KR102052445B1 - Method of fabricating flexible display device - Google Patents

Abstract

In the method of manufacturing the flexible display device of the present invention, in the case of using a glass substrate for the process of the flexible polyimide substrate, the same as the polyimide substrate on the opposite side of the glass substrate to which the polyimide substrate is attached Forming a compensation layer having a similar coefficient of thermal expansion to offset the warpage of the glass substrate generated during the process, thereby forming a compensation layer on the back surface of the glass substrate; Performing heat treatment on the glass substrate on which the compensation layer is formed; Coating a polyimide on the upper surface of the glass substrate subjected to the heat treatment to form a polyimide substrate; Forming a predetermined organic light emitting diode through a TFT process on the polyimide substrate; And removing the glass substrate from the polyimide substrate on which the organic light emitting diode is formed, wherein the compensation layer is formed of a material having a coefficient of thermal expansion similar to that of the polyimide substrate to warp the glass substrate generated during the TFT process. It is characterized by offsetting.

Description

Manufacturing method of flexible display device {METHOD OF FABRICATING FLEXIBLE DISPLAY DEVICE}

The present invention relates to a method of manufacturing a flexible display device, and more particularly, to a method of manufacturing a flexible display device using a flexible substrate.

In today's information society, display devices are being emphasized as a visual information transmission medium, and in order to gain a major position in the future, display devices must satisfy requirements such as low power consumption, thinness, light weight, and high quality.

The display device includes a cathode ray tube (CRT), an electroluminescent element (EL), a light emitting diode (LED), a vacuum fluorescence display (VFD), Emission type and liquid crystal display (LCD) such as organic light emitting device (OLED), field emission display (FED), plasma display panel (PDP) ) Can be divided into non-emitting type itself does not emit light.

Meanwhile, a flexible display device that is not damaged even when the display device is folded or rolled up is expected to emerge as a new technology in the display device field. Currently, there are various obstacles to the implementation of the flexible display device, but with the development of technology, the thin film transistor liquid crystal display device or the organic light emitting display device will become mainstream.

Hereinafter, the flexible display device will be described in detail with reference to the accompanying drawings.

1A and 1B are photographs illustrating a typical flexible display device as an example.

The flexible display device is called a display device. The flexible display device is one of the next-generation display devices that is implemented on a thin substrate such as plastic and is not damaged even when folded or rolled as shown in the drawing. Currently, the flexible display device can be made thinner than 1 mm. Liquid crystal display devices and organic light emitting display devices are promising.

A liquid crystal display is an apparatus that expresses an image by using optical anisotropy of liquid crystal. It is superior to conventional CRTs because it has better visibility and lower average power consumption than CRTs having the same screen size. It is attracting attention as a display device.

The organic light emitting display is excellent in visibility even in the dark or outside light because the device itself emits light, and the response speed, which is an important criterion for determining the performance of a mobile display, is fast among existing displays. You can implement a video. In addition, the organic light emitting display device can be made ultra-thin design to slim various mobile devices such as mobile phones.

In order to realize such a flexible display device, it is necessary to secure flexibility of the substrate, and to secure such substrate flexibility, a flexible substrate made of plastic such as polyimide is used instead of a conventional glass substrate.

Since the polyimide substrate is flexible, the polyimide is coated on the glass substrate using the glass substrate as an auxiliary substrate to perform the TFT process, and when the TFT process is completed, the glass substrate is separated from the polyimide substrate.

At this time, the polyimide substrate is bent by the heat applied during the TFT process, and the glass substrate is bent by the bending of the polyimide substrate.

FIG. 2 is a diagram illustrating the bending of the glass substrate due to the bending of the polyimide substrate.

Referring to FIG. 2, the polyimide substrate 11 is bent in a tension direction due to a high coefficient of thermal expansion (CTE) of the polyimide substrate 11 (˜35 ppm / ° C.). By bending of the polyimide substrate 11, the glass substrate 1 is bent in the same direction.

As such, the glass substrate may be bent to cause cracks in the glass substrate during loading and unloading of the glass substrate. This can lead to increased process tack times and equipment failures.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a flexible display device which prevents the glass substrate from bending during a TFT process when a glass substrate is used for the process of the flexible polyimide substrate. There is this.

Other objects and features of the present invention will be described in the configuration and claims of the invention which will be described later.

