Flexible base material and flexible electronic device

The invention provides a flexible base material and a flexible electronic device. The flexible base material includes a flexible substrate having a first surface and a second surface opposite to the first surface. A first organic composite barrier layer is deposited on the first surface of the flexible substrate, wherein the first organic composite barrier layer applies a first stress to the flexible substrate. An anti-curved layer is deposited on the second surface of the flexible substrate, wherein the anti-curved layer applies a second stress to the flexible substrate, and wherein the second stress applied by the anti-curved layer cancels off more than 90% of the first stress.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of Taiwan Patent Application No. 100117018, filed on May 16, 2011, the entirety of which is incorporated by reference herein.

BACKGROUND

1. Field of the Disclosure

The present disclosure relates to a flexible base material and a flexible electronic device, and in particular, to a flexible base material and a flexible electronic device with excellent moisture-barrier/gas-barrier and anti-curving performances.

2. Description of the Related Art

In recent years, flexible electronic devices have been developed. For example, an organic light emitting diode device (OLED) has the advantages of being self-luminous, light weight, and thin and having low power consumption. Compared with the conventional fluorescent lamp having a linear luminous body and the light emitting diode device (LED) having a spot-shaped luminous body, an OLED has a planar luminous body, and has replaced the fluorescent lamp. Also, laminating materials of OLEDs are flexible organic materials with the advantages of having high contrast, fast response time and a wide viewing-angle. The flexible OLED display, which is fabricated by forming OLEDs and organic thin film transistors for driving the OLEDs on a plastic substrate, has become the choice of preference for replacing the conventional rigid display. The flexible OLED display generally uses a plastic substrate as a substrate. However, the plastic substrate has poor moisture-barrier/gas-barrier performance. Also, organic light emitting polymer layers and high activity electrode materials in the flexible OLED display are very sensitive to moisture and oxygen. When moisture and oxygen in the atmosphere penetrate into the plastic substrate, the luminance of the OLED is reduced, and the driving voltage is increased, such that a dark spot problem and short circuit problem may occur, thereby decreasing the reliability and life span of the flexible OLED display. Therefore, developments in packaging technology are very important to the technology of the flexible OLED display.

The conventional moisture-barrier/gas-barrier technology uses an organic-inorganic alternating multilayer as a barrier layer formed on the flexible substrate by a sputtering or plasma enhanced chemical vapor deposition (PECVD) method to achieve the moisture-barrier/gas-barrier performance. However, the conventional barrier layer requires laminating at least three pairs of the organic-inorganic alternating multilayer to achieve the moisture-barrier/gas-barrier function. Also, the conventional organic-inorganic alternating multilayer is formed by alternate delivery and sputtering processes in different vacuum chambers. Thus, the fabrication cost and process time are increased. Further, after the barrier layer is sputtered on the flexible substrate, the internal stress in the barrier layer affects the flexible substrate, resulting in the bending or deformation of the substrate, thus, negatively affecting the moisture-barrier/gas-barrier performance of the conventional barrier layer.

BRIEF SUMMARY

A flexible base material and a flexible electronic device are provided. An exemplary embodiment of a flexible base material comprises a flexible substrate having a first surface and a second surface opposite to the first surface. A first organic composite barrier layer is deposited on the first surface of the flexible substrate, wherein the first organic composite barrier layer applies a first stress to the flexible substrate. An anti-curved layer is deposited on the second surface of the flexible substrate, wherein the anti-curved layer applies a second stress to the flexible substrate, and wherein the second stress applied by the anti-curved layer cancels off more than 90% of the first stress.

An exemplary embodiment of a flexible electronic device comprises a flexible base material comprising a flexible substrate having a first surface and a second surface opposite to the first surface. A first organic composite barrier layer is deposited on the first surface of the flexible substrate, wherein the first organic composite barrier layer applies a first stress to the flexible substrate. An anti-curved layer is deposited on the second surface of the flexible substrate, wherein the anti-curved layer applies a second stress to the flexible substrate, and wherein the second stress applied by the anti-curved layer cancels off more than 90% of the first stress. A flexible electronic component is deposited on the first organic composite layer. A second organic composite barrier layer is deposited on the flexible electronic component, encapsulating the flexible electronic component.

DETAILED DESCRIPTION

The following description is of a mode for carrying out the exemplary embodiments. This description is made for the purpose of illustrating the general principles of the disclosure and should not be taken in a limiting sense. The scope of the disclosure is best determined by reference to the appended claims. Wherever possible, the same reference numbers are used in the drawings and the descriptions to refer the same or like parts.

