Transparent display apparatus with transparent electroluminescent display unit

A display apparatus includes a driving substrate and an organic light emitting diode device. The driving substrate includes a display area, a non-display area, a substrate and a transparent driving element. The transparent driving element is disposed in the non-display area to form a transparent region. The organic light emitting diode device is disposed over the driving substrate and located in the display area to form a non-transparent region.

FIELD OF THE INVENTION

The present invention relates to an electroluminescent display unit and its applications, and more particularly to a transparent electroluminescent display unit of a transparent display apparatus and its applications.

BACKGROUND OF THE INVENTION

Since a transparent display apparatus itself contains a certain degree of light transmission, in addition to the original display function, the background behind the screen thus can be revealed. Such that, a transparent display apparatus can be applied to large-scale commercial demonstration and decoration of glass curtain walls, vehicle windows and shop windows. In terms of some design and performance aspects, the transparent display apparatus can show functions that many existing display technologies are difficult to achieve, hence it can be expected that the transparent display apparatus will replace parts of the existing display apparatuses in the future, and can be extensively applied to consumer electronic products, such as smart phones, notebook computers and portable electronic components.

An organic light emitting diode having advantages of simple processes, light, thin, flexible, colorful and a transparent self-luminous layer, has gradually become the main light source for producing the transparent display apparatus. In order to balance the injection carriers, transparent material of indium tin oxide (InSnO) with high work function is adopted by traditional organic light emitting diodes serving as the bottom anode electrodes. In addition, transparent or translucent material, mainly composed of InSnO, may be used to replacing the traditional metal layer to form a cathode electrode for purpose of enhancing its optical transmission property.

However, the cathode electrode mainly composed of transparent InSnO is difficult to be combined with the organic light emitting layer, such that the mass production technologies are still unable to be established. Moreover, traditional transparent display apparatus can simultaneously show images on both front side and back side. But this may bother the users who attach importance to privacy and don't want to show the contents displayed from the back side of the display apparatus.

Therefore, it is necessary to provide a transparent display apparatus with simple process, performing the functions of displaying images and revealing the background, as well as simultaneously taking the privacy of users into account.

SUMMARY OF THE INVENTION

One aspect of the present invention is to provide a display apparatus, wherein the display apparatus includes a driving substrate and an organic light emitting diode device. The driving substrate includes a display area, a non-display area, a substrate and a transparent driving element. The transparent driving element is disposed in the non-display area to form a transparent region. The organic light emitting diode device is disposed over the driving substrate and located in the display area to form a non-transparent region.

According to the aforementioned embodiments, a display apparatus including a driving substrate and an organic light emitting diode device is provided, wherein a transparent driving element is formed in a non-display area of the driving substrate by adopting chromium molybdenum (MoCr) thin layer and an InSnO layer to form conductive wires and electrodes of transparent thin film transistors (TFTs) involved in the transparent driving element, as well as by applying transparent oxide semiconductor material to form channel layers of the TFTs. Simultaneously, an organic light emitting diodes having an opaque cathode metal layer is adopted serving as a single-side light source and disposed in a display area of the driving substrate. As a result, the display apparatus can be essentially divided into a transparent area and a non-transparent area.

Because of the transparent area (which composed of the transparent driving element and the channel layers) allowing light passing there through, the background behind the screen thus can be revealed from the transparent area. Besides, since the image may be masked by the opaque cathode metal layer, thus the displayed images may not be observed from the back side of the display apparatus. Therefore, the privacy of users can be taken into account while the display apparatus performs the functions of image displaying and revealing the background behind the screen. Moreover, because the cathode metal layer which is competent to be easily combined with the organic light emitting layer of the organic light emitting diode is adopted, hence the display apparatus with the same elements is suitable for mass production.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is to provide a transparent display apparatus including the functions of displaying image, revealing the background behind the screen and taking the privacy of users into account. In order to make the objects aforementioned and other purposes, features and advantages of the present invention to be more easily understood, the transparent electroluminescence display apparatus10is described as a preferred embodiment.

