KR20160128649A - Flexible Substrate, Flexible Display Device Using the Same and Method for Manufacturing the Same - Google Patents

Abstract

The present invention relates to a flexible substrate, a flexible display device using the same, and a method for manufacturing the same for improving the characteristic of a barrier, heat resistant properties, and chemical and mechanical stability so as to be suitable for a roll-to-roll process. The flexible display device of the present invention includes: a first plastic film; a first flexible substrate having first and second stainless steel films which are attached to both sides of the first plastic film; a buffer layer which is disposed on the first flexible substrate; a thin film transistor array which is disposed on the buffer layer; an organic light emitting array which is connected to the thin film transistor array; and an encapsulation unit which covers the organic light emitting array and is in contact with the buffer layer.

Description

TECHNICAL FIELD [0001] The present invention relates to a flexible substrate, a flexible display device using the flexible substrate, and a method of manufacturing the flexible substrate.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible substrate, and more particularly, to a flexible substrate suitable for a roll-to-roll process by improving barrier properties, heat resistance, chemical and mechanical stability, a flexible display using the same, and a manufacturing method thereof.

Specific examples of the flat panel display include a liquid crystal display (LCD) device, an organic light emitting display device, a plasma display panel (PDP) device, a quantum dot display device ), A field emission display device (FED), and an electrophoretic display device (EPD). The flat display panel, which realizes images in common, is an essential component, The flat panel display panel has a structure in which a pair of transparent insulation substrates are bonded together with inherent light emission, polarization, or other optical material layers interposed therebetween.

BACKGROUND ART [0002] Recently, as a display device has become larger, a demand for a flat display device with a smaller space occupation is increasing. Techniques for an organic light emitting display device as one of such flat display devices are rapidly developing.

The organic light emitting display device does not require a separate light source and includes a self-luminous organic light emitting diode in a pixel unit, and the light source and the structure for assembling the light source with the display panel are omitted, Which is considered as a next generation display device.

The organic light emitting diode is a device that injects an electric charge into an organic film formed between an electron injection electrode (cathode) and a hole injection electrode (anode) to form an electron and a hole.

On the other hand, a display device including the above-described organic light emitting display device has recently been required to be used in a flexible form. Accordingly, the backplane substrate having the display device function is replaced with a flexible substrate in the glass substrate, that is, a flexible substrate.

As the flexible substrate, an insulating plastic film having heat resistance such as polyimide is preferred.

However, when a plastic film is used as a substrate, there arises a problem of substrate deformation in a number of roll-to-roll processes, and there is a large restriction on the elongation rate of the plastic film substrate during transportation, It can not be used for a display device requiring moisture resistance, such as an organic light emitting display.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a flexible substrate suitable for a roll-to-roll process by improving barrier properties, heat resistance, chemical and mechanical stability, And a method for producing the same.

To achieve the above object, the flexible substrate of the present invention comprises a plastic film and first and second stainless steel films on both sides of the plastic film.

Here, the thickness of the first and second stainless steel films is 1 占 퐉 to 5 占 퐉, respectively, and the first and second stainless steel films are coated with a thin thickness on the surface of the plastic film.

Wherein the plastic film comprises a copolymer comprising a polyester or a polyester, a copolymer comprising a polyimide or a polyimide, an olefinic copolymer, a polyacrylic acid or a polyacrylic acid, Copolymers comprising polystyrene, polystyrene, copolymers comprising polystyrene, copolymers comprising polysulfate or polysulfate, copolymers comprising polycarbonate or polycarbonate, polyamic acid, Or a copolymer including polyamic acid, a copolymer including polyamine and polyamic acid, a polyvinyl alcohol, and a polyallyamine. At this time, the plastic film has a thickness of 5 to 150 mu m desirable.

On the other hand, the water vapor transmission rate of the first and second stainless steel membranes is 10 ^-6 g / m ² ˙day or less, which is good in moisture permeability compared to a plastic film, and functions to lower the moisture permeability of the entire flexible substrate .

Optionally, a buffer layer may be further included on the first stainless steel film. The buffer layer may include at least one oxide insulating film or a nitride insulating film.