The present disclosure will be described with respect to particular embodiments and with reference to certain drawings, but the disclosure is not limited thereto and is only limited by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual dimensions to practice of the disclosure.

FIG. 1is a cross section showing one exemplary embodiment of a flexible base material500aof the disclosure. The flexible base material500acomprises a flexible substrate200having a first surface202and a second surface204opposite to the first surface. An organic composite barrier layer210is deposited on the first surface of the flexible substrate. An anti-curved layer212ais deposited on the second surface204of the flexible substrate200.

In one embodiment, the flexible substrate200may comprise organic materials of pet polyethylene terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), polyimide (PI), polycarbonate (PC), and etc. In one embodiment, the organic composite barrier layer210is used to block penetration by moisture and oxide from the outside environment. The first organic composite barrier layer210may comprise organic materials having an Si-(CH3)xor Si-(CH2)xbond. Additionally, the organic composite barrier layer210may by a composite structure formed by laminating of a first organic layer206and a second organic layer208. The first organic layer206is deposited between flexible substrate200and the second organic layer208. In one embodiment, the anti-curved layer212a is used to balance the stress generated by growing the organic composite layer. Therefore, the resulting organic composite barrier layer may have good film characteristics. Thus, the moisture-barrier/gas-barrier performance of the organic composite barrier layer210is improved. The anti-curved layer212a may comprise a signal layer formed by silicon oxide (SiOx), silicon nitride (SiNx), oxinitride nitride (SiOxNy), organic materials or metal oxides. Thicknesses of the anti-curved layer212aand the first organic layer206and the second organic layer208of the organic composite barrier layer210are accordingly to requirements, respectively, wherein a stress applied by the organic composite barrier layer210to the flexible substrate200is substantially cancelled off by a stress applied by the anti-curved layer212ato the flexible substrate200. For example, the stress applied by the organic composite barrier layer210to the flexible substrate200is cancelled off by more than 90% of the stress applied by the anti-curved layer212a to the flexible substrate200.

A method for fabricating one exemplary embodiment of a flexible base material500ais described as follows. First, a flexible substrate200is provided. Next, an anti-curved layer212ais formed on a second surface204of the flexible substrate200by a PECVD method. A thickness of the anti-curved layer212ais between about 5 nm and 5 μm. In one embodiment, a radio-frequency (RF) power for forming the anti-curved layer212ais between about 1000 watt and 2000 watt. Next, a first surface202of the flexible substrate200is cleaned using plasma bombarding only with the introduction of Ar by another PECVD method. Next, Ar and a thermal vapor of vaporized hexamethyldisiloxane (Si2OC6H18, HMDSO) are introduced into the vacuum chamber of a PECVD apparatus without O2. Another PECVD method is performed to heat and dissociate the precursor HMDSO, so that a first organic layer206of the organic composite barrier layer210is formed on the first surface202of the flexible substrate200. A thickness of the first organic layer206is between 1 nm and 10 μm. A molecular formula of HMDSO is shown as Equation (1):

In one embodiment, the plasma dissociation equation for forming the first organic layer206is shown as Equation (2):
Si3OC6H18+→Si2OC5H15++CH6−
Si2OC5H15+→SiC3H9++SiOC2H6−
SiC3H9+→SiCH3++C2H6+Equation (2)

Also, dissociation elements of the first organic layer206are shown as Equation (3):

From equations (2) and (3), in one embodiment, the first organic layer206may comprise ions of organosilicon compounds including SiOC2H6−, SiCH3+or C2H6−. The first organic layer206may contain a huge amount of SiCH3and Si—(CH3)x(x=2˜4) bonds in the film without being dissociated by plasma. Therefore, the formed first organic layer206may be an organic film containing Si—(CH3)x(x=1˜4) bond. The first organic layer206may further comprise an Si—O—Si bond, and a ratio of the Si—O—Si bond to the Si—(CH3)xbond is smaller than 1 or equal to 1. After forming the first organic layer206, another PECVD method is performed, and a mixed gas of Ar, O2and an HMDSO thermal vapor is introduced into the vacuum chamber, thereby forming the second organic layer208of the organic composite barrier layer210on the first organic layer206. In one embodiment, the plasma dissociation equation for forming the second organic layer208is equal to that for forming the first organic layer206. Dissociation elements of the second organic layer208are shown as Equation (4):

