Patent ID: 12262623

DETAILED DESCRIPTION OF THE INVENTION

Embodiments will be described below with reference to the drawings. Note that the embodiments can be implemented with many different modes, and it will be readily understood by those skilled in the art that modes and details thereof can be changed in various ways without departing from the spirit and scope thereof. Therefore, the present invention should not be construed as being limited to the description of embodiments below.

Note that in structures of the invention described below, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings, and the description thereof is not repeated. The same hatching pattern is used for portions having similar functions, and the portions are not denoted by specific reference numerals in some cases.

Note that in each drawing described in this specification, the size, the layer thickness, or the region of each component is exaggerated for clarity in some cases. Therefore, the size, the layer thickness, or the region is not limited to the illustrated scale.

Note that in this specification and the like, ordinal numbers such as “first” and “second” are used in order to avoid confusion among components and do not limit the number of components.

In this specification and the like, the terms “film” and “layer” can be interchanged with each other in some cases. For example, in some cases, the terms “conductive layer” and “insulating layer” can be changed into “conductive film” and “insulating film”, respectively.

In this specification and the like, a device formed using a metal mask or a fine metal mask (FMM) is sometimes referred to as a device having a metal mask (MM) structure. In this specification and the like, a device formed without using a metal mask or an FMM is sometimes referred to as a device having a metal maskless (MML) structure.

Embodiment 1

In this embodiment, structure examples of a display device of one embodiment of the present invention and manufacturing method examples of the display device will be described.

One embodiment of the present invention is a display device including a light-emitting element (also referred to as a light-emitting device). The display device includes at least two light-emitting elements that emit light of different colors. The light-emitting elements each include a pair of electrodes and an EL layer therebetween. The light-emitting element is preferably an organic electroluminescent element (organic EL element). The two or more light-emitting elements emitting light of different colors include respective EL layers containing different light-emitting materials. For example, three kinds of light-emitting elements emitting red (R), green (G), and blue (B) light are included, whereby a full-color display device can be obtained.

In the case of manufacturing a display device including a plurality of light-emitting elements emitting light of different colors, at least layers (light-emitting layers) containing light-emitting materials different in emission color each need to be formed in an island shape. In a known method for separately forming part or the whole of an EL layer, an island-shaped organic film is formed by an evaporation method using a shadow mask such as a metal mask. However, this method has difficulty in achieving high resolution and a high aperture ratio of a display device because in this method, a deviation from the designed shape and position of the island-shaped organic film is caused by various influences such as the low accuracy of the metal mask position, the positional deviation between the metal mask and a substrate, a warp of the metal mask, and the vapor-scattering-induced expansion of the outline of the formed film. In addition, the outline of a layer may blur during vapor deposition, whereby the thickness of its end portion may be small. That is, the thickness of an island-shaped light-emitting layer may vary from area to area. In the case of manufacturing a display device with a large size, high definition, or high resolution, the manufacturing yield might be reduced because of low dimensional accuracy of the metal mask and deformation due to heat or the like. Thus, a measure has been taken for pseudo improvement in resolution (also referred to pixel density). As a specific measure, a unique pixel arrangement such as a PenTile pattern has been employed.

Note that in this specification and the like, the term “island shape” refers to a state where two or more layers formed using the same material in the same step are physically separated from each other. For example, “island-shaped light-emitting layer” means a state where the light-emitting layer and its adjacent light-emitting layer are physically separated from each other.

In one embodiment of the present invention, fine patterning of an EL layer is performed by photolithography without a shadow mask such as a fine metal mask (FMM). With the patterning, a high-resolution display device with a high aperture ratio, which has been difficult to achieve, can be fabricated. Moreover, EL layers can be formed separately, enabling the display device to perform extremely clear display with high contrast and high display quality. Note that one embodiment of the present invention is not limited to the above structure. For example, a structure in which fine patterning of an EL layer is performed using both a metal mask and photolithography is also one embodiment of the present invention.

Part or the whole of the EL layer can be physically partitioned, inhibiting a leakage current flowing between adjacent light-emitting elements through a layer (also referred to as a common layer) shared by the light-emitting elements. This can prevent crosstalk due to unintended light emission, so that a display device with extremely high contrast can be obtained. Specifically, a display device having high current efficiency at low luminance can be obtained.

Note that a display device can also be obtained by combining white-light-emitting elements with a color filter. In that case, the light-emitting elements having the same structure can be provided in pixels (subpixels) emitting light of different colors, allowing all the layers to be common layers. Furthermore, part or the whole of the EL layer is partitioned by photolithography, which inhibits a leakage current from flowing through the common layers to achieve a display device with high contrast. In particular, when an element has a tandem structure in which a plurality of light-emitting layers are stacked with a highly conductive intermediate layer therebetween, a leakage current through the intermediate layer can be effectively prevented, achieving a display device with high luminance, high resolution, and high contrast.

In the case where the EL layer is processed into an island shape, when a resist mask is formed directly on the EL layer, a solvent or the like of a resin material to be the resist mask might dissolve part or the whole of the EL layer. Thus, in one embodiment of the present invention, a sacrificial layer is formed between the EL layer and the resist mask, preventing damage at the formation of the resist mask.

The sacrificial layer is preferably formed using a material soluble in a solvent that is unlikely to dissolve the EL layer and insoluble or poorly soluble in a solvent of the resin material to be the resist mask. In that case, after the EL layer is processed into an island shape, the sacrificial layer can be removed without causing damage to the EL layer. For example, a material soluble in water or alcohol is particularly preferably used for the sacrificial layer.

Furthermore, the resist mask and the EL layer are preferably formed using organic materials that can be etched in the same dry etching step. In that case, the resist mask does not need to be separated with a resist stripper or the like after processing of the EL layer, and can be removed in the etching step of the EL layer. This can prevent the EL layer from being unintentionally dissolved with the resist stripper. At this time, the sacrificial layer may be formed using an organic material that can be etched in the above dry etching step or a material that has etching resistance in the dry etching step.

The EL layer can be processed into an island shape in such a manner that, for example, a resist mask is formed immediately after formation of a light-emitting layer (a layer containing a light-emitting material) and then processing is performed. In such a method, damage to the light-emitting layer (e.g., processing damage) might be caused to significantly degrade the reliability. Thus, one embodiment of the present invention preferably employs a method in which a sacrificial layer and a resist mask are stacked over a layer above the light-emitting layer (e.g., a carrier-transport layer or a carrier-injection layer, and specifically an electron-transport layer or an electron-injection layer), and then the light-emitting layer is processed into an island shape. Such a method provides a highly reliable display device.

The interval between EL layers with different colors can be reduced to less than or equal to 3 μm, less than or equal to 2 μm, or less than or equal to 1 μm by the above-described method, whereas it is difficult to reduce the interval to less than 10 μm by a formation method using an FMM, for example. With the use of a light exposure tool for LSI, the interval between EL layers can be reduced to less than or equal to 500 nm, less than or equal to 200 nm, less than or equal to 100 nm, or even less than or equal to 50 nm, for example. Accordingly, the area of a non-light-emitting region that may exist between two light-emitting elements can be significantly reduced, and the aperture ratio can be close to 100%. For example, an aperture ratio higher than or equal to 50%, higher than or equal to 60%, higher than or equal to 70%, higher than or equal to 80%, or higher than or equal to 90% and lower than 100% can be achieved.

Furthermore, the size of the EL layer itself can be made much smaller than that in the case of using an FMM. For example, in the case where EL layers are separately formed using an FMM, the thickness differs between the center and the edge of an island-shaped EL layer, reducing an effective area that can be used as a light-emitting region with respect to the whole area of the EL layer. By contrast, in the above manufacturing method, a film deposited to have a uniform thickness is processed to form an island-shaped EL layer with a uniform thickness. Thus, even when the EL layer has a minute size, almost the whole area can be used as a light-emitting region. Thus, the above manufacturing method achieves both high resolution and a high aperture ratio.

As described above, with the above manufacturing method, a display device in which minute light-emitting elements are integrated can be obtained, and it is not necessary to conduct a pseudo improvement in resolution with a unique pixel arrangement such as a PenTile pattern. Thus, the display device can achieve resolution higher than or equal to 500 ppi, higher than or equal to 1000 ppi, higher than or equal to 2000 ppi, higher than or equal to 3000 ppi, or higher than or equal to 5000 ppi while having what is called a stripe pattern where R, G, and B are arranged in one direction.

Here, it is preferable that a partition covering an end portion of the pixel electrode be not provided. When such a partition is used, a region of the pixel electrode that is covered with the partition is made a non-light-emitting region, reducing the aperture ratio accordingly. In one embodiment of the present invention, the end portion of the pixel electrode has a tapered shape, improving the step coverage with an EL film deposited over the pixel electrode; thus, the EL layer can be prevented from being partitioned by a step at the end portion of the pixel electrode without using the partition. As a result, the aperture ratio can be significantly increased.

More specific structure examples and manufacturing method examples of the display device of one embodiment of the present invention will be described below with reference to drawings.

Structure Example 1

FIG.1Ais a schematic top view of a display device100of one embodiment of the present invention. The display device100includes, over a substrate101, a plurality of light-emitting elements110R exhibiting red, a plurality of light-emitting elements110G exhibiting green, and a plurality of light-emitting elements110B exhibiting blue. InFIG.1A, light-emitting regions of the light-emitting elements are denoted by R, G, and B to easily differentiate the light-emitting elements.

The light-emitting elements110R, the light-emitting elements110G, and the light-emitting elements110B are arranged in a matrix.FIG.1Ashows what is called a stripe arrangement, in which light-emitting elements of the same color are arranged in one direction. Note that the arrangement of the light-emitting elements is not limited thereto; another arrangement such as an S stripe, delta, Bayer, zigzag, PenTile, or diamond pattern may also be used.

As each of the light-emitting elements110R,110G, and110B, an EL element such as an organic light-emitting diode (OLED) or a quantum-dot light-emitting diode (QLED) is preferably used. Examples of a light-emitting substance contained in the EL element include a substance exhibiting fluorescence (fluorescent material), a substance exhibiting phosphorescence (phosphorescent material), and a substance exhibiting thermally activated delayed fluorescence (a thermally activated delayed fluorescent (TADF) material). Examples of the light-emitting substance contained in the EL element include not only organic compounds but also inorganic compounds (e.g., quantum dot materials).

FIGS.1B and1Care the schematic cross-sectional views taken along dashed-dotted line A1-A2and dashed-dotted line B1-B2inFIG.1A.FIG.1Bis a schematic cross-sectional view of the light-emitting element110R, the light-emitting element110G, and the light-emitting element110B, andFIG.1Cis a schematic cross-sectional view of the two light-emitting elements110G.

The light-emitting element110R includes a pixel electrode111R, an EL layer112R, and a common electrode113. The light-emitting element110G includes a pixel electrode111G, an EL layer112G, and the common electrode113. The light-emitting element110B includes a pixel electrode111B, an EL layer112B, and the common electrode113.

Hereafter, the term “light-emitting element110” is sometimes used to describe matters common to the light-emitting elements110R,110G, and110B. Likewise, in the description of matters common to the components that are distinguished using alphabets, such as the EL layers112R,112G, and112B, reference numerals without such alphabets are sometimes used.

The light-emitting element110R includes the EL layer112R between the pixel electrode111R and the common electrode113. The EL layer112R contains at least a light-emitting organic compound emitting red light. The EL layer112G included in the light-emitting element110G contains at least a light-emitting organic compound emitting green light. The EL layer112B included in the light-emitting element110B contains at least a light-emitting organic compound emitting blue light.

The EL layers112R,112G, and112B may each include one or more of an electron-injection layer, an electron-transport layer, a hole-injection layer, and a hole-transport layer in addition to a layer containing a light-emitting compound (a light-emitting layer).

The pixel electrode111R, the pixel electrode111G, and the pixel electrode111B are provided for the respective light-emitting elements. The common electrode113is provided as a continuous layer shared by the light-emitting elements. A conductive film that has a property of transmitting visible light is used for either the respective pixel electrodes or the common electrode113, and a reflective conductive film is used for the other. When the respective pixel electrodes are light-transmitting electrodes and the common electrode113is a reflective electrode, a bottom-emission display device is obtained. When the respective pixel electrodes are reflective electrodes and the common electrode113is a light-transmitting electrode, a top-emission display device is obtained. Note that when both the respective pixel electrodes and the common electrode113transmit light, a dual-emission display device can be obtained.

The pixel electrode111(the pixel electrode111R, the pixel electrode111G, and the pixel electrode111B) preferably has a tapered shape. This can improve the step coverage with the EL layer112. Note that in this specification and the like, an end portion of an object having a tapered shape indicates that the end portion of the object has a cross-sectional shape in which the angle between a surface (side surface) of the object and a surface on which the object is formed is greater than 0° and less than 90°, and the thickness continuously increases from the end portion. A typical example of the shape of the end portion is the one in which a bottom end portion has an acute angle and a top end portion has an obtuse angle. Note that the side surface is preferably flat, but may be concave or convex, or may have a step-like shape. Although the pixel electrode111shown here has a single-layer structure, the pixel electrode111may include a plurality of layers stacked.

The pixel electrode111has a taper angle (the angle of the end portion formed between the surface (side surface) and the surface on which the object is formed) greater than 0° and less than 90°, preferably greater than or equal to 10° and less than or equal to 85°, further preferably greater than or equal to 20° and less than or equal to 80°, and still further preferably greater than or equal to 30° and less than or equal to 75°.

The EL layer112is provided to cover the pixel electrode111. The EL layer112is provided in contact with a top surface and a side surface of the pixel electrode111. An end portion of the EL layer112is positioned outside the pixel electrode111. The end portion of the EL layer112is provided in contact with a top surface of a layer on which the pixel electrode111is formed (here, a top surface of the substrate101).

