TWI673170B - Method of fabricating flexible display - Google Patents

Abstract

The present invention provides a method for manufacturing a flexible display and a flexible display. The present invention provides a method for manufacturing a flexible display including the following steps. A first flexible material layer is formed on the carrier board. The first flexible material layer is cured at a first curing temperature to form a first flexible layer. A buffer layer is formed on the first flexible layer. A second flexible material layer is formed on the buffer layer. The second flexible material layer is cured at a second curing temperature to form a second flexible layer. The second curing temperature is lower than the first curing temperature. An element array is formed on the second flexible layer.

Description

Manufacturing method of flexible display

The present invention relates to a display and a method for manufacturing the same, and more particularly, to a flexible display and a method for manufacturing the same.

As portable displays are widely used, the development of flexible displays is becoming more and more active to achieve the purpose of displaying under different curved surfaces. The conventional flexible display includes a multilayer structure. However, in the process of manufacturing a flexible display, the bubbles generated by the heat treatment process are easy to form in the multilayer structure and make the surface uneven, so it is easy to generate when forming subsequent films. Defects, which cause display problems.

At least one embodiment of the present invention provides a method for manufacturing a flexible display, which can improve the process yield of the flexible display.

At least one embodiment of the present invention provides a flexible display, which can have good display quality.

Method package for manufacturing flexible display according to at least one embodiment of the present invention Include the following steps. A first flexible material layer is formed on the carrier board. The first flexible material layer is cured at a first curing temperature to form a first flexible layer. A buffer layer is formed on the first flexible layer. A second flexible material layer is formed on the buffer layer. The second flexible material layer is cured at a second curing temperature to form a second flexible layer. The second curing temperature is lower than the first curing temperature. An element array is formed on the second flexible layer.

A flexible display according to at least one embodiment of the present invention includes a first flexible layer, a buffer layer, a second flexible layer, and an element array. The buffer layer is located on the first flexible layer. The second flexible layer is on the buffer layer. The element array is on the second flexible layer. The first flexible layer and the second flexible layer have a first glass transition temperature and a second glass transition temperature, respectively. When the temperature is lower than the first glass transition temperature, the first thermal expansion coefficient of the second flexible layer is greater than the first thermal expansion coefficient of the first flexible layer. When between the first glass transition temperature and the second glass transition temperature, the second thermal expansion coefficient of the second flexible layer is greater than the second thermal expansion coefficient of the first flexible layer. When it is greater than the second glass transition temperature, the third thermal expansion coefficient of the second flexible layer is greater than the third thermal expansion coefficient of the first flexible layer.

Based on the above, the method for manufacturing a flexible display provided by at least one embodiment of the present invention can reduce the number of bubbles generated between the first flexible layer and the buffer layer, and can even avoid the first flexible layer and the buffer layer. Air bubbles are formed between the two to improve the problem of protrusions on the surface of the film layer caused by the air bubbles, thereby increasing the process yield of the flexible display. The flexible display provided by at least one embodiment of the present invention avoids or reduces the number of bubbles between the first flexible layer and the buffer layer, and has good display quality.

In order to make the above features and advantages of the present invention more comprehensible, the following enumerated The embodiments will be described in detail with the accompanying drawings.

10‧‧‧ Flexible display

100‧‧‧ Carrier Board

110‧‧‧first flexible layer

110a‧‧‧first flexible material layer

120‧‧‧ buffer layer

130‧‧‧second flexible layer

130a‧‧‧second flexible material layer

140‧‧‧element array

C1, C2 ‧‧‧ curing process

FS‧‧‧Flexible substrate

1A to 1F are schematic cross-sectional views of a method for manufacturing a flexible display according to an embodiment of the present invention.

FIG. 2 is a static thermomechanical analysis spectrum of the second flexible layer of the flexible displays of Examples 7 to 9 and Comparative Example 3. FIG.

Hereinafter, the present invention will be explained more fully with reference to the drawings of this embodiment. However, the present invention may be embodied in various forms and should not be limited to the embodiments described herein. The thicknesses of layers and regions in the drawings are exaggerated for clarity. The same or similar reference numbers indicate the same or similar elements, and the following paragraphs will not repeat them one by one. In addition, the directional terms mentioned in the embodiments, such as: up, down, left, right, front, or rear, are only directions referring to the attached drawings. Therefore, the directional terms used are used to illustrate and not to limit the present invention.

