Light-emitting device, display device, and method for manufacturing the same

It is known that a light-emitting element utilizing organic EL deteriorates due to moisture. Therefore, a sealing technique to prevent moisture permeation is important. A light-emitting device including a light-emitting element utilizing organic EL is manufactured over a support substrate having flexibility and a high heat dissipation property (e.g., stainless steel or duralumin), and the light-emitting device is sealed with a stack body having moisture impermeability and a high light-transmitting property or with glass having moisture impermeability and a high light-transmitting property and having a thickness greater than or equal to 20 μm and less than or equal to 100 μm.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light-emitting element utilizing organic electroluminescence (EL). The present invention relates to a light-emitting device, a lighting device, and a display device each including the light-emitting element.

2. Description of the Related Art

A light-emitting element utilizing organic EL has been actively researched and developed. A fundamental structure of the light-emitting element utilizing organic EL is a structure in which a layer containing a light-emitting organic compound is interposed between a pair of electrodes. By voltage application to this light-emitting element, light emission from the light-emitting organic compound can be obtained.

The light-emitting element utilizing organic EL can be formed in a film shape; thus, a large-area light-emitting device can be easily formed. Therefore, the light-emitting device has a high utility value as a surface light source.

For example, a lighting device to which a light-emitting element utilizing organic EL is applied is disclosed in Patent Document 1.

REFERENCE

SUMMARY OF THE INVENTION

It is known that a light-emitting element utilizing organic EL deteriorates due to moisture. Therefore, a sealing technique to prevent moisture permeation is important.

In the case where a light-emitting element is sealed, it is necessary to use a sealing material having a light-transmitting property and moisture impermeability at least on the irradiation side of light. For example, glass can be used as the sealing material having a light-transmitting property and moisture impermeability.

However, normal glass has a low heat dissipation property; therefore, a light-emitting element utilizing organic EL deteriorates due to heat generation when light is emitted at high luminance for a long time.

In addition, glass breaks easily because of its weak strength. However, there is another problem in which the weight of a light-emitting device including a light-emitting element utilizing organic EL is increased when the thickness is increased to obtain sufficient strength.

The present invention is made in view of the foregoing technical background. Therefore, an object of the present invention is to provide a light-emitting device utilizing organic EL, which has less deterioration and less weight.

Another object of the present invention is to provide a lighting device to which the light-emitting device according to one embodiment of the present invention is applied.

Further, another object of the present invention is to provide a display device to which the light-emitting device according to one embodiment of the present invention is applied.

In the light-emitting device according to one embodiment of the present invention, a light-emitting element utilizing organic EL is formed over a support substrate having flexibility and a high heat dissipation property (e.g., stainless steel (also referred to as SUS) or duralumin), and the light-emitting element is sealed with a stack body having moisture impermeability and a high light-transmitting property or with glass having a thickness greater than or equal to 20 μm and less than or equal to 100 μm which has moisture impermeability and a high light-transmitting property.

Alternatively, the light-emitting device according to one embodiment of the present invention is a light-emitting device in which a transistor formed over a glass substrate, a quartz substrate, a silicon wafer, or the like is transferred to a support substrate having flexibility and a high heat dissipation property by a separation technique. Note that in this specification, “moisture impermeability” or “low moisture permeability” means that a water vapor permeability coefficient is lower than or equal to 1×10−6g/(m2·day), preferably lower than or equal to 1×10−7g/(m2·day).

Alternatively, one embodiment of the present invention provides a light-emitting device including a base insulating film over a support substrate having flexibility and a high heat dissipation property; a first electrode over the base insulating film; an organic EL layer over the first electrode; a light-transmitting second electrode over the organic EL layer; and a stack body having moisture impermeability and a high light-transmitting property which is bonded with a sealant, or glass having a thickness greater than or equal to 20 μm and less than or equal to 100 μm which has moisture impermeability and a high light-transmitting property; and a method for manufacturing the light-emitting device.

Note that the first electrode preferably has a reflectance greater than or equal to 90% in a visible light region (in the wavelength of 400 nm to 800 nm). In addition, the second electrode preferably has transmittance greater than or equal to 80% in the visible light region.

Another embodiment of the present invention is a lighting device including the light-emitting device and a method for manufacturing the lighting device.

Another embodiment of the present invention is a display device including the light-emitting device and a method for manufacturing the display device.

According to one embodiment of the present invention, a light-emitting device utilizing organic EL, which has less deterioration and less weight, can be provided.

A lighting device to which the light-emitting device according to one embodiment of the present invention is applied can be provided.

Further, a display device to which the light-emitting device according to one embodiment of the present invention is applied can be provided.