In order to achieve the above object, a method of manufacturing a flexible display device according to an embodiment of the present invention comprises the steps of forming a compensation layer on the back of the glass substrate; Performing heat treatment on the glass substrate on which the compensation layer is formed; Coating a polyimide on the upper surface of the glass substrate subjected to the heat treatment to form a polyimide substrate; Forming a predetermined organic light emitting diode through a TFT process on the polyimide substrate; And removing the glass substrate from the polyimide substrate on which the organic light emitting diode is formed, wherein the compensation layer is formed of a material having a coefficient of thermal expansion similar to that of the polyimide substrate to warp the glass substrate generated during the TFT process. Can be offset.

Another method of manufacturing a flexible display device according to an embodiment of the present invention comprises the steps of forming a polyimide substrate by coating a polyimide on the upper surface of the glass substrate; Forming a compensation layer on a rear surface of the polyimide-coated glass substrate; Performing heat treatment on the glass substrate on which the compensation layer is formed; Forming a predetermined organic light emitting diode through a TFT process on the polyimide substrate; And removing the glass substrate from the polyimide substrate on which the organic light emitting diode is formed, wherein the compensation layer is formed of a material having a coefficient of thermal expansion similar to that of the polyimide substrate to warp the glass substrate generated during the TFT process. Can be offset.

In this case, the compensation layer may be formed of polyimide, silicon oxide film, or silicon nitride film.

In this case, the heat treatment may be performed within the deposition temperature during the TFT process proceeds on the polyimide substrate.

In this case, the heat treatment may proceed at the highest temperature of the deposition temperature of the TFT process.

The method may further include attaching a back film made of polyethylene terephthalate (PET) plastic or a metal of stainless steel to the back surface of the polyimide substrate from which the glass substrate is removed.

The method may further include attaching a polarizing plate to the polyimide substrate on which the organic light emitting diode is formed by using an adhesive.

The glass substrate removed from the polyimide substrate on which the organic light emitting diode is formed and the compensation layer formed on the rear surface of the glass substrate may be recycled to manufacture another flexible display device.

As described above, in the method of manufacturing the flexible display device according to the exemplary embodiment of the present invention, when a glass substrate is used to process the flexible polyimide substrate, the polyimide is opposite to the glass substrate on which the polyimide substrate is attached. It is possible to prevent the deformation of the glass substrate by forming a compensation layer having the same or similar thermal expansion coefficient as the substrate to offset the warpage of the glass substrate generated during the process. Accordingly, the tack time is shortened and the yield is improved.

1A and 1B are photographs illustrating a typical flexible display device, for example.
2 is a view showing an example of the bending of the glass substrate due to the bending of the polyimide substrate.
3 is a cross-sectional view illustrating a structure of a flexible display device according to the present invention.
4 is a cross-sectional view illustrating the display panel shown in FIG. 3 as an example.
5 is a flowchart sequentially illustrating a method of manufacturing a flexible display device according to a first embodiment of the present invention.
6A to 6E are perspective views sequentially illustrating a method of manufacturing a flexible display device according to a first embodiment of the present invention.
7 is a flowchart sequentially illustrating a method of manufacturing a flexible display device according to a second exemplary embodiment of the present invention.
8A to 8E are perspective views sequentially illustrating a method of manufacturing a flexible display device according to a second exemplary embodiment of the present invention.

Hereinafter, exemplary embodiments of a method of manufacturing a flexible display device according to the present invention will be described in detail with reference to the accompanying drawings so that a person skilled in the art can easily implement the present invention.

Advantages and features of the present invention, and methods for achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, only the present embodiments to make the disclosure of the present invention complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout. In the drawings, the size and relative size of layers and regions may be exaggerated for clarity.

When an element or layer is referred to as another element or "on" or "on", it includes both instances of another element or layer interposed therebetween, as well as other elements or layers. do. On the other hand, when a device is referred to as "directly on" or "directly on", it means not intervening another device or layer.

The spatially relative terms "below, beneath", "lower", "above", "upper", and the like, as shown in the figures, are one element or component. It may be used to easily describe the correlation between and other elements or components. Spatially relative terms are to be understood as including terms in different directions of the device in use or operation in addition to the directions shown in the figures. For example, when flipping a device shown in the figure, a device described as "below" or "beneath" of another device may be placed "above" of another device. Thus, the exemplary term "below" can encompass both an orientation of above and below.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, “comprise” and / or “comprising” refers to a component, step, operation and / or element that is present in one or more other components, steps, operations and / or elements. Or does not exclude additions.

