TW201824215A - Display device, display module, and electronic apparatus - Google Patents

Abstract

To provide a display device with low power consumption. A display device has a plurality of pixels, the plurality of pixels each having a liquid crystal element, a plurality of light emitting elements, and a capacitive element. With respect to the plurality of light emitting elements, the liquid crystal element is provided on the side of the light emitting elements to emit light. The liquid crystal element has a first electrode, a second electrode, and a liquid crystal layer sandwiched between the first electrode and the second electrode. The plurality of light emitting elements each have a third electrode, a fourth electrode, and an EL layer sandwiched between the third electrode and the fourth electrode. The capacitive element has one electrode as the first electrode and the other electrode as a fifth electrode. The first electrode and the fourth electrode reflect visible light. The second electrode and the third electrode allow the passage of visible light. The first electrode has a region not overlapping each of the plurality of light emitting elements.

Description

   Display device, display module and electronic device   

An embodiment of the present invention relates to a display device, a display module, an electronic device, and a method for manufacturing a display device.

Note that one embodiment of the present invention is not limited to the above technical field. Examples of the technical field of an embodiment of the present invention include a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, an electronic device, a lighting device, and an input device (for example, a touch sensor, etc.) ), An input-output device (for example, a touch panel, etc.), and a driving method or a manufacturing method of the above device.

In this specification and the like, a semiconductor device refers to all devices capable of operating by utilizing semiconductor characteristics. A transistor, a semiconductor circuit, an arithmetic device, a memory device, and the like are one embodiment of a semiconductor device. In addition, imaging devices, electro-optical devices, power generation devices (including thin-film solar cells, organic thin-film solar cells, and the like) and electronic devices may include semiconductor devices.

In recent years, display devices are expected to be applied to various applications. As the display device, for example, a light emitting display device including a light emitting element, a liquid crystal display device including a liquid crystal element, and the like have been developed.

For example, Patent Literature 1 discloses a flexible light-emitting display device using an organic EL (Electroluminescence) element.

Patent Document 2 discloses a transflective liquid crystal display device. The liquid crystal display device includes a region that reflects visible light and a region that transmits visible light. The liquid crystal display device can be used as a reflective liquid crystal display device in an environment where sufficient external light can be obtained. It can be used as a transmissive liquid crystal display device in an environment where sufficient external light is obtained.

[Patent Document 1] Japanese Patent Application Publication No. 2014-197522

[Patent Document 2] Japanese Patent Application Laid-Open No. 2011-191750

In the above display device, a portable terminal represented by a smart phone needs to accommodate a display panel, a touch panel, a battery, and the like in a limited space of a housing. Therefore, the battery size and battery capacity are also limited. Furthermore, the portable terminal is expected to be used in places where charging cannot be performed freely, such as outdoors.

In other words, a battery that supplies power to a display device tends to have insufficient power, and the use time of a portable terminal using the display device is limited. To solve this problem, it is important to reduce the power consumption of the display device.

An object of one embodiment of the present invention is to provide a display device with low power consumption. An object of one embodiment of the present invention is to provide a display device capable of being driven at a low frame frequency. An object of one embodiment of the present invention is to provide a display device having high visibility regardless of surrounding brightness. An object of one embodiment of the present invention is to provide an all-weather type display device. An object of one embodiment of the present invention is to provide a display device with high convenience. An object of one embodiment of the present invention is to provide a highly reliable display device. An object of one embodiment of the present invention is to reduce the thickness and weight of a display device. An object of one embodiment of the present invention is to provide a display device having flexibility or a curved surface. An object of one embodiment of the present invention is to provide a novel display device, input / output device, or electronic device.

Note that the recording of these purposes does not prevent the existence of other purposes. It is not necessary for one embodiment of the present invention to achieve all the above-mentioned objects. Objects other than those described above can be extracted from the description, drawings, and descriptions of the scope of patent applications.

An embodiment of the present invention is a display device including a plurality of pixels, each of the plurality of pixels including a liquid crystal element, a plurality of light emitting elements, a capacitor, and a first transistor. A light emitting element is disposed on a side where the light emitting element emits light. The liquid crystal element includes a first electrode, a second electrode, and a liquid crystal layer between the first electrode and the second electrode. Each of the plurality of light emitting elements includes a third electrode, The fourth electrode and the EL layer between the third electrode and the fourth electrode. The capacitor includes a first electrode as one electrode and a fifth electrode as the other electrode. One of the source and the drain of the first transistor and The first electrode is electrically connected, the first electrode includes a region that does not overlap with each of the plurality of light emitting elements, and the fifth electrode is located between the first electrode and the first transistor and includes a region that is not in contact with the first electrode and the first electrode. A region where the connection portion of one of the source and the drain of the crystal overlaps.

The above display device may also have a structure in which each of the plurality of pixels includes a plurality of second transistors, and one of a source and a drain of each of the plurality of second transistors is electrically connected to the third electrode.

The display device may have a structure in which the first electrode and the fourth electrode have a function of reflecting visible light, and the second electrode and the third electrode have a function of transmitting visible light.

The display device may have a structure in which the materials of the EL layers of the plurality of light emitting elements are different from each other.

The above display device may also have a structure in which each of the plurality of pixels includes first to third light emitting elements, the first light emitting element has a function of emitting red light, the second light emitting element has a function of emitting green light, and the third light emits The element has a function of emitting blue light.

The above display device may also have a structure in which each of the plurality of pixels includes first to fourth light emitting elements, the first light emitting element has a function of emitting red light, the second light emitting element has a function of emitting green light, and the third light emitting element It has a function of emitting blue light, and the fourth light-emitting element has a function of emitting white light.

The display device described above may have a structure in which the materials of the EL layers of the plurality of light emitting elements are the same, and a color layer is provided between each of the plurality of light emitting elements and the liquid crystal layer.

The above display device may have a structure in which each of the plurality of pixels includes first to third light emitting elements, the first to fourth light emitting elements have a function of emitting white light, and are provided between the first light emitting element and the liquid crystal layer. A color layer having a function of transmitting red light, a color layer having a function of transmitting green light is provided between the second light emitting element and the liquid crystal layer, and a third layer having a function of transmitting blue light is provided between the third light emitting element and the liquid crystal layer. Functional colored layers.

The above display device may have a structure in which each of the plurality of pixels includes first to fourth light emitting elements, the first to fourth light emitting elements have a function of emitting white light, and are provided between the first light emitting element and the liquid crystal layer. A color layer having a function of transmitting red light, a color layer having a function of transmitting green light is provided between the second light emitting element and the liquid crystal layer, and a third layer having a function of transmitting blue light is provided between the third light emitting element and the liquid crystal layer. Functional colored layers.

An embodiment of the present invention is a display device including a plurality of pixels, each of the plurality of pixels including a liquid crystal element, a first color layer, a plurality of second color layers, a plurality of light emitting elements, a plurality of A third color layer, a capacitor, a first transistor, and a plurality of second transistors, wherein the liquid crystal element is disposed on a light emitting element side with respect to the plurality of light emitting elements, and the first color layer and the second color layer are opposite to each other; The liquid crystal element is disposed on a side where the light emitting element emits light. The liquid crystal element includes a first electrode, a second electrode, and a liquid crystal layer between the first electrode and the second electrode. Each of the plurality of light emitting elements includes a third electrode, a first electrode, and a second electrode. The four electrodes and the EL layer between the third electrode and the fourth electrode. The capacitor includes a first electrode as one electrode and a fifth electrode as the other electrode. One of the source and the drain of the first transistor is connected to the first electrode. One electrode is electrically connected, and one of the source and the drain of each of the plurality of second transistors is electrically connected to the third electrode. The first electrode and the fourth electrode have a function of reflecting visible light. The second electrode and the third electrode have a function of transmitting visible light. The first electrode includes a region that does not overlap with each of the plurality of light-emitting elements. The fifth electrode is located between the first electrode and the first transistor and includes a region that does not overlap with the first electrode. A region overlapping the connection portion of one of the source and the drain of the first transistor is provided with a first color layer so as to overlap with the second electrode, and is provided so as to overlap with each of the plurality of light emitting elements. The plurality of second color layers are provided with a third color layer between each of the plurality of light emitting elements and the liquid crystal element, and the second color layer and the third color layer have a function of transmitting visible light of the same color.

The above display device may have a structure in which the second electrode is formed with a plurality of openings, and each of the plurality of light emitting elements includes a region overlapping with any one of the plurality of openings.

The display device described above may have a structure in which the second electrode is formed with a plurality of cutouts, and each of the plurality of light emitting elements includes a region overlapping with any one of the plurality of cutouts.

The display device may have a structure in which the second electrode is formed with one or more openings and one or more cutouts, and each of the plurality of light emitting elements includes a region overlapping with any one of the one or more openings and one or more cutouts. .

The display device may have a structure in which the fifth electrode includes a region that does not overlap with each of the plurality of light emitting elements.

The display device may have a structure in which the fifth electrode has a function of transmitting visible light.

In the display device described above, the resistivity of the liquid crystal layer is preferably 1.0 × 10 ¹⁴ (Ω.cm) or more.

In the above display device, the first transistor preferably includes a metal oxide in the channel formation region. The energy gap of the metal oxide is preferably 3.0 eV or more.

One embodiment of the present invention is a display module including the display device and a circuit board.

An embodiment of the present invention is an electronic device including at least one of an antenna, a battery, a housing, a camera, a speaker, a microphone, and an operation button, and the display module.

According to an embodiment of the present invention, a display device with low power consumption can be provided. According to an embodiment of the present invention, a display device capable of being driven at a low frame frequency can be provided. According to one embodiment of the present invention, it is possible to provide a display device having high visibility regardless of surrounding brightness. An embodiment of the present invention can provide an all-weather display device. According to an embodiment of the present invention, a display device with high convenience can be provided. According to an embodiment of the present invention, a highly reliable display device can be provided. According to one embodiment of the present invention, the thickness and weight of the display device can be reduced. According to an embodiment of the present invention, a display device having flexibility or a curved surface can be provided. According to an embodiment of the present invention, a novel display device, input / output device, or electronic device can be provided.

Note that the description of these effects does not prevent the existence of other effects. It is not necessary for one embodiment of the present invention to have all of the above effects. Effects other than the above effects can be extracted from the description, drawings, and description of the scope of patent application.

61‧‧‧Manufacture of substrates

62‧‧‧ peeling layer

63‧‧‧Insulation

100‧‧‧ display device

112‧‧‧LCD layer

113‧‧‧electrode

117‧‧‧ Insulation

121‧‧‧ Insulation

131a‧‧‧color layer

131aa‧‧‧color layer

131ab‧‧‧Color layer

131ac‧‧‧Color Layer

131ad‧‧‧color layer

131b‧‧‧color layer

131ba‧‧‧Color Layer

131bb‧‧‧Color Layer

131bc‧‧‧Color Layer

132‧‧‧Light-shielding layer

133a‧‧‧Alignment film

133b‧‧‧Alignment film

134‧‧‧color layer

134a‧‧‧color layer

134b‧‧‧color layer

134c‧‧‧Color Layer

135‧‧‧polarizing plate

141‧‧‧adhesive layer

142‧‧‧Adhesive layer

170‧‧‧Light-emitting element

170a‧‧‧Light-emitting element

170b‧‧‧Light-emitting element

170c‧‧‧Light-emitting element

170d‧‧‧Light-emitting element

180‧‧‧LCD element

191‧‧‧electrode

191a‧‧‧electrode

191b‧‧‧electrode

191c‧‧‧electrode

192‧‧‧EL layer

193‧‧‧electrode

194‧‧‧Insulation

200a‧‧‧ Transistor

200b‧‧‧Transistor

200c‧‧‧Transistor

200E‧‧‧Transistor

200L‧‧‧Transistor

201‧‧‧ Transistors

203‧‧‧Transistor

204‧‧‧ Connection Department

205‧‧‧Transistor

206‧‧‧Transistor

207‧‧‧Connection Department

208a‧‧‧connection

208b‧‧‧Connection Department

208c‧‧‧Connection Department

211‧‧‧insulation layer

212‧‧‧Insulation

212a‧‧‧Insulation

212b‧‧‧Insulation

213‧‧‧Insulation

214‧‧‧Insulation

215‧‧‧Insulation

216‧‧‧Insulation

217‧‧‧Insulation

218‧‧‧electrode

220‧‧‧ Insulation

221‧‧‧ conductive layer

221a‧‧‧ conductive layer

221b‧‧‧ conductive layer

222‧‧‧ conductive layer

222a‧‧‧ conductive layer

222a_1‧‧‧ conductive layer

222a_2‧‧‧ conductive layer

222a_3‧‧‧ conductive layer

222b‧‧‧ conductive layer

222b_1‧‧‧ conductive layer

222b_2‧‧‧ conductive layer

222b_3‧‧‧ conductive layer

223‧‧‧ conductive layer

224‧‧‧ Insulation

231‧‧‧ metal oxide layer

231_1‧‧‧ metal oxide layer

231_2‧‧‧ metal oxide layer

231d‧‧‧Drain

231i‧‧‧Channel area

231s‧‧‧Source area

235‧‧‧ opening

236a‧‧‧ opening

236b‧‧‧ opening

237‧‧‧ opening

242‧‧‧ Connection layer

243‧‧‧Connector

252‧‧‧Connection Department

261‧‧‧ metal oxide layer

263a‧‧‧ conductive layer

263b‧‧‧ conductive layer

270‧‧‧Capacitor

270_1‧‧‧ capacitor

270_2‧‧‧ capacitor

270_3‧‧‧Capacitor

281‧‧‧Transistor

284‧‧‧Transistor

285‧‧‧Transistor

286‧‧‧Transistor

295‧‧‧Transistor

296‧‧‧Transistor

300‧‧‧ display device

300A‧‧‧ display device

300B‧‧‧ display device

300C‧‧‧Display Device

311‧‧‧electrode

311_1‧‧‧ electrode

311_2‧‧‧electrode

311_3‧‧‧ electrode

311a‧‧‧electrode

311b‧‧‧electrode

311ba‧‧‧electrode

311bb‧‧‧electrode

311bc‧‧‧electrode

311bd‧‧‧electrode

312‧‧‧electrode

351‧‧‧ substrate

361‧‧‧ substrate

362‧‧‧Display

364‧‧‧Circuit

365‧‧‧Wiring

372‧‧‧FPC

373‧‧‧IC

410‧‧‧ pixels

410a‧‧‧pixels

410aa‧‧‧ subpixel

410ab‧‧‧ Subpixel

410ac‧‧‧ subpixel

410b‧‧‧pixels

410ba‧‧‧ subpixel

410bb‧‧‧ subpixel

410bc‧‧‧ Subpixel

410c‧‧‧pixel

410d‧‧‧pixel

410E‧‧‧pixel

410Ea‧‧‧pixel

410Eb‧‧‧pixel

410Ec‧‧‧pixel

410Ed‧‧‧pixel

410L‧‧‧pixel

410L_1‧‧‧ subpixel

410L_2‧‧‧ subpixel

410L_3‧‧‧ Subpixel

410LF‧‧‧pixel

451‧‧‧ opening

451a‧‧‧open

451b‧‧‧open

451c‧‧‧open

451d‧‧‧open

800‧‧‧ Portable Information Terminal

801‧‧‧shell

802‧‧‧shell

803‧‧‧Display

804‧‧‧Display

805‧‧‧hinge section

810‧‧‧Portable Information Terminal

811‧‧‧shell

812‧‧‧Display

813‧‧‧Operation buttons

814‧‧‧External port

815‧‧‧Speaker

816‧‧‧Microphone

817‧‧‧ Camera

820‧‧‧ Camera

821‧‧‧Shell

822‧‧‧Display

823‧‧‧Operation buttons

824‧‧‧Shutter button

826‧‧‧Lens

830‧‧‧TV

831‧‧‧Display

832‧‧‧shell

833‧‧‧Speaker

835‧‧‧ operation keys

836‧‧‧connection terminal

837‧‧‧Sensor

950A‧‧‧pixel

950B‧‧‧pixel

960‧‧‧ display device

962‧‧‧ display device

8000‧‧‧ Display Module

8001‧‧‧ Upper cover

8002‧‧‧ Lower cover

8005‧‧‧FPC

8006‧‧‧Display Panel

8009‧‧‧Frame

8010‧‧‧Printed Circuit Board

8011‧‧‧Battery

8015‧‧‧Lighting Department

8016‧‧‧Light receiving section

8017a‧‧‧Light guide

8017b‧‧‧Light guide

8018‧‧‧light

9000‧‧‧ shell

9001‧‧‧Display Department

9003‧‧‧ Speaker

9005‧‧‧ operation keys

9006‧‧‧Connection terminal

9007‧‧‧Sensor

9008‧‧‧ Microphone

9055‧‧‧ hinge

9200‧‧‧Portable Information Terminal

9201‧‧‧Portable Information Terminal

9202‧‧‧Portable Information Terminal

In the drawings: FIGS. 1A and 1B are a perspective view and a cross-sectional view showing an example of a display device; FIG. 2 is a cross-sectional view showing an example of a display device; and FIGS. 3A to 3D are views showing an example of a display device. 4A and 4B are plan views showing an example of a display device; FIGS. 5A to 5H are plan views showing an example of a display device; and FIGS. 6A to 6G are views showing a display device. A plan view of an example; FIG. 7 is a sectional view showing an example of a display device; FIG. 8 is a sectional view showing an example of a display device; and FIGS. 9A to 9C are views showing an example of a transistor for a display device. Top view and cross-sectional view of an example; FIGS. 10A to 10C are top and cross-sectional views showing an example of a transistor used in a display device; and FIGS. 11A to 11C are views of an example of a transistor used in a display device. Top view and sectional view; FIG. 12 is a sectional view showing an example of a display device; FIG. 13 is a sectional view showing an example of a display device; FIG. 14 is a sectional view showing an example of a display device; Figure 15B shows FIG. 16A to FIG. 16D are cross-sectional views illustrating an example of a manufacturing method of the display device; FIGS. 17A to 17C are cross-sectional views illustrating an example of a manufacturing method of the display device; 18A and 18B are sectional views showing an example of a manufacturing method of a display device; FIGS. 19A and 19B are sectional views showing an example of a manufacturing method of a display device; and FIG. 20 is a view showing an example of a display device Block diagram; FIG. 21 is a circuit diagram showing an example of a pixel circuit of a display device; FIG. 22 is a circuit diagram showing an example of a pixel circuit of a display device; FIGS. 23A and 23B are views showing an example of a pixel circuit of a display device Example top view; FIG. 24 is a top view showing an example of a pixel circuit of a display device; FIG. 25 is a circuit diagram showing an example of a pixel circuit of a display device; and FIG. 26 is a diagram illustrating display white and Graph of gray scale change after black; FIG. 27 is a graph showing the relationship between the resistivity of the liquid crystal layer and the dipole moment of the molecules of the liquid crystal layer; FIG. 28A and FIG. 28B are Top view of pixels of a display device; FIG. 29 is a diagram illustrating the relationship between the reflectance of the display device and the reflectance; FIG. 30 is a diagram illustrating the effect of the addition of a chiral agent in the liquid crystal layer on the reflectance of the display device; 31A and 31B are diagrams showing an example of a display module; FIGS. 32A to 32E are diagrams showing an example of an electronic device; and FIGS. 33A to 33E are diagrams showing an example of an electronic device.

The embodiment will be described in detail with reference to the drawings. Note that the present invention is not limited to the following description, and a person of ordinary skill in the art can easily understand the fact that the manner and details can be changed into various kinds without departing from the spirit and scope of the present invention. form. Therefore, the present invention should not be construed as being limited to the content described in the embodiments shown below.

Note that in the invention structure described below, the same element symbols are commonly used in different drawings to represent the same parts or parts having the same functions, and repeated descriptions are omitted. In addition, when parts having the same function are expressed, the same hatching is sometimes used, and element symbols are not particularly added.

For ease of understanding, the positions, sizes, and ranges of the components shown in the drawings sometimes do not indicate their actual positions, sizes, and ranges. Therefore, the disclosed invention is not necessarily limited to the position, size, scope, etc. disclosed in the drawings.

Depending on the situation or state, the "film" and "layer" can be swapped with each other. For example, the "conductive layer" may sometimes be converted into a "conductive film". In addition, the "insulation film" may be converted into an "insulation layer" in some cases.

In this specification and the like, the “substrate” preferably has a function of supporting at least one of a functional circuit, a functional element, a functional film, and the like. In addition, the “substrate” may not have a function of supporting these members, for example, a function of protecting the surface of the device or a function of sealing at least one of a functional circuit, a functional element, a functional film, and the like.

In this specification and the like, metal oxide refers to an oxide of a metal in a broad sense. Metal oxides are classified into oxide insulators, oxide conductors (including transparent oxide conductors), oxide semiconductors (also referred to as OS), and the like. For example, when a metal oxide is used as the active layer of a transistor, the metal oxide is sometimes referred to as an oxide semiconductor. In other words, in the case where the metal oxide has at least one of an amplification effect, a rectification effect, and a switching effect, the metal oxide may be referred to as a metal oxide semiconductor, or may be abbreviated as an OS. The OS FET may be referred to as a transistor including a metal oxide or an oxide semiconductor.

In this specification and the like, a metal oxide containing nitrogen may also be referred to as a metal oxide. In addition, a metal oxide containing nitrogen may be referred to as a metal oxynitride.

In this specification and the like, CAAC (c-axis aligned crystal) or CAC (Cloud-Aligned Composite) may be described. Note that CAAC is an example of a crystalline structure, and CAC is an example of a function or a material composition.

In this specification and the like, CAC-OS or CAC-metal oxide has a function of conductivity in a part of the material, a function of insulation in another part of the material, and a semiconductor function as a whole of the material. When using CAC-OS or CAC-metal oxide for the active layer of a transistor, the function of conductivity refers to the function of passing electrons (or holes) used as carriers, and the function of insulation refers to the function of Function to prevent electrons used as carriers from flowing. The complementary function of the conductive function and the insulating function enables the CAC-OS or CAC-metal oxide to have a switching function (a function to control on / off). By separating each function in CAC-OS or CAC-metal oxide, each function can be maximized.

In this specification and the like, CAC-OS or CAC-metal oxide includes a conductive region and an insulating region. The conductive region has the aforementioned function of conductivity, and the insulating region has the aforementioned function of insulation. In the material, the conductive region and the insulating region are sometimes separated at the nanoparticle level. In addition, the conductive region and the insulating region may be unevenly distributed in the material. In addition, conductive regions whose edges are blurred and connected in a cloud shape are sometimes observed.

In CAC-OS or CAC-metal oxide, the conductive region and the insulating region may be dispersed in the material at a size of 0.5 nm to 10 nm, preferably 0.5 nm to 3 nm.

CAC-OS or CAC-metal oxide is composed of components with different band gaps. For example, CAC-OS or CAC-metal oxide is composed of a component having a wide gap caused by an insulating region and a component having a narrow gap caused by a conductive region. In this structure, when a carrier is caused to flow, the carrier mainly flows in a component having a narrow gap. In addition, a component having a narrow gap and a component having a wide gap complement each other, and a carrier flows through the component having a wide gap in association with the component having a narrow gap. Therefore, when the above-mentioned CAC-OS or CAC-metal oxide is used in the channel region of the transistor, a high current driving force can be obtained in the conduction state of the transistor, that is, a large on-state current and a high field-effect mobility.

That is, CAC-OS or CAC-metal oxide may also be referred to as a matrix composite or a metal matrix composite.

    Embodiment 1    

In this embodiment mode, a display device and a manufacturing method thereof according to an embodiment of the invention will be described with reference to the drawings.

The display device of this embodiment includes a first display element that reflects visible light and a second display element that emits visible light.

The display device of this embodiment has a function of displaying an image by using one or both of light reflected by a first display element and light emitted by a second display element.

As the first display element, an element that displays external light can be used. Since this element does not include a light source, the power consumption during display can be made extremely small.

As the first display element, a reflective liquid crystal element can be typically used. In addition, as the first display element, a shutter type MEMS (Micro Electro Mechanical System) element, a light interference type MEMS element, an applied microcapsule method, an electrophoresis method, an electrowetting method, and an electronic powder fluid may be used. (Registered trademark) system, etc.

As the second display element, a light-emitting element is preferably used. Since the brightness and chromaticity of the light emitted by such display elements are not affected by external light, such pixels can perform vivid displays with high color reproducibility (wide color gamut) and high contrast.

As the second display element, for example, an OLED (Organic Light Emitting Diode), an LED (Light Emitting Diode), or a QLED (Quantum-dot Light Emitting Diode) can be used. ) And other self-luminous light-emitting elements.

The display device of this embodiment includes a first mode for displaying an image using only a first display element, a second mode for displaying an image using only a second display element, and a third mode for displaying an image using a first display element and a second display element, The display device can be used by automatically or manually switching between these modes.