The EL layer112is processed into an island shape by photolithography. Thus, the angle formed between a top surface and a side surface of the end portion of the EL layer112is approximately 90°. By contrast, an organic film formed using a fine metal mask (FMM) or the like has a thickness that tends to gradually decrease with decreasing distance to an end portion, and has a top surface forming a slope in an area extending greater than or equal to 1 μm and less than or equal to 10 μm from the end portion, for example; thus, such an organic film has a shape whose top surface and side surface cannot be easily distinguished from each other.

The EL layer112preferably has a taper angle greater than or equal to 45° and less than or equal to 135°, further preferably greater than or equal to 50° and less than or equal to 120°, still further preferably greater than or equal to 60° and less than or equal to 100°, and yet still further preferably greater than or equal to 70° and less than or equal to 90°. A taper angle less than or equal to 90° can improve the step coverage with a layer covering the EL layer112(e.g., the common electrode113and a protective layer121). Meanwhile, a taper angle less than 30° requires a larger distance between light-emitting elements, which might decrease the aperture ratio.

The common electrode113is provided to cover the top surface and the side surface of the EL layer112. Here, part of the common electrode113is provided in contact with the top surface of the layer on which the pixel electrode111is formed (here, the top surface of the substrate101).

The protective layer121is provided to cover the common electrode113. The protective layer121has a function of preventing diffusion of impurities such as water into each light-emitting element from above.

As the protective layer121, a stacked film of an inorganic insulating film and an organic insulating film can be used. For example, a structure in which an organic insulating film is sandwiched between a pair of inorganic insulating films is preferable. Furthermore, it is preferable that the organic insulating film function as a planarization film With this structure, a top surface of the organic insulating film can be flat, and accordingly, coverage with the inorganic insulating film over the organic insulating film is improved, leading to an improvement in barrier properties. Moreover, since a top surface of the protective layer121is flat, a preferable effect can be obtained; when a component (e.g., a color filter, an electrode of a touch sensor, a lens array, or the like) is provided above the protective layer121, the component is less affected by an uneven shape caused by the lower structure.

The protective layer121can have, for example, a single-layer structure or a stacked-layer structure at least including an inorganic insulating film Examples of the inorganic insulating film include an oxide film or a nitride film such as a silicon oxide film, a silicon oxynitride film, a silicon nitride oxide film, a silicon nitride film, an aluminum oxide film, an aluminum oxynitride film, or a hafnium oxide film. Alternatively, a semiconductor material such as indium gallium oxide or indium gallium zinc oxide may be used for the protective layer121.

Note that in this specification and the like, an oxynitride refers to a material in which an oxygen content is higher than a nitrogen content, and a nitride oxide refers to a material in which a nitrogen content is higher than an oxygen content. For example, silicon oxynitride refers to a material in which an oxygen content is higher than a nitrogen content, and silicon nitride oxide refers to a material in which a nitrogen content is higher than an oxygen content.

In the case where the common electrode113has a stacked-layer structure of a conductive layer including a metal and a light-transmitting conductive layer, the light-transmitting conductive layer can be referred to as the protective layer121. Particularly when a microcavity is used, the conductive layer including a metal needs to be thin enough to have a light-transmitting property; the light-transmitting conductive layer including a metal oxide to be stacked preferably has a larger thickness than the conductive layer including a metal. For the conductive layer including a metal oxide, a conductive material such as indium tin oxide or indium zinc oxide can be used.

As illustrated inFIG.1C, the EL layer112is preferably partitioned also between the light-emitting elements110of the same color. This inhibits crosstalk due to a leakage current between the light-emitting elements110of the same color, thereby displaying a high-contrast image with the outline clear, not blurred.

Manufacturing Method Example 1

A manufacturing method example of the display device of one embodiment of the present invention will be described below with reference to drawings. Here, the description is made with use of the display device100shown above in Structure example.FIGS.2A to2FandFIGS.3A to3Eare cross-sectional schematic views of steps in the manufacturing method of the display device described as an example below.

Thin films included in the display device (e.g., insulating films, semiconductor films, and conductive films) can be formed by a sputtering method, a chemical vapor deposition (CVD) method, a vacuum evaporation method, a pulsed laser deposition (PLD) method, an atomic layer deposition (ALD) method, or the like. Examples of the CVD method include a plasma-enhanced chemical vapor deposition (PECVD) method and a thermal CVD method. An example of the thermal CVD method is a metal organic CVD (MOCVD) method.

Thin films included in the display device (e.g., insulating films, semiconductor films, and conductive films) can also be formed by a method such as spin coating, dipping, spray coating, ink-jetting, dispensing, screen printing, offset printing, doctor blade coating, slit coating, roll coating, curtain coating, or knife coating.

Thin films included in the display device can be processed by a photolithography method, for example. Besides, a nanoimprinting method, a sandblasting method, a lift-off method, or the like may be used to process thin films. Alternatively, island-shaped thin films may be directly formed by a film formation method using a shielding mask such as a metal mask.

There are two typical examples of photolithography methods. In one of the methods, a resist mask is formed over a thin film that is to be processed, the thin film is processed by etching or the like, and then the resist mask is removed. In the other method, a photosensitive thin film is formed and then processed into a desired shape by light exposure and development.

As light used for light exposure in the photolithography method, for example, light with an i-line (wavelength: 365 nm), light with a g-line (wavelength: 436 nm), light with an h-line (wavelength: 405 nm), or light in which the i-line, the g-line, and the h-line are mixed can be used. Alternatively, ultraviolet light, KrF laser light, ArF laser light, or the like can be used. Exposure may be performed by liquid immersion exposure technique. As the light for exposure, extreme ultraviolet (EUV) light or X-rays may also be used. Furthermore, instead of the light used for the exposure, an electron beam can also be used. It is preferable to use EUV light, X-rays, or an electron beam because extremely minute processing can be performed. Note that when exposure is performed by scanning of a beam such as an electron beam, a photomask is not needed.

For etching of thin films, a dry etching method, a wet etching method, a sandblast method, or the like can be used.

{Preparation for Substrate101}

As the substrate101, a substrate that has heat resistance high enough to withstand at least heat treatment performed later can be used. As the substrate101having an insulating property, a glass substrate, a quartz substrate, a sapphire substrate, a ceramic substrate, an organic resin substrate, or the like can be used. Alternatively, it is possible to use a semiconductor substrate such as a single crystal semiconductor substrate or a polycrystalline semiconductor substrate of silicon, silicon carbide, or the like; a compound semiconductor substrate of silicon germanium or the like; or an SOI substrate.

As the substrate101, it is particularly preferable to use the above-described semiconductor substrate or insulating substrate where a semiconductor circuit including a semiconductor element such as a transistor is formed. The semiconductor circuit preferably forms a pixel circuit, a gate line driver circuit (a gate driver), a source line driver circuit (a source driver), or the like. In addition to the above, an arithmetic circuit, a memory circuit, or the like may be formed.

{Formation of Pixel Electrodes111R,111G, and111B}

Next, a plurality of pixel electrodes111are formed over the substrate101(FIG.2A). First, a conductive film to be a pixel electrode is deposited, a resist mask is formed by a photolithography method, and an unnecessary portion of the conductive film is removed by etching. After that, the resist mask is removed to form the pixel electrodes111R,111G, and111B.

At this time, etching is preferably performed so that the pixel electrodes111R,111G, and111B each have a tapered shape. The tapered shape can be obtained by, for example, performing dry etching under the condition that the resist mask can be etched concurrently with the conductive film Note that the processing method for obtaining the tapered shape is not limited thereto and the tapered shape can also be obtained by wet etching in some cases.

In the case where a conductive film that has a property of reflecting visible light is used as the pixel electrodes111, it is preferable to use a material having as high a reflectivity as possible in the entire wavelength range of visible light (e.g., silver or aluminum). This can increase both light extraction efficiency and color reproducibility of the light-emitting elements. A light-transmitting conductive film may be stacked over a reflective conductive film, and the light-transmitting conductive film may have a thickness different between the light-emitting elements.

{Formation of EL Film112Rf}

Subsequently, an EL film112Rf to be the EL layer112R is deposited over the pixel electrodes111R,111G, and111B (FIG.2B).

The EL film112Rf includes at least a film containing a light-emitting compound. In addition to this, one or more films functioning as an electron-injection layer, an electron-transport layer, a charge-generation layer, a hole-transport layer, and a hole-injection layer may be stacked. The EL film112Rf can be formed by, for example, an evaporation method, a sputtering method, an inkjet method, or the like. Without limitation to this, the above-described deposition method can be used as appropriate.

{Formation of Sacrificial Film141a}

Subsequently, a sacrificial film141ais formed over the EL film112Rf (FIG.2C). A method suitable for the formation of the sacrificial film141ais a wet deposition method such as spin coating, dipping, spray coating, ink-jetting, dispensing, screen printing, offset printing, doctor blade coating, slit coating, roll coating, curtain coating, or knife coating. Other deposition methods such as an evaporation method and the above-described deposition methods can also be used as appropriate.

The sacrificial film141ais preferably formed using a material that can be dissolved in a solvent chemically stable with respect to at least the uppermost film of the EL film112Rf. Specifically, a material that will be dissolved in water or alcohol can be suitably used for the sacrificial film141a. In deposition of the sacrificial film141a, it is preferable that application of such a material dissolved in a solvent such as water or alcohol be performed by the aforementioned wet process and followed by heat treatment for evaporating the solvent. At this time, the heat treatment is preferably performed in a reduced-pressure atmosphere, in which case the solvent can be removed at a low temperature in a short time and thermal damage to the EL film112Rf can be reduced accordingly.

For the sacrificial film141a, a water-soluble or alcohol-soluble organic material is preferably used. Examples of the organic material include polyvinyl alcohol (PVA), polyvinyl butyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, or an alcohol-soluble polyamide resin.

{Formation of Resist Mask143a}

Next, a resist mask143ais formed in a region that is over the sacrificial film141aand overlaps with the pixel electrode111R (FIG.2D). The resist mask143ais preferably formed using an organic resin material that can be etched under the same etching condition as the sacrificial film141a.

For the resist mask143a, a resist material containing a photosensitive resin such as a positive type resist material or a negative type resist material can be used.

{Etching of Sacrificial Film141a, Resist Mask143a, and EL Film112Rf}

Then, the sacrificial film141a, the resist mask143a, and the EL film112Rf are etched to expose part of the top surface of the substrate101, a top surface of the pixel electrode111G, and a top surface of the pixel electrode111B (FIG.2E). At this time, the etching conditions are determined so that parts of the sacrificial film141aand the EL film112Rf, which are not covered with the resist mask143a, are removed and the sacrificial film141aover the pixel electrode111R remains. Thus, the island-shaped EL layer112R and a sacrificial layer142aover the EL layer112R can be formed.

The etching is preferably performed under the conditions that the sacrificial film141a, the resist mask143a, and the EL film112Rf can be etched. It is particularly preferable to perform anisotropic dry etching, which can prevent an exposed side surface of the EL layer112R from being etched and the pattern of the EL layer112R from being reduced after the etching.

The sacrificial film141a, the resist mask143a, and the EL film112Rf are preferably etched by anisotropic dry etching using an etching gas containing oxygen, in which case the etching rate can be increased. Note that the etching gas is not limited thereto, and a hydrogen gas, a nitrogen gas, an oxygen gas, an ammonia gas, or a gas containing fluorine such as CF4or SF6can be used as the etching gas, for example. A mixed gas of two or more of the above gases may also be used. Alternatively, a gas in which a noble gas such as argon, helium, xenon, or krypton is mixed in any of the above gases may be used as the etching gas.

Note that the sacrificial film141a, the resist mask143a, and the EL film112Rf may be individually etched or any two of them may be etched in the same step. For example, the sacrificial film141amay be etched first; then, the resist mask143aand the EL film112Rf may be etched in the same step.

The sacrificial layer142apreferably remains over the EL layer112R when the etching is completed. This enables the sacrificial layer142ato function as a protective layer that protects the EL layer112R from damage in a later step.

{Formation of EL Film112Gf}

Subsequently, an EL film112Gf to be the EL layer112G is deposited over the sacrificial layer142a, the pixel electrode111G, and the pixel electrode111B.

The description of the EL film112Rf can be referred to for the formation method of the EL film120Gf.

{Formation of Sacrificial Film141b}

Subsequently, a sacrificial film141bis formed over the EL film112Gf. The sacrificial film141bcan be formed in a manner similar to that for the sacrificial film141a. In particular, the sacrificial film141band the sacrificial film141aare preferably formed using the same material.

{Formation of Resist Mask143b}

Next, a resist mask143bis formed over the sacrificial film141b(FIG.2F). The resist mask143bis formed in a region overlapping with the pixel electrode111G and a region overlapping with the pixel electrode111R.

The description of the resist mask143acan be referred to for the formation method of the resist mask143b.

{Etching of Sacrificial Film141b, Resist Mask143b, and EL Film112Gf}

Then, the sacrificial film141b, the resist mask143b, and the EL film112Gf are etched to expose part of the top surface of the substrate101and the top surface of the pixel electrode111B (FIG.3A). Thus, the island-shaped EL layer112G and a sacrificial layer142bcan be formed. For the etching method, the description of etching of the sacrificial film141a, the resist mask143a, and the EL film112Rf can be referred to.

The etching is preferably performed under the conditions that the sacrificial film141b, the resist mask143b, and the EL film112Gf can be etched. For example, when the etching is performed by anisotropic dry etching, part of the sacrificial film141bover the pixel electrode111B, which is not covered with the resist mask143b, disappears faster than the other part covered with the resist mask143b, so that the sacrificial layer142bcan remain.

In the case where the etching is performed by single etching treatment, the treatment is stopped when the etching of the EL film112Gf is completed. Thus, as illustrated inFIG.3A, the sacrificial layer142aover the EL layer112R can remain without disappearing.

{Formation of EL Film112Bf}

Subsequently, an EL film112Bf to be the EL layer112B is deposited over the sacrificial layer142a, the sacrificial layer142b, and the pixel electrode111B.

The description of the EL film112Rf can be referred to for the formation method of the EL film120Bf.

