Display device and flexible display device

Provided is a display device including: a base material; a display region over the base material; a wiring over the base material, the wiring extending from the display region to an outside of the display region; and a pair of metal films over the base material, where the wiring is located between the pair of metal films in a plane view. The display region may be positioned between the pair of metal films, and the wiring and the pair of metal films may exist in the same layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority from the prior Japanese Patent Application No. 2016-035351, filed on Feb. 26, 2016, the entire contents of which are incorporated herein by reference.

FIELD

The present invention relates to a display device exemplified by a flexible EL display device.

BACKGROUND

As a typical example of a display device, a liquid crystal display device and an organic EL (electroluminescence) display device respectively having a liquid crystal element and a light-emitting element in each pixel are represented. These display devices have a display element such as a liquid crystal element and an organic light-emitting element (hereinafter, referred to as a light-emitting element) in each of a plurality of pixels formed over a substrate. A liquid crystal element and a light-emitting element include a liquid crystal and a layer containing an organic compound (hereinafter, referred to as an organic layer), respectively, between a pair of electrodes and are driven by applying a voltage or supplying a current to the pair of electrodes.

Since a light-emitting element is an all-solid display element, display quality is not influenced in principle even if a display device is provided with flexibility and folded or bent. This feature has been utilized to fabricate a so-called flexible display (sheet display) in which a light-emitting element is formed over a flexible substrate. For example, a flexible organic EL display device which is foldable is disclosed in Japanese patent application publication 2013-15835.

SUMMARY

An embodiment of the present invention is a display device including: a base material; a display region over the base material; a wiring over the base material, the wiring extending from the display region to outside of the display region; and a pair of metal films over the base material, where the wiring is located between the pair of metal films.

An embodiment of the present invention is a display device including: a base material; a display region over the base material; a wiring over the base material, the wiring extending from the display region to an outside of the display region; and a metal film over the base material in a plane view. The base material is configured to provide a bent region which is folded and two flat regions sandwiching the bent region, and the metal film extends through the bent region and the two flat regions.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the embodiments of the present invention are explained with reference to the drawings. Note that the present invention can be implemented in a variety of modes within the concept of the invention, and the interpretation should not be limited by the disclosure in the embodiments represented below.

In the drawings, the width, thickness, shape, and the like of each component may be schematically illustrated and different from those of an actual mode in order to provide a clearer explanation. However, the drawings simply give an example and do not limit an interpretation of the present invention. In the specification and each of the drawings, elements which are the same as those explained in the preceding drawings are denoted with the same reference numbers, and their detailed explanation may be omitted appropriately.

In the present invention, when a plurality of films is formed by processing a single film, the plurality of films may have functions or roles different from each other. However, the plurality of films originates from the film which is formed as the same layer in the same process. Therefore, the plurality of films is defined as the films existing in the same layer.

First Embodiment

In the present embodiment, a display device according to an embodiment of the present invention is explained by usingFIG. 1toFIG. 4B.

A top view of the display device100according to the present embodiment is shown inFIG. 1. The display device100has a display region104including a plurality of pixels106and a gate side driver circuit (hereinafter, referred to as a driver circuit)108over one surface (top surface) of a base material102. The pixels106are arranged in a matrix form. Wirings110extend from the display region104to a side surface of the base material102(a short side of the display device100in the drawing). The wirings110are exposed at an edge portion of the base material102, and the exposed portions form terminals112. The terminals112are connected to a connector120such as a flexible printed circuit (FPC) by which the connector120is electrically connected to the display region104through the wirings110. In the present embodiment, two driver circuits108are disposed so as to sandwich the display region104. However, one driver circuit108may be provided. Additionally, the driver circuit108may not be formed over the base material102, and a driver circuit formed over another substrate may be formed over the connector120, for example. Note that a part of the connector120is not illustrated inFIG. 1in order to promote understanding.

The display region104is also electrically connected to an IC chip114through the wirings110. Image signals supplied from an external circuit (not shown) are provided to the pixels106via the driver circuits108and the IC chip114by which light emission of the pixels106is controlled, and an image is reproduced on the display region104. Although not shown, the display device100may possess, for example, a source side driver circuit instead of the IC chip114at a periphery of the display region104.

Flexibility can be provided to the whole of the display device100by using a film with flexibility as the base material102by which the display device100can be deformed by folding or bending the display device. The flexible base material102may also be called a base film.