1A to 1F are schematic cross-sectional views of a method for manufacturing a flexible display according to an embodiment of the present invention.

Referring to FIG. 1A, a first flexible material layer 110 a is formed on a carrier board 100. In some embodiments, the carrier board 100 may be a rigid substrate, which is not easily deformed by external forces during the manufacturing process, so that the carrier board 100 may be formed on the carrier board 100. The first flexible material layer 110a has a good flatness, so that the film layer formed on the first flexible material layer 110a has good stability. The material of the carrier plate 100 may be glass, polycarbonate (PC), stainless steel plate, or a combination thereof. The material of the first flexible material layer 110a may be polyimide (PI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), or A combination of the aforementioned at least two materials. In this embodiment, the material of the first flexible material layer 110a is polyimide. The method for forming the first flexible material layer 110 a is, for example, a slit coating method, a spin coating method, or a combination thereof.

Referring to FIG. 1A and FIG. 1B at the same time, the first flexible material layer 110 a is cured at a first curing temperature to form the first flexible layer 110. A method of curing the first flexible material layer 110 a is, for example, performing a curing process C1 at a first curing temperature. In this embodiment, the first curing temperature is 480 ° C or higher and 500 ° C or lower. The thickness of the first flexible layer 110 is, for example, 1 μm to 20 μm. In this embodiment, the material of the first flexible layer 110 may refer to the foregoing embodiment, and details are not described herein again.

In this embodiment, the first glass transition temperature of the first flexible layer 110 is 0 ° C to 350 ° C, and the second glass transition temperature of the first flexible layer 110 is 350 ° C to 550 ℃. The first flexible layer 110 has a first coefficient of thermal expansion when the ambient temperature is lower than the first glass transition temperature is 0 to 20 ppm / ° C, and is between the first glass transition temperature and the second glass transition temperature. Second thermal expansion coefficient at temperature from 5 to 100 ppm / ° C, and the third thermal expansion coefficient at an ambient temperature greater than the second glass transition temperature is 30 to 1000 ppm / ° C.

Referring to FIG. 1C, a buffer layer 120 is formed on the first flexible layer 110. In this embodiment, the buffer layer 120 has a single-layer structure, but is not limited thereto. In other embodiments, the buffer layer 120 may be a multilayer stack structure. The material of the buffer layer 120 may be an inorganic material, such as silicon oxide (SiO _x ), silicon nitride (SiN _x ), or a combination thereof. The thickness of the buffer layer 120 is, for example, 10 nm to 1000 nm. A method for forming the buffer layer is, for example, a chemical vapor deposition method (CVD), a physical vapor deposition method (PVD), an atomic layer deposition method (ALD), or a combination thereof.

Referring to FIG. 1D, a second flexible material layer 130 a is formed on the buffer layer 120. The material of the second flexible material layer 130a may be the same as or different from the material of the first flexible material layer 110a. The material of the second flexible material layer 130a may be polyimide, polyethylene naphthalate, polyethylene terephthalate, or a combination of at least two of the foregoing materials. In this embodiment, the material of the second flexible material layer 130a is polyimide. A method for forming the second flexible material layer 130a is, for example, a slit coating method, a spin coating method, or a combination thereof.

Referring to FIG. 1D and FIG. 1E at the same time, the second flexible material layer 130 a is cured at the second curing temperature to form the second flexible layer 130. A method of curing the second flexible material layer 130a is, for example, performing a curing process C2 at a second curing temperature. In this embodiment, the second curing temperature is greater than or equal to 450 ° C and less than 480 ° C. In this embodiment, the second curing temperature is lower than the first curing temperature when the first flexible material layer 110a is cured, but the present invention is not limited thereto, and in other embodiments Among them, the first curing temperature is 480 ° C or higher and the second curing temperature is 450 ° C or higher. In this embodiment, the difference between the first curing temperature and the second curing temperature is greater than or equal to 20 ° C. The thickness of the second flexible layer 130 is, for example, 1 μm to 20 μm. In this embodiment, the material of the second flexible layer 130 can refer to the foregoing embodiment, and details are not described herein again.