{Formation of Sacrificial Film141c}

Subsequently, a sacrificial film141cis formed over the EL film112Bf. The sacrificial film141ccan be formed in a manner similar to that for the sacrificial film141a. In particular, the sacrificial film141c, the sacrificial film141a, and the sacrificial film141bare preferably formed using the same material.

{Formation of Resist Mask143c}

Next, a resist mask143cis formed over the sacrificial film141c(FIG.3B). The resist mask143cis formed in a region overlapping with the pixel electrode111R, a region overlapping with the pixel electrode111G, and a region overlapping with the pixel electrode111B.

The description of the resist mask143acan be referred to for the formation method of the resist mask143c.

{Etching of Sacrificial Film141c, Resist Mask143c, and EL Film112Bf}

Then, the sacrificial film141c, the resist mask143c, and the EL film112Bf are etched to expose part of the top surface of the substrate101(FIG.3C). Thus, the island-shaped EL layer112B and a sacrificial layer142ccan be formed.

For the etching method, the description of etching of the sacrificial film141a, the resist mask143a, and the EL film112Rf can be referred to. The etching allows the sacrificial layer142aover the EL layer112R and the sacrificial layer142bover the EL layer112G to remain without disappearing.

{Removal of Sacrificial Layers}

Next, the sacrificial layers142a,142b, and142care removed, whereby top surfaces of the EL layers112R,112G, and112B are exposed (FIG.3D).

The sacrificial layers142a,142a, and142ccan be removed by wet etching or dry etching. At this time, a method that causes damage to the EL layers112R,112G, and112B as little as possible is preferably employed. In particular, a wet etching method is preferably used.

In particular, the sacrificial layers142a,142b, and142care preferably removed by being dissolved in a solvent such as water or alcohol.

Examples of the alcohol in which the sacrificial layers142a,142b, and142ccan be dissolved include ethyl alcohol, methyl alcohol, isopropyl alcohol (IPA), and glycerin.

After the sacrificial layers142a,142b, and142care removed, drying treatment is preferably performed in order to remove water contained in the EL layers112R,112G, and112B and water adsorbed on the surfaces of the EL layers112R,112G, and112B. For example, heat treatment is preferably performed in an inert gas atmosphere or a reduced-pressure atmosphere. The heat treatment can be performed with a substrate temperature higher than or equal to 50° C. and lower than or equal to 200° C., preferably higher than or equal to 60° C. and lower than or equal to 150° C., and further preferably higher than or equal to 70° C. and lower than or equal to 120° C.

The heat treatment is preferably performed in a reduced-pressure atmosphere because drying at a lower temperature is possible.

Through the above steps, the three kinds of EL layers can be separately formed.

{Formation of Common Electrode113}

Next, the common electrode113is formed to cover the EL layers112R,112G, and112B. The common electrode113can be formed by a sputtering method or a vacuum evaporation method, for example.

The common electrode113is not necessarily deposited over the entire surface of the substrate101; preferably, with the use of a shielding mask (also referred to as a metal mask or a rough metal mask) to define a deposition area, the common electrode113is deposited in a predetermined region including a region where the light-emitting elements are provided and a region where electrodes electrically connected to the common electrode113are provided.

Through the above steps, the light-emitting element110R, the light-emitting element110G, and the light-emitting element110B can be manufactured.

{Formation of Protective Layer121}

Next, the protective layer121is formed over the common electrode113(FIG.3E). An inorganic insulating film used for the protective layer121is preferably deposited by a sputtering method, a PECVD method, or an ALD method. In particular, the ALD method is preferable because a film deposited by ALD has good step coverage and is less likely to cause a defect such as pinhole. An organic insulating film is preferably deposited by an ink-jet method because a uniform film can be formed in a desired area.

The above is the description of the manufacturing method example of the display device.

Structure Example 2

A structure example of the display device partly different from Structure example 1 will be described below. Note that portions similar to those described above are not denoted below in some cases.

Structure Example 2-1

A display device100A illustrated inFIG.4Ais different from the display device100mainly in including a common layer114.

Like the common electrode113, the common layer114is provided across a plurality of light-emitting elements. The common layer114is provided to cover the EL layers112R,112G, and112B. The manufacturing process can be simplified by including the common layer114, reducing the manufacturing cost. The common layer114can be formed by, for example, a deposition method such as a vacuum evaporation method or a sputtering method after the removal of the sacrificial layer and before the formation of the common electrode113in Manufacturing method example 1.

Each of the EL layers112R,112G, and112B preferably includes at least a light-emitting layer containing a light-emitting material emitting one color. The common layer114preferably includes one or more of an electron-injection layer, an electron-transport layer, a hole-injection layer, and a hole-transport layer, for example. In the light-emitting element in which the pixel electrode serves as an anode and the common electrode serves as a cathode, a structure including the electron-injection layer or a structure including the electron-injection layer and the electron-transport layer can be used as the common layer114.

In the above case, it is preferable that a light-emitting layer in the EL layer112not be positioned closest to the common layer114. In particular, the layer in the EL layer112that is positioned closest to the common layer114is preferably an electron-transport layer or a hole-transport layer. This can prevent a top surface of the light-emitting layer from being exposed to the air in the manufacturing process of the display device, so that a highly reliable display device can be achieved.

Structure Example 2-2

A display device100B illustrated inFIG.4Bis different from the display device100A mainly in including a resin layer126.

The resin layer126is positioned between two adjacent light-emitting elements. The resin layer126is provided to cover end portions of the EL layer112. The common layer114is provided to cover the resin layer126. End portions of the resin layer126are preferably tapered.

The resin layer126functions as a planarization film that fills a step between the two adjacent light-emitting elements. The resin layer126can prevent the common electrode113from being partitioned (or disconnected) by a step at an end portion of the EL layer112, and the common electrode over the EL layer112from being insulated. The resin layer126can also be referred to as local filling planarization (LFP).

In the case where the resin layer126is provided in contact with the EL layer112, the resin layer126can be formed using a material dissolved in a solvent in which the EL layer112is not dissolved. Any of the materials that can be used for the sacrificial film can be suitably used for the resin layer126.

Structure Example 2-3

A display device100C illustrated inFIG.4Cis different from the display device100B mainly in including an insulating layer125.

The insulating layer125is provided in contact with side surfaces and top end portions of the EL layer112. Part of the insulating layer125is provided in contact with the top surface of the substrate101.

The insulating layer125is positioned between the resin layer126and the EL layer112to serve as a protective film for preventing contact between the resin layer126and the EL layer112. In the case where the resin layer126is in contact with the EL layer112, the EL layer112might be dissolved by an organic solvent or the like used in formation of the resin layer126. In view of this, the insulating layer125is provided between the EL layer112and the resin layer126as described in this embodiment to protect the side surface of the organic layer.

The insulating layer125can be an insulating layer containing an inorganic material. As the insulating layer125, an inorganic insulating film such as an oxide insulating film, a nitride insulating film, an oxynitride insulating film, or a nitride oxide insulating film can be used, for example. The insulating layer125may have a single-layer structure or a stacked-layer structure. Examples of the oxide insulating film include a silicon oxide film, an aluminum oxide film, a magnesium oxide film, an indium gallium zinc oxide film, a gallium oxide film, a germanium oxide film, an yttrium oxide film, a zirconium oxide film, a lanthanum oxide film, a neodymium oxide film, a hafnium oxide film, and a tantalum oxide film. Examples of the nitride insulating film include a silicon nitride film and an aluminum nitride film. Examples of the oxynitride insulating film include a silicon oxynitride film and an aluminum oxynitride film Examples of the nitride oxide insulating film include a silicon nitride oxide film and an aluminum nitride oxide film. In particular, when a metal oxide film such as an aluminum oxide film or a hafnium oxide film or an inorganic insulating film such as a silicon oxide film that is formed by an ALD method is used for the insulating layer125, the insulating layer125has a small number of pin holes and excels in a function of protecting the EL layer.

The insulating layer125can be formed by a sputtering method, a CVD method, a PLD method, an ALD method, or the like. The insulating layer125is preferably formed by an ALD method achieving good coverage.

An insulating layer containing an organic material can be suitably used as the resin layer126. Examples of materials used for the resin layer126include an acrylic resin, a polyimide resin, an epoxy resin, an imide resin, a polyamide resin, a polyimide-amide resin, a silicone resin, a siloxane resin, a benzocyclobutene-based resin, a phenol resin, and precursors of these resins. The resin layer126may be formed using an organic material such as polyvinyl alcohol (PVA), polyvinyl butyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, or an alcohol-soluble polyamide resin.

A photosensitive resin can also be used for the resin layer126. A photoresist may be used for the photosensitive resin. As the photosensitive resin, a positive photosensitive material or a negative photosensitive material can be used.

Between the insulating layer125and the resin layer126, a reflective film (e.g., a metal film containing one or more of silver, palladium, copper, titanium, aluminum, and the like) may be provided to reflect the light that is emitted from the light-emitting layer. In this case, the light extraction efficiency can be increased.

Structure Example 2-4

A display device100D illustrated inFIG.5Ais different from the display device100B mainly in the shape of the EL layer112. A display device100E illustrated inFIG.5Bis an example in which the insulating layer125of the display device100C is used for the display device100D.

FIGS.5A and5Beach illustrate an example in which the width of the EL layer112is smaller than that of the pixel electrode111. In other words, the end portion of the EL layer112is positioned over the pixel electrode111.

The resin layer126is provided to cover the end portion of the pixel electrode111. This can prevent an electrical short circuit between the common electrode113and the pixel electrode111.

InFIG.5B, the insulating layer125is provided in contact with top and side surfaces of the EL layer112, top and side surfaces of the pixel electrode, and the top surface of the substrate101.

Structure Example 2-5

A display device100F illustrated inFIG.5Cis another example of the display device100D illustrated inFIG.5A, in which the pixel electrode111and the EL layer112have substantially the same width. A display device100G illustrated inFIG.5Dis another example of the display device100F, to which the insulating layer125is added.

Structure Example 2-6

A display device100H illustrated inFIG.6Ais different from the display device100C mainly in including an optical adjustment layer.

The light-emitting element110R includes an optical adjustment layer115R between the pixel electrode111R and the EL layer112R. The light-emitting element110G includes an optical adjustment layer115G between the pixel electrode111G and the EL layer112G. The light-emitting element110B includes an optical adjustment layer115B between the pixel electrode111B and the EL layer112B.

The optical adjustment layers115R,115G, and115B each have a property of transmitting visible light. The optical adjustment layers115R,115G, and115B have different thicknesses. Thus, the optical path lengths of the light-emitting elements can differ from one another.

Here, a conductive film that has a property of reflecting visible light is used for the pixel electrode111R, the pixel electrode111G, and the pixel electrode111B, and a conductive film that has properties of reflecting and transmitting visible light is used for the common electrode113. In that case, each light-emitting element has what is called a microcavity structure to intensify light with a specific wavelength. As a result, a display device with high color purity can be achieved.

A conductive material that has a property of transmitting visible light can be used for each of the optical adjustment layers. For example, a conductive oxide such as indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, zinc oxide containing gallium, indium-tin oxide containing silicon, or an indium-zinc oxide containing silicon can be used.

The optical adjustment layers can be formed after the formation of the pixel electrodes111R,111G, and111B and before the formation of the EL film112Rf. The optical adjustment layers may be formed using conductive films with different thicknesses from each other or may have a single-layer structure, a two-layer structure, or a three-layer structure, in the order of thin thickness.

When the light-emitting element has a microcavity structure, the emission intensity of light with a specific wavelength can be increased, so that color purity can be improved and light with different wavelengths (monochromatic light) can be extracted even if the same EL layer is used. A combination of the microcavity structure with coloring layers (color filters) is also possible. Furthermore, the emission intensity of light with a specific wavelength in the front direction can be increased, whereby power consumption can be reduced.

When the pixel electrode111of the light-emitting element is a reflective electrode having a structure in which a reflective conductive film and a light-transmitting conductive film are stacked, the light-transmitting conductive film functions as an optical adjustment layer and optical adjustment can be performed by controlling the thickness of the light-transmitting conductive film. Specifically, when the wavelength of light from the light-emitting layer is λ, the distance between the pixel electrode111and the common electrode113is preferably adjusted to around mλ/2 (m is a natural number).

To amplify desired light (wavelength: A) obtained from the light-emitting layer, the optical path length from the pixel electrode111to a region where desired light is obtained (a light-emitting region) in the light-emitting layer and the optical path length from the common electrode113to the light-emitting region in the light-emitting layer are preferably adjusted to around (2 m′+1)λ/4 (m′ is a natural number). Here, the light-emitting region means a region where holes and electrons are recombined in the light-emitting layer.

By such optical adjustment, the spectrum of light obtained from the light-emitting element110can be narrowed and light emission with high color purity can be obtained.

Structure Example 2-7

A display device100J illustrated inFIG.6Bis different from the display device100H mainly in the structures of the optical adjustment layer and the EL layer.

The display device100J shows an example where a microcavity structure is achieved with the thicknesses of the EL layers112R,112G, and112B. Such a structure does not require an optical adjustment layer provided additionally, simplifying the process.

For example, in the display device100J, the EL layer112R of the light-emitting element110R emitting light whose wavelength is longest has the largest thickness, and the EL layer112B of the light-emitting element110B emitting light whose wavelength is shortest has the smallest thickness. Without limitation to this, the thickness of the EL layer can be adjusted in consideration of the wavelength of light emitted by the light-emitting element, the optical characteristics of the layer included in the light-emitting element, the electrical characteristics of the light-emitting element, and the like.

AlthoughFIG.6Billustrates an example in which the optical adjustment layers115R,115G, and115B having the same thickness are provided, these layers are not necessarily provided.

Structure Example 3

An example of using a white-light-emitting element will be described below.

FIG.7Ais a schematic cross-sectional view of a display device160.FIG.1Acan be referred to for the top view.