A light-emitting element is disposed in each pixel106. For example, arrangement of red-emissive, green-emissive, and blue-emissive light-emitting elements in the respective pixels106enables full-color display. Alternatively, a white-emissive light-emitting element may be used in all pixels106, and full-color display may be performed by extracting red, green, and blue colors from the respective pixels106by using a color filter. The color finally extracted is not limited to a combination of red, green, and blue colors, and four kinds of colors of red, green, blue, and white can be extracted from the pixels106, for example. The arrangement of the pixels106is also not limited, and a stripe arrangement, a delta arrangement, a mosaic arrangement, and the like can be employed.

The display device100further possesses a power source line116over the base material102. As described below, the light-emitting element provided in each pixel106has a pair of electrodes sandwiching an organic layer, and one electrode is formed to cover the organic layer, while being electrically connected to the power source line116. The power source line116also extends to the side surface of the base material102and is electrically connected to the connector120at the edge portion.

The display device100is provided with a metal film118along the side surface (long side of the display device100in the drawing) different from the side surface of the base material102used for the connection with the connector120. Two metal films118are disposed to form a pair in the present embodiment, and the wirings110are arranged so as to be sandwiched between the pair of metal films118. Furthermore, the power source line116is arranged so as to be sandwiched by the pair of metal films118. The metal films118may be electrically floated or applied with a constant potential. As shown inFIG. 1, the metal films118are preferably arranged so as to reach the side surface of the base material102used for the connection with the connector120.

Schematic cross-sectional views along straight lines A-B and C-D shown inFIG. 1are given inFIG. 2andFIG. 3, respectively. In the cross section A-B ofFIG. 2, the display region104and a region (contact region)105used for the connection of one electrode of the light-emitting element with the power source line116are illustrated.

As shown inFIG. 2, elements such as a transistor122, a capacitor124, and the light-emitting element126are disposed in the pixel106in the display region104. The configuration of each element in the pixel106is not limited to such a configuration, and the pixel106may include a plurality of transistors and a plurality of capacitors.

Referring toFIG. 2, a semiconductor film132is formed over the base material102with a base film130interposed therebetween. As a material usable for the base material102, glass, quartz, a metal, and the like are represented. When flexibility is provided to the display device100, a polymer material such as a polyimide, a polyester, and an acrylic resin can be used for the base material102, for example. The base film130can include an inorganic material such as silicon oxide, silicon nitride, silicon oxynitride, and silicon nitride oxide and can be formed with a chemical vapor deposition method (CVD method), a sputtering method, and the like. InFIG. 2, an example is illustrated in which the base film130has a three-layer structure. In such a case, the base film130may be formed, for example, by stacking a silicon oxide film, a silicon nitride film, and a silicon oxide film in this order. The lowest silicon oxide film is provided to improve adhesion with the base material102, the middle silicon nitride layer is provided as a blocking film to prevent entrance of impurities such as water from outside, and the upmost silicon oxide film is provided as a blocking film to prevent diffusion of hydrogen atoms included in the silicon nitride film to the elements such as the transistor122. However, the base film130is not particularly limited to this structure. Another layer may be additionally stacked, and the base film130having a single-layer or two-layer structure may be used.

The semiconductor film132can be formed with silicon or a metal oxide exhibiting a semiconductor property by applying a CVD method, a sputtering method, and the like. There is no limitation to the crystallinity of the semiconductor film132, and the semiconductor film132may have any crystal state selected from amorphous, polycrystalline, microcrystalline, and single crystalline states.

The display device100possesses a gate insulating film134over the semiconductor film132. An inorganic compound such as silicon oxide, silicon nitride, silicon oxynitride, and silicon nitride oxide can be used for the gate insulating film134, and the gate insulating film134can be formed by applying a CVD method, a sputtering method, and the like. A first metal layer is formed over the gate insulating film134, and etching processing thereof allows the formation of a gate electrode136of the transistor122and one electrode138of the capacitor124in the pixel106. Therefore, the gate electrode136and the electrode138exist in the same layer.

The first metal layer can be formed with a metal or an alloy by applying a sputtering method and the like. As a metal, aluminum, copper, titanium, tungsten, molybdenum, tantalum, and the like can be used, and the first metal layer may be formed in a single-layer structure or a stacked-layer structure. For example, a stacked layer of titanium and aluminum and a structure in which a highly conductive metal such as aluminum and copper is sandwiched by a metal with a high melting point, such as titanium and molybdenum, can be employed. Since the gate electrode136and the electrode138exist in the same layer, both have the same layer structure and include the same material.

