KR20130068561A - Flexible organic light emitting diode display device and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A flexible organic light emitting diode display device and a manufacturing method thereof are provided to minimize fault generation, by minimizing thermal stress applied to a display element. CONSTITUTION: A display layer (DL) is formed on a glass substrate. The display layer includes a thin film transistor layer and an organic light emitting diode layer. An upper panel (UPL) is attached to the top surface of the display layer by a first hot-setting adhesive. A lower panel (LPL) is attached to the rear of the display layer by a second hot-setting adhesive. Difference between a thermal expansion coefficient of the upper panel and a thermal expansion coefficient of the lower panel is 50 μm or less.

Description

Flexible organic light emitting diode display device and manufacturing method thereof {Flexible Organic Light Emitting Diode Display Device And Manufacturing Method Thereof}

The present invention relates to a flexible organic light emitting diode display and a method of manufacturing the same. In particular, the present invention relates to a flexible display device that prevents breakage of a display element due to heat in a manufacturing process by limiting a difference in thermal expansion coefficients of flexible support substrates attached to upper and lower surfaces within a specific condition.

2. Description of the Related Art Recently, various flat panel display devices capable of reducing weight and volume, which are disadvantages of cathode ray tubes (CRTs), have been developed. Such flat panel displays include liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), and electroluminescence devices (ELs). have.

Electroluminescent devices are roughly classified into inorganic electroluminescent devices and organic light emitting diode devices according to the material of the light emitting layer. The electroluminescent devices use self-luminous devices that emit light and have a high response speed and a high luminous efficiency, luminance, and viewing angle. The organic light emitting diode display has an organic light emitting diode (OLED).

The organic light emitting diode includes an organic electroluminescent compound layer that emits light by an electric field, and a cathode and an anode facing each other with the organic electroluminescent compound layer interposed therebetween. The organic electroluminescent compound layer includes a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and an electron injection layer layer, EIL). The OLED forms an excitation in the excitation process when holes and electrons injected into the cathode electrode and the cathode recombine in the emission layer EML and emit light due to energy from the excitons.

2. Description of the Related Art An organic light emitting diode display (OLEDD) using an organic light emitting diode (OLED) as an electroluminescent device includes a passive matrix type organic light emitting diode display (PMOLED) Type organic light emitting diode display device (Active Matrix type Organic Light Emitting Diode Display (AMOLED)). In addition, there is a top-emission method and a bottom-emission method according to the direction in which light is emitted.

The organic light emitting diode display device is formed using an organic thin film, and attention is focused on an optimal material that can be applied to a flexible display device by using the flexibility and elasticity that are characteristic of the organic thin film. An active matrix type flexible organic light emitting diode display device (flexible AMOLED) displays an image by controlling a current flowing in an organic light emitting diode using a thin film transistor (TFT).

1 is a plan view illustrating a structure of a flexible AMOLED. FIG. 2 is a cross-sectional view illustrating the structure of the flexible AMOLED taken along the line A-A 'of FIG. 1.

1 to 3, the flexible active matrix organic light emitting diode display includes a back panel BPL having flexibility and elasticity to protect the device. Also, for manufacturing reasons, the flexible layer FL may be formed on the back panel BPL. Display elements including a switching TFT SWT, a driving TFT connected to the switching TFT, and an organic light emitting diode OLED connected to the driving TFT are formed on the flexible layer FL.

The switching TFT SWT is formed at the intersection of the scan line SL and the data line DL. The switching TFT SWT functions to select a pixel. The switching TFT SWT includes a gate electrode GSW branching from the scan line SL, a semiconductor layer ASW, a source electrode SSW, and a drain electrode DSW. The driving TFT DRT serves to drive the organic light emitting diode OLED of the pixel selected by the switching TFT SWT. The driving TFT DRT includes the gate electrode GDR connected to the drain electrode DSW of the switching TFT SWT, the semiconductor layer ADR, the source electrode SDR connected to the driving current transmission line VDD, and the drain electrode DDR. ). The drain electrode DDR of the driving TFT DRT is connected to the cathode electrode CAT of the organic light emitting diode OLED.

