KR20110066769A - Plastic substrates coated with inorganic barrier layer and their manufacturing method - Google Patents

Abstract

PURPOSE: A plastic substrate having a coated inorganic barrier layer is provided to prevent thermal stress and to maintain stable junction. CONSTITUTION: A plastic substrate having a coated inorganic barrier layer comprises: a substrate made of plastic, and an inorganic barrier layer. The plastic substrate is used as a flexible display device. The plastic is PEN or PET. The inorganic material is magnesium oxide(MgO) or zirconium dioxide(ZrO_2). A transparent electrode layer is formed between the substrate and inorganic barrier layer. A flexible display device comprises the plastic substrate. The flexible solar cell device comprises the plastic substrate.

Description

Plastic substrates coated with inorganic barrier layer and their manufacturing method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic substrate commonly used in a flexible display device, and more particularly, to a plastic substrate coated with an inorganic barrier layer and a method of manufacturing the same, and more particularly, between a plastic substrate and an inorganic barrier layer. The thermal stress does not occur at the interface of the plastic substrate can be stably maintained without peeling even under repeated bending conditions.

There are many technical elements in providing flexibility to display devices such as liquid crystal display devices, FFL, OLED, inorganic EL, electronic paper, and solar cells, that is, implementing flexible displays. Is a plastic substrate.

Plastic substrates have disadvantages over glass substrates in terms of moisture and air permeability, low mechanical strength, low temperature process temperature, and poor thermal durability. Nevertheless, it becomes an indispensable material for implementing flexible displays. The coefficient of thermal expansion (CTE) of the plastic substrate is more than 10 times larger than that of the glass substrate, while the Young's Modulus of the plastic substrate is more than 10 times smaller than that of the glass substrate. Plastic substrates usually have a low glass transition temperature (Tg) of less than 200 and have very large moisture and air absorption and permeability compared to glass substrates.

The characteristics of PES (polyethersulphone) are not the major disadvantages as a substrate material, but the chemical resistance is relatively weak and the hygroscopicity is necessary. There is this. PC (polycarbonate) has excellent optical and mechanical properties, but has a disadvantage of weak chemical resistance. PET (polyethylene terephthalate) has superior chemical resistance to amorphous polymers and has a low price advantage, but has a low glass transition temperature (Tg), which limits the high temperature firing process. PEN (polyethylene naphthalate) has a low thermal expansion coefficient (CTE) compared to other plastic beams and is widely used in various display fields. PI (polyimide) has excellent chemical resistance and heat resistance, but it has a light transmittance of 30% based on 550nm and is colored so that it can be used only in specific areas. [Gregory P. Crawford, "Flexible flat panel display", Wiley -SID Series in Display Technology, 2005].

Because of the above limitations and problems in using a plastic substrate as a flexible display substrate, there are many restrictions in using the plastic substrate immediately. Thus, generally, a barrier layer is coated on a plastic substrate, which serves to suppress moisture and air permeability through the plastic substrate in various flexible display panels.

Conventionally, a multilayer barrier layer comprising an inorganic barrier layer on a plastic substrate as a single layer (PET / SiOx, PET / AlOx, PET / Al, PET / DLC, PET / ITO) or an inorganic-organic material composite layer It is used by coating in the form of (multilayer barrier) (PET / silicone / Si ₃ N ₄ , PET / acrylate / Alox). Coating of barrier layers can significantly reduce the penetration of air or moisture. In the case of oxygen, for example, the permeability can be reduced to <10 ^-5 mL / m ² or less per day. In the case of OLED, since the luminescent properties of OLDED light emitting materials are deteriorated very sensitively by moisture or oxygen, such a barrier layer coating is essential, and thus a multilayer barrier layer composed of organic materials and inorganic materials is coated.