DETAILED DESCRIPTION OF THE INVENTION

“Depositing” refers to, for example, forming a film by an evaporation method, a sputtering method, a pulse laser deposition (PLD) method, a molecular beam epitaxy (MBE) method, a plasma chemical vapor deposition (CVD) method, a thermal CVD method, a metal organic chemical vapor deposition (MOCVD) method, an atomic layer deposition (ALD) method, an ink-jet method, or the like.

“Processing” refers to, for example, obtaining a desired shape of by etching the deposited film. For example, a resist mask may be formed by a photolithography method, and etching treatment may be performed on a region which is not covered with the resist mask. Alternatively, a photosensitive material may be processed into a desired shape by a photolithography method. Note that a laser drawing method may be employed instead of a photolithography method.

The term “forming” indicates, for example, that a film is subjected to a deposition step and a processing step. However, in an ink-jet method, a desired shape can be obtained at the same time as deposition; therefore, the term “forming” is also used in such a case.

In this embodiment, a light-emitting device including a light-emitting element according to one embodiment of the present invention will be described with reference toFIGS. 1A and 1B,FIGS. 2A to 2D,FIGS. 3A and 3B, andFIGS. 4A to 4D.FIG. 1Ais a cross-sectional view taken along the dashed-dotted line A-B in the top view ofFIG. 1B.

FIG. 1Aillustrates a light-emitting device including: a first substrate100; a base insulating film102over the first substrate100; a plurality of adjacent first electrodes104provided over the base insulating film102; a partition wall106covering end portions of the adjacent first electrodes104; a partition wall108provided over each of the first electrodes104; a partition wall110provided over the first electrode104and the partition wall108; an organic EL layer112over the first electrodes104and the partition walls106,108, and110; a second electrode114which covers the organic EL layer112and is partly in contact with the first electrode104; and a protective insulating film116covering the second electrode114. In the partition wall110, the shape on the side in contact with the organic EL layer112is larger than the shape on the side in contact with the first electrode104when seen from the above. The light-emitting device is bonded to a second substrate150with a sealant118, and a resin151having a structure with a lens shape is provided over the second substrate150, and a resin154having a structure with a lens shape is provided over the resin151. Note that the resins151and154may be a resin having a three-dimensional structure such as a honeycomb structure instead of the structure with a lens shape.

Note that the protective insulating film116is provided so that moisture or the like does not enter the organic EL layer112; however, the protective insulating film116is not necessarily provided when there is sufficient sealing performance.

Note that the light-emitting device described in this embodiment is not necessary limited to the structure in which one or both of the resin151and the resin154are provided over the second substrate150. Since the resins151and154each have the structure with a lens shape, as an advantageous effect, the rate of total reflection of light emitted from a light-emitting region140including the first electrode104, the organic EL layer112, and the second electrode114on a surface from which light is emitted (an interface with the air) can be reduced. However, the rate of total reflection of light on the interface between the second substrate150and the air can also be reduced by appropriately controlling the refractive indexes of the layers and the substrate; therefore, the resins151and154are not needed in some cases. Here, a space120is generated between the light-emitting device and the second substrate150. A drying agent may be put in the space120in order to prevent deterioration of the organic EL layer112. A drying agent may also be included in the sealant118or the like. Note that the space120may be filled with an organic compound or an inorganic compound having a light-transmitting property in a visible light region, such as an epoxy resin.

For the first substrate100, a material having flexibility and a high heat dissipation property is used. For example, a metal material or a metal alloy such as aluminum, titanium, nickel, copper, silver, SUS, or duralumin may be used with a thickness greater than or equal to 20 μm and less than or equal to 700 μm, preferably greater than or equal to 50 μm and less than or equal to 300 μm. Note that duralumin is a material having low corrosion resistance; therefore, the surface of duralumin is preferably coated with a material having high corrosion resistance.

The base insulating film102is not particularly limited as long as a material having an insulating property is used. For example, an organic compound or an inorganic compound may be used. As an organic compound, acrylic, polyimide, epoxy, and siloxane can be given, for example. As an inorganic compound, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, aluminum oxynitride, aluminum nitride oxide, and aluminum nitride can be given, for example.

Silicon oxynitride contains more oxygen than nitrogen and for example, silicon oxynitride includes oxygen, nitrogen, silicon, and hydrogen at concentrations ranging from greater than or equal to 50 atomic % and less than or equal to 70 atomic %, greater than or equal to 0.5 atomic % and less than or equal to 15 atomic %, greater than or equal to 25 atomic % and less than or equal to 35 atomic %, and greater than or equal to 0 atomic % and less than or equal to 10 atomic %, respectively. In addition, silicon nitride oxide contains more nitrogen than oxygen and for example, silicon nitride oxide includes oxygen, nitrogen, silicon, and hydrogen at concentrations ranging from greater than or equal to 5 atomic % and less than or equal to 30 atomic %, greater than or equal to 20 atomic % and less than or equal to 55 atomic %, greater than or equal to 25 atomic % and less than or equal to 35 atomic %, and greater than or equal to 10 atomic % and less than or equal to 25 atomic %, respectively. Note that the above ranges are ranges for cases where measurement is performed using Rutherford backscattering spectrometry (RBS) or hydrogen forward scattering spectrometry (HFS). Moreover, the total of the percentages of the constituent elements does not exceed 100 atomic %.