Referring to FIG. 3 to examine in more detail, a scan line SL and a gate pad GP disposed at one end of each scan line SL are formed on the flexible layer FL. The gate electrodes GSW and GDR of the switching TFT SWT and the driving TFT DRT are branched from the scan line SL. The gate insulating layer GI is covered on the gate pad GP and the gate electrodes GSW and GDR. The semiconductor layers ASW and ADR are formed in a part of the gate insulating film GI overlapping the gate electrodes GSW and GDR.

The data line DL and the driving current line VDD are formed on the gate insulating layer GI so as to be orthogonal to the scan line SL. A data pad DP is formed at one end of each data line SL and the driving current VDD to connect to an external driving IC. On the semiconductor layers ASW and ADR, source electrodes SSW and SDR and drain electrodes DSW and DDR are formed to face each other at a predetermined interval. The source electrode SDR of the driving TFT DRT is formed to be a part of the driving current wiring VDD running in parallel with the data line DL. The drain electrode DSW of the switching TFT SWT contacts the gate electrode GDR of the driving TFT DRT through a contact hole formed in the gate insulating film GI. A protective film PAS covering the switching TFT SWT and the driving TFT DRT having such a structure is coated on the entire surface. The cathode electrode CAT of the organic light emitting diode OLED is formed on the passivation layer PAS. The cathode electrode CAT is connected to the drain electrode DDR of the driving TFT DRT through a contact hole formed in the passivation layer PAS.

On the flexible layer FL on which the cathode electrode CAT is formed, a non-emission area and an organic light emission in which a switching TFT SWT, a driving TFT DRT, and various wirings DL, SL, and VDD are formed to define a pixel area. A bank pattern BANK is formed to distinguish the light emitting region in which the diode OLED is formed. The bank pattern BANK is stepped when the TFTs SWT and DRT and the various wirings DL, SL, and VDD are formed so that the surface is not smooth, and the organic layer EL is formed on the bumpy surface. This is to prevent deterioration of organic matter in the part. That is, the non-light emitting region in which the switching TFT SWT and the driving TFT DRT, the various wirings DL, SL, and VDD are formed, and only thin films are stacked on the flat substrate to distinguish the flat light emitting region, The bank pattern BANK is formed. Therefore, the pixel region is determined by the bank pattern BANK. The cathode electrode CAT is exposed by the bank pattern BANK. The organic layer EL and the anode ANO are sequentially stacked on the bank pattern BANK and the cathode electrode CAT.

Finally, a barrier film (BF) for protecting the display elements of the flexible AMOLED is attached to the front of the top layer. The barrier film BF covers the entire surface of the display area except for the pad terminals GP and DP for receiving an external electric signal, so that organic materials constituting the OLED are not damaged by moisture and air. It is desirable to protect.

Looking at the process of manufacturing a flexible AMOLED having such a structure as follows. Display devices including thin film transistors and organic light emitting diodes are typically formed using a photolithography process. Due to the nature of the photolithography process, a fine pattern may be formed only by performing the process on a rigid substrate capable of maintaining flatness.

Therefore, in order to form a flexible AMOLED, first, display elements are formed on a rigid substrate such as glass, and then a method of separating the rigid substrate and the display element is used. As a method of separating a rigid substrate and a display element, there exists a method of removing a rigid substrate by the etching method, and the method of peeling off by changing the coupling structure of a sacrificial layer through a laser through a sacrificial layer between a rigid substrate and a display element.

The method of removing by the etching method has a problem that the etching process conditions are difficult, it is difficult to shorten the time required for the etching process, the manufacturing cost is high, and there is a limit in increasing productivity and yield. Thus, after forming the flexible display device on the sacrificial layer formed on the rigid substrate as a whole, a method of peeling the flexible display device from the rigid substrate by irradiating a laser to the sacrificial layer has been proposed. However, the stripping method also has to control the process conditions, and there are various conditions to consider in order to increase productivity and production yield, and specific manufacturing methods and manufacturing conditions for mass production are still under development.