It is noted that the plasma power for forming the second organic layer208is much larger than that for forming the first organic layer206. After dissociating HMDSO, more Si—CH3bonds are broken, and every oxygen atom is bonded to two Si atoms, which are formed after breaking the Si—CH3bonds, to make the Si—O—Si bonds. Therefore, from Equation (4), the second organic layer208may contain Si—O—Si, SiCH3or Si—(CH3)x(x=2˜4) bonds therein, and a number of Si—O—Si bonds in the second organic layer208is more than that in the first organic layer206. Therefore, a ratio of the Si—O—Si bond to the Si—(CH3)xbond is larger than 1. A thickness of the second organic layer208is between about 5 nm and 1 μm. In one embodiment, the anti-curved layer212ais used to balance the stress from the organic composite barrier layer210deposited on another side of the flexible substrate200. The film stress relates to a thickness of the film. Therefore, a thickness ratio of the anti-curved layer212ato the organic composite barrier layer210is required to be within a certain range to achieve a goal of stress balance. In one embodiment, a thickness ratio of the anti-curved layer212ato the organic composite barrier layer210may be between 0.1 and 3. In one embodiment, RF power for forming the first organic layer206is between about 100 watt and 800 watt, and a RF power for forming the second organic layer208is between about 1000 watt and 1800 watt. After forming the first organic layer206and the second organic layer208, one exemplary embodiment of a flexible base material500ahaving the organic composite barrier layer210constructed by a pair of organic layers (comprising the first organic layer206and the second organic layer208) is formed completely. Alternatively, the number of layers of the organic composite barrier layer210is not limited to the numbers stated above, but according to design. In one exemplary embodiment of the anti-curved layer212a, the first organic layer206and the second organic layer208may be continuously formed in the same vacuum chamber, wherein the process parameters of these layers are shown in Table 1.

FIG. 2is a cross section showing another exemplary embodiment of a flexible base material500bof the disclosure. In another embodiment, another organic composite barrier layer may serve as an anti-curved layer212bdeposited on the second surface204of the flexible substrate200. As shown inFIG. 2, the anti-curved layer212bis an organic composite structure constructed by laminating a third organic layer214and a fourth organic layer216to the flexible substrate200, wherein the third organic layer214is deposited between the flexible substrate200and the fourth organic layer216. In one embodiment, the third organic layer214and the first organic layer206may be formed by the same materials and have the same thickness. Also, the fourth organic layer216and the second organic layer208may be formed by the same materials and have the same thickness. The anti-curved layer212bdeposited on the second surface204of the flexible substrate200and the organic composite barrier layer210deposited on the first surface202of the flexible substrate200are symmetric to each other and formed by the same materials. Therefore, a stress applied by the organic composite barrier layer210to the flexible substrate200is substantially cancelled off by a stress applied by the anti-curved layer212bto the flexible substrate200. For example, the stress applied by the organic composite barrier layer210to the flexible substrate200is cancelled off by more than 90% of the stress applied by the anti-curved layer212bto the flexible substrate200. In other embodiments, the number of layers of the organic composite barrier layer210and the anti-curved layer212bare not limited to the numbers stated above, but according to design.

FIG. 4is a Fourier transform infrared spectroscopy (FTIR) analysis diagram of the first organic layer206and the second organic layer208of a first organic composite barrier layer of one exemplary embodiment of a flexible base material of the disclosure. Referring toFIG. 4, an FTIR signal404of the first organic layer206contains an Si—O—C/Si—CH2—Si bond (1038 cm−1), Si—CH3bond (1260 cm−1) and Si—(CH3)xbond (840 cm−1). Also, an FTIR signal402of the second organic layer208contains an Si—O—Si bond (1072 cm−1), Si—CH3bond (1260 cm−1) and Si—(CH3)xbond (840 cm−1). Because oxygen is not introduced into the vacuum chamber during the growing the first organic layer206(as show in Table 1), a ratio of the Si—O—Si bond to the Si—(CH3)xbond of the first organic layer206is smaller than 1 or equal to 1 (the Si—O—Si bond is provided by dissociating HMDSO). Because the vacuum chamber is introduced a huge amount of oxygen during the growing of the second organic layer208(as show in Table 1), the second organic layer208is an oxygen-rich organic film having a high Si—O—Si bond content, and a ratio of the Si—O—Si bond to the Si—(CH3)xbond of the first organic layer206is larger than 1. As shown inFIG. 4, a signal intensity of the Si—O—Si bond in the second organic layer208is larger than that in the first organic layer206. That is to say, the second organic layer208has a higher SiOxcomponent than the first organic layer206.

FIG. 5is a cross section showing one comparative example of a flexible base material700of the disclosure. The differences between the comparative example of the flexible base material700as shown inFIG. 5and the one exemplary embodiment of the flexible base material500aas shown inFIG. 1is that the flexible base material700does not have an anti-curved layer, wherein the other elements of the flexible base material700are the same as that of the flexible base material500a.