The display device160includes a light-emitting unit120R, a light-emitting unit120G, and a light-emitting unit120B. The light-emitting units120R,120G, and120B each include a light-emitting element110W. The light-emitting element110W includes the pixel electrode111, an EL layer112W, and the common electrode113. The EL layer112W and the common electrode113are shared by a plurality of pixels. The EL layer112W includes a light-emitting layer that emits white light. The light-emitting element110W is a light-emitting element that emits white light.

The protective layer121is provided to cover the light-emitting element110R, and a protective layer123is provided over the protective layer121. The protective layer123functions as a planarization film. The protective layer123is not necessarily provided.

The light-emitting unit120R, the light-emitting unit120G, and the light-emitting unit120B include a coloring layer122R, a coloring layer122G, and a coloring layer122B, respectively, over the protective layer123. For example, the coloring layer122R, the coloring layer122G, and the coloring layer122B transmit red light, green light, and blue light, respectively. This enables fabrication of a full-color display device. Since each coloring layer is formed over the protective layer123, the positional alignment of the light-emitting elements and the coloring layers is easy compared with the case where the coloring layers are formed over a substrate different from the substrate101and then the two substrates are bonded to each other. Thus, a display device with extremely high resolution can be achieved. In addition, the distance between the coloring layers and the light-emitting element110W can be shortened, which inhibits color mixture and also improves the viewing angle characteristics of luminance and chromaticity.

Here, the EL layer112W is partitioned between different light-emitting units. This suitably prevents unintentional light emission (also referred to as crosstalk) from being caused by a current flowing through the EL layer112W between adjacent light-emitting units. As a result, the contrast can be increased to achieve a display device with high display quality.

FIG.7Bis a schematic cross-sectional view of a display device160A.

The light-emitting element110W of the display device160A includes the optical adjustment layers115R,115G, and115B having different thicknesses. This achieves a microcavity structure so that light emission with high color purity can be obtained from each light-emitting unit.

The insulating layer125and the resin layer126are provided between two adjacent light-emitting elements110.

FIGS.7A and7Bshow that the coloring layer122R has the largest thickness and the coloring layer122B has the smallest thickness in the three coloring layers. However, one embodiment of the present invention is not limited thereto, and all the coloring layers may have substantially the same thickness.

Manufacturing Method Example 2

A manufacturing method example of a display device using a white-light-emitting element will be described below. Note that for the portions similar to those in Manufacturing method example 1, the above description is referred to and the repeated description is skipped in some cases.

As in Manufacturing method example 1, the pixel electrodes111R,111G, and111B are formed over the substrate101.

Subsequently, an EL film112Wf to be the EL layer112W is deposited over the pixel electrodes111R,111G, and111B (FIG.8A).

Subsequently, a sacrificial film141dis formed over the EL film112Wf (FIG.8B).

Next, an island-shaped resist mask143dis formed over the sacrificial film141d(FIG.8C). The resist mask143dis provided in a region overlapping with the pixel electrode111R, a region overlapping with the pixel electrode111G, and a region overlapping with the pixel electrode111B.

The sacrificial film141d, the EL film112Wf, and the resist mask143dare etched by anisotropic dry etching to expose part of the top surface of the substrate101(FIG.8D). Thus, the island-shaped EL layer112W and a sacrificial layer142dover the EL layer112W are formed over each of the pixel electrodes111R,111G, and111B. The resist mask143dis preferably removed when the etching is completed.

Subsequently, the sacrificial film142dis removed to expose a top surface of the EL layer112W (FIG.8E). In particular, the sacrificial layer142dis preferably removed by wet etching using water or alcohol.

After that, the common electrode113and the protective layer121are formed in this order, whereby a plurality of light-emitting elements110W can be obtained (FIG.8F).

In the case of employing the structure ofFIG.7A, the protective layer123is further formed over the protective layer121, and the coloring layer122R, the coloring layer122G, and the coloring layer122B are formed over the protective layer123. For the protective layer123, a resin material having a light-transmitting property can be used. Each of the coloring layers can be formed by a photolithography method using a photosensitive resin material containing pigment or the like. Heat treatment (e.g., pre-baking or post-baking for curing a resin) at the formation of the protective layer123and the coloring layers is preferably performed at lower temperatures because thermal damage to the light-emitting element110W can be reduced. For example, the heat treatment is performed at a temperature higher than or equal to 80° C. and lower than or equal to 200° C., preferably higher than or equal to 85° C. and lower than or equal to 150° C., and further preferably higher than or equal to 90° C. and lower than or equal to 130° C.

Through the above steps, the display device160described as an example in Structure example 3 can be manufactured.

[Pixel Layout]

Pixel layouts different from the layout inFIG.1Awill be mainly described below. There is no particular limitation on the arrangement of the light-emitting elements (subpixels), and a variety of methods can be employed.

Examples of a top surface shape of the subpixel include polygons such as a triangle, a tetragon (including a rectangle and a square), and a pentagon; polygons with rounded corners; an ellipse; and a circle. Here, a top surface shape of the subpixel corresponds to a top surface shape of a light-emitting region of the light-emitting element.

A pixel150illustrated inFIG.9Aemploys S-stripe arrangement. The pixel150inFIG.9Aconsists of three subpixels: light-emitting elements110a,110b, and110c. For example, the light-emitting element110amay be a blue-light-emitting element, the light-emitting element110bmay be a red-light-emitting element, and the light-emitting element110cmay be a green-light-emitting element.

The pixel150illustrated inFIG.9Bincludes the light-emitting element110awhose top surface has a rough trapezoidal shape with rounded corners, the light-emitting element110bwhose top surface has a rough triangle shape with rounded corners, and the light-emitting element110cwhose top surface has a rough tetragonal or rough hexagonal shape with rounded corners. The light-emitting element110ahas a larger light-emitting area than the light-emitting element110b. In this manner, the shapes and sizes of the light-emitting elements can be determined independently. For example, the size of a light-emitting element with higher reliability can be smaller. For example, the light-emitting element110amay be a green-light-emitting element, the light-emitting element110bmay be a red-light-emitting element, and the light-emitting element110cmay be a blue-light-emitting element.

Pixels124aand124billustrated inFIG.9Cemploy PenTile arrangement.FIG.9Cillustrates an example in which the pixels124aincluding the light-emitting elements110aand110band the pixels124bincluding the light-emitting elements110band110care alternately arranged. For example, the light-emitting element110amay be a red-light-emitting element, the light-emitting element110bmay be a green-light-emitting element, and the light-emitting element110cmay be a blue-light-emitting element.

The pixels124aand124billustrated inFIGS.9D and9Eemploy delta arrangement. The pixel124aincludes two light-emitting elements (the light-emitting elements110aand110b) in the upper row (first row) and one light-emitting element (the light-emitting element110c) in the lower row (second row). The pixel124bincludes one light-emitting element (the light-emitting element110c) in the upper row (first row) and two light-emitting elements (the light-emitting elements110aand110b) in the lower row (second row). For example, the light-emitting element110amay be a red-light-emitting element, the light-emitting element110bmay be a green-light-emitting element, and the light-emitting element110cmay be a blue-light-emitting element.

FIG.9Dshows an example where the top surface of each light-emitting element has a rough tetragonal shape with rounded corners, andFIG.9Eshows an example where the top surface of each light-emitting element is circular.

FIG.9Fshows an example where light-emitting elements of different colors are arranged in a zigzag manner. Specifically, the positions of the top sides of two light-emitting elements arranged in the column direction (e.g., the light-emitting element110aand the light-emitting element110bor the light-emitting element110band the light-emitting element110c) are not aligned in the top view. For example, the light-emitting element110amay be a red-light-emitting element, the light-emitting element110bmay be a green-light-emitting element, and the light-emitting element110cmay be a blue-light-emitting element.

In a photolithography method, as a pattern to be formed by processing becomes finer, the influence of light diffraction becomes more difficult to ignore; therefore, the fidelity in transferring a photomask pattern by light exposure is degraded, and it becomes difficult to process a resist mask into a desired shape. Thus, a pattern with rounded corners is likely to be formed even with a rectangular photomask pattern. Consequently, a top surface of a light-emitting element may have a polygonal shape with rounded corners, an elliptical shape, a circular shape, or the like.

Furthermore, in the manufacturing method of the display device of one embodiment of the present invention, the EL layer is processed into an island shape with the use of a resist mask. A resist film formed over the EL layer needs to be cured at a temperature lower than the upper temperature limit of the EL layer. Therefore, the resist film is insufficiently cured in some cases depending on the upper temperature limit of the material of the EL layer and the curing temperature of the resist material. An insufficiently cured resist film may have a shape different from a desired shape by processing. As a result, a top surface of the EL layer may have a polygonal shape with rounded corners, an elliptical shape, a circular shape, or the like. For example, when a resist mask with a square top surface is intended to be formed, a resist mask with a circular top surface may be formed, and the top surface of the EL layer may be circular.

To obtain a desired top surface shape of the EL layer, a technique of correcting a mask pattern in advance so that a transferred pattern agrees with a design pattern (an optical proximity correction (OPC) technique) may be used. Specifically, with the OPC technique, a pattern for correction is added to a corner portion or the like of a figure on a mask pattern.

The above is the description of the pixel layouts.

At least part of this embodiment can be implemented in combination with any of the other embodiments described in this specification, as appropriate.

Embodiment 2

In this embodiment, structure examples of a display device of one embodiment of the present invention will be described.

The display device of this embodiment can be used for display portions of electronic devices such as a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable game console, a smart phone, a wristwatch terminal, a tablet terminal, a portable information terminal, and an audio reproducing device, in addition to display portions of electronic devices with a relatively large screen, such as a television device, a desktop or laptop personal computer, a monitor of a computer or the like, digital signage, and a large game machine such as a pachinko machine.

[Display Device400]

FIG.10is a perspective view of a display device400, andFIG.11Ais a cross-sectional view of the display device400.

The display device400has a structure where a substrate452and a substrate451are bonded to each other. InFIG.10, the substrate452is denoted by a dashed line.

The display device400includes a display portion462, a circuit464, a wiring465, and the like.FIG.10illustrates an example in which an IC473and an FPC472are implemented on the display device400. Thus, the structure illustrated inFIG.10can be regarded as a display module including the display device400, the IC (integrated circuit), and the FPC.

As the circuit464, a scan line driver circuit can be used, for example.

The wiring465has a function of supplying a signal and power to the display portion462and the circuit464. The signal and power are input to the wiring465from the outside through the FPC472or from the IC473.

FIG.10illustrates an example in which the IC473is provided over the substrate451by a chip on glass (COG) method, a chip on film (COF) method, or the like. An IC including a scan line driver circuit, a signal line driver circuit, or the like can be used as the IC473, for example. Note that the display device400and the display module are not necessarily provided with an IC. The IC may be mounted on the FPC by a COF method or the like.

FIG.11Aillustrates an example of cross sections of part of a region including the FPC472, part of the circuit464, part of the display portion462, and part of a region including a connection portion of the display device400.FIG.11Aspecifically illustrates an example of a cross section of a region including a light-emitting element430b, which emits green light, and a light-emitting element430c, which emits blue light, in the display portion462.

The display device400illustrated inFIG.11Aincludes a transistor202, a transistor210, the light-emitting element430b, the light-emitting element430c, and the like between a substrate453and a substrate454.

The light-emitting element described in Embodiment 1 can be employed for the light-emitting element430band the light-emitting element430c.

In the case where a pixel of the display device includes three kinds of subpixels including light-emitting elements emitting different colors from each other, the three subpixels can be of three colors of red (R), green (G), and blue (B) or of three colors of yellow (Y), cyan (C), and magenta (M). In the case where four subpixels are included, the four subpixels can be of four colors of R, G, B, and white (W) or of four colors of R, G, B, and Y.

The substrate454and a protective layer416are bonded to each other with an adhesive layer442. The adhesive layer442is provided so as to overlap with the light-emitting element430band the light-emitting element430c; that is, the display device400employs a solid sealing structure.

The light-emitting element430band the light-emitting element430ceach include a conductive layer411a, a conductive layer411b, and a conductive layer411cas a pixel electrode. The conductive layer411breflects visible light and serves as a reflective electrode. The conductive layer411ctransmits visible light and serves as an optical adjustment layer.

The conductive layer411ais connected to a conductive layer222bincluded in the transistor210through an opening provided in an insulating layer214. The transistor210has a function of controlling the driving of the light-emitting element.

An EL layer412G or an EL layer412B is provided to cover the pixel electrode. An insulating layer421is provided in contact with a side surface of the EL layer412G and a side surface of the EL layer412B, and a resin layer422is provided to fill a recessed portion of the insulating layer421. A common layer414, a common electrode413, and the protective layer416are provided to cover the EL layer412G and the EL layer412B.

Light from the light-emitting element is emitted toward the substrate454. For the substrate454, a material having a high visible-light-transmitting property is preferably used.

The transistor202and the transistor210are formed over the substrate453. These transistors can be fabricated using the same materials in the same steps.

The substrate453and an insulating layer212are bonded to each other with an adhesive layer455.

As a method for manufacturing the display device400, first, a formation substrate provided with the insulating layer212, the transistors, the light-emitting elements, and the like is bonded to the substrate454with the adhesive layer442. Then, the substrate453is bonded to a surface exposed by separation of the formation substrate, whereby the components formed over the formation substrate are transferred onto the substrate453. The substrate453and the substrate454are preferably flexible. Accordingly, the display device400can be highly flexible.

The inorganic insulating film that can be used as an insulating layer211and an insulating layer215can be used as the insulating layer212.

A connection portion204is provided in a region of the substrate453that is not overlapped by the substrate454. In the connection portion204, the wiring465is electrically connected to the FPC472through a conductive layer466and a connection layer242. The conductive layer466can be obtained by processing the same conductive film as the pixel electrode. Thus, the connection portion204and the FPC472can be electrically connected to each other through the connection layer242.