3 is a cross-sectional view illustrating a structure of a flexible display device according to an exemplary embodiment of the present invention.

4 is a cross-sectional view illustrating the display panel illustrated in FIG. 3, for example, and illustrates an organic light emitting display device as the display panel.

Referring to FIG. 3, the flexible display device according to the present invention includes a display panel 110 for outputting an image, and a polarizer 120 is attached to the upper portion of the display panel 110 by using the adhesive 130. There is.

Here, the upper and lower portions of the display panel 110 do not limit a specific position, and thus, the polarizer 120 may be attached to the lower portion of the display panel 110 using the adhesive 130.

In addition, a protective film 140 of a hard coating may be additionally attached to the upper surface of the polarizing plate 120.

In this case, the display panel 110 may be configured as one of a liquid crystal display and an organic light emitting display. However, the present invention is not limited thereto.

When the display panel 110 is configured as an organic light emitting display device, referring to FIG. 4, an anode made of a transparent oxide is formed through a TFT process on a substrate 111 made of plastic such as polyimide. 112 is formed on the anode 112, a hole transport layer 113, an emission layer 114, an electron transport layer 115, an electron injection layer (electron) sequentially injection layer 116 and cathode 117 are stacked.

Based on the structure, the organic light emitting display device has a low hole after the holes injected from the anode 112 and the electrons injected from the cathode 117 are combined in the light emitting layer 114 via the transport layers 113 and 115 for respective transport. While moving to an energy level, light of a wavelength corresponding to an energy difference in the light emitting layer 114 is generated.

In this case, the light emitting layer 114 may be formed of the red light emitting layer 114a, the green light emitting layer 114b, and the blue light emitting layer 114c to emit white light. However, the present invention is not limited thereto.

As described above, the polarizing plate 120 is attached to the upper portion of the display panel 110 configured as described above using the adhesive 130, and the polarizing plate 120 is a circularly polarized polarizing plate to prevent external light reflection. Will be done.

In this case, when a polyimide material is used as the substrate 111, a back film made of plastic of polyethylene terephthalate (PET) or a metal of stainless steel may be attached to the rear surface of the substrate 111. have.

In contrast, when the display panel 110 is configured as a liquid crystal display device, an upper polarizing plate having, for example, a light absorption axis in a horizontal direction is disposed above the display panel 110. Although not shown in the drawings, a backlight unit is disposed under the display panel 110, and a lower polarizer is disposed between the display panel 110 and the backlight unit.

When the display panel 110 is configured as a liquid crystal display, the display panel 110 may include two substrates and a liquid crystal layer formed therebetween.

In this case, a thin film transistor array is formed on the lower substrate. The thin film transistor array includes a plurality of data lines supplied with R, G, and B data voltages, a plurality of gate lines provided with gate pulses crossing the data lines, and intersections of the data lines and the gate lines. A plurality of thin film transistors to be formed, a plurality of pixel electrodes for charging a data voltage to the liquid crystal cells, and a storage capacitor connected to the pixel electrodes to maintain the voltage of the liquid crystal cell. A color filter array is formed on the upper substrate, and the color filter array includes a black matrix and a color filter.

In the flexible display device according to the present invention configured as described above, the polarizing plate 120 is a polarization positioned between the first support 122a and the second support 122b and between the first support 122a and the second support 122b. The element 121 is included.

The first support 122a and the second support 122b may be formed of a general protection film without phase retardation, for example, a tri-acetyl cellulose (TAC) film. Can be done.

The polarizer 121 refers to a film that can be converted from natural light or polarized light into any polarized light. When the incident light is divided into two polarizing components orthogonal to the incident light, the polarizing element 121 has a function of passing one of the polarization components, and absorbs, reflects, and scatters the other polarization component. One having at least one function selected from can be used.

The optical film used for the polarizing element 121 is not particularly limited, but for example, stretching of a polymer film containing polyvinyl alcohol (PVA) -based resin containing iodine or a dichroic dye as a main component. O type polarizing element which orientated the liquid crystalline composition containing a film, a dichroic substance, and a liquid crystalline compound to a fixed direction, and E type polarizing element which orientated a lyotropic liquid crystal to a fixed direction, etc. are mentioned.

As described above, since the polyimide substrate is flexible, the flexible display device according to the present invention configured as described above performs a TFT process by coating a polyimide on the glass substrate using a glass substrate as an auxiliary substrate.