In this embodiment, the first glass transition temperature of the second flexible layer 130 is 0 ° C to 350 ° C, and the second glass transition temperature of the second flexible layer 130 is 350 ° C to 550 ° C. The second flexible layer 130 has a first thermal expansion coefficient of 0 to 20 ppm / ° C. at an ambient temperature less than the first glass transition temperature, and a second thermal expansion between the first glass transition temperature and the second glass transition temperature. The coefficient is 5 to 100 ppm / ° C, and the third thermal expansion coefficient is 30 to 1000 ppm / ° C at an ambient temperature greater than the second glass transition temperature. In this embodiment, the first, second, and third thermal expansion coefficients of the second flexible layer 130 may be greater than the first, second, and third thermal expansion coefficients of the first flexible layer 110, respectively. Three thermal expansion coefficients.

In this embodiment, the flexible substrate FS may be composed of the first flexible layer 110, the buffer layer 120, and the second flexible layer 130 (for example, PI / SiO _x / PI or PI / SiN _x / PI). In this embodiment, since the second curing temperature is made lower than the first curing temperature, it is difficult to form a bubble between the first flexible layer 110 and the buffer layer 120 when the second flexible material layer 130a is cured. Therefore, it is possible to prevent the second flexible layer 130 from being lifted up by the bubbles to generate protrusions on a part of the surface thereof, thereby improving the process yield.

In some embodiments, the air bubbles generated by the heat treatment process may be caused by particles in the environment (eg, particles of metal debris from the machine, the material of which includes iron, nickel, chromium and other elements). For example, particles have one or more pores, and the gas is stored in the pores of the particles. Therefore, during the heat treatment process, the gas in the pores of the particles will expand and diffuse out of the pores. With the number of heat treatment processes, As it increases, more and more gases diffuse out of the pores of the particles. In this case, since the second curing temperature is made lower than the first curing temperature in this embodiment, when curing the second flexible material layer 130a, it can be reduced to a value between the first flexible layer 110 and the buffer layer 120. The number of bubbles generated in between can even avoid the formation of bubbles between the first flexible layer 110 and the buffer layer 120.

Referring to FIG. 1F, a device array 140 is formed on the second flexible layer 130 to form a flexible display 10 on the carrier board 100. In this embodiment, the element array 140 may be an organic light emitting diode (OELD) pixel array, but the present invention is not limited thereto. The device array 140 may include multiple active devices (not shown), multiple scan lines (not shown), multiple data lines (not shown), and multiple sub pixels (not shown). Each sub pixel may be They are electrically connected to corresponding scanning lines and corresponding data lines in the element array 140, but the present invention is not limited thereto. The plurality of active devices may be, for example, low temperature polycrystalline silicon thin film transistor (LTPS-TFT) devices. In this embodiment, the process temperature for forming the element array 140 is lower than the first curing temperature and the second curing temperature. The process temperature for forming the element array 140 is, for example, 400 ° C to 650 ° C. In this embodiment, because the process temperature for forming the element array 140 is lower than the first curing temperature and the second curing temperature, the first flexible layer 110 and the second flexibility corresponding to the higher process temperature The formation step of the layer 130 is prior to the formation step of the element array 140 corresponding to the lower process temperature, so the element array 140 will not be affected or destroyed by the previous high-temperature process during formation, thereby stably forming the element array 140 on On the second flexible layer 130.

The manufacturing method of the element array 140 is briefly described below, but the invention is not limited thereto. After the second flexible layer 130 is formed, an amorphous silicon layer (not shown) is formed on the second flexible layer 130. Next, a heat treatment process is performed on the amorphous silicon layer to remove hydrogen, and an excimer laser annealing (ELA) process is performed on the amorphous silicon layer to form a polycrystalline silicon layer (not shown). The above-mentioned excimer laser annealing (ELA) process uses a laser beam to sequentially polymorphize amorphous silicon layers at different positions, so that the amorphous silicon is rearranged into polycrystalline silicon. After that, the polycrystalline silicon layer is partially doped, and then a gate insulating layer (not shown), a first metal layer (not shown), and an interlayer insulating layer (not shown) are sequentially formed. The formation method of the interlayer insulating layer is, for example, firstly depositing an interlayer insulating material layer by a chemical vapor deposition method or a physical vapor deposition method, and then activating the hydrogen in the interlayer insulating layer through a heat treatment process so that hydrogen can enter the polycrystalline silicon. Layer to repair defects. Then, a second metal layer (not shown), a first flat layer (not shown), a conductive layer (not shown), and a second flat layer (not shown) are sequentially formed.