Aluminum oxynitride contains more oxygen than nitrogen. Aluminum nitride oxide contains more nitrogen than oxygen.

For the first electrode104, a material which efficiently reflects light emitted from the organic EL layer112is preferably used. Further, the first electrode104may have a stacked-layer structure. For example, it is preferable to use a material including lithium, aluminum, titanium, magnesium, lanthanum, silver, silicon, or nickel.

The second electrode114is formed using a conductive film having a light-transmitting property in a visible light region. For the conductive film having a light-transmitting property in a visible light region, for example, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium tin oxide (also referred to as ITO), indium zinc oxide, and ITO to which silicon oxide is added can be given. Further, a metal thin film having a thickness enough to transmit light (preferably, approximately 5 nm to 30 nm) can also be used. For example, a silver film, a magnesium film, or a silver-magnesium (Ag—Mg) alloy film each having a thickness of 5 nm can be used as the second electrode114.

“Having a light-transmitting property in a visible light region” means that transmittance is higher than or equal to 80% in a visible light region.

Note that one of the first electrode104and the second electrode114functions as an anode, and the other functions as a cathode. It is preferable to use a material having a high work function for the electrode which functions as an anode, and a material having a low work function for the electrode which functions as a cathode. Note that in the case where a carrier generation layer is provided in contact with the anode, a variety of conductive materials can be used for the anode regardless of their work functions.

An organic compound may be used for the partition walls106and108. As an organic compound, acrylic, epoxy, polyimide, and siloxane can be given, for example.

For the partition wall110, a material similar to that of the partition walls106and108, a photosensitive resin, or the like may be used.

In the partition wall110, the top surface shape on the side in contact with the organic EL layer112is larger than the bottom surface shape on the side in contact with the first electrode104when seen from the above, that is, the partition wall110has an overhang shape or an inverted tapered shape. In the partition wall110, as long as the top surface shape on the side in contact with the organic EL layer112is larger than the bottom surface shape on the side in contact with the first electrode104when seen from the above, a structure including a partition wall122having a curved surface as illustrated inFIG. 4Cor a structure in which a partition wall124and a partition wall126, whose cross sections are each rectangular, are overlapped with each other as illustrated inFIG. 4Dmay be employed.

In the case of manufacturing a light-emitting device having a broad spectrum, plural kinds of light-emitting material or the like may be stacked as the organic EL layer112. For example, a structure illustrated inFIGS. 4A and 4Bmay be employed. Here,FIG. 4Ais an enlarged diagram of the light-emitting region140inFIG. 1A, andFIG. 4Bis a diagram illustrating an example of the stacked-layer structure of the organic EL layer112in detail.FIG. 4Billustrates a structure in which a first intermediate layer130, a first light-emitting layer131, a second intermediate layer132, a second light-emitting layer133, a third intermediate layer134, a third light-emitting layer135, and a fourth intermediate layer136are stacked in this order. At this time, when materials having appropriate emission colors are used for the first light-emitting layer131, the second light-emitting layer133, and the third light-emitting layer135, a light-emitting device with a higher color rending property or higher emission efficiency can be manufactured, which is preferable.

Although the structure in which three light-emitting layers and four intermediate layers are provided is shown here, the number of light-emitting layers and the number of intermediate layers can be changed as appropriate without limitation thereto. For example, the organic EL layer112can be formed with only the first intermediate layer130, the first light-emitting layer131, the second intermediate layer132, the second light-emitting layer133, and the third intermediate layer134. Alternatively, the organic EL layer112can be formed with only the first intermediate layer130, the first light-emitting layer131, the second intermediate layer132, the second light-emitting layer133, the third light-emitting layer135, and the fourth intermediate layer136with the third intermediate layer134omitted.

In addition, the intermediate layer can be formed using a stacked-layer structure of a hole-injection layer, a hole-transport layer, an electron-transport layer, an electron-injection layer, or the like. Note that not all of these layers need to be provided as the intermediate layer. Depending on the need, a layer or layers can be selected as appropriate from these layers, and each layer can be provided in duplicate or more. Further, an electron-relay layer or the like may be added as appropriate as the intermediate layer, in addition to a carrier generation layer.

As the second substrate150, extremely thin glass having a thickness greater than or equal to 20 μm and less than or equal to 100 μm, for example, approximately 50 μm, may be used. When extremely thin glass is used as the second substrate150, the second substrate150has flexibility to some extent in addition to low moisture permeability and therefore can have high resistance to bending and shock, which results in unlikeliness of breakage, for example.