The transistor202and the transistor210each include a conductive layer221functioning as a gate, the insulating layer211functioning as a gate insulating layer, a semiconductor layer231including a channel formation region231iand a pair of low-resistance regions231n, a conductive layer222aconnected to one of the low-resistance regions231n, the conductive layer222bconnected to the other low-resistance region231n, an insulating layer225functioning as a gate insulating layer, a conductive layer223functioning as a gate, and the insulating layer215covering the conductive layer223. The insulating layer211is positioned between the conductive layer221and the channel formation region231i. The insulating layer225is positioned between the conductive layer223and the channel formation region231i.

The conductive layer222aand the conductive layer222bare connected to the corresponding low-resistance regions231nthrough openings provided in the insulating layer215. One of the conductive layers222aand222bserves as a source, and the other serves as a drain.

FIG.11Ashows an example where the insulating layer225covers a top and side surfaces of the semiconductor layer. The conductive layer222aand the conductive layer222bare connected to the corresponding low-resistance regions231nthrough openings provided in the insulating layer225and the insulating layer215.

In a transistor209illustrated inFIG.11B, the insulating layer225overlaps with the channel formation region231iof the semiconductor layer231and does not overlap with the low-resistance regions231n. The structure illustrated inFIG.11Bis obtained by processing the insulating layer225with the conductive layer223as a mask, for example. InFIG.11B, the insulating layer215is provided to cover the insulating layer225and the conductive layer223, and the conductive layer222aand the conductive layer222bare connected to the low-resistance regions231nthrough the openings in the insulating layer215. Furthermore, an insulating layer218covering the transistor may be provided.

There is no particular limitation on the structure of the transistors included in the display device of this embodiment. For example, a planar transistor, a staggered transistor, or an inverted staggered transistor can be used. A top-gate transistor or a bottom-gate transistor can be used. Alternatively, gates may be provided above and below a semiconductor layer where a channel is formed.

The structure in which the semiconductor layer where a channel is formed is provided between two gates is used for the transistors202and210. The two gates may be connected to each other and supplied with the same signal to operate the transistor. Alternatively, the threshold voltage of the transistor may be controlled by applying a potential for controlling the threshold voltage to one of the two gates and a potential for driving to the other of the two gates.

There is no particular limitation on the crystallinity of a semiconductor material used in the semiconductor layer of the transistor, and an amorphous semiconductor, a single crystal semiconductor, or a semiconductor having crystallinity other than single crystal (a microcrystalline semiconductor, a polycrystalline semiconductor, or a semiconductor partly including crystal regions) can be used. It is preferable to use a single crystal semiconductor or a semiconductor having crystallinity, in which case deterioration of the transistor characteristics can be inhibited.

It is preferable that a semiconductor layer of a transistor contain a metal oxide (also referred to as an oxide semiconductor). That is, a transistor including a metal oxide in its channel formation region (hereinafter, also referred to as an OS transistor) is preferably used for the display device of this embodiment.

The band gap of a metal oxide included in the semiconductor layer of the transistor is preferably 2 eV or more, further preferably 2.5 eV or more. The use of such a metal oxide having a wide band gap can reduce the off-state current of the OS transistor.

A metal oxide preferably contains at least indium or zinc, and further preferably contains indium and zinc. A metal oxide preferably contains indium, M (M is one or more of gallium, aluminum, yttrium, tin, silicon, boron, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and cobalt), and zinc, for example.

Alternatively, a semiconductor layer of a transistor may contain silicon. Examples of silicon include amorphous silicon and crystalline silicon (e.g., low-temperature polysilicon or single crystal silicon).

The transistor included in the circuit464and the transistor included in the display portion462may have the same structure or different structures. One structure or two or more kinds of structures may be employed for a plurality of transistors included in the circuit464. Similarly, one structure or two or more kinds of structures may be employed for a plurality of transistors included in the display portion462.

A material through which impurities such as water and hydrogen do not easily diffuse is preferably used for at least one of the insulating layers covering the transistors. This is because such an insulating layer can function as a barrier layer. Such a structure can effectively inhibit diffusion of impurities into the transistors from the outside and increase the reliability of a display device.

An inorganic insulating film is preferably used as each of the insulating layers211,212,215,218, and225. As the inorganic insulating film, a silicon nitride film, a silicon oxynitride film, a silicon oxide film, a silicon nitride oxide film, an aluminum oxide film, or an aluminum nitride film can be used, for example. A hafnium oxide film, an yttrium oxide film, a zirconium oxide film, a gallium oxide film, a tantalum oxide film, a magnesium oxide film, a lanthanum oxide film, a cerium oxide film, a neodymium oxide film, or the like may be used. A stack including two or more of the above inorganic insulating films may also be used.

An organic insulating film is suitable for the insulating layer214functioning as a planarization layer. Examples of materials that can be used for the organic insulating film include an acrylic resin, a polyimide resin, an epoxy resin, a polyamide resin, a polyimide-amide resin, a siloxane resin, a benzocyclobutene-based resin, a phenol resin, and precursors of these resins.

A variety of optical members can be arranged on the inner or outer surface of the substrate454. Examples of the optical members include a light-blocking layer, a polarizing plate, a retardation plate, a light diffusion layer (e.g., a diffusion film), an anti-reflective layer, a microlens array, and a light-condensing film. Furthermore, an antistatic film inhibiting the attachment of dust, a water repellent film suppressing the attachment of stain, a hard coat film inhibiting generation of a scratch caused by the use, an impact-absorbing layer, or the like may be arranged on the outer surface of the substrate454.

When the protective layer416covering the light-emitting element is provided, which inhibits an impurity such as water from entering the light-emitting element. As a result, the reliability of the light-emitting element can be enhanced.

FIG.11Aillustrates a connection portion228. In the connection portion228, the common electrode413is electrically connected to a wiring.FIG.11Aillustrates an example in which the wiring has the same stacked-layer structure as the pixel electrode.

For each of the substrates453and454, glass, quartz, ceramic, sapphire, a resin, a metal, an alloy, a semiconductor, or the like can be used. The substrate on the side from which light from the light-emitting element is extracted is formed using a material that transmits the light.

When the substrates453and454are formed using a flexible material, the flexibility of the display device can be increased. Furthermore, a polarizing plate may be used as the substrate453or the substrate454.

For each of the substrates453and454, any of the following can be used, for example: polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), a polyacrylonitrile resin, an acrylic resin, a polyimide resin, a polymethyl methacrylate resin, a polycarbonate (PC) resin, a polyethersulfone (PES) resin, polyamide resins (e.g., nylon and aramid), a polysiloxane resin, a cycloolefin resin, a polystyrene resin, a polyamide-imide resin, a polyurethane resin, a polyvinyl chloride resin, a polyvinylidene chloride resin, a polypropylene resin, a polytetrafluoroethylene (PTFE) resin, an ABS resin, and cellulose nanofiber. Glass that is thin enough to have flexibility may be used for one or both of the substrates453and454.

As the adhesive layer, any of a variety of curable adhesives such as a reactive curable adhesive, a thermosetting curable adhesive, an anaerobic adhesive, and a photocurable adhesive such as an ultraviolet curable adhesive can be used. Examples of these adhesives include an epoxy resin, an acrylic resin, a silicone resin, a phenol resin, a polyimide resin, an imide resin, a polyvinyl chloride (PVC) resin, a polyvinyl butyral (PVB) resin, and an ethylene vinyl acetate (EVA) resin. In particular, a material with low moisture permeability, such as an epoxy resin, is preferred. A two-component-mixture-type resin may be used. An adhesive sheet or the like may be used.

As the connection layer242, an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), or the like can be used.

As materials for the gates, the source, and the drain of a transistor and conductive layers functioning as wirings and electrodes included in the display device, any of metals such as aluminum, titanium, chromium, nickel, copper, yttrium, zirconium, molybdenum, silver, tantalum, and tungsten, or an alloy containing any of these metals as its main component can be used. A single-layer structure or a stacked-layer structure including a film containing any of these materials can be used.

As a light-transmitting conductive material, a conductive oxide such as indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, or zinc oxide containing gallium, or graphene can be used. It is also possible to use a metal material such as gold, silver, platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, or titanium; or an alloy material containing any of these metal materials. Alternatively, a nitride of the metal material (e.g., titanium nitride) or the like may be used. Note that in the case of using the metal material or the alloy material (or the nitride thereof), the thickness is preferably set small enough to transmit light. Alternatively, a stacked film of any of the above materials can be used for the conductive layers. For example, a stacked film of indium tin oxide and an alloy of silver and magnesium is preferably used because conductivity can be increased. They can also be used for conductive layers such as wirings and electrodes included in the display device, and conductive layers (e.g., a conductive layer functioning as a pixel electrode or a common electrode) included in a light-emitting element.

Examples of insulating materials that can be used for the insulating layers include a resin such as an acrylic resin and an epoxy resin, and an inorganic insulating material such as silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, and aluminum oxide.

At least part of this embodiment can be implemented in combination with any of the other embodiments described in this specification, as appropriate.

Embodiment 3

In this embodiment, the display panel of one embodiment of the present invention will be described with reference to drawings.

The display panel of this embodiment can be a high-resolution display panel. Thus, the display device of one embodiment of the present invention can be used for display portions of information terminals (wearable devices) such as watch-type or bracelet-type information terminals and display portions of wearable devices capable of being worn on a head, such as a VR device such as a head-mounted display and a glasses-type AR device.

[Display Module]

FIG.12Ais a perspective view of a display module280. The display module280includes a display device200A and an FPC290. Note that a display panel included in the display module280is not limited to the display device200A, and may be any of display devices200B to200F, which are described later.

The display module280includes a substrate291and a substrate292. The display module280includes a display portion281. The display portion281is a region where an image is displayed.

FIG.12Bis a perspective view schematically illustrating a structure on the substrate291side. Over the substrate291, a circuit portion282, a pixel circuit portion283over the circuit portion282, and the pixel portion284over the pixel circuit portion283are stacked. In addition, a terminal portion285for connection to the FPC290is included in a portion not overlapping with the pixel portion284over the substrate291. The terminal portion285and the circuit portion282are electrically connected to each other through a wiring portion286formed of a plurality of wirings.

The pixel portion284includes a plurality of pixels284aarranged periodically. An enlarged view of one pixel284ais illustrated on the right side inFIG.12B. The pixel284aincludes the light-emitting element110R emitting red light, the light-emitting element110G emitting green light, and the light-emitting element110B emitting blue light.

The pixel circuit portion283includes a plurality of pixel circuits283aarranged periodically. One pixel circuit283ais a circuit that controls light emission from three light-emitting elements included in one pixel284a. One pixel circuit283amay be provided with three circuits each of which controls light emission of one light-emitting element. For example, the pixel circuit283acan include at least one selection transistor, one current control transistor (driving transistor), and a capacitor for one light-emitting element. In this case, a gate signal is input to a gate of the selection transistor, and a source signal is input to a source of the selection transistor. Thus, an active-matrix display panel is achieved.

The circuit portion282includes a circuit for driving the pixel circuits283ain the pixel circuit portion283. For example, one or both of a gate line driver circuit and a source line driver circuit are preferably included. In addition, at least one of an arithmetic circuit, a memory circuit, a power supply circuit, and the like may be included. A transistor included in the circuit portion282may constitute part of the pixel circuit283a. That is, the pixel circuit283amay be constituted by a transistor included in the pixel circuit portion283and a transistor included in the circuit portion282.

The FPC290serves as a wiring for supplying a video signal, a power supply potential, and the like to the circuit portion282from the outside. An IC may be mounted on the FPC290.

The display module280can have a structure in which one or both of the pixel circuit portion283and the circuit portion282are stacked below the pixel portion284; thus, the aperture ratio (the effective display area ratio) of the display portion281can be significantly high. For example, the aperture ratio of the display portion281can be greater than or equal to 40% and less than 100%, preferably greater than or equal to 50% and less than or equal to 95%, and further preferably greater than or equal to 60% and less than or equal to 95%. Furthermore, the pixels284acan be arranged extremely densely and thus the display portion281can have greatly high resolution. For example, the pixels284aare preferably arranged in the display portion281with a resolution greater than or equal to 2000 ppi, preferably greater than or equal to 3000 ppi, further preferably greater than or equal to 5000 ppi, and still further preferably greater than or equal to 6000 ppi, and less than or equal to 20000 ppi or less than or equal to 30000 ppi.

Such a display module280has extremely high resolution, and thus can be suitably used for a device for VR such as a head-mounted display or a glasses-type device for AR. For example, even in the case of a structure in which the display portion of the display module280is seen through a lens, pixels of the extremely-high-resolution display portion281included in the display module280are prevented from being seen when the display portion is enlarged by the lens, so that display providing a high sense of immersion can be performed. Without being limited thereto, the display module280can be suitably used for electronic devices including a relatively small display portion. For example, the display module280can be favorably used in a display portion of a wearable electronic device, such as a wrist watch.

[Display Device200A]

The display device200A illustrated inFIG.13includes a substrate301, the light-emitting elements110R,110G, and110B, a capacitor240, and a transistor310.

The substrate301corresponds to the substrate291inFIGS.12A and12B.

The transistor310is a transistor whose channel formation region is in the substrate301. As the substrate301, a semiconductor substrate such as a single crystal silicon substrate can be used, for example. The transistor310includes part of the substrate301, a conductive layer311, a low-resistance region312, an insulating layer313, and an insulating layer314. The conductive layer311functions as a gate electrode. The insulating layer313is positioned between the substrate301and the conductive layer311and functions as a gate insulating layer. The low-resistance region312is a region where the substrate301is doped with an impurity, and functions as one of a source and a drain. The insulating layer314is provided to cover a side surface of the conductive layer311.

An element isolation layer315is provided between two adjacent transistors310so as to be embedded in the substrate301.

Furthermore, an insulating layer261is provided to cover the transistor310, and the capacitor240is provided over the insulating layer261.

The capacitor240includes a conductive layer241, a conductive layer245, and an insulating layer243between the conductive layers241and245. The conductive layer241functions as one electrode of the capacitor240, the conductive layer245functions as the other electrode of the capacitor240, and the insulating layer243functions as a dielectric of the capacitor240.