In order to implement a display on a plastic substrate, various devices and structures, such as metal electrodes, ITO, organic / inorganic light emitting materials, barrier ribs, dielectric layers, or alignment layers, are formed depending on the type of display. During use, however, they are exposed to mechanical bending, thermal stress cycles, and penetration of moisture air. In this case, there is a problem that the interface bonding between the plastic substrate and the structures formed thereon is peeled off or cracks are generated.

In particular, when patterning the metal electrode on the plastic substrate in the manufacturing process, due to the difference in the coefficient of thermal expansion between the plastic substrate and the metal electrode, the bonding strength between the electrode is low, causing defects and problems in the manufacturing process. Above all, in the roll-to-roll manufacturing process, which is the greatest strength of the flexible display, when the panel substrate is rolled, the separation between the substrate and the electrodes, elements, and pixels formed thereon occurs. A problem arises. In addition, even after manufacturing, there is a problem that the bonding surface between the plastic, the electrode, and the driving element is peeled off when bending or rolling based on the flexibility, which is an advantage of the flexible display.

In addition, most of the barrier layers currently used are coated with a thin film of an inorganic material such as alumina. In this case, the interface joint is thermally fatigued due to the difference in coefficient of thermal expansion between the plastic substrate and the inorganic material. In the case of repeated cycles or mechanical bending stresses, the barrier layer and the plastic substrate are peeled off.

The above-mentioned interfacial bonding problem is a flat fluorescence lamp (FFL) {S.-M. Lee, SID07 Digest, pp 503-507, 2007} the same occurs when manufacturing using a plastic substrate to give flexibility (flexibility). That is, the problem of peeling of the interface bonding site with ITO, MgO, dielectric film, etc., metal electrode patterning, etc. to be formed on the plastic substrate occurs. That is, in most cases, when coating or patterning a material having a different thermal expansion coefficient on a plastic substrate, the bonding force is difficult to be stably maintained due to a difference in thermal expansion coefficient between the plastic substrate and the coating material. In addition, when the plasma discharge occurs, the plastic substrate is corroded and damaged by the plasma, and thus a protective layer capable of protecting the plastic substrate from the plasma is required.

The present invention for solving the above problems, a plastic substrate that can be stably maintained without peeling even under repeated bending conditions without thermal stress at the interface between the plastic substrate and the inorganic barrier layer and a method for producing the same It is to provide.

Plastic substrate coated with an inorganic barrier layer according to the present invention for achieving the above object, a substrate made of plastic; And an inorganic barrier layer coated on the substrate with the plastic and an inorganic material having a difference in the coefficient of thermal expansion (CTE) within a range of 0 to 3 ppm / ^° C.

The plastic substrate coated with the inorganic barrier layer may be used for a flexible device, a flexible display device, or a flexible solar cell device.

In addition, the inorganic material may have a difference in the coefficient of thermal expansion (CTE) of the plastic with the range of 0 to 1 ppm / ^o C. For example, the plastic is at least one selected from PEN and PET, and the inorganic material is at least one selected from magnesium oxide (MgO) and zirconium dioxide (ZrO ₂ ). In particular, the plastic is PEN, and the inorganic material is more preferably magnesium oxide (MgO).

In addition, the transparent electrode layer may be further included between the substrate and the inorganic barrier layer.

In addition, the substrate may have a thickness in the range of 10 ~ 1,000㎛, the inorganic barrier layer may have a thickness in the range of 300 ~ 5,000Å.

In addition, the inorganic barrier layer is preferably coated under the conditions of 0 ~ 200 ℃ by electron beam deposition method (Plasma Enhanced Chemical Vapor Deposion) method.

In addition, another embodiment of the present invention may be a flexible display device or a flexible solar cell device, characterized in that it comprises a plastic substrate coated with the above-described inorganic barrier layer.

Furthermore, another embodiment of the present invention comprises the steps of preparing a substrate made of plastic; And coating the plastic and an inorganic material having a difference in coefficient of thermal expansion (CTE) within a range of 0 to 3 ppm / ^o C on the substrate, wherein the inorganic barrier layer is coated with the plastic substrate. It is possible.