At this time, the polyimide substrate is bent by the heat (deposition temperature of ~ 350 ° C) applied during the TFT process, and the glass substrate is bent by the bending of the polyimide substrate.

To improve this, the present invention forms a compensation layer having the same or similar thermal expansion coefficient as that of the polyimide substrate on the opposite side of the glass substrate to which the polyimide substrate is attached, thereby deforming the glass substrate by canceling the warpage of the glass substrate generated during the process. Characterized in that to prevent.

That is, the present invention is characterized in that to compensate for the bending of the glass substrate generated during the process by forming a compensation layer having the same or similar bending degree as the polyimide substrate on the opposite side of the glass substrate with the polyimide substrate, Next, a method of manufacturing the flexible display device according to the present invention will be described in detail.

FIG. 5 is a flowchart sequentially illustrating a method of manufacturing a flexible display device according to a first exemplary embodiment of the present invention, and illustrates a case in which the display panel is configured of an organic light emitting display device.

6A to 6E are perspective views sequentially illustrating a method of manufacturing the flexible display device according to the first embodiment of the present invention.

As shown in FIG. 6A, a predetermined compensation layer 109 is formed on the rear surface of the glass substrate 101 for the auxiliary substrate (S110).

In this case, the rear surface of the glass substrate 101 means the opposite side of the glass substrate 101 to which the polyimide substrate is attached.

The compensation layer 109 may be formed of a polyimide, a silicon oxide film, or a silicon nitride film with a material having the same or similar stress value as that of the polyimide substrate, that is, the thermal expansion coefficient.

For example, when the polyimide is coated on the upper surface of the glass substrate 101 by the slit coating, the stress on the tension is measured to be about 100 to 120 MPa, and a silicon nitride film having a similar stress value is formed on the rear surface of the glass substrate 101. When deposited, it is possible to obtain a stress canceling effect of the polyimide. At this time, it may vary depending on other process conditions, but as an example, when the silicon nitride film is deposited at a thickness of about 3500 Pa at a temperature of about 350 ° C., the stress was measured to be about 96 to 108 MPa.

In this case, when a buffer layer is further formed on the polyimide, the compensation layer 109 may be formed of a material having a coefficient of thermal expansion equal to or similar to that of the polyimide and the buffer layer.

Thereafter, as illustrated in FIG. 6B, heat treatment is performed on the glass substrate 101 on which the compensation layer 109 is formed (S120).

In this case, the heat treatment may be performed within the deposition temperature during the TFT process to be carried out on the polyimide substrate, and preferably may be performed at the highest temperature of the deposition temperature.

Thereafter, as shown in FIG. 6C, the polyimide is coated on the upper surface of the glass substrate 101 subjected to the heat treatment to form the polyimide substrate 111 (S130).

6D, a predetermined organic light emitting diode 118 is formed on the polyimide substrate 111 through a TFT process (S140).

That is, as described above, an anode made of a transparent oxide is formed on the polyimide substrate 111, and a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a cathode may be sequentially stacked on the anode.

In this case, a polarizing plate may be attached to the organic light emitting diode 118 by using an adhesive, and a protective film of a hard coating may be additionally attached to the upper surface of the polarizing plate.

Thereafter, as shown in FIG. 6E, the glass substrate 101 is removed from the polyimide substrate 111 on which the organic light emitting diode 118 is formed.

In this case, the glass substrate 101 and the compensation layer 109 formed on the back surface of the glass substrate 101 may be recycled to manufacture another flexible display device.

In this case, a back film made of a plastic of PET or a metal of stainless steel may be attached to the rear surface of the polyimide substrate 111 from which the glass substrate 101 is removed.

Meanwhile, the present invention may form a compensation layer on the back surface of the glass substrate coated with the polyimide after coating the polyimide on the glass substrate, thereby manufacturing the flexible display device according to the second embodiment of the present invention. The method will be described in detail.

7 is a flowchart sequentially illustrating a method of manufacturing a flexible display device according to a second exemplary embodiment of the present invention.

8A through 8E are perspective views sequentially illustrating a method of manufacturing a flexible display device according to a second exemplary embodiment of the present invention.

As shown in FIG. 8A, the polyimide substrate 211 is formed by coating polyimide on the upper surface of the glass substrate 201 for the auxiliary substrate (S210).