In the first mode, an image is displayed using a first display element and external light. Because the first mode does not use a light source, power consumption is extremely low. For example, when external light is sufficiently incident on the display device (under a bright environment or the like), display can be performed using light reflected by the first display element. For example, the first mode is effective when the external light is sufficiently strong and the external light is white or similar light. The first mode is a mode suitable for displaying text. In addition, since light reflecting external light is used in the first mode, an eye-protection display can be performed, and there is an effect that the eyes are not easily tired.

In the second mode, an image is displayed by the light emission of the second display element. This makes it possible to perform extremely vivid (high contrast and high color reproducibility) display regardless of illuminance and chromaticity of external light. For example, the second mode is effective when the illuminance at night or in a dark room is extremely low. In addition, when the surroundings are dim, the bright display sometimes makes the user feel dazzling. In order to prevent such a problem from occurring, it is preferable to perform a display with reduced brightness in the second mode. Thereby, not only glare can be suppressed, but also power consumption can be reduced. The second mode is a mode suitable for displaying sharp images (still images and moving images) and the like.

In the third mode, display is performed using both the reflected light from the first display element and the light emitted from the second display element. Not only can the display be sharper than the first mode, but the power consumption can be made smaller than that in the second mode. For example, the third mode is effective when the illuminance is low under indoor lighting or in the morning and evening, and when the chromaticity of external light is not white.

By adopting the above structure, a display device or an all-weather display device having high visibility and high convenience regardless of the surrounding brightness can be realized.

A configuration example of the display device of the present embodiment will be described with reference to FIGS. 1A to 15B.

FIG. 1A is a schematic perspective view of a display device 300. The display device 300 has a structure in which the substrate 351 and the substrate 361 are bonded together. In FIG. 1A, the substrate 361 is indicated by a dotted line.

The display device 300 includes a display portion 362, a circuit 364, a wiring 365, and the like. The display unit 362 includes a liquid crystal element as a first display element and a light emitting element as a second display element. FIG. 1A shows an example in which an IC (Integrated Circuit) 373 and an FPC 372 are mounted on the display device 300. Therefore, the structure shown in FIG. 1A may also be referred to as a display module including a display device 300, an IC, and an FPC.

As the circuit 364, for example, a scanning line driving circuit can be used.

The wiring 365 has a function of supplying signals and power to the display portion 362 and the circuit 364. This signal and power are input to the wiring 365 from the outside via the FPC372 or from the IC373.

FIG. 1A shows an example in which the IC 373 is provided on the substrate 351 by a COG (Chip On Glass) method, a COF (Chip on Film) method, or the like. As the IC373, for example, an IC including a scanning line driving circuit or a signal line driving circuit can be used. Note that the display device 100 and the display module may not be provided with an IC. In addition, the IC may be mounted on an FPC using a COF method or the like.

FIG. 1A also shows an enlarged view of a part of the display section 362. The plurality of pixels 410 on the display section 362 are arranged in a matrix shape in a direction indicated by an arrow R (hereinafter referred to as the R direction) and a direction indicated by an arrow C (hereinafter referred to as the C direction). FIG. 1B is a schematic cross-sectional view of the pixel 410.

The pixel 410 includes a liquid crystal element 180 and a plurality of light emitting elements 170. FIG. 1A illustrates an example in which the pixel 410 includes three light emitting elements 170 (light emitting element 170a, light emitting element 170b, and light emitting element 170c).

In the pixel 410, a liquid crystal element 180, a light emitting element 170, a capacitor 270, a transistor 200L, a plurality of transistors 200E, and the like are provided between a pair of substrates (the substrate 351 and the substrate 361). In FIG. 1B, an insulating layer 220, an insulating layer 224, an insulating layer 214, an insulating layer 216, and an insulating layer 194 are provided in this order from a substrate 361 side between a pair of substrates. The liquid crystal element 180 is disposed between the insulating layer 220 and the substrate 361. The capacitor 270 is disposed on the layer where the insulating layer 220 and the insulating layer 224 are formed. The transistor 200L and the transistor 200E are disposed on the layer where the insulating layer 214 is formed. The light emitting element 170 is disposed between the insulating layer 214 and the insulating layer 194.

The liquid crystal element 180 includes an electrode 311 having a function of reflecting visible light, a liquid crystal layer 112, and an electrode 113 having a function of transmitting visible light. The liquid crystal layer 112 is sandwiched between the electrode 311 and the electrode 113.

The liquid crystal element 180 has a function of reflecting visible light. The liquid crystal element 180 emits reflected light toward the substrate 361 side.

The electrode 311 is electrically connected to one of the source and the drain of the transistor 200L through openings provided in the insulating layer 220 and the insulating layer 224 (hereinafter, this connection portion is referred to as a connection portion 207). The electrode 311 functions as a pixel electrode. The electrode 113 has a function of a common electrode.

The capacitor 270 includes an electrode 311 as one electrode and an electrode 312 as the other electrode. An insulating layer 220 provided between the electrodes 311 and 312 is used as a dielectric of the capacitor 270. The capacitor 270 is preferably provided between the liquid crystal element 180 and a layer on which the transistor 200L is formed. Therefore, the electrode 312 is preferably provided between the electrode 311 and the layer on which the transistor 200L is formed.

In FIG. 1B, an insulating layer 224 is formed between the insulating layer 214 where the transistor 200L is formed and the insulating layer 220 where the electrode 311 is formed, and an electrode 312 is also formed in the same layer as the insulating layer 224. Note that the display device shown in this embodiment mode is not limited to this. For example, a conductive layer in the same layer as the conductive layer included in the transistor 200L may be used as the electrode 312.

The electrode 312 includes a region that does not overlap the connection portion 207 to prevent conduction with the electrode 311. For example, an opening, a cutout, or the like may be formed in the electrode 312 and the connection portion 207 may be formed in a portion where the opening, the cutout, or the like is formed. In this way, the connection portion 207 may not be brought into contact with the electrode 312.

The light-emitting element 170 includes an electrode 191, an EL layer 192, and an electrode 193. The EL layer 192 is sandwiched between the electrode 191 and the electrode 193. The EL layer 192 contains at least a light-emitting substance. The electrode 191 has a function of transmitting visible light. The electrode 193 preferably has a function of reflecting visible light.

The light emitting element 170 has a function of emitting visible light. Specifically, the light emitting element 170 is an electric field light emitting element that emits light to the substrate 361 side when a voltage is applied between the electrodes 191 and 193.

Each of the electrodes 191 provided in the plurality of light emitting elements 170 is electrically connected to one of a source and a drain of the transistor 200E through an opening provided in the insulating layer 214. The electrode 191 functions as a pixel electrode. An end portion of the electrode 191 is covered with an insulating layer 216. The electrode 193 has a function of a common electrode.

The light emitting element 170 is preferably covered with an insulating layer 194. In FIG. 1A, the insulating layer 194 is provided in contact with the electrode 193. By providing the insulating layer 194, the intrusion of impurities into the light-emitting element 170 can be suppressed and the reliability of the light-emitting element 170 can be improved. The adhesive layer 142 is used to adhere the insulating layer 194 and the substrate 351.

The transistor 200L and the transistor 200E are provided in a layer between the liquid crystal element 180 and the light emitting element 170. The transistor 200L and the transistor 200E may be provided in the same layer, or may be provided in different layers. The transistor 200L has a function of controlling the driving of the liquid crystal element 180. The transistor 200E has a function of controlling the driving of the light emitting element 170.

The circuit electrically connected to the liquid crystal element 180 and the circuit electrically connected to the light emitting element 170 are preferably formed on the same surface. As a result, the thickness of the display device can be reduced and the number of layers can be reduced compared to a case where the two circuits are formed on different surfaces, so that the weight can be reduced. In addition, since two transistors can be manufactured by the same process, the process can be simplified compared to a case where two transistors are formed on different faces.

The electrode 311 serving as the pixel electrode of the liquid crystal element 180 is located at a position opposite to the gate insulating layer of the transistor 200L and the transistor 200E and opposite to the electrode 191 serving as the pixel electrode of the light emitting element 170. In this way, the liquid crystal element 180 is provided on the side where the plurality of light emitting elements 170 emit light with respect to the plurality of light emitting elements 170.

The electrode 311 has a function of reflecting light. Therefore, if the electrode 311 overlaps the light emitting element 170, the light emitting element 170 cannot emit light. Therefore, the electrode 311 includes a region that does not overlap the plurality of light emitting elements 170. For example, as shown in FIGS. 1A and 1B, a plurality of openings 451 may be provided in the electrode 311 and a plurality of light-emitting elements 170 (corresponding to the light-emitting element 170 a, the light-emitting element 170 b, and the light-emitting element 170 c in FIG. 1A) include and A region where any one of the plurality of openings 451 (corresponding to the openings 451a, 451b, and 451c in FIG. 1A) overlaps.

One of the area of the light-emitting area of the light-emitting element 170 and the area of the opening 451 is preferably larger than the other, because the margin for misalignment can be increased. The smaller the ratio of the total area of the opening 451 of the electrode 311 to the total area of the non-opening portion, the brighter the display using the liquid crystal element 180 can be. In addition, the larger the ratio of the total area of the opening 451 of the electrode 311 to the total area of the non-opening portion, the brighter the display using the light emitting element 170 can be.

The shape of the opening 451 may be, for example, a polygonal shape, a quadrangular shape, an oval shape, a circular shape, or a cross shape. In addition, the shape may be an elongated strip shape, a slit shape, or a checkered shape. In addition, as shown in FIG. 1A, the opening 451 may be arranged so as to be close to an adjacent pixel. At this time, it is preferable to arrange the opening 451 so as to be close to other pixels displaying the same color. This can suppress the occurrence of crosstalk.

In addition, in FIG. 1A, the shape of the electrode 311 is a square, but is not limited thereto, and may be rectangular, quadrangular, triangular, or other polygonal. The corners of these polygons may be curved.

Like the electrode 311, the electrode 312 preferably includes a region that does not overlap the plurality of light emitting elements 170. For example, the same opening as the opening 451 of the electrode 311 may be formed in the electrode 312. Note that the opening formed in the electrode 312 need not be exactly the same as the opening 451 of the electrode 311. As long as the light from the light emitting element 170 can be extracted to the substrate 361 side, the size or shape of the opening of the electrode 312 may be different from the opening 451.

The electrode 312 may have a function of transmitting visible light similarly to the electrode 113 or the electrode 191. In this case, as shown in FIG. 2, the light of the light emitting element 170 can be emitted to the substrate 361 side without forming an opening or the like at a portion of the electrode 312 that overlaps with the opening 451.

A portion of the pixel 410 including the liquid crystal element 180 is referred to as a first pixel 410L, and a portion of the pixel 410 including a plurality of light emitting elements 170 is referred to as a second pixel 410E. The first pixel 410L excluding the sub-pixels can perform monochrome display (for example, black-and-white display or gray-scale display, etc.), and the second pixel 410E including a plurality of sub-pixels can perform full-color display.

Each portion of the pixel 410 including a plurality of light-emitting elements 170 (corresponding to the light-emitting element 170a, the light-emitting element 170b, and the light-emitting element 170c in FIG. 1A) is regarded as a sub-pixel of the second pixel 410E. As shown in FIG. 1A, when three sub-pixels are included, the light-emitting element 170a, the light-emitting element 170b, and the light-emitting element 170c preferably have three colors of red (R), green (G), and blue (B). The function of any one of them.

The color of the light emitting element 170 is not limited thereto, and may be, for example, three colors of yellow (Y), cyan (C), and magenta (M). In addition, the number of sub-pixels may be four or more. For example, when the number of sub-pixels is four, the color of the light emitting element 170 may be four colors of red (R), green (G), blue (B), white (W), or red (R ), Green (G), blue (B), and yellow (Y).

In addition, when the number of sub-pixels is four, the first pixel 410L may be used as one of the sub-pixels. For example, the first pixel 410L may be used to emit white (W) and the light emitting elements 170a, 170b, and 170c may emit any one of three colors of red (R), green (G), and blue (B). Structure. In this way, by adding the liquid crystal element 180 for displaying using external light, power consumption can be reduced compared to when the display is performed using only the light emitting element 170.

Here, the pixel 410 and the pixel 410LF shown in this embodiment are compared. In the pixel 410LF, the first pixel 410L includes a sub-pixel 410L_1, a sub-pixel 410L_2, and a sub-pixel 410L_3, and a full-color display can be performed using a liquid crystal element. FIG. 3A shows a top view of the pixel 410, and FIG. 3B shows a top view of the pixel 410LF. FIG. 3C shows a cross-sectional view of a two-dot chain line A1-A2 corresponding to the pixel 410 shown in FIG. 3A, and FIG. 3D shows a cross-sectional view of a two-dot chain line B1-B2 corresponding to the pixel 410LF shown in FIG. 3B. The two-dot chain line shown in FIGS. 3A and 3B shows an electrode 312 used as one electrode of the capacitor 270. 3C and 3D schematically illustrate the insulating layer 220 and the vicinity of the insulating layer 224 of each pixel.

The pixel 410LF differs from the pixel 410 in that it includes a sub-pixel 410L_1, a sub-pixel 410L_2, and a sub-pixel 410L_3 instead of the first pixel 410L. The sub-pixel 410L_1 includes an electrode 311_1, the sub-pixel 410L_2 includes an electrode 311_2, and the sub-pixel 410L_3 includes an electrode 311_3. Therefore, the sub-pixel 410L_1 is provided with a capacitor 270_1 including an electrode 311_1 and an electrode 312, the sub-pixel 410L_2 is provided with a capacitor 270_2 including an electrode 311_2 and an electrode 312, and the sub-pixel 410L_3 is provided with a capacitor 270_3 including an electrode 311_3 and an electrode 312.

As shown in FIGS. 3A to 3D, by making the first pixel 410L perform monochrome display, as compared with the case where three sub-pixels are provided and the first pixel 410L is displayed in full color, the pixel electrode of the first pixel 410L can be increased. Area. This is because not only the area of the pixel electrode of the first pixel 410L in the monochrome display can be changed to approximately 3 times the area of the pixel electrode of any of the sub-pixels 410L_1, 410L_2, and 410L_3 in full-color display. 3C and 3D, and the space between the sub-pixels required for patterning the sub-pixels 410L_1, 410L_2, and 410L_3 for full-color display can also be used for the first display of the monochrome display. A pixel electrode of 410L of one pixel. By adopting the above structure, the memory capacity of the capacitor provided in the liquid crystal element 180 can be increased. Therefore, the charge leakage of the pixel electrode can be reduced, and the gray scale can be maintained in the first pixel 410L for a long time.

In addition, a metal oxide is preferably used as a channel formation region of the transistor 200L. The metal oxide has an energy gap of 2.0 eV or more, preferably 2.5 eV or more, and more preferably 3.0 eV or more. By using the metal oxide in a 200L transistor, the gap between the source and the drain in the closed state can be increased. The current (hereinafter, referred to as off-state current) is extremely small. By using such a transistor 200L, the charge leakage of the pixel electrode can be reduced. Therefore, when the liquid crystal element 180 is used to display a still image, the gray scale can be maintained even if the writing operation to the pixel is stopped. In other words, you can keep the display even if the frame frequency is extremely small. Furthermore, as described above, by allowing the first pixel 410L to perform monochrome display to increase the memory capacity of the liquid crystal element 180, the gray scale can be maintained in the first pixel 410L for a longer time.

When the first pixel 410L is to be displayed in full color, three transistors 200L for controlling the driving of the liquid crystal element 180 need to be provided in the first pixel 410L. In this case, only one transistor 200L is sufficient. Therefore, in the case where the first pixel 410L is subjected to monochrome display, the leakage path of the electric charges held in the pixel electrode can be reduced, and thus the gray scale can be maintained in the first pixel 410L for a longer time.

Here, the resistivity of the liquid crystal layer 112 is preferably 1.0 × 10 ¹⁴ (Ω · cm) or more. The liquid crystal layer 112 also preferably includes molecules having a dipole moment of 0 Debye or more and 3 Debye or less.

In this way, by reducing the dipole moment of the molecules in the liquid crystal layer 112, the concentration of the ionic impurities included in the liquid crystal layer 112 can be reduced. Accordingly, ion conduction is unlikely to occur in the liquid crystal layer 112, and the resistivity of the liquid crystal layer 112 is improved. In this way, the charge held in the pixel electrode can be reduced from leaking through the liquid crystal layer 112, and the gray scale can be maintained in the first pixel 410L for a longer time. Note that details of the operation of the dipole moment and the liquid crystal layer will be described in the following embodiments.

For example, by setting the dipole moment of the molecules in the liquid crystal layer 112 to 3 Debye or less, the resistivity of the liquid crystal layer 112 can be made 1.0 × 10 ¹⁴ (Ω · cm) or more. In such a liquid crystal layer 112, for example, after a voltage of 3 V is applied between the counter electrode 311 and the electrode 113 for 16.6 milliseconds, the voltage retention rate after 30 seconds has elapsed is measured. The voltage holding rate is approximately 98.8%. The voltage holding ratio indicates how much the voltage applied to the pixel is held after the voltage application is stopped, and is an index showing how much the alignment of the liquid crystal molecules is maintained. Therefore, if the resistivity of the liquid crystal layer 112 is 1.0 × 10 ¹⁴ (Ω · cm) or more, the charge drain of the pixel electrode can be extremely small, and the alignment of the liquid crystal molecules can be maintained almost completely.

By adopting the above structure, it is possible to reduce the charge of the pixel electrode from leaking from the transistor 200L and the liquid crystal layer 112. Therefore, when the first pixel 410L is used to display a still image, the display can be maintained even if the frame frequency is extremely small. Therefore, when the first pixel 410L is used for display, the frame frequency can be switched between moving image display and still image display. For example, when the dynamic image display is switched to the static image display, the frame frequency is switched from 60 Hz to 1 Hz or less, preferably 0.2 Hz or less. With the above display, the power consumption of the display device 300 can be reduced.

The display device 300 is provided with a first pixel 410L capable of performing monochrome display and capable of switching frame frequency between moving image display and still image display, and a second pixel 410E capable of performing full color display. For example, when the display device 300 is used as an e-book reader terminal, a first pixel 410L may be used to display text, and a second pixel 410E may be used to display a still image or a moving image such as an illustration or a photo. In many cases, the text portion of the e-book reader can be fully displayed at a frame frequency of 1 Hz or lower, and monochrome display such as black and white. In e-book readers, the area of the text portion is mostly larger than other portions (for example, illustrations, photos, etc.), so the text portion is displayed by using the first pixel 410L with low power consumption and the portion other than the text is displayed using the second pixel 410E Can reduce power consumption.

Next, a top view of the adjacent pixels 410 a and 410 b shown in FIG. 4A will be described. As shown in FIG. 4A, the pixel 410a includes a sub-pixel 410aa, a sub-pixel 410ab, and a sub-pixel 410ac, and the sub-pixel 410aa, the sub-pixel 410ab, and the sub-pixel 410ac are arranged in the R direction. The sub-pixel 410aa is provided with a light-emitting element 170a, the sub-pixel 410ab is provided with a light-emitting element 170b, and the sub-pixel 410ac is provided with a light-emitting element 170c. As shown in FIG. 4A, the pixel 410b includes a sub-pixel 410ba, a sub-pixel 410bb, and a sub-pixel 410bc, and the sub-pixel 410ba, the sub-pixel 410bb, and the sub-pixel 410bc are arranged in the R direction. The sub-pixel 410ba is provided with a light-emitting element 170a, the sub-pixel 410bb is provided with a light-emitting element 170b, and the sub-pixel 410bc is provided with a light-emitting element 170c.

The sub-pixels arranged in the R direction in the same pixel 410 are preferably arranged at different positions of the electrode 311 so as not to arrange the openings 451 in a row. Thereby, the two light emitting elements 170 can be separated, and crosstalk can be suppressed. In addition, since two adjacent light emitting elements 170 can be arranged separately, even when the EL layer 192 of the light emitting element 170 is formed using a shadow mask or the like, a high-definition display device can be realized.

In the pixels 410a and 410b, the closest distances of the light emitting elements 170 are substantially the same. For example, as shown in FIG. 4A, the closest light emitting element of the light emitting element 170b of the pixel 410b is the light emitting element 170a of the pixel 410a, the light emitting element 170c of the pixel 410a, the light emitting element 170a of the pixel 410b, and the light emitting element 170c of the pixel 410b. As shown in FIG. 4A, when the distance between these light-emitting elements 170 and the light-emitting element 170b of the pixel 410b is represented by d1, d2, d3, and d4, d1, d2, d3, and d4 are preferably substantially the same. In this case, it is preferable to arrange the light emitting elements 170 along the three sides of the electrode 311. By disposing the light-emitting element 170 by the above method, even when the EL layer 192 of the light-emitting element 170 is formed using a shadow mask or the like, a high-definition display device can be realized.

In FIG. 4A, the sub-pixels are arranged in the R direction within the pixel 410, but are not limited thereto. As shown in FIG. 4B, the sub-pixels may be arranged in the C direction within the pixel 410.

The shape of the electrode 311 and the arrangement of the light emitting element 170 are not limited to the examples shown in FIGS. 1A, 4A, and 4B. A modification example of the shape of the electrode 311 in the pixel 410 and the arrangement of the light emitting element 170 will be described with reference to the top views of the pixel 410 shown in FIGS. 5A to 5H.

In FIG. 1A and the like, the light emitting element 170a, the light emitting element 170b, and the light emitting element 170c are arranged along the three sides of the electrode 311, but the arrangement of the light emitting element 170 is not limited to this. For example, as shown in FIG. 5A, the light-emitting element 170 a and the light-emitting element 170 c may be disposed at the corners of the electrode 311.

In addition, any one of the light emitting elements 170 may be disposed near the center of the electrode 311. For example, as shown in FIG. 5B, the light-emitting element 170 a and the light-emitting element 170 c may be disposed at the corners of the electrode 311 and the light-emitting element 170 b may be disposed near the center of the electrode 311. By using the above-mentioned arrangement method of the light emitting elements, as shown in FIG. 4A, the closest distances of the light emitting elements 170 between adjacent pixels can be made substantially the same.

In addition, as shown in FIG. 5C, the light-emitting element 170 a, the light-emitting element 170 b, and the light-emitting element 170 c may be disposed at the corners of the electrode 311.

In the above-mentioned structure, the light of the light emitting element 170 is extracted by forming the opening 451 in the electrode 311, but is not limited to this, and a slit or the like may be formed to extract the light of the light emitting element 170.

FIG. 5D shows a structure in which the cutouts 452a, 452b, and 452c are formed in the portions of the electrode 311 shown in FIG. 5A where the openings 451a, 451b, and 451c are formed.

FIG. 5E illustrates a structure in which cutouts 452a and 452c are formed in the portion of the electrode 311 shown in FIG. 5B where the openings 451a and 451c are formed. Since the light emitting element 170b shown in FIG. 5E is located near the center of the electrode 311, it is preferable to form the opening 451b so as to overlap the light emitting element 170b. When a cut is formed near the center of the electrode 311, the area of the electrode 311 is greatly reduced. Therefore, when the light emitting element 170 is arranged near the center of the electrode 311, it is preferable to form an opening to extract light from the light emitting element 170.

FIG. 5F shows a structure in which the cutouts 452a, 452b, and 452c are formed in the portions of the electrode 311 shown in FIG. 5C where the openings 451a, 451b, and 451c are formed.

FIG. 5G shows a structure in which the cutouts 452a, 452b, and 452c are formed in portions of the electrode 311 shown in FIG. 1A where the openings 451a, 451b, and 451c are formed.

In this way, a plurality of openings and / or cutouts may be formed in the electrode 311 and the light emitting element 170 may include a region overlapping the openings and / or cutouts.

As shown in FIG. 5H, the light emitting element 170a, the light emitting element 170b, and the light emitting element 170c may be provided in a region where the electrode 311 is not provided.

In the above structure, the pixel 410 includes three light-emitting elements 170a to 170c, but is not limited thereto, and the pixel 410 may include four or more light-emitting elements 170. A case where the pixel 410 includes four light-emitting elements 170a to 170d will be described with reference to the top views of the pixel 410 shown in FIGS. 6A to 6G. Here, the light-emitting element 170a, the light-emitting element 170b, the light-emitting element 170c, and the light-emitting element 170d preferably each have four colors of red (R), green (G), blue (B), and white (W). The function of either light. Alternatively, four colors such as red (R), green (G), blue (B), and yellow (Y) may be used.