The semiconductor film132may have a source-drain region doped with an impurity and a channel region. In this case, the impurity is doped by using the gate electrode136as a mask. The semiconductor film132may further include, between the channel region and the source-drain region, a region (low-concentration impurity region) doped with an impurity at a concentration lower than that of the source-drain region.

An interlayer film140is disposed over the gate electrode136and the electrode138. The interlayer film140can be formed by using the material usable in the base film130and the gate insulating film134as a single-layer structure or a stacked-layer structure. For example, the interlayer film140may be formed as a stacked-layer structure of a silicon nitride film and a silicon oxide film. The interlayer film140has a function to protect the transistor122and simultaneously has a function as a dielectronic film of the capacitor124.

The display device further possesses a source electrode142and a drain electrode144over the interlayer film140. The source electrode142and the drain electrode144are electrically connected to the semiconductor film132in opening portions provided in the interlayer film140and the gate insulating film134. The transistor122is constructed by the semiconductor film132, the gate insulating film134, the gate electrode136, the source electrode142, and the drain electrode144. Note that the drain electrode144is also formed over the electrode138, and the capacitor124is structured by the electrode138, the interlayer film140and a portion of the drain electrode144, which overlaps with the electrode138. The source electrode142and the drain electrode144are formed by forming a second metal layer over the interlayer film140, followed by performing etching processing. Hence, the source electrode142and the drain electrode144exist in the same layer. The second metal layer can be formed with a material usable in the first metal layer by applying a CVD method, a sputtering method, and the like. For example, a stacked-layer structure in which an aluminum film is sandwiched by titanium films can be employed.

Note that the wirings110shown inFIG. 1can also be formed simultaneously with the source electrode142and the drain electrode144(seeFIG. 3). Therefore, the wirings110can exist in the same layer as the source electrode142and the drain electrode144.

A leveling film146is provided over the source electrode142and the drain electrode144in order to absorb steps caused by the transistor122and the capacitor124and give a flat top surface. The leveling film146can be formed with a polymer material such as an acrylic resin, a polyimide, and a polysiloxane by applying a spin-coating method, an ink-jet method, a printing method, a dip-coating method, and the like. As shown inFIG. 2, the base film130, the gate insulating film134, the interlayer film140, and the leveling film146are provided not only in the display region104but also in the contact region105. Note that, although the semiconductor film132is not included in the contact region105of the present embodiment, the semiconductor film132may be formed in the contact region105.

The display device100has connection wirings148and149over the leveling film146. In the contact region105, the connection wring149is formed over the flat top surface of the leveling film146. In the display region104, the connection wiring148is formed so as to cover an opening portion which is formed in the leveling film146and reaches the drain electrode144. Although not shown, the leveling film146over the terminals112shown inFIG. 1is also removed simultaneously when the opening portion is formed. The connection wirings148and149can be formed by forming, over the leveling film146, a film containing a conductive oxide with a light-transmitting property, such as indium-tin oxide (ITO) and indium-zinc oxide (IZO), under the application of a sputtering method and the like, followed by performing etching processing thereon, for example. Thus, the connection wirings148and149exist in the same layer. Note that the conductive oxide with a light-transmitting property is also formed over the terminals112simultaneously when the connection wirings148and149are formed, which allows a stable electrical connection between the terminals112and the connector120.

The display device100further includes an insulating film154over the capacitor wiring150and the auxiliary wiring152. The insulating film154can be formed by using a material such as silicon nitride which is usable in the gate insulating film134and the interlayer film140. The insulating film154has opening portions to expose a contact portion for the electrical connection between the transistor122and the light-emitting element126(i.e., a bottom surface of the connection wiring148formed in the opening portion of the leveling film146), a part of the power source line116, and a part of the surface of the leveling film146.

The display device100further has the first electrode158, the organic layer162, and the second electrode164which configure the light-emitting element126. When the light-emission from the light-emitting element126is extracted through the base material102, a material with a light-transmitting property exemplified by a conductive oxide such as ITO and IZO can be used for the first electrode158. On the other hand, when the light-emission from the light-emitting element126is extracted from a second electrode164side, a metal such as aluminum and silver or an alloy thereof can be used. Alternatively, a stacked layer of the aforementioned metal or alloy and a conductive oxide, such as a stacked-layer structure in which a metal is sandwiched by a conductive oxide (e.g., ITO/silver/ITO), can be employed. Note that a capacitor is additionally formed by the first electrode158, the capacitor wiring150, and the insulating film154interposed therebetween.