Here, the plastic is at least one selected from PEN and PET, and the inorganic material is preferably at least one selected from magnesium oxide (MgO) and zirconium dioxide (ZrO ₂ ).

Specific details of other embodiments are included in the detailed description and the drawings.

According to the present invention described above, it is possible to provide a plastic substrate that can stably maintain a bonding without peeling thermal stress at the interface between the plastic substrate and the inorganic barrier layer, even without repeated peeling conditions. That is, the barrier layer formed by coating the inorganic material according to the present invention can maintain excellent bonding under thermal cyclic stress or repeated bending stress, and in addition to excellent interfacial bonding, additionally prevents air permeation and prevents plasma It has the effect of protecting the plastic substrate from the atmosphere and increasing the stiffness of the plastic substrate.

In addition, the present invention provides a plastic substrate and a metal electrode, a transparent electrode, a driving element, a dielectric, an organic material, or a plastic substrate formed thereon under repeated bending or repeated thermal stress of the display panel and the substrate after the manufacturing process or the manufacturing process of the flexible display. It is possible to provide a method for producing a plastic substrate such that the joining surface with the partition and the like is not peeled off.

Hereinafter, one preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view showing an example of a plastic substrate coated with an inorganic barrier layer according to the present invention, and as shown herein, the present invention basically includes a substrate made of a plastic material and an inorganic material barrier coated on the substrate. It is a plastic substrate coated with an inorganic barrier layer. Among these, the present invention is characterized in that the difference between the coefficient of thermal expansion (CTE) of the inorganic material and the plastic forming the inorganic material barrier is in the range of 0 to 3 ppm / ^o C.

The inventors of the present invention provide a plastic substrate and a metal electrode, a transparent electrode, a driving element, a dielectric material, an organic material, formed on the plastic substrate even if the display panel and the substrate are repeatedly bent or thermally stressed after the manufacturing process or the manufacturing process of the flexible display. Or to prepare a plastic substrate to prevent the bonding surface to the partition and the like peeling.

To this end, the inventors of the present invention select the plastic and inorganic coating materials so that the interface between the plastic substrate and the barrier layer to be coated thereon has an excellent bonding force, so that the difference in the coefficient of thermal expansion (CTE) of each is zero. When it is in the range of ˜3 ppm / ^o C, it was found that thermal stress does not occur at the interface and that the bonding can be stably maintained without peeling even under repeated bending conditions, thereby completing the present invention.

Table 1 below shows the coefficients of thermal expansion (CTE) of the plastic substrate material and the inorganic material material which can be used as the plastic substrate material.

Table 1: Comparison of thermal properties of plastic substrates and inorganic materials

Material Plastic substrate material Inorganic material PEN PET PC PES PAR PI MgO ZrO ₂ Al ₂ O ₃ Si ₃ N ₄ Glass
(For TFT) CTE
(ppm / ^o C) 13 15 60-70 54 53 30-60 13.9 10.5 5.3 ~ 6.6 1.2
(Hexagonal) <4 Tg ( ^o C) 120 78 150 220 340 355 > 1000

1) PEN: Polyethylene naphthalate

2) PET: polyethylene terephthalate

3) PC: polycarbonate

4) PES: polyether sulfonate

5) PAR: polyacrylate

6) PI: polyimide

Conventionally, a plastic substrate including an inorganic barrier layer is formed of a single layer or an organic material layer such as SiO _x , Al ₂ O ₃ , Al, DLC (similar diamond), ITO, Si ₃ N ₄ , or the like on a plastic substrate made of a PC. Together, a multilayer composite layer was used. However, as shown in Table 1, the coefficient of thermal expansion (CTE) of the plastic substrate made of PC is 10 times larger than that of glass substrates and ordinary ceramic materials. Accordingly, according to the conventional method, the thermal expansion coefficient difference between the plastic substrate and the inorganic material is large, which causes a high thermal cycle at the junction of the interface during or during the manufacturing process and during the manufacturing process. Not only that, but also repeatedly subjected to mechanical bending stress has a problem that other components and barrier layer forming the display is peeled off by losing the bonding strength with the plastic substrate.