For example, as shown in FIG. 6A, the light emitting element 170a, the light emitting element 170b, the light emitting element 170c, and the light emitting element 170d may be arranged along the four sides of the electrode 311. The electrode 311 is formed with an opening 451a, an opening 451b, an opening 451c, and an opening 451d. The light-emitting element 170a to the light-emitting element 170d each include a region overlapping with any one of the openings 451a to 451d.

As shown in FIG. 6B, the light-emitting element 170 a, the light-emitting element 170 b, the light-emitting element 170 c, and the light-emitting element 170 d may be disposed at a corner of the electrode 311. The electrode 311 shown in FIG. 6B is also formed with openings 451 a to 451 d similarly to FIG. 6A.

In addition, any one of the light emitting elements 170 may be disposed near the center of the electrode 311. For example, as shown in FIG. 6C, the light-emitting element 170a, the light-emitting element 170c, and the light-emitting element 170d may be disposed at the corner of the electrode 311 and the light-emitting element 170b may be disposed near the center of the electrode 311. The electrode 311 shown in FIG. 6C is also formed with openings 451 a to 451 d in the same manner as in FIG. 6A.

Fig. 6D shows a structure in which the cutout 452a, the cutout 452b, the cutout 452c, and the cutout 452d are formed in portions of the electrode 311 shown in Fig. 6A where the openings 451a, 451b, 451c and 451d are formed.

FIG. 6E illustrates a configuration in which the cutout 452a, the cutout 452b, the cutout 452c, and the cutout 452d are formed in the electrode 311 shown in FIG. 6B where the openings 451a, 451b, 451c, and 451d are formed.

FIG. 6F illustrates a configuration in which cutouts 452a, 452c, and 452d are formed in portions of the electrode 311 shown in FIG. 6C where the openings 451a, 451c, and 451d are formed. Since the light-emitting element 170b shown in FIG. 6F is located near the center of the electrode 311, it is preferable to form the opening 451b so as to overlap the light-emitting element 170b.

In addition, as shown in FIG. 6G, the light emitting element 170a, the light emitting element 170c, and the light emitting element 170d may be provided in a region where the electrode 311 is not provided. A cutout 452c is formed at a corner of the electrode 311 shown in FIG. 6G, and a part of the light emitting element 170c overlaps the cutout 452c. In addition, an opening 451b is formed near the center of the electrode 311, and the light-emitting element 170b overlaps the opening 451b.

In addition, as shown in FIG. 6G, the light-emitting areas of the light-emitting elements 170a to 170d may be different. In FIG. 6G, the light emitting areas of the light emitting elements 170a to 170c are substantially the same, and the light emitting area of the light emitting element 170d is small. For example, a light-emitting element exhibiting red (R), green (G), and blue (B) can be used as the light-emitting element 170a to 170c, and a light-emitting element exhibiting white (W) can be used as the light-emitting element 170d.

The shape of the electrode 311 is described above with reference to FIGS. 4A to 6G. Openings or cutouts may be similarly formed in the electrodes 312 constituting the capacitor 270. Note that, unlike the electrode 311, the electrode 312 needs to be formed in such a manner as not to overlap the connection portion 207.

<Structural Example 1>

FIG. 7 shows an example of a cross section of a part of the area including the FPC 372, a part of the area including the circuit 364, and a part of the area including the display portion 362 of the display device 300 shown in FIGS. 1A and 1B.

The display device 300 shown in FIG. 7 includes a transistor 201, a transistor 203, a transistor 205, a transistor 206, a liquid crystal element 180, a light emitting element 170, a capacitor 270, an insulating layer 220, and the like between a substrate 351 and a substrate 361. The substrate 361 and the insulating layer 220 are bonded by an adhesive layer 141. The substrate 351 and the insulating layer 220 are bonded by an adhesive layer 142. In addition, the transistor 205 corresponds to the transistor 200E shown in FIG. 1B, and the transistor 206 corresponds to the transistor 200L shown in FIG. 1B.

The substrate 361 is provided with a light shielding layer 132, an insulating layer 121, an electrode 113 used as a common electrode of the liquid crystal element 180, an alignment film 133b, an insulating layer 117, and the like. A polarizing plate 135 is provided on the outer surface of the substrate 361. The insulating layer 121 may also be used as a planarization layer. Since the surface of the electrode 113 can be made substantially flat by using the insulating layer 121, the alignment state of the liquid crystal layer 112 can be made uniform. The insulating layer 117 is used as a spacer for maintaining a cell gap of the liquid crystal element 180. When the insulating layer 117 transmits visible light, the insulating layer 117 may overlap the display area of the liquid crystal element 180.

The liquid crystal element 180 is a reflective liquid crystal element. The liquid crystal element 180 has a stacked structure of an electrode 311a, a liquid crystal layer 112, and an electrode 113 used as pixel electrodes. An electrode 311b that reflects visible light is provided so as to be in contact with the substrate 351 side of the electrode 311a. The electrode 311b has an opening 451. The electrodes 311a and the electrodes 113 transmit visible light. An alignment film 133a is provided between the liquid crystal layer 112 and the electrode 311a. An alignment film 133b is provided between the liquid crystal layer 112 and the electrode 113.

In the liquid crystal element 180, the electrode 311b has a function of reflecting visible light, and the electrode 113 has a function of transmitting visible light. The light incident from the substrate 361 side is polarized by the polarizing plate 135, passes through the electrode 113 and the liquid crystal layer 112, and is reflected by the electrode 311b. Then, it passes through the liquid crystal layer 112 and the electrode 113 again and reaches the polarizing plate 135. At this time, the alignment of the liquid crystal is controlled by the voltage applied between the electrode 311b and the electrode 113, so that the optical modulation of light can be controlled. That is, the intensity of light emitted through the polarizing plate 135 can be controlled.

As shown in FIG. 7, an electrode 311 a that transmits visible light is preferably provided in the opening 451. As a result, the liquid crystal layer 112 is aligned in the same region as the other regions in the region overlapping the opening 451, and it is possible to suppress unintended light leakage due to poor alignment of the liquid crystal at the border portion of the region.

The stack of the electrodes 311a and 311b corresponds to the electrode 311 shown in FIGS. 1A and 1B. Note that since the electrode 311a transmits visible light, it is not necessary to form the above-mentioned openings, cutouts, and the like in the electrode 311a. Note that in the case where the electrode 311a is not provided, the electrode 311b corresponds to the electrode 311 shown in FIGS. 1A and 1B.

The capacitor 270 includes an electrode 311 a and an electrode 311 b used as one electrode, an electrode 312 used as the other electrode, and an insulating layer 220 used as a dielectric. An insulating layer 224 is provided so as to cover the electrode 312. When a metal that transmits visible light is used as the electrode 312, the electrode 312 may be provided so as to overlap the opening 451.

In the connection portion 207, the electrode 311b is electrically connected to the conductive layer 222a included in the transistor 206 through the conductive layer 221b. The transistor 206 has a function of controlling the driving of the liquid crystal element 180. The electrode 312 is provided so as not to contact the conductive layer 221 b of the connection portion 207. For example, it is preferable to provide an insulating layer 224 between the conductive layer 221b and the electrode 312.

A connection portion 252 is provided in a part of a region where the adhesive layer 141 is provided. In the connection portion 252, the connector 243 electrically connects a conductive layer obtained by processing the same conductive film as the electrode 311 a to a part of the electrode 113. Accordingly, a signal or a potential input from the FPC 372 connected to the substrate 351 side can be supplied to the electrode 113 formed on the substrate 361 side through the connection portion 252.

For example, as the connector 243, conductive particles can be used. As the conductive particles, particles such as organic resin or silicon dioxide whose surface is covered with a metal material can be used. As the metal material, nickel or gold is preferably used because it can reduce contact resistance. It is preferable to use particles in which two or more kinds of metal materials are covered in a layer form, such as covering gold with nickel. In addition, as the connector 243, a material capable of elastic deformation or plastic deformation is preferably used. At this time, the connector 243 as a conductive particle may have a shape crushed in the longitudinal direction as shown in FIG. 7. By having this shape, the contact area between the connector 243 and the conductive layer electrically connected to the connector 243 can be increased, so that the contact resistance can be reduced, and problems such as poor contact can be suppressed.

The connector 243 is preferably arranged so as to be covered with the adhesive layer 141. For example, the connectors 243 may be dispersed in the adhesive layer 141 before being cured.

The light emitting element 170 is a bottom emission type light emitting element. The light-emitting element 170 has a structure in which an electrode 191 serving as a pixel electrode, an EL layer 192, and an electrode 193 serving as a common electrode are stacked in this order from the insulating layer 220 side. The electrode 191 is connected to the conductive layer 222 b included in the transistor 205 through an opening formed in the insulating layer 214. The transistor 205 has a function of controlling the driving of the light emitting element 170. The insulating layer 216 covers an end portion of the electrode 191. The electrode 193 includes a conductive material that reflects visible light, and the electrode 191 includes a conductive material that transmits visible light. The insulating layer 194 is provided so as to cover the electrode 193. The light emitted from the light emitting element 170 is emitted to the substrate 361 side through the insulating layer 220, the opening 451, the electrode 311a, and the like.

In FIG. 7, a structure in which a light emitting element 170 is formed in each sub-pixel is shown. For example, as shown in FIG. 1A and the like, when the pixel 410 includes a light-emitting element 170a, a light-emitting element 170b, and a light-emitting element 170c, the materials of the EL layer included in each light-emitting element can be made different in structure to have red emission ( R), green (G), and blue (B). For example, the light emitting element 170a, the light emitting element 170b, and the light emitting element 170c may include different materials.

For example, as shown in FIG. 6A and the like, when the pixel 410 includes a light-emitting element 170a, a light-emitting element 170b, a light-emitting element 170c, and a light-emitting element 170d, the material configuration of the EL layer included in each light-emitting element can be made different to make it It has a function of emitting light in any of the four colors of red (R), green (G), blue (B), and white (W).

As described above, the display device 300 shown in FIG. 7 can perform color display using the light emitting element 170.

In addition, the display device 300 may perform color display without forming the light emitting element 170 in each sub-pixel. For example, as in the display device 300 shown in FIG. 8, a color layer 134 may be provided between the light emitting element 170 and the liquid crystal element 180. The color layer 134 is covered by the insulating layer 214 and overlaps the opening 451. In FIG. 8, a color layer 134 representing a different color is provided in each sub-pixel.

For example, as shown in FIG. 1A and the like, when the pixel 410 includes a light-emitting element 170a, a light-emitting element 170b, and a light-emitting element 170c, the structure of the material of the EL layer included in each light-emitting element can be made the same to have an emission white ( W) Light function. In addition, a color layer 134 having a function of transmitting light in any of three colors of red (R), green (G), and blue (B) is provided so as to overlap each light-emitting element.

For example, as shown in FIG. 6G and the like, when the pixel 410 includes a light-emitting element 170a, a light-emitting element 170b, a light-emitting element 170c, and a light-emitting element 170d, the materials of the EL layer included in each light-emitting element can be made to have the same structure to make them With the function of emitting white (W) light. In addition, the light emitting element 170a, the light emitting element 170c, and the light emitting element 170d may be provided with a function of transmitting light in any one of three colors of red (R), green (G), and blue (B) so as to overlap the light emitting element 170a, 170c, and 170d. Colored layer 134. The light-emitting element 170b does not need to be provided with a color layer 134 so that the light-emitting element emits white light.

As described above, the display device 300 shown in FIG. 8 can perform color display using the light emitting element 170 and the color layer 134.

The transistor 201, the transistor 203, the transistor 205, and the transistor 206 are all formed on the surface of the substrate 351 side of the insulating layer 224. These transistors can be manufactured by the same process.

The circuit electrically connected to the liquid crystal element 180 and the circuit electrically connected to the light emitting element 170 are preferably formed on the same surface. Thereby, compared with the case where two circuits are formed on different faces, the thickness of the display device can be reduced. In addition, since two transistors can be manufactured by the same process, the process can be simplified compared to a case where two transistors are formed on different faces.

The pixel electrode used as the liquid crystal element 180 is located at a position opposite to the pixel electrode used as the light emitting element 170 with respect to the gate insulating layer of the transistor.

Here, when the transistor 206 containing the metal oxide in the channel formation region and having a very low off-state current or a memory element electrically connected to the transistor 206 are used, even when a static image is displayed using the liquid crystal element 180, the Writing can also maintain gray levels. That is to say, even if the frame frequency is extremely small, the display can be maintained. In one embodiment of the present invention, the frame frequency can be made extremely small and driving with low power consumption can be performed.

In addition, the area of the electrode 311 b used as the pixel electrode is increased by performing a monochrome display on a pixel including the liquid crystal element 180, so that the memory capacity of a capacitor provided to the liquid crystal element 180 can be increased. Thereby, the off-state current of the transistor 206 can be further reduced.

The resistivity of the liquid crystal layer 112 is preferably 1.0 × 10 ¹⁴ (Ω · cm) or more. As a result, the voltage holding ratio of the liquid crystal layer 112 is improved, so that the gray scale can be maintained in the liquid crystal element 180 of the pixel 410 for a long time.

By adopting the above structure, when the liquid crystal element 180 using the pixel 410 displays a still image, the display can be maintained even if the frame frequency is extremely small. Therefore, when the liquid crystal element 180 of the pixel 410 can be used for display, the frame frequency can be switched between moving image display and still image display. For example, when the dynamic image display is switched to the static image display, the frame frequency is switched from 60 Hz to 1 Hz or less, preferably 0.2 Hz or less. With the above display, the power consumption of the display device 300 can be reduced.

The transistor 203 is a transistor (also referred to as a switching transistor or a selection transistor) that controls a selected / non-selected state of a pixel. The transistor 205 is a transistor (also referred to as a driving transistor) that controls a current flowing through the light emitting element 170.

An insulating layer such as an insulating layer 211, an insulating layer 212, an insulating layer 213, and an insulating layer 214 is provided on the substrate 351 side of the insulating layer 224. A part of the insulating layer 211 is used as a gate insulating layer of each transistor. The insulating layer 212 is provided so as to cover the transistor 206 and the like. The insulating layer 213 is provided so as to cover the transistor 205 and the like. The insulating layer 214 is used as a planarization layer. Note that the number of insulating layers covering the transistor is not particularly limited, and may be one, or two or more.

Preferably, a material that does not easily diffuse impurities such as water or hydrogen is used for at least one of the insulating layers covering each transistor. Thereby, an insulating layer can be used as a barrier film. By adopting such a structure, it is possible to effectively suppress impurities from diffusing into the transistor from the outside, so that a highly reliable display device can be realized.

The transistor 201, the transistor 203, the transistor 205, and the transistor 206 include a conductive layer 221a used as a gate electrode, an insulating layer 211 used as a gate insulating layer, and a conductive layer 222a used as a source and a drain. And a conductive layer 222b and a metal oxide layer 231. Here, a plurality of layers obtained by processing the same conductive film have the same hatching.

The transistor 201 and the transistor 205 include a conductive layer 223 used as a gate in addition to the components of the transistor 203 and the transistor 206.

The transistor 201 and the transistor 205 have a structure in which a semiconductor layer is formed by sandwiching two gates. In this way, the threshold voltage of the transistor can be controlled by the electric field of the two gate electrodes surrounding the metal oxide layer forming the channel region. This transistor structure can be referred to as a Surrounded Channel (S-channel) structure. At this time, the transistor can also be driven by connecting two gates and supplying the same signal to the two gates. Compared with other transistors, this transistor can improve the field effect mobility and increase the on-state current. As a result, a circuit capable of high-speed driving can be manufactured. Furthermore, the area occupied by the circuit portion can be reduced. By using a transistor with a large on-state current, even if the number of wirings increases when the display device is enlarged or sharpened, the signal delay of each wiring can be reduced, and display unevenness can be suppressed.

Alternatively, the threshold voltage of the transistor can be controlled by applying a potential for controlling the critical voltage to one of the two gates and applying a potential for driving to the other of the two gates.

There is no limitation on the structure of the transistor included in the display device. The transistor included in the circuit 364 and the transistor included in the display portion 362 may have the same structure or different structures. The plurality of transistors included in the circuit 364 may both have the same structure, or may combine two or more structures. Similarly, the plurality of transistors included in the display section 362 may all have the same structure, or two or more structures may be combined.

As the conductive layer 223, a conductive material containing an oxide is preferably used. By forming the conductive film constituting the conductive layer 223 in an atmosphere containing oxygen, oxygen can be supplied to the insulating layer 212. Preferably, the proportion of the oxygen gas in the deposition gas is 90% or more and 100% or less. The oxygen supplied to the insulating layer 212 is supplied to the metal oxide layer 231 by a subsequent heat treatment, whereby reduction of oxygen defects in the metal oxide layer 231 can be achieved.

In particular, as the conductive layer 223, a metal oxide having a reduced resistance is preferably used. At this time, as the insulating layer 213, an insulating film that releases hydrogen, such as a silicon nitride film, is preferably used. Hydrogen is supplied to the conductive layer 223 during or after the heat treatment when the insulating layer 213 is formed, whereby the resistance of the conductive layer 223 can be effectively reduced.

A connection portion 204 is provided in a region of the substrate 351 that does not overlap the substrate 361. In the connection portion 204, the wiring 365 is electrically connected to the FPC 372 through the connection layer 242. The connection portion 204 has the same structure as the connection portion 207. The conductive layer obtained by processing the same conductive film as the electrode 311a on the top of the connection portion 204 is exposed. Therefore, the connection portion 204 can be electrically connected to the FPC 372 through the connection layer 242.

As the polarizing plate 135 provided on the outer surface of the substrate 361, a linear polarizing plate or a circular polarizing plate may be used. As the circular polarizing plate, for example, a polarizing plate in which a linear polarizing plate and a quarter wave retardation plate are laminated can be used. This can suppress external light reflection. In addition, by adjusting the cell gap, alignment, driving voltage, and the like of the liquid crystal element used for the liquid crystal element 180 according to the type of the polarizing plate, a desired contrast can be achieved.

In addition, various optical members may be arranged on the outer surface of the substrate 361. As the optical member, a polarizing plate, a retardation plate, a light diffusion layer (such as a diffusion film), an anti-reflection layer, a condensing film, and the like can be used. In addition, an antistatic film that suppresses adhesion of dust, a water-repellent film that is not easily stained, a hard coating film that suppresses damage during use, and the like may be disposed on the outer surface of the substrate 361.

The substrate 351 and the substrate 361 can be made of glass, quartz, ceramics, sapphire, or organic resin. By using a flexible material for the substrate 351 and the substrate 361, the flexibility of the display device can be improved.

As the liquid crystal element 180, for example, a liquid crystal element using a VA (Vertical Alignment) mode can be used. As the vertical alignment mode, MVA (Multi-Domain Vertical Alignment) mode, PVA (Patterned Vertical Alignment) mode, ASV (Advanced Super View) mode, etc. can be used.

As the liquid crystal element 180, a liquid crystal element using various modes can be used. For example, in addition to the VA mode, TN (Twisted Nematic: twisted nematic) mode, IPS (In-Plane-Switching: plane switching) mode, FFS (Fringe Field Switching: edge electric field switching) mode, and ASM (Axially Symmetric aligned) can be used. Micro-cell: Axisymmetrically arranged microcells) mode, OCB (Optically Compensated Birefringence: optical compensation bending) mode, FLC (Ferroelectric Liquid Crystal) mode, AFLC (AntiFerroelectric Liquid Crystal) mode, etc. LCD element.

A liquid crystal element is an element that controls the transmission or non-transmission of light by using the optical modulation effect of liquid crystal. The optical modulation effect of a liquid crystal is controlled by an electric field (including a lateral electric field, a longitudinal electric field, or an oblique electric field) applied to the liquid crystal. As the liquid crystal used for the liquid crystal element, thermotropic liquid crystal, low-molecular liquid crystal, polymer liquid crystal, polymer dispersed liquid crystal (PDLC: Polymer Dispersed Liquid Crystal), ferroelectric liquid crystal, antiferroelectric liquid crystal, and the like can be used. These liquid crystal materials exhibit a cholesteric phase, a smectic phase, a cubic phase, a hand nematic phase, and isotropic isotropy according to conditions.

As described above, the liquid crystal material preferably contains molecules having a dipole moment of 0 Debye or more and 3 Debye or less, and the resistivity of the liquid crystal layer 112 is preferably 1.0 × 10 ¹⁴ (Ω · cm) or more. As the liquid crystal material, a positive type liquid crystal or a negative type liquid crystal can be used, and an appropriate liquid crystal material can be used depending on the mode or design used.

In order to control the alignment of the liquid crystal, an alignment film 133a, an alignment film 133b, and the like may be provided. When the lateral electric field method is used, a blue-phase liquid crystal that does not use an alignment film may be used. The blue phase is a type of liquid crystal phase, and refers to a phase that appears immediately before the transition from the cholesterol phase to the homogeneous phase when the temperature of the cholesteric liquid crystal is raised. Since the blue phase appears only in a narrow temperature range, a liquid crystal composition in which a chiral agent of several wt% or more is mixed is used for liquid crystal to expand the temperature range. A liquid crystal composition containing a blue phase-containing liquid crystal and a chiral agent has a fast response speed and is optically isotropic. In addition, a liquid crystal composition containing a liquid crystal exhibiting a blue phase and a chiral agent does not require alignment treatment, and has a low viewing angle dependency. In addition, since it is not necessary to provide an alignment film without rubbing treatment, electrostatic damage caused by rubbing treatment can be prevented, and defects and breakage of the liquid crystal display device in the manufacturing process can be reduced.

When a reflective liquid crystal element is used, the polarizing plate 135 is provided on the display surface side. In addition, when a light diffusing plate is additionally provided on the display surface side, it is possible to improve visibility, so it is preferable.

A front light source may be provided outside the polarizing plate 135. As the front light source, an edge-illumination type front light source is preferably used. When a front light source including an LED (Light Emitting Diode) is used, power consumption can be reduced, so it is preferable.

As the adhesive layer 141 and the adhesive layer 142, various hardening adhesives, such as a light hardening adhesive, such as an ultraviolet hardening adhesive, a reaction hardening adhesive, a thermosetting adhesive, and an anaerobic adhesive, can be used. Examples of these adhesives include epoxy resins, acrylic resins, silicone resins, phenol resins, polyimide resins, polyimide resins, PVC (polyvinyl chloride) resins, and PVB (polyvinyl butyral). Resin, EVA (ethylene-vinyl acetate) resin, etc. In particular, it is preferable to use a material having low moisture permeability such as epoxy resin. Alternatively, a two-liquid mixed resin may be used. Alternatively, an adhesive sheet or the like may be used.

As the connection layer 242, an anisotropic conductive film (ACF: Anisotropic Conductive Film), an anisotropic conductive paste (ACP: Anisotropic Conductive Paste), or the like can be used.

The light emitting element 170 has a top emission structure, a bottom emission structure, a double-sided emission structure, and the like. As the electrode on the light extraction side, a conductive film that transmits visible light is used. In addition, it is preferable to use a conductive film that reflects visible light as the electrode that does not extract light.

The EL layer 192 includes at least a light emitting layer. As a layer other than the light emitting layer, the EL layer 192 may further include a substance having a high hole injection property, a substance having a high hole transport property, a hole blocking material, a substance having a high electron transport property, a substance having a high electron injection property, or A layer of a polar substance (a substance having a high electron-transporting property and a hole-transporting property).

As the EL layer 192, a low-molecular compound or a high-molecular compound may be used, and an inorganic compound may be further included. The layer constituting the EL layer 192 can be formed by a method such as a vapor deposition method (including a vacuum vapor deposition method), a transfer method, a printing method, an inkjet method, and a coating method.

The EL layer 192 may include an inorganic compound such as a quantum dot. For example, by using a quantum dot for a light emitting layer, it can also be used as a light emitting material.

In addition, by using a combination of a color filter (color layer) and a microcavity structure (optical adjustment layer), light with high color purity can be extracted from a display device. The thickness of the optical adjustment layer changes according to the color of each pixel.

Examples of materials that can be used for conductive layers such as gates, sources and drains of transistors, and various wirings and electrodes constituting display devices include aluminum, titanium, chromium, nickel, copper, yttrium, zirconium, molybdenum, silver, Metals such as tantalum or tungsten, or alloys containing the above metals as main components. Single layers or laminates of films containing these materials can be used.

In addition, as a conductive material that transmits visible light, conductive oxides such as indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, and zinc oxide to which gallium is added, or graphene can be used. Alternatively, a metal material such as gold, silver, platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, or titanium, or an alloy material containing the metal material can be used. Alternatively, a nitride of the metal material (for example, titanium nitride) or the like may be used. In addition, when a metal material or an alloy material (or a nitride thereof) is used, it may be formed to be thin so as to have translucency. In addition, a laminated film of the above materials can be used as a conductive material that transmits visible light. For example, the use of a multilayer film of an alloy of silver and magnesium with indium tin oxide can improve the conductivity, and is therefore preferred. The above-mentioned materials can also be used for conductive layers constituting various wirings and electrodes of a display device, and conductive layers (conductive layers used as pixel electrodes and common electrodes) included in display elements.