When the light-emission from the light-emitting element126is extracted through the base material102, the second electrode164can be formed by using a metal such as aluminum and silver or an alloy thereof. On the contrary, when the light-emission from the light-emitting element126is extracted through the second electrode164, the second electrode164may be formed with the aforementioned metal or alloy to have a thickness which allows visible light to pass therethrough. Alternatively, the second electrode164may be formed with a material having a light-transmitting property, such as a conductive oxide exemplified by ITO and IZO. Furthermore, a stacked-layer structure of the aforementioned metal or alloy and a conductive oxide (e.g., Mg—Ag/ITO etc.) can be employed as the second electrode164.

Here, a partition wall160is provided over the first electrode158in order to absorb steps caused by an edge portion of the first electrode158and the opening portion provided in the leveling film146and to electrically insulate the first electrodes158of the adjacent pixels106from each other. The partition wall160is also called a bank (rib). The partition wall160can be formed with a material usable in the leveling film146. The partition wall160has an opening portion to expose the first electrode158and a part of the power source line116, and an edge portion thereof preferably has a moderately tapered shape. A steep incline of the edge portion of the opening portion with respect to the first electrode158readily leads to a coverage defect of the organic layer162and the second electrode164. The leveling film146and the partition wall160contact with each other via the opening156formed in the insulating film154. The use of such a structure allows a gas such as vapor, which is eliminated from the leveling film146in a heating treatment and the like conducted after the formation of the partition wall160, to be released through the partition wall160.

InFIG. 2, the organic layer162is illustrated so as to have a single-layer structure. However, the organic layer162may have a structure in which a plurality of layers is stacked. For example, the organic layer162can include a layer such as a charge-injection layer, a charge-transporting layer, an emission layer, a charge-blocking layer, and a charge-generation layer as appropriate. It is possible to employ the organic layer162with the same structure in all pixels106, and organic layers with different structures may be used in the adjacent pixels106. The organic layer162can be formed with an evaporation method, an ink-jet method, a printing method, a spin-coating method, and the like. Carriers (holes and electrons) are injected from the first electrode158and the second electrode164into the organic layer162, and the light-emission can be obtained through a process in which an excited state obtained by carrier recombination relaxes to a ground state. Hence, a region of the light-emitting element126, in which the organic layer162and the first electrode158are in direct contact with each other, is an emission region.

The second electrode164of the light-emitting element126extends to the contact region105and is electrically connected to the connection wiring149. Hence, when the first electrode158functions as an anode, the current supplied through the transistor122flows in the first electrode158, the organic layer162, the second electrode164, and the power source line116in this order.

The display device100further includes a protection film166(passivation film) over the second electrode164. The protection film166has a function to prevent moisture from entering to the light-emitting element126from outside and preferably has a high gas-barrier property. For example, it is preferred that the protection film166be prepared by using an inorganic material such as silicon nitride, silicon oxide, silicon nitride oxide, and silicon oxynitride. Alternatively, an organic resin including an acrylic resin, a polysiloxane, a polyimide, a polyester may be used. For instance, a stacked-layer structure of a film formed with an inorganic material and a film formed with an organic resin may be employed. Specifically, a stacked-layer structure of silicon nitride, silicon oxide, an acrylic resin, and silicon nitride is represented. Each of these layers may be formed with an evaporation method, a CVD method, a sputtering method, and the like.

As an optional structure, the display device100may have an opposing substrate over the protection film166. The opposing substrate is fixed to the base material102through the protection film166by using an adhesive. In this case, the display device100may contain an inert gas or a filler such as a resin in a space between the opposing substrate and the protection film166. When a filler is included, the filler preferably has high transparency with respect to visible light. The opposing substrate may have a light-shielding film having an opening in a region overlapping with the emission region and a color filter in a region overlapping with the emission region. The light-shielding film is formed with a metal having a relatively low reflectance, such as chromium and molybdenum, or a resin material containing a coloring material of black or a similar color and has a function to block scattered light and reflected ambient light other than the light directly obtained from the emission region. Optical properties of the color filter may be changed in every pixel106, and the color filter may be formed so as to extract red, green, and blue emissions, for example. The light-shielding film and the color filter may be provided to the opposing substrate with a base film interposed therebetween. An overcoat may be further disposed so as to cover the light-shielding film and the color filter.