In order to solve the above problems, in the present invention, in selecting the plastic substrate and the barrier layer coating material, thermal expansion by selecting and coating a plastic material and an inorganic material having a difference in thermal expansion coefficient of each other within 0 to 3 ppm / ^o C. It is possible to solve the problem of lowering the interfacial bonding force due to the difference in coefficient.

For example, as shown in Table 1, the coefficients of thermal expansion of PEN and PET among the plastic substrate materials are 3-4 times lower (13-15 pm) than other plastic substrate materials. In addition, among inorganic ceramic materials, MgO has a coefficient of thermal expansion (13.9 ppm / ^° C.) three to five times larger than that of other ceramic materials. Accordingly, the thermal expansion coefficients of PEN and PET may be the most ideal barrier layer / substrate combination in terms of thermal expansion coefficient because they have a difference within the thermal expansion coefficient of MgO within 1 ppm / ^° C., respectively.

On the other hand, the inorganic ceramic material from ZrO ₂ is also relatively large thermal expansion coefficient of the material (10.5ppm / ^o C) as has a difference in the PEN and PET with thermal expansion coefficient and 3 ~ 5ppm / ^o C is also capable of selecting a barrier material It is material.

Therefore, it is possible to select at least one of MgO and ZrO ₂ as the inorganic material barrier layer material, and at least one of PET and PEN as the plastic substrate. Preferably, to each use of the material of the plastic substrate and the inorganic barrier layer to the thermal expansion coefficient difference ^{0.9ppm / o C PEN (CTE =} 13ppm / o C) and ^{MgO (CTE = 13.9ppm / o C} ) of only It could have the best interfacial bonding force.

According to the present invention, a barrier layer coated substrate prepared by coating an MgO film on a PEN plastic substrate may maintain a stable bonding state without peeling the MgO thin film even under U-shaped repeated bending test conditions. The principle is that the thermal stress does not occur at the interface between the two materials during the cooling process after coating the MgO film by using a small difference in coefficient of thermal expansion between the two materials (preferably within 0 ~ 1ppm / ^oC ).

According to this invention, preferably MgO (CTE = 13.9 ppm / ^o C, 25) having a difference in coefficient of thermal expansion within 3 ppm on a PEN (CTE = 13 ppm / ^o C) or PET (CTE = 15 ppm / ^o C) plastic substrate ~ 1000 range) or by coating ZrO ₂ with a barrier layer, it is excellent in interfacial bonding force between the barrier layer and the plastic substrate, relieves thermal stress due to the difference in coefficient of thermal expansion between the metal electrode and the plastic substrate, Barrier plastic substrates for displays can be fabricated without peeling at the interface even under thermal cycle or mechanical cyclic bending stress. In addition, the PET or PEN substrate coated with MgO has an effect of reducing oxygen permeability and increasing stiffness of the substrate in various flexible display panels.

2 is a perspective view illustrating an example of a state in which a transparent electrode layer is included between an inorganic barrier layer and a plastic substrate according to the present invention, and as shown herein, the substrate may further include a transparent electrode layer. Do. That is, the present invention includes a substrate on which a transparent electrode layer is formed between the plastic substrate and the inorganic barrier layer.

In general, plastic substrates used for flexible displays are manufactured and commercialized in many cases with ITO coated (300-800 mm thick). Accordingly, the present invention may be coated with MgO or ZrO ₂ as an inorganic barrier layer on the ITO transparent electrode layer on a PEN or PET plastic substrate coated with ITO. The barrier layer thus formed can function to alleviate thermal stress due to a difference in thermal expansion coefficient with a plastic substrate when forming a metal electrode having a very large thermal expansion coefficient or a dielectric film having a small thermal expansion coefficient thereon.