Examples of the insulating material usable for each insulating layer include resins such as acrylic resins and epoxy resins, and inorganic insulating materials such as silicon oxide, silicon oxynitride, silicon oxynitride, silicon nitride, or aluminum oxide.

Examples of the material that can be used for the color layer include a metal material, a resin material, and a resin material containing a pigment or a dye.

The transistor 200a will be described as an example of the structure of the transistor 201, the transistor 203, the transistor 205, and the transistor 206 shown in FIG. 7 with reference to FIGS. 9A to 9C. FIG. 9A is a plan view of the transistor 200a. FIG. 9B corresponds to a cross-sectional view taken along the chain line X1-X2 shown in FIG. 9A, and FIG. 9C corresponds to a cross-sectional view taken along the chain line Y1-Y2 shown in FIG. 9A. Note that in FIG. 9A, a part of the components of the transistor 200 a (an insulating layer having a function of a gate insulating layer, etc.) is omitted for convenience. Hereinafter, the direction of the dotted line X1-X2 may be referred to as a channel length direction, and the direction of the dotted line Y1-Y2 may be referred to as a channel width direction. Note that a part of the components may be omitted in the top view of the subsequent transistor in the same manner as in FIGS. 9A to 9C.

The transistor 200a includes a conductive layer 221 on the insulating layer 224; an insulating layer 224 and an insulating layer 211 on the conductive layer 221; a metal oxide layer 231 on the insulating layer 211; a conductive layer 222a on the metal oxide layer 231; and metal oxidation The conductive layer 222b on the object layer 231; the metal oxide layer 231, the conductive layer 222a, and the insulating layer 212 on the conductive layer 222b; the conductive layer 223 on the insulating layer 212; the insulating layer 212 and the insulating layer 213 on the conductive layer 223.

Each component of the transistor 200 a corresponds to a component of the same symbol of the display device 300 shown in FIG. 7. Note that the conductive layer 221 of the transistor 200 a corresponds to the conductive layer 221 a of the display device 300.

The insulating layer 211 and the insulating layer 212 include an opening portion 235. The conductive layer 223 is electrically connected to the conductive layer 221 through the opening 235.

The insulating layer 211 is used as a first gate insulating layer of the transistor 200a, the insulating layer 212 is used as a second gate insulating layer of the transistor 200a, and the insulating layer 213 is used as a protective insulating layer of the transistor 200a. In addition, in the transistor 200a, the conductive layer 221 is used as the first gate, the conductive layer 222a is used as one of the source and the drain, and the conductive layer 222b is used as the other of the source and the drain. In addition, in the transistor 200a, the conductive layer 223 is used as a second gate.

The transistor 200a is a so-called channel-etched transistor and has a double-gate structure.

The transistor 200a may not include the conductive layer 223. When the transistor 200 a includes the conductive layer 223, the transistor 200 a has a structure corresponding to the transistor 201 and the transistor 205 shown in FIG. 7. When the transistor 200a does not include the conductive layer 223, it has a structure corresponding to the transistor 203 and the transistor 206 shown in FIG.

As shown in FIGS. 9B and 9C, the metal oxide layer 231 is located opposite to the conductive layer 221 and the conductive layer 223, and is sandwiched between two conductive layers used as gate electrodes. The length in the channel length direction of the conductive layer 223 and the length in the channel width direction of the conductive layer 223 are respectively longer than the length in the channel length direction of the metal oxide layer 231 and the length in the channel width direction of the metal oxide layer 231. The conductive layer 223 covers the entire metal oxide layer 231 via the insulating layer 212.

In other words, the conductive layer 221 and the conductive layer 223 are connected to each other in the opening portion 235 formed in the insulating layer 211 and the insulating layer 212, and include a region located outside the side end portion of the metal oxide layer 231.

By adopting such a structure, the electric field of the conductive layer 221 and the conductive layer 223 is used to surround the metal oxide layer 231 included in the transistor 200a.

Since the transistor 200a has an S-channel structure in which a metal oxide layer forming a channel region is surrounded by the electric field of the first gate electrode and the second gate electrode, the metal can be oxidized using the conductive layer 221 serving as the first gate electrode. The object layer 231 effectively applies an electric field for causing a channel. Thereby, the current driving ability of the transistor 200a is improved, and a high on-state current characteristic can be obtained. In addition, since the on-state current can be increased, the transistor 200a can be miniaturized. In addition, since the transistor 200a has a structure surrounded by the conductive layer 221 serving as the first gate electrode and the conductive layer 223 serving as the second gate electrode, the mechanical strength of the transistor 200a can be improved.

For example, the metal oxide layer 231 preferably contains In, M (M is gallium, aluminum, silicon, boron, yttrium, tin, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium , Neodymium, praseodymium, tantalum, tungsten or magnesium) and Zn.

The metal oxide layer 231 preferably includes a region where the atomic ratio of In is greater than the atomic ratio of M. For example, it is preferable to set the atomic ratio of In, M, and Zn of the metal oxide layer 231 to around In: M: Zn = 4: 2: 3. Here, "nearby" means that when In is 4, M is 1.5 or more and 2.5 or less, and Zn is 2 or more and 4 or less. Alternatively, it is preferable to set the atomic ratio of In, M, and Zn of the metal oxide layer 231 to around In: M: Zn = 5: 1: 6.

The metal oxide layer 231 is preferably CAC-OS or CAC-metal oxide. In the case where the metal oxide layer 231 includes a region where the atomic ratio of In is greater than the atomic ratio of M and is CAC-OS or CAC-metal oxide, the field effect mobility of the transistor 200a can be increased. Note that the details of CAC-OS or CAC-metal oxide will be described in detail later.

Because the transistor 200a with the s-channel structure has a high field-effect mobility and high driving capability, by using the transistor 200a for a driving circuit (typically a gate driver that generates a gate signal), a narrow frame width can be provided. (Also known as a narrow bezel) display device. In addition, the transistor 200a is used for a source driver (in particular, a demultiplexer connected to an output terminal of a shift register included in a source driver) included in a display device and supplying a signal from a signal line. ), It is possible to provide a display device with a small number of wirings connected to the display device.

In addition, since the transistor 200a is a transistor having a channel etching structure, the number of processes is smaller than that of a transistor using low-temperature polycrystalline silicon. In addition, since the channel of the transistor 200a uses a metal oxide layer, the transistor 200a does not require a laser crystallization process required for a transistor using low-temperature polycrystalline silicon. Therefore, even a display device using a large-area substrate can reduce manufacturing costs. Furthermore, large-scale displays with high resolution such as Ultra High Definition ("4K resolution", "4K2K", "4K") and Super High Definition ("8K resolution", "8K4K", "8K") In the device, a transistor having a high field effect mobility such as the transistor 200a is used for a driving circuit and a display unit, and it is possible to reduce writing in a short time and reduce display defects, so it is preferable.

The conductive layer 221, the conductive layer 222a, the conductive layer 222b, and the conductive layer 223 may be selected from chromium (Cr), copper (Cu), aluminum (Al), gold (Au), silver (Ag), zinc (Zn), and molybdenum. (Mo), tantalum (Ta), titanium (Ti), tungsten (W), manganese (Mn), nickel (Ni), iron (Fe), cobalt (Co), metallic elements, An alloy or an alloy in which the above-mentioned metal elements are combined is formed.

In addition, as the conductive layer 221, the conductive layer 222a, the conductive layer 222b, and the conductive layer 223, an oxide (In-Sn oxide) containing indium and tin, an oxide (In-W oxide) containing indium and tungsten may be used. ), An oxide containing indium, tungsten and zinc (In-W-Zn oxide), an oxide containing indium and titanium (In-Ti oxide), an oxide containing indium, titanium and tin (In-Ti- Sn oxide), oxide containing indium and zinc (In-Zn oxide), oxide containing indium, tin, and silicon (In-Sn-Si oxide), oxide containing indium, gallium, and zinc (In -Ga-Zn oxide) and other conductive oxides.

In addition, as the conductive layer 221, the conductive layer 222a, the conductive layer 222b, and the conductive layer 223, a Cu-X alloy film (X is Mn, Ni, Cr, Fe, Co, Mo, Ta, or Ti) may be used. By using a Cu-X alloy film, processing can be performed in a wet etching process, thereby suppressing manufacturing costs. Since the resistance of the Cu-X alloy film is low, by using the Cu-X alloy film to form the conductive layer 221, the conductive layer 222a, the conductive layer 222b, and the conductive layer 223, wiring delay can be reduced. Therefore, it is appropriate to use a Cu-X alloy film as a wiring in the manufacture of a large-scale display device.

As the insulating layer 224, the insulating layer 211, and the insulating layer 212, a silicon oxide film and a silicon oxynitride film formed by a plasma enhanced chemical vapor deposition (PECVD: Plasma Enhanced Chemical Vapor Deposition) method, a sputtering method, or the like can be used. Film, silicon oxynitride film, silicon nitride film, aluminum oxide film, hafnium oxide film, yttrium oxide film, zirconia film, gallium oxide film, tantalum oxide film, magnesium oxide film, lanthanum oxide film, cerium oxide film, and neodymium oxide film One or more insulating layers in a film. Note that the insulating layer 224, the insulating layer 211, and the insulating layer 212 may have a stacked structure or a stacked structure of three or more layers.

The insulating layer 211 and the insulating layer 212 that are in contact with the metal oxide layer 231 are preferably oxide insulating films, and preferably include a region (excess oxygen region) containing oxygen in excess of a stoichiometric composition. In other words, the insulating layer 211 and the insulating layer 212 are insulating films capable of releasing oxygen. In order to form an oxygen peroxo region in the insulating layer 211 and the insulating layer 212, for example, the insulating layer 211 and the insulating layer 212 are formed in an oxygen atmosphere, or the film-formed insulating layer 211 and the insulating layer 212 are heat-treated in an oxygen atmosphere.

As the metal oxide layer 231, the above-mentioned materials can be used.

When the metal oxide layer 231 is an In-M-Zn oxide, the atomic number of the metal element of the sputtering target used to form the In-M-Zn oxide is preferably to satisfy In> M. Examples of the atomic ratio of the metal elements of such a sputtering target include In: M: Zn = 2: 1: 3, In: M: Zn = 3: 1: 2, In: M: Zn = 4: 2: 4.1, In: M: Zn = 5: 1: 6, In: M: Zn = 5: 1: 7, In: M: Zn = 5: 1: 8, In: M: Zn = 6: 1: 6, In: M: Zn = 5: 2: 5 and so on.

In addition, when the metal oxide layer 231 is formed using an In-M-Zn oxide, it is preferable to use a target containing a polycrystalline In-M-Zn oxide as a sputtering target. By using a target material containing a polycrystalline In-M-Zn oxide, a crystalline metal oxide layer 231 can be easily formed. Note that the atomic ratio of the formed metal oxide layer 231 varies within a range of ± 40% including the atomic ratio of the metal element in the sputtering target. For example, when the composition of the sputtering target used for the metal oxide layer 231 is In: Ga: Zn = 4: 2: 4.1 [atomic number ratio], the composition of the formed metal oxide layer 231 may be In : Ga: Zn = 4: 2: 3 [atomic number ratio] and so on.

The energy gap of the metal oxide layer 231 is 2 eV or more, and preferably 2.5 eV or more. In this way, by using an oxide semiconductor having a wide energy gap, the off-state current of the transistor can be reduced.

The metal oxide layer 231 preferably has a non-single crystal structure. The non-single-crystal structure includes, for example, the following CAAC-OS (C Axis Aligned Crystalline Oxide Semiconductor), a polycrystalline structure, a microcrystalline structure, or an amorphous structure. Among non-single-crystal structures, the density of defect states is highest in the amorphous structure, while the density of defect states is the lowest in CAAC-OS.

The use of a metal oxide film having a low impurity concentration and a low density of defect states as the metal oxide layer 231 makes it possible to produce a transistor having excellent electrical characteristics, which is preferable. Here, the state where the impurity concentration is low and the density of defect states is low (there are few oxygen defects) is referred to as "high-purity essence" or "substantially high-purity essence". Typical examples of impurities in the metal oxide film are water, hydrogen, and the like. In this specification and the like, a treatment for reducing or removing water and hydrogen in a metal oxide film is sometimes referred to as dehydration and dehydrogenation. In addition, a process of adding oxygen to a metal oxide film or an oxide insulating film is sometimes referred to as oxidation, and a state in which oxidation is performed and contains oxygen in excess of a stoichiometric composition is sometimes referred to as a peroxidation state.

Since there are fewer carrier generation sources for a metal oxide film of high purity nature or substantially high purity nature, the carrier density can be reduced. Therefore, the transistor forming the channel region in the metal oxide film rarely has an electrical characteristic (also referred to as a normally-on characteristic) having a negative threshold voltage. Since a metal oxide film of high purity nature or substantially high purity nature has a lower density of defect states, it is possible to have a lower density of trap states. The off-state current of a high-purity or substantially high-purity metal oxide film is significantly low, even for a device with a channel width of 1 × 10 ⁶ μm and a channel length L of 10 μm. When the voltage (drain voltage) is in the range of 1V to 10V, the off-state current can also be below the measurement limit of the semiconductor parameter analyzer, that is, below 1 × 10 ^-13 A.

The insulating layer 213 contains one or both of hydrogen and nitrogen. The insulating layer 213 includes nitrogen and silicon. In addition, the insulating layer 213 has a function capable of blocking oxygen, hydrogen, water, an alkali metal, an alkaline earth metal, and the like. By providing the insulating layer 213, oxygen can be prevented from diffusing from the metal oxide layer 231 to the outside, oxygen contained in the insulating layer 212 can be prevented from diffusing to the outside, and hydrogen, water, and the like can be prevented from entering the metal oxide layer 231 from the outside. .

As the insulating layer 213, for example, a nitride insulating film can be used. Examples of the nitride insulating film include silicon nitride, silicon oxynitride, aluminum nitride, and aluminum nitride oxide.

Although the conductive layer, insulating layer, metal oxide layer, and the like described above can be formed by a sputtering method or a PECVD method, they can also be formed by, for example, a thermal CVD (Chemical Vapor Deposition) method. Examples of the thermal CVD method include a MOCVD (Metal Organic Chemical Vapor Deposition) method and an ALD (Atomic Layer Deposition) method.

Since the thermal CVD method is a film formation method that does not use a plasma, it has an advantage that defects due to plasma damage are not generated. In the thermal CVD method, a source gas is supplied into the chamber, and the pressure in the chamber is set to atmospheric pressure or reduced pressure, and a film is formed on the substrate.

In the ALD method, a source gas is supplied into a chamber, and the pressure in the chamber is set to atmospheric pressure or reduced pressure, and a film is formed on a substrate.

In addition, as the transistor of the display device 300, the transistor 200b shown in FIGS. 10A to 10C can be used. FIG. 10A is a plan view of the transistor 200b. FIG. 10B corresponds to a cross-sectional view taken along the chain line X1-X2 shown in FIG. 10A, and FIG. 10C corresponds to a cross-sectional view taken along the chain line Y1-Y2 shown in FIG. 10A.

The transistor 200b is different from the transistor 200a in that the metal oxide layer 231, the conductive layer 222a, the conductive layer 222b, and the insulating layer 212 have a stacked structure.

The insulating layer 212 includes: a metal oxide layer 231; a conductive layer 222a and an insulating layer 212a on the conductive layer 222b; and an insulating layer 212b on the insulating layer 212a. The insulating layer 212 has a function of supplying oxygen to the metal oxide layer 231. In other words, the insulating layer 212 contains oxygen. The insulating layer 212a is an insulating layer capable of transmitting oxygen. The insulating layer 212a is also used as a film that reduces damage to the metal oxide layer 231 when the insulating layer 212b is formed later.

As the insulating layer 212a, silicon oxide, silicon oxynitride, or the like having a thickness of 5 nm or more and 150 nm or less, preferably 5 nm or more and 50 nm or less can be used.

In addition, it is preferable to make the amount of defects in the insulating layer 212a small. Typically, a signal at g = 2.001 due to a dangling bond of silicon measured by electron spin resonance (ESR: Electron Spin Resonance) is typical. The spin density is preferably 3 × 10 ¹⁷ spins / cm ³ or less. This is because if the defect density of the insulating layer 212a is high, oxygen is bonded to the defect, and the oxygen permeability in the insulating layer 212a is reduced.

In the insulating layer 212a, not all of the oxygen entering the insulating layer 212a from the outside may move to the outside of the insulating layer 212a, but a part of it may remain inside the insulating layer 212a. In addition, when oxygen enters the insulating layer 212a, oxygen contained in the insulating layer 212a moves to the outside of the insulating layer 212a, and oxygen moves in the insulating layer 212a. When an oxide insulating layer capable of transmitting oxygen is formed as the insulating layer 212a, oxygen released from the insulating layer 212b provided on the insulating layer 212a can be moved to the metal oxide layer 231 through the insulating layer 212a.

The insulating layer 212a can be formed using an oxide insulating layer having a low state density due to an oxynitride. Note that the density of states due to the nitrogen oxide may be formed between the energy (Ev_os) at the top of the valence band of the metal oxide film and the energy (Ec_os) at the bottom of the conduction band of the metal oxide. As the oxide insulating layer, a silicon oxynitride film with a small amount of nitrogen oxides or an aluminum oxynitride film with a small amount of nitrogen oxides can be used.

In addition, in thermal desorption spectroscopy (TDS: Thermal Desorption Spectroscopy), a silicon oxynitride film having a small amount of nitrogen oxides is a film having a larger amount of ammonia than a nitrogen oxide, and typically, ammonia is released. The amount is 1 × 10 ¹⁸ cm / ³ or more and 5 × 10 ¹⁹ cm / ³ or less. Note that the amount of ammonia released is the amount released when the film surface temperature is 50 ° C or higher and 650 ° C or lower, preferably 50 ° C or higher and 550 ° C or lower.

Nitrogen oxides (NO _x , x is greater than or equal to 0 and less than or equal to 2 and preferably greater than or equal to 1 and less than or equal to 2), typically NO ₂ or NO, form an energy level in the insulating layer 212 a and the like. This energy level is located in the energy gap of the metal oxide layer 231. Therefore, when the oxynitride diffuses into the interface between the insulating layer 212a and the metal oxide layer 231, the energy level sometimes traps electrons on the insulating layer 212a side. As a result, the trapped electrons remain near the interface between the insulating layer 212a and the metal oxide layer 231, thereby shifting the threshold voltage of the transistor in the positive direction.

In addition, when heat treatment is performed, nitrogen oxides react with ammonia and oxygen. When the heat treatment is performed, the nitrogen oxide included in the insulating layer 212a reacts with the ammonia included in the insulating layer 212b, so that the nitrogen oxide included in the insulating layer 212a decreases. Therefore, it is not easy to trap electrons in the interface between the insulating layer 212a and the metal oxide layer 231.

By using the oxide insulating layer as the insulating layer 212a, the threshold voltage drift of the transistor can be reduced, and the variation of the electrical characteristics of the transistor can be reduced.

The nitrogen concentration of the oxide insulating layer measured by SIMS is 6 × 10 ²⁰ atoms / cm ³ or less.

By forming the oxide insulating layer by a PECVD method using silane and nitrous oxide at a substrate temperature of 220 ° C. or higher and 350 ° C. or lower, a dense and high-hardness film can be formed.

The insulating layer 212b is an oxide insulating layer containing oxygen in a stoichiometric composition. The oxide insulating layer is heated to remove part of the oxygen. The oxide insulating layer includes a region whose oxygen release amount measured by TDS analysis is 1.0 × 10 ¹⁹ atoms / cm ³ or more, and preferably 3.0 × 10 ²⁰ atoms / cm ³ or more. The oxygen release amount is the total amount of the heat treatment temperature in the TDS analysis in a range of 50 ° C or higher and 650 ° C or lower or 50 ° C or higher and 550 ° C or lower. The amount of oxygen released is the total amount of oxygen atoms converted in TDS.

As the insulating layer 212b, a silicon oxide film, a silicon oxynitride film, or the like having a thickness of 30 nm to 500 nm, preferably 50 nm to 400 nm, can be used.

In addition, it is preferable to make the amount of defects in the insulating layer 212b smaller. Typically, the spin density of the signal present at g = 2.001 due to the dangling bond of silicon measured by ESR is less than 1.5 × 10 ¹⁸ spins / cm ³ , more preferably 1 × 10 ¹⁸ spins / cm ³ or less. Since the insulating layer 212b is farther from the metal oxide layer 231 than the insulating layer 212a, the defect density of the insulating layer 212b may also be higher than that of the insulating layer 212a.

In addition, because the insulating layer 212 can be formed using an insulating film including the same kind of material, the interface between the insulating layer 212a and the insulating layer 212b may not be clearly confirmed in some cases. Therefore, in this embodiment, the interface between the insulating layer 212a and the insulating layer 212b is shown in a dotted line diagram. Note that in this embodiment, the two-layer structure of the insulating layer 212a and the insulating layer 212b is described, but it is not limited to this. For example, a single-layer structure of the insulating layer 212a or a stacked structure of three or more layers may be used.

In the transistor 200b, the metal oxide layer 231 includes a metal oxide layer 231_1 on the insulating layer 211 and a metal oxide layer 231_2 on the metal oxide layer 231_1. The metal oxide layer 231_1 and the metal oxide layer 231_2 include the same elements. For example, each of the metal oxide layer 231_1 and the metal oxide layer 231_2 preferably includes an element included in the metal oxide layer 231.

The metal oxide layer 231_1 and the metal oxide layer 231_2 preferably include a region where the atomic ratio of In is greater than the atomic ratio of M. For example, it is preferable to set the atomic ratio of In, M, and Zn of the metal oxide layer 231_1 and the metal oxide layer 231_2 to around In: M: Zn = 4: 2: 3. Here, "near" means that when In is 4, M is 1.5 or more and 2.5 or less, and Zn is 2 or more and 4 or less. Alternatively, it is preferable to set the atomic ratio of In, M, and Zn of the metal oxide layer 231_1 and the metal oxide layer 231_2 to around In: M: Zn = 5: 1: 6. As described above, since the metal oxide layer 231_1 and the metal oxide layer 231_2 have substantially the same composition and can be formed using the same sputtering target, the manufacturing cost can be suppressed. In addition, when the same sputtering target is used, the metal oxide layer 231_1 and the metal oxide layer 231_2 can be continuously formed in the same processing chamber under vacuum, so it is possible to suppress impurities from entering the metal oxide layer 231_1 and metal oxidation. The interface of the object layer 231_2.

The metal oxide layer 231_1 may include a region having a lower crystallinity than the metal oxide layer 231_2. For example, X-ray diffraction (XRD: X-Ray Diffraction) or transmission electron microscope (TEM) can be used to analyze the crystallinity of the metal oxide layer 231_1 and the metal oxide layer 231_2.

The region with low crystallinity of the metal oxide layer 231_1 is used as a diffusion path of peroxygen, and peroxygen can be diffused to the metal oxide layer 231_2 having higher crystallinity than the metal oxide layer 231_1. As described above, by using a stacked structure of metal oxide layers having different crystallinities and using a region with low crystallinity as a diffusion path of peroxygen, a highly reliable transistor can be provided.

When the metal oxide layer 231_2 includes a region having higher crystallinity than the metal oxide layer 231_1, impurities that may be mixed into the metal oxide layer 231 can be suppressed. In particular, by improving the crystallinity of the metal oxide layer 231_2, it is possible to suppress damage during processing of the conductive layer 222a and the conductive layer 222b. The surface of the metal oxide layer 231, that is, the surface of the metal oxide layer 231_2 is exposed to an etchant or an etching gas when the conductive layer 222a and the conductive layer 222b are processed. When the metal oxide layer 231_2 includes a region with high crystallinity, its etching resistance is higher than that of the metal oxide layer 231_1 with low crystallinity. Therefore, the metal oxide layer 231_2 is used as an etching stopper film.

When the metal oxide layer 231_1 includes a region whose crystallinity is lower than that of the metal oxide layer 231_2, the carrier density is sometimes improved.

When the carrier density of the metal oxide layer 231_1 is high, the Fermi level may be higher than the conduction band of the metal oxide layer 231_1. As a result, the conduction band bottom of the metal oxide layer 231_1 may be lowered, which may lower the conduction band bottom of the metal oxide layer 231_1 and the trap energy level that may be formed in the gate insulating film (here, the insulating layer 211). The energy difference becomes larger. When this energy difference becomes large, the electric charge trapped in the gate insulating film may decrease, and the fluctuation of the threshold voltage of the transistor may be reduced. In addition, when the carrier density of the metal oxide layer 231_1 is high, the field effect mobility of the metal oxide layer 231 can be increased.