The flexible display device of the present invention for the same purpose comprises: a first flexible substrate including a first plastic film, first and second stainless steel films abutting both surfaces of the first plastic film, and a second flexible film formed on the first flexible substrate And a sealing means covering the organic light emitting array and the organic light emitting array connected to the thin film transistor array and contacting the buffer layer.

Here, the sealing means may include an adhesive layer covering the organic light emitting array and the buffer layer, and a second flexible substrate contacting the front surface of the adhesive layer.

The water vapor transmission rate of the first flexible substrate may be 10 ^-1 g / m ² ˙day to 10 ^-3 g / m ² ˙day. The thickness of the first flexible substrate is preferably in the range of 7 탆 to 152 탆, and the thickness of the first and second stainless steel films may be in the range of 1 탆 to 5 탆.

Here, the second flexible substrate may further include a touch electrode array on a surface opposite to the adhesive layer. In this case, the sealing means is transparent.

A method of manufacturing a flexible display device includes the steps of preparing a first flexible substrate on which first and second stainless steel films are coated on both surfaces of a first plastic film and a first flexible substrate on which a buffer layer is formed on the first stainless steel film Forming a thin film transistor array and an organic light emitting array on the buffer layer, and bonding the buffer layer having the thin film transistor array and the organic light emitting array to the second flexible substrate via an adhesive layer.

The flexible substrate of the present invention, the flexible display device using the flexible substrate, and the manufacturing method thereof have the following effects.

First, in the case of a plastic film used as a substrate in a flexible display device, a roll process is performed. At this time, since the stretching change of the plastic film is large according to the load, deformation of the substrate such as sagging during conveyance or wrinkling of the plastic film is large . However, when a metal film having a rigidity such as a stainless steel film is coated on both sides of a plastic film, deformation of the entire flexible substrate can be prevented. Therefore, the mechanical stability of the flexible substrate to be used can be secured.

Second, by coating both sides of a plastic film with a stainless steel film, it is possible to increase the moisture permeability more than 100 times compared to a single plastic film and to secure the stability and reliability of the display device due to the chemical resistance and low thermal expansion coefficient of the stainless steel film .

Third, since the thickness of the coated stainless steel film is 5 占 퐉 or less, rigidity can be maintained even if the thickness of the flexible substrate is not greatly increased, and the slimness and rigidity of the device can be secured simultaneously.

Fourth, when a stainless steel film is used as a backplane substrate of an organic light emitting display device, even if the number of buffer layers required on a flexible substrate is reduced or omitted, a moisture permeability similar to that of a stainless steel film is obtained. Can be simplified.

1 is a cross-sectional view showing a flexible substrate of the present invention
2 is a cross-sectional view showing another example of the flexible substrate of the present invention
3 is a cross-sectional view showing a flexible display device of the present invention
Figs. 4A and 4B are cross-sectional views showing a process for producing a flexible substrate according to the present invention
5 is a process sectional view showing another example of the method for producing a flexible substrate of the present invention
Fig. 6 is a graph showing the elongation of the flexible substrate in accordance with the thickness of the plastic film and the roll-to-roll conveying tension of the flexible substrate different from the application of the stainless steel film
7A to 7E are cross-sectional views showing the steps of a method of manufacturing the flexible display device of the present invention

Hereinafter, a flexible substrate, a flexible display, and a method of manufacturing the flexible substrate of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view showing a flexible substrate of the present invention.

1, the flexible substrate 1000 of the present invention includes a plastic film 100 and first and second stainless steel films 110 and 120 which are in contact with both surfaces of the plastic film 100.

The thickness of the first and second stainless steel films 110 and 120 is 1 μm to 5 μm and is thinner than the thickness of the plastic film 100 by at least 10 times the thickness of the first and second stainless steel films 110 and 120, (110, 120). The coating method may be slit coating, spray coating, plating, dipping, or the like. In addition, annealing after coating is further applied to ensure surface uniformity.

In the case of slit coating or spray coating in the above coating method, the stainless steel film is coated on one side of the plastic film 100, and then the surface is flattened, and the plastic film 100 is inverted The other surface is coated with a stainless steel film and then the surface is planarized by annealing.