On the other hand, another embodiment of the present invention is a method for producing a plastic substrate coated with the inorganic barrier layer as described above, first preparing a substrate made of plastic, the inorganic material having a coefficient of thermal expansion similar to the plastic on the prepared substrate It consists of coating.

For example, barrier layers made of MgO or ZrO ₂ use physical vapor deposition, such as electron beam (EB) deposition, below 200 ^o C, below the working temperature range of PEN or PET plastic substrates. Or by chemical vapor deposition such as PECVD. EB evaporation or PECVD is the most suitable method for depositing the inorganic material according to the present invention on a plastic substrate having a low Tg temperature.

At this time, the thickness of the PEN or PET substrate may be 10 ~ 1,000㎛, among them is preferably 80 ~ 300㎛, the barrier layer material formed on the substrate may be coated with a thickness of several tens Å to thousands of Å. For example, the MgO or ZrO ₂ barrier layer is preferably coated within the range of 300 kPa to 5,000 kPa by electron beam deposition, and the thickness of the barrier layer may be appropriately adjusted according to the flexible device to be applied. Most preferably, about 1000 mW is suitable.

The substrate according to the present invention prepared as described above, can be used as a flexible substrate when manufacturing a flexible LCD, OLED, flexible flat light source, a flexible photovoltaic device, etc., whereby the thermal stress that may occur during the manufacturing process It does not occur at all, and there is an advantage that the peeling between the substrate and the barrier film does not occur even after repeated manufacturing bending conditions.

That is, the plastic substrate according to the present invention, which can maintain excellent bonding strength even under repeated bending and thermal stress conditions, has various flexible display panels requiring flexibility, such as various flexible display devices and flexible solar devices. It is useful as a board | substrate of a null.

Accordingly, the substrate according to the present invention can be used as a substrate for the production of various display panels or flexible photovoltaic devices requiring flexible properties. For example, it may be applied to plastic substrates such as flexible LCDs, OLEDs, inorganic ELs, flexible flat flourescent lamps, and solar cells.

The invention may be better understood by the following examples, which are intended for purposes of illustration of the invention and are not intended to limit the scope of protection defined by the appended claims.

Example 1 Preparation of PEG Substrate / MgO Thin Film Layer

The MgO film was coated to a thickness of about 4,800 mm 3 on a PEN plastic substrate having a thickness of 200 μm. The MgO ceramic target was deposited using an electron beam deposition apparatus while maintaining the PEN substrate temperature at 100 ^° C., 150 ^° C., and 180 ^° C., respectively. During deposition, the degree of vacuum was about ² × 10 ⁻⁶ Torr and the deposition rate was about 2 μs / s.

3 is a surface image taken by SEM of MgO thin films deposited at 100 ^° C (a), 150 ^° C (b), 180 ^° C (c) on the PEN substrate, respectively. It can be seen from the photographed image that the MgO film crystal phase was grown in a predetermined direction on the PEN substrate.

On the other hand, the coating of the MgO thin film on a PEN plastic substrate at 180 ^° C temperature was analyzed using a transmission electron microscope (TEM) between the PEN substrate and the MgO thin film, and the crystallinity of the MgO thin film. Figure 4 a) and b) is a photograph of a portion of the MgO thin film-coated PEN substrate TEM observation sample after the observation of the interface region by TEM. It is observed that the MgO crystal phase grows continuously in a direction perpendicular to the PEN substrate, and the bonding state of the interface between MgO and PEN is very good. 4C shows that the MgO thin film grows preferentially toward the (200) plane in the TEM SAED (Selection area electron diffraction pattern) pattern.

Example 2 Preparation of PC Substrate / MgO Thin Film Layer

As in Example 1, the MgO film was coated on a 200 μm PC plastic substrate to a thickness of about 4,800 mm 3. Coating method and conditions of the MgO thin film was carried out under the same conditions as in Example 1.