The transistor 200b is an example in which the metal oxide layer 231 has a stacked structure of two layers, but is not limited thereto, and may have a stacked structure of three or more layers.

The conductive layer 222a included in the transistor 200b includes a conductive layer 222a_1, a conductive layer 222a_2 on the conductive layer 222a_1, and a conductive layer 222a_3 on the conductive layer 222a_2. The conductive layer 222b included in the transistor 200b includes a conductive layer 222b_1, a conductive layer 222b_2 on the conductive layer 222b_1, and a conductive layer 222b_3 on the conductive layer 222b_2.

For example, the conductive layer 222a_1, the conductive layer 222b_1, the conductive layer 222a_3, and the conductive layer 222b_3 are preferably any one or more of titanium, tungsten, tantalum, molybdenum, indium, gallium, tin, and zinc. In addition, the conductive layer 222a_2 and the conductive layer 222b_2 preferably include any one or more of copper, aluminum, and silver.

More specifically, as the conductive layer 222a_1, the conductive layer 222b_1, the conductive layer 222a_3, and the conductive layer 222b_3, In-Sn oxide or In-Zn oxide can be used, and as the conductive layer 222a_2 and conductive layer 222b_2, copper can be used.

The end portion of the conductive layer 222a_1 includes a region located outside the end portion of the conductive layer 222a_2, and the conductive layer 222a_3 includes a region covering the top surface and side surfaces of the conductive layer 222a_2 and contacting the conductive layer 222a_1. In addition, the end portion of the conductive layer 222b_1 includes a region located outside the end portion of the conductive layer 222b_2, and the conductive layer 222b_3 includes a region covering the top surface and side surfaces of the conductive layer 222b_2 and contacting the conductive layer 222b_1.

By adopting the above-mentioned structure, the wiring resistance of the conductive layer 222a and the conductive layer 222b can be reduced, and the diffusion of copper into the metal oxide layer 231 can be suppressed, which is preferable.

In addition, as the transistor of the display device 300, a transistor 200c shown in FIGS. 11A to 11C can be used. FIG. 11A is a plan view of the transistor 200c. FIG. 11B corresponds to a cross-sectional view taken along the chain line X1-X2 shown in FIG. 11A, and FIG. 11C corresponds to a cross-sectional view taken along the chain line Y1-Y2 shown in FIG. 11A.

The transistor 200c shown in FIGS. 11A to 11C includes a conductive layer 221 on the insulating layer 224; an insulating layer 211 on the conductive layer 221; a metal oxide layer 231 on the insulating layer 211; and an insulating layer on the metal oxide layer 231. 212; a conductive layer 223 on the insulating layer 212; an insulating layer 211, a metal oxide layer 231, and an insulating layer 213 on the conductive layer 223. The metal oxide layer 231 includes a channel region 231i overlapping the conductive layer 223, a source region 231s in contact with the insulating layer 213, and a drain region 231d in contact with the insulating layer 213.

The insulating layer 213 contains nitrogen or hydrogen. By contacting the insulating layer 213 with the source region 231s and the drain region 231d, nitrogen or hydrogen in the insulating layer 213 is added to the source region 231s and the drain region 231d. When the source region 231s and the drain region 231d are added with nitrogen or hydrogen, their carrier density is increased.

The transistor 200c may also include an insulating layer 215 on the insulating layer 213, a conductive layer 222a electrically connected to the source region 231s through the opening portion 236a provided in the insulating layers 213, 215, and the insulating layer 213, 215. The opening portion 236b in the middle is electrically connected to the conductive layer 222b of the drain region 231d.

As the insulating layer 215, an oxide insulating film can be used. As the insulating layer 215, a laminated film of an oxide insulating film and a nitride insulating film can be used. As the insulating layer 215, for example, silicon oxide, silicon oxynitride, silicon oxynitride, aluminum oxide, hafnium oxide, gallium oxide, or Ga-Zn oxide can be used. The insulating layer 215 preferably has a function of blocking hydrogen, water, and the like from entering from the outside.

The insulating layer 211 has a function of a first gate insulating film, and the insulating layer 212 has a function of a second gate insulating film. The insulating layer 213 and the insulating layer 215 have a function of protecting an insulating film.

In addition, the insulating layer 212 includes a region of excess oxygen. When the insulating layer 212 includes an excessive oxygen region, the channel region 231 i included in the metal oxide layer 231 may be supplied with excessive oxygen. Therefore, since an oxygen defect that may be formed in the channel region 231i can be filled with excess oxygen, a semiconductor device with high reliability can be provided.

In addition, in order to supply an excessive amount of oxygen to the metal oxide layer 231, an excessive amount of oxygen may be supplied to the insulating layer 211 formed below the metal oxide layer 231. At this time, the excessive oxygen contained in the insulating layer 211 may be supplied to the source region 231s and the drain region 231d included in the metal oxide layer 231. When excessive oxygen is supplied to the source region 231s and the drain region 231d, the resistance of the source region 231s and the drain region 231d may increase.

On the other hand, when the insulating layer 212 formed on the metal oxide layer 231 contains excess oxygen, it is possible to selectively supply the excess oxygen only to the channel region 231i. Alternatively, after excessive oxygen is supplied to the channel region 231i, the source region 231s, and the drain region 231d, the carrier density of the source region 231s and the drain region 231d can be selectively increased, and the source region 231s and the drain region can be suppressed. The resistance of the region 231d increases.

The source region 231s and the drain region 231d included in the metal oxide layer 231 are each preferably an element forming an oxygen defect or an element bonded to the oxygen defect. Examples of the element that forms the oxygen defect or an element that is bonded to the oxygen defect include hydrogen, boron, carbon, nitrogen, fluorine, phosphorus, sulfur, chlorine, titanium, and a rare gas. In addition, typical examples of the rare gas element include helium, neon, argon, krypton, and xenon. When the insulating layer 213 includes one or more of the above-mentioned elements forming an oxygen defect, the element diffuses from the insulating layer 213 to and / or is added to the source region 231s and the drain region 231d by an impurity addition process.

When an impurity element is added to the oxide semiconductor film, the bond between the metal element and oxygen in the oxide semiconductor film is cut off to form an oxygen defect. Alternatively, when an impurity element is added to the oxide semiconductor film, oxygen bonded to the metal element in the oxide semiconductor film is bonded to the impurity element, and oxygen is separated from the metal element to form an oxygen defect. As a result, the carrier density is increased and the conductivity is improved in the oxide semiconductor film.

The conductive layer 221 is used as a first gate electrode, the conductive layer 223 is used as a second gate electrode, the conductive layer 222a is used as a source electrode, and the conductive layer 222b is used as a drain electrode.

As shown in FIG. 11C, the insulating layer 211 and the insulating layer 212 are formed with openings 237. The conductive layer 221 is electrically connected to the conductive layer 223 through the opening 237. Therefore, the same potential is applied to the conductive layer 221 and the conductive layer 223. In addition, instead of providing the opening portion 237, different potentials may be applied to the conductive layer 221 and the conductive layer 223. Alternatively, the opening portion 237 may not be provided, and the conductive layer 221 may be used as a light-shielding film. For example, by forming the conductive layer 221 using a light-shielding material, it is possible to suppress light from being radiated to the channel region 231i from below.

As shown in FIGS. 11B and 11C, the metal oxide layer 231 is located at a position opposite to each of the conductive layer 221 used as the first gate electrode and the conductive layer 223 used as the second gate electrode, sandwiched between Between two conductive films used as gate electrodes.

The transistor 200c also has an S-channel structure similarly to the transistor 200a and the transistor 200b. By adopting this structure, the metal oxide layer 231 included in the transistor 200c is electrically surrounded by the electric field of the conductive layer 221 used as the first gate electrode and the conductive layer 223 used as the second gate electrode.

Since the transistor 200c has an S-channel structure, the conductive layer 221 or the conductive layer 223 can be used to effectively apply an electric field for causing a channel to the metal oxide layer 231. Thereby, the current driving ability of the transistor 200c is improved, and a high on-state current characteristic can be obtained. In addition, since the on-state current can be increased, the transistor 200c can be miniaturized. In addition, since the transistor 200c has a structure surrounded by the conductive layer 221 and the conductive layer 223, the mechanical strength of the transistor 200c can be improved.

According to the position of the conductive layer 223 relative to the metal oxide layer 231 or the method of forming the conductive layer 223, the transistor 200c may be referred to as a TGSA (Top Gate Self Align) FET.

Like the transistor 200b, the metal oxide layer 231 of the transistor 200c may have two or more layers stacked.

In addition, in the transistor 200c, the insulating layer 212 is provided only at a portion overlapping the conductive layer 223, but is not limited thereto, and the insulating layer 212 may cover the metal oxide layer 231. The conductive layer 221 may not be provided.

[Structural example 2]

The main difference between the display device 300A shown in FIG. 12 and the display device 300 is that the transistor 201, the transistor 203, the transistor 205, and the transistor 206 are not included, and the transistor 281, the transistor 284, and the transistor are included 285 and transistor 286.

The positions of the insulating layer 117 and the connection portion 207 in FIG. 12 are also different from those in FIG. 8. FIG. 12 illustrates an end portion of a pixel. The insulating layer 117 is arranged so as to overlap the end of the liquid crystal element 180. The insulating layer 117 is disposed so as to overlap the end portion of the light shielding layer 132. In this way, the insulating layer may be provided at a portion (a portion overlapping with the light shielding layer 132) that does not overlap the display area.

Like the transistor 284 and the transistor 285, the two transistors included in the display device may be partially laminated. Thereby, the area occupied by the pixel circuit can be reduced, and the resolution can be improved. In addition, the light-emitting area of the light-emitting element 170 can be increased, and the aperture ratio can be increased. When the aperture ratio of the light-emitting element 170 is high, the current density for obtaining the required brightness can be reduced, and thus the reliability is improved.

The transistor 281, the transistor 284, and the transistor 286 include a conductive layer 221a, an insulating layer 211, a metal oxide layer 231, a conductive layer 222a, and a conductive layer 222b. The conductive layer 221a overlaps the metal oxide layer 231 via the insulating layer 211. The conductive layers 222a and 222b are electrically connected to the metal oxide layer 231. The transistor 281 includes a conductive layer 223.

The transistor 285 includes a conductive layer 222b, an insulating layer 217, a metal oxide layer 261, a conductive layer 223, an insulating layer 212, an insulating layer 213, a conductive layer 263a, and a conductive layer 263b. The conductive layer 222b overlaps the metal oxide layer 261 via the insulating layer 217. The conductive layer 223 overlaps the metal oxide layer 261 via the insulating layer 212 and the insulating layer 213. The conductive layers 263a and 263b are electrically connected to the metal oxide layer 261.

The conductive layer 221a is used as a gate electrode. The insulating layer 211 is used as a gate insulating layer. The conductive layer 222a is used as one of a source and a drain. The conductive layer 222b included in the transistor 286 is used as the other of the source and the drain.

The conductive layer 222 b used in common with the transistor 284 and the transistor 285 has a portion used as the other of the source and the drain of the transistor 284 and a portion used as the gate of the transistor 285. The insulating layer 217, the insulating layer 212, and the insulating layer 213 are used as a gate insulating layer. One of the conductive layers 263a and 263b is used as a source, and the other of the conductive layers 263a and 263b is used as a drain. The conductive layer 223 is used as a gate.

Similarly to the transistor 201, the transistor 203, the transistor 205, and the transistor 206 shown in FIG. 7 and the like, the transistor 281, the transistor 284, the transistor 285, and the transistor 286 are not limited to the shapes shown in FIG. For example, the transistor 281, the transistor 284, the transistor 285, and the transistor 286 may have the shapes of the transistor 200a to the transistor 200c shown in FIGS. 9A to 11C.

<Structural Example 3>

FIG. 13 is a cross-sectional view of a display portion of the display device 300B.

The display device 300B shown in FIG. 13 includes a transistor 295, a transistor 296, a liquid crystal element 180, a light emitting element 170, an insulating layer 220, an insulating layer 224, a color layer 134, and the like between the substrate 351 and the substrate 361.

The transistor 295 has the same structure as the transistor 200c shown in FIGS. 11A to 11C, and the transistor 296 has the same structure as the transistor 206 shown in FIG. Note that the transistor 295 and the transistor 296 are not limited to this, and the above-mentioned transistor structure can be appropriately used.

In the liquid crystal element 180, the electrode 311b reflects external light and emits the reflected light toward the substrate 361 side. The light emitting element 170 emits light toward the substrate 361 side. Regarding the structures of the liquid crystal element 180 and the light emitting element 170, reference may be made to the structure example 1.

The substrate 361 is provided with an insulating layer 121, an electrode 113 used as a common electrode of the liquid crystal element 180, and an alignment film 133b.

The electrode 311a and the electrode 113 sandwich the liquid crystal layer 112 via the alignment film 133a and the alignment film 133b.

The transistor 296 is covered with an insulating layer 212 and an insulating layer 213. The insulating layer 213 and the color layer 134 are bonded to the insulating layer 194 through an adhesive layer 142.

Since the transistor 296 that drives the liquid crystal element 180 and the transistor 295 that drives the light-emitting element 170 are formed on different faces in the display device 300B, it is easy to form using a structure and a material suitable for driving each display element.

<Structural Example 4>

Although the example in which the liquid crystal element is used for monochrome display is shown above, the display device of this embodiment can use the liquid crystal element for full color display. A display device 300C for performing full-color display using a liquid crystal element will be described with reference to FIGS. 14 and 15A and 15B. FIG. 14 is a cross-sectional view of a display device 300C, and FIGS. 15A and 15B are plan views of a part of the structure of the display device 300C.

The display device 300C shown in FIG. 14 is different from the display device 300 shown in FIG. 8 in that a color layer 131 a and a color layer 131 b are provided on a substrate 361. The color layers 131 a and 131 b are covered with an insulating layer 121. The color layer 131b overlaps the light emitting element 170 (the opening 451 and the color layer 134 can be said), and the color layer 131a includes a region overlapping the electrode 311b.

The external light incident through the color layer 131a is reflected by the liquid crystal element 180 and is emitted to the substrate 361 side through the color layer 131a. As such, the display device 300C can use the liquid crystal element 180 to emit a color corresponding to the color layer 131a.

The color layer 131b has a function of transmitting visible light of the same color as the color layer 134. Thereby, the light emitted from the light emitting element 170 and passed through the color layer 134 can be extracted to the substrate 361 side so as to avoid interference of the color layer 131a.

As shown in FIG. 14, the external light incident through the color layer 131 b passes through the color layer 131 b and the color layer 134 when it is incident, and also passes through the color layer 134 and the color layer 131 b when it is reflected. In this way, the external light incident through the color layer 131b is attenuated by the multiple passes of the color layer. Thereby, it is possible to prevent light of an unintended color from being mixed into light corresponding to the color of the color layer 131 a reflected by the liquid crystal element 180.

FIG. 15A is a plan view of the electrode 311b, and FIG. 15B is a plan view of the color layer 131a and the color layer 131b. As shown in FIGS. 15A and 15B, a pixel 410a, a pixel 410b, a pixel 410c, and a pixel 410d are arranged. Each pixel is provided with three light emitting elements 170, which are provided so as to overlap the light emitting element 170: a color layer 134a, an opening 451a, and a color layer 131ba; a color layer 134b, an opening 451b, and a color layer 131bb; a color layer 134c, an opening 451c, and a color Layer 131bc.

The pixel 410a is provided with an electrode 311ba and a color layer 131aa. The pixel 410b is provided with an electrode 311bb and a color layer 131ab. The pixel 410c is provided with an electrode 311bc and a color layer 131ac. The pixel 410d is provided with an electrode 311bd and a color layer 131ad.

The color layers 131aa, 131ab, 131ac, and 131ad have a function of transmitting light of different colors. For example, when the pixel 410a is red, the pixel 410b is green, and the pixel 410c is blue, and when the pixel 410d is yellow, the color layer 131aa transmits red light, the color layer 131ab transmits green light, and the color layer 131ac transmits blue light. The layer 131ad transmits yellow light. For example, in a case where the pixel 410d appears white instead of yellow, the color layer 131ad is not provided.

For example, in the pixel 410a, when the color layer 134a transmits red light, both the color layer 131ba and the color layer 134a transmit red light, and the color layers 131aa and 131ba also transmit red light. In this case, it is not necessary to form the color layers 131aa and 131ba separately, and they can be integrated color layers.

In this way, the pixels 410a to 410d perform full-color display using the light emitting element 170 and the color layers 134a to 134c and use the liquid crystal element 180 to display colors corresponding to the color layers 131aa to 131ad. Here, the combination of the pixels 410 a to 410 d can be regarded as one full-color display pixel in which each pixel is used as a sub-pixel using the liquid crystal element 180. In other words, in the display device 300C, full-color display can be performed using the liquid crystal element 180 and full-color display can be performed using the light-emitting element 170 at a resolution approximately twice that of the liquid crystal element 180.

For example, the display device 300C may be used for a portable terminal having an application capable of displaying AR (Augmented Reality) content. In this portable terminal, a first pixel 410L can be used to display a still image or a moving image obtained with the camera function, and a second pixel 410E can be used to display a place, building, article, person, etc. in the still image or moving image. data of.

Ancillary materials can be text, still images or moving images. For example, if the application is a description of a place, a building, an article, a person, or the like in a still image or a moving image obtained with the camera function, the attached data is mainly text. In addition, for example, if it is a game application that displays an image corresponding to a place, a building, an article, a character, or the like in a still image or a moving image obtained with a camera function, the attached data is mainly a still image or a moving image of the image.

In the above description, the area of the display portion of the still image or moving image obtained by the camera function is usually larger than that of the attached file. Therefore, the first pixel 410L with low power consumption can also be used to display the display portion of the still image or moving image. The second pixel 410E displays a part with data, thereby reducing power consumption.

When the first pixel 410L is used to display a still image, as described above, by displaying the still image at a frame frequency below 1 Hz, power consumption can be further reduced.

In addition, if it is a game application, in many cases, the still image or motion image obtained by the camera function is a background image, and incidental data (such as an image image) is the main goal of the game. Therefore, by using the second pixel 410E whose resolution is higher than that of the first pixel 410L displaying the background to display the image, a clearer image can be displayed and the user can feel greater excitement.

In the above description, the first pixel 410L may be used to display map data acquired using GPS or the like instead of still images or moving images acquired using a camera.

In the display device 300C, each pixel 410 performs full-color display using the color layers 134a to 134c and the light emitting element 170, but is not limited thereto. For example, a plurality of light emitting elements 170 may be formed in such a manner that each sub-pixel emits light of different colors without providing the color layer 134.

<Example of Manufacturing Method of Display Device 300>

Next, a method of manufacturing the display device according to this embodiment will be clearly described with reference to Figs. 16A to 19B. Hereinafter, an example of a method of manufacturing the display device 300 shown in FIG. 7 will be described. In FIGS. 16A to 19B, a manufacturing method will be described focusing on the display portion 362 of the display device 300. Note that the transistor 203 is not illustrated in FIGS. 16A to 19B.

First, an insulating layer 121 is formed on a substrate 361.

The insulating layer 121 is preferably used as a planarization layer. Resins such as acrylic resin, epoxy resin, and polyimide resin are suitable for the insulating layer 121.

An inorganic insulating film may be used as the insulating layer 121. As the insulating layer 121, for example, an inorganic insulating film such as a silicon nitride film, a silicon oxynitride film, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, or an aluminum nitride film can be used. In addition, a hafnium oxide film, a yttrium oxide film, a zirconia 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 can also be used. Alternatively, a stack of two or more of the insulating films may be used.

In the circuit 364 and the like shown in FIG. 7, a light-shielding layer 132 is formed on a substrate 361 and an insulating layer 121 is formed thereon.

When the display device 300C shown in FIG. 14 is manufactured, the color layer 131 a and the color layer 131 b are formed before the insulating layer 121 is formed. By forming the color layer 131a and the color layer 131b using a photosensitive material, they can be processed into an island shape by a photolithography method or the like.

Next, an electrode 113 is formed. The electrode 113 can be formed by forming a photoresist mask after forming a conductive film, etching the conductive film, and then removing the photoresist mask. The electrode 113 is formed using a conductive material that transmits visible light.

Next, an insulating layer 117 is formed on the electrode 113. As the insulating layer 117, an organic insulating film is preferably used.

Next, an alignment film 133b is formed on the electrode 113 and the insulating layer 117 (FIG. 16A). By performing a rubbing treatment after forming a thin film of a resin or the like, the alignment film 133b can be formed.

The processes shown in FIGS. 16B to 19A are performed independently of the processes described with reference to FIG. 16A.

First, a release layer 62 is formed on the manufacturing substrate 61, and an insulating layer 63 is formed on the release layer 62 (FIG. 16B).

In this process, an interface between the production substrate 61 and the release layer 62, an interface between the release layer 62 and the insulating layer 63, or a material in which separation occurs in the release layer 62 is selected when the production substrate 61 is peeled. In this embodiment, a case where separation occurs at the interface between the insulating layer 63 and the release layer 62 is exemplified, but depending on the materials of the release layer 62 and the insulation layer 63, the portion where the separation occurs is not limited to this.

The manufacturing substrate 61 has rigidity to the extent that it can be easily conveyed, and has heat resistance to the temperature during the manufacturing process. Examples of a material that can be used for manufacturing the substrate 61 include glass, quartz, ceramics, sapphire, resin, semiconductor, metal, or alloy. Examples of the glass include alkali-free glass, barium borosilicate glass, and aluminoborosilicate glass.

The release layer 62 may be formed using an organic material or an inorganic material.

Examples of the inorganic material usable for the release layer 62 include metals containing an element selected from the group consisting of tungsten, molybdenum, titanium, tantalum, niobium, nickel, cobalt, zirconium, zinc, ruthenium, rhodium, palladium, osmium, iridium, and silicon. , An alloy containing the element, a metal oxide containing the element, or a compound containing the element. The crystal structure of the silicon-containing layer may be any of amorphous, microcrystalline, or polycrystalline.

When an inorganic material is used, the thickness of the release layer 62 is preferably 1 nm or more and 1000 nm or less, more preferably 10 nm or more and 200 nm or less, and even more preferably 10 nm or more and 100 nm or less.

When an inorganic material is used, the release layer 62 can be formed by, for example, a sputtering method, a CVD method, an ALD method, a vapor deposition method, or the like.

Examples of the organic material that can be used for the release layer 62 include polyimide resin, acrylic resin, epoxy resin, polyimide resin, polyimide resin, siloxane resin, and benzocyclobutene. Resins and phenolic resins.

When an organic material is used, the thickness of the release layer 62 is preferably 0.01 μm or more and less than 10 μm, more preferably 0.1 μm or more and 3 μm or less, and still more preferably 0.5 μm or more and 1 μm or less. By setting the thickness of the release layer 62 within the above range, manufacturing costs can be reduced. Note that the thickness of the release layer 62 is not limited to this, and may be 10 μm or more, for example, 10 μm or more and 200 μm or less.

When an organic material is used, examples of the formation method of the release layer 62 include a spin coating method, a dipping method, a spray method, an inkjet method, a dispenser method, a screen printing method, a lithographic method, a doctor blade method, and a slit method. Coating method, roll coating method, curtain coating method, doctor blade coating method, and the like.

As the insulating layer 63, an inorganic insulating film is preferably used. As the insulating layer 63, for example, an inorganic insulating film such as a silicon nitride film, a silicon oxynitride film, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, or an aluminum nitride film can be used. In addition, a hafnium oxide film, a yttrium oxide film, a zirconia 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 can also be used. Alternatively, a stack of two or more of the insulating films may be used.

For example, a structure may be adopted in which a layered structure including a layer containing a high melting point metal material such as tungsten and a layer containing an oxide of the metal material is used as the release layer 62, and a plurality of silicon nitride and oxygen nitrogen are used as the insulating layer 63 Laminated structure of inorganic insulating films such as silicon oxide and silicon oxynitride. When a high-melting-point metal material is used for the release layer 62, the formation temperature of the layer formed after the release layer is formed can be increased, so that the impurity concentration can be reduced and a highly reliable display device can be realized. Moreover, you may have the process of removing the layer (the peeling layer 62, the insulating layer 63, etc.) unnecessary for a display device after peeling. In addition, the peeling layer 62 or the insulating layer 63 may be used as a component of a display device without removing the peeling layer 62 or the insulating layer 63.

Next, an electrode 311a is formed on the insulating layer 63, and an electrode 311b is formed on the electrode 311a (FIG. 16C). The electrode 311b has an opening 451 in the electrode 311a. The electrodes 311a and 311b may be formed by forming a photoresist mask after forming a conductive film, etching the conductive film, and then removing the photoresist mask. The electrode 311a is formed using a conductive material that transmits visible light. The electrode 311b is formed using a conductive material that reflects visible light.