The conductive layer241is provided over the insulating layer261and is embedded in an insulating layer254. The conductive layer241is electrically connected to one of the source and the drain of the transistor310through a plug271embedded in the insulating layer261. The insulating layer243is provided to cover the conductive layer241. The conductive layer245is provided in a region overlapping with the conductive layer241with the insulating layer243therebetween.

An insulating layer255ais provided to cover the capacitor240; an insulating layer255bis provided over the insulating layer255a; and an insulating layer255cis provided over the insulating layer255b.

An inorganic insulating film can be suitably used as each of the insulating layers255a,255b, and255c. For example, it is preferable that a silicon oxide film be used as the insulating layers255aand255cand a silicon nitride film be used as the insulating layer255b. This enables the insulating layer255bto function as an etching protective film Although this embodiment shows an example in which part of the insulating layer255cis etched to form a recessed portion, the recessed portion is not necessarily provided in the insulating layer255c.

The light-emitting element110R, the light-emitting element110G, and the light-emitting element110B are provided over the insulating layer255c. Embodiment 1 can be referred to for the structures of the light-emitting element110R, the light-emitting element110G, and the light-emitting element110B. A stacked structure including the substrate301and the components thereover up to the insulating layer255ccorresponds to the substrate101in Embodiment 1.

In the display device200A, since the light-emitting elements of different colors are separately formed, the difference between the chromaticity at low luminance emission and that at high luminance emission is small. Furthermore, since the EL layers112R,112G, and112B are separated from each other, crosstalk generated between adjacent subpixels can be prevented while the display device200A has high resolution. Accordingly, the display panel can have high resolution and high display quality.

In the region between adjacent light-emitting elements, the insulating layer125and the resin layer126are provided.

The pixel electrodes111R,111G, and111B of the light-emitting elements are each electrically connected to one of the source and the drain of the transistor310through a plug256embedded in the insulating layers255a,255b, and255c, the conductive layer241embedded in the insulating layer254, and the plug271embedded in the insulating layer261. A top surface of the insulating layer255cand a top surface of the plug256are level with or substantially level with each other. Any of a variety of conductive materials can be used for the plugs.

The protective layer121is provided over the light-emitting elements110R,110G, and110B. A substrate170is bonded above the protective layer121with an adhesive layer171.

An insulating layer covering an end portion of a top end portion of the pixel electrode111is not provided between two adjacent pixel electrodes111. Thus, the interval between adjacent light-emitting elements can be extremely shortened. Accordingly, the display device can have high resolution or high definition.

[Display Device200B]

The display device200B illustrated inFIG.14has a structure in which a transistor310A and a transistor310B each having a channel formed in a semiconductor substrate are stacked. Note that in the following description of display panels, the description of portions similar to those of the above-described display panel may be omitted.

In the display device200B, a substrate301B provided with the transistor310B, the capacitor240, and the light-emitting elements is bonded to a substrate301A provided with the transistor310A.

Here, an insulating layer345is provided on a bottom surface of the substrate301B. An insulating layer346is provided over the insulating layer261over the substrate301A. The insulating layers345and346function as protective layers and can inhibit diffusion of impurities into the substrate301B and the substrate301A. As the insulating layers345and346, an inorganic insulating film that can be used as the protective layer121or an insulating layer332can be used.

The substrate301B is provided with a plug343that penetrates the substrate301B and the insulating layer345. An insulating layer344functioning as a protective layer is preferably provided to cover a side surface of the plug343.

A conductive layer342is provided under the insulating layer345on the rear surface of the substrate301B. The conductive layer342is embedded in the insulating layer335. Bottom surfaces of the conductive layer342and the insulating layer335are planarized. The conductive layer342is electrically connected to the plug343.

A conductive layer341is provided over the insulating layer346over the substrate301A. The conductive layer341is embedded in the insulating layer336. Top surfaces of the conductive layer341and the insulating layer336are planarized.

The conductive layers341and342are preferably formed using the same conductive material. For example, it is possible to use a metal film containing an element selected from A1, Cr, Cu, Ta, Ti, Mo, and W, or a metal nitride film containing any of the above elements as a component (a titanium nitride film, a molybdenum nitride film, or a tungsten nitride film). Copper is particularly preferably used for the conductive layers341and342. In that case, it is possible to employ copper-to-copper (Cu-to-Cu) direct bonding (a technique for achieving electrical continuity by connecting copper (Cu) pads).

[Display Device200C]

The display device200C illustrated inFIG.15has a structure in which the conductive layer341and the conductive layer342are bonded to each other with a bump347.

As illustrated inFIG.15, providing the bump347between the conductive layer341and the conductive layer342enables the conductive layers341and342to be electrically connected to each other. The bump347can be formed using a conductive material containing gold (Au), nickel (Ni), indium (In), tin (Sn), or the like, for example. As another example, solder may be used for the bump347. An adhesive layer348may be provided between the insulating layer345and the insulating layer346. In the case where the bump347is provided, the insulating layer335and the insulating layer336may be omitted.

[Display Device200D]

The display device200D illustrated inFIG.16differs from the display device200A mainly in a structure of a transistor.

A transistor320is a transistor that contains a metal oxide (also referred to as an oxide semiconductor) in a semiconductor layer where a channel is formed (i.e., an OS transistor).

The transistor320includes a semiconductor layer321, an insulating layer323, a conductive layer324, a pair of conductive layers325, an insulating layer326, and a conductive layer327.

A substrate331corresponds to the substrate291illustrated inFIGS.12A and12B.

The insulating layer332is provided over the substrate331. The insulating layer332functions as a barrier layer that prevents diffusion of an impurity such as water or hydrogen from the substrate331into the transistor320and release of oxygen from the semiconductor layer321to the insulating layer332side. As the insulating layer332, it is possible to use, for example, a film in which hydrogen or oxygen is less likely to diffuse than in a silicon oxide film, such as an aluminum oxide film, a hafnium oxide film, or a silicon nitride film.

The conductive layer327is provided over the insulating layer332, and the insulating layer326is provided to cover the conductive layer327. The conductive layer327functions as a first gate electrode of the transistor320, and part of the insulating layer326functions as a first gate insulating layer. An oxide insulating film such as a silicon oxide film is preferably used as at least part of the insulating layer326that is in contact with the semiconductor layer321. A top surface of the insulating layer326is preferably planarized.

The semiconductor layer321is provided over the insulating layer326. A metal oxide film having semiconductor characteristics (also referred to as an oxide semiconductor film) is preferably used as the semiconductor layer321. The pair of conductive layers325are provided on and in contact with the semiconductor layer321, and function as a source electrode and a drain electrode.

An insulating layer328is provided to cover top and side surfaces of the pair of conductive layers325, a side surface of the semiconductor layer321, and the like, and an insulating layer264is provided over the insulating layer328. The insulating layer328functions as a barrier layer that prevents diffusion of an impurity such as water or hydrogen from the insulating layer264and the like into the semiconductor layer321and release of oxygen from the semiconductor layer321. As the insulating layer328, an insulating film similar to the insulating layer332can be used.

An opening reaching the semiconductor layer321is provided in the insulating layers328and264. The insulating layer323that is in contact with a top surface of the semiconductor layer321and the conductive layer324are embedded in the opening. The conductive layer324functions as a second gate electrode, and the insulating layer323functions as a second gate insulating layer.

A top surface of the conductive layer324, a top surface of the insulating layer323, and a top surface of the insulating layer264are planarized so that they are level with or substantially level with each other, and an insulating layer329and an insulating layer265are provided to cover these layers.

The insulating layers264and265each function as an interlayer insulating layer. The insulating layer329functions as a barrier layer that prevents diffusion of an impurity such as water or hydrogen from the insulating layer265or the like into the transistor320. As the insulating layer329, an insulating film similar to the insulating layers328and332can be used.

A plug274electrically connected to one of the pair of conductive layers325is provided to be embedded in the insulating layers265,329, and264. Here, the plug274preferably includes a conductive layer274athat covers a side surface of an opening formed in the insulating layers265,329,264, and328and part of the top surface of the conductive layer325, and a conductive layer274bin contact with a top surface of the conductive layer274a. For the conductive layer274a, a conductive material in which hydrogen and oxygen are less likely to diffuse is preferably used.

[Display Device200E]

The display device200E illustrated inFIG.17has a structure in which a transistor320A and a transistor320B each including an oxide semiconductor in a semiconductor where a channel is formed are stacked.

The description of the display device200D can be referred to for the transistor320A, the transistor320B, and the components around them.

Although the structure in which two transistors each including an oxide semiconductor are stacked is described, one embodiment of the present invention is not limited thereto. For example, three or more transistors may be stacked.

[Display Device200F]

The display device200F illustrated inFIG.18has a structure in which the transistor310having a channel formed in the substrate301and the transistor320including a metal oxide in a semiconductor layer where a channel is formed are stacked.

The insulating layer261is provided to cover the transistor310, and a conductive layer251is provided over the insulating layer261. An insulating layer262is provided to cover the conductive layer251, and a conductive layer252is provided over the insulating layer262. The conductive layer251and the conductive layer252each function as a wiring. An insulating layer263and the insulating layer332are provided to cover the conductive layer252, and the transistor320is provided over the insulating layer332. The insulating layer265is provided to cover the transistor320, and the capacitor240is provided over the insulating layer265. The capacitor240and the transistor320are electrically connected to each other through the plug274.

The transistor320can be used as a transistor included in the pixel circuit. The transistor310can be used as a transistor included in the pixel circuit or a transistor included in a driver circuit for driving the pixel circuit (a gate line driver circuit or a source line driver circuit). The transistor310and the transistor320can also be used as transistors included in a variety of circuits such as an arithmetic circuit and a memory circuit.

With such a structure, not only the pixel circuit but also the driver circuit and the like can be formed directly under the light-emitting elements; thus, the display panel can be downsized as compared with the case where a driver circuit is provided around a display region.

At least part of this embodiment can be implemented in combination with any of the other embodiments described in this specification, as appropriate.

Embodiment 4

In this embodiment, a light-emitting element (also referred to as light-emitting device) that can be used in the display device of one embodiment of the present invention will be described.

In this specification and the like, a structure in which light-emitting layers in light-emitting devices of different colors (here, blue (B), green (G), and red (R)) are separately formed or separately patterned may be referred to as a side-by-side (SBS) structure. In this specification and the like, a light-emitting device capable of emitting white light may be referred to as a white light-emitting device. Note that a combination of white light-emitting devices with coloring layers (e.g., color filters) enables a full-color display device.

[Light-Emitting Device]

Structures of light-emitting devices can be classified roughly into a single structure and a tandem structure. A light-emitting device having a single structure includes one light-emitting unit between a pair of electrodes. The light-emitting unit includes one or more light-emitting layers. To obtain white light emission with a single structure, two or more light-emitting layers are selected such that emission of the light-emitting layers can produce an achromatic color (e.g., white). For example, in the case of two colors, when emission colors of a first light-emitting layer and a second light-emitting layer are complementary colors, the light-emitting device can be configured to emit white light as a whole.

A light-emitting device having a tandem structure includes a plurality of light-emitting units between a pair of electrodes. Each light-emitting unit includes one or more light-emitting layers. When light-emitting layers that emit light of the same color are used in each light-emitting unit, luminance per predetermined current can be increased, and the light-emitting device can have higher reliability than that with a single structure. To obtain white light emission with a tandem structure, the light-emitting device is configured to obtain white light emission by combining light from light-emitting layers of a plurality of light-emitting units. Note that a combination of emission colors for obtaining white light emission is similar to that for a single structure. In the light-emitting device with a tandem structure, it is preferable that an intermediate layer such as a charge-generation layer be provided between the plurality of light-emitting units.

When the white light-emitting device and a light-emitting device with a SBS structure are compared to each other, the latter can have lower power consumption than the former. Meanwhile, the white light-emitting device is preferable in terms of lower manufacturing cost and higher manufacturing yield because the manufacturing process of the white light-emitting device is simpler than that of the light-emitting device with the SBS structure.

<Structure Example of Light-Emitting Device>

As illustrated inFIG.19A, the light-emitting device includes an EL layer790between a pair of electrodes (a lower electrode791and an upper electrode792). The EL layer790can be formed of a plurality of layers such as a layer720, a light-emitting layer711, and a layer730. The layer720can include, for example, a layer containing a substance with a high electron-injection property (an electron-injection layer) and a layer containing a substance with a high electron-transport property (an electron-transport layer). The light-emitting layer711contains a light-emitting compound, for example. The layer730can include, for example, a layer containing a substance with a high hole-injection property (a hole-injection layer) and a layer containing a substance with a high hole-transport property (a hole-transport layer).

The structure including the layer720, the light-emitting layer711, and the layer730, which is provided between a pair of electrodes, can function as a single light-emitting unit, and the structure inFIG.19Ais referred to as a single structure in this specification.

Specifically, the light-emitting device illustrated inFIG.19Bincludes, over the lower electrode791, a layer730-1, a layer730-2, the light-emitting layer711, a layer720-1, a layer720-2, and the upper electrode792. For example, when the lower electrode791functions as an anode and the upper electrode792functions as a cathode, the layer730-1functions as a hole-injection layer, the layer730-2functions as a hole-transport layer, the layer720-1functions as an electron-transport layer, and the layer720-2functions as an electron-injection layer. When the lower electrode791functions as a cathode and the upper electrode792functions as an anode, the layer730-1functions as an electron-injection layer, the layer730-2functions as an electron-transport layer, the layer720-1functions as a hole-transport layer, and the layer720-2functions as the hole-injection layer. With such a layered structure, carriers can be efficiently injected to the light-emitting layer711, and the efficiency of the recombination of carriers in the light-emitting layer711can be enhanced.

Note that structures in which a plurality of light-emitting layers (light-emitting layers711,712, and713) are provided between the layer720and the layer730as illustrated inFIGS.19C and19Dare other variations of the single structure.