Alternatively, the second substrate150may be a stack body having flexibility and moisture impermeability, which includes two or more materials selected from silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, aluminum oxynitride, aluminum nitride oxide, aluminum nitride, silicon carbide, diamond-like carbon, or a high molecular material, which is provided over a resin or a sheet having a gas barrier property.

Since the second electrode114, the protective insulating film116, the second substrate150, the resin151, and the resin154each have light-transmitting property in a visible light region, the light-emitting device described in this embodiment has a so-called top emission structure, in which a light emission surface is on the second substrate150side.

In addition, a substrate having a high heat dissipation property is used for the first substrate100, so that heat is easily released from the light-emitting device. Therefore, reduction in reliability due to heat can be suppressed.

Next, a method for manufacturing the light-emitting device illustrated in FIG.1A will be described.

First, the base insulating film102is deposited over the first substrate100(seeFIG. 2A).

Next, a conductive film is deposited over the base insulating film102and processed to form the first electrodes104(seeFIG. 2B).

Next, the partition wall106covering end portions of the first electrodes104and the partition wall108provided over the first electrode104are formed. Then, the partition wall110partly overlapped with the partition wall108are formed (seeFIG. 2C). Note that the partition wall108is provided to prevent the first electrode104and the second electrode114from being in contact with each other in a region where the partition wall108is formed.

The partition wall110can be formed using a negative photosensitive material by a photolithography method. The partition wall110having a structure illustrated inFIG. 4Ccan also be formed in a similar manner. The partition wall110having a structure illustrated inFIG. 4Dcan be obtained in a manner such that the partition wall124is formed using a positive photosensitive material and then the partition wall126is formed using a negative photosensitive material.

Next, the organic EL layer112, the second electrode114, and the protective insulating film116are deposited in this order over the first electrodes104and the partition walls106,108, and110(seeFIG. 2D). Through the above steps, the light-emitting device including the light-emitting region140can be manufactured.

In the case where the partition wall110is formed in an inverted tapered shape, the organic EL layer112, the second electrode114, and the protective insulating film116can be processed into a desired shape without a metal mask. When a metal mask is used, clogging of the metal mask is likely to be caused and dust is likely to be generated as the pattern has higher definition, and the light-emitting region140is damaged by being overlapped with the metal mask. As a result, the quality and the reliability of the light-emitting device are degraded.

At this time, only the peripheral portion of the first substrate100may be covered with a mask to deposit the organic EL layer112, the second electrode114, and the protective insulating film116so that films do not attach to the peripheral portion. Note that the protective insulating film116is not necessarily deposited.

For example, the organic EL layer112is deposited by a deposition method in which an amount of entry to the shadow of an object is small (e.g., an evaporation method, a long throw sputtering method, or a collimated sputtering method). Next, the second electrode114is deposited by a deposition method an amount of entry to the shadow of an object is large (e.g., a MOCVD method or a sputtering method). Then, the protective insulating film116is deposited by a deposition method in which an amount of entry to the shadow of an object is the same as or larger than that in the case of the second electrode114. With such methods, the first electrode104and the second electrode114, which are different light-emitting regions, can be in contact with each other at one place. That is, the adjacent light-emitting regions140are connected to each other in series. Therefore, a light-emitting device having a high driving voltage can be obtained.

The manufactured light-emitting device is subjected to appropriate sealing because it has low resistance to moisture. Specifically, after the light-emitting device is subjected to dry treatment, the first substrate100and the second substrate150are bonded to each other with the sealant118(seeFIG. 3A). As the dry treatment, heat treatment in a dry atmosphere is performed, for example. At this time, the space120is generated between the light-emitting device and the second substrate150. The space120may be filled with an organic compound or an inorganic compound having a light-transmitting property in a visible light region, such as an epoxy resin. In addition, it is preferable to seal a drying agent in the space120.

Next, the resin151having the structure with a lens shape and the resin154having the structure with a lens shape are provided over the second substrate150(seeFIG. 3B).

Through the above steps, the light-emitting device which is sealed and provided with the resins having the structure with a lens shape can be manufactured.

Note that in the case where the above manufacturing method is applied with a non-flexible substrate instead of the first substrate100, a light-emitting device may be separated from the non-flexible substrate by a separation method and bonded to the first substrate100.

Since a material having flexibility and a high heat dissipation property is used for the first substrate100and a substrate having flexibility and moisture impermeability is used for the second substrate150, the light-emitting device described in this embodiment has less deterioration due to moisture and heat, is lightweight, and has high resistance to bending and shock.

Further, a lighting device provided with the light-emitting device described in this embodiment, which has less deterioration and high resistance to bending and shock, can be provided.