FIGS. 6aand6bare secondary electron microscope (SEM) images of one exemplary embodiment of a flexible base material500aas shown inFIG. 1and one comparative example of a flexible base material700as shown inFIG. 5, showing surface statuses of the both. The magnification of the SEM images as shown inFIGS. 6aand6bis 50000. As shown inFIG. 6a, the second organic layer208(the oxygen-rich organic film) of the organic composite barrier layer210of the flexible base material700without the anti-curved layer had the occurrence of small cracks (as shown in the region surrounded by a circular ring). These cracks provide paths for moisture penetration. Therefore, the flexible base material700has poor moisture-barrier/gas-barrier performance, and the measured water vapor transmission rates (WVTR) of the flexible base material700were only 0.4 g/m2/day. As shown inFIG. 6b, the second organic layer208of the organic composite barrier layer210of the flexible base material500adid not have any cracks in the same magnification of the SEM image to the flexible base material700as shown inFIG. 6a. Therefore, the flexible base material500ahad good moisture-barrier/gas-barrier performance when compared to the flexible base material700, and the measured WVTR of the flexible base material500awere only 10−6g/m2/day.

FIG. 7is transmittance for the visible light of one embodiment of a flexible base material having three organic composite layers (formed by alternatively laminating the first organic layers and the second organic layers three times). As shown inFIG. 7, the transmittance for the visible light of one embodiment of a flexible base material having three organic composite layers is 95% and above. Therefore, the one embodiment of a flexible base material having three organic composite layers may be applied in a light emitting device package, for example, an OLED device, an optoelectronic display device or a thin film solar cell device.

FIG. 3is a cross section showing one exemplary embodiment of a flexible device600formed by the flexible base material500aas shown inFIG. 1or the flexible base material500bas shown inFIG. 2. As shown inFIG. 3, the one exemplary embodiment of a flexible device600may further comprise a flexible electronic component224deposited on the organic composite barrier layer210and another organic composite barrier layer222deposited on the flexible electronic component224by encapsulating the flexible electronic component224. In one embodiment, the flexible electronic component224may comprise an OLED device, an optoelectronic display device, a thin film solar cell device, a water/oxygen sensitive device or a metal of Ca, Mg or etc. In one embodiment, the organic composite barrier layer222may have the same materials and the same structural arrangement as the organic composite barrier layer210. More specifically, the organic composite barrier layer222is an organic composite structure constructed by laminating a fifth organic layer218and a sixth organic layer220to the flexible electronic component224, wherein the fifth organic layer218is disposed between the flexible electronic component224and the sixth organic layer220. The fifth organic layer218has the same materials and thickness as the first organic layer206. Also, the sixth organic layer220has the same materials and thickness as the second organic layer208. As shown inFIG. 3, the organic composite barrier layer210under the flexible electronic component224can block the moisture from under the flexible substrate200and prevent it from penetrating into the flexible electronic component224. Also, the organic composite barrier layer222above the flexible electronic component224can block the moisture from above the flexible substrate200or from the sides of the flexible substrate200and prevent it from penetrating into the flexible electronic component224. A main function of the anti-curved layer212ais to balance stresses generated during formation of the organic composite barrier layers210and220. Therefore, the organic composite barrier layers210and220have good film quality. A resulting flexible device is prevented from being bent or deformed due to the internal stresses in the organic composite barrier layers. In one embodiment, the anti-curved layer212may comprise a signal layer structure of the anti-curved layer212aas shown inFIG. 1or a composite structure of the anti-curved layer212bas shown inFIG. 2. In other embodiments, the number of the pair of the organic composite barrier layers comprising the organic composite barrier layers210and220is not limited to the numbers stated above, but according to design.

Embodiments provide a flexible base material having an organic composite barrier layer and an anti-curved layer, which are continuously growing in the same vacuum chamber. Therefore, the time for replacing and transmitting substrates for forming the barrier layers in different vacuum chambers for the conventional process can be reduced. Also, the stress generate from the organic composite barrier layer is cancelled off by more than 90% of the stress the stress generate from the anti-curved layer. Accordingly, one embodiment of a flexible base material can use a simple structure (constructed by, for example, an organic composite barrier layer constructed by a pair of organic layers and an anti-curved layer) to achieve the same moisture-barrier/gas-barrier performance as the conventional multi-layered barrier structure. Additionally, the transmittance for the visible light of one embodiment of a flexible base material is 95% and above. Also, one embodiment of a flexible base material has a good step coverage performance. Therefore, one embodiment of a flexible base material may be especially applied to fabrication processes of a flexible electronic device package, for example, a light emitting package, an OLED device, an optoelectronic display device or a thin film solar cell device.