5 is a surface shape of the MgO thin film deposited at 100 ^o C (a), 100 ^o C (b), 150 ^o C (c) on the PC substrate, respectively. In the photographed image, it can be confirmed that the crystal phase has grown in a specific direction. In particular, FIG. 5B is a cross-sectional view of MgO deposited on the PC substrate at 100 ^° C., and it can be seen that the substrate and the MgO film are normally bonded. It is observed that the MgO film is about 4,800 mm thick on the PC substrate.

Experimental Example 1: Repeated bending test of PEN substrate / MgO thin film layer

The experiment of bending the PEN substrates having MgO deposited according to Example 1 into a “U” shape as shown in FIG. 3 was repeated 30 times. The surface on which MgO was deposited was then observed by scanning electron microscopy (SEM) to test whether the MgO film on the plastic substrate of the present invention could maintain bonding strength under repeated bending conditions.

FIG. 7 shows repeated MgO-coated PEN substrates 30 times, followed by scanning electron microscopy (SEM). Three cases where the MgO thin film deposition temperature was different at three temperatures of 100 ^o C (a), 150 ^o C (b) and 180 ^o C (c) were compared. There was no change in the surface shape of the MgO thin film, and the bonding state between the MgO film and the PEN substrate was the same as before the bending test. That is, this embodiment shows that the bonding strength of the PEN and MgO thin films having a difference in thermal expansion coefficient of less than 1 ppm / ^o C has a very good bonding interface that does not occur even under repeated U-bending stress conditions. Give it.

Experimental Example 2: Repeated bending test of PC board / MgO thin film layer

MgO-coated PC substrates according to Example 2 were subjected to 30 repeated bending tests as shown in FIG. 3, and then the MgO thin film surface was observed by scanning electron microscopy (SEM).

Figure 8 is a U-shaped repeated bending experiments for 30 times the PC plate coated with MgO thin film according to the present invention, the surface shape example of the SEM observation (a and b) and an example of the peeled MgO film It is SEM photograph to show. The two cases where the MgO thin film deposition temperature was different from 100 ^o C (a) and 150 ^o C (b) were compared. In both cases, many cracks occurred on the surface of the MgO thin film after 30 U bending tests. FIG. 8C is a SEM observation of the MgO thin film peeled off from the PC substrate (150 ^° C. vapor deposition sample) and measured at about 5,000 kPa.

As described above, when Experimental Example 1 in which the bending test was performed on the MgO film on the PEN substrate and Experimental Example 2 in which the bending test was performed on the MgO film on the PC substrate are compared, the thermal expansion coefficient difference is very large. The composite layer composed of the PC substrate and the MgO thin film is easily peeled off by repeated bending, but the effect of the present invention is apparent from the fact that the MgO film on the PEN substrate having a very small thermal expansion coefficient is excellent after the bending test. It can be seen.

PC substrates with thermal expansion coefficient (CTE) of 60-70ppm / ^oC and PEN substrates with 13ppm / ^oC , respectively, are all peeled off at the bonding interface when observed with the naked eye or by scanning electron microscope (SEM) immediately after MgO thin film is deposited. The phenomenon is not observed. The MgO thin film on the PC substrate is easily peeled off under the bending test because the difference in thermal expansion coefficient between the PC substrate and the MgO thin film is very large at the interface during cooling from the MgO thin film deposition temperature (100 to 180 ^o C) to room temperature. Since the stress is formed, it is judged that the MgO thin film is easily peeled off by the bending test. On the other hand, since PEN and MgO have very small thermal expansion coefficients, thermal stress does not occur during cooling after deposition, and thus excellent bonding strength can be maintained by bending test.

Experimental Examples 1 and 2 show that the MgO thin film on the PEN has a very good bonding interface in which peeling does not occur even under repeated U-bending stress conditions and clearly shows the effect of the present invention.