In this embodiment, a display device according to one embodiment of the present invention and a method for manufacturing the display device will be described with reference toFIGS. 5A to 5C,FIGS. 6A to 6F,FIG. 7,FIGS. 8A to 8D,FIGS. 9A and 9B,FIGS. 10A to 10D,FIGS. 11A to 11D, andFIGS. 12A to 12C.

FIG. 5Ais a cross-sectional view taken along the dashed-dotted lines A-B in the top views ofFIGS. 5B and 5C. Here,FIG. 5Bis a top view of a first substrate200, which is observed from a second electrode224side. Note that the second electrode224, an organic EL layer222, and the like are omitted to avoid complication.FIG. 5Cis a top view of a second substrate250, which is observed from a coloring layer256,258,260, and262side.

A display device illustrated inFIG. 5Aincludes the first substrate200; a base insulating film202over the first substrate200; transistors240each including a drain electrode212over the base insulating film202; a plurality of first electrodes218each in contact with the drain electrodes212through respective openings provided in a planarization film216; a partition wall220covering end portions of the first electrodes218; the organic EL layer222provided over the first electrodes218and the partition wall220; the second electrode224provided over the organic EL layer222; a black matrix (BM)254provided between the coloring layers256and258, between the coloring layers258and260, and between the coloring layers260and262and over the second electrode224with a space264interposed; an insulating film252over the BM254and the coloring layers256,258,260, and262; and the second substrate250over the insulating film252. Note that the insulating film252is not necessarily provided. In addition, a protective film may be formed over the coloring layers256,258,260, and262.

Here, a protective insulating film which functions as a barrier film of the organic EL layer222may be provided over the second electrode224.

Note that as illustrated inFIG. 7, a structure in which a planarization film226is provided over the second electrode224; the BM254and the coloring layers256,258,260, and262are provided over the planarization film226; and the insulating film252and the second substrate250over the insulating film252are provided over the coloring layers256,258,260, and262with the space264interposed, may also be employed.

Here, the space264may be filled with an organic compound or an inorganic compound having a light-transmitting property in a visible light region, such as an epoxy resin. In addition, although not illustrated, a drying agent, a spacer, or a sealant may be provided in the space264.

In the above structure, a light-emitting region is constituted by the first electrode218, the organic EL layer222, and the second electrode224.

The transistor240includes a gate electrode204; a gate insulating film206covering the gate electrode204; a semiconductor film208provided over the gate electrode204with the gate insulating film206provided therebetween; a source electrode210and the drain electrode212partly in contact with the semiconductor film208; and a protective insulating film214covering at least the source electrode210, the drain electrode212, and the semiconductor film208.

The structure of the transistor240is not limited to the above structure, and the transistor240can have any of various structures. Examples of the transistor240are illustrated inFIGS. 6A to 6F.

A transistor illustrated inFIG. 6Ahas a structure which is the same as that of the transistor240illustrated inFIG. 5A.

A transistor illustrated inFIG. 6Bincludes a gate electrode204bover the first substrate200provided with the base insulating film202; a gate insulating film206bover the gate electrode204b;a source electrode210band a drain electrode212bover the gate insulating film206b;a semiconductor film208bpartly in contact with the source electrode210band the drain electrode212b;and a protective insulating film214bcovering at least the source electrode210b, the drain electrode212b, and the semiconductor film208b.

A transistor illustrated inFIG. 6Cincludes a semiconductor film208cover the first substrate200provided with the base insulating film202; a source electrode210cand a drain electrode212cpartly in contact with the semiconductor film208c;a gate insulating film206ccovering at least the source electrode210c, the drain electrode212c, and the semiconductor film208c;and a gate electrode204cprovided over the semiconductor film208cwith the gate insulating film206cprovided therebetween.

A transistor illustrated inFIG. 6Dincludes a source electrode210dand a drain electrode212dover the first substrate200provided with the base insulating film202; a semiconductor film208dpartly in contact with the source electrode210dand the drain electrode212d;a gate insulating film206dcovering at least the source electrode210d, the drain electrode212d, and the semiconductor film208d;and a gate electrode204dprovided over the semiconductor film208dwith the gate insulating film206dprovided therebetween.

A transistor illustrated inFIG. 6Eincludes a gate electrode204eover the first substrate200provided with the base insulating film202; a gate insulating film206eover the gate electrode204e;a semiconductor film208eover the gate insulating film206e;a protective insulating film214ecovering the semiconductor film208e;and a source electrode210eand a drain electrode212epartly in contact with the semiconductor film208ethrough openings provided in the protective insulating film214e. A source region and a drain region may be included in part of the semiconductor film208e.

A transistor illustrated inFIG. 6Fincludes a semiconductor film208fover the first substrate200provided with the base insulating film202; a gate insulating film206fover the semiconductor film208f;a gate electrode204fover the gate insulating film206f;a protective insulating film214fcovering the gate electrode204f;and a source electrode210fand a drain electrode212fpartly in contact with the semiconductor film208fthrough openings provided in the protective insulating film214fand the gate insulating film206f. A source region and a drain region may be included in part of the semiconductor film208f.