When the plating or dipping method is used, simultaneous coating on both sides of the plastic film 100 is possible.

The plastic film 100 may be a copolymer comprising a polyether or polyether, a copolymer comprising a polyester or a polyester, a copolymer comprising a polyimide or a polyimide, A copolymer comprising polyacrylic acid or polyacrylic acid, a copolymer comprising polystyrene or polystyrene, a copolymer comprising polycarbonate or polycarbonate, a polysulfate or polysulfate, A copolymer comprising a polycarbonate or polycarbonate, a copolymer comprising a polyamic acid or a polyamic acid, a copolymer comprising a polyamine and a polyamic acid, a copolymer comprising a polyvinyl alcohol (polyvinylalcohol), and polyallylamine Is selected document comprises at least one polymer compound.

For example, a film mainly used as the plastic film 100 is a film made of PET, polyethylene naphthalate (PEN), poly (methyl methacrylate), polyesters (PES), polycarbonate (PC) cyclo olefin polymer, PI (polyimide), COC (cyclic olefin copolymer) and PAR (poly acrylate).

In order to maintain the flexibility and the slimness, the thickness of the plastic film 100 used is preferably 5 占 퐉 to 150 占 퐉.

The reason why the flexible substrate of the present invention is provided with the first and second stainless steel films 110 and 120 is as follows.

The plastic film 100 of the above-described material is provided for satisfying the flexibility, but the heat resistance, the mechanical stability, the electro-optical characteristic, the chemical resistance, and the like do not satisfy the degree required for the glass substrate. Particularly, a high-temperature process is required in an array process such as a thin film transistor array, and the plastic film 100 repeats a roll-to-roll process in a film form. In this process, the substrate is deformed. The recovery to the original state is not possible. Particularly, considering that a plurality of layers are required to be patterned on the plastic film 100, after the substrate is deformed, the interlayer alignment before and after the formation of the substrate does not match.

Therefore, a metal film having mechanical rigidity, heat resistance, moisture resistance and chemical resistance, such as stainless steel films 110 and 120, is formed on both surfaces of the plastic film 100 as a bare film, The stability of the flexible substrate is ensured.

When the first and second stainless steel films 110 and 120 are applied, the water vapor transmission rate of the first and second stainless steel films 110 and 120 is 10 ^-6 g / m ² ˙day or less , The moisture permeability is better than that of a plastic film having a moisture permeability of about 1 to 10 g / m ² ˙day or more, and functions to lower the moisture permeability of the entire flexible substrate 1000 to a level of less than 1/100. The moisture permeability of the entire flexible substrate 1000 after the application of the first and second stainless steel films 110 and 120 is lowered to a level of 10 ^-1 g / m ² ˙day to 10 ^-3 g / m ² ˙day. Therefore, the number of layers of the buffer layer, which is excellent for barrier moisture resistance, and which is required for moisture resistance required when the flexible substrate 1000 is applied to a backplane substrate of an organic light emitting display panel, can be reduced or omitted.

Compare the properties of the polyimide (polyimide), which is one of the plastic films 100, with the stainless steel film.

First, the factors that should be taken into account in terms of heat resistance are glass transition temperature (Tg) and coefficient of thermal expansion (CTE).

The glass transition temperature of the polyimide is 320 ° C, and the glass transition temperature of the stainless steel film is 1200 ° C. The thermal expansion coefficient of the polyimide is 20 ppm, and the thermal expansion coefficient of the stainless steel film is 10.4. That is, from the viewpoint of heat resistance, it can be seen that the stainless steel film is more excellent than the polyimide. When the both surfaces of the plastic film 100 are covered with the stainless steel films 110 and 120, the characteristics of the entire flexible substrate 1000 are It can be seen that the flexible substrate of the present invention is superior in heat resistance to the plastic film of the single bare film in accordance with the characteristics of the stainless steel films 110 and 120.