Experimental Example 3: Light Transmittance Measurement Experiment

Under the same conditions as in Example 1, MgO thin films were deposited on glass, PEN, and PC substrates at 100 ^° C., 150 ^° C., and 180 ^° C., respectively, using electron beam deposition, and then light transmittance was measured. The light transmittance of the original substrate (denoted as none) before deposition and the light transmittance after MgO deposition were measured. Light transmittance was measured using BM-7 and He-Ne laser device.

Table 2 shows the light transmittance measurement results accordingly. Although the measured light transmittance varies slightly depending on the measuring device, it is slightly reduced to a value in the range of about 2 to 6% compared to the original substrates before coating, but it shows that the MgO coated substrate is not a problem to be applied as a display substrate material. . In the case where a crack is generated by bending a sample deposited with MgO at 100 ^° C. on a PC substrate, the light transmittance is reduced by about 10% than without the crack.

Table 2: Measurement of change in light transmittance when MgO film is deposited on plastic or organic substrate

Sample equipment Nothing MgO 100 ℃ MgO 150 ℃ MgO 180 ℃
glass
BM-7 91-93 90 87.5 88.5 He-Ne Laser 93 92 83 84
PEN
BM-7 86 85 85 85 He-Ne Laser 90 85 80 85
PC (shock / non-shock)
BM-7 90 78 / 86.5 88 87 He-Ne Laser 89/99 66 / 94.83 83 *

Impact: Before U-Bending Test (Measurement of Light Transmittance after Bending Test of MgO Deposited at 100 ^o C on PC Substrate)

-No impact: after U-bend test

-Zero: Original plastic substrate without MgO thin film

-BM-7, He-Ne laser: light transmittance measuring device

Example 3: Display Manufacturing

According to Example 1, a flexible FFL was manufactured by using a PEN substrate on which a MgO thin film was deposited as a substrate material of a flat fluorescent light source (FFL) having a structure as shown in FIG. 9.

As the details of the FFL fabricated in the present embodiment, the thickness of the PEN plastic substrate was 200 μm, the area of the fabricated lamp was 50 mm × 50 mm, the size of the discharge space between the partitions was 5 mm × 50 mm in length, and the initial injection discharge gas was Ne-. Xe (5%), gas injection pressure were 100 to 300 Torr, applied voltage was 0 to 1 kV, and applied power frequency was 0.4 kHz. The plastic bulkhead was fabricated using a PEN substrate, and the height of the bulkhead was about 400 μm.

10 is a photograph showing a shape of discharging when a voltage is applied to the flexible planar surface light source panel manufactured as described above. As shown here, it is shown that the PEN substrate coated with MgO thin film according to the present invention can be successfully applied to fabricate a flexible planar fluorescent light source using the plasma discharge principle.

Meanwhile, the flexible FFL manufactured using the PEN substrate coated with the MgO thin film as described above and the flexible FFL manufactured using the PEN substrate not coated with the MgO film as the comparative example were manufactured, respectively, and their driving voltages were measured. Thus, the effect of the MgO thin film coating on the discharge start voltage was confirmed.

FIG. 11 (a) is a graph showing a change in firing voltage according to the discharge gas pressure in the flexible FFL in which the MgO thin film is deposited. It can be seen that the discharge start voltage increases as the pressure of Ne-Xe (5%) increases. In addition, Figure 11 (b) is a graph showing the change in the firing voltage (firing voltage) according to the gas pressure of the flexible FFL not deposited MgO thin film can be seen that the discharge start voltage also increases as the pressure of the discharge gas increases. have. When comparing (a) and (b) of Figure 11 it can be seen that the discharge start voltage of the flexible FFL on which the MgO thin film is deposited is about 100V low.

On the other hand, while the present invention has been shown and described with respect to certain preferred embodiments, the invention is variously modified and modified without departing from the technical features or fields of the invention provided by the claims below It will be apparent to those skilled in the art that such changes can be made.

The plastic substrate according to the present invention can be used as a substrate in the manufacture of various display panels and flexible photovoltaic devices requiring flexible properties.