Here, the semiconductor film208and the semiconductor films208bto208fmay be formed using any one kind of an amorphous silicon film, a microcrystalline silicon film, a polycrystalline silicon film, a single crystal silicon film, and an oxide semiconductor film.

The oxide semiconductor film is formed using a material containing two or more kinds of elements selected from indium, gallium, zinc, tin, titanium, and aluminum.

The above-described oxide semiconductor film has a band gap of greater than or equal to 2.5 eV, preferably greater than or equal to 3.0 eV.

In the above-described oxide semiconductor film, hydrogen, an alkali metal, an alkaline earth metal, and the like are reduced and thus the concentration of impurities is extremely low. Therefore, in a transistor whose channel region is formed using the oxide semiconductor film, off-state current can be reduced.

The concentration of hydrogen contained in the oxide semiconductor film is lower than 5×1018/cm3, preferably lower than or equal to 1×1018/cm3, more preferably lower than or equal to 5×1017/cm3, still more preferably lower than or equal to 1×1016/cm3.

For the oxide semiconductor film, a four-component metal oxide such as an In—Sn—Ga—Zn—O-based material; a three-component metal oxide such as an In—Ga—Zn—O-based material, an In—Sn—Zn—O-based material, an In—Al—Zn—O-based material, a Sn—Ga—Zn—O-based material, an Al—Ga—Zn—O-based material, or a Sn—Al—Zn—O-based material; a two-component metal oxide such as an In—Zn—O-based material, a Sn—Zn—O-based material, an Al—Zn—O-based material, a Zn—Mg—O-based material, a Sn—Mg—O-based material, an In—Mg—O-based material, or an In—Ga—O-based material; an In—O-based material; a Sn—O-based material; a Zn—O-based material; or the like may be used. In addition, any of the above materials may contain silicon oxide. Here, for example, an In—Ga—Zn—O-based material means oxide containing indium (In), gallium (Ga), and zinc (Zn), and there is no particular limitation on the composition ratio. Further, the In—Ga—Zn—O-based oxide semiconductor may contain an element other than In, Ga, and Zn. In this case, the oxide semiconductor film preferably contains the amount of oxygen is in excess of the stoichiometric proportion. When the amount of oxygen is in excess of stoichiometric proportion, carrier generation which results from oxygen vacancy in the oxide semiconductor film can be suppressed.

For example, in the case where an In—Zn—O-based material is used for the oxide semiconductor film, the atomic ratio thereof is In/Zn=0.5 to 50, preferably In/Zn=1 to 20, more preferably In/Zn=3 to 15. When the atomic ratio of Zn is in the above range, the field effect mobility of the transistor can be improved. Here, when the atomic ratio of the compound is In:Zn:O=X:Y:Z, the relation Z>1.5X+Y is satisfied.

A material represented by a chemical formula, InMO3(ZnO)m(m>0) may also be used as the oxide semiconductor film. Here, M represents one or more metal elements selected from Ga, Al, Mn, and Co. For example, M may be Ga, Ga and Al, Ga and Mn, Ga and Co, or the like.

An oxide semiconductor film can be in a single crystal state, a polycrystalline (also referred to as polycrystal) state, an amorphous state, or the like.

An oxide semiconductor film is preferably a CAAC-OS (c-axis aligned crystalline oxide semiconductor) film.

The CAAC-OS film is not completely single crystal nor completely amorphous. The CAAC-OS film is an oxide semiconductor film with a crystal-amorphous mixed phase structure where crystal parts are included in an amorphous phase. Note that in most cases, the crystal part fits inside a cube whose one side is less than 100 nm. From an observation image obtained with a transmission electron microscope (TEM), a boundary between an amorphous part and a crystal part in the CAAC-OS film is not clear. Further, with the TEM, a grain boundary in the CAAC-OS film cannot be found. Thus, in the CAAC-OS film, a reduction in electron mobility, due to the grain boundary, is suppressed.

In each of the crystal parts included in the CAAC-OS film, a c-axis is aligned in a direction parallel to a normal vector of a surface where the CAAC-OS film is formed or a normal vector of a surface of the CAAC-OS film, triangular or hexagonal atomic arrangement which is seen from the direction perpendicular to the a-b plane is formed, and metal atoms are arranged in a layered manner or metal atoms and oxygen atoms are arranged in a layered manner when seen from the direction perpendicular to the c-axis. Note that, among crystal parts, the directions of the a-axis and the b-axis of one crystal part may be different from those of another crystal part. In this specification, a simple term “perpendicular” includes a range from 85° to 95°. In addition, a simple term “parallel” includes a range from −5° to 5°.