Further, even when the mechanical stiffness is compared, the modulus of elasticity of the polyimide is 2.94 GPa, and the modulus of elasticity of the stainless steel film is 200 GPa. The mechanical strength of the flexible substrate 1000 is higher than that of the stainless steel film 110. When the both surfaces of the plastic film 100 are covered with the stainless steel films 110 and 120, 110, and 120, it can be seen that the flexible substrate of the present invention has improved mechanical stiffness compared to the plastic film of a single bare film. Therefore, during the roll-to-roll process, the flexible substrate 100 is conveyed while maintaining a constant tension (several Kgf). During this process, the plastic film of the single bare film is wrinkled or stretched in a certain direction This problem can be solved because the film has a large deformation.

In terms of chemical resistance, the flexible substrate of the present invention is also improved in chemical resistance because the first and second stainless steel films 110 and 120 are reinforced with respect to the application of a single plastic film.

The reason why the components applied to the double-side coating of the flexible substrate of the present invention is applied to a stainless steel film is that heat resistance, chemical resistance, and moisture resistance are verified against other metals as described above.

Hereinafter, another example of the flexible substrate of the present invention will be described.

2 is a cross-sectional view showing another example of the flexible substrate of the present invention.

2 is another example of the flexible substrate of the present invention in that the buffer layer 150 is further applied on the plastic substrate 100 so as to cover the first stainless steel film 110 as compared with the structure of FIG.

The buffer layer 150 may include at least one oxide insulating film or a nitride insulating film. In addition to the inorganic film such as an oxide insulating film or a nitride insulating film, an organic film may be further included.

The reason why the buffer layer 150 is applied is that when the device having electrical characteristics such as a thin film transistor array is formed on the flexible substrate 1100, the buffer layer 150 is electrically insulated from the stainless steel films 110 and 120, This is to maintain the reliability of the device. In addition, since the flatness of the upper portion can not be maintained when the array is directly formed on the first stainless steel film 110 having a roughness compared to the plastic film 100, this is to prevent this.

3 is a cross-sectional view showing a flexible display device of the present invention.

Fig. 3 shows a flexible display device in which the above-described flexible substrate is applied as a substrate.

3, the flexible display device of the present invention includes a first plastic film 100 and a first plastic film 100 including first and second stainless steel films 110 and 120 which are in contact with both surfaces of the first plastic film 100. [ A flexible substrate 1000, a buffer layer 150 on the first flexible substrate 1000, a thin film transistor array 130 on the buffer layer, and an organic light emitting array 140 connected to the thin film transistor array 130 And an encapsulating unit 2000 covering the organic light emitting array 140 and contacting the buffer layer 150.

The sealing means 2000 includes an adhesive layer 250 covering the organic light emitting array 140 and contacting the buffer layer 150 and a second flexible substrate 200 contacting the front surface of the adhesive layer 250 do.

Further, on the first flexible substrate 100, it is possible to further include a protective layer 160 in the form of a laminate layer in which an organic film, an inorganic film, or an organic or inorganic film is alternately covered so as to completely cover the organic light emitting array 140 have.

Here, the second flexible substrate 200 may further include a touch electrode array 210 on a surface opposite to the adhesive layer 250. In this case, the sealing means 2000 including the second flexible substrate 200 is transparent so that the light emitted from the organic light emitting array 140 is projected onto the sealing means 2000.

In some cases, the second flexible substrate may be formed by applying a stainless steel film to both sides of the polyimide. In this case, the first flexible substrate on the lower side may be a transparent plastic film.

When the first flexible substrate 1000 is applied to both surfaces of the plastic film by applying a stainless steel film, the water vapor transmission rate of the first flexible substrate 1000 is 10 ^-1 g / m 2 ² ˙day to 10 ^-3 g / m ² ˙day, so that the application of a plastic film to a single bare film can improve the moisture permeability within the contrast. In this case, the thickness of the first flexible substrate 1000 is 7 占 퐉 to 152 占 퐉, which is smaller than that of the plastic film of the single bare film. This is because the thickness of the first and second stainless steel films 110 and 120 coated on both sides is a thin film of 1 탆 to 5 탆 each.

Hereinafter, some examples of the manufacturing method of the flexible substrate of the present invention will be described.

4A and 4B are process cross-sectional views showing a method of manufacturing a flexible substrate of the present invention.