1 is a perspective view showing an example of a plastic substrate coated with an inorganic barrier layer according to the present invention,

2 is a perspective view illustrating an example of a state in which a transparent electrode layer is included between an inorganic barrier layer and a plastic substrate according to the present invention;

3 is a SEM photograph showing an example of the surface of the MgO thin film observed after coating the MgO thin film on the PEN substrate according to the present invention,

4 are photographs (a and b) showing an example of observing an interface between a PEN substrate and an MgO thin film with a high magnification transmission electron microscope according to the present invention, and a photograph (c) showing an example of an SAED pattern of a MgO film.

5 is an SEM photograph showing an example of the surface of the MgO thin film observed after coating the MgO thin film on the PC substrate according to the present invention,

6 is a schematic diagram for explaining an example of the "U" type repeated bending test method used to evaluate the interfacial bonding strength of MgO-deposited plastic substrates according to the present invention,

FIG. 7 is a photograph of an example of the surface shape of the PEN substrate coated with MgO thin film according to the present invention after a U-shaped repeated bending test for 30 times.

Figure 8 is a U-shaped repeated bending experiments for 30 times the PC plate coated with MgO thin film according to the present invention, the surface shape example of the SEM observation (a and b) and an example of the peeled MgO film It is SEM photograph to show,

9 is a cross-sectional view illustrating an example of a structure of a flat fluorescent light source (FFL) manufactured by applying a PEN substrate on which an MgO thin film is deposited according to the present invention.

FIG. 10 is a photograph showing an example of a discharge state when a voltage is applied to the flexible planar light source panel having the structure of FIG.

FIG. 11 is a graph comparing driving voltages of a flexible FFL fabricated using a PEN substrate (a) coated with an MgO thin film and an uncoated PEN substrate (b) according to the present invention.

Claims (12)

A substrate made of plastic; And Plastic substrate coated with an inorganic barrier layer comprising an inorganic material having a difference between the plastic and the coefficient of thermal expansion (CTE) within the range of 0 ~ 3ppm / ^o C, the inorganic barrier layer coated on the substrate . The plastic substrate coated with an inorganic barrier layer according to claim 1, which is for a flexible display device. According to claim 1, wherein the inorganic material is a plastic substrate coated with an inorganic barrier layer, characterized in that the plastic and the coefficient of thermal expansion (CTE) has a difference within the range of 0 ~ 1ppm / ^o C. The method of claim 1, wherein the plastic is at least one selected from PEN and PET, and the inorganic material is coated with an inorganic barrier layer, characterized in that at least one selected from magnesium oxide (MgO) and zirconium dioxide (ZrO ₂ ). Plastic substrate. 2. The plastic substrate of claim 1, wherein the plastic is PEN and the inorganic material is magnesium oxide (MgO). 2. The plastic substrate of claim 1, further comprising a transparent electrode layer between the substrate and the inorganic barrier layer. The plastic substrate of claim 1, wherein the substrate has a thickness in the range of 10 to 1,000 μm, and the inorganic barrier layer has a thickness in the range of 300 to 5,000 μs. The inorganic barrier layer of claim 1, wherein the inorganic barrier layer is coated under conditions of 0 ° C. to 200 ° C. by electron beam deposition or plasma enhanced chemical vapor deposition (PECVD). Coated plastic substrate. A flexible display apparatus comprising the plastic substrate according to any one of claims 1 to 8. A flexible solar cell apparatus comprising the plastic substrate according to any one of claims 1 to 8. Preparing a substrate made of plastic; And Coating the plastic and an inorganic material having a difference in coefficient of thermal expansion (CTE) within a range of 0 to 3 ppm / ^o C on the substrate. The method of claim 11, wherein the plastic is at least one selected from PEN and PET, and the inorganic material is coated with an inorganic barrier layer, characterized in that at least one selected from magnesium oxide (MgO) and zirconium dioxide (ZrO ₂ ). Method for producing a plastic substrate.

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