Referring to FIG. 1E and FIG. 1F at the same time, after the element array 140 is formed, a peeling process may be selectively performed to separate the carrier board 100 and the first flexible layer 110, but the present invention is not limited thereto. In this embodiment, the peeling process is, for example, a laser peeling process. In other embodiments, other suitable methods may be used to separate the carrier plate 100 from the first flexible layer 110.

Based on the above, in an embodiment of the present invention, the method of manufacturing the flexible display 10 can reduce the number of bubbles generated between the first flexible layer 110 and the buffer layer 120, and can even avoid the first flexible layer. A bubble is formed between 110 and the buffer layer 120, thereby increasing the process yield of the flexible display 10.

Hereinafter, the flexible display of this embodiment will be described with reference to FIG. 1F. In addition, although the flexible display of this embodiment is manufactured by the manufacturing method mentioned above, this invention is not limited to this.

The flexible display 10 includes a first flexible layer 110, a buffer layer 120, a second flexible layer 130, and an element array 140. The buffer layer 120 is located on the first flexible layer 110. The second flexible layer 130 is located on the buffer layer 120. The element array 140 is located on the second flexible layer 130. In this embodiment, the first thermal expansion coefficient, the second thermal expansion coefficient, and the third thermal expansion coefficient of the second flexible layer 130 are greater than the first thermal expansion coefficient, the second thermal expansion coefficient, and the third thermal expansion coefficient of the first flexible layer 110, respectively. Thermal expansion coefficient.

Based on the above, in one embodiment of the present invention, the first thermal expansion coefficient, the second thermal expansion coefficient, and the third thermal expansion coefficient of the second flexible layer 130 of the flexible display 10 are larger than those of the first flexible layer 110, respectively. The first coefficient of thermal expansion, the second coefficient of thermal expansion, and the third coefficient of thermal expansion can reduce the number of bubbles generated between the first flexible layer 110 and the buffer layer 120, and can even avoid the first flexible layer 110 and the buffer Bubbles are formed between the layers 120, thereby increasing the process yield of the flexible display 10.

Hereinafter, the present invention will be described more specifically with reference to Experimental Example 1 and Experimental Example 2. Characteristics. Although the following examples are described, the materials used, their amounts and ratios, processing details, processing flow, and the like can be appropriately changed without going beyond the scope of the invention. Therefore, the present invention should not be interpreted restrictively by the examples described below.

Experimental example 1

In the following, embodiments 1 ~ implementation using different first curing temperature (hereinafter referred to as T1) and second curing temperature (hereinafter referred to as T2) to respectively cure the first flexible layer and the second flexible layer will be described. Examples 6 and Comparative Examples 1 to 2 are flexible displays. In addition, for the flexible displays of Examples 1 to 6 and Comparative Examples 1 to 2, the number of bubbles between the first flexible layer and the buffer layer was measured three times in three process stages, where The three process stages are: 1) after curing the first flexible layer and before forming the buffer layer; 2) after the heat treatment process of the amorphous silicon layer and before the excimer laser annealing process; 3) the interlayer insulation material After the layer is subjected to a heat treatment process and before the second metal layer is formed. The above-mentioned measurement data of the number of bubbles between the first flexible layer and the buffer layer in the three process stages are respectively arranged in Tables 1 to 3 below, where the measurement data includes the minimum value of the number of bubbles (hereinafter min), the maximum value of the number of bubbles (hereinafter referred to as max), and the average value of the number of bubbles (hereinafter referred to as μ).

As can be seen from Tables 1 and 3, compared with the flexible displays of Comparative Examples 1 and 2, since Examples 1 to 6 are cured at a second curing temperature of 450 ° C. or higher and 480 ° C. or lower, Because of the second flexible material layer in the flexible display, the number of bubbles between the first flexible layer and the buffer layer in Examples 1 to 6 is significantly smaller than the first flexible layer in Comparative Examples 1 to 2. The number of bubbles between the layer and the buffer layer. This situation is more apparent in the experimental results measured in the stage after 3) performing the heat treatment process on the interlayer insulating material layer and before forming the second metal layer.