In particular, a common feature is to form a display element on a rigid substrate, remove the rigid substrate, and then attach a flexible substrate to be used as a supporting substrate of the final display panel, whether etching or peeling. Therefore, with respect to various requirements that may arise in the process of attaching the flexible substrate, it is necessary to set conditions suitable for mass production with respect to the specific manufacturing method and the characteristics of the flexible substrate.

Disclosure of Invention An object of the present invention is to provide a flexible organic light emitting diode display device manufactured by a peeling method and a method of manufacturing the same. Another object of the present invention is to provide a method of manufacturing a flexible organic light emitting diode display device for preventing a display device from being damaged by a difference in thermal expansion coefficient during a heat treatment process, and a flexible organic light emitting diode display device according to the manufacturing method. There is.

In order to achieve the above object, the flexible display device according to the present invention, a display layer; An upper panel attached to an upper surface of the display layer by a first heat curing adhesive; And a lower panel attached to the rear surface of the display layer by a second thermal curing adhesive, wherein a difference between the thermal expansion coefficient of the upper panel and the thermal expansion coefficient of the lower panel is 50 μm (m ° C.) or less. .

The upper panel may include a cyclo olefin copolymer (COC) film, a cyclo olefin polymer (COP) film, a polycarbonate (PC) film, a polyethylene naphthalate (PEN) film, a polyethylene terephthalate (PET) film, and a polyether ether sulfate (PES) film. It characterized in that it comprises at least one of.

The lower panel may include a cyclo olefin copolymer (COC) film, a cyclo olefin polymer (COP) film, a polycarbonate (PC) film, a polyethylene naphthalate (PEN) film, a polyethylene terephthalate (PET) film, and a poly ether ether sulfate (PES) film. It characterized in that it comprises at least one of.

The display layer may include a thin film transistor layer including a plurality of pixel regions having a matrix array and a thin film transistor assigned to each pixel region; And an organic light emitting diode layer formed on the thin film transistor layer and formed in the pixel areas.

In addition, a method of manufacturing a flexible organic light emitting diode display according to the present invention includes forming a display layer on a rigid substrate; Attaching an upper panel to a front surface of the display layer through a first heat curing adhesive; Bonding the upper panel to the display layer and the upper panel in a first thermal process; Separating the rigid substrate and the display layer; Attaching a lower panel having a difference from a thermal expansion coefficient of the upper panel to 50 μm (m ° C.) or less through a second thermal curing adhesive on a rear surface of the display layer; And bonding the lower panel to the display layer and the upper panel in a second thermal process.

The said 1st heat process and a 2nd heat process are heat-processed for 1 to 3 hours at 70-100 degreeC, It is characterized by the above-mentioned.

The upper panel may include a cyclo olefin copolymer (COC) film, a cyclo olefin polymer (COP) film, a polycarbonate (PC) film, a polyethylene naphthalate (PEN) film, a polyethylene terephthalate (PET) film, and a polyether ether sulfate (PES) film. It characterized in that it comprises at least one of.

The lower panel may include a cyclo olefin copolymer (COC) film, a cyclo olefin polymer (COP) film, a polycarbonate (PC) film, a polyethylene naphthalate (PEN) film, a polyethylene terephthalate (PET) film, and a poly ether ether sulfate (PES) film. It characterized in that it comprises at least one of.

The forming of the display layer may include forming a thin film transistor having a matrix array on the rigid substrate; Forming pixel regions connected to the thin film transistors and arranged in the matrix array; And forming an organic light emitting diode layer in the pixel region.

The flexible organic light emitting diode display according to the present invention is manufactured to satisfy a condition that a difference between thermal expansion coefficient values of an upper flexible substrate and a lower flexible substrate is 50 μm / m ° C. or less. Therefore, in the heat treatment process of attaching the upper flexible substrate and the lower flexible substrate, the thermal stress applied to the display device by the thermal expansion coefficient difference between the two flexible substrates can be minimized. As a result, the organic light emitting diode element and the thin film transistor element do not cause unwanted peeling or cracking damage with the upper and lower flexible substrates. In addition, the warpage phenomenon of the flat panel display caused by the difference in thermal expansion coefficient between the upper and lower flexible substrates does not occur.