Next, an insulating layer 220 is formed (FIG. 16D). The insulating layer 220 can be used as a barrier layer for preventing impurities contained in the peeling layer 62 and the insulating layer 63 from diffusing into a transistor or a display element to be formed later. When an organic material is used as the peeling layer 62, the insulating layer 220 is preferably, for example, to prevent moisture or the like contained in the peeling layer 62 from being diffused to a transistor or a display element when the peeling layer 62 is heated. Therefore, the insulating layer 220 preferably has high barrier properties.

As the insulating layer 220, an inorganic insulating film, a resin, or the like that can be used for the insulating layer 121 can be used.

Next, an electrode 312 is formed on the insulating layer 220 (FIG. 16D). The electrode 312 is provided so as not to overlap the position where the connection portion 207 is formed. The electrode 312 preferably includes an opening overlapping the opening 451 of the electrode 311b. After the conductive film is formed, a photoresist mask is formed, the conductive film is etched, and then the photoresist mask is removed, so that each electrode 312 can be formed. The electrode 312 may be formed using a conductive material that reflects visible light, or may be formed using a conductive material that transmits visible light.

Next, an insulating layer 224 is formed. Then, an opening reaching the electrode 311 b is formed in the insulating layer 220 and the insulating layer 224 so as to correspond to the position where the connection portion 207 is formed. As the insulating layer 224, an inorganic insulating film, a resin, or the like that can be used for the insulating layer 121 can be used.

Next, a transistor 205 and a transistor 206 are formed on the insulating layer 224.

Here, a case where a transistor having a bottom gate structure including a metal oxide as the metal oxide layer 231 is manufactured as the transistor 206 is shown. The transistor 205 has a structure in which a conductive layer 223 and an insulating layer 212 are added to the structure of the transistor 206, that is, it includes two gate electrodes. Metal oxides can be used as oxide semiconductors. Here, by using an oxide semiconductor such as an oxide semiconductor as the metal oxide layer 231, a semiconductor material having a wider band gap than silicon and a smaller carrier density than silicon can reduce the off-state current of the transistor.

Specifically, first, a conductive layer 221 a and a conductive layer 221 b are formed on the insulating layer 224. The conductive layer 221a and the conductive layer 221b can be formed by forming a photoresist mask after forming a conductive film, etching the conductive film, and then removing the photoresist mask. Here, a connection portion 207 is formed in which the conductive layer 221b and the electrode 311b are connected through the openings of the insulating layer 220 and the insulating layer 224.

Next, an insulating layer 211 is formed.

As the insulating layer 211, for example, an inorganic insulating film such as a silicon nitride film, a silicon oxynitride film, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, or an aluminum nitride film can be used. In addition, a hafnium oxide film, a yttrium oxide film, a zirconia 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 can also be used. Alternatively, a stack of two or more of the insulating films may be used.

Since the inorganic insulating film becomes a dense and highly barrier film at a high film forming temperature, it is preferably formed at a high temperature. The substrate temperature when forming the inorganic insulating film is preferably room temperature (25 ° C) or higher and 350 ° C or lower, and more preferably 100 ° C or higher and 300 ° C or lower.

Next, a metal oxide layer 231 is formed. In this embodiment, a metal oxide is formed as the metal oxide layer 231. The metal oxide layer 231 can be formed by forming a photoresist mask after forming the metal oxide film, etching the metal oxide film, and then removing the photoresist mask.

The substrate temperature when forming the metal oxide film is preferably 350 ° C or lower, more preferably room temperature or higher and 200 ° C or lower, and still more preferably room temperature or higher and 130 ° C or lower.

The metal oxide film can be formed using any of an inert gas and an oxygen gas. Note that there is no particular limitation on the oxygen flow rate (oxygen partial pressure) when the metal oxide film is formed. However, when a transistor having a high field-effect mobility is to be obtained, the oxygen flow rate (oxygen partial pressure) when forming the metal oxide film is preferably 0% or more and 30% or less, more preferably 5% or more and 30% or less, more preferably 7% or more and 15% or less.

The metal oxide film preferably contains at least indium or zinc. It is particularly preferable to include indium and zinc.

The energy gap of the metal oxide is preferably 2 eV or more, more preferably 2.5 eV or more, and even more preferably 3 eV or more. In this way, by using a metal oxide with a wide energy gap, the off-state current of the transistor can be reduced.

The metal oxide film can be formed by a sputtering method. In addition, for example, a PLD method, a PECVD method, a thermal CVD method, an ALD method, or a vacuum evaporation method can be used.

Next, a conductive layer 222a and a conductive layer 222b are formed. The conductive layer 222a and the conductive layer 222b can be formed by forming a photoresist mask after forming a conductive film, etching the conductive film, and then removing the photoresist mask. Both the conductive layer 222a and the conductive layer 222b are connected to the metal oxide layer 231. Here, the conductive layer 222a included in the transistor 206 is electrically connected to the conductive layer 221b. Thereby, the electrode 311b and the conductive layer 222a can be electrically connected in the connection portion 207.

When the conductive layer 222a and the conductive layer 222b are processed, a part of the metal oxide layer 231 that is not covered with the photoresist mask may be thinned by the etching process.

Through the above steps, the transistor 206 can be manufactured (FIG. 17A). In the transistor 206, a part of the conductive layer 221a is used as a gate, a part of the insulating layer 211 is used as a gate insulating layer, and the conductive layer 222a and the conductive layer 222b are used as one of a source and a drain, respectively.

Next, an insulating layer 212 covering the transistor 206 is formed, and a conductive layer 223 is formed on the insulating layer 212.

The insulating layer 212 can be formed by the same method as the insulating layer 211.

The conductive layer 223 included in the transistor 205 can be formed by forming a photoresist mask after forming a conductive film, etching the conductive film, and then removing the photoresist mask.

Through the above steps, the transistor 205 can be manufactured (FIG. 17A). In the transistor 205, a part of the conductive layer 221a and a part of the conductive layer 223 are used as a gate, a part of the insulating layer 211 and a part of the insulating layer 212 are used as a gate insulating layer, and the conductive layer 222a and the conductive layer 222b are respectively Used as one of a source and a drain.

Next, an insulating layer 213 is formed (FIG. 17A). The insulating layer 213 can be formed by the same method as the insulating layer 211.

As the insulating layer 212, an oxide insulating film such as a silicon oxide film or a silicon oxynitride film formed in an atmosphere containing oxygen is preferably used. In addition, as the insulating layer 213, an insulating film such as a silicon nitride film or a silicon oxynitride film, which is difficult to diffuse and transmit oxygen, is preferably laminated on the silicon oxide film or the silicon oxynitride film. The oxide insulating film formed under an atmosphere containing oxygen may be an insulating film that easily releases a large amount of oxygen by heating. Oxygen can be supplied to the metal oxide layer 231 by performing a heat treatment in a state where such an oxide insulating film that releases oxygen and an insulating film that does not easily diffuse and permeate oxygen are laminated together. As a result, oxygen defects in the metal oxide layer 231 and defects in the interface between the metal oxide layer 231 and the insulating layer 212 can be filled, so that the defect energy level can be reduced. Thereby, a highly reliable display device can be realized.

When the display device 300 or the like shown in FIG. 8 is manufactured, a color layer 134 is formed on the insulating layer 213. The color layer 134 is arranged so as to overlap the opening 451 of the electrode 311b. The color layer 134 can be formed by the same method as the color layer 131a and the color layer 131b.

Next, an insulating layer 214 is formed on the insulating layer 213 (FIG. 17B). Since the insulating layer 214 is a layer having a formation surface of a display element to be formed later, it is preferably used as a planarization layer. As the insulating layer 214, a resin or an inorganic insulating film that can be used for the insulating layer 121 can be used.

Next, openings are formed in the insulating layer 212, the insulating layer 213, and the insulating layer 214 to reach the conductive layer 222b included in the transistor 205.

Next, an electrode 191 is formed (FIG. 17B). The electrode 191 can be formed by forming a photoresist mask after forming a conductive film, etching the conductive film, and then removing the photoresist mask. Here, the conductive layer 222 b included in the transistor 205 is connected to the electrode 191. The electrode 191 is formed using a conductive material that transmits visible light.

Next, an insulating layer 216 covering the end of the electrode 191 is formed (FIG. 17B). As the insulating layer 216, a resin or an inorganic insulating film that can be used for the insulating layer 121 can be used. The insulating layer 216 has an opening in a portion overlapping the opening 451.

Next, an EL layer 192 and an electrode 193 are formed (FIG. 17B). A part of the electrode 193 is used as a common electrode of the light emitting element 170. The electrode 193 is formed using a conductive material that reflects visible light.

The EL layer 192 can be formed by a method such as a vapor deposition method, a coating method, a printing method, or a spray method. When the EL layer 192 is formed in each pixel, an evaporation method or an inkjet method using a shadow mask such as a metal mask can be used. When the EL layer 192 is not formed in each pixel, an evaporation method without using a metal mask can be used.

As the EL layer 192, a low-molecular compound or a high-molecular compound may be used, and an inorganic compound may be further included.

In each process performed after the EL layer 192 is formed, the temperature for heating the EL layer 192 must be equal to or lower than the heat-resistant temperature of the EL layer 192. The electrode 193 can be formed by a vapor deposition method, a sputtering method, or the like.

Through the above process, the light emitting element 170 can be formed (FIG. 17B). The light-emitting element 170 has a structure in which an electrode 191 serving as a pixel electrode is partially used, an EL layer 192, and an electrode 193 serving as a common electrode is partially used. The light-emitting element 170 is manufactured such that the light-emitting region thereof overlaps with the color layer 134 and the opening 451 of the electrode 311 b.

Although an example of manufacturing a bottom emission type light emitting element as the light emitting element 170 is shown here, one embodiment of the present invention is not limited to this.

The light emitting element may have a top emission structure, a bottom emission structure, or a double-sided emission structure. As the electrode on the light extraction side, a conductive film that transmits visible light is used. In addition, it is preferable to use a conductive film that reflects visible light as the electrode that does not extract light.

Next, an insulating layer 194 is formed so as to cover the electrode 193 (FIG. 17B). The insulating layer 194 is used as a protective layer that suppresses the diffusion of impurities such as water to the light emitting element 170. The light emitting element 170 is sealed by an insulating layer 194. After the electrode 193 is formed, the insulating layer 194 is preferably formed so as not to be exposed to the atmosphere.

As the insulating layer 194, for example, an inorganic insulating film that can be used for the insulating layer 121 is preferably used. In particular, it is preferable to include an inorganic insulating film having high barrier properties. Alternatively, a laminate of an inorganic insulating film and an organic insulating film may be used.

The substrate temperature when the insulating layer 194 is formed is preferably a temperature equal to or lower than the heat-resistant temperature of the EL layer 192. The insulating layer 194 can be formed by an ALD method, a sputtering method, or the like. The ALD method and the sputtering method are preferable because they can form a film at a low temperature. When the ALD method is used, the coverage of the insulating layer 194 is high, so it is preferable.

Next, the substrate 351 is bonded to the surface of the insulating layer 194 using the adhesive layer 142 (FIG. 17C).

As the adhesive layer 142, various hardening adhesives such as a light hardening adhesive such as an ultraviolet hardening adhesive, a reaction hardening adhesive, a thermosetting adhesive, and an anaerobic adhesive can be used. Alternatively, an adhesive sheet or the like may be used.

As the substrate 351, for example, a polyester resin such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), a polyacrylonitrile resin, an acrylic resin, or a polyethylene resin can be used. Amine resin, polymethyl methacrylate resin, polycarbonate (PC) resin, polyether resin (PES) resin, polyamine resin (nylon, aromatic polyamine, etc.), polysiloxane resin, cycloolefin Resin, polystyrene resin, polyamido-imino resin, polyurethane resin, polyvinyl chloride resin, polyvinylidene chloride resin, polypropylene resin, polytetrafluoroethylene (PTFE) resin, ABS resin, and cellulose Rice fiber and so on. As the substrate 351, various materials such as glass, quartz, resin, metal, alloy, or semiconductor can be used. As the substrate 351, various materials such as glass, quartz, resin, metal, alloy, or semiconductor whose thickness is allowed to be used can also be used.

Next, the manufacturing substrate 61 is peeled (FIG. 18A).

The separation surface may be formed at different positions depending on materials, forming methods, and the like of the insulating layer 63, the release layer 62, and the manufacturing substrate 61.

FIG. 18A shows an example where separation occurs at the interface between the release layer 62 and the insulating layer 63. The insulation layer 63 is exposed by separation.

Before the separation, a separation starting point may be formed in the release layer 62. For example, a part or the entire surface of the release layer 62 may be irradiated with a laser. This makes it possible to embrittle the peeling layer 62 or reduce the adhesion between the peeling layer 62 and the insulating layer 63 (or the manufacturing substrate 61).

For example, the substrate 61 can be peeled off by applying a vertical pulling force to the peeling layer 62. Specifically, the manufacturing substrate 61 can be peeled off by stretching a part of the top surface of the suction substrate 351 upward.

A sharp-shaped device such as a knife may be inserted between the release layer 62 and the insulating layer 63 (or the manufacturing substrate 61) to form a separation starting point. Alternatively, a sharp-shaped instrument may be used to cut into the release layer 62 from the substrate 351 side to form a separation starting point.

Next, the insulating layer 63 is removed. For example, the insulating layer 63 can be removed by a dry etching method or the like. Thereby, the electrode 311a is exposed (FIG. 18B).

When an insulating film is provided between the insulating layer 63 and the electrode 311a, the insulating film can be removed or left. When removing the insulating film, a dry etching method or the like can be used.

Next, an alignment film 133a is formed on the surface of the exposed electrode 311a (FIG. 19A). By performing a rubbing treatment after forming a thin film of a resin or the like, the alignment film 133a can be formed.

Then, the substrate 351 that has completed the process described with reference to FIG. 16A and the substrate 361 that has completed the process up to FIG. 19A are bonded together with the liquid crystal layer 112 interposed therebetween (FIG. 19B). Although not shown in FIG. 19B, as shown in FIG. 7 and the like, the substrate 351 and the substrate 361 are bonded using the adhesive layer 141. As the adhesive layer 141, a material that can be used for the adhesive layer 142 can be used.

The liquid crystal element 180 shown in FIG. 19B has a structure in which an electrode 311 a (and an electrode 311 b), a portion of which is used as a pixel electrode, a liquid crystal layer 112, and an electrode 113 whose part is used as a common electrode are stacked.

A polarizing plate 135 is disposed on the outer surface of the substrate 361.

The display device 300 can be manufactured by the above steps.

This embodiment can be implemented in appropriate combination with other embodiments. In addition, a plurality of configurations shown in this embodiment can be appropriately combined.

    Embodiment 2    

In this embodiment mode, a more specific configuration example of the display device described in Embodiment Mode 1 will be described with reference to FIGS. 20 to 25.

FIG. 20A is a block diagram of the display device 300 shown in the embodiment. The display device 300 includes a display portion 362, a circuit GD, and a circuit SD. The display unit 362 includes a plurality of pixels 410 arranged in a matrix.

The display device 300 includes multiple wirings G1, multiple wirings G2, multiple wirings G3, multiple wirings ANO, multiple wirings CSCOM, multiple wirings S1, multiple wirings S2, and multiple wirings S3. The multiple wirings G1, multiple wirings G2, multiple wirings G3, multiple wirings ANO, and multiple wirings CSCOM are all electrically connected to multiple pixels 410 and circuits GD arranged in the R direction. The plurality of wirings S1, the plurality of wirings S2, and the plurality of wirings S3 are all electrically connected to the plurality of pixels 410 and the circuits SD arranged in the C direction.

Note that although a structure including one circuit GD and one circuit SD is shown here for simplicity, a circuit GD and a circuit SD for driving a liquid crystal element and a circuit GD and a circuit SD for driving a light emitting element may be provided separately.

As for the pixel 410, the structure shown in the first embodiment can be referred to.

Various sequential circuits such as a shift register can be used for the circuit GD. A transistor, a capacitor, or the like can be used for the circuit GD. The transistor included in the circuit GD can be formed by the same process as the transistor included in the pixel 410.

For example, an integrated circuit may be used for the circuit SD. Specifically, an integrated circuit formed on a silicon substrate can be used for the circuit SD.

For example, the circuit SD may be mounted on a pad electrically connected to the pixel 410 by using a COG method or a COF method. Specifically, an anisotropic conductive film can be used to mount the integrated circuit on the pad.

FIG. 21 is an example of a circuit diagram of the pixel 410. FIG. 21 illustrates a pixel 410 including three light emitting elements illustrated in FIGS. 5A to 5H and the like. The pixel 410 includes a first pixel 410L, a pixel 410Ea, a pixel 410Eb, and a pixel 410Ec. The first pixel 410L includes a liquid crystal element 180, the pixel 410Ea includes a light emitting element 170a, the pixel 410Eb includes a light emitting element 170b, and the pixel 410Ec includes a light emitting element 170c. The pixels 410Ea, 410Eb, and 410Ec are all used as sub-pixels of the second pixel 410E shown in FIG. 1B.

The first pixel 410L includes a switch SW1, a capacitor C1, a liquid crystal element 180, and the like. The pixels 410Ea to 410Ec include any one of the light emitting elements 170a to 170c, the switch SW2, the transistor M, the capacitor C2, the capacitor C3, and the like. The pixel 410 is electrically connected to the wiring G1, the wiring G2, the wiring G3, the wiring ANO, the wiring CSCOM1, the wiring CSCOM2, the wiring S1, the wiring S2, and the wiring S3. FIG. 21 shows a wiring VCOM1 electrically connected to the liquid crystal element 180 and a wiring VCOM2 electrically connected to the light emitting elements 170a to 170c. The capacitor C1 corresponds to the capacitor 270 shown in FIGS. 1A and 1B and the like, and the wiring CSCOM1 corresponds to the electrode 312 shown in FIGS. 1A and 1B and the like.

FIG. 21 shows an example in which transistors are used as the switches SW1 and SW2.

Next, a connection relationship between each element and wiring in the first pixel 410L will be described. The gate of the switch SW1 is connected to the wiring G1. One of the source and the drain of the switch SW1 is connected to the wiring S1, and the other is connected to one electrode of the capacitor C1 and one electrode of the liquid crystal element 180. The other electrode of the capacitor C1 is connected to the wiring CSCOM1. The other electrode of the liquid crystal element 180 is connected to the wiring VCOM1.

Next, a connection relationship between each element and wiring in the pixel 410Ea will be described. The gate of the switch SW2 is connected to the wiring G3. One of the source and the drain of the switch SW2 is connected to the wiring S2, and the other is connected to one electrode of the capacitor C2, one electrode of the capacitor C3, and one gate of the transistor M. The other electrode of the capacitor C2 is connected to one of the source and the drain of the transistor M and the wiring ANO. The other electrode of the capacitor C3 is connected to the wiring CSCOM2. The other of the source and the drain of the transistor M is connected to one electrode of the light-emitting element 170 a and the other gate of the transistor M. The other electrode of the light emitting element 170a is connected to the wiring VCOM2.

The pixel 410Eb is different from the pixel 410Ea in that the gate of the switch SW2 is connected to the wiring G2 and one of the source and the drain of the switch SW2 is connected to the wiring S3. The pixel 410Ec is different from the pixel 410Ea in that one of a source and a drain of the switch SW2 is connected to the wiring S3.

A signal to control the on / off state of the switch SW1 may be supplied to the wiring G1. A specified potential can be supplied to the wiring VCOM1. The wiring S1 may be supplied with a signal that controls the alignment state of the liquid crystal included in the liquid crystal element 180. A specified potential can be supplied to the wiring CSCOM1.

The wiring G2 and the wiring G3 may be supplied with a signal for controlling the on / off state of the switch SW2. The wiring VCOM2 and the wiring ANO may be supplied with a potential that generates a potential difference for emitting light from the light emitting element 170a to the light emitting element 170c. The wiring S2 and the wiring S3 may be supplied with a signal for controlling the conduction state of the transistor M. A specified potential can be supplied to the wiring CSCOM2.

When the pixel 410 shown in FIG. 21 is displayed in the first mode, for example, the first pixel 410L can be driven by signals supplied to the wiring G1 and the wiring S1, and the display can be performed by optical modulation of the liquid crystal element 180. When the display is performed in the second mode, the pixels 410Ea to 410Ec can be driven by the signals supplied to the wiring G2, the wiring G3, the wiring S2, and the wiring S3, and the light emitting elements 170a to 170c can emit light for display. When driving in the third mode, the driving can be performed by using signals supplied to the wiring G1, the wiring G2, the wiring G3, the wiring S1, the wiring S2, and the wiring S3, respectively.

A circuit different from the circuit shown in Fig. 21 will be described with reference to the circuit diagram shown in Fig. 22. The circuit shown in FIG. 22 is different from the circuit shown in FIG. 21 in that one gate of the transistor M is connected to the other gate, and the other of the source and the drain of the transistor M is not connected to the transistor. The other gate of M is connected, no capacitor C3 is provided, and the wiring ANO is arranged in the C direction.

The transistor M has a structure in which a semiconductor layer is formed by sandwiching two gates. In this way, by connecting two gates and supplying the same signal to the two gates, compared with other transistors, the field effect mobility of this transistor can be increased, and the on-state current can be increased. As a result, a circuit capable of high-speed driving can be manufactured. Furthermore, the area occupied by the circuit portion can be reduced. By using a transistor with a large on-state current, even if the number of wirings increases when the display device is enlarged or sharpened, the signal delay of each wiring can be reduced, and display unevenness can be suppressed.

23A and 23B illustrate top views corresponding to the pixel 410 of FIG. 22. The layer structure of FIG. 23A corresponds to FIG. 7 and the like. Note that in FIG. 23A, for the sake of simplicity, in the illustration of the layers corresponding to the wirings G1 to G3 and the like, a frame line is indicated by a dotted line, and a hatched line is illustrated in a manner capable of transmitting a hatched line of a lower layer. In addition, in FIG. 23A, the electrode 311 used as the pixel electrode of the liquid crystal element 180 is indicated by a broken line, and the wiring CSCOM1 (the electrode 312) is indicated by a chain line. 23B shows only the electrodes 311, 312, 191a, 191b, and 191c shown in FIG. 23A.

FIG. 23A shows: electrodes 191a to 191c (corresponding to the electrode 191 of FIG. 7) used as the pixel electrodes of the light-emitting elements 170a to 170c; and those located in the same layer as the wirings S1 to S2, the wiring ANO, and the like Electrode 218; conductive layer 223 used as the gate of transistor M; conductive layer 222 (corresponding to the figure) located in the same layer as transistor M, source or drain of switch 1 and switch 2, wiring S3, etc. 7 conductive layer 222a, conductive layer 222b); transistor M, metal oxide layer 231 of switch 1 and switch 2; located on the same layer as the gate of transistor M, switch 1 and switch 2, wiring G1 to wiring G3 The conductive layer 221 (corresponding to the conductive layer 221a and the conductive layer 221b in FIG. 7); the electrode 312 used as a part of the wiring OSCOM1; the electrode 311 (the electrode corresponding to FIG. 7) used as the pixel electrode of the liquid crystal element 180 311b).

For example, a structure may be adopted in which the light-emitting element 170a exhibits blue (B), the light-emitting element 170b exhibits red (R), and the light-emitting element 170c exhibits green (G).

In addition, as shown in FIGS. 23A and 23B, the electrode 311 is connected to the switch 1 through the connection portion 207, the electrode 191a is connected to the transistor M of the pixel 410Ea through the connection portion 208a, and the electrode 191b is connected to the pixel 410Eb through the connection portion 208b. The transistor M is connected, and the electrode 191c is connected to the transistor M of the pixel 410Ec through the connection portion 208c.

As shown in FIG. 23B, a portion where the electrode 311 and the electrode 312 overlap forms a capacitor C1 (corresponding to the capacitor 270 of FIG. 7) shown in FIG. 22. Here, the electrode 311 includes a region that does not overlap the electrodes 191a to 191c. In FIG. 23B, most of the electrodes 191a to 191c are exposed by forming a cut in the electrode 311. Thereby, the light from the light-emitting elements 170a to 170c can be extracted so as not to be blocked by the electrode 311. Note that the electrodes 191a to 191c do not easily emit light of a correct color at the connection portions 208a to 208c, and therefore the electrodes 311 are provided on the connection portions 208a to 208c so as to overlap therewith. Thereby, the display area of the liquid crystal element 180 used as a reflective liquid crystal can be enlarged.