Experimental example 2

Please refer to FIG. 2. FIG. 2 illustrates a static thermomechanical analysis spectrum of the second flexible layer of the flexible displays of Examples 7 to 9 and Comparative Example 3. The x-coordinate in FIG. 2 is the deformation amount (unit: ppm) of the second flexible layer, the y-coordinate is the ambient temperature (unit: ° C), and the slope is the coefficient of thermal expansion (unit: ppm / ° C). In addition, in FIG. 2, the second flexible layer has a first thermal expansion coefficient at a temperature lower than the first glass transition temperature (represented by Tg1 in FIG. 2), between the first glass transition temperature and the second glass transition temperature. (Indicated by Tg2 in Figure 2) And a third coefficient of thermal expansion that is greater than the second glass transition temperature.

The parameter information used to prepare the second flexible layer of the flexible displays of Examples 7 to 9 and Comparative Example 3 is shown in Table 4.

As can be seen from FIG. 2, the first thermal expansion coefficient, the second thermal expansion coefficient, and the third thermal expansion coefficient of the second flexible layer of the flexible display of Examples 7 and 9 are larger than those of the flexible display of Comparative Example 3, respectively. A first thermal expansion coefficient, a second thermal expansion coefficient, and a third thermal expansion coefficient of the second flexible layer.

In summary, in the flexible display and the method for manufacturing the flexible display according to an embodiment of the present invention, since the second curing temperature for curing the second flexible material layer is lower than that for curing the first The first curing temperature of the flexible material layer can reduce the number of bubbles generated between the first flexible layer and the buffer layer, and can even avoid the formation of bubbles between the first flexible layer and the buffer layer. This improves the problem of protrusions on the surface of the film layer caused by air bubbles, thereby increasing the process yield of the flexible display.

Although the present invention has been disclosed as above by way of examples, it is not intended to limit the present invention. Any person having ordinary knowledge in the technical field will not depart from the spirit of the present invention. Within the scope of God and Harmony, some modifications and retouching can be made. Therefore, the scope of protection of the present invention shall be determined by the scope of the attached patent application.

Claims (7)

A manufacturing method of a flexible display includes: forming a first flexible material layer on a carrier board; curing the first flexible material layer at a first curing temperature to form a first flexible material Layer; forming a buffer layer on the first flexible layer; forming a second flexible material layer on the buffer layer; curing the second flexible material layer at a second curing temperature to form a A second flexible layer, wherein the second curing temperature is lower than the first curing temperature; and an element array is formed on the second flexible layer. The method for manufacturing a flexible display as described in item 1 of the patent application range, wherein the second curing temperature is greater than or equal to 450 ° C and less than 480 ° C, wherein the first curing temperature is greater than or equal to 480 ° C and less than or equal to 500 ℃. The method for manufacturing a flexible display as described in item 1 of the patent application range, wherein the difference between the first curing temperature and the second curing temperature is greater than or equal to 20 ° C. The method for manufacturing a flexible display as described in item 1 of the patent application range, wherein the second curing temperature is greater than or equal to 450 ° C, the first curing temperature is greater than or equal to 480 ° C, and the The thickness is 1 μm to 20 μm, the thickness of the second flexible layer is 1 μm to 20 μm, and the thickness of the buffer layer is 10 nm to 1000 nm. The method for manufacturing a flexible display as described in item 1 of the patent application, wherein the first flexible layer and the second flexible layer have a first glass transition temperature and a second glass transition temperature, respectively, When it is less than the first glass transition temperature, a first thermal expansion coefficient of the second flexible layer is greater than a first thermal expansion coefficient of the first flexible layer; between the first glass transition temperature and the At a second glass transition temperature, a second thermal expansion coefficient of the second flexible layer is greater than a second thermal expansion coefficient of the first flexible layer; and at a temperature greater than the second glass transition temperature, the second thermal expansion coefficient A third thermal expansion coefficient of the flexible layer is greater than a third thermal expansion coefficient of the first flexible layer. The method for manufacturing a flexible display as described in item 5 of the patent application range, wherein the first glass transition temperature is 0 ° C to 350 ° C, and the second glass transition temperature is 350 ° C to 550 ° C. The method for manufacturing a flexible display as recited in item 1 of the patent application range, wherein a process temperature for forming the device array is less than the first curing temperature and the second curing temperature, the first flexible layer and the first The material of the two flexible layers includes polyimide, polyethylene terephthalate or polyethylene naphthalate.