FIG. 1Ais a schematic top-view for illustrating a portion of a transparent display apparatus10in accordance with an embodiment of the present invention. Typically, the transparent display apparatus10is constituted by a plurality of transparent electroluminescent display unit100. However, for the convenience of description, only one single electroluminescence display unit100is depicted inFIG. 1A.FIG. 1Bis a cross-sectional view depicted along a section line Si to illustrate a portion of the electroluminescent display unit100as shown inFIG. 1A; andFIG. 1Cis a cross-sectional view depicted along a section line S2to illustrate a portion of the electroluminescent display unit100as shown inFIG. 1A.

Each transparent electroluminescent display unit100includes a driving substrate110and an organic light emitting diode device102. The driving substrate110can be divided into a display area122and a non-display area123; and the driving substrate110includes a substrate101and at least one transparent driving element124disposed in the non-display area123, wherein the transparent driving element124includes a plurality transparent TFTs, such as transparent TFTs103and113, and a plurality transparent circuit layers, such as transparent circuit layers104and114.

The transparent TFTs103and113and the transparent circuit layers104and114are disposed over the substrate101and covered with a passivation layer105. The organic light emitting diode device102is disposed over the passivation layer105. The passivation layer105and the organic light emitting diode device102are all covered with a protection layer106. In order to keep the passivation layer105separated from the protection layer106for a constant distance, some spacers121, for example, may be inserted between the passivation layer105and the protection layer106.

The substrate101may be a semiconductor substrate (e.g. silicon substrate), or a flexible plasticized substrate. The passivation layer105and the protection106both are constituted by transparent materials. In other embodiment of the present invention, the material of the passivation layer105and the protection106may be a semiconductor material, such as silicon dioxide, silicon nitride and silicon oxynitride, plastic material, or other suitable transparent dielectric materials.

In one embodiment of the present invention, the electroluminescent display unit100includes at least two transparent circuit layers104and114which are sequentially stacked over the substrate101but not coplanar with etch other, wherein the two transparent circuit layers104and114are isolated from each other by an inner dielectric layer112disposed there between. Besides, the two transparent circuit layers104and114are respectively electrical connected to the transparent thin film TFTs103and113. The transparent circuit layer104preferably is a patterned conductive layer stacked by at least one chromium molybdenum (MoCr) thin layer104aand at least one indium tin oxide (InSnO) layer104b. The transparent circuit layer114is also a patterned conductive layer stacked by at least one MoCr thin layer114aand at least one ITO layer114b. The inner dielectric layer112is also constituted by transparent dielectric material, such as silicon dioxide, silicon nitride, silicon oxynitride, or other transparent dielectric material.

The transparent circuit layer114can be divided into a transparent scan line107and a transparent capacitance line (Cs line)111; the transparent circuit layer104can be divided into a transparent date line109, a transparent power supply line108, and transparent electrodes115and116. In the present embodiment, an extension part107aof the transparent scan line107, a portion of the transparent date line109and a portion of the transparent electrode115are overlapped, so as to constitute a transistor103; and likewise, an extension part108aof the transparent power supply line108, a portion of the Cs line111and a portion of the transparent electrode116are overlapped so as to constitute a transistor113(seeFIG. 1A). In addition, a capacitor (not shown) used to assist the operation of the transistor113may be constituted by the overlap of the Cs line111and another part of the transparent power supply line108.

The transparent TFT103includes a transparent gate electrode constituted by the extension part107aof the transparent scan line107, a transparent source electrode constituted by a portion of the transparent date line109, a transparent drain electrode constituted by a portion of the transparent electrode115, a gate insulator layer constituted by a portion of the inner dielectric layer112, and a semiconductor channel layer117(seeFIG. 1C). The transparent TFT113includes a transparent gate electrode constituted by a portion of the transparent capacitance line111, a transparent source electrode constituted by the extension part108aof the power supply line108, a transparent drain electrode constituted by a portion of the transparent electrode116, a gate insulator layer constituted by a portion of the inner dielectric layer112, and a semiconductor channel layer118(seeFIG. 1B).

Furthermore, the aforementioned drain electrode (the transparent electrode115) of the transparent TFT103is electrically connected to the transparent Cs line111by the interconnection line119penetrating through the inner dielectric layer112; and the drain electrode (the transparent electrode116) of the transparent TFT113is electrically connected to the organic light emitting diode device102by the interconnection line120penetrating through the passivation layer105. The luminescence of the organic light emitting diode device102can be controlled by turning on or off the transparent TFT103and113.