Structures in which a plurality of light-emitting units (EL layers790aand790b) are connected in series with an intermediate layer (charge-generation layer)740therebetween as illustrated inFIGS.19E and19Fare referred to as a tandem structure in this specification. A tandem structure may be referred to as a stack structure. The tandem structure enables a light-emitting device capable of high luminance light emission.

InFIG.19C, light-emitting materials that emit light of the same color, or moreover, the same light-emitting material may be used for the light-emitting layer711, the light-emitting layer712, and the light-emitting layer713. The stacked light-emitting layers can increase emission luminance.

Alternatively, different light-emitting materials may be used for the light-emitting layer711, the light-emitting layer712, and the light-emitting layer713. White light can be obtained when the light-emitting layer711, the light-emitting layer712, and the light-emitting layer713emit light of complementary colors.FIG.19Dshows an example in which a coloring layer795functioning as a color filter is provided. When white light passes through a color filter, light of a desired color can be obtained.

InFIG.19E, light-emitting materials that emit light of the same color may be used for the light-emitting layer711and the light-emitting layer712. Alternatively, light-emitting materials that emit light of different colors may be used for the light-emitting layer711and the light-emitting layer712. White light can be obtained when the light-emitting layer711and the light-emitting layer712emit light of complementary colors.FIG.19Fshows an example in which the coloring layer795is further provided.

InFIGS.19C to19F, the layer720and the layer730may each have a layered structure of two or more layers as inFIG.19B.

InFIG.19D, light-emitting materials that emit light of the same color may be used for the light-emitting layer711, the light-emitting layer712, and the light-emitting layer713. Similarly, inFIG.19F, light-emitting materials that emit light of the same color may be used for the light-emitting layer711and the light-emitting layer712. Here, when a color conversion layer is used instead of the coloring layer795, light of a desired color different from the emission color of the light-emitting material can be obtained. For example, a blue light-emitting material is used for each light-emitting layer and blue light passes through the color conversion layer, whereby light with a wavelength longer than that of blue light (e.g., red light or green light) can be obtained. For the color conversion layer, a fluorescent material, a phosphorescent material, quantum dots, or the like can be used.

The emission color of the light-emitting device can be changed to red, green, blue, cyan, magenta, yellow, white, or the like depending on the material of the EL layer790. When the light-emitting device has a microcavity structure, the color purity can be further increased.

The light-emitting device that emits white light may have a structure in which a light-emitting layer contains two or more kinds of light-emitting substances, or two or more light-emitting layers containing different light-emitting substances are stacked. In that case, the light-emitting substances are preferably selected such that the light-emitting substances emit light of complementary colors.

[Light-Emitting Device]

Here, a specific structure example of a light-emitting device will be described.

The light-emitting device includes at least a light-emitting layer. In addition to the light-emitting layer, the light-emitting device may further include a layer containing any of a substance with a high hole-injection property, a substance with a high hole-transport property, a hole-blocking material, a substance with a high electron-injection property, a substance with a high electron-transport property, an electron-blocking material, a substance with a bipolar property (a substance with a high electron- and hole-transport property), and the like.

Either a low molecular compound or a high molecular compound can be used in the light-emitting device, and an inorganic compound may also be included. Each layer included in the light-emitting device can be formed by any of the following methods: an evaporation method (including a vacuum evaporation method), a transfer method, a printing method, an inkjet method, a coating method, and the like.

For example, the light-emitting device can include one or more of a hole-injection layer, a hole-transport layer, a hole-blocking layer, an electron-blocking layer, an electron-transport layer, and an electron-injection layer in addition to the light-emitting layer.

The hole-injection layer injects holes from the anode to the hole-transport layer and contains a material with a high hole-injection property. Examples of a material with a high hole-injection property include an aromatic amine compound and a composite material containing a hole-transport material and an acceptor material (electron-accepting material).

The hole-transport layer transports holes injected from the anode by the hole-injection layer, to the light-emitting layer. The hole-transport layer contains a hole-transport material.

The hole-transport material preferably has a hole mobility higher than or equal to 1×10−6cm2/Vs. Note that other substances can also be used as long as the substances have a hole-transport property higher than an electron-transport property. As the hole-transport material, materials having a high hole-transport property, such as a π-electron rich heteroaromatic compound (e.g., a carbazole derivative, a thiophene derivative, and a furan derivative) and an aromatic amine (a compound having an aromatic amine skeleton), are preferred.

The electron-transport layer transports electrons injected from the cathode by the electron-injection layer, to the light-emitting layer. The electron-transport layer contains an electron-transport material. The electron-transport material preferably has an electron mobility higher than or equal to 1×10−6cm2/Vs. Note that other substances can also be used as long as the substances have an electron-transport property higher than a hole-transport property. As the electron-transport material, any of the following materials having a high electron-transport property can be used, for example: a metal complex having a quinoline skeleton, a metal complex having a benzoquinoline skeleton, a metal complex having an oxazole skeleton, a metal complex having a thiazole skeleton, an oxadiazole derivative, a triazole derivative, an imidazole derivative, an oxazole derivative, a thiazole derivative, a phenanthroline derivative, a quinoline derivative having a quinoline ligand, a benzoquinoline derivative, a quinoxaline derivative, a dibenzoquinoxaline derivative, a pyridine derivative, a bipyridine derivative, a pyrimidine derivative, and a n-electron deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound.

The electron-injection layer injects electrons from the cathode to the electron-transport layer and contains a material with a high electron-injection property. As the material with a high electron-injection property, an alkali metal, an alkaline earth metal, or a compound thereof can be used. As the material with a high electron-injection property, a composite material containing an electron-transport material and a donor material (electron-donating material) can also be used.

The electron-injection layer can be formed using an alkali metal, an alkaline earth metal, or a compound thereof, such as lithium, cesium, ytterbium, lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), 8-(quinolinolato)lithium (abbreviation: Liq), 2-(2-pyridyl)phenolatolithium (abbreviation: LiPP), 2-(2-pyridyl)-3-pyridinolatolithium (abbreviation: LiPPy), 4-phenyl-2-(2-pyridyl)phenolatolithium (abbreviation: LiPPP), lithium oxide (LiOx), or cesium carbonate, for example. The electron-injection layer may have a stacked-layer structure of two or more layers. In the stacked-layer structure, for example, lithium fluoride can be used for the first layer and ytterbium can be used for the second layer.

Alternatively, the electron-injection layer may be formed using an electron-transport material. For example, a compound having an unshared electron pair and an electron deficient heteroaromatic ring can be used as the electron-transport material. Specifically, it is possible to use a compound having at least one of a pyridine ring, a diazine ring (a pyrimidine ring, a pyrazine ring, or a pyridazine ring), and a triazine ring.

Note that the lowest unoccupied molecular orbital (LUMO) level of the organic compound having an unshared electron pair is preferably greater than or equal to −3.6 eV and less than or equal to −2.3 eV. In general, the highest occupied molecular orbital (HOMO) level and the LUMO level of an organic compound can be estimated by cyclic voltammetry (CV), photoelectron spectroscopy, optical absorption spectroscopy, inverse photoelectron spectroscopy, or the like.

For example, 4,7-diphenyl-1,10-phenanthroline (abbreviation: BPhen), 2,9-di(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen), diquinoxalino[2,3-a: 2′,3′-c]phenazine (abbreviation: HATNA), 2,4,6-tris[3′-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz), or the like can be used as the organic compound having an unshared electron pair. Note that NBPhen has a higher glass transition point (Tg) than BPhen and thus has high heat resistance.

The light-emitting layer contains a light-emitting substance. The light-emitting layer can contain one or more kinds of light-emitting substances. As the light-emitting substance, a substance whose emission color is blue, violet, bluish violet, green, yellowish green, yellow, orange, red, or the like is appropriately used. Alternatively, as the light-emitting substance, a substance that emits near-infrared light can be used.

Examples of the light-emitting substance include a fluorescent material, a phosphorescent material, a TADF material, and a quantum dot material.

Examples of a fluorescent material include a pyrene derivative, an anthracene derivative, a triphenylene derivative, a fluorene derivative, a carbazole derivative, a dibenzothiophene derivative, a dibenzofuran derivative, a dibenzoquinoxaline derivative, a quinoxaline derivative, a pyridine derivative, a pyrimidine derivative, a phenanthrene derivative, and a naphthalene derivative.

Examples of a phosphorescent material include an organometallic complex (particularly an iridium complex) having a 4H-triazole skeleton, a 1H-triazole skeleton, an imidazole skeleton, a pyrimidine skeleton, a pyrazine skeleton, or a pyridine skeleton; an organometallic complex (particularly an iridium complex) having a phenylpyridine derivative including an electron-withdrawing group as a ligand; a platinum complex; and a rare earth metal complex.

The light-emitting layer may contain one or more kinds of organic compounds (e.g., a host material or an assist material) in addition to the light-emitting substance (guest material). As one or more kinds of organic compounds, one or both of a hole-transport material and an electron-transport material can be used. Alternatively, as one or more kinds of organic compounds, a bipolar material or a TADF material may be used.

The light-emitting layer preferably includes a phosphorescent material and a combination of a hole-transport material and an electron-transport material that easily forms an exciplex, for example. With such a structure, light emission can be efficiently obtained by exciplex-triplet energy transfer (ExTET), which is energy transfer from the exciplex to the light-emitting substance (phosphorescent material). When a combination of materials is selected so as to form an exciplex that emits light whose wavelength overlaps with the wavelength of a lowest-energy-side absorption band of the light-emitting substance, energy can be transferred smoothly and light emission can be obtained efficiently. With the above structure, high efficiency, low-voltage driving, and a long lifetime of a light-emitting device can be achieved at the same time.

At least part of any of the structure examples, the drawings corresponding thereto, and the like described in this embodiment can be implemented in combination with any of the other structure examples, the other drawings corresponding thereto, and the like as appropriate.

At least part of this embodiment can be implemented in combination with any of the other embodiments described in this specification, as appropriate.

Embodiment 5

In this embodiment, electronic devices of one embodiment of the present invention will be described with reference toFIGS.20A to20D,FIGS.21A to21F, andFIGS.22A to22G.

Electronic devices in this embodiment are each provided with the display panel (display device) of one embodiment of the present invention in a display portion. The display panel of one embodiment of the present invention can be easily increased in resolution and definition and can achieve high display quality. Thus, the display panel of one embodiment of the present invention can be used for a display portion of a variety of electronic devices.

Examples of the electronic devices include a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable game console, a portable information terminal, and an audio reproducing device, in addition to electronic devices with a relatively large screen, such as a television device, desktop and laptop personal computers, a monitor of a computer and the like, digital signage, and a large game machine such as a pachinko machine.

In particular, the display panel of one embodiment of the present invention can have a high resolution, and thus can be favorably used for an electronic device having a relatively small display portion. Examples of such an electronic device include watch-type and bracelet-type information terminal devices (wearable devices) and wearable devices worn on the head, such as a VR device like a head-mounted display, a glasses-type AR device, and an MR device.

The definition of the display panel of one embodiment of the present invention is preferably as high as HD (number of pixels: 1280×720), FHD (number of pixels: 1920×1080), WQHD (number of pixels: 2560×1440), WQXGA (number of pixels: 2560×1600), 4K (number of pixels: 3840×2160), or 8K (number of pixels: 7680×4320). In particular, a definition of 4K, 8K, or higher is preferable. The pixel density (resolution) of the display panel of one embodiment of the present invention is preferably higher than or equal to 100 ppi, further preferably higher than or equal to 300 ppi, further preferably higher than or equal to 500 ppi, further preferably higher than or equal to 1000 ppi, further preferably higher than or equal to 2000 ppi, further preferably higher than or equal to 3000 ppi, still further preferably higher than or equal to 5000 ppi, and yet further preferably higher than or equal to 7000 ppi. The use of the display panel having one or both of such high definition and high resolution can further increase realistic sensation, sense of depth, and the like in personal use such as portable use and home use. There is no particular limitation on the screen ratio (aspect ratio) of the display panel of one embodiment of the present invention. For example, the display panel is compatible with a variety of screen ratios such as 1:1 (a square), 4:3, 16:9, and 16:10.

The electronic device in this embodiment may include a sensor (a sensor having a function of sensing, detecting, or measuring force, displacement, position, speed, acceleration, angular velocity, rotational frequency, distance, light, liquid, magnetism, temperature, a chemical substance, sound, time, hardness, electric field, current, voltage, electric power, radiation, flow rate, humidity, gradient, oscillation, a smell, or infrared rays).

The electronic device in this embodiment can have a variety of functions. For example, the electronic device in this embodiment can have a function of displaying a variety of data (a still image, a moving image, a text image, and the like) on the display portion, a touch panel function, a function of displaying a calendar, date, time, and the like, a function of executing a variety of software (programs), a wireless communication function, and a function of reading out a program or data stored in a recording medium.

Examples of head-mounted wearable devices are described with reference toFIGS.20A to20D. These wearable devices have one or both of a function of displaying AR contents and a function of displaying VR contents. Note that these wearable devices may have a function of displaying SR or MR contents, in addition to AR and VR contents. The electronic device having a function of displaying contents of at least one of AR, VR, SR, MR, and the like enables the user to feel a higher level of immersion.

An electronic device700A illustrated inFIG.20Aand an electronic device700B illustrated inFIG.20Beach include a pair of display panels751, a pair of housings721, a communication portion (not illustrated), a pair of wearing portions723, a control portion (not illustrated), an image capturing portion (not illustrated), a pair of optical members753, a frame757, and a pair of nose pads758.

The display panel of one embodiment of the present invention can be used in the display panels751. Thus, the electronic devices are capable of performing ultrahigh-resolution display.

The electronic devices700A and700B can each project images displayed on the display panels751onto display regions756of the optical members753. Since the optical members753have a light-transmitting property, the user can see images displayed on the display regions, which are superimposed on transmission images seen through the optical members753. Accordingly, the electronic devices700A and700B are electronic devices capable of AR display.

In the electronic devices700A and700B, a camera capable of capturing images of the front side may be provided as the image capturing portion. Furthermore, when the electronic devices700A and700B are provided with an acceleration sensor such as a gyroscope sensor, the orientation of the user's head can be sensed and an image corresponding to the orientation can be displayed on the display regions756.