1 is a plan view showing the structure of a flexible AMOLED.
FIG. 2 is a cross-sectional view illustrating a structure of a flexible AMOLED taken along a cutting line A-A 'in FIG. 1. FIG.
3A to 3D are schematic cross-sectional views illustrating a process of manufacturing a flexible AMOLED according to the present invention.
4 is a cross-sectional view showing the structure of a flexible AMOLED according to the present invention.
5 is a graph showing the failure rate according to the thermal expansion coefficient difference of the upper panel and the lower panel in the flexible AMOLED according to the present invention.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 3A to 3D and FIG. 4. In the following description, when it is determined that a detailed description of known functions or configurations related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

3A to 3D are schematic cross-sectional views illustrating a process of manufacturing the flexible AMOLED according to the present invention. 4 is a cross-sectional view showing the structure of a flexible AMOLED according to the present invention. The structure of the flexible organic light emitting diode display according to the present invention does not show a big difference from that of the related art in plan view, and a difference occurs in the cross-sectional structure. Therefore, a plan view of the flexible organic light emitting display device according to the present invention is omitted, and if necessary, reference is made to FIG. 1.

A transparent and rigid substrate GS is prepared. Here, rigidity means rigidity suitable for stably performing a thin film transistor process for mass production. According to the currently developed technology, a technique of manufacturing a thin film transistor using a glass substrate having a thickness of 0.5 mm shows the most stability. The display layer DL is formed on the glass substrate GS. The display layer DL is a thin film transistor layer TL including pixels having a matrix array, a thin film transistor assigned to each pixel region, and an organic light emitting layer in which an organic light emitting material is stacked on a pixel region driven by the thin film transistor. The diode layer EL is included. (FIG. 3A)

The upper panel UPL is attached to the entire surface of the display layer DL through the first heat curable adhesive HA1. The upper panel UPL is preferably a flexible substrate suitable for a flexible display device. Therefore, the upper panel UPL is preferably in the form of a film having both support performance and flexible performance. The first thermosetting adhesive HA1 is cured by performing a thermal process at a temperature of 70 to 100 ° C. for 1 to 3 hours to firmly adhere the upper panel UPL to the upper surface of the display layer DL. (FIG. 3B)

In particular, when the structure of the display layer DL uses a top emission method, image data is displayed through the upper panel UPL. Accordingly, the upper panel UPL should consider visibility of image data displayed even when the external light is bright. That is, it should have a high contrast ratio even in bright surroundings.

For this purpose, although not shown in the drawings, a polarizing film may be further attached to the upper portion of the upper panel UPL. In this case, if the polarization state is not evenly maintained when the polarized light is transmitted through the upper panel UPL, reflection of external light occurs, resulting in deterioration of image quality due to uneven ambient contrast ratio in front of the display panel. May occur.

In order to prevent this, the upper panel UPL preferably includes a film material having excellent polarization transmittance. For example, the upper panel UPL may include a material such as a cyclo olefin copolymer (COC) film, a cyclo olefin polymer (COP) film, or a poly-carbonate (PC) film. These film materials are characterized by having a coefficient of thermal expansion (CTE) of 70 μm (m ° C.) or more.

After attaching the upper panel UPL to the display layer DL, the rigid substrate GS is removed from the display layer DL by etching or peeling. (FIG. 3C)

Thereafter, the lower panel LPL is attached to the bottom surface of the display layer DL from which the rigid substrate GS is removed using the second thermosetting adhesive HA2. Like the upper panel UPL, the lower panel LPL may be a flexible substrate suitable for a flexible display device. Therefore, the lower panel LPL is preferably in the form of a film having both support performance and flexible performance. Similarly to the first heat curable adhesive HA1, the second heat curable adhesive HA2 is cured by performing a thermal process at a temperature of 70 to 100 ° C. for 1 to 3 hours to form the lower panel LPL as the display layer DL. I firmly adhere to the back of the. (FIG. 3D)

As a result, in the case of the organic light emitting diode display device, if the present invention is applied, a flexible display device having the structure as shown in FIG. 4 is obtained. 4 is a cross-sectional view showing the structure of a flexible AMOLED according to the present invention.