It is worth noting that both of the semiconductor channel layers117and118are made of transparent oxide semiconductor material including indium, gallium, zinc, or any combinations thereof. In some embodiments of the present invention, the oxide semiconductor material is selected from a group consisting of indium oxide (InO), gallium oxide (GaO), zinc oxide (ZnO), indium gallium zinc oxide (InGaZnO), gallium zinc oxide (GaZnO), indium gallium oxide (InGaO) and indium zinc oxide (InZnO). In the present embodiment, the preferred material used to constitute the semiconductor channel layers117and118is amorphous InGaZnO (a-IGZO).

The organic light emitting diode device102which is disposed in the display area122of the driving substrate110includes an anode layer constituted by a transparent electrode102a, an organic electroluminescent layer102band a cathode layer constituted by an opaque metal layer102c. The transparent electrode102a(the anode layer) is formed over the passivation layer105and electrically connected to the drain electrode (the transparent electrode116) of transparent TFT113by the interconnection line120. The organic electroluminescent layer102bis formed over the transparent electrode102aby vapor deposition or roller printing (roll to roll). The opaque metal layer102cis formed over the organic electroluminescent layer102b.

In one embodiment of the present invention, the transparent electrode102ais preferably, but not limited, made of ITO; the preferred material of the opaque metal layer102cis preferably, but not limited, made of aluminum. Light initiated from the organic electroluminescent layer102bcan directly emit out by way of passing through the transparent electrode102a, the passivation layer105and the substrate101; or otherwise emit out indirectly by way of being reflected by the opaque metal layer102cfirstly and then passing through the transparent electrode102a, the passivation layer105and the substrate101(shown as arrow L).

On one hand, because the organic light emitting diode device102includes an opaque metal layer102cserving as a mask to prevent light passing trough the display area122of the driving substrate110, such that a non-transparent area100acan be defined in the display area122. On the other hand, since the other elements (including the transparent driving element124including the transparent TFT103and the transparent circuit layer104) located in the non-display area123are constituted of the transparent material, thus light is allowed passing through the driving substrate110, and a transparent area100bis relatively defined in the non-display area123. As a result, the transparent electroluminescent display unit100can be substantially divided into a transparent area100band a non-transparent area100a(shown inFIG. 1B).

In other words, although the transparent electroluminescent display unit100adopts the opaque metal cathode, it still retains a certain degree of light transmission. Thus, the transparent electroluminescent display unit100has both functions of displaying photo images and displaying the background behind the screen. Furthermore, the privacy of users can be taken account by using the opaque metal layer102cserving as a mask to prevent the images from being observed from the back side of the display apparatus10, as well as to prevent the image contents from being double-sided spied.

It is noteworthy that, nevertheless the MoCr thin layer, the InSnO layer and the oxide semiconductor material has light transmittance greater than 90% which can make the transparent area100bhave good optical transmission property, in a preferred embodiment of the present invention, the transparent TFT103and the transparent circuit layer104are generally disposed in the transparent area100b, and not overlapping the organic light emitting diode device102, in order to enhance the luminous efficiency of the organic light emitting diode device102.

In sum, the embodiments of the present invention are to provide a display apparatus including a driving substrate and an organic light emitting diode device. On one hand, an organic light emitting diode device having an opaque cathode metal layer is disposed in the display area of the driving substrate serving as a single-side light source. On the other hand, MoCr thin layers and InS nO layers are used to form transparent wires and the electrodes of TFTs involved in the display apparatus; and transparent oxide semiconductor material is used to form the channel of the TFTs and the transparent driving element disposed in the non-display area of the driving substrate. Since the MoCr thin layers, the InS nO layers and the oxide semiconductor material have light transmittance greater than 90%, thus the portion of the display apparatus not being covered by the opaque organic light emitting diode device may have good optical transmission property. As a result, the display apparatus can be substantially divided into a transparent area and a non-transparent area.

Because the displayed images are masked by the opaque cathode metal layer, thus the image contents can not be observed from the back side of the display apparatus. Therefore, the privacy of users can be taken into account simultaneously while the display apparatus performs the functions of displaying images and revealing the background behind the screen. Moreover, it is no longer necessary adopting InSnO to form the cathode metal layer. Instead, a cathode metal layer competent to be easily combined with the organic light emitting layer of the organic light emitting diode is adopted. Such that, the process for forming the display apparatus can be simplified and thus is more suitable for mass production.