In addition, as shown in FIG. 23B, the electrode 312 does not overlap the connection portion 207 of the electrode 311. The electrode 312 includes a region that does not overlap the electrodes 191a to 191c. Thereby, the light from the light-emitting elements 170a to 170c can be extracted so as not to be blocked by the electrode 312.

Note that it is preferable to provide the electrode 312 so as not to overlap the vicinity of the connection portion 208a to the connection portion 208c of the electrode 191a to the electrode 191c as much as possible. As shown in FIG. 7 and the like, since the electrode 312 is relatively close to the conductive layer 222b and the electrode 191 in the vicinity of the connection portion 208a to the connection portion 208c, it is easy to form a parasitic capacitance on the source side (the electrode 311 side) of the transistor M. In addition, since many elements need to be provided in the pixel 410 shown in this embodiment mode, as shown in FIG. 23A, the area occupied by the capacitor C2 is small, and the driving of the pixel 410 is easily affected by the above-mentioned parasitic capacitance. Therefore, in order to reduce the parasitic capacitance described above, it is preferable to provide the electrode 312 so as not to overlap the vicinity of the connection portion 208a to the connection portion 208c as much as possible.

In the above structure, the light emitting element 170a is blue (B), the light emitting element 170b is red (R), and the light emitting element 170c is green (G), but this embodiment is not limited to this. For example, a structure may be adopted in which the light-emitting element 170a is green (G), the light-emitting element 170b is blue (B), and the light-emitting element 170c is red (R). In addition, for example, a structure may be adopted in which the light-emitting element 170 a exhibits red (R), the light-emitting element 170 b exhibits green (G), and the light-emitting element 170 c exhibits blue (B).

FIG. 24 shows a plan view in which the pixels 410 shown in FIG. 23B are arranged in a 3 × 3 matrix (hereinafter, referred to as pixels 410 (1, 1) to pixels 410 (3, 3)). In FIG. 23B, a slit is formed in the electrode 312. However, as shown in FIG. 24, the electrode 312 of an adjacent pixel may be integrated and an opening may be formed between each pixel.

As shown in FIG. 24, it is preferable that the light emitting elements 170 (electrodes 191 and EL layers 192) that emit light of the same color are arranged close to each other between adjacent pixels. For example, in FIG. 24, pixel 410 (1, 1), pixel 410 (1, 2), pixel 410 (2, 1), pixel 410 (2, 2), pixel 410 (3, 1), and pixel 410 ( 3, 2) The electrodes 191a of the light-emitting element 170a are arranged close to each other in the C direction. The electrodes 191b of the light-emitting elements 170b of the pixels 410 (1, 2), pixels 410 (1, 3), pixels 410 (2, 2), and pixels 410 (2, 3) are arranged close to each other. The electrodes 191c of the light-emitting elements 170c of the pixels 410 (2, 2), pixels 410 (2, 3), pixels 410 (3, 2), and pixels 410 (3, 3) are arranged close to each other.

As described above, by arranging the light emitting elements 170 that emit light of the same color close to each other, the EL layer 192 of the light emitting elements 170 that emit light of the same color can be formed together. Accordingly, the distance between the light-emitting element 170a and the light-emitting element 170b, the distance between the light-emitting element 170a and the light-emitting element 170c, and the distance between the light-emitting element 170b and the light-emitting element 170c can be made sufficiently large, so that it is easier even in a high-resolution panel. Each light emitting element 170 is formed. In addition, the contrast of the display device can be improved.

In addition, the display devices shown in FIGS. 22 to 24 may have a structure for performing full-color display using the liquid crystal element 180 shown in FIG. 14 and FIGS. 15A and 15B of the above-mentioned configuration example 4. For example, a color layer of each color may be provided on the liquid crystal element 180 so that the liquid crystal element 180 of the pixel 410 (2, 2) appears blue (B), and the liquid crystal element 180 of the pixel 410 (2, 3) appears red (R ), The liquid crystal element 180 of the pixel 410 (3, 2) appears green (G), and the liquid crystal element 180 of the pixel 410 (3, 3) appears white (W).

In this case, it is preferable that the color layer transmitting blue light is connected to the electrode 311 and the electrode 191a of the pixel 410 (2, 2), and the electrode 191a and the pixel 410 (3,1) of the pixel 410 (2,1). The electrodes 191a are provided so as to overlap. In addition, the color layer that transmits red light is preferably connected to the electrode 311 and the electrode 191b of the pixel 410 (2, 3), the electrode 191b of the pixel 410 (1,2), the electrode 191b of the pixel 410 (1, 3), The electrodes 191b of the pixels 410 (2, 2) are arranged so as to overlap. In addition, it is preferable that the color layer that transmits green light is connected to the electrodes 311 and 191c of the pixel 410 (3, 2), the electrode 191c of the pixel 410 (2, 2), and the electrode 191c of the pixel 410 (2, 3). The electrodes 191c of the pixels 410 (3, 3) are arranged so as to overlap. In addition, it is not necessary to provide a color layer on the electrode 311 of the pixel 410 (3, 3).

Here, when focusing on the pixel 410 (2, 2), the color layer transmitting blue light provided on the electrode 311 and the electrode 191a corresponds to the color layer 131a shown in FIG. 14, and the red light transmitting provided on the electrode 191b The colored layer and the colored layer that is disposed on the electrode 191c and transmits green light correspond to the colored layer 131b shown in FIG. In the structure shown in FIG. 24, it is not necessary to provide the color layer 134 shown in FIG. 14.

By adopting this structure, the combination of pixel 410 (2, 2), pixel 410 (2, 3), pixel 410 (3, 2), and pixel 410 (3, 3) can be regarded as each pixel being used separately. One full-color display pixel of the sub-pixels of the liquid crystal element 180.

FIG. 25 is an example of a circuit diagram of the pixel 410. FIG. 25 illustrates a pixel 410 including four light-emitting elements illustrated in FIGS. 6A to 6G and the like. The pixel 410 includes a first pixel 410L, a pixel 410Ea, a pixel 410Eb, a pixel 410Ec, and a pixel 410Ed. The first pixel 410L includes a liquid crystal element 180, the pixel 410Ea includes a light emitting element 170a, the pixel 410Eb includes a light emitting element 170b, the pixel 410Ec includes a light emitting element 170c, and the pixel 410Ed includes a light emitting element 170d. The pixels 410Ea, 410Eb, 410Ec, and 410Ed are all used as sub-pixels of the second pixel 410E.

The first pixel 410L includes a switch SW1, a capacitor C1, a liquid crystal element 180, and the like. The pixels 410Ea to 410Ed include any one of the light emitting element 170a to 170d, the switch SW2, the transistor M, the capacitor C2, and the like. The pixel 410 is electrically connected to the wiring G1, the wiring G2, the wiring G3, the wiring ANO, the wiring CSCOM, the wiring S1, the wiring S2, and the wiring S3. FIG. 25 shows a wiring VCOM1 electrically connected to the liquid crystal element 180 and a wiring VCOM2 electrically connected to the light emitting elements 170a to 170d.

FIG. 25 shows an example in which transistors are used as the switches SW1 and SW2.

The structure of the first pixel 410L is the same as that of the first pixel 410L shown in FIG. 21.

Next, a connection relationship between each element and wiring in the pixel 410Ea will be described. The gate of the switch SW2 is connected to the wiring G2. One of the source and the drain of the switch SW2 is connected to the wiring S2, and the other is connected to one electrode of the capacitor C2 and the gate of the transistor M. The other electrode of the capacitor C2 is connected to one of the source and the drain of the transistor M and the wiring ANO. The other of the source and the drain of the transistor M and one electrode of the light emitting element 170a. The other electrode of the light emitting element 170a is connected to the wiring VCOM2. In FIG. 25, the transistor M includes an example in which two gates sandwiching a semiconductor are connected to each other. This can increase the current that can flow through the transistor M.

The pixel 410Eb is different from the pixel 410Ea in that the gate of the switch SW2 is connected to the wiring G3. The pixel 410Ec is different from the pixel 410Ea in that one of a source and a drain of the switch SW2 is connected to the wiring S3. The pixel 410Ed is different from the pixel 410Eb in that one of the source and the drain of the switch SW2 is connected to the wiring S3.

The wiring G2 and the wiring G3 may be supplied with a signal for controlling the on / off state of the switch SW2. The wiring VCOM2 and the wiring ANO may be supplied with a potential that generates a potential difference for emitting light from the light emitting element 170a to the light emitting element 170d. The wiring S2 and the wiring S3 may be supplied with a signal for controlling the conduction state of the transistor M. A specified potential can be supplied to the wiring CSCOM2.

When the pixel 410 shown in FIG. 25 is displayed in the first mode, for example, the first pixel 410L can be driven by signals supplied to the wiring G1 and the wiring S1, and the display can be performed by optical modulation of the liquid crystal element 180. When the display is performed in the second mode, the pixels 410Ea to 410Ed can be driven by the signals supplied to the wiring G2, the wiring G3, the wiring S2, and the wiring S3, and the light-emitting elements 170a to 170d can emit light for display. When driving in the third mode, the driving can be performed by using signals supplied to the wiring G1, the wiring G2, the wiring G3, the wiring S1, the wiring S2, and the wiring S3, respectively.

In the example shown in FIG. 25, for example, as the four light-emitting elements 170a to 170d, light-emitting elements that exhibit red (R), green (G), blue (B), and white (W) can be used. As the liquid crystal element 180, a white reflective liquid crystal element can be used. Therefore, when displaying in the first mode, white display with high reflectance can be performed. In addition, when the display is performed in the second mode, high color rendering can be performed with low power consumption.

This embodiment can be combined with other embodiments as appropriate. In addition, a plurality of configurations shown in this embodiment can be appropriately combined.

    Embodiment 3    

In this embodiment, a configuration of a CAC (Cloud-Aligned Composite) -OS applicable to a transistor disclosed in one embodiment of the present invention will be described.

CAC-OS refers to, for example, a structure in which elements included in an oxide semiconductor are unevenly distributed, and a size of a material including the elements that are unevenly distributed is 0.5 nm or more and 10 nm or less, preferably 1 nm or more and 2 nm or less. Approximate dimensions. Note that in the following, a state in which one or more metal elements are unevenly distributed in the oxide semiconductor and a region containing the metal element is mixed is called a mosaic shape or a patch shape, and the size of the area is A size of 0.5 nm to 10 nm, preferably 1 nm to 2 nm or a similar size.

The oxide semiconductor preferably contains at least indium. It is particularly preferable to include indium and zinc. In addition, it may also contain aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, silicon, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, praseodymium, tantalum, tungsten And one or more of magnesium and the like.

For example, CAC-OS in In-Ga-Zn oxide (In CAC-OS, In-Ga-Zn oxide may be specifically referred to as CAC-IGZO) means that its material is divided into indium oxide (hereinafter, referred to as InO _X1 (X1 is a real number greater than 0)) or indium zinc oxide (hereinafter referred to as In _X2 Zn _Y2 O _Z2 (X2, Y2, and Z2 are real numbers greater than 0)) and gallium oxide (hereinafter referred to as GaO _X3 (X3 is a real number greater than 0)) or gallium zinc oxide (hereinafter referred to as Ga _X4 Zn _Y4 O _Z4 (X4, Y4, and Z4 are real numbers greater than 0)), etc., and become mosaic-like, and mosaic-like _{A structure in which X1} or In _X2 Zn _Y2 O _{Z2 is} uniformly distributed in a film (hereinafter, also referred to as a cloud shape).

In other words, CAC-OS is a composite oxide semiconductor having a structure in which a region containing GaO _X3 as a main component and a region containing In _X2 Zn _Y2 O _Z2 or InO _X1 as a main component are mixed together. In this specification, for example, when the atomic ratio of In to element M in the first region is greater than the atomic ratio of In to element M in the second region, the In concentration in the first region is higher than that in the second region.

Note that IGZO is a generic term and sometimes refers to a compound containing In, Ga, Zn, and O. As typical examples, InGaO ₃ (ZnO) _m1 (m1 is a natural number) or In _{(1 + x0)} Ga _(1-x0) O ₃ (ZnO) _m0 (-1 x0 1, m0 is an arbitrary number).

The crystalline compound has a single crystal structure, a polycrystalline structure, or a CAAC structure. The CAAC structure is a crystalline structure in which a plurality of IGZO nanocrystals have c-axis alignment and are connected in a non-alignment manner on the a-b plane.

On the other hand, CAC-OS is related to the material composition of an oxide semiconductor. CAC-OS refers to a region in which nano particles with Ga as a main component are partially observed and a region in which nano particles with In is a main component is partially observed in a material composition including In, Ga, Zn, and O. Mosaic-like irregularly dispersed composition. Therefore, in the CAC-OS configuration, the crystal structure is a secondary factor.

CAC-OS does not include a laminated structure of two or more films having different compositions. For example, a structure including two layers of a film containing In as a main component and a film containing Ga as a main component is not included.

Note that a clear boundary between a region containing GaO _X3 as a main component and a region containing In _X2 Zn _Y2 O _Z2 or InO _X1 as a main component may not be observed in some cases.

CAC-OS contains a material selected from the group consisting of aluminum, yttrium, copper, vanadium, beryllium, boron, silicon, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, praseodymium, tantalum, tungsten, and magnesium. In the case where one or more types are substituted for gallium, CAC-OS refers to a structure in which a nanoparticle-like region containing the metal element as a main component is observed in part, and a nanoparticle having In as a main component is observed in part. These regions are irregularly dispersed in a mosaic pattern.

CAC-OS can be formed by, for example, a sputtering method without intentionally heating the substrate. When the CAC-OS is formed by a sputtering method, as the deposition gas, one or more selected from an inert gas (typically argon), an oxygen gas, and a nitrogen gas can be used. The lower the oxygen gas flow rate relative to the total flow of the deposition gas during film formation, the better. For example, the flow rate of the oxygen gas is preferably 0% or more and less than 30%, and more preferably 0% or more and 10% or less. When forming a film, an In-Ga-Zn oxide target (In: Ga: Zn = 4: 2: 4.1 [atomic number ratio]) can be used.

An oxide semiconductor formed by a sputtering method at a substrate temperature of 100 ° C. to 130 ° C. using the above target is called sIGZO, and the above target is used to sputter at a substrate temperature of room temperature (RT) by sputtering. The oxide semiconductor formed by this method is called tIGZO. For example, sIGZO has a crystal structure of one or both of nc (nano crystal) and CAAC. In addition, tIGZO has a crystal structure of nc. Note that the room temperature (R.T.) referred to herein includes a temperature when the substrate is not intentionally heated.

CAC-OS has a feature that a clear peak is not observed during measurement by an θ / 2θ scan using an Out-of-plane method, which is one of X-ray diffraction (X-ray diffraction) measurement methods. That is, it can be seen from the X-ray diffraction that there is no alignment in the a-b plane direction and the c-axis direction in the measurement area.

In addition, in the electron diffraction pattern of CAC-OS obtained by irradiating an electron beam (also referred to as a nano-beam) having a beam diameter of 1 nm, a ring-shaped high-luminance region and many of the ring-shaped regions were observed. A highlight. Therefore, it is understood from the electron diffraction pattern that the crystal structure of the CAC-OS has a nc (nano-crystal) structure having no alignment in the planar direction and the cross-sectional direction.

In addition, for example, in CAC-OS of In-Ga-Zn oxide, the CAC-OS can be confirmed based on an EDX surface analysis image obtained by Energy Dispersive X-ray spectroscopy (EDX). A region having GaO _X3 as a main component and a region having In _X2 Zn _Y2 O _Z2 or InO _X1 as a main component are unevenly distributed and mixed.

CAC-OS has a different structure from IGZO compounds in which metal elements are uniformly distributed, and thus CAC-OS has properties different from those of IGZO compounds. In other words, CAC-OS has a mosaic-like structure in which a region including GaO _X3 and the like as a main component and a region including In _X2 Zn _Y2 O _Z2 or InO _X1 as a main component are separated from each other and a region including each element as a main component.

Here, the region containing In _X2 Zn _Y2 O _Z2 or InO _X1 as the main component has higher conductivity than the region containing GaO _X3 or the like as the main component. In other words, when a carrier flows through a region containing In _X2 Zn _Y2 O _Z2 or InO _X1 as a main component, the conductivity of the oxide semiconductor is exhibited. Therefore, when a region containing In _X2 Zn _Y2 O _Z2 or InO _X1 as a main component is distributed in a cloud shape in the oxide semiconductor, a high field-effect mobility (μ) can be achieved.

On the other hand, regions having GaO _X3 or the like as a main component have higher insulation properties than regions having In _X2 Zn _Y2 O _Z2 or InO _X1 as a main component. In other words, when a region mainly composed of GaO _X3 or the like is distributed in the oxide semiconductor, the off-state current can be reduced to achieve a good switching operation.

Therefore, when CAC-OS is used for a semiconductor device, the complementary effects of the insulation due to GaO _X3 and the like and the conductivity due to In _X2 Zn _Y2 O _Z2 or InO _X1 can achieve low off-state current and high on-state current ( I _on ) and high field effect mobility (μ).

In addition, a semiconductor element using CAC-OS has high reliability. Therefore, CAC-OS is suitable for various semiconductor devices such as displays.

This embodiment can be implemented in appropriate combination with other embodiments.

    Embodiment 4    

In this embodiment mode, physical properties and the like of a liquid crystal layer suitable for a display device including a liquid crystal layer will be described. In this embodiment, the imprint of the liquid crystal layer, the dipole moment of the liquid crystal layer, the influence of the pixel layout on the reflectance of the display device, and the effect of the addition of a chiral agent in the liquid crystal layer on the reflectance of the display device are described in detail. Instructions.

<1. Anisotropy of dielectric constant>

First, the anisotropy of the dielectric constant of the liquid crystal layer will be described with reference to FIG. 26.

In the present embodiment, the imprint of a display device when two materials with different anisotropy in dielectric constant are used as a material for a liquid crystal layer will be described.

In one display device, a liquid crystal material (Material 1) having a dielectric anisotropy of 3.85 is used for the liquid crystal layer. In another display device, a liquid crystal material (Material 1) having a dielectric anisotropy of 2.2 is used. 2) For liquid crystal layer.

The measurement method of the imprint of the display device is as follows: The grayscale and the grayscale when the intermediate grayscale (White → Half Tone) is displayed after the white is displayed are measured based on the grayscale when the intermediate grayscale is continuously displayed (Half Tone → Half Tone). The difference in grayscale when displaying the intermediate grayscale (Black → Half Tone) after displaying black. FIG. 26 shows the results of gray scale changes after displaying white and black. In FIG. 26, the vertical axis represents the change in gray level, and the horizontal axis represents the elapsed time after the middle gray level is written.

As can be seen from the results shown in FIG. 26, in a liquid crystal material (Material 1) having a dielectric constant anisotropy of 3.85, there is a 7.2 grayscale difference between White → Half Tone and Black → Half Tone. On the other hand, in a liquid crystal material (Material 2) with a dielectric anisotropy of 2.2, there is a 1.4 grayscale difference between White → Half Tone and Black → Half Tone. In the material of the liquid crystal material (Material 2) with a dielectric constant anisotropy of 2.2 as shown in FIG. 26, the data when the intermediate gray scale (Half Tone → Half Tone) is continuously displayed is almost superimposed on the display after displaying white Data in the middle gray scale (White → Half Tone).

From the results shown in FIG. 26, it can be understood that by using a material having a low dielectric constant anisotropy for the liquid crystal layer, it is possible to suppress a change in grayscale.

In addition, for example, when the transmission rate of 256 stages is controlled to display an image, the allowable range of the difference in gray levels when displaying the same still image is 0 gray levels or more and 3 gray levels or less. When the difference between gray levels when displaying the same still image is 0 gray level or more and 3 gray levels or less, it is not easy for the viewer to see flicker. In addition, as another example, when the transmission rate of 1024 steps is controlled to display an image, the allowable range of the difference in gray levels when displaying the same still image is 0 gray levels or more and 12 gray levels or less. In other words, the allowable range of the difference in gray levels when displaying the same still image is preferably 1% or more and 1.2% or less of the maximum grayscale value.

<2. Moment of dipole>

Next, the dipole moment of the liquid crystal layer will be described with reference to FIG. 27.

The graph shown in FIG. 27 shows the relationship between the dipole moment of a molecule and the resistivity as an example of a liquid crystal layer including molecules having a dipole moment of 0 or more Debye and 3 or less.

In the graph shown in FIG. 27, the vertical axis represents the dipole moment of a molecule. When the value shown in FIG. 27 is measured, a matrix liquid crystal and an additive material are mixed to constitute a liquid crystal layer. The dipole moment is the dipole moment of the molecules of the additive material. In Fig. 27, the horizontal axis represents the resistivity of a liquid crystal layer (in other words, a mixture of a matrix liquid crystal and an additive material). The matrix liquid crystal and the additive material are mixed so that the ratio of the additive material in the entire mixed material is 20 wt.%. Hereinafter, a mixture of the matrix liquid crystal and the additive material is referred to as a “mixed liquid crystal”. Each point in FIG. 27 is plotted by changing the type of the additive material added to the matrix liquid crystal and plotting the relationship between the dipole moment of the molecules of each additive material and the resistivity of each mixed liquid crystal added with the additive material.

As shown in FIG. 27, as the dipole moment of the molecules of the additive material decreases, the resistivity of the mixed liquid crystal increases. In other words, when the dipole moment of the added material is large, the resistivity decreases.

As shown in FIG. 27, the resistivity of the mixed liquid crystal with the dipole moment of the molecules of the additive material below 3 Debye is 1.0 × 10 ¹⁴ Ω. cm or more. The smaller the dipole moment of the molecules of the added material, the larger the resistivity. For example, in a molecular structure whose axis is symmetrical with respect to the center of the molecule, the charge distribution does not vary, so the dipole moment is zero. Therefore, in the display device according to an embodiment of the present invention, the permanent dipole moment of the molecules of the additive material is preferably 0 Debye or more and 3 Debye or less, and the resistivity is preferably 1.0 × 10 ¹⁴ Ω. cm or more.

<3. Relationship between the dipole moment and the operation of the liquid crystal layer>

The relationship between the dipole moment and the operation of the liquid crystal layer will be described. In molecules composed of different kinds of atoms, the electronegativity of each atom is usually different. Therefore, when these atoms are bonded to form a molecule, the difference in electronegativity causes a deviation in the charge distribution inside the molecule. The dipole moment is a value that quantitatively represents this amount of deviation. Note that the case where there is a charge deviation inside the molecule is sometimes expressed as "having a permanent dipole moment".

The charge distribution is schematically shown. In the case where there is a distance 1 between point charges + q and -q of different polarities, the dipole moment is the product q1. B. The unit is the product of charge and length. m (Coulomb. meters).

The dipole moment is represented by Debye. "Debye" is sometimes expressed as "Debye Unit", "debye", Latin "D" or "DU". Equation (1) shows the relationship between Debye and SI units. As can be seen from formula (1), when expressed in SI units, 1 Debye is a very small value. Since the dipole moment of a molecule is usually approximately 1 Debye, the dipole moment is generally expressed in Debye units. In this specification, the dipole moment is expressed by Debye, but it can be converted into a value expressed in SI units by using the relational expression of formula (1).

1 Debye = 3.33564 × 10 ^-30 C. m (1)

The molecules constituting the liquid crystal layer (hereinafter referred to as liquid crystal molecules) are compounds synthesized by different atomizations. Therefore, there is a deviation in the charge distribution inside the liquid crystal molecules. As a result, the liquid crystal layer has a dipole moment.

For example, the shape of the liquid crystal molecules suitable for the liquid crystal layer of the display device is a rod shape. The liquid crystal layer is dielectric, and the liquid crystal layer exhibits different dielectric constant anisotropy according to the arrangement direction of the rod-shaped liquid crystal molecules.

For example, an electron withdrawing group or an electron donating group such as a cyano group or a halogen inside the molecule affects the dielectric anisotropy. Dielectric anisotropy is a characteristic that is directly related to the response of liquid crystal molecules to external fields such as electric fields. For example, in order to increase the amount of the electron withdrawing group in order to increase the dielectric anisotropy, the charge deviation (i.e., the dipole moment) becomes too large, and ionic impurities are easily absorbed. When the concentration of the ionic impurities in the liquid crystal layer is increased, ion conduction tends to occur in the liquid crystal layer, and the voltage retention rate of the liquid crystal layer decreases. Therefore, the material of the liquid crystal layer is preferably selected so that the dipole moment is small.

As described above, when the molecular dipole moment exceeds 3 Debye, the influence of impurities included in the liquid crystal layer becomes significant. When the impurities remain in the liquid crystal layer, the resistivity of the liquid crystal layer decreases and the conductivity increases. At this time, if the refresh rate of the display device is reduced, it is difficult to maintain the voltage written into the pixel.