In the case of the lower panel LPL (when the upper panel UPL is the display surface), the lower panel LPL is responsible for supporting the entire display device, and therefore, it is preferable that the hardness and toughness are excellent. In some cases, the lower panel LPL may be thicker than the upper panel UPL. Therefore, since the conditions for selecting the lower panel LPL are different from those for selecting the upper panel UPL, it is preferable to use films of different materials. For example, the lower panel LPL may include a material such as a polyethylene naphthalate (PEN) film, a polyethylene terephthalate (PET) film, or a polyether sulfulfone (PES) film.

Due to the process of attaching the lower panel LPL, the thermal process is performed again while the display layer DL and the upper panel UPL are attached. Accordingly, when a difference in thermal expansion coefficient occurs between the upper panel UPL and the lower panel LPL, a difference occurs in the thermal stress applied to the display layer DL by the upper panel UPL and the lower panel LPL. do. If the difference in thermal expansion coefficient is too large, the difference in thermal stress increases, which causes a problem that the display layer DL is broken, peeled off, or severely bent to one side.

As described above, since the functions of the upper panel UPL and the lower panel LPL are different from each other, it is not preferable to form the same using the same material. In addition, a case may be required in which the thicknesses of the upper panel UPL and the lower panel LPL are different from each other. As described above, since the materials have different thicknesses, the upper panel UPL and the lower panel LPL are forced to apply different thermal stresses to the display layer DL in the heat curing process. Therefore, even if different thermal stresses are applied, the difference in thermal expansion coefficient between the upper panel UPL and the lower panel LPL is 50 μm (m ° C.) in order to minimize the damage of the display layer DL due to the difference in thermal stress. It is preferable to manufacture combining the following films.

Substantially, a number of experiments were conducted using various combinations of COC film, COP film, PC film, PEN film, PET film, and PES films with the materials of the upper panel UPL and the lower panel LPL. Could get 5 is a graph showing a failure rate according to the difference in thermal expansion coefficient of the upper panel and the lower panel in the flexible AMOLED according to the present invention.

The graph shown in FIG. 5 shows the number of display devices in which defects occur after the flexible organic light emitting diode display device having a size of 730 mm by 460 mm is manufactured by the process according to the present invention. At least 80 organic light emitting diode display devices were manufactured. In addition, at least 80 panels were manufactured in each of a combination consisting of a top panel and a bottom panel selected from one of a COC film, a COP film, a PC film, a PEN film, a PET film, and a PES film to measure the number of defective panels. .

Referring to FIG. 5, the number of defective panels when the difference in thermal expansion coefficient is 50 μm (m ° C.) and the number of defective panels when the difference is less than 50 μm (m ° C.) is determined. It can be seen that the number represents a sharp difference. That is, it can be seen that the difference in thermal expansion coefficient between the upper panel and the lower panel is 50 μm (m ° C.) is a failure occurrence threshold condition due to thermal stress of the flexible display.

The present invention relates to a method for manufacturing a flexible display device and a flexible display device by the method. Therefore, the use of a film material made of an organic material that is a flexible material for the upper panel and the lower panel is the first center of the invention. The second central point is to satisfy the condition that the difference in thermal expansion coefficient between the upper panel and the lower panel is 50 μm (m ° C.) or less.

In addition, after forming the upper panel and the lower panel using a flexible film material, a thin film type metal auxiliary substrate having flexible characteristics may be further attached to the upper panel or the lower panel to further supplement the rigidity of the display device. . For example, in the case of a top emission display device, if a thin metal substrate, such as aluminum foil, is additionally attached to the rear surface of the lower panel, the rigidity of the display device can be further supplemented and the flexible characteristics can be maintained. . Also in this case, when attaching the thin-film metal auxiliary substrate by the thermosetting method, it is preferable to select the material so that the difference in thermal expansion coefficient of the upper panel, the lower panel and the metal auxiliary substrate is 50 μm (m ° C.) or less.