Thereafter, as illustrated in FIG. 8B, a predetermined compensation layer 209 is formed on the rear surface of the polyimide-coated glass substrate 201 (S220).

In this case, the rear surface of the glass substrate 201 means the opposite side of the glass substrate 201 to which the polyimide substrate 211 is attached.

The compensation layer 209 may be formed of a polyimide, a silicon oxide film, or a silicon nitride film with a material having the same or similar stress value as that of the polyimide substrate 201, that is, a thermal expansion coefficient.

In this case, when the buffer layer is further formed on the polyimide, the compensation layer 209 may be formed of a material having a coefficient of thermal expansion equal to or similar to that of the polyimide and the buffer layer.

Thereafter, as illustrated in FIG. 8C, heat treatment is performed on the glass substrate 201 on which the compensation layer 209 is formed (S230).

In this case, the heat treatment may be performed within the deposition temperature during the TFT process to be performed on the polyimide substrate 211, and preferably may be performed at the highest temperature of the deposition temperature.

8D, a predetermined organic light emitting diode 218 is formed on the polyimide substrate 211 through a TFT process (S240).

That is, as described above, an anode made of a transparent oxide is formed on the polyimide substrate 211, and a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a cathode may be sequentially stacked on the anode.

In this case, a polarizing plate may be attached to the organic light emitting diode 218 by using an adhesive, and a protective film of a hard coating may be additionally attached to the upper surface of the polarizing plate.

Thereafter, as illustrated in FIG. 8E, the glass substrate 201 is removed from the polyimide substrate 211 on which the organic light emitting diode 218 is formed.

In this case, a back film made of a plastic of PET or a metal of stainless steel may be attached to the rear surface of the polyimide substrate 211 from which the glass substrate 201 is removed.

Many details are set forth in the foregoing description but should be construed as illustrative of preferred embodiments rather than to limit the scope of the invention. Therefore, the invention should not be defined by the described embodiments, but should be defined by the claims and their equivalents.

101,201 glass substrate 109,209 compensation layer
110: display panel 111,211: polyimide substrate
118,218 organic light emitting diode 120 polarizing plate

Claims (8)

Forming a compensation layer on a rear surface of the glass substrate;
Performing heat treatment on the glass substrate on which the compensation layer is formed;
Coating a polyimide on the upper surface of the glass substrate subjected to the heat treatment to form a polyimide substrate;
Forming a predetermined organic light emitting diode through a TFT process on the polyimide substrate; And
Removing the glass substrate from the polyimide substrate on which the organic light emitting diode is formed,
The compensation layer is formed of a material having a coefficient of thermal expansion within a range of thermal expansion coefficients of the polyimide substrate, and the glass substrate is generated during the TFT process by bending the glass substrate in one direction through the heat treatment. A method of manufacturing a flexible display device that cancels warpage in a direction. Coating a polyimide on the upper surface of the glass substrate to form a polyimide substrate;
Forming a compensation layer on a rear surface of the polyimide-coated glass substrate;
Performing heat treatment on the glass substrate on which the compensation layer is formed;
Forming a predetermined organic light emitting diode through a TFT process on the polyimide substrate; And
Removing the glass substrate from the polyimide substrate on which the organic light emitting diode is formed,
The compensation layer is formed of a material having a coefficient of thermal expansion within a range of thermal expansion coefficients of the polyimide substrate, and the glass substrate is generated during the TFT process by bending the glass substrate in one direction through the heat treatment. A method of manufacturing a flexible display device that cancels warpage in a direction. The method of claim 1, wherein the compensation layer is formed of a polyimide, a silicon oxide film, or a silicon nitride film. The method of claim 3, wherein the heat treatment is performed at a deposition temperature during a TFT process performed on the polyimide substrate. The method of claim 4, wherein the heat treatment is performed at the highest temperature among the deposition temperatures of the TFT process. 4. The method of claim 3, further comprising attaching a back film made of polyethylene terephthalate (PET) plastic or a metal of stainless steel to the back surface of the polyimide substrate from which the glass substrate is removed. A method of manufacturing a flexible display device. The method of claim 3, further comprising attaching a polarizing plate to the polyimide substrate on which the organic light emitting diode is formed by using an adhesive. The flexible display device of claim 1, wherein the glass substrate removed from the polyimide substrate on which the organic light emitting diode is formed and the compensation layer formed on the rear surface of the glass substrate are recycled to manufacture another flexible display device. Manufacturing method.

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