 34. The driving source 43 and the other capacitor plate 52 are connected to the common power line 63. The driving drain 44 is connected to the pixel electrode 25 of the organic light emitting element 240 via a contact hole.

According to the configuration described, 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 from the common power line 63 to the driving thin film transistor 40 and the data voltage transferred by the switching thin film transistor 30 is stored in the capacitor 50, and the current corresponding to the voltage stored in the capacitor 50 is then It flows to the organic light emitting element 240 to emit light.

According to an exemplary embodiment, the carrier substrate and the flexible substrate can be easily separated in a short time, such as a few microseconds (μs), and may not cause heat and/or heat to the thin film transistor and the light-emitting element on the flexible substrate. mechanical injury. This separate technique is suitable for manufacturing a wide area flexible display device in mass production. Furthermore, the flexible display device can be manufactured using an existing manufacturing system, thereby avoiding the difficulty and cost of providing a new manufacturing system.

Exemplary specific aspects have been disclosed herein; although specific vocabulary is employed, they are intended to be interpreted only in a generic and narrative sense without limitation. According to this, familiar with It will be understood by those skilled in the art that various changes can be made in the form and details without departing from the scope of the invention as set forth in the appended claims.

S10~S50‧‧‧ operation

Claims (18)

A method of manufacturing a flexible display device, the method comprising: forming a heat generator on a carrier substrate; forming a flexible substrate on the heat generator; forming a thin film transistor on the flexible substrate; forming a connection a light-emitting element of the thin film transistor; and separating the flexible substrate from the heat generator by applying heat to the flexible substrate, wherein applying heat includes generating heat by a heat generator, wherein the flexibility is separated from the heat generator The substrate includes applying heat to provide an interface temperature between the heat generator and the flexible substrate that is greater than the melting point of the flexible substrate. The method of claim 1, wherein forming the flexible substrate comprises forming a single layer on the heat generator. The method of claim 1, wherein forming the flexible substrate comprises: forming a sacrificial layer on the heat generator; forming a water vapor permeable layer on the sacrificial layer; and forming a body layer to prevent moisture permeation On the floor. The method of claim 3, wherein separating the sacrificial layer from the heat generator can include applying heat to provide an interface temperature between the heat generator and the sacrificial layer, the temperature being greater than a melting point of the sacrificial layer. A flexible display device manufactured by the method of claim 1, wherein the outer surface of the flexible substrate has a range of from about 1 nm to about 15 nm Square root roughness. A method of fabricating a flexible display device, the method comprising: forming a heat generator on a carrier substrate, the heat generator comprising a conductive material having a predetermined electrical resistance; forming a flexible substrate on the heat generator; forming a thin film comprising a driving circuit of the crystal on the flexible substrate; forming a light emitting element and an encapsulating member on the driving circuit; generating Joule heat by applying a voltage to the heat generator, and generating the Joule heat to be applied to the flexible substrate Separating the flexible substrate from the heat generator, wherein separating the flexible substrate from the heat generator includes providing an interface temperature between the heat generator and the flexible substrate that is greater than a melting point of the flexible substrate. The method of claim 6, wherein forming the heat generator comprises depositing at least one of a metal and a metal oxide on the carrier substrate to a uniform thickness. The method of claim 7, wherein generating the Joule heat comprises applying a voltage having a pulse waveform to the heat generator. The method of claim 6, wherein forming the flexible substrate comprises forming a single layer on the heat generator such that a predetermined portion of the single layer contact heat generator is decomposed by Joule heat of the heat generator. The method of claim 9, wherein the flexible substrate comprises polyamidoamine, polycarbonate, polyacrylate, polyether amide, polyether oxime, polyethylene terephthalate, polynaphthic acid At least one of the ethyl esters. The method of claim 10, wherein generating the Joule heat comprises heating the heat generator to a temperature of from about 300 ° C to about 900 ° C. The method of claim 6, wherein forming the flexible substrate comprises: forming a sacrificial layer on the heat generator; forming a water vapor permeable layer on the sacrificial layer; and forming a body layer on the water vapor permeable layer . The method of claim 12, wherein the sacrificial layer is formed thinner than the body layer, and at least a portion of the sacrificial layer is decomposed by the Joule heat of the heat generator, such that the water vapor permeable layer and the body layer are avoided The heat generators are separated. The method of claim 13, wherein the sacrificial layer is made of polyamidoamine, polycarbonate, polyacrylate, polyether amide, polyether oxime, polyethylene terephthalate, polynaphthic acid At least one of the esters is formed. The method of claim 14, wherein the Joule heating temperature of the heat generator is in the range of from about 300 °C to about 900 °C. The method of claim 6, wherein the light-emitting element comprises a plurality of organic light-emitting elements. The method of claim 16, wherein the encapsulating member is constructed in a plurality of layers including a plurality of organic layers and a plurality of inorganic layers. A flexible display device manufactured by the method of claim 6, wherein the outer surface of the flexible substrate has a root mean square roughness of about 1 nm to about 15 nm.