In the CAAC-OS film, distribution of crystal parts is not necessarily uniform. For example, in the formation process of the CAAC-OS film, in the case where crystal growth occurs from a surface side of the oxide semiconductor film, the proportion of crystal parts in the vicinity of the surface of the oxide semiconductor film is higher than that in the vicinity of the surface where the oxide semiconductor film is formed in some cases. Further, when an impurity is added to the CAAC-OS film, the crystal part in a region to which the impurity is added becomes amorphous in some cases.

Since the c-axes of the crystal parts included in the CAAC-OS film are aligned in the direction parallel to a normal vector of a surface where the CAAC-OS film is formed or a normal vector of a surface of the CAAC-OS film, the directions of the c-axes may be different from each other depending on the shape of the CAAC-OS film (the cross-sectional shape of the surface where the CAAC-OS film is formed or the cross-sectional shape of the surface of the CAAC-OS film). Note that when the CAAC-OS film is formed, the direction of c-axis of the crystal part is the direction parallel to a normal vector of the surface where the CAAC-OS film is formed or a normal vector of the surface of the CAAC-OS film. The crystal part is formed by film formation or by performing treatment for crystallization such as heat treatment after film formation.

With use of the CAAC-OS film in a transistor, change in electric characteristics of the transistor due to irradiation with visible light or ultraviolet light can be reduced. Thus, the transistor has high reliability.

As the planarization film216, an organic compound or an inorganic compound may be used. In the case of using an organic compound, acrylic, polyimide, and siloxane can be given, for example.

The first electrodes218, the partition wall220, the organic EL layer222, and the second electrode224can be formed using materials similar to those of the first electrodes104, the partition wall106, the organic EL layer112, and the second electrode114described in Embodiment 1.

As the coloring layers256,258,260, and262, appropriate coloring layers are provided. For example, coloring layers of red, green, blue, and yellow; or coloring layers of red, green, blue, and white are selected. Although four kinds of coloring layers are used in this embodiment, the number of colors of coloring layers is not limited thereto. For example, the number of colors of coloring layers may be less than or equal to 3 or greater than or equal to 5.

In the display device described in this embodiment, color images can be displayed in a manner such that white light emitted from the light-emitting region242is radiated outside through the coloring layer256,258,260, or262. At this time, the respective thicknesses of the coloring layers may be controlled so that color images are displayed with a higher color rending property.

With such a structure in which color images are displayed by white light and coloring layers, a step of separately forming light-emitting layers which emit light of different colors is omitted, unlike the case where light-emitting regions of the respective colors are arranged to form pixels. Therefore, a display device which has higher definition and higher reliability can be manufactured.

The BM254is provided between the coloring layers in order to prevent color mixture between the coloring layers. The BM254is formed using at least one of metal materials such as titanium, tantalum, molybdenum, and tungsten; and a black resin, for example.

The insulating film252may be formed using a material similar to that of the base insulating film202.

As the second substrate250, a material similar to that of the second substrate150described in Embodiment 1 may be used. That is, a material which has a low moisture permeability and a light-transmitting property in a visible light region, and is unlikely to break may be used.

Since the second electrode224, the insulating film252, and the second substrate250have light-transmitting properties in a visible light region, the display device described in this embodiment has a so-called top emission structure, in which a light emission surface is on the second substrate250side.

In addition, a substrate having a high heat dissipation property is used for the first substrate200so that heat is easily released from the display device. Therefore, reduction in reliability due to heat can be suppressed.

Next, an example of a method for manufacturing the display device having the structure illustrated inFIG. 5Awill be described.

Next, the planarization film216is formed over the transistors240, and openings through which the drain electrodes212of the transistors240are exposed are formed. After that, the plurality of first electrodes218in contact with the drain electrodes212through the openings is formed (seeFIG. 8B).

Next, the partition wall220that covers end portions of the first electrodes218(seeFIG. 8C).

Next, the organic EL layer222is formed over the first electrodes218and the partition wall220. After that, the second electrode224is formed over the organic EL layer222to form the light-emitting region242constituted by the first electrode218, the organic EL layer222, and the second electrode224(seeFIG. 8D).

Through the above steps, the transistor240and the light-emitting region242can be formed over the first substrate200.

Next, the second substrate250is prepared and the insulating film252is formed. After that, the BM254are formed (seeFIG. 9A). Note that the insulating film252is not necessarily provided.

Next, the coloring layers256,258,260, and262are formed over the insulating film252and the BM254(seeFIG. 9B).

Next, a sealant is applied to an exterior frame of the first substrate200or the second substrate250, and the first substrate200and the second substrate250are bonded to each other with the sealant, whereby the display device illustrated inFIG. 5Acan be manufactured.

Further, when a glass substrate having a thickness greater than 100 μm is used as the second substrate250, a side of the second substrate250, in which the insulating film252and the BMs254are not provided in the side, may be polished so as to be extremely thin glass having a thickness greater than or equal to 20 μm and less than or equal to 100 μm.