When the display device100possesses the opposing substrate, the opposing substrate and the base material102are bonded with an adhesion arranged at a periphery of the display region104so that the light-emitting element126is sandwiched between the opposing substrate and the base material102. The adhesive may contain a spacer to adjust an interval between the opposing substrate and the base material102. Alternatively, the display device100may have a structural member serving as a spacer between the pixels106in the display region104.

Referring toFIG. 3, the metal film118is formed over the gate insulating film134formed in the transistor122. This metal film118can also be prepared by performing etching processing on the first metal layer. Therefore, the metal film118exists in the same layer as the gate electrode136of the transistor122and the electrode138of the capacitor124. Specifically, the metal film118, the gate electrode136of the transistor122, and one electrode138of the capacitor124are disposed between two insulating films (gate insulating film134and interlayer film140). As described above, the wirings110are arranged over the interlayer film140and can be formed by performing etching processing on the second metal layer. Hence, the wirings110exist in the same layer as the source electrode142and the drain electrode144of the transistor122. The power source line116is formed over the leveling film146over which the insulating film154, the partition wall160, and the protection film166are arranged.

As described above, the use of the flexible base material102enables flexibility to be provided to the whole of the display device100. For example, as shown inFIG. 4A, the display device100can be folded by using an imaginary axis170shown inFIG. 1as a center so that the display region104is positioned outside. Here, the axis170is an axis of the bent region and a circumference of the axis has at least a part of the bent region. In this case, as shown inFIG. 4A, a bent region and two flat regions sandwiching the bent region are formed, where the bent region is positioned between the display region104and the connector120and the display region104and the terminals112are located in the two flat regions. When the display device100is thus folded, the largest stress is applied to the bent region. Therefore, this region is readily damaged when being bent. Damage tends to occur at the edge portion of the base material102, and a crack180is caused from the edge portion of the base material102in a region close to the axis170as shown inFIG. 4B. The crack180extends inside from the edge portion of the base material102, which induces damage and disconnection of the power source line116and the wirings110.

The display device100of the present embodiment has the pair of metal films118so that the wirings110and the power source line116are sandwiched between the pair of metal films118. Furthermore, the metal films118are arranged so as to overlap or intersect with the axis170about which the display device100is to be folded. InFIG. 1, the metal films118extend in a direction perpendicular to the axis170. When the display device100having such a structure is folded, the metal films118are included not only in the flat regions but also in the bent region. In this case, even if the crack180is caused at the edge portion of the base material102, extension of the crack180is terminated or an extension rate of the crack180is markedly decreased when the crack180reaches the metal films118. Hence, damage and disconnection of the power source line116and the wirings110can be prevented, which enables improvement of reliability of the display device100.

Second Embodiment

In the present embodiment, a display device according to an embodiment of the present invention is explained by usingFIG. 5AtoFIG. 7. Explanation of the structures which are the same as those of the First Embodiment is omitted.

In the First Embodiment, the metal films118exist in the same layer as the gate electrode136of the transistor122included in the pixel106, whereas the wirings110electrically connecting the connector120and the display region104exist in the same layer as the source electrode142and the drain electrode144of the transistor122. In the present embodiment, the positional relationship between the metal films118, the wirings110, and the power source line116is different from that of the First Embodiment.

Specifically, as shown inFIG. 5A, the metal films118can exist in the same layer as the wirings110and arranged over the interlayer film140of the transistor122and under the leveling film146. Hence, the metal films118can exist in the same layer as the source electrode142and the drain electrode144of the transistor122.

Alternatively, as shown inFIG. 5B, it is possible to arrange the metal films118over the gate insulating film134of the transistor122and under the interlayer film140although the metal films118exist in the same layer as the wirings110. Therefore, the metal films118can exist in the same layer as the gate electrode136of the transistor122.

Alternatively, as shown inFIG. 6A, it is also possible to arrange the metal films118between the interlayer film140and the leveling film146and arrange the wirings110between the gate insulating film134and the interlayer film140although the metal films118and the wirings110exist in different layers from each other. In other words, the metal films118can exist in the same layer as the source electrode142and the drain electrode144of the transistor122.

Alternatively, as shown inFIG. 6B, it is also possible to arrange the metal films118between the leveling film146and the insulating film154although the metal films118and the wirings110exist in different layers from each other. In other words, the metal films118can exist in the same layer as the power source line116or the auxiliary wiring152of the power source line116.