In addition, the idea of the present invention is not limited to the flexible display device. That is, even when the rigid substrate is used as it is, the condition for the difference in thermal expansion coefficient of the upper panel and the lower panel, which is the second central content, may be satisfied. Since the second center is to prevent the display layer from being damaged in the thermal process for attaching the panel, it is preferable to apply the same to the display device using the rigid substrate.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

GS: Rigid Glass Substrate DL: Display Layer
TL: thin film transistor layer EL: organic light emitting diode layer
HA1: first heat curing adhesive UPL: top panel
HA2: second heat cure adhesive LPL: bottom panel
BANK: Bank Pattern BF: Barrier Film
BPL: (flexible) back panel FL: flexible layer
DL: data line SL: and scan line
SWT: Switching TFT DRT: Driving TFT
OLED: organic light emitting diode VDD: drive current supply wiring
CAT: cathode electrode ANO: anode electrode
GSW, GDR: gate electrode SSW, SDR: source electrode
DSW, DDR: Drain Electrode ASW, ADR: Semiconductor Channel Layer
GI: gate insulating film PAS: protective film
GP: gate pad DP: data pad

Claims (9)

Display layer;
An upper panel attached to an upper surface of the display layer by a first heat curing adhesive; And
A lower panel attached to the rear surface of the display layer by a second heat curing adhesive,
The difference between the thermal expansion coefficient of the upper panel and the thermal expansion coefficient of the lower panel is 50μm (m ℃) or less flexible display device.
The method of claim 1,
The upper panel may include a cyclo olefin copolymer (COC) film, a cyclo olefin polymer (COP) film, a polycarbonate (PC) film, a polyethylene naphthalate (PEN) film, a polyethylene terephthalate (PET) film, and a polyether ether sulfate (PES) film. A flexible display device comprising at least one of the following.
The method of claim 1,
The lower panel may include a cyclo olefin copolymer (COC) film, a cyclo olefin polymer (COP) film, a polycarbonate (PC) film, a polyethylene naphthalate (PEN) film, a polyethylene terephthalate (PET) film, and a poly ether ether sulfate (PES) film. A flexible display device comprising at least one of the following.
The display device of claim 1, wherein the display layer is
A thin film transistor layer comprising a plurality of pixel regions having a matrix arrangement, and a thin film transistor assigned to each pixel region; And
And an organic light emitting diode layer formed on the thin film transistor layer and formed in the pixel areas.
Forming a display layer on the rigid substrate;
Attaching an upper panel to a front surface of the display layer through a first heat curing adhesive;
Bonding the upper panel to the display layer and the upper panel in a first thermal process;
Separating the rigid substrate and the display layer;
Attaching a lower panel having a difference from a thermal expansion coefficient of the upper panel to 50 μm (m ° C.) or less through a second thermal curing adhesive on a rear surface of the display layer; And
And bonding the lower panel to the display layer and the upper panel in a second thermal process.
The method of claim 5, wherein
The first thermal process and the second thermal process, the flexible display device, characterized in that the heat treatment for 1 to 3 hours at 70 ~ 100 ℃.
The method of claim 5, wherein
The upper panel may include a cyclo olefin copolymer (COC) film, a cyclo olefin polymer (COP) film, a polycarbonate (PC) film, a polyethylene naphthalate (PEN) film, a polyethylene terephthalate (PET) film, and a polyether ether sulfate (PES) film. A method of manufacturing a flexible display device comprising at least one of the following.
The method of claim 5, wherein
The lower panel may include a cyclo olefin copolymer (COC) film, a cyclo olefin polymer (COP) film, a polycarbonate (PC) film, a polyethylene naphthalate (PEN) film, a polyethylene terephthalate (PET) film, and a poly ether ether sulfate (PES) film. A method of manufacturing a flexible display device comprising at least one of the following.
The method of claim 5, wherein the forming of the display layer comprises:
Forming a thin film transistor having a matrix array on the rigid substrate;
Forming pixel regions connected to the thin film transistors and arranged in the matrix array; And
And forming an organic light emitting diode layer in the pixel area.

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