A method for manufacturing the display device illustrated inFIG. 5A, which is different from the above manufacturing method, will be described below.

First, a separation layer302is deposited over a substrate300, and the base insulating film202is deposited over the separation layer302. As the substrate300, a silicon wafer, a glass substrate, a quartz substrate, or the like may be employed. For the separation layer302, a metal material such as tungsten, molybdenum, chromium, copper, or tantalum may be used.

The separation layer302is a layer which enables separation at the interface between the separation layer302and the base insulating film202. The adhesion between the separation layer302and the base insulating film202needs to be strong enough for the separation with a trigger after the display device is manufactured but not strong enough for the separation during the manufacturing process of the display device.

Next, the transistors240are manufactured over the base insulating film202(seeFIG. 10A).

Next, the planarization film216having openings through which the drain electrodes212of the transistors240are exposed is formed, and the plurality of first electrodes218in contact with the drain electrode212through the openings is formed. Then, the partition wall220that covers end portions of the adjacent first electrodes218is formed. Then, the organic EL layer222and the second electrode224are stacked over the first electrodes218and the partition wall220(seeFIG. 10B).

Next, the separation layer302and the base insulating film202is separated from the end portion, which is triggered by laser treatment or the like (seeFIG. 10C).

Next, the first substrate200is bonded to the base insulating film202with an adhesive304provided therebetween (seeFIG. 10D).

Through the above steps, the transistor240and the light-emitting region242can be formed over the first substrate200.

The second substrate250side can also be formed in a similar manner.

In a similar manner, a separation layer352is deposited over a substrate350, and the insulating film252is deposited over the separation layer352. The substrate350and the separation layer352may have structures similar to those of the substrate300and the separation layer302.

Next, the BM254is formed over the insulating film252(seeFIG. 11A).

Next, the coloring layers256,258,260, and262are formed over the insulating film252and the BM254(seeFIG. 11B). Note that the coloring layers256,258,260, and262are not necessarily formed so as to be overlapped with each other but only needs to be formed so that regions where the BM254is not formed is filled with the coloring layers256,258,260, and262.

Next, the separation layer352and the insulating film252are separated from the end portion, which is triggered by laser treatment or the like (seeFIG. 11C).

Next, the second substrate250is bonded to the insulating film252with an adhesive308provided therebetween (seeFIG. 11D).

Through the above steps, the second substrate250including the BMs254and the coloring layers256,258,260, and262can be manufactured.

The first substrate200and the second substrate250are bonded to each other with a sealant, whereby a display device similar to the display device illustrated inFIG. 5Acan be manufactured.

Alternatively, the display device illustrated inFIG. 5Amay be manufactured in a manner such that the structure illustrated inFIG. 10Band the structure illustrated inFIG. 11Bare bonded to each other with a sealant (seeFIG. 12A); the light-emitting device and the substrates are separated at the interface between the substrate300and the separation layer302and the interface between the substrate350and the separation layer352(seeFIG. 12B); and both surfaces of the light-emitting device are sealed with the first substrate200and the second substrate250(seeFIG. 12C).

Although the step of forming the separation layers on both the first substrate200side and the second substrate250side is described in this embodiment, a separation layer may be formed only on the first substrate200side or only on the second substrate250side without limitation thereto.

Through the above steps, the display device capable of displaying color images, to which the light-emitting device utilizing organic EL is applied, can be manufactured.

Since a material having flexibility and a high heat dissipation property is used for the first substrate200and a substrate having flexibility and moisture impermeability is used for the second substrate250, the display device described in this embodiment has less deterioration due to moisture and heat and has high resistance to bending and shock.

In addition, since light-emitting layers that emit light of different colors are not separately formed, a display device which has high definition and high reliability can be manufactured.

In this embodiment, examples of a lighting device and a display device to which Embodiment 1 or Embodiment 2 is applied will be described.

FIG. 13Aillustrates a portable information terminal The portable information terminal includes a housing9300, a button9301, a microphone9302, a display portion9303, a speaker9304, and a camera9305, and has a function as a mobile phone. The display device according to one embodiment of the present invention can be applied to the display portion9303. By applying the display device according to one embodiment of the present invention, a portable information terminal which has high definition and high reliability can be obtained.

FIG. 13Billustrates a panel-type lighting device. The panel-type lighting device includes a housing9310and a light-emitting portion9311. The display device according to one embodiment of the present invention can be applied to the light-emitting portion9311. By applying the display device according to one embodiment of the present invention, a lighting device of a plane emission type, which has high resistance to bending and shock, can be obtained.

This application is based on Japanese Patent Application Serial No. 2011-028866 filed with Japan Patent Office on Feb. 14, 2011, the entire contents of which are hereby incorporated by reference.