4A, the plastic film 100 of the bare film is provided, and then the plastic film 100 is transported as shown in FIG. 4B to form a plastic film 100 corresponding to the slit coating equipment 400, The stainless steel film 110 is coated on one surface of the substrate 100. In this case, the other surface of the plastic film 100 on which slit coating has not proceeded is controlled to move by the transport roll 450. The slit coating apparatus 400 may include a slit nozzle at a plurality of locations of the plastic film 100.

After the stainless steel film 110 is formed on the one surface, the flatness of the formed surface is improved by annealing, and then the plastic film 100 is inverted and the same slit coating process is repeated.

5 is a process sectional view showing another example of the method of manufacturing the flexible substrate of the present invention.

5 shows a method of depositing a stainless steel film by a sputtering method. 5, a constant voltage is applied to the target 500 in a chamber (not shown) at a high frequency, the plastic film 100 is placed on the stage 510 facing the target, Ground. Then, when a reactive gas such as Ar is supplied, the reactive gas hits the target surface, and the impact causes the stainless steel component in the target 500 to be deposited on the plastic film 100.

The above-described sputtering method is also required to form a stainless steel film on one surface, then to invert the surface again and repeat the same process on the other surface.

Meanwhile, the stainless steel film can be formed by the plating or dipping coating or vapor deposition method described above in addition to the slit coating or sputtering shown in the drawings.

After the formation of the stainless steel film, annealing or planarization may be further performed to increase the flatness of the surface.

The reason why the stainless steel film is used as the object to be formed is that it is a material having a sufficient mechanical rigidity, moisture resistance, chemical resistance and heat resistance with a thin thickness. If the development of the material can maintain such characteristics with other metal materials, Substitution can be considered.

6 is a graph showing the elongation of the flexible substrate in accordance with the thickness of the plastic film and the roll-to-roll conveying tension of the flexible substrate in which the application of the stainless steel film is different.

Fig. 6 shows the degree of stretching according to the load between the flexible substrate of the present invention and the polyimide film of the bare film. In the experiment, the thickness of the polyimide as the bare film was 38 탆, 50 탆, 75 탆, In the flexible substrate of the present invention, a polyimide film of 75 μm and a double-sided stainless steel film of 1 μm were applied.

In the graph of FIG. 6, the polyimide of the bare film has a smaller elongation with respect to the load as the thickness of the polyimide increases. This means that when the thickness of the bare film of the flexible substrate 1000 is large, the deformation of the substrate is small. The flexible substrate according to the present invention exhibits less deformation of the substrate even when the polyimide thickness is reduced to 60% of the thickness level (75 占 퐉) than when the thickness of the polyimide film is 125 占 퐉, have.

When the stretch change of the polyimide of the bare film was 1000 ppm at approximately the conveying tension of 6 kgf, the flexible substrate of the present invention showed that the stretch change was reduced at 270 ppm by applying the 1 μm thick double-side stainless steel film, , It means that tensile deformation occurs at a level of about 1/4 when the stainless steel film is applied, and it can be confirmed that the stiffness is significantly increased compared with the case of simply reducing the thickness of the bare film. That is, it can be seen that the flexible substrate has mechanical stability in the roll-to-roll process in which the transporting is repeated several times when the flexible substrate of the present invention is applied.

7A to 7E are process cross-sectional views showing a manufacturing method of the flexible display device of the present invention.

As shown in FIG. 7A, a first flexible substrate 1000 having first and second stainless steel films 110 and 120 coated on both sides of a plastic film 100 by coating or vapor deposition as described above is prepared.

Next, as shown in FIG. 7B, a buffer layer 150 is formed on the first stainless steel film 110.

The thin film transistor array 130 and the organic light emitting array 140 are formed on the buffer layer 150 as shown in FIG.

7D, a second flexible substrate 200 having a touch electrode array 210 on its surface is prepared.

7E, the buffer layer 150 having the thin film transistor array 130 and the organic light emitting array 140 is bonded to the second flexible substrate 200 with the adhesive layer 250 interposed therebetween.

Here, the portion corresponding to the adhesive layer 250 is a region covering at least the organic light emitting array 140, and the adhesive layer 250 is a component having a sealing function and moisture resistance by a kind of face seal. The protective layer 160 may cover the thin film transistor array 130 and the organic light emitting array 140 in the final process of forming the organic light emitting array 140 before the adhesive layer 250 is formed. have.