Alternatively, as shown inFIG. 7, it is also possible to arrange the metal films118between the leveling film146and the insulating film154so as to exist in the same layer as the connection wiring149although the metal films118and the wirings110exist in different layers from each other.

Similar to the First Embodiment, the display device100of the present embodiment has the metal films118, and the wirings110and the power source line116are arranged in a position that is far from the edge portion of the base material102compared with the metal films118. Therefore, in the case where the base material102has flexibility, even if the crack180is caused at the edge portion of the base material102by deforming the display device100, extension of the crack180is terminated or an extension rate of the crack180is markedly decreased when the crack180reaches the metal films118. Hence, damage and disconnection of the power source lines116and the wirings110can be prevented, which enables improvement of reliability of the display device100.

Third Embodiment

In the present embodiment, a display device according to an embodiment of the present invention is explained by usingFIG. 8AtoFIG. 8C. Explanation of the structures which are the same as those of the First and Second Embodiments is omitted.

The metal films118of the present embodiment are different in plane shape from that of the First or Second Embodiment. Specifically, as shown in a region surrounded by a dotted ellipse inFIG. 8A, the metal films118can have a projected portion in a direction intersecting with the wirings110. Although the projected portion has a shape protruding to a direction opposing the edge portion of the base material102inFIG. 8A, the metal films118may have the projected portion protruding in a direction to the edge portion. In this case, the projected portion may reach the edge portion of the base material102. Furthermore, the metal films118may have a projected portion extending in both a direction to the edge portion of the base material102and a direction to the wirings110.

Alternatively, as shown inFIG. 8B, the metal films118may be arranged so that at least a part of the metal films118intersects with the wirings110and the power source lines116. In this case, the metal films118may be arranged so that a part of the metal films118perpendicularly intersects with the wirings110, the power source line116, or a part of these wirings. Additionally, the pair of metal films118shown inFIG. 1may be connected to each other. Alternatively, as shown inFIG. 8C, the whole of the metal films118may extend in a direction intersecting with the wirings110or may be arranged so as to perpendicularly intersect with the wirings110and the power source line116.

When the display device100is intended to be folded, the metal films118having the shapes shown in the present embodiment are provided in a portion giving the bent region, by which the metal films118can be arranged in parallel to the axis170about which the display device100is folded. Hence, even if the crack180is caused at the edge portion of the base material102in the bent region, the extension of the crack180can be effectively and certainly prevented, which enables production of a flexible display device with high reliability.

Fourth Embodiment

In the present embodiment, a display device according to an embodiment of the present invention is explained by usingFIG. 9andFIG. 10. Explanation of the structures which are the same as those of the First to Third Embodiments is omitted.

The metal films118of the present embodiment are different in plane layout from that of the First to Third Embodiments. Specifically, as shown inFIG. 9, the display device100is provided with a pair of metal films118so as to sandwich the display region104. Alternatively, as shown inFIG. 10, the pair of metal films118is arranged so as to sandwich both of the wirings110and the display region104.

When an image is reproduced on the display region104, frequency of folding the display region104is relatively low generally. However, in the case where the display region104is unintentionally folded, that is, in the case where the display device100is folded so that the display region104is included in the bent region, even if the crack180is caused at the edge portion of the base material102close to the display region104, extension of the crack180can be terminated or an extension rate of the crack180can be decreased. Accordingly, not only the wirings110but also the display region104can be prevented from being damaged, which enables production of a flexible display device with high reliability.

The aforementioned modes described as the embodiments of the present invention can be implemented by being appropriately combined with each other as long as no contradiction is caused. Furthermore, any mode which is realized by persons ordinarily skilled in the art through the appropriate addition, deletion, or design change of elements or through the addition, deletion, or condition change of a process is included in the scope of the present invention as long as they possess the concept of the present invention.

In the specification, although cases of the organic EL display device are exemplified, the embodiments can be applied to any kind of display devices of a flat panel type such as other self-emission type display devices, liquid crystal display devices, and electronic paper type display device having electrophoretic elements and the like. In addition, it is apparent that the size of the display device is not limited, and the embodiment can be applied to display devices having any size from medium to large.

It is properly understood that another effect different from that provided by the modes of the aforementioned embodiments is achieved by the present invention if the effect is obvious from the description in the specification or readily conceived by the persons ordinarily skilled in the art.