The communication portion includes a wireless communication device, and a video signal and the like can be supplied by the wireless communication device. Instead of or in addition to the wireless communication device, a connector that can be connected to a cable for supplying a video signal and a power supply potential may be provided.

The electronic devices700A and700B are provided with a battery so that they can be charged wirelessly and/or by wire.

A touch sensor module may be provided in the housing721. The touch sensor module has a function of detecting a touch on the outer surface of the housing721. Detecting a tap operation, a slide operation, or the like by the user with the touch sensor module enables various types of processing. For example, a video can be paused or restarted by a tap operation, and can be fast-forwarded or fast-reversed by a slide operation. When the touch sensor module is provided in each of the two housings721, the range of the operation can be increased.

Various touch sensors can be applied to the touch sensor module. For example, any of touch sensors of the following types can be used: a capacitive type, a resistive type, an infrared type, an electromagnetic induction type, a surface acoustic wave type, and an optical type. In particular, a capacitive sensor or an optical sensor is preferably used for the touch sensor module.

In the case of using an optical touch sensor, a photoelectric conversion device (also referred to as a photoelectric conversion element) can be used as a light-receiving device (also referred to as a light-receiving element). One or both of an inorganic semiconductor and an organic semiconductor can be used for an active layer of the photoelectric conversion device.

An electronic device800A illustrated inFIG.20Cand an electronic device800B illustrated inFIG.20Deach include a pair of display portions820, a housing821, a communication portion822, a pair of wearing portions823, a control portion824, a pair of image capturing portions825, and a pair of lenses832.

The display panel of one embodiment of the present invention can be used in the display portions820. Thus, the electronic devices are capable of performing ultrahigh-resolution display. Such electronic devices provide an enhanced sense of immersion to the user.

The display portions820are provided at positions where the user can see through the lenses832inside the housing821. When the pair of display portions820display different images, three-dimensional display using parallax can be performed.

The electronic devices800A and800B can be regarded as electronic devices for VR. The user who wears the electronic device800A or the electronic device800B can see images displayed on the display portions820through the lenses832.

The electronic devices800A and800B preferably include a mechanism for adjusting the lateral positions of the lenses832and the display portions820so that the lenses832and the display portions820are positioned optimally in accordance with the positions of the user's eyes. Moreover, the electronic devices800A and800B preferably include a mechanism for adjusting focus by changing the distance between the lenses832and the display portions820.

The electronic device800A or the electronic device800B can be mounted on the user's head with the wearing portions823.FIG.20Cand the like show examples where the wearing portion823has a shape like a temple of glasses; however, one embodiment of the present invention is not limited thereto. The wearing portion823can have any shape with which the user can wear the electronic device, for example, a shape of a helmet or a band.

The image capturing portion825has a function of obtaining information on the external environment. Data obtained by the image capturing portion825can be output to the display portion820. An image sensor can be used for the image capturing portion825. Moreover, a plurality of cameras may be provided so as to support a plurality of fields of view, such as a telescope field of view and a wide field of view.

Although an example where the image capturing portions825are provided is shown here, a range sensor (hereinafter also referred to as a sensing portion) capable of measuring a distance between the user and an object just needs to be provided. In other words, the image capturing portion825is one embodiment of the sensing portion. As the sensing portion, an image sensor or a range image sensor such as a light detection and ranging (LiDAR) sensor can be used, for example. By using images obtained by the camera and images obtained by the range image sensor, more information can be obtained and a gesture operation with higher accuracy is possible.

The electronic device800A may include a vibration mechanism that functions as bone-conduction earphones. For example, at least one of the display portion820, the housing821, and the wearing portion823can include the vibration mechanism. Thus, without additionally requiring an audio device such as headphones, earphones, or a speaker, the user can enjoy video and sound only by wearing the electronic device800A.

The electronic devices800A and800B may each include an input terminal. To the input terminal, a cable for supplying a video signal from a video output device or the like, power for charging the battery provided in the electronic device, and the like can be connected.

The electronic device of one embodiment of the present invention may have a function of performing wireless communication with earphones750. The earphones750include a communication portion (not illustrated) and has a wireless communication function. The earphones750can receive information (e.g., audio data) from the electronic device with the wireless communication function. For example, the electronic device700A inFIG.20Ahas a function of transmitting information to the earphones750with the wireless communication function. For another example, the electronic device800A inFIG.20Chas a function of transmitting information to the earphones750with the wireless communication function.

The electronic device may include an earphone portion. The electronic device700B inFIG.20Bincludes earphone portions727. For example, the earphone portion727can be connected to the control portion by wire. Part of a wiring that connects the earphone portion727and the control portion may be positioned inside the housing721or the wearing portion723.

Similarly, the electronic device800B inFIG.20Dincludes earphone portions827. For example, the earphone portion827can be connected to the control portion824by wire. Part of a wiring that connects the earphone portion827and the control portion824may be positioned inside the housing821or the wearing portion823. Alternatively, the earphone portions827and the wearing portions823may include magnets. This is preferred because the earphone portions827can be fixed to the wearing portions823with magnetic force and thus can be easily housed.

The electronic device may include an audio output terminal to which earphones, headphones, or the like can be connected. The electronic device may include one or both of an audio input terminal and an audio input mechanism. As the audio input mechanism, a sound collecting device such as a microphone can be used, for example. The electronic device may have a function of a headset by including the audio input mechanism.

As described above, both the glasses-type device (e.g., the electronic devices700A and700B) and the goggles-type device (e.g., the electronic devices800A and800B) are preferable as the electronic device of one embodiment of the present invention.

An electronic device6500illustrated inFIG.21Ais a portable information terminal that can be used as a smartphone.

The electronic device6500includes a housing6501, a display portion6502, a power button6503, buttons6504, a speaker6505, a microphone6506, a camera6507, a light source6508, and the like. The display portion6502has a touch panel function.

The display panel of one embodiment of the present invention can be used in the display portion6502.

FIG.21Bis a schematic cross-sectional view including an end portion of the housing6501on the microphone6506side.

A protection member6510having a light-transmitting property is provided on the display surface side of the housing6501. A display panel6511, an optical member6512, a touch sensor panel6513, a printed circuit board6517, a battery6518, and the like are provided in a space surrounded by the housing6501and the protection member6510.

The display panel6511, the optical member6512, and the touch sensor panel6513are fixed to the protection member6510with an adhesive layer (not illustrated).

Part of the display panel6511is folded back in a region outside the display portion6502, and an FPC6515is connected to the part that is folded back. An IC6516is mounted on the FPC6515. The FPC6515is connected to a terminal provided on the printed circuit board6517.

A flexible display of one embodiment of the present invention can be used as the display panel6511. Thus, an extremely lightweight electronic device can be achieved. Since the display panel6511is extremely thin, the battery6518with high capacity can be mounted without an increase in the thickness of the electronic device. Moreover, part of the display panel6511is folded back so that a connection portion with the FPC6515is provided on the back side of the pixel portion, whereby an electronic device with a narrow bezel can be achieved.

FIG.21Cillustrates an example of a television device. In a television device7100, a display portion7000is incorporated in a housing7101. Here, the housing7101is supported by a stand7103.

Operation of the television device7100illustrated inFIG.21Ccan be performed with an operation switch provided in the housing7101and a separate remote controller7111.

Alternatively, the display portion7000may include a touch sensor, and the television device7100may be operated by touch on the display portion7000with a finger or the like. The remote controller7111may be provided with a display portion for displaying information output from the remote controller7111. With operation keys or a touch panel provided in the remote controller7111, channels and volume can be controlled and videos displayed on the display portion7000can be controlled.

Note that the television device7100includes a receiver, a modem, and the like. A general television broadcast can be received with the receiver. When the television device is connected to a communication network with or without wires via the modem, one-way (from a transmitter to a receiver) or two-way (between a transmitter and a receiver or between receivers, for example) information communication can be performed.

FIG.21Dillustrates an example of a laptop personal computer. The laptop personal computer7200includes a housing7211, a keyboard7212, a pointing device7213, an external connection port7214, and the like. The display portion7000is incorporated in the housing7211.

FIGS.21E and21Fillustrate examples of digital signage.

Digital signage7300illustrated inFIG.21Eincludes a housing7301, the display portion7000, a speaker7303, and the like. The digital signage7300can also include an LED lamp, an operation key (including a power switch or an operation switch), a connection terminal, a variety of sensors, a microphone, and the like.

FIG.21Fshows digital signage7400attached to a cylindrical pillar7401. The digital signage7400includes the display portion7000provided along a curved surface of the pillar7401.

A larger area of the display portion7000can increase the amount of information that can be provided at a time. The larger display portion7000attracts more attention, so that the effectiveness of the advertisement can be increased, for example.

The use of a touch panel in the display portion7000is preferable because in addition to display of a still image or a moving image on the display portion7000, intuitive operation by a user is possible. Moreover, for an application for providing information such as route information or traffic information, usability can be enhanced by intuitive operation.

As illustrated inFIGS.21E and21F, it is preferable that the digital signage7300or the digital signage7400can work with an information terminal7311or an information terminal7411, such as a smartphone that a user has, through wireless communication. For example, information of an advertisement displayed on the display portion7000can be displayed on a screen of the information terminal7311or the information terminal7411. By operation of the information terminal7311or the information terminal7411, display on the display portion7000can be switched.

It is possible to make the digital signage7300or the digital signage7400execute a game with use of the screen of the information terminal7311or the information terminal7411as an operation means (controller). Thus, an unspecified number of users can join in and enjoy the game concurrently.

The display panel of one embodiment of the present invention can be used in the display portion7000illustrated in each ofFIGS.21C to21F.

Electronic devices illustrated inFIGS.22A to22Geach include a housing9000, a display portion9001, a speaker9003, an operation key9005(including a power switch or an operation switch), a connection terminal9006, a sensor9007(a sensor having a function of sensing, detecting, or measuring force, displacement, position, speed, acceleration, angular velocity, rotational frequency, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, electric power, radiation, flow rate, humidity, gradient, oscillation, a smell, or infrared rays), a microphone9008, and the like.

The electronic devices illustrated inFIGS.22A to22Ghave a variety of functions. For example, the electronic devices can have a function of displaying a variety of information (a still image, a moving image, a text image, and the like) on the display portion, a touch panel function, a function of displaying a calendar, date, time, and the like, a function of executing a variety of software (programs), a wireless communication function, and a function of reading out a program or data stored in a recording medium. Note that the functions of the electronic devices are not limited thereto, and the electronic devices can have a variety of functions. The electronic devices may include a plurality of display portions. The electronic devices may be provided with a camera or the like and have a function of capturing a still image or a moving image, a function of storing the captured image in a storage medium (an external storage medium or a storage medium incorporated in the camera), a function of displaying the captured image on the display portion, and the like.

The electronic devices illustrated inFIGS.22A to22Gare be described in detail below.

FIG.22Ais a perspective view of a portable information terminal9101. The portable information terminal9101can be used as a smartphone, for example. The portable information terminal9101may include the speaker9003, the connection terminal9006, the sensor9007, or the like. The portable information terminal9101can display text and image information on its plurality of surfaces.FIG.22Aillustrates an example in which three icons9050are displayed. Furthermore, information9051indicated by dashed rectangles can be displayed on another surface of the display portion9001. Examples of the information9051include notification of reception of an e-mail, an SNS message, or an incoming call, the title and sender of an e-mail, an SNS message, or the like, the date, the time, remaining battery, and the radio field intensity. Alternatively, the icon9050or the like may be displayed at the position where the information9051is displayed.

FIG.22Bis a perspective view of a portable information terminal9102. The portable information terminal9102has a function of displaying information on three or more surfaces of the display portion9001. Here, information9052, information9053, and information9054are displayed on different surfaces. For example, the user of the portable information terminal9102can check the information9053displayed such that it can be seen from above the portable information terminal9102, with the portable information terminal9102put in a breast pocket of his/her clothes. Thus, the user can see the display without taking out the portable information terminal9102from the pocket and decide whether to answer the call, for example.

FIG.22Cis a perspective view of a tablet terminal9103. The tablet terminal9103is capable of executing a variety of applications such as mobile phone calls, e-mailing, viewing and editing texts, music reproduction, Internet communication, and a computer game, for example. The tablet terminal9103includes the display portion9001, the camera9002, the microphone9008, and the speaker9003on the front surface of the housing9000; the operation keys9005as buttons for operation on the left side surface of the housing9000; and the connection terminal9006on the bottom surface of the housing9000.

FIG.22Dis a perspective view of a watch-type portable information terminal9200. The portable information terminal9200can be used as a Smartwatch (registered trademark), for example. The display surface of the display portion9001is curved, and an image can be displayed on the curved display surface. Furthermore, for example, mutual communication between the portable information terminal9200and a headset capable of wireless communication can be performed, and thus hands-free calling is possible. With the connection terminal9006, the portable information terminal9200can perform mutual data transmission with another information terminal and charging. Note that the charging operation may be performed by wireless power feeding.

FIGS.22E to22Gare perspective views of a foldable portable information terminal9201.FIG.22Eis a perspective view showing the portable information terminal9201that is opened.FIG.22Gis a perspective view showing the portable information terminal9201that is folded.FIG.22Fis a perspective view showing the portable information terminal9201that is shifted from one of the states inFIGS.22E and22Gto the other. The portable information terminal9201is highly portable when folded. When the portable information terminal9201is opened, a seamless large display region is highly browsable. The display portion9001of the portable information terminal9201is supported by three housings9000joined together by hinges9055. The display portion9001can be folded with a radius of curvature greater than or equal to 0.1 mm and less than or equal to 150 mm, for example.

At least part of this embodiment can be implemented in combination with any of the other embodiments described in this specification, as appropriate.

This application is based on Japanese Patent Application Serial No. 2021-108371 filed with Japan Patent Office on Jun. 30, 2021, the entire contents of which are hereby incorporated by reference.