In the illustrated example, the touch electrode array 210 is provided on the second flexible substrate 200 side. However, the touch electrode array 210 may be provided on the first flexible substrate 1000 side It is possible.

In addition, the touch electrode array 210 may be omitted in a non-touch sensing display device.

The first flexible substrate 1000 to which the double-sided stainless steel film is applied is applied to the first plastic film described above. In the manufacture of the flexible display device, the high temperature condition required several times in the array forming step and the repetitive conveyance It is possible to prevent deformation of the substrate of the flexible substrate and maintain the reliability and stability of the display device. Ultimately, yield improvement can be expected.

The above-described flexible display device has been described as an example including an organic light emitting diode. However, the present invention is not limited to this, and various display panels such as a liquid crystal panel, an electrophoretic panel, and a quantum dot panel can be realized by using the flexible substrate as a backplane substrate .

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Will be apparent to those of ordinary skill in the art.

100: (first) plastic film 110: first stainless steel film
120: second stainless steel film 130: thin film transistor array
140: organic light emitting array 150: buffer layer
160: protective layer 200: second flexible substrate
210: touch electrode array 250: adhesive layer
1000, 1100: flexible substrate 2000: sealing means

Claims (15)

Plastic film; And
Wherein the first and second stainless steel films are in contact with both surfaces of the plastic film. The method according to claim 1,
Wherein the thickness of the first and second stainless steel films is 1 占 퐉 to 5 占 퐉, respectively. The method according to claim 1,
Wherein the plastic film comprises a copolymer comprising a polyester or a polyester, a copolymer comprising a polyimide or a polyimide, an olefinic copolymer, a polyacrylic acid or a polyacrylic acid, Copolymers, including copolymers, including polystyrene or polystyrene polystyrene copolymers, polycarbonates or polycarbonates, copolymers containing polysulfates or polysulfates, polyamic acids or polyamic acids, And at least one polymer compound selected from the group consisting of a copolymer comprising a polyamine and a polyamic acid, a copolymer including a polyamine and a polyamic acid, a polyvinyl alcohol, and a polyallylamine. The method according to claim 1,
Wherein the plastic film has a thickness of 5 占 퐉 to 150 占 퐉. The method according to claim 1,
Wherein the first and second stainless steel membranes have a water vapor transmission rate of 10 ^-6 g / m ² ˙day or less. The method according to claim 1,
And a buffer layer on the first stainless steel film. The method according to claim 6,
Wherein the buffer layer comprises at least one layer of an oxide insulating film or a nitride insulating film. A first flexible substrate including a first plastic film and first and second stainless steel films abutting on both surfaces of the first plastic film;
A buffer layer on the first flexible substrate;
A thin film transistor array on the buffer layer;
An organic light emitting array connected to the thin film transistor array; And
And a sealing means covering the organic light emitting array and contacting the buffer layer. 9. The method of claim 8,
Wherein the sealing means comprises:
An adhesive layer covering the organic light emitting array and in contact with the buffer layer; And
And a second flexible substrate which is in contact with the adhesive layer. 9. The method of claim 8,
Wherein the first flexible substrate has a water vapor transmission rate of 10 ^-1 g / m ² ˙day to 10 ^-3 g / m ² ˙day. 9. The method of claim 8,
Wherein the first flexible substrate has a thickness of 7 탆 to 152 탆. 12. The method of claim 11,
Wherein the thickness of the first and second stainless steel films is 1 占 퐉 to 5 占 퐉, respectively. 9. The method of claim 8,
And the second flexible substrate further includes a touch electrode array on a surface facing the adhesive layer. 9. The method of claim 8,
Wherein the sealing means is transparent. Preparing a first flexible substrate having first and second stainless steel films coated on both surfaces of a first plastic film;
Forming a buffer layer on the first stainless steel film;
Forming a thin film transistor array and an organic light emitting array on the buffer layer; And
And adhering the buffer layer having the thin film transistor array and the organic light emitting array to the second flexible substrate via the adhesive layer.

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