Since the impurities in the liquid crystal layer can be reduced when the dipole moment of the molecules included in the liquid crystal layer is low, the conductivity of the liquid crystal layer can be reduced. Therefore, when the dipole moment of the molecules included in the liquid crystal layer is low, the voltage written into the pixel can be maintained for a longer time when the refresh rate is reduced, so it is advantageous.

However, if the dipole moment of the molecules included in the liquid crystal layer is simply reduced, the interaction with the electric field tends to decrease. At this time, the response of the liquid crystal layer when an electric field is applied to the liquid crystal layer becomes slow, so the driving voltage needs to be set high to promote high-speed operation. Therefore, when the refresh rate is reduced in order to reduce power consumption, the above-mentioned structure of the liquid crystal layer is not suitable. In particular, when a driving method with a low update rate is switched to a driving method with a high update rate in order to display a moving image, an increase in driving voltage causes a large increase in power consumption of the entire liquid crystal display device.

Therefore, as an embodiment of this embodiment, it is preferable to set the dipole moment of the molecules included in the liquid crystal layer to 0 or more Debye and 3 or less. By setting the dipole moments of the molecules included in the liquid crystal layer to be above 0 Debye and below 3 Debye, the proportion of impurities included in the liquid crystal layer can be reduced, and the power consumption when displaying a moving image can be increased without causing an increase. The large mode sets the driving voltage of the liquid crystal layer to a better range.

In addition, when the dipole moment of the molecules included in the liquid crystal layer is greater than or equal to 0 Debye and less than 3 Debye, it is preferable to increase the driving voltage of the liquid crystal layer within a range that does not cause an increase in power consumption. When the driving voltage of the liquid crystal layer is high, the allowable range of the difference in gray scales is expanded. In other words, the higher the driving voltage, the less the gray scale change caused by the voltage change, and the flicker can be reduced.

The structure in which the molecules of the liquid crystal layer have a dipole moment of 0 to 3 Debye and less than 3 Debye is described, but preferably 0 to 2.5 Debye and less. In addition, it is more preferably 0 Debye to 1.8 Debye.

As described above, by adopting a structure in which the dipole moments of the molecules included in the liquid crystal layer are 0 debye or more and 3 or less debye, the difference in gray scale when displaying the same still image can be within the allowable range, so Suppress flicker. As a result, the display quality can be improved.

In addition, it is preferable that the structure includes a structure in which the molecules of the liquid crystal layer have a dipole moment of 0 or more and 3 or less Debye and driving for switching the update rate of the dynamic image display and the static image display. The liquid crystal display device driven by switching the update rate switches the frame frequency from 60 Hz to 1 Hz or less when switching from dynamic image display to still image display, preferably to 0.2 Hz or less to reduce power consumption.

In a display device that switches the update rate for display, it is preferable to reduce power consumption and prevent degradation of display quality during moving image display or still image display. If the update rate is reduced when displaying a still image, the interval at which voltage is written to the pixel becomes larger. In other words, if the update rate is reduced when displaying a still image, the voltage is not written to the pixels for a certain period of time.

Therefore, in a driving method that reduces the update rate when displaying a still image, it is important whether or not the voltage written in the pixel can be maintained at a constant value. Furthermore, in the driving method for increasing the update rate when displaying a moving image, it is important to set the driving voltage to be low in order to reduce the power consumption in consideration of the increase of the frame frequency.

<4. Influence of pixel layout of a display device on reflectance>

Next, the influence of the pixel layout of the display device on the reflectance will be described with reference to FIGS. 28A to 29.

28A and 28B are plan views illustrating pixels of a display device.

FIG. 28A shows a top view of the pixel 950A. The pixel 950A includes sub-pixels 952R _G , 952R _B , and 952R _R and sub-pixels 952E _G , 952E _B , and 952E _R. The sub-pixels 952R _G , 952R _B , and 952R _R have a function of reflecting external light. In addition, the sub-pixels 952E _G , 952E _B , and 952E _R have a function of emitting visible light.

The sub-pixel 952R _G has a function of reflecting red, the sub-pixel 952R _B has a function of reflecting blue, and the sub-pixel 952R _G has a function of reflecting green. In addition, sub-pixel 952E _G has a function of emitting green, sub-pixel 952E _B has a function of emitting blue, and sub-pixel 952E _R has a function of emitting red.

FIG. 28B shows a top view of the pixel 950B. The pixel 950B includes sub-pixels 954R _G , 954R _B , 954R _R , 954R _W and sub-pixels 954E _G , 954E _B , 954E _R , 954R _W. In the pixel 950B, the sub-pixels 954R _G , 954R _B , 954R _R , and 954R _W have a function of reflecting external light. In addition, the sub-pixels 954E _G , 954E _B , 954E _R , and 954R _W have a function of emitting visible light.

The sub-pixel 954R _G has a function of reflecting red, the sub-pixel 954R _B has a function of reflecting blue, the sub-pixel 954R _G has a function of reflecting green, and the sub-pixel 954R _W has a function of reflecting white. In addition, sub-pixel 952E _G has a function of emitting green, sub-pixel 952E _B has a function of emitting blue, sub-pixel 952E _R has a function of emitting red, and sub-pixel 952E _W has a function of emitting white.

The pixel 950B is different from the pixel 950A in that it includes a sub-pixel 954R _W and a sub-pixel 952E _W.

The total area (also referred to as the reflection aperture ratio) of the sub-pixels 952R _G , 952R _B, and 952R _R in the pixel 950A is 76%. In addition, the total area (also referred to as a reflection aperture ratio) of the sub-pixels 954R _G , 954R _B , 954R _R, and 954R _W of the pixel 950B is 57%.

Next, a display device including pixels corresponding to the pixel 950A shown in FIG. 28A and the pixel 950B shown in FIG. 28B is manufactured, and the reflectance of each display device is measured. The measurement results are shown in FIG. 29. In FIG. 29, the horizontal axis represents the reflection aperture ratio, and the vertical axis represents the reflectance. In Fig. 29, the reflectance 100% refers to the reflectance when a standard white plate is used.

As shown in FIG. 29, the reflectance of the pixel 950B is higher than that of the pixel 950A. It is speculated that this is not only due to the influence of the arrangement of the sub-pixels, but also because the sub-pixels 954R _{W are provided} (in other words, a sub-pixel having a function of reflecting white).

<5. Display device>

Next, the influence of the addition of a chiral reagent in the liquid crystal layer on the reflectance of the display device will be described with reference to FIG. 30.

First, the distortion of the liquid crystal will be described. Here, the optical TN mode using liquid crystal will be described.

In the TN mode, the initial alignment of liquid crystal molecules between a pair of substrates is a state of being twisted by 90 °. In order to uniquely determine the direction of rotation of the liquid crystal molecules, a chiral agent mixed with the liquid crystal material may cause distortion. Without the use of a chiral reagent, twists in the opposite direction may occur, and the twists in the two directions may be mixed together, leading to the wrong direction.

Here, the display device 960 and the display device 962 are assumed. The liquid crystal layer of the display device 960 contains a liquid crystal material to which a chiral agent is added, and the liquid crystal layer of the display device 962 contains a liquid crystal material to which a chiral agent is not added. The results of the reflectance calculation performed on the display device 960 and the display device 962 will be described.

FIG. 30 shows calculation results of the reflectances of the display device 960 and the display device 962. The display device 960 and the display device 962 are both reflective liquid crystal display devices. In Fig. 30, the horizontal axis represents voltage, and the vertical axis represents normalized reflectance.

As shown in FIG. 30, the normalized reflectance of the display device 962 including a liquid crystal layer to which a chiral agent is not added is approximately 20% higher than that of the display device 960 including a liquid crystal layer to which a chiral agent is added. Therefore, in order to improve the reflectance of the reflective liquid crystal display device, it is preferable to adopt a structure that does not include a chiral agent in the liquid crystal layer. Note that misalignment may occur without using a chiral reagent. Therefore, in the case where a chiral agent is not used, in order to suppress the occurrence of misalignment, for example, a chiral agent may be added to the alignment membrane.

The structure described in this embodiment can be used in appropriate combination with the structures described in other embodiments.

    Embodiment 5    

In this embodiment, a display module and an electronic device according to an embodiment of the present invention will be described.

The display module 8000 shown in FIG. 31A includes a display panel 8006, a frame 8009, a printed circuit board 8010, and a battery 8011 connected to the FPC 8005 between the upper cover 8001 and the lower cover 8002. A printed circuit board is sometimes referred to as a circuit board.

For example, the display device described in the above embodiment can be used for the display panel 8006. This makes it possible to manufacture a display module having high visibility regardless of the surrounding brightness. In addition, a display module with low power consumption can be manufactured.

The upper cover 8001 and the lower cover 8002 can be appropriately changed in shape or size according to the size of the display panel 8006.

In addition, a touch panel may be provided so as to overlap the display panel 8006. As the touch panel, a resistive film touch panel or a capacitive touch panel superimposed on the display panel 8006 can be used. In addition, the display panel 8006 may be provided with a touch panel function without providing a touch panel.

The frame 8009 has a function of shielding the electromagnetic wave generated by the operation of the printed circuit board 8010 in addition to the function of protecting the display panel 8006. In addition, the frame 8009 may have a function of a heat sink.

The printed circuit board 8010 includes a power circuit and a signal processing circuit for outputting video signals and clock signals. As a power source for supplying power to the power supply circuit, an external commercial power source or a power source of a battery 8011 separately provided may be used. When using a commercial power source, the battery 8011 can be omitted.

In addition, the display module 8000 may further include components such as a polarizing plate, a retardation plate, and a cymbal.

FIG. 31B is a schematic cross-sectional view of a display module 8000 including an optical touch sensor.

The display module 8000 includes a light emitting portion 8015 and a light receiving portion 8016 provided on the printed circuit board 8010. A region surrounded by the upper cover 8001 and the lower cover 8002 is provided with a pair of light guide portions (light guide portion 8017a, light guide portion 8017b).

The display panel 8006 overlaps the printed circuit board 8010 and the battery 8011 via a frame 8009. The display panel 8006 and the frame 8009 are fixed to the light guide portion 8017a and the light guide portion 8017b.

The light 8018 emitted from the light emitting section 8015 passes through the light guiding section 8017a, the top of the display panel 8006, and the light guiding section 8017b, and reaches the light receiving section 8016. For example, when light 8018 is blocked by a detection object such as a finger or a stylus, a touch operation can be detected.

For example, the plurality of light emitting sections 8015 are provided along two adjacent sides of the display panel 8006. The plurality of light receiving units 8016 are arranged at positions facing the light emitting unit 8015 via the display panel 8006. As a result, information on the position of the touch operation can be obtained.

As the light emitting section 8015, for example, a light source such as an LED element can be used. In particular, as the light emitting section 8015, it is preferable to use a light source that emits infrared rays that are not seen by the user and are not harmful to the user.

As the light receiving unit 8016, a photoelectric element that receives light emitted from the light emitting unit 8015 and converts it into an electric signal can be used. It is preferable to use a photodiode capable of receiving infrared rays.

As the light guide portion 8017a and the light guide portion 8017b, a member that transmits at least the light 8018 can be used. By using the light guide portion 8017a and the light guide portion 8017b, the light emitting portion 8015 and the light receiving portion 8016 can be disposed below the display panel 8006, and it is possible to suppress the external sensor from erroneously operating the touch sensor due to the external light reaching the light receiving portion 8016. It is particularly preferable to use a resin that absorbs visible light and transmits infrared rays. Thereby, erroneous operation of the touch sensor is more effectively suppressed.

According to an embodiment of the present invention, an electronic device with low power consumption can be manufactured. Examples of electronic devices include: mobile phones; portable game consoles; portable information terminals; digital cameras; digital video cameras; digital photo frames; televisions; desktop or laptop personal computers; for computers, etc. Monitors; large game machines such as pinball machines.

The display device according to one embodiment of the present invention can achieve high visibility regardless of the intensity of external light. Therefore, it is suitable for use in portable electronic devices, wearable electronic devices, and e-book readers.

The portable information terminal 800 shown in FIGS. 32A and 32B includes a casing 801, a casing 802, a display portion 803, a display portion 804, a hinge portion 805, and the like.

The casing 801 and the casing 802 are connected together by a hinge portion 805. The portable information terminal 800 can be switched from the folded state (FIG. 32A) to the expanded state shown in FIG. 32B.

A display device according to an embodiment of the present invention can be used for at least one of the display section 803 and the display section 804. This makes it possible to manufacture a portable information terminal having high visibility regardless of the surrounding brightness. In addition, it is possible to manufacture a portable information terminal with low power consumption.

The display unit 803 and the display unit 804 can display at least one of file information, still images, and moving images. When the document information is displayed on the display section, the portable information terminal 800 can be used as an e-book reader.

The portable information terminal 800 can be folded, so it has high portability and excellent versatility.

The casing 801 and the casing 802 may also include a power button, an operation button, an external port, a speaker, a microphone, and the like.

The portable information terminal 810 shown in FIG. 32C includes a casing 811, a display portion 812, operation buttons 813, an external port 814, a speaker 815, a microphone 816, a camera 817, and the like.

A display device according to an embodiment of the present invention can be used for the display portion 812. This makes it possible to manufacture a portable information terminal having high visibility regardless of the surrounding brightness. In addition, it is possible to manufacture a portable information terminal with low power consumption.

The portable information terminal 810 includes a touch sensor in the display section 812. By touching the display portion 812 with a finger, a stylus, or the like, various operations such as making a call or entering a character can be performed.

In addition, by operating the operation button 813, the power can be turned on or off, or the type of image displayed on the display unit 812 can be switched. For example, you can switch the screen for writing emails to the main menu screen.

In addition, by installing a detection device such as a gyro sensor or an acceleration sensor in the portable information terminal 810, the orientation (vertical or horizontal) of the portable information terminal 810 can be determined, and the screen of the display portion 812 The display direction is automatically switched. In addition, the screen display can be switched by touching the display section 812, operating the operation button 813, or inputting sound using the microphone 816.

The portable information terminal 810 has, for example, one or more functions selected from the group consisting of a telephone, a notebook, and an information reading device. Specifically, the portable information terminal 810 can be used as a smartphone. The portable information terminal 810 can execute various applications such as mobile phones, emails, reading and editing of articles, music playback, animation playback, network communication, computer games, and the like.

The camera 820 shown in FIG. 32D includes a housing 821, a display portion 822, an operation button 823, a shutter button 824, and the like. A detachable lens 826 is attached to the camera 820.

A display device according to an embodiment of the present invention can be used for the display portion 822. Therefore, by having a display portion having high visibility regardless of the brightness around the surroundings, the convenience of the camera can be improved. In addition, a camera with low power consumption can be manufactured.

Here, although the camera 820 has a structure in which the lens 826 can be removed from the housing 821 and exchanged, the lens 826 and the housing 821 may be integrated.

By pressing the shutter button 824, the camera 820 can shoot a still image or a moving image. In addition, the display unit 822 may be provided with a function of a touch panel, and imaging may be performed by touching the display unit 822.

It is also possible to attach a flash device, a viewfinder, and the like to the camera 820. In addition, these members may be assembled in the housing 821.

The television 830 shown in FIG. 32E includes a display portion 831, a housing 832, a speaker 833, an operation key 835 (including a power switch or an operation switch), a connection terminal 836, and a sensor 837 (the sensor has a function of measuring the following factors : Force, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, fluid, magnetism, temperature, chemicals, sound, time, hardness, electric field, current, voltage, electricity, radiation, flow, humidity, tilt Degree, vibration, odor, or infrared). For the television 830, for example, a display portion 831 of 50 inches or more or 100 inches or more can be mounted.

A display device according to an embodiment of the present invention can be used for the display portion 831. This makes it possible to manufacture a television set having high visibility regardless of the surrounding brightness. In addition, a television with low power consumption can be manufactured.

33A to 33E are diagrams illustrating an electronic device. These electronic devices include a housing 9000, a display 9001, a speaker 9003, an operation key 9005 (including a power switch or an operation switch), a connection terminal 9006, and a sensor 9007 (the sensor has a function of measuring the following factors: force, displacement, Position, speed, acceleration, angular velocity, rotational speed, distance, light, fluid, magnetism, temperature, chemicals, sound, time, hardness, electric field, current, voltage, electricity, radiation, flow, humidity, tilt, vibration, odor Or infrared), microphone 9008, etc.

A display device according to an embodiment of the present invention is applied to a display portion 9001. This makes it possible to manufacture an electronic device including a display portion having high visibility regardless of the brightness of the surroundings. In addition, electronic devices with low power consumption can be manufactured.

The electronic device shown in FIGS. 33A to 33E may have various functions. For example, it can have the following functions: display various information (still images, moving images, text images, etc.) on the display; touch panel; display calendar, date or time, etc .; control processing by using various software (programs); Perform wireless communication; connect to various computer networks by using wireless communication functions; send or receive various data by using wireless communication functions; read out programs or data stored in storage media and display them on the display Department is superior; more than one of the functions. Note that the functions of the electronic device shown in FIGS. 33A to 33E are not limited to the functions described above, and may have other functions.

FIG. 33A is a perspective view showing a watch-type portable information terminal 9200, and FIG. 33B is a perspective view showing a watch-type portable information terminal 9201.

The portable information terminal 9200 shown in FIG. 33A can execute various applications such as mobile phones, emails, reading and editing of articles, music playback, network communication, computer games, and the like. In addition, the display surface of the display unit 9001 is curved, and display can be performed along the curved display surface. In addition, the portable information terminal 9200 can perform short-range wireless communication based on a communication standard. For example, by communicating with a headset capable of wireless communication, a hands-free call can be made. In addition, the portable information terminal 9200 includes a connection terminal 9006, which can directly exchange data with other information terminals through a connector. In addition, charging can also be performed through the connection terminal 9006. In addition, the charging operation can also be performed by wireless power supply without using the connection terminal 9006.

The portable information terminal 9201 shown in FIG. 33B is different from the portable information terminal shown in FIG. 33A in that the display surface of the display portion 9001 is not curved. In addition, the display unit of the portable information terminal 9201 has a non-rectangular shape (a circular shape in FIG. 33B).

33C to 33E are perspective views showing a portable information terminal 9202 that can be folded. In addition, FIG. 33C is a perspective view of a state where the portable information terminal 9202 is expanded, and FIG. 33D is a perspective view of a midway state when the portable information terminal 9202 is converted from one of the expanded state and the folded state to the other FIG. 33E is a perspective view of a state where the portable information terminal 9202 is folded.

The portable information terminal 9202 has good portability in the folded state, and in the unfolded state, has a large display area because it has a large display area that is seamlessly spliced. The display portion 9001 included in the portable information terminal 9202 is supported by three casings 9000 connected by a hinge 9055. By bending the two housings 9000 by the hinge 9055, the portable information terminal 9202 can be reversibly changed from the unfolded state to the folded state. For example, the portable information terminal 9202 can be bent with a curvature radius of 1 mm or more and 150 mm or less.

This embodiment can be combined with other embodiments as appropriate.

Claims (20)

    A display device includes a plurality of pixels, each of the plurality of pixels including a liquid crystal element, a plurality of light emitting elements, a capacitor, and a first transistor, wherein the liquid crystal element is disposed on the light emitting element with respect to the plurality of light emitting elements. One side of the element emitting light, the liquid crystal element includes a first electrode, a second electrode, and a liquid crystal layer between the first electrode and the second electrode, and each of the plurality of light emitting elements includes a third electrode and a fourth electrode And an EL layer between the third electrode and the fourth electrode, the capacitor includes the first electrode as one electrode and a fifth electrode as the other electrode, a source electrode and a drain electrode of the first transistor One is electrically connected to the first electrode, the first electrode includes a region that does not overlap with each of the plurality of light emitting elements, and the fifth electrode is located between the first electrode and the first transistor and includes And a region overlapping the connection portion of the first electrode with one of a source and a drain of the first transistor.         The display device according to item 1 of the scope of patent application, wherein each of the plurality of pixels includes a plurality of second transistors, and one of a source and a drain of each of the plurality of second transistors is identical to the first transistor. Three electrodes are electrically connected.         According to the display device of claim 1 or 2, the first electrode and the fourth electrode have a function of reflecting visible light, and the second electrode and the third electrode have a function of transmitting visible light.         The display device according to any one of claims 1 to 3, wherein the materials of the EL layers of the plurality of light-emitting elements are different from each other in composition.         The display device according to any one of claims 1 to 3, wherein each of the plurality of pixels includes first to third light emitting elements, the first light emitting element has a function of emitting red light, and the second light emitting element The third light emitting element has a function of emitting blue light.         The display device according to any one of claims 1 to 3, wherein each of the plurality of pixels includes first to fourth light emitting elements, the first light emitting element has a function of emitting red light, and the second light emitting element The third light emitting element has a function of emitting blue light, and the fourth light emitting element has a function of emitting white light.         The display device according to any one of claims 1 to 3, wherein a material composition of the EL layer of the plurality of light emitting elements is the same, and between each of the plurality of light emitting elements and the liquid crystal layer are provided Colored layers.         The display device according to any one of claims 1 to 3, wherein each of the plurality of pixels includes first to third light emitting elements, and the first to third light emitting elements have a function of emitting white light. A color layer having a function of transmitting red light is provided between the first light emitting element and the liquid crystal layer, a color layer having a function of transmitting green light is provided between the second light emitting element and the liquid crystal layer, and A color layer having a function of transmitting blue light is provided between the three light emitting elements and the liquid crystal layer.         The display device according to any one of claims 1 to 3, wherein each of the plurality of pixels includes first to fourth light-emitting elements, and the first to fourth light-emitting elements have a function of emitting white light. A color layer having a function of transmitting red light is provided between the first light emitting element and the liquid crystal layer, a color layer having a function of transmitting green light is provided between the second light emitting element and the liquid crystal layer, and A color layer having a function of transmitting blue light is provided between the three light emitting elements and the liquid crystal layer.         A display device includes a plurality of pixels, each of the plurality of pixels including a liquid crystal element, a first color layer, a plurality of second color layers, a plurality of light emitting elements, a plurality of third color layers, a capacitor, a first The transistor and a plurality of second transistors, wherein the liquid crystal element is disposed on a side where the light emitting element emits light relative to the plurality of light emitting elements, and the first color layer and the second color layer are disposed relative to the liquid crystal element. On the side where the light emitting element emits light, the liquid crystal element includes a first electrode, a second electrode, and a liquid crystal layer between the first electrode and the second electrode. Each of the plurality of light emitting elements includes a third electrode, A fourth electrode and an EL layer between the third electrode and the fourth electrode, the capacitor includes the first electrode as one electrode and a fifth electrode as the other electrode, and a source and a sink of the first transistor One of the electrodes is electrically connected to the first electrode, and one of a source and a drain of each of the plurality of second transistors is electrically connected to the third electrode, and the first electrode and the fourth electrode have reflections visible The second electrode and the third electrode have a function of transmitting visible light. The first electrode includes a region that does not overlap with each of the plurality of light emitting elements. The fifth electrode is located between the first electrode and the first electrode. The first color layer is provided between the transistors and does not overlap a connection portion of the first electrode with one of the source and the drain of the first transistor, so as to overlap the second electrode. A plurality of second color layers are provided in a manner overlapping each of the plurality of light emitting elements, a third color layer is provided between each of the plurality of light emitting elements and the liquid crystal element, and the second The color layer and the third color layer have a function of transmitting visible light of the same color.         The display device according to any one of claims 1 to 10, wherein the second electrode is formed with a plurality of openings, and each of the plurality of light emitting elements includes a region overlapping with any one of the plurality of openings.         The display device according to any one of claims 1 to 10, wherein the second electrode is formed with a plurality of cutouts, and each of the plurality of light emitting elements includes a region overlapping with any one of the plurality of cutouts.         The display device according to any one of claims 1 to 10, wherein the second electrode is formed with one or more openings and one or more cutouts, and each of the plurality of light emitting elements includes a plurality of openings and A region where any one of the one or more incisions overlaps.         The display device according to any one of claims 1 to 13, wherein the fifth electrode includes a region that does not overlap with each of the plurality of light emitting elements.         The display device according to any one of claims 1 to 14, wherein the fifth electrode has a function of transmitting visible light.     The display device according to any one of claims 1 to 15, wherein the resistivity of the liquid crystal layer is 1.0 × 10 ¹⁴ (Ω · cm) or more.     The display device according to any one of claims 1 to 16, wherein the first transistor includes a metal oxide in a channel formation region.         The display device according to any one of claims 1 to 16, wherein the energy gap of the metal oxide is 3.0 eV or more.         A display module includes: a display device according to any one of claims 1 to 18; and a circuit board.         An electronic device includes: a display module with a scope of 19 patent applications; at least one of an antenna, a battery, a housing, a camera, a speaker, a microphone, and an operation button.